Effective atomic numbers for photon energy absorption(ZPEA_(eff)) and their corresponding electron numbers (NPEA_(eff)), and effective macroscopic removal cross sections of fast neutrons(RR) were calculated for 27 dif...Effective atomic numbers for photon energy absorption(ZPEA_(eff)) and their corresponding electron numbers (NPEA_(eff)), and effective macroscopic removal cross sections of fast neutrons(RR) were calculated for 27 different types of three-dimensional dosimeters, four types of phantom materials, and water. The values of ZPEA_(eff) and NPEA_(eff) were obtained using the direct method for energies ranging from 10 keV to 20 MeV. Results are presented relative to water, for direct comparison over the range of examined energies. The effect of monomers that are used in polymer gel dosimeters on the water equivalence is discussed. The relation between Σ_R and hydrogen content was studied. Micelle gel dosimeters are highly promising because our results demonstrate perfect matching between the effective atomic number, electron density number, and fast neutron attenuation coefficient of water.展开更多
Fully differential cross sections (FDCS) are calculated within a four-body model for single ionization of helium by C6+ impact at the incident energy of 100 MeV/a.u. (atomic unit). The results are compared with e...Fully differential cross sections (FDCS) are calculated within a four-body model for single ionization of helium by C6+ impact at the incident energy of 100 MeV/a.u. (atomic unit). The results are compared with experimental data and other theoretical predictions. It is shown that our results are in very good agreement with experiment for three small momentum transfers in the scattering plane; however, some significant discrepancies are still present at the largest momentum transfer in both the scattering plane and the perpendicular plane. In actuality, the problem has not been explained by the theory during the last decade. Accordingly, the contributions of different scattering amplitudes to FDCS are analyzed. It is found that for the largest momentum transfer the cross section arising from a destructive interference of the three amplitudes is much smaller than the experimental data. However, the cross section due to the constructive interference of two scattering amplitudes between projectile-ionized electron interaction and projectile-passive electron interaction almost approaches the experimental data.展开更多
Probing in-medium nucleon-nucleon (NN) cross section σ1/NN(α) in heavy ion collisions has been investigated by means of the isospin-dependent quantum molecular dynamics (IQMD) with the isospin- and momentum-de...Probing in-medium nucleon-nucleon (NN) cross section σ1/NN(α) in heavy ion collisions has been investigated by means of the isospin-dependent quantum molecular dynamics (IQMD) with the isospin- and momentum-dependent interaction (IMDI(T)). It is found that there are the very obvious medium effect and the sensitive isospin-dependence of nuclear stopping R on the in-medium NN cross section α1/NN(α) in the nuclear reactions induced by halo-neutron projectile and the same-mass stable projectile. However, R induced by the neutron-halo projectile is obviously lower than that induced by the corresponding stable projectile. In particular, there is a very obvious dependence of R on the medium effect of σ1/NN(α) in the whole beam energy region for the above two kinds of projectiles. Therefore, the comparison between the results of R's in the reactions induced by the neutron-halo projectile and the corresponding same-mass stable projectile is a more favourable probe for extracting the information of σ1/NN(α) because of adding a new judgement.展开更多
This paper presents the fully differential cross sections (FDCS) for 102eV electron impact single ionization of helium for both the coplanar and perpendicular plane asymmetric geometries within the framework of dyna...This paper presents the fully differential cross sections (FDCS) for 102eV electron impact single ionization of helium for both the coplanar and perpendicular plane asymmetric geometries within the framework of dynamically screened three-Coulomb-wave theory. Comparisons are made with the experimental data and those of the three-Coulomb wave function model and second-order distorted-wave Born method. The angular distribution and relative heights of the present FDCS is found to be in very good agreement with the experimental data in the perpendicular plane geometry. It is shown that dynamical screening effects are significant in this geometry. Three-body coupling is expected to be weak in the coplanar geometry, although the precise absolute value of the cross section is still sensitive to the interaction details.展开更多
The four-body model has been used to calculate the fully differential cross-sections (FDCS) for the single ionization of helium by 100 MeV/amu Ca^+ impact in geometries. By comparing with experimental data and othe...The four-body model has been used to calculate the fully differential cross-sections (FDCS) for the single ionization of helium by 100 MeV/amu Ca^+ impact in geometries. By comparing with experimental data and other theories, we find the results of four-body model are in very good agreement in the scattering plane, but poor agreement out of the scattering plane. Accordingly, the contributions of different scattering amplitudes to FDCS are analyzed. It is found that the cross sections due to the interference of the scattering amplitudes between projectile-target nucleus interaction and projectile-ejected electron interaction almost tend to experimental results around the recoil region in geometries. In particular in the perpendicular plane, the cross section originating from interference of the scattering amplitudes between projectile-target nucleus and projectile-ejected electron interactions yields an experimental double-peak structure in the angular distribution. However, this feature could not be presented by the interference of the three amplitudes. Thus, the failure of the fourbody model predicting the feature in this geometry may be attributed to an inappropriate weighting of the three amplitudes.展开更多
