基于直接图解法的Salisbury屏吸波结构设计

采用直接图解法分析优化了典型的Salisbury屏吸波结构。借助Smith圆图对隔离层介电常数和阻抗层的参数进行了综合分析和合理优化,得到了特定频段的吸波效果最优的Salisbury屏吸波体结构参数,并采用有限元数值分析方法对Salisbury屏进行计算,验证了本研究中的直接图解法在设计非磁性雷达吸波结构时的准确性。     

水泥砂浆电磁屏蔽效能的研究

针对现代通讯与电子技术设备的发展带来的电磁辐射污染,采用电磁屏蔽功能建筑材料是解决电磁辐射危害的一种有效途径。本文对一种钢丝网水泥砂浆建筑材料具有屏蔽效能的原理进行了分析,在此基础上给出一种钢丝网网孔尺寸并计算其屏蔽效能,计算结果表明该钢丝网在中短波频段具有较高的屏蔽效能。将该网孔尺寸的钢丝网嵌入水泥砂浆制备出带钢丝网复合结构的水泥样板并对其屏蔽效能进行测试,通过对测试结果进行分析,验证了这种钢丝网水泥样板在中短波频段内具有较好的屏蔽效能。     

孔媛媛:千里走滏阳的女主播

在“2006绿色中国年度人物”评选活动网上推荐阶段,她的名字和事迹一屏一屏刷过。是谁能够获得网民们如此热情地支持?她就是国家一级播音员,河北省十大杰出青年志愿者,以“千里走滏阳”的壮举征服了众多网民的——孔媛媛。顽强的环保勇士2006年盛夏,为了挽救河北人的母亲河——     

两种不同生态区坡改梯对土壤氮磷含量影响的研究

分别在干热河谷生态区和华西雨屏生态区的坡改梯地区设置试验小区和对照试验区,通过采集土壤样品进行室内分析,研究在不同的坡位、不同的季节变化下两种生态区实施坡改梯措施对土壤养分保持的效果.干热河谷生态区以清溪小流域为例,华西雨屏生态区以凤鸣小流域为例.试验结果表明,在两个生态区的坡改梯工程试验区,空间上,各个坡位氮磷养分的...     

电磁屏蔽设计

电磁干扰(EMI)与防护技术在工业上及军事上都是很重要的课题。为了使电气、电子设备在日益密集的电磁频谱背景下正常工作,对有效屏蔽的需求也日益增加。本文阐述屏蔽设计的基本原则,并且阐述有关转移阻抗的概念。     

电子仪器干扰与屏蔽

电子仪器设计、生产过程中,抗干扰问题是线路设计者和结构设计者同时会遇到的重要问题。本文主要阐述了在作为结构设计者怎么解决和抑制干扰问题。干扰来自仪器的内部和外部,一种仪器既可以受到自身的干扰,同时也可以干扰别的仪器。消除和减弱这些干扰,在线路设计中可用滤波器、去耦电路等等。而在结构设计上就要进行屏蔽设计,用屏蔽来消除干扰。     

基于过热器布置的生物质锅炉选型对比

文章以GZ-130/6.7-G型生物质锅炉为例,针对三种过热器布置型式进行对比选型,方案一是在炉膛里布置屏式(半辐射)过热器,并在水平烟道上布置两级蛇形管(对流)过热器;方案二仅在水平烟道上布置三级蛇形管(对流)过热器;方案三是在炉膛里布置屏式(半辐射)过热器,并在水平烟道上布置一级蛇形管(对流)过热器.综合考虑锅炉经...     

接地对手持机电磁屏蔽效果影响的研究

本文探索运用屏蔽理论减少手持机对人体的电磁辐射过程中的接地因素对手持机近场电磁屏蔽效果的影响。     

电子设备的接地和接地设计

从电子设备的安全性和可靠性出发,论述了接地的重要性,并从接地类型、地线作用、接地设计等几方面介绍了有关接地技术的理论及应用。     

某雷达接收系统的电磁兼容设计

本文介绍了某３公分雷达中频接收系统的电磁兼容设计,计算屏蔽壳体的厚度、孔洞及缝隙的能量泄漏、实际屏蔽效果,通过合理选取结构参数,所设计屏蔽壳体能满足电磁屏蔽的要求。     

Shielding from ELF Magnetic Fields Emanating from Power Plants in Large Facilities

Summary Large facilities frequently have internal power plants. High power transformers and low voltage cables associated with these plants generate low-frequency magnetic fields of large amplitude, which can be above allowed exposure levels. In order to shield against these magnetic fields large shields are used. These plates are finite and their shielding effectiveness is compromised due to their finite dimensions. This paper evaluates the shielding afforded by such a plate, as related to the geometry of the placement of the source and victim and the dimensions and structure of the shield plate.     

