An Improved ID-Based Group Key Agreement Protocol

ID-based constant-round group key agreement protocols are efficient in both computation and communication, but previous protocols did not provide valid message authentication. An improvement based on attack analysis is proposed in this paper. The improved method takes full advantage of the data transmitted at various stages of the protocol. By guaranteeing the freshness of authentication messages, the authenticity of the generator of authentication messages, and the completeness of the authenticator, the improved protocol can resist various passive and active attacks. The forward secrecy of the improved protocol is proved under a Katz-Yung （KY） model. Compared with existing methods, the improved protocol is more effective and applicable.     

竖直U型地埋管传热性能数值模拟

对土壤源热泵系统在制冷季中垂直U型地埋管的传热性能进行数值模拟,揭示U型管入口水温、入口流速和回填材料导热系数对地埋管传热性能的影响规律.计算结果表明:在30~60°C的入口温度范围内,当雷诺数从3 000提高到11 000时,会使地埋管热流量增大10~23W,但会导致流体进出口温差降低0.2~1.34°C,在工程应用中流体进口流速要控制在一定范围内.水的入口温度和雷诺数分别为45°C和7 000时,回填材料导热系数从0.5 W/m·K增大至2.5 W/m·K,U型地埋管的热流量增大了将近2倍,也就是说在工程应用中,如果在回填土中掺混一定比例的保水材料将会增强埋管换热,并防止埋管长期运行时由于土壤本身保水性差使得土壤板结从而导致埋管失效.模拟结果与实验数据进行对比吻合较好.     

典型屋顶太阳能光伏板风压实测研究

对一栋多功能低层建筑平屋顶上的太阳能光伏板进行风压实测,根据风压时程特性选择适当的概率密度函数对各测点的风压系数进行非线性回归分析.运用6种概率密度函数对各测点的均值和极值(正极大值和负极小值)风压系数时程以及面积平均后的极值风压系数时程进行数值拟合,比较不同概率分布的拟合效果.回归分析结果表明:均值风压系数的概率分布近似无偏分布,t分布的拟合效果最好,其次是Logistic分布、正态分布、极值I型分布;负压极小值和正压极大值风压系数的概率分布分别为左偏分布和右偏分布,极值I型分布的拟合效果最好,其次是Lognormal分布和Gamma分布,而正态分布的拟合效果最差;最不利风压系数由极值负风压控制,即光伏板的风力由吸力主导;经面积平均后的最不利风压系数建议取值-2.3.     

混响室条件下辐射敏感度表征方法研究

为确定混响室条件下辐射敏感度的表征方法,分别对混响室步进模式和连续模式下的电磁环境特征进行分析,得出可能的几种表征方法. 再将某型电子设备分别在两种工作模式下进行电磁辐射敏感度测试,利用几种可能的表征方法分别得出其测试结果,并对各个表征方法进行分析. 基于贝塞尔公式对各个可能的表征方法进行重复性及不确定检测. 结果表明,为了获得良好的测试可重复性及不同模式的测试结果相关性,混响室步进模式时,可采用多个步进位置的平均值作为辐射敏感度的测试结果;混响室工作于连续模式时,应当选择适当的统计平均时间参数对测试结果进行表征.      

基于节点吸引力的可调参数复杂网络模型

针对真实网络的生长演化规律,以及BA无标度网络模型和原始的节点吸引力模型在择优连接以及生成网络统计特征方面所存在的问题,综合考虑复杂网络生长演化过程中节点度和节点吸引力的择优连接特性,提出了一种基于节点吸引力的可调参数复杂网络模型. 理论研究与仿真实验分析表明,基于节点吸引力的可调参数复杂网络模型可以有效生成结构稳定并与实际网络统计特征很接近的复杂网络,通过调节模型参数可以灵活调整网络的生长演化过程. 模型生成的网络度分布仍然服从幂律分布,并且具有较高的群集系数和平均路径长度.      

