微纳级双极晶体管的热耗散研究

对于双极性晶体管,由于自身存在的自加热现象,严重地影响着器件的特性。基于热电流方程、泊松方程及电流密度方程,在二维器件仿真环境下,进行了微纳级小尺寸npn双极性晶体管热现象的器件物理特性分析。重点研究了器件的集电极电流IC与晶格温度T的因变关系。研究结果显示,随着IC的增加,器件的晶格温度逐渐升高,VCE保持在3.0V、VBE达到最大值0.735V时,随器件晶格温度的升高VBE将减小。最后,笔者给出了描述晶体管温变关系的三维曲线。     

等径弯角挤压工艺(ECAEP)研究现状

等径弯角挤压是制备块状细晶材料的一种大塑性变形工艺，目前得到国内外高度重视．本文简要介绍了等径弯角挤压工艺的基本原理和变形特点，从理论上对其变形方式和机理进行了分析，并详细介绍了该工艺的应用领域。     

The Region 1 & 3 Broadcasting‐Satellite Service Plan after WRC‐03

The 1977 Broadcasting‐Satellite Service (BSS) Plan for Region 1 & 3 had been widely acknowledged to be out‐of‐date by the late 1980s. Development of digital modulation in the early 1990s provided an opportunity to update the technical provisions of the Plan to make it more economically viable. After a decade of work and three World Radiocommunication Conferences (WRCs), the revision of Region 1 & 3 BSS Plan was finally completed in 2003. The new Plan increased channel assignments from 5 to 10 analog‐equivalent channels for each country in Region 1, and from 4 to 12 channels for each country in Region 3. Yet, despite the increase in capacity, the new Plan is surprisingly similar to the original one in terms of the technical parameters. It is still based on national coverage, and the channel plan, orbital location, orbital spacing, and polarization are also the same. As a result, the new Plan is no more economically viable to implement than the old. To create economically viable BSS systems would most likely require modifications to the assignment in the Plan. Yet, modification procedures were made more difficult to apply after replanning. Less future implementation of BSS networks than would otherwise have occurred can be expected, and an inefficient usage of these frequency bands will likely result. On the other hand, less implemented systems will mean more capacity set aside for future use. This is important for countries that currently do not have satellite operations. In the end, BSS replanning reflects the eternal conflict between efficient usage and guaranteed future access. Copyright © 2005 John Wiley & Sons, Ltd.     

Measurement of the Timoshenko Shear Stiffness. II: Effect of Transverse Compressibility

This is the second of two papers devoted to the issue of measuring the Timoshenko shear stiffness of thin-walled composite beams. In the first paper, the effect of warping on the effective Timoshenko shear stiffness, as measured through bending tests, was studied. The bending test was simulated using finite-element analysis, and the results indicated that the warping effect was minimal. On the other hand, the evidence suggests that transverse flexibility may have a significant influence on the effective Timoshenko shear stiffness, decreasing the effective shear stiffness at shorter test spans. The purpose of the present study is to further investigate this effect and to explore the use of a sandwich theory to predict the measurement error. A higher-order sandwich theory, which captures the transverse strain at concentrated loads and supports, is applied to a commercially available thin-walled composite beam. The results indicate that the sandwich model does capture the decrease in the effective shear stiffness at short spans, and the dependence of the shear stiffness on span-to-depth ratio is similar to that calculated in the first paper, using the finite-element method.     

变形观测与高精度测量机器人系统

介绍了中南大学自行研制开发的高精度测量机器人系统的组成，工作原理，以及该系统实现高精度观测所采取的主要措施；仪器室内检定，野外边频同测，高精度气象改正，周日观测等，同时以某电站大坝的变形观测为例，简单介绍该系统可达到的精度及工程应用领域。     

热压/热变形Nd2Fe14B/α-Fe纳米双相永磁体的研究

为了制备各向异性块状Nd2Fe14B／α—Fe纳米双相永磁体，研究了热压／热变形工艺参数与样品微观组织结构、磁性能之间的关系。结果表明，饱和磁化强度Js随模压温度的升高而提高；而剩磁Jr、内禀矫顽力Hcj和最大磁能积(BH)max开始都随模压温度的升高而上升，但超过一定温度后反而降低；同时提高热压压力会使磁性能增加，而热变形温度对磁性能影响很小。热变形后样品垂直于压力方向的磁性能略高于平行于压力方向，呈现出轻微的各向异性。Nd2Fe14B／α—Fe纳米双相永磁材料在热压／热变形后没有产生晶粒的择优长大，在晶体学上仍然是各向同性的。     

大塑性变形制备纳米结构金属

细化晶粒是改善材料性能的有效手段，传统的压力加工技术(如轧制、挤压、拉拔和锻造等)可以细化晶粒(微米量级)。纳米结构金属由于具有很小的晶粒尺寸(20-500nm)和独特的缺陷结构，从而表现出优异的物理—力学性能。大塑性变形(SPD)具有将铸态粗晶金属的晶粒细化到纳米量级的巨大潜力，近年来已引起人们的极大关注。介绍了4种大塑性变形制备纳米结构金属的方法、原理、变形特点及应用，分析了纳米结构金属的强度和超塑性变形特征，以及当前研究中存在的主要问题，并对大塑性变形技术的应用前景进行了展望。     

Study on Hot Deformation Cracks of Steel D2 Using Procesing Map

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内蒙古大青山麻粒岩相糜棱岩石英的变形行为

在内蒙古大青山地区发育一套高温区域变质岩──麻粒岩，在这高温变质岩内有一系列的糜棱岩带．通过对糜棱岩带中石英的研究，对比深部地壳与浅部地壳石英的变形特点，获得一些新的认识．对石英显微构造、动态重结晶、TEM研究及石英岩组学方面进行了研究，发现石英的塑性变形显著，以缎带石英产出，发育各种塑性变形的显微构造，变形带、波状消光和亚颗粒显著：TEM观察到石英中有直线状的位错．岩组学研究显示出石英高温变形和多期构造叠加的特点．     

川东地区井下套管损坏的原因分析及对策

本文就近年来在钻井施工中遇到的４口井发套管损坏的问题进行了原因分析，提出了防止井下套管损坏对策。