In the paper, we propose a surface wave suppression method in time-frequency domain based on the wavelet transform, considering the characteristic difference of polarization attributes, amplitude energy and apparent v...In the paper, we propose a surface wave suppression method in time-frequency domain based on the wavelet transform, considering the characteristic difference of polarization attributes, amplitude energy and apparent velocity between the effective signals and strong surface waves. First, we use the proposed method to obtain time-frequency spectra of seismic signals by using the wavelet transform and calculate the instantaneous polarizability at each point based on instantaneous polarization analysis. Then, we separate the surface wave area from the signal area based on the surface-wave apparent velocity and the average energy of the signal. Finally, we combine the polarizability, energy, and frequency characteristic to identify and suppress the signal noise. Model and field data are used to test the proposed filtering method.展开更多
In this article, distributions of internal stress and internal electric fields around a triple point of ferroelectric polycrystals generated by the spontaneous deformation and spontaneous polarization were investigate...In this article, distributions of internal stress and internal electric fields around a triple point of ferroelectric polycrystals generated by the spontaneous deformation and spontaneous polarization were investigated. It was found that when all three grains consist of a single domain, the internal stresses and the internal electric fields do not vanish. Though it may be determined according to the principle of energy, the spontaneous configuration will not be unique without involving other conditions due to the symmetry of the crystal structure.展开更多
Based on polarization mechanisms, such as electronic, ionic and orientational polarizations, a new equation for dielectric permittivity of soil is proposed to interpret the dielectric behavior of a mixture like soil, ...Based on polarization mechanisms, such as electronic, ionic and orientational polarizations, a new equation for dielectric permittivity of soil is proposed to interpret the dielectric behavior of a mixture like soil, in terms of polarization process of its components and the interactions between its components. The dielectric permittivity is expressed in terms of a fre-quency-dependent part and a frequency-independent part. These two parts correspond to polarizations occurred at different fre-quency range. It is a new volumetric mixing model with theoretical background. Based on time domain reflectometry (TDR) measurements of saturated soil samples and test data from literature, comparisons of this model with some well established mixing models show that the curves for saturated sand soils and slurries resulted from the new equation, which agree well with TDR measurements, are close to those calculated from Birchak's model.展开更多
The electromagnetically induced reflection(EIR)effect of graphene metamaterials has been investigated by finite difference time domain(FDTD)method.In this study,a metamaterial sandwich structure composed of silica(SiO...The electromagnetically induced reflection(EIR)effect of graphene metamaterials has been investigated by finite difference time domain(FDTD)method.In this study,a metamaterial sandwich structure composed of silica(SiO2),gold and graphene on terahertz band is designed.By changing the width of the two ribbons of graphene length and the incident angle of electromagnetic wave,the EIR effect of the structure is discussed,and it can be found that SiO2 is a kind of excellent dielectric material.The simulation results show that graphene metamaterial is not sensitive to polarized incident electromagnetic wave.Therefore,such EIR phenomena as insensitive polarization and large incident angle can be applied to optical communication filters and terahertz devices.展开更多
Influence of spin–orbit coupling on spin-polarized electronic transport in magnetic semiconductor nanowires with nanosized sharp domain walls is investigated theoretically.It is shown that the Rashba spin–orbit coup...Influence of spin–orbit coupling on spin-polarized electronic transport in magnetic semiconductor nanowires with nanosized sharp domain walls is investigated theoretically.It is shown that the Rashba spin–orbit coupling can enhance significantly the spin-flip scattering of charge carriers from a nanosized sharp domain wall whose extension is much smaller than the carrier＇s Fermi wavelength.When there are more than one domain wall presented in a magnetic semiconductor nanowire,not only the spin-flip scattering of charge carriers from the domain walls but the quantum interference of charge carriers in the intermediate domain regions between neighboring domain walls may play important roles on spin-polarized electronic transport,and in such cases the influences of the Rashba spin–orbit coupling will depend sensitively both on the domain walls＇ width and the domain walls＇ separation.展开更多
探讨了不同极化方式下Pb(Mg_(1/3)Nb_(2/3))O_(3)–0.3Pb Ti O_(3)(PMN-0.3PT)单晶的压电性能的变化。实验结果表明,相比于直流电极化,交流电极化后PMN-0.3PT单晶的压电系数d33从1421 pC/N提升至1857 pC/N,相对介电系数εr从4800提升至6...探讨了不同极化方式下Pb(Mg_(1/3)Nb_(2/3))O_(3)–0.3Pb Ti O_(3)(PMN-0.3PT)单晶的压电性能的变化。实验结果表明,相比于直流电极化,交流电极化后PMN-0.3PT单晶的压电系数d33从1421 pC/N提升至1857 pC/N,相对介电系数εr从4800提升至6650,压电系数与相对介电系数分别提升了30.7%和38.5%。为探究交流电优化机理,采用了实验和模拟相结合的方法,从极化畴结构演化的角度给出了解释。用压电力显微镜对PMN-0.3PT的畴结构进行了扫描,并利用相场模型对PMN-0.3PT的畴结构演化进行了表征,实验和模拟结果展现出相同的演化趋势;同时建立了相应的晶格演化模型进行解释。对于未极化的PMN-0.3PT单晶,畴结构呈现随机分布的状态;经过直流电极化后,电畴沿偏向电场的方向翻转,畴结构形貌呈现树枝状;在交流电极化后,PMN-0.3PT内部只存在两个不同极化方向,畴结构形貌呈现条带状。数值计算的结果表明,随着极化方式由无极化到直流极化再到交流极化,PMN-0.3PT的畴壁能从727.578变化到160.060再到57.910,伴随着畴壁能的减小,畴壁密度逐渐降低,这是导致压电性能提升的主要原因。该研究成果对深入理解弛豫铁电材料电畴结构与压电性能的内在联系及作用机理有非常重要的意义,并为优化铁电材料的压电性能给出了可行方案。展开更多