GaAs/Al_xGa_(1-x)As非对称耦合双量子阱中的激子态

考虑三元混晶效应,采用变分法计算GaAs/AlxGa1-xAs非对称耦合双量子阱中激子的结合能及其尺寸和压力效应.结果表明:由于双阱的耦合作用,激子结合能表现出与对称情形显著不同的性质,随着阱宽的非对称变化,激子类型可在直接型和间接型之间相互转化.在中间垒厚取较小的固定值时,结合能随左阱宽的增加先减小到一极小值,后增大再减小;随着中间垒厚的增加,结合能最初展现微弱震荡变化,然后突然减小.结合能随Al组分和压力影响均受双阱的耦合和对称性影响较大.     

水、氮控制对荒漠草原植物群落特征的影响

以短花针茅荒漠草原为研究对象,设置了增雨施氮(WN)、增雨不施氮(W)、减雨施氮(RN)、减雨不施氮(R)、单独施氮(N)、自然状况(CK)6个处理,分析控制降雨量以及氮素添加对植被群落特征的影响,结果表明:(1)控制性降雨和氮素添加对群落组成、重要值产生了一定的影响.(2)增雨处理,显著提高了荒漠草原物种的多样性和均匀度(P0.05).(3)减雨施氮处理,提高了荒漠草原物种丰富度、使优势度指数上升.增雨施氮处理,有利于降低群落的生态优势度.(4)增雨施氮处理显著增加了群落地上生物量(P0.05).     

基于ANSYS Workbench软件的半导体制冷器性能模拟研究

利用ANSYS Workbench数值模拟软件研究了输入电压、热端温度、半导体单元属性、半导体电偶臂及级间绝缘材料属性等因素对二级半导体制冷器冷端温度、冷端冷量及制冷系数等性能的影响.研究表明:在一定范围内,保持半导体制冷器热端温度不变,冷端温度随着输入电压的增大而递减;保持输入电压不变,冷端温度随着热端温度的升高而递增;保持输入电压和热端温度不变,冷端冷量随着冷端温度的升高而递增;在冷端温度、热端温度一定时,制冷系数ε随着输入电压的增大而迅速减小;半导体单元高度的增加和单元间距的减小都可以使冷端达到更低温度;随着半导体电偶臂及级间绝缘材料属性即热导率、高度的增加,冷端温度均呈递增趋势.模拟结果与实验数据对比显示,两者具有较好的吻合性.     

Optimization of strand and final electromagnetic stirrers of round bloom casters with multiple sections

Strand electromagnetic stirring (S-EMS) and final electromagnetic stirring (F-EMS) are the main methods used to improve the center porosity and segregation for round blooms. To optimize the stirring conditions, nail shooting tests were conducted for three sections of large round blooms with diameters of ?380 mm, ?450 mm, and ?600 mm. Acid leaching and sulfur print tests were used to investigate the shell thickness. Based on the results of nail shooting tests, a mathematical model of solidification was established, and the variation of shell thickness and the central solid fraction were exactly calculated by the model. By taking all sections into account, the locations of S-EMS and F-EMS were optimized for each section. In the results, the macro-segregation of various sections is improved after the locations of S-EMS and F-EMS systems are changed.     

Mixed delay-independent/delay-dependent stability of uncertain linear time-delayed systems

Consider uncertain linear time delay systems described by the following state equation: x(t)=[A0+Δ A0(t)]x(t)+∑ri=1[Ai+ΔAi(t)]x(t-τi).(1) x(t)=(t)t∈[-,0];=maxri=1{τi}(2) where Δ A0(*) and Δ Ai(*)(i=1,…,r) are real matrix functions.Δ Ai(t)=LiFi(t)Ei,ΔA0(t)=L0F0(t)E0, where Li,Ei are known real constant matrices and Fi(t) are unknown real time-varying matrices with Lebesgue measurable elements satisfying ‖Fi(t)‖I,t(i=0,1,…,r). In this note, we develop the methods of robust stability which is dependent on the size of some delays but independent on the size of the others and is based on the solution of linear matrix inequalities.