Second-order Born calculations are performed to investigate the triple differential cross sections of coplanar asymmetric laser-assisted (e, 2e) collisions for hydrogen and helium targets. The incident electron is c...Second-order Born calculations are performed to investigate the triple differential cross sections of coplanar asymmetric laser-assisted (e, 2e) collisions for hydrogen and helium targets. The incident electron is considered to be dressed by the laser field in a nonperturbative manner by choosing the Volkov solutions in both the initial and final channels. Detailed calculations of the scattering amplitudes are performed using the Sturmian basis expansion. The state of the ejected electron is described by a Coulomb-Volkov wave function. Two geometries are investigated in which the laser polarization vector is either parallel to the incident momentum of the projectile or parallel to the momentum transfer. Our numerical results show that, in the low energy range, these two laser polarization orientations give the same shape and the same order of magnitude of laser-assisted ionization cross sections of helium and hydrogen targets.展开更多
We propose an approach for tuning the three-dimensional polarization of a focusing subwavelength spot by a high numerical aperture objective. The incident beams are composed of a radially polarized beam, an azimuthall...We propose an approach for tuning the three-dimensional polarization of a focusing subwavelength spot by a high numerical aperture objective. The incident beams are composed of a radially polarized beam, an azimuthally polarized beam, and a linearly polarized beam with three different weighting factors, respectively. A specially designed adjustable amplitude angular selector is also inserted at the back aperture of the objective for tuning the polarization azimuthally. It is shown that any desired overall polarization orientation can be obtained. We calculated the overall polarization orientation in the focal volume. It is found that the polar angle of the overall polarization orientation can be arbitrarily tuned by the combination of a radially polarized beam and a linearly polarized beam with different weighting factors, and the azimuthal angle can be tuned by rotating the orientation of the linearly polarized beam azimuthally.展开更多
Polycrystalline Bi_4Ti_3O_(12) thin films with various fractions of a-axis, c-axis and random orientations have been grown on Pt(111)/Ti/Si O_2/Si substrates by laser-ablation under different kinetic growth condit...Polycrystalline Bi_4Ti_3O_(12) thin films with various fractions of a-axis, c-axis and random orientations have been grown on Pt(111)/Ti/Si O_2/Si substrates by laser-ablation under different kinetic growth conditions. The relationship between the structure and ferroelectric property of the films was investigated, so as to explore the possibility of enhancing ferroelectric polarization by controlling the preferred orientation. The structural characterization indicated that the large growth rate and high oxygen background pressure were both favorable for the growth of non-c-axis oriented grains in the Bi_4Ti_3O_(12) thin films. The films with high fractions of a-axis and random orientations, i e, f(a-sxis) = 28.3% and f(random) = 69.6%, could be obtained at the deposition temperature of 973 K, oxygen partial pressure of 15 Pa and laser fluence of 4.6 J/cm^2, respectively. It was also noted that the variation of ferroelectric polarization was in accordance with the evolution non-c-axis orientation. A large value of remanent polarization(2 Pr = 35.5 μC/cm^2) was obtained for the Bi_4Ti_3O_(12) thin films with significant non-c-axis orientation, even higher than that of rare-earth-doped Bi_4Ti_3O_(12) films.展开更多
Systematic analyses of seismic data recorded by the Yunnan regional seismograph network reveal significant crustal and upper mantle anisotropy. Splitting of the S phase of local earthquakes and teleseismic SKS, PKS, a...Systematic analyses of seismic data recorded by the Yunnan regional seismograph network reveal significant crustal and upper mantle anisotropy. Splitting of the S phase of local earthquakes and teleseismic SKS, PKS, and SKKS phases indicates time-delays from 1.60 ms/km to 2.30 ms/km in the crust, and from 0.55 s to 1.65 s in the upper mantle which corresponds to an The polarization orientations of fast shear waves in direction, and the mantle anisotropy has a nearly styles and mechanisms exist between the crust and anisotropic layer with a thickness about between 55 165 km. the crust are complicated with a predominantly north-south west-east direction. Our results show different deformation upper mantle.展开更多
A total of 351 shear-wave splitting results at 25 stations were obtained from the seismic data recorded in period of January,2013 to December,2016,by a broadband seismic array deployed in the northern segment of Xiaoj...A total of 351 shear-wave splitting results at 25 stations were obtained from the seismic data recorded in period of January,2013 to December,2016,by a broadband seismic array deployed in the northern segment of Xiaojiang Fault Zone(n-XJFZ).Meanwhile,the stress field of the n-XJFZ was determined by inverting 140 focal mechanism solutions of the small earthquakes within the study area which were recorded in the same period.This determination confirmed a compressive stress in NW-SE orientation and an extensional stress in the NE-SW orientation,with little difference from those released by previous studies.The shear-wave splitting results show a spatial complexity in polarization orientation,different