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1.
Centroid-based summarization of multiple documents   总被引:2,自引:0,他引:2  
We present a multi-document summarizer, MEAD, which generates summaries using cluster centroids produced by a topic detection and tracking system. We describe two new techniques, a centroid-based summarizer, and an evaluation scheme based on sentence utility and subsumption. We have applied this evaluation to both single and multiple document summaries. Finally, we describe two user studies that test our models of multi-document summarization.  相似文献
2.
Proximity effects on the dynamics and outcomes of scientific collaborations   总被引:1,自引:0,他引:1  
This paper uses path overlap, an innovative measure of functional proximity, to examine how physical space shaped the formation and success of scientific collaborations among the occupants of two academic research buildings. We use research administration data on human subject protection, animal use management, and grant funding applications to construct new measures of collaboration formation and success. The “functional zones” investigators occupy in their buildings are defined by the shortest walking paths among assigned laboratory and office spaces, and the nearest elevators, stairs, and restrooms. When two investigators traverse paths with greater overlap, both their propensity to form new collaborations and to win grant funding for their joint work increase. This effect is robust across two very differently configured buildings. Implications for scientific collaboration and the design and allocation of research space are considered.  相似文献
3.
When public catalog users enter queries that exactly match the catalog's controlled vocabulary, online systems should respond with browsing lists of alphabetically arranged subject headings, because such displays guide users to retrievals based on the assignment of the matched subject headings to bibliographic records. Unfortunately, studies of online catalog searching demonstrate that alphabetical displays are no longer capable of managing large numbers of subdivided forms of subject headings, because searchers exhibit low levels of perseverance when faced with large numbers of retrievals. This paper introduces a new approach to displaying retrieved subject headings in subject searching—the exact-display approach—designed to encourage users to browse bibliographic information. The purpose of this paper is to emphasize the importance of the exact-display approach by showing how many user queries would be candidates for this approach, demonstrate an implementation of the exact-display approach in an experimental online catalog, and feature end-user experiences with this approach as implemented in the experimental catalog. End-user experiences gave the authors the opportunity to make several recommendations for enhancing the original design of the exact-display approach so that future implementations of this approach in operational online catalogs are responsive to the needs of online catalog users.  相似文献
4.
This research investigates how people’s perceptions of information retrieval (IR) systems, their perceptions of search tasks, and their perceptions of self-efficacy influence the amount of invested mental effort (AIME) they put into using two different IR systems: a Web search engine and a library system. It also explores the impact of mental effort on an end user’s search experience. To assess AIME in online searching, two experiments were conducted using these methods: Experiment 1 relied on self-reports and Experiment 2 employed the dual-task technique. In both experiments, data were collected through search transaction logs, a pre-search background questionnaire, a post-search questionnaire and an interview. Important findings are these: (1) subjects invested greater mental effort searching a library system than searching the Web; (2) subjects put little effort into Web searching because of their high sense of self-efficacy in their searching ability and their perception of the easiness of the Web; (3) subjects did not recognize that putting mental effort into searching was something needed to improve the search results; and (4) data collected from multiple sources proved to be effective for assessing mental effort in online searching.  相似文献
5.
In this paper, we estimate the impact of receiving an NIH postdoctoral training grant on subsequent publications and citations. Our sample consists of all applications for NIH postdoctoral training grants (unsuccessful as well as successful) from 1980 to 2000. Both ordinary least squares and regression discontinuity estimates show that receipt of an NIH postdoctoral fellowship leads to about one additional publication over the next five years, which reflects a 20% increase in research productivity.  相似文献
6.
We summarize a recently developed microtechnology for printing biomaterials on biological surfaces. The technique is based on the use of immiscible aqueous solutions of two biopolymers and allows spatially defined placement of cells and biomolecules suspended in the denser aqueous phase on existing cell layers and extracellular matrix hydrogel surfaces maintained in the second phase. Printing takes place due to an extremely small interfacial tension and density difference between the two aqueous phases. The contact-free printing process ensures that both printed cells and the underlying cell monolayer maintain full viability and functionality. The technique accommodates both arbitrarily shaped patterns and microarrays of cells and bioreagents. The capability to print cells and small molecules on existing cell layers enables unique interrogations of the effects of cell-cell and cell-material interaction on cell fate and function. Furthermore, the very gentle conditions and the ability to directly pattern nongel embedded cells over cells make this technology appealing to tissue engineering applications where patterned multicellar organization with minimal scaffolding materials is needed, such as in dense tissues of the skeletal muscle and liver.  相似文献
7.
随着场外衍生品的日益复杂化,定价的模型风险越来越受到重视。标的资产随机过程的设定是衍生品定价的关键环节,但随机过程选择与估计样本选择尚无公认的标准,这成为衍生品定价模型风险的主要来源。本文以中信泰富杠杆式外汇合约为例,根据已有文献选择了几何布朗运动、OU过程、Schwartz单因素模型来描述汇率走势,运用不同区间和频率的样本估计这3个随机过程的参数,进一步采用蒙特卡洛模拟法得到此合约的价格分布,使用业界普遍使用的"最坏情况"指标来度量买卖双方承担的模型风险。实证结果表明,随机过程设定导致的模型风险显著存在,模型风险会随着随机过程与估计样本的变化而变化,衍生品买卖双方的模型风险呈现非对称性特征,买方承担的模型风险显著高于卖方,这反映了模型风险管理的重要意义及非专业买方参与场外复杂衍生品交易时的困境。  相似文献
8.
A new approach for observer-based feedback control of time-delay systems is developed. Time-delays in systems lead to characteristic equations of infinite dimension, making the systems difficult to control with classical control methods. In this paper, a recently developed approach, based on the Lambert W function, is used to address this difficulty by designing an observer-based state feedback controller via assignment of eigenvalues. The designed observer provides estimation of the state, which converges asymptotically to the actual state, and is then used for state feedback control. The feedback controller and the observer take simple linear forms and, thus, are easy to implement when compared to nonlinear methods. This new approach is applied, for illustration, to the control of a diesel engine to achieve improvement in fuel efficiency and reduction in emissions. The simulation results show excellent closed-loop performance.  相似文献
9.
We present Biased LexRank, a method for semi-supervised passage retrieval in the context of question answering. We represent a text as a graph of passages linked based on their pairwise lexical similarity. We use traditional passage retrieval techniques to identify passages that are likely to be relevant to a user’s natural language question. We then perform a random walk on the lexical similarity graph in order to recursively retrieve additional passages that are similar to other relevant passages. We present results on several benchmarks that show the applicability of our work to question answering and topic-focused text summarization.  相似文献
10.
Access to information via handheld devices supports decision making away from one’s computer. However, limitations include small screens and constrained wireless bandwidth. We present a summarization method that transforms online content for delivery to small devices. Unlike previous algorithms, ours assumes nothing about document formatting, and induces a hierarchical structure based on the relative importance of sentences within the document. As compared to delivering full documents, the method reduces the bytes transferred by half. An experiment also demonstrates that when given hierarchical summaries, users are no less accurate in answering questions about the documents.  相似文献
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