Computational Methods in Engineering

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The start up dynamics of a one-million and two-hundred-thousand liter anaerobic digester of municipal waste treatment sludge was studied. In the digester, mixing was accomplished by circulation of the produced biogas at a rate of 0.13 m3 per hour of the digester volume per hour. During the nine-month study, no serious phenomena of foaming, getting sour, temperature fall, etc. were observed despite the fact that there were problems including gas leakage, sludge leakage, heating system shortcomings and weak mixing system. In the process of digestion of a 3:1 mixture of primary and secondary sludge at a rate of 25 m3/day, 25˚C and a residence time of 48 days, volatile content removal was as high as 60%. The experimental data collected in this study was checked against a theoretical model already published in the literature and a good comparison was observed between the measured values and those calculated based on this model.

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In this paper, nonlinear bending analysis of functionally graded rectangular and sectorial micro/nano plates is investigated using the modified couple stress theory. For this purpose, a higher-order shear deformation theory and von Kármán geometrically nonlinear theory are employed. The equilibrium equations and the boundary conditions for rectangular and annular sector plates are derived from the principle of minimum total potential energy and solved using the Semi-Analytical Polynomial Method (SAPM). One of the advantages of the implemented shear deformation theory is removing the defects of higher order shear deformation theory, and obtaining the response of the first and the third-order shear deformation theories at the same time. Afterwards, beside investigating the benefits of this theory compared with other ones, the results are verified with those by other researches. At the end, the effects of length scale parameter, boundary conditions, power law index, and geometrical dimensions are investigated