Hydrogenated amorphous silicon(a-Si:H) films were deposited by reactive facing target sputtering(FTS) technique with a mixture of Ar and H2 reaction gas.Fourier transform infrared(FTIR) absorption,Raman scattering and...Hydrogenated amorphous silicon(a-Si:H) films were deposited by reactive facing target sputtering(FTS) technique with a mixture of Ar and H2 reaction gas.Fourier transform infrared(FTIR) absorption,Raman scattering and ultraviolet-visible optical absorption are used to investigate the microstructure and optical properties of the deposited films.The decrease of the concentration of bonded hydrogen,especially that of(Si-H2)n with increasing substrate temperature(Ts),was observed in FTIR spectra,suggesting the atomic density increases and the concentration of microvoids decrease in a-Si:H films.The increase of both the short range order and the intermediate range order of amorphous network for a-Si:H films were verified by Raman scattering spectra,in which increasing Ts decreasing the band width of TO and the scattering intensity ratio ITA/ITO were obtained.All above results clarify the effect of increasing Ts on the microstructure amelioration for a-Si:H films.The reduction of disordered domains is correlated with the film growing process,where the increased surface diffusion mobility and etching of weak bonds is induced by increasing Ts.Furthermore,analysis of optical absorption indicates that the films with a lower optical band gap and a narrower band edge can be obtained by this FTS technique.展开更多
Using land-use types derived from satellite remote sensing data collected by the EOS Moderate Resolution Imaging Spectroradiometer （EOS/MODIS）, the mesoscale and turbulent fluxes generated by inhomogeneities of the ...Using land-use types derived from satellite remote sensing data collected by the EOS Moderate Resolution Imaging Spectroradiometer （EOS/MODIS）, the mesoscale and turbulent fluxes generated by inhomogeneities of the underlying surface over the Jinta Oasis, northwestern China, were simulated using the Regional Atmospheric Modeling System （RAMS4.4）. The results indicate that mesoscale circulation generated by land-surface inhomogeneities over the Jinta Oasis is more important than turbulence. Vertical heat fluxes and water vapor are transported to higher levels by mesoscale circulation. Mesoscale circulation also produces mesoscale synoptic systems and prevents water vapor over the oasis from running off. Mesoscale circulation transports moisture to higher atmospheric levels as the land-surface moisture over the oasis increases, favoring the formation of clouds, which sometimes leads to rainfall. Large-scale wind speed has a significant impact on mesoscale heat fluxes. During the active phase of mesoscale circulation, the stronger large-scale winds are associated with small mesoscale fluxes; however, background wind seems to intensify the turbulent sensible heat flux and turbulent latent heat flux. If the area of oasis is enlarged properly, mesoscale circulation will be able to transport moisture to higher levels, favoring the formation of rainfall in the oasis and protecting its ＂cold island＂ effect. The impact of irrigation on rainfall is important, and increasing irrigation across the oasis is necessary to protect the oasis.展开更多
Purpose: The dosimetric accuracy of the recently released Acuros XB advanced dose calculation algorithm (Varian Medical Systems, Palo Alto, CA) is investigated for single radiation fields incident on homogeneous and h...Purpose: The dosimetric accuracy of the recently released Acuros XB advanced dose calculation algorithm (Varian Medical Systems, Palo Alto, CA) is investigated for single radiation fields incident on homogeneous and heterogeneous geometries, as well as for two arc (VMAT) cases and compared against the analytical anisotropic algorithm (AAA), the collapsed cone convolution superposition algorithm (CCCS) and Monte Carlo (MC) calculations for the same geometries. Methods and Materials: Small open fields ranging from 1 × 1 cm2 to 5 × 5 cm2 were used for part of this study. The fields were incident on phantoms containing lung, air, and bone inhomogeneities. The dosimetric accuracy of Acuros XB, AAA and CCCS in the presence of the inhomogeneities was compared against BEAMnrc/DOSXYZnrc calculations that were considered as the benchmark. Furthermore, two clinical cases of arc deliveries were used to test the accuracy of the dose calculation algorithms against MC. Results: Open field tests in a homogeneous phantom showed good agreement between all dose calculation algorithms and MC. The dose agreement was +/?1.5% for all field sizes and energies. Dose calculation in heterogenous phantoms showed that the agreement between Acuros XB and CCCS was within 2% in the case of lung and bone. AAA calculations showed deviation of approximately 5%. In the case of the air heterogeneity, the differences were larger for all calculations algorithms. The calculation in the patient CT for a lung and bone (paraspinal targets) showed that all dose calculation algorithms predicted the dose in the middle of the target accurately;however, small differences (2% - 5%) were observed at the low dose region. Overall, when compared to MC, the Acuros XB and CCCS had better agreement than AAA. Conclusions: The Acuros XB calculation algorithm in the newest version of the Eclipse treatment planning system is an improvement over the existing AAA algorithm. The results are comparable to CCCS and MC calculations especially for both stylized and clinical ca展开更多
