基于局部网络拓扑特征的鲁棒节点定位算法

针对无线传感器网络的较大测距误差严重影响定位算法精度和鲁棒性的问题,利用节点均匀部署网络的拓扑特征,提出了一种基于局部网络拓扑特征的鲁棒节点定位算法(LFLS算法).该算法通过构建节点测距高估粗差阈值参数和测距低估粗差阈值参数,在对未知节点1跳测距数据集进行粗差识别及剔除等预处理滤波的基础上,使用高斯加权最小二乘定位算法实现节点定位.仿真结果表明,基于局部网络拓扑特征的鲁棒节点定位算法的定位精度明显优于未采用局部网络拓扑特征进行粗差预处理的加权最小二乘定位算法,其中粗差测距直接相关节点的定位精度改进尤为明显.     

卡尔曼滤波在无线传感器网络节点定位中的应用

为了减小无线传感器网络节点定位中节点测距误差和定位算法自身引入误差的积累对定位精度的影响,建立了适用于无线传感器网络的卡尔曼滤波模型.采用渐消自适应卡尔曼滤波对基于距离的初始定位算法进行求精,通过一跳节点间的相互制约,在全局范围对未知节点进行定位;基于卡尔曼滤波模型,对无线传感器网络的分布式算法和集中式算法的计算量进行了研究,得出计算量与节点数目的关系.研究结果表明,卡尔曼滤波能够有效提高节点的定位精度,尤其适用于网络节点密度小、信标节点比例低的情况.     

二次误差修正的DV-Hop优化定位算法

介绍了无线传感器网络中DV-Hop定位算法的原理,分析了其误差产生的主要原因.针对传统DV-Hop算法在定位过程中求出的平均每跳距离值误差较大以及最终定位结果精确度不高的问题,提出了一种改进型DV-Hop定位算法.在改进算法中,信标节点通过计算一次误差修正了平均每跳距离值,通过计算二次误差修正了信标节点定位误差区域,从而使最终计算出的节点坐标更接近于真实值.仿真结果表明,改进算法在无需额外增加硬件开销的前提下,可以有效地提高定位精度.     

稀疏无线传感器网络移动节点定位算法

为解决稀疏无线传感器网络的现有MCB移动节点定位算法存在定位精度低和无法定位的节点的数量多的问题,对MCB算法进行了改进,进而提出了一种新的移动节点定位算法MCBP,该算法把已定位的节点作为其它未定位节点的参考点(准信标节点),利用准信标节点的位置信息参与后续定位过程,使更多的节点可以定位,并且提高了定位精度。仿真结果表明,MCBP移动节点定位算法比前人的类似算法的定位误差最大可减少22%,平均减少16%。无法定位的节点的数量最大可减少26%,平均减少12%。     

一种低计算复杂度的无线传感器网络分簇定位算法

针对已有的集中式定位算法定位精度低,而分布式定位算法计算复杂度高、通信量大的问题,提出了一种适用于无线传感器网络的计算复杂度低的节点分簇定位算法.首先,提出满足最大连通度的多边界节点分簇算法,采用此算法把网络划分为若干个簇,各簇分别进行簇内节点定位;其次,各簇进行融合,最终实现全网节点的定位.仿真结果表明,这种分簇定位算法比分布式定位算法计算复杂度低、通信量小、定位精度相当或略差,比集中式定位算法计算复杂度低、通信量小、定位精度高.采用该算法可以降低传感器网络节点定位过程中的能耗,提高计算效率,延长网络寿命.     

一种改进混沌粒子群优化的节点定位算法

为提高无线传感器网络节点粒子群优化定位算法的收敛速度与定位精度,将混沌变异引入到算法中,加强算法的局部搜索能力,并通过改进粒子群优化算法中惯性权重的设置,提高定位速度和定位精度。仿真结果表明,该算法性能稳定,具有较快定位速度和较高定位精度,是一种可行的无线传感器网络节点定位的解决方案。     

基于Symlets小波变换的燃气管道泄漏诊断方法

提出一种新的基于无线传感器网络的管道泄漏诊断方法,以解决现有管道泄露诊断方法存在的定位精度差、距离受限和实时性差的问题.该方法采用分布式数据融合技术,在源节点处利用Symlets小波变换提取包含泄漏特征的单模态声发射信号,消除噪声干扰及频散现象;在汇聚节点处根据信号幅值大小将泄漏点两侧的信号排列组合,利用互相关时差定位和加权平均原理获得泄漏点位置坐标.实验结果表明,基于无线传感器网络的新型管道泄露诊断方法可显著提高泄漏点定位精度,其定位误差小于5%.     

