(BaTiO3)1-x + (Co0.5Ni0.5Nb0.06Fe1.94O4)x nanocomposites: Structure,morphology, magnetic and dielectric properties

Two phase-based nanocomposites consisting of dielectric barium titanate (BaTiO₃ or BTO) and magnetic spinel ferrite Co_0.5Ni_0.5Nb_0.06Fe_1.94O₄ (CNNFO) have been synthesized through solid state route. Series of (BaTiO₃)_1-x + (Co_0.5Ni_0.5Nb_0.06Fe_1.94O₄)_x nanocomposites with x content of 0.00, 0.25, 0.50, 0.75, and 1.00 were considered. The structure has been examined via X-rays diffraction (XRD) and indicated the occurrence of both perovskite BTO and spinel CNNFO phases in various nanocomposites. A phase transition from tetragonal BTO structure to cubic structure occurs with inclusion of CNNFO phase. The average crystallites size of BTO phase decreases, whereas that for the CNNFO phase increases with increasing x in various nanocomposites. The morphological observations revealed that the porosity is highly reduced, and the connectivity between grains is enhanced with increasing x content. The optical properties have been investigated by UV−vis diffuse reflectance spectroscopy. The deduced band gap energy (E_g) value is found to reduce with increasing the content of spinel ferrite phase. The magnetic as well as the dielectric properties were also investigated. The analysis showed that CNNFO ferrite phase greatly affects the magnetic properties and dielectric response of BTO material. The obtained findings can be useful to enhance the performances of magneto-dielectric composite-based systems.     

工科院校《大学计算机基础》模块化教学研究

鉴于我院大学计算机基础课程教学不适应形势发展的客观问题,提出了模块化教学思想的理论内涵和模式设计原则,并具体构建了大学计算机基础课程模块化教学模式。通过实验班测试,该教学模式取得较好教学效果。     

Dispersion Constraint Based Non-negative Sparse Coding Model

Based on advantages of basic non-negative sparse coding (NNSC) model, and considered the prior class constraint of image features, a novel NNSC model is discussed here. In this NNSC model, the sparseness criteria is selected as a two-parameter density estimation model and the dispersion ratio of within-class and between-class is used as the class constraint. Utilizing this NNSC model, image features can be extracted successfully. Further, the feature recognition task by using different classifiers can be implemented well. Simulation results prove that our NNSC model proposed is indeed effective in extracting image features and recognition task in application.     

Topology optimization of a coupled thermal-fluid system under a tangential thermal gradient constraint

This paper presents a continuous adjoint approach for topology optimization of a coupled heat transfer and laminar fluid flow system under tangential thermal gradient (TTG) constraints. In this system, the thermal gradient along the boundary of multiple heat sources needs to be controlled. The design goals are to minimize the temperature of the domain, the fluid power dissipation and the TTG along the boundary of the heat sources. The first two goals are combined into a single cost function with weight variables. The TTG is constrained in one of two forms, an integral form where the integral of TTG squares along the boundaries of heat sources is constrained, or a point-wise form where TTG is constrained point-wise. A gradient-based approach is developed to obtain the optimized designs. A salient feature of our approach is the use of the continuous adjoint approach to derive gradients of both the cost function and two forms of TTG constraints. Numerical examples demonstrate that the continuous adjoint approach leads to successful topological optimization of the constrained thermal-fluid system. The use of TTG constraint is effective in lowering the TTG along the heat source boundaries. The resulting designs exhibit clear black/white contrast.     

基于J2ME的人力资源管理系统的设计

基于J2ME技术、MVC模式,在手机客户端开发了人力资源管理系统,实现了企业级人力资源管理的移动办公。系统分为服务器端和客户端两部分,服务器端负责接收客户端请求并处理,客户端接收用户请求,并通过MVC模式使得界面和模型数据分离,便于维护。     

基于WinCC Flexible和PLC的高压发泡机控制系统设计

设计以西门子S7-300PLC和MP277 Touch触摸屏为控制核心、具有多种工作模式选择的高压发泡杌控制系统,解决了注射流量比例的精确控制、自动补料、故障报警、压力控制、工艺过程实时监控等问题,实践证明该系统稳定、可靠、易于操作,满足了系统的要求.     

Chord中路由公平性分析及改进

P2P系统中分配及检索目标的路由占据了大多数开销,通过公平性参数(FI)推导出影响路由公平性的因素.根据结论在没有增加任何负载的情况下对Chord finger选择算法进行改进,通过公平性参数(FI)及仿真对改进前后的Chord的公平性进行评估,结果表明改进后的EChord性能有较大提高.     

煤矿调度电话录音上传及远程回放的实现

文章介绍了煤矿现有的调度电话录音系统,设计了调度电话监控上传系统来实现录音文件的上传和调度电话查询系统实现录音文件的查询和远程回放。系统通过输入查询取代了传统的人工查询的工作方式,大大节约了生产调度成本,同时为煤矿人员考勤和定位也提供了准确依据。由于其配置容易、操作方便、实用性高,因此具有很好的维护性和推广性。     

基于JMS的安全通信模型研究与设计

面向消息中间件(MOM)的安全性是目前的一个研究热点,目的是设计确保数据传输完整性的安全机制.通过分析JMS的两种消息通信模型,针对它在安全性方面存在的不足,引入了数字签名和加密技术,提出了一个基于身份验证和混合加密的可扩展安全通信模型,并详细介绍了模型的各个组成部分.模型的基本思想是使用数字签名的信息进行双向身份认证,并且在消息传输的过程中,利用双方协商的会话密钥和非对称加密技术对消息进行加密.最后构建了原型系统对模型进行了验证,实验结果表明此模型提高了基于JMS的系统的安全性.