We have studied the forward I-V characteristics of In-pWSe2Schottky barrier diode with 1000 ? indium thickness in the temperature range 140 – 300 K well within the domain of thermionic emission theory with Gaussian d...We have studied the forward I-V characteristics of In-pWSe2Schottky barrier diode with 1000 ? indium thickness in the temperature range 140 – 300 K well within the domain of thermionic emission theory with Gaussian distribution of barrier height. However we found some anomalies in the low temperature range below 200 K. Hence we have considered a model that incorporates thermionic emission, generation recombination and tunneling components. The low temperature anomalies observed in the diode parameters were effectively construed in terms of the contribution of these multiple charge transport mechanisms across the interface of the fabricated diodes. Various Schottky diode parameters were also extracted and compared with that of 500 ? metal thickness In-pWSe2 diode.展开更多
From a limit model in electric field obtained by letting the frequency vanish in the time-harmonic Maxwell equations, we consider a limit perturbation model in the tangential boundary trace of the curl of the electric...From a limit model in electric field obtained by letting the frequency vanish in the time-harmonic Maxwell equations, we consider a limit perturbation model in the tangential boundary trace of the curl of the electric field for localizing numerically certain small electromagnetic inhomogeneities, in a three-dimensional bounded domain. We introduce here two localization procedures resulting from the combination of this limit perturbation model with each of the following inversion processes： the Current Projection method and an Inverse Fourier method. Each localization procedure uses, as data, a finite number of boundary measurements, and is employed in the single inhomogeneity case; only the one based on an Inverse Fourier method is required in the multiple inhomogeneities case. Our localization approach is numerically suitable for the context of inhomogeneities that are not purely electric. We compare the numerical results obtained from the two localization procedures in the single inhomogeneity configuration, and describe, in various settings of multiple inhomogeneities, the results provided by the procedure based on an Inverse Fourier method.展开更多
Asymptotic expansions of the voltage potential in terms of the "radius" of a diametrically small(or several diametrically small) material inhomogeneity(ies) are by now quite well-known. Such asymptotic expan...Asymptotic expansions of the voltage potential in terms of the "radius" of a diametrically small(or several diametrically small) material inhomogeneity(ies) are by now quite well-known. Such asymptotic expansions for diametrically small inhomogeneities are uniform with respect to the conductivity of the inhomogeneities.In contrast, thin inhomogeneities, whose limit set is a smooth, codimension 1 manifold,σ, are examples of inhomogeneities for which the convergence to the background potential,or the standard expansion cannot be valid uniformly with respect to the conductivity, a, of the inhomogeneity. Indeed, by taking a close to 0 or to infinity, one obtains either a nearly homogeneous Neumann condition or nearly constant Dirichlet condition at the boundary of the inhomogeneity, and this difference in boundary condition is retained in the limit.The purpose of this paper is to find a "simple" replacement for the background potential, with the following properties:(1) This replacement may be(simply) calculated from the limiting domain Ω\σ, the boundary data on the boundary of Ω, and the right-hand side.(2) This replacement depends on the thickness of the inhomogeneity and the conductivity,a, through its boundary conditions on σ.(3) The difference between this replacement and the true voltage potential converges to 0 uniformly in a, as the inhomogeneity thickness tends to 0.展开更多
