Elastic layer under axisymmetric indentation and surface energy effects

NASA Astrophysics Data System (ADS)

Intarit, Pong-in; Senjuntichai, Teerapong; Rungamornrat, Jaroon

2018-04-01

In this paper, a continuum-based approach is adopted to investigate the contact problem of an elastic layer with finite thickness and rigid base subjected to axisymmetric indentation with the consideration of surface energy effects. A complete Gurtin-Murdoch surface elasticity is employed to consider the influence of surface stresses. The indentation problem of a rigid frictionless punch with arbitrary axisymmetric profiles is formulated by employing the displacement Green's functions, derived with the aid of Hankel integral transform technique. The problem is solved by assuming the contact pressure distribution in terms of a linear combination of admissible functions and undetermined coefficients. Those coefficients are then obtained by employing a collocation technique and an efficient numerical quadrature scheme. The accuracy of proposed solution technique is verified by comparing with existing solutions for rigid indentation on an elastic half-space. Selected numerical results for the indenters with flat-ended cylindrical and paraboloidal punch profiles are presented to portray the influence of surface energy effects on elastic fields of the finite layer. It is found that the presence of surface stresses renders the layer stiffer, and the size-dependent behavior of elastic fields is observed in the present solutions. In addition, the surface energy effects become more pronounced with smaller contact area; thus, the influence of surface energy cannot be ignored in the analysis of indentation problem especially when the indenter size is very small such as in the case of nanoindentation.

Upper ocean moored current and density profiler applied to winter conditions near Bermuda

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

Eriksen, C.C.; Dahlen, J.M.; Shillingford, J.T. Jr.

1982-09-20

A new moored instrument which makes repeated high vertical resolution profiles of current, temperature, and salinity in the upper ocean over extended periods was used to observe midwinter conditions near Bermuda. The operation and performance of the instrument, called the profiling current meter (PCM), in the surface wave environment of winter storms is reported here. The PCM profiles along the upper portion of a slightly subsurface mooring by adjusting its buoyancy under computer control. This design decouples the instrument from vertical motions of the mooring induced by surface waves, so that its electromagnetic current sensor operates in a favorable mean-to-fluctuatingmore » flow regime. Current, temperature, and electrical conductivity are (vector) averaged into contiguous preselected bins several meters wide over the possible profile range of 20- to 250-m depth. The PCM is capable of collecting 1000--4000 profiles in a 6- to 12-month period, depending on depth range and ambient currents. A variety of baroclinic motions are evident in the Bermuda observations. Upper ocean manifestations of both Kelvin and superinertial island-trapped waves dominate longshore currents. Vertical coherence of onshore current and temperature suggest that internal wave vertical wave number energy distribution is independent of frequency but modified by island bathymetry. Kinetic energy in shear integrated over a 115.6-m-thick layer in the upper ocean is limited to values less than or equal to the potential energy required to mix the existing stratification. Mixing events occur when kinetic energy associated with shear drives the bulk Richardson number (defined by the ratio of energy integrals over the range profiles) to unity, where it remains while shear and stratification disappear together.« less

X-Ray Scattering Studies of the Liquid-Vapor Interface of Gallium.

NASA Astrophysics Data System (ADS)

Kawamoto, Eric Hitoshi

A UHV system was developed for performing X-ray scattering studies and in situ analyses of liquid metal surfaces. A nearly ideal choice for this study, gallium has a melting point just above room temperature; is amenable to handling in both air and vacuum; its surface oxides can be removed while its cleanliness is maintained and monitored. Using argon glow-discharge sputtering techniques to remove intervening surface oxides, thin wetting layers of gallium were prepared atop nonreactive substrates, to be used as samples suited for liquid surface scattering experiments. Preliminary measurements of X-ray reflectivity from the liquid-vapor interface of gallium were performed with the X-ray UHV chamber configured for use in conjunction with liquid surface spectrometers at two synchrotron beamlines. A novel technique for carrying out and interpreting scattering measurements from curved liquid surfaces was demonstrated. The energy tunability and intense focused white beam flux from a wiggler source was shown to place within reach the large values of wavevector transfer at which specular reflectivity data yield small length scale information about surface structure. Various theoretical treatments and simulations predict quasi-lamellar ordering of atoms near the free surface of metallic liquids due to energetics particular to metals (electron delocalization, the dependence of system energy on ion and electron densities, surface tension and electrostatic energy). However, the experimental data reported to date is insufficient to distinguish between a monotonic, sigmoidal electron density profile found at the free surfaces of dielectric liquids, and the damped oscillatory layer-like profiles anticipated for metallic liquids. Out to a wavevector transfer of Q = 0.55 A ^{-1}, the reflectivity data measured from a curved Ga surface is not inconsistent with what is expected for a liquid-vapor electron density profile of Gaussian width sigma = 1.3 +/- 0.2 A. Subsequent measurements roughly tripled the range of Q, but an oxidized surface led to poor data and hindered interpretation. The analysis presented is speculative at best, but within the context of the thermally excited capillary wave model of simple liquid surfaces, there seems to be no serious deviation from the simple Gaussian interfacial profile with the aforementioned roughness.

Quantitative assessment of interfacial interactions with rough membrane surface and its implications for membrane selection and fabrication in a MBR.

PubMed

Chen, Jianrong; Mei, Rongwu; Shen, Liguo; Ding, Linxian; He, Yiming; Lin, Hongjun; Hong, Huachang

2015-03-01

The interfacial interactions between a foulant particle and rough membrane surface in a submerged membrane bioreactor (MBR) were quantitatively assessed by using a new-developed method. It was found that the profile of total interaction versus separation distance was complicated. There were an energy barrier and two negative energy ranges in the profile. Further analysis showed that roughness scale significantly affected the strength and properties of interfacial interactions. It was revealed that there existed a critical range of roughness scale within which the total energy in the separation distance ranged from 0 to several nanometers was continually repulsive. Decrease in foulant size would increase the strength of specific interaction energy, but did not change the existence of a critical roughness scale range. These findings suggested the possibility to "tailor" membrane surface morphology for membrane fouling mitigation, and thus gave significant implications for membrane selection and fabrication in MBRs. Copyright © 2014 Elsevier Ltd. All rights reserved.

Rovibrational line-shape parameters for H2 in He and new H2-He potential energy surface

NASA Astrophysics Data System (ADS)

Thibault, Franck; Patkowski, Konrad; Żuchowski, Piotr S.; Jóźwiak, Hubert; Ciuryło, Roman; Wcisło, Piotr

2017-11-01

We report a new H2-He potential energy surface that, with respect to the previous one [Bakr et al.(2013)], covers much larger range of H2 stretching and exhibits more accurate asymptotic behavior for large separations between H2 and He. Close-coupling calculations performed on this improved potential energy surface allow us to provide line shape parameters for H2 between 5 and 2000 K for Raman isotropic Q lines and anisotropic Q lines (or electric quadrupole lines) and for vibrational bands from the ground up to v = 5 and rotational quantum numbers up to j = 5 . The parameters provided include the usual pressure -broadening and -shifting coefficients as well as the real and imaginary part of Dicke contribution to the Hess profile. The latter parameters can be readily implemented in other line-shape profiles like the most recent one of Hartmann and Tran.

From Aβ Filament to Fibril: Molecular Mechanism of Surface-Activated Secondary Nucleation from All-Atom MD Simulations.

PubMed

Schwierz, Nadine; Frost, Christina V; Geissler, Phillip L; Zacharias, Martin

2017-02-02

Secondary nucleation pathways in which existing amyloid fibrils catalyze the formation of new aggregates and neurotoxic oligomers are of immediate importance for the onset and progression of Alzheimer's disease. Here, we apply extensive all-atom molecular dynamics simulations in explicit water to study surface-activated secondary nucleation pathways at the extended lateral β-sheet surface of a preformed Aβ 9-40 filament. Calculation of free-energy profiles allows us to determine binding free energies and conformational intermediates for nucleation complexes consisting of 1-4 Aβ peptides. In addition, we combine the free-energy profiles with position-dependent diffusion profiles to extract complementary kinetic information and macroscopic growth rates. Single monomers bind to the β-sheet surface in a disordered, hydrophobically collapsed conformation, whereas dimers and larger oligomers can retain a cross-β conformation resembling a more ordered fibril structure. The association processes during secondary nucleation follow a dock/lock mechanism consisting of a fast initial encounter phase (docking) and a slow structural rearrangement phase (locking). The major driving forces for surface-activated secondary nucleation are the release of a large number of hydration water molecules and the formation of hydrophobic interface contacts, the latter being in contrast to the elongation process at filament tips, which is dominated by the formation of stable and highly specific interface hydrogen bonds. The calculated binding free energies and the association rates for the attachment of Aβ monomers and oligomers to the extended lateral β-sheet surface of the filament seed are higher compared to those for elongation at the filament tips, indicating that secondary nucleation pathways can become important once a critical concentration of filaments has formed.

Level crossings in the ionization of H(2) Rydberg molecules at a metal surface.

PubMed

McCormack, E A; Ford, M S; Softley, T P

2010-10-28

The ionization of H(2) Rydberg states at a metal surface is investigated using a molecular beam incident at grazing incidence on a gold surface. The H(2) molecules, excited by stepwise two-color laser excitation, are selected in each of the accessible Stark eigenstates of the N(+) = 2, n = 17 Rydberg manifold in turn and the ionization at the surface is characterized by applying a field to extract the ions formed. Profiles of extracted ion signal versus applied field show resonances that can be simulated by assuming an enhancement of surface ionization at fields corresponding to energy-level crossings between the populated N(+) = 2 manifold and the near-degenerate N(+) = 0 Stark manifolds. It is concluded that the slow (microsecond time scale) rotation-electronic energy transfer to N(+) = 0 states occurring at these crossings takes place in the time interval following application of the field ramp when the molecule is still distant from, and unperturbed by, the surface. However, the energy levels are strongly perturbed by image-dipole interactions as the molecule approaches close to the surface, leading to additional energy-level crossings. Adiabatic behavior at such crossings affects the intensity of the observed resonances in the surface ionization signal but not their field positions. Resonances are also observed in the surface ionization profiles at fields above the field-ionization threshold; some of these show asymmetric "Fano-type" line shapes due to quantum interference in the nonradiative coupling to degenerate bound and continuum states.

Numerical Study for a Large-Volume Droplet on the Dual-Rough Surface: Apparent Contact Angle, Contact Angle Hysteresis, and Transition Barrier.

PubMed

Dong, Jian; Jin, Yanli; Dong, He; Liu, Jiawei; Ye, Senbin

2018-06-26

The profile, apparent contact angle (ACA), contact angle hysteresis (CAH), and wetting state transmission energy barrier (WSTEB) are important static and dynamic properties of a large-volume droplet on the hierarchical surface. Understanding them can provide us with important insights into functional surfaces and promote the application in corresponding areas. In this paper, we establish three theoretical models (models 1-3) and the corresponding numerical methods, which were obtained by the free energy minimization and the nonlinear optimization algorithm, to predict the profile, ACA, CAH, and WSTEB of a large-volume droplet on the horizontal regular dual-rough surface. In consideration of the gravity, the energy barrier on the contact circle, the dual heterogeneous structures and their roughness on the surface, the models are more universal and accurate than the previous models. It showed that the predictions of the models were in good agreement with the results from the experiment or literature. The models are promising to become novel design approaches of functional surfaces, which are frequently applied in microfluidic chips, water self-catchment system, and dropwise condensation heat transfer system.

Machining Specific Fourier Power Spectrum Profiles into Plastics for High Energy Density Physics Experiments [Machining Specific Fourier Power Spectrum Profiles into Plastics for HEDP Experiments

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

Schmidt, Derek William; Cardenas, Tana; Doss, Forrest W.

In this paper, the High Energy Density Physics program at Los Alamos National Laboratory (LANL) has had a multiyear campaign to verify the predictive capability of the interface evolution of shock propagation through different profiles machined into the face of a plastic package with an iodine-doped plastic center region. These experiments varied the machined surface from a simple sine wave to a double sine wave and finally to a multitude of different profiles with power spectrum ranges and shapes to verify LANL’s simulation capability. The MultiMode-A profiles had a band-pass flat region of the power spectrum, while the MultiMode-B profilemore » had two band-pass flat regions. Another profile of interest was the 1-Peak profile, a band-pass concept with a spike to one side of the power spectrum. All these profiles were machined in flat and tilted orientations of 30 and 60 deg. Tailor-made machining profiles, supplied by experimental physicists, were compared to actual machined surfaces, and Fourier power spectra were compared to see the reproducibility of the machining process over the frequency ranges that physicists require.« less

Machining Specific Fourier Power Spectrum Profiles into Plastics for High Energy Density Physics Experiments [Machining Specific Fourier Power Spectrum Profiles into Plastics for HEDP Experiments

DOE PAGES

Schmidt, Derek William; Cardenas, Tana; Doss, Forrest W.; ...

2018-01-15

In this paper, the High Energy Density Physics program at Los Alamos National Laboratory (LANL) has had a multiyear campaign to verify the predictive capability of the interface evolution of shock propagation through different profiles machined into the face of a plastic package with an iodine-doped plastic center region. These experiments varied the machined surface from a simple sine wave to a double sine wave and finally to a multitude of different profiles with power spectrum ranges and shapes to verify LANL’s simulation capability. The MultiMode-A profiles had a band-pass flat region of the power spectrum, while the MultiMode-B profilemore » had two band-pass flat regions. Another profile of interest was the 1-Peak profile, a band-pass concept with a spike to one side of the power spectrum. All these profiles were machined in flat and tilted orientations of 30 and 60 deg. Tailor-made machining profiles, supplied by experimental physicists, were compared to actual machined surfaces, and Fourier power spectra were compared to see the reproducibility of the machining process over the frequency ranges that physicists require.« less

Soil Water and Temperature System (SWATS) Instrument Handbook

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

Cook, David R.

2016-04-01

The soil water and temperature system (SWATS) provides vertical profiles of soil temperature, soil-water potential, and soil moisture as a function of depth below the ground surface at hourly intervals. The temperature profiles are measured directly by in situ sensors at the Central Facility and many of the extended facilities of the U.S. Department of Energy (DOE)’s Atmospheric Radiation Measurement (ARM) Climate Research Facility Southern Great Plains (SGP) site. The soil-water potential and soil moisture profiles are derived from measurements of soil temperature rise in response to small inputs of heat. Atmospheric scientists use the data in climate models tomore » determine boundary conditions and to estimate the surface energy flux. The data are also useful to hydrologists, soil scientists, and agricultural scientists for determining the state of the soil.« less

Elimination of surface band bending on N-polar InN with thin GaN capping

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

Kuzmík, J., E-mail: Jan.Kuzmik@savba.sk; Haščík, Š.; Kučera, M.

2015-11-09

0.5–1 μm thick InN (0001) films grown by molecular-beam epitaxy with N- or In-polarity are investigated for the presence of native oxide, surface energy band bending, and effects introduced by 2 to 4 monolayers of GaN capping. Ex situ angle-resolved x-ray photo-electron spectroscopy is used to construct near-surface (GaN)/InN energy profiles, which is combined with deconvolution of In3d signal to trace the presence of InN native oxide for different types of polarity and capping. Downwards surface energy band bending was observed on bare samples with native oxide, regardless of the polarity. It was found that the In-polar InN surface is mostmore » readily oxidized, however, with only slightly less band bending if compared with the N-polar sample. On the other hand, InN surface oxidation was effectively mitigated by GaN capping. Still, as confirmed by ultra-violet photo-electron spectroscopy and by energy band diagram calculations, thin GaN cap layer may provide negative piezoelectric polarization charge at the GaN/InN hetero-interface of the N-polar sample, in addition to the passivation effect. These effects raised the band diagram up by about 0.65 eV, reaching a flat-band profile.« less

Temperature profile of graphite surface burning in a stream of oxygen

NASA Technical Reports Server (NTRS)

Kisch, D.

1978-01-01

Using methods for the objective measurement of the spectrum line reversal temperature in burning gases, the temperature profile at a graphite surface burning in a stream of oxygen was measured. From the behavior of the reversal temperature, it follows that particles in long-lived, high-energy states are present in the burning gas, and these bring about an overexcitation of the atomic species emitting the reversal line. Qualitative measurements show that a temperature maximum occurs at the expected distance of 1-2 mm from the graphite surface.

A Multidimensional B-Spline Correction for Accurate Modeling Sugar Puckering in QM/MM Simulations.

PubMed

Huang, Ming; Dissanayake, Thakshila; Kuechler, Erich; Radak, Brian K; Lee, Tai-Sung; Giese, Timothy J; York, Darrin M

2017-09-12

The computational efficiency of approximate quantum mechanical methods allows their use for the construction of multidimensional reaction free energy profiles. It has recently been demonstrated that quantum models based on the neglect of diatomic differential overlap (NNDO) approximation have difficulty modeling deoxyribose and ribose sugar ring puckers and thus limit their predictive value in the study of RNA and DNA systems. A method has been introduced in our previous work to improve the description of the sugar puckering conformational landscape that uses a multidimensional B-spline correction map (BMAP correction) for systems involving intrinsically coupled torsion angles. This method greatly improved the adiabatic potential energy surface profiles of DNA and RNA sugar rings relative to high-level ab initio methods even for highly problematic NDDO-based models. In the present work, a BMAP correction is developed, implemented, and tested in molecular dynamics simulations using the AM1/d-PhoT semiempirical Hamiltonian for biological phosphoryl transfer reactions. Results are presented for gas-phase adiabatic potential energy surfaces of RNA transesterification model reactions and condensed-phase QM/MM free energy surfaces for nonenzymatic and RNase A-catalyzed transesterification reactions. The results show that the BMAP correction is stable, efficient, and leads to improvement in both the potential energy and free energy profiles for the reactions studied, as compared with ab initio and experimental reference data. Exploration of the effect of the size of the quantum mechanical region indicates the best agreement with experimental reaction barriers occurs when the full CpA dinucleotide substrate is treated quantum mechanically with the sugar pucker correction.

Field theoretic approach to roughness corrections

NASA Astrophysics Data System (ADS)

Wu, Hua Yao; Schaden, Martin

2012-02-01

We develop a systematic field theoretic description of roughness corrections to the Casimir free energy of a massless scalar field in the presence of parallel plates with mean separation a. Roughness is modeled by specifying a generating functional for correlation functions of the height profile. The two-point correlation function being characterized by its variance, σ2, and correlation length, ℓ. We obtain the partition function of a massless scalar quantum field interacting with the height profile of the surface via a δ-function potential. The partition function is given by a holographic reduction of this model to three coupled scalar fields on a two-dimensional plane. The original three-dimensional space with a flat parallel plate at a distance a from the rough plate is encoded in the nonlocal propagators of the surface fields on its boundary. Feynman rules for this equivalent 2+1-dimensional model are derived and its counterterms constructed. The two-loop contribution to the free energy of this model gives the leading roughness correction. The effective separation, aeff, to a rough plate is measured to a plane that is displaced a distance ρ∝σ2/ℓ from the mean of its profile. This definition of the separation eliminates corrections to the free energy of order 1/a4 and results in unitary scattering matrices. We obtain an effective low-energy model in the limit ℓ≪a. It determines the scattering matrix and equivalent planar scattering surface of a very rough plate in terms of the single length scale ρ. The Casimir force on a rough plate is found to always weaken with decreasing correlation length ℓ. The two-loop approximation to the free energy interpolates between the free energy of the effective low-energy model and that of the proximity force approximation - the force on a very rough plate with σ≳0.5ℓ being weaker than on a planar Dirichlet surface at any separation.

Effect of crystal habits on the surface energy and cohesion of crystalline powders.

PubMed

Shah, Umang V; Olusanmi, Dolapo; Narang, Ajit S; Hussain, Munir A; Gamble, John F; Tobyn, Michael J; Heng, Jerry Y Y

2014-09-10

The role of surface properties, influenced by particle processing, in particle-particle interactions (powder cohesion) is investigated in this study. Wetting behaviour of mefenamic acid was found to be anisotropic by sessile drop contact angle measurements on macroscopic (>1cm) single crystals, with variations in contact angle of water from 56.3° to 92.0°. This is attributed to variations in surface chemical functionality at specific facets, and confirmed using X-ray photoelectron spectroscopy (XPS). Using a finite dilution inverse gas chromatography (FD-IGC) approach, the surface energy heterogeneity of powders was determined. The surface energy profile of different mefenamic acid crystal habits was directly related to the relative exposure of different crystal facets. Cohesion, determined by a uniaxial compression test, was also found to relate to surface energy of the powders. By employing a surface modification (silanisation) approach, the contribution from crystal shape from surface area and surface energy was decoupled. By "normalising" contribution from surface energy and surface area, needle shaped crystals were found to be ∼2.5× more cohesive compared to elongated plates or hexagonal cuboid shapes crystals. Copyright © 2014. Published by Elsevier B.V.

HCMM energy budget data as a model input for assessing regions of high potential groundwater pollution

NASA Technical Reports Server (NTRS)

Moore, D. G. (Principal Investigator); Heilman, J.; Tunheim, J. A.; Baumberger, V.

1978-01-01

The author has identified the following significant results. To investigate the general relationship between surface temperature and soil moisture profiles, a series of model calculations were carried out. Soil temperature profiles were calculated during a complete diurnal cycle for a variety of moisture profiles. Preliminary results indicate the surface temperature difference between two sites measured at about 1400 hours is related to the difference in soil moisture within the diurnal damping depth (about 50 cm). The model shows this temperature difference to vary considerably throughout the diurnal cycle.

Validation of the Land-Surface Energy Budget and Planetary Boundary Layer for Several Intensive field Experiments

NASA Technical Reports Server (NTRS)

Bosilovich, Michael G.; Schubert, Siegfried; Molod, Andrea; Houser, Paul R.

1999-01-01

Land-surface processes in a data assimilation system influence the lower troposphere and must be properly represented. With the recent incorporation of the Mosaic Land-surface Model (LSM) into the GEOS Data Assimilation System (DAS), the detailed land-surface processes require strict validation. While global data sources can identify large-scale systematic biases at the monthly timescale, the diurnal cycle is difficult to validate. Moreover, global data sets rarely include variables such as evaporation, sensible heat and soil water. Intensive field experiments, on the other hand, can provide high temporal resolution energy budget and vertical profile data for sufficiently long periods, without global coverage. Here, we evaluate the GEOS DAS against several intensive field experiments. The field experiments are First ISLSCP Field Experiment (FIFE, Kansas, summer 1987), Cabauw (as used in PILPS, Netherlands, summer 1987), Atmospheric Radiation Measurement (ARM, Southern Great Plains, winter and summer 1998) and the Surface Heat Budget of the Arctic Ocean (SHEBA, Arctic ice sheet, winter and summer 1998). The sites provide complete surface energy budget data for periods of at least one year, and some periods of vertical profiles. This comparison provides a detailed validation of the Mosaic LSM within the GEOS DAS for a variety of climatologic and geographic conditions.

Molecular-Scale Description of SPAN80 Desorption from a Squalane-Water Interface.

PubMed

Tan, L; Pratt, L R; Chaudhari, M I

2018-04-05

Extensive all-atom molecular dynamics calculations on the water-squalane interface for nine different loadings with sorbitan monooleate (SPAN80), at T = 300 K, are analyzed for the surface tension equation of state, desorption free-energy profiles as they depend on loading, and to evaluate escape times for adsorbed SPAN80 into the bulk phases. These results suggest that loading only weakly affects accommodation of a SPAN80 molecule by this squalane-water interface. Specifically, the surface tension equation of state is simple through the range of high tension to high loading studied, and the desorption free-energy profiles are weakly dependent on loading here. The perpendicular motion of the centroid of the SPAN80 headgroup ring is well-described by a diffusional model near the minimum of the desorption free-energy profile. Lateral diffusional motion is weakly dependent on loading. Escape times evaluated on the basis of a diffusional model and the desorption free energies are 7 × 10 -2 s (into the squalane) and 3 × 10 2 h (into the water). The latter value is consistent with desorption times of related lab-scale experimental work.

Interfacial thermodynamics of water and six other liquid solvents.

PubMed

Pascal, Tod A; Goddard, William A

2014-06-05

We examine the thermodynamics of the liquid-vapor interface by direct calculation of the surface entropy, enthalpy, and free energy from extensive molecular dynamics simulations using the two-phase thermodynamics (2PT) method. Results for water, acetonitrile, cyclohexane, dimethyl sulfoxide, hexanol, N-methyl acetamide, and toluene are presented. We validate our approach by predicting the interfacial surface tensions (IFT--excess surface free energy per unit area) in excellent agreement with the mechanical calculations using Kirkwood-Buff theory. Additionally, we evaluate the temperature dependence of the IFT of water as described by the TIP4P/2005, SPC/Ew, TIP3P, and mW classical water models. We find that the TIP4P/2005 and SPC/Ew water models do a reasonable job of describing the interfacial thermodynamics; however, the TIP3P and mW are quite poor. We find that the underprediction of the experimental IFT at 298 K by these water models results from understructured surface molecules whose binding energies are too weak. Finally, we performed depth profiles of the interfacial thermodynamics which revealed long tails that extend far into what would be considered bulk from standard Gibbs theory. In fact, we find a nonmonotonic interfacial free energy profile for water, a unique feature that could have important consequences for the absorption of ions and other small molecules.

ARM - Midlatitude Continental Convective Clouds Experiment (MC3E): Multi-Frequency Profilers, Surface Meteorology (williams-surfmet)

DOE Data Explorer

Williams, Christopher; Jensen, Mike

2012-11-06

This data was collected by the NOAA 449-MHz and 2.8-GHz profilers in support of the Department of Energy (DOE) and NASA sponsored Mid-latitude Continental Convective Cloud Experiment (MC3E). The profiling radars were deployed in Northern Oklahoma at the DOE Atmospheric Radiation Mission (ARM) Southern Great Plans (SGP) Central Facility from 22 April through 6 June 2011. NOAA deployed three instruments: a Parsivel disdrometer, a 2.8-GHz profiler, and a 449-MHz profiler. The parasivel provided surface estimates of the raindrop size distribution and is the reference used to absolutely calibrate the 2.8 GHz profiler. The 2.8-GHz profiler provided unattenuated reflectivity profiles of the precipitation. The 449-MHz profiler provided estimates of the vertical air motion during precipitation from near the surface to just below the freezing level. By using the combination of 2.8-GHz and 449-MHz profiler observations, vertical profiles of raindrop size distributions can be retrieved. The profilers are often reference by their frequency band: the 2.8-GHz profiler operates in the S-band and the 449-MHz profiler operates in the UHF band. The raw observations are available as well as calibrated spectra and moments. This document describes how the instruments were deployed, how the data was collected, and the format of the archived data.

Convergence of Free Energy Profile of Coumarin in Lipid Bilayer

PubMed Central

2012-01-01

Atomistic molecular dynamics (MD) simulations of druglike molecules embedded in lipid bilayers are of considerable interest as models for drug penetration and positioning in biological membranes. Here we analyze partitioning of coumarin in dioleoylphosphatidylcholine (DOPC) bilayer, based on both multiple, unbiased 3 μs MD simulations (total length) and free energy profiles along the bilayer normal calculated by biased MD simulations (∼7 μs in total). The convergences in time of free energy profiles calculated by both umbrella sampling and z-constraint techniques are thoroughly analyzed. Two sets of starting structures are also considered, one from unbiased MD simulation and the other from “pulling” coumarin along the bilayer normal. The structures obtained by pulling simulation contain water defects on the lipid bilayer surface, while those acquired from unbiased simulation have no membrane defects. The free energy profiles converge more rapidly when starting frames from unbiased simulations are used. In addition, z-constraint simulation leads to more rapid convergence than umbrella sampling, due to quicker relaxation of membrane defects. Furthermore, we show that the choice of RESP, PRODRG, or Mulliken charges considerably affects the resulting free energy profile of our model drug along the bilayer normal. We recommend using z-constraint biased MD simulations based on starting geometries acquired from unbiased MD simulations for efficient calculation of convergent free energy profiles of druglike molecules along bilayer normals. The calculation of free energy profile should start with an unbiased simulation, though the polar molecules might need a slow pulling afterward. Results obtained with the recommended simulation protocol agree well with available experimental data for two coumarin derivatives. PMID:22545027

Convergence of Free Energy Profile of Coumarin in Lipid Bilayer.

PubMed

Paloncýová, Markéta; Berka, Karel; Otyepka, Michal

2012-04-10

Atomistic molecular dynamics (MD) simulations of druglike molecules embedded in lipid bilayers are of considerable interest as models for drug penetration and positioning in biological membranes. Here we analyze partitioning of coumarin in dioleoylphosphatidylcholine (DOPC) bilayer, based on both multiple, unbiased 3 μs MD simulations (total length) and free energy profiles along the bilayer normal calculated by biased MD simulations (∼7 μs in total). The convergences in time of free energy profiles calculated by both umbrella sampling and z-constraint techniques are thoroughly analyzed. Two sets of starting structures are also considered, one from unbiased MD simulation and the other from "pulling" coumarin along the bilayer normal. The structures obtained by pulling simulation contain water defects on the lipid bilayer surface, while those acquired from unbiased simulation have no membrane defects. The free energy profiles converge more rapidly when starting frames from unbiased simulations are used. In addition, z-constraint simulation leads to more rapid convergence than umbrella sampling, due to quicker relaxation of membrane defects. Furthermore, we show that the choice of RESP, PRODRG, or Mulliken charges considerably affects the resulting free energy profile of our model drug along the bilayer normal. We recommend using z-constraint biased MD simulations based on starting geometries acquired from unbiased MD simulations for efficient calculation of convergent free energy profiles of druglike molecules along bilayer normals. The calculation of free energy profile should start with an unbiased simulation, though the polar molecules might need a slow pulling afterward. Results obtained with the recommended simulation protocol agree well with available experimental data for two coumarin derivatives.

Estimation of soil hydraulic properties with microwave techniques

NASA Technical Reports Server (NTRS)

Oneill, P. E.; Gurney, R. J.; Camillo, P. J.

1985-01-01

Useful quantitative information about soil properties may be obtained by calibrating energy and moisture balance models with remotely sensed data. A soil physics model solves heat and moisture flux equations in the soil profile and is driven by the surface energy balance. Model generated surface temperature and soil moisture and temperature profiles are then used in a microwave emission model to predict the soil brightness temperature. The model hydraulic parameters are varied until the predicted temperatures agree with the remotely sensed values. This method is used to estimate values for saturated hydraulic conductivity, saturated matrix potential, and a soil texture parameter. The conductivity agreed well with a value measured with an infiltration ring and the other parameters agreed with values in the literature.

Do we understand the temperature profile of air-water interface?

NASA Astrophysics Data System (ADS)

Solcerova, A.; van Emmerik, T. H. M.; Uittenbogaard, R.; van de Ven, F. H. M.; Van De Giesen, N.

2017-12-01

Lakes and reservoirs exchange energy with the atmosphere through long-wave radiation and turbulent heat fluxes. Calculation of those fluxes often depend on the surface temperature. Several recent studies used high resolution Distributed Temperature Sensing (DTS) to measure the temperature of air-water interface. We present results of three of such studies conducted on three different locations with three different climates (Ghana, Israel, The Netherland). Measurements from all presented studies show a distinct temperature drop close to the water surface during daytime. We provide several possible explanations for existence of such deviation of temperature, and discuss the plausibility of each. Explaining the measured temperature drop is crucial for a better understanding of the energy balance of lake surface, and estimation of the surface energy balance.

Measurement of conformability and adhesion energy of polymeric ultrathin film to skin model

NASA Astrophysics Data System (ADS)

Sugano, Junki; Fujie, Toshinori; Iwata, Hiroyasu; Iwase, Eiji

2018-06-01

We measured the conformability and adhesion energy of a polymeric ultrathin film “nanosheet” with hundreds of nanometer thickness to a skin model with epidermal depressions. To compare the confirmability of the nanosheets with different thicknesses and/or under different attaching conditions, we proposed a measurement method using skin models with the same surface profile and defined the surface strain εS as the quantified value of the conformability. Then, we measured the adhesion energy of the nanosheet at each conformability through a vertical tensile test. Experimental results indicate that the adhesion energy does not depend on the liquid used in wetting the nanosheet before attaching to the skin model and increases monotonously as the surface strain εS increases.

Rayleigh-wave dispersive energy imaging and mode separating by high-resolution linear Radon transform

USGS Publications Warehouse

Luo, Y.; Xu, Y.; Liu, Q.; Xia, J.

2008-01-01

In recent years, multichannel analysis of surface waves (MASW) has been increasingly used for obtaining vertical shear-wave velocity profiles within near-surface materials. MASW uses a multichannel recording approach to capture the time-variant, full-seismic wavefield where dispersive surface waves can be used to estimate near-surface S-wave velocity. The technique consists of (1) acquisition of broadband, high-frequency ground roll using a multichannel recording system; (2) efficient and accurate algorithms that allow the extraction and analysis of 1D Rayleigh-wave dispersion curves; (3) stable and efficient inversion algorithms for estimating S-wave velocity profiles; and (4) construction of the 2D S-wave velocity field map.

Depth profiling the solid electrolyte interphase on lithium titanate (Li4Ti5O12) using synchrotron-based photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Nordh, Tim; Younesi, Reza; Brandell, Daniel; Edström, Kristina

2015-10-01

The presence of a surface layer on lithium titanate (Li4Ti5O12, LTO) anodes, which has been a topic of debate in scientific literature, is here investigated with tunable high surface sensitive synchrotron-based photoelectron spectroscopy (PES) to obtain a reliable depth profile of the interphase. Li||LTO cells with electrolytes consisting of 1 M lithium hexafluorophosphate dissolved in ethylene carbonate:diethyl carbonate (LiPF6 in EC:DEC) were cycled in two different voltage windows of 1.0-2.0 V and 1.4-2.0 V. LTO electrodes were characterized after 5 and 100 cycles. Also the pristine electrode as such, and an electrode soaked in the electrolyte were analyzed by varying the photon energies enabling depth profiling of the outermost surface layer. The main components of the surface layer were found to be ethers, P-O containing compounds, and lithium fluoride.

Surface compositional profiles of self-assembled InAs/GaAs quantum rings

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

Magri, Rita; Heun, Stefan; Biasiol, Giorgio

2010-01-04

The surface composition profiles of self-assembled InAs/GaAs quantum rings (QR) are studied both experimentally and theoretically. By using X-ray Photoemission Electron Microscopy (XPEEM) we obtain a 2D composition mapping of unburied rings, which can be directly related to the QR topography measured by Atomic Force Microscopy (AFM). Top-surface composition mapping allows us to obtain information on structures which cannot be directly accessed with cross-sectional studies since overgrowing the QRs with a thick GaAs film alters both their morphology and composition. The 2D surface maps reveal a non-uniform distribution across the rings with an In richer InGaAs alloy in the centralmore » hole regions. Elastic energy calculations via a Valence Force Field (VFF) approach show that, for a given shape of the rings and a fixed total number of Ga and In atoms, an In enrichment of the alloy in the central hole region, together with an In enrichment of the surface layers, leads to a lowering of the total strain energy.« less

Experimental Simulation of Solar Wind Interaction with MagneticDipole Fields above Insulating Surfaces

NASA Astrophysics Data System (ADS)

Yeo, L. H.; Han, J.; Wang, X.; Werner, G.; Deca, J.; Munsat, T.; Horanyi, M.

2017-12-01

Magnetic anomalies on the surfaces of airless bodies such as the Moon interact with the solar wind, resulting in both magnetic and electrostatic deflection/reflection of thecharged particles. Consequently, surface charging in these regions will be modified. Using the Colorado Solar Wind Experiment facility, this interaction is investigated with high-energy flowing plasmas (100-800 eV beam ions) that are incident upon a magnetic dipole (0.13 T) embedded under various insulating surfaces. The dipole moment is perpendicular to the surface. Using an emissive probe, 2D plasma potential profiles are obtained above the surface. In the dipole lobe regions, the surfaces are charged to significantly positive potentials due to the impingement of the unmagnetized ions while the electrons are magnetically shielded. At low ion beam energies, the results agree with the theoretical predictions, i.e., the surface potential follows the energy of the beam ions in eV. However, at high energies, the surface potentials in the electron-shielded regions are significantly lower than the beam energies. A series of investigations have been conducted and indicate that the surface properties (e.g., modified surface conductance, ion induced secondary electrons and electron-neutral collision at the surface) are likely to play a role in determining the surface potential.

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

Wunderle, K; Wayne State University School of Medicine, Detroit, MI; Godley, A

Purpose: The purpose of this investigation is to characterize and quantify X-ray beam profiles for fluoroscopic x-ray beam spectra incorporating spectral (copper) filtration. Methods: A PTW (Freiburg, Germany) type 60016 silicon diode detector and PTW MP3 water tank were used to measure X-ray beam profiles for 60, 80, 100 and 120 kVp x-ray beams at five different copper filtration thicknesses ranging from 0–0.9 mm at 22 and 42 cm fields of view and depths of 1, 5, and 10 cm in both the anode-cathode axis (inplane) and cross-plane directions. All measurements were acquired on a Siemens (Erlangen, Germany) Artis ZeeGomore » fluoroscope inverted from the typical orientation providing an x-ray beam originating from above the water surface with the water level set at 60 cm from the focal spot. Results: X-ray beam profiles for beam spectra without copper filtration compared well to previously published data by Fetterly et al. [Med Phys, 28, 205 (2001)]. Our data collection benefited from the geometric orientation of the fluoroscope, providing a beam perpendicular to the tank water surface, rather than through a thin side wall as did the previously mentioned study. Profiles for beams with copper filtration were obtained which have not been previously investigated and published. Beam profiles in the anode-cathode axis near the surface and at lower x-ray energy exhibited substantial heel effect, which became less pronounced at greater depth. At higher energy with copper filtration in the beam, the dose falloff out-of-field became less pronounced, as would be anticipated given higher scatter photon energy. Conclusion: The x-ray beam profile data for the fluoroscopic x-ray beams incorporating copper filtration are intended for use as reference data for estimating doses to organs or soft tissue, including fetal dose, involving similar beam qualities or for comparison with mathematical models.« less

Use of low energy hydrogen ion implants in high efficiency crystalline silicon solar cells

NASA Technical Reports Server (NTRS)

Fonash, S. J.; Singh, R.

1985-01-01

This program is a study of the use of low energy hydrogen ion implantation for high efficiency crystalline silicon solar cells. The first quarterly report focuses on two tasks of this program: (1) an examination of the effects of low energy hydrogen implants on surface recombination speed; and (2) an examination of the effects of hydrogen on silicon regrowth and diffusion in silicon. The first part of the project focussed on the measurement of surface properties of hydrogen implanted silicon. Low energy hydrogen ions when bombarded on the silicon surface will create structural damage at the surface, deactivate dopants and introduce recombination centers. At the same time the electrically active centers such as dangling bonds will be passivated by these hydrogen ions. Thus hydrogen is expected to alter properties such as the surface recombination velocity, dopant profiles on the emitter, etc. In this report the surface recombination velocity of a hydrogen emplanted emitter was measured.

Analytical mass formula and nuclear surface properties in the ETF approximation. Part I: symmetric nuclei

NASA Astrophysics Data System (ADS)

Aymard, François; Gulminelli, Francesca; Margueron, Jérôme

2016-08-01

The problem of determination of nuclear surface energy is addressed within the framework of the extended Thomas Fermi (ETF) approximation using Skyrme functionals. We propose an analytical model for the density profiles with variationally determined diffuseness parameters. In this first paper, we consider the case of symmetric nuclei. In this situation, the ETF functional can be exactly integrated, leading to an analytical formula expressing the surface energy as a function of the couplings of the energy functional. The importance of non-local terms is stressed and it is shown that they cannot be deduced simply from the local part of the functional, as it was suggested in previous works.

Bernoulli potential in type-I and weak type-II superconductors: II. Surface dipole

NASA Astrophysics Data System (ADS)

Lipavský, P.; Morawetz, K.; Koláček, J.; Mareš, J. J.; Brandt, E. H.; Schreiber, M.

2004-09-01

The Budd-Vannimenus theorem is modified to apply to superconductors in the Meissner state. The obtained identity links the surface value of the electrostatic potential to the density of free energy at the surface which allows one to evaluate the electrostatic potential observed via the capacitive pickup without the explicit solution of the charge profile.

Approximate solution for the electronic density profile at the surface of jellium

NASA Astrophysics Data System (ADS)

Schmickler, Wolfgang; Henderson, Douglas

1984-09-01

A simple family of trial functions for the electronic density at the surface of jellium, which accounts for Friedel oscillations and incorporates the Budd-Vannimenus theorem, is proposed. The free parameters are determined by energy minimization. Model calculations give good results for the work function and for the induced surface charge in the presence of an external field.

Simulations of Coulomb systems confined by polarizable surfaces using periodic Green functions.

PubMed

Dos Santos, Alexandre P; Girotto, Matheus; Levin, Yan

2017-11-14

We present an efficient approach for simulating Coulomb systems confined by planar polarizable surfaces. The method is based on the solution of the Poisson equation using periodic Green functions. It is shown that the electrostatic energy arising from the surface polarization can be decoupled from the energy due to the direct Coulomb interaction between the ions. This allows us to combine an efficient Ewald summation method, or any other fast method for summing over the replicas, with the polarization contribution calculated using Green function techniques. We apply the method to calculate density profiles of ions confined between the charged dielectric and metal surfaces.

Microscopic description of a drop on a solid surface.

PubMed

Ruckenstein, Eli; Berim, Gersh O

2010-06-14

Two approaches recently suggested for the treatment of macro- or nanodrops on smooth or rough, planar or curved, solid surfaces, based on fluid-fluid and fluid-solid interaction potentials are reviewed. The first one employs the minimization of the total potential energy of a drop by assuming that the drop has a well defined profile and a constant liquid density in its entire volume with the exception of the monolayer nearest to the surface where the density has a different value. As a result, a differential equation for the drop profile as well as the necessary boundary conditions are derived which involve the parameters of the interaction potentials and do not contain such macroscopic characteristics as the surface tensions. As a consequence, the macroscopic and microscopic contact angles which the drop profile makes with the surface can be calculated. The macroscopic angle is obtained via the extrapolation of the circular part of the drop profile valid at some distance from the surface up to the solid surface. The microscopic angle is formed at the intersection of the real profile (which is not circular near the surface) with the surface. The theory provides a relation between these two angles. The ranges of the microscopic parameters of the interaction potentials for which (i) the drop can have any height (volume), (ii) the drop can have a restricted height but unrestricted volume, and (iii) a drop cannot be formed on the surface were identified. The theory was also extended to the description of a drop on a rough surface. The second approach is based on a nonlocal density functional theory (DFT), which accounts for the inhomogeneity of the liquid density and temperature effects, features which are missing in the first approach. Although the computational difficulties restrict its application to drops of only several nanometers, the theory can be applied indirectly to macrodrops by calculating the surface tensions and using the Young equation to determine the contact angle. Employing the canonical ensemble version of the DFT, nanodrops on smooth and rough solid surfaces could be investigated and their characteristics, such as the drop profile, contact angle, as well as the fluid density distribution inside the drop can be determined as functions of the parameters of the interaction potentials and temperature. It was found that the contact angle of the drop has a simple (quasi)universal dependence on the energy parameter epsilon(fs) of the fluid-solid interaction potential and temperature. The main feature of this dependence is the existence of a fixed value theta(0) of the contact angle theta which separates the solid substrates (characterized by the energy parameter epsilon(fs) of the fluid-solid interaction potential) into two classes with respect to their temperature dependence. For theta>theta(0) the contact angle monotonously increases and for theta

Measurement of the adsorption energy difference between ortho- and para-D2 on an amorphous ice surface.

PubMed

Amiaud, L; Momeni, A; Dulieu, F; Fillion, J H; Matar, E; Lemaire, J-L

2008-02-08

Molecular hydrogen interaction on water ice surfaces is a major process taking place in interstellar dense clouds. By coupling laser detection and classical thermal desorption spectroscopy, it is possible to study the effect of rotation of D(2) on adsorption on amorphous solid water ice surfaces. The desorption profiles of ortho- and para-D(2) are different. This difference is due to a shift in the adsorption energy distribution of the two lowest rotational states. Molecules in J''=1 rotational state are on average more strongly bound to the ice surface than those in J''=0 rotational state. This energy difference is estimated to be 1.4+/-0.3 meV. This value is in agreement with previous calculation and interpretation. The nonspherical wave function J'' =1 has an interaction with the asymmetric part of the adsorption potential and contributes positively in the binding energy.

The front end test stand high performance H- ion source at Rutherford Appleton Laboratory.

PubMed

Faircloth, D C; Lawrie, S; Letchford, A P; Gabor, C; Wise, P; Whitehead, M; Wood, T; Westall, M; Findlay, D; Perkins, M; Savage, P J; Lee, D A; Pozimski, J K

2010-02-01

The aim of the front end test stand (FETS) project is to demonstrate that chopped low energy beams of high quality can be produced. FETS consists of a 60 mA Penning Surface Plasma Ion Source, a three solenoid low energy beam transport, a 3 MeV radio frequency quadrupole, a chopper, and a comprehensive suite of diagnostics. This paper details the design and initial performance of the ion source and the laser profile measurement system. Beam current, profile, and emittance measurements are shown for different operating conditions.

Multi-scale modelling to relate beryllium surface temperature, deuterium concentration and erosion in fusion reactor environment

DOE PAGES

Safi, E.; Valles, G.; Lasa, A.; ...

2017-03-27

Beryllium (Be) has been chosen as the plasma-facing material for the main wall of ITER, the next generation fusion reactor. Identifying the key parameters that determine Be erosion under reactor relevant conditions is vital to predict the ITER plasma-facing component lifetime and viability. To date, a certain prediction of Be erosion, focusing on the effect of two such parameters, surface temperature and D surface content, has not been achieved. In this paper, we develop the first multi-scale KMC-MD modeling approach for Be to provide a more accurate database for its erosion, as well as investigating parameters that affect erosion. First,more » we calculate the complex relationship between surface temperature and D concentration precisely by simulating the time evolution of the system using an object kinetic Monte Carlo (OKMC) technique. These simulations provide a D surface concentration profile for any surface temperature and incoming D energy. We then describe how this profile can be implemented as a starting configuration in molecular dynamics (MD) simulations. We finally use MD simulations to investigate the effect of temperature (300–800 K) and impact energy (10–200 eV) on the erosion of Be due to D plasma irradiations. The results reveal a strong dependency of the D surface content on temperature. Increasing the surface temperature leads to a lower D concentration at the surface, because of the tendency of D atoms to avoid being accommodated in a vacancy, and de-trapping from impurity sites diffuse fast toward bulk. At the next step, total and molecular Be erosion yields due to D irradiations are analyzed using MD simulations. The results show a strong dependency of erosion yields on surface temperature and incoming ion energy. The total Be erosion yield increases with temperature for impact energies up to 100 eV. However, increasing temperature and impact energy results in a lower fraction of Be atoms being sputtered as BeD molecules due to the lower D surface concentrations at higher temperatures. Finally, these findings correlate well with different experiments performed at JET and PISCES-B devices.« less

Multi-scale modelling to relate beryllium surface temperature, deuterium concentration and erosion in fusion reactor environment

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

Safi, E.; Valles, G.; Lasa, A.

Beryllium (Be) has been chosen as the plasma-facing material for the main wall of ITER, the next generation fusion reactor. Identifying the key parameters that determine Be erosion under reactor relevant conditions is vital to predict the ITER plasma-facing component lifetime and viability. To date, a certain prediction of Be erosion, focusing on the effect of two such parameters, surface temperature and D surface content, has not been achieved. In this paper, we develop the first multi-scale KMC-MD modeling approach for Be to provide a more accurate database for its erosion, as well as investigating parameters that affect erosion. First,more » we calculate the complex relationship between surface temperature and D concentration precisely by simulating the time evolution of the system using an object kinetic Monte Carlo (OKMC) technique. These simulations provide a D surface concentration profile for any surface temperature and incoming D energy. We then describe how this profile can be implemented as a starting configuration in molecular dynamics (MD) simulations. We finally use MD simulations to investigate the effect of temperature (300–800 K) and impact energy (10–200 eV) on the erosion of Be due to D plasma irradiations. The results reveal a strong dependency of the D surface content on temperature. Increasing the surface temperature leads to a lower D concentration at the surface, because of the tendency of D atoms to avoid being accommodated in a vacancy, and de-trapping from impurity sites diffuse fast toward bulk. At the next step, total and molecular Be erosion yields due to D irradiations are analyzed using MD simulations. The results show a strong dependency of erosion yields on surface temperature and incoming ion energy. The total Be erosion yield increases with temperature for impact energies up to 100 eV. However, increasing temperature and impact energy results in a lower fraction of Be atoms being sputtered as BeD molecules due to the lower D surface concentrations at higher temperatures. Finally, these findings correlate well with different experiments performed at JET and PISCES-B devices.« less

Multi-scale modelling to relate beryllium surface temperature, deuterium concentration and erosion in fusion reactor environment

NASA Astrophysics Data System (ADS)

Safi, E.; Valles, G.; Lasa, A.; Nordlund, K.

2017-05-01

Beryllium (Be) has been chosen as the plasma-facing material for the main wall of ITER, the next generation fusion reactor. Identifying the key parameters that determine Be erosion under reactor relevant conditions is vital to predict the ITER plasma-facing component lifetime and viability. To date, a certain prediction of Be erosion, focusing on the effect of two such parameters, surface temperature and D surface content, has not been achieved. In this work, we develop the first multi-scale KMC-MD modeling approach for Be to provide a more accurate database for its erosion, as well as investigating parameters that affect erosion. First, we calculate the complex relationship between surface temperature and D concentration precisely by simulating the time evolution of the system using an object kinetic Monte Carlo (OKMC) technique. These simulations provide a D surface concentration profile for any surface temperature and incoming D energy. We then describe how this profile can be implemented as a starting configuration in molecular dynamics (MD) simulations. We finally use MD simulations to investigate the effect of temperature (300-800 K) and impact energy (10-200 eV) on the erosion of Be due to D plasma irradiations. The results reveal a strong dependency of the D surface content on temperature. Increasing the surface temperature leads to a lower D concentration at the surface, because of the tendency of D atoms to avoid being accommodated in a vacancy, and de-trapping from impurity sites diffuse fast toward bulk. At the next step, total and molecular Be erosion yields due to D irradiations are analyzed using MD simulations. The results show a strong dependency of erosion yields on surface temperature and incoming ion energy. The total Be erosion yield increases with temperature for impact energies up to 100 eV. However, increasing temperature and impact energy results in a lower fraction of Be atoms being sputtered as BeD molecules due to the lower D surface concentrations at higher temperatures. These findings correlate well with different experiments performed at JET and PISCES-B devices.

Comment on ``Experimental Free Energy Reconstruction From Single-Molecule Force Spectroscopy Using Jarzynski's Equality''

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

Friddle, R W

2008-01-14

Harris, Song and Kiang [1] (HSK) describe their results on reconstructing the free energy profiles for both the stretch of the titin polymer, and the unfolding of an individual I27 domain. The new finding reported in [1] is the measurement of the free energy barrier (or activation energy) to unfolding the I27 domain. Due to a misinterpretation of the mechanics involved, the free energy surface (and thus the energy barrier) to unfolding the I27 domain was not measured.

uleSIMS characterization of silver reference surfaces

NASA Astrophysics Data System (ADS)

Palitsin, V. V.; Dowsett, M. G.; Mata, B. Guzmán de la; Oloff, I. W.; Gibbons, R.

2006-07-01

Ultra low energy SIMS (uleSIMS) is a high sensitivity analytical technique that is normally used for ultra shallow profiling at a depth resolution of up to1 nm. This work describes the use of uleSIMS as both a spectroscopic and depth-profiling tool for the characterization of the early stages of corrosion formed on reference surfaces of silver. These samples are being developed to help with the characterization of tarnished surfaces in a cultural heritage context, and uleSIMS enables the tarnishing to be studied from its very earliest stages due to its high sensitivity (ppm-ppb) and surface specificity. We show that, uleSIMS can be used effectively to study the surface chemistry and aid the development of reference surfaces themselves. In particular, handling contaminants, surface dust, and residues from polishing are relatively easy to identify allowing them to be separated from the parts of the mass spectrum specific to the early stages of corrosion.

Non-linear, non-monotonic effect of nano-scale roughness on particle deposition in absence of an energy barrier: Experiments and modeling

PubMed Central

Jin, Chao; Glawdel, Tomasz; Ren, Carolyn L.; Emelko, Monica B.

2015-01-01

Deposition of colloidal- and nano-scale particles on surfaces is critical to numerous natural and engineered environmental, health, and industrial applications ranging from drinking water treatment to semi-conductor manufacturing. Nano-scale surface roughness-induced hydrodynamic impacts on particle deposition were evaluated in the absence of an energy barrier to deposition in a parallel plate system. A non-linear, non-monotonic relationship between deposition surface roughness and particle deposition flux was observed and a critical roughness size associated with minimum deposition flux or “sag effect” was identified. This effect was more significant for nanoparticles (<1 μm) than for colloids and was numerically simulated using a Convective-Diffusion model and experimentally validated. Inclusion of flow field and hydrodynamic retardation effects explained particle deposition profiles better than when only the Derjaguin-Landau-Verwey-Overbeek (DLVO) force was considered. This work provides 1) a first comprehensive framework for describing the hydrodynamic impacts of nano-scale surface roughness on particle deposition by unifying hydrodynamic forces (using the most current approaches for describing flow field profiles and hydrodynamic retardation effects) with appropriately modified expressions for DLVO interaction energies, and gravity forces in one model and 2) a foundation for further describing the impacts of more complicated scales of deposition surface roughness on particle deposition. PMID:26658159

Non-linear, non-monotonic effect of nano-scale roughness on particle deposition in absence of an energy barrier: Experiments and modeling

NASA Astrophysics Data System (ADS)

Jin, Chao; Glawdel, Tomasz; Ren, Carolyn L.; Emelko, Monica B.

2015-12-01

Deposition of colloidal- and nano-scale particles on surfaces is critical to numerous natural and engineered environmental, health, and industrial applications ranging from drinking water treatment to semi-conductor manufacturing. Nano-scale surface roughness-induced hydrodynamic impacts on particle deposition were evaluated in the absence of an energy barrier to deposition in a parallel plate system. A non-linear, non-monotonic relationship between deposition surface roughness and particle deposition flux was observed and a critical roughness size associated with minimum deposition flux or “sag effect” was identified. This effect was more significant for nanoparticles (<1 μm) than for colloids and was numerically simulated using a Convective-Diffusion model and experimentally validated. Inclusion of flow field and hydrodynamic retardation effects explained particle deposition profiles better than when only the Derjaguin-Landau-Verwey-Overbeek (DLVO) force was considered. This work provides 1) a first comprehensive framework for describing the hydrodynamic impacts of nano-scale surface roughness on particle deposition by unifying hydrodynamic forces (using the most current approaches for describing flow field profiles and hydrodynamic retardation effects) with appropriately modified expressions for DLVO interaction energies, and gravity forces in one model and 2) a foundation for further describing the impacts of more complicated scales of deposition surface roughness on particle deposition.

Modelling deuterium release during thermal desorption of D +-irradiated tungsten

NASA Astrophysics Data System (ADS)

Poon, M.; Haasz, A. A.; Davis, J. W.

2008-03-01

Thermal desorption profiles were modelled based on SIMS measurements of implantation profiles and using the multi-trap diffusion code TMAP7 [G.R. Longhurst, TMAP7: Tritium Migration Analysis Program, User Manual, Idaho National Laboratory, INEEL/EXT-04-02352 (2004)]. The thermal desorption profiles were the result of 500 eV/D + irradiations on single crystal tungsten at 300 and 500 K to fluences of 10 22-10 24 D +/m 2. SIMS depth profiling was performed after irradiation to obtain the distribution of trapped D within the top 60 nm of the surface. Thermal desorption spectroscopy (TDS) was performed subsequently to obtain desorption profiles and to extract the total trapped D inventory. The SIMS profiles were calibrated to give D concentrations. To account for the total trapped D inventory measured by TDS, SIMS depth distributions were used in the near-surface (surface to 30 nm), NRA measurements [V.Kh. Alimov, J. Roth, M. Mayer, J. Nucl. Mater. 337-339 (2005) 619] were used in the range 1-7 μm, and a linear drop in the D distribution was assumed in the intermediate sub-surface region (˜30 nm to 1 μm). Traps were assumed to be saturated so that the D distribution also represented the trap distribution. Three trap energies, 1.07 ± 0.03, 1.34 ± 0.03 and 2.1 ± 0.05 eV were required to model the 520, 640 and 900 K desorption peaks, respectively. The 1.34 and 1.07 eV traps correspond to trapping of a first and second D atom at a vacancy, respectively, while the 2.1 eV trap corresponds to atomic D trapping at a void. A fourth trap energy of 0.65 eV was used to fit the 400 K desorption peak observed by Quastel et al. [A.D. Quastel, J.W. Davis, A.A. Haasz, R.G. Macaulay-Newcombe, J. Nucl. Mater. 359 (2006) 8].

Diffusion induced atomic islands on the surface of Ni/Cu nanolayers

NASA Astrophysics Data System (ADS)

Takáts, Viktor; Csik, Attila; Hakl, József; Vad, Kálmán

2018-05-01

Surface islands formed by grain-boundary diffusion has been studied in Ni/Cu nanolayers by in-situ low energy ion scattering spectroscopy, X-ray photoelectron spectroscopy, scanning probe microscopy and ex-situ depth profiling based on ion sputtering. In this paper a new experimental approach of measurement of grain-boundary diffusion coefficients is presented. Appearing time of copper atoms diffused through a few nanometer thick nickel layer has been detected by low energy ion scattering spectroscopy with high sensitivity. The grain-boundary diffusion coefficient can be directly calculated from this appearing time without using segregation factors in calculations. The temperature range of 423-463 K insures the pure C-type diffusion kinetic regime. The most important result is that surface coverage of Ni layer by Cu atoms reaches a maximum during annealing and stays constant if the annealing procedure is continued. Scanning probe microscopy measurements show a Volmer-Weber type layer growth of Cu layer on the Ni surface in the form of Cu atomic islands. Depth distribution of Cu in Ni layer has been determined by depth profile analysis.

An Integrated Experimental and Computational Study of Heating due to Surface Catalysis under Hypersonic Conditions

DTIC Science & Technology

2012-08-01

17 1.1.1 Mass production / destruction terms . . . . . . . . . . . . . . . . . . . . 18 1.1.2 Energy exchange terms...that US3D does not cur- rently model electronic energy . If the US3D solution is post-processed to account for electronic energy modes, the computed...nonequilibrium model for electronic energy to the 12 Distribution A: Approved for public release; distribution is unlimited. Figure 9: (left) jet profile solution

Application of self-preservation in the diurnal evolution of the surface energy budget to determine daily evaporation

NASA Technical Reports Server (NTRS)

Brutsaert, Wilfried; Sugita, Michiaki

1992-01-01

Evaporation from natural land surfaces often exhibits a strong variation during the course of a day, mostly in response to the daily variation of radiative energy input at the surface. This makes it difficult to derive the total daily evaporation, when only one or a few instantaneous estimates of evaporation are available. It is often possible to resolve this difficulty by assuming self-preservation in the diurnal evolution of the surface energy budget. Thus if the relative partition of total incoming energy flux among the different components remains the same, the ratio of latent heat flux and any other flux component can be taken as constant through the day. This concept of constant flux ratios is tested by means of data obtained during the First ISLSCP Field Experiment; the instantaneous evaporation values were calculated by means of the atmospheric boundary layer bulk similarity approach with radiosonde profiles and radiative surface temperatures. Good results were obtained for evaporative flux ratios with available energy flux, with net radiation, and with incoming shortwave radiation.

Ordering of rods near planar and curved surfaces

NASA Astrophysics Data System (ADS)

Izzo, Dora; de Oliveira, Mário J.

2018-01-01

We study the orientational profile of a semi-infinite system of cylinders bounded in two different ways: by a flat and by a curved wall. The latter corresponds to the interior of a spherical shell, where the dimensions of the rods are comparable to the radius of curvature of the container: they have to accomodate to fill the available space, leading to a rich orientation profile. In order to study these problems, we make a mapping onto a three-state Potts model on a semi-infinite lattice, which is solved using a mean-field approach; we fix the boundary conditions on the surface and in the bulk. In the case of a curved surface, the increase in the effective volume interactions towards the bulk, due to compression, is obtained by increasing the nearest neighbor interactions. The mean-field equations are iterated numerically and we obtain various interesting results concerning the free energy and the orientation profile. We show that there is always a first order transition and the stability of the coexisting phases is strongly affected by the surface. When the surface is disordered and the bulk ordered, the profile may present a step that depends on the degree of disorder on the surface, on the rate of increase of the particle interactions and on the surface external potential. The existence of this step may be relevant to applications in nanotechnology.

Oxygen accumulation on metal surfaces investigated by XPS, AES and LEIS, an issue for sputter depth profiling under UHV conditions

NASA Astrophysics Data System (ADS)

Steinberger, R.; Celedón, C. E.; Bruckner, B.; Roth, D.; Duchoslav, J.; Arndt, M.; Kürnsteiner, P.; Steck, T.; Faderl, J.; Riener, C. K.; Angeli, G.; Bauer, P.; Stifter, D.

2017-07-01

Depth profiling using surface sensitive analysis methods in combination with sputter ion etching is a common procedure for thorough material investigations, where clean surfaces free of any contamination are essential. Hence, surface analytic studies are mostly performed under ultra-high vacuum (UHV) conditions, but the cleanness of such UHV environments is usually overrated. Consequently, the current study highlights the in principle known impact of the residual gas on metal surfaces (Fe, Mg, Al, Cr and Zn) for various surface analytics methods, like X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and low-energy ion scattering (LEIS). The investigations with modern, state-of-the-art equipment showed different behaviors for the metal surfaces in UHV during acquisition: (i) no impact for Zn, even after long time, (ii) solely adsorption of oxygen for Fe, slight and slow changes for Cr and (iii) adsorption accompanied by oxide formation for Al and Mg. The efficiency of different counter measures was tested and the acquired knowledge was finally used for ZnMgAl coated steel to obtain accurate depth profiles, which exhibited before serious artifacts when data acquisition was performed in an inconsiderate way.

Surface influence upon vertical profiles in the nocturnal boundary layer

NASA Astrophysics Data System (ADS)

Garratt, J. R.

1983-05-01

Near-surface wind profiles in the nocturnal boundary layer, depth h, above relatively flat, tree-covered terrain are described in the context of the analysis of Garratt (1980) for the unstable atmospheric boundary layer. The observations at two sites imply a surface-based transition layer, of depth z *, within which the observed non-dimensional profiles Φ M 0 are a modified form of the inertial sub-layer relation Φ _M ( {{z L}} = ( {{{1 + 5_Z } L}} ) according to Φ _M^{{0}} ˜eq ( {{{1 + 5z} L}} )exp [ { - 0.7( {{{1 - z} z}_ * } )] , where z is height above the zero-plane displacement and L is the Monin-Obukhov length. At both sites the depth z * is significantly smaller than the appropriate neutral value ( z * N ) found from the previous analysis, as might be expected in the presence of a buoyant sink for turbulent kinetic energy.

Experimental Simulation of Solar Wind Interactions with Magnetic Dipole Fields above Insulating Surfaces

NASA Astrophysics Data System (ADS)

Munsat, Tobin; Deca, Jan; Han, Jia; Horanyi, Mihaly; Wang, Xu; Werner, Greg; Yeo, Li Hsia; Fuentes, Dominic

2017-10-01

Magnetic anomalies on the surfaces of airless bodies such as the Moon interact with the solar wind, resulting in both magnetic and electrostatic deflection of the charged particles and thus localized surface charging. This interaction is studied in the Colorado Solar Wind Experiment with large-cross-section ( 300 cm2) high-energy flowing plasmas (100-800 eV beam ions) that are incident upon a magnetic dipole embedded under various insulating surfaces. Measured 2D plasma potential profiles indicate that in the dipole lobe regions, the surfaces are charged to high positive potentials due to the collection of unmagnetized ions, while the electrons are magnetically shielded. At low ion beam energies, the surface potential follows the beam energy in eV. However, at high energies, the surface potentials in the electron-shielded regions are significantly lower than the beam energies. A series of studies indicate that secondary electrons are likely to play a dominant role in determining the surface potential. Early results will also be presented from a second experiment, in which a strong permanent magnet with large dipole moment (0.55 T, 275 A*m2) is inserted into the flowing plasma beam to replicate aspects of the solar wind interaction with the earth's magnetic field. This work is supported by the NASA SSERVI program.

Aggregation, adsorption, and surface properties of multiply end-functionalized polystyrenes.

PubMed

Ansari, Imtiyaz A; Clarke, Nigel; Hutchings, Lian R; Pillay-Narrainen, Amilcar; Terry, Ann E; Thompson, Richard L; Webster, John R P

2007-04-10

The properties of polystyrene blends containing deuteriopolystyrene, multiply end-functionalized with C8F17 fluorocarbon groups, are strikingly analogous to those of surfactants in solution. These materials, denoted FxdPSy, where x is the number of fluorocarbon groups and y is the molecular weight of the dPS chain in kg/mol, were blended with unfunctionalized polystyrene, hPS. Nuclear reaction analysis experiments show that FxdPSy polymers adsorb spontaneously to solution and blend surfaces, resulting in a reduction in surface energy inferred from contact angle analysis. Aggregation of functionalized polymers in the bulk was found to be sensitive to FxdPSy structure and closely related to surface properties. At low concentrations, the functionalized polymers are freely dispersed in the hPS matrix, and in this range, the surface excess concentration grows sharply with increasing bulk concentration. At higher concentrations, surface excess concentrations and contact angles reach a plateau, small-angle neutron scattering data indicate small micellar aggregates of six to seven F2dPS10 polymer chains and much larger aggregates of F4dPS10. Whereas F2dPS10 aggregates are miscible with the hPS matrix, F4dPS10 forms a separate phase of multilamellar vesicles. Using neutron reflectometry (NR), we found that the extent of the adsorbed layer was approximately half the lamellar spacing of the multilamellar vesicles. NR data were fitted using an error function profile to describe the concentration profile of the adsorbed layer, and reasonable agreement was found with concentration profiles predicted by the SCFT model. The thermodynamic sticking energy of the fluorocarbon-functionalized polymer chains to the blend surface increases from 5.3kBT for x = 2 to 6.6kBT for x = 4 but appears to be somewhat dependent upon the blend concentration.

Etch Profile Simulation Using Level Set Methods

NASA Technical Reports Server (NTRS)

Hwang, Helen H.; Meyyappan, Meyya; Arnold, James O. (Technical Monitor)

1997-01-01

Etching and deposition of materials are critical steps in semiconductor processing for device manufacturing. Both etching and deposition may have isotropic and anisotropic components, due to directional sputtering and redeposition of materials, for example. Previous attempts at modeling profile evolution have used so-called "string theory" to simulate the moving solid-gas interface between the semiconductor and the plasma. One complication of this method is that extensive de-looping schemes are required at the profile corners. We will present a 2D profile evolution simulation using level set theory to model the surface. (1) By embedding the location of the interface in a field variable, the need for de-looping schemes is eliminated and profile corners are more accurately modeled. This level set profile evolution model will calculate both isotropic and anisotropic etch and deposition rates of a substrate in low pressure (10s mTorr) plasmas, considering the incident ion energy angular distribution functions and neutral fluxes. We will present etching profiles of Si substrates in Ar/Cl2 discharges for various incident ion energies and trench geometries.

Distribution of the near-inertial kinetic energy inside mesoscale eddies: Observations in the Gulf of Mexico

NASA Astrophysics Data System (ADS)

Ixetl Garcia Gomez, Beatriz; Pallas Sanz, Enric; Candela Perez, Julio

2017-04-01

The near-inertial oscillations (NIOs), generated by the wind stress on the surface mixed layer, are the inertia gravity waves with the lowest frequency and the highest kinetic energy. NIOs are important because they drive vertical mixing in the interior ocean during wave breaking events. Although the interaction between NIOs and mesoscale eddies has been reported by several authors, these studies are mostly analytical and numerical, and only few observational studies have attempted to show the differences in near-inertial kinetic energy (KEi) between anticyclonic and cyclonic eddies. In this work the spatial structure of the KEi inside the mesoscale eddies is computed using daily satellite altimetry and observations of horizontal velocity from 23 moorings equipped with acoustic Doppler current profilers in the western Gulf of Mexico. Consistent to theory, the obtained four-year KEi-composites show two times more KEi inside the anticyclonic eddies than inside the cyclonic ones. The vertical and horizontal cross-sections of the KEi-composites show that the KEi is mainly located near to the surface of the cyclonic eddies (positive vorticity), whereas the KEi in anticyclonic eddies (negative vorticity) is maximum in the eddy's center near to the base of the eddy where the NIOs become more inertial, are trapped, and amplified. The mean vertical profiles show that the cyclonic eddies present a maximum of KEi near to the surface at 50, while the maximum of KEi in the anticyclonic eddies occurs between 900 and 1100 m. Inside anticyclonic eddies another two relative maximums are observed, one in the mixed layer and the second at 300 m. In contrast, the mean profile of KEi outside the mesoscale eddies has the maximum value at the surface ( 50 m), with high values of KEi in the first 200 m and negligible energy beneath that depth. A different mean distribution of the KEi is observed depending on the type of wind generator: tropical storms or unidirectional wind.

Investigation of the physical scaling of sea spray spume droplet production

NASA Astrophysics Data System (ADS)

Fairall, C. W.; Banner, M. L.; Peirson, W. L.; Asher, W.; Morison, R. P.

2009-10-01

In this paper we report on a laboratory study, the Spray Production and Dynamics Experiment (SPANDEX), conducted at the University of New South Wales Water Research Laboratory in Australia. The goals of SPANDEX were to illuminate physical aspects of spume droplet production and dispersion; verify theoretical simplifications used to estimate the source function from ambient droplet concentration measurements; and examine the relationship between the implied source strength and forcing parameters such as wind speed, surface turbulent stress, and wave properties. Observations of droplet profiles give reasonable confirmation of the basic power law profile relationship that is commonly used to relate droplet concentrations to the surface source strength. This essentially confirms that, even in a wind tunnel, there is a near balance between droplet production and removal by gravitational settling. The observations also indicate considerable droplet mass may be present for sizes larger than 1.5 mm diameter. Phase Doppler Anemometry observations revealed significant mean horizontal and vertical slip velocities that were larger closer to the surface. The magnitude seems too large to be an acceleration time scale effect. Scaling of the droplet production surface source strength proved to be difficult. The wind speed forcing varied only 23% and the stress increased a factor of 2.2. Yet, the source strength increased by about a factor of 7. We related this to an estimate of surface wave energy flux through calculations of the standard deviation of small-scale water surface disturbance, a wave-stress parameterization, and numerical wave model simulations. This energy index only increased by a factor of 2.3 with the wind forcing. Nonetheless, a graph of spray mass surface flux versus surface disturbance energy is quasi-linear with a substantial threshold.

Sumatra-Andaman Megathrust Earthquake Slip: Insights From Mechanical Modeling of ICESat Surface Deformation Measurements

NASA Astrophysics Data System (ADS)

Harding, D. J.; Miuller, J. R.

2005-12-01

Modeling the kinematics of the 2004 Great Sumatra-Andaman earthquake is limited in the northern two-thirds of the rupture zone by a scarcity of near-rupture geodetic deformation measurements. Precisely repeated Ice, Cloud, and Land Elevation Satellite (ICESat) profiles across the Andaman and Nicobar Islands provide a means to more fully document the spatial pattern of surface vertical displacements and thus better constrain geomechanical modeling of the slip distribution. ICESat profiles that total ~45 km in length cross Car Nicobar, Kamorta, and Katchall in the Nicobar chain. Within the Andamans, the coverage includes ~350 km on North, Central, and South Andaman Islands along two NNE and NNW-trending profiles that provide elevations on both the east and west coasts of the island chain. Two profiles totaling ~80 km in length cross South Sentinel Island, and one profile ~10 km long crosses North Sentinel Island. With an average laser footprint spacing of 175 m, the total coverage provides over 2700 georeferenced surface elevations measurements for each operations period. Laser backscatter waveforms recorded for each footprint enable detection of forest canopy top and underlying ground elevations with decimeter vertical precision. Surface elevation change is determined from elevation profiles, acquired before and after the earthquake, that are repeated with a cross-track separation of less than 100 m by precision pointing of the ICESat spacecraft. Apparent elevation changes associated with cross-track offsets are corrected according to local slopes calculated from multiple post-earthquake repeated profiles. The surface deformation measurements recorded by ICESat are generally consistent with the spatial distribution of uplift predicted by a preliminary slip distribution model. To predict co-seismic surface deformation, we apply a slip distribution, derived from the released energy distribution computed by Ishii et al. (2005), as the displacement discontinuity boundary condition on the Sumatra-Andaman subduction interface fault. The direction of slip on the fault surface is derived from the slip directions computed by Tsai et al. (in review) for centroid moment tensor focal mechanisms spatially distributed along the rupture. The slip model will be refined to better correspond to the observed surface deformation as additional results from the ICESat profiles become available.

ARM - Midlatitude Continental Convective Clouds Experiment (MC3E): Multi-Frequency Profilers, 449 MHz Profiler(williams-449_prof)

DOE Data Explorer

Williams, Christopher; Jensen, Mike

2012-11-06

This data was collected by the NOAA 449-MHz and 2.8-GHz profilers in support of the Department of Energy (DOE) and NASA sponsored Mid-latitude Continental Convective Cloud Experiment (MC3E). The profiling radars were deployed in Northern Oklahoma at the DOE Atmospheric Radiation Mission (ARM) Southern Great Plans (SGP) Central Facility from 22 April through 6 June 2011. NOAA deployed three instruments: a Parsivel disdrometer, a 2.8-GHz profiler, and a 449-MHz profiler. The parasivel provided surface estimates of the raindrop size distribution and is the reference used to absolutely calibrate the 2.8 GHz profiler. The 2.8-GHz profiler provided unattenuated reflectivity profiles of the precipitation. The 449-MHz profiler provided estimates of the vertical air motion during precipitation from near the surface to just below the freezing level. By using the combination of 2.8-GHz and 449-MHz profiler observations, vertical profiles of raindrop size distributions can be retrieved. The profilers are often reference by their frequency band: the 2.8-GHz profiler operates in the S-band and the 449-MHz profiler operates in the UHF band. The raw observations are available as well as calibrated spectra and moments. This document describes how the instruments were deployed, how the data was collected, and the format of the archived data.

Evaluation of an atmospheric model with surface and ABL meteorological data for energy applications in structured areas

NASA Astrophysics Data System (ADS)

Triantafyllou, A. G.; Kalogiros, J.; Krestou, A.; Leivaditou, E.; Zoumakis, N.; Bouris, D.; Garas, S.; Konstantinidis, E.; Wang, Q.

2018-03-01

This paper provides the performance evaluation of the meteorological component of The Air Pollution Model (TAPM), a nestable prognostic model, in predicting meteorological variables in urban areas, for both its surface layer and atmospheric boundary layer (ABL) turbulence parameterizations. The model was modified by incorporating four urban land surface types, replacing the existing single urban surface. Control runs were carried out over the wider area of Kozani, an urban area in NW Greece. The model was evaluated for both surface and ABL meteorological variables by using measurements of near-surface and vertical profiles of wind and temperature. The data were collected by using monitoring surface stations in selected sites as well as an acoustic sounder (SOnic Detection And Ranging (SODAR), up to 300 m above ground) and a radiometer profiler (up to 600 m above ground). The results showed the model demonstrated good performance in predicting the near-surface meteorology in the Kozani region for both a winter and a summer month. In the ABL, the comparison showed that the model's forecasts generally performed well with respect to the thermal structure (temperature profiles and ABL height) but overestimated wind speed at the heights of comparison (mostly below 200 m) up to 3-4 ms-1.

Visible and Thermal Imaging of Sea Ice and Open Water from Coast Guard Arctic Domain Awareness Flights

DTIC Science & Technology

2014-09-30

dropsondes, micro- aircraft), cloud top/base heights Arctic Ocean Surface Temperature project Steele Buoy drops for SLP , SST, SSS, & surface velocity...Colón & Vancas (NIC) Drop buoys for SLP , temperature and surface velocity Waves & Fetch in the MIZ Thompson SWIFTS buoys measuring wave energy...Expendable CTD, AXCP= Air Expendable Current Profiler, SLP = Sea Level atmospheric Pressure, SST= Seas Surface Temperature, A/C= aircraft, FSD= Floe Size Distribution, SIC=Sea Ice Concentration

Roughening of surfaces under intense and rapid heating

NASA Astrophysics Data System (ADS)

Andersen, Michael Louis

The High Average Power Laser (HAPL) project is aimed at a chamber design with a solid first wall in pursuit of sustained Laser Inertial Confinement Fusion. The wall must be able to withstand cyclic high temperatures and the corresponding thermal stresses. Tungsten was proposed as a suitable armor for the wall, because as a refractory metal, it has a high melting temperature and can act as a stress dampener. The nature of the surface loading consists of x-rays, ions, and neutrons, which through mainly thermal loading, create a biaxial surface stress. This condition causes the surface to roughen as ridges and valleys form to relieve the elastic energy. As the valleys deepen they eventually become cracks and traditional fracture mechanics can be used to determine the life of the first wall. Beginning from the Asaro-Tiller-Grinfeld instability, sharp interface calculations can be performed to determine the surface profile as a result of the interplay between surface stress energy and mass transport mechanisms. One successful approach to determine interface evolution is phase field theory and its embodiment in the numerical level-set method. Applications of the method included problems of solid/liquid and solid/vapor interfaces. In the present method, however, we develop a numerical procedure for surface profile tracking directly without the need to develop partial differential equations for the phase field, which typically smooth out sharp interfaces. Surface roughening instabilities, which are driven by a competition between elastic and surface energy contributions, are shown to be significantly controlled by plastic energy dissipation. We consider here a general parametric description of the surface of a stressed solid and through a mechanical kinetic transport mechanism, follow the temporal evolution of the surface morphology. It is found that once a groove reaches a certain depth and curvature, an instability is created that cannot be followed through elasticity alone. It is shown in this thesis that these morphological instabilities do not experience unbounded growth, as predicted by consideration of elastic energy alone, and that their growth will be severely limited by dislocation emission from high curvature grooves. Comparisons between perturbation theory and the present numerical approach are given along with comparisons to results from laser, ion, and x-ray experiments. Finally, the model is applied to the conditions of Inertial Confinement Fusion chamber walls to determine the number of cycles for crack nucleation.

ARM - Midlatitude Continental Convective Clouds Experiment (MC3E): Multi-Frequency Profilers, S-band Radar (williams-s_band)

DOE Data Explorer

Williams, Christopher

2012-11-06

This data was collected by the NOAA 449-MHz and 2.8-GHz profilers in support of the Department of Energy (DOE) and NASA sponsored Mid-latitude Continental Convective Cloud Experiment (MC3E). The profiling radars were deployed in Northern Oklahoma at the DOE Atmospheric Radiation Mission (ARM) Southern Great Plans (SGP) Central Facility from 22 April through 6 June 2011. NOAA deployed three instruments: a Parsivel disdrometer, a 2.8-GHz profiler, and a 449-MHz profiler. The parasivel provided surface estimates of the raindrop size distribution and is the reference used to absolutely calibrate the 2.8 GHz profiler. The 2.8-GHz profiler provided unattenuated reflectivity profiles of the precipitation. The 449-MHz profiler provided estimates of the vertical air motion during precipitation from near the surface to just below the freezing level. By using the combination of 2.8-GHz and 449-MHz profiler observations, vertical profiles of raindrop size distributions can be retrieved. The profilers are often reference by their frequency band: the 2.8-GHz profiler operates in the S-band and the 449-MHz profiler operates in the UHF band. The raw observations are available as well as calibrated spectra and moments. This document describes how the instruments were deployed, how the data was collected, and the format of the archived data.

