霍尔元件测螺线管磁场分布实验的改进

现用霍尔元件测螺线管磁场分布实验仪为提供1×10 2T的磁感应强度,采用增大螺线管线圈层数和电流的方法.由于管内温度高,霍尔元件易损,实验数据也不稳定.本文以集成霍尔元件代替锗霍尔元件,可在线圈安匝数较小的条件下,使测量数据稳定、准确,且教学效果很好.     

利用霍尔元件测量金属丝的弹性模量

将霍尔元件应用于拉伸法测弹性模量实验,直接测量了微小位移.结果表明,霍尔元件在均匀梯度磁场中霍尔电压与微小位移有良好线性关系,采用拟合法计算得到钢丝弹性模量为1.96×1011 Pa.     

霍尔元件的动态特性曲线的测量及研究

以实验手段研究了霍尔元件在交变电流及交变磁场下的动态特性.实验以霍尔效应实验为基础,改变其中某一自变量,通以交变信号并保持其他条件不变,观察实验现象,得出霍尔电压的幅频特性以及相频特性.从实验结果可以看出霍尔元件的动态特性与静态特性有很大的不同.     

基于霍尔元件磁阻效应的微距测量演示装置

通过装置可以对霍尔磁阻效应、一种距离测量传感器原理和方法进行演示和探究。在课堂教学、课程设计等场合,直观显示霍尔元件的各种效应和技术应用,有着良好的教学效果。     

基于大学物理实验中霍尔元件的保护及探讨

结合大学物理实验教学中霍尔效应的讲解,阐述了霍尔效应的原理,提出了霍尔效应实验的一些改进方法,重点研究了霍尔元件的保护及对霍尔元件的应用进行了探讨.     

新型霍尔元件物理特性实验装置的制作

设计并制作了一套新型实验装置,通过线性和开关型霍尔元件特性测试的巧妙组合,得到开关型霍尔元件开关磁感应强度的大小及其磁滞回特性曲线.该实验装置可帮助学生加深对霍尔元件物理特性的认识.     

霍尔线位移传感器静态特性的研究

在不同环境温度下,互换霍尔位移传感器的输入/输出端,对其静态特性进行实验测试。结果表明：在霍尔元件顺、反接及不同的环境温度下,其静态特性差异明显,从理论上对实验现象进行了分析。     

可调梯度磁场下霍尔位置传感器与弯曲法杨氏模量的测量

在利用霍尔位置传感器采用弯曲法测量杨氏模量实验中,由于梯度磁场线性范围小于2mm,要求实验中霍尔元件必须在限定的±2 mm内移动。若操作不当,霍尔元件进入磁场非线性区,会致使实验数据的不准确测量,导致实验误差偏大。所测量杨氏模量值相对误差往往高于10%,甚至会高达40%。针对实验中梯度磁场线性范围小导致测量误差大的问题,采用反亥姆赫兹线圈实现梯度可调节大范围均匀梯度磁场的构建对仪器进行改进。结果表明,改进后的实验装置显著提高了实验测量结果的精度,并可实现较易形变固体材料杨氏模量的测量,并且可方便研究较易形变固体材料的应力及应变的关系。     

用于托卡马克磁场测量的金属霍尔探测器的研制

金属霍尔探测器被认为是未来磁约束聚变堆磁场测量的重要工具之一。介绍了金属霍尔探测器系统的研制,包括测量原理、探测器制作工艺、电子学系统研制、标定系统建设及测试结果等。采用金属铋作为霍尔材料,有源区厚度为100nm,放大器的放大倍数为2000～200000倍。测试结果显示,当待测磁场在3mT以上时,系统的测量精度优于±1%,可以达到磁探针的标定精度,能够满足托卡马克装置的磁场测量要求。     

霍尔效应测量磁场实验的拓展

利用霍尔效应测二维空间磁场分布的拓展方案,测量了马蹄形磁铁周围的磁场分布。并用Mathematica编程对测量数据进行处理,模拟了直观形象的磁场分布图,提高了实验结果的精确度。     

Study on the Range of Particles Size Measured by Backscattering Method in Visual‐infrared Incident Spectrum

For the measurement of particles size with backscattering method, the suitable range of particles size measurement have been presented by independent algorithm in Visual‐infrared incident spectrum. We defined the range according to the retrieved results based on the analysis and comparison to many kinds of R‐R distribution function. The simulation computation results showed that the particles size measurement range is from 0.05 μm to 18 μm with incident spectrum from 0.4 μm to 2 μm and different refractive index. The results retrieved were satisfied even if 1 % noise was added into the backscattering intensity.     

Measure Theoretic Entropy of Discrete Geodesic Flow on Nagao Lattice Quotient

The discrete geodesic flow on Nagao lattice quotient of the space of bi-infinite geodesics in regular trees can be viewed as the right diagonal action on the double quotient of PGL2Fq((t−1)) by PGL2Fq[t] and PGL2(Fq[[t−1]]). We investigate the measure-theoretic entropy of the discrete geodesic flow with respect to invariant probability measures.     