Based on the statistical model and taking into account the Q-value dependence and odd-even effects, we proposed a new empirical formula to reproduce the cross sections of the (n, p) reactions at 14.7 MeV neutron energ...Based on the statistical model and taking into account the Q-value dependence and odd-even effects, we proposed a new empirical formula to reproduce the cross sections of the (n, p) reactions at 14.7 MeV neutron energy and at the target mass number 14 ≤ A ≤ 198 for even A and 29 ≤ A ≤ 205 for odd A. All calculated results from the proposed empirical formula were compared to the experimental data as well as the available semi-empirical formula obtained by other authors. A high level of agreement has been found between the collected experimental data and the most of semiempirical formulae obtained by others.展开更多
In this paper, we studied the process of dissociation unimolecular of the evaporation of H+2n+1 hydrogen clusters according to size, using the Rice-Ramsperger-Kassel-Marcus (RRKM) theory. The rate constants k(E) were ...In this paper, we studied the process of dissociation unimolecular of the evaporation of H+2n+1 hydrogen clusters according to size, using the Rice-Ramsperger-Kassel-Marcus (RRKM) theory. The rate constants k(E) were determined with the use of statistical theory of unimolecular reactions using various approximations. In our work, we used the products frequencies instead of transitions frequencies in the calculation of unimolecular dissociation rates obtained by three models RRKM. The agreement between the experimental cross section ratio and calculated rate ratio with direct count approximation seems to be reasonable.展开更多
A numerical study has been conducted to explore the role of photoemission cross sections in the impurity photovoltaic(IPV) effect for silicon solar cells doped with indium. The photovoltaic parameters(short-circuit...A numerical study has been conducted to explore the role of photoemission cross sections in the impurity photovoltaic(IPV) effect for silicon solar cells doped with indium. The photovoltaic parameters(short-circuit current density, opencircuit voltage, and conversion efficiency) of the IPV solar cell were calculated as functions of variable electron and hole photoemission cross sections. The presented results show that the electron and hole photoemission cross sections play critical roles in the IPV effect. When the electron photoemission cross section is 10^-20cm^2, the conversion efficiencyη of the IPV cell always has a negative gain(△η 0) if the IPV impurity is introduced. A large hole photoemission cross section can adversely impact IPV solar cell performance. The combination of a small hole photoemission cross section and a large electron photoemission cross section can achieve higher conversion efficiency for the IPV solar cell since a large electron photoemission cross section can enhance the necessary electron transition from the impurity level to the conduction band and a small hole photoemission cross section can reduce the needless sub-bandgap absorption. It is concluded that those impurities with small(large) hole photoemission cross section and large(small) electron photoemission cross section,whose energy levels are near the valence(or conduction) band edge, may be suitable for use in IPV solar cells. These results may help in judging whether or not an impurity is appropriate for use in IPV solar cells according to its electron and hole photoemission cross sections.展开更多
Interference effects on the photoionization cross sections between two neighbouring atoms are considered based on the coherent scattering of the ionized electrons by the two nuclei when their separation is less than o...Interference effects on the photoionization cross sections between two neighbouring atoms are considered based on the coherent scattering of the ionized electrons by the two nuclei when their separation is less than or comparable to the de Broglie wave length of the ionized electrons. As an example, the single atomic nitrogen ionization cross section and the total cross sections of two nitrogen atoms with coherently added photoionization amplitudes are calculated from the threshold to about А (1 А=0.1 nm) of the photon energy. The photoionization cross sections of atomic nitrogen are obtained by using the close-coupling R-matrix method. In the calculation 19 states are included. The ionization energy of the atomic nitrogen and the photoionization cross sections agree well with the experimental results. Based on the R-matrix results of atomic nitrogen, the interference effects between two neighbouring nitrogen atoms are obtained. It is shown that the interference effects are considerable when electrons are ionized just above the threshold, even for the separations between the two atoms are larger than two times of the bond length of N2 molecules. Therefore, in hot and dense samples, effects caused by the coherent interference between the neighbours are expected to be observable for the total photoionization cross sections.展开更多
The influence of isospin on the excess of evaporation residue cross section over its standard statistical-model value for nuclei ^194pb, ^200Pb, and ^206pb is studied via a Langevin equation coupled with a statistical...The influence of isospin on the excess of evaporation residue cross section over its standard statistical-model value for nuclei ^194pb, ^200Pb, and ^206pb is studied via a Langevin equation coupled with a statistical decay model. The magnitude of this excess for a low-isospin fissioning nucleus is shown to be larger and its dependence on the nuclear viscosity coefficient to be stronger than those of a high-isospin fissioning nucleus. These results suggest that to obtain a more accurate information of viscosity coefficient inside the saddle point by measuring evaporation residue cross sections, we had better choose those compound systems with small isospin.展开更多
