Preparation and sintering of nano Fe coated Si3N4 composite powders

Fe/Si₃N₄ composite powder was synthesized by the heterogeneous precipitation-thermal reduction process, and then pressed into flakes under a pressure of 10 MPa. Flakes were sintered by pressureless and hot-pressing at 1 600 °C under 0.1 MPa N₂. The chemical composition, phases and microstructure of composite powder and sintered flakes were investigated by energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that the structure of composite powders is Si₃N₄ coated by nano Fe. The crystal phases of sintered flakes by pressureless are Fe(Si) compound, SiC and Si₃N₄. The crystal phases of the sintered samples by hot-pressing are Fe, Fe(Si) compound and Si₃N₄. It is found that crystal phases flakes obtained by pressureless and hot-pressing are very different. Foundation item: Project(50804016) supported by the National Natural Science Foundation of China     

基于扩展OpenC++植入技术研究与实现

本文首先介绍了常用的植入方法并分析了优缺点,重点详细分析了基于扩展OpenC+-植入技术的实现方法。     

氧化铝纳米流体在车用热交换器中的试验研究

研究纳米流体在车用热交换器中的强化传热效果,测试不同纳米粒子体积分数的氧化铝纳米流体在板翅式机油冷却器中的传热和流动特性,并与水、防冻液（乙二醇）及纳米流体基础液体进行对比.试验结果表明,在同一热交换器中,纳米流体的传热系数明显高于其他3种液体.当冷、热侧介质温度为90和120 ℃时,纳米粒子体积分数为5%的纳米流体的传热系数分别比水、乙二醇和基础液体提高6.52%、18.88%和24.62%;当冷、热侧介质温度为120和135 ℃时,体积分数为5%的纳米流体的传热系数比体积分数为1%的纳米流体提高104.72%.在试验条件下,热交换器的换热量随纳米粒子体积分数的增大而增大,但流动阻力并未明显增加,初步证明了纳米流体应用于车用热交换器的可行性.     

Key techniques for predicting the uncertain trajectories of moving objects with dynamic environment awareness

Railway Engineering Science - Emerging technologies of wireless and mobile communication enable people to accumulate a large volume of time-stamped locations, which appear in the form of a...     

基于虚拟技术的单闭环直流调速系统的研究

本文建立了他励直流电动机虚拟模型,通过模型进行仿真算法分析,并利用虚拟技术,在仿真平台上实现仿真,在上位机上显示数据,对单闭环直流调速系统进行可行性研究与优化。仿真做的主要前期工作为模型建立,通过电枢回路方程和动力方程进而推导出电动机的数学模型方程,并对模型进行分析计算。后期工作对所建立的模型进行仿真,并调试出模型数据,进而得到仿真结果。设计的虚拟模型建立在虚拟仿真平台上,利用平台的模拟和数字输入输出端口进行信号的采集和传递,并利用仿真平台强大的内部资源进行运算分析,从而达到期望的研究效果。     

一种基于非残差估计线性表示模型的人脸识别

Dantzig selector利用样本与残差之间的相关向量的L!范数来约束线性表示模型,为了克服传统的线性表示在处理表示残差时依赖于一个对残差特定的似然估计这一缺陷将这样一种处理残差的思路用于人脸识别,提出了一种基于Dantzig selector模型的人脸识别算法,并对Dantzig selector的一种有效的求解方法进行研究。在常用人脸库上实验表明,基于Dantzig selector人脸识别算法在不需要对残差进行估计的情况下也能取得了很好的识别效果。     

Survivability-oriented optimal node density for randomly deployed wireless sensor networks

The survivability is usually critical for wireless sensor networks,which are often deployed in the unattended harsh environment.Lots of technical schemes to improve the survivability depend on the redundant resources of the sensor networks.The amount of resources is usually determined by the node density during the deployment phase.For the random deployment and random node failures,the quantitative relation between the survivability and the node density is studied.Based on the conditional survivability,the node density to meet the required survivability level is presented.Finally,the survivability for unpredictable failures and the optimal node density to maximize the price–performance ratio are also discussed.     

Promotion of hydrogen permeation on metal-dispersed alumina membranes and its application to a membrane reactor for methane steam reforming

A mesoporous membrane for selective separation of hydrogen was prepared usingthe sol-gel method. Some metal salts such as RuCl₃, Pd(NH₃)₄Cl₂, RhCl₃,, and H ₂PtCl₆, were added to the boehmite sol and coated on a porous alumina substrate before firing at 500°C. It was foundthat the permeability of hydrogen and the separation factor for a hydrogen-nitrogen gaseous mixture of these metaldispersed membranes exceeded the limitations of the Knudsen diffusion mechanism. Although the gas permeation through a neat alumina membrane is governed by the Knudsen diffusion, the metals dispersed in alumina membranes were effective in promoting hydrogen permeation. These metaldispersed alumina membranes were also used in a membrane reactor for methane steam reforming at low temperature. In the temperature range of 300 to 500°C, the membrane reactor attained a methane conversion twice as high as the equilibrium value of the packed bed catalytic reactor system as a result of the selective removal of hydrogen from the reaction system.     

The Utility of Information Security Training and Education on Cybersecurity Incidents: An empirical evidence

As recent cyber-attacks have been increasing exponentially, the importance of security training for employees also has become growing ever than before. In addition, it is suggested that security training and education be an effective method for discerning cyber-attacks within academia and industries. Despite the importance and the necessity of the training, prior study did not investigate the quantitative utility of security training in an organizational level. Due to the absence of referential studies, many firms are having troubles in making decisions with respect to arranging optimal security training programs with limited security budgets. The main objective of this study is to find out a relationship between cybersecurity training and the number of incidents of organizations. Thus, this study quantified the effectiveness of security training on security incidents as the first study. This research examined the relationship among three main factors; education time, education participants, and outsourcing with numbers of cybersecurity incidents. 7089 firm level data is analyzed through Poisson regression method. Based on analysis results, we found that the negative relationship between security trainings and the occurrence of cybersecurity incidents. This study sheds light on the role of security training and education by suggesting its positive association with reducing the number of incidents in organizations from the quantitative perspective. The result of this study can be used as a referential guide for information security training decision-making procedure in organizations.

     

基于多目标优化的Holonic-C2组织协作式资源动态调度方法

针对Holonic-C2组织协作式资源的动态调度问题,对战场上的突发事件进行分析,面向任务属性变化、可用平台减少和任务数量变化3类基本突发事件,提出Holonic-C2组织双层结构下针对突发事件的协作机制,在战术决策Holon模块构建两种多目标优化模型,在战役决策Holon模块提出战术Holon协作选择方法.仿真实验表明,所提出的Holonic-C2组织协作式资源动态调度过程能够有效处理单个战术Holon无法处理突发事件的情况,可实现多个战术Holon的协作,验证了所提方法的可行性.