检索结果-内蒙古大学图书馆

The effect of discrete vs. continuous-valued ratings on reputation and ranking systems

EPL 2010年第4期91卷

作者： Medo, Matus Wakeling, Joseph Rushton Univ Fribourg Dept Phys CH-1700 Fribourg Switzerland CNRS Inst Jean Nicod F-75005 Paris France CREATE NET Res Consortium I-38123 Povo Italy

When users rate objects, a sophisticated algorithm that takes into account ability or reputation may produce a fairer or more accurate aggregation of ratings than the straightforward arithmetic average. Recently a number of authors have proposed different co-determination algorithms where estimates of user and object reputation are refined iteratively together, permitting accurate measures of both to be derived directly from the rating data. However, simulations demonstrating these methods' efficacy assumed a continuum of rating values, consistent with typical physical modelling practice, whereas in most actual rating systems only a limited range of discrete values (such as a 5-star system) is employed. We perform a comparative test of several co-determination algorithms with different scales of discrete ratings and show that this seemingly minor modification in fact has a significant impact on algorithms' performance. Paradoxically, where rating resolution is low, increased noise in users' ratings may even improve the overall performance of the system.

关键词： computer science and technology Social and economic systems World Wide Web, Internet

来源：评论

学校读者我要写书评

暂无评论

Link prediction in weighted networks: The role of weak ties

引用

EPL 2010年第1期89卷

作者： Lue, Linyuan Zhou, Tao Univ Fribourg Dept Phys CH-1700 Fribourg Switzerland Univ Sci & Technol China Dept Modern Phys Hefei 230026 Peoples R China

Plenty of algorithms for link prediction have been proposed and were applied to various real networks. Among these algorithms, the weights of links are rarely taken into account. In this letter, we use local similarity indices to estimate the likelihood of the existence of links in weighted networks, including Common Neighbor, Adamic-Adar Index, Resource Allocation Index, and their weighted versions. We have tested the prediction accuracy on real social, technological and biological networks. Overall speaking, the resource allocation index performs best. To our surprise, sometimes the weighted indices perform even worse than the unweighted indices, which reminds us of the well-known Weak-Ties Theory. Further experimental study shows that the weak ties play a significant role in the link prediction, and to emphasize the contributions of weak ties can remarkably enhance the prediction accuracy for some networks. We give a semi-quantitative explanation based on the motif analysis. This letter provides a start point for the possible weak-ties theory in information retrieval. Copyright (C) EPLA, 2010

关键词： computer science and technology Networks and genealogical trees Social and economic systems

来源：评论

学校读者我要写书评

暂无评论

Link prediction based on local random walk

引用

EPL 2010年第5期89卷

作者： Liu, Weiping Lue, Linyuan Univ Fribourg Dept Phys CH-1700 Fribourg Switzerland

The problem of missing link prediction in complex networks has attracted much attention recently. Two difficulties in link prediction are the sparsity and huge size of the target networks. Therefore, to design an efficient and effective method is of both theoretical interest and practical significance. In this letter, we proposed a method based on local random walk, which can give competitively good or even better prediction than other random-walk-based methods while having a much lower computational complexity. Copyright (C) EPLA, 2010

关键词： computer science and technology Networks and genealogical trees Social and economic systems

来源：评论

学校读者我要写书评

暂无评论

Empirical analysis of web-based user-object bipartite networks

引用

EPL 2010年第4期90卷

作者： Shang, Ming-Sheng Lue, Linyuan Zhang, Yi-Cheng Zhou, Tao Univ Elect Sci & Technol China Web Sci Ctr Sch Comp Sci & Engn Chengdu 610054 Peoples R China Univ Fribourg Dept Phys CH-1700 Fribourg Switzerland Univ Sci & Technol China Dept Modern Phys Hefei 230026 Peoples R China

Understanding the structure and evolution of web-based user-object networks is a significant task since they play a crucial role in e-commerce nowadays. This letter reports the empirical analysis on two large-scale web sites, *** and ***, where users are connected with music groups and bookmarks, respectively. The degree distributions and degree-degree correlations for both users and objects are reported. We propose a new index, named collaborative similarity, to quantify the diversity of tastes based on the collaborative selection. Accordingly, the correlation between degree and selection diversity is investigated. We report some novel phenomena well characterizing the selection mechanism of web users and outline the relevance of these phenomena to the information recommendation problem. Copyright (C) EPLA, 2010

关键词： Networks and genealogical trees Complex systems computer science and technology

来源：评论

学校读者我要写书评

暂无评论

MO-SAM-BRB-04: Use of Volumetric Modulated Arc Therapy for Intra and Extra Cranial Stereotactic Radiosurgery

