Ethiopian Journals Online (EJOL)
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Bacterial contamination of school’s drinking water in Addis Ababa, Ethiopia
No full textAccess to safe drinking water and hygienic living conditions is a global concern and these issues are especially serious in developing countries. The objective of this study is to evaluate the quality of water consumed by kindergarten schools’ children in Addis Ababa city, who are highly susceptible to issues associated with microbial contamination in water. Total coliforms, E. coli, pH and residual chlorine in the water distribution system were measured at three water sources and 38 schools. The microbial analysis result shows 7 out of 38 schools were contaminated with total coliform bacteria. However, E. coli was not detected in any of the samples, meaning that all samples were free from fecal contamination. In addition, the free chlorine level of the samples was also tested. The results indicated that 16 out of 38 (42.1%) of the water samples had a free chlorine value below the WHO recommended 0.2mg/L. It is therefore, possible to conclude that the efficiency of a water supply infrastructure determines the concentration levels of microbial contamination and residual chlorine that reaches the end users. The study addresses critical issues and methods to mitigate the problems caused by microbial contamination in water supply distribution infrastructure
ORGANIC THIN-FILM SOLAR CELLS: NEXT GENERATION LOW-COST PHOTOVOLTAIC APPLICATIONS
No full textThe growing concern about our environment and sustainable development focuses attention on renewable energy sources. One of these sources is the direct conversion of sunlight into electricity bymeans of photovoltaic cells. Solar energy has the potential to fulfil an important part of the sustainable energy demand for future powergenerations. Thereby, low-cost organic photovoltaic systems have come into the international research focus during the past couple of years. This report demonstrates external power conversion efficiencies of above 2.3% under AMI. 5 illumination (100 mWlcm2) and external quantum rfficiency over 50% for organic thin-film photovoltaic cells using a phthalocyanine-fullerene (ZnPdC60) bulk heterojunction as an active layer, embedded into a p-i-n type architecture with dopedwide-gap charge transport layers. The p-i-n architecture allows for the design of solar cells with high internal quantum efficiency where thephotoactive region absorbs visible light and recombination losses at contacts are avoided. The current-voltage characteristics, power conversion efficiencies, the dependence of short circuit currenton incident white light intensity, [PCE and the sUiface network morphology of these films by atomic force microscope (AFM) are discussed
THE USE OF SQUARE CROSS SECTIONS OF UNIT-LENGTH SIDE FOR THE ANALYSIS OF RECTANGULAR SOLID AND HOLLOW SECTIONS UNDER BIAXIALLY ECCENTRIC LOADS
No full textFLOW SIMULATION AND PERFORMANCE PREDICTION OF CENTRIFUGAL PUMPS USING CFD-TOOL
No full textWith the aid of computational fluid dynamics, the complex internal flows in water pump impellers can be well predicted, thus facilitating the product development process of pumps. In this paper acommercial CFD code was used to solve the governing equations of the flow field. A 2-D simulation of turbulent fluid flow is presented tovisualize the flow in a centrifugal pump, including the pressure and velocity distributions. The standard k- turbulence model and SIMPLECalgorithm were chosen for turbulence model and pressure-velocity coupling respectively. The simulation was steady and moving reference frame was used to consider the impeller-volute interaction. The head and efficiency at different flow rates are predicted and they agree well with those available in literature for similar pump. From the simulation results it was observed that the flow change has an important effect on the location and area of low pressure region behind the blade inlet and the direction of velocity at impeller inlet. From the study it was observed that FLUENT simulation results give good prediction of performance of centrifugal pump and may help to reduce the required experimental work for the study of centrifugal pump performanc
INSURANCE REQUIREMENTS AND PRACTICES OF ETHIOPIA'S CONSTRUCTION SECTOR
No full textThe principles of insurance and types of insurancepolicies in construCtion industry in general isdiscussed. The status of consultants and contractorsin Ethiopian construction sector is briefly reviewed.Questionnaires were designed to preliminary assesswhether relevant insurance policies are bought bycontracting and consulting firms, and the resultswere evaluated and discussed. Conclusions andrecommendations are given
PREDICTION OF SWELLING BEHAVIOR OF ADDIS ABABA EXPANSIVE SOIL USING SIMPLE MATHEMATICAL MODEL
No full textDamage due to soil swelling is very noticeable in wide spectrum of structures such as roads, buildings, canal linings, landfill liners, etc. Toevaluate severity of swelling, an accurate assessment of the swell potential is required. The main reason of swelling behavior is waterabsorption of soil mass in time. And the time required for completion of swelling is relatively long. In view of that several attempts have beenmade by researchers to obtain time-swell relationships for expansive soils. In this study a simple hyperbolic mathematical model is used topredict the swelling behavior of an expansive soil from Addis Ababa. The main parameters that are needed to run the model are the applied pressure and initial dry density. The other parameters of the model including the initial slope of the swell-time curve, the final slope, the reference swell, and the peak swell were investigated experimentally. Based on the experimental results, empirical relationships were developed for determination of these parameters as functions of the applied pressure and initial dry density. The model prediction werecompared with the experimental results and showed good agreements
