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

Mallow, Anne; Abdelaziz, Omar; Graham, Jr., Samuel

The thermal charging performance of paraffin wax combined with compressed expanded natural graphite foam was studied for different graphite bulk densities. Constant heat fluxes between 0.39 W/cm 2 and 1.55 W/cm 2 were applied, as well as a constant boundary temperature of 60 °C. Thermal charging experiments indicate that, in the design of thermal batteries, thermal conductivity of the composite alone is an insufficient metric to determine the influence of the graphite foam on the thermal energy storage. By dividing the latent heat of the composite by the time to end of melt for each applied boundary condition, the energymore » storage performance was calculated to show the effects of composite thermal conductivity, graphite bulk density, and latent heat capacity. For the experimental volume, the addition of graphite beyond a graphite bulk density of 100 kg/m 3 showed limited benefit on the energy storage performance due to the decrease in latent heat storage capacity. These experimental results are used to validate a numerical model to predict the time to melt and for future use in the design of heat exchangers with graphite-foam based phase change material composites. As a result, size scale effects are explored parametrically with the validated model.« less

Extremely large nonsaturating magnetoresistance and ultrahigh mobility due to topological surface states in the metallic Bi2Te3 topological insulator

NASA Astrophysics Data System (ADS)

Shrestha, K.; Chou, M.; Graf, D.; Yang, H. D.; Lorenz, B.; Chu, C. W.

2017-05-01

Weak antilocalization (WAL) effects in Bi2Te3 single crystals have been investigated at high and low bulk charge-carrier concentrations. At low charge-carrier density the WAL curves scale with the normal component of the magnetic field, demonstrating the dominance of topological surface states in magnetoconductivity. At high charge-carrier density the WAL curves scale with neither the applied field nor its normal component, implying a mixture of bulk and surface conduction. WAL due to topological surface states shows no dependence on the nature (electrons or holes) of the bulk charge carriers. The observations of an extremely large nonsaturating magnetoresistance and ultrahigh mobility in the samples with lower carrier density further support the presence of surface states. The physical parameters characterizing the WAL effects are calculated using the Hikami-Larkin-Nagaoka formula. At high charge-carrier concentrations, there is a greater number of conduction channels and a decrease in the phase coherence length compared to low charge-carrier concentrations. The extremely large magnetoresistance and high mobility of topological insulators have great technological value and can be exploited in magnetoelectric sensors and memory devices.

Poisson's ratio and the densification of glass under high pressure.

PubMed

Rouxel, T; Ji, H; Hammouda, T; Moréac, A

2008-06-06

Because of a relatively low atomic packing density, (Cg) glasses experience significant densification under high hydrostatic pressure. Poisson's ratio (nu) is correlated to Cg and typically varies from 0.15 for glasses with low Cg such as amorphous silica to 0.38 for close-packed atomic networks such as in bulk metallic glasses. Pressure experiments were conducted up to 25 GPa at 293 K on silica, soda-lime-silica, chalcogenide, and bulk metallic glasses. We show from these high-pressure data that there is a direct correlation between nu and the maximum post-decompression density change.

Disorder Effects in Charge Transport and Spin Response of Topological Insulators

NASA Astrophysics Data System (ADS)

Zhao, Lukas Zhonghua

Topological insulators are a class of solids in which the non-trivial inverted bulk band structure gives rise to metallic surface states that are robust against impurity backscattering. First principle calculations predicted Bi2Te3, Sb2Te3 and Bi2Se3 to be three-dimensional (3D) topological insulators with a single Dirac cone on the surface. The topological surface states were subsequently observed by angle-resolved photoemission (ARPES) and scanning tunneling microscopy (STM). The investigations of charge transport through topological surfaces of 3D topological insulators, however, have faced a major challenge due to large charge carrier densities in the bulk donated by randomly distributed defects such as vacancies and antisites. This bulk disorder intermixes surface and bulk conduction channels, thereby complicating access to the low-energy (Dirac point) charge transport or magnetic response and resulting in the relatively low measured carrier mobilities. Moreover, charge inhomogeneity arising from bulk disorder can result in pronounced nanoscale spatial fluctuations of energy on the surface, leading to the formation of surface `puddles' of different carrier types. Great efforts have been made to combat the undesirable effects of disorder in 3D topological insulators and to reduce bulk carriers through chemical doping, nanostructure fabrication, and electric gating. In this work we have developed a new way to reduce bulk carrier densities using high-energy electron irradiation, thereby allowing us access to the topological surface quantum channels. We also found that disorder in 3D topological insulators can be beneficial. It can play an important part in enabling detection of unusual magnetic response from Dirac fermions and in uncovering new excitations, namely surface superconductivity in Dirac `puddles'. In Chapter 3 we show how by using differential magnetometry we could probe spin rotation in the 3D topological material family (Bi2Se 3, Bi2Te3 and Sb2Te3), and describe our detection of paramagnetic singularity in the magnetic susceptibility at low magnetic fields that persists up to room temperature, and which we have demonstrated to arise from the surfaces of the samples. The singularity is universal to the entire family, largely independent of the bulk carrier density, and consistent with the existence of electronic states near the spin-degenerate Dirac point of the 2D helical metal. The exceptional thermal stability of the signal points to an intrinsic surface cooling process, probably of thermoelectric organ, and establishes a sustainable platform for the singular field-tunable Dirac spin response. In Chapter 4 we describe our discovery of surface superconductivity in a hole-conducting topological insulator Sb2Te3 with transition to zero resistance induced through a minor tuning of growth chemistry that depletes bulk conduction channels. The depletion shifts Fermi energy towards the Dirac point as witnessed by over two orders of magnitude reduced bulk hole density and by the largest carrier mobility (~ 25,000 cm 2 V-1 s-1) found in any topological material. Direct evidence from transport, the unprecedentedly large diamagnetic screening, and the presence of up to ~ 25 meV gaps in differential conductance detected by scanning tunneling spectroscopy (STM) reveal the superconducting condensate to emerge first in surface puddles at unexpectedly high temperature, near 50 K. Percolative Josephson paths mediated by diffusing quasiparticles establish global phase coherence around 9 K. Rich structure of this state lends itself to manipulation and tuning via growth conditions and the topological material's parameters such as Fermi velocity and mean free path. In Chapter 5 we describe a new approach we have developed to reaching stable charge neutrality in 3D topological materials. The technique uses swift (~ 2.5 MeV energy) electron beams to compensate charged bulk defects and bring the Fermi level back into the bulk gap. By controlling the beam fluence we could tune bulk conductivity from p- (hole-like) to n-type (electron-like), crossing the Dirac point and back, while preserving the robust topological signatures of surface channels. We establish that at charge neutrality conductance has a two-dimensional (2D) character with a minimum value on the order of ten conductance quanta G=e 2 /h. From quantum interference contribution to 2D conductance we demonstrate in two systems, Bi2Te3 and Bi2Se 3, that at charge neutrality only two quantum channels corresponding to two topological surfaces are present. The charge neutrality point achieved using electron irradiation with long penetration range shows a route to intrinsic quantum transport of the topological states unconstrained by the bulk size.

Impact of screw and edge dislocations on the thermal conductivity of individual nanowires and bulk GaN: a molecular dynamics study.

PubMed

Termentzidis, Konstantinos; Isaiev, Mykola; Salnikova, Anastasiia; Belabbas, Imad; Lacroix, David; Kioseoglou, Joseph

2018-02-14

We report the thermal transport properties of wurtzite GaN in the presence of dislocations using molecular dynamics simulations. A variety of isolated dislocations in a nanowire configuration are analyzed and found to considerably reduce the thermal conductivity while impacting its temperature dependence in a different manner. Isolated screw dislocations reduce the thermal conductivity by a factor of two, while the influence of edge dislocations is less pronounced. The relative reduction of thermal conductivity is correlated with the strain energy of each of the five studied types of dislocations and the nature of the bonds around the dislocation core. The temperature dependence of the thermal conductivity follows a physical law described by a T -1 variation in combination with an exponent factor that depends on the material's nature, type and the structural characteristics of the dislocation core. Furthermore, the impact of the dislocation density on the thermal conductivity of bulk GaN is examined. The variation and absolute values of the total thermal conductivity as a function of the dislocation density are similar for defected systems with both screw and edge dislocations. Nevertheless, we reveal that the thermal conductivity tensors along the parallel and perpendicular directions to the dislocation lines are different. The discrepancy of the anisotropy of the thermal conductivity grows with increasing density of dislocations and it is more pronounced for the systems with edge dislocations. Besides the fundamental insights of the presented results, these could also be used for the identification of the type of dislocations when one experimentally obtains the evolution of thermal conductivity with temperature since each type of dislocation has a different signature, or one could extract the density of dislocations with a simple measurement of thermal anisotropy.

Observation of cyclotron resonance and electron-phonon coupling in surface states of the bulk-insulating topological insulator Cu 0.02Bi 2Se 3

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

Wu, Liang; Tse, Wang-Kong; Morris, C. M.

2015-02-05

We have utilized magneto-optical time-domain spectroscopy to investigate the low frequency optical response of topological insulator Cu 0.02Bi 2Se 3 and Bi 2Se 3 films. With both field and frequency depedence, such experiments give sufficient information to measure the mobility and carrier density of multiple conduction channels simultaneously. We observe sharp cyclotron resonances (CRs) in both samples. The small amount of Cu substitution into the Cu 0.02Bi 2Se 3 induces a true bulk insulator with only a single conduction channel with total sheet carrier density 4.9 x 10 12/cm 2 and mobility as large as 4000 cm 2/V s. Thismore » is consistent with pure topological surface state (TSSs) conduction with a chemical potential 150 meV above the Dirac point. Hence, a true topological insulator with an insulating bulk is realized. The CR broadens at high fields, an e ect that we attribute to an electron-phonon interaction. This assignment is supported by an extended Drude model analysis on the zero field data. In contrast to Cu 0.02Bi 2Se 3, two charge channels were observed in normal Bi 2Se 3 films. We demonstrate a method to distinguish between the dominant TSSs and trivial bulk/2DEG states. The dominant channel exhibits a CR with a carrier density of ~2.0 x 10 13/cm 2 and mobility ~3200 cm 2/V s, consistent with TSSs with a chemical potential ~350meV above the Dirac point.« less

Saturated hydraulic conductivity of US soils grouped according to textural class and bulk density

USDA-ARS?s Scientific Manuscript database

Importance of the saturated hydraulic conductivity as soil hydraulic property led to the development of multiple pedotransfer functions for estimating it. One approach to estimating Ksat was using textural classes rather than specific textural fraction contents as pedotransfer inputs. The objective...

Saturated hydraulic conductivity of US soils grouped according textural class and bulk density

USDA-ARS?s Scientific Manuscript database

Importance of the saturated hydraulic conductivity as soil hydraulic property led to the development of multiple pedotransfer functions for estimating it. One approach to estimating Ksat was using textural classes rather than specific textural fraction contents as pedotransfer inputs. The objective...

Anharmonic, dimensionality and size effects in phonon transport

NASA Astrophysics Data System (ADS)

Thomas, Iorwerth O.; Srivastava, G. P.

2017-12-01

We have developed and employed a numerically efficient semi- ab initio theory, based on density-functional and relaxation-time schemes, to examine anharmonic, dimensionality and size effects in phonon transport in three- and two-dimensional solids of different crystal symmetries. Our method uses third- and fourth-order terms in crystal Hamiltonian expressed in terms of a temperature-dependent Grüneisen’s constant. All input to numerical calculations are generated from phonon calculations based on the density-functional perturbation theory. It is found that four-phonon processes make important and measurable contribution to lattice thermal resistivity above the Debye temperature. From our numerical results for bulk Si, bulk Ge, bulk MoS2 and monolayer MoS2 we find that the sample length dependence of phonon conductivity is significantly stronger in low-dimensional solids.

Spatial Variability of Soil Physical Properties Obtained with Laboratory Methods and Their Relation to Field Electrical Resistivity Measurements

NASA Astrophysics Data System (ADS)

Dathe, A.; Nemes, A.; Bloem, E.; Patterson, M.; Gimenez, D.; Angyal, A.; Koestel, J. K.; Jarvis, N.

2017-12-01

Soil spatial heterogeneity plays a critical role for describing water and solute transport processes in the unsaturated zone. Although we have a sound understanding of the physical properties underlying this heterogeneity (like macropores causing preferential water flow), their quantification in a spatial context is still a challenge. To improve existing knowledge and modelling approaches we established a field experiment on an agriculturally used silty clay loam (Stagnosol) in SE Norway. Centimeter to decimeter scale heterogeneities were investigated in the field using electrical resistivity tomography (ERT) in a quasi-3D and a real 3D approach. More than 100 undisturbed soil samples were taken in the 2x1x1 m3plot investigated with 3D ERT to determine soil water retention, saturated and unsaturated hydraulic conductivities and bulk density in the laboratory. A subset of these samples was scanned at the computer tomography (CT) facility at the Swedish University of Agricultural Sciences in Uppsala, Sweden, with special emphasis on characterizing macroporosity. Results show that the ERT measurements captured the spatial distribution of bulk densities and reflected soil water contents. However, ERT could not resolve the large variation observed in saturated hydraulic conductivities from the soil samples. Saturated hydraulic conductivity was clearly related to the macroporosity visible in the CT scans obtained from the respective soil cores. Hydraulic conductivities close to saturation mainly changed with depths in the soil profile and therefore with bulk density. In conclusion, to quantify the spatial heterogeneity of saturated hydraulic conductivities scanning methods with a resolution smaller than the size of macropores have to be used. This is feasible only when the information obtained from for example CT scans of soil cores would be upscaled in a meaningful way.

Disruption rates for one vulnerable soil in Organ Pipe Cactus National Monument, Arizona, USA

USGS Publications Warehouse

Webb, Robert H.; Esque, Todd C.; Nussear, Kenneth E.; Sturm, Mark

2013-01-01

Rates of soil disruption from hikers and vehicle traffic are poorly known, particularly for arid landscapes. We conducted an experiment in Organ Pipe Cactus National Monument (ORPI) in western Arizona, USA, on an air-dry very fine sandy loam that is considered to be vulnerable to disruption. We created variable-pass tracks using hikers, an all-terrain vehicle (ATV), and a four-wheel drive vehicle (4WD) and measured changes in cross-track topography, penetration depth, and bulk density. Hikers (one pass = 5 hikers) increased bulk density and altered penetration depth but caused minimal surface disruption up to 100 passes; a minimum of 10 passes were required to overcome surface strength of this dry soil. Both ATV and 4WD traffic significantly disrupted the soil with one pass, creating deep ruts with increasing passes that rendered the 4WD trail impassable after 20 passes. Despite considerable soil loosening (dilation), bulk density increased in the vehicle trails, and lateral displacement created berms of loosened soil. This soil type, when dry, can sustain up to 10 passes of hikers but only one vehicle pass before significant soil disruption occurs; greater disruption is expected when soils are wet. Bulk density increased logarithmically with applied pressure from hikers, ATV, and 4WD.

Accuracy of sample dimension-dependent pedotransfer functions in estimation of soil saturated hydraulic conductivity

USDA-ARS?s Scientific Manuscript database

Saturated hydraulic conductivity Ksat is a fundamental characteristic in modeling flow and contaminant transport in soils and sediments. Therefore, many models have been developed to estimate Ksat from easily measureable parameters, such as textural properties, bulk density, etc. However, Ksat is no...

Thermal charging study of compressed expanded natural graphite/phase change material composites

DOE PAGES

Mallow, Anne; Abdelaziz, Omar; Graham, Jr., Samuel

2016-08-12

The thermal charging performance of paraffin wax combined with compressed expanded natural graphite foam was studied for different graphite bulk densities. Constant heat fluxes between 0.39 W/cm 2 and 1.55 W/cm 2 were applied, as well as a constant boundary temperature of 60 °C. Thermal charging experiments indicate that, in the design of thermal batteries, thermal conductivity of the composite alone is an insufficient metric to determine the influence of the graphite foam on the thermal energy storage. By dividing the latent heat of the composite by the time to end of melt for each applied boundary condition, the energymore » storage performance was calculated to show the effects of composite thermal conductivity, graphite bulk density, and latent heat capacity. For the experimental volume, the addition of graphite beyond a graphite bulk density of 100 kg/m 3 showed limited benefit on the energy storage performance due to the decrease in latent heat storage capacity. These experimental results are used to validate a numerical model to predict the time to melt and for future use in the design of heat exchangers with graphite-foam based phase change material composites. As a result, size scale effects are explored parametrically with the validated model.« less

High-Resolution Faraday Rotation and Electron-Phonon Coupling in Surface States of the Bulk-Insulating Topological Insulator Cu_{0.02}Bi_{2}Se_{3}.

PubMed

Wu, Liang; Tse, Wang-Kong; Brahlek, M; Morris, C M; Aguilar, R Valdés; Koirala, N; Oh, S; Armitage, N P

2015-11-20

We have utilized time-domain magnetoterahertz spectroscopy to investigate the low-frequency optical response of the topological insulator Cu_{0.02}Bi_{2}Se_{3} and Bi_{2}Se_{3} films. With both field and frequency dependence, such experiments give sufficient information to measure the mobility and carrier density of multiple conduction channels simultaneously. We observe sharp cyclotron resonances (CRs) in both materials. The small amount of Cu incorporated into the Cu_{0.02}Bi_{2}Se_{3} induces a true bulk insulator with only a single type of conduction with a total sheet carrier density of ~4.9×10^{12}/cm^{2} and mobility as high as 4000 cm^{2}/V·s. This is consistent with conduction from two virtually identical topological surface states (TSSs) on the top and bottom of the film with a chemical potential ~145 meV above the Dirac point and in the bulk gap. The CR broadens at high fields, an effect that we attribute to an electron-phonon interaction. This assignment is supported by an extended Drude model analysis of the zero-field Drude conductance. In contrast, in normal Bi_{2}Se_{3} films, two conduction channels were observed, and we developed a self-consistent analysis method to distinguish the dominant TSSs and coexisting trivial bulk or two-dimensional electron gas states. Our high-resolution Faraday rotation spectroscopy on Cu_{0.02}Bi_{2}Se_{3} paves the way for the observation of quantized Faraday rotation under experimentally achievable conditions to push the chemical potential in the lowest Landau level.

Embankment Criteria and Performance Report: Adobe Dam Gila River Basin, New River and Phoenix City Streams, Arizona.

DTIC Science & Technology

1983-06-01

Field Control Results 18 - Record Test Results 18 GRAVEL DRAIN MATERIAL, 19 FILTER MATERIAL, 20 ABUTMET INFILL MATERIAL- 20 X. EMBANKMENT ANALYSIS 21 XI...Thirty-three in-situ density tests were conducted in the near surface embankment foundation materials by the sand displacement method . An additional...seven densities were obtained from undisturbed samples by the bulk density method . The results of density tests in the foundation are shown on plate

Poisson's Ratio and the Densification of Glass under High Pressure

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

Rouxel, T.; Ji, H.; Hammouda, T.

2008-06-06

Because of a relatively low atomic packing density, (C{sub g}) glasses experience significant densification under high hydrostatic pressure. Poisson's ratio ({nu}) is correlated to C{sub g} and typically varies from 0.15 for glasses with low C{sub g} such as amorphous silica to 0.38 for close-packed atomic networks such as in bulk metallic glasses. Pressure experiments were conducted up to 25 GPa at 293 K on silica, soda-lime-silica, chalcogenide, and bulk metallic glasses. We show from these high-pressure data that there is a direct correlation between {nu} and the maximum post-decompression density change.

UCB current detector experiment on Swedish auroral payloads. [ionospheric current and plasma flow measurements

NASA Technical Reports Server (NTRS)

Mozer, F.

1974-01-01

A split Langmuir probe has been developed to make in situ measurements of ionospheric current density and plasma bulk flow. The probe consists of two conducting elements that are separated by a thin insulator that shield each other over a 2 pi solid angle, and that are simultaneously swept from negative to positive with respect to the plasma. By measuring the current to each plate and the difference current between plates, information is obtained on the plasma's current density, bulk flow, electron temperature, and density. The instrument was successfully flown twice on sounding rockets into auroral events. Measurement data indicate that the total auroral current configuration is composed of several alternating east and west electrojets associated with several alternating up and down Birkeland currents.

Bulk substrate porosity verification by applying Monte Carlo modeling and Castaing's formula using energy-dispersive x-rays

NASA Astrophysics Data System (ADS)

Yung, Lai Chin; Fei, Cheong Choke; Mandeep, Jit Singh; Amin, Nowshad; Lai, Khin Wee

2015-11-01

The leadframe fabrication process normally involves additional thin-metal layer plating on the bulk copper substrate surface for wire bonding purposes. Silver, tin, and copper flakes are commonly adopted as plating materials. It is critical to assess the density of the plated metal layer, and in particular to look for porosity or voids underneath the layer, which may reduce the reliability during high-temperature stress. A fast, reliable inspection technique is needed to assess the porosity or void weakness. To this end, the characteristics of x-rays generated from bulk samples were examined using an energy-dispersive x-ray (EDX) detector to examine the porosity percentage. Monte Carlo modeling was integrated with Castaing's formula to verify the integrity of the experimental data. Samples with different porosity percentages were considered to test the correlation between the intensity of the collected x-ray signal and the material density. To further verify the integrity of the model, conventional cross-sectional samples were also taken to observe the porosity percentage using Image J software measurement. A breakthrough in bulk substrate assessment was achieved by applying EDX for the first time to nonelemental analysis. The experimental data showed that the EDX features were not only useful for elemental analysis, but also applicable to thin-film metal layer thickness measurement and bulk material density determination. A detailed experiment was conducted using EDX to assess the plating metal layer and bulk material porosity.

Thermal properties of soils: effect of biochar application

NASA Astrophysics Data System (ADS)

Usowicz, Boguslaw; Lukowski, Mateusz; Lipiec, Jerzy

2014-05-01

Thermal properties (thermal conductivity, heat capacity and thermal diffusivity) have a significant effect on the soil surface energy partitioning and resulting in the temperature distribution. Thermal properties of soil depend on water content, bulk density and organic matter content. An important source of organic matter is biochar. Biochar as a material is defined as: "charcoal for application as a soil conditioner". Biochar is generally associated with co-produced end products of pyrolysis. Many different materials are used as biomass feedstock for biochar, including wood, crop residues and manures. Additional predictions were done for terra preta soil (also known as "Amazonian dark earth"), high in charcoal content, due to adding a mixture of charcoal, bone, and manure for thousands of years i.e. approximately 10-1,000 times longer than residence times of most soil organic matter. The effect of biochar obtained from the wood biomass and other organic amendments (peat, compost) on soil thermal properties is presented in this paper. The results were compared with wetland soils of different organic matter content. The measurements of the thermal properties at various water contents were performed after incubation, under laboratory conditions using KD2Pro, Decagon Devices. The measured data were compared with predictions made using Usowicz statistical-physical model (Usowicz et al., 2006) for biochar, mineral soil and soil with addition of biochar at various water contents and bulk densities. The model operates statistically by probability of occurrence of contacts between particular fractional compounds. It combines physical properties, specific to particular compounds, into one apparent conductance specific to the mixture. The results revealed that addition of the biochar and other organic amendments into the soil caused considerable reduction of the thermal conductivity and diffusivity. The mineral soil showed the highest thermal conductivity and diffusivity that decreased in soil with addition of biochar and pure biochar. The reduction of both properties was mostly due to decrease in both particle density and bulk density. Both biochar and the organic amendments addition resulted in a decrease of the heat capacity of the mixtures in dry state and considerable increase in wet state. The lowest and highest reduction in the thermal conductivity with decreasing water content was obtained for pure biochar and mineral soil, respectively. The thermal diffusivity had a characteristic maximum at higher bulk densities and lower water contents. The wetland soil higher in organic matter content exhibit smaller temporal variation of the thermal properties compared to soils lower in organic matter content in response to changes of water content. The statistical-physical model was found to be useful for satisfactory predicting thermal properties of the soil with addition of biochar and organic amendments. Usowicz B. et al., 2006. Thermal conductivity modelling of terrestrial soil media - A comparative study. Planetary and Space Science 54, 1086-1095.

Inelastic neutron scattering study of phonon density of states in nanostructured Si1 xGex thermoelectrics

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

Dhital, Chetan; Abernathy, Douglas L; Zhu, Gaohua

2012-01-01

Inelastic neutron scattering measurements are utilized to explore relative changes in the generalized phonon density of states of nanocrystalline Si1 xGex thermoelectric materials prepared via ball-milling and hot-pressing techniques. Dynamic signatures of Ge clustering can be inferred from the data by referencing the resulting spectra to a density functional theoretical model assuming homogeneous alloying via the virtual-crystal approximation. Comparisons are also presented between as-milled Si nanopowder and bulk, polycrystalline Si where a preferential low-energy enhancement and lifetime broadening of the phonon density of states appear in the nanopowder. Negligible differences are however observed between the phonon spectra of bulk Simore » andhot-pressed, nanostructured Si samples suggesting that changes to the single-phonon dynamics above 4 meV play only a secondary role in the modified heat conduction of this compound.« less

Highly compressible 3D periodic graphene aerogel microlattices

PubMed Central

Zhu, Cheng; Han, T. Yong-Jin; Duoss, Eric B.; Golobic, Alexandra M.; Kuntz, Joshua D.; Spadaccini, Christopher M.; Worsley, Marcus A.

2015-01-01

Graphene is a two-dimensional material that offers a unique combination of low density, exceptional mechanical properties, large surface area and excellent electrical conductivity. Recent progress has produced bulk 3D assemblies of graphene, such as graphene aerogels, but they possess purely stochastic porous networks, which limit their performance compared with the potential of an engineered architecture. Here we report the fabrication of periodic graphene aerogel microlattices, possessing an engineered architecture via a 3D printing technique known as direct ink writing. The 3D printed graphene aerogels are lightweight, highly conductive and exhibit supercompressibility (up to 90% compressive strain). Moreover, the Young's moduli of the 3D printed graphene aerogels show an order of magnitude improvement over bulk graphene materials with comparable geometric density and possess large surface areas. Adapting the 3D printing technique to graphene aerogels realizes the possibility of fabricating a myriad of complex aerogel architectures for a broad range of applications. PMID:25902277

Site preparation effects on soil bulk density and pine seedling growth

Treesearch

John J. Stransky

1981-01-01

Soil bulk density was sampled the first and third growing seasons after site preparation and pine planting on three clearcut pine-hardwood forest sites in eastern Texas. Bulk density was measured 10 cm below the surface of mineral soil using a surface moisture-density probe. Plots that had been KG-bladed and chopped had significanlty higher bulk density than those that...

Comparison of different models for predicting soil bulk density. Case study - Slovakian agricultural soils

NASA Astrophysics Data System (ADS)

Makovníková, Jarmila; Širáň, Miloš; Houšková, Beata; Pálka, Boris; Jones, Arwyn

2017-10-01

Soil bulk density is one of the main direct indicators of soil health, and is an important aspect of models for determining agroecosystem services potential. By way of applying multi-regression methods, we have created a distributed prediction of soil bulk density used subsequently for topsoil carbon stock estimation. The soil data used for this study were from the Slovakian partial monitoring system-soil database. In our work, two models of soil bulk density in an equilibrium state, with different combinations of input parameters (soil particle size distribution and soil organic carbon content in %), have been created, and subsequently validated using a data set from 15 principal sampling sites of Slovakian partial monitoring system-soil, that were different from those used to generate the bulk density equations. We have made a comparison of measured bulk density data and data calculated by the pedotransfer equations against soil bulk density calculated according to equations recommended by Joint Research Centre Sustainable Resources for Europe. The differences between measured soil bulk density and the model values vary from -0.144 to 0.135 g cm-3 in the verification data set. Furthermore, all models based on pedotransfer functions give moderately lower values. The soil bulk density model was then applied to generate a first approximation of soil bulk density map for Slovakia using texture information from 17 523 sampling sites, and was subsequently utilised for topsoil organic carbon estimation.

K{sub 1.33}Mn{sub 8}O{sub 16} as an electrocatalyst and a cathode

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

Jalili, Seifollah, E-mail: sjalili@kntu.ac.ir; Computational Physical Sciences Research Laboratory, School of Nano-Science, Institute for Research in Fundamental Sciences; Moharramzadeh Goliaei, Elham

Density functional theory (DFT) calculations are carried out to investigate the electronic, magnetic and thermoelectric properties of bulk and nanosheet K{sub 1.33}Mn{sub 8}O{sub 16} materials. The catalytic activity and cathodic performance of bulk and nanosheet structures are examined using the Tran-Blaha modified Becke-Johnson (TB-mBJ) exchange potential. Electronic structure calculations reveal an anti-ferromagnetic ground state, with a TB-mMBJ band gap in bulk K{sub 1.33}Mn{sub 8}O{sub 16} that is in agreement with experimental results. Density of state plots indicate a partial reduction of Mn{sup 4+} ions to Mn{sup 3+}, without any obvious sign of Jahn-Teller distortion. Moreover, use of the O p-bandmore » center as a descriptor of catalytic activity suggests that the nanosheet has enhanced catalytic activity compared to the bulk structure. Thermoelectric parameters such as the Seebeck coefficient, electrical conductivity, and thermal conductivity are also calculated, and it is found that the Seebeck coefficients decrease with increasing temperature. High Seebeck coefficients for both spin-up and spin-down states are found in the nanosheet relative to their value in the bulk K{sub 1.33}Mn{sub 8}O{sub 16} structure, whereas the electrical and thermal conductivity are reduced relative to the bulk. In addition, figures of merit values are calculated as a function of the chemical potential and it is found that the nanosheet has a figure of merit of ~1 at room temperature, compared to 0.5 for the bulk material. All results suggest that K{sub 1.33}Mn{sub 8}O{sub 16} nanosheets can be used both as a material in waste heat recovery and as an electrocatalyst in fuel cells and batteries. - Graphical abstract: K{sub 1.33}Mn{sub 8}O{sub 16}: bulk and nanosheet. - Highlights: • Electronic properties of bulk and nanosheet forms of K{sub 1.33}Mn{sub 8}O{sub 16} have been studied. • The K{sub 1.33}Mn{sub 8}O{sub 16} nanosheet is a semiconductor while the bulk is a metal. • K{sub 1.33}Mn{sub 8}O{sub 16} Nanosheet is a more efficient electrocatalyst than bulk K{sub 1.33}Mn{sub 8}O{sub 16}. • High figure of merit of K{sub 1.33}Mn{sub 8}O{sub 16} nanosheet makes it an efficient cathode.« less

Thermally ruggedized ITO transparent electrode films for high power optoelectronics.

PubMed

Yoo, Jae-Hyuck; Matthews, Manyalibo; Ramsey, Phil; Barrios, Antonio Correa; Carter, Austin; Lange, Andrew; Bude, Jeff; Elhadj, Selim

2017-10-16

We present two strategies to minimize laser damage in transparent conductive films. The first consists of improving heat dissipation by selection of substrates with high thermal diffusivity or by addition of capping layer heatsinks. The second is reduction of bulk energy absorption by lowering free carrier density and increasing mobility, while maintaining film conductance with thicker films. Multi-pulse laser damage tests were performed on tin-doped indium oxide (ITO) films configured to improve optical lifetime damage performance. Conditions where improvements were not observed are also described. When bulk heating is not the dominant damage process, discrete defect-induced damage limits damage behavior.

Quantum and Classical Magnetoresistance in Ambipolar Topological Insulator Transistors with Gate-tunable Bulk and Surface Conduction

PubMed Central

Tian, Jifa; Chang, Cuizu; Cao, Helin; He, Ke; Ma, Xucun; Xue, Qikun; Chen, Yong P.

2014-01-01

Weak antilocalization (WAL) and linear magnetoresistance (LMR) are two most commonly observed magnetoresistance (MR) phenomena in topological insulators (TIs) and often attributed to the Dirac topological surface states (TSS). However, ambiguities exist because these phenomena could also come from bulk states (often carrying significant conduction in many TIs) and are observable even in non-TI materials. Here, we demonstrate back-gated ambipolar TI field-effect transistors in (Bi0.04Sb0.96)2Te3 thin films grown by molecular beam epitaxy on SrTiO3(111), exhibiting a large carrier density tunability (by nearly 2 orders of magnitude) and a metal-insulator transition in the bulk (allowing switching off the bulk conduction). Tuning the Fermi level from bulk band to TSS strongly enhances both the WAL (increasing the number of quantum coherent channels from one to peak around two) and LMR (increasing its slope by up to 10 times). The SS-enhanced LMR is accompanied by a strongly nonlinear Hall effect, suggesting important roles of charge inhomogeneity (and a related classical LMR), although existing models of LMR cannot capture all aspects of our data. Our systematic gate and temperature dependent magnetotransport studies provide deeper insights into the nature of both MR phenomena and reveal differences between bulk and TSS transport in TI related materials. PMID:24810663

Impedance Spectroscopy and AC Conductivity Studies of Bulk 3-Amino-7-(dimethylamino)-2-methyl-hydrochloride

NASA Astrophysics Data System (ADS)

El-Shabaan, M. M.

2018-02-01

Impedance spectroscopy and alternating-current (AC) conductivity (σ AC) studies of bulk 3-amino-7-(dimethylamino)-2-methyl-hydrochloride (neutral red, NR) have been carried out over the temperature (T) range from 303 K to 383 K and frequency (f) range from 0.5 kHz to 5 MHz. Dielectric data were analyzed using the complex impedance (Z *) and complex electric modulus (M *) for bulk NR at various temperatures. The impedance loss peaks were found to shift towards high frequencies, indicating an increase in the relaxation time (τ 0) and loss in the material, with increasing temperature. For each temperature, a single depressed semicircle was observed at high frequencies, originating from the bulk transport, and a spike in the low-frequency region, resulting from the electrode effect. Fitting of these curves yielded an equivalent circuit containing a parallel combination of a resistance R and constant-phase element (CPE) Q. The carrier transport in bulk NR is governed by the correlated barrier hopping (CBH) mechanism, some parameters of which, such as the maximum barrier height (W M), charge density (N), and hopping distance (r), were determined as functions of both temperature and frequency. The frequency dependence of σ AC at different temperatures indicated that the conduction in bulk NR is a thermally activated process. The σ AC value at different frequencies increased linearly with temperature.

Hydrologic properties of one major and two minor soil series of the Coast Ranges of northern California

Treesearch

Edward Pearson Wosika

1981-01-01

Abstract - The following properties of the Hugo, Mendocino, and Caspar soil series were analyzed at the 10 cm, 20 cm, 30 cm, 50 cm, 100 cm, and 150 cm depths: bulk density; porosity; particle density; saturated and unsaturated hydraulic conductivity; particle-size distribution; pore-size distribution; and water retention characteristics. The Hugo soil series exhibits...

The effect of moisture content on the thermal conductivity of moss and organic soil horizons from black spruce ecosystems in interior Alaska

Treesearch

Jonathan A. O' Donnell; Vladimir E. Romanovsky; Jennifer W. Harden; A. David McGuire

2009-01-01

Organic soil horizons function as important controls on the thermal state of near-surface soil and permafrost in high-latitude ecosystems. The thermal conductivity of organic horizons is typically lower than mineral soils and is closely linked to moisture content, bulk density, and water phase. In this study, we examined the relationship between thermal conductivity...

Statistical and Multifractal Evaluation of Soil Compaction in a Vineyard

NASA Astrophysics Data System (ADS)

Marinho, M.; Raposo, J. R.; Mirás Avalos, J. M.; Paz González, A.

2012-04-01

One of the detrimental effects caused by agricultural machines is soil compaction, which can be defined by an increase in soil bulk density. Soil compaction often has a negative impact on plant growth, since it reduces the macroporosity and soil permeability and increases resistance to penetration. Our research explored the effect of the agricultural machinery on soil when trafficking through a vineyard at a small spatial scale, based on the evaluation of the soil compaction status. The objectives of this study were: i) to quantify soil bulk density along transects following wine row, wheel track and outside track, and, ii) to characterize the variability of the bulk density along these transects using multifractal analysis. The field work was conducted at the experimental farm of EVEGA (Viticulture and Enology Centre of Galicia) located in Ponte San Clodio, Leiro, Orense, Spain. Three parallel transects were marked on positions with contrasting machine traffic effects, i.e. vine row, wheel-track and outside-track. Undisturbed samples were collected in 16 points of each transect, spaced 0.50 m apart, for bulk density determination using the cylinder method. Samples were taken in autumn 2011, after grape harvest. Since soil between vine rows was tilled and homogenized beginning spring 2011, cumulative effects of traffic during the vine growth period could be evaluated. The distribution patterns of soil bulk density were characterized by multifractal analysis carried out by the method of moments. Multifractality was assessed by several indexes derived from the mass exponent, τq, the generalized dimension, Dq, and the singularity spectrum, f(α), curves. Mean soil bulk density values determined for vine row, outside-track and wheel-track transects were 1.212 kg dm-3, 1.259 kg dm-3and 1.582 kg dm-3, respectively. The respective coefficients of variation (CV) for these three transects were 7.76%, 4.82% and 2.03%. Therefore mean bulk density under wheel-track was 30.5% higher than along the vine row. Vine row and outside-track positions showed not significant differences between means. The bulk density of the wheel-track transect also showed the lowest CV. The multifractal spectra of the three transects were asymmetric curves, rather short toward the left and much longer toward the right. The width of the right deviating shaped multifractal spectra was ranked as: wine row > outside-track ≈ wheel-track. Entropy dimension, D1, was 0.998, 0.992 and 0.992 for vine row, outside-track and track transects, respectively. These results show different patterns of variability of bulk density for parallel transects. They also suggest that multifractal parameters may be useful in assessing the variability of other soil properties such as soil particle density, soil porosity or soil water content, at different spatial scales as well. Acknowledgments. This work was funded in part by Spanish Ministry of Science and Innovation (MICINN) in the frame of project CGL2009-13700-C02. Financial support from CAPES/GOV., Brazil, is also acknowledged by Prof. M. Marinho.

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

Ginley, Theresa P.; Wang, Yong; Law, Stephanie

In this article, we will review recent progress in the growth of topological insulator (TI) thin films by molecular beam epitaxy (MBE). The materials we focus on are the V 2-VI 3 family of TIs. These materials are ideally bulk insulating with surface states housing Dirac excitations which are spin-momentum locked. These surface states are interesting for fundamental physics studies (such as the search for Majorana fermions) as well as applications in spintronics and other fields. However, the majority of TI films and bulk crystals exhibit significant bulk conductivity, which obscures these states. In addition, many TI films have amore » high defect density. This review will discuss progress in reducing the bulk conductivity while increasing the crystal quality. We will describe in detail how growth parameters, substrate choice, and growth technique influence the resulting TI film properties for binary and ternary TIs. We then give an overview of progress in the growth of TI heterostructures. Furthermore, we close by discussing the bright future for TI film growth by MBE.« less

Soil bulk density changes caused by mechanized harvesting: A case study in central Appalachia

Treesearch

Jingxin Wang; Chris B. LeDoux; Pam Edwards; Mark Jones; Mark Jones

2005-01-01

A mechanized harvesting system consisting of a feller-buncher and a grapple skidder was examined to quantify soil bulk density changes in a central Appalachian hardwood forest site. Soil bulk density was measured using a nuclear gauge pre-harvest and post-harvest systematically across the harvest unit and on transects across skid trails. Bulk density also was measured...

An environment-dependent semi-empirical tight binding model suitable for electron transport in bulk metals, metal alloys, metallic interfaces, and metallic nanostructures. II. Application—Effect of quantum confinement and homogeneous strain on Cu conductance

NASA Astrophysics Data System (ADS)

Hegde, Ganesh; Povolotskyi, Michael; Kubis, Tillmann; Charles, James; Klimeck, Gerhard

2014-03-01

The Semi-Empirical tight binding model developed in Part I Hegde et al. [J. Appl. Phys. 115, 123703 (2014)] is applied to metal transport problems of current relevance in Part II. A systematic study of the effect of quantum confinement, transport orientation, and homogeneous strain on electronic transport properties of Cu is carried out. It is found that quantum confinement from bulk to nanowire boundary conditions leads to significant anisotropy in conductance of Cu along different transport orientations. Compressive homogeneous strain is found to reduce resistivity by increasing the density of conducting modes in Cu. The [110] transport orientation in Cu nanowires is found to be the most favorable for mitigating conductivity degradation since it shows least reduction in conductance with confinement and responds most favorably to compressive strain.

Improvement of flow and bulk density of pharmaceutical powders using surface modification.

PubMed

Jallo, Laila J; Ghoroi, Chinmay; Gurumurthy, Lakxmi; Patel, Utsav; Davé, Rajesh N

2012-02-28

Improvement in flow and bulk density, the two most important properties that determine the ease with which pharmaceutical powders can be handled, stored and processed, is done through surface modification. A limited design of experiment was conducted to establish a standardized dry coating procedure that limits the extent of powder attrition, while providing the most consistent improvement in angle of repose (AOR). The magnetically assisted impaction coating (MAIC) was considered as a model dry-coater for pharmaceutical powders; ibuprofen, acetaminophen, and ascorbic acid. Dry coated drug powders were characterized by AOR, particle size as a function of dispersion pressure, particle size distribution, conditioned bulk density (CBD), Carr index (CI), flow function coefficient (FFC), cohesion coefficient using different instruments, including a shear cell in the Freeman FT4 powder rheometer, and Hansen flowability index. Substantial improvement was observed in all the measured properties after dry coating relative to the uncoated powders, such that each powder moved from a poorer to a better flow classification and showed improved dispersion. The material intrinsic property such as cohesion, plotted as a function of particle size, gave a trend similar to those of bulk flow properties, AOR and CI. Property improvement is also illustrated in a phase map of inverse cohesion (or FFC) as a function of bulk density, which also indicated a significant positive shift due to dry coating. It is hoped that such phase maps are useful in manufacturing decisions regarding the need for dry coating, which will allow moving from wet granulation to roller compaction or to direct compression based formulations. Copyright © 2011 Elsevier B.V. All rights reserved.

Using the Opposition Effect in Remotely Sensed Data to Assist in the Retrieval of Bulk Density

NASA Astrophysics Data System (ADS)

Ambeau, Brittany L.

Bulk density is an important geophysical property that impacts the mobility of military vehicles and personnel. Accurate retrieval of bulk density from remotely sensed data is, therefore, needed to estimate the mobility on "off-road" terrain. For a particulate surface, the functional form of the opposition effect can provide valuable information about composition and structure. In this research, we examine the relationship between bulk density and angular width of the opposition effect for a controlled set of laboratory experiments. Given a sample with a known bulk density, we collect reflectance measurements on a spherical grid for various illumination and view geometries -- increasing the amount of reflectance measurements collected at small phase angles near the opposition direction. Bulk densities are varied using a custom-made pluviation device, samples are measured using the Goniometer of the Rochester Institute of Technology-Two (GRIT-T), and observations are fit to the Hapke model using a grid-search method. The method that is selected allows for the direct estimation of five parameters: the single-scattering albedo, the amplitude of the opposition effect, the angular width of the opposition effect, and the two parameters that describe the single-particle phase function. As a test of the Hapke model, the retrieved bulk densities are compared to the known bulk densities. Results show that with an increase in the availability of multi-angular reflectance measurements, the prospects for retrieving the spatial distribution of bulk density from satellite and airborne sensors are imminent.

Electronic properties and surface reactivity of SrO-terminated SrTiO3 and SrO-terminated iron-doped SrTiO3

PubMed Central

Staykov, Aleksandar; Tellez, Helena; Druce, John; Wu, Ji; Ishihara, Tatsumi; Kilner, John

2018-01-01

Abstract Surface reactivity and near-surface electronic properties of SrO-terminated SrTiO3 and iron doped SrTiO3 were studied with first principle methods. We have investigated the density of states (DOS) of bulk SrTiO3 and compared it to DOS of iron-doped SrTiO3 with different oxidation states of iron corresponding to varying oxygen vacancy content within the bulk material. The obtained bulk DOS was compared to near-surface DOS, i.e. surface states, for both SrO-terminated surface of SrTiO3 and iron-doped SrTiO3. Electron density plots and electron density distribution through the entire slab models were investigated in order to understand the origin of surface electrons that can participate in oxygen reduction reaction. Furthermore, we have compared oxygen reduction reactions at elevated temperatures for SrO surfaces with and without oxygen vacancies. Our calculations demonstrate that the conduction band, which is formed mainly by the d-states of Ti, and Fe-induced states within the band gap of SrTiO3, are accessible only on TiO2 terminated SrTiO3 surface while the SrO-terminated surface introduces a tunneling barrier for the electrons populating the conductance band. First principle molecular dynamics demonstrated that at elevated temperatures the surface oxygen vacancies are essential for the oxygen reduction reaction. PMID:29535797

Tailoring properties of reticulated vitreous carbon foams with tunable density

NASA Astrophysics Data System (ADS)

Smorygo, Oleg; Marukovich, Alexander; Mikutski, Vitali; Stathopoulos, Vassilis; Hryhoryeu, Siarhei; Sadykov, Vladislav

2016-06-01

Reticulated vitreous carbon (RVC) foams were manufactured by multiple replications of a polyurethane foam template structure using ethanolic solutions of phenolic resin. The aims were to create an algorithm of fine tuning the precursor foam density and ensure an open-cell reticulated porous structure in a wide density range. The precursor foams were pyrolyzed in inert atmospheres at 700°C, 1100°C and 2000°C, and RVC foams with fully open cells and tunable bulk densities within 0.09-0.42 g/cm3 were synthesized. The foams were characterized in terms of porous structure, carbon lattice parameters, mechanical properties, thermal conductivity, electric conductivity, and corrosive resistance. The reported manufacturing approach is suitable for designing the foam microstructure, including the strut design with a graded microstructure.

A Novel Method for Measuring Electrical Conductivity of High Insulating Oil Using Charge Decay

NASA Astrophysics Data System (ADS)

Wang, Z. Q.; Qi, P.; Wang, D. S.; Wang, Y. D.; Zhou, W.

2016-05-01

For the high insulating oil, it is difficult to measure the conductivity precisely using voltammetry method. A high-precision measurementis proposed for measuring bulk electrical conductivity of high insulating oils (about 10-9--10-15S/m) using charge decay. The oil is insulated and charged firstly, and then grounded fully. During the experimental procedure, charge decay is observed to show an exponential law according to "Ohm" theory. The data of time dependence of charge density is automatically recorded using an ADAS and a computer. Relaxation time constant is fitted from the data using Gnuplot software. The electrical conductivity is calculated using relaxation time constant and dielectric permittivity. Charge density is substituted by electric potential, considering charge density is difficult to measure. The conductivity of five kinds of oils is measured. Using this method, the conductivity of diesel oil is easily measured to beas low as 0.961 pS/m, as shown in Fig. 5.

Thermally ruggedized ITO transparent electrode films for high power optoelectronics

DOE PAGES

Yoo, Jae-Hyuck; Matthews, Manyalibo; Ramsey, Phil; ...

2017-10-06

Here, we present two strategies to minimize laser damage in transparent conductive films. The first consists of improving heat dissipation by selection of substrates with high thermal diffusivity or by addition of capping layer heatsinks. The second is reduction of bulk energy absorption by lowering free carrier density and increasing mobility, while maintaining film conductance with thicker films. Multi-pulse laser damage tests were performed on tin-doped indium oxide (ITO) films configured to improve optical lifetime damage performance. Conditions where improvements were not observed are also described. Finally, when bulk heating is not the dominant damage process, discrete defect-induced damage limitsmore » damage behavior.« less

Highly compressible 3D periodic graphene aerogel microlattices

DOE PAGES

Zhu, Cheng; Han, T. Yong-Jin; Duoss, Eric B.; ...

2015-04-22

Graphene is a two-dimensional material that offers a unique combination of low density, exceptional mechanical properties, large surface area and excellent electrical conductivity. Recent progress has produced bulk 3D assemblies of graphene, such as graphene aerogels, but they possess purely stochastic porous networks, which limit their performance compared with the potential of an engineered architecture. Here we report the fabrication of periodic graphene aerogel microlattices, possessing an engineered architecture via a 3D printing technique known as direct ink writing. The 3D printed graphene aerogels are lightweight, highly conductive and exhibit supercompressibility (up to 90% compressive strain). Moreover, the Young’s modulimore » of the 3D printed graphene aerogels show an order of magnitude improvement over bulk graphene materials with comparable geometric density and possess large surface areas. Ultimately, adapting the 3D printing technique to graphene aerogels realizes the possibility of fabricating a myriad of complex aerogel architectures for a broad range of applications.« less

Effect of Fresh Poultry Litter and Compost on Soil Physical and Chemical Properties

NASA Technical Reports Server (NTRS)

Carr, Stacy; Tsegaye, Teferi; Coleman, Tommy

1998-01-01

Application of poultry litter and compost as a substitute for fertilizer not only uses unwanted waste and decreases expenditures for commercial fertilizer, it adds nutrients to soil for plant uptake. The properties of soil affected by poultry litter were analyzed to determine the positive and negative aspects of using this substitute fertilizer. This study focused on changes associated with saturated hydraulic conductivity, bulk density, nitrate concentrations, and pH after application of varying concentrations of poultry litter and compost. Soil samples from Tennessee Valley Substation in Alabama were analyzed in a laboratory at Alabama A&M University. As a result of the application of fresh poultry litter and compost, we found that the saturated hydraulic conductivity increased and the bulk density decreased, while the pH was generally not affected. Using poultry litter and compost as an alternative commercial fertilizers could be adapted by the farming community to protect the sustainability of our environment. Unwanted waste is used productively and soil is enriched for farming.

Influence of moisture content and temperature on thermal conductivity and thermal diffusivity of rice flours

USDA-ARS?s Scientific Manuscript database

The thermal conductivity and thermal diffusivity of four types of rice flours and one type of rice protein were determine at temperatures ranging from 4.8 to 36.8 C, bulk densities 535 to 875.8 kg/m3, and moisture contents 2.6 to 16.7 percent (w.b.), using a KD2 Thermal Properties Analyzer. It was ...

Correlations Between Magnetic Flux and Levitation Force of HTS Bulk Above a Permanent Magnet Guideway

NASA Astrophysics Data System (ADS)

Huang, Huan; Zheng, Jun; Zheng, Botian; Qian, Nan; Li, Haitao; Li, Jipeng; Deng, Zigang

2017-10-01

In order to clarify the correlations between magnetic flux and levitation force of the high-temperature superconducting (HTS) bulk, we measured the magnetic flux density on bottom and top surfaces of a bulk superconductor while vertically moving above a permanent magnet guideway (PMG). The levitation force of the bulk superconductor was measured simultaneously. In this study, the HTS bulk was moved down and up for three times between field-cooling position and working position above the PMG, followed by a relaxation measurement of 300 s at the minimum height position. During the whole processes, the magnetic flux density and levitation force of the bulk superconductor were recorded and collected by a multipoint magnetic field measurement platform and a self-developed maglev measurement system, respectively. The magnetic flux density on the bottom surface reflected the induced field in the superconductor bulk, while on the top, it reveals the penetrated magnetic flux. The results show that the magnetic flux density and levitation force of the bulk superconductor are in direct correlation from the viewpoint of inner supercurrent. In general, this work is instructive for understanding the connection of the magnetic flux density, the inner current density and the levitation behavior of HTS bulk employed in a maglev system. Meanwhile, this magnetic flux density measurement method has enriched present experimental evaluation methods of maglev system.

Pressure-Dependent Electronic and Transport Properties of Bulk Platinum Oxide by Density Functional Theory

NASA Astrophysics Data System (ADS)

Kansara, Shivam; Gupta, Sanjeev K.; Sonvane, Yogesh; Nekrasov, Kirill A.; Kichigina, Natalia V.

2018-02-01

The structural, electronic, and vibrational properties of bulk platinum oxide (PtO) at compressive pressures in the interval from 0 GPa to 35 GPa are investigated using the density functional theory. The calculated electronic band structure of PtO shows poor metallicity at very low density of states on the Fermi level. However, the hybrid pseudopotential calculation yielded 0.78 eV and 1.30 eV direct band and indirect gap, respectively. Importantly, our results predict that PtO has a direct band gap within the framework of HSE06, and it prefers equally zero magnetic order at different pressures. In the Raman spectra, peaks are slightly shifted towards higher frequency with the decrease in pressure. We have also calculated the thermoelectric properties, namely the electronic thermal conductivity and electrical conductivity, with respect to temperature and thermodynamic properties such as entropy, specific heat at constant volume, enthalpy and Gibbs free energy with respect to pressure. The result shows that PtO is a promising candidate for use as a catalyst, in sensors, as a photo-cathode in water electrolysis, for thermal decomposition of inorganic salt and fuel cells.

Investigation of nanoparticle agglomeration on the effective thermal conductivity of a composite material

NASA Astrophysics Data System (ADS)

Webb, Anthony J.

Phase Change Materials (PCMs), like paraffin wax, can be used for passive thermal management of portable electronics if their overall bulk thermal conductivity is increased through the addition of highly conducting nanoparticles. Finite Element Analysis (FEA) is used to investigate the influence of nanoparticle agglomeration on the overall conductive thermal transport in a nanoenhanced composite by dictating the thermal conductivity of individual elements according to their local inclusion volume fraction and characteristics inside a low conducting PCM matrix. The inclusion density distribution is dictated by an agglomeration factor, and the effective thermal conductivity of each element is calculated from the nanoparticle volume fraction using a method similar to the Representative Volume Element (RVE) methodology. FEA studies are performed for 2-D and 3-D models. In the 2-D model, the grain boundary is fixed at x = 0 for simplicity. For the 3-D model, the grain boundary geometry is randomly varied. A negligible 2-D effect on thermal transport in the 2-D model is seen, so a 1-D thermal resistance network is created for comparison, and the results agree within 4%.The influence of the agglomeration factor and contact Biot number on the overall bulk thermal conductivity is determined by applying Fourier's Law on the entire simulated composite. For the 2-D and 3-D models with a contact Biot number above 1, the overall bulk thermal conductivity decreases prior to the percolation threshold being met and then increases with increasing agglomeration. Finally, a MatlabRTM based image processing tool is created to estimate the agglomeration factor based on an experimental image of a nanoparticle distribution, with a calculated approximate agglomeration value of Beta*L = 5 which results in a bulk thermal conductivity of 0.278 W/(m-K).

Electronic transport in disordered MoS2 nanoribbons

NASA Astrophysics Data System (ADS)

Ridolfi, Emilia; Lima, Leandro R. F.; Mucciolo, Eduardo R.; Lewenkopf, Caio H.

2017-01-01

We study the electronic structure and transport properties of zigzag and armchair monolayer molybdenum disulfide nanoribbons using an 11-band tight-binding model that accurately reproduces the material's bulk band structure near the band gap. We study the electronic properties of pristine zigzag and armchair nanoribbons, paying particular attention to the edges states that appear within the MoS2 bulk gap. By analyzing both their orbital composition and their local density of states, we find that in zigzag-terminated nanoribbons these states can be localized at a single edge for certain energies independent of the nanoribbon width. We also study the effects of disorder in these systems using the recursive Green's function technique. We show that for the zigzag nanoribbons, the conductance due to the edge states is strongly suppressed by short-range disorder such as vacancies. In contrast, the local density of states still shows edge localization. We also show that long-range disorder has a small effect on the transport properties of nanoribbons within the bulk gap energy window.

Laboratory-Measured and Property-Transfer Modeled Saturated Hydraulic Conductivity of Snake River Plain Aquifer Sediments at the Idaho National Laboratory, Idaho

USGS Publications Warehouse

Perkins, Kim S.

2008-01-01

Sediments are believed to comprise as much as 50 percent of the Snake River Plain aquifer thickness in some locations within the Idaho National Laboratory. However, the hydraulic properties of these deep sediments have not been well characterized and they are not represented explicitly in the current conceptual model of subregional scale ground-water flow. The purpose of this study is to evaluate the nature of the sedimentary material within the aquifer and to test the applicability of a site-specific property-transfer model developed for the sedimentary interbeds of the unsaturated zone. Saturated hydraulic conductivity (Ksat) was measured for 10 core samples from sedimentary interbeds within the Snake River Plain aquifer and also estimated using the property-transfer model. The property-transfer model for predicting Ksat was previously developed using a multiple linear-regression technique with bulk physical-property measurements (bulk density [pbulk], the median particle diameter, and the uniformity coefficient) as the explanatory variables. The model systematically underestimates Ksat,typically by about a factor of 10, which likely is due to higher bulk-density values for the aquifer samples compared to the samples from the unsaturated zone upon which the model was developed. Linear relations between the logarithm of Ksat and pbulk also were explored for comparison.

A simplified regional-scale electromagnetic induction - Salinity calibration model using ANOCOVA modeling techniques

USDA-ARS?s Scientific Manuscript database

Directed soil sampling based on geospatial measurements of apparent soil electrical conductivity (ECa) is a potential means of characterizing the spatial variability of any soil property that influences ECa including soil salinity, water content, texture, bulk density, organic matter, and cation exc...

Kapton charging characteristics: Effects of material thickness and electron-energy distribution

NASA Technical Reports Server (NTRS)

Williamson, W. S.; Dulgeroff, C. R.; Hymann, J.; Viswanathan, R.

1985-01-01

Charging characteristics of polyimide (Kapton) of varying thicknesses under irradiation by a very-low-curent-density electron beam, with the back surface of the sample grounded are reported. These charging characteristics are in good agreement with a simple analytical model which predicts that in thin samples at low current density, sample surface potential is limited by conduction leakage through the bulk material. The charging of Kapton in a low-current-density electron beam in which the beam energy was modulated to simulate Maxwellian and biMaxwellian distribution functions is measured.

An International Round-Robin Study, Part II: Thermal Diffusivity, Specific Heat and Thermal Conductivity

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

Wang, Hsin; Porter, Wallace D; Bottner, Harold

2013-01-01

For bulk thermoelectrics, figure-of-merit, ZT, still needs to improve from the current value of 1.0 - 1.5 to above 2 to be competitive to other alternative technologies. In recent years, the most significant improvements in ZT were mainly due to successful reduction of thermal conductivity. However, thermal conductivity cannot be measured directly at high temperatures. The combined measurements of thermal diffusivity and specific heat and density are required. It has been shown that thermal conductivity is the property with the greatest uncertainty and has a direct influence on the accuracy of the figure of merit. The International Energy Agency (IEA)more » group under the implementing agreement for Advanced Materials for Transportation (AMT) has conducted two international round-robins since 2009. This paper is Part II of the international round-robin testing of transport properties of bulk bismuth telluride. The main focuses in Part II are on thermal diffusivity, specific heat and thermal conductivity.« less

Topological insulator film growth by molecular beam epitaxy: A review

DOE PAGES

Ginley, Theresa P.; Wang, Yong; Law, Stephanie

2016-11-23

In this article, we will review recent progress in the growth of topological insulator (TI) thin films by molecular beam epitaxy (MBE). The materials we focus on are the V 2-VI 3 family of TIs. These materials are ideally bulk insulating with surface states housing Dirac excitations which are spin-momentum locked. These surface states are interesting for fundamental physics studies (such as the search for Majorana fermions) as well as applications in spintronics and other fields. However, the majority of TI films and bulk crystals exhibit significant bulk conductivity, which obscures these states. In addition, many TI films have amore » high defect density. This review will discuss progress in reducing the bulk conductivity while increasing the crystal quality. We will describe in detail how growth parameters, substrate choice, and growth technique influence the resulting TI film properties for binary and ternary TIs. We then give an overview of progress in the growth of TI heterostructures. Furthermore, we close by discussing the bright future for TI film growth by MBE.« less

Soil Bulk Density by Soil Type, Land Use and Data Source: Putting the Error in SOC Estimates

NASA Astrophysics Data System (ADS)

Wills, S. A.; Rossi, A.; Loecke, T.; Ramcharan, A. M.; Roecker, S.; Mishra, U.; Waltman, S.; Nave, L. E.; Williams, C. O.; Beaudette, D.; Libohova, Z.; Vasilas, L.

2017-12-01

An important part of SOC stock and pool assessment is the assessment, estimation, and application of bulk density estimates. The concept of bulk density is relatively simple (the mass of soil in a given volume), the specifics Bulk density can be difficult to measure in soils due to logistical and methodological constraints. While many estimates of SOC pools use legacy data in their estimates, few concerted efforts have been made to assess the process used to convert laboratory carbon concentration measurements and bulk density collection into volumetrically based SOC estimates. The methodologies used are particularly sensitive in wetlands and organic soils with high amounts of carbon and very low bulk densities. We will present an analysis across four database measurements: NCSS - the National Cooperative Soil Survey Characterization dataset, RaCA - the Rapid Carbon Assessment sample dataset, NWCA - the National Wetland Condition Assessment, and ISCN - the International soil Carbon Network. The relationship between bulk density and soil organic carbon will be evaluated by dataset and land use/land cover information. Prediction methods (both regression and machine learning) will be compared and contrasted across datasets and available input information. The assessment and application of bulk density, including modeling, aggregation and error propagation will be evaluated. Finally, recommendations will be made about both the use of new data in soil survey products (such as SSURGO) and the use of that information as legacy data in SOC pool estimates.

Mapping soil moisture across an irrigated field using electromagnetic conductivity imaging

USDA-ARS?s Scientific Manuscript database

The ability to measure and map volumetric soil water theta quickly and accurately is important in irrigated agriculture. However, the traditional approach of using thermogravimetric moisture (w) and converting this to theta using measurements of bulk density (theta – cm3/cm3) is laborious and time c...

Physical properties of peats as related to degree of decomposition

Treesearch

D.H. Boelter

1969-01-01

Important physical characteristics, such as water retention, water yield coefficient, and hydraulic conductivity, vary greatly for representative northern Minnesota peat materials. The differences are related to the degree of decomposition, which largely determines the porosity and pore size distribution. Fiber content (> 0.1 mm) and bulk density are properties...

P-type conductivity in annealed strontium titanate

DOE PAGES

Poole, Violet M.; Corolewski, Caleb D.; McCluskey, Matthew D.

2015-12-17

In this study, Hall-effect measurements indicate p-type conductivity in bulk, single-crystal strontium titanate (SrTiO 3, or STO) samples that were annealed at 1200°C. Room temperature mobilities above 100 cm 2/Vs were measured, an order of magnitude higher than those for electrons (5-10 cm 2/Vs). Average hole densities were in the 10 9-10 10 cm -3 range, consistent with a deep acceptor.

Interrelationships among geotechnical and leaching properties of a cement-stabilized contaminated soil.

PubMed

Kogbara, Reginald B

2017-01-28

Relationships among selected performance properties have been established using experimental data from a cement-stabilized mixed contaminated soil. The sandy soil was spiked with 3,000 mg/kg each of Cd, Cu, Pb, Ni and Zn, and 10,000 mg/kg of diesel. It was then treated with 5%, 10%, 15%, and 20% dosages of Portland cement. Different water contents were considered for lower dosage mixes. Selected geotechnical and leaching properties were determined on 28-day old samples. These include unconfined compressive strength (UCS), bulk density, porosity, hydraulic conductivity, leachate pH and granular leachability of contaminants. Interrelationships among these properties were deduced using the most reasonable best fits determined by specialized curve fitting software. Strong quadratic and log-linear relationships exist between hydraulic conductivity and UCS, with increasing binder and water contents, respectively. However, the strength of interrelationships between hydraulic conductivity and porosity, UCS and porosity, and UCS and bulk density varies with binder and water contents. Leachate pH and granular leachability of contaminants are best related to UCS and hydraulic conductivity by a power law and an exponential function, respectively. These results suggest how the accuracy of not-easily-measurable performance properties may be constrained from simpler ones. Comparisons with some published performance properties data support this.

Antimonene: Experiments and theory of surface conductivity

NASA Astrophysics Data System (ADS)

Palacios, Juan Jose; Ares, Pablo; Pakdel, Sahar; Paz, Wendel; Zamora, Felix; Gomez-Herrero, Julio

Very recently antimony has been demonstrated to be amenable to standard exfoliation procedures opening the possibility of studying the electronic properties of isolated few-layers flakes of this material, a.k.a. antimonene. Antimony is a topological semimetal, meaning that its electronic structure presents spin-split helical states (or Dirac cones) on the surface, but it is still trivially metallic in bulk. Antimonene, on the other hand, may present a much reduced electronic bulk contribution for a small number of layers. A novel technique to make electrical contacts on the surface of individual thin flakes (5-10 monolayers) has allowed us to measure the (surface) conductivity of these in ambient conditions. Our measurements show a high conductivity in the range of 1 - 2e2 / h , which we attribute to the surface Dirac electrons. We have also carried out theoretical work to address the origin of this value, in particular, the importance of scattering between the Dirac electrons and the bulk bands. Our calculations are based on density functional theory for the electronic structure and Kubo formalism for the conductivity, the latter considering random disorder and the presence of water. Ministerio de Economia y Competitividad, Grant FIS2016-80434-P.

Temporal soil bulk density following tillage

USDA-ARS?s Scientific Manuscript database

Soil is the medium for air, energy, water, and chemical transport between the atmosphere and the solid earth. Soil bulk density is a key variable impacting the rate at which this transport occurs. Typically, soil bulk density is measured by the gravimetric method, where a sample of known volume is t...

Computer Modeling of the Thermal Conductivity of Cometary Ice

NASA Technical Reports Server (NTRS)

Bunch, Theodore E.; Wilson, Michael A.; Pohorille, Andrew

1998-01-01

The main objective of this research was to estimate the thermal conductivity of cometry ices from computer simulations of model amorphous ices. This was divided into four specific tasks: (1) Generating samples of amorphous water ices at different microporosities; (2) Comparing the resulting molecular structures of the ices with experimental results, for those densities where data was available; (3) Calculating the thermal conductivities of liquid water and bulk amorphous ices and comparing these results with experimentally determined thermal conductivities; and (4) Investigating how the thermal conductivity of amorphous ice depends upon the microscopic porosity of the samples. The thermal conductivity was found to be only weakly dependent on the microstructure of the amorphous ice. In general, the amorphous ices were found to have thermal conductivities of the same order of magnitude as liquid water. This is in contradiction to recent experimental estimates of the thermal conductivity of amorphous ice, and it is suggested that the extremely low value obtained experimentally is due to larger-scale defects in the ice, such as cracks, but it is not an intrinsic property of the bulk amorphous ice.

Effect of process variables on the quality characteristics of pelleted wheat distiller's dried grains with solubles

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

Jaya Shankar Tumuluru; Lope Tabil; Anthony Opoku

2011-04-01

The rapid expansion of ethanol processing plants in Canada has resulted in a significant increase in the production of wheat-based distiller's dried grains with solubles (DDGS). Transportation and flowability problems associated with DDGS necessitate investigations on pelleting. In the present study, the effect of process variables like die temperature (T) and feed moisture content (Mw) on the pellet properties like pellet moisture content, durability and pellet density was explored using a single pelleting machine; further studies on pelleting DDGS using a pilot-scale pellet mill were also conducted to understand the effect of die diameter and steam conditioning on durability andmore » bulk density of pellets. Proximate analysis of DDGS indicated that crude protein and dry matter were in the range of 37.37–40.33% and 91.27–92.60%, respectively. Linear regression models developed for pellet quality attributes like pellet moisture content, pellet density and durability adequately described the single pelleting process with R2 value of 0.97, 0.99 and 0.7, respectively. ANOVA results have indicated that linear terms T and Mw and the interaction term T × Mw were statistically significant at P < 0.01 and P < 0.1 for pellet moisture content and pellet density. Based on the trends of the surface plots, a medium T of about 50–80 °C and a low Mw of about 5.1% resulted in maximum pellet density and durability and minimum pellet moisture content. Results from pilot-scale studies indicated that bulk density, durability and throughput values were 436.8–528.9 kg m-3, 60.3–92.7% and 45.52–68.77 kg h-1, respectively. It was observed that both die diameter and steam addition had a significant effect on the bulk density and the durability values. The highest bulk density and durability were achieved with 6.4 mm die diameter with steam addition compared to 7.9 mm die with or without steam addition.« less

Investigation of Thermal Interface Materials Using Phase-Sensitive Transient Thermoreflectance Technique: Preprint

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

Feng, X.; King, C.; DeVoto, D.

