Document retrieval on repetitive string collections     

Travis Gagie  Aleksi Hartikainen  Kalle Karhu  Juha Kärkkäinen  Gonzalo Navarro  Simon J. Puglisi  Jouni Sirén 《Information Retrieval》2017,20(3):253-291

Most of the fastest-growing string collections today are repetitive, that is, most of the constituent documents are similar to many others. As these collections keep growing, a key approach to handling them is to exploit their repetitiveness, which can reduce their space usage by orders of magnitude. We study the problem of indexing repetitive string collections in order to perform efficient document retrieval operations on them. Document retrieval problems are routinely solved by search engines on large natural language collections, but the techniques are less developed on generic string collections. The case of repetitive string collections is even less understood, and there are very few existing solutions. We develop two novel ideas, interleaved LCPs and precomputed document lists, that yield highly compressed indexes solving the problem of document listing (find all the documents where a string appears), top-k document retrieval (find the k documents where a string appears most often), and document counting (count the number of documents where a string appears). We also show that a classical data structure supporting the latter query becomes highly compressible on repetitive data. Finally, we show how the tools we developed can be combined to solve ranked conjunctive and disjunctive multi-term queries under the simple \({\textsf{tf}}{\textsf{-}}{\textsf{idf}}\) model of relevance. We thoroughly evaluate the resulting techniques in various real-life repetitiveness scenarios, and recommend the best choices for each case.  相似文献   

There’s a creepy guy on the other end at Google!: engaging middle school students in a drawing activity to elicit their mental models of Google     

Christie Kodama  Beth St. Jean  Mega Subramaniam  Natalie Greene Taylor 《Information Retrieval》2017,20(5):403-432

Although youth are increasingly going online to fulfill their needs for information, many youth struggle with information and digital literacy skills, such as the abilities to conduct a search and assess the credibility of online information. Ideally, these skills encompass an accurate and comprehensive understanding of the ways in which a system, such as a Web search engine, functions. In order to investigate youths’ conceptions of the Google search engine, a drawing activity was conducted with 26 HackHealth after-school program participants to elicit their mental models of Google. The findings revealed that many participants personified Google and emphasized anthropomorphic elements, computing equipment, and/or connections (such as cables, satellites and antennas) in their drawings. Far fewer participants focused their drawings on the actual Google interface or on computer code. Overall, their drawings suggest a limited understanding of Google and the ways in which it actually works. However, an understanding of youths’ conceptions of Google can enable educators to better tailor their digital literacy instruction efforts and can inform search engine developers and search engine interface designers in making the inner workings of the engine more transparent and their output more trustworthy to young users. With a better understanding of how Google works, young users will be better able to construct effective queries, assess search results, and ultimately find relevant and trustworthy information that will be of use to them.  相似文献   

Jack Meadows (1934–2016): A tribute to a great information scientist          下载免费PDF全文

Anthony Watkinson 《Learned Publishing》2017,30(2):177-178

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Early career researchers: Scholarly behaviour and the prospect of change          下载免费PDF全文

David Nicholas  Anthony Watkinson  Cherifa Boukacem‐Zeghmouri  Blanca Rodríguez‐Bravo  Jie Xu  Abdullah Abrizah  Marzena Świgoń  Eti Herman 《Learned Publishing》2017,30(2):157-166

Early career researchers (ECRs) are of great interest because they are the new (and biggest) wave of researchers. They merit long and detailed investigation, and towards this end, this overarching paper provides a summary of the first‐year findings of a 3‐year, longitudinal study of 116 science and social science ECRs who have published nearly 1,200 papers and come from 7 countries and 81 universities. ECRs were interviewed in their own languages face‐to‐face, by Skype, or telephone. The study focused on the attitudes and behaviours of ECRs with respect to scholarly communications and the extent to which they are adopting new and disruptive technologies, such as social media, online communities, and Open Science. The main findings include: publishing in high‐impact factor journals is the only reputational game in town; online scholarly communities, and ResearchGate in particular, are gaining ground; social media are beginning to have an impact, especially in the dissemination arena; outreach activities have become more important; libraries are becoming increasingly invisible to ECRs; Open Science is not gaining traction; and more transformational ideas are being expressed, especially in the US and UK.  相似文献   

