均质三角形边框刚体对其质心轴的转动惯量的简明推导

利用任意三角形的边长与顶点坐标的关系, 直接推出任意三角形边框的质心到各边中点的距离与三 角形各边边长的关系, 从而方便地求得任意均质三角形边框刚体对其质心轴的转动惯量     

双生子佯谬的投影诠释

在表示洛伦兹变换的复平面上，考察各边平行于坐标轴的直角三角形，以其中各边比例关系为“投影关系”，用于简明地诠释双生长子倦廖的实质，并得出某种程度的一般性结论。     

临边成像光谱仪的发展现状与进展

介绍了临边观测模式的探测原理及其特点,给出了美国、欧洲等发达国家关于临边成像光谱仪的研究状况,并列出了各临边成像光谱仪的核心设计方案及具体的技术指标。最后,介绍了国内唯一一例临边成像光谱仪的开展情况,包括设计方案到技术指标。通过对比分析国内外临边成像光谱仪的研究进展,为我国进一步提高临边成像光谱仪的性能及技术指标提供了理论基础。     

对称性和叠加原理的简单应用

几乎所有普通物理教科书中都有这样一道流行的习题:以电阻均为R的十二条边组成一个立方体,求它们的等效电阻.要解决这一问题,必须算出通过各电阻的电流.运用对称性和叠加原理,这一问题是不难解决的. 先让我们来考虑如图一所示的那种情况.电流进入立方体的某一顶点,最后从同它相邻的顶点流出. 图中各电流是根据对称性而设的.平面AEGC两边的电流都对这个面对称,而且通过上表面各边的电流与通过下表面EHGF各边的电流大小相等、方向相反. 根据基尔霍夫电流定律可以知道,从C到G的电流为2k,并且,又根据基尔霍夫回路定律,得:解上述简单的方程…     

定态电磁场只有两个独立边值关系的一般证明

本文先将电荷守恒定律边值关系推广到有面电流分布情况下的边值关系，然后证明边值关系只有两个是独立的．     

场域中填充多介质且存在3种以上介质公共点或公共线的电磁场边值关系及其应用

文章分析讨论了场域空间填充有多介质且存在3种以上介质公共点或公共线上的电磁场边值关系一般形式,就简单可解的多介质分界面与电场线重合和多介质分界面与等势面重合的特殊情况举例说明其应用.结果表明多介质公共点或公共线上的边值关系并非是简单的两、两介质分界面边值关系的组合,多介质公共点或公共线上的边值关系确有必须遵循的特殊形式.     

稳态大视场偏振干涉成像光谱仪中视场补偿型Savart偏光镜透射率研究

论述了基于视场补偿型Savart偏光镜的稳态大视场偏振干涉成像光谱仪的分光机理.依据电磁场边值条件,分析了光在视场补偿型Savart偏光镜中各晶体分界面上的透射情况,得出了透射率的理论计算公式.采用计算机模拟,分析了在半波片为不同材料时,透射率随入射波长、视场角及半波片厚度的变化关系.研究表明,视场补偿型Savart偏光镜具有大视场、高通量、高探测灵敏度的显著特点.此研究可为新型干涉成像光谱技术的研究和新型偏振干涉成像光谱仪的设计、研制提供重要的理论指导. 关键词： 偏振干涉成像光谱仪 视场补偿型Savart偏光镜 透射率 电磁场边值条件     

四种解析解设计的短程透镜卷边对损耗的影响

根据光波导短程透镜母线曲率半径与光传输损耗的关系,利用数值计算的方法,通过计算不同母线参数条件下,四种解析解设计的短程透镜母线曲率半径,研究比较了短程透镜卷边对其损耗的影响,得出了短程透镜损耗与其有效区半径关系的曲线图,发现透镜凹面半径一定时,有效区半径越小,即卷边越大时,光传输损耗越小;短程透镜的解析改进解和最优解设计的透镜卷边存在曲率奇点.并由此得出了四种解析解设计的短程透镜有效区半径选取原则及其满足低损耗条件的取值范围.     

应变Ge空穴有效质量的各向异性与各向同性

在利用k·p微扰理论获得应变Ge/Si_1-xGe_x价带E（k）-k关系的基础上,研究得到了（001）,（101）,（111）面应变Ge/Si_1-xGe_x沿不同晶向及各向同性的价带空穴有效质量.结果显示,应变Ge/Si_1-xGe_x沿各晶向的带边有效质量随应力增大而减小,且沿[010]晶向最小;子带空穴有效质量在应力较大时变化不明显,并且在数值上与带边空穴有效质量相差不大.最后利用各向同性有效质量与文献结果进行比对,验证了结果的正确性.     

