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2003-2017 物理学
为您找到包含“”的内容共2851

Wang Liang,Cao Jinxiang

The reflection of X-band microwaves (8-12 GHz) from a metallic aluminum (Al) surface with groove grating corrugations was investigated experimentally. It was shown that the reflection of p-polarization is much less than the microwave reflected from the corresponding area of an unruled Al surface, with selective wavelength. The experimental results demonstrated that the anomalous microwave reflection is strongly associated with the excitation of spoof surface plasmons at the Al-air interface by the surface grating coupler. This near-total absence of reflected microwaves is similar to the famous Wood's anomaly in the optical regime and is of fundamental importance to the applications of spoof surface plasmons in the microwave regime.

2012-11-16

Key Laboratory of Basic Plasma Physics of Chinese Academy of Sciences and Department of Modern Physics, University of Science and Technology of China, HeFei 230026,Key Laboratory of Basic Plasma Physics of Chinese Academy of Sciences and Department of Modern Physics, University of Science and Technology of China, HeFei 230026

#Physics#

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Chen Wei,Meng Zhou

The thresholds of modulation instability (MI) in the 25 km, 50 km and 75 km single-mode fibers (SMFs) are investigated by analyzing the MI spectra. They decrease with the effective fiber length and agree with the theoretical values. It is found that the saturation power of MI does not change with the fiber length and is fixed at 136 mW for the three fibers. However, the maximum conversion efficiency of MI depends on effective fiber length. It is revealed that the 15 km and 20 km effective lengths correspond to the maximum conversion efficiency of 50% and 65%. The results provide guidance for the practical applications of long-haul fiber sensing systems.

2012-11-19

the Specialized Research Fund for the Doctoral Program of Higher Education (20104307110020

College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha, 410073,College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha, 410073

#Physics#

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Zhang Shichang

In a free-electron devices such as the free-electron laser and the electron cyclotron maser, the electric and magnetic fields generated by a relativistic electron beam substantially affect the electrons' motion and consequently the performance of the device. In this paper the expressions are analytically derived by means of the conservation of particle number for both the electric and magnetic fields generated by a solid electron beam with Gaussian profile, where the situations inside and outside regions of the electron beam are included, and all the explicit expressions are written in terms of the macroscopical radius, current and drifting velocity of the electron beam.

2012-11-22

School of Physics and Chemistry, Xihua University, Chengdu 610039, and Institute of Photoelectronics, Southwest Jiaotong University, ChengDu 610031

#Physics#

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ZHANG Shi-Chang

It is revealed that at anti-resonance in a free-electron laser with a reversed guide magnetic field, the beam self-fields can act to focus the beam transport and prevent the electrons from striking on the waveguide wall before the wiggler exit. It is found that the focusing function results from the modulation of the periodically-varying self-field tangential and normal components on the electron's Larmor rotation. As a potential application, substantial improvement of the wave gain and output power at anti-resonance could be expected, since the beam current loss can be obviated by using this modulation mechanism.

2012-11-22

School of Physics and Chemistry, Xihua University, and Institute of Photoelectronics, Southwest Jiaotong University

#Physics#

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ZHANG Jialiang,HAO Wentao,ZHENG Peng,TAN Yongqiang,JI Pengfei,WANG Chunlei

Temperature-stable, frequency-independent and low-loss dielectric properties are usually essential for a high-permittivity ferroelectric material to be practically applied in microwave devices. BaTiO3 ceramics are a type of important ferroelectric material in the viewpoints of both fundamental studies and technological applications. However, investigations of the microwave dielectric dispersion below room temperature have been rarely carried out so far. In this study, the temperature evolution of dielectric dispersion was examined for a coarse-grained BaTiO3 ceramic in the frequency range from 40 Hz to 1 GHz and over the temperature interval between -50 and 180 C, which thus includes the orthorhombic-tetragonal polymorphic phase transition and covers the large part of common usage temperature region. An important physical phenomenon that the phase transition has a notable influence on the microwave dielectric dispersion has been clearly disclosed. The dielectric permittivity ε' shows a maximum whereas the characteristic frequency fr exhibits a minimum in the vicinity of orthorhombic-tetragonal phase transition temperature. In addition, large difference in fr is observed between the heating process and the cooling process in the tetragonal phase. It is considered that the experimentally found phenomenon can be explained by the previously suggested mechanism of the emission of elastic shear waves from ferroelastic domain walls.

2012-11-23

the Doctoral Program of Higher Education (Grant No. 20090131110015

the Natural Science Foundation of Shandong Province (Grant No. ZR2010EM00

the National Natural Science Foundation of China (Grant No. 51172128

School of physics, State Key Laboratory of Crystal Materials, Shandong University, JiNan 250100,School of physics, State Key Laboratory of Crystal Materials, Shandong University,School of physics, State Key Laboratory of Crystal Materials, Shandong University,School of physics, State Key Laboratory of Crystal Materials, Shandong University,School of physics, State Key Laboratory of Crystal Materials, Shandong University,School of physics, State Key Laboratory of Crystal Materials, Shandong University

#Physics#

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YANG Bingfang,HAN Jinzhong,WANG Xuelei

In the framework of the Littlest Higgs Model with T-parity (LHT), we study the contributions of the new particles to Zbb couplings at one-loop level. Based on these results, we further study the branching ratio R_{b} and the unpolarized forward-backward asymmetry A_{FB}^{b}. We find that the correction of the new particles to Zbb couplings is mainly on the left-handed coupling and has small part of the parameter space to alleviate the deviation between theoretical predictions and experimental values. The precision measurement value of R_{b} can give severe constraints on the relevant parameters. The constraints from the precision measurement value of A_{FB}^{b} are very weak.