In correlated oxides,collaborative manipulation on light intensity,wavelength,pulse duration and polarization has yielded many exotic discoveries,such as phase transitions and novel quantum states.In view of potential...In correlated oxides,collaborative manipulation on light intensity,wavelength,pulse duration and polarization has yielded many exotic discoveries,such as phase transitions and novel quantum states.In view of potential optoelectronic applications,tailoring long-lived static properties by light-induced effects is highly desirable.So far,the polarization state of light has rarely been reported as a control parameter for this purpose.Here,we report polarization-dependent metal-to-insulator transition(MIT)in phaseseparated manganite thin films,introducing a new degree of freedom to control static MIT.Specifically,we observed giant photoinduced resistance jumps with striking features:(1)a single resistance jump occurs upon a linearly polarized light incident with a chosen polarization angle,and a second resistance jump occurs when the polarization angle changes;(2)the amplitude of the second resistance jump depends sensitively on the actual change of the polarization angles.Linear transmittance measurements reveal that the origin of the above phenomena is closely related to the coexistence of anisotropic micro-domains.Our results represent a first step to utilize light polarization as an active knob to manipulate static phase transitions,pointing towards new pathways for nonvolatile optoelectronic devices and sensors.展开更多
We have observed various polarization domains and a giant self-mode-locked pulse in a 130 m long erbium-doped fiber laser without any mode-locking devices.By adjusting the intracavity polarization controller,we invest...We have observed various polarization domains and a giant self-mode-locked pulse in a 130 m long erbium-doped fiber laser without any mode-locking devices.By adjusting the intracavity polarization controller,we investigated the evolution process of the polarization domain with the varying cavity birefringence.When the birefringence was close to zero,the polarization domains split into multidomains,and finally a giant self-mode-locked pulse formed for the first time.We analyzed that the generation of the self-mode-locked pulse was related to the multiple subdomains ascribed to the strong coherent cross coupling between the orthogonal polarization light components in the long fiber cavity.展开更多
An FDTD system associated with uniaxial perfectly matched layer（UPML） for an electromagnetic scattering problem in two-dimensional space in polar coordinates is considered.Particularly the FDTD system of an initial-...An FDTD system associated with uniaxial perfectly matched layer（UPML） for an electromagnetic scattering problem in two-dimensional space in polar coordinates is considered.Particularly the FDTD system of an initial-boundary value problems of the transverse magnetic（TM） mode to Maxwell＇s equations is obtained by Yee＇s algorithm,and the open domain of the scattering problem is truncated by a circle with a UPML.Besides,an artificial boundary condition is imposed on the outer boundary of the UPML.Afterwards,stability of the FDTD system on the truncated domain is established through energy estimates by the Gronwall inequality.Numerical experiments are designed to approve the theoretical analysis.展开更多
This paper presents a new design of dual polarized aperture coupled printed antenna array. The finite difference time domain (FDTD) analysis of an aperture coupled microstrip element is performed, and the effects ...This paper presents a new design of dual polarized aperture coupled printed antenna array. The finite difference time domain (FDTD) analysis of an aperture coupled microstrip element is performed, and the effects of antenna parameters on its characteristics are obtained to guide the design of the printed array. Then an 8×2 dual polarized array design in X band is introduced with configuration plots. In order to improve its isolation and cross polarization, an outphase displacement feeding technique is adopted in the feed network. Also, the round bends are used instead of conventional right angle bends so as to achieve better VSWR performance. Experimental results are presented, indicating the validity of the design. This dual polarized array can be applied as a sub array of spaceborne SAR systems.展开更多
基金supported by the National Science and Technology Major Project(No.2011ZX05002-004-002)the National Natural Science Foundation of China(No.41304111 and 41704132)+3 种基金Key Project of Science&Technology Department of Sichuan Province(No.2016JY0200)Natural Science project of Education Department of Sichuan Province(Nos.17ZA0025,16ZB0101 and 18CZ0008)the Sichuan Provincial Youth Science&Technology Innovative Research Group Fund(No.2016TD0023)the Cultivating Program of Excellent Innovation Team of Chengdu University of Technology(No.KYTD201410)
文摘In the paper, we propose a surface wave suppression method in time-frequency domain based on the wavelet transform, considering the characteristic difference of polarization attributes, amplitude energy and apparent velocity between the effective signals and strong surface waves. First, we use the proposed method to obtain time-frequency spectra of seismic signals by using the wavelet transform and calculate the instantaneous polarizability at each point based on instantaneous polarization analysis. Then, we separate the surface wave area from the signal area based on the surface-wave apparent velocity and the average energy of the signal. Finally, we combine the polarizability, energy, and frequency characteristic to identify and suppress the signal noise. Model and field data are used to test the proposed filtering method.
