Liteira de paricá, tatajuba e eucalipto em sistemas silvipastoris no Município de Paragominas - PA.

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Bayesian estimation of inefficiency heterogeneity in stochastic frontier models

Estimation of the one sided error component in stochastic frontier models may erroneously attribute firm characteristics to inefficiency if heterogeneity is unaccounted for. However, unobserved inefficiency heterogeneity has been little explored. In this work, we propose to capture it through a random parameter which may affect the location, scale, or both parameters of a truncated normal inefficiency distribution using a Bayesian approach. Our findings using two real data sets, suggest that the inclusion of a random parameter in the inefficiency distribution is able to capture latent heterogeneity and can be used to validate the suitability of observed covariates to distinguish heterogeneity from inefficiency. Relevant effects are also found on separating and shrinking individual posterior efficiency distributions when heterogeneity affects the location and scale parameters of the one-sided error distribution, and consequently affecting the estimated mean efficiency scores and rankings. In particular, including heterogeneity simultaneously in both parameters of the inefficiency distribution in models that satisfy the scaling property leads to a decrease in the uncertainty around the mean scores and less overlapping of the posterior efficiency distributions, which provides both more reliable efficiency scores and rankings

Statistical analysis of compressive strength of concrete specimens

This paper presents the statistical analysis of compressive strength of concrete specimens delivered in a laboratory of Northern of Portugal. Three types of concretes were analyzed defined as C20, C25 and C30. In the study we used the results of three years, 1995 to 1997. The one-sample Kolmogorov-Smirnov Test was used to verify the normal distribution of the strength results. The results presented in this paper are important for predicting the performance of structural elements and for calculating resistance factors for limit state design codes. As concrete is made in majority on site, conformity is more difficult than for other construction materials produced on factories. For the first analysis the concrete applied on the different sites were separated in groups. A total of 82 groups of concrete produced in 20 sites, were analyzed. We verified that in about 32% of the groups the characteristic compressive strength established for the design was not achieved. For the second analysis the total results were considered, without separation by site or by group. When the exigency was classes C20 or C25, the characteristic compressive strength was below the exigency. On the contrary, for the concrete mentioned as C30, the characteristic compressive strength was above the exigency

Paleomagnetism in speleothems: influence of calcite growth dip on the natural remanent magnetization

Recent studies recognized speleothems as excellent recorders of the Earth’s magnetic field. However, some questions remain about the origin of the natural remanent magnetization and about the influence of the speleothem shape on the recorded magnetic directions.info:eu-repo/semantics/publishedVersio

Speleothem shape and natural remanent magnetization

Speleothems might be of interest for high-resolution reconstruction of the Earth’s magnetic field. However, little is known about the influence of speleothem morphologies on their Natural Remanent Magnetization (NRM).info:eu-repo/semantics/publishedVersio

Effect of Polymer Hydration on the Kinetic Release of Drugs: A Study of Ibuprofen and Ketoprofen in HPMC Matrices

Samples of drug/hydroxypropylmethylcellulose (HPMC) mixtures and matrices (drug/HPMC mixtures plus excipients) were allowed to equilibrate in closed chambers with defined relative humidities (RHs). Their water uptake and drug release were evaluated by differential scanning calorimetry/thermogravimetric analysis and dissolution studies, respectively. Analysis of the thermal behaviors of the drug/HPMC mixtures and of the polymer alone, as functions of RH, leads to the conclusion that most of the hydration water is retained by the polymer, and points to the occurrence of different types of hydration water, from the strongly polymer-bound water molecules at RH values up to 81%, to the almost “free water” for RH values close to 100%. In addition, application of the Korsmeyer model to the dissolution results leads to the conclusion that the rate determining dissolution processes are predominantly of the fickian type.http://www.informaworld.com/10.1081/DDC-12001820