Thermal stress appears in metal matrix composite,complex phase ceramics,etc.during cooling from their manufactured temperature, which affects the mechanical behavior and the service life; therefore, much attention has...Thermal stress appears in metal matrix composite,complex phase ceramics,etc.during cooling from their manufactured temperature, which affects the mechanical behavior and the service life; therefore, much attention has been paid to investigating thermal stress in the composite. Up to now, researches in this field are展开更多
In this work we have realized a simplified model to analyze compositional inhomogeneities in commercial hydrogen storage alloys. We have used it to evaluate the effect of the thermal annealing, together with calorimet...In this work we have realized a simplified model to analyze compositional inhomogeneities in commercial hydrogen storage alloys. We have used it to evaluate the effect of the thermal annealing, together with calorimetric, PCIs and XRD measurement. We have compared results with composition distribution histograms based on Rietveld refinement of XRD patterns. Finally we studied the variation of α and β phases crystallographic parameters with H2 pressure.展开更多
We are concerned, in a static regime, with a three-dimensional bounded domain of certain an imaging approach of the locations in electromagnetic imperfections. This approach is related to Electrical Impedance Tomograp...We are concerned, in a static regime, with a three-dimensional bounded domain of certain an imaging approach of the locations in electromagnetic imperfections. This approach is related to Electrical Impedance Tomography and makes use of a new perturbation formula in the electric fields. We present two localization procedures, from a Current Pro- jection method that deals with the single imperfection context and an inverse Fourier process that is devoted to multiple imperfections configurations. These procedures extend those that were described in our previous work, since operating for a broader class of settings. Namely, the localization is additionally performed for certain purely electric imperfections, as established from numerical simulations.展开更多
A fibre laser at 1111.6 nm is frequency doubled by two inhomogeneous MgO：LiNbO3 waveguides and the output powers of 85 mW and 49 mW at 555.8 nm have been generated with the conversion efficiencies of 47% and 27% resp...A fibre laser at 1111.6 nm is frequency doubled by two inhomogeneous MgO：LiNbO3 waveguides and the output powers of 85 mW and 49 mW at 555.8 nm have been generated with the conversion efficiencies of 47% and 27% respectively. By analysing the second harmonic generation temperature tuning curves, we investigate the influence of the optical inhomogeneities upon the conversion efficiency. The final result shows that the efficiency difference is mainly affected by the optical inhomogeneities in our case.展开更多
Theoretical solid-state physicists formulate their models usually in the form of a Hamiltonian. In quantum mechanics, the Hamilton operator (Hamiltonian) is of fundamental importance in most formulations of quantum th...Theoretical solid-state physicists formulate their models usually in the form of a Hamiltonian. In quantum mechanics, the Hamilton operator (Hamiltonian) is of fundamental importance in most formulations of quantum theory. Mentioned operator corresponds to the total energy of the system and its spectrum determines the set of possible outcomes when one measures the total energy. Interpretation of results obtained by the applying of models based on the Hamiltonian indicates very specific mechanisms of some observed phenomena that are not fully consistent with the experience. Such approach may occasionally lead to surprises when obtained results are confronted with expectations. The aim of this work is to find Hamilton operator of acoustic phonons in inhomogeneous solids. The transport of energy in the vibrating crystal consisting of ions whose properties differ over long distances is described in the work. We modeled crystal lattice by 1D “inhomogeneous” ionic chain vibrating by acoustic frequencies and found the Hamiltonian of such system in the second quantization. The influence of long-distance inhomogeneities on the acoustic phonons quantum states can be discussed on basis of our results.展开更多
With the Riemann solver to the scalar hyperbolic conservation law with a spatially varying flux, a δ-mapping algorithm was proposed. The algorithm and its prospective application in traffic flow problems were briefed...With the Riemann solver to the scalar hyperbolic conservation law with a spatially varying flux, a δ-mapping algorithm was proposed. The algorithm and its prospective application in traffic flow problems were briefed in the paper.展开更多
