短切碳纤维混凝土电磁屏蔽规律的实验研究

随着电子产品普及和大功率电气设备数量的增加,导致电磁环境急剧恶化,从而带来了一系列隐患。简要阐述了电磁屏蔽的原理,介绍了碳纤维的性能,并对短切碳纤维水泥基复合材料的屏蔽性能进行了实验研究,制备出碳纤维吸波混凝土,测试了样品的电磁屏蔽性能,并比较3mm与6mm短切碳纤维在吸波混凝土中的屏蔽效能,分析、总结了实验样品中反映出来的规律,为设计高性能电磁屏蔽混凝土提供了依据。     

切向空气气流对激光辐照碳纤维复合材料的影响

实验研究了靶材表面存在和不存在切向空气气流时,975nm连续激光对碳纤维增强树脂基复合材料的辐照效应,发现切向气流的加载有利于激光对碳纤维复合材料的破坏.从理论上对激光辐照下碳纤维复合材料的破坏机理进行了初步分析,基于碳的氧化特性和氧化反应机理,推导了碳纤维的氧化速率方程.采用改进的光滑粒子方法,对激光辐照下复合材料树...     

短切碳纤维在甲基纤维素水溶液中的分散性能研究

研究了短切聚丙烯腈基碳纤维在甲基纤维素水溶液中的分散性能,根据电镜扫描图和实验数据曲线对分散机理进行了研究。结果表明：短切碳纤维因吸附甲基纤维素而分散,并且随着甲基纤维素浓度的增加分散量亦增加,但有一极值。     

3维C/SiC-ZrC复合材料的制备及其性能研究

针对超高温环境应用需求,采用化学气相渗透工艺(CVI)与先驱体浸渍-裂解工艺(PIP)联用制备了3维碳纤维增强SiC-ZrC基复合材料(C/SiC-zrC),并研究了SiC含量对C/SiC-ZrC复合材料力学性能、抗氧化性能和抗烧蚀性能的影响.结果表明,随着SiC含量的增加,C/SiC-ZrC复合材料的强度逐渐降低,静...     

微胶囊型自修复碳纤维增强复合材料性能研究

为了分析内嵌环氧树脂基微胶囊的碳纤维增强复合材料(CFRP)的力学性能,开展了材料在准静态载荷条件下力学性能试验研究,对比分析了有、无微胶囊时碳纤维增强复合材料的静态力学性能,详细探究了微胶囊的质量分数对碳纤维增强复合材料的力学性能和自修复性能的影响,分析了材料的拉伸强度,弹性模量,断裂伸长率以及自修复性能情况。在相同冲击能量下,采用落锤法对不同微胶囊含量的层合板进行冲击试验,研究其在冲击载荷作用下的动态力学响应。结果表明,微胶囊具有增韧效果和自修复能力。随着微胶囊质量分数的增加,自修复碳纤维增强复合材料的拉伸强度降低,弹性模量先略微升高后降低,断裂伸长率先降低后升高,但总体变化不大,修复效率随微胶囊含量的增加而升高。在相同冲击能量下,微胶囊含量越大,最大冲击力越小,材料的冲击力-位移曲线斜率越小,抗冲击性能越差。研究结果可以为推动自修复型CFRP材料的实际工程应用和理论研究提供相关参考。     

碳纤维增强聚合物基复合材料频率选择表面的电磁传输特性（复合材料专栏投稿）*

为了改善采用金属频率选择表面（Frequency Selective Surface,FSS）制备的天线罩中存在的热残余应力和弱粘接界面等问题,本文采用与聚合物基复合材料罩壁结构相容性好的碳纤维增强聚合物基复合材料制备FSS,利用自由空间法对试样的电磁传输性能进行测试,并采用数值分析模型对碳纤维复合材料FSS的电磁传输机制和电磁传输影响因子进行分析。结果表明：碳纤维复合材料FSS具有频率选择功能,但谐振频率处的电磁传输损耗较大;通过改变复合材料FSS的单元缝隙率、厚度、电导率以及介电常数可以实现对其电磁传输性能的调节。     

