数据库推理通道的动态控制

数据库推理问题是数据库安全研究的重要组成部分,主要研究推理通道的检测方法和控制策略。该文提出一种动态控制推理通道的方法。该方法为每个推理通道建立一个标识集合,利用集合中元素和推理通道中对象的关联来控制查询的处理,使用户能灵活地访问数据但又得不到足够的信息来推理。与以前提出的方案不同,该方案保证了数据的最大可用性,同时有效地阻止推理并保持了快速的查询处理能力。     

浅谈展示设计中图形符号的作用

展示设计作为一门较新的设计门类,在当今社会的发展日趋强大。对于展示设计而言,如何将展示的内容更好地表现出来,是设计成功与否的关键。图形符号作为一种装饰性的语言,在展示设计之中可以对表现展示主题和烘托展示气氛起到一定的帮助作用,使展示的内容得以更好的展现在参观者面前。     

指纹图象预处理

采用块方向图滤波的方法实现了沿指纹纹线方向的图象增强及图象的二值化,用细化模板匹配的迭代方法实现了纹线的细化,解决了指纹纹线复杂难以提取的问题,具体实现了指纹图象的预处理。经过预处理后提取出了纹线,且保留了纹线的关键信息,有利于下一步的特征提取工作。     

PCI总线在双谱段探测系统中的应用*

PCI是DSP应用系统与通用计算机高速通信的理想接口。介绍了一种双谱段探测系统的PCI接口方案,该方案采用TI公司的TMS320F2812 DSP作为控制单元主控芯片,采用Cypress公司PCIDP系列的CY7C09449PV作为PCI接口芯片,具有接口简单方便易于实现的优点。详细讨论了CY7C09449PV与TMS320F2812的硬件连接、参数配置与时序分析。     

Response to ‘Comments on: A cohesion measure for object‐oriented classes’

Indicating that CBMC does not satisfy the monotonic property in terms of the number of interactions, Xu and Zhou proposed an augmented definition of CBMC by adopting cut set instead of glue methods. The augmented CBMC clearly satisfies the monotonic property. However, CBMC is designed to overcome the problem with respect to the number of interactions and, therefore, focuses on the interaction pattern, especially, member connectivity. Consequently, it does not make sense to mention the monotonic property of CBMC with respect to interaction number. Moreover, the notion of glue methods allows several interpretations on the design quality of a class. However, that meaningful interpretation is not possible for the augmented definition due to the removal of the notion of glue methods. Copyright © 2001 John Wiley & Sons, Ltd.     

电脑黑客与网络安全

叙述了黑客对网络安全的破坏作用,说明了黑客对网络进行病毒攻击的手段和信息轰炸的攻击方法,并利用敌方网络系统进行情报窃取、情报欺骗。对网络安全的防护技术进行了探讨。     

熔体流动时间法测定PBT树脂特性粘数的研究

开发了一种新的特性粘数分析方法 ,该方法采用熔体流动时间计算特性粘数 ,与经典特性粘数分析方法有很好的相关性且具有分析时间短、费用低、无污染等优点。     

两性田菁胶在处理高浓度印染废水中的应用

研究了以聚合硫酸铁(PFS)为主凝剂、两性田菁胶(ASG)为助凝剂处理高浓度印染废水的各种影响因素。实验结果表明：PFS和ASG分别以2000mg／L和100mg／L的复配浓度、pH值接近中性时混凝效果为最佳，CODCr去除率达到80％，色度与浊度去除率均达99％以上。     

Characteristics of entropy generation and heat transfer in a microchannel with fan-shaped reentrant cavities and internal ribs

Three-dimensional laminar fluid flow and heat transfer in a micro heat sink with cavities and internal ribs are investigated us-ing numerical methods. Moreover, according to the second law of thermodynamics, the model of entropy generation is also established for variable cross section of the microchannel. The simulation encompasses Reynolds number of 198-600, relative cavity height e1/Dhvalues of 0-0.65, relative rib height e2/Dhrange of 0-0.2167. The results show that the effect of relative rib height on entropy generation is significant, while the relative cavity height has little effect on it. The combined effect of cavities and ribs in the microchannel has better performance of heat transfer than the smooth microchannel under similar conditions. Extensive simulations are conducted to collect data on the characteristics of heat transfer and fluid flow in a micro heat sink with cavities and internal ribs. Using these data, correlations for Nusselt number and friction factor in terms of Reynolds number and the geometry of cavity and rib have been developed.