ARM - Midlatitude Continental Convective Clouds Experiment (MC3E): Multi-Frequency Profilers, Parcivel Disdrometer (williams-disdro)

DOE Data Explorer

Williams, Christopher; Jensen, Mike

2012-11-06

This data was collected by the NOAA 449-MHz and 2.8-GHz profilers in support of the Department of Energy (DOE) and NASA sponsored Mid-latitude Continental Convective Cloud Experiment (MC3E). The profiling radars were deployed in Northern Oklahoma at the DOE Atmospheric Radiation Mission (ARM) Southern Great Plans (SGP) Central Facility from 22 April through 6 June 2011. NOAA deployed three instruments: a Parsivel disdrometer, a 2.8-GHz profiler, and a 449-MHz profiler. The parasivel provided surface estimates of the raindrop size distribution and is the reference used to absolutely calibrate the 2.8 GHz profiler. The 2.8-GHz profiler provided unattenuated reflectivity profiles of the precipitation. The 449-MHz profiler provided estimates of the vertical air motion during precipitation from near the surface to just below the freezing level. By using the combination of 2.8-GHz and 449-MHz profiler observations, vertical profiles of raindrop size distributions can be retrieved. The profilers are often reference by their frequency band: the 2.8-GHz profiler operates in the S-band and the 449-MHz profiler operates in the UHF band. The raw observations are available as well as calibrated spectra and moments. This document describes how the instruments were deployed, how the data was collected, and the format of the archived data.

ARM - Midlatitude Continental Convective Clouds Experiment (MC3E): Multi-Frequency Profilers, Vertical Air Motion (williams-vertair)

DOE Data Explorer

Williams, Christopher; Jensen, Mike

2012-11-06

This data was collected by the NOAA 449-MHz and 2.8-GHz profilers in support of the Department of Energy (DOE) and NASA sponsored Mid-latitude Continental Convective Cloud Experiment (MC3E). The profiling radars were deployed in Northern Oklahoma at the DOE Atmospheric Radiation Mission (ARM) Southern Great Plans (SGP) Central Facility from 22 April through 6 June 2011. NOAA deployed three instruments: a Parsivel disdrometer, a 2.8-GHz profiler, and a 449-MHz profiler. The parasivel provided surface estimates of the raindrop size distribution and is the reference used to absolutely calibrate the 2.8 GHz profiler. The 2.8-GHz profiler provided unattenuated reflectivity profiles of the precipitation. The 449-MHz profiler provided estimates of the vertical air motion during precipitation from near the surface to just below the freezing level. By using the combination of 2.8-GHz and 449-MHz profiler observations, vertical profiles of raindrop size distributions can be retrieved. The profilers are often reference by their frequency band: the 2.8-GHz profiler operates in the S-band and the 449-MHz profiler operates in the UHF band. The raw observations are available as well as calibrated spectra and moments. This document describes how the instruments were deployed, how the data was collected, and the format of the archived data.

The Gibbs free energy of homogeneous nucleation: From atomistic nuclei to the planar limit.

PubMed

Cheng, Bingqing; Tribello, Gareth A; Ceriotti, Michele

2017-09-14

In this paper we discuss how the information contained in atomistic simulations of homogeneous nucleation should be used when fitting the parameters in macroscopic nucleation models. We show how the number of solid and liquid atoms in such simulations can be determined unambiguously by using a Gibbs dividing surface and how the free energy as a function of the number of solid atoms in the nucleus can thus be extracted. We then show that the parameters (the chemical potential, the interfacial free energy, and a Tolman correction) of a model based on classical nucleation theory can be fitted using the information contained in these free-energy profiles but that the parameters in such models are highly correlated. This correlation is unfortunate as it ensures that small errors in the computed free energy surface can give rise to large errors in the extrapolated properties of the fitted model. To resolve this problem we thus propose a method for fitting macroscopic nucleation models that uses simulations of planar interfaces and simulations of three-dimensional nuclei in tandem. We show that when the chemical potentials and the interface energy are pinned to their planar-interface values, more precise estimates for the Tolman length are obtained. Extrapolating the free energy profile obtained from small simulation boxes to larger nuclei is thus more reliable.

Full-coverage film cooling: 3-dimensional measurements of turbulence structure and prediction of recovery region hydrodynamics

NASA Technical Reports Server (NTRS)

Yavuzkurt, S.; Moffat, R. J.; Kays, W. M.

1979-01-01

Hydrodynamic measurements were made with a triaxial hot-wire in the full-coverage region and the recovery region following an array of injection holes inclined downstream, at 30 degrees to the surface. The data were taken under isothermal conditions at ambient temperature and pressure for two blowing ratios: M = 0.9 and M = 0.4. Profiles of the three main velocity components and the six Reynolds stresses were obtained at several spanwise positions at each of the five locations down the test plate. A one-equation model of turbulence (using turbulent kinetic energy with an algebraic mixing length) was used in a two-dimensional computer program to predict the mean velocity and turbulent kinetic energy profiles in the recovery region. A new real-time hotwire scheme was developed to make measurements in the three-dimensional turbulent boundary layer over the full-coverage surface.

Laser nitriding of iron: Nitrogen profiles and phases

NASA Astrophysics Data System (ADS)

Illgner, C.; Schaaf, P.; Lieb, K. P.; Schubert, E.; Queitsch, R.; Bergmann, H.-W.

1995-07-01

Armco iron samples were surface nitrided by irradiating them with pulses of an excimer laser in a nitrogen atmosphere. The resulting nitrogen depth profiles measured by Resonant Nuclear Reaction Analysis (RNRA) and the phase formation determined by Conversion Electron Mössbauer Spectroscopy (CEMS) were investigated as functions of energy density and the number of pulses. The nitrogen content of the samples was found to be independent of the number of pulses in a layer of 50 nm from the surface and to increase in depths exceeding 150 nm. The phase composition did not change with the number of pulses. The nitrogen content can be related to an enhanced nitrogen solubility based on high temperatures and high pressures due to the laser-induced plasma above the sample. With increasing pulse energy density, the phase composition changes towards phases with higher nitrogen contents. Nitrogen diffusion seems to be the limiting factor for the nitriding process.

Improving depth resolutions in positron beam spectroscopy by concurrent ion-beam sputtering

NASA Astrophysics Data System (ADS)

John, Marco; Dalla, Ayham; Ibrahim, Alaa M.; Anwand, Wolfgang; Wagner, Andreas; Böttger, Roman; Krause-Rehberg, Reinhard

2018-05-01

The depth resolution of mono-energetic positron annihilation spectroscopy using a positron beam is shown to improve by concurrently removing the sample surface layer during positron beam spectroscopy. During ion-beam sputtering with argon ions, Doppler-broadening spectroscopy is performed with energies ranging from 3 keV to 5 keV allowing for high-resolution defect studies just below the sputtered surface. With this technique, significantly improved depth resolutions could be obtained even at larger depths when compared to standard positron beam experiments which suffer from extended positron implantation profiles at higher positron energies. Our results show that it is possible to investigate layered structures with a thickness of about 4 microns with significantly improved depth resolution. We demonstrated that a purposely generated ion-beam induced defect profile in a silicon sample could be resolved employing the new technique. A depth resolution of less than 100 nm could be reached.

Near-Surface Geophysical Imaging of Deformation Associated with the Daytona Beach Sand Blow Deposits, Lee County, Arkansas

NASA Astrophysics Data System (ADS)

Rohrer, M.; Harris, J. B.; Cearley, C.; Teague, M.

2017-12-01

Within the past decade or so, paleoseismologic and geophysical studies at the Daytona Beach (DB) site in east-central Arkansas have reported earthquake-induced liquefaction (sand blows) along a prominent NW-trending lineament dated to approximately 5.5 ka. A recent compressional-wave (P-wave) seismic reflection survey acquired by the U. S. Geological Survey (USGS) along Highway 243 in Lee County, Arkansas, across the DB sand blow cluster, identified a previously unknown fault zone that is likely associated with the liquefaction. However, the USGS data were not able to image the Quaternary section (<60 m deep) and show a direct connection between the deeper faulting and the sand blows. In order to investigate the near-surface structure of the fault zone, we acquired an integrated geophysical data set consisting of 430-m-long shear-wave (S-wave) seismic reflection and ground penetrating radar (GPR) profiles above the deformation imaged on the USGS profile. The S-wave reflection data were collected using a 24-channel, towable landstreamer and the seismic energy was generated by a sledgehammer/I-beam source. The GPR data were collected with a cart-mounted 250-MHz system, using a 0.5-m antenna spacing and a 0.10-m step size. The processed seismic profile exhibits coherent reflection energy throughout the Quaternary section. Changes in reflection amplitude and coherency, offset reflections, and abundant diffractions suggest the presence of a complex zone of high-angle faults in the shallow subsurface coincident with the mapped lineament. Folded shallow reflections show that the deformation extends upward to within 10 m of the surface. Furthermore, the GPR profile images a distinct zone of deformation in the very near surface (<1.5 m deep) that is coincident with the upward projection of the deformation imaged on the S-wave seismic reflection profile.

Surface roughness effects on bidirectional reflectance

NASA Technical Reports Server (NTRS)

Smith, T. F.; Hering, R. G.

1972-01-01

An experimental study of surface roughness effects on bidirectional reflectance of metallic surfaces is presented. A facility capable of irradiating a sample from normal to grazing incidence and recording plane of incidence bidirectional reflectance measurements was developed. Samples consisting of glass, aluminum alloy, and stainless steel materials were selected for examination. Samples were roughened using standard grinding techniques and coated with a radiatively opaque layer of pure aluminum. Mechanical surface roughness parameters, rms heights and rms slopes, evaluated from digitized surface profile measurements are less than 1.0 micrometers and 0.28, respectively. Rough surface specular, bidirectional, and directional reflectance measurements for selected values of polar angle of incidence and wavelength of incident energy within the spectral range of 1 to 14 micrometers are reported. The Beckmann bidirectional reflectance model is compared with reflectance measurements to establish its usefulness in describing the magnitude and spatial distribution of energy reflected from rough surfaces.

Simulation of Surface Energy Fluxes and Snow Interception Using a Higher Order Closure Multi-Layer Soil-Vegetation-Atmospheric Model: The Effect of Canopy Shape and Structure

NASA Astrophysics Data System (ADS)

McGowan, L. E.; Dahlke, H. E.; Paw U, K. T.

2015-12-01

Snow cover is a critical driver of the Earth's surface energy budget, climate change, and water resources. Variations in snow cover not only affect the energy budget of the land surface but also represent a major water supply source. In California, US estimates of snow depth, extent, and melt in the Sierra Nevada are critical to estimating the amount of water available for both California agriculture and urban users. However, accurate estimates of snow cover and snow melt processes in forested area still remain a challenge. Canopy structure influences the vertical and spatiotemporal distribution of snow, and therefore ultimately determines the degree and extent by which snow alters both the surface energy balance and water availability in forested regions. In this study we use the Advanced Canopy-Atmosphere-Soil algorithm (ACASA), a multi-layer soil-vegetation-atmosphere numerical model, to simulate the effect of different snow-covered canopy structures on the energy budget, and temperature and other scalar profiles within different forest types in the Sierra Nevada, California. ACASA incorporates a higher order turbulence closure scheme which allows the detailed simulation of turbulent fluxes of heat and water vapor as well as the CO2 exchange of several layers within the canopy. As such ACASA can capture the counter gradient fluxes within canopies that may occur frequently, but are typically unaccounted for, in most snow hydrology models. Six different canopy types were modeled ranging from coniferous forests (e.g. most biomass near the ground) to top-heavy (e.g. most biomass near the top of the crown) deciduous forests to multi-layered forest canopies (e.g. mixture of young and mature trees). Preliminary results indicate that the canopy shape and structure associated with different canopy types fundamentally influence the vertical scalar profiles (including those of temperature, moisture, and wind speed) in the canopy and thus alter the interception and snow melt dynamics in forested land surfaces. The turbulent transport dynamics, including counter-gradient fluxes, and radiation features including land surface albedo, are discussed in the context of the snow energy balance.

Observations of a two-layer soil moisture influence on surface energy dynamics and planetary boundary layer characteristics in a semiarid shrubland

NASA Astrophysics Data System (ADS)

Sanchez-Mejia, Zulia Mayari; Papuga, Shirley A.

2014-01-01

We present an observational analysis examining soil moisture control on surface energy dynamics and planetary boundary layer characteristics. Understanding soil moisture control on land-atmosphere interactions will become increasingly important as climate change continues to alter water availability. In this study, we analyzed 4 years of data from the Santa Rita Creosote Ameriflux site. We categorized our data independently in two ways: (1) wet or dry seasons and (2) one of the four cases within a two-layer soil moisture framework for the root zone based on the presence or absence of moisture in shallow (0-20 cm) and deep (20-60 cm) soil layers. Using these categorizations, we quantified the soil moisture control on surface energy dynamics and planetary boundary layer characteristics using both average responses and linear regression. Our results highlight the importance of deep soil moisture in land-atmosphere interactions. The presence of deep soil moisture decreased albedo by about 10%, and significant differences were observed in evaporative fraction even in the absence of shallow moisture. The planetary boundary layer height (PBLh) was largest when the whole soil profile was dry, decreasing by about 1 km when the whole profile was wet. Even when shallow moisture was absent but deep moisture was present the PBLh was significantly lower than when the entire profile was dry. The importance of deep moisture is likely site-specific and modulated through vegetation. Therefore, understanding these relationships also provides important insights into feedbacks between vegetation and the hydrologic cycle and their consequent influence on the climate system.

Reconstruction of Energy Surfaces from Friction Force Microscopy Measurements with the Jarzynski Equality

NASA Astrophysics Data System (ADS)

Berkovich, Ronen; Klafter, Joseph; Urbakh, Michael

Free energy is one of the most fundamental thermodynamic functions, determining relative phase stability and serving as a generating function for other thermodynamic quantities. The calculation of free energies is a challenging enterprise. In equilibrium statistical mechanics, the free energy is related to the canonical partition function. The partition function itself involves integrations over all degrees of freedom in the system and, in most cases, cannot be easily calculated directly. In 1997, Jarzynski proved a remarkable equality that allows computing the equilibrium free-energy difference between two states from the probability distribution of the nonequilibrium work done on the system to switch between the two states. The Jarzynski equality provides a powerful free-energy difference estimator from a set of irreversible experiments. This method is closely related to free-energy perturbation approach, which is also a computational technique for estimating free-energy differences. The ability to map potential profiles and topologies is of major significance to areas as diverse as biological recognition and nanoscale friction. This capability has been demonstrated for frictional studies where a force between the tip of the scanning force microscope and the surface is probed. The surface free-energy corrugation produces a detectable friction forces. Thus, friction force microscopy (FFM) should be able to discriminate between energetically different areas on the probed surface. Here, we apply the Jarzynski equality for the analysis of FFM measurements and thus obtain a variation of the free energy along a surface.

Antifouling enhancement of polysulfone/TiO2 nanocomposite separation membrane by plasma etching

NASA Astrophysics Data System (ADS)

Chen, Z.; Yin, C.; Wang, S.; Ito, K.; Fu, Q. M.; Deng, Q. R.; Fu, P.; Lin, Z. D.; Zhang, Y.

2017-01-01

A polysulfone/TiO2 nanocomposite membrane was prepared via casting method, followed by the plasma etching of the membrane surface. Doppler broadened energy spectra vs. positron incident energy were employed to elucidate depth profiles of the nanostructure for the as-prepared and treated membranes. The results confirmed that the near-surface of the membrane was modified by the plasma treatment. The antifouling characteristics for the membranes, evaluated using the degradation of Rhodamin B, indicated that the plasma treatment enhances the photo catalytic ability of the membrane, suggesting that more TiO2 nanoparticles are exposed at the membrane surface after the plasma treatment as supported by the positron result.

Darkening effect on AZ31B magnesium alloy surface induced by nanosecond pulse Nd:YAG laser

NASA Astrophysics Data System (ADS)

Guan, Y. C.; Zhou, W.; Zheng, H. Y.; Li, Z. L.

2013-09-01

Permanent darkening effect was achieved on surface of AZ31B Mg alloy irradiated with nanosecond pulse Nd:YAG laser, and special attention was made to examine how surface structure as well as oxidation affect the darkening effect. Experiments were carried out to characterize morphological evolution and chemical composition of the irradiated areas by optical reflection spectrometer, Talysurf surface profiler, SEM, EDS, and XPS. The darkening effect was found to be occurred at the surface under high laser energy. Optical spectra showed that the induced darkening surface was uniform over the spectral range from 200 nm to 1100 nm. SEM and surface profiler showed that surface morphology of darkening areas consisted of large number of micron scale cauliflower-like clusters and protruding particles. EDS and XPS showed that compared to non-irradiated area, oxygen content at the darkening areas increased significantly. It was proposed a mechanism that involved trapping of light in the surface morphology and chemistry variation of irradiated areas to explain the laser-induced darkening effect on AZ31B Mg alloy.

Biological Surface Adsorption Index of Nanomaterials: Modelling Surface Interactions of Nanomaterials with Biomolecules.

PubMed

Chen, Ran; Riviere, Jim E

2017-01-01

Quantitative analysis of the interactions between nanomaterials and their surrounding environment is crucial for safety evaluation in the application of nanotechnology as well as its development and standardization. In this chapter, we demonstrate the importance of the adsorption of surrounding molecules onto the surface of nanomaterials by forming biocorona and thus impact the bio-identity and fate of those materials. We illustrate the key factors including various physical forces in determining the interaction happening at bio-nano interfaces. We further discuss the mathematical endeavors in explaining and predicting the adsorption phenomena, and propose a new statistics-based surface adsorption model, the Biological Surface Adsorption Index (BSAI), to quantitatively analyze the interaction profile of surface adsorption of a large group of small organic molecules onto nanomaterials with varying surface physicochemical properties, first employing five descriptors representing the surface energy profile of the nanomaterials, then further incorporating traditional semi-empirical adsorption models to address concentration effects of solutes. These Advancements in surface adsorption modelling showed a promising development in the application of quantitative predictive models in biological applications, nanomedicine, and environmental safety assessment of nanomaterials.

Surface roughness measurements

NASA Technical Reports Server (NTRS)

Howard, Thomas G.

1994-01-01

The Optics Division is currently in the research phase of producing grazing-incidence mirrors to be used in x-ray detector applications. The traditional method of construction involves labor-intensive glass grinding. This also culminates in a relatively heavy mirror. For lower resolution applications, the mirrors may be of a replicated design which involves milling a mandrel as a negative of the final shape and electroplating the cylindrical mirror onto it. The mirror is then separated from the mandrel by cooling. The mandrel will shrink more than the 'shell' (mirror) allowing it to be pulled from the mandrel. Ulmer (2) describes this technique and its variations in more detail. To date, several mirrors have been tested at MSFC by the Optical Fabrication Branch by focusing x-ray energy onto a detector with limited success. Little is known about the surface roughness of the actual mirror. Hence, the attempt to gather data on these surfaces. The test involves profiling the surface of a sample, replicating the surface as described above, and then profiling the replicated surface.

Electron heat transport measured in a stochastic magnetic field.

PubMed

Biewer, T M; Forest, C B; Anderson, J K; Fiksel, G; Hudson, B; Prager, S C; Sarff, J S; Wright, J C; Brower, D L; Ding, W X; Terry, S D

2003-07-25

New profile measurements have allowed the electron thermal diffusivity profile to be estimated from power balance in the Madison Symmetric Torus where magnetic islands overlap and field lines are stochastic. The measurements show that (1) the electron energy transport is conductive not convective, (2) the measured thermal diffusivities are in good agreement with numerical simulations of stochastic transport, and (3) transport is greatly reduced near the reversal surface where magnetic diffusion is small.

Jumps in electric potential and in temperature at the electrode surfaces of the solid oxide fuel cell

NASA Astrophysics Data System (ADS)

Kjelstrup, S.; Bedeaux, D.

1997-02-01

The electric potential profile and the temperature profile across a formation cell have been derived for the first time, using irreversible thermodynamics for bulk and surface systems. The method was demonstrated with the solid oxide fuel cell. The expression for the cell potential reduces to the classical formula when we assume equilibrium for polarized oxygen atoms across the electrolyte. Using data from the literature, we show for some likely assumptions, how the cell potential is generated at the anode, and how the energy is dissipated throughout the cell. The thermal gradient amounts to 5 × 10 8 Km -1 when the current density is 10 4 Am -2 and the thermal resistance of the surface scales like the electrical resistance.

Surface structure of neutron stars with high magnetic fields

NASA Technical Reports Server (NTRS)

Fushiki, I.; Gudmundsson, E. H.; Pethick, C. J.

1989-01-01

The equation of state of cold dense matter in strong magnetic fields is calculated in the Thomas-Fermi and Thomas-Fermi-Dirac approximations. For use in the latter calculation, a new expression is derived for the exchange energy of the uniform electron gas in a strong magnetic field. Detailed calculations of the density profile in the surface region of a neutron star are described for a variety of equations of state, and these show that the surface density profile is strongly affected by the magnetic field, irrespective of whether or not matter in a magnetic field has a condensed state bound with respect to isolated atoms. It is also shown that, as a consequence of the field dependence of the screening potential, magnetic fields can significantly increase nuclear reaction rates.

JPL Experience with the Mars Pathfinder, Mission Simulation Battery

NASA Technical Reports Server (NTRS)

Perrone, Dave; Ewell, Richard

1997-01-01

A summary of the Mars Pathfinder Battery is given. The battery survived 47 days at 25 deg. C; it survived a 7 month stand at 10 to -5 deg. C; it met and exceeded 40 ampere-hour capacity for EDL; it met the 30 cycle minimum for Mars surface operation; and the project power profile for MArs surface operation does not yield energy balance.

Surface-layer turbulence, energy balance and links to atmospheric circulations over a mountain glacier in the French Alps

NASA Astrophysics Data System (ADS)

Litt, Maxime; Sicart, Jean-Emmanuel; Six, Delphine; Wagnon, Patrick; Helgason, Warren D.

2017-04-01

Over Saint-Sorlin Glacier in the French Alps (45° N, 6.1° E; ˜ 3 km2) in summer, we study the atmospheric surface-layer dynamics, turbulent fluxes, their uncertainties and their impact on surface energy balance (SEB) melt estimates. Results are classified with regard to large-scale forcing. We use high-frequency eddy-covariance data and mean air-temperature and wind-speed vertical profiles, collected in 2006 and 2009 in the glacier's atmospheric surface layer. We evaluate the turbulent fluxes with the eddy-covariance (sonic) and the profile method, and random errors and parametric uncertainties are evaluated by including different stability corrections and assuming different values for surface roughness lengths. For weak synoptic forcing, local thermal effects dominate the wind circulation. On the glacier, weak katabatic flows with a wind-speed maximum at low height (2-3 m) are detected 71 % of the time and are generally associated with small turbulent kinetic energy (TKE) and small net turbulent fluxes. Radiative fluxes dominate the SEB. When the large-scale forcing is strong, the wind in the valley aligns with the glacier flow, intense downslope flows are observed, no wind-speed maximum is visible below 5 m, and TKE and net turbulent fluxes are often intense. The net turbulent fluxes contribute significantly to the SEB. The surface-layer turbulence production is probably not at equilibrium with dissipation because of interactions of large-scale orographic disturbances with the flow when the forcing is strong or low-frequency oscillations of the katabatic flow when the forcing is weak. In weak forcing when TKE is low, all turbulent fluxes calculation methods provide similar fluxes. In strong forcing when TKE is large, the choice of roughness lengths impacts strongly the net turbulent fluxes from the profile method fluxes and their uncertainties. However, the uncertainty on the total SEB remains too high with regard to the net observed melt to be able to recommend one turbulent flux calculation method over another.

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

Ovcharov, A. V.; Karateev, I. A.; Mikhutkin, A. A.

The surface microstructure of Ni–W alloy tapes, which are used as substrates to form films of high-temperature superconductors and photovoltaic devices, has been studied. Several samples of a Ni{sub 95}W{sub 5} tape (Evico) annealed under different conditions were analyzed using scanning electron microscopy, energy-dispersive X-ray microanalysis, electron diffraction, and electron energy-loss spectroscopy. NiWO{sub 4} precipitates are found on the surface of annealed samples. The growth of precipitates at a temperature of 950°C is accompanied by the formation of pores on the surface or under an oxide film. Depressions with a wedge-shaped profile are found at the grain boundaries. Annealing inmore » a reducing atmosphere using a specially prepared chamber allows one to form a surface free of nickel tungstate precipitates.« less

Calculations of the heights, periods, profile parameters, and energy spectra of wind waves

NASA Technical Reports Server (NTRS)

Korneva, L. A.

1975-01-01

Sea wave behavior calculations require the precalculation of wave elements as well as consideration of the spectral functions of ocean wave formation. The spectrum of the random wave process is largely determined by the distribution of energy in the actual wind waves observed on the surface of the sea as expressed in statistical and spectral characteristics of the sea swell.

Hartree-Fock theory of the inhomogeneous electron gas at a jellium metal surface: Rigorous upper bounds to the surface energy and accurate work functions

NASA Astrophysics Data System (ADS)

Sahni, V.; Ma, C. Q.

1980-12-01

The inhomogeneous electron gas at a jellium metal surface is studied in the Hartree-Fock approximation by Kohn-Sham density functional theory. Rigorous upper bounds to the surface energy are derived by application of the Rayleigh-Ritz variational principle for the energy, the surface kinetic, electrostatic, and nonlocal exchange energy functionals being determined exactly for the accurate linear-potential model electronic wave functions. The densities obtained by the energy minimization constraint are then employed to determine work-function results via the variationally accurate "displaced-profile change-in-self-consistent-field" expression. The theoretical basis of this non-self-consistent procedure and its demonstrated accuracy for the fully correlated system (as treated within the local-density approximation for exchange and correlation) leads us to conclude these results for the surface energies and work functions to be essentially exact. Work-function values are also determined by the Koopmans'-theorem expression, both for these densities as well as for those obtained by satisfaction of the constraint set on the electrostatic potential by the Budd-Vannimenus theorem. The use of the Hartree-Fock results in the accurate estimation of correlation-effect contributions to these surface properties of the nonuniform electron gas is also indicated. In addition, the original work and approximations made by Bardeen in this attempt at a solution of the Hartree-Fock problem are briefly reviewed in order to contrast with the present work.

Darcy-Forchheimer flow of Maxwell nanofluid flow with nonlinear thermal radiation and activation energy

NASA Astrophysics Data System (ADS)

Sajid, T.; Sagheer, M.; Hussain, S.; Bilal, M.

2018-03-01

The present article is about the study of Darcy-Forchheimer flow of Maxwell nanofluid over a linear stretching surface. Effects like variable thermal conductivity, activation energy, nonlinear thermal radiation is also incorporated for the analysis of heat and mass transfer. The governing nonlinear partial differential equations (PDEs) with convective boundary conditions are first converted into the nonlinear ordinary differential equations (ODEs) with the help of similarity transformation, and then the resulting nonlinear ODEs are solved with the help of shooting method and MATLAB built-in bvp4c solver. The impact of different physical parameters like Brownian motion, thermophoresis parameter, Reynolds number, magnetic parameter, nonlinear radiative heat flux, Prandtl number, Lewis number, reaction rate constant, activation energy and Biot number on Nusselt number, velocity, temperature and concentration profile has been discussed. It is viewed that both thermophoresis parameter and activation energy parameter has ascending effect on the concentration profile.

Perspective on the reactions between F- and CH3CH2F: the free energy landscape of the E2 and SN2 reaction channels.

PubMed

Ensing, Bernd; Klein, Michael L

2005-05-10

Recently, we computed the 3D free energy surface of the base-induced elimination reaction between F(-) and CH(3)CH(2)F by using a powerful technique within Car-Parrinello molecular dynamics simulation. Here, the set of three order parameters is expanded to six, which allows the study of the competing elimination and substitution reactions simultaneously. The power of the method is exemplified by the exploration of the six-dimensional free energy landscape, sampling, and mapping out the eight stable states as well as the connecting bottlenecks. The free energy profile and barrier along the E2 and S(N)2 reaction channels are refined by using umbrella sampling. The two mechanisms do not share a common "E2C-like" transition state. Comparison with the zero temperature profiles shows a particularly significant entropy contribution to the S(N)2 channel.

Sub-saturation matter in compact stars: Nuclear modelling in the framework of the extended Thomas-Fermi theory

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

Aymard, François; Gulminelli, Francesca; Margueron, Jérôme

A recently introduced analytical model for the nuclear density profile [1] is implemented in the Extended Thomas-Fermi (ETF) energy density functional. This allows to (i) shed a new light on the issue of the sign of surface symmetry energy in nuclear mass formulas, as well as to (ii) show the importance of the in-medium corrections to the nuclear cluster energies in thermodynamic conditions relevant for the description of core-collapse supernovae and (proto)-neutron star crust.

Sub-saturation matter in compact stars: Nuclear modelling in the framework of the extended Thomas-Fermi theory

NASA Astrophysics Data System (ADS)

Aymard, François; Gulminelli, Francesca; Margueron, Jérôme

2015-02-01

A recently introduced analytical model for the nuclear density profile [1] is implemented in the Extended Thomas-Fermi (ETF) energy density functional. This allows to (i) shed a new light on the issue of the sign of surface symmetry energy in nuclear mass formulas, as well as to (ii) show the importance of the in-medium corrections to the nuclear cluster energies in thermodynamic conditions relevant for the description of core-collapse supernovae and (proto)-neutron star crust.

Higher modulus compositions incorporating particulate rubber

DOEpatents

Bauman, Bernard D.; Williams, Mark A.

1999-01-01

A plastic article having a number of surfaces with at least one surface being modified by contacting that surface with a reactive gas atmosphere containing F.sub.2, Cl.sub.2, O.sub.2, Ozone, SO.sub.3, oxidative acids, or mixtures thereof, at a temperature and gas partial pressure sufficient to increase the surface energy of the at least one surface being modified to at least 40 dynes/cm at a temperature of 20.degree. C., to enhance bonding of non-slip polymer coatings to the modified surface, to which coatings elastomeric or rigid particles may be admixed for imparting a surface profile and increasing the coefficient of friction between the coated surface and the counter-surface.

Process for forming retrograde profiles in silicon

DOEpatents

Weiner, K.H.; Sigmon, T.W.

1996-10-15

A process is disclosed for forming retrograde and oscillatory profiles in crystalline and polycrystalline silicon. The process consisting of introducing an n- or p-type dopant into the silicon, or using prior doped silicon, then exposing the silicon to multiple pulses of a high-intensity laser or other appropriate energy source that melts the silicon for short time duration. Depending on the number of laser pulses directed at the silicon, retrograde profiles with peak/surface dopant concentrations which vary are produced. The laser treatment can be performed in air or in vacuum, with the silicon at room temperature or heated to a selected temperature.

Global Validation of MODIS Atmospheric Profile-Derived Near-Surface Air Temperature and Dew Point Estimates

NASA Astrophysics Data System (ADS)

Famiglietti, C.; Fisher, J.; Halverson, G. H.

2017-12-01

This study validates a method of remote sensing near-surface meteorology that vertically interpolates MODIS atmospheric profiles to surface pressure level. The extraction of air temperature and dew point observations at a two-meter reference height from 2001 to 2014 yields global moderate- to fine-resolution near-surface temperature distributions that are compared to geographically and temporally corresponding measurements from 114 ground meteorological stations distributed worldwide. This analysis is the first robust, large-scale validation of the MODIS-derived near-surface air temperature and dew point estimates, both of which serve as key inputs in models of energy, water, and carbon exchange between the land surface and the atmosphere. Results show strong linear correlations between remotely sensed and in-situ near-surface air temperature measurements (R2 = 0.89), as well as between dew point observations (R2 = 0.77). Performance is relatively uniform across climate zones. The extension of mean climate-wise percent errors to the entire remote sensing dataset allows for the determination of MODIS air temperature and dew point uncertainties on a global scale.

Scalable patterning using laser-induced shock waves

NASA Astrophysics Data System (ADS)

Ilhom, Saidjafarzoda; Kholikov, Khomidkhodza; Li, Peizhen; Ottman, Claire; Sanford, Dylan; Thomas, Zachary; San, Omer; Karaca, Haluk E.; Er, Ali O.

2018-04-01

An advanced direct imprinting method with low cost, quick, and minimal environmental impact to create a thermally controllable surface pattern using the laser pulses is reported. Patterned microindents were generated on Ni50Ti50 shape memory alloys and aluminum using an Nd: YAG laser operating at 1064 nm combined with a suitable transparent overlay, a sacrificial layer of graphite, and copper grid. Laser pulses at different energy densities, which generate pressure pulses up to a few GPa on the surface, were focused through the confinement medium, ablating the copper grid to create plasma and transferring the grid pattern onto the surface. Scanning electron microscope and optical microscope images show that various patterns were obtained on the surface with high fidelity. One-dimensional profile analysis indicates that the depth of the patterned sample initially increases with the laser energy and later levels off. Our simulations of laser irradiation process also confirm that high temperature and high pressure could be generated when the laser energy density of 2 J/cm2 is used.

Planarization of Isolated Defects on ICF Target Capsule Surfaces by Pulsed Laser Ablation

DOE PAGES

Alfonso, Noel; Carlson, Lane C.; Bunn, Thomas L.

2016-08-09

Demanding surface quality requirements for inertial confinement fusion (ICF) capsules motivated the development of a pulsed laser ablation method to reduce or eliminate undesirable surface defects. The pulsed laser ablation technique takes advantage of a full surface (4π) capsule manipulation system working in combination with an optical profiling (confocal) microscope. Based on the defect topography, the material removal rate, the laser pulse energy and its beam profile, a customized laser raster pattern is derived to remove the defect. The pattern is a table of coordinates and number of pulses that dictate how the defect will be vaporized until its heightmore » is level with the capsule surface. This paper explains how the raster patterns are optimized to minimize surface roughness and how surface roughness after laser ablation is simulated. The simulated surfaces are compared with actual ablated surfaces. Large defects are reduced to a size regime where a tumble finishing process produces very high quality surfaces devoid of high mode defects. The combined polishing processes of laser ablation and tumble finishing have become routine fabrication steps for National Ignition Facility capsule production.« less

Theory of raman scattering from molecules adsorbed at semiconductor surfaces

NASA Astrophysics Data System (ADS)

Ueba, H.

1983-09-01

A theory is presented to calculate the Raman polarizability of an adsorbed molecule at a semiconductor surface, where the electronic excitation in the molecular site interacts with excitons (elementary excitations in the semiconductor) through non-radiative energy transfer between them, in an intermediate state in the Raman scattering process. The Raman polarizability thus calculated is found to exhibit a peak at the energy corresponding to a resonant excitation of excitons, thereby suggesting the possibility of surface enhanced Raman scattering on semiconductor surfaces. The mechanism studied here can also give an explanation of a recent observation of the Raman excitation profiles of p-NDMA and p-DMAAB adsorbed on ZnO or TiO 2, where those profiles were best described by assuming a resonant intermediate state of the exciton transition in the semiconductors. It is also demonstrated that in addition to vibrational Raman scattering, excitonic Raman scattering of adsorbed molecules will occur in the coupled molecule-semiconductor system, where the molecular returns to its ground electronic state by leaving an exciton in the semiconductor. A spectrum of the excitonic Raman scattering is expected to appear in the background of the vibrational Raman band and to be characterized by the electronic structure of excitons. A desirable experiment is suggested for an examination of the theory.

Dynamics of an optically confined nanoparticle diffusing normal to a surface.

PubMed

Schein, Perry; O'Dell, Dakota; Erickson, David

2016-06-01

Here we measure the hindered diffusion of an optically confined nanoparticle in the direction normal to a surface, and we use this to determine the particle-surface interaction profile in terms of the absolute height. These studies are performed using the evanescent field of an optically excited single-mode silicon nitride waveguide, where the particle is confined in a height-dependent potential energy well generated from the balance of optical gradient and surface forces. Using a high-speed cmos camera, we demonstrate the ability to capture the short time-scale diffusion dominated motion for 800-nm-diam polystyrene particles, with measurement times of only a few seconds per particle. Using established theory, we show how this information can be used to estimate the equilibrium separation of the particle from the surface. As this measurement can be made simultaneously with equilibrium statistical mechanical measurements of the particle-surface interaction energy landscape, we demonstrate the ability to determine these in terms of the absolute rather than relative separation height. This enables the comparison of potential energy landscapes of particle-surface interactions measured under different experimental conditions, enhancing the utility of this technique.

Identification of the protein folding transition state from molecular dynamics trajectories

NASA Astrophysics Data System (ADS)

Muff, S.; Caflisch, A.

2009-03-01

The rate of protein folding is governed by the transition state so that a detailed characterization of its structure is essential for understanding the folding process. In vitro experiments have provided a coarse-grained description of the folding transition state ensemble (TSE) of small proteins. Atomistic details could be obtained by molecular dynamics (MD) simulations but it is not straightforward to extract the TSE directly from the MD trajectories, even for small peptides. Here, the structures in the TSE are isolated by the cut-based free-energy profile (cFEP) using the network whose nodes and links are configurations sampled by MD and direct transitions among them, respectively. The cFEP is a barrier-preserving projection that does not require arbitrarily chosen progress variables. First, a simple two-dimensional free-energy surface is used to illustrate the successful determination of the TSE by the cFEP approach and to explain the difficulty in defining boundary conditions of the Markov state model for an entropically stabilized free-energy minimum. The cFEP is then used to extract the TSE of a β-sheet peptide with a complex free-energy surface containing multiple basins and an entropic region. In contrast, Markov state models with boundary conditions defined by projected variables and conventional histogram-based free-energy profiles are not able to identify the TSE of the β-sheet peptide.

Adsorption and reaction of CO and H2O on WC(0001) surface: A first-principles investigation

NASA Astrophysics Data System (ADS)

Tong, Yu-Jhe; Wu, Shiuan-Yau; Chen, Hsin-Tsung

2018-01-01

We have performed a spin-polarized density functional theory (DFT) study for understanding the detailed reaction mechanism of CO and H2O on WC (0001) surface. The adsorption properties and vibrational frequencies of H2O, OH, O, H, CO and CO2 on the WC (0001) surface were illustrated. These results are well in consistent with the experimental observations studied by temperature-programmed desorption (TPD) and high-resolution electron energy loss spectroscopy (HREELS). Based on the adsorption results, potential energy profiles of H2O and OH dehydrogenation and HCO, COH, COOH, and CO2 formation on the WC (0001) surface were predicted. The calculation results demonstrated that the WC (0001) surface as Fe (110) surface exhibits significantly reaction activity toward the dehydrogenation of H2O and OH but less activity toward the formation of HCO, COH, COOH and CO2 compared to the Cu (111) and Pt (111) surfaces.

Laser shock wave assisted patterning on NiTi shape memory alloy surfaces

NASA Astrophysics Data System (ADS)

Seyitliyev, Dovletgeldi; Li, Peizhen; Kholikov, Khomidkhodza; Grant, Byron; Karaca, Haluk E.; Er, Ali O.

2017-02-01

An advanced direct imprinting method with low cost, quick, and less environmental impact to create thermally controllable surface pattern using the laser pulses is reported. Patterned micro indents were generated on Ni50Ti50 shape memory alloys (SMA) using an Nd:YAG laser operating at 1064 nm combined with suitable transparent overlay, a sacrificial layer of graphite, and copper grid. Laser pulses at different energy densities which generates pressure pulses up to 10 GPa on the surface was focused through the confinement medium, ablating the copper grid to create plasma and transferring the grid pattern onto the NiTi surface. Scanning electron microscope (SEM) and optical microscope images of square pattern with different sizes were studied. One dimensional profile analysis shows that the depth of the patterned sample initially increase linearly with the laser energy until 125 mJ/pulse where the plasma further absorbs and reflects the laser beam. In addition, light the microscope image show that the surface of NiTi alloy was damaged due to the high power laser energy which removes the graphite layer.

Free energy landscape of dissociative adsorption of methane on ideal and defected graphene from ab initio simulations

NASA Astrophysics Data System (ADS)

Wlazło, M.; Majewski, J. A.

2018-03-01

We study the dissociative adsorption of methane at the surface of graphene. Free energy profiles, which include activation energies for different steps of the reaction, are computed from constrained ab initio molecular dynamics. At 300 K, the reaction barriers are much lower than experimental bond dissociation energies of gaseous methane, strongly indicating that the graphene surface acts as a catalyst of methane decomposition. On the other hand, the barriers are still much higher than on the nickel surface. Methane dissociation therefore occurs at a higher rate on nickel than on graphene. This reaction is a prerequisite for graphene growth from a precursor gas. Thus, the growth of the first monolayer should be a fast and efficient process while subsequent layers grow at a diminished rate and in a more controllable manner. Defects may also influence reaction energetics. This is evident from our results, in which simple defects (Stone-Wales defect and nitrogen substitution) lead to different free energy landscapes at both dissociation and adsorption steps of the process.

Plans for a sensitivity analysis of bridge-scour computations

USGS Publications Warehouse

Dunn, David D.; Smith, Peter N.

1993-01-01

Plans for an analysis of the sensitivity of Level 2 bridge-scour computations are described. Cross-section data from 15 bridge sites in Texas are modified to reflect four levels of field effort ranging from no field surveys to complete surveys. Data from United States Geological Survey (USGS) topographic maps will be used to supplement incomplete field surveys. The cross sections are used to compute the water-surface profile through each bridge for several T-year recurrence-interval design discharges. The effect of determining the downstream energy grade-line slope from topographic maps is investigated by systematically varying the starting slope of each profile. The water-surface profile analyses are then used to compute potential scour resulting from each of the design discharges. The planned results will be presented in the form of exceedance-probability versus scour-depth plots with the maximum and minimum scour depths at each T-year discharge presented as error bars.

Quantifying mesoscale eddies in the Lofoten Basin

NASA Astrophysics Data System (ADS)

Raj, R. P.; Johannessen, J. A.; Eldevik, T.; Nilsen, J. E. Ø.; Halo, I.

2016-07-01

The Lofoten Basin is the most eddy rich region in the Norwegian Sea. In this paper, the characteristics of these eddies are investigated from a comprehensive database of nearly two decades of satellite altimeter data (1995-2013) together with Argo profiling floats and surface drifter data. An automated method identified 1695/1666 individual anticyclonic/cyclonic eddies in the Lofoten Basin from more than 10,000 altimeter-based eddy observations. The eddies are found to be predominantly generated and residing locally. The spatial distributions of lifetime, occurrence, generation sites, size, intensity, and drift of the eddies are studied in detail. The anticyclonic eddies in the Lofoten Basin are the most long-lived eddies (>60 days), especially in the western part of the basin. We reveal two hotspots of eddy occurrence on either side of the Lofoten Basin. Furthermore, we infer a cyclonic drift of eddies in the western Lofoten Basin. Barotropic energy conversion rates reveals energy transfer from the slope current to the eddies during winter. An automated colocation of surface drifters trapped inside the altimeter-based eddies are used to corroborate the orbital speed of the anticyclonic and cyclonic eddies. Moreover, the vertical structure of the altimeter-based eddies is examined using colocated Argo profiling float profiles. Combination of altimetry, Argo floats, and surface drifter data is therefore considered to be a promising observation-based approach for further studies of the role of eddies in transport of heat and biomass from the slope current to the Lofoten Basin.

Trajectories and energy transfer of saltating particles onto rock surfaces : application to abrasion and ventifact formation on Earth and Mars

NASA Technical Reports Server (NTRS)

Bridges, Nathan T.; Phoreman, James; White, Bruce R.; Greeley, Ronald; Eddlemon, Eric E.; Wilson, Gregory R.; Meyer, Christine J.

2005-01-01

The interaction between saltating sand grains and rock surfaces is assessed to gauge relative abrasion potential as a function of rock shape, wind speed, grain size, and planetary environment. Many kinetic energy height profiles for impacts exhibit a distinctive increase, or kink, a few centimeters above the surface, consistent with previous field, wind tunnel, and theoretical investigations. The height of the kink observed in natural and wind tunnel settings is greater than predictions by a factor of 2 or more, probably because of enhanced bouncing off hard ground surfaces. Rebounded grains increase the effective flux and relative kinetic energy for intermediate slope angles. Whether abrasion occurs, as opposed to simple grain impact with little or no mass lost from the rock, depends on whether the grain kinetic energy (EG) exceeds a critical value (EC), as well as the flux of grains with energies above EC. The magnitude of abrasion and the shape change of the rock over time depends on this flux and the value of EG > EC. Considering the potential range of particle sizes and wind speeds, the predicted kinetic energies of saltating sand hitting rocks overlap on Earth and Mars. However, when limited to the most likely grain sizes and threshold conditions, our results agree with previous work and show that kinetic energies are about an order of magnitude greater on Mars.

Surface assessment and modification of concrete using abrasive blasting

NASA Astrophysics Data System (ADS)

Millman, Lauren R.

Composite systems are applied to concrete substrates to strengthen and extend the service life. Successful restoration or rehabilitation requires surface preparation prior to the application of the overlay. Surface coatings, waterproofing systems, and other external surface applications also require surface preparation prior to application. Abrasive blast media is often used to clean and uniformly roughen the substrate. The appropriate surface roughness is necessary to facilitate a strong bond between the existing substrate and overlay. Thus, surface modification using abrasive blast media (sand and dry ice), their respective environmental effects, surface roughness characterization prior to and after blasting, and the adhesion between the substrate and overlay are the focus of this dissertation. This dissertation is comprised of an introduction, a literature review, and four chapters, the first of which addresses the environmental effects due to abrasive blasting using sand, water, and dry ice. The assessment considered four response variables: carbon dioxide (CO2) emissions, fuel and energy consumption, and project duration. The results indicated that for sand blasting and water jetting, the primary factor contributing to environmental detriment was CO22 emissions from vehicular traffic near the construction site. The second chapter is an analysis of the International Concrete Repair Institute's (ICRI) concrete surface profiles (CSPs) using 3-D optical profilometry. The primary objective was to evaluate the suitability of approximating the 3-D surface (areal) parameters with those extracted from 2-D (linear) profiles. Four profile directions were considered: two diagonals, and lines parallel and transverse to the longitudinal direction of the mold. For any CSP mold, the estimation of the 3-D surface roughness using a 2-D linear profile resulted in underestimation and overestimation errors exceeding 50%, demonstrating the inadequacy of 2-D linear profiles to approximate the 3-D concrete surface profiles. The errors were reduced when a weighted average of the four linear profiles approximated the corresponding 3-D parameter. The following chapter considers the parametric and sensitivity of concrete surface topography measurements. The weighted average of the four 2-D profiles consistently resulted in underestimation of the corresponding 3-D parameters: the dispersion of surface elevations (Sq) and the roughness (Sa). Results indicated the 3-D parameter, Sq, had the least sensitivity to data point reduction. The final chapter investigated surface modification using dry ice and sand blasting. The overall objective was to evaluate the change in the 3-D surface roughness (Sa) following blasting as functions of mix design and as induced by freeze-thaw cycling, and to compare the results obtained using dry ice with those obtained using sand as the blasting media. In general, sand blasting produced larger changes in Sa compared to dry ice blasting for the concrete mix designs considered. The primary mechanism responsible for altering the surface topography of the concrete was the scaling of the superficial cement paste layer on the exposed surface, which was due to freeze-thaw cycling. The largest relative change in roughness following blasting occurred in the control samples, which had not undergone freeze-thaw cycling.

NEXAFS Depth Profiling of Surface Segregation in Block Copolymer Thin Films

DTIC Science & Technology

2010-01-01

a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. a...and compared with those of homopolymer and random copolymer controls . The carbon atoms from the relatively high surface energy phenyl groups were...e Chimica Industriale and UdR Pisa INSTM, Universita di Pisa, 56126 Pisa, Italy, ^Department of Materials, University of California, Santa Barbara

Energy storage considerations for a robotic Mars surface sampler

NASA Technical Reports Server (NTRS)

Odonnell, Patricia M.; Cataldo, Robert L.; Gonzalez-Sanabria, Olga D.

1988-01-01

A Mars Rover capable of obtaining surface samples will need a power system for motive power and to power scientific instrumentation. Several different power systems are considered along with a discussion of the location options. The weight and volume advantages of the different systems are described for a particular power profile. The conclusions are that a Mars Rover Sample Return Mission and Extended Mission can be accomplished utilizing photovoltaics and electrochemical storage.

Analysis of the Surface of Deposited Copper After Electroerosion Treatment

NASA Astrophysics Data System (ADS)

Ablyaz, T. R.; Simonov, M. Yu.; Shlykov, E. S.

2018-03-01

An electron microscope analysis of the surface of deposited copper is performed after a profiling-piercing electroerosion treatment. The deposited copper is treated with steel, duralumin, and copper electrode tools at different pulse energies. The treatment with the duralumin electrode produces on the treated surface a web-like structure and cubic-morphology polyhedral dimples about 10 μm in size. The main components of the surface treated with the steel electrode are developed polyhedral dimples with a size of 10 - 50 μm. After the treatment with the copper electrode the main components of the treated surface are large polyhedral dimples about 30 - 80 μm in size.

Calculation of recoil implantation profiles using known range statistics

NASA Technical Reports Server (NTRS)

Fung, C. D.; Avila, R. E.

1985-01-01

A method has been developed to calculate the depth distribution of recoil atoms that result from ion implantation onto a substrate covered with a thin surface layer. The calculation includes first order recoils considering projected range straggles, and lateral straggles of recoils but neglecting lateral straggles of projectiles. Projectile range distributions at intermediate energies in the surface layer are deduced from look-up tables of known range statistics. A great saving of computing time and human effort is thus attained in comparison with existing procedures. The method is used to calculate recoil profiles of oxygen from implantation of arsenic through SiO2 and of nitrogen from implantation of phosphorus through Si3N4 films on silicon. The calculated recoil profiles are in good agreement with results obtained by other investigators using the Boltzmann transport equation and they also compare very well with available experimental results in the literature. The deviation between calculated and experimental results is discussed in relation to lateral straggles. From this discussion, a range of surface layer thickness for which the method applies is recommended.

Using Tropospheric Ozone Profiles and Surface Data (2004 - 2012) to Determine Background Ozone Levels in Houston, Texas

NASA Astrophysics Data System (ADS)

Spychala, M. D.; Morris, G. A.; Lefer, B. L.; Rappenglueck, B.; Cohan, D. S.; zhou, W.

2012-12-01

The Tropospheric Ozone Pollution Project (TOPP) at Rice University (2004 - 2006) and the University of Houston (2006 - present) has gathered > 400 profiles of ozone, temperature, pressure, and relative humidity, and > 250 of those also have wind speed and wind direction near the core of the City of Houston, Texas. Houston continues to be plagued with difficulty in coming into compliance with EPA National Ambient Air Quality Standards (NAAQS) due to a combination of its geographic location, large commuter population, significant petrochemical and energy production, and favorable weather patterns. An outstanding question remains the relative partitioning of ozone between local and remote, anthropogenic and natural sources. In this presentation, we use TOPP ozone profiles to determine a "background" ozone concentration and compare this measure with surface monitor "background" ozone as determined from upwind and downwind Continuous Air Monitoring Stations (CAMS) in an effort to further our understanding of this partitioning. For periods studied with the Community Multiscale Air Quality (CMAQ) Model, we also compare the sonde and surface "background" ozone with that suggested by the model.

Dry texturing of solar cells

DOEpatents

Sopori, B.L.

1994-10-25

A textured backside of a semiconductor device for increasing light scattering and absorption in a semiconductor substrate is accomplished by applying infrared radiation to the front side of a semiconductor substrate that has a metal layer deposited on its backside in a time-energy profile that first produces pits in the backside surface and then produces a thin, highly reflective, low resistivity, epitaxial alloy layer over the entire area of the interface between the semiconductor substrate and a metal contact layer. The time-energy profile includes ramping up to a first energy level and holding for a period of time to create the desired pit size and density and then rapidly increasing the energy to a second level in which the entire interface area is melted and alloyed quickly. After holding the second energy level for a sufficient time to develop the thin alloy layer over the entire interface area, the energy is ramped down to allow epitaxial crystal growth in the alloy layer. The result is a textured backside on an optically reflective, low resistivity alloy interface between the semiconductor substrate and the metal electrical contact layer. 9 figs.

Dry texturing of solar cells

DOEpatents

Sopori, Bhushan L.

1994-01-01

A textured backside of a semiconductor device for increasing light scattering and absorption in a semiconductor substrate is accomplished by applying infrared radiation to the front side of a semiconductor substrate that has a metal layer deposited on its backside in a time-energy profile that first produces pits in the backside surface and then produces a thin, highly reflective, low resistivity, epitaxial alloy layer over the entire area of the interface between the semiconductor substrate and a metal contact layer. The time-energy profile includes ramping up to a first energy level and holding for a period of time to create the desired pit size and density and then rapidly increasing the energy to a second level in which the entire interface area is melted and alloyed quickly. After holding the second energy level for a sufficient time to develop the thin alloy layer over the entire interface area, the energy is ramped down to allow epitaxial crystal growth in the alloy layer. The result is a textured backside an optically reflective, low resistivity alloy interface between the semiconductor substrate and the metal electrical contact layer.

Heat and turbulent kinetic energy budgets for surface layer cooling induced by the passage of Hurricane Frances (2004)

NASA Astrophysics Data System (ADS)

Huang, Peisheng; Sanford, Thomas B.; Imberger, JöRg

2009-12-01

Heat and turbulent kinetic energy budgets of the ocean surface layer during the passage of Hurricane Frances were examined using a three-dimensional hydrodynamic model. In situ data obtained with the Electromagnetic-Autonomous Profiling Explorer (EM-APEX) floats were used to set up the initial conditions of the model simulation and to compare to the simulation results. The spatial heat budgets reveal that during the hurricane passage, not only the entrainment in the bottom of surface mixed layer but also the horizontal water advection were important factors determining the spatial pattern of sea surface temperature. At the free surface, the hurricane-brought precipitation contributed a negligible amount to the air-sea heat exchange, but the precipitation produced a negative buoyancy flux in the surface layer that overwhelmed the instability induced by the heat loss to the atmosphere. Integrated over the domain within 400 km of the hurricane eye on day 245.71 of 2004, the rate of heat anomaly in the surface water was estimated to be about 0.45 PW (1 PW = 1015 W), with about 20% (0.09 PW in total) of this was due to the heat exchange at the air-sea interface, and almost all the remainder (0.36 PW) was downward transported by oceanic vertical mixing. Shear production was the major source of turbulent kinetic energy amounting 88.5% of the source of turbulent kinetic energy, while the rest (11.5%) was attributed to the wind stirring at sea surface. The increase of ocean potential energy due to vertical mixing represented 7.3% of the energy deposited by wind stress.

A continuum model for meltwater flow through compacting snow

NASA Astrophysics Data System (ADS)

Meyer, Colin R.; Hewitt, Ian J.

2017-12-01

Meltwater is produced on the surface of glaciers and ice sheets when the seasonal energy forcing warms the snow to its melting temperature. This meltwater percolates into the snow and subsequently runs off laterally in streams, is stored as liquid water, or refreezes, thus warming the subsurface through the release of latent heat. We present a continuum model for the percolation process that includes heat conduction, meltwater percolation and refreezing, as well as mechanical compaction. The model is forced by surface mass and energy balances, and the percolation process is described using Darcy's law, allowing for both partially and fully saturated pore space. Water is allowed to run off from the surface if the snow is fully saturated. The model outputs include the temperature, density, and water-content profiles and the surface runoff and water storage. We compare the propagation of freezing fronts that occur in the model to observations from the Greenland Ice Sheet. We show that the model applies to both accumulation and ablation areas and allows for a transition between the two as the surface energy forcing varies. The largest average firn temperatures occur at intermediate values of the surface forcing when perennial water storage is predicted.

Relaxation dynamics of femtosecond-laser-induced temperature modulation on the surfaces of metals and semiconductors

NASA Astrophysics Data System (ADS)

Levy, Yoann; Derrien, Thibault J.-Y.; Bulgakova, Nadezhda M.; Gurevich, Evgeny L.; Mocek, Tomáš

2016-06-01

Formation of laser-induced periodic surface structures (LIPSS) is a complicated phenomenon which involves periodic spatial modulation of laser energy absorption on the irradiated surface, transient changes in optical response, surface layer melting and/or ablation. The listed processes strongly depend on laser fluence and pulse duration as well as on material properties. This paper is aimed at studying the spatiotemporal evolution of a periodic modulation of the deposited laser energy, once formed upon irradiation of metal (Ti) and semiconductor (Si) surfaces. Assuming that the incoming laser pulse interferes with a surface electromagnetic wave, the resulting sinusoidal modulation of the absorbed laser energy is introduced into a two-dimensional two-temperature model developed for titanium and silicon. Simulations reveal that the lattice temperature modulation on the surfaces of both materials following from the modulated absorption remains significant for longer than 50 ps after the laser pulse. In the cases considered here, the partially molten phase exists 10 ps in Ti and more than 50 ps in Si, suggesting that molten matter can be subjected to temperature-driven relocation toward LIPSS formation, due to the modulated temperature profile on the material surfaces. Molten phase at nanometric distances (nano-melting) is also revealed.

Flux threshold determination for tungsten nano-fuzz formation using an 80 eV He-ion beam

NASA Astrophysics Data System (ADS)

Meyer, Fred W.; Bannister, Mark E.; Parish, Chad M.

2017-10-01

At the ORNL Multicharged Ion Research Facility (MIRF), we have extended our investigation of flux thresholds for He-ion induced nano-fuzz formation on hot tungsten surfaces down to plasma-edge-relevant energies of 80 eV. We measured the size of the incident ion beam by accurate flux-profile measurements, and the size of the region where tungsten nano-fuzz was formed by post-exposure SEM surface analysis and real-time monitoring of the hot W surface-emissivity change throughout the beam exposure. If tungsten nano-fuzz formation had a fluence threshold, the size of the observed nano-fuzz region would be expected to increase with exposure time, eventually filling the entire ion beam spot. Instead, we found that the region of nano-fuzz formation (1) was always smaller than the beam spot itself and (2) did not increase in size with time, i.e. with accumulated He ion fluence. By comparison of the flux profile and the spatial extent of the fuzz region we determined a flux threshold of 9.5 +-3×1019/m2s at 80 eV He ion impact energy. We show that the observed flux-threshold energy dependence for nano-fuzz formation, which we have now mapped out from 80 eV to 8.5 keV, is well reproduced by the combined energy dependences of He-ion reflection, He-ion range and target-damage creation, determined using SRIM. Research sponsored by the LDRD program at ORNL, managed by UT-Battelle for the USDOE, and by the DOE OFES.

Near-surface energy transfers from internal tide beams to smaller vertical scale motions

NASA Astrophysics Data System (ADS)

Chou, S.; Staquet, C.; Carter, G. S.; Luther, D. S.

2016-02-01

Mechanical energy capable of causing diapycnal mixing in the ocean is transferred to the internal wave field when barotropic tides pass over underwater topography and generate internal tides. The resulting internal tide energy is confined in vertically limited structures, or beams. As internal tide beams (ITBs) propagate through regions of non-uniform stratification in the upper ocean, wave energy can be scattered through multiple reflections and refractions, be vertically trapped, or transferred to non-tidal frequencies through different nonlinear processes. Various observations have shown that ITBs are no longer detectable in horizontal kinetic energy beyond the first surface reflection. Importantly, this implies that some of the internal tide energy no longer propagates in to the abyssal ocean and consequently will not be available to maintain the density stratification. Using the NHM, a nonlinear and nonhydrostatic model based on the MITgcm, simulations of an ITB propagating up to the sea surface are examined in order to quantify the transformation of ITB energy to other motions. We compare and contrast the transformations enabled by idealized, smoothly-varying stratification with transformations enabled by realistic stratification containing a broad-band vertical wavenumber spectrum of variations. Preliminary two-dimensional results show that scattering due to small-scale structure in realistic stratification profiles from Hawaii can lead to energy being vertically trapped near the surface. Idealized simulations of "locally" generated internal solitary waves are analyzed in terms of energy flux transfers from the ITB to solitary waves, higher harmonics, and mean flow. The amount of internal tide energy which propagates back down after near-surface reflection of the ITB in different environments is quantified.

Step-induced deconstruction and step-height evolution of the Au(110) surface

NASA Astrophysics Data System (ADS)

Romahn, U.; von Blanckenhagen, P.; Kroll, C.; Göpel, W.

1993-05-01

We use temperature-dependent high-resolution low-energy electron diffraction and spot-profile analysis low-energy electron diffraction to study the Au(110) surface at room temperature up to 786 K. The experimental data were analyzed within the framework of the kinematic theory. Oscillations were determined of the positions of half order and fundamental Bragg peaks as well as of the full width at half maximum of the specular peak as a function of perpendicular momentum transfer. Evidence of mono- atomic steps occurring in the [001] direction was found below and around the (2×1)-->(1×1) transition at Tc. Above Tc, the surface gets smoother in the [001] direction; at the roughening temperature, TR, the evolution of multiple-height steps starts in both symmetry directions.

Suppressing breakers with polar oil films: Using an epic sea rescue to model wave energy budgets

NASA Astrophysics Data System (ADS)

Cox, Charles S.; Zhang, Xin; Duda, Timothy F.

2017-02-01

Oil has been used to still stormy seas for centuries, but the mechanisms are poorly understood. Here we examine the processes by using quantitative information from a remarkable 1883 sea rescue where oil was used to reduce large breakers during a storm. Modeling of the oil film's extent and waves under the film suggests that large breakers were suppressed by a reduction of wind energy input. Modification of surface roughness by the film is hypothesized to alter the wind profile above the sea and the energy flow. The results are central to understanding air-sea momentum exchange, including its role in such processes as cyclone growth and storm surge, although they address only one aspect of the complex problem of wind interaction with the ocean surface.

LASER ALTIMETER CANOPY HEIGHT PROFILES: METHODS AND VALIDATION FOR CLOSED-CANOPY, BROADLEAF FORESTS. (R828309)

EPA Science Inventory

Abstract

Waveform-recording laser altimeter observations of vegetated landscapes provide a time-resolved measure of laser pulse backscatter energy from canopy surfaces and the underlying ground. Airborne laser altimeter waveform data was acquired using the Scanning Lid...

Design, fabrication and calibration of alpha particle densitometers for measuring planetary atmospheric density

NASA Technical Reports Server (NTRS)

Sellers, B.; Hunerwadel, J. L.; Hanser, F. A.

1972-01-01

An alpha particle densitometer was developed for possible application to measurement of the atmospheric density-altitude profile on Martian entry. The device uses an Am-241 radioactive-foil source, which emits a distributed energy spectrum, located about 25 to 75 cm from a semiconductor detector. System response - defined as the number of alphas per second reaching the detector with energy above a fixed threshold - is given for Ar and CO2. The altitude profile of density measurement accuracy is given for a pure CO2 atmosphere with 5 mb surface pressure. The entire unit, including dc-dc converters, requires less than 350 milliwatts of power from +28 volts, weighs about 0.85 lb and occupies less than 15 cubic inches volume.

Energy loss and inelastic diffraction of fast atoms at grazing incidence

NASA Astrophysics Data System (ADS)

Roncin, Philippe; Debiossac, Maxime; Oueslati, Hanene; Raouafi, Fayçal

2018-07-01

The diffraction of fast atoms at grazing incidence on crystal surfaces (GIFAD) was first interpreted only in terms of elastic diffraction from a perfectly periodic rigid surface with atoms fixed at equilibrium positions. Recently, a new approach has been proposed, referred here as the quantum binary collision model (QBCM). The QBCM takes into account both the elastic and inelastic momentum transfers via the Lamb-Dicke probability. It suggests that the shape of the inelastic diffraction profiles are log-normal distributions with a variance proportional to the nuclear energy loss deposited on the surface. For keV Neon atoms impinging on a LiF(0 0 1) surface under an incidence angle θ , the predictions of the QBCM in its analytic version are compared with numerical trajectory simulations. Some of the assumptions such as the planar continuous form, the possibility to neglect the role of lithium atoms and the influence of temperature are investigated. A specific energy loss dependence ΔE ∝θ7 is identified in the quasi-elastic regime merging progressively to the classical onset ΔE ∝θ3 . The ratio of these two predictions highlights the role of quantum effects in the energy loss.

Structural analysis of the outermost hair surface using TOF-SIMS with gas cluster ion beam sputtering.

PubMed

Lshikawa, Kazutaka; Okamoto, Masayuki; Aoyagi, Satoka

2016-06-28

A hair cuticle, which consists of flat overlapping scales that surround the hair fiber, protects inner tissues against external stimuli. The outermost surface of the cuticle is covered with a thin membrane containing proteins and lipids called the epicuticle. In a previous study, the authors conducted a depth profile analysis of a hair cuticle's amino acid composition to characterize its multilayer structure. Time-of-flight secondary ion mass spectrometry with a bismuth primary ion source was used in combination with the C60 sputtering technique for the analysis. It was confirmed that the lipids and cysteine-rich layer exist on the outermost cuticle surface, which is considered to be the epicuticle, though the detailed structure of the epicuticle has not been clarified. In this study, depth profile analysis of the cuticle surface was conducted using the argon gas cluster ion beam (Ar-GCIB) sputtering technique, in order to characterize the structure of the epicuticle. The shallow depth profile of the cuticle surface was investigated using an Ar-GCIB impact energy of 5 keV. Compared to the other amino acid peaks rich in the epicuticle, the decay of 18-methyleicosanic acid (18-MEA) thiolate peak was the fastest. This result suggests that the outermost surface of the hair is rich in 18-MEA. In conclusion, our results indicate that the outermost surfaces of cuticles have a multilayer (lipid and protein layers), which is consistent with the previously proposed structure.

Distribution of free carriers near heavily-doped epitaxial surfaces of n-type Ge(100) upon HF and HCl treatments

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

Park, S. J.; Bolotov, L.; Uchida, N.

2015-10-15

Carrier distributions near n-type epitaxially-grown Ge(100) surfaces with high impurity concentrations (1 × 10{sup 20} cm{sup −3}) were studied using high resolution electron energy loss spectroscopy (HREELS) upon surface treatments in aqueous solutions of HF and HCl. After surface treatments with HCl and HF, the molecular vibration modes distinctly showed either chloride or hydride terminations of Ge surfaces with negligible oxidation. The free-carrier concentration profile was inferred from the conduction band plasmon measurements as a function of the incident electron energies employing a dielectric theory simulation with a 4-layer structure and an effective electron mass of 0.02m{sub 0}. A carrier-freemore » layer of 40 and 24 Å were derived for HCl- and HF-treated Ge(100), respectively. The surface band bending was estimated to be 0.32 eV for HF-treated Ge. HCl-treated Ge surfaces showed a band bending of 0.91 eV attributed to the strong effect of the surface Cl-Ge dipole.« less

Heat transport in an anharmonic crystal

NASA Astrophysics Data System (ADS)

Acharya, Shiladitya; Mukherjee, Krishnendu

2018-04-01

We study transport of heat in an ordered, anharmonic crystal in the form of slab geometry in three dimensions. Apart from attaching baths of Langevin type to two extreme surfaces, we also attach baths of same type to the intermediate surfaces of the slab. Since the crystal is uninsulated, it exchanges energy with the intermediate heat baths. We find that both Fourier’s law of heat conduction and the Newton’s law of cooling hold to leading order in anharmonic coupling. The leading behavior of the temperature profile is exponentially falling from high to low temperature surface of the slab. As the anharmonicity increases, profiles fall more below the harmonic one in the log plot. In the thermodynamic limit thermal conductivity remains independent of the environment temperature and its leading order anharmonic contribution is linearly proportional to the temperature change between the two extreme surfaces of the slab. A fast crossover from one-dimensional (1D) to three-dimensional (3D) behavior of the thermal conductivity is observed in the system.

Porosity and thickness effect of porous silicon layer on photoluminescence spectra

NASA Astrophysics Data System (ADS)

Husairi, F. S.; Eswar, K. A.; Guliling, Muliyadi; Khusaimi, Z.; Rusop, M.; Abdullah, S.

2018-05-01

The porous silicon nanostructures was prepared by electrochemical etching of p-type silicon wafer. Porous silicon prepared by using different current density and fix etching time with assistance of halogen lamp. The physical structure of porous silicon measured by the parameters used which know as experimental factor. In this work, we select one of those factors to correlate which optical properties of porous silicon. We investigated the surface morphology by using Surface Profiler (SP) and photoluminescence using Photoluminescence (PL) spectrometer. Different physical characteristics of porous silicon produced when current density varied. Surface profiler used to measure the thickness of porous and the porosity calculated using mass different of silicon. Photoluminescence characteristics of porous silicon depend on their morphology because the size and distribution of pore its self will effect to their exciton energy level. At J=30 mA/cm2 the shorter wavelength produced and it followed the trend of porosity with current density applied.

Hα line shape in front of the limiter in the HT-6M tokamak

NASA Astrophysics Data System (ADS)

Wan, Baonian; Li, Jiangang; Luo, Jiarong; Xie, Jikang; Wu, Zhenwei; Zhang, Xianmei; HT-6M Group

1999-11-01

The Hα line shape in front of the limiter in the HT-6M tokamak is analysed by multi-Gaussian fitting. The energy distribution of neutral hydrogen atoms reveals that Hα radiation is contributed by Franck-Condon atoms, atoms reflected at the limiter surface and charge exchange. Multi-Gaussian fitting of the Hα spectral profile indicates contributions of 60% from reflection particles and 40% from molecule dissociation to recycling. Ion temperatures in central regions are obtained from the spectral width of charge exchange components. Dissociation of hydrogen molecules and reflection of particles at the limiter surface are dominant in edge recycling. Reduction of particle reflection at the limiter surface is important for controlling edge recycling. The measured profiles of neutral hydrogen atom density are reproduced by a particle continuity equation and a simplified one dimensional Monte Carlo simulation code.

Wrapping conformations of a polymer on a curved surface

NASA Astrophysics Data System (ADS)

Lin, Cheng-Hsiao; Tsai, Yan-Chr; Hu, Chin-Kun

2007-03-01

The conformation of a polymer on a curved surface is high on the agenda for polymer science. We assume that the free energy of the system is the sum of bending energy of the polymer and the electrostatic attraction between the polymer and surface. As is also assumed, the polymer is very stiff with an invariant length for each segment so that we can neglect its tensile energy and view its length as a constant. Based on the principle of minimization of free energy, we apply a variation method with a locally undetermined Lagrange multiplier to obtain a set of equations for the polymer conformation in terms of local geometrical quantities. We have obtained some numerical solutions for the conformations of the polymer chain on cylindrical and ellipsoidal surfaces. With some boundary conditions, we find that the free energy profiles of polymer chains behave differently and depend on the geometry of the surface for both cases. In the former case, the free energy of each segment distributes within a narrower range and its value per unit length oscillates almost periodically in the azimuthal angle. However, in the latter case the free energy distributes in a wider range with larger value at both ends and smaller value in the middle of the chain. The structure of a polymer wrapping around an ellipsoidal surface is apt to dewrap a polymer from the endpoints. The dependence of threshold lengths for a polymer on the initially anchored positions is also investigated. With initial conditions, the threshold wrapping length is found to increase with the electrostatic attraction strength for the ellipsoidal surface case. When a polymer wraps around a sphere surface, the threshold length increases monotonically with the radius without the self-intersection configuration for a polymer. We also discuss potential applications of the present theory to DNA/protein complex and further researches on DNA on the curved surface.

Studying urban land-atmospheric interactions by coupling an urban canopy model with a single column atmospheric models

NASA Astrophysics Data System (ADS)

Song, J.; Wang, Z.

2013-12-01

Studying urban land-atmospheric interactions by coupling an urban canopy model with a single column atmospheric models Jiyun Song and Zhi-Hua Wang School of Sustainable Engineering and the Built Environment, Arizona State University, PO Box 875306, Tempe, AZ 85287-5306 Landuse landcover changes in urban area will modify surface energy budgets, turbulent fluxes as well as dynamic and thermodynamic structures of the overlying atmospheric boundary layer (ABL). In order to study urban land-atmospheric interactions, we coupled a single column atmospheric model (SCM) to a cutting-edge single layer urban canopy model (SLUCM). Modification of surface parameters such as the fraction of vegetation and engineered pavements, thermal properties of building and pavement materials, and geometrical features of street canyon, etc. in SLUCM dictates the evolution of surface balance of energy, water and momentum. The land surface states then provide lower boundary conditions to the overlying atmosphere, which in turn modulates the modification of ABL structure as well as vertical profiles of temperature, humidity, wind speed and tracer gases. The coupled SLUCM-SCM model is tested against field measurements of surface layer fluxes as well as profiles of temperature and humidity in the mixed layer under convective conditions. After model test, SLUCM-SCM is used to simulate the effect of changing urban land surface conditions on the evolution of ABL structure and dynamics. Simulation results show that despite the prescribed atmospheric forcing, land surface states impose significant impact on the physics of the overlying vertical atmospheric layer. Overall, this numerical framework provides a useful standalone modeling tool to assess the impacts of urban land surface conditions on the local hydrometeorology through land-atmospheric interactions. It also has potentially far-reaching implications to urban ecohydrological services for cities under future expansion and climate challenges.

Towards nanometric resolution in multilayer depth profiling: a comparative study of RBS, SIMS, XPS and GDOES.

PubMed

Escobar Galindo, Ramón; Gago, Raul; Duday, David; Palacio, Carlos

2010-04-01

An increasing amount of effort is currently being directed towards the development of new functionalized nanostructured materials (i.e., multilayers and nanocomposites). Using an appropriate combination of composition and microstructure, it is possible to optimize and tailor the final properties of the material to its final application. The analytical characterization of these new complex nanostructures requires high-resolution analytical techniques that are able to provide information about surface and depth composition at the nanometric level. In this work, we comparatively review the state of the art in four different depth-profiling characterization techniques: Rutherford backscattering spectroscopy (RBS), secondary ion mass spectrometry (SIMS), X-ray photoelectron spectroscopy (XPS) and glow discharge optical emission spectroscopy (GDOES). In addition, we predict future trends in these techniques regarding improvements in their depth resolutions. Subnanometric resolution can now be achieved in RBS using magnetic spectrometry systems. In SIMS, the use of rotating sample holders and oxygen flooding during analysis as well as the optimization of floating low-energy ion guns to lower the impact energy of the primary ions improves the depth resolution of the technique. Angle-resolved XPS provides a very powerful and nondestructive technique for obtaining depth profiling and chemical information within the range of a few monolayers. Finally, the application of mathematical tools (deconvolution algorithms and a depth-profiling model), pulsed sources and surface plasma cleaning procedures is expected to greatly improve GDOES depth resolution.

Elastomeric member for energy storage device

DOEpatents

Hoppie, Lyle O.; Chute, Richard

1985-01-01

An energy storage device (10) is disclosed consisting of a stretched elongated elastomeric member (16), disposed within a tubular housing (14), which elastomeric member (16) is adapted to be torsionally stressed to store energy. The elastomeric member (16) is configured in the relaxed state with a uniform diameter body section, transition end sections, and is attached to rigid end piece assemblies (22, 24) of a lesser diameter. The profile and deflection characteristic of the transition sections (76, 78) are such that upon stretching of the member, a substantially uniform diameter assembly results to minimize the required volume of the surrounding housing (14). During manufacture, woven wire mesh sleeves (26, 28) are forced against a forming surface and bonded to the associated transition section (76, 78) to provide the correct profile and helix angle. Each sleeve (26, 28) contracts with the contraction of the associated transition section to maintain the bond therebetween.

Virtual gonio-spectrophotometer for validation of BRDF designs

NASA Astrophysics Data System (ADS)

Mihálik, Andrej; Ďurikovič, Roman

2011-10-01

Measurement of the appearance of an object consists of a group of measurements to characterize the color and surface finish of the object. This group of measurements involves the spectral energy distribution of propagated light measured in terms of reflectance and transmittance, and the spatial energy distribution of that light measured in terms of the bidirectional reflectance distribution function (BRDF). In this article we present the virtual gonio-spectrophotometer, a device that measures flux (power) as a function of illumination and observation. Virtual gonio-spectrophotometer measurements allow the determination of the scattering profile of specimens that can be used to verify the physical characteristics of the computer model used to simulate the scattering profile. Among the characteristics that we verify is the energy conservation of the computer model. A virtual gonio-spectrophotometer is utilized to find the correspondence between industrial measurements obtained from gloss meters and the parameters of a computer reflectance model.

Parametric investigation of nano-gap thermophotovoltaic energy conversion

NASA Astrophysics Data System (ADS)

Lau, Japheth Z.-J.; Bong, Victor N.-S.; Wong, Basil T.

2016-03-01

Nano-gap thermophotovoltaic energy converters have the potential to be excellent generators of electrical power due to the near-field radiative effect which enhances the transfer of energy from one medium to another. However, there is still much to learn about this new form of energy converter. This paper seeks to investigate three parameters that affect the performance of nano-gap thermophotovoltaic devices: the emitter material, the thermophotovoltaic cell material, and the cell thickness. Furthermore, the temperature profiles in insulated thin films (cells exposed to below-band gap near-field radiation) are analysed. It was discovered that an effective emitter material is one that has a high generalised emissivity value and is also able to couple with the TPV cell material through surface polaritons while a cell material's electrical properties and its thickness has heavy bearing on its internal quantum efficiency. In regards to the temperature profile, the heat-flux absorbed causes a rise in temperature across the thin film, but is insufficient to generate a temperature gradient across the film.

Perspective on the reactions between F– and CH3CH2F: The free energy landscape of the E2 and SN2 reaction channels

PubMed Central

Ensing, Bernd; Klein, Michael L.

2005-01-01

Recently, we computed the 3D free energy surface of the base-induced elimination reaction between F– and CH3CH2F by using a powerful technique within Car–Parrinello molecular dynamics simulation. Here, the set of three order parameters is expanded to six, which allows the study of the competing elimination and substitution reactions simultaneously. The power of the method is exemplified by the exploration of the six-dimensional free energy landscape, sampling, and mapping out the eight stable states as well as the connecting bottlenecks. The free energy profile and barrier along the E2 and SN2 reaction channels are refined by using umbrella sampling. The two mechanisms do not share a common “E2C-like” transition state. Comparison with the zero temperature profiles shows a particularly significant entropy contribution to the SN2 channel. PMID:15863622

Inversion algorithms for the microwave remote sensing of soil moisture. Experiments with swept frequency microwaves

NASA Technical Reports Server (NTRS)

Hancock, G. D.; Waite, W. P.

1984-01-01

Two experiments were performed employing swept frequency microwaves for the purpose of investigating the reflectivity from soil volumes containing both discontinuous and continuous changes in subsurface soil moisture content. Discontinuous moisture profiles were artificially created in the laboratory while continuous moisture profiles were induced into the soil of test plots by the environment of an agricultural field. The reflectivity for both the laboratory and field experiments was measured using bi-static reflectometers operated over the frequency ranges of 1.0 to 2.0 GHz and 4.0 to 8.0 GHz. Reflectivity models that considered the discontinuous and continuous moisture profiles within the soil volume were developed and compared with the results of the experiments. This comparison shows good agreement between the smooth surface models and the measurements. In particular the comparison of the smooth surface multi-layer model for continuous moisture profiles and the yield experiment measurements points out the sensitivity of the specular component of the scattered electromagnetic energy to the movement of moisture in the soil.

A fundamental approach to adhesion: Synthesis, surface analysis, thermodynamics and mechanics

NASA Technical Reports Server (NTRS)

Chen, W.; Wightman, J. P.

1979-01-01

Adherend surfaces and fractography were studied using electron spectroscopy for chemical analysis and scanning electron microscopy/energy dispersive analysis of X-rays. In addition, Auger Electron Spectroscopy with depth profiling capability was used. It is shown that contamination of adhesion systems plays an important role not only in determining initial bond strengths but also in the durability of adhesive bonds. It is concluded that the analytical techniques used to characterize and monitor such contamination.

The interfacial energetics of the oil molecules interactions with shale media using molecular dynamics simulation

NASA Astrophysics Data System (ADS)

Zhang, Z.; Wang, J.