三维光子晶体中三能级原子的自发发射

研究了三维光子晶体中三能级原子自发发射的性质.由于各向异性色散关系,能带带边的态密度没有奇异性,局域场可以消失.在一定条件下弥散场会得到加强,并在辐射场中占主导地位.这些性质将与原子能级和能带带边的相对位置有关,且有别于各向同性色散关系的光子晶体中原子自发发射的性质. 关键词： 光子晶体 三能级原子 自发发射     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Characterization of PolyA and PolyC mismatches by Raman spectroscopy

A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands.     

Improvement of four-wave mixing-based wavelength conversion efficiency in dispersion shifted fiber by 40-GHz clock pumping

40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm.     

Multi-pulse operation of a Kerr-lens mode-locked femtosecond laser

Our experimental results show that the presence of a proper amount of negative group velocity dispersion is essential to multi-pulse operation of a Kerr-lens mode-locked femtosecond laser. We demonstrate that the pulse separations and the number of pulses contained within a cavity round trip are strongly dependent on the initial perturbations. The results allow us to get a better understanding on the influences of the convoluted self-phase modulation and intra-cavity dispersions on the stable multi-pulse oscillation in a Kerr-lens mode-locked femtosecond laser.     

Propagation of Helmholtz-Gauss beams in weak turbulent atmosphere

Based on the Rytov approximation of light propagation in weak turbulent atmosphere,the closed-form expressions of field and average irradiance of each one of the four fundamental families of Helmholtz-Gauss (HzG)beams:cosine-Gauss beams,stationary Mathieu-Gauss beams,stationary parabolic-Gauss beams,and Bessel-Gauss beams,which are propagating in weak turbulent atmosphere,are obtained.The results show that the field and average irradiance can be written as the product of four factors:complex amplitude depending on the z-coordinate only,a Ganssian beam.a factor of complex phase perturbation induced by atmospheric turbulence,and a complex scaled version of the transverse shape of the non-diffracting beam.The effect of weak atmospheric turbulence on irradiance distribution of the HzG beam can be ignored.     

An effective method for reducing speckle noise in digital holography

An effective method for reducing the speckle noise in digital holography is proposed in this paper.Different from the methods based on classical filtering technique,it utilizes the multiple holograms which are generated by rotating the illuminating light continuously.The intensity images reconstructed by a series of holograms generated by rotating the illuminating light possess different speckle patterns.Hence by properly averaging the reconstructed intensity fields,the speckle noises can be reduced greatly.Experimental results show that the proposed method is simple and effective to reduce speckle noise in digital holography.     

Influence of purity of HfO2 on reflectance of ultraviolet multilayer

The impurities in two kinds of HfO2 materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum technology and secondary ion mass spectrometry(SIMS) equipment respectively.It was found that ZrO2 was the main impurity in the two kinds of HfO2 either in the original HfO2 materials or in the electron beam deposited films.In addition,the difference of Zr content in the two kinds of HfO2 single laver films was much laxger than that of the other impurities such as Ti and Fe.which showed that it was just ZrO2 that made the difference between the optical performance of the film products including the two kinds of HfO2.With these two kinds of HfO2 and the same kind of SiO2.we deposited HfO2/SiO2 multilayer reflective coatings at the wavelength of 266 nm.Experimental results showed that the reflectances of these two mirrors were about 99.85% and 99.15% respectively,which agreed well with the designed results what were based on the optical constants obtained from the corresponding single layer thin films.     

Speech enhancement by array crosstalk resistant ANC and spectrum subtraction

Microphone array-based speech enhancement has great importance for speech communications and speech recognition. To reduce the aperture of the microphone array and to increase the effect of the speech enhancement will greatly broaden the application areas of the microphone array. An array crosstalk resistant adaptive noise cancellation method is therefore presented. And then an improved spectral subtraction algorithm is further cascaded to obtain better enhancement results. Theoretic analysis and experiments indicate that the proposed scheme needs only a very small microphone array while it simultaneously achieves a higher SNR improvement. Besides, the proposed scheme can be used in many noisy environments and is easy for real-time implementation.