霍尔传感器及其在物理实验中的应用

介绍了霍尔传感器的原理以及工程应用中的霍尔传感器种类 ,举例说明了开关型霍尔传感器在重力加速度测量实验中的应用 ,同时给出了具体的应用电路     

温度对霍尔位移传感器静态特性的影响

在不同环境温度下,对霍尔位移传感器的静态特性进行了测试.结果表明,随着环境温度的变化,霍尔传感器的静态特性差异明显,从理论上分析了产生差异的原因.并对其应用实例进行了说明.     

高性能石墨烯霍尔传感器

本文回顾了石墨烯霍尔传感器的相关研究工作.通过改善石墨烯生长转移和霍尔元件的微加工工艺,石墨烯霍尔元件和霍尔集成电路都展示出超越传统霍尔传感器的优异性能.石墨烯霍尔元件的灵敏度、分辨率、线性度和温度稳定性等重要指标都优于传统商用霍尔元件.通过开发一套钝化工艺,霍尔元件的稳定性有了明显提升.结合石墨烯材料的特点,展示了石墨烯在柔性磁传感和多功能传感领域的新颖应用.此外,成功实现了石墨烯/硅互补型金属-氧化物-半导体(CMOS)混合霍尔集成电路,并进行了应用展示.通过发展一套低温加工工艺(不超过180℃),将石墨烯霍尔元件制备在硅基CMOS芯片的钝化层上,从而与硅基CMOS电路实现了单片集成.本文的研究结果表明石墨烯在霍尔磁探测方向拥有重大的性能优势,在产业化应用中有巨大发展潜力.     

基于新型霍尔传感器的高精度直流隔离传送与检测

实验探究并验证了新型霍尔传感器在高精度直流隔离传送与检测中的应用,实验发现在直流隔离传送与检测中,霍尔传感器相比于其他传感器或互感器,具有传感精度高、非线性好等突出优点,能够满足高精度隔离传送与检测的要求.实验除具有实际应用价值外,还适合在高校物理基础试验中开设相关课程.     

位移传感器演示装置的制作

通过自制的位移传感器演示装置可以对霍尔磁阻效应、 一种小位移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     

霍尔效应在直流电压隔离传送中的应用

应用基于霍尔效应的磁平衡原理设计了直流电压高精度隔离传送传感器,并与光耦传感器进行了比较,结果表明:在温度变化的环境中,该传感器隔离传送直流电压的精度优于光耦传感器28倍.     

演示小位移传感器的装置制作

本文介绍了半导体材料的霍尔效应及磁阻效应,讨论了霍尔磁阻元件的特性,提出位移传感器的工作原理、结构设计,并详细说明安装和调试过程.演示装置结构简单、物理概念清晰、易于操作.它将磁场的变化无接触转化为材料的电阻变化,从而把与磁场变化相联的位移形式转化为电信号输出,形成位移传感器.由实验数据和图示曲线表明:测量桥路输出电压随磁钢和霍尔片之间的距离变化而变化;另外,测量桥路的测量灵敏度随工作电流IC增加而提高.通过本装置可以对霍尔磁阻效应、一种小位移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.     

用标准件对梯度磁场定标

就标准厚度卡片在霍尔传感器的定标方面的应用作了有益的探讨。在纵向测量微小长度时,霍尔片处于磁场边缘位置,其对磁场的梯度更大,即灵敏度更高,且靠中心位置的线性更好。     

伺服动力装置用霍尔型转速传感器的研制

为精确测量伺服动力装置变量柱塞泵的转速,为其设计了一种小型化、高灵敏、抗干扰、高可靠、宽温域的霍尔型转速传感器。针对电感式转速传感器对较低转速测量不灵敏、易受磁场干扰等缺点,提出了一种霍尔型转速传感器的设计方法：利用霍尔电路对磁场信号反应灵敏的特性,另外在转速变换电路中配合以较高的阈值电压,使其具有灵敏度高和抗干扰能力强的特点;并结合整体任务要求,对其进行了小型化设计、宽温域材料选用及元器件的降额设计等措施。经试验验证,霍尔型转速传感器可以精确测量电机全量程（从低到高）的转速,灵敏度不随转速的变化而变化,且不受外界磁场的干扰,参数性能满足整体要求,具有广泛的应用前景。     