This paper is an effort to extract the structure function, the EMC ratio, and the lepton scattering cross section in the convolution nuclear theory framework for 4He and 12C nuclei. We suppose that, in conventional ap...This paper is an effort to extract the structure function, the EMC ratio, and the lepton scattering cross section in the convolution nuclear theory framework for 4He and 12C nuclei. We suppose that, in conventional approach, based on harmonic oscillator model, one could consider for a nucleus shell different hw?parameters which are associated with the square root of the mean radius of the nucleus shells. We use GRV free nucleon structure function, which has good agreement with the proton and neutron structure function, extracted from experimental results. In addition, the lepton scattering cross sections of 4He and 12C nuclei are calculated in energy higher than 1 GeV. The extracted results show good agreement with experimental data.展开更多
Radar Cross Section (RCS) is one of the most considerable parameters for ship stealth design. As modern ships are larger than their predecessors, RCS must be managed at each design stage for its reduction. For predict...Radar Cross Section (RCS) is one of the most considerable parameters for ship stealth design. As modern ships are larger than their predecessors, RCS must be managed at each design stage for its reduction. For predicting RCS of ship, Radar Cross Section Analysis Program (RACSAN) based on Kirchhoff approximation in high frequency range has been developed. This program can present RCS including multi-bounce effect in exterior and interior structure by combination of geometric optics (GO) and physical optics (PO) methods, coating effect by using Fresnel reflection coefficient, and response time pattern for detected target. In this paper, RCS calculations of ship model with above effects are simulated by using this developed program and RCS results are discussed.展开更多
The pressure and horizontal particle velocity combined descriptions in the very low frequency acoustic field of shallow wa- ter integrated with the concept of effective depth of Pekeris wave- guide is proposed, especi...The pressure and horizontal particle velocity combined descriptions in the very low frequency acoustic field of shallow wa- ter integrated with the concept of effective depth of Pekeris wave- guide is proposed, especially the active component of the pressure and horizontal particle velocity cross-spectrum, also called ho- rizontal complex cross acoustic intensity, when only two normal modes are trapped in the waveguide. Both the approximate theo- retic analysis and the numerical results show that the sign of the horizontal complex cross acoustic intensity active component is independent of the range when vertically deployed receiving dual sensors are placed in appropriate depths, the sum of which is equal to the waveguide effective depth, so it can be used to tell whether the sound source is near the surface or underwater; while the range rate is expected to be measured by utilizing the sign distribution characteristic of the reactive component. The further robustness analysis of the depth classification algorithm shows that the existence of shear waves in semi infinite basement and the change of acoustic velocity profiles have few effects on the application of this method, and the seabed attenuation will limit the detection range, but the algorithm still has a good robustness in the valid detection range.展开更多
In this review, we highlight some recent methodological and theoretical develop- ments in estimation and testing of large panel data models with cross-sectional dependence. The paper begins with a discussion of issues...In this review, we highlight some recent methodological and theoretical develop- ments in estimation and testing of large panel data models with cross-sectional dependence. The paper begins with a discussion of issues of cross-sectional dependence, and introduces the concepts of weak and strong cross-sectional dependence. Then, the main attention is primarily paid to spatial and factor approaches for modeling cross-sectional dependence for both linear and nonlinear (nonparametric and semiparametric) panel data models. Finally, we conclude with some speculations on future research directions.展开更多
The elastic scattering properties for collisions between cold and ultracold 39K atoms in a triplet state are investigated. Based on the recent theoretical and experimental results, the improved hybrid potential is pre...The elastic scattering properties for collisions between cold and ultracold 39K atoms in a triplet state are investigated. Based on the recent theoretical and experimental results, the improved hybrid potential is presented for a triplet α3∑u^+ ground state of K2. Our calculated value of the s-wave scattering length a by using the Numerov method for the triplet state is 79.578α0 and found to be in good agreement with the previous ones. The numbers of bound states are supported by the molecular potential. Pronounced shape resonances appear for the l = 3 partial waves for the α3∑u^+ state. Furthermore, the s-wave scattering cross section, the total cross section and energy positions of shape resonances for the α3∑u^+ state are calculated.展开更多
