测定地下水流向的多计数管探头的研制

多计数管流向探头;;单孔;;总流向;;局部流向;;滤水管 掌握地下水的流动方向,有助于研究地下水的运动规律。利用放射性单孔法可以测定地下水流某一点流动方向。 应用放射性指示剂在单孔中测定地下水流向的方法由奥地利的梅尔霍费于1963年首先提出,1964年波兰的鲍劳斯齐克等把这种方法用于现场测量。放射性单孔流向测量方法有若干种,其原理基本相同,仅测量装置结构有区别,早期有单管旋转式探头。我们从1983年7月     

叠前地震数据的规则化

本文通过对动校正前积分法DMO原理的探讨，在借鉴Canning(1996)提出的利用DMO实现三维数据规则化的方法和Biondi(1998)提出的三维叠前地震数据方位角校正方法的基础上，从方位角校正的角度入手，利用DMO和DMO^-1相结合的处理流程对地震数据进行规则化，以得到新的规则的观测系统下具有所需特定方位角的观测数据。此方法可用于解决叠前地震数据道插值、陆上地震勘探中不规则观测数据的规则化和海上地震勘探中的羽状现象校正等问题，可将已有地震观测数据转变为特定观测系统的叠前地震数据，以便于某些处理方法的应用。此方法原理简单并具有广泛的适用性。     

Performance Evaluation of Packet Mobile Communications through Level Crossing Analysis

In this paper the performance of a packet mobile radio network is studied inthe presence of shadow fading outage intervals.Under quite general assumptions for the medium access protocol,the probability mass function of the sequence of packets that may be lostdue to an outage interval is derived. It is seen that long sequences of lostpackets are likely to occur for typical values of the mobile speed andshadowing correlation parameters.For delay constrained sources, e.g., voice, the analysis is mainly focused atderiving the probability function of the sequence of dropped packetsand the probability of dropping. For data sources, the delay statistic isalso derived. In the latter case, the effect of finite buffer length isaddressed. Simulation is used to verify the accuracy of approximations introduced in the analysis.     

A Novel UWB Pulse Shape Modulation System

In this paper novel modified Hermite polynomial functions for use in impulse radio (ultra-wideband) communications are proposed. With these functions pulse shapes which are orthogonal and have nearly constant pulse width regardless of the pulse order are generated. These properties hold under the effects of differentiation. An M-ary communication system is constructed using these pulse shapes. A Matlab model for generating the pulses is designed and the effect of timing jitter on the performance of the system is investigated by computer simulation.     

城市建设的休克疗法——大连现象解说

在启动大规模的现代化建设的进程中，应对发展中听中型城市实施“休克疗法”，强调性终止城市发展的无序而缓慢的自然进程。选择短暂的“回归”或“中断”历史的调整时，应以能否适当地的历史文化特质从而把握当代的发展机遇为依据。     

Effect of heating-rate on failure temperature of pre-loaded brass H62

The response and failure of brass H62 specimens subjected to different levels of pre-loaded stresses and heating rates were investigated using a Gleeble-1500 thermal-mechanical material testing system. The metallographs of the tested material were also observed and analyzed. It is found that the increase of either pre-loaded stress or heating-rate decreases the failure temperature. Metallographic analysis shows that high heating-rate may cause stronger local thermal inconsistency （LTI） and remarkably increase the microdefects in the material, which may markedly degrade the macroscopic mechanical properties of the material.     

三维频率复用环境中的信道偏移指配方法

一种新的信道指配法－信道偏移指配方法正受到越来越多的重视，这种方法能在现有的频率资源条件下，较大地提高移动通信系统的容量。本文主要讨论了三维频率复用环境中的信道偏移指配方法，详细地分析了同频复用和相邻信道使用距离，定量地计量了信道偏移系统的频谱节约效率。本文最后还通过几个实例验证了所提算法的实用性。     

我国有线电视事业的现状和发展

本文详细系统地介绍了我国有线是视发展历史和现状，及其经营和管理方法。重点介绍了北美的ＣＡＴＶ技术发展动向。最后，指出我国ＣＡＴＶ事业发展中的应用重视的问题。     

一个光纤综合业务环网的故障自动恢复

光纤综合业务区域网是近年来迅速发展的一个领域，环形网是这种网最常用的一种拓扑结构。由于环形网结点串联的特点，网络的可靠性是必须解决的问题。本文针对一个具有３４Ｍｂ／ｓ速率，可以传输计算机数据、话音、传真和会议电视的光纤综合业务环网（ＩＳＲ），研究了其故障的自动隔离。文中分析了ＩＳＲ的故障，讨论了故障的检测、定位和隔离的方法。为了适应综合业务的混合电路交换和分组交换技术，本文提出了采用二分搜索法来定     

无线数据通信网发展趋势

无线数据通信具有两大发展趋势，即低速的广域移动数据网及高速的局域无线数据网。本文介绍了其技术特点、应用情况和市场前景，分析了无线数据通信传输技术、网络结构和媒质接入控制等问题。