2012-11-30

Supported by Specialized Research Fund for the Doctoral Program of Higher Education (under Grant Nos.20094104110001

College of Physics and Information Engineering,Henan Normal University, Xinxiang 453007,College of Physics and Information Engineering,Henan Normal University, Xinxiang 453007,College of Physics and Information Engineering,Henan Normal University, Xinxiang 453007

#Physics#

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WANG Yabin,HAN Jinzhong,YANG Bingfang,WANG Xuelei

In the littlest Higgs model with T-parity(LHT), some new particles, such as the T-odd mirror quarks and goldstone bosons, can generate the contribution to some observables. We calculate their contribution to the Zcc coupling. Some observables are related to the Zcc coupling, for example, the effective vector and axial-vector Zcc coupling constants (g_{Vc},g_{Ac}) and the c-quark forward-backward asymmetry(A_{FB}^{c}). We give our predictions about g_{Vc},g_{Ac} in the LHT model and show the allowed regions of the mirror quark masses based on the experimental data of g_{Vc}-g_{Ac}.Then, we also give an explanation on A^{c}_{FB}.

2012-11-30

Supported by Specialized Research Fund for the Doctoral Program of Higher Education (under Grant Nos.20094104110001

College of Physics and Information Engineering,Henan Normal University, HeNan XinXiang 453007,College of Physics and Information Engineering,Henan Normal University, Xinxiang 453007,College of Physics and Information Engineering,Henan Normal University, Xinxiang 453007,College of Physics and Information Engineering,Henan Normal University, Xinxiang 453007

#Physics#

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Dong Zhiwei,Zhao Xu,Dong Yan,Li Gaolong,Wang Chenbo,Xia Yuanqin,Chen Deying

Fluorescence properties of DCM solution and solid dyes were researched applying femtosecond pulses under linear and nonlinear excitation. The reabsorption was found distinct in the solid dyes compared with that in solutions under similar conditions. Nonlinear fluorescence spectra of DCM and rhodamine 590 co-doped tunable laser dyes in ethanol were also researched. The energy transfer of rhodamine 590 to DCM was found neglectable in the nonlinear excitation spectra of the co-doped liquid dyes.

2012-11-21

National Natural Science Foundation of China (No. 11004042)

National Key Laboratory of Science and Technology on tunable laser, Harbin Institute of Technology,Harbin Institute of Technology,Harbin Institute of Technology,Harbin Institute of Technology,Harbin Institute of Technology,Harbin Institute of Technology,Harbin Institute of Technology

#Physics#

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张克声,王殊,朱明,胡轶

2012-11-27

行星大气中的声传播特性,与大气成分、环境温度和压强密切相关。本文给出了不同温度、压强条件下,混合气体声经典吸收、弛豫吸收和声速频散的计算模型。利用该模型,对比了地球、金星、火星以及土卫六不同大气条件下的声吸收和声速频散;并为探测行星大气分子弛豫特性时,选择声传感器的工作频点提供了理论数据。仿真结果表明:各行星较大差异的大气成分和环境条件,使得声无量纲弛豫吸收峰幅度从土卫六的2.71×10^(-8)变化到金星的0.193,声速从土卫六的200 m/s变化到金星的440 m/s;对于地球的干燥空气,分子弛豫特性声探测传感器选择测量频点的范围为0.6 Hz-66 Hz;对于金星大气,为8.16 MHz-816 MHz;对于火星大气,则为8.86 Hz-886 Hz。

中央高校基本科研业务费专项资金(批准号: 2012QN083

湖北省自然科学基金资助项目(批准号:2010CDB02701

国家自然科学基金(批准号:60971009

高等学校博士学科点专项科研基金(61001011

华中科技大学电子与信息工程系,武汉 430074,华中科技大学电子与信息工程系,武汉 430074,华中科技大学电子与信息工程系,武汉 430074,华中科技大学电子与信息工程系,武汉 430074

#物理学#

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刘艳红,董丽娟,刘丽想,石云龙

2012-11-28

本文研究了由各向异性光子晶体实现的窄带角度滤波特性。利用电磁有限元数值仿真方法计算出不同入射角的光子晶体的角度帯隙及参杂后光子晶体的角度缺陷模。数值计算结果表明,随着入射角度的改变各向异性光子晶体的帯隙是可调的,而在这个系统中参杂后能够产生随入射角度变化的窄带缺陷模,因此参杂的各向异性光子晶体具有角度滤波的特性,有望在未来的光子器件中发挥作用。

山西省自然科学基金(2010021006

高等学校博士学科点专项科研基金(20090072110052

国家自然科学基金(10974123,11104169

教育部科学技术研究重点项目基金(212018

山西大同大学固体物理研究所,山西 大同 037009,山西大同大学固体物理研究所,大同 037009,山西大同大学固体物理研究所,大同 037009,山西大同大学固体物理研究所,大同 037009;同济大学波耳固体物理研究所,上海 200092

#物理学#

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