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1.
黄震华  向阳  孙圣力  陈千 《电子学报》2013,41(8):1515-1520
轮廓查询是近年来信息服务领域的一个研究重点和热点.现有的三阶段算法TPAOSS (Three-Phase Algorithm for Optimizing Skyline Scalar)至少存在如下两个缺陷:(1)在TPAOSS算法的第3阶段中,当网络节点上的对象个数较多时,Bloom filter的长度将呈指数级增长,从而严重影响获取子空间重复值的效率以及占用内存空间的大小;(2)TPAOSS算法只考虑预处理阶段的时间代价,而没有考虑各网络节点进行局部或全局子空间轮廓查询计算的效率.为此,提出一种适合超对等网络(Super-Peer Architecture,SPA)的子空间轮廓查询方法EPSSQDN (Efficient Processing of Subspace Skyline Queries in Distributed Networks).EPSSQDN算法有效解决了TPAOSS算法的的两个主要性能问题,并且显著提高了SPA网络中的子空间轮廓查询处理的效率.此外,为了能够进一步降低子空间上轮廓查询的时间开销以及网络节点间的数据传输量,我们给出新颖且有效的优化策略.实验结果表明,EPSSQDN算法比TPAOSS算法更能够缩短SPA网络中子空间轮廓查询的时间开销.  相似文献   

2.
在流数据环境下,多维空间的Skyline计算会随着维度的增高影响滑动窗口上Skyline点集的计算效率.针对以上问题,提出SQTS算法,采用网格索引结构,对元组进行标记,排除部分非Skyline点集;引入SD队列触发Skyline维护,避免过期数据点的频繁排查,提高多维空间下的Skyline计算效率.仿真实验结果表明,SQTS算法在多维流数据环境下,提高了Skyline点集的计算效率,验证了算法有效性.  相似文献   

3.
容忍节点失效的传感器网络空间范围查询算法   总被引:1,自引:0,他引:1  
提出了一种容忍节点失效的空间范围查询处理算法GSA.给出了理论上最节省能量的网格大小设置.提出了一种基于网格的查询结果收集调度策略,以避免查询结果收集过程中的消息碰撞问题.系统地分析了算法在不同节点密度、节点失效概率和查询区域大小条件下的查询成功率,以及不同节点密度、查询消息大小、感知数据大小、查询区域大小、节点失效概率条件下的能量消耗.理论和实验表明,在多数情况下,GSA算法优于现有的IWQE算法.  相似文献   

4.
近年来,动态数据流环境下的聚集查询正成为一个热点研究问题.目前的相关算法主要是采用近似技术,以牺牲精度来换取处理速度的提高.然而,在高速数据流环境下,处理速度仍然难以满足需求.软硬件协同的高速数据流处理技术逐渐引起人们的关注.提出了一种基于硬件加速的高速数据流聚集查询方法,充分发挥硬件在处理速度上的优势和软件在灵活性方面的长处.算法是增量的,也实现了多窗口资源共享.最后,给出了算法的复杂度分析并实验验证了方法的有效性.  相似文献   

5.
针对数据流查询优化问题,分析了数据流查询处理的基本过程和查询共享模型的特点.设计了一种基于共享队列的二级索引作为数据流中间结果的存储结构,并相应地提出了一种数据流存储共享的迁移算法.该结构减少了数据流查询过程中对存储空间的占用,也为数据共享情况下的数据迁移提供了一定的灵活性.  相似文献   

6.
Top-K查询处理是不确定性数据管理中一项重要技术。本文在分析不确定性数据模型和可能世界模型的基础上,定义了不确定数据流元组的查询语义,提出了基于记录向量的Top-K查询算法,该算法根据K值,计算并返回分值最高前K个结果,其查询结果评价综合考虑了查询结果在可能世界语义下的概率大小。实验结果表明,与CSQ和SCSQ算法相比,本算法更具高效性和实用性。  相似文献   

7.
针对分布式计算环境,利用移动Agent技术提出了一种基于移动Agent的分布式Skyline查询算法,并进行了深入的分析。通过分析可知,该算法可以实现在分布式环境下求解全局Skyline点。  相似文献   

8.
随着Web网络和无线传感器网络的不断发展,大数据的出现对数据查询和处理产生了挑战。研究了MapReduce框架下移动对象的并行Skyline计算问题,采用基于角度划分的方法解决负载平衡问题,并提出了一种过滤策略进行剪枝提高计算效率,在此基础上分别实现了静态Skyline算法和基于事件跟踪的MR-Track算法。最后通过对比实验验证了算法的有效性。  相似文献   

