基于漫反射和随机编码理论提出一种应用于雷达散射截面积(RCS)缩减的超表面,并通过仿真和实验进行验证。首先,简要阐述了漫反射和随机编码理论,并设计一种基于金属分割线结构的线极化转换超单元。该结构基于"0"、"1"...基于漫反射和随机编码理论提出一种应用于雷达散射截面积(RCS)缩减的超表面,并通过仿真和实验进行验证。首先,简要阐述了漫反射和随机编码理论,并设计一种基于金属分割线结构的线极化转换超单元。该结构基于"0"、"1"两种基本单元进行编码,在宽频段范围内实现180°反射相位差。仿真结果表明,超表面在6~14GHz频段内,线极化转换率高达90%,RCS缩减大于10 d B的带宽达到6 GHz。然后,设计三种随机编码超表面,进行制备和实验测试。实验结果表明:在5.5~13 GHz频带范围内,三种随机超表面在垂直入射时的反射率小于–10d B,存在6 GHz带宽RCS缩减大于10 d B,与仿真结果基本一致。另外,斜入射情况下,同样能得到有效的RCS缩减,随机编码超表面具备宽角度入射RCS缩减特性。该设计为雷达隐身技术提供了一种新的途径。展开更多
In this study,we calculated the inclusive charged-current neutrino-nucleus scattering from ^(40)Ar in the quasielastic region.To explore the effect of uncertainties stemming from the nuclear structure,we used the KIDS...In this study,we calculated the inclusive charged-current neutrino-nucleus scattering from ^(40)Ar in the quasielastic region.To explore the effect of uncertainties stemming from the nuclear structure,we used the KIDS(Korea-IBS-Daegu-SKKU)nuclear energy density functional and Skyrme force models,namely SLy4,SkI3,and MSk7.These models were selected to have distinct behavior in terms of the density dependence of the symmetry energy and the effective mass of the nucleon.In the charged-current neutrino scattering,the single-and double-differential cross sections were calculated for various kinematics.Total cross sections are reported as a function of the incident neutrino energy.The theoretical cross sections were compared with experimental data,and the roles of the effective mass and symmetry energy were investigated in terms of charged-current neutrino-nucleus scattering.展开更多
Distortions caused by the neutron spectrum and scattered neutrons are major problems in fast neutron radiography and should be considered for improving the image quality. This paper puts emphasis on the removal of the...Distortions caused by the neutron spectrum and scattered neutrons are major problems in fast neutron radiography and should be considered for improving the image quality. This paper puts emphasis on the removal of these image distortions and deviations for fast neutron radiography performed at the NECTAR facility of the research reactor FRM-II in Technische Universit/it Mfinchen （TUM）, Germany. The NECTAR energy spectrum is analyzed and established to modify the influence caused by the neutron spectrum, and the Point Scattered Function （PSeF） simulated by the Monte-Carlo program MCNPX is used to evaluate scattering effects from the object and improve image quality. Good analysis results prove the sound effects of the above two corrections.展开更多
This work demonstrates the generation of short pulse duration and high-beam-quality laser pulses using transient stimulated Brillouin scattering at a high repetition rate.Thermal effects and optical breakdown are iden...This work demonstrates the generation of short pulse duration and high-beam-quality laser pulses using transient stimulated Brillouin scattering at a high repetition rate.Thermal effects and optical breakdown are identified as the main factors that restrict energy reflectivity and beam quality under high repetition rates and transient situations.Through experimental analysis,the interaction length and focal point size are determined to be the key parameters in reducing the thermal effect by reducing the absorption of the laser pulse by the medium.The obtained results show that pulses with a duration of 175 ps and beam quality M^(2)of around 1.2 can be achieved with a maximum energy reflectivity of over 40%under an interaction length of 50 mm.Furthermore,at an interaction length of 90 mm,a pulse output with a minimum duration of 115 ps(0.5τQ)is achieved.展开更多
After one century of nuclear physics, its underlying fundamental laws remain a puzzle. Rutherford scattering is well known to be electric at low kinetic energy. Nobody noticed that the Rutherford scattering formula wo...After one century of nuclear physics, its underlying fundamental laws remain a puzzle. Rutherford scattering is well known to be electric at low kinetic energy. Nobody noticed that the Rutherford scattering formula works also at high kinetic energy, needing only to replace the repulsive electric -2 exponent by the also repulsive magnetic -6 exponent. A proton attracts a not so neutral neutron as amber attracts dust. The nucleons have magnetic moments that interact as magnets, equilibrating statically the electric attraction between a proton and a not so neutral neutron. In this paper, the electromagnetic potential energies of the deuteron 2H and the α particle 4He have been calculated statically, using only electromagnetic fundamental laws and constants. Nuclear scattering and binding energy are both electromagnetic.展开更多