from one site to another.How-ever,the polarization orientations integrated for the subareas suggest that the fault trends seemingly played important roles.All the subareas bear two dominant orientations,N10°E and N90°E,both of which are different from the azimuths of the principal compressive stress,due to the fault distribution.The time delay averaged over the entire region is 4.56 ms/km,close to that of the upper boundary of the generally accepted interval worldwide but larger than those in most of the investigated regions in the Chinese mainland,which probably implies an alignment of more micro-cracks in the n-XJFZ.Interestingly,the 2014 Ms6.5 Ludian earthquake was found to have caused a variation in the time delays of the slow shear waves within the study area though its epicenter was outside.This earthquake resulted in an evident drop of the time delays remaining for 4 months,however,lifted a bit the time-delay level with respect to that prior to the earthquake.展开更多
Regulating orientation growth plays a dominant role in enhancing dielectric properties for the electromagnetic(EM)functional materials,which faces a huge challenge in the synthesis method.By sprayannealing strategy,hi...Regulating orientation growth plays a dominant role in enhancing dielectric properties for the electromagnetic(EM)functional materials,which faces a huge challenge in the synthesis method.By sprayannealing strategy,hierarchical ZnO microspheres assembled by ZnO nanorods and nanoparticles were successfully fabricated.With confined microsphere space and controlling crystal growth,oriented ZnO nanorods possess rich defects,Zn-polar,O-polar faces,and high permittivity.Meanwhile,temperaturedependency of exposed polarization surfaces is discovered in the semiconductor ZnO nanoparticles with evolved aspect ratios.As pure dielectric EM wave absorption material,the hierarchical ZnO microsphere exhibits adjustable complex permittivity and polarization behaviors.When the thickness is 2.4 mm,the hierarchical ZnO-1 absorber shows the widest efficient absorption(RL≤–10 d B)region from 9.9 to18.0 GHz(8.1 GHz,^50.6%testing frequency).The minimum reflection loss(RL)of ZnO-1 can reach–31.5 d B at only 2.0 mm.Because of the outstanding dielectric loss ability and wide absorption frequency,large-scale hierarchical ZnO microspheres can be a potential EM absorption candidate.展开更多
In this Letter, we study the molecular alignment and orientation driven by two elliptically polarized laser pulses.It is shown that the field-free molecular alignment can be achieved in a three-dimensional(3D) case,...In this Letter, we study the molecular alignment and orientation driven by two elliptically polarized laser pulses.It is shown that the field-free molecular alignment can be achieved in a three-dimensional(3D) case, while the field-free molecular orientation is only along the x and y directions, and that the field-free alignment and orientation along different axes are related to the populations of the rotational states. It is demonstrated that changing the elliptic parameter is efficient for controlling both in-pulse and post-pulse molecular alignment and orientation. The delay time also has an influence on the field-free molecular alignment and orientation.展开更多
Dielectric polymers are the materials of choice for high energy density film capacitors.The increasing demand for advanced electrical systems requires dielectric polymers to operate efficiently under extreme condition...Dielectric polymers are the materials of choice for high energy density film capacitors.The increasing demand for advanced electrical systems requires dielectric polymers to operate efficiently under extreme conditions,especially at elevated temperatures.However,the low permittivity and relatively low operating temperature of dielectric polymers limit the high-temperature capacitive energy storage applications.Fortunately,dipolar glass polymers are demonstrated as the preferred materials to achieve high dielectric constant,low dielectric loss and high energy density at elevated temperatures.In this review,we critically elaborate on the recent progress of dipolar glass polymers based on orientational polarization from molecular engineering.In addition,the general design considerations and various dipole moment entities of dipolar glass polymers are described in detail.High dipolar moment,high dipole density and rotation freedom of dipoles are essential for dipolar glass polymers to gain superior dielectric and energy storage properties.Challenges and future opportunities for dipolar glass polymers towards high-temperature energy storage applications are also provided.展开更多
文摘Second-order Born calculations are performed to investigate the triple differential cross sections of coplanar asymmetric laser-assisted (e, 2e) collisions for hydrogen and helium targets. The incident electron is considered to be dressed by the laser field in a nonperturbative manner by choosing the Volkov solutions in both the initial and final channels. Detailed calculations of the scattering amplitudes are performed using the Sturmian basis expansion. The state of the ejected electron is described by a Coulomb-Volkov wave function. Two geometries are investigated in which the laser polarization vector is either parallel to the incident momentum of the projectile or parallel to the momentum transfer. Our numerical results show that, in the low energy range, these two laser polarization orientations give the same shape and the same order of magnitude of laser-assisted ionization cross sections of helium and hydrogen targets.
