Multi-level delegations with trust management in access control systems

Delegation is a mechanism that allows one agent to act on another’s privilege. It is important that the privileges should be delegated to a person who is trustworthy. In this paper, we propose a multi-level delegation model with trust management in access control systems. We organize the delegation tasks into three levels, Low, Medium, and High, according to the sensitivity of the information contained in the delegation tasks. It motivates us that the more sensitive the delegated task is, the more trustworthy the delegatee should be. In order to assess how trustworthy a delegatee is, we devise trust evaluation techniques to describe a delegatee’s trust history and also predict the future trend of trust. In our proposed delegation model, a delegatee with a higher trust level could be assigned with a higher level delegation task. Extensive experiments show that our proposed multi-level delegation model is effective in accurately predicting trust and avoiding sensitive information disclosure.     

排球课学习效果的灰色关联分析

运用灰色系统理论的关联分析法,对齐齐哈尔大学体育专业学生近5年排球技术考试成绩进行分析研究,找出影响学生成绩提高的主要因素,对排球教学及排球各项技术之间关联度进行综合分析与评价。     

加捻对热致液晶聚芳酯初生纤维拉伸性能的影响

热致液晶聚芳酯（TLCP）的特殊化学结构使其具有高强度、高模量、低粘度、易加工等诸多优良特性,且TLCP纤维力学性能对其应用于纺织业具有举足轻重的作用。本论文主要研究加捻对TLCP纤维力学性能的影响,探究其影响机理。研究结果表明：加捻对其力学性能影响很大,TLCP纤维束的强力随着捻度的增加呈先增大后减小趋势。当TLCP纤维束的线密度为52.50 tex,捻度为130Tm时,最大强度为9.14 cN/dtex。未加捻TLCP单纤维的线密度为1.394 tex时,最大强度为11.3cN/dtex。     

Extraction behaviours of titanium and other impurities in the decompositio process of ilmenite by highly concentrated KOH solution

To effectively utilize ilmenite and recycle KOH solution,the extraction behaviours of titanium and other associated impurities in the decomposition process of ilmenite by highly concentrated KOH solution were studied.Experiments on the extraction behaviours of titanium as well as other associated impurities of ilmenite such as iron,silicon,calcium,and aluminiurn were carried out.The effects of various parameters,including reaction temperature,KOH concentration,reaction time,alkali-to-ore mass ratio,and particle size on the extraction rate of titanium and other impurities were examined.When the finely ground ore (58-75 μm) reacted with KOH solution (80wt％) in an alkali-to-ore mass ratio of 7:1 at 260°C for 60 min,almost complete extraction of titanium was achieved,while the extraction rate of aluminium was 78％ and that of other impurities was less than 22％.Moreover,high purity (98.2wt％) TiO2 with the anatase structure could be gained in the purification process.     

Thermodynamic analysis of simplified dual-pressure ammonia-water absorption power cycle

A simplified dual-pressure ammonia-water absorption power cycle (DPAPC-a) using low grade energy resources is presented and analyzed. This cycle uses turbine exhaust heat to distill the basic solution for desorption. The structure of the cycle is simple which comprises evaporator, turbine, regenerator (desorber), absorber, pump and throttle valves for both diluted solution and vapor. And it is of high efficiency, because the working medium has large temperature difference in evaporation and small temperature difference in absorptive condensation, which can match the sensible exothermal heat resource and the cooling water simultaneously. Orthogonal calculation was made to investigate the influence of the working concentration, the basic concentration and the circulation multiple on the cycle performance, with 85–110 °C heat resource and 20–32°C cooling water. An optimum scheme was given in the condition of 110 °C sensitive heat resource and 20 °C cooling water, with the working concentration of 0.6, basic concentration of 0.385, and circulation multiple of 5. The thermal efficiency and the power recovery efficiency are 8.06 % and 6.66%, respectively. The power recovery efficiency of the DPAPC-a is 28.8% higher than that of the steam Rankine cycle (SRC) and 12.7% higher than that of ORC (R134a) under the optimized situation.     

一种能量可计算的星型无线传感器网络协议

提出一种基于双向通信的无线传感器网络的超低功耗协议.通过分析协议的防碰撞原理,给出了网络参数的设计原则,以及传感器节点功耗与传感器网络寿命的关联算法,并通过OMNeT++网络仿真软件对协议进行了仿真验证.结果表明:该方法通过降低协议的复杂度,控制网络的工作流程,有效降低了整个无线传感器网络的能耗,延长了网络的使用寿命,并实现了预测无线传感器网路的寿命.     

卫星回传链路CPM信号调制识别研究

文章解决了DVB-RCS2标准中规定的卫星回传链路上连续相位调制信号(CPM)调制识别问题。根据调制参数的不同,标准中的CPM信号有5种类型,且在TDMA突发模式下传输。短突发长度和低信噪比环境下信号调制识别是实现信号正确解调的前提。提出了一种基于改进后的广义检测后积分(GPDI)匹配准则的调制识别方法。该算法采用改进后的GPDI匹配准则获得接收信号与每类CPM的匹配值;并按最大值准则估计得到信号类型从而实现信号调制识别。通过该方法可实现单个突发帧内调制识别。仿真实验表明,该算法不需符号速率的先验信息,对大频偏和相偏具有较好的鲁棒性,具有较低的复杂度和优异的抗噪声性能。     

基于P2P的短视频点播相似度分享系统

在线共享短视频改变了传统的客户/服务器(C/S)视频观看方式,但也增加了服务器带宽压力。针对这一问题,引入P2P技术,构建了SShare系统。研究了重叠网构建和基于点播相似度资源查找算法。仿真实验表明,SShare系统可大大减少服务器带宽资源的消耗。