Numerous articles have examined archival weather observations and attributed climate changes on time scales ranging from centuries to decades and in one case even days to human activity. This article gives examples sh...Numerous articles have examined archival weather observations and attributed climate changes on time scales ranging from centuries to decades and in one case even days to human activity. This article gives examples showing how climate variability and sudden changes in instruments affect trend determination. In particular, surface temperature and water vapor pressure trends in North America during 1948-2010 are discussed. Over 1/4 billion hourly observations taken at 309 stations, were first carefully examined for inhomogeneities. Positive and negative steps, for both temperature and water vapor pressure were found to not be evenly distributed in time. Inclusion of such data in a trend analysis would overstate decadal changes in temperature and water vapor. Time series free of such discontinuities show a statistically significant warming has primarily affected the western Arctic, Canadian prairies and the Midwestern U.S. during winter. Increases in water vapor pressure are most pronounced in summer in the eastern U.S. The decadal water vapor pressure trends are somewhat smaller than found in other studies that examined data for far shorter time periods. The claim of a change in the DTR （diurnal temperature range） during the 3 day flight ban following Sept. 11, 2011, is not substantiated. The observed change in the DTR was likely caused by a reduction in cloudiness during the flight ban.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 60940020)the Natural Foundation of Hebei Province (Grant Nos. E2008000619 and E2009000208)
文摘Hydrogenated amorphous silicon(a-Si:H) films were deposited by reactive facing target sputtering(FTS) technique with a mixture of Ar and H2 reaction gas.Fourier transform infrared(FTIR) absorption,Raman scattering and ultraviolet-visible optical absorption are used to investigate the microstructure and optical properties of the deposited films.The decrease of the concentration of bonded hydrogen,especially that of(Si-H2)n with increasing substrate temperature(Ts),was observed in FTIR spectra,suggesting the atomic density increases and the concentration of microvoids decrease in a-Si:H films.The increase of both the short range order and the intermediate range order of amorphous network for a-Si:H films were verified by Raman scattering spectra,in which increasing Ts decreasing the band width of TO and the scattering intensity ratio ITA/ITO were obtained.All above results clarify the effect of increasing Ts on the microstructure amelioration for a-Si:H films.The reduction of disordered domains is correlated with the film growing process,where the increased surface diffusion mobility and etching of weak bonds is induced by increasing Ts.Furthermore,analysis of optical absorption indicates that the films with a lower optical band gap and a narrower band edge can be obtained by this FTS technique.
基金supported by the National Basic Research Program (also called 973 Program) (Grant No. 2009CB421402)Chinese National Science Foundation Program (Grant No. 40975007),Chinese National Science Foundation Program (Grant No. 40633014)+1 种基金China Postdoctoral Science Foundation (Grant No. 119100581F)Important Program of State Key Laboratory of Severe Weather Chinese Academy of Meteorological Sciences (Grant No. 2010LASW-A02)
文摘Using land-use types derived from satellite remote sensing data collected by the EOS Moderate Resolution Imaging Spectroradiometer （EOS/MODIS）, the mesoscale and turbulent fluxes generated by inhomogeneities of the underlying surface over the Jinta Oasis, northwestern China, were simulated using the Regional Atmospheric Modeling System （RAMS4.4）. The results indicate that mesoscale circulation generated by land-surface inhomogeneities over the Jinta Oasis is more important than turbulence. Vertical heat fluxes and water vapor are transported to higher levels by mesoscale circulation. Mesoscale circulation also produces mesoscale synoptic systems and prevents water vapor over the oasis from running off. Mesoscale circulation transports moisture to higher atmospheric levels as the land-surface moisture over the oasis increases, favoring the formation of clouds, which sometimes leads to rainfall. Large-scale wind speed has a significant impact on mesoscale heat fluxes. During the active phase of mesoscale circulation, the stronger large-scale winds are associated with small mesoscale fluxes; however, background wind seems to intensify the turbulent sensible heat flux and turbulent latent heat flux. If the area of oasis is enlarged properly, mesoscale circulation will be able to transport moisture to higher levels, favoring the formation of rainfall in the oasis and protecting its ＂cold island＂ effect. The impact of irrigation on rainfall is important, and increasing irrigation across the oasis is necessary to protect the oasis.