引用

Medical Physics 2010年第6PART14期37卷 3333-3333页

作者： C Mayo P Balter S. Senan W Verbakel UMass Medical Center Worcester MA UT MD Anderson Cancer Center Houston TX VU University Medical Center Amsterdam The Netherlands

Volumetric modulated arc therapy (VMAT, aka. volumetric IMRT) burst upon the scene two years ago as a practical means of delivering IMRT as the gantry arcs continuously around the patient. The approach leads to shorter treatment times, fewer total MUs and may facilitate reducing normal tissue doses. The technology has come into ever wider use in clinics as the software for treatment planning has become further refined and supported in multiple treatment planning systems and accelerators. During that period, the literature detailing novel use of volumetric IMRT, clinical implementation and experience with outcome has also grown. As a planning and treatment approach, VMAT is well on its way to becoming standard of care for many anatomic sites. During this period, wider use of hypo-fractionated dose protocols for carrying out stereotactic radiation therapy/surgery for intra cranial lesions and for extra-cranial lesions in the lung, liver and spine have come into wider use. The concurrence of this trend with the emergence of the technology has quickly led to use of VMAT for stereotactic radiosurgery (SRS) in some centers. The aim of this lecture is to facilitate understanding the differences and similarities with conventional techniques and the potential implications for radiobiology, patient positioning equipment and QA issues. Effective treatment planning approaches for intra and extra cranial SRS targets will be presented along with normal tissue constraints used. Implications of reduced treatment time enabled by VMAT on radiobiological response of tumors and normal tissues will be discussed. Speakers have been selected to present information on a diverse set of equipment and clinical practices. Learning Objectives: 1. Able to compare and contrast dose distributions for conventional vs. VMAT techniques 2. Understand technical and potential radio-biological implications of using VMAT for SRS 3. Understand implications of single isocenter treatments of multi-focal targ

关键词： Radiosurgery Dosimetry Tissues Intensity modulated radiation therapy Medical treatment planning Tissue engineering Radiation treatment Drug delivery computer science and technology computer software

来源：评论

学校读者我要写书评

暂无评论

Jamming transition in traffic flow under the priority queuing protocol

引用

EPL 2009年第5期86卷

作者： Kim, K. Kahng, B. Kim, D. Seoul Natl Univ Dept Phys & Astron Seoul 151747 South Korea

Packet traffic in complex networks undergoes the jamming transition from free-flow to congested state as the number of packets in the system increases. Here we study such jamming transition when queues are operated by the priority queuing protocol and packets are guided by the dynamic routing protocol. We introduce a minimal model in which there are two types of packets distinguished by whether priority is assigned. Based on numerical simulations, we show that traffic is improved in the congested region under the priority queuing protocol, and it is worsened in the free-flow region. Also, we find that at the transition point, the waiting-time distribution follows a power law, and the power spectrum of traffic exhibits a crossover between two 1/f(alpha) behaviors with two different exponents alpha < 2 in low-and high-frequency regime, respectively. This crossover is originated from a characteristic waiting time of packets in the queue. Copyright (C) EPLA, 2009

关键词： Networks and genealogical trees Information and communication theory computer science and technology

来源：评论

学校读者我要写书评

暂无评论

SU‐FF‐T‐84: DIRART ‐ a Software Suite for Deformable Image Registration and Adaptive Radiotherapy Research

引用

Medical Physics 2009年第6PART10期36卷 2538-2539页

作者： D Yang I El Naqa A Apte Y Wu S Goddu S Mutic J Deasy D Low Washington University in St Louis St Louis MO Washington University in St Louis St Louis MO Washington University in St Louis St Louis MO Washington University in St Louis St Louis MO Washington University in St Louis St Louis MO Washington University in St Louis St Louis MO Washington University in St Louis St Louis MO Washington University in St Louis St Louis MO

Purpose: Recent years have witnessed tremendous progress in IGRT technology and potential possibilities for adapting treatment planning on a daily basis. However, there is a lack in having software tools toward this goal. Therefore, we have implemented a software suite, DIRART, for deformable image registration (DIR) plus adaptive radiotherapy (ART) research. Method: DIRART is a large set of programs developed using MATLAB. It contains DIR algorithms, common ART functions, integrated graphics user interfaces, visualization features, and dose metrics analysis functions. In addition, it complementarily works together with CERR (Computational Environment for Radiotherapy Research) to offer more functions. DIRART is designed around the concepts of the interactive RT objects, including images, structures, doses and deformation vector fields (DVF) etc. Results: By exchanging RT objects with TPS via DICOM-RT files, DIRART provides a full featured working environment for ART related research tasks. It is capable of transforming dose distributions and structures between the planning CT and the daily images according to the computed DVF so that such RT information could be viewed and evaluated on either image sets. It can also rescale, subtract and sum up the transformed doses, and convert isodose lines to structures. For DIR applications, DIRART is a toolbox which provides 20+ DIR algorithms, including the newer inverse consistency algorithms to provide consistency DVF in both directions with better accuracy. As a DIR research environment, DIRART dose not only provide a good set of image preprocessing algorithms and post-processing functions to facilitate the development and testing of DIR algorithms, but also offers a good amount of options for results visualization, evaluation and validation. Conclusion: DIRART is designed in a data-oriented style with focus on usability, user-friendliness, performance, accuracy, flexibility, features, configurability and stability. It has

