Secrecy performance analysis on cooperative CR-NOMA network

In order to improve the secrecy performance of communication system and make efficient use of limited spectrum,overlay cognitive radio (OCR) technology was combined with non-orthogonal multiple access (NOMA) technology and the communication model was proposed,in which secondary network realized dynamic switching between assisting primary network communication and secondary network communication by sensing whether the primary user occupied the spectrum or not.Artificial noise (AN) aided technology was used in primary and secondary networks respectively to further improve the secrecy performance of the system.The secrecy performance of the system was studied by deducing the expressions of the primary and secondary network secrecy outage probability and secrecy throughput respectively.The simulation results show that the proposed cognitive cooperative NOMA communication scheme is beneficial in reducing secrecy outage probability and increasing secrecy throughput.Furthermore,the influence of AN power allocation factor on system performance is given.     

浅谈信息系统的安全审计

本文首先介绍"审计"一词的由来、然后引入信息系统审计(IT审计)的社会背景、定义、意义和目的、对象和IT审计所包含的业务内容.紧接着介绍信息系统安全审计的概念,最后较详细的介绍信息系统安全审计需要做哪些工作.     

A novel cooperative spectrum sensing method based on cooperative game theory

A novel cooperative sensing method is proposed in this paper. The proposed scheme adopts sensing creditability degree to characterize the impact of the distance and the channel parameters on the sensing result, and considers that each user has different average SNR and different decision threshold, by using General Nash Bargaining Solution (GNBS) strategy in Cooperative Game Theory (CGT), the detec-tion performance for two-user case are derived. For multi-user case, the sensing performance is obtained with Hungarian method. Compared with the traditional schemes such as Nash Bargaining Solution (NBS) and AND, the proposed scheme covers all the factors mentioned above, and enhances the sensing rationality and reliability. Simulation results show that the proposed scheme can further improve the sensing performance and creditability.     

植物园一次科普活动分析——以2008年全国科普日北京主场活动为例

本调查是就植物园承办全国科普日活动情况开展的,调查结果显示,本次科普日上受众群体文化层次较高,年龄层次偏大,多为50岁以上人群,且多为女性;不同年龄的受众群体对科普活动项目类型要求不同,植物园举办科普活动满足了受众休闲、学习的双重要求;高新技术与生活化内容的科普项目是本次科普日的亮点,倍受大家关注;参与、互动、展览与游园相结合的形式是植物园科普日活动成功的重要经验。     

1.74μm压应变InGaAs/InGaAsP量子阱分布反馈激光器

制备了1.74μm脊波导结构压应变InGaAs/InGaAsP量子阱分布反馈激光器.采用低压金属有机化合物气相沉积法生长器件材料,应用应变缓冲层防止In的分凝.未镀膜的腔长为300μm的器件阈值电流为11.5mA,100mA时最大输出功率为14mW,边模抑制比为33.5dB.     

Power Management Based Grid Routing Protocol for IEEE 802.11 Based MANET

MANET(Mobile Ad Hoc Network)is a collection of wireless mobile nodes forming a temporary communica-tion network without the aid of any established infrastructure or centralized administration.The lifetime of a MANETdepends on the battery resources of the mobile nodes.So energy consumption may one of important design criterions forMANET.With changing the idle model to sleep model in the grid environment,this paper proposes a new energy-awarerouting protocol.Performance simulation results show that the proposed strategy can dynamic balance the traffic load in-side the whole network,extend the lifetime of a MANET,and without decreasing the throughput ratio.     

基于MATLAB GUI 的钻井工具姿态采集处理系统

本文主要涉及MATLAB在钻井工具空间姿态测量方面的应用,采用MATLAB环境下的GUI图形用户界面编程方法编制了上位机软件.该上位机软件通过对串口的操作和对Activex控件的调用,在室内模拟钻井实验中,实现了PC与片上系统C8051F060在115 200波特率下的串行通信、多路数据采集的控制及数据传输、处理,最终实现了对钻井工具空间姿态的测量.     

科学精神涵义的发展变化——关于新文化运动时期与改革开放以来科学精神讨论的比较

我国历史上与科学精神有关的讨论集中发生在新文化运动时期和改革开放以来至今这段时期.新文化运动时期科学精神内涵包括求真崇实精神、实践和探索精神、怀疑精神、无私精神等.改革开放以来科学精神包括两方面:第一,科学精神是人们在科学活动中所具备的意识和态度,主要包括实事求是精神、实践精神、创新精神、探索精神、怀疑精神、团队精神、平权精神、宽容精神等.第二,科学精神是从科学活动中提升出来的文化精髓和价值观念体系,其基本价值观是追求客观事实和真理,崇尚理性,注重实证,不断进取等.科学精神的内涵是不断变化和发展的,而这种发展和变化的根本原因是时代的进步和科学观的发展.而科学精神中追求真理、实事求是的最基本的内涵并没有变.     

基于Multisim8的运算放大器的线性应用仿真

在模拟电路的教学中,运算放大器的线性应用无疑是一个重点内容。如果在教学中应用Multisim8仿真辅助教学,可以避免理论教学过程中讲述枯燥,大大提高教学效率。通过仿真可以形象的将运算放大器的应用电路和结果展示在学生眼前,一方面加深学生对理论的理解,另一方面学生通过设计仿真软件看到了实际电路的结构和使用方法。     

用标度理论和蒙特卡洛方法研究微晶硅薄膜的生长机制

使用热丝化学气相沉积技术制备微晶硅薄膜(沉积速度为1.2nm/s),通过原子力显微镜研究了薄膜前期生长的粗糙化过程.按照标度理论获得微晶硅薄膜的生长因子为β≈O.67,粗糙度因子为α≈O.80,动力学因子为1/z=0.40.这些标度指数不能用一般的生长模型来解释.通过蒙特卡罗模拟给出与实验一致的结果.模拟表明,入射流方向、生长基元的类型和浓度、生长基元的粘滞、再发射和影蔽过程都对微晶硅薄膜的表面形貌有比较重要的影响.