2017-12-01

Characterizing the behavior of oil molecules in nanopore is vital to the understanding of geochemistry of hydrocarbon-bearing fluid in ultra-tight source rocks, such as shale. The heterogeneous nature of hydrocarbon system of nanoscale complicates experimental studies of oil / shale interfacial interaction. Therefore, to gain mechanistic understanding of the interplay of oil molecules in rock nanopore, molecular dynamics simulations have been applied to study the interactions of polar and non-polar oil on both calcite and kerogen surfaces. The effect of surface wetting, oil polarity, and temperature on the Gibbs free energy of adsorption have been investigated. The free energy, entropy, and enthalpy profiles have been calculated using advanced molecular dynamics method: umbrella sampling. In agreement with experiment, 1) surface with adsorbed water layer significantly reduces the oil adsorption energy on kerogen and turns the calcite surface to highly oil-repellent; 2) polar oil has overall stronger adsorption free energy than that of non-polar oil on both non-wetted calcite and kerogen surface; 3) organic interface (e.g. kerogen) exhibits stronger adsorption of oil molecules compared to inorganic one (e.g. calcite). The finding of this study indicates that oil displacement in nanopores can be enhanced by promoting the water adsorption on surface and reducing the polarity of oil on both inorganic and organic interfaces.

A novel feedback algorithm for simulating controlled dynamics and confinement in the advanced reversed-field pinch

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

Dahlin, J.-E.; Scheffel, J.

2005-06-15

In the advanced reversed-field pinch (RFP), the current density profile is externally controlled to diminish tearing instabilities. Thus the scaling of energy confinement time with plasma current and density is improved substantially as compared to the conventional RFP. This may be numerically simulated by introducing an ad hoc electric field, adjusted to generate a tearing mode stable parallel current density profile. In the present work a current profile control algorithm, based on feedback of the fluctuating electric field in Ohm's law, is introduced into the resistive magnetohydrodynamic code DEBSP [D. D. Schnack and D. C. Baxter, J. Comput. Phys. 55,more » 485 (1984); D. D. Schnack, D. C. Barnes, Z. Mikic, D. S. Marneal, E. J. Caramana, and R. A. Nebel, Comput. Phys. Commun. 43, 17 (1986)]. The resulting radial magnetic field is decreased considerably, causing an increase in energy confinement time and poloidal {beta}. It is found that the parallel current density profile spontaneously becomes hollow, and that a formation, being related to persisting resistive g modes, appears close to the reversal surface.« less

An evaluation method of the profile of plasma-induced defects based on capacitance-voltage measurement

NASA Astrophysics Data System (ADS)

Okada, Yukimasa; Ono, Kouichi; Eriguchi, Koji

2017-06-01

Aggressive shrinkage and geometrical transition to three-dimensional structures in metal-oxide-semiconductor field-effect transistors (MOSFETs) lead to potentially serious problems regarding plasma processing such as plasma-induced physical damage (PPD). For the precise control of material processing and future device designs, it is extremely important to clarify the depth and energy profiles of PPD. Conventional methods to estimate the PPD profile (e.g., wet etching) are time-consuming. In this study, we propose an advanced method using a simple capacitance-voltage (C-V) measurement. The method first assumes the depth and energy profiles of defects in Si substrates, and then optimizes the C-V curves. We applied this methodology to evaluate the defect generation in (100), (111), and (110) Si substrates. No orientation dependence was found regarding the surface-oxide layers, whereas a large number of defects was assigned in the case of (110). The damaged layer thickness and areal density were estimated. This method provides the highly sensitive PPD prediction indispensable for designing future low-damage plasma processes.

The importance of atmospheric monitoring at the Pierre Auger Observatory

NASA Astrophysics Data System (ADS)

Dawson, Bruce R.

The Pierre Auger Observatory is an ultra-high energy cosmic ray experiment employing a giant surface array of particle detectors together with telescopes to image fluorescence light from extensive air showers in the atmosphere. The atmosphere is the medium in which the incoming cosmic rays deposit their energy, and as a result we must monitor the characteristics of the atmosphere, including its density profile and light transmission properties, over the Observatory area of 3000 square kilometres.

Radial Surface Density Profiles of Gas and Dust in the Debris Disk Around 49 Ceti

NASA Technical Reports Server (NTRS)

Hughes, A. Meredith; Lieman-Sifry, Jesse; Flaherty, Kevin M.; Daley, Cail M.; Roberge, Aki; Kospal, Agnes; Moor, Attila; Kamp, Inga; Wilner, David J.; Andrews, Sean M.;

Potential energy surfaces related to the ion-molecule reaction C/sup +/ + H/sub 2/

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

Liskow, D.H.; Bender, C.F.; Schaefer, H.F. III

1974-10-01

The C/sup +/ + H/sub 2/ ion-molecule reaction has been studied by several experimental groups and appears likely to become the focal point of much experimental and theoretical activity. Ab initio self-consistent-field and configuration interaction calculations have accordingly been carried out for this system. A double zeta basis set of contracted Gaussian functions was employed and as many as 648 configurations included. For isosceles triangle configurations (C/sub 2V/ point group) the /sup 2/A/sub 1/, /sup 2/B/sub 1/, and /sup 2/B/sub 2/ potential surfaces were considered, while for linear geometries (C/sub infinity V) the /sup 2/..sigma../sup +/ and /sup 2/PI surfacesmore » were studied. For general (C/sub S/) geometry, the lowest /sup 2/A' potential surface was considered. Properties reported include minimum energy paths and energy profiles for the various processes considered. The intuitive correlation diagram of Mahan and Sloane is given qualitative reliability. Pathways to CH/sub 2//sup +/ complex formation are shown to depend crucially on the C/sub S/ potential surface.« less

Dynamic secondary ion mass spectroscopy of Au nanoparticles on Si wafer using Bi3+ as primary ion coupled with surface etching by Ar cluster ion beam: The effect of etching conditions on surface structure

NASA Astrophysics Data System (ADS)

Park, Eun Ji; Choi, Chang Min; Kim, Il Hee; Kim, Jung-Hwan; Lee, Gaehang; Jin, Jong Sung; Ganteför, Gerd; Kim, Young Dok; Choi, Myoung Choul

2018-01-01

Wet-chemically synthesized Au nanoparticles were deposited on Si wafer surfaces, and the secondary ions mass spectra (SIMS) from these samples were collected using Bi3+ with an energy of 30 keV as the primary ions. In the SIMS, Au cluster cations with a well-known, even-odd alteration pattern in the signal intensity were observed. We also performed depth profile SIMS analyses, i.e., etching the surface using an Ar gas cluster ion beam (GCIB), and a subsequent Bi3+ SIMS analysis was repetitively performed. Here, two different etching conditions (Ar1600 clusters of 10 keV energy or Ar1000 of 2.5 keV denoted as "harsh" or "soft" etching conditions, respectively) were used. Etching under harsh conditions induced emission of the Au-Si binary cluster cations in the SIMS spectra of the Bi3+ primary ions. The formation of binary cluster cations can be induced by either fragmentation of Au nanoparticles or alloying of Au and Si, increasing Au-Si coordination on the sample surface during harsh GCIB etching. Alternatively, use of the soft GCIB etching conditions resulted in exclusive emission of pure Au cluster cations with nearly no Au-Si cluster cation formation. Depth profile analyses of the Bi3+ SIMS combined with soft GCIB etching can be useful for studying the chemical environments of atoms at the surface without altering the original interface structure during etching.

Instability of Hydrogenated TiO2

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

Nandasiri, Manjula I.; Shutthanandan, V.; Manandhar, Sandeep

2015-11-06

Hydrogenated TiO2 (H-TiO2) is toted as a viable visible light photocatalyst. We report a systematic study on the thermal stability of H-implanted TiO2 using X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), Rutherford backscattering spectrometry (RBS) and nuclear reaction analysis (NRA). Protons (40 keV) implanted at a ~2 atom % level within a ~120 nm wide profile of rutile TiO2(110) were situated ~300 nm below the surface. NRA revealed that this H-profile broadened preferentially toward the surface after annealing at 373 K, dissipated out of the crystal into vacuum at 473 K, and was absent within the beam sampling depthmore » (~800 nm) at 523 K. Photoemission showed that the surface was reduced in concert with these changes. Similar anneals had no effect on pristine TiO2(110). The facile bulk diffusivity of H in rutile, as well as its activity toward interfacial reduction, significantly limits the utilization of H-TiO2 as a photocatalyst. This work was supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. Pacific Northwest National Laboratory (PNNL) is a multiprogram national laboratory operated for DOE by Battelle. The research was performed using the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory.« less

Interactions of anesthetics with the water-hexane interface. A molecular dynamics study

NASA Technical Reports Server (NTRS)

Chipot, C.; Wilson, M. A.; Pohorille, A.

1997-01-01

The free energy profiles characterizing the transfer of nine solutes across the liquid-vapor interfaces of water and hexane and across the water-hexane interface were calculated from molecular dynamics simulations. Among the solutes were n-butane and three of its halogenated derivatives, as well as three halogenated cyclobutanes. The two remaining molecules, dichlorodifluoromethane and 1,2-dichloroperfluoroethane, belong to series of halo-substituted methanes and ethanes, described in previous studies (J. Chem. Phys. 1996, 104, 3760; Chem. Phys. 1996, 204, 337). Each series of molecules contains structurally similar compounds that differ greatly in anesthetic potency. The accuracy of the simulations was tested by comparing the calculated and the experimental free energies of solvation of all nine compounds in water and in hexane. In addition. the calculated and the measured surface excess concentrations of n-butane at the water liquid-vapor interface were compared. In all cases, good agreement with experimental results was found. At the water-hexane interface, the free energy profiles for polar molecules exhibited significant interfacial minima, whereas the profiles for nonpolar molecules did not. The existence of these minima was interpreted in terms of a balance between the free energy contribution arising from solute-solvent interactions and the work to form a cavity that accommodates the solute. These two contributions change monotonically, but oppositely, across the interface. The interfacial solubilities of the solutes, obtained from the free energy profiles, correlate very well with their anesthetic potencies. This is the case even when the Meyer-Overton hypothesis, which predicts a correlation between anesthetic potency and solubility in oil, fails.

Temperature-mediated transition from Dyakonov-Tamm surface waves to surface-plasmon-polariton waves

NASA Astrophysics Data System (ADS)

Chiadini, Francesco; Fiumara, Vincenzo; Mackay, Tom G.; Scaglione, Antonio; Lakhtakia, Akhlesh

2017-08-01

The effect of changing the temperature on the propagation of electromagnetic surface waves (ESWs), guided by the planar interface of a homogeneous isotropic temperature-sensitive material (namely, InSb) and a temperature-insensitive structurally chiral material (SCM) was numerically investigated in the terahertz frequency regime. As the temperature rises, InSb transforms from a dissipative dielectric material to a dissipative plasmonic material. Correspondingly, the ESWs transmute from Dyakonov-Tamm surface waves into surface-plasmon-polariton waves. The effects of the temperature change are clearly observed in the phase speeds, propagation distances, angular existence domains, multiplicity, and spatial profiles of energy flow of the ESWs. Remarkably large propagation distances can be achieved; in such instances the energy of an ESW is confined almost entirely within the SCM. For certain propagation directions, simultaneous excitation of two ESWs with (i) the same phase speeds but different propagation distances or (ii) the same propagation distances but different phase speeds are also indicated by our results.

Predicting vertical phase segregation in polymer-fullerene bulk heterojunction solar cells by free energy analysis.

PubMed

Clark, Michael D; Jespersen, Michael L; Patel, Romesh J; Leever, Benjamin J

2013-06-12

Blends of poly(3-hexylthiophene) (P3HT) and C61-butyric acid methyl ester (PCBM) are widely used as a model system for bulk heterojunction active layers developed for solution-processable, flexible solar cells. In this work, vertical concentration profiles within the P3HT:PCBM active layer are predicted based on a thermodynamic analysis of the constituent materials and typical solvents. Surface energies of the active layer components and a common transport interlayer blend, poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS), are first extracted using contact angle measurements coupled with the acid-base model. From this data, intra- and interspecies interaction free energies are calculated, which reveal that the thermodynamically favored arrangement consists of a uniformly blended "bulk" structure capped with a P3HT-rich air interface and a slightly PCBM-rich buried interface. Although the "bulk" composition is solely determined by P3HT:PCBM ratio, composition near the buried interface is dependent on both the blend ratio and interaction free energy difference between solvated P3HT and PCBM deposition onto PEDOT:PSS. In contrast, the P3HT-rich overlayer is independent of processing conditions, allowing kinetic formation of a PCBM-rich sublayer during film casting due to limitations in long-range species diffusion. These thermodynamic calculations are experimentally validated by angle-resolved X-ray photoelectron spectroscopy (XPS) and low energy XPS depth profiling, which show that the actual composition profiles of the cast and annealed films closely match the predicted behavior. These experimentally derived profiles provide clear evidence that typical bulk heterojunction active layers are predominantly characterized by thermodynamically stable composition profiles. Furthermore, the predictive capabilities of the comprehensive free energy approach are demonstrated, which will enable investigation of structurally integrated devices and novel active layer systems including low band gap polymers, ternary systems, and small molecule blends.

Observing the seasonal cycle of the upper ocean in the Ross Sea, Antarctica, with autonomous profiling floats

NASA Astrophysics Data System (ADS)

Porter, D. F.; Springer, S. R.; Padman, L.; Fricker, H. A.; Bell, R. E.

2017-12-01

The upper layers of the Southern Ocean where it meets the Antarctic ice sheet undergoes a large seasonal cycle controlled by surface radiation and by freshwater fluxes, both of which are strongly influenced by sea ice. In regions where seasonal sea ice and icebergs limit use of ice-tethered profilers and conventional moorings, autonomous profiling floats can sample the upper ocean. The deployment of seven Apex floats (by sea) and six ALAMO floats (by air) provides unique upper ocean hydrographic data in the Ross Sea close to the Ross Ice Shelf front. A novel choice of mission parameters - setting parking depth deeper than the seabed - limits their drift, allowing us to deploy the floats close to the ice shelf front, while sea ice avoidance algorithms allow the floats to to sample through winter under sea ice. Hydrographic profiles show the detailed development of the seasonal mixed layer close to the Ross front, and interannual variability of the seasonal mixed layer and deeper water masses on the central Ross Sea continental shelf. After the sea ice breakup in spring, a warm and fresh surface mixed layer develops, further warming and deepening throughout the summer. The mixed layer deepens, with maximum temperatures exceeding 0ºC in mid-February. By March, the surface energy budget becomes negative and sea ice begins to form, creating a cold, saline and dense surface layer. Once these processes overcome the stable summer stratification, convection erodes the surface mixed layer, mixing some heat downwards to deeper layers. There is considerable interannual variability in the evolution and strength of the surface mixed layer: summers with shorter ice-free periods result in a cooler and shallower surface mixed layer, which accumulates less heat than the summers with longer ice-free periods. Early ice breakup occurred in all floats in 2016/17 summer, enhancing the absorbed solar flux leading to a warmer surface mixed layer. Together, these unique measurements from autonomous profilers provide insight into the hydrographic state of the Ross Sea at the start of the spring period of sea-ice breakup, and how ocean mixing and sea ice interact to initiate the summer open-water season.

Optimized Hypernetted-Chain Solutions for Helium -4 Surfaces and Metal Surfaces

NASA Astrophysics Data System (ADS)

Qian, Guo-Xin

This thesis is a study of inhomogeneous Bose systems such as liquid ('4)He slabs and inhomogeneous Fermi systems such as the electron gas in metal films, at zero temperature. Using a Jastrow-type many-body wavefunction, the ground state energy is expressed by means of Bogoliubov-Born-Green-Kirkwood -Yvon and Hypernetted-Chain techniques. For Bose systems, Euler-Lagrange equations are derived for the one- and two -body functions and systematic approximation methods are physically motivated. It is shown that the optimized variational method includes a self-consistent summation of ladder- and ring-diagrams of conventional many-body theory. For Fermi systems, a linear potential model is adopted to generate the optimized Hartree-Fock basis. Euler-Lagrange equations are derived for the two-body correlations which serve to screen the strong bare Coulomb interaction. The optimization of the pair correlation leads to an expression of correlation energy in which the state averaged RPA part is separated. Numerical applications are presented for the density profile and pair distribution function for both ('4)He surfaces and metal surfaces. Both the bulk and surface energies are calculated in good agreement with experiments.

Surface profile measurement by using the integrated Linnik WLSI and confocal microscope system

NASA Astrophysics Data System (ADS)

Wang, Wei-Chung; Shen, Ming-Hsing; Hwang, Chi-Hung; Yu, Yun-Ting; Wang, Tzu-Fong

2017-06-01

The white-light scanning interferometer (WLSI) and confocal microscope (CM) are the two major optical inspection systems for measuring three-dimensional (3D) surface profile (SP) of micro specimens. Nevertheless, in practical applications, WLSI is more suitable for measuring smooth and low-slope surfaces. On the other hand, CM is more suitable for measuring uneven-reflective and low-reflective surfaces. As for aspect of surface profiles to be measured, the characteristics of WLSI and CM are also different. WLSI is generally used in semiconductor industry while CM is more popular in printed circuit board industry. In this paper, a self-assembled multi-function optical system was integrated to perform Linnik white-light scanning interferometer (Linnik WLSI) and CM. A connecting part composed of tubes, lenses and interferometer was used to conjunct finite and infinite optical systems for Linnik WLSI and CM in the self-assembled optical system. By adopting the flexibility of tubes and lenses, switching to perform two different optical measurements can be easily achieved. Furthermore, based on the shape from focus method with energy of Laplacian filter, the CM was developed to enhance the on focal information of each pixel so that the CM can provide all-in-focus image for performing the 3D SP measurement and analysis simultaneously. As for Linnik WLSI, eleven-step phase shifting algorithm was used to analyze vertical scanning signals and determine the 3D SP.

Superhydrophobic Surface Coatings for Microfluidics and MEMs.

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

Branson, Eric D.; Singh, Seema; Houston, Jack E.

2006-11-01

Low solid interfacial energy and fractally rough surface topography confer to Lotus plants superhydrophobic (SH) properties like high contact angles, rolling and bouncing of liquid droplets, and self-cleaning of particle contaminants. This project exploits the porous fractal structure of a novel, synthetic SH surface for aerosol collection, its self-cleaning properties for particle concentration, and its slippery nature 3 to enhance the performance of fluidic and MEMS devices. We propose to understand fundamentally the conditions needed to cause liquid droplets to roll rather than flow/slide on a surface and how this %22rolling transition%22 influences the boundary condition describing fluid flow inmore » a pipe or micro-channel. Rolling of droplets is important for aerosol collection strategies because it allows trapped particles to be concentrated and transported in liquid droplets with no need for a pre-defined/micromachined fluidic architecture. The fluid/solid boundary condition is important because it governs flow resistance and rheology and establishes the fluid velocity profile. Although many research groups are exploring SH surfaces, our team is the first to unambiguously determine their effects on fluid flow and rheology. SH surfaces could impact all future SNL designs of collectors, fluidic devices, MEMS, and NEMS. Interfaced with inertial focusing aerosol collectors, SH surfaces would allow size-specific particle populations to be collected, concentrated, and transported to a fluidic interface without loss. In microfluidic systems, we expect to reduce the energy/power required to pump fluids and actuate MEMS. Plug-like (rather than parabolic) velocity profiles can greatly improve resolution of chip-based separations and enable unprecedented control of concentration profiles and residence times in fluidic-based micro-reactors. Patterned SH/hydrophilic channels could induce mixing in microchannels and enable development of microflow control elements. Acknowledgements This work was funded by Sandia National Laboratory's Laboratory Directed Research & Development program (LDRD). Some coating processes were conducted in the cleanroom facility located at the University of New Mexico's Center for High Technology Materials (CHTM). SEM images were performed at UNM's Center for Micro-Engineering on equipment funded by a NSF New Mexico EPSCoR grant. 4« less

Introducing sampling entropy in repository based adaptive umbrella sampling

NASA Astrophysics Data System (ADS)

Zheng, Han; Zhang, Yingkai

2009-12-01

Determining free energy surfaces along chosen reaction coordinates is a common and important task in simulating complex systems. Due to the complexity of energy landscapes and the existence of high barriers, one widely pursued objective to develop efficient simulation methods is to achieve uniform sampling among thermodynamic states of interest. In this work, we have demonstrated sampling entropy (SE) as an excellent indicator for uniform sampling as well as for the convergence of free energy simulations. By introducing SE and the concentration theorem into the biasing-potential-updating scheme, we have further improved the adaptivity, robustness, and applicability of our recently developed repository based adaptive umbrella sampling (RBAUS) approach [H. Zheng and Y. Zhang, J. Chem. Phys. 128, 204106 (2008)]. Besides simulations of one dimensional free energy profiles for various systems, the generality and efficiency of this new RBAUS-SE approach have been further demonstrated by determining two dimensional free energy surfaces for the alanine dipeptide in gas phase as well as in water.

Adsorption isotherms of some alkyl aromatic hydrocarbons and surface energies on partially dealuminated Y faujasite zeolite by inverse gas chromatography.

PubMed

Kondor, Anett; Dallos, András

2014-10-03

Adsorption isotherm data of some alkyl aromatic hydrocarbons (benzene, toluene, ethylbenzene, o-xylene, m-xylene and p-xylene) measured in the temperature range of 423-523K on a partially dealuminated faujasite type DAY F20 zeolite by inverse gas chromatography are presented in this work. The temperature dependent form of Tóth's equation has been fitted to the multiple temperature adsorption isotherms of benzene, toluene, ethylbenzene, o-xylene, m-xylene and p-xylene with standard deviations of 4.6, 5.0, 5.9, 4.3, 5.1 and 6.3mmolkg(-1) and coefficients of determinations (r(2)) of 0.977, 0.971, 0.974, 0.975, 0.991 and 0.991, respectively. The gas-solid equilibria and modeling were interpreted on the basis of the interfacial properties of the zeolite, by dispersive, specific and total surface energy heterogeneity profiles and distributions of the adsorbent measured by surface energy analysis. Copyright © 2014 Elsevier B.V. All rights reserved.

Fermi level pinning characterisation on ammonium fluoride-treated surfaces of silicon by energy-filtered doping contrast in the scanning electron microscope

PubMed Central

Chee, Augustus K. W.

2016-01-01

Two-dimensional dopant profiling using the secondary electron (SE) signal in the scanning electron microscope (SEM) is a technique gaining impulse for its ability to enable rapid and contactless low-cost diagnostics for integrated device manufacturing. The basis is doping contrast from electrical p-n junctions, which can be influenced by wet-chemical processing methods typically adopted in ULSI technology. This paper describes the results of doping contrast studies by energy-filtering in the SEM from silicon p-n junction specimens that were etched in ammonium fluoride solution. Experimental SE micro-spectroscopy and numerical simulations indicate that Fermi level pinning occurred on the surface of the treated-specimen, and that the doping contrast can be explained in terms of the ionisation energy integral for SEs, which is a function of the dopant concentration, and surface band-bending effects that prevail in the mechanism for doping contrast as patch fields from the specimen are suppressed. PMID:27576347

Surface layering and melting in an ionic liquid studied by resonant soft X-ray reflectivity

PubMed Central

Mezger, Markus; Ocko, Benjamin M.; Reichert, Harald; Deutsch, Moshe

2013-01-01

The molecular-scale structure of the ionic liquid [C18mim]+[FAP]− near its free surface was studied by complementary methods. X-ray absorption spectroscopy and resonant soft X-ray reflectivity revealed a depth-decaying near-surface layering. Element-specific interfacial profiles were extracted with submolecular resolution from energy-dependent soft X-ray reflectivity data. Temperature-dependent hard X-ray reflectivity, small- and wide-angle X-ray scattering, and infrared spectroscopy uncovered an intriguing melting mechanism for the layered region, where alkyl chain melting drove a negative thermal expansion of the surface layer spacing. PMID:23431181

Improved depth profiling with slow positrons of ion implantation-induced damage in silicon

NASA Astrophysics Data System (ADS)

Fujinami, M.; Miyagoe, T.; Sawada, T.; Akahane, T.

2003-10-01

Variable-energy positron annihilation spectroscopy (VEPAS) has been extensively applied to study defects in near-surface regions and buried interfaces, but there is an inherent limit for depth resolution due to broadening of the positron implantation profile. In order to overcome this limit and obtain optimum depth resolution, iterative chemical etching of the sample surface and VEPAS measurement are employed. This etch-and-measure technique is described in detail and the capabilities are illustrated by investigating the depth profile of defects in Si after B and P implantations with 2×1014/cm2 at 100 keV followed by annealing. Defect tails can be accurately examined and the extracted defect profile is proven to extend beyond the implanted ion range predicted by the Monte Carlo code TRIM. This behavior is more remarkable for P ion implantation than B, and the mass difference of the implanted ions is strongly related to it. No significant difference is recognized in the annealing behavior between B and P implantations. After annealing at 300 °C, the defect profile is hardly changed, but the ratio of the characteristic Doppler broadening, S, a parameter for defects, to that for the bulk Si rises by 0.01, indicating that divacancies, V2, are transformed into V4. Annealing at more than 500 °C causes diffusion of the defects toward the surface and positron traps are annealed out at 800 °C. It is proved that this resolution-enhanced VEPAS can eliminate some discrepancies in defect profiles extracted by conventional means.

Effect of film slicks on near-surface wind

NASA Astrophysics Data System (ADS)

Charnotskii, Mikhail; Ermakov, Stanislav; Ostrovsky, Lev; Shomina, Olga

2016-09-01

The transient effects of horizontal variation of sea-surface wave roughness due to surfactant films on near-surface turbulent wind are studied theoretically and experimentally. Here we suggest two practical schemes for calculating variations of wind velocity profiles near the water surface, the average short-wave roughness of which is varying in space and time when a film slick is present. The schemes are based on a generalized two-layer model of turbulent air flow over a rough surface and on the solution of the continuous model involving the equation for turbulent kinetic energy of the air flow. Wave tank studies of wind flow over wind waves in the presence of film slicks are described and compared with theory.

Surface-conductivity enhancement of PMMA by keV-energy metal-ion implantation

NASA Astrophysics Data System (ADS)

Bannister, M. E.; Hijazi, H.; Meyer, H. M.; Cianciolo, V.; Meyer, F. W.

2014-11-01

An experiment has been proposed to measure the neutron electric dipole moment (nEDM) with high precision at the Oak Ridge National Laboratory (ORNL) Spallation Neutron Source. One of the requirements of this experiment is the development of PMMA (Lucite) material with a sufficiently conductive surface to permit its use as a high-voltage electrode while immersed in liquid He. At the ORNL Multicharged Ion Research Facility, an R&D activity is under way to achieve suitable surface conductivity in poly-methyl methacrylate (PMMA) using metal ion implantation. The metal implantation is performed using an electron-cyclotron-resonance (ECR) ion source and a recently developed beam line deceleration module that is capable of providing high flux beams for implantation at energies as low as a few tens of eV. The latter is essential for reaching implantation fluences exceeding 1 × 1016 cm-2, where typical percolation thresholds in polymers have been reported. In this contribution, we report results on initial implantation of Lucite by Ti and W beams with keV energies to average fluences in the range 0.5-6.2 × 1016 cm-2. Initial measurements of surface-resistivity changes are reported as function of implantation fluence, energy, and sample temperature. We also report X-ray photoelectron spectroscopy (XPS) surface and depth profiling measurements of the ion implanted samples, to identify possible correlations between the near surface and depth resolved implanted W concentrations and the measured surface resistivities.

The impact of in-canopy wind profile formulations on heat flux estimation in an open orchard using the remote sensing-based two-source model

NASA Astrophysics Data System (ADS)

Cammalleri, C.; Anderson, M. C.; Ciraolo, G.; Durso, G.; Kustas, W. P.; La Loggia, G.; Minacapilli, M.

2010-12-01

For open orchard and vineyard canopies containing significant fractions of exposed soil (>50%), typical of Mediterranean agricultural regions, the energy balance of the vegetation elements is strongly influenced by heat exchange with the bare soil/substrate. For these agricultural systems a "two-source" approach, where radiation and turbulent exchange between the soil and canopy elements are explicitly modelled, appears to be the only suitable methodology for reliably assessing energy fluxes. In strongly clumped canopies, the effective wind speed profile inside and below the canopy layer can strongly influence the partitioning of energy fluxes between the soil and vegetation components. To assess the impact of in-canopy wind profile on model flux estimates, an analysis of three different formulations is presented, including algorithms from Goudriaan (1977), Massman (1987) and Lalic et al. (2003). The in-canopy wind profile formulations are applied to the thermal-based two-source energy balance (TSEB) model developed by Norman et al. (1995) and modified by Kustas and Norman (1999). High resolution airborne remote sensing images, collected over an agricultural area located in the western part of Sicily (Italy) comprised primarily of vineyards, olive and citrus orchards, are used to derive all the input parameters needed to apply the TSEB. The images were acquired from June to October 2008 and include a relatively wide range of meteorological and soil moisture conditions. A preliminary sensitivity analysis of the three wind profile algorithms highlights the dependence of wind speed just above the soil/substrate to leaf area index and canopy height over the typical range of canopy properties encountered in these agricultural areas. It is found that differences among the models in wind just above the soil surface are most significant under sparse and medium fractional cover conditions (15-50%). The TSEB model heat flux estimates are compared with micro-meteorological measurements from a small aperture scintillometer and an eddy covariance tower collected over an olive orchard characterized by moderate fractional vegetation cover (≍35%) and relatively tall crop (≍3.5 m). TSEB fluxes for the 7 image acquisition dates generated using both the Massman and Goudriaan in-canopy wind profile formulations give close agreement with measured fluxes, while the Lalic et al. equations yield poor results. The Massman wind profile scheme slightly outperforms that of Goudriaan, but it requires an additional parameter accounting for the roughness sub-layer of the underlying vegetative surface. The analysis also suggests that within-canopy wind profile model discrepancies become important, in terms of impact on modelled sensible heat flux, only for sparse canopies with moderate vegetation coverage.

Application of Data Assimilation with the Root Zone Water Quality Model for Soil Moisture Profile Estimation

USDA-ARS?s Scientific Manuscript database

Estimation of soil moisture has received considerable attention in the areas of hydrology, agriculture, meteorology and environmental studies because of its role in the partitioning water and energy at the land surface. In this study, the Ensemble Kalman Filter (EnKF), a popular data assimilation te...

Calibration of the Root Zone Water Quality Model and Application of Data Assimilation Techniques to Estimate Profile Soil Moisture

USDA-ARS?s Scientific Manuscript database

Estimation of soil moisture has received considerable attention in the areas of hydrology, agriculture, meteorology and environmental studies because of its role in the partitioning water and energy at the land surface. In this study, the USDA, Agricultural Research Service, Root Zone Water Quality ...

2D Process-based Microbialite Growth Model

NASA Astrophysics Data System (ADS)

Airo, A.; Smith, A.

2007-12-01

A 2D process-based microbialite growth model (MGM) has been developed that integrates the coupled effects of the microbialite growth and sediment distribution within a two-dimensional cross-section of a subaqueous bedrock profile. Sediment transport is realized through particle erosion and deposition that are a function of local wave energy which is computed on the basis of linear wave theory. Surface-normal microbialite growth is directly correlated to light intensity, which is computed for every point of the microbialite surface by using a Henyey- Greenstein-type relation for scattering and the Beer's Law for absorption in the water column. Shadowing effects by surrounding obstacles and/or overlying sediment are also considered. Sediment particles can be incorporated into the microbialite framework if growth occurs in the presence of sediment. The resulting meter-size microbialite constructs develop morphologies that correspond well to natural microbialites. Furthermore, changes of environmental factors such as light intensity, wave energy, and bedrock profile result in morphological variations of the microbialites that would be expected on the basis of the current understanding of microbialite growth and development.

[Line scanning analysis of white porcelain from Gong Kiln in early Tang dynasty by energy disperse X-ray fluorescence].

PubMed

Ling, Xue; Mao, Zhen-wei; Feng, Min; Hu, Yao-wu; Wang, Chang-sui; Liu, Hong-miao

2005-07-01

Gong kiln, for its long porcelain-firing history, was one of three representative white porcelain kilns in northern China. In order to improve the quality and whiteness of white porcelain, a decorating layer or cosmetic earth was laid on the body surface in Gong kiln during early Tang dynasty, which was able to blot out rough surface and weaken the influence of fuscous body upon surface color. In this paper the main chemical composition of the white porcelain's profile was analyzed by using energy disperse X-Ray fluorescence. The result showed that different materials were used as cosmetic earth during early Tang dynasty, in accordance with the phenomenon under optical microscope. In addition, the glaze belongs to calcium glaze in which plant ash was added.

Optothermal transfer simulation in laser-irradiated human dentin.

PubMed

Moriyama, Eduardo H; Zangaro, Renato A; Lobo, Paulo D C; Villaverde, Antonio Balbin; Pacheco, Marcos T; Watanabe, Ii-Sei; Vitkin, Alex

2003-04-01

Laser technology has been studied as a potential replacement to the conventional dental drill. However, to prevent pulpal cell damage, information related to the safety parameters using high-power lasers in oral mineralized tissues is needed. In this study, the heat distribution profiles at the surface and subsurface regions of human dentine samples irradiated with a Nd:YAG laser were simulated using Crank-Nicolson's finite difference method for different laser energies and pulse durations. Heat distribution throughout the dentin layer, from the external dentin surface to the pulp chamber wall, were calculated in each case, to investigate the details of pulsed laser-hard dental tissue interactions. The results showed that the final temperature at the pulp chamber wall and at the dentin surface are strongly dependent on the pulse duration, exposure time, and the energy contained in each pulse.

Application specific beam profiles: new surface and thin-film refinement processes using beam shaping technologies

NASA Astrophysics Data System (ADS)

Hauschild, Dirk

2017-02-01

Today, the use of laser photons for materials processing is a key technology in nearly all industries. Most of the applications use circular beam shapes with Gaussian intensity distribution that is given by the resonator of the laser or by the power delivery via optical fibre. These beam shapes can be typically used for material removal with cutting or drilling and for selective removal of material layers with ablation processes. In addition to the removal of materials, it is possible to modify and improve the material properties in case the dose of laser photons and the resulting light-material interaction addresses a defined window of energy and dwell-time. These process windows have typically dwell-times between µs and s because of using sintering, melting, thermal diffusion or photon induced chemical and physical reaction mechanisms. Using beam shaping technologies the laser beam profiles can be adapted to the material properties and time-temperature and the space-temperature envelopes can be modified to enable selective annealing or crystallization of layers or surfaces. Especially the control of the process energy inside the beam and at its edges opens a large area of laser applications that can be addressed only with an optimized spatial and angular beam profile with down to sub-percent intensity variation used in e.g. immersion lithography tools with ArF laser sources. LIMO will present examples for new beam shapes and related material refinement processes even on large surfaces and give an overview about new mechanisms in laser material processing for current and coming industrial applications.

Method of manufacturing large dish reflectors for a solar concentrator apparatus

DOEpatents

Angel, Roger P [Tucson, AZ; Olbert, Blain H [Tucson, AZ

2011-12-27

A method of manufacturing monolithic glass reflectors for concentrating sunlight in a solar energy system is disclosed. The method of manufacturing allows large monolithic glass reflectors to be made from float glass in order to realize significant cost savings on the total system cost for a solar energy system. The method of manufacture includes steps of heating a sheet of float glass positioned over a concave mold until the sheet of glass sags and stretches to conform to the shape of the mold. The edges of the dish-shaped glass are rolled for structural stiffening around the periphery. The dish-shaped glass is then silvered to create a dish-shaped mirror that reflects solar radiation to a focus. The surface of the mold that contacts the float glass preferably has a grooved surface profile comprising a plurality of cusps and concave valleys. This grooved profile minimizes the contact area and marring of the specular glass surface, reduces parasitic heat transfer into the mold and increases mold lifetime. The disclosed method of manufacture is capable of high production rates sufficiently fast to accommodate the output of a conventional float glass production line so that monolithic glass reflectors can be produced as quickly as a float glass production can make sheets of float glass to be used in the process.

Tyre-road contact using a particle-envelope surface model

NASA Astrophysics Data System (ADS)

Pinnington, Roger J.

2013-12-01

Determination of the contact forces is the central problem in all aspects of road-tyre interaction: i.e. noise, energy loss and friction. A procedure to find the contact forces under a rolling tyre is presented in four stages. First, the contact stiffness of a uniform peak array from indentations in the rubber tread, and also tyre carcass deflection, is described by some new simplified expressions. Second, a routine divides a single surface profile into equal search intervals, in which the highest peaks are identified. These are used to obtain the parameters for the interval, i.e. the mean envelope and the mean interval. The process is repeated at geometrically decreasing search intervals until the level of the data resolution, thereby describing the profile by a set of envelopes. The ‘strip profile’ ultimately used to describe the surface, is obtained by selecting the highest points across the profiles of one stone's width. The third stage is to combine the strip profile envelopes with the contact stiffness expressions, yielding the nonlinear stiffness-displacement, and force-displacement relationships for the chosen road-tyre combination. Finally the contact pressure distribution from a steady-state rolling tyre model is applied to the strip profile, via the force-displacement relationship, giving the local tyre displacements on the road texture. This displacement pattern is shown to be proportional to the time and space varying contact pressure, which then is incorporated into a wave equation for rolling contact.

Thick optical waveguides in lithium niobate induced by swift heavy ions (approximately 10 MeV/amu) at ultralow fluences.

PubMed

Olivares, José; Crespillo, Miguel L; Caballero-Calero, Olga; Ynsa, María D; García-Cabañes, Angel; Toulemonde, Marcel; Trautmann, Christina; Agulló-López, Fernando

2009-12-21

Heavy mass ions, Kr and Xe, having energies in the approximately 10 MeV/amu range have been used to produce thick planar optical waveguides at the surface of lithium niobate (LiNbO3). The waveguides have a thickness of 40-50 micrometers, depending on ion energy and fluence, smooth profiles and refractive index jumps up to 0.04 (lambda = 633 nm). They propagate ordinary and extraordinary modes with low losses keeping a high nonlinear optical response (SHG) that makes them useful for many applications. Complementary RBS/C data provide consistent values for the partial amorphization and refractive index change at the surface. The proposed method is based on ion-induced damage caused by electronic excitation and essentially differs from the usual implantation technique using light ions (H and He) of MeV energies. It implies the generation of a buried low-index layer (acting as optical barrier), made up of amorphous nanotracks embedded into the crystalline lithium niobate crystal. An effective dielectric medium approach is developed to describe the index profiles of the waveguides. This first test demonstration could be extended to other crystalline materials and could be of great usefulness for mid-infrared applications.

Study on two operating conditions of a full-scale oxidation ditch for optimization of energy consumption and effluent quality by using CFD model.

PubMed

Yang, Yin; Yang, Jiakuan; Zuo, Jiaolan; Li, Ye; He, Shu; Yang, Xiao; Zhang, Kai

2011-05-01

The operating condition of an oxidation ditch (OD) has significant impact on energy consumption and effluent quality of wastewater treatment plants (WWTPs). An experimentally validated numerical tool, based on computational fluid dynamics (CFD) model, was proposed to optimize the operating condition by considering two important factors: flow field and dissolved oxygen (DO) concentration profiles. The model is capable of predicting flow pattern and oxygen mass transfer characteristics in ODs equipped with surface aerators and submerged impellers. Performance demonstration and comparison of two operating conditions (existing and improved) were carried out in two full-scale Carrousel ODs at the Ping Dingshan WWTP in Henan, China. A moving wall model and a fan model were designed to simulate surface aerators and submerged impellers, respectively. Oxygen mass transfer in the ditch was predicted by using a unit analysis method. In aeration zones, the mass inlets representing the surface aerators were set as one source of DO. In the whole straight channel, the oxygen consumption was modeled by using modified BOD-DO model. The following results were obtained: (1) the CFD model characterized flow pattern and DO concentration profiles in the full-scale OD. The predicted flow field values were within 1.98 ± 4.28% difference from the actual measured values while the predicted DO concentration values were within -4.71 ± 4.15% of the measured ones, (2) a surface aerator should be relocated to around 15m from the curve bend entrance to reduce energy loss caused by fierce collisions at the wall of the curve bend, and (3) DO concentration gradients in the OD under the improved operating condition were more favorable for occurrence of simultaneous nitrification and denitrification (SND). Copyright © 2011 Elsevier Ltd. All rights reserved.

A density functional theory study on the effect of zero-point energy corrections on the methanation profile on Fe(100).

PubMed

Govender, Ashriti; Ferré, Daniel Curulla; Niemantsverdriet, J W Hans

2012-04-23

The thermodynamics and kinetics of the surface hydrogenation of adsorbed atomic carbon to methane, following the reaction sequence C+4H(-->/<--)CH+3H(-->/<--)CH(2)+2H(-->/<--)CH(3)+H(-->/<--)CH(4), are studied on Fe(100) by means of density functional theory. An assessment is made on whether the adsorption energies and overall energy profile are affected when zero-point energy (ZPE) corrections are included. The C, CH and CH(2) species are most stable at the fourfold hollow site, while CH(3) prefers the twofold bridge site. Atomic hydrogen is adsorbed at both the twofold bridge and fourfold hollow sites. Methane is physisorbed on the surface and shows neither orientation nor site preference. It is easily desorbed to the gas phase once formed. The incorporation of ZPE corrections has a very slight, if any, effect on the adsorption energies and does not alter the trends with regards to the most stable adsorption sites. The successive addition of hydrogen to atomic carbon is endothermic up to the addition of the third hydrogen atom resulting in the methyl species, but exothermic in the final hydrogenation step, which leads to methane. The overall methanation reaction is endothermic when starting from atomic carbon and hydrogen on the surface. Zero-point energy corrections are rarely provided in the literature. Since they are derived from C-H bonds with characteristic vibrations on the order of 2500-3000 cm(-1), the equivalent ZPE of 1/2 hν is on the order of 0.2-0.3 eV and its effect on adsorption energy can in principle be significant. Particularly in reactions between CH(x) and H, the ZPE correction is expected to be significant, as additional C-H bonds are formed. In this instance, the methanation reaction energy of +0.77 eV increased to +1.45 eV with the inclusion of ZPE corrections, that is, less favourable. Therefore, it is crucial to include ZPE corrections when reporting reactions involving hydrogen-containing species. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Catalytic Properties of Surfaces Sites on Metal Oxides and Their Characterization by X-Ray Photoelectron Spectroscopy

DTIC Science & Technology

1974-01-01

gas now supplies one third of our 9 national energy needs and its use is the fastest growing of all fossil fuels , conversion of coal to...the possibilities of profiling oxidation states and to gain further insight into the mechanism of the bombarding process . (2) Application of ESCA to...the surface sites—which will be measured using x-ray photoelectron spectroscopy. This technique has general applicability to a large atttibM of

Theoretical study of catalytic efficiency of a Diels-Alderase catalytic antibody: an indirect effect produced during the maturation process.

PubMed

Martí, Sergio; Andrés, Juan; Moliner, Vicent; Silla, Estanislao; Tuñón, Iñaki; Bertrán, Juan

2008-01-01

The Diels-Alder reaction is one of the most important and versatile transformations available to organic chemists for the construction of complex natural products, therapeutics agents, and synthetic materials. Given the lack of efficient enzymes capable of catalyzing this kind of reaction, it is of interest to ask whether a biological catalyst could be designed from an antibody-combining site. In the present work, a theoretical study of the different behavior of a germline catalytic antibody (CA) and its matured form, 39 A-11, that catalyze a Diels-Alder reaction has been carried out. A free-energy perturbation technique based on a hybrid quantum-mechanics/molecular-mechanics scheme, together with internal energy minimizations, has allowed free-energy profiles to be obtained for both CAs. The profiles show a smaller barrier for the matured form, which is in agreement with the experimental observation. Free-energy profiles were obtained with this methodology, thereby avoiding the much more demanding two-dimensional calculations of the energy surfaces that are normally required to study this kind of reaction. Structural analysis and energy evaluations of substrate-protein interactions have been performed from averaged structures, which allows understanding of how the single mutations carried out during the maturation process can be responsible for the observed fourfold enhancement of the catalytic rate constant. The conclusion is that the mutation effect in this studied germline CA produces a complex indirect effect through coupled movements of the backbone of the protein and the substrate.

Spatiotemporal structure of wind farm-atmospheric boundary layer interactions

NASA Astrophysics Data System (ADS)

Cervarich, Matthew; Baidya Roy, Somnath; Zhou, Liming

2013-04-01

Wind power is currently one of the fastest growing energy sources in the world. Most of the growth is in the utility sector consisting of large wind farms with numerous industrial-scale wind turbines. Wind turbines act as a sink of mean kinetic energy and a source of turbulent kinetic energy in the atmospheric boundary layer (ABL). In doing so, they modify the ABL profiles and land-atmosphere exchanges of energy, momentum, mass and moisture. This project explores theses interactions using remote sensing data and numerical model simulations. The domain is central Texas where 4 of the world's largest wind farms are located. A companion study of seasonally-averaged Land Surface Temperature data from the Moderate Resolution Imaging Spectroradiometer (MODIS) on TERRA and AQUA satellites shows a warming signal at night and a mixed cooling/warming signal during the daytime within the wind farms. In the present study, wind farm-ABL interactions are simulated with the Weather Research and Forecasting (WRF) model. The simulations show that the model is capable of replicating the observed signal in land surface temperature. Moreover, similar warming/cooling effect, up to 1C, was observed in seasonal mean 2m air temperature as well. Further analysis show that enhanced turbulent mixing in the rotor wakes is responsible for the impacts on 2m and surface air temperatures. The mixing is due to 2 reasons: (i) turbulent momentum transport to compensate the momentum deficit in the wakes of the turbines and (ii) turbulence generated due to motion of turbine rotors. Turbulent mixing also alters vertical profiles of moisture. Changes in land-atmosphere temperature and moisture gradient and increase in turbulent mixing leads to more than 10% change in seasonal mean surface sensible and latent heat flux. Given the current installed capacity and the projected installation across the world, wind farms are likely becoming a major driver of anthropogenic land use change on Earth. Hence, understanding WF-ABL interactions and its effects is of significant scientific and societal importance.

THE STRUCTURE AND STELLAR CONTENT OF THE OUTER DISKS OF GALAXIES: A NEW VIEW FROM THE Pan-STARRS1 MEDIUM DEEP SURVEY

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

Zheng, Zheng; Thilker, David A.; Heckman, Timothy M.

2015-02-20

We present the results of an analysis of Pan-STARRS1 Medium Deep Survey multi-band (grizy) images of a sample of 698 low-redshift disk galaxies that span broad ranges in stellar mass, star-formation rate, and bulge/disk ratio. We use population synthesis spectral energy distribution fitting techniques to explore the radial distribution of the light, color, surface mass density, mass/light ratio, and age of the stellar populations. We characterize the structure and stellar content of the galaxy disks out to radii of about twice Petrosian r {sub 90}, beyond which the halo light becomes significant. We measure normalized radial profiles for sub-samples ofmore » galaxies in three bins each of stellar mass and concentration. We also fit radial profiles to each galaxy. The majority of galaxies have down-bending radial surface brightness profiles in the bluer bands with a break radius at roughly r {sub 90}. However, they typically show single unbroken exponentials in the reddest bands and in the stellar surface mass density. We find that the mass/light ratio and stellar age radial profiles have a characteristic 'U' shape. There is a good correlation between the amplitude of the down-bend in the surface brightness profile and the rate of the increase in the M/L ratio in the outer disk. As we move from late- to early-type galaxies, the amplitude of the down-bend and the radial gradient in M/L both decrease. Our results imply a combination of stellar radial migration and suppression of recent star formation can account for the stellar populations of the outer disk.« less

Ultra-compact Marx-type high-voltage generator

DOEpatents

Goerz, David A.; Wilson, Michael J.

2000-01-01

An ultra-compact Marx-type high-voltage generator includes individual high-performance components that are closely coupled and integrated into an extremely compact assembly. In one embodiment, a repetitively-switched, ultra-compact Marx generator includes low-profile, annular-shaped, high-voltage, ceramic capacitors with contoured edges and coplanar extended electrodes used for primary energy storage; low-profile, low-inductance, high-voltage, pressurized gas switches with compact gas envelopes suitably designed to be integrated with the annular capacitors; feed-forward, high-voltage, ceramic capacitors attached across successive switch-capacitor-switch stages to couple the necessary energy forward to sufficiently overvoltage the spark gap of the next in-line switch; optimally shaped electrodes and insulator surfaces to reduce electric field stresses in the weakest regions where dissimilar materials meet, and to spread the fields more evenly throughout the dielectric materials, allowing them to operate closer to their intrinsic breakdown levels; and uses manufacturing and assembly methods to integrate the capacitors and switches into stages that can be arranged into a low-profile Marx generator.

Control of optical properties of metal-dielectric planar plasmonic nanostructures by adjusting their architecture in the case of TiAlN/Ag system

NASA Astrophysics Data System (ADS)

Wainstein, D. L.; Vakhrushev, V. O.; Kovalev, A. I.

2017-05-01

The multilayer Ag/(Ti34Al66)N metal-insulator-metal (MIM) heterostructures with different thicknesses of individual layers varied from several to several hundred nanometers were fabricated by DC-magnetron sputtering on the surfaces of Si single crystal wafers. The coatings structure was determined by STEM. The phase composition and crystallography of individual layers were studied by X-ray diffraction. The reflection indexes were measured in the photons energies range from 1 to 5 eV, or from 1240 to 248 nm. The spectroscopy of plasmon losses and plasmon microscopy allowed us to measure the plasmons losses characteristic energies and their surface distribution. The energies of plasmons peaks and their locations are strongly depending on Ag layers thickness in the MIM nanocomposite. The surface plasmon with energy about 4 eV was observed in the middle of 20 nm Ag layer. The plasmons were localized at the metal/dielectric interface for Ag layers 5 nm and less. The reflectance spectral profiles edges positions at long and short waves are correlated with plasmons energies and features of their spatial distribution. The MIMs based on the TiAlN/Ag can find applications as optical filters, photovoltaic energy conversion devices, etc.

Simulation of the Interaction Between Flywheel Energy Storage and Battery Energy Storage on the International Space Station

NASA Technical Reports Server (NTRS)

Trouong, Long V.; Wolff, Frederic J.; Dravid, Narayan V.; Li, Ponlee

2000-01-01

Replacement of one module of the battery charge discharge unit (BCDU) of the International Space Station (ISS) by a flywheel energy storage unit (FESU) is under consideration. Integration of these two dissimilar systems is likely to surface difficulties in areas of system stability and fault protection. Other issues that need to be addressed include flywheel charge and discharge profiles and their effect on the ISS power system as well as filter sizing for power Ability purposes. This paper describes a SABER based simulation to study these issues.

Physical and Chemical Behaviors of HCl on Ice Surface: Insights from an XPS and NEXAFS Study

NASA Astrophysics Data System (ADS)

Kong, X.; Waldner, A.; Orlando, F.; Birrer, M.; Artiglia, L.; Ammann, M.; Bartels-Rausch, T.

2016-12-01

Ice and snow play active roles for the water cycle, the energy budget of the Earth, and environmental chemistry in the atmosphere and cryosphere. Trace gases can be taken up by ice, and physical and chemical fates of the impurities could modify surface properties significantly and consequently influence atmospheric chemistry and the climate system. However, the understanding of chemical behaviour of impurities on ice surface are very poor, which is largely limited by the difficulties to apply high sensitivity experimental approaches to ambient air conditions, e.g. studies of volatile surfaces, because of the strict requirements of vacuum experimental conditions. In this study, we employed synchrotron-based X-ray photoelectron spectroscopy (XPS) and partial electron yield Near Edge X-ray Absorption Fine Structure (NEXAFS) in a state-of-the-art near-ambient pressure photoelectron (NAPP) spectroscopy end station. The NAPP enables to utilize the surface sensitive experimental methods, XPS and NEXAFS, on volatile surfaces, i.e. ice at temperatures approaching 0°C. XPS and NEXAFS together provide unique information of hydrogen bonding network, dopants surface concentration, dopant depth profile, and acidic dissociation on the surfaces1. Taking the advantages of the highly sensitive techniques, the adsorption, dissociation and depth profile of Hydrogen Chloride (HCl) on ice were studied. In brief, two states of Chloride on ice surface are identified from the adsorbed HCl, and they are featured with different depth profiles along the ice layers. Combining our results and previously reported constants from literatures (e.g. HCl diffusion coefficients in ice)2, a layered kinetic model has been constructed to fit the depth profiles of two states of Chloride. On the other side, pure ice and doped ice are compared for their surface structure change caused by temperature and the presence of HCl, which shows how the strong acid affect the ice surface in turn. 1. Orlando, F., et al., Top Catal 2016, 59, 591-604. 2. Huthwelker, T.; Malmstrom, M. E.; Helleis, F.; Moortgat, G. K.; Peter, T., J Phys Chem A 2004, 108, 6302-6318.

Surface analysis and depth profiling of corrosion products formed in lead pipes used to supply low alkalinity drinking water.

PubMed

Davidson, C M; Peters, N J; Britton, A; Brady, L; Gardiner, P H E; Lewis, B D

2004-01-01

Modern analytical techniques have been applied to investigate the nature of lead pipe corrosion products formed in pH adjusted, orthophosphate-treated, low alkalinity water, under supply conditions. Depth profiling and surface analysis have been carried out on pipe samples obtained from the water distribution system in Glasgow, Scotland, UK. X-ray diffraction spectrometry identified basic lead carbonate, lead oxide and lead phosphate as the principal components. Scanning electron microscopy/energy-dispersive x-ray spectrometry revealed the crystalline structure within the corrosion product and also showed spatial correlations existed between calcium, iron, lead, oxygen and phosphorus. Elemental profiling, conducted by means of secondary ion mass spectrometry (SIMS) and secondary neutrals mass spectrometry (SNMS) indicated that the corrosion product was not uniform with depth. However, no clear stratification was apparent. Indeed, counts obtained for carbonate, phosphate and oxide were well correlated within the depth range probed by SIMS. SNMS showed relationships existed between carbon, calcium, iron, and phosphorus within the bulk of the scale, as well as at the surface. SIMS imaging confirmed the relationship between calcium and lead and suggested there might also be an association between chloride and phosphorus.

Regional difference of the vertical structure of seasonal thermocline and its impact on sea surface temperature in the North Pacific

NASA Astrophysics Data System (ADS)

Yamaguchi, R.; Suga, T.

2016-12-01

Recent observational studies show that, during the warming season, a large amount of heat flux is penetrated through the base of thin mixed layer by vertical eddy diffusion, in addition to penetration of solar radiation [1]. In order to understand this heat penetration process due to vertical eddy diffusivity and its contribution to seasonal variation of sea surface temperature, we investigated the evolution of thermal stratification below the summertime thin mixed layer (i.e. evolution of seasonal thermocline) and its vertical structure in the North Pacific using high vertical resolution temperature profile observed by Argo floats. We quantified the vertical structure of seasonal thermocline as deviations from the linear structure where the vertical gradient of temperature is constant, that is, "shape anomaly". The shape anomaly is variable representing the extent of the bend of temperature profiles. We found that there are larger values of shape anomaly in the region where the seasonal sea surface temperature warming is relatively faster. To understand the regional difference of shape anomalies, we investigated the relationship between time changes in shape anomalies and net surface heat flux and surface kinetic energy flux. From May to July, the analysis indicated that, in a large part of North Pacific, there's a tendency for shape anomalies to develop strongly (weakly) under the conditions of large (small) downward net surface heat flux and small (large) downward surface kinetic energy flux. Since weak (strong) development of shape anomalies means efficient (inefficient) downward heat transport from the surface, these results suggest that the regional difference of the downward heat penetration below mixed layer is explained reasonably well by differences in surface heat forcing and surface wind forcing in a vertical one dimensional framework. [1] Hosoda et al. (2015), J. Oceanogr., 71, 541-556.

Hierarchical Coupling of First-Principles Molecular Dynamics with Advanced Sampling Methods.

PubMed

Sevgen, Emre; Giberti, Federico; Sidky, Hythem; Whitmer, Jonathan K; Galli, Giulia; Gygi, Francois; de Pablo, Juan J

2018-05-14

We present a seamless coupling of a suite of codes designed to perform advanced sampling simulations, with a first-principles molecular dynamics (MD) engine. As an illustrative example, we discuss results for the free energy and potential surfaces of the alanine dipeptide obtained using both local and hybrid density functionals (DFT), and we compare them with those of a widely used classical force field, Amber99sb. In our calculations, the efficiency of first-principles MD using hybrid functionals is augmented by hierarchical sampling, where hybrid free energy calculations are initiated using estimates obtained with local functionals. We find that the free energy surfaces obtained from classical and first-principles calculations differ. Compared to DFT results, the classical force field overestimates the internal energy contribution of high free energy states, and it underestimates the entropic contribution along the entire free energy profile. Using the string method, we illustrate how these differences lead to different transition pathways connecting the metastable minima of the alanine dipeptide. In larger peptides, those differences would lead to qualitatively different results for the equilibrium structure and conformation of these molecules.

Unique relation between surface-limited evaporation and relative humidity profiles holds in both field data and climate model simulations

NASA Astrophysics Data System (ADS)

Salvucci, G.; Rigden, A. J.; Gentine, P.; Lintner, B. R.

2013-12-01

A new method was recently proposed for estimating evapotranspiration (ET) from weather station data without requiring measurements of surface limiting factors (e.g. soil moisture, leaf area, canopy conductance) [Salvucci and Gentine, 2013, PNAS, 110(16): 6287-6291]. Required measurements include diurnal air temperature, specific humidity, wind speed, net shortwave radiation, and either measured or estimated incoming longwave radiation and ground heat flux. The approach is built around the idea that the key, rate-limiting, parameter of typical ET models, the land-surface resistance to water vapor transport, can be estimated from an emergent relationship between the diurnal cycle of the relative humidity profile and ET. The emergent relation is that the vertical variance of the relative humidity profile is less than what would occur for increased or decreased evaporation rates, suggesting that land-atmosphere feedback processes minimize this variance. This relation was found to hold over a wide range of climate conditions (arid to humid) and limiting factors (soil moisture, leaf area, energy) at a set of Ameriflux field sites. While the field tests in Salvucci and Gentine (2013) supported the minimum variance hypothesis, the analysis did not reveal the mechanisms responsible for the behavior. Instead the paper suggested, heuristically, that the results were due to an equilibration of the relative humidity between the land surface and the surface layer of the boundary layer. Here we apply this method using surface meteorological fields simulated by a global climate model (GCM), and compare the predicted ET to that simulated by the climate model. Similar to the field tests, the GCM simulated ET is in agreement with that predicted by minimizing the profile relative humidity variance. A reasonable interpretation of these results is that the feedbacks responsible for the minimization of the profile relative humidity variance in nature are represented in the climate model. The climate model components, in particular the land surface model and boundary layer representation, can thus be analyzed in controlled numerical experiments to discern the specific processes leading to the observed behavior. Results of this analysis will be presented.

Capillary wave theory of adsorbed liquid films and the structure of the liquid-vapor interface

NASA Astrophysics Data System (ADS)

MacDowell, Luis G.

2017-08-01

In this paper we try to work out in detail the implications of a microscopic theory for capillary waves under the assumption that the density is given along lines normal to the interface. Within this approximation, which may be justified in terms of symmetry arguments, the Fisk-Widom scaling of the density profile holds for frozen realizations of the interface profile. Upon thermal averaging of capillary wave fluctuations, the resulting density profile yields results consistent with renormalization group calculations in the one-loop approximation. The thermal average over capillary waves may be expressed in terms of a modified convolution approximation where normals to the interface are Gaussian distributed. In the absence of an external field we show that the phenomenological density profile applied to the square-gradient free energy functional recovers the capillary wave Hamiltonian exactly. We extend the theory to the case of liquid films adsorbed on a substrate. For systems with short-range forces, we recover an effective interface Hamiltonian with a film height dependent surface tension that stems from the distortion of the liquid-vapor interface by the substrate, in agreement with the Fisher-Jin theory of short-range wetting. In the presence of long-range interactions, the surface tension picks up an explicit dependence on the external field and recovers the wave vector dependent logarithmic contribution observed by Napiorkowski and Dietrich. Using an error function for the intrinsic density profile, we obtain closed expressions for the surface tension and the interface width. We show the external field contribution to the surface tension may be given in terms of the film's disjoining pressure. From literature values of the Hamaker constant, it is found that the fluid-substrate forces may be able to double the surface tension for films in the nanometer range. The film height dependence of the surface tension described here is in full agreement with results of the capillary wave spectrum obtained recently in computer simulations, and the predicted translation mode of surface fluctuations reproduces to linear order in field strength an exact solution of the density correlation function for the Landau-Ginzburg-Wilson Hamiltonian in an external field.

Radioactivities induced in some LDEF samples

NASA Technical Reports Server (NTRS)

Reedy, Robert C.; Moss, Calvin E.

1992-01-01

Final activities are reported for gamma ray emitting isotopes measured in 35 samples from LDEF. In 26 steel trunnion samples, activities of Mn-54 and Co-57 were measured and limits set on other isotopes. In five Al end support retainer plates and two Al keel plate samples, Na-22 was measured. In two Ti clip samples, Na-22 was measured, limits for Sc-46 were obtained, and high activities for impurity Uranium and daughter isotopes were observed. Four sets of depth vs activity profiles were measured for the D sections of the trunnion. For all 4 profiles, the activities first decreased with increasing distance from the surface of the trunnion but were fairly flat near the center. These profiles are consistent with production by both the lower energy (approx. 100 MeV) trapped particles and high energy (approx. 10 GeV) galactic-cosmic ray particles. For the near surface samples, the earth quadrant had more Mn-54 than the space quadrant. For the D sections, there was less Mn-54 in the east trunnion than in the west trunnion. Comparisons are made among the samples and with activities measured by others. The limit for Sc-46 in the Ti clips is compared with the activities of Mn-54 produced in the steel pieces by similar reactions. Activities predicted by several models are compared with the measured activities.

Effect of electrolyte on surface free energy components of feldspar minerals using thin-layer wicking method.

PubMed

Karagüzel, C; Can, M F; Sönmez, E; Celik, M S

2005-05-01

Application of the thin-layer wicking (TLW) technique on powdered minerals is useful for characterizing their surfaces. Albite (Na-feldspar) and orthoclase (K-feldspar) are feldspar minerals which are frequently found in the same matrix. Despite similarities in their physicochemical properties, separation of these minerals from each other by flotation is generally possible in the presence of monovalent salts such as NaCl. Both albite and orthoclase exhibit the same microflotation properties and rather close electrokinetic profiles in the absence of salt. In this study, contact angles of albite and orthoclase determined by the TLW technique yielded close values in the absence and presence of amine collector. While the calculated surface energies and their components determined using contact angle data reveal that the energy terms remain farther apart in the absence of the collector, the differences narrow down at collector concentrations where full flotation recoveries are obtained. However, the effect of addition of NaCl on contact angles and surface free energy components at constant amine concentration indicates that albite is significantly affected by salt addition, whereas orthoclase remains marginally affected. This interesting finding is explained on the basis of ion-exchange properties, the stability of the interface, flotation data, and zeta potential data in the presence of NaCl.

Deuterium supersaturation in low-energy plasma-loaded tungsten surfaces

NASA Astrophysics Data System (ADS)

Gao, L.; Jacob, W.; von Toussaint, U.; Manhard, A.; Balden, M.; Schmid, K.; Schwarz-Selinger, T.

2017-01-01

Fundamental understanding of hydrogen-metal interactions is challenging due to a lack of knowledge on defect production and/or evolution upon hydrogen ingression, especially for metals undergoing hydrogen irradiation with ion energy below the displacement thresholds reported in literature. Here, applying a novel low-energy argon-sputter depth profiling method with significantly improved depth resolution for tungsten (W) surfaces exposed to deuterium (D) plasma at 300 K, we show the existence of a 10 nm thick D-supersaturated surface layer (DSSL) with an unexpectedly high D concentration of ~10 at.% after irradiation with ion energy of 215 eV. Electron back-scatter diffraction reveals that the W lattice within this DSSL is highly distorted, thus strongly blurring the Kikuchi pattern. We explain this strong damage by the synergistic interaction of energetic D ions and solute D atoms with the W lattice. Solute D atoms prevent the recombination of vacancies with interstitial W atoms, which are produced by collisions of energetic D ions with W lattice atoms (Frenkel pairs). This proposed damaging mechanism could also be active on other hydrogen-irradiated metal surfaces. The present work provides deep insight into hydrogen-induced lattice distortion at plasma-metal interfaces and sheds light on its modelling work.

Molecular dynamics analysis of a equilibrium nanoscale droplet on a solid surface with periodic roughness

NASA Astrophysics Data System (ADS)

Furuta, Yuma; Surblys, Donatas; Yamaguchi, Yastaka

2016-11-01

Molecular dynamics simulations of the equilibrium wetting behavior of hemi-cylindrical argon droplets on solid surfaces with a periodic roughness were carried out. The rough solid surface is located at the bottom of the calculation cell with periodic boundary conditions in surface lateral directions and mirror boundary condition at the top boundary. Similar to on a smooth surface, the change of the cosine of the droplet contact angle was linearly correlated to the potential well depth of the inter-atomic interaction between liquid and solid on a surface with a short roughness period while the correlation was deviated on one with a long roughness period. To further investigate this feature, solid-liquid, solid-vapor interfacial free energies per unit projected area of solid surface were evaluated by using the thermodynamic integration method in independent quasi-one-dimensional simulation systems with a liquid-solid interface or vapor-solid interface on various rough solid surfaces at a constant pressure. The cosine of the apparent contact angles estimated from the density profile of the droplet systems corresponded well with ones calculated from Young's equation using the interfacial energies evaluated in the quasi-one dimensional systems.

Radial Surface Density Profiles of Gas and Dust in the Debris Disk around 49 Ceti

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

Hughes, A. Meredith; Lieman-Sifry, Jesse; Flaherty, Kevin M.

We present ∼0.″4 resolution images of CO(3–2) and associated continuum emission from the gas-bearing debris disk around the nearby A star 49 Ceti, observed with the Atacama Large Millimeter/Submillimeter Array (ALMA). We analyze the ALMA visibilities in tandem with the broadband spectral energy distribution to measure the radial surface density profiles of dust and gas emission from the system. The dust surface density decreases with radius between ∼100 and 310 au, with a marginally significant enhancement of surface density at a radius of ∼110 au. The SED requires an inner disk of small grains in addition to the outer diskmore » of larger grains resolved by ALMA. The gas disk exhibits a surface density profile that increases with radius, contrary to most previous spatially resolved observations of circumstellar gas disks. While ∼80% of the CO flux is well described by an axisymmetric power-law disk in Keplerian rotation about the central star, residuals at ∼20% of the peak flux exhibit a departure from axisymmetry suggestive of spiral arms or a warp in the gas disk. The radial extent of the gas disk (∼220 au) is smaller than that of the dust disk (∼300 au), consistent with recent observations of other gas-bearing debris disks. While there are so far only three broad debris disks with well characterized radial dust profiles at millimeter wavelengths, 49 Ceti’s disk shows a markedly different structure from two radially resolved gas-poor debris disks, implying that the physical processes generating and sculpting the gas and dust are fundamentally different.« less

Intermolecular and interfacial forces: Elucidating molecular mechanisms using chemical force microscopy

NASA Astrophysics Data System (ADS)

Ashby, Paul David

Investigation into the origin of forces dates to the early Greeks. Yet, only in recent decades have techniques for elucidating the molecular origin of forces been developed. Specifically, Chemical Force Microscopy uses the high precision and nanometer scale probe of Atomic Force Microscopy to measure molecular and interfacial interactions. This thesis presents the development of many novel Chemical Force Microscopy techniques for measuring equilibrium and time-dependant force profiles of molecular interactions, which led to a greater understanding of the origin of interfacial forces in solution. In chapter 2, Magnetic Feedback Chemical Force Microscopy stiffens the cantilever for measuring force profiles between self-assembled monolayer (SAM) surfaces. Hydroxyl and carboxyl terminated SAMs produce long-range interactions that extend one or three nanometers into the solvent, respectively. In chapter 3, an ultra low noise AFM is produced through multiple modifications to the optical deflection detection system and signal processing electronics. In chapter 4, Brownian Force Profile Reconstruction is developed for accurate measurement of steep attractive interactions. Molecular ordering is observed for OMCTS, 1-nonanol, and water near flat surfaces. The molecular ordering of the solvent produces structural or solvation forces, providing insight into the orientation and possible solidification of the confined solvent. Seven molecular layers of OMCTS are observed but the oil remains fluid to the last layer. 1-nonanol strongly orders near the surface and becomes quasi-crystalline with four layers. Water is oriented by the surface and symmetry requires two layers of water (3.7 A) to be removed simultaneously. In chapter 5, electronic control of the cantilever Q (Q-control) is used to obtain the highest imaging sensitivity. In chapter 6, Energy Dissipation Chemical Force Microscopy is developed to investigate the time dependence and dissipative characteristics of SAM interfacial interactions in solution. Long-range adhesive forces for hydroxyl and carboxyl terminated SAM surfaces arise from solvent, not ionic, interactions. Exclusion of the solvent and contact between the SAM surfaces leads to rearrangement of the SAM headgroups. The isolation of the chemical and physical interfacial properties from the topography by Energy Dissipation Chemical Force Microscopy produces a new quantitative high-sensitivity imaging mode.

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

Spong, D.A.; Hirshman, S.P.; Whitson, J.C.

A new class of low aspect ratio toroidal hybrid stellarators is found using more general plasma confinement optimization criterion than quasi-symmetrization. The plasma current profile and shape of the outer magnetic flux surface are used as control variables to achieve near constancy of the longitudinal invariant J* on internal flux surfaces (quasi-omnigeneity), in addition to a number of other desirable physics target properties. We find that a range of compact (small aspect ratio A), high {beta} (ratio of thermal energy to magnetic field energy), low plasma current devices exist which have significantly improved confinement both for thermal as well asmore » energetic (collisionless) particle components. With reasonable increases in magnetic field and geometric size, such devices can also be scaled to confine 3.5 MeV alpha particle orbits.« less

Surface diffusion of Sb on Ge(111) investigated by second harmonic microscopy

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

Schultz, K.A.

Surface diffusion of Sb on Ge(111) has been measured with the newly-developed technique of second harmonic microscopy. In this method, concentration profiles at submonolayer coverage are imaged directly by second harmonic generation with 5 [mu]m spatial resolution. A Boltzmann-Matano analysis of the concentration profiles yields the coverage dependence of the diffusivity D without parameterization. Experiments were performed at roughly 70% of the bulk melting temperature T[sub m]. In the coverage range of 0 < [theta] < 0.6, the activation energy E[sub diff] remains constant at 47.5 [+-] 1.5 kcal/mol. The corresponding pre-exponential factor decreases from 8.7 [times] 10[sup 3[+-]0.4] tomore » 1.6 [times] 10[sup 2[+-]0.4] cm[sup 2]/sec. The results are explained in terms of a new vacancy model for surface diffusion at high-temperatures. The model accounts semiquantitatively for the large values of E[sub diff] and D[sub o], and suggest that these quantities may be manipulated by bulk doping levels and photon illumination of the surface.« less

Using tethered triblock copolymers to mediate the interaction between substrates

NASA Astrophysics Data System (ADS)

Chern, Shyh-Shi; Zhulina, Ekaterina B.; Pickett, Galen T.; Balazs, Anna C.

1998-04-01

Using scaling analysis and a self-consistent field (SCF) theory, we compress two copolymer-coated surfaces and isolate conditions that yield multiple, distinct minima in the interaction profile. We focus on planar surfaces that are coated with ABC triblock copolymers. Tethered to the surface by the last monomer in the C block, the copolymers are grafted at relatively low densities. The surrounding solution is a poor solvent for both the A and C blocks, and is a good solvent for the B blocks. Through scaling theory, we pinpoint the parameters that yield two minima in the interaction profile. The SCF calculations reveal the changes in the morphology of the polymers as the layers are compressed. Through both studies, we determine how the morphological changes give rise to the observed surface interactions. The results provide guidelines for creating polymer-coated colloidal systems that can form two stable crystal structures. Such systems could be used for bistable, optical switches. The findings also yield a prescription for creating systems that exhibit additional minima in the free energy of interaction.

Molecular Dynamics Simulation of Hydrogen Trapping on Sigma 5 Tungsten Grain Boundaries

NASA Astrophysics Data System (ADS)

Al-Shalash, Aws Mohammed Taha

Tungsten as a plasma facing material is the predominant contender for future Tokamak reactor environments. The interaction between the plasma particles and tungsten is crucial to be studied for successful usage and design of tungsten in the plasma facing components ensuring the reliability and longevity of the fusion reactors. The bombardment of the sigma 5 polycrystalline tungsten was modeled using the molecular dynamics simulation through the large-scale atomic/molecular massively parallel simulator (LAMMPS) code and Tersoff type interatomic potential. By simulating the operational conditions of the Tokamak reactors, the hydrogen trapping rate, implantation distribution, and bubble formation was investigated at various temperatures (300-1200 K) and various hydrogen incident energy (20-100 eV). The substrate's temperature increases the deflected H atoms, and increases the penetration depth for the ones that go through. As well, the lower temperature tungsten substrates retain more H atoms. Increasing the bombarded hydrogen's energy increases the trapping and retention rate and the depth of penetration. Another experiments were conducted to determine whether the Sigma5 grain boundary's (GB) location affects the trapping profiles in H. The findings are ranges from small effect on deflection rates at low H energies to no effect at high H energies. However, there is a considerable effect on shifting the trapping depth profile upward toward the surface when raising the GB closer to the surface. Hydrogen atoms are highly mobile on tungsten substrate, yet no bubble formation was witnessed.

Depth dependence of defect evolution and TED during annealing

NASA Astrophysics Data System (ADS)

Colombeau, B.; Cowern, N. E. B.; Cristiano, F.; Calvo, P.; Lamrani, Y.; Cherkashin, N.; Lampin, E.; Claverie, A.

2004-02-01

A quantitative transmission electron microscopy (TEM) study on the depth profile of extended defects, formed after Si implantation, has been carried out. Two different Si + implant conditions have been considered. TEM analysis for the highest energy/dose shows that {1 1 3} defects evolve into dislocation loops whilst the defect depth distribution remains unchanged as a function of annealing time. For the lowest energy/dose, {1 1 3} defects grow and dissolve while the defect band shrinks preferentially on the surface side. At the same time, extraction of boron transient enhanced diffusion (TED) as a function of depth shows a decrease of the supersaturation towards the surface, starting at the location of the defect band. The study clearly shows that in these systems the silicon surface is the principal sink for interstitials. The results provide a critical test of the ability of physical models to simulate defect evolution and TED.

The effects on γ-LiAlO2 induced by nuclear energy losses during Ga ions implantation

NASA Astrophysics Data System (ADS)

Zhang, Jing; Song, Hong-Lian; Qiao, Mei; Yu, Xiao-Fei; Wang, Tie-Jun; Wang, Xue-Lin

2017-09-01

To explore the evolution of γ-LiAlO2 under ion irradiation at low energy, we implanted Ga ions of 30, 80 and 150 keV at fluences of 1 × 1014 and 1 × 1015 ions/cm2 in z-cut γ-LiAlO2 samples, respectively. The implantation resulted in damage regions dominated by nuclear energy losses at depth of 232 Å, 514 Å, and 911 Å beneath the surface, respectively, which was simulated by the Stopping and Range of Ions in Matter program. The irradiated γ-LiAlO2 were characterized with atomic force microscope, Raman spectroscopy, X-ray diffraction and Rutherford backscattering in a channeling mode for morphology evolution, structure information and damage profiles. The interesting and partly abnormal results showed the various behaviors in modification of surface by Ga ions implantation.

Similarity theory of the buoyantly interactive planetary boundary layer with entrainment

NASA Technical Reports Server (NTRS)

Hoffert, M. I.; Sud, Y. C.

1976-01-01

A similarity model is developed for the vertical profiles of turbulent flow variables in an entraining turbulent boundary layer of arbitrary buoyant stability. In the general formulation the vertical profiles, internal rotation of the velocity vector, discontinuities or jumps at a capping inversion and bulk aerodynamic coefficients of the boundary layer are given by solutions to a system of ordinary differential equations in the similarity variable. To close the system, a formulation for buoyantly interactive eddy diffusivity in the boundary layer is introduced which recovers Monin-Obukhov similarity near the surface and incorporates a hypothesis accounting for the observed variation of mixing length throughout the boundary layer. The model is tested in simplified versions which depend only on roughness, surface buoyancy, and Coriolis effects by comparison with planetary-boundary-layer wind- and temperature-profile observations, measurements of flat-plate boundary layers in a thermally stratified wind tunnel and observations of profiles of terms in the turbulent kinetic-energy budget of convective planetary boundary layers. On balance, the simplified model reproduced the trend of these various observations and experiments reasonably well, suggesting that the full similarity formulation be pursued further.

Background of SAM atom-fraction profiles

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

Ernst, Frank

Atom-fraction profiles acquired by SAM (scanning Auger microprobe) have important applications, e.g. in the context of alloy surface engineering by infusion of carbon or nitrogen through the alloy surface. However, such profiles often exhibit an artifact in form of a background with a level that anti-correlates with the local atom fraction. This article presents a theory explaining this phenomenon as a consequence of the way in which random noise in the spectrum propagates into the discretized differentiated spectrum that is used for quantification. The resulting model of “energy channel statistics” leads to a useful semi-quantitative background reduction procedure, which ismore » validated by applying it to simulated data. Subsequently, the procedure is applied to an example of experimental SAM data. The analysis leads to conclusions regarding optimum experimental acquisition conditions. The proposed method of background reduction is based on general principles and should be useful for a broad variety of applications. - Highlights: • Atom-fraction–depth profiles of carbon measured by scanning Auger microprobe • Strong background, varies with local carbon concentration. • Needs correction e.g. for quantitative comparison with simulations • Quantitative theory explains background. • Provides background removal strategy and practical advice for acquisition.« less

Oxy-nitrides characterization with a new ERD-TOF system

NASA Astrophysics Data System (ADS)

Chicoine, M.; Schiettekatte, F.; Laitinen, M. I.; Sajavaara, T.

2017-09-01

A new time-of-flight (TOF) camera was installed on Elastic Recoil Detection (ERD) measurement setup on the Tandem Accelerator at Université de Montréal. The camera consists of two timing detectors, developed and built by the Jyvaskyla group, that use a thin carbon foil and microchannel plates (MCP) to produce the start and stop signals. The position of the first detector is fixed at 18 cm from the target, while the position of the second detector can be varied between 50 and 90 cm from the first detector. This allows to increase time resolution by increasing the distance between the time-of-flight detectors or to increase solid angle by decreasing the distance. Moving the detector also helps determining the parameters such as the effective distance between detector foils and the delay time. Compared to the original system, which had only one timing detector and relied on a surface barrier energy detector to measure both the energy and the stop signal, in the new system the energy is now obtained from the timing signal with much better resolution, reaching ∼4 nm near the surface. There is also no more need to keep track of the surface barrier detector calibration for each element, including the pulse height defect. We show examples of quantitative depth profiles of oxy-nitride layers that has been characterized with this new system. It allows quantitative depth profiling of targets that would be difficult to analyze with other techniques, especially when light elements such as hydrogen, carbon, or nitrogen are mixed in various proportions in a heavy element matrix.

Mass and heat transfer between evaporation and condensation surfaces: Atomistic simulation and solution of Boltzmann kinetic equation.

PubMed

Zhakhovsky, Vasily V; Kryukov, Alexei P; Levashov, Vladimir Yu; Shishkova, Irina N; Anisimov, Sergey I

2018-04-16

Boundary conditions required for numerical solution of the Boltzmann kinetic equation (BKE) for mass/heat transfer between evaporation and condensation surfaces are analyzed by comparison of BKE results with molecular dynamics (MD) simulations. Lennard-Jones potential with parameters corresponding to solid argon is used to simulate evaporation from the hot side, nonequilibrium vapor flow with a Knudsen number of about 0.02, and condensation on the cold side of the condensed phase. The equilibrium density of vapor obtained in MD simulation of phase coexistence is used in BKE calculations for consistency of BKE results with MD data. The collision cross-section is also adjusted to provide a thermal flux in vapor identical to that in MD. Our MD simulations of evaporation toward a nonreflective absorbing boundary show that the velocity distribution function (VDF) of evaporated atoms has the nearly semi-Maxwellian shape because the binding energy of atoms evaporated from the interphase layer between bulk phase and vapor is much smaller than the cohesive energy in the condensed phase. Indeed, the calculated temperature and density profiles within the interphase layer indicate that the averaged kinetic energy of atoms remains near-constant with decreasing density almost until the interphase edge. Using consistent BKE and MD methods, the profiles of gas density, mass velocity, and temperatures together with VDFs in a gap of many mean free paths between the evaporation and condensation surfaces are obtained and compared. We demonstrate that the best fit of BKE results with MD simulations can be achieved with the evaporation and condensation coefficients both close to unity.

