Regression modeling of gas-particle partitioning of atmospheric oxidized mercury from temperature data

NASA Astrophysics Data System (ADS)

Cheng, Irene; Zhang, Leiming; Blanchard, Pierrette

2014-10-01

Models describing the partitioning of atmospheric oxidized mercury (Hg(II)) between the gas and fine particulate phases were developed as a function of temperature. The models were derived from regression analysis of the gas-particle partitioning parameters, defined by a partition coefficient (Kp) and Hg(II) fraction in fine particles (fPBM) and temperature data from 10 North American sites. The generalized model, log(1/Kp) = 12.69-3485.30(1/T) (R2 = 0.55; root-mean-square error (RMSE) of 1.06 m3/µg for Kp), predicted the observed average Kp at 7 of the 10 sites. Discrepancies between the predicted and observed average Kp were found at the sites impacted by large Hg sources because the model had not accounted for the different mercury speciation profile and aerosol compositions of different sources. Site-specific equations were also generated from average Kp and fPBM corresponding to temperature interval data. The site-specific models were more accurate than the generalized Kp model at predicting the observations at 9 of the 10 sites as indicated by RMSE of 0.22-0.5 m3/µg for Kp and 0.03-0.08 for fPBM. Both models reproduced the observed monthly average values, except for a peak in Hg(II) partitioning observed during summer at two locations. Weak correlations between the site-specific model Kp or fPBM and observations suggest the role of aerosol composition, aerosol water content, and relative humidity factors on Hg(II) partitioning. The use of local temperature data to parameterize Hg(II) partitioning in the proposed models potentially improves the estimation of mercury cycling in chemical transport models and elsewhere.

Synthesis and Characterization of Molybdenum Based Colloidal Particles.

PubMed

Moreno; Vidoni; Ovalles; Chaudret; Urbina; Krentzein

1998-11-15

The synthesis and characterization of molybdenum colloidal particles were evaluated using thermal and sonochemical methods and starting from different metal precursors, Mo(CO)6 and (NH4)2MoS4. The products were characterized by elemental analysis, spectroscopic (UV, FTIR), and surface analysis (XPS) techniques, as well as by transmission electron microscopy (TEM) for determining the particle sizes. Using Mo(CO)6 as metal source, particle sizes with an average diameter of 1.5 nm can be obtained using tert-amyl alcohol as solvent and tetrahydrothiophene as sulfurating ligand. The characterization of these particles showed that they are composed of molybdenum oxide MoO3. Using (NH4)2MoS4 as metal precursor, particles with average diameters of 4.7 and 2.5 nm were synthesized using thermal and sonochemical methods, respectively. The characterization of these particles showed them to be composed of molybdenum sulfide, MoS2. The sonochemical method proved to be the fastest and most convenient synthetic pathway of obtaining small colloidal particles at low temperatures and with control of the average size. Copyright 1998 Academic Press.

Binary collision rates of relativistic thermal plasmas. I Theoretical framework

NASA Technical Reports Server (NTRS)

Dermer, C. D.

1985-01-01

Binary collision rates for arbitrary scattering cross sections are derived in the case of a beam of particles interacting with a Maxwell-Boltzmann (MB) plasma, or in the case of two MB plasmas interacting at generally different temperatures. The expressions are valid for all beam energies and plasma temperatures, from the nonrelativistic to the extreme relativistic limits. The calculated quantities include the reaction rate, the energy exchange rate, and the average rate of change of the squared transverse momentum component of a monoenergetic particle beam as a result of scatterings with particles of a MB plasma. Results are specialized to elastic scattering processes, two-temperature reaction rates, or the cold plasma limit, reproducing previous work.

Elevated temperature slow plastic deformation of NiAl/TiB2 particulate composites

NASA Technical Reports Server (NTRS)

Whittenberger, J. Daniel; Mannan, S. K.; Sprissler, B.; Viswanadham, R. K.

1988-01-01

The 'XD' process for production of discontinuously-reinforced metal-matrix composites has been used to enhance the high-temperature strength of NiAl-TiB2 composites with particulate densities of up to 30 vol pct. SEM, TEM, and optical characterizations of the resulting microstructures showed the average TiB2 particle size to be about 1 micron, while the average grain of the NiAl matrix was of the order of 10 microns. Elevated temperature compression tests conducted at 1200 and 1300 K indicated flow strengths to increase with TiB2 content, so that the 20 vol pct TiB2-reinforced composite was three times stronger than the unreinforced NiAl; this is ascribed to the very high density of microstructural tangled dislocations, loops, and subgrain boundaries connecting the particles.

Temperature effects on drift of suspended single-domain particles induced by the Magnus force

NASA Astrophysics Data System (ADS)

Denisov, S. I.; Lyutyy, T. V.; Reva, V. V.; Yermolenko, A. S.

2018-03-01

We study the temperature dependence of the drift velocity of single-domain ferromagnetic particles induced by the Magnus force in a dilute suspension. A set of stochastic equations describing the translational and rotational dynamics of particles is derived, and the particle drift velocity that depends on components of the average particle magnetization is introduced. The Fokker-Planck equation for the probability density of magnetization orientations is solved analytically in the limit of strong thermal fluctuations for both the planar rotor and general models. Using these solutions, we calculate the drift velocity and show that the out-of-plane fluctuations of magnetization, which are not accounted for in the planar rotor model, play an important role. In the general case of arbitrary fluctuations, we investigate the temperature dependence of the drift velocity by numerically simulating a set of effective stochastic differential equations for the magnetization dynamics.

The Cold Land Processes Experiment (CLPX-1): Analysis and Modelling of LSOS Data (IOP3 Period)

NASA Technical Reports Server (NTRS)

Tedesco, Marco; Kim, Edward J.; Cline, Don; Graf, Tobias; Koike, Toshio; Hardy, Janet; Armstrong, Richard; Brodzik, Mary

2004-01-01

Microwave brightness temperatures at 18.7,36.5, and 89 GHz collected at the Local-Scale Observation Site (LSOS) of the NASA Cold-Land Processes Field Experiment in February, 2003 (third Intensive Observation Period) were simulated using a Dense Media Radiative Transfer model (DMRT), based on the Quasi Crystalline Approximation with Coherent Potential (QCA-CP). Inputs to the model were averaged from LSOS snow pit measurements, although different averages were used for the lower frequencies vs. the highest one, due to the different penetration depths and to the stratigraphy of the snowpack. Mean snow particle radius was computed as a best-fit parameter. Results show that the model was able to reproduce satisfactorily brightness temperatures measured by the University of Tokyo s Ground Based Microwave Radiometer system (CBMR-7). The values of the best-fit snow particle radii were found to fall within the range of values obtained by averaging the field-measured mean particle sizes for the three classes of Small, Medium and Large grain sizes measured at the LSOS site.

Effects of high-temperature pressure cooking and traditional cooking on soymilk: Protein particles formation and sensory quality.

PubMed

Zuo, Feng; Peng, Xingyun; Shi, Xiaodi; Guo, Shuntang

2016-10-15

This study focused on the effect of high-temperature pressure cooking on the sensory quality of soymilk. Soymilk was prepared by high-temperature pressure cooking (105-125°C and 0.12-0.235MPa) and traditional cooking (97°C and 0.1MPa). The size distribution and composition of protein particles and the rheological properties of soymilk were compared. Results showed that the content of protein particles and the average size of soymilk particles were higher in high-temperature pressure cooking than in traditional cooking (p<0.05). High-temperature pressure cooking affected soymilk protein denaturation and favored protein aggregation. Similar to traditional soymilk, soymilk cooked at 115°C was categorized as a Newtonian fluid but was found with increased viscosity in the rheological test. Soymilk cooked at 115°C for 10min exhibited a homogeneous, smooth, and creamy texture with a high acceptability in the sensory test. Copyright © 2016 Elsevier Ltd. All rights reserved.

Monte Carlo study of one-dimensional confined fluids with Gay-Berne intermolecular potential

NASA Astrophysics Data System (ADS)

Moradi, M.; Hashemi, S.

2011-11-01

The thermodynamic quantities of a one dimensional system of particles with Gay-Berne model potential confined between walls have been obtained by means of Monte Carlo computer simulations. For a number of temperatures, the systems were considered and their density profiles, order parameter, pressure, configurational temperature and average potential energy per particle are reported. The results show that by decreasing the temperature, the soft particles become more ordered and they align to the walls and also they don't show any tendency to be near the walls at very low temperatures. We have also changed the structure of the walls by embedding soft ellipses in them, this change increases the total density near the wall whereas, increasing or decreasing the order parameter depend on the angle of embedded ellipses.

Modeling the burnout of solid polydisperse fuel under the conditions of external heat transfer

NASA Astrophysics Data System (ADS)

Skorik, I. A.; Goldobin, Yu. M.; Tolmachev, E. M.; Gal'perin, L. G.

2013-11-01

A self-similar burnout mode of solid polydisperse fuel is considered taking into consideration heat transfer between fuel particles, gases, and combustion chamber walls. A polydisperse composition of fuel is taken into account by introducing particle distribution functions by radiuses obtained for the kinetic and diffusion combustion modes. Equations for calculating the temperatures of particles and gases are presented, which are written for particles average with respect to their distribution functions by radiuses taking into account the fuel burnout ratio. The proposed equations take into consideration the influence of fuel composition, air excess factor, and gas recirculation ratio. Calculated graphs depicting the variation of particle and gas temperatures, and the fuel burnout ratio are presented for an anthracite-fired boiler.

DOE Office of Scientific and Technical Information (OSTI.GOV)

I. J. van Rooyen; E. Olivier; J. H Neethlin

Electron microscopy examinations of selected coated particles from the first advanced gas reactor experiment (AGR-1) at Idaho National Laboratory (INL) provided important information on fission product distribution and chemical composition. Furthermore, recent research using STEM analysis led to the discovery of Ag at SiC grain boundaries and triple junctions. As these Ag precipitates were nano-sized, high resolution transmission electron microscopy (HRTEM) examination was used to provide more information at the atomic level. This paper describes some of the first HRTEM results obtained by examining a particle from Compact 4-1-1, which was irradiated to an average burnup of 19.26% fissions permore » initial metal atom (FIMA), a time average, volume-averaged temperature of 1072°C; a time average, peak temperature of 1182°C and an average fast fluence of 4.13 x 1021 n/cm2. Based on gamma analysis, it is estimated that this particle may have released as much as 10% of its available Ag-110m inventory during irradiation. The HRTEM investigation focused on Ag, Pd, Cd and U due to the interest in Ag transport mechanisms and possible correlation with Pd, Ag and U previously found. Additionally, Compact 4-1-1 contains fuel particles fabricated with a different fuel carrier gas composition and lower deposition temperatures for the SiC layer relative to the Baseline fabrication conditions, which are expected to reduce the concentration of SiC defects resulting from uranium dispersion. Pd, Ag, and Cd were found to co-exist in some of the SiC grain boundaries and triple junctions whilst U was found to be present in the micron-sized precipitates as well as separately in selected areas at grain boundaries. This study confirmed the presence of Pd both at inter- and intragranular positions; in the latter case specifically at stacking faults. Small Pd nodules were observed at a distance of about 6.5 micron from the inner PyC/SiC interface.« less

Study of aluminum particle combustion in solid propellant plumes using digital in-line holography and imaging pyrometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Yi; Guildenbecher, Daniel R.; Hoffmeister, Kathryn N. G.

The combustion of molten metals is an important area of study with applications ranging from solid aluminized rocket propellants to fireworks displays. Our work uses digital in-line holography (DIH) to experimentally quantify the three-dimensional position, size, and velocity of aluminum particles during combustion of ammonium perchlorate (AP) based solid-rocket propellants. Additionally, spatially resolved particle temperatures are simultaneously measured using two-color imaging pyrometry. To allow for fast characterization of the properties of tens of thousands of particles, automated data processing routines are proposed. In using these methods, statistics from aluminum particles with diameters ranging from 15 to 900 µm are collectedmore » at an ambient pressure of 83 kPa. In the first set of DIH experiments, increasing initial propellant temperature is shown to enhance the agglomeration of nascent aluminum at the burning surface, resulting in ejection of large molten aluminum particles into the exhaust plume. The resulting particle number and volume distributions are quantified. In the second set of simultaneous DIH and pyrometry experiments, particle size and velocity relationships as well as temperature statistics are explored. The average measured temperatures are found to be 2640 ± 282 K, which compares well with previous estimates of the range of particle and gas-phase temperatures. The novel methods proposed here represent new capabilities for simultaneous quantification of the joint size, velocity, and temperature statistics during the combustion of molten metal particles. The proposed techniques are expected to be useful for detailed performance assessment of metalized solid-rocket propellants.« less

Study of aluminum particle combustion in solid propellant plumes using digital in-line holography and imaging pyrometry

DOE PAGES

Chen, Yi; Guildenbecher, Daniel R.; Hoffmeister, Kathryn N. G.; ...

2017-05-05

The combustion of molten metals is an important area of study with applications ranging from solid aluminized rocket propellants to fireworks displays. Our work uses digital in-line holography (DIH) to experimentally quantify the three-dimensional position, size, and velocity of aluminum particles during combustion of ammonium perchlorate (AP) based solid-rocket propellants. Additionally, spatially resolved particle temperatures are simultaneously measured using two-color imaging pyrometry. To allow for fast characterization of the properties of tens of thousands of particles, automated data processing routines are proposed. In using these methods, statistics from aluminum particles with diameters ranging from 15 to 900 µm are collectedmore » at an ambient pressure of 83 kPa. In the first set of DIH experiments, increasing initial propellant temperature is shown to enhance the agglomeration of nascent aluminum at the burning surface, resulting in ejection of large molten aluminum particles into the exhaust plume. The resulting particle number and volume distributions are quantified. In the second set of simultaneous DIH and pyrometry experiments, particle size and velocity relationships as well as temperature statistics are explored. The average measured temperatures are found to be 2640 ± 282 K, which compares well with previous estimates of the range of particle and gas-phase temperatures. The novel methods proposed here represent new capabilities for simultaneous quantification of the joint size, velocity, and temperature statistics during the combustion of molten metal particles. The proposed techniques are expected to be useful for detailed performance assessment of metalized solid-rocket propellants.« less

Effect of Nozzle Geometry on the Microstructure and Properties of HVAF-Sprayed WC-10Co4Cr and Cr3C2-25NiCr Coatings

NASA Astrophysics Data System (ADS)

Matikainen, V.; Koivuluoto, H.; Vuoristo, P.; Schubert, J.; Houdková, Š.

2018-04-01

Thermally sprayed hard metal coatings are the industrial standard solution for numerous demanding applications to improve wear resistance. In the aim of improving coating quality by utilising finer particle size distributions, several approaches have been studied to control the spray temperature. The most viable solution is to use the modern high velocity air-fuel (HVAF) spray process, which has already proven to produce high-quality coatings with dense structures. In HVAF spray process, the particle heating and acceleration can be efficiently controlled by changing the nozzle geometry. In this study, fine WC-10Co4Cr and Cr3C2-25NiCr powders were sprayed with three nozzle geometries to investigate their effect on the particle temperature, velocity and coating microstructure. The study demonstrates that the particle melting and resulting carbide dissolution can be efficiently controlled by changing the nozzle geometry from cylindrical to convergent-divergent. Moreover, the average particle velocity was increased from 780 to over 900 m/s. The increase in particle velocity significantly improved the coating structure and density. Further evaluation was carried out to resolve the effect of particle in-flight parameters on coating structure and cavitation erosion resistance, which was significantly improved in the case of WC-10Co4Cr coatings with the increasing average particle velocity.

Measuring kinetic energy changes in the mesoscale with low acquisition rates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roldán, É.; GISC–Grupo Interdisciplinar de Sistemas Complejos, Madrid; Martínez, I. A.

2014-06-09

We report on the measurement of the average kinetic energy changes in isothermal and non-isothermal quasistatic processes in the mesoscale, realized with a Brownian particle trapped with optical tweezers. Our estimation of the kinetic energy change allows to access to the full energetic description of the Brownian particle. Kinetic energy estimates are obtained from measurements of the mean square velocity of the trapped bead sampled at frequencies several orders of magnitude smaller than the momentum relaxation frequency. The velocity is tuned applying a noisy electric field that modulates the amplitude of the fluctuations of the position and velocity of themore » Brownian particle, whose motion is equivalent to that of a particle in a higher temperature reservoir. Additionally, we show that the dependence of the variance of the time-averaged velocity on the sampling frequency can be used to quantify properties of the electrophoretic mobility of a charged colloid. Our method could be applied to detect temperature gradients in inhomogeneous media and to characterize the complete thermodynamics of biological motors and of artificial micro and nanoscopic heat engines.« less

Particle size effect of redox reactions for Co species supported on silica

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chotiwan, Siwaruk; Tomiga, Hiroki; Katagiri, Masaki

Conversions of chemical states during redox reactions of two silica-supported Co catalysts, which were prepared by the impregnation method, were evaluated by using an in situ XAFS technique. The addition of citric acid into the precursor solution led to the formation on silica of more homogeneous and smaller Co particles, with an average diameter of 4 nm. The supported Co{sub 3}O{sub 4} species were reduced to metallic Co via the divalent CoO species during a temperature-programmed reduction process. The reduced Co species were quantitatively oxidized with a temperature-programmed oxidation process. The higher observed reduction temperature of the smaller CoO particlesmore » and the lower observed oxidation temperature of the smaller metallic Co particles were induced by the higher dispersion of the Co oxide species, which apparently led to a stronger interaction with supporting silica. The redox temperature between CoO and Co{sub 3}O{sub 4} was found to be independent of the particle size. - Graphical abstract: Chemical state conversions of SiO{sub 2}-supported Co species and the particle size effect have been analyzed by means of in situ XAFS technique. The small CoO particles have endurance against the reduction and exist in a wide temperature range. Display Omitted - Highlights: • The conversions of the chemical state of supported Co species during redox reaction are evaluated. • In operando XAFS technique were applied to measure redox properties of small Co particles. • A small particle size affects to the redox temperatures of cobalt catalysts.« less

Stress relaxation in pre-stressed aluminum core–shell particles: X-ray diffraction study, modeling, and improved reactivity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Levitas, Valery I.; McCollum, Jena; Pantoya, Michelle L.

Stress relaxation in aluminum micron-scale particles covered by alumina shell after pre-stressing by thermal treatment and storage was measured using X-ray diffraction with synchrotron radiation. Pre-stressing was produced by annealing Al particles at 573K followed by fast cooling. While averaged dilatational strain in Al core was negligible for untreated particles, it was measured at 4.40×10 -5 and 2.85×10 -5 after 2 and 48 days of storage. Consistently, such a treatment leads to increase in flame propagation speed for Al+CuO mixture by 37% and 25%, respectively. Analytical model for creep in alumna shell and stress relaxation in Al core-alumina shellmore » structure is developed and activation energy and pre-exponential multiplier are estimated. The effect of storage temperature and annealing temperature on the kinetics of stress relaxation was evaluated theoretically. These results provide estimates for optimizing Al reactivity with the holding time at annealing temperature and allowable time for storage of Al particles for various environmental temperatures.« less

Stress relaxation in pre-stressed aluminum core–shell particles: X-ray diffraction study, modeling, and improved reactivity

DOE PAGES

Levitas, Valery I.; McCollum, Jena; Pantoya, Michelle L.; ...

2016-05-30

Stress relaxation in aluminum micron-scale particles covered by alumina shell after pre-stressing by thermal treatment and storage was measured using X-ray diffraction with synchrotron radiation. Pre-stressing was produced by annealing Al particles at 573K followed by fast cooling. While averaged dilatational strain in Al core was negligible for untreated particles, it was measured at 4.40×10 -5 and 2.85×10 -5 after 2 and 48 days of storage. Consistently, such a treatment leads to increase in flame propagation speed for Al+CuO mixture by 37% and 25%, respectively. Analytical model for creep in alumna shell and stress relaxation in Al core-alumina shellmore » structure is developed and activation energy and pre-exponential multiplier are estimated. The effect of storage temperature and annealing temperature on the kinetics of stress relaxation was evaluated theoretically. These results provide estimates for optimizing Al reactivity with the holding time at annealing temperature and allowable time for storage of Al particles for various environmental temperatures.« less

Synthesis of Aluminum-Aluminum Nitride Nanocomposites by a Gas-Liquid Reaction II. Microstructure and Mechanical Properties

NASA Astrophysics Data System (ADS)

Borgonovo, Cecilia; Makhlouf, Makhlouf M.

2016-04-01

In situ fabrication of the reinforcing particles in the metal matrix is an answer to many of the challenges encountered in manufacturing aluminum matrix nanocomposites. In this method, the nanoparticles are formed directly within the melt by means of a chemical reaction between a specially designed aluminum alloy and a gas. In this publication, we describe a process for synthesizing aluminum-aluminum nitride nanocomposites by reacting a nitrogen-containing gas with a molten aluminum-lithium alloy. We quantify the effect of the process parameters on the average particle size and particle distribution, as well as on the tendency of the particles to cluster in the alloy matrix, is quantified. Also in this publication, we present the measured room temperature and elevated temperature tensile properties of the nanocomposite material as well as its measured room temperature impact toughness.

Growth of raspberry-, prism- and flower-like ZnO particles using template-free low-temperature hydrothermal method and their application as humidity sensors

NASA Astrophysics Data System (ADS)

Pál, Edit; Hornok, Viktória; Kun, Robert; Chernyshev, Vladimir; Seemann, Torben; Dékány, Imre; Busse, Matthias

2012-08-01

Zinc oxide particles with different morphologies were prepared by hydrothermal method at 60-90 °C. The structure formation was controlled by the addition rate and temperature of hydrolyzing agent, while the particles size (10 nm-2.5 μm) was influenced by the preparation (hydrothermal) temperature. Scanning electron microscopy studies showed that raspberry-, prism- and flower-like ZnO particles were prepared, whose average size decreased with increasing reaction temperature. X-ray diffraction investigations confirmed that ZnO particles with hexagonal crystal structure formed in all syntheses. The raspberry-, prism- and flower-like ZnO particles showed a weak UV-emission in the range of 390-395 nm and strong visible emission with a maximum at 586, 593 and 598 nm, respectively. Morphology effect on electrical and water vapour sensing properties of ZnO samples was investigated by impedance spectroscopy and quartz crystal microbalance, respectively. The absolute impedance of raspberry-, prism- and flower-like ZnO particles was found to be strong dependent on the morphology. Space-charge-limited conductivity transport mechanism was proved by the oscillatory behaviour of impedance. Humidity sensor tests also revealed morphology and specific surface area dependency on the sensitivity and water vapour adsorption property.

Mobility of large clusters on a semiconductor surface: Kinetic Monte Carlo simulation results

NASA Astrophysics Data System (ADS)

M, Esen; A, T. Tüzemen; M, Ozdemir

2016-01-01

The mobility of clusters on a semiconductor surface for various values of cluster size is studied as a function of temperature by kinetic Monte Carlo method. The cluster resides on the surface of a square grid. Kinetic processes such as the diffusion of single particles on the surface, their attachment and detachment to/from clusters, diffusion of particles along cluster edges are considered. The clusters considered in this study consist of 150-6000 atoms per cluster on average. A statistical probability of motion to each direction is assigned to each particle where a particle with four nearest neighbors is assumed to be immobile. The mobility of a cluster is found from the root mean square displacement of the center of mass of the cluster as a function of time. It is found that the diffusion coefficient of clusters goes as D = A(T)Nα where N is the average number of particles in the cluster, A(T) is a temperature-dependent constant and α is a parameter with a value of about -0.64 < α < -0.75. The value of α is found to be independent of cluster sizes and temperature values (170-220 K) considered in this study. As the diffusion along the perimeter of the cluster becomes prohibitive, the exponent approaches a value of -0.5. The diffusion coefficient is found to change by one order of magnitude as a function of cluster size.

Fluidizable particulate materials and methods of making same

DOEpatents

Gupta, Raghubir P.

1999-01-01

The invention provides fluidizable, substantially spherical particulate material of improved attrition resistance having an average particle size from about 100 to about 400 microns useful as sorbents, catalysts, catalytic supports, specialty ceramics or the like. The particles are prepared by spray drying a slurry comprising inorganic starting materials and an organic binder. Exemplary inorganic starting materials include mixtures of zinc oxide with titanium dioxide, or with iron oxide, alumina or the like. Exemplary organic binders include polyvinyl alcohol, hydroxypropylemethyl cellulose, polyvinyl acetate and the like. The spray dried particles are heat treated at a first temperature wherein organic binder material is removed to thereby provide a porous structure to the particles, and thereafter the particles are calcined at a higher temperature to cause reaction of the inorganic starting materials and to thereby form the final inorganic particulate material.

In situ measurements of plasma properties during gas-condensation of Cu nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koten, M. A., E-mail: mark.koten@gmail.com; Shield, J. E.; Voeller, S. A.

2016-03-21

Since the mean, standard deviation, and modality of nanoparticle size distributions can vary greatly between similar input conditions (e.g., power and gas flow rate), plasma diagnostics were carried out in situ using a double-sided, planar Langmuir probe to determine the effect the plasma has on the heating of clusters and their final size distributions. The formation of Cu nanoparticles was analyzed using cluster-plasma physics, which relates the processes of condensation and evaporation to internal plasma properties (e.g., electron temperature and density). Monitoring these plasma properties while depositing Cu nanoparticles with different size distributions revealed a negative correlation between average particlemore » size and electron temperature. Furthermore, the modality of the size distributions also correlated with the modality of the electron energy distributions. It was found that the maximum cluster temperature reached during plasma heating and the material's evaporation point regulates the growth process inside the plasma. In the case of Cu, size distributions with average sizes of 8.2, 17.3, and 24.9 nm in diameter were monitored with the Langmuir probe, and from the measurements made, the cluster temperatures for each deposition were calculated to be 1028, 1009, and 863 K. These values are then compared with the onset evaporation temperature of particles of this size, which was estimated to be 1059, 1068, and 1071 K. Thus, when the cluster temperature is too close to the evaporation temperature, less particle growth occurs, resulting in the formation of smaller particles.« less

The effect of reaction temperature on the particle size of bismuth oxide nanoparticles synthesized via hydrothermal method

NASA Astrophysics Data System (ADS)

Zulkifli, Zulfa Aiza; Razak, Khairunisak Abdul; Rahman, Wan Nordiana Wan Abdul

2018-05-01

Bismuth oxide (Bi2O3) nanoparticles have been synthesized at different temperatures from 70 to 120˚C without any subsequent heat treatment using hydrothermal method. The particle size, and crystal structure of as-synthesized particles were investigated by X-ray diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), Energy-dispersive X-ray spectroscopy (EDX) and Fourier transform Infra-Red (FTIR). The nanoparticles are of a pure moniclinic Bi2O3 phase with rods shape. The average size of nanoparticles increases with the increase of reaction temperature. It was clear that longer reaction temperature allows precipitation completely occured and form larger nanoparticles (NPs). The crystallinity of Bi2O3 also are of high purity even at lower reaction temperature. The FTIR spectrum showed the absorption band at 845 cm-1 which is attributed to Bi-O-Bi bond, and the strong absorption band recorded at 424 cm-1 that is due to the stretching mode of Bi-O.

Particle Fluxes Over a Ponderosa Pine Plantation

NASA Astrophysics Data System (ADS)

Baker, B.; Goldstein, A.

2006-12-01

Atmospheric aerosols can affect visibility, climate, and health. Particle fluxes were measured continuously over a 15 year-old ponderosa pine plantation in the foothills of the Sierra Nevada from mid July to the end of September in the year 2005. Air at this field site is affected by both biogenic emissions from the dense forests of the surrounding area and by urban pollution transported from the Sacramento valley. It is believed that fluxes of very reactive hydrocarbons from plants to the atmosphere have an impact on the production and growth of atmospheric particles at this site. Two condensation particle counters (CPCs) were located near the top of a 12 m measurement tower, several meters above the top of the tree canopy. Particle count data was collected at 10 Hz and particle fluxes were determined using the eddy covariance method. A set of diffusion screens was added to the inlet of one of the CPCs such that the lower particle size limit for detection was increased to a diameter of approximately 40 nm. The other CPC counted particles with minimum diameters of 3 nm. Particle concentrations showed a distinct diurnal pattern with minimum daily average concentrations of 2000 particles cm-3 occurring at dawn, and average daily maximum concentrations of 5700 particles cm-3 occurring at dusk. The evening increase of particle number corresponded to the arrival of polluted air from the Sacramento region. During the day, deposition of particles to the forest canopy (daytime average of 5.8x106 particles m-2 s-1 was generally observed. Concentrations and fluxes of particles under 40 nm could be examined by subtracting the data of one CPC from the other. On average, the fraction of particles under 40 nm increased from less than 20% at dawn to more than 50% at dusk; indicating that air coming from the Sacramento region was enriched in smaller, newly formed aerosol. Daily average deposition fluxes of particles under 40 nm were 1.0x107 particles m-2 s-1. Much of this flux was due to large deposition fluxes during the final three weeks of the experiment. Deposition of particles above 40 nm averaged 1.0x106 particles m-2 s-1. Deposition velocities for the particles under 40 nm were typically between 1 and 10 mm s-1. Particle deposition was correlated most strongly with temperature, and also showed some correlation with relative humidity, particle number concentration, and ozone.

Coulomb structures of charged macroparticles in static magnetic traps at cryogenic temperatures

NASA Astrophysics Data System (ADS)

Vasiliev, M. M.; Petrov, O. F.; Statsenko, K. B.

2015-12-01

Electrically charged (up to 107 e) macroscopic superconducting particles with sizes in the micrometer range confined in a static magnetic trap in liquid nitrogen and in nitrogen vapor at temperatures of 77-91 K are observed experimentally. The macroparticles with sizes up to 60 μm levitate in a nonuniform static magnetic field B ~ 2500 G. The formation of strongly correlated structures comprising as many as ~103 particles is reported. The average particle distance in these structures amounts to 475 μm. The coupling parameter and the Lindemann parameter of these structures are estimated to be ~107 and ~0.03, respectively, which is characteristic of strongly correlated crystalline or glasslike structures.

Heavy flavours production in quark-gluon plasma formed in high energy nuclear reactions

NASA Technical Reports Server (NTRS)

Kloskinski, J.

1985-01-01

Results on compression and temperatures of nuclear fireballs and on relative yield of strange and charmed hadrons are given . The results show that temperatures above 300 MeV and large compressions are unlikely achieved in average heavy ion collision. In consequence, thermal production of charm is low. Strange particle production is, however, substantial and indicates clear temperature - threshold behavior.

Strain-Detecting Composite Materials

NASA Technical Reports Server (NTRS)

Wallace, Terryl A. (Inventor); Smith, Stephen W. (Inventor); Piascik, Robert S. (Inventor); Horne, Michael R. (Inventor); Messick, Peter L. (Inventor); Alexa, Joel A. (Inventor); Glaessgen, Edward H. (Inventor); Hailer, Benjamin T. (Inventor)

2016-01-01

A composite material includes a structural material and a shape-memory alloy embedded in the structural material. The shape-memory alloy changes crystallographic phase from austenite to martensite in response to a predefined critical macroscopic average strain of the composite material. In a second embodiment, the composite material includes a plurality of particles of a ferromagnetic shape-memory alloy embedded in the structural material. The ferromagnetic shape-memory alloy changes crystallographic phase from austenite to martensite and changes magnetic phase in response to the predefined critical macroscopic average strain of the composite material. A method of forming a composite material for sensing the predefined critical macroscopic average strain includes providing the shape-memory alloy having an austenite crystallographic phase, changing a size and shape of the shape-memory alloy to thereby form a plurality of particles, and combining the structural material and the particles at a temperature of from about 100-700.degree. C. to form the composite material.

Soft-sphere simulations of a planar shock interaction with a granular bed

NASA Astrophysics Data System (ADS)

Stewart, Cameron; Balachandar, S.; McGrath, Thomas P.

2018-03-01

Here we consider the problem of shock propagation through a layer of spherical particles. A point particle force model is used to capture the shock-induced aerodynamic force acting upon the particles. The discrete element method (DEM) code liggghts is used to implement the shock-induced force as well as to capture the collisional forces within the system. A volume-fraction-dependent drag correction is applied using Voronoi tessellation to calculate the volume of fluid around each individual particle. A statistically stationary frame is chosen so that spatial and temporal averaging can be performed to calculate ensemble-averaged macroscopic quantities, such as the granular temperature. A parametric study is carried out by varying the coefficient of restitution for three sets of multiphase shock conditions. A self-similar profile is obtained for the granular temperature that is dependent on the coefficient of restitution. A traveling wave structure is observed in the particle concentration downstream of the shock and this instability arises from the volume-fraction-dependent drag force. The intensity of the traveling wave increases significantly as inelastic collisions are introduced. Downstream of the shock, the variance in Voronoi volume fraction is shown to have a strong dependence upon the coefficient of restitution, indicating clustering of particles induced by collisional dissipation. Statistics of the Voronoi volume are computed upstream and downstream of the shock and compared to theoretical results for randomly distributed hard spheres.

Ten-gram-scale preparation of PTMS-based monodisperse ORMOSIL nano- and microparticles and conversion to silica particles

NASA Astrophysics Data System (ADS)

Kim, Jung Soo; Jung, Gyu Il; Kim, Soo Jung; Koo, Sang Man

2018-03-01

Monodisperse organically modified silica (ORMOSIL) particles, with an average diameter ranging from 550 nm to 4.2 μm, were prepared at low temperature at a scale of about 10 g/batch by a simple one-step self-emulsion process. The reaction mixture was composed only of water, phenyltrimethoxysilane (PTMS), and a base catalyst, without any surfactants. The size control of the particles and the monodispersity of resultant particles were achieved through the controlled supply of hydrolyzed PTMS monomer molecules, which was enabled by manipulating the reaction parameters, such as monomer concentration, type and amount of base catalyst, stirring rate, and reaction temperature. PTMS-based ORMOSIL particles were converted into silica particles by employing either a wet chemical reaction with an oleum-sulfuric acid mixture or thermal treatment above 650 °C. Complete removal of organic groups from the ORMOSIL particles was achieved by the thermal treatment while 74% removal was done by the chemical process used. [Figure not available: see fulltext.

Practical development of continuous supercritical fluid process using high pressure and high temperature micromixer

NASA Astrophysics Data System (ADS)

Kawasaki, Shin-Ichiro; Sue, Kiwamu; Ookawara, Ryuto; Wakashima, Yuichiro; Suzuki, Akira

2015-12-01

In the synthesis of metal oxide fine particles by continuous supercritical hydrothermal method, the particle characteristics are greatly affected by not only the reaction conditions (temperature, pressure, residence time, concentration, etc.), but also the heating rate from ambient to reaction temperature. Therefore, the heating method by direct mixing of starting solution at room temperature with supercritical water is a key technology for the particle production having smaller size and narrow distribution. In this paper, mixing engineering study through comparison between conventional T-shaped mixers and recently developed swirl mixers was carried out in the hydrothermal synthesis of NiO nanoparticles from Ni(NO3)2 aqueous solution at 400 °C and 30 MPa. Inner diameter in the mixers and total flow rates were varied. Furthermore, the heating rate was calculated by computational fluid dynamics (CFD) simulation. Relationship between the heating rate and the average particle size were discussed. It was clarified that the miniaturization of mixer inner diameter and the use of the swirl flow were effective for improving mixing performance and contributed to produce small and narrow distribution particle under same experimental condition of flow rate, temperature, pressure, residence time, and concentration of the starting materials. We have focused the mixer optimization due to a difference in fluid viscosity.

Study of aniline polymerization reactions through the particle size formation in acidic and neutral medium

NASA Astrophysics Data System (ADS)

Aribowo, Slamet; Hafizah, Mas Ayu Elita; Manaf, Azwar; Andreas

2018-04-01

In the present paper, we reported particle size kinetic studies on the conducting polyaniline (PANI) which synthesized through a chemical oxidative polymerization technique from aniline monomer. PANI was prepared using ammonium persulfate (APS) as oxidizing agent which carried out in acidic and neutral medium at various batch temperatures of respectively 20, 30 and 50 °C. From the studies, it was noticed that the complete polymerization reaction progressed within 480 minutes duration time. The pH of the solution during reaction kinetic reached values 0.8 - to 1.2 in acidic media, while in the neutral media the pH value reached values 3.8 - 4.9. The batch temperature controlled the polymerization reaction in which the reaction progressing, which followed by the temperature rise of solution above the batch temperature before settled down to the initial temperature. An increment in the batch temperature gave highest rise in the solution temperature for the two media which cannot be more than 50 °C. The final product of polymerization reaction was PANI confirmed by Fourier Transform Infra-Red (FTIR) spectrophotometer for molecule structure identification. The averages particle size of PANI which carried out in the two different media is evidently similar in the range 30 - 40 μm and insensitive to the batch temperature. However, the particle size of PANI which obtained from the polymerization reaction at a batch temperature of 50 °C under acidic condition reached ˜53.1 μm at the tip of the propagation stage which started in the first 5 minutes. The size is obviously being the largest among the batch temperatures. Whereas, under neutral condition the particle size is much larger which reached the size 135 μm at the batch temperature of 20 °C. It is concluded that the particle size formation during the polymerization reaction being one of the important parameter to determine particle growing of polymer which indicated the reaction kinetics mechanism of synthesize polyaniline.

Thermodynamics of a time-dependent and dissipative oval billiard: A heat transfer and billiard approach.

PubMed

Leonel, Edson D; Galia, Marcus Vinícius Camillo; Barreiro, Luiz Antonio; Oliveira, Diego F M

2016-12-01

We study some statistical properties for the behavior of the average squared velocity-hence the temperature-for an ensemble of classical particles moving in a billiard whose boundary is time dependent. We assume the collisions of the particles with the boundary of the billiard are inelastic, leading the average squared velocity to reach a steady-state dynamics for large enough time. The description of the stationary state is made by using two different approaches: (i) heat transfer motivated by the Fourier law and (ii) billiard dynamics using either numerical simulations and theoretical description.

Production of zinc and manganese oxide particles by pyrolysis of alkaline and Zn-C battery waste.

PubMed

Ebin, Burçak; Petranikova, Martina; Steenari, Britt-Marie; Ekberg, Christian

2016-05-01

Production of zinc and manganese oxide particles from alkaline and zinc-carbon battery black mass was studied by a pyrolysis process at 850-950°C with various residence times under 1L/minN2(g) flow rate conditions without using any additive. The particular and chemical properties of the battery waste were characterized to investigate the possible reactions and effects on the properties of the reaction products. The thermodynamics of the pyrolysis process were studied using the HSC Chemistry 5.11 software. The carbothermic reduction reaction of battery black mass takes place and makes it possible to produce fine zinc particles by a rapid condensation, after the evaporation of zinc from a pyrolysis batch. The amount of zinc that can be separated from the black mass is increased by both pyrolysis temperature and residence time. Zinc recovery of 97% was achieved at 950°C and 1h residence time using the proposed alkaline battery recycling process. The pyrolysis residue is mainly MnO powder with a low amount of zinc, iron and potassium impurities and has an average particle size of 2.9μm. The obtained zinc particles have an average particle size of about 860nm and consist of hexagonal crystals around 110nm in size. The morphology of the zinc particles changes from a hexagonal shape to s spherical morphology by elevating the pyrolysis temperature. Copyright © 2015 Elsevier Ltd. All rights reserved.

The role of size polydispersity in magnetic fluid hyperthermia: average vs. local infra/over-heating effects.

PubMed

Munoz-Menendez, Cristina; Conde-Leboran, Ivan; Baldomir, Daniel; Chubykalo-Fesenko, Oksana; Serantes, David

2015-11-07

An efficient and safe hyperthermia cancer treatment requires the accurate control of the heating performance of magnetic nanoparticles, which is directly related to their size. However, in any particle system the existence of some size polydispersity is experimentally unavoidable, which results in a different local heating output and consequently a different hyperthermia performance depending on the size of each particle. With the aim to shed some light on this significant issue, we have used a Monte Carlo technique to study the role of size polydispersity in heat dissipation at both the local (single particle) and global (macroscopic average) levels. We have systematically varied size polydispersity, temperature and interparticle dipolar interaction conditions, and evaluated local heating as a function of these parameters. Our results provide a simple guide on how to choose, for a given polydispersity degree, the more adequate average particle size so that the local variation in the released heat is kept within some limits that correspond to safety boundaries for the average-system hyperthermia performance. All together we believe that our results may help in the design of more effective magnetic hyperthermia applications.

Cloud-In-Cell modeling of shocked particle-laden flows at a ``SPARSE'' cost

NASA Astrophysics Data System (ADS)

Taverniers, Soren; Jacobs, Gustaaf; Sen, Oishik; Udaykumar, H. S.

2017-11-01

A common tool for enabling process-scale simulations of shocked particle-laden flows is Eulerian-Lagrangian Particle-Source-In-Cell (PSIC) modeling where each particle is traced in its Lagrangian frame and treated as a mathematical point. Its dynamics are governed by Stokes drag corrected for high Reynolds and Mach numbers. The computational burden is often reduced further through a ``Cloud-In-Cell'' (CIC) approach which amalgamates groups of physical particles into computational ``macro-particles''. CIC does not account for subgrid particle fluctuations, leading to erroneous predictions of cloud dynamics. A Subgrid Particle-Averaged Reynolds-Stress Equivalent (SPARSE) model is proposed that incorporates subgrid interphase velocity and temperature perturbations. A bivariate Gaussian source distribution, whose covariance captures the cloud's deformation to first order, accounts for the particles' momentum and energy influence on the carrier gas. SPARSE is validated by conducting tests on the interaction of a particle cloud with the accelerated flow behind a shock. The cloud's average dynamics and its deformation over time predicted with SPARSE converge to their counterparts computed with reference PSIC models as the number of Gaussians is increased from 1 to 16. This work was supported by AFOSR Grant No. FA9550-16-1-0008.

Physical characteristics of cometary dust from optical studies

NASA Technical Reports Server (NTRS)

Hanner, M. S.

1980-01-01

Observations of the sunlight scattered and thermal emission from cometary dust, which may be used to infer the physical properties of the dust grains, are reviewed. Consideration is given to the observed wavelength dependence of the scattered light from cometary coma and tails, the average scattering function of the dust grains, the average grain Bond albedo, the polarization of the scattered light, and grain temperatures deduced from thermal infrared emission. The thermal properties of dust grains are illustrated for models based on magnetite or olivine grain materials, with consideration given to the variation of thermal properties with particle radius and heliocentric distance. Comparison of the models with observations indicates that a disordered or amorphous olivine composition can give a reasonable fit to the data for appropriate grain sizes and temperatures. The observations acquired are noted to indicate an optically important particle size of 1 micron, with silicate particles not larger than a few microns usually present although pure silicate grains can not be responsible for the thermal emission, and the cometary dust grains are most likely not spherical. Further observations needed in the infrared are indicated.

High temperature refractory of MgCr.sub.2 O.sub.4 matrix and unstabilized ZrO.sub.2 particles

DOEpatents

Singh, Jitendra P.; James, Jawana J.; Picciolo, John J.

1987-01-01

A high chromia refractory composite has been developed with improved thermal shock resistance and containing about 5-30 wt. % of unstabilized ZrO.sub.2 having a temperature-dependent phase change resulting in large expansion mismatch between the ZrO.sub.2 and the chromia matrix which causes microcracks to form during cooling in the high chromia matrix. The particle size preferably is primarily between about 0.6-5 microns and particularly below about 3 microns with an average size in the order of 1.2-1.8 microns.

Interfacial kinetics in nanosized Au/Ge films: An in situ TEM study

NASA Astrophysics Data System (ADS)

Kryshtal, Aleksandr P.; Minenkov, Alexey A.; Ferreira, Paulo J.

2017-07-01

We investigate the morphology and crystalline structure of Au/Ge films in a wide range of temperatures by in situ TEM heating. Au/Ge films with Au mass thickness of 0.2-0.3 nm and Ge thickness of 5 nm were produced in vacuum by the sequential deposition of components on a carbon substrate at room temperature. It has been shown that particles with an average size of 4 nm, formed by Au film de-wetting, melt on the germanium substrate at temperatures 110-160 °C, which are below the eutectic temperature for the bulk. The effect of crystallization-induced capillary motion of liquid eutectic particles over Ge surface has been found in this work. Formation of metastable fcc phase of Ge has been observed at the liquid-germanium interface and behind the moving particle. Formation of a liquid phase with its subsequent crystallization at the metal-semiconductor interface seems to play a key role in the metal-induced crystallization effect.

Heating without heat: Thermodynamics of passive energy filters between finite systems

NASA Astrophysics Data System (ADS)

Muñoz-Tapia, R.; Brito, R.; Parrondo, J. M. R.

2017-09-01

Passive filters allowing the exchange of particles in a narrow band of energy are currently used in microrefrigerators and energy transducers. In this Rapid Communication, we analyze their thermal properties using linear irreversible thermodynamics and kinetic theory, and discuss a striking phenomenon: the possibility of simultaneously increasing or decreasing the temperatures of two systems without any supply of energy. This occurs when the filter induces a flow of particles whose energy is between the average energies of the two systems. Here we show that this selective transfer of particles does not need the action of any sort of Maxwell demon and can be carried out by passive filters without compromising the second law of thermodynamics. This phenomenon allows us to design cycles between two reservoirs at temperatures T1

Evaluation of Low-Gravity Smoke Particulate for Spacecraft Fire Detection

NASA Technical Reports Server (NTRS)

Urban, David; Ruff, Gary A.; Mulholland George; Meyer, Marit; Yuan, Zeng guang; Cleary, Thomas; Yang, Jiann; Greenberg, Paul; Bryg, Victoria

2013-01-01

Tests were conducted on the International Space Station to evaluate the smoke particulate size from materials and conditions that are typical of those expected in spacecraft fires. Five different materials representative of those found in spacecraft (Teflon, Kapton, cotton, silicone rubber and Pyrell) were heated to temperatures below the ignition point with conditions controlled to provide repeatable sample surface temperatures and air flow. The air flow past the sample during the heating period ranged from quiescent to 8 cm/s. The effective transport time to the measurement instruments was varied from 11 to 800 seconds to simulate different smoke transport conditions in spacecraft. The resultant aerosol was evaluated by three instruments which measured different moments of the particle size distribution. These moment diagnostics were used to determine the particle number concentration (zeroth moment), the diameter concentration (first moment), and the mass concentration (third moment). These statistics were combined to determine the diameter of average mass and the count mean diameter and by assuming a log-normal distribution, the geometric mean diameter and the geometric standard deviations were also calculated. Smoke particle samples were collected on TEM grids using a thermal precipitator for post flight analysis. The TEM grids were analyzed to determine the particle morphology and shape parameters. The different materials produced particles with significantly different morphologies. Overall the majority of the average smoke particle sizes were found to be in the 200 to 400 nanometer range with the quiescent cases and the cases with increased transport time typically producing with substantially larger particles. The results varied between materials but the smoke particles produced in low gravity were typically twice the size of particles produced in normal gravity. These results can be used to establish design requirements for future spacecraft smoke detectors.

Testing of alkaline and enzymatic hydrolysis pretreatments for fat particles in slaughterhouse wastewater.

PubMed

Masse, L; Kennedy, K J; Chou, S

2001-04-01

Four pretreatments to hydrolyse and/or reduce the size of fat particles in slaughterhouse wastewater (SHW) were tested: sodium hydroxide and three lipases of plant, bacterial and animal (pancreatic) origin. Hydrolysing agents and SHW containing between 2.5 and 3 g/l of fat particles were mixed at room temperature for 4 h. Additions of 5-400 meq NaOH/l did not increase soluble COD (SCOD) in SHW, but the average particle size was reduced to 73% +/- 7% of the initial average particle size (D(in)) at NaOH concentrations ranging from 150 to 300 meq/l. Pretreatment with pancreatic lipase PL-250 reduced the average particle size to a maximum of 60% +/- 3% of D(in). As D(in) was decreased from 359 to 68 microns, the enzyme concentration required to obtain the maximum particle size reduction increased from 200 to 1000 mg/l. A 4-h pretreatment with PL-250 also increased the free long-chain fatty acid (LCFA) concentration to a maximum of 15.5 mg/l, indicating some solubilization of the pork fat particles in SHW. SCOD was not significantly increased by the pretreatment, but SCOD was not found to be a good indicator of enzymatic lipolysis because of enzyme adsorption on the fat particle surface. Pancreatic lipase appeared more efficient with beef fat than pork fat, possibly because beef fat contains less polyunsaturated fatty acids than pork fat. The bacterial lipase LG-1000 was also efficient in reducing average fat particle size, but high doses (> 1000 mg/l) were required to obtain a significant reduction after 4 h of pretreatment. SCOD was not increased by pretreatment with LG-1000. No particle size reduction or changes in SCOD were noted after 4 h of pretreatment with the plant lipase EcoSystem Plus. It was concluded that PL-250 was the best pretreatment to hydrolyse fat particles in SHW. However, its impact on the efficiency of a downstream anaerobic digestion process remains to be tested.

Denitrification and nitrification in the Arctic stratosphere during the winter of 1996-1997

NASA Astrophysics Data System (ADS)

Kondo, Y.; Irie, H.; Koike, M.; Bodeker, G. E.

2000-02-01

The concentrations of HNO3, N2O, ozone, and aerosol in the lower stratosphere inside the Arctic vortex were observed by the Improved Limb Atmospheric Spectrometer (ILAS) in the winter of 1996-1997. These data demonstrate that irreversible loss of reactive nitrogen by sedimentation of HNO3 containing particles (denitrification) at 18-23 km occurred in mid-late February soon after the Arctic vortex cooled below ice saturation temperature (TICE). Denitrification exceeding 40% was observed only in air masses which experienced temperature below TICE. It occurred within 2 days in some of these air masses. Increases in HNO3 by evaporation of the particles (nitrification) at 13-15 km occurred 0-3 days after denitrification was observed, indicating particle radii of 5-10 µm or larger. It is likely that these particles were composed of nitric acid trihydrate (NAT) or NAT-coated ice particles, given that the temperatures below 16 km were higher than TICE. Continued exposure of air masses below NAT saturation temperature for 1-4 days did not lead to any significant denitrification as long as the temperature did not fall below TICE, indicating that possible nucleation of NAT at these temperatures within 4 days did not play a significant role in causing denitrification. There was little change in the average HNO3 column from February 11 to 28 since HNO3 decreases at 18-23 km were almost completely offset by increases at 12-17 km.

[Preparation and characterization of magnetic nano-particles with radiofrequency-induced hyperthermia for cancer treatment].

PubMed

Fan, Xiangshan; Zhang, Dongsheng; Zheng, Jie; Gu, Ning; Ding, Anwei; Jia, Xiupeng; Qing, Hongyun; Jin, Liqiang; Wan, Meiling; Li, Qunhui

2006-08-01

Mn0.5Zn0.5Fe2O4 nano-particles were prepared by the chemical co-precipitation, their characteristics were observed with transmission electron microscope (TEM), X-ray diffractometer (XRD) and thermal analysis system, and etc. The temperature changes of the nano-particles of Mn0.5Zn0.5Fe2O4 and its magnetic fluid explored in radiofrequency(RF,200 KHz, 4 KW) were measured. The proliferation ratio of L929 cells cultured in soak of Mn0.5Zn0.5Fe2O4 nano-particles were observed. The experiment indicates that the magnetic particles were about 40 nm diameter in average, round, had strong magnetism, and were proved to be consistent with the standard data of chart of XRD. Its magnetic fluid exposed to RF could be heated up to temperature range from 40 degrees C to 51 degrees C due to the amount of the magnetic nano-particles and intensity of the alternating magnetic field. Magnetic nano-particles were found to have no obvious cytotoxicity to L929 cells.

Efficiency of single-particle engines

NASA Astrophysics Data System (ADS)

Proesmans, Karel; Driesen, Cedric; Cleuren, Bart; Van den Broeck, Christian

2015-09-01

We study the efficiency of a single-particle Szilard and Carnot engine. Within a first order correction to the quasistatic limit, the work distribution is found to be Gaussian and the correction factor to average work and efficiency only depends on the piston speed. The stochastic efficiency is studied for both models and the recent findings on efficiency fluctuations are confirmed numerically. Special features are revealed in the zero-temperature limit.

Effects of Ni content on nanocrystalline Fe-Co-Ni ternary alloys synthesized by a chemical reduction method

NASA Astrophysics Data System (ADS)

Chokprasombat, Komkrich; Pinitsoontorn, Supree; Maensiri, Santi

2016-05-01

Magnetic properties of Fe-Co-Ni ternary alloys could be altered by changing of the particle size, elemental compositions, and crystalline structures. In this work, Fe50Co50-xNix nanoparticles (x=10, 20, 40, and 50) were prepared by the novel chemical reduction process. Hydrazine monohydrate was used as a reducing agent under the concentrated basic condition with the presence of poly(vinylpyrrolidone). We found that the nanoparticles were composed of Fe, Co and Ni with compositions according to the molar ratio of the metal sources. Interestingly, the particles were well-crystalline at the as-prepared state without post-annealing at high temperature. Increasing Ni content resulted in phase transformation from body centered cubic (bcc) to face centered cubic (fcc). For the fcc phase, the average particle size decreased when increased the Ni content; the Fe50Ni50 nanoparticles had the smallest average size with the narrowest size distribution. In additions, the particles exhibited ferromagnetic properties at room temperature with the coercivities higher than 300 Oe, and the saturation magnetiation decreased with increasing Ni content. These results suggest that the structural and magnetic properties of Fe-Co-Ni alloys could be adjusted by varying the Ni content.

Magnetic and structural properties of nanoparticles of nickel oxide

NASA Astrophysics Data System (ADS)

Shim, Hyunja (Jenny)

In this dissertation, magnetic properties of NiO nanoparticles (NP) prepared by the sol-gel method in the size range D = 5 nm to 20 nm, with and without oleic acid (OA) coating, are reported. Transmission electron microscopy (TEM) studies show the morphology of the smaller particles to be primarily rod-like, changing over to nearly spherical shapes for D >10 nm. Average sizes D of NP determined by x-ray diffraction (XRD) are compared with the results from TEM. From the analysis of the XRD line intensities, the particle size dependence of the Debye-Waller factors for Ni and O atoms are derived. It is found that the Debye-Waller factors of nickel and oxygen atoms in smaller particles are larger than those in bulk NiO. For the coated and uncoated NiO nanorods of 5 nm diameter, variations of the magnetization M with temperature T (5 K to 370 K) and temperature variations of the EMR (electron magnetic resonance) spectra were measured to determine the respective blocking temperatures TB(m) and TB(EMR). The following differences are noted: (1) TB(m) is reduced from 230 K (uncoated) to 85 K(coated) for H = 25 Oe; (2) Decrease of TB(m) with H is weaker and the ratio TB(EMR)/T B(m) is smaller for the uncoated particles. These differences are due to stronger interparticle interaction present in the uncoated particles. Temperature variation (5 K-300 K) of the AC magnetic susceptibilities (chi' and chi") at various frequencies f (0.1-10,000 Hz) are reported for the coated and uncoated 5 nm diameter nanorods of NiO. Using the peak in chi' as the blocking temperature TB, it is observed that TB increases with increasing f. The data for the two samples fit the Vogel-Fulcher law: f = f0exp[-Ea/k(TB-T0)] with f 0 = 9.2 x 1011 Hz, Ea/k = 1085 K and T0 = 162 K (0 K) for the uncoated (coated) particles. This shows that T0 provides a good measure of the effects of interparticle interactions on magnetic relaxation and that these interactions are essentially eliminated with the OA coating. For all the particles, measurements of M versus T (5 K-370 K) in the zero-field cooled (ZFC) and field-cooled (FC) modes are used to determine the average blocking temperature TP. For the OA coated particles, TP increases with increase in size D as expected for superparamagnetic particles. However for the uncoated NP, TP decreases initially with increase in size for D < 10 nm; but for D > 10 nm, TP follows the same trend as for the coated NP. These differences are interpreted in terms of significant interparticle interaction. The data of M vs. the applied field H for T > TP are fit to the modified Langevin function: M = M0 L (muPH/kBT) + chiaH, to determine the magnetic moment muP per particle as a function of size D. The variation of muP with size D is interpreted in terms of the fraction of spins on the surface layer of the particles which contribute to mu P. It is observed that this fraction varies as 1/D reaching nearly 100 % for the 5 nm particles. From the temperature dependence of M0 and extrapolating to M0 → 0, the Neel temperatures TN for various sizes are determined. TN for NiO nanoparticles is found to decreases rapidly with decrease in size for D < 10 nm.

Strongly coupled fluid-particle flows in vertical channels. I. Reynolds-averaged two-phase turbulence statistics

NASA Astrophysics Data System (ADS)

Capecelatro, Jesse; Desjardins, Olivier; Fox, Rodney O.

2016-03-01

Simulations of strongly coupled (i.e., high-mass-loading) fluid-particle flows in vertical channels are performed with the purpose of understanding the fundamental physics of wall-bounded multiphase turbulence. The exact Reynolds-averaged (RA) equations for high-mass-loading suspensions are presented, and the unclosed terms that are retained in the context of fully developed channel flow are evaluated in an Eulerian-Lagrangian (EL) framework for the first time. A key distinction between the RA formulation presented in the current work and previous derivations of multiphase turbulence models is the partitioning of the particle velocity fluctuations into spatially correlated and uncorrelated components, used to define the components of the particle-phase turbulent kinetic energy (TKE) and granular temperature, respectively. The adaptive spatial filtering technique developed in our previous work for homogeneous flows [J. Capecelatro, O. Desjardins, and R. O. Fox, "Numerical study of collisional particle dynamics in cluster-induced turbulence," J. Fluid Mech. 747, R2 (2014)] is shown to accurately partition the particle velocity fluctuations at all distances from the wall. Strong segregation in the components of granular energy is observed, with the largest values of particle-phase TKE associated with clusters falling near the channel wall, while maximum granular temperature is observed at the center of the channel. The anisotropy of the Reynolds stresses both near the wall and far away is found to be a crucial component for understanding the distribution of the particle-phase volume fraction. In Part II of this paper, results from the EL simulations are used to validate a multiphase Reynolds-stress turbulence model that correctly predicts the wall-normal distribution of the two-phase turbulence statistics.

Strongly coupled fluid-particle flows in vertical channels. I. Reynolds-averaged two-phase turbulence statistics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Capecelatro, Jesse, E-mail: jcaps@illinois.edu; Desjardins, Olivier; Fox, Rodney O.

Simulations of strongly coupled (i.e., high-mass-loading) fluid-particle flows in vertical channels are performed with the purpose of understanding the fundamental physics of wall-bounded multiphase turbulence. The exact Reynolds-averaged (RA) equations for high-mass-loading suspensions are presented, and the unclosed terms that are retained in the context of fully developed channel flow are evaluated in an Eulerian–Lagrangian (EL) framework for the first time. A key distinction between the RA formulation presented in the current work and previous derivations of multiphase turbulence models is the partitioning of the particle velocity fluctuations into spatially correlated and uncorrelated components, used to define the components ofmore » the particle-phase turbulent kinetic energy (TKE) and granular temperature, respectively. The adaptive spatial filtering technique developed in our previous work for homogeneous flows [J. Capecelatro, O. Desjardins, and R. O. Fox, “Numerical study of collisional particle dynamics in cluster-induced turbulence,” J. Fluid Mech. 747, R2 (2014)] is shown to accurately partition the particle velocity fluctuations at all distances from the wall. Strong segregation in the components of granular energy is observed, with the largest values of particle-phase TKE associated with clusters falling near the channel wall, while maximum granular temperature is observed at the center of the channel. The anisotropy of the Reynolds stresses both near the wall and far away is found to be a crucial component for understanding the distribution of the particle-phase volume fraction. In Part II of this paper, results from the EL simulations are used to validate a multiphase Reynolds-stress turbulence model that correctly predicts the wall-normal distribution of the two-phase turbulence statistics.« less

``Elastic properties'' of magnetic fluids

NASA Astrophysics Data System (ADS)

Nikolaev, V. I.; Shipilin, A. M.; Shkolnicov, E. N.; Zaharova, I. N.

1999-07-01

The results of Mössbauer investigations of the viscous magnetic liquids at temperatures of 100-300 K are discussed. The investigated ferrofluids were the colloidal dispersions of magnetite particles with average diameters of 7.5 and 10 nm in silicone carrier fluid. Supposing that the intensity of the Mössbauer line is determined by the factor f=f'ṡf″ (f' is Mössbauer factor for magnetite powder; f″ is a similar factor depending on oscillations of particles in a liquid), we estimated the values of the factor f″(T) at various temperatures. To describe the dependence f'(T), the Debye approximation was used. By means of the data on the dependence f″(T) the estimations of frequencies of particles oscillations Ω and "elasticity modulus" E of the investigated substances were obtained.

Size-controlled synthesis, surface functionalization, and biological applications of thiol-organosilica particles.

PubMed

Nakamura, Michihiro; Ozaki, Shuji; Abe, Masahiro; Doi, Hiroyuki; Matsumoto, Toshio; Ishimura, Kazunori

2010-08-01

Thiol-organosilica particles of a narrow size distribution, made from 3-mercaptopropyltrimethoxysilane (MPMS), were prepared by means of a one-pot synthesis. We examined three synthetic conditions at high temperature (100 degrees C), including the Stöber synthesis and two entirely aqueous syntheses. Under all conditions, the sizes of MPMS particles were well controlled, and the average of the coefficient of variation for the size distribution was less than 20%. The incubation times required for formation of MPMS particles were shorter at high temperature than at low temperature. MPMS particles internally functionalized with fluorescent dye were also prepared by means of the same one-pot synthesis. On flow cytometry analysis these MPMS particles showed distinct peaks of scattering due to well-controlled sizes of particles as well as due to fluorescence signals. Real-time observation of interaction between fluorescent MPMPS particles and cultured cells could be observed under fluorescent microscopy with bright light. The surface of the as-prepared MPMS particles contained exposed mercaptopropyl residues, and the ability to adsorb proteins was at least 6 times higher than that of gold nanopaticles. In addition, fluorescein-labeled proteins adsorbed to the surface of the particles were quantitatively detected at the pg/ml level by flow cytometry. MPMS particles surface functionalized with anti-CD20 antibody using adsorption could bind with lymphoma cells expressing CD20 specifically. In this paper, we demonstrated the possibility of size-controlled thiol-organosilica particles for wild range of biological applications. Crown Copyright 2010. Published by Elsevier B.V. All rights reserved.

Multilevel quantum Otto heat engines with identical particles

NASA Astrophysics Data System (ADS)

Huang, X. L.; Guo, D. Y.; Wu, S. L.; Yi, X. X.

2018-02-01

A quantum Otto heat engine is studied with multilevel identical particles trapped in one-dimensional box potential as working substance. The symmetrical wave function for Bosons and the anti-symmetrical wave function for Fermions are considered. In two-particle case, we focus on the ratios of W^i (i=B,F) to W_s, where W^B and W^F are the work done by two Bosons and Fermions, respectively, and W_s is the work output of a single particle under the same conditions. Due to the symmetrical of the wave functions, the ratios are not equal to 2. Three different regimes, low-temperature regime, high-temperature regime, and intermediate-temperature regime, are analyzed, and the effects of energy level number and the differences between the two baths are calculated. In the multiparticle case, we calculate the ratios of W^i_M/M to W_s, where W^i_M/M can be seen as the average work done by a single particle in multiparticle heat engine. For other working substances whose energy spectrum has the form of E_n˜ n^2, the results are similar. For the case E_n˜ n, two different conclusions are obtained.

How the Emitted Size Distribution and Mixing State of Feldspar Affect Ice Nucleating Particles in a Global Model

NASA Technical Reports Server (NTRS)

Perlwitz, Jan P.; Fridlind, Ann M.; Knopf, Daniel A.; Miller, Ron L.; García-Pando, Carlos Perez

2017-01-01

The effect of aerosol particles on ice nucleation and, in turn, the formation of ice and mixed phase clouds is recognized as one of the largest sources of uncertainty in climate prediction. We apply an improved dust mineral specific aerosol module in the NASA GISS Earth System ModelE, which takes into account soil aggregates and their fragmentation at emission as well as the emission of large particles. We calculate ice nucleating particle concentrations from K-feldspar abundance for an active site parameterization for a range of activation temperatures and external and internal mixing assumption. We find that the globally averaged INP concentration is reduced by a factor of two to three, compared to a simple assumption on the size distribution of emitted dust minerals. The decrease can amount to a factor of five in some geographical regions. The results vary little between external and internal mixing and different activation temperatures, except for the coldest temperatures. In the sectional size distribution, the size range 24 micrometer contributes the largest INP number.

How the Emitted Size Distribution and Mixing State of Feldspar Affect Ice Nucleating Particles in a Global Model

NASA Astrophysics Data System (ADS)

Perlwitz, J. P.; Fridlind, A. M.; Knopf, D. A.; Miller, R. L.; Pérez García-Pando, C.

2017-12-01

The effect of aerosol particles on ice nucleation and, in turn, the formation of ice and mixed phase clouds is recognized as one of the largest sources of uncertainty in climate prediction. We apply an improved dust mineral specific aerosol module in the NASA GISS Earth System ModelE, which takes into account soil aggregates and their fragmentation at emission as well as the emission of large particles. We calculate ice nucleating particle concentrations from K-feldspar abundance for an active site parameterization for a range of activation temperatures and external and internal mixing assumption. We find that the globally averaged INP concentration is reduced by a factor of two to three, compared to a simple assumption on the size distribution of emitted dust minerals. The decrease can amount to a factor of five in some geographical regions. The results vary little between external and internal mixing and different activation temperatures, except for the coldest temperatures. In the sectional size distribution, the size range 2-4 μm contributes the largest INP number.

Glyoxal and methylglyoxal in Atlantic seawater and marine aerosol particles: method development and first application during the Polarstern cruise ANT XXVII/4

NASA Astrophysics Data System (ADS)

van Pinxteren, M.; Herrmann, H.

2013-12-01

An analytical method for the determination of the alpha dicarbonyls glyoxal (GLY) and methylglyoxal (MGLY) from seawater and marine aerosol particles is presented. The method is based on derivatization with o-(2,3,4,5,6-Pentafluorobenzyl)-hydroxylamine (PFBHA) reagent, solvent extraction and GC-MS (SIM) analysis. The method showed good precision (RSD < 10%), sensitivity (detection limits in the low ng L-1 range), and accuracy (good agreement between external calibration and standard addition). The method was applied to determine GLY and MGLY in oceanic water sampled during the Polarstern cruise ANT XXVII/4 from Capetown to Bremerhaven in spring 2011. GLY and MGLY were determined in the sea surface microlayer (SML) of the ocean and corresponding bulk water (BW) with average concentrations of 228 ng L-1 (GLY) and 196 ng L-1 (MGLY). The results show a significant enrichment (factor of 4) of GLY and MGLY in the SML. Furthermore, marine aerosol particles (PM1) were sampled during the cruise and analyzed for GLY (average concentration 0.19 ng m-3) and MGLY (average concentration 0.15 ng m-3). On aerosol particles, both carbonyls show a very good correlation with oxalate, supporting the idea of a secondary formation of oxalic acid via GLY and MGLY. Concentrations of GLY and MGLY in seawater and on aerosol particles were correlated to environmental parameters such as global radiation, temperature, distance to the coastline and biological activity. There are slight hints for a photochemical production of GLY and MGLY in the SML (significant enrichment in the SML, higher enrichment at higher temperature). However, a clear connection of GLY and MGLY to global radiation as well as to biological activity cannot be concluded from the data. A slight correlation between GLY and MGLY in the SML and in aerosol particles could be a hint for interactions, in particular of GLY, between seawater and the atmosphere.

[Preparation of curcumin-EC sustained-release composite particles by supercritical CO2 anti-solvent technology].

PubMed

Bai, Wei-li; Yan, Ting-yuan; Wang, Zhi-xiang; Huang, De-chun; Yan, Ting-xuan; Li, Ping

2015-01-01

Curcumin-ethyl-cellulose (EC) sustained-release composite particles were prepared by using supercritical CO2 anti-solvent technology. With drug loading and yield of inclusion complex as evaluation indexes, on the basis of single factor tests, orthogonal experimental design was used to optimize the preparation process of curcumin-EC sustained-release composite particles. The experiments such as drug loading, yield, particle size distribution, electron microscope analysis (SEM) , infrared spectrum (IR), differential scanning calorimetry (DSC) and in vitro dissolution were used to analyze the optimal process combination. The orthogonal experimental optimization process conditions were set as follows: crystallization temperature 45 degrees C, crystallization pressure 10 MPa, curcumin concentration 8 g x L(-1), solvent flow rate 0.9 mL x min(-1), and CO2 velocity 4 L x min(-1). Under the optimal conditions, the average drug loading and yield of curcumin-EC sustained-release composite particles were 33.01% and 83.97%, and the average particle size of the particles was 20.632 μm. IR and DSC analysis showed that curcumin might complex with EC. The experiments of in vitro dissolution showed that curcumin-EC composite particles had good sustained-release effect. Curcumin-EC sustained-release composite particles can be prepared by supercritical CO2 anti-solvent technology.

Irradiation effects in oxide dispersion strengthened (ODS) Ni-base alloys for Gen. IV nuclear reactors

NASA Astrophysics Data System (ADS)

Oono, Naoko; Ukai, Shigeharu; Kondo, Sosuke; Hashitomi, Okinobu; Kimura, Akihiko

2015-10-01

Oxide particle dispersion strengthened (ODS) Ni-base alloys are irradiated by using simulation technique (Fe/He dual-ion irradiation) to investigate the reliability to Gen. IV high-temperature reactors. The fine oxide particles with less than 10 nm in average size and approximately 8.0 × 1022 m-3 in number density remained after 101 dpa irradiation. The tiny helium bubbles were inside grains, not at grain-boundaries; it is advantageous effect of oxide particles which trap the helium atoms at the particle-matrix interface. Ni-base ODS alloys demonstrated their great ability to overcome He embrittlement.

Synthesis of Calcite Nano Particles from Natural Limestone assisted with Ultrasonic Technique

NASA Astrophysics Data System (ADS)

Handayani, M.; Sulistiyono, E.; Firdiyono, F.; Fajariani, E. N.

2018-03-01

This article represents a precipitation method assisted with ultrasonic process to synthesize precipitated calcium carbonate nano particles from natural limestone. The synthesis of nanoparticles material of precipitated calcium carbonate from commercial calcium carbonate was done for comparison. The process was performed using ultrasonic waves at optimum condition, that is, at temperature of 80oC for 10 minutes with various amplitudes. Synthesized precipitated calcium carbonate nanoparticles were characterized using X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM) and Particle Size Analyzer (PSA). The result of PSA measurements showed that precipitated calcium carbonate nano particles was obtained with the average size of 109 nm.

Particle Morphology and Size Results from the Smoke Aerosol Measurement Experiment-2

NASA Technical Reports Server (NTRS)

Urban, David L.; Ruff, Gary A.; Greenberg, Paul S.; Fischer, David; Meyer, Marit; Mulholland, George; Yuan, Zeng-Guang; Bryg, Victoria; Cleary, Thomas; Yang, Jiann

2012-01-01

Results are presented from the Reflight of the Smoke Aerosol Measurement Experiment (SAME-2) which was conducted during Expedition 24 (July-September 2010). The reflight experiment built upon the results of the original flight during Expedition 15 by adding diagnostic measurements and expanding the test matrix. Five different materials representative of those found in spacecraft (Teflon, Kapton, cotton, silicone rubber and Pyrell) were heated to temperatures below the ignition point with conditions controlled to provide repeatable sample surface temperatures and air flow. The air flow past the sample during the heating period ranged from quiescent to 8 cm/s. The smoke was initially collected in an aging chamber to simulate the transport time from the smoke source to the detector. This effective transport time was varied by holding the smoke in the aging chamber for times ranging from 11 to 1800 s. Smoke particle samples were collected on Transmission Electron Microscope (TEM) grids for post-flight analysis. The TEM grids were analyzed to observe the particle morphology and size parameters. The diagnostics included a prototype two-moment smoke detector and three different measures of moments of the particle size distribution. These moment diagnostics were used to determine the particle number concentration (zeroth moment), the diameter concentration (first moment), and the mass concentration (third moment). These statistics were combined to determine the diameter of average mass and the count mean diameter and, by assuming a log-normal distribution, the geometric mean diameter and the geometric standard deviations can also be calculated. Overall the majority of the average smoke particle sizes were found to be in the 200 nm to 400 nm range with the quiescent cases producing some cases with substantially larger particles.

Brominated flame retardants in the urban atmosphere of Northeast China: concentrations, temperature dependence and gas-particle partitioning.

PubMed

Qi, Hong; Li, Wen-Long; Liu, Li-Yan; Song, Wei-Wei; Ma, Wan-Li; Li, Yi-Fan

2014-09-01

57 pairs of air samples (gas and particle phases) were collected using a high volume air sampler in a typical city of Northeast China. Brominated flame retardants (BFRs) including 13 polybrominated diphenyl ethers (PBDEs, including BDEs 17, 28, 47, 49, 66, 85, 99, 100, 138, 153, 154, 183, and 209) and 9 alternative BFRs (p-TBX, PBBZ, PBT, PBEB, DPTE, HBBZ, γ-HBCD, BTBPE, and DBDPE) were analyzed. The annual average total concentrations of the 13 PBDEs and the 9 alternative BFRs were 69 pg/m(3) and 180 pg/m(3), respectively. BDE 209 and γ-HBCD were the dominant congeners, according to the one-year study. The partial pressure of BFRs in the gas phase was significantly correlated with the ambient temperature, except for BDE 85, γ-HBCD and DBDPE, indicating the important influence of ambient temperature on the behavior of BFRs in the atmosphere. It was found that the gas-particle partitioning coefficients (logKp) for most low molecular weight BFRs were highly temperature dependent as well. Gas-particle partitioning coefficients (logKp) also correlated with the sub-cooled liquid vapor pressure (logPL(o)). Our results indicated that absorption into organic matter is the main control mechanism for the gas-particle partitioning of atmospheric PBDEs. Copyright © 2014 Elsevier B.V. All rights reserved.

Solid oxide fuel cell cathode infiltrate particle size control and oxygen surface exchange resistance determination

NASA Astrophysics Data System (ADS)

Burye, Theodore E.

Over the past decade, nano-sized Mixed Ionic Electronic Conducting (MIEC) -- micro-sized Ionic Conducting (IC) composite cathodes produced by the infiltration method have received much attention in the literature due to their low polarization resistance (RP) at intermediate (500-700°C) operating temperatures. Small infiltrated MIEC oxide nano-particle size and low intrinsic MIEC oxygen surface exchange resistance (Rs) have been two critical factors allowing these Nano-Micro-Composite Cathodes (NMCCs) to achieve high performance and/or low temperature operation. Unfortunately, previous studies have not found a reliable method to control or reduce infiltrated nano-particle size. In addition, controversy exists on the best MIEC infiltrate composition because: 1) Rs measurements on infiltrated MIEC particles are presently unavailable in the literature, and 2) bulk and thin film Rs measurements on nominally identical MIEC compositions often vary by up to 3 orders of magnitude. Here, two processing techniques, precursor nitrate solution desiccation and ceria oxide pre-infiltration, were developed to systematically produce a reduction in the average La0.6Sr0.4Co0.8Fe 0.2O3-delta (LSCF) infiltrated nano-particle size from 50 nm to 22 nm. This particle size reduction reduced the SOFC operating temperature, (defined as the temperature where RP=0.1 Ocm 2) from 650°C to 540°C. In addition, Rs values for infiltrated MIEC particles were determined for the first time through finite element modeling calculations on 3D Focused Ion Beam-Scanning Electron Microscope (FIB-SEM) reconstructions of electrochemically characterized infiltrated electrodes.

Swelling Kinetics of Waxy Maize Starch

NASA Astrophysics Data System (ADS)

Desam, Gnana Prasuna Reddy

Starch pasting behavior greatly influences the texture of a variety of food products such as canned soup, sauces, baby foods, batter mixes etc. The annual consumption of starch in the U.S. is 3 million metric tons. It is important to characterize the relationship between the structure, composition and architecture of the starch granules with its pasting behavior in order to arrive at a rational methodology to design modified starch of desirable digestion rate and texture. In this research, polymer solution theory was applied to predict the evolution of average granule size of starch at different heating temperatures in terms of its molecular weight, second virial coefficient and extent of cross-link. Evolution of granule size distribution of waxy native maize starch when subjected to heating at constant temperatures of 65, 70, 75, 80, 85 and 90 C was characterized using static laser light scattering. As expected, granule swelling was more pronounced at higher temperatures and resulted in a shift of granule size distribution to larger sizes with a corresponding increase in the average size by 100 to 120% from 13 mum to 25-28 mum. Most of the swelling occurred within the first 10 min of heating. Pasting behavior of waxy maize at different temperatures was also characterized from the measurements of G' and G" for different heating times. G' was found to increase with temperature at holding time of 2 min followed by its decrease at larger holding times. This behavior is believed to be due to the predominant effect of swelling at small times. However, G" was insensitive to temperature and holding times. The structure of waxy maize starch was characterized by cryoscanning electron microscopy. Experimental data of average granule size vs time at different temperatures were compared with model predictions. Also the Experimental data of particle size distribution vs particle size at different times and temperatures were compared with model predictions.

On the v-representability of ensemble densities of electron systems

NASA Astrophysics Data System (ADS)

Gonis, A.; Däne, M.

2018-05-01

Analogously to the case at zero temperature, where the density of the ground state of an interacting many-particle system determines uniquely (within an arbitrary additive constant) the external potential acting on the system, the thermal average of the density over an ensemble defined by the Boltzmann distribution at the minimum of the thermodynamic potential, or the free energy, determines the external potential uniquely (and not just modulo a constant) acting on a system described by this thermodynamic potential or free energy. The paper describes a formal procedure that generates the domain of a constrained search over general ensembles (at zero or elevated temperatures) that lead to a given density, including as a special case a density thermally averaged at a given temperature, and in the case of a v-representable density determines the external potential leading to the ensemble density. As an immediate consequence of the general formalism, the concept of v-representability is extended beyond the hitherto discussed case of ground state densities to encompass excited states as well. Specific application to thermally averaged densities solves the v-representability problem in connection with the Mermin functional in a manner analogous to that in which this problem was recently settled with respect to the Hohenberg and Kohn functional. The main formalism is illustrated with numerical results for ensembles of one-dimensional, non-interacting systems of particles under a harmonic potential.

On the v-representability of ensemble densities of electron systems

DOE PAGES

Gonis, A.; Dane, M.

2017-12-30

Analogously to the case at zero temperature, where the density of the ground state of an interacting many-particle system determines uniquely (within an arbitrary additive constant) the external potential acting on the system, the thermal average of the density over an ensemble defined by the Boltzmann distribution at the minimum of the thermodynamic potential, or the free energy, determines the external potential uniquely (and not just modulo a constant) acting on a system described by this thermodynamic potential or free energy. The study describes a formal procedure that generates the domain of a constrained search over general ensembles (at zeromore » or elevated temperatures) that lead to a given density, including as a special case a density thermally averaged at a given temperature, and in the case of a v-representable density determines the external potential leading to the ensemble density. As an immediate consequence of the general formalism, the concept of v-representability is extended beyond the hitherto discussed case of ground state densities to encompass excited states as well. Specific application to thermally averaged densities solves the v-representability problem in connection with the Mermin functional in a manner analogous to that in which this problem was recently settled with respect to the Hohenberg and Kohn functional. Finally, the main formalism is illustrated with numerical results for ensembles of one-dimensional, non-interacting systems of particles under a harmonic potential.« less

The effective temperature for the thermal fluctuations in hot Brownian motion

NASA Astrophysics Data System (ADS)

Srivastava, Mayank; Chakraborty, Dipanjan

2018-05-01

We revisit the effective parameter description of hot Brownian motion—a scenario where a colloidal particle is kept at an elevated temperature than the ambient fluid. Due to the time scale separation between heat diffusion and particle motion, a stationary halo of hot fluid is carried along with the particle resulting in a spatially varying comoving temperature and viscosity profile. The resultant Brownian motion in the overdamped limit can be well described by a Langevin equation with effective parameters such as effective temperature THBM and friction coefficient ζHBM that quantifies the thermal fluctuations and the diffusivity of the particle. These parameters can exactly be calculated using the framework of fluctuating hydrodynamics and require the knowledge of the complete flow field and the temperature field around the particle. Additionally, it was also observed that configurational and kinetic degrees of freedom admit to different effective temperatures, THB M x and THB M v, respectively, with the former predicted accurately from fluctuating hydrodynamics. A more rigorous calculation by Falasco et al. [Phys. Rev. E 90, 032131-10 (2014)] extends the overdamped description to a generalized Langevin equation where the effective temperature becomes frequency dependent and consequently, for any temperature measurement from a Brownian trajectory requires the knowledge of this frequency dependence. We use this framework to expand on the earlier work and look at the first order correction to the limiting values in the hydrodynamic limit and the kinetic limit. We use the linearized Stokes equation and a constant viscosity approximation to calculate the dissipation function in the fluid. The effective temperature is calculated from the weighted average of the temperature field with the dissipation function. Further, we provide a closed form analytical result for effective temperature in the small as well as high frequency limit. Since hot Brownian motion can be used to probe the local environment in complex systems, we have also calculated the effective diffusivity of the particle in the small frequency limit. To look into the kinetic temperature, the velocity autocorrelation function is computed from the generalized Langevin equation and the Wiener-Khinchine theorem and numerically integrated to evaluate THB M v as a function of the ratio of particle density and fluid density ρP/ρ0. The two limiting cases of ρP/ρ0 → 0 and ρP/ρ0 → ∞ is also discussed.

Alloying-Element Loss during High-Temperature Processing of a Nickel-Base Superalloy (Preprint)

DTIC Science & Technology

2013-01-01

precipitates, and the fine white/gray particles are carbides and borides . ............................................. 23 Figure 2. Aluminum...comparable size, and submicron carbides and borides . A fifteen-minute heat treatment at the subsolvus temperature used in the present work (i.e...precipitates, and ~0.3 volume pct. of carbides and borides with an average diameter of ~0.3 m (Figure 1) [5, 6]. B. Procedures To establish the

A comprehensive laboratory study on the immersion freezing behavior of illite NX particles: a comparison of 17 ice nucleation measurement techniques

NASA Astrophysics Data System (ADS)

Hiranuma, N.; Augustin-Bauditz, S.; Bingemer, H.; Budke, C.; Curtius, J.; Danielczok, A.; Diehl, K.; Dreischmeier, K.; Ebert, M.; Frank, F.; Hoffmann, N.; Kandler, K.; Kiselev, A.; Koop, T.; Leisner, T.; Möhler, O.; Nillius, B.; Peckhaus, A.; Rose, D.; Weinbruch, S.; Wex, H.; Boose, Y.; DeMott, P. J.; Hader, J. D.; Hill, T. C. J.; Kanji, Z. A.; Kulkarni, G.; Levin, E. J. T.; McCluskey, C. S.; Murakami, M.; Murray, B. J.; Niedermeier, D.; Petters, M. D.; O'Sullivan, D.; Saito, A.; Schill, G. P.; Tajiri, T.; Tolbert, M. A.; Welti, A.; Whale, T. F.; Wright, T. P.; Yamashita, K.

2015-03-01

Immersion freezing is the most relevant heterogeneous ice nucleation mechanism through which ice crystals are formed in mixed-phase clouds. In recent years, an increasing number of laboratory experiments utilizing a variety of instruments have examined immersion freezing activity of atmospherically relevant ice-nucleating particles. However, an intercomparison of these laboratory results is a difficult task because investigators have used different ice nucleation (IN) measurement methods to produce these results. A remaining challenge is to explore the sensitivity and accuracy of these techniques and to understand how the IN results are potentially influenced or biased by experimental parameters associated with these techniques. Within the framework of INUIT (Ice Nuclei Research Unit), we distributed an illite-rich sample (illite NX) as a representative surrogate for atmospheric mineral dust particles to investigators to perform immersion freezing experiments using different IN measurement methods and to obtain IN data as a function of particle concentration, temperature (T), cooling rate and nucleation time. A total of 17 measurement methods were involved in the data intercomparison. Experiments with seven instruments started with the test sample pre-suspended in water before cooling, while 10 other instruments employed water vapor condensation onto dry-dispersed particles followed by immersion freezing. The resulting comprehensive immersion freezing data set was evaluated using the ice nucleation active surface-site density, ns, to develop a representative ns(T) spectrum that spans a wide temperature range (-37 °C < T < -11 °C) and covers 9 orders of magnitude in ns. In general, the 17 immersion freezing measurement techniques deviate, within a range of about 8 °C in terms of temperature, by 3 orders of magnitude with respect to ns. In addition, we show evidence that the immersion freezing efficiency expressed in ns of illite NX particles is relatively independent of droplet size, particle mass in suspension, particle size and cooling rate during freezing. A strong temperature dependence and weak time and size dependence of the immersion freezing efficiency of illite-rich clay mineral particles enabled the ns parameterization solely as a function of temperature. We also characterized the ns(T) spectra and identified a section with a steep slope between -20 and -27 °C, where a large fraction of active sites of our test dust may trigger immersion freezing. This slope was followed by a region with a gentler slope at temperatures below -27 °C. While the agreement between different instruments was reasonable below ~ -27 °C, there seemed to be a different trend in the temperature-dependent ice nucleation activity from the suspension and dry-dispersed particle measurements for this mineral dust, in particular at higher temperatures. For instance, the ice nucleation activity expressed in ns was smaller for the average of the wet suspended samples and higher for the average of the dry-dispersed aerosol samples between about -27 and -18 °C. Only instruments making measurements with wet suspended samples were able to measure ice nucleation above -18 °C. A possible explanation for the deviation between -27 and -18 °C is discussed. Multiple exponential distribution fits in both linear and log space for both specific surface area-based ns(T) and geometric surface area-based ns(T) are provided. These new fits, constrained by using identical reference samples, will help to compare IN measurement methods that are not included in the present study and IN data from future IN instruments.