基金National Natural Science Foundation of China(No.19672053)Special Funds for Doctoral Programs(No.96061305)
文摘In this article, distributions of internal stress and internal electric fields around a triple point of ferroelectric polycrystals generated by the spontaneous deformation and spontaneous polarization were investigated. It was found that when all three grains consist of a single domain, the internal stresses and the internal electric fields do not vanish. Though it may be determined according to the principle of energy, the spontaneous configuration will not be unique without involving other conditions due to the symmetry of the crystal structure.
基金Project (Nos. 50278087 and 50308026) supported by the NationalNatural Science Foundation of China
文摘Based on polarization mechanisms, such as electronic, ionic and orientational polarizations, a new equation for dielectric permittivity of soil is proposed to interpret the dielectric behavior of a mixture like soil, in terms of polarization process of its components and the interactions between its components. The dielectric permittivity is expressed in terms of a fre-quency-dependent part and a frequency-independent part. These two parts correspond to polarizations occurred at different fre-quency range. It is a new volumetric mixing model with theoretical background. Based on time domain reflectometry (TDR) measurements of saturated soil samples and test data from literature, comparisons of this model with some well established mixing models show that the curves for saturated sand soils and slurries resulted from the new equation, which agree well with TDR measurements, are close to those calculated from Birchak's model.
基金Research Project of Anhui Province Education Department(No.KJ2020A0684)Innovation and Entrepreneurship Training Program for College Students(Nos.S201910375072,201910375050,201910375052,202010375030)。
文摘The electromagnetically induced reflection(EIR)effect of graphene metamaterials has been investigated by finite difference time domain(FDTD)method.In this study,a metamaterial sandwich structure composed of silica(SiO2),gold and graphene on terahertz band is designed.By changing the width of the two ribbons of graphene length and the incident angle of electromagnetic wave,the EIR effect of the structure is discussed,and it can be found that SiO2 is a kind of excellent dielectric material.The simulation results show that graphene metamaterial is not sensitive to polarized incident electromagnetic wave.Therefore,such EIR phenomena as insensitive polarization and large incident angle can be applied to optical communication filters and terahertz devices.
文摘Influence of spin–orbit coupling on spin-polarized electronic transport in magnetic semiconductor nanowires with nanosized sharp domain walls is investigated theoretically.It is shown that the Rashba spin–orbit coupling can enhance significantly the spin-flip scattering of charge carriers from a nanosized sharp domain wall whose extension is much smaller than the carrier＇s Fermi wavelength.When there are more than one domain wall presented in a magnetic semiconductor nanowire,not only the spin-flip scattering of charge carriers from the domain walls but the quantum interference of charge carriers in the intermediate domain regions between neighboring domain walls may play important roles on spin-polarized electronic transport,and in such cases the influences of the Rashba spin–orbit coupling will depend sensitively both on the domain walls＇ width and the domain walls＇ separation.
