低反射、高吸收海水电磁屏蔽体

目的通过在有耗海水电磁屏蔽体上加载阻抗匹配层,研究具有低反射、高吸收特性海水电磁屏蔽体结构。方法基于有耗海水电磁屏蔽体的输入阻抗,并利用传输线原理,计算对应匹配媒质层的结构与电磁参数。针对初始具有较好电磁屏蔽效能的反射型海水电磁屏蔽体样本,计算和加载工作在ISM 433 MHz频段的匹配媒质层。结果加载了匹配媒质层的海水电磁屏蔽体能展示出良好的低反射、高吸收电磁屏蔽特性。当入射电磁波全部穿透进入海水层,产生传导和极化衰减后,对屏蔽效能影响较小。结论由海水层和匹配媒质层组成的多元材料电磁屏蔽体,可以实现低反射、高吸收电磁屏蔽效果,并保持良好电磁屏效能的优势。低反射电磁屏蔽体有望在精度仪器、目标反探测等领域发挥重要作用。     

舰船电磁环境数据库的设计与实现

在分析国内外舰船电磁环境极限值的基础上,归纳数据库功能需求,以设计结构模块及运算规则,运用Django框架实现Web数据库,动态生成舰船不同区域分频段的场强极限值,为电磁辐射环境下舰面作业安全提供数据支撑。     

一种可原位修复和循环使用的包覆涂层材料及其耐蚀性能研究

目的 制备纤维素基的包覆涂层材料,研究其原位修复与循环性能。方法 以乙基纤维素、蓖麻油和矿物油等为主要原料,采用熔融共混的方法制备得到可循环使用的包覆涂层材料。通过扫描电子显微镜(SEM)、X射线衍射仪(XRD)和红外光谱(FT-IR)研究包覆涂层材料的微观结构,通过电化学交流阻抗技术(EIS)、溶液浸泡实验和中性盐雾试验研究涂层的耐蚀性能。采用自建电磁感应设备研究包覆涂层材料的自修复性能和循环使用性能。结果 在包覆涂层材料中添加Ni粉后,使得涂层具有一定的磁响应特性。当Ni的质量分数达到15%后,有明显的团聚现象。随着Ni含量的增加,包覆涂层材料的磁性能逐渐增强。含10% Ni的包覆涂层材料在5%的HCl溶液中浸泡28天以及中性盐雾10 000 h后均无变化,同时在磁场作用下热熔循环20次,性能和结构没有太大变化。结论 添加10% Ni粉后不会对包覆涂层材料的结构和性能产生影响,同时赋予了较好的电磁感应性能。通过磁场的作用可以修复包覆涂层材料的物理损伤,同时由于包覆涂层材料具有热塑性,可以多次修复损伤以及循环使用。     

电磁环境监测传感器部署效率评估方法

目的提升电磁环境的全域、精细化监测能力。方法基于单个传感器监测能力和多个传感器协同监测效率,建立相应的评估指标模型,利用多属性决策方法将多指标量化为单一指标,获得监测传感器部署效率评估结果。结果以待评估方案与理想方案的贴近度作为部署效率评估指标,建立了部署效率评估指标体系,提出了基于逼近理想解排序法(TOPSIS)和网络分析法(ANP)的综合评估方法。结论通过仿真验证了该方法的可行性和有效性,为监测传感器部署方案优化和动态调度提供量化评估数据支撑。     

磁路形状对电磁制动器制动安全性的研究

电磁制动器是一种新开发的新型车用制动器,保证制动性能并对该制动器的关键部件电磁体进行优化设计十分重要。通过分析车辆制动过程中电磁制动器的工作机理,得到电磁体的受力与磨损状况,提出并设计了非轴对称准椭圆形电磁体磁路,采用Ansoft3D电磁场软件计算电磁力和磁密,选取合理磁密制作了样品。由仿真计算和试验表明,制动时工作平稳,磨损均匀,满足了特定制动器制动力及制动安全的要求,为开发不同型号的新型电磁制动器打下了基础。     

New Device Against Non-Thermal Effects from Mobile Telephones

Summary Objectives: The aim of this study is to initiate research in the field of biomedical engineering geared towards a reduction of non-thermal effects on the brain due to the use of mobile telephones. This line of research employs devices attached to the back of cellular-telephone cases. Methods: Under electromagnetic-environment controlled conditions EEG records have been obtained in 16 healthy subjects, with their eyes open at the base-line. These records were compared with the use of the mobile telephone with and without one of these devices for five minutes each, and having them statistically tested with Wilcoxon matched-pairs. Results: Differences between experimental EEG, with and without the use of the device, have been observed. These subtle changes basically affect Delta and Theta wave bands. Their distribution, (changes in the affected areas of the brain), also varies, above all in the frontal areas. Conclusions: The use of this device could reduce non-thermal effects of mobile telephones on the human EEG.     

