短小厂房内兼容棒材和不锈钢高线的设计改造

针对郑州永通特钢公司在长度仅185m的厂房内原有1条轴承钢棒材生产线的基础上欲再增加1条不锈钢高线的情况,北京科技大学轧钢研究所对其进行了设计改造,本文分析了其技术难点,采用了吐丝机与散冷辊道垂直布置,以及导管加侧活套的方案。生产实践证明,该工艺合理可行,为其他厂家提供了可供借鉴的模式     

叠加Y环单元频率选择表面的设计

对Y环单元进行改造得到了叠加Y环单元图形,以延迟频率选择表面(FSS)的高次谐振,实现无干扰的单通带滤波器.运用谱域法分析得到的叠加Y环单元,并与Y环单元进行对比,分别讨论其角度稳定性、极化稳定性、-3 dB带宽和高次谐振点.分析表明:当中心频点同为17.6 GHz时,叠加Y环单元具有更窄的带宽,而高次谐波向后延迟6....     

多级质量归零管理系统中的访问控制

针对航天企业在质量归零管理信息化过程中遇到的对归零信息和归零过程的多级、多任务和多角色访问控制问题展开研究.在构建面向集团-院-厂所的三级归零管理业务模型的基础上,分析质量归零过程中对归零信息和归零流程的访问控制需求,提出基于任务和角色的扩展访问控制( Extended Task&Role Based Access Control,ETRBAC)模型,该模型将型号权限、产品权限、组织权限和任务权限进行综合,实现了对归零信息和归零流程的多维度访问控制.在理论研究的基础上,设计开发了访问控制组件,并通过软件的实施,验证该访问控制策略的有效性.     

医疗器械的电磁兼容标准体系概况

电磁干扰对医疗器械造成的影响并导致的危害会严重影响设备的安全性和有效性,给患者和操作者带来严重的后果。本文介绍国内外医用电气设备的电磁兼容标准体系,并着重概述体外诊断设备的电磁兼容标准体系。     

Reflection and absorption characteristics of electromagnetic waves for PV modules

In this paper, the authors investigated the reflection and absorption characteristics of a general photovoltaic (PV) module. As a result, the electromagnetic waves could be attenuated only 6 dB in typical PV module. However, if the PV module is installed in the outer wall of buildings, electromagnetic interference is caused by the surroundings. To reduce this electromagnetic interference, the authors suggested a method to absorb electromagnetic wave using multiple PV modules that have deference impedance, and simulation was performed. As a result, it was confirmed that using a typical PV module and the PV module including electronic device, the reflection waves of those PV modules could be attenuated up to 12 dB.     

一种新型高效敞开式空调系统

报道了一种应用于敞开吸收式空调系统的新型空气循环方式，它可以显著地改善系统进行特性，提高效率，减小设备尺寸，降低造价，同时还可提高系统致冷贮存能力。     

Study on heat transfer characteristics of reservoir embedded loop heat pipe (1st report,Influence of evaporator orientation against gravity and charged liquid weight on heat transfer characteristics)

High‐powered satellites need larger heat rejection areas. A deployable radiator is one of the key technologies for a high‐powered satellite bus. A Reservoir Embedded Loop Heat Pipe (RELHP) is a two‐phase heat transfer device that constitutes a deployable radiator. RELHP has an evaporator core which is used as a liquid reservoir to enhance operational reliability. This paper presents the heat transport characteristics of a RELHP under changing evaporator orientation against gravity and charged ammonia weight by experiment and calculation. Liquid slug position in the reservoir has a great influence on heat transport characteristics, caused by changing heat transfer coefficients between returned liquid into the evaporator and vapor in the reservoir. © 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(3): 143– 157, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20150     

250～300MW等级CFB锅炉分离回料系统简介

250~300MW等级CFB锅炉分离回料系统的组成、整体布置及结构特点。     

Kinetic modelling of quantum effects in laser-beam interaction

We present the results of kinetic modelling of quantum effects in laser-beam interaction. In the developed numerical model, electron-positron pair production by hard photons, hard photon emission and the electromagnetic fields generated by the created charged particles are taken into account. Interaction of a relativistic electron beam with a strong laser pulse is analyzed. It is shown that the quantum effects can be important even for moderately intense laser pulses when the number of emitted photons by single electron is not large. Electron-positron pair plasma production in extremely intense laser field via development of electromagnetic cascades is also studied. The simulation results confirm the prediction of strong laser field absorption in the self-generated electron-positron plasma. It is shown that the self-generated electron-positron plasma can be an efficient source of energetic gamma-quanta.     

Microwave absorption properties of carbon nanotubes dispersed in alumina ceramic

Ceramic nanocomposites of alumina and carbon nanotubes (CNTs) are experimentally studied for use as microwave absorbers in particle accelerators. The weight percentage of multi-walled CNTs in SPS sintered nanocomposite samples is varied from 0.5 to 10% and the complex permittivity is measured. The RF absorption is strong and relatively flat in the frequency band 1-40 GHz for a CNT weight percentage in the range 1-2.5%, which is just above the percolation threshold. The permittivity is observed to increase dramatically with increasing CNT weight percentage above the percolation threshold as observed elsewhere, and in accordance with theoretical treatments. The electromagnetic properties of the nanocomposites are little changed in going from 294 K to 77 K. The DC conductivity of the alumina-CNT nanocomposite is also sufficient to drain static charge in particle accelerator beamline environments, even at cryogenic temperatures. Fabrication of the nanocomposites using an industrial RF sintering process compatible with large sizes shows that the microwave absorption properties of small samples are similar to those of the SPS sintered samples.