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MDP-Based Network Selection with Reward Optimization in HetNets

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Chinese Journal of Electronics 2018年第1期27卷 183-190页

作者： CHEN Xin LI Zhuo WANG Kai XING Lei School of computer science Beijing Information Science and Technology University Beijing Key Laboratory of Internet Culture and Digital Dissemination Research Beijing Information Science and Technology University

We investigate the network selection problem over heterogeneous networks. We formulate the decision making problem as a Markov decision process(MDP).Two Poisson processes are introduced to model user arrival and departure, and the change of the number of user in a specific network is described by Skellam *** apply the Total order preference by similarity to the ideal solution(TOPSIS) method to address the issue of state space explosion in MDP model. To acquire the optimal network selection scheme, the value iteration algorithm is employed to solve the MDP model. We take simulations in Matlab to prove the effectiveness of the proposed scheme. From the experiment results, it is found that our proposed scheme can reduce handover probability by 7.5%and 40.4% at the early stage of connection, compared with the Infinite MDP-based(IMDP) strategy and TOPSISonly strategy. It can also reduce blocking probability by6.1% compared with IMDP, while maintaining desirable throughput for the target user.

关键词： Heterogeneous networks Network selection Markov decision process(MDP) Multiple attributes decision making

A Survey on Routing Algorithms for Opportunistic Mobile Social Networks

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China Communications 2021年第2期18卷 86-109页

作者： Ying Cai Haochen Zhang Yanfang Fan Hongke Xia Department of computer science and technology Beijing Information Science and Technology UniversityBeijing 100101China

Opportunistic Mobile Social Networks(OMSNs)are kind of Delay Tolerant Networks(DTNs)that leverage characteristics of Mobile Ad Hoc Networks(MANETs)and Social Networks,particularly the social features,to boost performance of routing *** in OMSNs communicate to share and disseminate data to meet needs for variety of *** networks have attracted tremendous attention lately due to the data transmission requirement from emerging applications such as IoT and smart city *** carried by human is the carrier of message transmission,so the social features of human can be used to improve the ability of data *** this paper,we conduct a comparative survey on routing algorithms in *** first analyze routing algorithms based on three social *** node selfishness is not really considered previously in aforementioned routing algorithms,but has significant impact on network performance,we treat node selfishness as another social feature,classify and elaborate routing algorithms based on incentive *** assess the impact of social features on routing algorithms,we conducted simulation for six routing algorithms and analyzed the simulation ***,we conclude the paper with challenges on design of routing in OMSNs and point out some future research directions.

关键词： OMSNs routing algorithms social features selfishness incentive mechanism

Ginix: Generalized Inverted Index for Keyword Search

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Tsinghua science and technology 2013年第1期18卷 77-87页

作者： Hao Wu Guoliang Li Lizhu Zhou the Department of computer science and technology Tsinghua National Laboratory for Information Science and Technology Tsinghua University

Keyword search has become a ubiquitous method for users to access text data in the face of information explosion. Inverted lists are usually used to index underlying documents to retrieve documents according to a set of keywords efficiently. Since inverted lists are usually large, many compression techniques have been proposed to reduce the storage space and disk I/O time. However, these techniques usually perform decompression operations on the fly, which increases the CPU time. This paper presents a more efficient index structure, the Generalized INverted IndeX （Ginix）, which merges consecutive IDs in inverted lists into intervals to save storage space. With this index structure, more efficient algorithms can be devised to perform basic keyword search operations, i.e., the union and the intersection operations, by taking the advantage of intervals. Specifically, these algorithms do not require conversions from interval lists back to ID lists. As a result, keyword search using Ginix can be more efficient than those using traditional inverted indices. The performance of Ginix is also improved by reordering the documents in datasets using two scalable algorithms. Experiments on the performance and scalability of Ginix on real datasets show that Ginix not only requires less storage space, but also improves the keyword search performance, compared with traditional inverted indexes.

关键词： keyword search index compression document reordering

DeltaFuzz: Historical Version information Guided Fuzz Testing

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Journal of computer science & technology 2022年第1期37卷 29-49页

作者： Jia-Ming Zhang Zhan-Qi Cui Xiang Chen Huan-Huan Wu Li-Wei Zheng Jian-Bin Liu computer School Beijing Information Science and Technology UniversityBeijing 100101China School of information science and technology Nantong UniversityNantong 226019China

With the widespread use of agile software development methods,such as agile and scrum,software is iteratively updated more *** ensure the quality of the software,regression testing is conducted before new versions are ***,to improve the efficiency of regression testing,testing efforts should be concentrated on the modified and impacted parts of a ***,the costs of manually constructing new test cases for the modified and impacted parts are relatively *** testing is an effective method for generating test data automatically,but it is usually devoted to achieving higher code coverage,which makes fuzz testing unsuitable for direct regression testing *** this reason,we propose a fuzz testing method based on the guidance of historical version ***,the differences between the program being tested and the last version are analyzed,and the results of the analysis are used to locate change ***,change impact analysis is performed to find the corresponding impacted basic ***,the fitness values of test cases are calculated according to the execution traces,and new test cases are generated iteratively by the genetic *** on the proposed method,we implement a prototype tool DeltaFuzz and conduct experiments on six open-source *** with the fuzzing tool AFLGo,AFLFast and AFL,DeltaFuzz can reach the target faster,and the time taken by DeltaFuzz was reduced by 20.59%,30.05%and 32.61%,respectively.