The impact of in-canopy wind profile formulations on heat flux estimation using the remote sensing-based two-source model for an open orchard canopy in southern Italy

NASA Astrophysics Data System (ADS)

Cammalleri, C.; Anderson, M. C.; Ciraolo, G.; D'Urso, G.; Kustas, W. P.; La Loggia, G.; Minacapilli, M.

2010-07-01

For open orchard and vineyard canopies containing significant fractions of exposed soil (>50%), typical of Mediterranean agricultural regions, the energy balance of the vegetation elements is strongly influenced by heat exchange with the bare soil/substrate. For these agricultural systems a "two-source" approach, where radiation and turbulent exchange between the soil and canopy elements are explicitly modelled, appears to be the only suitable methodology for reliably assessing energy fluxes. In strongly clumped canopies, the effective wind speed profile inside and below the canopy layer can highly influence the partitioning of energy fluxes between the soil and vegetation components. To assess the impact of in-canopy wind profile on model flux estimates, an analysis of three different formulations is presented, including algorithms from Goudriaan (1977), Massman (1987) and Lalic et al. (2003). The in-canopy wind profile formulations are applied to the thermal-based Two-Source Energy Balance (TSEB) model developed by Norman et al. (1995) and modified by Kustas and Norman (1999). High resolution airborne remote sensing images, collected over an agricultural area located in the western part of Sicily (Italy) comprised primarily of vineyards, olive and citrus orchards, are used to derive all the input parameters need to apply the TSEB. The images were acquired from June to October 2008 and include a relatively wide range of meteorological and soil moisture conditions. A preliminary sensitivity analysis of the three wind profile algorithms highlight the dependence of wind speed just above the soil/substrate to leaf area index and canopy height over the typical canopy properties range of these agricultural area. It is found that differences in wind just above surface among the models is most significant under sparse and medium fractional cover conditions (20-60%). The TSEB model heat flux estimates are compared with micrometeorological measurements from a small aperture scintillometer and an eddy covariance tower collected over an olive orchard characterized by moderate fractional vegetation cover (≈35%) and relatively tall crop height (≈3.5 m). TSEB fluxes for the 7 image acquisition dates generated using both the Massman and Goudriaan in-canopy wind profile formulations give close agreement with measured fluxes, while the Lalic et al. equations yield poor results. The Massman wind profile scheme slightly outperforms that of Goudriaan, but it requires an additional parameter describing the roughness of the underlying vegetative surface. This parameter is not directly obtainable using remote sensing, hence this study suggests that the Goudriaan formulation for landscape applications is most suitable when detailed site-specific information regarding canopy architecture is unavailable.

In Vivo Simulator for Microwave Treatment

NASA Technical Reports Server (NTRS)

Arndt, G. Dickey (Inventor); Carl, James R. (Inventor); Raffoul, George W. (Inventor); Karasack, Vincent G. (Inventor); Pacifico, Antonio (Inventor); Pieper, Carl F. (Inventor)

2001-01-01

Method and apparatus are provided for propagating microwave energy into heart tissues to produce a desired temperature profile therein at tissue depths sufficient for thermally ablating arrhythmogenic cardiac tissue to treat ventricular tachycardia and other arrhythmias while preventing excessive heating of surrounding tissues, organs, and blood. A wide bandwidth double-disk antenna is effective for this purpose over a bandwidth of about 6 GHz. A computer simulation provides initial screening capabilities for an antenna such as antenna. frequency, power level, and power application duration. The simulation also allows optimization of techniques for specific patients or conditions. In operation, microwave energy between about 1 GHz and 12 GHz is applied to monopole microwave radiator having a surface wave limiter. A test setup provides physical testing of microwave radiators to determine the temperature profile created in actual heart tissue or ersatz heart tissue. Saline solution pumped over the heart tissue with a peristaltic pump simulates blood flow. Optical temperature sensors disposed at various tissue depths within the heart tissue detect the temperature profile without creating any electromagnetic interference. The method may be used to produce a desired temperature profile in other body tissues reachable by catheter such as tumors and the like.

Transcatheter Antenna For Microwave Treatment

NASA Technical Reports Server (NTRS)

Arndt, G. Dickey (Inventor); Carl, James R. (Inventor); Raffoul, George W. (Inventor); Karasack, Vincent G. (Inventor); Pacifico, Antonio (Inventor); Pieper, Carl F. (Inventor)

2000-01-01

Method and apparatus are provided for propagating microwave energy into heart tissues to produce a desired temperature profile therein at tissue depths sufficient for thermally ablating arrhythmogenic cardiac tissue to treat ventricular tachycardia and other arrhythmias while preventing excessive heating of surrounding tissues, organs, and blood. A wide bandwidth double-disk antenna is effective for this purpose over a bandwidth of about six gigahertz. A computer simulation provides initial screening capabilities for an antenna such as antenna, frequency, power level, and power application duration. The simulation also allows optimization of techniques for specific patients or conditions. In operation, microwave energy between about 1 Gigahertz and 12 Gigahertz is applied to monopole microwave radiation having a surface wave limiter. A test setup provides physical testing of microwave radiators to determine the temperature profile created in actual heart tissue or ersatz heart tissue. Saline solution pumped over the heart tissue with a peristaltic pump simulates blood flow. Optical temperature sensors disposed at various tissue depths within the heart tissue detect the temperature profile without creating any electromagnetic interference. The method may he used to produce a desired temperature profile in other body tissues reachable by catheter such as tumors and the like.

Microwave Treatment for Cardiac Arrhythmias

NASA Technical Reports Server (NTRS)

Arndt, G. Dickey (Inventor); Carl, James R. (Inventor); Raffoul, George W. (Inventor); Pacifico, Antonio (Inventor)

1999-01-01

Method and apparatus are provided for propagating microwave energy into heart tissues to produce a desired temperature profile therein at tissue depths sufficient for thermally ablating arrhythmogenic cardiac tissue to treat ventricular tachycardia and other arrhythmias while preventing excessive heating of surrounding tissues, organs, and blood. A wide bandwidth double-disk antenna is effective for this purpose over a bandwidth of about six gigahertz. A computer simulation provides initial screening capabilities for an antenna such as antenna, frequency, power level, and power application duration. The simulation also allows optimization of techniques for specific patients or conditions. In operation, microwave energy between about 1 Gigahertz and 12 Gigahertz is applied to monopole microwave radiator having a surface wave limiter. A test setup provides physical testing of microwave radiators to determine the temperature profile created in actual heart tissue or ersatz heart tissue. Saline solution pumped over the heart tissue with a peristaltic pump simulates blood flow. Optical temperature sensors disposed at various tissue depths within the heart tissue detect the temperature profile without creating any electromagnetic interference. The method may be used to produce a desired temperature profile in other body tissues reachable by catheter such as tumors and the like.

Surface cleaning techniques and efficient B-field profiles for lithium ion sources on extraction ion diodes

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

Cuneo, M.E.; Menge, P.R.; Hanson, D.L.

Application of ion beams to Inertial Confinement Fusion requires efficient production, transport and focusing of an intense, low microdivergence beam of an appropriate range ion. At Sandia, the authors are studying the production of lithium ion beams in extraction applied-B ion diodes on the SABRE accelerator (5 MV, 250 kA). Evidence on both SABRE (1 TW) and PBFA-II (20 TW) indicates that the lithium beam turns off and is replaced by a beam of mostly protons and carbon, possibly due to electron thermal and stimulated desorption of hydrocarbon surface contamination with subsequent avalanche ionization. Turn-off of the lithium beam ismore » accompanied by rapid impedance collapse. Surface cleaning techniques are being developed to reduce beam contamination, increase the total lithium energy and reduce the rate of diode impedance collapse. Application of surface cleaning techniques has increased the production of lithium from passive LiF sources by a factor of 2. Improved diode electric and magnetic field profiles have increased the diode efficiency and production of lithium by a factor of 5, without surface cleaning. Work is ongoing to combine these two advances which are discussed here.« less

LOTOS: A Proposed Lower Tropospheric Observing System from the Land Surface through the Atmospheric Boundary Layer

NASA Astrophysics Data System (ADS)

Cohn, S. A.; Lee, W. C.; Carbone, R. E.; Oncley, S.; Brown, W. O. J.; Spuler, S.; Horst, T. W.

2015-12-01

Advances in sensor capabilities, but also in electronics, optics, RF communication, and off-the-grid power are enabling new measurement paradigms. NCAR's Earth Observing Laboratory (EOL) is considering new sensors, new deployment modes, and integrated observing strategies to address challenges in understanding within the atmospheric boundary layer and the underlying coupling to the land surface. Our vision is of a network of deployable observing sites, each with a suite of complementary instruments that measure surface-atmosphere exchange, and the state and evolution of the boundary layer. EOL has made good progress on distributed surface energy balance and flux stations, and on boundary layer remote sensing of wind and water vapor, all suitable for deployments of combined instruments and as network of such sites. We will present the status of the CentNet surface network development, the 449-MHz modular wind profiler, and a water vapor and temperature profiling differential absorption lidar (DIAL) under development. We will further present a concept for a test bed to better understand the value of these and other possible instruments in forming an instrument suite flexible for multiple research purposes.

Current and turbulence measurements at the FINO1 offshore wind energy site: analysis using 5-beam ADCPs

NASA Astrophysics Data System (ADS)

Bakhoday-Paskyabi, Mostafa; Fer, Ilker; Reuder, Joachim

2018-01-01

We report concurrent measurements of ocean currents and turbulence at two sites in the North Sea, one site at upwind of the FINO1 platform and the other 200-m downwind of the Alpha Ventus wind farm. At each site, mean currents, Reynolds stresses, turbulence intensity and production of turbulent kinetic energy are obtained from two bottom-mounted 5-beam Nortek Signature1000s, high-frequency Doppler current profiler, at a water depth of approximately 30 m. Measurements from the two sites are compared to statistically identify the effects of wind farm and waves on ocean current variability and the turbulent structure in the water column. Profiles of Reynolds stresses are found to be sensible to both environmental forcing and the wind farm wake-induced distortions in both boundary layers near the surface and the seabed. Production of turbulent kinetic energy and turbulence intensity exhibit approximately similar, but less pronounced, patterns in the presence of farm wake effects.

Investigation of the Wave Propagation of Vector Modes of Light in a Spherically Symmetric Refractive Index Profile

NASA Astrophysics Data System (ADS)

Pozderac, Preston; Leary, Cody

We investigated the solutions to the Helmholtz equation in the case of a spherically symmetric refractive index using three different methods. The first method involves solving the Helmholtz equation for a step index profile and applying further constraints contained in Maxwell's equations. Utilizing these equations, we can simultaneously solve for the electric and magnetic fields as well as the allowed energies of photons propagating in this system. The second method applies a perturbative correction to these energies, which surfaces when deriving a Helmholtz type equation in a medium with an inhomogeneous refractive index. Applying first order perturbation theory, we examine how the correction term affects the energy of the photon. In the third method, we investigate the effects of the above perturbation upon solutions to the scalar Helmholtz equation, which are separable with respect to its polarization and spatial degrees of freedom. This work provides insights into the vector field structure of a photon guided by a glass microsphere.

Adsorption and solvation of ethanol at the water liquid-vapor interface: a molecular dynamics study

NASA Technical Reports Server (NTRS)

Wilson, M. A.; Pohorille, A.

1997-01-01

The free energy profiles of methanol and ethanol at the water liquid-vapor interface at 310K were calculated using molecular dynamics computer simulations. Both alcohols exhibit a pronounced free energy minimum at the interface and, therefore, have positive adsorption at this interface. The surface excess was computed from the Gibbs adsorption isotherm and was found to be in good agreement with experimental results. Neither compound exhibits a free energy barrier between the bulk and the surface adsorbed state. Scattering calculations of ethanol molecules from a gas phase thermal distribution indicate that the mass accommodation coefficient is 0.98, and the molecules become thermalized within 10 ps of striking the interface. It was determined that the formation of the solvation structure around the ethanol molecule at the interface is not the rate-determining step in its uptake into water droplets. The motion of an ethanol molecule in a water lamella was followed for 30 ns. The time evolution of the probability distribution of finding an ethanol molecule that was initially located at the interface is very well described by the diffusion equation on the free energy surface.

Measurements of solar and terrestrial heating and cooling rate profiles in Arctic and sub-tropic stratocumulus

NASA Astrophysics Data System (ADS)

Gottschalk, Matthias; Lauermann, Felix; Ehrlich, André; Siebert, Holger; Wendisch, Manfred

2017-04-01

Stratocumulus covers approximately 20 % (annually averaged) of the Earth's surface and thus strongly influences the atmospheric and surface radiative energy budget resulting in radiative cooling and heating effects. Globally, the solar cooling effect of the widespread sub-tropical stratocumulus dominates. However, in the Arctic the solar cloud albedo effect (cooling) is often smaller than the thermal-infrared greenhouse effect (warming), which is a result of the lower incoming solar radiation and the low cloud base height. Therefore, Arctic stratocumulus mostly warms the atmosphere and surface below the cloud. Additionally, different environmental conditions lead to differences between sub-tropical and Arctic stratocumulus. Broadband pyranometers and pyrgeometers will be used to measure heating and cooling rate profiles in and above stratocumulus. For this purpose two slowly moving platforms are used (helicopter and tethered balloon) in order to consider for the long response times of both broadband radiation sensors. Two new instrument packages are developed for the applied tethered balloon and helicopter platforms, which will be operated within Arctic and sub-tropical stratocumulus, respectively. In June 2017, the balloon will be launched from a sea ice floe north of 80 °N during the Arctic Balloon-borne profiling Experiment (ABEX) as part of (AC)3 (Arctic Amplification: Climate Relevant Atmospheric and Surface Processes and Feedback Mechanisms) Transregional Collaborative Research Center. The helicopter will sample sub-tropical stratocumulus over the Azores in July 2017.

Changes in surface morphology of enamel after Er:YAG laser irradiation

NASA Astrophysics Data System (ADS)

Rechmann, Peter; Goldin, Dan S.; Hennig, Thomas

1998-04-01

Aim of the study was to investigate the surface and subsurface structure of enamel after irradiation with an Er:YAG laser (wavelength 2.94 micrometer, pulse duration 250 - 500 microseconds, free running, beam profile close to tophead, focus diameter 600 micrometer, focus distance 13 mm, different power settings, air-water spray 2 ml/min; KAVO Key Laser 1242, Kavo Biberach, Germany). The surface of more than 40 freshly extracted wisdom teeth were irradiated using a standardized application protocol (pulse repetition rate 4 and 6 Hz, moving speed of the irradiation table 2 mm/sec and 3 mm/sec, respectively). On each surface between 3 and 5 tracks were irradiated at different laser energies (60 - 500 mJ/pulse) while each track was irradiated between one and ten times respectively. For the scanning electron microscope investigation teeth were dried in alcohol and sputtered with gold. For light microscopic examinations following laser impact, samples were fixed in formaldehyde, dried in alcohol and embedded in acrylic resin. Investigations revealed that at subsurface level cracks can not be observed even at application of highest energies. Borders of the irradiated tracks seem to be sharp while melted areas of different sizes are observed on the bottom of the tracks depending on applied energy. Small microcracks can be seen on the surface of these melted areas.

TRANSCRIPTIONAL PROFILING USING THE FLOWTHROUGH GENOSENSOR FINAL CRADA REPORT C/ORNL97-00472

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

Doktycz, M. J.; Yang, H.

1999-06-01

A Cooperative Research and Development Agreement (CRADA) between Lockheed Martin Energy Research Corporation (Contractor) and Gene Logic, Inc., (Participant) was carried out to evaluate the technical feasibility study of the application of the flowthrough genosensor for gene expression (transcriptional) profiling, over the current industry practice of using flat surface hybridization arrays to monitor the relative abundance of individual mRNA species in a cell. Various parameters, including substrate preparation, flow rates, hybridization conditions and sample concentrations, were evaluated on the flowthrough genosensor. The superiority of the flowthrough genosensor, in terms of hybridization rate and sensitivity were established.

Influence of surface morphology on adsorption of potassium stearate molecules on diamond-like carbon substrate: A molecular dynamics study

NASA Astrophysics Data System (ADS)

Guo, Shusen; Cao, Yongzhi; Sun, Tao; Zhang, Junjie; Gu, Le; Zhang, Chuanwei; Xu, Zhiqiang

2018-05-01

Molecular dynamics (MD) simulations were used to provide insights into the influence of nano-scale surface morphology on adsorptive behavior of Potassium stearate molecules on diamond-like carbon (DLC) substrates. Particular focus was given to explain that how the distinctive geometric properties of different surface morphologies affect the equilibrium structures and substrate-molecules interactions of monolayers, which was achieved through adsorptive analysis methods including adsorptive process, density profile, density distribution and surface potential energy. Analysis on surface potential energy demonstrated that the adsorptivity of amorphous smooth substrate is uniformly distributed over the surface, while DLC substrates with different surface morphologies appear to be more potentially corrugated, which improves the adsorptivity significantly. Because of the large distance of molecules from carbon atoms located at the square groove bottom, substrate-molecules interactions vanish significantly, and thus potassium stearate molecules cannot penetrate completely into the square groove. It can be observed that the equilibrium substrate-molecules interactions of triangle groove and semi-circle groove are much more powerful than that of square groove due to geometrically advantageous properties. These findings provided key information of optimally design of solid substrates with controllable adsorptivity.

The relevance of rooftops: Analyzing the microscale surface energy balance in the Chicago region

NASA Astrophysics Data System (ADS)

Khosla, Radhika

Spatial structure in climate variables often exist over very short length scales within an urban area, and this structure is a result of various site-specific features. In order to analyze the seasonal and diurnal energy flows that take place at a microclimatic surface, this work develops a semi-empirical energy balance model. For this, radiation fluxes and meteorological measurements are determined by direct observation; sensible heat and latent heat fluxes by parameterizations; and the heat storage flux by a 1-D mechanistic model that allows analysis of the temperature profile and heat storage within an underlying slab. Two sites receive detailed study: an anthropogenic site, being a University of Chicago building rooftop, and a natural site, outside Chicago in the open country. Two identical sets of instruments record measurements contemporaneously from these locations during June-November 2007, the entire period for which analyses are carried out. The study yields seasonal trends in surface temperature, surface-to-air temperature contrast and net radiation. At both sites, a temporal hysteresis between net radiation and heat storage flux indicates that surplus energy absorbed during daylight is released to the atmosphere later in the evening. The surface energy balance model responds well to site specific features for both locations. An analysis of the surface energy balance shows that the flux of sensible heat is the largest non-radiative contributor to the roof's surface cooling, while the flux of latent heat (also referred to as evaporative cooling) is the largest heat sink for the soil layer. In the latter part of the study, the surface energy balance model is upgraded by adding the capability to compute changes in surface temperature and non-radiative fluxes for any specified set of thermal and reflective roof properties. The results of this analysis allow an examination of the relationship between the roof temperature, the heat flux entering the building interior through the roof, and the physical properties of the surface. These results hold particular relevance for urban heat island mitigation strategies. Based on the results of this work, recommendations are proposed for widespread adoption of various techniques that enhance building energy efficiency (particularly targeting rooftops), mitigate the negative impacts of the urban heat island, and overcome the current barriers to transforming the market.

Electron Stimulated Desorption Yields at the Mercury's Surface Based On Hybrid Simulation Results

NASA Astrophysics Data System (ADS)

Travnicek, P. M.; Schriver, D.; Orlando, T. M.; Hellinger, P.

2016-12-01

In terms of previous research concerning the solar wind sputtering process, most of the focus has been on ion sputtering by precipitating solar wind protons, however, precipitating electrons can also result in the desorption of neutrals and ions from Mercury's surface and represents a potentially significant source of exospheric and heavy ion components. Electron stimulated desorption (ESD) is not bound by optical selection rules and electron impact energies can vary over a much wider range, including core-level excitations that easily lead to multi-electron shake up events that can cascade into localized multiple charged states that Coulomb explode with extreme kinetic energy release (up to 8 eV = 186,000 K). While considered for the lunar exosphere, ESD has not been adequately studied or quantified as a producer of neutrals and ions. ESD is a well known process which involves the excitation (often ionization) of a surface target followed by charge ejection, bond breaking and ion expulsion due to the resultant Coulomb repulsion. Though the role of ESD processes has not been discussed much with respect to Mercury, the impinging energetic electrons that are transported through the magnetosphere and precipitate can induce significant material removal. Given the energetics and the wide band-gap nature of the minerals, the departing material may also be primarily ionic. The possible role of 5 eV - 1 keV electron stimulated desorption and dissociation in "weathering" the regolith can be significant. ESD yields will be calculated based on the ion and electron precipitation profiles for the already carried out hybrid and electron simulations. Neutral and ion cloud profiles around Mercury will be calculated and combined with those profiles expected from PSD and MIV.

MEPSA: minimum energy pathway analysis for energy landscapes.

PubMed

Marcos-Alcalde, Iñigo; Setoain, Javier; Mendieta-Moreno, Jesús I; Mendieta, Jesús; Gómez-Puertas, Paulino

2015-12-01

From conformational studies to atomistic descriptions of enzymatic reactions, potential and free energy landscapes can be used to describe biomolecular systems in detail. However, extracting the relevant data of complex 3D energy surfaces can sometimes be laborious. In this article, we present MEPSA (Minimum Energy Path Surface Analysis), a cross-platform user friendly tool for the analysis of energy landscapes from a transition state theory perspective. Some of its most relevant features are: identification of all the barriers and minima of the landscape at once, description of maxima edge profiles, detection of the lowest energy path connecting two minima and generation of transition state theory diagrams along these paths. In addition to a built-in plotting system, MEPSA can save most of the generated data into easily parseable text files, allowing more versatile uses of MEPSA's output such as the generation of molecular dynamics restraints from a calculated path. MEPSA is freely available (under GPLv3 license) at: http://bioweb.cbm.uam.es/software/MEPSA/ CONTACT: pagomez@cbm.csic.es. Supplementary data are available at Bioinformatics online. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Germanium diffusion with vapor-phase GeAs and oxygen co-incorporation in GaAs

NASA Astrophysics Data System (ADS)

Wang, Wei-Fu; Cheng, Kai-Yuan; Hsieh, Kuang-Chien

2018-01-01

Vapor-phase germanium diffusion has been demonstrated in Zn-doped and semi-insulating GaAs in sealed ampoules with GeAs powders and excess arsenic. Secondary-ion-mass spectroscopy (SIMS) profiles indicate the presence of unintentional co-incorporation of oxygen in high densities (>1017/cm3) along with diffused germanium donors whose concentration (>>1018/cm3) determined by electro-chemical capacitance-voltage (ECV) profiler shows significant compensation near the surface. The source of oxygen mainly originates from the GeAs powder which contains Ge-O surface oxides. Variable-temperature photoluminescence (PL) shows that in GeAs-diffused samples, a broad peak ranging from 0.86-1.38 eV with the peak position around 1.1 eV predominates at low temperatures while the near band-edge luminescence quenches. The broad band is attributed to the GeGa-VGa self-activated (SA) centers possibly associated with nearby oxygen-related defect complex, and its luminescence persists up to 400 K. The configurational-coordinate modeling finds that the SA defect complex has a thermal activation energy of 150-180 meV and a vibrational energy 26.8 meV. The presence of oxygen does not much affect the SA emission intensity but may have influenced the peak position, vibration frequency and activation energy as compared to other common donor-VGa defects in GaAs.

Describing Site Amplification for Surface Waves in Realistic Basins

NASA Astrophysics Data System (ADS)

Bowden, D. C.; Tsai, V. C.

2017-12-01

Standard characterizations of site-specific site response assume a vertically-incident shear wave; given a 1D velocity profile, amplification and resonances can be calculated based on conservation of energy. A similar approach can be applied to surface waves, resulting in an estimate of amplification relative to a hard rock site that is different in terms of both amount of amplification and frequency. This prediction of surface-wave site amplification has been well validated through simple simulations, and in this presentation we explore the extent to which a 1D profile can explain observed amplifications in more realistic scenarios. Comparisons of various simple 2D and 3D simulations, for example, allow us to explore the effect of different basin shapes and the relative importance of effects such as focusing, conversion of wave-types and lateral surface wave resonances. Additionally, the 1D estimates for vertically-incident shear waves and for surface waves are compared to spectral ratios of historic events in deep sedimentary basins to demonstrate the appropriateness of the two different predictions. This difference in amplification responses between the wave types implies that a single measurement of site response, whether analytically calculated from 1D models or empirically observed, is insufficient for regions where surface waves play a strong role.

Calculation of nanodrop profile from fluid density distribution.

PubMed

Berim, Gersh O; Ruckenstein, Eli

2016-05-01

Two approaches are examined, which can be used to determine the drop profile from the fluid density distributions (FDDs) obtained on the basis of microscopic theories. For simplicity, only two-dimensional (cylindrical, or axisymmetrical) distributions are examined and it is assumed that the fluid is either in contact with a smooth solid or separated from the smooth solid by a lubricating liquid film. The first approach is based on the sharp-kink interface approximation in which the density of the liquid inside and the density of the vapor outside the drop are constant with the exception of the surface layer of the drop where the density is different from the above ones. In this case, the drop profile was calculated by minimizing the total potential energy of the system. The second approach is based on a nonuniform FDD obtained either by the density functional theory or molecular dynamics simulations. To determine the drop profile from such an FDD, which does not contain sharp interfaces, three procedures can be used. In the first two procedures, P1 and P2, the one-dimensional FDDs along straight lines which are parallel to the surface of the solid are extracted from the two-dimensional FDD. Each of those one-dimensional FDDs has a vapor-liquid interface at which the fluid density changes from vapor-like to liquid-like values. Procedure P1 uses the locations of the equimolar dividing surfaces for the one-dimensional FDDs as points of the drop profile. Procedure P2 is based on the assumption that the fluid density is constant on the surface of the drop, that density being selected either arbitrarily or as a fluid density at the location of the equimolar dividing surface for one of the one-dimensional FDDs employed in procedure P1. In the third procedure, P3, which is suggested for the first time in this paper, the one-dimensional FDDs are taken along the straight lines passing through a selected point inside the drop (radial line). Then, the drop profile is calculated like in procedure P1. It is shown, that procedure P3 provides a drop profile which is more reasonable than the other ones. Relationship of the discussed procedures to those used in image analysis is briefly discussed. Copyright © 2016 Elsevier B.V. All rights reserved.

Assessment of Optical Turbulence Profiles Derived From Probabilistic Climatology

DTIC Science & Technology

2007-03-01

654.3.1 Transformed Data Results . . . . . . . . . . . . 664.3.2 Untransformed Data Results . . . . . . . . . . . 704.4 Application of ...the needed repower to destroy surface based enemy targets.Courtesy of Boeing Corporation. http://www.boeing.com/news/ fea-ture/aa2004/backgrounders...medium is cornerstone to successful employ-ment of these HELs. 1.3 Introduction to Optical Turbulence Lethal application of directed energy repower

Influence Of Secondary Electrons Produced From Plasma Material Interaction In Presence Of Crossed Electric And Magnetic Fields

NASA Astrophysics Data System (ADS)

Sawlani, Kapil; Herzog, Joshua M.; Kwak, Joowon; Foster, John

2012-10-01

The electron energy distribution function (EEDF) plays a very important role in determining thruster efficiency as it determines various gas phase reaction rates. In Hall thrusters, secondary electron emission derived from the interaction of energetic electrons with ceramic channel surfaces influence the overall shape of the EEDF as well as determine the potential difference between the plasma and wall. The role of secondary electrons on the discharge operation of Hall thrusters is poorly understood. Experimentally, determining this effect is even more taxing as the secondary electron yield (SEY) varies drastically based on many parameters such as incident electron energies, flux and impact angle, and also on the surface properties such as temperature and roughness. The electron transport is also affected by the profile of the magnetic field, which is not uniform across the length of the accelerating channel. The goal of this work is to map out the variation of the EEDF and potential profile in response to the controlled introduction of secondary electrons. This data is expected to serve as a tool to validate and improve existing numerical models by providing boundary conditions and SEY for various situations that are encountered in Hall thrusters.

Cosmogenic Cl-36 production rates in meteorites and the lunar surface

NASA Technical Reports Server (NTRS)

Nishiizumi, K.; Arnold, J. R.; Kubik, P. W.; Elmore, D.; Reedy, R. C.

1989-01-01

Activity vs. depth profiles of cosmic ray produced Cl-36 were measured in metal from two cores each in the St. Severin and Jilin chondrites and in lunar core 15008. Production of Cl-36 in these samples range from high-energy reactions with Fe and Ni to low-energy reactions with Ca and K and possibly neutron-capture reactions with Cl-36. The cross sections used in the Reedy-Arnold model for neutron-induced reactions were adjusted to get production rates that fit the measured Cl-36 activities in St. Severin metal and in the lunar soil of core 15008. The Cl-36 in metal from St. Severin has a fairly flat activity-vs-depth profile, unlike most other cosmogenic nuclides in bulk samples from St. Severin, which increase in concentration with depth. In metal from Jilin, a decrease in Cl-36 was observed near its center. The length of Jilin's most recent cosmic-ray exposure was approximately 0.5 My. Lunar core 15008 has an excess in Cl-36 of about 4 dpm/kg near its surface that was produced by solar-proton-induced reactions. The calculated production rates are consistent with these measured trends in 15008.

Long-Term (4 mo) Oxygen Isotope Exchange Experiment between Zircon and Hydrothermal Fluid

NASA Astrophysics Data System (ADS)

Bindeman, I. N.; Schmitt, A. K.; Lundstrom, C.; Golledge, S.

2013-12-01

Knowing oxygen diffusivity in zircon has several critical applications: 1) establishing zircon stability and solubility in hot silica-saturated hydrothermal solutions; 2) deriving metamorphic and magmatic heating timescales from intra-crystal oxygen isotopic gradients; 3) assessing the survivability of oxygen isotopic signatures in Hadean zircons. We report results of a microanalytical investigation of an isotope exchange experiment using a cold-seal pressure apparatus at 850°C and 500 MPa over 4 months duration. Natural zircon, quartz and rutile were sealed with a silica-rich solution doped with 18-O, D, 7-Li and 10-B in a gold capsule. The diffusion length-scales were examined by depth profiling using time-of-flight (TOF) and high-sensitivity dynamic secondary ionization mass spectrometry (SIMS). Starting materials had distinct and homogeneous δ18O: zircon from Mesa Falls tuff of Yellowstone (+3.6‰), rutile from Karelia (-29‰), Bishop Tuff Quartz (+8.4‰), and δ18O doped water (+400‰). Starting material zircon showed invariant 18O/16O during depth profiling. After the 4 month experiment, rutile crystal surfaces displayed etching (100's of nm), while zircon exteriors lacked visible change. Quartz was completely dissolved and reprecipitated in a minor residue. Rutile developed ~2 μm long Fickian diffusion profiles largely consistent with the wet diffusion coefficients for rutile previously reported [1]. Surface U-Pb dating of zircon detected no significant Pb loss from the outermost ~300 nm of the crystal face and returned identical core-face ages. We performed δ18O depth profiling of zircon in two directions. First, forward profiles (crystal rim inwards) by dynamic SIMS (no surface treatment besides Au-coating; Cs+ beam of 20 kV impact energy) showed initially high and decreasing 18O/16O over ~130 nm; TOF-SIMS forward profiles using a 2 kV Cs+ sputter beam and 25 kV Bi3+ primary ions on uncoated zircon surfaces (cleaned for 2 min with HF) yielded decreasing 18O/16O over a similar length scale. These profile lengths are largely consistent with wet diffusion coefficient for zircon reported by [2]. In contrast, back-side depth profiling was conducted by dynamic SIMS on a 1 μm thick wafer cut from the zircon by FIB. No significant elevation in 18O/16O was detected when the surface layer was penetrated, consistent with dry diffusion coefficients of [2]. The results suggest that nm-scale SIMS surface analysis of isotope ratios is challenging. We are investigating if they can be critically affected by knock-on effects and/or continuous mixing of a very thin enriched surface layer during depth profiling in our and previous experiments. [1] Moore et al., 1998, Am. Min. 83, 700-711 [2] Watson and Cherniak, 1997, EPSL 148, 537-544

Importance of length and sequence order on magnesium binding to surface-bound oligonucleotides studied by second harmonic generation and atomic force microscopy.

PubMed

Holland, Joseph G; Geiger, Franz M

2012-06-07

The binding of magnesium ions to surface-bound single-stranded oligonucleotides was studied under aqueous conditions using second harmonic generation (SHG) and atomic force microscopy (AFM). The effect of strand length on the number of Mg(II) ions bound and their free binding energy was examined for 5-, 10-, 15-, and 20-mers of adenine and guanine at pH 7, 298 K, and 10 mM NaCl. The binding free energies for adenine and guanine sequences were calculated to be -32.1(4) and -35.6(2) kJ/mol, respectively, and invariant with strand length. Furthermore, the ion density for adenine oligonucleotides did not change as strand length increased, with an average value of 2(1) ions/strand. In sharp contrast, guanine oligonucleotides displayed a linear relationship between strand length and ion density, suggesting that cooperativity is important. This data gives predictive capabilities for mixed strands of various lengths, which we exploit for 20-mers of adenines and guanines. In addition, the role sequence order plays in strands of hetero-oligonucleotides was examined for 5'-A(10)G(10)-3', 5'-(AG)(10)-3', and 5'-G(10)A(10)-3' (here the -3' end is chemically modified to bind to the surface). Although the free energy of binding is the same for these three strands (averaged to be -33.3(4) kJ/mol), the total ion density increases when several guanine residues are close to the 3' end (and thus close to the solid support substrate). To further understand these results, we analyzed the height profiles of the functionalized surfaces with tapping-mode atomic force microscopy (AFM). When comparing the average surface height profiles of the oligonucleotide surfaces pre- and post- Mg(II) binding, a positive correlation was found between ion density and the subsequent height decrease following Mg(II) binding, which we attribute to reductions in Coulomb repulsion and strand collapse once a critical number of Mg(II) ions are bound to the strand.

Estimation of Key Parameters of the Coupled Energy and Water Model by Assimilating Land Surface Data

NASA Astrophysics Data System (ADS)

Abdolghafoorian, A.; Farhadi, L.

2017-12-01

Accurate estimation of land surface heat and moisture fluxes, as well as root zone soil moisture, is crucial in various hydrological, meteorological, and agricultural applications. Field measurements of these fluxes are costly and cannot be readily scaled to large areas relevant to weather and climate studies. Therefore, there is a need for techniques to make quantitative estimates of heat and moisture fluxes using land surface state observations that are widely available from remote sensing across a range of scale. In this work, we applies the variational data assimilation approach to estimate land surface fluxes and soil moisture profile from the implicit information contained Land Surface Temperature (LST) and Soil Moisture (SM) (hereafter the VDA model). The VDA model is focused on the estimation of three key parameters: 1- neutral bulk heat transfer coefficient (CHN), 2- evaporative fraction from soil and canopy (EF), and 3- saturated hydraulic conductivity (Ksat). CHN and EF regulate the partitioning of available energy between sensible and latent heat fluxes. Ksat is one of the main parameters used in determining infiltration, runoff, groundwater recharge, and in simulating hydrological processes. In this study, a system of coupled parsimonious energy and water model will constrain the estimation of three unknown parameters in the VDA model. The profile of SM (LST) at multiple depths is estimated using moisture diffusion (heat diffusion) equation. In this study, the uncertainties of retrieved unknown parameters and fluxes are estimated from the inverse of Hesian matrix of cost function which is computed using the Lagrangian methodology. Analysis of uncertainty provides valuable information about the accuracy of estimated parameters and their correlation and guide the formulation of a well-posed estimation problem. The results of proposed algorithm are validated with a series of experiments using a synthetic data set generated by the simultaneous heat and water (SHAW) model. In addition, the feasibility of extending this algorithm to use remote sensing observations that have low temporal resolution is examined by assimilating the limited number of land surface moisture and temperature observations.

Complementary study of the internal porous silicon layers formed under high-dose implantation of helium ions

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

Lomov, A. A., E-mail: lomov@ftian.ru; Myakon’kikh, A. V.; Chesnokov, Yu. M.

The surface layers of Si(001) substrates subjected to plasma-immersion implantation of helium ions with an energy of 2–5 keV and a dose of 5 × 10{sup 17} cm{sup –2} have been investigated using high-resolution X-ray reflectivity, Rutherford backscattering, and transmission electron microscopy. The electron density depth profile in the surface layer formed by helium ions is obtained, and its elemental and phase compositions are determined. This layer is found to have a complex structure and consist of an upper amorphous sublayer and a layer with a porosity of 30–35% beneath. It is shown that the porous layer has the sharpestmore » boundaries at a lower energy of implantable ions.« less

Surface energy balance measurements and modeling on the ice cap of King George Island, West Antarctica

NASA Astrophysics Data System (ADS)

Falk, U.; Braun, M.; Sala, H.; Menz, G.

2012-04-01

The Antarctic Peninsula is amongst the fastest warming places on Earth and further temperature increase is to be expected. It has undergone rapid environmental changes in the past decades. Exceptional rates of surface air temperature increases (2.5K in 50 years) are concurrent with retreating glacier fronts, an increase in melt areas, surface lowering and rapid retreat, break-up and disintegration of ice shelves. The South Shetland Islands are located on the northern tip of the Peninsula and are especially vulnerable to climate change due to their maritime climate. For King George Island we have compiled a unique data set comprising direct measurements of evaporation and sensible heat flux by eddy covariance on the Warszawa Icefield for the austral summers November 2010 to March 2011 and January to February 2012 in combination with a fully equipped automated weather station measuring long- and short-wave radiation components, profiles of temperature, humidity and wind velocities as well as glacier ice temperatures in profile. The combination with the eddy covariance data allows for analysis of variability and seasonality of surface energy balance components on a glacier for an entire year. Repeat measurements of surface lowering at different locations on King George Island are used for analysis of multi-sensor satellite data to identify melt patterns and bare ice areas during summer. In combination with long-term time series of weather data, these data give indication of the sensitivity of the inland ice cap to the ongoing changes. This research is part of the ESF project IMCOAST funded by BMBF. Field work was carried out at the Dallmann laboratory (Jubany, King George Island) in cooperation of the Instituto Antartico Argentino (Argentina) and the Alfred-Wegener Institute (German).

How Consistent are Recent Variations in the Tropical Energy and Water Cycle Resolved by Satellite Measurements?

NASA Technical Reports Server (NTRS)

Robertson, F. R.; Lu, H.-I.

2004-01-01

One notable aspect of Earth's climate is that although the planet appears to be very close to radiative balance at top-of-atmosphere (TOA), the atmosphere itself and underlying surface are not. Profound exchanges of energy between the atmosphere and oceans, land and cryosphere occur over a range of time scales. Recent evidence from broadband satellite measurements suggests that even these TOA fluxes contain some detectable variations. Our ability to measure and reconstruct radiative fluxes at the surface and at the top of atmosphere is improving rapidly. One question is 'How consistent, physically, are these diverse remotely-sensed data sets'? The answer is of crucial importance to understanding climate processes, improving physical models, and improving remote sensing algorithms. In this work we will evaluate two recently released estimates of radiative fluxes, focusing primarily on surface estimates. The International Satellite Cloud Climatology Project 'FD' radiative flux profiles are available from mid-1983 to near present and have been constructed by driving the radiative transfer physics from the Goddard Institute for Space Studies (GISS) global model with ISCCP clouds and TOVS (TIROS Operational Vertical Sounder)thermodynamic profiles. Full and clear sky SW and LW fluxes are produced. A similar product from the NASA/GEWEX Surface Radiation Budget Project using different radiative flux codes and thermodynamics from the NASA/Goddard Earth Observing System (GEOS-1) assimilation model makes a similar calculation of surface fluxes. However this data set currently extends only through 1995. We also employ precipitation measurements from the Global Precipitation Climatology Project (GPCP) and the Tropical Rainfall Measuring Mission (TRMM). Finally, ocean evaporation estimates from the Special Sensor Microwave Imager (SSM/I) are considered as well as derived evaporation from the NCAR/NCEP Reanalysis. Additional information is included in the original extended abstract.

Impact of radon gas concentration in the aerosoles profile

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

Lukaj, Edmond, E-mail: mondilukaj@yahoo.com; Vila, Floran, E-mail: floranvila@yahoo.com; Mandija, Florian, E-mail: fmandija@yahoo.com

Radon gases relased from building materials and from earth surface are the major responsibility of air ionization. Radon nuclear decay can produce an alpha particle with high energy and Radon progeny. This particle and gamma rays can deliver particles in the air and produce ions with different polarities. This ions, because of induced electric charge, can attach with air aerosols and charge them with their electric charge. The charged aerosols can interact with the other aerosols and ions. Because of this exchange, the air conductivity and the aerosol profiles will change dependently by Radon gas concentration and gamma radiation. Observationsmore » show an increase in concentration of Radon during the night, and a decrease during the daylight time. The Radon gas concentration changed hour by hour can induce aerosol profile to change. This dependency between the aerosol profiles and the Radon gas concentrations is discussed.« less

Investigation of Ion-Implanted Photosensitive Silicon Structures by Electrochemical Capacitance–Voltage Profiling

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

Yakovlev, G. E., E-mail: geyakovlev@etu.ru; Frolov, D. S.; Zubkova, A. V.

2016-03-15

The method of electrochemical capacitance–voltage profiling is used to study boron-implanted silicon structures for CCD matrices with backside illumination. A series of specially prepared structures with different energies and doses of ion implantation and also with various materials used for the coating layers (aluminum, silicon oxide, and their combinations) is studied. The profiles of the depth distribution of majority charge carriers of the studied structures are obtained experimentally. Also, using the Poisson equation and the Fredholm equation of the first kind, the distributions of the charge-carrier concentration and of the electric field in the structures are calculated. On the basismore » of the analysis and comparison of theoretical and experimental concentration profiles, recommendations concerning optimization of the structures’ parameters in order to increase the value of the pulling field and decrease the effect of the surface potential on the transport of charge carriers are suggested.« less

XPS investigation of depth profiling induced chemistry

NASA Astrophysics Data System (ADS)

Pratt, Quinn; Skinner, Charles; Koel, Bruce; Chen, Zhu

2017-10-01

Surface analysis is an important tool for understanding plasma-material interactions. Depth profiles are typically generated by etching with a monatomic argon ion beam, however this can induce unintended chemical changes in the sample. Tantalum pentoxide, a sputtering standard, and PEDOT:PSS, a polymer that was used to mimic the response of amorphous carbon-hydrogen co-deposits, were studied. We compare depth profiles generated with monatomic and gas cluster argon ion beams (GCIB) using X-ray photoelectron spectroscopy (XPS) to quantify chemical changes. In both samples, monatomic ion bombardment led to beam-induced chemical changes. Tantalum pentoxide exhibited preferential sputtering of oxygen and the polymer experienced significant bond modification. Depth profiling with clusters is shown to mitigate these effects. We present sputtering rates for Ta2O5 and PEDOT:PSS as a function of incident energy and flux. Support was provided through DOE Contract Number DE-AC02-09CH11466.

Differential absorption lidar measurements of atmospheric temperature and pressure profiles

NASA Technical Reports Server (NTRS)

Korb, C. L.

1981-01-01

The theory and methodology of using differential absorption lidar techniques for the remote measurement of atmospheric pressure profiles, surface pressure, and temperature profiles from ground, air, and space-based platforms are presented. Pressure measurements are effected by means of high resolution measurement of absorption at the edges of the oxygen A band lines where absorption is pressure dependent due to collisional line broadening. Temperature is assessed using measurements of the absorption at the center of the oxygen A band line originating from a quantum state with high ground state energy. The population of the state is temperature dependent, allowing determination of the temperature through the Boltzmann term. The results of simulations of the techniques using Voigt profile and variational analysis are reported for ground-based, airborne, and Shuttle-based systems. Accuracies in the 0.5-1.0 K and 0.1-0.3% range are projected.

Improvement in Clouds and the Earth's Radiant Energy System/Surface and Atmosphere Radiation Budget Dust Aerosol Properties, Effects on Surface Validation of Clouds and Radiative Swath

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

Rutan, D.; Rose, F.; Charlock, T.P.

2005-03-18

Within the Clouds and the Earth's Radiant Energy System (CERES) science team (Wielicki et al. 1996), the Surface and Atmospheric Radiation Budget (SARB) group is tasked with calculating vertical profiles of heating rates, globally, and continuously, beneath CERES footprint observations of Top of Atmosphere (TOA) fluxes. This is accomplished using a fast radiative transfer code originally developed by Qiang Fu and Kuo-Nan Liou (Fu and Liou 1993) and subsequently highly modified by the SARB team. Details on the code and its inputs can be found in Kato et al. (2005) and Rose and Charlock (2002). Among the many required inputsmore » is characterization of the vertical column profile of aerosols beneath each footprint. To do this SARB combines aerosol optical depth information from the moderate-resolution imaging spectroradiometer (MODIS) instrument along with aerosol constituents specified by the Model for Atmosphere and Chemical Transport (MATCH) of Collins et al. (2001), and aerosol properties (e.g. single scatter albedo and asymmetry parameter) from Tegen and Lacis (1996) and OPAC (Hess et al. 1998). The publicly available files that include these flux profiles, called the Clouds and Radiative Swath (CRS) data product, available from the Langley Atmospheric Sciences Data Center (http://eosweb.larc.nasa.gov/). As various versions of the code are completed, publishable results are named ''Editions.'' After CRS Edition 2A was finalized it was found that dust aerosols were too absorptive. Dust aerosols have subsequently been modified using a new set of properties developed by Andy Lacis and results have been released in CRS Edition 2B. This paper discusses the effects of changing desert dust aerosol properties, which can be significant for the radiation budget in mid ocean, a few thousand kilometers from the source regions. Resulting changes are validated via comparison of surface observed fluxes from the Saudi Solar Village surface site (Myers et al. 1999), and the E13 site at the Atmospheric Radiation Measurement (ARM), Southern Great Plains (SGP) central facility.« less

Infrared temperature measurements over bare soil and vegetation - A HAPEX perspective

NASA Technical Reports Server (NTRS)

Carlson, Toby N.; Perry, Eileen M.; Taconet, Odile

1987-01-01

Preliminary analyses of aircraft and ground measurements made in France during the HAPEX experiment show that horizontal radiometric surface temperature variations, as viewed by aircraft, can reflect the vertical profile of soil moisture (soil versus root zone) because of horizontal variations in vegetation density. Analyses based on one day's data show that, although horizontal variations in soil moisture were small, the vertical differences between a dry surface and a wet root zone were large. Horizontal temperature differences between bare soil, corn and oats reflect differences in the fractional vegetation cover, as seen by the radiometer. On the other hand, these horizontal variations in radiometric surface temperature seem to reflect real horizontal variations in surface turbulent energy fluxes.

Surface holograms for sensing application

NASA Astrophysics Data System (ADS)

Zawadzka, M.; Naydenova, I.

2018-01-01

Surface gratings with periodicity of 2 μm and amplitude in the range of 175 and 240 nm were fabricated in a plasticized polyvinylchloride doped with a metalloporphyrin (ZnTPP), via a single laser pulse holographic ablation process. The effect of the laser pulse energy on the profiles of the fabricated surface structure was investigated. The sensing capabilities of the fabricated diffractive structures towards amines (triethylamine, diethylamine) and pyridine vapours were then explored; the holographic structures were exposed to the analyte vapours and changes in the intensity of the diffracted light were monitored in real time at 473 nm. It was demonstrated that surface structures, fabricated in a polymer doped with a metalloporphyrin which acts as analyte receptor, have a potential in sensing application.

Turbulence in a convective marine atmospheric boundary layer

NASA Technical Reports Server (NTRS)

Chou, S.-H.; Atlas, D.; Yeh, E.-N.

1986-01-01

The structure and kinetic energy budget of turbulence in the convective marine atmospheric boundary layer as observed by aircraft during a cold air outbreak have been studied using mixed layer scaling. The results are significantly different from those of previous studies under conditions closer to free convection. The normalized turbulent kinetic energy and turbulent transport are about twice those found during the Air Mass Transformation Experiment (AMTEX). This implies that for a given surface heating the present case is dynamically more active. The difference is mainly due to the greater importance of wind shear in the present case. This case is closer to the roll vortex regime, whereas AMTEX observed mesoscale cellular convection which is closer to free convection. Shear generation is found to provide a significant energy source, in addition to buoyancy production, to maintain a larger normalized turbulent kinetic energy and to balance a larger normalized dissipation. The interaction between turbulent pressure and divergence (i.e., pressure scrambling) is also found to transfer energy from the vertical to the horizontal components, and is expected to be stronger in roll vortices than in m esoscale cells. The sensible heat flux is found to fit well with a linear vertical profile in a clear or subcloud planetary boundary layer (PBL), in good agreement with the results of Lenschow et al., (1980). The heat flux ratio between the PBL top and the surface, derived from the linear fitted curve, is approximately -0.14, in good agreement with that derived from the lidar data for the same case. Near the PBL top, the heat flux profiles are consistent with those of Deardoff (1979) and Deardorff et al. (1980).

Harmonic Fourier beads method for studying rare events on rugged energy surfaces.

PubMed

Khavrutskii, Ilja V; Arora, Karunesh; Brooks, Charles L

2006-11-07

We present a robust, distributable method for computing minimum free energy paths of large molecular systems with rugged energy landscapes. The method, which we call harmonic Fourier beads (HFB), exploits the Fourier representation of a path in an appropriate coordinate space and proceeds iteratively by evolving a discrete set of harmonically restrained path points-beads-to generate positions for the next path. The HFB method does not require explicit knowledge of the free energy to locate the path. To compute the free energy profile along the final path we employ an umbrella sampling method in two generalized dimensions. The proposed HFB method is anticipated to aid the study of rare events in biomolecular systems. Its utility is demonstrated with an application to conformational isomerization of the alanine dipeptide in gas phase.

Lunar Polar Illumination for Power Analysis

NASA Technical Reports Server (NTRS)

Fincannon, James

2008-01-01

This paper presents illumination analyses using the latest Earth-based radar digital elevation model (DEM) of the lunar south pole and an independently developed analytical tool. These results enable the optimum sizing of solar/energy storage lunar surface power systems since they quantify the timing and durations of illuminated and shadowed periods. Filtering and manual editing of the DEM based on comparisons with independent imagery were performed and a reduced resolution version of the DEM was produced to reduce the analysis time. A comparison of the DEM with lunar limb imagery was performed in order to validate the absolute heights over the polar latitude range, the accuracy of which affects the impact of long range, shadow-casting terrain. Average illumination and energy storage duration maps of the south pole region are provided for the worst and best case lunar day using the reduced resolution DEM. Average illumination fractions and energy storage durations are presented for candidate low energy storage duration south pole sites. The best site identified using the reduced resolution DEM required a 62 hr energy storage duration using a fast recharge power system. Solar and horizon terrain elevations as well as illumination fraction profiles are presented for the best identified site and the data for both the reduced resolution and high resolution DEMs compared. High resolution maps for three low energy storage duration areas are presented showing energy storage duration for the worst case lunar day, surface height, and maximum absolute surface slope.

The use of remote sensing and linear wave theory to model local wave energy around Alphonse Atoll, Seychelles

NASA Astrophysics Data System (ADS)

Hamylton, S.

2011-12-01

This paper demonstrates a practical step-wise method for modelling wave energy at the landscape scale using GIS and remote sensing techniques at Alphonse Atoll, Seychelles. Inputs are a map of the benthic surface (seabed) cover, a detailed bathymetric model derived from remotely sensed Compact Airborne Spectrographic Imager (CASI) data and information on regional wave heights. Incident energy at the reef crest around the atoll perimeter is calculated as a function of its deepwater value with wave parameters (significant wave height and period) hindcast in the offshore zone using the WaveWatch III application developed by the National Oceanographic and Atmospheric Administration. Energy modifications are calculated at constant intervals as waves transform over the forereef platform along a series of reef profile transects running into the atoll centre. Factors for shoaling, refraction and frictional attenuation are calculated at each interval for given changes in bathymetry and benthic coverage type and a nominal reduction in absolute energy is incorporated at the reef crest to account for wave breaking. Overall energy estimates are derived for a period of 5 years and related to spatial patterning of reef flat surface cover (sand and seagrass patches).

Visualization and analysis of pulsed ion beam energy density profile with infrared imaging

NASA Astrophysics Data System (ADS)

Isakova, Y. I.; Pushkarev, A. I.

2018-03-01

Infrared imaging technique was used as a surface temperature-mapping tool to characterize the energy density distribution of intense pulsed ion beams on a thin metal target. The technique enables the measuring of the total ion beam energy and the energy density distribution along the cross section and allows one to optimize the operation of an ion diode and control target irradiation mode. The diagnostics was tested on the TEMP-4M accelerator at TPU, Tomsk, Russia and on the TEMP-6 accelerator at DUT, Dalian, China. The diagnostics was applied in studies of the dynamics of the target cooling in vacuum after irradiation and in the experiments with target ablation. Errors caused by the target ablation and target cooling during measurements have been analyzed. For Fluke Ti10 and Fluke Ti400 infrared cameras, the technique can achieve surface energy density sensitivity of 0.05 J/cm2 and spatial resolution of 1-2 mm. The thermal imaging diagnostics does not require expensive consumed materials. The measurement time does not exceed 0.1 s; therefore, this diagnostics can be used for the prompt evaluation of the energy density distribution of a pulsed ion beam and during automation of the irradiation process.

Modeling surface backgrounds from radon progeny plate-out

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

Perumpilly, G.; Guiseppe, V. E.; Snyder, N.

2013-08-08

The next generation low-background detectors operating deep underground aim for unprecedented low levels of radioactive backgrounds. The surface deposition and subsequent implantation of radon progeny in detector materials will be a source of energetic background events. We investigate Monte Carlo and model-based simulations to understand the surface implantation profile of radon progeny. Depending on the material and region of interest of a rare event search, these partial energy depositions can be problematic. Motivated by the use of Ge crystals for the detection of neutrinoless double-beta decay, we wish to understand the detector response of surface backgrounds from radon progeny. Wemore » look at the simulation of surface decays using a validated implantation distribution based on nuclear recoils and a realistic surface texture. Results of the simulations and measured α spectra are presented.« less

Layered Model for Radiation-Induced Chemical Evolution of Icy Surface Composition on Kuiper Belt and Oort Cloud Bodies

NASA Technical Reports Server (NTRS)

Cooper, John F.; Hill, Matthew E.; Richardson, John D.; Sturner, Steven J.

2010-01-01

The diversity of albedos and surface colors on observed Kuiper Belt and Inner Oort Cloud objects remains to be explained in terms of competition between primordial intrinsic versus exogenic drivers of surface and near-surface evolution. Earlier models have attempted without success to attribute this diversity to the relations between surface radiolysis from cosmic ray irradiation and gardening by meteoritic impacts. A more flexible approach considers the different depth-dependent radiation profiles produced by low-energy plasma, suprathermal, and maximally penetrating charged particles of the heliospheric and local interstellar radiation environments. Generally red objects of the dynamically cold (low inclination, circular orbit) Classical Kuiper Belt might be accounted for from erosive effects of plasma ions and reddening effects of high energy cosmic ray ions, while suprathermal keV-MeV ions could alternatively produce more color neutral surfaces. The deepest layer of more pristine ice can be brought to the surface from meter to kilometer depths by larger impact events and potentially by cryovolcanic activity. The bright surfaces of some larger objects, e.g. Eris, suggest ongoing resurfacing activity. Interactions of surface irradiation, resultant chemical oxidation, and near-surface cryogenic fluid reservoirs have been proposed to account for Enceladus cryovolcanism and may have further applications to other icy irradiated bodies. The diversity of causative processes must be understood to account for observationally apparent diversities of the object surfaces.

Laser altimetry simulator. Version 3.0: User's guide

NASA Technical Reports Server (NTRS)

Abshire, James B.; Mcgarry, Jan F.; Pacini, Linda K.; Blair, J. Bryan; Elman, Gregory C.

1994-01-01

A numerical simulator of a pulsed, direct detection laser altimeter has been developed to investigate the performance of space-based laser altimeters operating over surfaces with various height profiles. The simulator calculates the laser's optical intensity waveform as it propagates to and is reflected from the terrain surface and is collected by the receiver telescope. It also calculates the signal and noise waveforms output from the receiver's optical detector and waveform digitizer. Both avalanche photodiode and photomultiplier detectors may be selected. Parameters of the detected signal, including energy, the 50 percent rise-time point, the mean timing point, and the centroid, can be collected into histograms and statistics calculated after a number of laser firings. The laser altimeter can be selected to be fixed over the terrain at any altitude. Alternatively, it can move between laser shots to simulate the terrain profile measured with the laser altimeter.

Iron deposition in modern and archaeological teeth

NASA Astrophysics Data System (ADS)

Williams, A.-M. M.; Siegele, R.

2014-09-01

Iron surface concentrations and profile maps were measured on the enamel of archaeological and modern teeth to determine how iron is deposited in tooth enamel and if it was affected by the post-mortem environment. Teeth from Australian children who died in the second half of the 19th century were compared with contemporary teeth extracted for orthodontic purposes. Surface analysis of the teeth was performed using the 3 MV Van Der Graff Accelerator at The Australian Nuclear Science and Technology Organisation (ANSTO), Sydney, Australia. A small sample of teeth were then cut in the mid sagittal plane and analysed using ANSTO High Energy Heavy Ion Microprobe. Maps and linear profiles were produced showing the distribution of iron across the enamel. Results show that both the levels and distribution of iron in archaeological teeth is quite different to contemporary teeth, raising the suggestion that iron has been significantly altered by the post-mortem environment.

Automated Mars surface sample return mission concepts for achievement of essential scientific objectives

NASA Technical Reports Server (NTRS)

Weaver, W. L.; Norton, H. N.; Darnell, W. L.

1975-01-01

Mission concepts were investigated for automated return to Earth of a Mars surface sample adequate for detailed analyses in scientific laboratories. The minimum sample mass sufficient to meet scientific requirements was determined. Types of materials and supporting measurements for essential analyses are reported. A baseline trajectory profile was selected for its low energy requirements and relatively simple implementation, and trajectory profile design data were developed for 1979 and 1981 launch opportunities. Efficient spacecraft systems were conceived by utilizing existing technology where possible. Systems concepts emphasized the 1979 launch opportunity, and the applicability of results to other opportunities was assessed. It was shown that the baseline missions (return through Mars parking orbit) and some comparison missions (return after sample transfer in Mars orbit) can be accomplished by using a single Titan III E/Centaur as the launch vehicle. All missions investigated can be accomplished by use of Space Shuttle/Centaur vehicles.

TrackEtching - A Java based code for etched track profile calculations in SSNTDs

NASA Astrophysics Data System (ADS)

Muraleedhara Varier, K.; Sankar, V.; Gangadathan, M. P.

2017-09-01

A java code incorporating a user friendly GUI has been developed to calculate the parameters of chemically etched track profiles of ion-irradiated solid state nuclear track detectors. Huygen's construction of wavefronts based on secondary wavelets has been used to numerically calculate the etched track profile as a function of the etching time. Provision for normal incidence and oblique incidence on the detector surface has been incorporated. Results in typical cases are presented and compared with experimental data. Different expressions for the variation of track etch rate as a function of the ion energy have been utilized. The best set of values of the parameters in the expressions can be obtained by comparing with available experimental data. Critical angle for track development can also be calculated using the present code.

High gain photoconductive semiconductor switch having tailored doping profile zones

DOEpatents

Baca, Albert G.; Loubriel, Guillermo M.; Mar, Alan; Zutavern, Fred J; Hjalmarson, Harold P.; Allerman, Andrew A.; Zipperian, Thomas E.; O'Malley, Martin W.; Helgeson, Wesley D.; Denison, Gary J.; Brown, Darwin J.; Sullivan, Charles T.; Hou, Hong Q.

2001-01-01

A photoconductive semiconductor switch with tailored doping profile zones beneath and extending laterally from the electrical contacts to the device. The zones are of sufficient depth and lateral extent to isolate the contacts from damage caused by the high current filaments that are created in the device when it is turned on. The zones may be formed by etching depressions into the substrate, then conducting epitaxial regrowth in the depressions with material of the desired doping profile. They may be formed by surface epitaxy. They may also be formed by deep diffusion processes. The zones act to reduce the energy density at the contacts by suppressing collective impact ionization and formation of filaments near the contact and by reducing current intensity at the contact through enhanced current spreading within the zones.

Cavitation in a metallic liquid: Homogeneous nucleation and growth of nanovoids

NASA Astrophysics Data System (ADS)

Cai, Y.; Wu, H. A.; Luo, S. N.

2014-06-01

Large-scale molecular dynamics (MD) simulations are performed to investigate homogeneous nucleation and growth of nanovoids during cavitation in liquid Cu. We characterize in detail the atomistic cavitation processes by following the temporal evolution of cavities or voids, analyze the nucleation behavior with the mean first-passage time (MFPT) and survival probability (SP) methods, and discuss the results against classical nucleation theory (CNT), the Tolman equation for surface energy, independent calculation of surface tension via integrating the stress profiles, the Johnson-Mehl-Avrami (JMA) growth law, and the power law for nucleus size distributions. Cavitation in this representative metallic liquid is a high energy barrier Poisson processes, and the steady-state nucleation rates obtained from statistical runs with the MFPT and SP methods are in agreement. The MFPT method also yields the critical nucleus size and the Zeldovich factor. Fitting with the Tolman's equation to the MD simulations yields the surface energy of a planar interface (˜0.9 J {m}^{-2}) and the Tolman length (0.4-0.5 Å), and those values are in accord with those from integrating the stress profiles of a planar interface. Independent CNT predictions of the nucleation rate (1033 - 34 s-1 m-3) and critical size (3-4 Å in radius) are in agreement with the MFPT and SP results. The JMA law can reasonably describe the nucleation and growth process. The size distribution of subcritical nuclei appears to follow a power law with an exponent decreasing with increasing tension owing to coupled nucleation and growth, and that of the supercritical nuclei becomes flattened during further stress relaxation due to void coalescence.

Cavitation in a metallic liquid: homogeneous nucleation and growth of nanovoids.

PubMed

Cai, Y; Wu, H A; Luo, S N

2014-06-07

Large-scale molecular dynamics (MD) simulations are performed to investigate homogeneous nucleation and growth of nanovoids during cavitation in liquid Cu. We characterize in detail the atomistic cavitation processes by following the temporal evolution of cavities or voids, analyze the nucleation behavior with the mean first-passage time (MFPT) and survival probability (SP) methods, and discuss the results against classical nucleation theory (CNT), the Tolman equation for surface energy, independent calculation of surface tension via integrating the stress profiles, the Johnson-Mehl-Avrami (JMA) growth law, and the power law for nucleus size distributions. Cavitation in this representative metallic liquid is a high energy barrier Poisson processes, and the steady-state nucleation rates obtained from statistical runs with the MFPT and SP methods are in agreement. The MFPT method also yields the critical nucleus size and the Zeldovich factor. Fitting with the Tolman's equation to the MD simulations yields the surface energy of a planar interface (~0.9 J m⁻²) and the Tolman length (0.4-0.5 Å), and those values are in accord with those from integrating the stress profiles of a planar interface. Independent CNT predictions of the nucleation rate (10(33 - 34) s(-1) m(-3)) and critical size (3-4 Å in radius) are in agreement with the MFPT and SP results. The JMA law can reasonably describe the nucleation and growth process. The size distribution of subcritical nuclei appears to follow a power law with an exponent decreasing with increasing tension owing to coupled nucleation and growth, and that of the supercritical nuclei becomes flattened during further stress relaxation due to void coalescence.

High efficiency, low cost, thin film silicon solar cell design and method for making

DOEpatents

Sopori, Bhushan L.

2001-01-01

A semiconductor device having a substrate, a conductive intermediate layer deposited onto said substrate, wherein the intermediate layer serves as a back electrode, an optical reflector, and an interface for impurity gettering, and a semiconductor layer deposited onto said intermediate layer, wherein the semiconductor layer has a grain size at least as large as the layer thickness, and preferably about ten times the layer thickness. The device is formed by depositing a metal layer on a substrate, depositing a semiconductive material on the metal-coated substrate to produce a composite structure, and then optically processing the composite structure by illuminating it with infrared electromagnetic radiation according to a unique time-energy profile that first produces pits in the backside surface of the semiconductor material, then produces a thin, highly reflective, low resistivity alloy layer over the entire area of the interface between the semiconductor material and the metal layer, and finally produces a grain-enhanced semiconductor layer. The time-energy profile includes increasing the energy to a first energy level to initiate pit formation and create the desired pit size and density, then ramping up to a second energy level in which the entire device is heated to produce an interfacial melt, and finally reducing the energy to a third energy level and holding for a period of time to allow enhancement in the grain size of the semiconductor layer.

High efficiency low cost thin film silicon solar cell design and method for making

DOEpatents

Sopori, Bhushan L.

1999-01-01

A semiconductor device having a substrate, a conductive intermediate layer deposited onto said substrate, wherein the intermediate layer serves as a back electrode, an optical reflector, and an interface for impurity gettering, and a semiconductor layer deposited onto said intermediate layer, wherein the semiconductor layer has a grain size at least as large as the layer thickness, and preferably about ten times the layer thickness. The device is formed by depositing a metal layer on a substrate, depositing a semiconductive material on the metal-coated substrate to produce a composite structure, and then optically processing the composite structure by illuminating it with infrared electromagnetic radiation according to a unique time-energy profile that first produces pits in the backside surface of the semiconductor material, then produces a thin, highly reflective, low resistivity alloy layer over the entire area of the interface between the semiconductor material and the metal layer, and finally produces a grain-enhanced semiconductor layer. The time-energy profile includes increasing the energy to a first energy level to initiate pit formation and create the desired pit size and density, then ramping up to a second energy level in which the entire device is heated to produce an interfacial melt, and finally reducing the energy to a third energy level and holding for a period of time to allow enhancement in the grain size of the semiconductor layer.

Frequency Upconversion and Parametric Surface Instabilities in Microwave Plasma Interactions.

NASA Astrophysics Data System (ADS)

Rappaport, Harold Lee

In this thesis the interaction of radiation with plasmas whose density profiles are nearly step functions of space and/or time are studied. The wavelengths of radiation discussed are large compared with plasma density gradient scale lengths. The frequency spectra are evaluated and the energy balance investigated for the transmitted and reflected transient electromagnetic waves that are generated when a monochromatic source drives a finite width plasma in which a temporal step increase in density occurs. Transmission resonances associated with the abrupt boundaries manifest themselves as previously unreported multiple frequency peaks in the transmitted electromagnetic spectrum. A tunneling effect is described in which a burst of energy is transmitted from the plasma immediately following a temporal density transition. Stability of an abruptly bounded plasma, one for which the incident radiation wavelength is large compared with the plasma density gradient scale length, is investigated for both s and p polarized radiation types. For s-polarized radiation a new formalism is introduced in which pump induced perturbations are expressed as an explicit superposition of linear and non-linear plasma half-space modes. Results for a particular regime and a summary of relevant literature is presented. We conclude that when s-polarized radiation acts alone on an abrupt diffusely bounded underdense plasma stimulated excitation of electron surface modes is suppressed. For p-polarized radiation the recently proposed Lagrangian Frame Two-Plasmon Decay mode (LFTPD) ^dag is investigated in the regime in which the instability is not resonantly coupled to surface waves propagating along the boundary region. In this case, spatially dependent growth rate profiles and spatially dependent transit layer magnetic fields are reported. The regime is of interest because we have found that when the perturbation wavenumber parallel to the boundary is less than the pump frequency divided by twice the speed of light, energy radiates from the boundary region and these emissions can serve as an experimental signature for this mode. The theory of surface wave linear mode conversion is reviewed with special attention paid to power flow and energy conservation in this system. ftn^ dagYu. M. Aliev and G. Brodin, Phys. Rev. A 42, 2374 (1990).

Surface atmosphere exchange in dry and a wet regime over the Ganges valley: a comprehensive investigation with direct observations and numerical simulations

NASA Astrophysics Data System (ADS)

Sathyanadh, Anusha; Prabhakaran, Thara; Karipot, Anandakumar

2017-04-01

Land atmosphere interactions in the Ganges Valley basin is a topic of significant importance as it is most vulnerable region due to extreme weather, air pollution, etc. The complete energy balance observations over this region was conducted as part of the CAIPEEX-IGOC (Cloud Aerosol Interaction and Precipitation Enhancement Experiment - Integrated Ground based Observational Campaign) experiment for an entire year. These observations give first insight into the partitioning of energy in this vulnerable environment during the dry and wet regimes, which are typically part of the intraseasonal oscillations during the Indian monsoon season. These transitions wet-dry and dry-wet are poorly represented in GCMs and is the motivation for the detailed investigation here. Observations conducted with micrometeorological tower instrumented with eddy covariance sensors, radiation balance, soil heat flux measurements, microwave radiometer, sodar, radiosonde data are used in the present study. A set of numerical investigations of different Planetary Boundary Layer (PBL) schemes is also carried out to investigate features of the diurnal cycle during the wet and dry regimes. General behaviour of both local and nonlocal PBL schemes found from the investigation is to accomplish enhanced mixing, leading to a deeper PBL in the valley. However, observations give clear evidence of residual boundary layer characterised by a weak stratification, playing a key role in the exchange of PBL air mass with that of free atmosphere. Impact of changes in parameterization and controlling factors on the PBL height are investigated. Case studies for a dry phase during the incidence of a heat wave and a wet phase during a land depression are presented. Observed diurnal features of the surface meteorological parameters including the surface energy budget components were well captured by local and nonlocal PBL schemes during both the cases. Vertical profiles of temperature, mixing ratio and winds from microwave radiometer, radiosonde sounding and SODAR measurements compared well with the model vertical profiles. All the schemes are able to capture the development of a drying phase, its persistence and revival after the drying, similar to observation. The characteristic features of the drying such as decrease in mixing ratio, PBL warming, enhanced PBL growth, variations in wind speed, etc were reproduced by the model simulations. Results indicate that model is simulating a drier and deeper surface and mixed layer, compared to the observations, which is assisted by enhanced mixing through deep updrafts rooted from the surface layer and downdrafts associated with the subsiding air reaching down to the surface. Two issues are identified with model as a) relating to enhanced mixing also assisted by the subsiding air at top of the boundary layer and b) the energy partitioning at the surface with significantly excess energy partitioned in to sensible heat flux, thus warming the model surface layer. A few aircraft observations are used to investigate entrainment issue and results from these analysis and inferences will be presented. The surface layer eddy covariance measurements of sensible and latent heat fluxes and surface layer relationships are used to tune the surface layer exchanges.

Keck/NIRC2 Imaging of the Warped, Asymmetric Debris Disk Around HD 32297

NASA Technical Reports Server (NTRS)

Currie, Thayne; Rodigas, Timothy J.; Debes, John; Plavchan, Peter; Kuchner, Marc; Jang, Condell, Hannah; Wilner, David; Andrews, Sean; Dahm, Scott; Robitaille,Thomas

2012-01-01

We present Keck/NIRC2 K(sub s) band high-contrast coronagraphic imaging of the luminous debris disk around the nearby, young A star HD 32297 resolved at a projected separation of r = 0.3 - 2.5" (approx equals 35 - 280 AU). The disk is highly warped to the north and exhibits a complex, "wavy" surface brightness profile interior to r approx equals 110 AU, where the peaks/plateaus in the profiles are shifted between the NE and SW disk lobes. The SW side of the disk is 50 - 100% brighter at r = 35 - 80 AU, and the location of its peak brightness roughly coincides with the disk's mm emission peak. Spectral energy distribution modeling suggests that HD 32297 has at least two dust populations that may originate from two separate belts likely at different locations, possibly at distances coinciding with the surface brightness peaks. A disk model fur a single dust belt including a phase function with two components and a 5 - 10 AU pericenter offset explains the disk's warped structure and reproduces some of the surface brightness profile's shape (e.g. the overall "wavy" profile, the SB peak/plateau shifts) but more poorly reproduces the disk's brightness asymmetry and the profile at wider separations (r > 110 AU). Although there may be a1ternate explanations, agreement between the SW disk brightness peak and disk's peak rom emission is consistent with an overdensity of very small, sub-blowout-sized dust and large, 0.1 - 1 mm-sized grains at approx equal 45 AU tracing the same parent population of planetesimals. New near-IR and submm observations may be able to clarify whether even more complex grain scattering properties or dynamical sculpting by an unseen planet are required to explain HD 32297's disk structure.

Layered Model for Radiation-Induced Chemical Evolution of Icy Surface Composition and Dynamics on Kuiper Belt and Oort Cloud Bodies

NASA Technical Reports Server (NTRS)

Cooper, John F.; Richardson, John D.

2010-01-01

The diversity of albedos and surface colors on observed Kuiper Belt and Inner Oort Cloud objects remains to be explained in terms of competition between primordial intrinsic versus exogenic drivers of surface and near-surface evolution. Earlier models have attempted without success to attribute this diversity to the relations between surface radiolysis from cosmic ray irradiation and gardening by meteoritic impacts. A more flexible approach considers the different depth-dependent radiation profiles produced by low-energy plasma, suprathermal, and maximally penetrating charged particles of the heliospheric and local interstellar radiation environment. Generally red objects of the dynamically cold (low inclination, circular orbit) Classical Kuiper Belt might be accounted for from erosive effects of plasma ions and reddening effects of high energy cosmic ray ions, while suprathermal keV-MeV ions could alternatively produce more color neutral surfaces. The deepest layer of more pristine ice can be brought to the surface from meter to kilometer depths by larger impact events and potentially by cryovolcanic activity. The bright surfaces of some larger objects, e.g. Eris, suggest ongoing resurfacing activity. Cycles of atmospheric formation and surface freezeout can further account for temporal variation as observed on Pluto. The diversity of causative processes must therefore be understood to account for observationally apparent diversities of the object surfaces.

Atmospheric pressure and temperature profiling using near IR differential absorption lidar

NASA Technical Reports Server (NTRS)

Korb, C. L.; Schwemmer, G. K.; Dombrowski, M.; Weng, C. Y.

1983-01-01

The present investigation is concerned with differential absorption lidar techniques for remotely measuring the atmospheric temperature and pressure profile, surface pressure, and cloud top pressure-height. The procedure used in determining the pressure is based on the conduction of high-resolution measurements of absorption in the wings of lines in the oxygen A band. Absorption with respect to these areas is highly pressure sensitive in connection with the mechanism of collisional line broadening. The method of temperature measurement utilizes a determination of the absorption at the center of a selected line in the oxygen A band which originates from a quantum state with high ground state energy.

Application of genetic algorithm in the evaluation of the profile error of archimedes helicoid surface

NASA Astrophysics Data System (ADS)

Zhu, Lianqing; Chen, Yunfang; Chen, Qingshan; Meng, Hao

2011-05-01

According to minimum zone condition, a method for evaluating the profile error of Archimedes helicoid surface based on Genetic Algorithm (GA) is proposed. The mathematic model of the surface is provided and the unknown parameters in the equation of surface are acquired through least square method. Principle of GA is explained. Then, the profile error of Archimedes Helicoid surface is obtained through GA optimization method. To validate the proposed method, the profile error of an Archimedes helicoid surface, Archimedes Cylindrical worm (ZA worm) surface, is evaluated. The results show that the proposed method is capable of correctly evaluating the profile error of Archimedes helicoid surface and satisfy the evaluation standard of the Minimum Zone Method. It can be applied to deal with the measured data of profile error of complex surface obtained by three coordinate measurement machines (CMM).

Derivation of Cloud Heating Rate Profiles using observations of Mixed-Phase Arctic Clouds: Impacts of Solar Zenith Angle

NASA Astrophysics Data System (ADS)

Zhang, G.; McFarquhar, G.; Poellot, M.; Verlinde, J.; Heymsfield, A.; Kok, G.

2005-12-01

Arctic stratus clouds play an important role in the energy balance of the Arctic region. Previous studies have suggested that Arctic stratus persist due to a balance among cloud top radiation cooling, latent heating, ice crystal fall out and large scale forcing. In this study, radiative heating profiles through Arctic stratus are computed using cloud, surface and thermodynamic observations obtained during the Mixed-Phase Arctic Cloud Experiment (M-PACE) as input to the radiative transfer model STREAMER. In particular, microphysical and macrophycial cloud properties such as phase, water content, effective particle size, particle shape, cloud height and cloud thickness were derived using data collected by in-situ sensors on the University of North Dakota (UND) Citation and ground-based remote sensors at Barrow and Oliktok Point. Temperature profiles were derived from radiosonde launches and a fresh snow surface was assumed. One series of sensitivity studies explored the dependence of the heating profile on the solar zenith angle. For smaller solar zenith angles, more incoming solar radiation is received at cloud top acting to counterbalance infrared cooling. As solar zenith angle in the Arctic is large compared to low latitudes, a large solar zenith angle may contribute to the longevity of these clouds.

Causes of plasma column contraction in surface-wave-driven discharges in argon at atmospheric pressure

NASA Astrophysics Data System (ADS)

Ridenti, Marco Antonio; de Amorim, Jayr; Dal Pino, Arnaldo; Guerra, Vasco; Petrov, George

2018-01-01

In this work we compute the main features of a surface-wave-driven plasma in argon at atmospheric pressure in view of a better understanding of the contraction phenomenon. We include the detailed chemical kinetics dynamics of Ar and solve the mass conservation equations of the relevant neutral excited and charged species. The gas temperature radial profile is calculated by means of the thermal diffusion equation. The electric field radial profile is calculated directly from the numerical solution of the Maxwell equations assuming the surface wave to be propagating in the TM00 mode. The problem is considered to be radially symmetrical, the axial variations are neglected, and the equations are solved in a self-consistent fashion. We probe the model results considering three scenarios: (i) the electron energy distribution function (EEDF) is calculated by means of the Boltzmann equation; (ii) the EEDF is considered to be Maxwellian; (iii) the dissociative recombination is excluded from the chemical kinetics dynamics, but the nonequilibrium EEDF is preserved. From this analysis, the dissociative recombination is shown to be the leading mechanism in the constriction of surface-wave plasmas. The results are compared with mass spectrometry measurements of the radial density profile of the ions Ar+ and Ar2+. An explanation is proposed for the trends seen by Thomson scattering diagnostics that shows a substantial increase of electron temperature towards the plasma borders where the electron density is small.

Characterization of CdTe and (CdZn)Te detectors with different metal contacts

NASA Astrophysics Data System (ADS)

Pekárek, J.; Belas, E.; Grill, R.; Uxa, Å.; James, R. B.

2013-09-01

In the present work we studied an influence of different types of surface etching and surface passivation of high resistivity CdZnTe-based semiconductor detector material. The aim was to find the optimal conditions to improve the properties of metal-semiconductor contact. The main effort was to reduce the leakage current and thus get better X-ray and gamma-ray spectrum, i.e. to create a detector operating at room temperature based on this semiconductor material with sufficient energy resolution and the maximum charge collection efficiency. Individual surface treatments were characterized by I-V characteristics, spectral analysis and by determination of the profile of the internal electric field.

Evaluating abiotic influences on soil salinity of inland managed wetlands and agricultural croplands in a semi-arid environment

USGS Publications Warehouse

Fowler, D.; King, Sammy L.; Weindorf, David C.

