开发定制功率模块解决方案:哪些是必须要考虑的

在过去的几年中,由于最终应用中节约成本和提高效率的严格功率设计约束,使得功率模块市场的需求迅速变化。本文概述了提供定制解决方案,在满足不断变化的功率模块设计和性能的市场需求时所要考虑的方方面面。     

东北黑土地区主要土壤肥力质量指标的空间变异性

采用地理信息系统(G IS)和地统计学相结合的方法研究了本世纪初东北黑土区土壤表层(0~20 cm)pH、有机质、速效磷、速效钾、粘粒这5种土壤肥力指标的空间变异性。结果表明:土壤pH和粘粒的理论模型均为指数模型;有机质、速效磷和速效钾的理论模型均为球状模型。速效磷、速效钾的C0/(C0 C)较大,为46.63%和49.91%,说明这2种肥力指标具有中等的空间相关性;而pH、有机质、粘粒的C0/(C0 C)分别为10.80%、16.57%、12.88%,说明这3种肥力指标具有较强的空间相关性。根据每个采样点的指标数据计算出该地区土壤肥力质量综合评价指数,最终得到研究区土壤肥力质量的分布图。     

电容器单元爆破能量与电容器组接线结构方式之关系

在工程项目中,经常有用户提出电容器单元的耐爆能量要求,因此,认真分析爆破能量与电容器组及其结构的关系十分重要。文章就针对这个问题进行了探讨。     

硬件组合技术在数据库查询优化中的应用

查询优化技术是关系数据库成功运作的关键技术之一。随着现代数据库规模不断扩大到以十亿字节(GB)计量,对能够处理如此巨大的数据信息的系统的需求也随之而来。找到一种高效的信息提取方法对于使研发过程更快、更容易地进行是十分必要的。文章介绍了一种将与或图和数字逻辑电路技术应用于SQL查询优化,得到数据库中有效信息的技术方法。该方法中把与或图作为一种中间数据结构,用来描述布尔值域上的查询集合的子集;数字逻辑电路则用来表示二进制数集合上的各项逻辑运算功能的一种实现方式。该文同时给出了相关实验结果,实验表明这是一个十分有效的方法。     

基于无线应用协议的移动地理信息系统的研究

随着移动通信技术和地理信息技术的高速发展,二者的有机结合已成必然。该文重点研究了基于无线应用协议的移动地理信息系统的设计和实施,提出了一个WAP内容提供服务器的设计框架以及多用户并发控制和负载平衡分配、地理信息服务内容动态缓存、分布式异构数据源共享的解决方法。最后,给出了一个应用实例。     

经济地理信息系统

经济地理信息系统是基于地理信息系统开发平台，实现对大量资源数据信息进行计算机管理与辅助决策的大型软件系统。它利用计算机技术、地理信息系统(GIS)技术，在现有的基础信息库的基础上，联系相关部门的业务需要，实现经济信息管理的科学化和自动化。     

Fundamental Limits of Organic Packages and Boards and the Need for Novel Ceramic Boards for Next Generation Electronic Packaging

The system-on-a-package (SOP) paradigm proposes a package level integration of digital, RF/analog and opto-electronic functions to address future convergent microsystems. Two major components of SOP fabrication are sequential build-up of multiple layers (4–8) of conducting copper patterns with interlayer dielectrics on a board and multiple ICs flip-chip bonded on the top layer. A wide range of passives, wave-guides and other RF and opto-electronic components buried within the dielectric layers provide the multiple functions on a single microminiaturized platform.The routing of future nanoscale ICs with 10,000+ I/Os require multiple build-up layers of ultra fine board feature sizes of 10 m lines/space widths and 40 m pad diameters. Current FR4 boards cannot achieve this build-up technology because of dimensional instability during processing. These boards also undergo high warpage during the sequential build-up process which limits the fine-line lithography and also causes misalignment between the vias and their corresponding landing pads. In addition, the CTE mismatch between the silicon die and the board leads to IC-package interconnect reliability concerns, particularly in future fine-pitch assemblies where underfilling becomes complicated and expensive.This work reports experimental and analytical work comparing the performance of organic and novel ceramic boards for SOP requirements. The property requirements as deduced from these results indicate that a high stiffness and tailorable CTE from 2–4 ppm/C is required to enable SOP microminiaturized board fabrication and assembly without underfill. A novel ceramic board technology is proposed to address these requirements.     

海归派建筑师?

文章从探讨“海归派建筑师”这个外加的身份定义下,是否存在着某种行为方式的共性,是否存在一种有意识的社会身份和权力的自我建构等这一系列问题入手,认为由于缺乏主体的自我认同,“海归派建筑师”的身份在当代是难以成立的,在操作层面,比较突出的共性特征是非本土化,这与经济全球化的大环境的明显悖论,其社会根基,源自由于东西方社会落差而产生的市民大众心理深层的对西方榜样的需求,并且其异化而且虚设的话语权力是被社会赋予的。文章最终结论,在全球化环境下,地域身份划分方法的不可靠是产生“海归派建筑师”身份定义可疑的根本原因,因而对于“海归派建筑师”而言．正视地域身份模糊这一事实,或许能够带来基于社会立场的更深层次的思考,而这对检视当代中国建筑转型期的过程,无疑也是有益的。     

Design research for cadastral systems

Cadastral information is a reference data component, of any spatial data infrastructure (SDI). During recent years, several organisational and individual research projects have investigated the cadastral domain. Two paradigms characterize much of this research and their methodologies: a behavioural paradigm or, alternatively, a ‘design research’ paradigm. While some efforts have focused on behavioural research methodologies, design research methodologies have not been addressed by the cadastral, geographical information system (GIS) and SDI research community so far. The present article, therefore, aims to demonstrate usage of the design research paradigm through a methodological analysis of recent cadastral research, which addresses information system issues and within this context, designs information system artefact. The analysis is based on five doctoral dissertations and an array of papers representing the development of the ISO/WD 19152.3 Land Administration Domain Model. The analysis is supplemented with a review of related theory. The main contribution of this article is an explication of a design research methodology and a theoretical framework for research in cadastral information, cadastral systems and the units of property rights reflected in these systems.