共查询到20条相似文献,搜索用时 62 毫秒
1.
2.
脉冲电磁场对雄性小白鼠生物效应的研究 总被引:5,自引:1,他引:5
本文分析了生物体所处电磁环境的类型以及外电磁场对生物体的作用方式,并以雄性小白鼠为研究对象.采用血细胞计数及细胞电泳实验的方法研究了脉冲电场及脉冲磁场对其影响。在生物电介质介电模型的基础上,探讨了脉冲电磁场对生物体及其细胞作用的机理。 相似文献
3.
4.
5.
通过不同模式的脉冲电流电磁场PCEMFs对离体的人体外周血淋巴细胞进行电磁辐射,初步得出PCEMFs对淋巴细胞微核率MNR的影响的规律:细胞MNR和破坏的程度与PCEMFs的磁感应强度Bm以及其变化梯度dB/dt呈正相关关系,并提出使细胞SCE发生变异的临界参考指标,其中Bm为0.15T,dB/dt为1.8×104T/s;而破坏的临界参考指标分别为2.64T和3.3×104T/s,为强电流脉冲放电环境的电磁防护研究提供了实验依据.细胞SCE和破坏的程度和PCEMFs中电场和磁场的空间相对位置有关,电场和磁场相互垂直的PCEMFs对细胞的影响程度比其它结构形式的PCEMFs显著. 相似文献
6.
7.
脉冲电磁场促进骨折愈合的研究进展与展望 总被引:1,自引:0,他引:1
上世纪70年代,美国哥伦比亚大学Bassett率先将脉冲电磁场用于骨折治疗,证实了脉冲电磁场可以促进骨折愈合。经过30多年的发展,脉冲电磁场已作为一种非侵入的疗法成功运用于临床,并取得了非常好的效果。通过细胞实验研究、动物实验研究、临床应用研究、作用机理4方面综述了脉冲电磁场促进骨折愈合的研究进展,分析了影响脉冲电磁场作用效果的各种因素,并在此基础上介绍了此方面研究中还需进一步探讨的问题,以及脉冲电磁场用于治疗骨折的广阔应用前景。 相似文献
8.
在飞机和风机叶片电脉冲除冰中,为了提高线圈的脉冲效果,降低除冰装置质量,实现系统的微功耗设计,需要优化线圈结构。脉冲线圈作为脉冲除冰、脉冲焊接等应用中能源转换的关键部件,其瞬态电磁场求解复杂,一般难以得到解析解。为了研究线圈结构参数对脉冲效果的影响,该文通过推导脉冲线圈的场-路数学方程,建立脉冲线圈和目标物的物理模型,并采用有限元软件对脉冲线圈的瞬态电磁场进行计算,得到脉冲线圈电磁参数时变特性。通过脉冲线圈的脉冲冲量试验对模型的准确性进行验证,在此基础上,分析线圈匝数、截面尺寸和线圈匝间距等结构参数对脉冲电流、脉冲力、脉冲效果的影响,为电脉冲除冰应用微功耗化设计提供优化思路和技术路线。 相似文献
9.
10.
《高电压技术》2016,(8)
由通信基站、移动电话、无绳电话、无线路由器等产生射频电磁场(RF-EMFs)已经成为现代生活不可缺少的一部分,为了阐述射频电磁场对人类健康可能存在的风险,评述了近几年射频电磁场健康效应的研究成果。在介绍射频电磁场物理特性的基础上,着重综述了近年来射频电磁场在流行病学调查、人体志愿者、动物实验、细胞和分子、生物物理学等领域的研究进展。大多数流行病学调查表明使用手机与脑瘤呈阴性结果,但也有阳性报道。人体志愿者实验研究主要包括认知、感觉放大、听力和脑电图等方面,以阴性结果为多。动物实验研究主要包括认知、记忆、生殖、血脑屏障、感觉、免疫等方面。细胞和分子研究主要包括脱氧核糖核酸(DNA)损伤与修复、干细胞增值和分化、生殖和发育、细胞凋亡、氧化应激、组织结构、昼夜节律等方面。生物物理学研究主要包括非热效应理论、窗效应、活性氧自由基(ROS)机理、钙离子(Ca2+)等方面。射频电磁场的国际标准有国际非电离辐射防护委员会(ICNIRP)指南和电气与电子工程师协会(IEEE)标准,国内标准有电磁环境控制限值标准。结论是为人类健康应该管理好电磁场;加强电磁生物效应整体论研究;开发实时研究的相关技术;关注生物效应原初作用的电磁能量。 相似文献
11.