Diagnostics of Particles emitted from a Laser generated Plasma: Experimental Data and Simulations

NASA Astrophysics Data System (ADS)

Costa, Giuseppe; Torrisi, Lorenzo

2018-01-01

The charge particle emission form laser-generated plasma was studied experimentally and theoretically using the COMSOL simulation code. The particle acceleration was investigated using two lasers at two different regimes. A Nd:YAG laser, with 3 ns pulse duration and 1010 W/cm2 intensity, when focused on solid target produces a non-equilibrium plasma with average temperature of about 30-50 eV. An Iodine laser with 300 ps pulse duration and 1016 W/cm2 intensity produces plasmas with average temperatures of the order of tens keV. In both cases charge separation occurs and ions and electrons are accelerated at energies of the order of 200 eV and 1 MeV per charge state in the two cases, respectively. The simulation program permits to plot the charge particle trajectories from plasma source in vacuum indicating how they can be deflected by magnetic and electrical fields. The simulation code can be employed to realize suitable permanent magnets and solenoids to deflect ions toward a secondary target or detectors, to focalize ions and electrons, to realize electron traps able to provide significant ion acceleration and to realize efficient spectrometers. In particular it was applied to the study two Thomson parabola spectrometers able to detect ions at low and at high laser intensities. The comparisons between measurements and simulation is presented and discussed.

[Preparation of titanium dioxide particles and properties for flue gas desulfurization].

PubMed

Luo, Yonggang; Li, Daji; Huang, Zhen

2003-01-01

Under different sintering temperatures(340 degrees C, 440 degrees C, 540 degrees C, 640 degrees C), four TiO2 particles were prepared. The crystal types of all four samples were found to possess anatase structures by XRD. It was obtained by N2 experimental adsorption at low temperature (77K) that their surface areas and average pore size were between 79 and 124 m2/g, 56.8 and 254.8 A respectively. The pore structure of TiO2 particles was characterized by scanning electron microscope (SEM). The tests of adsorption dynamics for FGD and the performance of SO2 removal were investigated in a fixed-bed system for different samples. The results show that SG540 sample which made at 540 degrees C sintering temperature had the most quality among the four samples. It can adsorb SO2 of 38.9 mg for one gram SG540 sample. Different operating conditions for SG540 such as adsorption temperature, SO2 concentration in flue gas and the superficial velocity of flue gas were investigated. TiO2 particles for FGD had more efficiency than other physical sorbents such as active carbon and zeolite. The mechanism for SO2 removal was demonstrated by infrared (IR) spectroscopy and desorption test results to be mainly physical adsorption.

Electron Microscopic Examination of Irradiated TRISO Coated Particles of Compact 6-3-2 of AGR-1 Experiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Van Rooyen, Isabella Johanna; Demkowicz, Paul Andrew; Riesterer, Jessica Lori

2012-12-01

The electron microscopic examination of selected irradiated TRISO coated particles of the AGR-1 experiment of fuel compact 6-3-2 are presented in this report. Compact 6-3-2 refers to the compact in Capsule 6 at level 3 of Stack 2. The fuel used in capsule 6 compacts, are called the “baseline” fuel as it is fabricated with refined coating process conditions used to fabricate historic German fuel, because of its excellent irradiation performance with UO2 kernels. The AGR-1 fuel is however made of low-enriched uranium oxycarbide (UCO). Kernel diameters are approximately 350 µm with a U-235 enrichment of approximately 19.7%. Compact 6-3-2more » has been irradiated to 11.3% FIMA compact average burn-up with a time average, volume average temperature of 1070.2°C and with a compact average fast fluence of 2.38E21 n/cm« less

Electron Microscopic Examination of Irradiated TRISO Coated Particles of Compact 6-3-2 of AGR-1 Experiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Van Rooyen, Isabella Johanna; Demkowicz, Paul Andrew; Riesterer, Jessica Lori

2012-12-01

The electron microscopic examination of selected irradiated TRISO coated particles of the AGR-1 experiment of fuel compact 6-3-2 are presented in this report. Compact 6-3-2 refers to the compact in Capsule 6 at level 3 of Stack 2. The fuel used in capsule 6 compacts, are called the “baseline” fuel as it is fabricated with refined coating process conditions used to fabricate historic German fuel, because of its excellent irradiation performance with UO 2 kernels. The AGR-1 fuel is however made of low-enriched uranium oxycarbide (UCO). Kernel diameters are approximately 350 µm with a U-235 enrichment of approximately 19.7%. Compactmore » 6-3-2 has been irradiated to 11.3% FIMA compact average burn-up with a time average, volume average temperature of 1070.2°C and with a compact average fast fluence of 2.38E21 n/cm« less

Superparamagnetic iron oxide nanoparticles with variable size and an iron oxidation state as prospective imaging agents.

PubMed

Kucheryavy, Pavel; He, Jibao; John, Vijay T; Maharjan, Pawan; Spinu, Leonard; Goloverda, Galina Z; Kolesnichenko, Vladimir L

2013-01-15

Magnetite nanoparticles in the size range of 3.2-7.5 nm were synthesized in high yields under variable reaction conditions using high-temperature hydrolysis of the precursor iron(II) and iron(III) alkoxides in diethylene glycol solution. The average sizes of the particles were adjusted by changing the reaction temperature and time and by using a sequential growth technique. To obtain γ-iron(III) oxide particles in the same range of sizes, magnetite particles were oxidized with dry oxygen in diethylene glycol at room temperature. The products were characterized by DLS, TEM, X-ray powder diffractometry, TGA, chemical analysis, and magnetic measurements. NMR r(1) and r(2) relaxivity measurements in water and diethylene glycol (for OH and CH(2) protons) have shown a decrease in the r(2)/r(1) ratio with the particle size reduction, which correlates with the results of magnetic measurements on magnetite nanoparticles. Saturation magnetization of the oxidized particles was found to be 20% lower than that for Fe(3)O(4) with the same particle size, but their r(1) relaxivities are similar. Because the oxidation of magnetite is spontaneous under ambient conditions, it was important to learn that the oxidation product has no disadvantages as compared to its precursor and therefore may be a better prospective imaging agent because of its chemical stability.

Waste tyre pyrolysis: modelling of a moving bed reactor.

PubMed

Aylón, E; Fernández-Colino, A; Murillo, R; Grasa, G; Navarro, M V; García, T; Mastral, A M

2010-12-01

This paper describes the development of a new model for waste tyre pyrolysis in a moving bed reactor. This model comprises three different sub-models: a kinetic sub-model that predicts solid conversion in terms of reaction time and temperature, a heat transfer sub-model that calculates the temperature profile inside the particle and the energy flux from the surroundings to the tyre particles and, finally, a hydrodynamic model that predicts the solid flow pattern inside the reactor. These three sub-models have been integrated in order to develop a comprehensive reactor model. Experimental results were obtained in a continuous moving bed reactor and used to validate model predictions, with good approximation achieved between the experimental and simulated results. In addition, a parametric study of the model was carried out, which showed that tyre particle heating is clearly faster than average particle residence time inside the reactor. Therefore, this fast particle heating together with fast reaction kinetics enables total solid conversion to be achieved in this system in accordance with the predictive model. Copyright © 2010 Elsevier Ltd. All rights reserved.

The role of adsorbed water on the friction of a layer of submicron particles

USGS Publications Warehouse

Sammis, Charles G.; Lockner, David A.; Reches, Ze’ev

2011-01-01

Anomalously low values of friction observed in layers of submicron particles deformed in simple shear at high slip velocities are explained as the consequence of a one nanometer thick layer of water adsorbed on the particles. The observed transition from normal friction with an apparent coefficient near μ = 0.6 at low slip speeds to a coefficient near μ = 0.3 at higher slip speeds is attributed to competition between the time required to extrude the water layer from between neighboring particles in a force chain and the average lifetime of the chain. At low slip speeds the time required for extrusion is less than the average lifetime of a chain so the particles make contact and lock. As slip speed increases, the average lifetime of a chain decreases until it is less than the extrusion time and the particles in a force chain never come into direct contact. If the adsorbed water layer enables the otherwise rough particles to rotate, the coefficient of friction will drop to μ = 0.3, appropriate for rotating spheres. At the highest slip speeds particle temperatures rise above 100°C, the water layer vaporizes, the particles contact and lock, and the coefficient of friction rises to μ = 0.6. The observed onset of weakening at slip speeds near 0.001 m/s is consistent with the measured viscosity of a 1 nm thick layer of adsorbed water, with a minimum particle radius of approximately 20 nm, and with reasonable assumptions about the distribution of force chains guided by experimental observation. The reduction of friction and the range of velocities over which it occurs decrease with increasing normal stress, as predicted by the model. Moreover, the analysis predicts that this high-speed weakening mechanism should operate only for particles with radii smaller than approximately 1 μm. For larger particles the slip speed required for weakening is so large that frictional heating will evaporate the adsorbed water and weakening will not occur.

The absence of an Atlantic imprint on the multidecadal variability of wintertime European temperature.

PubMed

Yamamoto, Ayako; Palter, Jaime B

2016-03-15

Northern Hemisphere climate responds sensitively to multidecadal variability in North Atlantic sea surface temperature (SST). It is therefore surprising that an imprint of such variability is conspicuously absent in wintertime western European temperature, despite that Europe's climate is strongly influenced by its neighbouring ocean, where multidecadal variability in basin-average SST persists in all seasons. Here we trace the cause of this missing imprint to a dynamic anomaly of the atmospheric circulation that masks its thermodynamic response to SST anomalies. Specifically, differences in the pathways Lagrangian particles take to Europe during anomalous SST winters suppress the expected fluctuations in air-sea heat exchange accumulated along those trajectories. Because decadal variability in North Atlantic-average SST may be driven partly by the Atlantic Meridional Overturning Circulation (AMOC), the atmosphere's dynamical adjustment to this mode of variability may have important implications for the European wintertime temperature response to a projected twenty-first century AMOC decline.

Sintering behavior of ultrafine silicon carbide powders obtained by vapor phase reaction

NASA Technical Reports Server (NTRS)

Okabe, Y.; Miyachi, K.; Hojo, J.; Kato, A.

1984-01-01

The sintering behavior of ultrafine SiC powder with average particle size of about 0.01-0.06 microns produced by a vapor phase reaction of the Me4Si-H2 system was studied at the temperature range of 1400-2050 deg. It was found that the homogeneous dispersion of C on SiC particles is important to remove the surface oxide layer effectively. B and C and inhibitive effect on SiC grain growth.

Preparation of poly(BMA-co-MMA) particles by soap-free emulsion polymerization and its optical properties as photonic crystals.

PubMed

Lee, Ki-Chang; Choo, Hun-Seung

2014-11-01

Narrowly dispersed poly(BMA-co-MMA) and PBMA latices with particle diameters ranging within 216-435 nm were synthesized successfully by surfactant-free emulsion polymerization with KPS and AIBA. The average particle diameter and particle size distribution, average molecular weight and its distribution, glass transition temperature, reflectance spectra in visible wavelength, and refractive indices for the respective poly(BMA-co-MMA) latices and their photonic crystals were systematically investigated in terms of BMA/MMA ratio, BMA content, polymerization temperature, and DVB effect. The rate of polymerization increased with increasing MMA concentration in BMA/MMA ratio. The particle diameter increased with BMA concentration in BMA/MMA ratio. The molecular weight increased with BMA concentration in BMA/MMA ratio and monomer concentration. The drying of the latices offered self-assembled shiny colloidal crystal films showing the characteristic structural colors in visible wavelength. All the poly(BMA-co-MMA) latices prepared in the study were fallen within the range of photonic grade microspheres. The reflectance measurement on the colloidal photonic crystals having different particle diameters clearly exhibited narrow stopbands. The reflection maxima (λ(max)) measured in this study were well close to the λ(max) calculated, derived from the Bragg's equation. The refractive indices of poly(BMA-co-MMA) photonic crystals were found to be almost same as the theoretical values and increased proportionally from 1.50 to 1.57 with BMA content in BMA/MMA ratios. It was, thus, found that the optical reflectance properties of the poly(BMA-co-MMA) colloidal photonic crystals can be controlled easily by adjusting the reaction conditions and BMA/MMA ratio in soap-free emulsion copolymerization of BMA and MMA.

Low-Temperature Synthesis of Superconducting Nanocrystalline MgB 2

DOE PAGES

Lu, Jun; Xiao, Zhili; Lin, Qiyin; ...

2010-01-01

Magnesium diboride (MgB 2 ) is considered a promising material for practical application in superconducting devices, with a transition temperature near 40 K. In the present paper, nanocrystalline MgB 2 with an average particle size of approximately 70 nm is synthesized by reacting LiBH 4 with MgH 2 at temperatures as low as 450 ° C. This synthesis approach successfully bypasses the usage of either elemental boron or toxic diborane gas. The superconductivity of the nanostructures is confirmed by magnetization measurements, showing a superconducting critical temperature of 38.7 K.

Infinite charge mobility in muscovite at 300 K

NASA Astrophysics Data System (ADS)

Russell, F. Michael; Archilla, Juan F. R.; Frutos, Fabian; Medina-Carrasco, Santiago

2017-11-01

Evidence is presented for infinite charge mobility in natural crystals of muscovite mica at room temperature. Muscovite has a basic layered structure containing a flat monatomic sheet of potassium sandwiched between mirror silicate layers. It is an excellent electrical insulator. Studies of defects in muscovite crystals indicated that positive charge could propagate over great distances along atomic chains in the potassium sheets in the absence of an applied electric potential. The charge moved in association with anharmonic lattice excitations that moved at about sonic speed and created by nuclear recoil of the radioactive isotope 40K. This was verified by measuring currents passing through crystals when irradiated with energetic alpha particles at room temperature. The charge propagated more than 1000 times the range of the alpha particles of average energy and 250 times the range of channelling particles of maximum energy. The range is limited only by size of the crystal.

Heat, temperature and Clausius inequality in a model for active Brownian particles

PubMed Central

Marconi, Umberto Marini Bettolo; Puglisi, Andrea; Maggi, Claudio

2017-01-01

Methods of stochastic thermodynamics and hydrodynamics are applied to a recently introduced model of active particles. The model consists of an overdamped particle subject to Gaussian coloured noise. Inspired by stochastic thermodynamics, we derive from the system’s Fokker-Planck equation the average exchanges of heat and work with the active bath and the associated entropy production. We show that a Clausius inequality holds, with the local (non-uniform) temperature of the active bath replacing the uniform temperature usually encountered in equilibrium systems. Furthermore, by restricting the dynamical space to the first velocity moments of the local distribution function we derive a hydrodynamic description where local pressure, kinetic temperature and internal heat fluxes appear and are consistent with the previous thermodynamic analysis. The procedure also shows under which conditions one obtains the unified coloured noise approximation (UCNA): such an approximation neglects the fast relaxation to the active bath and therefore yields detailed balance and zero entropy production. In the last part, by using multiple time-scale analysis, we provide a constructive method (alternative to UCNA) to determine the solution of the Kramers equation and go beyond the detailed balance condition determining negative entropy production. PMID:28429787

Heat, temperature and Clausius inequality in a model for active Brownian particles.

PubMed

Marconi, Umberto Marini Bettolo; Puglisi, Andrea; Maggi, Claudio

2017-04-21

Methods of stochastic thermodynamics and hydrodynamics are applied to a recently introduced model of active particles. The model consists of an overdamped particle subject to Gaussian coloured noise. Inspired by stochastic thermodynamics, we derive from the system's Fokker-Planck equation the average exchanges of heat and work with the active bath and the associated entropy production. We show that a Clausius inequality holds, with the local (non-uniform) temperature of the active bath replacing the uniform temperature usually encountered in equilibrium systems. Furthermore, by restricting the dynamical space to the first velocity moments of the local distribution function we derive a hydrodynamic description where local pressure, kinetic temperature and internal heat fluxes appear and are consistent with the previous thermodynamic analysis. The procedure also shows under which conditions one obtains the unified coloured noise approximation (UCNA): such an approximation neglects the fast relaxation to the active bath and therefore yields detailed balance and zero entropy production. In the last part, by using multiple time-scale analysis, we provide a constructive method (alternative to UCNA) to determine the solution of the Kramers equation and go beyond the detailed balance condition determining negative entropy production.

The preparation of tantalum powder using a MR-EMR combination process

NASA Astrophysics Data System (ADS)

Yoon, Jae Sik; Kim, Byung Il

2007-04-01

In the conventional metallothermic reduction (MR) process used to obtain tantalum powder in batch-type operation, it is difficult to control the morphology and location of the tantalum deposits. In contrast, an electronically mediated reaction (EMR) process is capable of overcoming this difficulty. It has the advantage of being a continuous process, but has the disadvantage of a poor reduction yield. A process known as the MR-EMR combination process is able to overcome the shortcomings of the MR and EMR processes. In this study, an MR-EMR combination process is applied to the production of tantalum powder via sodium reduction of K2TaF7. In the MR-EMR combination process, the total charge passed through an external circuit and the average particle size (FSSS) increase as the reduction temperature increases. In addition, the proportion of fine particles (-325 mesh) decreases as the reduction temperature increasess. The tantalum yield improved from 65 to 74% as the reduction temperature increased. Taking into account the charge, impurities, morphology, particle size and yield, a reduction temperature of 1123 K was found to be optimum for the MR-EMR combination process.

A Lagrangian parcel based mixing plane method for calculating water based mixed phase particle flows in turbo-machinery

NASA Astrophysics Data System (ADS)

Bidwell, Colin S.

2015-05-01

A method for calculating particle transport through turbo-machinery using the mixing plane analogy was developed and used to analyze the energy efficient engine . This method allows the prediction of temperature and phase change of water based particles along their path and the impingement efficiency and particle impact property data on various components in the engine. This methodology was incorporated into the LEWICE3D V3.5 software. The method was used to predict particle transport in the low pressure compressor of the . The was developed by NASA and GE in the early 1980s as a technology demonstrator and is representative of a modern high bypass turbofan engine. The flow field was calculated using the NASA Glenn ADPAC turbo-machinery flow solver. Computations were performed for a Mach 0.8 cruise condition at 11,887 m assuming a standard warm day for ice particle sizes of 5, 20 and 100 microns and a free stream particle concentration of . The impingement efficiency results showed that as particle size increased average impingement efficiencies and scoop factors increased for the various components. The particle analysis also showed that the amount of mass entering the inner core decreased with increased particle size because the larger particles were less able to negotiate the turn into the inner core due to particle inertia. The particle phase change analysis results showed that the larger particles warmed less as they were transported through the low pressure compressor. Only the smallest 5 micron particles were warmed enough to produce melting with a maximum average melting fraction of 0.18. The results also showed an appreciable amount of particle sublimation and evaporation for the 5 micron particles entering the engine core (22.6 %).

Oil shale combustor model developed by Greek researchers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1986-09-01

Work carried out in the Department of Chemical Engineering at the University of Thessaloniki, Thessaloniki, Greece has resulted in a model for the combustion of retorted oil shale in a fluidized bed combustor. The model is generally applicable to any hot-solids retorting process, whereby raw oil shale is retorted by mixing with a hot solids stream (usually combusted spent shale), and then the residual carbon is burned off the spent shale in a fluidized bed. Based on their modelling work, the following conclusions were drawn by the researchers. (1) For the retorted particle size distribution selected (average particle diameter 1600more » microns) complete carbon conversion is feasible at high pressures (2.7 atmosphere) and over the entire temperature range studied (894 to 978 K). (2) Bubble size was found to have an important effect, especially at conditions where reaction rates are high (high temperature and pressure). (3) Carbonate decomposition increases with combustor temperature and residence time. Complete carbon conversion is feasible at high pressures (2.7 atmosphere) with less than 20 percent carbonate decomposition. (4) At the preferred combustor operating conditions (high pressure, low temperature) the main reaction is dolomite decomposition while calcite decomposition is negligible. (5) Recombination of CO/sub 2/ with MgO occurs at low temperatures, high pressures, and long particle residence times.« less

The impact of ambient particle pollution during extreme-temperature days in Guangzhou City, China.

PubMed

Li, Guoxing; Jiang, Lai; Zhang, Yajuan; Cai, Yue; Pan, Xiaochuan; Zhou, Maigeng

2014-11-01

The aim of this study is to explore whether the effect of PM10 (particulate matter with an aerodynamic diameter of <10 µm) on daily mortality was modified by extreme temperatures in Guangzhou from 2005 to 2009. The present study used time-series analysis to explore the modification effects of temperature on the association between PM10 and the cause-specific mortalities for cardiovascular, respiratory, cardiopulmonary, and nonaccidental mortality. The interactions between PM10 and temperature were statistically significant on respiratory mortality. The effect estimates per 10-µg/m(3) increase in PM10 concentrations at the moving average of lags of 0 and 1 day on high-temperature days were 2.34% (95% confidence interval = 0.55, 4.16) for nonaccidental, 1.35% (-1.69, 4.48) for cardiovascular, 6.09% (2.42, 9.89) for respiratory, and 3.36% (0.92, 5.86) for cardiopulmonary mortalities. The results suggest that it is important to control and reduce the emission of air particles in Guangzhou, particularly on extreme-high-temperature days. © 2014 APJPH.

Influence of hydrothermal synthesis parameters on the properties of hydroxyapatite nanoparticles.

PubMed

Kuśnieruk, Sylwia; Wojnarowicz, Jacek; Chodara, Agnieszka; Chudoba, Tadeusz; Gierlotka, Stanislaw; Lojkowski, Witold

2016-01-01

Hydroxyapatite (HAp) nanoparticles of tunable diameter were obtained by the precipitation method at room temperature and by microwave hydrothermal synthesis (MHS). The following parameters of the obtained nanostructured HAp were determined: pycnometric density, specific surface area, phase purity, lattice parameters, particle size, particle size distribution, water content, and structure. HAp nanoparticle morphology and structure were determined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). X-ray diffraction measurements confirmed crystalline HAp was synthesized, which was pure in terms of phase. It was shown that by changing the synthesis parameters, the diameter of HAp nanoparticles could be controlled. The average diameter of the HAp nanoparticles was determined by Scherrer's equation via the Nanopowder XRD Processor Demo web application, which interprets the results of specific surface area and TEM measurements using the dark-field technique. The obtained nanoparticles with average particle diameter ranging from 8-39 nm were characterized by having homogeneous morphology with a needle shape and a narrow particle size distribution. Strong similarities were found when comparing the properties of some types of nanostructured hydroxyapatite with natural occurring apatite found in animal bones and teeth.

Negative DC corona discharge current characteristics in a flowing two-phase (air + suspended smoke particles) fluid

NASA Astrophysics Data System (ADS)

Berendt, Artur; Domaszka, Magdalena; Mizeraczyk, Jerzy

2017-04-01

The electrical characteristics of a steady-state negative DC corona discharge in a two-phase fluid (air with suspended cigarette smoke particles) flowing along a chamber with a needle-to-plate electrode arrangement were experimentally investigated. The two-phase flow was transverse in respect to the needle-to-plate axis. The velocity of the transverse two-phase flow was limited to 0.8 m/s, typical of the electrostatic precipitators. We found that three discharge current modes of the negative corona exist in the two-phase (air + smoke particles) fluid: the Trichel pulses mode, the "Trichel pulses superimposed on DC component" mode and the DC component mode, similarly as in the corona discharge in air (a single-phase fluid). The shape of Trichel pulses in the air + suspended particles fluid is similar to that in air. However, the Trichel pulse amplitudes are higher than those in "pure" air while their repetition frequency is lower. As a net consequence of that the averaged corona discharge current in the two-phase fluid is lower than in "pure" air. It was also found that the average discharge current decreases with increasing suspended particle concentration. The calculations showed that the dependence of the average negative corona current (which is a macroscopic corona discharge parameter) on the particle concentration can be explained by the particle-concentration dependencies of the electric charge of Trichel pulse and the repetition frequency of Trichel pulses, both giving a microscopic insight into the electrical phenomena in the negative corona discharge. Our investigations showed also that the average corona discharge current in the two-phase fluid is almost unaffected by the transverse fluid flow up to a velocity of 0.8 m/s. Contribution to the topical issue "The 15th International Symposium on High Pressure Low Temperature Plasma Chemistry (HAKONE XV)", edited by Nicolas Gherardi and Tomáš Hoder

Synthesis and characterization of nanostructured titanium carbide for fuel cell applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, Paviter; Singh, Harwinder; Singh, Bikramjeet

2016-04-13

Titanium carbide (TiC) nanoparticles have been successfully synthesized by carbo-thermic reaction of titanium and acetone at 800 °C. This method is relatively low temperature synthesis route. It can be used for large scale production of TiC. The synthesized nanoparticles have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and differential thermal analyzer (DTA) techniques. XRD analysis confirmed the formation of single phase TiC. XRD analysis confirmed that the particles are spherical in shape with an average particle size of 13 nm. DTA analysis shows that the phase is stable upto 900 °C and the material can be used formore » high temperature applications.« less

Enhancement of crystallinity and magnetization in Fe3O4 nanoferrites induced by a high synthesized magnetic field

NASA Astrophysics Data System (ADS)

Ma, Xinxiu; Zhang, Zhanxian; Chen, Shijie; Lei, Wei; Xu, Yan; Lin, Jia; Luo, Xiaojing; Liu, Yongsheng

2018-05-01

A one-step hydrothermal method in different dc magnetic fields was used to prepare the Fe3O4 nanoparticles. Under the magnetic field, the average particle size decreased from 72.9 to 41.6 nm, meanwhile, the particle crystallinity is greatly improved. The magnetic field enhances its saturation magnetization and coercivity. The high magnetic field induce another magnetic structure. At room temperature, these nanoparticles exhibit superparamagnetism whose critical size (D sp) is about 26 nm. The Verwey transition is observed in the vicinity of 120 K of Fe3O4 nanoparticles. The effective magnetic anisotropy decreases with the increase of the test temperature because of the H c decreased.

Spatial Temperature Mapping within Polymer Nanocomposites Undergoing Ultrafast Photothermal Heating via Gold Nanorods

PubMed Central

Maity, Somsubhra; Wu, Wei-Chen; Xu, Chao; Tracy, Joseph B.; Gundogdu, Kenan; Bochinski, Jason R.; Clarke, Laura I.

2015-01-01

Heat emanates from gold nanorods (GNRs) under ultrafast optical excitation of the localized surface plasmon resonance. The steady state nanoscale temperature distribution formed within a polymer matrix embedded with GNRs undergoing pulsed femtosecond photothermal heating is determined experimentally using two independent ensemble optical techniques. Physical rotation of the nanorods reveals the average local temperature of the polymer melt in the immediate spatial volume surrounding them while fluorescence of homogeneously-distributed perylene molecules monitors temperature over sample regions at larger distances from the GNRs. Polarization-sensitive fluorescence measurements of the perylene probes provide an estimate of the average size of the quasi-molten region surrounding each nanorod (that is, the boundary between softened polymer and solid material as the temperature decreases radially away from each particle) and distinguishes the steady state temperature in the solid and melt regions. Combining these separate methods enables nanoscale spatial mapping of the average steady state temperature distribution caused by ultrafast excitation of the GNRs. These observations definitively demonstrate the presence of a steady-state temperature gradient and indicate that localized heating via the photothermal effect within materials enables nanoscale thermal manipulations without significantly altering the bulk sample temperature in these systems. These quantitative results are further verified by reorienting nanorods within a solid polymer nanofiber without inducing any morphological changes to the highly temperature-sensitive nanofiber surface. Temperature differences of 70 – 90 °C were observed over a distances of ~100 nm. PMID:25379775

On the use of the double floating probe method to infer the difference between the electron and the heavy particles temperatures in an atmospheric pressure, vortex-stabilized nitrogen plasma jet

NASA Astrophysics Data System (ADS)

Prevosto, L.; Kelly, H.; Mancinelli, B. R.

2014-05-01

Sweeping double probe measurements in an atmospheric pressure direct current vortex-stabilized plasma jet are reported (plasma conditions: 100 A discharge current, N2 gas flow rate of 25 Nl/min, thoriated tungsten rod-type cathode, copper anode with 5 mm inner diameter). The interpretation of the double probe characteristic was based on a generalization of the standard double floating probe formulae for non-uniform plasmas coupled to a non-equilibrium plasma composition model. Perturbations caused by the current to the probe together with collisional and thermal processes inside the probe perturbed region were taken into account. Radial values of the average electron and heavy particle temperatures as well as the electron density were obtained. The calculation of the temperature values did not require any specific assumption about a temperature relationship between different particle species. An electron temperature of 10 900 ± 900 K, a heavy particle temperature of 9300 ± 900 K, and an electron density of about 3.5 × 1022 m-3 were found at the jet centre at 3.5 mm downstream from the torch exit. Large deviations from kinetic equilibrium were found toward the outer border of the plasma jet. These results showed good agreement with those previously reported by the authors by using a single probe technique. The calculations have shown that this method is particularly useful for studying spraying-type plasma torches operated at power levels of about 15 kW.

On the use of the double floating probe method to infer the difference between the electron and the heavy particles temperatures in an atmospheric pressure, vortex-stabilized nitrogen plasma jet.

PubMed

Prevosto, L; Kelly, H; Mancinelli, B R

2014-05-01

Sweeping double probe measurements in an atmospheric pressure direct current vortex-stabilized plasma jet are reported (plasma conditions: 100 A discharge current, N2 gas flow rate of 25 Nl/min, thoriated tungsten rod-type cathode, copper anode with 5 mm inner diameter). The interpretation of the double probe characteristic was based on a generalization of the standard double floating probe formulae for non-uniform plasmas coupled to a non-equilibrium plasma composition model. Perturbations caused by the current to the probe together with collisional and thermal processes inside the probe perturbed region were taken into account. Radial values of the average electron and heavy particle temperatures as well as the electron density were obtained. The calculation of the temperature values did not require any specific assumption about a temperature relationship between different particle species. An electron temperature of 10,900 ± 900 K, a heavy particle temperature of 9300 ± 900 K, and an electron density of about 3.5 × 10(22) m(-3) were found at the jet centre at 3.5 mm downstream from the torch exit. Large deviations from kinetic equilibrium were found toward the outer border of the plasma jet. These results showed good agreement with those previously reported by the authors by using a single probe technique. The calculations have shown that this method is particularly useful for studying spraying-type plasma torches operated at power levels of about 15 kW.

High-Temperature Stability and Grain Boundary Complexion Formation in a Nanocrystalline Cu-Zr Alloy

NASA Astrophysics Data System (ADS)

Khalajhedayati, Amirhossein; Rupert, Timothy J.

2015-12-01

Nanocrystalline Cu-3 at.% Zr powders with ~20 nm average grain size were created with mechanical alloying and their thermal stability was studied from 550-950°C. Annealing drove Zr segregation to the grain boundaries, which led to the formation of amorphous intergranular complexions at higher temperatures. Grain growth was retarded significantly, with 1 week of annealing at 950°C, or 98% of the solidus temperature, only leading to coarsening of the average grain size to 54 nm. The enhanced thermal stability can be connected to both a reduction in grain boundary energy with doping as well as the precipitation of ZrC particles. High mechanical strength is retained even after these aggressive heat treatments, showing that complexion engineering may be a viable path toward the fabrication of bulk nanostructured materials with excellent properties.

INITIAL ANALYSIS OF TRANSIENT POWER TIME LAG DUE TO HETEROGENEITY WITHIN THE TREAT FUEL MATRIX.

DOE Office of Scientific and Technical Information (OSTI.GOV)

D.M. Wachs; A.X. Zabriskie, W.R. Marcum

2014-06-01

The topic Nuclear Safety encompasses a broad spectrum of focal areas within the nuclear industry; one specific aspect centers on the performance and integrity of nuclear fuel during a reactivity insertion accident (RIA). This specific accident has proven to be fundamentally difficult to theoretically characterize due to the numerous empirically driven characteristics that quantify the fuel and reactor performance. The Transient Reactor Test (TREAT) facility was designed and operated to better understand fuel behavior under extreme (i.e. accident) conditions; it was shutdown in 1994. Recently, efforts have been underway to commission the TREAT facility to continue testing of advanced accidentmore » tolerant fuels (i.e. recently developed fuel concepts). To aid in the restart effort, new simulation tools are being used to investigate the behavior of nuclear fuels during facility’s transient events. This study focuses specifically on the characterizing modeled effects of fuel particles within the fuel matrix of the TREAT. The objective of this study was to (1) identify the impact of modeled heterogeneity within the fuel matrix during a transient event, and (2) demonstrate acceptable modeling processes for the purpose of TREAT safety analyses, specific to fuel matrix and particle size. Hypothetically, a fuel that is dominantly heterogeneous will demonstrate a clearly different temporal heating response to that of a modeled homogeneous fuel. This time difference is a result of the uniqueness of the thermal diffusivity within the fuel particle and fuel matrix. Using MOOSE/BISON to simulate the temperature time-lag effect of fuel particle diameter during a transient event, a comparison of the average graphite moderator temperature surrounding a spherical particle of fuel was made for both types of fuel simulations. This comparison showed that at a given time and with a specific fuel particle diameter, the fuel particle (heterogeneous) simulation and the homogeneous simulation were related by a multiplier relative to the average moderator temperature. As time increases the multiplier is comparable to the factor found in a previous analytical study from literature. The implementation of this multiplier and the method of analysis may be employed to remove assumptions and increase fidelity for future research on the effect of fuel particles during transient events.« less

Brownian dynamics of self-regulated particles with additional degrees of freedom: Symmetry breaking and homochirality

NASA Astrophysics Data System (ADS)

Bhattacharyya, Debankur; Paul, Shibashis; Ghosh, Shyamolina; Ray, Deb Shankar

2018-04-01

We consider the Brownian motion of a collection of particles each with an additional degree of freedom. The degree of freedom of a particle (or, in general, a molecule) can assume distinct values corresponding to certain states or conformations. The time evolution of the additional degree of freedom of a particle is guided by those of its neighbors as well as the temperature of the system. We show that the local averaging over these degrees of freedom results in emergence of a collective order in the dynamics in the form of selection or dominance of one of the isomers leading to a symmetry-broken state. Our statistical model captures the basic features of homochirality, e.g., autocatalysis and chiral inhibition.

Thermophoretic force on nonspherical particles in the free-molecule regime

NASA Astrophysics Data System (ADS)

Yu, Song; Wang, Jun; Xia, Guodong; Zong, Luxiang

2018-05-01

The present paper is devoted to studying the thermophoresis of a nonspherical convex particle suspended in a gas with nonuniform temperature distribution in the free-molecule regime. Based on the gas kinetic theory and the assumption of a rigid-body collision for the gas-particle interaction, analytical expressions for the thermophoretic forces are obtained for several typical nonspherical bodies, including cylinders, spheroids, needles, disks, and cuboids. The orientation dependences of the thermophoretic forces and thermophoretic velocities are evaluated based on these expressions. It is found that the influence of the pitching effect of the nonspheres can be significant. The expressions for the orientation-averaged thermophoretic forces are also obtained under the assumption of a uniform particle orientation distribution.

Spatial glass transition temperature variations in polymer glass: application to a maltodextrin-water system.

PubMed

van Sleeuwen, Rutger M T; Zhang, Suying; Normand, Valéry

2012-03-12

A model was developed to predict spatial glass transition temperature (T(g)) distributions in glassy maltodextrin particles during transient moisture sorption. The simulation employed a numerical mass transfer model with a concentration dependent apparent diffusion coefficient (D(app)) measured using Dynamic Vapor Sorption. The mass average moisture content increase and the associated decrease in T(g) were successfully modeled over time. Large spatial T(g) variations were predicted in the particle, resulting in a temporary broadening of the T(g) region. Temperature modulated differential scanning calorimetry confirmed that the variation in T(g) in nonequilibrated samples was larger than in equilibrated samples. This experimental broadening was characterized by an almost doubling of the T(g) breadth compared to the start of the experiment. Upon reaching equilibrium, both the experimental and predicted T(g) breadth contracted back to their initial value.

Temperature and humidity profiles in the atmosphere from spaceborne lasers: A feasibility study

NASA Technical Reports Server (NTRS)

Grassl, H.; Schluessel, P.

1984-01-01

Computer simulations of the differential absorption lidar technique in a space craft for the purpose of temperature and humidity profiling indicate: (1) Current technology applied to O2 and H2O lines in the .7 to .8 micrometers wavelength band gives sufficiently high signal-to-noise ratios (up to 50 for a single pulse pair) if backscattering by aerosol particles is high, i.e. profiling accurate to 2 K for temperature and 10% for humidity should be feasible within the turbid lower troposphere in 1 km layers and with an averaging over approximately 100 pulses. (2) The impact of short term fluctuations in aerosol particle concentration is too big for a one laser system. Only a two laser system firing at a time lag of about 1 millisecond can surmount these difficulties. (3) The finite width of the laser line and the quasi-random shift of this line introduce tolerable, partly systematic errors.

An alternative NMR method to determine nuclear shielding anisotropies for molecules in liquid-crystalline solutions with (13)C shielding anisotropy of methyl iodide as an example.

PubMed

Tallavaara, Pekka; Jokisaari, Jukka

2008-03-28

An alternative NMR method for determining nuclear shielding anisotropies in molecules is proposed. The method is quite simple, linear and particularly applicable for heteronuclear spin systems. In the technique, molecules of interest are dissolved in a thermotropic liquid crystal (LC) which is confined in a mesoporous material, such as controlled pore glass (CPG) used in this study. CPG materials consist of roughly spherical particles with a randomly oriented and connected pore network inside. LC Merck Phase 4 was confined in the pores of average diameter from 81 to 375 A and LC Merck ZLI 1115 in the pores of average diameter 81 A. In order to demonstrate the functionality of the method, the (13)C shielding anisotropy of (13)C-enriched methyl iodide, (13)CH(3)I, was determined as a function of temperature using one dimensional (13)C NMR spectroscopy. Methane gas, (13)CH(4), was used as an internal chemical shift reference. It appeared that methyl iodide molecules experience on average an isotropic environment in LCs inside the smallest pores within the whole temperature range studied, ranging from bulk solid to isotropic phase. In contrast, in the spaces in between the particles, whose diameter is approximately 150 microm, LCs behave as in the bulk. Consequently, isotropic values of the shielding tensor can be determined from spectra arising from molecules inside the pores at exactly the same temperature as the anisotropic ones from molecules outside the pores. Thus, for the first time in the solution state, shielding anisotropies can easily be determined as a function of temperature. The effects of pore size as well as of different LC media on the shielding anisotropy are examined and discussed.

Anomalous magnetic behavior of Sm0.8Ca0.2MnO3 nanoparticles.

PubMed

Mogilyansky, D; Fita, I; Wisniewski, A; Markovich, V; Puzniak, R; Gorodetsky, G

2012-11-01

Magnetic properties of compacted Sm0.8Ca0.2MnO3 (SCMO) particles with average particle size of 23-100 nm, prepared by the glycine-nitrate method, have been investigated. It was found that the relative volume of the ferromagnetic phase decreases with decreasing particle size. Curves of field cooled and zero filed cooled magnetization (M(ZFC)) exhibit a bifurcation just below the Curie temperature (T(c) approximately 55-64 K) for all particles studied. The field dependence of M(ZFC) peak follows de Almeida-Thouless line. Both features are characteristic of spin-glasses (SG). Measurements of ac-susceptibility in the temperature range 5-300 K and the frequency range f = 10 Hz-10 kHz show a sharp peak for both real and imaginary components in the vicinity of T(c), apparently attributed to the Hopkinson effect. A second small peak is seemingly associated with antiferromagnetic or ferrimagnetic ordering. Though, for smaller particles both peaks depend on frequency, no shift to higher temperatures with increasing f, characteristic for SG systems, was observed. The dissimilarity in magnetic properties and dynamic characteristics observed for SCMO and for La0.8Ca0.2MnO3 nanoparticles is discussed, taking into account a difference in the width of the band and the strength of double exchange and interparticle interactions.

Parametric study of ion heating in a burnout device (HIP-1)

NASA Technical Reports Server (NTRS)

Sigman, D. R.; Reinmann, J. J.; Lauver, M. R.

1974-01-01

Results of further studies on the Lewis Research Center hot-ion plasma source (HIP-1) are reported. Changes have been made in both the electrode geometry and materials to produce higher ion temperatures. Ion temperature increased significantly with increased vacuum pumping speed. The best ion temperatures achieved, so far, for H(+), D(+), and He(+) plasmas are estimated to be equal to, or greater than 0.6, equal to, or greater than 0.9, and equal to, greater than 2.0 keV, respectively. Electrode pairs produced high ion temperatures whether on the magnetic axis or off it by 5.5 cm. Multiple sources, one on-axis and one off-axis, were run simultaneously from a single power supply by using independent gas feed rates. A momentum analyzer has been added to the charge-exchange neutral particle analyzer to identify particles according to mass, as well as energy. Under any given plasma condition, the higher mass ions have higher average energies but not by as much as the ratio of their respective masses.

Impact of torrefaction on the grindability and fuel characteristics of forest biomass.

PubMed

Phanphanich, Manunya; Mani, Sudhagar

2011-01-01

Thermal pretreatment or torrefaction of biomass under anoxic condition can produce an energy dense and consistent quality solid biomass fuel for combustion and co-firing applications. This paper investigates the fuel characteristics and grindability of pine chips and logging residues torrefied at temperatures ranging from 225 °C to 300 °C and 30 min residence time. Grinding performance of torrefied biomass evaluated by determining energy required for grinding, particle size distribution and average particle size were compared with raw biomass and coal. Specific energy required for grinding of torrefied biomass decreased significantly with increase in torrefaction temperatures. The grinding energy of torrefied biomass was reduced to as low as 24 kW h/t at 300 °C torrefaction temperature. The gross calorific value of torrefied chips increased with increase in torrefaction temperature. Torrefaction of biomass clearly showed the improved fuel characteristics and grinding properties closer to coal. Copyright © 2010 Elsevier Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Apaydin, Ramazan Oguzhan; Ebin, Burcak; Gurmen, Sebahattin

Copper-Nickel (CuNi) nanostructured alloy particles were produced by Ultrasonic Spray Pyrolysis and Hydrogen Reduction Method (USP-HR) from high purity copper and nickel nitrate aqueous solutions. The effect of the precursor solution in the range of 0.1 and 0.5 mol/L on the morphology and crystallite size of CuNi nanoparticles were investigated under 2 h running time, 700 °C operating temperature and 0.5 L/min H{sub 2} flow rate. Particle size, morphology, composition and crystallite structure were characterized by Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and X-Ray Diffraction (XRD). Particle characterization studies show that nanostructured alloy particles have cubic crystal structuremore » and they are in submicron size range with spherical morphology. The crystallite sizes of the particles calculated with Scherrer formula are 40 and 34 nm and average particles sizes observed from the SEM images are 300 and 510 nm for each experiment respectively.« less

Irradiation performance of AGR-1 high temperature reactor fuel

DOE PAGES

Demkowicz, Paul A.; Hunn, John D.; Ploger, Scott A.; ...

2015-10-23

The AGR-1 experiment contained 72 low-enriched uranium oxide/uranium carbide TRISO coated particle fuel compacts in six capsules irradiated to burnups of 11.2 to 19.6% FIMA, with zero TRISO coating failures detected during the irradiation. The irradiation performance of the fuel including the extent of fission product release and the evolution of kernel and coating microstructures was evaluated based on detailed examination of the irradiation capsules, the fuel compacts, and individual particles. Fractional release of 110mAg from the fuel compacts was often significant, with capsule-average values ranging from 0.01 to 0.38. Analysis of silver release from individual compacts indicated that itmore » was primarily dependent on fuel temperature history. Europium and strontium were released in small amounts through intact coatings, but were found to be significantly retained in the outer pyrocarbon and compact matrix. The capsule-average fractional release from the compacts was 1 × 10 –4 to 5 × 10 –4 for 154Eu and 8 × 10 –7 to 3 × 10 –5 for 90Sr. The average 134Cs fractional release from compacts was <3 × 10 –6 when all particles maintained intact SiC. An estimated four particles out of 2.98 × 10 5 in the experiment experienced partial cesium release due to SiC failure during the irradiation, driving 134Cs fractional release in two capsules to approximately 10 –5. Identification and characterization of these particles has provided unprecedented insight into the nature and causes of SiC coating failure in high-quality TRISO fuel. In general, changes in coating morphology were found to be dominated by the behavior of the buffer and inner pyrolytic carbon (IPyC), and infrequently observed SiC layer damage was usually related to cracks in the IPyC. Palladium attack of the SiC layer was relatively minor, except for the particles that released cesium during irradiation, where SiC corrosion was found adjacent to IPyC cracks. In conclusion, palladium, silver, and uranium were found in the SiC layer of irradiated particles, and characterization of these elements within the SiC microstructure is the subject of ongoing focused study.« less

Control of Partial Coalescence of Self-Assembled Metal Nano-Particles across Lyotropic Liquid Crystals Templates towards Long Range Meso-Porous Metal Frameworks Design

PubMed Central

Dumée, Ludovic F.; Lemoine, Jean-Baptiste; Ancel, Alice; Hameed, Nishar; He, Li; Kong, Lingxue

2015-01-01

The formation of purely metallic meso-porous metal thin films by partial interface coalescence of self-assembled metal nano-particles across aqueous solutions of Pluronics triblock lyotropic liquid crystals is demonstrated for the first time. Small angle X-ray scattering was used to study the influence of the thin film composition and processing conditions on the ordered structures. The structural characteristics of the meso-structures formed demonstrated to primarily rely on the lyotropic liquid crystal properties while the nature of the metal nano-particles used as well as the their diameters were found to affect the ordered structure formation. The impact of the annealing temperature on the nano-particle coalescence and efficiency at removing the templating lyotropic liquid crystals was also analysed. It is demonstrated that the lyotropic liquid crystal is rendered slightly less thermally stable, upon mixing with metal nano-particles and that low annealing temperatures are sufficient to form purely metallic frameworks with average pore size distributions smaller than 500 nm and porosity around 45% with potential application in sensing, catalysis, nanoscale heat exchange, and molecular separation. PMID:28347094

Effect of wheat flour characteristics on sponge cake quality.

PubMed

Moiraghi, Malena; de la Hera, Esther; Pérez, Gabriela T; Gómez, Manuel

2013-02-01

To select the flour parameters that relate strongly to cake-making performance, in this study the relationship between sponge cake quality, solvent retention capacity (SRC) profile and flour physicochemical characteristics was investigated using 38 soft wheat samples of different origins. Particle size average, protein, damaged starch, water-soluble pentosans, total pentosans, SRC and pasting properties were analysed. Sponge cake volume and crumb texture were measured to evaluate cake quality. Cluster analysis was applied to assess differences in flour quality parameters among wheat lines based on the SRC profile. Cluster 1 showed significantly higher sponge cake volume and crumb softness, finer particle size and lower SRC sucrose, SRC carbonate, SRC water, damaged starch and protein content. Particle size, damaged starch, protein, thickening capacity and SRC parameters correlated negatively with sponge cake volume, while total pentosans and pasting temperature showed the opposite effect. The negative correlations between cake volume and SRC parameters along with the cluster analysis results indicated that flours with smaller particle size, lower absorption capacity and higher pasting temperature had better cake-making performance. Some simple analyses, such as SRC, particle size distribution and pasting properties, may help to choose flours suitable for cake making. Copyright © 2012 Society of Chemical Industry.

Size-dependent phase diagrams of metallic alloys: A Monte Carlo simulation study on order–disorder transitions in Pt–Rh nanoparticles

PubMed Central

Stahl, Christian; Albe, Karsten

2012-01-01

Summary Nanoparticles of Pt–Rh were studied by means of lattice-based Monte Carlo simulations with respect to the stability of ordered D022- and 40-phases as a function of particle size and composition. By thermodynamic integration in the semi-grand canonical ensemble, phase diagrams for particles with a diameter of 7.8 nm, 4.3 nm and 3.1 nm were obtained. Size-dependent trends such as the lowering of the critical ordering temperature, the broadening of the compositional stability range of the ordered phases, and the narrowing of the two-phase regions were observed and discussed in the context of complete size-dependent nanoparticle phase diagrams. In addition, an ordered surface phase emerges at low temperatures and low platinum concentration. A decrease of platinum surface segregation with increasing global platinum concentration was observed, when a second, ordered phase is formed inside the core of the particle. The order–disorder transitions were analyzed in terms of the Warren–Cowley short-range order parameters. Concentration-averaged short-range order parameters were used to remove the surface segregation bias of the conventional short-range order parameters. Using this procedure, it was shown that the short-range order in the particles at high temperatures is bulk-like. PMID:22428091

Effect of surfactant concentration and solidification temperature on the characteristics and stability of nanostructured lipid carrier (NLC) prepared from rambutan (Nephelium lappaceum L.) kernel fat.

PubMed

Witayaudom, Pimchanok; Klinkesorn, Utai

2017-11-01

Nanostructured lipid carrier (NLC) was fabricated from rambutan (Nephelium lappaceum L.) kernel fat stabilized with Tween 80 in this present work. The influence of the Tween 80 concentration (0.025, 0.05, 0.1, 0.2, 0.5 and 1.0wt%) and solidification temperature (5 and 25°C) on the characteristics and stability of the NLC were investigated. The results showed that an increase in the Tween 80 concentration caused decreased zeta-potential (ζ-potential) and particle size (Z-average) with no significant effect on the polydispersity index (PDI). Lipid particles in the NLC at all Tween 80 concentrations had a tendency to grow and the PDI tended to increase due to Ostwald ripening upon storage over 28days. At least 0.2wt% Tween 80 concentrations could be used to stabilize 1wt% rambutan NLC. The solidification temperature affected the microstructure, melting behavior and stability of rambutan NLC. Pre-solidification at 5°C could create stable NLC with monodispersed-spherical lipid particles. Consequently, these stable NLC particles produced from rambutan kernel fat may serve as useful carriers for the delivery of bioactive lipophilic nutraceuticals. Copyright © 2017 Elsevier Inc. All rights reserved.

Studies on metal hydride electrodes containing no binder additives

NASA Astrophysics Data System (ADS)

Rogulski, Z.; Dłubak, J.; Karwowska, M.; Krebs, M.; Pytlik, E.; Schmalz, M.; Gumkowska, A.; Czerwiński, A.

Electrochemical properties of hydrogen storage alloys (AB 5 type: LaMm-Ni 4.1Al 0.3Mn 0.4Co 0.45) were studied in 6 M KOHaq using Limited Volume Electrode (LVE) method. Working electrodes were prepared by pressing alloy powder (without binding and conducting additives) into a metal net wire serving as a support and as a current collector. Cyclic voltammetry curves reveal well defined hydrogen sorption and desorption peaks which are separated from other faradic processes, such as surface oxidation. Voltammograms of LVE resemble the curves obtained by various authors for single particle metal alloy electrodes. Hydrogen diffusion coefficient calculated at room temperature for LV electrodes and for 100% state of charge reaches a constant value of ca. 3.3 × 10 -9 and 2.1 × 10 -10 cm 2 s -1, for chronoamperometric and chronopotentiometric measurements, respectively. A comparison of the electrodes with average alloy particle sizes of ca. 50 and 4 μm allows us to conclude that at room temperature hydrogen storage capability of AB 5 alloy studied is independent on the alloy particle size. On the other hand, reduction of the particle size increases alloy capacity at temperatures below -10 °C and reduces time of electrochemical activation of the electrode.

Effect of drying environment on grain size of titanium dioxide nano-powder synthesized via sol-gel method

NASA Astrophysics Data System (ADS)

Zandi, Pegah; Hosseini, Elham; Rashchi, Fereshteh

2018-01-01

Titanium dioxide Nano powder has been synthesized from titanium isopropoxide (TTIP) in chloride media by sol-gel method. In this research, the effect of the drying environment, from air to oven drying at 100 °C, calcination time and temperature on nano TiO2 grain size was investigated. The synthesized powder was analyzed by x-ray diffraction and scanning electron microscope. Based on the results, the powder has been crystallized in anatase and rutile phases, due to different calcination temperatures. At temperatures above 600 °C, the Titanium dioxide nano powder has been crystallized as rutile. The crystalline structure of titanium dioxide nano powder changed because of the different calcination temperatures and time applied. The average particle size of the powder dried in air was larger than the powder dried in oven. The minimum particle size of the powder dried in air was 50 nm and in the oven was 9 nm, observed and calculated Williamson-Hall equation. All in all, with overall increasing of calcination time and temperature the grain size increased. Moreover, in the case of temperature, after a certain temperature, the grain size became constant and didn't change significantly.

T-Burner Testing of Metallized Solid Propellants

DTIC Science & Technology

1974-10-01

The heat exchanger reduces the temperature of the combustion products and, therefore, serves to decrease the pressure build up in the overall system by...transducer (4-5). The high temperature gases will not affect the flush mounted Kistler unit for duratiens of several seconds, with only a thin film of sili...Assume that the average speeds of the particles and gases are the same, and that the local value of p p/pg = C at the edge of the combustion zone is

Comparison of primary and secondary particle formation from natural gas engine exhaust and of their volatility characteristics

NASA Astrophysics Data System (ADS)

Alanen, Jenni; Simonen, Pauli; Saarikoski, Sanna; Timonen, Hilkka; Kangasniemi, Oskari; Saukko, Erkka; Hillamo, Risto; Lehtoranta, Kati; Murtonen, Timo; Vesala, Hannu; Keskinen, Jorma; Rönkkö, Topi

2017-07-01

Natural gas usage in the traffic and energy production sectors is a growing trend worldwide; thus, an assessment of its effects on air quality, human health and climate is required. Engine exhaust is a source of primary particulate emissions and secondary aerosol precursors, which both contribute to air quality and can cause adverse health effects. Technologies, such as cleaner engines or fuels, that produce less primary and secondary aerosols could potentially significantly decrease atmospheric particle concentrations and their adverse effects. In this study, we used a potential aerosol mass (PAM) chamber to investigate the secondary aerosol formation potential of natural gas engine exhaust. The PAM chamber was used with a constant UV-light voltage, which resulted in relatively long equivalent atmospheric ages of 11 days at most. The studied retro-fitted natural gas engine exhaust was observed to form secondary aerosol. The mass of the total aged particles, i.e., particle mass measured downstream of the PAM chamber, was 6-268 times as high as the mass of the emitted primary exhaust particles. The secondary organic aerosol (SOA) formation potential was measured to be 9-20 mg kgfuel-1. The total aged particles mainly consisted of organic matter, nitrate, sulfate and ammonium, with the fractions depending on exhaust after-treatment and the engine parameters used. Also, the volatility, composition and concentration of the total aged particles were found to depend on the engine operating mode, catalyst temperature and catalyst type. For example, a high catalyst temperature promoted the formation of sulfate particles, whereas a low catalyst temperature promoted nitrate formation. However, in particular, the concentration of nitrate needed a long time to stabilize - more than half an hour - which complicated the conclusions but also indicates the sensitivity of nitrate measurements on experimental parameters such as emission source and system temperatures. Sulfate was measured to have the highest evaporation temperature, and nitrate had the lowest. The evaporation temperature of ammonium depended on the fractions of nitrate and sulfate in the particles. The average volatility of the total aged particles was measured to be lower than that of primary particles, indicating better stability of the aged natural gas engine-emitted aerosol in the atmosphere. According to the results of this study, the exhaust of a natural gas engine equipped with a catalyst forms secondary aerosol when the atmospheric ages in a PAM chamber are several days long. The secondary aerosol matter has different physical characteristics from those of primary particulate emissions.

Accurate and efficient integration for molecular dynamics simulations at constant temperature and pressure

NASA Astrophysics Data System (ADS)

Lippert, Ross A.; Predescu, Cristian; Ierardi, Douglas J.; Mackenzie, Kenneth M.; Eastwood, Michael P.; Dror, Ron O.; Shaw, David E.

2013-10-01

In molecular dynamics simulations, control over temperature and pressure is typically achieved by augmenting the original system with additional dynamical variables to create a thermostat and a barostat, respectively. These variables generally evolve on timescales much longer than those of particle motion, but typical integrator implementations update the additional variables along with the particle positions and momenta at each time step. We present a framework that replaces the traditional integration procedure with separate barostat, thermostat, and Newtonian particle motion updates, allowing thermostat and barostat updates to be applied infrequently. Such infrequent updates provide a particularly substantial performance advantage for simulations parallelized across many computer processors, because thermostat and barostat updates typically require communication among all processors. Infrequent updates can also improve accuracy by alleviating certain sources of error associated with limited-precision arithmetic. In addition, separating the barostat, thermostat, and particle motion update steps reduces certain truncation errors, bringing the time-average pressure closer to its target value. Finally, this framework, which we have implemented on both general-purpose and special-purpose hardware, reduces software complexity and improves software modularity.

Mechanical Properties and Fracture Behaviors of the As-Extruded Mg-5Al-3Ca Alloys Containing Yttrium at Elevated Temperature.

PubMed

Son, Hyeon-Taek; Kim, Yong-Ho; Kim, Taek-Soo; Lee, Seong-Hee

2016-02-01

Effects of yttrium (Y) addition on mechanical properties and fracture behaviors of the as-extruded Mg-Al-Ca based alloys at elevated temperature were investigated by a tensile test. After hot extrusion, the average grain size was refined by Y addition and eutectic phases were broken down into fine particles. Y addition to Mg-5Al-3Ca based alloy resulted in the improvement of strength and ductility at elevated temperature due to fine grain and suppression of grain growth by formation of thermally stable Al2Y intermetallic compound.

Processes affecting the movement of organochlorine pesticides (OCPs) between soil and air in an industrial site in Turkey.

PubMed

Bozlaker, Ayse; Muezzinoglu, Aysen; Odabasi, Mustafa

2009-11-01

Soil and atmospheric concentrations, dry deposition and soil-air gas exchange of organochlorine pesticides (OCPs) were investigated at an industrial site in Aliaga, Izmir, Turkey. Current-use pesticides, endosulfan and chlorpyrifos, had the highest atmospheric levels in summer and winter. Summertime total (gas+particle) OCP concentrations in air were higher, probably due to increased volatilization at higher temperatures and seasonal local/regional applications of current-use pesticides. Particle deposition fluxes were generally higher in summer than in winter. Overall average dry particle deposition velocity for all the OCPs was 4.9+/-4.1 cm s(-1) (average+/-SD). SigmaDDXs (sum of p,p'-DDT, p,p'-DDD, and p,p'-DDE) were the most abundant OCPs in Aliaga soils (n=48), probably due to their heavy historical use and persistence. Calculated fugacity ratios and average net gas fluxes across the soil-air interface indicated volatilization for alpha-CHL, gamma-CHL, heptachlorepoxide, cis-nonachlor, trans-nonachlor, and p,p'-DDT in summer, and for alpha-CHL, gamma-CHL, trans-nonachlor, endosulfan sulfate, and p,p'-DDT in winter. For the remaining OCPs, soil acted as a sink during both seasons. Comparison of the determined fluxes showed that dry particle, gas-phase, and wet deposition are significant OCP input mechanisms to the soil in the study area.

Particle transport in low-energy ventilation systems. Part 1: theory of steady states.

PubMed

Bolster, D T; Linden, P F

2009-04-01

Many modern low-energy ventilation schemes, such as displacement or natural ventilation, take advantage of temperature stratification in a space, extracting the warmest air from the top of the room. The adoption of these energy-efficient ventilation systems still requires the provision of acceptable indoor air quality. In this work we study the steady state transport of particulate contaminants in a displacement-ventilated space. Representing heat sources as ideal sources of buoyancy, analytical models are developed that allow us to compare the average efficiency of contaminant removal between traditional and modern low-energy systems. We found that on average traditional and low-energy systems are similar in overall pollutant removal efficiency, although quite different vertical distributions of contaminant can exist, thus affecting individual exposure. While the main focus of this work is on particles where the dominant mode of deposition is by gravitational settling, we also discuss additional deposition mechanisms and show that the qualitative observations we make carry over to cases where such mechanisms must be included. We illustrate that while average concentration of particles for traditional mixing systems and low energy displacement systems are similar, local concentrations can vary significantly with displacement systems. Depending on the source of the particles this can be better or worse in terms of occupant exposure and engineers should take due diligence accordingly when designing ventilation systems.

Adsorption of acids and bases from aqueous solutions onto silicon dioxide particles.

PubMed

Zengin, Huseyin; Erkan, Belgin

2009-12-30

The adsorption of acids and bases onto the surface of silicon dioxide (SiO(2)) particles was systematically studied as a function of several variables, including activation conditions, contact time, specific surface area, particle size, concentration and temperature. The physical properties of SiO(2) particles were investigated, where characterizations were carried out by FT-IR spectroscopy, and morphology was examined by scanning electron microscopy (SEM). The SEM of samples showed good dispersion and uniform SiO(2) particles with an average diameter of about 1-1.5 microm. The adsorption results revealed that SiO(2) surfaces possessed effective interactions with acids and bases, and greatest adsorption capacity was achieved with NaOH, where the best fit isotherm model was the Freundlich adsorption model. The adsorption properties of raw SiO(2) particles were further improved by ultrasonication. Langmuir monolayer adsorption capacity of NaOH adsorbate at 25 degrees C on sonicated SiO(2) (182.6 mg/g) was found to be greater than that of the unsonicated SiO(2) (154.3mg/g). The spontaneity of the adsorption process was established by decreases in DeltaG(ads)(0), which varied from -10.5 to -13.6 kJ mol(-1), in the temperature range 283-338K.

Quantization and fractional quantization of currents in periodically driven stochastic systems. I. Average currents

NASA Astrophysics Data System (ADS)

Chernyak, Vladimir Y.; Klein, John R.; Sinitsyn, Nikolai A.

2012-04-01

This article studies Markovian stochastic motion of a particle on a graph with finite number of nodes and periodically time-dependent transition rates that satisfy the detailed balance condition at any time. We show that under general conditions, the currents in the system on average become quantized or fractionally quantized for adiabatic driving at sufficiently low temperature. We develop the quantitative theory of this quantization and interpret it in terms of topological invariants. By implementing the celebrated Kirchhoff theorem we derive a general and explicit formula for the average generated current that plays a role of an efficient tool for treating the current quantization effects.

A comprehensive laboratory study on the immersion freezing behavior of illite NX particles. A comparison of 17 ice nucleation measurement techniques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hiranuma, Naruki; Augustin-Bauditz, Stefanie; Bingemer, Heinz

Immersion freezing is the most relevant heterogeneous ice nucleation mechanism through which ice crystals are formed in mixed-phase clouds. In recent years, an increasing number of laboratory experiments utilizing a variety of instruments have examined immersion freezing activity of atmospherically relevant ice-nucleating particles. However, an intercomparison of these laboratory results is a difficult task because investigators have used different ice nucleation (IN) measurement methods to produce these results. A remaining challenge is to explore the sensitivity and accuracy of these techniques and to understand how the IN results are potentially influenced or biased by experimental parameters associated with these techniques.more » Within the framework of INUIT (Ice Nuclei Research Unit), we distributed an illite-rich sample (illite NX) as a representative surrogate for atmospheric mineral dust particles to investigators to perform immersion freezing experiments using different IN measurement methods and to obtain IN data as a function of particle concentration, temperature ( T), cooling rate and nucleation time. A total of 17 measurement methods were involved in the data intercomparison. Experiments with seven instruments started with the test sample pre-suspended in water before cooling, while 10 other instruments employed water vapor condensation onto dry-dispersed particles followed by immersion freezing. The resulting comprehensive immersion freezing data set was evaluated using the ice nucleation active surface-site density, n s, to develop a representative n s( T) spectrum that spans a wide temperature range (-37 °C < T < -11 °C) and covers 9 orders of magnitude in n s. In general, the 17 immersion freezing measurement techniques deviate, within a range of about 8 °C in terms of temperature, by 3 orders of magnitude with respect to n s. In addition, we show evidence that the immersion freezing efficiency expressed in n s of illite NX particles is relatively independent of droplet size, particle mass in suspension, particle size and cooling rate during freezing. A strong temperature dependence and weak time and size dependence of the immersion freezing efficiency of illite-rich clay mineral particles enabled the n s parameterization solely as a function of temperature. We also characterized the n s( T) spectra and identified a section with a steep slope between -20 and -27 °C, where a large fraction of active sites of our test dust may trigger immersion freezing. This slope was followed by a region with a gentler slope at temperatures below -27 °C. While the agreement between different instruments was reasonable below ~ -27 °C, there seemed to be a different trend in the temperature-dependent ice nucleation activity from the suspension and dry-dispersed particle measurements for this mineral dust, in particular at higher temperatures. For instance, the ice nucleation activity expressed in n s was smaller for the average of the wet suspended samples and higher for the average of the dry-dispersed aerosol samples between about -27 and -18 °C. Only instruments making measurements with wet suspended samples were able to measure ice nucleation above -18 °C. A possible explanation for the deviation between -27 and -18 °C is discussed. Multiple exponential distribution fits in both linear and log space for both specific surface area-based n s( T) and geometric surface area-based n s( T) are provided. These new fits, constrained by using identical reference samples, will help to compare IN measurement methods that are not included in the present study and IN data from future IN instruments.« less

A comprehensive laboratory study on the immersion freezing behavior of illite NX particles. A comparison of 17 ice nucleation measurement techniques

DOE PAGES

Hiranuma, Naruki; Augustin-Bauditz, Stefanie; Bingemer, Heinz; ...

2015-03-06

Immersion freezing is the most relevant heterogeneous ice nucleation mechanism through which ice crystals are formed in mixed-phase clouds. In recent years, an increasing number of laboratory experiments utilizing a variety of instruments have examined immersion freezing activity of atmospherically relevant ice-nucleating particles. However, an intercomparison of these laboratory results is a difficult task because investigators have used different ice nucleation (IN) measurement methods to produce these results. A remaining challenge is to explore the sensitivity and accuracy of these techniques and to understand how the IN results are potentially influenced or biased by experimental parameters associated with these techniques.more » Within the framework of INUIT (Ice Nuclei Research Unit), we distributed an illite-rich sample (illite NX) as a representative surrogate for atmospheric mineral dust particles to investigators to perform immersion freezing experiments using different IN measurement methods and to obtain IN data as a function of particle concentration, temperature ( T), cooling rate and nucleation time. A total of 17 measurement methods were involved in the data intercomparison. Experiments with seven instruments started with the test sample pre-suspended in water before cooling, while 10 other instruments employed water vapor condensation onto dry-dispersed particles followed by immersion freezing. The resulting comprehensive immersion freezing data set was evaluated using the ice nucleation active surface-site density, n s, to develop a representative n s( T) spectrum that spans a wide temperature range (-37 °C < T < -11 °C) and covers 9 orders of magnitude in n s. In general, the 17 immersion freezing measurement techniques deviate, within a range of about 8 °C in terms of temperature, by 3 orders of magnitude with respect to n s. In addition, we show evidence that the immersion freezing efficiency expressed in n s of illite NX particles is relatively independent of droplet size, particle mass in suspension, particle size and cooling rate during freezing. A strong temperature dependence and weak time and size dependence of the immersion freezing efficiency of illite-rich clay mineral particles enabled the n s parameterization solely as a function of temperature. We also characterized the n s( T) spectra and identified a section with a steep slope between -20 and -27 °C, where a large fraction of active sites of our test dust may trigger immersion freezing. This slope was followed by a region with a gentler slope at temperatures below -27 °C. While the agreement between different instruments was reasonable below ~ -27 °C, there seemed to be a different trend in the temperature-dependent ice nucleation activity from the suspension and dry-dispersed particle measurements for this mineral dust, in particular at higher temperatures. For instance, the ice nucleation activity expressed in n s was smaller for the average of the wet suspended samples and higher for the average of the dry-dispersed aerosol samples between about -27 and -18 °C. Only instruments making measurements with wet suspended samples were able to measure ice nucleation above -18 °C. A possible explanation for the deviation between -27 and -18 °C is discussed. Multiple exponential distribution fits in both linear and log space for both specific surface area-based n s( T) and geometric surface area-based n s( T) are provided. These new fits, constrained by using identical reference samples, will help to compare IN measurement methods that are not included in the present study and IN data from future IN instruments.« less

Structure and properties of polymer nanocomposite coatings applied by the HVOF process

NASA Astrophysics Data System (ADS)

Petrovicova, Elena

1999-11-01

A high velocity oxy-fuel (HVOF) combustion spray process was used to produce coatings from nylon 11 powders with average starting particle diameters of 30 and 60 gin. Silica and carbon black were used as nanosized reinforcements, and their nominal content was varied from 0 to 15 vol. %. Optimization of the HVOF processing parameters was based on an assessment of the degree of splatting of polymer particles, and was accomplished by varying the jet temperature (via the hydrogen/oxygen ratio). Gas mixtures with low hydrogen contents minimized polymer particle degradation. Analytical modeling of particle temperature profiles confirmed the effect of the gas velocity and temperature on the particle heating and resulting coating properties. The morphology of the polymer and the microstructure of the coatings depended on the reinforcement surface chemistry and the volume fraction of the reinforcement, as well as the initial nylon 11 particle size. Although all reinforced coatings had higher crystallinities than pure nylon 11 coatings, coatings produced from a smaller starting polymer particle size (30 mum) exhibited improved spatial distribution of the silica in the matrix and lower crystallinity. In addition, coatings produced from the smaller polymer particles had a higher density and lower porosity due to a higher degree of melting and splatting compared to coatings produced from larger particles (60 mum). Nanoreinforced coatings exhibited increased scratch and sliding wear resistance and improved mechanical and barrier properties. Improvements of up to 35% in scratch and 67% in wear resistance were obtained for coatings with nominal 15 vol. % contents of hydrophobic silica or carbon black, relative to nonreinforced coatings. Reinforcement of the polymer matrix resulted in increases of ca. 200% in the storage modulus both below and above the glass transition temperature. The increase in crystallinity seemed to further enhance the reinforcement provided by the nanoparticulates. Results also showed a decrease in the water vapor transmission rate through nanoreinforced coatings by up to 50% compared to pure polymer coatings. The aqueous permeability of coatings produced from 30 mum polymer particles was lower due to the decrease in porosity. Crystallinity seemed to have a strong influence on the mechanical properties, whereas permeability of thermally sprayed coatings was dominated by coating porosity.

Preparation and in vitro evaluation of simvastatin ethosome.

PubMed

An, Keyao; Sun, Yong; Xu, Lisa; Cui, Xiangzhen

2011-12-01

To prepare ethosome loading simvastatin,an orthogonal test was applied to optimize the prescriptions, and the qualities of simvastatin ethosome were characterized by the shape, particle size, encapsulation efficiency (EE), and stability. The formation of 40% (v/v) ethanol, 0.02% (m/v) cholesterol, 2.0% (m/v) soy lecithin, and 5% (m/v) polyoxyethylene hydrogenated castor oil showed the maximal EE (69.3%). We observed the shape of simvastatin ethosome through TEM. The average size of the particles was 52.4 ± 3.24 nm, which was detected by a N5 submicron particle size analyzer. After 120 days storage in 4? and at room temperature, the simvastatin ethosome had no significant change.

Inference of Ice Cloud Properties from High-spectral Resolution Infrared Observations. Appendix 4

NASA Technical Reports Server (NTRS)

Huang, Hung-Lung; Yang, Ping; Wei, Heli; Baum, Bryan A.; Hu, Yongxiang; Antonelli, Paolo; Ackerman, Steven A.

2005-01-01

The theoretical basis is explored for inferring the microphysical properties of ice crystal from high-spectral resolution infrared observations. A radiative transfer model is employed to simulate spectral radiances to address relevant issues. The extinction and absorption efficiencies of individual ice crystals, assumed as hexagonal columns for large particles and droxtals for small particles, are computed from a combination of the finite- difference time-domain (FDTD) technique and a composite method. The corresponding phase functions are computed from a combination of FDTD and an improved geometric optics method (IGOM). Bulk scattering properties are derived by averaging the single- scattering properties of individual particles for 30 particle size distributions developed from in situ measurements and for additional four analytical Gamma size distributions for small particles. The non-sphericity of ice crystals is shown to have a significant impact on the radiative signatures in the infrared (IR) spectrum; the spherical particle approximation for inferring ice cloud properties may result in an overest&ation of the optical thickness and an inaccurate retrieval of effective particle size. Furthermore, we show that the error associated with the use of the Henyey-Greenstein phase function can be as larger as 1 K in terms of brightness temperature for larger particle effective size at some strong scattering wavenumbers. For small particles, the difference between the two phase functions is much less, with brightness temperatures generally differing by less than 0.4 K. The simulations undertaken in this study show that the slope of the IR brightness temperature spectrum between 790-960/cm is sensitive to the effective particle size. Furthermore, a strong sensitivity of IR brightness temperature to cloud optical thickness is noted within the l050-1250/cm region. Based on this spectral feature, a technique is presented for the simultaneous retrieval of the visible optical thickness and effective particle size from high spectral resolution infrared data under ice cloudy con&tion. The error analysis shows that the uncertainty of the retrieved optical thickness and effective particle size has a small range of variation. The error for retrieving particle size in conjunction with an uncertainty of 5 K in cloud'temperature, or a surface temperature uncertainty of 2.5 K, is less than 15%. The corresponding e m r in the uncertainty of optical thickness is within 5-2096, depending on the value of cloud optical thickness. The applicability of the technique is demonstrated using the aircraft-based High- resolution Interferometer Sounder (HIS) data from the Subsonic Aircraft: Contrail and Cloud Effects Special Study (SUCCESS) in 1996 and the First ISCCP Regional Experiment - Arctic Clouds Experiment (FIRE-ACE) in 1998.

The absence of an Atlantic imprint on the multidecadal variability of wintertime European temperature

PubMed Central

Yamamoto, Ayako; Palter, Jaime B.

2016-01-01

Northern Hemisphere climate responds sensitively to multidecadal variability in North Atlantic sea surface temperature (SST). It is therefore surprising that an imprint of such variability is conspicuously absent in wintertime western European temperature, despite that Europe's climate is strongly influenced by its neighbouring ocean, where multidecadal variability in basin-average SST persists in all seasons. Here we trace the cause of this missing imprint to a dynamic anomaly of the atmospheric circulation that masks its thermodynamic response to SST anomalies. Specifically, differences in the pathways Lagrangian particles take to Europe during anomalous SST winters suppress the expected fluctuations in air–sea heat exchange accumulated along those trajectories. Because decadal variability in North Atlantic-average SST may be driven partly by the Atlantic Meridional Overturning Circulation (AMOC), the atmosphere's dynamical adjustment to this mode of variability may have important implications for the European wintertime temperature response to a projected twenty-first century AMOC decline. PMID:26975331

Ionospheric absorption, typical ionization, conductivity, and possible synoptic heating parameters in the upper atmosphere

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walker, J.K.; Bhatnagar, V.P.

1989-04-01

Relations for the average energetic particle heating and the typical Hall and Pedersen conductances, as functions of the ground-based Hf radio absorption, are determined. Collis and coworkers used the geosynchronous GEOS 2 particle data to relate or ''calibrate'' the auroral absorption on the same magnetic field lines with five levels of D region ionization. These ionospheric models are related to a Chapman layer that extends these models into the E region. The average energetic particle heating is calculated for each of these models using recent expressions for the effective recombination coefficient. The corresponding height-integrated heating rates are determined and relatedmore » to the absorption with a quadratic expression. The average Hall and Pedersen conductivities are calculated for each of the nominal absorption ionospheric models. The corresponding height-integrated conductances for nighttime conditions are determined and related to the absorption. Expressions for these conductances during disturbed sunlit conditions are also determined. These relations can be used in conjunction with simultaneous ground-based riometric and magnetic observations to determines the average Hall and Pedersen currents and the Joule heating. The typical daily rate of temperature increase in the mesosphere for storm conditions is several 10 K for both the energetic particle and the Joule heating. The increasing importance of these parameters of the upper and middle atmospheres is discussed. It is proposed that northern hemisphere ionospheric, current, and heating synoptic models and parameters be investigated for use on a regular basis. copyright American Geophysical Union 1989« less

Size-driven magnetic transitions in La1/3Ca2/3MnO3 nanoparticles

NASA Astrophysics Data System (ADS)

Markovich, V.; Fita, I.; Wisniewski, A.; Mogilyansky, D.; Puzniak, R.; Titelman, L.; Gorodetsky, G.

2010-09-01

Magnetic properties of electron-doped La1/3Ca2/3MnO3 manganite nanoparticles with average particle size ranging from 12 to 42 nm, prepared by the glycine-nitrate method, have been investigated in temperature range 5-300 K and in magnetic fields up to 90 kOe. Reduction in the particle size suppresses antiferromagnetism and decreases the Néel temperature. In contrast to bulk crystals, the charge ordering does not occur in all studied nanoparticles, while a weak ferromagnetism appears above 200 K. Low temperature magnetic hysteresis loops indicate upon exchange bias effect displayed by horizontal and vertical shifts in field cooled processes. The spontaneous and remanent magnetization at low temperature shows a relatively complex variation with particle size. The size-induced structural/magnetic disorder drives the La1/3Ca2/3MnO3 nanoparticles to a pronounced glassy behavior for the smallest 12 nm particles, as evidenced by large difference between zero field cooled and field cooled magnetization, frequency dependent ac-susceptibility, as well as characteristic slowing down in the spin dynamics. Time evolution of magnetization recorded in magnetic fields after field cooling to low temperatures exhibits pronounced relaxation and a very noisy behavior that may be caused by formation of some collective states. Magnetic properties of the nanoparticle samples are compared with those of La0.2Ca0.8MnO3 nanoparticles. These results shed some light on the coupling between charges and spin degrees of freedom in antiferromagnetic manganite nanoparticles.

Distinguishing between heating power and hyperthermic cell-treatment efficacy in magnetic fluid hyperthermia.

PubMed

Munoz-Menendez, Cristina; Conde-Leboran, Ivan; Serantes, David; Chantrell, Roy; Chubykalo-Fesenko, Oksana; Baldomir, Daniel

2016-11-04

In the magnetic fluid hyperthermia (MFH) research field, it is usually assumed that achieving a uniform temperature enhancement (ΔT) of the entire tumour is a key-point for treatment. However, various experimental works reported successful cell apoptosis via MFH without a noticeable ΔT of the system. A possible explanation of the success of these negligible-ΔT experiments is that a local ΔT restricted to the particle nanoenvironment (i.e. with no significant effect on the global temperature T) could be enough to trigger cell death. Shedding light on such a possibility requires accurate knowledge of heat dissipation at the local level in relation to the usually investigated global (average) one. Since size polydispersity is inherent to all synthesis techniques and the heat released is proportional to the particle size, heat dissipation spots with different performances - and thus different effects on the cells - will likely exist in every sample. In this work we aim for a double objective: (1) to emphasize the necessity to distinguish between the total dissipated heat and hyperthermia effectiveness, and (2) to suggest a theoretical approach on how to select, for a given size polydispersity, a more adequate average size so that most of the particles dissipate within a desired heating power range. The results are reported in terms of Fe 3 O 4 nanoparticles as a representative example.

Glyoxal and methylglyoxal in Atlantic seawater and marine aerosol particles: method development and first application during the Polarstern cruise ANT XXVII/4

NASA Astrophysics Data System (ADS)

van Pinxteren, M.; Herrmann, H.

2013-06-01

An analytical method for the determination of the alpha dicarbonyls glyoxal (GLY) and methylglyoxal (MGLY) from seawater and marine aerosol samples is presented. The method is based on derivatisation with o-(2,3,4,5,6-Pentafluorobenzyl)-hydroxylamine (PFBHA) reagent, solvent extraction and GC-MS (SIM) analysis. The method showed good precision (RSD <10%), sensitivity (detection limits in the low ng L-1 range), and accuracy (good agreement between external calibration and standard addition). The method was applied to determine GLY and MGLY in oceanic water sampled during the POLARSTERN cruise ANT XXVII/4 from Capetown to Bremerhaven in spring 2011. GLY and MGLY were determined in the sea surface microlayer (SML) of the ocean and corresponding bulkwater (BW) with average concentrations of 228 ng L-1 (GLY) and 196 ng L-1 (MGLY). The results show a significant enrichment (factor of 4) of GLY and MGLY in the SML. Furthermore, marine aerosol particles (PM1) were sampled during the cruise and analyzed for GLY (average concentration 0.19 ng m-3) and MGLY (average concentration 0.15 ng m-3). On aerosol particles, both carbonyls show a very good correlation with oxalate, supporting the idea of a secondary formation of oxalic acid via GLY and MGLY. Concentrations of GLY and MGLY in seawater and on aerosol particles were correlated to environmental parameters such as global radiation, temperature, distance to the coastline and biological activity. There are slight hints for a photochemical production of GLY and MGLY in the SML (significant enrichment in the SML, higher enrichment at higher temperature). However, a clear connection of GLY and MGLY to global radiation as well as to biological activity cannot be concluded from the data. A slight correlation between GLY and MGLY in the SML and in aerosols could be a hint for interactions of especially GLY between seawater and the atmosphere.

Measurement of the spatially distributed temperature and soot loadings in a laminar diffusion flame using a Cone-Beam Tomography technique

NASA Astrophysics Data System (ADS)

Zhao, Huayong; Williams, Ben; Stone, Richard

2014-01-01

A new low-cost optical diagnostic technique, called Cone Beam Tomographic Three Colour Spectrometry (CBT-TCS), has been developed to measure the planar distributions of temperature, soot particle size, and soot volume fraction in a co-flow axi-symmetric laminar diffusion flame. The image of a flame is recorded by a colour camera, and then by using colour interpolation and applying a cone beam tomography algorithm, a colour map can be reconstructed that corresponds to a diametral plane. Look-up tables calculated using Planck's law and different scattering models are then employed to deduce the temperature, approximate average soot particle size and soot volume fraction in each voxel (volumetric pixel). A sensitivity analysis of the look-up tables shows that the results have a high temperature resolution but a relatively low soot particle size resolution. The assumptions underlying the technique are discussed in detail. Sample data from an ethylene laminar diffusion flame are compared with data in the literature for similar flames. The comparison shows very consistent temperature and soot volume fraction profiles. Further analysis indicates that the difference seen in comparison with published results are within the measurement uncertainties. This methodology is ready to be applied to measure 3D data by capturing multiple flame images from different angles for non-axisymmetric flame.

SPARSE—A subgrid particle averaged Reynolds stress equivalent model: testing with a priori closure

PubMed Central

Davis, Sean L.; Sen, Oishik; Udaykumar, H. S.

2017-01-01

A Lagrangian particle cloud model is proposed that accounts for the effects of Reynolds-averaged particle and turbulent stresses and the averaged carrier-phase velocity of the subparticle cloud scale on the averaged motion and velocity of the cloud. The SPARSE (subgrid particle averaged Reynolds stress equivalent) model is based on a combination of a truncated Taylor expansion of a drag correction function and Reynolds averaging. It reduces the required number of computational parcels to trace a cloud of particles in Eulerian–Lagrangian methods for the simulation of particle-laden flow. Closure is performed in an a priori manner using a reference simulation where all particles in the cloud are traced individually with a point-particle model. Comparison of a first-order model and SPARSE with the reference simulation in one dimension shows that both the stress and the averaging of the carrier-phase velocity on the cloud subscale affect the averaged motion of the particle. A three-dimensional isotropic turbulence computation shows that only one computational parcel is sufficient to accurately trace a cloud of tens of thousands of particles. PMID:28413341

SPARSE-A subgrid particle averaged Reynolds stress equivalent model: testing with a priori closure.

PubMed

Davis, Sean L; Jacobs, Gustaaf B; Sen, Oishik; Udaykumar, H S

2017-03-01

A Lagrangian particle cloud model is proposed that accounts for the effects of Reynolds-averaged particle and turbulent stresses and the averaged carrier-phase velocity of the subparticle cloud scale on the averaged motion and velocity of the cloud. The SPARSE (subgrid particle averaged Reynolds stress equivalent) model is based on a combination of a truncated Taylor expansion of a drag correction function and Reynolds averaging. It reduces the required number of computational parcels to trace a cloud of particles in Eulerian-Lagrangian methods for the simulation of particle-laden flow. Closure is performed in an a priori manner using a reference simulation where all particles in the cloud are traced individually with a point-particle model. Comparison of a first-order model and SPARSE with the reference simulation in one dimension shows that both the stress and the averaging of the carrier-phase velocity on the cloud subscale affect the averaged motion of the particle. A three-dimensional isotropic turbulence computation shows that only one computational parcel is sufficient to accurately trace a cloud of tens of thousands of particles.

