A distributed expansible authentication model based on Kerberos

There is a potential server bottleneck problem when the Kerberos model is applied in large-scale networks because the model uses centralized management. To enlarge its application scope, researchers must consider how to build a trust relation among those Kerberos servers located on different isolated domains, but have not provided a way to prevent the potential bottleneck that can occur with Kerberos servers. With the development of across-domain authentication techniques, the local server bottleneck problem has not been alleviated; in fact, it has become more serious.Adopting the rigorous binary tree code algorithm, we present an authentication model based on Kerberos. Compared with similar models, our model has several advantages. First, it overcomes the potential server bottleneck problem and can balance the load automatically. Second, it can process across-domain authentication and enlarge the authentication boundary. Finally, its authentication path is short, with no more than two Kerberos servers being involved when authenticating a user.     

Design of distributed compliant micromechanisms with an implicit free boundary representation

In this paper, a parameterization approach is presented for structural shape and topology optimization of compliant mechanisms using a moving boundary representation. A level set model is developed to implicitly describe the structural boundary by embedding into a scalar function of higher dimension as zero level set. The compactly supported radial basis function of favorable smoothness and accuracy is used to interpolate the level set function. Thus, the temporal and spatial initial value problem is now converted into a time-separable parameterization problem. Accordingly, the more difficult shape and topology optimization of the Hamilton–Jacobi equation is then transferred into a relatively easy size optimization with the expansion coefficients as design variables. The design boundary is therefore advanced by applying the optimality criteria method to iteratively evaluate the size optimization so as to update the level set function in accordance with expansion coefficients of the interpolation. The optimization problem of the compliant mechanism is established by including both the mechanical efficiency as the objective function and the prescribed material usage as the constraint. The design sensitivity analysis is performed by utilizing the shape derivative. It is noted that the present method is not only capable of simultaneously addressing shape fidelity and topology changes with a smooth structural boundary but also able to avoid some of the unfavorable numerical issues such as the Courant–Friedrich–Levy condition, the velocity extension algorithm, and the reinitialization procedure in the conventional level set method. In particular, the present method can generate new holes inside the material domain, which makes the final design less insensitive to the initial guess. The compliant inverter is applied to demonstrate the availability of the present method in the framework of the implicit free boundary representation.     

基于神经网络的光电系统空中目标威胁估计

结合光电干扰武器系统的工作过程,对影响目标威胁评估的各种因素进行了分析,讨论了常用威胁评估方法的缺点和不足,提出了基于神经网络的空中目标的威胁估计算法,利用神经网络良好的自适应能力和自学习能力,通过样本数据训练,确定各个因素之间的非线性复杂关系,并通过示例介绍了目标威胁值的解算过程;与层次分析法进行了比较,结果表明,神经网络可以很好地逼近各个因素之间的权重关系,提高了空中目标威胁估计算法的准确性和适应性。     

高性能光纤通道上实现1553B协议的研究

当前机动平台上广泛使用的1553B协议越来越不适应数据传输的需求增长,需要找到一个1553B协议在光纤通道上实现的方法,以获得光纤通道所具有的优势性能;1553B协议原设计实行在线缆上,因此就必须实现其到光纤通道的转换接口;1553B协议使用的是命令/响应模式,并以消息、字为传输单位,而光纤通道则是以交换、序列、帧为传输单位,对两者传输单位的映射和传输机制进行设计,完成1553B协议在光纤通道上的实现;最终通过测试验证了设计的正确性,经过转换的协议可以支持原有协议的功能,并且在性能上达到光纤通道提供的传输速率。     

超声波检测的AE传感器设计与实现

针对目前国内用于结构健康监测的无线传感器频带不够宽,不能检测声波信号的现状,提出了一种可以检测声波信号的新型无线压电传感器的设计和制作方法;研究了ZigBee协议栈内容,设计和实现了体积小、功耗低的无线传感器节点和基站的硬件和软件程序部分,并对制成的传感器进行初步测试;试验表明它有较好的精度,频带更宽,可以用于较高频段的结构健康监测,具有广阔的应用前景。     

基于Labwindows/CVI雾化试验台测控系统设计

燃料的雾化状态对燃烧性能有很大影响,为了研究煤油等液态燃料在不同功率和空燃比下的雾化特性,对液态燃料雾化特性的实验测量进行了研究,设计了一套自动化的雾化实验台;试验台测控系统软件基于LabWindows/CVI编写,可实现参数设置、设备检测、数据采集和数据处理等功能,软件架构采用多线程编程方法,能有效防止采集过程中进行其他操作引起的数据丢失,并保证用户操作的及时响应;为了提高系统的可靠性和稳定性,程序中设计了操作顺序和异常情况处理功能;系统具有开发周期短、稳定、使用方便、易升级的特点。     

基于LabVIEW的EAST纵场电流实时测控系统

EAST纵场超导磁体是用来产生纵向磁场约束等离子体使其稳态运行的重要装置,其中的电流控制及失超检测对于保证托克马卡装置正常运行是非常重要的;通过对传统的纵场电流测控系统进行分析,提出了使用LabVIEW及相应硬件实现托克马卡纵场电流测量与控制,并详细介绍了系统的硬件结构、软件设计和实现;通过仿真和实际使用,验证了该系统稳定可靠,大大减小了系统长时间运行过程中引起的纵场电流漂移,在可维护性、集成度、人机界面和易操作性上都有了较大的提高。     

基于小波区域分解的头部三维模型重构

从二维图像还原三维形状的头部三维模型重构的实验中发现,配准三幅图像中所有点的计算量太大,于是提出了基于小波区域分解的方法;小波变换能够多尺度地从粗到精将头部地分离成头形、眼、鼻、嘴、痣、纹理等不同层次的特征区域,按精度对特征区域重建,减小配准时的搜索范围;对每个区域,使用灰度配准法则,然后用BP网络计算点深度,重构特征;这样精简了配准点数目,将处理速度提高了3～4个数量级。实验表明,该方法适应性良好,精度能达到1mm内。     

基于模糊PID控制的循环水自动加药与监测系统

工业生产中加强对循环水质的处理变得越来越重要,在对循环水系统存在问题进行分析后,利用西门子S7-200 PLC和WinCC组态软件开发设计了新型工业循环水水质在线监测与自动加药系统,解决了传统控制难以保证加药量准确与均匀的问题;针对加酸中pH值过程具有非线性、时变和大时滞等特点,采用了以控制人员的经验为基础的模糊控制方法,结果表明pH值控制误差完全满足系统要求;系统已在化工厂中投入运行,经实践证明,该系统人机交互性好、可靠性高、抗干扰能力强,满足了现代工业循环水质监管的要求。     

轴向受力梁结构线弹性碰撞问题求解

研究了质点对轴向受力的Euler-Bernoulli梁结构任意位置的横向撞击问题.把撞击体系简化为质量-弹簧体系模型,采用积分变换方法,对撞击体系的控制微分方程、边界条件和连续条件进行Laplace变换,在频域内求得其解析表达式,然后采用Crump逆变换方法进行数值反演,得到时域内的各种动力响应.数值算例给出了撞击力、弯曲应力和剪力随时间变化的曲线,通过与有限元比较验证了本方法的正确性.最后研究了撞击位置、轴向压力、撞击质量、撞击速度和柔度系数等参数对撞击力的影响,得出了一些有用的结论.