基于星地通信系统的变速率通信质量控制方法

为有效地提高星地通信系统的通信质量,提出了一种改变信息传输速率的方法VCTRM。该方法根据当前星地信道状况自适应地改变调制方式和码元传输速率,克服了采用变调制方式传输时在低信噪比时不能满足系统误比特率的缺陷,同时又解决了采用变码元传输速率在高信噪比时不能提高系统吞吐量的问题。通过Matlab对变调制方式、变码率及VCTRM三种传输方式进行了仿真,结果表明,VCTRM在不同信道状况下均能满足系统对误比特率(BER)的要求,且获得的系统吞吐量明显高于其他方法。     

Nonlinear state estimation for rigid-body motion with low-pass sensors

In this paper, we consider the state estimation problem for the nonlinear kinematic equations of a rigid body observed under low-pass sensors. The problem is motivated from a walking robot application where inclinometers and gyros are the sensors used. We show that a non-local high gain observer exists for the nonlinear rigid-body kinematic equations and that it under a small angle assumption is possible to use one inclinometer only to estimate two angles.     

CSMA/CD的建模和性能分析

文章对CSMA／CD（载波侦听多址访问／冲突检测）网络建立分析模型,主要对其时延、吞吐量和介质利用率进行了性能分析,分析了该三项性能指标随网络参数的变化。最后总结出了CSMA／CD网络的优缺点。     

Linux下视频流多播速率控制方法的设计与实现

针对目前流媒体中视频数据发送速度难以控制的问题,以当前广泛使用的MPEG2视频解码模型为例,设计并实现了一种Linux下视频流多播速率控制方法。这种方法能够有效的控制服务器视频数据的发送速率,具有占用服务器资源少,适应各种网络要求的优点。经Linux平台验证结果表明,传送视频数据的网络速度平稳,未出现视频数据溢出现象,可以得到良好的视频效果,具有很好的实用价值。     

MPEG—4视频的实时传输

MPEG－4是一个全新的多媒体标准,采用了基于对象和模型的编码方法。简要总结了MPEG－4视频编码的各种特点,对网络实时传输MPEG－4视频提出了各种评估标准,并针对面临的困难介绍了相应的解决方案。     

一种改进的基于WinPcap的快速抓包方法*

根据WinPcap的抓包原理和高速网络环境对网络抓包性能的要求,提出了一种改进的快速抓包方法－FHW法,并且在VC++ 6.0编译器中实现了该方法。试验结果表明,在高流量网络环境中,与传统的抓包方法相比,FHW法能显著地提高抓包性能、降低丢包率。     

On the rate of heterogeneous catalytic reactions with ionic intermediates

A facile way to compute the rate law of a catalytic reaction with ionic intermediates is proposed, based on the theory of complex reactions. When the ionic nature of intermediates is taken into account it is necessary to add balance equations which correspond to the electroneutrality of the catalyst. Several mechanisms of the olefin hydrogenation were considered as examples.     

高精度光纤陀螺组件标定方法

为了提高光纤陀螺组件的标定精度,从三轴惯导测试转台技术指标入手,根据惯导测试转台定位精度高的特点,设计了六位置静态分立式标定方案.通过设计一定的标定路径,利用地球转速和当地地理纬度,激励出陀螺的标度因数、安装误差和零位等12个参数,新的标定方案避免了标度因数和安装误差对零位的影响.对自研光纤陀螺捷联惯导系统在三轴惯导测试转台进行传统标定和六位置静态分立式标定,并将标定结果用于静态导航实验,多次实验结果表明,与采用传统标定结果的导航定位误差相比,采用六位置静态分立式标定结果的导航定位误差显著降低.     

Fire fighting and its influence on the body

Working conditions for fire fighters can be described according to the environment temperature and the incident radiant heat flux. Measurements for this study in buildings for fire fighting training have shown that fire fighters are typically exposed to radiant heat fluxes of between 5 and 10 kWm ^-2 during this kind of exercise. The heat load can nevertheless be much higher. In one case, 42 kWm ^-2 was measured. The temperatures reached between 100 and 190°C at 1 m above ground, going up to 278°C in one case. Human trials have been performed with 17 fire fighters. After exercises (about 15 min) in a heated room, the mean core temperature of the fire fighters rose by 0.6°C with a surrounding temperature of 31°C and 1.0°C with 38°C. The sweat production varied from 0.7 to 2.1 lh ^-1; 16% to 45% of sweat remained in the clothing layers. During the exercises in the training buildings, a mean of 48°C has been measured between fire fighters' clothing and workwear. These conditions lead to an increase of the relative humidity in all the jackets up to 100%. When the fire fighters came out of the fire, the humidity remained at this level in the PVC coated jackets while it was in some cases strongly reduced in breathable jackets.     

基于CAN总线的煤矿井下安全监测系统浅析

煤矿生产的特殊性,导致其监测监控系统呈跳跃式发展态势。本文浅要介绍了基于CAN总线的煤矿监测系统,并简要分析了基于CAN总线的煤矿安全监控系统的结构框图。