Thermal Field Imaging Using Ultrasound

NASA Technical Reports Server (NTRS)

Andereck, D.; Rahal, S.; Fife, S.

2000-01-01

It is often desirable to be able to determine the temperature field in the interiors of opaque fluids forced into convection by externally imposed temperature gradients. To measure the temperature at a point in an opaque fluid in the usual fashion requires insertion of a probe, and to determine the full field therefore requires either the ability to move this probe or the introduction of multiple probes. Neither of these solutions is particularly satisfactory, although they can lead to quite accurate measurements. As an alternative we have investigated the use of ultrasound as a relatively non-intrusive probe of the temperature field in convecting opaque fluids. The temperature dependence of the sound velocity can be sufficiently great to permit a determination of the temperature from timing the traversal of an ultrasound pulse across a chamber. In this paper we will present our results on convecting flows of transparent and opaque fluids. Our experimental cells consist of relatively narrow rectangular cavities made of thermally insulating materials on the sides, and metal top and bottom plates. The ultrasound transducer is powered by a pulser/receiver, the signal output of which goes to a very high speed signal averager. The average of several hundred to several thousand signals is then sent to a computer for storage and analysis. The experimental procedure is to establish a convective flow by imposing a vertical temperature gradient on the chamber, and then to measure, at several regularly spaced locations, the transit time for an ultrasound pulse to traverse the chamber horizontally (parallel to the convecting rolls) and return to the transducer. The transit time is related to the temperature of the fluid through which the sound pulse travels. Knowing the relationship between transit time and temperature (determined in a separate experiment), we can extract the average temperature across the chamber at that location. By changing the location of the transducer it is then possible to find the average temperature at different locations along the chamber, thereby determining the temperature profile along the system. (In the future we will construct an array of transducers. This will give us the capability to determine the temperature profile much more rapidly than at present, an important consideration if time-dependent phenomena are to be studied.) To validate our procedure we introduced encapsulated liquid crystal particles into glycerol. The liquid crystal particles' color varies depending on the temperature of the fluid. A photograph of the fluid through transparent sidewalls therefore gives a picture of the temperature field of the convecting fluid, independent of our ultrasound imaging. A representative result is shown in the Figure 1, which reveals a very satisfying correspondence between the two techniques. Therefore we have a great deal of confidence that the ultrasound imaging approach is indeed measuring the actual temperature profile of the fluid. The technique has also been applied to convecting liquid metal flows, and representative data will be presented from those experiments as well.

Investigating phase transition temperatures of size separated gadolinium silicide magnetic nanoparticles

DOE PAGES

Hunagund, Shivakumar G.; Harstad, Shane M.; El-Gendy, Ahmed A.; ...

2018-01-11

Gadolinium silicide (Gd 5Si 4) nanoparticles (NPs) exhibit different properties compared to their parent bulk materials due to finite size, shape, and surface effects. NPs were prepared by high energy ball-milling of the as-cast Gd 5Si 4 ingot and size separated into eight fractions using time sensitive sedimentation in an applied dc magnetic field with average particle sizes ranging from 700 nm to 82 nm. The largest Gd 5Si 4 NPs order ferromagnetically at 316 K. A second anomaly observed at 110 K can be ascribed to a Gd 5Si 3 impurity. Here as the particle sizes decrease, the volumemore » fraction of Gd 5Si 3 phase increases at the expense of the Gd 5Si 4 phase, and the ferromagnetic transition temperature of Gd 5Si 4 is reduced from 316 K to 310 K, while the ordering of the minor phase is independent of the particle size, remaining at 110 K.« less

Ferromagnetic phases of lunar fines and breccias - Electron magnetic resonance spectra of Apollo 16 samples

NASA Technical Reports Server (NTRS)

Weeks, R. A.

1973-01-01

Electron magnetic resonance measurements have been made at 9 GHz and at temperatures from 1.2 to 400 K and 35 GHz (300 K) on samples of fines and breccias from Apollo 11-16. Unsorted Apollo 16 fines (less than 1 mm) have Delta H (average) = 580 G and specific intensities that have the same range as fines from the other Apollo collections. The magnetic properties of the 'characteristic' resonance are not in accord with those of iron particles. On the bases of the properties of the 'characteristic' resonance as a function of temperature and Apollo site, laboratory heat treatments on synthetic materials and lunar crystalline rocks and a comparison with the 'characteristic' resonance of the resonance spectra of breccia specimens for which iron particle sizes have been determined from other measurements, it is suggested that some fraction (about 20%) of the 'characteristic' resonance is due to sub-micron particles of ferric oxide phases.

A facile self-assembly approach to prepare palladium/carbon nanotubes catalyst for the electro-oxidation of ethanol

NASA Astrophysics Data System (ADS)

Wen, Cuilian; Zhang, Xinyuan; Wei, Ying; Zhang, Teng; Chen, Changxin

2018-02-01

A facile self-assembly approach is reported to prepare palladium/carbon nanotubes (Pd/CNTs) catalyst for the electro-oxidation of ethanol. In this method, the Pd-oleate/CNTs was decomposed into the Pd/CNTs at an optimal temperature of 195 °C in air, in which no inert gas is needed for the thermal decomposition process due to the low temperature used and the decomposed products are also environmental friendly. The prepared Pd/CNTs catalyst has a high metallic Pd0 content and the Pd particles in the catalyst are disperse, uniform-sized with an average size of ˜2.1 nm, and evenly distributed on the CNTs. By employing our strategy, the problems including the exfoliation of the metal particles from the CNTs and the aggregation of the metal particles can be solved. Comparing with the commercial Pd/C one, the prepared Pd/CNTs catalyst exhibits a much higher electrochemical activity and stability for the electro-oxidation of ethanol in the direct ethanol fuel cells.

Investigating phase transition temperatures of size separated gadolinium silicide magnetic nanoparticles

NASA Astrophysics Data System (ADS)

Hunagund, Shivakumar G.; Harstad, Shane M.; El-Gendy, Ahmed A.; Gupta, Shalabh; Pecharsky, Vitalij K.; Hadimani, Ravi L.

2018-05-01

Gadolinium silicide (Gd5Si4) nanoparticles (NPs) exhibit different properties compared to their parent bulk materials due to finite size, shape, and surface effects. NPs were prepared by high energy ball-milling of the as-cast Gd5Si4 ingot and size separated into eight fractions using time sensitive sedimentation in an applied dc magnetic field with average particle sizes ranging from 700 nm to 82 nm. The largest Gd5Si4 NPs order ferromagnetically at 316 K. A second anomaly observed at 110 K can be ascribed to a Gd5Si3 impurity. As the particle sizes decrease, the volume fraction of Gd5Si3 phase increases at the expense of the Gd5Si4 phase, and the ferromagnetic transition temperature of Gd5Si4 is reduced from 316 K to 310 K, while the ordering of the minor phase is independent of the particle size, remaining at 110 K.

Investigating phase transition temperatures of size separated gadolinium silicide magnetic nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hunagund, Shivakumar G.; Harstad, Shane M.; El-Gendy, Ahmed A.

Gadolinium silicide (Gd 5Si 4) nanoparticles (NPs) exhibit different properties compared to their parent bulk materials due to finite size, shape, and surface effects. NPs were prepared by high energy ball-milling of the as-cast Gd 5Si 4 ingot and size separated into eight fractions using time sensitive sedimentation in an applied dc magnetic field with average particle sizes ranging from 700 nm to 82 nm. The largest Gd 5Si 4 NPs order ferromagnetically at 316 K. A second anomaly observed at 110 K can be ascribed to a Gd 5Si 3 impurity. Here as the particle sizes decrease, the volumemore » fraction of Gd 5Si 3 phase increases at the expense of the Gd 5Si 4 phase, and the ferromagnetic transition temperature of Gd 5Si 4 is reduced from 316 K to 310 K, while the ordering of the minor phase is independent of the particle size, remaining at 110 K.« less

Numerical simulation on the powder propellant pickup characteristics of feeding system at high pressure

NASA Astrophysics Data System (ADS)

Sun, Haijun; Hu, Chunbo; Zhu, Xiaofei

2017-10-01

A numerical study of powder propellant pickup progress at high pressure was presented in this paper by using two-fluid model with kinetic theory of granular flow in the computational fluid dynamics software package ANSYS/Fluent. Simulations were conducted to evaluate the effects of initial pressure, initial powder packing rate and mean particle diameter on the flow characteristics in terms of velocity vector distribution, granular temperature, pressure drop, particle velocity and volume. The numerical results of pressure drop were also compared with experiments to verify the TFM model. The simulated results show that the pressure drop value increases as the initial pressure increases, and the granular temperature under the conditions of different initial pressures and packing rates is almost the same in the area of throttling orifice plate. While there is an appropriate value for particle size and packing rate to form a ;core-annulus; structure in powder box, and the time-averaged velocity vector distribution of solid phase is inordinate.

Associations between air temperature and cardio-respiratory mortality in the urban area of Beijing, China: a time-series analysis.

PubMed

Liu, Liqun; Breitner, Susanne; Pan, Xiaochuan; Franck, Ulrich; Leitte, Arne Marian; Wiedensohler, Alfred; von Klot, Stephanie; Wichmann, H-Erich; Peters, Annette; Schneider, Alexandra

2011-05-25

Associations between air temperature and mortality have been consistently observed in Europe and the United States; however, there is a lack of studies for Asian countries. Our study investigated the association between air temperature and cardio-respiratory mortality in the urban area of Beijing, China. Death counts for cardiovascular and respiratory diseases for adult residents (≥15 years), meteorological parameters and concentrations of particulate air pollution were obtained from January 2003 to August 2005. The effects of two-day and 15-day average temperatures were estimated by Poisson regression models, controlling for time trend, relative humidity and other confounders if necessary. Effects were explored for warm (April to September) and cold periods (October to March) separately. The lagged effects of daily temperature were investigated by polynomial distributed lag (PDL) models. We observed a J-shaped exposure-response function only for 15-day average temperature and respiratory mortality in the warm period, with 21.3°C as the threshold temperature. All other exposure-response functions could be considered as linear. In the warm period, a 5°C increase of two-day average temperature was associated with a RR of 1.098 (95% confidence interval (95%CI): 1.057-1.140) for cardiovascular and 1.134 (95%CI: 1.050-1.224) for respiratory mortality; a 5°C decrease of 15-day average temperature was associated with a RR of 1.040 (95%CI: 0.990-1.093) for cardiovascular mortality. In the cold period, a 5°C increase of two-day average temperature was associated with a RR of 1.149 (95%CI: 1.078-1.224) for respiratory mortality; a 5°C decrease of 15-day average temperature was associated with a RR of 1.057 (95%CI: 1.022-1.094) for cardiovascular mortality. The effects remained robust after considering particles as additional confounders. Both increases and decreases in air temperature are associated with an increased risk of cardiovascular mortality. The effects of heat were immediate while the ones of cold became predominant with longer time lags. Increases in air temperature are also associated with an immediate increased risk of respiratory mortality.

Associations between air temperature and cardio-respiratory mortality in the urban area of Beijing, China: a time-series analysis

PubMed Central

2011-01-01

Background Associations between air temperature and mortality have been consistently observed in Europe and the United States; however, there is a lack of studies for Asian countries. Our study investigated the association between air temperature and cardio-respiratory mortality in the urban area of Beijing, China. Methods Death counts for cardiovascular and respiratory diseases for adult residents (≥15 years), meteorological parameters and concentrations of particulate air pollution were obtained from January 2003 to August 2005. The effects of two-day and 15-day average temperatures were estimated by Poisson regression models, controlling for time trend, relative humidity and other confounders if necessary. Effects were explored for warm (April to September) and cold periods (October to March) separately. The lagged effects of daily temperature were investigated by polynomial distributed lag (PDL) models. Results We observed a J-shaped exposure-response function only for 15-day average temperature and respiratory mortality in the warm period, with 21.3°C as the threshold temperature. All other exposure-response functions could be considered as linear. In the warm period, a 5°C increase of two-day average temperature was associated with a RR of 1.098 (95% confidence interval (95%CI): 1.057-1.140) for cardiovascular and 1.134 (95%CI: 1.050-1.224) for respiratory mortality; a 5°C decrease of 15-day average temperature was associated with a RR of 1.040 (95%CI: 0.990-1.093) for cardiovascular mortality. In the cold period, a 5°C increase of two-day average temperature was associated with a RR of 1.149 (95%CI: 1.078-1.224) for respiratory mortality; a 5°C decrease of 15-day average temperature was associated with a RR of 1.057 (95%CI: 1.022-1.094) for cardiovascular mortality. The effects remained robust after considering particles as additional confounders. Conclusions Both increases and decreases in air temperature are associated with an increased risk of cardiovascular mortality. The effects of heat were immediate while the ones of cold became predominant with longer time lags. Increases in air temperature are also associated with an immediate increased risk of respiratory mortality. PMID:21612647

Fabrication, characterization and simulation of 4H-SiC Schottky diode alpha particle detectors for pyroprocessing actinide monitoring

NASA Astrophysics Data System (ADS)

Garcia, Timothy Richard

Pyroprocessing is a method of using high-temperature molten salts and electric fields to separate and collect fuel isotopes of used nuclear fuel. It has been has been tested in the U.S. at Idaho National Laboratory as a key step in closing the nuclear fuel cycle. One technical problem with the pyroprocessing method is a lack of knowledge regarding the actinide concentrations in the salt bath during operation, since on-line techniques for measuring these concentrations are not presently available. 4H-SiC Schottky diode detectors can potentially fulfill this need. Such detectors would operate in contact with the molten salt, and measure concentrations via alpha-particle spectroscopy. This work seeks to fabricate and characterize 4H-SiC Schottky diode detectors at high temperature, model the alpha particle spectrum expected in a molten salt, and model the operation of the detectors to confirm the physics of operation is as expected. In this work, 4H-SiC Schottky diode detectors were fabricated at OSU Nanotech West. After fabrication, these detectors were characterized using both I-V curves and Am-241 alpha-particle energy spectra. All measurements were made as a function of temperature, from room temperature up to 500°C. The average energy required to create an electron-hole pair was observed to decrease with an increase of temperature, due to a decrease of both the 4H-SiC bandgap and non-linear energy loss terms. Furthermore, the FWHM of the spectra was observed to be dependent on the leakage current at a certain temperature, and not dependent on the temperature itself. Secondly, the alpha particle energy spectrum in the pyroprocessing environment was modeled using SRIM. The molten salt was modeled in 3 different geometries, with or without a protective cover material on top of the detector. Due to the loss of alpha-particle energy in the molten salt itself, a high-energy alpha emitter may completely cover the spectrum from a lower-energy alpha emitter. Each of the geometries simulated showed a different sensitivity to the lower-energy alpha emitter. Regardless of which geometry was modeled, it was observed that it is possible to measure both the emission energy of the alpha particles, as well as the concentration of the alpha emitter in the liquid. Lastly, Sentaurus TCAD was used to simulate the detection of alpha-particle charge collection in situations that are relevant to the molten salt alpha particle energy spectra. The effect of electric field negation was investigated, as well as velocity saturation. Finally, the dependence of charge recombination on temperature, alpha particle energy, and angle of incidence was investigated. These simulations captured the measurements performed at room temperature. With changed angle of incidence, the change in the amount of charge collected was less than 1 percent, indicating a weak dependence. Also, the amount of charge lost to Auger recombination was seen to increase with temperature. This disagrees with observations from experiment, indicating that the temperature dependence of one or more parameters of the model may not be accurate.

[Distribution of atmospheric ultrafine particles during haze weather in Hangzhou].

PubMed

Chen, Qiu-Fang; Sun, Zai; Xie, Xiao-Fang

2014-08-01

Atmospheric ultrafine particles (UFPs) were monitored with fast mobility particle sizer (FMPS) in continuous haze weather and the haze fading process during December 6 to 11, 2013 in Hangzhou. Particle concentration and size distribution were studied associated with meteorological factors. The results showed that number concentrations were the highest at night and began to reduce in the morning. There was a small peak at 8 o'clock in the morning and 18 o'clock in the afternoon. It showed an obvious peak traffic source, which indicated that traffic emissions played a great role in the atmospheric pollution. During haze weather, the highest number concentration of UFPs reached 8 x 10(4) cm(-3). Particle size spectrum distribution was bimodal, the peak particle sizes were 15 nm and 100 nm respectively. Majority of UFPs were Aitken mode and Accumulation mode and the size of most particles concentrated near 100 nm. Average CMD(count medium diameter) was 85.89 nm. During haze fading process, number concentration and particles with size around 100 nm began to reduce and peak size shifted to small size. Nuclear modal particles increased and were more than accumulation mode. Average CMD was 58.64 nm. Meteorological factors such as the visibility and wind were negatively correlated with the particle number concentration. Correlation coefficient R were -0.225 and - 0.229. The humidity was correlated with number concentration. Correlation coefficient R was 0.271. The atmosphere was stable in winter and the level temperature had small correlation with number concentration. Therefore, study on distribution of atmospheric ultrafine particles during haze weather had the significance on the formation mechanism and control of haze weather.

Size effects on the magnetic properties of LaCoO3 nanoparticles

NASA Astrophysics Data System (ADS)

Wei, Q.; Zhang, T.; Wang, X. P.; Fang, Q. F.

2012-02-01

Magnetic properties of LaCoO3 nanoparticles prepared by a sol-gel method with average particle size (D) ranging from 20 to 500 nm are investigated. All samples exhibit obvious ferromagnetic transition. With decreasing particle size from 500 to 120 nm, the transition temperature Tc decreases slightly from 85 K, however Tc decreases dramatically when D ≤ 85 nm. Low-field magnetic moment at 10 K decreases with reduction of particle size, while the high-field magnetization exhibits a converse behavior, which is different with previous reports. The coercivity Hc decreases as the particle size is reduced. It is different with other nanosystems that no exchange bias effect is observed in nanosized LaCoO3 particles. These interesting results arise from the surface effect induced by sized effect and the structure change in LaCoO3 nanoparticles.

Self ordering threshold and superradiant backscattering to slow a fast gas beam in a ring cavity with counter propagating pump

NASA Astrophysics Data System (ADS)

Maes, C.; Asbóth, J. K.; Ritsch, H.

2007-05-01

We study the dynamics of a fast gaseous beam in a high Q ring cavity counter propagating a strong pump laser with large detuning from any particle optical resonance. As spontaneous emission is strongly suppressed the particles can be treated as polarizable point masses forming a dynamic moving mirror. Above a threshold intensity the particles exhibit spatial periodic ordering enhancing collective coherent backscattering which decelerates the beam. Based on a linear stability analysis in their accelerated rest frame we derive analytic bounds for the intensity threshold of this selforganization as a function of particle number, average velocity, kinetic temperature, pump detuning and resonator linewidth. The analytical results agree well with time dependent simulations of the N-particle motion including field damping and spontaneous emission noise. Our results give conditions which may be easily evaluated for stopping and cooling a fast molecular beam.

Self ordering threshold and superradiant backscattering to slow a fast gas beam in a ring cavity with counter propagating pump.

PubMed

Maes, C; Asbóth, J K; Ritsch, H

2007-05-14

We study the dynamics of a fast gaseous beam in a high Q ring cavity counter propagating a strong pump laser with large detuning from any particle optical resonance. As spontaneous emission is strongly suppressed the particles can be treated as polarizable point masses forming a dynamic moving mirror. Above a threshold intensity the particles exhibit spatial periodic ordering enhancing collective coherent backscattering which decelerates the beam. Based on a linear stability analysis in their accelerated rest frame we derive analytic bounds for the intensity threshold of this selforganization as a function of particle number, average velocity, kinetic temperature, pump detuning and resonator linewidth. The analytical results agree well with time dependent simulations of the N-particle motion including field damping and spontaneous emission noise. Our results give conditions which may be easily evaluated for stopping and cooling a fast molecular beam.

Nanomodified heat-accumulating materials controlled by a magnetic field

NASA Astrophysics Data System (ADS)

Shchegolkov, Alexander; Shchegolkov, Alexey; Dyachkova, Tatyana; Bodin, Nikolay; Semenov, Alexander

2017-11-01

The paper presents studies of nanomodified heat-accumulating materials controlled by a magnetic field. In order to obtain controlled heat-accumulating materials, synthetic motor oil CASTROL 0W30, ferromagnetic particles, CNTs and paraffin were used. Mechanically activated carbon nanotubes with ferromagnetic particles were used for the nanomodification of paraffin. Mechanoactivation ensured the production of ferromagnetic particles with an average particle size of 5 µm. Using an extrusion plant, a mixture of CNTs and ferromagnetic particles was introduced into the paraffin. Further, the nanomodified paraffin in a granular form was introduced into synthetic oil. To conduct experimental studies, a contactless method for measuring temperature was used. The thermal contact control with the help of the obtained nanomodified material is possible with a magnetic induction of 1250 mT, and a heat flux of about 74 kW/m2 is provided at the same time.

Numerical study of a confined slot impinging jet with nanofluids

PubMed Central

2011-01-01

Background Heat transfer enhancement technology concerns with the aim of developing more efficient systems to satisfy the increasing demands of many applications in the fields of automotive, aerospace, electronic and process industry. A solution for obtaining efficient cooling systems is represented by the use of confined or unconfined impinging jets. Moreover, the possibility of increasing the thermal performances of the working fluids can be taken into account, and the introduction of nanoparticles in a base fluid can be considered. Results In this article, a numerical investigation on confined impinging slot jet working with a mixture of water and Al2O3 nanoparticles is described. The flow is turbulent and a constant temperature is applied on the impinging. A single-phase model approach has been adopted. Different geometric ratios, particle volume concentrations and Reynolds number have been considered to study the behavior of the system in terms of average and local Nusselt number, convective heat transfer coefficient and required pumping power profiles, temperature fields and stream function contours. Conclusions The dimensionless stream function contours show that the intensity and size of the vortex structures depend on the confining effects, given by H/W ratio, Reynolds number and particle concentrations. Furthermore, for increasing concentrations, nanofluids realize increasing fluid bulk temperature, as a result of the elevated thermal conductivity of mixtures. The local Nusselt number profiles show the highest values at the stagnation point, and the lowest at the end of the heated plate. The average Nusselt number increases for increasing particle concentrations and Reynolds numbers; moreover, the highest values are observed for H/W = 10, and a maximum increase of 18% is detected at a concentration equal to 6%. The required pumping power as well as Reynolds number increases and particle concentrations grow, which is almost 4.8 times greater than the values calculated in the case of base fluid. List of symbols PMID:21711743

DOE Office of Scientific and Technical Information (OSTI.GOV)

Demkowicz, Paul Andrew; Harp, Jason M.; Winston, Philip L.

Destructive post-irradiation examination was performed on AGR-1 fuel Compact 4-1-1, which was irradiated to a final compact-average burnup of 19.4% FIMA (fissions per initial metal atom) and a time-average, volume-average temperature of 1072°C. The analysis of this compact focused on characterizing the extent of fission product release from the particles and examining particles to determine the condition of the kernels and coating layers. The work included deconsolidation of the compact and leach-burn-leach analysis, visual inspection and gamma counting of individual particles, metallurgical preparation of selected particles, and examination of particle cross-sections with optical microscopy, electron microscopy, and elemental analysis. Deconsolidation-leach-burn-leachmore » (DLBL) analysis revealed no particles with failed TRISO or failed SiC layers (as indicated by very low uranium inventory in all of the leach solutions). The total fractions of the predicted compact inventories of fission products Ce-144, Cs-134, Cs-137, and Sr-90 that were present in the compact outside of the SiC layers were <2×10 -6, based on DLBL data. The Ag-110m fraction in the compact outside the SiC layers was 3.3×10 -2, indicating appreciable release of silver through the intact coatings and subsequent retention in the OPyC layers or matrix. The Eu-154 fraction was 2.4×10 -4, which is equivalent to the inventory in one average particle, and indicates a small but measurable level of release from the intact coatings. Gamma counting of 61 individual particles indicated no particles with anomalously low fission product retention. The average ratio of measured inventory to calculated inventory was close to a value of 1.0 for several fission product isotopes (Ce-144, Cs-134, and Cs-137), indicating good retention and reasonably good agreement with the predicted inventories. Measured-to-calculated (M/C) activity ratios for fission products Eu-154, Eu-155, Ru-106, Sb-125, and Zr-95 were significantly less than 1.0. However, as no significant release of these fission products from compacts was noted during previous analysis of the AGR-1 capsule components, the low M/C ratios are most likely an indication of a bias in the inventories predicted by physics simulations of the AGR-1 experiment. The distribution of Ag-110m M/C ratios was centered on a value of 1.02 and was fairly broad (standard deviation of 0.18, with values as high as 1.42 and as low as 0.68). Based on all data gathered to date, it is believed that silver retention in the particles was on average relatively high, but that the broad distribution in values among the particles represents significant variation in the inventory of Ag-110m generated in the particles. Ceramographic analysis of particle cross-sections revealed many of the characteristic microstructures often observed in irradiated AGR-1 particles from other fuel compacts. Palladium-rich fission product clusters were observed in the IPyC and SiC layers near the IPyC-SiC interface of three Compact 4-1-1 particle cross-sections. In spite of the presence of fission product clusters in the SiC layer, no significant corrosion or degradation of the layer was observed in any of the particles examined.« less

Gasification Characteristics of Coal/Biomass Mixed Fuels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mitchell, Reginald

2014-09-01

A research project was undertaken that had the overall objective of developing the models needed to accurately predict conversion rates of coal/biomass mixtures to synthesis gas under conditions relevant to a commercially-available coal gasification system configured to co-produce electric power as well as chemicals and liquid fuels. In our efforts to accomplish this goal, experiments were performed in an entrained flow reactor in order to produce coal and biomass chars at high heating rates and temperatures, typical of the heating rates and temperatures fuel particles experience in real systems. Mixed chars derived from coal/biomass mixtures containing up to 50% biomassmore » and the chars of the pure coal and biomass components were subjected to a matrix of reactivity tests in a pressurized thermogravimetric analyzer (TGA) in order to obtain data on mass loss rates as functions of gas temperature, pressure and composition as well as to obtain information on the variations in mass specific surface area during char conversion under kinetically-limited conditions. The experimental data were used as targets when determining the unknown parameters in the chemical reactivity and specific surface area models developed. These parameters included rate coefficients for the reactions in the reaction mechanism, enthalpies of formation and absolute entropies of adsorbed species formed on the carbonaceous surfaces, and pore structure coefficients in the model used to describe how the mass specific surface area of the char varies with conversion. So that the reactivity models can be used at high temperatures when mass transport processes impact char conversion rates, Thiele modulus – effectiveness factor relations were also derived for the reaction mechanisms developed. In addition, the reactivity model and a mode of conversion model were combined in a char-particle gasification model that includes the effects of chemical reaction and diffusion of reactive gases through particle pores and energy exchange between the particle and its environment. This char-particle gasification model is capable of predicting the average mass loss rates, sizes, apparent densities, specific surface areas, and temperatures of the char particles produced when co-firing coal and biomass to the type environments established in entrained flow gasifiers operating at high temperatures and elevated pressures.« less

Effect of iron particle size and volume fraction on the magnetic properties of Fe/silicate glass soft magnetic composites

NASA Astrophysics Data System (ADS)

Ding, Wei; Jiang, Longtao; Liao, Yaqin; Song, Jiabin; Li, Bingqing; Wu, Gaohui

2015-03-01

Fe/silicate glass soft magnetic composites (SMC) were fabricated by powder metallurgy with 1000 MPa pressure at room temperature, and then annealed at 700 °C for 90 min. The iron particles distributed uniformly in the composites, and have been separated from each other by a continuous silicate glass insulating layer. Fe/glass interface was well bonded and a quasi-continuous layer Fe3O4 and FeO exited. Very fine crystalline phases Na12Ca3Fe2(Si6O18)2 were formed in silicate glass. Composite containing 57 vol% 75 μm iron particles demonstrated highest resistivity of 7.8×10-3 Ω m. The μm, Bs and Bt increased while Hc of Fe/silicate glass composites decreased with the increase of average size of iron particles. The composite with highest amount (82 vol%) and largest average size (140 μm) of iron particles demonstrated best μm, Bs and Bt and Hc, which were 622, 1.57 T, 1.43 T, 278 A/m, respectively. The composite containing 57 vol% 75 μm iron particles demonstrated minimum core loss of 3.5 W/kg at 50 Hz and 28.1 W/kg at 400 Hz, while the composite containing 82 vol% 140 μm iron particles exhibited maximum core loss of 5.2 W/kg at 50 Hz and 67.7 W/kg at 400 Hz.

Space reactor fuel element testing in upgraded TREAT

NASA Astrophysics Data System (ADS)

Todosow, M.; Bezler, P.; Ludewig, H.; Kato, W. Y.

The testing of candidate fuel elements at prototypic operating conditions with respect to temperature, power density, hydrogen coolant flow rate, etc.; a crucial component in the development and qualification of nuclear rocket engines based on the Particle Bed Reactor (PBR); NERVA-derivative; and other concepts are discussed. Such testing may be performed at existing reactors, or at new facilities. A scoping study has been performed to assess the feasibility of testing PBR based fuel elements at the TREAT reactor. Initial results suggest that full-scale PBR elements could be tested at an average energy deposition of approximately 60-80 MW-s/L in the current TREAT reactor. If the TREAT reactor was upgraded to include fuel elements with a higher temperature limit, average energy deposition of approximately 100 MW/L may be achievable.

High surface area neodymium phosphate nano particles by modified aqueous sol-gel method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sankar, Sasidharan; Warrier, Krishna Gopakumar, E-mail: wwarrierkgk@yahoo.co.in; Komban, Rajesh

2011-12-15

Graphical abstract: Synthesis of nano rod shaped neodymium phosphate particles with specific surface area as high as 107 m{sup 2} g{sup -1} and particles could be compacted and sintered at as low as 1300 Degree-Sign C to a density of 98.5% (theoretical) with an average grain size of {approx}1 {mu}m. Highlights: Black-Right-Pointing-Pointer Nano size neodymium phosphate is synthesized and characterized using a novel modified aqueous sol gel process. Black-Right-Pointing-Pointer Specific surface area above 100 m{sup 2} g{sup -1} achieved without the addition of any complexing agents. Black-Right-Pointing-Pointer High sintered density reported than the density obtained for powder synthesized through conventionalmore » solid state reaction. Black-Right-Pointing-Pointer The particles are nano sized and have rod shape morphology and are retained at higher temperatures. Black-Right-Pointing-Pointer An average grain size of {approx}1 {mu}m obtained for sintered NdPO{sub 4} after thermal etching at 1400 Degree-Sign C. -- Abstract: Synthesis of nano rod shaped neodymium phosphate (NdPO{sub 4}) particles with specific surface area as high as 107 m{sup 2}g{sup -1} and an average length of 50 nm with aspect ratio 5 was achieved using modified sol gel method. Crystallite size calculated from the X-ray diffraction data by applying Scherer equation was 5 nm for the precursor gel after calcination at 400 Degree-Sign C. NdPO{sub 4} was first precipitated from neodymium nitrate solution using phosphoric acid followed by peptization using dilute nitric acid and further gelation in ammonia atmosphere. The calcined gel powders were further characterized by surface area (Brunauer-Emmet-Teller nitrogen adsorption analysis), Transmission electron microscopy, scanning electron microscopy, UV-vis and FT-IR analysis. Transmission electron microscopy confirms the formation of rod like morphology from the sol, gel and the calcined particles in nano size range. These particles could be compacted and sintered at as low as 1300 Degree-Sign C to a density of 98.5% (theoretical) with an average grain size of {approx}1 {mu}m.« less

Calibration approach for extremely variable laser induced plasmas and a strategy to reduce the matrix effect in general

NASA Astrophysics Data System (ADS)

Lazic, V.; De Ninno, A.

2017-11-01

The laser induced plasma spectroscopy was applied on particles attached on substrate represented by a silica wafer covered with a thin oil film. The substrate itself weakly interacts with a ns Nd:YAG laser (1064 nm) while presence of particles strongly enhances the plasma emission, here detected by a compact spectrometer array. Variations of the sample mass from one laser spot to another exceed one order of magnitude, as estimated by on-line photography and the initial image calibration for different sample loadings. Consequently, the spectral lines from particles show extreme intensity fluctuations from one sampling point to another, between the detection threshold and the detector's saturation in some cases. In such conditions the common calibration approach based on the averaged spectra, also when considering ratios of the element lines i.e. concentrations, produces errors too large for measuring the sample compositions. On the other hand, intensities of an analytical and the reference line from single shot spectra are linearly correlated. The corresponding slope depends on the concentration ratio and it is weakly sensitive to fluctuations of the plasma temperature inside the data set. A use of the slopes for constructing the calibration graphs significantly reduces the error bars but it does not eliminate the point scattering caused by the matrix effect, which is also responsible for large differences in the average plasma temperatures among the samples. Well aligned calibration points were obtained after identifying the couples of transitions less sensitive to variations of the plasma temperature, and this was achieved by simple theoretical simulations. Such selection of the analytical lines minimizes the matrix effect, and together with the chosen calibration approach, allows to measure the relative element concentrations even in highly unstable laser induced plasmas.

Catalytic membranes for CO oxidation in fuel cells

DOEpatents

Sandi-Tapia, Giselle; Carrado Gregar, Kathleen; Kizilel, Riza

2010-06-08

A hydrogen permeable membrane, which includes a polymer stable at temperatures of about 200 C having clay impregnated with Pt or Au or Ru or Pd particles or mixtures thereof with average diameters of less than about 10 nanometers (nms) is disclosed. The membranes are useful in fuel cells or any device which requires hydrogen to be separated from carbon monoxide.

Diffusion of a particle in the spatially correlated exponential random energy landscape: Transition from normal to anomalous diffusion.

PubMed

Novikov, S V

2018-01-14

Diffusive transport of a particle in a spatially correlated random energy landscape having exponential density of states has been considered. We exactly calculate the diffusivity in the nondispersive quasi-equilibrium transport regime for the 1D transport model and found that for slow decaying correlation functions the diffusivity becomes singular at some particular temperature higher than the temperature of the transition to the true non-equilibrium dispersive transport regime. It means that the diffusion becomes anomalous and does not follow the usual ∝ t 1/2 law. In such situation, the fully developed non-equilibrium regime emerges in two stages: first, at some temperature there is the transition from the normal to anomalous diffusion, and then at lower temperature the average velocity for the infinite medium goes to zero, thus indicating the development of the true dispersive regime. Validity of the Einstein relation is discussed for the situation where the diffusivity does exist. We provide also some arguments in favor of conservation of the major features of the new transition scenario in higher dimensions.

Nanotwinning and structural phase transition in CdS quantum dots

NASA Astrophysics Data System (ADS)

Kumar, Pragati; Saxena, Nupur; Chandra, Ramesh; Gupta, Vinay; Agarwal, Avinash; Kanjilal, Dinakar

2012-10-01

Nanotwin structures are observed in high-resolution transmission electron microscopy studies of cubic phase CdS quantum dots in powder form by chemical co-precipitation method. The deposition of thin films of nanocrystalline CdS is carried out on silicon, glass, and TEM grids keeping the substrates at room temperature (RT) and 200°C by pulsed laser ablation. These films are then subjected to thermal annealing at different temperatures. Glancing angle X-ray diffraction results confirm structural phase transitions after thermal annealing of films deposited at RT and 200°C. The variation of average particle size and ratio of intensities in Raman peaks I 2LO/ I 1LO with annealing temperature are studied. It is found that electron-phonon interaction is a function of temperature and particle size and is independent of the structure. Besides Raman modes LO, 2LO and 3LO of CdS at approximately 302, 603, and 903 cm-1 respectively, two extra Raman modes at approximately 390 and 690 cm-1 are studied for the first time. The green and orange emissions observed in photoluminescence are correlated with phase transition.

Nanotwinning and structural phase transition in CdS quantum dots.

PubMed

Kumar, Pragati; Saxena, Nupur; Chandra, Ramesh; Gupta, Vinay; Agarwal, Avinash; Kanjilal, Dinakar

2012-10-23

Nanotwin structures are observed in high-resolution transmission electron microscopy studies of cubic phase CdS quantum dots in powder form by chemical co-precipitation method. The deposition of thin films of nanocrystalline CdS is carried out on silicon, glass, and TEM grids keeping the substrates at room temperature (RT) and 200°C by pulsed laser ablation. These films are then subjected to thermal annealing at different temperatures. Glancing angle X-ray diffraction results confirm structural phase transitions after thermal annealing of films deposited at RT and 200°C. The variation of average particle size and ratio of intensities in Raman peaks I2LO/I1LO with annealing temperature are studied. It is found that electron-phonon interaction is a function of temperature and particle size and is independent of the structure. Besides Raman modes LO, 2LO and 3LO of CdS at approximately 302, 603, and 903 cm-1 respectively, two extra Raman modes at approximately 390 and 690 cm-1 are studied for the first time. The green and orange emissions observed in photoluminescence are correlated with phase transition.

Effects of temperature and dissolved oxygen on Se(IV) removal and Se(0) precipitation by Shewanella sp. HN-41.

PubMed

Lee, Ji-Hoon; Han, Jaehong; Choi, Heechul; Hur, Hor-Gil

2007-08-01

Facultative anaerobic Shewanella sp. strain HN-41 was able to utilize selenite (Se(IV)) as a sole electron acceptor for respiration in anaerobic condition, resulting in reduction of Se(IV) and then precipitation of elemental Se nano-sized spherical particles, which were identified using energy-dispersive X-ray spectroscopy and X-ray absorption near-edge structure spectroscopy. When the effects on Se(IV) reduction to elemental Se were studied by varying incubation temperatures and dissolved oxygen contents, Se(IV) reduction occurred more actively with higher removal rate of Se(IV) in aqueous phase and well-shaped spherical Se(0) nanoparticles were formed from the incubations under N(2) (100%) or N(2):O(2) (80%:20%) at 30 degrees C with average diameter values of 181+/-40 nm and 164+/-24 nm, respectively, while relatively less amounts of irregular-shaped Se(0) nanoparticles were produced with negligible amount of Se(IV) reduction and removal under 100% of O(2). The Se particle size distributions based on scanning electron microscopy also showed a general tendency towards decreased Se particle size as oxygen content increased, whereas the particle size seemed uncorrelated to the change in the incubation temperature. These results also suggest that the size-controlled biological Se(0) nanospheres production may be achieved simply by changing the culture conditions.

Polarimetric Scattering Database for Non-spherical Ice Particles at Microwave Wavelengths

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aydin, Kultegin; Verlinde, Johannes; Clothiaux, Eugene

A database containing polarimetric single-scattering properties of various types of ice particles at millimeter to centimeter wavelengths is presented. This database is complementary to earlier ones in that it contains complete (polarimetric) scattering property information for each ice particle - 44 plates, 30 columns, 405 branched planar crystals, 660 aggregates, and 640 conical graupel - and direction of incident radiation but is limited to four frequencies (W-, Ka-, Ku- and X-bands), does not include temperature dependencies of the single-scattering properties and does not include scattering properties averaged over randomly oriented ice particles. Rules for constructing the morphologies of ice particlesmore » from one database to the next often differ; consequently, analyses that incorporate all of the different databases will contain the most variability, while illuminating important differences between them.« less

Particle size studies to reveal crystallization mechanisms of the metal organic framework HKUST-1 during sonochemical synthesis.

PubMed

Armstrong, Mitchell R; Senthilnathan, Sethuraman; Balzer, Christopher J; Shan, Bohan; Chen, Liang; Mu, Bin

2017-01-01

Systematic studies of key operating parameters for the sonochemical synthesis of the metal organic framework (MOF) HKUST-1(also called CuBTC) were performed including reaction time, reactor volume, sonication amplitude, sonication tip size, solvent composition, and reactant concentrations analyzed through SEM particle size analysis. Trends in the particle size and size distributions show reproducible control of average particle sizes between 1 and 4μm. These results along with complementary studies in sonofragmentation and temperature control were conducted to compare these results to kinetic crystal growth models found in literature to develop a plausible hypothetical mechanism for ultrasound-assisted growth of metal-organic-frameworks composed of a competitive mechanism including constructive solid-on-solid (SOS) crystal growth and a deconstructive sonofragmentation. Copyright © 2016 Elsevier B.V. All rights reserved.

Preparation and characterization of Phase change material microcapsules by a core-shell-like emulsion polymerization method

NASA Astrophysics Data System (ADS)

Ding, Li-ming; Pei, Guang-ling

2015-07-01

Phase change material microcapsules (MicroPCMs) were synthesized by a coreshell-like emulsion polymerization method. Styrene and methylacrylic acid copolymer (PS- MAA) was used as a wall material, and paraffin was used as a core material in order to prepare spherical, high resistance and high enthalpy MicroPCMs. Scanning Electron Microscope (SEM), laser particle size analyzer, Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetry (TG) and Differential Scanning Calorimeter (DSC) were employed to characterize the MicroPCMs. The results indicated that the average particle size of MicroPCMs was 42.29 μm, and the content of paraffin within microcapsules was 57.6%. The melting temperature and crystallization temperature were 30.7°C and 25.2°C.The melting enthalpy and crystallization enthalpy were -84.1 J/g and 91.3 J/g, respectively.

Saccharification of bamboo carbohydrates for the production of ethanol

DOE Office of Scientific and Technical Information (OSTI.GOV)

De Menezes, T.J.B.; Azzini, A.; Dos Santos, C.L.M.

1983-04-01

Bamboo carbohydrates were hydrolyzed with commercial amylases and a mixture of fungal culture broths containing cellulolytic and hemicellulolytic enzymes. The effects of cooking temperature and the size of fiber particles were also investigated. It was found that the higher the cooking temperature, the higher the rate of sugar formation and the lower the viscosity of the slurry. Additions of cellulose and hemicellulose digesting enzymes increased the sugar yield and decreased the viscosity of both the cooked and noncooked slurries. A smaller size of particle appeared to favor the average saccharification rate. Although glucose, xylose, and cellobiose were present in themore » hydrolysates, only 50% of the total carbohydrate was digested, and 78.9% of this was converted to reducing sugars. The alcohol efficiency for the fermentation of cooked and noncooked mashes by Saccharomyces was about 85%.« less

Efficient production of ultrapure manganese oxides via electrodeposition.

PubMed

Cheney, Marcos A; Joo, Sang Woo; Banerjee, Arghya; Min, Bong-Ki

2012-08-01

A new process for the production of electrolytic amorphous nanomanganese oxides (EAMD) with uniform size and morphology is described. EAMD are produced for the first time by cathodic deposition from a basic aqueous solution of potassium permanganate at a constant temperature of 16°C. The synthesized materials are characterized by XRD, SEM, TEM, and HRTEM. The materials produced at 5.0 V at constant temperature are amorphous with homogeneous size and morphology with an average particle size around 20 nm, which appears to be much lesser than the previously reported anodic EAMD. A potentiostatic electrodeposition with much lesser deposition rate (with respect to previously reported anodic depositions) is considered to be the reason behind the very low and homogenous particle size distribution due to the lesser agglomeration of our as-synthesized nanoparticles. Copyright © 2012 Elsevier Inc. All rights reserved.

Thermo-responsive human α-elastin self-assembled nanoparticles for protein delivery.

PubMed

Kim, Jae Dong; Jung, Youn Jae; Woo, Chang Hee; Choi, Young Chan; Choi, Ji Suk; Cho, Yong Woo

2017-01-01

Self-assembled nanoparticles based on PEGylated human α-elastin were prepared as a potential vehicle for sustained protein delivery. The α-elastin was extracted from human adipose tissue and modified with methoxypolyethyleneglycol (mPEG) to control particle size and enhance the colloidal stability. The PEGylated human α-elastin showed sol-to-particle transition with a lower critical solution temperature (LCST) of 25°C-40°C in aqueous media. The PEGylated human α-elastin nanoparticles (PhENPs) showed a narrow size distribution with an average diameter of 330±33nm and were able to encapsulate significant amounts of insulin and bovine serum albumin (BSA) upon simple mixing at low temperature in water and subsequent heating to physiological temperature. The release profiles of insulin and BSA showed sustained release for 72h. Overall, the thermo-responsive self-assembled PhENPs provide a useful tool for a range of protein delivery and tissue engineering applications. Copyright © 2016 Elsevier B.V. All rights reserved.

Effect of oxidizer to fuel molar ratio on particle size and DC conductivity of CeO{sub 2} nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harish, B. M.; Rajeeva, M. P.; Naveen, C. S.

2016-05-06

Cerium oxide nanoparticles were synthesized by solution combustion method with varying the oxidizer (cerium nitrate hexa hydrate) to fuel (Glycine) molar ratio. The prepared samples were characterized by UV-visible spectrometer, X-ray diffractometer (XRD), Scanning electron microscope (SEM) and Energy dispersive X-Ray analysis (EDAX). XRD pattern reveals the formation of cubic fluorite structure of CeO{sub 2}. It was observed that finest crystallites were found at extreme fuel-deficient condition and it is good enough to produce favorable powder characteristics. The average crystallite size was found to be 14.46 nm to 21.57 nm. The temperature dependent dc conductivity was carried out using Keithleymore » source meter between the temperature range from 300 K to 573 K. From this study it was found that the conductivity increases with increase of temperature due to semiconducting behavior of CeO{sub 2} and it decreases with particle size due to increase in the energy band gap.« less

Effect of ultrasonic treatment and temperature on nanocrystalline TiO 2

NASA Astrophysics Data System (ADS)

Kim, D. H.; Ryu, H. W.; Moon, J. H.; Kim, J.

Nanocrystalline TiO 2 particles were precipitated from the ethanol solution of titanium isopropoxide (Ti(O- iPr) 4) and H 2O 2 by refluxing at 80 °C for 48 h. The obtained particles were filtered and dried at 100 °C for 12 h. The dried powder itself, the sample with heating at 400 °C, and the sample with ultrasonically treating were prepared to investigate the effects of post treatments on materials characteristics and electrochemical properties of nanocrystalline TiO 2. The X-ray diffraction patterns of all of the samples were fitted well to the anatase phase. The field emission-TEM image of as-prepared sample shows a uniform spherical morphology with 5 nm particle size and the sample heated at 400 °C shows slightly increased particle size of about 10 nm while maintaining spherical shape. The sample treated with ultrasonic for 5 h or more at room temperature shows high aspect ratio particle shape with an average diameter of 5 nm and a length of 20 nm. According to the results of the electrochemical testing, as-prepared sample, the sample heated at 400 °C for 3 h, and the sample treated with ultrasonic show initial capacities of 270, 310 and 340 mAh g -1, respectively.

Comparison of silver release predictions using PARFUME with results from the AGR-2 irradiation experiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Collin, Blaise P.; Demkowicz, Paul A.; Baldwin, Charles A.

2016-11-01

The PARFUME (PARticle FUel ModEl) code was used to predict silver release from tristructural isotropic (TRISO) coated fuel particles and compacts during the second irradiation experiment (AGR-2) of the Advanced Gas Reactor Fuel Development and Qualification program. The PARFUME model for the AGR-2 experiment used the fuel compact volume average temperature for each of the 559 days of irradiation to calculate the release of fission product silver from a representative particle for a select number of AGR-2 compacts and individual fuel particles containing either mixed uranium carbide/oxide (UCO) or 100% uranium dioxide (UO2) kernels. Post-irradiation examination (PIE) measurements were performedmore » to provide data on release of silver from these compacts and individual fuel particles. The available experimental fractional releases of silver were compared to their corresponding PARFUME predictions. Preliminary comparisons show that PARFUME under-predicts the PIE results in UCO compacts and is in reasonable agreement with experimental data for UO2 compacts. The accuracy of PARFUME predictions is impacted by the code limitations in the modeling of the temporal and spatial distributions of the temperature across the compacts. Nevertheless, the comparisons on silver release lie within the same order of magnitude.« less

Measurement of Ultrafine Particles and Other Air Pollutants Emitted by Cooking Activities

PubMed Central

Zhang, Qunfang; Gangupomu, Roja H.; Ramirez, David; Zhu, Yifang

2010-01-01

Cooking emissions show a strong dependence on cooking styles and parameters. Measurements of the average ultrafine particle (UFP) concentration, PM2.5 and black carbon concentrations emitted by cooking activities ranged from 1.34 × 104 to 6.04 × 105 particles/cm3, 10.0 to 230.9 μg/m3 and 0.1 to 0.8 μg/m3, respectively. Lower UFP concentrations were observed during boiling, while higher levels were emitted during frying. The highest UFP concentrations were observed when using a gas stove at high temperature with the kitchen exhaust fan turned off. The observed UFP profiles were similar in the kitchen and in another room, with a lag of approximately 10 min. PMID:20617057

Study of the preparation of NI-Mn-Zn ferrite using spent NI-MH and alkaline Zn-Mn batteries

NASA Astrophysics Data System (ADS)

Xi, Guoxi; Xi, Yuebin; Xu, Huidao; Wang, Lu

2016-01-01

Magnetic nanoparticles of Ni-Mn-Zn ferrite have been prepared by a sol-gel method making use of spent Ni-MH and Zn-Mn batteries as source materials. Characterization by X-ray diffraction was carried out to study the particle size. The presence of functional groups was identified by Fourier transform infrared spectroscopy. From studies by thermogravimetry and differential scanning calorimetry, crystallization occurred at temperatures above 560 °C. The magnetic properties of the final products were found to be directly influenced by the average particle size of the product. The Ms values increase and the Hc values decrease as the size of the Ni-Mn-Zn ferrite particles increases.

Rapid Solidification of Sn-Cu-Al Alloys for High-Reliability, Lead-Free Solder: Part I. Microstructural Characterization of Rapidly Solidified Solders

NASA Astrophysics Data System (ADS)

Reeve, Kathlene N.; Choquette, Stephanie M.; Anderson, Iver E.; Handwerker, Carol A.

2016-12-01

Particles of Cu x Al y in Sn-Cu-Al solders have previously been shown to nucleate the Cu6Sn5 phase during solidification. In this study, the number and size of Cu6Sn5 nucleation sites were controlled through the particle size refinement of Cu x Al y via rapid solidification processing and controlled cooling in a differential scanning calorimeter. Cooling rates spanning eight orders of magnitude were used to refine the average Cu x Al y and Cu6Sn5 particle sizes down to submicron ranges. The average particle sizes, particle size distributions, and morphologies in the microstructures were analyzed as a function of alloy composition and cooling rate. Deep etching of the samples revealed the three-dimensional microstructures and illuminated the epitaxial and morphological relationships between the Cu x Al y and Cu6Sn5 phases. Transitions in the Cu6Sn5 particle morphologies from faceted rods to nonfaceted, equiaxed particles were observed as a function of both cooling rate and composition. Initial solidification cooling rates within the range of 103 to 104 °C/s were found to be optimal for realizing particle size refinement and maintaining the Cu x Al y /Cu6Sn5 nucleant relationship. In addition, little evidence of the formation or decomposition of the ternary- β phase in the solidified alloys was noted. Solidification pathways omitting the formation of the ternary- β phase agreed well with observed room temperature microstructures.

Rapid Solidification of Sn-Cu-Al Alloys for High-Reliability, Lead-Free Solder: Part I. Microstructural Characterization of Rapidly Solidified Solders

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reeve, Kathlene N.; Choquette, Stephanie M.; Anderson, Iver E.

Particles of Cu x Al y in Sn-Cu-Al solders have previously been shown to nucleate the Cu 6Sn 5 phase during solidification. In this study, the number and size of Cu 6Sn 5 nucleation sites were controlled through the particle size refinement of Cu x Al y via rapid solidification processing and controlled cooling in a differential scanning calorimeter. Cooling rates spanning eight orders of magnitude were used to refine the average Cu x Al y and Cu 6Sn 5 particle sizes down to submicron ranges. The average particle sizes, particle size distributions, and morphologies in the microstructures were analyzedmore » as a function of alloy composition and cooling rate. Deep etching of the samples revealed the three-dimensional microstructures and illuminated the epitaxial and morphological relationships between the Cu x Al y and Cu 6Sn 5 phases. Transitions in the Cu 6Sn 5 particle morphologies from faceted rods to nonfaceted, equiaxed particles were observed as a function of both cooling rate and composition. Initial solidification cooling rates within the range of 10 3 to 10 4 °C/s were found to be optimal for realizing particle size refinement and maintaining the Cu x Al y /Cu 6Sn 5 nucleant relationship. In addition, little evidence of the formation or decomposition of the ternary-β phase in the solidified alloys was noted. As a result, solidification pathways omitting the formation of the ternary-β phase agreed well with observed room temperature microstructures.« less

Rapid Solidification of Sn-Cu-Al Alloys for High-Reliability, Lead-Free Solder: Part I. Microstructural Characterization of Rapidly Solidified Solders

DOE PAGES

Reeve, Kathlene N.; Choquette, Stephanie M.; Anderson, Iver E.; ...

2016-10-06

Particles of Cu x Al y in Sn-Cu-Al solders have previously been shown to nucleate the Cu 6Sn 5 phase during solidification. In this study, the number and size of Cu 6Sn 5 nucleation sites were controlled through the particle size refinement of Cu x Al y via rapid solidification processing and controlled cooling in a differential scanning calorimeter. Cooling rates spanning eight orders of magnitude were used to refine the average Cu x Al y and Cu 6Sn 5 particle sizes down to submicron ranges. The average particle sizes, particle size distributions, and morphologies in the microstructures were analyzedmore » as a function of alloy composition and cooling rate. Deep etching of the samples revealed the three-dimensional microstructures and illuminated the epitaxial and morphological relationships between the Cu x Al y and Cu 6Sn 5 phases. Transitions in the Cu 6Sn 5 particle morphologies from faceted rods to nonfaceted, equiaxed particles were observed as a function of both cooling rate and composition. Initial solidification cooling rates within the range of 10 3 to 10 4 °C/s were found to be optimal for realizing particle size refinement and maintaining the Cu x Al y /Cu 6Sn 5 nucleant relationship. In addition, little evidence of the formation or decomposition of the ternary-β phase in the solidified alloys was noted. As a result, solidification pathways omitting the formation of the ternary-β phase agreed well with observed room temperature microstructures.« less

Continual model of magnetic dynamics for antiferromagnetic particles in analyzing size effects on Morin transition in hematite nanoparticles

NASA Astrophysics Data System (ADS)

Mishchenko, I.; Chuev, M.; Kubrin, S.; Lastovina, T.; Polyakov, V.; Soldatov, A.

2018-05-01

Alternative explanation to the effect of disappearance of the Morin transition on hematite nanoparticles with their size decreasing is proposed basing on an idea of the predominant role of the shape anisotropy for nanosize particles. Three types of the magnetic structure of hematite nanoparticles with various sizes are found by Mössbauer spectroscopy: coexistence of the well-pronounced antiferromagnetic and weakly ferromagnetic phases for particles with average diameters of about 55 nm, non-uniform distribution of the magnetization axes which concentrate on the vicinity of the basal plane (111) for prolonged particles with cross sections of about 20 nm, and uniform distribution of the easy axes in regard to the crystalline directions for 3-nm particles. Description of the temperature evolution of experimental data within novel model of the magnetic dynamics for antiferromagnetic particles which accounts the exchange, relativistic, and anisotropy interactions is provided, and the structural as well as energy characteristics of the studied systems are reconstructed.

Electroscavenging and Inferred Effects on Precipitation Efficiency

NASA Astrophysics Data System (ADS)

Tinsley, B. A.

2002-12-01

The evaporation of charged droplets leaves charged aerosol particles that can act as cloud condensation nuclei and ice forming nuclei. New calculations of scavenging of such charged particles by droplets have been made, that now include the effects of inertia and variable particle density, and variable cloud altitudes ranging into the stratosphere. They show that the Greenfield Gap closes for particles of low density, or for high altitude clouds, or for a few hundred elementary charges on the particles. A few tens of elementary charges on the particles gives collision efficiencies typically an order of magnitude greater than that due to phoretic forces alone. The numerical integrations show that electroscavenging of ice forming nuclei leading to contact ice nucleation is competitive with deposition ice nucleation, for cloud top temperatures in the range 0§C to -15§C and droplet size distributions extending past 10-15 mm radius. This implies that for marine stratocumulus or nimbostratus clouds with tops just below freezing temperature, where precipitation is initiated by the Wegener-Bergeron-Findeisen process, the precipitation efficiency can be affected by the amount of charge on the ice-forming nuclei. This in turn depends on the extent of the (weak) electrification of the cloud. Similarly, electroscavenging of condensation nuclei can increase the average droplet size in successive cycles of cloud evaporation and formation, and can also affect precipitation efficiency.

Thermal Modeling of the Main Rings of Saturn through random distribution particle arrays and ray-tracing simulations

NASA Astrophysics Data System (ADS)

Flandes, Alberto; Spilker, Linda; Déau, Estelle

2016-10-01

Saturn's rings are a complex collection of icy particles with diameters from 1 m to few meters. Their natural window of study is the infrared because its temperatures are between 40K and 120K. The main driver of the temperature of these rings is the direct solar radiation as well as the solar radiation reflected off Saturn's atmosphere. The second most important energy source is the infrared radiation coming from Saturn itself. The study of the variations of temperatures of the rings, or, in general, their thermal behavior, may provide important information on their composition, their structure and their dynamics. Models that consider these and other energy sources are able to explain, to a first approximation, the observed temperature variations of the rings. The challenge for these models is to accurately describe the variation of illumination on the rings, i. e., how the illuminated and non-illuminated regions of the ring particles change at the different observation geometries. This shadowing mainly depends on the optical depth, as well as the general structure of the rings.In this work, We show a semi-analytical model that considers the main energy sources of the rings and their average properties (e.g., optical depth, particle size range and vertical distribution). In order to deal with the shadowing at specific geometries, the model uses the ray-tracing technique. The goal is to describe the ring temperatures observed by the Composite Infrared Spectrometer, CIRS, onboard the Cassini spacecraft, which is in orbit around Saturn since 2004. So far, the model is able to reproduce some of the general features of specific regions of the A, B and C rings.

Characterization of particulate matter from diesel passenger cars tested on chassis dynamometers.

PubMed

Jung, Sungwoon; Lim, Jaehyun; Kwon, Sangil; Jeon, Sangwoo; Kim, Jeongsoo; Lee, Jongtae; Kim, Sunmoon

2017-04-01

Emission characterization of particle number as well as particle mass from three diesel passenger cars equipped with diesel particulate filter (DPF), diesel oxidation catalyst (DOC) and exhaust gas recirculation (EGR) under the vehicle driving cycles and regulatory cycle. Total particle number emissions (PNEs) decreased gradually during speed-up of vehicle from 17.3 to 97.3km/hr. As the average vehicle speed increases, the size-segregated peak of particle number concentration shifts to smaller size ranges of particles. The correlation analysis with various particulate components such as particle number concentration (PNC), ultrafine particle number concentration (UFPNC) and particulate matter (PM) mass was conducted to compare gaseous compounds (CO, CO 2 , HC and NO x ). The UFPNC and PM were not only emitted highly in Seoul during severe traffic jam conditions, but also have good correlation with hydrocarbons and NO x influencing high potential on secondary aerosol generation. The effect of the dilution temperature on total PNC under the New European Driving Cycle (NEDC), was slightly higher than the dilution ratio. In addition, the nuclei mode (D P : ≤13nm) was confirmed to be more sensitive to the dilution temperature rather than other particle size ranges. Comparison with particle composition between vehicle speed cycles and regulatory cycle showed that sulfate was slightly increased at regulatory cycle, while other components were relatively similar. During cold start test, semivolatile nucleation particles were increased due to effect of cold environment. Research on particle formation dependent on dilution conditions of diesel passenger cars under the NEDC is important to verify impact on vehicular traffic and secondary aerosol formation in Seoul. Copyright © 2016. Published by Elsevier B.V.

Synthesis of Nanometric-Sized Barium Titanate Powders Using Acetylacetone as the Chelating Agent in a Sol-Precipitation Process

NASA Astrophysics Data System (ADS)

Hung, Kun Ming; Hsieh, Ching Shieh; Yang, Wein Duo; Tsai, Hui Ju

2007-03-01

Nanometric-sized barium titanate powders were prepared by using titanium isopropoxid as the raw material and acetylacetone as a chelating agent, in a strong alkaline solution (pH > 13) through the sol-precipitation method. The preparatory variables affect the extent of cross-linking in the structure, change the mode of condensation of the gels, and even control the particle size of the powder. The reaction rate of forming powder, at a higher temperature such as 100°C and more water content (the molar ratio of water to titanium isopropoxide is 25) or fewer acetylacetone (the molar ratio of acetylacetone to titanium isopropoxide is 1), is rapid and the particle size formed is finer at 60 80 nm. On the contrary, that of forming powder, at lower temperature (40°C) and less water content (molar ratio of water/titanium isopropoxide = 5) or higher acetylacetone (acetylacetone/titanium isopropoxide = 7), is slow and the particle size of the powder is larger. The optimal preparatory conditions were obtained by using the experimental statistical method; as a result, nanometric-sized BaTiO3 powder with an average particle size of about 50 nm was prepared.

Synthesis of thoria nano-particles at low temperature through base electrogeneration on steel 316L surface: Effect of current density

NASA Astrophysics Data System (ADS)

Yousefi, Taher; Torab-Mostaedi, Meisam; Mobtaker, Hossein Ghasemi; Keshtkar, Ali Reza

2016-10-01

The strategy developed in this study, offers significant advantages (simplicity and cleanness of method and also a product purity and new morphology of the product) over the conventional routes for the synthesis of ThO2 nanostructure. The effect of current density on morphology was studied. The synthesized powder was characterized by means of Powder X-ray Diffraction (PXRD), Transmission Electron Microscopy (TEM, Phillips EM 2085) Brunauer-Emmett-Teller (BET) and Fourier Transform Infrared (FT-IR) spectroscopy. The results show that the current density has a great effect on the morphology of the samples. The average size of the particles decreases as the applied current density increases and the average size of the samples decreases from 50 to 15 nm when the current density increases from 2 to 5 mA cm-2.

Improved synthesis of fine zinc borate particles using seed crystals

NASA Astrophysics Data System (ADS)

Gürhan, Deniz; Çakal, Gaye Ö.; Eroğlu, İnci; Özkar, Saim

2009-03-01

Zinc borate is a flame retardant additive used in polymers, wood applications and textile products. There are different types of zinc borate having different chemical compositions and structures. In this study, the production of zinc borate having the molecular formula of 2ZnO·3B 2O 3·3.5H 2O was reexamined by studying the effects of reaction parameters on the properties of product as well as the reaction kinetics. Production of zinc borate from the reaction of boric acid and zinc oxide in the presence of seed crystals was performed in a continuously stirred, temperature-controlled batch reactor having a volume of 1.5 L. Samples taken in regular time intervals during the experiments were analyzed for the concentration of zinc oxide and boron oxide in the solid as well as for the conversion of zinc oxide to zinc borate versus time. The zinc borate production reaction was fit to the logistic model. The reaction rate, reaction completion time, composition and particle size distribution of zinc borate product were determined by varying the following parameters: the boric acid to zinc oxide ratio (H 3BO 3:ZnO=3:1, 3.5:1, 5:1 and 7:1), the particle size of zinc oxide (10 and 25 μm), stirring rate (275, 400, 800 and 1600 rpm), temperature (75, 85 and 95 °C) and the size of seed crystals (10 and 2 μm). The products were also analyzed for particle size distribution. The experimental results showed that the reaction rate increases with the increase in H 3BO 3:ZnO ratio, particle size of zinc oxide, stirring rate and temperature. Concomitantly, the reaction completion time is decreased by increasing the H 3BO 3:ZnO ratio, stirring rate and temperature. The average particle sizes of the zinc borate products are in the range 4.3-16.6 μm (wet dispersion analysis).

Determination of octanol-air partition coefficients and supercooled liquid vapor pressures of PAHs as a function of temperature: Application to gas-particle partitioning in an urban atmosphere

NASA Astrophysics Data System (ADS)

Odabasi, Mustafa; Cetin, Eylem; Sofuoglu, Aysun

Octanol-air partition coefficients ( KOA) for 14 polycyclic aromatic hydrocarbons (PAHs) were determined as a function of temperature using the gas chromatographic retention time method. log KOA values at 25° ranged over six orders of magnitude, between 6.34 (acenaphthylene) and 12.59 (dibenz[ a,h]anthracene). The determined KOA values were within factor of 0.7 (dibenz[ a,h]anthracene) to 15.1 (benz[ a]anthracene) of values calculated as the ratio of octanol-water partition coefficient to dimensionless Henry's law constant. Supercooled liquid vapor pressures ( PL) of 13 PAHs were also determined using the gas chromatographic retention time technique. Activity coefficients in octanol calculated using KOA and PL ranged between 3.2 and 6.2 indicating near-ideal solution behavior. Atmospheric concentrations measured in this study in Izmir, Turkey were used to investigate the partitioning of PAHs between particle and gas-phases. Experimental gas-particle partition coefficients ( Kp) were compared to the predictions of KOA absorption and KSA (soot-air partition coefficient) models. Octanol-based absorptive partitioning model predicted lower partition coefficients especially for relatively volatile PAHs. Ratios of measured/modeled partition coefficients ranged between 1.1 and 15.5 (4.5±6.0, average±SD) for KOA model. KSA model predictions were relatively better and measured to modeled ratios ranged between 0.6 and 5.6 (2.3±2.7, average±SD).

Pseudocapacitance of Co doped NiO nanoparticles and its room temperature ferromagnetic behavior

NASA Astrophysics Data System (ADS)

Bharathy, G.; Raji, P.

2018-02-01

Co doped NiO nanoparticles CoxNi1-xO (x = 0.0, 0.1, 0.2, 0.3, 0.4) were synthesized by the Sol-gel technique. The impact of Co doping concentration on structural, functional and magnetic properties of NiO nanoparticles was analyzed by X-ray diffraction (XRD), FESEM with EDAX, FTIR and VSM. The average crystallite size was measured to be 34 nm and 11 nm for NiO and Co doped NiO nanoparticles respectively. FESEM reveals that particles are spherical in shape with average size around 30 nm. The elemental composition was analyzed by EDAX. FTIR spectra reveal the existence of NiO peaks in the prepared samples, room temperature ferromagnetism was observed for pure and Co doped NiO nanoparticles by VSM. Pure NiO particles shows ferromagnetic behavior with low coercivity and it increases gradually when doping ratio increases. Higher saturation magnetization was obtained for the sample 0.1 M of Co doped NiO nanoparticle as 22.09 emu/gm. An attempt has been made to study the pseudocapacitance behavior of pure and Co doped NiO nano particles in various scan rates. Electrochemical studies show that 0.4 M Co doped sample gives better charge storage capacity with maximum specific capacitance of 379 Fg-1 at a scan rate of 20 mVs-1. It reveals that it is a promising electrode material for super capacitor applications.

Chemical composition and source of fine and nanoparticles from recent direct injection gasoline passenger cars: Effects of fuel and ambient temperature

NASA Astrophysics Data System (ADS)

Fushimi, Akihiro; Kondo, Yoshinori; Kobayashi, Shinji; Fujitani, Yuji; Saitoh, Katsumi; Takami, Akinori; Tanabe, Kiyoshi

2016-01-01

Particle number, mass, and chemical compositions (i.e., elemental carbon (EC), organic carbon (OC), elements, ions, and organic species) of fine particles emitted from four of the recent direct injection spark ignition (DISI) gasoline passenger cars and a port fuel injection (PFI) gasoline passenger car were measured under Japanese official transient mode (JC08 mode). Total carbon (TC = EC + OC) dominated the particulate mass (90% on average). EC dominated the TC for both hot and cold start conditions. The EC/TC ratios were 0.72 for PFI and 0.88-1.0 (average = 0.92) for DISI vehicles. A size-resolved chemical analysis of a DISI car revealed that the major organic components were the C20-C28 hydrocarbons for both the accumulation-mode particles and nanoparticles. Contribution of engine oil was estimated to be 10-30% for organics and the sum of the measured elements. The remaining major fraction likely originated from gasoline fuel. Therefore, it is suggested that soot (EC) also mainly originated from the gasoline. In experiments using four fuels at three ambient temperatures, the emission factors of particulate mass were consistently higher with regular gasoline than with premium gasoline. This result suggest that the high content of less-volatile compounds in fuel increase particulate emissions. These results suggest that focusing on reducing fuel-derived EC in the production process of new cars would effectively reduce particulate emission from DISI cars.

Fabrication and characterization of fine ceramic based on alumina, bentonite, and glass bead

NASA Astrophysics Data System (ADS)

Sebayang, P.; Nurdina; Simbolon, S.; Kurniawan, C.; Yunus, M.; Setiadi, E. A.; Sitorus, Z.

2018-03-01

Fabrication of fine ceramics based on alumina, bentonite and glass bead has been carried out by powder metallurgy. The preparation of powder has been performed using High Energy Milling (HEM) with wet milling process and using toluene as medium for 2 hours. The powder milling result was dried in oven at 100 °C for 24 hours. After that, the powder was compacted into pellet by using hydraulic press with 80 kgf/cm2 pressure at room temperature. Then, the pellet was sintered at 900 °C for 4 hours. Materials characterization such as physical properties (true density, bulk density, porosity, and water absorption), average particle diameter, hardness, microstructure and phase were measured by Archimedes method, Particle Size Analyzer (PSA), Hardness Vickers (HV), Scanning Electron Microscope (SEM-EDX) and X-Ray Diffraction (XRD). From the result, the optimum condition is sample D (with addition of 30 wt.% γ-Al2O3) with sintering temperature of 900 °C for 4 hours. At this condition, these properties were measured: average particle diameter of 4.27 μm, true density of 2.32 g/cm3, porosity of 5.57%, water absorption of 2.46%, bulk density of 2.39 g/cm3, and hardness of 632 HV. The fine ceramic has four phases with albite (Al2NaO8Si3) and quartz (SiO2) as dominant phases and corundum (Al2O3) and nepheline (AlNaO4Si) as minor phases.

Study of heat generation and cutting force according to minimization of grain size (500 nm to 180 nm) of WC ball endmill using FEM

NASA Astrophysics Data System (ADS)

Byeon, J. H.; Ahmed, F.; Ko, T. J.; lee, D. K.; Kim, J. S.

2018-03-01

As the industry develops, miniaturization and refinement of products are important issues. Precise machining is required for cutting, which is a typical method of machining a product. The factor determining the workability of the cutting process is the material of the tool. Tool materials include carbon tool steel, alloy tool steel, high-speed steel, cemented carbide, and ceramics. In the case of a carbide material, the smaller the particle size, the better the mechanical properties with higher hardness, strength and toughness. The specific heat, density, and thermal diffusivity are also changed through finer particle size of the material. In this study, finite element analysis was performed to investigate the change of heat generation and cutting power depending on the physical properties (specific heat, density, thermal diffusivity) of tool material. The thermal conductivity coefficient was obtained by measuring the thermal diffusivity, specific heat, and density of the material (180 nm) in which the particle size was finer and the particle material (0.05 μm) in the conventional size. The coefficient of thermal conductivity was calculated as 61.33 for 180nm class material and 46.13 for 0.05μm class material. As a result of finite element analysis using this value, the average temperature of exothermic heat of micronized particle material (180nm) was 532.75 °C and the temperature of existing material (0.05μm) was 572.75 °C. Cutting power was also compared but not significant. Therefore, if the thermal conductivity is increased through particle refinement, the surface power can be improved and the tool life can be prolonged by lowering the temperature generated in the tool during machining without giving a great influence to the cutting power.

Magnetic study of Co-doped CdSe nanoparticles

NASA Astrophysics Data System (ADS)

Das, Sayantani; Banerjee, Sourish; Sinha, T. P.

2018-04-01

Cobalt (2 %, 5 % and 10 %) doped cadmium selenide (CdSe) nanoparticles have been synthesized by soft chemical route. The XRD pattern shows the cubic structure of the sample. Crystallization temperature of the samples is calculated using differential scanning calorimeter. The average particle size of all the samples is found to be ˜ 25 nm. Field dependent (M-H) and temperature dependent (M-T) magnetization explains the presence of ferromagnetic components in the samples at room temperature and low temperature. In order to estimate the antiferromagnetic coupling among the doped TM atoms, an M-T measurement at 500 Oe has been carried out under zero field cooled (ZFC) and field cooled (FC) conditions and Curie-Weiss temperature θ of the samples has been estimated from 1/χ vs T plots.

Langmuir probe diagnostics of an atmospheric pressure, vortex-stabilized nitrogen plasma jet

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prevosto, L.; Mancinelli, B. R.; Kelly, H.

Langmuir probe measurements in an atmospheric pressure direct current (dc) plasma jet are reported. Sweeping probes were used. The experiment was carried out using a dc non-transferred arc torch with a rod-type cathode and an anode of 5 mm diameter. The torch was operated at a nominal power level of 15 kW with a nitrogen flow rate of 25 Nl min{sup -1}. A flat ion saturation region was found in the current-voltage curve of the probe. The ion saturation current to a cylindrical probe in a high-pressure non local thermal equilibrium (LTE) plasma was modeled. Thermal effects and ionization/recombination processesmore » inside the probe perturbed region were taken into account. Averaged radial profiles of the electron and heavy particle temperatures as well as the electron density were obtained. An electron temperature around 11 000 K, a heavy particle temperature around 9500 K and an electron density of about 4 Multiplication-Sign 10{sup 22} m{sup -3}, were found at the jet centre at 3.5 mm downstream from the torch exit. Large deviations from kinetic equilibrium were found throughout the plasma jet. The electron and heavy particle temperature profiles showed good agreement with those reported in the literature by using spectroscopic techniques. It was also found that the temperature radial profile based on LTE was very close to that of the electrons. The calculations have shown that this method is particularly useful for studying spraying-type plasma jets characterized by electron temperatures in the range 9000-14 000 K.« less

Revisiting the definition of the electronic chemical potential, chemical hardness, and softness at finite temperatures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Franco-Pérez, Marco, E-mail: qimfranco@hotmail.com, E-mail: jlgm@xanum.uam.mx; Department of Chemistry, McMaster University, Hamilton, Ontario L8S 4M1; Gázquez, José L., E-mail: qimfranco@hotmail.com, E-mail: jlgm@xanum.uam.mx

We extend the definition of the electronic chemical potential (μ{sub e}) and chemical hardness (η{sub e}) to finite temperatures by considering a reactive chemical species as a true open system to the exchange of electrons, working exclusively within the framework of the grand canonical ensemble. As in the zero temperature derivation of these descriptors, the response of a chemical reagent to electron-transfer is determined by the response of the (average) electronic energy of the system, and not by intrinsic thermodynamic properties like the chemical potential of the electron-reservoir which is, in general, different from the electronic chemical potential, μ{sub e}.more » Although the dependence of the electronic energy on electron number qualitatively resembles the piecewise-continuous straight-line profile for low electronic temperatures (up to ca. 5000 K), the introduction of the temperature as a free variable smoothens this profile, so that derivatives (of all orders) of the average electronic energy with respect to the average electron number exist and can be evaluated analytically. Assuming a three-state ensemble, well-known results for the electronic chemical potential at negative (−I), positive (−A), and zero values of the fractional charge (−(I + A)/2) are recovered. Similarly, in the zero temperature limit, the chemical hardness is formally expressed as a Dirac delta function in the particle number and satisfies the well-known reciprocity relation with the global softness.« less

Optical, electrical and magnetic properties of nanostructured Mn3O4 synthesized through a facile chemical route

NASA Astrophysics Data System (ADS)

Bose, Vipin C.; Biju, V.

2015-02-01

Nanostructured Mn3O4 sample with an average crystallite size of ˜15 nm is synthesized via the reduction of potassium permanganate using hydrazine. The average particle size obtained from the Transmission Electron Microscopy analysis is in good agreement with the average crystallite size estimated from X-ray diffraction analysis. The presence of Mn4+ ions at the octahedral sites is inferred from the results of Raman, UV-visible absorption and X-ray photoelectron spectroscopy analyzes. DC electrical conductivity of the sample in the temperature range 313-423 K, is about five orders of magnitude larger than that reported for single crystalline Mn3O4 sample. The dominant conduction mechanism is identified to be of the polaronic hopping of holes between cations in the octahedral sites. The zero field cooled and field cooled magnetization of the sample is studied in the range 20-300 K. The Curie temperature for the sample is about 45 K, below which the sample is ferrimagnetic. A blocking temperature of 35 K is observed in the field cooled curve. It is observed that the sample shows hysteresis at temperatures below the Curie temperature with no saturation, even at an applied field (20 kOe). The presence of an ordered core and disordered surface of spin arrangements is observed from the magnetization studies. Above the Curie temperature, the sample shows linear dependence of magnetization on applied field with no hysteresis characteristic of paramagnetic phase.

A comparative study on the frequency effects of the electrical characteristics of the pulsed dielectric barrier discharge in He/O{sub 2} and in Ar/O{sub 2} at atmospheric pressure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pan, Guangsheng; Tan, Zhenyu, E-mail: tzy@sdu.edu.cn; Pan, Jie

In this work, a comparative study on the frequency effects of the electrical characteristics of the pulsed dielectric barrier discharges in He/O{sub 2} and in Ar/O{sub 2} at atmospheric pressure has been performed by means of the numerical simulation based on a 1-D fluid model at frequencies below 100 kHz. The frequency dependences of the characteristic quantities of the discharges in the two gases have been systematically calculated and analyzed under the oxygen concentrations below 2%. The characteristic quantities include the discharge current density, the averaged electron density, the electric field, and the averaged electron temperature. Especially, the frequency effects onmore » the averaged particle densities of the reactive species have also been calculated. This work gives the following significant results. For the two gases, there are two bipolar discharges in one period of applied voltage pulse under the considered frequency range and oxygen concentrations, as occurred in the pure noble gases. The frequency affects the two discharges in He/O{sub 2}, but in Ar/O{sub 2}, it induces a strong effect only on the first discharge. For the first discharge in each gas, there is a characteristic frequency at which the characteristic quantities reach their respective minimum, and this frequency appears earlier for Ar/O{sub 2}. For the second discharge in Ar/O{sub 2}, the averaged electron density presents a slight variation with the frequency. In addition, the discharge in Ar/O{sub 2} is strong and the averaged electron temperature is low, compared to those in He/O{sub 2.} The total averaged particle density of the reactive species in Ar/O{sub 2} is larger than those in He/O{sub 2} by about one order of magnitude.« less

Dry deposition and soil-air gas exchange of polychlorinated biphenyls (PCBs) in an industrial area.

PubMed

Bozlaker, Ayse; Odabasi, Mustafa; Muezzinoglu, Aysen

2008-12-01

Ambient air and dry deposition, and soil samples were collected at the Aliaga industrial site in Izmir, Turkey. Atmospheric total (particle+gas) Sigma(41)-PCB concentrations were higher in summer (3370+/-1617 pg m(-3), average+SD) than in winter (1164+/-618 pg m(-3)), probably due to increased volatilization with temperature. Average particulate Sigma(41)-PCBs dry deposition fluxes were 349+/-183 and 469+/-328 ng m(-2) day(-1) in summer and winter, respectively. Overall average particulate deposition velocity was 5.5+/-3.5 cm s(-1). The spatial distribution of Sigma(41)-PCB soil concentrations (n=48) showed that the iron-steel plants, ship dismantling facilities, refinery and petrochemicals complex are the major sources in the area. Calculated air-soil exchange fluxes indicated that the contaminated soil is a secondary source to the atmosphere for lighter PCBs and as a sink for heavier ones. Comparable magnitude of gas exchange and dry particle deposition fluxes indicated that both mechanisms are equally important for PCB movement between air and soil in Aliaga.

Quantum Szilard engines with arbitrary spin.

PubMed

Zhuang, Zekun; Liang, Shi-Dong

2014-11-01

The quantum Szilard engine (QSZE) is a conceptual quantum engine for understanding the fundamental physics of quantum thermodynamics and information physics. We generalize the QSZE to an arbitrary spin case, i.e., a spin QSZE (SQSZE), and we systematically study the basic physical properties of both fermion and boson SQSZEs in a low-temperature approximation. We give the analytic formulation of the total work. For the fermion SQSZE, the work might be absorbed from the environment, and the change rate of the work with temperature exhibits periodicity and even-odd oscillation, which is a generalization of a spinless QSZE. It is interesting that the average absorbed work oscillates regularly and periodically in a large-number limit, which implies that the average absorbed work in a fermion SQSZE is neither an intensive quantity nor an extensive quantity. The phase diagrams of both fermion and boson SQSZEs give the SQSZE doing positive or negative work in the parameter space of the temperature and the particle number of the system, but they have different behaviors because the spin degrees of the fermion and the boson play different roles in their configuration states and corresponding statistical properties. The critical temperature of phase transition depends sensitively on the particle number. By using Landauer's erasure principle, we give the erasure work in a thermodynamic cycle, and we define an efficiency (we refer to it as information-work efficiency) to measure the engine's ability of utilizing information to extract work. We also give the conditions under which the maximum extracted work and highest information-work efficiencies for fermion and boson SQSZEs can be achieved.

Development and Characterization of Chitosan Cross-Linked With Tripolyphosphate as a Sustained Release Agent in Tablets, Part I: Design of Experiments and Optimization.

PubMed

Pinto, Colin A; Saripella, Kalyan K; Loka, Nikhil C; Neau, Steven H

2018-04-01

Certain issues with the use of particles of chitosan (Ch) cross-linked with tripolyphosphate (TPP) in sustained release formulations include inefficient drug loading, burst drug release, and incomplete drug release. Acetaminophen was added to Ch:TPP particles to test for advantages of drug addition extragranularly over drug addition made during cross-linking. The influences of Ch concentration, Ch:TPP ratio, temperature, ionic strength, and pH were assessed. Design of experiments allowed identification of factors and 2-factor interactions that have significant effects on average particle size and size distribution, yield, zeta potential, and true density of the particles, as well as drug release from the directly compressed tablets. Statistical model equations directed production of a control batch that minimized span, maximized yield, and targeted a t 50 of 90 min (sample A); sample B that differed by targeting a t 50 of 240-300 min to provide sustained release; and sample C that differed from sample B by maximizing span. Sample B maximized yield and provided its targeted t 50 and the smallest average particle size, with the higher zeta potential and the lower span of samples B and C. Extragranular addition of a drug to Ch:TPP particles achieved 100% drug loading, eliminated a burst drug release, and can accomplish complete drug release. Copyright © 2018 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Microstructural changes in steel 10Kh9V2MFBR during creep for 40000 hours at 600°C

NASA Astrophysics Data System (ADS)

Fedoseeva, A. E.; Kozlov, P. A.; Dudko, V. A.; Skorobogatykh, V. N.; Shchenkova, I. A.; Kaibyshev, R. O.

2015-10-01

In this work, we have investigated microstructural changes in steel 10Kh9V2MFBR (analog of P02 steel) after long-term creep tests at a temperature of 600°C under an initial stress of 137 MPa. Time to rupture was found to be more than 40000 h. It has been established that, in the zone of grips and in the neck region of the sample, the size of the particles of the M 23C6 carbides increases from 85 nm to 152 nm and 182 nm, respectively. In addition, large particles of the Laves phase with an average size of 295 nm are separated. The particles of these phases are located along high-angle boundaries. During prolonged aging and creep, the transformation of the M(C,N) particles enriched in V into the Z phase occurs. The average size of particles of the Z phase after prolonged ageing was 48 nm; after creep, it reached 97 nm. The size of M(C,N) particles enriched by Nb increases from 26 nm after tempering to 55 nm after prolonged aging and creep. It has been established that, in spite of an increase in the transverse size of the laths of tempered martensite from 0.4 to 0.9 µm in the neck of the sample, the misorientation of the lath boundaries does not increase. No recrystallization processes were found to develop in the steel during creep.

Numerical study into the morphology and formation mechanisms of three-dimensional particle structures in vibrated cylindrical cavities with various heating conditions

NASA Astrophysics Data System (ADS)

Lappa, Marcello

2016-10-01

The present analysis extends the author's earlier work [Lappa, Phys. Fluids 26, 093301 (2014), 10.1063/1.4893078] on the properties of patterns formed by the spontaneous accumulation and ordering of solid particles in certain types of flow. It is shown that under certain conditions, when subjected to vibrations to induce natural flow, nonisothermal fluids with dispersed solid particles are characterized by intervals of solid-pattern-forming behavior due to particle rearrangements preceded by intervals in which no recognizable structures of solid matter can be detected. The dynamics of these systems are highly nonlinear in nature. Because this family of particle attractors is known to exhibit strong sensitivity to the symmetry properties of the considered vibrated system and related geometrical constraints, the present study attempts to clarify the related dynamics in a geometry with curved walls (cylindrical enclosure). In particular, by assuming vibrations always directed perpendicularly to the imposed temperature gradient, we show that the morphology, spatial extension (percentage of physical volume occupied), separation (spatial distance), and mechanisms responsible for the formation of the resulting particle structures change significantly according to whether the temperature gradient is parallel or perpendicular to the symmetry axis of the cylinder. This indicates that the physics is not invariant with respect to 90° rotations in space of the specific forcing considered (direction of the imposed temperature gradient and associated perpendicular vibrations). Additional insights into the problem are obtained by assessing separately the influence played by the time-averaged (mean) and oscillatory effects. According to the numerical results, the intriguing diversity of particle agglomerates results from the different role or importance played by (curved or straight) boundaries in constraining particles and from the different structure and topology of the resulting macroscopic (large-scale) thermovibrational flow oscillating in time at the same frequency of the imposed vibrations.