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。     

A study on the best irradiation dose of X-ray for Hep-2 cells by Fourier transform infrared spectroscopy

Fourier transform infrared spectroscopy (FTIR) was employed to study the human epidermis larynx carcinoma cell lines (Hep-2) which were irradiated by different doses of X-ray.The results show that (1) the irradiation of X-ray damages the structure of the CH3 groups of the thymine in DNA,which restrains the reproduction of Hep-2 cells effectively,(2) the 8 Gy dose of X-ray irradiation changes the framework and the relative contents of some proteins,lipids and the nucleic acid molecules intercellular in the greatest degree,and (3) the 8 Gy dose of X-ray irradiation is the best irradiation dose for lowering the degree of the cancerization of Hep-2 cells according to the criteria for the degree of the cancerization reported recently.Meanwhile,the apoptosis of these cells were detected by using flow cytometry (FCM) primarily.It shows that the apoptotic ratio of the Hep-2 cells depends on the irradiation dose to some extent,but is not linearly.And the apoptotic ratio of the 12 Gy dose group is the maximum (20.36%),but the apoptotic ratios of the 2 to 8 Gy dose groups change little.     

Study on the radiation problem caused by electron beam loss in accelerator tubes

The beam dynamic code PARMELA was used to simulate the transportation process of accelerating electrons in S-band SW linacs with different energies of 2.5, 6 and 20 MeV. The results indicated that in the ideal condition, the percentage of electron beam loss was 50% in accelerator tubes. Also we calculated the spectrum, the location and angular distribution of the lost electrons. Calculation performed by Monte Carlo code MCNP demonstrated that the radiation distribution of lost electrons was nearly uniform along the tube axis, the angular distributions of the radiation dose rates of the three tubes were similar, and the highest leaking dose was at the angle of 160° with respect to the axis. The lower the energy of the accelerator, the higher the radiation relative leakage. For the 2.5 MeV accelerator, the maximum dose rate reached 5% of the main dose and the one on the head of the electron gun was 1%, both of which did not meet the eligible protection requirement for accelerators. We adopted different shielding designs for different accelerators. The simulated result showed that the shielded radiation leaking dose rates fulfilled the requirement.     

Analysis of Laser-generated Rayleigh wave on viscoelastic materials

In order to understand the viscoelasticity of material, this research has been conducted to study the propagation characteristics of viscoelastic Rayleigh wave theoretically. A model is presented for the pulsed laser generation of ultrasound on viscoelastic medium surface. Referred to the Kelvin model, the frequency equation and the normal displacement of viscoelastic Rayleigh wave were derived, the influence of the viscoelastic modulus on dispersion and attenuation was discussed. From the theoretical calculation, it is shown that the effect of viscoelasticity on the attenuation of Rayleigh wave is more than that on its dispersion. In the case of a weak viscosity, the attenuation of viscoelastic Rayleigh wave is directly proportional to viscosity modulus; the effect of shear viscosity on the attenuation is much more than that of bulk viscosity. The transient response of viscoelastic Rayleigh wave was also simulated using Laplace and Hankel inversion transform, which are showed in good agreement with the theoretic predictions. The model provides a useful tool for the determination of viscoelastic parameters of medium.     

Synergistic effects on iodine release in potassium iodide solution by combination of ultrasound and visible light irradiations

Iodine release in potassium iodide solution has been investigated under the irradiations of ultrasound and visible light respectively and simultaneously. We have observed that the amount of iodine liberated under the combined irradiation of ultrasound and visible light is larger than the sum of that under the respective irradiations of ultrasound and visible light, indicating a synergistic effect of ultrasound and visible light irradiations. Based on the investigation of the reaction kinetics of iodine liberated, we have ascribed the synergistic effect to the perfect stirring of the photochemical reactor induced by the applying simultaneous ultrasound. The ideal stirring can result in the homogenization of the primary light effect in the whole reaction medium, which induces the acceleration of the photochemical reaction. On behavior of our knowledge, there are few reports on the investigations of utilizing the combination of ultrasonic energy and light energy to accelerate the reaction yield and rate as well as the kinetics of the reaction.     

