检索结果-南通市图书馆

Approximate Continuous Top-k Query over sliding window

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Computer Science & Technology 2017年第1期32卷 93-109页

作者： Rui Zhu Bin Wang Shi-Ying Luo Xiao-Chun Yang Guo-Ren Wang College of Computer Science and Engineering Northeastern University Shenyang 110819 China

Continuous top-k query over sliding window is a fundamental problem in database, which retrieves k objects with the highest scores when the window slides. Existing studies mainly adopt exact algorithms to tackle this type of queries, whose key idea is to maintain a subset of objects in the window, and try to retrieve answers from it. However, all the existing algorithms are sensitive to query parameters and data distribution. In addition, they suffer from expensive overhead for incremental maintenance, and thus cannot satisfy real-time requirement. In this paper, we define a novel query named （ε, δ）-approximate continuous top-κ query, which returns approximate answers for top-κ query. In order to efficiently support this query, we propose an efficient framework, named PABF （Probabilistic Approximate Based Framework）, to support approximate top-κ query over sliding window. We firstly maintain a self-adaptive pruning value, which could filter out newly arrived objects who have a probability less than 1 - 5 of being a query result. For those objects that are not filtered, we combine them together, if the score difference among them is less than a threshold. To efficiently maintain these combined results, the framework PABF also proposes a multi-phase merging algorithm. Theoretical analysis indicates that even in the worst case, we require only logarithmic complexity for maintaining each candidate.

关键词： continuous top-k query approximate sliding window

Enhanced remote astronomical archive system based on the file-level Unlimited sliding-window technique

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2021年第10期21卷 119-126页

作者： Cong-Ming Shi Hui Deng Feng Wang Ying Mei Shao-Guang Guo Chen Yang Chen Wu Shou-Lin Wei Andreas Wicenec Center For Astrophysics Guangzhou UniversityGuangzhou 510006China School of Software Engineering Anyang Normal UniversityAnyang 455000China Shanghai Astronomical Observatory Chinese Academy of SciencesShanghai 200030China International Center for Radio Astronomy Research(ICRAR) The University of Western AustraliaCrawleyPerthWAAustralia Kunming University Of Science And Technology Kunming 650500China

Data archiving is one of the most critical issues for modern astronomical observations.With the development of a new generation of radio telescopes,the transfer and archiving of massive remote data have become urgent problems to be solved.Herein,we present a practical and robust file-level flow-control approach,called the Unlimited sliding-window(USW),by referring to the classic flow-control method in the TCP protocol.Based on the USW and the Next Generation Archive System(NGAS)developed for the Murchison Widefield Array telescope,we further implemented an enhanced archive system(ENGAS)using ZeroMQ middleware.The ENGAS substantially improves the transfer performance and ensures the integrity of transferred files.In the tests,the ENGAS is approximately three to twelve times faster than the NGAS and can fully utilize the bandwidth of network links.Thus,for archiving radio observation data,the ENGAS reduces the communication time,improves the bandwidth utilization,and solves the remote synchronous archiving of data from observatories such as Mingantu spectral radioheliograph.It also provides a better reference for the future construction of the Square Kilometer Array(SKA)Science Regional Center.

关键词： remote data archive NGAS sliding window

呼吸运动对sliding window调强射野剂量学的影响

在线全文

学校读者我要写书评

暂无评论

呼吸运动对Sliding Window调强射野剂量学的影响

作者：沐金明北京协和医学院

学位级别：硕士

背景和目的:目前,动态调强放疗广泛地应用于肿瘤的放射治疗,并且越来越多地应用于胸腹部肿瘤的治疗。随着临床上对剂量分布等要求的不断提高,动态调强射野的子野越来越小,呼吸等生理运动引起的剂量学差异越来越显著。对于呼吸运动引起... 详细信息

