Revisiting the cluster-based paradigm for implicit search result diversification     

Hai-Tao Yu  Adam Jatowt  Roi Blanco  Hideo Joho  Joemon M. Jose  Long Chen  Fajie Yuan 《Information processing & management》2018,54(4):507-528

To cope with ambiguous and/or underspecified queries, search result diversification (SRD) is a key technique that has attracted a lot of attention. This paper focuses on implicit SRD, where the subtopics underlying a query are unknown. Many existing methods appeal to the greedy strategy for generating diversified results. A common practice is using a heuristic criterion for making the locally optimal choice at each round. As a result, it is difficult to know whether the failures are caused by the optimization criterion or the setting of parameters. Different from previous studies, we formulate implicit SRD as a process of selecting and ranking k exemplar documents through integer linear programming (ILP). The key idea is that: for a specific query, we expect to maximize the overall relevance of the k exemplar documents. Meanwhile, we wish to maximize the representativeness of the selected exemplar documents with respect to the non-selected documents. Intuitively, if the selected exemplar documents concisely represent the entire set of documents, the novelty and diversity will naturally arise. Moreover, we propose two approaches ILP4ID (Integer Linear Programming for Implicit SRD) and AP4ID (Affinity Propagation for Implicit SRD) for solving the proposed formulation of implicit SRD. In particular, ILP4ID appeals to the strategy of bound-and-branch and is able to obtain the optimal solution. AP4ID being an approximate method transforms the target problem as a maximum-a-posteriori inference problem, and the message passing algorithm is adopted to find the solution. Furthermore, we investigate the differences and connections between the proposed models and prior models by casting them as different variants of the cluster-based paradigm for implicit SRD. To validate the effectiveness and efficiency of the proposed approaches, we conduct a series of experiments on four benchmark TREC diversity collections. The experimental results demonstrate that: (1) The proposed methods, especially ILP4ID, can achieve substantially improved performance over the state-of-the-art unsupervised methods for implicit SRD. (2) The initial runs, the number of input documents, query types, the ways of computing document similarity, the pre-defined cluster number and the optimization algorithm significantly affect the performance of diversification models. Careful examinations of these factors are highly recommended in the development of implicit SRD methods. Based on the in-depth study of different types of methods for implicit SRD, we provide additional insight into the cluster-based paradigm for implicit SRD. In particular, how the methods relying on greedy strategies impact the performance of implicit SRD, and how a particular diversification model should be fine-tuned.  相似文献   

优秀女子足球运动员间歇性恢复能力的评价研究     

秦旸  张娜 《南京体育学院学报(社会科学版)》2016,(2):103-107

目的：：探讨运用限定级数YO-YO IR2测试以及心率恢复速率评价我国优秀女足运动员的间歇恢复能力。方法：运用测试法对2013年冬训期间的10名国家女足运动员进行YO-YO IR2测试、心率监控以及比赛监测，采集运动员测试跑动距离、心率特征以及比赛中高强度跑动距离，进行统计学分析。结论：女足运动员YO-YO IR2测试结果以及心率恢复速率与比赛中的高强度跑动能力具有紧密相关性，提示YO-YO IR2测试以及心率监控可以作为评价女足运动员间歇性恢复能力的有效方法。与传统的力竭性YO-YO IR2测试法相比，采用限定级数的YO-YO IR2测试后的心率恢复速率评价更易于女足运动员接受，在训练中具有更好的适用性。  相似文献   

北五味子果实中多糖的提取与纯化研究   总被引：30，自引：0，他引：30  

张兰杰  张维华  赵珊红 《鞍山师范学院学报》2002,4(1):58-60

经提取、醇析、Savage法脱蛋白、脱脂、脱色、DEAE纤维素柱色谱等步骤,从北五味子中分离出两种多糖组分,并经紫外光谱、红外光谱确证纯度.北五味子中粗多糖含量6.1%,三次提取率分别为:55.6%,38.5%,4.6%,Savage法脱蛋白粗多糖损失率为7.2%,北五味子中两种纯多糖含量分别为0.387%,0.061%.  相似文献   

红外光谱在MAPO-5合成与表征中的应用     

徐羽展 《浙江教育学院学报》2006,(4):65-69

红外光谱是催化研究中最重要的工具之一，用于表征催化剂的表面性质．磷酸铝分子筛（APO）作为一类新型的分子筛，本身是中性骨架结构，只有微弱的酸性．通过同晶取代，会出现具有特殊催化性能的新材料．而IR光谱技术能直接用于表征掺杂元素的存在方式，及取代对分子筛酸性质的影响．  相似文献   

