自旋极化输运的方法讨论

电子自旋注入和自旋相关输运是自旋电子学中被广泛研究的课题。本文将介绍在自旋电子学器件上具有广泛应用前景的不同结构中物理原理相关的材料问题,如F/I/S隧穿、F/I/F隧穿、Andreev反射。     

《了不起的盖茨比》中的另一个旁观者

美国作家菲茨杰拉德的小说《了不起的盖茨比》被认为是美国20世纪文学杰作之一。作者巧妙地选择小说的第二主人公尼克作为小说故事的主要叙述者,使整部小说取得了极好的艺术效果。本文认为小说中还有另一个隐藏的叙述者乔丹·贝克,她的叙述不仅起着补充小说故事情节的作用,而且还传达着作者的潜藏话语。     

三种贝母核型的比较研究

The present paper deals with a comparative karyotypic study of three species in Fri- tillaria-F. thuncergii Miq., F. anhuiensis S.  . Chen et S. F. Yin and F. hupehensis Hsiao et K. C. Hsia.  The karyotype of F. anhuiensis S. C. Chen et S. F. Yin is first reported.       The karyotypes of the three species of Fritillaria are rather similar, all with K(2n)=24= 2m+2sm+12t+4st+4m (SAT), showing a close interspecific relationship.  They all have two pairs of st chromosomes, one of which is the third chromosome in all the three species studied, but the other is the seventh in F. thunbergii Miq, the eighth in F. anhuiensis S. C. Chen et S. F. Yin, and the fifth in F. hupehensis Hsiao et K. C. Hsia.  It tells us that there are some differences in their karyotypes.  All of the three species possess two pairs of satellite chromosomes with the satellites located on the long arms. A heterochromatic zone is found sometimes on long arms of No. IX chromosome in each species of Fritillaria and on one of No. I chromosomes in both F. thun- bergii Miq. and F. anhuiensis S. C. Chen et S. F. Yin, a chromosome polymorphism occurring between populations of Fritillaria. In addition, three B chromosomes are always found in most root-tip cells of F. hupehensis Hsiao et K. C. Hsiao.     

安徽百合科二新种

Two new species of the Liliaceae are described from Anhui Province, China. i. e. Fritillaria qimenensis D. C. Zhang et J. Z. Shao and Lilium anhuiense D. C. Zhang et J. Z.Shao.     

单片机A/D转换接口的两种实现方法

本文论述了用V/F变换器和VCO压控振荡器与单片机接口进行A/D转换的方法,并给出了硬件电路和转换程序.这种方法简化了硬件结构,提高了A/D转换精度,有较强的实用性.     

混合集成电路STR-S6708A工作原理

本文对电视机常用电源ICSTR-S6708A及开关电源工作原理进行了分析。     

基于MC55远程便携报警系统的研制

分析市场现有报警仪器的缺点,介绍了一种基于增强型微控制器C8051F020控制GSM引擎对远程、便携式报警系统的成功实现.从电源部分、传感器部分、微控制器部分、GSM无线模块等硬件部分和软件部分分别进行了详细的论述.     

DSP芯片SCI模块在电力电子控制装置中的应用

TMS320F28335是52位浮点DSP（数字信号处理器）芯片,在电力电子装置中的应用日益广泛。本文介绍了利用DSP芯片的SCI（串行通信接口）模块与Visual Basic中的MSComm控件在电力电子控制装置中实现符合IEC60870-5—101规范的串行数据通信方案。该方案可应用于多种基于DSP的电力电子控制装置与上位机间的数据交换。在实际环境下运行表明谈方案简单有效、移植方便,便于系统的开发与调试,具有较强的实用性。     

Knowledge protection strategies of multinational firms—A cross-country comparison

International knowledge spillovers, especially through multinational companies (MNCs), have recently been a major topic of discussion among academics and practitioners. Most research in this field focuses on knowledge sharing activities of MNC subsidiaries. Relatively little is known about their capabilities for protecting valuable knowledge from spilling over to host country competitors. We extend this stream of research by investigating both formal protection strategies (e.g. patenting) as well as strategic ones (secrecy, lead time, complex design). We conceptualize the breadth of firm's knowledge protection strategies and relate it to the particular situation of MNC subsidiaries. Moreover, we argue that their approaches differ with regard to host country challenges and opportunities. We address these issues empirically, based on a harmonized survey of innovation activities of more than 1800 firms located in Portugal and Germany. We find evidence that MNCs prefer broader sets of knowledge protection strategies in a host country with fewer opportunities for knowledge sourcing (Portugal). In Germany, though, they opt for narrower sets of knowledge protection strategies if they invest in innovation activities themselves. We deduce that these results are due to a need for reciprocity in knowledge exchanges to benefit fully from promising host country knowledge flows.     

AC-13F型沥青混合料目标配合比设计实例

文章对AC-13沥青混合料目标配合比进行了分析设计计算,并对其性能进行了验证,指出其可作为沥青混合料目标配合比设计的一般过程加以参考。