A new variational Bayesian algorithm with application to human mobility pattern modeling

A new variational Bayesian (VB) algorithm, split and eliminate VB (SEVB), for modeling data via a Gaussian mixture model (GMM) is developed. This new algorithm makes use of component splitting in a way that is more appropriate for analyzing a large number of highly heterogeneous spiky spatial patterns with weak prior information than existing VB-based approaches. SEVB is a highly computationally efficient approach to Bayesian inference and like any VB-based algorithm it can perform model selection and parameter value estimation simultaneously. A significant feature of our algorithm is that the fitted number of components is not limited by the initial proposal giving increased modeling flexibility. We introduce two types of split operation in addition to proposing a new goodness-of-fit measure for evaluating mixture models. We evaluate their usefulness through empirical studies. In addition, we illustrate the utility of our new approach in an application on modeling human mobility patterns. This application involves large volumes of highly heterogeneous spiky data; it is difficult to model this type of data well using the standard VB approach as it is too restrictive and lacking in the flexibility required. Empirical results suggest that our algorithm has also improved upon the goodness-of-fit that would have been achieved using the standard VB method, and that it is also more robust to various initialization settings.     

Contents of Volume 18, 2002

Volume Contents

Contents of Volume 18, 2002     

Identities in Northern Ireland: A Multidimensional Approach

The conflict in Northern Ireland is often described in terms of a clash of identities, national and religious. This study aimed to determine the relative importance of these identities using a multidimensional approach to examine the identity structures of students (N = 216). Analyses revealed that national and religious identities were accorded low salience and centrality relative to other identities. The study also investigated relations between a variety of identity dimensions derived from two identity traditions, social identity theory and identity theory. The differing patterns of relationships to emerge across groups and across identities suggest that the process of identification in Northern Ireland is a complex one. The implications of these findings for the analysis of the Northern Ireland conflict are discussed.     

Children and Young People “In Care” Participating in a Peer‐Mentoring Relationship: An Exploration of Resilience

The aim of this study was to explore how a 1‐year peer‐mentoring relationship contributed to change in young women “in care.” Twenty semistructured, one‐to‐one interviews were conducted with mentors (n = 11) and mentees (n = 9) recruited from two different London local authorities. Participants’ accounts were interpreted through a developmental lens to uncover developmental aspects and locus mechanisms through which transformative change took place. Resilience as a healthy outcome was the result of the dual function the mentoring relationship performed. The mentoring relationship was protective against the risks associated with transitioning to independent living and/or adulthood, and promoted internal assets and competencies whereby the mentees’ ability to resist them was enhanced. Establishing a trustworthy connection with a role model promoted developmental domains within mentees.     

Broadening the Intersectional Path: Revealing Organizational Practices through ‘Working Mothers’ Narratives about Time

This article is concerned with the complex inequality experienced by mothers in employment, and applies ‘strong intersectionality’ to women's narratives about time to reveal the intersecting inequalities women experience and gendered organizational practices. Drawing on empirical research with 30 Irish ‘working mothers’, this article explores the way time is ordered and managed to create gendered inequalities for women at the intersection of maternity with paid work. By conceptualizing gender, maternity and class as simultaneous processes of identity practice, institutional practice and social practice, following Holvino, women's narratives reveal that organizations manage and order time to fit with notions of ‘ideal workers’, which perpetrate older hierarchies and gendered inequalities, and which create regimes of inequality for women at the intersection of maternity with paid work.     

Beyond the Activist Ghetto: A Deductive Blockmodelling Approach to Understanding the Relationship between Contact with Environmental Organisations and Public Attitudes and Behaviour

Current research on the behavioural impacts of social movements tends to focus on their influence on those most intensely involved. Consequently it overlooks the impacts that social movement organisations might have on those outside the activist ghetto. To begin to address this gap in the literature, this article examines the relationship between contact with environmental organisations and public attitudes and behaviour. Monitoring the electricity use of 72 households has facilitated analysis of its association with their environmental attitudes and contact with environmental organisations. Although standard statistical approaches fail to uncover a relationship between contact with environmental organisations and attitudes and behaviour, a deductive blockmodelling approach tells a different story. Low household electricity use is associated with households sharing pro-environmental attitudes and contact with environmental organisations. High energy use is associated with households not sharing any of these; and moderate energy use is associated with a moderate degree of sharing. Our findings reveal the need for systematic studies of environmental movement organisations' impact on the public's pro-environmental behaviours.