工频电磁场测量仪的设计与研究

以空间电磁场分布为研究对象，根据电磁感应法理论和计算机技术研制了工频电磁场测量仪。详细介绍了基于单片机P89C51RC＋，高精度低噪声仪用差动放大器AD624，以及具有三态缓冲电路，可与8／16位微处理器总线挂接，12位逐次逼近式模数转换芯片AD574的工频电磁场测量系统软硬件设计。     

A356铝合金半固态浆料电磁搅拌法制备过程的数值模拟

建立电磁搅拌法制备A356铝合金半固态浆料过程的电磁场、温度场和流体力学场多场耦合的二维数值模型,采用Powerlaw cut-off(PLCO)半固态模型来描述铝合金浆料的流场,并利用有限元软件ANSYS和编程软件INTEL FORTRAN相结合对电磁场、温度场和流场耦合模拟,研究多场搅拌参数对电磁场、温度场和流场的影响规律。模拟结果表明,搅拌频率和搅拌电流增加时会使电磁场增大且分布不均匀,从而造成浆料流速迅速增大并且分布不均匀。进一步获得电磁搅拌法制备A356铝合金半固态浆料的合理搅拌参数。在所研制的试验装置上验证了数值模拟的可靠性。     

大型汽轮发电机定子绕组端部电磁力解析计算

为了研究汽轮发电机运行时定子绕组端部承受的电磁力,根据电磁场的基本理论,推导了汽轮发电机定子端部区域电磁场以及绕组所受电磁力的计算公式,利用镜像法建立了定子绕组端部电磁场的数学模型.通过解析计算,分别得到了定子绕组端部在稳态运行和短路运行条件下所受电磁力的分布情况,并对计算结果进行了详细分析.分析结果显示,该解析计算具有一定的实际应用价值.     

准恒力电磁铁的吸力特性研究

阐述了有限元法在电磁场数值分析中的应用。为此首先建立了630 kN多点成形机用电磁铁的数学模型,并用Maxwell应力张量法求解电磁铁的牵引力。对电磁铁进行较大改进,得到了电磁场的等磁力线及动铁心的吸力分布曲线,同时得到了最大吸力与工作吸力之比为2.3的准恒力电磁铁。     

基于场路耦合法的大型异步电机气隙磁场研究

电机气隙谐波磁场影响电机的转矩特性、附加损耗和振动噪声等,准确计算电机电磁场尤其是气隙磁场的分布显得尤为重要.利用ANSYS软件,基于场路耦合法,建立大型异步电机电磁场场路耦合分析模型,通过对大型异步电机的电磁场进行计算,得出样机在不同运行状态下的磁力线分布图.在此基础上,分析空载和额定运行状态时电机的气隙谐波磁场,研究电机气隙磁场谐波成分与电机开槽和电机负载的关系,为大型异步电机性能的优化提供理论依据.     

防止电磁场辐射危害的措施及方法

分析了电磁场对于人体的危害及预防措施.介绍了高频电磁场对人体的生理危害及影响.详细介绍了高频电磁场对人体伤害的机制.并进一步提出了对设备的维护和对操作人员的安全注意事项.根据电磁辐射对人体的伤害,电磁场伤害的影响因素,分析并提出了防止电磁场辐射的具体措施.为了防止电磁场对人体的危害,必须做到加强防护,加强严格的检查制度...     

军用技术转民用推广目录(续)

<正>45海洋环境和船舶水下电磁场测试技术【技术开发单位】中国船舶重工集团公司第七六〇研究所【技术简介】该技术针对海洋环境和船舶的水下电磁场测试需要,建立了环境及船舶的水下电磁场测试方法,研制了基于磁场、电场的三分量水下电磁场测试系统,形成了测试系统的海上布放回收方法、水下测量体快速精确定位方法及系统海上标校方法,能够有效开展长期的海洋环境电磁场观测以及船舶的水下电磁场动态、静态测试。     

