Optimum design of electromagnetic shielding rooms with minimum usage of absorbing materials

In this article, a novel method has been proposed to optimize the electromagnetic shielding rooms. This method is based on using minimum electromagnetic absorbing materials on the inner surface of the rooms. The positions of the absorbing materials are found optimally to produce a “best” performance for the shielding rooms. The ray‐tracing method is used to predict the shielding effectiveness (SE) of the electromagnetic shielding rooms with apertures. The performance of the proposed method is verified by a comprehensive example. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE 2010.     

一种实时可靠的移动无线传感器网络贪婪地理路由协议

随着定位装置和定位算法的成熟,基于地理位置信息的贪婪地理路由协议受到广泛的关注与研究.但是,在移动无线传感器网络贪婪地理路由协议中,周期性信标交换条件下采用贪婪转发策略会引起通信暂盲现象,造成数据的丢失.基于右手法则的面遍历算法,对路由空洞的形状不能进行感知,数据转发具有很大的盲目性,转发路径有时比最优路径长很多,造成数据传输时延的增加.针对上述问题提出一种实时可靠的QoS贪婪地理路由协议,该协议通过自适应信标交换算法、基于过渡带思想的贪婪转发策略和基于路标迭代提取和剔除的自适应空洞处理算法,使得数据分组能够实时可靠地传输.NS-2仿真结果表明该协议在不增加控制开销的情况下,能够有效减缓通信暂盲现象,高效地处理路由空洞问题,大大提高协议的实时性和可靠性,可应用于对实时性和可靠性有一定要求的大规模移动无线传感网络.     

Semiempirical and ab initio conformational analysis of 2-methylene-8,8-dimethyl-1,4,6,10-tetraoxaspiro[4.5] decane with application of GIAO-SCF methods to NMR spectrum interpretation

The GIAO-SCF method for calculating isotropic nuclear magnetic shielding values has been utilized to explain certain features in the ¹H-NMR spectrum of 2-methylene-8,8-dimethyl-1,4,6,10-tetraoxaspiro[4.5] decane. Population distributions of the low-energy conformers based on their ab initio energies were used to produce weighting factors for the individual calculated shielding values to calculate the weighted average of the shielding values for a complete set of conformers. The differences in ¹H chemical shifts between the hydrogens of the two methyl groups and between the axial and equatorial hydrogens in 2-methylene-8,8-dimethyl-1,4,6,10-tetraoxaspiro[4.5] decane were shown to be due to energy differences between the chair and boat orientations of the six-membered ring and contribution from a twist-boat conformation. Results suggest a hypothesis that intramolecular differences in chemical shift might be calculated to a greater degree of accuracy than chemical shifts calculated relative to a standard.     

带孔缝机箱的屏蔽效能仿真研究

利用Ansoft HFSS软件研究了电磁兼容设计中的孔缝耦合问题,介绍了有限元法的基本原理,对比仿真结果与对数周期天线的测量值,验证了此有限元法的可靠性.通过对带孔缝机箱建模,改变其孔缝的形状、面积等因素进行机箱的屏蔽效能仿真分析,获得了不同情况下的屏蔽效能仿真结果,并指导机箱内电路板的布置.     

The use of energy windowing to discriminate SNM from NORM in radiation portal monitors

Energy windowing is an algorithmic alarm method that can be applied to plastic scintillator-based radiation portal monitor (RPM) systems to improve operational sensitivity to certain threat sources while reducing the alarm rates from naturally occurring radioactive material. Various implementations of energy windowing have been tested and documented by industry and at Pacific Northwest National Laboratory, and are available in commercial RPMs built by several manufacturers. Moreover, energy windowing is being used in many deployed RPMs to reduce nuisance alarms and improve operational sensitivity during the screening of cargo. This paper describes energy windowing algorithms and demonstrates how these algorithms succeed when applied to “controlled” experimental measurements and “real world” vehicle traffic data.     

导电纤维填充型导电塑料在电磁屏蔽中的应用研究进展

简要阐述了电磁屏蔽的途径和机理，并着重介绍了导电碳纤维填充型导电塑料、金属纤维填充型导电塑料以及导电有机纤维填充型导电塑料的研究进展，此外，还概述了其各自的优缺点。     

Coping With Stereotype Threat: Denial as an Impression Management Strategy.

