Adama University

About: Adama University is a education organization based out in Nazrēt, Ethiopia. It is known for research contribution in the topics: Population & Adsorption. The organization has 840 authors who have published 1010 publications receiving 5547 citations. The organization is also known as: Adama Science and Technology University & ቴክኖሎጂ ዩኒቨርሲቲ, አዳማ ሳይንስና ቴክኖሎጂ ዩኒቨርሲቲ.

Effect of Ba Co-Doping on Sr5(PO4)3Cl:Ce3+ Blue Emitting Phosphor Application for White Light Emitting Diodes

Abstract: Ce3+-activated Sr5-2x-yBay(PO4)3Cl:xCe3+,xNa+ phosphors were synthesized via the solid statereaction methods. The substitution of Ba2+ for Sr2+ ions was confirmed by Raman spectra. The broadest Raman width in Sr2.45Ba2.45(PO4)3Cl:Ce3+ phosphor supported its highest disorder of the host lattice, leading to the emission spectral broadening with a half width of 95.5 nm due to the larger variation in crystal filed strength. The thermal stability of the luminescence was evaluated by the temperature-dependent luminescence intensity. The simulating a spectra of blue-emitting Sr2.45Ba2.45(PO4)3Cl:0.05Ce3+,0.05Na+ and orange emitting Sr3SiO5:Eu2+ phosphors as light converters, an intense white GaN-based near-UV-LED (400 nm) was exhibit good color-rendering index Ra of 90.8 at a correlated color temperature of 6473 K and CIE coordinates of (0.3165, 0.3051). These characteristics makes Sr2.45Ba2.45(PO4)3Cl: 0.05Ce3+,0.05Na+ should be a promising blue-emitting phosphors for the production of white light in phosphor conversion white-LEDs.

Fitted Numerical Scheme for Singularly Perturbed Differential Equations Having Two Small Delays

Abstract: In this paper, singularly perturbed differential equations having delay on the convection and reaction terms are considered. The highest order derivative term in the equation is multiplied by a perturbation parameter epsilon taking arbitrary values in the interval (0; 1]. For small epsilon, the problem involves a boundary layer on the left or right side of the domain depending on the sign of the coefficient of the convective term. The terms involving the delay are approximated using Taylor series approximation. The resulting singularly perturbed boundary value problem is treated using exponentially fitted upwind finite difference method. The stability of the proposed scheme is analysed and investigated using maximum principle and barrier functions for solution bound. The formulated scheme converges independent of the perturbation parameter with rate of convergence O(N−1). Richardson extrapolation technique is applied to accelerate the rate of convergence of the scheme to order O(N−2). To validate the theoretical finding, three model examples having boundary layer behaviour are considered. The maximum absolute error and rate of convergence of the scheme are computed. The proposed scheme gives accurate and parameter uniformly convergent result.

Neuro-fuzzy sliding mode controller: design and stability analysis

Abstract: In this paper, design and stability analysis of neuro-fuzzy sliding mode controller is discussed. The controller has two parts: fuzzy logic system and neural network. They are used concurrently but each part is responsible for one phase of sliding mode controller. The fuzzy logic system is utilised to control reaching phase dynamics and the feed-forward neural network is employed to keep the system states on the sliding surface. The neural network is trained online using modified back-propagation algorithm. Initially, fuzzy logic system is dominant and as the system moves from reaching phase to sliding phase, neural network becomes more active and hence, a hybrid computing paradigm is achieved. The stability of the system is analysed using Lyapunov's direct method. The proposed controller is implemented to regulate a second-order nonlinear uncertain system and simulation results confirm that the proposed system reduces chattering and improves transient response.

Higher order sliding mode control of a parallel robot

Abstract: In this paper a two degree of freedom parallel robot is modeled using the principle of virtual work. In order to achieve smooth trajectory tracking a regularized third order sliding mode controller is developed. Simulation results show that steady state tracking is met in approximately 2 seconds for a circular trajectory of 300 mm radius. The maximum tracking error is shown to be 4mm. Chattering is eliminated and the closed loop system is also shown to be robust against external disturbances and mass uncertainties.

Evolution of Hydroforming Technologies and Its Applications — A Review

Abstract: Advanced forming technologies have been evolving at a rapid pace with the products applicability in the industrial fields of aerospace and automobile especially for the materials like aluminum and