Sorcery: Overcoming deceptive votes in P2P content sharing systems

Deceptive voting behaviors of malicious users are known as the main reason of causing content pollution in Peer-to-Peer (P2P) content sharing systems. Due to the nature of P2P overlay network such as self-organization and anonymity, the existing methods on identifying deceptive votes are not effective, especially for collusive attackers. This paper presents Sorcery, a novel active challenge-response mechanism based on the notion that one side of interaction with the dominant information can detect whether the other side is telling a lie. To make each client obtain the dominant information, our approach introduces the social network to the P2P content sharing system; therefore, clients can establish the friend-relationships with the users who are either acquaintances in reality or those reliable online friends. Using the confidential voting histories of friends as own dominant information, the client challenges target content providers with the overlapping votes of both his friends and the target content provider, thus detecting whether the content provider is a deceptive user. Moreover, Sorcery provides the punishment mechanism which can reduce the impact brought by deceptive voting behaviors, and our work also discusses some key practical issues. The experimental results illustrate that Sorcery can effectively overcome the problem of deceptive voting behaviors in P2P content sharing systems, and work better than the existing reputation models.     

微电子器件温度分布测试技术研究

为改善微电子器件性能,提高可靠性,确定筛选、考核条件等都必须对器件的结温、表面温度分布以及热斑等热特性进行精确测量,红外热像法是当前测量微电子器件热特性最有效的方法之一。文章针对InfrascopeⅡ型显微红外热像仪在实际应用中如何提高其测温准确度和一致性等问题进行了研究,重点分析了样品发射率、背景环境和大气衰减等因素的影响,并给出验证解决方案,取得了满意的结果。     

基于影像引导的计算机辅助肝癌微波消融

为了方便临床医生使用医学影像进行手术的规划和引导,提出了一种新颖的计算机辅助肝癌微波消融手术方法.采用基于GPU加速的三维可视化技术实时重构影像的三维模型,显示出患者器官的解剖关系;采用基于生物传热学的三维热场计算技术,规划手术路径及消融设备的作用时间和功率.经过大量的临床应用以及手术影像对比,表明该方法能够有效计算消融手术的作用效果,并在手术的引导过程中发挥了重要的作用,提高了手术的临床精度和效果.     

Exploiting effective features for chinese sentiment classification

Features play a fundamental role in sentiment classification. How to effectively select different types of features to improve sentiment classification performance is the primary topic of this paper. Ngram features are commonly employed in text classification tasks; in this paper, sentiment-words, substrings, substring-groups, and key-substring-groups, which have never been considered in sentiment classification area before, are also extracted as features. The extracted features are then compared and analyzed. To demonstrate generality, we use two authoritative Chinese data sets in different domains to conduct our experiments. Our statistical analysis of the experimental results indicate the following: (1) different types of features possess different discriminative capabilities in Chinese sentiment classification; (2) character bigram features perform the best among the Ngram features; (3) substring-group features have greater potential to improve the performance of sentiment classification by combining substrings of different lengths; (4) sentiment words or phrases extracted from existing sentiment lexicons are not effective for sentiment classification; (5) effective features are usually at varying lengths rather than fixed lengths.     

Global sampled-data output feedback stabilisation for a class of nonlinear systems with unknown output function

This paper discusses the problem of global sampled-data output feedback stabilisation for a class of nonlinear systems whose output function is unknown. A systematic design scheme is developed to construct a linear output feedback control law in sampled-data form. An explicit formula for the maximum allowable sampling period is computed to guarantee global stability of the uncertain nonlinear systems under the proposed controller with appropriate gains. Two examples are given to demonstrate the effectiveness of the proposed design procedure.     

Global finite-time stabilization for a class of switched nonlinear systems via output feedback

This paper addresses the problem of global finite-time stabilization for a class of uncertain switched nonlinear systems via output feedback under arbitrary switchings. Based on the adding a power integrator approach, we design a homogeneous observer and controller for the nominal switched system without the perturbing nonlinearities. Then, a scaling gain is introduced into the proposed output feedback stabilizer to implement global finite-time stability of the closed-loop system. In addition, the proposed approach can be also extended to a class of switched nonlinear systems with upper-triangular growth condition. Two examples are given to illustrate the effectiveness of the proposed method.     

基于PLC的地面能源远程控制方案

传统伺服地面能源系统的远程控制主要通过模拟量来实现,其自动化程度低、抗干扰能力差;为了解决以上问题,提出了一种基于PLC的地面能源远程控制方案,其分别采用了基于Profibus现场总线的分布式PLC控制技术、基于高压输出反馈的闭环控制技术、OPC Server与PLC远程通讯技术,实现了伺服地面能源系统的远程自动化控制功能,用基于虚拟仪器技术的人机交互界面取代模拟器件,用基于MODBUS协议的数字式网络传感器取代模拟传感器,实现了伺服地面能源系统数字化,提高了伺服地面能源系统的抗干扰能力。     

The Ground Process Segment of SAR Altimeter

The key innovation technology of SAR Altimeter (Synthetic Aperture Radar Altimeter)are Doppler\|beam sharpen and delay/Doppler range compensation.The cooperation of these two technologies makes it has high along track resolution and high precision in height measurement.The ground processor is the key hinge to make sure that SAR altimeter could obtain these superiorities.Many key technologies for SAR altimeter processor,such as Doppler beam\|sharpen,delay/Doppler compensation and the second range correction,multilook,echo model and gradient function for retracker,are introduced in the paper.Based on the processor and related work,some simulation work and airborne experiment were tested by the processor,and both of the quantity results show that the SAR altimeter has more potential superiorities.     

面向手持式3维扫描设备的本征纹理重建

目的 针对目前手持式3维扫描设备生成的模型纹理分辨率不够,且部分区域存在高光、阴影及明暗变化等问题,提出一种基于多幅实拍照片的纹理重建方法。方法 首先使用基于特征匹配的方法将照片图像与几何模型进行配准;其次根据重建纹理大小,采用特殊编码方式的位置纹理建立照片像素到纹理像素直接且精确的对应关系;然后根据多幅使用闪光灯作为光源拍摄的照片,通过位置纹理建立联立方程,求解漫反射分量;最后采用改进的基于混合权重的融合方法对求解的漫反射分量进行纹理融合。结果 使用本文方法对3个实验模型进行本征纹理重建,与3维扫描设备生成纹理和直接用照片生成纹理相比,该方法操作简单、使用方便,可获得高度清晰的,不含高光和明暗效果的本征纹理图像。结论 实验结果表明,重建纹理质量在分辨率、色彩还原性及一致性方面明显优于原有纹理,且该方法具有很高的精确性和鲁棒性,可满足高质量的纹理重建需求。     

基于抗恶劣环境计算机的电磁兼容与热设计

为了解决抗恶劣环境计算机的电磁兼容与散热问题,通过对基于抗恶劣环境计算机电磁兼容与热设计的研究,提出了基于抗恶劣环境计算机电磁兼容与热设计方法。该方法中包括基于抗恶劣环境计算机电磁兼容与热设计的思路和实现过程。在该方法采用了仿真与测试的手段保证了设计的正确性。该方法已经投入应用,在应用过程中取得了良好的效果。