Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99


Search Results: 1 - 10 of 104 matches for " Sihen Getachew "
All listed articles are free for downloading (OA Articles)
Page 1 /104
Display every page Item
Coffee Wilt Disease (Gibberella xylarioides Heim and Saccas) in Forest Coffee Systems of Southwest and Southeast Ethiopia
Sihen Getachew,Girma Adugna,Fikre Lemessa,H. Hindorf
Plant Pathology Journal , 2012,
Abstract: Coffee diseases are presumed to be less important in the forest coffee as compared to the garden and plantation systems of coffee production in Ethiopia. In this article, the results of a study conducted on the occurrence and incidence of Coffee Wilt Disease (CWD) and the major factors influencing the disease in four major forests coffee sites in southwest and southeast Ethiopia are discussed. In each forest coffee site, coffee wilt syndrome was assessed in three systematically selected sample plots during dry and wet seasons of 2008 and 2009. Concurrently, three to four samples of infected coffee trees were randomly collected from each plot and the causal pathogen was isolated and identified in the laboratory. The result indicted that CWD was prevalent in the four forest coffee sites, with mean incidence of 27.1 and 29.2% in Harenna during 2008 and 2009 wet seasons, respectively, followed by Berhane-Kontir with mean incidences of 22.1 (2008) and 27.7% (2009). Whereas, Bonga and Yayu forest coffees had comparatively low wilt severity (<10%). The wood samples of most of the infected coffee trees (90.6%) yielded Gibberella xylarioides in the laboratory proving that this pathogen is the main cause of coffee tree death in the forest. The difference in incidence of CWD across the four sites and among fields was strongly associated with human factors and variations in coffee populations. The forest coffee trees in Harenna and Berhane-Kontir (high CWD) are almost transformed to semiforest type by sub-planting coffee seedlings after thinning the dense vegetation cover. These activities are known to create wound to the host and disseminate the fungus spores from tree to tree and from one field to the other. The two independent seedling inoculation tests in the greenhouse evidenced that there were significant variations among coffee accessions in reactions to CWD though most accessions were susceptible. The study showed that CWD is one of the potential biotic factors threatening the genetic diversity of Arabica coffee in most forest coffee sites and thus the disease management practices should duly be considered in planning and implementing forest coffee conservation strategy.
Influence of Soil Water Deficit and Phosphorus Application on Phosphorus Uptake and Yield of Soybean (Glycine max L.) at Dejen, North-West Ethiopia  [PDF]
Merkebu Getachew
American Journal of Plant Sciences (AJPS) , 2014, DOI: 10.4236/ajps.2014.513203

A green house experiment was conducted at Dejen, Northwest Ethiopia, with the objective of quantifying the critical soil water deficit and P levels that affect yield and yield components of soybean, and determine the critical soil water deficit levels influencing P uptake in soybean. The treatment consisted of factorial combination of four available soil water (ASW) deficit levels (0%, 25%, 50% and 75%) and four levels of phosphorus (0, 10, 20, and 30 kg·ha-1) laid out in RCBD with four replications using soy bean variety Jalale as a planting material. The experiment was conducted under green house condition at Dejen, South Ethiopia during the 2011 academic year. Air dried soil was filled in the pots and seeds were sown on May 13, 2011. Four plants were maintained on each pot after thinning till flowering but after flowering, the total number of plants per pot was reduced to three as one plant which was used for measurement of root biomass. The water deficit treatments were imposed after the plants have been fully established 2 weeks after emergence just before branching stage. The water deficiency was imposed through maintaining the soil moisture content below field capacity at the deficit levels of 25%, 50% and 75%. The 75% of ASW deficit resulted in the longest days (45) to flowering and maturity (99) compared to the 0%, 25% and 50% deficit levels. Also, the 75% of ASW deficit level resulted in shorter plants (55 cm), the lowest leaf area (82.6 cm2), the highest root to shoot ratio (0.0168) and the lowest DM accumulation (161.3 gm-2) compared to the other ASW deficit levels. Likewise, the 75% of ASW deficit level gave the lowest number of pods per plant (4.13), seeds per pod (1.69), 100 seed weight (2.54 g), seed yield (13.4 g·m-1), above ground biomass (174.6 g·plant-1) and harvest index (0.08) compared to the other ASW deficit treatments. The degree of sensitivity to drought increased dramatically (from 0.0423 at 25% to 0.9604 at 75%) with increase in water deficit level. Tissue analysis results indicated that the highest seed P concentration (1.285%) and uptake

RETRACTED:Generation of Bright Squeezed Light from N Three-Level Atoms Pumped by a Coherent Light: Open Quantum System  [PDF]
Getachew A. Gebru
Journal of Quantum Information Science (JQIS) , 2016, DOI: 10.4236/jqis.2016.62011

Short Retraction Notice?

