基于动态路网的分布式邻近目标查询算法

提出了一种基于实时路况信息的分布式邻近目标查询算法,采用基于Voronoi图的划分将地理信息存储在离它最近路口的智能摄像头上,实时路况信息由智能摄像头采集,通过对路口的畅通程度进行建模,估算出路口间通行所需要的时间。当有车辆查询邻近目标时,网络中的智能摄像头根据所在路口的畅通程度和到邻近路口的距离,在分布式查询过程中加入延时转发机制,广播目标路径询问的数据分组,使数据分组的发送能模拟当前的路况进行传输,从而获得到达邻近目标的路径。基于真实数据的实验结果表明算法是有效的,处理大量并发查询时的性能优于现有方法。     

空间近似关键字反远邻查询

空间数据集中的点普遍由空间信息及描述文本信息组成.空间近似关键字反远邻查询(Approximate String Reverse Furthest Neighbors Search,ASRFNS)问题是在一个空间数据集中搜索所有以给定查询点为最远邻,且满足文本相似度条件的目标.基于现有的空间反远邻查询算法以及近似关键字查询算法,我们提出了两个基本的解决算法:凸包最远单元交集(CHFCsJoin)算法和凸包最远单元近似字符串串行查询(CHFCASSS)算法;我们又设计了一种包含空间和关键字信息的外存索引结构Filter-Rtree,并给出了相应的凸包最远单元过滤R树(CHFilterRtree)高效算法.通过真实数据集的实验测试,验证这三种算法的有效性,并分析比较了其性能与效率.     

移动对象全局K最接近邻居查询研究

基于两个对象在一段时间内的范围距离度量,给出了一种新的时空查询形式-全局最接近邻居查询。该查询检索移动对象在一段时间内范围距离最小的运动对象。通过考察查询和连续最接近邻居之间关系,给出了一个基本查询处理算法。根据数据对象集的运动性不同,精化了运动和静止数据集下的全局距离的定义,并对R树结构索引的数据集给出了裁减、更新和访问启发式规则。采用分支界定技术和给出的启发式规则,设计了迭代的深度优先和基于堆的最好优先的查询处理算法。大量的实验表明,最好优先的查询处理算法具有突出的性能。     

Improved SpaceTwist privacy protection method based on anchor optimization algorithm

With location-based services worldwide used,private location data appealed easily in query process which caused serious security problems.So the introduction of SpaceTwist incremental nearest neighbor query algorithm,proposes protection of privacy method combined with improved SpaceTwist location optimization algorithm.The anchor point authentication server added to distributed system structure,user generate a k anonymous area according to their privacy preference and actual environment,using optimization algorithm to generate the anchor point.Forwarding users use the incremental nearest neighbor query throught the anchor point and accurate.Experiments in road network environment with different data sets show that the privacy protection works well in the algorithm,and own high work efficiency.     

一种基于HSFC的云资源定位算法

针对云计算环境下,云资源的模糊查询问题,提出了一种云资源定位算法。该算法建立在双层Chord环模型上,同时结合Hilbert空间填充曲线(HSFC),实现多维属性的降维,进而完成云资源的定位。另外,该算法将整个资源空间划分成多个资源区间,并提出邻居区间的概念,通过邻居区间,可较好地实现云资源的模糊查询,此外该算法还为每个属性设置属性权值,以此减少网络请求数量。实验表明,该算法不但能有效解决云资源的模糊查询,且能降低查询时延,提高查询效率。     

Spatial query processing in road networks for wireless data broadcast

Recently, wireless broadcast environments have attracted significant attention due to its high scalability to broadcast information to a large number of mobile subscribers. It is especially a promising and desirable dissemination method for the heavily loaded environment where a great number of the same type of requests are sent from the users. There have been many studies on processing spatial queries via broadcast model recently. However, not much attention is paid to the spatial queries in road networks on wireless broadcast environments. In this paper, we focus on three common types of spatial queries, namely, k nearest neighbor (kNN) queries, range queries and reverse nearest neighbor (RNN) queries in spatial networks for wireless data broadcast. Specially, we propose a novel index for spatial queries in wireless broadcast environments (ISW). With the reasonable organization and the effectively pre-computed bounds, ISW provides a powerful framework for spatial queries. Furthermore, efficient algorithms are designed to cope with kNN, range and RNN queries separately based on ISW. The search space can be obviously reduced and subsequently the client can download as less as possible data for query processing, which can conserve the energy while not significantly influence the efficiency. The detailed theory analysis of cost model and the experimental results are presented for verifying the efficiency and effectiveness of ISW and our methods.     

The condensed nearest neighbor rule using the concept of mutual nearest neighborhood (Corresp.)

A two-stage iterative algorithm for selecting a subset of a training set of samples for use in a condensed nearest neighbor (CNN) decision rule is introduced. The proposed method uses the concept of mutual nearest neighborhood for selecting samples close to the decision line. The efficacy of the algorithm is brought out by means of an example.     

