Relabelling algorithms for mixture models with applications for large data sets

Mixture models are flexible tools in density estimation and classification problems. Bayesian estimation of such models typically relies on sampling from the posterior distribution using Markov chain Monte Carlo. Label switching arises because the posterior is invariant to permutations of the component parameters. Methods for dealing with label switching have been studied fairly extensively in the literature, with the most popular approaches being those based on loss functions. However, many of these algorithms turn out to be too slow in practice, and can be infeasible as the size and/or dimension of the data grow. We propose a new, computationally efficient algorithm based on a loss function interpretation, and show that it can scale up well in large data set scenarios. Then, we review earlier solutions which can scale up well for large data set, and compare their performances on simulated and real data sets. We conclude with some discussions and recommendations of all the methods studied.     

Construction and selection of tightened–normal–tightened variables sampling scheme of type TNTVSS (n 1, n 2; k)

This paper provides tables for the construction and selection of tightened–normal–tightened variables sampling scheme of type TNTVSS (n ₁, n ₂; k). The method of designing the scheme indexed by (AQL, α) and (LQL, β) is indicated. The TNTVSS (n _T , n _N; k) is compared with conventional single sampling plans for variables and with TNT (n ₁, n ₂; c) scheme for attributes, and it is shown that the TNTVSS is more efficient.     

语言态度对普通话与陕西话语码转换的影响研究

本课题通过问卷调查、实地访谈等方法,从社会语言学的视角,探讨西安地区人们的语言态度对普通话与陕西话语码转换的影响。试图解读陕西方言文化自信与官方语言推广之间的矛盾与和谐。研究发现,人们对于这两种语言变体的态度中既包含了对语言交际功能的认知因素,也包含了情感因素,因此,在大力推广普通话的同时,不可忽视西安人对其地域方言的认同感与文化自豪感。     

基于MSVAR模型的有色金属价格波动影响因素的非线性效应研究

由于新兴市场需求增长和指数化投资同时出现在金属期货市场上,且供需因素与金融因素相互作用使得有色金属价格形成机制更为复杂,呈现出非线性、动态性以及结构异化等特征。基于此背景,本文提炼供需因素与金融因素影响有色金属价格波动的作用机理,选取2000年2月至2014年3月的月度数据,并构建MSVAR模型以铜为例展开实证分析。结果表明:铜价波动存在显著的区制转换特征,即膨胀期、平稳期、低迷期三种状态;三种状态下,金融因素都可以很好地解释期铜价格波动,但作用机制明显不同,而"中国因素"则被明显夸大,与原有研究结论相左;短期内各个因素在不同区制下对国际期铜价格的影响在作用方向、持续时间、作用强度上表现出显著的差异性。这些研究结论与构建的非线性计量经济模型为解释大宗商品金融化提供了新的思路与分析工具。     

转移成本对感知质量与满意之间关系的调节作用——对B2B电子中介买方用户的实证研究

如何提高用户满意,对于为买卖双方提供交易支持服务的B2B电子中介而言,是扩大平台运营规模和增加市场竞争力的基础。本文以B2B电子中介的买方用户为研究对象,建立了基于转移成本调节的感知质量与用户满意因果关系概念模型,借助于国内知名的B2B电子中介采集了覆盖五大洲114个国家的649份样本数据,然后运用无约束方法验证了用户感知质量与满意之间、转移成本与满意之间的正向影响关系,以及转移成本对感知质量和满意之间关系影响的负向调节作用。实证研究结果显示,较高的转移成本会减弱买方用户的感知质量对满意的影响,有利于B2B电子中介提高买方用户的满意水平,进而为B2B电子中介如何从转移成本角度提高买方用户满意提供了实证基础。     