2014-01-01

Agriculture and moist-soil management are important management techniques used on wildlife refuges to provide adequate energy for migrant waterbirds. In semi-arid systems, the accumulation of soluble salts throughout the soil profile can limit total production of wetland plants and agronomic crops and thus jeopardize meeting waterbird energy needs. This study evaluates the effect of distinct hydrologic regimes associated with moist-soil management and agricultural production on salt accumulation in a semi-arid floodplain. We hypothesized that the frequency of flooding and quantity of floodwater in a moist-soil management hydroperiod results in a less saline soil profile compared to profiles under traditional agricultural management. Findings showed that agricultural croplands differed (p-value < 0.001, df = 9) in quantities of total soluble salts (TSS) compared to moist-soil impoundments and contained greater concentrations (TSS range = 1,160-1,750 (mg kg-1)) at depth greater than 55 cm below the surface of the profile, while moist-soil impoundments contained lower concentrations (TSS range = 307-531 (mg kg-1)) at the same depths. Increased salts in agricultural may be attributed to the lack of leaching afforded by smaller summer irrigations while larger periodic flooding events in winter and summer flood irrigations in moist-soil impoundments may serve as leaching events.

Unitized Regenerative Fuel Cell System Gas Storage-Radiator Development

NASA Technical Reports Server (NTRS)

Burke, Kenneth A.; Jakupta, Ian

2005-01-01

High-energy-density regenerative fuel cell systems that are used for energy storage require novel approaches to integrating components in order to preserve mass and volume. A lightweight unitized regenerative fuel cell (URFC) energy storage system concept is being developed at the NASA Glenn Research Center. This URFC system minimizes mass by using the surface area of the hydrogen and oxygen storage tanks as radiating heat surfaces for overall thermal control of the system. The waste heat generated by the URFC stack during charging and discharging is transferred from the cell stack to the surface of each tank by loop heat pipes, which are coiled around each tank and covered with a thin layer of thermally conductive carbon composite. The thin layer of carbon composite acts as a fin structure that spreads the heat away from the heat pipe and across the entire tank surface. Two different-sized commercial-grade composite tanks were constructed with integral heat pipes and tested in a thermal vacuum chamber to examine the feasibility of using the storage tanks as system radiators. The storage tank-radiators were subjected to different steady-state heat loads and varying heat load profiles. The surface emissivity and specific heat capacity of each tank were calculated. In the future, the results will be incorporated into a model that simulates the performance of similar radiators using lightweight, spacerated carbon composite tanks.

Insight into Nucleation Mechanisms of Tetrahedral Materials from Advanced Molecular Dynamics Simulations

NASA Astrophysics Data System (ADS)

Bi, Yuanfei

This dissertation studies the nucleation mechanisms of ice, clathrate hydrate and silicon clathrate which all belong to tetrahedral materials and carry significant importance to modern society. Because of the stochastic nature and the ultra-fine scale of nucleation, the mechanisms through which these important tetrahedral materials form from liquid remain poorly understood. Our goal is to address the current knowledge gap between experiment and theory on the nucleation mechanisms by conducting molecular dynamics (MD) studies. To overcome the rare event nature of nucleation, an advanced sampling method Forward Flux Sampling (FFS) is integrated with classical MD simulations. This integration allows obtaining not only nucleation rate explicitly but also an ensemble of nucleation trajectories with their correct statistical weights. By analyzing the ensemble of trajectories obtained from FFS, we reveal the important details of nucleation at the molecular level, particular at the early stage of nucleation. By combining Backward Flux Sampling (BFS) with FFS, we can also compute the free energy profile of nucleation explicitly, which allows a comparison against the classical nucleation theory (CNT). We began our investigation by studying heterogeneous ice nucleation, which is the most relevant form of ice formation. In this part of study, we aim to understand the key microscopic factors that control ice formation, including surface hydrophilicity, surface crystallinity, and surface geometry. Our simulations reveal that heterogeneous ice nucleation on graphitic surfaces is controlled by the coupling of surface crystallinity and surface hydrophilicity. In particular, our analysis shows that the crystalline graphitic lattice with an appropriate hydrophilicity may indeed template ice basal plane by forming a strained ice layer, thus significantly enhance its ice nucleation efficiency. The templating effect is further found to transit from within the first contact layer of water to the second as the surface hydrophilicity increases, which yields an oscillating distinction between the crystalline and amorphous graphitic surfaces in their ice nucleation efficiency. With this understanding, we then shifted our focus on the role of surface geometry, where we find that an atomically sharp, concave wedge can further promote ice nucleation. Remarkably, our molecular analysis shows a significant enhancement of ice nucleation can emerge both when the geometry of a wedge matches the ice lattice and when such lattice match does not exist. We then investigated the nucleation of gas hydrate, a binary compound composed of water and natural gas, e.g., methane. To facilitate the application of FFS in studying gas hydrate nucleation, we proposed a new order parameter: Half-Cage Order Parameter (H-COP), based on the topological signature of hydrate structure, and conducted a pB histogram analysis to verify the effectiveness of the H-COP order parameter. Our analyses show that the nucleation of M-hydrate (M can be methane or carbon dioxide) starts in the vicinity of water-M interface, and gradually transit from amorphous to crystalline structures. This is the direct support to the proposed two-step nucleation mechanism of methane hydrate. However, within the ensemble of nucleation trajectories, we also identified some direct crystallization pathways without going through a amorphous phase in the nucleation of both M-hydrate and L-hydrate. Remarkably the free energy profile of L-hydrate nucleation, which is obtained independent of nucleation theory, is found to fit well against the CNT, albeit with noticeable differences when the nucleus is small. Therefore, the CNT-like free energy profile and the existence of multiple nucleation pathways indicate the near degeneracy of these pathways in their free energy profiles and highlight the complexity of hydrate nucleation. On the basis of these results, we further proposed a new perspective of gas hydrate nucleation, which can be considered to be an entropically driven, kinetic process that proceeds via multiple pathways that have similar free energy profiles. Finally, inspired by our insight gained in studying gas hydrate nucleation, we proposed a novel synthesis route to obtain inert gas silicon clathrate, which has an attractive opto-electronic property for energy application, but remains as an experimental challenge for synthesis. We thoroughly examined this proposal through high-throughput computational studies that show the novel phases of silicon could form spontaneously from liquid silicon in the presence of noble gases under high pressure and high temperature. In particular, our results show that a medium size of noble gas, e.g., Ar, can trigger the nucleation and growth of inert-gas silicon clathrate, whereas a small noble gas such as He is able to induce the formation of an unconventional, inclusion-type compound Si2He. Our findings, along with the gained molecular insights, thus strongly suggest it is viable to experimentally synthesize novel silicon phases with noble gas through high pressure and high temperature. (Abstract shortened by ProQuest.).

Atomistic simulations of bulk, surface and interfacial polymer properties

NASA Astrophysics Data System (ADS)

Natarajan, Upendra

In chapter I, quasi-static molecular mechanics based simulations are used to estimate the activation energy of phenoxy rings flips in the amorphous region of a semicrystalline polyimide. Intra and intermolecular contributions to the flip activation energy, the torsional cooperativity accompanying the flip, and the effect of the flip on the motion in the glassy bulk state, are looked at. Also, comparison of the weighted mean activation energy is made with experimental data from solid state NMR measurements; the simulated value being 17.5 kcal/mol., while the experimental value was observed to be 10.5 kcal/mol. Chapter II deals with construction of random copolymer thin films of styrene-butadiene (SB) and styrene-butadiene-acrylonitrile (SBA). The structure and properties of the free surfaces presented by these thin films are analysed by, the atom mass density profiles, backbone bond orientation function, and the spatial distribution of acrylonitrile groups and styrene rings. The surface energies of SB and SBA are calculated using an atomistic equation and are compared with experimental data in the literature. In chapter III, simulations of polymer-polymer interfaces between like and unlike polymers, specifically cis-polybutadiene (PBD) and atatic polypropylene (PP), are presented. The structure of an incompatible polymer-polymer interface, and the estimation of the thermodynamic work of adhesion and interfacial energy between different incompatible polymers, form the focus here. The work of adhesion is calculated using an atomistic equation and is further used in a macroscopic equation to estimate the interfacial energy. The interfacial energy is compared with typical values for other immiscible systems in the literature. The interfacial energy compared very well with interfacial energy values for a few other immiscible hydrocarbon pairs. In chapter IV, the study proceeds to look at the interactions between nonpolar and polar small molecules with SB and SBA thin film surfaces. Toluene, hexadecane and water molecules are separately simulated to interact with SB and SBA surfaces in vacuum. The energetics of interaction are calculated atomistically and used in the atomistic equation to calculate the interfacial energy or the interaction energy. Comparisons with experimental data are not made due to the small concentrations of the molecules on the polymer surface. However, fundamental understanding of the structure of the system and the breakup of the energetics are provided by such a study.

Measurements of the differential cross sections for recoil tritons in 4He- 3T scattering at energies between 0.5 and 2.5 MeV

NASA Astrophysics Data System (ADS)

Sawicki, J. A.

1988-03-01

Differential cross-sections for recoil detection of tritons from elastic scattering of α-particles on tritium were measured at forward recoil angles from 10° and 40° and over incident 4He energies ranging from 0.5 to 2.5 MeV. Thin solid state targets consisted of about 10 16T {at.}/{cm 2} either absorbed in a thin film of titanium or implanted at low energy in the matrix of amorphous silicon. The recoil yields were normalized against the yields of the T(d, α)n reaction measured on the same targets. It is found that the cross sections obtained are considerably enhanced as compared to the Rutherford recoil cross section, what can be attributed to the combined effect of Coulomb and nuclear potentials and formation of compound 7Li nuclei. The applications of the elastic recoil detection as a means for depth profiling of tritium in materials are briefly considered. The measured dependence of the triton recoil cross section on the incident energy of 4He + ions allows profiling the concentration of tritium across a range ˜ l μm below the surface of solids.

A model SN2 reaction ‘on water’ does not show rate enhancement

NASA Astrophysics Data System (ADS)

Nelson, Katherine V.; Benjamin, Ilan

2011-05-01

Molecular dynamics calculations of the benchmark nucleophilic substitution reaction (SN2) Cl- + CH3Cl are carried out at the water liquid/vapor interface. The reaction free energy profile and the activation free energy are determined as a function of the reactants' location normal to the surface. The activation free energy remains almost constant relative to that in bulk water, despite the fact that the barrier is expected to significantly decrease as the reaction is carried out near the vapor phase. We show that this is due to the combined effects of a clustering of water molecules around the nucleophile and a relatively weak hydration of the transition state.

Energetic properties' investigation of removing flattening filter at phantom surface: Monte Carlo study using BEAMnrc code, DOSXYZnrc code and BEAMDP code

NASA Astrophysics Data System (ADS)

Bencheikh, Mohamed; Maghnouj, Abdelmajid; Tajmouati, Jaouad

2017-11-01

The Monte Carlo calculation method is considered to be the most accurate method for dose calculation in radiotherapy and beam characterization investigation, in this study, the Varian Clinac 2100 medical linear accelerator with and without flattening filter (FF) was modelled. The objective of this study was to determine flattening filter impact on particles' energy properties at phantom surface in terms of energy fluence, mean energy, and energy fluence distribution. The Monte Carlo codes used in this study were BEAMnrc code for simulating linac head, DOSXYZnrc code for simulating the absorbed dose in a water phantom, and BEAMDP for extracting energy properties. Field size was 10 × 10 cm2, simulated photon beam energy was 6 MV and SSD was 100 cm. The Monte Carlo geometry was validated by a gamma index acceptance rate of 99% in PDD and 98% in dose profiles, gamma criteria was 3% for dose difference and 3mm for distance to agreement. In without-FF, the energetic properties was as following: electron contribution was increased by more than 300% in energy fluence, almost 14% in mean energy and 1900% in energy fluence distribution, however, photon contribution was increased 50% in energy fluence, and almost 18% in mean energy and almost 35% in energy fluence distribution. The removing flattening filter promotes the increasing of electron contamination energy versus photon energy; our study can contribute in the evolution of removing flattening filter configuration in future linac.

Ag out-surface diffusion in crystalline SiC with an effective SiO 2 diffusion barrier

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

Xue, H.; Xiao, H. Y.; Zhu, Z.

2015-05-07

For applications of tristructural isotropic (TRISO) fuel particles in high temperature reactors, release of radioactive Ag isotope ( 110mAg) through the SiC coating layer is a safety concern. In order to understand the diffusion mechanism, Ag ion implantations near the surface and in the bulk were performed by utilizing different ion energies and energy-degrader foils. High temperature annealing was carried out on the as-irradiated samples to study the possible out-surface diffusion. Before and after annealing, Rutherford backscattering spectrometry (RBS) and secondary ion mass spectrometry (SIMS) measurements were employed to obtain the elemental profiles of the implanted samples. Our results suggestmore » little migration of buried Ag in the bulk, and an out-diffusion of the implanted Ag in the near-surface region of single crystal SiC. It is also found that a SiO 2 layer, which was formed during annealing, may serve as an effective barrier to reduce or prevent Ag out diffusion through the SiC coating layer.« less

Ag Out-surface Diffusion In Crystalline SiC With An Effective SiO2 Diffusion Barrier

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

Xue, H.; Xiao, Haiyan Y.; Zhu, Zihua

2015-09-01

For applications of tristructural isotropic (TRISO) fuel particles in high temperature reactors, release of radioactive Ag isotope (110mAg) through the SiC coating layer is a safety concern. To understand the diffusion mechanism, Ag ion implantations near the surface and in the bulk were performed by utilizing different ion energies and energy-degrader foils. High temperature annealing was carried out on the as-irradiated samples to study the possible out-surface diffusion. Before and after annealing, Rutherford backscattering spectrometry (RBS) and secondary ion mass spectrometry (SIMS) measurements were employed to obtain the elemental profiles of the implanted samples. The results suggest little migration ofmore » buried Ag in the bulk, and an out-diffusion of the implanted Ag in the near-surface region of single crystal SiC. It is also found that a SiO2 layer, which was formed during annealing, may serve as an effective barrier to reduce or prevent Ag out diffusion through the SiC coating layer.« less

CAD/CAM milled complete removable dental prostheses: An in vitro evaluation of biocompatibility, mechanical properties, and surface roughness.

PubMed

Srinivasan, Murali; Gjengedal, Harald; Cattani-Lorente, Maria; Moussa, Mira; Durual, Stéphane; Schimmel, Martin; Müller, Frauke

2018-03-06

This study compared the biocompatibility, mechanical properties, and surface roughness of a pre-polymerized polymethyl methacrylate (PMMA) resin for CAD/CAM complete removable dental prostheses (CRDPs) and a traditional heat-polymerized PMMA resin. Two groups of resin substrates [Control (RC): conventional PMMA; Test (RA): CAD/CAM PMMA] were fabricated. Human primary osteoblasts and mouse embryonic-fibroblasts were cultured for biocompatibility assays. Mechanical properties and surface roughness were compared. ANOVA revealed no difference between the resin groups in the biocompatibility assays. RA demonstrated a higher elastic modulus (p=0.002), young's modulus (p=0.002), plastic energy (p=0.002), ultimate strength (p=0.0004), yield point (p=0.016), strain at yield point (p=0.037), and toughness (p<0.0001); while RC displayed a higher elastic energy (p<0.0001). Laser profilometry concluded a rougher surface profile (p<0.0001) for RA. This study concluded that the tested CAD/CAM resin was equally biocompatible and presented with improved mechanical properties than the traditional heat-polymerized PMMA resin used in the fabrication of CRDPs.

X-ray microfocusing with off-axis ellipsoidal mirror

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

Yumoto, Hirokatsu, E-mail: yumoto@spring8.or.jp; Koyama, Takahisa; Matsuyama, Satoshi

2016-07-27

High-precision ellipsoidal mirrors for two-dimensionally focusing X-rays to nanometer sizes have not been realized because of technical problems in their fabrication processes. The objective of the present study is to develop fabrication techniques for ellipsoidal focusing mirrors in the hard-X-ray region. We design an off-axis ellipsoidal mirror for use under total reflection conditions up to the X-ray energy of 8 keV. We fabricate an ellipsoidal mirror with a surface roughness of 0.3 nm RMS (root-mean-square) and a surface figure error height of 3.0 nm RMS by utilizing a surface profiler and surface finishing method developed by us. The focusing propertiesmore » of the mirror are evaluated at the BL29XUL beamline in SPring-8. A focusing beam size of 270 nm × 360 nm FWHM (full width at half maximum) at an X-ray energy of 7 keV is observed with the use of the knife-edge scanning method. We expect to apply the developed fabrication techniques to construct ellipsoidal nanofocusing mirrors.« less

Binding free energy and counterion release for adsorption of the antimicrobial peptide lactoferricin B on a POPG membrane.

PubMed

Tolokh, Igor S; Vivcharuk, Victor; Tomberli, Bruno; Gray, C G

2009-09-01

Molecular dynamics (MD) simulations are used to study the interaction of an anionic palmitoyl-oleoyl-phosphatidylglycerol (POPG) bilayer with the cationic antimicrobial peptide bovine lactoferricin (LFCinB) in a 100 mM NaCl solution at 310 K. The interaction of LFCinB with a POPG bilayer is employed as a model system for studying the details of membrane adsorption selectivity of cationic antimicrobial peptides. Seventy eight 4 ns MD production run trajectories of the equilibrated system, with six restrained orientations of LFCinB at 13 different separations from the POPG membrane, are generated to determine the free energy profile for the peptide as a function of the distance between LFCinB and the membrane surface. To calculate the profile for this relatively large system, a variant of constrained MD and thermodynamic integration is used. A simplified method for relating the free energy profile to the LFCinB-POPG membrane binding constant is employed to predict a free energy of adsorption of -5.4+/-1.3 kcal/mol and a corresponding maximum adsorption binding force of about 58 pN. We analyze the results using Poisson-Boltzmann theory. We find the peptide-membrane attraction to be dominated by the entropy increase due to the release of counterions and polarized water from the region between the charged membrane and peptide, as the two approach each other. We contrast these results with those found earlier for adsorption of LFCinB on the mammalianlike palmitoyl-oleoyl-phosphatidylcholine membrane.

Thermal desorption of formamide and methylamine from graphite and amorphous water ice surfaces

NASA Astrophysics Data System (ADS)

Chaabouni, H.; Diana, S.; Nguyen, T.; Dulieu, F.

2018-04-01

Context. Formamide (NH2CHO) and methylamine (CH3NH2) are known to be the most abundant amine-containing molecules in many astrophysical environments. The presence of these molecules in the gas phase may result from thermal desorption of interstellar ices. Aims: The aim of this work is to determine the values of the desorption energies of formamide and methylamine from analogues of interstellar dust grain surfaces and to understand their interaction with water ice. Methods: Temperature programmed desorption (TPD) experiments of formamide and methylamine ices were performed in the sub-monolayer and monolayer regimes on graphite (HOPG) and non-porous amorphous solid water (np-ASW) ice surfaces at temperatures 40-240 K. The desorption energy distributions of these two molecules were calculated from TPD measurements using a set of independent Polanyi-Wigner equations. Results: The maximum of the desorption of formamide from both graphite and ASW ice surfaces occurs at 176 K after the desorption of H2O molecules, whereas the desorption profile of methylamine depends strongly on the substrate. Solid methylamine starts to desorb below 100 K from the graphite surface. Its desorption from the water ice surface occurs after 120 K and stops during the water ice sublimation around 150 K. It continues to desorb from the graphite surface at temperatures higher than160 K. Conclusions: More than 95% of solid NH2CHO diffuses through the np-ASW ice surface towards the graphitic substrate and is released into the gas phase with a desorption energy distribution Edes = 7460-9380 K, which is measured with the best-fit pre-exponential factor A = 1018 s-1. However, the desorption energy distribution of methylamine from the np-ASW ice surface (Edes = 3850-8420 K) is measured with the best-fit pre-exponential factor A = 1012 s-1. A fraction of solid methylamine monolayer of roughly 0.15 diffuses through the water ice surface towards the HOPG substrate. This small amount of methylamine desorbs later with higher binding energies (5050-8420 K) that exceed that of the crystalline water ice (Edes = 4930 K), which is calculated with the same pre-exponential factor A = 1012 s-1. The best wetting ability of methylamine compared to H2O molecules makes CH3NH2 molecules a refractory species for low coverage. Other binding energies of astrophysical relevant molecules are gathered and compared, but we could not link the chemical functional groups (amino, methyl, hydroxyl, and carbonyl) with the binding energy properties. Implications of these high binding energies are discussed.

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

Yang, Zhaoqing; Wang, Taiping

A three-dimensional coastal ocean model with a tidal turbine module was used in this paper to study the effects of tidal energy extraction on temperature and salinity stratification and density driven two-layer estuarine circulation. Numerical experiments with various turbine array configurations were carried out to investigate the changes in tidally mean temperature, salinity and velocity profiles in an idealized stratified estuary that connects to coastal water through a narrow tidal channel. The model was driven by tides, river inflow and sea surface heat flux. To represent the realistic size of commercial tidal farms, model simulations were conducted based on amore » small percentage of the total number of turbines that would generate the maximum extractable energy in the system. Model results indicated that extraction of tidal energy will increase the vertical mixing and decrease the stratification in the estuary. Extraction of tidal energy has stronger impact on the tidally-averaged salinity, temperature and velocity in the surface layer than the bottom. Energy extraction also weakens the two-layer estuarine circulation, especially during neap tides when tidal mixing the weakest and energy extraction is the smallest. Model results also show that energy generation can be much more efficient with higher hub height with relatively small changes in stratification and two-layer estuarine circulation.« less

Soil moisture profile variability in land-vegetation- atmosphere continuum

NASA Astrophysics Data System (ADS)

Wu, Wanru

Soil moisture is of critical importance to the physical processes governing energy and water exchanges at the land-air boundary. With respect to the exchange of water mass, soil moisture controls the response of the land surface to atmospheric forcing and determines the partitioning of precipitation into infiltration and runoff. Meanwhile, the soil acts as a reservoir for the storage of liquid water and slow release of water vapor into the atmosphere. The major motivation of the study is that the soil moisture profile is thought to make a substantial contribution to the climate variability through two-way interactions between the land-surface and the atmosphere in the coupled ocean-atmosphere-land climate system. The characteristics of soil moisture variability with soil depth may be important in affecting the atmosphere. The natural variability of soil moisture profile is demonstrated using observations. The 16-year field observational data of soil moisture with 11-layer (top 2.0 meters) measured soil depths over Illinois are analyzed and used to identify and quantify the soil moisture profile variability, where the atmospheric forcing (precipitation) anomaly propagates down through the land-branch of the hydrological cycle with amplitude damping, phase shift, and increasing persistence. Detailed statistical data analyses, which include application of the periodogram method, the wavelet method and the band-pass filter, are made of the variations of soil moisture profile and concurrently measured precipitation for comparison. Cross-spectral analysis is performed to obtain the coherence pattern and phase correlation of two time series for phase shift and amplitude damping calculation. A composite of the drought events during this time period is analyzed and compared with the normal (non-drought) case. A multi-layer land surface model is applied for modeling the soil moisture profile variability characteristics and investigating the underlying mechanisms. Numerical experiments are conducted to examine the impacts of some potential controlling factors, which include atmospheric forcing (periodic and pulse) at the upper boundary, the initial soil moisture profile, the relative root abundance and the soil texture, on the variability of soil moisture profile and the corresponding evapotranspiration. Similar statistical data analyses are performed for the experimental data. Observations from the First International Satellite Land Surface Climatological Project (ISLSCP) Field Experiment (FIFE) are analyzed and used for the testing of model. The integration of the observational and modeling approaches makes it possible to better understand the mechanisms by which the soil moisture profile variability is generated with phase shift, fluctuation amplitude damping and low-pass frequency filtering with soil depth, to improve the strategies of parameterizations in land surface schemes, and furthermore, to assess its contribution to climate variability.

A large area high resolution imaging detector for fast atom diffraction

NASA Astrophysics Data System (ADS)

Lupone, Sylvain; Soulisse, Pierre; Roncin, Philippe

2018-07-01

We describe a high resolution imaging detector based on a single 80 mm micro-channel-plate (MCP) and a phosphor screen mounted on a UHV flange of only 100 mm inner diameter. It relies on standard components and we describe its performance with one or two MCPs. A resolution of 80 μm rms is observed on the beam profile. At low count rate, individual impact can be pinpointed with few μm accuracy but the resolution is probably limited by the MCP channel diameter. The detector has been used to record the diffraction of fast atoms at grazing incidence on crystal surfaces (GIFAD), a technique probing the electronic density of the topmost layer only. The detector was also used to record the scattering profile during azimuthal scan of the crystal to produce triangulation curves revealing the surface crystallographic directions of molecular layers. It should also be compatible with reflection high energy electron (RHEED) experiment when fragile surfaces require a low exposure to the electron beam. The discussions on the mode of operation specific to diffraction experiments apply also to commercial detectors.

Micro Solar Cells with Concentration and Light Trapping Optics

NASA Astrophysics Data System (ADS)

Li, Lanfang; Breuckner, Eric; Corcoran, Christopher; Yao, Yuan; Xu, Lu; Nuzzo, Ralph

2013-03-01

Compared with conventional bulk plate semiconductor solar cells, micro solar cells provide opportunity for novel design geometry and provide test bed for light trapping at the device level as well as module level. Surface recombination, however, will have to be addressed properly as the much increased surface area due to the reduced dimension is more prominent in these devices than conventional solar cells. In this poster, we present experimental demonstration of silicon micro solar cells with concentration and light trapping optics. Silicon micro solar cell with optimized surface passivation and doping profile that exhibit high efficiency is demonstrated. Effective incorporation of high quantum yield fluorescent centers in the polymer matrix into which micro solar cell was encapsulated was investigated for luminescent solar concentration application. Micro-cell on a semi-transparent, nanopatterned reflector formed by soft-imprint lithography was investigated for near field effect related solar conversion performance enhancement. This work is supported by the DOE `Light-Material Interactions in Energy Conversion' Energy Frontier Research Center under grant DE-SC0001293

Desorption of oxygen from alloyed Ag/Pt(111)

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

Jankowski, Maciej; Wormeester, Herbert, E-mail: h.wormeester@utwente.nl; Zandvliet, Harold J. W.

2014-06-21

We have investigated the interaction of oxygen with the Ag/Pt(111) surface alloy by thermal desorption spectroscopy (TDS). The surface alloy was formed during the deposition of sub-monolayer amounts of silver on Pt(111) at 800 K and subsequent cooling to 300 K. The low-temperature phase of the surface alloy is composed of nanometer-sized silver rich stripes, embedded within platinum-rich domains, which were characterized with spot profile analysis low energy electron diffraction. The TDS measurements show that oxygen adsorption is blocked on Ag sites: the saturation coverage of oxygen decreases with increasing Ag coverage. Also, the activation energy for desorption (E{sub des})more » decreases with Ag coverage. The analysis of the desorption spectra from clean Pt(111) shows a linear decay of E{sub des} with oxygen coverage, which indicates repulsive interactions between the adsorbed oxygen atoms. In contrast, adsorption on alloyed Ag/Pt(111) leads to an attractive interaction between adsorbed oxygen atoms.« less

Morphological Evolution of Pit-Patterned Si(001) Substrates Driven by Surface-Energy Reduction

NASA Astrophysics Data System (ADS)

Salvalaglio, Marco; Backofen, Rainer; Voigt, Axel; Montalenti, Francesco

2017-09-01

Lateral ordering of heteroepitaxial islands can be conveniently achieved by suitable pit-patterning of the substrate prior to deposition. Controlling shape, orientation, and size of the pits is not trivial as, being metastable, they can significantly evolve during deposition/annealing. In this paper, we exploit a continuum model to explore the typical metastable pit morphologies that can be expected on Si(001), depending on the initial depth/shape. Evolution is predicted using a surface-diffusion model, formulated in a phase-field framework, and tackling surface-energy anisotropy. Results are shown to nicely reproduce typical metastable shapes reported in the literature. Moreover, long time scale evolutions of pit profiles with different depths are found to follow a similar kinetic pathway. The model is also exploited to treat the case of heteroepitaxial growth involving two materials characterized by different facets in their equilibrium Wulff's shape. This can lead to significant changes in morphologies, such as a rotation of the pit during deposition as evidenced in Ge/Si experiments.

Morphological Evolution of Pit-Patterned Si(001) Substrates Driven by Surface-Energy Reduction.

PubMed

Salvalaglio, Marco; Backofen, Rainer; Voigt, Axel; Montalenti, Francesco

2017-09-29

Lateral ordering of heteroepitaxial islands can be conveniently achieved by suitable pit-patterning of the substrate prior to deposition. Controlling shape, orientation, and size of the pits is not trivial as, being metastable, they can significantly evolve during deposition/annealing. In this paper, we exploit a continuum model to explore the typical metastable pit morphologies that can be expected on Si(001), depending on the initial depth/shape. Evolution is predicted using a surface-diffusion model, formulated in a phase-field framework, and tackling surface-energy anisotropy. Results are shown to nicely reproduce typical metastable shapes reported in the literature. Moreover, long time scale evolutions of pit profiles with different depths are found to follow a similar kinetic pathway. The model is also exploited to treat the case of heteroepitaxial growth involving two materials characterized by different facets in their equilibrium Wulff's shape. This can lead to significant changes in morphologies, such as a rotation of the pit during deposition as evidenced in Ge/Si experiments.

SU-E-T-607: Performance Quantification of the Nine Detectors Used for Dosimetry Measurements in Advanced Radiation Therapy Treatments

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

Markovic, M; Stathakis, S; Jurkovic, I

2015-06-15

Purpose: The purpose of this study was to quantify performance of the nine detectors used for dosimetry measurements in advanced radiation therapy treatments. Methods: The 6 MV beam was utilized for measurements of the field sizes with the lack of lateral charge particle equilibrium. For dose fidelity aspect, energy dependence was studied by measuring PDD and profiles at different depths. The volume effect and its influence on the measured dose profiles have been observed by measuring detector’s response function. Output factor measurements with respect to change in energy spectrum have been performed and collected data has been analyzed. The linearitymore » of the measurements with the dose delivered has been evaluated and relevant comparisons were done. Results: The measured values of the output factors with respect to change in energy spectrum indicated presence of the energy dependence. The detectors with active volume size ≤ 0.3 mm3 maximum deviation from the mean is 5.6% for the field size 0.5 x 0.5 cm2 while detectors with active volume size > 0.3 mm3 have maximum deviation from the mean 7.1%. Linearity with dose at highest dose rate examined for diode detectors showed maximum deviation of 4% while ion chambers showed maximum deviation of 2.2%. Dose profiles showed energy dependence at shallow depths (surface to dmax) influenced by low energy particles with 12 % maximum deviation from the mean for 5 mm2 field size. In relation to Monte Carlo calculation, the detector’s response function σ values were between (0.42±0.25) mm and (1.2±0.25) mm. Conclusion: All the detectors are appropriate for the dosimetry measurements in advanced radiation therapy treatments. The choice of the detectors has to be determined by the application and the scope of the measurements in respect to energy dependence and ability to accurately resolve dose profiles as well as to it’s intrinsic characteristics.« less

Excimer laser delivery system for astigmatic and hyperopic photorefractive surgery

NASA Astrophysics Data System (ADS)

Beck, Rasmus; Foerster, Werner

1994-06-01

Ablation of corneal tissue with excimer laser light is an effective way to correct refractive errors of the eye. For this purpose a beam-stop (iris diaphragm or interchangeable masks) is illuminated by the laser radiation. The beam-stop is imaged onto the cornea, and circular or elliptic ablations are produced. The computer-controlled process varies the diameter of the ablation area in a way that the inner portions of the treatment zone receive more laser energy than the outer portions, thus flattening the curvature of the refractive surface. For the treatment of hyperopia, the outer portions of the ablation area receive more laser energy to steepen the surface profile of the cornea. The beam delivery system employs several sets of circular, elliptic and ring shaped masks which are etched into a stainless-steel tape.

Nanoparticle-wetted surfaces for relays and energy transmission contacts.

PubMed

Voevodin, Andrey A; Vaia, Richard A; Patton, Steven T; Diamanti, Steven; Pender, Mark; Yoonessi, Mitra; Brubaker, Jennifer; Hu, Jian-Jun; Sanders, Jeffrey H; Phillips, Benjamin S; MacCuspie, Robert I

2007-11-01

Submonolayer coatings of noble-metal nanoparticle liquids (NPLs) are shown to provide replenishable surfaces with robust asperities and metallic conductivity that extends the durability of electrical relays by 10 to 100 times (depending on the current driven through the contact) as compared to alternative approaches. NPLs are single-component materials consisting of a metal nanoparticle core (5-20 nm Au or Pt nanoparticles) surrounded by a covalently tethered ionic-liquid corona of 1.5 to 2 nm. Common relay failure modes, such as stiction, surface distortion, and contact shorting, are suppressed with the addition of a submonolayer of NPLs to the contact surfaces. This distribution of NPLs results in a force profile for a contact-retraction cycle that is distinct from bare Au contacts and thicker, multilayer coatings of NPLs. Postmortem examination reveals a substantial decrease in topological change of the electrode surface relative to bare contacts, as well as an indication of lateral migration of the nanoparticles from the periphery towards the contact. A general extension of this concept to dynamic physical interfaces experiencing impact, sliding, or rolling affords alternatives to increase reliability and reduced losses for transmittance of electrical and mechanical energy.

A molecularly based theory for electron transfer reorganization energy.

PubMed

Zhuang, Bilin; Wang, Zhen-Gang

2015-12-14

Using field-theoretic techniques, we develop a molecularly based dipolar self-consistent-field theory (DSCFT) for charge solvation in pure solvents under equilibrium and nonequilibrium conditions and apply it to the reorganization energy of electron transfer reactions. The DSCFT uses a set of molecular parameters, such as the solvent molecule's permanent dipole moment and polarizability, thus avoiding approximations that are inherent in treating the solvent as a linear dielectric medium. A simple, analytical expression for the free energy is obtained in terms of the equilibrium and nonequilibrium electrostatic potential profiles and electric susceptibilities, which are obtained by solving a set of self-consistent equations. With no adjustable parameters, the DSCFT predicts activation energies and reorganization energies in good agreement with previous experiments and calculations for the electron transfer between metallic ions. Because the DSCFT is able to describe the properties of the solvent in the immediate vicinity of the charges, it is unnecessary to distinguish between the inner-sphere and outer-sphere solvent molecules in the calculation of the reorganization energy as in previous work. Furthermore, examining the nonequilibrium free energy surfaces of electron transfer, we find that the nonequilibrium free energy is well approximated by a double parabola for self-exchange reactions, but the curvature of the nonequilibrium free energy surface depends on the charges of the electron-transferring species, contrary to the prediction by the linear dielectric theory.

Surface modification of tantalum pentoxide coatings deposited by magnetron sputtering and correlation with cell adhesion and proliferation in in vitro tests

NASA Astrophysics Data System (ADS)

Zykova, A.; Safonov, V.; Goltsev, A.; Dubrava, T.; Rossokha, I.; Donkov, N.; Yakovin, S.; Kolesnikov, D.; Goncharov, I.; Georgieva, V.

2016-03-01

The effect was analyzed of surface treatment by argon ions on the surface properties of tantalum pentoxide coatings deposited by reactive magnetron sputtering. The structural parameters of the as-deposited coatings were investigated by means of transmission electron microscopy, atomic force microscopy and scanning electron microscopy. X-ray diffraction profiles and X-ray photoelectron spectra were also acquired. The total surface free energy (SFE), the polar, dispersion parts and fractional polarities, were estimated by the Owens-Wendt-Rabel-Kaeble method. The adhesive and proliferative potentials of bone marrow cells were evaluated for both Ta2O5 coatings and Ta2O5 coatings deposited by simultaneous bombardment by argon ions in in vitro tests.

Modeling laser-induced periodic surface structures: Finite-difference time-domain feedback simulations

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

Skolski, J. Z. P., E-mail: j.z.p.skolski@utwente.nl; Vincenc Obona, J.; Römer, G. R. B. E.

2014-03-14

A model predicting the formation of laser-induced periodic surface structures (LIPSSs) is presented. That is, the finite-difference time domain method is used to study the interaction of electromagnetic fields with rough surfaces. In this approach, the rough surface is modified by “ablation after each laser pulse,” according to the absorbed energy profile, in order to account for inter-pulse feedback mechanisms. LIPSSs with a periodicity significantly smaller than the laser wavelength are found to “grow” either parallel or orthogonal to the laser polarization. The change in orientation and periodicity follow from the model. LIPSSs with a periodicity larger than the wavelengthmore » of the laser radiation and complex superimposed LIPSS patterns are also predicted by the model.« less

Improving energy partitioning and the nighttime energy balance by implementation of a multi-layer energy budget in ORCHIDEE-CAN

NASA Astrophysics Data System (ADS)

Chen, Yiying; Ryder, James; Naudts, Kim; McGrath, Matthew J.; Otto, Juliane; Bastriko, Vladislav; Valade, Aude; Launiainen, Samuli; Ogée, Jérôme; Elbers, Jan A.; Foken, Thomas; Tiedemann, Frank; Heinesch, Bernard; Black, Andrew; Haverd, Vanessa; Loustau, Denis; Ottlé, Catherine; Peylin, Philippe; Polcher, Jan; Luyssaert, Sebastiaan

2015-04-01

Canopy structure is one of the most important vegetation characteristics for land-atmosphere interactions as it determines the energy and scalar exchanges between land surface and overlay air mass. In this study we evaluated the performance of a newly developed multi-layer energy budget (Ryder et al., 2014) in a land surface model, ORCHIDEE-CAN (Naudts et al., 2014), which simulates canopy structure and can be coupled to an atmospheric model using an implicit procedure. Furthermore, a vertical discrete drag parametrization scheme was also incorporated into this model, in order to obtain a better description of the sub-canopy wind profile simulation. Site level datasets, including the top-of-the-canopy and sub-canopy observations made available from eight flux observation sites, were collected in order to conduct this evaluation. The geo-location of the collected observation sites crossed climate zones from temperate to boreal and the vegetation types included deciduous, evergreen broad leaved and evergreen needle leaved forest with maximum LAI ranging from 2.1 to 7.0. First, we used long-term top-of-the-canopy measurements to analyze the performance of the current one-layer energy budget in ORCHIDEE-CAN. Three major processes were identified for improvement through the implementation of a multi-layer energy budget: 1) night time radiation balance, 2) energy partitioning during winter and 3) prediction of the ground heat flux. Short-term sub-canopy observations were used to calibrate the parameters in sub-canopy radiation, turbulence and resistances modules with an automatic tuning process following the maximum gradient of the user-defined objective function. The multi-layer model is able to capture the dynamic of sub-canopy turbulence, temperature and energy fluxes with imposed LAI profile and optimized parameter set at a site level calibration. The simulation result shows the improvement both on the nighttime energy balance and energy partitioning during winter and presents a better Taylor skill score, compared to the result from single layer simulation. The importance of using the multi-layer energy budget in a land surface model for coupling to the atmospheric model will also be discussed in this presentation. Reference: Ryder, J., J. Polcher, P. Peylin, C. Ottlé, Y. Chen, E. Van Gorsel, V. Haverd, M. J. McGrath, K.Naudts, J. Otto, A. Valade, and S. Luyssaert, 2014. "A multi-layer land surface energy budget model for implicit coupling with global atmospheric simulations", Geosci. Model Dev. Discuss. 7, 8649-8701 Naudts, K. J. Ryder, M. J. McGrath, J. Otto, Y. Chen, A. Valade, V. Bellasen, G. Berhongaray, G. Bönisch, M. Campioli, J. Ghattas, T. De Groote, V. Haverd, J. Kattge, N. MacBean, F. Maignan, P. Merilä, J. Penuelas, P. Peylin, B. Pinty, H. Pretzsch, E. D. Schulze, D. Solyga, N. Vuichard, Y. Yan, and S. Luyssaert, 2014. "A vertically discretised canopy description for ORCHIDEE (SVN r2290) and the modifications to the energy, water and carbon fluxes", Geosci. Model Dev. Discuss. 7, 8565-8647

Measuring the Impact of Rising CO2 and CH4 on the Surface Energy Balance

NASA Astrophysics Data System (ADS)

Feldman, D.; Collins, W.; Biraud, S.; Turner, D. D.; Mlawer, E. J.; Gero, P. J.; Xie, S.; Shippert, T.; Torn, M. S.

2015-12-01

We use observations at the North Slope of Alaska (NSA) and Southern Great Plains (SGP) ARM sites to improve understanding both of the distribution of CO2 and CH4and their influence on the surface energy balance. We use aircraft and ground-based in situ data to characterize the temporal distribution of these greenhouse gases, and spectroscopic observations to derive their collocated surface radiative forcing. The spectroscopically-measured surface radiative forcing from rising CO2 is 0.2 W/m2/decade at both sites, with a seasonal cycle of 0.2 W/m2. This finding is largely consistent with theoretical predictions, providing robust evidence of radiative perturbations to the Earth's surface energy budget due to anthropogenic influences. The contribution from CH4 to the surface energy balance is more spatially and temporally heterogeneous. The ground-based measurements of CH4 at NSA and SGP indicate rising atmospheric concentrations except for a hiatus from 1995-2005, while more recent aircraft profiles indicate that concentrations in the boundary layer and free troposphere are correlated at NSA and decorrelated at SGP. The probability density functions of boundary layer concentrations of CH4 at NSA show little skew, but at SGP show positive skewness, which increased with the introduction of nearby fossil-fuel extraction. The correlated increases in atmospheric measurements of C2H6 and CH4that only occur at SGP are consistent with an anthropogenic influence there. Time-series of spectroscopically-measured CH4 surface radiative forcing at SGP and NSA also indicate positive trends of 0.1 W/m2/decade associated with the end of the hiatus, marked seasonal cycles, and little skew at NSA and a positive skew at SGP. The combination of in situ and spectroscopic measurements at these sites enables the quantification of surface radiative forcing from anthropogenic CH4. Implications are discussed for how advanced spectroscopic remote sensing measurements of CH4 can be used to quantify the impact of fossil fuel extraction on surface energy budget.

A pitfall of muting and removing bad traces in surface-wave analysis

NASA Astrophysics Data System (ADS)

Hu, Yue; Xia, Jianghai; Mi, Binbin; Cheng, Feng; Shen, Chao

2018-06-01

Multi-channel analysis of surface/Love wave (MASW/MALW) has been widely used to construct the shallow shear (S)-wave velocity profile. The key step in surface-wave analysis is to generate accurate dispersion energy and pick the dispersive curves for inversion along the peaks of dispersion energy at different frequencies. In near-surface surface-wave acquisition, bad traces are very common and inevitable due to the imperfections in the recording instruments or others. The existence of bad traces will cause some artifacts in the dispersion energy image. To avoid the interference of bad traces on the surface-wave analysis, the bad traces should be alternatively muted (zeroed) or removed (deleted) from the raw surface-wave data before dispersion measurement. Most geophysicists and civil engineers, however, are not aware of the differences and implications between muting and removing of bad traces in surface-wave analysis. A synthetic test and a real-world example demonstrate the potential pitfalls of applying muting and removing on bad traces when using different dispersion-imaging methods. We implement muting and removing on bad traces respectively before dispersion measurement, and compare the influence of the two operations on three dispersion-imaging methods, high-resolution linear Radon transform (HRLRT), f-k transformation, and phase shift method. Results indicate that when using the HRLRT to generate the dispersive energy, muting bad traces will cause an even more complicated and discontinuous dispersive energy. When f-k transformation is utilized to conduct dispersive analysis, bad traces should be muted instead of removed to generate an accurate dispersion image to avoid the uneven sampling problem in the Fourier transform. As for the phase shift method, the difference between the two operations is slight, but we suggest that removal should be chosen because the integral for the phase-shift operator of the zeroed traces would bring in the sloped aliasing. This study provides a pre-process guidance for the real-world surface-wave data processing when the recorded shot gather contains inevitable bad traces.

Energy profiles of four American states

NASA Astrophysics Data System (ADS)

Song, Jiamei

2018-06-01

Energy production and usage are the major portion of any economy. With the constant consumption of the polluting energy and the deteriorating environment, people are paying more and more attention to clean, renewable energy. Based on autoregressive model and TOPSIS, though analyzing the past data, this paper establishes the energy profiles of four American states from 1960 to 2009, predict the energy profiles for 2025 and 2050 and obtain the ideal criteria for future clean, renewable energy usage at last. This study finds that by analyzing and predicting the energy profile, human beings can better understand and grasp the trend of energy development and take appropriate measures to deal with future energy trends.

High-Resolution Seismic Reflection Imaging of the Reelfoot Fault, New Madrid, Missouri

NASA Astrophysics Data System (ADS)

Rosandich, B.; Harris, J. B.; Woolery, E. W.

2017-12-01

Earthquakes in the Lower Mississippi Valley are mainly concentrated in the New Madrid Seismic Zone and are associated with reactivated faults of the Reelfoot Rift. Determining the relationship between the seismogenic faults (in crystalline basement rocks) and deformation at the Earth's surface and in the shallow subsurface has remained an active research topic for decades. An integrated seismic data set, including compressional (P-) wave and shear (S-) wave seismic reflection profiles, was collected in New Madrid, Missouri, across the "New Madrid" segment of the Reelfoot Fault, whose most significant rupture produced the M 7.5, February 7, 1812, New Madrid earthquake. The seismic reflection profiles (215 m long) were centered on the updip projection of the fault, which is associated with a surface drainage feature (Des Cyprie Slough) located at the base of a prominent east-facing escarpment. The seismic reflection profiles were collected using 48-channel (P-wave) and 24-channel (S-wave) towable landsteamer acquisition equipment. Seismic energy was generated by five vertical impacts of a 1.8-kg sledgehammer on a small aluminum plate for the P-wave data and five horizontal impacts of the sledgehammer on a 10-kg steel I-beam for the S-wave data. Interpretation of the profiles shows a west-dipping reverse fault (Reelfoot Fault) that propagates upward from Paleozoic sedimentary rocks (>500 m deep) to near-surface Quaternary sediments (<10 m deep). The hanging wall of the fault is anticlinally folded, a structural setting almost identical to that imaged on the Kentucky Bend and Reelfoot Lake segments (of the Reelfoot Fault) to the south.

Geophysical Investigation of Subsurface Characteristics of Icy Debris Fans with Ground Penetrating Radar in the Wrangell Mountains, Alaska

NASA Astrophysics Data System (ADS)

Smith, T. D.; Jacob, R. W.

2013-12-01

Authors Tracey Smith^1, Rob Jacob^1, Jeffrey Trop^1, Keith Williams^2 and Craig Kochel^1 Bucknell University, Geology and Environmental Geoscience Department, Lewisburg, PA UNAVCO, 6350 Nautilus Dr., Boulder, CO 80301 Icy debris fans have recently been described as deglaciation features on Earth and similar features have been observed on Mars, however, the subsurface characteristics remain unknown. We used ground penetrating radar (GPR) to non-invasively investigate the subsurface characteristics of icy debris fans near McCarthy, Alaska, USA. The three fans investigated in Alaska are the East, West, and Middle fans which are between the Nabesna ice cap and the McCarthy Glacier. Icy debris fans in general are a largely unexplored suite of paraglacial landforms and processes in alpine regions. Recent field studies focused on direct observations and depositional processes. The results showed that each fan's composition is primarily influenced by the type and frequency of mass wasting processes that supply the fan. Photographic studies show that the East fan receives far more ice and snow avalanches whereas the Middle and West fan receive fewer mass wasting events but more clastic debris is deposited on the Middle and West fan from rock falls and icy debris flows. GPR profiles and WARR surveys consisting of both, common mid-point (CMP), and common shot-point (CSP) surveys investigated the subsurface geometry of the fans and the McCarthy Glacier.All GPR surveys were collected in 2013 with 100MHz bi-static antennas. Four axial profiles and three cross-fan profiles were done on the West and Middle fans as well as the McCarthy Glacier in order to investigate the relationship between the three features. Terrestrial laser surveying of the surface and real-time kinematic GPS provided the surface elevation used to correct the GPR data for topographic changes. GPR profiles yielded reflectors that were continuous for 10+ m and hyperbolic reflections in the subsurface. The WARR surveys provided the GPR signal velocity through the subsurface material and allowed transformation of two-way traveltimes (TWTT) in GPR profiles to be converted to depth. In addition, the eight WARR surveys spaced on the fans and on the glacier provide information on variability of subsurface velocities. The profiles of the Middle and West fan have more energy returning to the surface and therefore many more reflections than profiles done on the McCarthy Glacier. Based on the WARR surveys, we interpret the lower energy return in the glacier to be caused by two reasons. 1) The increased attenuation due to wet ice versus drier ice and on the fan with GPR velocities >0.15m/ns. 2) Lack of interfaces in the glacier compared to those in the fans which are produced by the events depositing material to an ablated icy debris fan surface. The GPR profiles on the West and Middle fans show multiple point scatters at TWTT of less than 200ns. The Middle fan is distinguished from the West fan by its multiple point scatters at TWTT greater than 200ns, clearly showing the Middle fan with a greater thickness. The observations from the GPR profiles correlate with the photographic evidence for types of processes and the composition of their deposits on each fan respectively.

Computer program for calculating laminar, transitional, and turbulent boundary layers for a compressible axisymmetric flow

NASA Technical Reports Server (NTRS)

Albers, J. A.; Gregg, J. L.

1974-01-01

A finite-difference program is described for calculating the viscous compressible boundary layer flow over either planar or axisymmetric surfaces. The flow may be initially laminar and progress through a transitional zone to fully turbulent flow, or it may remain laminar, depending on the imposed boundary conditions, laws of viscosity, and numerical solution of the momentum and energy equations. The flow may also be forced into a turbulent flow at a chosen spot by the data input. The input may contain the factors of arbitrary Reynolds number, free-stream Mach number, free-stream turbulence, wall heating or cooling, longitudinal wall curvature, wall suction or blowing, and wall roughness. The solution may start from an initial Falkner-Skan similarity profile, an approximate equilibrium turbulent profile, or an initial arbitrary input profile.

Ocean Dynamics: Vietnam DRI

DTIC Science & Technology

2014-09-30

floor. OBJECTIVES To identify the phenomena involved in the cascade of energy from mesoscales to turbulent scales. In particular, we wish to quantify the...data from the profiler to the surface buoy. The WW Iridium telemetry system was tested on the WW moored over the continental shelf. Telemetry...2580 email: ajlucas@ucsd.edu Award: N00014-12-1-0635 LONG-TERM GOALS To gain a more complete understanding of ocean dynamical processes

a Study of the Tungsten (001) Surface Using Low Energy Electron Diffraction and Other Electron Spectroscopies.

NASA Astrophysics Data System (ADS)

Kalceff, Marion Anne Stevens

The properties of the clean Tungsten (001) surfaces (both (1 x 1) and reconstructed (SQRT.(2 x SQRT.(2)R45(DEGREES) phases) and the effects of the common absorbates Hydrogen and Oxygen have been investigated using the techniques of Low Energy Electron Diffraction, Auger Electron Spectroscopy and Characteristic Electron Energy Loss Spectroscopy. The origins of features observed in Characteristic Energy Loss Spectra, very low energy (<10 eV) Secondary Electron Emission spectra and low energy (<40 eV) Auger spectra, are deduced and compared with recent relevant independently obtained theoretical data and with other, sometimes conflicting, analyses. The use of these spectroscopies as monitors of surface cleanliness is evaluated. In particular a previously unreported emission, observed during Oxygen adsorption, is attributed to an Auger transition involving the Oxygen 2s and 2p adsorbate levels. Experimental conventional LEED and improved resolution very low energy intensity versus energy spectra are compared with Dynamical spectra, calculated using the program package of M. A. Van Hove and S. Y. Tong or calculated by R. O. Jones using a previously determined saturated image barrier, within a spin dependent scattering model, respectively. Structural information about the clean (1 x 1), clean reconstructed (SQRT.(2 x SQRT.(2)R45(DEGREES) and Hydrogen saturated (1 x 1)-H surfaces have been obtained via visual comparison or R factor (E. Zanazzi and F. Jona) analysis of the conventional data. The conventional methods of LEED Intensity data collection are assessed and procedures to improve experimental reproducibility are proposed. From the analysis of the improved resolution data, and with reference to the corresponding set of very low energy electron reflection data also obtained for comparison, conclusions are made about the origins of fine structure observed in the experimental profiles and about the W(001) surface order before and after the temperature dependent reconstruction and during Hydrogen adsorption. Further information about the clean W(001)-(SQRT.(2 x SQRT.(2)R45(DEGREES) surface, including the clean surface transition temperature, the mode of reconstruction, and structural information is determined from the analyses of the LEED intensity pattern and temperature dependence. In particular it is found that the reconstruction involves both vertical and horizontal components of atomic displacement and is dependent upon the surface topography and defect structure. All results are evaluated in comparison with other relevant independent experimental or theoretical analyses, where possible.

Energetics of a two-phase model of lithospheric damage, shear localization and plate-boundary formation

NASA Astrophysics Data System (ADS)

Bercovici, David; Ricard, Yanick

2003-03-01

The two-phase theory for compaction and damage proposed by Bercovici et al. (2001a, J. Geophys. Res.,106, 8887-8906) employs a nonequilibrium relation between interfacial surface energy, pressure and viscous deformation, thereby providing a model for damage (void generation and microcracking) and a continuum description of weakening, failure and shear localization. Here we examine further variations of the model which consider (1) how interfacial surface energy, when averaged over the mixture, appears to be partitioned between phases; (2) how variability in deformational-work partitioning greatly facilitates localization; and (3) how damage and localization are manifested in heat output and bulk energy exchange. Microphysical considerations of molecular bonding and activation energy suggest that the apparent partitioning of surface energy between phases goes as the viscosity of the phases. When such partitioning is used in the two-phase theory, it captures the melt-compaction theory of McKenzie (1984, J. Petrol.,25, 713-765) exactly, as well as the void-damage theory proposed in a companion paper (Ricard & Bercovici, submitted). Calculations of 1-D shear localization with this variation of the theory still show at least three possible regimes of damage and localization: at low stress is weak localization with diffuse slowly evolving shear bands; at higher stress strong localization with narrow rapidly growing bands exists; and at yet higher shear stress it is possible for the system to undergo broadly distributed damage and no localization. However, the intensity of localization is strongly controlled by the variability of the deformational-work partitioning with dilation rate, represented by the parameter γ. For γ>> 1, extreme localization is allowed, with sharp profiles in porosity (weak zones), nearly discontinuous separation velocities and effectively singular dilation rates. Finally, the bulk heat output is examined for the 1-D system to discern how much deformational work is effectively stored as surface energy. In the high-stress, distributed-damage cases, heat output is reduced as more interfacial surface energy is created. Yet, in either the weak or strong localizing cases, the system always releases surface energy, regardless of the presence of damage or not, and thus slightly more heat is in fact released than energy is input through external work. Moreover, increased levels of damage (represented by the maximum work-partitioning f*) make the localizing system release surface energy faster as damage enhances phase separation and focusing of the porosity field, thus yielding more rapid loss of net interfacial surface area. However, when cases with different levels of damage are compared at similar stages of development (say, the peak porosity of the localization) it is apparent that increased damage causes smaller relative heat release and retards loss of net interfacial surface energy. The energetics and energy partitioning of this damage and shear-localization model are applied to estimating the energy costs of forming plate boundaries and generating plates from mantle convection.

Analysis of surface segregation in polymer mixtures: A combination of mean field and statistical associated fluid theories

NASA Astrophysics Data System (ADS)

Krawczyk, Jaroslaw; Croce, Salvatore; Chakrabarti, Buddhapriya; Tasche, Jos

The surface segregation in polymer mixtures remains a challenging problem for both academic exploration as well as industrial applications. Despite its ubiquity and several theoretical attempts a good agreement between computed and experimentally observed profiles has not yet been achieved. A simple theoretical model proposed in this context by Schmidt and Binder combines Flory-Huggins free energy of mixing with the square gradient theory of wetting of a wall by fluid. While the theory gives us a qualitative understanding of the surface induced segregation and the surface enrichment it lacks the quantitative comparison with the experiment. The statistical associating fluid theory (SAFT) allows us to calculate accurate free energy for a real polymeric materials. In an earlier work we had shown that increasing the bulk modulus of a polymer matrix through which small molecules migrate to the free surface causes reduction in the surface migrant fraction using Schmidt-Binder and self-consistent field theories. In this work we validate this idea by combining mean field theories and SAFT to identify parameter ranges where such an effect should be observable. Department of Molecular Physics, Łódź University of Technology, Żeromskiego 116, 90-924 Łódź, Poland.

Mass-velocity and size-velocity distributions of ejecta cloud from shock-loaded tin surface using large scale molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Durand, Olivier; Soulard, Laurent

2015-06-01

The mass (volume and areal densities) versus velocity as well as the size versus velocity distributions of a shock-induced cloud of particles are investigated using large scale molecular dynamics (MD) simulations. A generic 3D tin crystal with a sinusoidal free surface roughness is set in contact with vacuum and shock-loaded so that it melts directly on shock. At the reflection of the shock wave onto the perturbations of the free surface, 2D sheets/jets of liquid metal are ejected. The simulations show that the distributions may be described by an analytical model based on the propagation of a fragmentation zone, from the tip of the sheets to the free surface, within which the kinetic energy of the atoms decreases as this zone comes closer to the free surface on late times. As this kinetic energy drives (i) the (self-similar) expansion of the zone once it has broken away from the sheet and (ii) the average size of the particles which result from fragmentation in the zone, the ejected mass and the average size of the particles progressively increase in the cloud as fragmentation occurs closer to the free surface. Though relative to nanometric scales, our model reproduces quantitatively experimental profiles and may help in their analysis.

Passive Acoustic Detection of Wind Turbine In-Flow Conditions for Active Control and Optimization

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

Murray, Nathan E.

2012-03-12

Wind is a significant source of energy; however, the human capability to produce electrical energy still has many hurdles to overcome. One of these is the unpredictability of the winds in the atmospheric boundary layer (ABL). The ABL is highly turbulent in both stable and unstable conditions (based on the vertical temperature profile) and the resulting fluctuations can have a dramatic impact on wind turbine operation. Any method by which these fluctuations could be observed, estimated, or predicted could provide a benefit to the wind energy industry as a whole. Based on the fundamental coupling of velocity fluctuations to pressuremore » fluctuations in the nearly incompressible flow in the ABL, This work hypothesizes that a ground-based array of infrasonic pressure transducers could be employed to estimate the vertical wind profile over a height relevant for wind turbines. To analyze this hypothesis, experiments and field deployments were conducted. Wind tunnel experiments were performed for a thick turbulent boundary layer over a neutral or heated surface. Surface pressure and velocity probe measurements were acquired simultaneously. Two field deployments yielded surface pressure data from a 49 element array. The second deployment at the Reese Technology Center in Lubbock, TX, also included data from a smaller aperture, 96-element array and a 200-meter tall meteorological tower. Analysis of the data successfully demonstrated the ability to estimate the vertical velocity profile using coherence data from the pressure array. Also, dynamical systems analysis methods were successful in identifying and tracking a gust type event. In addition to the passive acoustic profiling method, this program also investigated a rapid response Doppler SODAR system, the optimization of wind turbine blades for enhanced power with reduced aeroacoustic noise production, and the implementation of a wireless health monitoring system for the wind turbine blades. Each of these other objectives was met successfully. The use of phase unwrapping applied to SODAR data was found to yield reasonable results for per-pulse measurements. A health monitoring system design analysis was able to demonstrate the ability to use a very small number of sensors to monitor blade health based on the blade's overall structural modes. Most notable was the development of a multi-objective optimization methodology that successfully yielded an aerodynamic blade design that produces greater power output with reduced aerodynamic loading noise. This optimization method could be significant for future design work.« less

Performance profiling for brachytherapy applications

NASA Astrophysics Data System (ADS)

Choi, Wonqook; Cho, Kihyeon; Yeo, Insung

2018-05-01

In many physics applications, a significant amount of software (e.g. R, ROOT and Geant4) is developed on novel computing architectures, and much effort is expended to ensure the software is efficient in terms of central processing unit (CPU) time and memory usage. Profiling tools are used during the evaluation process to evaluate the efficiency; however, few such tools are able to accommodate low-energy physics regions. To address this limitation, we developed a low-energy physics profiling system in Geant4 to profile the CPU time and memory of software applications in brachytherapy applications. This paper describes and evaluates specific models that are applied to brachytherapy applications in Geant4, such as QGSP_BIC_LIV, QGSP_BIC_EMZ, and QGSP_BIC_EMY. The physics range in this tool allows it to be used to generate low energy profiles in brachytherapy applications. This was a limitation in previous studies, which caused us to develop a new profiling tool that supports profiling in the MeV range, in contrast to the TeV range that is supported by existing high-energy profiling tools. In order to easily compare the profiling results between low-energy and high-energy modes, we employed the same software architecture as that in the SimpliCarlo tool developed at the Fermilab National Accelerator Laboratory (FNAL) for the Large Hadron Collider (LHC). The results show that the newly developed profiling system for low-energy physics (less than MeV) complements the current profiling system used for high-energy physics (greater than TeV) applications.

Illustrating the Effect of pH on Enzyme Activity Using Gibbs Energy Profiles

ERIC Educational Resources Information Center

Bearne, Stephen L.

2014-01-01

Gibbs energy profiles provide students with a visual representation of the energy changes that occur during enzyme catalysis, making such profiles useful as teaching and learning tools. Traditional kinetic topics, such as the effect of pH on enzyme activity, are often not discussed in terms of Gibbs energy profiles. Herein, the symbolism of Gibbs…

Development of a Novel Method for Determination of Momentum Transport Parameters

NASA Astrophysics Data System (ADS)

Peters, Michael J.; Guttenfelder, Walter; Scotti, Filippo; Kaye, Stanley M.; Solomon, Wayne M.

2015-11-01

The toroidal momentum pinch velocity Vφ and diffusivity χφ in NSTX were previously determined from the transient response of the toroidal rotation Ω following applied n =3 magnetic perturbations that brake the plasma. Assuming Π = nmR2(-χϕ ∇Ω + Vϕ Ω), where the momentum flux Π is determined using TRANSP, these local analyses used fits to Ω and ∇Ω to obtain χϕ and Vϕ one flux surface at a time. This work attempts to improve the accuracy of the inferred χϕ(r) and Vϕ(r) profiles by utilizing many flux surfaces simultaneously. We employ nonlinear least-squares minimization that compares the entire perturbed rotation profile evolution Ω(r,t) against the profile evolution generated by solving the momentum transport equation. We compare the local and integrated approaches and discuss their limitations. We also apply the integrated approach to determine whether an additional residual stress contribution (independent of Ω or ∇Ω) can be inferred given experimental uncertainties. This work supported by the U.S. Department of Energy SULI program and contract DE-AC02-09/CH11466, as well as the LLNL contract DE-AC52-07NA27344.

Non-axisymmetric equilibrium reconstruction and suppression of density limit disruptions in a current-carrying stellarator

NASA Astrophysics Data System (ADS)

Ma, Xinxing; Ennis, D. A.; Hanson, J. D.; Hartwell, G. J.; Knowlton, S. F.; Maurer, D. A.

2017-10-01

Non-axisymmetric equilibrium reconstructions have been routinely performed with the V3FIT code in the Compact Toroidal Hybrid (CTH), a stellarator/tokamak hybrid. In addition to 50 external magnetic measurements, 160 SXR emissivity measurements are incorporated into V3FIT to reconstruct the magnetic flux surface geometry and infer the current distribution within the plasma. Improved reconstructions of current and q profiles provide insight into understanding the physics of density limit disruptions observed in current-carrying discharges in CTH. It is confirmed that the final scenario of the density limit of CTH plasmas is consistent with classic observations in tokamaks: current profile shrinkage leads to growing MHD instabilities (tearing modes) followed by a loss of MHD equilibrium. It is also observed that the density limit at a given current linearly increases with increasing amounts of 3D shaping fields. Consequently, plasmas with densities up to two times the Greenwald limit are attained. Equilibrium reconstructions show that addition of 3D fields effectively moves resonance surfaces towards the edge of the plasma where the current profile gradient is less, providing a stabilizing effect. This work is supported by US Department of Energy Grant No. DE-FG02-00ER54610.

Using the acoustic-pulse conservation law in estimating the energy of surface acoustic sources by remote sounding

NASA Astrophysics Data System (ADS)

Kulichkov, S. N.; Popov, O. Ye.; Mishenin, A. A.; Chunchuzov, I. P.; Chkhetiani, O. G.; Tsybulskaya, N. D.

2017-11-01

The atmospheric effect on the characteristics of infrasonic signals from explosions has been studied. New methods have been proposed to remotely estimate the energy of explosions using the data of infrasonic wave registration. One method is based on the law of conservation of acoustic pulse I, which is equal to the product of the wave profile area S/2 of the studied infrasonic signal and the distance to the source E I [kt] = 1.38 × 10-10 (I [kg/s])1.482. The second method is based on the relationship between the explosion energy and the dominant period T of the recorded signal, ET [kt] =1.02 × ( T [s]2/σ)3/2, where σ is a dimensionless distance used for determining the degree of manifestation of nonlinear effects in the propagation of sound along ray trajectories. When compared to the conventional E W (Whitaker's) relation, the advantage of the EI relation is that it can be used for pulsed sources located at an arbitrary height over the land surface and having an arbitrary form of the initial-pulse profile and for any type of infrasonic arrivals. A distinctive feature of the expression for E T is that the atmospheric effect on the characteristics of recorded infrasonic signals is explicitly taken into account. These methods have been tested using infrasonic data recorded at a distance of 322 km from the sources (30 explosions caused by a fire that occurred at the Pugachevo armory in Udmurtia on June 2, 2011). For the same explosion, empirical relations have been found between energy values obtained by different methods: E I = 1.107 × E W , E T = 2.201 × E I .

Diagnosing land management and climate change impacts on snowmelt in semi-arid agricultural cold regions with an improved snowmelt model

NASA Astrophysics Data System (ADS)

Harder, P.; Pomeroy, J. W.; Helgason, W.

2017-12-01

Spring snowmelt is the most important hydrological event in semi-arid agricultural cold regions, recharging soil moisture and generating the majority of annual runoff. Adoption of no-till agricultural practices means vast areas of the Canadian Prairies, and other analogous regions, are characterized by standing crop stubble. The emergence of stubble during snowmelt will have important implications for the snowpack energy balance. In addition, spatiotemporally dynamic snowcover heterogeneity leads to enhancement of turbulent flux contributions to melt by advection of energy from warm moist bare ground to snow. Stubble emergence and advection are generally unaccounted for in snow models. To address these challenges a stubble-snow-atmosphere surface energy balance model is developed that relates stubble parameters to the snow surface energy balance. Existing fractal understandings of snowcover geometry are applied to a conceptualized boundary layer integration model to estimate a sensible and latent heat advection efficiency. The small-scale nature of stubble-snow-atmosphere interactions makes direct validation of the energy balance terms challenging. However, the energy balance estimates are assessed by comparing to measured snow and stubble surface temperatures, snow surface incoming shortwave radiation and areal average turbulent fluxes. Advection estimates are validated from a two-dimensional air temperature, water vapor and windspeed profiles. Snowcover geometry relationships are validated/updated with unmanned air vehicle observations. Observations for model assessment occurred in 2015 and 2016 on wheat and canola stubble fields in north-central Saskatchewan, Canada. The model is not calibrated to melt rates, yet compares well with available observations, providing confidence in the model structure and parameterization. Sensitivity analysis using the model revealed compensatory relationships in energy balance terms resulting in limited reduction of energy available for snowmelt as stubble height increases. The proposed model is used to diagnose the influence of stubble management and climate change on melt processes to reveal the potential implications on runoff generation, infiltration and land-atmosphere interactions.

The Effect of Bond Albedo on Venus' Atmospheric and Surface Temperatures

NASA Astrophysics Data System (ADS)

Bullock, M. A.; Limaye, S. S.; Grinspoon, D. H.; Way, M.

2017-12-01

In spite of Venus' high planetary albedo, sufficient solar energy reaches the surface to drive a powerful greenhouse effect. The surface temperature is three times higher than it would be without an atmosphere. However, the details of the energy balance within Venus' atmosphere are poorly understood. Half of the solar energy absorbed within the clouds, where most of the solar energy is absorbed, is due to an unknown agent. One of the challenges of modeling Venus' atmosphere has been to account for all the sources of opacity sufficient to generate a globally averaged surface temperature of 735 K, when only 2% of the incoming solar energy is deposited at the surface. The wavelength and spherically integrated albedo, or Bond albedo, has typically been cited as between 0.7 and 0.82 (Colin 1983). Yet, recent photometry of Venus at extended phase angles between 2 and 179° indicate a Bond albedo of 0.90 (Mallama et al., 2006). The authors note an increase in cloud top brightness at phase angles < 2°, which effectively increases the spherically integrated albedo. They suggest that forward scattering by the H2SO4/H2O aerosols of the upper cloud is responsible for Venus' high albedo at very low phase angles. The present work investigates the implications of such a high albedo for understanding and modeling the energy balance of Venus' atmosphere. Using the successful 1D radiative transfer model SimVenus that incorporates the opacity due to 9 major gases in Venus' atmosphere, as well as multiple scattering calculations of radiation within the clouds, the sensitivity of surface temperature was studied as a function of Bond albedo. Results of these model calculations are shown in Fig. 1. Figure 1a (left). Venus' atmospheric temperature profile for different values of Bond albedo. The structure and radiative effects of the clouds are fixed. Figure 1b (right). Venus surface temperature as Bond Albedo changes. Radiative-convective equilibrium models predict the correct globally averaged surface temperature at a=0.81. Calculations here show that a Bond albedo of a=0.9 would yield a surface temperature of 666.4 K, about 70 K too low, unless there is additional thermal absorption within the atmosphere that is not understood. Colin, L.,, Venus, University of Arizona Press, Tucson, 1983, pp 10-26. Mallama, A., et al., 2006. Icarus. 182, 10-22.

High efficiency low cost thin film silicon solar cell design and method for making

DOEpatents

Sopori, B.L.

1999-04-27

A semiconductor device is described having a substrate, a conductive intermediate layer deposited onto said substrate, wherein the intermediate layer serves as a back electrode, an optical reflector, and an interface for impurity gettering, and a semiconductor layer deposited onto said intermediate layer, wherein the semiconductor layer has a grain size at least as large as the layer thickness, and preferably about ten times the layer thickness. The device is formed by depositing a metal layer on a substrate, depositing a semiconductive material on the metal-coated substrate to produce a composite structure, and then optically processing the composite structure by illuminating it with infrared electromagnetic radiation according to a unique time-energy profile that first produces pits in the backside surface of the semiconductor material, then produces a thin, highly reflective, low resistivity alloy layer over the entire area of the interface between the semiconductor material and the metal layer, and finally produces a grain-enhanced semiconductor layer. The time-energy profile includes increasing the energy to a first energy level to initiate pit formation and create the desired pit size and density, then ramping up to a second energy level in which the entire device is heated to produce an interfacial melt, and finally reducing the energy to a third energy level and holding for a period of time to allow enhancement in the grain size of the semiconductor layer. 9 figs.

HCMM energy budget data as a model input for assessing regions of high potential groundwater pollution. [South Dakota

NASA Technical Reports Server (NTRS)

Moore, D. G. (Principal Investigator); Heilman, J. L.

1980-01-01

The author has identified the following significant results. Day thermal data were analyzed to assess depth to groundwater in the test site. HCMM apparent temperature was corrected for atmospheric effects using lake temperature of the Oahe Reservoir in central South Dakota. Soil surface temperatures were estimated using an equation developed for ground studies. A significant relationship was found between surface soil temperature and depth to groundwater, as well as between the surface soil-maximum air temperature differential and soil water content (% of field capacity) in the 0 cm and 4 cm layer of the profile. Land use for the data points consisted of row crops, small grains, stubble, and pasture.

Discussion of flight experiments with an entry research vehicle

NASA Technical Reports Server (NTRS)

Potter, J. L.

1985-01-01

The focus of interest is the maneuvering flight of advanced entry vehicles operating at altitudes above 50 km and at velocities of 5 to 8 km/s. Information resulting in more accurate aerodynamic analysis is sought and measurement techniques that appear to be applicable are identified. Measurements discussed include: shock layer or boundary layer profiles of velocity, temperature, species mass fractions, and other gas properties associated with aerodynamic heating; surface energy transfer process; nonequilibrium flow processes and pressure distribution; separated, vortic leeside flow of nonequilibrium fluid; boundary layer transition on highly swept configurations; and shock and surface slip and gas/surface interaction. Further study should focus on evolving measurement techniques, installation requirements, and on identification of the portions of flights where successful results seem probable.

Aerodynamic performance of transonic and subsonic airfoils: Effects of surface roughness, turbulence intensity, Mach number, and streamline curvature-airfoil shape

NASA Astrophysics Data System (ADS)

Zhang, Qiang

The effects of surface roughness, turbulence intensity, Mach number, and streamline curvature-airfoil shape on the aerodynamic performance of turbine airfoils are investigated in compressible, high speed flows. The University of Utah Transonic Wind Tunnel is employed for the experimental part of the study. Two different test sections are designed to produce Mach numbers, Reynolds numbers, passage mass flow rates, and physical dimensions, which match values along turbine blades in operating engines: (i) a nonturning test section with a symmetric airfoil, and (ii) a cascade test section with a cambered turbine vane. The nonuniform, irregular, three-dimensional surface roughness is characterized using the equivalent sand grain roughness size. Changing the airfoil surface roughness condition has a substantial effect on wake profiles of total pressure loss coefficients, normalized Mach number, normalized kinetic energy, and on the normalized and dimensional magnitudes of Integrated Aerodynamic Losses produced by the airfoils. Comparisons with results for a symmetric airfoil and a cambered vane show that roughness has more substantial effects on losses produced by the symmetric airfoil than the cambered vane. Data are also provided that illustrate the larger loss magnitudes are generally present with flow turning and cambered airfoils, than with symmetric airfoils. Wake turbulence structure of symmetric airfoils and cambered vanes are also studied experimentally. The effects of surface roughness and freestream turbulence levels on wake distributions of mean velocity, turbulence intensity, and power spectral density profiles and vortex shedding frequencies are quantified one axial chord length downstream of the test airfoils. As the level of surface roughness increases, all wake profile quantities broaden significantly and nondimensional vortex shedding frequencies decrease. Wake profiles produced by the symmetric airfoil are more sensitive to variations of surface roughness and freestream turbulence, compared with data from the cambered vane airfoil. Stanton numbers, skin friction coefficients, aerodynamic losses, and Reynolds analogy behavior are numerically predicted for a turbine vane using the FLUENT with a k-epsilon RNG model to show the effects of Mach number, mainstream turbulence level, and surface roughness. Comparisons with wake aerodynamic loss experimental data are made. Numerically predicted skin friction coefficients and Stanton numbers are also used to deduce Reynolds analogy behavior on the vane suction and pressure sides.

Wind energy potential analysis in Al-Fattaih-Darnah

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

Tjahjana, Dominicus Danardono Dwi Prija, E-mail: danar1405@gmail.com; Salem, Abdelkarim Ali, E-mail: keemsalem@gmail.com; Himawanto, Dwi Aries, E-mail: dwiarieshimawanto@gmail.com

2016-03-29

In this paper the wind energy potential in Al-Fattaih-Darnah, Libya, had been studied. Wind energy is very attractive because it can provide a clean and renewable energy. Due mostly to the uncertainty caused by the chaotic characteristics of wind near the earth’s surface, wind energy characteristic need to be investigated carefully in order to get consistent power generation. This investigation was based on one year wind data measured in 2003. As a result of the analysis, wind speed profile and wind energy potential have been developed. The wind energy potential of the location is looked very promising to generate electricity.more » The annual wind speed of the site is 8.21 m/s and the wind speed carrying maximum energy is 7.97 m/s. The annual power density of the site is classified into class 3. The Polaris P50-500 wind turbine can produce 768.39 M Wh/year and has capacity factor of 17.54%.« less

Laser range profile of cones

NASA Astrophysics Data System (ADS)

Zhou, Wenzhen; Gong, Yanjun; Wang, Mingjun; Gong, Lei

2016-10-01

technology. Laser one-dimensional range profile can reflect the characteristics of the target shape and surface material. These techniques were motivated by applications of laser radar to target discrimination in ballistic missile defense. The radar equation of pulse laser about cone is given in this paper. This paper demonstrates the analytical model of laser one-dimensional range profile of cone based on the radar equation of the pulse laser. Simulations results of laser one-dimensional range profiles of some cones are given. Laser one-dimensional range profiles of cone, whose surface material with diffuse lambertian reflectance, is given in this paper. Laser one-dimensional range profiles of cone, whose surface mater with diffuse materials whose retroreflectance can be modeled closely with an exponential term that decays with increasing incidence angles, is given in this paper. Laser one-dimensional range profiles of different pulse width of cone is given in this paper. The influences of surface material, pulse width, attitude on the one-dimensional range are analyzed. The laser two-dimensional range profile is two-dimensional scattering imaging of pulse laser of target. The two-dimensional range profile of roughness target can provide range resolved information. An analytical model of two-dimensional laser range profile of cone is proposed. The simulations of two-dimensional laser range profiles of some cones are given. Laser two-dimensional range profiles of cone, whose surface mater with diffuse lambertian reflectance, is given in this paper. Laser two-dimensional range profiles of cone, whose surface mater with diffuse materials whose retroreflectance can be modeled closely with an exponential term that decays with increasing incidence angles, is given in this paper. The influence of pulse width, surface material on laser two-dimensional range profile is analyzed. Laser one-dimensional range profile and laser two-dimensional range profile are called as laser range profile (LRP).

Mapping the Excited State Potential Energy Surface of a Retinal Chromophore Model with Multireference and Equation-of-Motion Coupled-Cluster Methods.

PubMed

Gozem, Samer; Melaccio, Federico; Lindh, Roland; Krylov, Anna I; Granovsky, Alexander A; Angeli, Celestino; Olivucci, Massimo

2013-10-08

The photoisomerization of the retinal chromophore of visual pigments proceeds along a complex reaction coordinate on a multidimensional surface that comprises a hydrogen-out-of-plane (HOOP) coordinate, a bond length alternation (BLA) coordinate, a single bond torsion and, finally, the reactive double bond torsion. These degrees of freedom are coupled with changes in the electronic structure of the chromophore and, therefore, the computational investigation of the photochemistry of such systems requires the use of a methodology capable of describing electronic structure changes along all those coordinates. Here, we employ the penta-2,4-dieniminium (PSB3) cation as a minimal model of the retinal chromophore of visual pigments and compare its excited state isomerization paths at the CASSCF and CASPT2 levels of theory. These paths connect the cis isomer and the trans isomer of PSB3 with two structurally and energetically distinct conical intersections (CIs) that belong to the same intersection space. MRCISD+Q energy profiles along these paths provide benchmark values against which other ab initio methods are validated. Accordingly, we compare the energy profiles of MRPT2 methods (CASPT2, QD-NEVPT2, and XMCQDPT2) and EOM-SF-CC methods (EOM-SF-CCSD and EOM-SF-CCSD(dT)) to the MRCISD+Q reference profiles. We find that the paths produced with CASSCF and CASPT2 are topologically and energetically different, partially due to the existence of a "locally excited" region on the CASPT2 excited state near the Franck-Condon point that is absent in CASSCF and that involves a single bond, rather than double bond, torsion. We also find that MRPT2 methods as well as EOM-SF-CCSD(dT) are capable of quantitatively describing the processes involved in the photoisomerization of systems like PSB3.

High-precision drop shape analysis on inclining flat surfaces: introduction and comparison of this special method with commercial contact angle analysis.

