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Adama University

EducationNazrēt, Ethiopia
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.


Papers
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Book ChapterDOI
01 Jan 2021
TL;DR: In this paper, the authors proposed a modification of the muffler geometry based on transmission loss prediction, prototype manufacturing, and testing experimentally to improve the acoustic performance of a vehicle by modifying the geometry of existing muffler components.
Abstract: Internal combustion (IC) engines generate higher acoustic pulse due to combustion process. In order to minimize the acoustic pulse to certain level, IC engine use muffler in the exhaust system. Thus, the exhaust gas with reduced sound pressure gets released to the surrounding passing through the exhaust pipe. Inefficient muffler design causes sound pollution, vibration to vehicle components, increase in back pressure to the engine, and increases toxic exhaust gas emission to the environment. In this research work specific vehicle was considered which releases higher sound pressure. For the effectiveness of the work data was gathered from passengers and drivers to know what they feel and suggest about the sound emission of this vehicle. The goal of this research was to improve the acoustic performance of a given vehicle by modifying the geometry of existing muffler components. Muffler modification was done based on transmission loss prediction, prototype manufacturing, and testing experimentally. A part modelling was done by using Auto CAD tool. The design was analyzed and prediction of muffler performance was done using COMSOL Multiphysics simulation. From the result of the simulation, it was shown that the modified model has increased transmission loss by an average of 3.2 dB with little increase in back pressure, which is acceptable. The sound pressure level at the exit of the existing and manufactured muffler was measured experimentally and the modified muffler gives about 2 dB sound reduction at idling and 3.7 dB at full throttle position.
Journal ArticleDOI
TL;DR: In this paper, an empirical comparison of time-invariant and time-varying technical inefficiency measures obtained from an econometric estimation of different panel data stochastic production frontier models is presented.
Abstract: This paper does an empirical comparison of time-invariant and time-varying technical inefficiency measures obtained from an econometric estimation of different panel data stochastic production frontier models. It estimates four panel data specifications of frontier models widely used in empirical applications using a panel dataset from the Ethiopian cereal farming sector. The empirical results show that estimates of both the magnitude and the individual farms’ rankings of persistent and transient productive efficiencies differ considerably across models and based on their agro-ecological zones location. The results further show that the cereal growing farms experience much more transient inefficiency as compared to persistent inefficiency.
Journal Article
TL;DR: In this paper, the influence of fixed ventilation opening on indoor CO2 concentration, temperature and relative humidity which consequently affect yield were investigated and a generic tool or a model set up in Matlab software was employed.
Abstract: In Ethiopia almost most greenhouses are equipped with fixed ventilation owing to the fact that its influence on CO2 concentration, indoor temperature and RH% which affects plant growth is not clearly understood or due to lack of capacity. Particularly, relative humidity in the greenhouse not only affects plant growth but also major factor for pest-disease which should be maintained at the required range. In this study, the influences of fixed ventilation opening on indoor CO2 concentration, temperature and relative humidity which consequently affect yield were investigated. To execute simulation and examine the influence of ventilation opening on indoor climate and yield a generic tool or a model set up in Matlab software was employed. For the existing ventilation configuration, simulation of indoor climate was conducted and the result illustrated that low CO2 particularly during day time and high and low temperatures are major problems in the greenhouse. The observed indoor climate beyond the required range inhibits growth.The result of the sensitivity analysis for summer period showed that one percent increase in ventilation opening increases the CO2 concentration by 0.013%, decreases canopy temperature and vapor concentration by 0.065% and 0.114% respectively and increases yield by 0.328%. During winter period, a percent increase in ventilation area resulted in 0.036% and 0.075% reduction in canopy temperature and vapor concentration respectively, 0.012% increased indoor CO2 concentration and 0.03% increment in dry matter harvest. A yearly base sensitivity analysis illustrated that, a percent increase in ventilation opening area increases the dry matter harvest and interior CO2 by 0.231% and 0.012% respectively and decreases the canopy temperature and vapor concentration by 0.057% and 0.102% respectively.Thus, production in Ethiopian highland can be improved by providing better ventilation so as to increase the CO2 concentration and reducing extreme high temperature and vapor concentration in the greenhouse which influence the rate of photosynthesis. However, increased ventilation opening should be taken into consideration in relation to evapo-transpiration as a consequence of outdoor wind effect and the cost of insect screen to cover the larger ventilation opening.
Journal ArticleDOI
TL;DR: In this article , the authors used nitrogen and phosphorus codoped carbon dots (N & P-CDs) as an interfacial modification layer for ZnO ETL.
Abstract: The interface between the active layer and the charge-transporting layer is critical for performance improvement in polymer solar cells (PSCs). The use of zinc oxide (ZnO) as an electron transport layer (ETL) in PSCs was limited due to inherent defects in the surface of ZnO prepared by the sol-gel method, mismatched energy bands with the photoactive layer, and incompatibility between the photoactive layer and ZnO ETL. In this study, nitrogen and phosphorus codoped carbon dots (N & P-CDs) were prepared from Ensete ventricosum (false banana) and used as an interfacial modification layer for ZnO ETL. The inverted devices with structures ITO/ZnO/N & P-CD/PTB7:PC70BM/Al were fabricated to investigate the charge transfer dynamic between the active layer and ETL interface modification with N & P-CDs. We have observed that the interfacial modification between the ZnO ETL and the active layer, using N & P-CDs, improves the charge transfer between ZnO ETL and PTB7:PC70BM active layer. The obtained result shows that the ETL/BHJ interface resistance of the devices with ZnO:undoped CDs, ZnO:N-CDs, ZnO:P-CDs, and ZnO:N & P-CD ETLs decreases dramatically from 103.4 to 84.04, 78.16, 37.88, and 28.9 Ω, respectively. This is due to the improvement of charge extraction efficiency by smoothing ZnO surface defects and minimizing the band mismatch between the active layer and ZnO using N & P-CDs. The results indicate that the water-soluble N & P-CDs developed in this study have the potential to be used for efficient free charge carrier extraction for PSCs.

Authors

Showing all 856 results

NameH-indexPapersCitations
Delfim F. M. Torres6070114369
Trilok Singh5437310286
Dattatray J. Late4620511647
Jung Ho Je403286264
Gobena Ameni372074732
Jong Heo372555289
Mahendra A. More362684871
Gyanendra Singh322483198
Dilip S. Joag301273014
Tesfaye Biftu281293225
Salmah Ismail22792151
Rabab Mohammed21921785
Mooha Lee1649821
T. Ganesh1526735
Pandi Anandakumar1518777
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
20239
202226
2021332
2020203
2019125
2018101