The paper does not meet the standards of \"Journal of Quantum Information Science\". This article has been retracted to straighten the academic record. In making this decision the Editorial Board follows COPE's Retraction Guidelines. The aim is to promote the circulation of scientific research by offering an ideal research publication platform with due consideration of internationally accepted standards on publication ethics. The Editorial Board would like to extend its sincere apologies for any inconvenience this retraction may have caused.?

Please see the article page for more details. The full retraction notice in PDF is preceding the original paper which is marked \"RETRACTED\".

High Wind Power Penetration Large-Scale Hybrid Renewable Energy System Design for Remote Off-Grid Application  [PDF]
Samuel L. Tesema, Getachew Bekele
Journal of Power and Energy Engineering (JPEE) , 2019, DOI: 10.4236/jpee.2019.73002
Abstract: This study looks into the resource assessment, technology economics and modeling of different energy alternatives and proposes a rechargeable battery storage-based large-scale wind/photovoltaic hybrid power system to meet an average electrical load demand of 2.4 MW and peak load of 2.9 MW for a remote rural district in Ethiopia called Geladin. The district is 682 km away from nearby grid. The site enjoys high solar and wind resources that can be harnessed for electric power generation to electrify the community. HOMER simulation software is used for optimal sizing and techno-economic analysis. The diesel generator is used as back up to fill the gaps in case both resources are out. Average monthly solar irradiation data of 6.2 kWh/m2 is determined from measured sunshine duration data by implementing a suitable specific model for the site. NASA satellite based estimated wind speed data of 10 years average at hub height of 50 m for the site in question is extracted from the SWERA (Solar and Wind Energy Resource Assessment) database (with annual average of 6.1 m/s) and its weigh-bull distribution parameter, k of 1.98 is estimated which indicates a fair wind speed distribution of the site to generate electric power using wind turbine. The proposed optimal system results electricity generation indicates that 92% from wind turbine, 3% from photovoltaic, 5% from diesel generator and managed to obtain a much lower cost of energy (COE = 0.11USD/kWh) than other alternatives investigated in this study such as grid extension and diesel generator.
Can computer simulations substitute real laboratory apparatus?
Getachew Tarekegn
Latin-American Journal of Physics Education , 2009,
Abstract: This study investigates the effectiveness of computer simulations in teacher centered (STC) and student-centered(SSC) approaches in replacing real equipment laboratory (REL) in grade 12 physics course. The direct current (DC)circuit experiment was adopted to compare simulations in both cases with the real equipment. Particular attention wasgiven to students’ conceptual understanding and skills of manipulating real equipment. Sixty four students weredivided into three instructional groups. The students in computer simulation teacher-centered (STC) group observedand participated when the experiment was done; students in computer simulation student centered (SSC) groupperformed computer simulation by themselves; and real equipment laboratory (REL) group used traditional way toperform the experiment by themselves. Students’ understandings of DC circuit concepts were assessed usingDetermining and Interpreting Resistive Electric circuit Concepts Test (DIRECT). Other assessment measures includedthe time taken by a laboratory group of three students to construct a circuit of series-parallel combination. T-teststatistics revealed statistically significant difference between instructional treatment and students’ understanding of DCcircuits as measured by DIRECT. The results of this study show that the use of simulation in either setting can serve toenhance students’ achievement. Results of the statistical analysis for voltage and schematic diagram questions alsoshowed no significant difference between treatment and understanding of these concepts, while a significant differencebetween concepts such as current and resistance and the instruction methods was observed. The resulting mean timetaken on building the given circuit was 15.171 minutes for REL, 15.029 for STC and 13.457 for SSC. Both SSC andSTC groups get the skill of using real equipments though they did not use real instruments.
Cross-layer Optimization for Next Generation Wi-Fi
Getachew Redieteab
Computer Science , 2013,