基于网络Voronoi图的道路网络连续k近邻查询

道路网络中的连续查询是查找在一条路径上满足查询条件的对象。它是空间网络数据库中的一种重要查询类型。现提出了道路网络中基于k阶Voronoi图的连续k近邻查询方法，该查询方法用分枝限界的思想动态地创建局部Voronoi图，降低了查询代价。     

Efficient algorithms for scheduling data broadcast

With the increasing acceptance of wireless technology, mechanisms to efficiently transmit information to wireless clients are of interest. The environment under consideration is asymmetric in that the information server has much more bandwidth available, as compared to the clients. It has been proposed that in such systems the server should broadcast the information periodically. A broadcast schedule determines what is broadcast by the server and when. This paper makes the simple, yet useful, observation that the problem of broadcast scheduling is related to the problem of fair queueing. Based on this observation, we present a log‐time algorithm for scheduling broadcast, derived from an existing fair queueing algorithm. This algorithm significantly improves the time‐complexity over previously proposed broadcast scheduling algorithms. Modification of this algorithm for transmissions that are subject to errors is considered. Also, for environments where different users may be listening to different number of broadcast channels, we present an algorithm to coordinate broadcasts over different channels. Simulation results are presented for proposed algorithms.     

Continuous Monitoring of Spatial Queries in Wireless Broadcast Environments

Wireless data broadcast is a promising technique for information dissemination that leverages the computational capabilities of the mobile devices in order to enhance the scalability of the system. Under this environment, the data are continuously broadcast by the server, interleaved with some indexing information for query processing. Clients may then tune in the broadcast channel and process their queries locally without contacting the server. Previous work on spatial query processing for wireless broadcast systems has only considered snapshot queries over static data. In this paper, we propose an air indexing framework that 1) outperforms the existing (i.e., snapshot) techniques in terms of energy consumption while achieving low access latency and 2) constitutes the first method supporting efficient processing of continuous spatial queries over moving objects.     

基于Voronoi图预划分的LBS位置隐私保护方法

为了解决服务器面临大量用户请求时匿名效率下降的问题,分别提出适用于静态用户和动态用户的协作匿名方法。首先基于Voronoi图划分全局区域,再由中心服务器组织本区域内用户实现协作匿名,由于服务器无需为每个用户单独构造匿名区,降低了服务端的负担;针对查询过程中用户提供真实位置信息带来位置隐私泄露的问题,提出了逆向增量近邻查询算法。用户以固定锚点代替真实位置,向位置服务器逐步获取兴趣点候选集并计算出想要的结果,避免位置隐私直接泄漏的同时获取精准查询结果。该算法同时解决了锚点与用户过近而带来的位置隐私被推断问题。实验表明本方法在有效保护用户位置隐私的同时,具有良好的工作效率。     

结合双树复小波变换和改进密度峰值快速搜索聚类的乳腺MR图像分割

针对乳腺MR图像组织复杂、灰度不均匀、难分割的特点,本文提出双树复小波（DTCWT）变换结合密度聚类的图像分割方法.首先利用复小波域双变量模型结合各向异性扩散函数对图像进行去噪处理;进而通过简单线性迭代聚类（SLIC）算法将图像划分成一定数量的超像素区域,根据事先设置的阈值搜索每个超像素的近邻,从而降低基于K近邻的密度峰值快速搜索聚类（KNN-DPC）算法寻找每个样本近邻的时间;最终,引入超像素区域的近邻信息度量样本密度,采用KNN-DPC算法的分配策略自适应聚类.仿真和临床数据分割结果表明,所提算法能有效的实现乳腺MR图像的分割.     

Broadcast scheduling with MIMO links in multi-hop ad hoc networks

As the current medium access control protocols with Multiple Input Multiple Output (MIMO) links only bear point to point service, broadcast scheduling algorithm in ad hoc networks with MIMO links is proposed. The key to the proposed broadcast scheduling algorithm is the time slot scheduling algorithm which guarantees collision-free transmissions for every node and the mini- mum frame length. The proposed algorithm increases the simultaneous transmissions of MIMO links efficiently. Due to the interference null capacity of MIMO links, the interference node set of each node can decrease from two-hop neighbors to one-hop neighbors possibly. Simulation results show that our algorithm can greatly improve network capacity and decrease average packet delay.     