含氯化石蜡润滑油在电磁场中的摩擦学性能

在改进后四球摩擦磨损试验机上考察载荷和电磁场强度对不同氯化石蜡(T301)含量的润滑油的摩擦学性能的影响,使用扫描电子显微镜(SEM)和能谱仪(EDS)对磨损表面进行分析,初步探讨电磁场作用下的摩擦学机制。结果表明,在不同工况下,电磁场作用下钢球的磨斑直径和摩擦因数均小于无电磁场作用时的数值,说明电磁场有利于改善氯化石蜡的抗磨减摩性能,且电磁场强度越大,对抗磨减摩性能的改善效果越显著;电磁场作用下钢球表面O和Cl元素的含量比无电磁场时高,表明电磁场有利于氯化铁膜在钢球表面的吸附,并对摩擦副表面摩擦化学反应膜的形成有促进作用。     

大挠度四边固定矩形薄板的磁弹性混沌运动

针对大挠度四边固定矩形薄板,研究其在机械载荷、电磁场耦合作用下的混沌运动。在板壳与磁弹性力学理论的基础上,推导出薄板在横向稳恒磁场和机械载荷共同作用下的非线性磁弹性耦合振动方程。利用Melnikov函数法,求出该动力系统Smale马蹄变换意义下出现混沌运动的条件,并对该系统振动方程进行数值模拟。通过具体算例,得到系统的分岔图、位移波形图、相图以及庞加莱截面图。讨论机械载荷、电磁场参数对系统混沌运动的影响,由仿真结果可知,通过变化机械载荷、电磁场参数,可以控制系统的振动特性。     

基于ANSYS永磁同步发电机的电磁分析

主要介绍如何在ANSYS软件下对永磁同步发电机的电磁场进行模拟分析,较详细介绍了用ANSYS软件进行电磁场静态模拟分析的具体步骤。运用电磁场有限元理论,对所设计的电机模型进行了静态电磁场模拟分析,验证了发电机理论设计的合理性和可行性。     

Electromagnetic flow meters for open channels: Current state and development prospects

Electromagnetic method to measure water flow has been known for nearly 180 years. This paper presents how the method has undergone development and describes in detail the most common electromagnetic flowmeters used for open channels. It also presents specific methods of signal processing used in this type of flowmeters. The analysis is associated directly with the relevant types of induced magnetic field. Some of the analyzed types of magnetic fields considered are sine waves and bipolar rectangular fields. The concept of low-energy electromagnetic flow meter was introduced as part of deliberations concerning current development trends.     

用电磁阀调节压力

在分析了用传统的减压阀调节压力的弊端后,提出了采用电磁阀进行压力调节的优点,即可进行多种压力值调节、出口压力的调整精度可以控制得更高等.对电磁阀调压的两种方法进行了阐述,一种是采用脉宽调制技术调节压力,另一种是采用Bang-bang控制方法调节压力,并对两种方法的适用范围进行了说明.     

基于FEM的电磁缩径耦合场数值模拟

对管件电磁缩径的磁场力和动态变形进行了耦合场FEM数值模拟。应用ANSYS计算作用在管件上的瞬态磁场力,然后以该力为边界条件模拟工件高速变形,实现管件变形与磁场力之间的耦合。研究结果表明,作用于工件的磁场力及其径向变形分布不均匀;工件变形可以间接说明磁感应强度和磁场力的分布;工件变形较大时,全耦合模拟结果较半耦合模拟更合理,而变形较小时,二者模拟结果相近。管件变形的模拟值与测量结果吻合较好。     

Exposure of biological preparations to radiofrequency electromagnetic fields under low gravity

