高压条件下伴随化学反应两相流动的数值模拟

建立了高装填密度火药床在高压条件下的一维两相流体力学方程组，探讨了两相自由射流边界的处理方法，并对其进行了数值求解．揭示了对流燃烧过程的燃烧机理．数值结果与实验测得的压力曲线和火焰阵面曲线有较好的一致性     

Optimal Performance in Tracking Stochastic Signal Under Disturbance Rejection

The analysis method of optimal tracking performance is proposed for multiple‐input multiple‐output (MIMO) linear time‐invariant (LTI) systems under disturbance rejection. An H₂ criterion of the error signal between the output of the plant and the reference signal is used as a measure for the tracking performance. Spectral factorization is applied to obtain the optimal solution of the system tracking error. The explicit expressions are derived for this minimal tracking error with respect to random reference signals under disturbance rejection. It is shown that the nonminimum phase zeros, the zero direction, the unstable poles, the pole direction of a given plant, statistical characteristics of the reference input signal, and disturbance signal have a negative effect on a feedback system's ability to reduce the system error with disturbance rejection. The results show that the optimal tracking performance will further be damaged because of disturbance rejection. Some typical examples are given to illustrate the theoretical results.     

无双线性对的无证书两方密钥协商方案*

近几年来,有许多无证书密钥协商方案相继被提出,它们都需要双线性对运算,而且它们中大部分不能抵抗密钥泄露伪装攻击和临时私钥泄露产生的攻击。2009年,Lippold等人提出一个可证安全无证书密钥协商协议,但该协议需要较大计算量。为了解决上述问题,给出了一个新的无双线性对运算无证书两方密钥协商方案,并分析了它的安全属性,只要每方至少有一个未泄露的秘密,那么新方案就是安全的。因此,即使密钥生成中心知道双方的临时私钥,新方案也是安全的。与Lippold等人的协议相比,新方案降低了计算复杂度。     

强化两相混合的超临界技术制备聚乳酸微粒

针对商品化聚乳酸微球粒径分布较宽难于适用气溶胶给药要求的不足,采用水力空化混合强化超临界流体辅助雾化技术(SAA-HCM)制备聚乳酸(PLA)超细微粒.该技术主要特点是通过在超临界流体和液相进料处引入水力空化混合器,强化两相间的混合.考察SAA-HCM过程混合器压力、温度、沉淀器温度、进料中CO2与液体溶液质量流量比和溶液质量浓度等操作参数对微粒形态和粒径分布的影响,成功制备出球形度较好,粒径分布较窄(1～3μm)的PLA微球.经X射线衍射(XRD)分析和差示扫描量热(DSC)分析显示,与原料PLA相比,微球晶型及热曲线变化不大,但结晶度下降.同时把操作参数与相行为进行关联,探讨了影响颗粒形貌的机理.对比超临界流体辅助雾化法(SAA)的实验结果表明:水力空化的引入能有效强化混合器内的两相传质,混合更好,能制备出适用于气溶胶给药要求的超细微粒.     

Modal analysis of human body vibration model for Indian subjects under sitting posture

Need and importance of modelling in human body vibration research studies are well established. The study of biodynamic responses of human beings can be classified into experimental and analytical methods. In the past few decades, plenty of mathematical models have been developed based on the diverse field measurements to describe the biodynamic responses of human beings. In this paper, a complete study on lumped parameter model derived from 50th percentile anthropometric data for a seated 54- kg Indian male subject without backrest support under free un-damped conditions has been carried out considering human body segments to be of ellipsoidal shape. Conventional lumped parameter modelling considers the human body as several rigid masses interconnected by springs and dampers. In this study, concept of mass of interconnecting springs has been incorporated and eigenvalues thus obtained are found to be closer to the values reported in the literature. Results obtained clearly establish decoupling of vertical and fore-and-aft oscillations.     

一种适用连续不确定XML数据的索引

针对连续不确定XML数据概率阈值范围查询,提出一种新的CUXI索引树。该索引树的构建方法是借鉴U树对空间数据自顶向下递归构建索引树的思想,将连续不确定XML文档中具有相同父亲的叶子节点构建二维数据矩形,在聚类的基础上来构建相应的CUXI索引树,其中叶子节点存储连续不确定数据辅助信息。为了提高查询效率,对连续不确定数据制定了过滤策略,通过遍历索引树过滤掉不满足查询范围的子树。理论和实验结果表明,此索引技术可提高查询处理的性能。     

烧结烟气氨法脱硫塔气液两相流数值模拟

为研究脱硫塔内的气液分布情况对脱硫效率的影响,选用FLUENT作为计算工具,以烧结烟气氨法脱硫塔作为研究对象,对塔内气相湍流采用Euler方法描述,对喷淋液滴采用Lagrange颗粒轨道模型描述,研究烟气入口倾角和入口距离浆液池液面高度对脱硫塔内气液两相流场分布的影响,并对脱硫塔的关键参数取值给出建议.     

Novel ultra‐compact two‐dimensional waveguide‐based metasurface for electromagnetic coupling reduction of microstrip antenna array

A novel ultracompact two‐dimensional (2D) waveguide‐based metasurface is proposed herein and applied for the first time to reduce mutual coupling in antenna array for multiple‐input multiple‐output applications. The unit cell of the proposed 2D waveguide‐based metasurface is ultracompact (8.6 mm × 4.8 mm, equal to λ₀/14.2 × λ₀/25.5) mainly due to the symmetrical spiral lines etched on the ground. The metasurface exhibits a bandgap with two transmission zeros attributing to the negative permeability in the vicinity of magnetic resonance and the negative permittivity in the vicinity of electric resonance. Taking advantage of these two features, a microstrip antenna array is then designed, fabricated, and measured by embedding an 8 × 1 array of the well‐engineered 2D waveguide‐based metasurface elements between two closely spaced (9.2 mm, equal to λ₀/13.3) H‐plane coupled rectangular patches. There is good agreement between the simulated and measured results, indicating that the metasurface effectively reduces antenna mutual coupling by more than 11.18 dB and improves forward gain. The proposed compact structure has one of the highest reported decoupling efficiencies among similar periodic structures with comparable dimensions. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:789–794, 2015.     

面向航空电子的分区操作系统

伴随新一代航空电子的综合化趋势,机载软件对机载操作系统提出新的要求.通过管理系统的软硬件资源,包括内存、CPU、通信等,机载操作系统将各类机载软件融合在同一个CPU上,实现综合化.该文给出一种面向航空电子的分区操作系统的实现框架,支持二级调度,对于各类机载软件实施分区调度,并且分区的运行互不干扰,保证了分区的安全性.