A high-efficiency Brillouin fiber ring laser is demonstrated using the standard single-mode fiber. The laser exhibits a 3.6-mW threshold. The output power is 22 mW with 40-mW pump power, and the maximum optical-to-opt...A high-efficiency Brillouin fiber ring laser is demonstrated using the standard single-mode fiber. The laser exhibits a 3.6-mW threshold. The output power is 22 mW with 40-mW pump power, and the maximum optical-to-optical efficiency is 5570. The output is single wavelength with a 3-dB linewidth of 5 MHz, and the interval of center frequency between the laser and the pump light is 11 GHz （0.088 nm）. It is shown that the stimulated Brillouin scattering threshold of ring resonator is lower and the energy transfer efficiency is higher than those in fiber.展开更多
We obtain the output of a 284 ps pulse duration without tail modulation based on stimulated Brillouin scattering（SBS） pulse compression pumped by an 8 ns-pulse-duration, 1064 nm-wavelength Q-switched Nd：YAG laser. ...We obtain the output of a 284 ps pulse duration without tail modulation based on stimulated Brillouin scattering（SBS） pulse compression pumped by an 8 ns-pulse-duration, 1064 nm-wavelength Q-switched Nd：YAG laser. To suppress the tail modulation in SBS pulse compression, proper attenuators, which can control the pump energy within a rational range, are added in a generator-amplifier setup. The experimental result shows that the effective energy conversion efficiency triples when the pump energy reaches 700 m J to 51%, compared with the conventional generator-amplifier setup.展开更多
We developed a cluster ion beam system that produces negative cluster beams of C 1-C 10 with ion current of 4.5 nA-50 A at extraction voltages ranging from 6 to 20 kV.The system uses the injector of a tandetron accele...We developed a cluster ion beam system that produces negative cluster beams of C 1-C 10 with ion current of 4.5 nA-50 A at extraction voltages ranging from 6 to 20 kV.The system uses the injector of a tandetron accelerator and was established by inserting an electrostatic scanner on its ion-optical line and modifying its Faraday cup into a substrate holder.Utilization of clusters enables ultrashallow ion implantation at energies as low as 600 eV/atom without deceleration.Small carbon clusters C 2 and C 4 were implanted into Ni/SiO 2 /Si substrates and following post-thermal treatment graphene was obtained.Raman spectroscopy showed characteristic 2D peaks with G-to-2D peak ratios revealing formation of 2-3 layers of graphene.The Raman data reveals clear effect of nonlinear cluster-surface interaction in ion beam synthesis of two-dimensional nanomaterials.展开更多
文摘基于漫反射和随机编码理论提出一种应用于雷达散射截面积(RCS)缩减的超表面,并通过仿真和实验进行验证。首先,简要阐述了漫反射和随机编码理论,并设计一种基于金属分割线结构的线极化转换超单元。该结构基于"0"、"1"两种基本单元进行编码,在宽频段范围内实现180°反射相位差。仿真结果表明,超表面在6~14GHz频段内,线极化转换率高达90%,RCS缩减大于10 d B的带宽达到6 GHz。然后,设计三种随机编码超表面,进行制备和实验测试。实验结果表明:在5.5~13 GHz频带范围内,三种随机超表面在垂直入射时的反射率小于–10d B,存在6 GHz带宽RCS缩减大于10 d B,与仿真结果基本一致。另外,斜入射情况下,同样能得到有效的RCS缩减,随机编码超表面具备宽角度入射RCS缩减特性。该设计为雷达隐身技术提供了一种新的途径。
基金Supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(2018R1A5A1025563,2023R1A2C1003177,IBS-R031-D1)。
文摘In this study,we calculated the inclusive charged-current neutrino-nucleus scattering from ^(40)Ar in the quasielastic region.To explore the effect of uncertainties stemming from the nuclear structure,we used the KIDS(Korea-IBS-Daegu-SKKU)nuclear energy density functional and Skyrme force models,namely SLy4,SkI3,and MSk7.These models were selected to have distinct behavior in terms of the density dependence of the symmetry energy and the effective mass of the nucleon.In the charged-current neutrino scattering,the single-and double-differential cross sections were calculated for various kinematics.Total cross sections are reported as a function of the incident neutrino energy.The theoretical cross sections were compared with experimental data,and the roles of the effective mass and symmetry energy were investigated in terms of charged-current neutrino-nucleus scattering.