文摘Purpose: The dosimetric accuracy of the recently released Acuros XB advanced dose calculation algorithm (Varian Medical Systems, Palo Alto, CA) is investigated for single radiation fields incident on homogeneous and heterogeneous geometries, as well as for two arc (VMAT) cases and compared against the analytical anisotropic algorithm (AAA), the collapsed cone convolution superposition algorithm (CCCS) and Monte Carlo (MC) calculations for the same geometries. Methods and Materials: Small open fields ranging from 1 × 1 cm2 to 5 × 5 cm2 were used for part of this study. The fields were incident on phantoms containing lung, air, and bone inhomogeneities. The dosimetric accuracy of Acuros XB, AAA and CCCS in the presence of the inhomogeneities was compared against BEAMnrc/DOSXYZnrc calculations that were considered as the benchmark. Furthermore, two clinical cases of arc deliveries were used to test the accuracy of the dose calculation algorithms against MC. Results: Open field tests in a homogeneous phantom showed good agreement between all dose calculation algorithms and MC. The dose agreement was +/?1.5% for all field sizes and energies. Dose calculation in heterogenous phantoms showed that the agreement between Acuros XB and CCCS was within 2% in the case of lung and bone. AAA calculations showed deviation of approximately 5%. In the case of the air heterogeneity, the differences were larger for all calculations algorithms. The calculation in the patient CT for a lung and bone (paraspinal targets) showed that all dose calculation algorithms predicted the dose in the middle of the target accurately;however, small differences (2% - 5%) were observed at the low dose region. Overall, when compared to MC, the Acuros XB and CCCS had better agreement than AAA. Conclusions: The Acuros XB calculation algorithm in the newest version of the Eclipse treatment planning system is an improvement over the existing AAA algorithm. The results are comparable to CCCS and MC calculations especially for both stylized and clinical ca
文摘We have studied the forward I-V characteristics of In-pWSe2Schottky barrier diode with 1000 ? indium thickness in the temperature range 140 – 300 K well within the domain of thermionic emission theory with Gaussian distribution of barrier height. However we found some anomalies in the low temperature range below 200 K. Hence we have considered a model that incorporates thermionic emission, generation recombination and tunneling components. The low temperature anomalies observed in the diode parameters were effectively construed in terms of the contribution of these multiple charge transport mechanisms across the interface of the fabricated diodes. Various Schottky diode parameters were also extracted and compared with that of 500 ? metal thickness In-pWSe2 diode.
基金supported by ACI NIM(171)from the French Ministry of Education and Scientific Research
文摘From a limit model in electric field obtained by letting the frequency vanish in the time-harmonic Maxwell equations, we consider a limit perturbation model in the tangential boundary trace of the curl of the electric field for localizing numerically certain small electromagnetic inhomogeneities, in a three-dimensional bounded domain. We introduce here two localization procedures resulting from the combination of this limit perturbation model with each of the following inversion processes： the Current Projection method and an Inverse Fourier method. Each localization procedure uses, as data, a finite number of boundary measurements, and is employed in the single inhomogeneity case; only the one based on an Inverse Fourier method is required in the multiple inhomogeneities case. Our localization approach is numerically suitable for the context of inhomogeneities that are not purely electric. We compare the numerical results obtained from the two localization procedures in the single inhomogeneity configuration, and describe, in various settings of multiple inhomogeneities, the results provided by the procedure based on an Inverse Fourier method.
基金partially supported by NSF grant DMS-12-11330 while CD was a postdoctoral visitor at Rutgers University and by the NSF IR/D program while MSV served at the National Science Foundation
文摘Asymptotic expansions of the voltage potential in terms of the "radius" of a diametrically small(or several diametrically small) material inhomogeneity(ies) are by now quite well-known. Such asymptotic expansions for diametrically small inhomogeneities are uniform with respect to the conductivity of the inhomogeneities.In contrast, thin inhomogeneities, whose limit set is a smooth, codimension 1 manifold,σ, are examples of inhomogeneities for which the convergence to the background potential,or the standard expansion cannot be valid uniformly with respect to the conductivity, a, of the inhomogeneity. Indeed, by taking a close to 0 or to infinity, one obtains either a nearly homogeneous Neumann condition or nearly constant Dirichlet condition at the boundary of the inhomogeneity, and this difference in boundary condition is retained in the limit.The purpose of this paper is to find a "simple" replacement for the background potential, with the following properties:(1) This replacement may be(simply) calculated from the limiting domain Ω\σ, the boundary data on the boundary of Ω, and the right-hand side.(2) This replacement depends on the thickness of the inhomogeneity and the conductivity,a, through its boundary conditions on σ.(3) The difference between this replacement and the true voltage potential converges to 0 uniformly in a, as the inhomogeneity thickness tends to 0.
