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101.
Document length is widely recognized as an important factor for adjusting retrieval systems. Many models tend to favor the
retrieval of either short or long documents and, thus, a length-based correction needs to be applied for avoiding any length
bias. In Language Modeling for Information Retrieval, smoothing methods are applied to move probability mass from document
terms to unseen words, which is often dependant upon document length. In this article, we perform an in-depth study of this
behavior, characterized by the document length retrieval trends, of three popular smoothing methods across a number of factors,
and its impact on the length of documents retrieved and retrieval performance. First, we theoretically analyze the Jelinek–Mercer,
Dirichlet prior and two-stage smoothing strategies and, then, conduct an empirical analysis. In our analysis we show how Dirichlet
prior smoothing caters for document length more appropriately than Jelinek–Mercer smoothing which leads to its superior retrieval
performance. In a follow up analysis, we posit that length-based priors can be used to offset any bias in the length retrieval
trends stemming from the retrieval formula derived by the smoothing technique. We show that the performance of Jelinek–Mercer
smoothing can be significantly improved by using such a prior, which provides a natural and simple alternative to decouple
the query and document modeling roles of smoothing. With the analysis of retrieval behavior conducted in this article, it
is possible to understand why the Dirichlet Prior smoothing performs better than the Jelinek–Mercer, and why the performance
of the Jelinek–Mercer method is improved by including a length-based prior.
相似文献
Leif AzzopardiEmail: |
102.
A three-dimensional, exact analysis is presented in this paper for the problem of an external circular crack in a transversely
isotropic piezoelectric medium subjected to arbitrary antisymmetric shear loading. A recently proposed general solution of
three-dimensional piezoelectricity is employed. It is shown that four quasi harmonic functions involved in the general solution
can be respresented by just one complex potential. Previous results in potential theory are then used to obtain the exact
solution of the problem. For point shear loading, Green’s functions for the elastoelectric field are derived in terms of elementary
functions.
Project supported by Scientific Research Foundation for Returned Overseas Chinese Scholars, State Education Ministry and partly
by National Natural Science Foundation of China (NSFC) (10002016). 相似文献
103.
104.
利用等效线弹簧模型近似计算了含裂纹转动轴的自由振动基频。裂纹轴的横向位移看成是由无裂纹轴的横向位移和由裂纹引起的附加位移的叠加。具体讨论了裂纹深度、裂纹所处的位置以及裂纹角对轴自由振动基频的影响,其结果与实际情况吻合。 相似文献
105.
高层建筑大体积混凝土裂缝的预防 总被引:1,自引:0,他引:1
马燕 《淮南职业技术学院学报》2008,8(3):42-44
阐述如何控制大体积泵送混凝土水泥水化热引起的混凝土内外温差和混凝土收缩产生的裂缝,指出在水泥中加入纤维可以提高混凝土抗拉强度,控制基体中微裂缝的形成和发展,结合某工程混凝土抗裂安全度计算,提出采用掺入杜拉纤维方法来防止高层建筑大体积混凝土温度裂缝产生是可行有效的。 相似文献
106.
本文对t重n阶同余数的性质进行了初步探讨并应用这些性质给出了任意数同余初阶的简易求法,并提出一类循环小数的循环节等长问题供讨论。 相似文献
107.
108.
Jules L. Ellis 《Educational and psychological measurement》2021,81(3):549
This study develops a theoretical model for the costs of an exam as a function of its duration. Two kind of costs are distinguished: (1) the costs of measurement errors and (2) the costs of the measurement. Both costs are expressed in time of the student. Based on a classical test theory model, enriched with assumptions on the context, the costs of the exam can be expressed as a function of various parameters, including the duration of the exam. It is shown that these costs can be minimized in time. Applied in a real example with reliability .80, the outcome is that the optimal exam time would be much shorter and would have reliability .675. The consequences of the model are investigated and discussed. One of the consequences is that optimal exam duration depends on the study load of the course, all other things being equal. It is argued that it is worthwhile to investigate empirically how much time students spend on preparing for resits. Six variants of the model are distinguished, which differ in their weights of the errors and in the way grades affect how much time students study for the resit. 相似文献
109.
110.