Taking into consideration the changes of the geometric shielding effect in a molecule as the energy of incident electrons varies, this paper presents an empirical fraction, which depends on the energy of incident elec...Taking into consideration the changes of the geometric shielding effect in a molecule as the energy of incident electrons varies, this paper presents an empirical fraction, which depends on the energy of incident electrons, the target's molecular dimension and the atomic and electronic numbers in the molecule. Using this empirical fraction, it proposes a new formulation of the additivity rule. Employing the new additivity rule, it calculates the total cross sections of electron scattering by C2H4, C6H6, C6H14 and C8H18 over the energy range from 50 to 5000eV. In order to exclude the calculation deviations caused by solving the radial Schrodinger equation of electron scattering by atoms, here the atomic cross sections are derived from the experimental total cross section results of simple molecules (H2, O2, CO) via the inversion algorithm. The quantitative total cross sections are compared with those obtained by experiments and other theories, and good agreement is obtained over a wide energy range, even at energy of several tens of eV.展开更多
The K<SUP>+</SUP> scattering cross section with the in-medium virtual pion is evaluated in the lowest-order chiral perturbation theory with the density-dependent pion decay constant and mass. The contribut...The K<SUP>+</SUP> scattering cross section with the in-medium virtual pion is evaluated in the lowest-order chiral perturbation theory with the density-dependent pion decay constant and mass. The contribution of nuclear pions to the total K<SUP>+</SUP>-nucleus cross section is found to be about 5% and 12% when the excess pion numbers per nucleon n<SUB>?</SUB> = 0.057 and 0.13 are used. The inclusion of the off-mass-shell behavior of the K<SUP>+</SUP>? amplitude produced a significant improvement in the K<SUP>+</SUP>-nucleus cross section.展开更多
Two-photon fluorescence dyes have shown promising applications in biomedical imaging.However,the substitution site effect on geometric structures and photophysical properties of fluorescence dyes is rarely illustrated...Two-photon fluorescence dyes have shown promising applications in biomedical imaging.However,the substitution site effect on geometric structures and photophysical properties of fluorescence dyes is rarely illustrated in detail.In this work,a series of new lipid droplets detection dyes are designed and studied,molecular optical properties and non-radiative transitions are analyzed.The intramolecular weak interaction and electron-hole analysis reveal its inner mechanisms.All dyes are proven to possess excellent photophysical properties with high fluorescence quantum efficiency and large stokes shift as well as remarkable two-photon absorption cross section.Our work reasonably elucidates the experimental measurements and the effects of substitution site on two-photon absorption and excited states properties of lipid droplets detection NAPBr dyes are highlighted,which could provide a theoretical perspective for designing efficient organic dyes for lipid droplets detection in biology and medicine fields.展开更多
The modified Coulomb-Born approximation with and without the internuclear interaction (MCB-NN and MCB) is used to calculate the fully differential cross sections (FDCS) for the single ionization of helium by lOO M...The modified Coulomb-Born approximation with and without the internuclear interaction (MCB-NN and MCB) is used to calculate the fully differential cross sections (FDCS) for the single ionization of helium by lOO MeV/amu C6+ impact. The effects of the internuclear interaction on the FDCS are examined in geometries. The results are compared with experimental data and theoretical predictions from a three-body distorted-wave (3DW) model and a time-dependent close-coupling model. It is shown that the present MCB-NN results are in good agreement with the experiments in the scattering plane and the MCB results qualitatively reproduce the experimental structure outside the scattering plane. In particular, the MCB theory predicts the 'double-peak' structure in the perpendicular plane.展开更多
The values of direct double- to-single ionization ratio R of helium atoms induced by C^q+, O^q+ (q = 1 -4) ions at incident energies from 0.2 to 8.5MeV are measured. Based on the existing model (Shao J X, Chen X ...The values of direct double- to-single ionization ratio R of helium atoms induced by C^q+, O^q+ (q = 1 -4) ions at incident energies from 0.2 to 8.5MeV are measured. Based on the existing model (Shao J X, Chen X M and Ding B W 2007 Phys. Rev. A 75 012701) the effective charge of the projectile is introduced to theoretically estimate the value of R for the partially stripped ions impacting on helium atoms. The results calculated from our "effective charge" model are in good agreement with the experimental data, and the dependence of the effective charge on the ionization energy of the projectile is also discussed qualitatively.展开更多
文摘Effective atomic numbers for photon energy absorption(ZPEA_(eff)) and their corresponding electron numbers (NPEA_(eff)), and effective macroscopic removal cross sections of fast neutrons(RR) were calculated for 27 different types of three-dimensional dosimeters, four types of phantom materials, and water. The values of ZPEA_(eff) and NPEA_(eff) were obtained using the direct method for energies ranging from 10 keV to 20 MeV. Results are presented relative to water, for direct comparison over the range of examined energies. The effect of monomers that are used in polymer gel dosimeters on the water equivalence is discussed. The relation between Σ_R and hydrogen content was studied. Micelle gel dosimeters are highly promising because our results demonstrate perfect matching between the effective atomic number, electron density number, and fast neutron attenuation coefficient of water.