PubMed

Schmitt, Michael; Heib, Florian

2013-10-07

Drop shape analysis is one of the most important and frequently used methods to characterise surfaces in the scientific and industrial communities. An especially large number of studies, which use contact angle measurements to analyse surfaces, are characterised by incorrect or misdirected conclusions such as the determination of surface energies from poorly performed contact angle determinations. In particular, the characterisation of surfaces, which leads to correlations between the contact angle and other effects, must be critically validated for some publications. A large number of works exist concerning the theoretical and thermodynamic aspects of two- and tri-phase boundaries. The linkage between theory and experiment is generally performed by an axisymmetric drop shape analysis, that is, simulations of the theoretical drop profiles by numerical integration onto a number of points of the drop meniscus (approximately 20). These methods work very well for axisymmetric profiles such as those obtained by pendant drop measurements, but in the case of a sessile drop onto real surfaces, additional unknown and misunderstood effects on the dependence of the surface must be considered. We present a special experimental and practical investigation as another way to transition from experiment to theory. This procedure was developed to be especially sensitive to small variations in the dependence of the dynamic contact angle on the surface; as a result, this procedure will allow the properties of the surface to be monitored with a higher precession and sensitivity. In this context, water drops onto a 111 silicon wafer are dynamically measured by video recording and by inclining the surface, which results in a sequence of non-axisymmetric drops. The drop profiles are analysed by commercial software and by the developed and presented high-precision drop shape analysis. In addition to the enhanced sensitivity for contact angle determination, this analysis technique, in combination with innovative fit algorithms and data presentations, can result in enhanced reproducibility and comparability of the contact angle measurements in terms of the material characterisation in a comprehensible way.

High-precision drop shape analysis on inclining flat surfaces: Introduction and comparison of this special method with commercial contact angle analysis

NASA Astrophysics Data System (ADS)

Schmitt, Michael; Heib, Florian

2013-10-01

Drop shape analysis is one of the most important and frequently used methods to characterise surfaces in the scientific and industrial communities. An especially large number of studies, which use contact angle measurements to analyse surfaces, are characterised by incorrect or misdirected conclusions such as the determination of surface energies from poorly performed contact angle determinations. In particular, the characterisation of surfaces, which leads to correlations between the contact angle and other effects, must be critically validated for some publications. A large number of works exist concerning the theoretical and thermodynamic aspects of two- and tri-phase boundaries. The linkage between theory and experiment is generally performed by an axisymmetric drop shape analysis, that is, simulations of the theoretical drop profiles by numerical integration onto a number of points of the drop meniscus (approximately 20). These methods work very well for axisymmetric profiles such as those obtained by pendant drop measurements, but in the case of a sessile drop onto real surfaces, additional unknown and misunderstood effects on the dependence of the surface must be considered. We present a special experimental and practical investigation as another way to transition from experiment to theory. This procedure was developed to be especially sensitive to small variations in the dependence of the dynamic contact angle on the surface; as a result, this procedure will allow the properties of the surface to be monitored with a higher precession and sensitivity. In this context, water drops onto a 111 silicon wafer are dynamically measured by video recording and by inclining the surface, which results in a sequence of non-axisymmetric drops. The drop profiles are analysed by commercial software and by the developed and presented high-precision drop shape analysis. In addition to the enhanced sensitivity for contact angle determination, this analysis technique, in combination with innovative fit algorithms and data presentations, can result in enhanced reproducibility and comparability of the contact angle measurements in terms of the material characterisation in a comprehensible way.

Laser characterization of the depth profile of complex refractive index of PMMA implanted with 50 keV silicon ions

NASA Astrophysics Data System (ADS)

Stefanov, Ivan L.; Stoyanov, Hristiyan Y.; Petrova, Elitza; Russev, Stoyan C.; Tsutsumanova, Gichka G.; Hadjichristov, Georgi B.

2013-03-01

The depth profile of the complex refractive index of silicon ion (Si+) implanted polymethylmethacrylate (PMMA) is studied, in particular PMMA implanted with Si+ ions accelerated to a relatively low energy of 50 keV and at a fluence of 3.2 × 1015 cm-2. The ion-modified material with nano-clustered structure formed in the near(sub)surface layer of a thickness of about 100 nm is optically characterized by simulation based on reflection ellipsometry measurements at a wavelength of 632.8 nm (He-Ne laser). Being of importance for applications of ion-implanted PMMA in integrated optics, optoelectronics and optical communications, the effect of the index depth profile of Si+-implanted PMMA on the profile of the reflected laser beam due to laser-induced thermo-lensing in reflection is also analyzed upon illumination with a low power cw laser (wavelength 532 nm, optical power 10 - 50 mW).

A family of models for spherical stellar systems

NASA Technical Reports Server (NTRS)

Tremaine, Scott; Richstone, Douglas O.; Byun, Yong-Ik; Dressler, Alan; Faber, S. M.; Grillmair, Carl; Kormendy, John; Lauer, Tod R.

1994-01-01

We describe a one-parameter family of models of stable sperical stellar systems in which the phase-space distribution function depends only on energy. The models have similar density profiles in their outer parts (rho propotional to r(exp -4)) and central power-law density cusps, rho proportional to r(exp 3-eta), 0 less than eta less than or = 3. The family contains the Jaffe (1983) and Hernquist (1990) models as special cases. We evaluate the surface brightness profile, the line-of-sight velocity dispersion profile, and the distribution function, and discuss analogs of King's core-fitting formula for determining mass-to-light ratio. We also generalize the models to a two-parameter family, in which the galaxy contains a central black hole; the second parameter is the mass of the black hole. Our models can be used to estimate the detectability of central black holes and the velocity-dispersion profiles of galaxies that contain central cusps, with or without a central black hole.

Estimating the aerodynamic roughness of debris covered glacier ice

NASA Astrophysics Data System (ADS)

Quincey, Duncan; Smith, Mark; Rounce, David; Ross, Andrew; King, Owen; Watson, Scott

2017-04-01

Aerodynamic roughness length (z0), the height above the ground surface at which the extrapolated horizontal wind velocity profile drops to zero, is one of the most poorly parameterised elements of the glacier surface energy balance equation. Microtopographic methods for estimating z0 are becoming increasingly well used, but are rarely validated against independent measures and are yet to be comprehensively analysed for scale or data resolution dependency. Here, we present the results of a field investigation conducted on the debris covered Khumbu Glacier during the post-monsoon season of 2015. We focus on two sites. The first is characterised by gravels and cobbles supported by a fine sandy matrix. The second comprises cobbles and boulders separated by voids. Vertical profiles of wind speed measured over both sites enable us to derive measurements of aerodynamic roughness that reflect their observed surface characteristics (0.0184 m vs 0.0243 m). z0 at the second site also varied through time following snowfall (0.0055 m) and during its subsequent melt (0.0129 m), showing the importance of fine resolution topography for near-surface airflow. We conducted Structure from Motion Multi-View Stereo (SfM-MVS) surveys across each patch and calculated z0 using three microtopographic methods. The fully three-dimensional cloud-based approach is shown to be most stable across different scales and these z0 values are most correct in relative order when compared to the wind tower data. Popular profile-based methods perform less well providing highly variable values across different scales and when using data of differing resolution.

Prediction of Protein-Protein Interaction Sites Using Electrostatic Desolvation Profiles

PubMed Central

Fiorucci, Sébastien; Zacharias, Martin

2010-01-01

Abstract Protein-protein complex formation involves removal of water from the interface region. Surface regions with a small free energy penalty for water removal or desolvation may correspond to preferred interaction sites. A method to calculate the electrostatic free energy of placing a neutral low-dielectric probe at various protein surface positions has been designed and applied to characterize putative interaction sites. Based on solutions of the finite-difference Poisson equation, this method also includes long-range electrostatic contributions and the protein solvent boundary shape in contrast to accessible-surface-area-based solvation energies. Calculations on a large set of proteins indicate that in many cases (>90%), the known binding site overlaps with one of the six regions of lowest electrostatic desolvation penalty (overlap with the lowest desolvation region for 48% of proteins). Since the onset of electrostatic desolvation occurs even before direct protein-protein contact formation, it may help guide proteins toward the binding region in the final stage of complex formation. It is interesting that the probe desolvation properties associated with residue types were found to depend to some degree on whether the residue was outside of or part of a binding site. The probe desolvation penalty was on average smaller if the residue was part of a binding site compared to other surface locations. Applications to several antigen-antibody complexes demonstrated that the approach might be useful not only to predict protein interaction sites in general but to map potential antigenic epitopes on protein surfaces. PMID:20441756

Saliva analysis by surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF-MS) in orthodontic treatment: first pilot study.

PubMed

Ciavarella, Domenico; Mastrovincenzo, Mario; D'Onofrio, Valentina; Chimenti, Claudio; Parziale, Vincenzo; Barbato, Ersilia; Lo Muzio, Lorenzo

2011-11-01

SELDI-TOF-MS (Surface-Enhanced Laser Desorption/Ionization Time-Of-Flight Mass Spectrometry) allows the generation of an accurate protein profile from minimal amounts of biological samples and may executes proteomic profile of saliva. The aim of this work is to compare the proteomic profile of saliva of patients in orthodontic treatment to the beginning of treatment and after three months by using the surface enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF-MS) technology. Saliva was collected from 14 patients, between the 11 and 17 years, to the beginning of the orthodontic treatment and after three months. Specimens were centrifuged (10 min, 13000 x g); the Q10 ProteinChips were prepared according to the manufacturer's instructions and were loaded with the supernatants. A saturated solution of sinapinic acid was used as energy-absorbing matrix. The analysis was performed in a m/z range from 2500 to 25000 Da, and the proteomic profiles were compared by a specific data analysis software. Saliva (5 mL) was collected by spitting directly into a clean 15 mL conical tube. The samples were then aliquotted and stored at -80°C until use. Profile of saliva of patients before orthodontic treatment present a number of peaks different respect profile of saliva after three months of treatment. The average intensities of peaks at m/z 3372, 5232, 4045 and 10128 were significantly higher after three months then at beginning of treatment in the same patients and among these one. The Roc Plot has demonstrated high sensitivity and specificity. Many differences were noted in salivary proteomic profile obtained using the SELDI-TOF-MS technology in patients in orthodontic treatment to beginning and after three months. These data suggest that the proteomic analysis of saliva is a promising new tool for a non-invasive study of oral mucosa and bone changes. Copyright © 2011 Società Italiana di Ortodonzia SIDO. Published by Elsevier Srl. All rights reserved.

Thermal modeling of grinding for process optimization and durability improvements

NASA Astrophysics Data System (ADS)

Hanna, Ihab M.

Both thermal and mechanical aspects of the grinding process are investigated in detail in an effort to predict grinding induced residual stresses. An existing thermal model is used as a foundation for computing heat partitions and temperatures in surface grinding. By numerically processing data from IR temperature measurements of the grinding zone; characterizations are made of the grinding zone heat flux. It is concluded that the typical heat flux profile in the grinding zone is triangular in shape, supporting this often used assumption found in the literature. Further analyses of the computed heat flux profiles has revealed that actual grinding zone contact lengths exceed geometric contact lengths by an average of 57% for the cases considered. By integrating the resulting heat flux profiles; workpiece energy partitions are computed for several cases of dry conventional grinding of hardened steel. The average workpiece energy partition for the cases considered was 37%. In an effort to more accurately predict grinding zone temperatures and heat fluxes, refinements are made to the existing thermal model. These include consideration of contact length extensions due to local elastic deformations, variations of the assumed contact area ratio as a function of grinding process parameters, consideration of coolant latent heat of vaporization and its effect on heat transfer beyond the coolant boiling point, and incorporation of coolant-workpiece convective heat flux effects outside the grinding zone. The result of the model refinements accounting for contact length extensions and process-dependant contact area ratios is excellent agreement with IR temperature measurements over a wide range of grinding conditions. By accounting for latent heat of vaporization effects, grinding zone temperature profiles are shown to be capable of reproducing measured profiles found in the literature for cases on the verge of thermal surge conditions. Computed peak grinding zone temperatures for the aggressive grinding examples given are 30--50% lower than those computed using the existing thermal model formulation. By accounting for convective heat transfer effects outside the grinding zone, it is shown that while surface temperatures in the wake of the grinding zone may be significantly affected under highly convective conditions, computed residual stresses are less sensitive to such conditions. Numerical models are used to evaluate both thermally and mechanically induced stress fields in an elastic workpiece, while finite element modeling is used to evaluate residual stresses for workpieces with elastic-plastic material properties. Modeling of mechanical interactions at the local grit-workpiece length scale is used to create the often measured effect of compressive surface residual stress followed by a subsurface tensile peak. The model is shown to be capable of reproducing trends found in the literature of surface residual stresses which are compressive for low temperature grinding conditions, with surface stresses increasing linearly and becoming tensile with increasing temperatures. Further modifications to the finite element model are made to allow for transiently varying inputs for more complicated grinding processes of industrial components such as automotive cam lobes.

Plant temperatures and heat flux in a Sonoran Desert ecosystem.

PubMed

Gibbs, Joan G; Patten, D T

1970-09-01

In the extreme desert environment the potential energy load is high, consequently high temperatures might be a limiting factor for plant survival. Field measurements of plant temperatures in a Sonoran Desert ecosystem were made using fine thermocouples. Temperatures of six desert species were measured: Opuntia engelmannii, Opuntia bigelovii, Opuntia acanthocarpa, Echinocereus engelmannii, Larrea tridentata and Franseria deltoidea. Daily temperature profiles were used to compare the different responses of cacti and shrubs to the desert heat load and also to compare spring and summer responses. Leaf temperature of shrubs was at or near air temperature during both the mild, spring season and the hotter dry season. The cacti, on the other hand, absorbed and stored heat, thus temperatures were often above air temperature. The energy absorbed is determined largely by plant orientation and surface area exposed to the sun. Actual energy absorbed by the plants was estimated from energy diagrams.The flat stem pads of Opuntia engelmannii plants are oriented to receive maximum sunlight without long periods of continuous heating. Opuntia bigelovii spines reflect and absorb much of the environmental energy load, thereby protecting the thick, succulent stems from overheating. The smaller stems of Opuntia acanthocarpa dissipate heat more effectively by their large surface area exposed to convective air currents. Leaves on desert shrubs remain nearer to air temperature than do succulent stems of cacti, because their very large surface to volume ratio allows them to dissipate much heat by convection.

Methylene blue adsorption on a DMPA lipid langmuir monolayer.

PubMed

Giner Casares, Juan José; Camacho, Luis; Martín-Romero, Maria Teresa; López Cascales, José Javier

2010-07-12

Adsorption of methylene blue (MB) onto a dimyristoylphosphatidic acid (DMPA) Langmuir air/water monolayer is studied by molecular dynamics (MD) simulations, UV reflection spectroscopy and surface potential measurements. The free-energy profile associated with MB transfer from water to the lipid monolayer shows two minima of -66 and -60 kJ mol(-1) for its solid and gas phase, respectively, corresponding to a spontaneous thermodynamic process. From the position of the free-energy minima, it is possible to predict the precise location of MB in the interior of the DMPA monolayer. Thus, MB is accommodated in the phosphoryl or carbonyl region of the DMPA Langmuir air/water interface, depending on the isomorphic state (solid or gas phase, respectively). Reorientation of MB, measured from the bulk solution to the interior of the lipid monolayer, passes from a random orientation in bulk solution to an orientation parallel to the surface of the lipid monolayer when MB is absorbed.

Limitations to laser machining of silicon using femtosecond micro-Bessel beams in the infrared

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

Grojo, David, E-mail: grojo@lp3.univ-mrs.fr; Mouskeftaras, Alexandros; Delaporte, Philippe

We produce and characterize high-angle femtosecond Bessel beams at 1300-nm wavelength leading to nonlinearly ionized plasma micro-channels in both glass and silicon. With microjoule pulse energy, we demonstrate controlled through-modifications in 150-μm glass substrates. In silicon, strong two-photon absorption leads to larger damages at the front surface but also a clamping of the intensity inside the bulk at a level of ≈4 × 10{sup 11 }W cm{sup −2} which is below the threshold for volume and rear surface modification. We show that the intensity clamping is associated with a strong degradation of the Bessel-like profile. The observations highlight that the inherent limitation tomore » ultrafast energy deposition inside semiconductors with Gaussian focusing [Mouskeftaras et al., Appl. Phys. Lett. 105, 191103 (2014)] applies also for high-angle Bessel beams.« less

Characterisation of vibration input to flywheel used on urban bus

NASA Astrophysics Data System (ADS)

Wang, L.; Kanarachos, S.; Christensen, J.

2016-09-01

Vibration induced from road surface has an impact on the durability and reliability of electrical and mechanical components attached on the vehicle. There is little research published relevant to the durability assessment of a flywheel energy recovery system installed on city and district buses. Relevant international standards and legislations were reviewed and large discrepancy was found among them, in addition, there are no standards exclusively developed for kinetic energy recovery systems on vehicles. This paper describes the experimentation of assessment of road surface vibration input to the flywheel on a bus as obtained at the MIRA Proving Ground. Power density spectra have been developed based on the raw data obtained during the experimentation. Validation of this model will be carried out using accelerated life time tests that will be carried out on a shaker rig using an accumulated profile based on the theory of fatigue damage equivalence in time and frequency domain aligned with the model predictions.

Rapid laser fabrication of microlens array using colorless liquid photopolymer for AMOLED devices

NASA Astrophysics Data System (ADS)

Kim, Kwang-Ryul; Jeong, Han-Wook; Lee, Kong-Soo; Yi, Junsin; Yoo, Jae-Chern; Cho, Myung-Woo; Cho, Sung-Hak; Choi, Byoungdeog

2011-01-01

Microlens array (MLA) is microfabricated using Ultra Violet (UV) laser for display device applications. A colorless liquid photopolymer, Norland Optical Adhesive (NOA) 60, is spin-coated and pre-cured via UV light for completing the laser process. The laser energy controlled by a galvano scanner is radiated on the surface of the NOA 60. A rapid thermal volume expansion inside the material creates microlens array when the Gaussian laser energy is absorbed. The fabrication process conditions for various shapes and densities of MLA using a non-contact surface profiler are investigated. Furthermore, we analyze the optical and display characteristics for the Organic Light Emitting Diode (OLED) devices. Optimized condition furnishes the OLED with the enhancement of light emission by 15%. We show that UV laser technique, which is installed with NOA 60 MLA layer, is eligible for improving the performance of the next generation display devices.

Development of an ion time-of-flight spectrometer for neutron depth profiling

NASA Astrophysics Data System (ADS)

Cetiner, Mustafa Sacit

Ion time-of-flight spectrometry techniques are investigated for applicability to neutron depth profiling. Time-of-flight techniques are used extensively in a wide range of scientific and technological applications including energy and mass spectroscopy. Neutron depth profiling is a near-surface analysis technique that gives concentration distribution versus depth for certain technologically important light elements. The technique uses thermal or sub-thermal neutrons to initiate (n, p) or (n, alpha) reactions. Concentration versus depth distribution is obtained by the transformation of the energy spectrum into depth distribution by using stopping force tables of the projectiles in the substrate, and by converting the number of counts into concentration using a standard sample of known dose value. Conventionally, neutron depth profiling measurements are based on charged particle spectrometry, which employs semiconductor detectors such as a surface barrier detector (SBD) and the associated electronics. Measurements with semiconductor detectors are affected by a number of broadening mechanisms, which result from the interactions between the projectile ion and the detector material as well as fluctuations in the signal generation process. These are inherent features of the detection mechanism that involve the semiconductor detectors and cannot be avoided. Ion time-of-flight spectrometry offers highly precise measurement capabilities, particularly for slow particles. For high-energy low-mass particles, measurement resolution tends to degrade with all other parameters fixed. The threshold for more precise ion energy measurements with respect to conventional techniques, such as direct energy measurement by a surface barrier detector, is directly related to the design and operating parameters of the device. Time-of-flight spectrometry involves correlated detection of two signals by a coincidence unit. In ion time-of-flight spectroscopy, the ion generates the primary input signal. Without loss of generality, the secondary signal is obtained by the passage of the ion through a thin carbon foil, which produces ion-induced secondary electron emission (IISEE). The time-of-flight spectrometer physically acts as an ion/electron separator. The electrons that enter the active volume of the spectrometer are transported onto the microchannel plate detector to generate the secondary signal. The electron optics can be designed in variety of ways depending on the nature of the measurement and physical requirements. Two ion time-of-flight spectrometer designs are introduced: the parallel electric and magnetic (PEM) field spectrometer and the cross electric and magnetic (CEM) field spectrometer. The CEM field spectrometers have been extensively used in a wide range of applications where precise mass differentiation is required. The PEM field spectrometers have lately found interest in mass spectroscopy applications. The application of the PEM field spectrometer for energy measurements is a novel approach. The PEM field spectrometer used in the measurements employs axial electric and magnetic fields along the nominal direction of the incident ion. The secondary electrons are created by a thin carbon foil on the entrance disk and transported on the microchannel plate that faces the carbon foil. The initial angular distribution of the secondary electrons has virtually no effect on the transport time of the secondary electrons from the surface of the carbon foil to the electron microchannel plate detector. Therefore, the PEM field spectrometer can offer high-resolution energy measurement for relatively lower electric fields. The measurements with the PEM field spectrometer were made with the Tandem linear particle accelerator at the IBM T. J. Watson Research Center at Yorktown Heights, NY. The CEM field spectrometer developed for the thesis employs axial electric field along the nominal direction of the ion, and has perpendicular magnetic field. As the electric field accelerates and then decelerates the emitted secondary electron beam, the magnetic field steers the beam away from the source and focuses it onto the electron microchannel plate detector. The initial momentum distribution of the electron beam is observed to have profound effect on the electron transport time. Hence, the CEM field spectrometer measurements suffer more from spectral broadening at similar operating parameters. The CEM field spectrometer measurements were obtained with a 210Po alpha source at the Penn State Radiation Science and Engineering Center, University Park, PA. Although the PEM field spectrometer suffers less from electron transport time dispersion, the CEM field spectrometer is more suited for application to neutron depth profiling. The multiple small-diameter apertures used in the PEM field configuration considerably reduces the geometric efficiency of the spectrometer. Most of the neutron depth profiling measurements, where isotropic emission of charged particles is observed, have relatively low count rates; hence, high detection efficiency is essential.

Idealized Cloud-System Resolving Modeling for Tropical Convection Studies

NASA Astrophysics Data System (ADS)

Anber, Usama M.

A three-dimensional limited-domain Cloud-Resolving Model (CRM) is used in idealized settings to study the interaction between tropical convection and the large scale dynamics. The model domain is doubly periodic and the large-scale circulation is parameterized using the Weak Temperature Gradient (WTG) Approximation and Damped Gravity Wave (DGW) methods. The model simulations fall into two main categories: simulations with a prescribed radiative cooling profile, and others in which radiative cooling profile interacts with clouds and water vapor. For experiments with a prescribed radiative cooling profile, radiative heating is taken constant in the vertical in the troposphere. First, the effect of turbulent surface fluxes and radiative cooling on tropical deep convection is studied. In the precipitating equilibria, an increment in surface fluxes produces a greater increase in precipitation than an equal increment in column-integrated radiative heating. The gross moist stability remains close to constant over a wide range of forcings. With dry initial conditions, the system exhibits hysteresis, and maintains a dry state with for a wide range of net energy inputs to the atmospheric column under WTG. However, for the same forcings the system admits a rainy state when initialized with moist conditions, and thus multiple equilibria exist under WTG. When the net forcing is increased enough that simulations, which begin dry, eventually develop precipitation. DGW, on the other hand, does not have the tendency to develop multiple equilibria under the same conditions. The effect of vertical wind shear on tropical deep convection is also studied. The strength and depth of the shear layer are varied as control parameters. Surface fluxes are prescribed. For weak wind shear, time-averaged rainfall decreases with shear and convection remains disorganized. For larger wind shear, rainfall increases with shear, as convection becomes organized into linear mesoscale systems. This non-monotonic dependence of rainfall on shear is observed when the imposed surface fluxes are moderate. For larger surface fluxes, convection in the unsheared basic state is already strongly organized, but increasing wind shear still leads to increasing rainfall. In addition to surface rainfall, the impacts of shear on the parameterized large-scale vertical velocity, convective mass fluxes, cloud fraction, and momentum transport are also discussed. For experiments with interactive radiative cooling profile, the effect of cloud-radiation interaction on cumulus ensemble is examined in sheared and unsheared environments with both fixed and interactive sea surface temperature (SST). For fixed SST, interactive radiation, when compared to simulations in which radiative profile has the same magnitude and vertical shape but does not interact with clouds or water vapor, is found to suppress mean precipitation by inducing strong descent in the lower troposphere, increasing the gross moist stability. For interactive SST, using a slab ocean mixed layer, there exists a shear strength above which the system becomes unstable and develops oscillatory behavior. Oscillations have periods of wet precipitating states followed by periods of dry non-precipitating states. The frequencies of oscillations are intraseasonal to subseasonal, depending on the mixed layer depth. Finally, the model is coupled to a land surface model with fully interactive radiation and surface fluxes to study the diurnal and seasonal radiation and water cycles in the Amazon basin. The model successfully captures the afternoon precipitation and cloud cover peak and the greater latent heat flux in the dry season for the first time; two major biases in GCMs with implications for correct estimates of evaporation and gross primary production in the Amazon. One of the key findings is that the fog layer near the surface in the west season is crucial for determining the surface energy budget and precipitation. This suggests that features on the diurnal time scale can significantly impact climate on the seasonal time scale.

Binding free energy and counterion release for adsorption of the antimicrobial peptide lactoferricin B on a POPG membrane

NASA Astrophysics Data System (ADS)

Tolokh, Igor S.; Vivcharuk, Victor; Tomberli, Bruno; Gray, C. G.

2009-09-01

Molecular dynamics (MD) simulations are used to study the interaction of an anionic palmitoyl-oleoyl-phosphatidylglycerol (POPG) bilayer with the cationic antimicrobial peptide bovine lactoferricin (LFCinB) in a 100 mM NaCl solution at 310 K. The interaction of LFCinB with a POPG bilayer is employed as a model system for studying the details of membrane adsorption selectivity of cationic antimicrobial peptides. Seventy eight 4 ns MD production run trajectories of the equilibrated system, with six restrained orientations of LFCinB at 13 different separations from the POPG membrane, are generated to determine the free energy profile for the peptide as a function of the distance between LFCinB and the membrane surface. To calculate the profile for this relatively large system, a variant of constrained MD and thermodynamic integration is used. A simplified method for relating the free energy profile to the LFCinB-POPG membrane binding constant is employed to predict a free energy of adsorption of -5.4±1.3kcal/mol and a corresponding maximum adsorption binding force of about 58 pN. We analyze the results using Poisson-Boltzmann theory. We find the peptide-membrane attraction to be dominated by the entropy increase due to the release of counterions and polarized water from the region between the charged membrane and peptide, as the two approach each other. We contrast these results with those found earlier for adsorption of LFCinB on the mammalianlike palmitoyl-oleoyl-phosphatidylcholine membrane.

Dissociation free-energy profiles of specific and nonspecific DNA-protein complexes.

PubMed

Yonetani, Yoshiteru; Kono, Hidetoshi

2013-06-27

DNA-binding proteins recognize DNA sequences with at least two different binding modes: specific and nonspecific. Experimental structures of such complexes provide us a static view of the bindings. However, it is difficult to reveal further mechanisms of their target-site search and recognition only from static information because the transition process between the bound and unbound states is not clarified by static information. What is the difference between specific and nonspecific bindings? Here we performed adaptive biasing force molecular dynamics simulations with the specific and nonspecific structures of DNA-Lac repressor complexes to investigate the dissociation process. The resultant free-energy profiles showed that the specific complex has a sharp, deep well consistent with tight binding, whereas the nonspecific complex has a broad, shallow well consistent with loose binding. The difference in the well depth, ~5 kcal/mol, was in fair agreement with the experimentally obtained value and was found to mainly come from the protein conformational difference, particularly in the C-terminal tail. Also, the free-energy profiles were found to be correlated with changes in the number of protein-DNA contacts and that of surface water molecules. The derived protein spatial distributions around the DNA indicate that any large dissociation occurs rarely, regardless of the specific and nonspecific sites. Comparison of the free-energy barrier for sliding [~8.7 kcal/mol; Furini J. Phys. Chem. B 2010, 114, 2238] and that for dissociation (at least ~16 kcal/mol) calculated in this study suggests that sliding is much preferred to dissociation.

Directed-energy process technology efforts

NASA Technical Reports Server (NTRS)

Alexander, P.

1985-01-01

A summary of directed-energy process technology for solar cells was presented. This technology is defined as directing energy or mass to specific areas on solar cells to produce a desired effect in contrast to exposing a cell to a thermal or mass flow environment. Some of these second generation processing techniques are: ion implantation; microwave-enhanced chemical vapor deposition; rapid thermal processing; and the use of lasers for cutting, assisting in metallization, assisting in deposition, and drive-in of liquid dopants. Advantages of directed energy techniques are: surface heating resulting in the bulk of the cell material being cooler and unchanged; better process control yields; better junction profiles, junction depths, and metal sintering; lower energy consumption during processing and smaller factory space requirements. These advantages should result in higher-efficiency cells at lower costs. The results of the numerous contracted efforts were presented as well as the application potentials of these new technologies.

Equilibrium shape of 4He crystal under zero gravity below 200 mK

PubMed Central

Takahashi, Takuya; Ohuchi, Haruka; Nomura, Ryuji; Okuda, Yuichi

2015-01-01

Equilibrium crystal shape is the lowest energy crystal shape that is hardly realized in ordinary crystals because of their slow relaxation. 4He quantum crystals in a superfluid have been expected as unique exceptions that grow extremely fast at very low temperatures. However, on the ground, gravity considerably deforms the crystals and conceals the equilibrium crystal shape, and thus, gravity-free environment is needed to observe the equilibrium shape of 4He. We report the relaxation processes of macroscopic 4He crystals in a superfluid below 200 mK under zero gravity using a parabolic flight of a jet plane. When gravity was removed from a gravity-flattened 4He crystal, the crystal rapidly transformed into a shape with flat surfaces. Although the relaxation processes were highly dependent on the initial condition, the crystals relaxed to a nearly homothetic shape in the end, indicating that they were truly in an equilibrium shape minimizing the interfacial free energy. Thanks to the equilibrium shape, we were able to determine the Wulff’s origin and the size of the c-facet together with the vicinal surface profile next to the c-facet. The c-facet size was extremely small in the quantum crystals, and the facet-like flat surfaces were found to be the vicinal surfaces. At the same time, the interfacial free energy of the a-facet and s-facet was also obtained. PMID:26601315

Equilibrium shape of (4)He crystal under zero gravity below 200 mK.

PubMed

Takahashi, Takuya; Ohuchi, Haruka; Nomura, Ryuji; Okuda, Yuichi

2015-10-01

Equilibrium crystal shape is the lowest energy crystal shape that is hardly realized in ordinary crystals because of their slow relaxation. (4)He quantum crystals in a superfluid have been expected as unique exceptions that grow extremely fast at very low temperatures. However, on the ground, gravity considerably deforms the crystals and conceals the equilibrium crystal shape, and thus, gravity-free environment is needed to observe the equilibrium shape of (4)He. We report the relaxation processes of macroscopic (4)He crystals in a superfluid below 200 mK under zero gravity using a parabolic flight of a jet plane. When gravity was removed from a gravity-flattened (4)He crystal, the crystal rapidly transformed into a shape with flat surfaces. Although the relaxation processes were highly dependent on the initial condition, the crystals relaxed to a nearly homothetic shape in the end, indicating that they were truly in an equilibrium shape minimizing the interfacial free energy. Thanks to the equilibrium shape, we were able to determine the Wulff's origin and the size of the c-facet together with the vicinal surface profile next to the c-facet. The c-facet size was extremely small in the quantum crystals, and the facet-like flat surfaces were found to be the vicinal surfaces. At the same time, the interfacial free energy of the a-facet and s-facet was also obtained.

Cavity formation and surface modeling of laser milling process under a thin-flowing water layer

NASA Astrophysics Data System (ADS)

Tangwarodomnukun, Viboon

2016-11-01

Laser milling process normally involves a number of laser scans over a workpiece to selectively remove the material and then to form cavities with shape and dimensions required. However, this process adversely causes a heat accumulation in work material, which can in turn damage the laser-milled area and vicinity in terms of recast deposition and change of material properties. Laser milling process performing in a thin-flowing water layer is a promising method that can overcome such damage. With the use of this technique, water can flush away the cut debris and at the same time cool the workpiece during the ablation. To understand the potential of this technique for milling application, the effects of process parameters on cavity dimensions and surface roughness were experimentally examined in this study. Titanium sheet was used as a workpiece to be milled by a nanosecond pulse laser under different water flow velocities. A smooth and uniform cut feature can be obtained when the metal was ablated under the high laser pulse frequency and high water flow velocity. Furthermore, a surface model based on the energy balance was developed in this study to predict the cavity profile and surface roughness. By comparing to the experiments, the predicted profiles had a good agreement with the measured ones.

Lake Energy Budget and Temperature Profiles Under Future Greenhouse Gas Scenarios

NASA Astrophysics Data System (ADS)

Lofgren, B. M.; Xiao, C.

2017-12-01

Future climates under higher concentrations of greenhouse gases are expected to feature higher air and water temperatures, and shifts in surface heat fluxes. We investigate in greater detail the evolution of this in terms of the annual cycle of lake temperature profiles, stratification, and ice formation. Other work has found that, although shallower water promotes more rapid changes in surface water temperature within a season, change in surface water temperature across decades is more prominent in locations with greater water depth. Our simulations using the Weather Research and Forecasting (WRF) model and its lake module, WRF-Lake, show a trend toward longer periods of summer stratification, both through earlier onset in the spring and later decay of stratification in the fall. They also show a general increase in temperature throughout the water column, but most pronounced near the surface during the summer. Likewise, ice duration is much shorter and more restricted to shallow embayments. High latent and sensible heat flux during the fall and winter are less intense but longer lasting under the future scenario. Sources of uncertainty are cumulative—actual future greenhouse gas concentrations, global sensitivity of climate change, cloud feedbacks, the combined formulation of the regional climate model (WRF) and its global driving model, and more.

Layered surface structure of gas-atomized high Nb-containing TiAl powder and its impact on laser energy absorption for selective laser melting

NASA Astrophysics Data System (ADS)

Zhou, Y. H.; Lin, S. F.; Hou, Y. H.; Wang, D. W.; Zhou, P.; Han, P. L.; Li, Y. L.; Yan, M.

2018-05-01

Ti45Al8Nb alloy (in at.%) is designed to be an important high-temperature material. However, its fabrication through laser-based additive manufacturing is difficult to achieve. We present here that a good understanding of the surface structure of raw material (i.e. Ti45Al8Nb powder) is important for optimizing its process by selective laser melting (SLM). Detailed X-ray photoelectron spectroscopy (XPS) depth profiling and transmission electron microscopy (TEM) analyses were conducted to determine the surface structure of Ti45Al8Nb powder. An envelope structure (∼54.0 nm in thickness) was revealed for the powder, consisting of TiO2 + Nb2O5 (as the outer surface layer)/Al2O3 + Nb2O5 (as the intermediate layer)/Al2O3 (as the inner surface layer)/Ti45Al8Nb (as the matrix). During SLM, this layered surface structure interacted with the incident laser beam and improved the laser absorptivity of Ti45Al8Nb powder by ∼32.21%. SLM experiments demonstrate that the relative density of the as-printed parts can be realized to a high degree (∼98.70%), which confirms good laser energy absorption. Such layered surface structure with appropriate phase constitution is essential for promoting SLM of the Ti45Al8Nb alloy.

Surface Condensation of CO2 onto Kaolinite

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

Schaef, Herbert T.; Glezakou, Vassiliki Alexandra; Owen, Antionette T.

2014-02-11

The fundamental adsorption behavior of gaseous and supercritical carbon dioxide (CO2) onto poorly crystalline kaolinite (KGa-2) at conditions relevant to geologic sequestration has been investigated using a quartz crystal microbalance (QCM) and density functional theory (DFT) methods. The QCM data indicated linear adsorption of CO2 (0-0.3 mmol CO2/g KGa-2) onto the kaolinite surface up through the gaseous state (0.186 g/cm3). However in the supercritical region, CO2 adsorption increases dramatically, reaching a peak (0.9-1.0 mmol CO2/g KGa-2) near 0.43 g/cm3, before declining rapidly to surface adsorption values equivalent or below gaseous CO2. This adsorption profile was not observed with He ormore » N2. Comparative density functional studies of CO2 interactions with kaolinite surface models rule out CO2 intercalation and confirm that surface adsorption is favored up to approximately 0.35 g/cm3 of CO2, showing distorted T-shaped CO2-CO2 clustering, typical of supercritical CO2 aggregation over the surface as the density increases. Beyond this point, the adsorption energy gain for any additional CO2 becomes less than the CO2 interaction energy (~0.2 eV) in the supercritical medium resulting in overall desorption of CO2 from the kaolinite surface.« less

Sensitivity of WallDYN material migration modeling to uncertainties in mixed-material surface binding energies

DOE PAGES

Nichols, J. H.; Jaworski, M. A.; Schmid, K.

2017-03-09

The WallDYN package has recently been applied to a number of tokamaks to self-consistently model the evolution of mixed-material plasma facing surfaces. A key component of the WallDYN model is the concentration-dependent surface sputtering rate, calculated using SDTRIM.SP. This modeled sputtering rate is strongly influenced by the surface binding energies (SBEs) of the constituent materials, which are well known for pure elements but often are poorly constrained for mixed-materials. This work examines the sensitivity of WallDYN surface evolution calculations to different models for mixed-material SBEs, focusing on the carbon/lithium/oxygen/deuterium system present in NSTX. A realistic plasma background is reconstructed frommore » a high density, H-mode NSTX discharge, featuring an attached outer strike point with local density and temperature of 4 × 10 20 m -3 and 4 eV, respectively. It is found that various mixed-material SBE models lead to significant qualitative and quantitative changes in the surface evolution profile at the outer divertor, with the highest leverage parameter being the C-Li binding model. Uncertainties of order 50%, appearing on time scales relevant to tokamak experiments, highlight the importance of choosing an appropriate mixed-material sputtering representation when modeling the surface evolution of plasma facing components. Lastly, these results are generalized to other fusion-relevant materials with different ranges of SBEs.« less

Sensitivity of WallDYN material migration modeling to uncertainties in mixed-material surface binding energies

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

Nichols, J. H.; Jaworski, M. A.; Schmid, K.

The WallDYN package has recently been applied to a number of tokamaks to self-consistently model the evolution of mixed-material plasma facing surfaces. A key component of the WallDYN model is the concentration-dependent surface sputtering rate, calculated using SDTRIM.SP. This modeled sputtering rate is strongly influenced by the surface binding energies (SBEs) of the constituent materials, which are well known for pure elements but often are poorly constrained for mixed-materials. This work examines the sensitivity of WallDYN surface evolution calculations to different models for mixed-material SBEs, focusing on the carbon/lithium/oxygen/deuterium system present in NSTX. A realistic plasma background is reconstructed frommore » a high density, H-mode NSTX discharge, featuring an attached outer strike point with local density and temperature of 4 × 10 20 m -3 and 4 eV, respectively. It is found that various mixed-material SBE models lead to significant qualitative and quantitative changes in the surface evolution profile at the outer divertor, with the highest leverage parameter being the C-Li binding model. Uncertainties of order 50%, appearing on time scales relevant to tokamak experiments, highlight the importance of choosing an appropriate mixed-material sputtering representation when modeling the surface evolution of plasma facing components. Lastly, these results are generalized to other fusion-relevant materials with different ranges of SBEs.« less

Surface Modification of ICF Target Capsules by Pulsed Laser Ablation

DOE PAGES

Carlson, Lane C.; Johnson, Michael A.; Bunn, Thomas L.

2016-06-30

Topographical modifications of spherical surfaces are imprinted on National Ignition Facility (NIF) target capsules by extending the capabilities of a recently developed full surface (4π) laser ablation and mapping apparatus. The laser ablation method combines the precision, energy density and long reach of a focused laser beam to pre-impose sinusoidal modulations on the outside surface of High Density Carbon (HDC) capsules and the inside surface of Glow Discharge Polymer (GDP) capsules. Sinusoidal modulations described in this paper have sub-micron to 10’s of microns vertical scale and wavelengths as small as 30 μm and as large as 200 μm. The modulatedmore » patterns are created by rastering a focused laser fired at discrete capsule surface locations for a specified number of pulses. The computer program developed to create these raster patterns uses inputs such as laser beam intensity profile, the material removal function, the starting surface figure and the desired surface figure. The patterns are optimized to minimize surface roughness. Lastly, in this paper, simulated surfaces are compared with actual ablated surfaces measured using confocal microscopy.« less

An experimental investigation of pulsed laser-assisted machining of AISI 52100 steel

NASA Astrophysics Data System (ADS)

Panjehpour, Afshin; Soleymani Yazdi, Mohammad R.; Shoja-Razavi, Reza

2014-11-01

Grinding and hard turning are widely used for machining of hardened bearing steel parts. Laser-assisted machining (LAM) has emerged as an efficient alternative to grinding and hard turning for hardened steel parts. In most cases, continuous-wave lasers were used as a heat source to cause localized heating prior to material removal by a cutting tool. In this study, an experimental investigation of pulsed laser-assisted machining of AISI 52100 bearing steel was conducted. The effects of process parameters (i.e., laser mean power, pulse frequency, pulse energy, cutting speed and feed rate) on state variables (i.e., material removal temperature, specific cutting energy, surface roughness, microstructure, tool wear and chip formation) were investigated. At laser mean power of 425 W with frequency of 120 Hz and cutting speed of 70 m/min, the benefit of LAM was shown by 25% decrease in specific cutting energy and 18% improvement in surface roughness, as compared to those of the conventional machining. It was shown that at constant laser power, the increase of laser pulse energy causes the rapid increase in tool wear rate. Pulsed laser allowed efficient control of surface temperature and heat penetration in material removal region. Examination of the machined subsurface microstructure and microhardness profiles showed no change under LAM and conventional machining. Continuous chips with more uniform plastic deformation were produced in LAM.

Magnetorheological Finishing for Imprinting Continuous Phase Plate Structure onto Optical Surfaces

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

Menapace, J A; Dixit, S N; Genin, F Y

2004-01-05

Magnetorheological finishing (MRF) techniques have been developed to manufacture continuous phase plates (CPP's) and custom phase corrective structures on polished fused silica surfaces. These phase structures are important for laser applications requiring precise manipulation and control of beam-shape, energy distribution, and wavefront profile. The MRF's unique deterministic-sub-aperture polishing characteristics make it possible to imprint complex topographical information onto optical surfaces at spatial scale-lengths approaching 1 mm. In this study, we present the results of experiments and model calculations that explore imprinting two-dimensional sinusoidal structures. Results show how the MRF removal function impacts and limits imprint fidelity and what must bemore » done to arrive at a high quality surface. We also present several examples of this imprinting technology for fabrication of phase correction plates and CPPs for use at high fluences.« less

Flame front propagation in a channel with porous walls

NASA Astrophysics Data System (ADS)

Golovastov, S. V.; Bivol, G. Yu

2016-11-01

Propagation of the detonation front in hydrogen-air mixture was investigated in rectangular cross-section channels with sound-absorbing boundaries. The front of luminescence was detected in a channel with acoustically absorbing walls as opposed to a channel with solid walls. Flame dynamics was recorded using a high-speed camera. The flame was observed to have a V-shaped profile in the acoustically absorbing section. The possible reason for the formation of the V-shaped flame front is friction under the surface due to open pores. In these shear flows, the kinetic energy of the flow on the surface can be easily converted into heat. A relatively small disturbance may eventually lead to significant local stretching of the flame front surface. Trajectories of the flame front along the axis and the boundary are presented for solid and porous surfaces.

High-Temperature Surface-Acoustic-Wave Transducer

NASA Technical Reports Server (NTRS)

Zhao, Xiaoliang; Tittmann, Bernhard R.

2010-01-01

Aircraft-engine rotating equipment usually operates at high temperature and stress. Non-invasive inspection of microcracks in those components poses a challenge for the non-destructive evaluation community. A low-profile ultrasonic guided wave sensor can detect cracks in situ. The key feature of the sensor is that it should withstand high temperatures and excite strong surface wave energy to inspect surface/subsurface cracks. As far as the innovators know at the time of this reporting, there is no existing sensor that is mounted to the rotor disks for crack inspection; the most often used technology includes fluorescent penetrant inspection or eddy-current probes for disassembled part inspection. An efficient, high-temperature, low-profile surface acoustic wave transducer design has been identified and tested for nondestructive evaluation of structures or materials. The development is a Sol-Gel bismuth titanate-based surface-acoustic-wave (SAW) sensor that can generate efficient surface acoustic waves for crack inspection. The produced sensor is very thin (submillimeter), and can generate surface waves up to 540 C. Finite element analysis of the SAW transducer design was performed to predict the sensor behavior, and experimental studies confirmed the results. One major uniqueness of the Sol-Gel bismuth titanate SAW sensor is that it is easy to implement to structures of various shapes. With a spray coating process, the sensor can be applied to surfaces of large curvatures. Second, the sensor is very thin (as a coating) and has very minimal effect on airflow or rotating equipment imbalance. Third, it can withstand temperatures up to 530 C, which is very useful for engine applications where high temperature is an issue.

Mass composition results from the Pierre Auger Observatory

NASA Astrophysics Data System (ADS)

Riggi, Simone; Pierre Auger Collaboration

2011-03-01

The present paper reports the recent composition results obtained by the Pierre Auger Observatory using both hybrid and surface detector data. The reconstruction of the shower longitudinal profile and depth of maximum with the fluorescence detector is described. The measured average depth of maximum and its fluctuations as function of the primary energy is presented. The sensitivity of rise time parameters measured with the ground stations and the obtained composition results are discussed.

CONSERVB: A numerical method to compute soil water content and temperature profiles under a bare surface

NASA Technical Reports Server (NTRS)

Vanbavel, C. H. M.; Lascano, R. J.

1982-01-01

A comprehensive, yet fairly simple model of water disposition in a bare soil profile under the sequential impact of rain storms and other atmospheric influences, as they occur from hour to hour is presented. This model is intended mostly to support field studies of soil moisture dynamics by our current team, to serve as a background for the microwave measurements, and, eventually, to serve as a point of departure for soil moisture predictions for estimates based in part upon airborne measurements. The main distinction of the current model is that it accounts not only for the moisture flow in the soil-atmosphere system, but also for the energy flow and, hence, calculates system temperatures. Also, the model is of a dynamic nature, capable of supporting any required degree of resolution in time and space. Much critical testing of the sample is needed before the complexities of the hydrology of a vegetated surface can be related meaningfully to microwave observations.

Evaporation of LOX under supercritical and subcritical conditions

NASA Technical Reports Server (NTRS)

Yang, A. S.; Hsieh, W. H.; Kuo, K. K.; Brown, J. J.

1993-01-01

The evaporation of LOX under supercritical and subcritical conditions was studied experimentally and theoretically. In experiments, the evaporation rate and surface temperature were measured for LOX strand vaporizing in helium environments at pressures ranging from 5 to 68 atmospheres. Gas sampling and chromatography analysis were also employed to profile the gas composition above the LOX surface for the purpose of model validation. A comprehensive theoretical model was formulated and solved numerically to simulate the evaporation process of LOX at high pressures. The model was based on the conservation equations of mass, momentum, energy, and species concentrations for a multicomponent system, with consideration of gravitational body force, solubility of ambient gases in liquid, and variable thermophysical properties. Good agreement between predictions and measured oxygen mole fraction profiles was obtained. The effect of pressure on the distribution of the Lewis number, as well as the effect of variable diffusion coefficient, were further examined to elucidate the high-pressure transport behavior exhibited in the LOX vaporization process.

Development of a two-dimensional binning model for N{sub 2}–N relaxation in hypersonic shock conditions

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

Zhu, Tong, E-mail: tongzhu2@illinois.edu; Levin, Deborah A., E-mail: deblevin@illinois.edu; Li, Zheng, E-mail: zul107@psu.edu

2016-08-14

A high fidelity internal energy relaxation model for N{sub 2}–N suitable for use in direct simulation Monte Carlo (DSMC) modeling of chemically reacting flows is proposed. A novel two-dimensional binning approach with variable bin energy resolutions in the rotational and vibrational modes is developed for treating the internal mode of N{sub 2}. Both bin-to-bin and state-specific relaxation cross sections are obtained using the molecular dynamics/quasi-classical trajectory (MD/QCT) method with two potential energy surfaces as well as the state-specific database of Jaffe et al. The MD/QCT simulations of inelastic energy exchange between N{sub 2} and N show that there is amore » strong forward-preferential scattering behavior at high collision velocities. The 99 bin model is used in homogeneous DSMC relaxation simulations and is found to be able to recover the state-specific master equation results of Panesi et al. when the Jaffe state-specific cross sections are used. Rotational relaxation energy profiles and relaxation times obtained using the ReaxFF and Jaffe potential energy surfaces (PESs) are in general agreement but there are larger differences between the vibrational relaxation times. These differences become smaller as the translational temperature increases because the difference in the PES energy barrier becomes less important.« less

Quantitatively identifying the roles of interfacial water and solid surface in governing peptide adsorption.

PubMed

Xu, Zhijun; Yang, Xiao; Wei, Qichao; Zhao, Weilong; Cui, Beiliang; Yang, Xiaoning; Sahai, Nita

2018-06-11

Understanding the molecular mechanism of protein adsorption on solids is critical to their applications in materials synthesis and tissue engineering. Though the water phase at the surface/water interface has been recognized as three types: free water in the bulk region, intermediate water phase and surface-bound water layers adjacent to the surface, the roles of the water and surface in determining the protein adsorption are not clearly identified, particularly at the quantitative level. Herein, we provide a methodology involving the combination of microsecond strengthen sampling simulation and force integration to quantitatively characterize the water-induced contribution and the peptide-surface interactions into the adsorption free energy. Using hydroxyapatite and graphene surfaces as examples, we demonstrate how the distinct interfacial features dominate the delicate force balance between these two thermodynamics parameters, leading to surface preference/resistance to peptide adsorption. Specifically, the water layer provides sustained repelling force against peptide adsorption, as indicated by a monotonic increase in the water-induced free energy profile, whereas the contribution to the free energy from the surface effect is thermodynamically favorable, thus acting as the dominant driving force for peptide adsorptions. More importantly, the revealed adsorption mechanism is critically dictated by the distribution of water phase at the solid/water interface, which plays a crucial role in establishing the force balance between the interactions of the peptide with the water layer and the surface. For the HAP surface, the charged peptide exhibits strong binding affinity to the surface, which is ascribed to the controlling contribution of peptide-surface interaction in the intermediate water phase and the surface-bound water layers are observed as the origin of bioresistance of solid surfaces towards the adsorption of charge-neutral peptides. The preferred peptide adsorption on the graphene, however, is dominated by the surface-induced component at the water layers adjacent to the surface. Our results further elucidate that the intermediate water phase significantly shortens the effective range of the surface dispersion force to guide the diffusion of the peptide to the interface, in sharp contrast to the observation in interfacial systems involving the strong water-surface interaction.

NuSTAR Observations of the Magnetar 1E 2259+586

NASA Technical Reports Server (NTRS)

Vogel, Julia K.; Hascoet, Romain; Kaspi, Victoria M.; An, Hongjun; Archibald, Robert; Beloborodov, Andrei M.; Boggs, Steven E.; Christensen, Finn E.; Craig, William W.; Gotthelf, Eric V.;

Thermal shock tests with beryllium coupons in the electron beam facility JUDITH

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

Roedig, M.; Duwe, R.; Schuster, J.L.A.

1995-09-01

Several grades of American and Russian beryllium have been tested in high heat flux tests by means of an electron beam facility. For safety reasons, major modifications of the facility had to be fulfilled in advance to the tests. The influence of energy densities has been investigated in the range between 1 and 7 MJ/m{sup 2}. In addition the influence of an increasing number of shots at constant energy density has been studied. For all samples, surface profiles have been measured before and after the experiments. Additional information has been gained from scanning electron microscopy, and from metallography.

Elastomeric member and method of manufacture therefor

DOEpatents

Hoppie, L.O.

1985-12-10

An energy storage device is disclosed consisting of a stretched elongated elastomeric member disposed within a tubular housing, which elastomeric member is adapted to be torsionally stressed to store energy. The elastomeric member is configured in the relaxed state with a uniform diameter body section, and transition end sections, attached to rigid end piece assemblies of a lesser diameter. The profile and deflection characteristic of the transition sections are such that upon stretching of the elastomeric member, a substantially uniform diameter assembly results, to minimize the required volume of the surrounding housing. Each of the transition sections are received within and bonded to a woven wire mesh sleeve having helical windings at a particular helix angle to control the deflection of the transition section. Each sleeve also contracts with the contraction of the associated transition section to maintain the bond therebetween. During manufacture, the sleeves are forced against a forming surface and bonded to the associated transition section to provide the correct profile and helix angle. 12 figs.

Elastomeric member

DOEpatents

Hoppie, L.O.

1985-07-30

An energy storage device is disclosed consisting of a stretched elongated elastomeric member disposed within a tubular housing, which elastomeric member is adapted to be torsionally stressed to store energy. The elastomeric member is configured in the relaxed state with a uniform diameter body section, and transition end sections, attached to rigid end piece assemblies of a lesser diameter. The profile and deflection characteristic of the transition sections are such that upon stretching of the elastomeric member, a substantially uniform diameter assembly results, to minimize the required volume of the surrounding housing. Each of the transition sections are received within and bonded to a woven wire mesh sleeve having helical windings at a particular helix angle to control the deflection of the transition section. Each sleeve also contracts with the contraction of the associated transition section to maintain the bond there between. During manufacture, the sleeves are forced against a forming surface and bonded to the associated transition section to provide the correct profile and helix angle. 12 figs.

Spent nuclear fuel/water interface behavior: Alpha dose rate profile determination for model surfaces and microcracks by using Monte-Carlo methods

NASA Astrophysics Data System (ADS)

Tribet, M.; Mougnaud, S.; Jégou, C.

2017-05-01

This work aims to better understand the nature and evolution of energy deposits at the UO2/water reactional interface subjected to alpha irradiation, through an original approach based on Monte-Carlo-type simulations, using the MCNPX code. Such an approach has the advantage of describing the energy deposit profiles on both sides of the interface (UO2 and water). The calculations have been performed on simple geometries, with data from an irradiated UOX fuel (burnup of 47 GWd.tHM-1 and 15 years of alpha decay). The influence of geometric parameters such as the diameter and the calculation steps at the reactional interface are discussed, and the exponential laws to be used in practice are suggested. The case of cracks with various different apertures (from 5 to 35 μm) has also been examined and these calculations have also enabled new information on the mean range of radiolytic species in cracks, and thus on the local chemistry.

Rayleigh-wave dispersive energy imaging using a high-resolution linear radon transform

USGS Publications Warehouse

Luo, Y.; Xia, J.; Miller, R.D.; Xu, Y.; Liu, J.; Liu, Q.

2008-01-01

Multichannel Analysis of Surface Waves (MASW) analysis is an efficient tool to obtain the vertical shear-wave profile. One of the key steps in the MASW method is to generate an image of dispersive energy in the frequency-velocity domain, so dispersion curves can be determined by picking peaks of dispersion energy. In this paper, we propose to image Rayleigh-wave dispersive energy by high-resolution linear Radon transform (LRT). The shot gather is first transformed along the time direction to the frequency domain and then the Rayleigh-wave dispersive energy can be imaged by high-resolution LRT using a weighted preconditioned conjugate gradient algorithm. Synthetic data with a set of linear events are presented to show the process of generating dispersive energy. Results of synthetic and real-world examples demonstrate that, compared with the slant stacking algorithm, high-resolution LRT can improve the resolution of images of dispersion energy by more than 50%. ?? Birkhaueser 2008.

Determination of Principal Curvatures and Contact Ellipse for Profile Crowned Helical Gears

NASA Technical Reports Server (NTRS)

Feng, P.-H.; Litvin, F. L.; Townsend, D. P.; Handschuh, R. F.

1999-01-01

Helical gears with localized bearing contact of tooth surfaces achieved by profile crowning of tooth surfaces are considered. Profile crowning is provided by application of two imaginary rack-cutters with mismatched surfaces. The goal is to determine the dimensions and orientation of the instantaneous contact ellipse that requires the determination of principle curvatures of pinion-gear tooth surfaces. A simplified solution to this problem is proposed based on the approach development for correlation of principal curvatures and directions of generating and generated tooth surfaces. The obtained equations are applied for profile crowning where the normal profiles of the rack-cutters are either a circular arc or a straight line.

Global minimum profile error (GMPE) - a least-squares-based approach for extracting macroscopic rate coefficients for complex gas-phase chemical reactions.

PubMed

Duong, Minh V; Nguyen, Hieu T; Mai, Tam V-T; Huynh, Lam K

2018-01-03

Master equation/Rice-Ramsperger-Kassel-Marcus (ME/RRKM) has shown to be a powerful framework for modeling kinetic and dynamic behaviors of a complex gas-phase chemical system on a complicated multiple-species and multiple-channel potential energy surface (PES) for a wide range of temperatures and pressures. Derived from the ME time-resolved species profiles, the macroscopic or phenomenological rate coefficients are essential for many reaction engineering applications including those in combustion and atmospheric chemistry. Therefore, in this study, a least-squares-based approach named Global Minimum Profile Error (GMPE) was proposed and implemented in the MultiSpecies-MultiChannel (MSMC) code (Int. J. Chem. Kinet., 2015, 47, 564) to extract macroscopic rate coefficients for such a complicated system. The capability and limitations of the new approach were discussed in several well-defined test cases.

Interaction of a sodium ion with the water liquid-vapor interface

NASA Technical Reports Server (NTRS)

Wilson, M. A.; Pohorille, A.; Pratt, L. R.; MacElroy, R. D. (Principal Investigator)

1989-01-01

Molecular dynamics results are presented for the density profile of a sodium ion near the water liquid-vapor interface at 320 K. These results are compared with the predictions of a simple dielectric model for the interaction of a monovalent ion with this interface. The interfacial region described by the model profile is too narrow and the profile decreases too abruptly near the solution interface. Thus, the simple model does not provide a satisfactory description of the molecular dynamics results for ion positions within two molecular diameters from the solution interface where appreciable ion concentrations are observed. These results suggest that surfaces associated with dielectric models of ionic processes at aqueous solution interfaces should be located at least two molecular diameters inside the liquid phase. A free energy expense of about 2 kcal/mol is required to move the ion within two molecular layers of the free water liquid-vapor interface.

Quantitative Analysis of Etching Rate Profiles for 11B+-Implanted Si3N4 Film

NASA Astrophysics Data System (ADS)

Nakata, Jyoji; Kajiyama, Kenji

1983-01-01

Etching rate enhancement for 11B+-implanted Si3N4 film was investigated both experimentally and theoretically. The etching solution was concentrated H3PO4 at ˜165°C Film thicknesses were precisely measured by ellipsometry. Enhancement resulted from Si-N bond breaking. This was confirmed by a decrease of infrared absorption at a 12.0 μm wavelength for Si-N bond vibration. Main and additional peaks were observed in the etching rate profile. The former was due to nuclear damage and was well represented by the calculated etching rate profile deduced from the nuclear deposited energy density distribution. The latter existed in the surface region only when the ion projected range was shorter than the film thickness. This peak was possibly caused by charge accumulation in the insulating Si3N4 film during 11B+ implantation.

Energy filtering transmission electron microscopy immunocytochemistry and antigen retrieval of surface layer proteins from Tannerella forsythensis using microwave or autoclave heating with citraconic anhydride

PubMed Central

2012-01-01

Tannerella forsythensis (Bacteroides forsythus), an anaerobic Gram-negative species of bacteria that plays a role in the progression of periodontal disease, has a unique bacterial protein profile. It is characterized by two unique protein bands with molecular weights of more than 200 kDa. It also is known to have a typical surface layer (S-layer) consisting of regularly arrayed subunits outside the outer membrane. We examined the relationship between high molecular weight proteins and the S-layer using electron microscopic immunolabeling with chemical fixation and an antigen retrieval procedure consisting of heating in a microwave oven or autoclave with citraconic anhydride. Immunogold particles were localized clearly at the outermost cell surface. We also used energy-filtering transmission electron microscopy (EFTEM) to visualize 3, 3′-diaminobenzidine tetrahydrochloride (DAB) reaction products after microwave antigen retrieval with 1% citraconic anhydride. The three-window method for electron spectroscopic images (ESI) of nitrogen by the EFTEM reflected the presence of moieties demonstrated by the DAB reaction with horseradish peroxidase (HRP)-conjugated secondary antibodies instead of immunogold particles. The mapping patterns of net nitrogen were restricted to the outermost cell surface. PMID:22984898

Energy filtering transmission electron microscopy immunocytochemistry and antigen retrieval of surface layer proteins from Tannerella forsythensis using microwave or autoclave heating with citraconic anhydride.

PubMed

Moriguchi, K; Mitamura, Y; Iwami, J; Hasegawa, Y; Higuchi, N; Murakami, Y; Maeda, H; Yoshimura, F; Nakamura, H; Ohno, N

2012-11-01

Tannerella forsythensis (Bacteroides forsythus), an anaerobic Gram-negative species of bacteria that plays a role in the progression of periodontal disease, has a unique bacterial protein profile. It is characterized by two unique protein bands with molecular weights of more than 200 kDa. It also is known to have a typical surface layer (S-layer) consisting of regularly arrayed subunits outside the outer membrane. We examined the relationship between high molecular weight proteins and the S-layer using electron microscopic immunolabeling with chemical fixation and an antigen retrieval procedure consisting of heating in a microwave oven or autoclave with citraconic anhydride. Immunogold particles were localized clearly at the outermost cell surface. We also used energy-filtering transmission electron microscopy (EFTEM) to visualize 3, 3'-diaminobenzidine tetrahydrochloride (DAB) reaction products after microwave antigen retrieval with 1% citraconic anhydride. The three-window method for electron spectroscopic images (ESI) of nitrogen by the EFTEM reflected the presence of moieties demonstrated by the DAB reaction with horseradish peroxidase (HRP)-conjugated secondary antibodies instead of immunogold particles. The mapping patterns of net nitrogen were restricted to the outermost cell surface.

Seismic signatures of carbonate caves affected by near-surface absorptions

NASA Astrophysics Data System (ADS)

Rao, Ying; Wang, Yanghua

2015-12-01

The near-surface absorption within a low-velocity zone generally has an exponential attenuation effect on seismic waves. But how does this absorption affect seismic signatures of karstic caves in deep carbonate reservoirs? Seismic simulation and analysis reveals that, although this near-surface absorption attenuates the wave energy of a continuous reflection, it does not alter the basic kinematic shape of bead-string reflections, a special seismic characteristic associated with carbonate caves in the Tarim Basin, China. Therefore, the bead-strings in seismic profiles can be utilized, with a great certainty, for interpreting the existence of caves within the deep carbonate reservoirs and for evaluating their pore spaces. Nevertheless, the difference between the central frequency and the peak frequency is increased along with the increment in the absorption. While the wave energy of bead-string reflections remains strong, due to the interference of seismic multiples generated by big impedance contrast between the infill materials of a cave and the surrounding carbonate rocks, the central frequency is shifted linearly with respect to the near-surface absorption. These two features can be exploited simultaneously, for a stable attenuation analysis of field seismic data.

Plastic strain and grain size effects in the surface roughening of a model aluminum alloy

NASA Astrophysics Data System (ADS)

Moore, Eric Joseph

To address issues surrounding improved automotive fuel economy, an experiment was designed to study the effect of uniaxial plastic tensile deformation on surface roughness and on slip and grain rotation. Electron backscatter diffraction (EBSD) and scanning laser confocal microscopy (SLCM) were used to track grain size, crystallographic texture, and surface topography as a function of incremental true strain for a coarse-grained binary alloy that is a model for AA5xxx series aluminum alloys. One-millimeter thick sheets were heat treated at 425°C to remove previous rolling texture and to grow grains to sizes in the range ˜10-8000 mum. At five different strain levels, 13 sample regions, containing 43 grains, were identified in both EBSD and SLCM micrographs, and crystallographic texture and surface roughness were measured. After heat treatment, a strong cube texture matrix emerged, with bands of generally non-cube grains embedded parallel to the rolling direction (RD). To characterize roughness, height profiles from SLCM micrographs were extracted and a filtered Fourier transform approach was used to separate the profiles into intergranular (long wavelength) and intragranular (short wavelength) signatures. The commonly-used rms roughness parameter (Rq) characterized intragranular results. Two important parameters assess intergranular results in two grain size regimes: surface tilt angle (Deltatheta) and surface height discontinuity (DeltazH) between neighboring grains at a boundary. In general, the magnitude of Rq and Deltatheta increase monotonically with strain and indicate that intergranular roughness is the major contributor to overall surface roughness for true strains up to epsilon = 0.12. Surface height discontinuity DeltazH is defined due to exceptions in surface tilt angle analyses. The range of observed Deltatheta= 1-10° are consistent with the observed 3-12° rotation of individual grains as measured with EBSD. For some grain boundaries with Deltatheta< 4°, the surface height discontinuity DeltazH characterizes the response of adjacent grains in which one or more are large (˜1000-2000 mum), making a 3-12° rotation of the grain highly unlikely. This can be understood by postulating that the energy associated with rotating large grains would exceed the energy to shear along the boundary. Slip and grain boundary shearing are the active mechanisms in these instances.

Estimation of Land Surface Fluxes and Their Uncertainty via Variational Data Assimilation Approach

NASA Astrophysics Data System (ADS)

Abdolghafoorian, A.; Farhadi, L.

2016-12-01

Accurate estimation of land surface heat and moisture fluxes as well as root zone soil moisture is crucial in various hydrological, meteorological, and agricultural applications. "In situ" measurements of these fluxes are costly and cannot be readily scaled to large areas relevant to weather and climate studies. Therefore, there is a need for techniques to make quantitative estimates of heat and moisture fluxes using land surface state variables. In this work, we applied a novel approach based on the variational data assimilation (VDA) methodology to estimate land surface fluxes and soil moisture profile from the land surface states. This study accounts for the strong linkage between terrestrial water and energy cycles by coupling the dual source energy balance equation with the water balance equation through the mass flux of evapotranspiration (ET). Heat diffusion and moisture diffusion into the column of soil are adjoined to the cost function as constraints. This coupling results in more accurate prediction of land surface heat and moisture fluxes and consequently soil moisture at multiple depths with high temporal frequency as required in many hydrological, environmental and agricultural applications. One of the key limitations of VDA technique is its tendency to be ill-posed, meaning that a continuum of possibilities exists for different parameters that produce essentially identical measurement-model misfit errors. On the other hand, the value of heat and moisture flux estimation to decision-making processes is limited if reasonable estimates of the corresponding uncertainty are not provided. In order to address these issues, in this research uncertainty analysis will be performed to estimate the uncertainty of retrieved fluxes and root zone soil moisture. The assimilation algorithm is tested with a series of experiments using a synthetic data set generated by the simultaneous heat and water (SHAW) model. We demonstrate the VDA performance by comparing the (synthetic) true measurements (including profile of soil moisture and temperature, land surface water and heat fluxes, and root water uptake) with VDA estimates. In addition, the feasibility of extending the proposed approach to use remote sensing observations is tested by limiting the number of LST observations and soil moisture observations.

On the appropriate definition of soil profile configuration and initial conditions for land surface-hydrology models in cold regions

NASA Astrophysics Data System (ADS)

Sapriza-Azuri, Gonzalo; Gamazo, Pablo; Razavi, Saman; Wheater, Howard S.

2018-06-01

Arctic and subarctic regions are amongst the most susceptible regions on Earth to global warming and climate change. Understanding and predicting the impact of climate change in these regions require a proper process representation of the interactions between climate, carbon cycle, and hydrology in Earth system models. This study focuses on land surface models (LSMs) that represent the lower boundary condition of general circulation models (GCMs) and regional climate models (RCMs), which simulate climate change evolution at the global and regional scales, respectively. LSMs typically utilize a standard soil configuration with a depth of no more than 4 m, whereas for cold, permafrost regions, field experiments show that attention to deep soil profiles is needed to understand and close the water and energy balances, which are tightly coupled through the phase change. To address this gap, we design and run a series of model experiments with a one-dimensional LSM, called CLASS (Canadian Land Surface Scheme), as embedded in the MESH (Modélisation Environmentale Communautaire - Surface and Hydrology) modelling system, to (1) characterize the effect of soil profile depth under different climate conditions and in the presence of parameter uncertainty; (2) assess the effect of including or excluding the geothermal flux in the LSM at the bottom of the soil column; and (3) develop a methodology for temperature profile initialization in permafrost regions, where the system has an extended memory, by the use of paleo-records and bootstrapping. Our study area is in Norman Wells, Northwest Territories of Canada, where measurements of soil temperature profiles and historical reconstructed climate data are available. Our results demonstrate a dominant role for parameter uncertainty, that is often neglected in LSMs. Considering such high sensitivity to parameter values and dependency on the climate condition, we show that a minimum depth of 20 m is essential to adequately represent the temperature dynamics. We further show that our proposed initialization procedure is effective and robust to uncertainty in paleo-climate reconstructions and that more than 300 years of reconstructed climate time series are needed for proper model initialization.

Variable neutron star free precession in Hercules X-1 from evolution of RXTE X-ray pulse profiles with phase of the 35-d cycle

NASA Astrophysics Data System (ADS)

Postnov, K.; Shakura, N.; Staubert, R.; Kochetkova, A.; Klochkov, D.; Wilms, J.

2013-10-01

Accretion of matter on to the surface of a freely precessing neutron star (NS) with a complex non-dipole magnetic field can explain the change of X-ray pulse profiles of Her X-1 observed by RXTE with the phase of the 35-d cycle. We demonstrate this using all available measurements of X-ray pulse profiles in the 9-13 keV energy range obtained with the RXTE/Proportional Counter Array (PCA). The measured profiles guided the elaboration of a geometrical model and the definition of locations of emitting poles, arcs and spots on the NS surface which satisfactorily reproduce the observed pulse profiles and their dependence on free precession phase. We have found that the observed trend of the times of the 35-d turn-ons on the O-C diagram, which can be approximated by a collection of consecutive linear segments around the mean value, can be described by our model by assuming a variable free precession period, with a fractional period change of about a few per cent. Under this assumption and using our model, we have found that the times of phase zero of the NS free precession (which we identify with the maximum separation of the brightest spot on the NS surface with the NS spin axis) occur about 1.6 d after the mean turn-on times inside each `stable' epoch, producing a linear trend on the O-C diagram with the same slope as the observed times of turn-ons. We propose that the 2.5 per cent changes in the free precession period that occur on time scales of several to tens of 35-d cycles can be related to wandering of the principal inertia axis of the NS body due to variations in the patterns of accretion on to the NS surface. The closeness of periods of the disc precession and the NS free precession can be explained by the presence of a synchronization mechanism in the system, which modulates the dynamical interaction of the gas streams and the accretion disc with the NS free precession period.

Water-mediated interactions between hydrophobic and ionic species in cylindrical nanopores

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

Vaitheeswaran, S.; Reddy, G.; Thirumalai, D.

2009-03-07

We use Metropolis Monte Carlo and umbrella sampling to calculate the free energies of interaction of two methane molecules and their charged derivatives in cylindrical water-filled pores. Confinement strongly alters the interactions between the nonpolar solutes and completely eliminates the solvent separated minimum (SSM) that is seen in bulk water. The free energy profiles show that the methane molecules are either in contact or at separations corresponding to the diameter and the length of the cylindrical pore. Analytic calculations that estimate the entropy of the solutes, which are solvated at the pore surface, qualitatively explain the shape of the freemore » energy profiles. Adding charges of opposite sign and magnitude 0.4e or e (where e is the electronic charge) to the methane molecules decreases their tendency for surface solvation and restores the SSM. We show that confinement induced ion-pair formation occurs whenever l{sub B}/D{approx}O(1), where l{sub B} is the Bjerrum length and D is the pore diameter. The extent of stabilization of the SSM increases with ion charge density as long as l{sub B}/D<1. In pores with D{<=}1.2 nm, in which the water is strongly layered, increasing the charge magnitude from 0.4e to e reduces the stability of the SSM. As a result, ion-pair formation that occurs with negligible probability in the bulk is promoted. In larger diameter pores that can accommodate a complete hydration layer around the solutes, the stability of the SSM is enhanced.« less

Keck/NIRC2 Imaging of the Warped, Asymmetric Debris Disk Around HD 32297

NASA Technical Reports Server (NTRS)

Currie, Thayne; Rodigas, Timothy J.; Debes, John; Plavchan, Peter; Kuchner, Marc; Jang-Condell, Hannah; Wilner, David; Andrews, Sean; Kraus, Adam; Dahm, Scott;

Effect of laser shot peening on precipitation hardened aluminum alloy 6061-T6 using low energy laser

NASA Astrophysics Data System (ADS)

Sathyajith, S.; Kalainathan, S.

2012-03-01

Mechanical properties of engineering material can be improved by introducing compressive residual stress on the material surface and refinement of their microstructure. Variety of mechanical process such as shot peening, water jet peening, ultrasonic peening, laser shot peening were developed in the last decades on this contrast. Among these, lasers shot peening emerged as a novel industrial treatment to improve the crack resistance of turbine blades and the stress corrosion cracking (SCC) of austenic stainless steel in power plants. In this study we successfully performed laser shot peening on precipitation hardened aluminum alloy 6061-T6 with low energy (300 mJ, 1064 nm) Nd:YAG laser using different pulse densities of 22 pulses/mm 2 and 32 pulses/mm 2. Residual stress evaluation based on X-ray diffraction sin 2 ψ method indicates a maximum of 190% percentage increase on surface compressive stress. Depth profile of micro-hardness shows the impact of laser generated shock wave up to 1.2 mm from the surface. Apart from that, the crystalline size and micro-strain on the laser shot peened surfaces have been investigated and compared with the unpeened surface using X-ray diffraction in conjunction with line broadening analysis through the Williamson-Hall plot.

Improvement of mechanical properties and life extension of high reliability structural components by laser shock processing

NASA Astrophysics Data System (ADS)

Ocaña, J. L.; Morales, M.; Porro, J. A.; Iordachescu, D.; Díaz, M.; Ruiz de Lara, L.; Correa, C.

2011-05-01

Profiting by the increasing availability of laser sources delivering intensities above 109 W/cm2 with pulse energies in the range of several Joules and pulse widths in the range of nanoseconds, laser shock processing (LSP) is being consolidating as an effective technology for the improvement of surface mechanical and corrosion resistance properties of metals and is being developed as a practical process amenable to production engineering. The main acknowledged advantage of the laser shock processing technique consists on its capability of inducing a relatively deep compression residual stresses field into metallic alloy pieces allowing an improved mechanical behaviour, explicitly, the life improvement of the treated specimens against wear, crack growth and stress corrosion cracking. Following a short description of the theoretical/computational and experimental methods developed by the authors for the predictive assessment and experimental implementation of LSP treatments, experimental results on the residual stress profiles and associated surface properties modification successfully reached in typical materials (specifically Al and Ti alloys) under different LSP irradiation conditions are presented. In particular, the analysis of the residual stress profiles obtained under different irradiation parameters and the evaluation of the corresponding induced surface properties as roughness and wear resistance are presented.

Spoof surface plasmon polaritons excitation and wavefront control by Pancharatnam–Berry phase manipulating metasurface

NASA Astrophysics Data System (ADS)

Meng, Yueyu; Ma, Hua; Li, Yongfeng; Feng, Mingde; Wang, Jiafu; Li, Zhiqiang; Qu, Shaobo

2018-05-01

Realizing fine control of surface plasmon polaritons (SPPs) and spoof surface plasmon polaritons (SSPPs) is highly desired in many integrated photonic and microwave applications, but the flexibility to control the wavefront of SPPs and SSPPs still need addressing. In this paper, a Pancharatnam–Berry (PB) phase manipulating metasurface (PMM) was designed to achieve SSPPs excitation and wavefront control. Under circular polarization (CP) incidence, simply by designing the rotation angle of the unit cells the reflection phase spatial distribution can be manipulated. By means of different phase profiles on the 2D unit cells array, the SSPPs can be excited with various wavefront shapes, without the need of special excitation structure pattern. Meanwhile, a plasmonic metal is also designed to support SSPPs with both TE and TM polarizations, which can efficiently guide out the energies from the input CP waves. As a proof of concept, a PB PMM composed of N-shape metallic structure was designed. Through designing the rotation of the unit cells, two typical phase profiles were designed to excite SSPPs in arbitrary slant direction or focusing. This scheme could be used to achieve SSPPs excitation with many other wavefront shapes, and would also enable promising applications in other spectra.

Deducing noninductive current profile from surface voltage evolution

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

Litwin, C.; Wukitch, S.; Hershkowitz, N.

Solving the resistive diffusion equation in the presence of a noninductive current source determines the time-evolution of the surface voltage. By inverting the problem the current drive profile can be determined from the surface voltage evolution. We show that under wide range of conditions the deduced profile is unique. If the conductivity profile is known, this method can be employed to infer the noninductive current profile, and, ipso facto, the profile of the total current. We discuss the application of this method to analyze the Alfven wave current drive experiments in Phaedrus-T.

New figuring model based on surface slope profile for grazing-incidence reflective optics

DOE PAGES

Zhou, Lin; Huang, Lei; Bouet, Nathalie; ...

2016-08-09

Surface slope profile is widely used in the metrology of grazing-incidence reflective optics instead of surface height profile. Nevertheless, the theoretical and experimental model currently used in deterministic optical figuring processes is based on surface height, not on surface slope. This means that the raw slope profile data from metrology need to be converted to height profile to perform the current height-based figuring processes. The inevitable measurement noise in the raw slope data will introduce significant cumulative error in the resultant height profiles. As a consequence, this conversion will degrade the determinism of the figuring processes, and will have anmore » impact on the ultimate surface figuring results. To overcome this problem, an innovative figuring model is proposed, which directly uses the raw slope profile data instead of the usual height data as input for the deterministic process. In this article, first the influence of the measurement noise on the resultant height profile is analyzed, and then a new model is presented; finally a demonstration experiment is carried out using a one-dimensional ion beam figuring process to demonstrate the validity of our approach.« less

Full area covered 3D profile measurement of special-shaped optics based on a new prototype non-contact profiler

NASA Astrophysics Data System (ADS)

Du, Hui-Lin; Zhou, Zhao-Zhong; Sun, Ze-Qing; Ju, Bing-Feng; Xu, Shaoning; Sun, Anyu

2017-06-01

A new prototype non-contact profiler based on surface tracking has been specially developed. Surface tracking is carried out by a specially designed dual stage probe system with the aid of a four-Degree Of Freedom high-precision motion platform. The dual stage probe system keeps a short-range optical probe constantly tracking the surface by a self-developed voice coil motor servo, by which a wide measuring range of up to 10 mm is realized. The system performance evaluation including resolution, repeatability, and scanning speed proved the good capability of the new prototype non-contact profiler. To realize a full area covered 3D profile measurement of special-shaped optics within one scanning procedure, a signal intensity monitor integrated in the surface tracking controller is specially developed. In the experiment, a snip-single-corner-rectangular-shaped freeform surface was successfully measured over full area by the new non-contact profiler. This work provides an effective solution for 3D profile measurement of special-shaped optical surfaces over full reflecting area. Experimental results demonstrate that the proposed measuring system is of great significance in quality evaluation of optical surfaces.

Full area covered 3D profile measurement of special-shaped optics based on a new prototype non-contact profiler.

PubMed

Du, Hui-Lin; Zhou, Zhao-Zhong; Sun, Ze-Qing; Ju, Bing-Feng; Xu, Shaoning; Sun, Anyu

2017-06-01

A new prototype non-contact profiler based on surface tracking has been specially developed. Surface tracking is carried out by a specially designed dual stage probe system with the aid of a four-Degree Of Freedom high-precision motion platform. The dual stage probe system keeps a short-range optical probe constantly tracking the surface by a self-developed voice coil motor servo, by which a wide measuring range of up to 10 mm is realized. The system performance evaluation including resolution, repeatability, and scanning speed proved the good capability of the new prototype non-contact profiler. To realize a full area covered 3D profile measurement of special-shaped optics within one scanning procedure, a signal intensity monitor integrated in the surface tracking controller is specially developed. In the experiment, a snip-single-corner-rectangular-shaped freeform surface was successfully measured over full area by the new non-contact profiler. This work provides an effective solution for 3D profile measurement of special-shaped optical surfaces over full reflecting area. Experimental results demonstrate that the proposed measuring system is of great significance in quality evaluation of optical surfaces.

