利用激光诱导炽光研究高压环境下液体燃料层流扩散火焰碳烟分布的二维图像

研究了在高压环境下压力对液体燃料的碳烟的层流扩散火焰碳烟生成的影响。利用激光诱导炽光和消光法相结合的方法,获得了层流扩散火焰的碳烟分布二维图像,测量和分析了正庚烷的层流扩散火焰的碳烟体积分数生成随压力变化的规律。然后,引入特别设计的"滴入式火焰"装置,该设计为两种以上液体混合燃料的层流扩散火焰碳烟生成的测量提供了保障。最后,定量地分析和对比了饱和环状分子结构(环己烷和环己醇)和直链分子结构(正己烷和1-己醇)的液体燃油的层流扩散火焰的碳烟生成趋势,结果表明,环状分子结构燃油的碳烟生成倾向要强于它们对应的线性分子结构的燃油。     

耐高温可溶性聚酰亚胺树脂及其复合材料

制备了2种耐高温可溶型聚酰亚胺树脂(PI-1, PI-2)及其复合材料, 系统研究了树脂的工艺性, 纯树脂固化物的热性能及其复合材料的界面形貌、 介电性能和力学性能. 研究结果表明, 树脂低聚物在极性非质子溶剂中具有良好的溶解性, 且熔体黏度较低, 表明其具有优异的加工性能. 两种树脂固化物在空气中的5%热失重温度均高于550 ℃, PI-1树脂的玻璃化转变温度(T_g)为430 ℃, PI-2树脂的T_g为380 ℃. 石英纤维/PI-1和石英纤维/PI-2复合材料具有较低的介电常数和介电损耗. 碳纤维/PI-1复合材料在420 ℃下的弯曲强度保持率可达62%, 层间剪切强度保持率可达48%, 具有较优异的高温力学性能. 采用普通模压工艺制备了厚度高达45 mm的复合材料制件, 进一步证明这2种树脂具有优异的工艺性.     

涡发生器对质子交换膜燃料电池性能影响

通过数值模拟,研究了涡发生器的形状、间距、攻角和组数对于质子交换膜燃料电池性能的影响。结果表明,在燃料电池阴极流道中安装5组、12 mm间距、攻角为45?的矩形小翼涡流发生器,对于燃料电池性能的提升最为明显,电流密度最高提升了33.3%;电流密度随着涡发生器间距、攻角和组数的增加而增大;涡发生器改善了燃料电池内部的温度、水含量和氧含量分布,有利于积水的排出,且可以明显的观察到涡量大小与电流密度呈正相关。     

$\mathcal{H}_{\infty }$ state estimation for Markov jump neural networks with transition probabilities subject to the persistent dwell-time switching rule

We investigate the problem of $\mathcal{H}_{\infty}$ state estimation for discrete-time Markov jump neural networks. The transition probabilities of the Markov chain are assumed to be piecewise time-varying, and the persistent dwell-time switching rule, as a more general switching rule, is adopted to describe this variation characteristic. Afterwards, based on the classical Lyapunov stability theory, a Lyapunov function is established, in which the information about the Markov jump feature of the system mode and the persistent dwell-time switching of the transition probabilities is considered simultaneously. Furthermore, via using the stochastic analysis method and some advanced matrix transformation techniques, some sufficient conditions are obtained such that the estimation error system is mean-square exponentially stable with an $\mathcal{H}_{\infty}$ performance level, from which the specific form of the estimator can be obtained. Finally, the rationality and effectiveness of the obtained results are verified by a numerical example.     

过渡金属基催化剂降解纤维素应用研究进展

使用廉价过渡金属替代强酸和贵金属催化剂实现纤维素的高效转化是绿色化工的发展方向,一直是众多研究者关注的焦点。本文分别从纤维素热解(包括热解液化和热解气化)、纤维素水解、纤维素氢解和纤维素降解转化为5-羟甲基糠醛(5-HMF)等方面综述了过渡金属基催化剂在纤维素转化过程中的应用,从催化剂类型、反应条件和反应机理等方面介绍了过渡金属基催化剂催化的纤维素转化应用研究进展;最后,指出了催化过程中存在的问题,并对未来的研究方向进行展望。     

车辆线缆瞬态电磁脉冲耦合仿真与抑制技术

瞬态电磁脉冲可通过车辆互联线缆耦合至电子系统内部，造成电子设备受扰甚至损毁，研究瞬态防护器件对电磁脉冲的抑制特性可为车辆电磁防护设计与实施提供有力支撑。本文以发动机电控系统为研究对象，考虑关键金属结构、线缆与电子设备，建立发动机电磁仿真模型，计算获取了瞬态电磁脉冲作用下线缆端口耦合干扰特性；基于电磁脉冲注入方法设计并搭建了瞬态防护器件测试平台，获取了瞬态电压抑制器与压敏电阻两类典型瞬态防护器件的响应时间、钳位电压、尖峰泄露等响应特性；在仿真与测试结果的基础上，选取一型瞬态电压抑制器应用于凸轮轴位置传感器信号线的电磁防护。研究结果表明，该型瞬态电压抑制器对线缆瞬态电磁脉冲耦合干扰抑制能力接近20 dB，置于滤波器前端可有效抑制线缆耦合干扰，保护终端设备。     

A new image encryption algorithm based on the fractional-order hyperchaotic Lorenz system

We propose a new image encryption algorithm on the basis of the fractional-order hyperchaotic Lorenz system. While in the process of generating a key stream, the system parameters and the derivative order are embedded in the proposed algorithm to enhance the security. Such an algorithm is detailed in terms of security analyses, including correlation analysis, information entropy analysis, run statistic analysis, mean-variance gray value analysis, and key sensitivity analysis. The experimental results demonstrate that the proposed image encryption scheme has the advantages of large key space and high security for practical image encryption.     

Word diversity can accelerate consensus in naming game

In this paper,we introduce word diversity that reflects the inhomogeneity of words in a communication into the naming game.Diversity is realized by assigning a weight factor to each word.The weight is determined by three different distributions(uniform,exponential,and power-law distributions).During the communication,the probability that a word is selected from speaker’s memory depends on the introduced word diversity.Interestingly,we find that the word diversity following three different distributions can remarkably promote the final convergency,which is of high importance in the self-organized system.In particular,for all the ranges of amplitude of distribution,the powerlaw distribution enables the fastest consensus,while uniform distribution gives the slowest consensus.We provide an explanation of this effect based on both the number of different names and the number of total names,and find that a wide spread of names induced by the segregation of words is the main promotion factor.Other quantities,including the evolution of the averaging success rate of negotiation and the scaling behavior of consensus time,are also studied.These results are helpful for better understanding the dynamics of the naming game with word diversity.