背景和目的:目前,动态调强放疗广泛地应用于肿瘤的放射治疗,并且越来越多地应用于胸腹部肿瘤的治疗。随着临床上对剂量分布等要求的不断提高,动态调强射野的子野越来越小,呼吸等生理运动引起的剂量学差异越来越显著。对于呼吸运动引起的剂量学差异的研究目前主要集中在对单次治疗剂量分布或全疗程的剂量分布在有无呼吸运动时差异比较,和呼吸管理方面的研究。并未对具体的子野参数进行研究。本研究首次针对动态调强射野的两个重要特性:子野宽度(射野宽度)与MLC叶片移动速度(叶片速度)来设计、研究呼吸运动对动态调强射野剂量学的影响。并分析动态调强技术能否应用于乳腺癌的放疗。材料和方法:使用Quasar驱动平台驱动调强验证模体模拟呼吸运动。设计一组不同射野宽度和不同叶片速度的照射野照射调强验证模体。在验证模体中放置辐射自显影胶片分别在有无呼吸运动时采集一个呼吸周期内射野剂量分布。处理胶片并生成剂量分布曲线分析胶片,对运动模式、叶片速度、射野宽度等多个因素分组进行比对并分析原因。使用一组实际患者的动态调强射野对验证模体进行照射。在连续呼吸情况下,分别在有无呼吸运动时采集射野中心的剂量分布。处理胶片并生成剂量分布曲线后对比并分析原因。结果:在单次呼吸模式下,不同的运动模式对剂量分布影响差异显著不同。随着叶片速度的增大,射野内剂量波动幅度随之显著增大;随着射野宽度的增大,射野内剂量波动幅度随之减小;射野宽度小叶片速度高,对剂量分布的影响最为显著。模式A中最大剂量无统计学意义,但最小剂量为49.93%± 13.49%;在模式B中最大剂量为204.79%±49.35%,最小剂量为27.53%±6.96%。在实际射野中射野照射范围内剂量波动幅度明显减小,剂量分布曲线相似,剂量差异主要表现为剂量分布的偏移。结论:有呼吸运动影响时,应通过提高射野宽度和(或)减小叶片速度等方法来减小呼吸运动对SW调强射野剂量分布的影响。

关键词：呼吸运动 sliding window 剂量分布

KaKs_Calculator 2.0:A Toolkit Incorporating Gamma-Series Methods and sliding window Strategies

同方学位论文库评论

在线全文

同方学位论文库

学校读者我要写书评

暂无评论

Genomics, Proteomics & Bioinformatics 2010年第1期8卷 77-80页

作者： Dapeng Wang Yubin Zhang Zhang Zhang Jiang Zhu Jun Yu AS Key Laboratory of Genome Sciences and Information Beijing Institute of Genomics Chinese Academy of Sciences Beijing 100029 China Institute of Computing Technology Chinese Academy of Sciences Beijing 100190 China Graduate University of Chinese Academy of Sciences Beijing 100049 China Plant Stress Genomics Research Center Division of Chemical and Life Sciences & Engineering King Abdullah University of Science and Technology Thuwa123955-6900 Saudi Arabia.

We present an integrated stand-alone software package named KaKs_Calculator 2.0 as an updated version. It incorporates 17 methods for the calculation of nonsynonymous and synonymous substitution rates; among them, we added our modified versions of several widely used methods as the gamma series including y-NG, y-LWL, ）,-MLWL, y-LPB, y-MLPB, y-YN and y-MYN, which have been demonstrated to perform better under certain conditions than their original forms and are not implemented in the previous version. The package is readily used for the identification of positively selected sites based on a sliding window across the sequences of interests in 5＇ to 3＇ direction of protein-coding sequences, and have improved the overall performance on sequence analysis for evolution studies. A toolbox, including C＋＋ and Java source code and executable files on both windows and Linux platforms together with a user instruction, is downloadable from the website for academic purpose at https：//***/projects/kakscalculator2/.

关键词： Ka/Ks gamma-series methods sliding window positively selected sites

Dynamically Computing Approximate Frequency Counts in sliding window over Data Stream

在线全文

学校读者我要写书评

暂无评论

Wuhan University Journal of Natural Sciences 2006年第1期11卷 283-288页

作者： NIE Guo-liang LU Zheng-ding School of Computer Science and Technology Huazhong University of Science and Technology Wuhan 430074Hubei China

This paper presents two one-pass algorithms for dynamically computing frequency counts in sliding window over a data stream-computing frequency counts exceeding user-specified threshold ε. The first algorithm constructs subwindows and deletes expired sub-windows periodically in sliding window, and each sub-window maintains a summary data structure. The first algorithm outputs at most 1/ε ＋ 1 elements for frequency queries over the most recent N elements. The second algorithm adapts multiple levels method to deal with data stream. Once the sketch of the most recent N elements has been constructed, the second algorithm can provides the answers to the frequency queries over the most recent n （ n≤N） elements. The second algorithm outputs at most 1/ε ＋ 2 elements. The analytical and experimental results show that our algorithms are accurate and effective.

关键词： data stream sliding window approximation algorithms frequency counts

Research on Multi-satellites Fusion Inversion Model of Soil Moisture Based on sliding window

在线全文

学校读者我要写书评

暂无评论

Research on Multi-satellites Fusion Inversion Model of Soil ...

