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61.
为减少电子设备中通风散热孔洞耦合的电磁干扰,采用金属波导来屏蔽孔洞.从干扰源的种类、波导长度、波导形状3方面研究金属波导对电子设备中心点处电场与屏蔽效能的影响.UWB对金属腔体的影响最大,快速HEMP对腔体的影响最小;增加矩形波导长度,有利于抑制低频段电磁干扰;圆形波导和方形波导对干扰源的抑制能力较强.研究结果能为电子设备的电磁防护提供理论参考,指导工程防护设计,具有重要的应用价值. 相似文献
62.
Effect of oxyfluorination on electromagnetic interference shielding behavior of MWCNT/PVA/PAAc composite microcapsules 总被引:1,自引:0,他引:1
Jumi Yun 《European Polymer Journal》2010,46(5):900-158
Composite microcapsules of poly(vinyl alcohol)/poly(acrylic acid)/multi-walled carbon nanotubes were prepared and the electromagnetic interference shielding behavior was evaluated for the composite microcapsules. The dispersion and adhesion of multi-walled carbon nanotubes in microcapsules were improved by the surface modification through direct oxyfluorination which introduced polar groups on the multi-walled carbon nanotubes. The composite microcapsules containing the oxyfluorinated multi-walled carbon nanotubes showed significant increases in permittivity, permeability, and electromagnetic interference shielding efficiency. The electromagnetic interference shielding efficiency of composite microcapsule increased up to 51 dB mainly base on the absorption mechanism. 相似文献
63.
64.
莫晓虎 张建勇 张清江 Achasov Mikhail 蔡啸 傅成栋 Harris Fred 刘倩 Muchnoi Nikolay 秦庆 屈化民 王贻芳 徐金强 张天保 《中国物理 C》2011,35(7):642-655
Understanding the radiation background at the north crossing point (NCP) in the tunnel of BEPCII is crucial for the performance safety of the High Purity Germanium (HPGe) detector, and in turn of great significance for long-term stable running of the energy measurement system. Therefore, as the first step, a NaI(Tl) detector is constructed to continuously measure the radiation level of photons as background for future experiments. Furthermore, gamma and neutron dosimeters are utilized to explore the radiation distribution in the vicinity of the NCP where the HPGe detector will be located. Synthesizing all obtained information, the shielding for neutron irradiation is studied based on model-dependent theoretical analysis. 相似文献
65.
The construction of China Spallation Neutron Source (CSNS) has been initiated in Dongguan, Guangdong, China. Thus a detailed radiation transport analysis of the shutter neutron beam stop is of vital importance. The analyses are performed using the coupled Monte Carlo and multi-dimensional discrete ordinates method. The target of calculations is to optimize the neutron beamline shielding design to guarantee personal safety and minimize cost. Successful elimination of the primary ray effects via the two-dimensional uncollided flux and the first collision source methodology is also illustrated. Two-dimensional dose distribution is calculated. The dose at the end of the neutron beam line is less than 2.5 μSv/h. The models have ensured that the doses received by the hall staff members are below the standard limit required. 相似文献
66.
Andrei V. Afonin Dmitry V. Pavlov Igor A. Ushakov Natalia A. Keiko 《Magnetic resonance in chemistry : MRC》2012,50(7):502-510
In the 13C NMR spectra of methylglyoxal bisdimethylhydrazone, the 13C‐5 signal is shifted to higher frequencies, while the 13C‐6 signal is shifted to lower frequencies on going from the EE to ZE isomer following the trend found previously. Surprisingly, the 1H‐6 chemical shift and 1J(C‐6,H‐6) coupling constant are noticeably larger in the ZE isomer than in the EE isomer, although the configuration around the –CH═N– bond does not change. This paradox can be rationalized by the C–H?N intramolecular hydrogen bond in the ZE isomer, which is found from the quantum‐chemical calculations including Bader's quantum theory of atoms in molecules analysis. This hydrogen bond results in the increase of δ(1H‐6) and 1J(C‐6,H‐6) parameters. The effect of the C–H?N hydrogen bond on the 1H shielding and one‐bond 13C–1H coupling complicates the configurational assignment of the considered compound because of these spectral parameters. The 1H, 13C and 15N chemical shifts of the 2‐ and 8‐(CH3)2N groups attached to the –C(CH3)═N– and –CH═N– moieties, respectively, reveal pronounced difference. The ab initio calculations show that the 8‐(CH3)2N group conjugate effectively with the π‐framework, and the 2‐(CH3)2N group twisted out from the plane of the backbone and loses conjugation. As a result, the degree of charge transfer from the N‐2– and N‐8– nitrogen lone pairs to the π‐framework varies, which affects the 1H, 13C and 15N shieldings. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
67.
Marta Bugaj Piotr A. Baran Piotr Bernatowicz Patrycja Brożek Krystyna Kamieńska‐Trela Adam Krówczyński Bohdan Kamieński 《Magnetic resonance in chemistry : MRC》2009,47(10):830-842
A series of aryl‐substituted enaminoketones and their thio analogues in CDCl3 solution and in the solid state were studied by the use of high‐resolution 1H and 13C as well as 13C cross polarization magic angle spinning (CP MAS) NMR spectra in combination with gauge including atomic orbitals‐density functional theory (GIAO‐DFT) calculations performed at the B3PW91/6–311 + + G(d,p) level of theory using the B3PW91/6‐311 + + G(d,p)‐optimized geometries. The analysis of the 13C NMR spectra in solution was done by using the Incredible Natural Abundance DoublE QUAntum Transfer Experiment (INADEQUATE) technique, whereas trends observed in the 13C shielding constants, calculated for the compounds studied, were a great help in assigning most of the signals in the 13C CP MAS NMR spectra. It was established on the basis of the experimental and theoretical NMR data that both groups of compounds exist in the form of Z‐s‐Z‐s‐E isomers in CDCl3 solution as well as in the solid state, with the NH hydrogen atom involved in intramolecular hydrogen bonding. This conclusion is in agreement with the fact that some of the compounds studied reveal liquid‐crystalline properties. Three‐bond H, H and C, H coupling constants measured in solution played a crucial role in the structure elucidation. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
68.
电磁屏蔽技术在通信设备结构设计中的应用 总被引:1,自引:0,他引:1
分析了电磁干扰形成的原因及其危害,介绍了工程上运用电磁屏蔽技术解决电磁干扰问题的几种常用方法。提出在工程实际应用中,采用定性分析和经验公式相结合的方式进行估算。 相似文献
69.
空心介质球对静磁场的屏蔽 总被引:1,自引:0,他引:1
石长柏 《邵阳学院学报(自然科学版)》2004,1(2):17-18
文章通过对空心介质球的静磁场屏蔽进行理论推导,并分析静磁场屏蔽的因素. 相似文献
70.
实验室自主研发“葫芦娃”机器人在完成自动换装过程中需要倾角传感器对机械臂转动角度进行实时反馈。针对电子元器件耐辐照能力较弱的情况,本文为倾角传感器设计辐射屏蔽装置,利用MCNP程序建立屏蔽装置模型,通过对5个面的辐射通量分析,通过优化各面铅的厚度,减小整个屏蔽体的重量,研究开散热孔对屏蔽体整体性能的影响以及辐射衰减与距离之间的关系,初步验证了本文设计的辐射屏蔽装置作为高辐射场下屏蔽γ射线的模型所具有的合理性。 相似文献