http://dspace.beu.edu.tr:8080/xmlui/handle/123456789/13721 2026-04-23T06:57:36Z http://dspace.beu.edu.tr:8080/xmlui/handle/123456789/13773 Combined effect of compressibility, height and thickness on the nonlinear behaviour of polyurethane, simply-supported spherical shells under apical loads Yıldırım, Bülent; Yükseler, Recep Faruk Previously, the effect of compressibility on the nonlinear buckling behaviour of thin, polyurethane, simplysupported spherical shells subjected to apical loads has been presented without considering the orders of the thickness and height of the spherical shells. In the meantime; it has been observed that although the variations of the thickness and height of the spherical shells do not affect the comments made for the effect of the compressibility on the buckling loads, they do affect the comments made for the effect of the compressibility on the buckling deflections considerably. In this study; combined effect of the compressibility, height and thickness on the buckling loads, buckling deflections and the apical load– apical deflection diagrams of polyurethane, thin, simply-supported spherical shells subjected to apical loads is investigated. Comparing the force–deflection diagrams corresponding to various values of the parameters pertaining to the compressibility of the material used, the height and the thickness of the shell; the variations of the buckling loads, buckling deflections and forms of the force–deflection diagrams corresponding to the various combinations of the mentioned parameters are discussed. 2014-01-01T00:00:00Z http://dspace.beu.edu.tr:8080/xmlui/handle/123456789/13772 Calculated pressure induced electronic and structural transitions in transition metals Dagıstanlı, Hamdi The partial occupation numbers and the density of states (DOS) at the Fermi level were calculated as a function of reduced atomic volume for transition metals by employing the linear-muffin-tin-orbital (LMTO) method. The pressure induced electronic transitions from sp states to d states are confirmed for early metals; and for the heavier elements, on the otherhand, pressure induced d→p electronic transitions were found. By means of the abrupt changes obtained in the p-DOS values, good agreement with regard to experiment were found in predicting the structural phase transition volumes and it is concluded that the phase stability of transition metals under pressure is related to the characteristic shape of DOS near the Fermi level. 2014-01-01T00:00:00Z http://dspace.beu.edu.tr:8080/xmlui/handle/123456789/13771 A review of non iterative friction factor correlations for the calculation of pressure drop in pipes Asker, Mustafa; Turgut, Oguz Emrah; Coban, Mustafa Turhan Pressure drop in pipes can be calculated by using the Darcy-Weisbach formula. In order to use this formula, the Darcy friction factor should be known. The best approximation to the Darcy friction factor for turbulent flow is given by the Colebrook-White equation. This equation can only be solved by numerical root finding methods. There are several other approximate correlations to the Darcy friction factor with some relative error compared to the Colebrook-White equation. It was found that in some of these correlations, the percentage error is so small that they can be used directly in place of the Colebrook equation. In this study, a review of several friction factor correlations is performed. Relative error of these correlations is re-evaluated against the Reynolds number for a different value of relative pipe roughness. Also statistical analyses will be given for each correlation. 2014-01-01T00:00:00Z