红外光谱法确认辽宁三地区苹果中黄烷醇类化合物     

侯冬岩  回瑞华  关崇新  王婧楠 《鞍山师范学院学报》2001,3(1):91-94

黄烷醇基本结构为C6·C3·C6型化合物 ,具有一定的抗癌活性 .其衍生形成的多酚类化合物对人体具有较强的抗衰老作用 ,它广泛存在于各种水果及一些植物中 .本文利用红外光谱法对辽宁三地区不同种类苹果的提取物进行了分析、比较 ,结果是辽南地区的苹果黄烷醇类化合物的含量少于辽西地区的苹果黄烷醇类化合物的含量 ,富士苹果的黄烷醇类化合物的含量高于国光苹果的黄烷醇类化合物的含量 ,为进一步研究开发提供了依据  相似文献   

Study of Cellular Experiment of Electric Pulse Imposed on Cancer Cell     

XIONGLan  HUYa 《重庆大学学报(英文版)》2002,1(1):53-55

The objective of the study is the cytocidal and inhibitory effect of energy-controllable pulse on ovarian cancer cell line SKOV3.Ovarian cancer cell suspension were treated by electric pulse with different parameters,.The inhibitory rate(IR) was assayed by modified colorimetric MTT methods,the growth curves of two test groups and one control group were also measured.and the ultrasturctureal changes were observed under electron microscopy(EM) and scan electron microscopy (SEM),It was found that the treated SKOV3 cell proliferated more slowly.IR was increased with the enhancement of pulse paramters,The ultrastructural study showed that morphological changes occured obviously.Swollen mitochondria,fracutured ridges,cytoplasmic vacuoles and membrane holes appeard in most of the processed cells,and a part of bilayer membrane was ruptured.It is indicated that irreversible electric breakdown occurred in some of the treated cells,and the electric pulse could kill cancer cell and inhibit its recovery and growth.  相似文献   

Technology survey and invalidity search: A comparative study of different tasks for Japanese patent document retrieval     

Sumio Fujita 《Information processing & management》2007

A comparative study of two types of patent retrieval tasks, technology survey and invalidity search, using the NTCIR-3 and -4 test collections is described, with a focus on pseudo-feedback effectiveness and different retrieval models. Invalidity searches are peculiar to patent retrieval tasks and feature small numbers of relevant documents and long queries. Different behaviors of effectiveness are observed when applying different retrieval models and pseudo-feedback. These different behaviors are analyzed in terms of the “weak cluster hypothesis”, i.e., terminological cohesiveness through relevant documents.  相似文献   

一种新型开链螯合剂的合成     

毕建洪 《商丘师范学院学报》2001,17(2):86-88

近年来，人们对改变开链螯合变电站的末端取代基和链的长度的研究很感兴趣，因为此类螯合剂具有选择螯合金属离子的能力。为此，设计并合成出一种末端为肟基的新型开链聚醚螯合剂：1，7－二（2'－肟甲基苯基）－1，4，7－三氧杂庚烷，采用元素分析、红外光谱、质谱等方法对其结构进行了表征，并较详细地讨论了它的质谱裂解机理。  相似文献   

世界主义的价值诉求——国际关系规范理论的视角   总被引：2，自引：0，他引：2  

张旺 《教学与研究》2006,103(12):60-66

世界主义是一种具有悠久传统的哲学理念,它主张世界是一个单一的共同体,所有人皆为其中的平等成员。近年来随着国际关系规范理论的复兴,世界主义再次走向前台。在当前全球化的背景下,面对国际政治、经济秩序的重大变迁,一系列关乎人类命运问题的显现,以个人主义的价值前提和全球共同体的道德理想为基础,世界主义在人权的普遍性、全球范围的分配正义和世界主义民主等不同领域都表达了自己的道德诉求。然而,作为一种普遍性的价值目标,其在具体实施过程中可能产生的负面影响同样不容忽视。  相似文献   

一类Henstock可积而非Lebesgue可积的函数     

王璞杰 《天津工程师范学院学报》2001,11(4):8-10

通过讨论(L)积分、(IR)积分及(H)积分三者的关系,给出一类(H)可积而非(L)可积的函数.  相似文献