无线传感器网络定位求精方法

为了提高传感器节点定位精度,将多种节点坐标计算方案(如极大似然估计、基于泰勒展开的最小二乘法和加权最小二乘法等)应用于定位求精中,并分析和比较了它们的性能.为了解决实际定位过程中锚节点存在的自身位置偏差,设计了相应的坐标求精方法,如总体最小二乘法和约束总体最小二乘法,在此基础上针对无线传感器网络定位误差的特点推广了定位误差的估计下限(参数无偏估计的Cramer-Rao下限).仿真实验结果给出了不同求精方案各自的求精性能和适用场合.在锚节点无位置误差的情况下,在泰勒展开基础上形成的加权最小二乘法更有利于精度提高;在锚节点有位置误差的情况下,约束总体最小二乘法对提高定位精度更有效.     

无线传感器网络自适应定位方法研究

针对无线传感器网络中基于RSSI测距的定位问题,在无线信号传播信道模型的研究基础上,提出了利用信标节点间的相互通信,实时建立和修正信号强度与距离之间的映射关系的方法,提高了定位系统对环境的适应能力;提出了一种循环极大似然算法,该算法在极大似然算法的基础上进行了改进,大大降低了含有较大测距误差的数据对定位的影响。实验证明,自适应定位方法能够根据系统所处的环境自动建立映射关系,在低成本条件下,达到较高的定位精度。     

基于DV-Hop的无线传感器网络定位算法

针对无线传感器网络中DV-Hop经典算法定位精度低的不足,提出了一种改DV-Hop定位算法;改进后的算法对锚节点的选取进行了优化,并改进节点跳数,还采用平均计算方法计算节点平均每跳距离。仿真表明,改进的DV-Hop算法对未知节点的定位精度有显著提高。     

Preventing the impact of selfish behavior under MANET using Neighbor Credit Value based AODV routing algorithm

Mobile Ad hoc Network (MANET) nodes exchange information using the multi-hop wireless communications without the need for any pre-existing infrastructure. Routing protocols of MANET are designed with an assumption that the nodes will cooperate in routing process. To achieve high throughput and reliable communication, the nodes are expected to cooperate with each other. Routing protocol plays a crucial role in an effective communication between nodes and operates on the assumption that the nodes are fully cooperative. Due to the open structure and limited battery-based energy in MANET, some nodes may not cooperate correctly or behave maliciously and such kind of misbehavior impacts the fairness, reliability and efficiency in MANET. Previous work addressed the ways to overcome these kinds of node misbehaviors and attacks. Most of the existing works need time to analyse the neighbor traffic and decide whether a neighbor is behaving maliciously or not. Further, the existing credit-based detection mechanisms may mark a genuine idle node as a malicious node. This work addresses a simple Neighbor Credit Value based AODV (NCV-AODV) routing algorithm for the detection of selfish behavior which avoids such false detection. The proposed idea is implemented in Ad hoc On Demand Distance Vector (AODV) routing protocol and an extensive analysis on the performance of the proposed detection mechanism against the selfish behavior of some MANET nodes are conducted.     

无线传感器网络中基于信誉的恶意节点检测

提出一种基于信誉的恶意节点检测方法——RMDMN,在分簇的网络结构基础上,对节点的行为属性(如丢包率、转发率、位置匹配信息等)和网络攻击进行建模,结合阈值比较法动态地更新节点信誉值并进行恶意节点判断.实验仿真显示,该方法具有一定的恶意节点检测能力.     

医疗服务行为监管博弈分析

采用博弈论方法研究探讨了政府监管与医院、医生违规行为之间的关系问题.对医生与医院之间的博弈进行了简要分析,建立了政府与院方之间的博弈模型,并对模型的均衡进行了求解.根据求解结果,揭示了政府监管与院方违规行为之间的关系,并给出了降低医院与医生违规行为发生几率的方法.     

Whose criterion standard is it anyway?