新媒体使用对农户生物农药采纳行为的影响研究

基于湖北和河南两省７６４户水稻和小麦种植户的实地调查数据,运用内生转 换概率模型,在反事实框架下评估了新媒体在农技推广中的应用对农户生物农药采纳行为 的影响效应,同时检验不同类型新媒体的作用差异,并进一步探讨其影响机制.研究发现: ①新媒体使用对农户生物农药采纳行为具有显著的正向影响,表现为在反事实假设下,实际 使用新媒体的农户若未使用新媒体,其生物农药采纳概率将下降２６．５％,实际未使用新媒体 的农户若使用新媒体,其生物农药采纳概率将提高３２．９％.②不同类型新媒体对农户生物 农药采纳行为的影响具有差异性,促进作用大小依次为短视频类、社交通信类和内容聚合 类.③从群组差异性来看,新媒体对受教育程度较高、种植面积较小的农户生物农药采纳促 进作用更大.④信息能力在新媒体影响农户生物农药采纳过程中起到中介作用.因此,建 议完善农业技术信息传播机制,增加有效信息供给,加大信息技术的教育和培训力度,有序 引导不同资本禀赋农户使用新媒体获取学习农业技术信息知识.     

A grouped beta process model for multivariate resting‐state EEG microstate analysis on twins

EEG microstate analysis investigates the collection of distinct temporal blocks that characterize the electrical activity of the brain. Brain activity within each microstate is stable, but activity switches rapidly between different microstates in a nonrandom way. We propose a Bayesian nonparametric model that concurrently estimates the number of microstates and their underlying behaviour. We use a Markov switching vector autoregressive (VAR) framework, where a hidden Markov model (HMM) controls the nonrandom state switching dynamics of the EEG activity and a VAR model defines the behaviour of all time points within a given state. We analyze the resting‐state EEG data from twin pairs collected through the Minnesota Twin Family Study, consisting of 70 epochs per participant, where each epoch corresponds to 2 s of EEG data. We fit our model at the twin pair level, sharing information within epochs from the same participant and within epochs from the same twin pair. We capture within twin‐pair similarity, using an Indian buffet process, to consider an infinite library of microstates, allowing each participant to select a finite number of states from this library. The state spaces of highly similar twins may completely overlap while dissimilar twins could select distinct state spaces. In this way, our Bayesian nonparametric model defines a sparse set of states that describe the EEG data. All epochs from a single participant use the same set of states and are assumed to adhere to the same state switching dynamics in the HMM model, enforcing within‐participant similarity.     

基于马尔科夫切换模型的上证指数周收益率时间序列分析

本文先对上证指数收益率时间序列做非线性检测,再对时间序列进行结构性变化检测,发现上证指数收益序列既是非线性时间序列又有结构性变化;通过构建一个3状态,3阶滞后的异方差马尔可夫切换模型对1990年12月21日至2008年8月22日上证指数周收益率时间序列规律进行了实证分析,采用极大似然估计法对模型参数进行估计,识别出股市波动的三种主要的状态:慢涨、慢跌和快涨;实证结果表明马尔可夫切换模型能够比较有效的刻画股市波动的阶段性特征.     

多媒体课件视觉效果与文本切换频率对文本理解的影响

采用3(课件视觉效果)×3(文本的切换频率)两因素混合实验设计,考察多媒体课件的不同视觉效果及文本的切换频率对理解文本内容的影响。结果显示:不同视觉效果多媒体课件的主效应极其显著,视觉效果Ⅱ优于视觉效果Ⅰ和视觉效果Ⅲ;不同的切换频率主效应显著,文本字数500左右的幻灯片切换5次效果较好;对课件的理想程度评定结果表明,被试对视觉效果Ⅱ的评价得分较高。     

消费者重复购买意向及其影响因素的实证研究

探究了感知价值、顾客满意、转移成本和消费时间间隔4个因素对重复购买意向的影响。结果发现感知价值、顾客满意、转移成本对重复购买意向有正相关关系,而消费时间间隔对重复购买意向并无显著的影响关系。同时,感知价值与顾客满意之间存在正向的影响关系,转移成本与顾客满意之间并不存在显著的影响关系。