Using The Censored Gamma Distribution for Modeling Fractional Response Variables with an Application to Loss Given Default

Regression models for limited continuous dependent variables having a non-negligible probability of attaining exactly their limits are presented. The models differ in the number of parameters and in their flexibility. Fractional data being a special case of limited dependent data, the models also apply to variables that are a fraction or a proportion. It is shown how to fit these models and they are applied to a Loss Given Default dataset from insurance to which they provide a good fit

A dynamic nonstationary spatio-temporal model for short term prediction of precipitation

Precipitation is a complex physical process that varies in space and time. Predictions and interpolations at unobserved times and/or locations help to solve important problems in many areas. In this paper, we present a hierarchical Bayesian model for spatio-temporal data and apply it to obtain short term predictions of rainfall. The model incorporates physical knowledge about the underlying processes that determine rainfall, such as advection, diffusion and convection. It is based on a temporal autoregressive convolution with spatially colored and temporally white innovations. By linking the advection parameter of the convolution kernel to an external wind vector, the model is temporally nonstationary. Further, it allows for nonseparable and anisotropic covariance structures. With the help of the Voronoi tessellation, we construct a natural parametrization, that is, space as well as time resolution consistent, for data lying on irregular grid points. In the application, the statistical model combines forecasts of three other meteorological variables obtained from a numerical weather prediction model with past precipitation observations. The model is then used to predict three-hourly precipitation over 24 hours. It performs better than a separable, stationary and isotropic version, and it performs comparably to a deterministic numerical weather prediction model for precipitation and has the advantage that it quantifies prediction uncertainty.Comment: Published in at http://dx.doi.org/10.1214/12-AOAS564 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

A remark on the equation of a vibrating plate

We consider the von Karman equations, which describe a vibrating plate either with a clamped boundary or with completely free boundary. In both cases we obtain a unique, classical solution. As the main tool we use a set of integral equations, which we deduce from the well known "variations of constants” formul

A Remark on the Equation of a Vibrating Plate

SynopsisWe consider the von Karman equations, which describe a vibrating plate either with a clamped boundary or with completely free boundary. In both cases we obtain a unique, classical solution. As the main tool we use a set of integral equations, which we deduce from the well known “variations of constants” formula

Existence and uniqueness of solutions to degenerate semilinear parabolic equations

AbstractAn elementary proof for the existence of solutions to semilinear degenerate parabolic equations is given. The assumptions are such that solutions to approximating parabolic problems are a priori bounded in L∞. Then an Ascoli-Arzela argument is used. Under more restrictive conditions on the coefficients, uniqueness of the solutions is shown separately and a regularity result is provided

Why Do Journalists Face Varying Degrees of Digital Hostility? Examining the Interplay Between Minority Identity and Celebrity Capital

This study compares two explanations why some journalists are targeted more than others, both by general digital hostility and specifically by identity-based hostility, job-related hostility, and severe hostility such as threats and repeat offences. The first explains targeting by identity, especially of historically disadvantaged groups such as women and migrants; the second explains targeting by celebrity: journalists with larger audiences, greater social media presence, more television work, and focus on political coverage are targeted more. A Swiss survey of 568 journalists shows that celebrity mainly explains targeting with general hostility, whereas the effects of identity vary for different types of hostility. Additional interactions suggest that historically disadvantaged groups tend to experience more digital hostility, but only with increasing celebrity capital. This study emphasizes how hostility types differentiate explanatory values. Further, it contributes an innovative celebrity explanation and demonstrates how interactions can illuminate the tangled relation between identity, visibility, and hostility

XXI century cities facing the challenge of peak oil

En este artículo se pretende analizar el acelerado proceso de urbanización característico de la Edad Moderna y su tendencia a la concentración y sobreescala urbana con el surgimiento de las megalópolis actuales. Se analiza la forma y los mecanismos que permiten a estas grandes ciudades subordinar y transformar el territorio en función de sus necesidades de un creciente flujo de materia, energía e información que las atraviesa y por ellas es transformado y degradado, para sostener su metabolismo social. Analizando las fuerzas subyacentes al proceso, se indica el rol y la importancia fundamental que asume en ello la abundante disponibilidad de combustibles fósiles y el reto que supone para las ciudades del siglo XXI el fin del denominado ‘petróleo barato’ por el pico del petróleo.En aquest article s’analitza el procés d’urbanització característic de l’Edat Moderna, amb la seva tendència a la concentració i a la sobre-escala urbana amb el sorgiment de les grans metròpolis actuals. S’analitzen els mecanismes que permeten a les ciutats subordinar i transformar el territori en funció de les seves necessitats creixents d’un flux de matèria, energia e informació que les alimenta i es degradat al llarg d’aquest procés. Analitzant aquest procés s’indica la importància fonamental que en té l’abundant disponibilitat de combustibles fòssils per alimentar-ho i el repte que suposa per les ciutats del segle XXI la fi de l’anomenat ‘petroli barat’ resultant del pic del petroli.In this article the modern urbanization process with its tendency to higher concentration and urban over-scale of its megalopolis is analyzed. The ways in which these urban centres manage to subordinate the territory to their interests in order to gain the needed mater, energy and information to maintain their socioeconomic metabolism are described, pointing to the central role played therein by the existence of abundant fossil fuels. From this perspective, the challenge for modern cities implied by the end of ‘cheap oil’ due to peak oil scenarios is described and how conflicting interests may generate unsustainable urban scenarios in the XXI century.Peer Reviewe