9.
面向时空数据流的移动对象空间索引构建   总被引:1,自引:0,他引:1  
杨良怀  沈东海  范玉雷  高楠 《电子学报》2021,49(5):992-1000
本文针对时空数据流提出了一种基于时间窗口数据排序和批量装载的移动对象空间索引构建方法HSTRCL.该方法用固定长度的时间窗口将连续的时空数据流进行切分,每当一个时间窗口完成数据缓存,采用优化的索引批量装载技术,从传统的构建流程中尽可能分离出耗时的数据划分和排序操作,将数据流的接收及其他构建操作并行执行,避免不必要的加锁同步开销,加快索引的构建效率;同时,采用基于Hash和STR的主、辅索引构建技术,满足高性能且多样化的查询需求.另外,为进一步提高对象查询性能,引入聚合技术划分对象,提出了一种基于时间窗口对象聚合和批量装载的移动对象空间索引构建方法OAHSTRCL,对象查询时间约为HSTRCL的65%,但对空间查询性能会有一定程度的影响.通过理论分析和多种实验验证了所提方法的有效性.  相似文献   

10.
多查询优化问题是从一组查询中找出公共子结构,将其结果缓存起来,每个查询可以利用缓存结果构建自己的结果.由于知识图谱上的多查询优化是NP-hard问题,现有方法无法在大量查询同时到达时高效地查找公共子结构,也无法保证优化后查询时间一定减少.因此,本文提出了一个新的分布式,基于内存的RDF查询引擎Leon来处理多查询优化问题.Leon使用了基于特征集合的索引和划分方法,具有简单高效、空间占用小的特点.针对现有检测查询之间公共子结构检测算法时间复杂度高的特点,本文提出了一个新颖的多查询优化算法:利用特征集合快速过滤没必要优化的查询,在剩下来的查询中精确、高效地查找公共子结构.实验结果证明:引入多查询优化情形下,时间是基准方法的1/10.  相似文献   

11.
Skyline查询能够计算大规模的数据集中满足多个标准的最优解,被广泛应用于多目标决策等领域.动态skyline查询作为skyline查询的一种重要变体,其结果随着查询点的不同而动态改变,为用户在指定查询要求方面提供了更大的灵活性.然而,随着数据量的不断增加,动态skyline查询会产生大量的查询结果,忽略了查询点的维度方向性和数据的全局整体性,给用户的选择带来极大困难.因此,需要进一步优化动态skyline查询的结果集,提高全局整体性,过滤冗余数据.针对上述问题,提出一种基于MapReduce的增广动态skyline查询处理方法.该方法将原始数据按照维度信息进行分区,在多个节点并行计算动态skyline,优化传统动态skyline结果集,同时提供全局更优的结果供用户选择.在此基础上,针对用户给出某些维度的容忍度的情况,提出一种引入用户容忍度的增广动态skyline查询处理方法.该方法可以根据用户容忍度缩减增广动态skyline查询的原始数据集,很大程度上减少中间结果的比较次数,并且提高了结果集的准确度.大量实验证明,基于MapReduce的增广动态skyline查询处理方法具有更好的有效性、准确性和可用性.  相似文献   

12.
有效降低分布式SKYLINE查询网络传输代价   总被引:1,自引:1,他引:0       下载免费PDF全文
黄震华  向阳  林琛 《电子学报》2010,38(4):848-0852
 分布式网络中的skyline查询是近年来信息检索学科的一个研究重点.目前大多数研究工作均没有考虑在分布式网络中,如何有效降低skyline查询的网络传输代价.为此,提出一种在分布式网络中,有效降低skyline查询传输代价的方法RTCSQDN(Reducing the Transferring Cost of Skyline Queries over Distributed Networks).RTCSQDN算法充分利用父空间skyline对象集与子空间skyline对象集间的语义关系通过三个阶段来平衡网络传输量和查询时间开销.同时,文章给出一种新颖的多维对象传送策略PTGPV(Policy for Transferring Grouping Position Values)来避免直接传送skyline对象本身,从而最小化数据传输量.详细的理论分析和大量实验评估表明,文章给出的算法具有有效性和实用性.  相似文献   

13.
He Li  Jaesoo Yoo 《ETRI Journal》2016,38(6):1197-1206
Performing continuous skyline queries of dynamic data sets is now more challenging as the sizes of data sets increase and as they become more volatile due to the increase in dynamic updates. Although previous work proposed support for such queries, their efficiency was restricted to small data sets or uniformly distributed data sets. In a production database with many concurrent queries, the execution of continuous skyline queries impacts query performance due to update requirements to acquire exclusive locks, possibly blocking other query threads. Thus, the computational costs increase. In order to minimize computational requirements, we propose a method based on a multi‐layer grid structure. First, relational data object, elements of an initial data set, are processed to obtain the corresponding multi‐layer grid structure and the skyline influence regions over the data. Then, the dynamic data are processed only when they are identified within the skyline influence regions. Therefore, a large amount of computation can be pruned by adopting the proposed multi‐layer grid structure. Using a variety of datasets, the performance evaluation confirms the efficiency of the proposed method.  相似文献   

