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1.
一、引言逻辑函数具有表格式(真值表)、代数式及图形(K图)等三种表示形式,其中的K图表示由于具有相邻格可以合并的特点,因此,它在二值或多值逻辑函数的简化中提供了直观与方便的综合程序。然而,逻辑函数的图形表示受到变量数的限制,这是由于随变量数的增加,K图的规模按基数的幂次规律迅速增加。在二值逻辑中,为了扩大K图的适用范围已引入了降维K图的方法,它乃是把一个n变量的函数用一个m维(m相似文献   

2.
黄瑞祥  孙浙永  肖林荣 《科技通报》2007,23(4):540-543,567
图形化简法是逻辑函数化简的有效工具。bi图和西图分别是RM展开式、CRM展开式的图珏表示。通过对RM展开式、CRM展开式系数关系的分析,提出了2种bj图和dj图的图形转换方法,并廷各种方法予以实例说明。对于5变量以下的逻辑函数,这二种方法具有简单、直观等特点。  相似文献   

3.
浅谈Linux下的多线程编程   总被引:1,自引:0,他引:1  
本文主要研究了在LINUX操作系统下多线程的编程方法,主要包括多线程的基本创建方法、如何修改多线程的属性以及线程之间的数据处理。核心论述了多线程数据处理的方法中的互斥锁和条件变量。  相似文献   

4.
刘观生  陈偕雄 《科技通报》2003,19(4):297-299
通过对Hadamand矩阵的分析,并结合谱系数图与K图的自身特点,从中找出两种图之间的对应关系,进而提出了一种谱系数图与K图互换的改进算法。此外,还对积项谱与K图的转换关系进行了探讨,得到了相应的积项谱转化为K图的方法。文中对这两种方法分别进行了仔细的说明,并通过一系列例子进行了验证。实例证明,改进的算法具有简单、直接、方便等特点。  相似文献   

5.
讨论了逻辑函数最大项展开式和COD展开式的矩阵转换方法,分析了K图和gj图之间转换的图形方法.在此基础上提出了最大项展开系数和除一符合展开系数转换的表格方法.与图形方法相比,表格方法具有不受变量数目约束,易于计算机的实现等优点.具有较好的实用性.  相似文献   

6.
互斥剪接是产生蛋白多样性的调控途径,但是人们对其背后的机制却了解很少。我们利用比较基因组分析揭示了控制14-3—3 Xi pre-mRNA的互斥剪接的内置内含子元件。这些元件具有类群特异性.但在二级结构水平却是进化保守的。组合证据揭示在这些跨内含子RNA配对的三个功能:  相似文献   

7.
对于操作系统课程,进程同步与互斥的内容是其中一个重点和难点。进程概念较为抽象,进程同步与互斥更是老师难讲、学生难学的内容。作者经过多年的教学总结,在该文中阐述了如何用P、V原语实现进程同步与互斥的教学方法,按该方法从易到难,循序渐进,边分析边讲解,教学效果良好,学生能够更好地理解进程同步与互斥关系的实现。  相似文献   

8.
在光学显微镜和扫描电镜下对南五味子属Kadsura 11种植物36个样品的种子宏观形态及种皮微 形态特征进行了研究。结果表明其种子形状为肾形、椭球形、心形或肾状扁球形。在扫描电镜下种子表 面特征有种间差异,其纹饰可分为3种类型,即近平滑型、负网纹型和网纹型。短梗南五味子K. borneensis和披针叶南五味子K.lanceolata为近平滑型,其种子表面近平滑;黑老虎K.coccinea和柄果 南五味子K.verrucosa 为负网纹型,其种子表面具负网纹,网眼凸起,网脊凹陷;异形南五味子K.hetero- clita、毛南五味子K.induta、南五味子K.japonica、冷饭藤K.oblongifloia、狭叶南五味子K.  angustifolia、 南洋南五味子K.scandens 和大叶南五味子K.marmorata为网纹型,其种子表面具网纹,网眼凹陷,网脊 凸起,此类型在南五味子属中最为普遍。种皮微形态特征在种内相当稳定,在一些种的划分上具有较重 要的意义。南五味子属种皮微形态特征的研究结果支持将多子南五味子K.polysperma和凤庆南五味子 K. interior 归并入异形南五味子以及将长梗南五味子K.longipedunculata归并入南五味子的分类学处理。本文还对南五味子属植物种皮微形态的各种类型的演化趋势作了讨论。  相似文献   

9.
卡诺图是简化逻辑函数的重要工具。但随着变量的增多 ,卡诺图变得愈加复杂 ,相邻项愈难辨认 ,因而它只适用于 6变量以下。利用引入变量卡诺图则可以扩大卡诺图的应用范围。1 引入变量卡诺图 ( VEM)例 1 一个三变量函数的卡诺图如图 ( 1 )所示其逻辑表达式为 :F=ABC ABC ABC ABC图 1        图 2若提出变量 A,B的最小项 ,则上式可变换 F=AB( C) AB( 0 ) AB( C C) AB( C)显然 ,AB=0 0 ,F =C;AB=0 1 ,F =0 ;AB=1 0 ,F =C C=1 ;AB=1 1 ,F=C据此以 A,B为变量 ,可画出如图 2所示 F的二变量卡诺图 ,该卡诺图中除填 0 ,1外还填入了变量 C及变量表达式 ,故称它为引入变量卡诺图。因此具有 n个变量的逻辑函数可用 n- 1 ,n-2 ,…个变量来表示 ,称为降维卡诺图。2 VEM的应用2 .1 利用 VEM化简逻辑函数例 2  F=ABC ABC D ACD ABC ABC D解 :以 D为引入变量作 F的 VEM,F的四变...  相似文献   

10.
在要求时延较小的仿真系统中,声音采集与播放是一个并发互斥过程。就单核CPU下的并发互斥技术,特别是当前国内虚拟电台系统中应用的并发互斥技术进行了分析研究,针对其在多核CPU下可能存在的问题进行了讨论,在此基础上提出了一种基于录音优先算法的改进算法,并从技术对比和算法复杂度方面进行了论证。  相似文献   

11.
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.  相似文献   

12.
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.  相似文献   

13.
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.  相似文献   

14.
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.  相似文献   

15.
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.  相似文献   

16.
CAS should stick to the principle of rendering service to, and giving impetus for, the development of China's science enterprise by making S&T innovations, said CAS President LU Yongxiang. The CAS president made the remarks in a recent talk to communicate the gist of the winter session of the Party's Leading-member Group at CAS, which was held from 7 to 11 January in Beijing.  相似文献   

17.
With great care, Dr. ZHOU Zhonghe takes out a package wrapped by cotton tissue from a drawer and says: "This is the gem of our collections: the fossil of a bird that lived 125 million years ago!" Then, pointing at a tiny mound, he explains: "Look, this is the claw and that is the head. It was in the egg shell and ready to hatch ... The species fell into a family of waterside inhabitants."  相似文献   

18.
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.  相似文献   

19.
This essay focuses on universal service and the Internet as means to support social and political participation. The emphasis on access to telecommunications systems in conventional approaches to universal service is contrasted with access to content. A model of the information environment is described that accounts for the roles of content and conduit, both of which are necessary conditions to achieve true access. A method is outlined for employing information indicators to observe or measure the information environment.  相似文献   

20.
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.  相似文献   

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