A COMPARATIVE ANALYSIS OF SCANDINAVIAN AND ETHIOPIAN APPROACHES TO HOUSING WITH SPECIAL EMp·HASIS ON HOUSING TENURE AND HOUSING FINANCE
No full textHousing constitutes the major part of all cities. Itsdevelopment or lack of it affects all urbandwellers. In fact, .housing condition is the measureof the success and failure of most urban policies.Two of the' most important issues in housing arehousing tenure and housing finance. The mode ofproduction, owning and disposal of housesinvolves the making of policies regarding propertyrights and the establishment of institutions thatfacilitate implementation.This paper deals with a comparative analysis ofthe policies and their rsesults in Scandinaviancountries and in Ethiopia. The study shows thatthere are significant differences in policyformulation and implementation. In the case ofEthiopia anomalies are observed betweenobjectives of policies and the instruments used toeffect them. In some cases innovative approachesare initiated but are not followed through. It ishoped the issues raised in this paper willcontribute to the debate on housing. Furthermore,it will show the merits of comparative analysis,which are very much neglected in housing studie
CO-FERMENTATION OF KOCHO WITH BARLEY FOR AN IMPROVED INJERA
Get PDFInjera, a pancake type sour bread, was prepared by co-fermentingkocho with barley to determine its nutrient composition and the microorganisms involved in the fermentation process. The predominant organisms identified were Lactobacillus, Bacillus and yeasts. The fermentation process was characterized by the fall in pH from 5.0 to 4.2 and rise in the titratable acidity from 0.20% to 0.50% during 96 hrs of fermentation. The co-fermentation of kocho with barley increased the protein content of the fermented injera by 2.6-fold. The injeraprepared from co-fermented dough of kocho and barley was found to be acceptable to Ethiopian consumers and bad very good keeping qualities. A fermentation scheme was therefore developed for the production of injera with improved protein content in which kocho and barley flour were fermented for 96 hrs with barley flour
Mn-Mg OLIVINES OF LANGBAN-TYPE AND THEIR SYNTHETIC EQUIVALENTS
Get PDFTephroites and Mn-Mg olivines are the major olivines in theLangban ore region, while forsterite is rare. Forsterite solid solution in tephroitevaries over a wide range, from Fo60Te40 to pure tephroite. Compositions in therange of Fo90 TelO to Fo60 Te40 have not been encountered in the studied population of 30 samples. Most of the Mn-Mg oiivines, especially those from the Umgban mine, have a nearly ideal "picrotephroite" composition which is half-way between forsterite and tephroite. With occasional exceptions the olivines may be consideredas binary systems with only subordinate amounts of other cations whichmakes it possible to determine cation ordering from plotting a- against b-axis and to estimate the crystallisation temperature, The Umgban "picrotephroitesll are approximately 62-94 % ordered, with a mean ordering of 75 %, Such extensive ordering implies that the crystallisation temperature of the olivines could not have been very high. Synthesis experiments have been performed in the forsteritetephroite system at temperatures below 7000 C and at a pressure of 1 kbar. The results are not very conclusive because of the sluggishness of the reactions butthey may suggest a temperature range of 500-600° C and moderate to low pressures for the formation of the Ungban "picrotephroites"
Abundance and diurnal activity patterns of hooded vulture (Necrosyrtes monachus Temminck,) in Addis Ababa abattoirs enterprise, Addis Ababa, Ethiopia
No full textHooded vulture (Necrosyrtes monachus) is an African endemic scavenger listed as Critically Endangered species. The population is declining across its range and there is threat of significant decline in population and distribution in Ethiopia. Little efforts have been made to properly document the status of vulture population and their diurnal activity patterns in the country for ensuring long term conservation measures. A study was conducted in Addis Ababa Abattoirs enterprise, Ethiopia from November 2019 to January 2020 to investigate the abundance and diurnal activity patterns of hooded vultures. The abundance of these vultures was estimated by direct counts method at their feeding sites and scan sampling was employed to study the diurnal activity patterns of hooded vultures from dawn to dusk. Hooded vulture mean abundance was 216±40 at the abattoir. Their diurnal activity pattern showed that they were observed feeding, resting (perching, watching and basking), preening, roosting and others activities such as walking, drinking, chasing and flying. They spent 37.73% of their time in resting followed by others (including walking, drinking, chasing and flying) (27.73%). The major threat recorded for theses vultures in the abattoir includes shortage of food, human disturbances, negative attitudes and lack of awareness on the importance of the species. Further ecological studies and impacts of human activities on Addis Ababa Abattoirs enterprise should be conducted for the conservation of hooded vulture and other conspecifics in the area