Abstract: From the initial 1997 specification to the undergoing IEEE 802.11ac standardization, a leap in throughput has been observed with every new generation. The expectations for next generations on issues like throughput, range, reliability, and power consumption are even higher. This is quite a challenge considering all the work already done. Cross-layer optimization of physical (PHY) and medium access control (MAC) layers can be an interesting exploration path for further enhancement. During this thesis we have studied cross-layer optimization techniques, with a focus on the IEEE 802.11ac standard. A new multichannel aggregation scheme involving cross-knowledge between PHY and MAC layers has been proposed to improve performance in collision-prone environments. We have shown that some functionalities directly involved PHY and MAC layers. An accurate modeling of both PHY and MAC mechanisms is thus needed to have a realistic characterization of such functionalities. A cross-layer simulator, compliant with IEEE 802.11ac specifications, has thus been implemented. To the best of our knowledge, this is the first simulator incorporating detailed PHY and MAC functionalities for the IEEE 802.11ac standard. The multiple-user multiple-input, multiple-output (MU-MIMO) technique, which is one of the main innovations of the IEEE 802.11ac, needs both PHY and MAC layer considerations. We have thus used the implemented cross-layer simulator to evaluate the performance of MU-MIMO and compared it with the single-user MIMO (SU-MIMO). The aim of these studies was to evaluate the 'real' gains of MU-MIMO solutions (accounting for PHY+MAC) over SU-MIMO solutions and not the generally accepted ones. The impact of the channel sounding interval has particularly been studied. Finally, we have proposed a short PHY layer version of acknowledgment frames for overhead reduction in IEEE 802.11ah communications.
Nitrogen fertilization effects on grain quality of durum wheat (Triticum turgidum L. var. durum) varieties in central Ethiopia  [PDF]
Leta Gerba, Belay Getachew, Worku Walelign
Agricultural Sciences (AS) , 2013, DOI: 10.4236/as.2013.43019
Abstract: Four released durum wheat varieties, two medium tall (Arsi-Robe and Kilinto) and two recently released semidwarfs (Ude and Yerer) were evaluated under five different N rates (0, 60, 120, 180 and 240 kg·ha-1) in 2005/06 growing season at Akaki and Debre Zeit, central Ethiopia. The quality responses of durum wheat varieties to different N-fertilizer rates and the N responses between tall and short durum wheat varieties were assessed. Protein and gluten content, vitreous kernel count, thousand kernel weight, test weight and lodging were considered. Vitreous kernel count, protein and gluten content were higher at Debre Zeit than at Akaki. Unlike Debre Zeit, there were significant relationships between response variables and fertilizer levels at Akaki. Lodging slightly affected the medium tall varieties at Debre Zeit whereas it was not a problem at Akaki. At Akaki, varieties response to each additional N rate was entirely below the quality standard set by ICC, 2000 except for thousandkernel weight. Therefore, it is unwise to promote durum wheat scaling up/out program for quality production at Akaki.
Assessment of Early Sexual Initiation and Associated Factors among Preparatory School Students of FaggetaLekoma District, Awi Zone, Northwest Ethiopia, 2015  [PDF]
Dessalew Bizu, Zewdie Aderaw, Getachew Mullu Kassa
International Journal of Clinical Medicine (IJCM) , 2015, DOI: 10.4236/ijcm.2015.68070
Abstract: Introduction: Almost half of the world’s population is concentrated under the age of less than 25 years. The highest number of this population is living in developing countries. Sub-Saharan Africa youths constitute 20% - 30% of this population. Early sexual initiation is common among young people, and it has several sexual and reproductive health consequences. So, the objective of this research was to assess the prevalence of early sexual initiation and associated factors among preparatory school students of FaggetaLekoma district, Awi zone, Northwest Ethiopia, 2015. Methods and Materials: Institutional based cross-sectional study design with stratified sampling technique was used. Completeness of questionnaires was checked visually and data were coded and entered into Epi-Info version 3.5.4. and transported to SPSS version 16 software package for analysis. Bivariate and multivariate logistic regression was used to determine factors associated with early sexual initiation at 95% confidence interval. Result: A total of 270 students were included in the study. The mean age of the respondents was 18.82 ± 1.91 years, of which 117 (43.3%) were females, and 156 (57.8%) were rural residents. Among the total students who attended their class within the study period, 55 (20.4%) students had early sexual initiation. The results of multivariable model revealed that age AOR = 4.38, 95% CI (1.75 - 10.94), grade AOR = 4.18, 95% CI (1.58 - 11.04), existence of a boy/girl friend OR = 8.56, 95% CI (3.16 - 23.14), parental supervision AOR = 0.20, 95% CI (0.04 - 0.94) and peer pressure AOR = 3.56, 95% CI (1.31 - 9.66) were found to be significantly associated with early sexual initiation in multivariable analysis with P-value < 0.05. Conclusion and Recommendation: The current study found that early sexual initiation is still the problem. Among those who had initiated sex early, most of them had sex within the past 12 months, most of them had sex with their boy/girl friends and majority of them did not use condom. Age, grade, existence of a boy/girl friend, parental supervision and peer pressure of respondents were factors affecting early sexual initiation in the study area. In order to reduce early sexual initiation in preparatory school students, stakeholders should prioritize to educate young peoples, couples, and parents about sexual and reproductive health issues.
