The isomorphism classes of several types of graph coverings of a graph have been enumerated by many authors [M. Hofmeister, Graph covering projections arising from finite vector space over finite fields, Discrete Math. 143 (1995) 87–97; S. Hong, J.H. Kwak, J. Lee, Regular graph coverings whose covering transformation groups have the isomorphism extention property, Discrete Math. 148 (1996) 85–1...

The current study presents the design features and photovoltaic requirements of a floating photovoltaic plant (FPVP) whose purpose is to reduce the evaporation from the surface of a water reservoir while generating electricity. A summary of the energy budget method is also introduced to calculate the rate of evaporation from the water reservoir behind 15-Khordad dam. The top of the reservoi...

A K3 surface X is a compact complex surface with KX ∼ 0 and H (X,OX) = 0. An Enriques surface is a compact complex surface with H(Y,OY ) = H (Y,OY ) = 0 and 2KY ∼ 0. The universal covering of an Enriques surface is a K3 surface. Conversely every quotient of a K3 surface by a free involution is an Enriques surface. Here a free involution is an automorphism of order 2 without any fixed points. Th...

A direct determination of the fractal dimensions of a fracture surface is essential for a better understanding of its complete topographic characteristics. In this paper, a laser profilometer is employed to measure the topography of a rock’s fracture surface. With the use of the triangular prism surface area and projective covering methods, the resultant data set enables us to directly determin...

We exhibit a locally biholomorphic mapping with simply connected image, which fails to be a topological covering. Introduction In [1], A.F.Beardon shows an example of a ’covering surface’ over the unit disc D ⊂ C, which is not a topological covering. We recall that a ’covering surface’ of a regionD ⊂ C, is a Riemann surface S admitting surjective conformal mapping onto D, whereas a continuous m...

this study is aimed to evaluate the effect of covering exposed root surface by collagen membrane and to compare this method with coronoally advanced flap covering. 26 teeth in 20 patients (12m/8f) with miller1 gingival recession were selected. 14 teeth were allocated into test group and 12 teeth in control group. following first phase of treatment, clinical parameters including the height and w...