Four experiments tested the hypothesis that people who are concerned with impression management cope with stereotype threat through denial. Consistent with this hypothesis, temporary employees threatened by a stereotype of incompetence (Study 1) and hostel-dwelling older adults (Study 2) were more likely to deny incompetence if they were high in impression management. African Americans (Study 3) showed a similar pattern of denying cognitive incompetence, which emerged primarily when they were interviewed by a White experimenter and had attended a predominantly Black high school. In Study 4, White students who expected to take an IQ test and were threatened by a stereotype of being less intelligent than Asians were more likely to deny that intelligence is important if they were high in impression management. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Physiological cost of energy-equivalent noise exposures with a rating level of 85 dB(A):: Hearing threshold shifts associated with energetically negligible continuous and impulse noise

In industry continuous or impulse noise does not occur exclusively; rather it is a combination of both. If low-level continuous noise or impulse noise (below 120 dB) is added to an already existing high-level continuous noise this often numerically causes no essential increase in the rating level. Yet, it cannot be expected that also aural strain of these exposures is always negligible. Therefore, in a cross-over test series, ten male subjects (Ss) were exposed to white noise of 94 dB(A) for 1 h (TS I), energy-equivalent to an 8 h-rating level L_Ard of 85 dB(A). In a second test series (TS II) the same exposure was combined with 900 energetically negligible 5-ms impulses with a noise level of 113 dB(A) which increased the rating level by only 0.4 dB. The noise exposure of TS I and TS II was followed by an idealized resting phase in a soundproof cabin. In a third test series (TS III) the continuous noise of 94 dB(A) / 1 h was followed by 3 h of white noise at 70 dB(A). Such an additional load increases the L_Ard by merely 0.1 dB to 85.1 dB(A). In all three test series, the noise-induced temporary threshold shift (TTS₂) and its restitution were measured. The continuous noise exposure of 94 dB(A) for 1 h was associated with a TTS₂ of around 20 dB which disappeared completely after about 2 h. The additional impulse noise caused a small increase in the TTS₂ and a prolongation of the restitution time. The maximum mean temporary threshold shift for the group increased only slightly (from 22.5 to 25.9 dB, which nevertheless can be statistically proven at a significance level of p 0.99). Yet, more importantly, the restitution time increased from 126 to 175 min, i. e. 3 h, which can be statistically proven at a significance level of p0.95. The TTS₂-values of TS III did not differ significantly from those resulting from TS I. That was expected as the conditions up to that point in time were identical. But due to the additional subsequent exposure, the mean restitution time increased considerably from 126 min up to 240 min (4 h). The mean total physiological cost represented by the integrated restitution temporary threshold shift (IRTTS) increased in TS II by approximately 40% and in TS III even by 140%.

Relevance to industry

The results of the study show that levels of noise which have no influence on the rating level which traditionally is calculated according to the energy-equivalence principle are often of great importance, as they can lead to considerably prolonged restitution times. Therefore, the purely energy-equivalent determination of the rating level of both impulse noise and low sound levels can lead to an underestimation of latent problems so that over time a reversible TTS can evolve into a permanent threshold shift. The results are also of importance for the acoustic design of break rooms for noise-exposed workers. There should be conditions that allow an undisturbed restitution of hearing.     

辊套材料对铸轧区磁感应强度影响的实验研究

电磁场快速铸轧技术要求辊套材料不仅具有高导热系数、高承载能力和高抗疲劳能力，而且要具有磁场控制能力，保证铸轧区足够的磁感应强度，达到细化晶粒、改善板坯组织性能的目的．本文主要从介质对电磁场的集肤效应、涡流效应、磁场衰减以及屏蔽效应的角度，研究辊套对铸轧区电磁场的影响．     

对皖北地区500kV输电线路耐雷性能的研究

根据安徽电网皖电东送通道8条500 kV线路的运行情况,结合皖北地区500 kV输电线路跳闸原因,分析输电线路设备耐雷状况,提出了综合防治措施,以便改进皖北地区500 kV线路的耐雷性能,提高其安全稳定运行水平。