2014-08-01

With increasing power density in electronics packages/modules, thermal resistances at multiple interfaces are a bottleneck to efficient heat removal from the package. In this work, the performance of thermal interface materials such as grease, thermoplastic adhesives and diffusion-bonded interfaces are characterized using the phase-sensitive transient thermoreflectance technique. A multi-layer heat conduction model was constructed and theoretical solutions were derived to obtain the relation between phase lag and the thermal/physical properties. This technique enables simultaneous extraction of the contact resistance and bulk thermal conductivity of the TIMs. With the measurements, the bulk thermal conductivity of Dow TC-5022 thermal grease (70 tomore » 75 um bondline thickness) was 3 to 5 W/(m-K) and the contact resistance was 5 to 10 mm2-K/W. For the Btech thermoplastic material (45 to 80 μm bondline thickness), the bulk thermal conductivity was 20 to 50 W/(m-K) and the contact resistance was 2 to 5 mm2-K/W. Measurements were also conducted to quantify the thermal performance of diffusion-bonded interface for power electronics applications. Results with the diffusion-bonded sample showed that the interfacial thermal resistance is more than one order of magnitude lower than those of traditional TIMs, suggesting potential pathways to efficient thermal management.« less

Evidence for a Low Bulk Crustal Density for Mars from Gravity and Topography.

PubMed

Goossens, Sander; Sabaka, Terence J; Genova, Antonio; Mazarico, Erwan; Nicholas, Joseph B; Neumann, Gregory A

2017-08-16

Knowledge of the average density of the crust of a planet is important in determining its interior structure. The combination of high-resolution gravity and topography data has yielded a low density for the Moon's crust, yet for other terrestrial planets the resolution of the gravity field models has hampered reasonable estimates. By using well-chosen constraints derived from topography during gravity field model determination using satellite tracking data, we show that we can robustly and independently determine the average bulk crustal density directly from the tracking data, using the admittance between topography and imperfect gravity. We find a low average bulk crustal density for Mars, 2582 ± 209 kg m -3 . This bulk crustal density is lower than that assumed until now. Densities for volcanic complexes are higher, consistent with earlier estimates, implying large lateral variations in crustal density. In addition, we find indications that the crustal density increases with depth.

Optical and electronic properties of 2 H -Mo S2 under pressure: Revealing the spin-polarized nature of bulk electronic bands

NASA Astrophysics Data System (ADS)

Brotons-Gisbert, Mauro; Segura, Alfredo; Robles, Roberto; Canadell, Enric; Ordejón, Pablo; Sánchez-Royo, Juan F.

2018-05-01

Monolayers of transition-metal dichalcogenide semiconductors present spin-valley locked electronic bands, a property with applications in valleytronics and spintronics that is usually believed to be absent in their centrosymmetric (as the bilayer or bulk) counterparts. Here we show that bulk 2 H -Mo S2 hides a spin-polarized nature of states determining its direct band gap, with the spin sequence of valence and conduction bands expected for its single layer. This relevant finding is attained by investigating the behavior of the binding energy of A and B excitons under high pressure, by means of absorption measurements and density-functional-theory calculations. These results raise an unusual situation in which bright and dark exciton degeneracy is naturally broken in a centrosymmetric material. Additionally, the phonon-assisted scattering process of excitons has been studied by analyzing the pressure dependence of the linewidth of discrete excitons observed at the absorption coefficient edge of 2 H -Mo S2 . Also, the pressure dependence of the indirect optical transitions of bulk 2 H -Mo S2 has been analyzed by absorption measurements and density-functional-theory calculations. These results reflect a progressive closure of the indirect band gap as pressure increases, indicating that metallization of bulk Mo S2 may occur at pressures higher than 26 GPa.

Lattice dynamics in elemental modulated Sb 2 Te 3 films: Lattice dynamics in elemental modulated Sb 2 Te 3 films

DOE PAGES

Bessas, D.; Winkler, M.; Sergueev, I.; ...

2015-09-03

We investigate the crystallinity and the lattice dynamics in elemental modulated Sbinline imageTeinline image films microscopically using high energy synchrotron radiation diffraction combined with inline imageSb nuclear inelastic scattering. The correlation length is found to be finite but less than 100 . Moreover, the element specific density of phonon states is extracted. A comparison with the element specific density of phonon states in bulk Sbinline imageTeinline image confirms that the main features in the density of phonon states arise from the layered structure. The average speed of sound at inline image inline image, is almost the same compared to bulkmore » Sbinline imageTeinline image at inline image, inline image. Similarly, the change in the acoustic cut-off energy is within the experimental detection limit. Therefore, we suggest that the lattice thermal conductivity in elemental modulated Sbinline imageTeinline image films should not be significantly changed from its bulk value.« less

Samarium Hexaboride: The First True 3D Topological Insulator?

NASA Astrophysics Data System (ADS)

Wolgast, Steven G.

The recent theoretical prediction of a topologically protected surface state in the mixed-valent insulator SmB6 has motivated a series of charge transport studies, which are presented here. It is first studied using a specialized configuration designed to distinguish bulk-dominated conduction from surface-dominated conduction. As the material is cooled below 4 K, it exhibits a crossover from thermally activated bulk transport to metallic surface conduction with a fully insulating bulk. The robustness and magnitude of the surface conductivity, as is manifest in the literature of SmB6, is strong evidence for the topological insulator (TI) metallic surface states predicted for this material. This resolves a decades-old puzzle surrounding the low-temperature behavior of SmB6. Next, the magnetotransport properties of the surface are investigated using a Corbino disk geometry, which can directly measure the conductivity of individual surfaces. Both (011) and (001) crystal surfaces show a strong negative magnetoresistance at all magnetic field angles, due primarily to changes in the carrier density. The low mobility value accounts for the failure so far to observe Shubnikov-de Haas oscillations below 95 T. Small variations in the mobility and temperature dependence suggest a suppression of Kondo scattering from native oxide-layer magnetic moments. At low fields, a dynamical field-sweep-rate-dependent hysteretic behavior is observed. It persists at the slowest sweep rates, and cannot be explained by quantum interference corrections; it is likely due to extrinsic effects such as the magnetocaloric effect or glassy ordering of the native oxide moments. Pulsed magnetic field measurements up to 60 T at temperatures throughout the crossover regime clearly distinguish the surface magnetoresistance from the bulk magnetoresistance. The bulk magnetoresistance is due to a reduction in the bulk gap with increasing magnetic field. Finally, small subsurface cracks formed in SmB6 via systematic scratching or sanding results in a counter-intuitive increase in the electrical conduction due to the unique surface-conducting property of TIs, strengthening the building case for SmB 6's topological nature. This material is attractive as a TI because its bulk is fully insulating at a readily achieved 2 K, but it presents a large number of scientific mysteries and experimental challenges for future research.

Porous materials produced from incineration ash using thermal plasma technology.

PubMed

Yang, Sheng-Fu; Chiu, Wen-Tung; Wang, To-Mai; Chen, Ching-Ting; Tzeng, Chin-Ching

2014-06-01

This study presents a novel thermal plasma melting technique for neutralizing and recycling municipal solid waste incinerator (MSWI) ash residues. MSWI ash residues were converted into water-quenched vitrified slag using plasma vitrification, which is environmentally benign. Slag is adopted as a raw material in producing porous materials for architectural and decorative applications, eliminating the problem of its disposal. Porous materials are produced using water-quenched vitrified slag with Portland cement and foaming agent. The true density, bulk density, porosity and water absorption ratio of the foamed specimens are studied here by varying the size of the slag particles, the water-to-solid ratio, and the ratio of the weights of the core materials, including the water-quenched vitrified slag and cement. The thermal conductivity and flexural strength of porous panels are also determined. The experimental results show the bulk density and the porosity of the porous materials are 0.9-1.2 g cm(-3) and 50-60%, respectively, and the pore structure has a closed form. The thermal conductivity of the porous material is 0.1946 W m(-1) K(-1). Therefore, the slag composite materials are lightweight and thermal insulators having considerable potential for building applications. Copyright © 2013 Elsevier Ltd. All rights reserved.

Military vehicle trafficking impacts on vegetation and soil bulk density at Fort Benning, Georgia

USDA-ARS?s Scientific Manuscript database

Potential increases in wind erosion that might be brought about by military vehicles travelling on off-road sites during training are of concern to the Military establishment. Field studies were conducted in the summer of 2012 at Fort Benning, Georgia. The objective of the experiment was to assess t...

Assessing soil impacts related to forest harvest operations

Treesearch

E.A. Carter; John M. III. Grace

2011-01-01

Three studies conducted in Alabama evaluated impacts associated with a clear cut harvest in three physiographic regions. Machine impacts were assessed via tabulation of soil disturbance classes, measurement of bulk density and soil strength, or a combination of the two. Soil disturbance classes were similar among all locations with untrafficked areas comprising...

Military vehicle trafficking impacts vegetation and soil bulk density at Fort Benning, Georgia

USDA-ARS?s Scientific Manuscript database

Potential increases in wind erosion that might be brought about by military vehicles travelling off-road during training are of concern to the United States military. Field studies were conducted in the summer of 2012 at Fort Benning, Georgia. The objective of the experiment was to assess the traffi...

Suns-VOC characteristics of high performance kesterite solar cells

NASA Astrophysics Data System (ADS)

Gunawan, Oki; Gokmen, Tayfun; Mitzi, David B.

2014-08-01

Low open circuit voltage (VOC) has been recognized as the number one problem in the current generation of Cu2ZnSn(Se,S)4 (CZTSSe) solar cells. We report high light intensity and low temperature Suns-VOC measurement in high performance CZTSSe devices. The Suns-VOC curves exhibit bending at high light intensity, which points to several prospective VOC limiting mechanisms that could impact the VOC, even at 1 sun for lower performing samples. These VOC limiting mechanisms include low bulk conductivity (because of low hole density or low mobility), bulk or interface defects, including tail states, and a non-ohmic back contact for low carrier density CZTSSe. The non-ohmic back contact problem can be detected by Suns-VOC measurements with different monochromatic illuminations. These limiting factors may also contribute to an artificially lower JSC-VOC diode ideality factor.

Measured acoustic properties of variable and low density bulk absorbers

NASA Technical Reports Server (NTRS)

Dahl, M. D.; Rice, E. J.

1985-01-01

Experimental data were taken to determine the acoustic absorbing properties of uniform low density and layered variable density samples using a bulk absober with a perforated plate facing to hold the material in place. In the layered variable density case, the bulk absorber was packed such that the lowest density layer began at the surface of the sample and progressed to higher density layers deeper inside. The samples were placed in a rectangular duct and measurements were taken using the two microphone method. The data were used to calculate specific acoustic impedances and normal incidence absorption coefficients. Results showed that for uniform density samples the absorption coefficient at low frequencies decreased with increasing density and resonances occurred in the absorption coefficient curve at lower densities. These results were confirmed by a model for uniform density bulk absorbers. Results from layered variable density samples showed that low frequency absorption was the highest when the lowest density possible was packed in the first layer near the exposed surface. The layers of increasing density within the sample had the effect of damping the resonances.

Meteoroid Bulk Density and Ceplecha Types

NASA Technical Reports Server (NTRS)

Blaauw, R. C.; Moser, D. E.; Moorhead, A. V.

2017-01-01

Determination of asteroid bulk density is an important aspect of NEO characterization, yet difficult to measure. As a fraction of meteoroids originate from asteroids (including some NEOs), a study of meteoroid bulk densities can potentially provide useful insights into the densities of NEOs and PHOs in lieu of mutual perturbations, satellite, or expensive spacecraft missions. NASA's Meteoroid Environment Office characterizes the meteoroid environment for the purpose of spacecraft risk and operations. To accurately determine the risk, a distribution of meteoroid bulk densities are needed. This is not trivial to determine. If the particle survives to the ground the bulk density can be directly measured, however only the most dense particles land on the Earth. The next best approach is to model the meteor's ablation, which is not straightforward. Clear deceleration is necessary to do this and there are discrepancies in results between models. One approach to a distribution of bulk density is to use a measured proxy for the densities, then calibrate the proxy with known densities from meteorite falls, ablation modelling, and other sources. An obvious proxy choice is the Ceplecha type, K(sub B), thought to indicate the strength of a meteoroid. KB is frequented cited as a good proxy for meteoroid densities, but we find it is poorly correlated with density. However, a distinct split by dynamical type was seen with Jovian Tisserand parameter, T(sub J), with meteoroids from Halley Type comets (T(sub J less than 2 ) exhibiting much lower densities than those originating from Jupiter and asteroids (T(sub J greater than 2).

Impurities or a neutral Fermi surface? A further examination of the low-energy ac optical conductivity of SmB6

NASA Astrophysics Data System (ADS)

Laurita, N. J.; Morris, C. M.; Koohpayeh, S. M.; Phelan, W. A.; McQueen, T. M.; Armitage, N. P.

2018-05-01

Recent experiments have uncovered evidence of low energy excitations in the bulk of SmB6 that are perhaps associated with unconventional quasiparticles, bringing into question whether this Kondo "insulator" is truly insulating in the bulk. Recently, we demonstrated that SmB6 possesses significant in-gap bulk ac conduction far in excess of typical disordered semiconductors. Whether such conduction is an intrinsic feature of SmB6, suggesting the formation of an exotic state, or residual conduction from impurities continues to be a topic of debate. Here, we further examine the origin of the ac optical conductivity of SmB6 in light of recent experimental and theoretical developments. The optical conductivity of SmB6 is shown to possess distinct regimes of either dominant free carrier or localized response contributions. The free carrier response is found to be in good qualitative agreement with previous literature, although quantitative differences are revealed and discussed. The localized response, which dominates at the lowest temperatures, is analyzed in the context of models of either in-gap impurity states or an exotic neutral Fermi surface. The charge density or effective mass of this low temperature in-gap conductivity is extracted through a conductivity sum rule analysis and found to be in general alignment with both models in the appropriate limits. Our results shed further light on the nature of the in-gap states of SmB6.

A Combined Molecular Dynamics and Experimental Study of Doped Polypyrrole.

PubMed

Fonner, John M; Schmidt, Christine E; Ren, Pengyu

2010-10-01

Polypyrrole (PPy) is a biocompatible, electrically conductive polymer that has great potential for battery, sensor, and neural implant applications. Its amorphous structure and insolubility, however, limit the experimental techniques available to study its structure and properties at the atomic level. Previous theoretical studies of PPy in bulk are also scarce. Using ab initio calculations, we have constructed a molecular mechanics force field of chloride-doped PPy (PPyCl) and undoped PPy. This model has been designed to integrate into the OPLS force field, and parameters are available for the Gromacs and TINKER software packages. Molecular dynamics (MD) simulations of bulk PPy and PPyCl have been performed using this force field, and the effects of chain packing and electrostatic scaling on the bulk polymer density have been investigated. The density of flotation of PPyCl films has been measured experimentally. Amorphous X-ray diffraction of PPyCl was obtained and correlated with atomic structures sampled from MD simulations. The force field reported here is foundational for bridging the gap between experimental measurements and theoretical calculations for PPy based materials.

A correlation between secondary structure and rheological properties of low-density lipoproteins at air/water interfaces.

PubMed

Khattari, Ziad

2017-09-01

The secondary structure of apolipoprotein B-100 is studied within the bulk phase and at the air/water interface. In these "in viro" experiments, infrared reflection absorption spectroscopy (IRRAS) study was performed at the air/water interface while circular dichroism (CD) was conducted in the bulk phase. In the bulk phase, the conformational structure containing a significant amount of β-structure, whereas varying amount of α-helix, unordered structures, and β-sheet were observed at the air/water interface depending on the low-density lipoprotein (LDL) film interfacial pressure. The present IRRAS results demonstrate the importance of interfacial pressure-induced structural conformations on the apoB-100. A correlation between the secondary structure of the apoB-100 protein and the monomolecular film elasticity at the air/water interface was also established. The orientation of apoB-100 with respect to the LDL film-normal was found to depend on the interfacial pressure exhibited by the monomolecular film. These results may shed light on LDL's pivotal role in the progression of atherosclerotic coronary artery disease as demonstrated previously by clinical trials.

Is the bulk mode conversion important in high density helicon plasma?

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

Isayama, Shogo; Hada, Tohru; Shinohara, Shunjiro

2016-06-15

In a high-density helicon plasma production process, a contribution of Trivelpiece-Gould (TG) wave for surface power deposition is widely accepted. The TG wave can be excited either due to an abrupt density gradient near the plasma edge (surface conversion) or due to linear mode conversion from the helicon wave in a density gradient in the bulk region (bulk mode conversion). By numerically solving the boundary value problem of linear coupling between the helicon and the TG waves in a background with density gradient, we show that the efficiency of the bulk mode conversion strongly depends on the dissipation included inmore » the plasma, and the bulk mode conversion is important when the dissipation is small. Also, by performing FDTD simulation, we show the time evolution of energy flux associated with the helicon and the TG waves.« less

Effects of biochars on hydraulic properties of clayey soil

NASA Astrophysics Data System (ADS)

Zhen, Jingbo; Palladino, Mario; Lazarovitch, Naftali; Bonanomi, Giuliano; Battista Chirico, Giovanni

2017-04-01

Biochar has gained popularity as an amendment to improve soil hydraulic properties. Since biochar properties depend on feedstocks and pyrolysis temperatures used for its production, proper selection of biochar type as soil amendment is of great importance for soil hydraulic properties improvement. This study investigated the effects of eight types of biochar on physical and hydraulic properties of clayey soil. Biochars were derived from four different feedstocks (Alfalfa hay, municipal organic waste, corn residues and wood chip) pyrolyzed at two different temperatures (300 and 550 °C). Clayey soil samples were taken from Leone farm (40° 26' 15.31" N, 14° 59' 45.54" E), Italy, and were oven-dried at 105 °C to determine dry bulk density. Biochars were mixed with the clayey soil at 5% by mass. Bulk densities of the mixtures were also determined. Saturated hydraulic conductivities (Ks) of the original clayey soil and corresponding mixtures were measured by means of falling-head method. Soil water retention measurements were conducted for clayey soil and mixtures using suction table apparatus and Richards' plate with the pressure head (h) up to 12000 cm. van Genuchten retention function was selected to evaluate the retention characteristics of clayey soil and mixtures. Available water content (AWC) was calculated by field capacity (h = - 500 cm) minus wilting pointing (h = -12000 cm). The results showed that biochar addition decreased the bulk density of clayey soil. The Ks of clayey soil increased due to the incorporation of biochars except for waste and corn biochars pyrolyzed at 550 °C. AWC of soils mixed with corn biochar pyrolyzed at 300 °C and wood biochar pyrolyzed at 550 °C, increased by 31% and 7%, respectively. Further analysis will be conducted in combination of biochar properties such as specific surface area and total pore volume. Better understanding of biochar impact on clayey soil will be helpful in biochar selection for soil amendment and improving water use efficiency in agriculture.

Bulk and surface states carried supercurrent in ballistic Nb-Dirac semimetal Cd3As2 nanowire-Nb junctions

NASA Astrophysics Data System (ADS)

Li, Cai-Zhen; Li, Chuan; Wang, Li-Xian; Wang, Shuo; Liao, Zhi-Min; Brinkman, Alexander; Yu, Da-Peng

2018-03-01

A three-dimensional Dirac semimetal has bulk Dirac cones in all three momentum directions and Fermi arc like surface states, and can be converted into a Weyl semimetal by breaking time-reversal symmetry. However, the highly conductive bulk state usually hides the electronic transport from the surface state in Dirac semimetal. Here, we demonstrate the supercurrent carried by bulk and surface states in Nb -Cd3As2 nanowire-Nb short and long junctions, respectively. For the ˜1 -μ m -long junction, the Fabry-Pérot interferences-induced oscillations of the critical supercurrent are observed, suggesting the ballistic transport of the surface states carried supercurrent, where the bulk states are decoherent and the topologically protected surface states still stay coherent. Moreover, a superconducting dome is observed in the long junction, which is attributed to the enhanced dephasing from the interaction between surface and bulk states as tuning gate voltage to increase the carrier density. The superconductivity of topological semimetal nanowire is promising for braiding of Majorana fermions toward topological quantum computing.

Diameter dependent thermoelectric properties of individual SnTe nanowires

DOE PAGES

Xu, E. Z.; Li, Z.; Martinez, J. A.; ...

2015-01-15

The lead-free compound tin telluride (SnTe) has recently been suggested to be a promising thermoelectric material. In this work, we report on the first thermoelectric study of individual single-crystalline SnTe nanowires with different diameters ranging from ~ 218 to ~ 913 nm. Measurements of thermopower S, electrical conductivity σ and thermal conductivity κ were carried out on the same nanowires over a temperature range of 25 - 300 K. While the electrical conductivity does not show a strong diameter dependence, the thermopower increases by a factor of two when the nanowire diameter is decreased from ~ 913 nm to ~more » 218 nm. The thermal conductivity of the measured NWs is lower than that of the bulk SnTe, which may arise from the enhanced phonon - surface boundary scattering and phonon-defect scattering. Lastly, temperature dependent figure of merit ZT was determined for individual nanowires and the achieved maximum value at room temperature is about three times higher than that in bulk samples of comparable carrier density.« less

Density functional theory study of defect energies and space charge distribution at a solid-oxide electrolyte surface

NASA Astrophysics Data System (ADS)

Han, Chu; Bongiorno, Angelo

2014-03-01

Yttrium-doped barium zirconate (BZY) is a proton conducting electrolyte forming a class of novel materials for new generation of solid oxide fuel cells, for hydrogen separation and purification, and for electrolysis of water. Here we use density functional theory calculations to compute the energy of protons and oxygen vacancies at the surface and in the bulk of lightly Y-doped BZY materials. We found that protons are energetically more stable at the surface termination than in the bulk of BZY by about 1 eV. In contrast, doubly-positively charged oxygen vacancies are found to form iso-energetic defects at both the terminal surface layer and in the bulk of BZY, while in the sub-surface region the defect energy raises by about 1 eV with respect to the value in the bulk. The energetic behavior of protons and oxygen vacancies in the near surface region of BZY is attributed to the competition of strain and electrostatic effects. Lattice model representations of BZY surfaces are then used in combination with Monte Carlo simulations to solve the Poisson-Boltzmann equation and investigate the implication of the results above on the structure of the space charge region at the surface of BZY materials.

Sample sizes to control error estimates in determining soil bulk density in California forest soils

Treesearch

Youzhi Han; Jianwei Zhang; Kim G. Mattson; Weidong Zhang; Thomas A. Weber

2016-01-01

Characterizing forest soil properties with high variability is challenging, sometimes requiring large numbers of soil samples. Soil bulk density is a standard variable needed along with element concentrations to calculate nutrient pools. This study aimed to determine the optimal sample size, the number of observation (n), for predicting the soil bulk density with a...

40 CFR 721.9675 - Titanate [Ti6O13 (2-)], di-po-tas-sium.

Code of Federal Regulations, 2012 CFR

2012-07-01

... bulk density measurements of the PMN substance in the pure form are less than 0.4 g/cm3 or greater than 0.6 g/cm3. The bulk density of each shipment must be verified, by lot, prior to clearing U.S... method of manufacture and bulk density measurements. (2) Limitations or revocation of certain...

40 CFR 721.9675 - Titanate [Ti6O13 (2-)], di-po-tas-sium.

Code of Federal Regulations, 2014 CFR

2014-07-01

... bulk density measurements of the PMN substance in the pure form are less than 0.4 g/cm3 or greater than 0.6 g/cm3. The bulk density of each shipment must be verified, by lot, prior to clearing U.S... method of manufacture and bulk density measurements. (2) Limitations or revocation of certain...

40 CFR 721.9675 - Titanate [Ti6O13 (2-)], di-po-tas-sium.

Code of Federal Regulations, 2011 CFR

2011-07-01

... bulk density measurements of the PMN substance in the pure form are less than 0.4 g/cm3 or greater than 0.6 g/cm3. The bulk density of each shipment must be verified, by lot, prior to clearing U.S... method of manufacture and bulk density measurements. (2) Limitations or revocation of certain...

Surface flux density distribution characteristics of bulk high- Tc superconductor in external magnetic field

NASA Astrophysics Data System (ADS)

Torii, S.; Yuasa, K.

2004-10-01

Various magnetic levitation systems using oxide superconductors are developed as strong pinning forces are obtained in melt-processed bulk. However, the trapped flux of superconductor is moved by flux creep and fluctuating magnetic field. Therefore, to examine the internal condition of superconductor, the authors measure the dynamic surface flux density distribution of YBCO bulk. Flux density measurement system has a structure with the air-core coil and the Hall sensors. Ten Hall sensors are arranged in series. The YBCO bulk, which has 25 mm diameter and 13 mm thickness, is field cooled by liquid nitrogen. After that, magnetic field is changed by the air-core coil. This paper describes about the measured results of flux density distribution of YBCO bulk in the various frequencies of air-core coils currents.

Enhanced charging kinetics of porous electrodes: surface conduction as a short-circuit mechanism.

PubMed

Mirzadeh, Mohammad; Gibou, Frederic; Squires, Todd M

2014-08-29

We use direct numerical simulations of the Poisson-Nernst-Planck equations to study the charging kinetics of porous electrodes and to evaluate the predictive capabilities of effective circuit models, both linear and nonlinear. The classic transmission line theory of de Levie holds for general electrode morphologies, but only at low applied potentials. Charging dynamics are slowed appreciably at high potentials, yet not as significantly as predicted by the nonlinear transmission line model of Biesheuvel and Bazant. We identify surface conduction as a mechanism which can effectively "short circuit" the high-resistance electrolyte in the bulk of the pores, thus accelerating the charging dynamics and boosting power densities. Notably, the boost in power density holds only for electrode morphologies with continuous conducting surfaces in the charging direction.

Bulk and interface quantum states of electrons in multi-layer heterostructures with topological materials

NASA Astrophysics Data System (ADS)

Nikolic, Aleksandar; Zhang, Kexin; Barnes, C. H. W.

2018-06-01

In this article we describe the bulk and interface quantum states of electrons in multi-layer heterostructures in one dimension, consisting of topological insulators (TIs) and topologically trivial materials. We use and extend an effective four-band continuum Hamiltonian by introducing position dependence to the eight material parameters of the Hamiltonian. We are able to demonstrate complete conduction-valence band mixing in the interface states. We find evidence for topological features of bulk states of multi-layer TI heterostructures, as well as demonstrating both complete and incomplete conduction-valence band inversion at different bulk state energies. We show that the linear k z terms in the low-energy Hamiltonian, arising from overlap of p z orbitals between different atomic layers in the case of chalcogenides, control the amount of tunneling from TIs to trivial insulators. Finally, we show that the same linear k z terms in the low-energy Hamiltonian affect the material’s ability to form the localised interface state, and we demonstrate that due to this effect the spin and probability density localisation in a thin film of Sb2Te3 is incomplete. We show that changing the parameter that controls the magnitude of the overlap of p z orbitals affects the transport characteristics of the topologically conducting states, with incomplete topological state localisation resulting in increased backscattering.

Bulk and interface quantum states of electrons in multi-layer heterostructures with topological materials.

PubMed

Nikolic, Aleksandar; Zhang, Kexin; Barnes, C H W

2018-06-13

In this article we describe the bulk and interface quantum states of electrons in multi-layer heterostructures in one dimension, consisting of topological insulators (TIs) and topologically trivial materials. We use and extend an effective four-band continuum Hamiltonian by introducing position dependence to the eight material parameters of the Hamiltonian. We are able to demonstrate complete conduction-valence band mixing in the interface states. We find evidence for topological features of bulk states of multi-layer TI heterostructures, as well as demonstrating both complete and incomplete conduction-valence band inversion at different bulk state energies. We show that the linear k z terms in the low-energy Hamiltonian, arising from overlap of p z orbitals between different atomic layers in the case of chalcogenides, control the amount of tunneling from TIs to trivial insulators. Finally, we show that the same linear k z terms in the low-energy Hamiltonian affect the material's ability to form the localised interface state, and we demonstrate that due to this effect the spin and probability density localisation in a thin film of Sb 2 Te 3 is incomplete. We show that changing the parameter that controls the magnitude of the overlap of p z orbitals affects the transport characteristics of the topologically conducting states, with incomplete topological state localisation resulting in increased backscattering.

Effects of Mass Fluctuation on Thermal Transport Properties in Bulk Bi2Te3

NASA Astrophysics Data System (ADS)

Huang, Ben; Zhai, Pengcheng; Yang, Xuqiu; Li, Guodong

2017-05-01

In this paper, we applied large-scale molecular dynamics and lattice dynamics to study the influence of mass fluctuation on thermal transport properties in bulk Bi2Te3, namely thermal conductivity ( K), phonon density of state (PDOS), group velocity ( v g), and mean free path ( l). The results show that total atomic mass change can affect the relevant vibrational frequency on the micro level and heat transfer rate in the macro statistic, hence leading to the strength variation of the anharmonic phonon processes (Umklapp scattering) in the defect-free Bi2Te3 bulk. Moreover, it is interesting to find that the anharmonicity of Bi2Te3 can be also influenced by atomic differences of the structure such as the mass distribution in the primitive cell. Considering the asymmetry of the crystal structure and interatomic forces, it can be concluded by phonon frequency, lifetime, and velocity calculation that acoustic-optical phonon scattering shows the structure-sensitivity to the mass distribution and complicates the heat transfer mechanism, hence resulting in the low lattice thermal conductivity of Bi2Te3. This study is helpful for designing the material with tailored thermal conductivity via atomic substitution.

Effect of CNT as a Nucleating Agent on Cell Morphology and Thermal Insulation Property of the Rigid Polyurethane Foams.

PubMed

Ahn, WonSool; Lee, Joon-Man

2015-11-01

The effects of MWCNT on the cell sizes, cell uniformities, thermal conductivities, bulk densities, foaming kinetics, and compressive mechanical properties of the rigid PUFs were investigated. To obtain the better uniform dispersed state of MWCNT, grease-type master batch of MWCNT/surfactant was prepared by three-roll mill. Average cell size of the PUF samples decreased from 185.1 for the neat PUF to 162.9 μm for the sample of 0.01 phr of MWCNT concentration. Cell uniformity was also enhanced showing the standard cell-size deviation of 61.7 and 35.2, respectively. While the thermal conductivity of the neat PUF was 0.0222 W/m(o)K, that of the sample with 0.01 phr of MWCNT showed 0.0204 W/m(o)K, resulting 8.2% reduction of the thermal conductivity. Bulk density of the PUF samples was observed as nearly the same values as 30.0 ± 1.0 g/cm3 regardless of MWCNT. Temperature profiles during foaming process showed that an indirect indication of the nucleation effect of MWCNT for the PUF foaming system, showing faster and higher temperature rising with time. The compressive yield stress is nearly the same as 0.030 x 10(5) Pa regardless of MWCNT.

Determination of bulk and interface density of states in metal oxide semiconductor thin-film transistors by using capacitance-voltage characteristics

NASA Astrophysics Data System (ADS)

Wei, Xixiong; Deng, Wanling; Fang, Jielin; Ma, Xiaoyu; Huang, Junkai

2017-10-01

A physical-based straightforward extraction technique for interface and bulk density of states in metal oxide semiconductor thin film transistors (TFTs) is proposed by using the capacitance-voltage (C-V) characteristics. The interface trap density distribution with energy has been extracted from the analysis of capacitance-voltage characteristics. Using the obtained interface state distribution, the bulk trap density has been determined. With this method, for the interface trap density, it is found that deep state density nearing the mid-gap is approximately constant and tail states density increases exponentially with energy; for the bulk trap density, it is a superposition of exponential deep states and exponential tail states. The validity of the extraction is verified by comparisons with the measured current-voltage (I-V) characteristics and the simulation results by the technology computer-aided design (TCAD) model. This extraction method uses non-numerical iteration which is simple, fast and accurate. Therefore, it is very useful for TFT device characterization.

Hydrologic and water quality effects of thinning Loblolly Pine

Treesearch

Johnny M. Grace; R. W. Skaggs; G. M. Chescheir

2006-01-01

Forest operations such as harvesting, thinning, and site preparation can affect the hydrologic behavior of watersheds on poorly drained soils. The influence of these operations conducted on organic soil sites can be more pronounced than on mineral soil sites due to the differences in bulk density and soil moisture relationships that exist between mineral and organic...

Water deficit stress effects on corn (Zea mays, L.) root: shoot ratio

USDA-ARS?s Scientific Manuscript database

A study was conducted at Akron, CO, USA, on a Weld silt loam in 2004 to quantify the effects of water deficit stress on corn (Zea mays, L.) root and shoot biomass. Corn plants were grown under a range of soil bulk density and water conditions caused by previous tillage, crop rotation, and irrigation...

Fluid property measurements study

NASA Technical Reports Server (NTRS)

Devaney, W. E.

1976-01-01

Fluid properties of refrigerant-21 were investigated at temperatures from the freezing point to 423 Kelvin and at pressures to 1.38 x 10 to the 8th power N/sq m (20,000 psia). The fluid properties included were: density, vapor pressure, viscosity, specific heat, thermal conductivity, thermal expansion coefficient, freezing point and bulk modulus. Tables of smooth values are reported.

Changes in soil bulk density resulting from construction and conventional cable skidding using preplanned skid trails

Treesearch

Jingxin Wang; Chris B. LeDoux; Pam Edwards

2007-01-01

A harvesting system consisting of chainsaw felling and cable skidder extraction was studied to determine soil bulk density changes in a central Appalachian hardwood forest site. Soil bulk density was measured using a nuclear gauge preharvest and postharvest systematically across the harvest site, on transects across skid trails, and for a subset of skid trail transects...

Dynamics of bulk electron heating and ionization in solid density plasmas driven by ultra-short relativistic laser pulses

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

Huang, L. G., E-mail: lingen.huang@hzdr.de; Kluge, T.; Cowan, T. E.

The dynamics of bulk heating and ionization is investigated both in simulations and theory, which determines the crucial plasma parameters such as plasma temperature and density in ultra-short relativistic laser-solid target interactions. During laser-plasma interactions, the solid density plasma absorbs a fraction of laser energy and converts it into kinetic energy of electrons. A portion of the electrons with relativistic kinetic energy goes through the solid density plasma and transfers energy into the bulk electrons, which results in bulk electron heating. The bulk electron heating is finally translated into the processes of bulk collisional ionization inside the solid target. Amore » simple model based on the Ohmic heating mechanism indicates that the local and temporal profile of bulk return current is essential to determine the temporal evolution of bulk electron temperature. A series of particle-in-cell simulations showing the local heating model is robust in the cases of target with a preplasma and without a preplasma. Predicting the bulk electron heating is then benefit for understanding the collisional ionization dynamics inside the solid targets. The connection of the heating and ionization inside the solid target is further studied using Thomas-Fermi model.« less

Battery materials for ultrafast charging and discharging.

PubMed

Kang, Byoungwoo; Ceder, Gerbrand

2009-03-12

The storage of electrical energy at high charge and discharge rate is an important technology in today's society, and can enable hybrid and plug-in hybrid electric vehicles and provide back-up for wind and solar energy. It is typically believed that in electrochemical systems very high power rates can only be achieved with supercapacitors, which trade high power for low energy density as they only store energy by surface adsorption reactions of charged species on an electrode material. Here we show that batteries which obtain high energy density by storing charge in the bulk of a material can also achieve ultrahigh discharge rates, comparable to those of supercapacitors. We realize this in LiFePO(4) (ref. 6), a material with high lithium bulk mobility, by creating a fast ion-conducting surface phase through controlled off-stoichiometry. A rate capability equivalent to full battery discharge in 10-20 s can be achieved.

Electrical conduction at domain walls in multiferroic BiFeO3

NASA Astrophysics Data System (ADS)

Seidel, Jan; Martin, Lane; He, Qing; Zhan, Qian; Chu, Ying-Hao; Rother, Axel; Hawkridge, Michael; Maksymovych, Peter; Yu, Pu; Gajek, Martin; Balke, Nina; Kalinin, Sergei; Gemming, Sybille; Wang, Feng; Catalán, Gustau; Scott, James; Spaldin, Nicola; Orenstein, Joseph; Ramesh, Ramamoorthy

2009-03-01

We report the observation of room temperature electronic conductivity at ferroelectric domain walls in BiFeO3. The origin and nature of the observed conductivity is probed using a combination of conductive atomic force microscopy, high resolution transmission electron microscopy and first-principles density functional computations. We show that a structurally driven change in both the electrostatic potential and local electronic structure (i.e., a decrease in band gap) at the domain wall leads to the observed electrical conductivity. We estimate the conductivity in the wall to be several orders of magnitude higher than for the bulk material. Additionally we demonstrate the potential for device applications of such conducting nanoscale features.

Variability of bulk density of distillers dried grains with solubles (DDGS) during gravity-driven discharge.

PubMed

Clementson, C L; Ileleji, K E

2010-07-01

Loading railcars with consistent tonnage has immense cost implications for the shipping of distillers' dried grains with soluble (DDGS) product. Therefore, this study was designed to investigate the bulk density variability of DDGS during filling of railcar hoppers. An apparatus was developed similar to a spinning riffler sampler in order to simulate the filling of railcars at an ethanol plant. There was significant difference (P<0.05) between the initial and final measures of bulk density and particle size as the hoppers were emptied in both mass and funnel flow patterns. Particle segregation that takes place during filling of hoppers contributed to the bulk density variation and was explained by particle size variation. This phenomenon is most likely the same throughout the industry and an appropriate sampling procedure should be adopted for measuring the bulk density of DDGS stored silos or transported in railcar hoppers. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

Non-grazing and gophers lower bulk density and acidity in annual-plant soil

Treesearch

Raymond D. Ratliff; Stanley E. Westfall

1971-01-01

The effects of non-grazing on Ahwahnee coarse sandy loam were studied at the San Joaquin Experimental Range in central California. An exclosure, on which there had been no livestock grazing for 34 years, had a lower surface bulk density and lower acidity than an adjacent range that had been grazed. Bulk density averaged 1.08 gm./cc. on the ungrazed range, and 1.43 gm./...

Estimating carbon and nitrogen pools in a forest soil: Influence of soil bulk density methods and rock content

Treesearch

Martin F. Jurgensen; Deborah S. Page-Dumroese; Robert E. Brown; Joanne M. Tirocke; Chris A. Miller; James B. Pickens; Min Wang

2017-01-01

Soils with high rock content are common in many US forests, and contain large amounts of stored C. Accurate measurements of soil bulk density and rock content are critical for calculating and assessing changes in both C and nutrient pool size, but bulk density sampling methods have limitations and sources of variability. Therefore, we evaluated the use of small-...

Critical soil bulk density for soybean growth in Oxisols

NASA Astrophysics Data System (ADS)

Keisuke Sato, Michel; Veras de Lima, Herdjania; Oliveira, Pedro Daniel de; Rodrigues, Sueli

2015-10-01

The aim of this study was to evaluate the critical soil bulk density from the soil penetration resistance measurements for soybean root growth in Brazilian Amazon Oxisols. The experiment was carried out in a greenhouse using disturbed soil samples collected from the northwest of Para characterized by different texture. The treatments consisted of a range of soil bulk densities for each soil textural class. Three pots were used for soybean growth of and two for the soil penetration resistance curve. From the fitted model, the critical soil bulk density was determined considering the penetration resistance values of 2 and 3 MPa. After sixty days, plants were cut and root length, dry mass of root, and dry mass of shoots were determined. At higher bulk densities, the increase in soil water content decreased the penetration resistance, allowing unrestricted growth of soybean roots. Regardless of soil texture, the penetration resistance of 2 and 3 MPa had a slight effect on root growth in soil moisture at field capacity and a reduction of 50% in the soybean root growth was achieved at critical soil bulk density of 1.82, 1.75, 1.51, and 1.45 Mg m-3 for the sandy loam, sandy clay loam, clayey, and very clayey soil.

Performance of exchange-correlation functionals in density functional theory calculations for liquid metal: A benchmark test for sodium.

PubMed

Han, Jeong-Hwan; Oda, Takuji

2018-04-14

The performance of exchange-correlation functionals in density-functional theory (DFT) calculations for liquid metal has not been sufficiently examined. In the present study, benchmark tests of Perdew-Burke-Ernzerhof (PBE), Armiento-Mattsson 2005 (AM05), PBE re-parameterized for solids, and local density approximation (LDA) functionals are conducted for liquid sodium. The pair correlation function, equilibrium atomic volume, bulk modulus, and relative enthalpy are evaluated at 600 K and 1000 K. Compared with the available experimental data, the errors range from -11.2% to 0.0% for the atomic volume, from -5.2% to 22.0% for the bulk modulus, and from -3.5% to 2.5% for the relative enthalpy depending on the DFT functional. The generalized gradient approximation functionals are superior to the LDA functional, and the PBE and AM05 functionals exhibit the best performance. In addition, we assess whether the error tendency in liquid simulations is comparable to that in solid simulations, which would suggest that the atomic volume and relative enthalpy performances are comparable between solid and liquid states but that the bulk modulus performance is not. These benchmark test results indicate that the results of liquid simulations are significantly dependent on the exchange-correlation functional and that the DFT functional performance in solid simulations can be used to roughly estimate the performance in liquid simulations.

Performance of exchange-correlation functionals in density functional theory calculations for liquid metal: A benchmark test for sodium

NASA Astrophysics Data System (ADS)

Han, Jeong-Hwan; Oda, Takuji

2018-04-01

The performance of exchange-correlation functionals in density-functional theory (DFT) calculations for liquid metal has not been sufficiently examined. In the present study, benchmark tests of Perdew-Burke-Ernzerhof (PBE), Armiento-Mattsson 2005 (AM05), PBE re-parameterized for solids, and local density approximation (LDA) functionals are conducted for liquid sodium. The pair correlation function, equilibrium atomic volume, bulk modulus, and relative enthalpy are evaluated at 600 K and 1000 K. Compared with the available experimental data, the errors range from -11.2% to 0.0% for the atomic volume, from -5.2% to 22.0% for the bulk modulus, and from -3.5% to 2.5% for the relative enthalpy depending on the DFT functional. The generalized gradient approximation functionals are superior to the LDA functional, and the PBE and AM05 functionals exhibit the best performance. In addition, we assess whether the error tendency in liquid simulations is comparable to that in solid simulations, which would suggest that the atomic volume and relative enthalpy performances are comparable between solid and liquid states but that the bulk modulus performance is not. These benchmark test results indicate that the results of liquid simulations are significantly dependent on the exchange-correlation functional and that the DFT functional performance in solid simulations can be used to roughly estimate the performance in liquid simulations.

Quality Assessment of Physical and Organoleptic Instant Corn Rice on Scale-Up Process

NASA Astrophysics Data System (ADS)

Kumalasari, R.; Ekafitri, R.; Indrianti, N.

2017-12-01

Development of instant corn rice product has been successfully conducted on a laboratory scale. Corn has high carbohydrate content but low in fiber. The addition of fiber in instant corn rice, intended to improve the functioning of the product, and replace fiber loss during the process. Scale up process of Instant corn rice required to increase the production capacity. Scale up was the process to get identic output on a larger scale based on predetermined production scale. This study aimed to assess the changes and differences in the quality of instant corn rice during scale up. Instant corn rice scale up was done on production capacity 3 kg, 4 kg and 5 kg. Results showed that scale up of instant corn rice producing products with rehydration ratio ranges between 514% - 570%, the absorption rate ranged between 414% - 470%, swelling rate ranging between 119% - 134%, bulk density ranged from 0.3661 to 0.4745 (g/ml) and porosity ranging between 30-37%. The physical quality of instant corn rice on scale up were stable from the ones at laboratory scale on swelling rate, rehydration ratio, and absorption rate but not stable on bulk density and porosity. Organoleptic qualities were stable at increased scale compared on a laboratory scale. Bulk density was higher than those at laboratory scale, and the porosity was lower than those at laboratory scale.

Compaction of AWBA fuel pellets without binders (AWBA Development Program)

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

Johnson, R.G.R.

1982-08-01

Highly active oxide fuel powders, composed of UO/sub 2/, UO/sub 2/-ThO/sub 2/, or ThO/sub 2/, were compacted into ultra-high density pellets without the use of binders. The objective of the study was to select the optimum die lubricant for compacting these powders into pellets in preparation for sintering to densities in excess of 97% Theoretical Density. The results showed that sintered density was a function of both the lubricant bulk density and concentration with the lowest bulk density lubricant giving the highest sintered densities with a lubricant concentration of 0.1 weight percent. Five calcium and zinc stearates were evaluated withmore » a calcium stearate with a 15 lb/ft/sup 3/ bulk density being the best lubricant.« less

Plutonium hexaboride is a correlated topological insulator.

PubMed

Deng, Xiaoyu; Haule, Kristjan; Kotliar, Gabriel

2013-10-25

We predict that plutonium hexaboride (PuB(6)) is a strongly correlated topological insulator, with Pu in an intermediate valence state of Pu(2.7+). Within the combination of dynamical mean field theory and density functional theory, we show that PuB(6) is an insulator in the bulk, with nontrivial Z(2) topological invariants. Its metallic surface states have a large Fermi pocket at the X[over ¯] point and the Dirac cones inside the bulk derived electronic states, causing a large surface thermal conductivity. PuB(6) has also a very high melting temperature; therefore, it has ideal solid state properties for a nuclear fuel material.

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

Gardiner, W.W.; Barrows, E.S.; Antrim, L.D

Buttermilk Channel was one of seven waterways that was sampled and evaluated for dredging and sediment disposal. Sediment samples were collected and analyses were conducted on sediment core samples. The evaluation of proposed dredged material from the channel included bulk sediment chemical analyses, chemical analyses of site water and elutriate, water column and benthic acute toxicity tests, and bioaccumulation studies. Individual sediment core samples were analyzed for grain size, moisture content, and total organic carbon. A composite sediment samples, representing the entire area proposed for dredging, was analyzed for bulk density, polynuclear aromatic hydrocarbons, and 1,4-dichlorobenzene. Site water and elutriatemore » were analyzed for metals, pesticides, and PCBs.« less

Three-dimensional carbon nanotubes for high capacity lithium-ion batteries

NASA Astrophysics Data System (ADS)

Kang, Chiwon; Patel, Mumukshu; Rangasamy, Baskaran; Jung, Kyu-Nam; Xia, Changlei; Shi, Sheldon; Choi, Wonbong

2015-12-01

Carbon nanotubes (CNTs) have been considered as a potential anode material for next generation Lithium-ion batteries (LIBs) due to their high conductivity, flexibility, surface area, and lithium-ion insertion ability. However, the low mass loading and bulk density of carbon nanomaterials hinder their use in large-scale energy storage because their high specific capacity may not scale up linearly with the thickness of the electrode. To address this issue, a novel three-dimensional (3D) architecture is rationally designed by stacking layers of free-standing CNTs with the increased areal density to 34.9 mg cm-2, which is around three-times higher than that of the state-of-the-art graphitic anodes. Furthermore, a thermal compression process renders the bulk density of the multi-stacked 3D CNTs to be increased by 1.85 g cm-3, which yields an excellent volumetric capacity of 465 mAh cm-3 at 0.5C. Our proposed strategy involving the stacking of 3D CNT based layers and post-thermal compression provides a powerful platform for the utilization of carbon nanomaterials in the advanced LIB technology.

Density functional theory based molecular dynamics study of hydration and electronic properties of aqueous La(3+).

PubMed

Terrier, Cyril; Vitorge, Pierre; Gaigeot, Marie-Pierre; Spezia, Riccardo; Vuilleumier, Rodolphe

2010-07-28

Structural and electronic properties of La(3+) immersed in bulk water have been assessed by means of density functional theory (DFT)-based Car-Parrinello molecular dynamics (CPMD) simulations. Correct structural properties, i.e., La(III)-water distances and La(III) coordination number, can be obtained within the framework of Car-Parrinello simulations providing that both the La pseudopotential and conditions of the dynamics (fictitious mass and time step) are carefully set up. DFT-MD explicitly treats electronic densities and is shown here to provide a theoretical justification to the necessity of including polarization when studying highly charged cations such as lanthanoids(III) with classical MD. La(3+) was found to strongly polarize the water molecules located in the first shell, giving rise to dipole moments about 0.5 D larger than those of bulk water molecules. Finally, analyzing Kohn-Sham orbitals, we found La(3+) empty 4f orbitals extremely compact and to a great extent uncoupled from the water conduction band, while the 5d empty orbitals exhibit mixing with unoccupied states of water.

Effects of varying bulk densities of steam-flaked corn and dietary roughage concentration on in vitro fermentation, performance, carcass quality, and acid-base balance measurements in finishing steers

USDA-ARS?s Scientific Manuscript database

Effects of varying bulk densities of steam-flaked corn (SFC) and level of inclusion of roughage in feedlot diets were evaluated in three experiments. In Experiment 1, 128 beef steers were used in a 2 x 2 factorial arrangement to evaluate effects of bulk density of SFC (335 or 386 g/L) and roughage...

Development of property-transfer models for estimating the hydraulic properties of deep sediments at the Idaho National Engineering and Environmental Laboratory, Idaho

USGS Publications Warehouse

Winfield, Kari A.

2005-01-01

Because characterizing the unsaturated hydraulic properties of sediments over large areas or depths is costly and time consuming, development of models that predict these properties from more easily measured bulk-physical properties is desirable. At the Idaho National Engineering and Environmental Laboratory, the unsaturated zone is composed of thick basalt flow sequences interbedded with thinner sedimentary layers. Determining the unsaturated hydraulic properties of sedimentary layers is one step in understanding water flow and solute transport processes through this complex unsaturated system. Multiple linear regression was used to construct simple property-transfer models for estimating the water-retention curve and saturated hydraulic conductivity of deep sediments at the Idaho National Engineering and Environmental Laboratory. The regression models were developed from 109 core sample subsets with laboratory measurements of hydraulic and bulk-physical properties. The core samples were collected at depths of 9 to 175 meters at two facilities within the southwestern portion of the Idaho National Engineering and Environmental Laboratory-the Radioactive Waste Management Complex, and the Vadose Zone Research Park southwest of the Idaho Nuclear Technology and Engineering Center. Four regression models were developed using bulk-physical property measurements (bulk density, particle density, and particle size) as the potential explanatory variables. Three representations of the particle-size distribution were compared: (1) textural-class percentages (gravel, sand, silt, and clay), (2) geometric statistics (mean and standard deviation), and (3) graphical statistics (median and uniformity coefficient). The four response variables, estimated from linear combinations of the bulk-physical properties, included saturated hydraulic conductivity and three parameters that define the water-retention curve. For each core sample,values of each water-retention parameter were estimated from the appropriate regression equation and used to calculate an estimated water-retention curve. The degree to which the estimated curve approximated the measured curve was quantified using a goodness-of-fit indicator, the root-mean-square error. Comparison of the root-mean-square-error distributions for each alternative particle-size model showed that the estimated water-retention curves were insensitive to the way the particle-size distribution was represented. Bulk density, the median particle diameter, and the uniformity coefficient were chosen as input parameters for the final models. The property-transfer models developed in this study allow easy determination of hydraulic properties without need for their direct measurement. Additionally, the models provide the basis for development of theoretical models that rely on physical relationships between the pore-size distribution and the bulk-physical properties of the media. With this adaptation, the property-transfer models should have greater application throughout the Idaho National Engineering and Environmental Laboratory and other geographic locations.

Variation of surficial soil hydraulic properties across land uses in the southern Blue Ridge Mountains, North Carolina, USA

Treesearch

Katie Price; C. Rhett Jackson; Albert J. Parker

2010-01-01

A full understanding of hydrologic response to human impact requires assessment of land-use impacts on key soil physical properties such as saturated hydraulic conductivity, bulk density, and moisture retention. Such properties have been shown to affect watershed hydrology by influencing pathways and transmission rates of precipitation to stream networks. Human land...

Interaction Among Machine Traffic, Soil Physical Properties and Loblolly Pine Root Prolifereation in a Piedmont Soil

Treesearch

Emily A. Carter; Timothy P. McDonald

1997-01-01

The impact of forwarder traffic on soil physical properties was evaluated on a Gwinnett sandy loam, a commonly found soil of the Piedmont. Soil strength and saturated hydraulic conductivity were significantly altered by forwarder traffic, but reductions in air-filled porosity also occurred. Bulk density did not increase significantly in trafficked treatments. The...

The relationship between Vickers microhardness and compressive strength of functional surface geopolymers

NASA Astrophysics Data System (ADS)

Subaer, Ekaputri, Januari Jaya; Fansuri, Hamzah; Abdullah, Mustafa Al Bakri

2017-09-01

An experimental study to investigate the relationship between Vickers microhardness and compressive strength of geopolymers made from metakaolin has been conducted. Samples were prepared by using metakaolin activated with a sodium silicate solution at a different ratio of Si to Al and Na to Al and cured at 70°C for one hour. The resulting geopolymers were stored in an open air for 28 days before conducting any measurement. Bulk density and apparent porosity of the samples were measured by using Archimedes's method. Vickers microhardness measurements were performed on a polished surface of geopolymers with a load ranging from 0.3 - 1.0 kg. The topographic of indented samples were examined by using scanning electron microscopy (SEM). Compressive strength of the resulting geopolymers was measured on the cylindrical samples with a ratio of height to the diameter was 2:1. The results showed that the molar ratios of geopolymers compositions play important roles in the magnitude of bulk density, porosity, Vickers's microhardness as well as the compressive strength. The porosity reduced exponentially the magnitude of the strength of geopolymers. It was found that the relationship between Vickers microhardness and compressive strength was linear.

Sizable band gap in organometallic topological insulator

NASA Astrophysics Data System (ADS)

Derakhshan, V.; Ketabi, S. A.

2017-01-01

Based on first principle calculation when Ceperley-Alder and Perdew-Burke-Ernzerh type exchange-correlation energy functional were adopted to LSDA and GGA calculation, electronic properties of organometallic honeycomb lattice as a two-dimensional topological insulator was calculated. In the presence of spin-orbit interaction bulk band gap of organometallic lattice with heavy metals such as Au, Hg, Pt and Tl atoms were investigated. Our results show that the organometallic topological insulator which is made of Mercury atom shows the wide bulk band gap of about ∼120 meV. Moreover, by fitting the conduction and valence bands to the band-structure which are produced by Density Functional Theory, spin-orbit interaction parameters were extracted. Based on calculated parameters, gapless edge states within bulk insulating gap are indeed found for finite width strip of two-dimensional organometallic topological insulators.

Merely Measuring the UV-Visible Spectrum of Gold Nanoparticles Can Change Their Charge State.

PubMed

Navarrete, Jose; Siefe, Chris; Alcantar, Samuel; Belt, Michael; Stucky, Galen D; Moskovits, Martin

2018-02-14

Metallic nanostructures exhibit a strong plasmon resonance at a wavelength whose value is sensitive to the charge density in the nanostructure, its size, shape, interparticle coupling, and the dielectric properties of its surrounding medium. Here we use UV-visible transmission and reflectance spectroscopy to track the shifts of the plasmon resonance in an array of gold nanoparticles buried under metal-oxide layers of varying thickness produced using atomic layer deposition (ALD) and then coated with bulk layers of one of three metals: aluminum, silver, or gold. A significant shift in the plasmon resonance was observed and a precise value of ω p , the plasmon frequency of the gold comprising the nanoparticles, was determined by modeling the composite of gold nanoparticles and metal-oxide layer as an optically homogeneous film of core-shell particles bounded by two substrates: one of quartz and the other being one of the aforementioned metals, then using a Maxwell-Garnett effective medium expression to extract ω p for the gold nanoparticles before and after coating with the bulk metals. Under illumination, the change in the charge density of the gold nanoparticles per particle determined from the change in the values of ω p is found to be some 50-fold greater than what traditional electrostatic contact electrification models compute based on the work function difference of the two conductive materials. Moreover, when using bulk gold as the capping layer, which should have resulted in a negligible charge exchange between the gold nanoparticles and the bulk gold, a significant charge transfer from the bulk gold layer to the nanoparticles was observed as with the other metals. We explain these observations in terms of the "plasmoelectric effect", recently described by Atwater and co-workers, in which the gold nanoparticles modify their charge density to allow their resonant wavelength to match that of the incident light, thereby achieving, a lower value of the chemical potential due to the entropy increase resulting from the conversion of the plasmon's energy to heat. We conclude that even the act of registering the spectrum of nanoparticles is at times sufficient to alter their charge densities and hence their UV-visible spectra.

Mitigation of explosions of hydrogen-air mixtures using bulk materials and aqueous foam

NASA Astrophysics Data System (ADS)

Medvedev, S. P.; Khomik, S. V.; Mikhalkin, V. N.; Ivantsov, A. N.; Agafonov, G. L.; Cherepanov, A. A.; Cherepanova, T. T.; Betev, A. S.

2018-01-01

The objective of this work is to determine experimentally the effectiveness of protective barriers under conditions when blast waves are generated during premixed hydrogen- air combustion in various regimes. Experiments are conducted in a vertical tube having a diameter of 54 mm and a length of up to 2 m. Blast loads are produced by acceleration of premixed hydrogen-air flames in the tube with ring obstacles. Comparative tests are performed between protection barriers made of bulk materials with different densities and aqueous foams with different expansion ratios. It is demonstrated that the degree of blast load attenuation by an aqueous foam barrier increases with decreasing molecular weight of the filling gas and increasing density (decreasing expansion ratio) of the foam. An Aerosil barrier three times thicker than a titanium-dioxide one is found to have a similar attenuating effect on blast action. However, the mass per unit area of an Aerosil barrier is lower than titanium dioxide by a factor of 6 and is comparable to foam. The observed dependence of blast load attenuation on parameters of bulk materials and aqueous foams must be taken into account in systems designed to mitigate the consequences of accidental hydrogen release and combustion.

The geochemical and petrological characteristics of prenatal caldera volcano: a case of the newly formed small dacitic caldera, Hijiori, Northeast Japan

NASA Astrophysics Data System (ADS)

Miyagi, Isoji; Kita, Noriko; Morishita, Yuichi

2017-09-01

Evaluating the magma depth and its physical properties is critical to conduct a better geophysical assessment of magma chambers of caldera volcanoes that may potentially cause future volcanic hazards. To understand pre-eruptive conditions of a magma chamber before its first appearance at the surface, this paper describes the case of Hijiori caldera volcano in northeastern Japan, which emerged approximately 12,000 years ago at a place where no volcano ever existed. We estimated the depth, density, bulk modulus, vesicularity, crystal content, and bulk H_2O content of the magma chamber using petrographic interpretations, bulk and microchemical compositions, and thermodynamic calculations. The chemical mass balance calculations and thermodynamic modeling of the erupted magmas indicate that the upper portion of the Hijiori magmatic plumbing system was located at depths between 2 and 4 km, and had the following characteristics: (1) pre-eruptive temperature: about 780 °C; (2) bulk magma composition: 66 ± 1.5 wt% SiO2; (3) bulk magmatic H_2O: approximately 2.5 wt%, and variable characteristics that depend on depth; (4) crystal content: ≤57 vol%; (5) bulk modulus of magma: 0.1-0.8 GPa; (6) magma density: 1.8-2.3 g/cm3; and (7) amount of excess magmatic H_2O: 11-32 vol% or 48-81 mol%. The range of melt water contents found in quartz-hosted melt inclusions (2-9 wt%) suggests the range of depth phenocrysts growth to be wide (2˜13 km). Our data suggest the presence of a vertically elongated magma chamber whose top is nearly solidified but highly vesiculated; this chamber has probably grown and re-mobilized by repeated injections of a small amount of hot dacitic magma originated from the depth.

Bulk density of small meteoroids

NASA Astrophysics Data System (ADS)

Kikwaya, J.-B.; Campbell-Brown, M.; Brown, P. G.

2011-06-01

Aims: Here we report on precise metric and photometric observations of 107 optical meteors, which were simultaneously recorded at multiple stations using three different intensified video camera systems. The purpose is to estimate bulk meteoroid density, link small meteoroids to their parent bodies based on dynamical and physical density values expected for different small body populations, to better understand and explain the dynamical evolution of meteoroids after release from their parent bodies. Methods: The video systems used had image sizes ranging from 640 × 480 to 1360 × 1036 pixels, with pixel scales from 0.01° per pixel to 0.05° per pixel, and limiting meteor magnitudes ranging from Mv = +2.5 to +6.0. We find that 78% of our sample show noticeable deceleration, allowing more robust constraints to be placed on density estimates. The density of each meteoroid is estimated by simultaneously fitting the observed deceleration and lightcurve using a model based on thermal fragmentation, conservation of energy and momentum. The entire phase space of the model free parameters is explored for each event to find ranges of parameters which fit the observations within the measurement uncertainty. Results: (a) We have analysed our data by first associating each of our events with one of the five meteoroid classes. The average density of meteoroids whose orbits are asteroidal and chondritic (AC) is 4200 kg m-3 suggesting an asteroidal parentage, possibly related to the high-iron content population. Meteoroids with orbits belonging to Jupiter family comets (JFCs) have an average density of 3100 ± 300 kg m-3. This high density is found for all meteoroids with JFC-like orbits and supports the notion that the refractory material reported from the Stardust measurements of 81P/Wild 2 dust is common among the broader JFC population. This high density is also the average bulk density for the 4 meteoroids with orbits belonging to the Ecliptic shower-type class (ES) also related to JFCs. Both categories we suggest are chondritic based on their high bulk density. Meteoroids of HT (Halley type) orbits have a minimum bulk density value of 360+400-100 kg m-3 and a maximum value of 1510+400-900 kg m-3. This is consistent with many previous works which suggest bulk cometary meteoroid density is low. SA (Sun-approaching)-type meteoroids show a density spread from 1000 kg m-3 to 4000 kg m-3, reflecting multiple origins. (b) We found two different meteor showers in our sample: Perseids (10 meteoroids, ~11% of our sample) with an average bulk density of 620 kg m-3 and Northern Iota Aquariids (4 meteoroids) with an average bulk density of 3200 kg m-3, consistent with the notion that the NIA derive from 2P/Encke.

Near surface bulk density estimates of NEAs from radar observations and permittivity measurements of powdered geologic material

NASA Astrophysics Data System (ADS)

Hickson, Dylan; Boivin, Alexandre; Daly, Michael G.; Ghent, Rebecca; Nolan, Michael C.; Tait, Kimberly; Cunje, Alister; Tsai, Chun An

2018-05-01

The variations in near-surface properties and regolith structure of asteroids are currently not well constrained by remote sensing techniques. Radar is a useful tool for such determinations of Near-Earth Asteroids (NEAs) as the power of the reflected signal from the surface is dependent on the bulk density, ρbd, and dielectric permittivity. In this study, high precision complex permittivity measurements of powdered aluminum oxide and dunite samples are used to characterize the change in the real part of the permittivity with the bulk density of the sample. In this work, we use silica aerogel for the first time to increase the void space in the samples (and decrease the bulk density) without significantly altering the electrical properties. We fit various mixing equations to the experimental results. The Looyenga-Landau-Lifshitz mixing formula has the best fit and the Lichtenecker mixing formula, which is typically used to approximate planetary regolith, does not model the results well. We find that the Looyenga-Landau-Lifshitz formula adequately matches Lunar regolith permittivity measurements, and we incorporate it into an existing model for obtaining asteroid regolith bulk density from radar returns which is then used to estimate the bulk density in the near surface of NEA's (101955) Bennu and (25143) Itokawa. Constraints on the material properties appropriate for either asteroid give average estimates of ρbd = 1.27 ± 0.33g/cm3 for Bennu and ρbd = 1.68 ± 0.53g/cm3 for Itokawa. We conclude that our data suggest that the Looyenga-Landau-Lifshitz mixing model, in tandem with an appropriate radar scattering model, is the best method for estimating bulk densities of regoliths from radar observations of airless bodies.

Physical Quality Indicators and Mechanical Behavior of Agricultural Soils of Argentina.

PubMed

Imhoff, Silvia; da Silva, Alvaro Pires; Ghiberto, Pablo J; Tormena, Cássio A; Pilatti, Miguel A; Libardi, Paulo L

2016-01-01

Mollisols of Santa Fe have different tilth and load support capacity. Despite the importance of these attributes to achieve a sustainable crop production, few information is available. The objectives of this study are i) to assess soil physical indicators related to plant growth and to soil mechanical behavior; and ii) to establish relationships to estimate the impact of soil loading on the soil quality to plant growth. The study was carried out on Argiudolls and Hapludolls of Santa Fe. Soil samples were collected to determine texture, organic matter content, bulk density, water retention curve, soil resistance to penetration, least limiting water range, critical bulk density for plant growth, compression index, pre-consolidation pressure and soil compressibility. Water retention curve and soil resistance to penetration were linearly and significantly related to clay and organic matter (R2 = 0.91 and R2 = 0.84). The pedotransfer functions of water retention curve and soil resistance to penetration allowed the estimation of the least limiting water range and critical bulk density for plant growth. A significant nonlinear relationship was found between critical bulk density for plant growth and clay content (R2 = 0.98). Compression index was significantly related to bulk density, water content, organic matter and clay plus silt content (R2 = 0.77). Pre-consolidation pressure was significantly related to organic matter, clay and water content (R2 = 0.77). Soil compressibility was significantly related to initial soil bulk density, clay and water content. A nonlinear and significantly pedotransfer function (R2 = 0.88) was developed to predict the maximum acceptable pressure to be applied during tillage operations by introducing critical bulk density for plant growth in the compression model. The developed pedotransfer function provides a useful tool to link the mechanical behavior and tilth of the soils studied.

Physical Quality Indicators and Mechanical Behavior of Agricultural Soils of Argentina

PubMed Central

Pires da Silva, Alvaro; Ghiberto, Pablo J.; Tormena, Cássio A.; Pilatti, Miguel A.; Libardi, Paulo L.

2016-01-01

Mollisols of Santa Fe have different tilth and load support capacity. Despite the importance of these attributes to achieve a sustainable crop production, few information is available. The objectives of this study are i) to assess soil physical indicators related to plant growth and to soil mechanical behavior; and ii) to establish relationships to estimate the impact of soil loading on the soil quality to plant growth. The study was carried out on Argiudolls and Hapludolls of Santa Fe. Soil samples were collected to determine texture, organic matter content, bulk density, water retention curve, soil resistance to penetration, least limiting water range, critical bulk density for plant growth, compression index, pre-consolidation pressure and soil compressibility. Water retention curve and soil resistance to penetration were linearly and significantly related to clay and organic matter (R2 = 0.91 and R2 = 0.84). The pedotransfer functions of water retention curve and soil resistance to penetration allowed the estimation of the least limiting water range and critical bulk density for plant growth. A significant nonlinear relationship was found between critical bulk density for plant growth and clay content (R2 = 0.98). Compression index was significantly related to bulk density, water content, organic matter and clay plus silt content (R2 = 0.77). Pre-consolidation pressure was significantly related to organic matter, clay and water content (R2 = 0.77). Soil compressibility was significantly related to initial soil bulk density, clay and water content. A nonlinear and significantly pedotransfer function (R2 = 0.88) was developed to predict the maximum acceptable pressure to be applied during tillage operations by introducing critical bulk density for plant growth in the compression model. The developed pedotransfer function provides a useful tool to link the mechanical behavior and tilth of the soils studied. PMID:27099925

Roles of Bulk and Surface Chemistry in the Oxygen Exchange Kinetics and Related Properties of Mixed Conducting Perovskite Oxide Electrodes

PubMed Central

Perry, Nicola H.; Ishihara, Tatsumi

2016-01-01

Mixed conducting perovskite oxides and related structures serving as electrodes for electrochemical oxygen incorporation and evolution in solid oxide fuel and electrolysis cells, respectively, play a significant role in determining the cell efficiency and lifetime. Desired improvements in catalytic activity for rapid surface oxygen exchange, fast bulk transport (electronic and ionic), and thermo-chemo-mechanical stability of oxygen electrodes will require increased understanding of the impact of both bulk and surface chemistry on these properties. This review highlights selected work at the International Institute for Carbon-Neutral Energy Research (I2CNER), Kyushu University, set in the context of work in the broader community, aiming to characterize and understand relationships between bulk and surface composition and oxygen electrode performance. Insights into aspects of bulk point defect chemistry, electronic structure, crystal structure, and cation choice that impact carrier concentrations and mobilities, surface exchange kinetics, and chemical expansion coefficients are emerging. At the same time, an understanding of the relationship between bulk and surface chemistry is being developed that may assist design of electrodes with more robust surface chemistries, e.g., impurity tolerance or limited surface segregation. Ion scattering techniques (e.g., secondary ion mass spectrometry, SIMS, or low energy ion scattering spectroscopy, LEIS) with high surface sensitivity and increasing lateral resolution are proving useful for measuring surface exchange kinetics, diffusivity, and corresponding outer monolayer chemistry of electrodes exposed to typical operating conditions. Beyond consideration of chemical composition, the use of strain and/or a high density of active interfaces also show promise for enhancing performance. PMID:28773978

Modeling of Interfacial Modification Effects on Thermal Conductivity of Carbon Nanotube Composites

NASA Technical Reports Server (NTRS)

Clancy, Thomas C.; Gates, Thomas S.

