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由于移动无线传感器网络支持节点的移动性,使其面临更加复杂的安全性挑战,很难防御一些极具破坏力的攻击,比如节点复制攻击和女巫攻击等。本文提出了在移动异构无线传感器网络模型下一种安全高效的密钥管理方法。所提方法采用椭圆曲线密码学加密算法实现移动节点位置信息到基站的安全上传,以及基于密钥哈希的消息认证码来实现消息源的身份认证。基站则对收集的移动节点位置信息进行统计分析来协助完成固定节点与移动节点间的身份认证及会话密钥建立。实验结果表明,所提方法在密钥建立过程节省了网络资源,同时可有效防御攻击者发起重放攻击、节点复制攻击和女巫攻击等,增强了网络安全性。 相似文献
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针对移动机器人在复杂地图环境中移动耗时长、易陷入局部最优等问题,设计了一种基于双向搜索的改进蚁群路径规划算法。基于K-means算法对地图预处理,量化地图的局部复杂度程度,并将局部环境信息融合到状态转移概率函数,使机器人优先选择在复杂程度小的区域进行寻优,减少路径拐点。设定双向搜索规则,改进启发函数,提高算法的局部方向搜索精度和全局搜索效率。针对蚁群算法中蚂蚁遇到U障碍物陷入死锁的问题,提出死锁判断系数,增加了有效蚂蚁的数量,进一步提高了算法性能。仿真结果表明所设计的算法在复杂地图环境中相较于传统蚁群算法移动机器人的路径搜索效率更高。 相似文献
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为了提高双目直接稀疏里程计(Stereo Direct Sparse Odometry, Stereo DSO)的定位速度和精度, 使得移动机器人可以更有效地执行任务, 提出了一种基于双目强约束的直接稀疏视觉里程计系统。基于直接法的即时定位与地图构建(Simultaneous Localization and Mapping, SLAM)系统直接对图像像素构建光度误差优化函数, 无需提取特征点, 克服了基于特征点法的SLAM系统在弱纹理场景下不鲁棒的缺陷, 并且在前端跟踪阶段效率更高。提出一种快速、准确的双目初始化方法, 结合三角化不确定性为不同类型的点赋予不同的深度范围, 加速深度滤波器的收敛。同时, 在运动估计阶段引入双目约束, 使得该系统在绝对尺度上的定位更加准确。通过在公开的KITTI数据集11个序列上进行实验, 实验结果表明所提出的算法在定位精度上明显优于同样采用直接法的Stereo Large Scale Direct SLAM(LSD-SLAM2)和Stereo DSO, 并达到与基于特征点法的ORB-SLAM3相近的水平, 为直接法SLAM提供一种更优的定位方案。 相似文献
5.
Iqbal Ahmad Syed Mujtaba Shah Muhammad Nadeem Zafar Muhammad Naeem Ashiq Wei Tang Uzma Jabeen 《Ceramics International》2021,47(3):3760-3771
Ferrites are materials of interest due to their broad applications in high technological devices and a lot of research has been focused to synthesize new ferrites. In this regard, an effort has been devoted to synthesize spinel Pr–Ni co-substituted strontium ferrites with a nominal formula of Sr1-xPrxFe2-yNiyO4 (0.0 ≤ x ≤ 0.1, 0.0 ≤ y ≤ 1.0). The cubic structure of pure and Pr–Ni co-substituted strontium ferrite samples calcinated at 1073 K for 3 h has been confirmed through X-ray diffraction (XRD). Average sizes of crystallites (18–25 nm) have been estimated from XRD analysis and nanometer particle sizes of synthesized ferrites have been further verified by scanning electron microscopy (SEM). SEM results have also shown that particles are mostly agglomerated and all the samples possess porosity. It has been observed that at 298 K, the values of resistivity (ρ) increase, while that of AC conductivity, dielectric loss, and dielectric constants decrease with increasing amounts of Pr3+ and Ni2+ ions. The values of dielectric parameters initially decrease with frequency and later become constant and can be explained on the basis of dielectric polarization. Electrochemical impedance spectroscopy (EIS) studies show that the charge transport phenomenon in ferrite materials is mainly controlled via grain boundaries. Overall, synthesized ferrite materials own enhanced resistivity values in the range of 1.38 × 109–1.94 × 109 Ω cm and minimum dielectric losses, which makes them suitable candidates for high frequency devices applications. 相似文献
6.