Dynamic Analysis of Soil Structure Interaction Effect on Multi Story RC Frame  [PDF]
Hailu Getachew Kabtamu, Gang Peng, Denghong Chen
Open Journal of Civil Engineering (OJCE) , 2018, DOI: 10.4236/ojce.2018.84030
Abstract: In this study dynamic analysis of Soil Structure Interaction (SSI) effect on multi story reinforced concrete (RC) frame founded on soft soil (flexible base) is made and compared with fixed base. Two model 2D RC frames with 7 and 12 story are selected for analysis. Winkler Spring and half space direct method models are used for flexible base for the frames founded on two types of soft soils with shear velocity Vs < 150 m/s Asper Seismic Codes of Chinese GB50011-2010 Soil IV and Ethiopian ES8-2015 soil D. The frames are subjected to strong ground motion matched to response spectrums of soft soil of Chinese GB50011-2010 and Ethiopian ES8-2015 for linear time history analysis. The dynamic analysis result shows Spring and Fixed base mass participation 90% reaches in 2 or 3 modes but in direct method 11 to 30 modes for story 12 and 7 respectively. However, both flexible base models have bigger fundamental period of vibration and inter story drift but smaller base shear than fixed base. In addition, within the flexible base models the inter-story drift, second order effect (P-Δ) and Story shear distribution are different along the height of frames. The spring model shows larger Story drift and second order effect (P-Δ) at the bottom of Story for both soft soils types. On the other hand, half space direct method model indicates value reverse to spring model; it gives bigger Story drift and P-Δ effect in the top stories than fixed base. Finally, this study concludes that base shear reduction due to SSI may not be always beneficial. Because the gravity load is constant in both fixed and flexible bases that cause bigger P-Δ effect at the bottom stories due to increase, inter story drift and decrease story shear in flexible base.
Assessment of the Trend, Cause and Effect of Deforestation Using GIS and Remote Sensing in Goba District, Bale Zone, South Eastern Ethiopia  [PDF]
Getachew Legesse, Hussein Hayicho, Mersha Alemu
Agricultural Sciences (AS) , 2019, DOI: 10.4236/as.2019.104044
Abstract: The conversion of forested areas to non-forest land was a series problem in study area of Goba district. The objectives of this study were to assess the trends, causes and effects of deforestation in Goba district, Bale zone, Ethiopia. Descriptive research method was employed to achieve these stated objectives. Satellite image of the three times and socio-economic survey were the main data sources for this study. ERDAS imagine 9.2 and ArcGIS 10 tools were applied for land use and land cover type classification, and analysis and mapping. These land use land and over change data were obtained from USGS. Socio-economic data collected through questionnaires, focus group discussions and interviews on the causes and impacts of land use and land cover change were analyzed quantitatively using SPSS software and content analysis for qualitative data. These analyzed data were expressed in percent and in words. The result shows that there was variation in the extent of land use and land cover change among different categories/classes at different study periods. Open area and Bush land showed decreasing change during first period of comparison and increasing change in the second period of comparison. In contrast, agricultural area, Bale temperate vegetation and built up area showed increasing. Built up area, agricultural area and Bale temperate vegetation increased by 80.05, 15.84, and 7.40 percent respectively, however, open area, grassland, forest land and bush land decreased by 1.58, 1.21, 0.97, and 0.28 percent per year for the last 29 years respectively. In general, in study district forest cover was 50.87% of the total area in 1986 and decreased to 36.57% in 2015 whereas agricultural area was increased from 3.45% to 19.28% respectively. This implies an increasing agricultural area at the expense of other land use cover categories, particularly natural forest. The study indicated that increasing population, forest fire and fuel wood consumption, overgrazing, and agriculture and settlement expansion and road construction caused forest cover change in the district. A decrease in livelihood incomes, volume of the surface water and in contrary increase in rain fall and temperature variability and forest product costs were among the major observed effects of deforestation in study area. Based on these findings, the study recommends the need to introduce and develop agricultural extension services, alternative energy sources and awareness raising services to the study area.
Page 1 /104
Display every page Item

Copyright © 2008-2017 Open Access Library. All rights reserved.