2006-01-01

The effect of functionalization of carbon nanotubes on the thermal conductivity of nanocomposites has been studied using a multi-scale modeling approach. These results predict that grafting linear hydrocarbon chains to the surface of a single wall carbon nanotube with covalent chemical bonds should result in a significant increase in the thermal conductivity of these nanocomposites. This is due to the decrease in the interfacial thermal (Kapitza) resistance between the single wall carbon nanotube and the surrounding polymer matrix upon chemical functionalization. The nanocomposites studied here consist of single wall carbon nanotubes in a bulk poly(ethylene vinyl acetate) matrix. The nanotubes are functionalized by end-grafting linear hydrocarbon chains of varying length to the surface of the nanotube. The effect which this functionalization has on the interfacial thermal resistance is studied by molecular dynamics simulation. Interfacial thermal resistance values are calculated for a range of chemical grafting densities and with several chain lengths. These results are subsequently used in an analytical model to predict the resulting effect on the bulk thermal conductivity of the nanocomposite.

Sorption Phase of Supercritical CO2 in Silica Aerogel: Experiments and Mesoscale Computer Simulations

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

Rother, Gernot; Vlcek, Lukas; Gruszkiewicz, Miroslaw

2014-01-01

Adsorption of supercritical CO2 in nanoporous silica aerogel was investigated by a combination of experiments and molecular-level computer modeling. High-pressure gravimetric and vibrating tube densimetry techniques were used to measure the mean pore fluid density and excess sorption at 35 C and 50 C and pressures of 0-200 bar. Densification of the pore fluid was observed at bulk fluid densities below 0.7 g/cm3. Far above the bulk fluid density, near-zero sorption or weak depletion effects were measured, while broad excess sorption maxima form in the vicinity of the bulk critical density region. The CO2 sorption properties are very similar formore » two aerogels with different bulk densities of 0.1 g/cm3 and 0.2 g/cm3, respectively. The spatial distribution of the confined supercritical fluid was analyzed in terms of sorption- and bulk-phase densities by means of the Adsorbed Phase Model (APM), which used data from gravimetric sorption and small-angle neutron scattering experiments. To gain more detailed insight into supercritical fluid sorption, large-scale lattice gas GCMC simulations were utilized and tuned to resemble the experimental excess sorption data. The computed three-dimensional pore fluid density distributions show that the observed maximum of the excess sorption near the critical density originates from large density fluctuations pinned to the pore walls. At this maximum, the size of these fluctuations is comparable to the prevailing pore sizes.« less

Estimating canopy bulk density and canopy base height for conifer stands in the interior Western United States using the Forest Vegetation Simulator Fire and Fuels Extension.

Treesearch

Seth Ex; Frederick Smith; Tara Keyser; Stephanie Rebain

2017-01-01

The Forest Vegetation Simulator Fire and Fuels Extension (FFE-FVS) is often used to estimate canopy bulk density (CBD) and canopy base height (CBH), which are key indicators of crown fire hazard for conifer stands in the Western United States. Estimated CBD from FFE-FVS is calculated as the maximum 4 m running mean bulk density of predefined 0.3 m thick canopy layers (...

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

Miller, D. H.; Reigel, M. M.

A full-scale formed core sampler was designed and functionally tested for use in the Saltstone Disposal Facility (SDF). Savannah River National Laboratory (SRNL) was requested to compare properties of the formed core samples and core drilled samples taken from adjacent areas in the full-scale sampler. While several physical properties were evaluated, the primary property of interest was hydraulic conductivity. Differences in hydraulic conductivity between the samples from the formed core sampler and those representing the bulk material were noted with respect to the initial handling and storage of the samples. Due to testing conditions, the site port samples were exposedmore » to uncontrolled temperature and humidity conditions prior to testing whereas the formed core samples were kept in sealed containers with minimal exposure to an uncontrolled environment prior to testing. Based on the results of the testing, no significant differences in porosity or density were found between the formed core samples and those representing the bulk material in the test stand.« less

Volumes and bulk densities of forty asteroids from ADAM shape modeling

NASA Astrophysics Data System (ADS)

Hanuš, J.; Viikinkoski, M.; Marchis, F.; Ďurech, J.; Kaasalainen, M.; Delbo', M.; Herald, D.; Frappa, E.; Hayamizu, T.; Kerr, S.; Preston, S.; Timerson, B.; Dunham, D.; Talbot, J.

2017-05-01

Context. Disk-integrated photometric data of asteroids do not contain accurate information on shape details or size scale. Additional data such as disk-resolved images or stellar occultation measurements further constrain asteroid shapes and allow size estimates. Aims: We aim to use all the available disk-resolved images of approximately forty asteroids obtained by the Near-InfraRed Camera (Nirc2) mounted on the W.M. Keck II telescope together with the disk-integrated photometry and stellar occultation measurements to determine their volumes. We can then use the volume, in combination with the known mass, to derive the bulk density. Methods: We downloaded and processed all the asteroid disk-resolved images obtained by the Nirc2 that are available in the Keck Observatory Archive (KOA). We combined optical disk-integrated data and stellar occultation profiles with the disk-resolved images and use the All-Data Asteroid Modeling (ADAM) algorithm for the shape and size modeling. Our approach provides constraints on the expected uncertainty in the volume and size as well. Results: We present shape models and volume for 41 asteroids. For 35 of these asteroids, the knowledge of their mass estimates from the literature allowed us to derive their bulk densities. We see a clear trend of lower bulk densities for primitive objects (C-complex) and higher bulk densities for S-complex asteroids. The range of densities in the X-complex is large, suggesting various compositions. We also identified a few objects with rather peculiar bulk densities, which is likely a hint of their poor mass estimates. Asteroid masses determined from the Gaia astrometric observations should further refine most of the density estimates.

Constraining Bulk Densities of Near-Earth Asteroid Surfaces from Radar Observations Using Laboratory Measurements of Permittivity

NASA Astrophysics Data System (ADS)

Hickson, D. C.; Boivin, A.; Daly, M. G.; Ghent, R. R.; Nolan, M. C.; Tait, K.; Cunje, A.; Tsai, C. A.

2017-12-01

Planetary radar is widely used to survey the Near-Earth Asteroid (NEA) population and can provide insight into target shapes, sizes, and spin states. The dual-polarization reflectivity is sensitive to surface roughness as well as material properties, specifically the real part of the complex permittivity, or dielectric constant. Knowledge of the behavior of the dielectric constant of asteroid regolith analogue material with environmental parameters can be used to inversely solve for such parameters, such as bulk density, from radar observations. In this study laboratory measurements of the complex permittivity of powdered aluminum oxide and dunite samples are performed in a low-pressure environment chamber using a coaxial transmission line from roughly 1 GHz to 8.5 GHz. The bulk densities of the samples are varied across the measurements by incrementally adding silica aerogel, a low-density material with a very low dielectric constant. This allows the alteration of the proportions of void space to solid particle grains to achieve microgravity-relevant porosities without significantly altering the dielectric properties of the powder sample. The data are then modeled using various electromagnetic mixing equations to characterize the change in dielectric constant with increasing volume fractions of void space (decreasing bulk density). Using spectral analogues as constraints on the composition of NEAs allows us to calculate the range in bulk densities in the near surface of NEAs that have been observed by planetary radar. Utilizing existing radar data from Arecibo Observatory we calculate the bulk density in the near-surface on (101955) Bennu, the target of NASA's OSIRIS-Rex mission, to be ρ = 1.27 ± 0.33 g cm-3 based on an average of the likely range in particle density and dielectric constant of the regolith material.

Effects of controlled burns on the bulk density and thermal conductivity of soils at a southern Colorado site

Treesearch

W. J. Massman; J. M. Frank

2006-01-01

Throughout the world fire plays an important role in the management and maintenance of ecosystems. However, if a fire is sufficiently intense, soil can be irreversibly altered and the ability of vegetation, particularly forests, to recover after a fire can be seriously compromised. Because fire is frequently used by land managers to reduce surface fuels, it is...

46 CFR 151.03-21 - Filling density.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 5 2010-10-01 2010-10-01 false Filling density. 151.03-21 Section 151.03-21 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CERTAIN BULK DANGEROUS CARGOES BARGES CARRYING BULK LIQUID HAZARDOUS MATERIAL CARGOES Definitions § 151.03-21 Filling density. The ratio, expressed as...

46 CFR 151.03-21 - Filling density.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 5 2014-10-01 2014-10-01 false Filling density. 151.03-21 Section 151.03-21 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CERTAIN BULK DANGEROUS CARGOES BARGES CARRYING BULK LIQUID HAZARDOUS MATERIAL CARGOES Definitions § 151.03-21 Filling density. The ratio, expressed as...

46 CFR 151.03-21 - Filling density.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 5 2012-10-01 2012-10-01 false Filling density. 151.03-21 Section 151.03-21 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CERTAIN BULK DANGEROUS CARGOES BARGES CARRYING BULK LIQUID HAZARDOUS MATERIAL CARGOES Definitions § 151.03-21 Filling density. The ratio, expressed as...

46 CFR 151.03-21 - Filling density.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 5 2013-10-01 2013-10-01 false Filling density. 151.03-21 Section 151.03-21 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CERTAIN BULK DANGEROUS CARGOES BARGES CARRYING BULK LIQUID HAZARDOUS MATERIAL CARGOES Definitions § 151.03-21 Filling density. The ratio, expressed as...

46 CFR 151.03-21 - Filling density.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 5 2011-10-01 2011-10-01 false Filling density. 151.03-21 Section 151.03-21 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CERTAIN BULK DANGEROUS CARGOES BARGES CARRYING BULK LIQUID HAZARDOUS MATERIAL CARGOES Definitions § 151.03-21 Filling density. The ratio, expressed as...

Detecting the environmental impact of off-road vehicles on Rawdat Al Shams in central Saudi Arabia by remote sensing.

PubMed

Dewidar, K; Thomas, J; Bayoumi, S

2016-07-01

Off-road vehicles can have a devastating impact on vegetation and soil. Here, we sought to quantify, through a combination of field vegetation, bulk soil, and image analyses, the impact of off-road vehicles on the vegetation and soils of Rawdat Al Shams, which is located in central Saudi Arabia. Soil compaction density was measured in the field, and 27 soil samples were collected for bulk density analysis in the lab to quantify the impacts of off-road vehicles. High spatial resolution images, such as those obtained by the satellites GeoEye-1 and IKONOS-2, were used for surveying the damage to vegetation cover and soil compaction caused by these vehicles. Vegetation cover was mapped using the Normalized Difference Vegetation Index (NDVI) technique based on high-resolution images taken at different times of the year. Vehicle trails were derived from satellite data via visual analysis. All damaged areas were determined from high-resolution image data. In this study, we conducted quantitative analyses of vegetation cover change, the impacts of vehicle trails (hereafter "trail impacts"), and a bulk soil analysis. Image data showed that both vegetation cover and trail impacts increased from 2008 to 2015, with the average percentage of trail impacts nearly equal to that of the percentage of vegetation cover during this period. Forty-six species of plants were found to be present in the study area, consisting of all types of life forms, yet trees were represented by a single species, Acacia gerrardii. Herbs composed the largest share of plant life, with 29 species, followed by perennial herbs (12 species), grasses (5 species), and shrubs (3 species). Analysis of soil bulk density for Rawdat Al Shams showed that off-road driving greatly impacts soil density. Twenty-two plant species were observed on the trails, the majority of which were ephemerals. Notoceras bicorne was the most common, with a frequency rate of 93.33 %, an abundance value of 78.47 %, and a density of 0.1 in transect 1, followed by Plantago ovata.

Calculated electronic, transport, and related properties of zinc blende boron arsenide (zb-BAs)

NASA Astrophysics Data System (ADS)

Nwigboji, Ifeanyi H.; Malozovsky, Yuriy; Franklin, Lashounda; Bagayoko, Diola

2016-10-01

We present the results from ab-initio, self-consistent density functional theory (DFT) calculations of electronic, transport, and bulk properties of zinc blende boron arsenide. We utilized the local density approximation potential of Ceperley and Alder, as parameterized by Vosko and his group, the linear combination of Gaussian orbitals formalism, and the Bagayoko, Zhao, and Williams (BZW) method, as enhanced by Ekuma and Franklin (BZW-EF), in carrying out our completely self-consistent calculations. With this method, the results of our calculations have the full, physical content of density functional theory (DFT). Our results include electronic energy bands, densities of states, effective masses, and the bulk modulus. Our calculated, indirect band gap of 1.48 eV, from Γ to a conduction band minimum close to X, for the room temperature lattice constant of 4.777 Å, is in an excellent agreement with the experimental value of 1.46 ± 0.02 eV. We thoroughly explain the reasons for the excellent agreement between our findings and corresponding, experimental ones. This work provides a confirmation of the capability of DFT to describe accurately properties of materials, if the computations adhere strictly to the conditions of validity of DFT, as done by the BZW-EF method.

In-situ growth of MnO2 crystals under nanopore-constraint in carbon nanofibers and their electrochemical performance

PubMed Central

Le, TrungHieu; Yang, Ying; Yu, Liu; Huang, Zheng-hong; Kang, Feiyu

2016-01-01

Growing MnO2 nanocrystals in the bulk of porous carbon nanofibers is conducted in a KMnO4 aqueous solution aimed to enhance the electrochemical performance of MnO2. The rate of redox reaction between KMnO4 and carbon was controlled by the concentration of KMnO4 in a neutral solution. The MnO2 nanoparticles grow along with (211) crystal faces when the redox reaction happens on the surface of fibers under 1D constraint, while the nanoparticles grow along with (200) crystal faces when the redox reaction happens in the bulk of fibers under 3D constraint. The composite, where MnO2 nanoparticles are formed in the bulk under a constraint, yields an electrode material for supercapacitors showing good electron transport, rapid ion penetration, fast and reversible Faradaic reaction, and excellent rate performance. The capacitance of the composite electrode could be 1282 F g−1 under a current density of 0.2 A g−1 in 1 M Na2SO4 electrolyte. A symmetric supercapacitor delivers energy density of 36 Wh kg−1 with power density of 39 W kg−1, and can maintain 7.5 Wh kg−1 at 10.3 kW kg−1. It exhibits an excellent electrochemical cycling stability with 101% initial capacitance and 95% columbic efficiency even after 1000 cycles of charge/discharge. PMID:27869184

Links between soil properties and steady-state solute transport through cultivated topsoil at the field scale

NASA Astrophysics Data System (ADS)

Koestel, J. K.; Norgaard, T.; Luong, N. M.; Vendelboe, A. L.; Moldrup, P.; Jarvis, N. J.; Lamandé, M.; Iversen, B. V.; Wollesen de Jonge, L.

2013-02-01

It is known that solute transport through soil is heterogeneous at all spatial scales. However, little data are available to allow quantification of these heterogeneities at the field scale or larger. In this study, we investigated the spatial patterns of soil properties, hydrologic state variables, and tracer breakthrough curves (BTCs) at the field scale for the inert solute transport under a steady-state irrigation rate which produced near-saturated conditions. Sixty-five undisturbed soil columns approximately 20 cm in height and diameter were sampled from the loamy topsoil of an agricultural field site in Silstrup (Denmark) at a sampling distance of approximately 15 m (with a few exceptions), covering an area of approximately 1 ha (60 m × 165 m). For 64 of the 65 investigated soil columns, we observed BTC shapes indicating a strong preferential transport. The strength of preferential transport was positively correlated with the bulk density and the degree of water saturation. The latter suggests that preferential macropore transport was the dominating transport process. Increased bulk densities were presumably related with a decrease in near-saturated hydraulic conductivities and as a consequence to larger water saturation and the activation of larger macropores. Our study provides further evidence that it should be possible to estimate solute transport properties from soil properties such as soil texture or bulk density. We also demonstrated that estimation approaches established for the column scale have to be upscaled when applied to the field scale or larger.

A Permeable Active Amendment Concrete (PAAC) for Contaminant Remediation and Erosion Control

DTIC Science & Technology

2012-06-01

124: 131 -143. SRNL-STI-2012-00356 70 Tessier, A., Campbell, P.G.C., and Bisson, M. 1979. Sequential extraction procedure for the speciation of...Bulk Density, Dry, (AI( C-D)]* p, pcf 134.85 Bulk Dens ity after Immersion, [BI(C-D)]* p, pcf 146.65 Bulk Density after Immersion & Boiling1 jCI (C

Effect of olive mill waste addition on the properties of porous fired clay bricks using Taguchi method.

PubMed

Sutcu, Mucahit; Ozturk, Savas; Yalamac, Emre; Gencel, Osman

2016-10-01

Production of porous clay bricks lightened by adding olive mill waste as a pore making additive was investigated. Factors influencing the brick manufacturing process were analyzed by an experimental design, Taguchi method, to find out the most favorable conditions for the production of bricks. The optimum process conditions for brick preparation were investigated by studying the effects of mixture ratios (0, 5 and 10 wt%) and firing temperatures (850, 950 and 1050 °C) on the physical, thermal and mechanical properties of the bricks. Apparent density, bulk density, apparent porosity, water absorption, compressive strength, thermal conductivity, microstructure and crystalline phase formations of the fired brick samples were measured. It was found that the use of 10% waste addition reduced the bulk density of the samples up to 1.45 g/cm(3). As the porosities increased from 30.8 to 47.0%, the compressive strengths decreased from 36.9 to 10.26 MPa at firing temperature of 950 °C. The thermal conductivities of samples fired at the same temperature showed a decrease of 31% from 0.638 to 0.436 W/mK, which is hopeful for heat insulation in the buildings. Increasing of the firing temperature also affected their mechanical and physical properties. This study showed that the olive mill waste could be used as a pore maker in brick production. Copyright © 2016 Elsevier Ltd. All rights reserved.

Physicochemical properties of extrudates from white yam and bambara nut blends

NASA Astrophysics Data System (ADS)

Oluwole, O. B.; Olapade, A. A.; Awonorin, S. O.; Henshaw, F. O.

2013-01-01

This study was conducted to investigate effects of extrusion conditions on physicochemical properties of blend of yam and bambara nut flours. A blend of white yam grit (750 μm) and Bambara nut flour (500 μm) in a ratio of 4:1, respectively was extrusion cooked at varying screw speeds 50-70 r.p.m., feed moisture 12.5-17.5% (dry basis) and barrel temperatures 130-150°C. The extrusion variables employed included barrel temperature, screw speed, and feed moisture content, while the physicochemical properties of the extrudates investigated were the expansion ratio, bulk density, and trypsin inhibition activity. The results revealed that all the extrusion variables had significant effects (p<0.05) on the product properties considered in this study. The expansion ratio values ranged 1.55-2.06, bulk density values ranged 0.76-0.94 g cm-3, while trypsin inhibition activities were 1.01-8.08 mg 100 g-1 sample.

Co-melting technology in resource recycling of sludge derived from stone processing.

PubMed

Hu, Shao-Hua; Hu, Shen-Chih; Fu, Yen-Pei

2012-12-01

Stone processing sludge (SPS) is a by-product of stone-processing wastewater treatment; it is suitable for use as a raw material for making artificial lightweight aggregates (ALWAs). In this study, boric acid was utilized as a flux to lower sintering temperature. The formation of the viscous glassy phase was observed by DTA curve and changes in XRD patterns. Experiments were conducted to find the optimal combination of sintering temperature, sintering time, and boric acid dosage to produce an ALWA of favorable characteristics in terms of water absorption, bulk density, apparent porosity, compressive strength and weight loss to satisfy Taiwan's regulatory requirements for construction and insulation materials. Optimal results gave a sintering temperature of 850 degrees C for 15 min at a boric acid dosage of 15% by weight of SPS. Results for ALWA favorable characteristics were: 0.21% (water absorption), 0.35% (apparent porosity), 1.67 g/cm3 (bulk density), 66.94 MPa (compressive strength), and less than 0.1% (weight loss).

Co-melting technology in resource recycling of sludge derived from stone processing.

PubMed

Hu, Shao-Hua; Hu, Shen-Chih; Fu, Yen-Pei

2012-12-01

Stone processing sludge (SPS) is a by-product of stone-processing wastewater treatment; it is suitable for use as a raw material for making artificial lightweight aggregates (ALWAs). In this study, boric acid was utilized as a flux to lower sintering temperature. The formation of the viscous glassy phase was observed by DTA curve and changes in XRD patterns. Experiments were conducted to find the optimal combination of sintering temperature, sintering time, and boric acid dosage to produce an ALWA of favorable characteristics in terms of water absorption, bulk density, apparent porosity, compressive strength and weight loss to satisfy Taiwan's regulatory requirements for construction and insulation materials. Optimal results gave a sintering temperature of 850 °C for 15 min at a boric acid dosage of 15 % by weight of SPS. Results for ALWA favorable characteristics were: 0.21 % (water absorption), 0.35 %(apparent porosity), 1.67 g/cm3 (bulk density), 66.94 MPa (compressive strength), and less than 0.1% (weight loss). [Box: see text].

Properties of medium-density fiberboard related to hardwood specific gravity

Treesearch

George E. Woodson

1976-01-01

Boards of acceptable quality were made from barky material, pressure-refined from 14 species of southern hardwoods. Static bending and tensile properties (parallel to surface) of specimens were negatively correlated to stem specific gravity (wood plus bark), chip bulk density, and fiber bulk density. Bending and tensile properties increased with increasing...

Bulk densities of materials from selected pine-site hardwoods

Treesearch

Clyde Vidrine; George E. Woodson

1982-01-01

Bulk densities of hardwood materials from low and high density species were determined for green and air-dry conditions. Materials consisted of whole-tree chips, bark-free chips, bark as collected from three types of debarkers (ring, rosser head, and drum debarkers) sawdust, planer shavings, flakes, logging residues, baled branchwood, steel-strapped firewood, and...

Soil water retention of a bare soil with changing bulk densities

USDA-ARS?s Scientific Manuscript database

Tillage changes the bulk density of the soil, lowering the density initially after which it increases as the soil settles. Implications of this for soil water content and soil water potential are obvious, but limited efforts have been made to monitor these changes continuously. We present in-situ me...

Intrinsic point defects in β-In2S3 studied by means of hybrid density-functional theory

NASA Astrophysics Data System (ADS)

Ghorbani, Elaheh; Albe, Karsten

2018-03-01

We have employed first principles total energy calculations in the framework of density functional theory, with plane wave basis sets and screened exchange hybrid functionals to study the incorporation of intrinsic defects in bulk β-In2S3. The results are obtained for In-rich and S-rich experimental growth conditions. The charge transition level is discussed for all native defects, including VIn, VS, Ini, Si, SIn, and InS, and a comparison between the theoretically calculated charge transition levels and the available experimental findings is presented. The results imply that β-In2S3 shows n-type conductivity under both In-rich and S-rich growth conditions. The indium antiisite (InS), the indium interstitial (Ini), and the sulfur vacancy ( VS ' ) are found to be the leading sources of sample's n-type conductivity. When going from the In-rich to the S-rich condition, the conductivity of the material decreases; however, the type of conductivity remains unchanged.

Effect of the disturbance of plateau pika (Ochotona curzoniae) on soil water and soil temperature characteristics at Alpine Meadows in Qinghai-Tibet Plateau, China

NASA Astrophysics Data System (ADS)

Ma, Yujun; Wu, Yinan; Wang, Xiaoxing; Li, Xiaoyan

2015-04-01

The plateau pika (Ochotona curzoniae) is one of main small rodents at Alpine Meadows in Qinghai-Tibet Plateau, and has a positive effect on the maintenance of regional soil biodiversity. But, its excessive disturbance was also known as an important factor that leads to the vegetation degradation. Based on the field experiment, sampling analysis and continuous observation, this study compared the difference of soil water and soil temperature characteristics at different disturbance stages, which included native grassland, new mound, old mound and bare land formed by old mound. The findings of this study revealed that, after the disturbance of plateau pika, the soil bulk density at the shallow layer (0-20 cm) increased with the time-lapse. At the 20-30 cm depth, the soil bulk density of old mound, bare land and native grassland were similar, and were all higher than that of new mound. At the deep layer (under 30 cm), the soil bulk density had no significant difference between four stages, which showed that the disturbance of plateau pika mainly distributed within the shallow 30 cm depth. The unsaturated hydraulic conductivity of new mound was higher than old mound, bare soil and native grassland, with the multiple of 3.08-8.71, 4.63-16.27 and 3.70-15.25, respectively, and led to the obvious variance of soil water change for different types of land surface. After the precipitation, the soil water content change of new mound and old mound were more significant than that of bare land and native grassland. Because of the disturbance of plateau pika, the soil temperature characteristics changed, too. The heat conductivity rate of new mound and old mound decreased, significantly, and their daily temperature difference were obvious higher than bare land and native grassland. These results were essential for the study of vegetation recovery after the disturbance of plateau pika.

Effect of process variables on the density and durability of the pellets made from high moisture corn stover

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

Jaya Shankar Tumuluru

2014-03-01

A flat die pellet mill was used to understand the effect of high levels of feedstock moisture content in the range of 28–38% (w.b.), with die rotational speeds of 40–60 Hz, and preheating temperatures of 30–110 °C on the pelleting characteristics of 4.8 mm screen size ground corn stover using an 8 mm pellet die. The physical properties of the pelletised biomass studied are: (a) pellet moisture content, (b) unit, bulk and tapped density, and (c) durability. Pelletisation experiments were conducted based on central composite design. Analysis of variance (ANOVA) indicated that feedstock moisture content influenced all of the physicalmore » properties at P < 0.001. Pellet moisture content decreased with increase in preheating temperature to about 110 °C and decreasing the feedstock moisture content to about 28% (w.b.). Response surface models developed for quality attributes with respect to process variables has adequately described the process with coefficient of determination (R2) values of >0.88. The other pellet quality attributes such as unit, bulk, tapped density, were maximised at feedstock moisture content of 30–33% (w.b.), die speeds of >50 Hz and preheating temperature of >90 °C. In case of durability a medium moisture content of 33–34% (w.b.) and preheating temperatures of >70 °C and higher die speeds >50 Hz resulted in high durable pellets. It can be concluded from the present study that feedstock moisture content, followed by preheating, and die rotational speed are the interacting process variables influencing pellet moisture content, unit, bulk and tapped density and durability.« less

Experimental constraints on the sulfur content in the Earth's core

NASA Astrophysics Data System (ADS)

Fei, Y.; Huang, H.; Leng, C.; Hu, X.; Wang, Q.

2015-12-01

Any core formation models would lead to the incorporation of sulfur (S) into the Earth's core, based on the cosmochemical/geochemical constraints, sulfur's chemical affinity for iron (Fe), and low eutectic melting temperature in the Fe-FeS system. Preferential partitioning of S into the melt also provides petrologic constraint on the density difference between the liquid outer and solid inner cores. Therefore, the center issue is to constrain the amount of sulfur in the core. Geochemical constraints usually place 2-4 wt.% S in the core after accounting for its volatility, whereas more S is allowed in models based on mineral physics data. Here we re-examine the constraints on the S content in the core by both petrologic and mineral physics data. We have measured S partitioning between solid and liquid iron in the multi-anvil apparatus and the laser-heated diamond anvil cell, evaluating the effect of pressure on melting temperature and partition coefficient. In addition, we have conducted shockwave experiments on Fe-11.8wt%S using a two-stage light gas gun up to 211 GPa. The new shockwave experiments yield Hugoniot densities and the longitudinal sound velocities. The measurements provide the longitudinal sound velocity before melting and the bulk sound velocity of liquid. The measured sound velocities clearly show melting of the Fe-FeS mix with 11.8wt%S at a pressure between 111 and 129 GPa. The sound velocities at pressures above 129GPa represent the bulk sound velocities of Fe-11.8wt%S liquid. The combined data set including density, sound velocity, melting temperature, and S partitioning places a tight constraint on the required sulfur partition coefficient to produce the density and velocity jumps and the bulk sulfur content in the core.

High-temperature superconductor bulk magnets that can trap magnetic fields of over 17 tesla at 29 K.

PubMed

Tomita, Masaru; Murakami, Masato

2003-01-30

Large-grain high-temperature superconductors of the form RE-Ba-Cu-O (where RE is a rare-earth element) can trap magnetic fields of several tesla at low temperatures, and so can be used for permanent magnet applications. The magnitude of the trapped field is proportional to the critical current density and the volume of the superconductor. Various potential engineering applications for such magnets have emerged, and some have already been commercialized. However, the range of applications is limited by poor mechanical stability and low thermal conductivity of the bulk superconductors; RE-Ba-Cu-O magnets have been found to fracture during high-field activation, owing to magnetic pressure. Here we present a post-fabrication treatment that improves the mechanical properties as well as thermal conductivity of a bulk Y-Ba-Cu-O magnet, thereby increasing its field-trapping capacity. First, resin impregnation and wrapping the materials in carbon fibre improves the mechanical properties. Second, a small hole drilled into the centre of the magnet allows impregnation of Bi-Pb-Sn-Cd alloy into the superconductor and inclusion of an aluminium wire support, which results in a significant enhancement of thermal stability and internal mechanical strength. As a result, 17.24 T could be trapped, without fracturing, in a bulk Y-Ba-Cu-O sample of 2.65 cm diameter at 29 K.

An investigation of crown fuel bulk density effects on the dynamics of crown fire initiation in shrublands

Treesearch

Watcharapong Tachajapong; Jesse Lozano; Shankar Mahalingam; Xiangyang Zhou; David R. Weise

2008-01-01

Crown fire initiation is studied by using a simple experimental and detailed physical modeling based on Large Eddy Simulation (LES). Experiments conducted thus far reveal that crown fuel ignition via surface fire occurs when the crown base is within the continuous flame region and does not occur when the crown base is located in the hot plume gas region of the surface...

First-principles simulation of the optical response of bulk and thin-film α-quartz irradiated with an ultrashort intense laser pulse

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

Lee, Kyung-Min; Min Kim, Chul; Moon Jeong, Tae, E-mail: jeongtm@gist.ac.kr

A computational method based on a first-principles multiscale simulation has been used for calculating the optical response and the ablation threshold of an optical material irradiated with an ultrashort intense laser pulse. The method employs Maxwell's equations to describe laser pulse propagation and time-dependent density functional theory to describe the generation of conduction band electrons in an optical medium. Optical properties, such as reflectance and absorption, were investigated for laser intensities in the range 10{sup 10} W/cm{sup 2} to 2 × 10{sup 15} W/cm{sup 2} based on the theory of generation and spatial distribution of the conduction band electrons. The method was applied tomore » investigate the changes in the optical reflectance of α-quartz bulk, half-wavelength thin-film, and quarter-wavelength thin-film and to estimate their ablation thresholds. Despite the adiabatic local density approximation used in calculating the exchange–correlation potential, the reflectance and the ablation threshold obtained from our method agree well with the previous theoretical and experimental results. The method can be applied to estimate the ablation thresholds for optical materials, in general. The ablation threshold data can be used to design ultra-broadband high-damage-threshold coating structures.« less

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

Selamat, Mohd Zulkefli, E-mail: azulkeflis@utem.edu.my; Yusuf, Muhammad Yusri Md, E-mail: yusri.cheras@gmail.com; Wer, Tio Kok, E-mail: to91@hotmail.my

Bipolar plates are key components in Proton Exchange Membrane (PEM) fuel cells. They carry current away from the cell and withstand the clamping force of the stack assembly. Therefore, PEM fuel cell bipolar plates must have high electrical conductivity and adequate mechanical strength, in addition to being light weight and low cost in terms of both applicable materials and production methods. In this research, the raw materials used to fabricate the high performance bipolar plate are Graphite (Gr), Stannum (Sn) and Polypropylene (PP). All materials used was in powder form and Gr and Sn act as fillers and the PPmore » acts as binder. The ratio of fillers (Gr/Sn) and binder (PP) was fixed at 80:20. For the multi-conductive filler, small amount of Sn, which is 10 up to 20wt% (from the total weight of fillers 80%) have been added into Gr/Sn/PP composite. The fillers were mixed by using the ball mill machine. The second stage of mixing process between the mixer of fillers and binder is also carried out by using ball mill machine before the compaction process by the hot press machine. The effect of formation temperatures (160°C-170°C) on the properties of Gr/Sn/PP composite had been studied in detail, especially the electrical conductivity, bulk density, hardness and microstructure analysis of Gr/Sn/PP composite. The result shows that there are significant improvement in the electrical conductivity and bulk density, which are exceeding the US-DoE target with the maximum value of 265.35 S/cm and 1.682g/cm{sup 3} respectively.« less

Revised Thickness of the Lunar Crust from GRAIL Data: Implications for Lunar Bulk Composition

NASA Technical Reports Server (NTRS)

Taylor, G. Jeffrey; Wieczorek, Mark A.; Neumann, Gregory A.; Nimmo, Francis; Kiefer, Walter S.; Melosh, H. Jay; Phillips, Roger J.; Solomon, Sean C.; Andrews-Hanna, Jeffrey C.; Asmar, Sami W.;

Effects of Nitrogen Fixing Pre-Crops and Fertilizers on Physical and Chemical Properties Down the Soil Profile

NASA Astrophysics Data System (ADS)

Hobley, E.; Honermeier, B.; Don, A.; Gocke, M. I.; Amelung, W.; Kogel-Knabner, I.

2016-12-01

We investigated the effects of pre-crops with and without biological nitrogen fixation capacity (fava beans, clover mulch, fodder maize) and fertilization (no fertilizer, NPK fertilizer, PK fertilizer) on soil physico-chemical properties (bulk density, electrical conductivity, soil organic carbon (SOC) concentration and stocks, N concentration and stocks) and their depth distribution (down to 1 m) at a long-term field experiment set up in 1982 in Gießen, Germany. Fertilization had significant but small impacts on the soil chemical environment, most particularly the salt content of the soil, with PK fertilization increasing electrical conductivity throughout the soil profile. Similarly, fertilization resulted in a small reduction of soil pH throughout the entire soil profile. The soil was physically and chemically affected by the type of pre-crop. Plots with fava beans and maize had lower bulk densities in the subsoil than those with clover. Pre-crop type also significantly affected the depth distribution of both N and SOC. Specifically, clover pre-cropping led to an enrichment of N at the surface compared with fava beans and maize. SOC enrichment at the surface was also observed under clover, with the effect most pronounced under PK fertilization. Combined with the bulk density effects, this shift in N distribution resulted in significantly higher N stocks under clover than under fava beans. However, the total stocks of SOC were not affected by pre-crop or fertilizer regime. Our results indicate that humans influence C and N cycling and distribution in soils through the selection of pre-crops and that the influence of crop type is greater than that of fertilization regimes. Pre-cropping with clover, which is used as a mulch, leads to N enrichment in the topsoil, reducing the need for N fertilizer for the subsequent cereal crop. In contrast, the use of fava beans as a pre-crop does not lead to N enrichment. We believe this is due to the greater rooting depth of fava beans compared with clover, resulting in lower bulk density in the subsoil and associated lower stocks. Additionally, the harvest of fava beans removes N-rich biomass from the soil, lowering N-input. Lastly, the uptake of water at depth may facilitate subsoil N uptake, so that fava bean N is utilized by the cereal crop but does not lead to its enrichment in the subsoil.

Calculated in situ rock density from gravity observations, UA-1 (Cannikin) emplacement hole, Amchitka Island, Alaska

USGS Publications Warehouse

Healey, D.L.

1971-01-01

Gravity observations were made on the ground surface and at a depth of 5,854 feet in drill hole UA-1. Two attempts to measure the free-air gradient utilizing the headframe over the drill hole were unsuccessful owing to mechanical vibrations in the structure. Because of the uncertainty in the measured free-air gradients these values were discarded and the average value (0.09406 mgal/ft) was used in the calculations. The calculated in situ bulk density is 2.36 g/cc. The weighted average bulk density determined from 47 core samples taken in the adjacent UAE-1 drill hole is also 2.36 g/cc. An analysis of selected portions of density logs provides an in situ bulk density of 2.37 g/cc.

Topological surface states interacting with bulk excitations in the Kondo insulator SmB6 revealed via planar tunneling spectroscopy.

PubMed

Park, Wan Kyu; Sun, Lunan; Noddings, Alexander; Kim, Dae-Jeong; Fisk, Zachary; Greene, Laura H

2016-06-14

Samarium hexaboride (SmB6), a well-known Kondo insulator in which the insulating bulk arises from strong electron correlations, has recently attracted great attention owing to increasing evidence for its topological nature, thereby harboring protected surface states. However, corroborative spectroscopic evidence is still lacking, unlike in the weakly correlated counterparts, including Bi2Se3 Here, we report results from planar tunneling that unveil the detailed spectroscopic properties of SmB6 The tunneling conductance obtained on the (001) and (011) single crystal surfaces reveals linear density of states as expected for two and one Dirac cone(s), respectively. Quite remarkably, it is found that these topological states are not protected completely within the bulk hybridization gap. A phenomenological model of the tunneling process invoking interaction of the surface states with bulk excitations (spin excitons), as predicted by a recent theory, provides a consistent explanation for all of the observed features. Our spectroscopic study supports and explains the proposed picture of the incompletely protected surface states in this topological Kondo insulator SmB6.

Topological surface states interacting with bulk excitations in the Kondo insulator SmB6 revealed via planar tunneling spectroscopy

PubMed Central

Park, Wan Kyu; Sun, Lunan; Noddings, Alexander; Kim, Dae-Jeong; Fisk, Zachary; Greene, Laura H.

2016-01-01

Samarium hexaboride (SmB6), a well-known Kondo insulator in which the insulating bulk arises from strong electron correlations, has recently attracted great attention owing to increasing evidence for its topological nature, thereby harboring protected surface states. However, corroborative spectroscopic evidence is still lacking, unlike in the weakly correlated counterparts, including Bi2Se3. Here, we report results from planar tunneling that unveil the detailed spectroscopic properties of SmB6. The tunneling conductance obtained on the (001) and (011) single crystal surfaces reveals linear density of states as expected for two and one Dirac cone(s), respectively. Quite remarkably, it is found that these topological states are not protected completely within the bulk hybridization gap. A phenomenological model of the tunneling process invoking interaction of the surface states with bulk excitations (spin excitons), as predicted by a recent theory, provides a consistent explanation for all of the observed features. Our spectroscopic study supports and explains the proposed picture of the incompletely protected surface states in this topological Kondo insulator SmB6. PMID:27233936

Magnetism and Metal-Insulator Transition in Oxygen Deficient SrTiO 3

DOE PAGES

Lopez-Bezanilla, Alejandro; Ganesh, Panchapakesan; Littlewood, Peter B.

2015-09-08

First-principles calculations to study the electronic and magnetic properties of bulk, oxygen-deficient SrTiO 3 (STO) under different doping conditions and densities have been conducted. The appearance of magnetism in oxygen-deficient STO is not determined solely by the presence of a single oxygen vacancy but by the density of free carriers and the relative proximity of the vacant sites. We find that while an isolated vacancy behaves as a nonmagnetic double donor, manipulation of the doping conditions allows the stability of a single-donor state, with emergent local moments coupled ferromagnetically by carriers in the conduction band. Strong local lattice distortions enhancemore » the binding of this state. As a result, the energy of the in-gap local moment can be further tuned by orthorhombic strain. Consequently we find that the free-carrier density and strain are fundamental components to obtaining trapped spin-polarized electrons in oxygen-deficient STO, which may have important implications in the design of optical devices.« less

Fluid dynamic propagation of initial baryon number perturbations on a Bjorken flow background

DOE PAGES

Floerchinger, Stefan; Martinez, Mauricio

2015-12-11

Baryon number density perturbations offer a possible route to experimentally measure baryon number susceptibilities and heat conductivity of the quark gluon plasma. We study the fluid dynamical evolution of local and event-by-event fluctuations of baryon number density, flow velocity, and energy density on top of a (generalized) Bjorken expansion. To that end we use a background-fluctuation splitting and a Bessel-Fourier decomposition for the fluctuating part of the fluid dynamical fields with respect to the azimuthal angle, the radius in the transverse plane, and rapidity. Here, we examine how the time evolution of linear perturbations depends on the equation of statemore » as well as on shear viscosity, bulk viscosity, and heat conductivity for modes with different azimuthal, radial, and rapidity wave numbers. Finally we discuss how this information is accessible to experiments in terms of the transverse and rapidity dependence of correlation functions for baryonic particles in high energy nuclear collisions.« less

Ambipolar surface state thermoelectric power of topological insulator Bi2Se3.

PubMed

Kim, Dohun; Syers, Paul; Butch, Nicholas P; Paglione, Johnpierre; Fuhrer, Michael S

2014-01-01

We measure gate-tuned thermoelectric power of mechanically exfoliated Bi2Se3 thin films in the topological insulator regime. The sign of the thermoelectric power changes across the charge neutrality point as the majority carrier type switches from electron to hole, consistent with the ambipolar electric field effect observed in conductivity and Hall effect measurements. Near the charge neutrality point and at low temperatures, the gate-dependent thermoelectric power follows the semiclassical Mott relation using the expected surface state density of states but is larger than expected at high electron doping, possibly reflecting a large density of states in the bulk gap. The thermoelectric power factor shows significant enhancement near the electron-hole puddle carrier density ∼0.5 × 10(12) cm(-2) per surface at all temperatures. Together with the expected reduction of lattice thermal conductivity in low-dimensional structures, the results demonstrate that nanostructuring and Fermi level tuning of three-dimensional topological insulators can be promising routes to realize efficient thermoelectric devices.

Titanium subhydride potassium perchlorate (TiH1.65/KClO4) burn rates from hybrid closed bomb-strand burner experiments.

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

Cooper, Marcia A.; Oliver, Michael S.

2012-08-01

A hybrid closed bomb-strand burner is used to measure the burning behavior of the titanium subhydride potassium perchlorate pyrotechnic with an equivalent hydrogen concentration of 1.65. This experimental facility allows for simultaneous measurement of the closed bomb pressure rise and pyrotechnic burn rate as detected by electrical break wires over a range of pressures. Strands were formed by pressing the pyrotechnic powders to bulk densities between 60% and 90% theoretical maximum density. The burn rate dependance on initial density and vessel pressure are measured. At all initial strand densities, the burn is observed to transition from conductive to convective burningmore » within the strand. The measured vessel pressure history is further analyzed following the closed bomb analysis methods developed for solid propellants.« less

75 FR 40843 - International Conference on Harmonisation; Draft Guidance on Q4B Evaluation and Recommendation of...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-07-14

... Texts for Use in the International Conference on Harmonisation Regions; Annex 13 on Bulk Density and... guidance entitled ``Q4B Evaluation and Recommendation of Pharmacopoeial Texts for Use in the ICH Regions... evaluation of the Bulk Density and Tapped Density of Powders General Chapter harmonized text from each of the...

Mesoscopic pairing without superconductivity

NASA Astrophysics Data System (ADS)

Hofmann, Johannes

2017-12-01

We discuss pairing signatures in mesoscopic nanowires with a variable attractive pairing interaction. Depending on the wire length, density, and interaction strength, these systems realize a simultaneous bulk-to-mesoscopic and BCS-BEC crossover, which we describe in terms of the parity parameter that quantifies the odd-even energy difference and generalizes the bulk Cooper pair binding energy to mesoscopic systems. We show that the parity parameter can be extracted from recent measurements of conductance oscillations in SrTiO3 nanowires by Cheng et al. [Nature (London) 521, 196 (2015), 10.1038/nature14398], where it marks the critical magnetic field that separates pair and single-particle currents. Our results place the experiment in the fluctuation-dominated mesoscopic regime on the BCS side of the crossover.

Broken symmetries, zero-energy modes, and quantum transport in disordered graphene: from supermetallic to insulating regimes.

PubMed

Cresti, Alessandro; Ortmann, Frank; Louvet, Thibaud; Van Tuan, Dinh; Roche, Stephan

2013-05-10

The role of defect-induced zero-energy modes on charge transport in graphene is investigated using Kubo and Landauer transport calculations. By tuning the density of random distributions of monovacancies either equally populating the two sublattices or exclusively located on a single sublattice, all conduction regimes are covered from direct tunneling through evanescent modes to mesoscopic transport in bulk disordered graphene. Depending on the transport measurement geometry, defect density, and broken sublattice symmetry, the Dirac-point conductivity is either exceptionally robust against disorder (supermetallic state) or suppressed through a gap opening or by algebraic localization of zero-energy modes, whereas weak localization and the Anderson insulating regime are obtained for higher energies. These findings clarify the contribution of zero-energy modes to transport at the Dirac point, hitherto controversial.

Conductance of a quantum wire at low electron density

NASA Astrophysics Data System (ADS)

Matveev, Konstantin

2006-03-01

We study the transport of electrons through a long quantum wire connecting two bulk leads. As the electron density in the wire is lowered, the Coulomb interactions lead to short-range crystalline ordering of electrons. In this Wigner crystal state the spins of electrons form an antiferromagnetic Heisenberg spin chain with exponentially small exchange coupling J. Inhomogeneity of the electron density due to the coupling of the wire to the leads results in violation of spin-charge separation in the device. As a result the spins affect the conductance of the wire. At zero temperature the low-energy spin excitations propagate freely through the wire, and its conductance remains 2e^2/h. At finite temperature some of the spin excitations are reflected by the wire and contribute to its resistance. Since the energy of the elementary excitations in the spin chain (spinons) cannot exceed πJ/2, the conductance of the wire acquires an exponentially small negative correction δG - (-πJ/2T) at low temperatures T J. At higher temperatures, T J, most of the spin excitations in the leads are reflected by the wire, and the conductance levels off at a new universal value e^2/h. This result is consistent with experimental observations of a mini-plateau of conductance at e^2/h in quantum wires in the absence of magnetic field.

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

NREL developed a modeling and experimental strategy to characterize thermal performance of materials. The technique provides critical data on thermal properties with relevance for electronics packaging applications. Thermal contact resistance and bulk thermal conductivity were characterized for new high-performance materials such as thermoplastics, boron-nitride nanosheets, copper nanowires, and atomically bonded layers. The technique is an important tool for developing designs and materials that enable power electronics packaging with small footprint, high power density, and low cost for numerous applications.

Calculated electronic, transport, and related properties of zinc blende boron arsenide (zb-BAs)

DOE PAGES

Nwigboji, Ifeanyi H.; Malozovsky, Yuriy; Franklin, Lashounda; ...

2016-10-11

Here, we present the results from ab-initio, self-consistent density functional theory (DFT) calculations of electronic, transport, and bulk properties of zinc blende boron arsenide. We utilized the local density approximation potential of Ceperley and Alder, as parameterized by Vosko and his group, the linear combination of Gaussian orbitals formalism, and the Bagayoko, Zhao, and Williams (BZW) method, as enhanced by Ekuma and Franklin (BZW-EF), in carrying out our completely self-consistent calculations. With this method, the results of our calculations have the full, physical content of density functional theory (DFT). Our results include electronic energy bands, densities of states, effective masses,more » and the bulk modulus. Our calculated, indirect band gap of 1.48 eV, from C to a conduction band minimum close to X, for the room temperature lattice constant of 4.777 Å, is in an excellent agreement with the experimental value of 1.46 6 0.02 eV. We thor-oughly explain the reasons for the excellent agreement between our findings and corresponding, experimental ones. This work provides a confirmation of the capability of DFT to describe accu-rately properties of materials, provides a confirmation of the capability of DFT to describe accu-rately properties of materials, if the computations adhere strictly to the conditions of validity of DFT, as done by the BZW-EF method.« less

Bench and Riser Soil Water Content on Semiarid Hillslopes with Terracettes

NASA Astrophysics Data System (ADS)

Heinse, R.; Corrao, M.; Eitel, J.; Link, T. E.

2015-12-01

Microtopographic features known as terracettes are found throughout many semiarid rangelands. These path-like features roughly perpendicular to the slope are frequently traversed by grazing animals on steep hillslopes. The soil properties and hydrologic function, however, are virtually unknown. This research aimed to identify differences in soil properties between terracette bench and riser features, and their influence on soil water content for two terracetted sites and two non-terracetted control sites (grazed and ungrazed) in Eastern Washington State. Measurements of volumetric water content (θ_v), bulk density, soil texture, saturated hydraulic conductivity, pH, and ECa_a were collected along with compaction, vegetative cover and cattle density throughout the 2013 and 2014 field seasons. Results show small but significant volumetric water content differences between terracette benches and risers in the upper 10 cm with benches exhibiting higher mean θ_v than risers throughout the year. Soil bulk density on benches (1600 kg m-3^{-3}) was significantly higher than that of risers (1300 kg m-3^{-3}) with no differences in soil texture. The saturated hydraulic conductivity on benches was roughly half of that for risers. No significant soil differences were noted below 20 cm depth. Terracetted sites showed greater field-averaged θ_v compared to non-terracetted sites suggesting a positive trend with animal stocking rates. Higher water content on terracette benches is attributed to shifts in pore size distribution with compaction, and a reduction in root-water uptake due to plant-root impedance. This increased soil water does not however increase forage production as it is not accessible to plants.

Electric microwave absorption for the study of GaAs/AlGaAs heterostructure systems

NASA Astrophysics Data System (ADS)

Zappe, Hans P.; Jantz, Wolfgang

1990-12-01

The use of magnetic-field-dependent microwave absorption as a nondestructive and contact-free means to study transport behavior in GaAs/AlGaAs devices is explored. This technique allows quick measurement of resistance, mobility, and carrier concentration in bulk substrates as well as in the two-dimensional electron gas of heterostructure quantum wells. The two- and three-dimensional conductivities may be separably evaluated, allowing detailed study of conduction in the active layer of high-electron-mobility devices. A brief theoretical foundation is provided, followed by application of the approach to examination of device structural dependencies, carrier-density conduction behavior, and the effects of etch processing on quantum-well integrity.

The diversity of (13)C isotope discrimination in a Quercus robur full-sib family is associated with differences in intrinsic water use efficiency, transpiration efficiency, and stomatal conductance.

PubMed

Roussel, Magali; Dreyer, Erwin; Montpied, Pierre; Le-Provost, Grégoire; Guehl, Jean-Marc; Brendel, Oliver

2009-01-01

(13)C discrimination in organic matter with respect to atmospheric CO(2) (Delta(13)C) is under tight genetic control in many plant species, including the pedunculate oak (Quercus robur L.) full-sib progeny used in this study. Delta(13)C is expected to reflect intrinsic water use efficiency, but this assumption requires confirmation due to potential interferences with mesophyll conductance to CO(2), or post-photosynthetic discrimination. In order to dissect the observed Delta(13)C variability in this progeny, six genotypes that have previously been found to display extreme phenotypic values of Delta(13)C [either very high ('high Delta') or low ('low Delta') phenotype] were selected, and transpiration efficiency (TE; accumulated biomass/transpired water), net CO(2) assimilation rate (A), stomatal conductance for water vapour (g(s)), and intrinsic water use efficiency (W(i)=A/g(s)) were compared with Delta(13)C in bulk leaf matter, wood, and cellulose in wood. As expected, 'high Delta' displayed higher values of Delta(13)C not only in bulk leaf matter, but also in wood and cellulose. This confirmed the stability of the genotypic differences in Delta(13)C recorded earlier. 'High Delta' also displayed lower TE, lower W(i), and higher g(s). A small difference was detected in photosynthetic capacity but none in mesophyll conductance to CO(2). 'High Delta' and 'low Delta' displayed very similar leaf anatomy, except for higher stomatal density in 'high Delta'. Finally, diurnal courses of leaf gas exchange revealed a higher g(s) in 'high Delta' in the morning than in the afternoon when the difference decreased. The gene ERECTA, involved in the control of water use efficiency, leaf differentiation, and stomatal density, displayed higher expression levels in 'low Delta'. In this progeny, the variability of Delta(13)C correlated closely with that of W(i) and TE. Genetic differences of Delta(13)C and W(i) can be ascribed to differences in stomatal conductance and stomatal density but not in photosynthetic capacity.

Electrical and Optical Characteristics of Undoped and Se-Doped Bi2S3 Transistors

NASA Astrophysics Data System (ADS)

Kilcoyne, Colin; Alsaqqa, Ali; Rahman, Ajara A.; Whittaker-Brooks, Luisa; Sambandamurthy, G.

Semiconducting chalcogenides have been drawing increased attention due to their interesting physical properties, especially in low dimensional structures. Bi2S3 has demonstrated a high optical absorption coefficient, a large bulk mobility, small bandgap, high Seebeck coefficient, and low thermal conductivity. These properties make it a good candidate for optical, electric and thermoelectric applications. However, control over the electrical properties for enhanced thermoelectric performance and optical applications is desired. We present electrical transport and optical properties from individual nanowire and few-layer transistors of single crystalline undoped and Se-doped Bi2S3-xSex. All devices exhibit n-type semiconducting behavior and the ON/OFF ratio, mobility, and conductivity noise behavior are studied as functions of dopant concentration, temperature, and charge carrier density in different conduction regimes. The roles of dopant driven scattering mechanisms and mobility/carrier density fluctuations will be discussed. The potential for this series of materials as optical and electrical switches will be presented. NSF DMR.

A two-population sporadic meteoroid bulk density distribution and its implications for environment models

NASA Astrophysics Data System (ADS)

Moorhead, Althea V.; Blaauw, Rhiannon C.; Moser, Danielle E.; Campbell-Brown, Margaret D.; Brown, Peter G.; Cooke, William J.

2017-12-01

The bulk density of a meteoroid affects its dynamics in space, its ablation in the atmosphere, and the damage it does to spacecraft and lunar or planetary surfaces. Meteoroid bulk densities are also notoriously difficult to measure, and we are typically forced to assume a density or attempt to measure it via a proxy. In this paper, we construct a density distribution for sporadic meteoroids based on existing density measurements. We considered two possible proxies for density: the KB parameter introduced by Ceplecha and Tisserand parameter, TJ. Although KB is frequently cited as a proxy for meteoroid material properties, we find that it is poorly correlated with ablation-model-derived densities. We therefore follow the example of Kikwaya et al. in associating density with the Tisserand parameter. We fit two density distributions to meteoroids originating from Halley-type comets (TJ < 2) and those originating from all other parent bodies (TJ > 2); the resulting two-population density distribution is the most detailed sporadic meteoroid density distribution justified by the available data. Finally, we discuss the implications for meteoroid environment models and spacecraft risk assessments. We find that correcting for density increases the fraction of meteoroid-induced spacecraft damage produced by the helion/antihelion source.

46 CFR 98.25-65 - Filling density.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 4 2011-10-01 2011-10-01 false Filling density. 98.25-65 Section 98.25-65 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CARGO AND MISCELLANEOUS VESSELS SPECIAL CONSTRUCTION, ARRANGEMENT, AND OTHER PROVISIONS FOR CERTAIN DANGEROUS CARGOES IN BULK Anhydrous Ammonia in Bulk...

46 CFR 98.25-65 - Filling density.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 4 2010-10-01 2010-10-01 false Filling density. 98.25-65 Section 98.25-65 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CARGO AND MISCELLANEOUS VESSELS SPECIAL CONSTRUCTION, ARRANGEMENT, AND OTHER PROVISIONS FOR CERTAIN DANGEROUS CARGOES IN BULK Anhydrous Ammonia in Bulk...

46 CFR 98.25-65 - Filling density.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 4 2014-10-01 2014-10-01 false Filling density. 98.25-65 Section 98.25-65 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CARGO AND MISCELLANEOUS VESSELS SPECIAL CONSTRUCTION, ARRANGEMENT, AND OTHER PROVISIONS FOR CERTAIN DANGEROUS CARGOES IN BULK Anhydrous Ammonia in Bulk...

46 CFR 98.25-65 - Filling density.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 4 2013-10-01 2013-10-01 false Filling density. 98.25-65 Section 98.25-65 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CARGO AND MISCELLANEOUS VESSELS SPECIAL CONSTRUCTION, ARRANGEMENT, AND OTHER PROVISIONS FOR CERTAIN DANGEROUS CARGOES IN BULK Anhydrous Ammonia in Bulk...

46 CFR 98.25-65 - Filling density.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 4 2012-10-01 2012-10-01 false Filling density. 98.25-65 Section 98.25-65 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CARGO AND MISCELLANEOUS VESSELS SPECIAL CONSTRUCTION, ARRANGEMENT, AND OTHER PROVISIONS FOR CERTAIN DANGEROUS CARGOES IN BULK Anhydrous Ammonia in Bulk...

Effect of Sodium Hydroxide Molarity on Physical, Mechanical and Thermal Conductivity of Metakaolin Geopolymers

NASA Astrophysics Data System (ADS)

Ain Jaya, Nur; Yun-Ming, Liew; Bakri Abdullah, Mohd Mustafa Al; Cheng-Yong, Heah; Hussin, Kamarudin

2018-03-01

In the present work, the effect of different sodium hydroxide (NaOH) molarity (6M, 8M, 10M, 12M and 14M) on the physical, mechanical and thermal conductivity of metakaolin geopolymers (MkGPs) was investigated. Geopolymers were prepared by activating the metakaolin with a mixture of NaOH with sodium silicate (Na2SiO3). The products obtained were characterized after 28 days of curing. The density, porosity, compressive strength and thermal conductivity (TC) were determined. In general, the NaOH molarity has a significant effect on the compressive strength of the MkGPs. The highest compressive strength was 14.6 MPa achieved with 10M of NaOH solution. The thermal conductivity of MkGPs measured in this work was low in the range between 0.71-0.97 W/mK. NaOH molarity had a significant effect on compressive strength but a marginal effect on thermal conductivity of MkGPs. The thermal conductivity was mainly affected by the bulk density and thus the total porosity. The results showed that the geopolymer can be considered to be used as the thermal insulating material.

Radical re-appraisal of water structure in hydrophilic confinement.

PubMed

Soper, Alan K

2013-12-18

The structure of water confined in MCM41 silica cylindrical pores is studied to determine whether confined water is simply a version of the bulk liquid which can be substantially supercooled without crystallisation. A combination of total neutron scattering from the porous silica, both wet and dry, and computer simulation using a realistic model of the scattering substrate is used. The water in the pore is divided into three regions: core, interfacial and overlap. The average local densities of water in these simulations are found to be about 20% lower than bulk water density, while the density in the core region is below, but closer to, the bulk density. There is a decrease in both local and core densities when the temperature is lowered from 298 K to 210 K. The radical proposal is made here that water in hydrophilic confinement is under significant tension, around -100 MPa, inside the pore.

Structural and transport properties of double perovskite Dy{sub 2}NiMnO{sub 6}

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

Chanda, Sadhan, E-mail: sadhan.physics@gmail.com; Saha, Sujoy; Dutta, Alo

2015-02-15

Highlights: • Sol–gel citrate method is used to prepare the double perovskite Dy{sub 2}NiMnO{sub 6}. • Structure and dielectric relaxation of the sample are studied for nano and bulk phases. • The relaxation mechanism of the sample is modeled by Cole–Cole equation. • With increasing sintering temperature conductivity increases. • Electronic structures and magnetic properties have been studied by DFT calculations. - Abstract: The double perovskite oxide Dy{sub 2}NiMnO{sub 6} (DNMO) is synthesized in nano and bulk phase by the sol–gel citrate method. The Rietveld refinement of X-ray diffraction pattern of the sample at room temperature shows the monoclinic P2{submore » 1}/n phase. Dielectric relaxation of the sample is investigated in the impedance and electric modulus formalisms in the frequency range from 50 Hz to 1 MHz and in the temperature range from 253 to 415 K. The Cole–Cole model is used to explain the relaxation mechanism in DNMO. The frequency-dependent maxima in the imaginary part of impedance are found to obey an Arrhenius law with activation energy of 0.346 and 0.344 eV for nano and bulk DNMO, respectively. A significant increase in conductivity of bulk DNMO has been observed than that of the nanoceramic. Electronic structures and magnetic properties of DNMO have been studied by performing first principles calculation based on density functional theory.« less

The crust of the Moon as seen by GRAIL.

PubMed

Wieczorek, Mark A; Neumann, Gregory A; Nimmo, Francis; Kiefer, Walter S; Taylor, G Jeffrey; Melosh, H Jay; Phillips, Roger J; Solomon, Sean C; Andrews-Hanna, Jeffrey C; Asmar, Sami W; Konopliv, Alexander S; Lemoine, Frank G; Smith, David E; Watkins, Michael M; Williams, James G; Zuber, Maria T

2013-02-08

High-resolution gravity data obtained from the dual Gravity Recovery and Interior Laboratory (GRAIL) spacecraft show that the bulk density of the Moon's highlands crust is 2550 kilograms per cubic meter, substantially lower than generally assumed. When combined with remote sensing and sample data, this density implies an average crustal porosity of 12% to depths of at least a few kilometers. Lateral variations in crustal porosity correlate with the largest impact basins, whereas lateral variations in crustal density correlate with crustal composition. The low-bulk crustal density allows construction of a global crustal thickness model that satisfies the Apollo seismic constraints, and with an average crustal thickness between 34 and 43 kilometers, the bulk refractory element composition of the Moon is not required to be enriched with respect to that of Earth.

Geoacoustic provinces and physical properties of surface sediments in the southern part of the East Sea, Korea

NASA Astrophysics Data System (ADS)

Kim, Sora; Bahk, Jang-Jun; Kim, Daechoul; Lee, Gwang Soo; Kim, Seong-Pil

2017-04-01

A total of 288 piston and box core samples were collected and analyzed to characterize the physical properties and geoacoustic provinces of surficial sediments in the southern part of the East Sea. Based on in-situ condition sound velocity (converted laboratory sound velocity to in-situ condition sound velocity) and sediment properties (sediment textures and physical properties), the study area was divided into eight provinces (Province IA, IB, IC, II, III, IV, VA, and VB) : (1) Province IA : hemi-pelagic mud partially mixed with intermittent sandy sediments originating from the outer shelf due to slide/slump or mass flows (in-situ condition sound velocity: 1439 m/s, mean grain size: 8.5Φ, bulk density: 1.24 g/cm3,and porosity: 84%); (2) Province IB : Holocene muddy sediments are dominant, but in some area that is influenced by the surrounding land and coast (in-situ condition sound velocity: 1448 m/s, mean grain size: 8.3Φ, bulk density: 1.32 g/cm3, and porosity: 79%); (3) Province IC : muddy sediments that were deposited during the Holocene (in-situ condition sound velocity: 1457 m/s, mean grain size: 7.8Φ, bulk density: 1.36 g/cm3, and porosity: 78%); (4) Province II : mixed recent and relict sediments (in-situ condition sound velocity: 1493 m/s, mean grain size: 5.9Φ, bulk density: 1.53 g/cm3, and porosity: 68%); (5) Province III (Pohang) : there is a mixture of muddy sediments and sandy sediments and sediments from Hyeongsan River are mostly deposited (in-situ condition sound velocity: 1586 m/s, mean grain size: 4.1Φ, bulk density: 1.74 g/cm3, and porosity: 57%); (6) Province IV : coarse-grained relict sediments formed during the Pleistocene (in-situ condition sound velocity: 1572 m/s, mean grain size: 4.1Φ, bulk density: 1.76 g/cm3, and porosity: 55%); (7) Province VA : relict sand with some gravel, show marked differences from the area in which muddy sediments are deposited (in-situ condition sound velocity: 1662 m/s, mean grain size: 3.3Φ, bulk density: 1.82 g/cm3, and porosity: 51%), and (8) Province VB : similar to but coarser sediments than Province IV (in-situ condition sound velocity: 1667 m/s, mean grain size: 3.2Φ, bulk density: 1.87 g/cm3, and porosity: 46%). The in-situ condition sound velocity, mean grain size, and bulk density increased from Province IA to Province VB, whereas the porosity and water content decrease. Variability of the physical and acoustic properties tended to follow the general of the mean grain size. The classification of each province using the in-situ condition sound velocity corrected with the temperature and sediment type provides a better reflection of the sediment properties and sedimentary environment.

Electronic and optical properties of graphene-like InAs: An ab initio study

NASA Astrophysics Data System (ADS)

Sohrabi, Leila; Boochani, Arash; Ali Sebt, S.; Mohammad Elahi, S.

2018-03-01

The present work initially investigates structural, optical, and electronic properties of graphene-like InAs by using the full potential linear augmented plane wave method in the framework of density functional theory and is then compared with the bulk Indium Arsenide in the wurtzite phase. The lattice parameters are optimized with GGA-PBE and LDA approximations for both 2D- and 3D-InAs. In order to study the electronic properties of graphene-like InAs and bulk InAs in the wurtzite phase, the band gap is calculated by GGA-PBG and GGA-EV approximations. Moreover, optical parameters of graphene-like InAs and bulk InAs such as the real and imaginary parts of dielectric function, electron energy loss function, refractivity, extinction and absorption coefficients, and optical conductivity are investigated. Plasmonic frequencies of 2D- and 3D-InAs are also calculated by using maximum electron energy loss function and the roots of the real part of the dielectric function.

Effect of formation temperature on properties of graphite/stannum composite for bipolar plate

NASA Astrophysics Data System (ADS)

Selamat, Mohd Zulkefli; Yusuf, Muhammad Yusri Md; Wer, Tio Kok; Sahadan, Siti Norbaya; Malingam, Sivakumar Dhar; Mohamad, Noraiham

2016-03-01

Bipolar plates are key components in Proton Exchange Membrane (PEM) fuel cells. They carry current away from the cell and withstand the clamping force of the stack assembly. Therefore, PEM fuel cell bipolar plates must have high electrical conductivity and adequate mechanical strength, in addition to being light weight and low cost in terms of both applicable materials and production methods. In this research, the raw materials used to fabricate the high performance bipolar plate are Graphite (Gr), Stannum (Sn) and Polypropylene (PP). All materials used was in powder form and Gr and Sn act as fillers and the PP acts as binder. The ratio of fillers (Gr/Sn) and binder (PP) was fixed at 80:20. For the multi-conductive filler, small amount of Sn, which is 10 up to 20wt% (from the total weight of fillers 80%) have been added into Gr/Sn/PP composite. The fillers were mixed by using the ball mill machine. The second stage of mixing process between the mixer of fillers and binder is also carried out by using ball mill machine before the compaction process by the hot press machine. The effect of formation temperatures (160°C-170°C) on the properties of Gr/Sn/PP composite had been studied in detail, especially the electrical conductivity, bulk density, hardness and microstructure analysis of Gr/Sn/PP composite. The result shows that there are significant improvement in the electrical conductivity and bulk density, which are exceeding the US-DoE target with the maximum value of 265.35 S/cm and 1.682g/cm3 respectively.

Effect of confinement on anharmonic phonon scattering and thermal conductivity in pristine silicon nanowires

NASA Astrophysics Data System (ADS)

Rashid, Zahid; Zhu, Liyan; Li, Wu

2018-02-01

The effect of confinement on the anharmonic phonon scattering rates and the consequences thereof on the thermal transport properties in ultrathin silicon nanowires with a diameter of 1-4 nm have been characterized using atomistic simulations and the phonon Boltzmann transport equation. The phonon density of states (PDOS) for ultrathin nanowires approaches a constant value in the vicinity of the Γ point and increases with decreasing diameter, which indicates the increasing importance of the low-frequency phonons as heat carriers. The anharmonic phonon scattering becomes dramatically enhanced with decreasing thickness of the nanowires. In the thinnest nanowire, the scattering rates for phonons above 1 THz are one order of magnitude higher than those in the bulk Si. Below 1 THz, the increase in scattering rates is even much more appreciable. Our numerical calculations revealed that the scattering rates for transverse (longitudinal) acoustic modes follow √{ω } (1 /√{ω } ) dependence at the low-frequency limit, whereas those for the degenerate flexural modes asymptotically approach a constant value. In addition, the group velocities of phonons are reduced compared with bulk Si except for low-frequency phonons (<1 -2 THz depending on the thickness of the nanowires). The increased scattering rates combined with reduced group velocities lead to a severely reduced thermal conductivity contribution from the high-frequency phonons. Although the thermal conductivity contributed by those phonons with low frequencies is instead increased mainly due to the increased PDOS, the total thermal conductivity is still reduced compared to that of the bulk. This work reveals an unexplored mechanism to understand the measured ultralow thermal conductivity of silicon nanowires.

