硼砂对磷酸镁水泥性能影响及微观作用机理分析

研究了硼砂对磷酸镁水泥凝结时间与抗压强度的影响,分析了硼砂对水泥性能影响的微观作用机制.研究发现:随着硼砂对MgO质量分数增加,磷酸镁水泥凝结时间延长,其早期抗压强度迅速降低,后期抗压强度所受影响相对较小;磷酸镁水泥应用于快速修补及抢修抢建时,硼砂质量为氧化镁质量的5％～10％为宜;硼砂对磷酸镁水泥水化产物的早期生成量...     

模拟放射性核素Cs对磷酸镁水泥性能的影响

以重烧氧化镁、磷酸二氢钾和硼砂为主要原料制备磷酸镁水泥,研究模拟放射性核素Cs对磷酸镁水泥性能的影响。结果表明:掺入Cs使磷酸镁水泥抗压强度下降;随着Cs掺量的增大,磷酸镁水泥流动度先减小后增大,凝结时间明显延长;Cs掺量为磷酸镁水泥质量的1.2%时,试件1 d抗压强度为32.5 MPa,远高于国家标准对低、中水平放射性废物固化体7 MPa的要求;磷酸镁水泥对Cs+有较高的吸附率,12 h吸附率可以达到61.28%;Cs掺量达到磷酸镁水泥质量的0.8%时,磷酸镁水泥水化放热降低、水化产物形成受阻。     

含模拟放射性核素~(133)Cs磷酸钾镁水泥固化体性能

按照GB 14569.1—2011要求对含Cs磷酸钾镁水泥固化体抗压强度、抗浸泡性、抗冻融性、抗冲击性和抗浸出性进行了研究,探讨固化体物相组成、微观形貌和固化机理。研究结果表明:含Cs磷酸钾镁水泥固化体具有较好的抗压强度、抗浸泡性、抗冻融性和抗冲击性;磷酸钾镁水泥对Cs的固化能力优越,42 d时Cs+累积浸出分数为38.761×10-3cm,远低于GB 14569.1—2011要求的0.26 cm;固化体物相分析和微观形貌分析表明,Cs Cl会参加水化反应生成Mg Cs PO4·6H2O晶体,固化体结构密实,机械固化效果好。     

煅烧高岭土对磷酸钾镁水泥性能的影响

采用煅烧高岭土等量取代磷酸钾镁水泥(MKPC)的方法研究了煅烧高岭土对MKPC凝结时间、流动度、强度、水化热和早期收缩的影响,并采用X射线衍射仪(XRD)对水化产物进行了分析。结果表明:煅烧高岭土降低了MKPC的凝结时间、流动度和强度,为保证施工时间和良好流动度,其质量分数应控制在10%左右;煅烧高岭土可以降低放热量和放热速率,减少其早期收缩,会影响MKPC的水化过程,但不会影响水化产物的种类和结晶程度。     

海空背景下目标红外辐射特征分析

根据海空复杂背景下点目标的红外特征 ,提出了目标红外特征的一般计算方法 .根据不同的气象条件、不同海域背景 ,计算分析了环境对红外辐射两个大气窗口 ,即 3～ 5 μm和 8～ 12 μm双波段大气透过率的影响 ,并给出了相应结论     

粉末燃料冲压发动机内镁粉尘云层流燃烧模型

对粉末燃料冲压发动机预燃室内镁粉尘云燃烧过程进行了研究,建立了镁粉尘云的一维层流预混燃烧模型。研究表明,镁粉尘云层流火焰传播很稳定,燃烧过程中火焰结构基本不变,燃烧区很薄,而预热区厚度约是燃烧区的2-3倍。粉尘云中镁颗粒的蒸发和气相镁与氧气的均相反应是产生火焰的直接原因,也是火焰得以传播的关键。预热区气相温度升高主要靠燃烧区气体的导热和扩散过来的气相镁与氧气反应释放热量,而预热区颗粒相温度升高主要靠气相对其对流传热。分析了各参数对粉尘云燃烧的影响,颗粒相对浓度对粉尘云燃烧的影响比较复杂,在浓度较低的情况下,增大颗粒相对浓度有利于粉尘云快速燃烧;而在浓度较高的情况下,增大颗粒相对浓度则不利于粉尘云快速燃烧。随颗粒粒径的增加,火焰传播速度减小,火焰温度升高,预热区厚度增大。火焰传播速度和火焰温度随粉尘云初温增加线性增长,预热区厚度随粉尘云初温增加抛物线增长。数值模拟与文献中试验结果的变化趋势相一致。     

基于动力学和扩散分段控制的Mg/H2O反应模型及数值分析

为了数值研究宽广温度范围内Mg/H2O的反应特性,分别建立了考虑部分MgO在液滴表面凝聚的Mg/H2O扩散燃烧模型和基于Arrhenius公式的Mg/H2O反应动力学模型.数值研究了Mg/H2O反应速率在扩散控制和化学动力学控制下随反应条件变化的规律.研究结果表明,Mg液滴扩散燃烧时间计算结果与文献值相符;提高温度和水...     

喷气式飞机尾焰红外辐射的理论计算与仿真

通过对喷气式飞机尾焰流场特点的深入分析,绘制了尾焰的等温线图和各组分等压图.考虑了谱线的碰撞展宽效应和多普勒展宽效应,利用单谱带模型C-G近似法,计算了尾焰各控制体的吸收系数,同时给出了尾焰红外辐射强度的计算方法和步骤.最后,计算了某单管型号的喷气式飞机在非加力状态下的3 μm～5 μm红外辐射强度,并与实际的测量数据...     

空地ARM红外辐射特性研究

深入研究反辐射导弹的红外辐射特征,并建立其红外辐射简化模型.以导弹蒙皮、发动机尾喷管及尾喷焰作为导弹的主要红外辐射源,计算某型反辐射导弹在3μm～5μm和8 μm～12μm波段在不同方向上的红外辐射强度,并针对计算结果进行了分析,可为红外告警系统探测反辐射导弹提供一定理论依据.     

石蜡/硅藻土定型相变材料对磷酸钾镁水泥性能的影响

制备了石蜡/硅藻土定型相变材料(PA/D-PCMs),对其亲水性和热性能进行了表征,同时研究了PA/D-PCMs对磷酸钾镁水泥(MKPC)水化温升、工作性能、抗压强度和水化产物的影响。结果表明:PA/D-PCMs具有疏水性和较高热焓,PA/D-PCMs的掺入能有效降低MKPC水化温升峰值,但同时也降低了MKPC的流动度、凝结时间及抗压强度。为满足施工的可操作性和强度要求,PA/D-PCMs的质量分数应控制在4%左右。PA/D-PCMs不会与MKPC各原料组分之间发生反应生成新的水化产物,但将降低原有水化产物的结晶度。     

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     

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.     

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.     

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.