PCB阻焊膜下方线路腐蚀失效案例研究

近年来一些PCB组件在使用或储存一段时间后出现表面线路发黑甚至开路,导致产品失效。本文通过电路分析、电镜能谱、金相切片、离子色谱等一系列分析,确定失效为线路腐蚀所致,并分析了线路腐蚀的原因以及提出了解决方法。     

论DISPATCH系统在大型露天矿的作用

本文全面介绍了露天矿计算机卡车调度系统（ＤＩＳＰＡＴＣＨ）的原理和功能,分析了使用的效益和风险,论证了露天矿采用该系统指挥和管理生产的必要性。     

国内外金属露天矿的分期开采技术

阐述了国内外金属露天矿分期开采的典型事例。论述分期开采的原则、形成条件、分类方式和实施分期开采的方法。     

发射分集技术及在WCDMA系统中的应用

发射分集是近年来才发展起来的一种技术，在第三代移动通信系统中已经开始普遍采用。本文简单介绍了几种发射分集技术，并分析了各自的优缺点。特别针对发射信号设计的新技术－空时码进行了详细讨论，然后论述了WCDMA中发射分集技术的应用，并进行了性能仿真比较。     

Patterns in environmental priorities revealed through government open data portals

The ways in which environmental priorities are framed are varied and influenced by political forces. One technological advance--the proliferation of government open data portals (ODPs)--has the potential to improve governance through facilitating access to data. Yet it is also known that the data hosted on ODPs may simply reflect the goals and interests of multiple levels of political power. In this article, I use traditional statistical correlation and regression techniques along with newer natural language processing and machine learning algorithms to analyze the corpus of datasets hosted on government ODPs (total: 49,066) to extract patterns that relate scales of governance and political liberalism/conservatism to the priorities and meaning attached to environmental issues. I find that state-level and municipal-level ODPs host different categories of environmental datasets, with municipal-level ODPs generally hosting more datasets pertaining to services and amenities and state-level ODPs hosting more datasets pertaining to resource protection and extraction. Stronger trends were observed for the influences of political conservatism/liberalism among state-level ODPs than for municipal-level ODPs.     

Information and Telecommunications Project for a Digital City: A Brazilian case study

Making information and telecommunications available is a permanent challenge for cities concerned to their social, urban and local planning and development, focused on life quality of their citizens and on the effectiveness of public management. Such a challenge requires the involvement of everyone in the city. The objective is to describe the information and telecommunications project from the planning of a digital city carried out in Vinhedo-SP, Brazil. It was built as a telecommunications infrastructure of the kind of “open access metropolitan area networks” which enables the integration of citizens in a single telecommunications environment. The research methodology was emphasized by a case study which turned to be a research-action, comprising the municipal administration and its local units. The results achieved describe, by means of a methodology, the phases, sub-phases, activities, approval points and resulting products, and formalize their respective challenges and difficulties. The contributions have to do with the practical feasibility of the project and execution of its methodology. The conclusion reiterates the importance of the project, collectively implemented and accepted, as a tool to help the management of cities, in the implementation of Strategic Digital City Projects, in the decisions of public administration managers, and in the quality of life of their citizens.     

一种微带反射阵列天线单元特性研究

带开路短截线的贴片是微带反射阵列天线设计中最常用的单元形式之一。结合应用于民用航天领域的薄膜反射阵列天线设计,比较和分析不同物理参数、阵列环境下单元电讯性能变化特点,并优化设计单层薄膜反射阵列天线试验阵面,给出分析结果,供不同应用背景下的反射阵列天线设计参考。     

浅谈空压机变频节能改造的运用与研究

随着电力电子技术的高速发展,变频器在调速领域中的运用越来越广泛。它具有性能稳定、操作方便、节能效果明显等显著优点。而空压机在工厂中能耗大、噪声大、自动化程度不高等缺点。现结合PLC与变频器对空压机进行节能改造,具有很明显的节能效果。而今在全球推进低碳经济,节能减排的大趋势下,如何节能、高效地解决空压机的节能减排问题,已经成为社会研究的热点,而针对降低工厂空压机能耗对我国完成节能减排目标与推动建设为节约型社会具有非常重要的作用。     

Performance of closed loop transmit diversity in a Rayleigh fading channel

In this paper, the closed loop transmit diversity technology for the Wideband Code Division Multiple Access（WCDMA） systems is investigated in a multipath Rayleigh fading channel. The RAKE receiver model and the weighing vector algorithm are presented. The performance is theoretically analyzed in terms of the average maximal Signal-to-Noise Ratio（SNR） gain available over the Space-Time block coding based Transmit Diversity（STTD） technology. Theoretic analysis and simulation results show that the closed loop transmit diversity can provide a 3dB performance gain over the open loop scheme in a single path fading channel, while the performance gain decreases dramatically with the increasing inherent multipath diversity of the wireless channel.     

Solar drying vs. open sun drying: A framework for financial evaluation

Initiatives towards large-scale dissemination of solar dryers for drying of agri-produce face severe competition from the largely prevalent practice of open sun drying in most of the developing countries. Therefore, solar drying systems must offer exceptionally attractive financial gains to enhance their acceptance among the potential users. A modest attempt to develop a simple framework to facilitate a comparison of the financial feasibility of solar drying as against open sun drying has been made in the present work. Results of some exemplifying calculations are presented and briefly discussed.