Microwave sensing of moisture content and bulk density in flowing grain

USDA-ARS?s Scientific Manuscript database

Moisture content and bulk density were determined from measurement of the dielectric properties of flowing wheat kernels at a single microwave frequency (5.8 GHz). The measuring system consisted of two high-gain microwave patch antennas mounted on opposite sides of rectangular chute and connected to...

The influence of Zr substitution for Nb on the corrosion behaviors of the Ni-Nb-Zr bulk metallic glasses

NASA Astrophysics Data System (ADS)

Li, DengKe; Zhu, ZhengWang; Zhang, HaiFeng; Wang, AiMin; Hu, ZhuangQi

2012-12-01

The influence of Zr content on corrosion behaviors of the Ni61.5Nb38.5- x Zr x ( x=1, 3, 5, 7, 9 at.%) bulk metallic glasses (BMGs) in 1 M HCl aqueous solution was investigated by potentiodynamic polarization measurements and X-ray photo-electron spectroscopy (XPS). It was found that these BMG alloys possess superior corrosion resistance, that is, with large passive region of about 1.5 V and low passive current density (as low as 0.05 Am-2 for Ni61.5Nb31.5Zr7). XPS analysis indicates that the high corrosion resistance is attributed to the formation of Nb- and Zr-enriched surface films formed in the aggressive acid solution. The Zr substitution for Nb effectively reduces the Ni content, particularly the metallic state Ni content in the surface films, which depresses the electrical conduction of the surface films and reduces the passive current density, thus leading to the enhancement of the corrosion resistance of these Ni-Nb-Zr BMGs. These alloys may potentially be useful for engineering applications.

Self-interaction corrected LDA + U investigations of BiFeO3 properties: plane-wave pseudopotential method

NASA Astrophysics Data System (ADS)

Yaakob, M. K.; Taib, M. F. M.; Lu, L.; Hassan, O. H.; Yahya, M. Z. A.

2015-11-01

The structural, electronic, elastic, and optical properties of BiFeO3 were investigated using the first-principles calculation based on the local density approximation plus U (LDA + U) method in the frame of plane-wave pseudopotential density functional theory. The application of self-interaction corrected LDA + U method improved the accuracy of the calculated properties. Results of structural, electronic, elastic, and optical properties of BiFeO3, calculated using the LDA + U method were in good agreement with other calculation and experimental data; the optimized choice of on-site Coulomb repulsion U was 3 eV for the treatment of strong electronic localized Fe 3d electrons. Based on the calculated band structure and density of states, the on-site Coulomb repulsion U had a significant effect on the hybridized O 2p and Fe 3d states at the valence and the conduction band. Moreover, the elastic stiffness tensor, the longitudinal and shear wave velocities, bulk modulus, Poisson’s ratio, and the Debye temperature were calculated for U = 0, 3, and 6 eV. The elastic stiffness tensor, bulk modulus, sound velocities, and Debye temperature of BiFeO3 consistently decreased with the increase of the U value.

The Influence of Sintering Temperature on the Microstructure and Thermoelectric Properties of n-Type Bi2Te3- x Se x Nanomaterials

NASA Astrophysics Data System (ADS)

Du, Y.; Cai, K. F.; Li, H.; An, B. J.

2011-05-01

Pure Bi2Te3 and Bi2Se3 nanopowders were hydrothermally synthesized, and n-type Bi2Te3- x Se x bulk samples were prepared by hot pressing a mixture of Bi2Te3 and Bi2Se3 nanopowders at 623 K, 648 K or 673 K and 80 MPa in vacuum. The phase composition of the powders and bulk samples were characterized by x-ray diffraction. The morphology of the powders was examined by transmission electron microscopy. The microstructure and composition of the bulk samples were characterized by field-emission scanning electron microscopy and energy-dispersive x-ray spectroscopy, respectively. The density of the samples increased with sintering temperature. The samples were somewhat oxidized, and the amount of oxide (Bi2TeO5) present increased with sintering temperature. The samples consisted of sheet-like grains with a thickness less than 100 nm. Seebeck coefficient, electrical conductivity, and thermal conductivity of the samples were measured from room temperature up to 573 K. Throughout the temperature range investigated, the sample sintered at 623 K had a higher power factor than the samples sintered at 648 K or 673 K.

Real time monitoring of powder blend bulk density for coupled feed-forward/feed-back control of a continuous direct compaction tablet manufacturing process.

PubMed

Singh, Ravendra; Román-Ospino, Andrés D; Romañach, Rodolfo J; Ierapetritou, Marianthi; Ramachandran, Rohit

2015-11-10

The pharmaceutical industry is strictly regulated, where precise and accurate control of the end product quality is necessary to ensure the effectiveness of the drug products. For such control, the process and raw materials variability ideally need to be fed-forward in real time into an automatic control system so that a proactive action can be taken before it can affect the end product quality. Variations in raw material properties (e.g., particle size), feeder hopper level, amount of lubrication, milling and blending action, applied shear in different processing stages can affect the blend density significantly and thereby tablet weight, hardness and dissolution. Therefore, real time monitoring of powder bulk density variability and its incorporation into the automatic control system so that its effect can be mitigated proactively and efficiently is highly desired. However, real time monitoring of powder bulk density is still a challenging task because of different level of complexities. In this work, powder bulk density which has a significant effect on the critical quality attributes (CQA's) has been monitored in real time in a pilot-plant facility, using a NIR sensor. The sensitivity of the powder bulk density on critical process parameters (CPP's) and CQA's has been analyzed and thereby feed-forward controller has been designed. The measured signal can be used for feed-forward control so that the corrective actions on the density variations can be taken before they can influence the product quality. The coupled feed-forward/feed-back control system demonstrates improved control performance and improvements in the final product quality in the presence of process and raw material variations. Copyright © 2015 Elsevier B.V. All rights reserved.

The Fall and Recovery of the Tagish Lake Meteorite

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

Hildebrand, Alan R.; McCausland, Phil J.; Brown, Peter G.

2006-03-01

The Tagish Lake C2 (ungrouped) carbonaceous chondrite fall of January 18, 2000 delivered >10 kg of one of the most primitive and physically weak meteorites yet studied. In this paper we report the detailed circumstances of the fall and the recovery of all documented Tagish Lake fragments. We also provide measurements of bulk physical properties (mass, grain and bulk density), bulk triple oxygen-isotope ratios, and short-lived cosmogenic radionuclides counts for several fragments. Ground eyewitnesses and recorded observations of the Tagish Lake fireball event provide a refined estimate of the fireball trajectory, and hence, its pre-atmospheric orbit. From its calculated orbitmore » and its similarity to the remotely-sensed properties of the D and P-class asteroids, the Tagish Lake carbonaceous chondrite represents these outer belt asteroids, and is not of cometary origin. The bulk oxygen-isotope compositions reported here are among the highest known for meteorites. These data plot just below the Terrestrial Fractionation Line, following a trend similar to the CM meteorite mixing line. The bulk density of the Tagish Lake material (1.66 ±0.02 g/cm3) is the same, within error, as the total bulk densities of many C-class and especially D- and P-class asteroids. The high microporosity of Tagish Lake samples (~40%) provides an obvious candidate material for the composition of low bulk density primitive asteroids such as Phobos, Deimos and the P-class binary 87 Sylvia, without requiring a substantial contribution from macroporosity in the form of ice, thick regolith or “rubble pile” assemblages with large interior voids.« less

Development of Advanced Ill-Nitride Materials

DTIC Science & Technology

2008-09-24

have continued to work on InN and related materials. During the last year, we have completed many of our basic materials studies and extended our...conductivity of InN films The origin of bulk electrons in In-face InN has been studied by considering the effects of both unintentionally incorporated... studied in In- and N-face InN films grown on GaN by plasma-assisted molecular beam epitaxy. The TD densities were determined by non-destructive x-ray

Physical and thermal properties of mud-dominant sediment from the Joetsu Basin in the eastern margin of the Japan Sea

NASA Astrophysics Data System (ADS)

Goto, Shusaku; Yamano, Makoto; Morita, Sumito; Kanamatsu, Toshiya; Hachikubo, Akihiro; Kataoka, Satsuki; Tanahashi, Manabu; Matsumoto, Ryo

2017-12-01

Physical properties (bulk density and porosity) and thermal properties (thermal conductivity, heat capacity, specific heat, and thermal diffusivity) of sediment are crucial parameters for basin modeling. We measured these physical and thermal properties for mud-dominant sediment recovered from the Joetsu Basin, in the eastern margin of the Japan Sea. To determine thermal conductivity, heat capacity, and thermal diffusivity, the dual-needle probe method was applied. Grain density and grain thermal properties for the mud-dominant sediment were estimated from the measured physical and thermal properties by applying existing models of physical and thermal properties of sediment. We suggest that the grain density, grain thermal conductivity, and grain thermal diffusivity depend on the sediment mineral composition. Conversely, the grain heat capacity and grain specific heat showed hardly any dependency on the mineral composition. We propose empirical formulae for the relationships between: thermal diffusivity and thermal conductivity, and heat capacity and thermal conductivity for the sediment in the Joetsu Basin. These relationships are different from those for mud-dominant sediment in the eastern flank of the Juan de Fuca Ridge presented in previous work, suggesting a difference in mineral composition, probably mainly in the amount of quartz, between the sediments in that area and the Joetsu Basin. Similar studies in several areas of sediments with various mineral compositions would enhance knowledge of the influence of mineral composition.

Influence of Ag, Cd or Pb Addition on Electrical and Dielectric Properties of Bulk Glassy Se-Ge

NASA Astrophysics Data System (ADS)

El-Metwally, E. G.; Shakra, A. M.

2018-05-01

Bulk glassy samples of Se0.7Ge0.3 and Se0.7Ge0.25 X 0.05 (X = Ag, Cd or Pb) chalcogenide glass have been prepared by melt-quenching method. The studied compositions were examined in powder form by x-ray diffraction analysis. The direct-current (dc) conductivity σ_{{dc}} was measured for bulk samples in the temperature range from 303 K to 433 K, revealing enhancement with temperature for all samples. The results indicate two values of activation energy ( Δ E_{{σ1 }} and Δ E_{{σ2 }} ) due to two conduction mechanisms. Measurements of the alternating-current (ac) conductivity σ_{{ac}} ( ω ) and dielectric properties for bulk samples were carried out in the temperature range from 303 K to 433 K and frequency range from 1 kHz to 1 MHz. The ac conductivity σ_{{ac}} ( ω ) was temperature dependent and proportional to ωS , where S is the frequency exponent, which reduced with rising temperature, and ω is the angular frequency. These results are discussed based on a correlated barrier hopping model. The calculated values of the maximum height of the barrier W_{{M}} for each composition are consistent with carrier hopping over a potential barrier. The density of localized states N( {E_{{F}} } ) at the Fermi level lay in the range from 1019 eV-1 cm-3 to 1020 eV-1 cm-3, and increased with temperature. The dielectric constant ɛ1 ( ω ) and loss ɛ2 ( ω ) increased with temperature but decreased with frequency. The values of σ_{{dc}} , σ_{{ac}} ( ω ) , ɛ1 ( ω ) , and ɛ2 ( ω ) increased with temperature and with addition of Ag, Cd or Pb. The observed increase was greater for Se0.7Ge0.25Pb0.05 than for Se0.7Ge0.25Cd0.05, which was greater than for Se0.7Ge0.25Ag0.05.

Mars Express 10 years at Mars: Observations by the Mars Express Radio Science Experiment (MaRS)

NASA Astrophysics Data System (ADS)

Pätzold, M.; Häusler, B.; Tyler, G. L.; Andert, T.; Asmar, S. W.; Bird, M. K.; Dehant, V.; Hinson, D. P.; Rosenblatt, P.; Simpson, R. A.; Tellmann, S.; Withers, P.; Beuthe, M.; Efimov, A. I.; Hahn, M.; Kahan, D.; Le Maistre, S.; Oschlisniok, J.; Peter, K.; Remus, S.

2016-08-01

The Mars Express spacecraft is operating in Mars orbit since early 2004. The Mars Express Radio Science Experiment (MaRS) employs the spacecraft and ground station radio systems (i) to conduct radio occultations of the atmosphere and ionosphere to obtain vertical profiles of temperature, pressure, neutral number densities and electron density, (ii) to conduct bistatic radar experiments to obtain information on the dielectric and scattering properties of the surface, (iii) to investigate the structure and variation of the crust and lithosphere in selected target areas, (iv) to determine the mass, bulk and internal structure of the moon Phobos, and (v) to track the MEX radio signals during superior solar conjunction to study the morphology of coronal mass ejections (CMEs). Here we report observations, results and discoveries made in the Mars environment between 2004 and 2014 over almost an entire solar cycle.

Modeling multidomain hydraulic properties of shrink-swell soils

NASA Astrophysics Data System (ADS)

Stewart, Ryan D.; Abou Najm, Majdi R.; Rupp, David E.; Selker, John S.

2016-10-01

Shrink-swell soils crack and become compacted as they dry, changing properties such as bulk density and hydraulic conductivity. Multidomain models divide soil into independent realms that allow soil cracks to be incorporated into classical flow and transport models. Incongruously, most applications of multidomain models assume that the porosity distributions, bulk density, and effective saturated hydraulic conductivity of the soil are constant. This study builds on a recently derived soil shrinkage model to develop a new multidomain, dual-permeability model that can accurately predict variations in soil hydraulic properties due to dynamic changes in crack size and connectivity. The model only requires estimates of soil gravimetric water content and a minimal set of parameters, all of which can be determined using laboratory and/or field measurements. We apply the model to eight clayey soils, and demonstrate its ability to quantify variations in volumetric water content (as can be determined during measurement of a soil water characteristic curve) and transient saturated hydraulic conductivity, Ks (as can be measured using infiltration tests). The proposed model is able to capture observed variations in Ks of one to more than two orders of magnitude. In contrast, other dual-permeability models assume that Ks is constant, resulting in the potential for large error when predicting water movement through shrink-swell soils. Overall, the multidomain model presented here successfully quantifies fluctuations in the hydraulic properties of shrink-swell soil matrices, and are suitable for use in physical flow and transport models based on Darcy's Law, the Richards Equation, and the advection-dispersion equation.

STS studies of the surface of Bi2Se3

NASA Astrophysics Data System (ADS)

Romanowich, Megan; Lee, Mal-Soon; Mahanti, S. D.; Tessmer, Stuart; Chung, Duck Young; Song, Jung-Hwan; Kanatzidis, Mercouri

2012-02-01

We apply scanning tunneling spectroscopy to characterize the surface of the topological insulator Bi2Se3. Spectroscopy reveals that the minimum in the local density of states (LDOS) does not actually vanish in the region where Dirac cone states exist. We demonstrate with density functional theory calculations that this can be understood in terms of an asymmetric addition to the LDOS associated with a contribution from the bulk valence band that overlaps in energy with the Dirac point. We will discuss the origin of the fluctuations in the LDOS seen in the experiment near 0.2 eV above the Dirac point, which are associated with tunneling into the lowest conduction band states.

Grain boundary stability and influence on ionic conductivity in a disordered perovskite -- a first-principles investigation of lithium lanthanum titanate

DOE PAGES

Alexander, Kathleen C.; Ganesh, P.; Chi, Miaofang; ...

2016-12-01

The origin of ionic conductivity in bulk lithium lanthanum titanate, a promising solid electrolyte for Li-ion batteries, has long been under debate, with experiments showing lower conductivity than predictions. Recent microscopy images show Type I and Type II grain boundaries. Using first-principles based calculations we find that experimentally observed Type I boundaries are more stable compared to the Type II grain boundaries, consistent with their observed relative abundance. Grain boundary stability appears to strongly anti-correlate with the field strength as well as the spatial extent of the space charge region. Ion migration is faster along Type II grain boundaries thanmore » across, consistent with recent experiments of increased conductivity when Type II densities were increased.« less

Dielectric properties-based method for rapid and nondestructive moisture sensing in almonds

USDA-ARS?s Scientific Manuscript database

A dielectric-based method is presented for moisture determination in almonds independent of bulk density. The dielectric properties of almond were measured between 5 and 15 GHz, with a 1-GHz increments, for samples with moisture contents ranging from 4.8% to 16.5%, wet basis, bulk densities ranging ...

Soil compaction and initial height growth of planted ponderosa pine.

Treesearch

P. H. Cochran; Terry. Brock

1985-01-01

Early height growth of ponderosa pine (Pinus ponderosa Dougl. ex Laws.) seedlings planted in clearcuts in central Oregon was negatively correlated with increasing soil bulk density. Change in bulk density accounted for less than half the total variation in height growth. Although many other factors affect the development of seedlings, compaction...

Petrophysical Properties of Twenty Drill Cores from the Los Azufres, Mexico, Geothermal Field

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

Iglesias, E.R.; Contreras L., E.; Garcia G., A.

1987-01-20

For this study we selected 20 drill cores covering a wide range of depths (400-3000 m), from 15 wells, that provide a reasonable coverage of the field. Only andesite, the largely predominant rock type in the field, was included in this sample. We measured bulk density, grain (solids) density, effective porosity and (matrix) permeability on a considerable number of specimens taken from the cores; and inferred the corresponding total porosity and fraction of interconnected total porosity. We characterized the statistical distributions of the measured and inferred variables. The distributions of bulk density and grain density resulted approximately normal; the distributionsmore » of effective porosity, total porosity and fraction of total porosity turned out to be bimodal; the permeability distribution resulted highly skewed towards very small (1 mdarcy) values, though values as high as 400 mdarcies were measured. We also characterized the internal inhomogeneity of the cores by means of the ratio (standard deviation/mean) corresponding to the bulk density in each core (in average there are 9 specimens per core). The cores were found to present clearly discernible inhomogeneity; this quantitative characterization will help design new experimental work and interpret currently available and forthcoming results. We also found statistically significant linear correlations between total density and density of solids, effective porosity and total density, total porosity and total density, fraction of interconnected total porosity and the inverse of the effective porosity, total porosity and effective porosity; bulk density and total porosity also correlate with elevation. These results provide the first sizable and statistically detailed database available on petrophysical properties of the Los Azufres andesites. 1 tab., 16 figs., 4 refs.« less

Structural differences existing in bulk and nanoparticles of Y{sub 2}Sn{sub 2}O{sub 7}: Investigated by experimental and theoretical methods

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

Nigam, Sandeep, E-mail: snigam@barc.gov.in; Sudarsan, V., E-mail: vsudar@barc.gov.in; Majumder, C.

Present manuscript deals with the structural changes associated with transformation of bulk Y{sub 2}Sn{sub 2}O{sub 7} into nanoparticles of Y{sub 2}Sn{sub 2}O{sub 7}. Nanoparticles of Y{sub 2}Sn{sub 2}O{sub 7} both undoped and Eu{sup 3+} doped, were prepared at a relatively low temperature (700 °C) and investigated for their structural and luminescence properties and compared them with that of bulk Y{sub 2}Sn{sub 2}O{sub 7} sample prepared by the solid-state method at 1300 °C. Significant distortion in geometry and electron density distribution around Y{sup 3+}/Eu{sup 3+} ions in nanoparticles are confirmed from the Rietveld refinement of the powder X-ray diffraction patterns andmore » theoretical calculations based on the density functional theory (DFT). The SnO{sub 6} octahedron in Y{sub 2}Sn{sub 2}O{sub 7} is more expanded in nanoparticles compared to bulk. Iso-surface density distribution reveals that while bulk sample shows typical ionic feature in Y/Eu--O bonds, nanoparticle sample shows sharing of electron density along bond axis pertaining to covalent character. These inferences are further supported by the doped Eu{sup 3+} luminescence and calculated Ω{sub 2} and Ω{sub 4} parameters. - Graphical abstract: YO{sub 8} scalenohedron present in bulk and nanoparticles of Y{sub 2}Sn{sub 2}O{sub 7}.Variation of the electron density around Y{sup 3+} ions in YO{sub 8} polyhedron is also shown in bulk and nanoparticles of Y{sub 2}Sn{sub 2}O{sub 7}. The difference in the extent of ionic/covalent nature of the Y--O bond is clearly seen the contour plot of electron density. Highlights: ► YO{sub 8} scalenohedron is axially and equatorially distorted in Y{sub 2}Sn{sub 2}O{sub 7} nanoparticles. ► Enlargement of SnO{sub 6} octahedron in nanoparticles of Y{sub 2}Sn{sub 2}O{sub 7} compared to bulk. ► Less symmetric charge distribution around Y{sup 3+} ions in Y{sub 2}Sn{sub 2}O{sub 7} nanoparticles.« less

Tunable non-interacting free-energy functionals: development and applications to low-density aluminum

NASA Astrophysics Data System (ADS)

Trickey, Samuel; Karasiev, Valentin

We introduce the concept of tunable orbital-free non-interacting free-energy density functionals and present a generalized gradient approximation (GGA) with a subset of parameters defined from constraints and a few free parameters. Those free parameters are tuned to reproduce reference Kohn-Sham (KS) static-lattice pressures for Al at T=8 kK for bulk densities between 0.6 and 2 g/cm3. The tuned functional then is used in OF molecular dynamics (MD) simulations for Al with densities between 0.1 and 2 g/cm3 and T between 6 and 50 kK to calculate the equation of state and generate configurations for electrical conductivity calculations. The tunable functional produces accurate results. Computationally it is very effective especially at elevated temperature. Kohn-Shiam calculations for such low densities are affordable only up to T=10 kK, while other OF approximations, including two-point functionals, fail badly in that regime. Work supported by US DoE Grant DE-SC0002139.

A Semi-Analytical Extraction Method for Interface and Bulk Density of States in Metal Oxide Thin-Film Transistors

PubMed Central

Chen, Weifeng; Wu, Weijing; Zhou, Lei; Xu, Miao; Wang, Lei; Peng, Junbiao

2018-01-01

A semi-analytical extraction method of interface and bulk density of states (DOS) is proposed by using the low-frequency capacitance–voltage characteristics and current–voltage characteristics of indium zinc oxide thin-film transistors (IZO TFTs). In this work, an exponential potential distribution along the depth direction of the active layer is assumed and confirmed by numerical solution of Poisson’s equation followed by device simulation. The interface DOS is obtained as a superposition of constant deep states and exponential tail states. Moreover, it is shown that the bulk DOS may be represented by the superposition of exponential deep states and exponential tail states. The extracted values of bulk DOS and interface DOS are further verified by comparing the measured transfer and output characteristics of IZO TFTs with the simulation results by a 2D device simulator ATLAS (Silvaco). As a result, the proposed extraction method may be useful for diagnosing and characterising metal oxide TFTs since it is fast to extract interface and bulk density of states (DOS) simultaneously. PMID:29534492

Soil physical and X-ray computed tomographic measurements to investigate small-scale structural differences under strip tillage compared to mulch till and no-till

NASA Astrophysics Data System (ADS)

Pöhlitz, Julia; Rücknagel, Jan; Schlüter, Steffen; Vogel, Hans-Jörg

2017-04-01

In recent years there has been an increasing application of conservation tillage techniques where the soil is no longer turned, but only loosened or left completely untilled. Dead plant material remains on the soil surface, which provides environmental and economic benefits such as the conservation of water, preventing soil erosion and saving time during seedbed preparation. There is a variety of conservation tillage systems, e.g. mulch till, no-till and strip tillage, which is a special feature. In strip tillage, the seed bed is divided into a seed zone (strip-till within the seed row: STWS) and a soil management zone (strip-till between the seed row: STBS). However, each tillage application affects physical soil properties and processes. Here, the combined application of classical soil mechanical and computed tomographic methods is used on a Chernozem (texture 0-30 cm: silt loam) to show small-scale structural differences under strip tillage (STWS, STBS) compared to no-till (NT) and mulch till (MT). In addition to the classical soil physical parameters dry bulk density and saturated conductivity (years: 2012, 2014, 2015) at soil depths 2-8 and 12-18 cm, stress-strain tests were carried out to map mechanical behavior. The stress-strain tests were performed for a load range from 5-550 kPa at 12-18 cm depth (year 2015). Mechanical precompression stress was determined on the stress-dry bulk density curves. Further, CT image cross sections and computed tomographic examinations (average pore size, porosity, connectivity, and anisotropy) were used from the same soil samples. For STBS and NT, a significant increase in dry bulk density was observed over the course of time compared to STWS and MT, which was more pronounced at 2-8 cm than at 12-18 cm depth. Despite higher dry bulk density, STBS displayed higher saturated conductivity in contrast to STWS, which can be attributed to higher earthworm abundance. In strip tillage, structural differences were identified. Mechanical precompression stress was significantly higher for STBS (141 kPa) than STWS (38 kPa). In addition, the CT image cross sections and the computed tomographic parameters confirmed the mechanically more stable soil structure observed under STBS with a higher initial average pore size but lower porosity and connectivity values compared to STWS. The reason for this is the lack of tillage. On the other hand, tillage at STWS created a loosened, porous and connective substrate. For all variants, the increasing load application led to progressive homogenization processes of the soil structure. At the same time, as stress application increased in all variants, the increase in dry bulk density led to a decrease in average pore size, porosity, and connectivity, while anisotropy increased. It was possible to confirm that strip tillage combines the advantages of no-till and a deeper conservation primary tillage, since on the one hand MT and STWS and on the other hand STBS and NT showed very similar soil structures. The computed tomographic parameters therefore provide valuable information about the impact of tillage on microscopic pore space attributes that improve our understanding about soil functional behavior at much larger scales.

Effect of particle size of rice flour on physical and sensory properties of Sel-roti.

PubMed

Subba, Dilip; Katawal, Surendra Bahadur

2013-02-01

Sel-roti is a delicious, deep-fat fried, puffed, ring shaped spongy doughnut like Nepalese indigenous food prepared from the batter of rice flour, ghee and sugar. A study was conducted to determine the effect of particle size of rice flour on bulk density, oil uptake and texture of Sel-roti. Rice was soaked in water and ground with the help of iron mortar and pestle and the flour was analyzed for particle size distribution by using standard sieves and separated into three particle size categories as coarse (> 890 u), medium (120-890 u) and fine (< 120 u). The rice flour of different particle sizes were mixed in different proportions and Sel-roti was prepared from these flours. Bulk density and oil uptake were determined and sensory test was carried out. The results showed significant good positive correlation between mean particle size and bulk density (r = 0.97, p ≤ 0.05) and a good negative correlation between mean particle size and oil-uptake (r = 0.90, p ≤ 0.05). Good positive correlation of mean particle size with texture attributes like hardness (r = 0.99, p ≤ 0.05) and fracturability (r = 0.96, p ≤ 0.05) and good negative correlation with smoothness (r  = -0.97, p ≤ 0.05), cohesiveness (r = -0.92, p ≤ 0.05), stickiness (r = -0.76, p ≤ 0.05) and oily mouth feel (r = -0.85, p ≤ 0.05) and fair positive correlation with chewiness (r = 0.65, p > 0.05) were found.

Effect of soil structure on the growth of bacteria in soil quantified using CARD-FISH

NASA Astrophysics Data System (ADS)

Juyal, Archana; Eickhorst, Thilo; Falconer, Ruth; Otten, Wilfred

2014-05-01

It has been reported that compaction of soil due to use of heavy machinery has resulted in the reduction of crop yield. Compaction affects the physical properties of soil such as bulk density, soil strength and porosity. This causes an alteration in the soil structure which limits the mobility of nutrients, water and air infiltration and root penetration in soil. Several studies have been conducted to explore the effect of soil compaction on plant growth and development. However, there is scant information on the effect of soil compaction on the microbial community and its activities in soil. Understanding the effect of soil compaction on microbial community is essential as microbial activities are very sensitive to abrupt environmental changes in soil. Therefore, the aim of this work was to investigate the effect of soil structure on growth of bacteria in soil. The bulk density of soil was used as a soil physical parameter to quantify the effect of soil compaction. To detect and quantify bacteria in soil the method of catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH) was used. This technique results in high intensity fluorescent signals which make it easy to quantify bacteria against high levels of autofluorescence emitted by soil particles and organic matter. In this study, bacterial strains Pseudomonas fluorescens SBW25 and Bacillus subtilis DSM10 were used. Soils of aggregate size 2-1mm were packed at five different bulk densities in polyethylene rings (4.25 cm3).The soil rings were sampled at four different days. Results showed that the total number of bacteria counts was reduced significantly (P

Opposing effects of stacking faults and antisite domain boundaries on the conduction band edge in kesterite quaternary semiconductors

NASA Astrophysics Data System (ADS)

Park, Ji-Sang; Kim, Sunghyun; Walsh, Aron

2018-01-01

We investigated stability and the electronic structure of extended defects including antisite domain boundaries and stacking faults in the kesterite-structured semiconductors, Cu2ZnSnS4 (CZTS) and Cu2ZnSnSe4 (CZTSe). Our hybrid density functional theory calculations show that stacking faults in CZTS and CZTSe induce a higher conduction band edge than the bulk counterparts, and thus the stacking faults act as electron barriers. Antisite domain boundaries, however, accumulate electrons as the conduction band edge is reduced in energy, having an opposite role. An Ising model was constructed to account for the stability of stacking faults, which shows the nearest-neighbor interaction is stronger in the case of the selenide.

Thermal conductivity anisotropy in nanostructures and nanostructured materials

NASA Astrophysics Data System (ADS)

Termentzidis, Konstantinos

2018-03-01

Thermal conductivity anisotropy is a subject for both fundamental and application interests. The anisotropy can be induced either by van der Waals forces in bulk systems or by nanostructuration. Here, we will examine four cases in which thermal anisotropy has been observed: (i) Si/Ge superlattices which exhibit higher thermal anisotropy between in-plane and cross-plane directions for the case of smooth interfaces, (ii) amorphous/crystalline superlattices with much higher anisotropy than the crystalline/crystalline superlattices and which can reach a factor of six when the amorphous fraction increases, (iii) the impact of the density of edge and screw dislocations on the thermal anisotropy of defected GaN, and (iv) the influence of the growth direction of Bi2Te3 nanowires on thermal conductivity.

Method of fabricating high-density hermetic electrical feedthroughs

DOEpatents

Shah, Kedar G.; Pannu, Satinderpall S.; Delima, Terri L.

2015-06-02

A method of fabricating electrical feedthroughs selectively removes substrate material from a first side of an electrically conductive substrate (e.g. a bio-compatible metal) to form an array of electrically conductive posts in a substrate cavity. An electrically insulating material (e.g. a bio-compatible sealing glass) is then flowed to fill the substrate cavity and surround each post, and solidified. The solidified insulating material is then exposed from an opposite second side of the substrate so that each post is electrically isolated from each other as well as the bulk substrate. In this manner a hermetic electrically conductive feedthrough construction is formed having an array of electrical feedthroughs extending between the first and second sides of the substrate from which it was formed.

Effective Thermal Conductivity of Spherical Particulate Nanocomposites: Comparison with Theoretical Models, Monte Carlo Simulations and Experiments

NASA Astrophysics Data System (ADS)

Machrafi, Hatim; Lebon, Georgy

2014-11-01

The purpose of this work is to study heat conduction in systems that are composed out of spherical micro-and nanoparticles dispersed in a bulk matrix. Special emphasis will be put on the dependence of the effective heat conductivity on various selected parameters as dimension and density of particles, interface interaction with the matrix. This is achieved by combining the effective medium approximation and extended irreversible thermodynamics, whose main feature is to elevate the heat flux vector to the status of independent variable. The model is illustrated by three examples: Silicium-Germanium, Silica-epoxy-resin and Copper-Silicium systems. Predictions of our model are in good agreement with other theoretical models, Monte-Carlo simulations and experimental data.

Spatial variability of shelf sediments in the STRATAFORM natural laboratory, Northern California

USGS Publications Warehouse

Goff, J.A.; Wheatcroft, R.A.; Lee, H.; Drake, D.E.; Swift, D.J.P.; Fan, S.

2002-01-01

The "Correlation Length Experiment", an intensive box coring effort on the Eel River shelf (Northern California) in the summer of 1997, endeavored to characterize the lateral variability of near-surface shelf sediments over scales of meters to kilometers. Coring focused on two sites, K60 and S60, separated by ??? 15 km along the 60 m isobath. The sites are near the sand-to-mud transition, although K60 is sandier owing to its proximity to the Eel River mouth. Nearly 140 cores were collected on dip and strike lines with core intervals from < 10m to 1 km. Measurements on each core included bulk density computed from gamma-ray attenuation, porosity converted from resistivity measurements, and surficial grain size. Grain size was also measured over the full depth range within a select subset of cores. X-radiograph images were also examined. Semi-variograms were computed for strike, dip, and down-hole directions at each site. The sand-to-mud transition exerts a strong influence on all measurements: on average, bulk density increases and porosity decreases with regional increases in mean grain size. Analysis of bulk density measurements indicates very strong contrasts in the sediment variability at K60 and S60. No coherent bedding is seen at K60; in the strike direction, horizontal variability is "white" (fully uncorrelated) from the smallest scales examined (a few meters) to the largest (8 km), with a variance equal to that seen within the cores. In contrast, coherent bedding exists at S60 related to the preservation of the 1995 flood deposit. A correlatable structure is found in the strike direction with a decorrelation distance of ??? 800 m, and can be related to long-wavelength undulations in the topography and/or thickness of the flood layer or overburden. We hypothesize that the high degree of bulk density variability at K60 is a result of more intense physical reworking of the seabed in the sandier environment. Without significant averaging, the resistivity-based porosity measurements are only marginally correlated to gamma-ray-bulk density measurements, and are largely independent of mean grain size. Furthermore, porosity displays a high degree of incoherent variability at both sites. Porosity, with a much smaller sample volume than bulk density, may therefore resolve small-scale biogenic variability which is filtered out in the bulk density measurement. ?? 2002 Elsevier Science Ltd. All rights reserved.

The Electronic Thermal Conductivity of Graphene.

PubMed

Kim, Tae Yun; Park, Cheol-Hwan; Marzari, Nicola

2016-04-13

Graphene, as a semimetal with the largest known thermal conductivity, is an ideal system to study the interplay between electronic and lattice contributions to thermal transport. While the total electrical and thermal conductivity have been extensively investigated, a detailed first-principles study of its electronic thermal conductivity is still missing. Here, we first characterize the electron-phonon intrinsic contribution to the electronic thermal resistivity of graphene as a function of doping using electronic and phonon dispersions and electron-phonon couplings calculated from first-principles at the level of density-functional theory and many-body perturbation theory (GW). Then, we include extrinsic electron-impurity scattering using low-temperature experimental estimates. Under these conditions, we find that the in-plane electronic thermal conductivity κe of doped graphene is ∼300 W/mK at room temperature, independently of doping. This result is much larger than expected and comparable to the total thermal conductivity of typical metals, contributing ∼10% to the total thermal conductivity of bulk graphene. Notably, in samples whose physical or domain sizes are of the order of few micrometers or smaller, the relative contribution coming from the electronic thermal conductivity is more important than in the bulk limit, because lattice thermal conductivity is much more sensitive to sample or grain size at these scales. Last, when electron-impurity scattering effects are included we find that the electronic thermal conductivity is reduced by 30 to 70%. We also find that the Wiedemann-Franz law is broadly satisfied at low and high temperatures but with the largest deviations of 20-50% around room temperature.

Estimation of Phonon and Carrier Thermal Conductivities for Bulk Thermoelectric Materials Using Transport Properties

NASA Astrophysics Data System (ADS)

Otsuka, Mioko; Homma, Ryoei; Hasegawa, Yasuhiro

2017-05-01

The phonon and carrier thermal conductivities of thermoelectric materials were calculated using the Wiedemann-Franz law, Boltzmann equation, and a method we propose in this study called the Debye specific heat method. We prepared polycrystalline n-type doped bismuth telluride (BiTe) and bismuth antimony (BiSb) bulk alloy samples and measured six parameters (Seebeck coefficient, resistivity, thermal conductivity, thermal diffusivity, magneto-resistivity, and Hall coefficient). The carrier density and mobility were estimated for calculating the carrier thermal conductivity by using the Boltzmann equation. In the Debye specific heat method, the phonon thermal diffusivity, and thermal conductivity were calculated from the temperature dependence of the effective specific heat by using not only the measured thermal conductivity and Debye model, but also the measured thermal diffusivity. The carrier thermal conductivity was also evaluated from the phonon thermal conductivity by using the specific heat. The ratio of carrier thermal conductivity to thermal conductivity was evaluated for the BiTe and BiSb samples, and the values obtained using the Debye specific heat method at 300 K were 52% for BiTe and <5.5% for BiSb. These values are either considerably larger or smaller than those obtained using other methods. The Dulong-Petit law was applied to validate the Debye specific heat method at 300 K, which is significantly greater than the Debye temperature of the BiTe and BiSb samples, and it was confirmed that the phonon specific heat at 300 K has been accurately reproduced using our proposed method.

Superconducting magnet

NASA Technical Reports Server (NTRS)

1985-01-01

Extensive computer based engineering design effort resulted in optimization of a superconducting magnet design with an average bulk current density of approximately 12KA/cm(2). Twisted, stranded 0.0045 inch diameter NbTi superconductor in a copper matrix was selected. Winding the coil from this bundle facilitated uniform winding of the small diameter wire. Test coils were wound using a first lot of the wire. The actual packing density was measured from these. Interwinding voltage break down tests on the test coils indicated the need for adjustment of the wire insulation on the lot of wire subsequently ordered for construction of the delivered superconducting magnet. Using the actual packing densities from the test coils, a final magnet design, with the required enhancement and field profile, was generated. All mechanical and thermal design parameters were then also fixed. The superconducting magnet was then fabricated and tested. The first test was made with the magnet immersed in liquid helium at 4.2K. The second test was conducted at 2K in vacuum. In the latter test, the magnet was conduction cooled from the mounting flange end.

Valence and spin states of iron are invisible in Earth’s lower mantle

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

Liu, Jiachao; Dorfman, Susannah M.; Zhu, Feng

Heterogeneity in Earth’s mantle is a record of chemical and dynamic processes over Earth’s history. The geophysical signatures of heterogeneity can only be interpreted with quantitative constraints on effects of major elements such as iron on physical properties including density, compressibility, and electrical conductivity. However, deconvolution of the effects of multiple valence and spin states of iron in bridgmanite (Bdg), the most abundant mineral in the lower mantle, has been challenging. Here we show through a study of a ferric-iron-only (Mg 0.46Fe 3+0.53)(Si 0.49Fe 3+ 0.51)O 3 Bdg that Fe 3+ in the octahedral site undergoes a spin transition betweenmore » 43 and 53 GPa at 300 K. The resolved effects of the spin transition on density, bulk sound velocity, and electrical conductivity are smaller than previous estimations, consistent with the smooth depth profiles from geophysical observations. For likely mantle compositions, the valence state of iron has minor effects on density and sound velocities relative to major cation composition.« less

Indium oxide co-doped with tin and zinc: A simple route to highly conducting high density targets for TCO thin-film fabrication

NASA Astrophysics Data System (ADS)

Saadeddin, I.; Hilal, H. S.; Decourt, R.; Campet, G.; Pecquenard, B.

2012-07-01

Indium oxide co-doped with tin and zinc (ITZO) ceramics have been successfully prepared by direct sintering of the powders mixture at 1300 °C. This allowed us to easily fabricate large highly dense target suitable for sputtering transparent conducting oxide (TCO) films, without using any cold or hot pressing techniques. Hence, the optimized ITZO ceramic reaches a high relative bulk density (˜ 92% of In2O3 theoretical density) and higher than the well-known indium oxide doped with tin (ITO) prepared under similar conditions. All X-ray diagrams obtained for ITZO ceramics confirms a bixbyte structure typical for In2O3 only. This indicates a higher solubility limit of Sn and Zn when they are co-doped into In2O3 forming a solid-solution. A very low value of electrical resistivity is obtained for [In2O3:Sn0.10]:Zn0.10 (1.7 × 10-3 Ω cm, lower than ITO counterpart) which could be fabricated to high dense ceramic target suing pressure-less sintering.

Valence and spin states of iron are invisible in Earth’s lower mantle

DOE PAGES

Liu, Jiachao; Dorfman, Susannah M.; Zhu, Feng; ...

2018-03-29

Heterogeneity in Earth’s mantle is a record of chemical and dynamic processes over Earth’s history. The geophysical signatures of heterogeneity can only be interpreted with quantitative constraints on effects of major elements such as iron on physical properties including density, compressibility, and electrical conductivity. However, deconvolution of the effects of multiple valence and spin states of iron in bridgmanite (Bdg), the most abundant mineral in the lower mantle, has been challenging. Here we show through a study of a ferric-iron-only (Mg 0.46Fe 3+0.53)(Si 0.49Fe 3+ 0.51)O 3 Bdg that Fe 3+ in the octahedral site undergoes a spin transition betweenmore » 43 and 53 GPa at 300 K. The resolved effects of the spin transition on density, bulk sound velocity, and electrical conductivity are smaller than previous estimations, consistent with the smooth depth profiles from geophysical observations. For likely mantle compositions, the valence state of iron has minor effects on density and sound velocities relative to major cation composition.« less

Method for determining transport critical current densities and flux penetration depth in bulk superconductors

NASA Technical Reports Server (NTRS)

Israelsson, Ulf E. (Inventor); Strayer, Donald M. (Inventor)

1992-01-01

A contact-less method for determining transport critical current density and flux penetration depth in bulk superconductor material. A compressor having a hollow interior and a plunger for selectively reducing the free space area for distribution of the magnetic flux therein are formed of superconductor material. Analytical relationships, based upon the critical state model, Maxwell's equations and geometrical relationships define transport critical current density and flux penetration depth in terms of the initial trapped magnetic flux density and the ratio between initial and final magnetic flux densities whereby data may be reliably determined by means of the simple test apparatus for evaluating the current density and flux penetration depth.

Method of altering the effective bulk density of solid material and the resulting product

DOEpatents

Kool, Lawrence B.; Nolen, Robert L.; Solomon, David E.

1983-01-01

A method of adjustably tailoring the effective bulk density of a solid material in which a mixture comprising the solid material, a film-forming polymer and a volatile solvent are sprayed into a drying chamber such that the solvent evaporates and the polymer dries into hollow shells having the solid material captured within the shell walls. Shell density may be varied as a function of solid/polymer concentration, droplet size and drying temperature.

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

Emin, David, E-mail: emin@unm.edu; Akhtari, Massoud; Ellingson, B. M.

We analyze the transient-dc and frequency-dependent electrical conductivities between blocking electrodes. We extend this analysis to measurements of ions’ transport in freshly excised bulk samples of human brain tissue whose complex cellular structure produces blockages. The associated ionic charge-carrier density and diffusivity are consistent with local values for sodium cations determined non-invasively in brain tissue by MRI (NMR) and diffusion-MRI (spin-echo NMR). The characteristic separation between blockages, about 450 microns, is very much shorter than that found for sodium-doped gel proxies for brain tissue, >1 cm.

The effect of various sintering temperature on used refractory towards its physical properties

NASA Astrophysics Data System (ADS)

Sudibyo; Wulandari, Y. R.; Amin, M.; Azhar

2018-01-01

The used magnesia refractory from the kiln of cement industry was successfully recycled to new refractory using Kaolin as an adhesive. In this work, the temperatures of sintering were varied from 1000°C to 1500°C. The result shows that the increment temperature effects in sintering process will enhance refractory physical properties such as bulk density, cold crushing strength or pressure strength and thermal conductivity. Meanwhile, the porosity was decreased as the increase of the sintering temperature.

Mechanical Properties of the Solid Li-ion Conducting Electrolyte: Li0.33La0.57TiO3

DTIC Science & Technology

2012-01-01

was determined from the mass and physical dimensions. In the second method, the bulk density was determined using the Archimedes method with water as...materials were respectively, 97 ± 4 and 95 ± 5 % (the large scatter is due to the small size of the sample) using the Archimedes method, 98 ± 0.2 and 95...SS using (1) Archimedes method, (2) physical measurement, and (3) image analysis Material Archimedes method Physical measurement Image analysis LLTO-SG

Estimating canopy bulk density and canopy base height for interior western US conifer stands

Treesearch

Seth A. Ex; Frederick W. Smith; Tara L. Keyser; Stephanie A. Rebain

2016-01-01

Crown fire hazard is often quantified using effective canopy bulk density (CBD) and canopy base height (CBH). When CBD and CBH are estimated using nonlocal crown fuel biomass allometries and uniform crown fuel distribution assumptions, as is common practice, values may differ from estimates made using local allometries and nonuniform...

Estimating forest canopy bulk density using six indirect methods

Treesearch

Robert E. Keane; Elizabeth D. Reinhardt; Joe Scott; Kathy Gray; James Reardon

2005-01-01

Canopy bulk density (CBD) is an important crown characteristic needed to predict crown fire spread, yet it is difficult to measure in the field. Presented here is a comprehensive research effort to evaluate six indirect sampling techniques for estimating CBD. As reference data, detailed crown fuel biomass measurements were taken on each tree within fixed-area plots...

BDEN: A timesaving computer program for calculating soil bulk density and water content.

Treesearch

Lynn G. Starr; Michael J. Geist

1983-01-01

This paper presents an interactive computer program written in BASIC language that will calculate soil bulk density and moisture percentage by weight and volume. Coarse fragment weights are required. The program will also summarize the resulting data giving mean, standard deviation, and 95-percent confidence interval on one or more groupings of data.

Susceptibility of volcanic ash-influenced soil in northern Idaho to mechanical compaction

Treesearch

Deborah S. Page-Dumroese

1993-01-01

Timber harvesting and mechanical site preparation can reduce site productivity if they excessively disturb or compact the soil. Volcanic ash-influenced soils with low undisturbed bulk densities and rock content are particularly susceptible. This study evaluates the effects of harvesting and site preparation on changes in the bulk density of ash-influenced forest soils...

Soil Compaction Absent in Plantation Thinning

Treesearch

Tony King; Sharon Haines

1979-01-01

We examine the effects on soil bulk density by using a TH-105 Thinner Harvester and two forwarders in a mechanically thinned slash pine (Pinus elliottii Engelm.) plantation. Points in the machine tracks were sampled before and after harvesting at depths of 5 and 10 cm (2 and 4 in) for moisture and bulk density. Both the standard gravimetric method...

Experimental investigation of fire propagation in single live shrubs

Treesearch

Jing Li; Shankar Mahalingam; David R. Weise

2017-01-01

This work focuses broadly on individual, live shrubs and, more specifically, it examines bulk density in chaparral and its combined effects with wind and ignition location on the resulting fire behaviour. Empirical functions to predict bulk density as a function of height for 4-year-old chaparral were developed for two typical species of shrub fuels in southern...

Identification of Defect Candidates and their Effects on Carrier Lifetimes and Dark Currents in InAs/InAsSb Strained-Layer Superlattices for Infrared Detectors

NASA Astrophysics Data System (ADS)

Kioussis, Nicholas

The InAs/GaSb and InAs/InAsSb type-II strain-layer superlattices (T2SLS) are of great importance and show great promise for mid-wave and long-wave infrared (IR) detectors for a variety of civil and military applications. The T2SLS offer several advantages over present day detection technologies including suppressed Auger recombination relative to the bulk MCT material, high quantum efficiencies, and commercial availability of low defect density substrates. While the T2SLS detectors are approaching the empirical Rule-07 benchmark of MCT's performance level, the dark-current density is still significantly higher than that of bulk MCT detectors. One of the major origins of dark current is associated with the Shockley-Read- Hall (SRH) process in the depletion region of the detector. I will present results of ab initio electronic structure calculations of the stability of a wide range of point defects [As and In vacancies, In, As and Sb antisites, In interstitials, As interstitials, and Sb interstitials] in various charged states in bulk InAs, InSb, and InAsSb systems and T2SLS. I will also present results of the transition energy levels. The calculations reveal that compared to defects in bulk materials, the formation and defect properties in InAs/InAsSb T2SLS can be affected by various structural features, such as strain, interface, and local chemical environment. I will present examples where the effect of strain or local chemical environment shifts the transition energy levels of certain point defects either above or below the conduction band minimum, thus suppressing their contribution to the SRH recombination.

A Multi-Moment Bulkwater Ice Microphysics Scheme with Consideration of the Adaptive Growth Habit and Apparent Density for Pristine Ice in the WRF Model

NASA Astrophysics Data System (ADS)

Tsai, T. C.; Chen, J. P.; Dearden, C.

2014-12-01

The wide variety of ice crystal shapes and growth habits makes it a complicated issue in cloud models. This study developed the bulk ice adaptive habit parameterization based on the theoretical approach of Chen and Lamb (1994) and introduced a 6-class hydrometeors double-moment (mass and number) bulk microphysics scheme with gamma-type size distribution function. Both the proposed schemes have been implemented into the Weather Research and Forecasting model (WRF) model forming a new multi-moment bulk microphysics scheme. Two new moments of ice crystal shape and volume are included for tracking pristine ice's adaptive habit and apparent density. A closure technique is developed to solve the time evolution of the bulk moments. For the verification of the bulk ice habit parameterization, some parcel-type (zero-dimension) calculations were conducted and compared with binned numerical calculations. The results showed that: a flexible size spectrum is important in numerical accuracy, the ice shape can significantly enhance the diffusional growth, and it is important to consider the memory of growth habit (adaptive growth) under varying environmental conditions. Also, the derived results with the 3-moment method were much closer to the binned calculations. A field campaign of DIAMET was selected to simulate in the WRF model for real-case studies. The simulations were performed with the traditional spherical ice and the new adaptive shape schemes to evaluate the effect of crystal habits. Some main features of narrow rain band, as well as the embedded precipitation cells, in the cold front case were well captured by the model. Furthermore, the simulations produced a good agreement in the microphysics against the aircraft observations in ice particle number concentration, ice crystal aspect ratio, and deposition heating rate especially within the temperature region of ice secondary multiplication production.

Inverted Resistance Measurements as a Method for Characterizing the Bulk and Surface Conductivities of Three-Dimensional Topological Insulators

NASA Astrophysics Data System (ADS)

Eo, Y. S.; Sun, K.; Kurdak, ć.; Kim, D.-J.; Fisk, Z.

2018-04-01

We introduce a resistance measurement method that is useful in characterizing materials with both surface and bulk conduction, such as three-dimensional topological insulators. The transport geometry for this resistance measurement configuration consists of one current lead as a closed loop that fully encloses the other current lead on the surface, and two voltage leads that are both placed outside the loop. We show that, in the limit where the transport is dominated by the surface conductivity of the material, the four-terminal resistance measured from such a transport geometry is proportional to σb/σs2, where σb and σs are the bulk and surface conductivities of the material, respectively. We call this type of measurement inverted resistance measurement, as the resistance scales inversely with the bulk resistivity. We discuss possible implementations of this method by performing numerical calculations on different geometries and introduce strategies to extract the bulk and surface conductivities. We also demonstrate inverted resistance measurements on SmB6 , a topological Kondo insulator, using both single-sided and coaxially aligned double-sided Corbino disk transport geometries. Using this method, we are able to measure the bulk conductivity, even at low temperatures, where the bulk conduction is much smaller than the surface conduction in this material.

Accurate heterogeneous dose calculation for lung cancer patients without high‐resolution CT densities

PubMed Central

Li, Jonathan G.; Liu, Chihray; Olivier, Kenneth R.; Dempsey, James F.

2009-01-01

The aim of this study was to investigate the relative accuracy of megavoltage photon‐beam dose calculations employing either five bulk densities or independent voxel densities determined by calibration of the CT Houndsfield number. Full‐resolution CT and bulk density treatment plans were generated for 70 lung or esophageal cancer tumors (66 cases) using a commercial treatment planning system with an adaptive convolution dose calculation algorithm (Pinnacle3, Philips Medicals Systems). Bulk densities were applied to segmented regions. Individual and population average densities were compared to the full‐resolution plan for each case. Monitor units were kept constant and no normalizations were employed. Dose volume histograms (DVH) and dose difference distributions were examined for all cases. The average densities of the segmented air, lung, fat, soft tissue, and bone for the entire set were found to be 0.14, 0.26, 0.89, 1.02, and 1.12 g/cm3, respectively. In all cases, the normal tissue DVH agreed to better than 2% in dose. In 62 of 70 DVHs of the planning target volume (PTV), agreement to better than 3% in dose was observed. Six cases demonstrated emphysema, one with bullous formations and one with a hiatus hernia having a large volume of gas. These required the additional assignment of density to the emphysemic lung and inflammatory changes to the lung, the regions of collapsed lung, the bullous formations, and the hernia gas. Bulk tissue density dose calculation provides an accurate method of heterogeneous dose calculation. However, patients with advanced emphysema may require high‐resolution CT studies for accurate treatment planning. PACS number: 87.53.Tf

A niching genetic algorithm applied to optimize a SiC-bulk crystal growth system

NASA Astrophysics Data System (ADS)

Su, Juan; Chen, Xuejiang; Li, Yuan; Pons, Michel; Blanquet, Elisabeth

2017-06-01

A niching genetic algorithm (NGA) was presented to optimize a SiC-bulk crystal growth system by PVT. The NGA based on clearing mechanism and its combination method with heat transfer model for SiC crystal growth were described in details. Then three inverse problems for optimization of growth system were carried out by NGA. Firstly, the radius of blind hole was optimized to decrease the radial temperature gradient along the substrate while the center temperature on the surface of substrate is fixed at 2500 K. Secondly, insulation materials with anisotropic thermal conductivities were selected to obtain much higher growth rate as 600, 800 and 1000 μm/h. Finally, the density of coils was also rearranged to minimize the temperature variation in the SiC powder. All the results were analyzed and discussed.

Investigation of the bulk modulus of silica aerogel using molecular dynamics simulations of a coarse-grained model.

PubMed

Ferreiro-Rangel, Carlos A; Gelb, Lev D

2013-06-13

Structural and mechanical properties of silica aerogels are studied using a flexible coarse-grained model and a variety of simulation techniques. The model, introduced in a previous study (J. Phys. Chem. C 2007, 111, 15792-15802), consists of spherical "primary" gel particles that interact through weak nonbonded forces and through microscopically motivated interparticle bonds that may break and form during the simulations. Aerogel models are prepared using a three-stage protocol consisting of separate simulations of gelation, aging, and a final relaxation during which no further bond formation is permitted. Models of varying particle size, density, and size dispersity are considered. These are characterized in terms of fractal dimensions and pore size distributions, and generally good agreement with experimental data is obtained for these metrics. The bulk moduli of these materials are studied in detail. Two different techniques for obtaining the bulk modulus are considered, fluctuation analysis and direct compression/expansion simulations. We find that the fluctuation result can be subject to systematic error due to coupling with the simulation barostat but, if performed carefully, yields results equivalent with those of compression/expansion experiments. The dependence of the bulk modulus on density follows a power law with an exponent between 3.00 and 3.15, in agreement with reported experimental results. The best correlate for the bulk modulus appears to be the volumetric bond density, on which there is also a power law dependence. Polydisperse models exhibit lower bulk moduli than comparable monodisperse models, which is due to lower bond densities in the polydisperse materials.

Soil permittivity response to bulk electrical conductivity for selected soil water sensors

USDA-ARS?s Scientific Manuscript database

Bulk electrical conductivity can dominate the low frequency dielectric loss spectrum in soils, masking changes in the real permittivity and causing errors in estimated water content. We examined the dependence of measured apparent permittivity (Ka) on bulk electrical conductivity in contrasting soil...

Atomically thick bismuth selenide freestanding single layers achieving enhanced thermoelectric energy harvesting.

PubMed

Sun, Yongfu; Cheng, Hao; Gao, Shan; Liu, Qinghua; Sun, Zhihu; Xiao, Chong; Wu, Changzheng; Wei, Shiqiang; Xie, Yi

2012-12-19

Thermoelectric materials can realize significant energy savings by generating electricity from untapped waste heat. However, the coupling of the thermoelectric parameters unfortunately limits their efficiency and practical applications. Here, a single-layer-based (SLB) composite fabricated from atomically thick single layers was proposed to optimize the thermoelectric parameters fully. Freestanding five-atom-thick Bi(2)Se(3) single layers were first synthesized via a scalable interaction/exfoliation strategy. As revealed by X-ray absorption fine structure spectroscopy and first-principles calculations, surface distortion gives them excellent structural stability and a much increased density of states, resulting in a 2-fold higher electrical conductivity relative to the bulk material. Also, the surface disorder and numerous interfaces in the Bi(2)Se(3) SLB composite allow for effective phonon scattering and decreased thermal conductivity, while the 2D electron gas and energy filtering effect increase the Seebeck coefficient, resulting in an 8-fold higher figure of merit (ZT) relative to the bulk material. This work develops a facile strategy for synthesizing atomically thick single layers and demonstrates their superior ability to optimize the thermoelectric energy harvesting.

Density Functional Theory Calculations Revealing Metal-like Band Structures for Ultrathin Ge {111} and {211} Surface Layers.

PubMed

Tan, Chih-Shan; Huang, Michael Hsuan-Yi

2018-05-21

To find out if germanium should also possess facet-dependent electrical conductivity properties, surface state density functional theory (DFT) calculations were performed on 1-6 layers of Ge (100), (110), (111), and (211) planes. Tunable Ge (100) and (110) planes always present the same semiconducting band structure with a band gap of 0.67 eV expected of bulk germanium. In contrast, 1, 2, 4, and 5 layers of Ge (111) and (211) plane models show metal-like band structures with continuous density of states (DOS) throughout the entire band. For 3 and 6 layers of Ge (111) and (211) plane models, the normal semiconducting band structure was obtained. The plane layers with metal-like band structures also show Ge-Ge bond length deviations and bond distortions, as well as significantly different 4s and 4p frontier orbital electron count and their relative percentages integrated over the valence and conduction bands from those of the semiconducting state. These differences should contribute to strikingly dissimilar band structures. The calculation results suggest observation of facet-dependent electrical conductivity properties of germanium materials, and transistors made of germanium may also need to consider the facet effects with shrinking dimensions approaching 3 nm. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Relationships between Soil compaction and harvest season, soil texture, and landscape position for aspen forests

Treesearch

Randy Kolka; Aaron Steber; Ken Brooks; Charles H. Perry; Matt Powers

2012-01-01

Although a number of harvesting studies have assessed compaction, no study has considered the interacting relationships of harvest season, soil texture, and landscape position on soil bulk density and surface soil strength for harvests in the western Lake States. In 2005, we measured bulk density and surface soil strength in recent clearcuts of predominantly aspen...

Factors influencing soil-surface bulk density on oak savanna rangeland in the southern Sierra Nevada foothills

Treesearch

Dennis M. Dudley; Kenneth W. Tate; Neil K. McDougald; Melvin R. George

2002-01-01

The objectives of this study were to compare soil-surface bulk density between rangeland pastures not grazed since 1935, 1975, and 1995 to grazed areas with a 15-year record of light (>1,000 lbs ac-1 RDM), moderate (600-800 lbs ac-1 RDM), and heavy (-1 RDM) grazing by beef cattle; and...

Soil compaction after yarding of small-diameter Douglas-fir with a small tractor in southwest Oregon.

Treesearch

Michael P. Amaranthus; David E. Steinfeld

1997-01-01

This study evaluated the effect on soil bulk density of yarding small-diameter Douglas-fir (Pseudosuga menziesii var. glauca (Beissn.) Franco) with a small tractor. Levels of compaction were measured before yarding and after one trip, three trips, and six trips by the tractor. Bulk densities in the surface (10 cm) and...

Soil bulk density and soil moisture calculated with a FORTRAN 77 program.

Treesearch

G.L. Starr; J.M. Geist

1988-01-01

This paper presents an improved version of BDEN, an interactive computer program written in FORTRAN 77 that will calculate soil bulk density and moisture percentage by weight and volume. Calculations allow for deducting coarse fragment weight and volume. The program will also summarize the resulting data by giving the mean, standard deviation, and 95-percent confidence...

Apparatus for in situ prediction of the thermal conductivity of fiberglass batts using acoustic propagation constant

NASA Astrophysics Data System (ADS)

Tinianov, Brandon D.; Nakagawa, Masami; Muñoz, David R.

2006-02-01

This article describes a novel technique for the measurement of the thermal conductivity of low-density (12-18kg/m3) fiberglass insulation and other related fibrous insulation materials using a noninvasive acoustic apparatus. The experimental method is an extension of earlier acoustic methods based upon the evaluation of the propagation constant from the acoustic pressure transfer function across the test material. To accomplish this, an analytical model is employed that describes the behavior of sound waves at the outlet of a baffled waveguide. The model accounts for the behavior of the mixed impedance interface introduced by the test material. Current results show that the technique is stable for a broad range of absorber thicknesses and densities. Experimental results obtained in the laboratory show excellent correlation between the thermal conductivity and both the real and imaginary components of the propagation constant. Correlation of calculated propagation constant magnitude versus measured thermal conductivity gave an R2 of 0.94 for the bulk density range (12-18kg/m3) typical for manufactured fiberglass batt materials. As an improvement to earlier acoustic techniques, measurement is now possible in noisy manufacturing environments with a moving test material. Given the promise of such highly correlated measurements in a robust method, the acoustic technique is well suited to continuously measure the thermal conductivity of the material during its production, replacing current expensive off-line methods. Test cycle time is reduced from hours to seconds.

Influence of wood-derived biochar on the compactibility and strength of silt loam soil

NASA Astrophysics Data System (ADS)

Ahmed, Ahmed; Gariepy, Yvan; Raghavan, Vijaya

2017-04-01

Biochar is proven to enhance soil fertility and increase crop productivity. Given that the influence of biochar on soil compaction remains unclear, selected physico-mechanical properties of soil amended with wood-derived biochar were assessed. For unamended silt loam, the bulk density, maximum bulk density, optimum moisture content, plastic limit, liquid limit, and plasticity index were 1.05 Mg m-3, 1.69 Mg m-3, 16.55, 17.1, 29.3, and 12.2%, respectively. The penetration resistance and shear strength of the unamended silt loam compacted in the standard compaction Proctor mold and at its optimum moisture content were 1800 kPa and 850 kPa, respectively. Results from amending the silt loam with 10% particle size ranges (0.5-212 μm) led to relative decreases of 18.1, 17.75, 66.66, and 97.4% in bulk density, maximum bulk density, penetration resistance, and shear strength, respectively; a 26.8% relative increase in optimum moisture content; along with absolute increases in plastic limit, liquid limit, and plasticity index of 5.3, 13.7, and 8.4%, respectively. While the biochar-amended silt loam soil was more susceptible to compaction, however, soil mechanical impedance enhanced.

Measurement of carrier transport and recombination parameter in heavily doped silicon

NASA Technical Reports Server (NTRS)

Swanson, Richard M.

1986-01-01

The minority carrier transport and recombination parameters in heavily doped bulk silicon were measured. Both Si:P and Si:B with bulk dopings from 10 to the 17th and 10 to the 20th power/cu cm were studied. It is shown that three parameters characterize transport in bulk heavily doped Si: the minority carrier lifetime tau, the minority carrier mobility mu, and the equilibrium minority carrier density of n sub 0 and p sub 0 (in p-type and n-type Si respectively.) However, dc current-voltage measurements can never measure all three of these parameters, and some ac or time-transient experiment is required to obtain the values of these parameters as a function of dopant density. Using both dc electrical measurements on bipolar transitors with heavily doped base regions and transients optical measurements on heavily doped bulk and epitaxially grown samples, lifetime, mobility, and bandgap narrowing were measured as a function of both p and n type dopant densities. Best fits of minority carrier mobility, bandgap narrowing and lifetime as a function of doping density (in the heavily doped range) were constructed to allow accurate modeling of minority carrier transport in heavily doped Si.

Processing and characterization of multi-cellular monolithic bioceramics for bone regenerative scaffolds

NASA Astrophysics Data System (ADS)

Ari-Wahjoedi, Bambang; Ginta, Turnad Lenggo; Parman, Setyamartana; Abustaman, Mohd Zikri Ahmad

2014-10-01

Multicellular monolithic ceramic body is a ceramic material which has many gas or liquid passages partitioned by thin walls throughout the bulk material. There are many currently known advanced industrial applications of multicellular ceramics structures i.e. as supports for various catalysts, electrode support structure for solid oxide fuel cells, refractories, electric/electronic materials, aerospace vehicle re-entry heat shields and biomaterials for dental as well as orthopaedic implants by naming only a few. Multicellular ceramic bodies are usually made of ceramic phases such as mullite, cordierite, aluminum titanate or pure oxides such as silica, zirconia and alumina. What make alumina ceramics is excellent for the above functions are the intrinsic properties of alumina which are hard, wear resistant, excellent dielectric properties, resists strong acid and alkali attacks at elevated temperatures, good thermal conductivities, high strength and stiffness as well as biocompatible. In this work the processing technology leading to truly multicellular monolithic alumina ceramic bodies and their characterization are reported. Ceramic slip with 66 wt.% solid loading was found to be optimum as impregnant to the polyurethane foam template. Mullitic ceramic composite of alumina-sodium alumino disilicate-Leucite-like phases with bulk and true densities of 0.852 and 1.241 g cm-3 respectively, pore linear density of ±35 cm-1, linear and bulk volume shrinkages of 7-16% and 32 vol.% were obtained. The compressive strength and elastic modulus of the bioceramics are ≈0.5-1.0 and ≈20 MPa respectively.

Field Trial Assessment of Biological, Chemical, and Physical Responses of Soil to Tillage Intensity, Fertilization, and Grazing

NASA Astrophysics Data System (ADS)

Vargas Gil, Silvina; Becker, Analia; Oddino, Claudio; Zuza, Mónica; Marinelli, Adriana; March, Guillermo

2009-08-01

Soil microbial populations can fluctuate in response to environmental changes and, therefore, are often used as biological indicators of soil quality. Soil chemical and physical parameters can also be used as indicators because they can vary in response to different management strategies. A long-term field trial was conducted to study the effects of different tillage systems (NT: no tillage, DH: disc harrow, and MP: moldboard plough), P fertilization (diammonium phosphate), and cattle grazing (in terms of crop residue consumption) in maize ( Zea mays L.), sunflower ( Heliantus annuus L.), and soybean ( Glycine max L.) on soil biological, chemical, and physical parameters. The field trial was conducted for four crop years (2000/2001, 2001/2002, 2002/2003, and 2003/2004). Soil populations of Actinomycetes, Trichoderma spp., and Gliocladium spp. were 49% higher under conservation tillage systems, in soil amended with diammonium phosphate (DAP) and not previously grazed. Management practices also influenced soil chemical parameters, especially organic matter content and total N, which were 10% and 55% higher under NT than under MP. Aggregate stability was 61% higher in NT than in MP, 15% higher in P-fertilized soil, and also 9% higher in not grazed strips, bulk density being 12% lower in NT systems compared with MP. DAP application and the absence of grazing also reduced bulk density (3%). Using conservation tillage systems, fertilizing crops with DAP, and avoiding grazing contribute to soil health preservation and enhanced crop production.