Controlling drug delivery kinetics from mesoporous titania thin films by pore size and surface energy.

PubMed

Karlsson, Johan; Atefyekta, Saba; Andersson, Martin

2015-01-01

The osseointegration capacity of bone-anchoring implants can be improved by the use of drugs that are administrated by an inbuilt drug delivery system. However, to attain superior control of drug delivery and to have the ability to administer drugs of varying size, including proteins, further material development of drug carriers is needed. Mesoporous materials have shown great potential in drug delivery applications to provide and maintain a drug concentration within the therapeutic window for the desired period of time. Moreover, drug delivery from coatings consisting of mesoporous titania has shown to be promising to improve healing of bone-anchoring implants. Here we report on how the delivery of an osteoporosis drug, alendronate, can be controlled by altering pore size and surface energy of mesoporous titania thin films. The pore size was varied from 3.4 nm to 7.2 nm by the use of different structure-directing templates and addition of a swelling agent. The surface energy was also altered by grafting dimethylsilane to the pore walls. The drug uptake and release profiles were monitored in situ using quartz crystal microbalance with dissipation (QCM-D) and it was shown that both pore size and surface energy had a profound effect on both the adsorption and release kinetics of alendronate. The QCM-D data provided evidence that the drug delivery from mesoporous titania films is controlled by a binding-diffusion mechanism. The yielded knowledge of release kinetics is crucial in order to improve the in vivo tissue response associated to therapeutic treatments.

AERI Observations of Antarctic Clouds Properties During AWARE

NASA Astrophysics Data System (ADS)

Gero, P. J.; Rowe, P. M.; Walden, V. P.

2017-12-01

The ARM West Antarctic Radiation Experiment (AWARE) was a recent field campaign by the US Dept. of Energy's Atmospheric Radiation Measurement (ARM) program, in collaboration with the National Science Foundation, to measure the state of the atmosphere, the surface energy balance, and cloud properties in Antarctica. The main observing facility for AWARE, located near McMurdo Station, consisted of a wide variety of instrumentation, including an eddy-covariance system, surface aerosol measurements, cloud radar and lidar, broadband radiometers, microwave radiometer, and an infrared spectroradiometer (AERI). Collectively these measurements can be used to improve our understanding of the connections between the atmospheric state, cloud processes, and their effects on the surface energy budget. Thus, AWARE data have the potential to revolutionize our understanding of how the atmosphere and clouds impact the surface energy budget in this important region. The Atmospheric Emitted Radiance Interferometer (AERI) is a ground-based instrument developed at the University of Wisconsin-Madison that measures downwelling thermal infrared radiance from the atmosphere. Observations are made in the 400-3020 cm-1 (3.3-19 μm) spectral range with a resolution of 1 cm-1, with an accuracy better than 1% of ambient radiance. These observations can be used to obtain vertical profiles of tropospheric temperature and water vapor in the lower troposphere, as well as measurements of the concentration of various trace gases and microphysical and optical properties of clouds. We present some preliminary results from the AERI dataset from AWARE, including analysis of the downwelling radiation and cloud structure over the annual cycle.

Accurate study on the quantum dynamics of the He + HeH(+) (X1Σ+) reaction on a new ab initio potential energy surface for the lowest 1(1)A' electronic singlet state.

PubMed

Xu, Wenwu; Zhang, Peiyu

2013-02-21

A time-dependent quantum wave packet method is used to investigate the dynamics of the He + HeH(+)(X(1)Σ(+)) reaction based on a new potential energy surface [Liang et al., J. Chem. Phys.2012, 136, 094307]. The coupled channel (CC) and centrifugal-sudden (CS) reaction probabilities as well as the total integral cross sections are calculated. A comparison of the results with and without Coriolis coupling revealed that the number of K states N(K) (K is the projection of the total angular momentum J on the body-fixed z axis) significantly influences the reaction threshold. The effective potential energy profiles of each N(K) for the He + HeH(+) reaction in a collinear geometry indicate that the barrier height gradually decreased with increased N(K). The calculated time evolution of CC and CS probability density distribution over the collision energy of 0.27-0.36 eV at total angular momentum J = 50 clearly suggests a lower reaction threshold of CC probabilities. The CC cross sections are larger than the CS results within the entire energy range, demonstrating that the Coriolis coupling effect can effectively promote the He + HeH(+) reaction.

Multiscale gyrokinetics for rotating tokamak plasmas: fluctuations, transport and energy flows.

PubMed

Abel, I G; Plunk, G G; Wang, E; Barnes, M; Cowley, S C; Dorland, W; Schekochihin, A A

2013-11-01

This paper presents a complete theoretical framework for studying turbulence and transport in rapidly rotating tokamak plasmas. The fundamental scale separations present in plasma turbulence are codified as an asymptotic expansion in the ratio ε = ρi/α of the gyroradius to the equilibrium scale length. Proceeding order by order in this expansion, a set of coupled multiscale equations is developed. They describe an instantaneous equilibrium, the fluctuations driven by gradients in the equilibrium quantities, and the transport-timescale evolution of mean profiles of these quantities driven by the interplay between the equilibrium and the fluctuations. The equilibrium distribution functions are local Maxwellians with each flux surface rotating toroidally as a rigid body. The magnetic equilibrium is obtained from the generalized Grad-Shafranov equation for a rotating plasma, determining the magnetic flux function from the mean pressure and velocity profiles of the plasma. The slow (resistive-timescale) evolution of the magnetic field is given by an evolution equation for the safety factor q. Large-scale deviations of the distribution function from a Maxwellian are given by neoclassical theory. The fluctuations are determined by the 'high-flow' gyrokinetic equation, from which we derive the governing principle for gyrokinetic turbulence in tokamaks: the conservation and local (in space) cascade of the free energy of the fluctuations (i.e. there is no turbulence spreading). Transport equations for the evolution of the mean density, temperature and flow velocity profiles are derived. These transport equations show how the neoclassical and fluctuating corrections to the equilibrium Maxwellian act back upon the mean profiles through fluxes and heating. The energy and entropy conservation laws for the mean profiles are derived from the transport equations. Total energy, thermal, kinetic and magnetic, is conserved and there is no net turbulent heating. Entropy is produced by the action of fluxes flattening gradients, Ohmic heating and the equilibration of interspecies temperature differences. This equilibration is found to include both turbulent and collisional contributions. Finally, this framework is condensed, in the low-Mach-number limit, to a more concise set of equations suitable for numerical implementation.

Effects of limiter biasing on the ATF torsatron

NASA Astrophysics Data System (ADS)

Uckan, T.; Aceto, S. C.; Baylor, L. R.; Bell, J. D.; Bigelow, T. S.; England, A. C.; Harris, J. H.; Isler, R. C.; Jernigan, T. C.; Lyon, J. F.; Ma, C. H.; Mioduszewski, P. K.; Murakami, M.; Rasmussen, D. A.; Wilgen, J. B.; Zielinski, J. J.

1992-12-01

Positive limiter biasing on the currentless ATF torsatron produces a significant increase in the particle confinement with no improvement in the energy confinement. Experiments have been carried out in 1-T plasmas with ˜400 kW of ECH. Two rail limiters located at the last closed flux surface (LCFS), one at the top and one at the bottom of the device, are biased at positive and negative potentials with respect to the vessel. When the limiters are positively biased at up to 300 V, the density increases sharply to the ECH cutoff value. At the same time, the H α radiation drops, indicating that the particle confinement improves. When the density is kept constant, the H α radiation is further reduced and there is almost no change of plasma stored energy. Under these conditions, the density profiles become peaked and the electric field becomes outward-pointing outside the LCFS and more negative inside the LCFS. In contrast, negative biasing yields some reduction of the density and stored energy at constant gas feed, and the plasma potential profile remains the same. Biasing has almost no effect on the intrinsic impurity levels in the plasma.

Characterization of Lunar Polar Illumination from a Power System Perspective

NASA Technical Reports Server (NTRS)

Fincannon, James

2008-01-01

This paper presents the results of illumination analyses for the lunar south and north pole regions obtained using an independently developed analytical tool and two types of digital elevation models (DEM). One DEM was based on radar height data from Earth observations of the lunar surface and the other was a combination of the radar data with a separate dataset generated using Clementine spacecraft stereo imagery. The analysis tool enables the assessment of illumination at most locations in the lunar polar regions for any time and any year. Maps are presented for both lunar poles for the worst case winter period (the critical power system design and planning bottleneck) and for the more favorable best case summer period. Average illumination maps are presented to help understand general topographic trends over the regions. Energy storage duration maps are presented to assist in power system design. Average illumination fraction, energy storage duration, solar/horizon terrain elevation profiles and illumination fraction profiles are presented for favorable lunar north and south pole sites which have the potential for manned or unmanned spacecraft operations. The format of the data is oriented for use by power system designers to develop mass optimized solar and energy storage systems.

Uncovering glacier dynamics beneath a debris mantle

NASA Astrophysics Data System (ADS)

Lefeuvre, P.-M.; Ng, F. S. L.

2012-04-01

Debris-covered glaciers (DCGs) have an extensive sediment mantle whose low albedo influences their surface energy balance to cause a buffering effect that could enhance or reduce ablation rates depending on the sediment thickness. The last effect suggests that some DCGs may be less sensitive to climate change and survive for longer than debris-free (or 'clean') glaciers under sustained climatic warming. However, the origin of DCGs is debated and the precise impact of the debris mantle on their flow dynamics and surface geometry has not been quantified. Here we investigate these issues with a numerical model that encapsulates ice-flow physics and surface debris evolution and transport along a glacier flow-line, as well as couples these with glacier mass balance. We model the impact of surface debris on ablation rates by a mathematical function based on published empirical data (including Ostrem's curve). A key interest is potential positive feedback of ablation on debris thickening and lowering of surface albedo. Model simulations show that when DCGs evolve to attain steady-state profiles, they reach lower elevations than clean glaciers do for the same initial and climatic conditions. Their mass-balance profile at steady state displays an inversion near the snout (where the debris cover is thickest) that is not observed in the clean-glacier simulations. In these cases, where the mantle causes complete buffering to inhibit ablation, the DCG does not reach a steady-state profile, and the sediment thickness evolves to a steady value that depends sensitively on the glacier surface velocities. Variation in the assumed englacial debris concentration in our simulations also determines glacier behaviour. With low englacial debris concentration, the DCG retreats initially while its mass-balance gradient steepens, but the glacier re-advances if it subsequently builds up a thick enough debris cover to cause complete buffering. We identify possible ways and challenges of testing this model with field observations of DCGs, given the inherent difficulty that such glaciers may not be in steady state.

Temperature distribution of a water droplet moving on a heated super-hydrophobic surface under the icing condition

NASA Astrophysics Data System (ADS)

Yamazaki, Masafumi; Sumino, Yutaka; Morita, Katsuaki

2017-11-01

In the aviation industry, ice accretion on the airfoil has been a hazardous issue since it greatly declines the aerodynamic performance. Electric heaters and bleed air, which utilizes a part of gas emissions from engines, are used to prevent the icing. Nowadays, a new de-icing system combining electric heaters and super hydrophobic coatings have been developed to reduce the energy consumption. In the system, the heating temperature and the coating area need to be adjusted. Otherwise, the heater excessively consumes energy when it is set too high and when the coating area is not properly located, water droplets which are once dissolved possibly adhere again to the rear part of the airfoil as runback ice In order to deal with these problems, the physical phenomena of water droplets on the hydrophobic surface demand to be figured out. However, not many investigations focused on the behavior of droplets under the icing condition have been conducted. In this research, the temperature profiling of the rolling droplet on a heated super-hydrophobic surface is experimentally observed by the dual luminescent imaging.

ExoMol molecular line lists - XXVII: spectra of C2H4

NASA Astrophysics Data System (ADS)

Mant, Barry P.; Yachmenev, Andrey; Yurchenko, Jonathan Tennyson Sergei N.

2018-05-01

A new line list for ethylene, 12C21H4 is presented. The line list is based on high level ab initiopotential energy and dipole moment surfaces. The potential energy surface is refined by fitting to experimental energies. The line list covers the range up to 7000 cm-1(1.43 μm) with all ro-vibrational transitions (50 billion) with the lower state below 5000 cm-1included and thus should be applicable for temperatures up to 700 K. A technique for computing molecular opacities from vibrational band intensities is proposed and used to provide temperature dependent cross sections of ethylene for shorter wavelength and higher temperatures. When combined with realistic band profiles (such as the proposed three-band model), the vibrational intensity technique offers a cheap but reasonably accurate alternative to the full ro-vibrational calculations at high temperatures and should be reliable for representing molecular opacities. The C2H4 line list, which is called MaYTY, is rmade available in electronic form from the CDS (http://cdsarc.u-strasbg.fr) and ExoMol (www.exomol.com) databases.

Muons in air showers at the Pierre Auger Observatory: Mean number in highly inclined events

DOE PAGES

Aab, Alexander

2015-03-09

We present the first hybrid measurement of the average muon number in air showers at ultra-high energies, initiated by cosmic rays with zenith angles between 62° and 80° . Our measurement is based on 174 hybrid events recorded simultaneously with the Surface Detector array and the Fluorescence Detector of the Pierre Auger Observatory. The muon number for each shower is derived by scaling a simulated reference profile of the lateral muon density distribution at the ground until it fits the data. A 10 19 eV shower with a zenith angle of 67°, which arrives at the Surface Detector array atmore » an altitude of 1450 m above sea level, contains on average (2.68 ± 0.04 ± 0.48 (sys.)) × 10 7 muons with energies larger than 0.3 GeV. Finally, the logarithmic gain d ln N µ/d ln E of muons with increasing energy between 4 × 10 18 eV and 5 × 10 19 eV is measured to be (1.029 ± 0.024 ± 0.030 (sys.)).« less

Muons in air showers at the Pierre Auger Observatory: Mean number in highly inclined events

NASA Astrophysics Data System (ADS)

Aab, A.; Abreu, P.; Aglietta, M.; Ahn, E. J.; Al Samarai, I.; Albuquerque, I. F. M.; Allekotte, I.; Allen, J.; Allison, P.; Almela, A.; Alvarez Castillo, J.; Alvarez-Muñiz, J.; Alves Batista, R.; Ambrosio, M.; Aminaei, A.; Anchordoqui, L.; Andringa, S.; Aramo, C.; Aranda, V. M.; Arqueros, F.; Asorey, H.; Assis, P.; Aublin, J.; Ave, M.; Avenier, M.; Avila, G.; Badescu, A. M.; Barber, K. B.; Bäuml, J.; Baus, C.; Beatty, J. J.; Becker, K. H.; Bellido, J. A.; Berat, C.; Bertaina, M. E.; Bertou, X.; Biermann, P. L.; Billoir, P.; Blanco, M.; Bleve, C.; Blümer, H.; Boháčová, M.; Boncioli, D.; Bonifazi, C.; Bonino, R.; Borodai, N.; Brack, J.; Brancus, I.; Brogueira, P.; Brown, W. C.; Buchholz, P.; Bueno, A.; Buitink, S.; Buscemi, M.; Caballero-Mora, K. S.; Caccianiga, B.; Caccianiga, L.; Candusso, M.; Caramete, L.; Caruso, R.; Castellina, A.; Cataldi, G.; Cazon, L.; Cester, R.; Chavez, A. G.; Chiavassa, A.; Chinellato, J. A.; Chudoba, J.; Cilmo, M.; Clay, R. W.; Cocciolo, G.; Colalillo, R.; Coleman, A.; Collica, L.; Coluccia, M. R.; Conceição, R.; Contreras, F.; Cooper, M. J.; Cordier, A.; Coutu, S.; Covault, C. E.; Cronin, J.; Curutiu, A.; Dallier, R.; Daniel, B.; Dasso, S.; Daumiller, K.; Dawson, B. R.; de Almeida, R. M.; De Domenico, M.; de Jong, S. J.; de Mello Neto, J. R. T.; De Mitri, I.; de Oliveira, J.; de Souza, V.; del Peral, L.; Deligny, O.; Dembinski, H.; Dhital, N.; Di Giulio, C.; Di Matteo, A.; Diaz, J. C.; Díaz Castro, M. L.; Diogo, F.; Dobrigkeit, C.; Docters, W.; D'Olivo, J. C.; Dorofeev, A.; Dorosti Hasankiadeh, Q.; Dova, M. T.; Ebr, J.; Engel, R.; Erdmann, M.; Erfani, M.; Escobar, C. O.; Espadanal, J.; Etchegoyen, A.; Facal San Luis, P.; Falcke, H.; Fang, K.; Farrar, G.; Fauth, A. C.; Fazzini, N.; Ferguson, A. P.; Fernandes, M.; Fick, B.; Figueira, J. M.; Filevich, A.; Filipčič, A.; Fox, B. D.; Fratu, O.; Fröhlich, U.; Fuchs, B.; Fujii, T.; Gaior, R.; García, B.; Garcia Roca, S. T.; Garcia-Gamez, D.; Garcia-Pinto, D.; Garilli, G.; Gascon Bravo, A.; Gate, F.; Gemmeke, H.; Ghia, P. L.; Giaccari, U.; Giammarchi, M.; Giller, M.; Glaser, C.; Glass, H.; Gómez Berisso, M.; Gómez Vitale, P. F.; Gonçalves, P.; Gonzalez, J. G.; González, N.; Gookin, B.; Gordon, J.; Gorgi, A.; Gorham, P.; Gouffon, P.; Grebe, S.; Griffith, N.; Grillo, A. F.; Grubb, T. D.; Guardincerri, Y.; Guarino, F.; Guedes, G. P.; Hampel, M. R.; Hansen, P.; Harari, D.; Harrison, T. A.; Hartmann, S.; Harton, J. L.; Haungs, A.; Hebbeker, T.; Heck, D.; Heimann, P.; Herve, A. E.; Hill, G. C.; Hojvat, C.; Hollon, N.; Holt, E.; Homola, P.; Hörandel, J. R.; Horvath, P.; Hrabovský, M.; Huber, D.; Huege, T.; Insolia, A.; Isar, P. G.; Islo, K.; Jandt, I.; Jansen, S.; Jarne, C.; Josebachuili, M.; Kääpä, A.; Kambeitz, O.; Kampert, K. H.; Kasper, P.; Katkov, I.; Kégl, B.; Keilhauer, B.; Keivani, A.; Kemp, E.; Kieckhafer, R. M.; Klages, H. O.; Kleifges, M.; Kleinfeller, J.; Krause, R.; Krohm, N.; Krömer, O.; Kruppke-Hansen, D.; Kuempel, D.; Kunka, N.; LaHurd, D.; Latronico, L.; Lauer, R.; Lauscher, M.; Lautridou, P.; Le Coz, S.; Leão, M. S. A. B.; Lebrun, D.; Lebrun, P.; Leigui de Oliveira, M. A.; Letessier-Selvon, A.; Lhenry-Yvon, I.; Link, K.; López, R.; Louedec, K.; Lozano Bahilo, J.; Lu, L.; Lucero, A.; Ludwig, M.; Malacari, M.; Maldera, S.; Mallamaci, M.; Maller, J.; Mandat, D.; Mantsch, P.; Mariazzi, A. G.; Marin, V.; Mariş, I. C.; Marsella, G.; Martello, D.; Martin, L.; Martinez, H.; Martínez Bravo, O.; Martraire, D.; Masías Meza, J. J.; Mathes, H. J.; Mathys, S.; Matthews, J. J.; Matthews, A. J.; Matthiae, G.; Maurel, D.; Maurizio, D.; Mayotte, E.; Mazur, P. O.; Medina, C.; Medina-Tanco, G.; Melissas, M.; Melo, D.; Menshikov, A.; Messina, S.; Meyhandan, R.; Mićanović, S.; Micheletti, M. I.; Middendorf, L.; Minaya, I. A.; Miramonti, L.; Mitrica, B.; Molina-Bueno, L.; Mollerach, S.; Monasor, M.; Monnier Ragaigne, D.; Montanet, F.; Morello, C.; Mostafá, M.; Moura, C. A.; Muller, M. A.; Müller, G.; Münchmeyer, M.; Mussa, R.; Navarra, G.; Navas, S.; Necesal, P.; Nellen, L.; Nelles, A.; Neuser, J.; Newton, D.; Niechciol, M.; Niemietz, L.; Niggemann, T.; Nitz, D.; Nosek, D.; Novotny, V.; Nožka, L.; Ochilo, L.; Olinto, A.; Oliveira, M.; Olmos-Gilbaja, V. M.; Pacheco, N.; Pakk Selmi-Dei, D.; Palatka, M.; Pallotta, J.; Palmieri, N.; Papenbreer, P.; Parente, G.; Parra, A.; Paul, T.; Pech, M.; Pekala, J.; Pelayo, R.; Pepe, I. M.; Perrone, L.; Petermann, E.; Peters, C.; Petrera, S.; Petrov, Y.; Phuntsok, J.; Piegaia, R.; Pierog, T.; Pieroni, P.; Pimenta, M.; Pirronello, V.; Platino, M.; Plum, M.; Porcelli, A.; Porowski, C.; Prado, R. R.; Privitera, P.; Prouza, M.; Purrello, V.; Quel, E. J.; Querchfeld, S.; Quinn, S.; Rautenberg, J.; Ravel, O.; Ravignani, D.; Revenu, B.; Ridky, J.; Riggi, S.; Risse, M.; Ristori, P.; Rizi, V.; Roberts, J.; Rodrigues de Carvalho, W.; Rodriguez Fernandez, G.; Rodriguez Rojo, J.; Rodríguez-Frías, M. D.; Ros, G.; Rosado, J.; Rossler, T.; Roth, M.; Roulet, E.; Rovero, A. C.; Saffi, S. J.; Saftoiu, A.; Salamida, F.; Salazar, H.; Saleh, A.; Salesa Greus, F.; Salina, G.; Sánchez, F.; Sanchez-Lucas, P.; Santo, C. E.; Santos, E.; Santos, E. M.; Sarazin, F.; Sarkar, B.; Sarmento, R.; Sato, R.; Scharf, N.; Scherini, V.; Schieler, H.; Schiffer, P.; Scholten, O.; Schoorlemmer, H.; Schovánek, P.; Schröder, F. G.; Schulz, A.; Schulz, J.; Schumacher, J.; Sciutto, S. J.; Segreto, A.; Settimo, M.; Shadkam, A.; Shellard, R. C.; Sidelnik, I.; Sigl, G.; Sima, O.; Śmiałkowski, A.; Šmída, R.; Snow, G. R.; Sommers, P.; Sorokin, J.; Squartini, R.; Srivastava, Y. N.; Stanič, S.; Stapleton, J.; Stasielak, J.; Stephan, M.; Stutz, A.; Suarez, F.; Suomijärvi, T.; Supanitsky, A. D.; Sutherland, M. S.; Swain, J.; Szadkowski, Z.; Szuba, M.; Taborda, O. A.; Tapia, A.; Tartare, M.; Tepe, A.; Theodoro, V. M.; Timmermans, C.; Todero Peixoto, C. J.; Toma, G.; Tomankova, L.; Tomé, B.; Tonachini, A.; Torralba Elipe, G.; Torres Machado, D.; Travnicek, P.; Trovato, E.; Ulrich, R.; Unger, M.; Urban, M.; Valdés Galicia, J. F.; Valiño, I.; Valore, L.; van Aar, G.; van den Berg, A. M.; van Velzen, S.; van Vliet, A.; Varela, E.; Vargas Cárdenas, B.; Varner, G.; Vázquez, J. R.; Vázquez, R. A.; Veberič, D.; Verzi, V.; Vicha, J.; Videla, M.; Villaseñor, L.; Vlcek, B.; Vorobiov, S.; Wahlberg, H.; Wainberg, O.; Walz, D.; Watson, A. A.; Weber, M.; Weidenhaupt, K.; Weindl, A.; Werner, F.; Widom, A.; Wiencke, L.; Wilczyńska, B.; Wilczyński, H.; Will, M.; Williams, C.; Winchen, T.; Wittkowski, D.; Wundheiler, B.; Wykes, S.; Yamamoto, T.; Yapici, T.; Younk, P.; Yuan, G.; Yushkov, A.; Zamorano, B.; Zas, E.; Zavrtanik, D.; Zavrtanik, M.; Zaw, I.; Zepeda, A.; Zhou, J.; Zhu, Y.; Zimbres Silva, M.; Ziolkowski, M.; Zuccarello, F.; Pierre Auger Collaboration

2015-02-01

We present the first hybrid measurement of the average muon number in air showers at ultrahigh energies, initiated by cosmic rays with zenith angles between 62° and 80°. The measurement is based on 174 hybrid events recorded simultaneously with the surface detector array and the fluorescence detector of the Pierre Auger Observatory. The muon number for each shower is derived by scaling a simulated reference profile of the lateral muon density distribution at the ground until it fits the data. A 1019 eV shower with a zenith angle of 67°, which arrives at the surface detector array at an altitude of 1450 m above sea level, contains on average (2.68 ±0.04 ±0.48 (sys))×107 muons with energies larger than 0.3 GeV. The logarithmic gain d ln Nμ/d ln E of muons with increasing energy between 4 ×1018 eV and 5 ×1019 eV is measured to be (1.029 ±0.024 ±0.030 (sys)) .

Compressor seal rub energetics study

NASA Technical Reports Server (NTRS)

Laverty, W. F.

1978-01-01

The rub mechanics of compressor abradable blade tip seals at simulated engine conditions were investigated. Twelve statistically planned, instrumented rub tests were conducted with titanium blades and Feltmetal fibermetal rubstrips. The tests were conducted with single stationary blades rubbing against seal material bonded to rotating test disks. The instantaneous rub torque, speed, incursion rate and blade temperatures were continuously measured and recorded. Basic rub parameters (incursion rate, rub depth, abradable density, blade thickness and rub velocity) were varied to determine the effects on rub energy and heat split between the blade, rubstrip surface and rub debris. The test data was reduced, energies were determined and statistical analyses were completed to determine the primary and interactive effects. Wear surface morphology, profile measurements and metallographic analysis were used to determine wear, glazing, melting and material transfer. The rub energies for these tests were most significantly affected by the incursion rate while rub velocity and blade thickness were of secondary importance. The ratios of blade wear to seal wear were representative of those experienced in engine operation of these seal system materials.

Seasonal surface circulation, temperature, and salinity in Prince William Sound, Alaska

NASA Astrophysics Data System (ADS)

Musgrave, David L.; Halverson, Mark J.; Scott Pegau, W.

2013-02-01

Salinity, temperature, and depth profiles from 1973 to 2010 were used to construct a seasonal climatology of surface temperature, surface salinity, mixed layer depth (MLD), potential energy of mixing, and surface geostrophic circulation in Prince William Sound (PWS) and the adjacent Gulf of Alaska. Surface salinity is greatest in winter and least in summer due to the influence of increased freshwater runoff in summer. It is generally lowest in the northwest and highest in the Gulf of Alaska. The surface temperature is lowest in the winter and highest in the summer when surface heating is greatest, with little spatial variability across the Sound. The MLD is deepest in winter (9-27 m) and shallowest in summer (4-5 m). The work by winds was estimated from meteorological buoy data in central PWS and compared to the potential energy of mixing of the upper water column. The potential depth to which winds mix the upper water column was generally consistent with the MLD. The surface geostrophic circulation in the central Sound has: a southerly flow in the western central Sound in the winter; a closed, weak anticyclonic cell in spring; a closed, cyclonic cell in the summer; an open, cyclonic circulation in the fall. In the western passages, a southerly flow occurs in spring, summer, and fall. These results have important implications for oil spill response in PWS, the use of oil dispersants, and for comparison to numerical studies.

Residential Consumption Scheduling Based on Dynamic User Profiling

NASA Astrophysics Data System (ADS)

Mangiatordi, Federica; Pallotti, Emiliano; Del Vecchio, Paolo; Capodiferro, Licia

Deployment of household appliances and of electric vehicles raises the electricity demand in the residential areas and the impact of the building's electrical power. The variations of electricity consumption across the day, may affect both the design of the electrical generation facilities and the electricity bill, mainly when a dynamic pricing is applied. This paper focuses on an energy management system able to control the day-ahead electricity demand in a residential area, taking into account both the variability of the energy production costs and the profiling of the users. The user's behavior is dynamically profiled on the basis of the tasks performed during the previous days and of the tasks foreseen for the current day. Depending on the size and on the flexibility in time of the user tasks, home inhabitants are grouped in, one over N, energy profiles, using a k-means algorithm. For a fixed energy generation cost, each energy profile is associated to a different hourly energy cost. The goal is to identify any bad user profile and to make it pay a highest bill. A bad profile example is when a user applies a lot of consumption tasks and low flexibility in task reallocation time. The proposed energy management system automatically schedules the tasks, solving a multi-objective optimization problem based on an MPSO strategy. The goals, when identifying bad users profiles, are to reduce the peak to average ratio in energy demand, and to minimize the energy costs, promoting virtuous behaviors.

Direct measurements of multiple adhesive alignments and unbinding trajectories between cadherin extracellular domains.

PubMed Central

Sivasankar, S; Gumbiner, B; Leckband, D

2001-01-01

Direct measurements of the interactions between antiparallel, oriented monolayers of the complete extracellular region of C-cadherin demonstrate that, rather than binding in a single unique orientation, the cadherins adhere in three distinct alignments. The strongest adhesion is observed when the opposing extracellular fragments are completely interdigitated. A second adhesive alignment forms when the interdigitated proteins separate by 70 +/- 10 A. A third complex forms at a bilayer separation commensurate with the approximate overlap of cadherin extracellular domains 1 and 2 (CEC1-2). The locations of the energy minima are independent of both the surface density of bound cadherin and the stiffness of the force transducer. Using surface element integration, we show that two flat surfaces that interact through an oscillatory potential will exhibit discrete minima at the same locations in the force profile measured between hemicylinders covered with identical materials. The measured interaction profiles, therefore, reflect the relative separations at which the antiparallel proteins adhere, and are unaffected by the curvature of the underlying substrate. The successive formation and rupture of multiple protein contacts during detachment can explain the observed sluggish unbinding of cadherin monolayers. Velocity-distance profiles, obtained by quantitative video analysis of the unbinding trajectory, exhibit three velocity regimes, the transitions between which coincide with the positions of the adhesive minima. These findings suggest that cadherins undergo multiple stage unbinding, which may function to impede adhesive failure under force. PMID:11259289

Stand-off molecular composition analysis

NASA Astrophysics Data System (ADS)

Hughes, Gary B.; Lubin, Philip; Meinhold, Peter; O'Neill, Hugh; Brashears, Travis; Zhang, Qicheng; Griswold, Janelle; Riley, Jordan; Motta, Caio

2015-09-01

Molecular composition of distant stars is explored by observing absorption spectra. The star produces blackbody radiation that passes through the molecular cloud of vaporized material surrounding the star. Characteristic absorption lines are discernible with a spectrometer, and molecular composition is investigated by comparing spectral observations with known material profiles. Most objects in the solar system—asteroids, comets, planets, moons—are too cold to be interrogated in this manner. Molecular clouds around cold objects consist primarily of volatiles, so bulk composition cannot be probed. Additionally, low volatile density does not produce discernible absorption lines in the faint signal generated by low blackbody temperatures. This paper describes a system for probing the molecular composition of cold solar system targets from a distant vantage. The concept utilizes a directed energy beam to melt and vaporize a spot on a distant target, such as from a spacecraft orbiting the object. With sufficient flux (~10 MW/m2), the spot temperature rises rapidly (to ~2 500 K), and evaporation of all materials on the target surface occurs. The melted spot creates a high-temperature blackbody source, and ejected material creates a molecular plume in front of the spot. Bulk composition is investigated by using a spectrometer to view the heated spot through the ejected material. Spatial composition maps could be created by scanning the surface. Applying the beam to a single spot continuously produces a borehole, and shallow sub-surface composition profiling is also possible. Initial simulations of absorption profiles with laser heating show great promise for molecular composition analysis.

Orchestrating TRANSP Simulations for Interpretative and Predictive Tokamak Modeling with OMFIT

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

Grierson, B. A.; Yuan, X.; Gorelenkova, M.

TRANSP simulations are being used in the OMFIT work- flow manager to enable a machine independent means of experimental analysis, postdictive validation, and predictive time dependent simulations on the DIII-D, NSTX, JET and C-MOD tokamaks. The procedures for preparing the input data from plasma profile diagnostics and equilibrium reconstruction, as well as processing of the time-dependent heating and current drive sources and assumptions about the neutral recycling, vary across machines, but are streamlined by using a common workflow manager. Settings for TRANSP simulation fidelity are incorporated into the OMFIT framework, contrasting between-shot analysis, power balance, and fast-particle simulations. A previouslymore » established series of data consistency metrics are computed such as comparison of experimental vs. calculated neutron rate, equilibrium stored energy vs. total stored energy from profile and fast-ion pressure, and experimental vs. computed surface loop voltage. Discrepancies between data consistency metrics can indicate errors in input quantities such as electron density profile or Zeff, or indicate anomalous fast-particle transport. Measures to assess the sensitivity of the verification metrics to input quantities are provided by OMFIT, including scans of the input profiles and standardized post-processing visualizations. For predictive simulations, TRANSP uses GLF23 or TGLF to predict core plasma profiles, with user defined boundary conditions in the outer region of the plasma. ITPA validation metrics are provided in post-processing to assess the transport model validity. By using OMFIT to orchestrate the steps for experimental data preparation, selection of operating mode, submission, post-processing and visualization, we have streamlined and standardized the usage of TRANSP.« less

Orchestrating TRANSP Simulations for Interpretative and Predictive Tokamak Modeling with OMFIT

DOE PAGES

Grierson, B. A.; Yuan, X.; Gorelenkova, M.; ...

2018-02-21

TRANSP simulations are being used in the OMFIT work- flow manager to enable a machine independent means of experimental analysis, postdictive validation, and predictive time dependent simulations on the DIII-D, NSTX, JET and C-MOD tokamaks. The procedures for preparing the input data from plasma profile diagnostics and equilibrium reconstruction, as well as processing of the time-dependent heating and current drive sources and assumptions about the neutral recycling, vary across machines, but are streamlined by using a common workflow manager. Settings for TRANSP simulation fidelity are incorporated into the OMFIT framework, contrasting between-shot analysis, power balance, and fast-particle simulations. A previouslymore » established series of data consistency metrics are computed such as comparison of experimental vs. calculated neutron rate, equilibrium stored energy vs. total stored energy from profile and fast-ion pressure, and experimental vs. computed surface loop voltage. Discrepancies between data consistency metrics can indicate errors in input quantities such as electron density profile or Zeff, or indicate anomalous fast-particle transport. Measures to assess the sensitivity of the verification metrics to input quantities are provided by OMFIT, including scans of the input profiles and standardized post-processing visualizations. For predictive simulations, TRANSP uses GLF23 or TGLF to predict core plasma profiles, with user defined boundary conditions in the outer region of the plasma. ITPA validation metrics are provided in post-processing to assess the transport model validity. By using OMFIT to orchestrate the steps for experimental data preparation, selection of operating mode, submission, post-processing and visualization, we have streamlined and standardized the usage of TRANSP.« less

Experimental investigation on densification behavior and surface roughness of AlSi10Mg powders produced by selective laser melting

NASA Astrophysics Data System (ADS)

Wang, Lin-zhi; Wang, Sen; Wu, Jiao-jiao

2017-11-01

Effects of laser energy density (LED) on densities and surface roughness of AlSi10Mg samples processed by selective laser melting were studied. The densification behaviors of the SLM manufactured AlSi10Mg samples at different LEDs were characterized by a solid densitometer, an industrial X-ray and CT detection system. A field emission scanning electron microscope, an automatic optical measuring system, and a surface profiler were used for measurements of surface roughness. The results show that relatively high density can be obtained with the point distance of 80-105 μm and the exposure time of 140-160 μs. The LED has an important influence on the surface morphology of the forming part, too high LED may lead to balling effect, while too low LED tends to produce defects, such as porosity and microcrack, and then affect surface roughness and porosities of the parts finally.

Effects of exogenous xylanase on performance, nutrient digestibility and caecal thermal profiles of broilers given wheat-based diets.

PubMed

Cowieson, A J; Masey O'Neill, H V

2013-06-01

1. Five dietary treatments were used in a 49 d broiler trial to assess the effect of xylanase on performance, nutrient digestibility and thermal profiles of the caeca and head. Treatments included an industry-standard control diet and four further diets where xylanase was introduced with or without a metabolisable energy density dilution either from day one or the introduction was delayed until d 28. 2. The addition of xylanase with no associated energy dilution from day one resulted in the most consistent beneficial effects on performance, with significant improvements in weight gain compared with the industry-standard to d 28 and at d 49. Addition of xylanase from d 28 (with no energy dilution) was the second most successful strategy and resulted in a significant improvement in feed conversion ratio (FCR) from d 29 to 49 and overall. 3. Addition of xylanase improved ileal digestible energy values at d 28 by around 0.35 MJ/kg and ileal nitrogen digestibility coefficients by around 3%. On d 49 xylanase improved ileal digestible energy values by around 0.9 MJ/kg and ileal nitrogen digestibility coefficients by around 4.6%. 4. Thermal imaging of the head and caeca of three birds per replicate on d 49 revealed a significant increase in caecal surface temperature following xylanase addition with no effect on head temperature profile. These increases were particularly large (around 1.4ºC, or 3.9%) when xylanase was added from day one with no corresponding energy dilution in feed formulation. 5. It can be concluded that supplemental xylanase is effective in improving performance and nutrient digestibility in broilers given wheat-based diets. The correlation between the magnitude of this effect and the increased temperature in the caeca presents additional evidence that the hind-gut microflora may play an important, if yet unquantified, role in the outworking of these mechanisms.

Tidal asymmetries of velocity and stratification over a bathymetric depression in a tropical inlet

NASA Astrophysics Data System (ADS)

Waterhouse, Amy F.; Valle-Levinson, Arnoldo; Morales Pérez, Rubén A.

2012-10-01

Observations of current velocity, sea surface elevation and vertical profiles of density were obtained in a tropical inlet to determine the effect of a bathymetric depression (hollow) on the tidal flows. Surveys measuring velocity profiles were conducted over a diurnal tidal cycle with mixed spring tides during dry and wet seasons. Depth-averaged tidal velocities during ebb and flood tides behaved according to Bernoulli dynamics, as expected. The dynamic balance of depth-averaged quantities in the along-channel direction was governed by along-channel advection and pressure gradients with baroclinic pressure gradients only being important during the wet season. The vertical structure of the along-channel flow during flood tides exhibited a mid-depth maximum with lateral shear enhanced during the dry season as a result of decreased vertical stratification. During ebb tides, along-channel velocities in the vicinity of the hollow were vertically sheared with a weak return flow at depth due to choking of the flow on the seaward slope of the hollow. The potential energy anomaly, a measure of the amount of energy required to fully mix the water column, showed two peaks in stratification associated with ebb tide and a third peak occurring at the beginning of flood. After the first mid-ebb peak in stratification, ebb flows were constricted on the seaward slope of the hollow resulting in a bottom return flow. The sinking of surface waters and enhanced mixing on the seaward slope of the hollow reduced the potential energy anomaly after maximum ebb. The third peak in stratification during early flood occurred as a result of denser water entering the inlet at mid-depth. This dense water mixed with ambient deep waters increasing the stratification. Lateral shear in the along-channel flow across the hollow allowed trapping of less dense water in the surface layers further increasing stratification.

Linear particle accelerator with seal structure between electrodes and insulators

DOEpatents

Broadhurst, John H.

1989-01-01

An electrostatic linear accelerator includes an electrode stack comprised of primary electrodes formed or Kovar and supported by annular glass insulators having the same thermal expansion rate as the electrodes. Each glass insulator is provided with a pair of fused-in Kovar ring inserts which are bonded to the electrodes. Each electrode is designed to define a concavo-convex particle trap so that secondary charged particles generated within the accelerated beam area cannot reach the inner surface of an insulator. Each insulator has a generated inner surface profile which is so configured that the electrical field at this surface contains no significant tangential component. A spark gap trigger assembly is provided, which energizes spark gaps protecting the electrodes affected by over voltage to prevent excessive energy dissipation in the electrode stack.

Analysis and optimization of surface profile correcting mechanism of the pitch lap in large-aperture annular polishing

NASA Astrophysics Data System (ADS)

Zhang, Huifang; Yang, Minghong; Xu, Xueke; Wu, Lunzhe; Yang, Weiguang; Shao, Jianda

2017-10-01

The surface figure control of the conventional annular polishing system is realized ordinarily by the interaction between the conditioner and the lap. The surface profile of the pitch lap corrected by the marble conditioner has been measured and analyzed as a function of kinematics, loading conditions, and polishing time. The surface profile measuring equipment of the large lap based on laser alignment was developed with the accuracy of about 1μm. The conditioning mechanism of the conditioner is simply determined by the kinematics and fully fitting principle, but the unexpected surface profile deviation of the lap emerged frequently due to numerous influencing factors including the geometrical relationship, the pressure distribution at the conditioner/lap interface. Both factors are quantitatively evaluated and described, and have been combined to develop a spatial and temporal model to simulate the surface profile evolution of pitch lap. The simulations are consistent with the experiments. This study is an important step toward deterministic full-aperture annular polishing, providing a beneficial guidance for the surface profile correction of the pitch lap.

Application of the SHARP Toolkit to Sodium-Cooled Fast Reactor Challenge Problems

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

Shemon, E. R.; Yu, Y.; Kim, T. K.

The Simulation-based High-efficiency Advanced Reactor Prototyping (SHARP) toolkit is under development by the Nuclear Energy Advanced Modeling and Simulation (NEAMS) Campaign of the U.S. Department of Energy, Office of Nuclear Energy. To better understand and exploit the benefits of advanced modeling simulations, the NEAMS Campaign initiated the “Sodium-Cooled Fast Reactor (SFR) Challenge Problems” task, which include the assessment of hot channel factors (HCFs) and the demonstration of zooming capability using the SHARP toolkit. If both challenge problems are resolved through advanced modeling and simulation using the SHARP toolkit, the economic competitiveness of a SFR can be significantly improved. The effortsmore » in the first year of this project focused on the development of computational models, meshes, and coupling procedures for multi-physics calculations using the neutronics (PROTEUS) and thermal-hydraulic (Nek5000) components of the SHARP toolkit, as well as demonstration of the HCF calculation capability for the 100 MWe Advanced Fast Reactor (AFR-100) design. Testing the feasibility of the SHARP zooming capability is planned in FY 2018. The HCFs developed for the earlier SFRs (FFTF, CRBR, and EBR-II) were reviewed, and a subset of these were identified as potential candidates for reduction or elimination through high-fidelity simulations. A one-way offline coupling method was used to evaluate the HCFs where the neutronics solver PROTEUS computes the power profile based on an assumed temperature, and the computational fluid dynamics solver Nek5000 evaluates the peak temperatures using the neutronics power profile. If the initial temperature profile used in the neutronics calculation is reasonably accurate, the one-way offline method is valid because the neutronics power profile has weak dependence on small temperature variation. In order to get more precise results, the proper temperature profile for initial neutronics calculations was obtained from the STAR-CCM+ calculations. The HCFs of the peak temperatures at cladding outer surface, cladding inner wall surface, and fuel centerline induced by cladding manufacturing tolerance and uncertainties on the cladding, coolant, and fuel properties were evaluated for the AFR-100. Some assessment on the effect of wire wrap configuration and size of the bundle shows that it is practical to use the 7-pin bare rod bundle to calculate the HCFs. The resulting HCFs obtained from the high-fidelity SHARP calculations are generally smaller than those developed for the earlier SFRs because the most uncertainties involved in the modeling and simulations were disappeared. For completeness, additional investigations are planned in FY 2018, which will use random sampling techniques.« less

How Well are Recent Climate Variability Signals Resolved by Satellite Radiative Flux Estimates?

NASA Technical Reports Server (NTRS)

Robertson, Franklin R.; Lu, H.-L.

2004-01-01

One notable aspect of Earth s climate is that although the planet appears to be very close to radiative balance at top-of-atmosphere (TOA), the atmosphere itself and underlying surface are not. Profound exchanges of energy between the atmosphere and oceans, land and cryosphere occur over a range of time scales. Recent evidence from broadband satellite measurements suggests that even these TOA fluxes contain some detectable variations. Our ability to measure and reconstruct radiative fluxes at the surface and at the top of atmosphere is improving rapidly. Understanding the character of radiative flux estimates and relating them to variations in other energy fluxes and climate state variables is key to improving our understanding of climate. In this work we will evaluate several recently released estimates of radiative fluxes, focusing primarily on surface estimates. The International Satellite Cloud Climatology Project FD radiative flux profiles are available from rnid-1983 to near present and have been constructed by driving the radiative transfer physics from the Goddard Institute for Space Studies (GISS) global model with ISCCP clouds and HlRS operational soundings profiles. Full and clear sky SW and LW fluxes are produced. A similar product from the NASA/GEWEX Surface Radiation Budget Project using different radiative flux codes and thermodynamics from the NASA/Goddard Earth Observing System assimilation model makes a similar calculation of surface fluxes. However this data set currently extends only through 1995. Several estimates of downward LW flux at the surface inferred from microwave data are also examined. Since these products have been evaluated with Baseline Surface Radiation Network data over land we focus over ocean regions and use the DOE/NOAA/NASA Shipboard Ocean Atmospheric Radiation (SOAR) surface flux measurements to characterize performance of these data sets under both clear and cloudy conditions. Some aspects of performance are stratified according to SST and vertical motion regimes. Comparisons to the TRMM/CERES SRB data in 1998 are also interpreted. These radiative fluxes are then analyzed to determine how surface (and TOA) radiative exchanges respond to interannual signals of ENS0 warm and cold events. Our analysis includes regional changes as well as integrated signals over land, ocean and various latitude bands. Changes in water vapor and cloud forcing signatures are prominent on interannual time scales. Prominent signals are also found in the SW fluxes for the Pinatubo volcanic event. These systematic changes in fluxes are related to changes in large-scale circulations and energy transport in the atmosphere and ocean. Some estimates of signal-to-noise and reliability are discussed to place our results in context.

Transonic streamline of symmetric wing under the influence unilateral oscillations characterized by the spectrum of two frequencies

NASA Astrophysics Data System (ADS)

Zamuraev, V. P.; Kalinina, A. P.

2017-10-01

Forced high-frequency vibrations of the airfoil surface part with the amplitude almost equal to the sound velocity can change significantly the lift force of the symmetric profile streamlined at zero angle of attack. The oscillation consists of two harmonics. The ratio of harmonics frequencies values is equal to 2. The present work shows that the aerodynamic properties depend significantly on the specific energy contribution of each frequency.

SU-F-T-371: Development of a Linac Monte Carlo Model to Calculate Surface Dose

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

Prajapati, S; Yan, Y; Gifford, K

2016-06-15

Purpose: To generate and validate a linac Monte Carlo (MC) model for surface dose prediction. Methods: BEAMnrc V4-2.4.0 was used to model 6 and 18 MV photon beams for a commercially available linac. DOSXYZnrc V4-2.4.0 calculated 3D dose distributions in water. Percent depth dose (PDD) and beam profiles were extracted for comparison to measured data. Surface dose and at depths in the buildup region was measured with radiochromic film at 100 cm SSD for 4 × 4 cm{sup 2} and 10 × 10 cm{sup 2} collimator settings for open and MLC collimated fields. For the 6 MV beam, films weremore » placed at depths ranging from 0.015 cm to 2 cm and for 18 MV, 0.015 cm to 3.5 cm in Solid Water™. Films were calibrated for both photon energies at their respective dmax. PDDs and profiles were extracted from the film and compared to the MC data. The MC model was adjusted to match measured PDD and profiles. Results: For the 6 MV beam, the mean error(ME) in PDD between film and MC for open fields was 1.9%, whereas it was 2.4% for MLC. For the 18 MV beam, the ME in PDD for open fields was 2% and was 3.5% for MLC. For the 6 MV beam, the average root mean square(RMS) deviation for the central 80% of the beam profile for open fields was 1.5%, whereas it was 1.6% for MLC. For the 18 MV beam, the maximum RMS for open fields was 3%, and was 3.1% for MLC. Conclusion: The MC model of a linac agreed to within 4% of film measurements for depths ranging from the surface to dmax. Therefore, the MC linac model can predict surface dose for clinical applications. Future work will focus on adjusting the linac MC model to reduce RMS error and improve accuracy.« less

The impact of surface area, volume, curvature, and Lennard-Jones potential to solvation modeling.

PubMed

Nguyen, Duc D; Wei, Guo-Wei

2017-01-05

This article explores the impact of surface area, volume, curvature, and Lennard-Jones (LJ) potential on solvation free energy predictions. Rigidity surfaces are utilized to generate robust analytical expressions for maximum, minimum, mean, and Gaussian curvatures of solvent-solute interfaces, and define a generalized Poisson-Boltzmann (GPB) equation with a smooth dielectric profile. Extensive correlation analysis is performed to examine the linear dependence of surface area, surface enclosed volume, maximum curvature, minimum curvature, mean curvature, and Gaussian curvature for solvation modeling. It is found that surface area and surfaces enclosed volumes are highly correlated to each other's, and poorly correlated to various curvatures for six test sets of molecules. Different curvatures are weakly correlated to each other for six test sets of molecules, but are strongly correlated to each other within each test set of molecules. Based on correlation analysis, we construct twenty six nontrivial nonpolar solvation models. Our numerical results reveal that the LJ potential plays a vital role in nonpolar solvation modeling, especially for molecules involving strong van der Waals interactions. It is found that curvatures are at least as important as surface area or surface enclosed volume in nonpolar solvation modeling. In conjugation with the GPB model, various curvature-based nonpolar solvation models are shown to offer some of the best solvation free energy predictions for a wide range of test sets. For example, root mean square errors from a model constituting surface area, volume, mean curvature, and LJ potential are less than 0.42 kcal/mol for all test sets. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Response of Moist Convection to Multi-scale Surface Flux Heterogeneity

NASA Astrophysics Data System (ADS)

Kang, S. L.; Ryu, J. H.

2015-12-01

We investigate response of moist convection to multi-scale feature of the spatial variation of surface sensible heat fluxes (SHF) in the afternoon evolution of the convective boundary layer (CBL), utilizing a mesoscale-domain large eddy simulation (LES) model. The multi-scale surface heterogeneity feature is analytically created as a function of the spectral slope in the wavelength range from a few tens of km to a few hundreds of m in the spectrum of surface SHF on a log-log scale. The response of moist convection to the κ-3 - slope (where κ is wavenumber) surface SHF field is compared with that to the κ-2 - slope surface, which has a relatively weak mesoscale feature, and the homogeneous κ0 - slope surface. Given the surface energy balance with a spatially uniform available energy, the prescribed SHF has a 180° phase lag with the latent heat flux (LHF) in a horizontal domain of (several tens of km)2. Thus, warmer (cooler) surface is relatively dry (moist). For all the cases, the same observation-based sounding is prescribed for the initial condition. For all the κ-3 - slope surface heterogeneity cases, early non-precipitating shallow clouds further develop into precipitating deep thunderstorms. But for all the κ-2 - slope cases, only shallow clouds develop. We compare the vertical profiles of domain-averaged fluxes and variances, and the contribution of the mesoscale and turbulence contributions to the fluxes and variances, between the κ-3 versus κ-2 slope cases. Also the cross-scale processes are investigated.

N-Type delta Doping of High-Purity Silicon Imaging Arrays

NASA Technical Reports Server (NTRS)

Blacksberg, Jordana; Hoenk, Michael; Nikzad, Shouleh

2005-01-01

A process for n-type (electron-donor) delta doping has shown promise as a means of modifying back-illuminated image detectors made from n-doped high-purity silicon to enable them to detect high-energy photons (ultraviolet and x-rays) and low-energy charged particles (electrons and ions). This process is applicable to imaging detectors of several types, including charge-coupled devices, hybrid devices, and complementary metal oxide/semiconductor detector arrays. Delta doping is so named because its density-vs.-depth characteristic is reminiscent of the Dirac delta function (impulse function): the dopant is highly concentrated in a very thin layer. Preferably, the dopant is concentrated in one or at most two atomic layers in a crystal plane and, therefore, delta doping is also known as atomic-plane doping. The use of doping to enable detection of high-energy photons and low-energy particles was reported in several prior NASA Tech Briefs articles. As described in more detail in those articles, the main benefit afforded by delta doping of a back-illuminated silicon detector is to eliminate a "dead" layer at the back surface of the silicon wherein high-energy photons and low-energy particles are absorbed without detection. An additional benefit is that the delta-doped layer can serve as a back-side electrical contact. Delta doping of p-type silicon detectors is well established. The development of the present process addresses concerns specific to the delta doping of high-purity silicon detectors, which are typically n-type. The present process involves relatively low temperatures, is fully compatible with other processes used to fabricate the detectors, and does not entail interruption of those processes. Indeed, this process can be the last stage in the fabrication of an imaging detector that has, in all other respects, already been fully processed, including metallized. This process includes molecular-beam epitaxy (MBE) for deposition of three layers, including metallization. The success of the process depends on accurate temperature control, surface treatment, growth of high-quality crystalline silicon, and precise control of thicknesses of layers. MBE affords the necessary nanometer- scale control of the placement of atoms for delta doping. More specifically, the process consists of MBE deposition of a thin silicon buffer layer, the n-type delta doping layer, and a thin silicon cap layer. The n dopant selected for initial experiments was antimony, but other n dopants as (phosphorus or arsenic) could be used. All n-type dopants in silicon tend to surface-segregate during growth, leading to a broadened dopant-concentration- versus-depth profile. In order to keep the profile as narrow as possible, the substrate temperature is held below 300 C during deposition of the silicon cap layer onto the antimony delta layer. The deposition of silicon includes a silicon- surface-preparation step, involving H-termination, that enables the growth of high-quality crystalline silicon at the relatively low temperature with close to full electrical activation of donors in the surface layer.

Recoil implantation of boron into silicon by high energy silicon ions

NASA Astrophysics Data System (ADS)

Shao, L.; Lu, X. M.; Wang, X. M.; Rusakova, I.; Mount, G.; Zhang, L. H.; Liu, J. R.; Chu, Wei-Kan

2001-07-01

A recoil implantation technique for shallow junction formation was investigated. After e-gun deposition of a B layer onto Si, 10, 50, or 500 keV Si ion beams were used to introduce surface deposited B atoms into Si by knock-on. It has been shown that recoil implantation with high energy incident ions like 500 keV produces a shallower B profile than lower energy implantation such as 10 keV and 50 keV. This is due to the fact that recoil probability at a given angle is a strong function of the energy of the primary projectile. Boron diffusion was showed to be suppressed in high energy recoil implantation and such suppression became more obvious at higher Si doses. It was suggested that vacancy rich region due to defect imbalance plays the role to suppress B diffusion. Sub-100 nm junction can be formed by this technique with the advantage of high throughput of high energy implanters.

`Surface-Layer' momentum fluxes in nocturnal slope flows over steep terrain

NASA Astrophysics Data System (ADS)

Oldroyd, H. J.; Pardyjak, E.; Higgins, C. W.; Parlange, M. B.

2017-12-01

A common working definition for the `surface layer' is the lowest 10% of the atmospheric boundary layer (ABL) where the turbulent fluxes are essentially constant. The latter part of this definition is a critical assumption that must hold for accurate flux estimations from land-surface models, wall models, similarity theory, flux-gradient relations and bulk transfer methods. We present cases from observed momentum fluxes in nocturnal slope flows over steep (35.5 degree), alpine terrain in Val Ferret, Switzerland that satisfy the classical definitions of the surface layer and other cases where no traditional surface layer is observed. These cases broadly fall into two distinct flow regimes occurring under clear-sky conditions: (1) buoyancy-driven, `katabatic flow', characterized by an elevated velocity maximum (katabatic jet peak) and (2) `downslope winds', for which larger-scale forcing prevents formation of a katabatic jet. Velocity profiles in downslope wind cases are quite similar to logarithmic profiles typically observed over horizontal and homogeneous terrain, and the corresponding momentum fluxes roughly resemble a constant-flux surface-layer. Contrastingly, velocity profiles in the katabatic regime exhibit a jet-like shape. This jet strongly modulates the corresponding momentum fluxes, which exhibit strong gradients over the shallow katabatic layer and usually change sign near the jet peak, where the velocity gradients also change sign. However, a counter-gradient momentum flux is frequently observed near the jet peak (and sometimes at higher levels), suggesting strong non-local turbulent transport within the katabatic jet layer. We compare our observations with katabatic flow theories and observational studies over shallow-angle slopes and use co-spectral analyses to better identify and understand the non-local transport dynamics. Finally, we show that because of the counter-gradient momentum fluxes, surface layer stability and even local stability can be difficult to characterize because the counter-gradient momentum flux represents a sink in the shear term of turbulence kinetic energy budget equation. These results have broad implications for stability-based modeling and general definitions and assumptions used for the ABL and so-called `surface layer' over steep terrain.

From the chlorophyll a in the surface layer to its vertical profile: a Greenland Sea relationship for satellite applications

NASA Astrophysics Data System (ADS)

Cherkasheva, A.; Nöthig, E.-M.; Bauerfeind, E.; Melsheimer, C.; Bracher, A.

2013-04-01

Current estimates of global marine primary production range over a factor of two. Improving these estimates requires an accurate knowledge of the chlorophyll vertical profiles, since they are the basis for most primary production models. At high latitudes, the uncertainty in primary production estimates is larger than globally, because here phytoplankton absorption shows specific characteristics due to the low-light adaptation, and in situ data and ocean colour observations are scarce. To date, studies describing the typical chlorophyll profile based on the chlorophyll in the surface layer have not included the Arctic region, or, if it was included, the dependence of the profile shape on surface concentration was neglected. The goal of our study was to derive and describe the typical Greenland Sea chlorophyll profiles, categorized according to the chlorophyll concentration in the surface layer and further monthly resolved profiles. The Greenland Sea was chosen because it is known to be one of the most productive regions of the Arctic and is among the regions in the Arctic where most chlorophyll field data are available. Our database contained 1199 chlorophyll profiles from R/Vs Polarstern and Maria S. Merian cruises combined with data from the ARCSS-PP database (Arctic primary production in situ database) for the years 1957-2010. The profiles were categorized according to their mean concentration in the surface layer, and then monthly median profiles within each category were calculated. The category with the surface layer chlorophyll (CHL) exceeding 0.7 mg C m-3 showed values gradually decreasing from April to August. A similar seasonal pattern was observed when monthly profiles were averaged over all the surface CHL concentrations. The maxima of all chlorophyll profiles moved from the greater depths to the surface from spring to late summer respectively. The profiles with the smallest surface values always showed a subsurface chlorophyll maximum with its median magnitude reaching up to three times the surface concentration. While the variability of the Greenland Sea season in April, May and June followed the global non-monthly resolved relationship of the chlorophyll profile to surface chlorophyll concentrations described by the model of Morel and Berthon (1989), it deviated significantly from the model in the other months (July-September), when the maxima of the chlorophyll are at quite different depths. The Greenland Sea dimensionless monthly median profiles intersected roughly at one common depth within each category. By applying a Gaussian fit with 0.1 mg C m-3 surface chlorophyll steps to the median monthly resolved chlorophyll profiles of the defined categories, mathematical approximations were determined. They generally reproduce the magnitude and position of the CHL maximum, resulting in an average 4% underestimation in Ctot (and 2% in rough primary production estimates) when compared to in situ estimates. These mathematical approximations can be used as the input to the satellite-based primary production models that estimate primary production in the Arctic regions.

Recoverable stress induced two-way shape memory effect on NiTi surface using laser-produced shock wave

NASA Astrophysics Data System (ADS)

Seyitliyev, Dovletgeldi; Li, Peizhen; Kholikov, Khomidkhodza; Grant, Byron; Thomas, Zachary; Alal, Orhan; Karaca, Haluk E.; Er, Ali O.

2017-02-01

The surfaces of Ni50Ti50 shape memory alloys (SMAs) were patterned by laser scribing. This method is more simplistic and efficient than traditional indentation techniques, and has also shown to be an effective method in patterning these materials. Different laser energy densities ranging from 5 mJ/pulse to 56 mJ/pulse were used to observe recovery on SMA surface. The temperature dependent heat profiles of the NiTi surfaces after laser scribing at 56 mJ/pulse show the partially-recovered indents, which indicate a "shape memory effect (SME)" Experimental data is in good agreement with theoretical simulation of laser induced shock wave propagation inside NiTi SMAs. Stress wave closely followed the rise time of the laser pulse to its peak values and initial decay. Further investigations are underway to improve the SME such that the indents are recovered to a greater extent.

Experimental and Numerical Analysis of Microstructures and Stress States of Shot-Peened GH4169 Superalloys

NASA Astrophysics Data System (ADS)

Hu, Dianyin; Gao, Ye; Meng, Fanchao; Song, Jun; Wang, Rongqiao

2018-04-01

Combining experiments and finite element analysis (FEA), a systematic study was performed to analyze the microstructural evolution and stress states of shot-peened GH4169 superalloy over a variety of peening intensities and coverages. A dislocation density evolution model was integrated into the representative volume FEA model to quantitatively predict microstructural evolution in the surface layers and compared with experimental results. It was found that surface roughness and through-depth residual stress profile are more sensitive to shot-peening intensity compared to coverage due to the high kinetic energy involved. Moreover, a surface nanocrystallization layer was discovered in the top surface region of GH4169 for all shot-peening conditions. However, the grain refinement was more intensified under high shot-peening coverage, under which enough time was permitted for grain refinement. The grain size gradient predicted by the numerical framework showed good agreement with experimental observations.

A Self-Organizing Map Based Evaluation of the Antarctic Mesoscale Prediction System Using Observations from a 30-m Instrumented Tower on the Ross Ice Shelf, Antarctica

NASA Astrophysics Data System (ADS)

Nigro, M. A.; Cassano, J. J.; Wille, J.; Bromwich, D. H.; Lazzara, M. A.

2015-12-01

An accurate representation of the atmospheric boundary layer in numerical weather prediction models is important for predicting turbulence and energy exchange in the atmosphere. This study uses two years of observations from a 30-m automatic weather station (AWS) installed on the Ross Ice Shelf, Antarctica to evaluate forecasts from the Antarctic Mesoscale Prediction System (AMPS), a numerical weather prediction system based on the polar version of the Weather Research and Forecasting (Polar WRF) model that uses the MYJ planetary boundary layer scheme and that primarily supports the extensive aircraft operations of the U.S. Antarctic Program. The 30-m AWS has six levels of instrumentation, providing vertical profiles of temperature, wind speed, and wind direction. The observations show the atmospheric boundary layer over the Ross Ice Shelf is stable approximately 80% of the time, indicating the influence of the permanent ice surface in this region. The observations from the AWS are further analyzed using the method of self-organizing maps (SOM) to identify the range of potential temperature profiles that occur over the Ross Ice Shelf. The SOM analysis identified 30 patterns, which range from strong inversions to slightly unstable profiles. The corresponding AMPS forecasts were evaluated for each of the 30 patterns to understand the accuracy of the AMPS near surface layer under different atmospheric conditions. The results indicate that under stable conditions AMPS with MYJ under predicts the inversion strength by as much as 7.4 K over the 30-m depth of the tower and over predicts the near surface wind speed by as much as 3.8 m s-1. Conversely, under slightly unstable conditions, AMPS predicts both the inversion strength and near surface wind speeds with reasonable accuracy.

Gravity waves in Titan's atmosphere

NASA Technical Reports Server (NTRS)

Friedson, A. James

1994-01-01

Scintillations (high frequency variations) observed in the radio signal during the occultation of Voyager 1 by Titan (Hinson and Tyler, 1983) provide information concerning neutral atmospheric density fluctuations on scales on hundreds of meters to a few kilometers. Those seen at altitudes higher than 25 km above the surface were interpreted by Hinson and Tyler as being caused by linear, freely propagating (energy-conserving) gravity waves, but this interpretation was found to be inconsistent with the scintillation data below the 25-km altitude level. Here an attempt is made to interpret the entire scintillation profile between the surface and the 90-km altitude level in terms of gravity waves generated at the surface. Numerical calculations of the density fluctuations caused by two-dimensional, nonhydrostatic, finite-amplitude gravity waves propagating vertically through Titan's atmosphere are performed to produce synthetic scintillation profiles for comparison with the observations. The numerical model accurately treats the effects of wave transience, nonlinearity, and breakdown due to convective instability in the overturned part of the wave. The high-altitude scintillation data were accurately recovered with a freely propagating wave solution, confirming the analytic model of Hinson and Tyler. It is found that the low-altitude scintillation data can be fit by a model where a component of the gravity waves becomes convectively unstable and breaks near the 15 km level. The large-scale structure of the observed scintillation profile in the entire altitude range between 5 and 85 km can be simulated by a model where the freely propagating and breaking waves are forced at the surface simultaneously. Further analysis of the Voyager 1 Titan low-altitude scintillation data, using inversion theory appropriate for strong scattering, could potentially remove some of the ambiguities remaining in this analysis and allow a better determination of the strength and source of the waves.

Effect of surface modification on hydration kinetics of carbamazepine anhydrate using isothermal microcalorimetry.

PubMed

Otsuka, Makoto; Ishii, Mika; Matsuda, Yoshihisa

2003-01-01

The purpose of this research was to improve the stability of carbamazepine (CBZ) bulk powder under high humidity by surface modification. The surface-modified anhydrates of CBZ were obtained in a specially designed surface modification apparatus at 60 degrees C via the adsorption of n-butanol, and powder x-ray diffraction, Fourier-Transformed Infrared spectra, and differential scanning calorimetry were used to determine the crystalline characteristics of the samples. The hydration process of intact and surface-modified CBZ anhydrate at 97% relative humidity (RH) and 40 +/-C 1 degrees C was automatically monitored by using isothermal microcalorimetry (IMC). The dissolution test for surface-modified samples (20 mg) was performed in 900 mL of distilled water at 37 +/-C 0.5 degrees C with stirring by a paddle at 100 rpm as in the Japanese Pharmacopoeia XIII. The heat flow profiles of hydration of intact and surface-modified CBZ anhydrates at 97% RH by using IMC profiles showed a maximum peak at around 10 hours and 45 hours after 0 and 10 hours of induction, respectively. The result indicated that hydration of CBZ anhydrate was completely inhibited at the initial stage by surface modification of n-butanol and thereafter transformed into dihydrate. The hydration of surface-modified samples followed a 2-dimensional phase boundary process with an induction period (IP). The IP of intact and surface-modified samples decreased with increase of the reaction temperature, and the hydration rate constant (k) increased with increase of the temperature. The crystal growth rate constants of nuclei of the intact sample were significantly larger than the surface-modified sample's at each temperature. The activation energy (E) of nuclei formation and crystal growth process for hydration of surface-modified CBZ anhydrate were evaluated to be 20.1 and 32.5 kJ/mol, respectively, from Arrhenius plots, but the Es of intact anhydrate were 56.3 and 26.8 kJ/mol, respectively. The dissolution profiles showed that the surface-modified sample dissolved faster than the intact sample at the initial stage. The dissolution kinetics were analyzed based on the Hixon-Crowell equation, and the dissolution rate constants for intact and surface-modified anhydrates were found to be 0.0102 +/-C 0.008 mg(1/3) x min(-1) and 0.1442 +/-C 0.0482 mg(1/3) x min(-1). The surface-modified anhydrate powders were more stable than the nonmodified samples under high humidity and showed resistance against moisture. However, surface modification induced rapid dissolution in water compared to the control.

How well Can We Classify SWOT-derived Water Surface Profiles?

NASA Astrophysics Data System (ADS)

Frasson, R. P. M.; Wei, R.; Picamilh, C.; Durand, M. T.

2015-12-01

The upcoming Surface Water Ocean Topography (SWOT) mission will detect water bodies and measure water surface elevation throughout the globe. Within its continental high resolution mask, SWOT is expected to deliver measurements of river width, water elevation and slope of rivers wider than ~50 m. The definition of river reaches is an integral step of the computation of discharge based on SWOT's observables. As poorly defined reaches can negatively affect the accuracy of discharge estimations, we seek strategies to break up rivers into physically meaningful sections. In the present work, we investigate how accurately we can classify water surface profiles based on simulated SWOT observations. We assume that most river sections can be classified as either M1 (mild slope, with depth larger than the normal depth), or A1 (adverse slope with depth larger than the critical depth). This assumption allows the classification to be based solely on the second derivative of water surface profiles, with convex profiles being classified as A1 and concave profiles as M1. We consider a HEC-RAS model of the Sacramento River as a representation of the true state of the river. We employ the SWOT instrument simulator to generate a synthetic pass of the river, which includes our best estimates of height measurement noise and geolocation errors. We process the resulting point cloud of water surface heights with the RiverObs package, which delineates the river center line and draws the water surface profile. Next, we identify inflection points in the water surface profile and classify the sections between the inflection points. Finally, we compare our limited classification of simulated SWOT-derived water surface profile to the "exact" classification of the modeled Sacramento River. With this exercise, we expect to determine if SWOT observations can be used to find inflection points in water surface profiles, which would bring knowledge of flow regimes into the definition of river reaches.

Nonequilibrium study of the intrinsic free-energy profile across a liquid-vapour interface

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

Braga, Carlos, E-mail: ccorreia@imperial.ac.uk; Muscatello, Jordan, E-mail: jordan.muscatello@imperial.ac.uk; Lau, Gabriel, E-mail: gabriel.lau07@imperial.ac.uk

2016-01-28

We calculate an atomistically detailed free-energy profile across a heterogeneous system using a nonequilibrium approach. The path-integral formulation of Crooks fluctuation theorem is used in conjunction with the intrinsic sampling method to calculate the free-energy profile for the liquid-vapour interface of the Lennard-Jones fluid. Free-energy barriers are found corresponding to the atomic layering in the liquid phase as well as a barrier associated with the presence of an adsorbed layer as revealed by the intrinsic density profile. Our findings are in agreement with profiles calculated using Widom’s potential distribution theorem applied to both the average and the intrinsic profiles asmore » well as the literature values for the excess chemical potential.« less

Surface characterization protocol for precision aspheric optics

NASA Astrophysics Data System (ADS)

Sarepaka, RamaGopal V.; Sakthibalan, Siva; Doodala, Somaiah; Panwar, Rakesh S.; Kotaria, Rajendra

2017-10-01

In Advanced Optical Instrumentation, Aspherics provide an effective performance alternative. The aspheric fabrication and surface metrology, followed by aspheric design are complementary iterative processes for Precision Aspheric development. As in fabrication, a holistic approach of aspheric surface characterization is adopted to evaluate actual surface error and to aim at the deliverance of aspheric optics with desired surface quality. Precision optical surfaces are characterized by profilometry or by interferometry. Aspheric profiles are characterized by contact profilometers, through linear surface scans to analyze their Form, Figure and Finish errors. One must ensure that, the surface characterization procedure does not add to the resident profile errors (generated during the aspheric surface fabrication). This presentation examines the errors introduced post-surface generation and during profilometry of aspheric profiles. This effort is to identify sources of errors and is to optimize the metrology process. The sources of error during profilometry may be due to: profilometer settings, work-piece placement on the profilometer stage, selection of zenith/nadir points of aspheric profiles, metrology protocols, clear aperture - diameter analysis, computational limitations of the profiler and the software issues etc. At OPTICA, a PGI 1200 FTS contact profilometer (Taylor-Hobson make) is used for this study. Precision Optics of various profiles are studied, with due attention to possible sources of errors during characterization, with multi-directional scan approach for uniformity and repeatability of error estimation. This study provides an insight of aspheric surface characterization and helps in optimal aspheric surface production methodology.

Implantation of sodium ions into germanium

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

Korol', V. M., E-mail: vkorol@ctsnet.ru; Kudriavtsev, Yu.

The donor properties of Na atoms introduced by ion implantation into p-Ge with the resistivity 20-40 {Omega} cm are established for the first time. Na profiles implanted into Ge (the energies 70 and 77 keV and the doses (0.8, 3, 30) Multiplication-Sign 10{sup 14} cm{sup -2}) are studied. The doses and annealing temperatures at which the thermoprobe detects n-type conductivity on the sample surface are established. After implantation, the profiles exhibit an extended tail. The depth of the concentration maximum is in good agreement with the calculated mean projected range of Na ions R{sub p}. Annealing for 30 min atmore » temperatures of 250-700 Degree-Sign C brings about a redistribution of Na atoms with the formation of segregation peaks at a depth, which is dependent on the ion dose, and is accompanied by the diffusion of Na atoms to the surface with subsequent evaporation. After annealing at 700 Degree-Sign C less than 7% of the implanted ions remain in the matrix. The shape of the profile tail portions measured after annealing at temperatures 300-400 Degree-Sign C is indicative of the diffusion of a small fraction of Na atoms into the depth of the sample.« less

The Effect of Wind-Turbine Wakes on Summertime US Midwest Atmospheric Wind Profiles as Observed with Ground-Based Doppler Lidar

NASA Astrophysics Data System (ADS)

Rhodes, Michael E.; Lundquist, Julie K.

2013-07-01

We examine the influence of a modern multi-megawatt wind turbine on wind and turbulence profiles three rotor diameters (D) downwind of the turbine. Light detection and ranging (lidar) wind-profile observations were collected during summer 2011 in an operating wind farm in central Iowa at 20-m vertical intervals from 40 to 220 m above the surface. After a calibration period during which two lidars were operated next to each other, one lidar was located approximately 2D directly south of a wind turbine; the other lidar was moved approximately 3D north of the same wind turbine. Data from the two lidars during southerly flow conditions enabled the simultaneous capture of inflow and wake conditions. The inflow wind and turbulence profiles exhibit strong variability with atmospheric stability: daytime profiles are well-mixed with little shear and strong turbulence, while nighttime profiles exhibit minimal turbulence and considerable shear across the rotor disk region and above. Consistent with the observations available from other studies and with wind-tunnel and large-eddy simulation studies, measurable reductions in wake wind-speeds occur at heights spanning the wind turbine rotor (43-117 m), and turbulent quantities increase in the wake. In generalizing these results as a function of inflow wind speed, we find the wind-speed deficit in the wake is largest at hub height or just above, and the maximum deficit occurs when wind speeds are below the rated speed for the turbine. Similarly, the maximum enhancement of turbulence kinetic energy and turbulence intensity occurs at hub height, although observations at the top of the rotor disk do not allow assessment of turbulence in that region. The wind shear below turbine hub height (quantified here with the power-law coefficient) is found to be a useful parameter to identify whether a downwind lidar observes turbine wake or free-flow conditions. These field observations provide data for validating turbine-wake models and wind-tunnel observations, and for guiding assessments of the impacts of wakes on surface turbulent fluxes or surface temperatures downwind of turbines.

Prediction of protein-protein interaction sites using electrostatic desolvation profiles.

PubMed

Fiorucci, Sébastien; Zacharias, Martin

2010-05-19

Protein-protein complex formation involves removal of water from the interface region. Surface regions with a small free energy penalty for water removal or desolvation may correspond to preferred interaction sites. A method to calculate the electrostatic free energy of placing a neutral low-dielectric probe at various protein surface positions has been designed and applied to characterize putative interaction sites. Based on solutions of the finite-difference Poisson equation, this method also includes long-range electrostatic contributions and the protein solvent boundary shape in contrast to accessible-surface-area-based solvation energies. Calculations on a large set of proteins indicate that in many cases (>90%), the known binding site overlaps with one of the six regions of lowest electrostatic desolvation penalty (overlap with the lowest desolvation region for 48% of proteins). Since the onset of electrostatic desolvation occurs even before direct protein-protein contact formation, it may help guide proteins toward the binding region in the final stage of complex formation. It is interesting that the probe desolvation properties associated with residue types were found to depend to some degree on whether the residue was outside of or part of a binding site. The probe desolvation penalty was on average smaller if the residue was part of a binding site compared to other surface locations. Applications to several antigen-antibody complexes demonstrated that the approach might be useful not only to predict protein interaction sites in general but to map potential antigenic epitopes on protein surfaces. Copyright (c) 2010 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Photocarrier Radiometry for Non-contact Evaluation of Monocrystalline Silicon Solar Cell Under Low-Energy (< 200 keV) Proton Irradiation

NASA Astrophysics Data System (ADS)

Oliullah, Md.; Liu, J. Y.; Song, P.; Wang, Y.

2018-06-01

A three-layer theoretical model is developed for the characterization of the electronic transport properties (lifetime τ, diffusion coefficient D, and surface recombination velocity s) with energetic particle irradiation on solar cells using non-contact photocarrier radiometry. Monte Carlo (MC) simulation is carried out to obtain the depth profiles of the proton irradiation layer at different low energies (< 200 keV). The monocrystalline silicon (c-Si) solar cells are investigated under different low-energy proton irradiation, and the carrier transport parameters of the three layers are obtained by best-fitting of the experimental results. The results show that the low-energy protons have little influence on the transport parameters of the non-irradiated layer, but high influences on both of the p and n-region irradiation layers which are consisted of MC simulation.

Resistivity profile effects in numerical magnetohydrodynamic simulations of the reversed-field pinch

NASA Astrophysics Data System (ADS)

Sätherblom, H.-E.; Mazur, S.; Nordlund, P.

1996-12-01

The influence of the resistivity profile on reversed-field pinch (RFP) dynamics is investigated numerically using a three-dimensional resistive magnetohydrodynamic code. This investigation is motivated by experimental observations on the EXTRAP-T1 RFP (Nordlund P et al 1994 Int. Conf. Plasma Physics and Controlled Nuclear Fusion Research IAEA-CN-60/A6/C-P-6). Two cases with profiles mainly differing in the edge region, i.e. in the region outside the reversal surface, are simulated. It is found that increasing the resistivity in this region results in a factor of two increase in magnetic fluctuation energy and an equal amount in the fluctuation-induced electric field. In spite of this, the parallel current decreases in the edge region, resulting in a factor two reduction of the field reversal ratio. The dynamics become more irregular and the characteristic timescale is reduced. The final state is characterized by a higher loop voltage, slightly lower values of the total (fluctuating plus mean part) magnetic energy and the magnetic helicity, but almost unchanged Taylor relaxation ratio. The results indicate that the edge region can be important for RFP confinement since cooling of the plasma in this region can lead to an increased fluctuation level and degraded performance.

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

Machado, Thales R.; QIO-UJI, Universitat Jaume I, 12071 Castellón; Sczancoski, Júlio C.

Defect-related photoluminescence (PL) in materials have attracted interest for applications including near ultraviolet (NUV) excitable light-emitting diodes and in biomedical field. In this paper, hydroxyapatite [Ca{sub 10}(PO{sub 4}){sub 6}(OH){sub 2}] nanorods with intense PL bands (bluish- and yellowish-white emissions) were obtained when excited under NUV radiation at room temperature. These nanoparticles were synthesized via chemical precipitation at 90 °C followed by distinct heat treatments temperatures (200–800 °C). Intense and broad emission profiles were achieved at 350 °C (380–750 nm) and 400 °C (380–800 nm). UV–Vis spectroscopy revealed band gap energies (5.58–5.78 eV) higher than the excitation energies (~3.54 and ~2.98more » eV at 350 and 415 nm, respectively), confirming the contribution of defect energy levels within the forbidden zone for PL emissions. The structural features were characterized by X-ray diffraction, Rietveld refinement, thermogravimetric analysis, and Fourier transform infrared spectroscopy. By means of these techniques, the relation between structural order-disorder induced by defects, chemical reactions at both lattice and surface of the materials as well as the PL, without activator centers, was discussed in details. - Graphical abstract: The self-activated photoluminescence emissions of chemically precipitated hydroxyapatite nanorods were improved by different heat treatment temperatures. - Highlights: • HA nanorods were synthesized with improved self-activated PL at room temperature. • PL profile and intensity dependents on the temperature of posterior heat treatments. • Bluish- and yellowish-white emissions under NUV excitation (350 and 415 nm). • Broad and intense profiles achieved at 350 °C (380–750 nm) and 400 °C (380–800 nm). • PL from the e′–h{sup •} recombination between defect energy levels within the band gap.« less

Investigation of Surface Treatments to Improve the Friction and Wear of Titanium Alloys for Diesel Engine Components

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

Blau, Peter J.; Cooley, Kevin M.; Kirkham, Melanie J.

