用于微弱信号检测的锁定放大器设计

以嵌入式微处理器C8051F020为控制核心,结合锁相放大原理完成微弱信号检测,系统主要由纯电阻分压网络、加法器、带通滤波器、相敏检波、移相器及ADC采集和单片机控制显示等电路组成.系统以相敏检波器为基础,其中加法器和纯电阻分压网络生成微小信号,将微小信号经过交流放大电路和带通滤波器进行选频放大,输出给相敏检波器的一端;将参考信号经过移相器移相,再经过比较器产生方波,相敏检波器比较两路信号后产生直流信号,最后经低通滤波器和放大器输出直流信号并检测出微弱信号,将直流信号经AD7705采样送入单片机处理后,通过液晶显示.经测试,本系统能较好地完成微弱信号的检测.     

多样性攻击下的WSN位置隐私保护方案

研究无线传感器网络节点隐私保护问题,节点位置隐私是无线传感器网络领域中所研究的一个基本问题。传统的位置隐私保护算法存在抵御攻击类型单一、保护目标单一以及无法应对复杂多样性攻击等问题。为了解决上述问题,在传统的位置隐私保护算法基础上提出了针对多样性攻击的位置隐私保护方案。通过增加冗余抵御数据包流量分析,破坏数据包之间的相关性抵御数据包追踪,利用数据包分组、概率丢弃冗余包等方式降低网络资源消耗,达到抵御攻击类型、保护目标多样和应对多样性攻击的目的。理论分析和仿真结果表明,上述方案能够保证事件检测率和降低网络时延,同时实现多样性攻击下的位置隐私保护。     

行政管理信息化发展模式探讨

随着全球信息化建设的高速发展,我国在信息化应用领域也实现了巨大的突破。近年来,我国信息化建设的投入不断增加,信息化建设成为了企事业单位、行政机关缩短办事时间、提高工作效率的重要抓手和工具,信息化成为企事业单位走上快速发展的高速公路。然而,信息化的实现过程因受各方面条件的影响也并非一帆风顺,单位往往缺少相关的专业知识,缺少相关技术人员,虽知信息化会给企业带来巨大的实时便利性,但不知道该如何进行信息化。因此,本文对行政管理信息化建设的发展模式进行深入的探讨。     

无线传感器网络分簇路由节能研究

在大规模传感和环境监测中,节约能源延长传感器节点生命已成为无线传感器网络最重要的研究课题之一。提供合理的能源消耗和改善无线网络生命周期的传感器网络系统,必须设计一种新的有效的节能方案和节能路由体系。方案采用一种聚类算法减少无线传感器网络的能量消耗,创建一种cluster-tree分簇路由结构的传感器网络。该方案主要目标是做一个理想的分簇分配,减少传感器节点之间的数据传输距离,降低传感器节点能源消耗,延长寿命。实验结果表明,该方案有效地降低了能源消耗从而延长无线传感器网络生命。     

一种基于项目属性评分的协同过滤推荐算法

协同过滤是电子商务推荐系统中应用最成功的推荐技术之一,但面临着严峻的用户评分数据稀疏性和推荐精度低等问题。针对数据稀疏性高和单一评分导致的推荐精度低等问题,提出一种基于项目属性评分的协同过滤推荐算法。首先通过均值法或缩放法构造用户-项目属性评分矩阵将单一评分转化为多评分;其次基于每个属性评分矩阵,计算用户间的偏好相似度,得到目标用户的偏好最近邻居集;然后针对每个最近邻居集,在用户-项目评分矩阵上完成对目标用户的初步评分预测;最后,将多个初步预测评分加权求和作为综合评分,完成推荐。在Movie Lens扩展数据集上的实验结果表明,该算法能有效提高推荐精度。     

水利工程造价管理与控制

分析了以设计阶段为控制重点的全过程造价管理及目前我国水利工程造价管理中存在的一些问题,并就水利工程造价管理与控制提出了一些建议。     

Design of a compact dual‐band folded‐waveguide bandpass filter using multilayer waveguide resonators

A novel compact dual‐band bandpass filter based on multilayer folded‐waveguide (FWG) structure is presented in this article.In this design, slots are used to realize direct coupling between adjacent resonators and apertures are adopted to implement cross coupling between non‐adjacent resonators.A new technique of external quality factor of FWG resonator and coupling coefficients between different resonators are studied using full‐wave simulator. In order to demonstrate the proposed technique, a four‐pole dual‐band bandpass filter is designed, fabricated and measured using vector network analyzer. Measurement results which are well agreed with simulation results are presented. Moreover, four‐pole substrate integrated folded waveguide SIFW dual‐band bandpass filter, using two layers of slotted folded waveguide resonators, is demonstrated. The proposed filter has a compact size and it is excellent candidate for the application of wireless communication systems. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:780–788, 2015.     

Haptics-equiped interactive PCI simulation for patient-specific surgery training and rehearsing针对特定病人的可交互经皮冠状动脉介入手术模拟

Despite the long history of medical simulations, suffering from the patient-specific heterogeneous heart physiological structure and complex intravascular procedures, it is still challenging for patient-specific percutaneous coronary intervention (PCI) surgery simulation. In this paper, we advocate a haptics-equiped interactive prototype system towards PCI surgeons training and patient-specific surgery rehearsing, which can afford trainees the opportunity to approximately experience the entire PCI procedures and customized emergency cases that might occur in common clinical settings. The full simulation covers tissue deformation, catheter and wire simulation, X-ray simulation, haptic feedback, and 3D realistic rendering, which in all give rise to the integrated physical, visual, haptic, and procedural realism. Our system can accommodate various comprehensive operations involved in PCI-related procedures, including feeding wires, releasing stents, injecting contrast medium, simulating X-ray, bleeding, etc. Moreover, our system framework is fully built upon CUDA, and thus can achieve real-time performance even on a common desktop. The high-fidelity, real-time efficiency and stableness of our system show great potentials for its practical applications in clinical training fields.     

Effects of residual motion compensation errors on the performance of airborne along-track interferometric SAR

Two approximations, center-beam approximation and reference digital elevation model (DEM) approximation, are used in synthetic aperture radar (SAR) motion compensation procedures. They usually introduce residual motion compensation errors for airborne single-antenna SAR imaging and SAR interferometry. In this paper, we investigate the effects of residual uncompensated motion errors, which are caused by the above two approximations, on the performance of airborne along-track interferometric SAR (ATI-SAR). The residual uncompensated errors caused by center-beam approximation in the absence and in the presence of elevation errors are derived, respectively. Airborne simulation parameters are used to verify the correctness of the analysis and to show the impacts of residual uncompensated errors on the interferometric phase errors for ATI-SAR. It is shown that the interferometric phase errors caused by the center-beam approximation with an accurate DEM could be neglected, while the interferometric phase errors caused by the center-beam approximation with an inaccurate DEM cannot be neglected when the elevation errors exceed a threshold. This research provides theoretical bases for the error source analysis and signal processing of airborne ATI-SAR.