Quantifying the effects of wildfire on changes in soil properties by surface burning of soils from the Boulder Creek Critical Zone Observatory

USGS Publications Warehouse

Wieting, Celeste; Ebel, Brian A.; Singha, Kamini

2017-01-01

Study regionThis study used intact soil cores collected at the Boulder Creek Critical Zone Observatory near Boulder, Colorado, USA to explore fire impacts on soil properties.Study focusThree soil scenarios were considered: unburned control soils, and low- and high-temperature burned soils. We explored simulated fire impacts on field-saturated hydraulic conductivity, dry bulk density, total organic carbon, and infiltration processes during rainfall simulations.New hydrological insights for the regionSoils burned to high temperatures became more homogeneous with depth with respect to total organic carbon and bulk density, suggesting reductions in near-surface porosity. Organic matter decreased significantly with increasing soil temperature. Tension infiltration experiments suggested a decrease in infiltration rates from unburned to low-temperature burned soils, and an increase in infiltration rates in high-temperature burned soils. Non-parametric statistical tests showed that field-saturated hydraulic conductivity similarly decreased from unburned to low-temperature burned soils, and then increased with high-temperature burned soils. We interpret these changes result from the combustion of surface and near-surface organic materials, enabling water to infiltrate directly into soil instead of being stored in the litter and duff layer at the surface. Together, these results indicate that fire-induced changes in soil properties from low temperatures were not as drastic as high temperatures, but that reductions in surface soil water repellency in high temperatures may increase infiltration relative to low temperatures.

The relationship between vickers microhardness and compressive strength of functional surface geopolymers

NASA Astrophysics Data System (ADS)

Subaer, Ekaputri, Januari Jaya; Fansuri, Hamzah; Abdullah, Mustafa Al Bakri

2017-09-01

An experimental study to investigate the relationship between Vickers microhardness and compressive strength of geopolymers made from metakaolin has been conducted. Samples were prepared by using metakaolin activated with a sodium silicate solution at a different ratio of Si to Al and Na to Al and cured at 70oC for one hour. The resulting geopolymers were stored in an open air for 28 days before conducting any measurement. Bulk density and apparent porosity of the samples were measured by using Archimedes's method. Vickers microhardness measurements were performed on a polished surface of geopolymers with a load ranging from 0.3 - 1.0 kg. The topographic of indented samples were examined by using scanning electron microscopy (SEM). Compressive strength of the resulting geopolymers was measured on the cylindrical samples with a ratio of height to the diameter was 2:1. The results showed that the molar ratios of geopolymers compositions play important roles in the magnitude of bulk density, porosity, Vickers's microhardness as well as the compressive strength. The porosity reduced exponentially the magnitude of the strength of geopolymers. It was found that the relationship between Vickers microhardness and compressive strength was linear. At the request of all authors and with the approval of the proceedings editor, article 020188 titled, "The relationship between vickers microhardness and compressive strength of functional surface geopolymers," is being retracted from the public record due to the fact that it is a duplication of article 020170 published in the same volume.

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

Wang, Dong, E-mail: wang.dong.539@m.kyushu-u.ac.jp; Maekura, Takayuki; Kamezawa, Sho

We demonstrated direct band gap (DBG) electroluminescence (EL) at room temperature from n-type bulk germanium (Ge) using a fin type asymmetric lateral metal/Ge/metal structure with TiN/Ge and HfGe/Ge contacts, which was fabricated using a low temperature (<400 °C) process. Small electron and hole barrier heights were obtained for TiN/Ge and HfGe/Ge contacts, respectively. DBG EL spectrum peaked at 1.55 μm was clearly observed even at a small current density of 2.2 μA/μm. Superlinear increase in EL intensity was also observed with increasing current density, due to superlinear increase in population of elections in direct conduction band. The efficiency of hole injection was alsomore » clarified.« less

Electronic structure of hydrogenated diamond: Microscopical insight into surface conductivity

NASA Astrophysics Data System (ADS)

Iacobucci, S.; Alippi, Paola; Calvani, P.; Girolami, M.; Offi, F.; Petaccia, L.; Trucchi, D. M.

2016-07-01

We have correlated the surface conductivity of hydrogen-terminated diamond to the electronic structure in the Fermi region. Significant density of electronic states (DOS) in proximity of the Fermi edge has been measured by photoelectron spectroscopy (PES) on surfaces exposed to air, corresponding to a p -type electric conductive regime, while upon annealing a depletion of the DOS has been achieved, resembling the diamond insulating state. The surface and subsurface electronic structure has been determined, exploiting the different probing depths of PES applied in a photon energy range between 7 and 31 eV. Ab initio density functional calculations including surface charge depletion and band-bending effects favorably compare with electronic states measured by angular-resolved photoelectron spectroscopy. Such states are organized in the energy-momentum space in a twofold structure: one, bulk-derived, band disperses in the Γ -X direction with an average hole effective mass of (0.43 ±0.02 ) m0 , where m0 is the bare electron mass; a second flatter band, with an effective mass of (2.2 ±0.9 ) m0 , proves that a hole gas confined in the topmost layers is responsible for the conductivity of the (2 ×1 ) hydrogen-terminated diamond (100 ) surface.

[Study on nano-CaCO3 applicated in Xin Yue Shu Capsules preliminarily].

PubMed

Jiang, Yan-Rong; Zhang, Zhen-Hai; Cui, Li; He, Jun-Jie; Hu, Shao-Ying; Jia, Xiao-Bin

2012-11-01

To investigate the characteristics of nano-CaCO3 applicated in Xin Yue Shu Capsules. Studied the effect of different dosages of aerosil or nano-CaCO3 on fluidity, bulk density, moisture absorption of Xin Yue Shu capsules spray drying powder. In vitro dissolution and ferulic acid stability of Xin Yue Shu capsules was observed. It significantly improved powder fluidity and bulk density of Xin Yue Shu spray drying powder when aerosil or nano-CaCO3 was added. But there was no significant effect on powder moisture absorption, ferulic acid in vitro dissolution and ferulic acid stability. The effect of Nano-CaCO3 on improving powder fluidity and bulk density applicated in the spray drying powder of traditional Chinese medicine deserves studying further.

Viscous Dissipation and Heat Conduction in Binary Neutron-Star Mergers.

PubMed

Alford, Mark G; Bovard, Luke; Hanauske, Matthias; Rezzolla, Luciano; Schwenzer, Kai

2018-01-26

Inferring the properties of dense matter is one of the most exciting prospects from the measurement of gravitational waves from neutron star mergers. However, it requires reliable numerical simulations that incorporate viscous dissipation and energy transport as these can play a significant role in the survival time of the post-merger object. We calculate time scales for typical forms of dissipation and find that thermal transport and shear viscosity will not be important unless neutrino trapping occurs, which requires temperatures above 10 MeV and gradients over length scales of 0.1 km or less. On the other hand, if direct-Urca processes remain suppressed, leaving modified-Urca processes to establish flavor equilibrium, then bulk viscous dissipation could provide significant damping to density oscillations right after merger. When comparing with data from state-of-the-art merger simulations, we find that the bulk viscosity takes values close to its resonant maximum in a typical merger, motivating a more careful assessment of the role of bulk viscous dissipation in the gravitational-wave signal from merging neutron stars.

Viscous Dissipation and Heat Conduction in Binary Neutron-Star Mergers

NASA Astrophysics Data System (ADS)

Alford, Mark G.; Bovard, Luke; Hanauske, Matthias; Rezzolla, Luciano; Schwenzer, Kai

2018-01-01

Inferring the properties of dense matter is one of the most exciting prospects from the measurement of gravitational waves from neutron star mergers. However, it requires reliable numerical simulations that incorporate viscous dissipation and energy transport as these can play a significant role in the survival time of the post-merger object. We calculate time scales for typical forms of dissipation and find that thermal transport and shear viscosity will not be important unless neutrino trapping occurs, which requires temperatures above 10 MeV and gradients over length scales of 0.1 km or less. On the other hand, if direct-Urca processes remain suppressed, leaving modified-Urca processes to establish flavor equilibrium, then bulk viscous dissipation could provide significant damping to density oscillations right after merger. When comparing with data from state-of-the-art merger simulations, we find that the bulk viscosity takes values close to its resonant maximum in a typical merger, motivating a more careful assessment of the role of bulk viscous dissipation in the gravitational-wave signal from merging neutron stars.

Fracture Toughness Properties of Gd123 Superconducting Bulks

NASA Astrophysics Data System (ADS)

Fujimoto, H.; Murakami, A.

Fracture toughness properties of melt growth GdBa2Cu3Ox (Gd123) large single domain superconducting bulks with Ag2O of 10 wt% and Pt of 0.5 wt%; 45 mm in diameter and 25 mm in thickness with low void density were evaluated at 77 K through flexural tests of specimens cut from the bulks, and compared to those of a conventional Gd123 with voids. The densified Gd123 bulks were prepared with a seeding and temperature gradient method; first melt processed in oxygen, then crystal growth in air; two-step regulated atmosphere heat treatment. The plane strain fracture toughness, KIC was obtained by the three point flexure test of the specimens with through precrack, referring to the single edge pre-cracked beam (SEPB) method, according to the JIS-R-1607, Testing Methods for Fracture Toughness of High Performance Ceramics. The results show that the fracture toughness of the densified Gd123 bulk with low void density was higher than that of the standard Gd123 bulk with voids, as well as the flexural strength previously reported. We also compared the fracture toughness of as-grown bulks with that of annealed bulks. The relation between the microstructure and the fracture toughness of the Gd123 bulk was clearly shown.

Effects of soil tillage on the microwave emission of soils

NASA Technical Reports Server (NTRS)

Jackson, T. J.; Koopman, G. J.; Oneill, P. E.; Wang, J. R.

1985-01-01

In order to understand the interactions of soil properties and microwave emission better, a series of field experiments were conducted in 1984. Small plots were measured with a truck-mounted passive microwave radiometer operating at 1.4 GHz. These data were collected concurrent with ground observations of soil moisture and bulk density. Treatment effects studied included different soil moisture contents and bulk densities. Evaluations of the data have shown that commonly used models of the dielectric properties of wet soils do not explain the observations obtained in these experiments. This conclusion was based on the fact that the roughness parameters determined through optimization were significantly larger than those observed in similar investigations. These discrepancies are most likely due to the soil structure. Commonly used models assume a homogeneous three phase mixture of soil solids, air and water. Under tilled conditions the soil is actually a two phase mixture of aggregates and voids. Appropriate dielectric models for this tilled condition were evaluated and found to explain the observations. These results indicate that previous conclusions concerning the effects of surface roughness in tilled fields may be incorrect, and they may explain some of the inconsistencies encountered in roughness modeling.

Organic heterojunctions: Contact-induced molecular reorientation, interface states, and charge re-distribution

PubMed Central

Opitz, Andreas; Wilke, Andreas; Amsalem, Patrick; Oehzelt, Martin; Blum, Ralf-Peter; Rabe, Jürgen P.; Mizokuro, Toshiko; Hörmann, Ulrich; Hansson, Rickard; Moons, Ellen; Koch, Norbert

2016-01-01

We reveal the rather complex interplay of contact-induced re-orientation and interfacial electronic structure – in the presence of Fermi-level pinning – at prototypical molecular heterojunctions comprising copper phthalocyanine (H16CuPc) and its perfluorinated analogue (F16CuPc), by employing ultraviolet photoelectron and X-ray absorption spectroscopy. For both layer sequences, we find that Fermi-level (EF) pinning of the first layer on the conductive polymer substrate modifies the work function encountered by the second layer such that it also becomes EF-pinned, however, at the interface towards the first molecular layer. This results in a charge transfer accompanied by a sheet charge density at the organic/organic interface. While molecules in the bulk of the films exhibit upright orientation, contact formation at the heterojunction results in an interfacial bilayer with lying and co-facial orientation. This interfacial layer is not EF-pinned, but provides for an additional density of states at the interface that is not present in the bulk. With reliable knowledge of the organic heterojunction’s electronic structure we can explain the poor performance of these in photovoltaic cells as well as their valuable function as charge generation layer in electronic devices. PMID:26887445

Preparation and characterization of starch-based loose-fill packaging foams

NASA Astrophysics Data System (ADS)

Fang, Qi

Regular and waxy corn starches were blended in various ratios with biodegradable polymers including polylactic acid (PLA), Eastar Bio Copolyester 14766 (EBC) and Mater-Bi ZF03U (MBI) and extruded with a C. W. Brabender laboratory twin screw extruder using a 3-mm die nozzle at 150°C and 150 rev/min. Physical characteristics including radial expansion, unit density and bulk density and water solubility index, water absorption characteristics, mechanical properties including compressibility, Young's modulus, spring index, bulk compressibility and bulk spring index and abrasion resistance were investigated as affected by the ingredient formulations, i.e. type of polymers, type of starches, polymer to starch ratio and starch moisture content. A completely randomized factorial blocking experimental design was used. Fifty-four treatments resulted. Each treatment was replicated three times. SAS statistical software package was used to analyze the data. Foams made of waxy starch had better radial expansion, lower unit density and bulk density than did foams made of regular starch. Regular starch foams had significantly lower water solubility index than did the waxy starch foams. PLA-starch foams had the lowest compressibility and Young's modulus. MBI-starch foams were the most rigid. All foams had excellent spring indices and bulk spring indices which were comparable to the spring index of commercial expanded polystyrene foam. Correlations were established between the foam mechanical properties and the physical characteristics. Foam compressibility and Young's modulus decreased as increases in radial expansion and decreases in unit and bulk densities. Their relationships were modeled with power law equations. No correlation was observed between spring index and bulk spring index and foam physical characteristics. MBI-starch foams had the highest equilibrium moisture content. EBC-starch and PLA-starch foams had similar water absorption characteristics. No significant difference existed in water absorption characteristics between foams made of regular and waxy starches. Empirical models were developed to correlate foam water absorption characteristics with relative humidity and polymer content. The developed models fit the data well with relatively small standard errors and uniformly scattered residual plots. Foams with higher polymer content had better abrasion resistance than did foams with lower polymer content.

Bulk density and compaction behavior of knife mill chopped switchgrass,wheat straw, and corn stover

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

Chevanan, Nehru; Womac, A.R.; Bitra, V.S.P.

2009-08-01

Bulk density of comminuted biomass significantly increased by vibration during handling and transportation, and by normal pressure during storage. Compaction characteristics affecting the bulk density of switchgrass, wheat straw, and corn stover chopped in a knife mill at different operating conditions and using four different classifying screens were studied. Mean loose-filled bulk densities were 67.5 18.4 kg/m3 for switchgrass, 36.1 8.6 kg/m3 for wheat straw, and 52.1 10.8 kg/m3 for corn stover. Mean tapped bulk densities were 81.8 26.2 kg/m3 for switchgrass, 42.8 11.7 kg/m3 for wheat straw, and 58.9 13.4 kg/m3 for corn stover. Percentage changes in compressibility duemore » to variation in particle size obtained from a knife mill ranged from 64.3 to 173.6 for chopped switchgrass, 22.2 51.5 for chopped wheat straw and 42.1 117.7 for chopped corn stover within the tested consolidation pressure range of 5 120 kPa. Pressure and volume relationship of chopped biomass during compression with application of normal pressure can be characterized by the Walker model and Kawakita and Ludde model. Parameter of Walker model was correlated to the compressibility with Pearson correlation coefficient greater than 0.9. Relationship between volume reduction in chopped biomass with respect to number of tappings studied using Sone s model indicated that infinite compressibility was highest for chopped switchgrass followed by chopped wheat straw and corn stover. Degree of difficulty in packing measured using the parameters of Sone s model indicated that the chopped wheat straw particles compacted very rapidly by tapping compared to chopped switchgrass and corn stover. These results are very useful for solving obstacles in handling bulk biomass supply logistics issues for a biorefinery.« less

Bulk density and compaction behavior of knife mill chopped switchgrass, wheat straw, and corn stover.

PubMed

Chevanan, Nehru; Womac, Alvin R; Bitra, Venkata S P; Igathinathane, C; Yang, Yuechuan T; Miu, Petre I; Sokhansanj, Shahab

2010-01-01

Bulk density of comminuted biomass significantly increased by vibration during handling and transportation, and by normal pressure during storage. Compaction characteristics affecting the bulk density of switchgrass, wheat straw, and corn stover chopped in a knife mill at different operating conditions and using four different classifying screens were studied. Mean loose-filled bulk densities were 67.5+/-18.4 kg/m(3) for switchgrass, 36.1+/-8.6 kg/m(3) for wheat straw, and 52.1+/-10.8 kg/m(3) for corn stover. Mean tapped bulk densities were 81.8+/-26.2 kg/m(3) for switchgrass, 42.8+/-11.7 kg/m(3) for wheat straw, and 58.9+/-13.4 kg/m(3) for corn stover. Percentage changes in compressibility due to variation in particle size obtained from a knife mill ranged from 64.3 to 173.6 for chopped switchgrass, 22.2-51.5 for chopped wheat straw and 42.1-117.7 for chopped corn stover within the tested consolidation pressure range of 5-120 kPa. Pressure and volume relationship of chopped biomass during compression with application of normal pressure can be characterized by the Walker model and Kawakita and Ludde model. Parameter of Walker model was correlated to the compressibility with Pearson correlation coefficient greater than 0.9. Relationship between volume reduction in chopped biomass with respect to number of tappings studied using Sone's model indicated that infinite compressibility was highest for chopped switchgrass followed by chopped wheat straw and corn stover. Degree of difficulty in packing measured using the parameters of Sone's model indicated that the chopped wheat straw particles compacted very rapidly by tapping compared to chopped switchgrass and corn stover. These results are very useful for solving obstacles in handling bulk biomass supply logistics issues for a biorefinery.

Fuels planning: science synthesis and integration; environmental consequences fact sheet 14: Fuels reduction and compaction

Treesearch

Deborah Page-Dumroese

2005-01-01

Moving equipment and logs over the surface of forest soils causes gouges and ruts in the mineral soil, displaces organic matter, and can cause compaction. Compaction is the component of soil productivity most influenced by forest management, but the degree to which soils may be compacted depends on initial soil bulk density. For example, low bulk density soils (such as...

Establishment and early growth of conifers on compact soils in urban areas

Treesearch

Robert P. Zisa; Howard G. Halverson; Benjamin B. Stout

1979-01-01

A study of pitch pine, Austrian pine, and Norway spruce on two different urban soils compacted to bulk densities of 1.2, 1.3, 1.6, and 1.8 g•cm-3 and maintained at high water potentials showed that all three species could become established from seed at high soil bulk densities. Pitch pine was the most suceessful species in establishment...

Inferences of Strength of Soil Deposits along MER Rover Traverses

NASA Astrophysics Data System (ADS)

Richter, L.; Schmitz, N.; Weiss, S.; Mer/Athena Team

As the two MER Mars Exploration Rovers ,Spirit' and ,Opportunity' traverse terrains within Gusev crater and at Meridiani Planum, respectively, they leave behind wheel tracks that are routinely imaged by the different sets of cameras as part of the Athena instrument suite. Stereo observations of these tracks reveal wheel sinkage depths which are diagnostic of the strength of the soil-like deposits crossed by the vehicles, and observations of track morphology at different imaging scales - including that of the Microscopic Imager - allow estimations of soil grain size distributions. This presentation will discuss results of systematic analyses of MER-A and -B wheel track observations with regard to solutions for soil bearing strength and soil shear strength. Data are analyzed in the context of wheel-soil theory calibrated to the shape of the MER wheel and by consulting comparisons with terrestrial soils. Results are applicable to the top ˜20-30 cm of the soil deposits, the depth primarily affected by the stress distribution under the wheels. The large number of wheel track observations per distance travelled enables investigations of variations of soil physical properties as a function of spatial scale, type of surface feature encountered, and local topography. Exploiting relationships between soil strength and degree of soil consolidation known from lunar regolith and dry terrestrial soils allows one to relate inferred soil strengths to bulk density. This provides a means to ground-truth radar Fresnel reflection coefficients obtained for the landing sites from Earth-based observations. Moreover, bulk density is correlated with soil dielectric constant, a parameter of direct relevance also for Mars-orbiting radars. The obtained estimates for soil bulk density are also used to determine local thermal conductivity of near-surface materials, based on correlations between the two quantities, and to subsequently estimate thermal inertia. This represents an independent method to provide ground truth to thermal inertia determined from orbital thermal measurements of the MER landing sites (MGS TES, MODY THEMIS, MEX PFS & OMEGA), in addition to thermal inertia retrievals from the Athena Mini-TES instrument. Key results suggest different types of soils as judged from their strength, with most materials encountered being similar in consistency to terrestrial sandy loams. Relatively looser soils have been identified on the slopes of crater walls and in local 1 soil patches of smooth appearance, being interpreted as deposits of unconsolidated dust-like soils. Bulk densities for the different soils vary between ˜1100 and ˜1500 kgm-3 . Results of chemical measurements are currently being exploited to relate soil strength to inferred enrichments in salts possibly acting as cementing agents. Thermal inertias of the soil component obtained from the bulk density estimates range between ˜130 and ˜150 Jm-2 s-1/2 K-1 for the MER-A Gusev site and between ˜130 and ˜140 Jm-2 s-1/2 K-1 for the MER-B Meridiani site. 2

Prediction of changes in important physical parameters during composting of separated animal slurry solid fractions.

PubMed

Chowdhury, Md Albarune; de Neergaard, Andreas; Jensen, Lars Stoumann

2014-01-01

Solid-liquid separation of animal slurry, with solid fractions used for composting, has gained interest recently. However, efficient composting of separated animal slurry solid fractions (SSFs) requires a better understanding of the process dynamics in terms of important physical parameters and their interacting physical relationships in the composting matrix. Here we monitored moisture content, bulk density, particle density and air-filled porosity (AFP) during composting of SSF collected from four commercially available solid-liquid separators. Composting was performed in laboratory-scale reactors for 30 days (d) under forced aeration and measurements were conducted on the solid samples at the beginning of composting and at 10-d intervals during composting. The results suggest that differences in initial physical properties of SSF influence the development of compost maximum temperatures (40-70 degreeC). Depending on SSF, total wet mass and volume losses (expressed as % of initial value) were up to 37% and 34%, respectively. After 30 d of composting, relative losses of total solids varied from 17.9% to 21.7% and of volatile solids (VS) from 21.3% to 27.5%, depending on SSF. VS losses in all composts showed different dynamics as described by the first-order kinetic equation. The estimated component particle density of 1441 kg m-3 for VS and 2625 kg m-3 for fixed solids can be used to improve estimates of AFP for SSF within the range tested. The linear relationship between wet bulk density and AFP reported by previous researchers held true for SSF.

Two-dimensional Coupled Petrological-tectonic Modelling of Extensional Basins

NASA Astrophysics Data System (ADS)

Kaus, B. J. P.; Podladchikov, Y. Y.; Connolly, J. A. D.

Most numerical codes that simulate the deformation of a lithosphere assume the den- sity of the lithosphere to be either constant or depend only on temperature and pres- sure. It is, however, well known that rocks undergo phase transformations in response to changes in pressure and temperature. Such phase transformations may substantially alter the bulk properties of the rock (i.e., density, thermal conductivity, thermal ex- pansivity and elastic moduli). Several previous studies demonstrated that the density effects due to phase transitions are indeed large enough to have an impact on the litho- sphere dynamics. These studies were however oversimplified in that they accounted for only one or two schematic discontinuous phase transitions. The current study there- fore takes into account all the reactions that occur for a realistic lithospheric composi- tion. Calculation of the phase diagram and bulk physical properties of the stable phase assemblages for the crust and mantle within the continental lithosphere was done ac- counting for mineral solution behaviour using a free energy minimization program for natural rock compositions. The results of these calculations provide maps of the varia- tions in rock properties as a function of pressure and temperature that are easily incor- porated in any dynamic model computations. In this contribution we implemented a density map in the two-dimensional basin code TECMOD2D. We compare the results of the model with metamorphic reactions with a model without reactions and define some effective parameters that allow the use of a simpler model that still mimics most of the density effects of the metamorphic reactions.

Sensitivity of simulated snow cloud properties to mass-diameter parameterizations.

NASA Astrophysics Data System (ADS)

Duffy, G.; Nesbitt, S. W.; McFarquhar, G. M.

2015-12-01

Mass to diameter (m-D) relationships are used in model parameterization schemes to represent ice cloud microphysics and in retrievals of bulk cloud properties from remote sensing instruments. One of the most common relationships, used in the current Global Precipitation Measurement retrieval algorithm for example, assigns the density of snow as a constant tenth of the density of ice (0.1g/m^3). This assumption stands in contrast to the results of derived m-D relationships of snow particles, which imply decreasing particle densities at larger sizes and result in particle masses orders of magnitude below the constant density relationship. In this study, forward simulations of bulk cloud properties (e.g., total water content, radar reflectivity and precipitation rate) derived from measured size distributions using several historical m-D relationships are presented. This expands upon previous studies that mainly focused on smaller ice particles because of the examination of precipitation-sized particles here. In situ and remote sensing data from the GPM Cold season Experiment (GCPEx) and Canadian CloudSAT/Calypso Validation Program (C3VP), both synoptic snowstorm field experiments in southern Ontario, Canada, are used to evaluate the forward simulations against total water content measured by the Nevzorov and Cloud Spectrometer and Impactor (CSI) probe, radar reflectivity measured by a C band ground based radar and a nadir pointing Ku/Ka dual frequency airborne radar, and precipitation rate measured by a 2D video disdrometer. There are differences between the bulk cloud properties derived using varying m-D relations, with constant density assumptions producing results differing substantially from the bulk measured quantities. The variability in bulk cloud properties derived using different m-D relations is compared against the natural variability in those parameters seen in the GCPEx and C3VP field experiments.

Homogeneity and variation of donor doping in Verneuil-grown SrTiO3:Nb single crystals

PubMed Central

Rodenbücher, C.; Luysberg, M.; Schwedt, A.; Havel, V.; Gunkel, F.; Mayer, J.; Waser, R.

2016-01-01

The homogeneity of Verneuil-grown SrTiO3:Nb crystals was investigated. Due to the fast crystal growth process, inhomogeneities in the donor dopant distribution and variation in the dislocation density are expected to occur. In fact, for some crystals optical studies show variations in the density of Ti3+ states on the microscale and a cluster-like surface conductivity was reported in tip-induced resistive switching studies. However, our investigations by TEM, EDX mapping, and 3D atom probe reveal that the Nb donors are distributed in a statistically random manner, indicating that there is clearly no inhomogeneity on the macro-, micro-, and nanoscale in high quality Verneuil-grown crystals. In consequence, the electronic transport in the bulk of donor-doped crystals is homogeneous and it is not significantly channelled by extended defects such as dislocations which justifies using this material, for example, as electronically conducting substrate for epitaxial oxide film growth. PMID:27577508

Liquefaction of oak tree bark with different biomass/phenol mass ratios and utilizing bio-based polyols for carbon foam production

NASA Astrophysics Data System (ADS)

Ozbay, N.; Yargic, A. S.

2017-02-01

Carbon foam is sponge like carbonaceous material with low density, high conductivity and high strength; which is used in various applications such as catalyst supports, membrane separations, high thermally conductive heat sinks, energy absorption materials, high temperature thermal insulation. Coal or fossil oils are conventionally used to fabricate pitch, phenolic resin and polyurethane as carbon foam precursor. Biomass liquefaction is a developing technique to convert biomass resources into the industrial chemicals. In this study, oak tree bark was liquefied under mild conditions with different mass ratio of biomass/phenol; and the liquefaction product was used as polyol to produce porous resin foams. Obtained resin foams were carbonized at 400 °C, and then activated at 800 °C under nitrogen atmosphere. Structure evaluation of resin foams, carbonized foams and activated carbon foams from liquefied oak tree bark was investigated by using elemental analysis, x-ray diffraction, nitrogen adsorption/desorption isotherms, scanning electron microscopy, bulk density and compressive strength tests.

Soil resistivity over root area ratio, soil humidity, and bulk density: laboratory tests

NASA Astrophysics Data System (ADS)

Guastini, Enrico; Giambastiani, Yamuna; Preti, Federico

2015-04-01

Knowledge about root system distribution covers an important role in slope shallow stability stud-ies, as this factor grants an increase in soil geotechnical properties (soil cohesion and friction an-gle) and determines a different underground water circulation. Published studies (Amato et al., 2008 and 2011; Censini et al., 2014) about in situ application of ERT (Electrical Resistivity Tomo-graphy) analysis show how the root presence affects the measurable soil resistivity values, confirm-ing the suitability to investigate the application of such technique, aiming to estimate root density in soil with an indirect and non-invasive method. This study, laboratory-based and led on reconstructed samples in controlled condition, aim to find a correlation between the resistivity variations and the various factors that can affect them (humid-ity, bulk density, presence of foreign bodies, temperature). The tests involved a clay-loam soil (USDA classification) taken from Quaracchi (Florence, Italy), in an experimental fir-wood (Picea abies) owned by the Department of Agricultural, Food and For-estry System, Florence University, a previously chosen site for field ERT applications. The row ma-terial has been dried out in a lab stove, grounded and sieved at 2 mm, and then placed in a lexan box (30 x 20 x 20 cm) without compaction. Inside the sample have been inserted 3 series of 4 iron electrodes, insulated along the shaft and with the conductive end placed at three different depth: 2 cm from surface, in the middle of the sample and in contact with the bottom of the box; resistivity measures are conducted on the three levels using a Syscal R2 with electrodes connected in a dipole-dipole configuration. Root presence is simulated inserting bamboo spits (simple geometry, replicable "R.A.R.") in varying number from 0 to 16 in every area between two contiguous electrodes. The tests are repeated in time, monitoring the natural variations in humidity (evapotranspiration) and bulk density (compac-tion). The first results show an increase of resistivity with the decrease of mean humidity that follows a potential trend; data measured in the spitted sample can be statistically considered as a different population in respect to the data from the bare earth sample, giving credit to the hypothesis that the wooden spit presence could be indirectly quantified from geoelectric data. Acknowledgements Italian Research Project of Relevant Interest (PRIN2010-2011), prot. 20104ALME4, National network for monitoring, modeling, and sustainable management of erosion processes in agricultural land and hilly-mountainous area

Thermal imaging diagnostics of high-current electron beams.

PubMed

Pushkarev, A; Kholodnaya, G; Sazonov, R; Ponomarev, D

2012-10-01

The thermal imaging diagnostics of measuring pulsed electron beam energy density is presented. It provides control of the electron energy spectrum and a measure of the density distribution of the electron beam cross section, the spatial distribution of electrons with energies in the selected range, and the total energy of the electron beam. The diagnostics is based on the thermal imager registration of the imaging electron beam thermal print in a material with low bulk density and low thermal conductivity. Testing of the thermal imaging diagnostics has been conducted on a pulsed electron accelerator TEU-500. The energy of the electrons was 300-500 keV, the density of the electron current was 0.1-0.4 kA/cm(2), the duration of the pulse (at half-height) was 60 ns, and the energy in the pulse was up to 100 J. To register the thermal print, a thermal imager Fluke-Ti10 was used. Testing showed that the sensitivity of a typical thermal imager provides the registration of a pulsed electron beam heat pattern within one pulse with energy density over 0.1 J/cm(2) (or with current density over 10 A/cm(2), pulse duration of 60 ns and electron energy of 400 keV) with the spatial resolution of 0.9-1 mm. In contrast to the method of using radiosensitive (dosimetric) materials, thermal imaging diagnostics does not require either expensive consumables, or plenty of processing time.

Polaronic and ionic conduction in NaMnO2: influence of native point defects

NASA Astrophysics Data System (ADS)

Zhu, Zhen; Peelaers, Hartwin; van de Walle, Chris G.

Layered NaMnO2 has promising applications as a cathode material for sodium ion batteries. We will discuss strategies to improve the electrical performance of NaMnO2, including how to optimize the conditions of synthesis and how impurity doping affects the performance. Using hybrid density functional theory, we explored the structural, electronic, and defect properties of bulk NaMnO2. It is antiferromagnetic in the ground state with a band gap of 3.75 eV. Small hole and electron polarons can form in the bulk either through self-trapping or adjacent to point defects. We find that both Na and Mn vacancies are shallow acceptors with the induced holes trapped as small polarons, while O vacancies are deep defect centers. Cation antisites, especially MnNa, are found to have low formation energies. As a result, we expect that MnNa exists in as-grown NaMnO2 in moderate concentrations, rather than forming only at a later stage of the charging process, at which point it causes undesirable structural phase transitions. Both electronic conduction, via polaron hopping, and ionic conduction, through VNa migration, are significantly affected by the presence of point defects. This work was supported by DOE.

Design Principles for Metal Oxide Redox Materials for Solar-Driven Isothermal Fuel Production.

PubMed

Michalsky, Ronald; Botu, Venkatesh; Hargus, Cory M; Peterson, Andrew A; Steinfeld, Aldo

2015-04-01

The performance of metal oxides as redox materials is limited by their oxygen conductivity and thermochemical stability. Predicting these properties from the electronic structure can support the screening of advanced metal oxides and accelerate their development for clean energy applications. Specifically, reducible metal oxide catalysts and potential redox materials for the solar-thermochemical splitting of CO 2 and H 2 O via an isothermal redox cycle are examined. A volcano-type correlation is developed from available experimental data and density functional theory. It is found that the energy of the oxygen-vacancy formation at the most stable surfaces of TiO 2 , Ti 2 O 3 , Cu 2 O, ZnO, ZrO 2 , MoO 3 , Ag 2 O, CeO 2 , yttria-stabilized zirconia, and three perovskites scales with the Gibbs free energy of formation of the bulk oxides. Analogously, the experimental oxygen self-diffusion constants correlate with the transition-state energy of oxygen conduction. A simple descriptor is derived for rapid screening of oxygen-diffusion trends across a large set of metal oxide compositions. These general trends are rationalized with the electronic charge localized at the lattice oxygen and can be utilized to predict the surface activity, the free energy of complex bulk metal oxides, and their oxygen conductivity.

Probing spin helical surface states in topological HgTe nanowires

NASA Astrophysics Data System (ADS)

Ziegler, J.; Kozlovsky, R.; Gorini, C.; Liu, M.-H.; Weishäupl, S.; Maier, H.; Fischer, R.; Kozlov, D. A.; Kvon, Z. D.; Mikhailov, N.; Dvoretsky, S. A.; Richter, K.; Weiss, D.

2018-01-01

Nanowires with helical surface states represent key prerequisites for observing and exploiting phase-coherent topological conductance phenomena, such as spin-momentum locked quantum transport or topological superconductivity. We demonstrate in a joint experimental and theoretical study that gated nanowires fabricated from high-mobility strained HgTe, known as a bulk topological insulator, indeed preserve the topological nature of the surface states, that moreover extend phase-coherently across the entire wire geometry. The phase-coherence lengths are enhanced up to 5 μ m when tuning the wires into the bulk gap, so as to single out topological transport. The nanowires exhibit distinct conductance oscillations, both as a function of the flux due to an axial magnetic field and of a gate voltage. The observed h /e -periodic Aharonov-Bohm-type modulations indicate surface-mediated quasiballistic transport. Furthermore, an in-depth analysis of the scaling of the observed gate-dependent conductance oscillations reveals the topological nature of these surface states. To this end we combined numerical tight-binding calculations of the quantum magnetoconductance with simulations of the electrostatics, accounting for the gate-induced inhomogeneous charge carrier densities around the wires. We find that helical transport prevails even for strongly inhomogeneous gating and is governed by flux-sensitive high-angular momentum surface states that extend around the entire wire circumference.

Bulk density of asteroid 243 Ida from the orbit of its satellite Dactyl

USGS Publications Warehouse

Belton, M.J.S.; Chapmant, C.R.; Thomas, P.C.; Davies, M.E.; Greenberg, R.; Klaasen, K.; Byrnes, D.; D'Amario, L.; Synnott, S.; Johnson, T.V.; McEwen, A.; Merline, W.J.; Davis, D.R.; Petit, J.-M.; Storrs, A.; Veverka, J.; Zellner, B.

1995-01-01

DURING its reconnaissance of the asteroid 243 Ida, the Galileo spacecraft returned images of a second object, 1993(243)1 Dactyl1 - the first confirmed satellite of an asteroid. Sufficient data were obtained on the motion of Dactyl to determine its orbit as a function of Ida's mass. Here we apply statistical and dynamical arguments to constrain the range of possible orbits, and hence the mass of Ida. Combined with the volume of Ida2, this yields a bulk density of 2.6??0.5 g cm-3. Allowing for the uncertainty in the porosity of Ida, this density range is consistent with a bulk chondritic composition, and argues against some (but not all) classes of meteoritic igneous rock types that have been suggested as compositionally representative of S-type asteroids like Ida.

Bulk density of asteroid 243 Ida from the orbit of its satellite Dactyl

USGS Publications Warehouse

Belton, M.J.S.; Chapman, C.R.; Thomas, P.C.; Davies, M.E.; Greenberg, R.; Klaasen, K.; Byrnes, D.; D'Amario, L.; Synnott, S.; Johnson, T.V.; McEwen, A.; Merline, W.J.; Davis, D.R.; Petit, J.-M.; Storrs, A.; Veverka, J.; Zellner, B.

1995-01-01

DURING its reconnaissance of the asteroid 243 Ida, the Galileo spacecraft returned images of a second object, 1993(243)1 Dactyl1 - the first confirmed satellite of an asteroid. Sufficient data were obtained on the motion of Dactyl to determine its orbit as a function of Ida's mass. Here we apply statistical and dynamical arguments to constrain the range of possible orbits, and hence the mass of Ida. Combined with the volume of Ida2, this yields a bulk density of 2.6 ?? 0.5 g cm-3. Allowing for the uncertainty in the porosity of Ida, this density range is consistent with a bulk chon-dritic composition, and argues against some (but not all) classes of meteoritic igneous rock types that have been suggested as compositionally representative of S-type asteroids like Ida. ?? 2002 Nature Publishing Group.

First-principles studies of electronic, transport and bulk properties of pyrite FeS2

NASA Astrophysics Data System (ADS)

Banjara, Dipendra; Mbolle, Augustine; Malozovsky, Yuriy; Franklin, Lashounda; Bagayoko, Diola

We present results of ab-initio, self-consistent density functional theory (DFT) calculations of electronic, transport, and bulk properties of pyrite FeS2. We employed a local density approximation (LDA) potential and the linear combination of atomic orbitals (LCAO) formalism, following the Bagayoko, Zhao and Williams (BZW) method, as enhanced by Ekuma and Franklin (BZW-EF). The BZW-EF method requires successive, self consistent calculations with increasing basis sets to reach the ground state of the system under study. We report the band structure, the band gap, total and partial densities of states, effective masses, and the bulk modulus. Work funded in part by the US Department of Energy (DOE), National Nuclear Security Administration (NNSA) (Award No.DE-NA0002630), the National Science Foundation (NSF) (Award No, 1503226), LaSPACE, and LONI-SUBR.

Density and Habitat Relationships of the Endemic White Mountain Fritillary (Boloria chariclea montinus) (Lepidoptera: Nymphalidae).

PubMed

McFarland, Kent P; Lloyd, John D; Hardy, Spencer P

2017-06-04

We conducted point counts in the alpine zone of the Presidential Range of the White Mountains, New Hampshire, USA, to estimate the distribution and density of the rare endemic White Mountain Fritillary ( Boloria chariclea montinus ). Incidence of occurrence and density of the endemic White Mountain Fritillary during surveys in 2012 and 2013 were greatest in the herbaceous-snowbank plant community. Densities at points in the heath-shrub-rush plant community were lower, but because this plant community is more widespread in the alpine zone, it likely supports the bulk of adult fritillaries. White Mountain Fritillary used cushion-tussock, the other alpine plant community suspected of providing habitat, only sparingly. Detectability of White Mountain Fritillaries varied as a consequence of weather conditions during the survey and among observers, suggesting that raw counts yield biased estimates of density and abundance. Point counts, commonly used to study and monitor populations of birds, were an effective means of sampling White Mountain Fritillary in the alpine environment where patches of habitat are small, irregularly shaped, and widely spaced, rendering line-transect methods inefficient and difficult to implement.

Soil Physical, Chemical, and Thermal Characterization, Teller Road Site, Seward Peninsula, Alaska, 2016

DOE Data Explorer

Graham, David; Kholodov, Alexander; Wilson, Cathy; Moon, Ji-Won; Romanovsky, Vladimir; Busey, Bob

2018-02-05

This dataset provides the results of physical, chemical, and thermal characterization of soils at the Teller Road Site, Seward Peninsula, Alaska. Soil pits were dug from 7-14 September 2016 at designated Intensive Stations 2 through 9 at the Teller Road MM 27 Site. This dataset includes field observations and descriptions of soil layers or horizons, field measurements of soil volumetric water content, soil temperature, thermal conductivity, and heat capacity. Laboratory measurements of soil properties include gravimetric water content, bulk density, volumetric water content, and total carbon and nitrogen.

Soil Physical, Chemical, and Thermal Characterization, Council Road Site, Seward Peninsula, Alaska, 2016

DOE Data Explorer

Alexander Kholodov; David Graham; Ji-Won Moon

2018-01-22

This dataset provides the results of physical, chemical, and thermal characterization of soils at the Council Road Site at MM71, Seward Peninsula, Alaska. Soil pits were dug on 11 September 2016 at three sites. This dataset includes field observations and descriptions of soil layers or horizons, field measurements of soil volumetric water content, soil temperature, thermal conductivity, and heat capacity. Laboratory measurements of soil properties include gravimetric water content, bulk density, volumetric water content, total carbon and nitrogen, and elemental composition from X-ray fluorescence for some elements.

Fundamental Thermal and Mechanical Properties of Boride Ceramics

DTIC Science & Technology

2014-02-28

Zr ,Y)B2 ( Zr ,Hf)B2 ( Zr ,Ti)B2 ZrB2 El ec tri ca l R es is tiv ity (µ Ω -c m ) Temperature (°C) Figure 17. Electrical resistivity as a function...family as Zr , namely Ti and Hf, had minimal effect on thermal conductivity, while others such as Nb , Ta, and W had an increasing impact based on their...diffusivity (α), heat capacity (Cp) from the NIST-JANAF tables, and bulk density (ρ) using Equation 6. (5) (6) Electrical resistivity

Semiflexible polymers confined in a slit pore with attractive walls: two-dimensional liquid crystalline order versus capillary nematization.

PubMed

Milchev, Andrey; Egorov, Sergei A; Binder, Kurt

2017-03-01

Semiflexible polymers under good solvent conditions interacting with attractive planar surfaces are investigated by Molecular Dynamics (MD) simulations and classical Density Functional Theory (DFT). A bead-spring type potential complemented by a bending potential is used, allowing variation of chain stiffness from completely flexible coils to rod-like polymers whose persistence length by far exceeds their contour length. Solvent is only implicitly included, monomer-monomer interactions being purely repulsive, while two types of attractive wall-monomer interactions are considered: (i) a strongly attractive Mie-type potential, appropriate for a strictly structureless wall, and (ii) a corrugated wall formed by Lennard-Jones particles arranged on a square lattice. It is found that in dilute solutions the former case leads to the formation of a strongly adsorbed surface layer, and the profile of density and orientational order in the z-direction perpendicular to the wall is predicted by DFT in nice agreement with MD. While for very low bulk densities a Kosterlitz-Thouless type transition from the isotropic phase to a phase with power-law decay of nematic correlations is suggested to occur in the strongly adsorbed layer, for larger densities a smectic-C phase in the surface layer is detected. No "capillary nematization" effect at higher bulk densities is found in this system, unlike systems with repulsive walls. This finding is attributed to the reduction of the bulk density (in the center of the slit pore) due to polymer adsorption on the attractive wall, for a system studied in the canonical ensemble. Consequently in a system with two attractive walls nematic order in the slit pore can occur only at a higher density than for a bulk system.

Evaluation of dredged material proposed for ocean disposal from Shark River Project area

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

Antrim, L.D.; Gardiner, W.W.; Barrows, E.S.

1996-09-01

The objective of the Shark River Project was to evaluate proposed dredged material to determine its suitability for unconfined ocean disposal at the Mud Dump Site. Tests and analyses were conducted on the Shark River sediments. The evaluation of proposed dredged material consisted of bulk sediment chemical and physical analysis, chemical analyses of dredging site water and elutriate, water-column and benthic acute toxicity tests, and bioaccumulation tests. Individual sediment core samples collected from the Shark River were analyzed for grain size, moisture content, and total organic carbon (TOC). One sediment composite was analyzed for bulk density, specific gravity, metals, chlorinatedmore » pesticides, polychlorinated biphenyl (PCB) congeners, polynuclear aromatic hydrocarbons (PAHs), and 1,4- dichlorobenzene. Dredging site water and elutriate, prepared from suspended-particulate phase (SPP) of the Shark River sediment composite, were analyzed for metals, pesticides, and PCBs. Benthic acute toxicity tests and bioaccumulation tests were performed.« less

Role of the interlayer coupling for the thermoelectric properties of CuSbS2 and CuSbSe2

NASA Astrophysics Data System (ADS)

Alsaleh, Najebah; Singh, Nirpendra; Schwingenschlogl, Udo

The electronic and transport properties of bulk and monolayer CuSbS2 and CuSbSe2 are determined using density functional theory and semi-classical Boltzmann transport theory, in order to investigate the role of the interlayer coupling for the thermoelectric properties. The calculated band gaps of the bulk compounds are in agreement with experiments and significantly higher than those of the monolayers, which thus show lower Seebeck coefficients. Since also the electrical conductivity is lower, the monolayers are characterised by lower power factors. Therefore, the interlayer coupling is found to be essential for the excellent thermoelectric response of CuSbS2 and CuSbSe2 even though it is of weak van der Waals type. The research reported in this publication was supported by funding from King Abdullah University of Science and Technology (KAUST).

ZrCuAl Bulk Metallic Glass spall induced by laser shock

NASA Astrophysics Data System (ADS)

Jodar, Benjamin; Loison, Didier; Yokoyama, Yoshihiko; Lescoute, Emilien; Berthe, Laurent; Sangleboeuf, Jean-Christophe

2017-06-01

To face High Velocity Impacts, the aerospace industry is always seeking for innovative materials usable as debris shielding components. Bulk Metallic Glasses (BMG) revealed interesting mechanical properties in case of static and quasi-static loading conditions: high elasticity, high tenacity, low density and high fracture threshold... The department of Mechanics and Glass of the Institut of Physics Rennes conducted on the ELFIE facility, laser shock experiments to study the behavior of a ternary ZrCuAl BMG under high strain rate, up-to fragmentation process. On the one hand, in-situ diagnostics were used to measure ejection velocities with PDV and debris morphologies were observed by Shadowgraphy. On the other hand, spalled areas (dimensions and features) were characterized through post-mortem analysis (optical observations, profilometry and SEM). These results are compared to experimental and numerical data on the crystalline forms of the ZrCuAl basic compounds.

Superconductivity in Ta3Pd3Te14 with quasi-one-dimensional PdTe2 chains.

PubMed

Jiao, Wen-He; He, Lan-Po; Liu, Yi; Xu, Xiao-Feng; Li, Yu-Ke; Zhang, Chu-Hang; Zhou, Nan; Xu, Zhu-An; Li, Shi-Yan; Cao, Guang-Han

2016-02-15

We report bulk superconductivity at 1.0 K in a low-dimensional ternary telluride Ta3Pd3Te14 containing edge-sharing PdTe2 chains along crystallographic b axis, similar to the recently discovered superconductor Ta4Pd3Te16. The electronic heat capacity data show an obvious anomaly at the transition temperature, which indicates bulk superconductivity. The specific-heat jump is ΔC/(γ(n)T(c)) ≈ 1.35, suggesting a weak coupling scenario. By measuring the low-temperature thermal conductivity, we conclude that Ta3Pd3Te14 is very likely a dirty s-wave superconductor. The emergence of superconductivity in Ta3Pd3Te14 with a lower T(c), compared to that of Ta4Pd3Te16, may be attributed to the lower density of states.

Electronic, Mechanical, and Dielectric Properties of Two-Dimensional Atomic Layers of Noble Metals

NASA Astrophysics Data System (ADS)

Kapoor, Pooja; Kumar, Jagdish; Kumar, Arun; Kumar, Ashok; Ahluwalia, P. K.

2017-01-01

We present density functional theory-based electronic, mechanical, and dielectric properties of monolayers and bilayers of noble metals (Au, Ag, Cu, and Pt) taken with graphene-like hexagonal structure. The Au, Ag, and Pt bilayers stabilize in AA-stacked configuration, while the Cu bilayer favors the AB stacking pattern. The quantum ballistic conductance of the noble-metal mono- and bilayers is remarkably increased compared with their bulk counterparts. Among the studied systems, the tensile strength is found to be highest for the Pt monolayer and bilayer. The noble metals in mono- and bilayer form show distinctly different electron energy loss spectra and reflectance spectra due to the quantum confinement effect on going from bulk to the monolayer limit. Such tunability of the electronic and dielectric properties of noble metals by reducing the degrees of freedom of electrons offers promise for their use in nanoelectronics and optoelectronics applications.

Study on dielectric properties of fresh vegetables and jamun

NASA Astrophysics Data System (ADS)

Usha, P.; Kumar, Sanjeev

2017-08-01

The Present work is concerned with the measurement of the complex dielectric permittivity, conductivity, and loss tangent and penetration depth of some vegetables and jamun frouit.. The measurement makes use of the “Von-Hipple method” for bulk sample. If the sample is not available with the dimension of the wave guide then reflectrometry technique is used for the pulverized (Powder) form of the sample and computed all the above parameters and relaxation time for the sample Jamun Seed (Scientific Name of Jamun is Syzygium cumini Lin). The measurement were performed for different packing densities at 9.85 GHz. at different temperature (20°c, 35°c and 50°c). The result was correlated with Landau-Lifshitz-Looyenga and Bottcher. There is fair agreement between the calculated values of dielectric parameters and the values obtained experimentally for solid bulk and pulverized one.

Theory of space charge limited currents in films and nanowires with dopants

NASA Astrophysics Data System (ADS)

Zhang, Xiaoguang; Pantelides, Sokrates

2015-03-01

We show that proper description of the space charge limited currents (SCLC) in a homogeneous bulk material must account fully for the effect of the dopants and the interplay between dopants and traps. The sharp rise in the current at the trap-filled-limit (TFL) is partially mitigated by the dopant energy levels and the Frenkel effect, namely the lowering of the ionization energy by the electric field, which is screened by the free carriers. In nanowires, lack of effective screening causes the trap occupation at small biases to reach a high level comparable to the TFL in bulk. This explains the high current density in SCLCs observed in nanowires. This work is supported by the LDRD program at ORNL. Portion of this research was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility.

Bulk density and soil resistance to penetration as affected by commercial thinning in northeastern Washington.

Treesearch

Johanna D. Landsberg; Richard E. Miller; Harry W. Anderson; Jeffrey S. Tepp

2003-01-01

Bulk density and soil resistance to penetration were measured in ten, 3- to 11-ha operational units in overstocked, mixed-conifer stands in northeast Washington. Resistance was measured with a recording penetrometer to the 33-cm depth (13 in) at 10 stations on each of 8 to 17, 30.5-m-long, randomly located transects in each unit. Subsequently, different combinations of...

Effect of Alkali Concentration on Fly Ash Geopolymers

NASA Astrophysics Data System (ADS)

Fatimah Azzahran Abdullah, Siti; Yun-Ming, Liew; Bakri, Mohd Mustafa Al; Cheng-Yong, Heah; Zulkifly, Khairunnisa; Hussin, Kamarudin

2018-03-01

This paper presents the effect of NaOH concentration on fly ash geopolymers with compressive up to 56 MPa at 12M. The physical and mechanical on fly ash geopolymer are investigated. Test results show that the compressive strength result complied with bulk density result whereby the higher the bulk density, the higher the strength. Thus, the lower water absorption and porosity due to the increasing of NaOH concentration.

[Effects of ex situ rice straw incorporation on organic matter content and main physical properties of hilly red soil].

PubMed

Zhu, Han-hua; Huang, Dao-you; Liu, Shou-long; Zhu, Qi-hong

2007-11-01

Two typical land-use types, i.e., newly cultivated slope land and mellow upland, were selected to investigate the effects of ex situ rice straw incorporation on the organic matter content, field water-holding capacity, bulk density, and porosity of hilly red soil, and to approach the correlations between these parameters. The results showed that ex situ incorporation of rice straw increased soil organic matter content, ameliorated soil physical properties, and improved soil water storage. Comparing with non-fertilization and applying chemical fertilizers, ex situ incorporation of rice straw increased the contents of organic matter (5.8%-28.9%) and > 0.25 mm water-stable aggregates in 0-20 cm soil layer, and increased the field water-holding capacity (6.8%-16.2%) and porosity (4.8%-7.7%) significantly (P < 0.05) while decreased the bulk density (4.5%-7.5%) in 10-15 cm soil layer. The organic matter content in 0-20 cm soil layer was significantly correlated to the bulk density, porosity, and field water-holding capacity in 10-15 cm soil layer (P < 0.01), and the field water-holding capacity in 0-20 cm and 10-15 cm soil layers was significantly correlated to the bulk density and porosity in these two layers (P < 0.05).

Characterization and analysis of thermoelectric transport using SPB model in nanostructured aluminum doped zinc tellurium

NASA Astrophysics Data System (ADS)

Bhaskar, Ankam; Pai, Yi-Hsuan; Liu, Chia-Jyi

2017-11-01

Low-temperature electronic and thermal transport measurements are carried out on nanostructured Zn1-x Al x Te (0  ⩽  x  ⩽  0.15) fabricated using hydrothermal synthesis followed by evacuated-and-encapsulated sintering. A single parabolic band with acoustic phonon scattering is used to analyze thermoelectric transport data. It is found that reduced Fermi energy gets closer to the valence band edge and density of states effective mass, effective density of states, and Hall factor decrease with increasing x in doped samples. The chemical carrier concentration, carrier density independent mobility, β, and theoretical zT values increase with increasing x in doped samples. The nanostructured Zn1-x Al x Te exhibits significant reduction of thermal conductivity at 300 K (1.82-3.71 W m-1 K-1) as compared to bulk ZnTe (18 W m-1 K-1). The point-defect scattering and phonon-grain scattering play an important role in reducing the lattice thermal conductivity. In addition, partial substitution of Al3+ for Zn2+ significantly improves both the power factor and zT values.

Natural gas storage with activated carbon from a bituminous coal

USGS Publications Warehouse

Sun, Jielun; Rood, M.J.; Rostam-Abadi, M.; Lizzio, A.A.

1996-01-01

Granular activated carbons ( -20 + 100 mesh; 0.149-0.84 mm) were produced by physical activation and chemical activation with KOH from an Illinois bituminous coal (IBC-106) for natural gas storage. The products were characterized by BET surface area, micropore volume, bulk density, and methane adsorption capacities. Volumetric methane adsorption capacities (Vm/Vs) of some of the granular carbons produced by physical activation are about 70 cm3/cm3 which is comparable to that of BPL, a commercial activated carbon. Vm/Vs values above 100 cm3/cm3 are obtainable by grinding the granular products to - 325 mesh (<0.044 mm). The increase in Vm/Vs is due to the increase in bulk density of the carbons. Volumetric methane adsorption capacity increases with increasing pore surface area and micropore volume when normalizing with respect to sample bulk volume. Compared with steam-activated carbons, granular carbons produced by KOH activation have higher micropore volume and higher methane adsorption capacities (g/g). Their volumetric methane adsorption capacities are lower due to their lower bulk densities. Copyright ?? 1996 Elsevier Science Ltd.

Dielectric and impedance spectral characteristics of bulk ZnIn2Se4

NASA Astrophysics Data System (ADS)

El-Nahass, M. M.; Attia, A. A.; Salem, G. F.; Ali, H. A. M.; Ismail, M. I.

2014-02-01

The frequency and temperature dependence of ac conductivity, dielectric constant and dielectric loss of ZnIn2Se4 in a pellet form were investigated in the frequency range of 102-106 Hz and temperature range of 293-356 K. The behavior of ac conductivity was interpreted by the correlated barrier hopping (CBH) model. Temperature dependence of ac conductivity indicates that ac conduction is a thermally activated process. The density of localized states N(EF) and ac activation energy were estimated for various frequencies. Dielectric constant and dielectric loss showed a decrease with increasing frequency and an increase with increasing in temperature. The frequency dependence of real and imaginary parts of the complex impedance was investigated. The relaxation time decreases with the increase in temperature. The impedance spectrum exhibits the appearance of the single semicircular arc. The radius of semicircular arcs decreases with increasing temperature which suggests a mechanism of temperature-dependent on relaxation.

Ionic Conductivity and its Role in Oxidation Reactions

NASA Astrophysics Data System (ADS)

Tamimi, Mazin Abdulla

In the field of solid oxide fuel cells (SOFCs), a substantial portion of research is focused on the ability of some oxide materials to conduct oxygen anions through their structure. For electrolytes, the benefits of improving bulk transport of ions are obvious: decrease the resistive losses of the electrolyte, and device efficiency goes up and higher power densities are possible. Even for cathode materials, better bulk ion transport leads to an increase in the oxygen exchange rate at the cathode surface, and the oxygen reduction reaction at the cathode surface is the rate limiting step for SOFC operation at intermediate temperatures (500-700ºC). As operation in this regime is a key step towards lowering the manufacturing cost and increasing the lifetime of devices, much effort is spent searching for new, more conductive materials, and analyzing existing materials to discover the structure-activity relationships that influence ionic conductivity. In the first part of this work, an overview is given of the neutron powder diffraction (NPD) techniques that are used to probe the structure of the materials in later parts. In the second part, NPD was used to analyze the structures of perovskite-type cathode materials, and show that increases in bulk conductivity led to increases in the surface oxygen exchange rate of these materials. In the final part, the methods used for SOFC cathode design were applied towards the design of oxide catalysts used for certain hydrocarbon partial oxidation reactions. The reactions studied follow the Mars van Krevelen mechanism, where oxygen atoms in the catalyst are consumed as part of the reaction and are subsequently replenished by oxygen in the gas phase. Similar to SOFC cathode operation, these processes include an oxygen reduction step, so it was hypothesized that increasing the ionic conductivity of the catalysts would improve their performance, just as it does for SOFC cathode materials. While the results are preliminary, the combination of a reference catalyst for the oxidative coupling of methane with a support with very high oxygen conductivity demonstrated a small increase in performance at low temperatures.

Restoring the consistency with the contact density theorem of a classical density functional theory of ions at a planar electrical double layer.

PubMed

Gillespie, Dirk

2014-11-01

Classical density functional theory (DFT) of fluids is a fast and efficient theory to compute the structure of the electrical double layer in the primitive model of ions where ions are modeled as charged, hard spheres in a background dielectric. While the hard-core repulsive component of this ion-ion interaction can be accurately computed using well-established DFTs, the electrostatic component is less accurate. Moreover, many electrostatic functionals fail to satisfy a basic theorem, the contact density theorem, that relates the bulk pressure, surface charge, and ion densities at their distances of closest approach for ions in equilibrium at a smooth, hard, planar wall. One popular electrostatic functional that fails to satisfy the contact density theorem is a perturbation approach developed by Kierlik and Rosinberg [Phys. Rev. A 44, 5025 (1991)PLRAAN1050-294710.1103/PhysRevA.44.5025] and Rosenfeld [J. Chem. Phys. 98, 8126 (1993)JCPSA60021-960610.1063/1.464569], where the full free-energy functional is Taylor-expanded around a bulk (homogeneous) reference fluid. Here, it is shown that this functional fails to satisfy the contact density theorem because it also fails to satisfy the known low-density limit. When the functional is corrected to satisfy this limit, a corrected bulk pressure is derived and it is shown that with this pressure both the contact density theorem and the Gibbs adsorption theorem are satisfied.

Inspection of wood density by spectrophotometry and a diffractive optical element based sensor

NASA Astrophysics Data System (ADS)

Palviainen, Jari; Silvennoinen, Raimo

2001-03-01

Correlation among gravimetric, spectrophotometric and radiographic data from dried wood samples of Scots pine (Pinus sylvestris L) was observed. A diffractive optical element (DOE) based sensor was applied to investigate density variations as well as optical anisotropy inside year rings of the wood samples. The correlation between bulk density of wood and spectrophotometric data (reflectance and transmittance) was investigated for the wavelength range 200-850 nm and the highest correlation was found at wavelengths from 800 to 850 nm. The correlation at this wavelength was smaller than the correlation between bulk density and radiography data. The DOE sensor was found to be capable of sensing anisotropy of the wood samples inside the year ring.

Calculation of density of states of transition metals: From bulk sample to nanocluster

NASA Astrophysics Data System (ADS)

Krasavin, Andrey V.; Borisyuk, Petr V.; Vasiliev, Oleg S.; Zhumagulov, Yaroslav V.; Kashurnikov, Vladimir A.; Kurelchuk, Uliana N.; Lebedinskii, Yuriy Yu.

2018-03-01

A technique is presented of restoring the electronic density of states of the valence band from data of X-ray photoelectron spectroscopy (XPS). The originality of the technique consists in using a stochastic procedure to solve an integral equation relating the density of states and the experimental X-ray photoelectron spectra via the broadening function. To obtain the broadening function, only the XPS spectra of the core levels are needed. The results are presented for bulk sample of gold and tungsten and nanoclusters of tantalum; the possibility of using the results to determine the density of states of low-dimensional structures, including ensembles of metal nanoclusters, is demonstrated.

Analysis of the conduction mechanism and dielectric properties of N, N', N" tris(4-methylphenyl)phosphoric triamide

NASA Astrophysics Data System (ADS)

Ali, H. A. M.

2016-03-01

The structure for the powder of N,N', N"-tris(4-methylphenyl)phosphoric triamide, TMP-TA, was characterized using X-ray diffraction (XRD) and differential thermal analysis (DTA) techniques. The ac conductivity and dielectric properties were measured in the frequency range of 42-105 Hz for the bulk TMP-TA in a pellet form at different temperatures. The frequency dependence of ac conductivity was expressed by a Jonscher's universal power law. The frequency exponent (s) was determined from the fitting of experimental data of ac conductivity. The correlated barrier hopping (CBH) model was found to be responsible for the ac conduction mechanism in TMP-TA. The activation energy was calculated from the temperature dependence of ac conductivity. The values of the density of states at the Fermi level were determined for different frequencies. The components of the electric modulus (M' and M") were calculated and used to estimate the relaxation time.

Hydrodynamic correlation functions of hard-sphere fluids at short times

NASA Astrophysics Data System (ADS)

Leegwater, Jan A.; van Beijeren, Henk

1989-11-01

The short-time behavior of the coherent intermediate scattering function for a fluid of hard-sphere particles is calculated exactly through order t 4, and the other hydrodynamic correlation functions are calculated exactly through order t 2. It is shown that for all of the correlation functions considered the Enskog theory gives a fair approximation. Also, the initial time behavior of various Green-Kubo integrands is studied. For the shear-viscosity integrand it is found that at density nσ3=0.837 the prediction of the Enskog theory is 32% too low. The initial value of the bulk viscosity integrand is nonzero, in contrast to the Enskog result. The initial value of the thermal conductivity integrand at high densities is predicted well by Enskog theory.

Radar remote sensing for crop classification and canopy condition assessment: Ground-data documentation

NASA Technical Reports Server (NTRS)

Ulaby, F. T. (Principal Investigator); Jung, B.; Gillespie, K.; Hemmat, M.; Aslam, A.; Brunfeldt, D.; Dobson, M. C.

1983-01-01

A vegetation and soil-moisture experiment was conducted in order to examine the microwave emission and backscattering from vegetation canopies and soils. The data-acquisition methodology used in conjunction with the mobile radar scatterometer (MRS) systems is described and associated ground-truth data are documented. Test fields were located in the Kansas River floodplain north of Lawrence, Kansas. Ten fields each of wheat, corn, and soybeans were monitored over the greater part of their growing seasons. The tabulated data summarize measurements made by the sensor systems and represent target characteristics. Target parameters describing the vegetation and soil characteristics include plant moisture, density, height, and growth stage, as well as soil moisture and soil-bulk density. Complete listings of pertinent crop-canopy and soil measurements are given.

NASCAP-2K Version 4.2 Users Manual

DTIC Science & Technology

2014-10-31

the surface element is metal or dielectric coating , the conductivity and capacitance (if a coating ), and the electron emission stimulated by incident...film covering an underlying conductor in meters. It is ignored for conductors . Bulk conductivity . This property is the bulk conductivity of the...surface material in ohms-1 m-1. A negative value indicates that the material is a conductor . If the bulk conductivity is in excess of 10-4 Ω-1 m-1, the

Direct Measurements of Pore Fluid Density by Vibrating Tube Densimetry

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

Gruszkiewicz, Miroslaw S.; Rother, Gernot; Wesolowski, David J.

2012-02-27

The densities of pore-confined fluids were measured for the first time by means of a vibrating tube method. Isotherms of total adsorption capacity were measured directly making the method complementary to the conventional gravimetric or volumetric/piezometric adsorption techniques, which yield the excess adsorption (the Gibbsian surface excess). A custom-made high-pressure, high-temperature vibrating tube densimeter (VTD) was used to measure the densities of subcritical and supercritical propane (between 35 °C and 97 °C) and supercritical carbon dioxide (between 32 C and 50°C) saturating hydrophobic silica aerogel (0.2 g/cm 3, 90% porosity) synthesized inside Hastelloy U-tubes. Additionally, excess adsorption isotherms for supercriticalmore » CO 2 and the same porous solid were measured gravimetrically using a precise magnetically-coupled microbalance. Pore fluid densities and total adsorption isotherms increased monotonically with increasing density of the bulk fluid, in contrast to excess adsorption isotherms, which reached a maximum at a subcritical density of the bulk fluid, and then decreased towards zero or negative values at supercritical densities. Compression of the confined fluid significantly beyond the density of the bulk liquid at the same temperature was observed at subcritical temperatures. The features of the isotherms of confined fluid density are interpreted to elucidate the observed behavior of excess adsorption. The maxima of excess adsorption were found to occur below the critical density of the bulk fluid at the conditions corresponding to the beginning of the plateau of total adsorption, marking the end of the transition of pore fluid to a denser, liquid-like pore phase. The results for propane and carbon dioxide showed similarity in the sense of the principle of corresponding states. No measurable effect of pore confinement on the liquid-vapor critical point was found. Quantitative agreement was obtained between excess adsorption isotherms determined from VTD total adsorption results and those measured gravimetrically at the same temperature, confirming the validity of the vibrating tube measurements. Vibrating tube densimetry was demonstrated as a novel experimental approach capable of providing the average density of pore-confined fluids.« less

Accurate bulk density determination of irregularly shaped translucent and opaque aerogels

NASA Astrophysics Data System (ADS)

Petkov, M. P.; Jones, S. M.

2016-05-01

We present a volumetric method for accurate determination of bulk density of aerogels, calculated from extrapolated weight of the dry pure solid and volume estimates based on the Archimedes' principle of volume displacement, using packed 100 μm-sized monodispersed glass spheres as a "quasi-fluid" media. Hard particle packing theory is invoked to demonstrate the reproducibility of the apparent density of the quasi-fluid. Accuracy rivaling that of the refractive index method is demonstrated for both translucent and opaque aerogels with different absorptive properties, as well as for aerogels with regular and irregular shapes.

Trapping effects in irradiated and avalanche-injected MOS capacitors

NASA Technical Reports Server (NTRS)

Bakowski, M.; Cockrum, R. H.; Zamani, N.; Maserjian, J.; Viswanathan, C. R.

1978-01-01

The trapping parameters for holes, and for electrons in the presence of trapped holes, have been measured from a set of wafers with different oxide thickness processed under controlled conditions. The trap cross-sections and densities indicate at least three trap species, including an interfacial species, a dominant bulk species which is determined to tail off from the silicon interface, and a third, lower density bulk species that is distributed throughout the oxide.

Theory of the interface between a classical plasma and a hard wall

NASA Astrophysics Data System (ADS)

Ballone, P.; Pastore, G.; Tosi, M. P.

1983-09-01

The interfacial density profile of a classical one-component plasma confined by a hard wall is studied in planar and spherical geometries. The approach adapts to interfacial problems a modified hypernetted-chain approximation developed by Lado and by Rosenfeld and Ashcroft for the bulk structure of simple liquids. The specific new aim is to embody selfconsistently into the theory a contact theorem, fixing the plasma density at the wall through an equilibrium condition which involves the electrical potential drop across the interface and the bulk pressure. The theory is brought into fully quantitative contact with computer simulation data for a plasma confined in a spherical cavity of large but finite radius. The interfacial potential at the point of zero charge is accurately reproduced by suitably combining the contact theorem with relevant bulk properties in a simple, approximate representation of the interfacial charge density profile.

