The main goal of this paper is to study the spectrum and resonances of several classes of Schrodinger operators. Two important examples occurring in mathematical physics are discussed: harmonic oscillator and Hamiltonian of hydrogen atom. Keywords: Schrodinger operator, Spectrum, Periodic potential, Resonances.
{"title":"Structure of the Spectra and Resonances of Schrödinger Operators","authors":"T. Bouguetaia, B. Messirdi","doi":"10.4314/MEJS.V12I1.6","DOIUrl":"https://doi.org/10.4314/MEJS.V12I1.6","url":null,"abstract":"The main goal of this paper is to study the spectrum and resonances of several classes of Schrodinger operators. Two important examples occurring in mathematical physics are discussed: harmonic oscillator and Hamiltonian of hydrogen atom. \u0000Keywords: Schrodinger operator, Spectrum, Periodic potential, Resonances.","PeriodicalId":18948,"journal":{"name":"Momona Ethiopian Journal of Science","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2020-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41932642","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this paper, we address a single item supplier selection, economic lot-sizing, and order assignment problem under quantity discount environment and transportation costs. A mixed-integer nonlinear program (MINP) model is developed with minimization of cost as its objective, while lead-time, the capacity of the supplier and demand of the product are incorporated as constraints. The total cost considered includes annual inventory holding cost, ordering cost, transportation cost and purchase cost. An efficient and effective genetic algorithm (GA) with problem-specific operators is developed and used to solve the proposed MINP model. The model is illustrated through a numerical example and the results show that the GA can solve the model in less than a minute. Moreover, the results of the numerical illustration show that the item cost and transportation cost are the deciding factors in selecting suppliers and allocating orders. Keywords: Supplier selection, Economic Order Quantity, Order allocation, Mixed-integer nonlinear programming.
{"title":"Single Item Supplier Selection and Order Allocation Problem with a Quantity Discount and Transportation Costs","authors":"Getachew Basa, T. Becker, Abdelkader Kedir","doi":"10.4314/mejs.v12i1.2","DOIUrl":"https://doi.org/10.4314/mejs.v12i1.2","url":null,"abstract":"In this paper, we address a single item supplier selection, economic lot-sizing, and order assignment problem under quantity discount environment and transportation costs. A mixed-integer nonlinear program (MINP) model is developed with minimization of cost as its objective, while lead-time, the capacity of the supplier and demand of the product are incorporated as constraints. The total cost considered includes annual inventory holding cost, ordering cost, transportation cost and purchase cost. An efficient and effective genetic algorithm (GA) with problem-specific operators is developed and used to solve the proposed MINP model. The model is illustrated through a numerical example and the results show that the GA can solve the model in less than a minute. Moreover, the results of the numerical illustration show that the item cost and transportation cost are the deciding factors in selecting suppliers and allocating orders. \u0000Keywords: Supplier selection, Economic Order Quantity, Order allocation, Mixed-integer nonlinear programming.","PeriodicalId":18948,"journal":{"name":"Momona Ethiopian Journal of Science","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2020-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.4314/mejs.v12i1.2","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41803975","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
H. Meles, Desta B. Gebrehiwot, Fireweini Gebrearegay Tela, Gebretsadik Gebru Wubet, Teodros Gebregergis
Background : The car accident injury level is known to be a result of a complex interaction of factors to drivers’ behavior, vehicle characteristics and environmental condition. Therefore it is obvious that identifying the contribution of the factors to the accident injury is very critical. The objective of study was to perform descriptive analysis to see the characteristics of car accident, to assess the prevalence and determinants of road safety practices in Mekelle City, Tigray, Ethiopia. Methods : A random sample of data was extracted from traffic police office from September 2014- July 2017. An ordered logistic regression model was used to examine factors that worsen the car accident level. Result : A total sample of 385 car accidents were considered in the study of which 56.7% were fatal, 28.6% serious and 14.7% slight injury. The model estimation result showed that, being experienced drivers (Coef. = 0.686; p-value< = 0.050) were found to increase the level of injury. On the other hand, being private vehicle (Coef. = -1.160; p-value <= 0.010), the type of accident of vehicle with pedestrian (Coef. = -2.852; p-value <= 0.010), being heavy truck (Coef. = -0.656; p-value <= 0.050), being a cross country buss (Coef. = -0.889; p-value <= 0.050) and being owner of vehicle is the driver himself (Coef. = -.690, p-value <= 0.050) were found to decrease the level of car accident injury severity. Therefore, it is better to create continued awareness to those who are experienced drivers, who carelessly follow the traffic rules. Special attention is required to government owned vehicle drivers, as they were found to increase the level of car accident injury through different short term trainings.
