A cognitive TV white space-broadband power line MIMO system for indoor communication networks

Broadband power line communication (BPLC) is a promising solution to satisfy the growing data rate demands for broadband indoor communication networks. However, the BPLC transmission power spectral density (PSD) is restricted in the very high frequency (VHF) band to avoid harmful interference to the existing wireless services. In this paper, a new hybrid system is proposed utilizing BPLC and cognitive radio over TV white space (TVWS) to enhance the system capacity over BPLC in VHF, forming a VHF TVWS BPLC multiple-input multiple-output (MIMO) system. An iterative precoding algorithm is proposed to satisfy the interference limit at the TV primary user (PU) receiver (Rx) and enhance the ergodic capacity. Moreover, a power allocation algorithm is developed for the MIMO system to achieve the maximum ergodic capacity subject to the average total power constraint and limit of interference to TV PU. Simulation results demonstrate the significant enhancement in the achieved capacity by our proposed system in the VHF band compared to both previous cognitive and hybrid BPLC systems.     

重建的岁月——简述美国内战后南方为维持地方自治体制所进行的文化宣扬

提要美国内战之后,南方人通过修建的一系列的战后纪念雕塑工程来重新构建他们对战前的记忆,他们通过这种方式来维护他们之前所拥有的地方权力机构和体制。战后,南方人努力把奴隶制从他们的历史中删除,从而使他们的体制合法化,另一方面他们又向他们的接班人灌输只有相信并继续这样的文化渗透,他们原有的权利体制才不会遇到来自北方政府的质疑。     

防御定向、动机氛围对企业中知识隐藏的影响

知识隐藏是组织中个体面对知识请求时的故意隐瞒行为,抑制创新并削弱组织绩效。对注重安全和风险厌恶的防御定向员工来说,控制与保留知识可以维持自身优势,动机氛围调节了防御定向对知识隐藏的影响。为了揭示知识隐藏的动机和主要影响因素,本文运用实证研究方法,提出研究假设,并通过大样本分析检验假设得出结论。研究验证了防御定向对企业中知识隐藏具有促进作用,绩效氛围能够增强防御定向对知识隐藏的影响,且弱绩效氛围和强绩效氛围起的调节效果随防御定向变化而改变。掌控氛围削弱了防御定向对知识隐藏的影响,当防御定向较低时强掌控氛围起到更大的调节作用,当防御定向较高时弱掌控氛围作用更明显。绩效氛围和掌控氛围有相互抵消的倾向,组织中同时存在两种动机氛围时,各自的作用都会减弱。     

人际不信任、消极情感与知识隐藏行为研究

人际不信任作为判断人际关系质量的重要标准会导致知识隐藏,但至今鲜有研究探讨二者之间的内在机制,削弱了实践指导性。依据情感事件理论和心理所有权理论,重点关注消极情感在人际不信任影响员工知识隐藏行为过程中的中介作用,以及员工知识心理所有权在上述关系中的调节作用。通过对324个样本的层级回归分析发现：（1）消极情感部分中介人际不信任对员工知识隐藏行为的影响;（2）知识心理所有权不仅对消极情感与知识隐藏行为之间的关系具有显著的调节作用,而且显著调节人际不信任通过消极情感影响员工知识隐藏行为的中介作用,表现为员工的知识心理所有权水平越高,消极情感在人际不信任和员工知识隐藏行为关系间的中介作用越弱。     

A reversible and secure patient information hiding system for IoT driven e-health

Internet of things (IoT) coupled with mobile cloud computing has made a paradigm shift in the service sector. IoT-assisted mobile cloud based e-healthcare services are making giant strides and are likely to change the conventional ways of healthcare service delivery. Though numerous approaches for preventing unauthorized access to information exchanged between a mobile phone and cloud platform do exist, but there is no security mechanism to prevent unauthorized access by the cloud administrators. With an aim to ensure security of client data such as Electronic Patient Records (EPR), we propose a novel high-capacity and reversible data hiding approach for securely embedding EPR within the medical images using Optimal Pixel Repetition (OPR). OPR converts every pixel of the input image to a 2 × 2 block to facilitate reversibility by ensuring all the pixels in a 2 × 2 block to have different values. Since a 2 × 2 block is comprised of 4-pixel elements, which could be arranged in sixteen possible ways; we generate a lookup table corresponding to sixteen possible positions of pixels. EPR hiding in each block is achieved by permuting the pixels of a block according to the four-bit word of secret data, resulting in a histogram invariant stego image. The histogram invariance improves the robustness of the proposed scheme to statistical attacks. A stego image is said to hide embedded data securely, when it provides better imperceptivity for an appreciably high payload. Thus, while using information embedding approach for securing client data on a mobile-cloud platform, high imperceptivity is a desirable feature. Experimental results show that average PSNR obtained is 42 dB for payload 1.25 bpp by our scheme, showing its effectiveness for preventing unauthorized access to client’s sensitive data.     

自来水厂供电稳定性浅析

供电稳定可靠是自来水厂正常生产的关键。提升水厂供电可靠性可从以下几方面考虑:供电回路设计,母线设计,用电设备的技术水平与质量水平,管理制度与操作规程等。文章从这几方面论述如何提升水厂的供电可靠性。     

“学术权力”和“行政权力”融合对学术资源配置的影响效应分析——基于国家社科基金立项项目的实证研究

基于高校学术行政化趋势的加深,选取2008年和2014年共5 128项国家社科基金立项项目数据及主持人信息为样本,从"行政化教师"角度出发,利用多元有序Probit模型和倾向得分匹配方法(PSM)实证研究了"双权融合"对学术资源配置的影响。结果显示,probit估计发现在控制自身禀赋后,"双权"会对资源配置产生正向显著影响,倾向得分匹配法发现"双权"会达到约11%的影响效应。研究还发现,行政权力获得优质学术资源概率相较学术权力要高出约3%,但呈现疲软态势;随着行政级别的提升,"双权"对资源的影响程度会趋于加强,且越高级别资源这种趋势会越显著。     

基于对战模式的信息隐藏技术课程教学改革

针对信息隐藏技术课程交叉性极强,学习难度大、学生缺乏学习热情等教学实际问题,分析目前开设的信息隐藏课程的现状和症状,提出优化教学内容、启发式教学方式以及以学生为中心,创建对战模式的课堂教学改革模式,力求激发学生的学习兴趣,全面提升学生的动手能力和创新能力,最终达到最优的教学效果。