基金supported by the National Natural Science Foundation of China(Grant No.11274215)the Natural Science Foundation of Shanxi Province,China(Grants Nos.20051008 and 2010011009)the Technology Project of Shanxi Provincial Education Department,China(Grant No.20111011)
文摘Fully differential cross sections (FDCS) are calculated within a four-body model for single ionization of helium by C6+ impact at the incident energy of 100 MeV/a.u. (atomic unit). The results are compared with experimental data and other theoretical predictions. It is shown that our results are in very good agreement with experiment for three small momentum transfers in the scattering plane; however, some significant discrepancies are still present at the largest momentum transfer in both the scattering plane and the perpendicular plane. In actuality, the problem has not been explained by the theory during the last decade. Accordingly, the contributions of different scattering amplitudes to FDCS are analyzed. It is found that for the largest momentum transfer the cross section arising from a destructive interference of the three amplitudes is much smaller than the experimental data. However, the cross section due to the constructive interference of two scattering amplitudes between projectile-ionized electron interaction and projectile-passive electron interaction almost approaches the experimental data.
基金Project supported by the State Key Development Program for Basic Research of China (Grant No G2000077400), the Major Program of the National Natural Science Foundation of China (Grant Nos 10435080 and 105350101), the National Natural Science Foundation of China (Grant Nos 10447006 and 10575075), the CAS Knowledge Innovation Project Program (Grant No KJCX2-SW-N02).
文摘Probing in-medium nucleon-nucleon (NN) cross section σ1/NN(α) in heavy ion collisions has been investigated by means of the isospin-dependent quantum molecular dynamics (IQMD) with the isospin- and momentum-dependent interaction (IMDI(T)). It is found that there are the very obvious medium effect and the sensitive isospin-dependence of nuclear stopping R on the in-medium NN cross section α1/NN(α) in the nuclear reactions induced by halo-neutron projectile and the same-mass stable projectile. However, R induced by the neutron-halo projectile is obviously lower than that induced by the corresponding stable projectile. In particular, there is a very obvious dependence of R on the medium effect of σ1/NN(α) in the whole beam energy region for the above two kinds of projectiles. Therefore, the comparison between the results of R's in the reactions induced by the neutron-halo projectile and the corresponding same-mass stable projectile is a more favourable probe for extracting the information of σ1/NN(α) because of adding a new judgement.
基金Project supported by the Natural Science Foundation of Shanxi Province,China (Grant No 20051008)the Science Foundation for Returnee of Shanxi Province of China (Grant No 02-16)
文摘This paper presents the fully differential cross sections (FDCS) for 102eV electron impact single ionization of helium for both the coplanar and perpendicular plane asymmetric geometries within the framework of dynamically screened three-Coulomb-wave theory. Comparisons are made with the experimental data and those of the three-Coulomb wave function model and second-order distorted-wave Born method. The angular distribution and relative heights of the present FDCS is found to be in very good agreement with the experimental data in the perpendicular plane geometry. It is shown that dynamical screening effects are significant in this geometry. Three-body coupling is expected to be weak in the coplanar geometry, although the precise absolute value of the cross section is still sensitive to the interaction details.
