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.

Assessment of biannual seasonal variations in hydrochemistry of Kerwa reservoir located in hard rock formations of Central India

Abstract: An investigation on the Kerwa reservoir water located in central parts of India (Bhopal, Madhya Pradesh) has been carried out to assess the hydrochemical variations in different seasons and possible influencing factors. Temporal chemical variations in reservoir water were evaluated for all the three seasons by analyzing two hundred forty surface water samples from ten different sites along the reservoir periphery covering inlet and outlet points. The analytical results indicate that Kerwa reservoir water is mildly alkaline, and the order of dominance for ions was found to be Ca2+ > Mg2+ > Na+ > K+ and HCO3− > Cl− > SO42−. The major chemical facies present are Ca-Mg-HCO3, Ca-Mg-Na-HCO3-Cl, Ca-Mg-HCO3-Cl, and Ca-Mg-Cl-HCO3. Piper and Chadha plots infer that seasonality exert a strong control on the water chemistry. Rainwater dominate the reservoir water chemistry during monsoon, evaporation dominates during summer, while multiple geochemical reactions control the reservoir water chemistry during winter. The extent of ion exchange was evaluated by chloro-alkaline indices as well as (Ca2+ + Mg2+)/(Na+ + K+) versus Na+-Cl− plot. Contribution of carbonate and silicate minerals was evaluated using characteristic ionic ratios and scatter plots. It is found that weathering of silicate rocks lead to higher Ca2+ and Mg2+ in the reservoir water, while evaporite dissolution and to a some extent ion exchange and base flows are found to control the Na+ and K+ concentrations. With the growing scenario of contamination in adjoining water bodies, the study on water quality and associated geochemical processes becomes necessary for Kerwa reservoir, which can form a potential freshwater reserve in this region for future generations.

Investigation of dopant centres dominating the conduction process in the bulk of un-doped GaSb

Abstract: In this paper, first, the theoretical description of the effects of the dopant densities and the activation energies on the ionization densities, the chemical potentials corresponding to each dopant levels, the majority carrier densities and the Fermi-energy levels in one-acceptor-level system, highly compensated system and two-acceptor-level system are described in detail. Upon fitting the theoretical to the experimental results obtained by the temperature-dependent Hall effect measurements for three samples of un-doped GaSb, the dopant densities and the activation energies for a system with different dopants are investigated. The obtained results revealed that the dopant activation energy has less (no) effect on the Fermi-energy level and the majority carrier density in the highest temperature regimes. The doping density has also less (no) effect on the Fermi-energy level in the lowest temperature regimes. Finally, fitting of the theoretical to the experimental Hall effect measurements results confirmed the presence of three acceptor and one donor levels dominating the majority carrier densities at different temperature regions in all the samples of un-doped GaSb semiconductor.

Modeling of Induction Heating Inverter Using System Identification

Abstract: In this paper, Auto Regressive eXogenous input (ARX), Auto Regressive Moving Average eXogenous input (ARMAX), Output error and BJ models of class D voltage-source half-bridge series-resonant inverter used for induction heating are identified and studied based on prior knowledge and measured data from PSIM simulation Environment. The output data are generated by applying Pseudo-Random-Binary-sequence (PRBS) as an input through the inverter MOSFET gate in the PSIM software. PRBS signal is generated using standard components such as flip-flops or XOR gates to approximate the white noise in the PSIM software. The generated output and input data are loaded in the MATLAB to identify the unknown system parameters of induction heating inverter by using MATLAB system identification toolbox. Estimation of models with pre-selected structures can be performed using system identification toolbox. To validate the models and their limitations, the fitness properties of the models based on percentage best fit and their resonant frequencies are examined.

Effect of injection timing in multiple injections on NOx and smoke from CRDI diesel engine fueled with biodiesel blend

Abstract: Diesel engines with their high thermal efficiency and fuel economy are very much successful in commercial applications compared to their counterpart gasoline engines. The emissions like HC and CO from diesel engines are less compared to gasoline engines because they run mostly with lean mixtures. But due to heterogeneous combustion NOx and smoke emissions from Diesel engines is high. Due to contradicting requirements for the reduction of NOx and smoke, the tradeoff between NOx and smoke emission without compromising fuel economy is a big challenge being faced by automotive industries and researchers in the field. Also to have sustainable civilization, there is a need to find eco friendly and renewable alternative fuel to petro diesel to conserve fast depleting petroleum resources and to minimize environmental pollution. Biodiesel produced from non-edible feed stock is found to be a good alternative to petro diesel. It is observed that the formation of NOx is very much dependent on the peak temperature in the combustion chamber. Various types of techniques are being tried by the researchers to reduce high NOx emission from usage of biodiesel blended fuel in diesel engines. The techniques used are like dilution using EGR, injection of water, retardation of injection timing etc. With the development of CRDI systems split and multiple injection strategy attracting the attention of researchers as a promising technique in reducing the NOx emissions. In this work an attempt is made to study the effect of retardation of injection timing of a selected multiple injection with pilot-main-post strategy. The selected strategy is with 10% pilot fuel quantity with a dwell of 10 CAD and closely coupled fixed quantity of 0.5 mg post injection with 3 CAD after main injection. The main injection timing along with pilot and post was retarded from the recommended 23o bTDC in steps of 3 degrees. It is observed that the combination of multiple injection and retardation of injection reduced NOx emissions effectively without compromising power output and thermal efficieny.

Performance analysis and evaluation of software defined networking distributed controllers in datacentre networks

Abstract: Today network works under several problems. To solve these problems OpenFlowbased programmable software-defined network (SDN) was released. Datacenter network is one of the application areas that r...