Feasibility of a Lidar Utilizing the Glory for Measuring Particle Size of Water Clouds

A new lidar method for measuring water cloud particle size is proposed, and the feasibility of the measurement is discussed. The method utilizes the phenomenon known as the glory which is observed in open air. The proposed lidar consists of a multicolor laser transmitter and two receiver systems looking at the scattering from the target cloud with different scattering angles. Results of the theoretical study show that a system with five laser wavelengths (355, 532, 750, 1064 and 1500 nm) and two receivers located at scattering angles of 180 and 177.5–179 deg is useful for measuring particle size (mode radius of the size distribution) in a range of 4 to 12μm.     

Influence of Interface Scattering and Quantum Size Effect on the Giant Magnetoresistance in a Magnetic Sandwich Structure

An analytical Green's function approach to the study of the electronic transport in a magnetic sandwich structure is presented. Taking into account the quantum size effect and considering three types of scattering from bulk impurities, rough surface, and two rough interfaces, we calculate the one-particle Green's function and the in-plane conductivity, yield a new formula for conductivity. It is found that (i). the magnetoresistance in the ultrathin spin-value sandwiches shows oscillation as a function of thickness with a period of half Fermi wavelength; (ii) in the thin-film limit and the lowest-order approximation of the surface and interface scatterings, the total conductivity is given by a sum of conductivities of all the subbands and the two spin channels, for each subband and each spin channel the scattering rates due to the impurities, surfaces and interfaces are additive.     

不同粒径大气气溶胶含量及其透过率研究

运用FA-3型Anderson撞击式气溶胶粒度分布采样器采集南京北郊生活区大气中的可吸入颗粒物,用称重法测量大气中不同粒径可吸入颗粒物的质量浓度,同时用光学系统测量不同粒径上可吸入颗粒物的透过率,分析不同粒径大气气溶胶的透过率变化关系。结果表明：小于2．1μm颗粒物所占比例达59．88％,表明大气中细粒子污染严重;可吸入颗粒物粒径越小,其透过率也越小;细颗粒物质量浓度与其透过率呈很高的负相关;粗颗粒物对可见光波长的选择性弱。     

The Fundamentals of Particle Size Analysis by Transmission Fluctuation Spectrometry.

A transmission signal measured on a flowing suspension of particles with a high spatial and temporal resolution shows significant fluctuations, which contain the complete information on particle size distribution and particle concentration. In Parts 1 and 2, the basic properties of signal fluctuations were studied for temporal averaging by a gliding time window and for spatial averaging by a circular beam of uniform intensity. However, the experimental implementation of such conditions is difficult. Now, the theory is extended for Gaussian beams of variable diameter and averaging by signal filtering in the frequency domain. This provides the basis for an experimental implementation by transmission of a laser beam and analog signal processing by an array of low pass filters.     

探测器像素尺寸对PMP测量精度的影响研究

以阶跃型反射率分布为例,分析了像素尺寸对相位测量轮廓术（PMP）测量精度的影响情况。仿真结果表明相位测量误差大小随感光单元覆盖的相位范围增加而增加,即采用高分辨率探测器可以得到高的测量精度;相位测量误差大小与阶跃在感光单元上的位置有关,存在导致最大误差的位置,并且该位置与阶跃相对幅值有关;相位测量误差大小随阶跃相对幅值增大而增大,偏向反射率高的方向。研究结果为PMP测量系统设计中图像探测器选择、测量精度评价提供了依据。     

Analysis of Particle Size Distribution by Particle Tracking

Particle tracking is performed using a combination of dark field or fluorescence video microscopy with automatic image analysis. The optical detection together with the image analysis software allows for the time resolved localization of individual particles with diameters between 100 and 1000 nm. Observation of their Brownian motion over a set of time intervals leads to the determination of their mean square displacements under the given room temperature and viscosity. Hereby, the radii of a set of particles visible within a given optical frame are derived simultaneously. Rapid data analysis leads to reliable particle size histograms. The applicability of this method is demonstrated on polystyrene latices and PMMA nanospheres with radii between 51 nm and 202 nm.     

线性磁场装置的研制及实验研究

介绍了一种可获取线性磁场的装置。该装置由两匝数及半径相同的环形线圈组成,相向平行同轴放置,两线圈之间的距离等于线圈半径,通以大小相同,方向相反的电流,可获得磁感应强度与其线圈中心轴线位置成线性关系的区域。此装置不仅具有独创性,更有实时性及可调的优点,可将其拓展到实际应用,尤其是传感领域,有重要的应用前景和经济价值。     

束流传输管道孔径变化引起的束团场能差

由直线加速器提供的用于自由电子激光(FEL)的电子束团,在其传输过程中常会遇到传输管道孔径变化的情况.本文在电荷密度均匀分布假定下,应用直线加速器中空间电荷束团的有限长柱模型,推导得到了束流传输管道孔径变化引起的束团场能变化及场能差公式.数值计算结果表明,它与国外以往所采用的以连续束流来代表直线加速器中电荷束团而得到的结果,有很大的差别,并且是更符合直线加速器中的电荷束团的实际情况,因而是更精确和可靠的.