三线摆实验中用大摆角测量转动惯量

利用智能手机APP的陀螺仪传感器可以获得三线摆运动过程中角速度的运动轨迹.对测量数据分析发现初始摆角很小时三线摆周期的测量数据不一定可靠,这与传统测量方法强调的小角度转动有出入.通常对大角度摆动的周期修正基于测出的初始摆角,但一般实验室中不易对其进行准确测定而难以应用于实际测量中.通过测量多个不同初始摆角测量的最大振幅及对应周期,再对振幅与周期相关数据进行多项式拟合,得到初始摆角趋于零的最佳周期值T0.运用此法测量标准圆环的转动惯量,由T0值获得的转动惯量测量结果与理论值比较精度优于0.2%.     

用三线摆研究垂直轴定理

用三线摆对刚体薄圆盘绕不同轴转动时的转动惯量进行测量,通过实验与数据分析,验证了反映刚体转动惯量重要性质的垂直轴定理,从而实现了对刚体转动惯量实验内容的扩充.     

三线摆测量刚体转动惯量实验的改进

对F D I M I I型新型刚体转动惯量测量仪进行了改进, 从仪器的摆角, 上下圆盘的高度, 下圆盘水平3 个方面进行改进, 用改进后的仪器对圆环的转动惯量进行测量, 从实验结果发现, 改进后的仪器可以有效地减小实 验误差     

摆角对三线扭摆周期的影响

摆角对三线扭摆周期的影响卢佃清（淮海工学院基础系连云港市２２２００５）测定则体转动惯量的方法有多种，三线扭摆法就是其中之一．大学物理实验在处理这个问题时大多认为摆角较小时可作为谐振动，给出谐振动周期，从而求出刚体的转动惯量．可是学生在具体实验时经常使...     

微机在三线摆实验中的应用

在三线摆测量转动惯量的实验中，利用微机的串行口来记录三线摆的振动周期。     

对三线摆测物体转动惯量实验的改进

本文介绍了三线摆测物体转动惯量实验中用光控数字毫秒计测量周期的方法，提高了测量精度。     

用气垫摆测物体的转动惯量

介绍用自己研制的气垫摆测量物体的转动惯量,叙述了相关理论,推导了计算公式,给出了实验结果。     

红外地球敏感器扫描镜摆角激光动态测试方法

为解决扫描镜摆角实时动态非接触测量问题,基于激光检测技术和CCD探测技术,提出一种红外地球敏感器扫描镜摆角激光动态测试方法,并研制了扫描镜摆角动态测试系统,其可实现扫描镜的摆动频率、零位角、幅值、峰峰值平均等参量的动静态激光非接触测量。介绍了系统的组成和总体结构,着重对扫描镜摆角动态测量理论和大视场、大相对孔径特殊线性扫描光学系统的设计方法进行了分析与探讨,通过建立系统的数学模型,解决了测量数据误差修正与图形处理问题。对测量系统的精度进行了验证,结果表明系统的摆角测量范围为0~±12°,分辨力为0.01°,动静态测量精度优于±0.04°。     

另一种用物理摆测重力加速度的方法

本实验针对实验室用物理摆的特性,设计出另一种用物理摆测量重力加速的方法。该方法的核心思想是找出周期与转动惯量的关系。     

三线摆转动角度控制装置的设计

用FD-IM-II新型转动惯量测定仪测刚体转动惯量的实验条件之一是转动圆盘角度要小于5°,在实验中发现该仪器没有配置角度控制装置,因此无法准确控制角度,会造成实验结果误差增大。文章为FD-IM-II新型转动惯量测定仪的三线摆设计了2种转动角度控制装置的方案,这样转动角度就可以精确控制在5°范围之内,保证实验条件的满足,从而使实验结果的误差减小。     

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.