Theory of the interface between a classical plasma and a hard wall

NASA Astrophysics Data System (ADS)

Ballone, P.; Pastore, G.; Tosi, M. P.

1984-12-01

The interfacial density profile of a classical one-component plasma confined by a hard wall is studied in planar and spherical geometries. The approach adapts to interfacial problems a modified hypernetted-chain approximation developed by Lado and by Rosenfeld and Ashcroft for the bulk structure of simple liquids. The specific new aim is to embody self-consistently into the theory a “contact theorem”, fixing the plasma density at the wall through an equilibrium condition which involves the electrical potential drop across the interface and the bulk pressure. The theory is brought into fully quantitative contact with computer simulation data for a plasma confined in a spherical cavity of large but finite radius. It is also shown that the interfacial potential at the point of zero charge is accurately reproduced by suitably combining the contact theorem with relevant bulk properties in a simple, approximate representation of the interfacial charge density profile.

Processing and characterization of multi-cellular monolithic bioceramics for bone regenerative scaffolds

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

Ari-Wahjoedi, Bambang, E-mail: bambang-ariwahjoedi@petronas.com.my; Centre for Intelligent Signal and Imaging Research, Universiti Teknologi PETRONAS, Bandar Seri Iskandar; Ginta, Turnad Lenggo

2014-10-24

Multicellular monolithic ceramic body is a ceramic material which has many gas or liquid passages partitioned by thin walls throughout the bulk material. There are many currently known advanced industrial applications of multicellular ceramics structures i.e. as supports for various catalysts, electrode support structure for solid oxide fuel cells, refractories, electric/electronic materials, aerospace vehicle re-entry heat shields and biomaterials for dental as well as orthopaedic implants by naming only a few. Multicellular ceramic bodies are usually made of ceramic phases such as mullite, cordierite, aluminum titanate or pure oxides such as silica, zirconia and alumina. What make alumina ceramics ismore » excellent for the above functions are the intrinsic properties of alumina which are hard, wear resistant, excellent dielectric properties, resists strong acid and alkali attacks at elevated temperatures, good thermal conductivities, high strength and stiffness as well as biocompatible. In this work the processing technology leading to truly multicellular monolithic alumina ceramic bodies and their characterization are reported. Ceramic slip with 66 wt.% solid loading was found to be optimum as impregnant to the polyurethane foam template. Mullitic ceramic composite of alumina-sodium alumino disilicate-Leucite-like phases with bulk and true densities of 0.852 and 1.241 g cm{sup −3} respectively, pore linear density of ±35 cm{sup −1}, linear and bulk volume shrinkages of 7-16% and 32 vol.% were obtained. The compressive strength and elastic modulus of the bioceramics are ≈0.5-1.0 and ≈20 MPa respectively.« less

Implications of the observed Pluto-Charon density contrast

NASA Astrophysics Data System (ADS)

Bierson, C. J.; Nimmo, F.; McKinnon, W. B.

2018-07-01

Observations by the New Horizons spacecraft have determined that Pluto has a larger bulk density than Charon by 153 ± 44 kg m-3 (2σ uncertainty). We use a thermal model of Pluto and Charon to determine if this density contrast could be due to porosity variations alone, with Pluto and Charon having the same bulk composition. We find that Charon can preserve a larger porous ice layer than Pluto due to its lower gravity and lower heat flux but that the density contrast can only be explained if the initial ice porosity is ≳ 30%, extends to ≳100 km depth and Pluto retains a subsurface ocean today. We also find that other processes such as a modern ocean on Pluto, self-compression, water-rock interactions, and volatile (e.g., CO) loss cannot, even in combination, explain this difference in density. Although an initially high porosity cannot be completely ruled out, we conclude that it is more probable that Pluto and Charon have different bulk compositions. This difference could arise either from forming Charon via a giant impact, or via preferential loss of H2O on Pluto due to heating during rapid accretion.

Doping induced carrier and band-gap modulation in bulk versus nano for topological insulators: A test case of Stibnite

NASA Astrophysics Data System (ADS)

Maji, Tuhin Kumar; Pal, Samir Kumar; Karmakar, Debjani

2018-04-01

We aim at comparing the electronic properties of topological insulator Sb2S3 in bulk and Nanorod using density-functional scheme and investigating the effects of Se-doping at chalcogen-site. While going from bulk to nano, there is a drastic change in the band gap due to surface-induced strain. However, the trend of band gap modulation with increased Se doping is more prominent in bulk. Interestingly, Se-doping introduces different type of carriers in bulk and nano.

Near Surface Investigation of Agricultural Soils using a Multi-Frequency Electromagnetic Sensor

NASA Astrophysics Data System (ADS)

Sadatcharam, K.; Unc, A.; Krishnapillai, M.; Cheema, M.; Galagedara, L.

2017-12-01

Electromagnetic induction (EMI) sensors have been used as precision agricultural tools over decades. They are being used to measure spatiotemporal variability of soil properties and soil stratification in the sense of apparent electrical conductivity (ECa). We mapped the ECa variability by horizontal coplanar (HCP) and by vertical coplanar (VCP) orientation of a multi-frequency EMI sensor and identified its interrelation with physical properties of soil. A broadband, multi-frequency handheld EMI sensor (GEM-2) was used on a loamy sand soil cultivated with silage-corn in western Newfoundland, Canada. Log and line spaced, three frequency ranges (weak, low, and high), based on the factory calibration were tested using HCP and VCP orientation to produce spatiotemporal data of ECa. In parallel, we acquired data on soil moisture content, texture and bulk density. We then assessed the statistical significance of the relationship between ECa and soil physical properties. The test site had three areas of distinct soil properties corresponding to the elevation, in particular. The same spatial variability was also identified by ECa mapping at different frequencies and the two modes of coil orientations. Data analysis suggested that the high range frequency (38 kHz (log-spaced) and 49 kHz (line-spaced)) for both HCP and VCP orientations produced accurate ECa maps, better than the weak and low range frequencies tested. Furthermore, results revealed that the combined effects of soil texture, moisture content and bulk density affect ECameasurements as obtained by both frequencies and two coil orientations. Keywords: Apparent electrical conductivity, Electromagnetic induction, Horizontal coplanar, Soil properties, Vertical coplanar

Grinding energy and physical properties of chopped and hammer-milled barley, wheat, oat, and canola straws

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

J.S. Tumuluru; L.G. Tabil; Y. Song

2014-01-01

In the present study, specific energy for grinding and physical properties of wheat, canola, oat and barley straw grinds were investigated. The initial moisture content of the straw was about 0.13–0.15 (fraction total mass basis). Particle size reduction experiments were conducted in two stages: (1) a chopper without a screen, and (2) a hammer mill using three screen sizes (19.05, 25.4, and 31.75 mm). The lowest grinding energy (1.96 and 2.91 kWh t-1) was recorded for canola straw using a chopper and hammer mill with 19.05-mm screen size, whereas the highest (3.15 and 8.05 kWh t-1) was recorded for barleymore » and oat straws. The physical properties (geometric mean particle diameter, bulk, tapped and particle density, and porosity) of the chopped and hammer-milled wheat, barley, canola, and oat straw grinds measured were in the range of 0.98–4.22 mm, 36–80 kg m-3, 49–119 kg m-3, 600–1220 kg m-3, and 0.9–0.96, respectively. The average mean particle diameter was highest for the chopped wheat straw (4.22-mm) and lowest for the canola grind (0.98-mm). The canola grinds produced using the hammer mill (19.05-mm screen size) had the highest bulk and tapped density of about 80 and 119 kg m-3; whereas, the wheat and oat grinds had the lowest of about 58 and 88–90 kg m-3. The results indicate that the bulk and tapped densities are inversely proportional to the particle size of the grinds. The flow properties of the grinds calculated are better for chopped straws compared to hammer milled using smaller screen size (19.05 mm).« less

Examining the Effects of Stiffness and Mass Difference on the Thermal Interface Conductance Between Lennard-Jones Solids

NASA Astrophysics Data System (ADS)

Gordiz, Kiarash; Henry, Asegun

2015-12-01

To date, the established methods that describe thermal interface conductance (TIC) and include mode-level dependence have not included anharmonicity. The current intuition is therefore based on the behavior in the harmonic limit, whereby the extent of overlap in the bulk phonon density of states (DoS) (e.g., frequency overlap) dictates the TIC and more frequency overlap leads to higher TIC. Here, we study over 2,000 interfaces described by the Lennard-Jones potential using equilibrium molecular dynamics simulations, whereby we systematically change the mass and stiffness of each side. We show that the trends in TIC do not generally follow that of the bulk phonon DoS overlap, but instead more closely follow the vibrational power spectrum overlap for the interfacial atoms. We then identify the frequency overlap in the interfacial power spectra as an improved descriptor for understanding the qualitative trends in TIC. Although improved, the results show that the basic intuition of frequency overlap is still insufficient to explain all of the features, as the remaining variations are shown to arise from anharmonicity, which is a critical effect to include in interface calculations above cryogenic temperatures.

Hydrodynamics with conserved current via AdS/CFT correspondence in the Maxwell-Gauss-Bonnet gravity

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

Hu Yapeng; Sun Peng; Zhang Jianhui

2011-06-15

Using the AdS/CFT correspondence, we study the hydrodynamics with conserved current from the dual Maxwell-Gauss-Bonnet gravity. After constructing the perturbative solution to the first order based on the boosted black brane solution in the bulk Maxwell-Gauss-Bonnet gravity, we extract the stress tensor and conserved current of the dual conformal fluid on its boundary, and also find the effect of the Gauss-Bonnet term on the dual conformal fluid. Our results show that the Gauss-Bonnet term can affect the parameters such as the shear viscosity {eta}, entropy density s, thermal conductivity {kappa} and electrical conductivity {sigma}. However, it does not affect themore » so-called Wiedemann-Franz law which relates {kappa} to {sigma}, while it affects the ratio {eta}/s. In addition, another interesting result is that {eta}/s can also be affected by the bulk Maxwell field in our case, which is consistent with some previous results predicted through the Kubo formula. Moreover, the anomalous magnetic and vortical effects by adding the Chern-Simons term are also considered in our case in the Maxwell-Gauss-Bonnet gravity.« less

Tissue Acoustoelectric Effect Modeling From Solid Mechanics Theory.

PubMed

Song, Xizi; Qin, Yexian; Xu, Yanbin; Ingram, Pier; Witte, Russell S; Dong, Feng

2017-10-01

The acoustoelectric (AE) effect is a basic physical phenomenon, which underlies the changes made in the conductivity of a medium by the application of focused ultrasound. Recently, based on the AE effect, several biomedical imaging techniques have been widely studied, such as ultrasound-modulated electrical impedance tomography and ultrasound current source density imaging. To further investigate the mechanism of the AE effect in tissue and to provide guidance for such techniques, we have modeled the tissue AE effect using the theory of solid mechanics. Both bulk compression and thermal expansion of tissue are considered and discussed. Computation simulation shows that the muscle AE effect result, conductivity change rate, is 3.26×10 -3 with 4.3-MPa peak pressure, satisfying the theoretical value. Bulk compression plays the main role for muscle AE effect, while thermal expansion makes almost no contribution to it. In addition, the AE signals of porcine muscle are measured at different focal positions. With the same magnitude order and the same change trend, the experiment result confirms that the simulation result is effective. Both simulation and experimental results validate that tissue AE effect modeling using solid mechanics theory is feasible, which is of significance for the further development of related biomedical imaging techniques.

Probing Carrier Transport and Structure-Property Relationship of Highly Ordered Organic Semiconductors at the Two-Dimensional Limit.

PubMed

Zhang, Yuhan; Qiao, Jingsi; Gao, Si; Hu, Fengrui; He, Daowei; Wu, Bing; Yang, Ziyi; Xu, Bingchen; Li, Yun; Shi, Yi; Ji, Wei; Wang, Peng; Wang, Xiaoyong; Xiao, Min; Xu, Hangxun; Xu, Jian-Bin; Wang, Xinran

2016-01-08

One of the basic assumptions in organic field-effect transistors, the most fundamental device unit in organic electronics, is that charge transport occurs two dimensionally in the first few molecular layers near the dielectric interface. Although the mobility of bulk organic semiconductors has increased dramatically, direct probing of intrinsic charge transport in the two-dimensional limit has not been possible due to excessive disorders and traps in ultrathin organic thin films. Here, highly ordered single-crystalline mono- to tetralayer pentacene crystals are realized by van der Waals (vdW) epitaxy on hexagonal BN. We find that the charge transport is dominated by hopping in the first conductive layer, but transforms to bandlike in subsequent layers. Such an abrupt phase transition is attributed to strong modulation of the molecular packing by interfacial vdW interactions, as corroborated by quantitative structural characterization and density functional theory calculations. The structural modulation becomes negligible beyond the second conductive layer, leading to a mobility saturation thickness of only ∼3  nm. Highly ordered organic ultrathin films provide a platform for new physics and device structures (such as heterostructures and quantum wells) that are not possible in conventional bulk crystals.

Bulk Thermoelectric Materials Reinforced with SiC Whiskers

NASA Astrophysics Data System (ADS)

Akao, Takahiro; Fujiwara, Yuya; Tarui, Yuki; Onda, Tetsuhiko; Chen, Zhong-Chun

2014-06-01

SiC whiskers have been incorporated into Zn4Sb3 compound as reinforcements to overcome its extremely brittle nature. The bulk samples were prepared by either hot-extrusion or hot-pressing techniques. The obtained products containing 1 vol.% to 5 vol.% SiC whiskers were confirmed to exhibit sound appearance, high density, and fine-grained microstructure. Mechanical properties such as the hardness and fracture resistance were improved by the addition of SiC whiskers, as a result of dispersion strengthening and microstructural refinement induced by a pinning effect. Furthermore, crack deflection and/or bridging/pullout mechanisms are invoked by the whiskers. Regarding the thermoelectric properties, the Seebeck coefficient and electrical resistivity values comparable to those of the pure compound are retained over the entire range of added whisker amount. However, the thermal conductivity becomes large with increasing amount of SiC whiskers because of the much higher conductivity of SiC relative to the Zn4Sb3 matrix. This results in a remarkable degradation of the dimensionless figure of merit in the samples with addition of SiC whiskers. Therefore, the optimum amount of SiC whiskers in the Zn4Sb3 matrix should be determined by balancing the mechanical properties and thermoelectric performance.

Probing Carrier Transport and Structure-Property Relationship of Highly Ordered Organic Semiconductors at the Two-Dimensional Limit

NASA Astrophysics Data System (ADS)

Zhang, Yuhan; Qiao, Jingsi; Gao, Si; Hu, Fengrui; He, Daowei; Wu, Bing; Yang, Ziyi; Xu, Bingchen; Li, Yun; Shi, Yi; Ji, Wei; Wang, Peng; Wang, Xiaoyong; Xiao, Min; Xu, Hangxun; Xu, Jian-Bin; Wang, Xinran

2016-01-01

One of the basic assumptions in organic field-effect transistors, the most fundamental device unit in organic electronics, is that charge transport occurs two dimensionally in the first few molecular layers near the dielectric interface. Although the mobility of bulk organic semiconductors has increased dramatically, direct probing of intrinsic charge transport in the two-dimensional limit has not been possible due to excessive disorders and traps in ultrathin organic thin films. Here, highly ordered single-crystalline mono- to tetralayer pentacene crystals are realized by van der Waals (vdW) epitaxy on hexagonal BN. We find that the charge transport is dominated by hopping in the first conductive layer, but transforms to bandlike in subsequent layers. Such an abrupt phase transition is attributed to strong modulation of the molecular packing by interfacial vdW interactions, as corroborated by quantitative structural characterization and density functional theory calculations. The structural modulation becomes negligible beyond the second conductive layer, leading to a mobility saturation thickness of only ˜3 nm . Highly ordered organic ultrathin films provide a platform for new physics and device structures (such as heterostructures and quantum wells) that are not possible in conventional bulk crystals.

Evaluation of dredged material proposed for ocean disposal from Hudson River, New York

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

Gardiner, W.W.; Barrows, E.S.; Antrim, L.D.

1996-09-01

The Hudson River (Federal Project No. 41) was one of seven waterways that the U.S. Army Corps of Engineers-New York District (USACE-NYD) requested the Battelle Marine Sciences Laboratory (MSL) to sample and evaluate for dredging and disposal in March 1994. Sediment samples were collected from the Hudson River. Tests and analyses were conducted on Hudson River sediment core samples. The evaluation of proposed dredged material from the Hudson River included bulk sediment chemical analyses, chemical analyses of site water and elutriate, water-column and benthic acute toxicity tests, and bioaccumulation studies. Individual sediment core samples collected from Hudson River were analyzedmore » for grain size, moisture content, and total organic carbon (TOC). A composite sediment sample, representing the entire area proposed for dredging, was analyzed for bulk density, specific gravity, metals, chlorinated pesticides, polychlorinated biphenyl (PCB) congeners, polynuclear aromatic hydrocarbons (PAH), and 1,4-dichlorobenzene. Site water and elutriate water, prepared from the suspended-particulate phase (SPP) of Hudson River sediment, were analyzed for metals, pesticides, and PCBS. Water-column or SPP toxicity tests were performed with three species. Benthic acute toxicity tests were performed. Bioaccumulation tests were also conducted.« less

Quantifying the heterogeneity of soil compaction, physical soil properties and soil moisture across multiple spatial scales

NASA Astrophysics Data System (ADS)

Coates, Victoria; Pattison, Ian; Sander, Graham

2016-04-01

England's rural landscape is dominated by pastoral agriculture, with 40% of land cover classified as either improved or semi-natural grassland according to the Land Cover Map 2007. Since the Second World War the intensification of agriculture has resulted in greater levels of soil compaction, associated with higher stocking densities in fields. Locally compaction has led to loss of soil storage and an increased in levels of ponding in fields. At the catchment scale soil compaction has been hypothesised to contribute to increased flood risk. Previous research (Pattison, 2011) on a 40km2 catchment (Dacre Beck, Lake District, UK) has shown that when soil characteristics are homogeneously parameterised in a hydrological model, downstream peak discharges can be 65% higher for a heavy compacted soil than for a lightly compacted soil. However, at the catchment scale there is likely to be a significant amount of variability in compaction levels within and between fields, due to multiple controlling factors. This research focusses in on one specific type of land use (permanent pasture with cattle grazing) and areas of activity within the field (feeding area, field gate, tree shelter, open field area). The aim was to determine if the soil characteristics and soil compaction levels are homogeneous in the four areas of the field. Also, to determine if these levels stayed the same over the course of the year, or if there were differences at the end of the dry (October) and wet (April) periods. Field experiments were conducted in the River Skell catchment, in Yorkshire, UK, which has an area of 120km2. The dynamic cone penetrometer was used to determine the structural properties of the soil, soil samples were collected to assess the bulk density, organic matter content and permeability in the laboratory and the Hydrosense II was used to determine the soil moisture content in the topsoil. Penetration results show that the tree shelter is the most compacted and the open field area is least compacted in both periods. The falling head test showed that soil permeability was lowest around the feeding area and highest in the open field area in both periods. Laboratory tests showed that the tree shelter had the lowest bulk density values, due to the higher levels of organic matter content and the field gate had the highest levels of bulk density in both periods. There was also a significant difference in bulk density at the field gate and open field areas between the two periods. These results highlight statistically significant differences between heavily compacted areas where animals congregate and less-trampled areas of the field.

Highly conductive ultrathin Co films by high-power impulse magnetron sputtering

NASA Astrophysics Data System (ADS)

Jablonka, L.; Riekehr, L.; Zhang, Z.; Zhang, S.-L.; Kubart, T.

2018-01-01

Ultrathin Co films deposited on SiO2 with conductivities exceeding that of Cu are demonstrated. Ionized deposition implemented by high-power impulse magnetron sputtering (HiPIMS) is shown to result in smooth films with large grains and low resistivities, namely, 14 µΩ cm at a thickness of 40 nm, which is close to the bulk value of Co. Even at a thickness of only 6 nm, a resistivity of 35 µΩ cm is obtained. The improved film quality is attributed to a higher nucleation density in the Co-ion dominated plasma in HiPIMS. In particular, the pulsed nature of the Co flux as well as shallow ion implantation of Co into SiO2 can increase the nucleation density. Adatom diffusion is further enhanced in the ionized process, resulting in a dense microstructure. These results are in contrast to Co deposited by conventional direct current magnetron sputtering where the conductivity is reduced due to smaller grains, voids, rougher interfaces, and Ar incorporation. The resistivity of the HiPIMS films is shown to be in accordance with models by Mayadas-Shatzkes and Sondheimer which consider grain-boundary and surface-scattering.

The solvent component of macromolecular crystals

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

Weichenberger, Christian X.; Afonine, Pavel V.; Kantardjieff, Katherine

2015-04-30

On average, the mother liquor or solvent and its constituents occupy about 50% of a macromolecular crystal. Ordered as well as disordered solvent components need to be accurately accounted for in modelling and refinement, often with considerable complexity. The mother liquor from which a biomolecular crystal is grown will contain water, buffer molecules, native ligands and cofactors, crystallization precipitants and additives, various metal ions, and often small-molecule ligands or inhibitors. On average, about half the volume of a biomolecular crystal consists of this mother liquor, whose components form the disordered bulk solvent. Its scattering contributions can be exploited in initialmore » phasing and must be included in crystal structure refinement as a bulk-solvent model. Concomitantly, distinct electron density originating from ordered solvent components must be correctly identified and represented as part of the atomic crystal structure model. Herein, are reviewed (i) probabilistic bulk-solvent content estimates, (ii) the use of bulk-solvent density modification in phase improvement, (iii) bulk-solvent models and refinement of bulk-solvent contributions and (iv) modelling and validation of ordered solvent constituents. A brief summary is provided of current tools for bulk-solvent analysis and refinement, as well as of modelling, refinement and analysis of ordered solvent components, including small-molecule ligands.« less

Microwave dielectric spectrum of rocks

NASA Technical Reports Server (NTRS)

Ulaby, F. T.; Bengal, T.; East, J.; Dobson, M. C.; Garvin, J.; Evans, D.

1988-01-01

A combination of several measurement techniques was used to investigate the dielectric properties of 80 rock samples in the microwave region. The real part of the dielectric constant, epsilon', was measured in 0.1 GHz steps from 0.5 to 18 GHz, and the imaginary part, epsilon'', was measured at five frequencies extending between 1.6 and 16 GHz. In addition to the dielectric measurements, the bulk density was measured for all the samples and the bulk chemical composition was determined for 56 of the samples. The study shows that epsilon' is frequency-dependent over the 0.5 to 18 GHz range for all rock samples, and that the bulk density rho accounts for about 50 percent of the observed variance of epsilon'. For individual rock types (by genesis), about 90 percent of the observed variance may be explained by the combination of density and the fractional contents of SiO2, Fe2O3, MgO, and TiO2. For the loss factor epsilon'', it was not possible to establish statistically significant relationships between it and the measured properties of the rock samples (density and chemical composition).

Materials, properties, and applications of nitrogen-doped organic semiconductors

NASA Astrophysics Data System (ADS)

Chan, Calvin Kar-Fai

As organic semiconducting materials draw increasing attention for many promising applications, including efficient organic light-emitting diodes (OLEDs), large-area organic photovoltaic (OPV) cells, and flexible organic thin-film transistors (OTFTs), chemical doping of organic materials is emerging as an important technique for overcoming performance deficiencies and material limitations of intrinsic organic films. Although p-doping has been amply demonstrated, molecular n-type doping has been difficult to study because of the inherent instability of easily oxidized n-dopants. In this work, the facile use of two low ionization energy (IE) small molecules that are suitable for n-doping a wide range of organic electronic materials is demonstrated. Cobaltocene (CoCp2) and its derivative, decamethylcobaltocene ( CoCp*2 ), were found to have fairly low IEs for organic compounds. Co-deposition of the n-dopants with different host molecules results in pronounced shifts of the Fermi-level towards unoccupied molecular states, indicating a significant increase in electron concentration. The Fermi-level shifts, measured with ultra-violet photoemission spectroscopy (UPS), are correlated with excess carrier densities using a model based on Fermi-Dirac (F-D) statistics and a Gaussian distributed density of states. The calculated electron densities suggest full dopant ionization at low concentrations, and diminished efficiency at high donor concentrations. The concentration of incorporated dopants is examined by chemical composition analysis of doped films using X-ray photoemission spectroscopy (XPS). Atomic concentration depth profiling determined by Rutherford backscattering (RBS) suggests that the incorporation of CoCp2 and CoCp*2 is well-controlled and the dopants are minimally diffusive. Organic films n-doped using CoCp2 and CoCp*2 show several orders of magnitude increase in current density resulting from both enhanced electron injection and increased electron conductivity in the bulk. Increases in the bulk conductivity suggest both improved electron mobility and higher electron concentrations. These findings are applied with previous work on p-doping to fabricate organic p-i-n homojunction devices that exhibit strong rectification and large built-in potentials. Heterojunction OPVs using undoped CuPc and n-doped C60 display significant increases in open-circuit voltage (Voc), short-circuit current (Isc), fill-factor (FF), and efficiency.

Topological crystalline insulator SnTe nanoribbons

NASA Astrophysics Data System (ADS)

Dahal, Bishnu R.; Dulal, Rajendra P.; Pegg, Ian L.; Philip, John

2017-03-01

Topological crystalline insulators are systems in which a band inversion that is protected by crystalline mirror symmetry gives rise to nontrivial topological surface states. SnTe is a topological crystalline insulator. It exhibits p-type conductivity due to Sn vacancies and Te antisites, which leads to high carrier density in the bulk. Thus growth of high quality SnTe is a prerequisite for understanding the topological crystalline insulating behavior. We have grown SnTe nanoribbons using a solution method. The width of the SnTe ribbons varies from 500 nm to 2 μm. They exhibit rock salt crystal structure with a lattice parameter of 6.32 Å. The solution method that we have adapted uses low temperature, so the Sn vacancies can be controlled. The solution grown SnTe nanoribbons exhibit strong semiconducting behavior with an activation energy of 240 meV. This activation energy matches with the calculated band gap for SnTe with a lattice parameter of 6.32 Å, which is higher than that reported for bulk SnTe. The higher activation energy makes the thermal excitation of bulk charges very difficult on the surface. As a result, the topological surfaces will be free from the disturbance caused by the thermal excitations

Impacts of harvesting and postharvest treatments on soil bulk density, soil strength, and ealry growth of Pinus taeda in the Gulf Coastal Plain: a long-term soil productivity affiliated study

Treesearch

Mason C. Carter; Thomas J. Dean; Ziyin Wang; Ray A. Newbold

2006-01-01

At four sites in the Gulf Coastal Plain, mechanical whole-tree harvesting (MWT) removed from biomass and nutrients than hand-fell bole-only harvesting (HFBO). Soil compaction and loblolly pine (Pinus taeda L.) regeneration growth varied among sites. At one location, MWT increased soil bulk density by 0.1 Mgm-3, from 1.14 to 1....

Spherical nitroguanidine process

DOEpatents

Sanchez, John A.; Roemer, Edward L.; Stretz, Lawrence A.

1990-01-01

A process of preparing spherical high bulk density nitroguanidine by dissing low bulk density nitroguanidine in N-methyl pyrrolidone at elevated temperatures and then cooling the solution to lower temperatures as a liquid characterized as a nonsolvent for the nitroguanidine is provided. The process is enhanced by inclusion in the solution of from about 1 ppm up to about 250 ppm of a metal salt such as nickel nitrate, zinc nitrate or chromium nitrate, preferably from about 20 to about 50 ppm.

ZnO for solar cell and thermoelectric applications

NASA Astrophysics Data System (ADS)

Zhou, Chuanle; Ghods, Amirhossein; Yunghans, Kelcy L.; Saravade, Vishal G.; Patel, Paresh V.; Jiang, Xiaodong; Kucukgok, Bahadir; Lu, Na; Ferguson, Ian

2017-03-01

ZnO-based materials show promise in energy harvesting applications, such as piezoelectric, photovoltaic and thermoelectric. In this work, ZnO-based vertical Schottky barrier solar cells were fabricated by MOCVD de- position of ZnO thin films on ITO back ohmic contact, while Ag served as the top Schottky contact. Various rapid thermal annealing conditions were studied to modify the carrier density and crystal quality. Greater than 200 nm thick ZnO films formed polycrystalline crystal structure, and were used to demonstrate Schottky solar cells. I-V characterizations of the devices showed photovoltaic performance, but but need further development. This is the first demonstration of vertical Schottky barrier solar cell based on wide bandgap ZnO film. Thin film and bulk ZnO grown by MOCVD or melt growth were also investigated in regards to their room- temperature thermoelectric properties. The Seebeck coefficient of bulk ZnO was found to be much larger than that of thin film ZnO at room temperature due to the higher crystal quality in bulk materials. The Seebeck coefficients decrease while the carrier concentration increases due to the crystal defects caused by the charge carriers. The co-doped bulk Zn0:96Ga0:02Al0:02O showed enhanced power factors, lower thermal conductivities and promising ZT values in the whole temperature range (300-1300 K).

Retrospective Analysis of NIST Standard Reference Material 1450, Fibrous Glass Board, for Thermal Insulation Measurements.

PubMed

Zarr, Robert R; Heckert, N Alan; Leigh, Stefan D

2014-01-01

Thermal conductivity data acquired previously for the establishment of Standard Reference Material (SRM) 1450, Fibrous Glass Board, as well as subsequent renewals 1450a, 1450b, 1450c, and 1450d, are re-analyzed collectively and as individual data sets. Additional data sets for proto-1450 material lots are also included in the analysis. The data cover 36 years of activity by the National Institute of Standards and Technology (NIST) in developing and providing thermal insulation SRMs, specifically high-density molded fibrous-glass board, to the public. Collectively, the data sets cover two nominal thicknesses of 13 mm and 25 mm, bulk densities from 60 kg·m(-3) to 180 kg·m(-3), and mean temperatures from 100 K to 340 K. The analysis repetitively fits six models to the individual data sets. The most general form of the nested set of multilinear models used is given in the following equation: [Formula: see text]where λ(ρ,T) is the predicted thermal conductivity (W·m(-1)·K(-1)), ρ is the bulk density (kg·m(-3)), T is the mean temperature (K) and ai (for i = 1, 2, … 6) are the regression coefficients. The least squares fit results for each model across all data sets are analyzed using both graphical and analytic techniques. The prevailing generic model for the majority of data sets is the bilinear model in ρ and T. [Formula: see text] One data set supports the inclusion of a cubic temperature term and two data sets with low-temperature data support the inclusion of an exponential term in T to improve the model predictions. Physical interpretations of the model function terms are described. Recommendations for future renewals of SRM 1450 are provided. An Addendum provides historical background on the origin of this SRM and the influence of the SRM on external measurement programs.

Analysis of the Effect of Module Thickness Reduction on Thermoelectric Generator Output

NASA Astrophysics Data System (ADS)

Brito, F. P.; Figueiredo, L.; Rocha, L. A.; Cruz, A. P.; Goncalves, L. M.; Martins, J.; Hall, M. J.

2016-03-01

Conventional thermoelectric generators (TEGs) used in applications such as exhaust heat recovery are typically limited in terms of power density due to their low efficiency. Additionally, they are generally costly due to the bulk use of rare-earth elements such as tellurium. If less material could be used for the same output, then the power density and the overall cost per kilowatt (kW) of electricity produced could drop significantly, making TEGs a more attractive solution for energy harvesting of waste heat. The present work assesses the effect of reducing the amount of thermoelectric (TE) material used (namely by reducing the module thickness) on the electrical output of conventional bismuth telluride TEGs. Commercial simulation packages (ANSYS CFX and thermal-electric) and bespoke models were used to simulate the TEGs at various degrees of detail. Effects such as variation of the thermal and electrical contact resistance and the component thickness and the effect of using an element supporting matrix (e.g., eggcrate) instead of having air conduction in void areas have been assessed. It was found that indeed it is possible to reduce the use of bulk TE material while retaining power output levels equivalent to thicker modules. However, effects such as thermal contact resistance were found to become increasingly important as the active TE material thickness was decreased.

Heat transfer from high-temperature surfaces to fluids II : correlation of heat-transfer and friction data for air flowing in inconel tube with rounded entrance

NASA Technical Reports Server (NTRS)

Lowdermilk, Warren H; Grele, Milton D

1949-01-01

A heat transfer investigation, which was an extension of a previously reported NACA investigation, was conducted with air flowing through an electrically heated inconel tube with a rounded entrance,an inside diameter of 0.402 inch, and a length of 24 inches over a range of conditions, which included Reynolds numbers up to 500,000, average surface temperatures up to 2050 degrees R, and heat-flux densities up to 150,000 Btu per hour per square foot. Conventional methods of correlating heat-transfer data wherein properties of the air were evaluated at the average bulk, film, and surface temperatures resulted in reductions of Nusselt number of about 38, 46, and 53 percent, respectively, for an increase in surface temperature from 605 degrees to 2050 degrees R at constant Reynolds number. A modified correlation method in which the properties of air were based on the surface temperature and the Reynolds number was modified by substituting the product of the density at the inside tube wall and the bulk velocity for the conventional mass flow per unit cross-sectional area, resulted in a satisfactory correlation of the data for the extended ranges of conditions investigated.

Ab initio DFT+U study of He atom incorporation into UO(2) crystals.

PubMed

Gryaznov, Denis; Heifets, Eugene; Kotomin, Eugene

2009-09-07

We present and discuss results of the density functional theory (DFT) for perfect UO(2) crystals with He atoms in octahedral interstitial positions therein. We have calculated basic bulk crystal properties and He incorporation energies into the low temperature anti-ferromagnetic UO(2) phase using several exchange-correlation functionals within the spin-polarized local density (LDA) and generalized gradient (GGA) approximations. In all DFT calculations we included the on-site correlation corrections using the Hubbard model (DFT+U approach). We analysed a potential crystalline symmetry reduction from tetragonal down to orthorhombic structure and confirmed the presence of the Jahn-Teller effect in a perfect UO(2). We discuss also the problem of a conducting electronic state arising when He is placed into a tetragonal antiferromagnetic phase of UO(2) commonly used in defect modelling. Consequently, we found a specific monoclinic lattice distortion which allowed us to restore the semiconducting state and properly estimate He incorporation energies. Unlike the bulk properties, the He incorporation energy strongly depends on several factors, including the supercell size, the use of spin polarization, the exchange-correlation functionals and on-site correlation corrections. We compare our results for the He incorporation with the previous shell model and ab initio DFT calculations.

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

Wang, Siwei; Chen, Yan; Zhang, Lingling

Ceramic-based proton conductors enable high-temperature hydrogen economy applications such as hydrogen separation membranes, fuel cells, and steam electrolyzers. BaZr 0.8Y 0.2O 3-δ(BZY) proton-conducting oxide possesses the highest level of proton conductivity reported to date, but poor sinterability hinders its widespread utilization. In this paper, we report a two-step reactive aid sintering (TRAS) method involving the introduction of BaCO 3 and B 2O 3-Li 2O for the preparation of dense BZY ceramics sintered at 1500°C. The resulting BZY samples showed a pure perovskite structure with a dramatic increase in the relative density to 91.5%. In addition, the shrinkage during sintering wasmore » improved to 19.3% by a TRAS method as compared to 2.6% by the conventional solid date reaction method. In conclusion, the bulk conductivity was improved due to enhanced densification, while the grain boundary conductivity decreased due to the blocking behavior of the sintering aid resulting in a decrease in the total conductivity of the samples.« less

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

Wang, Siwei; Chen, Yan; Zhang, Lingling

Ceramic-based proton conductors enable high-temperature hydrogen economy applications such as hydrogen separation membranes, fuel cells, and steam electrolyzers. BaZr 0.8Y 0.2O 3-δ (BZY) proton-conducting oxide possesses the highest level of proton conductivity reported to date, but poor sinterability hinders its widespread utilization. Here, we report a two-step reactive aid sintering (TRAS) method involving the introduction of BaCO 3 and B 2O 3-Li 2O for the preparation of dense BZY ceramics sintered at 1500°C. The resulting BZY samples showed a pure perovskite structure with a dramatic increase in the relative density to 91.5%. In addition, the shrinkage during sintering was improvedmore » to 19.3% by a TRAS method as compared to 2.6% by the conventional solid date reaction method. Moreover, the bulk conductivity was improved due to enhanced densification, while the grain boundary conductivity decreased due to the blocking behavior of the sintering aid resulting in a decrease in the total conductivity of the samples.« less

Dense garnet-like Li5La3Nb2O12 solid electrolyte prepared by self-consolidation method

NASA Astrophysics Data System (ADS)

Zhao, Pengcheng; Xiang, Yu; Xu, Yan; Wen, Yuehua; Zhang, Wenfeng; Zhu, Xiayu; Li, Meng; Zhang, Sontong; Ming, Hai; Jin, Zhaoqing; Cao, Gaoping

2018-06-01

Li5La3Nb2O12 (LLNO) is a typical garnet-like solid electrolyte with solitary cubic structure. However, its ionic conductivity is relatively low due to the low relative density when prepared by cold isostatic pressing method, which usually involves high-pressure machines, poor productivity, tedious pressing operations, and low density. In this paper, self-consolidation method is developed to sinter dense LLNO electrolyte. Although not any pressing operations are employed in the entire process, the relative density of LLNO is promoted up to 95%, which is much higher than the reported values of 45-80%. SEM images reveal that the sample is built by huge particles in size of 80 μm indicating that there are few boundaries in the sample. Moreover, a rich content of Li-Al-O compounds is detected out in the boundary areas, which may act as sintering aids for the sample to consolidate automatically. According to the highest density, the bulk ionic conductivity of LLNO sample reaches up to 1.61 × 10-4 S cm-1 at 30 °C, which is in the same order of magnitude as the value of cubic Li7La3Zr2O12 electrolyte. This work verifies the self-consolidation mechanism for the sintering of ceramic electrolytes and could significantly facilitate the development of LLNO membrane technology.

Effect of implanted Cu/low-density polyethylene nanocomposite on the morphology of endometrium in the mouse.

PubMed

Xia, Xianping; Xie, Changsheng; Zhu, Changhong; Cai, Shuizhou; Yang, Xiangliang

2007-08-01

To investigate the damage of endometrium caused by the implanted Cu/low-density polyethylene (LDPE) nanocomposite and the contraceptive effect of this novel copper-containing intrauterine device material. Experimental animal study. TongJi Medical College of Huazhong University of Science and Technology. Sixty healthy female mice. Twenty mice received no implants, 20 mice received the Cu/LDPE nanocomposite, and 20 mice received bulk copper. Morphologic features of the endometrium, contraceptive effect, and surface condition of the implanted implants. The contraceptive effect of both the Cu/LDPE nanocomposite and bulk copper is 100%, the damage of the endometrium caused by the Cu/LDPE nanocomposite is much less than that caused by bulk copper, and the surface of the implanted Cu/LDPE nanocomposite is much smoother and much softer than that of the implanted bulk copper. The contraceptive effect of the Cu/LDPE nanocomposite is comparable with that of bulk copper, and the damage of the endometrium caused by the Cu/LDPE nanocomposite is much less than that caused by bulk copper. The endometrium injury is related to the surface condition of the implanted intrauterine device material.

A low-dimensional analogue of holographic baryons

NASA Astrophysics Data System (ADS)

Bolognesi, Stefano; Sutcliffe, Paul

2014-04-01

Baryons in holographic QCD correspond to topological solitons in the bulk. The most prominent example is the Sakai-Sugimoto model, where the bulk soliton in the five-dimensional spacetime of AdS-type can be approximated by the flat space self-dual Yang-Mills instanton with a small size. Recently, the validity of this approximation has been verified by comparison with the numerical field theory solution. However, multi-solitons and solitons with finite density are currently beyond numerical field theory computations. Various approximations have been applied to investigate these important issues and have led to proposals for finite density configurations that include dyonic salt and baryonic popcorn. Here we introduce and investigate a low-dimensional analogue of the Sakai-Sugimoto model, in which the bulk soliton can be approximated by a flat space sigma model instanton. The bulk theory is a baby Skyrme model in a three-dimensional spacetime with negative curvature. The advantage of the lower-dimensional theory is that numerical simulations of multi-solitons and finite density solutions can be performed and compared with flat space instanton approximations. In particular, analogues of dyonic salt and baryonic popcorn configurations are found and analysed.

Development of interface-dominant bulk Cu/V nanolamellar composites by cross accumulative roll bonding

PubMed Central

Zeng, L. F.; Gao, R.; Xie, Z. M.; Miao, S.; Fang, Q. F.; Wang, X. P.; Zhang, T.; Liu, C. S.

2017-01-01

Traditional nanostructured metals are inherently comprised of a high density of high-energy interfaces that make this class of materials not stable in extreme conditions. Therefore, high performance bulk nanostructured metals containing stable interfaces are highly desirable for extreme environments applications. Here, we reported an attractive bulk Cu/V nanolamellar composite that was successfully developed by integrating interface engineering and severe plastic deformation techniques. The layered morphology and ordered Cu/V interfaces remained stable with respect to continued rolling (total strain exceeding 12). Most importantly, for layer thickness of 25 nm, this bulk Cu/V nanocomposite simultaneously achieves high strength (hardness of 3.68 GPa) and outstanding thermal stability (up to 700 °C), which are quite difficult to realize simultaneously in traditional nanostructured materials. Such extraordinary property in our Cu/V nanocomposite is achieved via an extreme rolling process that creates extremely high density of stable Cu/V heterophase interfaces and low density of unstable grain boundaries. In addition, high temperature annealing result illustrates that Rayleigh instability is the dominant mechanism driving the onset of thermal instability after exposure to 800 °C. PMID:28094346

3D-Laser-Scanning Technique Applied to Bulk Density Measurements of Apollo Lunar Samples

NASA Technical Reports Server (NTRS)

Macke, R. J.; Kent, J. J.; Kiefer, W. S.; Britt, D. T.

2015-01-01

In order to better interpret gravimetric data from orbiters such as GRAIL and LRO to understand the subsurface composition and structure of the lunar crust, it is import to have a reliable database of the density and porosity of lunar materials. To this end, we have been surveying these physical properties in both lunar meteorites and Apollo lunar samples. To measure porosity, both grain density and bulk density are required. For bulk density, our group has historically utilized sub-mm bead immersion techniques extensively, though several factors have made this technique problematic for our work with Apollo samples. Samples allocated for measurement are often smaller than optimal for the technique, leading to large error bars. Also, for some samples we were required to use pure alumina beads instead of our usual glass beads. The alumina beads were subject to undesirable static effects, producing unreliable results. Other investigators have tested the use of 3d laser scanners on meteorites for measuring bulk volumes. Early work, though promising, was plagued with difficulties including poor response on dark or reflective surfaces, difficulty reproducing sharp edges, and large processing time for producing shape models. Due to progress in technology, however, laser scanners have improved considerably in recent years. We tested this technique on 27 lunar samples in the Apollo collection using a scanner at NASA Johnson Space Center. We found it to be reliable and more precise than beads, with the added benefit that it involves no direct contact with the sample, enabling the study of particularly friable samples for which bead immersion is not possible

High density crystalline boron prepared by hot isostatic pressing in refractory metal containers

DOEpatents

Hoenig, C.L.

1993-08-31

Boron powder is hot isostatically pressed in a refractory metal container to produce a solid boron monolith with a bulk density at least 2.22 g/cc and up to or greater than 2.34 g/cc. The refractory metal container is formed of tantalum, niobium, tungsten, molybdenum or alloys thereof in the form of a canister or alternatively plasma sprayed or chemical vapor deposited onto a powder compact. Hot isostatic pressing at 1,800 C and 30 PSI (206.8 MPa) argon pressure for four hours produces a bulk density of 2.34 g/cc. Complex shapes can be made.

High density crystalline boron prepared by hot isostatic pressing in refractory metal containers

DOEpatents

Hoenig, Clarence L.

1993-01-01

Boron powder is hot isostatically pressed in a refractory metal container to produce a solid boron monolith with a bulk density at least 2.22 g/cc and up to or greater than 2.34 g/cc. The refractory metal container is formed of tantalum, niobium, tungsten, molybdenum or alloys thereof in the form of a canister or alternatively plasma sprayed or chemical vapor deposited onto a powder compact. Hot isostatic pressing at 1800.degree. C. and 30 KSI (206.8 MPa) argon pressure for four hours produces a bulk density of 2.34 g/cc. Complex shapes can be made.

High density-high purity graphite prepared by hot isostatic pressing in refractory metal containers

DOEpatents

Hoenig, Clarence L.

1994-01-01

Porous graphite in solid form is hot isostatically pressed in a refractory metal container to produce a solid graphite monolith with a bulk density greater than or equal to 2.10 g/cc. The refractory metal container is formed of tantalum, niobium, tungsten, molybdenum or alloys thereof in the form of a canister or alternatively plasma sprayed, chemically vapor deposited, or coated by some other suitable means onto graphite. Hot isostatic pressing at 2200.degree. C. and 30 KSI (206.8 MPa) argon pressure for two hours produces a bulk density of 2.10 g/cc. Complex shapes can be made.

High density-high purity graphite prepared by hot isostatic pressing in refractory metal containers

DOEpatents

Hoenig, C.L.

1994-08-09

Porous graphite in solid form is hot isostatically pressed in a refractory metal container to produce a solid graphite monolith with a bulk density greater than or equal to 2.10 g/cc. The refractory metal container is formed of tantalum, niobium, tungsten, molybdenum or alloys thereof in the form of a canister or alternatively plasma sprayed, chemically vapor deposited, or coated by some other suitable means onto graphite. Hot isostatic pressing at 2,200 C and 30 KSI (206.8 MPa) argon pressure for two hours produces a bulk density of 2.10 g/cc. Complex shapes can be made. 1 fig.

Why do gallium clusters have a higher melting point than the bulk?

PubMed

Chacko, S; Joshi, Kavita; Kanhere, D G; Blundell, S A

2004-04-02

Density functional molecular dynamical simulations have been performed on Ga17 and Ga13 clusters to understand the recently observed higher-than-bulk melting temperatures in small gallium clusters [Phys. Rev. Lett. 91, 215508 (2003)

Results of Physical Property Measurements Obtained during the CHIKYU Cruise CK16-01 to Hydrothermal Fields of the Middle Okinawa Trough

NASA Astrophysics Data System (ADS)

Tanikawa, W.; Masaki, Y.; Komori, S.; Torimoto, J.; Makio, M.; Ohta, Y.; Nozaki, T.; Ishibashi, J. I.; Kumagai, H.; Maeda, L.; Hamada, Y.

2016-12-01

The middle Okinawa trough, along the Ryukyu-arc on the margin of the western Pacific, fosters several hydrothermal fields. The cruise CK16-01 of D/V CHIKYU targeted the Iheya-North Field and Noho hydrothermal site. More than ten-days extensive coring was carried out with Logging While Drilling (LWD) and deployment of Kuroko cultivation apparatus between February 29th to March 17th2016. Here we present the results of the physical property measurements obtained using Chikyu's on-board laboratory. Cores were sampled among three sites where the seafloor environments were quite different: the Noho site (C9017), a site between the Natsu and Aki sites of the Iheya-North field (C9021), and the Iheya-North Aki site (C9023). Site C9017 was near the center of the hydrothermal activity, and the obtained core was limited 36 m in length and 30 % in the recovery rate. At 70 mbsf (meters below seafloor), the grain density and bulk density of the sediment reached their maxim (3.7 g/m3 and 2.7 g/cm3, respectively), while thermal conductivity reached its lowest value (0.6 W/m·K). Site C9021 yielded a 54 m core, with a core recovery rate of 50 %. Coarse pumiceous layers were found at 68 mbsf, with a hydrothermally altered layer appearing below 68 mbsf. The mean grain density value was 2.4 g/cm3 and was uniform throughout the core. The mean bulk density value of the pumiceous layers was 1.3 g/cm3, and of the hydrothermally altered layer was 2.1 g/cm3. Site C9023 was close to the active hydrothermal chimneys of the Iheya-North Aki site, and yielded 33 m of core with a core recovery rate of 16 %. Massive sulfide layers were found below 48 mbsf with grain density and bulk density values varying between 2.8-4.7 g/cm3 and 1.5-3.9 g/cm3, respectively. Magnetic susceptibility exhibited a high anomaly in a sedimented anhydrite layer found between 95 and 135 mbsf, and a high porosity and low resistivity zone was found below 150 mbsf. Together, these data from drilling cores and onboard analysis provide the first insights into the physical properties of hydrothermal fields in the Okinawa trough. This work was supported by the Council for Science, Technology and Innovation (CSTI) Cross-ministerial Strategic Innovation Promotion Program (SIP), "Next-generation technology for ocean resources exploration" (Lead agency: JAMSTEC)

The light response of mesophyll conductance is controlled by structure across leaf profiles.

PubMed

Théroux-Rancourt, Guillaume; Gilbert, Matthew E

2017-05-01

Mesophyll conductance to CO 2 (g m ) may respond to light either through regulated dynamic mechanisms or due to anatomical and structural factors. At low light, some layers of cells in the leaf cross-section approach photocompensation and contribute minimally to bulk leaf photosynthesis and little to whole leaf g m (g m,leaf ). Thus, the bulk g m,leaf will appear to respond to light despite being based upon cells having an anatomically fixed mesophyll conductance. Such behaviour was observed in species with contrasting leaf structure using the variable J or stable isotope method of measuring g m,leaf . A species with bifacial structure, Arbutus × 'Marina', and an isobilateral species, Triticum durum L., had contrasting responses of g m,leaf upon varying adaxial or abaxial illumination. Anatomical observations, when coupled with the proposed model of g m,leaf to photosynthetic photon flux density (PPFD) response, successfully represented the observed gas exchange data. The theoretical and observed evidence that g m,leaf apparently responds to light has large implications for how g m,leaf values are interpreted, particularly limitation analyses, and indicates the importance of measuring g m under full light saturation. Responses of g m,leaf to the environment should be treated as an emergent property of a distributed 3D structure, and not solely a leaf area-based phenomenon. © 2016 John Wiley & Sons Ltd.

Piezoelectric coefficients of bulk 3R transition metal dichalcogenides

NASA Astrophysics Data System (ADS)

Konabe, Satoru; Yamamoto, Takahiro

2017-09-01

The piezoelectric properties of bulk transition metal dichalcogenides (TMDCs) with a 3R structure were investigated using first-principles calculations based on density functional theory combined with the Berry phase treatment. Values for the elastic constant Cijkl , the piezoelectric coefficient eijk , and the piezoelectric coefficient dijk are given for bulk 3R-TMDCs (MoS2, MoSe2, WS2, and WSe2). The piezoelectric coefficients of bulk 3R-TMDCs are shown to be sufficiently large or comparable to those of conventional bulk piezoelectric materials such as α-quartz, wurtzite GaN, and wurtzite AlN.

Few layered MoO3 nano sheets-SWCNT composite thin film as supercapacitor electrode

NASA Astrophysics Data System (ADS)

Dutta, Shibsankar; Akther, Jasim; De, Sukanta

2017-05-01

The increasing demands for clean and renewable energy, the advantages of high power density, long lasting and high efficiency have made Supercapacitor as one of the major emerging energy storage device.The 2D layered metal oxide nanocomposite with SWCNT is the promising candidate for energy storage and conversion. In this work we exfoliate the crystalline bulk MoO3 by simple liquid phase exfoliation to give multi-layer MoO3 dispersed in a suitable solvent. As the electrical conductivity of MoO3 is very low so, the dispersion was used to make hybrid material with SWCNT dispersion by vacuum filtration. The SWCNT-MoO3 composite showed an areal capacitance value of 1290 µF/cm2 at 10 mV/s in PVA-H2 SO4 solid gel electrolyte. This composite based electrode provides an energy density of 0.092 µWh/cm2 and a power density of 9.54 µW/cm2 at 0.01 mA/cm2

Ab-initio study of electronic structure and elastic properties of ZrC

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

Mund, H. S., E-mail: hmoond@gmail.com; Ahuja, B. L.

2016-05-23

The electronic and elastic properties of ZrC have been investigated using the linear combination of atomic orbitals method within the framework of density functional theory. Different exchange-correlation functionals are taken into account within generalized gradient approximation. We have computed energy bands, density of states, elastic constants, bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio, lattice parameters and pressure derivative of the bulk modulus by calculating ground state energy of the rock salt structure type ZrC.

Elastic Anomaly and Polyamorphic Transition in (La, Ce)-based Bulk Metallic Glass under Pressure

DOE PAGES

Qi, Xintong; Zou, Yongtao; Wang, Xuebing; ...

2017-04-07

In this paper, we discovered that in association with the polyamorphism of La 32Ce 32Al 16Ni 5Cu 15 bulk metallic glass, the acoustic velocities, measured up to 12.3 GPa using ultrasonic interferometry, exhibit velocity minima at 1.8 GPa for P wave and 3.2 GPa for S wave. The low and high density amorphous states are distinguished by their distinct pressure derivatives of the bulk and shear moduli. The elasticity, permanent densification, and polyamorphic transition are interpreted by the topological rearrangement of solute-centered clusters in medium-range order (MRO) mediated by the 4f electron delocalization of Ce under pressure. The precisely measuredmore » acoustic wave travel times which were used to derive the velocities and densities provided unprecedented data to document the evolution of the bulk and shear elastic moduli associated with a polyamorphic transition in La 32Ce 32Al 16Ni 5Cu 15 bulk metallic glass and can shed new light on the mechanisms of polyamorphism and structural evolution in metallic glasses under pressure.« less

Structural and electronic properties of chiral single-wall copper nanotubes

NASA Astrophysics Data System (ADS)

Duan, YingNi; Zhang, JianMin; Xu, KeWei

2014-04-01

The structural, energetic and electronic properties of chiral ( n, m) (3⩽ n⩽6, n/2⩽ m⩽ n) single-wall copper nanotubes (CuNTs) have been investigated by using projector-augmented wave method based on density-functional theory. The (4, 3) CuNT is energetically stable and should be observed experimentally in both free-standing and tip-suspended conditions, whereas the (5, 5) and (6, 4) CuNTs should be observed in free-standing and tip-suspended conditions, respectively. The number of conductance channels in the CuNTs does not always correspond to the number of atomic strands comprising the nanotube. Charge density contours show that there is an enhanced interatomic interaction in CuNTs compared with Cu bulk. Current transporting states display different periods and chirality, the combined effects of which lead to weaker chiral currents on CuNTs.

Physical and hydraulic properties of volcanic rocks from Yucca Mountain, Nevada

USGS Publications Warehouse

Flint, Lorraine E.

2003-01-01

A database of physical and hydraulic properties was developed for rocks in the unsaturated zone at Yucca Mountain, Nevada, a site under consideration as a geologic repository for high-level radioactive waste. The 5320 core samples were collected from 23 shallow (<100 m) and 10 deep (500-1000 m) vertical boreholes. Hydrogeologic units have been characterized in the unsaturated zone [Flint, 1998] that represent rocks with ranges of welding, lithophysae, and high and low temperature alteration (as a result of the depositional, cooling, and alterational history of the lithostratigraphic layers). Lithostratigraphy, the hydrogeologic unit, and the corresponding properties are described. In addition, the physical properties of bulk density, porosity, and particle density; the hydraulic properties of saturated hydraulic conductivity and moisture retention characteristics; and the field water content were measured and compiled for each core sample.

High-density two-dimensional electron system induced by oxygen vacancies in ZnO

NASA Astrophysics Data System (ADS)

Rödel, T. C.; Dai, J.; Fortuna, F.; Frantzeskakis, E.; Le Fèvre, P.; Bertran, F.; Kobayashi, M.; Yukawa, R.; Mitsuhashi, T.; Kitamura, M.; Horiba, K.; Kumigashira, H.; Santander-Syro, A. F.

2018-05-01

We realize a two-dimensional electron system (2DES) in ZnO by simply depositing pure aluminum on its surface in ultrahigh vacuum and characterize its electronic structure by using angle-resolved photoemission spectroscopy. The aluminum oxidizes into alumina by creating oxygen vacancies that dope the bulk conduction band of ZnO and confine the electrons near its surface. The electron density of the 2DES is up to two orders of magnitude higher than those obtained in ZnO heterostructures. The 2DES shows two s -type subbands, that we compare with the d -like 2DESs in titanates, with clear signatures of many-body interactions that we analyze through a self-consistent extraction of the system self-energy and a modeling as a coupling of a two-dimensional Fermi liquid with a Debye distribution of phonons.

Packing microstructure and local density variations of experimental and computational pebble beds

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

Auwerda, G. J.; Kloosterman, J. L.; Lathouwers, D.

2012-07-01

In pebble bed type nuclear reactors the fuel is contained in graphite pebbles, which form a randomly stacked bed with a non-uniform packing density. These variations can influence local coolant flow and power density and are a possible cause of hotspots. To analyse local density variations computational methods are needed that can generate randomly stacked pebble beds with a realistic packing structure on a pebble-to-pebble level. We first compare various properties of the local packing structure of a computed bed with those of an image made using computer aided X-ray tomography, looking at properties in the bulk of the bedmore » and near the wall separately. Especially for the bulk of the bed, properties of the computed bed show good comparison with the scanned bed and with literature, giving confidence our method generates beds with realistic packing microstructure. Results also show the packing structure is different near the wall than in the bulk of the bed, with pebbles near the wall forming ordered layers similar to hexagonal close packing. Next, variations in the local packing density are investigated by comparing probability density functions of the packing fraction of small clusters of pebbles throughout the bed. Especially near the wall large variations in local packing fractions exists, with a higher probability for both clusters of pebbles with low (<0.6) and high (>0.65) packing fraction, which could significantly affect flow rates and, together with higher power densities, could result in hotspots. (authors)« less

From clusters to bulk: A relativistic density functional investigation on a series of gold clusters Aun, n=6,…,147

NASA Astrophysics Data System (ADS)

Häberlen, Oliver D.; Chung, Sai-Cheong; Stener, Mauro; Rösch, Notker

1997-03-01

A series of gold clusters spanning the size range from Au6 through Au147 (with diameters from 0.7 to 1.7 nm) in icosahedral, octahedral, and cuboctahedral structure has been theoretically investigated by means of a scalar relativistic all-electron density functional method. One of the main objectives of this work was to analyze the convergence of cluster properties toward the corresponding bulk metal values and to compare the results obtained for the local density approximation (LDA) to those for a generalized gradient approximation (GGA) to the exchange-correlation functional. The average gold-gold distance in the clusters increases with their nuclearity and correlates essentially linearly with the average coordination number in the clusters. An extrapolation to the bulk coordination of 12 yields a gold-gold distance of 289 pm in LDA, very close to the experimental bulk value of 288 pm, while the extrapolated GGA gold-gold distance is 297 pm. The cluster cohesive energy varies linearly with the inverse of the calculated cluster radius, indicating that the surface-to-volume ratio is the primary determinant of the convergence of this quantity toward bulk. The extrapolated LDA binding energy per atom, 4.7 eV, overestimates the experimental bulk value of 3.8 eV, while the GGA value, 3.2 eV, underestimates the experiment by almost the same amount. The calculated ionization potentials and electron affinities of the clusters may be related to the metallic droplet model, although deviations due to the electronic shell structure are noticeable. The GGA extrapolation to bulk values yields 4.8 and 4.9 eV for the ionization potential and the electron affinity, respectively, remarkably close to the experimental polycrystalline work function of bulk gold, 5.1 eV. Gold 4f core level binding energies were calculated for sites with bulk coordination and for different surface sites. The core level shifts for the surface sites are all positive and distinguish among the corner, edge, and face-centered sites; sites in the first subsurface layer show still small positive shifts.

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

Takaki, Hirokazu; Kobayashi, Kazuaki; Shimono, Masato

We present the thermoelectric properties of TiN/MgO superlattices employing first-principles calculation techniques. The Seebeck coefficients, the electrical conductances, the thermal conductances, and the figure of merit are investigated employing electrical and thermal transport calculations based on density functional theory combined with the nonequilibrium Green's function and nonequilibrium molecular dynamics simulation methods. The TiN/MgO superlattices with a small lattice mismatch at the interfaces are ideal systems to study the way for an enhancement of thermoelectric properties in artificial nanostructures. We find that the interfacial scattering between the two materials in the metal/insulator superlattices causes the electrical conductance to change rapidly, whichmore » enhances the Seebeck coefficient significantly. We show that the figure of merit for the artificial superlattice nanostructures has a much larger value compared with that of the bulk material and changes drastically with the superlattice configurations at the atomistic level.« less

Thermal conductive heating in fractured bedrock: Screening calculations to assess the effect of groundwater influx

NASA Astrophysics Data System (ADS)

Baston, Daniel P.; Kueper, Bernard H.

2009-02-01

A two-dimensional semi-analytical heat transfer solution is developed and a parameter sensitivity analysis performed to determine the relative importance of rock material properties (density, thermal conductivity and heat capacity) and hydrogeological properties (hydraulic gradient, fracture aperture, fracture spacing) on the ability to heat fractured rock using thermal conductive heating (TCH). The solution is developed using a Green's function approach in which an integral equation is constructed for the temperature in the fracture. Subsurface temperature distributions are far more sensitive to hydrogeological properties than material properties. The bulk ground water influx ( q) can provide a good estimate of the extent of influx cooling when influx is low to moderate, allowing the prediction of temperatures during heating without specific knowledge of the aperture and spacing of fractures. Target temperatures may not be reached or may be significantly delayed when the groundwater influx is large.

Decoupling the deep: crop rotations, fertilization and soil physico-chemical properties down the profile

NASA Astrophysics Data System (ADS)

Hobley, Eleanor; Honermeier, Bernd; Don, Axel; Amelung, Wulf; Kögel-Knabner, Ingrid

2017-04-01

Crop fertilization provides vital plant nutrients (e.g. NPK) to ensure yield security but is also associated with negative environmental impacts. In particular, inorganic, mineral nitrogen (Nmin) fertilization leads to emissions during its energy intensive production as well as Nmin leaching to receiving waters. Incorporating legumes into crop rotations can provide organic N to the soil and subsequent crops, reducing the need for mineral N fertilizer and its negative environmental impacts. An added bonus is the potential to enhance soil organic carbon stocks, thereby reducing atmospheric CO2 concentrations. In this study we assessed the effects of legumes in rotation and fertilization regimes on the depth distribution - down to 1 m - of total soil nitrogen (Ntot), soil organic carbon (SOC) as well as isotopic composition (δ13C, δ15N), electrical conductivity and bulk density as well as agricultural yields at a long-term field experiment in Gießen, Germany. Fertilization had significant but small impacts on the soil chemical environment, most particularly the salt content of the soil, with PK fertilization increasing electrical conductivity throughout the soil profile. Similarly, fertilization resulted in a small reduction of soil pH throughout the soil profile. N fertilization, in particular, significantly increased yields, whereas PK fertilizer had only marginal yield effects, indicating that these systems are N limited. This N limitation was confirmed by significant yield benefits with leguminous crops in rotation, even in combination with mineral N fertilizer. The soil was physically and chemically influenced by the choice of crop rotation. Adding clover as a green mulch crop once every 4 years resulted in an enrichment of total N and SOC at the surface compared with fava beans and maize, but only in combination with PK fertilization. In contrast, fava beans and to a lesser extent maize in rotation lowered bulk densities in the subsoil compared with clover. This resulted in a reduction of N density at depth, which was not mirrored in C densities, indicating that fava beans decouple C and N cycles in the deep soil profile. We then tested whether these effects are a result of plant (i.e. enhanced rooting depth associated with lowered subsoil bulk density) or microbial (i.e. N-cycling and denitrification processes) activities, by investigating the isotopic signatures of C and N down the profile. Our results indicate that the selection of crop rotation influences soil C and N cycling and depth distribution. Although mineral N fertilizer has significant benefits for yield, the choice of crop rotation has a greater influence on soil C and N cycling and specifically the addition of leguminous plants into rotation can provide additional yield benefits and stability. Incorporating legumes into crop rotations affects soil physical and chemical properties and decouples C and N cycles in the deep soil profile, indicating different nutrient and water cycling processes in the deep soil profile.

Ab initio study on half-metallic, electronic and thermodynamic attributes of LaFeO3

NASA Astrophysics Data System (ADS)

Tariq, Saad; Saad, Saher; Jamil, M. Imran; Sohail Gilani, S. M.; Mahmood Ramay, Shahid; Mahmood, Asif

2018-03-01

By using the density functional theory (DFT) the systematic study of the structural, electronic and thermodynamic properties of lanthanum ferrite (LaFeO3) has been conducted. The elastic stability criterion and structural tolerance factor reveal that LaFeO3 exists in the cubic phase and is found to be stable under the ambient conditions. In electronic properties, the optical spectrum of the compound has been found to fall in the range of 488 to 688nm which has been calculated from the electronic band gap values by using the PBE-GGA and mBJ-GGA techniques. The light between 488 to 688nm would cause the valence electrons to jump in the conduction band showing the photoconductivity. The pronounced half-metallic character has been discussed by using the projected electronic density of states. The ferromagnetic response has been observed which may be attributed to the Fe-O bonding situation. The compound exhibits ductile, indirect band gap and half-metallic traits in the bulk phase. We expect the compound to be felicitous for the novel spintronic applications.

An overview of rotating machine systems with high-temperature bulk superconductors

NASA Astrophysics Data System (ADS)

Zhou, Difan; Izumi, Mitsuru; Miki, Motohiro; Felder, Brice; Ida, Tetsuya; Kitano, Masahiro

2012-10-01

The paper contains a review of recent advancements in rotating machines with bulk high-temperature superconductors (HTS). The high critical current density of bulk HTS enables us to design rotating machines with a compact configuration in a practical scheme. The development of an axial-gap-type trapped flux synchronous rotating machine together with the systematic research works at the Tokyo University of Marine Science and Technology since 2001 are briefly introduced. Developments in bulk HTS rotating machines in other research groups are also summarized. The key issues of bulk HTS machines, including material progress of bulk HTS, in situ magnetization, and cooling together with AC loss at low-temperature operation are discussed.

Data analysis on physical and mechanical properties of cassava pellets.

PubMed

Oguntunde, Pelumi E; Adejumo, Oluyemisi A; Odetunmibi, Oluwole A; Okagbue, Hilary I; Adejumo, Adebowale O

2018-02-01

In this data article, laboratory experimental investigation results carried out at National Centre for Agricultural Mechanization (NCAM) on moisture content, machine speed, die diameter of the rig, and the outputs (hardness, durability, bulk density, and unit density of the pellets) at different levels of cassava pellets were observed. Analysis of variance using randomized complete block design with factorial was used to perform analysis for each of the outputs: hardness, durability, bulk density, and unit density of the pellets. A clear description on each of these outputs was considered separately using tables and figures. It was observed that for all the output with the exception of unit density, their main factor effects as well as two and three ways interactions is significant at 5% level. This means that the hardness, bulk density and durability of cassava pellets respectively depend on the moisture content of the cassava dough, the machine speed, the die diameter of the extrusion rig and the combinations of these factors in pairs as well as the three altogether. Higher machine speeds produced more quality pellets at lower die diameters while lower machine speed is recommended for higher die diameter. Also the unit density depends on die diameter and the three-way interaction only. Unit density of cassava pellets is neither affected by machine parameters nor moisture content of the cassava dough. Moisture content of cassava dough, speed of the machine and die diameter of the extrusion rig are significant factors to be considered in pelletizing cassava to produce pellets. Increase in moisture content of cassava dough increase the quality of cassava pellets.

Physiochemical Characterization of Briquettes Made from Different Feedstocks

PubMed Central

Karunanithy, C.; Wang, Y.; Muthukumarappan, K.; Pugalendhi, S.