Linked-Tree: An Aggregate Query Algorithm Based on sliding window over Data Stream

第九届中国卫星导航学术年会

作者： Yueji Liang Chao Ren Yibang Huang

Global Positioning System Interferometric Reflectometry(GPS-IR) is a new remote sensing technique,and it can be used to estimate near surface soil moisture from signal-to-noise ratio data.Considering the advantages of multi-satellite convergence and the time and space scale of soil moisture,a multi-satellites fusion inversion model of soil moisture based on sliding window is proposed.Firstly,the direct and reflection signals of GPS satellites are separated by a low order polynomial fitting,and then the sinusoidal fitting model of reflection signals is established,the relative phase of the SNR interferogram is obtained.Finally,a sliding window is established to select the relative phases of the satellites effectively,and the best input variables of the inversion model are determined.Then,the soil moisture is retrieved by least square support vector machine.Based on the monitoring data provided by US Plate Boundary Observations Project,the feasibility and effectiveness of using single and different GPS satellites to sliding estimate soil moisture are compared and analyzed.The experimental results show that sliding window can effectively select GPS satellites and determine the best input variables for the model.The model fully takes the advantage of non-linear weight determination.The sliding type can achieve a longer time inversion.To a certain extent,this model improves the phenomenon that the inversion process is prone to jump when using single satellite inversion.Based on the inversion of more than four satellites,RMSE and MAE is less than 0.07 and 0.06,respectively,and R2 is increased by at least 21.9% compared with inversion result of a single satellite.Therefore,the inversion of soil moisture can be treated as nonlinear event,and multi-satellites fusion inversion is feasible and effective.

关键词： GPS-IR Soil moisture Multi-satellites fusion sliding window Least squares support vector machine

来源： cnki会议评论

在线全文

cnki会议

学校读者我要写书评

暂无评论

Wuhan University Journal of Natural Sciences 2006年第5期11卷 1114-1119页

作者： YU Yaxin WANG Guoren SU Dong ZHU Xinhua School of Computer Science and Engineering Northeastern University Shenyang 110004 I.iaoning China Neusoft Group Ltd Shenyang 110179 LiaoningChina

How to process aggregate queries over data streams efficiently and effectively have been becoming hot re search topics in both academic community and industrial community. Aiming at the issues, a novel Linked-tree algorithm based on sliding window is proposed in this paper. Due to the proposal of concept area, the Linked-tree algorithm reuses many primary results in last window and then avoids lots of unnecessary repeated comparison operations between two successive windows. As a result, execution efficiency of MAX query is improved dramatically. In addition, since the size of memory is relevant to the number of areas but irrelevant to the size of sliding window, memory is economized greatly. The extensive experimental results show that the performance of Linked-tree algorithm has significant improvement gains over the traditional SC （Simple Compared） algorithm and Ranked-tree algorithm.

关键词： data streams sliding window aggregate query area hop

鼻咽癌sliding window和Step and shoot调强方式的剂量学比较

在线全文

学校读者我要写书评

暂无评论

鼻咽癌Sliding window和Step and shoot调强方式的剂量学比较

作者：马栋辉新疆医科大学

学位级别：硕士

目的：探讨鼻咽癌sliding window和Step and shoot调强方式的剂量学差异。方法：采用CADPLAN 6.4.7（helios）治疗计划系统对15例鼻咽癌需调强治疗的患者，用sliding window和Step and shoot两种实现方式四种强度水平（Intensity Level... 详细信息

目的：探讨鼻咽癌sliding window和Step and shoot调强方式的剂量学差异。方法：采用CADPLAN 6.4.7（helios）治疗计划系统对15例鼻咽癌需调强治疗的患者，用sliding window和Step and shoot两种实现方式四种强度水平（Intensity Level）进行剂量学差异的比较，强度水平分为sliding window（SW），Step and shoot intensityLevel 10（SSL10），Step and shoot intensity Level 7（SSL7），Step and shoot intensity Level 5（SSL5）4个组。剂量学评估参数：PTV最大剂量（Dmax），剂量体积直方图（DVH），适型指数（Conformity index，CI），剂量不均匀性指数（Heterogeneity Index，HI），MU（机器跳数），Segment（子野数目）等数据进行评价。结果：各组PTV最大剂量SW组和SSL10，SSL7，SSL5组比较有统计学意义（P＜0.05），而SSL10，SSL7，SSL5组比较（P＞0.05）无统计学意义，随着Intensity level的降低，最大剂量增高;通过对MU的观察，SW组与SSL10，SSL7，SSL5组比较有统计学意义（P＜0.01），而SSL10，SSL7，SSL5组之间没有统计学意义（P＞0.05）;Segment（子野数目）各组间均有统计学意义（P＜0.01）;CI，HI：各组均无统计学意义（P＞0.05）。脊髓，脑干，晶体，视交叉，腮腺等保护器官的最大剂量均无统计学意义。结论：鼻咽癌不同调强方式和强度水平的治疗计划均能为临床提供较满意的剂量学分布，但剂量上有差异。sliding window方式略优于不同强度水平的Step and shoot方式，但MU和Segment较多。

关键词：调强放射治疗 sliding window Step and Shoot 剂量学计划比较

A graph-based sliding window multi-join over data stream

同方学位论文库评论

在线全文

同方学位论文库

学校读者我要写书评

暂无评论

A graph-based sliding window multi-join over data stream