Silver particle monolayers — Formation, stability, applications.

PubMed

Oćwieja, Magdalena; Adamczyk, Zbigniew; Morga, Maria; Kubiak, Katarzyna

2015-08-01

The formation of silver particle monolayers at solid substrates in self-assembly processes is thoroughly reviewed. Initially, various silver nanoparticle synthesis routes are discussed with the emphasis focused on the chemical reduction in aqueous media. Subsequently, the main experimental methods aimed at bulk suspension characterization are critically reviewed by pointing out their advantages and limitations. Also, various methods enabling the in situ studies of particle deposition and release kinetics, especially the streaming potential method are discussed. In the next section, experimental data are invoked illustrating the most important features of particle monolayer formation, in particular, the role of bulk suspension concentration, particle size, ionic strength, temperature and pH. Afterward, the stability of monolayers and particle release kinetics are extensively discussed. The results obtained by the ex situ AFM/SEM imaging of particles are compared with the in situ streaming potential measurements. An equivalency of both methods is demonstrated, especially in respect to the binding energy determination. It is shown that these experimental results can be adequately interpreted in terms of the hybrid theoretical approach that combines the bulk transport step with the surface blocking effects derived from the random sequential adsorption model. It is also concluded that the particle release kinetics is governed by the discrete electrostatic interactions among ion pairs on particle and substrate surfaces. The classical theories based on the mean-field (averaged) zeta potential concept proved inadequate. Using the ion pair concept the minor dependence of the binding energy on particle size, ionic strength, pH and temperature is properly explained. The final sections of this review are devoted to the application of silver nanoparticles and their monolayers in medicine, analytical chemistry and catalysis. Copyright © 2014 Elsevier B.V. All rights reserved.

Ice Particle Analysis of the Honeywell AL502 Engine Booster

NASA Technical Reports Server (NTRS)

Bidwell, Colin S.; Rigby, David L.

2015-01-01

A flow and ice particle trajectory analysis was performed for the booster of the Honeywell ALF502 engine. The analysis focused on two closely related conditions one of which produced an icing event and another which did not during testing of the ALF502 engine in the Propulsion Systems Lab (PSL) at NASA Glenn Research Center. The flow analysis was generated using the NASA Glenn GlennHT flow solver and the particle analysis was generated using the NASA Glenn LEWICE3D v3.63 ice accretion software. The inflow conditions for the two conditions were similar with the main differences being that the condition that produced the icing event was 6.8 K colder than the non-icing event case and the inflow ice water content (IWC) for the non-icing event case was 50% less than for the icing event case. The particle analysis, which considered sublimation, evaporation and phase change, was generated for a 5 micron ice particle with a sticky impact model and for a 24 micron median volume diameter (MVD), 7 bin ice particle distribution with a supercooled large droplet (SLD) splash model used to simulate ice particle breakup. The particle analysis did not consider the effect of the runback and re-impingement of water resulting from the heated spinner and anti-icing system. The results from the analysis showed that the amount of impingement for the components were similar for the same particle size and impact model for the icing and non-icing event conditions. This was attributed to the similar aerodynamic conditions in the booster for the two cases. The particle temperature and melt fraction were higher at the same location and particle size for the non-icing event than for the icing event case due to the higher incoming inflow temperature for the non-event case. The 5 micron ice particle case produced higher impact temperatures and higher melt fractions on the components downstream of the fan than the 24 micron MVD case because the average particle size generated by the particle breakup was larger than 5 microns which yielded less warming and melting. The analysis also showed that the melt fraction and wet bulb temperature icing criterion developed during tests in the Research Altitude Test Facility (RATFac) at the National Research Council (NRC) of Canada were useful in predicting icing events in the ALF502 engine. The development of an ice particle impact model which includes the effects of particle breakup, phase change, and surface state is necessary to further improve the prediction of ice particle transport with phase change through turbomachinery.

Combustion Synthesis of Sm0.5Sr0.5CoO3-x and La0.6Sr0.4CoO3-x Nanopowders for Solid Oxide Fuel Cell Cathodes

NASA Technical Reports Server (NTRS)

Bansal, Narottam P.; Zhong, zhimin

2005-01-01

Nanopowders of Sm0.5Sr0.5CoO(3-x) (SSC) and La0.6Sr0.4CoO(3-x) (LSC) compositions, which are being investigated as cathode materials for intermediate temperature solid oxide fuel cells, were synthesized by a solution-combustion method using metal nitrates and glycine as fuel. Development of crystalline phases in the as-synthesized powders after heat treatments at various temperatures was monitored by x-ray diffraction. Perovskite phase in LSC formed more readily than in SSC. Single phase perovskites were obtained after heat treatment of the combustion synthesized LSC and SSC powders at 1000 and 1200 C, respectively. The as-synthesized powders had an average particle size of 12 nm as determined from x-ray line broadening analysis using the Scherrer equation. Average grain size of the powders increased with increase in calcination temperature. Morphological analysis of the powders calcined at various temperatures was done by scanning electron microscopy.

The Detached Haze Layer in Titan's Mesosphere

NASA Astrophysics Data System (ADS)

Lavvas, P.; Yelle, R. V.; Vuitton, V.

2008-12-01

The Cassini observations reveal the presence of a detached haze layer in Titan's mesosphere at an altitude of 520 km, well above the stratosphere. Observations of scattered light made by the Imaging Science Subsystem (ISS) reveal a clearly defined layer encircling low and mid-latitude regions. The aerosol layer is also detected in stellar occultation measurements of UV extinction by the UltraViolet Imaging Spectrometer (UVIS). The haze is a global and permanent feature of Titan's atmosphere. Furthermore the location of the detached haze layer is coincident with and the likely cause of a local maximum in the temperature profile measured by the Huygens Atmospheric Structure Instrument (HASI). This temperature inversion is also permanent and global, having been detected in ground-based stellar occultations. The correlation between the extinction profile and the temperature maximum imply that the detached haze cannot be due to condensation, as previously suggested. Previously, Voyager high phase angle images at 500 nm revealed a detached haze layer near 350 km, more than 150 km lower than the Cassini layer. Close examination of the Voyager images suggests that the Cassini detached layer at 520 km is a separate phenomenon rather than a change in the Voyager detached layer. Analysis of the observed optical properties suggests that the average size of particles in the Cassini detached layer is < 45 nm, with an imaginary index k < 0.3 at 187.5 nm, while Non-LTE calculations of the temperature perturbation induced by the detached haze show that the average particle size must be greater than 35 nm for reproducing the heating rate implied by the HASI temperature profile. Calculation of the sedimentation velocity of the particles, coupled with the derived number density, imply a mass flux of 1.9-3.2 × 10-14 g cm-2 s-1. This is approximately equal to the mass flux required to explain the main haze layer and suggests that the stratospheric haze is formed primarily by sedimentation and coagulation of particles in the detached layer. This is further supported from the particle size range retrieved for the detached layer (35-45 nm), being approximately equal to the radii of ~50 nm for the monomers of the aggregate aerosols in the main haze layer. It follows that aerosols on Titan are formed primarily in the thermosphere, rather than the stratosphere as assumed in many pre-Cassini studies. This is consistent with the detection of negatively charged aerosols in the thermosphere by Cassini/CAPS. These conclusions are supported by microphysical aerosol models that couple the detached haze layer and the main haze layer and extend into the thermosphere. Our calculations suggest that the detached haze layer is due to the transition in the growth of particles from spherical shape to aggregates of fractal structure. The rapid increase in the size of the particles with the onset of fractal growth, in combination with the decrease of their settling velocity, casts them invisible in the transition region. This optical illusion process explains the well-defined and symmetric structure of the detached layer, something difficult to explain under a pure advection scenario. Further investigation of the processes defining the growth of the particles is required in order to understand why the transition takes place at this region and how the particles produced at higher altitudes by high energy radical and ion chemistry, are defining the vertical haze opacity in Titan's atmosphere.

Evaluation of the Mechanism of the Gold Cluster Growth during Heating of the Composite Gold-Polytetrafluoroethylene Thin Film.

PubMed

Grytsenko, Konstantin; Lozovski, Valeri; Strilchuk, Galyna; Schrader, Sigurd

2012-11-07

Nanocomposite films consisting of gold inclusions in the polytetrafluoroethylene (PTFE) matrix were obtained by thermal vacuum deposition. Annealing of the obtained films with different temperatures was used to measure varying of film morphologies. The dependence of optical properties of the films on their morphology was studied. It was established that absorption and profile of the nanocomposite film obtained by thermal vacuum deposition can be changed with annealing owing to the fact that different annealing temperatures lead to different average particle sizes. A method to calculate the optical properties of nanocomposite thin films with inclusions of different sizes was proposed. Thus, comparison of experimental optical spectra with the spectra obtained during the simulation enables estimating average sizes of inclusions. The calculations give the possibility of understanding morphological changes in the structures.

Space reactor fuel element testing in upgraded TREAT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Todosow, M.; Bezler, P.; Ludewig, H.

1993-01-14

The testing of candidate fuel elements at prototypic operating conditions with respect to temperature, power density, hydrogen coolant flow rate, etc., a crucial component in the development and qualification of nuclear rocket engines based on the Particle Bed Reactor (PBR), NERVA-derivative, and other concepts. Such testing may be performed at existing reactors, or at new facilities. A scoping study has been performed to assess the feasibility of testing PBR based fuel elements at the TREAT reactor. initial results suggest that full-scale PBR, elements could be tested at an average energy deposition of {approximately}60--80 MW-s/L in the current TREAT reactor. Ifmore » the TREAT reactor was upgraded to include fuel elements with a higher temperature limit, average energy deposition of {approximately}100 MW/L may be achievable.« less

Space reactor fuel element testing in upgraded TREAT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Todosow, M.; Bezler, P.; Ludewig, H.

1993-05-01

The testing of candidate fuel elements at prototypic operating conditions with respect to temperature, power density, hydrogen coolant flow rate, etc., a crucial component in the development and qualification of nuclear rocket engines based on the Particle Bed Reactor (PBR), NERVA-derivative, and other concepts. Such testing may be performed at existing reactors, or at new facilities. A scoping study has been performed to assess the feasibility of testing PBR based fuel elements at the TREAT reactor. initial results suggest that full-scale PBR, elements could be tested at an average energy deposition of {approximately}60--80 MW-s/L in the current TREAT reactor. Ifmore » the TREAT reactor was upgraded to include fuel elements with a higher temperature limit, average energy deposition of {approximately}100 MW/L may be achievable.« less

CdS quantum dots in a novel glass with a very low activation energy and its variation of diffusivity with temperature

NASA Astrophysics Data System (ADS)

Nagpal, Swati

2011-07-01

CdS quantum dots of different average sizes in the range 2 to 3.8 nm were grown by diffusion-limited growth process in indigenously made silicate glass. The absorption spectra showed a strong quantum confinement effect with a blue shift of the order of 500 meV depending on the average size. Critical radius of quantum dots was found to be 1.8 nm. The size dispersion decreased from 15.2 to 12.5% with a 20% increase in the particle size. The activation energy for diffusion was found to be very low i.e. 193 kJ mol-1 and the diffusion coefficient increased by 60% for 10 K rise in temperature. The PL emission spectra showed the presence of only deep traps around 600 nm with a red shift of 200 nm. No shallow traps or band edge emission was observed. The PL peak position changed from 560 to 640 nm with a 35 K increase in annealing temperature.

Observation of low energy protons in the geomagnetic tail at lunar distances. M.S. Thesis

NASA Technical Reports Server (NTRS)

Hardy, D. A.

1974-01-01

Three suprathermal ion detectors stationed on the moon were used to detect a region of plasma flowing antisunward along the ordered field lines of the geomagnetic tail, exterior to the plasma sheet. The particle flow displays an integral flux, a bulk velocity, temperatures, and number densities uniquely different from the other particle regimes traversed by the moon. No consistent deviation in the field was found to correspond with the occurrence of the events, which have an angular distribution extending between 50 and 100 deg and a spatial distribution over a wide region in both the Y sub sm and Z sub sm directions. The duration of observable particles varies widely between tail passages, with an apparent correlation between the number of hours of observation and the Kp index averages over these times. It is proposed that these particles may have entered through the cusp region.

Effect of K3PO4 addition as sintering inhibitor during calcination of Y2O3 nanoparticles

NASA Astrophysics Data System (ADS)

Soga, K.; Okumura, Y.; Tsuji, K.; Venkatachalam, N.

2009-11-01

Erbium-doped yttrium oxide nanoparticle is one of the most important for fluorescence bioimaging under near infrared excitation. Particle size of it below 100 nm is an important requirement for a cellular bioimaging. However, the synthesis with such small particles is difficult at the calcination temperature above 1200 °C due to the sintering and crystal growth of the particles. In this study, yttrium oxide nanoparticles with average size of 30 nm were successfully synthesized by using K3PO4 as a sintering inhibitor during the calcination. A single phase of cubic Y2O3 as the resultant material was confirmed by XRD, which was also confirmed to emit a bright upconversion emission under 980-nm excitation. Improvement of chemical durability due to the introduction of phosphate group on the surface of the Y2O3 particles is also reported.

Aggregation state and magnetic properties of magnetite nanoparticles controlled by an optimized silica coating

NASA Astrophysics Data System (ADS)

Pérez, Nicolás; Moya, C.; Tartaj, P.; Labarta, A.; Batlle, X.

2017-01-01

The control of magnetic interactions is becoming essential to expand/improve the applicability of magnetic nanoparticles (NPs). Here, we show that an optimized microemulsion method can be used to obtain homogenous silica coatings on even single magnetic nuclei of highly crystalline Fe3-xO4 NPs (7 and 16 nm) derived from a high-temperature method. We show that the thickness of this coating is controlled almost at will allowing much higher average separation among particles as compared to the oleic acid coating present on pristine NPs. Magnetic susceptibility studies show that the thickness of the silica coating allows the control of magnetic interactions. Specifically, as this effect is better displayed for the smallest particles, we show that dipole-dipole interparticle interactions can be tuned progressively for the 7 nm NPs, from almost non-interacting to strongly interacting particles at room temperature. The quantitative analysis of the magnetic properties unambiguously suggests that dipolar interactions significantly broaden the effective distribution of energy barriers by spreading the distribution of activation magnetic volumes.

Ferromagnetic resonance studies of granular materials (abstract)

NASA Astrophysics Data System (ADS)

Rubinstein, Mark; Das, Badri; Chrisey, D. B.; Horwitz, J.; Koon, N. C.

1994-05-01

We have investigated the ferromagnetic resonance (FMR) spectra of several granular alloys displaying giant magnetoresistance (GMR). For this task, we have produced melt-spun ribbons of Fe5Co15Cu80 and Co20Cu80 by rapid quenching and thin films of Co80Cu20 by pulsed laser deposition. The salient feature of the FMR spectra is the increase of the resonance linewidth as a function of increasing annealing temperature. We have deconvoluted the FMR spectra to a single-domain powder pattern and a multidomain powder pattern. As a function of annealing temperature, the GMR of these samples attains a maximum value. Near the peak of the GMR curve, the FMR spectrum reveals that the ferromagnetic particles are half mono- and half multidomain. Since the maximum size of a single-domain particle is known, this enables us to estimate the spin diffusion length of the Cu conduction electrons. We have also demonstrated, theoretically and experimentally, that the appropriate demagnetizing field to apply to the ensemble of spherical magnetic particles that comprise our granular thin film is simply the field corresponding to the average magnetization.

Size dependent magnetic and magneto-optical properties of Ni0.2Zn0.8Fe2O4 nanoparticles

NASA Astrophysics Data System (ADS)

Li, Oksana A.; Lin, Chun-Rong; Chen, Hung-Yi; Hsu, Hua-Shu; Shih, Kun-Yauh; Edelman, Irina S.; Wu, Kai-Wun; Tseng, Yaw-Teng; Ovchinnikov, Sergey G.; Lee, Jiann-Shing

2016-06-01

Ni0.2Zn0.8Fe2O4 spinel nanoparticles have been synthesized by combustion method. Average particles size varies from 15.5 to 50.0 nm depending on annealing temperature. Correlations between particles size and magnetic and magneto-optical properties are investigated. Magnetization dependences on temperature and external magnetic field correspond to the sum of paramagnetic and superparamagnetic response. Critical size of single-domain transition is found to be 15.9 nm. Magnetic circular dichroism (MCD) studies of nickel zinc spinel are presented here for the first time. The features in magnetic circular dichroism spectrum are assigned to the one-ion d-d transitions in Fe3+ and Ni2+ ions, as well to the intersublattice and intervalence charge transfer transitions. The MCD spectrum rearrangement was revealed with the change of the nanoparticles size.

The Influence of Al4C3 Nanoparticles on the Physical and Mechanical Properties of Metal Matrix Composites at High Temperatures

NASA Astrophysics Data System (ADS)

Vorozhtsov, S.; Kolarik, V.; Promakhov, V.; Zhukov, I.; Vorozhtsov, A.; Kuchenreuther-Hummel, V.

2016-05-01

Metal matrix composites (MMC) based on aluminum and reinforced with nonmetallic particles are of great practical interest due to their potentially high physico-mechanical properties. In this work, Al-Al4C3 composites were obtained by a hot-compacting method. Introduction of nanodiamonds produced by detonation to the Al powder in an amount of 10 wt.% led to the formation of ~15 wt.% of aluminum carbide during hot compacting. It was found that composite materials with the diamond content of 10 wt.% in the initial powder mix have an average microhardness of 1550 MPa, whilst the similarly compacted aluminum powder without reinforcing particles shows a hardness of 750 MPa. The mechanical properties of an Al-Al4C3 MMC at elevated test temperatures exceeded those of commercial casting aluminum alloys such as A356.

Upgrading producer gas quality from rubber wood gasification in a radio frequency tar thermocatalytic treatment reactor.

PubMed

Anis, Samsudin; Zainal, Z A

2013-12-01

This study focused on improving the producer gas quality using radio frequency (RF) tar thermocatalytic treatment reactor. The producer gas containing tar, particles and water was directly passed at a particular flow rate into the RF reactor at various temperatures for catalytic and thermal treatments. Thermal treatment generates higher heating value of 5.76 MJ Nm(-3) at 1200°C. Catalytic treatments using both dolomite and Y-zeolite provide high tar and particles conversion efficiencies of about 97% on average. The result also showed that light poly-aromatic hydrocarbons especially naphthalene and aromatic compounds particularly benzene and toluene were still found even at higher reaction temperatures. Low energy intensive RF tar thermocatalytic treatment was found to be effective for upgrading the producer gas quality to meet the end user requirements and increasing its energy content. Copyright © 2013 Elsevier Ltd. All rights reserved.

Y2O3:Eu phosphor particles prepared by spray pyrolysis from a solution containing citric acid and polyethylene glycol

NASA Astrophysics Data System (ADS)

Roh, H. S.; Kang, Y. C.; Park, H. D.; Park, S. B.

Y2O3:Eu phosphor particles were prepared by large-scale spray pyrolysis. The morphological control of Y2O3:Eu particles in spray pyrolysis was attempted by adding polymeric precursors to the spray solution. The effect of composition and amount of polymeric precursors on the morphology, crystallinity and photoluminescence characteristics of Y2O3:Eu particles was investigated. Particles prepared from a solution containing polyethylene glycol (PEG) with an average molecular weight of 200 had a hollow structure, while those prepared from solutions containing adequate amounts of citric acid (CA) and PEG had a spherical shape, filled morphology and clean surfaces after post-treatment at high temperature. Y2O3:Eu particles prepared from an aqueous solution with no polymeric precursors had a hollow structure and rough surfaces after post-treatment. The phosphor particles prepared from solutions with inadequate amounts of CA and/or PEG also had hollow and/or fragmented structures. The particles prepared from the solution containing 0.3 M CA and 0.3 M PEG had the highest photoluminescence emission intensity, which was 56% higher than that of the particles prepared from aqueous solution without polymeric precursors.

[Preparation of ibuprofen/EC-PVP sustained-release composite particles by supercritical CO2 anti-solvent technology].

PubMed

Cai, Jin-Yuan; Huang, De-Chun; Wang, Zhi-Xiang; Dang, Bei-Lei; Wang, Qiu-Ling; Su, Xin-Guang

2012-06-01

Ibuprofen/ethyl-cellulose (EC)-polyvinylpyrrolidone (PVP) sustained-release composite particles were prepared by using supercritical CO2 anti-solvent technology. With drug loading as the main evaluation index, orthogonal experimental design was used to optimize the preparation process of EC-PVP/ibuprofen composite particles. The experiments such as encapsulation efficiency, particle size distribution, electron microscope analysis, infrared spectrum (IR), differential scanning calorimetry (DSC) and in vitro dissolution were used to analyze the optimal process combination. The orthogonal experimental optimization process conditions were set as follows: crystallization temperature 40 degrees C, crystallization pressure 12 MPa, PVP concentration 4 mgmL(-1), and CO2 velocity 3.5 Lmin(-1). Under the optimal conditions, the drug loading and encapsulation efficiency of ibuprofen/EC-PVP composite particles were 12.14% and 52.21%, and the average particle size of the particles was 27.621 microm. IR and DSC analysis showed that PVP might complex with EC. The experiments of in vitro dissolution showed that ibuprofen/EC-PVP composite particles had good sustained-release effect. Experiment results showed that, ibuprofen/EC-PVP sustained-release composite particles can be prepared by supercritical CO2 anti-solvent technology.

The statistical average of optical properties for alumina particle cluster in aircraft plume

NASA Astrophysics Data System (ADS)

Li, Jingying; Bai, Lu; Wu, Zhensen; Guo, Lixin

2018-04-01

We establish a model for lognormal distribution of monomer radius and number of alumina particle clusters in plume. According to the Multi-Sphere T Matrix (MSTM) theory, we provide a method for finding the statistical average of optical properties for alumina particle clusters in plume, analyze the effect of different distributions and different detection wavelengths on the statistical average of optical properties for alumina particle cluster, and compare the statistical average optical properties under the alumina particle cluster model established in this study and those under three simplified alumina particle models. The calculation results show that the monomer number of alumina particle cluster and its size distribution have a considerable effect on its statistical average optical properties. The statistical average of optical properties for alumina particle cluster at common detection wavelengths exhibit obvious differences, whose differences have a great effect on modeling IR and UV radiation properties of plume. Compared with the three simplified models, the alumina particle cluster model herein features both higher extinction and scattering efficiencies. Therefore, we may find that an accurate description of the scattering properties of alumina particles in aircraft plume is of great significance in the study of plume radiation properties.

Ab initio simulation of particle momentum distributions in high-pressure water

NASA Astrophysics Data System (ADS)

Ceriotti, M.

2014-12-01

Applying pressure to water reduces the average oxygen-oxygen distance, and facilitates the delocalisation of protons along the hydrogen bond. This pressure-induced delocalisation is further enhanced by the quantum nature of hydrogen nuclei, which is very significant even well above room temperature. Here we will evaluate the quantum kinetic energy and the particle momentum distribution of hydrogen and oxygen nuclei in water at extreme pressure, using ab initio path integral molecular dynamics. We will show that (transient) dissociation of water molecules induce measurable changes in the kinetic energy hydrogen atoms, although current deep inelastic scattering experiments are probably unable to capture the heterogeneity of the sample.

Temperature dependence of the Henry's law constant for hydrogen storage in NaA zeolites: a Monte Carlo simulation study.

PubMed

Sousa, João Miguel; Ferreira, António Luís; Fagg, Duncan Paul; Titus, Elby; Krishna, Rahul; Gracio, José

2012-08-01

Grand canonical Monte Carlo simulations of hydrogen adsorption in zeolites NaA were carried out for a wide range of temperatures between 77 and 300 K and pressures up to 180 MPa. A potential model was used that comprised of three main interactions: van der Waals, coulombic and induced polarization by the electric field in the system. The computed average number of adsorbed molecules per unit cell was compared with available results and found to be in agreement in the regime of moderate to high pressures. The particle insertion method was used to calculate the Henry coefficient for this model and its dependence on temperature.

Low Temperature Regolith Bricks for In-Situ Structural Material

NASA Technical Reports Server (NTRS)

Grossman, Kevin; Sakthivel, Tamil S.; Mantovani, James; Seal, Sudipta

2016-01-01

Current technology for producing in-situ structural materials on future missions to Mars or the moon relies heavily on energy-intensive sintering processes to produce solid bricks from regolith. This process requires heating the material up to temperatures in excess of 1000 C and results in solid regolith pieces with compressive strengths in the range of 14000 to 28000 psi, but are heavily dependent on the porosity of the final material and are brittle. This method is currently preferred over a low temperature cementation process to prevent consumption of precious water and other non-renewable materials. A high strength structural material with low energy requirements is still needed for future colonization of other planets. To fulfill these requirements, a nano-functionalization process has been developed to produce structural bricks from regolith simulant and shows promising mechanical strength results. Functionalization of granular silicate particles into alkoxides using a simple low temperature chemical process produces a high surface area zeolite particles that are held together via inter-particle oxygen bonding. Addition of water in the resulting zeolite particles produces a sol-gel reaction called "inorganic polymerization" which gives a strong solid material after a curing process at 60 C. The aqueous solution by-product of the reaction is currently being investigated for its reusability; an essential component of any ISRU technology. For this study, two batches of regolith bricks are synthesized from JSC-1A; the first batch from fresh solvents and chemicals, the second batch made from the water solution by-product of the first batch. This is done to determine the feasibility of recycling necessary components of the synthesis process, mainly water. Characterization including BET surface area, SEM, and EDS has been done on the regolith bricks as well as the constituent particles,. The specific surface area of 17.53 sq m/g (average) of the granular regolith material was obtained from nitrogen adsorption isotherm measurement. The size, shape and textures of regolith from SEM shows that the particles are 25-50 micrometers in size and mostly irregular in shape (Figure 1a). The elemental composition of regolith was identified from EDS analysis showed the presence of Si, Al, Fe, Na, Mg, Ca, Ti, O and C (see figure 1b). Each set of cylindrical brick samples were prepared by low energy process, and cured for 21 and 28 days, respectively to compare their compressive strength. Figure 1c, and d shows the JSC-1A brick and the compressive strength measurements. The results from the 21 day cured bricks (2 bricks) have been done and yielded an aver-age strength of 3050 psi, considerably higher than Portland cement mortars (Type IV and V). This promising technology provides the benefits of construction material similar to concrete, with a low complexity, low energy synthesis process and the likelihood of complete reusability of precious resources. Compressive strength using this method can be improved by increasing the surface area of the particles, using bi-modal particle size distribution, and adding certain additives to increase inter-particle forces.

Mirror symmetry of ions and electron temperature variations within the dusty dynamo layer of the auroral ionosphere

NASA Astrophysics Data System (ADS)

Timofeev, Evgeny; Kangas, Jorma; Vallinkoski, Matti

Quasi-periodic (consisting of a dozen electro-thermal structures, ETS) variations of ionospheric parameters during April, 10 and March, 23 1988 substorms were investigated using the data of EISCAT radars in Tromso. These variations were measured at the lower edge of dynamo-layer 106 km and include the ion and electron temperature, electron density and ionospheric electric field; all data were smoothed out using moving average with optimal lag window. It was shown that: 1) ETS clusters are observed when value of the electric field is < 10 mV/m and average electron density is about (5-10)*10 (4) /sm (3) , 2) For each ETS the envelop demonstrate the so called mirror symmetry, that is antiphased variations of the ion and electron temperature (when Ti increases and Te decreases), 3) The symmetry breaks when the electric field is larger than FB instability threshold (15-20 mVm), 4) The periods of these variations is in the range of 3-10 min, 5) The self-similarity of the scales is observed: smaller scales are included into the larger scales, 6) Temperature variations were accompanied by the electric field variations with amplitude of 4-7 mV/m, 7) Large scale structures (and sometimes dyads formed by two subsequent structures) were accompanied by the electric field rotation up to the whole circle. Specific ETS and plasma parameters variations can be interpreted as a result of Ekman-type instability in the dusty plasma of the dynamo layer. The mirror symmetry of plasma temperature variations is an evidence of a partial blocking of energy transfer between the ions and electrons at low values of the external electric field (below FB instability threshold) because the main energy in such a kind of plasma is attributed to dusty macro-particles (Fortov et al., 2010). Under these conditions the time scale of the dust particle energy variations are considerably larger than the corresponding scales of the temperature variations. According to our previous results (Timofeev et al, 2009-2013) the coherent increase of correlation coefficient (CC) of plasma temperature time variations and smoothed value of the electric field means that the CC can be used as an indicator of the ETS "rigidity" (hence the energy and charge of macro-particles). We used this coherence to estimate the time scale of the macro-particles energy growth (during preliminary phase of March 23, 1988 substorm) and get values of 12-19 min. In the present study we used the same event to estimate the time scale of the plasma temperatures mirror variations and obtained that they are at least 2-3 times shorter. Such a difference in the time scale determines the ETS formation. Finally, after FB instability excitation the electrons can quickly exchange their energy with plasmons, so that the mirror symmetry in temperature variations breaks down.

Phase and microstructural development in alumina sol-gel coatings on CoCr alloy.

PubMed

Bae, I J; Standard, O C; Roger, G J; Brazil, D

2004-09-01

Phase transformation of gamma-Al(2)O(3) to alpha-Al(2)O(3) in alumina sol gel coatings on biomedical CoCr alloy was studied as function of heat treatment temperature and time. Transformation in unseeded coatings was significant only above approximately 1200 degrees C. Addition of alpha-Al(2)O(3) seed particles having an average size of approximately 40 nm lowered the phase transformation temperature to around 800 degrees C. These particles were considered to act as heterogeneous nucleation sites for epitaxial growth of the alpha-Al(2)O(3) phase. The kinetics and activation energy (420 kJ/mol) for the phase transformation in the seeded coatings were similar to those reported for seeded monolithic alumina gels indicating that the transformation mechanism is the same in the two material configurations. Avrami growth parameters indicated that the mechanism was diffusion controlled and invariant over the temperature range studied but that growth was possibly constrained by the finite size of the seed particles and/or coating thickness. The phase transformation occurred by the growth of alpha-Al(2)O(3) grains at the expense of the precursor fine-grained gamma-Al(2)O(3) matrix and near-complete transformation coincided with physical impingement of the growing grains. The grain size at impingement was approximately 100 nm which agreed well with that predicted from the theoretical linear spacing of seed particles in the initial sol.

Improved high temperature refractory. [MgCr/sub 2/O/sub 4/ composite with ZrO/sub 2/

DOEpatents

Singh, J.P.; James, J.; Picciolo, J.J.

1985-12-10

A high chromia refractory composite has been developed with improved thermal shock resistance and containing about 5 to 30 wt % of unstabilized ZrO/sub 2/ having a temperature-dependent phase change resulting in large expansion mismatch between the ZrO/sub 2/ and the chromia matrix which causes microcracks to form during cooling in the high chromia matrix. The particle size preferably is primarily between about 0.6 to 5 microns and particularly below about 3 microns with an average size in the order of 1.2 to 1.8 microns.

Maxwell boundary condition and velocity dependent accommodation coefficient

DOE Office of Scientific and Technical Information (OSTI.GOV)

Struchtrup, Henning, E-mail: struchtr@uvic.ca

2013-11-15

A modification of Maxwell's boundary condition for the Boltzmann equation is developed that allows to incorporate velocity dependent accommodation coefficients into the microscopic description. As a first example, it is suggested to consider the wall-particle interaction as a thermally activated process with three parameters. A simplified averaging procedure leads to jump and slip boundary conditions for hydrodynamics. Coefficients for velocity slip, temperature jump, and thermal transpiration flow are identified and compared with those resulting from the original Maxwell model and the Cercignani-Lampis model. An extension of the model leads to temperature dependent slip and jump coefficients.

Primary marine aerosol physical flux and chemical composition during a nutrient enrichment experiment in mesocosms in the Mediterranean Sea

NASA Astrophysics Data System (ADS)

Schwier, Allison N.; Sellegri, Karine; Mas, Sébastien; Charrière, Bruno; Pey, Jorge; Rose, Clémence; Temime-Roussel, Brice; Jaffrezo, Jean-Luc; Parin, David; Picard, David; Ribeiro, Mickael; Roberts, Greg; Sempéré, Richard; Marchand, Nicolas; D'Anna, Barbara

2017-12-01

While primary marine aerosol (PMA) is an important part of global aerosol total emissions, its chemical composition and physical flux as a function of the biogeochemical properties of the seawater still remain highly uncharacterized due to the multiplicity of physical, chemical and biological parameters that are involved in the emission process. Here, two nutrient-enriched mesocosms and one control mesocosm, both filled with Mediterranean seawater, were studied over a 3-week period. PMA generated from the mesocosm waters were characterized in term of chemical composition, size distribution and size-segregated cloud condensation nuclei (CCN), as a function of the seawater chlorophyll a (Chl a) concentration, pigment composition, virus and bacteria abundances. The aerosol number size distribution flux was primarily affected by the seawater temperature and did not vary significantly from one mesocosm to the other. The aerosol number size distribution flux was primarily affected by the seawater temperature and did not vary significantly from one mesocosm to the other. Particle number and CCN aerosol fluxes increase by a factor of 2 when the temperature increases from 22 to 32 °C, for all particle submicron sizes. This effect, rarely observed in previous studies, could be specific to oligotrophic waters and/or to this temperature range. In all mesocosms (enriched and control mesocosms), we detected an enrichment of calcium (+500 %) and a deficit in chloride (-36 %) in the submicron PMA mass compared to the literature inorganic composition of the seawater. There are indications that the chloride deficit and calcium enrichment are linked to biological processes, as they are found to be stronger in the enriched mesocosms. This implies a non-linear transfer function between the seawater composition and PMA composition, with complex processes taking place at the interface during the bubble bursting. We found that the artificial phytoplankton bloom did not affect the CCN activation diameter (Dp, 50, average = 59.85±3.52 nm and Dp,50,average = 93.42±5.14 nm for supersaturations of 0.30 and 0.15 % respectively) or the organic fraction of the submicron PMA (average organic to total mass = 0.31±0.07) compared to the control mesocosm. Contrary to previous observations in natural bloom mesocosm experiments, the correlation between the particle organic fraction and the seawater Chl a was poor, indicating that Chl a is likely not a straightforward proxy for predicting, on a daily scale, PMA organic fraction in models for all types of sea and ocean waters. Instead, the organic fraction of the Aitken mode particles were more significantly linked to heterotrophic flagellates, viruses and dissolved organic carbon (DOC). We stress that different conclusions may be obtained in natural (non-enriched) or non-oligotrophic systems.

Concentrations and Sources of Airborne Particles in a Neonatal Intensive Care Unit

PubMed Central

Licina, Dusan; Bhangar, Seema; Brooks, Brandon; Baker, Robyn; Firek, Brian; Tang, Xiaochen; Morowitz, Michael J.; Banfield, Jillian F.; Nazaroff, William W.

2016-01-01

Premature infants in neonatal intensive care units (NICUs) have underdeveloped immune systems, making them susceptible to adverse health consequences from air pollutant exposure. Little is known about the sources of indoor airborne particles that contribute to the exposure of premature infants in the NICU environment. In this study, we monitored the spatial and temporal variations of airborne particulate matter concentrations along with other indoor environmental parameters and human occupancy. The experiments were conducted over one year in a private-style NICU. The NICU was served by a central heating, ventilation and air-conditioning (HVAC) system equipped with an economizer and a high-efficiency particle filtration system. The following parameters were measured continuously during weekdays with 1-min resolution: particles larger than 0.3 μm resolved into 6 size groups, CO2 level, dry-bulb temperature and relative humidity, and presence or absence of occupants. Altogether, over sixteen periods of a few weeks each, measurements were conducted in rooms occupied with premature infants. In parallel, a second monitoring station was operated in a nearby hallway or at the local nurses’ station. The monitoring data suggest a strong link between indoor particle concentrations and human occupancy. Detected particle peaks from occupancy were clearly discernible among larger particles and imperceptible for submicron (0.3–1 μm) particles. The mean indoor particle mass concentrations averaged across the size range 0.3–10 μm during occupied periods was 1.9 μg/m3, approximately 2.5 times the concentration during unoccupied periods (0.8 μg/m3). Contributions of within-room emissions to total PM10 mass in the baby rooms averaged 37–81%. Near-room indoor emissions and outdoor sources contributed 18–59% and 1–5%, respectively. Airborne particle levels in the size range 1–10 μm showed strong dependence on human activities, indicating the importance of indoor-generated particles for infant’s exposure to airborne particulate matter in the NICU. PMID:27175913

Concentrations and Sources of Airborne Particles in a Neonatal Intensive Care Unit.

PubMed

Licina, Dusan; Bhangar, Seema; Brooks, Brandon; Baker, Robyn; Firek, Brian; Tang, Xiaochen; Morowitz, Michael J; Banfield, Jillian F; Nazaroff, William W

2016-01-01

Premature infants in neonatal intensive care units (NICUs) have underdeveloped immune systems, making them susceptible to adverse health consequences from air pollutant exposure. Little is known about the sources of indoor airborne particles that contribute to the exposure of premature infants in the NICU environment. In this study, we monitored the spatial and temporal variations of airborne particulate matter concentrations along with other indoor environmental parameters and human occupancy. The experiments were conducted over one year in a private-style NICU. The NICU was served by a central heating, ventilation and air-conditioning (HVAC) system equipped with an economizer and a high-efficiency particle filtration system. The following parameters were measured continuously during weekdays with 1-min resolution: particles larger than 0.3 μm resolved into 6 size groups, CO2 level, dry-bulb temperature and relative humidity, and presence or absence of occupants. Altogether, over sixteen periods of a few weeks each, measurements were conducted in rooms occupied with premature infants. In parallel, a second monitoring station was operated in a nearby hallway or at the local nurses' station. The monitoring data suggest a strong link between indoor particle concentrations and human occupancy. Detected particle peaks from occupancy were clearly discernible among larger particles and imperceptible for submicron (0.3-1 μm) particles. The mean indoor particle mass concentrations averaged across the size range 0.3-10 μm during occupied periods was 1.9 μg/m3, approximately 2.5 times the concentration during unoccupied periods (0.8 μg/m3). Contributions of within-room emissions to total PM10 mass in the baby rooms averaged 37-81%. Near-room indoor emissions and outdoor sources contributed 18-59% and 1-5%, respectively. Airborne particle levels in the size range 1-10 μm showed strong dependence on human activities, indicating the importance of indoor-generated particles for infant's exposure to airborne particulate matter in the NICU.

Particles in a karstic spring, Swabian Alb: Physicochemical and hydraulic effects during a snow melt event.

NASA Astrophysics Data System (ADS)

Schiperski, Ferry; Zirlewagen, Johannes; Hillebrand, Olav; Scheytt, Traugott; Licha, Tobias

2013-04-01

The studied karst spring 'Gallusquelle' is located on the Swabian Alb in Southwest Germany. The catchment area of the 'Gallusquelle' measures about 45 km². An average annual discharge of 0.5 m³/s serves drinking water to about 40,000 people via a waterworks. The study is part of the research project 'AGRO' (www.projekt-agro.de). The main objective of the project 'AGRO' is to develop a tool for the process-based risk management of micropollutants and pathogens in rural karst aquifers on catchment scale. As particle related transport could play an important role for micropollutants and pathogens, the characterization of particles in the spring water is one focus of this work. Furthermore we will attempt to correlate physicochemical parameters with the characteristics of particles in the spring water in order to enhance the knowledge of the transport mechanisms within the karst aquifer. For the measurement of the particle concentration and the particle size distribution the CIS 1 (GALAI) was used. The system works in a range of 0.5 to 150 µm with a resolution of at least 0.5 µm. The measurement is based on time-of-transition method using a laser beam. The turbidity was measured with an ULTRATURB PLUS (DR.LANGE) and a Fluorometer (GGUN-FL30, ALBILLIA), both working with scattering light method. To verify these measurements we used a portable turbidimeter (2100P IS PORTABLE TURBIDIMETER, HACH) working with the ratio of the signals from the scattered and the transmitted light. Temperature and electrical conductivity where also measured with the GGUN-FL30, whereby the electrical conductivity was verified with a portable multimeter (HQ 40D, HACH). Discharge, pH, water hardness, anion- and cation concentration, total organic carbon (TOC) and dissolved organic carbon (DOC) were also determined. To characterize the particles, the spring water was filtered onsite and the filter cake was analyzed in the laboratory. For SEM (scanning electron microscopy) including EDAX (energy dispersive X-ray spectroscopy) the water was filtered through PC membrane filters (∅=25mm) using a polycarbonate syringe. For X-ray diffraction the water was filtered through CA membrane filters (∅=142 mm) using a stainless steel pressure holder and a peristaltic pump. Both filters had an average pore size of 0.45 µm. Also we have analyzed sediments that where collected downstream of the online measurements and in the raw water tank of a waterworks that is located about 250 m downstream of the spring. During an average discharge the turbidity and the number of particles are around the limit of detection. Both increase with increasing discharge while the average particle size does not increase until a considerably higher-than-average discharge is reached. Particles in the size range of 0.5 - 2.0 µm display the main numeric amount (70 - 100 %) of the measurable particles under present discharge conditions. Only under high discharge conditions particles sizes > 5 µm increase significantly. Particles > 20 µm are rare during the whole period of measurement. In contrast to other works we include mineralogical studies of the particles in the spring water. Thus we can examine the relevance of mineralogical properties of the particles for the transport of micropollutants. Actual results of XRD analyses indicate that calcite, quartz and clay minerals dominate the turbidity. EDAX analyses with SEM confirm these measurements.

Nanotwinning and structural phase transition in CdS quantum dots

PubMed Central

2012-01-01

Nanotwin structures are observed in high-resolution transmission electron microscopy studies of cubic phase CdS quantum dots in powder form by chemical co-precipitation method. The deposition of thin films of nanocrystalline CdS is carried out on silicon, glass, and TEM grids keeping the substrates at room temperature (RT) and 200°C by pulsed laser ablation. These films are then subjected to thermal annealing at different temperatures. Glancing angle X-ray diffraction results confirm structural phase transitions after thermal annealing of films deposited at RT and 200°C. The variation of average particle size and ratio of intensities in Raman peaks I2LO/I1LO with annealing temperature are studied. It is found that electron-phonon interaction is a function of temperature and particle size and is independent of the structure. Besides Raman modes LO, 2LO and 3LO of CdS at approximately 302, 603, and 903 cm−1 respectively, two extra Raman modes at approximately 390 and 690 cm−1 are studied for the first time. The green and orange emissions observed in photoluminescence are correlated with phase transition. PMID:23092351

Structural and Optical Properties of Ag Nanoparticles Synthesized by Thermal Treatment Method.

PubMed

Gharibshahi, Leila; Saion, Elias; Gharibshahi, Elham; Shaari, Abdul Halim; Matori, Khamirul Amin

2017-04-12

The modified thermal treatment method via alternate oxygen and nitrogen flow was successfully employed to synthesize very narrow and pure Ag nanoparticles. The structural and optical properties of the obtained metal nanoparticles at different calcination temperatures between 400 and 800 °C were studied using various techniques. The FTIR and EDX confirmed the formation of Ag nanoparticles without a trace of impurities. The XRD spectra revealed that the amorphous sample at 30 °C had transformed into the cubic crystalline nanostructures at the calcination temperature of 400 °C and higher. The TEM images showed the formation of spherical Ag nanoparticles in which the average particle size decreased with increasing calcination temperature from 7.88 nm at 400 °C to 3.29 nm at 800 °C. The optical properties were determined by UV-vis absorption spectrophotometer, which showed an increase in the conduction band of Ag nanoparticles with increasing calcination temperature from 2.75 eV at 400 °C to 3.04 eV at 800 °C. This was due to less attraction between conduction electrons and metal ions as the particle size decreases in corresponding to fewer numbers of atoms that made up the metal nanoparticles.

Structural and Optical Properties of Ag Nanoparticles Synthesized by Thermal Treatment Method

PubMed Central

Gharibshahi, Leila; Saion, Elias; Gharibshahi, Elham; Shaari, Abdul Halim; Matori, Khamirul Amin

2017-01-01

The modified thermal treatment method via alternate oxygen and nitrogen flow was successfully employed to synthesize very narrow and pure Ag nanoparticles. The structural and optical properties of the obtained metal nanoparticles at different calcination temperatures between 400 and 800 °C were studied using various techniques. The FTIR and EDX confirmed the formation of Ag nanoparticles without a trace of impurities. The XRD spectra revealed that the amorphous sample at 30 °C had transformed into the cubic crystalline nanostructures at the calcination temperature of 400 °C and higher. The TEM images showed the formation of spherical Ag nanoparticles in which the average particle size decreased with increasing calcination temperature from 7.88 nm at 400 °C to 3.29 nm at 800 °C. The optical properties were determined by UV-vis absorption spectrophotometer, which showed an increase in the conduction band of Ag nanoparticles with increasing calcination temperature from 2.75 eV at 400 °C to 3.04 eV at 800 °C. This was due to less attraction between conduction electrons and metal ions as the particle size decreases in corresponding to fewer numbers of atoms that made up the metal nanoparticles. PMID:28772762

Rapid microwave-assisted synthesis of sub-30nm lipid nanoparticles.

PubMed

Dunn, Stuart S; Beckford Vera, Denis R; Benhabbour, S Rahima; Parrott, Matthew C

2017-02-15

Accessing the phase inversion temperature by microwave heating may enable the rapid synthesis of small lipid nanoparticles. Nanoparticle formulations consisted of surfactants Brij 78 and Vitamin E TPGS, and trilaurin, trimyristin, or miglyol 812 as nanoparticle lipid cores. Each formulation was placed in water and heated by microwave irradiation at temperatures ranging from 65°C to 245°C. We observed a phase inversion temperature (PIT) for these formulations based on a dramatic decrease in particle Z-average diameters. Subsequently, nanoparticles were manufactured above and below the PIT and studied for (a) stability toward dilution, (b) stability over time, (c) fabrication as a function of reaction time, and (d) transmittance of lipid nanoparticle dispersions. Lipid-based nanoparticles with distinct sizes down to 20-30nm and low polydispersity could be attained by a simple, one-pot microwave synthesis. This was carried out by accessing the phase inversion temperature using microwave heating. Nanoparticles could be synthesized in just one minute and select compositions demonstrated high stability. The notable stability of these particles may be explained by the combination of van der Waals interactions and steric repulsion. 20-30nm nanoparticles were found to be optically transparent. Published by Elsevier Inc.

Synthesis of transparent dispersions of aluminium hydroxide nanoparticles

NASA Astrophysics Data System (ADS)

Chen, Bo; Wang, Jie-Xin; Wang, Dan; Zeng, Xiao-Fei; Clarke, Stuart M.; Chen, Jian-Feng

2018-07-01

Transparent dispersions of inorganic nanoparticles are attractive materials in many fields. However, a facile method for preparing such dispersions of aluminium hydroxide nanoparticles is yet to be realized. Here, we report a direct reactive method to prepare transparent dispersions of pseudo-boehmite nanoparticles (1 wt%) without any surface modification, and with an average particle size of 80 nm in length and 10 nm in width, as well as excellent optical transparency over 94% in the visible range. Furthermore, transparent dispersions of boehmite nanoparticles (1.5 wt%) were also achieved after an additional hydrothermal treatment. However, the optical transparency of dispersions decreased with the rise of hydrothermal temperature and the shape of particles changed from rhombs to hexagons. In particular, monodisperse hexagonal boehmite nanoplates with an average lateral size of 58 nm and a thickness of 12.5 nm were obtained at a hydrothermal temperature of 220 °C. The selectivity of crystal growth direction was speculated as the possible formation mechanism of these as-prepared aluminium hydroxide nanoparticles. Besides, two values of 19.6 wt% and 14.64 wt% were separately measured for the weight loss of pseudo-boehmite and boehmite nanoparticles after a continuous heating, indicating their potential flame-resistant applications in the fabrication of plastic electronics and optical devices with high transparency.

Synthesis of transparent dispersions of aluminium hydroxide nanoparticles.

PubMed

Chen, Bo; Wang, Jie-Xin; Wang, Dan; Zeng, Xiao-Fei; Clarke, Stuart M; Chen, Jian-Feng

2018-07-27

Transparent dispersions of inorganic nanoparticles are attractive materials in many fields. However, a facile method for preparing such dispersions of aluminium hydroxide nanoparticles is yet to be realized. Here, we report a direct reactive method to prepare transparent dispersions of pseudo-boehmite nanoparticles (1 wt%) without any surface modification, and with an average particle size of 80 nm in length and 10 nm in width, as well as excellent optical transparency over 94% in the visible range. Furthermore, transparent dispersions of boehmite nanoparticles (1.5 wt%) were also achieved after an additional hydrothermal treatment. However, the optical transparency of dispersions decreased with the rise of hydrothermal temperature and the shape of particles changed from rhombs to hexagons. In particular, monodisperse hexagonal boehmite nanoplates with an average lateral size of 58 nm and a thickness of 12.5 nm were obtained at a hydrothermal temperature of 220 °C. The selectivity of crystal growth direction was speculated as the possible formation mechanism of these as-prepared aluminium hydroxide nanoparticles. Besides, two values of 19.6 wt% and 14.64 wt% were separately measured for the weight loss of pseudo-boehmite and boehmite nanoparticles after a continuous heating, indicating their potential flame-resistant applications in the fabrication of plastic electronics and optical devices with high transparency.

Response of jammed packings to thermal fluctuations

NASA Astrophysics Data System (ADS)

Wu, Qikai; Bertrand, Thibault; Shattuck, Mark D.; O'Hern, Corey S.

2017-12-01

We focus on the response of mechanically stable (MS) packings of frictionless, bidisperse disks to thermal fluctuations, with the aim of quantifying how nonlinearities affect system properties at finite temperature. In contrast, numerous prior studies characterized the structural and mechanical properties of MS packings of frictionless spherical particles at zero temperature. Packings of disks with purely repulsive contact interactions possess two main types of nonlinearities, one from the form of the interaction potential (e.g., either linear or Hertzian spring interactions) and one from the breaking (or forming) of interparticle contacts. To identify the temperature regime at which the contact-breaking nonlinearities begin to contribute, we first calculated the minimum temperatures Tc b required to break a single contact in the MS packing for both single- and multiple-eigenmode perturbations of the T =0 MS packing. We find that the temperature required to break a single contact for equal velocity-amplitude perturbations involving all eigenmodes approaches the minimum value obtained for a perturbation in the direction connecting disk pairs with the smallest overlap. We then studied deviations in the constant volume specific heat C¯V and deviations of the average disk positions Δ r from their T =0 values in the temperature regime TC ¯V100 for linear spring interactions is independent of system size. This result emphasizes that contact-breaking nonlinearities are dominant over form nonlinearities in the low-temperature range Tc b

Aggregation in particle rich environments: a textural study of examples from volcanic eruptions, meteorite impacts, and fluidized bed processing

NASA Astrophysics Data System (ADS)

Mueller, Sebastian B.; Kueppers, Ulrich; Huber, Matthew S.; Hess, Kai-Uwe; Poesges, Gisela; Ruthensteiner, Bernhard; Dingwell, Donald B.

2018-04-01

Aggregation is a common process occurring in many diverse particulate gas mixtures (e.g. those derived from explosive volcanic eruptions, meteorite impact events, and fluid bed processing). It results from the collision and sticking of particles suspended in turbulent gas/air. To date, there is no generalized model of the underlying physical processes. Here, we investigate aggregates from 18 natural deposits (16 volcanic deposits and two meteorite impact deposits) as well as aggregates produced experimentally via fluidized bed techniques. All aggregates were analyzed for their size, internal structuring, and constituent particle size distribution. Commonalities and differences between the aggregate types are then used to infer salient features of the aggregation process. Average core to rim ratios of internally structured aggregates (accretionary lapilli) is found to be similar for artificial and volcanic aggregates but up to an order of magnitude different than impact-related aggregates. Rim structures of artificial and volcanic aggregates appear to be physically similar (single, sub-spherical, regularly-shaped rims) whereas impact-related aggregates more often show multiple or irregularly shaped rims. The particle size distributions (PSDs) of all three aggregate types are similar (< 200 μm). This proves that in all three environments, aggregation occurs under broadly similar conditions despite the significant differences in source conditions (particle volume fraction, particle size distribution, particle composition, temperature), residence times, plume conditions (e.g., humidity and temperature), and dynamics of fallout and deposition. Impact-generated and volcanic aggregates share many similarities, and in some cases may be indistinguishable without their stratigraphic context.

Aggregation in particle rich environments: a textural study of examples from volcanic eruptions, meteorite impacts, and fluidized bed processing.

PubMed

Mueller, Sebastian B; Kueppers, Ulrich; Huber, Matthew S; Hess, Kai-Uwe; Poesges, Gisela; Ruthensteiner, Bernhard; Dingwell, Donald B

2018-01-01

Aggregation is a common process occurring in many diverse particulate gas mixtures (e.g. those derived from explosive volcanic eruptions, meteorite impact events, and fluid bed processing). It results from the collision and sticking of particles suspended in turbulent gas/air. To date, there is no generalized model of the underlying physical processes. Here, we investigate aggregates from 18 natural deposits (16 volcanic deposits and two meteorite impact deposits) as well as aggregates produced experimentally via fluidized bed techniques. All aggregates were analyzed for their size, internal structuring, and constituent particle size distribution. Commonalities and differences between the aggregate types are then used to infer salient features of the aggregation process. Average core to rim ratios of internally structured aggregates (accretionary lapilli) is found to be similar for artificial and volcanic aggregates but up to an order of magnitude different than impact-related aggregates. Rim structures of artificial and volcanic aggregates appear to be physically similar (single, sub-spherical, regularly-shaped rims) whereas impact-related aggregates more often show multiple or irregularly shaped rims. The particle size distributions (PSDs) of all three aggregate types are similar (< 200 μm). This proves that in all three environments, aggregation occurs under broadly similar conditions despite the significant differences in source conditions (particle volume fraction, particle size distribution, particle composition, temperature), residence times, plume conditions (e.g., humidity and temperature), and dynamics of fallout and deposition. Impact-generated and volcanic aggregates share many similarities, and in some cases may be indistinguishable without their stratigraphic context.

Comparison of silver, cesium, and strontium release predictions using PARFUME with results from the AGR-1 irradiation experiment

DOE PAGES

Collin, Blaise P.; Petti, David A.; Demkowicz, Paul A.; ...

2015-08-22

Here, the PARFUME (PARticle FUel ModEl) code was used to predict the release of fission products silver, cesium, and strontium from tristructural isotropic coated fuel particles and compacts during the first irradiation experiment (AGR-1) of the Advanced Gas Reactor Fuel Development and Qualification program. The PARFUME model for the AGR-1 experiment used the fuel compact volume average temperature for each of the 620 days of irradiation to calculate the release of silver, cesium, and strontium from a representative particle for a select number of AGR-1 compacts. Post-irradiation examination measurements provided data on release of these fission products from fuel compactsmore » and fuel particles, and retention of silver in the compacts outside of the silicon carbide (SiC) layer. PARFUME-predicted fractional release of silver, cesium, and strontium was determined and compared to the PIE measurements. For silver, comparisons show a trend of over-prediction at low burnup and under-prediction at high burnup. PARFUME has limitations in the modeling of the temporal and spatial distributions of the temperature and burnup across the compacts, which affects the accuracy of its predictions. Nevertheless, the comparisons on silver release lie in the same order of magnitude. Results show an overall over-prediction of the fractional release of cesium by PARFUME. For particles with failed SiC layers, the over-prediction is by a factor of up to 3, corresponding to a potential over-estimation of the diffusivity in uranium oxycarbide (UCO) by a factor of up to 250. For intact particles, whose release is much lower, the over-prediction is by a factor of up to 100, which could be attributed to an over-estimated diffusivity in SiC by about 40% on average. The release of strontium from intact particles is also over-predicted by PARFUME, which also points towards an over-estimated diffusivity of strontium in either SiC or UCO, or possibly both. The measured strontium fractional release from intact particles varied considerably from compact to compact, making it difficult to assess the effective over-estimation of the diffusivities. Moreover, the release of strontium from particles with failed SiC is difficult to observe experimentally due to the release from intact particles, preventing any conclusions to be made on the accuracy or validity of the PARFUME predictions and the modeled diffusivity of strontium in UCO.« less

Comparison of silver, cesium, and strontium release predictions using PARFUME with results from the AGR-1 irradiation experiment

NASA Astrophysics Data System (ADS)

Collin, Blaise P.; Petti, David A.; Demkowicz, Paul A.; Maki, John T.

2015-11-01

The PARFUME (PARticle FUel ModEl) code was used to predict the release of fission products silver, cesium, and strontium from tristructural isotropic coated fuel particles and compacts during the first irradiation experiment (AGR-1) of the Advanced Gas Reactor Fuel Development and Qualification program. The PARFUME model for the AGR-1 experiment used the fuel compact volume average temperature for each of the 620 days of irradiation to calculate the release of silver, cesium, and strontium from a representative particle for a select number of AGR-1 compacts. Post-irradiation examination (PIE) measurements provided data on release of these fission products from fuel compacts and fuel particles, and retention of silver in the compacts outside of the silicon carbide (SiC) layer. PARFUME-predicted fractional release of silver, cesium, and strontium was determined and compared to the PIE measurements. For silver, comparisons show a trend of over-prediction at low burnup and under-prediction at high burnup. PARFUME has limitations in the modeling of the temporal and spatial distributions of the temperature and burnup across the compacts, which affects the accuracy of its predictions. Nevertheless, the comparisons on silver release lie in the same order of magnitude. Results show an overall over-prediction of the fractional release of cesium by PARFUME. For particles with failed SiC layers, the over-prediction is by a factor of up to 3, corresponding to a potential over-estimation of the diffusivity in uranium oxycarbide (UCO) by a factor of up to 250. For intact particles, whose release is much lower, the over-prediction is by a factor of up to 100, which could be attributed to an over-estimated diffusivity in SiC by about 40% on average. The release of strontium from intact particles is also over-predicted by PARFUME, which also points towards an over-estimated diffusivity of strontium in either SiC or UCO, or possibly both. The measured strontium fractional release from intact particles varied considerably from compact to compact, making it difficult to assess the effective over-estimation of the diffusivities. Furthermore, the release of strontium from particles with failed SiC is difficult to observe experimentally due to the release from intact particles, preventing any conclusions to be made on the accuracy or validity of the PARFUME predictions and the modeled diffusivity of strontium in UCO.

Growth of juvenile Arctica islandica under experimental conditions

NASA Astrophysics Data System (ADS)

Witbaard, R.; Franken, R.; Visser, B.

1998-02-01

In two laboratory experiments, the effects of temperature and food availability on the growth of 10- to 23-mm high specimens of the bivalve Arctica islandica were estimated. Each experimental set-up consisted of 5 treatments in which either the food supply or the temperature differed. It was demonstrated that Arctica is able to grow at temperatures as low as 1°C. A tenfold increase of shell growth was observed at temperatures between 1° and 12°C. The greatest change in growth rate took place between 1° and 6°C. Average instantaneous shell growth varies between 0.0003 at 1°C to 0.0032/day at 12°C. The results suggest that temperature hardly affects the time spent in filtration, whereas particle density strongly influences that response. Starved animals at 9°C have their siphons open during only 12% of the time, whereas the siphons of optimally fed animals were open on average during 76% of the observations. Increased siphon activity corresponded to high shell and tissue growth. At 9°C, average shell growth at the optimum cell density of 20×106 cell/l was 3.1 mm corresponding to an instantaneous rate of 0.0026/day. An algal cell density ( Isochrysis galbana, Dunaliella marina) ranging between 5 and 7×106 cell/l is just enough to keep shells alive at 9°C. Carbon conversion efficiency at 9°C is estimated to vary between 11 and 14%.

The effect of temperature and chitosan concentration during storage on the growth of chitosan nanoparticle produced by ionic gelation method

NASA Astrophysics Data System (ADS)

Handani, Wenny Rinda; Sediawan, Wahyudi Budi; Tawfiequrrahman, Ahmad; Wiratni, Kusumastuti, Yuni

2017-05-01

The objective of this research was to get the mechanism of nano size chitosan particle growth during storage by observing the effect of temperature and initial concentration of chitosan. The products were analyzed using PSA to have the average of particle radius. Nanochitosan solution was prepared by ionic gelation method. This method is described as an electrostatic interaction between positively charged amine with negatively charged polyanion, such as tripolyphosphate (TPP). Chitosan was dissolved in 1% acetic acid and was stirred for 30 minutes. Tween 80 was added to avoid agglomeration. TPP was prepared by dissolving 0.336 g into distilled water. The nano size chitosan was obtained by mixing TPP and chitosan solution dropwise while stirring for 30 minutes. This step was done at 15°C and ambient temperature (about 30°C) and chitosan concentration 0.2%, 0.4% and 0.6%. The results show that temperature during ionic gelation process (15°C and 30°C) does not affect the initial size of the nanoparticles produced as well as the growth of the nanoparticles during storage. On the other hand, initial chitosan concentration strongly affects initial size of the nanoparticles produced and the growth of the nanoparticles during storage. The concentration of chitosan at 0.2%, 0.4%, 0.6% gave initial size of nanoparticle chitosan of 175.3 nm, 337.9 nm, 643.3 nm respectively. On the other hand, the growth mechanism of chitosan nanoparticle depended on its radius(R). At R<500 nm, the growth rate of nanoparticles is controlled by adsorption at the surface of the particles, while at R>500 nm, it is controlled by diffusion in the liquid film around the particles.

Hot spot temperature measurements in DT layered implosions

NASA Astrophysics Data System (ADS)

Patel, Pravesh; Ma, T.; Macphee, A.; Callahan, D.; Chen, H.; Cerjan, C.; Clark, D.; Edgell, D.; Hurricane, O.; Izumi, N.; Khan, S.; Jarrott, L.; Kritcher, A.; Springer, P.

2015-11-01

The temperature of the burning DT hot spot in an ICF implosion is a crucial parameter in understanding the thermodynamic conditions of the fuel at stagnation and and the performance of the implosion in terms of alpha-particle self-heating and energy balance. The continuum radiation spectrum emitted from the hot spot provides an accurate measure of the emissivity-weighted electron temperature. Absolute measurements of the emitted radiation are made with several independent instruments including spatially-resolved broadband imagers, and space- and time-integrated monochromatic detectors. We present estimates of the electron temperature in DT layered implosions derived from the radiation spectrum most consistent with the available measurements. The emissivity-weighted electron temperatures are compared to the neutron-averaged apparent ion temperatures inferred from neutron time-of-flight detectors. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

The influence of metal-support interactions on the accurate determination of Ru dispersion for Ru/TiO{sub 2}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Komaya, Takashi; Bell, A.T.; Weng-Sieh, Zara

1994-09-01

Titania-supported Ru catalysts have been characterized by TEM, {sup 1}H NMR, and H{sub 2} chemisorption to determine the metal particle size, the fraction of the metal surface available for H{sub 2} chemisorption, and the H{sub 2} adsorption capacity of the catalyst, as functions of the reduction temperature. TEM micrographs show that as the reduction temperature rises from 573 to 773K, the average particle size of Ru remains the same but the surface of the particles is covered to an increasing extent by an amorphous layer of titania. Quantitative estimates of the fraction of the Ru particle surface available for H{submore » 2} chemisorption were obtained by {sup 1}H NMR. The NMR spectra also show that a fraction of the adsorbed H{sub 2} spills over onto the support and that as a consequence measurements of total H{sub 2} chemisorption overestimate the number of Ru sites available for H{sub 2} adsorption. The implications of these results for the correct calculation of Ru dispersion and the determination of turnover frequencies for reactions carried out over Ru/TiO{sub 2} are discussed. 16 refs., 5 figs., 1 tab.« less

Variation and co-variation of PM10, particle number concentration, NOx and NO2 in the urban air - Relationships with wind speed, vertical temperature gradient and weather type

NASA Astrophysics Data System (ADS)

Grundström, M.; Hak, C.; Chen, D.; Hallquist, M.; Pleijel, H.

2015-11-01

Atmospheric ultrafine particles (UFP; diameter < 0.1 μm) represent a growing global health concern in urban environments and has a strong link to traffic related emissions. UFP is usually the dominating fraction of atmospheric particle number concentrations (PNC) despite being a minor part of total particle mass. The aim of this study was to empirically investigate the relationship between PNC and other air pollutants (NOX, NO2 and PM10) in the urban environment and their dependence on meteorology and weather type, using the Lamb Weather Type (LWT) classification scheme. The study was carried out in Gothenburg, Sweden, at an urban background site during April 2007-May 2008. It was found that daily average [PNC] correlated very well with [NOx] (R2 = 0.73) during inversion days, to a lesser extent with [NO2] (R2 = 0.58) and poorly with [PM10] (R2 = 0.07). Both PNC and NOx had similar response patterns to wind speed and to the strength of temperature inversions. PNC displayed two regimes, one strongly correlated to NOx and a second poorly correlated to NOx which was characterised by high wind speed. For concentration averages based on LWTs, the PNC-[NOx] relationship remained strong (R2 = 0.70) where the windy LWT W deviated noticeably. Exclusion of observations with wind speed >5 ms-1 or ΔT < 0 °C from LWTs produced more uniform and stronger relationships (R2 = 0.90; R2 = 0.93). Low wind speeds and positive vertical temperature gradients were most common during LWTs A, NW, N and NE. These weather types were also associated with the highest daily means of NOx (∼30 ppb) and PNC (∼10 000 # cm-3). A conclusion from this study is that NOx (but not PM10) is a good proxy for PNC especially during calm and stable conditions and that LWTs A, NW, N and NE are high risk weather types for elevated NOx and PNC.

Preparation of steam activated carbon from rubberwood sawdust (Hevea brasiliensis) and its adsorption kinetics.

PubMed

Prakash Kumar, B G; Shivakamy, K; Miranda, Lima Rose; Velan, M

2006-08-25

Activated carbon was produced from a biowaste product, rubberwood sawdust (RWSD) using steam in a high temperature fluidized bed reactor. Experiments were carried out to investigate the influence of various process parameters such as activation time, activation temperature, particle size and fluidising velocity on the quality of the activated carbon. The activated carbon was characterized based on its iodine number, methylene blue number, Brauner Emmet Teller (BET) surface area and surface area obtained using the ethylene glycol mono ethyl ether (EGME) retention method. The best quality activated carbon was obtained at an activation time and temperature of 1h and 750 degrees C for an average particle size of 0.46 mm. The adsorption kinetics shows that pseudo-second-order rate fitted the adsorption kinetics better than pseudo-first-order rate equation. The adsorption capacity of carbon produced from RWSD was found to be 1250 mg g(-1) for the Bismark Brown dye. The rate constant and diffusion coefficient for intraparticle transport were determined for steam activated carbon. The characteristic of the prepared activated carbon was found comparable to the commercial activated carbon.

Facile Synthesis of Calcium Borate Nanoparticles and the Annealing Effect on Their Structure and Size

PubMed Central

Erfani, Maryam; Saion, Elias; Soltani, Nayereh; Hashim, Mansor; Wan Abdullah, Wan Saffiey B.; Navasery, Manizheh

2012-01-01

Calcium borate nanoparticles have been synthesized by a thermal treatment method via facile co-precipitation. Differences of annealing temperature and annealing time and their effects on crystal structure, particle size, size distribution and thermal stability of nanoparticles were investigated. The formation of calcium borate compound was characterized by X-ray diffraction (XRD) and Fourier Transform Infrared spectroscopy (FTIR), Transmission electron microscopy (TEM), and Thermogravimetry (TGA). The XRD patterns revealed that the co-precipitated samples annealed at 700 °C for 3 h annealing time formed an amorphous structure and the transformation into a crystalline structure only occurred after 5 h annealing time. It was found that the samples annealed at 900 °C are mostly metaborate (CaB2O4) nanoparticles and tetraborate (CaB4O7) nanoparticles only observed at 970 °C, which was confirmed by FTIR. The TEM images indicated that with increasing the annealing time and temperature, the average particle size increases. TGA analysis confirmed the thermal stability of the annealed samples at higher temperatures. PMID:23203073

Temperature scaling in a dense vibrofluidized granular material.

PubMed

Sunthar, P; Kumaran, V

1999-08-01

The leading order "temperature" of a dense two-dimensional granular material fluidized by external vibrations is determined. The grain interactions are characterized by inelastic collisions, but the coefficient of restitution is considered to be close to 1, so that the dissipation of energy during a collision is small compared to the average energy of a particle. An asymptotic solution is obtained where the particles are considered to be elastic in the leading approximation. The velocity distribution is a Maxwell-Boltzmann distribution in the leading approximation. The density profile is determined by solving the momentum balance equation in the vertical direction, where the relation between the pressure and density is provided by the virial equation of state. The temperature is determined by relating the source of energy due to the vibrating surface and the energy dissipation due to inelastic collisions. The predictions of the present analysis show good agreement with simulation results at higher densities where theories for a dilute vibrated granular material, with the pressure-density relation provided by the ideal gas law, are in error.

Preparation and the influencing factors of timozolomide liposomes.

PubMed

Kong, Bin; Sun, Yong; Li, Yongjian; Hu, Dejian

2009-01-01

To prepare timozolomide liposomes for administration through nasal mucous membrane, we studied the factors of the preparation of the liposomes. The timozolomide liposomes were prepared by the ammonium sulphate gradient method; electroscopy and laser particle analyzer were utilized to determine the conformation, size and distribution of timozolomide liposomes; high performance liquid chromatography (HPLC) was applied to determine the entrapping efficiency of timozolomide liposomes; then we studied the influences of the concentration of ammonium sulphate solution, temperature, and the drug-to-lipid ratio on the entrapping efficiency. The average size of timozolomide liposomes was 185 nm; the entrapping efficiency was 90.3%. The entrapping efficiency was enhanced with the increasing of the concentration of ammonium sulphate solution and the rising of temperature, and decreased with the increasing of the drug-to-lipid ratio. The timozolomide liposomes with high entrapping efficiency, small and even particle sizes could be prepared by the simple and convenient ammonium sulphate gradient method. The primary influencing factors on the entrapping efficiency of timozolomide liposomes were the concentration of ammonium sulphate solution, the temperature, and the drug-to-lipid ratio.

IF-WS{sub 2} nanoparticles size design and synthesis via chemical reduction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghoreishi, S.M., E-mail: ghoreshi@cc.iut.ac.ir; Meshkat, S.S.; Dadkhah, A.A.

2010-05-15

An innovative synthesis of inorganic fullerene-like disulfide tungsten (IF-WS{sub 2}) nanoparticles was developed using a chemical reduction reaction in a horizontal quartz reactor. In this process, first tungsten trisulfide (WS{sub 3}) was formed via a chemical reaction of tetra thiotungstate ammonium ((NH{sub 4}){sub 2}WS{sub 4}), polyethylene glycol (PEG), and hydrochloric acid (HCl) at ambient temperature and pressure. Subsequently, WS{sub 3} was reacted with hydrogen (H{sub 2}) at high temperature (1173-1373 K) in a quartz tube. The produced WS{sub 2} nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDAX), and transmission electron microscopy (TEM). Themore » characterization results indicated that the high-purity (100%) IF-WS{sub 2} nanoparticles were produced. Moreover, addition of surfactant (PEG) and higher operating temperature (1173-1373 K) decreased the particles agglomeration, and consequently led to the reduction of average diameter of WS{sub 2} particles in the range of 50-78 nm. The developed method is simple, environmentally compatible, and cost-effective in contrast to the conventional techniques.« less

High-temperature ratchets with sawtooth potentials

NASA Astrophysics Data System (ADS)

Rozenbaum, Viktor M.; Shapochkina, Irina V.; Sheu, Sheh-Yi; Yang, Dah-Yen; Lin, Sheng Hsien

2016-11-01

The concept of the effective potential is suggested as an efficient instrument to get a uniform analytical description of stochastic high-temperature on-off flashing and rocking ratchets. The analytical representation for the average particle velocity, obtained within this technique, allows description of ratchets with sharp potentials (and potentials with jumps in particular). For sawtooth potentials, the explicit analytical expressions for the average velocity of on-off flashing and rocking ratchets valid for arbitrary frequencies of potential energy fluctuations are derived; the difference in their high-frequency asymptotics is explored for the smooth and cusped profiles, and profiles with jumps. The origin of the difference as well as the appearance of the jump behavior in ratchet characteristics are interpreted in terms of self-similar universal solutions which give the continuous description of the effect. It is shown how the jump behavior in motor characteristics arises from the competition between the characteristic times of the system.

Intrinsic dependence of the magnetic properties of CoFe2O4 nanoparticles prepared via chemical methods with addition of chelating agents

NASA Astrophysics Data System (ADS)

Mendonça, E. C.; Tenório, Mayara A.; Mecena, S. G.; Zucolotto, B.; Silva, L. S.; Jesus, C. B. R.; Meneses, C. T.; Duque, J. G. S.

2015-12-01

In this work, the effect of addition of different chelating agents on the magnetic properties of cobalt ferrite nanoparticles produced by the combining of both co-precipitation and hydrothermal methods is reported. The Rietveld analyses of X-ray diffraction patterns reveal that our samples are single phase (space group: Fd-3m) with small average sizes. The weight losses observed in the thermogravimetric measurements together with the M×H curves show that the organic contamination coming from chelating agent decomposition can give rise to misinterpretation of the magnetization measurements. Besides, analyses of the zero-field-cooled (ZFC) and field-cooled (FC) magnetization measurements and the M×H curves measured at room temperature allows us to state that both the average blocking temperature and particles size distribution are sensitive to the kind of chelating agent.

Laser heating tunability by off-resonant irradiation of gold nanoparticles.

PubMed

Hormeño, Silvia; Gregorio-Godoy, Paula; Pérez-Juste, Jorge; Liz-Marzán, Luis M; Juárez, Beatriz H; Arias-Gonzalez, J Ricardo

2014-01-29

Temperature changes in the vicinity of a single absorptive nanostructure caused by local heating have strong implications in technologies such as integrated electronics or biomedicine. Herein, the temperature changes in the vicinity of a single optically trapped spherical Au nanoparticle encapsulated in a thermo-responsive poly(N-isopropylacrylamide) shell (Au@pNIPAM) are studied in detail. Individual beads are trapped in a counter-propagating optical tweezers setup at various laser powers, which allows the overall particle size to be tuned through the phase transition of the thermo-responsive shell. The experimentally obtained sizes measured at different irradiation powers are compared with average size values obtained by dynamic light scattering (DLS) from an ensemble of beads at different temperatures. The size range and the tendency to shrink upon increasing the laser power in the optical trap or by increasing the temperature for DLS agree with reasonable accuracy for both approaches. Discrepancies are evaluated by means of simple models accounting for variations in the thermal conductivity of the polymer, the viscosity of the aqueous solution and the absorption cross section of the coated Au nanoparticle. These results show that these parameters must be taken into account when considering local laser heating experiments in aqueous solution at the nanoscale. Analysis of the stability of the Au@pNIPAM particles in the trap is also theoretically carried out for different particle sizes. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Heat transfer in freeboard region of fluidized beds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Biyikli, S.; Tuzla, K.; Chen, J.C.

1983-10-01

This research involved the study of heat transfer and fluid mechanic characteristics around a horizontal tube in the freeboard region of fluidized beds. Heat transfer coefficients were experimetnally measured for different bed temperatures, particle sizes, gas flow rates, and tube elevations in the freeboard region of air fluidized beds at atmospheric pressure. Local heat transfer coefficients were found to vary significantly with angular position around the tube. Average heat transfer coefficients were found to decrease with increasing freeboard tube elevation and approach the values for gas convection plus radiation for any given gas velocity. For a fixed tube elevation, heatmore » transfer coefficients generally increased with increasing gas velocity and with high particle entrainment they can approach the magnitudes found for immersed tubes. Heat transfer coefficients were also found to increase with increasing bed temperature. It was concluded that this increase is partly due to increase of radiative heat transfer and partly due to change of thermal properties of the fluidizing gas and particles. To investigate the fluid mechanic behavior of gas and particles around a freeboard tube, transient particle tube contacts were measured with a special capacitance probe in room temperature experiments. The results indicated that the tube surface experiences alternating dense and lean phase contacts. Quantitative information for local characteristics was obtained from the capacitance signals and used to develop a phenomenological model for prediction of the heat transfer coefficients around freeboard tubes. The packet renewal theory was modified to account for the dense phase heat transfer and a new model was suggested for the lean phase heat transfer. Finally, an empirical freeboard heat transfer correlation was developed from functional analysis of the freeboard heat transfer data using nondimensional groups representing gas velocity and tube elevation.« less

Humid Heat Autoclaving of Hybrid Nanoparticles Achieved by Decreased Nanoparticle Concentration and Improved Nanoparticle Stability Using Medium Chain Triglycerides as a Modifier.

PubMed

Gou, Jingxin; Chao, Yanhui; Liang, Yuheng; Zhang, Ning; He, Haibing; Yin, Tian; Zhang, Yu; Xu, Hui; Tang, Xing

2016-09-01

Humid heat autoclaving is a facile technique widely used in the sterilization of injections, but the high temperature employed would destroy nanoparticles composed of biodegradable polymers. The aim of this study was to investigate whether incorporation of medium chain triglycerides (MCT) could stabilize nanoparticles composed of poly (ethylene glycol)-b-polycaprolactone (PEG-b-PCL) during autoclaving (121°C, 10 min). Polymeric nanoparticles with different MCT contents were prepared by dialysis. Block copolymer degradation was studied by GPC. The critical aggregation concentrations of nanoparticles at different temperatures were determined using pyrene fluorescence. The size, morphology and weight averaged molecular weight of pristine/autoclaved nanoparticles were studied using DLS, TEM and SLS, respectively. Drug loading content and release profile were determined using RP-HPLC. The protecting effect of MCT on nanoparticles was dependent on the amount of MCT incorporated. Nanoparticles with high MCT contents, which assumed an emulsion-like morphology, showed reduced block copolymer degradation and particle disassociation after incubation at 100°C for 24 h. Nanoparticles with high MCT content showed the lowest critical aggregation concentration (CAC) under either room temperature or 60°C and the lowest particle concentration among all samples. And the particle size, drug loading content, physical stability and release profile of nanoparticles with high MCT contents remained nearly unchanged after autoclaving. Incorporation of high amount of MCT changed the morphology of PEG-b-PCL based nanoparticles to an emulsion-like structure and the nanoparticles prepared could withstand autoclaving due to improved particle stability and decreased particle concentration caused by MCT incorporation.

Impact of formulation and particle size on stability and immunogenicity of oil-in-water emulsion adjuvants

PubMed Central

Iyer, Vidyashankara; Cayatte, Corinne; Guzman, Bernardo; Schneider-Ohrum, Kirsten; Matuszak, Ryan; Snell, Angie; Rajani, Gaurav Manohar; McCarthy, Michael P; Muralidhara, Bilikallahalli

2015-01-01

Oil-in-water emulsions have gained consideration as vaccine adjuvants in recent years due to their ability to elicit a differentiated immunogenic response compared to traditional aluminum salt adjuvants. Squalene, a cholesterol precursor, is a natural product with immunostimulatory properties, making it an ideal candidate for such oil-in-water emulsions. Particle size is a key parameter of these emulsions and its relationship to stability and adjuvanticity has not been extensively studied. This study evaluates the effect of particle size on the stability and immunogenicity of squalene emulsions. We investigated the effect of formulation parameters such as surfactant concentration on particle size, resulting in particles with average diameter of 80 nm, 100 nm, 150 nm, 200 nm, or 250 nm. Emulsions were exposed to shear and temperature stresses, and stability parameters such as pH, osmolarity, size, and in-depth visual appearance were monitored over time. In addition, adjuvanticity of different particle size was assessed in a mouse model using Respiratory Syncytial Virus Fusion protein (RSV-F) as a model antigen. Temperature dependent phase separation appeared to be the most common route of degradation occurring in the higher particle sizes emulsions. The emulsions below 150 nm size maintained stability at either 5°C or 25°C, and the 80 nm diameter ones showed no measurable changes in size even after one month at 40°C. In vivo studies using the emulsions as an adjuvant with RSV F antigen revealed that superior immunogenicity could be achieved with the 80 nm particle size emulsion. PMID:26090563

Plume-exit modeling to determine cloud condensation nuclei activity of aerosols from residential biofuel combustion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mena, Francisco; Bond, Tami C.; Riemer, Nicole

Residential biofuel combustion is an important source of aerosols and gases in the atmosphere. The change in cloud characteristics due to biofuel burning aerosols is uncertain, in part, due to the uncertainty in the added number of cloud condensation nuclei (CCN) from biofuel burning. We provide estimates of the CCN activity of biofuel burning aerosols by explicitly modeling plume dynamics (coagulation, condensation, chemical reactions, and dilution) in a young biofuel burning plume from emission until plume exit, defined here as the condition when the plume reaches ambient temperature and specific humidity through entrainment. We found that aerosol-scale dynamics affect CCNmore » activity only during the first few seconds of evolution, after which the CCN efficiency reaches a constant value. Homogenizing factors in a plume are co-emission of semi-volatile organic compounds (SVOCs) or emission at small particle sizes; SVOC co-emission can be the main factor determining plume-exit CCN for hydrophobic or small particles. Coagulation limits emission of CCN to about 10 16 per kilogram of fuel. Depending on emission factor, particle size, and composition, some of these particles may not activate at low supersaturation ( s sat). Hygroscopic Aitken-mode particles can contribute to CCN through self-coagulation but have a small effect on the CCN activity of accumulation-mode particles, regardless of composition differences. Simple models (monodisperse coagulation and average hygroscopicity) can be used to estimate plume-exit CCN within about 20 % if particles are unimodal and have homogeneous composition, or when particles are emitted in the Aitken mode even if they are not homogeneous. On the other hand, if externally mixed particles are emitted in the accumulation mode without SVOCs, an average hygroscopicity overestimates emitted CCN by up to a factor of 2. This work has identified conditions under which particle populations become more homogeneous during plume processes. This homogenizing effect requires the components to be truly co-emitted, rather than sequentially emitted.« less

Plume-exit modeling to determine cloud condensation nuclei activity of aerosols from residential biofuel combustion

NASA Astrophysics Data System (ADS)

Mena, Francisco; Bond, Tami C.; Riemer, Nicole

2017-08-01

Residential biofuel combustion is an important source of aerosols and gases in the atmosphere. The change in cloud characteristics due to biofuel burning aerosols is uncertain, in part, due to the uncertainty in the added number of cloud condensation nuclei (CCN) from biofuel burning. We provide estimates of the CCN activity of biofuel burning aerosols by explicitly modeling plume dynamics (coagulation, condensation, chemical reactions, and dilution) in a young biofuel burning plume from emission until plume exit, defined here as the condition when the plume reaches ambient temperature and specific humidity through entrainment. We found that aerosol-scale dynamics affect CCN activity only during the first few seconds of evolution, after which the CCN efficiency reaches a constant value. Homogenizing factors in a plume are co-emission of semi-volatile organic compounds (SVOCs) or emission at small particle sizes; SVOC co-emission can be the main factor determining plume-exit CCN for hydrophobic or small particles. Coagulation limits emission of CCN to about 1016 per kilogram of fuel. Depending on emission factor, particle size, and composition, some of these particles may not activate at low supersaturation (ssat). Hygroscopic Aitken-mode particles can contribute to CCN through self-coagulation but have a small effect on the CCN activity of accumulation-mode particles, regardless of composition differences. Simple models (monodisperse coagulation and average hygroscopicity) can be used to estimate plume-exit CCN within about 20 % if particles are unimodal and have homogeneous composition, or when particles are emitted in the Aitken mode even if they are not homogeneous. On the other hand, if externally mixed particles are emitted in the accumulation mode without SVOCs, an average hygroscopicity overestimates emitted CCN by up to a factor of 2. This work has identified conditions under which particle populations become more homogeneous during plume processes. This homogenizing effect requires the components to be truly co-emitted, rather than sequentially emitted.

