文本检索模型综述

文本检索是信息检索一个重要的分支。随着互联网信息的迅速膨胀,如何检索到用户最需要的信息变得越来越关键。文本检索模型是文本检索中的核心技术,其性能直接影响到搜索引擎的检索质量。本文对当前的经典检索模型及其研究进展进行介绍,并分析各个模型之间的优缺点。     

Capturing system level activities and impacts of mental health consumer-run organizations

Since the 1970s mental health consumer-run organizations have come to offer not only mutual support, but they have also adopted agendas for broader social change. Despite an awareness of the need for system level efforts that create supportive environments for their members, there has been limited research demonstrating how their system level activities can be documented or their impacts evaluated. The purpose of this paper is to feature a method of evaluating systems change activities and impacts. The paper is based on a longitudinal study evaluating four mental health consumer-run organizations in Ontario, Canada. The study tracked system level activities and impacts using both qualitative and quantitative methodologies. The article begins by describing the development and implementation of these methods. Next it offers a critical analysis of the methods used. It concludes by reflecting on three lessons learned about capturing system level activities and impacts of mental health consumer-run organizations.     

Putting the system back into systems change: a framework for understanding and changing organizational and community systems

Systems change has emerged as a dominant frame through which local, state, and national funders and practitioners across a wide array of fields approach their work. In most of these efforts, change agents and scholars strive to shift human services and community systems to create better and more just outcomes and improve the status quo. Despite this, there is a dearth of frameworks that scholars, practitioners, and funders can draw upon to aid them in understanding, designing, and assessing this process from a systemic perspective. This paper provides one framework--grounded in systems thinking and change literatures--for understanding and identifying the fundamental system parts and interdependencies that can help to explain system functioning and leverage systems change. The proposed framework highlights the importance of attending to both the deep and apparent structures within a system as well as the interactions and interdependencies among these system parts. This includes attending to the dominant normative, resource, regulative, and operational characteristics that dictate the behavior and lived experiences of system members. The value of engaging critical stakeholders in problem definition, boundary construction, and systems analysis are also discussed. The implications of this framework for systems change researchers and practitioners are discussed.     

Developing operating principles for systems change

Based on an analysis of the articles in this special issue, the authors propose five operating principles for systems change work. These principles are: clarifying the purpose of the systems change; identifying whether the change is one to an existing system or the change is to create a new system; conceptualize the work as systems change from the beginning; use an eclectic approach; and be open to opportunities that emerge while also undertaking forma analysis to identify leverage points. The authors argue that the time is now ripe to develop such principles and encourage community change agents to engage in a dialogue to explore, revise, eliminate or expand on these principles.     

What Determines Visual Statistical Learning Performance? Insights From Information Theory

In order to extract the regularities underlying a continuous sensory input, the individual elements constituting the stream have to be encoded and their transitional probabilities (TPs) should be learned. This suggests that variance in statistical learning (SL) performance reflects efficiency in encoding representations as well as efficiency in detecting their statistical properties. These processes have been taken to be independent and temporally modular, where first, elements in the stream are encoded into internal representations, and then the co‐occurrences between them are computed and registered. Here, we entertain a novel hypothesis that one unifying construct—the rate of information in the sensory input—explains learning performance. This theoretical approach merges processes related to encoding of events and those related to learning their regularities into a single computational principle. We present data from two large‐scale experiments with over 800 participants tested in support for this hypothesis, showing that rate of information in a visual stream clearly predicts SL performance, and that similar rate of information values leads to similar SL performance. We discuss the implications for SL theory and its relation to regularity learning.     

Diagnosticity,confidence, and the need for information

Recent research has suggested that people prefer to use the most diagnostic available information as the basis for their choices and decisions, and are most confident in those decisions when information is highly diagnostic. However, the effect of information diagnosticity on the need for additional information has yet to be investigated; that is, in an optional stopping task, will the amount of information requested depend upon information diagnosticity? Three models of the role of diagnosticity in information use were examined; expected value, a confidence criterion, and information cost. Subjects attempted to categorize stimuli with the aid of information of varying costs and diagnosticity levels. They requested more information when it was obtained at a low cost. More importantly, across cost conditions, subjects consistently requested greater amounts of information when that information was of a low diagnosticity. These data seem most consistent with use of a confidence criterion that is adjusted for information costs.     

A call for a statement of expectations for the global information infrastructure

This paper considers the relationship between ethics, technology and law, and the roles and limitations each has in this relationship. It argues that ethics has the key role in establishing a resilient, comprehensive and sensitive information infrastructure. It puts forward a Bill of Rights and Responsibilities for the electronic community.

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