This final report summarizes experimental and analytical work performed under an agreement between the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Office of Transportation Technologies, and UT-Battelle LLC. The project was directed by Jerry Gibbs, of the U.S. Department of Energy’s Propulsion Materials Program, with management by D. P. Stinton and J. A. Haynes of ORNL. Participants included Peter J. Blau (Principal Investigator), Kevin M. Cooley (senior technician), Melanie J. Kirkham (materials scientist) of the Materials Science and Technology Division or ORNL, and Dinesh G. Bansal, a post doctoral fellow employed by Oak Ridge Associated Universitiesmore » (ORAU) and who, at the time of this writing, is an engineer with Cummins, Inc. This report covers a three-year effort that involved two stages. In the first stage, and after a review of the literature and discussions with surface treatment experts, a series of candidate alloys and surface treatments for titanium alloy (Ti-6Al-4V) was selected for initial screening. After pre-screening using an ASTM standard test method, the more promising surface treatments were tested in Phase 2 using a variable loading apparatus that was designed and built to simulate the changing load patterns in a typical connecting rod bearing. Information on load profiles from the literature was supplemented with the help of T.C. Chen and Howard Savage of Cummins, Inc. Considering the dynamic and evolving nature of materials technology, this report presents a snapshot of commercial and experimental bearing surface technologies for titanium alloys that were available during the period of this work. Undoubtedly, further improvements in surface engineering methods for titanium will evolve.« less

Nature of the Lowstand Surface on the Gulf of Cádiz Shelf and the Guadiana Incised-Valley System: Preliminary Results from the LASEA 2013 Cruise

NASA Astrophysics Data System (ADS)

Lobo, F.; Lebreiro, S.; Antón, L.; Delivet, S.; Espinosa, S.; Fernández-Puga, M. C.; García, M.; Ibáñez, J.; Luján, M.; Mendes, I.; Reguera, M. I.; Sevillano, P.; Sinde, C.; Van Rooij, D.; Zarandona, P.

2014-12-01

The LASEA 2013 cruise was executed in August 2013 in the northern margin of the Gulf of Cádiz, with the main goal of collecting data from the Guadiana River-influenced shelf, in order to: (1) study changes affecting the entire drainage basin; (2) correlate shelf unit sequences with the upper slope sedimentary record, composed dominantly of contourite deposits in specific stretches of the margin. As a first approach, attention is paid to the most obvious sedimentary manifestation of the influence of the river on the shelf domain, represented by the Guadiana incised-valley system. The database comprises both geophysical and sedimentological records. Geophysical data include multibeam bathymetry, TOPAS profiles and single-channel Sparker seismic profiles. Sedimentological data include sediment cores collected with gravity- and vibro-corer devices. The lowstand erosional surface was mapped across the shelf. The lowstand surface exhibits two clearly contrasting patterns. In the outer shelf the surface isrepresented by an erosional truncation that can be planar or irregular. The lowstand surface is much more difficult to follow in the inner shelf, due to the amalgamation of erosional surfaces and the frequent stacking of coarse-grained deposits. Incised valleys are recognized at shallow waters (20-30 m) the most significant of them is at least 1.5 km wide in the most proximal (recognized) section, decreasing seawards in width. The internal architecture of the valley exhibits the intercalation of laterally prograding sediment bodies and high-amplitude, subparallel configurations laterally related to valley margin prograding wedges. The internal facies architecture suggests a transition from relatively high-energy fluvial to proximal estuarine environment to a lower-energy estuarine depositional environment. Thus, the study of the valley extension into the shelf is expected to provide clues for the recent reorganization of the entire fluvial system, during the course of the postglacial sea-level rise and ensuing sea-level stabilization. Acknowledgements: this study was completed in the framework of the project CGL2011-30302-C02-02. It is also a contribution to the INQUA International Focus Group on Rapid environmental changes and human activity impacting continental shelf systems.

Free-energy analysis of spin models on hyperbolic lattice geometries.

PubMed

Serina, Marcel; Genzor, Jozef; Lee, Yoju; Gendiar, Andrej

2016-04-01

We investigate relations between spatial properties of the free energy and the radius of Gaussian curvature of the underlying curved lattice geometries. For this purpose we derive recurrence relations for the analysis of the free energy normalized per lattice site of various multistate spin models in the thermal equilibrium on distinct non-Euclidean surface lattices of the infinite sizes. Whereas the free energy is calculated numerically by means of the corner transfer matrix renormalization group algorithm, the radius of curvature has an analytic expression. Two tasks are considered in this work. First, we search for such a lattice geometry, which minimizes the free energy per site. We conjecture that the only Euclidean flat geometry results in the minimal free energy per site regardless of the spin model. Second, the relations among the free energy, the radius of curvature, and the phase transition temperatures are analyzed. We found out that both the free energy and the phase transition temperature inherit the structure of the lattice geometry and asymptotically approach the profile of the Gaussian radius of curvature. This achievement opens new perspectives in the AdS-CFT correspondence theories.

Application of high-resolution linear Radon transform for Rayleigh-wave dispersive energy imaging and mode separating

USGS Publications Warehouse

Luo, Y.; Xia, J.; Miller, R.D.; Liu, J.; Xu, Y.; Liu, Q.

2008-01-01

Multichannel Analysis of Surface Waves (MASW) analysis is an efficient tool to obtain the vertical shear-wave profile. One of the key steps in the MASW method is to generate an image of dispersive energy in the frequency-velocity domain, so dispersion curves can be determined by picking peaks of dispersion energy. In this paper, we image Rayleigh-wave dispersive energy and separate multimodes from a multichannel record by high-resolution linear Radon transform (LRT). We first introduce Rayleigh-wave dispersive energy imaging by high-resolution LRT. We then show the process of Rayleigh-wave mode separation. Results of synthetic and real-world examples demonstrate that (1) compared with slant stacking algorithm, high-resolution LRT can improve the resolution of images of dispersion energy by more than 50% (2) high-resolution LRT can successfully separate multimode dispersive energy of Rayleigh waves with high resolution; and (3) multimode separation and reconstruction expand frequency ranges of higher mode dispersive energy, which not only increases the investigation depth but also provides a means to accurately determine cut-off frequencies.

Segregation Phenomena in Size-Selected Bimetallic CuNi Nanoparticle Catalysts

DOE PAGES

Pielsticker, Lukas; Zegkinoglou, Ioannis; Divins, Nuria J.; ...

2017-10-25

Surface segregation, restructuring, and sintering phenomena in size-selected copper–nickel nanoparticles (NPs) supported on silicon dioxide substrates were systematically investigated as a function of temperature, chemical state, and reactive gas environment. Using near-ambient pressure (NAP-XPS) and ultrahigh vacuum X-ray photoelectron spectroscopy (XPS), we showed that nickel tends to segregate to the surface of the NPs at elevated temperatures in oxygen- or hydrogen-containing atmospheres. It was found that the NP pretreatment, gaseous environment, and oxide formation free energy are the main driving forces of the restructuring and segregation trends observed, overshadowing the role of the surface free energy. The depth profile ofmore » the elemental composition of the particles was determined under operando CO 2 hydrogenation conditions by varying the energy of the X-ray beam. The temperature dependence of the chemical state of the two metals was systematically studied, revealing the high stability of nickel oxides on the NPs and the important role of high valence oxidation states in the segregation behavior. Atomic force microscopy (AFM) studies revealed a remarkable stability of the NPs against sintering at temperatures as high as 700 °C. The results provide new insights into the complex interplay of the various factors which affect alloy formation and segregation phenomena in bimetallic NP systems, often in ways different from those previously known for their bulk counterparts. In conclusion, this leads to new routes for tuning the surface composition of nanocatalysts, for example, through plasma and annealing pretreatments.« less

The role of the continuous wavelet transform in mineral identification using hyperspectral imaging in the long-wave infrared by using SVM classifier

NASA Astrophysics Data System (ADS)

Sojasi, Saeed; Yousefi, Bardia; Liaigre, Kévin; Ibarra-Castanedo, Clemente; Beaudoin, Georges; Maldague, Xavier P. V.; Huot, François; Chamberland, Martin

2017-05-01

Hyperspectral imaging (HSI) in the long-wave infrared spectrum (LWIR) provides spectral and spatial information concerning the emissivity of the surface of materials, which can be used for mineral identification. For this, an endmember, which is the purest form of a mineral, is used as reference. All pure minerals have specific spectral profiles in the electromagnetic wavelength, which can be thought of as the mineral's fingerprint. The main goal of this paper is the identification of minerals by LWIR hyperspectral imaging using a machine learning scheme. The information of hyperspectral imaging has been recorded from the energy emitted from the mineral's surface. Solar energy is the source of energy in remote sensing, while a heating element is the energy source employed in laboratory experiments. Our work contains three main steps where the first step involves obtaining the spectral signatures of pure (single) minerals with a hyperspectral camera, in the long-wave infrared (7.7 to 11.8 μm), which measures the emitted radiance from the minerals' surface. The second step concerns feature extraction by applying the continuous wavelet transform (CWT) and finally we use support vector machine classifier with radial basis functions (SVM-RBF) for classification/identification of minerals. The overall accuracy of classification in our work is 90.23+/- 2.66%. In conclusion, based on CWT's ability to capture the information of signals can be used as a good marker for classification and identification the minerals substance.

Three-Dimensional Wind Profiling of Offshore Wind Energy Areas With Airborne Doppler Lidar

NASA Technical Reports Server (NTRS)

Koch, Grady J.; Beyon, Jeffrey Y.; Cowen, Larry J.; Kavaya, Michael J.; Grant, Michael S.

2014-01-01

A technique has been developed for imaging the wind field over offshore areas being considered for wind farming. This is accomplished with an eye-safe 2-micrometer wavelength coherent Doppler lidar installed in an aircraft. By raster scanning the aircraft over the wind energy area (WEA), a three-dimensional map of the wind vector can be made. This technique was evaluated in 11 flights over the Virginia and Maryland offshore WEAs. Heights above the ocean surface planned for wind turbines are shown to be within the marine boundary layer, and the wind vector is seen to show variation across the geographical area of interest at turbine heights.

Caesium sputter ion source compatible with commercial SIMS instruments

NASA Astrophysics Data System (ADS)

Belykh, S. F.; Palitsin, V. V.; Veryovkin, I. V.; Kovarsky, A. P.; Chang, R. J. H.; Adriaens, A.; Dowsett, M.; Adams, F.

2006-07-01

A simple design for a caesium sputter cluster ion source compatible with commercially available secondary ion mass spectrometers is reported. This source has been tested with the Cameca IMS 4f instrument using the cluster Si n- and Cu n- ions, and will shortly be retrofitted to the floating low energy ion gun (FLIG) of the type used on the Cameca 4500/4550 quadruple instruments. Our experiments with surface characterization and depth profiling conducted to date demonstrate improvements of analytical capabilities of the SIMS instrument due to the non-additive enhancement of secondary ion emission and shorter ion ranges of polyatomic projectiles compared to atomic ions with the same impact energy.

Theoretical aspects of femtosecond double-pump single-molecule spectroscopy. I. Weak-field regime.

PubMed

Palacino-González, Elisa; Gelin, Maxim F; Domcke, Wolfgang

2017-12-13

We present a theoretical description of double-pump femtosecond single-molecule signals with fluorescence detection. We simulate these signals in the weak-field regime for a model mimicking a chromophore with a Franck-Condon-active vibrational mode. We establish several signatures of these signals which are characteristic for the weak-field regime. The signatures include the quenching of vibrational beatings by electronic dephasing and a pronounced tilt of the phase-time profiles in the two-dimensional (2D) maps. We study how environment-induced slow modulations of the electronic dephasing and relevant chromophore parameters (electronic energy, orientation, vibrational frequency and relative shift of the potential energy surfaces) affect the signals.

A theoretical investigation on bio-transformation of third generation anti-cancer drug Heptaplatin and its interaction with DNA purine bases

NASA Astrophysics Data System (ADS)

Reddy B., Venkata P.; Mukherjee, Subhajit; Mitra, Ishani; Moi, Sankar Ch.

2017-12-01

Heptaplatin is an approved platinum based cytostatic drug for the treatment of gastric cancers. The hydrolytic bio-transformation of Heptaplatin and the platination processes of guanine (G) and adenine (A) with resulting mono and di-aquated species of Heptaplatin have been investigated using density functional theory (DFT) combined with the conductor like dielectric continuum model (CPCM) approach, to spotlight the drug activation energy profiles and their binding mechanisms. The stationary points on the potential energy surfaces were fully optimized and characterized. The mono-functional binding of Heptaplatin, guanine as target over adenine due to electronic factors and more favorable hydrogen-bonds pattern.

Beam Simulation Studies of Plasma-Surface Interactions in Fluorocarbon Etching of Silicon and Silicon Dioxide

NASA Astrophysics Data System (ADS)

Gray, David C.

1992-01-01

A molecular beam apparatus has been constructed which allows the synthesis of dominant species fluxes to a wafer surface during fluorocarbon plasma etching. These species include atomic F as the primary etchant, CF _2 as a potential polymer forming precursor, and Ar^{+} or CF _{rm x}^{+} type ions. Ionic and neutral fluxes employed are within an order of magnitude of those typical of fluorocarbon plasmas and are well characterized through the use of in -situ probes. Etching yields and product distributions have been measured through the use of in-situ laser interferometry and line-of-sight mass spectrometry. XPS studies of etched surfaces were performed to assess surface chemical bonding states and average surface stoichiometry. A useful design guide was developed which allows optimal design of straight -tube molecular beam dosers in the collisionally-opaque regime. Ion-enhanced surface reaction kinetics have been studied as a function of the independently variable fluxes of free radicals and ions, as well as ion energy and substrate temperature. We have investigated the role of Ar ^{+} ions in enhancing the chemistries of F and CF_2 separately, and in combination on undoped silicon and silicon dioxide surfaces. We have employed both reactive and inert ions in the energy range most relevant to plasma etching processes, 20-500 eV, through the use of Kaufman and ECR type ion sources. The effect of increasing ion energy on the etching of fluorine saturated silicon and silicon dioxide surfaces was quantified through extensions of available low energy physical sputtering theory. Simple "site"-occupation models were developed for the quantification of the ion-enhanced fluorine etching kinetics in these systems. These models are suitable for use in topography evolution simulators (e.g. SAMPLE) for the predictive modeling of profile evolution in non-depositing fluorine-based plasmas such as NF_3 and SF_6. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617 -253-5668; Fax 617-253-1690.) (Abstract shortened with permission of school.).

Surface reflectance drives nest box temperature profiles and thermal suitability for target wildlife.

PubMed

Griffiths, Stephen R; Rowland, Jessica A; Briscoe, Natalie J; Lentini, Pia E; Handasyde, Kathrine A; Lumsden, Linda F; Robert, Kylie A

2017-01-01

Thermal properties of tree hollows play a major role in survival and reproduction of hollow-dependent fauna. Artificial hollows (nest boxes) are increasingly being used to supplement the loss of natural hollows; however, the factors that drive nest box thermal profiles have received surprisingly little attention. We investigated how differences in surface reflectance influenced temperature profiles of nest boxes painted three different colors (dark-green, light-green, and white: total solar reflectance 5.9%, 64.4%, and 90.3% respectively) using boxes designed for three groups of mammals: insectivorous bats, marsupial gliders and brushtail possums. Across the three different box designs, dark-green (low reflectance) boxes experienced the highest average and maximum daytime temperatures, had the greatest magnitude of variation in daytime temperatures within the box, and were consistently substantially warmer than light-green boxes (medium reflectance), white boxes (high reflectance), and ambient air temperatures. Results from biophysical model simulations demonstrated that variation in diurnal temperature profiles generated by painting boxes either high or low reflectance colors could have significant ecophysiological consequences for animals occupying boxes, with animals in dark-green boxes at high risk of acute heat-stress and dehydration during extreme heat events. Conversely in cold weather, our modelling indicated that there are higher cumulative energy costs for mammals, particularly smaller animals, occupying light-green boxes. Given their widespread use as a conservation tool, we suggest that before boxes are installed, consideration should be given to the effect of color on nest box temperature profiles, and the resultant thermal suitability of boxes for wildlife, particularly during extremes in weather. Managers of nest box programs should consider using several different colors and installing boxes across a range of both orientations and shade profiles (i.e., levels of canopy cover), to ensure target animals have access to artificial hollows with a broad range of thermal profiles, and can therefore choose boxes with optimal thermal conditions across different seasons.

Surface reflectance drives nest box temperature profiles and thermal suitability for target wildlife

PubMed Central

Rowland, Jessica A.; Briscoe, Natalie J.; Lentini, Pia E.; Handasyde, Kathrine A.; Lumsden, Linda F.; Robert, Kylie A.

2017-01-01

Thermal properties of tree hollows play a major role in survival and reproduction of hollow-dependent fauna. Artificial hollows (nest boxes) are increasingly being used to supplement the loss of natural hollows; however, the factors that drive nest box thermal profiles have received surprisingly little attention. We investigated how differences in surface reflectance influenced temperature profiles of nest boxes painted three different colors (dark-green, light-green, and white: total solar reflectance 5.9%, 64.4%, and 90.3% respectively) using boxes designed for three groups of mammals: insectivorous bats, marsupial gliders and brushtail possums. Across the three different box designs, dark-green (low reflectance) boxes experienced the highest average and maximum daytime temperatures, had the greatest magnitude of variation in daytime temperatures within the box, and were consistently substantially warmer than light-green boxes (medium reflectance), white boxes (high reflectance), and ambient air temperatures. Results from biophysical model simulations demonstrated that variation in diurnal temperature profiles generated by painting boxes either high or low reflectance colors could have significant ecophysiological consequences for animals occupying boxes, with animals in dark-green boxes at high risk of acute heat-stress and dehydration during extreme heat events. Conversely in cold weather, our modelling indicated that there are higher cumulative energy costs for mammals, particularly smaller animals, occupying light-green boxes. Given their widespread use as a conservation tool, we suggest that before boxes are installed, consideration should be given to the effect of color on nest box temperature profiles, and the resultant thermal suitability of boxes for wildlife, particularly during extremes in weather. Managers of nest box programs should consider using several different colors and installing boxes across a range of both orientations and shade profiles (i.e., levels of canopy cover), to ensure target animals have access to artificial hollows with a broad range of thermal profiles, and can therefore choose boxes with optimal thermal conditions across different seasons. PMID:28472147

Studies of worn surfaces by relocation profilometry

NASA Astrophysics Data System (ADS)

Rîpă, M.; Iliuță, V.

2018-01-01

By relocation profilometry, a series of surface profiles can be recorded from the same track on a specimen. These techniques are used for monitoring specific particular points on the surface subjected to wear processes, in a more accurate manner as comparing to those involving average statistical information for surface. The method is providing a much more significant information about the surface, in a more efficient way, assuring that the same unworn investigated surface is studied after wear test. The studied roughness digital profiles were obtained before and after the testing of rolling/sliding line contacts, characteristic for spur gears, which has been simulated on SAE sets, with a two rollers test machine. The acquisition of the relocated profiles is performed on the same generatrix of the roller, before and after wear testing. To correlate the unworn and worn profiles, a spheroconical indentation was created on the circumferential surface of the disk, in the zone of the tested roller that remain unworn during the test. Measuring changes of the profiles by relocation techniques, two methods for wear assessment are presented: linear wear estimation by simulating the profile wearing and estimation of the volume wear.

An Estimation of Turbulent Kinetic Energy and Energy Dissipation Rate Based on Atmospheric Boundary Layer Similarity Theory

NASA Technical Reports Server (NTRS)

Han, Jongil; Arya, S. Pal; Shaohua, Shen; Lin, Yuh-Lang; Proctor, Fred H. (Technical Monitor)

2000-01-01

Algorithms are developed to extract atmospheric boundary layer profiles for turbulence kinetic energy (TKE) and energy dissipation rate (EDR), with data from a meteorological tower as input. The profiles are based on similarity theory and scalings for the atmospheric boundary layer. The calculated profiles of EDR and TKE are required to match the observed values at 5 and 40 m. The algorithms are coded for operational use and yield plausible profiles over the diurnal variation of the atmospheric boundary layer.

Characterization of cathode keeper wear by surface layer activation

NASA Technical Reports Server (NTRS)

Polk, James E.

2003-01-01

In this study, the erosion rates of the discharge cathode keeper in a 30 cm NSTAR configuration ion thruster were measured using a technique known as Surface Layer Activation (SLA). This diagnostic technique involves producing a radioactive tracer in a given surface by bombardment with high energy ions. The decrease in activity of the tracer material may be monitored as the surface is subjected to wear processes and correlated to a depth calibration curve, yielding the eroded depth. Analysis of the activities was achieved through a gamma spectroscopy system. The primary objectives of this investigation were to reproduce erosion data observed in previous wear studies in order to validate the technique, and to determine the effect of different engine operating parameters on erosion rate. The erosion profile at the TH 15 (23 kw) setting observed during the 8200 hour Life Demonstration Test (LDT) was reproduced. The maximum keeper erosion rate at this setting was determined to be 0.085 pm/hr. Testing at the TH 8 (1.4 kw) setting demonstrated lower erosion rates than TH 15, along with a different wear profile. Varying the keeper voltage was shown to have a significant effect on the erosion, with a positive bias with respect to cathode potential decreasing the erosion rate significantly. Accurate measurements were achieved after operating times of only 40 to 70 hours, a significant improvement over other erosion diagnostic methods.

Optical monitoring of proteins at solid interfaces

NASA Astrophysics Data System (ADS)

Dunne, G.; McDonnell, L.; Miller, R.; McMillan, N. D.; O'Rourke, B.; Mitchell, C. I.

2005-06-01

The adsorption properties of polymers are of great importance for implant studies. A better understanding of these properties can lead to improved implant materials. In this study the surface energy of different polymers was derived from contact angle measurements taken using profile analysis tensiometry (PAT) of sessile drops of water. The contact angles were measured for advancing and receding water drops on polished polymer surfaces and also on polymer surfaces modified by adsorbing protein to the surface prior to analysis of the sessile drop. The protein used was bovine serum albumin (BSA) and the surfaces were poly-methylmethacrylate (PMMA), poly-ether-ether-ketone (PEEK) and stainless steel. The polymer surfaces were also studied using atomic force microscopy (AFM). Images of the surfaces were taken in different states: rough, smooth and with albumin adsorbed. As a method to identify the proteins on the surface easier, anti-albumin antibodies with 30nm nano gold particles attached were adsorbed to the albumin on the surfaces. Using nano gold particles made the imaging more straightforward and thus made identification of the protein on the surface easier. The results from this work show the differing hydrophobicities of polymer surfaces under different conditions and a new nanotechnological method of protein identification.

Virtual environment assessment for laser-based vision surface profiling

NASA Astrophysics Data System (ADS)

ElSoussi, Adnane; Al Alami, Abed ElRahman; Abu-Nabah, Bassam A.

2015-03-01

Oil and gas businesses have been raising the demand from original equipment manufacturers (OEMs) to implement a reliable metrology method in assessing surface profiles of welds before and after grinding. This certainly mandates the deviation from the commonly used surface measurement gauges, which are not only operator dependent, but also limited to discrete measurements along the weld. Due to its potential accuracy and speed, the use of laser-based vision surface profiling systems have been progressively rising as part of manufacturing quality control. This effort presents a virtual environment that lends itself for developing and evaluating existing laser vision sensor (LVS) calibration and measurement techniques. A combination of two known calibration techniques is implemented to deliver a calibrated LVS system. System calibration is implemented virtually and experimentally to scan simulated and 3D printed features of known profiles, respectively. Scanned data is inverted and compared with the input profiles to validate the virtual environment capability for LVS surface profiling and preliminary assess the measurement technique for weld profiling applications. Moreover, this effort brings 3D scanning capability a step closer towards robust quality control applications in a manufacturing environment.

Surface characterization and testing II; Proceedings of the Meeting, San Diego, CA, Aug. 10, 11, 1989

NASA Technical Reports Server (NTRS)

Greivenkamp, John E. (Editor); Young, Matt (Editor)

1989-01-01

Various papers on surface characterization and testing are presented. Individual topics addressed include: simple Hartmann test data interpretation, optimum configuration of the Offner null corrector, system for phase-shifting interferometry in the presence of vibration, fringe variation and visibility in speckle-shearing interferometry, functional integral representation of rough surfaces, calibration of surface heights in an interferometric optical profiler, image formation in common path differential profilometers, SEM of optical surfaces, measuring surface profiles with scanning tunneling microscopes, surface profile measurements of curved parts, high-resolution optical profiler, scanning heterodyne interferometer with immunity from microphonics, real-time crystal axis measurements of semiconductor materials, radial metrology with a panoramic annular lens, surface analysis for the characterization of defects in thin-film processes, Spacelab Optical Viewport glass assembly optical test program for the Starlab mission, scanning differential intensity and phase system for optical metrology.

An experimental study of the dynamics of saltation within a three-dimensional framework

NASA Astrophysics Data System (ADS)

O'Brien, Patrick; McKenna Neuman, Cheryl

2018-04-01

Our understanding of aeolian sand transport via saltation lacks an experimental determination of the particle borne kinetic energy partitioned into 3 dimensions relative to the mean flow direction. This in turn creates a disconnect between global wind erosion estimates and particle scale processes. The present study seeks to address this deficiency through an extended analysis of data obtained from a series of particle tracking velocimetry experiments conducted in a boundary layer wind tunnel under transport limited conditions. Particle image diameter, as it appeared within each camera frame, was extensively calibrated against that obtained by sieving, and the ballistic trajectories detected were disassembled into discrete particle image pairs whose distribution and dynamics were then examined in vertical profile with sub-millimeter resolution. The vertical profile of the wind aligned particle transport rate was found to follow a power relation within 10 mm of the bed surface. The exponent of this power function changes with increasing spanwise angle (θ) to produce a family of curves representing particle diffusion in 3 dimensions. Particle mass was found to increase with θ, and the distribution of the total particle kinetic energy was found to be very similar to that for the particle concentration. The spanwise component of the kinetic energy of a saltating particle peaks at θ = 45°, with the stream-aligned component an order of magnitude higher in value. Low energy, splashed particles near the bed account for a majority of the kinetic energy distributed throughout the particle cloud, regardless of their orientation.

Thermal Modeling on Planetary Regoliths

NASA Technical Reports Server (NTRS)

Hale, A. S.; Hapke, B.W.

2002-01-01

The thermal region of the spectrum is one of special interest in planetary science as it is the only region where planetary emission is significant. Studying how planetary surfaces emit in the thermal infrared can tell us about their physical makeup and chemical composition, as well as their temperature profile with depth. This abstract will discuss a model of thermal energy transfer in planetary regoliths on airless bodies which includes both conductive and radiative processes while including the time dependence of the solar input function.

From the chlorophyll a in the surface layer to its vertical profile: a Greenland Sea relationship for satellite applications

NASA Astrophysics Data System (ADS)

Cherkasheva, A.; Bracher, A.; Nöthig, E.-M.; Bauerfeind, E.; Melsheimer, C.

2012-11-01

Current estimates of global marine primary production range over a factor of two. At high latitudes, the uncertainty is even larger than globally because here in-situ data and ocean color observations are scarce, and the phytoplankton absorption shows specific characteristics due to the low-light adaptation. The improvement of the primary production estimates requires an accurate knowledge on the chlorophyll vertical profile, which is the basis for most primary production models. To date, studies describing the typical chlorophyll profile based on the chlorophyll in the surface layer did not include the Arctic region or, if it was included, the dependence of the profile shape on surface concentration was neglected. The goal of our study was to derive and describe the typical Greenland Sea chlorophyll profiles, categorized according to the chlorophyll concentration in the surface layer and further monthly resolved. The Greenland Sea was chosen because it is known to be one of the most productive regions of the Arctic and is among the Arctic regions where most chlorophyll field data are available. Our database contained 1199 chlorophyll profiles from R/Vs Polarstern and Maria S Merian cruises combined with data of the ARCSS-PP database (Arctic primary production in-situ database) for the years 1957-2010. The profiles were categorized according to their mean concentration in the surface layer and then monthly median profiles within each category were calculated. The category with the surface layer chlorophyll exceeding 0.7 mg C m-3 showed a clear seasonal cycle with values gradually decreasing from April to August. Chlorophyll profiles maxima moved from lower depths in spring towards the surface in late summer. Profiles with smallest surface values always showed a subsurface chlorophyll maximum with its median magnitude reaching up to three times the surface concentration. While the variability in April, May and June of the Greenland Sea season is following the global non-monthly resolved relationship of the chlorophyll profile to surface chlorophyll concentrations described by the model of Morel and Berthon (1989), it deviates significantly from that in other months (July-September) where the maxima of the chlorophyll are at quite different depths. The Greenland Sea dimensionless monthly median profiles intersect roughly at one common depth within each category. Finally, by applying a Gaussian fitting with 0.1 mg C m-3 surface chlorophyll steps to the median monthly resolved chlorophyll profiles of the defined categories, mathematical approximations have been determined. These will be used as the input to the satellite-based primary production models estimating primary production in Arctic regions.

On the Origins of the Linear Free Energy Relationships: Exploring the Nature of the Off-Diagonal Coupling Elements in SN2 Reactions

PubMed Central

Rosta, Edina; Warshel, Arieh

2012-01-01

Understanding the relationship between the adiabatic free energy profiles of chemical reactions and the underlining diabatic states is central to the description of chemical reactivity. The diabatic states form the theoretical basis of Linear Free Energy Relationships (LFERs) and thus play a major role in physical organic chemistry and related fields. However, the theoretical justification for some of the implicit LFER assumptions has not been fully established by quantum mechanical studies. This study follows our earlier works1,2 and uses the ab initio frozen density functional theory (FDFT) method3 to evaluate both the diabatic and adiabatic free energy surfaces and to determine the corresponding off-diagonal coupling matrix elements for a series of SN2 reactions. It is found that the off-diagonal coupling matrix elements are almost the same regardless of the nucleophile and the leaving group but change upon changing the central group. Furthermore, it is also found that the off diagonal elements are basically the same in gas phase and in solution, even when the solvent is explicitly included in the ab initio calculations. Furthermore, our study establishes that the FDFT diabatic profiles are parabolic to a good approximation thus providing a first principle support to the origin of LFER. These findings further support the basic approximation of the EVB treatment. PMID:23329895

A 3D Laser Profiling System for Rail Surface Defect Detection

PubMed Central

Li, Qingquan; Mao, Qingzhou; Zou, Qin

2017-01-01

Rail surface defects such as the abrasion, scratch and peeling often cause damages to the train wheels and rail bearings. An efficient and accurate detection of rail defects is of vital importance for the safety of railway transportation. In the past few decades, automatic rail defect detection has been studied; however, most developed methods use optic-imaging techniques to collect the rail surface data and are still suffering from a high false recognition rate. In this paper, a novel 3D laser profiling system (3D-LPS) is proposed, which integrates a laser scanner, odometer, inertial measurement unit (IMU) and global position system (GPS) to capture the rail surface profile data. For automatic defect detection, first, the deviation between the measured profile and a standard rail model profile is computed for each laser-imaging profile, and the points with large deviations are marked as candidate defect points. Specifically, an adaptive iterative closest point (AICP) algorithm is proposed to register the point sets of the measured profile with the standard rail model profile, and the registration precision is improved to the sub-millimeter level. Second, all of the measured profiles are combined together to form the rail surface through a high-precision positioning process with the IMU, odometer and GPS data. Third, the candidate defect points are merged into candidate defect regions using the K-means clustering. At last, the candidate defect regions are classified by a decision tree classifier. Experimental results demonstrate the effectiveness of the proposed laser-profiling system in rail surface defect detection and classification. PMID:28777323

Regional aerosol radiative and hydrological effects over the mid-Atlantic corridor

NASA Astrophysics Data System (ADS)

Creekmore, Torreon N.

A thorough assessment of direct, indirect, and semi-direct influences of aerosols on Earth's energy budget is required to better understand climate and estimate how it may change in the future. Clear-sky surface broadband (measured and modeled) irradiance, spectral aerosol optical depth, heating rate profiles, and non-radiative flux measurements were conducted at a state-of-the-art site, developed by the NOAA-Howard University Center for Atmospheric Sciences (NCAS) program, providing a best estimate of aerosol radiative atmosphere-surface interactions. Methods developed by the Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Program were applied to: (1) temporally quantify regional aerosol forcing, (2) to derive an empirical equation describing a relationship between aerosol optical depth and normalized diffuse ratio, (3) evaluate aerosol impacts on atmospheric heating, and (4) evaluate how aerosol forcing impacts may possibly reduce latent and sensible fluxes. Measurements were obtained during the period of May--September for the years of 2005, 2006, and 2007. Atmospheric aerosols are among the key uncertainties affecting the Earth's climate and atmospheric radiative processes. Present-day increases in aerosol concentrations directly, indirectly, and semi-directly impact the Earth's energy budget (i.e., cooling the surface and heating the atmosphere), thereby contributing to climate change. The Howard University Beltsville Site (HUBS) has experienced a greater loss in mean normalized aerosol radiative forcing with time, as observations show a decrease from --0.9 in 2005 to --3.1 and --3.4 W/m2 for 2006 and 2007 respectively, in mean net surface irradiance. The mean normalized aerosol radiative forcing estimated for the period considered was --2.5 W/m2. The reduction in surface solar insolation is due to increased scattering and absorption related to increased aerosol burdens v for the period, promoting surface cooling and atmospheric heating. Calculation of radiative flux and heating rates profiles, which are constrained by HUBS observations, were performed by the 1-D Fu-Liou radiative transfer model to investigate the effect of polluted and pristine aerosol conditions on the surface energy budget and hydrological cycle. For HUBS the surface forcing (--14.2 W/m2) and atmospheric forcing (9.9 W/m2) were significantly larger than the TOA (--4.3 W/m2) radiative forcing. Associated aerosol heating, as well as reduced surface insolation, may lead to increasing near surface static stability, and reduced vertical transport of moisture into the atmospheric boundary layer, and over time, a possible spin-down of the hydrological cycle. It is shown that HUBS provides an ideal opportunity for improving measurements and datasets, thus allowing for both the study and understanding of aerosol impacts on the climate system. Further, results show that in order to provide reference quality data and constrain aerosol radiative effects over land, ground-based research sites must conform to HUBS standards of: (1) instrumentation (e.g. passive and active sensors); (2) operational protocols (e.g. calibration and routine cleaning); (3) rigorous cloud screening protocols; and (4) incorporation of ARM QC and modified FFA algorithms. HUBS surface measurements provides the reference quality data necessary and capability required to help enhance measurements and constrain current uncertainties in estimates of aerosol direct effects over land. Incorporating a combined technique of both active and passive instruments reduced the direct radiative forcing estimates by ˜82 W/m2. The analysis of aerosol effects over HUBS helps continue in bridging the gap of applying measurements for improvement of climate simulations by generating observational products, which describes aerosol and radiation field characteristics in detail.

Specification for a surface-search radar-detection-range model

NASA Astrophysics Data System (ADS)

Hattan, Claude P.

1990-09-01

A model that predicts surface-search radar detection range versus a variety of combatants has been developed at the Naval Ocean Systems Center. This model uses a simplified ship radar cross section (RCS) model and the U.S. Navy Oceanographic and Atmospheric Mission Library Standard Electromagnetic Propagation Model. It provides the user with a method of assessing the effects of the environment of the performance of a surface-search radar system. The software implementation of the model is written in ANSI FORTRAN 77, with MIL-STD-1753 extensions. The program provides the user with a table of expected detection ranges when the model is supplied with the proper environmental radar system inputs. The target model includes the variation in RCS as a function of aspect angle and the distribution of reflected radar energy as a function of height above the waterline. The modeled propagation effects include refraction caused by a multisegmented refractivity profile, sea-surface roughness caused by local winds, evaporation ducting, and surface-based ducts caused by atmospheric layering.

In Situ Guided Wave Structural Health Monitoring System

NASA Technical Reports Server (NTRS)

Zhao, George; Tittmann, Bernhard R.

2011-01-01

Aircraft engine rotating equipment operates at high temperatures and stresses. Noninvasive inspection of microcracks in those components poses a challenge for nondestructive evaluation. A low-cost, low-profile, high-temperature ultrasonic guided wave sensor was developed that detects cracks in situ. The transducer design provides nondestructive evaluation of structures and materials. A key feature of the sensor is that it withstands high temperatures and excites strong surface wave energy to inspect surface and subsurface cracks. The sol-gel bismuth titanate-based surface acoustic wave (SAW) sensor can generate efficient SAWs for crack inspection. The sensor is very thin (submillimeter) and can generate surface waves up to 540 C. Finite element analysis of the SAW transducer design was performed to predict the sensor behavior, and experimental studies confirmed the results. The sensor can be implemented on structures of various shapes. With a spray-coating process, the sensor can be applied to the surface of large curvatures. It has minimal effect on airflow or rotating equipment imbalance, and provides good sensitivity.

Spatial and temporal variability of soil temperature, moisture and surface soil properties

NASA Technical Reports Server (NTRS)

Hajek, B. F.; Dane, J. H.

1993-01-01

The overall objectives of this research were to: (l) Relate in-situ measured soil-water content and temperature profiles to remotely sensed surface soil-water and temperature conditions; to model simultaneous heat and water movement for spatially and temporally changing soil conditions; (2) Determine the spatial and temporal variability of surface soil properties affecting emissivity, reflectance, and material and energy flux across the soil surface. This will include physical, chemical, and mineralogical characteristics of primary soil components and aggregate systems; and (3) Develop surface soil classes of naturally occurring and distributed soil property assemblages and group classes to be tested with respect to water content, emissivity and reflectivity. This document is a report of studies conducted during the period funded by NASA grants. The project was designed to be conducted over a five year period. Since funding was discontinued after three years, some of the research started was not completed. Additional publications are planned whenever funding can be obtained to finalize data analysis for both the arid and humid locations.

On the modeling of wave-enhanced turbulence nearshore

NASA Astrophysics Data System (ADS)

Moghimi, Saeed; Thomson, Jim; Özkan-Haller, Tuba; Umlauf, Lars; Zippel, Seth

2016-07-01

A high resolution k-ω two-equation turbulence closure model, including surface wave forcing was employed to fully resolve turbulence dissipation rate profiles close to the ocean surface. Model results were compared with observations from Surface Wave Instrument Floats with Tracking (SWIFTs) in the nearshore region at New River Inlet, North Carolina USA, in June 2012. A sensitivity analysis for different physical parameters and wave and turbulence formulations was performed. The flux of turbulent kinetic energy (TKE) prescribed by wave dissipation from a numerical wave model was compared with the conventional prescription using the wind friction velocity. A surface roughness length of 0.6 times the significant wave height was proposed, and the flux of TKE was applied at a distance below the mean sea surface that is half of this roughness length. The wave enhanced layer had a total depth that is almost three times the significant wave height. In this layer the non-dimensionalized Terray scaling with power of - 1.8 (instead of - 2) was applicable.

Time-dependent convection models of mantle thermal structure constrained by seismic tomography and geodynamics: implications for mantle plume dynamics and CMB heat flux

NASA Astrophysics Data System (ADS)

Glišović, P.; Forte, A. M.; Moucha, R.

2012-08-01

One of the outstanding problems in modern geodynamics is the development of thermal convection models that are consistent with the present-day flow dynamics in the Earth's mantle, in accord with seismic tomographic images of 3-D Earth structure, and that are also capable of providing a time-dependent evolution of the mantle thermal structure that is as 'realistic' (Earth-like) as possible. A successful realization of this objective would provide a realistic model of 3-D mantle convection that has optimal consistency with a wide suite of seismic, geodynamic and mineral physical constraints on mantle structure and thermodynamic properties. To address this challenge, we have constructed a time-dependent, compressible convection model in 3-D spherical geometry that is consistent with tomography-based instantaneous flow dynamics, using an updated and revised pseudo-spectral numerical method. The novel feature of our numerical solutions is that the equations of conservation of mass and momentum are solved only once in terms of spectral Green's functions. We initially focus on the theory and numerical methods employed to solve the equation of thermal energy conservation using the Green's function solutions for the equation of motion, with special attention placed on the numerical accuracy and stability of the convection solutions. A particular concern is the verification of the global energy balance in the dissipative, compressible-mantle formulation we adopt. Such validation is essential because we then present geodynamically constrained convection solutions over billion-year timescales, starting from present-day seismically constrained thermal images of the mantle. The use of geodynamically constrained spectral Green's functions facilitates the modelling of the dynamic impact on the mantle evolution of: (1) depth-dependent thermal conductivity profiles, (2) extreme variations of viscosity over depth and (3) different surface boundary conditions, in this case mobile surface plates and a rigid surface. The thermal interpretation of seismic tomography models does not provide a radial profile of the horizontally averaged temperature (i.e. the geotherm) in the mantle. One important goal of this study is to obtain a steady-state geotherm with boundary layers which satisfies energy balance of the system and provides the starting point for more realistic numerical simulations of the Earth's evolution. We obtain surface heat flux in the range of Earth-like values : 37 TW for a rigid surface and 44 TW for a surface with tectonic plates coupled to the mantle flow. Also, our convection simulations deliver CMB heat flux that is on the high end of previously estimated values, namely 13 TW and 20 TW, for rigid and plate-like surface boundary conditions, respectively. We finally employ these two end-member surface boundary conditions to explore the very-long-time scale evolution of convection over billion-year time windows. These billion-year-scale simulations will allow us to determine the extent to which a 'memory' of the starting tomography-based thermal structure is preserved and hence to explore the longevity of the structures in the present-day mantle. The two surface boundary conditions, along with the geodynamically inferred radial viscosity profiles, yield steady-state convective flows that are dominated by long wavelengths throughout the lower mantle. The rigid-surface condition yields a spectrum of mantle heterogeneity dominated by spherical harmonic degree 3 and 4, and the plate-like surface condition yields a pattern dominated by degree 1. Our exploration of the time-dependence of the spatial heterogeneity shows that, for both types of surface boundary condition, deep-mantle hot upwellings resolved in the present-day tomography model are durable and stable features. These deeply rooted mantle plumes show remarkable longevity over very long geological time spans, mainly owing to the geodynamically inferred high viscosity in the lower mantle.

Cavitation in a metallic liquid: Homogeneous nucleation and growth of nanovoids

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

Cai, Y.; The Peac Institute of Multiscale Sciences, Chengdu, Sichuan 610207; Wu, H. A., E-mail: wuha@ustc.edu.cn

2014-06-07

Large-scale molecular dynamics (MD) simulations are performed to investigate homogeneous nucleation and growth of nanovoids during cavitation in liquid Cu. We characterize in detail the atomistic cavitation processes by following the temporal evolution of cavities or voids, analyze the nucleation behavior with the mean first-passage time (MFPT) and survival probability (SP) methods, and discuss the results against classical nucleation theory (CNT), the Tolman equation for surface energy, independent calculation of surface tension via integrating the stress profiles, the Johnson-Mehl-Avrami (JMA) growth law, and the power law for nucleus size distributions. Cavitation in this representative metallic liquid is a high energymore » barrier Poisson processes, and the steady-state nucleation rates obtained from statistical runs with the MFPT and SP methods are in agreement. The MFPT method also yields the critical nucleus size and the Zeldovich factor. Fitting with the Tolman's equation to the MD simulations yields the surface energy of a planar interface (∼0.9 J m{sup −2}) and the Tolman length (0.4–0.5 Å), and those values are in accord with those from integrating the stress profiles of a planar interface. Independent CNT predictions of the nucleation rate (10{sup 33−34} s{sup −1} m{sup −3}) and critical size (3–4 Å in radius) are in agreement with the MFPT and SP results. The JMA law can reasonably describe the nucleation and growth process. The size distribution of subcritical nuclei appears to follow a power law with an exponent decreasing with increasing tension owing to coupled nucleation and growth, and that of the supercritical nuclei becomes flattened during further stress relaxation due to void coalescence.« less

Surface kinetics for catalytic combustion of hydrogen-air mixtures on platinum at atmospheric pressure in stagnation flows

NASA Astrophysics Data System (ADS)

Ikeda, H.; Sato, J.; Williams, F. A.

1995-03-01

Experimental studies of the combustion of premixed hydrogen-air mixtures impinging on the surface of a heated platinum plate at normal atmospheric pressure were performed and employed to draw inferences concerning surface reaction mechanisms and rate parameters applicable under practical conditions of catalytic combustion. Plate and gas temperatures were measured by thermocouples, and concentration profiles of major stable species in the gas were measured by gas-chromatographic analyses of samples withdrawn by quartz probes. In addition, ignition and extinction phenomena were recorded and interpreted with the aid of a heat balance at the surface and a previous flow-field analysis of the stagnation-point boundary layer. From the experimental and theoretical results, conclusions were drawn concerning the surface chemical-kinetic mechanisms and values of the elementary rate parameters that are consistent with the observations. In particular, the activation energy for the surface oxidation step H + OH → H 2O is found to be appreciably less at these high surface coverages than in the low-coverage limit.

Frequency power analyses of seismic sources on firn

NASA Astrophysics Data System (ADS)

Sanz, Christopher; Diez, Anja; Coen, Hofstede; Kristoffersen, Yngve; Mayer, Christoph; Lambrecht, Astrid; Miller, Heinz; Eisen, Olaf

2013-04-01

A great obstacle for seismic surveys on firn-covered ice masses is the ability of firn to strongly attenuate seismic energy and divert downward ray paths away from the vertical because of the velocity gradient. The standard way to overcome these limitations is the drilling of shotholes about 10-30 m deep. However, drilling of shotholes is a time and energy consuming task. Another possibility is to use vibroseismic sources at the surface and increase the signal-to-noise ratio by repeated stacking. However, compared to explosive charges, vibroseismic signals are bandlimited per se. As a third variant, we investigate the usage of ordered patterns of surface charges consisting of detonation cord. Previous applications of detonation cord only explored their general comparison to bulk explosives when deployed in a linear fashion, i.e. a single line. Our approach extends these results to other geometries, like fan- or comb-shaped patterns. These have two advantages: first, over the pattern area a locally plane wave is generated, limiting the spherical and velocity-gradient induced spreading of energy during propagation; second, the ratio between seismic wave speed of the firn and the detonation cord of typically about 1:5 causes the wave to propagate in an angle downward. When using large offsets like a snow streamer, it is possible to direct the refected energy towards the streamer, depending on offset range and reflector depth. We compare the different source types for several surveys conducted in Antarctica in terms of frequency spectra. Our results show that ordered patterns of detonation cord serve as suitable seismic surface charges, avoiding the need to drill shotholes. Moreover, an example of a short profile with patterned surface charges is presented. The technique can be of advantage for surveys in remote areas, which can only be accessed by aircrafts.

Thermal effects on electronic properties of CO/Pt(111) in water.

PubMed

Duan, Sai; Xu, Xin; Luo, Yi; Hermansson, Kersti; Tian, Zhong-Qun

2013-08-28

Structure and adsorption energy of carbon monoxide molecules adsorbed on the Pt(111) surfaces with various CO coverages in water as well as work function of the whole systems at room temperature of 298 K were studied by means of a hybrid method that combines classical molecular dynamics and density functional theory. We found that when the coverage of CO is around half monolayer, i.e. 50%, there is no obvious peak of the oxygen density profile appearing in the first water layer. This result reveals that, in this case, the external force applied to water molecules from the CO/Pt(111) surface almost vanishes as a result of the competitive adsorption between CO and water molecules on the Pt(111) surface. This coverage is also the critical point of the wetting/non-wetting conditions for the CO/Pt(111) surface. Averaged work function and adsorption energy from current simulations are consistent with those of previous studies, which show that thermal average is required for direct comparisons between theoretical predictions and experimental measurements. Meanwhile, the statistical behaviors of work function and adsorption energy at room temperature have also been calculated. The standard errors of the calculated work function for the water-CO/Pt(111) interfaces are around 0.6 eV at all CO coverages, while the standard error decreases from 1.29 to 0.05 eV as the CO coverage increases from 4% to 100% for the calculated adsorption energy. Moreover, the critical points for these electronic properties are the same as those for the wetting/non-wetting conditions. These findings provide a better understanding about the interfacial structure under specific adsorption conditions, which can have important applications on the structure of electric double layers and therefore offer a useful perspective for the design of the electrochemical catalysts.

Pulsed Discharge Through Wetland Vegetation as a Control on Bed Shear Stress and Sediment Transport Affecting Everglades Restoration

NASA Astrophysics Data System (ADS)

Larsen, L. E.; Harvey, J. W.; Crimaldi, J. P.

2007-12-01

The ridge and slough landscape is a patterned peatland within the Florida Everglades in which elevated ridges of emergent vegetation are regularly interspersed among open-water sloughs with floating and submerged vegetation. Landscape features are aligned parallel to the historic flow direction. Degradation of patterning over the past 100 years coincides with diminished flow resulting from drainage and construction of levees and canals. A goal of restoration is to increase flow velocities and redistribution of particles and solutes in attempt to preserve remnant patterning and restore degraded portions of the ridge and slough landscape. To explore different management strategies that could induce sediment redistribution in the ridge and slough landscape, we simulated velocity profiles and bed shear stresses for different combinations of surface water stage, water surface slope, and vegetation community structure, based on field measurements and laboratory experiments. A mixing length approach, in which the minimum of stem spacing and distance from a solid boundary determined eddy scale, was used to simulate velocity profiles and bed shear stress in vegetated arrays. Simplified velocity profiles based only on vegetation frontal area above the bed and the Karman-Prandtl logarithmic law near the bed closely were used to approximate solutions of the one-dimensional Navier-Stokes equations for large-scale simulation. Estimates of bed shear stress were most sensitive to bed roughness, vegetation community structure, and energy slope. Importantly, our simulations illustrate that velocity and bed shear stress cannot be increased substantially in the Everglades simply by increasing surface-water stage. This result comes directly from the dependence of velocity and shear stress on vegetation frontal area and the fact that emergent vegetation stems protrude through the water column even during times of relatively deep water in the Everglades. Since merely increasing water depth is not likely to increase water velocity and entrainment, it is necessary instead that restoration focus on increasing energy slope as a means to entrain sediment within sloughs and redistribute it to ridges. Surface-water gravity waves caused by hurricanes or pulsed releases of water from impounded areas may be the most effective mechanism for achieving sediment redistribution in the Everglades and other wetland and riparian environments with abundant emergent vegetation.

Anharmonic Effects on the Electron-Energy Spectra of Surface Vibrations

NASA Astrophysics Data System (ADS)

Ariyasu, Janice Carol

First, we consider the effect of lateral interactions on double losses and overtones in electron-energy-loss studies of surface vibrations. We develop a theory of two-phonon losses in the dipole-dominated regime of small -angle scattering. Our calculation employs the simple model of an ordered overlayer of molecules adsorbed on a crystal surface. With this model, we can identify two features; one which corresponds to the double loss and another which corresponds the excitation of an overtone. We then study the role of lateral interactions in each. We find that the presence of lateral interactions affects the position of the overtone relative to the double loss, and influences both its width and shape. The implications of these results are discussed, particularly as they relate to estimates of dissociation energies by the Birge-Sponer procedure. Next, we consider the anharmonic damping of adsorbate vibrations, with specific applications to species (S, O, and CO) adsorbed on the Ni(100) and Ni(111) surfaces. Our attention is restricted to adsorbate modes that can decay by two-phonon processes to one substrate phonon and either another substrate mode phonon or to a phonon of a mode that is localized on the adsorbate. The magnitude and temperature variation of the linewidth of adsorbate modes by this mechanism is explored; we find that near room temperature the calculated linewidths vary linearly with temperature. We also simulate the inhomogeneous broadening produced by disorder by considering the eigenfrequencies of infrared -active modes. Finally, we consider the diffuse scattering of electrons from surfaces by long-wavelength, acoustic phonons. The mechanism that we explore is the modulation of the image potential from ripples induced in the surface profile by thermally-excited surface and bulk phonons. We compare our results with earlier studies, and with the scattering produced by the dynamic-dipole moment of the surface atoms.

Effective Field Theory of Surface-mediated Forces in Soft Matter

NASA Astrophysics Data System (ADS)

Yolcu, Cem

We propose a field theoretic formalism for describing soft surfaces modified by the presence of inclusions. Examples include particles trapped at a fluid-fluid interface, proteins attached to (or embedded in) a biological membrane, etc. We derive the energy functional for near-flat surfaces by an effective field theory approach. The two disparate length scales, particle sizes and inter-particle separations, afford the expansion parameters for controlling the accuracy of the effective theory, which is arbitrary in principle. We consider the following two surface types: (i) one where tension determines the behavior, such as a fluid-fluid interface (referred to as a film), and (ii) one where bending-elasticity dominates (referred to as a membrane). We also restrict to rigid inclusions with a circular footprint, and discuss generalizations briefly. As a result of the localized constraints imposed on the surface by the inclusions, the free energy of the system depends on their spatial arrangement, i.e. forces arise between them. Such surface-mediated interactions are believed to play an important role in the aggregation behavior of colloidal particles at interfaces and proteins on membranes. The interaction free energy consists of two parts: (i) the ground-state of the surface determined by possible deformations imposed by the particles, and (ii) the fluctuation correction. The former is analogous to classical electrostatics with the height profile of the surface playing the role of the electrostatic potential, while the latter is analogous to the Casimir effect and originates from the mere presence of constraints. We compute both interactions in truncated expansions. The efficiency of the formalism allows us to predict, with remarkable ease, quite a few orders of subleading corrections to existing results which are only valid when the inclusions are infinitely far apart. We also found that the few previous studies on finite distance corrections were incomplete. In addition to pairwise additive interactions, we compute the leading behavior of several many-body interactions, as well as subleading corrections where the leading contribution was previously calculated.

Laser shock peening studies on SS316LN plate with various sacrificial layers

NASA Astrophysics Data System (ADS)

Yella, Pardhu; Venkateswarlu, P.; Buddu, Ramesh K.; Vidyasagar, D. V.; Sankara Rao, K. Bhanu; Kiran, P. Prem; Rajulapati, Koteswararao V.

2018-03-01

Laser shock peening (LSP) has been utilized to modify the surface characteristics of SS316LN plates of 6 mm thickness. Laser pulse widths employed are 30 ps and 7 ns and the laser energy was varied in the range 5-90 mJ. Peening was performed in direct ablation mode as well as with various sacrificial layers such as black paint, transparent adhesive tape and absorbing adhesive tape. The surface characteristics were greatly influenced by the type of sacrificial layer employed. The average surface roughness values are about 0.4 μm when the black paint and transparent adhesive tape were used as sacrificial layers. In contrast to this, using absorbent adhesive tape as a sacrificial layer has resulted in an average surface roughness of about 0.04 μm. Irrespective of pulse durations (30 ps or 7 ns), absorbent adhesive tape has always resulted in compressive residual stresses whereas other layers appear to be not that effective. In case of 30 ps pulse, as the laser energy was increased from 5 mJ to 25 mJ, there was a texture observed in (111) reflection of X-ray diffractograms and the center of the peak has also gradually shifted to left. X-ray line profile analysis suggests that with the increase in laser energy, lattice microstrain also has increased. This lattice microstrain appears to be resulting from the increased dislocation density in the peened sample as evidenced during transmission electron microscopic investigations. Cross-sectional scanning electron microscopy performed on peened samples suggests that absorbing adhesive tape brings no surface damage to the samples whereas other sacrificial layers have resulted in some surface damage. Based on all these structural and microstructural details, it is recommended that absorbent tape could be used as a sacrificial layer during LSP process which induces surface residual stresses with no damage to the sample surface.

Steered Molecular Dynamics for Investigating the Interactions Between Insulin Receptor Tyrosine Kinase (IRK) and Variants of Protein Tyrosine Phosphatase 1B (PTP1B).

PubMed

Nguyen, Hung; Do, Nhat; Phan, Tuyn; Pham, Tri

2018-02-01

The aim of this study is to use steered molecular dynamics to investigate the dissociation process between IRK and PTP1Bs for wild type and five mutants (consisting of p.D181E, p.D181A, p.Q262A, p.D181A-Y46F, and p.D181A-Q262A). The gained results are observed not only the unbinding mechanism of IRK-PTP1B complexes came from pulling force profile, number of hydrogen bonds, and interaction energy between IRK and PTP1Bs but also described PTP1B's point mutations could variably change its binding affinity towards IRK. Additionally, the binding free energy calculated by Molecular Mechanics/Poisson-Boltzmann Surface Area (MM-PBSA) is also revealed that electrostatic energy and polar solvation energy mainly made up the binding free energy of PTP1B-IRK complexes.

Interaction between amphiphilic ionic liquid 1-butyl-3-methylimidazolium octyl sulfate and anionic polymer of sodium polystyrene sulfonate in aqueous medium

NASA Astrophysics Data System (ADS)

Barhoumi, Z.; Saini, M.; Amdouni, N.; Pal, A.

2016-09-01

The micellization of an aqueous solution of the surface active ionic liquid (SAIL), 1-butyl-3-methylimidazolium octylsufate (C4mim)(C8OSO3) and its interaction with an anionic polymer sodium polystyrene sulfonate, (NaPSS) were studied using conductimetry, tensiometry and fluorimetry. Surface tension profile shows a more dramatic increase in the value of surface tension of aqueous (C4mim)(C8OSO3) before the critical micelle concentration (cmc) of IL. The critical micelle concentration (cmc) value of this surfactant was found out from conductance measurements. The thermodynamic parameters, i.e., Gibb's free energy, enthalpy, and entropy of micellization of the IL in aqueous solution have been calculated. Behavior of fluorescence probe confirms the binding interactions between SAIL and the polyelectrolyte.

Gold-implanted shallow conducting layers in polymethylmethacrylate

NASA Astrophysics Data System (ADS)

Teixeira, F. S.; Salvadori, M. C.; Cattani, M.; Brown, I. G.

2009-03-01

PMMA (polymethylmethacrylate) was ion implanted with gold at very low energy and over a range of different doses using a filtered cathodic arc metal plasma system. A nanometer scale conducting layer was formed, fully buried below the polymer surface at low implantation dose, and evolving to include a gold surface layer as the dose was increased. Depth profiles of the implanted material were calculated using the Dynamic TRIM computer simulation program. The electrical conductivity of the gold-implanted PMMA was measured in situ as a function of dose. Samples formed at a number of different doses were subsequently characterized by Rutherford backscattering spectrometry, and test patterns were formed on the polymer by electron beam lithography. Lithographic patterns were imaged by atomic force microscopy and demonstrated that the contrast properties of the lithography were well maintained in the surface-modified PMMA.

Heat Transfer to a Thin Solid Combustible in Flame Spreading at Microgravity

NASA Technical Reports Server (NTRS)

Bhattacharjee, S.; Altenkirch, R. A.; Olson, S. L.; Sotos, R. G.

1991-01-01

The heat transfer rate to a thin solid combustible from an attached diffusion flame, spreading across the surface of the combustible in a quiescent, microgravity environment, was determined from measurements made in the drop tower facility at NASA-Lewis Research Center. With first-order Arrhenius pyrolysis kinetics, the solid-phase mass and energy equations along with the measured spread rate and surface temperature profiles were used to calculate the net heat flux to the surface. Results of the measurements are compared to the numerical solution of the complete set of coupled differential equations that describes the temperature, species, and velocity fields in the gas and solid phases. The theory and experiment agree on the major qualitative features of the heat transfer. Some fundamental differences are attributed to the neglect of radiation in the theoretical model.

Local Turbulence Suppression and Shear Flow Dynamics During qmin-Triggered Internal Transport Barriers on DIII-D

NASA Astrophysics Data System (ADS)

Shafer, M. W.; McKee, G. R.; Schlossberg, D. J.; Austin, M. E.; Burrell, K. H.

2008-11-01

Long-wavelength turbulence (kρi< 1) is locally suppressed simultaneously with a rapid but transient increase in local poloidal flow shear at the appearance of low-order rational qmin surfaces in negative central shear discharges. At these events, reductions in energy transport are observed and Internal Transport Barriers (ITBs) may form. Application of off-axis ECH slows the q-profile evolution and increases ρqmin, both of which enhance turbulence measurements using a new high-sensitivity large-area (8x,8) 2D BES array. The measured transient turbulence suppression is localized to the low-order rational surface (qmin= 2, 5/2, 3, etc.). Measured poloidal flow shear transiently exceeds the turbulence decorrelation rate, which is consistent with shear suppression. The localized suppression zone propagates radially outward, nearly coincident with the low-order surface.

Manufacturing of mushroom-shaped structures and its hydrophobic robustness analysis based on energy minimization approach

NASA Astrophysics Data System (ADS)

Wang, Li; Yang, Xiaonan; Wang, Quandai; Yang, Zhiqiang; Duan, Hui; Lu, Bingheng

2017-07-01

The construction of stable hydrophobic surfaces has increasingly gained attention owing to its wide range of potential applications. However, these surfaces may become wet and lose their slip effect owing to insufficient hydrophobic stability. Pillars with a mushroom-shaped tip are believed to enhance hydrophobicity stability. This work presents a facile method of manufacturing mushroom-shaped structures, where, compared with the previously used method, the modulation of the cap thickness, cap diameter, and stem height of the structures is more convenient. The effects of the development time on the cap diameter and overhanging angle are investigated and well-defined mushroom-shaped structures are demonstrated. The effect of the microstructure geometry on the contact state of a droplet is predicted by taking an energy minimization approach and is experimentally validated with nonvolatile ultraviolet-curable polymer with a low surface tension by inspecting the profiles of liquid-vapor interface deformation and tracking the trace of the receding contact line after exposure to ultraviolet light. Theoretical and experimental results show that, compared with regular pillar arrays having a vertical sidewall, the mushroom-like structures can effectively enhance hydrophobic stability. The proposed manufacturing method will be useful for fabricating robust hydrophobic surfaces in a cost-effective and convenient manner.

The Response of the Ocean Thermal Skin Layer to Variations in Incident Infrared Radiation

NASA Astrophysics Data System (ADS)

Wong, Elizabeth W.; Minnett, Peter J.

2018-04-01

Ocean warming trends are observed and coincide with the increase in concentrations of greenhouse gases in the atmosphere resulting from human activities. At the ocean surface, most of the incoming infrared (IR) radiation is absorbed within the top micrometers of the ocean's surface where the thermal skin layer (TSL) exists. Thus, the incident IR radiation does not directly heat the upper few meters of the ocean. This paper investigates the physical mechanism between the absorption of IR radiation and its effect on heat transfer at the air-sea boundary. The hypothesis is that given the heat lost through the air-sea interface is controlled by the TSL, the TSL adjusts in response to variations in incident IR radiation to maintain the surface heat loss. This modulates the flow of heat from below and hence controls upper ocean heat content. This hypothesis is tested using the increase in incoming longwave radiation from clouds and analyzing vertical temperature profiles in the TSL retrieved from sea-surface emission spectra. The additional energy from the absorption of increasing IR radiation adjusts the curvature of the TSL such that the upward conduction of heat from the bulk of the ocean into the TSL is reduced. The additional energy absorbed within the TSL supports more of the surface heat loss. Thus, more heat beneath the TSL is retained leading to the observed increase in upper ocean heat content.

Radiation Environments on Mars and Their Implications for Terrestrial Planetary Habitability

NASA Astrophysics Data System (ADS)

Schneider, I.; Kasting, J. F.

2009-12-01

The understanding of the surface and subsurface radiation environments of a terrestrial planet such as Mars is crucial to its potential past and/or present habitability. Despite this, the subject of high energy radiation is rarely contemplated within the field of Astrobiology as an essential factor determining the realistic parameter space for the development and preservation of life. Furthermore, not much is known of the radiation environment on the surface of Mars due to the fact that no real data exist on this contribution. There are no direct measurements available as no surface landers/probes have ever carried nuclear radiation detection equipment to characterize the interactions arising from cosmic ray bombardment, solar particle events and the atmosphere striking the planetary surface. The first mission set to accomplish this task, the Mars Science Laboratory, is not scheduled to launch until 2011. Presented here are some of such simulations performed with the HZETRN NASA code offering radiation depth profiles as well as a characterization of the diverse radiation environments. A discussion of the implications that these projected doses would have on terrestrial planetary habitability on Mars is presented as well as its implications for the habitability of terrestrial planets elsewhere. This work does not provide an estimate of the UV radiation fields on the Martian surface instead it focuses on the high energy radiation fields as composed by galactic cosmic rays (GCRs)

A review of the remote sensing of lower tropospheric thermodynamic profiles and its indispensable role for the understanding and the simulation of water and energy cycles: REMOTE SENSING OF THERMODYNAMIC PROFILES

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

Wulfmeyer, Volker; Hardesty, R. Michael; Turner, David D.

A review of remote sensing technology for lower tropospheric thermodynamic (TD) profiling is presented with focus on high accuracy and high temporal-vertical resolution. The contributions of these instruments to the understanding of the Earth system are assessed with respect to radiative transfer, land surface-atmosphere feedback, convection initiation, and data assimilation. We demonstrate that for progress in weather and climate research, TD profilers are essential. These observational systems must resolve gradients of humidity and temperature in the stable or unstable atmospheric surface layer close to the ground, in the mixed layer, in the interfacial layer—usually characterized by an inversion—and the lowermore » troposphere. A thorough analysis of the current observing systems is performed revealing significant gaps that must be addressed to fulfill existing needs. We analyze whether current and future passive and active remote sensing systems can close these gaps. A methodological analysis and demonstration of measurement capabilities with respect to bias and precision is executed both for passive and active remote sensing including passive infrared and microwave spectroscopy, the global navigation satellite system, as well as water vapor and temperature Raman lidar and water vapor differential absorption lidar. Whereas passive remote sensing systems are already mature with respect to operational applications, active remote sensing systems require further engineering to become operational in networks. However, active remote sensing systems provide a smaller bias as well as higher temporal and vertical resolutions. For a suitable mesoscale network design, TD profiler system developments should be intensified and dedicated observing system simulation experiments should be performed.« less

Numerical investigation on aluminum foam application in a tubular heat exchanger

NASA Astrophysics Data System (ADS)

Buonomo, Bernardo; di Pasqua, Anna; Ercole, Davide; Manca, Oronzio; Nardini, Sergio

2018-02-01

A numerical study has been conducted to examine the thermal and fluiddynamic behaviors of a tubular heat exchanger in aluminum foam. A plate in metal foam with a single array of five circular tubes is the geometrical domain under examination. Darcy-Forchheimer flow model and the thermal non-equilibrium energy model are used to execute two-dimensional simulations on metal foam heat exchanger. The foam is characterized by porosity and (number) pores per inch respectively equal to 0.935 and 20. Different air flow rates are imposed to the entrance of the heat exchanger with an assigned surface tube temperature. The results are provided in terms of local heat transfer coefficient and Nusselt number evaluated on the external surface of the tubes. Furthermore, local air temperature and velocity profiles in the smaller cross section, between two consecutive tubes are given. Finally, the Energy Performance Ratio (EPR) is evaluated in order to demonstrate the effectiveness of the metal foam.

Thin films structural properties: results of the full-atomistic supercomputer simulation

NASA Astrophysics Data System (ADS)

Grigoriev, F. V.; Sulimov, V. B.; Tikhonravov, A. V.

2017-12-01

The previously developed full-atomistic approach to the thin film growth simulation is applied for the investigation of the dependence of silicon dioxide films properties on deposition conditions. It is shown that the surface roughness and porosity are essentially reduced with the growth of energy of deposited silicon atoms. The growth of energy from 0.1 eV to 10 eV results in the increase of the film density for 0.2 - 0.4 g/cm3 and of the refractive index for 0.04-0.08. The compressive stress in films structures is observed for all deposition conditions. Absolute values of the stress tensor components increase with the growth of e energy of deposited atoms. The increase of the substrate temperature results in smoothing of the density profiles of the deposited films.

Tuning the density profile of surface-grafted hyaluronan and the effect of counter-ions.

PubMed

Berts, Ida; Fragneto, Giovanna; Hilborn, Jöns; Rennie, Adrian R

2013-07-01

The present paper investigates the structure and composition of grafted sodium hyaluronan at a solid-liquid interface using neutron reflection. The solvated polymer at the surface could be described with a density profile that decays exponentially towards the bulk solution. The density profile of the polymer varied depending on the deposition protocol. A single-stage deposition resulted in denser polymer layers, while layers created with a two-stage deposition process were more diffuse and had an overall lower density. Despite the diffuse density profile, two-stage deposition leads to a higher surface excess. Addition of calcium ions causes a strong collapse of the sodium hyaluronan chains, increasing the polymer density near the surface. This effect is more pronounced on the sample prepared by two-stage deposition due to the initial less dense profile. This study provides an understanding at a molecular level of how surface functionalization alters the structure and how surface layers respond to changes in calcium ions in the solvent.

Observations of the Evolution of Turbulent Dissipation within the Ocean Surface Boundary Layer: an OSMOSIS study

NASA Astrophysics Data System (ADS)

Lucas, N. S.; Allen, J.; Belcher, S. E.; Boyd, T.; Brannigan, L.; Inall, M.; Palmer, M.; Polton, J.; Rippeth, T. P.

2016-02-01

This study presents a new 9.5 day dataset showing the evolution of the Ocean Surface Boundary Layer (OSBL) and dissipation of turbulence kinetic energy (TKE), carried out as part of OSMOSIS[i], at a location in the North East Atlantic Ocean in September 2012. The TKE dissipation measurements were made using three methods; (i) repeated profiling between 100m and the surface by an Ocean Microstructure glider, (ii) three series of profiles made using a loosely tethered velocity microstructure glider and (iii) a moored pulse-pulse coherent high frequency ADCP. Supporting measurements show the evolution of the water column structure, including surface wave measurements from a TRIAXYS wave buoy. This data shows two distinct regimes; the first, spanning 4 days with relatively low winds, displays a distinct diurnal cycle with the deepening of the active mixing layer during the night which shoaled during the day. The second spanned a significant storm, (with maximum winds speeds reaching 20 m s-1 and significant wave heights reaching 6 m), during which, rather than a deepening of the mixed layer as predicted by classical theory, the primary effect was a broadening of the transition layer, similar to that found by Dohan and Davies (2011). During the storm, significant dissipation was observed throughout the surface mixed layer and into the transition layer, driving fluxes of heat downwards through the base of the surface mixed layer. [i] Ocean Surface Mixing and Submesoscale Interaction Study Dohan, K. & Davis, R.E., 2011. Mixing in the Transition Layer during Two Storm Events. Journal of Physical Oceanography. 41 (1). pp. 42-66.

Full particle orbit effects in regular and stochastic magnetic fields

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

Ogawa, Shun; Cambon, Benjamin P.; Leoncini, Xavier

Here we present a numerical study of charged particle motion in a time-independent magnetic field in cylindrical geometry. The magnetic field model consists of an unperturbed reversed-shear (non-monotonic q-profile) helical part and a perturbation consisting of a superposition of modes. Contrary to most of the previous studies, the particle trajectories are computed by directly solving the full Lorentz force equations of motion in a six-dimensional phase space using a sixth-order, implicit, symplectic Gauss-Legendre method. The level of stochasticity in the particle orbits is diagnosed using averaged, effective Poincare sections. It is shown that when only one mode is present, themore » particle orbits can be stochastic even though the magnetic field line orbits are not stochastic (i.e., fully integrable). The lack of integrability of the particle orbits in this case is related to separatrix crossing and the breakdown of the global conservation of the magnetic moment. Some perturbation consisting of two modes creates resonance overlapping, leading to Hamiltonian chaos in magnetic field lines. Then, the particle orbits exhibit a nontrivial dynamics depending on their energy and pitch angle. It is shown that the regions where the particle motion is stochastic decrease as the energy increases. The non-monotonicity of the q-profile implies the existence of magnetic ITBs (internal transport barriers) which correspond to shearless flux surfaces located in the vicinity of the q-profile minimum. It is shown that depending on the energy, these magnetic ITBs might or might not confine particles. That is, magnetic ITBs act as an energy-dependent particle confinement filter. Magnetic field lines in reversed-shear configurations exhibit topological bifurcations (from homoclinic to heteroclinic) due to separatrix reconnection. Finally, we show that a similar but more complex scenario appears in the case of particle orbits that depend in a non-trivial way on the energy and pitch angle of the particles.« less

Full particle orbit effects in regular and stochastic magnetic fields

DOE PAGES

Ogawa, Shun; Cambon, Benjamin P.; Leoncini, Xavier; ...

2016-07-18

Here we present a numerical study of charged particle motion in a time-independent magnetic field in cylindrical geometry. The magnetic field model consists of an unperturbed reversed-shear (non-monotonic q-profile) helical part and a perturbation consisting of a superposition of modes. Contrary to most of the previous studies, the particle trajectories are computed by directly solving the full Lorentz force equations of motion in a six-dimensional phase space using a sixth-order, implicit, symplectic Gauss-Legendre method. The level of stochasticity in the particle orbits is diagnosed using averaged, effective Poincare sections. It is shown that when only one mode is present, themore » particle orbits can be stochastic even though the magnetic field line orbits are not stochastic (i.e., fully integrable). The lack of integrability of the particle orbits in this case is related to separatrix crossing and the breakdown of the global conservation of the magnetic moment. Some perturbation consisting of two modes creates resonance overlapping, leading to Hamiltonian chaos in magnetic field lines. Then, the particle orbits exhibit a nontrivial dynamics depending on their energy and pitch angle. It is shown that the regions where the particle motion is stochastic decrease as the energy increases. The non-monotonicity of the q-profile implies the existence of magnetic ITBs (internal transport barriers) which correspond to shearless flux surfaces located in the vicinity of the q-profile minimum. It is shown that depending on the energy, these magnetic ITBs might or might not confine particles. That is, magnetic ITBs act as an energy-dependent particle confinement filter. Magnetic field lines in reversed-shear configurations exhibit topological bifurcations (from homoclinic to heteroclinic) due to separatrix reconnection. Finally, we show that a similar but more complex scenario appears in the case of particle orbits that depend in a non-trivial way on the energy and pitch angle of the particles.« less

Full particle orbit effects in regular and stochastic magnetic fields

NASA Astrophysics Data System (ADS)

Ogawa, Shun; Cambon, Benjamin; Leoncini, Xavier; Vittot, Michel; del Castillo-Negrete, Diego; Dif-Pradalier, Guilhem; Garbet, Xavier

2016-07-01

We present a numerical study of charged particle motion in a time-independent magnetic field in cylindrical geometry. The magnetic field model consists of an unperturbed reversed-shear (non-monotonic q-profile) helical part and a perturbation consisting of a superposition of modes. Contrary to most of the previous studies, the particle trajectories are computed by directly solving the full Lorentz force equations of motion in a six-dimensional phase space using a sixth-order, implicit, symplectic Gauss-Legendre method. The level of stochasticity in the particle orbits is diagnosed using averaged, effective Poincare sections. It is shown that when only one mode is present, the particle orbits can be stochastic even though the magnetic field line orbits are not stochastic (i.e., fully integrable). The lack of integrability of the particle orbits in this case is related to separatrix crossing and the breakdown of the global conservation of the magnetic moment. Some perturbation consisting of two modes creates resonance overlapping, leading to Hamiltonian chaos in magnetic field lines. Then, the particle orbits exhibit a nontrivial dynamics depending on their energy and pitch angle. It is shown that the regions where the particle motion is stochastic decrease as the energy increases. The non-monotonicity of the q-profile implies the existence of magnetic ITBs (internal transport barriers) which correspond to shearless flux surfaces located in the vicinity of the q-profile minimum. It is shown that depending on the energy, these magnetic ITBs might or might not confine particles. That is, magnetic ITBs act as an energy-dependent particle confinement filter. Magnetic field lines in reversed-shear configurations exhibit topological bifurcations (from homoclinic to heteroclinic) due to separatrix reconnection. We show that a similar but more complex scenario appears in the case of particle orbits that depend in a non-trivial way on the energy and pitch angle of the particles.

Simultaneous Conduction and Valence Band Quantization in Ultrashallow High-Density Doping Profiles in Semiconductors

NASA Astrophysics Data System (ADS)

Mazzola, F.; Wells, J. W.; Pakpour-Tabrizi, A. C.; Jackman, R. B.; Thiagarajan, B.; Hofmann, Ph.; Miwa, J. A.

2018-01-01

We demonstrate simultaneous quantization of conduction band (CB) and valence band (VB) states in silicon using ultrashallow, high-density, phosphorus doping profiles (so-called Si:P δ layers). We show that, in addition to the well-known quantization of CB states within the dopant plane, the confinement of VB-derived states between the subsurface P dopant layer and the Si surface gives rise to a simultaneous quantization of VB states in this narrow region. We also show that the VB quantization can be explained using a simple particle-in-a-box model, and that the number and energy separation of the quantized VB states depend on the depth of the P dopant layer beneath the Si surface. Since the quantized CB states do not show a strong dependence on the dopant depth (but rather on the dopant density), it is straightforward to exhibit control over the properties of the quantized CB and VB states independently of each other by choosing the dopant density and depth accordingly, thus offering new possibilities for engineering quantum matter.

Ultraviolet laser transverse profile shaping for improving x-ray free electron laser performance

DOE PAGES

Li, S.; Alverson, S.; Bohler, D.; ...

2017-08-17

The photocathode rf gun is one of the most critical components in x-ray free electron lasers. The drive laser strikes the photocathode surface, which emits electrons with properties that depend on the shape of the drive laser. Most free electron lasers use photocathodes with work function in the ultraviolet, a wavelength where direct laser manipulation becomes challenging. In this paper, we present a novel application of a digital micromirror device (DMD) for the 253 nm drive laser at the Linear Coherent Light Source. Laser profile shaping is accomplished through an iterative algorithm that takes into account shaping error and efficiency.more » Next, we use laser shaping to control the X-ray laser output via an online optimizer, which shows improvement in FEL pulse energy. Lastly, as a preparation for electron beam shaping, we use the DMD to measure the photocathode quantum efficiency across cathode surface with an averaged laser rms spot size of 59 μm. In conclusion, our experiments demonstrate promising outlook of using DMD to shape ultraviolet lasers for photocathode rf guns with various applications.« less

Thermal performance of an integrated collector storage solar water heater (ICSSWH) with a storage tank equipped with radial fins of rectangular profile

NASA Astrophysics Data System (ADS)

Chaabane, Monia; Mhiri, Hatem; Bournot, Philippe

2013-01-01

The thermal behavior of an integrated collector storage solar water heater (ICSSWH) is numerically studied using the package Fluent 6.3. Based on the good agreement between the numerical results and the experimental data of Chaouachi and Gabsi (Renew Energy Revue 9(2):75-82, 2006), an attempt to improve this solar system operating was made by equipping the storage tank with radial fins of rectangular profile. A second 3D CFD model was developed and a series of numerical simulations were conducted for various SWH designs which differ in the depth of this extended surface for heat exchange. As the modified surface presents a higher characteristic length for convective heat transfer from the storage tank to the water, the fins equipped storage tank based SWH is determined to have a higher water temperature and a reduced thermal losses coefficient during the day-time period. Regarding the night operating of this water heater, the results suggest that the modified system presents higher thermal losses.

Interaction and dispersion of waveguide modes in an optical fiber with microirregularities of the core surface

NASA Astrophysics Data System (ADS)

Zadorin, A. S.; Kruglov, R. S.; Surkova, G. A.

2012-08-01

A self-consistent linear model is proposed for the transformation of the average intensity of the mode spectrum I( z) of the waveguide field in a multimode optical fiber with a stepped refractive index profile and the core having a rough surface. The model is based on the concept of the intermodal dispersion matrix of an elementary segment of the fiber, ∆, whose elements characterize the mutual transfer of energy between the waveguide modes, as well as their conversion to radiation modes on the specified interval. On this basis, the features of the transformation of the mode spectrum I( z) in a multimode optical fiber with a stepped refractive index profile are considered that is due to the effects of multiple dispersion of the signal by the stochastic irregularities of the duct. The effect of self-filtering of I( z) is described that results in the formation of a stable (normalized) distribution I*. The features of the normalization of the radiative damping of a group of modes I i ( z) in an optical fiber are considered.