基金Supported by National Natural Science Foundation of China(11079001)
文摘Distortions caused by the neutron spectrum and scattered neutrons are major problems in fast neutron radiography and should be considered for improving the image quality. This paper puts emphasis on the removal of these image distortions and deviations for fast neutron radiography performed at the NECTAR facility of the research reactor FRM-II in Technische Universit/it Mfinchen （TUM）, Germany. The NECTAR energy spectrum is analyzed and established to modify the influence caused by the neutron spectrum, and the Point Scattered Function （PSeF） simulated by the Monte-Carlo program MCNPX is used to evaluate scattering effects from the object and improve image quality. Good analysis results prove the sound effects of the above two corrections.
基金supported by the National Natural Science Foundation of China(Nos.62075056 and 61927815)the Natural Science Foundation of Tianjin(No.20JCZDJC00430)
文摘This work demonstrates the generation of short pulse duration and high-beam-quality laser pulses using transient stimulated Brillouin scattering at a high repetition rate.Thermal effects and optical breakdown are identified as the main factors that restrict energy reflectivity and beam quality under high repetition rates and transient situations.Through experimental analysis,the interaction length and focal point size are determined to be the key parameters in reducing the thermal effect by reducing the absorption of the laser pulse by the medium.The obtained results show that pulses with a duration of 175 ps and beam quality M^(2)of around 1.2 can be achieved with a maximum energy reflectivity of over 40%under an interaction length of 50 mm.Furthermore,at an interaction length of 90 mm,a pulse output with a minimum duration of 115 ps(0.5τQ)is achieved.
文摘After one century of nuclear physics, its underlying fundamental laws remain a puzzle. Rutherford scattering is well known to be electric at low kinetic energy. Nobody noticed that the Rutherford scattering formula works also at high kinetic energy, needing only to replace the repulsive electric -2 exponent by the also repulsive magnetic -6 exponent. A proton attracts a not so neutral neutron as amber attracts dust. The nucleons have magnetic moments that interact as magnets, equilibrating statically the electric attraction between a proton and a not so neutral neutron. In this paper, the electromagnetic potential energies of the deuteron 2H and the α particle 4He have been calculated statically, using only electromagnetic fundamental laws and constants. Nuclear scattering and binding energy are both electromagnetic.
文摘A high-efficiency Brillouin fiber ring laser is demonstrated using the standard single-mode fiber. The laser exhibits a 3.6-mW threshold. The output power is 22 mW with 40-mW pump power, and the maximum optical-to-optical efficiency is 5570. The output is single wavelength with a 3-dB linewidth of 5 MHz, and the interval of center frequency between the laser and the pump light is 11 GHz （0.088 nm）. It is shown that the stimulated Brillouin scattering threshold of ring resonator is lower and the energy transfer efficiency is higher than those in fiber.
基金supported by the National Natural Science Foundation of China(Nos.61378007 and61138005)the Fundamental Research Funds for the Central Universities(No.HIT.IBRSEM.A.201409)
文摘We obtain the output of a 284 ps pulse duration without tail modulation based on stimulated Brillouin scattering（SBS） pulse compression pumped by an 8 ns-pulse-duration, 1064 nm-wavelength Q-switched Nd：YAG laser. To suppress the tail modulation in SBS pulse compression, proper attenuators, which can control the pump energy within a rational range, are added in a generator-amplifier setup. The experimental result shows that the effective energy conversion efficiency triples when the pump energy reaches 700 m J to 51%, compared with the conventional generator-amplifier setup.
基金supported by the International Cooperation Program of the Ministry of Science and Technology of China (2010DFA02010)
文摘We developed a cluster ion beam system that produces negative cluster beams of C 1-C 10 with ion current of 4.5 nA-50 A at extraction voltages ranging from 6 to 20 kV.The system uses the injector of a tandetron accelerator and was established by inserting an electrostatic scanner on its ion-optical line and modifying its Faraday cup into a substrate holder.Utilization of clusters enables ultrashallow ion implantation at energies as low as 600 eV/atom without deceleration.Small carbon clusters C 2 and C 4 were implanted into Ni/SiO 2 /Si substrates and following post-thermal treatment graphene was obtained.Raman spectroscopy showed characteristic 2D peaks with G-to-2D peak ratios revealing formation of 2-3 layers of graphene.The Raman data reveals clear effect of nonlinear cluster-surface interaction in ion beam synthesis of two-dimensional nanomaterials.
