动态轴向载荷对超空泡航行体振动特性的影响

根据超空泡航行体水下运动特点,理论分析了作用在航行体上的动态轴向载荷,并采用有限单元法对超空泡航行体自由振动特性和动态轴向载荷作用下的动响应特性进行了数值仿真研究.数值计算结果表明:超空泡航行体轴向分布的径向振动模态具有颈缩特点,其振型呈现喇叭状,首阶径向振动模态固有频率为238.13 Hz;动态轴向载荷作用下超空泡航行体壳中各部分的振动特性不完全相同,特别是锥壳首部,其应变幅值逐步累积直至达到一个稳定的水平;在超空泡航行体上工作的设备需要避开一定的工作频率才能稳定工作.     

“委派型”国家工作人员再认识

我国刑法第93条第2款规定了"委派型"国家工作人员。随着市场经济的发展和社会的变迁,这类人员已经不具备国家工作人员"从事公务"的特征。因此,本文主张该类人员不属于国家工作人员范畴,并对此类人员实施的行为予以重新定性,同时提出修改刑法的建议。     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

B2C环境下基于多属性效用理论的消费者行为模式

通过对网络消费者购买决策过程的分析,提出了基于多属性效用理论研究网络消费者行为模式的方法,依据价格、性能、支付风险、质量风险、投递服务和售后服务6个指标构建了网络消费者购买序列曲线.购买序列曲线反映了网络消费者购买商品的态度、偏好.在上述研究基础上,对商品效用值分布进行了分析,进一步揭示了网络消费者行为模式的特点.将定性研究与定量分析相结合,为网络消费者行为模式的研究提供了一个更为有效的方法.     

Characterization of root-nodulating bacteria on Retama raetam in arid Tunisian soils

The aim of this study is to investigate the diversity of Retama raetam root-nodule bacteria isolated from arid regions of Tunisia. Twelve isolates, chosen as representative for different 16S rRNA gene patterns, were characterized by 16S rRNA gene sequencing and phenotypic analysis. Isolates were assigned to Sinorhizobium, Rhizobium and Agrobacterium. Symbiotic properties of Sinorhizobium and Rhizobium isolates showed a large diversity in their capacity to infect their host plant and fix atmospheric nitrogen. Strain RK 22 identified as Rhizobium was the most effective isolate.     

基于属性委托模型中的自动委托撤销

基于属性的扩展委托模型中(ABDMA),受托者必须同时满足委托先决条件和委托属性表达式才能被委托权限或角色.为提高委托的安全性,方便撤销操作,对该模型进行了扩展.首先定义了用户委托撤销类型,委托者可由此自行撤销委托出去的角色.然后为了支持自动撤销,在模型中引入了自动撤销机制,提出了4种自动撤销类型:由委托有效时间区间、用户先决角色变化、用户属性表达式变化和委托角色属性表达式变化引起的自动委托撤销.接着讨论了自动撤消的系统开销和自动撤销引起的多步委托安全性问题.最后给出了自动撤销算法和系统实现框架.     

创作课教学探讨

创作课程的开设是全面提高学生综合素质的一个重要环节。文章讲述了创作课程开设的方式和教学安排。     

间断基因的检测

叙述了某些不含遗传信息的碱基顺序,介绍了发现和检测间断基因的方法。     

基于集合覆盖理论的Agent协作问题研究

多智能Agent系统中的协作体现多Agent系统(MAS)的灵活性、整体性,通过协作提高Agent群体完成任务的效率.将集合覆盖理论(SCP)引入MAS系统协作行为中的任务分配问题求解,使用改进的低logarithmic ratio bound集合覆盖理论求解方法,详细阐述了利用SCP理论求解Agent任务分配问题的算法,并根据一个战场作战Agent任务分配实例进行了计算,有效地解决战场作战Agent的任务分配问题.     

IEEE 802.16协议的研究及系统仿真

基于最新的宽带无线接入协议IEEE 802.16,通过计算机仿真平台,实现了工作在TDMA-DAMA/FDD模式的仿真系统,设计了上行链路接入的带宽调度机制来实现动态带宽分配.仿真的结果评估了在具有CBR和VBR两种业务终端的系统环境中,对该带宽调度机制的性能,以及其对系统队列长度、网络时延等各项性能指标的影响.