Small molecule substances as molecular probes of structure and texture of coal under sorption process and modelling

Multiple Sorption Model (MSM) is used to simulate sorption isotherms and the effect of the multiplicity of physicochemical parameters is reduced by introducing an invariant procedure using a few sorbates that are small molecules. This study presents the use of water, methanol, carbon dioxide and methane as test molecules to determine the structure and texture of coal and energy parameters. Parallel calculations for a set of sorption systems on the same coal sample recursively yield the most probable estimates. The procedure was tested for 6 coal samples with different carbon content. Effect of simulations made by MSM is evaluated on measurements of sorption isotherms. Result obtained by the analysis shows that smaller submicropores are in better contact with sorbate molecule and bigger one contact is weaker-contacts play vital role in energy contribution to the molecule. Tendency of significant absorption for CO2 and CH3OH and insignificant for H2O and CH4 is confirmed on the basis of thermodynamic dissertation/calculation.

COMPARAÇÃO DE DIFERENTES ABORDAGENS NA MODELAGEM DA DISTRIBUIÇÃO DIAMÉTRICA

O objetivo deste estudo foi avaliar a eficiência da função de distribuição de probabilidade Weibull truncada à direita em relação ao procedimento de passo invariante baseado na relação de percentis da distribuição diamétrica. Verificou-se que o modelo de passo invariante apresenta ajustes e predições mais precisas quando comparado com o procedimento tradicional, sendo mais eficiente.Palavras-chave:Passo invariante; função Weibull; avaliação de modelo. AbstractComparison of different approaches to diameter distribution modeling. This study evaluated the efficiency of the Weibull probability distribution function truncated to the right in comparison with the step-invariant procedure to characterize the percentiles of the diameter distribution. The results indicated that the step-invariant procedure provides more accurate adjustments and predictions and is more efficient than the traditional procedure.Keywords: Step invariant; Weibull function; model evaluation.

Procedures for theoretical redistribution of diameters in eucalyptus stands

This study aimed to evaluate the application of a procedure referred to as step invariant for theoretical redistribution of diameters by class in a diameter distribution model, using the Weibull probability density function. Data from the first rotation of hybrid eucalyptus stands (Eucalyptus grandis x Eucalyptus urophylla) planted with spacings of 3 x 2 m, located in northeastern Bahia state were used. Measurements were taken annually with measurement age ranging between 25 and 89 months. The step invariant procedure provided satisfactory results in comparison to the traditional procedure, being therefore recommended for future applications due to its unbiased results and ease of fit.