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Öğe Clustering in some randomly occupied two- and three-dimensional lattices(Natl Research Council Canada, 2004) Ulug, A; Karakaplan, M; Ulug, BClustering in some two- and three-dimensional lattices is investigated using an algorithm similar to that of Hoshen-Kopelman. The total number of clusters reveals a maximum at an occupation probability, p(max), where the average cluster size, 2.03 +/- 0.07, is found to be independent of the size, dimension, coordination number, and the type of lattice. We discussed the fact that the clustering effectively begins at p(max). The percolation threshold, p(c) and P-max are found to get closer to each other as the coordination number increases.Öğe Conduction in Y1-xScxBa2Cu3Oy(Slovak Acad Sciences Inst Physics, 2005) Ulug, A; Ulug, B; Adiguzel, HIA variational problem for three-dimensional (3D) classical lattice models is considered with trial state given by two-dimensional (2D) uniform product of local variational weights. This approach, the tensor product variational approach (TPVA), has been applied to 3D classical models (the Ising and the Potts models). We consider a way of estimating the magnetic critical exponent $\beta$ for the simple 3D Ising model assuming a functional form of the spontaneous magnetization in the off critical region, where the TPVA provides reliable data.Öğe Semiconductivity in YBa2-xSrxCu3Oy(Amer Inst Physics, 1996) Ulug, A; Ulug, B; Sener, EStructural and electrical properties of YBa(2-x)Sr(x)Cu3O(y) prepared under ambient oxygen pressure were systematically investigated for 0 less than or equal to x less than or equal to 2.0. Samples with high Sr contents, x greater than or equal to 1.7, showed semiconductive properties with an activation energy of similar to 150 meV at high temperature, T greater than or equal to 80 K. At low temperatures, T less than or equal to 80 K, activation energy dropped to similar to 3.00 and similar to 0.85 meV for x=1.7-1.8 and x=1.9-2.0, respectively. It is argued that YSr2Cu3Oy is likely to have a tetragonal structure and that the disorder introduced by Sr substitution affects electrical conduction, which involves charge hopping between the CuO chains at high Sr contents. (C) 1996 American Institute of Physics.Öğe Structure of C60-aliphatic diamine adducts(Marcel Dekker Inc, 1997) Ulug, A; Mete, A; Ulug, BProducts based on C-60 and aliphatic diamines are synthesized. Results indicate that C-60 molecules are partially connected to one another via aliphatic diamines, It is shown that d-spaces of the products can be varied by 50% when the number of C atoms in the aliphatic diamine is varied between 2 and 12. XRD analyses indicate that d-spaces are influenced by the repulsive interactions between C-60 molecules.Öğe Synthesis of C-60-furfural adduct(Marcel Dekker Inc, 1996) Mete, A; Ulug, A; Ulug, BDiels-Alder cycloaddition of furfural to C-60 in toluene has been realised. UV-VIS, FTIR and H-1-NMR investigations suggest that the conjugated structure of furfural was changed into a non-conjugated structure in the product.