基金supported by the National Natural Science Foundation of China(Nos.61675093 and 61775140)the Shandong Natural Science Foundation(No.ZR2017MA035)
文摘We propose an approach for tuning the three-dimensional polarization of a focusing subwavelength spot by a high numerical aperture objective. The incident beams are composed of a radially polarized beam, an azimuthally polarized beam, and a linearly polarized beam with three different weighting factors, respectively. A specially designed adjustable amplitude angular selector is also inserted at the back aperture of the objective for tuning the polarization azimuthally. It is shown that any desired overall polarization orientation can be obtained. We calculated the overall polarization orientation in the focal volume. It is found that the polar angle of the overall polarization orientation can be arbitrarily tuned by the combination of a radially polarized beam and a linearly polarized beam with different weighting factors, and the azimuthal angle can be tuned by rotating the orientation of the linearly polarized beam azimuthally.
基金Funded by the International Science and Technology Cooperation Project of Hubei Province(2016AHB008)the Natural Science Foundation of Hubei Province(2015CFB724,2016CFA006)+1 种基金the National Natural Science Foundation of China(51272195,51521001)the National Key Research and Development Program of China(2017YFB0310400)
文摘Polycrystalline Bi_4Ti_3O_(12) thin films with various fractions of a-axis, c-axis and random orientations have been grown on Pt(111)/Ti/Si O_2/Si substrates by laser-ablation under different kinetic growth conditions. The relationship between the structure and ferroelectric property of the films was investigated, so as to explore the possibility of enhancing ferroelectric polarization by controlling the preferred orientation. The structural characterization indicated that the large growth rate and high oxygen background pressure were both favorable for the growth of non-c-axis oriented grains in the Bi_4Ti_3O_(12) thin films. The films with high fractions of a-axis and random orientations, i e, f(a-sxis) = 28.3% and f(random) = 69.6%, could be obtained at the deposition temperature of 973 K, oxygen partial pressure of 15 Pa and laser fluence of 4.6 J/cm^2, respectively. It was also noted that the variation of ferroelectric polarization was in accordance with the evolution non-c-axis orientation. A large value of remanent polarization(2 Pr = 35.5 μC/cm^2) was obtained for the Bi_4Ti_3O_(12) thin films with significant non-c-axis orientation, even higher than that of rare-earth-doped Bi_4Ti_3O_(12) films.
基金supported by National NaturalScience Foundation of China Project(No.41174042)China National Special Fund for Earthquake Scientific Research in Public Interest(No.201008001)Basic Research Project of Institute of Earthquake Science,CEA(No.2009-21)
文摘Systematic analyses of seismic data recorded by the Yunnan regional seismograph network reveal significant crustal and upper mantle anisotropy. Splitting of the S phase of local earthquakes and teleseismic SKS, PKS, and SKKS phases indicates time-delays from 1.60 ms/km to 2.30 ms/km in the crust, and from 0.55 s to 1.65 s in the upper mantle which corresponds to an The polarization orientations of fast shear waves in direction, and the mantle anisotropy has a nearly styles and mechanisms exist between the crust and anisotropic layer with a thickness about between 55 165 km. the crust are complicated with a predominantly north-south west-east direction. Our results show different deformation upper mantle.
基金This study is supported by the National Key R&D Program of China(No.2018YFC1503400)the National Natural Science Foundation of China(No.41804088).Some of the figures were made using the Generic Mapping Tools(Wessel et al.,2013).
