关于触发器简化教学的一些思考

触发器是数字电路中的一个重要单元电路,是组成时序逻辑电路的重要单元。并且触发器按功能可以分为RS触发器、JK触发器、D触发器、T触发器等;按组成结构可以分为基本结构触发器、同步结构触发器、主从结构触发器、边沿结构触发器等。这样的话,关于触发器可以组合成很多类型,如同步JK触发器、基本RS触发器、边沿D触发器等,为了简化教学,我们可以把这些触发器电路中相同功能、不同结构的电路进行简化分析。     

"不定"与"不定义"状态的再定义

基本RS触发器、同步RS触发器状态定义,有些教材定义不准。严格区分“不定”和“不定义”状态是十分必要的。     

三值主从触发器结构分析及其nMOS电路实现

分析了主从触发器的逻辑结构，提出了主从触发器由特征锁存器和通用锁存器构成的设计模式．基于这一模式，用限幅电压开关理论指导设计了ｎＭＯＳ三值Ｄ型、ＪＫＬ型和Ｔ型主从触发器．结果表明，这一设计模式可克服ＪＫＬ型和Ｔ型通过Ｄ型主从触发器转换得到的缺点，并且证明了限幅电压开关理论可在开关级指导触发器设计     

RS触发器指令实现顺序控制的编程方法

PLC的编程教学中,常常会遇到顺序控制系统的编程问题,需要根据控制要求设计出系统的顺序功能图,再选用合适的指令将功能图转换成梯形图指令。本文以组合机床动力头控制为例,介绍采用RS触发器指令实现顺序控制的编程方法。     

555定时器功能及应用的探讨

555定时器是一种中规模集成电路,只要在外部配上适当阻容元件,就可以方便地构成各种脉冲产生和整形电路,例如多谐振荡器、施密特触发器和单稳态触发器等。主要介绍555定时器以及由555定时器构成的单稳态触发器的基本功能,并举例说明了单稳态触发器的应用。     

触发器在图书资料智能管理系统中的应用

为提高触发器的使用效率,对触发器的原理、运行机制和作用进行了剖析、分解,分析了SQL Server2008中两个相关的临时表,结合图书资料智能管理系统阐述了如何应用触发器解决实际问题,探讨了触发器技术在保证数据库完整性中的应用。     

基于低功耗双边沿JK触发器的异步减法计数器和可逆计数器设计

从JK触发器的激励表和状态转换矢量K图出发,导出了基于单边沿JK触发器的同步、异步减法计数器和可逆计数器的设计方法,给出了双边沿JK触发器的完整状态方程,并以此为基础提出了基于双边沿JK触发器的异步减法计数器和可逆计数器的设计方法。     

RS,JK触发器教学中的联想点滴

在讲解由与非门组成的基本ＲＳ ,同步ＲＳ ,和主从ＲＳ触发器及ＪＫ触发器的过程中 ,由于涉及的触发器各类较多 ,因此 ,对这些触发器逻辑功能的理解和记忆比较困难。为了使学生便于学习与记忆 ,可将这些触发器联系起来 ,使教与学都变得较为简单。首先 ,将基本ＲＳ触发器与同步ＲＳ触发器联系。基本ＲＳ触发器的逻辑功能可由逻辑电路直接分析出 ,如真值表 ( 1)所示。为便于记忆 ,可强调低电平有效 ,- Ｒ端为置Ｏ端 ,- Ｓ为置 1端。在基本ＲＳ触发器的基础上 ,构成了同步ＲＳ触发器 ,教学时 ,强调同步ＲＳ触发器在ＣＰ =1期间接收信号 ,其逻辑…     

RS/GIS集成技术在油气勘探中的应用研究

本文从地理信息系统和遥感的互补性出发，说明了二者集成的原理根据当今石油工业面临的问题和挑战．结合RS／GIS集成技术的优点，讨论了RS／GIS集成技术在油气勘探中的应用．     

SQL Server 2005中触发器的应用

触发器是一种保证数据完整性的方法,它是一种特殊的存储过程,本文简述了SQL Server 2005中的重种触发器对象：After,DDL和Instead of触发器的概念、工作原理,并给出了应用实例。     

Students' Reactions to the Introduction of Videoconferencing for Classroom Instruction

This study examined how students who had no prior experience with videoconferencing would react to the use of videoconferencing as an instructional medium. Students enrolled in seven different courses completed a questionnaire at the beginning of the semester and again at the end of the semester. Students at the origination and remote sites did not differ in their reactions toward videoconferencing but there was a significant difference for gender. Women reacted less favorably to videoconferencing. Compared to the beginning of the semester, students reported significantly less positive attitudes toward taking a course through videoconferencing at the end of the semester. There were no significant differences in students' attitudes toward videoconferencing across courses at the beginning of the semester but there were significant differences across the courses at the end of the semester. The results suggest the need for better preparation for both students and instructors.     

Cooler temperatures inductive to locust outbreaks

Ajoint study by Prof. ZHANG Zhibin from the CAS Institute of Zoology and his co-workers from Norway, US and Swiss have indicated that historical outbreaks of migratory locusts in China were associated with cold spells, suggesting that China＇s projected climate warming could decrease the pest＇s numbers. The study was published in Proceedings of theNational Academy of Sciences on 17 September, 2007.     