2012-01-01

Densification of biomass can address handling, transportation, and storage problems and also lend itself to an automated loading and unloading of transport vehicles and storage systems. The purpose of this study is to compare the physicochemical properties of briquettes made from different feedstocks. Feedstocks such as corn stover, switchgrass, prairie cord grass, sawdust, pigeon pea grass, and cotton stalk were densified using a briquetting system. Physical characterization includes particle size distribution, geometrical mean diameter (GMD), densities (bulk and true), porosity, and glass transition temperature. The compositional analysis of control and briquettes was also performed. Statistical analyses confirmed the existence of significant differences in these physical properties and chemical composition of control and briquettes. Correlation analysis confirms the contribution of lignin to bulk density and durability. Among the feedstocks tested, cotton stalk had the highest bulk density of 964 kg/m3 which is an elevenfold increase compared to control cotton stalk. Corn stover and pigeon pea grass had the highest (96.6%) and lowest (61%) durability. PMID:22792471

Near-surface bulk densities of asteroids derived from dual-polarization radar observations

NASA Astrophysics Data System (ADS)

Virkki, A.; Taylor, P. A.; Zambrano-Marin, L. F.; Howell, E. S.; Nolan, M. C.; Lejoly, C.; Rivera-Valentin, E. G.; Aponte, B. A.

2017-09-01

We present a new method to constrain the near-surface bulk density and surface roughness of regolith on asteroid surfaces using planetary radar measurements. The number of radar observations has increased rapidly during the last five years, allowing us to compare and contrast the radar scattering properties of different small-body populations and compositional types. This provides us with new opportunities to investigate their near-surface physical properties such as the chemical composition, bulk density, porosity, or the structural roughness in the scale of centimeters to meters. Because the radar signal can penetrate into a planetary surface up to a few decimeters, radar can reveal information that is hidden from other ground-based methods, such as optical and infrared measurements. The near-surface structure of asteroids and comets in centimeter-to-meter scale is essential information for robotic and human space missions, impact threat mitigation, and understanding the history of these bodies as well as the formation of the whole Solar System.

Microstructure and critical current density in MgB2 bulk made of 4.5 wt% carbon-coated boron

NASA Astrophysics Data System (ADS)

Higuchi, M.; Muralidhar, M.; Jirsa, M.; Murakami, M.

2017-07-01

Superconducting performance and its uniformity was studied in the single-step sintered MgB2 bulk prepared with 4.5 wt% of carbon in the carbon-encapsulated boron. The 20 mm in diameter MgB2 pellet was cut into several pieces from bottom to top and the microstructure, superconducting transition temperature (Tc onset), and critical current density at 20 K were studied. DC magnetization measurements showed a sharp superconducting transition with onset Tc at around 35.5 K in all positions. SEM analysis indicated a dispersion of grains between 200 and 300 nm in size, as the main pinning medium in this MgB2 superconductors. The critical current density at 20 K was quite uniform, around 330 kA/cm2 and 200 kA/cm2 at self-field and 1 T, respectively, for all measured positions. The results indicate that the carbon-encapsulated boron is very promising for production of high quality bulk MgB2 material for various industrial applications.

Global and critical test of the perturbation density-functional theory based on extensive simulation of Lennard-Jones fluid near an interface and in confined systems.

PubMed

Zhou, Shiqi; Jamnik, Andrej

2005-09-22

The structure of a Lennard-Jones (LJ) fluid subjected to diverse external fields maintaining the equilibrium with the bulk LJ fluid is studied on the basis of the third-order+second-order perturbation density-functional approximation (DFA). The chosen density and potential parameters for the bulk fluid correspond to the conditions situated at "dangerous" regions of the phase diagram, i.e., near the critical temperature or close to the gas-liquid coexistence curve. The accuracy of DFA predictions is tested against the results of a grand canonical ensemble Monte Carlo simulation. It is found that the DFA theory presented in this work performs successfully for the nonuniform LJ fluid only on the condition of high accuracy of the required bulk second-order direct correlation function. The present report further indicates that the proposed perturbation DFA is efficient and suitable for both supercritical and subcritical temperatures.

Combined Molecular Dynamics, Atoms in Molecules, and IR Studies of the Bulk Monofluoroethanol and Bulk Ethanol To Understand the Role of Organic Fluorine in the Hydrogen Bond Network.

PubMed

Biswas, Biswajit; Mondal, Saptarsi; Singh, Prashant Chandra

2017-02-16

The presence of the fluorocarbon group in fluorinated alcohols makes them an important class of molecules that have diverse applications in the field of separation techniques, synthetic chemistry, polymer industry, and biology. In this paper, we have performed the density function theory calculation along with atom in molecule analysis, molecular dynamics simulation, and IR measurements of bulk monofluoroethanol (MFE) and compared them with the data for bulk ethanol (ETH) to understand the effect of the fluorocarbon group in the structure and the hydrogen bond network of bulk MFE. It has been found that the intramolecular O-H···F hydrogen bond is almost absent in bulk MFE. Molecular dynamics simulation and density function theory calculation along with atom in molecule analysis clearly depict that in the case of bulk MFE, a significant amount of intermolecular O-H···F and C-H···F hydrogen bonds are present along with the intermolecular O-H···O hydrogen bond. The presence of intermolecular O-H···F and C-H···F hydrogen bonds causes the difference in the IR spectrum of bulk MFE as compared to bulk ETH. This study clearly depicts that the organic fluorine (fluorocarbon) of MFE acts as a hydrogen bond acceptor and plays a significant role in the structure and hydrogen bond network of bulk MFE through the formation of weak O-H···F as well C-H···F hydrogen bonds, which may be one of the important reasons behind the unique behavior of the fluoroethanols.

Toughening mechanism in elastomer-modified epoxy resins, part 2

NASA Technical Reports Server (NTRS)

Yee, A. F.; Pearson, R. A.

1984-01-01

The role of matrix ductility on the toughenability and toughening mechanism of elastomer-modified DGEBRA epoxies was investigated. Matrix ductility was varied by using epoxide resins of varying epoxide monomer molecular weights. These epoxide resins were cured using 4,4' diaminodiphenyl sulfone (DDS) and, in some cases, modified with 10% HYCAR(r)CTBN 1300X8. Fracture roughness values for the neat epoxies were found to be almost independent on the monomer molecular weight of the epoxide resin used. However, it was found that the fracture toughness of the elastomer-modified epoxies was very dependent upon the epoxide monomer molecular weight. Tensile dilatometry indicated that the toughening mechanism, when present, is similar to the mechanisms found for the piperidine cured epoxies in Part 1. SEM and OM corroborate this finding. Dynamic mechanical studies were conducted to shed light on the toughenability of the epoxies. The time-dependent small strain behavior of these epoxies were separated into their bulk and shear components. The bulk component is related to brittle fracture, whereas the shear component is related to yielding. It can be shown that the rates of shear and bulk strain energy buildup for a given stress are uniquely determined by the values of Poisson's ratio, nu. It was found that nu increases as the monomer molecular weight of the epoxide resin used increases. This increase in nu can be associated with the low temperature beta relaxation. The effect of increasing cross-link density is to shift the beta relaxation to higher temperatures and to decrease the magnitude of the beta relaxation. Thus, increasing cross-link density decreases nu and increases the tendency towards brittle fracture.

EFFECTIVE POROSITY IMPLIES EFFECTIVE BULK DENSITY IN SORBING SOLUTE TRANSPORT

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

Flach, G.

2012-02-27

The concept of an effective porosity is widely used in solute transport modeling to account for the presence of a fraction of the medium that effectively does not influence solute migration, apart from taking up space. This non-participating volume or ineffective porosity plays the same role as the gas phase in single-phase liquid unsaturated transport: it increases pore velocity, which is useful towards reproducing observed solute travel times. The prevalent use of the effective porosity concept is reflected by its prominent inclusion in popular texts, e.g., de Marsily (1986), Fetter (1988, 1993) and Zheng and Bennett (2002). The purpose ofmore » this commentary is to point out that proper application of the concept for sorbing solutes requires more than simply reducing porosity while leaving other material properties unchanged. More specifically, effective porosity implies the corresponding need for an effective bulk density in a conventional single-porosity model. The reason is that the designated non-participating volume is composed of both solid and fluid phases, both of which must be neglected for consistency. Said another way, if solute does not enter the ineffective porosity then it also cannot contact the adjoining solid. Conceptually neglecting the fluid portion of the non-participating volume leads to a lower (effective) porosity. Likewise, discarding the solid portion of the non-participating volume inherently leads to a lower or effective bulk density. In the author's experience, practitioners virtually never adjust bulk density when adopting the effective porosity approach.« less

Bulk and interfacial structures of reline deep eutectic solvent: A molecular dynamics study

NASA Astrophysics Data System (ADS)

Kaur, Supreet; Sharma, Shobha; Kashyap, Hemant K.

2017-11-01

We apply all-atom molecular dynamics simulations to describe the bulk morphology and interfacial structure of reline, a deep eutectic solvent comprising choline chloride and urea in 1:2 molar ratio, near neutral and charged graphene electrodes. For the bulk phase structural investigation, we analyze the simulated real-space radial distribution functions, X-ray/neutron scattering structure functions, and their partial components. Our study shows that both hydrogen-bonding and long-range correlations between different constituents of reline play a crucial role to lay out the bulk structure of reline. Further, we examine the variation of number density profiles, orientational order parameters, and electrostatic potentials near the neutral and charged graphene electrodes with varying electrode charge density. The present study reveals the presence of profound structural layering of not only the ionic components of reline but also urea near the electrodes. In addition, depending on the electrode charge density, the choline ions and urea molecules render different orientations near the electrodes. The simulated number density and electrostatic potential profiles for reline clearly show the presence of multilayer structures up to a distance of 1.2 nm from the respective electrodes. The observation of positive values of the surface potential at zero charge indicates the presence of significant nonelectrostatic attraction between the choline cation and graphene electrode. The computed differential capacitance (Cd) for reline exhibits an asymmetric bell-shaped curve, signifying different variation of Cd with positive and negative surface potentials.

Bulk and interfacial structures of reline deep eutectic solvent: A molecular dynamics study.

PubMed

Kaur, Supreet; Sharma, Shobha; Kashyap, Hemant K

2017-11-21

We apply all-atom molecular dynamics simulations to describe the bulk morphology and interfacial structure of reline, a deep eutectic solvent comprising choline chloride and urea in 1:2 molar ratio, near neutral and charged graphene electrodes. For the bulk phase structural investigation, we analyze the simulated real-space radial distribution functions, X-ray/neutron scattering structure functions, and their partial components. Our study shows that both hydrogen-bonding and long-range correlations between different constituents of reline play a crucial role to lay out the bulk structure of reline. Further, we examine the variation of number density profiles, orientational order parameters, and electrostatic potentials near the neutral and charged graphene electrodes with varying electrode charge density. The present study reveals the presence of profound structural layering of not only the ionic components of reline but also urea near the electrodes. In addition, depending on the electrode charge density, the choline ions and urea molecules render different orientations near the electrodes. The simulated number density and electrostatic potential profiles for reline clearly show the presence of multilayer structures up to a distance of 1.2 nm from the respective electrodes. The observation of positive values of the surface potential at zero charge indicates the presence of significant nonelectrostatic attraction between the choline cation and graphene electrode. The computed differential capacitance (C d ) for reline exhibits an asymmetric bell-shaped curve, signifying different variation of C d with positive and negative surface potentials.

The legacy of wetland drainage on the remaining peat in the Sacramento-San Joaquin Delta, California, USA

USGS Publications Warehouse

Drexler, Judith Z.; Christian S. de Fontaine,; Steven J. Deverel,

2009-01-01

Throughout the world, many extensive wetlands, such as the Sacramento-San Joaquin Delta of California (hereafter, the Delta), have been drained for agriculture, resulting in land-surface subsidence of peat soils. The purpose of this project was to study the in situ effects of wetland drainage on the remaining peat in the Delta. Peat cores were retrieved from four drained, farmed islands and four relatively undisturbed, marsh islands. Core samples were analyzed for bulk density and percent organic carbon. Macrofossils in the peat were dated using radiocarbon age determination. The peat from the farmed islands is highly distinct from marsh island peat. Bulk density of peat from the farmed islands is generally greater than that of the marsh islands at a given organic carbon content. On the farmed islands, increased bulk density, which is an indication of compaction, decreases with depth within the unoxidized peat zone, whereas, on the marsh islands, bulk density is generally constant with depth except near the surface. Approximately 55–80% of the original peat layer on the farmed islands has been lost due to landsurface subsidence. For the center regions of the farmed islands, this translates into an estimated loss of between 2900-5700 metric tons of organic carbon/hectare. Most of the intact peat just below the currently farmed soil layer is over 4000 years old. Peat loss will continue as long as the artificial water table on the farmed islands is held below the land surface.

Simulation of Space Charge Dynamic in Polyethylene Under DC Continuous Electrical Stress

NASA Astrophysics Data System (ADS)

Boukhari, Hamed; Rogti, Fatiha

2016-10-01

The space charge dynamic plays a very important role in the aging and breakdown of polymeric insulation materials under high voltage. This is due to the intensification of the local electric field and the attendant chemical-mechanical effects in the vicinity around the trapped charge. In this paper, we have investigated the space charge dynamic in low-density polyethylene under high direct-current voltage, which is evaluated by experimental conditions. The evaluation is on the basis of simulation using a bipolar charge transport model consisting of charge injection, transports, trapping, detrapping, and recombination phenomena. The theoretical formulation of the physical problem is based on the Poisson, the continuity, and the transport equations. Numerical results provide temporal and local distributions of the electric field, the space charge density for the different kinds of charges (net charge density, mobile and trapped of electron density, mobile hole density), conduction and displacement current densities, and the external current. The result shows the appearance of the negative packet-like space charge with a large amount of the bulk under the dc electric field of 100 kV/mm, and the induced distortion of the electric field is largely near to the anode, about 39% higher than the initial electric field applied.

Quasiparticle band gap in the topological insulator Bi2Te3

NASA Astrophysics Data System (ADS)

Nechaev, I. A.; Chulkov, E. V.

2013-10-01

We present a theoretical study of dispersion of states that form the bulk band-gap edges in the three-dimensional topological insulator Bi2Te3. Within density functional theory, we analyze the effect of atomic positions varied within the error range of the available experimental data and approximation chosen for the exchange-correlation functional on the bulk band gap and k-space location of valence- and conduction-band extrema. For each set of the positions with different exchange-correlation functionals, we show how many-body corrections calculated within a one-shot GW approach affect the mentioned characteristics of electronic structure of Bi2Te3. We thus also illustrate to what degree the one-shot GW results are sensitive to the reference one-particle band structure in the case of bismuth telluride. We found that for this topological insulator the GW corrections enlarge the fundamental band gap and for certain atomic positions and reference band structure bring its value in close agreement with experiment.

Wavefunction Properties and Electronic Band Structures of High-Mobility Semiconductor Nanosheet MoS2

NASA Astrophysics Data System (ADS)

Baik, Seung Su; Lee, Hee Sung; Im, Seongil; Choi, Hyoung Joon; Ccsaemp Team; Edl Team

2014-03-01

Molybdenum disulfide (MoS2) nanosheet is regarded as one of the most promising alternatives to the current semiconductors due to its significant band-gap and electron-mobility enhancement upon exfoliating. To elucidate such thickness-dependent properties, we have studied the electronic band structures of bulk and monolayer MoS2 by using the first-principles density-functional method as implemented in the SIESTA code. Based on the wavefunction analyses at the conduction band minimum (CBM) points, we have investigated possible origins of mobility difference between bulk and monolayer MoS2. We provide formation energies of substitutional impurities at the Mo and S sites, and discuss feasible electron sources which may induce a significant difference in the carrier lifetime. This work was supported by NRF of Korea (Grant Nos. 2009-0079462 and 2011-0018306), Nano-Material Technology Development Program (2012M3a7B4034985), and KISTI supercomputing center (Project No. KSC-2013-C3-008). Center for Computational Studies of Advanced Electronic Material Properties.

Alkaline earth lead and tin compounds Ae2Pb, Ae2Sn, Ae = Ca, Sr, Ba, as thermoelectric materials

PubMed Central

Parker, David; Singh, David J

2013-01-01

We present a detailed theoretical study of three alkaline earth compounds Ca2Pb, Sr2Pb and Ba2Pb, which have undergone little previous study, calculating electronic band structures and Boltzmann transport and bulk moduli using density functional theory. We also study the corresponding tin compounds Ca2Sn, Sr2Sn and Ba2Sn. We find that these are all narrow band gap semiconductors with an electronic structure favorable for thermoelectric performance, with substantial thermopowers for the lead compounds at temperature ranges from 300 to 800 K. For the lead compounds, we further find very low calculated bulk moduli—roughly half of the values for the lead chalcogenides, suggestive of soft phonons and hence low lattice thermal conductivity. All these facts indicate that these materials merit experimental investigation as potential high performance thermoelectrics. We find good potential for thermoelectric performance in the environmentally friendly stannide materials, particularly at high temperature. PMID:27877610

Momentum and charge transport in non-relativistic holographic fluids from Hořava gravity

NASA Astrophysics Data System (ADS)

Davison, Richard A.; Grozdanov, Sašo; Janiszewski, Stefan; Kaminski, Matthias

2016-11-01

We study the linearized transport of transverse momentum and charge in a conjectured field theory dual to a black brane solution of Hořava gravity with Lifshitz exponent z = 1. As expected from general hydrodynamic reasoning, we find that both of these quantities are diffusive over distance and time scales larger than the inverse temperature. We compute the diffusion constants and conductivities of transverse momentum and charge, as well the ratio of shear viscosity to entropy density, and find that they differ from their relativistic counterparts. To derive these results, we propose how the holographic dictionary should be modified to deal with the multiple horizons and differing propagation speeds of bulk excitations in Hořava gravity. When possible, as a check on our methods and results, we use the covariant Einstein-Aether formulation of Hořava gravity, along with field redefinitions, to re-derive our results from a relativistic bulk theory.

Charge Carrier Dynamics in Cs2AgBiBr6 Double Perovskite

PubMed Central

2018-01-01

Double perovskites, comprising two different cations, are potential nontoxic alternatives to lead halide perovskites. Here, we characterized thin films and crystals of Cs2AgBiBr6 by time-resolved microwave conductance (TRMC), which probes formation and decay of mobile charges upon pulsed irradiation. Optical excitation of films results in the formation of charges with a yield times mobility product, φΣμ > 1 cm2/Vs. On excitation of millimeter-sized crystals, the TRMC signals show, apart from a fast decay, a long-lived tail. Interestingly, this tail is dominant when exciting close to the bandgap, implying the presence of mobile charges with microsecond lifetimes. From the temperature and intensity dependence of the TRMC signals, we deduce a shallow trap state density of around 1016/cm3 in the bulk of the crystal. Despite this high concentration, trap-assisted recombination of charges in the bulk appears to be slow, which is promising for photovoltaic applications. PMID:29545908

Novel strategy to improve the Li-storage performance of micro silicon anodes

NASA Astrophysics Data System (ADS)

Choi, Min-Jae; Xiao, Ying; Hwang, Jang-Yeon; Belharouak, Ilias; Sun, Yang-Kook

2017-04-01

Silicon (Si)-based materials have attracted significant research as an outstanding candidate for the anode material of lithium-ion batteries. However, the tremendous volume change and poor electron conductivity of bulk silicon result in inferior capacity retention and low Coulombic efficiency. Designing special Si with high energy density and good stability in a bulk electrode remains a significant challenge. In this work, we introduce an ingenious strategy to modify micro silicon by designing a porous structure, constructing nanoparticle blocks, and introducing carbon nanotubes as wedges. A disproportion reaction, coupled with a chemical etching process and a ball-milling reaction, are applied to generate the desired material. The as-prepared micro silicon material features porosity, small primary particles, and effective CNT-wedging, which combine to endow the resultant anode with a high reversible specific capacity of up to 2028.6 mAh g-1 after 100 cycles and excellent rate capability. The superior electrochemical performance is attributed to the unique architecture and optimized composition.

High density hexagonal boron nitride prepared by hot isostatic pressing in refractory metal containers

DOEpatents

Hoenig, Clarence L.

1992-01-01

Boron nitride powder with less than or equal to the oxygen content of starting powder (down to 0.5% or less) is hot isostatically pressed in a refractory metal container to produce hexagonal boron nitride with a bulk density greater than 2.0 g/cc. The refractory metal container is formed of tantalum, niobium, tungsten, molybdenum or alloys thereof in the form of a canister or alternatively plasma sprayed or chemical vapor deposited onto a powder compact. Hot isostatic pressing at 1800.degree. C. and 30 KSI (206.8 MPa) argon pressure for four hours produces a bulk density of 2.21 g/cc. Complex shapes can be made.

Bipolar stacked quasi-all-solid-state lithium secondary batteries with output cell potentials of over 6 V

PubMed Central

Matsuo, Takahiro; Gambe, Yoshiyuki; Sun, Yan; Honma, Itaru

2014-01-01

Designing a lithium ion battery (LIB) with a three-dimensional device structure is crucial for increasing the practical energy storage density by avoiding unnecessary supporting parts of the cell modules. Here, we describe the superior secondary battery performance of the bulk all-solid-state LIB cell and a multilayered stacked bipolar cell with doubled cell potential of 6.5 V, for the first time. The bipolar-type solid LIB cell runs its charge/discharge cycle over 200 times in a range of 0.1–1.0 C with negligible capacity decrease despite their doubled output cell potentials. This extremely high performance of the bipolar cell is a result of the superior battery performance of the single cell; the bulk all-solid-state cell has a charge/discharge cycle capability of over 1500 although metallic lithium and LiFePO4 are employed as anodes and cathodes, respectively. The use of a quasi-solid electrolyte consisting of ionic liquid and Al2O3 nanoparticles is considered to be responsible for the high ionic conductivity and electrochemical stability at the interface between the electrodes and the electrolyte. This paper presents the effective applications of SiO2, Al2O3, and CeO2 nanoparticles and various Li+ conducting ionic liquids for the quasi-solid electrolytes and reports the best ever known cycle performances. Moreover, the results of this study show that the bipolar stacked three-dimensional device structure would be a smart choice for future LIBs with higher cell energy density and output potential. In addition, our report presents the advantages of adopting a three-dimensional cell design based on the solid-state electrolytes, which is of particular interest in energy-device engineering for mobile applications. PMID:25124398

Selected physical properties of rocks from the Baid al Jimalah West tungsten deposit, Kingdom of Saudi Arabia, and recommendations for geophysical surveys

USGS Publications Warehouse

Gettings, M.E.

1983-01-01

Bulk density and magnetic susceptibility of 11 outcrop samples representing the Proterozoic lithologic units at the Baid al Jimalah West tungsten deposit, Kingdom of Saudi Arabia were measured. Induced polarization response, apparent resistivity, and electromagnetic conductivity were determined for four specimens of the sample suite. Measurements show that there is a negative density contrast of about -0.17 g-cm^-3 between metasedimentary rocks of the Murdama group and the Bald al Jimalah graaite and that this contrast decreases with increasing mineralization of the granite. Similarly, the bulk magnetic susceptibility of the granite is about one-third that of the Murdama rocks for this sample suite; however, magnetic susceptibility increases with increasing mineralization in the granite specimens. Electromagnetic conductivities are uniformly low, in part because the specimens are weathered, but probably also because intense silicification accompanies the mineralization. Induced polarization chargeability increases in the granitic specimens with increasing mineralization and reflects higher percentages of sulfide minerals. Chargeability for the mineralized rocks is about four times higher than for the Murdama host rocks, and apparent resistivity values are about one-fifth the values of host rocks. Based on these results, it is recommended that during reconnaissance exploration of the area 15 detailed high-precision gravity profiles at 10 m to 50 m station spacing and eight induced polarization dipole-dipole profiles at 25 m dipole spacing and maximum 'n' of 6 be measured. To help define subsurface structure, a high-precision, ground-magnetic survey (map at 2-gamma contour interval) and a four-channel gamma ray spectrometric survey on a 25x50 m grid covering the area of the profiles are recommended.

On the Astrid asteroid family

NASA Astrophysics Data System (ADS)

Carruba, V.

2016-09-01

Among asteroid families, the Astrid family is peculiar because of its unusual inclination distribution. Objects at a ≃ 2.764 au are quite dispersed in this orbital element, giving the family a `crab-like' appearance. Recent works showed that this feature is caused by the interaction of the family with the s - sC nodal secular resonance with Ceres, that spreads the inclination of asteroids near its separatrix. As a consequence, the currently observed distribution of the vW component of terminal ejection velocities obtained from inverting Gauss equation is quite leptokurtic, since this parameter mostly depends on the asteroids inclination. The peculiar orbital configuration of the Astrid family can be used to set constraints on key parameters describing the strength of the Yarkovsky force, such as the bulk and surface density and the thermal conductivity of surface material. By simulating various fictitious families with different values of these parameters, and by demanding that the current value of the kurtosis of the distribution in vW be reached over the estimated lifetime of the family, we obtained that the thermal conductivity of Astrid family members should be ≃0.001 W m-1 K-1, and that the surface and bulk density should be higher than 1000 kg m-3. Monte Carlo methods simulating Yarkovsky and stochastic Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) evolution of the Astrid family show its age to be T = 140 ± 30 Myr old, in good agreement with estimates from other groups. Its terminal ejection velocity parameter is in the range V_{EJ}= 5^{+17}_{-5} m s-1. Values of VEJ larger than 25 m s-1 are excluded from constraints from the current inclination distribution.

Thermoelectric and phonon transport properties of two-dimensional IV-VI compounds.

PubMed

Shafique, Aamir; Shin, Young-Han

2017-03-30

We explore the thermoelectric and phonon transport properties of two-dimensional monochalcogenides (SnSe, SnS, GeSe, and GeS) using density functional theory combined with Boltzmann transport theory. We studied the electronic structures, Seebeck coefficients, electrical conductivities, lattice thermal conductivities, and figures of merit of these two-dimensional materials, which showed that the thermoelectric performance of monolayer of these compounds is improved in comparison compared to their bulk phases. High figures of merit (ZT) are predicted for SnSe (ZT = 2.63, 2.46), SnS (ZT = 1.75, 1.88), GeSe (ZT = 1.99, 1.73), and GeS (ZT = 1.85, 1.29) at 700 K along armchair and zigzag directions, respectively. Phonon dispersion calculations confirm the dynamical stability of these compounds. The calculated lattice thermal conductivities are low while the electrical conductivities and Seebeck coefficients are high. Thus, the properties of the monolayers show high potential toward thermoelectric applications.

Two-Step Reactive Aid Sintering of BaZr0.8Y0.2O3- δ Proton-Conducting Ceramics

NASA Astrophysics Data System (ADS)

Wang, Siwei; Chen, Yan; Zhang, Lingling; Ren, Cong; Chen, Fanglin; Brinkman, Kyle S.

2015-12-01

Ceramic-based proton conductors enable high-temperature hydrogen economy applications such as hydrogen separation membranes, fuel cells, and steam electrolyzers. BaZr0.8Y0.2O3- δ (BZY) proton-conducting oxide possesses the highest level of proton conductivity reported to date, but poor sinterability hinders its widespread utilization. In this paper, we report a two-step reactive aid sintering (TRAS) method involving the introduction of BaCO3 and B2O3-Li2O for the preparation of dense BZY ceramics sintered at 1500°C. The resulting BZY samples showed a pure perovskite structure with a dramatic increase in the relative density to 91.5%. In addition, the shrinkage during sintering was improved to 19.3% by a TRAS method as compared to 2.6% by the conventional solid date reaction method. The bulk conductivity was improved due to enhanced densification, while the grain boundary conductivity decreased due to the blocking behavior of the sintering aid resulting in a decrease in the total conductivity of the samples.

Seeded growth of boron arsenide single crystals with high thermal conductivity

NASA Astrophysics Data System (ADS)

Tian, Fei; Song, Bai; Lv, Bing; Sun, Jingying; Huyan, Shuyuan; Wu, Qi; Mao, Jun; Ni, Yizhou; Ding, Zhiwei; Huberman, Samuel; Liu, Te-Huan; Chen, Gang; Chen, Shuo; Chu, Ching-Wu; Ren, Zhifeng

2018-01-01

Materials with high thermal conductivities are crucial to effectively cooling high-power-density electronic and optoelectronic devices. Recently, zinc-blende boron arsenide (BAs) has been predicted to have a very high thermal conductivity of over 2000 W m-1 K-1 at room temperature by first-principles calculations, rendering it a close competitor for diamond which holds the highest thermal conductivity among bulk materials. Experimental demonstration, however, has proved extremely challenging, especially in the preparation of large high quality single crystals. Although BAs crystals have been previously grown by chemical vapor transport (CVT), the growth process relies on spontaneous nucleation and results in small crystals with multiple grains and various defects. Here, we report a controllable CVT synthesis of large single BAs crystals (400-600 μm) by using carefully selected tiny BAs single crystals as seeds. We have obtained BAs single crystals with a thermal conductivity of 351 ± 21 W m-1 K-1 at room temperature, which is almost twice as conductive as previously reported BAs crystals. Further improvement along this direction is very likely.

Two-Step Reactive Aid Sintering of BaZr 0.8Y 0.2O 3-δ Proton-Conducting Ceramics

DOE PAGES

Wang, Siwei; Chen, Yan; Zhang, Lingling; ...

2015-10-14

Ceramic-based proton conductors enable high-temperature hydrogen economy applications such as hydrogen separation membranes, fuel cells, and steam electrolyzers. BaZr 0.8Y 0.2O 3-δ (BZY) proton-conducting oxide possesses the highest level of proton conductivity reported to date, but poor sinterability hinders its widespread utilization. Here, we report a two-step reactive aid sintering (TRAS) method involving the introduction of BaCO 3 and B 2O 3-Li 2O for the preparation of dense BZY ceramics sintered at 1500°C. The resulting BZY samples showed a pure perovskite structure with a dramatic increase in the relative density to 91.5%. In addition, the shrinkage during sintering was improvedmore » to 19.3% by a TRAS method as compared to 2.6% by the conventional solid date reaction method. Moreover, the bulk conductivity was improved due to enhanced densification, while the grain boundary conductivity decreased due to the blocking behavior of the sintering aid resulting in a decrease in the total conductivity of the samples.« less

A density functional theory for association of fluid molecules with a functionalized surface: fluid-wall single and double bonding.

PubMed

Haghmoradi, Amin; Wang, Le; Chapman, Walter G

2017-02-01

In this manuscript we extend Wertheim's two-density formalism beyond its first order to model a system of fluid molecules with a single association site close to a planar hard wall with association sites on its surface in a density functional theory framework. The association sites of the fluid molecules are small enough that they can form only one bond, while the wall association sites are large enough to bond with more than one fluid molecule. The effects of temperature and of bulk fluid and wall site densities on the fluid density profile, extent of association, and competition between single and double bonding of fluid segments at the wall sites versus distance from the wall are presented. The theory predictions are compared with new Monte Carlo simulation results and they are in good agreement. The theory captures the surface coverage over wide ranges of temperature and bulk density by introducing the effect of steric hindrance in fluid association at a wall site.

IN SITU APPARENT CONDUCTIVITY MEASUREMENTS AND MICROBIAL POPULATION DISTRIBUTION AT A HYDROCARBON CONTAMINATED SITE

EPA Science Inventory

We investigated the bulk electrical conductivity and microbial population distribution in sediments at a site contaminated with light non-aqueous phase liquid (LNAPL). The bulk conductivity was measured using in situ vertical resistivity probes, while the most probable number met...

Cometary water-group ions in the region surrounding Comet Giacobini-Zinner - Distribution functions and bulk parameter estimates

NASA Astrophysics Data System (ADS)

Staines, K.; Balogh, A.; Cowley, S. W. H.; Hynds, R. J.; Yates, T. S.; Richardson, I. G.; Sanderson, T. R.; Wenzel, K. P.; McComas, D. J.; Tsurutani, B. T.

1991-03-01

The bulk parameters (number density and thermal energy density) of cometary water-group ions in the region surrounding Comet Giacobini-Zinner have been derived using data from the EPAS instrument on the ICE spacecraft. The derivation is based on the assumption that the pick-up ion distribution function is isotropic in the frame of the bulk flow, an approximation which has previously been shown to be reasonable within about 400,000 km of the comet nucleus along the spacecraft trajectory. The transition between the pick-up and mass-loaded regions occurs at the cometary shock, which was traversed at a cometocentric distance of about 100,000 km along the spacecraft track. Examination of the ion distribution functions in this region, transformed to the bulk flow frame, indicates the occurrence of a flattened distribution in the vicinity of the local pick-up speed, and a steeply falling tail at speeds above, which may be approximated as an exponential in ion speed.

Excess electrons in ice: a density functional theory study.

PubMed

Bhattacharya, Somesh Kr; Inam, Fakharul; Scandolo, Sandro

2014-02-21

We present a density functional theory study of the localization of excess electrons in the bulk and on the surface of crystalline and amorphous water ice. We analyze the initial stages of electron solvation in crystalline and amorphous ice. In the case of crystalline ice we find that excess electrons favor surface states over bulk states, even when the latter are localized at defect sites. In contrast, in amorphous ice excess electrons find it equally favorable to localize in bulk and in surface states which we attribute to the preexisting precursor states in the disordered structure. In all cases excess electrons are found to occupy the vacuum regions of the molecular network. The electron localization in the bulk of amorphous ice is assisted by its distorted hydrogen bonding network as opposed to the crystalline phase. Although qualitative, our results provide a simple interpretation of the large differences observed in the dynamics and localization of excess electrons in crystalline and amorphous ice films on metals.

Arrhenius Behavior of the Bulk Na-Ion Conductivity in Na3Sc2(PO4)3 Single Crystals Observed by Microcontact Impedance Spectroscopy.

PubMed

Rettenwander, Daniel; Redhammer, Günther J; Guin, Marie; Benisek, Artur; Krüger, Hannes; Guillon, Olivier; Wilkening, Martin; Tietz, Frank; Fleig, Jürgen

2018-03-13

NASICON-based solid electrolytes with exceptionally high Na-ion conductivities are considered to enable future all solid-state Na-ion battery technologies. Despite 40 years of research the interrelation between crystal structure and Na-ion conduction is still controversially discussed and far from being fully understood. In this study, microcontact impedance spectroscopy combined with single crystal X-ray diffraction, and differential scanning calorimetry is applied to tackle the question how bulk Na-ion conductivity σ bulk of sub-mm-sized flux grown Na 3 Sc 2 (PO 4 ) 3 (NSP) single crystals is influenced by supposed phase changes (α, β, and γ phase) discussed in literature. Although we found a smooth structural change at around 140 °C, which we assign to the β → γ phase transition, our conductivity data follow a single Arrhenius law from room temperature (RT) up to 220 °C. Obviously, the structural change, being mainly related to decreasing Na-ion ordering with increasing temperature, does not cause any jumps in Na-ion conductivity or any discontinuities in activation energies E a . Bulk ion dynamics in NSP have so far rarely been documented; here, under ambient conditions, σ bulk turned out to be as high as 3 × 10 -4 S cm -1  at RT ( E a, bulk = 0.39 eV) when directly measured with microcontacts for individual small single crystals.

Arrhenius Behavior of the Bulk Na-Ion Conductivity in Na3Sc2(PO4)3 Single Crystals Observed by Microcontact Impedance Spectroscopy

PubMed Central

2018-01-01

NASICON-based solid electrolytes with exceptionally high Na-ion conductivities are considered to enable future all solid-state Na-ion battery technologies. Despite 40 years of research the interrelation between crystal structure and Na-ion conduction is still controversially discussed and far from being fully understood. In this study, microcontact impedance spectroscopy combined with single crystal X-ray diffraction, and differential scanning calorimetry is applied to tackle the question how bulk Na-ion conductivity σbulk of sub-mm-sized flux grown Na3Sc2(PO4)3 (NSP) single crystals is influenced by supposed phase changes (α, β, and γ phase) discussed in literature. Although we found a smooth structural change at around 140 °C, which we assign to the β → γ phase transition, our conductivity data follow a single Arrhenius law from room temperature (RT) up to 220 °C. Obviously, the structural change, being mainly related to decreasing Na-ion ordering with increasing temperature, does not cause any jumps in Na-ion conductivity or any discontinuities in activation energies Ea. Bulk ion dynamics in NSP have so far rarely been documented; here, under ambient conditions, σbulk turned out to be as high as 3 × 10–4 S cm–1 at RT (Ea, bulk = 0.39 eV) when directly measured with microcontacts for individual small single crystals. PMID:29606799

Spontaneous time reversal symmetry breaking in atomically confined two-dimensional impurity bands in silicon and germanium

NASA Astrophysics Data System (ADS)

Ghosh, Arindam

Three-dimensional bulk-doped semiconductors, in particular phosphorus (P)-doped silicon (Si) and germanium (Ge), are among the best studied systems for many fundamental concepts in solid state physics, ranging from the Anderson metal-insulator transition to the many-body Coulomb interaction effects on quantum transport. Recent advances in material engineering have led to vertically confined doping of phosphorus (P) atoms inside bulk crystalline silicon and germanium, where the electron transport occurs through one or very few atomic layers, constituting a new and unique platform to investigate many of these phenomena at reduced dimensions. In this talk I shall present results of extensive quantum transport experiments in delta-doped silicon and germanium epilayers, over a wide range of doping density that allow independent tuning of the on-site Coulomb interaction and hopping energy scales. We find that low-frequency flicker noise, or the 1 / f noise, in the electrical conductance of these systems is exceptionally low, and in fact among the lowest when compared with other low-dimensional materials. This is attributed to the physical separation of the conduction electrons, embedded inside the crystalline semiconductor matrix, from the charged fluctuators at the surface. Most importantly, we find a remarkable suppression of weak localization effects, including the quantum correction to conductivity and universal conductance fluctuations, with decreasing doping density or, equivalently, increasing effective on-site Coulomb interaction. In-plane magneto-transport measurements indicate the presence of intrinsic local spin fluctuations at low doping although no signatures of long range magnetic order could be identified. We argue that these results indicate a spontaneous breakdown of time reversal symmetry, which is one of the most fundamental and robust symmetries of nonmagnetic quantum systems. While the microscopic origin of this spontaneous time reversal symmetry breaking remains unknown, we believe this indicates a new many-body electronic phase in two-dimensionally doped silicon and germanium with a half-filled impurity band. We acknowledge financial support from Department of Science and Technology, Government of India, and Australia-India Strategic Research Fund (AISRF).

Transport of water and ions in partially water-saturated porous media. Part 1. Constitutive equations

NASA Astrophysics Data System (ADS)

Revil, A.

2017-05-01

I developed a model of cross-coupled flow in partially saturated porous media based on electrokinetic coupling including the effect of ion filtration (normal and reverse osmosis) and the multi-component nature of the pore water (wetting) phase. The model also handles diffusion and membrane polarization but is valid only for saturations above the irreducible water saturation. I start with the local Nernst-Planck and Stokes equations and I use a volume-averaging procedure to obtain the generalized Ohm, Fick, and Darcy equations with cross-coupling terms at the scale of a representative elementary volume of the porous rock. These coupling terms obey Onsager's reciprocity, which is a required condition, at the macroscale, to keep the total dissipation function of the system positive. Rather than writing the electrokinetic terms in terms of zeta potential (the double layer electrical potential on the slipping plane located in the pore water), I developed the model in terms of an effective charge density dragged by the flow of the pore water. This effective charge density is found to be strongly controlled by the permeability and the water saturation. I also developed an electrical conductivity equation including the effect of saturation on both bulk and surface conductivities, the surface conductivity being associated with electromigration in the electrical diffuse layer coating the grains. This surface conductivity depends on the CEC of the porous material.

Physical properties of sidewall cores from Decatur, Illinois

USGS Publications Warehouse

Morrow, Carolyn A.; Kaven, Joern; Moore, Diane E.; Lockner, David A.

2017-10-18

To better assess the reservoir conditions influencing the induced seismicity hazard near a carbon dioxide sequestration demonstration site in Decatur, Ill., core samples from three deep drill holes were tested to determine a suite of physical properties including bulk density, porosity, permeability, Young’s modulus, Poisson’s ratio, and failure strength. Representative samples of the shale cap rock, the sandstone reservoir, and the Precambrian basement were selected for comparison. Physical properties were strongly dependent on lithology. Bulk density was inversely related to porosity, with the cap rock and basement samples being both least porous (

Electrical method for the measurements of volume averaged electron density and effective coupled power to the plasma bulk

NASA Astrophysics Data System (ADS)

Henault, M.; Wattieaux, G.; Lecas, T.; Renouard, J. P.; Boufendi, L.

2016-02-01

Nanoparticles growing or injected in a low pressure cold plasma generated by a radiofrequency capacitively coupled capacitive discharge induce strong modifications in the electrical parameters of both plasma and discharge. In this paper, a non-intrusive method, based on the measurement of the plasma impedance, is used to determine the volume averaged electron density and effective coupled power to the plasma bulk. Good agreements are found when the results are compared to those given by other well-known and established methods.

Bianchi type-VIh string cloud cosmological models with bulk viscosity

NASA Astrophysics Data System (ADS)

Tripathy, Sunil K.; Behera, Dipanjali

2010-11-01

String cloud cosmological models are studied using spatially homogeneous and anisotropic Bianchi type VIh metric in the frame work of general relativity. The field equations are solved for massive string cloud in presence of bulk viscosity. A general linear equation of state of the cosmic string tension density with the proper energy density of the universe is considered. The physical and kinematical properties of the models have been discussed in detail and the limits of the anisotropic parameter responsible for different phases of the universe are explored.

CONDUCTIVITY PROFILE RATE OF CHANGE FROM FIELD AND LABORATORY DATA WITHIN BIODEGRADING PETROLEUM HYDROCARBON

EPA Science Inventory

We present the results of long term (500 days) measurements of the bulk conductivity in a field and laboratory experiment. Our objective was to determine the rate of change in bulk conductivity and whether this rate of change correlated with the petroleum hydrocarbon degradation...

On-surface synthesis on a bulk insulator surface

NASA Astrophysics Data System (ADS)

Richter, Antje; Floris, Andrea; Bechstein, Ralf; Kantorovich, Lev; Kühnle, Angelika

2018-04-01

On-surface synthesis has rapidly emerged as a most promising approach to prepare functional molecular structures directly on a support surface. Compared to solution synthesis, performing chemical reactions on a surface offers several exciting new options: due to the absence of a solvent, reactions can be envisioned that are otherwise not feasible due to the insolubility of the reaction product. Perhaps even more important, the confinement to a two-dimensional surface might enable reaction pathways that are not accessible otherwise. Consequently, on-surface synthesis has attracted great attention in the last decade, with an impressive number of classical reactions transferred to a surface as well as new reactions demonstrated that have no classical analogue. So far, the majority of the work has been carried out on conducting surfaces. However, when aiming for electronic decoupling of the resulting structures, e.g. for the use in future molecular electronic devices, non-conducting surfaces are highly desired. Here, we review the current status of on-surface reactions demonstrated on the (10.4) surface of the bulk insulator calcite. Besides thermally induced C-C coupling of halogen-substituted aryls, photochemically induced [2  +  2] cycloaddition has been proven possible on this surface. Moreover, experimental evidence exists for coupling of terminal alkynes as well as diacetylene polymerization. While imaging of the resulting structures with dynamic atomic force microscopy provides a direct means of reaction verification, the detailed reaction pathway often remains unclear. Especially in cases where the presence of metal atoms is known to catalyze the corresponding solution chemistry reaction (e.g. in the case of the Ullmann reaction), disclosing the precise reaction pathway is of importance to understand and generalize on-surface reactivity on a bulk insulator surface. To this end, density-functional theory calculations have proven to provide atomic-scale insights that have greatly contributed to unravelling the details of on-surface synthesis on a bulk insulator surface.

Simultaneous measurement of thermal conductivity and heat capacity of bulk and thin film materials using frequency-dependent transient thermoreflectance method.

PubMed

Liu, Jun; Zhu, Jie; Tian, Miao; Gu, Xiaokun; Schmidt, Aaron; Yang, Ronggui

2013-03-01

The increasing interest in the extraordinary thermal properties of nanostructures has led to the development of various measurement techniques. Transient thermoreflectance method has emerged as a reliable measurement technique for thermal conductivity of thin films. In this method, the determination of thermal conductivity usually relies much on the accuracy of heat capacity input. For new nanoscale materials with unknown or less-understood thermal properties, it is either questionable to assume bulk heat capacity for nanostructures or difficult to obtain the bulk form of those materials for a conventional heat capacity measurement. In this paper, we describe a technique for simultaneous measurement of thermal conductivity κ and volumetric heat capacity C of both bulk and thin film materials using frequency-dependent time-domain thermoreflectance (TDTR) signals. The heat transfer model is analyzed first to find how different combinations of κ and C determine the frequency-dependent TDTR signals. Simultaneous measurement of thermal conductivity and volumetric heat capacity is then demonstrated with bulk Si and thin film SiO2 samples using frequency-dependent TDTR measurement. This method is further testified by measuring both thermal conductivity and volumetric heat capacity of novel hybrid organic-inorganic thin films fabricated using the atomic∕molecular layer deposition. Simultaneous measurement of thermal conductivity and heat capacity can significantly shorten the development∕discovery cycle of novel materials.

Technical issues of a high-Tc superconducting bulk magnet

NASA Astrophysics Data System (ADS)

Fujimoto, Hiroyuki

2000-06-01

Superconducting magnets made of high-Tc superconductors are promising for industrial applications. It is well known that REBa2Cu3O7-x superconductors prepared by melt processes have a high critical current density, Jc, at 77 K and high magnetic fields. The materials are very promising for high magnetic field applications as a superconducting permanent/bulk magnet with liquid-nitrogen refrigeration. Light rare-earth (LRE) BaCuO bulks, compared with REBaCuO bulks, exhibit a larger Jc in high magnetic fields and a much improved irreversibility field, Hirr, at 77 K. In this study, we discuss technical issues of a high-Tc superconducting bulk magnet, namely the aspects of the melt processing for bulk superconductors, their characteristic superconducting properties and mechanical properties, and trapped field properties of a superconducting bulk magnet. One of the possible applications is a superconducting bulk magnet for the magnetically levitated (Maglev) train in the future.

Aerogel Beads as Cryogenic Thermal Insulation System

NASA Technical Reports Server (NTRS)

Fesmire, J. E.; Augustynowicz, S. D.; Rouanet, S.; Thompson, Karen (Technical Monitor)

2001-01-01

An investigation of the use of aerogel beads as thermal insulation for cryogenic applications was conducted at the Cryogenics Test Laboratory of NASA Kennedy Space Center. Steady-state liquid nitrogen boiloff methods were used to characterize the thermal performance of aerogel beads in comparison with conventional insulation products such as perlite powder and multilayer insulation (MLI). Aerogel beads produced by Cabot Corporation have a bulk density below 100 kilograms per cubic meter (kg/cubic m) and a mean particle diameter of 1 millimeter (mm). The apparent thermal conductivity values of the bulk material have been determined under steady-state conditions at boundary temperatures of approximately 293 and 77 kelvin (K) and at various cold vacuum pressures (CVP). Vacuum levels ranged from 10(exp -5) torr to 760 torr. All test articles were made in a cylindrical configuration with a typical insulation thickness of 25 mm. Temperature profiles through the thickness of the test specimens were also measured. The results showed the performance of the aerogel beads was significantly better than the conventional materials in both soft-vacuum (1 to 10 torr) and no-vacuum (760 torr) ranges. Opacified aerogel beads performed better than perlite powder under high-vacuum conditions. Further studies for material optimization and system application are in progress.

Transmission through a potential barrier in Luttinger liquids with a topological spin gap

NASA Astrophysics Data System (ADS)

Kainaris, Nikolaos; Carr, Sam T.; Mirlin, Alexander D.

2018-03-01

We study theoretically the transport of the one-dimensional single-channel interacting electron gas through a strong potential barrier in the parameter regime where the spin sector of the low-energy theory is gapped by interaction (Luther-Emery liquid). There are two distinct phases of this nature, of which one is of particular interest as it exhibits nontrivial interaction-induced topological properties. Focusing on this phase and using bosonization and an expansion in the tunneling strength we calculate the conductance through the barrier as a function of the temperature as well as the local density of states (LDOS) at the barrier. Our main result concerns the mechanism of bound-state-mediated tunneling. The characteristic feature of the topological phase is the emergence of protected zero-energy bound states with fractional spin located at the impurity position. By flipping this fractional spin, single electrons can tunnel across the impurity even though the bulk spectrum for spin excitations is gapped. This results in a finite LDOS below the bulk gap and in a nonmonotonic behavior of the conductance. The system represents an important physical example of an interacting symmetry-protected topological phase, which combines features of a topological spin insulator and a topological charge metal, in which the topology can be probed by measuring transport properties.

A new theoretical formulation of coupling thermo-electric breakdown in LDPE film under dc high applied fields

NASA Astrophysics Data System (ADS)

Boughariou, F.; Chouikhi, S.; Kallel, A.; Belgaroui, E.

2015-12-01

In this paper, we present a new theoretical and numerical formulation for the electrical and thermal breakdown phenomena, induced by charge packet dynamics, in low-density polyethylene (LDPE) insulating film under dc high applied field. The theoretical physical formulation is composed by the equations of bipolar charge transport as well as by the thermo-electric coupled equation associated for the first time in modeling to the bipolar transport problem. This coupled equation is resolved by the finite-element numerical model. For the first time, all bipolar transport results are obtained under non-uniform temperature distributions in the sample bulk. The principal original results show the occurring of very sudden abrupt increase in local temperature associated to a very sharp increase in external and conduction current densities appearing during the steady state. The coupling between these electrical and thermal instabilities reflects physically the local coupling between electrical conduction and thermal joule effect. The results of non-uniform temperature distributions induced by non-uniform electrical conduction current are also presented for several times. According to our formulation, the strong injection current is the principal factor of the electrical and thermal breakdown of polymer insulating material. This result is shown in this work. Our formulation is also validated experimentally.

Exploring packaging strategies of nano-embedded thermoelectric generators

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

Singha, Aniket; Muralidharan, Bhaskaran, E-mail: bm@ee.iitb.ac.in; Mahanti, Subhendra D.

2015-10-15

Embedding nanostructures within a bulk matrix is an important practical approach towards the electronic engineering of high performance thermoelectric systems. For power generation applications, it ideally combines the efficiency benefit offered by low dimensional systems along with the high power output advantage offered by bulk systems. In this work, we uncover a few crucial details about how to embed nanowires and nanoflakes in a bulk matrix so that an overall advantage over pure bulk may be achieved. First and foremost, we point out that a performance degradation with respect to bulk is inevitable as the nanostructure transitions to a multimore » moded one. It is then shown that a nano embedded system of suitable cross-section offers a power density advantage over a wide range of efficiencies at higher packing fractions, and this range gradually narrows down to the high efficiency regime, as the packing fraction is reduced. Finally, we introduce a metric - the advantage factor, to elucidate quantitatively, the enhancement in the power density offered via nano-embedding at a given efficiency. In the end, we explore the maximum effective width of nano-embedding which serves as a reference in designing generators in the efficiency range of interest.« less

The homogeneity of levitation force in single domain YBCO bulk

NASA Astrophysics Data System (ADS)

Zhou, Keran; Xu, Ke-Xi; Wu, Xing-da; Pan, Peng-jun

2007-11-01

The pellet homogeneity of levitation force versus the position in comparison to the seed or to the top surface has been studied in the entire volume of a single domain YBa 2Cu 3O 7-δ bulk sample processed by the top-seeded melt texturing growth (TSMTG). It is found that the levitation forces increase and peak at a depth of 3 mm from the top of the sample at liquid nitrogen temperature. In other words, the second disk has the largest levitation force density. The phenomenon can be interpreted by the interaction between the microcracks or pores produced by crystal growth and the oxygenation. We propose a model in which Y211 particles distribution leading to microcracks and pores reduces the effective induced shielding current loops (ISCL) and increases the perimeters of ISCL. This corresponds to a decrease in the grain size and results in greatly reduced levitation forces of the bottom of the bulk. From the research, we know that the density of the YBCO bulk is also an important parameter for the levitation properties. The result is very attractive and useful for the fundamental studies and fabrication of TSMTG YBa 2Cu 3O 7-δ bulk.

Estimates of olivine-basaltic melt electrical conductivity using a digital rock physics approach

NASA Astrophysics Data System (ADS)

Miller, Kevin J.; Montési, Laurent G. J.; Zhu, Wen-lu

2015-12-01

Estimates of melt content beneath fast-spreading mid-ocean ridges inferred from magnetotelluric tomography (MT) vary between 0.01 and 0.10. Much of this variation may stem from a lack of understanding of how the grain-scale melt geometry influences the bulk electrical conductivity of a partially molten rock, especially at low melt fraction. We compute bulk electrical conductivity of olivine-basalt aggregates over 0.02 to 0.20 melt fraction by simulating electric current in experimentally obtained partially molten geometries. Olivine-basalt aggregates were synthesized by hot-pressing San Carlos olivine and high-alumina basalt in a solid-medium piston-cylinder apparatus. Run conditions for experimental charges were 1.5 GPa and 1350 °C. Upon completion, charges were quenched and cored. Samples were imaged using synchrotron X-ray micro-computed tomography (μ-CT). The resulting high-resolution, 3-dimensional (3-D) image of the melt distribution constitutes a digital rock sample, on which numerical simulations were conducted to estimate material properties. To compute bulk electrical conductivity, we simulated a direct current measurement by solving the current continuity equation, assuming electrical conductivities for olivine and melt. An application of Ohm's Law yields the bulk electrical conductivity of the partially molten region. The bulk electrical conductivity values for nominally dry materials follow a power-law relationship σbulk = Cσmeltϕm with fit parameters m = 1.3 ± 0.3 and C = 0.66 ± 0.06. Laminar fluid flow simulations were conducted on the same partially molten geometries to obtain permeability, and the respective pathways for electrical current and fluid flow over the same melt geometry were compared. Our results indicate that the pathways for flow fluid are different from those for electric current. Electrical tortuosity is lower than fluid flow tortuosity. The simulation results are compared to existing experimental data, and the potential influence of volatiles and melt films on electrical conductivity of partially molten rocks is discussed.

Modeling of Bulk Evaporation and Condensation

NASA Technical Reports Server (NTRS)

Anghaie, S.; Ding, Z.

1996-01-01

This report describes the modeling and mathematical formulation of the bulk evaporation and condensation involved in liquid-vapor phase change processes. An internal energy formulation, for these phase change processes that occur under the constraint of constant volume, was studied. Compared to the enthalpy formulation, the internal energy formulation has a more concise and compact form. The velocity and time scales of the interface movement were obtained through scaling analysis and verified by performing detailed numerical experiments. The convection effect induced by the density change was analyzed and found to be negligible compared to the conduction effect. Two iterative methods for updating the value of the vapor phase fraction, the energy based (E-based) and temperature based (T-based) methods, were investigated. Numerical experiments revealed that for the evaporation and condensation problems the E-based method is superior to the T-based method in terms of computational efficiency. The internal energy formulation and the E-based method were used to compute the bulk evaporation and condensation processes under different conditions. The evolution of the phase change processes was investigated. This work provided a basis for the modeling of thermal performance of multi-phase nuclear fuel elements under variable gravity conditions, in which the buoyancy convection due to gravity effects and internal heating are involved.

Superelastic Few-Layer Carbon Foam Made from Natural Cotton for All-Solid-State Electrochemical Capacitors.

PubMed

Lin, Tianquan; Liu, Fengxin; Xu, Feng; Bi, Hui; Du, Yahui; Tang, Yufeng; Huang, Fuqiang

2015-11-18

Flexible/stretchable devices for energy storage are essential for future wearable and flexible electronics. Electrochemical capacitors (ECs) are an important technology for supplement batteries in the energy storage and harvesting field, but they are limited by relatively low energy density. Herein, we report a superelastic foam consisting of few-layer carbon nanowalls made from natural cotton as a good scaffold to growth conductive polymer polyaniline for stretchable, lightweight, and flexible all-solid-state ECs. As-prepared superelastic bulk tubular carbon foam (surface area ∼950 m(2)/g) can withstand >90% repeated compression cycling and support >45,000 times its own weight but no damage. The flexible device has a high specific capacitance of 510 F g(-1), a specific energy of 25.5 Wh kg(-1) and a power density of 28.5 kW kg(-1) in weight of the total electrode materials and withstands 5,000 charging/discharging cycles.

Impact of Different Binders on the Roughness, Adhesion Strength, and Other Properties of Mortars with Expanded Cork.

PubMed

Barnat-Hunek, Danuta; Widomski, Marcin K; Szafraniec, Małgorzata; Łagód, Grzegorz

2018-03-01

The aim of the research that is presented in this paper was to evaluate the physical and mechanical properties of heat-insulating mortars with expanded cork aggregates and different binders. In this work, the measurements of surface roughness and adhesion strength, supported by determination of basic mechanical and physical parameters, such as density, bulk density, open porosity, total porosity, absorbability, thermal conductivity coefficient, compressive strength, flexural strength, and frost resistance of mortars containing expanded oak cork, were performed. The scanning electron microscope (SEM) investigations demonstrated the microstructure, contact zone, and distribution of pores in the heat-insulating mortars containing expanded cork. The results indicated that the addition of expanded cork and different binders in heat-insulating mortars triggers changes in their roughness and adhesion strength. The SEM research confirmed the very good adhesion of the paste to the cork aggregate.

Impact of Different Binders on the Roughness, Adhesion Strength, and Other Properties of Mortars with Expanded Cork

PubMed Central

Barnat-Hunek, Danuta; Widomski, Marcin K.; Szafraniec, Małgorzata; Łagód, Grzegorz

2018-01-01

The aim of the research that is presented in this paper was to evaluate the physical and mechanical properties of heat-insulating mortars with expanded cork aggregates and different binders. In this work, the measurements of surface roughness and adhesion strength, supported by determination of basic mechanical and physical parameters, such as density, bulk density, open porosity, total porosity, absorbability, thermal conductivity coefficient, compressive strength, flexural strength, and frost resistance of mortars containing expanded oak cork, were performed. The scanning electron microscope (SEM) investigations demonstrated the microstructure, contact zone, and distribution of pores in the heat-insulating mortars containing expanded cork. The results indicated that the addition of expanded cork and different binders in heat-insulating mortars triggers changes in their roughness and adhesion strength. The SEM research confirmed the very good adhesion of the paste to the cork aggregate. PMID:29494525

Growth and Transport Studies of LaTiO3 / KTaO3 Heterostructures

NASA Astrophysics Data System (ADS)

Zou, K.; Walker, F. J.; Ahn, C. H.

2014-03-01

Perovskite oxide heterostructures provide a rich platform for exploring emergent electronic properties, such as 2D electron gases (2DEGs) at interfaces. In this talk, we present results on the growth of LaTiO3 / KTaO3 heterostructures by molecular beam epitaxy and subsequent measurements of transport properties. Although both oxide materials are insulating in the bulk, metallic conduction is observed from T = 2 - 300 K. We achieve a room temperature carrier mobility of ~ 25 cm2 /Vs at a carrier density of ~ 1014 /cm2. By comparison, 2DEGs in LaTiO3 / SrTiO3 and LaAlO3 / SrTiO3 have lower carrier mobility, but the same carrier density. We attribute some of the increase in mobility to the smaller band effective mass of the Ta 4d electrons compared to the Ti 3d electrons.

Ultralight nanofibre-assembled cellular aerogels with superelasticity and multifunctionality.

PubMed

Si, Yang; Yu, Jianyong; Tang, Xiaomin; Ge, Jianlong; Ding, Bin

2014-12-16

Three-dimensional nanofibrous aerogels (NFAs) that are both highly compressible and resilient would have broad technological implications for areas ranging from electrical devices and bioengineering to damping materials; however, creating such NFAs has proven extremely challenging. Here we report a novel strategy to create fibrous, isotropically bonded elastic reconstructed (FIBER) NFAs with a hierarchical cellular structure and superelasticity by combining electrospun nanofibres and the fibrous freeze-shaping technique. Our approach causes the intrinsically lamellar deposited electrospun nanofibres to assemble into elastic bulk aerogels with tunable densities and desirable shapes on a large scale. The resulting FIBER NFAs exhibit densities of >0.12 mg cm(-3), rapid recovery from deformation, efficient energy absorption and multifunctionality in terms of the combination of thermal insulation, sound absorption, emulsion separation and elasticity-responsive electric conduction. The successful synthesis of such fascinating materials may provide new insights into the design and development of multifunctional NFAs for various applications.

Development of a carbon formation reactor for carbon dioxide reduction

NASA Technical Reports Server (NTRS)

Noyes, G.

1985-01-01

Applied research, engineering development, and performance evaluation were conducted on a process for formation of dense carbon by pyrolysis of methane. Experimental research showed that dense (0.7 to 1.6 g/cc bulk density and 1.6 to 2.2 g/cc solid density) carbon can be produced by methane pyrolysis in quartzwool-packed quartz tubes at temperatrues of 1100 to 1300 C. This result supports the condensation theory of pyrolytic carbon formation from gaseous hydrocarbons. A full-scale Breadboard Carbon Formation Reactor (CFR) was designed, fabricated, and tested at 1100 to 1200 C with 380 to 2280 sccm input flows of methane. Single-pass conversion of methane to carbon ranged from 60 to 100 percent, with 89 percent average conversion. Performance was projected for an Advanced Carbon Reactor Subsystem (ACRS) which indicated that the ACRS is a viable option for management of metabolic carbon on long-duration space missions.

Expanded graphite embedded with aluminum nanoparticles as superior thermal conductivity anodes for high-performance lithium-ion batteries

PubMed Central

Zhao, Tingkai; She, Shengfei; Ji, Xianglin; Guo, Xinai; Jin, Wenbo; Zhu, Ruoxing; Dang, Alei; Li, Hao; Li, Tiehu; Wei, Bingqing

2016-01-01

The development of high capacity and long-life lithium-ion batteries is a long-term pursuing and under a close scrutiny. Most of the researches have been focused on exploring electrode materials and structures with high store capability of lithium ions and at the same time with a good electrical conductivity. Thermal conductivity of an electrode material will also have significant impacts on boosting battery capacity and prolonging battery lifetime, which is, however, underestimated. Here, we present the development of an expanded graphite embedded with Al metal nanoparticles (EG-MNPs-Al) synthesized by an oxidation-expansion process. The synthesized EG-MNPs-Al material exhibited a typical hierarchical structure with embedded Al metal nanoparticles into the interspaces of expanded graphite. The parallel thermal conductivity was up to 11.6 W·m−1·K−1 with a bulk density of 453 kg·m−3 at room temperature, a 150% improvement compared to expanded graphite (4.6 W·m−1·K−1) owing to the existence of Al metal nanoparticles. The first reversible capacity of EG-MNPs-Al as anode material for lithium ion battery was 480 mAh·g−1 at a current density of 100 mA·g−1, and retained 84% capacity after 300 cycles. The improved cycling stability and system security of lithium ion batteries is attributed to the excellent thermal conductivity of the EG-MNPs-Al anodes. PMID:27671848

Expanded graphite embedded with aluminum nanoparticles as superior thermal conductivity anodes for high-performance lithium-ion batteries.

PubMed

Zhao, Tingkai; She, Shengfei; Ji, Xianglin; Guo, Xinai; Jin, Wenbo; Zhu, Ruoxing; Dang, Alei; Li, Hao; Li, Tiehu; Wei, Bingqing

2016-09-27

The development of high capacity and long-life lithium-ion batteries is a long-term pursuing and under a close scrutiny. Most of the researches have been focused on exploring electrode materials and structures with high store capability of lithium ions and at the same time with a good electrical conductivity. Thermal conductivity of an electrode material will also have significant impacts on boosting battery capacity and prolonging battery lifetime, which is, however, underestimated. Here, we present the development of an expanded graphite embedded with Al metal nanoparticles (EG-MNPs-Al) synthesized by an oxidation-expansion process. The synthesized EG-MNPs-Al material exhibited a typical hierarchical structure with embedded Al metal nanoparticles into the interspaces of expanded graphite. The parallel thermal conductivity was up to 11.6 W·m -1 ·K -1 with a bulk density of 453 kg·m -3 at room temperature, a 150% improvement compared to expanded graphite (4.6 W·m -1 ·K -1 ) owing to the existence of Al metal nanoparticles. The first reversible capacity of EG-MNPs-Al as anode material for lithium ion battery was 480 mAh·g -1 at a current density of 100 mA·g -1 , and retained 84% capacity after 300 cycles. The improved cycling stability and system security of lithium ion batteries is attributed to the excellent thermal conductivity of the EG-MNPs-Al anodes.

Equations of state and anisotropy of Fe-Ni-Si alloys

NASA Astrophysics Data System (ADS)

Morrison, R. A.; Jackson, J. M.; Sturhahn, W.; Zhang, D.; Greenberg, E.

2017-12-01

Seismic observations provide constraints on the density, bulk sound speed, and bulk modulus of Earth's inner core, and x-ray diffraction (XRD) experiments can experimentally constrain such properties of iron alloys. The deviation of these seismically-inferred values from the properties of iron suggests the presence of light elements (e.g. Si, O, S, C, H) inside the core. While cosmochemical studies suggest Earth's core is composed primarily of iron alloyed with 5 wt% nickel, existing experimental XRD studies constraining pressure-density relations have predominantly focused on iron and iron alloyed with light elements, while neglecting the effect of nickel. In this study, we present high-precision equations of state for bcc- and hcp-structured Fe0.91Ni0.09 and Fe0.80Ni0.10Si0.10 using powder XRD at room temperature up to 167 GPa and 175 GPa, respectively. By using tungsten powder as a pressure calibrant and helium as a pressure transmitting medium, we minimize error due to pressure calibration and non-hydrostatic stresses. The results are high fidelity equations of state (EOS). By systematically comparing our findings to an established EOS of hcp-Fe [Dewaele et al. 2006], we constrain the effect of nickel and silicon on the density, bulk sound speed, and bulk modulus of iron alloys, which is a critical step towards constraining the inner core's composition. We find that for iron alloys, high quality ambient temperature EOSs can dramatically improve the extrapolated high temperature equations of state to inner core conditions. By combining seismic observations and their associated uncertainties with our data and existing Fe light-element-alloy EOSs, we estimate their densities, bulk moduli, and bulk sound speeds at inner core conditions and propose an experimentally and seismologically consistent range of inner core compositions. Additionally, we obtain an unprecedented constraint on the effect of nickel and silicon on the axial ratio of iron alloys. Nickel has a measurably distinct effect on the c/a axial ratio of iron, as does alloying iron-nickel with silicon. We investigate the relationship between the c/a axial ratio and elastic anisotropy of iron alloys and discuss the implications for inner core seismic anisotropy.

[Spatial variation of soil properties and quality evaluation for arable Ustic Cambosols in central Henan Province].

PubMed

Zhang, Xue-Lei; Feng, Wan-Wan; Zhong, Guo-Min

2011-01-01

A GIS-based 500 m x 500 m soil sampling point arrangement was set on 248 points at Wenshu Town of Yuzhou County in central Henan Province, where the typical Ustic Cambosols locates. By using soil digital data, the spatial database was established, from which, all the needed latitude and longitude data of the sampling points were produced for the field GPS guide. Soil samples (0-20 cm) were collected from 202 points, of which, bulk density measurement were conducted for randomly selected 34 points, and the ten soil property items used as the factors for soil quality assessment, including organic matter, available K, available P, pH, total N, total P, soil texture, cation exchange capacity (CEC), slowly available K, and bulk density, were analyzed for the other points. The soil property items were checked by statistic tools, and then, classified with standard criteria at home and abroad. The factor weight was given by analytic hierarchy process (AHP) method, and the spatial variation of the major 10 soil properties as well as the soil quality classes and their occupied areas were worked out by Kriging interpolation maps. The results showed that the arable Ustic Cambosols in study area was of good quality soil, over 95% of which ranked in good and medium classes and only less than 5% were in poor class.

Evaluation of a microwave resonator for predicting grain moisture independent of bulk density

USDA-ARS?s Scientific Manuscript database

This work evaluated the ability of a planar whispering mode resonator to predict moisture considering moisture and densities expected in an on-harvester application. A calibration model was developed to accurately predict moisture over the moisture, density and temperature ranges evaluated. This mod...

Evaluation of techniques for determining the density of fine woody debris

Treesearch

Becky Fasth; Mark E. Harmon; Christopher W. Woodall; Jay. Sexton

2010-01-01

Evaluated various techniques for determining the density (i.e., bulk density) of fine woody debris during forest inventory activities. It was found that only experts in dead wood inventory may be able to identify fine woody debris stages of decay. Suggests various future research directions such as...