文摘A total of 351 shear-wave splitting results at 25 stations were obtained from the seismic data recorded in period of January,2013 to December,2016,by a broadband seismic array deployed in the northern segment of Xiaojiang Fault Zone(n-XJFZ).Meanwhile,the stress field of the n-XJFZ was determined by inverting 140 focal mechanism solutions of the small earthquakes within the study area which were recorded in the same period.This determination confirmed a compressive stress in NW-SE orientation and an extensional stress in the NE-SW orientation,with little difference from those released by previous studies.The shear-wave splitting results show a spatial complexity in polarization orientation,different from one site to another.How-ever,the polarization orientations integrated for the subareas suggest that the fault trends seemingly played important roles.All the subareas bear two dominant orientations,N10°E and N90°E,both of which are different from the azimuths of the principal compressive stress,due to the fault distribution.The time delay averaged over the entire region is 4.56 ms/km,close to that of the upper boundary of the generally accepted interval worldwide but larger than those in most of the investigated regions in the Chinese mainland,which probably implies an alignment of more micro-cracks in the n-XJFZ.Interestingly,the 2014 Ms6.5 Ludian earthquake was found to have caused a variation in the time delays of the slow shear waves within the study area though its epicenter was outside.This earthquake resulted in an evident drop of the time delays remaining for 4 months,however,lifted a bit the time-delay level with respect to that prior to the earthquake.
基金financially supported by the National Natural Science Foundation of China(Nos.51725101,11727807,51672050,61790581,22088101)the Ministry of Science and Technology of China(No.2018YFA0209102)the Infrastructure and Facility Construction Project of Zhejiang Laboratory。
文摘Regulating orientation growth plays a dominant role in enhancing dielectric properties for the electromagnetic(EM)functional materials,which faces a huge challenge in the synthesis method.By sprayannealing strategy,hierarchical ZnO microspheres assembled by ZnO nanorods and nanoparticles were successfully fabricated.With confined microsphere space and controlling crystal growth,oriented ZnO nanorods possess rich defects,Zn-polar,O-polar faces,and high permittivity.Meanwhile,temperaturedependency of exposed polarization surfaces is discovered in the semiconductor ZnO nanoparticles with evolved aspect ratios.As pure dielectric EM wave absorption material,the hierarchical ZnO microsphere exhibits adjustable complex permittivity and polarization behaviors.When the thickness is 2.4 mm,the hierarchical ZnO-1 absorber shows the widest efficient absorption(RL≤–10 d B)region from 9.9 to18.0 GHz(8.1 GHz,^50.6%testing frequency).The minimum reflection loss(RL)of ZnO-1 can reach–31.5 d B at only 2.0 mm.Because of the outstanding dielectric loss ability and wide absorption frequency,large-scale hierarchical ZnO microspheres can be a potential EM absorption candidate.
基金supported by the National Natural Science Foundation of China(No.11674198)the Taishan Scholar Project of Shandong Province
文摘In this Letter, we study the molecular alignment and orientation driven by two elliptically polarized laser pulses.It is shown that the field-free molecular alignment can be achieved in a three-dimensional(3D) case, while the field-free molecular orientation is only along the x and y directions, and that the field-free alignment and orientation along different axes are related to the populations of the rotational states. It is demonstrated that changing the elliptic parameter is efficient for controlling both in-pulse and post-pulse molecular alignment and orientation. The delay time also has an influence on the field-free molecular alignment and orientation.
基金financially supported by the National Natural Science Foundation of China(Nos.51973080,92066104 and 51903100)。
文摘Dielectric polymers are the materials of choice for high energy density film capacitors.The increasing demand for advanced electrical systems requires dielectric polymers to operate efficiently under extreme conditions,especially at elevated temperatures.However,the low permittivity and relatively low operating temperature of dielectric polymers limit the high-temperature capacitive energy storage applications.Fortunately,dipolar glass polymers are demonstrated as the preferred materials to achieve high dielectric constant,low dielectric loss and high energy density at elevated temperatures.In this review,we critically elaborate on the recent progress of dipolar glass polymers based on orientational polarization from molecular engineering.In addition,the general design considerations and various dipole moment entities of dipolar glass polymers are described in detail.High dipolar moment,high dipole density and rotation freedom of dipoles are essential for dipolar glass polymers to gain superior dielectric and energy storage properties.Challenges and future opportunities for dipolar glass polymers towards high-temperature energy storage applications are also provided.