电磁操动机构的电磁缓冲仿真实验研究 总被引:1,自引:1,他引:0
为弥补弹簧缓冲的不足,提出一种适用于电磁操动机构合闸过程的电磁缓冲控制思想。在触头合闸运动中对通过缓冲线圈施加反向激磁电流,利用反向电磁力来相对减小合闸吸力,从而降低机械冲击、减少触头弹跳、实现合闸缓冲。采用ANSYS三维矢量分析法,针对不同缓冲电流以及不同缓冲位置时电磁操动机构的合闸吸力特性进行了仿真计算;利用实验装置对不同缓冲控制条件下的触头振动情况进行了实验研究。初步研究表明,缓冲电流的大小以及缓冲电流的施加位置、施加时间对电磁操动机构的吸力特性具有重要影响,只有综合考虑这三种因素、选择合适的控制条件才能得到较为理想的合闸特性和缓冲效果。电磁缓冲控制对于其它操动机构中存在的合闸冲击问题也具有一定的借鉴意义。 相似文献
12.
基于电磁式的力触觉再现系统中,磁性单元所受电磁力的大小和精度直接决定了力触觉再现的真实感和性能。本文构建了基于微型传感器的三维电磁作用力测量系统,用以验证通过有限元仿真方法得出的磁性单元受力的正确性。以实际绕制的线圈为实验对象研究了磁性单元受力和其与线圈之间的距离关系,实验数据表明,力测量系统测得的磁性单元受力与有限元仿真结果基本一致。本文研制的三维电磁力测量系统能够验证电磁力有限元仿真模型的正确性,对于促进电磁式力触觉再现的发展具有重要的意义。 相似文献
13.
Electromagnetic pollution has been categorized as a new form of pollution. The ability to reflect electromagnetic energy can be defined as shielding effectiveness. This shielding effectiveness depends on the frequency of the electromagnetic wave and the electromagnetic properties of the shielding material. This article presents a comparison of shielding effectiveness of double-square and ring patches reflecting at 900 and 1,800 MHz. 相似文献
14.
15.
《Electric Power Systems Research》2001,59(2):83-88
This paper deals with the design concept and test results of the experimental development phase of a new electromagnetic contactor. The contactor is used for making, switching and breaking of apparatuses and devices at voltage levels up to 1 kV. The use of this contactor will be illustrated in the example of a star-delta starter for induction motors. Currently, starters consist of three contactors, together with its power-, control- and signal connections. An experimental prototype of the new contactor has already been made. Among the tests performed on this prototype are tests for temperature rise limits, dielectric properties and partial tests of mechanical properties. The tests of the rated making and breaking capacities have also been executed. After some constructional modifications, the electromagnetic contactor has successfully passed all the above mentioned tests. 相似文献
16.
Yu. V. Smirnov 《Russian Electrical Engineering》2009,80(5):244-246
Advanced three-phase electromagnetic ac motors based on electromagnetic gate-inductor motors are proposed. The concept of development and the constructive scheme of a three-phase electromagnetic ac motor are given. Advantages of the proposed motors compared to asynchronous motors are shown. 相似文献
17.