Exploring Multiplexity: Social Network Structures in a Computer-Supported Distance Learning Class

A computer-mediated group is a complex entity whose members exchange many types of information via multiple means of communication in pursuit of goals specific to their environment. Over time, they coordinate technical features of media with locally enacted use to achieve a viable working arrangement. To explore this complex interaction, a case study is presented of the social networks of interactions and media use among members of a class of computer-supported distance learners. Results show how group structures associated with project teams dominated who communicated with whom, about what, and via which media over the term, and how media came to occupy their own communication niches: Webboard for diffuse class-wide communication; Internet Relay Chat more to named others but still for general communication across the class; and e-mail primarily for intrateam communication. Face-to-face interaction, occurring only during a short on-campus session, appears to have had a catalytic effect on social and emotional exchanges. Results suggest the need to structure exchanges to balance class-wide sharing of ideas with subgroup interactions that facilitate project completion, and to provide media that support these two modes of interaction.     

The Role of Intermediating Institutions in the Diffusion of Electronic Data Interchange (EDI): How Industry Associations Intervened in Denmark, Finland, and Hong Kong

Electronic data interchange (EDI) provides means for interorganizational communication, creates network externalities, requires an advanced information technology (IT) infrastructure, and relies on standards. In the diffusion of such innovations, institutional involvement is imperative. Such institutions contain governmental agencies, national and global standardization organizations, local government, and nonprofit private organizations like industry associations. The last type of organizations we call intermediating institutions. They intermediate or coordinate ("inscribe") the activities of a group of would-be adopters. Unfortunately, little is known of how these organizations shape the EDI diffusion trajectory. In this article we examine one specific type of intermediating organizations?industry associations?and how they advanced the EDI diffusion process in the grocery sectors of Hong Kong, Denmark and Finland. We identify six institutional measures, placed into a matrix formed by the mode of involvement (influence vs. regulation) and the type of diffusion force (supply push vs. demand pull), that can be mobilized to further the EDI diffusion. Industry associations were found to be active users of all these measures to varying degrees. Their role was critical especially in knowledge building, knowledge deployment, and standard setting. Furthermore, institutional involvement varied due to policy and cultural contingencies and power dependencies.     

Low doses of a red wine ingredient figh diabetes in mice

Aresearch group led by Prof. ZHAI Qiwei from the Institute for Nutritional Sciences under the CAS Shanghai Institutes for Biological Sciences has discovered that even relatively low doses of resveratrol--a chemical found in the skins of red grapes and in red wine--can improve the sensitivity of mice to the hormone insulin, according to a report in the October,2007 issue of Cell Metabolism. As insulin resistance is often characterized as the most critical factor contributing to the development of Type 2 diabetes, the findings“provide a potential new therapeutic approach for preventing or treating” both conditions, the researchers said.     

How Electronic Publishers are Protecting Against Piracy: Doubts About Technical Systems of Protection

The increasing prospects of digital piracy has prompted the perceived need by electronic publishers to adopt technical systems of protection, and governments to reform their copyright laws. This article is a preliminary study of the management of intellectual property by electronic publishers, defined as those involved in the production of online databases, and CD-ROMs. It focuses on three main issues: (1) how electronic publishers view the increasing threat of piracy; (2) the methods of protection employed to protect intellectual property in digital format; and (3) the importance of technological protection of intellectual property in electronic publications. The analysis is based on a sample of 23 UK electronic publishers. The interviews revealed an interesting assortment of protection methods and did not show that technological protection was a preferred way. Instead, the means of protection, in addition to copyright law, comprised niche markets, pricing, trust, bad publicity, and nontechnical and technical means.     

Rough Justice: A Statistical Assessment of ICANN's Uniform Dispute Resolution Policy

Long-standing conflict between domain name registrants and trademark holders prompted the Internet Corporation for Assigned Names and Numbers (ICANN) to create a global, mandatory arbitration procedure known as the Uniform Dispute Resolution Policy (UDRP). The UDRP has been used in 2166 cases involving 3938 domain names as of 1 November 2000. The policy gives the initiator of a complaint, generally a trademark holder, the right to choose which ICANN-accredited dispute resolution service provider (RSP) will handle the case. During the preparation of the UDRP,some feared that complainant selection would lead to "forum shopping" that might bias the results. This article performs a statistical assessment of the forum-shopping thesis and finds support for it. There are statistically significant differences in the various RSPs' propensity to take away names from defendants; there are also major differences in the number of cases brought to each RSP. RSPs who take away names have the larger share of cases. The study examines other variables that might explain differences in market share, such as price, the plaintiff's nationality, or the time taken to decide a case. It finds that nationality and time also are correlated with market share. The study concludes that shopping for a favorable outcome is an important factor in the UDRP.     

Prevalence of soft neurological signs in Chinese people

Prof. Raymond C.K. Chen, a neuropsychologist with the CAS Institute of Psychology, has made novel progress in his studies of schizophrenia. His work has been reported by a recent issue of Behavioural Neurology.     

Molecular motor assembly of a biomimetic system

Active biological molecules and functional structures can be fabricated into a bio-mimetic system by using molecular assembly method. Such materials can be used for the drug delivery, disease diagnosis and therapy, and new nanodevice construction.     

Monoculture Rubber Plantations Have Negative Ef ects on Controlling Splash Erosion

<正>In Xishuangbanna,one of China’s most biodiverse regions,landscape has changed dramatically during the past three decades due to the conversion of tropical rainforest to rubber plantations.In steep areas,terraces are often constructed before planting rubber trees,which causes two important changes in the soil:the destabilization of soil in the bench terraces and the increased vulnerability of unvegetated riser faces to erosion.Few studies have documented the nature and intensity of erosion on bench terraces.Prof.LIU Wenjie and his colleagues from the Xishuangbanna Tropical Botanical Garden(XTBG)conducted a study in Menglun County(21°5′39″N,101°15′55″E),Xishuangbanna to evaluate the influence