Plume-exit modeling to determine cloud condensation nuclei activity of aerosols from residential biofuel combustion

DOE PAGES

Mena, Francisco; Bond, Tami C.; Riemer, Nicole

2017-08-07

Residential biofuel combustion is an important source of aerosols and gases in the atmosphere. The change in cloud characteristics due to biofuel burning aerosols is uncertain, in part, due to the uncertainty in the added number of cloud condensation nuclei (CCN) from biofuel burning. We provide estimates of the CCN activity of biofuel burning aerosols by explicitly modeling plume dynamics (coagulation, condensation, chemical reactions, and dilution) in a young biofuel burning plume from emission until plume exit, defined here as the condition when the plume reaches ambient temperature and specific humidity through entrainment. We found that aerosol-scale dynamics affect CCNmore » activity only during the first few seconds of evolution, after which the CCN efficiency reaches a constant value. Homogenizing factors in a plume are co-emission of semi-volatile organic compounds (SVOCs) or emission at small particle sizes; SVOC co-emission can be the main factor determining plume-exit CCN for hydrophobic or small particles. Coagulation limits emission of CCN to about 10 16 per kilogram of fuel. Depending on emission factor, particle size, and composition, some of these particles may not activate at low supersaturation ( s sat). Hygroscopic Aitken-mode particles can contribute to CCN through self-coagulation but have a small effect on the CCN activity of accumulation-mode particles, regardless of composition differences. Simple models (monodisperse coagulation and average hygroscopicity) can be used to estimate plume-exit CCN within about 20 % if particles are unimodal and have homogeneous composition, or when particles are emitted in the Aitken mode even if they are not homogeneous. On the other hand, if externally mixed particles are emitted in the accumulation mode without SVOCs, an average hygroscopicity overestimates emitted CCN by up to a factor of 2. This work has identified conditions under which particle populations become more homogeneous during plume processes. This homogenizing effect requires the components to be truly co-emitted, rather than sequentially emitted.« less

Averaging processes in granular flows driven by gravity

NASA Astrophysics Data System (ADS)

Rossi, Giulia; Armanini, Aronne

2016-04-01

One of the more promising theoretical frames to analyse the two-phase granular flows is offered by the similarity of their rheology with the kinetic theory of gases [1]. Granular flows can be considered a macroscopic equivalent of the molecular case: the collisions among molecules are compared to the collisions among grains at a macroscopic scale [2,3]. However there are important statistical differences in dealing with the two applications. In the two-phase fluid mechanics, there are two main types of average: the phasic average and the mass weighed average [4]. The kinetic theories assume that the size of atoms is so small, that the number of molecules in a control volume is infinite. With this assumption, the concentration (number of particles n) doesn't change during the averaging process and the two definitions of average coincide. This hypothesis is no more true in granular flows: contrary to gases, the dimension of a single particle becomes comparable to that of the control volume. For this reason, in a single realization the number of grain is constant and the two averages coincide; on the contrary, for more than one realization, n is no more constant and the two types of average lead to different results. Therefore, the ensamble average used in the standard kinetic theory (which usually is the phasic average) is suitable for the single realization, but not for several realization, as already pointed out in [5,6]. In the literature, three main length scales have been identified [7]: the smallest is the particles size, the intermediate consists in the local averaging (in order to describe some instability phenomena or secondary circulation) and the largest arises from phenomena such as large eddies in turbulence. Our aim is to solve the intermediate scale, by applying the mass weighted average, when dealing with more than one realizations. This statistical approach leads to additional diffusive terms in the continuity equation: starting from experimental results, we aim to define the scales governing the diffusive phenomenon, introducing the diffusive terms following the Boussinesq model. The diffusive coefficient will be experimentally defined; it will be probably proportional to the square root of the granular temperature θ and the diameter of the particles d or, alternatively, the flow height h. REFERENCES 1 Chapman S., Cowling T.G., 1971. Cambridge University Press, Cambridge, England. 2 Jenkins J.T., Savage S.B., 1983 J. Fluid.Mech., 130: 187-202 3 Savage S.B.,1984. J. Fluid.Mech., 24: 289-366 4 D.A.Drew, 1983. Annu. Rev. Fluid Mech. 15:261-291 5 I. Goldhirsch, 2003. Annu. Rev. Fluid Mech., 35:267-293. 6 I. Goldhirsch, 2008. Powder Technology, 182: 130-136. 7 T.J. Hsu, J.T. Jenkins, P.L. Liu 2004. Proc. Royal Soc.

NMR relaxation induced by iron oxide particles: testing theoretical models.

PubMed

Gossuin, Y; Orlando, T; Basini, M; Henrard, D; Lascialfari, A; Mattea, C; Stapf, S; Vuong, Q L

2016-04-15

Superparamagnetic iron oxide particles find their main application as contrast agents for cellular and molecular magnetic resonance imaging. The contrast they bring is due to the shortening of the transverse relaxation time T 2 of water protons. In order to understand their influence on proton relaxation, different theoretical relaxation models have been developed, each of them presenting a certain validity domain, which depends on the particle characteristics and proton dynamics. The validation of these models is crucial since they allow for predicting the ideal particle characteristics for obtaining the best contrast but also because the fitting of T 1 experimental data by the theory constitutes an interesting tool for the characterization of the nanoparticles. In this work, T 2 of suspensions of iron oxide particles in different solvents and at different temperatures, corresponding to different proton diffusion properties, were measured and were compared to the three main theoretical models (the motional averaging regime, the static dephasing regime, and the partial refocusing model) with good qualitative agreement. However, a real quantitative agreement was not observed, probably because of the complexity of these nanoparticulate systems. The Roch theory, developed in the motional averaging regime (MAR), was also successfully used to fit T 1 nuclear magnetic relaxation dispersion (NMRD) profiles, even outside the MAR validity range, and provided a good estimate of the particle size. On the other hand, the simultaneous fitting of T 1 and T 2 NMRD profiles by the theory was impossible, and this occurrence constitutes a clear limitation of the Roch model. Finally, the theory was shown to satisfactorily fit the deuterium T 1 NMRD profile of superparamagnetic particle suspensions in heavy water.

Particle number concentrations near the Rome-Ciampino city airport

NASA Astrophysics Data System (ADS)

Stafoggia, M.; Cattani, G.; Forastiere, F.; Di Menno di Bucchianico, A.; Gaeta, A.; Ancona, C.

2016-12-01

Human exposure to ultrafine particles (UFP) has been postulated to be associated with adverse health effects, and there is interest regarding possible measures to reduce primary emissions. One important source of UFP are airport activities, with aircraft take-offs being the most relevant one. We implemented two measurement campaigns of total particle number concentrations (PNC), a proxy for UFP, near a medium-size airport in central Italy. One-minute PNC averages were collected on June 2011 and January 2012 concurrently with 30-min average meteorological data on temperature and wind speed/direction. Data on minute-specific take-offs and landings were obtained by the airport authorities. We applied statistical regression models to relate PNC data to the presence of aircraft activities while adjusting for time trends and meteorology, and estimated the increases in PNC ±15 min before and after take-offs and landings. We repeated the analyses considering prevalent wind direction and by size of the aircraft. We estimated PNC increases of 5400 particles/cm3/minute during the 15 min before and after take-offs, with a peak of 19,000 particles/cm3/minute within 5 min after take-offs. Corresponding figures for landings were 1300 and 1000 particles, respectively. The highest PNC estimates were obtained when the prevailing wind came from the runway direction, and led to estimated PNC increases of 60,000 particles/cm3/minute within 5 min after take-offs. No main differences were noted from the exhaust of different types of aircrafts. The area surrounding Ciampino airport is densely inhabited, raising concerns about the potential adverse effects of long-term and short-term exposure to airport-borne UFP. A close monitoring of airport activities and emissions is mandatory to reduce the public health impact of the airport on the nearby population.

Codeformation processing of mechanically-dissimilar metal/intermetallic composites

NASA Astrophysics Data System (ADS)

Marte, Judson Sloan

A systematic and scientific approach has been applied to the study of codeformation processing. A series of composites having mechanically-dissimilar phases were developed in which the high temperature flow behavior of the reinforcement material could be varied independent of the matrix. This was accomplished through the use of a series of intermetallic matrix composites (IMCs) as discontinuous reinforcements in an otherwise conventional metal matrix composite. The IMCs are produced using an in-situ reaction synthesis technique, called the XD(TM) process. The temperature of the exothermic synthesis reaction, called the adiabatic temperature, has been calculated and shown to increase with increasing volume percentage of TiB2 reinforcement. Further, this temperature has been shown to effect the size and spacing of the TiB2, microstructural features which are often used in discontinuous composite strength models. Study of the high temperature flow behavior of the components of the metal/IMC composite is critical to the development of an understanding of codeformation. A series of compression tests performed at 1000° to 1200°C and strain-rates of 10-3 and 10-4 sec-1. Peak flow stresses were used to evaluate the influence of material properties and process conditions. These data were incorporated into phenomenologically-based constitutive equations that have been used to predict the flow behavior. It has been determined that plastic deformation of the IMCs occurs readily, and is largely TiB2 independent, at temperatures approaching the melting point of the intermetallic matrices. Ti-6Al-4V/IMC powder blends were extruded at high temperatures to achieve commensurately deformed microstructures. The results of codeformation processing were analyzed in terms of the plastic strain of the IMC particulates. IMC particle deformation was shown to increase with increasing IMC particle size, volume percentage of IMC, extrusion temperature, homologous temperature, extrusion strain-rate, and decreasing TiB2 reinforcement within the IMCs. A series of finite element models were developed to simulate codeformation processing via the extrusion of a discontinuously-reinforced composite. The results were evaluated through comparison between average equivalent strain in matrix and reinforcement elements. These results show that codeformation should increase with increasing volume percentage of IMC, homologous temperature, volume percentage of IMC, and decreasing IMC particle size. With the exception of the particle size, these results correlate to those of the experimental extrusion analysis.

Combustion synthesis and structural analysis of nanocrystalline nickel ferrite at low temperature regime

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shanmugavel, T., E-mail: gokulrajs@hotmail.com, E-mail: shanmugavelnano@gmail.com; Raj, S. Gokul, E-mail: gokulrajs@hotmail.com, E-mail: shanmugavelnano@gmail.com; Rajarajan, G.

2015-06-24

Combustion synthesis of single phase Nickel ferrite was successfully achieved at low temperature regime. The obtained powders were calcinated to increase the crystallinity and their characterization change due to calcinations is investigated in detail. Citric acid used as a chelating agent for the synthesis of nickel ferrite. Pure single phase nickel ferrites were found at this low temperature. The average crystalline sizes were measured by using powder XRD measurements. Surface morphology was investigated through Transmission Electron Microscope (TEM). Particle size calculated in XRD is compared with TEM results. Magnetic behaviour of the samples is analyzed by using Vibrating Sample Magnetometermore » (VSM). Saturation magnetization, coercivity and retentivity are measured and their results are discussed in detail.« less

Solvothermal synthesis of nanocrystalline TiO 2 in toluene with surfactant

NASA Astrophysics Data System (ADS)

Kim, Chung-Sik; Moon, Byung Kee; Park, Jong-Ho; Choi, Byung-Chun; Seo, Hyo-Jin

2003-10-01

Synthesis of narrow-dispersed nanocrystalline TiO 2 was investigated by surfactant-aided solvothermal synthetic method in toluene solutions. Titanium isopropoxide (TIP) was used as precursor, which was decomposed at high temperature in the surfactant-dissolved solution. After the solution was thermally treated at 250°C for 20 h in an autoclave, low-dispersed TiO 2 nanocrystalline particles with average size of <6 nm were synthesized. When sufficient amount of TIP or surfactant was added in the solution, long dumbbell-shaped nanorods were formed, which may be due to the oriented growth of particles along [0 0 1] axis. Characterization of products was investigated by X-ray diffraction and transmission electron microscopy.

Assessing the accuracy of ANFIS, EEMD-GRNN, PCR, and MLR models in predicting PM2.5

NASA Astrophysics Data System (ADS)

Ausati, Shadi; Amanollahi, Jamil

2016-10-01

Since Sanandaj is considered one of polluted cities of Iran, prediction of any type of pollution especially prediction of suspended particles of PM2.5, which are the cause of many diseases, could contribute to health of society by timely announcements and prior to increase of PM2.5. In order to predict PM2.5 concentration in the Sanandaj air the hybrid models consisting of an ensemble empirical mode decomposition and general regression neural network (EEMD-GRNN), Adaptive Neuro-Fuzzy Inference System (ANFIS), principal component regression (PCR), and linear model such as multiple liner regression (MLR) model were used. In these models the data of suspended particles of PM2.5 were the dependent variable and the data related to air quality including PM2.5, PM10, SO2, NO2, CO, O3 and meteorological data including average minimum temperature (Min T), average maximum temperature (Max T), average atmospheric pressure (AP), daily total precipitation (TP), daily relative humidity level of the air (RH) and daily wind speed (WS) for the year 2014 in Sanandaj were the independent variables. Among the used models, EEMD-GRNN model with values of R2 = 0.90, root mean square error (RMSE) = 4.9218 and mean absolute error (MAE) = 3.4644 in the training phase and with values of R2 = 0.79, RMSE = 5.0324 and MAE = 3.2565 in the testing phase, exhibited the best function in predicting this phenomenon. It can be concluded that hybrid models have accurate results to predict PM2.5 concentration compared with linear model.

Mars atmospheric CO2 condensation above the north and south poles as revealed by radio occultation, climate sounder, and laser ranging observations

NASA Astrophysics Data System (ADS)

Hu, Renyu; Cahoy, Kerri; Zuber, Maria T.

2012-07-01

We study the condensation of CO2 in Mars' atmosphere using temperature profiles retrieved from radio occultation measurements from Mars Global Surveyor (MGS) as well as the climate sounding instrument onboard the Mars Reconnaissance Orbiter (MRO), and detection of reflective clouds by the MGS Mars Orbiter Laser Altimeter (MOLA). We find 11 events in 1999 where MGS temperature profiles indicate CO2 condensation and MOLA simultaneously detects reflective clouds. We thus provide causal evidence that MOLA non-ground returns are associated with CO2 condensation, which strongly indicates their nature being CO2 clouds. The MGS and MRO temperature profiles together reveal the seasonal expansion and shrinking of the area and the vertical extent of atmospheric saturation. The occurrence rate of atmospheric saturation is maximized at high latitudes in the middle of winter. The atmospheric saturation in the northern polar region exhibits more intense seasonal variation than in the southern polar region. In particular, a shrinking of saturation area and thickness from LS ˜ 270° to ˜300° in 2007 is found; this is probably related to a planet-encircling dust storm. Furthermore, we integrate the condensation area and the condensation occurrence rate to estimate cumulative masses of CO2 condensates deposited onto the northern and southern seasonal polar caps. The precipitation flux is approximated by the particle settling flux which is estimated using the impulse responses of MOLA filter channels. With our approach, the total atmospheric condensation mass can be estimated from these observational data sets with average particle size as the only free parameter. By comparison with the seasonal polar cap masses inferred from the time-varying gravity of Mars, our estimates indicate that the average condensate particle radius is 8-22 μm in the northern hemisphere and 4-13 μm in the southern hemisphere. Our multi-instrument data analysis provides new constraints on modeling the global climate of Mars.

Mass transfer equation for proteins in very high-pressure liquid chromatography.

PubMed

Gritti, Fabrice; Guiochon, Georges

2009-04-01

The mass transfer kinetics of human insulin was investigated on a 50 mm x 2.1 mm column packed with 1.7 microm BEH-C(18) particles, eluted with a water/acetonitrile/trifluoroacetic acid (TFA) (68/32/0.1, v/v/v) solution. The different contributions to the mass transfer kinetics, e.g., those of longitudinal diffusion, eddy dispersion, the film mass transfer resistance, cross-particle diffusivity, adsorption-desorption kinetics, and transcolumn differential sorption, were incorporated into a general mass transfer equation designed to account for the mass transfer kinetics of proteins under high pressure. More specifically, this equation includes the effects of pore size exclusion, pressure, and temperature on the band broadening of a protein. The flow rate was first increased from 0.001 to 0.250 mL/min, the pressure drop increasing from 2 to 298 bar, and the column being placed in stagnant air at 296.5 K, in order to determine the effective diffusivity of insulin through the porous particles, the mass transfer rate constants, and the adsorption equilibrium constant in the low-pressure range. Then, the column inlet pressure was increased by using capillary flow restrictors downstream the column, at the constant flow rate of 0.03 mL/min. The column temperature was kept uniform by immersing the column in a circulating water bath thermostatted at 298.7 and 323.15 K, successively. The results showed that the surface diffusion coefficient of insulin decreases faster than its bulk diffusion coefficient with increasing average column pressure. This is consistent with the adsorption energy of insulin onto the BEH-C(18) surface increasing strongly with increasing pressure. In contrast, given the precision of the height equivalent to a theoretical plate (HETP) measurement (+/-12%), the adsorption kinetics of insulin appears to be rather independent of the pressure. On average, the adsorption rate constant of insulin is doubled from about 40 to 80 s(-1) when the temperature increases from 298.7 to 323.15 K.

Electrostatic forces in planetary rings

NASA Technical Reports Server (NTRS)

Goertz, C. K.; Shan, Linhua; Havnes, O.

1988-01-01

The average charge on a particle in a particle-plasma cloud, the plasma potential inside the cloud, and the Coulomb force acting on the particle are calculated. The net repulsive electrostatic force on a particle depends on the plasma density, temperature, density of particles, particle size, and the gradient of the particle density. In a uniformly dense ring the electrostatic repulsion is zero. It is also shown that the electrostatic force acts like a pressure force, that even a collisionless ring can be stable against gravitational collapse, and that a finite ring thickness does not necessarily imply a finite velocity dispersion. A simple criterion for the importance of electrostatic forces in planetary rings is derived which involves the calculation of the vertical ring thickness which would result if only electrostatic repulsion were responsible for the finite ring thickness. Electrostatic forces are entirely negligible in the main rings of Saturn and the E and G rings. They may also be negligible in the F ring. However, the Uranian rings and Jupiter's ring seem to be very much influenced by electrostatic repulsion. In fact, electrostatic forces could support a Jovian ring which is an order of magnitude more dense than observed.

Modelling and validation of particle size distributions of supported nanoparticles using the pair distribution function technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gamez-Mendoza, Liliana; Terban, Maxwell W.; Billinge, Simon J. L.

The particle size of supported catalysts is a key characteristic for determining structure–property relationships. It is a challenge to obtain this information accurately andin situusing crystallographic methods owing to the small size of such particles (<5 nm) and the fact that they are supported. In this work, the pair distribution function (PDF) technique was used to obtain the particle size distribution of supported Pt catalysts as they grow under typical synthesis conditions. The PDF of Pt nanoparticles grown on zeolite X was isolated and refined using two models: a monodisperse spherical model (single particle size) and a lognormal size distribution.more » The results were compared and validated using scanning transmission electron microscopy (STEM) results. Both models describe the same trends in average particle size with temperature, but the results of the number-weighted lognormal size distributions can also accurately describe the mean size and the width of the size distributions obtained from STEM. Since the PDF yields crystallite sizes, these results suggest that the grown Pt nanoparticles are monocrystalline. This work shows that refinement of the PDF of small supported monocrystalline nanoparticles can yield accurate mean particle sizes and distributions.« less

Synthesis and characterization of monosodium urate (MSU) nano particles

NASA Astrophysics Data System (ADS)

Tank, Nirali S.; Rathod, K. R.; Parekh, B. B.; Parikh, K. D.; Joshi, M. J.

2016-05-01

In Gout the deposition of crystals of Monosodium Urate (MSU) in various connective tissues and joints occurs, which is very painful with immflamation. The deposition likely to begin with nano particles form and expected to grow in to micro-paricles and hence it is important to synthesize and characrterize MSU nano-particles. The MSU nano particles were synthesized by wet chemical method using NaOH and uric acid (C5H4N4O3) and then characterized by powder XRD, TEM, FT-IR and thermal analysis. From the powder XRD the triclinic structure was found and 40 nm average particle size was estimated by using Scherrer's formula. From TEM the particle size was found to be in the range of 20 to 60 nm. The FT-IR spectrum for the MSU nano particles confirmed the presence of O-H stretching, N-H stretching, N-H rocking, C = O, C = C Enol or Keto and C = N vibrations. The thermal analysis was carried out from room temperature to 900°C. With comparison to the bulk MSU the thermal stability of MSU nano particles was slightly higher and 1.5 water molecules were found to be associated with MSU nano particles. Present results are compared with the bulk MSU.

The effect of steam sterilization on recombinant spider silk particles.

PubMed

Lucke, Matthias; Winter, Gerhard; Engert, Julia

2015-03-15

In this work, the recombinant spider silk protein eADF4(C16) was used to fabricate particles in the submicron range using a micromixing method. Furthermore, particles in the micrometer range were produced using an ultrasonic atomizer system. Both particle species were manufactured by an all-aqueous process. The submicroparticles were 332 nm in average diameter, whereas 6.70 μm was the median size of the microparticles. Both particle groups showed a spherical shape and exhibited high β-sheet content in secondary structure. Submicro- and microparticles were subsequently steam sterilized and investigated with respect to particle size, secondary structure and thermal stability. Sterilization temperature and time were increased to assess the thermal stability of eADF4(C16) particles. Actually, particles remained stable and their properties did not change even after autoclaving at 134°C. Both, the untreated and the autoclaved submicroparticles showed no overt cytotoxicity on human dermal fibroblasts after incubation for 72 h. The eADF4(C16) particles were already loaded with proteins and small molecules in previous studies. With that, we can provide a highly promising parenteral drug delivery system based on a defined polypeptide carrier, manufactured with an all-aqueous process and being fully sterilizable. Copyright © 2015 Elsevier B.V. All rights reserved.

Preparation and magnetic properties of nano size nickel ferrite particles using hydrothermal method

PubMed Central

2012-01-01

Background Nickel ferrite, a kind of soft magnetic materials is one of the most attracting class of materials due to its interesting and important properties and has many technical applications, such as in catalysis, sensors and so on. In this paper the synthesis of NiFe2O4 nanoparticles by the hydrothermal method is reported and the inhibition of surfactant (Glycerol or Sodium dodecyl sulfate) on the particles growth is investigated. Methods For investigation of the inhibition effect of surfactant on NiFe2O4 particles growth, the samples were prepared in presence of Glycerol and Sodium dodecyl sulfate. The X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometer (VSM) and inductively coupled plasma atomic emission spectrometer (ICP-AES) techniques were used to characterize the samples. Results The results of XRD and ICP-AES show that the products were pure NiFe2O4 and also nanoparticles grow with increasing the temperature, while surfactant prevents the particle growth under the same condition. The average particle size was determined from the Scherrer's equation and TEM micrographs and found to be in the range of 50-60 nm that decreased up to 10-15 nm in presence of surfactant. The FT-IR results show two absorption bands near to 603 and 490 cm-1 for the tetrahedral and octahedral sites respectively. Furthermore, the saturated magnetization and coercivity of NiFe2O4 nanoparticles were in the range of 39.60 emu/g and 15.67 Qe that decreased for samples prepared in presence of surfactant. As well as, the nanoparticles exhibited a superparamagnetic behavior at room temperature. Conclusions Nanosized nickel ferrite particles were synthesized with and without surfactant assisted hydrothermal methods. The results show that with increasing of temperature, the crystallinity of nanoparticles is increased. In the presence of surfactants, the crystallinity of NiFe2O4 nanoparticles decreased in comparison with surfactant- free prepared samples. All of the nickel ferrite nanoparticles were superparamagnetic at room temperature. Graphical abstract PMID:22462726

Preparation and magnetic properties of nano size nickel ferrite particles using hydrothermal method.

PubMed

Nejati, Kamellia; Zabihi, Rezvanh

2012-03-30

Nickel ferrite, a kind of soft magnetic materials is one of the most attracting class of materials due to its interesting and important properties and has many technical applications, such as in catalysis, sensors and so on. In this paper the synthesis of NiFe2O4 nanoparticles by the hydrothermal method is reported and the inhibition of surfactant (Glycerol or Sodium dodecyl sulfate) on the particles growth is investigated. For investigation of the inhibition effect of surfactant on NiFe2O4 particles growth, the samples were prepared in presence of Glycerol and Sodium dodecyl sulfate. The X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometer (VSM) and inductively coupled plasma atomic emission spectrometer (ICP-AES) techniques were used to characterize the samples. The results of XRD and ICP-AES show that the products were pure NiFe2O4 and also nanoparticles grow with increasing the temperature, while surfactant prevents the particle growth under the same condition. The average particle size was determined from the Scherrer's equation and TEM micrographs and found to be in the range of 50-60 nm that decreased up to 10-15 nm in presence of surfactant. The FT-IR results show two absorption bands near to 603 and 490 cm-1 for the tetrahedral and octahedral sites respectively. Furthermore, the saturated magnetization and coercivity of NiFe2O4 nanoparticles were in the range of 39.60 emu/g and 15.67 Qe that decreased for samples prepared in presence of surfactant. As well as, the nanoparticles exhibited a superparamagnetic behavior at room temperature. Nanosized nickel ferrite particles were synthesized with and without surfactant assisted hydrothermal methods. The results show that with increasing of temperature, the crystallinity of nanoparticles is increased. In the presence of surfactants, the crystallinity of NiFe2O4 nanoparticles decreased in comparison with surfactant- free prepared samples. All of the nickel ferrite nanoparticles were superparamagnetic at room temperature. GRAPHICAL

Auto-ignitions of a methane/air mixture at high and intermediate temperatures

NASA Astrophysics Data System (ADS)

Leschevich, V. V.; Martynenko, V. V.; Penyazkov, O. G.; Sevrouk, K. L.; Shabunya, S. I.

2016-09-01

A rapid compression machine (RCM) and a shock tube (ST) have been employed to study ignition delay times of homogeneous methane/air mixtures at intermediate-to-high temperatures. Both facilities allow measurements to be made at temperatures of 900-2000 K, at pressures of 0.38-2.23 MPa, and at equivalence ratios of 0.5, 1.0, and 2.0. In ST experiments, nitrogen served as a diluent gas, whereas in RCM runs the diluent gas composition ranged from pure nitrogen to pure argon. Recording pressure, UV, and visible emissions identified the evolution of chemical reactions. Correlations of ignition delay time were generated from the data for each facility. At temperatures below 1300 K, a significant reduction of average activation energy from 53 to 15.3 kcal/mol was obtained. Moreover, the RCM data showed significant scatter that dramatically increased with decreasing temperature. An explanation for the abnormal scatter in the data was proposed based on the high-speed visualization of auto-ignition phenomena and experiments performed with oxygen-free and fuel-free mixtures. It is proposed that the main reason for such a significant reduction of average activation energy is attributable to the premature ignition of ultrafine particles in the reactive mixture.

Modeling the mechanical behavior of ceramic and heterophase structures manufactured using selective laser sintering and spark plasma sintering

NASA Astrophysics Data System (ADS)

Skripnyak, Vladimir A.; Skripnyak, Evgeniya G.; Skripnyak, Vladimir V.; Vaganova, Irina K.

A model for predicting mechanical properties of ultra-high temperature ceramics and composites manufactured by selective laser sintering (SLS) and spark plasma sintering (SPS) under shock loading is presented. The model takes into account the porous structure, the specific volume and average sizes of phases, and the temperature of sintering. Residual stresses in ceramic composites reinforced with particles of refractory borides, carbides and nitrides after SLS or SPS were calculated. It is shown that the spall strength of diboride-zirconium matrix composites can be increased by the decreasing of porosity and the introduction of inclusions of specially selected refractory strengthening phases.

Temperature effects on particulate emissions from DPF-equipped diesel trucks operating on conventional and biodiesel fuels.

PubMed

Book, Emily K; Snow, Richard; Long, Thomas; Fang, Tiegang; Baldauf, Richard

2015-06-01

Emissions tests were conducted on two medium heavy-duty diesel trucks equipped with a particulate filter (DPF), with one vehicle using a NOx absorber and the other a selective catalytic reduction (SCR) system for control of nitrogen oxides (NOx). Both vehicles were tested with two different fuels (ultra-low-sulfur diesel [ULSD] and biodiesel [B20]) and ambient temperatures (70ºF and 20ºF), while the truck with the NOx absorber was also operated at two loads (a heavy weight and a light weight). The test procedure included three driving cycles, a cold start with low transients (CSLT), the federal heavy-duty urban dynamometer driving schedule (UDDS), and a warm start with low transients (WSLT). Particulate matter (PM) emissions were measured second-by-second using an Aethalometer for black carbon (BC) concentrations and an engine exhaust particle sizer (EEPS) for particle count measurements between 5.6 and 560 nm. The DPF/NOx absorber vehicle experienced increased BC and particle number concentrations during cold starts under cold ambient conditions, with concentrations two to three times higher than under warm starts at higher ambient temperatures. The average particle count for the UDDS showed an opposite trend, with an approximately 27% decrease when ambient temperatures decreased from 70ºF to 20ºF. This vehicle experienced decreased emissions when going from ULSD to B20. The DPF/SCR vehicle tested had much lower emissions, with many of the BC and particle number measurements below detectable limits. However, both vehicles did experience elevated emissions caused by DPF regeneration. All regeneration events occurred during the UDDS cycle. Slight increases in emissions were measured during the WSLT cycles after the regeneration. However, the day after a regeneration occurred, both vehicles showed significant increases in particle number and BC for the CSLT drive cycle, with increases from 93 to 1380% for PM number emissions compared with tests following a day with no regeneration. The use of diesel particulate filters (DPFs) on trucks is becoming more common throughout the world. Understanding how DPFs affect air pollution emissions under varying operating conditions will be critical in implementing effective air quality standards. This study evaluated particulate matter (PM) and black carbon (BC) emissions with two DPF-equipped heavy-duty diesel trucks operating on conventional fuel and a biodiesel fuel blend at varying ambient temperatures, loads, and drive cycles.

Chromatographic performance of synthetic polycrystalline diamond as a stationary phase in normal phase high performance liquid chromatography.

PubMed

Peristyy, Anton; Paull, Brett; Nesterenko, Pavel N

2015-04-24

The chromatographic properties of high pressure high temperature synthesised diamond (HPHT) are investigated in normal phase mode of high performance liquid chromatography. Purified nonporous irregular shape particles of average particles size 1.2 μm and specific surface area 5.1 m(2) g(-1) were used for packing 100×4.6 mm ID or 50×4.6 mm ID stainless steel columns. The retention behaviour of several classes of compounds including alkyl benzenes, polyaromatic hydrocarbons (PAH), alkylphenylketones, phenols, aromatic acids and bases were studied using n-hexane-2-propanol mixtures as mobile phase. The results are compared with those observed for microdispersed sintered detonation nanodiamond (MSDN) and porous graphitic carbon (PGC). HPHT diamond revealed distinctive separation selectivity, which is orthogonal to that observed for porous graphitic carbon; while selectivities of HPHT diamond and microdispersed sintered detonation nanodiamonds are similar. Owing to non-porous particle nature, columns packed with high pressure high temperature diamond exhibited excellent mass transfer and produce separations with maximum column efficiency of 128,200 theoretical plates per meter. Copyright © 2015 Elsevier B.V. All rights reserved.

Constant pressure and temperature discrete-time Langevin molecular dynamics

NASA Astrophysics Data System (ADS)

Grønbech-Jensen, Niels; Farago, Oded

2014-11-01

We present a new and improved method for simultaneous control of temperature and pressure in molecular dynamics simulations with periodic boundary conditions. The thermostat-barostat equations are built on our previously developed stochastic thermostat, which has been shown to provide correct statistical configurational sampling for any time step that yields stable trajectories. Here, we extend the method and develop a set of discrete-time equations of motion for both particle dynamics and system volume in order to seek pressure control that is insensitive to the choice of the numerical time step. The resulting method is simple, practical, and efficient. The method is demonstrated through direct numerical simulations of two characteristic model systems—a one-dimensional particle chain for which exact statistical results can be obtained and used as benchmarks, and a three-dimensional system of Lennard-Jones interacting particles simulated in both solid and liquid phases. The results, which are compared against the method of Kolb and Dünweg [J. Chem. Phys. 111, 4453 (1999)], show that the new method behaves according to the objective, namely that acquired statistical averages and fluctuations of configurational measures are accurate and robust against the chosen time step applied to the simulation.

A solid colloidal drug delivery system for the eye: encapsulation of pilocarpin in nanoparticles.

PubMed

Harmia, T; Speiser, P; Kreuter, J

1986-01-01

The present study was undertaken in order to encapsulate pilocarpin into nanoparticles. Two principally different methods for manufacturing these particles were investigated. Firstly, pilocarpin was dissolved in an aqueous medium in which the polymerization was carried out, and secondly, the polymerizing monomer was kept saturated with the drug solution under acidic conditions resulting in an incorporation into the nanoparticles in an aqueous environment. The amount of pilocarpin that could be incorporated into the nanoparticles was found to be largely influenced by the temperature at which the nanoparticles were produced and by the stabilizers used. At low temperatures, up to 60 per cent of pilocarpin nitrate could be encapsulated into butylcyanoacrylate nanoparticles using emulsion polymerization techniques. Larger amounts of pilocarpin could not be incorporated because of the hydrophilicity of the salts of this drug. The physico-chemical characteristics of the nanoparticles are reported: the particle size and morphology were determined by scanning and transmission electron microscopy and photon correlation spectrometry. The average particle size was about 100 nm. The results obtained in this study show that photon correlation spectrometry is a suitable method for the sizing of nanoparticles.

Iron-based soft magnetic composites with Mn-Zn ferrite nanoparticles coating obtained by sol-gel method

NASA Astrophysics Data System (ADS)

Wu, Shen; Sun, Aizhi; Xu, Wenhuan; Zhang, Qian; Zhai, Fuqiang; Logan, Philip; Volinsky, Alex A.

2012-11-01

This paper focuses on iron-based soft magnetic composites which were synthesized by utilizing Mn-Zn ferrite nanoparticles to coat iron powder. The nanocrystalline iron powders, with an average particle diameter of 20 nm, were obtained via the sol-gel method. Scanning electron microscopy, energy dispersive X-ray spectroscopy and distribution maps show that the iron particle surface is covered with a thin layer of Mn-Zn ferrites. Mn-Zn ferrite uniformly coated the surface of the powder particles, resulting in a reduced imaginary permeability, increased electrical resistivity and a higher operating frequency of the synthesized magnets. Mn-Zn ferrite coated samples have higher permeability and lower magnetic loss when compared with the non-magnetic epoxy resin coated compacts. The real part of permeability increases by 33.5% when compared with the epoxy resin coated samples at 10 kHz. The effects of heat treatment temperature on crystalline phase formation and on the magnetic properties of the Mn-Zn ferrite were investigated via X-ray diffraction and a vibrating sample magnetometer. Ferrites decomposed to FeO and MnO after annealing above 400 °C in nitrogen; thus it is the optimum annealing temperature to attain the desired permeability.

Production and Application of Olivine Nano-Silica in Concrete

NASA Astrophysics Data System (ADS)

Mardiana, Oesman; Haryadi

2017-05-01

The aim of this research was to produce nano silica by synthesis of nano silica through extraction and dissolution of ground olivine rock, and applied the nano silica in the design concrete mix. The producing process of amorphous silica used sulfuric acid as the dissolution reagent. The separation of ground olivine rock occurred when the rock was heated in a batch reactor containing sulfuric acid. The results showed that the optimum mole ratio of olivine- acid was 1: 8 wherein the weight ratio of the highest nano silica generated. The heating temperature and acid concentration influenced the mass of silica produced, that was at temperature of 90 °C and 3 M acid giving the highest yield of 44.90%. Characterization using Fourier Transform Infrared (FTIR ) concluded that amorphous silica at a wavenumber of 1089 cm-1 indicated the presence of siloxane, Si-O-Si, stretching bond. Characterization using Scanning Electron Microscope - Energy Dispersive Spectroscopy (SEM-EDS) showed the surface and the size of the silica particles. The average size of silica particles was between 1-10 μm due to the rapid aggregation of the growing particles of nano silica into microparticles, caused of the pH control was not fully achieved.

Particle transport in low-collisionality H-mode plasmas on DIII-D

DOE PAGES

Mordijck, Saskia; Wang, Xin; Doyle, Edward J.; ...

2015-10-05

In this article we show that changing from an ion temperature gradient (ITG) to trapped electron mode (TEM) dominant turbulence regime (based on linear gyrokinetic simulations) results experimentally in a strong density pump-out (defined as a reduction in line-averaged density) in low collisionality, low power H-mode plasmas. We vary the turbulence drive by changing the heating from pre-dominantly ion heatedusing neutral beam injection to electron heated using electron cyclotron heating, which changes the T e/T i ratio and the temperature gradients. Perturbed gas puff experiments show an increase in transport outside ρ = 0.6, through a strong increase in themore » perturbed diffusion coefficient and a decrease in the inward pinch. Linear gyrokinetic simulations with TGLF show an increase in the particle flux outside the mid-radius. In conjunction an increase in intermediate-scale length density fluctuations is observed, which indicates an increase in turbulence intensity at typical TEM wavelengths. However, although the experimental changes in particle transport agree with a change from ITG to TEM turbulence regimes, we do not observe a reduction in the core rotation at mid-radius, nor a rotation reversal.« less

Contact freezing of supercooled cloud droplets on collision with mineral dust particles: effect of particle size

NASA Astrophysics Data System (ADS)

Hoffmann, Nadine; Duft, Denis; Kiselev, Alexei; Leisner, Thomas

2013-04-01

The contact freezing of supercooled cloud droplets is one of the potentially important and the least investigated heterogeneous mechanism of ice formation in the tropospheric clouds [1]. On the time scales of cloud lifetime the freezing of supercooled water droplets via contact mechanism may occur at higher temperature compared to the same IN immersed in the droplet. However, the laboratory experiments of contact freezing are very challenging due to the number of factors affecting the probability of ice formation. In our experiment we study single water droplets freely levitated in the laminar flow of mineral dust particles acting as the contact freezing nuclei. By repeating the freezing experiment sufficient number of times we are able to reproduce statistical freezing behavior of large ensembles of supercooled droplets and measure the average rate of freezing events. We show that the rate of freezing at given temperature is governed only by the rate of droplet -particle collision and by the properties of the contact ice nuclei. In this contribution we investigate the relationship between the freezing probability and the size of mineral dust particle (represented by illite) and show that their IN efficiency scales with the particle size. Based on this observation, we discuss the similarity between the freezing of supercooled water droplets in immersion and contact modes and possible mechanisms of apparent enhancement of the contact freezing efficiency. [1] - K.C. Young, The role of contact nucleation in ice phase initiation in clouds, Journal of the Atmospheric Sciences 31, 1974

Structural and luminescence properties of self-yellow emitting undoped and (Ca, Ba, Sr)-doped Zn2V2O7 phosphors synthesized by combustion method

NASA Astrophysics Data System (ADS)

Foka, Kewele E.; Dejene, Birhanu F.; Koao, Lehlohonolo F.; Swart, Hendrik C.

2018-04-01

A self-activated yellow emitting Zn2V2O7 was synthesized by combustion method. The influence of the processing parameters such as synthesis temperature and dopants concentration on the structure, morphology and luminescence properties was investigated. The X-ray diffraction (XRD) analysis confirmed that the samples have a tetragonal structure and no significant structural change was observed in varying both the synthesis temperature and the dopants concentration. The estimated average crystallite size was 78 nm for the undoped samples synthesized at different temperatures and 77 nm for the doped samples. Scanning electron microscope (SEM) images showed agglomerated hexagonal-shaped particles with straight edges at low temperatures and the shape of the particles changed to cylindrical structures at moderate temperatures. At higher temperatures, the morphology changed completely. However, the morphologies of the doped samples looked alike. The photoluminescence (PL) of the product exhibited broad emission bands ranging from 400 to 800 nm. The best luminescence intensity was observed for the undoped Zn2V2O7 samples and those synthesized at 600 ℃ . Any further increase in synthesis temperature, type and concentration of dopants led to a decrease in the luminescence intensity. The broad band emission peak of Zn2V2O7 consisted of two broad bands corresponding to emissions from the Em1 (3T2→1A1) and Em2 (3T1→1A1) transitions.

Probability density functions characterizing PSC particle size distribution parameters for NAT and STS derived from in situ measurements between 1989 and 2010 above McMurdo Station, Antarctica, and between 1991-2004 above Kiruna, Sweden

NASA Astrophysics Data System (ADS)

Deshler, Terry

2016-04-01

Balloon-borne optical particle counters were used to make in situ size resolved particle concentration measurements within polar stratospheric clouds (PSCs) over 20 years in the Antarctic and over 10 years in the Arctic. The measurements were made primarily during the late winter in the Antarctic and in the early and mid-winter in the Arctic. Measurements in early and mid-winter were also made during 5 years in the Antarctic. For the analysis bimodal lognormal size distributions are fit to 250 meter averages of the particle concentration data. The characteristics of these fits, along with temperature, water and nitric acid vapor mixing ratios, are used to classify the PSC observations as either NAT, STS, ice, or some mixture of these. The vapor mixing ratios are obtained from satellite when possible, otherwise assumptions are made. This classification of the data is used to construct probability density functions for NAT, STS, and ice number concentration, median radius and distribution width for mid and late winter clouds in the Antarctic and for early and mid-winter clouds in the Arctic. Additional analysis is focused on characterizing the temperature histories associated with the particle classes and the different time periods. The results from theses analyses will be presented, and should be useful to set bounds for retrievals of PSC properties from remote measurements, and to constrain model representations of PSCs.

Transient anomalous diffusion in periodic systems: ergodicity, symmetry breaking and velocity relaxation

PubMed Central

Spiechowicz, Jakub; Łuczka, Jerzy; Hänggi, Peter

2016-01-01

We study far from equilibrium transport of a periodically driven inertial Brownian particle moving in a periodic potential. As detected for a SQUID ratchet dynamics, the mean square deviation of the particle position from its average may involve three distinct intermediate, although extended diffusive regimes: initially as superdiffusion, followed by subdiffusion and finally, normal diffusion in the asymptotic long time limit. Even though these anomalies are transient effects, their lifetime can be many, many orders of magnitude longer than the characteristic time scale of the setup and turns out to be extraordinarily sensitive to the system parameters like temperature or the potential asymmetry. In the paper we reveal mechanisms of diffusion anomalies related to ergodicity of the system, symmetry breaking of the periodic potential and ultraslow relaxation of the particle velocity towards its steady state. Similar sequences of the diffusive behaviours could be detected in various systems including, among others, colloidal particles in random potentials, glass forming liquids and granular gases. PMID:27492219

A pharmacologic study on the mechanism of action of Kakkon-to: body temperature elevation and phagocytic activation of macrophages in dogs.

PubMed

Muraoka, Kenichi; Yoshida, Satoshi; Hasegawa, Kazumasa; Nakanishi, Nobuo; Fukuzawa, Isao; Tomita, Akio; Cyong, Jong Chol

2004-10-01

The phagocytic activity of macrophages as a novel approach to scientific elucidation of the effects of Chinese medicines was studied through administration of a kampo preparation, by measuring the rise in body temperature, which is thought to stimulate innate defensive functions of organisms and enhance the immune systems. Using dogs as experimental models, a rise in body temperature following administration of Kakkon-to was observed, and the average number and average rate of phagocytosis of macrophages in blood using latex micro-particles was investigated. The body temperature of the treated animals significantly increased 30 minutes after administration (p<0.01), and remained elevated for more than 5 hours. A comparison of body temperatures before and after administration showed significant increases over controls from 1 to 11 hours, p<0.01; and at 12 hours, p<0.05 after administration. The average number and the average rate of phagocytosis were significantly increased 1 (p<0.05) and 2 (p<0.01) hours after administration. The mean number of phagocytized cells significantly increased (p<0.05) at 1 hour after administration compared with that before administration, and the mean phagocytic rate also increased significantly (p<0.01) 2 hours after administration. Increases (p<0.01) in both the rate of phagocytosis and the number of cells phagocytized were found at every measurement point from 2 to 24 hours after administration. Significant increases (p<0.01) were also observed in both the rate of phagocytosis and the number of cells phagocytized 3 hours after administration, when compared with the control group. This paper demonstrates that ingestion of Kakkon-to not only increases the body temperature but also enhances the phagocytic activity of macrophages, an in vivo defense mechanism, suggesting that Kakkon-to contributes to the suppression of multiplication of common cold viruses and influenza viruses, which consequently results in improvement of various symptoms during infection with common cold viruses.

Near-Earth Reconnection Ejecta at Lunar Distances

NASA Astrophysics Data System (ADS)

Runov, A.; Angelopoulos, V.; Artemyev, A.; Lu, S.; Zhou, X.-Z.

2018-04-01

Near-Earth magnetotail reconnection leads to formation of earthward and tailward directed plasma outflows with an increased north-south magnetic field strength(|Bz|) at their leading edges. We refer to these regions of enhanced |Bz| and magnetic flux transport Ey as reconnection ejecta. They are composed of what have been previously referred to as earthward dipolarizing flux bundles (DFBs) and tailward rapid flux transport (RFT) events. Using two-point observations of magnetic and electric fields and particle fluxes by the Acceleration, Reconnection, Turbulence, and Electrodynamics of Moon's Interaction with the Sun probes orbiting around Moon at geocentric distances R ˜ 60RE, we statistically studied plasma moments and particle energy spectra in RFTs and compared them with those observed within DFBs in the near-Earth plasma sheet by the Time History of Events and Macroscale Interactions during Substorms probes. We found that the ion average temperatures and spectral slopes in RFTs at R ˜ 60RE are close to those in DFBs observed at 15 < R < 25RE, just earthward of the probable reconnection region location. Assuming plasma sheet pressure balance, the average RFT ion temperature corresponds to a lobe field BL˜20 nT. This leads us to suggest that the ion population within the tailward ejecta originated in the midtail plasma sheet at 20≤R≤30RE and propagated to the Acceleration, Reconnection, Turbulence, and Electrodynamics of Moon's Interaction with the Sun location without undergoing any further energy gain. Conversely, electron temperatures in DFBs at 15 < R < 25RE are a factor of 2.5 higher than those in RFTs at R ˜ 60RE.

Microstructural changes in cast martensitic steel after creep at 620°C

NASA Astrophysics Data System (ADS)

Borisova, Yu. I.; Dudko, V. A.; Skorobogatykh, V. N.; Shchenkova, I. A.; Kaibyshev, R. O.

2017-10-01

Microstructural changes in the cast steel GX12CrMoWVNbN10-1-1 (Fe-0.11 C-0.31 Si-0.89 Mn-9.57 Cr-0.66 Ni-1.01 Mo-1.00 W-0.21 V-0.06 Nb-0.05 Cu-0.05 N in wt %) have been investigated after tests for long-term strength at a temperature of 620°C in the range of stresses of 120-160 MPa. Upon short-term creep (up to 5000 h), the tempered troostite structure and distribution of particles of proeutectoid constituents change insignificantly, except for the precipitation of particles of the Laves phase ˜100 nm in size along boundaries of laths, blocks, packets, and initial austenite grains. Upon long-term creep (to 10000 h), the tempered troostite partially transforms into the subgrain structure, which is accompanied by a decrease in the dislocation density from 6.4 × 1014 to 3.1 × 1013 m-2 and connected with growth of sizes of M23C6 carbides of 105-150 nm and particles of the Laves phase to 380 nm, due to the dissolution of these particles located along path boundaries. Upon long-term creep, the average size of V(C,N) particles increases from 45 to 64 nm (while Nb(C,N) particles increase from 48 to 87 nm), and the Nb content in V-enriched carbonitrides and the V content in Nb-enriched M(C,N) particles substantially decrease. No formation of the Z phase has been revealed. The combination of M(C,N) nanoparticles with the presence of W in the solid solution has been found to be responsible for the enhanced high-temperature strength of the steel.

Outdoor and indoor UFP in primary schools across Barcelona.

PubMed

Reche, C; Viana, M; Rivas, I; Bouso, L; Àlvarez-Pedrerol, M; Alastuey, A; Sunyer, J; Querol, X

2014-09-15

Indoor and outdoor measurements of real-time ultrafine particles (UFP; N10-700 in this study) number concentration and average diameter were collected twice at 39 primary schools located in Barcelona (Spain), with classrooms naturally ventilated under warm weather conditions. Simultaneous outdoor N concentration measurements at schools under different traffic exposures showed the important role of this source, with higher levels by 40% on average at schools near heavy traffic, highlighting thus the increased exposure of children due to urban planning decisions. A well-defined spatial pattern of outdoor UFP levels was observed. Midday increases in outdoor N levels mainly attributed to nucleation processes have been recorded both at high and low temperatures in several of the outdoor school sites (increasing levels by 15%-70%). The variation of these increases also followed a characteristic spatial pattern, pointing at schools' location as a key variable in terms of UFP load owing to the important contribution of traffic emissions. Indoor N concentrations were to some extent explained by outdoor N concentrations during school hours, together with average temperatures, related with natural ventilation. Outdoor midday increases were generally mimicked by indoor N concentrations, especially under warm temperatures. At specific cases, indoor concentrations during midday were 30%-40% higher than outdoor. The time scale of these observations evidenced the possible role of: a) secondary particle formation enhanced by indoor precursors or conditions, maybe related with surface chemistry reactions mediated by O3, and/or b) UFP from cooking activities. Significant indoor N increases were detected after school hours, probably associated with cleaning activities, resulting in indoor N concentrations up to 3 times higher than those in outdoor. A wide variability of indoor/outdoor ratios of N concentrations and mean UFP sizes was detected among schools and measurement periods, which seems to be partly associated with climatic conditions and O3 levels, although further research is required. Copyright © 2014 Elsevier B.V. All rights reserved.

Characterization of Ablation Product Radiation Signatures of PICA and FiberForm

NASA Technical Reports Server (NTRS)

Winter, Michael; Butler, Bradley D.; Diao, Zhaojin; Panerai, Francesco; Martin, Alexandre; Bailey, Sean C. C.; Danehy, Paul M.; Splinter, Scott

2016-01-01

Emission spectroscopy measurements in the post-shock layer in front of low density ablative material samples of different shapes were obtained in the NASA Langley HYMETS arcjet facility. A horizontal line of measurement positions was imaged on the entrance slit of the spectrometer allowing detection of the entire stagnation line in front of the samples. The stagnation line measurements were used to compare the post-shock layer emission signatures in front of PICA and FiberForm. The emission signatures of H, NH, and OH are characteristic for pyrolysis gases and consequently were only observed in front of the PICA samples. CN and C were found in front of both materials and are mainly due to interactions of the carbon fibers with the plasma. In all tests with instrumented samples, the emission of Mn, Cr, and Ni was observed when the thermocouple temperatures reached or exceeded 1,500 K, strongly indicating erosion of the molten thermocouple tips. Temperatures in the post-shock layer were estimated from comparing the CN band emission to spectral simulation. The resulting rotational and vibrational temperatures were on the order of 7,000 to 9,000 K and close to each other indicating a plasma condition close to equilibrium. In addition to the stagnation line configurations, off-axis lines of observation were investigated to gather information about spalled particles in the flow. From a comparison of measured continuum emission with simulated Planck radiation, average particle temperatures along the measured line of observation were determined for two cases. Particle temperatures between 3,500 and 2,000 K were found. A comprehensive investigation of the entire amount of data set is ongoing.

[The short-term effects of air pollution on mortality: the results of the EMECAM project in the city of Pamplona, 1991-95. Estudio Multicéntrico Español sobre la Relación entre la Contaminación Atmosférica y la Mortalidad].

PubMed

Aguinaga Ontoso, I; Guillén Grima, F; Oviedo de Sola, P J; Floristan Floristan, M Y; Laborda Santesteban, M S; Martínez Ramírez, M T; Martínez González, M A

1999-01-01

To assess the short-term impact of air pollution on the daily death rate in the city of Pamplona. Ecological study with a population of 212,000 inhabitants. A time series data analysis is conducted by means of multiple linear regression and Poisson regression, with the daily death rate data, air pollution levels for Particles and SO2, weather parameters of average relative humidity and temperature daily and number of cases weekly of flu for the 1991-1995 period. The average number of deaths daily for non-external causes is that of 4.15 deaths, with a range from zero to 13 deaths. The city of Pamplona has a mean annual temperature of 12.7 degrees C (-2.3 degrees C to 31.6 degrees C) and a relative humidity of 68.5%. In the model, the temperature (with a one-day time lag and a six-day time lag temperature squared) and the humidity (with a one-day time lag) is related to the death rate for all causes. But the death rate for non-external causes is only related in the model with the temperature (one-day time lag, P: 0.035) and five-day time lag with temperature squared (p: 0.028). The timely estimates of the relative particle-related risk show that the highest risk of dying stems from respiratory causes with a relative risk of 1.13. However, none of these relationships is statistically significant. In the case of Sulfur Dioxide, the estimates closely near the zero figure, and none of them is significant. The Temperature has an impact of the death rate for all causes, both external and non-external, and the relative humidity solely has an impact on the death rate for non-external causes. It has not been possible to prove any influence of the daily environmental pollution levels on the daily death rate.

Room temperature ferromagnetism in Fe-doped CuO nanoparticles.

PubMed

Layek, Samar; Verma, H C

2013-03-01

The pure and Fe-doped CuO nanoparticles of the series Cu(1-x)Fe(x)O (x = 0.00, 0.02, 0.04, 0.06 and 0.08) were successfully prepared by a simple low temperature sol-gel method using metal nitrates and citric acid. Rietveld refinement of the X-ray diffraction data showed that all the samples were single phase crystallized in monoclinic structure of space group C2/c with average crystallite size of about 25 nm and unit cell volume decreases with increasing iron doping concentration. TEM micrograph showed nearly spherical shaped agglomerated particles of 4% Fe-doped CuO with average diameter 26 nm. Pure CuO showed weak ferromagnetic behavior at room temperature with coercive field of 67 Oe. The ferromagnetic properties were greatly enhanced with Fe-doping in the CuO matrix. All the doped samples showed ferromagnetism at room temperature with a noticeable coercive field. Saturation magnetization increases with increasing Fe-doping, becomes highest for 4% doping then decreases for further doping which confirms that the ferromagnetism in these nanoparticles are intrinsic and are not resulting from any impurity phases. The ZFC and FC branches of the temperature dependent magnetization (measured in the range of 10-350 K by SQUID magnetometer) look like typical ferromagnetic nanoparticles and indicates that the ferromagnetic Curie temperature is above 350 K.

Structural, magnetic and impedance spectroscopic analysis of LaFeO3 nano-particles

NASA Astrophysics Data System (ADS)

Rao, T. Lakshmana; Pradhan, M. K.; Dash, S.

2018-04-01

Physical properties are known to be drastically varied with crystallite size and in a multifunctional material this size reduction is seem to be interesting. One such material is chosen as LaFeO3 nanoparticles which have been prepared by wet-chemical route. The average particle size found to be in the order of 45nm in which the chemical content of the unit cell has been verified. A distorted orthorhombic structure with Pbnm space group is possessed by this nanoparticle. From the bifurcation of ZFC and FC in low field, behavior of inverse susceptibility and the small hysteresis loop favors the material to be in a weak FM state well below the Neel temperature. The electrical behavior and the conduction mechanism above room temperature have been studied by cole-cole plot of the Impedance spectra. The high frequency depressed semi circles represent the grain conduction while the intermediate frequency semi circles appear may be due to grain boundary effect.

Boltzmann distribution in a nonequilibrium steady state: measuring local potential by granular Brownian particles.

PubMed

To, Kiwing

2014-06-01

We investigate experimentally the steady state motion of a millimeter-sized granular polyhedral object on vertically vibrating platforms of flat, conical, and parabolic surfaces. We find that the position distribution of the granular object is related to the shape of the platform, just like that of a Brownian particle trapped in a potential at equilibrium, even though the granular object is intrinsically not at equilibrium due to inelastic collisions with the platform. From the collision dynamics, we derive the Langevin equation which describes the motion of the object under an effective potential that equals the gravitational potential along the platform surface. The potential energy is found to agree with the equilibrium equipartition theorem while the kinetic energy does not. Furthermore, the granular temperature is found to be higher than the effective temperature associated with the average potential energy, suggesting the presence of heat transfer from the kinetic part to the potential part of the granular object.

Boltzmann distribution in a nonequilibrium steady state: Measuring local potential by granular Brownian particles

NASA Astrophysics Data System (ADS)

To, Kiwing

2014-06-01

We investigate experimentally the steady state motion of a millimeter-sized granular polyhedral object on vertically vibrating platforms of flat, conical, and parabolic surfaces. We find that the position distribution of the granular object is related to the shape of the platform, just like that of a Brownian particle trapped in a potential at equilibrium, even though the granular object is intrinsically not at equilibrium due to inelastic collisions with the platform. From the collision dynamics, we derive the Langevin equation which describes the motion of the object under an effective potential that equals the gravitational potential along the platform surface. The potential energy is found to agree with the equilibrium equipartition theorem while the kinetic energy does not. Furthermore, the granular temperature is found to be higher than the effective temperature associated with the average potential energy, suggesting the presence of heat transfer from the kinetic part to the potential part of the granular object.

Effect of particle pinch on the fusion performance and profile features of an international thermonuclear experimental reactor-like fusion reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Shijia, E-mail: wangsg@mail.ustc.edu.cn; Wang, Shaojie

2015-04-15

The evolution of the plasma temperature and density in an international thermonuclear experimental reactor (ITER)-like fusion device has been studied by numerically solving the energy transport equation coupled with the particle transport equation. The effect of particle pinch, which depends on the magnetic curvature and the safety factor, has been taken into account. The plasma is primarily heated by the alpha particles which are produced by the deuterium-tritium fusion reactions. A semi-empirical method, which adopts the ITERH-98P(y,2) scaling law, has been used to evaluate the transport coefficients. The fusion performances (the fusion energy gain factor, Q) similar to the ITERmore » inductive scenario and non-inductive scenario (with reversed magnetic shear) are obtained. It is shown that the particle pinch has significant effects on the fusion performance and profiles of a fusion reactor. When the volume-averaged density is fixed, particle pinch can lower the pedestal density by ∼30%, with the Q value and the central pressure almost unchanged. When the particle source or the pedestal density is fixed, the particle pinch can significantly enhance the Q value by  60%, with the central pressure also significantly raised.« less

Preparation of Porous Stainless Steel Hollow-Fibers through Multi-Modal Particle Size Sintering towards Pore Engineering

PubMed Central

Allioux, Francois-Marie; Etxeberria Benavides, Miren

2017-01-01

The sintering of metal powders is an efficient and versatile technique to fabricate porous metal elements such as filters, diffusers, and membranes. Neck formation between particles is, however, critical to tune the porosity and optimize mass transfer in order to minimize the densification process. In this work, macro-porous stainless steel (SS) hollow-fibers (HFs) were fabricated by the extrusion and sintering of a dope comprised, for the first time, of a bimodal mixture of SS powders. The SS particles of different sizes and shapes were mixed to increase the neck formation between the particles and control the densification process of the structure during sintering. The sintered HFs from particles of two different sizes were shown to be more mechanically stable at lower sintering temperature due to the increased neck area of the small particles sintered to the large ones. In addition, the sintered HFs made from particles of 10 and 44 μm showed a smaller average pore size (<1 μm) as compared to the micron-size pores of sintered HFs made from particles of 10 μm only and those of 10 and 20 μm. The novel HFs could be used in a range of applications, from filtration modules to electrochemical membrane reactors. PMID:28777352

Influence of gas temperature on ignition, burning and extinction of carbon particles-gas suspension

NASA Astrophysics Data System (ADS)

Orlovskaya, S. G.; Zuy, O. N.; Liseanskaia, M. V.

2017-11-01

The ignition and burning of monodisperse and two-fraction suspensions of carbon particles at gas temperature in the range 1100 ÷ 1500 K are modeled. The critical gas temperature of the suspension ignition, the particles ignition delay and burning time, the burning temperature, and the extinction parameters are determined. The data obtained are compared with burning characteristics of single particle of equal size. The ignition temperatures of the fine fraction (the particle diameter 60 μm) and the coarse one (120 μm) are practically the same. The ignition temperatures of the equivalent single particles are much higher and they differ by 100 K and more. The gas temperature is found below which the ignition delay of the fine fraction exceeds the one of the coarse fraction. It is found that, at critical ignition temperatures the burning temperature of the fine fraction is lower than that of the coarse fraction. At gas temperatures above 1250 K, the burning temperature of the fine fraction is higher. It is established that, in contrast to single particles, the temperature difference between the particles and the gas is small during gas-suspension extinction. Further oxidation of the particles occurs in the kinetic regime, so it is possible to estimate the time of their complete conversion.

Incorporation of New Convective Ice Microphysics into the NASA GISS GCM and Impacts on Cloud Ice Water Path (IWP) Simulation

NASA Technical Reports Server (NTRS)

Elsaesser, Greg; Del Genio, Anthony

2015-01-01

The CMIP5 configurations of the GISS Model-E2 GCM simulated a mid- and high latitude ice IWP that decreased by 50 relative to that simulated for CMIP3 (Jiang et al. 2012; JGR). Tropical IWP increased by 15 in CMIP5. While the tropical IWP was still within the published upper-bounds of IWP uncertainty derived using NASA A-Train satellite observations, it was found that the upper troposphere (200 mb) ice water content (IWC) exceeded the published upper-bound by a factor of 2. This was largely driven by IWC in deep-convecting regions of the tropics.Recent advances in the model-E2 convective parameterization have been found to have a substantial impact on tropical IWC. These advances include the development of both a cold pool parameterization (Del Genio et al. 2015) and new convective ice parameterization. In this presentation, we focus on the new parameterization of convective cloud ice that was developed using data from the NASA TC4 Mission. Ice particle terminal velocity formulations now include information from a number of NASA field campaigns. The new parameterization predicts both an ice water mass weighted-average particle diameter and a particle cross sectional area weighted-average size diameter as a function of temperature and ice water content. By assuming a gamma-distribution functional form for the particle size distribution, these two diameter estimates are all that are needed to explicitly predict the distribution of ice particles as a function of particle diameter.GCM simulations with the improved convective parameterization yield a 50 decrease in upper tropospheric IWC, bringing the tropical and global mean IWP climatologies into even closer agreement with the A-Train satellite observation best estimates.

Incorporation of New Convective Ice Microphysics into the NASA GISS GCM and Impacts on Cloud Ice Water Path (IWP) Simulation

NASA Astrophysics Data System (ADS)

Elsaesser, G.; Del Genio, A. D.

2015-12-01

The CMIP5 configurations of the GISS Model-E2 GCM simulated a mid- and high-latitude ice IWP that decreased by ~50% relative to that simulated for CMIP3 (Jiang et al. 2012; JGR). Tropical IWP increased by ~15% in CMIP5. While the tropical IWP was still within the published upper-bounds of IWP uncertainty derived using NASA A-Train satellite observations, it was found that the upper troposphere (~200 mb) ice water content (IWC) exceeded the published upper-bound by a factor of ~2. This was largely driven by IWC in deep-convecting regions of the tropics. Recent advances in the model-E2 convective parameterization have been found to have a substantial impact on tropical IWC. These advances include the development of both a cold pool parameterization (Del Genio et al. 2015) and new convective ice parameterization. In this presentation, we focus on the new parameterization of convective cloud ice that was developed using data from the NASA TC4 Mission. Ice particle terminal velocity formulations now include information from a number of NASA field campaigns. The new parameterization predicts both an ice water mass weighted-average particle diameter and a particle cross sectional area weighted-average size diameter as a function of temperature and ice water content. By assuming a gamma-distribution functional form for the particle size distribution, these two diameter estimates are all that are needed to explicitly predict the distribution of ice particles as a function of particle diameter. GCM simulations with the improved convective parameterization yield a ~50% decrease in upper tropospheric IWC, bringing the tropical and global mean IWP climatologies into even closer agreement with the A-Train satellite observation best estimates.

Transient Macroscopic Chemistry in the DSMC Method

NASA Astrophysics Data System (ADS)

Goldsworthy, M. J.; Macrossan, M. N.; Abdel-Jawad, M.

2008-12-01

In the Direct Simulation Monte Carlo method, a combination of statistical and deterministic procedures applied to a finite number of `simulator' particles are used to model rarefied gas-kinetic processes. Traditionally, chemical reactions are modelled using information from specific colliding particle pairs. In the Macroscopic Chemistry Method (MCM), the reactions are decoupled from the specific particle pairs selected for collisions. Information from all of the particles within a cell is used to determine a reaction rate coefficient for that cell. MCM has previously been applied to steady flow DSMC simulations. Here we show how MCM can be used to model chemical kinetics in DSMC simulations of unsteady flow. Results are compared with a collision-based chemistry procedure for two binary reactions in a 1-D unsteady shock-expansion tube simulation and during the unsteady development of 2-D flow through a cavity. For the shock tube simulation, close agreement is demonstrated between the two methods for instantaneous, ensemble-averaged profiles of temperature and species mole fractions. For the cavity flow, a high degree of thermal non-equilibrium is present and non-equilibrium reaction rate correction factors are employed in MCM. Very close agreement is demonstrated for ensemble averaged mole fraction contours predicted by the particle and macroscopic methods at three different flow-times. A comparison of the accumulated number of net reactions per cell shows that both methods compute identical numbers of reaction events. For the 2-D flow, MCM required similar CPU and memory resources to the particle chemistry method. The Macroscopic Chemistry Method is applicable to any general DSMC code using any viscosity or non-reacting collision models and any non-reacting energy exchange models. MCM can be used to implement any reaction rate formulations, whether these be from experimental or theoretical studies.

Diabetes enhances vulnerability to particulate air pollution-associated impairment in vascular reactivity and endothelial function.

PubMed

O'Neill, Marie S; Veves, Aristidis; Zanobetti, Antonella; Sarnat, Jeremy A; Gold, Diane R; Economides, Panayiotis A; Horton, Edward S; Schwartz, Joel

2005-06-07

Epidemiological studies suggest that people with diabetes are vulnerable to cardiovascular health effects associated with exposure to particle air pollution. Endothelial and vascular function is impaired in diabetes and may be related to increased cardiovascular risk. We examined whether endothelium-dependent and -independent vascular reactivity was associated with particle exposure in individuals with and without diabetes. Study subjects were 270 greater-Boston residents. We measured 24-hour average ambient levels of air pollution (fine particles [PM2.5], particle number, black carbon, and sulfates [SO4(2-)]) approximately 500 m from the patient examination site. Pollutant concentrations were evaluated for associations with vascular reactivity. Linear regressions were fit to the percent change in brachial artery diameter (flow mediated and nitroglycerin mediated), with the particulate pollutant index, apparent temperature, season, age, race, sex, smoking history, and body mass index as predictors. Models were fit to all subjects and then stratified by diagnosed diabetes versus at risk for diabetes. Six-day moving averages of all 4 particle metrics were associated with decreased vascular reactivity among patients with diabetes but not those at risk. Interquartile range increases in SO4(2-) were associated with decreased flow-mediated (-10.7%; 95% CI, -17.3 to -3.5) and nitroglycerin-mediated (-5.4%; 95% CI, -10.5 to -0.1) vascular reactivity among those with diabetes. Black carbon increases were associated with decreased flow-mediated vascular reactivity (-12.6%; 95% CI, -21.7 to -2.4), and PM2.5 was associated with nitroglycerin-mediated reactivity (-7.6%; 95% CI, -12.8 to -2.1). Effects were stronger in type II than type I diabetes. Diabetes confers vulnerability to particles associated with coal-burning power plants and traffic.

Thermo-sensitive polymer nanospheres as a smart plugging agent for shale gas drilling operations.

PubMed

Wang, Wei-Ji; Qiu, Zheng-Song; Zhong, Han-Yi; Huang, Wei-An; Dai, Wen-Hao

2017-01-01

Emulsifier-free poly(methyl methacrylate-styrene) [P(MMA-St)] nanospheres with an average particle size of 100 nm were synthesized in an isopropyl alcohol-water medium by a solvothermal method. Then, through radical graft copolymerization of thermo-sensitive monomer N -isopropylacrylamide (NIPAm) and hydrophilic monomer acrylic acid (AA) onto the surface of P(MMA-St) nanospheres at 80 °C, a series of thermo-sensitive polymer nanospheres, named SD-SEAL with different lower critical solution temperatures (LCST), were prepared by adjusting the mole ratio of NIPAm to AA. The products were characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, thermogravimetric analysis, particle size distribution, and specific surface area analysis. The temperature-sensitive behavior was studied by light transmittance tests, while the sealing performance was investigated by pressure transmission tests with Lungmachi Formation shales. The experimental results showed that the synthesized nanoparticles are sensitive to temperature and had apparent LCST values which increased with an increase in hydrophilic monomer AA. When the temperature was higher than its LCST value, SD-SEAL played a dual role of physical plugging and chemical inhibition, slowed down pressure transmission, and reduced shale permeability remarkably. The plugged layer of shale was changed to being hydrophobic, which greatly improved the shale stability.

Synthesis of AuPd alloyed nanoparticles via room-temperature electron reduction with argon glow discharge as electron source.

PubMed

Yang, Manman; Wang, Zongyuan; Wang, Wei; Liu, Chang-Jun

2014-01-01

Argon glow discharge has been employed as a cheap, environmentally friendly, and convenient electron source for simultaneous reduction of HAuCl4 and PdCl2 on the anodic aluminum oxide (AAO) substrate. The thermal imaging confirms that the synthesis is operated at room temperature. The reduction is conducted with a short time (30 min) under the pressure of approximately 100 Pa. This room-temperature electron reduction operates in a dry way and requires neither hydrogen nor extra heating nor chemical reducing agent. The analyses using X-ray photoelectron spectroscopy (XPS) confirm all the metallic ions have been reduced. The characterization with X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) shows that AuPd alloyed nanoparticles are formed. There also exist some highly dispersed Au and Pd monometallic particles that cannot be detected by XRD and transmission electron microscopy (TEM) because of their small particle sizes. The observed AuPd alloyed nanoparticles are spherical with an average size of 14 nm. No core-shell structure can be observed. The room-temperature electron reduction can be operated in a larger scale. It is an easy way for the synthesis of AuPd alloyed nanoparticles.

Henry's Constants of Persistent Organic Pollutants by a Group-Contribution Method Based on Scaled-Particle Theory.

PubMed

Razdan, Neil K; Koshy, David M; Prausnitz, John M

2017-11-07

A group-contribution method based on scaled-particle theory was developed to predict Henry's constants for six families of persistent organic pollutants: polychlorinated benzenes, polychlorinated biphenyls, polychlorinated dibenzodioxins, polychlorinated dibenzofurans, polychlorinated naphthalenes, and polybrominated diphenyl ethers. The group-contribution model uses limited experimental data to obtain group-interaction parameters for an easy-to-use method to predict Henry's constants for systems where reliable experimental data are scarce. By using group-interaction parameters obtained from data reduction, scaled-particle theory gives the partial molar Gibbs energy of dissolution, Δg̅ 2 , allowing calculation of Henry's constant, H 2 , for more than 700 organic pollutants. The average deviation between predicted values of log H 2 and experiment is 4%. Application of an approximate van't Hoff equation gives the temperature dependence of Henry's constants for polychlorinated biphenyls, polychlorinated naphthalenes, and polybrominated diphenyl ethers in the environmentally relevant range 0-40 °C.

Synthesis, Dielectric, Electrical and Optical characterization of ZnO synthesized by chemical route using polymer precursors

NASA Astrophysics Data System (ADS)

Mishra, Raman; Bajpai, P. K.

2011-11-01

Nano-size ZnO (particle size 7.8 nm) have been prepared from a versatile, efficient and technically simple polymer matrix based precursor solution. The precursor solution constituted of zinc nitrates with polymer PVA in presence of mono-/disaccharides. Annealing the precursor mass at 900 °C single phase zinc oxide nano-particles are obtained. X-ray diffraction analysis confirms hexagonal crystal structure with lattice parameter a = b = 3.261 A0, c = 5.220 A0. The estimated average particle size obtained from XRD data is ≈7.8 nm. The impedance analysis reveals that the grain resistance decreases with increase in temperature as expected for a semi-conducting material. The relaxation is polydispersive and conduction is mainly through grains. Optical properties and AC/DC conduction activation energies are estimated from Arrhenius plots and conduction mechanism is discussed.

Magnetic field distribution in superconducting composites as revealed by ESR-probe and magnetization

NASA Astrophysics Data System (ADS)

Davidov, D.; Bontemps, N.; Golosovsky, M.; Waysand, G.

1998-03-01

The distribution of a static magnetic field in superconductor-insulator composites consisting of BSCCO (YBCO) powder in paraffin wax is studied by ESR bulk probing and magnetization. The average field and field variance in the non-superconducting host are measured as function of temperature and volume fraction of superconductor. We develop a model of the field distribution in dilute magnetic and superconducting composites that relates the field inhomogeneity to magnetization and particle shape. We find that this model satisfactorily describes field distribution in our superconducting composites in the regime of strong flux pinning, i.e. below irreversibility line. We find deviations from the model above the irreversibility line and attribute this to flux motion. We show that the field distribution in superconducting composites is determined not only by magnetization and particle shape, but is strongly affected by the flux profile within the superconducting particles.

Size effects on electrical properties of chemically grown zinc oxide nanoparticles

NASA Astrophysics Data System (ADS)

Rathod, K. N.; Joshi, Zalak; Dhruv, Davit; Gadani, Keval; Boricha, Hetal; Joshi, A. D.; Solanki, P. S.; Shah, N. A.

2018-03-01

In the present article, we study ZnO nanoparticles grown by cost effective sol–gel technique for various electrical properties. Structural studies performed by x-ray diffraction (XRD) revealed hexagonal unit cell phase with no observed impurities. Transmission electron microscopy (TEM) and particle size analyzer showed increased average particle size due to agglomeration effect with higher sintering. Dielectric constant (ε‧) decreases with increase in frequency because of the disability of dipoles to follow higher electric field. With higher sintering, dielectric constant reduced owing to the important role of increased formation of oxygen vacancy defects. Universal dielectric response (UDR) was verified by straight line fitting of log (fε‧) versus log (f) plots. All samples exhibit UDR behavior and with higher sintering more contribution from crystal cores. Impedance studies suggest an important role of boundary density while Cole–Cole (Z″ versus Z‧) plots have been studied for the relaxation behavior of the samples. Average normalized change (ANC) in impedance has been studied for all the samples wherein boundaries play an important role. Frequency dependent electrical conductivity has been understood on the basis of Jonscher’s universal power law. Jonscher’s law fits suggest that conduction of charge carrier is possible in the context of correlated barrier hopping (CBH) mechanism for lower temperature sintered sample while for higher temperature sintered ZnO samples, Maxwell–Wagner (M–W) relaxation process has been determined.

Bio-synthesis of triangular and hexagonal gold nanoparticles using palm oil fronds’ extracts at room temperature

NASA Astrophysics Data System (ADS)

Usman, Adamu Ibrahim; Aziz, Azlan Abdul; Abu Noqta, Osama

2018-01-01

Development of bio-reduction techniques for nanoparticles (NPs) synthesis in medical application remains a challenge to numerous researchers. This work reports a novel technique for the synthesis of triangular and hexagonal gold nanoparticles (AuNP) using palm oil fronds’ (POFs) extracts. The functional groups in the POFs’ extracts operate as a persuasive capping and reducing agent to growth AuNPs. The prepared AuNPs were characterized using UV-vis spectrophotometry, Fourier-transform infrared (FTIR) spectroscopy, dynamic light scattering, energy filtered transmission electron microscopy (EFTEM), and x-ray diffraction (XRD). The analysis of FTIR validates the coating of alkynes and phenolic composites on the AuNPs. This shows a feasible function of biomolecules for efficient stabilization of the AuNPs. EFTEM clearly show the triangular and hexagonal shapes of the prepared AuNPs. The XRD patterns display the peaks of fcc crystal structures at (111), (200), (220), (311) and (222), with average particle sizes of 66.7 and 79.02 nm for 1% and 5% POFs extracts concentrations respectively at room temperature. While at 120 °C the average particles size recorded for 1% and 5% of POFs extract concentrations were 32.17 nm and 45.66 nm respectively, and the reaction completed in less than 2 min. The prepared NPs could be potentially applied in biomedical application, due to their excellent stability and refine morphology without agglomeration.

Intercomparison study and optical asphericity measurements of small ice particles in the CERN CLOUD experiment

NASA Astrophysics Data System (ADS)

Nichman, Leonid; Järvinen, Emma; Dorsey, James; Connolly, Paul; Duplissy, Jonathan; Fuchs, Claudia; Ignatius, Karoliina; Sengupta, Kamalika; Stratmann, Frank; Möhler, Ottmar; Schnaiter, Martin; Gallagher, Martin

2017-09-01

Optical probes are frequently used for the detection of microphysical cloud particle properties such as liquid and ice phase, size and morphology. These properties can eventually influence the angular light scattering properties of cirrus clouds as well as the growth and accretion mechanisms of single cloud particles. In this study we compare four commonly used optical probes to examine their response to small cloud particles of different phase and asphericity. Cloud simulation experiments were conducted at the Cosmics Leaving OUtdoor Droplets (CLOUD) chamber at European Organisation for Nuclear Research (CERN). The chamber was operated in a series of multi-step adiabatic expansions to produce growth and sublimation of ice particles at super- and subsaturated ice conditions and for initial temperatures of -30, -40 and -50 °C. The experiments were performed for ice cloud formation via homogeneous ice nucleation. We report the optical observations of small ice particles in deep convection and in situ cirrus simulations. Ice crystal asphericity deduced from measurements of spatially resolved single particle light scattering patterns by the Particle Phase Discriminator mark 2 (PPD-2K, Karlsruhe edition) were compared with Cloud and Aerosol Spectrometer with Polarisation (CASPOL) measurements and image roundness captured by the 3View Cloud Particle Imager (3V-CPI). Averaged path light scattering properties of the simulated ice clouds were measured using the Scattering Intensity Measurements for the Optical detectioN of icE (SIMONE) and single particle scattering properties were measured by the CASPOL. We show the ambiguity of several optical measurements in ice fraction determination of homogeneously frozen ice in the case where sublimating quasi-spherical ice particles are present. Moreover, most of the instruments have difficulties of producing reliable ice fraction if small aspherical ice particles are present, and all of the instruments cannot separate perfectly spherical ice particles from supercooled droplets. Correlation analysis of bulk averaged path depolarisation measurements and single particle measurements of these clouds showed higher R2 values at high concentrations and small diameters, but these results require further confirmation. We find that none of these instruments were able to determine unambiguously the phase of the small particles. These results have implications for the interpretation of atmospheric measurements and parametrisations for modelling, particularly for low particle number concentration clouds.

Sintering behavior of spin-coated FePt and FePtAu nanoparticles

NASA Astrophysics Data System (ADS)

Kang, Shishou; Jia, Zhiyong; Zoto, I.; Reed, D.; Nikles, David E.; Harrell, J. W.; Thompson, Gregory; Mankey, Gary; Krishnamurthy, Vemuru V.; Porcar, L.

2006-04-01

FePt and [FePt]95Au5 nanoparticles with an average size of about 4 nm were chemically synthesized and spin coated onto silicon substrates. Samples were subsequently thermally annealed at temperatures ranging from 250 to 500 °C for 30 min. Three-dimensional structural characterization was carried out with small-angle neutron scattering (SANS) and small-angle x-ray diffraction (SAXRD) measurements. For both FePt and [FePt]95Au5 particles before annealing, SANS measurements gave an in-plane coherence length parameter a=7.3 nm, while SAXRD measurements gave a perpendicular coherence length parameter c=12.0 nm. The ratio of c/a is about 1.64, indicating the as-made particle array has a hexagonal close-packed superstructure. For both FePt and FePtAu nanoparticles, the diffraction peaks shifted to higher angles and broadened with increasing annealing temperature. This effect corresponds to a shrinking of the nanoparticle array, followed by agglomeration and sintering of the nanoparticles, resulting in the eventual loss of positional order with increasing annealing temperature. The effect is more pronounced for FePtAu than for FePt. Dynamic coercivity measurements show that the FePtAu nanoparticles have both higher intrinsic coercivity and higher switching volume at the same annealing temperature. These results are consistent with previous studies that show that additive Au both lowers the chemical ordering temperature and promotes sintering.

Temperature histories in liquid and solid polar stratospheric cloud formation

NASA Astrophysics Data System (ADS)

Larsen, Niels; Knudsen, Bjørn M.; Rosen, James M.; Kjome, Norman T.; Neuber, Roland; Kyrö, Esko

1997-10-01

Polar stratospheric clouds (PSCs) have been observed by balloonborne backscatter sondes from Alert, Thule, Heiss Island, Scoresbysund, Sodankylä, Søndre Strømfjord, and Ny Ȧlesund during winters 1989, 1990, 1995, and 1996 in 30 flights. The observations can be categorized into two main groups: type 1a and type 1b PSC particles. Type 1b PSCs show the characteristics expected from liquid ternary solution (HNO3/H2SO4/H2O) particles, consistent with model simulations. Type 1a PSCs are observed at all temperatures below the condensation temperature TNAT of nitric acid trihydrate (NAT), consistent with solid NAT composition. Air parcel trajectories have been calculated for all observations to provide synoptic temperature histories of the observed particles. A number of cases have been identified, where the particles have experienced temperatures close to or above the sulfuric acid tetrahydrate melting temperatures within 20 days prior to observation. This assures a knowledge of the physical phase (liquid) of the particles at this time, prior to observation. The subsequent synoptic temperature histories, between melting and the time of observation, show pronounced differences for type 1a and type 1b PSC particles, indicating the qualitative temperature conditions, necessary to generate solid type 1a PSCs. The temperature histories of type 1b particles show smoothly, in most cases monotonic, decreasing temperatures. The temperature can apparently decrease to the frost point without causing the particles to freeze. The type 1b PSC particles are mostly observed shortly after entering a cold region. The observed type 1a particles have spent several days at temperatures close to or below TNAT prior to observation, often associated with several synoptic temperature oscillations around TNAT, and the particles are observed in aged clouds. It appears that the PSC particles may freeze, if they experience synoptic temperatures below TNAT with a duration of at least 1 day, possibly accompanied by several temperature oscillations. However, liquid particles that experience a smooth cooling, even to very low temperatures, or single smooth cooling/heating below TNAT without synoptic temperature fluctuations do not seem to freeze.

Induction Curing of Thiol-acrylate and Thiolene Composite Systems

PubMed Central

Ye, Sheng; Cramer, Neil B.; Stevens, Blake E.; Sani, Robert L.; Bowman, Christopher N.

2011-01-01

Induction curing is demonstrated as a novel type of in situ radiation curing that maintains most of the advantages of photocuring while eliminating the restriction of light accessibility. Induction curing is utilized to polymerize opaque composites comprised of thiol-acrylate and thiol-ene resins, nanoscale magnetic particles, and carbon nanotubes. Nanoscale magnetic particles are dispersed in the resin and upon exposure to the magnetic field, these particles lead to induction heating that rapidly initiates the polymerization. Heat transfer profiles and reaction kinetics of the samples are modeled during the reactions with varying induction heater power, species concentration, species type and sample thickness, and the model is compared with the experimental results. Thiol-ene polymerizations achieved full conversion between 1.5 minutes and 1 hour, depending on the field intensity and the composition, with the maximum reaction temperature decreasing from 146 – 87 °C when the induction heater power was decreased from 8 – 3 kW. The polymerization reactions of the thiol-acrylate system were demonstrated to achieve full conversion between 0.6 and 30 minutes with maximum temperatures from 139 to 86 °C. The experimental behavior was characterized and the temperature profile modeled for the thiol-acrylate composite comprised of sub100nm nickel particles and induction heater power in the range of 32 to 20 kW. A 9°C average deviation was observed between the modeling and experimental results for the maximum temperature rise. The model also was utilized to predict reaction temperatures and kinetics for systems with varying thermal initiator concentration, initiator half-life, monomer molecular weight and temperature gradients in samples with varying thickness, thereby demonstrating that induction curing represents a designable and tunable polymerization method. Finally, induction curing was utilized to cure thiol-acrylate systems containing carbon nanotubes where 1 wt% carbon nanotubes resulted in systems where the storage modulus increased from 17.6 ± 0.2 to 21.6 ± 0.1 MPa and an electrical conductivity that increased from <10−7 to 0.33 ± 0.5 S/m. PMID:21765552

Evaluation of Diesel Exhaust Continuous Monitors in Controlled Environmental Conditions

PubMed Central

Yu, Chang Ho; Patton, Allison P.; Zhang, Andrew; Fanac, Zhi-Hua (Tina); Weisel, Clifford P.; Lioy, Paul J.