基金ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China (No.11274215), the Natural Science Foundation of Shanxi Province, China (No.20051008 and No.2010011009), and the Technology Project of Shanxi Provincial Education Department, China (No.20111011).
文摘The four-body model has been used to calculate the fully differential cross-sections (FDCS) for the single ionization of helium by 100 MeV/amu Ca^+ impact in geometries. By comparing with experimental data and other theories, we find the results of four-body model are in very good agreement in the scattering plane, but poor agreement out of the scattering plane. Accordingly, the contributions of different scattering amplitudes to FDCS are analyzed. It is found that the cross sections due to the interference of the scattering amplitudes between projectile-target nucleus interaction and projectile-ejected electron interaction almost tend to experimental results around the recoil region in geometries. In particular in the perpendicular plane, the cross section originating from interference of the scattering amplitudes between projectile-target nucleus and projectile-ejected electron interactions yields an experimental double-peak structure in the angular distribution. However, this feature could not be presented by the interference of the three amplitudes. Thus, the failure of the fourbody model predicting the feature in this geometry may be attributed to an inappropriate weighting of the three amplitudes.
文摘Based on the statistical model and taking into account the Q-value dependence and odd-even effects, we proposed a new empirical formula to reproduce the cross sections of the (n, p) reactions at 14.7 MeV neutron energy and at the target mass number 14 ≤ A ≤ 198 for even A and 29 ≤ A ≤ 205 for odd A. All calculated results from the proposed empirical formula were compared to the experimental data as well as the available semi-empirical formula obtained by other authors. A high level of agreement has been found between the collected experimental data and the most of semiempirical formulae obtained by others.
文摘In this paper, we studied the process of dissociation unimolecular of the evaporation of H+2n+1 hydrogen clusters according to size, using the Rice-Ramsperger-Kassel-Marcus (RRKM) theory. The rate constants k(E) were determined with the use of statistical theory of unimolecular reactions using various approximations. In our work, we used the products frequencies instead of transitions frequencies in the calculation of unimolecular dissociation rates obtained by three models RRKM. The agreement between the experimental cross section ratio and calculated rate ratio with direct count approximation seems to be reasonable.
基金supported by the National Natural Science Foundation of China(Grant Nos.61464007,61306084,11664025,and 51561022)the Postdoctoral Science Foundation of Jiangxi Province of China(Grant Nos.2014KY32,2013RC08,and 2015KY12)+1 种基金the Natural Science Foundation of Jiangxi Province of China(Grant Nos.20151BAB207055 and 20161BAB201012)the Postdoctoral Science Foundation of China(Grant No.2016M592115)
文摘A numerical study has been conducted to explore the role of photoemission cross sections in the impurity photovoltaic(IPV) effect for silicon solar cells doped with indium. The photovoltaic parameters(short-circuit current density, opencircuit voltage, and conversion efficiency) of the IPV solar cell were calculated as functions of variable electron and hole photoemission cross sections. The presented results show that the electron and hole photoemission cross sections play critical roles in the IPV effect. When the electron photoemission cross section is 10^-20cm^2, the conversion efficiencyη of the IPV cell always has a negative gain(△η 0) if the IPV impurity is introduced. A large hole photoemission cross section can adversely impact IPV solar cell performance. The combination of a small hole photoemission cross section and a large electron photoemission cross section can achieve higher conversion efficiency for the IPV solar cell since a large electron photoemission cross section can enhance the necessary electron transition from the impurity level to the conduction band and a small hole photoemission cross section can reduce the needless sub-bandgap absorption. It is concluded that those impurities with small(large) hole photoemission cross section and large(small) electron photoemission cross section,whose energy levels are near the valence(or conduction) band edge, may be suitable for use in IPV solar cells. These results may help in judging whether or not an impurity is appropriate for use in IPV solar cells according to its electron and hole photoemission cross sections.
基金Project supported by the National Natural Science Foundation of China (Grant No 10734140)the National Basic Research Program of China (Grant No 2007CB815105)
文摘Interference effects on the photoionization cross sections between two neighbouring atoms are considered based on the coherent scattering of the ionized electrons by the two nuclei when their separation is less than or comparable to the de Broglie wave length of the ionized electrons. As an example, the single atomic nitrogen ionization cross section and the total cross sections of two nitrogen atoms with coherently added photoionization amplitudes are calculated from the threshold to about А (1 А=0.1 nm) of the photon energy. The photoionization cross sections of atomic nitrogen are obtained by using the close-coupling R-matrix method. In the calculation 19 states are included. The ionization energy of the atomic nitrogen and the photoionization cross sections agree well with the experimental results. Based on the R-matrix results of atomic nitrogen, the interference effects between two neighbouring nitrogen atoms are obtained. It is shown that the interference effects are considerable when electrons are ionized just above the threshold, even for the separations between the two atoms are larger than two times of the bond length of N2 molecules. Therefore, in hot and dense samples, effects caused by the coherent interference between the neighbours are expected to be observable for the total photoionization cross sections.