Fogle A.D. Don Darling Blish R.C. II Daszko G. 《Device and Materials Reliability, IEEE Transactions on》2006,6(2):266-276
This paper analyzes the radiated electromagnetic compatibility (EMC) behavior of AMD/Spansion Flash memory integrated circuits. Using The Engineering Society For Advanced Mobility Land Sea Air and Space (SAE) J1752/3 method, the peak RF noise (EMC with respect to radiated emissions) was measured for various technologies and product features, determining statistically valid sensitivity factors for several independent variables. The findings show that radiated emissions vary based on technology shrink, memory size, access time, and package. The authors are able to predict a device's radiated EMI to a precision of /spl sim/4dB/spl mu/V (one sigma) and with good accuracy by fitting noise performance as a function of a density parameter (a combination of technology critical dimensions and number of bits) and the logarithm of the access time. It was found that devices built on current technologies generate much less noise than their predecessors primarily due to slew rate control to permit simultaneous read/write operations, output buffer driver design improvements, and smaller radiating antennae. 相似文献
18.
Low-resolution electromagnetic tomography neurofeedback 总被引:2,自引:0,他引:2
Congedo M. Lubar J.F. Joffe D. 《IEEE transactions on neural systems and rehabilitation engineering》2004,12(4):387-397
Through continuous feedback of the electroencephalogram (EEG) humans can learn how to shape their brain electrical activity in a desired direction. The technique is known as EEG biofeedback, or neurofeedback, and has been used since the late 1960s in research and clinical applications. A major limitation of neurofeedback relates to the limited information provided by a single or small number of electrodes placed on the scalp. We establish a method for extracting and feeding back intracranial current density and we carry out an experimental study to ascertain the ability of the participants to drive their own EEG power in a desired direction. To derive current density within the brain volume, we used the low-resolution electromagnetic tomography (LORETA). Six undergraduate students (three males, three females) underwent tomographic neurofeedback (based on 19 electrodes placed according to the 10-20 system) to enhance the current density power ratio between the frequency bands beta (16-20 Hz) and alpha (8-10 Hz). According to LORETA modeling, the region of interest corresponded to the Anterior Cingulate (cognitive division). The protocol was designed to improve the performance of the subjects on the dimension of sustained attention. Two hypotheses were tested: 1) that the beta/alpha current density power ratio increased over sessions and 2) that by the end of the training subjects acquired the ability of increasing that ratio at will. Both hypotheses received substantial experimental support in this study. This is the first application of an EEG inverse solution to neurofeedback. Possible applications of the technique include the treatment of epileptic foci, the rehabilitation of specific brain regions damaged as a consequence of traumatic brain injury and, in general, the training of any spatial specific cortical electrical activity. These findings may also have relevant consequences for the development of brain-computer interfaces. 相似文献
19.
电磁阀电磁场有限元计算软件 总被引:1,自引:0,他引:1
针对电磁阀计算的手工演算程序和基于磁路方法的不足,根据工程需求情况,选择了简单、成熟的二维有限元法,提出了电磁阀的二维电磁场有限元计算模型,为利用已有的计算程序,对外施电压约束采取了迭代计算的处理方法。软件界面采用易于掌握的VB编程,计算结果的后处理则利用了Manab的强大功能。该方法有效地解决了常用的基于磁路方法无法处理涡流场问题,并减少了设计、开发的工作量。 相似文献
20.
《Electric Power Systems Research》1997,41(1):19-27
This paper presents the development of a new time domain simulation program for the computation of electromagnetic transients over a wide frequency spectrum. The application of the program to investigate the Subsynchronous Resonance phenomenon is given.The proposed technique depends on applying the implicit trapezoidal integration method to the differential equations simultaneously to get algebraic equations which are solved simultaneously using the Newton-Raphson method. The sparsity technique and factorization have been adopted to reduce computing time and storage.The IEEE Benchmark model is used to apply the proposed technique. The results of the new technique have been compared with the results of both the EMTP technique and the Runge-Kutta-Merson method. The comparison shows the superiority of the proposed technique. 相似文献