牛顿第三定律与介质中的静电场

本文根据静电场的唯一性定理,运用两介质区内的电热分布试探函Φ１和Φ２,证明两均匀介质中位于无限大分界平面两侧的电荷之间的相互作用力服从牛顿第三定律。     

多结超导环在外磁场中的行为

分析和计算了双结超导环在无偏置电流时的磁通、环流、自由能与外磁场的关系.发现双结环与单结环在磁场中的行为有所不同.当两个结的Ic相等时，双结环在1＜β=2πLIcΦ0＜2时，若无偏置电流，总磁通Φ、环流I与外磁通Φe的关系仍然是非回滞的曲线.仅当β≥2时，曲线才出现回滞.另外双结环有两支解，并且每支解的周期为2Φ0. 关键词： 双结环 双支解 2Φ0周期 回滞     

肾器官多孔参数的测定温度场重构

首先通过实验测定了肾脏作为多孔介质的两项最基本的特性参数孔隙率和渗透率。结果表明,猪肾脏的孔隙率为Φ=15.64%,渗透率为K=14.5μm~2。利用血管铸型对肾脏的动静脉血管和肾脏外形进行三维重建得到肾脏的物理模型,以管内非线性流动模型和多孔介质模型相结合的方式,对肾脏冷灌注过程的三维温度场进行重构。将模拟结果与实验结果对比,探索冷刺激作用下,降温作用引起的肾脏热力学响应,并对温度场模拟结果进行了分析。     

光学元件库——欧普特科技

北京欧普特公司参照国际通常规格及技术指标,备有完整系列的精密光学零部件(备有产品样本供参考),供国内各大专院校、科研机构、实验室随时选用,公司同时可为用户提供技术咨询.光学透镜:平凸、双凸、平凹、双凹,消色差胶合透镜等,直径Φ1~150 mm;焦距1~1000 mm;材料包括光学玻璃,紫外石英玻璃,有色光学玻璃,红外材料.光学棱镜:1~50 mm各种规格直角棱镜,及其他常用棱镜.光学反射镜:各种尺寸规格的镀铝,镀银,镀金,及介质反射镜.直径Φ5~200 mm.光学窗口:各种尺寸规格、材料的光学平面窗口,平晶.直径Φ5~200 mm.各种有色玻璃滤光片:规格Φ5…     

弱锚泊条件下超扭曲向列相液晶显示的光学阈值电压

在超扭曲向列相液晶显示（ＳＴＮ－ＬＣＤ）中，用倾角θ和扭曲角Φ确定液晶指向矢。基于液晶连续体理论，得到θ、Φ和电势Ｕ满足的常微分方程组及其边界条件。通过松弛方法解常微分方法组两点边值问题，计算了光学阈值电压对锚泊强度的依赖关系。     

平面冲击波在有机玻璃中的衰减规律

采用PVDF压电式压力传感器测量了在Φ100mm平面波透镜加载下经不同厚度Φ100mm有机玻璃隔板衰减后的冲击波压力历程,实验结果与LS-DYNA数值模拟结果符合较好。研究结果表明,冲击波压力在有机玻璃中服从衰减系数为0.028 89的指数衰减规律。与其他研究者的研究结果对比说明,密实介质的衰减系数反映了其衰减特性,但受加载冲击波及装置尺寸的影响较大,应根据实际情况进行合理选择。     

轻型反射镜研究与发展

应用有限元分析方法研究了自重对轻型反射镜变形的影响，反射镜轻量化技术及关键材料，并研制出Φ６３０ｍｍ轻型熔石英反射镜；高温２００℃、低温－４０℃及５年时效对面形稳定性影响；轻型熔石英反射镜加工技术；轻型反射镜宽带高反射膜系及镀膜技术。利用上述技术研制出Φ３００ｍｍ、Φ４１０ｍｍ、Φ４７０ｍｍ及Φ６３０ｍｍ球面及非球面熔石英轻型反射镜及平面反射镜。轻型反射镜减重达７０％，Φ６３０ｍｍ轻型非球面反射镜仅重２０．２ｋｇ。Φ４７０ｍｍ球面轻型反射镜加工后面形ＰＶ值０．１１７λ，ＲＭＳ值０．０２４λ（λ∶６３２．８ｎｍ）。     

量子体系状态波函数的一点讨论

本文从量子力学的基本原理出发,对描述量子系统的状态波函数Φ=sum from n to C_nφ_n和Φ'=sum from n to C_ne~((ia)n )φ_n之间的关系作了详细的讨论。由自旋了1/2粒子的简单特例到一般系统状态的等价表示形式,阐明了Φ和Φ’之间是一等价变换的关系,它们是系统同一状态的两种表示形式,或者说是描写系统的两个等价状态。     

一种高陡度离轴非球面的加工检测

因为离轴椭球镜中心遮拦区是不需要的，我们选择如下检验方案（如图１）。用一个直径Φ３ｍｍ的钢珠做辅助球面镜。先在已成型的轴对称椭球镜毛坯中心打一个Φ１０ｍｍ的通光孔，检验时此镜与夹具一起放在一稳定的Ｖ型块中。钢珠用胶粘在一直径Φ２ｍｍ的金属棒上，并固定在有两个自由度的调节支架上，以便在检验时调节焦距及光轴的重合精度。采用照明的光源是刀口仪拆去刀口和前组透镜，在筒口端面放一０．５ｍｍ厚的薄铜板做的Φ３ｍｍ的小孔光阑，从被加工镜后面作近似平行光的照明。可以用此方法来检验一轴对称高陡度椭球镜，合格后再采用辅助块与此镜粘贴，最后切磨取下所需的离轴镜。     

填充多层互易手征介质金属同轴线传播特性

 采用在圆柱坐标系中分离变量的方法，推出填充多层互易手征介质的金属同轴线各层电磁场之间的关系，得到其模式特征方程和圆波导模式特征方程，给出了填充两层手征介质金属同轴线部分模式的色散特性的数值计算结果，分析了手征介质参量及两层手征介质厚度变化等对手征同轴线传播特性的影响。如果互易手征介质的手征参数等于零，可得填充普通介质的同轴线的模式特征方程。与填充普通介质的同轴线中的模式相比，手征同轴线中的模式发生了分叉。当同轴线中所填介质的折射率增大时，其模式归一化截止频率和进行基模单模传输的带宽归一化频率都将减小。     

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.