基于加权自学习散列的高维数据最近邻查询算法

因为查询和存储具有高效性,学习型散列逐渐被应用于解决最近邻查询问题.学习型散列将高维数据转化成二进制编码,并使得原始高维空间中越相似的数据对应二进制编码的汉明距离越小.在实际应用中,每次查询都会返回许多与查询点汉明距离相同而编码互不相同的数据.如何对这些数据进行排序是一个难题.提出了一种基于加权自学习散列的近邻查找算法.实验结果表明,算法能够高效地对具有相同汉明距离的不同编码进行重排序,加权排序后查询的F1值约是原来的2倍并优于同系算法,时间开销可比直接计算原始距离进行排序降低一个数量级.     

k nearest neighbor pattern match queries over spatio-temporal label trajectories

Spatio-temporal label trajectories extended traditional spatio-temporal trajectories with semantic labels.k nearest neighbor pattern match was proposed to return the k nearest trajectories that fulfilled the temporal pattern condition.The Label R-Tree (LR-Tree for short) was proposed,which appending a label table and adding label bitmap in each entry,and k nearest neighbor pattern match query algorithm based on LR-Tree was designed.Using both real and synthetic datasets,the LR-Tree was extensively evaluated in comparison with 3DR-Tree,SETI and TB-Tree.The experimental results demonstrate that LR-Tree showing better pruning ability,and verify the effectiveness of proposed algorithm and index.     

基于参考标签的射频识别室内定位算法研究

针对现有基于RFID的LANDMARC室内定位系统会因外界环境因素导致优良的邻近参考标签丢失、不良的参考标签引入的问题,为此提出了一种改进的最近邻居算法,通过筛选已选取的邻近参考标签,实现最近邻标签的最佳选取。实验结果表明待测标签的定位精度得到有效提高。该算法有效获取到优良的参考标签,从而获得了满意的定位精度和定位性能。     

基于均衡增量近邻查询的位置隐私保护方法

针对用户在获得位置服务的同时,用户的位置隐私可能会被泄露的问题,采用协作的分布式模型,移动终端和LBS服务器这两端都使用k-匿名机制,提出基于k-匿名的均衡增量近邻(KHINN)查询方法。该方法在移动终端构造匿名用户组时,利用安全多方求和的技术计算锚点以保证用户隐私;在处理查询结果时,使用基于k-匿名的SpaceTwist方法提高查询隐私度和准确度。经过性能分析和实验结果表明,在考虑用户节点之间半可信或不可信的情况下,可以解决SpaceTwist方法中的查询兴趣点围绕锚点分布不均衡的缺陷问题,提高查询准确度。     

A game theoretic approach to power aware wireless data access

We consider a basic scenario in wireless data access: a number of mobile clients are interested in a set of data items kept at a common server. Each client independently sends requests to inform the server of its desired data items and the server replies with a broadcast channel. We are interested in studying the energy consumption characteristics in such a scenario. First, we define a utility function for quantifying performance. Based on the utility function, we formulate the wireless data access scenario as a noncooperative game - wireless data access (WDA) game. Although our proposed probabilistic data access scheme does not rely on client caching, game theoretical analysis shows that clients do not always need to send requests to the server. Simulation results also indicate that our proposed scheme, compared with a simple always-request one, increases the utility and lifetime of every client while reducing the number of requests sent, with a cost of slightly larger average query delay. We also compare the performance of our proposed scheme with two popular schemes that employ client caching. Our results show that caching-only benefits clients with high query rates at the expense of both shorter lifetime and smaller utility in other clients.     

Energy saving proactive neighbor discovery algorithm in mobile low-duty-cycle wireless sensor network

Mobile low-duty-cycle wireless sensor network is a new kind of wireless multi-hop network,which is self-organized by a large number of nodes that have mobile ability and are able to get into sleep for a long time.Such networks have wide application prospects in national defense,industry,agriculture and other fields that need long term monitoring in severe environments.However,the movement and the sleeping features of nodes lead to constantly change of network topology,which makes the nodes difficult to discover their neighbors quickly.Therefore,the nodes cannot achieve optimal distribution decisions.In order to solve this problem,a new proactive neighbor discovery algorithm was proposed.This algorithm made the nodes in the network take the initiative to find their neighbors when they woke up,and avoided the delay caused by long time waiting in the traditional passive neighbor discovery.In addition,by predicting the movement speed and distance of neighbors,the neighbor set at the next moment can be quickly determined,which can further reduce the delay and obtain more accurate neighbor discovery results.Theoretical analysis and experimental results show that compared with the existing algorithms,the algorithm can find all the neighbors in MLDC-WSN with less energy consumption and lower delay.     

基于ECC和ID签名的WSN广播快速认证方案

广播认证是无线传感器网络(WSN)的一种基本安全服务,针对现有认证方案的计算量大、认证速度慢等问题,提出一种基于椭圆曲线加密(ECC)和身份(ID)签名的WSN广播快速认证方案.对现有EIBAS签名认证方案进行改进,通过节点间的合作,共享中间计算结果来减少邻居节点的计算量,以此提高认证速度,减少能量消耗.同时,提出一种安全机制,通过对多个邻居共享数据的对比来抵御恶意节点的攻击.实验结果表明,该方案相对于传统的椭圆曲线加密算法能够提高约42％的签名认证速度,降低约36％的能耗,大大延长网络生命周期.