Factors affecting the spectrum of an electromagnetic light wave on scattering from a semisoft boundary medium

The spectrum of an electromagnetic light wave on scattering from a semisoft boundary medium is discussed within the accuracy of the first-order Born approximation. It is shown that spectral shifts and spectral switches are affected both by the polarization of the incident light wave and by the characters of the scat-tering medium. Moreover, numerical results show that the direction at which the spectral switch occurs is governed by the characters of the scattering medium, whereas the magnitude of the spectral switch is affected by the polarization of the incident light wave.     

Tropical Monsoon Forest Thermodynamics Based on Remote Sensing Data

This paper addresses thermodynamic variables that characterize the energy balance and structure of the solar energy transformation by the ecosystems of deciduous tropical forests. By analyzing the seasonal dynamics of these variables, two main states of the thermodynamic system are determined: the end of the drought season and the end of the wet season. Two sub-systems of solar energy transformation are also defined: a balance system that is responsible for the moisture transportation between the ecosystem and atmosphere; and a structural bioproductional system responsible for biological productivity. Several types of thermodynamic systems are determined based on the ratio between the invariants of the variables. They match the main classes of the landscape cover. A seasonal change of thermodynamic variables for different types of thermodynamic systems is additionally studied. The study reveals that temperature above the forest ecosystems is about 4° lower than above the open areas during most of the year.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Time domain finite volume method for the transient response and natural characteristics of structural-acoustic coupling in an enclosed cavity

A time domain finite volume method（TDFVM）based on wave theory is developed to analyze the transient response and natural characteristics of structural-acoustic coupling problems in an enclosed cavity.In the present method,the elastic dynamic equations and acoustic equation in heterogeneous medium are solved in solid domains and fluid domains respectively.The structural-acoustic coupling is implemented according to the continuity condition of the particle velocity along the normal direction and the normal traction equilibrium condition on the interface.Several numerical examples are presented to validate the effectiveness and accuracy of the present TDFVM.Then the effects of water depth on the acoustic and vibration characteristics and the natural characteristics of a structural-acoustic coupling system are analyzed.The numerical results show that the increase of water depth leads to a stronger coupling between the water and structure and the decrease of natural frequencies of coupling system,The computational cost and memory of this method are small and it can be applicable to structural-acoustic coupling problems in the heterogeneous fluid.     

Study on the denoising method for the electromagnetic ultrasonic echoes from multiple interfaces

The electromagnetic ultrasound is used in the detection of interfaces of the adhesive multilayer structures to solve the unstable coupling problem in ultrasonic testing by traditional piezoelectric transducers. Based on the analysis of the transforming mechanism of electromag-netic ultrasound energy and the resultant dead zone from mutual inductance of the transducer, the wavelet filtering by soft-thresholding and adaptive noise canceling methods are used simul-taneously to the detected electromagnetic ultrasonic signals to overcome the drawbacks of the low signal to noise ratio （SNR） and the wide intrinsic dead zone of the transducer. Processed results in the interface detection of a three layered adhesive sample of steel and rubber materials demonstrate that the wavelet filtering enhances the SNR about 12dB while the adaptive noise canceling narrows the dead zone effectively.     

Temperature Sensitivity Control and Mechanical Stress Effect of Boron-Doped Long-Period Fiber Gratings

We will present in this work the quantitative analysis of the relationship between the doping concentrations of GeO 2 and B 2 O 3 in the core and cladding regions and the temperature sensitivity of the resonance wavelength shift in long-period fiber gratings (LPFGs). Based on this analysis, the temperature sensitivity was suppressed and enhanced to 0.002 nm/°C and 0.28 nm/°C, respectively. We will also discuss the effect of the residual mechanical stress on the optical and mechanical properties of LPFGs. In particular, we will present the measurement results of the dependence of the refractive index change and mechanical strength on the residual mechanical stress in the boron-doped fibers with depressed clad and matched clad.