Characterization of the CO2 fluid adsorption in coal as a function of pressure using neutron scattering techniques (SANS and USANS)

USGS Publications Warehouse

Melnichenko, Y.B.; Radlinski, A.P.; Mastalerz, Maria; Cheng, G.; Rupp, J.

2009-01-01

Small angle neutron scattering techniques have been applied to investigate the phase behavior of CO2 injected into coal and possible changes in the coal pore structure that may result from this injection. Three coals were selected for this study: the Seelyville coal from the Illinois Basin (Ro = 0.53%), Baralaba coal from the Bowen Basin (Ro = 0.67%), and Bulli 4 coal from the Sydney Basin (Ro = 1.42%). The coals were selected from different depths to represent the range of the underground CO2 conditions (from subcritical to supercritical) which may be realized in the deep subsurface environment. The experiments were conducted in a high pressure cell and CO2 was injected under a range of pressure conditions, including those corresponding to in-situ hydrostatic subsurface conditions for each coal. Our experiments indicate that the porous matrix of all coals remains essentially unchanged after exposure to CO2 at pressures up to 200??bar (1??bar = 105??Pa). Each coal responds differently to the CO2 exposure and this response appears to be different in pores of various sizes within the same coal. For the Seelyville coal at reservoir conditions (16????C, 50??bar), CO2 condenses from a gas into liquid, which leads to increased average fluid density in the pores (??pore) with sizes (r) 1 ?? 105 ??? r ??? 1 ?? 104???? (??pore ??? 0.489??g/cm3) as well as in small pores with size between 30 and 300???? (??pore ??? 0.671??g/cm3). These values are by a factor of three to four higher than the density of bulk CO2 (??CO2) under similar thermodynamic conditions (??CO2 ??? 0.15??g/cm3). At the same time, in the intermediate size pores with r ??? 1000???? the average fluid density is similar to the density of bulk fluid, which indicates that adsorption does not occur in these pores. At in situ conditions for the Baralaba coal (35 OC, 100??bar), the average fluid density of CO2 in all pores is lower than that of the bulk fluid (??pore / ??CO2 ??? 0.6). Neutron scattering from the Bulli 4 coal did not show any significant variation with pressure, a phenomenon which we assign to the extremely small amount of porosity of this coal in the pore size range between 35 and 100,000????. ?? 2008 Elsevier B.V.

Increasing strength and conductivity of Cu alloy through abnormal plastic deformation of an intermetallic compound

PubMed Central

Han, Seung Zeon; Lim, Sung Hwan; Kim, Sangshik; Lee, Jehyun; Goto, Masahiro; Kim, Hyung Giun; Han, Byungchan; Kim, Kwang Ho

2016-01-01

The precipitation strengthening of Cu alloys inevitably accompanies lowering of their electric conductivity and ductility. We produced bulk Cu alloys arrayed with nanofibers of stiff intermetallic compound through a precipitation mechanism using conventional casting and heat treatment processes. We then successfully elongated these arrays of nanofibers in the bulk Cu alloys to 400% of original length without breakage at room temperature using conventional rolling process. By inducing such an one-directional array of nanofibers of intermetallic compound from the uniform distribution of fine precipitates in the bulk Cu alloys, the trade-off between strength and conductivity and between strength and ductility could be significantly reduced. We observed a simultaneous increase in electrical conductivity by 1.3 times and also tensile strength by 1.3 times in this Cu alloy bulk compared to the conventional Cu alloys. PMID:27488621

Soil Mesocosm CO2 Emissions after 13C-glucose Addition, Soil Physical and Chemical Characteristics, and Microbial Biomass, Barrow, Alaska, 2014-2016

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

Lydia Vaughn; Biao Zhu; Carolin Bimueller

Measurements made from a 2014-2016 field glucose addition experiment. Dataset includes measurements of surface trace gas emissions (Delta13C of ecosystem respiration and source-partitioned surface CO2 flux, CH4 flux, and GPP), soil profile information (concentrations of carbon, nitrogen, and soil microbial biomass carbon, Delta13C of soil organic matter and microbial biomass, gravimetric water content, and bulk density), soil mineral nitrogen availability, and field-measured soil temperature, air temperature and soil moisture. Experiment was conducted in a region of high-centered polygons on the BEO. Data will be available Fall 2017.

A self-consistent model of an isothermal tokamak

NASA Astrophysics Data System (ADS)

McNamara, Steven; Lilley, Matthew

2014-10-01

Continued progress in liquid lithium coating technologies have made the development of a beam driven tokamak with minimal edge recycling a feasibly possibility. Such devices are characterised by improved confinement due to their inherent stability and the suppression of thermal conduction. Particle and energy confinement become intrinsically linked and the plasma thermal energy content is governed by the injected beam. A self-consistent model of a purely beam fuelled isothermal tokamak is presented, including calculations of the density profile, bulk species temperature ratios and the fusion output. Stability considerations constrain the operating parameters and regions of stable operation are identified and their suitability to potential reactor applications discussed.

SOLID-STATE SYNTHESIS AND SOME PROPERTIES OF MAGNESIUM-DOPED COPPER ALUMINUM OXIDES

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

Liu, Chang; Ren, Fei; Wang, Hsin

2010-01-01

Copper aluminum oxide (CuAlO2) with delafossite structure is a promising candidate for high temperature thermoelectric applications because of its modest band gap, high stability and low cost. We investigate magnesium doping on the aluminum site as a means of producing higher electrical conductivity and optimized Seebeck coefficient. Powder samples were synthesized using solid-state reaction and bulk samples were prepared using both cold-pressing and hot-pressing techniques. Composition analysis, microstructural examination and transport property measurements were performed, and the results suggest that while hot-pressing can achieve high density samples, secondary phases tend to form and lower the performance of the materials.

Effect of composition on physical properties of food powders

NASA Astrophysics Data System (ADS)

Szulc, Karolina; Lenart, Andrzej

2016-04-01

The paper presents an influence of raw material composition and technological process applied on selected physical properties of food powders. Powdered multi-component nutrients were subjected to the process of mixing, agglomeration, coating, and drying. Wetting liquids ie water and a 15% water lactose solution, were used in agglomeration and coating. The analyzed food powders were characterized by differentiated physical properties, including especially: particle size, bulk density, wettability, and dispersibility. The raw material composition of the studied nutrients exerted a statistically significant influence on their physical properties. Agglomeration as well as coating of food powders caused a significant increase in particle size, decreased bulk density, increased apparent density and porosity, and deterioration in flowability in comparison with non-agglomerated nutrients.

Assessment of the Density Functional Tight Binding Method for Protic Ionic Liquids

PubMed Central

2015-01-01

Density functional tight binding (DFTB), which is ∼100–1000 times faster than full density functional theory (DFT), has been used to simulate the structure and properties of protic ionic liquid (IL) ions, clusters of ions and the bulk liquid. Proton affinities for a wide range of IL cations and anions determined using DFTB generally reproduce G3B3 values to within 5–10 kcal/mol. The structures and thermodynamic stabilities of n-alkyl ammonium nitrate clusters (up to 450 quantum chemical atoms) predicted with DFTB are in excellent agreement with those determined using DFT. The IL bulk structure simulated using DFTB with periodic boundary conditions is in excellent agreement with published neutron diffraction data. PMID:25328497

Stored grain pack factors for wheat: comparison of three methods to field measurements

USDA-ARS?s Scientific Manuscript database

Storing grain in bulk storage units results in grain packing from overbearing pressure, which increases grain bulk density and storage-unit capacity. This study compared pack factors of hard red winter (HRW) wheat in vertical storage bins using different methods: the existing packing model (WPACKING...

AC conductivity and dielectric behavior of bulk Furfurylidenemalononitrile

NASA Astrophysics Data System (ADS)

El-Nahass, M. M.; Ali, H. A. M.

2012-06-01

AC conductivity and dielectric behavior for bulk Furfurylidenemalononitrile have been studied over a temperature range (293-333 K) and frequency range (50-5×106 Hz). The frequency dependence of ac conductivity, σac, has been investigated by the universal power law, σac(ω)=Aωs. The variation of the frequency exponent (s) with temperature was analyzed in terms of different conduction mechanisms, and it was found that the correlated barrier hopping (CBH) model is the predominant conduction mechanism. The temperature dependence of σac(ω) showed a linear increase with the increase in temperature at different frequencies. The ac activation energy was determined at different frequencies. Dielectric data were analyzed using complex permittivity and complex electric modulus for bulk Furfurylidenemalononitrile at various temperatures.

Understanding the effects of decompaction maintenance on the infill state and play performance of third-generation artificial grass pitches

PubMed Central

Forrester, Stephanie E; McLaren, Nicholas J

2015-01-01

Third generation artificial grass pitches have been observed to get harder over time. The maintenance technique of rubber infill decompaction is intended to help slow, or reverse, this process. At present, little is understood about either the science of the infill compaction process or the efficacy of decompaction maintenance. The objective of this study was to measure the changes in rubber infill net bulk density, force reduction (impact absorption) and vertical ball rebound under various levels of compactive effort in controlled laboratory-based testing. The assessments were repeated after the systems had been raked to simulate the decompaction maintenance techniques. These tests defined the limits of compaction (loose to maximally compacted) in terms of the change in rubber infill net bulk density, force reduction and vertical ball rebound. Site testing was also undertaken at four third generation pitches immediately pre and post decompaction, to determine the measurable effects in the less well controlled field environment. Rubber infill net bulk density was found to increase as compactive effort increased, resulting in increased hardness. Decompacting the surface was found to approximately fully reverse these effects. In comparison, the site measurements demonstrated similar but notably smaller magnitudes of change following the decompaction process suggesting that the field state pre and post decompaction did not reach the extremes obtained in the laboratory. The findings suggest that rubber infill net bulk density is an important parameter influencing the hardness of artificial grass and that decompactions can be an effective method to reverse compaction related hardness changes. PMID:29708108

The legacy of wetland drainage on the remaining peat in the Sacramento San Joaquin Delta, California, USA

USGS Publications Warehouse

Drexler, J.Z.; De Fontaine, C. S.; Deverel, S.J.

2009-01-01

Throughout the world, many extensive wetlands, such as the Sacramento-San Joaquin Delta of California (hereafter, the Delta), have been drained for agriculture, resulting in land-surface subsidence of peat soils. The purpose of this project was to study the in situ effects of wetland drainage on the remaining peat in the Delta. Peat cores were retrieved from four drained, farmed islands and four relatively undisturbed, marsh islands. Core samples were analyzed for bulk density and percent organic carbon. Macrofossils in the peat were dated using radiocarbon age determination. The peat from the farmed islands is highly distinct from marsh island peat. Bulk density of peat from the farmed islands is generally greater than that of the marsh islands at a given organic carbon content. On the farmed islands, increased bulk density, which is an indication of compaction, decreases with depth within the unoxidized peat zone, whereas, on the marsh islands, bulk density is generally constant with depth except near the surface. Approximately 5580 of the original peat layer on the farmed islands has been lost due to land-surface subsidence. For the center regions of the farmed islands, this translates into an estimated loss of between 29005700 metric tons of organic carbon/hectare. Most of the intact peat just below the currently farmed soil layer is over 4000 years old. Peat loss will continue as long as the artificial water table on the farmed islands is held below the land surface. ?? 2009 The Society of Wetland Scientists.

Quantum transport of two-species Dirac fermions in dual-gated three-dimensional topological insulators

DOE PAGES

Xu, Yang; Miotkowski, Ireneusz; Chen, Yong P.

2016-05-04

Topological insulators are a novel class of quantum matter with a gapped insulating bulk, yet gapless spin-helical Dirac fermion conducting surface states. Here, we report local and non-local electrical and magneto transport measurements in dual-gated BiSbTeSe 2 thin film topological insulator devices, with conduction dominated by the spatially separated top and bottom surfaces, each hosting a single species of Dirac fermions with independent gate control over the carrier type and density. We observe many intriguing quantum transport phenomena in such a fully tunable two-species topological Dirac gas, including a zero-magnetic-field minimum conductivity close to twice the conductance quantum at themore » double Dirac point, a series of ambipolar two-component half-integer Dirac quantum Hall states and an electron-hole total filling factor zero state (with a zero-Hall plateau), exhibiting dissipationless (chiral) and dissipative (non-chiral) edge conduction, respectively. As a result, such a system paves the way to explore rich physics, ranging from topological magnetoelectric effects to exciton condensation.« less

Web interface for Brownian dynamics simulation of ion transport and its applications to beta-barrel pores.

PubMed

Lee, Kyu Il; Jo, Sunhwan; Rui, Huan; Egwolf, Bernhard; Roux, Benoît; Pastor, Richard W; Im, Wonpil

2012-01-30

Brownian dynamics (BD) based on accurate potential of mean force is an efficient and accurate method for simulating ion transport through wide ion channels. Here, a web-based graphical user interface (GUI) is presented for carrying out grand canonical Monte Carlo (GCMC) BD simulations of channel proteins: http://www.charmm-gui.org/input/gcmcbd. The webserver is designed to help users avoid most of the technical difficulties and issues encountered in setting up and simulating complex pore systems. GCMC/BD simulation results for three proteins, the voltage dependent anion channel (VDAC), α-Hemolysin (α-HL), and the protective antigen pore of the anthrax toxin (PA), are presented to illustrate the system setup, input preparation, and typical output (conductance, ion density profile, ion selectivity, and ion asymmetry). Two models for the input diffusion constants for potassium and chloride ions in the pore are compared: scaling of the bulk diffusion constants by 0.5, as deduced from previous all-atom molecular dynamics simulations of VDAC, and a hydrodynamics based model (HD) of diffusion through a tube. The HD model yields excellent agreement with experimental conductances for VDAC and α-HL, while scaling bulk diffusion constants by 0.5 leads to underestimates of 10-20%. For PA, simulated ion conduction values overestimate experimental values by a factor of 1.5-7 (depending on His protonation state and the transmembrane potential), implying that the currently available computational model of this protein requires further structural refinement. Copyright © 2011 Wiley Periodicals, Inc.

Web Interface for Brownian Dynamics Simulation of Ion Transport and Its Applications to Beta-Barrel Pores

PubMed Central

Lee, Kyu Il; Jo, Sunhwan; Rui, Huan; Egwolf, Bernhard; Roux, Benoît; Pastor, Richard W.; Im, Wonpil

2011-01-01

Brownian dynamics (BD) in a suitably constructed potential of mean force is an efficient and accurate method for simulating ion transport through wide ion channels. Here, a web-based graphical user interface (GUI) is presented for grand canonical Monte Carlo (GCMC) BD simulations of channel proteins: http://www.charmm-gui.org/input/gcmcbd. The webserver is designed to help users avoid most of the technical difficulties and issues encountered in setting up and simulating complex pore systems. GCMC/BD simulation results for three proteins, the voltage dependent anion channel (VDAC), α-Hemolysin, and the protective antigen pore of the anthrax toxin (PA), are presented to illustrate system setup, input preparation, and typical output (conductance, ion density profile, ion selectivity, and ion asymmetry). Two models for the input diffusion constants for potassium and chloride ions in the pore are compared: scaling of the bulk diffusion constants by 0.5, as deduced from previous all-atom molecular dynamics simulations of VDAC; and a hydrodynamics based model (HD) of diffusion through a tube. The HD model yields excellent agreement with experimental conductances for VDAC and α-Hemolysin, while scaling bulk diffusion constants by 0.5 leads to underestimates of 10–20%. For PA, simulated ion conduction values overestimate experimental values by a factor of 1.5 to 7 (depending on His protonation state and the transmembrane potential), implying that the currently available computational model of this protein requires further structural refinement. PMID:22102176

Reverse Non-Equilibrium Molecular Dynamics Demonstrate That Surface Passivation Controls Thermal Transport at Semiconductor-Solvent Interfaces.

PubMed

Hannah, Daniel C; Gezelter, J Daniel; Schaller, Richard D; Schatz, George C

2015-06-23

We examine the role played by surface structure and passivation in thermal transport at semiconductor/organic interfaces. Such interfaces dominate thermal transport in semiconductor nanomaterials owing to material dimensions much smaller than the bulk phonon mean free path. Utilizing reverse nonequilibrium molecular dynamics simulations, we calculate the interfacial thermal conductance (G) between a hexane solvent and chemically passivated wurtzite CdSe surfaces. In particular, we examine the dependence of G on the CdSe slab thickness, the particular exposed crystal facet, and the extent of surface passivation. Our results indicate a nonmonotonic dependence of G on ligand-grafting density, with interfaces generally exhibiting higher thermal conductance for increasing surface coverage up to ∼0.08 ligands/Å(2) (75-100% of a monolayer, depending on the particular exposed facet) and decreasing for still higher coverages. By analyzing orientational ordering and solvent penetration into the ligand layer, we show that a balance of competing effects is responsible for this nonmonotonic dependence. Although the various unpassivated CdSe surfaces exhibit similar G values, the crystal structure of an exposed facet nevertheless plays an important role in determining the interfacial thermal conductance of passivated surfaces, as the density of binding sites on a surface determines the ligand-grafting densities that may ultimately be achieved. We demonstrate that surface passivation can increase G relative to a bare surface by roughly 1 order of magnitude and that, for a given extent of passivation, thermal conductance can vary by up to a factor of ∼2 between different surfaces, suggesting that appropriately tailored nanostructures may direct heat flow in an anisotropic fashion for interface-limited thermal transport.

Mesoscopic Metal-Insulator Transition at Ferroelastic Domain Walls in VO2

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

Jones, Keith M; Kalinin, Sergei V; Kolmakov, Andrei

2010-01-01

The novel phenomena induced by symmetry breaking at homointerfaces between ferroic variants in ferroelectric and ferroelastic materials have attracted recently much attention. Using variable temperature scanning microwave microscopy, we demonstrate the mesoscopic strain-induced metal-insulator phase transitions in the vicinity of ferroelastic domain walls in the semiconductive VO2 that nucleated at temperatures as much as 10-12 C below bulk transition, resulting in the formation of conductive channels in the material. Density functional theory is used to rationalize the process low activation energy. This behavior, linked to the strain inhomogeneity inherent in ferroelastic materials, can strongly affect interpretation of phase-transition studies inmore » VO2 and similar materials with symmetry-lowering transitions, and can also be used to enable new generations of electronic devices though strain engineering of conductive and semiconductive regions.« less

Characterization of structure and thermophysical properties of three ESR slags

NASA Astrophysics Data System (ADS)

Plotkowski, A.; deBarbadillo, J.; Krane, Matthew J. M.

2016-07-01

The structure and properties of electroslag remelting (ESR) slags were characterized. Slags samples of three compositions were obtained from industrial remelting processes at Special Metals Corporation and from casting in a laboratory vacuum induction melter. The structure of the slag samples was observed using optical and electron microscopy, and phases were identified and their relative amounts quantified using X-ray diffraction. Laser flash thermal diffusivity, density, and differential scanning calorimetry measurements for specific heat were performed to determine the bulk thermal conductivity of the samples. Sample porosity was measured as a function of depth using a serial sectioning technique, and a onedimensional computational model was developed to estimate the thermal conductivity of the fully dense slags. These results are discussed in context with previous studies, and opportunities for future research are identified. AFRL Case Number: 88ABW-2015-1871.

Effects of densification of precursor pellets on microstructures and critical current properties of YBCO melt-textured bulks

NASA Astrophysics Data System (ADS)

Setoyama, Yui; Shimoyama, Jun-ichi; Motoki, Takanori; Kishio, Kohji; Awaji, Satoshi; Kon, Koichi; Ichikawa, Naoki; Inamori, Satoshi; Naito, Kyogo

2016-12-01

Effects of densification of precursor disks on the density of residual voids and critical current properties for YBCO melt-textured bulk superconductors were systematically investigated. Six YBCO bulks were prepared from precursor pellets with different initial particle sizes of YBa2Cu3Oy (Y123) powder and applied pressures for pelletization. It was revealed that use of finer Y123 powder and consolidation using cold-isostatic-pressing (CIP) with higher pressures result in reduction of residual voids at inner regions of bulks and enhance Jc especially under low fields below the second peak.

Thermal equation of state of hcp-iron: Constraint on the density deficit of Earth's solid inner core: THERMAL EQUATION OF STATE OF HCP-IRON

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

Fei, Yingwei; Murphy, Caitlin; Shibazaki, Yuki

We conducted high-pressure experiments on hexagonal close packed iron (hcp-Fe) in MgO, NaCl, and Ne pressure-transmitting media and found general agreement among the experimental data at 300 K that yield the best fitted values of the bulk modulus K 0 = 172.7(±1.4) GPa and its pressure derivative K 0'= 4.79(±0.05) for hcp-Fe, using the third-order Birch-Murnaghan equation of state. Using the derived thermal pressures for hcp-Fe up to 100 GPa and 1800 K and previous shockwave Hugoniot data, we developed a thermal equation of state of hcp-Fe. The thermal equation of state of hcp-Fe is further used to calculate themore » densities of iron along adiabatic geotherms to define the density deficit of the inner core, which serves as the basis for developing quantitative composition models of the Earth's inner core. We determine the density deficit at the inner core boundary to be 3.6%, assuming an inner core boundary temperature of 6000 K.« less

Predictive Simulation of Process Windows for Powder Bed Fusion Additive Manufacturing: Influence of the Powder Bulk Density.

PubMed

Rausch, Alexander M; Küng, Vera E; Pobel, Christoph; Markl, Matthias; Körner, Carolin

2017-09-22

The resulting properties of parts fabricated by powder bed fusion additive manufacturing processes are determined by their porosity, local composition, and microstructure. The objective of this work is to examine the influence of the stochastic powder bed on the process window for dense parts by means of numerical simulation. The investigations demonstrate the unique capability of simulating macroscopic domains in the range of millimeters with a mesoscopic approach, which resolves the powder bed and the hydrodynamics of the melt pool. A simulated process window reveals the influence of the stochastic powder layer. The numerical results are verified with an experimental process window for selective electron beam-melted Ti-6Al-4V. Furthermore, the influence of the powder bulk density is investigated numerically. The simulations predict an increase in porosity and surface roughness for samples produced with lower powder bulk densities. Due to its higher probability for unfavorable powder arrangements, the process stability is also decreased. This shrinks the actual parameter range in a process window for producing dense parts.

Predictive Simulation of Process Windows for Powder Bed Fusion Additive Manufacturing: Influence of the Powder Bulk Density

PubMed Central

Rausch, Alexander M.; Küng, Vera E.; Pobel, Christoph; Körner, Carolin

2017-01-01

The resulting properties of parts fabricated by powder bed fusion additive manufacturing processes are determined by their porosity, local composition, and microstructure. The objective of this work is to examine the influence of the stochastic powder bed on the process window for dense parts by means of numerical simulation. The investigations demonstrate the unique capability of simulating macroscopic domains in the range of millimeters with a mesoscopic approach, which resolves the powder bed and the hydrodynamics of the melt pool. A simulated process window reveals the influence of the stochastic powder layer. The numerical results are verified with an experimental process window for selective electron beam-melted Ti-6Al-4V. Furthermore, the influence of the powder bulk density is investigated numerically. The simulations predict an increase in porosity and surface roughness for samples produced with lower powder bulk densities. Due to its higher probability for unfavorable powder arrangements, the process stability is also decreased. This shrinks the actual parameter range in a process window for producing dense parts. PMID:28937633

Density functional theory study of bulk and single-layer magnetic semiconductor CrPS4

NASA Astrophysics Data System (ADS)

Zhuang, Houlong L.; Zhou, Jia

2016-11-01

Searching for two-dimensional (2D) materials with multifunctionality is one of the main goals of current research in 2D materials. Magnetism and semiconducting are certainly two desirable functional properties for a single 2D material. In line with this goal, here we report a density functional theory (DFT) study of bulk and single-layer magnetic semiconductor CrPS4. We find that the ground-state magnetic structure of bulk CrPS4 exhibits the A-type antiferromagnetic ordering, which transforms to ferromagnetic (FM) ordering in single-layer CrPS4. The calculated formation energy and phonon spectrum confirm the stability of single-layer CrPS4. The band gaps of FM single-layer CrPS4 calculated with a hybrid density functional are within the visible-light range. We also study the effects of FM ordering on the optical absorption spectra and band alignments for water splitting, indicating that single-layer CrPS4 could be a potential photocatalyst. Our work opens up ample opportunities of energy-related applications of single-layer CrPS4.

First-principles study of the structural, electronic and thermal properties of CaLiF3

NASA Astrophysics Data System (ADS)

Chouit, N.; Amara Korba, S.; Slimani, M.; Meradji, H.; Ghemid, S.; Khenata, R.

2013-09-01

Density functional theory calculations have been performed to study the structural, electronic and optical properties of CaLiF3 cubic fluoroperovskite. Our calculations were carried out by means of the full-potential linearized augmented plane-wave method. The exchange-correlation potential is treated by the local density approximation and the generalized gradient approximation (GGA) (Perdew, Burke and Ernzerhof). Moreover, the alternative form of GGA proposed by Engel and Vosko is also used for band structure calculations. The calculated total energy versus volume allows us to obtain structural properties such as the lattice constant (a0), bulk modulus (B0) and pressure derivative of the bulk modulus (B'0 ). Band structure, density of states and band gap pressure coefficients are also given. Our calculations show that CaLiF3 has an indirect band gap (R-Γ). Following the quasi-harmonic Debye model, in which the phononic effects are considered, the temperature and pressure effects on the lattice constant, bulk modulus, thermal expansion coefficient, Debye temperature and heat capacities are calculated.

Self-consistent pseudopotential calculation of the bulk properties of Mo and W

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

Zunger, A.; Cohen, M.L.

The bulk properties of Mo and W are calculated using the recently developed momentum-space approach for calculating total energy via a nonlocal pseudopotential. This approach avoids any shape approximation to the variational charge density (e.g., muffin tins), is fully self-consistent, and replaces the multidimensional and multicenter integrals akin to real-space representations by simple and readily convergent reciprocal-space lattice sums. We use first-principles atomic pseudopotentials which have been previously demonstrated to yield band structures and charge densities for both semiconductors and transition metals in good agreement with experiment and all-electron calculations. Using a mixed-basis representation for the crystalline wave function, wemore » are able to accurately reproduce both the localized and itinerant features of the electronic states in these systems. These first-principles pseudopotentials, together with the self-consistent density-functional representation for both the exchange and the correlation screening, yields agreement with experiment of 0.2% in the lattice parameters, 2% and 11% for the binding energies of Mo and W, respectively, and 12% and 7% for the bulk moduli of Mo and W, respectively.« less

The effect of grain size and cement content on index properties of weakly solidified artificial sandstones

NASA Astrophysics Data System (ADS)

Atapour, Hadi; Mortazavi, Ali

2018-04-01

The effects of textural characteristics, especially grain size, on index properties of weakly solidified artificial sandstones are studied. For this purpose, a relatively large number of laboratory tests were carried out on artificial sandstones that were produced in the laboratory. The prepared samples represent fifteen sandstone types consisting of five different median grain sizes and three different cement contents. Indices rock properties including effective porosity, bulk density, point load strength index, and Schmidt hammer values (SHVs) were determined. Experimental results showed that the grain size has significant effects on index properties of weakly solidified sandstones. The porosity of samples is inversely related to the grain size and decreases linearly as grain size increases. While a direct relationship was observed between grain size and dry bulk density, as bulk density increased with increasing median grain size. Furthermore, it was observed that the point load strength index and SHV of samples increased as a result of grain size increase. These observations are indirectly related to the porosity decrease as a function of median grain size.

Extended hot carrier lifetimes observed in bulk In{sub 0.265±0.02}Ga{sub 0.735}N under high-density photoexcitation

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

Zhang, Yi; Tayebjee, Murad J. Y.; Smyth, Suntrana

2016-03-28

We have investigated the ultrafast carrier dynamics in a 1 μm bulk In{sub 0.265}Ga{sub 0.735}N thin film grown using energetic neutral atom-beam lithography/epitaxy molecular beam epitaxy. Cathodoluminescence and X-ray diffraction experiments are used to observe the existence of indium-rich domains in the sample. These domains give rise to a second carrier population and bi-exponential carrier cooling is observed with characteristic lifetimes of 1.6 and 14 ps at a carrier density of 1.3 × 10{sup 16 }cm{sup −3}. A combination of band-filling, screening, and hot-phonon effects gives rise to a two-fold enhanced mono-exponential cooling rate of 28 ps at a carrier density of 8.4 × 10{sup 18 }cm{sup −3}. Thismore » is the longest carrier thermalization time observed in bulk InGaN alloys to date.« less

The deformation and failure response of closed-cell PMDI foams subjected to dynamic impact loading

DOE PAGES

Koohbor, Behrad; Mallon, Silas; Kidane, Addis; ...

2015-04-07

The present work aims to investigate the bulk deformation and failure response of closed-cell Polymeric Methylene Diphenyl Diisocyanate (PMDI) foams subjected to dynamic impact loading. First, foam specimens of different initial densities are examined and characterized in quasi-static loading conditions, where the deformation behavior of the samples is quantified in terms of the compressive elastic modulus and effective plastic Poisson's ratio. Then, the deformation response of the foam specimens subjected to direct impact loading is examined by taking into account the effects of material compressibility and inertia stresses developed during deformation, using high speed imaging in conjunction with 3D digitalmore » image correlation. The stress-strain response and the energy absorption as a function of strain rate and initial density are presented and the bulk failure mechanisms are discussed. As a result, it is observed that the initial density of the foam and the applied strain rates have a substantial influence on the strength, bulk failure mechanism and the energy dissipation characteristics of the foam specimens.« less

From chemistry to mechanics: bulk modulus evolution of Li-Si and Li-Sn alloys via the metallic electronegativity scale.

PubMed

Li, Keyan; Xie, Hui; Liu, Jun; Ma, Zengsheng; Zhou, Yichun; Xue, Dongfeng

2013-10-28

Toward engineering high performance anode alloys for Li-ion batteries, we proposed a useful method to quantitatively estimate the bulk modulus of binary alloys in terms of metallic electronegativity (EN), alloy composition and formula volume. On the basis of our proposed potential viewpoint, EN as a fundamental chemistry concept can be extended to be an important physical parameter to characterize the mechanical performance of Li-Si and Li-Sn alloys as anode materials for Li-ion batteries. The bulk modulus of binary alloys is linearly proportional to the combination of average metallic EN and atomic density of alloys. We calculated the bulk moduli of Li-Si and Li-Sn alloys with different Li concentrations, which can agree well with the reported data. The bulk modulus of Li-Si and Li-Sn alloys decreases with increasing Li concentration, leading to the elastic softening of the alloys, which is essentially caused by the decreased strength of constituent chemical bonds in alloys from the viewpoint of EN. This work provides a deep understanding of mechanical failure of Si and Sn anodes for Li-ion batteries, and permits the prediction of the composition dependent bulk modulus of various lithiated alloys on the basis of chemical formula, metallic EN and cell volume (or alloy density), with no structural details required.

On the meniscus formation and the negative hydrogen ion extraction from ITER neutral beam injection relevant ion source

NASA Astrophysics Data System (ADS)

Mochalskyy, S.; Wünderlich, D.; Ruf, B.; Fantz, U.; Franzen, P.; Minea, T.

2014-10-01

The development of a large area (Asource,ITER = 0.9 × 2 m2) hydrogen negative ion (NI) source constitutes a crucial step in construction of the neutral beam injectors of the international fusion reactor ITER. To understand the plasma behaviour in the boundary layer close to the extraction system the 3D PIC MCC code ONIX is exploited. Direct cross checked analysis of the simulation and experimental results from the ITER-relevant BATMAN source testbed with a smaller area (Asource,BATMAN ≈ 0.32 × 0.59 m2) has been conducted for a low perveance beam, but for a full set of plasma parameters available. ONIX has been partially benchmarked by comparison to the results obtained using the commercial particle tracing code for positive ion extraction KOBRA3D. Very good agreement has been found in terms of meniscus position and its shape for simulations of different plasma densities. The influence of the initial plasma composition on the final meniscus structure was then investigated for NIs. As expected from the Child-Langmuir law, the results show that not only does the extraction potential play a crucial role on the meniscus formation, but also the initial plasma density and its electronegativity. For the given parameters, the calculated meniscus locates a few mm downstream of the plasma grid aperture provoking a direct NI extraction. Most of the surface produced NIs do not reach the plasma bulk, but move directly towards the extraction grid guided by the extraction field. Even for artificially increased electronegativity of the bulk plasma the extracted NI current from this region is low. This observation indicates a high relevance of the direct NI extraction. These calculations show that the extracted NI current from the bulk region is low even if a complete ion-ion plasma is assumed, meaning that direct extraction from surface produced ions should be present in order to obtain sufficiently high extracted NI current density. The calculated extracted currents, both ions and electrons, agree rather well with the experiment.

Habitat management affects soil chemistry and allochthonous organic inputs mediating microbial structure and exo-enzyme activity in Wadden Sea salt-marsh soils

NASA Astrophysics Data System (ADS)

Mueller, Peter; Granse, Dirk; Thi Do, Hai; Weingartner, Magdalena; Nolte, Stefanie; Hoth, Stefan; Jensen, Kai

2016-04-01

The Wadden Sea (WS) region is Europe's largest wetland and home to approximately 20% of its salt marsh area. Mainland salt marshes of the WS are anthropogenically influenced systems and have traditionally been used for livestock grazing in wide parts. After foundation of WS National Parks in the late 1980s and early 1990s, artificial drainage has been abandoned; however, livestock grazing is still common in many areas of the National Parks and is under ongoing discussion as a habitat-management practice. While studies so far focused on effects of livestock grazing on biodiversity, little is known about how biogeochemical processes, element cycling, and particularly carbon sequestration are affected. Here, we present data from a recent field study focusing on grazing effects on soil properties, microbial exo-enzyme activity, microbial abundance and structure. Exo-enzyme activity was studied conducting digestive enzyme assays for various enzymes involved in C- and N cycling. Microbial abundance and structure was assessed measuring specific gene abundance of fungi and bacteria using quantitative PCR. Soil compaction induced by grazing led to higher bulk density and decreases in soil redox (Δ >100 mV). Soil pH was significantly lower in grazed parts. Further, the proportion of allochthonous organic matter (marine input) was significantly smaller in grazed vs. ungrazed sites, likely caused by a higher sediment trapping capacity of the taller vegetation in the ungrazed sites. Grazing induced changes in bulk density, pH and redox resulted in reduced activity of enzymes involved in microbial C acquisition; however, there was no grazing effect on enzymes involved in N acquisition. While changes in pH, bulk density or redox did not affect microbial abundance and structure, the relative amount of marine organic matter significantly reduced the relative abundance of fungi (F:B ratio). We conclude that livestock grazing directly affects microbial exo-enzyme activity, thus slowing down C turnover, and indirectly changes microbial structure, namely relative fungal abundance, by reducing high-quality marine organic matter inputs.

Closer Look at Lunar Highland Crust

NASA Image and Video Library

2012-12-05

This image depicting the porosity of the lunar highland crust was derived using bulk density data from NASA GRAIL mission and independent grain density measurements from NASA Apollo moon mission samples as well as orbital remote-sensing data.

Physical properties of wild mango fruit and nut

NASA Astrophysics Data System (ADS)

Ehiem, J.; Simonyan, K.

2012-02-01

Physical properties of two wild mango varieties were studied at 81.9 and 24.5% moisture (w.b.) for the fruits and nuts, respectively. The shape and size of the fruit are the same while that of nuts differs at P = 0.05. The mass, density and bulk density of the fruits are statistically different at P = 0.05 but the volume is the same. The shape and size, volume and bulk density of the nuts are statistically the same at P = 0.05. The nuts of both varieties are also the same at P = 0.05 in terms of mass and density. The packing factor for both fruits and nut of the two varieties are the same at 0.95. The relevant data obtained for the two varieties would be useful for design and development of machines and equipment for processing and handling operations.

Quantifying the density and utilization of active sites in non-precious metal oxygen electroreduction catalysts

PubMed Central

Sahraie, Nastaran Ranjbar; Kramm, Ulrike I.; Steinberg, Julian; Zhang, Yuanjian; Thomas, Arne; Reier, Tobias; Paraknowitsch, Jens-Peter; Strasser, Peter

2015-01-01

Carbon materials doped with transition metal and nitrogen are highly active, non-precious metal catalysts for the electrochemical conversion of molecular oxygen in fuel cells, metal air batteries, and electrolytic processes. However, accurate measurement of their intrinsic turn-over frequency and active-site density based on metal centres in bulk and surface has remained difficult to date, which has hampered a more rational catalyst design. Here we report a successful quantification of bulk and surface-based active-site density and associated turn-over frequency values of mono- and bimetallic Fe/N-doped carbons using a combination of chemisorption, desorption and 57Fe Mössbauer spectroscopy techniques. Our general approach yields an experimental descriptor for the intrinsic activity and the active-site utilization, aiding in the catalyst development process and enabling a previously unachieved level of understanding of reactivity trends owing to a deconvolution of site density and intrinsic activity. PMID:26486465

Sampling Error in Relation to Cyst Nematode Population Density Estimation in Small Field Plots.

PubMed

Župunski, Vesna; Jevtić, Radivoje; Jokić, Vesna Spasić; Župunski, Ljubica; Lalošević, Mirjana; Ćirić, Mihajlo; Ćurčić, Živko

2017-06-01

Cyst nematodes are serious plant-parasitic pests which could cause severe yield losses and extensive damage. Since there is still very little information about error of population density estimation in small field plots, this study contributes to the broad issue of population density assessment. It was shown that there was no significant difference between cyst counts of five or seven bulk samples taken per each 1-m 2 plot, if average cyst count per examined plot exceeds 75 cysts per 100 g of soil. Goodness of fit of data to probability distribution tested with χ 2 test confirmed a negative binomial distribution of cyst counts for 21 out of 23 plots. The recommended measure of sampling precision of 17% expressed through coefficient of variation ( cv ) was achieved if the plots of 1 m 2 contaminated with more than 90 cysts per 100 g of soil were sampled with 10-core bulk samples taken in five repetitions. If plots were contaminated with less than 75 cysts per 100 g of soil, 10-core bulk samples taken in seven repetitions gave cv higher than 23%. This study indicates that more attention should be paid on estimation of sampling error in experimental field plots to ensure more reliable estimation of population density of cyst nematodes.

Structure-based coarse-graining for inhomogeneous liquid polymer systems.

PubMed

Fukuda, Motoo; Zhang, Hedong; Ishiguro, Takahiro; Fukuzawa, Kenji; Itoh, Shintaro

2013-08-07

The iterative Boltzmann inversion (IBI) method is used to derive interaction potentials for coarse-grained (CG) systems by matching structural properties of a reference atomistic system. However, because it depends on such thermodynamic conditions as density and pressure of the reference system, the derived CG nonbonded potential is probably not applicable to inhomogeneous systems containing different density regimes. In this paper, we propose a structure-based coarse-graining scheme to devise CG nonbonded potentials that are applicable to different density bulk systems and inhomogeneous systems with interfaces. Similar to the IBI, the radial distribution function (RDF) of a reference atomistic bulk system is used for iteratively refining the CG nonbonded potential. In contrast to the IBI, however, our scheme employs an appropriately estimated initial guess and a small amount of refinement to suppress transfer of the many-body interaction effects included in the reference RDF into the CG nonbonded potential. To demonstrate the application of our approach to inhomogeneous systems, we perform coarse-graining for a liquid perfluoropolyether (PFPE) film coated on a carbon surface. The constructed CG PFPE model favorably reproduces structural and density distribution functions, not only for bulk systems, but also at the liquid-vacuum and liquid-solid interfaces, demonstrating that our CG scheme offers an easy and practical way to accurately determine nonbonded potentials for inhomogeneous systems.

Initial report of the physical property measurement, ChikyuOman core description Phase I: sheeted dike and gabbro boundary from ICDP Holes GT1A, GT2A and GT3A

NASA Astrophysics Data System (ADS)

Abe, N.; Okazaki, K.; Hatakeyama, K.; Ildefonse, B.; Leong, J. A. M.; Tateishi, Y.; Teagle, D. A. H.; Takazawa, E.; Kelemen, P. B.; Michibayashi, K.; Coggon, J. A.; Harris, M.; de Obeso, J. C.

2017-12-01

We report results on the physical property measurements of the core samples from ICDP Holes GT1A, GT2A and GT3A drilled at Samail Ophiolite, Sultanate of Oman. Cores from Holes GT1A and GT2A in the lower crust section are mainly composed of gabbros (gabbro and olivine gabbro), and small amounts of ultramafic rocks (wehrlite and dunite), while cores from Hole GT3A at the boundary between sheeted dikes and gabbro are mainly composed of basalt and diabase, followed by gabbros (gabbro, olivine gabbro and oxide gabbro), and less common felsic dikes, trondhjemite and tonalite, intrude the mafic rocks. Measurements of physical properties were undertaken to characterize recovered core material. Onboard the Drilling Vessel Chikyu, whole-round measurements included X-ray CT image, natural gamma radiation, and magnetic susceptibility for Leg 1, and additional P-wave velocity, gamma ray attenuation density, and electrical resistivity during Leg 2. Split-core point magnetic susceptibility and color spectroscopy were measured for all core sections. P-wave velocity, bulk/grain density and porosity of more than 500 discrete cube samples, and thermal conductivity on more than 240 pieces from the working half of the split core sections were also measured. Physical Properties of gabbroic rocks from Holes GT1A and GT2A are similar to typical oceanic gabbros from ODP and IODP expeditions at Atlantis Bank, Southwestern Indian Ridge (ODP Legs 118, 176 and 179; IODP Exp 360) and at Hess Deep, Eastern Pacific (ODP Leg 147 and IODP Exp. 345). Average P-wave velocity, bulk density, grain density, porosity and thermal conductivity are 6.7 km/s, 2.92 g/cm^3, 2.93 g/cm^3, 0.98% and 2.46 W/m/K, respectively. P-wave velocity of samples from all three holes is inversely correlated with porosity. No clear correlation between the original lithology and physical properties is observed. GT3A cores show a wider range (e.g., Vp from 2.2 to 7.1 km/s) of values for the measured physical properties, compared to gabbros from Holes GT1A and GT2A.

Abnormal temperature dependence of conductance of single Cd-doped ZnO nanowires

NASA Astrophysics Data System (ADS)

Li, Q. H.; Wan, Q.; Wang, Y. G.; Wang, T. H.

2005-06-01

Positive temperature coefficient of resistance is observed on single Cd-doped ZnO nanowires. The current along the nanowire increases linearly with the bias and saturates at large biases. The conductance is greatly enhanced either by ultraviolet illumination or infrared illumination. However, the conductance decreases with increasing temperature, in contrast to the reported temperature behavior either for ZnO nanostructures or for CdO nanoneedles. The increase of the conductance under illumination is related to surface effect and the decrease with increasing temperature to bulk effect. These results show that Cd doping does not change surface effect but affects bulk effect. Such a bulk effect could be used to realize on-chip temperature-independent varistors.

Density of very small meteoroids

NASA Astrophysics Data System (ADS)

Kikwaya Eluo, Jean-Baptiste

2015-08-01

Knowing the density of meteoroids helps to determine the physical structure and gives insight into the composition of their parent bodies. The density of meteoroids can provide clues to their origins, whether cometary or asteroidal. Density helps also to characterize the risk meteoroids may pose to artificial satellites.Ceplecha (1968) calculated the density of small meteoroids based on a parameter KB (meteoroid beginning height) and classified them in four categories (A,B,C,D) with densities going from 2700 to 180 kgm-3.Babadzhanov(2002) applied a model based on quasi-continuous fragmentation (QCF) on 413 photographic Super-Schmidt meteors by solely fitting their light curves. Their densities range from 400 to 7800 kgm-3. Bellot Rubio et al. (2002) analyzed the same 413 photographic meteors assuming the single body theory based on meteoroid dynamical properties and found densities ranging from 400 to 4800 kgm-3. A thermal erosion model was used by Borovicka et al. (2007) to analyze, simultaneously, the observed decelerations and light curves of six Draconid meteors. The density was found to be 300 kgm-3, consistent with the fact that the Draconid meteors are porous aggregates of grains associated with the Jupiter-family-comet 21P/Giacobini-Zinner (Jacchia, L.G., 1950).We used the Campbell-Brown and Koschny (2004) model of meteoroid ablation to determine the density of faint meteoroids from the analysis of both observed decelerations and light curves of meteoroids (Kikwaya et al., 2009; Kikwaya et al., 2011). Our work was based on a collection of six and ninety-two sporadic meteors. The grain masses used in the modeling ranged from 10-12 Kg to 10-9 Kg. We computed the orbit of each meteoroid and determined its Tisserand parameter. We found that meteoroids with asteroidal orbits have bulk densities ranging from 3000-5000 kgm-3. Meteoroids consistent with HTC/NIC parents have bulk densities from 400 kgm-3 to 1600 kg m-3. JFC meteoroids were found to have surprisingly chondritic-like bulk densities, suggesting either the sintering of the meteoroids through evolutionary processes, or the original radial transportation of chondritic materials up to the Kuiper Belt region.

Soil water sensor response to bulk electrical conductivity

USDA-ARS?s Scientific Manuscript database

Soil water monitoring using electromagnetic (EM) sensors can facilitate observations of water content at high temporal and spatial resolutions. These sensors measure soil dielectric permittivity (Ka) which is largely a function of volumetric water content. However, bulk electrical conductivity BEC c...

Gravitational potential wells and the cosmic bulk flow

NASA Astrophysics Data System (ADS)

Wang, Yuyu; Kumar, Abhinav; Feldman, Hume; Watkins, Richard

2016-03-01

The bulk flow is a volume average of the peculiar velocities and a useful probe of the mass distribution on large scales. The gravitational instability model views the bulk flow as a potential flow that obeys a Maxwellian Distribution. We use two N-body simulations, the LasDamas Carmen and the Horizon Run, to calculate the bulk flows of various sized volumes in the simulation boxes. Once we have the bulk flow velocities as a function of scale, we investigate the mass and gravitational potential distribution around the volume. We found that matter densities can be asymmetrical and difficult to detect in real surveys, however, the gravitational potential and its gradient may provide better tools to investigate the underlying matter distribution. This study shows that bulk flows are indeed potential flows and thus provides information on the flow sources. We also show that bulk flow magnitudes follow a Maxwellian distribution on scales > 10h-1 Mpc.

Improvement of the GaSb/Al2O3 interface using a thin InAs surface layer

NASA Astrophysics Data System (ADS)

Greene, Andrew; Madisetti, Shailesh; Nagaiah, Padmaja; Yakimov, Michael; Tokranov, Vadim; Moore, Richard; Oktyabrsky, Serge

2012-12-01

The highly reactive GaSb surface was passivated with a thin InAs layer to limit interface trap state density (Dit) at the III-V/high-k oxide interface. This InAs surface was subjected to various cleaning processes to effectively reduce native oxides before atomic layer deposition (ALD). Ammonium sulfide pre-cleaning and trimethylaluminum/water ALD were used in conjunction to provide a clean interface and annealing in forming gas (FG) at 350 °C resulted in an optimized fabrication for n-GaSb/InAs/high-k gate stacks. Interface trap density, Dit ≈ 2-3 × 1012 cm-2eV-1 resided near the n-GaSb conductance band which was extracted and compared with three different methods. Conductance-voltage-frequency plots showed efficient Fermi level movement and a sub-threshold slope of 200 mV/dec. A composite high-k oxide process was also developed using ALD of Al2O3 and HfO2 resulting in a Dit ≈ 6-7 × 1012 cm-2eV-1. Subjecting these samples to a higher (450 °C) processing temperature results in increased oxidation and a thermally unstable interface. p-GaSb displayed very fast minority carrier generation/recombination likely due to a high density of bulk traps in GaSb.

Lateral Charge Transport in Silicon Nanomembranes

NASA Astrophysics Data System (ADS)

Hu, Weiwei

Silicon nanomembranes, also called SiNMs, Si thin sheets or films, are a great platform to study surface sciences, since the bulk is diminished and the surface-to-volume ratio is large. In a single crystalline material, atoms on the surface experience different forces, electric fields, thermodynamic surroundings, etc., than those within the bulk. Therefore, unique structural, mechanical, electronic, optical, and many other properties associated with surfaces overweigh bulk effects; novel phenomena emerge. In particular, electronic features of Si are of significance due to the extensive use of Si in integrated circuit devices and biochemical sensor technologies. As a result, especially with the size of transistors quickly decreasing nowadays, the exploration of electronic characteristics of Si surfaces become much more significant. This is also interesting as a topic within the area of fundamental surface science. Silicon-on-insulator (SOI) provides a new structure for studying charge transport in the SiNM, which is monocrystalline and sits on top of the SOI wafer. I use SOI based SiNMs with two surface orientations: Si (001) and Si (111). The former is pervasive in industrial applications while the latter has interesting metallic surface states when 7x7 reconstruction occurs on a clean surface. My goal is to measure/infer the sheet conductance in the true surface layer with different surface situations, and to further investigate the surface band structure and how carriers distribute and move accordingly. The biggest challenge is to eliminate interferences, e.g., bulk effects. The following are two solutions. 1) The thickness of the used SiNMs spans 40 nm to 500 nm, with a nominal doping level of 1015 cm -3 in our experiment. A straightforward calculation of areal dopant density indicates that charge carriers from the extrinsic doping are 1˜2 orders of magnitude fewer than the trap states at the interface between the buried oxide in SOI and the top SiNM, meaning that moderate doping is irrelevant and the SiNM acts like an intrinsic one. 2) The back gate that is applied to the measured sample is an innovative design among myriad analogous studies. It enables the tuning of the Fermi level (EF) throughout the SiNMs and makes it possible for a membrane to reach its most depleted status, thus efficiently removing the bulk conduction path. The four-probe van der Pauw measurements of film conductance are taken inside an ultrahigh vacuum chamber, where the surface condition remains stable and controllable. On Si (111) 7x7 surfaces, we find from the independence of conductance on membrane thickness that we are measuring the surface transport only. The sheet conductance is high, as it is on the microS/□scale, which supports the 7x7 surface having metallicity in lateral charge transport, a point which has been debated extensively. Nevertheless, weak semiconductor behavior is still present. For hydrogenated Si (001), which is obtained after hydrogen fluoric acid (HF) treatment, surface Fermi level is found around mid-bandgap based on temperature dependent measurements. No surface Fermi level pinning to closely below the conduction band minimum exists in my HF treated Si (001) NMs.

Stable topological insulators achieved using high energy electron beams

PubMed Central

Zhao, Lukas; Konczykowski, Marcin; Deng, Haiming; Korzhovska, Inna; Begliarbekov, Milan; Chen, Zhiyi; Papalazarou, Evangelos; Marsi, Marino; Perfetti, Luca; Hruban, Andrzej; Wołoś, Agnieszka; Krusin-Elbaum, Lia

2016-01-01

Topological insulators are potentially transformative quantum solids with metallic surface states which have Dirac band structure and are immune to disorder. Ubiquitous charged bulk defects, however, pull the Fermi energy into the bulk bands, denying access to surface charge transport. Here we demonstrate that irradiation with swift (∼2.5 MeV energy) electron beams allows to compensate these defects, bring the Fermi level back into the bulk gap and reach the charge neutrality point (CNP). Controlling the beam fluence, we tune bulk conductivity from p- (hole-like) to n-type (electron-like), crossing the Dirac point and back, while preserving the Dirac energy dispersion. The CNP conductance has a two-dimensional character on the order of ten conductance quanta and reveals, both in Bi2Te3 and Bi2Se3, the presence of only two quantum channels corresponding to two topological surfaces. The intrinsic quantum transport of the topological states is accessible disregarding the bulk size. PMID:26961901

Preparation and characterisation of crystalline tris(acetylacetonato)Fe(III) films grown on p-Si substrate for dielectric applications

NASA Astrophysics Data System (ADS)

Dakhel, A. A.; Ali-Mohamed, A. Y.

2007-02-01

Thin tris(acetylacetonato)iron(III) films were prepared by sublimation in vacuum on glass and p-Si substrates. Then comprehensive studies of X-ray fluorescence (XRF), X-ray diffraction (XRD), optical absorption spectroscopy, AC-conductivity, and dielectric permittivity as a function of frequency and temperature have been performed. The prepared films show a polycrystalline of orthorhombic structure. The optical absorption spectrum of the film was identical with that of the bulk powder layer. For electrical measurements of the complex as insulator, sample in form of metal insulator semiconductor (MIS) structure was prepared and characterised by the measurement of the capacitance and AC-conductance as a function of gate voltage. From those measurements, the state density Dit at insulator/semiconductor interface and the density of the fixed charges in the complex film were determined. It was found that Dit was of order 1010 eV-1/cm2 and the surface charge density in the insulator film was of order 1010 cm-2. The frequency dependence of the electrical conductivity and dielectric properties of MIS structures were studied at room temperature. It was observed that the experimental data follow the correlated barrier-hopping (CBH) model, from which the fundamental absorption edge, the cut off hopping distance, and other parameters of the model were determined. It was found that the capacitance of the complex increases as temperature increases. Generally, the present study shows that the tris(acetylacetonato)iron(III) films grown on p-Si is a promising candidate for low-k dielectric applications, it displays low-k value around 2.0.

Simulated glass transition of poly(ethylene oxide) bulk and film: a comparative study.

PubMed

Wu, Chaofu

2011-09-29

Stepwise cooling molecular dynamics (MD) simulations have been carried out on the bulk and film models for poly(ethylene oxide) (PEO) to understand glass transition of amorphous polymer films. Three types of properties--density, energy, and dynamics--are computed and plotted against the temperature for the two systems. It has been confirmed that all these properties can reveal glass transition in both PEO bulk and film systems. All the determined glass transition temperatures (T(g)'s) drop in the same order of magnitude to the experimental data available. Among various methods, the T(g)'s obtained from the density and energy data are close to each other if the same space regions are defined, which can suggest the same free volume theory, and dynamic T(g)'s obtained from mean-squared displacements (MSDs) are highest, which can suggest the kinetic theory for structural relaxation. Consistently, all these T(g)'s obtained using different methods show that the T(g)'s of PEO film are lower than those of PEO bulk. The free surface layers of polymer films dictate this offset. © 2011 American Chemical Society

Retrospective Analysis of NIST Standard Reference Material 1450, Fibrous Glass Board, for Thermal Insulation Measurements

PubMed Central

Zarr, Robert R; Heckert, N Alan; Leigh, Stefan D

2014-01-01

Thermal conductivity data acquired previously for the establishment of Standard Reference Material (SRM) 1450, Fibrous Glass Board, as well as subsequent renewals 1450a, 1450b, 1450c, and 1450d, are re-analyzed collectively and as individual data sets. Additional data sets for proto-1450 material lots are also included in the analysis. The data cover 36 years of activity by the National Institute of Standards and Technology (NIST) in developing and providing thermal insulation SRMs, specifically high-density molded fibrous-glass board, to the public. Collectively, the data sets cover two nominal thicknesses of 13 mm and 25 mm, bulk densities from 60 kg·m−3 to 180 kg·m−3, and mean temperatures from 100 K to 340 K. The analysis repetitively fits six models to the individual data sets. The most general form of the nested set of multilinear models used is given in the following equation: λ(ρ,T)=a0+a1ρ+a2T+a3T3+a4e−(T−a5a6)2where λ(ρ,T) is the predicted thermal conductivity (W·m−1·K−1), ρ is the bulk density (kg·m−3), T is the mean temperature (K) and ai (for i = 1, 2, … 6) are the regression coefficients. The least squares fit results for each model across all data sets are analyzed using both graphical and analytic techniques. The prevailing generic model for the majority of data sets is the bilinear model in ρ and T. λ(ρ,T)=a0+a1ρ+a2T One data set supports the inclusion of a cubic temperature term and two data sets with low-temperature data support the inclusion of an exponential term in T to improve the model predictions. Physical interpretations of the model function terms are described. Recommendations for future renewals of SRM 1450 are provided. An Addendum provides historical background on the origin of this SRM and the influence of the SRM on external measurement programs. PMID:26601034

Non-noble electrocatalysts for alkaline fuel cells

NASA Technical Reports Server (NTRS)

Sarangapani, S.; Lessner, P.; Manoukian, M.; Giner, J.

1989-01-01

Carbons activated with macrocyclics have attracted increasing attention as alternative electrocatalysts for oxygen reduction. Initial activity of these catalysts is good, but performance declines rapidly. Pyrolyzing the macrocyclic on the carbon support leads to enhanced stability and the catalysts retain good activity. The approach described is designed to develop bulk doped catalysts with similar structures to pyrolyzed macrocyclic catalysts. The transition metal and coordinated ligands are dispersed throughout the bulk of the conductive carbon skeleton. Two approaches to realizing this concept are being pursued, both involving the doping of carbon precursors. In one approach, the precursor is a solid phase carbon-containing ion-exchange resin. The precursor is doped with a transition metal and/or nitrogen, and the resulting mixture is pyrolyzed. In the other approach, the precursor is a gas-phase hydrocarbon. This is introduced with a transition metal species and nitrogen species into a reactor and pyrolyzed. Several studies have been conducted to determine if there is a synergistic effect between the transition metal and nitrogen and the effect of different methods of introducing the metal-nitrogen (M-N) coordination on performance. One approach was to introduce the metal and nitrogen separately, for example, by sequentially doping FeCl3 and NH4OH into the resin. Catalysts were prepared from an undoped ion-exchange resin, a resin doped only with N, a resin doped only with Fe, and a resin doped with both Fe and N. Introduction of nitrogen alone has no beneficial effect on the performance of the catalysts. The introduction of the Fe alone significantly improves the performance in both the high and low current density regions. When both Fe and N are introduced, the performance at lower current densities (catalytic activity) is increased beyond that of the Fe-doped carbon, but the performance at higher current densities is similar to the carbon containing only Fe. Catalysts prepared from resins-Fe(bipy)3SO4 precursors have performance that is only slightly less then CoTMPP adsorbed and pyroloyzed on Vulcan XC-72. Their performance is much better than carbons which have had the N and Fe introduced separately.

Influence of density and environmental factors on decomposition kinetics of amorphous polylactide - Reactive molecular dynamics studies.

PubMed

Mlyniec, A; Ekiert, M; Morawska-Chochol, A; Uhl, T

2016-06-01

In this work, we investigate the influence of the surrounding environment and the initial density on the decomposition kinetics of polylactide (PLA). The decomposition of the amorphous PLA was investigated by means of reactive molecular dynamics simulations. A computational model simulates the decomposition of PLA polymer inside the bulk, due to the assumed lack of removal of reaction products from the polymer matrix. We tracked the temperature dependency of the water and carbon monoxide production to extract the activation energy of thermal decomposition of PLA. We found that an increased density results in decreased activation energy of decomposition by about 50%. Moreover, initiation of decomposition of the amorphous PLA is followed by a rapid decline in activation energy caused by reaction products which accelerates the hydrolysis of esters. The addition of water molecules decreases initial energy of activation as well as accelerates the decomposition process. Additionally, we have investigated the dependency of density on external loading. Comparison of pressures needed to obtain assumed densities shows that this relationship is bilinear and the slope changes around a density equal to 1.3g/cm(3). The conducted analyses provide an insight into the thermal decomposition process of the amorphous phase of PLA, which is particularly susceptible to decomposition in amorphous and semi-crystalline PLA polymers. Copyright © 2016 Elsevier Inc. All rights reserved.

Electronic and Optical Properties of Titanium Nitride Bulk and Surfaces from First Principles Calculations (Postprint)

DTIC Science & Technology

2015-11-18

thickness of the film, or substrate. In this work, we report calculations for titanium nitride ( TiN ), a promising material for plasmonic applications...stoichiometric bulk TiN , as well as of the TiN (100), TiN (110), and TiN (111) outermost surfaces. Density functional theory (DFT) and many-body GW methods...and the band structure for bulk TiN were shown to be consistent with previous work. Calculated dielectric functions, plasma frequencies, reflectivity

Diamagnetic currents

NASA Astrophysics Data System (ADS)

Macris, N.; Martin, Ph. A.; Pulé, J. V.

1988-06-01

We study the diamagnetic surface currents of particles in thermal equilibrium submitted to a constant magnetic field. The current density of independent electrons with Boltzmann (respectively Fermi) statistics has a gaussian (respectively exponential) bound for its fall off into the bulk. For a system of interacting particles at low activity with Boltzmann statistics, the current density is localized near to the boundary and integrable when the two-body potential decays as |x|-α, α >4, α>4, in three dimensions. In all cases, the integral of the current density is independent of the nature of the confining wall and correctly related to the bulk magnetisation. The results hold for hard and soft walls and all field strength. The analysis relies on the Feynman-Kac-Ito representation of the Gibbs state and on specific properties of the Brownian bridge process.

Modification of electrical properties of topological insulators

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

Sharma, Peter Anand

Ion implantation or deposition can be used to modify the bulk electrical properties of topological insulators. More particularly, ion implantation or deposition can be used to compensate for the non-zero bulk conductivity due to extrinsic charge carriers. The direct implantation of deposition/annealing of dopants allows better control over carrier concentrations for the purposes of achieving low bulk conductivity. Ion implantation or deposition enables the fabrication of inhomogeneously doped structures, enabling new types of device designs.

Mechanical performance and thermal stability of glass fiber reinforced silica aerogel composites based on co-precursor method by freeze drying

NASA Astrophysics Data System (ADS)

Zhou, Ting; Cheng, Xudong; Pan, Yuelei; Li, Congcong; Gong, Lunlun; Zhang, Heping

2018-04-01

In order to maintain the integrity, glass fiber (GF) reinforced silica aerogel composites were synthesized using methltrimethoxysilane (MTMS) and water glass co-precursor by freeze drying method. The composites were characterized by scanning electron microscopy, Brunauer-Emmett-Teller analysis, uniaxial compressive test, three-point bending test, thermal conductivity analysis, contact angle test, TG-DSC analysis. It was found that the molar ratio of MTMS/water glass could significantly affect the properties of composites. The bulk density and thermal conductivity first decreased and then increased with the increasing molar ratio. The composites showed remarkable mechanical strength and flexibility compared with pure silica aerogel. Moreover, when the molar ratio is 1.8, the composites showed high specific surface area (870.9 m2/g), high contact angle (150°), great thermal stability (560 °C) and low thermal conductivity (0.0248 W/m·K). These outstanding properties indicate that GF/aerogels have broad prospects in the field of thermal insulation.

Impact of small-scale saline tracer heterogeneity on electrical resistivity monitoring in fully and partially saturated porous media: Insights from geoelectrical milli-fluidic experiments

NASA Astrophysics Data System (ADS)

Jougnot, Damien; Jiménez-Martínez, Joaquín; Legendre, Raphaël; Le Borgne, Tanguy; Méheust, Yves; Linde, Niklas

2018-03-01

Time-lapse electrical resistivity tomography (ERT) is a geophysical method widely used to remotely monitor the migration of electrically-conductive tracers and contaminant plumes in the subsurface. Interpretations of time-lapse ERT inversion results are generally based on the assumption of a homogeneous solute concentration below the resolution limits of the tomogram depicting inferred electrical conductivity variations. We suggest that ignoring small-scale solute concentration variability (i.e., at the sub-resolution scale) is a major reason for the often-observed apparent loss of solute mass in ERT tracer studies. To demonstrate this, we developed a geoelectrical milli-fluidic setup where the bulk electric conductivity of a 2D analogous porous medium, consisting of cylindrical grains positioned randomly inside a Hele-Shaw cell, is monitored continuously in time while saline tracer tests are performed through the medium under fully and partially saturated conditions. High resolution images of the porous medium are recorded with a camera at regular time intervals, and provide both the spatial distribution of the fluid phases (aqueous solution and air), and the saline solute concentration field (where the solute consists of a mixture of salt and fluorescein, the latter being used as a proxy for the salt concentration). Effective bulk electrical conductivities computed numerically from the measured solute concentration field and the spatial distributions of fluid phases agree well with the measured bulk conductivities. We find that the effective bulk electrical conductivity is highly influenced by the connectivity of high electrical conductivity regions. The spatial distribution of air, saline tracer fingering, and mixing phenomena drive temporal changes in the effective bulk electrical conductivity by creating preferential paths or barriers for electrical current at the pore-scale. The resulting heterogeneities in the solute concentrations lead to strong anisotropy of the effective bulk electrical conductivity, especially for partially saturated conditions. We highlight how these phenomena contribute to the typically large apparent mass loss observed when conducting field-scale time-lapse ERT.

Depositing bulk or micro-scale electrodes

DOEpatents

Shah, Kedar G.; Pannu, Satinderpall S.; Tolosa, Vanessa; Tooker, Angela C.; Sheth, Heeral J.; Felix, Sarah H.; Delima, Terri L.

2016-11-01

Thicker electrodes are provided on microelectronic device using thermo-compression bonding. A thin-film electrical conducting layer forms electrical conduits and bulk depositing provides an electrode layer on the thin-film electrical conducting layer. An insulating polymer layer encapsulates the electrically thin-film electrical conducting layer and the electrode layer. Some of the insulating layer is removed to expose the electrode layer.

Quantum mechanical/molecular mechanical modeling finds Diels-Alder reactions are accelerated less on the surface of water than in water.

PubMed

Thomas, Laura L; Tirado-Rives, Julian; Jorgensen, William L

2010-03-10

Quantum and molecular mechanics calculations for the Diels-Alder reactions of cyclopentadiene with 1,4-naphthoquinone, methyl vinyl ketone, and acrylonitrile have been carried out at the vacuum-water interface and in the gas phase. In conjunction with previous studies of these cycloadditions in dilute solution, a more complete picture of aqueous environmental effects emerges with implications for the origin of observed rate accelerations using heterogeneous aqueous suspensions, "on water" conditions. The pure TIP4P water slab maintains the bulk density and hydrogen-bonding properties in central water layers. The bulk region merges to vacuum over a ca. 5 A band with progressive diminution of the density and hydrogen bonding. The relative free energies of activation and transition structures for the reactions at the interface are found to be intermediate between those calculated in the gas phase and in bulk water; i.e., for the reaction with 1,4-naphthoquinone, the DeltaDeltaG(++) values relative to the gas phase are -3.6 and -7.3 kcal/mol at the interface and in bulk water, respectively. Thus, the results do not support the notion that a water surface is more effective than bulk water for catalysis of such pericyclic reactions. The trend is in qualitative agreement with expectations based on density considerations and estimates of experimental rate constants for the gas phase, a heterogeneous aqueous suspension, and a dilute aqueous solution for the reaction of cyclopentadiene with methyl vinyl ketone. Computed energy pair distributions reveal a uniform loss of 0.5-1.0 hydrogen bond for the reactants and transition states in progressing from bulk water to the vacuum-water interface. Orientational effects are apparent at the surface; e.g., the carbonyl group in the methyl vinyl ketone transition structure is preferentially oriented into the surface. Also, the transition structure for the 1,4-naphthoquinone case is buried more in the surface, and the free energy of activation for this reaction is most similar to the result in bulk water.

High pressure-resistant nonincendive emulsion explosive

DOEpatents

Ruhe, Thomas C.; Rao, Pilaka P.

1994-01-01

An improved emulsion explosive composition including hollow microspheres/bulking agents having high density and high strength. The hollow microspheres/bulking agents have true particle densities of about 0.2 grams per cubic centimeter or greater and include glass, siliceous, ceramic and synthetic resin microspheres, expanded minerals, and mixtures thereof. The preferred weight percentage of hollow microspheres/bulking agents in the composition ranges from 3.0 to 10.0 A chlorinated paraffin oil, also present in the improved emulsion explosive composition, imparts a higher film strength to the oil phase in the emulsion. The emulsion is rendered nonincendive by the production of sodium chloride in situ via the decomposition of sodium nitrate, a chlorinated paraffin oil, and sodium perchlorate. The air-gap sensitivity is improved by the in situ formation of monomethylamine perchlorate from dissolved monomethylamine nitrate and sodium perchlorate. The emulsion explosive composition can withstand static pressures to 139 bars and dynamic pressure loads on the order of 567 bars.