2015-01-01

Diesel exhaust (DE) contains a variety of toxic air pollutants, including diesel particulate matter (DPM) and gaseous contaminants (e.g., carbon monoxide (CO)). DPM is dominated by fine (PM2.5) and ultrafine particles (UFP), and can be representatively determined by its thermal-optical refractory as elemental carbon (EC) or light-absorbing characteristics as black carbon (BC). The currently accepted reference method for sampling and analysis of occupational exposure to DPM is the National Institute for Occupational Safety and Health (NIOSH) Method 5040. However, this method cannot provide in-situ short-term measurements of DPM. Thus, real-time monitors are gaining attention to better examine DE exposures in occupational settings. However, real-time monitors are subject to changing environmental conditions. Field measurements have reported interferences in optical sensors and subsequent real-time readings, under conditions of high humidity and abrupt temperature changes. To begin dealing with these issues, we completed a controlled study to evaluate five real-time monitors: Airtec real-time DPM/EC Monitor, TSI SidePak Personal Aerosol Monitor AM510 (PM2.5), TSI Condensation Particle Counter 3007, microAeth AE51 BC Aethalometer, and Langan T15n CO Measurer. Tests were conducted under different temperatures (55, 70, and 80 °F), relative humidity (10, 40, and 80%), and DPM concentrations (50 and 200 µg/m3) in a controlled exposure facility. The 2-hour averaged EC measurements from the Airtec instrument showed relatively good agreement with NIOSH Method 5040 (R2=0.84; slope=1.17±0.06; N=27) and reported ~17% higher EC concentrations than the NIOSH reference method. Temperature, relative humidity, and DPM levels did not significantly affect relative differences in 2-hour averaged EC concentrations obtained by the Airtec instrument versus the NIOSH method (p<0.05). Multiple linear regression analyses, based on 1-min averaged data, suggested combined effects of up to 5% from relative humidity and temperature on real-time measurements. The overall deviations of these real-time monitors from the NIOSH method results were ≤20%. However, simultaneous monitoring of temperature and relative humidity is recommended in field investigations to understand and correct for environmental impacts on real-time monitoring data. PMID:25894766

Factors Affecting Pathogen Survival in Finished Dairy Compost with Different Particle Sizes Under Greenhouse Conditions.

PubMed

Diao, Junshu; Chen, Zhao; Gong, Chao; Jiang, Xiuping

2015-09-01

This study investigated the survival of Escherichia coli O157:H7 and Salmonella Typhimurium in finished dairy compost with different particle sizes during storage as affected by moisture content and temperature under greenhouse conditions. The mixture of E. coli O157:H7 and S. Typhimurium strains was inoculated into the finished composts with moisture contents of 20, 30, and 40%, separately. The finished compost samples were then sieved into 3 different particle sizes (>1000, 500-1000, and <500 μm) and stored under greenhouse conditions. For compost samples with moisture contents of 20 and 30%, the average Salmonella reductions in compost samples with particle sizes of >1000, 500-1000, and <500 μm were 2.15, 2.27, and 2.47 log colony-forming units (CFU) g(-1) within 5 days of storage in summer, respectively, as compared with 1.60, 2.03, and 2.26 log CFU g(-1) in late fall, respectively, and 2.61, 3.33, and 3.67 log CFU g(-1) in winter, respectively. The average E. coli O157:H7 reductions in compost samples with particle sizes of >1000, 500-1000, and <500 μm were 1.98, 2.30, and 2.54 log CFU g(-1) within 5 days of storage in summer, respectively, as compared with 1.70, 2.56, and 2.90 log CFU g(-1) in winter, respectively. Our results revealed that both Salmonella and E. coli O157:H7 in compost samples with larger particle size survived better than those with smaller particle sizes, and the initial rapid moisture loss in compost may contribute to the fast inactivation of pathogens in the finished compost. For the same season, the pathogens in the compost samples with the same particle size survived much better at the initial moisture content of 20% compared to 40%.

Particle withdrawal from fluidized bed systems

DOEpatents

Salvador, Louis A.; Andermann, Ronald E.; Rath, Lawrence K.

1982-01-01

Method and apparatus for removing ash formed within, and accumulated at the lower portion of, a fluidized bed coal gasification reactor vessel. A supplemental fluidizing gas, at a temperature substantially less than the average fluidized bed combustion operating temperature, is injected into the vessel and upwardly through the ash so as to form a discrete thermal interface region between the fluidized bed and the ash. The elevation of the interface region, which rises with ash accumulation, is monitored by a thermocouple and interrelated with a motor controlled outlet valve. When the interface rises above the temperature indicator, the valve opens to allow removal of some of the ash, and the valve is closed, or positioned at a minimum setting, when the interface drops to an elevation below that of the thermocouple.

Polymer nanocomposite dielectric and electrical properties with quantum dots nanofiller

NASA Astrophysics Data System (ADS)

Ahmed, R. M.; Morsi, R. M. M.

2017-10-01

Nanocomposite films of different contents of CdSe/ZnS quantum dots nanoparticles embedded in hosting matrix of polyvinyl chloride (PVC) were prepared by simple solution casting method. Electrical and dielectric properties of nanocomposites films were investigated in the temperature range 323-393 (K) and at frequencies (50-2000) kHz. The frequency dependence of AC conductivity was following the universal power law. The values of the frequency exponent, s, revealed that the conduction mechanism at low temperature is considered by small polaron tunneling model, whereas at high temperature, it is related to CBH model. The activation energy values (ΔE) were depending on nanoparticle concentration as well as frequency. Also, X-ray diffraction (XRD) enabled approximately estimating the average particle size of the nanoparticles incorporated in PVC.

Microstructure of the irradiated U 3Si 2/Al silicide dispersion fuel

NASA Astrophysics Data System (ADS)

Gan, J.; Keiser, D. D.; Miller, B. D.; Jue, J.-F.; Robinson, A. B.; Madden, J. W.; Medvedev, P. G.; Wachs, D. M.

2011-12-01

The silicide dispersion fuel of U 3Si 2/Al is recognized as the best performance fuel for many nuclear research and test reactors with up to 4.8 gU/cm 3 fuel loading. An irradiated U 3Si 2/Al dispersion fuel ( 235U ˜ 75%) from the high-flux side of a fuel plate (U0R040) from the Reduced Enrichment for Research and Test Reactors (RERTR)-8 test was characterized using transmission electron microscopy (TEM). The fuel was irradiated in the Advanced Test Reactor (ATR) for 105 days. The average irradiation temperature and fission density of the U 3Si 2 fuel particles for the TEM sample are estimated to be approximately 110 °C and 5.4 × 10 27 f/m 3. The characterization was performed using a 200-kV TEM. The U/Si ratio for the fuel particle and (Si + Al)/U for the fuel-matrix-interaction layer are approximately 1.1 and 4-10, respectively. The estimated average diameter, number density and volume fraction for small bubbles (<1 μm) in the fuel particle are ˜94 nm, 1.05 × 10 20 m -3 and ˜11%, respectively. The results and their implication on the performance of the U 3Si 2/Al silicide dispersion fuel are discussed.

Characterization of bismuth selenide (Bi2Se3) thin films obtained by evaporating the hydrothermally synthesised nano-particles

NASA Astrophysics Data System (ADS)

Indirajith, R.; Rajalakshmi, M.; Gopalakrishnan, R.; Ramamurthi, K.

2016-03-01

Bismuth selenide (Bi2Se3) was synthesized by hydrothermal method at 200 °C and confirmed by powder X-ray diffraction (XRD) studies. The synthesized material was utilized to deposit bismuth selenide thin films at various substrate temperatures (Room Temperature-RT, 150 °C, 250 °C, 350 °C and 450 °C) by electron beam evaporation technique. XRD study confirmed the polycrystalline nature of the deposited Bi2Se3films. Optical transmittance spectra showed that the deposited (at RT) films acquire relatively high average transmittance of 60%in near infrared region (1500-2500 nm). An indirect allowed optical band gap calculated from the absorption edge for the deposited films is ranging from 0.62 to 0.8 eV. Scanning electron and atomic force microscopy analyses reveal the formation of nano-scale sized particles on the surface and that the nature of surface microstructures is influenced by the substrate temperature. Hall measurements showed improved electrical properties, for the films deposited at 350 °C which possess 2.8 times the mobility and 0.9 times the resistivity of the films deposited at RT.

Ultrasonic agitation-floating classification of nano-sized Ba-Mg ferrites particles formed by using self-propagating high temperature synthesis and fabrication of nickel-ferrites thin sheet by pulse-electroforming.

PubMed

Choi, Yong

2013-01-01

Nickel-nano-sized ferrites composites sheet for electromagnetic shielding was produced by pulse-electroforming in a modified nickel sulfamate solution. The ferrite particles were prepared by self-propagating high temperature synthesis (SHS) followed by mechanical milling, and classified with an ultrasonic agitation-floating unit to obtain about 100 nm in size. Average combustion temperature and combustion propagating rate during SHS reaction were 1190 K and 5.8 mm/sec at the oxygen pressure of 1.0 MPa, respectively. The nickel-ferrite composite sheet had preferred orientation which (100) pole clearly concentrated to normal direction, whereas, (110) and (111) poles tended to split to the longitudinal direction, respectively. Maximum magnetization, residual magnetization and coercive force of the nano-sized ferrites were 27.13 A x m2/kg, 6.4 A x m2/kg and 14.58 kA/m, respectively. Complex permeability of the composites decreased with an increase in frequency, and its real value (mu'r) had the maximum at about 0.3 GHz. The dielectric constants of the composites were epsilon'r = 6.7 and epsilon"r = 0.

Electrophysical Properties of Onion-Like Carbon

NASA Astrophysics Data System (ADS)

Tkachev, E. N.; Romanenko, A. I.; Zhdanov, K. R.; Anikeeva, O. B.; Buryakov, T. I.; Kuznetsov, V. L.; Moseenkov, S. I.

2016-06-01

The paper examines electrophysical properties of onion-like carbon (OLC) samples, where particles have the average size of 4-8 nm and are formed by 5-10 nested fullerene-like spheres connected by 1-3 common curved graphene shells into aggregates with a size of 50-300 nm. We measured the temperature dependence of electrical resistance from 4.2 to 300 K and dependence of magnetoresistance in magnetic fields up to 6 T at the temperature of 4.2 K. Temperature dependences of electrical resistance of samples can be described within the framework of the Mott law with variable hop length for the one-dimensional case or within the framework of the Efros-Shklovskii Coulomb gap. We observed the quadratically increasing positive magnetoresistance up to 6 T associated with compression of wave functions of conduction electrons. Negative magnetoresistance was observed in the range of magnetic fields up to 1-2 T in the case of some samples. This is due to the fact that magnetic field suppresses the contributions to magnetoresistance made by interference effects in the area of hopping conductivity. The measurements were used to estimate the localization radius that is comparable to the diameter of OLC particles (nano-onions).

Optical and superparamagnetic behavior of ZnFe2O4 nanoparticles

NASA Astrophysics Data System (ADS)

Lal, Ganesh; Punia, Khushboo; Dolia, S. N.; Kumar, Sudhish

2018-05-01

Nanoparticles of zinc ferrite have been synthesized using a low temperature citrate sol-gel route and characterized by powder X-ray diffraction (XRD), Raman & UV-Vis-NIR spectroscopic and SQUID magnetometry measurements. Analysis of XRD pattern and Raman spectrum confirmed that the synthesized ZnFe2O4 sample crystallizes in single phase fcc spinel ferrite structure and the average particle size of nanoparticles is estimated to 24nm. Optical absorption study shows that maximum photo absorption take place in the visible band and peaking in UV band at 206nm and the band gap energy is estimated to Eg = 2.1eV. Zero Field Cooled (ZFC) and Field Cooled (FC) modes of magnetization down to 5K and in fields up to 20kOe shows that ZnFe2O4 nanoparticles exhibits superparamagnetism with high magneto-crystalline anisotropy and high magnetization. Small difference of 9K between the separation temperature TS=˜30K and blocking temperature TB= 21K are suggestive of the formation of ferromagnetic clusters and a narrow particle size distribution of the nanoparticles in superparamagnetic ZnFe2O4 nanoparticles.

Nonlinear Burn Control and Operating Point Optimization in ITER

NASA Astrophysics Data System (ADS)

Boyer, Mark; Schuster, Eugenio

2013-10-01

Control of the fusion power through regulation of the plasma density and temperature will be essential for achieving and maintaining desired operating points in fusion reactors and burning plasma experiments like ITER. In this work, a volume averaged model for the evolution of the density of energy, deuterium and tritium fuel ions, alpha-particles, and impurity ions is used to synthesize a multi-input multi-output nonlinear feedback controller for stabilizing and modulating the burn condition. Adaptive control techniques are used to account for uncertainty in model parameters, including particle confinement times and recycling rates. The control approach makes use of the different possible methods for altering the fusion power, including adjusting the temperature through auxiliary heating, modulating the density and isotopic mix through fueling, and altering the impurity density through impurity injection. Furthermore, a model-based optimization scheme is proposed to drive the system as close as possible to desired fusion power and temperature references. Constraints are considered in the optimization scheme to ensure that, for example, density and beta limits are avoided, and that optimal operation is achieved even when actuators reach saturation. Supported by the NSF CAREER award program (ECCS-0645086).

Synthesis and characterization of polyvinylimidazole-grafted superparamagnetic iron oxide nanoparticles (Si-PVIm-grafted SPION)

NASA Astrophysics Data System (ADS)

Erdemi, H.; Sözeri, H.; Şenel, M.; Baykal, A.

2012-08-01

Polyvinylimidazole (PVIm)-grafted superparamagnetic iron oxide nanoparticles (SPION) (Si-PVIm-grafted Fe3O4 NPs) were prepared by grafting of telomere of PVIm on the SPION. The product identified as magnetite, which has an average crystallite size of 9 ± 2 nm as estimated from X-ray line profile fitting. Particle size was estimated as 10.0 ± 0.5 nm from TEM micrographs. Mean particle size is found as 8.4 ± 1.0 nm which agrees well with the values calculated from XRD patterns (9 ± 2 nm). Vibrating Sample Magnetometer (VSM) analysis explained the superparamagnetic nature of the nanocomposite. Thermogravimetric analysis showed that the Si-Imi is 25 % of the Si-PVIm-grafted SPION, which means an inorganic content is about 75 %. Detailed electrical and dielectric properties of the properties of the product are also presented. The conductivity of the sample increases significantly with temperature and has the value in the range of 1.14 × 10-7-1.78 × 10-4 S cm-1. Analysis of the real and imaginary parts of the permittivities indicated temperature and frequency dependency representing interfacial polarization and temperature-assisted reorganization effects.

Structure in sheared supercooled liquids: Dynamical rearrangements of an effective system of icosahedra.

PubMed

Pinney, Rhiannon; Liverpool, Tanniemola B; Royall, C Patrick

2016-12-21

We consider a binary Lennard-Jones glassformer whose super-Arrhenius dynamics are correlated with the formation of particles organized into icosahedra under simple steady state shear. We recast this glassformer as an effective system of icosahedra [Pinney et al., J. Chem. Phys. 143, 244507 (2015)]. From the observed population of icosahedra in each steady state, we obtain an effective temperature which is linearly dependent on the shear rate in the range considered. Upon shear banding, the system separates into a region of high shear rate and a region of low shear rate. The effective temperatures obtained in each case show that the low shear regions correspond to a significantly lower temperature than the high shear regions. Taking a weighted average of the effective temperature of these regions (weight determined by region size) yields an estimate of the effective temperature which compares well with an effective temperature based on the global mesocluster population of the whole system.

Development of Hydroxyl Tagging Velocimetry for Low Velocity Flows

NASA Technical Reports Server (NTRS)

Andre, Matthieu A.; Bardet, Philippe M.; Burns, Ross A.; Danehy, Paul M.

2016-01-01

Hydroxyl tagging velocimetry (HTV) is a molecular tagging technique that relies on the photo-dissociation of water vapor into OH radicals and their subsequent tracking using laser induced fluorescence. Velocities are then obtained from time-of-flight calculations. At ambient temperature in air, the OH species lifetime is relatively short (<50 µs), making it suited for high speed flows. Lifetime and radicals formation increases with temperature, which allows HTV to also probe low-velocity, high-temperature flows or reacting flows such as flames. The present work aims at extending the domain of applicability of HTV, particularly towards low-speed (<10 m/s) and moderate (<500 K) temperature flows. Results are compared to particle image velocimetry (PIV) measurements recorded in identical conditions. Single shot and averaged velocity profiles are obtained in an air jet at room temperature. By modestly raising the temperature (100-200 degC) the OH production increases, resulting in an improvement of the signal-to-noise ratio (SNR). Use of nitrogen - a non-reactive gas with minimal collisional quenching - extends the OH species lifetime (to over 500 µs), which allows probing of slower flows or, alternately, increases the measurement precision at the expense of spatial resolution. Instantaneous velocity profiles are resolved in a 100degC nitrogen jet (maximum jet-center velocity of 6.5 m/s) with an uncertainty down to 0.10 m/s (1.5%) at 68% confidence level. MTV measurements are compared with particle image velocimetry and show agreement within 2%.

Crossover behavior of stock returns and mean square displacements of particles governed by the Langevin equation

NASA Astrophysics Data System (ADS)

Ma, Wen-Jong; Wang, Shih-Chieh; Chen, Chi-Ning; Hu, Chin-Kun

2013-06-01

It is found that the mean square log-returns calculated from the high-frequency one-day moving average of US and Taiwan stocks with the time internal τ show ballistic behavior \\theta \\tau^{\\alpha_1} with the exponent \\alpha_1 \\approx 2 for small τ and show diffusion-like behavior D \\tau^{\\alpha_2} with the exponent \\alpha_2 \\approx 1 for large τ. Such a crossover behavior can be well described by the mean square displacements of particles governed by the Langevin equation of motion. Thus, θ and D can be considered, respectively, as the temperature-like and diffusivity-like kinetic parameters of the market, and they can be used to characterize the behavior of the market.

Measurement of charged-particle stopping in warm-dense plasma

DOE PAGES

Zylstra, A.  B.; Frenje, J.  A.; Grabowski, P. E.; ...

2015-05-27

We measured the stopping of energetic protons in an isochorically-heated solid-density Be plasma with an electron temperature of ~32 eV, corresponding to moderately-coupled [(e²/a/(k BT e + E F ) ~ 0.3] and moderately-degenerate [k BT e/E F ~2] 'warm dense matter' (WDM) conditions. We present the first high-accuracy measurements of charged-particle energy loss through dense plasma, which shows an increased loss relative to cold matter, consistent with a reduced mean ionization potential. The data agree with stopping models based on an ad-hoc treatment of free and bound electrons, as well as the average-atom local-density approximation; this work is themore » first test of these theories in WDM plasma.« less

Magnetic Properties of Copper Doped Nickel Ferrite Nanoparticles Synthesized by Co Precipitation Method

NASA Astrophysics Data System (ADS)

Anjana, V.; John, Sara; Prakash, Pooja; Nair, Amritha M.; Nair, Aravind R.; Sambhudevan, Sreedha; Shankar, Balakrishnan

2018-02-01

Nickel ferrite nanoparticles with copper atoms as dopant have been prepared using co-precipitation method with general formula Ni1-xCuxFe2O4 (x=0.2, 0.4, 0.6, 0.8 and 1) and are sintered at quite ambient temperature. Structural and magnetic properties were examined using Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction method (XRD) and Vibrating Sample Magnetometer (VSM) to study the influence of copper doping in nickel ferrite magnetic nanoparticles. X-ray studies proves that the particles are possessing single phase spinel structure with an average particle size calculated using Debye Scherer formula. Magnetic measurements reveal that saturation magnetization value (Ms) decreases while magnetic coercivity (Hc) increases upon doping.

Supercritical fluid route for synthesizing crystalline Barium Strontium Titanate nanoparticles.

PubMed

Reverón, H; Elissalde, C; Aymonier, C; Bidault, O; Maglione, M; Cansell, F

2005-10-01

Pure and well-crystallized Barium Strontium Titanate (BST) nanoparticles with controlled Ba/Sr ratio have been successfully synthesized under supercritical conditions using a continuous-flow reactor in the temperature range of 150-380 degrees C at 26 MPa. To synthesize the Ba0.6Sr0.4TiO3 composition, alkoxides, ethanol and water were used. The resulting nanopowder consists of fine particles with an average particle size of 23 nm. The results show that the Ba/Sr ratio of this powder can be accurately controlled from the composition of precursor. The characterization of the as-synthesized Ba0.6Sr0.4TiO3 solid-solution and the dielectric properties of the sintered ceramics are here reported.

High magnetization Fe-Co and Fe-Ni submicron and nanosize particles by thermal decomposition and hydrogen reduction

NASA Astrophysics Data System (ADS)

Cui, B. Z.; Marinescu, M.; Liu, J. F.

2014-05-01

This paper reports morphology, structure, and magnetic properties of air-stable soft magnetic FexCo100-x (x = 65, 50, and 34) and Fe50Ni50 (at. %) submicron and nanosize particles fabricated by template-free thermal decomposition of nitrates of Fe, Co, and Ni and subsequent hydrogen reduction. The particle compositions were tuned by modification of the precursor solution concentrations. The as-synthesized Fe-Co and Fe50Ni50 particles have body centered cubic and face centered cubic poly-nanocrystalline structures, respectively. The Fe-Co and Fe50Ni50 particles have particle sizes in the range of 28-200 nm and 70-480 nm, and average grain sizes of 16-29 nm and 20-24 nm, respectively. The particle and grain sizes were controlled by tuning particle composition, and the temperature and time of hydrogen reduction. Saturation magnetization Ms as high as 207-224 emu/g and intrinsic coercivity Hci of 59-228 Oe were obtained in the Fe-Co particles reduced at 550 °C for 90 min. Of special note, the Ms of 224 emu/g (˜2.3 T) obtained in the Fe65Co35 particles is among the highest values for Fe-Co particles reported so far. Ms of 135-137 emu/g and Hci of 59-111 Oe were obtained in the Fe50Ni50 particles reduced at 500 or 550 °C for 20 min.

Temperature and magnetic field responsive hyaluronic acid particles with tunable physical and chemical properties

NASA Astrophysics Data System (ADS)

Ekici, Sema; Ilgin, Pinar; Yilmaz, Selahattin; Aktas, Nahit; Sahiner, Nurettin

2011-01-01

We report the preparation and characterization of thiolated-temperature-responsive hyaluronic acid-cysteamine-N-isopropyl acrylamide (HA-CYs-NIPAm) particles and thiolated-magnetic-responsive hyaluronic acid (HA-Fe-CYs) particles. Linear hyaluronic acid (HA) crosslinked with divinyl sulfone as HA particles was prepared using a water-in-oil micro emulsion system which were then oxidized HA-O with NaIO4 to develop aldehyde groups on the particle surface. HA-O hydrogel particles were then reacted with cysteamine (CYs) which interacted with aldehydes on the HA surface to form HA particles with cysteamine (HA-CYs) functionality on the surface. HA-CYs particles were further exposed to radical polymerization with NIPAm to obtain temperature responsive HA-CYs-NIPAm hydrogel particles. To acquire magnetic field responsive HA composites, magnetic iron particles were included in HA to form HA-Fe during HA particle preparation. HA-Fe hydrogel particles were also chemically modified. The prepared HA-CYs-NIPAm demonstrated temperature dependent size variations and phase transition temperature. HA-CYs-NIPAm and HA-Fe-CYs particles can be used as drug delivery vehicles. Sulfamethoxazole (SMZ), an antibacterial drug, was used as a model drug for temperature-induced release studies from these particles.

Time-Average Measurement of Velocity, Density, Temperature, and Turbulence Using Molecular Rayleigh Scattering

NASA Technical Reports Server (NTRS)

Mielke, Amy F.; Seasholtz, Richard G.; Elam, Krisie A.; Panda, Jayanta

2004-01-01

Measurement of time-averaged velocity, density, temperature, and turbulence in gas flows using a nonintrusive, point-wise measurement technique based on molecular Rayleigh scattering is discussed. Subsonic and supersonic flows in a 25.4-mm diameter free jet facility were studied. The developed instrumentation utilizes a Fabry-Perot interferometer to spectrally resolve molecularly scattered light from a laser beam passed through a gas flow. The spectrum of the scattered light contains information about velocity, density, and temperature of the gas. The technique uses a slow scan, low noise 16-bit depth CCD camera to record images of the fringes formed by Rayleigh scattered light passing through the interferometer. A kinetic theory model of the Rayleigh scattered light is used in a nonlinear least squares fitting routine to estimate the unknown parameters from the fringe images. The ability to extract turbulence information from the fringe image data proved to be a challenge since the fringe is broadened by not only turbulence, but also thermal fluctuations and aperture effects from collecting light over a range of scattering angles. Figure 1 illustrates broadening of a Rayleigh spectrum typical of flow conditions observed in this work due to aperture effects and turbulence for a scattering angle, chi(sub s), of 90 degrees, f/3.67 collection optics, mean flow velocity, u(sub k), of 300 m/s, and turbulent velocity fluctuations, sigma (sub uk), of 55 m/s. The greatest difficulty in processing the image data was decoupling the thermal and turbulence broadening in the spectrum. To aid in this endeavor, it was necessary to seed the ambient air with smoke and dust particulates; taking advantage of the turbulence broadening in the Mie scattering component of the spectrum of the collected light (not shown in the figure). The primary jet flow was not seeded due to the difficulty of the task. For measurement points lacking particles, velocity, density, and temperature information could reliably be recovered, however the turbulence estimates contained significant uncertainty. Resulting flow parameter estimates are presented for surveys of Mach 0.6, 0.95, and 1.4 jet flows. Velocity, density, and temperature were determined with accuracies of 5 m/s, 1.5%, and 1%, respectively, in flows with no particles present, and with accuracies of 5 m/s, 1-4%, and 2% in flows with particles. Comparison with hotwire data for the Mach 0.6 condition demonstrated turbulence estimates with accuracies of about 5 m/s outside the jet core where Mie scattering from dust/smoke particulates aided in the estimation of turbulence. Turbulence estimates could not be recovered with any significant accuracy for measurement points where no particles were present.

High level gamma radiation effects on Cernox™ cryogenic temperature sensors

NASA Astrophysics Data System (ADS)

Courts, S. S.

2017-12-01

Cryogenic temperature sensors are used in high energy particle colliders to monitor the temperatures of superconducting magnets, superconducting RF cavities, and cryogen infrastructure. While not intentional, these components are irradiated by leakage radiation during operation of the collider. A common type of cryogenic thermometer used in these applications is the Cernox™ resistance thermometer (CxRT) manufactured by Lake Shore Cryotronics, Inc. This work examines the radiation-induced calibration offsets on CxRT models CX-1050-SD-HT and CX-1080-SD-HT resulting from exposure to very high levels of gamma radiation. Samples from two different wafers of each of the two models tested were subjected to a gamma radiation dose ranging from 10 kGy to 5 MGy. Data were analysed in terms of the temperature-equivalent resistance change between pre- and post-irradiation calibrations. The data show that the resistance of these devices decreased following irradiation resulting in positive temperature offsets across the 1.4 K to 330 K temperature range. Variations in response were observed between wafers of the same CxRT model. Overall, the offsets increased with increasing temperature and increasing gamma radiation dose. At 1.8 K, the average offset increased from 0 mK to +13 mK as total dose increased from 10 kGy to 5 MGy. At 4.2 K, the average offset increased from +4 mK to +33 mK as total dose increased from 10 kGy to 5 MGy. Equivalent temperature offset data are presented over the 1.4 K to 330 K temperature range by CxRT model, wafer, and total gamma dose.

THE VIABILITY OF THE PNEUMOCOCCUS AFTER DRYING: A STUDY OF ONE OF THE FACTORS IN PNEUMONIC INFECTION

PubMed Central

Wood, Francis Carter

1905-01-01

I. In moist sputum kept in the dark at room temperatures the average life of the pneumococcus is eleven days, though considerable variations may be noted in different specimens of sputum. In the same sputum kept at o° C. the average life of the organism is thirty-five days. In sputum kept at room temperature and in a strong light the pneumococcus lives less than five days. II. In dried sputum (a) in the dark the pneumococcus lives on an average thirty-five days; (b) in diffuse light, thirty days; (c) in sunlight, less than four hours. III. In powdered sputum even when kept in the dark the death of the pneumococcus takes place in from one to four hours. When exposed to sunlight death occurs within an hour. IV. No important differences were noted in the life of the pneumococcus when dried on glass, tin, or wood. On cloth the life was usually slightly longer than on non-absorbing surfaces. V. Sprayed sputum particles remain in suspension for twenty-four hours, but all masses of a size sufficient to contain bacteria settle at a rate of about 40 cm. per hour. VI. When sputum containing pneumococci is sprayed the organisms rarely survive for more than an hour, and often die in less time. The substance upon which the particles fall makes but little difference in the life of the organism. On cloth a slight prolongation is occasionally noted, due perhaps to the slow drying. VII. The mucus of the sputum exerts a destructive action on the pneumococcus. VIII. Exposure of bacterial spray to sunlight while in suspension results in the destruction of the pneumococcus within half an hour. PMID:19867014

Crossover in growth laws for phase-separating binary fluids: molecular dynamics simulations.

PubMed

Ahmad, Shaista; Das, Subir K; Puri, Sanjay

2012-03-01

Pattern and dynamics during phase separation in a symmetrical binary (A+B) Lennard-Jones fluid are studied via molecular dynamics simulations after quenching homogeneously mixed critical (50:50) systems to temperatures below the critical one. The morphology of the domains, rich in A or B particles, is observed to be bicontinuous. The early-time growth of the average domain size is found to be consistent with the Lifshitz-Slyozov law for diffusive domain coarsening. After a characteristic time, dependent on the temperature, we find a clear crossover to an extended viscous hydrodynamic regime where the domains grow linearly with time. Pattern formation in the present system is compared with that in solid binary mixtures, as a function of temperature. Important results for the finite-size and temperature effects on the small-wave-vector behavior of the scattering function are also presented.

Modelling and validation of particle size distributions of supported nanoparticles using the pair distribution function technique

DOE PAGES

Gamez-Mendoza, Liliana; Terban, Maxwell W.; Billinge, Simon J. L.; ...

2017-04-13

The particle size of supported catalysts is a key characteristic for determining structure–property relationships. It is a challenge to obtain this information accurately and in situ using crystallographic methods owing to the small size of such particles (<5 nm) and the fact that they are supported. In this work, the pair distribution function (PDF) technique was used to obtain the particle size distribution of supported Pt catalysts as they grow under typical synthesis conditions. The PDF of Pt nanoparticles grown on zeolite X was isolated and refined using two models: a monodisperse spherical model (single particle size) and a lognormalmore » size distribution. The results were compared and validated using scanning transmission electron microscopy (STEM) results. Both models describe the same trends in average particle size with temperature, but the results of the number-weighted lognormal size distributions can also accurately describe the mean size and the width of the size distributions obtained from STEM. Since the PDF yields crystallite sizes, these results suggest that the grown Pt nanoparticles are monocrystalline. As a result, this work shows that refinement of the PDF of small supported monocrystalline nanoparticles can yield accurate mean particle sizes and distributions.« less

Modelling and validation of particle size distributions of supported nanoparticles using the pair distribution function technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gamez-Mendoza, Liliana; Terban, Maxwell W.; Billinge, Simon J. L.

The particle size of supported catalysts is a key characteristic for determining structure–property relationships. It is a challenge to obtain this information accurately and in situ using crystallographic methods owing to the small size of such particles (<5 nm) and the fact that they are supported. In this work, the pair distribution function (PDF) technique was used to obtain the particle size distribution of supported Pt catalysts as they grow under typical synthesis conditions. The PDF of Pt nanoparticles grown on zeolite X was isolated and refined using two models: a monodisperse spherical model (single particle size) and a lognormalmore » size distribution. The results were compared and validated using scanning transmission electron microscopy (STEM) results. Both models describe the same trends in average particle size with temperature, but the results of the number-weighted lognormal size distributions can also accurately describe the mean size and the width of the size distributions obtained from STEM. Since the PDF yields crystallite sizes, these results suggest that the grown Pt nanoparticles are monocrystalline. As a result, this work shows that refinement of the PDF of small supported monocrystalline nanoparticles can yield accurate mean particle sizes and distributions.« less

Electrical performance comparison BSFR-/bifacial solar cell array

NASA Astrophysics Data System (ADS)

Hoffmann, U.; Reissmann, F.

1986-11-01

Conventional and bifacial solar arrays were compared on subsystem level using the Space Telescope-solar array mission as reference. Calculations show that the bifacial solar cell has a performance advantage of 18 to 21 percent. This is due to a 5 C average lower temperature of the bifacial cell at the same orbit conditions; the rearside albedo irradiation of 86 to 170 W/sqm (average of 180 deg and 0 deg orbit orientation respectively); and the fact that the temperature difference between the hot case (satellite between Earth and Sun) and the cold case (before eclipse) is lower for the bifacial cell than for the BSFR cell. This lower difference has the advantage that the operation point for the bifacial cells is closer to maximum voltage point over the orbit. Resistivity of the bifacial solar cells against particle radiation, and absorptivity of front and rearside of the bifacial cell for infrared radiation must be verified. Statistical deviations of the albedo intensity and spectrum are not known.

Voyager observations of O(+6) and other minor ions in the solar wind

NASA Technical Reports Server (NTRS)

Villanueva, Louis; Mcnutt, Ralph L., Jr.; Lazarus, Alan J.; Steinberg, John T.

1994-01-01

The plasma science (PLS) experiments on the Voyager 1 and 2 spacecraft began making measurements of the solar wind shortly after the two launches in the fall of 1977. In reviewing the data obtained prior to the Jupiter encounters in 1979, we have found that the large dynamic range of the PLS instrument generally allows a clean separation of signatures of minor ions (about 2.5% of the time) during a single instrument scan in energy per charge. The minor ions, most notably O(+6), are well separated from the protons and alpha particles during times when the solar wind Mach number (ratio of streaming speed to thermal speed) is greater than approximately 15. During the Earth to Jupiter cruise we find that the average ratio of alpha particle number density to that of oxygen is 66 +/- 7 (Voyager 1) and 71 +/- 17 (Voyager 2). These values are consistent with the value 75 +/- 20 inferred from the Ion Composition Instrument on ISEE 3 during the period spanning 1978 and 1982. We have inferred an average coronal temperature of (1.7 +/- 0.1) x 10(exp 6) K based on the ratio of O(+7) to O(+6) number densities. Our observations cover a period of increasing solar activity. During this time we have found that the alpha particle to proton number density ratio is increasing with the solar cycle, the oxygen to proton ratio increases, and the alpha particle to oxygen ratio remains relatively constant in time.

Facile and green synthesis of highly stable L-cysteine functionalized copper nanoparticles

NASA Astrophysics Data System (ADS)

Kumar, Nikhil; Upadhyay, Lata Sheo Bachan

2016-11-01

A simple eco-friendly method for L-cysteine capped copper nanoparticles (CCNPs) synthesis in aqueous solution has been developed. Glucose and L-cysteine were used as reducing agent and capping/functionalizing agent, respectively. Different parameters such as capping agent concentration, pH, reaction temperature, and reducing agent concentration were optimized during the synthesis. The L-cysteine capped copper nanoparticle were characterized by ultraviolet-visible spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, Particle size and zeta potential analyser, and high resolution transmission electron microscopy. Spherical shaped cysteine functionalized/capped copper nanoparticles with an average size of 40 nm were found to be highly stable at room temperature (RT) for a period of 1 month

Influence of spark plasma sintering parameters on magnetic properties of FeCo alloy

NASA Astrophysics Data System (ADS)

Albaaji, Amar J.; Castle, Elinor G.; Reece, Mike J.; Hall, Jeremy P.; Evans, Sam L.

2018-04-01

Equiatomic FeCo alloys with average particle size of 24 μm were sintered using spark plasma sintering (SPS) system at sintering temperatures of 1100, 800, and 850 °C for heating rates 50, 100, 300 °C/min by applying pressure of 50 MPa instantly at room temperature for sintering time of 5 and 15 minutes. The highest saturation induction was achieved at SPS conditions of 50 MPa, 50 °C/min, 1100 °C, without dwelling, of value 2.39 T. The saturation induction was improved with extending sintering time, the coercivity was higher in samples sintered at a fast heating rate in comparison to the slowest heating rate.

Deformation characteristics and time-dependent notch sensitivity of Udimet 700 at intermediate temperatures

NASA Technical Reports Server (NTRS)

Wilson, D. J.

1974-01-01

Time dependent notch sensitivity was observed in Udimet 700 sheet, bar, and investment castings between 1000 and 1400 F (538 -760 C), but not at 1600 F (871 C). As was the case for modified Waspaloy, Waspaloy and Inconel 718, it occurred in notched specimens loaded below the yield strength when the creep deformation was localized. For each alloy and notched specimen geometry, a stress-average particle size zone can be defined that characterizes the notch sensitive behavior.

Surface-stabilized gold nanocatalysts

DOEpatents

Dai, Sheng [Knoxville, TN; Yan, Wenfu [Oak Ridge, TN

2009-12-08

A surface-stabilized gold nanocatalyst includes a solid support having stabilizing surfaces for supporting gold nanoparticles, and a plurality of gold nanoparticles having an average particle size of less than 8 nm disposed on the stabilizing surfaces. The surface-stabilized gold nanocatalyst provides enhanced stability, such as at high temperature under oxygen containing environments. In one embodiment, the solid support is a multi-layer support comprising at least a first layer having a second layer providing the stabilizing surfaces disposed thereon, the first and second layer being chemically distinct.

Interactions in Micellar Solutions of β-Casein

NASA Astrophysics Data System (ADS)

Leclerc, E.; Calmettes, P.

1997-01-01

β-casein is a flexible amphiphilic milk protein which forms spherical micelles in very dilute solution. The magnitude of the weight-average interactions between the solute particles has been inferred from small-angle neutron scattering experiments. At relatively high protein concentrations the interactions between micelles are repulsive, whatever the temperature. At lower concentration these interactions vanish and become more and more attractive when the critical micelle concentration is approached. Although indispensable for micelle formation, this fact seems to have not been previously reported.

Integration of process diagnostics and three dimensional simulations in thermal spraying

NASA Astrophysics Data System (ADS)

Zhang, Wei

Thermal spraying is a group of processes in which the metallic or ceramic materials are deposited in a molten or semi-molten state on a prepared substrate. In atmospheric plasma spray process, a thermal plasma jet is used to heat up and accelerate loading particles. The process is inherently complex due to the deviation from equilibrium conditions, three dimensional nature, multitude of interrelated variables involved, and stochastic variability at different stages. This dissertation is aimed at understanding the in-flight particle state and plasma plume characteristics in atmospheric plasma spray process through the integration of process diagnostics and three-dimensional simulation. Effects of injection angle and carrier gas flow rate on in-flight particle characteristics are studied experimentally and interpreted through numerical simulation. Plasma jet perturbation by particle injection angle, carrier gas, and particle loading are also identified. Maximum particle average temperature and velocity at any given spray distance is systematically quantified. Optimum plasma plume position for particle injection which was observed in experiments was verified numerically along with description of physical mechanisms. Correlation of spray distance with in-flight particle behavior for various kinds of materials is revealed. A new strategy for visualization and representation of particle diagnostic results for thermal spray processes has been presented. Specifically, 1 st order process maps (process-particle interactions) have been addressed by converting the Temperature-Velocity of particles obtained via diagnostics into non-dimensional group parameters [Melting Index-Reynolds number]. This approach provides an improved description of the thermal and kinetic energy of particles and allows for cross-comparison of diagnostic data within a given process for different materials, comparison of a single material across different thermal spray processes, and detailed assessment of the melting behavior through recourse to analysis of the distributions. An additional group parameter, Oxidation Index, has been applied to relatively track the oxidation extent of metallic particles under different operating conditions. The new mapping strategies have also been proposed in circumstances where only ensemble particle diagnostics are available. Through the integration of process diagnostics and numerical simulation, key issues concerning in-flight particle status as well as the controlling physical mechanisms have been analyzed. A scientific and intellectual strategy for universal description of particle characteristics has been successfully developed.

Synthesis, characterization and magnetic properties of CoxCu1-x (x ∼ 0.01 - 0.3) granular alloys

NASA Astrophysics Data System (ADS)

Dhara, S.; Roy Chowdhury, R.; Lahiri, S.; Ray, P.; Bandyopadhyay, B.

2015-01-01

Nanostructured CoCu granular alloys have been prepared by borohydride reduction of CuCl2 and CoCl2 salt solutions using cetyltrimethylammonium bromide (CTAB) as a surfactant. Characterization by inductively coupled plasma optical emission spectroscopy (ICPOES), X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies yields spherical particles of CoxCu1-x (x ∼ 0.01 - 0.3) of average size 8-25 nm formed in a face-centered-cubic (fcc) lattice as in copper. Studies of zero-field-cooled/field-cooled (ZFC/FC) magnetization and thermoremanent magnetization (TRM) have been performed in the temperature range 4-300 K, and the results have been analyzed by independent particle model. At the lowest cobalt concentration (x ∼ 0.01), the alloy is superparamagnetic and there is no blocking of magnetization down to 4 K. For all other samples, the magnetization at low magnetic field is characterized by a blocking temperature distribution which is not influenced by the Co content in samples. Study of hysteresis loops shows that the magnetization at any temperature 4-300 K is a sum of ferromagnetic (FM), superparamagnetic (SPM) and paramagnetic (PM) contributions. The FM part increases and SPM part decreases with increase in Co content. However, the values of coercivity and magnetic anisotropy constant do not depend on Co content. The results suggest that CoxCu1-x alloys are formed in a spherical core-shell type structure with cobalt being concentrated near the core of particles.

HIGH-TEMPERATURE SAFETY TESTING OF IRRADIATED AGR-1 TRISO FUEL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stempien, John D.; Demkowicz, Paul A.; Reber, Edward L.

High-Temperature Safety Testing of Irradiated AGR-1 TRISO Fuel John D. Stempien, Paul A. Demkowicz, Edward L. Reber, and Cad L. Christensen Idaho National Laboratory, P.O. Box 1625 Idaho Falls, ID 83415, USA Corresponding Author: john.stempien@inl.gov, +1-208-526-8410 Two new safety tests of irradiated tristructural isotropic (TRISO) coated particle fuel have been completed in the Fuel Accident Condition Simulator (FACS) furnace at the Idaho National Laboratory (INL). In the first test, three fuel compacts from the first Advanced Gas Reactor irradiation experiment (AGR-1) were simultaneously heated in the FACS furnace. Prior to safety testing, each compact was irradiated in the Advanced Testmore » Reactor to a burnup of approximately 15 % fissions per initial metal atom (FIMA), a fast fluence of 3×1025 n/m2 (E > 0.18 MeV), and a time-average volume-average (TAVA) irradiation temperature of about 1020 °C. In order to simulate a core-conduction cool-down event, a temperature-versus-time profile having a peak temperature of 1700 °C was programmed into the FACS furnace controllers. Gaseous fission products (i.e., Kr-85) were carried to the Fission Gas Monitoring System (FGMS) by a helium sweep gas and captured in cold traps featuring online gamma counting. By the end of the test, a total of 3.9% of an average particle’s inventory of Kr-85 was detected in the FGMS traps. Such a low Kr-85 activity indicates that no TRISO failures (failure of all three TRISO layers) occurred during the test. If released from the compacts, condensable fission products (e.g., Ag-110m, Cs-134, Cs-137, Eu-154, Eu-155, and Sr-90) were collected on condensation plates fitted to the end of the cold finger in the FACS furnace. These condensation plates were then analyzed for fission products. In the second test, five loose UCO fuel kernels, obtained from deconsolidated particles from an irradiated AGR-1 compact, were heated in the FACS furnace to a peak temperature of 1600 °C. This test had two primary goals. First, the test was intended to assess the retention of fission products in loose kernels without the effects of the other TRISO layers (buffer, IPyC, SiC, and OPyC) or the graphitic matrix material comprising the compact. Second, this test served as an evaluation of the FACS fission product condensation plate collection efficiency.« less

Modeling particle number concentrations along Interstate 10 in El Paso, Texas

PubMed Central

Olvera, Hector A.; Jimenez, Omar; Provencio-Vasquez, Elias

2014-01-01

Annual average daily particle number concentrations around a highway were estimated with an atmospheric dispersion model and a land use regression model. The dispersion model was used to estimate particle concentrations along Interstate 10 at 98 locations within El Paso, Texas. This model employed annual averaged wind speed and annual average daily traffic counts as inputs. A land use regression model with vehicle kilometers traveled as the predictor variable was used to estimate local background concentrations away from the highway to adjust the near-highway concentration estimates. Estimated particle number concentrations ranged between 9.8 × 103 particles/cc and 1.3 × 105 particles/cc, and averaged 2.5 × 104 particles/cc (SE 421.0). Estimates were compared against values measured at seven sites located along I10 throughout the region. The average fractional error was 6% and ranged between -1% and -13% across sites. The largest bias of -13% was observed at a semi-rural site where traffic was lowest. The average bias amongst urban sites was 5%. The accuracy of the estimates depended primarily on the emission factor and the adjustment to local background conditions. An emission factor of 1.63 × 1014 particles/veh-km was based on a value proposed in the literature and adjusted with local measurements. The integration of the two modeling techniques ensured that the particle number concentrations estimates captured the impact of traffic along both the highway and arterial roadways. The performance and economical aspects of the two modeling techniques used in this study shows that producing particle concentration surfaces along major roadways would be feasible in urban regions where traffic and meteorological data are readily available. PMID:25313294

Structural evaluations and temperature dependent photoluminescence characterizations of Eu3+-activated SrZrO3 hollow spheres for luminescence thermometry applications

PubMed Central

Das, Subrata; Som, Sudipta; Yang, Che-Yuan; Chavhan, Sudam; Lu, Chung-Hsin

2016-01-01

This research is focused on the temperature sensing ability of perovskite SrZrO3:Eu3+ hollow spheres synthesized via the sol-gel method followed by heating. The Rietveld refinement indicated that the precursors annealed at 1100 °C were crystallized to form orthorhombic SrZrO3. SrZrO3 particles exhibited non-agglomerated hollow spherical morphology with an average particle size of 300 nm. The UV-excited photoluminescence spectrum of SrZrO3:Eu3+ consisted of two regions. One region was associated with SrZrO3 trap emission, and the other one was related to the emission of Eu3+ ions. The intensity ratio of the emission of Eu3+ ions to the host emission (FIR) and the emission lifetime of Eu3+ ions were measured in the temperature range of 300–550 K. The sensitivity obtained via the lifetime method was 7.3× lower than that measured via the FIR. Within the optimum temperature range of 300–460 K, the as-estimated sensor sensitivity was increased from 0.0013 to 0.028 K−1. With a further increase in temperatures, the sensitivity started to decline. A maximum relative sensitivity was estimated to be 2.22%K−1 at 460 K. The resolutions in both methods were below 1K in the above temperature range. The results indicated the suitability of SrZrO3:Eu3+ for the distinct high temperature sensing applications. PMID:27189117

Saturn's icy satellites investigated by Cassini-VIMS. IV. Daytime temperature maps

NASA Astrophysics Data System (ADS)

Filacchione, Gianrico; D'Aversa, Emiliano; Capaccioni, Fabrizio; Clark, Roger N.; Cruikshank, Dale P.; Ciarniello, Mauro; Cerroni, Priscilla; Bellucci, Giancarlo; Brown, Robert H.; Buratti, Bonnie J.; Nicholson, Phillip D.; Jaumann, Ralf; McCord, Thomas B.; Sotin, Christophe; Stephan, Katrin; Dalle Ore, Cristina M.

2016-06-01

The spectral position of the 3.6 μm continuum peak measured on Cassini-VIMS I/F spectra is used as a marker to infer the temperature of the regolith particles covering the surfaces of Saturn's icy satellites. This feature is characterizing the crystalline water ice spectrum which is the dominant compositional endmember of the satellites' surfaces. Laboratory measurements indicate that the position of the 3.6 μm peak of pure water ice is temperature-dependent, shifting towards shorter wavelengths when the sample is cooled, from about 3.65 μm at T=123 K to about 3.55 μm at T=88 K. A similar method was already applied to VIMS Saturn's rings mosaics to retrieve ring particles temperature (Filacchione, G., Ciarniello, M., Capaccioni, F., et al., 2014. Icarus, 241, 45-65). We report here about the daytime temperature variations observed on the icy satellites as derived from three different VIMS observation types: (a) a sample of 240 disk-integrated I/F observations of Saturn's regular satellites collected by VIMS during years 2004-2011 with solar phase in the 20°-40° range, corresponding to late morning-early afternoon local times. This dataset is suitable to exploit the temperature variations at hemispherical scale, resulting in average temperature T <88 K for Mimas, T ≪88 K for Enceladus, T <88 K for Tethys, T=98-118 K for Dione, T=108-128 K for Rhea, T=118-128 K for Hyperion, T=128-148 and T > 168 K for Iapetus' trailing and leading hemispheres, respectively. A typical ±5 K uncertainty is associated to the temperature retrieval. On Tethys and Dione, for which observations on both leading and trailing hemispheres are available, in average daytime temperatures higher of about 10 K on the trailing than on the leading hemisphere are inferred. (b) Satellites disk-resolved observations taken at 20-40 km pixel-1 resolution are suitable to map daytime temperature variations across surfaces' features, such as Enceladus' tiger stripes and Tethys' equatorial dark lens. These datasets allow to disentangle solar illumination conditions from temperature distribution when observing surface's features with strong thermal contrast. (c) Daytime average maps covering large regions of the surfaces are used to compare the inferred temperature with geomorphological features (impact craters, chasmatae, equatorial radiation lenses and active areas) and albedo variations. Temperature maps are built by mining the complete VIMS dataset collected in years 2004-2009 (pre-equinox) and in 2009-2012 (post equinox) by selecting pixels with max 150 km pixel-1 resolution. VIMS-derived temperature maps allow to identify thermal anomalies across the equatorial lens of Mimas and Tethys. A temperature T > 115K is measured above Enceladus' Damascus and Alexandria sulci in the south pole region. VIMS has the sensitivity to follow seasonal temperature changes: on Tethys, Dione and Rhea higher temperature are measured above the south hemisphere during pre-equinox and above the north hemisphere during post-equinox epochs. The measured temperature distribution appears correlated with surface albedo features: in fact temperature increases on low albedo units located on Tethys, Dione and Rhea trailing hemispheres. The thermal anomaly region on Rhea's Inktomi crater detected by CIRS (Howett, C. J. A., Spencer, J. R., Hurford, T., et al., 2014. Icarus, 241, 239-247) is confirmed by VIMS: this area appears colder with respect to surrounding terrains when observed at the same local solar time.

Robust estimation of event-related potentials via particle filter.

PubMed

Fukami, Tadanori; Watanabe, Jun; Ishikawa, Fumito

2016-03-01

In clinical examinations and brain-computer interface (BCI) research, a short electroencephalogram (EEG) measurement time is ideal. The use of event-related potentials (ERPs) relies on both estimation accuracy and processing time. We tested a particle filter that uses a large number of particles to construct a probability distribution. We constructed a simple model for recording EEG comprising three components: ERPs approximated via a trend model, background waves constructed via an autoregressive model, and noise. We evaluated the performance of the particle filter based on mean squared error (MSE), P300 peak amplitude, and latency. We then compared our filter with the Kalman filter and a conventional simple averaging method. To confirm the efficacy of the filter, we used it to estimate ERP elicited by a P300 BCI speller. A 400-particle filter produced the best MSE. We found that the merit of the filter increased when the original waveform already had a low signal-to-noise ratio (SNR) (i.e., the power ratio between ERP and background EEG). We calculated the amount of averaging necessary after applying a particle filter that produced a result equivalent to that associated with conventional averaging, and determined that the particle filter yielded a maximum 42.8% reduction in measurement time. The particle filter performed better than both the Kalman filter and conventional averaging for a low SNR in terms of both MSE and P300 peak amplitude and latency. For EEG data produced by the P300 speller, we were able to use our filter to obtain ERP waveforms that were stable compared with averages produced by a conventional averaging method, irrespective of the amount of averaging. We confirmed that particle filters are efficacious in reducing the measurement time required during simulations with a low SNR. Additionally, particle filters can perform robust ERP estimation for EEG data produced via a P300 speller. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

ZnO/TiO2 nanocomposite rods synthesized by microwave-assisted method for humidity sensor application

NASA Astrophysics Data System (ADS)

Ashok, CH.; Venkateswara Rao, K.

2014-12-01

The nanocomposite rods shows well known properties compared with nano structured materials for various applications like light-emitting diodes, electron field emitters, solar cells, optoelectronics, sensors, transparent conductors and fabrication of nano devices. Present paper investigates the properties of ZnO/TiO2 nanocomposite rods. The bi component of ZnO/TiO2 nanocomposite rods was synthesized by microwave-assisted method which is very simple, rapid and uniform in heating. The frequency of microwaves 2.45 GHz was used and temperature maintained 180 °C. Zinc acetate and titanium isopropoxide precursors were used in the preparation. The obtained ZnO/TiO2 nanocomposite rods were annealed at 500 °C and 600 °C. ZnO/TiO2 nanocomposite rods have been characterized by X-ray Diffraction (XRD) for average crystallite size and phase of the composite material, Particle Size Analyser (PSA) for average particle size, Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) for morphology study, Energy Dispersive X-ray Spectrometry (EDX) for elemental analysis, and Thermal Gravimetric and Differential Thermal Analysis (TG-DTA) for thermal property.

Fast synthesis and consolidation of porous FeAl by pressureless Spark Plasma Sintering

NASA Astrophysics Data System (ADS)

Dudina, D. V.; Brester, A. E.; Anisimov, A. G.; Bokhonov, B. B.; Legan, M. A.; Novoselov, A. N.; Skovorodin, I. N.; Uvarov, N. F.

2017-07-01

We report one-step fast synthesis and consolidation of iron aluminide FeAl of high open porosity by pressureless reactive Spark Plasma Sintering (SPS). The starting material of the Fe-40at.%Al composition was a mixture of an iron powder with an average particle diameter of 4 μm and an aluminum powder with an average particle diameter of 6 μm. The rationale behind the choice of the SPS as a processing technique and fine and comparable sizes of the two reactants for the synthesis of high-open porosity FeAl was realization of fast full chemical conversion of Fe and Al into single-phase FeAl reducing the time available for the compact shrinkage. According to the XRD phase analysis, single-phase FeAl compacts formed after SPS at 800 and 900°C. These compacts had open porosities of 41 and 46%, respectively. The transverse rupture strength of the compacts sintered at 700-900°C was found to change little with the sintering temperature in the selected range.

Uncertainty in particle number modal analysis during transient operation of compressed natural gas, diesel, and trap-equipped diesel transit buses.

PubMed

Holmén, Britt A; Qu, Yingge

2004-04-15

The relationships between transient vehicle operation and ultrafine particle emissions are not well-known, especially for low-emission alternative bus technologies such as compressed natural gas (CNG) and diesel buses equipped with particulate filters/traps (TRAP). In this study, real-time particle number concentrations measured on a nominal 5 s average basis using an electrical low pressure impactor (ELPI) for these two bus technologies are compared to that of a baseline catalyst-equipped diesel bus operated on ultralow sulfur fuel (BASE) using dynamometer testing. Particle emissions were consistently 2 orders of magnitude lower for the CNG and TRAP compared to BASE on all driving cycles. Time-resolved total particle numbers were examined in terms of sampling factors identified as affecting the ability of ELPI to quantify the particulate matter number emissions for low-emitting vehicles such as CNG and TRAP as a function of vehicle driving mode. Key factors were instrument sensitivity and dilution ratio, alignment of particle and vehicle operating data, sampling train background particles, and cycle-to-cycle variability due to vehicle, engine, after-treatment, or driver behavior. In-cycle variability on the central business district (CBD) cycle was highest for the TRAP configuration, but this could not be attributed to the ELPI sensitivity issues observed for TRAP-IDLE measurements. Elevated TRAP emissions coincided with low exhaust temperature, suggesting on-road real-world particulate filter performance can be evaluated by monitoring exhaust temperature. Nonunique particle emission maps indicate that measures other than vehicle speed and acceleration are necessary to model disaggregated real-time particle emissions. Further testing on a wide variety of test cycles is needed to evaluate the relative importance of the time history of vehicle operation and the hysteresis of the sampling train/dilution tunnel on ultrafine particle emissions. Future studies should monitor particle emissions with high-resolution real-time instruments and account for the operating regime of the vehicle using time-series analysis to develop predictive number emissions models.

Positive matrix factorization of PM2.5 - eliminating the effects of gas/particle partitioning of semivolatile organic compounds.

PubMed

Xie, M; Barsanti, K C; Hannigan, M P; Dutton, S J; Vedal, S

2013-01-01

Gas-phase concentrations of semi-volatile organic compounds (SVOCs) were calculated from gas/particle (G/P) partitioning theory using their measured particle-phase concentrations. The particle-phase data were obtained from an existing filter measurement campaign (27 January 2003-2 October 2005) as a part of the Denver Aerosol Sources and Health (DASH) study, including 970 observations of 71 SVOCs (Xie et al., 2013). In each compound class of SVOCs, the lighter species (e.g. docosane in n alkanes, fluoranthene in PAHs) had higher total concentrations (gas + particle phase) and lower particle-phase fractions. The total SVOC concentrations were analyzed using positive matrix factorization (PMF). Then the results were compared with source apportionment results where only particle-phase SVOC concentrations were used (particle only-based study; Xie et al., 2013). For the particle only-based PMF analysis, the factors primarily associated with primary or secondary sources ( n alkane, EC/sterane and inorganic ion factors) exhibit similar contribution time series ( r = 0.92-0.98) with their corresponding factors ( n alkane, sterane and nitrate+sulfate factors) in the current work. Three other factors (light n alkane/PAH, PAH and summer/odd n alkane factors) are linked with pollution sources influenced by atmospheric processes (e.g. G/P partitioning, photochemical reaction), and were less correlated ( r = 0.69-0.84) with their corresponding factors (light SVOC, PAH and bulk carbon factors) in the current work, suggesting that the source apportionment results derived from particle-only SVOC data could be affected by atmospheric processes. PMF analysis was also performed on three temperature-stratified subsets of the total SVOC data, representing ambient sampling during cold (daily average temperature < 10 °C), warm (≥ 10 °C and ≤ 20 °C) and hot (> 20 °C) periods. Unlike the particle only-based study, in this work the factor characterized by the low molecular weight (MW) compounds (light SVOC factor) exhibited strong correlations ( r = 0.82-0.98) between the full data set and each sub-data set solution, indicating that the impacts of G/P partitioning on receptor-based source apportionment could be eliminated by using total SVOC concentrations.

Effects of filtration temperature, humic acid level and alum dose on cryptosporidium sized particle breakthrough.

PubMed

Xu, G R; Fitzpatrick, C S B; Deng, L Y

2006-01-01

Recent Cryptosporidium outbreaks have highlighted concerns about filter efficiency and especially particle breakthrough. Understanding the causes of breakthrough is essential, as the parasite cannot be destroyed by conventional disinfection with chlorine. Particle breakthrough depends on many factors. This research aims to investigate the influence of temperature, humic acid (HA) level and chemical dosing on particle breakthrough in filtration. A series of temperatures were set at 5 degrees C, 15 degrees C and 25 degrees C; humic acid level was 5 mg L(-1). Each was combined with a series of Al doses. A laser particle counter was used to assess the particle breakthrough online. Turbidity, zeta potential, and UV254 absorption were measured before and after filtration. The results showed that particle breakthrough was influenced significantly by temperature, humic acid and dosing. Particle breakthrough occurred earlier at lower temperature, while at higher temperature it was reduced at the same coagulant dose. With coagulants, even at low dose, particle breakthrough was significantly reduced. With HA 5 mg L(-1), particle breakthrough was earlier and the amount was much larger than without HA even at high temperature. There was an optimal dose in filtration and it was well correlated with zeta potential.

Relationship between neighbor number and vibrational spectra in disordered colloidal clusters with attractive interactions

NASA Astrophysics Data System (ADS)

Yunker, Peter J.; Zhang, Zexin; Gratale, Matthew; Chen, Ke; Yodh, A. G.

2013-03-01

We study connections between vibrational spectra and average nearest neighbor number in disordered clusters of colloidal particles with attractive interactions. Measurements of displacement covariances between particles in each cluster permit calculation of the stiffness matrix, which contains effective spring constants linking pairs of particles. From the cluster stiffness matrix, we derive vibrational properties of corresponding "shadow" glassy clusters, with the same geometric configuration and interactions as the "source" cluster but without damping. Here, we investigate the stiffness matrix to elucidate the origin of the correlations between the median frequency of cluster vibrational modes and average number of nearest neighbors in the cluster. We find that the mean confining stiffness of particles in a cluster, i.e., the ensemble-averaged sum of nearest neighbor spring constants, correlates strongly with average nearest neighbor number, and even more strongly with median frequency. Further, we find that the average oscillation frequency of an individual particle is set by the total stiffness of its nearest neighbor bonds; this average frequency increases as the square root of the nearest neighbor bond stiffness, in a manner similar to the simple harmonic oscillator.

Optimal size for heating efficiency of superparamagnetic dextran-coated magnetite nanoparticles for application in magnetic fluid hyperthermia

NASA Astrophysics Data System (ADS)

Shaterabadi, Zhila; Nabiyouni, Gholamreza; Soleymani, Meysam

2018-06-01

Dextran-coated magnetite (Fe3O4) nanoparticles with average particle sizes of 4 and 19 nm were synthesized through in situ and semi-two-step co-precipitation methods, respectively. The experimental results confirm the formation of pure phase of magnetite as well as the presence of dextran layer on the surface of modified magnetite nanoparticles. The results also reveal that both samples have the superparamagnetic behavior. Furthermore, calorimetric measurements show that the dextran-coated Fe3O4 nanoparticles with an average size of 4 nm cannot produce any appreciable heat under a biologically safe alternating magnetic field used in hyperthermia therapy; whereas, the larger ones (average size of 19 nm) are able to increase the temperature of their surrounding medium up to above therapeutic range. In addition, measured specific absorption rate (SAR) values confirm that magnetite nanoparticles with an average size of 19 nm are very excellent candidates for application in magnetic hyperthermia therapy.

Understanding the effects of process parameters on the properties of cold gas dynamic sprayed pure titanium coatings

NASA Astrophysics Data System (ADS)

Wong, Wilson

The cold gas dynamic spraying of commercially pure titanium coatings was investigated. Specifically, the relationship between several key cold spray parameters on the quality of the resulting coatings was studied in order to gain a more thorough understanding of the cold spray process. To achieve this goal, three distinct investigations were performed. The first part of the investigation focussed on the effect of propelling gas, particularly helium and nitrogen, during the cold spraying of titanium coatings. Coatings were characterised by SEM and were evaluated for their deposition efficiency (DE), microhardness, and porosity. In selected conditions, three particle velocities were investigated such that for each condition, the propelling gasses temperature and pressure were attuned to attain similar particle velocities for each gas. In addition, a thick and fully dense cold sprayed titanium coating was achieved with optimised spray parameters and nozzle using helium. The corresponding average particle velocity was 1173 m/s. The second part of the investigation studied the effect of particle morphology (spherical, sponge, and irregular) and size distributions (mean particle sizes of 20, 29, and 36 mum) of commercially pure titanium on the mechanical properties of the resulting cold sprayed coatings. Numerous powder and coating characterisations were performed. From these data, semi-empirical flow (stress-strain) curves were generated based on the Johnson-Cook plasticity model which could be used as a measure of cold sprayability. Cold sprayability can be defined as the ease with which a powder can be cold sprayed. It was found that the sponge and irregular commercially pure titanium powders had higher oxygen content, poorer powder flowability, higher compression ratio, lower powder packing factor, and higher average particle impact velocities compared to the spherical powders. XRD results showed no new phases present when comparing the various feedstock powders to their corresponding coatings. For all feedstock powder morphologies, it was observed that the larger the particle size, the higher the temperature generated on impact. For the spherical powders, the higher the temperature generated on impact, the lower the stress needed to deform the particle. In addition, as the kinetic energy of the impacting particle increased, the flow peak stress decreased while the final strain increased. Furthermore, higher final flow strains were associated with higher coating DeltaHV 10 (between the coatings and the feedstock powders). Similar relationships are expected to exist for the sponge and irregular feedstock powders. Based on porosity, the spherical medium powder was found to have the best cold sprayability. The final part of the investigation focussed on the effect of substrate surface roughness and coating thickness on the adhesion strength of commercially pure titanium cold sprayed coatings onto Steel 1020, Al 6061, and Ti substrates. Adhesion strength was measured by tensile/pull tests according to ASTM C-633-01 standard. Through-thickness residual stresses of selected coatings were measured using the modified layer removal method (MLRM). In addition, mean coating residual stresses were calculated from MLRM results. It was found that adhesion strength increases with increasing substrate surface roughness and decreases with increasing coating thickness. Furthermore, mean coating residual stresses were correlated with adhesion strength and it was suggested that higher adhesion strengths are associated with higher mean compressive stresses and a higher probability for adiabatic shear instability to occur due to the higher particle impact velocities. In general, it was found that under similar cold spray conditions and substrate surface preparation method, adhesion strength was strongest for commercially pure titanium coatings deposited onto Al 6061, followed by Ti, then Steel 1020.

Deuterium-tritium experiments on the Tokamak Fusion Test reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hosea, J.; Adler, J.H.; Alling, P.

The deuterium-tritium (D-T) experimental program on the Tokamak Fusion Test Reactor (TFTR) is underway and routine tritium operations have been established. The technology upgrades made to the TFTR facility have been demonstrated to be sufficient for supporting both operations and maintenance for an extended D-T campaign. To date fusion power has been increased to {approx}9 MW and several physics results of importance to the D-T reactor regime have been obtained: electron temperature, ion temperature, and plasma stored energy all increase substantially in the D-T regime relative to the D-D regime at the same neutral beam power and comparable limiter conditioning;more » possible alpha electron heating is indicated and energy confinement improvement with average ion mass is observed; and alpha particle losses appear to be classical with no evidence of TAE mode activity up to the PFUS {approx}6 MW level. Instability in the TAE mode frequency range has been observed at PFUS > 7 MW and its effect on performance in under investigation. Preparations are underway to enhance the alpha particle density further by increasing fusion power and by extending the neutral beam pulse length to permit alpha particle effects of relevance to the ITER regime to be more fully explored.« less

Power-law partition and entropy production of high-energy cosmic rays: Knee-ankle structure of the all-particle spectrum

NASA Astrophysics Data System (ADS)

Tomaschitz, Roman

2013-10-01

A statistical description of the all-particle cosmic-ray spectrum is given in the 10^{14}\\ \\text{eV} to 10^{20}\\ \\text{eV} interval. The high-energy cosmic-ray flux is modeled as an ultra-relativistic multi-component plasma, whose components constitute a mixture of nearly ideal but nonthermal gases of low density and high temperature. Each plasma component is described by an ultra-relativistic power-law density manifested as spectral peak in the wideband fit. The “knee” and “ankle” features of the high- and ultra-high-energy spectrum turn out to be the global and local extrema of the double-logarithmic E3-scaled flux representation in which the spectral fit is performed. The all-particle spectrum is covered by recent data sets from several air shower arrays, and can be modeled as three-component plasma in the indicated energy range extending over six decades. The temperature, specific number density, internal energy and entropy of each plasma component are extracted from the partial fluxes in the broadband fit. The grand partition function and the extensive entropy functional of a non-equilibrated gas mixture with power-law components are derived in phase space by ensemble averaging.

Synthesis of nano-sized ZnO particles by co-precipitation method with variation of heating time

DOE Office of Scientific and Technical Information (OSTI.GOV)

Purwaningsih, S. Y., E-mail: sriyanisaputri@gmail.com; Pratapa, S.; Triwikantoro

Zinc oxide powders have been synthesized by a co-precipitation method at low temperature (85 °C), using zinc acetate dihydrate, ammonia, hydrochloric acid solutions as the reactants. A number of process parameters such as reaction temperature, solution basicity or pH and heating time are the main factors affecting the morphology and physical properties of the ZnO nanostructures. In this work the effect of heating time on the morphology and particles size were studied. The as-synthesized ZnO powders were characterized using transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques. The samples were also analyzed using Fourier transform infrared (FTIR). Rietveld refinementmore » of XRD data confirms that ZnO crystallizes in the hexagonal wurtzite structure with high degree of purity and the (101) plane predominant. The XRD results show that the average crystallite sizes were about 66, 27 and 12 nm for 3, 4 and 5 h of heating times, respectively. The XRD analysis indicated that a fraction of nano-sized ZnO powders were in the form of aggregates, which was also verified by TEM image. The TEM photograph demonstrated that the nano-sized ZnO particles were a pseudo-spherical shape.« less

A Comparison of Two Methods for Initiating Air Mass Back Trajectories

NASA Astrophysics Data System (ADS)

Putman, A.; Posmentier, E. S.; Faiia, A. M.; Sonder, L. J.; Feng, X.

2014-12-01

Lagrangian air mass tracking programs in back cast mode are a powerful tool for estimating the water vapor source of precipitation events. The altitudes above the precipitation site where particle's back trajectories begin influences the source estimation. We assume that precipitation comes from water vapor in condensing regions of the air column, so particles are placed in proportion to an estimated condensation profile. We compare two methods for estimating where condensation occurs and the resulting evaporation sites for 63 events at Barrow, AK. The first method (M1) uses measurements from a 35 GHz vertically resolved cloud radar (MMCR), and algorithms developed by Zhao and Garrett1 to calculate precipitation rate. The second method (M2) uses the Global Data Assimilation System reanalysis data in a lofting model. We assess how accurately M2, developed for global coverage, will perform in absence of direct cloud observations. Results from the two methods are statistically similar. The mean particle height estimated by M2 is, on average, 695 m (s.d. = 1800 m) higher than M1. The corresponding average vapor source estimated by M2 is 1.5⁰ (s.d. = 5.4⁰) south of M1. In addition, vapor sources for M2 relative to M1 have ocean surface temperatures averaging 1.1⁰C (s.d. = 3.5⁰C) warmer, and reported ocean surface relative humidities 0.31% (s.d. = 6.1%) drier. All biases except the latter are statistically significant (p = 0.02 for each). Results were skewed by events where M2 estimated very high altitudes of condensation. When M2 produced an average particle height less than 5000 m (89% of events), M2 estimated mean particle heights 76 m (s.d. = 741 m) higher than M1, corresponding to a vapor source 0.54⁰ (s.d. = 4.2⁰) south of M1. The ocean surface at the vapor source was an average of 0.35⁰C (s.d. = 2.35⁰C) warmer and ocean surface relative humidities were 0.02% (s.d. = 5.5%) wetter. None of the biases was statistically significant. If the vapor source meteorology estimated by M2 is used to determine vapor isotopic properties it would produce results similar to M1 in all cases except the occasional very high cloud. The methods strive to balance a sufficient number of tracked air masses for meaningful vapor source estimation with minimal computational time. Zhao, C and Garrett, T.J. 2008, J. Geophys. Res.

Substantial large-scale feedbacks between natural aerosols and climate

NASA Astrophysics Data System (ADS)

Scott, C. E.; Arnold, S. R.; Monks, S. A.; Asmi, A.; Paasonen, P.; Spracklen, D. V.

2018-01-01

The terrestrial biosphere is an important source of natural aerosol. Natural aerosol sources alter climate, but are also strongly controlled by climate, leading to the potential for natural aerosol-climate feedbacks. Here we use a global aerosol model to make an assessment of terrestrial natural aerosol-climate feedbacks, constrained by observations of aerosol number. We find that warmer-than-average temperatures are associated with higher-than-average number concentrations of large (>100 nm diameter) particles, particularly during the summer. This relationship is well reproduced by the model and is driven by both meteorological variability and variability in natural aerosol from biogenic and landscape fire sources. We find that the calculated extratropical annual mean aerosol radiative effect (both direct and indirect) is negatively related to the observed global temperature anomaly, and is driven by a positive relationship between temperature and the emission of natural aerosol. The extratropical aerosol-climate feedback is estimated to be -0.14 W m-2 K-1 for landscape fire aerosol, greater than the -0.03 W m-2 K-1 estimated for biogenic secondary organic aerosol. These feedbacks are comparable in magnitude to other biogeochemical feedbacks, highlighting the need for natural aerosol feedbacks to be included in climate simulations.

Effects of types of ventilation system on indoor particle concentrations in residential buildings.

PubMed

Park, J S; Jee, N-Y; Jeong, J-W

2014-12-01

The objective of this study was to quantify the influence of ventilation systems on indoor particle concentrations in residential buildings. Fifteen occupied, single-family apartments were selected from three sites. The three sites have three different ventilation systems: unbalanced mechanical ventilation, balanced mechanical ventilation, and natural ventilation. Field measurements were conducted between April and June 2012, when outdoor air temperatures were comfortable. Number concentrations of particles, PM2.5 and CO2 , were continuously measured both outdoors and indoors. In the apartments with natural ventilation, I/O ratios of particle number concentrations ranged from 0.56 to 0.72 for submicron particles, and from 0.25 to 0.60 for particles larger than 1.0 μm. The daily average indoor particle concentration decreased to 50% below the outdoor level for submicron particles and 25% below the outdoor level for fine particles, when the apartments were mechanically ventilated. The two mechanical ventilation systems reduced the I/O ratios by 26% for submicron particles and 65% for fine particles compared with the natural ventilation. These results showed that mechanical ventilation can reduce exposure to outdoor particles in residential buildings. Results of this study confirm that mechanical ventilation with filtration can significantly reduce indoor particle levels compared with natural ventilation. The I/O ratios of particles substantially varied at the naturally ventilated apartments because of the influence of variable window opening conditions and unsteadiness of wind flow on the penetration of outdoor air particles. For better prediction of the exposure to outdoor particles in naturally ventilated residential buildings, it is important to understand the penetration of outdoor particles with variable window opening conditions. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Thermodynamics of phase-separating nanoalloys: Single particles and particle assemblies

NASA Astrophysics Data System (ADS)

Fèvre, Mathieu; Le Bouar, Yann; Finel, Alphonse

2018-05-01

The aim of this paper is to investigate the consequences of finite-size effects on the thermodynamics of nanoparticle assemblies and isolated particles. We consider a binary phase-separating alloy with a negligible atomic size mismatch, and equilibrium states are computed using off-lattice Monte Carlo simulations in several thermodynamic ensembles. First, a semi-grand-canonical ensemble is used to describe infinite assemblies of particles with the same size. When decreasing the particle size, we obtain a significant decrease of the solid/liquid transition temperatures as well as a growing asymmetry of the solid-state miscibility gap related to surface segregation effects. Second, a canonical ensemble is used to analyze the thermodynamic equilibrium of finite monodisperse particle assemblies. Using a general thermodynamic formulation, we show that a particle assembly may split into two subassemblies of identical particles. Moreover, if the overall average canonical concentration belongs to a discrete spectrum, the subassembly concentrations are equal to the semi-grand-canonical equilibrium ones. We also show that the equilibrium of a particle assembly with a prescribed size distribution combines a size effect and the fact that a given particle size assembly can adopt two configurations. Finally, we have considered the thermodynamics of an isolated particle to analyze whether a phase separation can be defined within a particle. When studying rather large nanoparticles, we found that the region in which a two-phase domain can be identified inside a particle is well below the bulk phase diagram, but the concentration of the homogeneous core remains very close to the bulk solubility limit.

Numerical analysis of temperature field improvement with nanoparticles designed to achieve critical power dissipation in magnetic hyperthermia

NASA Astrophysics Data System (ADS)

Tang, Yundong; Flesch, Rodolfo C. C.; Jin, Tao

2017-07-01

Magnetic nanoparticle (MNP) hyperthermia is a promising emerging therapy for cancer treatment that is minimally invasive and has been successfully used to treat different types of tumors. The power dissipation of MNPs, which is one of the most important factors during a hyperthermia treatment, is determined by the properties of MNPs and characteristics of the magnetic field. This paper proposes a method based on the finite element analysis for determining the value of the power dissipation of particles (PDP) that can maximize the average temperature of the tumor during treatment and at the same time guarantee that the maximum temperature is within the therapeutic range. The application of the critical PDP value can improve the effectiveness of the treatment since it increases the average temperature in the tumor region while limiting the damage to the healthy tissue that surrounds it. After the critical PDP is determined for a specific model, it is shown how the properties of the MNPs can be chosen to achieve the desired PDP value. The transient behavior of the temperature distribution for two different models considering blood vessels is analyzed as a case study, showing that the presence of a blood vessel inside the tumor region can significantly decrease the uniformity of the temperature field and also increase the treatment duration given its cooling effects. To present a solution that does not depend upon a good model of the tumor region, an alternative method that uses MNPs with low Curie temperature is proposed, given the temperature self-regulating properties of such MNPs. The results demonstrate that the uniformity of the temperature field can be significantly increased by combining the optimization procedure proposed in this paper with the use of low-Curie-temperature MNPs.

The thermal structure of Titan’s upper atmosphere, I: Temperature profiles from Cassini INMS observations

NASA Astrophysics Data System (ADS)

Snowden, D.; Yelle, R. V.; Cui, J.; Wahlund, J.-E.; Edberg, N. J. T.; Ågren, K.

2013-09-01

We derive vertical temperature profiles from Ion Neutral Mass Spectrometer (INMS) N2 density measurements from 32 Cassini passes. We find that the average temperature of Titan’s thermosphere varies significantly from pass-to-pass between 112 and 175 K. The temperatures from individual temperature profiles also varies considerably, with many passes exhibiting wave-like temperature perturbations and large temperature gradients. Wave-like temperature perturbations have wavelengths between 150 and 420 km and amplitudes between 3% and 22% and vertical wave power spectra of the INMS data and HASI data have a slope between -2 and -3, which is consistent with vertically propagating atmospheric waves. The lack of a strong correlation between temperature and latitude, longitude, solar zenith angle, or local solar time indicates that the thermal structure of Titan’s thermosphere is not primarily determined by the absorption of solar EUV flux. At N2 densities greater than 108 cm-3, Titan’s thermosphere is colder when Titan is observed in Saturn’s magnetospheric lobes compared to Saturn’s plasma sheet as proposed by Westlake et al. (Westlake, J.H. et al. [2011]. J. Geophys. Res. 116, A03318. http://dx.doi.org/10.1029/2010JA016251). This apparent correlation suggests that magnetospheric particle precipitation causes the temperature variability in Titan’s thermosphere; however, at densities smaller than 108 cm-3 the lobe passes are hotter than the plasma sheet passes and we find no correlation between the temperature of Titan’s thermosphere and ionospheric signatures of enhanced particle precipitation, which suggests that the correlation is not indicative of a physical connection. The temperature of Titan’s thermosphere also may have decreased by ∼10 K around mid-2007. Finally, we classify the vertical temperature profiles to show which passes are hot and cold and which passes have the largest temperature variations. In a companion paper (Part II), we estimate the strength of energy sources and sinks in Titan’s thermosphere.

Temperature dependent barrier height and ideality factor of electrodeposited n-CdSe/Cu Schottky barrier diode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mahato, S., E-mail: som.phy.ism@gmail.com; Shiwakoti, N.; Kar, A. K.

2015-06-24

This article reports the measurement of temperature-dependent barrier height and ideality factor of n-CdSe/Cu Schottky barrier diode. The Cadmium Selenide (CdSe) thin films have been deposited by simple electrodeposition technique. The XRD measurements ravels the deposited single phase CdSe films are highly oriented on (002) plane and the average particle size has been calculated to be ~18 nm. From SEM characterization, it is clear that the surface of CdSe thin films are continuous, homogeneous and the film is well adhered to the substrate and consists of fine grains which are irregular in shape and size. Current-Voltage characteristics have been measured atmore » different temperatures in the range (298 K – 353 K). The barrier height and ideality factor are found to be strongly temperature dependent. The inhomogenious barrier height increases and ideality factor decreases with increase in temperature. The expectation value has been calculated and its value is 0.30 eV.« less

Photothermal heating as a methodology for post processing of polymeric nanofibers

NASA Astrophysics Data System (ADS)

Gorga, Russell; Clarke, Laura; Bochinski, Jason; Viswanath, Vidya; Maity, Somsubhra; Dong, Ju; Firestone, Gabriel

2015-03-01

Metal nanoparticles embedded within polymeric systems can be made to act as localized heat sources thereby aiding in-situ polymer processing. This is made possible by the surface plasmon resonance (SPR) mediated photothermal effect of metal (in this case gold) nanoparticles, wherein incident light absorbed by the nanoparticle generates a non-equilibrium electron distribution which subsequently transfers this energy into the surrounding medium, resulting in a temperature increase in the immediate region around the particle. Here we demonstrate this effect in polymer nanocomposite systems, specifically electrospun polyethylene oxide nanofibrous mats, which have been annealed at temperatures above the glass transition. A non-contact temperature measurement technique utilizing embedded fluorophores (perylene) has been used to monitor the average temperature within samples. The effect of annealing methods (conventional and photothermal) and annealing conditions (temperature and time) on the fiber morphology, overall crystallinity, and mechanical properties is discussed. This methodology is further utilized in core-sheath nanofibers to crosslink the core material, which is a pre-cured epoxy thermoset. NSF Grant CMMI-1069108.

Research for Brazing Materials of High-Temperature Thermoelectric Modules with CoSb3 Thermoelectric Materials

NASA Astrophysics Data System (ADS)

Lee, Yu Seong; Kim, Suk Jun; Kim, Byeong Geun; Lee, Soonil; Seo, Won-Seon; Kim, Il-Ho; Choi, Soon-Mok

2017-05-01

Metallic glass (MG) can be a candidate for an alternative brazing material of high-temperature thermoelectric modules, since we can expect both a lower brazing temperature and a high operating temperature for the junction from the MG brazers. Another advantage of MG powders is their outstanding oxidation resistance, namely, high-temperature durability in atmosphere. We fabricated three compositions of Al-based MGs—Al-Y-Ni, Al-Y-Ni-Co, and Al-Y-Ni-Co-La—by using the melt spinning process, and their T gs were 273°C, 264°C, and 249°C, respectively. The electrical resistivity of the Al-Y-Ni MG ribbon dropped significantly after annealing at 300°C. The electrical resistivity of crystallized Al-Y-Ni reduced down to 0.03 mΩ cm, which is an order of magnitude lower than that of the amorphous one. After the MG ribbons were pulverized to sub-100 μm, the average particle size was about 400 μm.

Soft-Bake Purification of SWCNTs Produced by Pulsed Laser Vaporization

NASA Technical Reports Server (NTRS)

Yowell, Leonard; Nikolaev, Pavel; Gorelik, Olga; Allada, Rama Kumar; Sosa, Edward; Arepalli, Sivaram

2013-01-01

The "soft-bake" method is a simple and reliable initial purification step first proposed by researchers at Rice University for single-walled carbon nanotubes (SWCNT) produced by high-pressure carbon mon oxide disproportionation (HiPco). Soft-baking consists of annealing as-produced (raw) SWCNT, at low temperatures in humid air, in order to degrade the heavy graphitic shells that surround metal particle impurities. Once these shells are cracked open by the expansion and slow oxidation of the metal particles, the metal impurities can be digested through treatment with hydrochloric acid. The soft-baking of SWCNT produced by pulsed-laser vaporization (PLV) is not straightforward, because the larger average SWCNT diameters (.1.4 nm) and heavier graphitic shells surrounding metal particles call for increased temperatures during soft-bake. A part of the technology development focused on optimizing the temperature so that effective cracking of the graphitic shells is balanced with maintaining a reasonable yield, which was a critical aspect of this study. Once the ideal temperature was determined, a number of samples of raw SWCNT were purified using the soft-bake method. An important benefit to this process is the reduced time and effort required for soft-bake versus the standard purification route for SWCNT. The total time spent purifying samples by soft-bake is one week per batch, which equates to a factor of three reduction in the time required for purification as compared to the standard acid purification method. Reduction of the number of steps also appears to be an important factor in improving reproducibility of yield and purity of SWCNT, as small deviations are likely to get amplified over the course of a complicated multi-step purification process.

Time and size resolved Measurement of Mass Concentration at an Urban Site

NASA Astrophysics Data System (ADS)

Karg, E.; Ferron, G. A.; Heyder, J.

2003-04-01

Time- and size-resolved measurements of ambient particles are necessary for modelling of atmospheric particle transport, the interpretation of particulate pollution events and the estimation of particle deposition in the human lungs. In the size range 0.01 - 2 µm time- and size-resolved data are obtained from differential mobility and optical particle counter measurements and from gravimetric filter analyses on a daily basis (PM2.5). By comparison of the time averaged and size integrated particle volume concentration with PM2.5 data, an average density of ambient particles can be estimated. Using this density, the number concentration data can be converted in time- and size-resolved mass concentration. Such measurements were carried out at a Munich downtown crossroads. The spectra were integrated in the size ranges 10 - 100 nm, 100 - 500 nm and 500 - 2000 nm. Particles in these ranges are named ultrafine, fine and coarse particles. These ranges roughly represent freshly emitted particles, aged/accumulated particles and particles entrained by erosive processes. An average number concentration of 80000 1/cm3 (s.d. 67%), a particle volume concentration of 53 µm3/cm3 (s.d. 76%) and a PM2.5 mass concentration of 27 µg/m3 was found. These particle volume- and PM2.5 data imply an average density of 0.51 g/cm3. Average number concentration showed 95.3%, 4.7% and 0.006% of the total particle concentration in the size ranges mentioned above. Mass concentration was 14.7%, 80.2% and 5.1% of the total, assuming the average density to be valid for all particles. The variability in mass concentration was 94%, 75% and 33% for the three size ranges. Nearly all ambient particles were in the ultrafine size range, whereas most of the mass concentration was in the fine size range. However, a considerable mass fraction of nearly 15% was found in the ultrafine size range. As the sampling site was close to the road and traffic emissions were the major source of the particles, 1) the density was very low due to agglomerated and porous structures of freshly emitted combustion particles and 2) the variability was highest in the ultrafine range, obviously correlated to traffic activity and lowest in the micron size range. In conclusion, almost all ambient particles were ultrafine particles, whereas most of the particle mass was associated with fine particles. Nevertheless, a considerable mass fraction was found in the ultrafine size range. These particles had a very low density so that they can be considered as agglomerated and porous particles emitted from vehicles passing the crossroads. Therefore they showed a much higher variation in mass concentration than the fine and coarse particles.