文摘Thermal stress appears in metal matrix composite,complex phase ceramics,etc.during cooling from their manufactured temperature, which affects the mechanical behavior and the service life; therefore, much attention has been paid to investigating thermal stress in the composite. Up to now, researches in this field are
文摘In this work we have realized a simplified model to analyze compositional inhomogeneities in commercial hydrogen storage alloys. We have used it to evaluate the effect of the thermal annealing, together with calorimetric, PCIs and XRD measurement. We have compared results with composition distribution histograms based on Rietveld refinement of XRD patterns. Finally we studied the variation of α and β phases crystallographic parameters with H2 pressure.
文摘We are concerned, in a static regime, with a three-dimensional bounded domain of certain an imaging approach of the locations in electromagnetic imperfections. This approach is related to Electrical Impedance Tomography and makes use of a new perturbation formula in the electric fields. We present two localization procedures, from a Current Pro- jection method that deals with the single imperfection context and an inverse Fourier process that is devoted to multiple imperfections configurations. These procedures extend those that were described in our previous work, since operating for a broader class of settings. Namely, the localization is additionally performed for certain purely electric imperfections, as established from numerical simulations.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10774044)the National Key Basic Research and Development Program of China (Grant No. 2010CB922903)+1 种基金the Shanghai Pujiang Talent Program of China (Grant No. 07PJ14038)the Ph D Program Scholarship Fund of East China Normal University 2009 (Grant No. 2009049)
文摘A fibre laser at 1111.6 nm is frequency doubled by two inhomogeneous MgO：LiNbO3 waveguides and the output powers of 85 mW and 49 mW at 555.8 nm have been generated with the conversion efficiencies of 47% and 27% respectively. By analysing the second harmonic generation temperature tuning curves, we investigate the influence of the optical inhomogeneities upon the conversion efficiency. The final result shows that the efficiency difference is mainly affected by the optical inhomogeneities in our case.
文摘Theoretical solid-state physicists formulate their models usually in the form of a Hamiltonian. In quantum mechanics, the Hamilton operator (Hamiltonian) is of fundamental importance in most formulations of quantum theory. Mentioned operator corresponds to the total energy of the system and its spectrum determines the set of possible outcomes when one measures the total energy. Interpretation of results obtained by the applying of models based on the Hamiltonian indicates very specific mechanisms of some observed phenomena that are not fully consistent with the experience. Such approach may occasionally lead to surprises when obtained results are confronted with expectations. The aim of this work is to find Hamilton operator of acoustic phonons in inhomogeneous solids. The transport of energy in the vibrating crystal consisting of ions whose properties differ over long distances is described in the work. We modeled crystal lattice by 1D “inhomogeneous” ionic chain vibrating by acoustic frequencies and found the Hamiltonian of such system in the second quantization. The influence of long-distance inhomogeneities on the acoustic phonons quantum states can be discussed on basis of our results.
文摘With the Riemann solver to the scalar hyperbolic conservation law with a spatially varying flux, a δ-mapping algorithm was proposed. The algorithm and its prospective application in traffic flow problems were briefed in the paper.
文摘Numerous articles have examined archival weather observations and attributed climate changes on time scales ranging from centuries to decades and in one case even days to human activity. This article gives examples showing how climate variability and sudden changes in instruments affect trend determination. In particular, surface temperature and water vapor pressure trends in North America during 1948-2010 are discussed. Over 1/4 billion hourly observations taken at 309 stations, were first carefully examined for inhomogeneities. Positive and negative steps, for both temperature and water vapor pressure were found to not be evenly distributed in time. Inclusion of such data in a trend analysis would overstate decadal changes in temperature and water vapor. Time series free of such discontinuities show a statistically significant warming has primarily affected the western Arctic, Canadian prairies and the Midwestern U.S. during winter. Increases in water vapor pressure are most pronounced in summer in the eastern U.S. The decadal water vapor pressure trends are somewhat smaller than found in other studies that examined data for far shorter time periods. The claim of a change in the DTR （diurnal temperature range） during the 3 day flight ban following Sept. 11, 2011, is not substantiated. The observed change in the DTR was likely caused by a reduction in cloudiness during the flight ban.
