Heat spreading in a thin longitudinal fin

In view of the trend towards higher power densities in ever shrinking geometries, understanding heat spreading fundamentals is gaining importance. In this paper heat spreading in thin longitudinal geometries is considered. This geometry is of practical interest in one-dimensional Cartesian geometries. A characteristic length is derived and it is shown that this has physical significance for the distance that heat spreads, and for the total amount of heat cooled away. Furthermore, it is investigated when “thin” is a viable assumption. The use of the characteristic length is illustrated for the case of a line source cooling to a plate and for the case of the fins of a plate heatsink. The results are compared to numerical simulations. The work is an extension of the authors' earlier work on heat spreading in infinite longitudinal geometries and heat spreading in infinite and finite circular geometries.     

基于热释电红外传感器的火灾探测系统设计

介绍了热释电红外传感器的结构、工作原理及特点;设计了一个基于此类传感器的红外火灾探测系统;运用BP神经网络分析了火灾识别算法;促进了消防技术的发展.     

火控观瞄系统仿真的多目标定位与跟踪算法

火控观瞄系统的仿真是以飞行模拟器中相对应的火控仿真系统为核心的训练功能,研究在火控观瞄仿真中多目标的定位和跟踪算法。算法以目标和本机的三维空间计算为基础,通过对动态数据的误差分析,利用支持向量回归的机器学习算法对目标跟踪和预测。算法目前已被应用于实时训练,解决了目标定位和跟踪仿真的实际攻击训练难题。     

基于BP神经网络的某型飞机火控系统故障诊断

根据某型飞机火控系统的特点,给出了BP神经网络数学模型及其学习算法,在此基础上以某型飞机火控系统作为为被诊断对象,运用BP神经网络数学模型及其学习算法对其进行故障诊断。诊断结果表明BP神经网络不仅能识别出样本自身的故障,而且能准确诊断出样本以外数据故障,提高某型飞机火控系统一线维修保障效率。     

高速实时的一种邮件蠕虫异常检测模型

提出了一种基于带泄漏的积分触发测量方法的电子邮件蠕虫异常检测方法,用来检测邮件蠕虫在传播过程中的流量异常。根据邮件流量所表现出的明显的日周期特性和周周期特性,首先计算出当前邮件流量和历史邮件流量的最小Hellinger距离,通过带泄漏的积分触发方法把邮件流量的Hellinger积累起来,从而把邮件蠕虫在传播过程中没有明显流量特征的慢速酝酿阶段的异常特征进行积累,达到在其进入快速传播期之前检测出异常的目的。检测过程只需要检查邮件的流量信息,因而适合大规模高速网络的异常检测。     

基于WCDMA和太阳能的森林火灾监测系统设计

设计了一种基于WCDMA网络和太阳能技术的森林火灾监测系统设计,实现对森林的远程实时监测、实时数据存储、历史数据查看、超标报警等功能.介绍了系统框架,硬件设计方案和软件设计方案,对关键硬件组成部分和软件设计流程做了阐述,结合模拟仿真的实时数据和图像对终端测试情况进行了说明.     

烟雾浓度及粒径的激光探测实验研究

烟雾是火灾的前兆和伴随产物,是火灾过程中的重要物理现象。烟雾浓度和平均粒径是烟雾的两个重要特性参数,是早期火灾探测的基础。本文对激光与烟雾相互作用进行了具体分析,提出了一种基于激光消光法和角散射法,同时探测烟雾的浓度和平均粒径的方法。本方法可用来进行早期火灾的探测报警,能克服传统的光电感烟探测技术存在的缺点,大大提高火灾探测的可靠性和灵敏度。     

A multi‐access method for BPL based on orthogonal pulse division multiplexing,barker‐code‐based spectrum spreading and orthogonal frequency division multiplexing

A highly efficient multi‐access scheme of broadband power line (BPL) communication, named as OFDM‐BPS‐OPDMA, is proposed based on the Orthogonal Pulse Division Multiplexing Access (OPDMA), Barker‐code‐based Spectrum Spreading (BSS) and Orthogonal Frequency Division Multiplexing (OFDM) method. The orthogonal pulses are generated by using the eigenvectors of Hermitian matrix. At the same time, a specific pulse will be allocated to every user of the communication system. The transmitting data are first modulated by OFDM. Then, it is processed with OPDMA and BSS. Finally, the data is sent to the power line channel. On the receiving side, the data is processed with BSS demodulation, OPDMA demodulation and OFDM demodulation, and the receiving data for each user is acquired. Because of the orthogonality between these pulses, the multi‐user interference could be eliminated; when BSS is used, the waveform restoration is enhanced. Meanwhile, with the help of OFDM, the multi‐path interference is mitigated. Particularly, all users can share the resources of time and spectrum without interfering with others, and get excellent reliability in the concerned scheme. When OFDM is used, the sub‐carriers may be allocated dynamically, and the legal radio frequency band could be shunned by sharing the common bandwidth with other communication systems. Copyright © 2009 John Wiley & Sons, Ltd.     

三维LDV测量火旋风的实验研究

应用三维激光多普勒测速计LDV（Laser Doppler Velocimeter）系统,通过观察和测量火旋风的卷吸的现象,对火旋风速度场进行了有效的测量,获取了火旋风的径向速度、切向速度和轴向速度等特件参数,深化认识火旋风的卷吸机理;用热成像和热电偶方法采集得到了火旋风的温度场的结构和形状。为下一步进行火旋风卷吸的现象的实验研究打下了良好的基础。     

基于虚拟实现的矿井智能消防系统设计

考虑到矿井安全事故频发,煤矿企业提出可靠的装备、实用的技术和称职的人员等要求来保障生产安全.主要讨论采用系统集成和虚拟实现技术,设计具有智能虚拟交互控制和近似实战条件下的场景模拟培训功能的消防集成系统.该系统满足企业的实际需求,具有设计的必要性和应用的可行性,能有效地帮助企业提升安全水平.