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.

Fabrication, Characterization and Evaluation of Mechanical Properties of Aluminium Hybrid Matrix Composite (Al6063/SiC-Bagasse Fly-Ash)

Abstract: The fabrication and mechanical performance of Al-Mg-Si alloy matrix composites reinforced with silicon carbide (SiC) and bagasse fly-ash has been explored in this work. The fabrication and experimental investigation of mechanical properties of aluminium matrix (Al/SiC) composite with and without addition of bagasse fly-ash by varying wt% of reinforcements were investigated. Chemical composition of reinforcement, weighted required amount of matrix and reinforcements, powder mixing, stirring the slurry at 500 rpm speed and 5–10 min were the parameters used to develop the Al/SiC-bagasse fly-ash hybrid composite. Bagasse fly-ash particulates added with 7.5, 10, and 12 wt% SiC were utilized to prepare 10 and 12 wt% of the reinforcing phase with Al-Mg-Si alloy as matrix using stir casting method. The cast samples were machined for evaluating the properties by performing tensile testing, compression strength testing, and micro-hardness measurement. The results disclosed that the hardness of the hybrid composites increased with increase in bagasse fly-ash content with a maximum increment of 17% observed for the Al6063-7.5% SiC-10% bagasse ash composition (in comparison with the Al-10 wt% SiC-7.5 fly-ash reinforced composition). Tensile strength reduced of maximum value of 90–68 MPa at 7.5 SiC-7.5 bagasse ash compositions.

Emission Characteristics of CSOME in CRDI Diesel Engine with Multiple Injection Strategy

Abstract: Diesel engines are successful in commercial applications both on-road and off-road due to their higher thermal efficiency and fuel economy. CO and HC emissions are less from diesel engines compared to its counterpart gasoline engine. But NO and PM (smoke) emissions are higher due to heterogeneous combustion. Simultaneous reduction of NOx and smoke became a tough task faced by researchers to comply with the stringent emission regulations imposed upon. On the other hand, biodiesel as a replacement of petro-diesel in diesel engine applications is found to be a good means of solving the problems like depletion of fossil fuel and environmental degradation. The high temperature in the combustion chamber causes the formation of NOx and heterogeneous mixing that causes smoke formation. In this work, an attempt is made to study the influence of splitting injection on NOx and smoke in CRDI diesel engine operated with cottonseed oil biodiesel blend (B20). The injection was split into three pulses, namely pre, main, and post. The dwell between pre and main was varied, and dwell between main and post was fixed at 3° CAD. A fixed quantity of 0.5 mg/cycle fuel was injected in the post, whereas the fuel injection in pre is 10% of the main injection. At different main injection timings, the dwell between mail and pilot varied. The post-injection is maintained with a dwell of 3 CAD, which is very closely coupled with the main injection. From the recommended injection timing of 23° bTDC, the main injection timing along with post and pilot was retarded in steps of 3°. Baseline data was obtained with a petro-diesel single injection and B20 single injection at recommended 23° bTDC. For smoke reduction, the dwell of 10 CAD observed to be the best at all main injection timings. For NOx reduction 20 CAD is better. For trade-off between NOx and Smoke, in overall Dwell 10 CAD is observed to be better. It is found that splitting injection is very much helpful in simultaneous reduction of harmful emissions like NOx and smoke from diesel engines.

Growth and characterization of nonlinear optical crystal Gamma glycine by the additive of lithium bromide

Abstract: Single crystal of γ-glycine, a polymorphic form of glycine, was grown by slow solvent evaporation technique by the additive of lithium bromide. It was grown from the aqueous solution of glycine and lithium bromide in 2:1 M ratio respectively at room temperature. Good quality of γ-glycine single crystals was harvested up to the dimension of 25 × 22 × 20 mm3. In order to reveal its properties, the grown single crystals were subjected to various characterizations. Powder X-ray diffraction of the grown crystal was recorded and indexed. The unit cell parameters of the crystals were estimated by single crystal x-ray diffraction and they were compared with the literature values. The identification of the functional groups and hence the compound present in the crystalline sample by FTIR analysis confirms the polymorphic form of glycine. Optical transmittance studies were carried out by UV–Vis-NIR transmission spectrum in the range of 200–1100 nm wavelength. The powdered sample of the crystal was subjected to Kurtz Perry powder technique to find the coefficient of Second harmonic generation. The second harmonic generation (SHG) conversion efficiency of γ-glycine crystal is more than twice when compared with KDP crystal. The grown γ-glycine crystal was further characterized by Thermo gravimetric analysis (TGA) and Differential thermal analysis, to find its thermal stability and decomposition temperature. Dielectric constant and Dielectric loss were determined at different frequencies with respect to various temperatures. The mechanical properties such as microhardness and yield strength were evaluated by Vicker’s microhardness tester.

Effect of greenhouse cover spectral properties on rose yield for Ethiopia highland

Abstract: In different agro-climates the greenhouse horticulture are making use of various types of plastic cover where its influence on production in relation to crop, indoor climate and outside climate not considered in selection. In this study, major spectral properties of mainly used greenhouse cover for Ethiopian highland and their effect on yield were investigated. Cover spectral properties such as cover near-infrared (NIR) transmission, photosynthetic active radiation (PAR) transmission and cover longwave emission coefficient were major parameters that are considered in this study to determine their effect on dry matter harvest. To examine the influence of the cover parameters on biomass production, a generic tool or a model constructed in Matlab software was used. The model comprises energy balance equations, mass balance equations and growth model. The measured greenhouse indoor temperature data was considered for validation of the model. Simulations of indoor temperature, canopy temperature and vapor concentration were conducted for the existing greenhouse configuration. The result of the simulation showed that in Ethiopian greenhouse for highland, high and low temperature, night time high humidity and low CO2 during day time are major problems which inhibit the growth and on the other hand create favorable condition for well know disease in the region that is botrytis. According to sensitivity analysis output of the model, 1% increase in PAR transmission resulted 0.009% increase dry matter harvest, whereas a percent increase in cover NIR transmission has caused 0.259% reduction in yield. Moreover, increment of cover long wave emission coefficient by 1 percent positively influences (0.044%) the rose production. The resulted depicted that as compared to low temperature problem during rainy season (2-3 months), high temperature problem during summer season (9-10 months) would become a foremost problem in Ethiopian highland greenhouse horticulture. Thus, plastic cover with lower NIR transmission and higher PAR transmission and long-wave emission coefficient is desirable for Ethiopian highland greenhouses. However, the study revealed that night time low temperature particularly during rainy season should be studied to incorporate in respective growth model.