30MHz以下电动车辆电磁兼容测试方法研究

本文深入研究SAE J551-5:2012,剖析30MHz以下电动车辆的电场辐射发射、磁场辐射发射和传导发射的测试布置、最大发射工况选择、测试过程、场分量和检波器组合、限值等方面;对比SAE J551-5:2004,针对GB/T18387-2008,提出若干修订建议,以提高其实用性和可操作性。     

Some 2D–3D aspects of shielding of longitudinal sources of extremely low frequency magnetic fields

Typical sources of extremely low frequency magnetic fields include components of the power network and, as an extension, AC railway powering. The majority of these sources have longitudinal shapes. There is sometimes the need to reduce these fields in specific areas of interest. In this article, practical aspects are studied of shielding design when this type of source is involved. The focus is on design features not often treated in the shielding literature. One aspect relates to the differences between 2D and 3D simulations and experimental validation for a relatively long system of conductor and shield; as an example, the screening of the magnetic field of a railway system is presented. Another aspect relates to issues that arise when edge effects become relevant for actual systems. It is established that shielding factors are considerably improved when shielding of the edges is properly taken into account. The presence of gaps or loose contacts that are often responsible for low shielding efficiency is also studied. Experimental tests show that overlapping shields or the use of conductive patches significantly improves shielding efficiency. A last aspect is related to cost-effectiveness of shielding designs; in this case, numerical computations are used for benchmarking shielding properties for long busbars in secondary substations.     

振动台漏磁屏蔽应用研究

根据电动振动台的工作原理,详细分析电动振动台磁路结构及漏磁场的来源,通过进行测量分析,并提出一种有效的漏磁场屏蔽措施。     

Influence of DC electric and magnetic fields on silicon solar cells/modules

ABSTRACT

In this study, the impact of DC electric and magnetic fields on the output power, open-circuit voltage, and photocurrent density of a silicon photovoltaic (PV) cell/module is assessed. In this regard, the influence of DC electric and magnetic fields is first evaluated in theory by formulating and discussing related basis and concepts. Then, experimental measurements and data obtained from two different sets of experiments are given that verify theoretical results. In theory and practice, it is shown that depending on the direction of a DC electric field applied to a silicon PV cell/module, it causes an increase or reduction in the output power and open-circuit voltage of the PV cell/module. In detail, when the DC electric field points in the direction of the junction electric field of the PV cell(s), the output power and open-circuit voltage of the silicon PV cell/module increase, otherwise the output power and open-circuit voltage decrease. Regarding the magnetic field, it is proved that depending on the direction of a DC magnetic field applied to a silicon PV cell/module, different effects are observed. In detail, when the DC magnetic field points along the junction electric field of the PV cell(s), it has no effect on the output power and open-circuit voltage of the silicon PV cell/module. But, the output power and open-circuit voltage of the silicon PV cell/module decrease when the DC magnetic field points in the other directions. Moreover, the reduction in the output power and open-circuit voltage reaches its peak when the DC magnetic field is applied in the direction perpendicular to the junction electric field.     

变电站与输电线路的电磁环境影响水平分析与测试评估——以部分220kV及110kV输变电设施为例

通过对220kV及110kV户内布置、户外布置方式的变电站,架空输电线路以及地下电缆线的工频电场强度、工频磁场强度的监测,分析比较了变电站及输电线路对环境的贡献水平以及衰减规律。结果表明输变电设施对环境的贡献值非常有限,且随与之距离的增加而明显衰减。     

220kV拟建输变电工程环境影响评价分析

随着电网规模的不断扩大,220 k V电压等级的输变电网络将越来越多地介入人们的日常生活,如何对民众关心的220 k V输变电工程进行客观的环境影响评价分析成为越来越重要的实际问题。以某拟建220 k V输变电工程环境影响评价为例,介绍了评价因子尤其是电磁环境的现状监测、类比监测及模式预测综合分析,深入分析了该拟建输变电工程环境影响评价全过程,对输变电工程环境影响评价工作具有一定的指导意义。     

Choice of parameters for passive shielding of power-frequency magnetic fields

Epidemiological studies suggesting the possibility of harmful effects on human (specifically children’s leukaemia) due to long-term exposure to magnetic fields of extremely low frequency (e.g. 50/60 Hz) and relatively low values (i.e. over the microtesla range) have stirred high activity in the topic of magnetic field mitigation. To reduce these fields, it is common to use passive metal screens (e.g. plates made of aluminium or steel). To design them, effective and fast numerical computations are highly desirable. In this article, a method is presented, which computes various parameters of screens in a given shielding problem and yields magnetic field distribution and shielding factors. The method takes into consideration the 3D field distribution and is able to solve systems with large aspect ratios (thin thickness in comparison with its other dimensions); this is a common problem where other methods such as finite elements often experience difficulties. The presented method computes separately the field inside and outside the screens. Afterwards, the solutions are “stitched” together along the border of the subregions. Two practical examples are given of the developed numerical method.     

Simulations of ELF magnetic shields

This paper describes a multistage algorithm for efficient calculation of magnetic flux contours, for optimizing the design of structural magnetic shielding. It is part II of the article presented in Pekar and Netzer (2006). The Environmentalist. The multi-stage algorithm enables albeit medium-power computer system to calculate the effect of shielding materials with a given geometry, in a reasonable timeframe without compromising precision. The outcome results are a large number of electrical utility models and the best cost-effective shielding materials and geometries for ELF magnetic flux reduction per Authority regulations and requirements. This article reviews methods and principles for calculation of an extremely low frequency (50/60 Hz) electromagnetic field originating from power utilities and power lines, for the purpose of constructing efficient magnetic shielding. The paper points out difficulties in existing methods and proposes a new algorithm for analysis and construction of magnetic shielding.     

某倾角传感器敏感元件的电磁干扰抑制

某型号液压调平装置上的高精度双轴倾角传感器的控制电路单元与敏感元件同腔体,腔内敏感元件受其内部直流电场干扰,本文对此提出了一种硬件抑制直流电场对敏感元件电磁干扰的特效方法,可广泛应用于同类各形倾角传感器电磁兼容设计和电磁兼容质量控制.