基金supported by National Natural Science Foundation of China under Grant No.10405007
文摘The influence of isospin on the excess of evaporation residue cross section over its standard statistical-model value for nuclei ^194pb, ^200Pb, and ^206pb is studied via a Langevin equation coupled with a statistical decay model. The magnitude of this excess for a low-isospin fissioning nucleus is shown to be larger and its dependence on the nuclear viscosity coefficient to be stronger than those of a high-isospin fissioning nucleus. These results suggest that to obtain a more accurate information of viscosity coefficient inside the saddle point by measuring evaporation residue cross sections, we had better choose those compound systems with small isospin.
文摘This paper is an effort to extract the structure function, the EMC ratio, and the lepton scattering cross section in the convolution nuclear theory framework for 4He and 12C nuclei. We suppose that, in conventional approach, based on harmonic oscillator model, one could consider for a nucleus shell different hw?parameters which are associated with the square root of the mean radius of the nucleus shells. We use GRV free nucleon structure function, which has good agreement with the proton and neutron structure function, extracted from experimental results. In addition, the lepton scattering cross sections of 4He and 12C nuclei are calculated in energy higher than 1 GeV. The extracted results show good agreement with experimental data.
文摘Radar Cross Section (RCS) is one of the most considerable parameters for ship stealth design. As modern ships are larger than their predecessors, RCS must be managed at each design stage for its reduction. For predicting RCS of ship, Radar Cross Section Analysis Program (RACSAN) based on Kirchhoff approximation in high frequency range has been developed. This program can present RCS including multi-bounce effect in exterior and interior structure by combination of geometric optics (GO) and physical optics (PO) methods, coating effect by using Fresnel reflection coefficient, and response time pattern for detected target. In this paper, RCS calculations of ship model with above effects are simulated by using this developed program and RCS results are discussed.
基金supported by the National Natural Science Foundation of China(1140440611374072)
文摘The pressure and horizontal particle velocity combined descriptions in the very low frequency acoustic field of shallow wa- ter integrated with the concept of effective depth of Pekeris wave- guide is proposed, especially the active component of the pressure and horizontal particle velocity cross-spectrum, also called ho- rizontal complex cross acoustic intensity, when only two normal modes are trapped in the waveguide. Both the approximate theo- retic analysis and the numerical results show that the sign of the horizontal complex cross acoustic intensity active component is independent of the range when vertically deployed receiving dual sensors are placed in appropriate depths, the sum of which is equal to the waveguide effective depth, so it can be used to tell whether the sound source is near the surface or underwater; while the range rate is expected to be measured by utilizing the sign distribution characteristic of the reactive component. The further robustness analysis of the depth classification algorithm shows that the existence of shear waves in semi infinite basement and the change of acoustic velocity profiles have few effects on the application of this method, and the seabed attenuation will limit the detection range, but the algorithm still has a good robustness in the valid detection range.
基金Supported by the National Natural Science Foundation of China(71131008(Key Project)and 71271179)
文摘In this review, we highlight some recent methodological and theoretical develop- ments in estimation and testing of large panel data models with cross-sectional dependence. The paper begins with a discussion of issues of cross-sectional dependence, and introduces the concepts of weak and strong cross-sectional dependence. Then, the main attention is primarily paid to spatial and factor approaches for modeling cross-sectional dependence for both linear and nonlinear (nonparametric and semiparametric) panel data models. Finally, we conclude with some speculations on future research directions.
基金Project supported by the National Natural Science Foundation of China (Grant No 10574039) and the Science Foundation for Young Scientists of Henan Normal University, China (Grant No 2005004).
文摘The elastic scattering properties for collisions between cold and ultracold 39K atoms in a triplet state are investigated. Based on the recent theoretical and experimental results, the improved hybrid potential is presented for a triplet α3∑u^+ ground state of K2. Our calculated value of the s-wave scattering length a by using the Numerov method for the triplet state is 79.578α0 and found to be in good agreement with the previous ones. The numbers of bound states are supported by the molecular potential. Pronounced shape resonances appear for the l = 3 partial waves for the α3∑u^+ state. Furthermore, the s-wave scattering cross section, the total cross section and energy positions of shape resonances for the α3∑u^+ state are calculated.