Understanding the mechanisms leading to the rise and dissemination of antimicrobial resistance (AMR) is crucially important for the preservation of power of antimicrobials and controlling infectious diseases. Measures to monitor and detect AMR, however, have been significantly delayed and introduced much later after the beginning of industrial production and consumption of antimicrobials. However, monitoring and detection of AMR is largely focused on bacterial pathogens, thus missing multiple key events which take place before the emergence and spread of AMR among the pathogens. In this regard, careful analysis of AMR development towards recently introduced antimicrobials may serve as a valuable example for the better understanding of mechanisms driving AMR evolution. Here, the example of evolution of tet(X), which confers resistance to the next-generation tetracyclines, is summarised and discussed. Initial mechanisms of resistance to these antimicrobials among pathogens were mostly via chromosomal mutations leading to the overexpression of efflux pumps. High-level resistance was achieved only after the acquisition of flavin-dependent monooxygenase-encoding genes from the environmental microbiota. These genes confer resistance to all tetracyclines, including the next-generation tetracyclines, and thus were termed tet(X). ISCR2 and IS26, as well as a variety of conjugative and mobilizable plasmids of different incompatibility groups, played an essential role in the acquisition of tet(X) genes from natural reservoirs and in further dissemination among bacterial commensals and pathogens. This process, which took place within the last decade, demonstrates how rapidly AMR evolution may progress, taking away some drugs of last resort from our arsenal. 相似文献
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In the past, thinking of carrying electronic devices inside our bodies was only posed by non-real scenarios. The emergence of insertable devices has changed this. Since this technology is still in its initial development stages, few studies have investigated factors that influence its acceptance. This paper analyzes the predictors of the intention to use non-medical insertable devices in two Latin American contexts. We used partial least squares structural equation modeling to examine whether six constructs predicted intention to use insertable devices. A questionnaire was administered to undergraduate students located in Colombia and Chile (n = 672). We also examined whether these predictors influenced intention differently for both of them. Four common constructs significantly and positively influenced both Chilean and Colombian respondents to use insertable devices (hedonic motivation, habit, performance expectancy, and social influence). Also, the habit has a complementary mediating effect on the relationship between social influence and behavioral intention. By contrast, effort expectations were a positive and significant predictor, but only among Chilean respondents. Findings suggest that when technologies are emerging, well-known predictors of intention (e.g., performance and effort expectations) are less influential than predictors related to self-efficacy (e.g., habit and hedonic motivation). The use of insertable devices has a significant impact on society. Thus, a better understanding of what motivates their use has implications for both academia and industry. 相似文献
9.
802.11规定的切换过程十分耗时,同时移动终端根据接收到的信号强度来选择AP往往不能满足通信带宽的需求,这两点对于需要依靠不间断通信来进行作业的工业机器人十分不利.本文面向工业机器人场景提出一种基于动态无线地图的带宽保证快速切换技术.利用预先建立和下载的无线地图,机器人不需扫描信道即可获得附近可用的AP基站,同时利用服务器实时收集AP的工作负载并向机器人提供AP选择服务,可同时满足低切换延时和带宽保证两个切换目标.本文在网络仿真平台NS3上实现了所提出的快速切换框架,并与已有的切换方案进行比较.实验结果表明,本文方案在任何情况下都优于已有的切换方案,并且只要机器人附近存在带宽可满足的AP,本文方案总是可以关联到最佳的AP. 相似文献
10.
考虑移动边缘计算下的联邦学习,其中全局服务器通过网络连接大量移动设备共同训练深度神经网络模型.全局类别不平衡和设备本地类别不平衡的数据分布往往会导致标准联邦平均算法性能下降.提出了一种基于组合式多臂老虎机在线学习算法框架的设备选择算法,并设计了一种类别估计方案.通过每一轮通信中选取与前次全局模型的类别测试性能偏移最互补的设备子集,使得训练后线性组合的全局模型各类别测试性能更平衡,从而获得更快的收敛性、更稳定的训练过程以及更好的测试性能.数值实验充分探究了不同参数对基于类别不平衡联邦平均算法的影响,以及验证了所提设备选择算法的有效性. 相似文献