美籍华裔专家讲通信工程技术新动态

本文扼要介绍１９９５年北京中美工程技术研讨会通信组五位美籍华裔专家关于通信技术新动态的专题报告。一是宽带综合业务数字网的同步数字系列（ＳＤＨ）和异步转移模式（ＡＴＭ）；二是光纤通信系统的光放大器（ＯＦＡ）、波分多路（ＷＤＭ）、光电子集成（ＯＥＩＣ）、色散补偿和新型光纤；三是蜂窝网车载移动通信和全国性个人通信业务（ＰＣＳ）、时分多址（ＴＤＭＡ）和码分多址（ＣＤＭＡ），四是智能网（ＩＮ）体系结构、概念模型和业务管理系统（ＳＭＳ）；五是数字传输网的恢复（ＦＡＳＴＡＲ）、维护（ＴＭＰ）和供应（ＴＳＮＯＷ）三种管理平台，及综合网络管理系统（ＩＮＭＳ）。     

热处理WO3电变色膜稳定性研究

采用电子束蒸发淀积ＷＯ３薄膜。根据已有的ＷＯ３薄膜脱水过程结论而选择适当温度对薄膜进行退火处理。在大量含水的和不含水的两类Ｌｉ＾＋电解质中进行比较性着色和消色循环实验，表明在２９０℃以下热退火处理能明显增加ＷＯ３薄膜在含水 电解质中的循环寿命。     

钛酸铅系薄膜的热释电性能及其应用

叙述了钛酸铅系薄膜的热释电原理，介绍了国际上近几年钛酸铅系薄膜材料、制备工艺及热释电性能，并与块状陶瓷材料进行了比较，分析表明钛酸铅系薄膜具有优良的热释电性能及可观的应用前景。     

Energy Value of Resistant Starch

Resistant starch was evaluated for energy value using fine silica and normal starch as controls and young rats as a test model. The net increase in rats' carcass energy due to the test materials fed over a 3-wk period formed the basis for assessing energy value. Rats fed normal starch deposited about twice as much fat and significantly more protein in the carcass than those fed either resistant starch or silica. Rats fed resistant starch or silica showed similar growth responses and increases in components of body composition and carcass energy content. This suggested that resistant starch provided, like silica, no energy.     

Storage Stability of Antioxidant-Washed Myofibrils From Chicken White and Red Muscle

Oxidation and gel-forming ability of chicken white (breast) and red (leg) muscle myofibrillar proteins during storage at 0°C were examined. Breast myofibril gels exhibited greater shear moduli than leg myofibril gels throughout 8 days storage. Shear moduli of both breast and leg gels in the intermediate temperature zone (45–55°C) decreased during storage, but at >55°C, they either increased or remained unchanged. Lipid oxidation was inhibited by washing myofibrils with antioxidants propyl gal-late, ascorbate, and tripolyphosphate. However, these antioxidants did not affect the content of protein carbonyls, and only slightly decreased the amine content during storage. Storage affected the kinetic process of myofibril gelation independently of antioxidant treatments.     

强度调制／直接检测（IM／DD）光纤通信系统色散限制的研究

通过引入归一化脉宽Ｐ和相对脉冲展宽因子ｑ，提出了一个适用于ＩＭ／ＤＤ系统中各种眼图恶化量ｘ和归一化脉宽Ｐ的色散限制改进公式。通过与其它理论的比较、计算机仿真和对实验数据的分析，验证了该公式的正确性，并给出了其它结果的限制条件。研究表明：当眼图恶化量ｘ为１ｄＢ左右时，对２．５Ｇｂ／；外调制信号（α＝０）而言，非色散位移光纤ＩＭ／ＤＤ系统的色散因子γ约等于０．７９，所对应的系统再生中继距离约为９００余公里。     

The mechanics of compressive kinking in unidirectional fiber reinforced ductile matrix composites

Three distinct stages of kink band formation and propagation exist in ductile matrix composites subjected to compressive loading. These stages are called incipient kinking, transient kinking and kink band broadening. Each stage involves a different deformation mode. The mechanics governing each stage are discussed. Incipient kinking, where the peak load is attained, and kink band broadening, where the load attains a steady-state, are important in structural design. Two design philosophies are presented. References to pertinent literature are made throughout.     

G.652光纤上的2.5Gbit／s色散受限系统

本文根据色散受限中继段长度的计算，对实际工程中１５５０ｎｍ波长２．５Ｇｂｉｔ／ｓ系统进行计算比较得出啁啾声引起的色散不容忽视，它使２．５Ｇｂｉｔ／ｓ成为色散受限系统。对１３１０ｎｍ波长６２２Ｍｂｉｔ／ｓ系统，当使用多纵模激光器时，往往也会成为色散受限系统。     

Improvement of the optical properties of electrodeposited CuInSe2 thin films by thermal and chemical treatments

Cu, In and Se have been codeposited in thin films by potentiostatic one-step electrodeposition. The as-deposited material has shown direct optical transitions attributable to the CuInSe₂ semiconductor, but also additional absorption corresponding to another semimetallic phase. The secondary phases are selenium and copper selenide compounds which have been determined by composition measurements. In order to eliminate the semimetallic phases and to improve the semiconductor behaviour of the electrodeposited material, thermal and chemical treatments have been performed. After heat-treatment of the samples at 400°C in flowing argon, elemental selenium loss has been detected together with an enhancement of the allowed direct optical transition. The subsequent chemical etching of the layers in a KCN solution has showed to be successful in eliminating the copper selenide phases which were responsible of the remaining sub-bandgap absorption.     

The As-prepared surfaces of C-axis-oriented Nd1Ba2Cu3Oy thin films characterized using scanning probe microscopes

Recently, superconducting Nd₁Ba₂Cu₃O_y (Ndl23) thin films with high superconducting transition temperature (T _c) have been successfully fabricated at our institute employing the standard laser ablation method. In this paper, we report the results of surface characterization of the Nd123 thin films using an ultrahigh vacuum scanning tunneling microscope/spectroscopy (UHV-STM/STS) and an atomic force microscope (AFM) system operated in air. Clear spiral pattern is observed on the surfaces of Nd123 thin films by STM and AFM, suggesting that films are formed by two-dimensional island growth mode. Contour plots of the spirals show that the step heights of the spirals are not always the integer or half-integer number of thec-axis parameter of the structure. This implies that the surface natural termination layer of the films may not be unique. This result is supported byI-V STS measurements. The surface morphology of the Nd123 thin films is compared with that of thec-axis-oriented Y₁Ba₂Cu₃S_y thin films. Surface atomic images of the as-prepared Nd123 thin films are obtained employing both STM and AFM. STS measurements show that most of the surfaces are semiconductive. The results of STS measurements together with the fact that we are able to see the surface atomic images using scanning probe microscopes suggest that exposure to air does not cause serious degradation to the as-prepared surfaces of Nd123 thin films.