中文摘要：

[目的／意义]社交媒介不仅提供了用户间知识交流的平台，而且形成了知识复用的渠道。一部分社交网络用户在信息传播、知识共享等方面都能够对其他用户产生影响，称之为“小众专家”。对“小众专家”群体的研究对于社交网络中信息传播具有促进作用。[方法／过程]以MetaFiher数据集为例，利用用户社交网络活动数据，生成用户关系网络，结合网络分析与时序分析筛选“小众专家”，分析“小众专家”群体在不同语义环境下的“稳定－迁移”特征，并提出评测指标，进行验证分析。[结果／结论]结果显示：只有极少部分“小众专家”能够在多种语义环境下保持稳定性，而大部分“小众专家”只能在单一语义环境中保持稳定性。

英文摘要：

[ Purpose/significance] Social media not only provides a platform for knowledge exchange for users, but also forms a channel for knowledge reuse. Some social network users can affect others in information communication and knowledge sharing. These users are called ＂niche experts＂. The study of ＂niche experts＂ helps to promote information dissemination. [ Method/process] In this paper, the authors made use of user activity data from a popular community weblog named MetaFilter to construct social network. Then the authors got the niche experts by network analysis and time series analysis and analyzed the ＂stability-change＂ feature of niche experts under different semantic circumstances. The paper also introduced an index to measure this feature and it was proved to be correct. [ Result/conclusion ] The result of the study shows that only few niche experts can maintain stability under multiple semantic circumstances and the majority of niche experts can maintain stability only under single semantic circumstance.