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http://hdl.handle.net/10646/3378
2020-02-19T20:35:08ZThe Gutman Index and the Edge-Wiener Index of Graphs with given Vertex-Connectivity
http://hdl.handle.net/10646/3472
Title: The Gutman Index and the Edge-Wiener Index of Graphs with given Vertex-Connectivity
Authors: Mazorodze, Jaya Percival; Mukwembi, Simon; Tomáš, Vetrík
Abstract: The Gutman index and the edge-Wiener index have been extensively investigated particularly in the last decade. An important stream of re- search on graph indices is to bound indices in terms of the order and other parameters of given graph. In this paper we present asymptotically sharp upper bounds on the Gutman index and the edge-Wiener index for graphs of given order and vertex-connectivity κ, where κ is a constant. Our results substantially generalize and extend known results in the area.2015-12-30T00:00:00ZApplication of citrus sinensis solid waste as a pseudo- catalyst for free cyanide conversion under alkaline conditions
http://hdl.handle.net/10646/3459
Title: Application of citrus sinensis solid waste as a pseudo- catalyst for free cyanide conversion under alkaline conditions
Authors: Santos, Bruno Alexandre Quistorp; Ntwampe, Seteno Karabo Obed; Doughari, James Hamuel; Muchatibaya, Gift
Abstract: In this study, Citrus sinensis (C. sinensis) solid waste was used to catalyze the conversion of free cyanide (F-CN) under alkaline conditions; conditions which represent most industrial wastewater containing F-CN. Acid hydrolysis of the solid waste increased the catalytic conversion of F- CN by 3.86 compared to the unhydrolysed solid waste. The conversion of F-CN using unhydrolysed and hydrolysed solid waste increased linearly with an increase in pH and temperature. The maximum catalytic conversion of a 100 mg F-CN/L solution containing 0.1% (w/v) of unhydrolysed and hydrolysed C. sinensis solid waste was 17.82% and 62.48%, respectively, at a pH of 12 and a temperature of 50 °C. The catalytic process was largely dependent on the availability of activated hydroxyl groups in the solid waste. As most wastewater contains heavy metals, it was determined that the presence of metallic species (Ni, Zn, and Cu) reduced the conversion of F-CN as the metallic ions attached to the hydroxyl groups. The observed reduction was 26.35% when 10 mg/L of heavy metals were present in the F-CN solution containing the hydrolysed solid waste at a pH of 12 and 40 °C.2013-05-08T00:00:00ZUnsteady contact melting of a rectangular cross section material on a flat plate.
http://hdl.handle.net/10646/3458
Title: Unsteady contact melting of a rectangular cross section material on a flat plate.
Authors: Myer, T G; Mitchell, S L; Muchatibaya, Gift
Abstract: The work in this paper concerns a mathematical model of the contact melting process of a rectangular material in contact with a hot plate. The problem is described by a coupled system of heat equations in the solid and melt layer, ﬂuid ﬂow in the melt, a Stefan condition at the melt interface, and a force balance between the weight of the solid and the ﬂuid pressure. Since the melt layer remains thin throughout the process, we use the lubrication approximation to the ﬂuid equations and assume that the heat ﬂow in the ﬂuid is dominated by conduction across the thin ﬁlm. In the solid we employ a heat balance integral method. Results show that the ﬁlm height has initial and ﬁnal rapid increases, whereas for intermediate times the height slowly increases. The quasisteady state of previous models is never attained: This is shown to be an effect of neglecting the change in mass and conduction in the solid. The previously observed initial inﬁnite velocity of the melt is shown to be a result of the perfect thermal contact assumption. For a water-ice system the melting rate is shown to be approximately linear, this allows us to reduce the problem to solving a single ﬁrst order differential equation for the liquid layer thickness. The main analysis is carried out in two dimensions, but we brieﬂy highlight the extension to three dimensions. The method is veriﬁed by comparison with previously published experimental results on the melting of n-octadecane.2008-10-06T00:00:00ZA Note on the Discrete Spectrum of Gaussian Wells (I): The Ground State Energy in One Dimension
http://hdl.handle.net/10646/3456
Title: A Note on the Discrete Spectrum of Gaussian Wells (I): The Ground State Energy in One Dimension
Authors: Muchatibaya, Gift; Fassari, S.; Rinaldi, F.; Mushanyu, Josiah
Abstract: The ground state energy 𝐸 0(𝜆) of 𝐻 𝜆 = − 𝑑 2 /𝑑𝑥 2 − 𝜆 𝑒 −𝑥2 is computed for small values of 𝜆 by means of an approximation of an integral operator in momentum space. Such an approximation leads to a transcendental equation for which 𝜖 0 ( 𝜆 ) = | 𝐸 0 (𝜆)| 1/2 is
the root2016-02-07T00:00:00Z