Partially linear models and their applications to change point detection of chemical process data

In many chemical data sets, the amount of radiation absorbed (absorbance) is related to the concentration of the element in the sample by Lambert–Beer's law. However, this relation changes abruptly when the variable concentration reaches an unknown threshold level, the so-called change point. In the context of analytical chemistry, there are many methods that describe the relationship between absorbance and concentration, but none of them provide inferential procedures to detect change points. In this paper, we propose partially linear models with a change point separating the parametric and nonparametric components. The Schwarz information criterion is used to locate a change point. A back-fitting algorithm is presented to obtain parameter estimates and the penalized Fisher information matrix is obtained to calculate the standard errors of the parameter estimates. To examine the proposed method, we present a simulation study. Finally, we apply the method to data sets from the chemistry area. The partially linear models with a change point developed in this paper are useful supplements to other methods of absorbance–concentration analysis in chemical studies, for example, and in many other practical applications.     

Generalized poisson regression for positive count data

This paper suggests a flexible parametrization of the generalized Poisson regression, which is likely to be particularly useful when the sample is truncated at zero. Suitable specification tests for this case are also studied. The use of the models and tests suggested is illustrated with an application to the number of recreational fishing trips taken by households in Alaska     

Copula, marginal distributions and model selection: a Bayesian note

Copula functions and marginal distributions are combined to produce multivariate distributions. We show advantages of estimating all parameters of these models using the Bayesian approach, which can be done with standard Markov chain Monte Carlo algorithms. Deviance-based model selection criteria are also discussed when applied to copula models since they are invariant under monotone increasing transformations of the marginals. We focus on the deviance information criterion. The joint estimation takes into account all dependence structure of the parameters’ posterior distributions in our chosen model selection criteria. Two Monte Carlo studies are conducted to show that model identification improves when the model parameters are jointly estimated. We study the Bayesian estimation of all unknown quantities at once considering bivariate copula functions and three known marginal distributions.     

An Intuitive Geometric Approach to the Gauss Markov Theorem

Algebraic proofs of Gauss–Markov theorem are very disappointing from an intuitive point of view. An alternative is to use geometry that emphasizes the essential statistical ideas behind the result. This article presents a truly geometrical intuitive approach to the theorem, based only in simple geometrical concepts, like linear subspaces and orthogonal projections.     

On-Site Storage of High Level Nuclear Waste: Attitudes and Perceptions of Local Residents

No public policy issue has been as difficult as high-level nuclear waste. Debates continue regarding Yucca Mountain as a disposal site, and—more generally—the appropriateness of geologic disposal and the need to act quickly. Previous research has focused on possible social, political, and economic consequences of a facility in Nevada. Impacts have been predicted to be potentially large and to emanate mainly from stigmatization of the region due to increased perceptions of risk. Analogous impacts from leaving waste at power plants have been either ignored or assumed to be negligible. This paper presents survey results on attitudes of residents in three counties where nuclear waste is currently stored. Topics include perceived risk, knowledge of nuclear waste and radiation, and impacts on jobs, tourism, and housing values from leaving waste on site. Results are similar to what has been reported for Nevada; the public is concerned about possible adverse effects from on-site storage of waste.     

The changing dynamics of land conflict in the Brazilian Amazon: The rural-urban complex and its environmental implications

The Brazilian Amazon is an area of both serious environmental degradation and social instability. Despite billions of dollars spent on economic development and the rapid pace of urbanization, deforestation is extreme and violent land conflict is intense. Although episodes of conflict over land are common in Brazilian history, this paper focuses on agrarian issues that arose with the opening of the Amazon frontier in the 1970s. The paper argues that the nature of land conflict in the eastern Brazilian Amazon is dynamic, and proposes a two-stage model to illustrate how the struggle has evolved from an agrarian phenomenon to an organized resistance that is urban-based. Recognizing the interaction between cities and rural areas in the frontier reaches of the Brazilian Amazon is key to understanding the land struggle in the face of urbanization. The analytical framework deployed considers the transformation of the region from an agrarian frontier to an urbanized frontier, assessing the dynamic nature of the land struggle and examining the implications for land cover change.     

AN URBAN ENCOUNTER

Computing research has long been interested in location-aware mobile games, such as hybrid reality games, location-based games and urban games. With an increasingly pervasive IT infrastructure and comparatively affordable mobile devices, such games are becoming part of everyday play around the world. A study of an urban night-game called Encounter widely played in the Former Soviet Union and the Russian-speaking Diaspora is presented. The ways in which IT enables a complex interaction between the local experience of play in the urban environment and the geographically distributed nature of the player community are considered. The findings illustrate how this form of location-aware mobile game-play pulled together local engagement and global player communities into socio-technical assemblages, showing the interplay between local attachments, distant connections and the location-based communication in daily experience. The most important outcome of these games then was not the direct individual engagement with the urban environment through technology or the collaboration with strangers in the course of play (although these were the necessary prerequisites), but the social relationships that, while gained in-game, could be leveraged for civic engagement, belonging and mutual support. While the local, physical experience of the everyday and the game was important, the connections to the distributed community resulted in expanded horizons and changed the nature of the local experience as players felt they could belong to something larger than the locales they physically inhabited.     

Negotiating Tradition and Nation: Mediations and Mediators in the Making of Urban Timor-Leste

In discussing marriage negotiations, this article analyses certain mediations and mediators that make up the dialectics of modernisation among contemporary urban middle-class elites in Timor-Leste. It brings to the fore the way particular Christian values are strategically used to reproduce, change or even enhance people's agency regarding customary practices, and to circumscribe the marriage exchanges to the gift regime. Attitudes about fulfilling customary obligations vary, for they are correlated to the distinct government practices from which they derive. The social profile of brokers and the sources of their legitimacy to perform marriage negotiations are also discussed. Finally, these negotiations are analysed against the backdrop of contemporary arguments about the syncretic or anti-syncretic character of some social experiences in Timor-Leste.