14.
With the deployment of wireless sensor networks (WSNs) for environmental monitoring and event surveillance, WSNs can be treated as virtual databases to respond to user queries. It thus becomes more urgent that such databases are able to support complicated queries like skyline queries. Skyline query which is one of popular queries for multi-criteria decision making has received much attention in the past several years. In this paper we study skyline query optimization and maintenance in WSNs. Specifically, we first consider skyline query evaluation on a snapshot dataset, by devising two algorithms for finding skyline points progressively without examining the entire dataset. Two key strategies are adopted: One is to partition the dataset into several disjoint subsets and produce the skyline points in each subset progressively. Another is to employ a global filter that consists of some skyline points in the processed subsets to filter out unlikely skyline points from the rest of unexamined subsets. We then consider the query maintenance issue by proposing an algorithm for incremental maintenance of the skyline in a streaming dataset. A novel maintenance mechanism is proposed, which is able to identify which skyline points from past skylines to be the global filter and determine when the global filter is broadcast. We finally conduct extensive experiments by simulations to evaluate the performance of the proposed algorithms on both synthetic and real sensing datasets, and the experimental results demonstrate that the proposed algorithms significantly outperform existing algorithms in terms of network lifetime prolongation.  相似文献   

15.
A geo-localization method is proposed for military and civilian applications, which is used when no global navigation satellite system (GNSS) information is available. The open graphics library (OpenGL) is used to build a three-dimensional geographic model of the test area using digital elevation model (DEM) data, and the skyline can thus be extracted with the model to form a database. Then, MultiSkip DeepLab (MS-DeepLab), a fully convolutional semantic segmentation network with multiple skip structures, is proposed to extract the skyline from the query image. Finally, a matching model based on convolutional neural network (CNN) feature is adopted to calculate the similarity between the skyline features of the query image and the DEM database to realize automatic geo-localization. The experiments are conducted at a 202.6 km2 test site in north-eastern Changsha, China. 50 test points are selected to verify the effectiveness of the proposed method, and an excellent result with an average positioning error of 49.29 m is obtained.  相似文献   

16.
In an in-home digital network it may be expected that several data streams (audio, video) run simultaneously over a shared communication device, e.g., a bus. The burstiness of a data stream can be reduced by buffering data at the sending and receiving side, thereby allowing a lower bus share allocation for the stream. In this paper we present an algorithm that determines how much of the bus capacity and buffer space should be allocated to each stream, in order to have a feasible transmission schedule for each stream. Furthermore, the algorithm determines a transmission schedule for each stream, indicating how much data is transmitted over time. We show how this multiple-stream problem can be solved by repeatedly solving single-stream problems. We present efficient algorithms to solve these single-stream problems. Furthermore, we present some experimental results. This revised version was published online in September 2006 with corrections to the Cover Date.  相似文献   

17.
The fields of bioinformatics and biotechnology rely on the collection, processing and analysis of huge numbers of biocellular images, including cell features such as cell size, shape, and motility. Thus, cell tracking is of crucial importance in the study of cell behaviour and in drug and disease research. Such a multitarget tracking is essentially an assignment problem, NP-hard, with the solution normally found in practice in a reduced hypothesis space. In this paper we introduce a novel approach to find the exact association solution over time for single-frame scan-back stem cell tracking. Our proposed method employs a class of linear programming optimization methods known as the Hungarian method to find the optimal joint probabilistic data association for nonlinear dynamics and non-Gaussian measurements. The proposed method, an optimal joint probabilistic data association approach, has been successfully applied to track hematopoietic stem cells.  相似文献   

18.
语音感知是无人系统的重要组成部分,已有的工作大多集中于单个智能体的语音感知,受噪声、混响等因素的影响,性能存在上限。因此研究多智能体语音感知,通过多智能体自组织、相互协作,提高感知性能非常必要。假设每个智能体输出一个通道的语音流条件下,本文提出一种多智能体自组织语音系统,旨在综合利用所有通道提高感知性能;并进一步以语音识别为例,提出能处理大规模多智能体语音识别的通道选择方法。基于Sparsemax算子的端到端语音识别流注意机制,将带噪通道权重置零,使流注意力具备通道选择能力,但Sparsemax算子会将过多通道权重置零。本文提出Scaling Sparsemax算子,只将带噪较强的通道权重置零;同时提出了多层流注意力结构,有效降低了计算复杂度。在30个智能体的无人系统环境下,基于conformer架构的识别系统实验结果表明,在通道数失配的测试环境下,提出的Scaling Sparsemax在仿真数据集上的文字差错率(WER)相比Softmax降低30%以上,在半真实数据集上降低20%以上。  相似文献   

19.
黄震华  向阳  林琛  孙圣力 《电子学报》2009,37(8):1639-1645
现有的研究工作只考虑如何对单个底层关系表进行skyline计算,即它们假定用户所提交的skyline查询不涉及任何传统的关系操作,并且所有skyline维度均落入同一个关系表中.显然,在实际应用中,由于这种假设的不成立,使得在多数情况下用户查询的效率极其低下.基于此,将skyline计算作为一个特殊的关系操作符,研究它与传统关系操作符间执行顺序变换的等价规则.从而,利用这些等价变换规则,通过改变skyline操作符与传统关系操作符之间的执行顺序来有效提高查询的效率.同时,给出充分的理论证明来论证所给等价变换规则的正确性,并通过实验验证其有效性.  相似文献   

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