OpenFOAM Modeling of Particle Heating and Acceleration in Cold Spraying

NASA Astrophysics Data System (ADS)

Leitz, K.-H.; O'Sullivan, M.; Plankensteiner, A.; Kestler, H.; Sigl, L. S.

2018-01-01

In cold spraying, a powder material is accelerated and heated in the gas flow of a supersonic nozzle to velocities and temperatures that are sufficient to obtain cohesion of the particles to a substrate. The deposition efficiency of the particles is significantly determined by their velocity and temperature. Particle velocity correlates with the amount of kinetic energy that is converted to plastic deformation and thermal heating. The initial particle temperature significantly influences the mechanical properties of the particle. Velocity and temperature of the particles have nonlinear dependence on the pressure and temperature of the gas at the nozzle entrance. In this contribution, a simulation model based on the reactingParcelFoam solver of OpenFOAM is presented and applied for an analysis of particle velocity and temperature in the cold spray nozzle. The model combines a compressible description of the gas flow in the nozzle with a Lagrangian particle tracking. The predictions of the simulation model are verified based on an analytical description of the gas flow, the particle acceleration and heating in the nozzle. Based on experimental data, the drag model according to Plessis and Masliyah is identified to be best suited for OpenFOAM modeling particle heating and acceleration in cold spraying.

Using sieving and pretreatment to separate plastics during end-of-life vehicle recycling.

PubMed

Stagner, Jacqueline A; Sagan, Barsha; Tam, Edwin Kl

2013-09-01

Plastics continue to be a challenge for recovering materials at the end-of-life for vehicles. However, it may be possible to improve the recovery of plastics by exploiting material characteristics, such as shape, or by altering their behavior, such as through temperature changes, in relation to recovery processes and handling. Samples of a 2009 Dodge Challenger front fascia were shredded in a laboratory-scale hammer mill shredder. A 2 × 2 factorial design study was performed to determine the effect of sample shape (flat versus curved) and sample temperature (room temperature versus cryogenic temperature) on the size of the particles exiting from the shredder. It was determined that sample shape does not affect the particle size; however, sample temperature does affect the particle size. At cryogenic temperatures, the distribution of particle sizes is much narrower than at room temperature. Having a more uniform particle size could make recovery of plastic particles, such as these more efficient during the recycling of end-of-life vehicles. Samples of Chrysler minivan headlights were also shredded at room temperature and at cryogenic temperatures. The size of the particles of the two different plastics in the headlights is statistically different both at room temperature and at cryogenic temperature, and the particles are distributed narrowly. The research suggests that incremental changes in end-of-life vehicle processing could be effective in aiding materials recovery.

Mechanochemical synthesis of LaCo5 magnetically hard anisotropic powder

NASA Astrophysics Data System (ADS)

Gabay, A. M.; Hadjipanayis, G. C.

2014-05-01

LaCo5 particles were prepared from La2O3 and Co powders processed in the presence of Ca as a reducing agent and a CaO dispersant. After high-energy ball milling followed by a short annealing at 900 °C, the particles exhibited a room-temperature intrinsic coercivity of 24.5 kOe. Separation of the hard magnetic particles with water is accompanied by the release of hydrogen and this leads to replacement of the LaCo5 structure by various LaCo5Hx hydrides. The LaCo5 structure was restored by removing hydrogen via vacuum annealing. The resulting particles were polydispersed with an average size of 540 nm and crystallographically anisotropic; they exhibited a remanent magnetization of 83.8 emu g-1 (8.7 kG) and a coercivity of 9.6 kOe. The dramatic improvement of the hard magnetic properties as compared to those obtained by standard milling is attributed to a lower density of anisotropy defects at the surface of the mechanochemically synthesized particles. This advantage may allow for the commercial utilization of more abundant/less expensive raw materials for permanent magnets.

Determination of the Residence Time of Food Particles During Aseptic Sterilization

NASA Technical Reports Server (NTRS)

Carl, J. R.; Arndt, G. D.; Nguyen, T. X.

1994-01-01

The paper describes a non-invasive method to measure the time an individual particle takes to move through a length of stainless steel pipe. The food product is in two phase flow (liquids and solids) and passes through a pipe with pressures of approximately 60 psig and temperatures of 270-285 F. The proposed problem solution is based on the detection of transitory amplitude and/or phase changes in a microwave transmission path caused by the passage of the particles of interest. The particles are enhanced in some way, as will be discussed later, such that they will provide transitory changes that are distinctive enough not to be mistaken for normal variations in the received signal (caused by the non-homogeneous nature of the medium). Two detectors (transmission paths across the pipe) will be required and place at a known separation. A minimum transit time calculation is made from which the maximum velocity can be determined. This provides the minimum residence time. Also average velocity and statistical variations can be computed so that the amount of 'over-cooking' can be determined.

The Effect of Particle Properties on Hot Particle Spot Fire Ignition

NASA Astrophysics Data System (ADS)

Zak, Casey David

The ignition of natural combustible material by hot metal particles is an important fire ignition pathway by which wildland and wildland-urban-interface spot fires are started. There are numerous cases reported of wild fires started by clashing power-lines or from sparks generated by machines or engines. Similarly there are many cases reported of fires caused by grinding, welding and cutting sparks. Up to this point, research on hot particle spot fire ignition has largely focused on particle generation and transport. A small number of studies have examined what occurs after a hot particle contacts a natural fuel bed, but until recently the process remained poorly understood. This work describes an investigation of the effect of particle size, temperature and thermal properties on the ability of hot particles to cause flaming ignition of cellulosic fuel beds. Both experimental and theoretical approaches are used, with a focus on understanding the physics underlying the ignition process. For the experimental study, spheres of stainless steel, aluminum, brass and copper are heated in a tube furnace and dropped onto a powdered cellulose fuel bed; the occurrence of flaming ignition or lack thereof is visually observed and recorded. This procedure is repeated a large number of times for each metal type, varying particle diameter from 2 to 11 mm and particle temperature between 575 and 1100°C. The results of these experiments are statistically analyzed to find approximate ignition boundaries and identify boundary trends with respect to the particle parameters of interest. Schlieren images recorded during the ignition experiments are also used to more accurately describe the ignition process. Based on these images, a simple theoretical model of hot particle spot fire ignition is developed and used to explore the experimental trends further. The model under-predicts the minimum ignition temperatures required for small spheres, but agrees qualitatively with the experimental data. Model simulations identify the important physics controlling ignition for different sized particles and clarify many of the experimental trends. The results show a hyperbolic relationship between particle size and temperature, with the larger particles requiring lower temperatures to ignite the cellulose than the smaller particles. For very small spheres, the temperature required for ignition is very sensitive to particle size, while for very large spheres, ignition temperature shows only a weak dependence on that variable. Flaming ignition of powdered cellulose by particles ≤ 11 mm in size requires particle temperatures of at least 600°C. Ignition has not been observed for 2 mm particles at temperatures up to 1100°C, but the statistical analysis indicates that ignition by particles 2 mm and smaller may be possible at temperatures above 950°C. No clear trend is observed with particle metal type, but copper particles require slightly higher ignition temperatures and seem more sensitive to experimental variation, likely due to their relatively high thermal conductivity. High-speed Schlieren images taken during the ignition experiments show that once particles land, they volatilize the powdered cellulose and the fuel vapor diffuses out into the surrounding air. Ignition occurs in the mixing layer between the vapor and the air, either during the initial expansion of the pyrolyzate away from the particle, or after a stable plume of volatiles has formed. Modeling results indicate that in the large-particle, high-conductivity limit, the particle's surface temperature remains close to its impact temperature over the timescales of ignition. As a result, particle thermal properties are unimportant and ignition occurs when heat generation in the mixing layer overcomes losses to the surrounding air. When the large-particle limit does not apply, the particle cools upon impact with the fuel bed. In addition to the losses to the surrounding air, the reaction zone experiences losses to the cooling particle and must generate a larger amount of heat for ignition to occur. Because cooling is so important, the initial bulk energy is more useful than impact temperature for predicting ignition by smaller particles. Along those lines, the additional heat of melting available to molten particles helps to resist particle cooling; as such, molten aluminum particles 3.5 -- 7 mm in diameter can ignite at lower temperatures than solid particles of the same size with similar thermal properties. Decreasing volumetric heat capacity does increase minimum ignition temperature somewhat, but this effect is reduced for larger particles. Emissivity does not appear to have a significant effect on ignition propensity, suggesting that, over the timescales of ignition, radiation heat transfer is small relative to other modes of particle heat loss.

Elemental concentrations of ambient particles and cause specific mortality in Santiago, Chile: a time series study

PubMed Central

2012-01-01

Background The health effects of particulate air pollution are widely recognized and there is some evidence that the magnitude of these effects vary by particle component. We studied the effects of ambient fine particles (aerodynamic diameter < 2.5μm, PM2.5) and their components on cause-specific mortality in Santiago, Chile, where particulate pollution is a major public health concern. Methods Air pollution was collected in a residential area in the center of Santiago. Daily mortality counts were obtained from the National Institute of Statistic. The associations between PM2.5 and cause-specific mortality were studied by time series analysis controlling for time trends, day of the week, temperature and relative humidity. We then included an interaction term between PM2.5 and the monthly averages of the mean ratios of individual elements to PM2.5 mass. Results We found significant effects of PM2.5 on all the causes analyzed, with a 1.33% increase (95% CI: 0.87-1.78) in cardiovascular mortality per 10μg/m3 increase in the two days average of PM2.5. We found that zinc was associated with higher cardiovascular mortality. Particles with high content of chromium, copper and sulfur showed stronger associations with respiratory and COPD mortality, while high zinc and sodium content of PM2.5 amplified the association with cerebrovascular disease. Conclusions Our findings suggest that PM2.5 with high zinc, chromium, copper, sodium, and sulfur content have stronger associations with mortality than PM2.5 mass alone in Santiago, Chile. The sources of particles containing these elements need to be determined to better control their emissions. PMID:23116481

Particle Size of CO2 Condensates in Mars Atmosphere Revealed by Climate Sounder and Laser Ranging Observations

NASA Astrophysics Data System (ADS)

Hu, Renyu

Current-generation Mars Climate Sounder (MCS) onboard the Mars Reconnaissance Orbiter (MRO) offers extensive coverage of the latitudinal and seasonal distribution of CO_2 condensation in Mars’s atmosphere. The atmospheric temperature profiles measured by MCS reveal that the thickness of CO_2 condensation layer reaches a maximum of 10-15 km (north) or ˜20 km (south) during the middle of winter. There is a shrinking of the CO_2 condensation layer from L_S ˜270(°) to ˜300(°) in 2007, probably related to a planet-encircling dust storm. We integrate the condensation area and the condensation occurrence rate synthesized from the MCS observations to estimate cumulative masses of CO2 condensates deposited onto the northern and southern seasonal polar caps. The mass loading of CO_2 condensate particles, when condensation occurs, can be independently inferred from the detections of reflective clouds by the Mars Orbiter Laser Altimetry (MOLA) onboard the Mars Global Surveyor (MGS). Therefore, we approximate the precipitation flux by the particle settling flux, which is estimated using the impulse responses of MOLA filter channels. With our approach, the total atmospheric condensation mass can be estimated from these observational data sets, with average particle size as the only free parameter. By comparison with the seasonal polar cap masses inferred from the time-varying gravity of Mars, our estimates indicate that the average condensate particle radius is 8 - 22 mum in the northern hemisphere and 4 - 13 mum in the southern hemisphere. This multi-instrument data analysis provides new constraints on modeling the microphysics of CO_2 clouds on Mars.

Stimuli-Responsive, Shape-Transforming Nanostructured Particles.

PubMed

Lee, Junhyuk; Ku, Kang Hee; Kim, Mingoo; Shin, Jae Man; Han, Junghun; Park, Chan Ho; Yi, Gi-Ra; Jang, Se Gyu; Kim, Bumjoon J

2017-08-01

Development of particles that change shape in response to external stimuli has been a long-thought goal for producing bioinspired, smart materials. Herein, the temperature-driven transformation of the shape and morphology of polymer particles composed of polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) block copolymers (BCPs) and temperature-responsive poly(N-isopropylacrylamide) (PNIPAM) surfactants is reported. PNIPAM acts as a temperature-responsive surfactant with two important roles. First, PNIPAM stabilizes oil-in-water droplets as a P4VP-selective surfactant, creating a nearly neutral interface between the PS and P4VP domains together with cetyltrimethylammonium bromide, a PS-selective surfactant, to form anisotropic PS-b-P4VP particles (i.e., convex lenses and ellipsoids). More importantly, the temperature-directed positioning of PNIPAM depending on its solubility determines the overall particle shape. Ellipsoidal particles are produced above the critical temperature, whereas convex lens-shaped particles are obtained below the critical temperature. Interestingly, given that the temperature at which particle shape change occurs depends solely on the lower critical solution temperature (LCST) of the polymer surfactants, facile tuning of the transition temperature is realized by employing other PNIPAM derivatives with different LCSTs. Furthermore, reversible transformations between different shapes of PS-b-P4VP particles are successfully demonstrated using a solvent-adsorption annealing with chloroform, suggesting great promise of these particles for sensing, smart coating, and drug delivery applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The component content of active particles in a plasma-chemical reactor based on volume barrier discharge

NASA Astrophysics Data System (ADS)

Soloshenko, I. A.; Tsiolko, V. V.; Pogulay, S. S.; Terent'yeva, A. G.; Bazhenov, V. Yu; Shchedrin, A. I.; Ryabtsev, A. V.; Kuzmichev, A. I.

2007-02-01

In this paper the results of theoretical and experimental studies of the component content of active particles formed in a plasma-chemical reactor composed of a multiple-cell generator of active particles, based on volume barrier discharge, and a working chamber are presented. For calculation of the content of uncharged plasma components an approach is proposed which is based on averaging of the power introduced over the entire volume. Advantages of such an approach lie in an absence of fitting parameters, such as the dimensions of microdischarges, their surface density and rate of breakdown. The calculation and the experiment were accomplished with the use of dry air (20% relative humidity) as the plasma generating medium. Concentrations of O3, HNO3, HNO2, N2 O5 and NO3 were measured experimentally in the discharge volume and working chamber for the residence time of particles on a discharge of 0.3 s and more and discharge specific power of 1.5 W cm-3. It has been determined that the best agreement between the calculation and the experiment occurs at calculated gas medium temperatures in the discharge plasma of about 400-425 K, which correspond to the experimentally measured rotational temperature of nitrogen. In most cases the calculated concentrations of O3, HNO3, HNO2, N2O5 and NO3 for the barrier discharge and the working chamber are in fairly good agreement with the respective measured values.

Effect of Mg content on the thermal stability and mechanical behaviour of PLLA/Mg composites processed by hot extrusion.

PubMed

Cifuentes, S C; Lieblich, M; López, F A; Benavente, R; González-Carrasco, J L

2017-03-01

In the field of bioabsorbable composites for biomedical applications, extrusion has been employed as a method to prepare homogeneous blends of polymeric matrices with bioactive ceramic fillers. In this work, the suitability of processing poly-l-lactic acid/Magnesium (PLLA/Mg) composites by hot extrusion has been assessed by a systematic characterization of PLLA/Mg composites containing different amounts of Mg particles up to 7wt%. The results show that extrusion causes a reduction of almost 20% in the viscosity average molecular weight of PLLA, which further decreases with increasing Mg content. Extrusion gave always rise to a homogeneous distribution of Mg particles within the PLLA matrix. This composite processing was not compromised by the degradation of the polymeric matrix because the processing temperature was always below the onset degradation temperature. In the processing conditions employed in the present work, degradation of the composite slightly increases as more Mg is added up to 5wt%, but is very high at 7wt%. This was also evident from the mechanical behaviour, so that Mg particles improved the stiffness and compression strength of neat PLLA until 5wt% of Mg content, which dropped drastically when the material had 7wt% of Mg. The filler strengthening factor decreases with the increment in Mg content. In order to obtain an optimised contribution of Mg particles, a balance between thermal degradation and mechanical resistance of PLLA must be achieved. Copyright © 2016 Elsevier B.V. All rights reserved.

Interparticle interaction effects on magnetic behaviors of hematite (α-Fe2O3) nanoparticles

NASA Astrophysics Data System (ADS)

Can, Musa Mutlu; Fırat, Tezer; Özcan, Şadan

2011-07-01

The interparticle magnetic interactions of hematite (α-Fe2O3) nanoparticles were investigated by temperature and magnetic field dependent magnetization curves. The synthesis were done in two steps; milling metallic iron (Fe) powders in pure water (H2O), known as mechanical milling technique, and annealing at 600 °C. The crystal and molecular structure of prepared samples were determined by X-ray powder diffraction (XRD) spectra and Fourier transform infrared (FTIR) spectra results. The average particle sizes and the size distributions were figured out using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The magnetic behaviors of α-Fe2O3 nanoparticles were analyzed with a vibrating sample magnetometer (VSM). As a result of the analysis, it was observed that the prepared α-Fe2O3 nanoparticles did not perform a sharp Morin transition (the characteristic transition of α-Fe2O3) due to lack of unique particle size distribution. However, the transition can be observed in the wide temperature range as “a continuously transition”. Additionally, the effect of interparticle interaction on magnetic behavior was determined from the magnetization versus applied field (σ(M)) curves for 26±2 nm particles, dispersed in sodium oxalate matrix under ratios of 200:1, 300:1, 500:1 and 1000:1. The interparticle interaction fields, recorded at 5 K to avoid the thermal interactions, were found as ∼1082 Oe for 26±2 nm particles.

Electric field measurements during the blowing snow in a cryogenic wind tunnel by a non-contact voltmeter

NASA Astrophysics Data System (ADS)

Sato, A.; Omiya, S.

2011-12-01

It is known that the average atmospheric electric field is +100V/m in fair weather (positive electric field vector points downward). An increase of atmospheric electric field is reported when the blowing snow occurred. This phenomenon is mainly explained by the fact that the blowing snow particles have negative charge in average. It is suggested that an electrostatic force, given by the product of the electric field and the charge of the particle, may influence the particle trajectory and change those movements, saltation and suspension. The purpose of this experiment is to clarify the characteristics of the electric field during blowing snow event. Experiments were carried out in the cryogenic wind tunnel of Snow and Ice Research Center, NIED. A non-contact voltmeter was used to measure the electric field. An artificial blowing snow was generated by a snow particle supply machine. The rolling brushes of the machine scratch the snow surface and supply snow particles into the airflow. This machine made it possible to supply the snow particles at an arbitrary rate. This experiment was conducted in the following experimental conditions; wind speed of 5 to 7 m/s (3 patterns), supply snow quantity of 8.7 to 34.9 g/m/s (4 patterns), air temperature of -10 degree Celsius, fetch of 10 m and hard snow surface. Measured electric field was all negative, which is opposite direction to the previous measurements. This means that the blowing snow particles had positive charges. The negative electric field tended to increase with increase of the wind speed and the mass flux. These results can be explained from the previous experiment by Omiya and Sato (2010). The snow particles gain positive charges by the friction with the rolling brush which is made from polypropylene, however the particles accumulate negative charges gradually with increase of the collisions to the snow surface. Probably, the positive charges might have remained on the snow particles that had passed over the measurement point. Moreover, it is thought that because the saltation length is longer when the wind speed is higher, fewer collision frequencies left the particles more positive charges. REFERENCE:Omiya and Sato(2010): Measurement of electrostatic charge of blowing snow particles in a wind tunnel focusing on collision frequency to the snow surface. Hokkaido University Collection of Scholarly and Academic Papers

Saharan Dust Particle Size And Concentration Distribution In Central Ghana

NASA Astrophysics Data System (ADS)

Sunnu, A. K.

2010-12-01

A.K. Sunnu*, G. M. Afeti* and F. Resch+ *Department of Mechanical Engineering, Kwame Nkrumah University of Science and Technology (KNUST) Kumasi, Ghana. E-mail: albertsunnu@yahoo.com +Laboratoire Lepi, ISITV-Université du Sud Toulon-Var, 83162 La Valette cedex, France E-mail: resch@univ-tln.fr Keywords: Atmospheric aerosol; Saharan dust; Particle size distributions; Particle concentrations. Abstract The Saharan dust that is transported and deposited over many countries in the West African atmospheric environment (5°N), every year, during the months of November to March, known locally as the Harmattan season, have been studied over a 13-year period, between 1996 and 2009, using a location at Kumasi in central Ghana (6° 40'N, 1° 34'W) as the reference geographical point. The suspended Saharan dust particles were sampled by an optical particle counter, and the particle size distributions and concentrations were analysed. The counter gives the total dust loads as number of particles per unit volume of air. The optical particle counter used did not discriminate the smoke fractions (due to spontaneous bush fires during the dry season) from the Saharan dust. Within the particle size range measured (0.5 μm-25 μm.), the average inter-annual mean particle diameter, number and mass concentrations during the northern winter months of January and February were determined. The average daily number concentrations ranged from 15 particles/cm3 to 63 particles/cm3 with an average of 31 particles/cm3. The average daily mass concentrations ranged from 122 μg/m3 to 1344 μg/m3 with an average of 532 μg/m3. The measured particle concentrations outside the winter period were consistently less than 10 cm-3. The overall dust mean particle diameter, analyzed from the peak representative Harmattan periods over the 13-year period, ranged from 0.89 μm to 2.43 μm with an average of 1.5 μm ± 0.5. The particle size distributions exhibited the typical distribution pattern for atmospheric aerosols with a coarse mode diameter situated at about 3.5 μm. The experimental results reported in this study will be important in validating satellite based observations and simulation models of the African dust plume towards the Gulf of Guinea during winter.

Effects of temperature and particles on nitrification in a eutrophic coastal bay in southern China

NASA Astrophysics Data System (ADS)

Zheng, Zhen-Zhen; Wan, Xianhui; Xu, Min Nina; Hsiao, Silver Sung-Yun; Zhang, Yao; Zheng, Li-Wei; Wu, Yanhua; Zou, Wenbin; Kao, Shuh-Ji

2017-09-01

Despite being the only link between reduced and oxidized nitrogen, the impact of environmental factors on nitrification, temperature and particles, in particular, remains unclear for coastal zones. By using the 15NH4+-labeling technique, we determined nitrification rates in bulk (NTRB) and free-living (NTRF, after removing particles >3 μm) for water samples with varying particle concentrations (as sampled at different tidal stages) during autumn, winter, and summer in a eutrophic coastal bay in southern China. The highest NTRB occurred in autumn, when particle concentrations were highest. In general, particle-associated nitrification rates (NTRP, >3 μm) were higher than NTRF and increased with particle abundance. Regardless of seasonally distinctive temperature and particle concentrations, nitrification exhibited consistent temperature dependence in all cases (including bulk, particle-associated, and free-living) with a Q10 value of 2.2. Meanwhile, the optimum temperature for NTRP was 29°C, 5°C higher than that for NTRF although the causes for such a difference remained unclear. Strong temperature dependence and particle association suggest that nitrification is sensitive to temperature change (seasonality and global warming) and to ocean dynamics (wave and tide). Our results can potentially be applied to biogeochemical models of the nitrogen cycle for future predictions.

Luminescent properties of YVO4:Eu/SiO2 core-shell composite particles

NASA Astrophysics Data System (ADS)

Bao, Amurisana; Lai, Hua; Yang, Yuming; Liu, Zhilong; Tao, Chunyan; Yang, Hua

2010-02-01

We report an efficient process for preparing monodisperse SiO2@Y0.95Eu0.05VO4 core-shell phosphors using a simple citrate sol-gel method and without the use of surface-coupling silane agents or large stabilizers. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and photoluminescence (PL) spectra were used to characterize the resulting SiO2@Y0.95Eu0.05VO4 core-shell phosphors. The XRD results demonstrate that the Y0.95Eu0.05VO4 particles crystallization on the surface of SiO2 annealing at 800 °C is perfectly and the crystallinity increases with raising the annealing temperature. The obtained core-shell phosphors have a near perfect spherical shape with narrow size distribution (average size ca. 500 nm and an average thickness of 50 nm), are not agglomerated, and have a smooth surface. The thickness of the YVO4:Eu3+ shells on the SiO2 cores could be easily tailored by changing the mass ratio of shell to core ( W = [YVO4]/[SiO2]) ( 50 nm for W = 30%). The Eu3+ shows a strong PL luminescence (dominated by 5D0 - 7F2 red emission at 618 nm) under the excitation of 320 nm UV light. The PL intensity of Eu3+ increases with increasing the annealing temperature and the values of W.

Effects of applied pressure on hot-pressing of Beta-SiC

NASA Technical Reports Server (NTRS)

Kinoshita, M.; Matsumura, H.; Iwasa, M.; Hayami, R.

1984-01-01

The effects of applied pressure on the densification during hot pressing of beta-SiC compacts were investigated. Beta-SiC powder is Starck made and has the average particle size of about 0.7 micrometer. Hot pressing experiments were carried out in graphite dies at temperatures of 1700 deg to 2300 deg C and at the pressures up to 1000 kg/sq cm. The compacts containing 1 weight percent B4C were examined. Sintered compacts were examined for microstructure and the Rockwell A-scale hardness was measured. The B4C addition was very effective to mitigate the hot pressing conditions. It is found that densification goes with the strengthening of the bonding and does not occur in particle deformation due to concentrated stress.

Particle model for nonlocal heat transport in fusion plasmas.

PubMed

Bufferand, H; Ciraolo, G; Ghendrih, Ph; Lepri, S; Livi, R

2013-02-01

We present a simple stochastic, one-dimensional model for heat transfer in weakly collisional media as fusion plasmas. Energies of plasma particles are treated as lattice random variables interacting with a rate inversely proportional to their energy schematizing a screened Coulomb interaction. We consider both the equilibrium (microcanonical) and nonequilibrium case in which the system is in contact with heat baths at different temperatures. The model exhibits a characteristic length of thermalization that can be associated with an interaction mean free path and one observes a transition from ballistic to diffusive regime depending on the average energy of the system. A mean-field expression for heat flux is deduced from system heat transport properties. Finally, it is shown that the nonequilibrium steady state is characterized by long-range correlations.

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Emission of charged particles from the surface of a moving target acted on by cw CO2 laser radiation

NASA Astrophysics Data System (ADS)

Kuznetsov, S. I.; Petrov, A. L.; Shadrin, A. N.

1990-06-01

An experimental investigation was made of the emission of charged particles due to the irradiation of moving steel and graphite targets with cw CO2 laser radiation. The characteristics of the emission current signals were determined for different laser irradiation regimes. The maximum emission current density from the surface of a melt pool ( ~ 1.1 × 10 - 2 A/cm2) and the average temperature of the liquid metal (~ 2040 K) were measured for an incident radiation power density of 550 W and for horizontal and vertical target velocities of respectively ~ 1.5 mm/s and ~ 0.17 mm/s. The authors propose to utilize this phenomenon for monitoring the laser processing of materials.

Statistics of particle time-temperature histories.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hewson, John C.; Lignell, David O.; Sun, Guangyuan

2014-10-01

Particles in non - isothermal turbulent flow are subject to a stochastic environment tha t produces a distribution of particle time - temperature histories. This distribution is a function of the dispersion of the non - isothermal (continuous) gas phase and the distribution of particles relative to that gas phase. In this work we extend the one - dimensional turbulence (ODT) model to predict the joint dispersion of a dispersed particle phase and a continuous phase. The ODT model predicts the turbulent evolution of continuous scalar fields with a model for the cascade of fluctuations to smaller sc ales (themore » 'triplet map') at a rate that is a function of the fully resolved one - dimens ional velocity field . Stochastic triplet maps also drive Lagrangian particle dispersion with finite Stokes number s including inertial and eddy trajectory - crossing effect s included. Two distinct approaches to this coupling between triplet maps and particle dispersion are developed and implemented along with a hybrid approach. An 'instantaneous' particle displacement model matches the tracer particle limit and provide s an accurate description of particle dispersion. A 'continuous' particle displacement m odel translates triplet maps into a continuous velocity field to which particles respond. Particles can alter the turbulence, and modifications to the stochastic rate expr ession are developed for two - way coupling between particles and the continuous phase. Each aspect of model development is evaluated in canonical flows (homogeneous turbulence, free - shear flows and wall - bounded flows) for which quality measurements are ava ilable. ODT simulations of non - isothermal flows provide statistics for particle heating. These simulations show the significance of accurately predicting the joint statistics of particle and fluid dispersion . Inhomogeneous turbulence coupled with the in fluence of the mean flow fields on particles of varying properties alter s particle dispersion. The joint particle - temperature dispersion leads to a distribution of temperature histories predicted by the ODT . Predictions are shown for the lower moments an d the full distributions of the particle positions, particle - observed gas temperatures and particle temperatures. An analysis of the time scales affecting particle - temperature interactions covers Lagrangian integral time scales based on temperature autoco rrelations, rates of temperature change associated with particle motion relative to the temperature field and rates of diffusional change of temperatures. These latter two time scales have not been investigated previously; they are shown to be strongly in termittent having peaked distributions with long tails. The logarithm of the absolute value of these time scales exhibits a distribution closer to normal. A cknowledgements This work is supported by the Defense Threat Reduction Agency (DTRA) under their Counter - Weapons of Mass Destruction Basic Research Program in the area of Chemical and Biological Agent Defeat under award number HDTRA1 - 11 - 4503I to Sandia National Laboratories. The authors would like to express their appreciation for the guidance provi ded by Dr. Suhithi Peiris to this project and to the Science to Defeat Weapons of Mass Destruction program.« less

Heat transfer in suspensions of rigid particles

NASA Astrophysics Data System (ADS)

Brandt, Luca; Niazi Ardekani, Mehdi; Abouali, Omid

2016-11-01

We study the heat transfer in laminar Couette flow of suspensions of rigid neutrally buoyant particles by means of numerical simulations. An Immersed Boundary Method is coupled with a VOF approach to simulate the heat transfer in the fluid and solid phase, enabling us to fully resolve the heat diffusion. First, we consider spherical particles and show that the proposed algorithm is able to reproduce the correlations between heat flux across the channel, the particle volume fraction and the heat diffusivity obtained in laboratory experiments and recently proposed in the literature, results valid in the limit of vanishing inertia. We then investigate the role of inertia on the heat transfer and show an increase of the suspension diffusivity at finite particle Reynolds numbers. Finally, we vary the relativity diffusivity of the fluid and solid phase and investigate its effect on the effective heat flux across the channel. The data are analyzed by considering the ensemble averaged energy equation and decomposing the heat flux in 4 different contributions, related to diffusion in the solid and fluid phase, and the correlations between wall-normal velocity and temperature fluctuations. Results for non-spherical particles will be examined before the meeting. Supported by the European Research Council Grant No. ERC-2013- CoG-616186, TRITOS. The authors acknowledge computer time provided by SNIC (Swedish National Infrastructure for Computing).

The effect of particle size on the dehydration/rehydration behaviour of lactose.

PubMed

Crisp, J L; Dann, S E; Edgar, M; Blatchford, C G

2010-05-31

Ethanolic suspensions of spray dried and micronized alpha lactose monohydrate (L(alpha)xH(2)O) with average particle size between 3 and 200 microm, have been prepared and their dehydration behaviour was investigated by (13)C CP-MASNMR spectroscopy. Sub-micron lactose suspension prepared by a novel high pressure homogenisation method has been compared with the standard ethanolic suspensions of (L(alpha).H(2)O prepared by reflux or static room temperature methods. In all cases, suspensions were shown to contain the stable anhydrous form of lactose ((L(alpha)(S)). Several approaches were employed to remove ethanol from these suspensions and the resulting dry lactose powders were then analysed by FT-IR, PXRD and SEM to evaluate the effect of drying procedure on type and distribution of lactose polymorphs and particle size. For samples with mean particle size greater than 1 microm, the stable anhydrous polymorphic form of lactose was retained on removal of the ethanol, although differences in the morphology and particle size of the crystals were apparent depending on method of suspension formation. Sub-micron (L(alpha)(S), while stable in dry conditions, has been shown to be less stable to atmospheric water vapour than (L(alpha)(S) with particle size between 3 and 200 microm. Copyright (c) 2010 Elsevier B.V. All rights reserved.

Polyhedral 3D structure of human plasma very low density lipoproteins by individual particle cryo-electron tomography

DOE PAGES

Yu, Yadong; Kuang, Yu-Lin; Lei, Dongsheng; ...

2016-08-18

Human VLDLs assembled in the liver and secreted into the circulation supply energy to peripheral tissues. VLDL lipolysis yields atherogenic LDLs and VLDL remnants that strongly correlate with CVD. Although the composition of VLDL particles has been well-characterized, their 3D structure is elusive because of their variations in size, heterogeneity in composition, structural flexibility, and mobility in solution. Here, we employed cryo-electron microscopy and individual-particle electron tomography to study the 3D structure of individual VLDL particles (without averaging) at both below and above their lipid phase transition temperatures. The 3D reconstructions of VLDL and VLDL bound to antibodies revealed anmore » unexpected polyhedral shape, in contrast to the generally accepted model of a spherical emulsion-like particle. The smaller curvature of surface lipids compared with HDL may also reduce surface hydrophobicity, resulting in lower binding affinity to the hydrophobic distal end of the N-terminal β-barrel domain of cholesteryl ester transfer protein (CETP) compared with HDL. The directional binding of CETP to HDL and VLDL may explain the function of CETP in transferring TGs and cholesteryl esters between these particles. This first visualization of the 3D structure of VLDL could improve our understanding of the role of VLDL in atherogenesis.« less

Transport of active ellipsoidal particles in ratchet potentials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ai, Bao-Quan, E-mail: aibq@scnu.edu.cn; Wu, Jian-Chun

2014-03-07

Rectified transport of active ellipsoidal particles is numerically investigated in a two-dimensional asymmetric potential. The out-of-equilibrium condition for the active particle is an intrinsic property, which can break thermodynamical equilibrium and induce the directed transport. It is found that the perfect sphere particle can facilitate the rectification, while the needlelike particle destroys the directed transport. There exist optimized values of the parameters (the self-propelled velocity, the torque acting on the body) at which the average velocity takes its maximal value. For the ellipsoidal particle with not large asymmetric parameter, the average velocity decreases with increasing the rotational diffusion rate, whilemore » for the needlelike particle (very large asymmetric parameter), the average velocity is a peaked function of the rotational diffusion rate. By introducing a finite load, particles with different shapes (or different self-propelled velocities) will move to the opposite directions, which is able to separate particles of different shapes (or different self-propelled velocities)« less

Structural and magnetic properties of cobalt ferrite nanoparticles synthesized by co-precipitation at increasing temperatures

NASA Astrophysics Data System (ADS)

Stein, C. R.; Bezerra, M. T. S.; Holanda, G. H. A.; André-Filho, J.; Morais, P. C.

2018-05-01

This study reports on the synthesis and characterization of cobalt ferrite (CoFe2O4) nanoparticles (NPs) synthesized by chemical co-precipitation in alkaline medium at increasing temperatures in the range of 27 °C to 100 °C. High-quality samples in the size range of 5 to 10 nm were produced using very low stirring speed (250 rpm) and moderate alkaline aqueous solution concentration (4.8 mol/L). Three samples were synthesized and characterized by x-ray diffraction (XRD) and room-temperature (RT) magnetization measurements. All samples present superparamagnetic (SPM) behavior at RT and Rietveld refinements confirm the inverse cubic spinel structure (space group Fd-3m (227)) with minor detectable impurity phase. As the synthesis temperature increases, structural parameters such as lattice constant and grain size change monotonically from 8.385 to 8.383 Å and from 5.8 to 7.4 nm, respectively. Likewise, as the synthesis temperature increases the NPs' magnetic moment and saturation magnetization increases monotonically from 2.6 ×103 to 16×103 μB and from 37 to 66 emu/g, respectively. The RT magnetization (M) versus applied field (H) curves were analyzed by the first-order Langevin function averaged out by a lognormal distribution function of magnetic moments. The excellent curve-fitting of the M versus H data is credited to a reduced particle-particle interaction due to both the SPM behavior and the existence of a surface amorphous shell layer (dead layer), the latter reducing systematically as the synthesis temperature increases.

Design, fabrication, and evaluation of a partially melted ice particle cloud facility

NASA Astrophysics Data System (ADS)

Soltis, Jared T.

High altitude ice crystal clouds created by highly convective storm cells are dangerous to jet transport aircraft because the crystals are ingested into the compressor section, partially melt, accrete, and cause roll back or flame out. Current facilities to test engine particle icing are not ideal for fundamental mixed-phase ice accretion experiments or do not generate frozen droplet clouds under representative conditions. The goal of this research was to develop a novel facility capable of testing fundamental partially melted ice particle icing physics and to collect ice accretion data related to mixed-phase ice accretion. The Penn State Icing Tunnel (PSIT) has been designed and fabricated to conduct partially melted ice particle cloud accretion. The PSIT generated a cloud with air assisted atomizing nozzles. The water droplets cool from the 60psi pressure drop as the water exited the nozzle and fully glaciate while flowing in the -11.0°C tunnel air flow. The glaciated cloud flowed through a duct in the center of the tunnel where hot air was introduced. The temperature of the duct was regulated from 3.3°C to 24°C which melted particle the frozen particle from 0% to 90%. The partially melted particle cloud impinged on a temperature controlled flat plate. Ice accretion data was taken for a range of duct temperature from 3.3°C to 24°C and plate temperature from -4.5°C to 7.0°C. The particle median volumetric diameter was 23mum, the total water content was 4.5 g/m 3, the specific humidity was 1.12g/kg, and the wet bulb temperature ranged from 1.0°C to 7.0°C depending on the duct temperature. The boundaries between ice particle bounce off, ice accretion, and water run off were determined. When the particle were totally frozen and the plate surface was below freezing, the ice particle bounced off as expected. Ice accretion was seen for all percent melts tested, but the plate temperature boundary between water runoff and ice accretion increased from 0°C at 8% melt to 3°C at 90%. There were two types of ice accretion with a transition zone in between. The first type of ice was opaque in color and had a rough surface. This ice occurred roughly from 6.0°C to 12.0°C duct temperatures (8% to 50% melt). The qualitative characteristics of the ice were produced from the low water content in the cloud. The water that was available froze instantly and trapped ice particle. Duct temperatures greater than 17.5°C (80% melt) produced ice that was clear and smooth. The water in the surface did not freeze instantly due to the high water content creating a water film that froze. A mixed-phase cloud dynamics model from NASA Glenn was used to estimate the percent melt of the cloud exiting the duct. There was no way to validate the model by directly measuring the percent melt of the cloud, so single particle melt experiments were conducted and compared to the model. A 0.05g/L solution of rhodamine b was sprayed into a levitator and droplets formed at the nodes of the wave. A 532nm green laser was used to illuminate the dye, and the water emitted orange 593nm light given the luminescent properties of the ink. The emitted light intensity was recorded, and a linear relationship between the light intensity of ice to the light intensity of water was used to determine the percent melt of a droplet. The droplets were frozen with a cold flow of nitrogen gas via a liquid nitrogen heat exchanger. The droplets melted under natural convection when the cold nitrogen was shut off. Fifteen cases were compared with droplet diameters ranging from 324mum to 1112mum, air temperatures from 16°C to 31°C, and relative humidities from 41% to 100%. The average discrepancy between predictions and results for the cases that melted slower than ten seconds was 13% while the cases that melted faster than 10 second had 64% discrepancy between the model and experiment. To explain the discrepancy between the experiment and model, sensitivity studies of the model were conducted. It was seen that the melt time from the model was most sensitive to ambient temperature (1s/°C). It was also seen that the thermistors used in the experiment were accurate to 0.7°C. Transient effects of the rhodamine b caused an overshoot in light intensity, making it difficult to accurately determine the melting stop time. These factors led to the difference in melt time between the model and experiments. A 2.7s difference between model and experiments was deemed to be a successful correlation between predictions and experimental results given the model sensitivity to temperature, the difficulty in measuring temperatures at the position of the droplet, and the transient characteristics of rhodamine b.

Improved estimation of anomalous diffusion exponents in single-particle tracking experiments

NASA Astrophysics Data System (ADS)

Kepten, Eldad; Bronshtein, Irena; Garini, Yuval

2013-05-01

The mean square displacement is a central tool in the analysis of single-particle tracking experiments, shedding light on various biophysical phenomena. Frequently, parameters are extracted by performing time averages on single-particle trajectories followed by ensemble averaging. This procedure, however, suffers from two systematic errors when applied to particles that perform anomalous diffusion. The first is significant at short-time lags and is induced by measurement errors. The second arises from the natural heterogeneity in biophysical systems. We show how to estimate and correct these two errors and improve the estimation of the anomalous parameters for the whole particle distribution. As a consequence, we manage to characterize ensembles of heterogeneous particles even for rather short and noisy measurements where regular time-averaged mean square displacement analysis fails. We apply this method to both simulations and in vivo measurements of telomere diffusion in 3T3 mouse embryonic fibroblast cells. The motion of telomeres is found to be subdiffusive with an average exponent constant in time. Individual telomere exponents are normally distributed around the average exponent. The proposed methodology has the potential to improve experimental accuracy while maintaining lower experimental costs and complexity.

Hydrogen generation from water using Mg nanopowder produced by arc plasma method.

PubMed

Uda, Masahiro; Okuyama, Hideo; Suzuki, Tohru S; Sakka, Yoshio

2012-04-01

We report that hydrogen gas can be easily produced from water at room temperature using a Mg nanopowder (30-1000 nm particles, average diameter 265 nm). The Mg nanopowder was produced by dc arc melting of a Mg ingot in a chamber with mixed-gas atmosphere (20% N 2 -80% Ar) at 0.1 MPa using custom-built nanopowder production equipment. The Mg nanopowder was passivated with a gas mixture of 1% O 2 in Ar for 12 h in the final step of the synthesis, after which the nanopowder could be safely handled in ambient air. The nanopowder vigorously reacted with water at room temperature, producing 110 ml of hydrogen gas per 1 g of powder in 600 s. This amount corresponds to 11% of the hydrogen that could be generated by the stoichiometric reaction between Mg and water. Mg(OH) 2 flakes formed on the surface of the Mg particles as a result of this reaction. They easily peeled off, and the generation of hydrogen continued until all the Mg was consumed.

A blood-mimicking fluid for particle image velocimetry with silicone vascular models

NASA Astrophysics Data System (ADS)

Yousif, Majid Y.; Holdsworth, David W.; Poepping, Tamie L.

2011-03-01

For accurate particle image velocimetry measurements in hemodynamics studies, it is important to use a fluid with a refractive index ( n) matching that of the vascular models (phantoms) and ideally a dynamic viscosity matching human blood. In this work, a blood-mimicking fluid (BMF) composed of water, glycerol, and sodium iodide was formulated for a range of refractive indices to match most common silicone elastomers ( n = 1.40-1.43) and with corresponding dynamic viscosity within the average cited range of healthy human blood (4.4 ± 0.5 cP). Both refractive index and viscosity were attained at room temperature (22.2 ± 0.2°C), which eliminates the need for a temperature-control system. An optimally matched BMF, suitable for use in a vascular phantom ( n = 1.4140 ± 0.0008, Sylgard 184), was demonstrated with composition (by weight) of 47.38% water, 36.94% glycerol (44:56 glycerol-water ratio), and 15.68% sodium iodide salt, resulting in a dynamic viscosity of 4 .31 ± 0 .03 cP.

Microstructure and Mechanical Property of 12Cr Oxide Dispersion Strengthened Steel

NASA Astrophysics Data System (ADS)

Xu, Haijian; Lu, Zheng; Jia, Chunyan; Gao, Hao; Liu, Chunming

2016-03-01

Nanostructured oxide dispersion strengthened (ODS) steels with nominal compositions (wt%): Fe-12Cr-2W-0.3Ti-0.3Y2O3 were produced by mechanical alloying and hot isostatic pressing. The microstructure was characterized by means of electron microscopy (EBSD, TEM and HRTEM) and the hardness and the tensile properties at different temperatures were measured. The results showed that the ultimate tensile strength of the fabricated 12Cr-ODS steel reached nearly 1,100 MPa at room temperature and maintained around 340 MPa at 700°C. Nano-oxide particles with size ranging from several nm to 30 nm and the number density was 3.6 × 1020/m3 were observed by TEM. Following heat treatment, including normalizing at 1,100°C for 1 h and tempering at 750°C for 2 h, the average grain size was a little decreased. The number of nano-oxide particles increased and the number density was 8.9 × 1020/m3. Specimens showed much higher ductility and there was a slight increase of ultimate tensile strength and Vickers hardness at the same time.

Thermodynamic Theory of Spherically Trapped Coulomb Clusters

NASA Astrophysics Data System (ADS)

Wrighton, Jeffrey; Dufty, James; Bonitz, Michael; K"{A}Hlert, Hanno

2009-11-01

The radial density profile of a finite number of identical charged particles confined in a harmonic trap is computed over a wide ranges of temperatures (Coulomb coupling) and particle numbers. At low temperatures these systems form a Coulomb crystal with spherical shell structure which has been observed in ultracold trapped ions and in dusty plasmas. The shell structure is readily reproduced in simulations. However, analytical theories which used a mean field approachfootnotetext[1]C. Henning et al., Phys. Rev. E 74, 056403 (2006) or a local density approximationfootnotetext[2]C. Henning et al., Phys. Rev. E 76, 036404 (2007) have, so far, only been able to reproduce the average density profile. Here we present an approach to Coulomb correlations based on the hypernetted chain approximation with additional bridge diagrams. It is demonstrated that this model reproduces the correct shell structure within a few percent and provides the basis for a thermodynamic theory of Coulomb clusters in the strongly coupled fluid state.footnotetext[3]J. Wrighton, J.W. Dufty, H. K"ahlert and M. Bonitz, J. Phys. A 42, 214052 (2009) and Phys. Rev. E (2009) (to be submitted)

Effect of Nb on microstructure and yield strength of a high temperature tempered martensitic steel

NASA Astrophysics Data System (ADS)

Wang, Qian; Sun, Yu; Zhang, Chuanyou; Wang, Qingfeng; Zhang, Fucheng

2018-04-01

Martensitic steels based on a composition of 25CrMo47NbVTi with different concentrations of Nb (0.003%–0.060%) were quenched (Q) at 900 °C and tempered (T) at 700 °C to obtain oil country tubular goods (OCTG) with higher yield strength. The precipitation and microstructures were characterized and quantified by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and x-ray diffraction (XRD). The results show that the increased Nb content led to an enhanced overall precipitation, the rising solution-precipitation temperature, the increased mass or volume fraction of the Nb-containing precipitates, and the decreased average diameter of Nb-containing particles. With the enhanced precipitation of small sized Nb-containing particles, the austenite grain and corresponding martensitic packet and block were evidently refined. In addition, the dislocation density increased slightly with increasing Nb addition. The yield strength was experimentally measured and quantitatively estimated. The findings based on theoretical calculations indicated that as a consequence of intensified strengthening from grain boundaries, precipitates and dislocations, the yield strength was enhanced significantly by Nb addition.

Modelling mass and heat transfer in nano-based cancer hyperthermia.

PubMed

Nabil, M; Decuzzi, P; Zunino, P

2015-10-01

We derive a sophisticated mathematical model for coupled heat and mass transport in the tumour microenvironment and we apply it to study nanoparticle delivery and hyperthermic treatment of cancer. The model has the unique ability of combining the following features: (i) realistic vasculature; (ii) coupled capillary and interstitial flow; (iii) coupled capillary and interstitial mass transfer applied to nanoparticles; and (iv) coupled capillary and interstitial heat transfer, which are the fundamental mechanisms governing nano-based hyperthermic treatment. This is an improvement with respect to previous modelling approaches, where the effect of blood perfusion on heat transfer is modelled in a spatially averaged form. We analyse the time evolution and the spatial distribution of particles and temperature in a tumour mass treated with superparamagnetic nanoparticles excited by an alternating magnetic field. By means of numerical experiments, we synthesize scaling laws that illustrate how nano-based hyperthermia depends on tumour size and vascularity. In particular, we identify two distinct mechanisms that regulate the distribution of particle and temperature, which are characterized by perfusion and diffusion, respectively.

Burn Control in Fusion Reactors via Isotopic Fuel Tailoring

NASA Astrophysics Data System (ADS)

Boyer, Mark D.; Schuster, Eugenio

2011-10-01

The control of plasma density and temperature are among the most fundamental problems in fusion reactors and will be critical to the success of burning plasma experiments like ITER. Economic and technological constraints may require future commercial reactors to operate with low temperature, high-density plasma, for which the burn condition may be unstable. An active control system will be essential for stabilizing such operating points. In this work, a volume-averaged transport model for the energy and the densities of deuterium and tritium fuel ions, as well as the alpha particles, is used to synthesize a nonlinear feedback controller for stabilizing the burn condition. The controller makes use of ITER's planned isotopic fueling capability and controls the densities of these ions separately. The ability to modulate the DT fuel mix is exploited in order to reduce the fusion power during thermal excursions without the need for impurity injection. By moving the isotopic mix in the plasma away from the optimal 50:50 mix, the reaction rate is slowed and the alpha-particle heating is reduced to desired levels. Supported by the NSF CAREER award program (ECCS-0645086).

School bus pollution and changes in the air quality at schools: a case study.

PubMed

Li, Chunlei; Nguyen, Quyen; Ryan, Patrick H; Lemasters, Grace K; Spitz, Henry; Lobaugh, Megan; Glover, Samuel; Grinshpun, Sergey A

2009-05-01

Millions of children attending US schools are exposed to traffic-related air pollutants, including health-relevant ultrafine aerosols generated from school buses powered with diesel fuel. This case study was established in a midwestern (USA) metropolitan area to determine the concentration and elemental composition of aerosol in the vicinity of a public school during morning hours when the bus traffic in and out of the adjacent depot was especially intense. Simultaneous measurements were performed at a control site. The ambient aerosol was first characterized in real time using a particle size selective aerosol spectrometer and then continuously monitored at each site with a real-time non-size-selective instrument that detected particles of 20 nm to >1 microm. In addition, air samples were collected with PM2.5 Harvard Impactors and analyzed for elemental composition using the X-ray fluorescence technique (for 38 elements) and thermal-optical transmittance (for carbon). The measurements were conducted during two seasons: in March at ambient temperature around 0 degrees C and in May when it ranged mostly between 10 and 20 degrees C. The particle number concentration at the test site exhibited high temporal variability while it was time independent at the control site. Overall, the aerosol particle count at the school was 4.7 +/- 1.0 times (March) and 2.2 +/- 0.4 times (May) greater than at the control site. On some days, a 15 min-averaged particle number concentration showed significant correlation with the number of school bus arrivals and departures during these time intervals. On other days, the correlation was less than statistically significant. The 3 h time-averaged particle concentrations determined in the test site on days when the school buses operated were found to be more than two-fold greater (on average) than those measured on bus-free days at the same location, and this difference was statistically significant. Overall, the data suggest a possible association between the number of detected aerosol particles and the school bus traffic intensity. Analysis of the filter samples collected at the school site between 6:00 and 9:00 AM revealed higher concentrations of elemental carbon as compared to the control site (2.8 +/- 0.9 times in March and 3.1 +/- 1.1 times in May). The data collected in this case study suggest that school buses significantly contribute to exposure of children to aerosol pollutants (including diesel exhaust particles) in the school vicinity.

Mass and heat transfer in crushed oil shale

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carley, J.F.; Straub, J.S.; Ott, L.L.

1984-04-01

Heat and mass transfer between gases and oil-shale particles are both important for all proposed retorting processes. Past studies of transfer in packed beds, which have disagreed substantially in their results, have nearly all been done with beds of regular particles of uniform size, whereas oil-shale retorting involves particles of diverse shapes and widely ranging sizes. To resolve these questions, we have made 349 runs in which we measured mass-transfer rates from naphthalene particles of diverse shapes buried in packed beds through which air was passed at room temperature. This technique permits calculation of the mass-transfer coefficient for each activemore » particle in the bed rather than, as in most past studies, for the bed as a whole. The data were analyzed in two ways: (1) by the traditional correlation of Colburn j/sub D/ vs Reynolds number and (2) by multiple regression of the mass-transfer coefficient on air rate, traditional correlation of Colburn j/sub D/ vs Reynolds number and (3) by multiple regression of the mass-transfer coefficient on air rate, sizes of active and inert particles, void fraction, and temperature. Principal findings are: (1) local Reynolds number should be based on active particle size rather than average size for the bed; (2) no appreciable differences were seen between shallow beds and deep ones; (3) mass transfer was 26% faster for spheres and lozenges buried in shale than for all-sphere beds; (4) orientation of lozenges in shale beds has little effect on mass-transfer rate; (5) a useful summarizing equation for either mass or heat transfer in shale beds is log j.epsilon = -.0747 - .6344 log Re + .0592 log/sup 2/Re where j = either j/sub D/ or j/sub H/, the Chilton-Colburn j-factors for mass and heat transfer, Re = the Reynolds number defined for packed beds, and epsilon = the void fraction in the bed. 12 references, 15 figures.« less

A polarimetric scattering database for non-spherical ice particles at microwave wavelengths

NASA Astrophysics Data System (ADS)

Lu, Yinghui; Jiang, Zhiyuan; Aydin, Kultegin; Verlinde, Johannes; Clothiaux, Eugene E.; Botta, Giovanni

2016-10-01

The atmospheric science community has entered a period in which electromagnetic scattering properties at microwave frequencies of realistically constructed ice particles are necessary for making progress on a number of fronts. One front includes retrieval of ice-particle properties and signatures from ground-based, airborne, and satellite-based radar and radiometer observations. Another front is evaluation of model microphysics by application of forward operators to their outputs and comparison to observations during case study periods. Yet a third front is data assimilation, where again forward operators are applied to databases of ice-particle scattering properties and the results compared to observations, with their differences leading to corrections of the model state. Over the past decade investigators have developed databases of ice-particle scattering properties at microwave frequencies and made them openly available. Motivated by and complementing these earlier efforts, a database containing polarimetric single-scattering properties of various types of ice particles at millimeter to centimeter wavelengths is presented. While the database presented here contains only single-scattering properties of ice particles in a fixed orientation, ice-particle scattering properties are computed for many different directions of the radiation incident on them. These results are useful for understanding the dependence of ice-particle scattering properties on ice-particle orientation with respect to the incident radiation. For ice particles that are small compared to the wavelength, the number of incident directions of the radiation is sufficient to compute reasonable estimates of their (randomly) orientation-averaged scattering properties. This database is complementary to earlier ones in that it contains complete (polarimetric) scattering property information for each ice particle - 44 plates, 30 columns, 405 branched planar crystals, 660 aggregates, and 640 conical graupel - and direction of incident radiation but is limited to four frequencies (X-, Ku-, Ka-, and W-bands), does not include temperature dependencies of the single-scattering properties, and does not include scattering properties averaged over randomly oriented ice particles. Rules for constructing the morphologies of ice particles from one database to the next often differ; consequently, analyses that incorporate all of the different databases will contain the most variability, while illuminating important differences between them. Publication of this database is in support of future analyses of this nature and comes with the hope that doing so helps contribute to the development of a database standard for ice-particle scattering properties, like the NetCDF (Network Common Data Form) CF (Climate and Forecast) or NetCDF CF/Radial metadata conventions.

Low temperature growth of ultra-high mass density carbon nanotube forests on conductive supports

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sugime, Hisashi; Esconjauregui, Santiago; Yang, Junwei

2013-08-12

We grow ultra-high mass density carbon nanotube forests at 450 °C on Ti-coated Cu supports using Co-Mo co-catalyst. X-ray photoelectron spectroscopy shows Mo strongly interacts with Ti and Co, suppressing both aggregation and lifting off of Co particles and, thus, promoting the root growth mechanism. The forests average a height of 0.38 μm and a mass density of 1.6 g cm{sup −3}. This mass density is the highest reported so far, even at higher temperatures or on insulators. The forests and Cu supports show ohmic conductivity (lowest resistance ∼22 kΩ), suggesting Co-Mo is useful for applications requiring forest growth onmore » conductors.« less

Note: A temperature-stable low-noise transimpedance amplifier for microcurrent measurement.

PubMed

Xie, Kai; Shi, Xueyou; Zhao, Kai; Guo, Lixin; Zhang, Hanlu

2017-02-01

Temperature stability and noise characteristics often run contradictory in microcurrent (e.g., pA-scale) measurement instruments because low-noise performance requires high-value resistors with relatively poor temperature coefficients. A low-noise transimpedance amplifier with high-temperature stability, which involves an active compensation mechanism to overcome the temperature drift mainly caused by high-value resistors, is presented. The implementation uses a specially designed R-2R compensating network to provide programmable current gain with extra-fine trimming resolution. The temperature drifts of all components (e.g., feedback resistors, operational amplifiers, and the R-2R network itself) are compensated simultaneously. Therefore, both low-temperature drift and ultra-low-noise performance can be achieved. With a current gain of 10 11 V/A, the internal current noise density was about 0.4 fA/√Hz, and the average temperature coefficient was 4.3 ppm/K at 0-50 °C. The amplifier module maintains accuracy across a wide temperature range without additional thermal stabilization, and its compact size makes it especially suitable for high-precision, low-current measurement in outdoor environments for applications such as electrochemical emission supervision, air pollution particles analysis, radiation monitoring, and bioelectricity.

Note: A temperature-stable low-noise transimpedance amplifier for microcurrent measurement

NASA Astrophysics Data System (ADS)

Xie, Kai; Shi, Xueyou; Zhao, Kai; Guo, Lixin; Zhang, Hanlu

2017-02-01

Temperature stability and noise characteristics often run contradictory in microcurrent (e.g., pA-scale) measurement instruments because low-noise performance requires high-value resistors with relatively poor temperature coefficients. A low-noise transimpedance amplifier with high-temperature stability, which involves an active compensation mechanism to overcome the temperature drift mainly caused by high-value resistors, is presented. The implementation uses a specially designed R-2R compensating network to provide programmable current gain with extra-fine trimming resolution. The temperature drifts of all components (e.g., feedback resistors, operational amplifiers, and the R-2R network itself) are compensated simultaneously. Therefore, both low-temperature drift and ultra-low-noise performance can be achieved. With a current gain of 1011 V/A, the internal current noise density was about 0.4 fA/√Hz, and the average temperature coefficient was 4.3 ppm/K at 0-50 °C. The amplifier module maintains accuracy across a wide temperature range without additional thermal stabilization, and its compact size makes it especially suitable for high-precision, low-current measurement in outdoor environments for applications such as electrochemical emission supervision, air pollution particles analysis, radiation monitoring, and bioelectricity.

Microstructure and thermal conductivity of surfactant-free NiO nanostructures

NASA Astrophysics Data System (ADS)

Sahoo, Pranati; Misra, Dinesh K.; Salvador, Jim; Makongo, Julien P. A.; Chaubey, Girija S.; Takas, Nathan J.; Wiley, John B.; Poudeu, Pierre F. P.

2012-06-01

High purity, nanometer sized surfactant-free nickel oxide (NiO) particles were produced in gram scale using a solution combustion method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), gas pycnometry and gas adsorption analysis (BET). The average particle size of the as-synthesized NiO increases significantly with the preheating temperature of the furnace, while the specific surface area decreases. A BET specific surface area of ∼100 m2/g was obtained for NiO nanoparticles with size as small as 3 nm synthesized at 300 °C. The thermal conductivity (κ) of pressed pellets of the synthesized NiO nanoparticles obtained using spark plasma sintering (SPS) and uniaxial hot pressing is drastically decreased (∼60%) compared to that of NiO single crystal. This strong reduction in κ with particle size suggests the suitability of the synthesized surfactant-free NiO nanoparticles for use as nanoinclusions when designing high performance materials for waste heat recovery.

Sliding states of a soft-colloid cluster crystal: Cluster versus single-particle hopping

NASA Astrophysics Data System (ADS)

Rossini, Mirko; Consonni, Lorenzo; Stenco, Andrea; Reatto, Luciano; Manini, Nicola

2018-05-01

We study a two-dimensional model for interacting colloidal particles which displays spontaneous clustering. Within this model we investigate the competition between the pinning to a periodic corrugation potential and a sideways constant pulling force which would promote a sliding state. For a few sample particle densities and amplitudes of the periodic corrugation potential we investigate the depinning from the statically pinned to the dynamically sliding regime. This sliding state exhibits the competition between a dynamics where entire clusters are pulled from a minimum to the next and a dynamics where single colloids or smaller groups leave a cluster and move across the corrugation energy barrier to join the next cluster downstream in the force direction. Both kinds of sliding states can occur either coherently across the entire sample or asynchronously: the two regimes result in different average mobilities. Finite temperature tends to destroy separate sliding regimes, generating a smoother dependence of the mobility on the driving force.

Electrode materials and lithium battery systems

DOEpatents

Amine, Khalil [Downers Grove, IL; Belharouak, Ilias [Westmont, IL; Liu, Jun [Naperville, IL

2011-06-28

A material comprising a lithium titanate comprising a plurality of primary particles and secondary particles, wherein the average primary particle size is about 1 nm to about 500 nm and the average secondary particle size is about 1 .mu.m to about 4 .mu.m. In some embodiments the lithium titanate is carbon-coated. Also provided are methods of preparing lithium titanates, and devices using such materials.

Ultrafine particle levels at an international port of entry between the US and Mexico: exposure implications for users, workers, and neighbors.

PubMed

Olvera, Hector A; Lopez, Mario; Guerrero, Veronica; Garcia, Humberto; Li, Wen-Whai

2013-01-01

Exposure to diesel-emitted particles has been linked to increased cancer risk and cardiopulmonary diseases. Because of their size (<100 nm), exposure to ultrafine particles (UFPs) emitted from heavy-duty diesel vehicles (HDDV) might result in greater health risks than those associated with larger particles. Seasonal UFP levels at the International Bridge of the Americas, which connects the US and Mexico and has high HDDV traffic demands, were characterized. Hourly average UFP concentrations ranged between 1.7 × 10(3)/cc and 2.9 × 10(5)/cc with a mean of 3.5 × 10(4)/cc. Wind speeds <2 m s(-1) and temperatures <15 °C were associated with particle number concentrations above normal conditions. The presence of HDDV had the strongest impact on local UFP levels. Varying particle size distributions were associated with south- and northbound HDDV traffic. Peak exposure occurred on weekday afternoons. Although in winter, high exposure episodes were also observed in the morning. Particle number concentrations were estimated to reach background levels at 400 m away from traffic. The populations exposed to UFP above background levels include law enforcement officers, street vendors, private commuters, and commercial vehicle drivers as well as neighbors on both sides of the border, including a church and several schools.

High-Temperature Mechanical Properties of the P/M Extruded Mg -SiCp Composites

NASA Astrophysics Data System (ADS)

Labib, F.; Mahmudi, R.; Ghasemi, H. M.

2018-03-01

In the present study, pure magnesium reinforced with 0, 5, 10 and 15 vol.% SiC particulates was successfully prepared by powder metallurgy technique before being hot extruded. The average 14 μm grain size of the composite specimens remained almost unchanged after addition of SiC particles, while their dimensional stability was improved because of the reduction in the coefficient of thermal expansion (CTE) from 28.6 × 10-6 K-1 in pure Mg to 27.3, 25.3 and 23.4 × 10-6 K-1 in the Mg-5% SiC, Mg-10% SiC and Mg-15% SiC composites, respectively. Mechanical properties of the specimens were investigated in the temperature range of 298-498 K, implementing shear punch testing and hot hardness techniques. Depending on the test temperature, addition of SiC particles to the pure Mg matrix increased shear yield stress and ultimate shear strength of the materials by 5-25 and 6-23 MPa, respectively. The shear strength improvement was mainly attributed to the CTE mismatch strengthening mechanism (9.5-25.5 MPa), and to a lesser extent (1-4.5 MPa), to the load transfer mechanism. Finally, using the modified Clyne model, the contribution of different strengthening mechanisms to the total shear strength improvement in the composites was evaluated.

Brachial artery responses to ambient pollution, temperature, and humidity in people with type 2 diabetes: a repeated-measures study.

PubMed

Zanobetti, Antonella; Luttmann-Gibson, Heike; Horton, Edward S; Cohen, Allison; Coull, Brent A; Hoffmann, Barbara; Schwartz, Joel D; Mittleman, Murray A; Li, Yongsheng; Stone, Peter H; de Souza, Celine; Lamparello, Brooke; Koutrakis, Petros; Gold, Diane R

2014-03-01

Extreme weather and air pollution are associated with increased cardiovascular risk in people with diabetes. In a population with diabetes, we conducted a novel assessment of vascular brachial artery responses both to ambient pollution and to weather (temperature and water vapor pressure, a measure of humidity). Sixty-four 49- to 85-year-old Boston residents with type 2 diabetes completed up to five study visits (279 repeated measures). Brachial artery diameter (BAD) was measured by ultrasound before and after brachial artery occlusion [i.e., flow-mediated dilation (FMD)] and before and after nitroglycerin-mediated dilation (NMD). Ambient concentrations of fine particulate mass (PM2.5), black carbon (BC), organic carbon (OC), elemental carbon, particle number, and sulfate were measured at our monitoring site; ambient concentrations of carbon monoxide, nitrogen dioxide, and ozone were obtained from state monitors. Particle exposure in the home and during each trip to the clinic (home/trip exposure) was measured continuously and as a 5-day integrated sample. We used linear models with fixed effects for participants, adjusting for date, season, temperature, and water vapor pressure on the day of each visit, to estimate associations between our outcomes and interquartile range increases in exposure. Baseline BAD was negatively associated with particle pollution, including home/trip-integrated BC (-0.02 mm; 95% CI: -0.04, -0.003, for a 0.28 μg/m3 increase in BC), OC (-0.08 mm; 95% CI: -0.14, -0.03, for a 1.61 μg/m3 increase) as well as PM2.5, 5-day average ambient PM2.5, and BC. BAD was positively associated with ambient temperature and water vapor pressure. However, exposures were not consistently associated with FMD or NMD. Brachial artery diameter, a predictor of cardiovascular risk, decreased in association with particle pollution and increased in association with ambient temperature in our study population of adults with type 2 diabetes. Zanobetti A, Luttmann-Gibson H, Horton ES, Cohen A, Coull BA, Hoffmann B, Schwartz JD, Mittleman MA, Li Y, Stone PH, de Souza C, Lamparello B, Koutrakis P, Gold DR. 2014. Brachial artery responses to ambient pollution, temperature, and humidity in people with type 2 diabetes: a repeated-measures study. Environ Health Perspect 122:242-248; http://dx.doi.org/10.1289/ehp.1206136.

Sources and chemical composition of atmospheric fine and coarse particles in the Helsinki area

NASA Astrophysics Data System (ADS)

Pakkanen, Tuomo A.; Loukkola, Kati; Korhonen, Christina H.; Aurela, Minna; Mäkelä, Timo; Hillamo, Risto E.; Aarnio, Päivi; Koskentalo, Tarja; Kousa, Anu; Maenhaut, Willy

During April 1996-June 1997 size-segregated atmospheric aerosol particles were collected at an urban and a rural site in the Helsinki area by utilising virtual impactors (VI) and Berner low-pressure impactors (BLPI). In addition, VI samples were collected at a semi-urban site during October 1996-May 1997. The average PM 2.3 (fine particle) concentrations at the urban and rural sites were 11.8 and 8.4 μg/m 3, and the PM 2.3-15 (coarse particle) concentrations were 12.8 and about 5 μg/m 3, respectively. The difference in fine particle mass concentrations suggests that on average, more than one third of the fine mass at the urban site is of local origin. Evaporation of fine particle nitrate from the VI Teflon filters during sampling varied similarly at the three sites, the average evaporation being about 50-60%. The average fine particle concentrations of the chemical components (25 elements and 13 ions) appeared to be fairly similar at the three sites for most components, which suggests that despite the long-range transport, the local emissions of these components were relatively evenly distributed in the Helsinki area. Exceptions were the average fine particles Ba, Fe, Sb and V concentrations that were clearly highest at the urban site pointing to traffic (Ba, Fe, Sb) and to combustion of heavy fuel oil (V) as the likely local sources. The average coarse particle concentrations for most components were highest at the urban site and lowest at the rural site. Average chemical composition of fine particles was fairly similar at the urban and rural sites: non-analysed fraction (mainly carbonaceous material and water) 43% and 37%, sulphate 21% and 25%, crustal matter 12% and 13%, nitrate 12% and 11%, ammonium 9% and 10% and sea-salt 2.5% and 3.2%, respectively. At the semi-urban site also, the average fine particle composition was similar. At the urban site, the year round average composition of coarse particles was dominated by crustal matter (59%) and the non-analysed components (28%, mainly carbonaceous material and water), while the other contributions were much lower: sea-salt 7%, nitrate 4% and sulphate 2%. At the rural site, the coarse samples were collected in spring and summer and the percentage was clearly lower for crustal matter (37%) and sea-salt (3%) but higher for the not-analysed fraction (51%). At the semi-urban site, the average composition of coarse particles was nearly identical to that at the urban site. Correlations between the chemical components were calculated separately for fine and coarse particles. In urban fine particles sulphate, ammonium, Tl, oxalate and PM 2.3 mass correlated with each other and originated mainly from long-range transport. The sea-salt ions Na +, Cl - and Mg 2+ formed another group and still another group was formed by the organic anions oxalate, malonate, succinate, glutarate and methane sulphonate. Ni and V correlated strongly pointing to combustion of heavy fuel oil as the likely source. In addition, some groups with lower correlations were detected. At the rural and semi-urban sites, the correlating components were rather similar to those at the urban site, although differences were also observed.

Temperature-responsive nanogel multilayers of poly(N-vinylcaprolactam) for topical drug delivery.

PubMed

Zavgorodnya, Oleksandra; Carmona-Moran, Carlos A; Kozlovskaya, Veronika; Liu, Fei; Wick, Timothy M; Kharlampieva, Eugenia

2017-11-15

We report nanothin temperature-responsive hydrogel films of poly(N-vinylcaprolactam) nanoparticles (νPVCL) with remarkably high loading capacity for topical drug delivery. Highly swollen (νPVCL) n multilayer hydrogels, where n denotes the number of nanoparticle layers, are produced by layer-by-layer hydrogen-bonded assembly of core-shell PVCL-co-acrylic acid nanoparticles with linear PVPON followed by cross-linking of the acrylic acid shell with either ethylene diamine (EDA) or adipic acid dihydrazide (AAD). We demonstrate that a (νPVCL) 5 film undergoes dramatic and reversible swelling up to 9 times its dry thickness at pH = 7.5, indicating 89v/v % of water inside the network. These hydrogels exhibit highly reversible ∼3-fold thickness changes with temperature variations from 25 to 50°C at pH = 5, the average pH of human skin. We also show that a (νPVCL) 30 hydrogel loaded with ∼120µgcm -2 sodium diclofenac, a non-steroidal anti-inflammatory drug used for osteoarthritis pain management, provides sustained permeation of this drug through an artificial skin membrane for up to 24h at 32°C (the average human skin surface temperature). The cumulative amount of diclofenac transported at 32°C from the (νPVCL) 30 hydrogel after 24h is 12 times higher than that from the (νPVCL) 30 hydrogel at 22°C. Finally, we demonstrate that the (νPVCL) hydrogels can be used for multiple drug delivery by inclusion of Nile red, fluorescein and DAPI dyes within the νPVCL nanoparticles prior to hydrogel assembly. Using confocal microscopy we observed the presence of separate dye-loaded νPVCL compartments within the hydrogel matrix with all three dyes confined to the nanogel particles without intermixing between the dyes. Our study provides opportunity for development of temperature-responsive multilayer hydrogel coatings made via the assembly of core-shell nanogel particles which can be used for skin-sensitive materials for topical drug delivery. Copyright © 2017 Elsevier Inc. All rights reserved.

Lignin nanoparticle synthesis

DOEpatents

Dirk, Shawn M.; Cicotte, Kirsten Nicole; Wheeler, David R.; Benko, David A.

2015-08-11

A method including reducing a particle size of lignin particles to an average particle size less than 40 nanometers; after reducing the particle size, combining the lignin particles with a polymeric material; and forming a structure of the combination. A method including exposing lignin to a diazonium precursor including a functional group; modifying the lignin by introducing the functional group to the lignin; and combining the modified lignin with a polymeric material to form a composite. An apparatus including a composite of a polymer and lignin wherein the lignin has an average particle size less than 100 micrometers.

Nanostructure investigation of magnetic nanomaterial Ni{sub 0.5}Zn{sub 0.3}Cu{sub 0.2}Fe{sub 2}O{sub 4} synthesized by sol-gel method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pransisco, Prengki, E-mail: prengkipransisco@gmail.com; Badan Lingkungan Hidup Derah Kabupaten Empat Lawang South of Sumatera; Shafie, Afza, E-mail: afza@petronas.com.my

2015-07-22

Magnetic nanomaterial Ni{sub 0.5}Zn{sub 0.3}Cu{sub 0.2}Fe{sub 2}O{sub 4} was successfully prepared by using sol-gel method. Heat treatment on material is always giving defect on properties of material. This paper investigates the effect of heat treatment on nanostructure of magnetic nanomaterial Ni{sub 0.5}Zn{sub 0.3}Cu{sub 0.2}Fe{sub 2}O{sub 4}. According to thermo gravimetric analysis (TGA) that after 600°C there is no more weight loss detected and it was decided as minimum calcination temperature. Intensity, crystallite size, structure, lattice parameter and d-spacing of the material were investigated by using X-ray diffraction (XRD). High resolution transmission electron microscope (HRTEM) was used to examine nanostructure, nanosize,more » shape and distribution particle of magnetic material Ni{sub 0.5}Zn{sub 0.3}Cu{sub 0.2}Fe{sub 2}O{sub 4} and variable pressure field emission scanning electron microscope (VP-FESEM) was used to investigate the surface morphology and topography of the material. The XRD result shows single-phase cubic spinel structure with average crystallite size in the range of 25.6-95.9 nm, the value of the intensity of the material was increased with increasing temperature, and followed by lattice parameter was increased with increasing calcination temperature, value of d-spacing was relatively decreased with accompanied increasing temperature. From HRTEM result the distribution of particles was tend to be agglomerates with particle size of 7.8-17.68 nm. VP-FESEM result shows that grain size of the material increases with increasing calcination temperature and the surface morphology shows that the material is in hexagonal shape and it was also proved by mapping result which showing the presence each of constituents inside the compound.« less

Fresnel Lorentz Microscopy Imaging of Domains in Fe3O4 Nanoparticle Arrays

NASA Astrophysics Data System (ADS)

Majetich, S. A.; Evarts, E. R.; Hogg, C.; Yamamoto, K.; Hirayama, T.

2009-03-01

Fresnel Lorentz microscopy was used to study the magnetic domain structures of self-assembled nanoparticle arrays as a function of temperature, from 24 to 605 C. 11 nm diameter Fe3O4 nanoparticles with an edge-to-edge spacing of 2.5 nm form magnetic domains through magnetostatic interactions alone. At room temperature stripe domains were evident in monolayer arrays. The average domain size in monolayer regions is larger than that in bilayers. Mean field theories predict a reduced stabilization energy for bilayers, relative to that for monolayers. The domain wall positions were fairly stable up to 500 C, though the contrast in the walls diminished, indicating reduced magnetic order. Above 500 C there were large temperature-dependent changes. The walls surrounding the smaller domains disappeared at lower temperatures than those of the larger domains. Some magnetic contrast was visible up to 575 C, close to the Curie temperature of Fe3O4 (585 C). Transmission electron microscopy after cooling showed that the particle shape and position in the ordered arrays had been preserved during the high temperature imaging experiments.

KEY RESULTS FROM IRRADIATION AND POST-IRRADIATION EXAMINATION OF AGR-1 UCO TRISO FUEL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Demkowicz, Paul A.; Hunn, John D.; Petti, David A.

The AGR-1 irradiation experiment was performed as the first test of tristructural isotropic (TRISO) fuel in the US Advanced Gas Reactor Fuel Development and Qualification Program. The experiment consisted of 72 right cylinder fuel compacts containing approximately 3×105 coated fuel particles with uranium oxide/uranium carbide (UCO) fuel kernels. The fuel was irradiated in the Advanced Test Reactor for a total of 620 effective full power days. Fuel burnup ranged from 11.3 to 19.6% fissions per initial metal atom and time average, volume average irradiation temperatures of the individual compacts ranged from 955 to 1136°C. This paper focuses on key resultsmore » from the irradiation and post-irradiation examination, which revealed a robust fuel with excellent performance characteristics under the conditions tested and have significantly improved the understanding of UCO coated particle fuel irradiation behavior within the US program. The fuel exhibited a very low incidence of TRISO coating failure during irradiation and post-irradiation safety testing at temperatures up to 1800°C. Advanced PIE methods have allowed particles with SiC coating failure to be isolated and meticulously examined, which has elucidated the specific causes of SiC failure in these specimens. The level of fission product release from the fuel during irradiation and post-irradiation safety testing has been studied in detail. Results indicated very low release of krypton and cesium through intact SiC and modest release of europium and strontium, while also confirming the potential for significant silver release through the coatings depending on irradiation conditions. Focused study of fission products within the coating layers of irradiated particles down to nanometer length scales has provided new insights into fission product transport through the coating layers and the role various fission products may have on coating integrity. The broader implications of these results and the application of lessons learned from AGR-1 to fuel fabrication and post-irradiation examination for subsequent fuel irradiation experiments as part of the US fuel program is also discussed.« less

Key results from irradiation and post-irradiation examination of AGR-1 UCO TRISO fuel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Demkowicz, Paul A.; Hunn, John D.; Petti, David A.

The AGR-1 irradiation experiment was performed as the first test of tristructural isotropic (TRISO) fuel in the US Advanced Gas Reactor Fuel Development and Qualification Program. The experiment consisted of 72 right cylinder fuel compacts containing approximately 3 × 105 coated fuel particles with uranium oxide/uranium carbide (UCO) fuel kernels. The fuel was irradiated in the Advanced Test Reactor for a total of 620 effective full power days. Fuel burnup ranged from 11.3 to 19.6% fissions per initial metal atom and time-average, volume-average irradiation temperatures of the individual compacts ranged from 955 to 1136 °C. This paper focuses on keymore » results from the irradiation and post-irradiation examination, which revealed a robust fuel with excellent performance characteristics under the conditions tested and have significantly improved the understanding of UCO coated particle fuel irradiation behavior. The fuel exhibited zero TRISO coating failures (failure of all three dense coating layers) during irradiation and post-irradiation safety testing at temperatures up to 1700 °C. Advanced PIE methods have allowed particles with SiC coating failure that were discovered to be present in a very-low population to be isolated and meticulously examined, which has elucidated the specific causes of SiC failure in these specimens. The level of fission product release from the fuel during irradiation and post-irradiation safety testing has been studied in detail. Results indicated very low release of krypton and cesium through intact SiC and modest release of europium and strontium, while also confirming the potential for significant silver release through the coatings depending on irradiation conditions. Focused study of fission products within the coating layers of irradiated particles down to nanometer length scales has provided new insights into fission product transport through the coating layers and the role various fission products may have on coating integrity. The broader implications of these results and the application of lessons learned from AGR-1 to fuel fabrication and post-irradiation examination for subsequent fuel irradiation experiments as part of the US fuel program are also discussed.« less

Key results from irradiation and post-irradiation examination of AGR-1 UCO TRISO fuel

DOE PAGES

Demkowicz, Paul A.; Hunn, John D.; Petti, David A.; ...

2017-09-10

The AGR-1 irradiation experiment was performed as the first test of tristructural isotropic (TRISO) fuel in the US Advanced Gas Reactor Fuel Development and Qualification Program. The experiment consisted of 72 right cylinder fuel compacts containing approximately 3 × 105 coated fuel particles with uranium oxide/uranium carbide (UCO) fuel kernels. The fuel was irradiated in the Advanced Test Reactor for a total of 620 effective full power days. Fuel burnup ranged from 11.3 to 19.6% fissions per initial metal atom and time-average, volume-average irradiation temperatures of the individual compacts ranged from 955 to 1136 °C. This paper focuses on keymore » results from the irradiation and post-irradiation examination, which revealed a robust fuel with excellent performance characteristics under the conditions tested and have significantly improved the understanding of UCO coated particle fuel irradiation behavior. The fuel exhibited zero TRISO coating failures (failure of all three dense coating layers) during irradiation and post-irradiation safety testing at temperatures up to 1700 °C. Advanced PIE methods have allowed particles with SiC coating failure that were discovered to be present in a very-low population to be isolated and meticulously examined, which has elucidated the specific causes of SiC failure in these specimens. The level of fission product release from the fuel during irradiation and post-irradiation safety testing has been studied in detail. Results indicated very low release of krypton and cesium through intact SiC and modest release of europium and strontium, while also confirming the potential for significant silver release through the coatings depending on irradiation conditions. Focused study of fission products within the coating layers of irradiated particles down to nanometer length scales has provided new insights into fission product transport through the coating layers and the role various fission products may have on coating integrity. The broader implications of these results and the application of lessons learned from AGR-1 to fuel fabrication and post-irradiation examination for subsequent fuel irradiation experiments as part of the US fuel program are also discussed.« less

New Particle Formation and Growth in an Isoprene-Dominated Ozark Forest: From Sub-5 nm to CCN-Active Sizes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, Huan; Ortega, John; Smith, James N.

Particle Investigations at a Northern Ozarks Tower: NOx, Oxidant, Isoprene Research (PINOT-NOIR) were conducted in a Missouri forest dominated by isoprene emissions, from May to October 2012. This study presents results of new particle formation (NPF) and the growth of new particles to cloud condensation nuclei (CCN)-active sizes (~100 nm) observed from this field campaign. The measured sub-5 nm particles were up to ~20000 cm-3 during a typical NPF event. Nucleation rates J1 were relatively high (11.0±10.6 cm-3s-1), and one order of magnitude higher than formation rates of 5 nm particles (J5). Sub-5 nm particle events were observed on 64%more » of the measurement days, with a high preference in biogenic volatile organic compounds (BVOCs)- and SO2-poor northwesterly (90%) air masses than in BVOCs-rich southerly air masses (13%). About 80% of sub-5 nm particle events led to the further growth. While high temperatures and high aerosol loadings in the southerly air masses were not favorable for nucleation, high BVOCs in the southerly air masses facilitated the growth of new particles to CCN-active sizes. In overall, 0.4-9.4% of the sub-5 nm particles grew to CCN-active sizes within a NPF event. During a regional NPF event period that took place consecutively over several days, concentrations of CCN size particles increased by a factor of 5 in average. This enhanced production of CCN particles from new particles was commonly observed during all 13 regional NPF events observed during the campaign.« less

Characteristics of Fine Particles in an Urban Atmosphere-Relationships with Meteorological Parameters and Trace Gases.

PubMed

Zhang, Tianhao; Zhu, Zhongmin; Gong, Wei; Xiang, Hao; Fang, Ruimin

2016-08-10

Atmospheric fine particles (diameter < 1 μm) attract a growing global health concern and have increased in urban areas that have a strong link to nucleation, traffic emissions, and industrial emissions. To reveal the characteristics of fine particles in an industrial city of a developing country, two-year measurements of particle number size distribution (15.1 nm-661 nm), meteorological parameters, and trace gases were made in the city of Wuhan located in central China from June 2012 to May 2014. The annual average particle number concentrations in the nucleation mode (15.1 nm-30 nm), Aitken mode (30 nm-100 nm), and accumulation mode (100 nm-661 nm) reached 4923 cm(-3), 12193 cm(-3) and 4801 cm(-3), respectively. Based on Pearson coefficients between particle number concentrations and meteorological parameters, precipitation and temperature both had significantly negative relationships with particle number concentrations, whereas atmospheric pressure was positively correlated with the particle number concentrations. The diurnal variation of number concentration in nucleation mode particles correlated closely with photochemical processes in all four seasons. At the same time, distinct growth of particles from nucleation mode to Aitken mode was only found in spring, summer, and autumn. The two peaks of Aitken mode and accumulation mode particles in morning and evening corresponded obviously to traffic exhaust emissions peaks. A phenomenon of "repeated, short-lived" nucleation events have been created to explain the durability of high particle concentrations, which was instigated by exogenous pollutants, during winter in a case analysis of Wuhan. Measurements of hourly trace gases and segmental meteorological factors were applied as proxies for complex chemical reactions and dense industrial activities. The results of this study offer reasonable estimations of particle impacts and provide references for emissions control strategies in industrial cities of developing countries.

Seasonal Dynamics of Particle-Associated Ammonia-Oxidizing Archaea in Monterey Bay, CA

NASA Astrophysics Data System (ADS)

Powell, D. R.; Tolar, B. B.; Francis, C.

