模数变换器的几种典型结构及其应用

ADC(模数变换器)作为连接模拟电路与数字信号处理器之间的桥梁，围绕看精度和速度2个方向快速发展，并出现了多种结构，且各具特色。文中主要对目前主流的4种结构的性能特点、电路的复杂程度、采样速度和应用领域等方面进行了对比研究，最后介绍了被广泛地应用于软件无线电、数字中频接收机等系统中的流水线型ADC的现状及其发展趋势。     

SRD倍频器自给偏压温度补偿研究

由世界贸易组织上海研究中心、上海市对外服务有限公司、上海对外贸易学院、上海海关高等专科学校主办的“世界贸易组织与中国服务贸易研讨会”于1997年4月19～20日在上海银河宾馆举行。世界贸易组织总干事雷纳托·鲁杰罗应邀出席了这次研讨会,并在会上发表专题演讲。现将鲁杰罗先生的演讲编译刊载如下,以飨读者。     

Exchange Rate and Inflation Dynamics in a Resource Rich Setting: The Case of Zambia

This paper investigates the relationship between copper prices, the exchange rate and consumer price inflation in Zambia using a structural vector autoregression with quarterly data for 1995–2014 and a combination of sign and zero restrictions to identify relevant global and domestic shocks. The paper makes two contributions. First, it provides new measures of exchange rate pass through (ERPT), based on less restrictive assumptions than previous estimates, to show how changes in the value of the kwacha are reflected in changes in consumer prices (distinguishing food and non‐food inflation). Second, the ERPT is disaggregated to demonstrate that measured ERPT depends on the nature of the shock, with implications for policy responses. Although the price of copper is the most important driver of the exchange rate, the fluctuations it caused are associated with a low pass‐through of about 7% (consistent with a period of relatively low inflation). Exchange rate fluctuations caused by monetary shocks, in contrast, come with a pass‐through of up to 25% (and even more for food prices). A fast response by monetary authorities can mitigate the adverse effects of exchange rate shocks.     

The guided tour a sociological approach

In an exploratory study of guides and based on data derived from research combining observation and extended interviews, the relationship between guides, drivers, and their passengers is examined. The evidence suggests that the guiding role is not yet institutionalized, and remains open to interpretation by guides and passengers alike. The role of guiding involves a number of subsidiary and sometimes conflicting sub-roles, of which the information-giving function is emphasized by guides themselves, in their drive for professional status. Guides are found to develop manipulative and dramaturgical skills to satisfy their passengers' quest for a unique touristic experience. The mediation of the guide as “culture-broker” eases and may make more meaningful the contrived and artificial relationship between tourists and their hosts.     

线性模型参数的最优估计——基于对最小P乘估计的研究

本文通过随机模拟计算研究了线性回归模型参数的LP估计量的一些特性,当误差项服从不同的分布时,在LP估计量中寻找最优或接近最优的估计。     

可生物降解包装材料的性能和应用研究

目前,可生物降解包装材料已经成为替代传统合成材料的重要环保型材料。早期,已有研究人员将可生物降解聚合物应用于包装材料领域。近年来,随着环境问题,原油储量压力的加剧和普通消费者的偏爱,生物基及可生物降解聚合物得到进一步发展。本文介绍了可生物降解包装材料的发展过程,重点综述了材料的性能和应用。     

高职院校《高频电子线路》课程改革探讨

《高频电子线路》是一门理论性和实践性都很强的综合性专业课程,难度较大,学好这门课对学生的专业基础知识有较高要求。如何让高职院校的学生对这门课感兴趣并且学好它,需要教师花费大量心力。本文结合《高频电子线路》课程建设实践,从教学方法、实践教学及考核形式等方面,对如何提高教学效果及实践能力进行了探讨。     

大调制指数调相信号锁相解调器的分析与设计

<正> 自1994年元月始,我国对现行外汇制度进行了改革。这一改革至今已取得了显著的成效,但也产生了一个问题:人民币在对外币(主要是美元)升值的同时对国内商品却表现为贬值,即通货膨胀,这是有悖于一般经济规律的。对于这两种情况的同时出现,有观点认为它们是密切相关的,将近期出现的通胀完全归咎于结售汇制下大量外汇占款。本文认为这种观点有失偏颇,但同时也承认大量的外汇占款确实对国内高幅通胀负有责任。因此,当务之急是深入进行外汇体制改革。随着各专业银行逐步向商业化转变,各货币、资产、国债等配套市场走向成熟,我国的外汇市场将逐渐放松管制,外汇宏观控制也将分步减轻对结售汇制的依赖。那时,结售汇制下大量外汇占款问题将迎刃而解,由此引致的通货膨胀压力也可望得到缓解。     

控哮涂膜剂的皮肤致敏性实验研究

目的 考察控哮涂膜剂对动物皮肤是否具有致敏性,为其临床安全性评价提供依据.方法 皮肤致敏性实验通过与2,4-二硝基氯苯对照,采用豚鼠同体左右侧自身比较法研究控哮涂膜剂对皮肤的致敏性.结果 控哮涂膜剂反复致敏后使用,未发生皮肤过敏反应.结论 本品局部用药后,对正常皮肤无致敏性.     

一种基于单片机的峰值检波器

介绍一种应用于红外分光测油仪的低频受调信号的峰值检波电路,它的特点是充分利用单片计算机技术实现准确的峰值定位检波,不仅能保证检波的效率,而且还能保证A/D变换的可靠性。该电路也可应用于其他低频受调信号的峰值检波领域,在实际应用中获得了很好的效果。