In Vitro Evaluation of Biological Effects on Human Keratinocytes Exposed to 900 MHz Electromagnetic Field

Summary The biological effects of electromagnetic radiation at ultra high frequency on human keratinocytes were investigated. HaCaT cell system, a spontaneously immortalized human keratinocytes cell line, was chosen as model since skin is usually exposed to electromagnetic radiation at considered frequency more than inner tissues. HaCaT cells were exposed to a pure sinusoidal field at a frequency of 900 MHz (average SAR levels ranging from 0.04 to 0.08 W/kg) in plane wave condition inside a GTEM chamber for time intervals of 18 hours at a controlled temperature of 37^∘C. Growth curves were obtained for exposed and control cells, and a reduction in the number of exposed cells in comparison to unexposed ones was found; however the number of dead cells was not significantly different in exposed and unexposed samples. In order to investigate whether the reduction in cell proliferation of exposed cells was due to the activation of a differentiative process, the expression of two hallmarks of differentiation was examined. Both keratin 1 and involucrin expression was increased in exposed in comparison to unexposed cells. These results suggest that this protocol of exposure to 900 MHz electromagnetic field can trigger a differentiation program in HaCaT cells.     

Graphical Presentation of 50/60 Hz Magnetic Field Contours as an Engineering Tool for Minimizing ELF Fields

Summary Since IARC classified ELF magnetic field as Possibly Carcinogenic to Human the fear from 50/60 Hz magnetic field exposure had been increased to the state of public “panic”. Subsequently, environment quality preservation organizations increased their pressure on their government to adopt the “precautionary principle” and to reduce the allowable ELF Magnetic Field exposure to much lower values than are recommended by ICNIRP-1998. As an example the present Environmental Ministry in Israel recommendation is to lower the ELF Field exposure to 10 mG averaged over 24 h. As a result of this stringent exposure guideline imposed by the government, electrical engineers who are involved in the deployment and installation of large and medium electrical utilities, such as overhead power lines, transformers, UPS systems, electrical public transportation, switching stations, etc., are much more aware to the need to employ special measures and methods for reducing the magnetic fields that might be emitted from such utilities. There are few computer codes that are capable of analyzing with great accuracy magnetic and electric fields surrounding single phase and three phase electrical utilities in a 3-D system. The best presentations of the analysis results are by equi-value contours depicting electric and magnetic fields. This graphical presentation is a powerful design tool that enables better deployment and installation design aided to reduce the magnetic field emissions from high-power electrical utilities. This paper describes the various types of graphical presentations available for ELF field contours, the dependent and independent variants and parameters, magnetic field animation for optimization of power line installation and routing, and finally an example that demonstrates the usefulness of the graphical presentation tools.     

Thermal Effects of Photon-Phonon Interaction on a Simple Tissue

Summary The thermal effect due to electromagnetic absorption by human tissues is investigated at different frequencies ranging from 10¹–10¹⁶ Hz. Special emphasis is being considered in the microwave band used in wireless communications of the mobile industry. The present work examines basically the thermal effect that arises as the duration of exposure to the electromagnetic radiation and its dosage is increased. Using a computer simulation, a semi-classical model is adopted, were the photon-phonon interaction is mediated by a homogenous sample of identical elements, which are naturally in harmonic modes of vibration. The phonon lifetime is also included in this work. These thermal effects decrease with frequency in conformity with experimental results. This model is then extrapolated to the individual cells of a human tissue and the possible rise in temperature is estimated.     

Three-Dimensional Ground-Based Measurements of Urban Air Quality to Evaluate Satellite Derived Interpretations for Urban Air Pollution

Urban air quality and meteorological measurements were carried out in the region of Brescia (Italy) simultaneously to the acquisition of satellite data during winter and summer smog conditions in 1999. The main objectives of the campaigns were: delivery of data for the validation of air pollution interpretations based on satellite imagery, and determination of the aerosol optical thickness in spectral ranges similar to those used by satellites. During the winter campaign the ground-based network was complemented by local stations and by SODAR, DOAS, and FTIR remote sensing measurements. Size distributions of aerosol particles up to 4,000 m a.s.l. were measured by means of an ultra-light aircraft, which was also equipped with meteorological sensors and an ozone sensor. During the summer campaign an interference filter actinometer, an integrating nephelometer and an ozone LIDAR were operated additionally. The satellite images acquired and processed were taken from SPOT. Optical thickness retrieved from interference filter actinometer measurements were compared with the retrievals from the satellite imagery in the same spectral intervals. It is concluded that remaining aerosols in the reference image yield an off-set in the satellite retrieval data and that information about the vertical structure of the boundary layer is very important.