关键词： Dosimetry Medical imaging Radiation therapy computer software Image registration Vector fields User interfaces Medical treatment planning computer science and technology Image guided radiation therapy

来源：评论

学校读者我要写书评

暂无评论

Generalized Ising model for dynamic adaptation in autonomous systems

引用

EPL 2009年第1期87卷

作者： Gupta, S. Ray, A. Phoha, S. Penn State Univ Complex Syst Simulat Lab University Pk PA 16802 USA Penn State Univ Appl Res Lab University Pk PA 16802 USA

The paper presents a concept of Statistical Mechanics for observation-based adaptation in autonomous systems, which is typically exhibited by simple biological systems. Time-critical operations of autonomous systems (e. g., unmanned undersea vehicles (UUVs)), require in situ adaptation in the original plan of action and rapid response to evolving contextual changes and situation awareness for enhanced autonomy. In this regard, a concept of dynamic plan adaptation (DPA) is formulated in the setting of a generalized Ising model (e. g., the Potts model) over a discretized configuration space, where the targets (e. g., undersea mines) are distributed. An exogenous time-dependent potential field is defined that controls the movements of the autonomous system in the configuration space, while the decision-theoretic tool for dynamic plan adaptation is built upon local neighborhood interactions. The efficacy of the DPA algorithm has been evaluated by simulation experiments that demonstrate early detection of localized neighborhood targets as compared to a conventional search method involving back and forth motions. Copyright (C) EPLA, 2009

关键词： Self-organized systems computer science and technology Classical spin models

来源：评论

学校读者我要写书评

暂无评论

Gaussian belief with dynamic data and in dynamic network

引用

EPL 2009年第6期87卷

作者： Aurell, E. Pfitzner, R. Royal Inst Technol KTH Linnaeus Ctr ACCESS Stockholm Sweden Aalto Univ TKK Dept Informat & Comp Sci FIN-02150 Espoo Finland Univ Jena D-6900 Jena Germany

In this paper we analyze Belief Propagation over a Gaussian model in a dynamic environment. Recently, this has been proposed as a method to average local measurement values by a distributed protocol (Consensus Propagation, Moallemi C. C. and Van Roy B., IEEE Trans. Inf. Theory, 52 (2006) 4753) where the average is available for read-out at every single node. In the case that the underlying network is constant but the values to be averaged fluctuate ("dynamic data"), convergence and accuracy are determined by the spectral properties of an associated Ruelle-Perron-Frobenius operator. For Gaussian models on Erdos-Renyi graphs, numerical computation points to a spectral gap remaining in the large- size limit, implying exceptionally good scalability. In a model where the underlying network also fluctuates ("dynamic network"), averaging is more effective than in the dynamic data case. Altogether, this implies very good performance of these methods in very large systems, and opens a new field of statistical physics of large (and dynamic) information systems. Copyright (C) EPLA, 2009

关键词： Other topics in areas of applied and interdisciplinary physics computer science and technology

来源：评论

学校读者我要写书评

暂无评论

Relevance is more significant than correlation: Information filtering on sparse data

引用

EPL 2009年第6期88卷

作者： Shang, Ming-Sheng Lue, Linyuan Zeng, Wei Zhang, Yi-Cheng Zhou, Tao Univ Elect Sci & Technol China Web Sci Ctr Sch Engn & Comp Sci Chengdu 610054 Peoples R China Univ Fribourg Dept Phys CH-1700 Fribourg Switzerland Univ Elect Sci & Technol China Lab Informat Econ & Internet Res Chengdu 610054 Peoples R China Univ Sci & Technol China Dept Modern Phys Hefei 230026 Peoples R China

In some recommender systems where users can vote objects by ratings, the similarity between users can be quantified by a benchmark index, namely the Pearson correlation coefficient, which reflects the rating correlations. Another alternative way is to calculate the similarity based solely on the relevance information, namely whether a user has voted an object. The former one uses more information than the latter, and is intuitively expected to give more accurate rating predictions under the standard collaborative filtering framework. However, according to the extensive experimental analysis, this letter reports the opposite results that the latter method, making use of only the relevance information, can outperform the former method, especially when the data set is sparse. Our finding challenges the routine knowledge on information filtering, and suggests some alternatives to address the sparsity problem. Copyright (C) EPLA, 2009

关键词： computer science and technology Networks and genealogical trees Complex systems

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：