文摘探讨了不同极化方式下Pb(Mg_(1/3)Nb_(2/3))O_(3)–0.3Pb Ti O_(3)(PMN-0.3PT)单晶的压电性能的变化。实验结果表明,相比于直流电极化,交流电极化后PMN-0.3PT单晶的压电系数d33从1421 pC/N提升至1857 pC/N,相对介电系数εr从4800提升至6650,压电系数与相对介电系数分别提升了30.7%和38.5%。为探究交流电优化机理,采用了实验和模拟相结合的方法,从极化畴结构演化的角度给出了解释。用压电力显微镜对PMN-0.3PT的畴结构进行了扫描,并利用相场模型对PMN-0.3PT的畴结构演化进行了表征,实验和模拟结果展现出相同的演化趋势;同时建立了相应的晶格演化模型进行解释。对于未极化的PMN-0.3PT单晶,畴结构呈现随机分布的状态;经过直流电极化后,电畴沿偏向电场的方向翻转,畴结构形貌呈现树枝状;在交流电极化后,PMN-0.3PT内部只存在两个不同极化方向,畴结构形貌呈现条带状。数值计算的结果表明,随着极化方式由无极化到直流极化再到交流极化,PMN-0.3PT的畴壁能从727.578变化到160.060再到57.910,伴随着畴壁能的减小,畴壁密度逐渐降低,这是导致压电性能提升的主要原因。该研究成果对深入理解弛豫铁电材料电畴结构与压电性能的内在联系及作用机理有非常重要的意义,并为优化铁电材料的压电性能给出了可行方案。
基金supported by the National Key Research and Development Program of China(2022YFA1403300 and 2020YFA0309100)the National Natural Science Foundation of China(11991060,12074075,12074073,12074071,12074080,and 12274088)+3 种基金the Shanghai Municipal Science and Technology Major Project(2019SHZDZX01)the Shanghai Municipal Natural Science Foundation(20501130600,22ZR1408100,22ZR1407400,and 23ZR1407200)support from the National Key Research and Development Program of China(2021YFA1400503 and 2021YFA1400202)the National Natural Science Foundation of China(12125403,11874123,and 12221004).
文摘In correlated oxides,collaborative manipulation on light intensity,wavelength,pulse duration and polarization has yielded many exotic discoveries,such as phase transitions and novel quantum states.In view of potential optoelectronic applications,tailoring long-lived static properties by light-induced effects is highly desirable.So far,the polarization state of light has rarely been reported as a control parameter for this purpose.Here,we report polarization-dependent metal-to-insulator transition(MIT)in phaseseparated manganite thin films,introducing a new degree of freedom to control static MIT.Specifically,we observed giant photoinduced resistance jumps with striking features:(1)a single resistance jump occurs upon a linearly polarized light incident with a chosen polarization angle,and a second resistance jump occurs when the polarization angle changes;(2)the amplitude of the second resistance jump depends sensitively on the actual change of the polarization angles.Linear transmittance measurements reveal that the origin of the above phenomena is closely related to the coexistence of anisotropic micro-domains.Our results represent a first step to utilize light polarization as an active knob to manipulate static phase transitions,pointing towards new pathways for nonvolatile optoelectronic devices and sensors.
基金supported by the National Key Research and Development Program of China(No.2018YFE0117400)National Natural Science Foundation of China(No.62275093)China Postdoctoral Science Foundation(No.2018M642823)。
文摘We have observed various polarization domains and a giant self-mode-locked pulse in a 130 m long erbium-doped fiber laser without any mode-locking devices.By adjusting the intracavity polarization controller,we investigated the evolution process of the polarization domain with the varying cavity birefringence.When the birefringence was close to zero,the polarization domains split into multidomains,and finally a giant self-mode-locked pulse formed for the first time.We analyzed that the generation of the self-mode-locked pulse was related to the multiple subdomains ascribed to the strong coherent cross coupling between the orthogonal polarization light components in the long fiber cavity.
文摘An FDTD system associated with uniaxial perfectly matched layer（UPML） for an electromagnetic scattering problem in two-dimensional space in polar coordinates is considered.Particularly the FDTD system of an initial-boundary value problems of the transverse magnetic（TM） mode to Maxwell＇s equations is obtained by Yee＇s algorithm,and the open domain of the scattering problem is truncated by a circle with a UPML.Besides,an artificial boundary condition is imposed on the outer boundary of the UPML.Afterwards,stability of the FDTD system on the truncated domain is established through energy estimates by the Gronwall inequality.Numerical experiments are designed to approve the theoretical analysis.
文摘This paper presents a new design of dual polarized aperture coupled printed antenna array. The finite difference time domain (FDTD) analysis of an aperture coupled microstrip element is performed, and the effects of antenna parameters on its characteristics are obtained to guide the design of the printed array. Then an 8×2 dual polarized array design in X band is introduced with configuration plots. In order to improve its isolation and cross polarization, an outphase displacement feeding technique is adopted in the feed network. Also, the round bends are used instead of conventional right angle bends so as to achieve better VSWR performance. Experimental results are presented, indicating the validity of the design. This dual polarized array can be applied as a sub array of spaceborne SAR systems.