A criterion-referenced standard is an important element of most successful professional testing programs. A growing body of evidence suggests that judge decisions are influenced by characteristics related to the normative experience of the individual judge (e.g. gender, age, etc.). This investigation used two health-care related boards to explore the effects of judge characteristics on the standards established. Two judge panels (composed of 26 and 30 members respectively) were used in a simplified Objective Standard Setting exercise to define examination cutoff points. Multi-faceted Rasch analyses were employed to detect and explore differences in judgment making. Significant but not necessarily consistent differences were found between panel judges on several examined characteristics. Results suggest that criterion-referenced standards defined by judge panels are inexorably connected to their normative experiences and are therefore wholly sample dependent. While stratification of judge panels is clearly an important element in defining standards, if they are ever to achieve the goals of Glaser (1963) and Majer (1962) including meaningful independence, more must be done to investigate these and other concerns. The case for the predictive validity of criterion-referenced standards has not thusfar been made in any convincing fashion.     

Some Curious Results with a Gallium Fixed-Point Cell

In 2009, most of the gallium fixed-point cells in use in different INRIM laboratories were compared with Italy??s national standard. The comparison has uncovered problems with one of the commercial devices, realizing a temperature about 0.7 mK too low which initially was even changing linearly with time. An additional series of measurements was undertaken to find out the reason for this behavior, but not being allowed to open the cell, only a suspicion on the possible cause has remained. A way is suggested that might give users an indication of such misbehavior of their cell. The results underline the importance for those NMIs with only a single cell, for any fixed point, to undertake regular comparisons with another cell as a check on its behavior.     

A Distributed Privacy Preservation Approach for Big Data in Public Health Emergencies Using Smart Contract and SGX

Security and privacy issues have become a rapidly growing problem with the fast development of big data in public health. However, big data faces many ongoing serious challenges in the process of collection, storage, and use. Among them, data security and privacy problems have attracted extensive interest. In an effort to overcome this challenge, this article aims to present a distributed privacy preservation approach based on smart contracts and Intel Software Guard Extensions (SGX). First of all, we define SGX as a trusted edge computing node, design data access module, data protection module, and data integrity check module, to achieve hardware-enhanced data privacy protection. Then, we design a smart contract framework to realize distributed data access control management in a big data environment. The crucial role of the smart contract was revealed by designing multiple access control contracts, register contracts, and history contracts. Access control contracts provide access control methods for different users and enable static access verification and dynamic access verification by checking the user’s properties and history behavior. Register contract contains user property information, edge computing node information, the access control and history smart contract information, and provides functions such as registration, update, and deletion. History contract records the historical behavior information of malicious users, receives the report information of malicious requestors from the access control contract, implements a misbehavior check method to determines whether the requestor has misbehavior, and returns the corresponding result. Finally, we design decentralized system architecture, prove the security properties, and analysis to verify the feasibility of the system. Results demonstrate that our method can effectively improve the timeliness of data, reduce network latency, and ensure the security, reliability, and traceability of data.     

Scientists’ referencing (mis)behavior revealed by the dissemination network of referencing errors

This study illustrates scientists’ referencing (mis)behavior by structuring the dissemination network of referencing errors. The sample set consists of 16,622 referencing errors of a highly cited paper published by Laemmli, UK in Nature in 1970. Dissemination networks of thirteen types of volume-page double errors and one type of page-only error are constructed and analyzed. Focusing on papers which carry the same volume-page double error, or the same page error, the citing-cited relationship between any two of them was identified and author bylines were compared to find common author(s). Our investigation results in three disseminating routes of referencing errors. Route 1: Citing a paper and copying its reference; Route 2: Copying a reference from another paper but without citing this paper; Route 3: Copying references from an earlier paper published by the author himself (herself) without rechecking the accuracy of the reference. The first two routes reflect scientists’ referencing misbehavior while the third calls attention to self-copying of references.     

National security challenges and competition: US defense and space R&D in a strategic context

This paper addresses the evolution of the role of science and technology as a strategic national security advantage. From World War II and the Cold War to the present and projected future, this role has changed. Advances in digitized sensors, processors, storage, communications, and display have proliferated across the globe. The network connectivity enabled by this revolution has itself revolutionized almost all aspects of global life. The technology from which national security systems are derived is increasingly drawn from the vibrant, globalized industrial base that is the foundation of commercial and economic success. The desire for secrecy and technology control that is natural to the creation of national security capabilities is now in conflict with this globalized and open commercial marketplace. Contending pressures for cooperation among nations and the need to protect against misbehavior by some of those same nations makes managing national security technologies increasingly challenging.     

火灾运行模式模拟计算中最复杂模式的确定

在地铁隧道通风设计中，有很多种模式，其中有一种是最复杂的，由最复杂的这种模式就可以判断在最不利情况下设备的配置是否能满足火灾要求。本文讲述了最简单的几种最不利工况的判断方法。