Department of Physics & Materials Science: Recent submissions
Now showing items 121-140 of 160
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Supporting Information for: Rheological Properties of Blends of Isotactic Polystyrene–
(2013)Figure S1: Optical micrographs and atomic force microscopy (AFM) images for the 95% iPpMS–5% iPS binary system dewetted at 𝑇dew= 240℃ and at different incubation times.(a) shows a 200 nm film before the dewetting ... -
Effect of Ga Incorporation and Film Thickness on the Optical Properties of as-Deposited Amorphous GaxSel-x Thin Films
(University if Nairobi Research archive, 2014)Flash evaporated amorphous GaxSe1-x (x = 0, 1, 2, 3, and 4 atomic %) on glass substrates have been investigated within a 500nm-1500nm spectral range. Film thicknesses explored were ; 200±10nm, 265±10nm, 330±10nm, and ... -
Optical properties and Raman studies of amorphous Se-Bi thin films
(The African Review of Physics, 2014)Flash evaporated amorphous Se Bi (x = 0, 1, 2, 3, and 4 at. %) thin films of 350 ± 10 thickness have been investigated in the wavelength range of 200nm − 3000nm. It is found that the effect of increasing bismuth ... -
Investigation of the Effect of Film Thickness on the Optical Properties of Amorphous Se85-xTe15Sbx Thin Films
(Africa Journal of Physical Sciences, 2014)Amorphous thin films of Se85-xTe15Sbx (x = 0.0, 0.5, 2.5, and 5.0 at. %) deposited by flash evaporation technique, have been investigated in the wavelength range of 500nm-3000nm. It is found that the effect of increasing ... -
Stability Investigation in the Optical Properties of Thermally Evaporated Ge5Se95-x Znx Thin Films
(University of Nairobi, Kenya, 2015)Selenium-based chalcogenides are useful in telecommunication devices like infrared optics and threshold switching devices. The investigated system of Ge5Se95-xZnx (0.0 ≤ x ≤ 4 at.%) has been prepared from high purity ... -
Role of bismuth and substrate temperature on the optical properties of some flash evaporated se100-x bix glassy system
(University of Nairobi, Kenya, 2015)Chalcogenide glasses are very important in the modern technology especially selenium-based. These glasses are sensitive to electromagnetic radiation useful in the infrared optics. The study investigated the effect of ... -
Compositional and Thickness Effects on the Optical Properties of Zinc–Doped Selenium–Antimony Thin Films
(Tanzania Journal of Science, 2018)Chalcogenide system of antimony (Sb)-selenium (Se)-zinc (Zn) system is a promising semiconductor for phase change memory devices due to its thermal stability and low power consumption. The study investigated the effect of ... -
Dewetting Rheology for Determining Viscoelastic Properties of Nonequilibrated Thin Polymer Films
(American Chemical Society, 2019)We performed systematic dewetting experiments on isotactic poly(para-methylstyrene) (iPpMS) films to explore the temperature dependence of the viscoelastic behavior of these films. We quantified the amount of residual ... -
Rheological Properties of Blends of Isotactic Polystyrene–Isotactic Poly(para-methylstyrene) Films Derived from a Comparative Dewetting Study
(American Chemical Society, 2020)We examined changes in rheological properties of nonequilibrated spin-coated thin films of isotactic polystyrene (iPS) and isotactic poly(para-methylstyrene) and blends thereof by dewetting experiments. For 200 nm thick ... -
General analytical solution for the one dimensional regular Cauchy problem of Euler-Poisson-Darboux equation
(Hikari Ltd, 2017)A general analytical solution to the one dimensional regular Cauchy problem of Euler-Poisson-Darboux (EPD) equation has been investigated. The one dimensional EPD which is a Partial Differential Equation (PDE) with initial ... -
The Acoustic Wave Propagation Equation: Discontinuous Galerkin Time Domain Solution Approach
(Hikari Ltd, 2019)This paper discusses a finite element method, discontinuous Galerkin time domain approach that solves the 2-D acoustic wave equation in cylindrical coordinates. The method is based on discretization of the wave field ... -
AN ESTIMATE OF VELOCITY PROFILE IN LAMINAR BOUNDARY LAYER
(Academic Publications, Ltd., 2011-09-02)This paper examines the boundary layer thickness developed for an incompressible viscous fluid flowing over a flat plate. The solution of the Blasius problem is considered. In this paper, the authors propose a polynomial ... -
AN INVESTIGATION OF THE EFFECTS OF BOUNDARY LAYER THICKNESS ON A THIN FILM OF LIQUID FLOW DOWN AN INCLINED PLANE
(2012-12-30)The motion of fluid substances may be described by the Navier-Stokes (N-S) equations. The equations arise from the application of Newton’s second Law of motion to a fluid. In this paper, N-S equations in two dimensions ... -
Mathematical modelling of the Olkaria Geothermal Reservoir
(School of Mathematics, University of Nairobi, 1996-05)The basic equations which govern the flow of fluids in a geothermal reservoir (often a two-phase mixture of steam. and water) are outlined. The governing nonlinear system of partial differential equations that arises is ... -
3-DIMENSIONAL MATHEMATICAL MODELLING OF TEMPERATURE DISTRIBUTION IN POROUS MEDIA
(Academic Publications, Ltd., 2011)An alternative method of the numerical solution of the heat equation is presented. A three-dimensional modelling approach is used in this paper rather than one or two dimensional models in order to account for the lateral ... -
ON SINGULAR CAUCHY PROBLEM OF EULER-POISSON DARBOUX EQUATION
(2012)We solve the singular Cauchy problem of Euler-Poisson-Darboux equation. The Riemann function, a solution corresponding to the adjoint equation is calculated and it enables us to evaluate any solution at a point by the ... -
Weak Solution of the Singular Cauchy Problem of Euler-Poisson-Darboux Equation for n= 4
(2013)We consider the singular Cauchy problem of Euler-Poisson-Darboux equation (EPD) of the form utt+ k t ut=∇ 2u u (x, 0)= f (x), ut (x, 0)= 0 where∇ 2 is the Laplacian operator in R n, n will refer to dimension and k a real ... -
On the Solution of Confined Aquifer Flow Equations: Finite Difference Approximations
(Hikari Ltd, 2013)In general, groundwater flow in porous media on a microscopic level is three-dimensional. However, when considering regional flow problems ie groundwater flow on a macroscopic level, it is noted that because of the low ... -
Solutions of second-order partial differential equations in two independent variables using method of characteristics
(nternational Journal of Engineering and Mathematical Sciences, 2013-06-01)In this paper we have classified second order linear PDEs into three types, hyperbolic, parabolic and elliptic. Hyperbolic equations have two distinct families of (real) characteristic curves, parabolic equations have a ... -
Elementary partial differential equations
(Lambert, 2013-06-01)The importance of partial differential equations cannot be gainsaid. They are used in science and engineering. Many natural phenomena such as sound, heat, electrostatics, electrodynamics, fluid flow etc occurring in science ...