基金Project supported by the National Natural Science Foundation of China (Grant No 10574039)the Program for Science and Technology Innovation Talents in Universities of Henan Province in China (Grant No 2008HASTIT008)
文摘Taking into consideration the changes of the geometric shielding effect in a molecule as the energy of incident electrons varies, this paper presents an empirical fraction, which depends on the energy of incident electrons, the target's molecular dimension and the atomic and electronic numbers in the molecule. Using this empirical fraction, it proposes a new formulation of the additivity rule. Employing the new additivity rule, it calculates the total cross sections of electron scattering by C2H4, C6H6, C6H14 and C8H18 over the energy range from 50 to 5000eV. In order to exclude the calculation deviations caused by solving the radial Schrodinger equation of electron scattering by atoms, here the atomic cross sections are derived from the experimental total cross section results of simple molecules (H2, O2, CO) via the inversion algorithm. The quantitative total cross sections are compared with those obtained by experiments and other theories, and good agreement is obtained over a wide energy range, even at energy of several tens of eV.
文摘The K<SUP>+</SUP> scattering cross section with the in-medium virtual pion is evaluated in the lowest-order chiral perturbation theory with the density-dependent pion decay constant and mass. The contribution of nuclear pions to the total K<SUP>+</SUP>-nucleus cross section is found to be about 5% and 12% when the excess pion numbers per nucleon n<SUB>?</SUB> = 0.057 and 0.13 are used. The inclusion of the off-mass-shell behavior of the K<SUP>+</SUP>? amplitude produced a significant improvement in the K<SUP>+</SUP>-nucleus cross section.
基金This work was supported by the National Natural Science Foundation of China(No.11804196 and No.11904210)the Project funded by China Postdoctoral Science Foundation(No.2018M642689)the Open Fund of Guangdong Provincial Key Laboratory of Luminescence from Molecular Aggregates,(South China University of Technology)(No.2019B030301003).
文摘Two-photon fluorescence dyes have shown promising applications in biomedical imaging.However,the substitution site effect on geometric structures and photophysical properties of fluorescence dyes is rarely illustrated in detail.In this work,a series of new lipid droplets detection dyes are designed and studied,molecular optical properties and non-radiative transitions are analyzed.The intramolecular weak interaction and electron-hole analysis reveal its inner mechanisms.All dyes are proven to possess excellent photophysical properties with high fluorescence quantum efficiency and large stokes shift as well as remarkable two-photon absorption cross section.Our work reasonably elucidates the experimental measurements and the effects of substitution site on two-photon absorption and excited states properties of lipid droplets detection NAPBr dyes are highlighted,which could provide a theoretical perspective for designing efficient organic dyes for lipid droplets detection in biology and medicine fields.
基金Supported by the National Natural Science Foundation of China under Grant No 11274215the Natural Science Foundation of Shanxi Province under Grant No 2010011009
文摘The modified Coulomb-Born approximation with and without the internuclear interaction (MCB-NN and MCB) is used to calculate the fully differential cross sections (FDCS) for the single ionization of helium by lOO MeV/amu C6+ impact. The effects of the internuclear interaction on the FDCS are examined in geometries. The results are compared with experimental data and theoretical predictions from a three-body distorted-wave (3DW) model and a time-dependent close-coupling model. It is shown that the present MCB-NN results are in good agreement with the experiments in the scattering plane and the MCB results qualitatively reproduce the experimental structure outside the scattering plane. In particular, the MCB theory predicts the 'double-peak' structure in the perpendicular plane.
基金Project supported by the National Natural Science Foundation of China (Grant No 10775063)
文摘The values of direct double- to-single ionization ratio R of helium atoms induced by C^q+, O^q+ (q = 1 -4) ions at incident energies from 0.2 to 8.5MeV are measured. Based on the existing model (Shao J X, Chen X M and Ding B W 2007 Phys. Rev. A 75 012701) the effective charge of the projectile is introduced to theoretically estimate the value of R for the partially stripped ions impacting on helium atoms. The results calculated from our "effective charge" model are in good agreement with the experimental data, and the dependence of the effective charge on the ionization energy of the projectile is also discussed qualitatively.