Estimation of financial loss ratio for E-insurance: a quantitative model     

钟元生  陈德人  施敏华 《浙江大学学报(A卷英文版)》2002,3(2):140-147

In view of the risk of E-commerce and the response of the insurance industry to it, this paper is aimed at one important point of insurance, that is, estimation of financial loss ratio, which is one of the most difficult problems facing the E-insurance industry. This paper proposes a quantitative analyzing model for estimating E-insurance financial loss ratio. The model is based on gross income per enterprise and CSI/FBI computer crime and security survey. The analysis results presented are reasonable and valuable for both insurer and the insured and thus can be accepted by both of them. What we must point out is that according to our assumption, the financial loss ratio varied very little, 0.233% in 1999 and 0.236% in 2000 although there was much variation in the main data of the CSI/FBI survey.  相似文献   

Baecklund Transformation and Localized Coherent Structure for the （2＋1）—Dimensional Asymmetric Nizhnik—Novikov—Veselov Equation     

张解放  刘宇陆 《上海大学学报(英文版)》2002,6(3):191-195

This article is concerned with the extended homogeneous balance method for studying the abundant lacalized solution structure of the (2 1)-dimensional asymmetric Nizhnik-novikov-Veselov equation.A Baecklund transformation was first obtained.and then the richness of the localized coherent structures was found,which was caused by the entrance of two variable-separated arbitrary functions,in the model.For some spectial choices of the arbitrary functions,it is shown that the localized structures of the model may be dromions,lumps,and rinmg solitons.  相似文献   

Noise assisted directed motion at the molecular level — 1     

Mangal C. Mahato  A. M. Jayannavar 《Resonance》2003,8(7):33-45

Noise affects most of the activities. The term noise is used to describe fluctuations about the mean deterministic stationary value of a physical quantity. Noise is generally associated, for example, with inaccuracies in measurements or impurities in signals such as musical notes and hence is undesirable. However, its essential role in physical processes was pointed out in the beginning the last century by Smoluchowski and others. It is only in the last two decades or so that the positive (active) aspects of its role has come to light and is being subjected to intense scrutiny. It is now being increasingly realised that noise is an important ingredient to bring order in dynamical processes. Though it appears counterintuitive, noise seems to help in directing transport processes in biological systems at the molecular level.  相似文献   

Values,interests and attitudes within vocational behaviour     

Monique Wach  Patrick Gosling 《European Journal of Psychology of Education - EJPE》2004,19(3):223-226

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Computer-mediated instruction: a comparison of online and face-to-face collaboration     

Jeremy I. Tutty  James D. Klein 《Educational technology research and development : ETR & D》2008,56(4):507-507

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Multiple Outcomes of Class Visits to Natural History Museums: The Students’ View   总被引：2，自引：0，他引：2  

Yael Bamberger  Tali Tal 《Journal of Science Education and Technology》2008,17(3):274-284

The purpose of this study was to describe and understand the range of outcomes of class visits to natural history museums. The theoretical framework is based on the multifaceted process of learning in free choice learning environments, and emphasizes the unique and individual learning experience in museum settings. The study’s significance is in highlighting several possible cognitive as well as non-cognitive learning effects in museums class visits, by providing the student’s point of view. Data was collected by semi-structured interviews with 50 students in grades 6–8 on the day following the visit. We present evidence that students expressed several learning outcomes, connected directly and indirectly to the scientific content of the visit. Content oriented outcomes included acquiring scientific knowledge and making connections to prior knowledge; social oriented outcomes were identified in students’ statements regarding communicating knowledge and social aspects of learning; and interest oriented outcomes were evidenced by students’ expressions about emotions, interest and curiosity. The aggregate data addressed the common outcomes and the impact of class visits to natural history museums in the short term. Comparisons between two types of museums show significant differences in several aspects, regarding the exhibit and/or the activity type. Practical ideas for structuring the ultimate experience are included.  相似文献