Extracting and evaluating method of web dense cores

This paper focuses on some key problems in web community discovery and link analysis.Based on the topic-oriented technology,the characteristics of a bipartite graph are studied.An Х bipartite core set is introduced to more clearly define extracting ways.By scanning the topic subgraph to construct Х bipartite graph and then prune the graph with i and j ,an Х bipartite core set,which is also the minimum element of a community,can be found.Finally,a hierarchical clustering algorithm is applied to many Х bipartite core sets and the dendrogram of the community inner construction is obtained.The correctness of the constructing and pruning method is proved and the algorithm is designed.The typical datasets in the experiment are prepared according to the way in HITS（hyperlink-induced topic search）.Ten topics and four search engines are chosen and the returned results are integrated.The modularity,which is a measure of the strength of the community structure in the social network,is used to validate the efficiency of the proposed method.The experimental results show that the proposed algorithm is effective and efficient.

新型冠状病毒感染者密切接触者的密切接触者感染风险分析

目的研究新型冠状病毒(新冠病毒)感染者密切接触者(密接)的密接(次密接)感染率,评估新冠病毒感染者次密接的感染风险。方法采用前瞻性研究的方法,对进入集中隔离医学观察时且采样检测核酸结果为阴性的密接(与指示病例有明确的暴露时间)及其次密接进行持续医学观察,收集新冠病毒感染者密接和次密接的动态核酸检测结果,评估密接和次密接的感染风险。结果追踪调查了符合纳入条件的密接4533例,14例密接转归为新冠病毒感染者,感染率为0.31%。共追踪了次密接4201例,均未发生后续感染。结论密接进入集中隔离医学观察时采样检测核酸结果为阴性,该次密接无感染风险。