There is interest as to whether the electromagnetic fields used in mobile radiotelephony might affect biological processes. Other weak fields such as gravity intervene in a number of physical and biological processes. Under appropriate in vitro conditions, the macroscopic self-organization of microtubules, a major cellular component, is triggered by gravity. We wished to investigate whether self-organization might also be affected by radiotelephone electromagnetic fields. Detecting a possible effect requires removing the obscuring effects triggered by gravity. A simple manner of doing this is by rotating the sample about the horizontal. However, if the external field does not also rotate with the sample, its possible effect might also be averaged down by rotation. Here, we describe an apparatus in which both the sample and an applied radiofrequency electromagnetic field (1.8 GHz) are stationary with respect to one another while undergoing horizontal rotation. The electromagnetic field profile within the apparatus has been measured and the apparatus tested by reproducing the in vitro behavior of microtubule preparations under conditions of weightlessness. Specific adsorption rates of electromagnetic energy within a sample are measured from the initial temperature rise the incident field causes. The apparatus can be readily adapted to expose samples to various other external fields and factors under conditions of weightlessness.     

A Sommerfeld surface wave in probe measurements of electromagnetic fields

It has been shown experimentally that signals of a capacitive probe—a short antenna at the end of a coaxial line used for spatial measurements of electromagnetic fields—are subject to distortions associated with the simultaneous excitation of an E ₀₀-type surface wave on the outer side of the coaxial line. Being reflected from various obstacles, the surface wave returns to the probe antenna in a random phase and induces a distorted signal in it. A detailed analysis of the considered phenomenon and methods for eliminating it, which allow one to lift the restrictions in the application of capacitive probes to spatial measurements of electromagnetic fields, are presented.     

Impacts of external longitudinal magnetic field on arc plasma and droplet during short-circuit GMAW

In gas metal arc welding, electromagnetic force, plasma stream force, gravity, and surface tension are the most important factors that affect metal transfer and spatter generation rate. In this paper, different kinds of external electromagnetic fields were introduced to gas metal arc welding (GMAW). The photos of arc plasma and droplet and electric signals covering welding current and arc voltage were acquired synchronously by an analysis and evaluation system based on LabView for GMAW. It was confirmed that the metal transfer frequency was improved, and spatter generation rate was diminished under controls of external electromagnetic fields. The influencing rules of external electromagnetic fields on electromagnetic force, the gravity, the plasma stream force, and surface tension were studied by three physical models, and the mechanism of external electromagnetic fields was revealed. This paper is for the purpose of discussing these factors and will make a profit for the application of electromagnetic coupling control to short-circuit GMAW.     

Dynamic analysis of electromagnetic sheet metal forming process using finite element method

This paper presents a simple and efficient method for the analysis of dynamic behavior of the workpiece in the electromagnetic forming process. A two-dimensional (2D) axisymmetric finite element model with the equations of electrical equivalent circuit, electromagnetic field, and mechanical field has been developed for calculating the discharge currents through the forming coil, the magnetic forces acting on the workpiece, and the plastic deformation of the workpiece. By considering the effects of the sheet geometry and velocity on the above parameters, the method realizes the full coupling between the electromagnetic fields and the workpiece deformation, which should be more accurate than the existing loose coupling and sequential coupling simulation methods.     

半固态成形技术及其应用

介绍了半固态成形技术的工艺原理,分析了机械搅拌、电磁搅拌、应变诱导、冷却斜坡等浆料制备方法和流变加工、触变加工、注射加工等成形方法。分析了各种计算机模拟技术和模拟方法在半固态成形方面的应用,论述了目前国内外半固态成形技术的应用状况和发展趋势。随着半固态成形技术研究水平的不断提高,成形产品及应用不断增多,发展前景广阔。     

极低频电磁场对免疫低下小鼠免疫功能影响的实验研究

目的：研究极低频电磁场对环磷酰胺所致的免疫抑制小鼠免疫功能的影响。方法：极低频电磁场连续全身作用4周龄免疫低下小鼠60天后,测定小鼠血清抗体（IgG、IgM、IgA）、补体（C3、C4）的含量、腹腔巨噬细胞吞噬功能、胸腺指数和脾脏指数。结果显示：极低频电磁场对免疫低下小鼠的免疫功能有增强作用。