关键词： fuzz testing regression testing change impact analysis fitness function

Detection of engineering vehicles in high-resolution monitoring images

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Frontiers of information technology & Electronic Engineering 2015年第5期16卷 346-357页

作者： Xun LIU Yin ZHANG San-yuan ZHANG Ying WANG Zhong-yan LIANG Xiu-zi YE College of computer science and technology Zhejiang University College of Mathematics and information science Wenzhou University

This paper presents a novel formulation for detecting objects with articulated rigid bodies from highresolution monitoring images, particularly engineering vehicles. There are many pixels in high-resolution monitoring images, and most of them represent the background. Our method first detects ob ject patches from monitoring images using a coarse detection process. In this phase, we build a descriptor based on histograms of oriented gradient, which contain color frequency information. Then we use a linear support vector machine to rapidly detect many image patches that may contain ob ject parts, with a low false negative rate and a high false positive rate. In the second phase, we apply a refinement classification to determine the patches that actually contain ob jects. In this stage, we increase the size of the image patches so that they include the complete ob ject using models of the ob ject *** an accelerated and improved salient mask is used to improve the performance of the dense scale-invariant feature transform descriptor. The detection process returns the absolute position of positive ob jects in the original images. We have applied our methods to three datasets to demonstrate their effectiveness.

关键词： Object detection Histogram of oriented gradient (HOG) Dense scale-invariant feature transform(dense SIFT) Saliency Part models Engineering vehicles

Stochastic Workflow Nets Based Workflow Pattern Modeling

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Chinese Journal of Electronics 2014年第1期23卷 6-12页

作者： ZHOU Huan LIN Chuang MENG Kun CHEN Yarui Tsinghua National Laboratory for information science and technology Department of Computer Science and Technology Tsinghua University

Petri nets are widely used in describing workflow models of management systems, and also functioning in process management and resource *** number of workflow patterns are increasing along with the demands of business process modeling. The Petri net and its extensions can no longer meet the requirement of model description, due to the limitation of their *** models of some patterns are very sophisticated and even grow exponentially in complexity. Also the performance of these new patterns are not well studied. This paper extends Petri nets to Stochastic workflow nets(SWNs)and introduces stochastic or state related variables into arc weights, transition enabling guard and execution *** the new features, SWNs can describe models more accurately and flexibly. And performance of common patterns is calculated under the assumption of exponentially distributed time. The paper also illustrates how to simplify the model with equivalent patterns.

关键词： Stochastic workflow nets Workflow patterns Performance analysis

Modeling and Verifying Concurrent Programs with Finite Chu Spaces

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Journal of computer science & technology 2010年第6期25卷 1168-1183页

作者：杜旭涛刑春晓周立柱 Department of computer science and technology Tsinghua University Research Institute of information technology Tsinghua University

Finite Chu spaces are proposed for the modeling and verification of concurrent *** order to model not only typical concurrent behaviors but also modern exception handling and synchronization mechanisms,we design an enriched process algebra of Chu spaces from a practical point of *** illustrate the power of finite Chu spaces and the process algebra while abstracting away from language-specific details,an imaginary concurrent programming language（ICL） is designed.A denotational semantics of ICL is presented using finite Chu spaces and the enriched process *** valuation functions are fairly straightforward since the carefully designed operators have done much of the *** enriched process algebra is also used as the specification language for Chu spaces,with which process-algebraic properties can be *** algorithms are presented with their time complexities discussed.

关键词： Chu spaces process algebra verification denotational semantics concurrency

Multiview Visibility Estimation for Image-Based Modeling

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Journal of computer science & technology 2011年第6期26卷 1000-1010页

作者：张柳新裴明涛贾云得 CCF Beijing Laboratory of Intelligent information technology School of Computer ScienceBeijing Institute of Technology

In this paper, we investigate the problem of determining regions in 3D scene visible to some given viewpoints when obstacles are present in the scene. We assume that the obstacles are composed of some opaque objects with closed surfaces. The problem is formulated in an implicit framework where the obstacles are represented by a level set function. The visible and invisible regions of the given viewpoints are determined through an efficient implicit ray tracing technique. As an extension of our approach, we apply the multiview visibility estimation to an image-based modeling technique. The unknown scene geometry and multiview visibility information are incorporated into a variational energy functional. By minimizing the energy functional, the true scene geometry as well as the accurate visibility information of the multiple views can be recovered from a number of scene images. This makes it feasible to handle the visibility problem of multiple views by our approach when the true scene geometry is unknown.

关键词： visibility estimation image-based modeling multiple views level set implicit surface

Audio Retrieval Based on Manifold Ranking and Relevance Feedback

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Tsinghua science and technology 2015年第6期20卷 613-619页

作者： Jing Qin Xinyue Liu Hongfei Lin School of computer science and technology Dalian University of Technology College of information Engineering Dalian University

An audio information retrieval model based on Manifold Ranking(MR) is proposed, and ranking results are improved using a Relevance Feedback(RF) algorithm. Timbre components are employed as the model’s main feature. To compute timbre similarity, extracting the spectrum features for each frame is necessary; the large set of frames is clustered using a Gaussian Mixture Model(GMM) and expectation maximization. The typical spectra frame from GMM is drawn as data points, and MR assigns each data point a relative ranking score, which is treated as a distance instead of as traditional similarity metrics based on pair-wise distance. Furthermore, the MR algorithm can be easily generalized by adding positive and negative examples from the RF algorithm and improves the final result. Experimental results show that the proposed approach effectively improves the ranking capabilities of existing distance functions.

关键词： audio information retrieval manifold ranking relev