2016-12-01

Within the past decade, significant research has shed light on key players within the nitrogen cycle. Ammonia-oxidizing Archaea (AOA) were discovered and found to be more abundant than ammonia-oxidizing Bacteria in marine systems, and therefore play a vital role in ammonia oxidation, the rate-limiting step in nitrification that converts NH3 to NO2-. Here we investigated seasonal dynamics of particle-associated (> 10 µm) AOA within Monterey Bay at Station M1 over a year-long sampling period from May 2015 to February 2016. We used quantitative PCR to amplify the archaeal amoA gene and collect data on the abundance of this gene at various depths (5-500 m). Our results indicate that particle-associated AOA are found throughout the upper water column in Monterey Bay, with archaeal amoA gene abundances ranging from 3.9 x 101 to 1.0 x 104 copies/L, with an average of 1.7 x 103 copies/L. Seasonal trends indicate that gene abundance is higher during the winter than in summer. We also quantified `shallow' versus `deep' ecotypes of water column AOA (WCA and WCB, respectively. These data will be compared to environmental data (temperature, salinity, chlorophyll a, etc.) collected during sampling. In comparison to the 0.2µm samples analyzed (mean = 2.2 x 107 copies/L; range = 2.4 x 104 to 1.1 x 108 copies/L), particle-associated archaeal amoA genes were on average 0.01% of the 0.2-10 µm size fraction. Although relatively small, the combined total abundance between the two size fractions may lead to additional correlations. Overall, particle-associated AOA may be important indicators of changing environmental conditions and provide seasonal context into abundance and distribution of these AOA. We also suggest that it may be a useful practice to analyze prefilters for AOA, as particle-associated AOA may contribute significantly to gene abundance estimates and possibly correlations with nitrification rates.

Public health risks of prolonged fine particle events associated with stagnation and air quality index based on fine particle matter with a diameter <2.5 μm in the Kaoping region of Taiwan

NASA Astrophysics Data System (ADS)

Lai, Li-Wei

2016-12-01

The increasing frequency of droughts in tropical and sub-tropical areas since 1970 due to climate change requires a better understanding of the relationship between public health and long-duration fine particle events (FPE; defined as a day with an average PM2.5 ≥ 35.5 μg/m3) associated with rainfall and wind speed. In the Kaoping region of Taiwan, 94.46 % of the daily average PM2.5 in winter exceeds the limit established by 2005 World Health Organization (WHO) guidelines. This study investigated the differences in winter weather characteristics and health effects between non-FPE and FPE days, and the performance of air quality indexes on FPE days. Z-statistics for one-tailed tests, multiplicative decomposition models, logarithmic regression, and product-moment correlations were used for the analysis. The results indicate that mean wind speeds, rainfall hours, and air temperature were significantly decreased on FPE days. Daily mean PM2.5 concentrations were positively correlated to the duration of FPE days. The duration of FPE days was positively related to the length of drought ( r = 0.97, P < 0.05). The number of respiratory admissions was positively correlated with the FPE duration ( r 2 = 0.60). The age groups >15 years experienced the largest average reduction in asthma admissions on lag-days. Compared to the pollutant standard index (PSI) and revised air quality index (RAQI), the PM2.5 index is more representative and sensitive to changes in PM2.5 concentrations.

Modeling Interactions Among Turbulence, Gas-Phase Chemistry, Soot and Radiation Using Transported PDF Methods

NASA Astrophysics Data System (ADS)

Haworth, Daniel

2013-11-01

The importance of explicitly accounting for the effects of unresolved turbulent fluctuations in Reynolds-averaged and large-eddy simulations of chemically reacting turbulent flows is increasingly recognized. Transported probability density function (PDF) methods have emerged as one of the most promising modeling approaches for this purpose. In particular, PDF methods provide an elegant and effective resolution to the closure problems that arise from averaging or filtering terms that correspond to nonlinear point processes, including chemical reaction source terms and radiative emission. PDF methods traditionally have been associated with studies of turbulence-chemistry interactions in laboratory-scale, atmospheric-pressure, nonluminous, statistically stationary nonpremixed turbulent flames; and Lagrangian particle-based Monte Carlo numerical algorithms have been the predominant method for solving modeled PDF transport equations. Recent advances and trends in PDF methods are reviewed and discussed. These include advances in particle-based algorithms, alternatives to particle-based algorithms (e.g., Eulerian field methods), treatment of combustion regimes beyond low-to-moderate-Damköhler-number nonpremixed systems (e.g., premixed flamelets), extensions to include radiation heat transfer and multiphase systems (e.g., soot and fuel sprays), and the use of PDF methods as the basis for subfilter-scale modeling in large-eddy simulation. Examples are provided that illustrate the utility and effectiveness of PDF methods for physics discovery and for applications to practical combustion systems. These include comparisons of results obtained using the PDF method with those from models that neglect unresolved turbulent fluctuations in composition and temperature in the averaged or filtered chemical source terms and/or the radiation heat transfer source terms. In this way, the effects of turbulence-chemistry-radiation interactions can be isolated and quantified.

Application of asymmetric flow-field flow fractionation to the characterization of colloidal dispersions undergoing aggregation.

PubMed

Lattuada, Marco; Olivo, Carlos; Gauer, Cornelius; Storti, Giuseppe; Morbidelli, Massimo

2010-05-18

The characterization of complex colloidal dispersions is a relevant and challenging problem in colloidal science. In this work, we show how asymmetric flow-field flow fractionation (AF4) coupled to static light scattering can be used for this purpose. As an example of complex colloidal dispersions, we have chosen two systems undergoing aggregation. The first one is a conventional polystyrene latex undergoing reaction-limited aggregation, which leads to the formation of fractal clusters with well-known structure. The second one is a dispersion of elastomeric colloidal particles made of a polymer with a low glass transition temperature, which undergoes coalescence upon aggregation. Samples are withdrawn during aggregation at fixed times, fractionated with AF4 using a two-angle static light scattering unit as a detector. We have shown that from the analysis of the ratio between the intensities of the scattered light at the two angles the cluster size distribution can be recovered, without any need for calibration based on standard elution times, provided that the geometry and scattering properties of particles and clusters are known. The nonfractionated samples have been characterized also by conventional static and dynamic light scattering to determine their average radius of gyration and hydrodynamic radius. The size distribution of coalescing particles has been investigated also through image analysis of cryo-scanning electron microscopy (SEM) pictures. The average radius of gyration and the average hydrodynamic radius of the nonfractionated samples have been calculated and successfully compared to the values obtained from the size distributions measured by AF4. In addition, the data obtained are also in good agreement with calculations made with population balance equations.

Complex Refractive Index of Ice Fog at a Radio Wavelength of 3 mm

DTIC Science & Technology

1974-10-01

particles on mirror surface 55 41. Liberally dusting mirror with 3-// polystyrene dust produces almost no effect 56 —" -.-.—-- ■ .■..^„^-^aa...spheres, as Debye (1929) did in his original theory. The rotation of these spheres in a viscous medium is opposed by forces related by Stoke’s law to...given by a relation of the form ,_ C „D/kT E/RT Z 0 where R k ■ M.C \\s only slightly temperature dependent, and n/w is the average time required by

Optical enhancement of phosphor-converted wLEDs using glass beads

NASA Astrophysics Data System (ADS)

Güner, Tuğrul; Şentürk, Ufuk; Demir, Mustafa M.

2017-10-01

YAG:Ce3+ is a yellow-source compound commonly used in phosphor conversion layers for direct coating or remote phosphor configurations in LED illumination. This material, however, suffers from a high correlated color temperature, and low color-rendering index due to its deficiency in the red spectrum. In this study, glass beads (GB) with an average particle diameter of 10 μm were introduced to the conversion layer of a YAG:Ce3+ particulate-filled polydimethylsiloxane matrix composite structure and found to improve the optical features of the resulting composite.

Deformation characteristics and time-dependent notch sensitivity of Udimet 700 at intermediate temperatures

NASA Technical Reports Server (NTRS)

Wilson, D. J.

1975-01-01

Time-dependent notch sensitivity of Udimet 700 sheet, bar, and investment castings was observed between 1000 and 1400 F (538-760 C) but not at 1600 F (871 C). As was the case for Modified Waspaloy, Waspaloy, Rene 41, Inconel 718, and TD-NiCr, it occurred when notched specimens were loaded below the yield strength and when creep deformation was localized. For each gamma-prime strengthened alloy and notched specimen geometry, a stress-average particle size zone can be defined to characterize the notch-sensitive behavior.

Collisionless dissipation in quasi-perpendicular shocks. [in terresrial bow waves

NASA Technical Reports Server (NTRS)

Forslund, D. W.; Quest, K. B.; Brackbill, J. U.; Lee, K.

1984-01-01

Microscopic dissipation processes in quasi-perpendicular shocks are studied by two-dimensional plasma simulations in which electrons and ions are treated as particles moving in self-consistent electric and magnetic fields. Cross-field currents induce substantial turbulence at the shock front reducing the reflected ion fraction, increasing the bulk ion temperature behind the shock, doubling the average magnetic ramp thickness, and enhancing the upstream field aligned electron heat flow. The short scale length magnetic fluctuations observed in the bow shock are probably associated with this turbulence.

Effective temperatures of hot Brownian motion.

PubMed

Falasco, G; Gnann, M V; Rings, D; Kroy, K

2014-09-01

We derive generalized Langevin equations for the translational and rotational motion of a heated Brownian particle from the fluctuating hydrodynamics of its nonisothermal solvent. The temperature gradient around the particle couples to the hydrodynamic modes excited by the particle itself so that the resulting noise spectrum is governed by a frequency-dependent temperature. We show how the effective temperatures at which the particle coordinates and (angular) velocities appear to be thermalized emerge from this central quantity.

Reduction of particle deposition on substrates using temperature gradient control

DOEpatents

Rader, Daniel J.; Dykhuizen, Ronald C.; Geller, Anthony S.

2000-01-01

A method of reducing particle deposition during the fabrication of microelectronic circuitry is presented. Reduction of particle deposition is accomplished by controlling the relative temperatures of various parts of the deposition system so that a large temperature gradient near the surface on which fabrication is taking place exists. This temperature gradient acts to repel particles from that surface, thereby producing cleaner surfaces, and thus obtaining higher yields from a given microelectronic fabrication process.

Formation characteristics of aerosol particles from pulverized coal pyrolysis in high-temperature environments.

PubMed

Chen, Wei-Hsin; Du, Shan-Wen; Yang, Hsi-Hsien; Wu, Jheng-Syun

2008-05-01

The formation characteristics of aerosol particles from pulverized coal pyrolysis in high temperatures are studied experimentally. By conducting a drop-tube furnace, fuel pyrolysis processes in industrial furnaces are simulated in which three different reaction temperatures of 1000, 1200, and 1400 degrees C are considered. Experimental observations indicate that when the reaction temperature is 1000 degrees C, submicron particles are produced, whereas the particle size is dominated by nanoscale for the temperature of 1400 degrees C. Thermogravimetric analysis of the aerosol particles stemming from the pyrolysis temperature of 1000 degrees C reveals that the thermal behavior of the aerosol is characterized by a three-stage reaction with increasing heating temperature: (1) a volatile-reaction stage, (2) a weak-reaction stage, and (3) a soot-reaction stage. However, with the pyrolysis temperature of 1400 degrees C, the volatile- and weak-reaction stages almost merge together and evolve into a chemical-frozen stage. The submicron particles (i.e., 1000 degrees C) are mainly composed of volatiles, tar, and soot, with the main component of the nanoscale particles (i.e., 1400 degrees C) being soot. The polycyclic aromatic hydrocarbons (PAHs) contained in the aerosols are also analyzed. It is found that the PAH content in generated aerosols decreases dramatically as the pyrolysis temperature increases.

Space reactor fuel element testing in upgraded TREAT

NASA Astrophysics Data System (ADS)

Todosow, Michael; Bezler, Paul; Ludewig, Hans; Kato, Walter Y.

1993-01-01

The testing of candidate fuel elements at prototypic operating conditions with respect to temperature, power density, hydrogen coolant flow rate, etc., is a crucial component in the development and qualification of nuclear rocket engines based on the Particle Bed Reactor (PBR), NERVA-derivative, and other concepts. Such testing may be performed at existing reactors, or at new facilities. A scoping study has been performed to assess the feasibility of testing PBR based fuel elements at the TREAT reactor. Initial results suggests that full-scale PBR elements could be tested at an average energy deposition of ˜60-80 MW-s/L in the current TREAT reactor. If the TREAT reactor was upgraded to include fuel elements with a higher temperture limit, average energy deposition of ˜100 MW/L may be achievable.

High-average-power laser medium based on silica glass

NASA Astrophysics Data System (ADS)

Fujimoto, Yasushi; Nakatsuka, Masahiro

2000-01-01

Silica glass is one of the most attractive materials for a high-average-power laser. We have developed a new laser material base don silica glass with zeolite method which is effective for uniform dispersion of rare earth ions in silica glass. High quality medium, which is bubbleless and quite low refractive index distortion, must be required for realization of laser action. As the main reason of bubbling is due to hydroxy species remained in the gelation same, we carefully choose colloidal silica particles, pH value of hydrochloric acid for hydrolysis of tetraethylorthosilicate on sol-gel process, and temperature and atmosphere control during sintering process, and then we get a bubble less transparent rare earth doped silica glass. The refractive index distortion of the sample also discussed.

Drift turbulence, particle transport, and anomalous dissipation at the reconnecting magnetopause

NASA Astrophysics Data System (ADS)

Le, A.; Daughton, W.; Ohia, O.; Chen, L.-J.; Liu, Y.-H.; Wang, S.; Nystrom, W. D.; Bird, R.

2018-06-01

Using fully kinetic 3D simulations, the reconnection dynamics of asymmetric current sheets are examined at the Earth's magnetopause. The plasma parameters are selected to model MMS magnetopause diffusion region crossings with guide fields of 0.1, 0.4, and 1 of the reconnecting magnetosheath field. In each case, strong drift-wave fluctuations are observed in the lower-hybrid frequency range at the steep density gradient across the magnetospheric separatrix. These fluctuations give rise to cross-field electron particle transport. In addition, this turbulent mixing leads to significantly enhanced electron parallel heating in comparison to 2D simulations. We study three different methods of quantifying the anomalous dissipation produced by the drift fluctuations, based on spatial averaging, temporal averaging, and temporal averaging followed by integrating along magnetic field lines. A comparison of different methods reveals complications in identifying and measuring the anomalous dissipation. Nevertheless, the anomalous dissipation from short wavelength drift fluctuations appears weak for each case, and the reconnection rates observed in 3D are nearly the same as in 2D models. The 3D simulations feature a number of interesting new features that are consistent with recent MMS observations, including cold beams of magnetosheath electrons that penetrate into the hotter magnetospheric inflow, the related observation of decreasing temperature in regions of increasing total density, and an effective turbulent diffusion coefficient that agrees with predictions from quasi-linear theory.

Atmospheric thermal structure and cloud features in the southern hemisphere of Venus as retrieved from VIRTIS/VEX radiation measurements

NASA Astrophysics Data System (ADS)

Haus, R.; Kappel, D.; Arnold, G.

2014-04-01

Thermal structure and cloud features in the atmosphere of Venus are investigated using spectroscopic nightside measurements recorded by the Visible and InfraRed Thermal Imaging Spectrometer (VIRTIS) aboard ESA’s Venus Express mission in the moderate resolution infrared mapping channel (M-IR, 1-5 μm). New methodical approaches and retrieval results for the northern hemisphere have been recently described by Haus et al. (Haus, R., Kappel, D., Arnold, G. [2013]. Planet. Space Sci. 89, 77-101. http://dx.doi.org/10.1016/j.pss.2013.09.020). Now, southern hemisphere maps of mesospheric temperature and cloud parameter fields are presented that cover variations with altitude, latitude, local time, and mission time. Measurements from the entire usable data archive are utilized comprising radiation spectra recorded during eight Venus solar days between April 2006 and October 2008. Zonal averages of retrieved temperature altitude profiles in both hemispheres are very similar and give evidence of global N-S axial symmetry of atmospheric temperature structure. Cold collar and warmer polar vortex regions exhibit the strongest temperature variability with standard deviations up to 8.5 K at 75°S and 63 km altitude compared with about 1.0 K at low and mid latitudes above 75 km. The mesospheric temperature field strongly depends on local time. At altitudes above about 75 km, the atmosphere is warmer in the second half of night, while the dawn side at lower altitudes is usually colder than the dusk side by about 8 K. Local minimum temperature of 220 K occurs at 03:00 h local time at 65 km and 60°S. Temperature standard deviation at polar latitudes is particularly large near midnight. Temperature variability with solar longitude is forced by solar thermal tides with a dominating diurnal component. The influence of observed cloud parameter changes on retrieved mesospheric zonal average temperature structure is moderate and does not exceed 2-3 K at altitudes between 60 and 75 km. The mesospheric thermal structure was essentially stable with Julian date between 2006 and 2008. Global N-S axial symmetry is also observed in cloud structures. Cloud top altitude at 1 μm slowly decreases from 71 km at the equator to 70 km at 45-50° and rapidly drops poleward of 50°. It reaches 61 km over both poles. Average particle size in the vertical cloud column increases from mid latitudes toward the poles and also toward the equator resulting in minimum and maximum zonal average cloud opacities of about 32 and 42 and a planetary average of 36.5 at 1 μm. Zonal averages of cloud features are similar at different solar days, but variations with local time are very complex and inseparably associated with the superrotation of the clouds.

Magnetic Correlations In A Magnetite Nanoparticle Assembly Investigated Using Polarized SANS

NASA Astrophysics Data System (ADS)

Krycka, Kathryn; Hogg, Charles; Ijiri, Yumi; Booth, Ryan; Borchers, Julie; Chen, Wangchun; Laver, Mark; Gentile, Thomas; Maranville, Brian; Breslauer, Benjamin; Majetich, Sara

2008-03-01

Using small angle neutron scattering (SANS) with polarization analysis, we have studied ferromagnetic magnetite monodisperse nanospheres in order to determine the field (0 and 1.3 Tesla) and temperature (50, 100, and 200 K) dependence of the magnetic interparticle correlations. These particles were 7 nm in diameter with an average edge-to-edge separation of 2.5 nm. Preparation techniques are described elsewhere [1]. An FeSi supermirror polarized the incident neutrons, and a polarized 3He cell was used as a spin analyzer. While a typical magnetic SANS experiment observes the convolution of the nuclear and magnetic terms, we have implemented and further developed an algorithm to separate the four spin dependent cross sections. This provides an unambiguous separation and measurement of magnetic and nuclear contributions. At low temperatures, magnetic correlation lengths have been found to be significantly larger than at high temperatures.[1] J. Am. Chem. Soc. 2002, 124, 8204-8205.

Synthesis, structural and optical properties of nanocrystalline vanadium doped zinc oxide aerogel

NASA Astrophysics Data System (ADS)

El Ghoul, J.; Barthou, C.; El Mir, L.

2012-06-01

We report the synthesis of vanadium-doped ZnO nanoparticles prepared by a sol-gel processing technique. In our approach, the water for hydrolysis was slowly released by esterification reaction followed by a supercritical drying in ethyl alcohol. Vanadium doping concentration of 10 at% has been investigated. After treatment in air at different temperatures, the obtained nanopowder was characterized by various techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and photoluminescence (PL). Analysis by scanning electron microscopy at high resolution shows that the grain size increases with increasing temperature. Thus, in the case of thermal treatment at 500 °C in air, the powder with an average particle size of 25 nm shows a strong luminescence band in the visible range. The intensity and energy position of the obtained PL band depends on the temperature measurement increase. The mechanism of this emission band is discussed.

Versatile magnetometer assembly for characterizing magnetic properties of nanoparticles.

PubMed

Araujo, J F D F; Bruno, A C; Louro, S R W

2015-10-01

We constructed a versatile magnetometer assembly for characterizing iron oxide nanoparticles. The magnetometer can be operated at room temperature or inside a cryocooler at temperatures as low as 6 K. The magnetometer's sensor can be easily exchanged and different detection electronics can be used. We tested the assembly with a non-cryogenic commercial Hall sensor and a benchtop multimeter in a four-wire resistance measurement scheme. A magnetic moment sensitivity of 8.5 × 10(-8) Am(2) was obtained with this configuration. To illustrate the capability of the assembly, we synthesized iron oxide nanoparticles coated with different amounts of a triblock copolymer, Pluronic F-127, and characterized their magnetic properties. We determined that the polymer coating does not affect the magnetization of the particles at room temperature and demonstrates that it is possible to estimate the average size of coating layers from measurements of the magnetic field of the sample.

Versatile magnetometer assembly for characterizing magnetic properties of nanoparticles

NASA Astrophysics Data System (ADS)

Araujo, J. F. D. F.; Bruno, A. C.; Louro, S. R. W.

2015-10-01

We constructed a versatile magnetometer assembly for characterizing iron oxide nanoparticles. The magnetometer can be operated at room temperature or inside a cryocooler at temperatures as low as 6 K. The magnetometer's sensor can be easily exchanged and different detection electronics can be used. We tested the assembly with a non-cryogenic commercial Hall sensor and a benchtop multimeter in a four-wire resistance measurement scheme. A magnetic moment sensitivity of 8.5 × 10-8 Am2 was obtained with this configuration. To illustrate the capability of the assembly, we synthesized iron oxide nanoparticles coated with different amounts of a triblock copolymer, Pluronic F-127, and characterized their magnetic properties. We determined that the polymer coating does not affect the magnetization of the particles at room temperature and demonstrates that it is possible to estimate the average size of coating layers from measurements of the magnetic field of the sample.

Combined Experimental and Numerical Simulations of Thermal Barrier Coated Turbine Blades Erosion

NASA Technical Reports Server (NTRS)

Hamed, Awate; Tabakoff, Widen; Swar, Rohan; Shin, Dongyun; Woggon, Nthanial; Miller, Robert

2013-01-01

A combined experimental and computational study was conducted to investigate the erosion of thermal barrier coated (TBC) blade surfaces by alumina particles ingestion in a single stage turbine. In the experimental investigation, tests of particle surface interactions were performed in specially designed tunnels to determine the erosion rates and particle restitution characteristics under different impact conditions. The experimental results show that the erosion rates increase with increased impingement angle, impact velocity and temperature. In the computational simulations, an Euler-Lagrangian two stage approach is used in obtaining numerical solutions to the three-dimensional compressible Reynolds Averaged Navier-Stokes equations and the particles equations of motion in each blade passage reference frame. User defined functions (UDF) were developed to represent experimentally-based correlations for particle surface interaction models which were employed in the three-dimensional particle trajectory simulations to determine the particle rebound characteristics after each surface impact. The experimentally based erosion UDF model was used to predict the TBC erosion rates on the turbine blade surfaces based on the computed statistical data of the particles impact locations, velocities and angles relative to the blade surface. Computational results are presented for the predicted TBC blade erosion in a single stage commercial APU turbine, for a NASA designed automotive turbine, and for the NASA turbine scaled for modern rotorcraft operating conditions. The erosion patterns in the turbines are discussed for uniform particle ingestion and for particle ingestion concentrated in the inner and outer 5 percent of the stator blade span representing the flow cooling the combustor liner.

Microwave noise temperature and attenuation of clouds - Statistics of these effects at various sites in the United States, Alaska, and Hawaii

NASA Technical Reports Server (NTRS)

Slobin, S. D.

1982-01-01

The microwave attenuation and noise temperature effects of clouds can result in serious degradation of telecommunications link performance, especially for low-noise systems presently used in deep-space communications. Although cloud effects are generally less than rain effects, the frequent presence of clouds will cause some amount of link degradation a large portion of the time. This paper presents a general review of cloud types and their water particle densities, attenuation and noise temperature calculations, and basic link signal-to-noise ratio calculations. Tabular results of calculations for 12 different cloud models are presented for frequencies in the range 10-50 GHz. Curves of average-year attenuation and noise temperature statistics at frequencies ranging from 10 to 90 GHz, calculated from actual surface and radiosonde observations, are given for 15 climatologically distinct regions in the contiguous United States, Alaska, and Hawaii. Nonuniform sky cover is considered in these calculations.

Structural and magnetic analysis of La0.67Ca0.33MnO3 nanoparticles thermally treated: Acoustic detection of the magnetocaloric effect

NASA Astrophysics Data System (ADS)

Pena, C. F.; Soffner, M. E.; Mansanares, A. M.; Sampaio, J. A.; Gandra, F. C. G.; da Silva, E. C.; Vargas, H.

2017-10-01

Nanoparticles of La0.67Ca0.33MnO3 were synthesized via the sol-gel method, thermally treated and characterized using X-ray diffraction, magnetization, electron spin resonance and magnetoacoustic experiments. The formation of the desired perovskite structure was verified and the average size of the nanoparticles was also determined. An increase of the particle size by rising the treatment temperature was observed. The Curie temperature and the isothermal entropy variation of the samples were obtained from the magnetization data. The isothermal entropy change, produced under the application of an external magnetic field, which expresses the magnetocaloric effect, became significantly larger for the samples treated at higher temperatures. These results are in good agreement with those obtained by magnetoacoustics, based on the direct and contactless measurement of the temperature change, validating the ability of the technique to study the magnetocaloric effect in reduced mass and nanoparticles samples.

Fuel retention under elevated wall temperature in KSTAR with a carbon wall

NASA Astrophysics Data System (ADS)

Cao, B.; Hong, S. H.

2018-03-01

The fuel retention during KSTAR discharges with elevated wall temperature (150 °C) has been studied by using the method of global particle balance. The results show that the elevated wall temperature could reduce the dynamic retention via implantation and absorption, especially for the short pulse shots with large injected fuel particles. There is no signature changing of long-term retention, which related to co-deposition, under elevated wall temperature. For soft-landing shots (normal shots), the exhausted fuel particles during discharges is larger with elevated wall temperature than without, but the exhausted particles after discharges within 90 s looks similar. The outgassing particles because of disruption could be exhausted within 15 s.

Advanced PIC-MCC simulation for the investigation of step-ionization effect in intermediate-pressure capacitively coupled plasmas

NASA Astrophysics Data System (ADS)

Kim, Jin Seok; Hur, Min Young; Kim, Chang Ho; Kim, Ho Jun; Lee, Hae June

2018-03-01

A two-dimensional parallelized particle-in-cell simulation has been developed to simulate a capacitively coupled plasma reactor. The parallelization using graphics processing units is applied to resolve the heavy computational load. It is found that the step-ionization plays an important role in the intermediate gas pressure of a few Torr. Without the step-ionization, the average electron density decreases while the effective electron temperature increases with the increase of gas pressure at a fixed power. With the step-ionization, however, the average electron density increases while the effective electron temperature decreases with the increase of gas pressure. The cases with the step-ionization agree well with the tendency of experimental measurement. The electron energy distribution functions show that the population of electrons having intermediate energy from 4.2 to 12 eV is relaxed by the step-ionization. Also, it was observed that the power consumption by the electrons is increasing with the increase of gas pressure by the step-ionization process, while the power consumption by the ions decreases with the increase of gas pressure.

Self-Sorting of Bidispersed Colloidal Particles Near Contact Line of an Evaporating Sessile Droplet.

PubMed

Patil, Nagesh D; Bhardwaj, Rajneesh; Sharma, Atul

2018-06-13

Here, we investigate deposit patterns and associated morphology formed after the evaporation of an aqueous droplet containing mono- and bidispersed colloidal particles. In particular, the combined effect of substrate heating and particle diameter is investigated. We employ high-speed visualization, optical microscopy, and scanning electron microscopy to characterize the evaporating droplets, particle motion, and deposit morphology, respectively. In the context of monodispersed colloidal particles, an inner deposit and a typical ring form for smaller and larger particles, respectively, on a nonheated surface. The formation of the inner deposit is attributed to early depinning of the contact line, explained by a mechanistic model based on the balance of several forces acting on a particle near the contact line. At larger substrate temperature, a thin ring with inner deposit forms, explained by the self-pinning of the contact line and advection of the particles from the contact line to the center of the droplet due to the Marangoni flow. In the context of bidispersed colloidal particles, self-sorting of the colloidal particles within the ring occurs at larger substrate temperature. The smaller particles deposit at the outermost edge compared to the larger particles, and this preferential deposition in a stagnation region near the contact line is due to the spatially varying height of the liquid-gas interface above the substrate. The sorting occurs at a smaller ratio of the diameters of the smaller and larger particles. At larger substrate temperature and larger ratio, the particles do not get sorted and mix into each other. Our measurements show that there exists a critical substrate temperature as well as a diameter ratio to achieve the sorting. We propose regime maps on substrate temperature-particle diameter and substrate temperature-diameter ratio plane for mono- and bidispersed solutions, respectively.

Cosmic rays and other rpace phenomena influenced on the Earth's climate

NASA Astrophysics Data System (ADS)

Lev, Dorman

2016-07-01

We consider effects of cosmic rays (CR) and some other space phenomena on the Earth's climate change. It is well known that the system of internal and external factors formatting the Earth's climate is very unstable: decreasing of planetary average annual temperature leads to an increase of planetary snow surface, and decreasing of the total annual solar energy input into the system decreases the planetary temperature even more. And inverse: increasing planetary temperature leads to an decrease of snow surface, and increasing of the total solar energy input into the system increases the planetary temperature even more. From this follows that even energetically small factors acted long time in one direction may have a big influence on climate change. In our opinion, the most important of these factors are CR (mostly through its influence on planetary cloudiness) and space dust (SD) through their influence on the flux of solar irradiation and on formation of clouds (these actions are in one direction). It is important that CR and SD influenced on global climate change in the same direction. Increasing of CR planetary intensity leads to increasing of formation clouds (especially low clouds on altitudes smaller than 3 km), increasing annual average of raining and decreasing of annual average planetary temperature. Increasing of SD decreases of solar irradiation and increases cloudiness what leads also to decreasing of annual average planetary temperature. Moreover, interactions of CR particles with dust granules decreases their dimensions what increased effectiveness of their actions on clouds. We consider data great variations of planetary temperature much before the beginning of the Earth's technological civilization (mostly caused by moving of the solar system around our Galaxy centre and collisions with molecular-dust clouds). We consider in details not only situation during the last hundred years, but also situation in the last one thousand years (and especially situation during Maunder minimum of solar activity), during many thousand and many millions years. It is shown that very big changes in climate were caused also by some rarely phenomena as impacts of asteroids and nearby supernova explosions with great influence on biosphere. We discuss also the problem on forecasting of global climate change what is especially important for saving present civilization from great climate catastrophes.

Thermal diffusion behavior of hard-sphere suspensions.

PubMed

Ning, Hui; Buitenhuis, Johan; Dhont, Jan K G; Wiegand, Simone

2006-11-28

We studied the thermal diffusion behavior of octadecyl coated silica particles (R(h)=27 nm) in toluene between 15.0 and 50.0 degrees C in a volume fraction range of 1%-30% by means of thermal diffusion forced Rayleigh scattering. The colloidal particles behave like hard spheres at high temperatures and as sticky spheres at low temperatures. With increasing temperature, the obtained Soret coefficient S(T) of the silica particles changed sign from negative to positive, which implies that the colloidal particles move to the warm side at low temperatures, whereas they move to the cold side at high temperatures. Additionally, we observed also a sign change of the Soret coefficient from positive to negative with increasing volume fraction. This is the first colloidal system for which a sign change with temperature and volume fraction has been observed. The concentration dependence of the thermal diffusion coefficient of the colloidal spheres is related to the colloid-colloid interactions, and will be compared with an existing theoretical description for interacting spherical particles. To characterize the particle-particle interaction parameters, we performed static and dynamic light scattering experiments. The temperature dependence of the thermal diffusion coefficient is predominantly determined by single colloidal particle properties, which are related to colloid-solvent molecule interactions.

A stochastic model of particle dispersion in turbulent reacting gaseous environments

NASA Astrophysics Data System (ADS)

Sun, Guangyuan; Lignell, David; Hewson, John

2012-11-01

We are performing fundamental studies of dispersive transport and time-temperature histories of Lagrangian particles in turbulent reacting flows. The particle-flow statistics including the full particle temperature PDF are of interest. A challenge in modeling particle motions is the accurate prediction of fine-scale aerosol-fluid interactions. A computationally affordable stochastic modeling approach, one-dimensional turbulence (ODT), is a proven method that captures the full range of length and time scales, and provides detailed statistics of fine-scale turbulent-particle mixing and transport. Limited results of particle transport in ODT have been reported in non-reacting flow. Here, we extend ODT to particle transport in reacting flow. The results of particle transport in three flow configurations are presented: channel flow, homogeneous isotropic turbulence, and jet flames. We investigate the functional dependence of the statistics of particle-flow interactions including (1) parametric study with varying temperatures, Reynolds numbers, and particle Stokes numbers; (2) particle temperature histories and PDFs; (3) time scale and the sensitivity of initial and boundary conditions. Flow statistics are compared to both experimental measurements and DNS data.

Survey of shock-wave structures of smooth-particle granular flows.

PubMed

Padgett, D A; Mazzoleni, A P; Faw, S D

2015-12-01

We show the effects of simulated supersonic granular flow made up of smooth particles passing over two prototypical bodies: a wedge and a disk. We describe a way of computationally identifying shock wave locations in granular flows and tabulate the shock wave locations for flow over wedges and disks. We quantify the shock structure in terms of oblique shock angle for wedge impediments and shock standoff distance for disk impediments. We vary granular flow parameters including upstream volume fraction, average upstream velocity, granular temperature, and the collision coefficient of restitution. Both wedges and disks have been used in the aerospace community as prototypical impediments to flowing air in order to investigate the fundamentally different shock structures emanating from sharp and blunt bodies, and we present these results in order to increase the understanding of the fundamental behavior of supersonic granular flow.

Synthesis and luminescence properties of vanadium-doped nanosized zinc oxide aerogel

NASA Astrophysics Data System (ADS)

El Mir, L.; El Ghoul, J.; Alaya, S.; Ben Salem, M.; Barthou, C.; von Bardeleben, H. J.

2008-05-01

We report the elaboration of vanadium-doped ZnO nanoparticles prepared by a sol-gel processing technique. In our approach, the water for hydrolysis was slowly released by esterification reaction followed by a supercritical drying in ethyl alcohol. Vanadium doping concentration of 10 at% has been investigated. The obtained nanopowder was characterised by various techniques such as particle size analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and photoluminescence (PL). In the as-prepared state, the powder with an average particle size of 25 nm presents a strong luminescence band in the visible range after thermal treatment at 500 °C in air. The energy position of the obtained PL band depends on the wavelength excitation and presents a blue shift with measurement temperature increase. Different possible attributions of this emission band will be discussed.

Octenylsuccinate starch spherulites as a stabilizer for Pickering emulsions.

PubMed

Wang, Chan; Fu, Xiong; Tang, Chuan-He; Huang, Qiang; Zhang, Bin

2017-07-15

This study investigated structure and morphology of starch spherulites prepared from debranched waxy maize and waxy potato starches. Debranched waxy potato starch favored the formation of B-type crystals with longer branch chains (average chain length, 26.14), whereas A-type polymorphic aggregates were generated from debranched waxy maize under same recrystallization condition. Spherulites had smaller particle size distribution (D[3,2], ∼3.7μm), higher dissociation temperature (80-120°C) and crystallinity (80∼90%), compared to native waxy starches. Intact spherulites could be used as an edible particle emulsifier after modifying by octenylsuccinic anhydride (OSA). The emulsion produced using 2wt.% of octenylsuccinate (OS) starch spherulites as emulsifier was quite stable over 2months, and its Pickering emulsions displayed protective effect on stability of oil droplets. Copyright © 2017 Elsevier Ltd. All rights reserved.

Ignition and Combustion of Pulverized Coal and Biomass under Different Oxy-fuel O2/N2 and O2/CO2 Environments

NASA Astrophysics Data System (ADS)

Khatami Firoozabadi, Seyed Reza

This work studied the ignition and combustion of burning pulverized coals and biomasses particles under either conventional combustion in air or oxy-fuel combustion conditions. Oxy-fuel combustion is a 'clean-coal' process that takes place in O2/CO2 environments, which are achieved by removing nitrogen from the intake gases and recirculating large amounts of flue gases to the boiler. Removal of nitrogen from the combustion gases generates a high CO2-content, sequestration-ready gas at the boiler effluent. Flue gas recirculation moderates the high temperatures caused by the elevated oxygen partial pressure in the boiler. In this study, combustion of the fuels took place in a laboratory laminar-flow drop-tube furnace (DTF), electrically-heated to 1400 K, in environments containing various mole fractions of oxygen in either nitrogen or carbon-dioxide background gases. The experiments were conducted at two different gas conditions inside the furnace: (a) quiescent gas condition (i.e., no flow or inactive flow) and, (b) an active gas flow condition in both the injector and furnace. Eight coals from different ranks (anthracite, semi-snthracite, three bituminous, subbituminous and two lignites) and four biomasses from different sources were utilized in this work to study the ignition and combustion characteristics of solid fuels in O2/N2 or O2/CO2 environments. The main objective is to study the effect of replacing background N2 with CO2, increasing O2 mole fraction and fuel type and rank on a number of qualitative and quantitative parameters such as ignition/combustion mode, ignition temperature, ignition delay time, combustion temperatures, burnout times and envelope flame soot volume fractions. Regarding ignition, in the quiescent gas condition, bituminous and sub-bituminous coal particles experienced homogeneous ignition in both O2/N 2 and O2/CO2 atmospheres, while in the active gas flow condition, heterogeneous ignition was evident in O2/CO 2. Anthracite, semi-anthracite and lignites mostly experienced heterogeneous ignition in either O2/N2 or O2/CO2 atmospheres in both flow conditions. Replacing the N2 by CO 2 slightly increased the ignition temperature (30--40K). Ignition temperatures increased with the enhancement of coal rank in either air or oxy-fuel combustion conditions. However, increasing oxygen mole fraction decreased the ignition temperature for all coals. The ignition delay of coal particles was prolonged in the slow-heating O2/CO2 atmospheres, relative to the faster-heating O2/N2 atmospheres, particularly at high-diluent mole fractions. At higher O2 mole fractions, ignition delays decreased in both environments. Higher rank fuels such as anthracite and semi-anthracite experienced higher ignition delays while lower rank fuels such as lignite and biomasses experienced lower igniton delay times. In combustion, fuel particles were observed to burn in different modes, such as two-mode, or in one-mode combustion, depending on their rank and the furnace conditions. Strong tendencies were observed for all fuels to burn in one-mode when N2 was replaced by CO2, and when O 2 mole fraction increased in both environments. Moreover, increasing the coal rank, from lignite to bituminous, enhanced the tendency of coal particles to exhibit a two-mode combustion behavior. Particle luminosity, fragmentation and deduced temperatures were higher in O2/N2 than in O2/CO2 atmospheres, and corresponding burnout times were shorter, at the same O2 mole fractions. Particle luminosity and temperatures increased with increasing O2 mole fractions in both N2 and in CO2 background gases, and corresponding burnout times decreased with increasing O2 mole fractions. Bituminous coal particles swelled, whereas sub-bituminous coal particles exhibited limited fragmentation prior to and during the early stages of combustion. Lignite coal particles fragmented extensively and burned in one-mode regardless of the O2 mole fraction and the background gas. The timing of fragmentation (prior or after ignition) and the number of fragments depended on the type of the lignite and on the particle shape. Temperatures and burnout times of particles were also affected by the combustion mode. In nearly all bituminous and biomass particles combustion, sooty envelope flames were formed around the particles. Replacement of background N 2 by CO2 gas decreased the average soot volume fraction, fv, whereas increasing O2 from 20% to 30--40% increased the fv and then further increasing O2 to 100% decreased the soot volume fraction drastically. bituminous coal particle flames generated lower soot volume fractions in the range 2x10 -5--9x10-5, depending on O2 mole fraction. Moreover, biomass particle flames were optically thin and of equal-sized at all O2 mole fractions. (Abstract shortened by UMI.).

Ice nucleation activity of agricultural soil dust aerosols from Mongolia, Argentina, and Germany

NASA Astrophysics Data System (ADS)

Steinke, I.; Funk, R.; Busse, J.; Iturri, A.; Kirchen, S.; Leue, M.; Möhler, O.; Schwartz, T.; Schnaiter, M.; Sierau, B.; Toprak, E.; Ullrich, R.; Ulrich, A.; Hoose, C.; Leisner, T.

2016-11-01

Soil dust particles emitted from agricultural areas contain considerable mass fractions of organic material. Also, soil dust particles may act as carriers for potentially ice-active biological particles. In this work, we present ice nucleation experiments conducted in the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) cloud chamber. We investigated the ice nucleation efficiency of four types of soil dust from different regions of the world. The results are expressed as ice nucleation active surface site (INAS) densities and presented for the immersion freezing and the deposition nucleation mode. For immersion freezing occurring at 254 K, samples from Argentina, China, and Germany show ice nucleation efficiencies which are by a factor of 10 higher than desert dusts. On average, the difference in ice nucleation efficiencies between agricultural and desert dusts becomes significantly smaller at temperatures below 247 K. In the deposition mode the soil dusts showed higher ice nucleation activity than Arizona Test Dust over a temperature range between 232 and 248 K and humidities RHice up to 125%. INAS densities varied between 109 and 1011 m-2 for these thermodynamic conditions. For one soil dust sample (Argentinian Soil), the effect of treatments with heat was investigated. Heat treatments (383 K) did not affect the ice nucleation efficiency observed at 249 K. This finding presumably excludes proteinaceous ice-nucleating entities as the only source of the increased ice nucleation efficiency.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parker, Scott; Chen, Yang

This is the Final Technical Report for University of Colorado's portion of the SciDAC project 'Center for Gyrokinetic Particle Simulation of Turbulent Transport.' This is funded as a multi-institutional SciDAC Center and W.W. Lee at the Princeton Plasma Physics Laboratory is the lead Principal Investigator. Scott Parker is the local Principal Investigator for University of Colorado and Yang Chen is a Co-Principal Investigator. This is Cooperative Agreement DE-FC02-05ER54816. Research personnel include Yang Chen (Senior Research Associate), Jianying Lang (Graduate Research Associate, Ph.D. Physics Student) and Scott Parker (Associate Professor). Research includes core microturbulence studies of NSTX, simulation of trapped electronmore » modes, development of efficient particle-continuum hybrid methods and particle convergence studies of electron temperature gradient driven turbulence simulations. Recently, the particle-continuum method has been extended to five-dimensions in GEM. We find that actually a simple method works quite well for the Cyclone base case with either fully kinetic or adiabatic electrons. Particles are deposited on a 5D phase-space grid using nearest-grid-point interpolation. Then, the value of delta-f is reset, but not the particle's trajectory. This has the effect of occasionally averaging delta-f of nearby (in the phase space) particles. We are currently trying to estimate the dissipation (or effective collision operator). We have been using GEM to study turbulence and transport in NSTX with realistic equilibrium density and temperature profiles, including impurities, magnetic geometry and ExB shear flow. Greg Rewoldt, PPPL, has developed a TRANSP interface for GEM that specifies the equilibrium profiles and parameters needed to run realistic NSTX cases. Results were reported at the American Physical Society - Division of Plasma Physics, and we are currently running convergence studies to ensure physical results. We are also studying the effect of parallel shear flows, which can be quite strong in NSTX. Recent long-time simulations of electron temperature gradient driven turbulence, show that zonal flows slowly grow algebraically via the Rosenbluth-Hinton random walk mechanism. Eventually, the zonal flow gets to a level where it shear suppresses the turbulence. We have demonstrated this behavior with Cyclone base-case parameters, except with a 30% lower temperature gradient. We can demonstrate the same phenomena at higher gradients, but so far, have been unable to get a converged result at the higher temperature gradient. We find that electron ion collisions cause the zonal flows to grow at a slower rate and results in a higher heat flux. So, far all ETG simulations that come to a quasi-steady state show continued build up of zonal flow, see it appears to be a universal phenomena (for ETG). Linear and nonlinear simulations of Collisional and Collisionless trapped electron modes are underway. We find that zonal flow is typically important. We can, however, reproduce the Tannert and Jenko result (that zonal flow is unimportant) using their parameters with the electron temperature three times the ion temperature. For a typical weak gradient core value of density gradient and no temperature gradient, the CTEM is dominant. However, for a steeper density gradient (and still no temperature gradient), representative of the edge, higher k drift-waves are dominant. For the weaker density gradient core case, nonlinear simulations using GEM are routine. For the steeper gradient edge case, the nonlinear fluctuations are very high and a stationary state has not been obtained. This provides motivation for the particle-continuum algorithm. We also note that more physics, e.g. profile variation and equilibrium ExB shear flow should be significantly stabilizing, making such simulations feasible using standard delta-f techniques. This research is ongoing.« less

Effects of particle-fluid density ratio on the interactions between the turbulent channel flow and finite-size particles

NASA Astrophysics Data System (ADS)

Yu, Zhaosheng; Lin, Zhaowu; Shao, Xueming; Wang, Lian-Ping

2017-09-01

A parallel direct-forcing fictitious domain method is employed to perform fully resolved numerical simulations of turbulent channel flow laden with finite-size particles. The effects of the particle-fluid density ratio on the turbulence modulation in the channel flow are investigated at the friction Reynolds number of 180, the particle volume fraction of 0.84 % , and the particle-fluid density ratio ranging from 1 to 104.2. The results show that the variation of the flow drag with the particle-fluid density ratio is not monotonic, with a larger flow drag for the density ratio of 10.42, compared to those of unity and 104.2. A significant drag reduction by the particles is observed for large particle-fluid density ratios during the transient stage, but not at the statistically stationary stage. The intensity of particle velocity fluctuations generally decreases with increasing particle inertia, except that the particle streamwise root-mean-square velocity and streamwise-transverse velocity correlation in the near-wall region are largest at the density ratio of the order of 10. The averaged momentum equations are derived with the spatial averaging theorem and are used to analyze the mechanisms for the effects of the particles on the flow drag. The results indicate that the drag-reduction effect due to the decrease in the fluid Reynolds shear stress is counteracted by the drag-enhancement effect due to the increase in the total particle stress or the interphase drag force for the large particle-inertia case. The sum of the total Reynolds stress and particle inner stress contributions to the flow drag is largest at the density ratio of the order of 10, which is the reason for the largest flow drag at this density ratio. The interphase drag force obtained from the averaged momentum equation (the balance theory) is significantly smaller than (but agrees qualitatively with) that from the empirical drag formula based on the phase-averaged slip velocity for large density ratios. For the neutrally buoyant case, the balance theory predicts a positive interphase force on the particles arising from the negative gradient of the particle inner stress, which cannot be predicted by the drag formula based on the phase-averaged slip velocity. In addition, our results show that both particle collision and particle-turbulence interaction play roles in the formation of the inhomogeneous distribution of the particles at the density ratio of the order of 10.

Effects of particle-fluid density ratio on the interactions between the turbulent channel flow and finite-size particles.

PubMed

Yu, Zhaosheng; Lin, Zhaowu; Shao, Xueming; Wang, Lian-Ping

2017-09-01

A parallel direct-forcing fictitious domain method is employed to perform fully resolved numerical simulations of turbulent channel flow laden with finite-size particles. The effects of the particle-fluid density ratio on the turbulence modulation in the channel flow are investigated at the friction Reynolds number of 180, the particle volume fraction of 0.84%, and the particle-fluid density ratio ranging from 1 to 104.2. The results show that the variation of the flow drag with the particle-fluid density ratio is not monotonic, with a larger flow drag for the density ratio of 10.42, compared to those of unity and 104.2. A significant drag reduction by the particles is observed for large particle-fluid density ratios during the transient stage, but not at the statistically stationary stage. The intensity of particle velocity fluctuations generally decreases with increasing particle inertia, except that the particle streamwise root-mean-square velocity and streamwise-transverse velocity correlation in the near-wall region are largest at the density ratio of the order of 10. The averaged momentum equations are derived with the spatial averaging theorem and are used to analyze the mechanisms for the effects of the particles on the flow drag. The results indicate that the drag-reduction effect due to the decrease in the fluid Reynolds shear stress is counteracted by the drag-enhancement effect due to the increase in the total particle stress or the interphase drag force for the large particle-inertia case. The sum of the total Reynolds stress and particle inner stress contributions to the flow drag is largest at the density ratio of the order of 10, which is the reason for the largest flow drag at this density ratio. The interphase drag force obtained from the averaged momentum equation (the balance theory) is significantly smaller than (but agrees qualitatively with) that from the empirical drag formula based on the phase-averaged slip velocity for large density ratios. For the neutrally buoyant case, the balance theory predicts a positive interphase force on the particles arising from the negative gradient of the particle inner stress, which cannot be predicted by the drag formula based on the phase-averaged slip velocity. In addition, our results show that both particle collision and particle-turbulence interaction play roles in the formation of the inhomogeneous distribution of the particles at the density ratio of the order of 10.

Wintertime water-soluble aerosol composition and particle water content in Fresno, California

NASA Astrophysics Data System (ADS)

Parworth, Caroline L.; Young, Dominique E.; Kim, Hwajin; Zhang, Xiaolu; Cappa, Christopher D.; Collier, Sonya; Zhang, Qi

2017-03-01

The composition and concentrations of water-soluble gases and ionic aerosol components were measured from January to February 2013 in Fresno, CA, with a particle-into-liquid sampler with ion chromatography and annular denuders. The average (±1σ) ionic aerosol mass concentration was 15.0 (±9.4) µg m-3, and dominated by nitrate (61%), followed by ammonium, sulfate, chloride, potassium, nitrite, and sodium. Aerosol-phase organic acids, including formate and glycolate, and amines including methylaminium, triethanolaminium, ethanolaminium, dimethylaminium, and ethylaminium were also detected. Although the dominant species all came from secondary aerosol formation, there were primary sources of ionic aerosols as well, including biomass burning for potassium and glycolate, sea spray for sodium, chloride, and dimethylamine, and vehicles for formate. Particulate methanesulfonic acid was also detected and mainly associated with terrestrial sources. On average, the molar concentration of ammonia was 49 times greater than nitric acid, indicating that ammonium nitrate formation was limited by nitric acid availability. Particle water was calculated based on the Extended Aerosol Inorganics Model (E-AIM) thermodynamic prediction of inorganic particle water and κ-Köhler theory approximation of organic particle water. The average (±1σ) particle water concentration was 19.2 (±18.6) µg m-3, of which 90% was attributed to inorganic species. The fractional contribution of particle water to total fine particle mass averaged at 36% during this study and was greatest during early morning and night and least during the day. Based on aqueous-phase concentrations of ions calculated by using E-AIM, the average (±1σ) pH of particles in Fresno during the winter was estimated to be 4.2 (±0.2).

Commuter exposure to ultrafine particles in different urban locations, transportation modes and routes

NASA Astrophysics Data System (ADS)

Ragettli, Martina S.; Corradi, Elisabetta; Braun-Fahrländer, Charlotte; Schindler, Christian; de Nazelle, Audrey; Jerrett, Michael; Ducret-Stich, Regina E.; Künzli, Nino; Phuleria, Harish C.

2013-10-01

A better understanding of ultrafine particle (UFP) exposure in different urban transport microenvironments is important for epidemiological exposure assessments and for policy making. Three sub-studies were performed to characterize personal exposure to UFP concentration and average particle size distribution diameters in frequently traveled commuter microenvironments in the city of Basel, Switzerland. First, the spatial variation of sidewalk UFP exposures within urban areas and transport-specific microenvironments was explored. Second, exposure to UFP concentration and average particle size were quantified for five modes of transportation (walking, bicycle, bus, tram, car) during different times of the day and week, along the same route. Finally, the contribution of bicycle commuting along two different routes (along main roads, away from main roads) to total daily exposures was assessed by 24-h personal measurements. In general, smaller average particle sizes and higher UFP levels were measured at places and for travel modes in close proximity to traffic. Average trip UFP concentrations were higher in car (31,784 particles cm-³) and on bicycle (22,660 particles cm-³) compared to walking (19,481 particles cm-³) and public transportation (14,055-18,818 particles cm-³). Concentrations were highest for all travel modes during weekday morning rush hours, compared to other time periods. UFP concentration was lowest in bus, regardless of time period. Bicycle travel along main streets between home and work place (24 min on average) contributed 21% and 5% to total daily UFP exposure in winter and summer, respectively. Contribution of bicycle commutes to total daily UFP exposure could be reduced by half if main roads are avoided. Our results show the importance of considering commuter behavior and route choice in exposure assessment studies.

Integrating laboratory and field data to quantify the immersion freezing ice nucleation activity of mineral dust particles

NASA Astrophysics Data System (ADS)

DeMott, P. J.; Prenni, A. J.; McMeeking, G. R.; Sullivan, R. C.; Petters, M. D.; Tobo, Y.; Niemand, M.; Möhler, O.; Snider, J. R.; Wang, Z.; Kreidenweis, S. M.

2014-06-01

Data from both laboratory studies and atmospheric measurements are used to develop a simple parametric description for the immersion freezing activity of natural mineral dust particles. Measurements made with the Colorado State University (CSU) continuous flow diffusion chamber (CFDC) when processing mineral dust aerosols at a nominal 105% relative humidity with respect to water (RHw) are taken to approximate the immersion freezing nucleation activity of particles. Ice active frozen fractions vs. temperature for dusts representative of Saharan and Asian desert sources were consistent with similar measurements in atmospheric dust plumes for a limited set of comparisons available. The parameterization developed follows the form of one suggested previously for atmospheric particles of non-specific composition in quantifying ice nucleating particle concentrations as functions of temperature and the total number concentration of particles larger than 0.5 μm diameter. Such an approach does not explicitly account for surface area and time dependencies for ice nucleation, but sufficiently encapsulates the activation properties for potential use in regional and global modeling simulations, and possible application in developing remote sensing retrievals for ice nucleating particles. A correction factor is introduced to account for the apparent underestimate (by approximately 3, on average) of the immersion freezing fraction of mineral dust particles for CSU CFDC data processed at an RHw of 105% vs. maximum fractions active at higher RHw. Instrumental factors that affect activation behavior vs. RHw in CFDC instruments remain to be fully explored in future studies. Nevertheless, the use of this correction factor is supported by comparison to ice activation data obtained for the same aerosols from Aerosol Interactions and Dynamics of the Atmosphere (AIDA) expansion chamber cloud parcel experiments. Further comparison of the new parameterization to the immersion freezing surface active site density parameterization for mineral dust particles, developed separately from AIDA experimental data alone, shows excellent agreement for data collected in a descent through a Saharan aerosol layer. These studies support the utility of laboratory measurements to obtain atmospherically-relevant data on the ice nucleation properties of dust and other particle types, and suggest the suitability of considering all mineral dust as a single type of ice nucleating particle as a useful first order approximation in numerical modeling investigations.

Integrating laboratory and field data to quantify the immersion freezing ice nucleation activity of mineral dust particles

NASA Astrophysics Data System (ADS)

DeMott, P. J.; Prenni, A. J.; McMeeking, G. R.; Sullivan, R. C.; Petters, M. D.; Tobo, Y.; Niemand, M.; Möhler, O.; Snider, J. R.; Wang, Z.; Kreidenweis, S. M.

2015-01-01

Data from both laboratory studies and atmospheric measurements are used to develop an empirical parameterization for the immersion freezing activity of natural mineral dust particles. Measurements made with the Colorado State University (CSU) continuous flow diffusion chamber (CFDC) when processing mineral dust aerosols at a nominal 105% relative humidity with respect to water (RHw) are taken as a measure of the immersion freezing nucleation activity of particles. Ice active frozen fractions vs. temperature for dusts representative of Saharan and Asian desert sources were consistent with similar measurements in atmospheric dust plumes for a limited set of comparisons available. The parameterization developed follows the form of one suggested previously for atmospheric particles of non-specific composition in quantifying ice nucleating particle concentrations as functions of temperature and the total number concentration of particles larger than 0.5 μm diameter. Such an approach does not explicitly account for surface area and time dependencies for ice nucleation, but sufficiently encapsulates the activation properties for potential use in regional and global modeling simulations, and possible application in developing remote sensing retrievals for ice nucleating particles. A calibration factor is introduced to account for the apparent underestimate (by approximately 3, on average) of the immersion freezing fraction of mineral dust particles for CSU CFDC data processed at an RHw of 105% vs. maximum fractions active at higher RHw. Instrumental factors that affect activation behavior vs. RHw in CFDC instruments remain to be fully explored in future studies. Nevertheless, the use of this calibration factor is supported by comparison to ice activation data obtained for the same aerosols from Aerosol Interactions and Dynamics of the Atmosphere (AIDA) expansion chamber cloud parcel experiments. Further comparison of the new parameterization, including calibration correction, to predictions of the immersion freezing surface active site density parameterization for mineral dust particles, developed separately from AIDA experimental data alone, shows excellent agreement for data collected in a descent through a Saharan aerosol layer. These studies support the utility of laboratory measurements to obtain atmospherically relevant data on the ice nucleation properties of dust and other particle types, and suggest the suitability of considering all mineral dust as a single type of ice nucleating particle as a useful first-order approximation in numerical modeling investigations.

Integrating laboratory and field data to quantify the immersion freezing ice nucleation activity of mineral dust particles

DOE PAGES

DeMott, P. J.; Prenni, A. J.; McMeeking, G. R.; ...

2014-06-27

Data from both laboratory studies and atmospheric measurements are used to develop a simple parametric description for the immersion freezing activity of natural mineral dust particles. Measurements made with the Colorado State University (CSU) continuous flow diffusion chamber (CFDC) when processing mineral dust aerosols at a nominal 105% relative humidity with respect to water (RH w) are taken to approximate the immersion freezing nucleation activity of particles. Ice active frozen fractions vs. temperature for dusts representative of Saharan and Asian desert sources were consistent with similar measurements in atmospheric dust plumes for a limited set of comparisons available. The parameterizationmore » developed follows the form of one suggested previously for atmospheric particles of non-specific composition in quantifying ice nucleating particle concentrations as functions of temperature and the total number concentration of particles larger than 0.5 μm diameter. Such an approach does not explicitly account for surface area and time dependencies for ice nucleation, but sufficiently encapsulates the activation properties for potential use in regional and global modeling simulations, and possible application in developing remote sensing retrievals for ice nucleating particles. A correction factor is introduced to account for the apparent underestimate (by approximately 3, on average) of the immersion freezing fraction of mineral dust particles for CSU CFDC data processed at an RH w of 105% vs. maximum fractions active at higher RH w. Instrumental factors that affect activation behavior vs. RH w in CFDC instruments remain to be fully explored in future studies. Nevertheless, the use of this correction factor is supported by comparison to ice activation data obtained for the same aerosols from Aerosol Interactions and Dynamics of the Atmosphere (AIDA) expansion chamber cloud parcel experiments. Further comparison of the new parameterization to the immersion freezing surface active site density parameterization for mineral dust particles, developed separately from AIDA experimental data alone, shows excellent agreement for data collected in a descent through a Saharan aerosol layer. These studies support the utility of laboratory measurements to obtain atmospherically-relevant data on the ice nucleation properties of dust and other particle types, and suggest the suitability of considering all mineral dust as a single type of ice nucleating particle as a useful first order approximation in numerical modeling investigations.« less

Integrating laboratory and field data to quantify the immersion freezing ice nucleation activity of mineral dust particles

DOE PAGES

DeMott, P. J.; Prenni, A. J.; McMeeking, G. R.; ...

2015-01-13

Data from both laboratory studies and atmospheric measurements are used to develop an empirical parameterization for the immersion freezing activity of natural mineral dust particles. Measurements made with the Colorado State University (CSU) continuous flow diffusion chamber (CFDC) when processing mineral dust aerosols at a nominal 105% relative humidity with respect to water (RH w) are taken as a measure of the immersion freezing nucleation activity of particles. Ice active frozen fractions vs. temperature for dusts representative of Saharan and Asian desert sources were consistent with similar measurements in atmospheric dust plumes for a limited set of comparisons available. Themore » parameterization developed follows the form of one suggested previously for atmospheric particles of non-specific composition in quantifying ice nucleating particle concentrations as functions of temperature and the total number concentration of particles larger than 0.5 μm diameter. Such an approach does not explicitly account for surface area and time dependencies for ice nucleation, but sufficiently encapsulates the activation properties for potential use in regional and global modeling simulations, and possible application in developing remote sensing retrievals for ice nucleating particles. A calibration factor is introduced to account for the apparent underestimate (by approximately 3, on average) of the immersion freezing fraction of mineral dust particles for CSU CFDC data processed at an RH w of 105% vs. maximum fractions active at higher RH w. Instrumental factors that affect activation behavior vs. RH w in CFDC instruments remain to be fully explored in future studies. Nevertheless, the use of this calibration factor is supported by comparison to ice activation data obtained for the same aerosols from Aerosol Interactions and Dynamics of the Atmosphere (AIDA) expansion chamber cloud parcel experiments. Further comparison of the new parameterization, including calibration correction, to predictions of the immersion freezing surface active site density parameterization for mineral dust particles, developed separately from AIDA experimental data alone, shows excellent agreement for data collected in a descent through a Saharan aerosol layer. These studies support the utility of laboratory measurements to obtain atmospherically relevant data on the ice nucleation properties of dust and other particle types, and suggest the suitability of considering all mineral dust as a single type of ice nucleating particle as a useful first-order approximation in numerical modeling investigations.« less

Understanding the synergistic effect and the main factors influencing the enzymatic hydrolyzability of corn stover at low enzyme loading by hydrothermal and/or ultrafine grinding pretreatment.

PubMed

Zhang, Haiyan; Li, Junbao; Huang, Guangqun; Yang, Zengling; Han, Lujia

2018-05-26

A thorough assessment of the microstructural changes and synergistic effects of hydrothermal and/or ultrafine grinding pretreatment on the subsequent enzymatic hydrolysis of corn stover was performed in this study. The mechanism of pretreatment was elucidated by characterizing the particle size, specific surface area (SSA), pore volume (PV), average pore size, cellulose crystallinity (CrI) and surface morphology of the pretreated samples. In addition, the underlying relationships between the structural parameters and final glucose yields were elucidated, and the relative significance of the factors influencing enzymatic hydrolyzability were assessed by principal component analysis (PCA). Hydrothermal pretreatment at a lower temperature (170 °C) combined with ultrafine grinding achieved a high glucose yield (80.36%) at a low enzyme loading (5 filter paper unit (FPU)/g substrate) which is favorable. The relative significance of structural parameters in enzymatic hydrolyzability was SSA > PV > average pore size > CrI/cellulose > particle size. PV and SSA exhibited logarithmic correlations with the final enzymatic hydrolysis yield. Copyright © 2018 Elsevier Ltd. All rights reserved.

Measurements of gas temperature in a radiatively heated particle laden turbulent duct flow

NASA Astrophysics Data System (ADS)

Kim, Ji Hoon; Banko, Andrew; Villafane, Laura; Elkins, Chris; Eaton, John

2017-11-01

Predicting the absorption of radiation through a turbulent, particle laden flow is relevant in atmospheric sciences, turbulent combustion, and in the design of a particle solar receivers. In order to better understand the coupling between the particle phase, the turbulent fluid phase, and the incident radiation, the effects of radiation absorption by disperse inertial particles in a turbulent duct flow was studied experimentally. A fully-developed turbulent duct flow at Reynolds numbers of O(104) , laden with particles at mass loading ratios of 0.1-0.8, was subject to infrared radiation at varying incident powers. The particle Stokes number based on the Kolmogorov length scale was approximately 12, resulting in a preferentially concentrated particle phase. Measurements of the mean and fluctuating components of the gas phase temperature were made along the wall bisector. Results from mean temperature traverses of the gas phase show that a one-dimensional model can account for much of the mean gas temperature rise. Temperature fluctuations due to preferential concentration are significant and can reach approximately 50% of the mean temperature rise. This work was funded by the U.S. Department of Energy under Grant No. DE-NA0002373-1.

Heat Source Characterization In A TREAT Fuel Particle Using Coupled Neutronics Binary Collision Monte-Carlo Calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schunert, Sebastian; Schwen, Daniel; Ghassemi, Pedram

This work presents a multi-physics, multi-scale approach to modeling the Transient Test Reactor (TREAT) currently prepared for restart at the Idaho National Laboratory. TREAT fuel is made up of microscopic fuel grains (r ˜ 20µm) dispersed in a graphite matrix. The novelty of this work is in coupling a binary collision Monte-Carlo (BCMC) model to the Finite Element based code Moose for solving a microsopic heat-conduction problem whose driving source is provided by the BCMC model tracking fission fragment energy deposition. This microscopic model is driven by a transient, engineering scale neutronics model coupled to an adiabatic heating model. Themore » macroscopic model provides local power densities and neutron energy spectra to the microscpic model. Currently, no feedback from the microscopic to the macroscopic model is considered. TREAT transient 15 is used to exemplify the capabilities of the multi-physics, multi-scale model, and it is found that the average fuel grain temperature differs from the average graphite temperature by 80 K despite the low-power transient. The large temperature difference has strong implications on the Doppler feedback a potential LEU TREAT core would see, and it underpins the need for multi-physics, multi-scale modeling of a TREAT LEU core.« less

Phase control during the synthesis of nickel sulfide nanoparticles from dithiocarbamate precursors

NASA Astrophysics Data System (ADS)

Roffey, Anna; Hollingsworth, Nathan; Islam, Husn-Ubayda; Mercy, Maxime; Sankar, Gopinathan; Catlow, C. Richard A.; Hogarth, Graeme; de Leeuw, Nora H.

2016-05-01

Square-planar nickel bis(dithiocarbamate) complexes, [Ni(S2CNR2)2], have been prepared and utilised as single source precursors to nanoparticulate nickel sulfides. While they are stable in the solid-state to around 300 °C, heating in oleylamine at 230 °C, 5 mM solutions afford pure α-NiS, where the outcome is independent of the substituents. DFT calculations show an electronic effect rather than steric hindrance influences the resulting particle size. Decomposition of the iso-butyl derivative, [Ni(S2CNiBu2)2], has been studied in detail. There is a temperature-dependence of the phase of the nickel sulfide formed. At low temperatures (150 °C), pure α-NiS is formed. Upon raising the temperature, increasing amounts of β-NiS are produced and at 280 °C this is formed in pure form. A range of concentrations (from 5-50 mM) was also investigated at 180 °C and while in all cases pure α-NiS was formed, particle sizes varied significantly. Thus at low concentrations average particle sizes were ca. 100 nm, but at higher concentrations they increased to ca. 150 nm. The addition of two equivalents of tetra-iso-butyl thiuram disulfide, (iBu2NCS2)2, to the decomposition mixture was found to influence the material formed. At 230 °C and above, α-NiS was generated, in contrast to the results found without added thiuram disulfide, suggesting that addition of (iBu2NCS2)2 stabilises the metastable α-NiS phase. At low temperatures (150-180 °C) and concentrations (5 mM), mixtures of α-NiS and Ni3S4, result. A growing proportion of Ni3S4 is noted upon increasing precursor concentration to 10 mM. At 20 mM a metastable phase of nickel sulfide, NiS2 is formed and as the concentration is increased, α-NiS appears alongside NiS2. Reasons for these variations are discussed.Square-planar nickel bis(dithiocarbamate) complexes, [Ni(S2CNR2)2], have been prepared and utilised as single source precursors to nanoparticulate nickel sulfides. While they are stable in the solid-state to around 300 °C, heating in oleylamine at 230 °C, 5 mM solutions afford pure α-NiS, where the outcome is independent of the substituents. DFT calculations show an electronic effect rather than steric hindrance influences the resulting particle size. Decomposition of the iso-butyl derivative, [Ni(S2CNiBu2)2], has been studied in detail. There is a temperature-dependence of the phase of the nickel sulfide formed. At low temperatures (150 °C), pure α-NiS is formed. Upon raising the temperature, increasing amounts of β-NiS are produced and at 280 °C this is formed in pure form. A range of concentrations (from 5-50 mM) was also investigated at 180 °C and while in all cases pure α-NiS was formed, particle sizes varied significantly. Thus at low concentrations average particle sizes were ca. 100 nm, but at higher concentrations they increased to ca. 150 nm. The addition of two equivalents of tetra-iso-butyl thiuram disulfide, (iBu2NCS2)2, to the decomposition mixture was found to influence the material formed. At 230 °C and above, α-NiS was generated, in contrast to the results found without added thiuram disulfide, suggesting that addition of (iBu2NCS2)2 stabilises the metastable α-NiS phase. At low temperatures (150-180 °C) and concentrations (5 mM), mixtures of α-NiS and Ni3S4, result. A growing proportion of Ni3S4 is noted upon increasing precursor concentration to 10 mM. At 20 mM a metastable phase of nickel sulfide, NiS2 is formed and as the concentration is increased, α-NiS appears alongside NiS2. Reasons for these variations are discussed. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr00053c

Multifunctional particles for melanoma-targeted drug delivery.

PubMed

Wadajkar, Aniket S; Bhavsar, Zarna; Ko, Cheng-Yu; Koppolu, Bhanuprasanth; Cui, Weina; Tang, Liping; Nguyen, Kytai T

2012-08-01

New magnetic-based core-shell particles (MBCSPs) were developed to target skin cancer cells while delivering chemotherapeutic drugs in a controlled fashion. MBCSPs consist of a thermo-responsive shell of poly(N-isopropylacrylamide-acrylamide-allylamine) and a core of poly(lactic-co-glycolic acid) (PLGA) embedded with magnetite nanoparticles. To target melanoma cancer cells, MBCSPs were conjugated with Gly-Arg-Gly-Asp-Ser (GRGDS) peptides that specifically bind to the α(5)β(3) receptors of melanoma cells. MBCSPs consist of unique multifunctional and controlled drug delivery characteristics. Specially, they can provide dual drug release mechanisms (a sustained release of drugs through degradation of PLGA core and a controlled release in response to changes in temperature via thermo-responsive polymer shell), and dual targeting mechanisms (magnetic localization and receptor-mediated targeting). Results from in vitro studies indicate that GRGDS-conjugated MBCSPs have an average diameter of 296 nm and exhibit no cytotoxicity towards human dermal fibroblasts up to 500 μg ml(-1). Further, a sustained release of curcumin from the core and a temperature-dependent release of doxorubicin from the shell of MBCSPs were observed. The particles also produced a dark contrast signal in magnetic resonance imaging. Finally, the particles were accumulated at the tumor site in a B16F10 melanoma orthotopic mouse model, especially in the presence of a magnet. Results indicate great potential of MBCSPs as a platform technology to target, treat and monitor melanoma for targeted drug delivery to reduce side effects of chemotherapeutic reagents. Copyright © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Preparation of improved catalytic materials for water purification

NASA Astrophysics Data System (ADS)

Cherkezova-Zheleva, Z.; Paneva, D.; Tsvetkov, M.; Kunev, B.; Milanova, M.; Petrov, N.; Mitov, I.

2014-04-01

The aim of presented paper was to study preparation of catalytic materials for water purification. Iron oxide (Fe3O4) samples supported on activated carbon were prepared by wet impregnation method and low temperature heating in an inert atmosphere. The as-prepared, activated and samples after catalytic test were characterized by Mössbauer spectroscopy and X-ray diffraction. The obtained X-ray diffraction patterns of prepared samples show broad and low-intensity peaks of magnetite phase and the characteristic peaks of the activated carbon. The average crystallite size of magnetite particles was calculated below 20 nm. The registered Mössbauer spectra of prepared materials show a superposition of doublet lines or doublet and sextet components. The calculated hyperfine parameters after spectra evaluation reveal the presence of magnetite phase with nanosize particles. Relaxation phenomena were registered in both cases, i.e. superparamagnetism or collective magnetic excitation behavior, respectively. Low temperature Mössbauer spectra confirm this observation. Application of materials as photo-Fenton catalysts for organic pollutions degradation was studied. It was obtained high adsorption degree of dye, extremely high reaction rate and fast dye degradation. Photocatalytic behaviour of a more active sample was enhanced using mechanochemical activation (MCA). The nanometric size and high dispersion of photocatalyst particles influence both the adsorption and degradation mechanism of reaction. The results showed that all studied photocatalysts effectively decompose the organic pollutants under UV light irradiation. Partial oxidation of samples after catalytic tests was registered. Combination of magnetic particles with high photocatalytic activity meets both the requirements of photocatalytic degradation of water contaminants and that of recovery for cyclic utilization of material.

Particle-scale CO2 adsorption kinetics modeling considering three reaction mechanisms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Suh, Dong-Myung; Sun, Xin

2013-09-01

In the presence of water (H2O), dry and wet adsorptions of carbon dioxide (CO2) and physical adsorption of H2O happen concurrently in a sorbent particle. The three reactions depend on each other and have a complicated, but important, effect on CO2 capturing via a solid sorbent. In this study, transport phenomena in the sorbent were modeled, including the tree reactions, and a numerical solving procedure for the model also was explained. The reaction variable distribution in the sorbent and their average values were calculated, and simulation results were compared with experimental data to validate the proposed model. Some differences, causedmore » by thermodynamic parameters, were observed between them. However, the developed model reasonably simulated the adsorption behaviors of a sorbent. The weight gained by each adsorbed species, CO2 and H2O, is difficult to determine experimentally. It is known that more CO2 can be captured in the presence of water. Still, it is not yet known quantitatively how much more CO2 the sorbent can capture, nor is it known how much dry and wet adsorptions separately account for CO2 capture. This study addresses those questions by modeling CO2 adsorption in a particle and simulating the adsorption process using the model. As adsorption temperature changed into several values, the adsorbed amount of each species was calculated. The captured CO2 in the sorbent particle was compared quantitatively between dry and wet conditions. As the adsorption temperature decreased, wet adsorption increased. However, dry adsorption was reduced.« less

Treatment of breast cancers by magnetic thermoablation: in vivo experiments in mice

NASA Astrophysics Data System (ADS)

Hilger, I.; Andra, W.; Hergt, R.; Hiergeist, R.; Kaiser, W. A.

2001-09-01

The objective of the present study was to investigate the feasibility of a minimal-invasive method for the elimination of tumors in the breast by local heating. Heating is generated by an intratumoral iron oxide (magnetite) loading of the tumor and exposure of the breast to an alternating magnetic field. The methodology consisted in the implantation of human adenocarcinomas (MX-1 cells) into 10 immunodeficient mice. After application of coated iron oxide particles (average total particle diameter: 10 nm) the intratumoral particle deposition was controlled by radiography. Iron contents in selected organs were determined using atomic absorption spectrometry at 50 min p.i.. During exposure of mice (4 min) to an AC magnetic field (frequency: 400 kHz, amplitude: 6.5 kA/m) intratumoral and rectal temperatures were measured. 6.7±2.3%; 2.8± 0.9% and 2.4 ± 0.1% of injected iron dose per g dried tissue was found in the spleen, liver and blood, respectively at 50 min p.i.. No injected iron was found in the lung. Temperatures of 87 ± 7°C and 71 ± 8°C (distal and proximal tumor periphery, respectively) were measured at the end of magnetic field exposure. From the data we deduce that the method enables the generation of localized heat spots that damage tumor cells within several minutes and that the prototype particles are adequately retained at the tumor site. The introduction of the technique in future interventional radiological procedures is promising. Tables 1, Figs 4, Refs 14.

The influence of meteorological factors and biomass burning on surface ozone concentrations at Tanah Rata, Malaysia

NASA Astrophysics Data System (ADS)

Toh, Ying Ying; Lim, Sze Fook; von Glasow, Roland

2013-05-01

The surface ozone concentrations at the Tanah Rata regional Global Atmosphere Watch (GAW) station, Malaysia (4°28‧N, 101°23‧E, 1545 m above Mean Sea Level (MSL)) from June 2006 to August 2008 were analyzed in this study. Overall the ozone mixing ratios are very low; the seasonal variations show the highest mixing ratios during the Southwest monsoon (average 19.1 ppb) and lowest mixing ratios during the spring intermonsoon (average 14.2 ppb). The diurnal variation of ozone is characterised by an afternoon maximum and night time minimum. The meteorological conditions that favour the formation of high ozone levels at this site are low relative humidity, high temperature and minimum rainfall. The average ozone concentration is lower during precipitation days compared to non-precipitation days. The hourly averaged ozone concentrations show significant correlations with temperature and relative humidity during the Northeast monsoon and spring intermonsoon. The highest concentrations are observed when the wind is blowing from the west. We found an anticorrelation between the atmospheric pressure tide and ozone concentrations. The ozone mixing ratios do not exceed the recommended Malaysia Air Quality Guidelines for 1-h and 8-h averages. Five day backward trajectories on two high ozone episodes in 07 August 2006 (40.0 ppb) and 24 February 2008 (45.7 ppb) are computed using the HYbrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model to investigate the origin of the pollutants and influence of regional transport. The high ozone episode during 07 August 2006 (burning season during southwest monsoon) is mainly attributed to regional transport from biomass burning in Sumatra, whereas favourable meteorological conditions (i.e. low relative humidity, high temperature and solar radiation, zero rainfall) and long range transport from Indo-China have elevated the ozone concentrations during 24 February 2008.

Particulate organic carbon mass distribution at the Bermuda Atlantic Time-series Study (BATS) site

NASA Astrophysics Data System (ADS)

Gundersen, Kjell; Orcutt, Karen M.; Purdie, Duncan A.; Michaels, Anthony F.; Knap, Anthony H.

Errors in total particulate organic carbon (total POC) measurements caused by particles settling in Niskin water samplers, loss of bacterial cells during filtration and undersampling of rare particles such as the diazotrophic cyanobacterium Trichodesmium spp. were investigated at the Bermuda Atlantic Time-series Study (BATS) site. Regular core samples of temperature, primary production, bacterial abundance, chlorophyll- a (Chl- a) and POC were collected at monthly intervals from 1991 to 1996. During this period of time, shorter investigations of particles settling in water samples (1991-1992), bacterial cells lost during filtration (1992-1993), and Trichodesmium abundance (1995-1996) were performed at the BATS site. The BATS site shows striking seasonal patterns in hydrography and phytoplankton primary productivity, with a strong maximum immediately following the deep winter mixing of the water column. Following the peak in primary production, bacterial abundance showed only slightly elevated levels in spring. Maxima of Chl- a and POC also were associated with the primary production peaks, but these particle concentrations became less pronounced through summer and fall. An average of 26% of total POC collected in Niskin water bottles settled below the spigot before it could be sampled. An average of 47% of all bacterial cells passed the nominal pore size of a Whatman GF/F filter, and total POC measurements generated from GF/F filtered seawater samples had to be corrected for this loss. The average integrated stocks of total POC in the upper 65 m of the water column was 32% pigmented phytoplankton, 15% microheterotrophs, 54% other detrital matter (32 : 15 : 54). Phytoplankton C equaled bacterial C in the 65-135 m depth range (16 : 19 : 65), but phytoplankton C was virtually non-existent deeper than 135 m (2 : 14 : 74). Bacterial C biomass was higher than phytoplankton in surface waters outside the spring bloom period, but carbon not accounted for by phytoplankton and bacteria (other C) showed an overall dominance throughout the year. Uncorrected, suspended POC collected on GF/F filters (POC SW) was nearly equal to the sum of phytoplankton C and bacterial C alone, and hence, the other C fraction of total POC was largely generated by the addition of settling particles (POC Dreg). Seasonal occurrences of rare particles such as Trichodesmium colonies in surface waters in late summer may account for as much as 17-56% of total POC. Settling particles and Trichodesmium colonies, seldom included in POC estimates from temperate and tropical regions, constituted more than half of total POC measured in surface waters at BATS.

Spray-dry desulfurization of flue gas from heavy oil combustion.

PubMed

Scala, Fabrizio; Lancia, Amedeo; Nigro, Roberto; Volpicelli, Gennaro

2005-01-01

An experimental investigation on sulfur dioxide removal in a pilot-scale spray dryer from the flue gas generated by combustion of low-sulfur (S) heavy oil is reported. A limewater slurry was sprayed through an ultrasonic two-fluid atomizer in the spray-dry chamber, and the spent sorbent was collected downstream in a pulse-jet baghouse together with fly ash. Flue gas was sampled at different points to measure the desulfurization efficiency after both the spray-dry chamber and the baghouse. Parametric tests were performed to study the effect of the following variables: gas inlet temperature, difference between gas outlet temperature and adiabatic saturation temperature, lime-to-S ratio, and average size of lime particles in the slurry. Results indicated that spray drying is an effective technology for the desulfurization of low-S fuel oil flue gas, provided operating conditions are chosen carefully. In particular, the lowest gas inlet and outlet temperatures compatible with baghouse operation should be selected, as should a sufficiently high lime-to-S ratio. The attainment of a small lime particle size in the slurry is critical for obtaining a high desulfurization efficiency. A previously presented spray-dry flue gas desulfurization model was used to simulate the pilot-scale desulfurization tests, to check the ability of the model to predict the S capture data and its usefulness as a design tool, minimizing the need for pilot-scale experimentation. Comparison between model and experimental results was fairly good for the whole range of calcium/S ratios considered.

Deposition velocity of ultrafine particles measured with the Eddy-Correlation Method over the Nansen Ice Sheet (Antarctica)

NASA Astrophysics Data System (ADS)

Contini, D.; Donateo, A.; Belosi, F.; Grasso, F. M.; Santachiara, G.; Prodi, F.

2010-08-01

This work reports an analysis of the concentration, size distribution, and deposition velocity of atmospheric particles over snow and iced surfaces on the Nansen Ice Sheet (Antarctica). Measurements were performed using the eddy-correlation method at a remote site during the XXII Italian expedition of the National Research Program in Antarctica (PNRA) in 2006. The measurement system was based on a condensation particle counter (CPC) able to measure particles down to 9 nm in diameter with a 50% efficiency and a Differential Mobility Particle Sizer for evaluating particle size distributions from 11 to 521 nm diameter in 39 channels. A method based on postprocessing with digital filters was developed to take into account the effect of the slow time response of the CPC. The average number concentration was 1338 cm-3 (median, 978 cm-3; interquartile range, 435-1854 cm-3). Higher concentrations were observed at low wind velocities. Results gave an average deposition velocity of 0.47 mm/s (median, 0.19 mm/s; interquartile range, -0.21 -0.88 mm/s). Deposition increased with the friction velocity and was on average 0.86 mm/s during katabatic wind characterized by velocities higher than 4 m/s. Observed size distributions generally presented two distinct modes, the first at approximately 15-20 nm and the second (representing on average 70% of the total particles) at 60-70 nm. Under strong-wind conditions, the second mode dominated the average size distribution.

Self-averaging and weak ergodicity breaking of diffusion in heterogeneous media

NASA Astrophysics Data System (ADS)

Russian, Anna; Dentz, Marco; Gouze, Philippe

2017-08-01

Diffusion in natural and engineered media is quantified in terms of stochastic models for the heterogeneity-induced fluctuations of particle motion. However, fundamental properties such as ergodicity and self-averaging and their dependence on the disorder distribution are often not known. Here, we investigate these questions for diffusion in quenched disordered media characterized by spatially varying retardation properties, which account for particle retention due to physical or chemical interactions with the medium. We link self-averaging and ergodicity to the disorder sampling efficiency Rn, which quantifies the number of disorder realizations a noise ensemble may sample in a single disorder realization. Diffusion for disorder scenarios characterized by a finite mean transition time is ergodic and self-averaging for any dimension. The strength of the sample to sample fluctuations decreases with increasing spatial dimension. For an infinite mean transition time, particle motion is weakly ergodicity breaking in any dimension because single particles cannot sample the heterogeneity spectrum in finite time. However, even though the noise ensemble is not representative of the single-particle time statistics, subdiffusive motion in q ≥2 dimensions is self-averaging, which means that the noise ensemble in a single realization samples a representative part of the heterogeneity spectrum.

Improving La0.6Sr0.4Co0.8Fe0.2O3-δ infiltrated solid oxide fuel cell cathode performance through precursor solution desiccation

NASA Astrophysics Data System (ADS)

Burye, Theodore E.; Nicholas, Jason D.

2015-02-01

Here, for the first time, the average size of solid oxide fuel cell (SOFC) electrode nano-particles was reduced through the chemical desiccation of infiltrated precursor nitrate solutions. Specifically, after firing at 700 °C, CaCl2-desiccated La0.6Sr0.4Co0.8Fe0.2O3-δ (LSCF) - Ce0.9Gd0.1O1.95 (GDC) cathodes contained LSCF infiltrate particles with an average size of 22 nm. This is in contrast to comparable, undesiccated LSCF-GDC cathodes which contained LSCF infiltrate particles with an average size of 48 nm. X-ray diffraction, scanning electron microscopy, and controlled atmosphere electrochemical impedance spectroscopy revealed that desiccation reduced the average infiltrate particle size without altering the infiltrate phase purity, the cathode concentration polarization resistance, or the cathode electronic resistance. Compared to undesiccated LSCF-GDC cathodes achieving polarization resistances of 0.10 Ωcm2 at 640 °C, comparable CaCl2-dessicated LSCF-GDC cathodes achieved 0.10 Ωcm2 at 575 °C. Mathematical modeling suggested that these performance improvements resulted solely from average infiltrate particle size reductions.