Document retrieval on repetitive string collections

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.     

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

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.     

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

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.     

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

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.     

Noise assisted directed motion at the molecular level — 1

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.     

Multiple Outcomes of Class Visits to Natural History Museums: The Students’ View

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.     

Profiling the Beliefs of the Forgotten Teachers: An Analysis of Intern Teachers’ Frameworks for Urban Science Teaching

The need to equip science teachers with knowledge, skills, and habits of mind to face the challenges of teaching science through inquiry informed this study, which analyzed the secondary science intern teachers’ beliefs about inquiry before, during, and following a series of 2 consecutive science methods courses in an attempt to document the effect of such experiences on their ability and willingness to infuse science inquiry in their science curricula. Nine science credentialing interns participated in the study. Data was gathered from their written reflections and various assignments throughout the methods courses. Results suggested that their beliefs changed significantly after the science methods courses. The implications of the study to secondary science teacher educators and researchers were highlighted.     

Principal Leadership for Technology-enhanced Learning in Science

Reforms such as technology-enhanced instruction require principal leadership. Yet, many principals report that they need help to guide implementation of science and technology reforms. We identify strategies for helping principals provide this leadership. A two-phase design is employed. In the first phase we elicit principals’ varied ideas about the Technology-enhanced Learning in Science (TELS) curriculum materials being implemented by teachers in their schools, and in the second phase we engage principals in a leadership workshop designed based on the ideas they generated. Analysis uses an emergent coding scheme to categorize principals’ ideas, and a knowledge integration framework to capture the development of these ideas. The analysis suggests that principals frame their thinking about the implementation of TELS in terms of: principal leadership, curriculum, educational policy, teacher learning, student outcomes and financial resources. They seek to improve their own knowledge to support this reform. The principals organize their ideas around individual school goals and current political issues. Principals prefer professional development activities that engage them in reviewing curricula and student work with other principals. Based on the analysis, this study offers guidelines for creating learning opportunities that enhance principals’ leadership abilities in technology and science reform.