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31.
With the popularity of sensor-rich mobile devices, mobile crowdsensing (MCS) has emerged as an effective method for data collection and processing. However, MCS platform usually need workers’ precise locations for optimal task execution and collect sensing data from workers, which raises severe concerns of privacy leakage. Trying to preserve workers’ location and sensing data from the untrusted MCS platform, a differentially private data aggregation method based on worker partition and location obfuscation (DP-DAWL method) is proposed in the paper. DP-DAWL method firstly use an improved K-means algorithm to divide workers into groups and assign different privacy budget to the group according to group size (the number of workers). Then each worker’s location is obfuscated and his/her sensing data is perturbed by adding Laplace noise before uploading to the platform. In the stage of data aggregation, DP-DAWL method adopts an improved Kalman filter algorithm to filter out the added noise (including both added noise of sensing data and the system noise in the sensing process). Through using optimal estimation of noisy aggregated sensing data, the platform can finally gain better utility of aggregated data while preserving workers’ privacy. Extensive experiments on the synthetic datasets demonstrate the effectiveness of the proposed method. 相似文献
32.
《Advanced Powder Technology》2021,32(10):3845-3859
Catalyst layers (CL), as an active component of the catalyst coated membrane (CCM), form the heart of the polymer electrolyte membrane fuel cell (PEMFC). For optimum performance of the fuel cell, obtaining suitable structural and functional characteristics for the CL is crucial. Direct tuning of the microstructure and morphology of the CL is non-trivial; hence catalyst inks as CL precursors need to be modulated, which are then applied onto a membrane to form the CCM. Obtaining favorable dispersion characteristics forms an important prerequisite in engineering catalyst inks for large scale manufacturing. In order to facilitate a knowledge-based approach for developing fuel cell inks, this work introduces new tools and methods to study both the dispersion state and stability characteristics, simultaneously. Catalyst inks were prepared using different processing methods, which include stirring and ultrasonication. The proposed tools are used to characterize and elucidate the effects of the processing method. Structural characterization of the dispersed particles and their assemblages was carried out by means of transmission electron microscopy. Analytical centrifugation (AC) was used to study the state and stability of the inks. Herein, we introduce new concepts, S score, and stability trajectory, for a time-resolved assessment of inks in their native state using AC. The findings were validated and rationalized using transmittograms as a direct visualization technique. The flowability of inks was investigated by rheological measurements. It was found that probe sonication only up to an optimum amplitude leads to a highly stable colloidal ink. 相似文献
33.
利用传统的k匿名技术在社会网络中进行隐私保护时会存在聚类准则单一、图中数据信息利用不足等问题. 针对该问题, 提出了一种利用Kullback-Leibler (KL)散度衡量节点1-邻居图相似性的匿名技术(anonymization techniques for measuring the similarity of node 1-neighbor graph based on Kullback-Leibler divergence, SNKL). 根据节点1-邻居图分布的相似性对原始图节点集进行划分, 按照划分好的类进行图修改, 使修改后的图满足k匿名, 完成图的匿名发布. 实验结果表明, SNKL方法与HIGA方法相比在聚类系数上的改变量平均降低了17.3%, 同时生成的匿名图与原始图重要性节点重合度保持在95%以上. 所提方法在有效保证隐私的基础上, 可以显著的降低对原始图结构信息的改变. 相似文献
34.
Delegation mechanism in Internet of Things (IoT) allows users to share some of their permissions with others. Cloud-based delegation solutions require that only the user who has registered in the cloud can be delegated permissions. It is not convenient when a permission is delegated to a large number of temporarily users. Therefore, some works like CapBAC delegate permissions locally in an offline way. However, this is difficult to revoke and modify the offline delegated permissions. In this work, we propose a traceable capability-based access control approach (TCAC) that can revoke and modify permissions by tracking the trajectories of permissions delegation. We define a time capability tree (TCT) that can automatically extract permissions trajectories, and we also design a new capability token to improve the permission verification, revocation and modification efficiency. The experiment results show that TCAC has less token verification and revocation/modification time than those of CapBAC and xDBAuth. TCAC can discover 73.3% unvisited users in the case of delegating and accessing randomly. This provides more information about the permissions delegation relationships, and opens up new possibilities to guarantee the global security in IoT delegation system. To the best of our knowledge, TCAC is the first work to capture the unvisited permissions. 相似文献
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36.
徐爱华 《土木建筑与环境工程》2002,24(6):10-12
随着生活和物质水平的提高,现在的住宅已不仅仅是给人们提供一个简单的满足人的吃住等生理要求的场所,他应是在满足人们生理要求的同时,还满足人们的心理要求,这也是健康住宅的基本要求之一。住宅的动静分区可以避免动静干扰,给人们的生活,学习,工作带来安静,舒适的环境,从而在一定程度上满足人的心理要求,提高居住质量。文章对近些年来各种动静分区的方法从设计,施工及使用几个方面进行了分析比较,找出了各自的优点和缺点,并提出在设计施工中应注意的事项。另在选择动静分区方式时,还应综合考虑各种因素,以满足不同地区,不同人群的需求。 相似文献
37.
以连续性公共空间组织为主线的小区规划 总被引:4,自引:0,他引:4
文章从传统城镇空间中借鉴有益的空间关联性和行进感等组织特点,提出居住小区私密层次“二级化”思维方式,引入了“等量空间”与“变量空间”的概念,阐述了利用二者的图—底关系对居住小区公共空间进行组织的设计方法,并举例说明上述理念运用于小区规划的设计实践。 相似文献
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39.
高超声速临近空间飞行器铰链力矩最小俯冲弹道设计 总被引:2,自引:0,他引:2
为解决高超声速临近空间飞行器俯冲段铰链力矩过大问题,给出了一种降低铰链力矩的俯冲弹道设计方法.在建立俯冲弹道优化模型的基础上,利用Gauss伪谱法将弹道优化问题转化为非线性规划问题,进而将其作为极大极小优化问题采用序列二次规划方法进行求解,其中优化的初值由按照最优导引方式生成的初始弹道获得.在普通台式机上耗时约2min,获得的优化弹道铰链力矩峰值下降达67%,并且各种约束条件均可满足,采用美国GAV-H飞行器总体和气动参数进行了铰链力矩最小俯冲弹道仿真,分析了最优俯冲起点的选取策略,结果表明,该铰链力矩最小俯冲弹道设计方法具有可行性. 相似文献
40.