On k-type spacelike slant helices lying on lightlike surfaces

© University of Nis. All rights reserved. In this paper, we define k-type spacelike slant helices lying on a lightlike surface in Minkowski space E3 according to their Darboux frame for k ∈ {0, 1, 2}. We obtain the necessary and the sufficient 1 conditions for spacelike curves with non-null and null principal normal lying on lightlike surface to be the k-type spacelike slant helices in terms of their geodesic curvature, normal curvature and geodesic torsion. Additionally, we determine their axes and show that the Darboux frame of a spacelike curve lying on a lightlike surface coincides with its Bishop frame if and only if it has zero geodesic torsion. Finally, we give some examples

On t-slant, n-slant and b-slant helices in pseudo-galilean space G¹<inf>3</inf>

© 2018, University of Nis. All rights reserved. In this paper, we introduce T-slant, N-slant and B-slant helices in the pseudo-Galilean space G13 and define an angle between the spacelike and the timelike isotropic vector lying in the pseudo-Euclidean plane x = 0. In particular, we obtain the explicit parameter equations of the T-slant helices and prove that there are no N-slant and B-slant helices in G13. We also prove that there are no Darboux helices in the same space

A note on Lamarle formula in Minkowski 3-space

© 2018 Tamkang University. All rights reserved. The Lamarle formula is known as a simple relation between the Gaussian curvature and the distribution parameter of a non-developable ruled surface. In this paper, we obtain the Lamarle formula of a non-developable ruled surface with pseudo null base curve and null director vector field in Minkowski 3-space. We also obtain the corresponding striction line and distribution parameter of such surface. We prove that there is no Lamarle formula when the director vector field is spacelike and its derivative is null, because the ruled surface in that case is a lightlike plane. Finally, we give some examples

Energy performance of the Serbian and Estonian family house with a selective absorption facade

© Published under licence by IOP Publishing Ltd. In this paper the influence of selective absorption facade on heating energy consumption of the family house is analyzed. Two houses built according to Serbian and Estonian building energy performance regulation (minimum requirements) are simulated by EnergyPlus software. For simulation process the appropriate weather data are used (Serbia-Kragujevac and Estonia-Tallinn). Heat transfer by radiation, gains and losses can be a significant part of the energy consumption, during heating season. Using selective absorption facade those gains and losses could be increased and reduced, respectively. Several simulation scenarios of Serbian and Estonian house are carried out. Different weather conditions in case of the defined houses point on specific impact of the applied improvement on family house energy performance. Maximum annual percentage savings of heating energy compared to house without selective facade, in case of Serbian house are obtained as 8.32%. In case of Estonian house maximum savings are obtained as 1.92%