多普勒效应测试仪的改进

为了解决电磁波多普勒效应在实验室演示的困难，采用单片机和一系列大规模集成电路设计了一种演示电磁波多普勒效应的测试仪器，分析了电磁波的多普勒效应原理，给出了该仪器的组成结构，介绍了该仪器铁特点。     

东大完成的合作开发项目受到UNESCO赞赏

东南大学物理系物理仪器研究室于1986年接受联合国教科组织(UNESCO)时资助与该组织合作开发15种可提供给第三世界使用的物理实验仪器。这15种仪器包话课堂演示用物理实验仪器，普通物理实验仪器和近代物理实验仪器等。     

铂电阻温度计的分度与实验装置

铂电阻温度计的分度与实验装置李文成，谢家春（天津大学物理系３０００７２）一、前言电阻温度计是科学实验及生产中用于测温的主要仪器之一，而铂电阻温度计被国际规定为用于１３．８１～６３０．７４℃的测温标准仪器．因此，在物理实验教学中使学生了解铂电阻温度计的...     

转动实验仪器的比较研究

测物体转动拨量，验证转动定律是普物实验的基本内容．目前测转动馈量的仪器已有几种：如三线摆、扭摆和塔轮型转动实验仪；1984年南开大学物理系谭成章教授等设计、研制成功新型转动仪器——气垫转盘．笔者根据教学使用情况，对上述三线摆和气垫转盘作了一点比较研究，现分述如下：一、直观教学效果比较出物体转动保量是这个实验的基本内容，验证转动定律、平行轴定理都要通过出转动惯量I的值进行验证．测I值的方法有几种，笔者认为直接用转动定律I一M／卢的测量方法最简捷，实验教学效果最好．这是因为，按定义转动惯量是物体保持原有转…     

利用小家电做物理演示实验

用小家电做演示实验，取材容易，现象明显，生动直观，同时弥补了实验仪器的缺乏，而且实验过程有声有色，学生很感兴趣．     

用于开放性实验和演示实验的自制磁场测定仪

介绍作设计制作的磁场测定仪的原理、选材、制作、调试、使用方法及相关的讨论，该仪器可测狭小空间的磁场，确定磁场的性质和空间分布，该制作，既可以由教师精心制作为演示仪器，也可以作为开放性实验为大学生开设，本制作和材料均取自废旧仪器中的零散元件，成本十分低廉，如果不计较成本，对电路和元件进行精确优化，并认真定标，还可用于定量测量。     

浅谈我校的"学生自主实验"

我校（初中）在这两年开展了“学生自主实验”．这是因为新的物理课程，要求教师尽快地从“为考试而教”转变为“为创造而教”，不再是“教参～教材一学生”的教学程序和模式，而要变成“学生一活动一教材”的物理教学新模式，从而进入到教育创新的广阔天地．基于这种教学理念，我校“学生自主实验”区别于课堂上的教师演示实验与学生实验，是学生在已有知识基础上自主质疑，应用学校实验室提供的仪器及化学药品（仪器及药品目录挂在实验室外墙上，学生可以随时查阅），自拟探究课题，或选择实验室提供的课题（课题也在实验室外墙上），     

仪器保有量中的相关因素

分析了影响仪器保有量的相关因素，通过定级得修正值，确定仪器保有量。     

高炉炉墙厚度在线测量实验--科研成果用于开放性实验和演示实验

将高炉炉墙厚度在线监测技术这一科研成果引入开放性实验和演示实验，介绍了实验教材的编写、电路制作、仪器标定以及实验教学的内容。     

夫兰克-赫兹实验的计算机仿真

为了利用现代化的手段改进实验教学，我们研制了F-H实验的计算机仿真系统。该系统以计算机动画技术模拟了F-H实验的各种仪器。学生脱离现实的实验仪器，通过键盘操作完成实验操作。实验中教师专家系统随时进行指导和评估，加深学生对实验原理的理解。该系统把教材、教师指导、实验操作和学生的独立思考熔为一体，增加了实验的趣味性和可重复性，激发了学生做实验的热情，极大地提高了实验教学的效果。     

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.     

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.     

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.