Bayesian Analysis of Doubly Inflated Poisson Regression for Correlated Count Data: Application to DMFT Data

Outcome variables in clinical studies sometimes include count data with inflation in two points (usually zero and k (k>0)). Doubly inflated models can be adopted for modeling these types of data. In statistical modeling, the association among subjects due to longitudinal or cluster study designs is considered by random effects models. In this article, we proposed a doubly inflated random effects model using the Bayesian approach for correlated count data with inflation in two values, and compared this model with Bayesian zero-inflated Poisson and Bayesian Poisson models. The parameters’ estimates by these models were obtained by Markov Chain Monte Carlo method using OpenBUGS software. Bayesian models were compared using the deviance information criterion. To this end, we utilized the total number of decayed, missed, and filled teeth of 12-year-old children and also conducted a simulation study.  Results of real data and the simulation study revealed that the proposed model is fitted better than previous models.&nbsp

Unsteady laminar natural convection, radiation and conduction within an enclosure with an obstruction

A numerical unsteady two-dimensional heat transfer and fluid flow analysis has been conducted on a square enclosure with a centered square obstruction. The analysis includes conduction, laminar natural convection and radiation with a radiatively non-participating fluid. Uniform temperature boundary conditions are prescribed on the left and right enclosure surfaces whereas, the top and bottom surfaces are maintained at adiabatic condition. Non-dimensionalized governing equations are solved using a control volume finite difference scheme coupled to a radiation algorithm. The calculations are performed for three enclosure lengths (L = 0.025 m, 0.050 m, 0.100 m), for six maximum enclosure temperature differences (ΔT = 20°, 50°, 100°, 200°, 300°, 400°K) a cold wall temperature of Tc = 293°K and, for two thermal diffusivity ratios (α* = 0.115, 2.902). Results are displayed in the form of streamline and isotherm plots, velocity and radiation heat flux plots and, tabulated radiation and convective Nusselt numbers. They are also compared with recent literature in radiation and convection within enclosures

Parameter estimation approach to the thermal characterization of intumescent fire retardant paints

Intumescent paints are widely used as passive fire retardant materials in the building sector. They swell on heating to form a highly insulating char, protecting steel members. Intumescent coatings for use in buildings are typically certified according to the standard cellulosic fire resistance test. This test is expensive, often non-representative of realistic fire conditions, and not enough versatile to gather detailed performance information on the response of reactive coatings. A promising approach, that could offer a helpful tool to the engineering community involved in fire safety, is found in the modelling of the behaviour of the intumescent coating. Under this approach, the knowledge of the equivalent thermal conductivity of the intumescent material is a fundamental issue, since it represents the main parameter that allows predicting the thermal protecting capability of the layer. The purpose of this paper is to optimize an estimation procedure intended to the restoration of the equivalent thermal conductivity of intumescent layers. The thermal stress is activated by the action of a cone calorimetric apparatus, while the estimation procedure is based on the inverse heat conduction problem approach under steady state assumption, where the temperature values measured at some locations inside the layer during the expansion process are used as input known data. This procedure was successfully applied to steel samples protected with an intumescent paint; the estimated equivalent thermal conductivity of the layer results to temperature dependent while the initial thickness of the paint does not seem to have a great effect