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21.
提出了一种基于任意网络拓扑的分布式选举领导人算法。每一处理机既不知道系统的网络拓扑,也不知道系统中处理机的台数。对于由n台处理机组成的分布式系统,算法的消息复杂度最好为3#E,最坏不超过#E(2N+1)-N+n;对于同步分布式系统,其时间复杂度最好不超过3(n-1)△t,最坏不超过4(n-1)△t。  相似文献   
22.
提出了一种基于事务冲突图的并发控制方法.事务在执行前要提交其读集和写集,系统根据事务的读集和写集构造出一无圈的事务冲突图,并根据事务冲突图进行并发控制.这种并发控制方法具有对数据库无结构要求、无死锁、非两阶段等优点.讨论了其集中式并发控制方法和分布式并发控制方法.  相似文献   
23.
Two African apes are the closest living relatives of humans: the chimpanzee (Pan troglodytes) and the bonobo (Pan paniscus). Although they are similar in many respects, bonobos and chimpanzees differ strikingly in key social and sexual behaviours, and for some of these traits they show more similarity with humans than with each other. Here we report the sequencing and assembly of the bonobo genome to study its evolutionary relationship with the chimpanzee and human genomes. We find that more than three per cent of the human genome is more closely related to either the bonobo or the chimpanzee genome than these are to each other. These regions allow various aspects of the ancestry of the two ape species to be reconstructed. In addition, many of the regions that overlap genes may eventually help us understand the genetic basis of phenotypes that humans share with one of the two apes to the exclusion of the other.  相似文献   
24.
The possibility of using a centrifugal-gravity concentrator to reject Mg-bearing minerals and minimize metal losses in the flotation of base metals was evaluated. Sample characterization, batch scoping tests, pilot-scale tests, and regrind-flotation tests were conducted on a Ni flotation tailings stream. Batch tests revealed that the Mg grade decreased dramatically in the concentrate products. Pilot-scale testing of a continuous centrifugal concentrator (Knelson CVD6) on the flotation tailings revealed that a concentrate with a low mass yield, low Mg content, and high Ni upgrade ratio could be achieved. Under optimum conditions, a concentrate at 6.7% mass yield was obtained with 0.85% Ni grade at 12.9% Ni recovery and with a low Mg distribution (1.7%). Size partition curves demonstrated that the CVD also operated as a size classifier, enhancing the rejection of talc fines. Overall, the CVD was capable of rejecting Mg-bearing minerals. Moreover, an opportunity exists for the novel use of centrifugal-gravity concentration for scavenging flotation tailings and/or after comminution to minimize amount of Mg-bearing minerals reporting to flotation.  相似文献   
25.
Neuronal activity patterns contain information in their temporal structure, indicating that information transfer between neurons may be optimized by temporal filtering. In the zebrafish olfactory bulb, subsets of output neurons (mitral cells) engage in synchronized oscillations during odour responses, but information about odour identity is contained mostly in non-oscillatory firing rate patterns. Using optogenetic manipulations and odour stimulation, we found that firing rate responses of neurons in the posterior zone of the dorsal telencephalon (Dp), a target area homologous to olfactory cortex, were largely insensitive to oscillatory synchrony of mitral cells because passive membrane properties and synaptic currents act as low-pass filters. Nevertheless, synchrony influenced spike timing. Moreover, Dp neurons responded primarily during the decorrelated steady state of mitral cell activity patterns. Temporal filtering therefore tunes Dp neurons to components of mitral cell activity patterns that are particularly informative about precise odour identity. These results demonstrate how temporal filtering can extract specific information from multiplexed neuronal codes.  相似文献   
26.
数控设备E-服务技术研究   总被引:2,自引:0,他引:2  
针对数控设备售后服务与技术支持问题,提出基于Web的服务保障系统.系统由E-服务平台、数控机床网关和远程终端三部分组成.E-服务平台是一个特殊网站,它通过Internet向客户提供技术支持与服务.数控机床网关是一个移动PC,当机床发生故障时将其带到现场,采集机床PLC信息、视频信息和传感器信息,并将信息传送到E-服务平台供诊断分析.远程终端可以是连接在Internet上的任何PC机,客户通过远程终端访问E-服务平台,获得快速和高质量的产品售后服务.  相似文献   
27.
基于空间曲面共轭原理,建立螺旋锥齿轮的齿面矢量方程,由空间坐标系的变换,确定出刀具相对工件的位置和姿态,实现刀具与工件的相对运动,在综合考虑齿面形状、刀具形态及机床结构等因素的基础上,分析了五坐标螺旋锥齿轮面NC过程插补误差,建立考虑齿面NC插补误差的螺旋齿轮数控加工方法,计算结果与加工实验结果基本一致。  相似文献   
28.
数控加工中心误差G代码补偿技术   总被引:1,自引:0,他引:1  
提出了数控加工中心误差的G代码补偿方法,应用刚体运动学理论和齐次坐标变换技术建立了多轴数控加工中心空间误差的通用模型,把加工患具相对工件的终端误差表示为各个误差源和刀具位置的函数,给出了全部运动误差参数的激光干涉仪识别方法,提出了数控加工中心三种基本运动的误差补偿算法,在立式加工中心上进行了该方法的实验,结果表明引入误差补偿后使加工中心的系统误差减小80%-90%。  相似文献   
29.
可重构的虚拟数控远程操作面板生成系统研究   总被引:3,自引:0,他引:3  
介绍了虚拟数控系统软件芯片的构建方法,研究了基于可重构的虚拟数控操作面板设计原理和实现技术;利用COM/DOOM技术,开发实现了可重构的、可定制的虚拟数控操作面板生成系统,采用ASP,ActiveX等技术和通用的协议标准TCP/IP,实现了了基于Web的虚拟数控系统的远程操作与监控,并给出了系统的运行实例。  相似文献   
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