Technological development of Brazilian telecommunications in past decades

Brazilian telecommunications sector has undergone important modifications in the last 40 years. From a badly structured system of municipal level operators in 1960, with barely one million fixed lines to a large, nation-wide system with about 50 million fixed plus another 75 million mobile lines in 2005. This work paper reviews the institutional framework of telecommunications industrial and technological policy in Brazil in the last four decades, its results and present situation. Infrastructure and services modernisation and expansion process that happened in early 1970s were carried out at the expense of massive import of products and technology. A government strategy was, then, devised to stimulate local industrial and technological development in telecommunications, under the general guidelines of import substitution policy. Essential to this strategy was the creation of an innovation system around TELEBRÁS Research and Development Centre. This technological development model was successful while a protectionist economic policy existed. When economic and political circumstances could not anymore sustain an import substitution approach, in the 1990-decade, the model fell apart and has not been replaced by any other sectorial policy. A critical assessment is carried out, analysing the adopted actions in face of the digital technology maturing process that occurred in meantime.     

Microanalysis for microelectronics

Microanalytical methods are powerful tools for the diagnosis and elimination of failures in materials and components in microelectronics. Because of the very small structure dimensions, especially methods with extremely high spatial resolution were used for characterization of microstructure details or for identification and quantitative estimation of chemical composition in very small areas or very thin layers. In this publication a short overview of the most important microanalytical methods is given and particle beam methods are described in more detail. Their principles are explained and their performance is described with examples of analytic problems of development and production of microelectronic components.     

Gluings of modular lattices

The notions of gluing, tolerance relations, and Mal'cev products of varieties have been used by various authors to investigate varieties of lattices. In this paper the authors introduce a general framework for all these concepts and apply it to varieties of modular and Arguesian lattices.     

宽带综合业务数字网的发展与关键技术

90年代世界较发达国家都在加速研究开发宽带综合业务数字网(B-ISDN),以及为最终实现B-ISDN而进行网络演变和宽带业务应用等研究工作。本文概要介绍了包括中国在内的几个国家B-ISDN的发展策略和进展情况,以及B-ISDN关键技术。     

The evolution of starting vortex and secondary separation on an elliptic cylinder

Flow visualization was used to investigate experimentally the evolution process from symmetrical shedding to staggered shedding of the starting vortex and the phenomenon of secondary separation on an elliptic cylinder at moderate Reynolds numbers. The vortex structure of the flow separation was studied. The temporal variation of separation angle and length of wake vortex were given. The photographs and experimental results provided basis for further investigation of the complicated feature of the starting process of unsteady separated flows around an elliptic cylinder. The project supported by the National Natural Science Foundation of China.     

光学设计的发展

本文概述了光学设计所处的历史发展阶段,对智能化光学设计给出了定性的描述,指出了目前光学设计要解决的问题以及发展方向。     

近500年来新疆巴里坤湖相沉积物的生物地层学古气候意义

本文通过运用对应分析法处理孢粉资料,定量地恢复了近500年来北疆东部巴里坤地区气候变化状况,并得出下述结论:近500年来巴里坤地区是以持续变暖变干为主要特征的;且由孢粉揭示,近500年来巴里坤地区大致经历了以下五个冷或凉期:<1564A.D,1620～1720A.D.,1750～1810A.D.,1830～1900A.D.和1960～1988A.D.,以及四个暖期:1588～1620A.D.,1720～1750A.D.,1810～1830A.D.和1900～1960A.D.,的交替变化。广泛的区域性对比表明,本地区近500年以来气候变化同我国及世界其它地区具有良好的吻合。但它也具有鲜明的区域性特色,除气候期的起止时间有所差异,还表现在它以不同程度的相对冷(凉)湿与暖干的交替变化有别于我国东部季风区冷干与暖湿交替变化的气格演变格局,短年代生物地层学的研究在一定程度上丰富了干旱区短年代环境演变的研究方法,从而能够通过多手段、多方法的对比、验证,以期取得更为精确的古环境演变信息。     

PTC热敏元件的进展与发展趋势

根据近几年搜集的资料及进行的调研，叙述了国内外ＰＴＣ材料、重点产品、生产技术等方面的进展情况及今后的发展趋势。结合ＰＴＣ热敏元件的特点及国情，进行了分析，提出了见解。     

浅论我国工业经济效益的发展趋势和提高的途径

近40多年来，我国的社会主义工业经济效益有的时期比较好，但大部分时期工业经济效益不高，有的时期考核工业经济效益的一些主要指标为负数，总体工业经济效益很不理想。本文从我国40多年来社会主义工业经济效益的发展史实中，描绘出这一时期我国工业经济效益的发展概况和轨迹，从而研究我国近期工业经济效益的发展趋势和提高工业经济效益的途径。