碳纤维增强聚合物基复合材料频率选择表面的电磁传输特性

为了避免采用金属频率选择表面制备的天线罩中存在的热残余应力和弱黏接界面等问题,采用与聚合物基复合材料罩壁结构相容性好的碳纤维增强聚合物基复合材料制备频率选择表面,利用自由空间法对试样的电磁传输性能进行测试,并采用数值分析模型对碳纤维复合材料频率选择表面的电磁传输机制和电磁传输影响因子进行分析。结果表明:碳纤维复合材料频率选择表面具有频率选择功能,但谐振频率处的电磁传输损耗较大;通过改变复合材料频率选择表面的单元缝隙率、厚度、电导率以及介电常数可以实现对其电磁传输性能的调节。     

不同裂解温度对制备SiCf/Si-O-C复合材料性能研究

以聚硅氧烷为先驱体,研究先驱体转化过程中在不同的裂解温度下对制备SiCf/Si-O-C复合材料性能影响.结果表明,当裂解温度在700℃、800℃时,陶瓷基复合材料的弯曲强度分别为255.2 MPa、309.0 MPa;当裂解温度在1000℃时,陶瓷基复合材料的弯曲强度为45.3 MPa.对SiCf/Si-O-C复合材料的微观结构及载荷-位移曲线进行分析,发现界面结构是影响SiCf/Si-O-C复合材料性能的主要因素.     

准陶瓷Cf/SiC复合材料的制备

采用热重-差热(TG-DTA)、红外(IR)等分析测试手段,研究了聚碳硅烷(PCS)的裂解及化学转化过程,从理论上验证了先驱体聚碳硅烷(PCS)600℃裂解产物的准陶瓷特性.先驱体聚碳硅烷在600℃呈现一种半有机、半无机状态,其产物具有准陶瓷的特征,在大约750℃出现无机化转变高峰,固称其为准陶瓷.以碳布、准三维编织体、三维编织体为增强体,采用先驱体浸渍裂解(PIP)工艺在600℃制备了碳纤维增强碳化硅(Cf/SiC)准陶瓷基复合材料.结果表明,以三维编织体增强的准陶瓷Cf/SiC复合材料获得了较理想的结构、性能,所制备3D-Cf/SiC复合材料密度仅有1.27g/cm3,弯曲强度达到193.69MPa,室温拉伸强度为197.69MPa,600℃拉伸强度为167.33MPa.复合材料断口形貌分析表明,在低温600℃制备的准陶瓷Cf/SiC复合材料呈现明显的韧性断裂特征.     

T300和JC2#纤维增强C/SiC复合材料力学性能对比

以聚碳硅烷(PCS)为先驱体,采用聚合物浸渍裂解法(PIP)分别制备得到T300碳纤维和JC2#碳纤维增强C/SiC复合材料。JC2#C/SiC复合材料具有优异的力学性能,抗弯强度和断裂韧性分别达到662MPa和19.5MPa.m1/2;T300 C/SiC复合材料表现出低强度、高脆性,其抗弯强度和断裂韧性不足前者的四分之一。T300 C/SiC复合材料低性能的根本原因在于T300纤维在PCS裂解过程中性能严重下降,复合材料中纤维与基体间存在强界面结合是另一个影响因素。     

Reviews

Douglas S. Derrer, We Are All the Target: A Handbook of Terrorism Avoidance and Hostage Survival. Annapolis, MD: US Naval Institute Press, 1992. Pp. x+135, notes, index. $14.95. ISBN 01–55750–150–5

Ian Knight, Zulu: Isandlwana and Rorke's Drift, 22–23 January 1879. London: Windrow & Greene, 1992. Pp.136, 150 illus., incl 8 colour plates, maps, biblio. £35. ISBN 1–872004–23–7

Ian Knight, By the Orders of the Great White Queen: Campaigning in Zululand through the Eyes of the British Soldiers, 1879. London: Greenhill Books and Novato: Presidio Press, 1992. Pp. 272, 17 illus., 1 map. £18.95. ISBN 1–85367–122–3

Manfried Rauchensteiner and Erwin A. Schmidl (eds.), Formen des Krieges: vom Mittelalter zum ‘Low‐intensity’ Conflict’. Graz : Verlag Styria, 1991. Pp.208. DM35. ISBN 3–22–12139–7

Harold J. Kearsley, Maritime Power and the Twenty‐First Century. Dartmouth: Dartmouth Publishing Company, Limited, 1992. Pp.xv + 203, 13 diagrams, index. £32.50. ISBN 1–85521–288–9     

Panjwai: a tale of two COINs in Afghanistan

The US Army has two approaches to counterinsurgency operations in Afghanistan. One is hard, or combat-focused, and the other is soft, or development-focused. This study examines two US Army task forces deployed to Panjwai District, Afghanistan from 2012 to 2013. CTF 4-9 and 1-38 offer a meaningful comparison because they pursued these contrasting approaches among the same population and against the same enemy at the same time and place. The study compares each unit’s approach and finds that neither approach was successful absent the other. The article concludes by recommending further research into combining the approaches at the operational level.     

