对比度因素对彩色CRT视觉工效的影响

作者用实验方法研究了CRT彩色显示中对比度因素与视觉工效的关系。实验的自变量为彩色目标一背景的亮度对比度．取值范畴为-0.68-14.1。实验的因变量为视觉通道容量。实验的刺激材料为8个不同开口方向的兰道环。实验结果表明：对比度是影响彩色CRT视觉工效的重要因素。当目标一背景的亮度对比度值小于-0．3(暗目标／亮背景)或大于 1．3(亮目标／暗背景)时，视觉工效较高．继续增大反差，视觉工效改善不明显；当对比度值从负端增大至-0．13或从正端减小至 1．3时，视觉工教急剧下降，而后继续减小反差，视觉工效的降低也不明显。     

Adaptive subcarrier allocation and bit loading for voice/data transmission in multiuser OFDM systems

A new algorithm of adaptive subcarrier allocation and bit loading (A‐SABL) is proposed for simultaneous voice and data transmission in multiuser OFDM systems. The algorithm takes advantage of the frequency diversity and the voice/data transmission requirements to dynamically assign the number of subcarriers and bits/per symbol on each subcarrier for each user in a single cell. Due to the strict delay requirement of voice service, the subcarriers with low channel gains are assigned for voice transmission with a small number of bits per symbol to guarantee its required bit‐error‐rate (BER) and transmission rate. Based on the remaining subcarriers with high channel gains and the transmission power, the throughput of data transmission is then maximized by loading as many bits as possible on each subcarrier to achieve the required transmission bit rate and BER. Theoretical analysis and simulation on the proposed algorithm show that a better performance is obtained than previously reported schemes. Copyright © 2008 John Wiley & Sons, Ltd.     

长江流域的坡耕地治理

长期以来，由于人口增长和土地资源的不合理利用，长江中上游山丘地区的坡耕地多达１０６６．７万ｈｍ＾２，成为流域水土流失的主要地类和侵蚀泥沙的重要来源。长江中上游水土保持工程坚持将坡耕地作为治理重点，采取的主要措施有（１）以改造坡耕地，兴修水平梯田，配套小型水利设施为突破口，提高作产量，满足治理区的粮食需求，为陡耕地创造条件；（２）对一时不能改为梯田而又无法退耕的坡耕地因地制宜地采取各种保土耕作措施，     

碎石桩复合地基桩土应力比的试验研究

该文简要阐述了碎石桩复合地基桩体与桩间土压缩变形之间的关系,通过工程实例介绍了复合地基桩土应力比的测试方法,并分析了桩土应力比与荷载、置换率、桩土模量比之间的关系,进而得出一些有益的结论。     

Fabrication,structure and properties of quasi-carbon fibres

Partially carbonized fibres, termed quasi-carbon fibres (QCF), with good thermal stability and acceptable mechanical properties were developed from a polyacrylonitrile-based precursor. Heat treatment temperature (HTT), in the 400–950 °C range, played a major role in determining the thermal, mechanical and electrical properties of the QCF. The thermal stability of the QCF was increased by increasing the HTT. An appreciable amount of the graphite-like structure in QCF began to develop at ca. 650 °C. The Young modulus magnitudes of QCF scaled almost linearly with the pyrolysis temperature. In contrast, the QCF exhibited a decreasing trend in both tensile strength and failure strain up to a HTT of 650 °C, above which both the tensile strength and failure strain of the QCF increased with the HTT. Electrical resistivity values of the QCF covered a very wide range from 10⁷to 10^–2 cm. QCF showed semiconducting behaviours with activation energies falling between 0.690 and 0.0052 eV when the pyrolysis temperature was in the 400–850 °C range.     

紧凑型线路发展现状及在我国应用的前景

分析了国际上紧凑型线路的发展趋势，提出了在我国应用紧凑型线路的设计、运行上应注意的问题。     

喷气织机微机控制系统与主板分析

喷气引纬系统所特有的高速运行之潜能，有赖于其微机监测与控制技术为保证而得以发挥。本文在介绍一种国外喷气织机的微机控制系统的基础上，着重分析了其主机电路板的硬件系统及工作原理。     

钢筋混凝土圆形截面偏心受压构件配筋计算方法

混凝土结构设计规范(GBJ10—89)增加了圆形截面偏心受压构件正截面强度计算公式。本文把计算圆形截面的配筋问题视为求解数学方程组问题,分析了α和As的函数关系及变化规律,采用分区间逐次逼近法求解α和As,可获得精度很高的计算结果。按同样思路,结合As的初值估算公式,可得到圆形截面配筋计算的手算方法。     

特细砂高强砼力学性能的试验研究

本文通过试验,研究了特细砂高强砼的基本力学性能及应力-应变关系特征,提出了特细砂高强砼的各项强度指标和弹性模量计算公式。为推广应用特细砂高强砼提供了依据。     

椭圆形管式密封铅酸电池在铁路内燃机车上的应用

本文叙述了内燃机车起动用椭圆形管式密封铅酸电池的设计。性能测试表明起动性能良好，在机车上的使用寿命预期比原有电池提高一倍左右，且无需维护。