孔缝箱体屏蔽效能电磁拓扑分析模型

基于Robinson等效电路法,提出了一种电磁拓扑模型,用于任意平面波入射条件下的孔缝箱体屏蔽效能分析。该模型将孔缝及其所在平面等效为连接自由空间(等效为特性阻抗为Z0的传输线)和剩余箱体(等效为特性阻抗为Zg的短路矩形波导)的二端口网络,并通过等效电路模型计算了该二端口网络的散射矩阵,进而推导出描述孔缝耦合的广义BLT(Baum-Liu-Tesche)方程。设计了4组实验模型用于电磁拓扑理论(EMT)算法、Robinson算法和CST软件的对比分析,仿真结果证明:EMT算法较Robinson算法具有更高的准确率,尤其是在高频域;EMT算法继承了Robinson算法简洁高效的特性,且能直观反映箱体参数、孔逢参数对屏蔽系数的影响,较CST软件实用性更强。     

Experimental study on supersonic film cooling on the surface of a blunt body in hypersonic flow

The experimental study focuses on the heat flux on a double cone blunt body in the presence of tangential-slot super- sonic injection into hypersonic flow. The tests are conducted in a contoured axisymmetric nozzle with Mach numbers of 7.3 and 8.1, and the total temperature is about 900 K. The injection Mach number is 3.2, and total temperature is 300 K. A constant voltage circuit is developed to supply the temperature detectors instead of the normally used constant current circuit. The schlieren photographs are presented additionally to visualize the flow and help analyze the pressure relationship between the cooling flow and the main flow. The dependence of the film-cooling effectiveness on flow parameters, i.e. the blow ratio, the convective Mach number, and the attack angle, is determined. A semi-empirical formula is tested by the present data, and is improved for a better correlation.     

The economics of social computing: Some preliminary findings on healthcare organizations

Large-scale organizations have used social computing platforms for various purposes. This research focuses on how hospitals utilize these platforms to attract potential customers (which represents the “extensivity” of a social computing platform) and generate interests in specific topics (which represents the “intensivity” of a platform). Specifically, we examine the effects of size of a hospital (or “size”) and the time that the social computing platform has been in existence (or “time”) on extensivity and intensivity. Our findings show that time is a significant variable on both dimensions; whereas size affects intensivity under certain conditions. We discuss the implications of these findings, and set the stage for future research.     

Freestanding conducting polyaniline film for the control of electromagnetic radiations

Electromagnetic interference is pollution generated due to dense nature of circuitry in electronic devices and is required to be control at its source. Polyaniline is an environmentally stable conducting polymer which can be cast as thin film, which can replace the corrosive metals as a shield for the control of electromagnetic radiations. In this communication we discuss our results on the preparation of flexible freestanding conducting polyaniline film of varied thickness using either p-toluenesulphonic acid (PTSA) or camphor-10-sulphonic acid as a primary dopant and 4-chloro-3-methyl phenol (CMC) as a secondary dopant. The resulting films were characterized by conductivity, scanning electron micrograph and shielding effectiveness measurements (SE). The SE measurements were carried out using co-axial transmission line method in the frequency range of 0.1–1000 MHz. We noticed that only the change of 2% in the shielding effectiveness of these films over the period of 3 years indicating the environmental stability of polyaniline films.     

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??We establish best-possible supremum bounds of copulas with the degree of non-exchangeabilityt=3/4, t=3/5 and t=3/6=1/2, and study the structures of these sets of copulas. The volumes between the upper and lower bounds are calculated to illustrate that the supremum bounds are specific practical and effective in narrowing the Fr\'{e}chet-Hoeffding bounds.     

Features of the Distribution of Aluminum in Mordeniteclinoptilolite Catalysts for the Hydroisomerization of n-Hexane

The content of tetrahedral, extraskeletal, and ion-exchanged aluminum in zeolites consisting of natural and decationized forms of mordeniteclinoptilolite rocks after acidic activation were studied. The results were compared with acidity and catalytic activity properties of modified samples of rocks and synthetic mordenite in the hydroisomerization of n-hexane.     

磁场对超细镍粉的磁性能及电磁屏蔽性能的影响

分别在水和乙二醇溶液中,于搅拌条件下采用液相还原法制备超细镍粉,研究反应过程中外加磁场对产物形貌及性能的影响。结果表明,水中得到的产品为刺球状颗粒,外加磁场对产物的形貌影响不大;乙二醇中得到类球形颗粒,加磁场后得到短链状结构。外加磁场使超细镍粉的饱和磁化强度值降低而矫顽力值升高。将水体系中得到的超细镍粉作为导电填料制备电磁屏蔽涂料,结果发现外加磁场条件下得到的超细镍粉/树脂复合涂料在130 MHz～1.5 GHz频段内具有更好的电磁屏蔽性能。     

探月飞行器效能评估研究与实践

航天器飞行效能评估是整器级测试验证以及在轨飞行结果评价中不可或缺的重要环节,针对我国探月三期月地高速再入返回飞行试验,提出了一种基于任务剖面的航天器飞行效能评估方案;提取7个任务剖面、17个约束条件,建立面向月地再入返回过程的指标评估体系;通过定量、定性指标量化计算、权重系数层次分析法计算各任务剖面的能力度量值,解决了系统目标完成能力不易定量描述的难题,实现了对月地转移段、大气层外自由飞行段、再入段、跃出段等过程自主飞行能力的科学定量评估,对后续月球无人采样返回、火星探测等探测器系统的效能评估具有一定参考意义;该方法已应用于月地高速再入返回飞行器系统。