线性核时频信号表示及其仿真

根据ｃｈｉｒｐ信号在模糊域的特点,本文提出了线性核时频表示方法。这种方法在提高分辨率、消除交叉项以及抑制噪声等方面都具有较高的性能。理论分析和实验结果都证实了这种方法的有效性     

Putin – the masked nemesis of the strategy of ambiguity

Recent events demonstrate the complex and adaptive approach employed by Russia to reassert influence in Europe. The changing face of Russia’s strategy commenced in 2007 when it launched a crippling cyber-attack against Estonia. This was followed by a large Russian conventional attack against Georgia in 2008, occupying two large areas of the nation. 2014 witnessed the Russian annexation of Crimea where in just a week, Russia seized control of Crimea “without firing a shot.” The annexation of Crimea was rapidly followed by a Russian inspired and led subversive war in eastern Ukraine. The common thread among these diverse Russian operations is its use of ambiguity to confound and confuse decision makers in the West.     

Forecasting a Hurricane: Israeli and American Estimations of the Khomeini Revolution

The surprising ‘Arab Spring’ raises the question as to what would enable national intelligence to provide high quality warnings prior to the eruption of popular revolutions. This article uses new sources of evidence to trace and explain Israel's success in comparison to US failure at correctly estimating the course of the Iranian Revolution in 1977–79. In explaining this variance, the article shows that it was mainly the result of the intimate acquaintance of Israel's representatives in Iran with the local language, history and culture, as well as the ability to communicate with locals – tools which the Americans completely lacked.     

关于教师继续教育培训模式的思考

继续教育作为终身教育的重要组成部分和基本形式,对教师的发展成长意义重大。继续教育工作开展十多年来,取得了一定的成绩,但还存在不少问题,如学习动机较为被动,管理认识不到位,教学内容陈旧空泛,教学方法呆板机械等。随着课程改革的不断深入,继续教育必须采取相应的改进措施,树立以人为本,服务至上的观点,教学内容的前瞻性与实用性并重,教学人员进行整合,教学方法灵活多样,评价考核规范科学等,以此激活受训教师内在的学习动机,更大程度地提高继续教育培训的实际效果。     

用DirectShow实现网络视频

目前市场上的网络监控技术一般用昂贵的硬件设备来支撑,投资较大。在深入研究微软的DirectX9.0的基础上,提出如何用DirectShow软件技术和普通的数字摄像头来实现网络视频的监控和实现技术,内容涉及通信协议、视频的编码与解码技术、视频的编码格式和COM组件编程技术等,最终的实验结果令人满意,且费用低廉,技术可靠,为在高速局域网内构建视频监控系统提供有效的技术支持。     

Interpreting the Ribchester Helmet

In 1796 a 13-year-old boy playing on wasteland behind his father’s house in Ribchester, Lancashire discovered an assemblage of over 30 Roman artefacts, including a decorated brass helmet. Although partially corroded the Ribchester helmet is a fine example of a first-century AD cavalry sports helmet. This article considers how the interpretation of the helmet has evolved since its discovery. The multi-faceted iconography of the helmet with its mural crown diadem is that of an elite soldier and is paralleled in other examples of cavalry sports helmets of the Ribchester type. The long-neglected imagery on the helmet bowl is reinterpreted and seen not as a haphazard collection of randomly placed combatants but as a highly structured, symmetrical composition specifically designed to be viewed from different directions.     

Desert insurgency: lessons from the third Tuareg rebellion

This article provides an in-depth examination and analysis of the 2006–2009 Tuareg rebellion in Mali and Niger. It identifies the underlying reasons behind the rebellion, explores contrasting counter-insurgency (COIN) strategies employed by the two governments, and presents some lessons learned. While both COIN approaches ultimately produced similar peace settlements, the article argues that the Malian strategy of reconciliation combined with the selective use of force was far more effective than the Nigerien iron fist approach at limiting the size and scope of the insurgency and producing a more sustainable peace. It concludes by looking at the role of external actors, particularly the United States, and how the failure to internationalize the conflict was actually more beneficial to the local COIN effort, as well as to the longer strategic interests of the United States in the region.