{"title":"Identification of Determinant Factors for Car Accident Levels Occurred in Mekelle City, Tigray, Ethiopia: Ordered Logistic Regression Model Approach.","authors":"H. Meles, Desta B. Gebrehiwot, Fireweini Gebrearegay Tela, Gebretsadik Gebru Wubet, Teodros Gebregergis","doi":"10.21203/rs.2.19228/v1","DOIUrl":"https://doi.org/10.21203/rs.2.19228/v1","url":null,"abstract":"\u0000 Background : The car accident injury level is known to be a result of a complex interaction of factors to drivers’ behavior, vehicle characteristics and environmental condition. Therefore it is obvious that identifying the contribution of the factors to the accident injury is very critical. The objective of study was to perform descriptive analysis to see the characteristics of car accident, to assess the prevalence and determinants of road safety practices in Mekelle City, Tigray, Ethiopia. Methods : A random sample of data was extracted from traffic police office from September 2014- July 2017. An ordered logistic regression model was used to examine factors that worsen the car accident level. Result : A total sample of 385 car accidents were considered in the study of which 56.7% were fatal, 28.6% serious and 14.7% slight injury. The model estimation result showed that, being experienced drivers (Coef. = 0.686; p-value< = 0.050) were found to increase the level of injury. On the other hand, being private vehicle (Coef. = -1.160; p-value <= 0.010), the type of accident of vehicle with pedestrian (Coef. = -2.852; p-value <= 0.010), being heavy truck (Coef. = -0.656; p-value <= 0.050), being a cross country buss (Coef. = -0.889; p-value <= 0.050) and being owner of vehicle is the driver himself (Coef. = -.690, p-value <= 0.050) were found to decrease the level of car accident injury severity. Therefore, it is better to create continued awareness to those who are experienced drivers, who carelessly follow the traffic rules. Special attention is required to government owned vehicle drivers, as they were found to increase the level of car accident injury through different short term trainings.","PeriodicalId":18948,"journal":{"name":"Momona Ethiopian Journal of Science","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2019-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46085336","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The interest in using ecological bioindicators - species or higher taxa, whose presence/absence or abundance reflect the abiotic or biotic state of an ecosystem - as cost-effective means of ecological monitoring has been globally increasing. The main aim of this study was to assess if such ecological bioindicator species could be identified within Afromontane grassland avifauna that would be used for monitoring the effects of livestock grazing on ecosystem in the Bale Mountains of Ethiopia. We collected data on birds and vegetation structure along 14 transects each in the light (protected) and heavy (unprotected) grazing sites in June 2014 (referred to as the first sampling period) and in December 2014 (the second sampling period). Then, we (i) initially identified potential bioindicator species for the light grazing site, based on data collected during the first sampling period; (ii) examined relationships between abundance of these bioindicators and level of grazing pressure; (iii) tested the consistency of those initially selected bioindicator species, based on independent data collected during the second sampling period. We used the Indicator Value (IndVal) Analysis method to identify bioindicator species for the light grazing site. Species with significant IndVal>60% were considered as potential bioindicator for the site compared to the heavy grazing site. Six species were initially identified as potential bioindicators from the first sampling period dataset, and four of these species were again consistently identified from the second sampling period. Furthermore, abundance of the bioindicators had significantly declined with increasing grazing pressure, but positively correlated with four habitat variables (i.e. heights of shrub, herb and grass, and cover of shrub). These findings suggest that those consistently identified four species represent suite of reliable bioindicators that can successfully be used for monitoring of changes in habitat structure in the site. Recommendations on how to apply these findings for ecological monitoring are provided.
{"title":"The Selection, Testing, and Application of Ecological Bioindicator Birds: A Case Study of the Bale Mountains, Southeast Ethiopia","authors":"A. Addisu, Mengesha Girma","doi":"10.4314/mejs.v11i2.2","DOIUrl":"https://doi.org/10.4314/mejs.v11i2.2","url":null,"abstract":"The interest in using ecological bioindicators - species or higher taxa, whose presence/absence or abundance reflect the abiotic or biotic state of an ecosystem - as cost-effective means of ecological monitoring has been globally increasing. The main aim of this study was to assess if such ecological bioindicator species could be identified within Afromontane grassland avifauna that would be used for monitoring the effects of livestock grazing on ecosystem in the Bale Mountains of Ethiopia. We collected data on birds and vegetation structure along 14 transects each in the light (protected) and heavy (unprotected) grazing sites in June 2014 (referred to as the first sampling period) and in December 2014 (the second sampling period). Then, we (i) initially identified potential bioindicator species for the light grazing site, based on data collected during the first sampling period; (ii) examined relationships between abundance of these bioindicators and level of grazing pressure; (iii) tested the consistency of those initially selected bioindicator species, based on independent data collected during the second sampling period. We used the Indicator Value (IndVal) Analysis method to identify bioindicator species for the light grazing site. Species with significant IndVal>60% were considered as potential bioindicator for the site compared to the heavy grazing site. Six species were initially identified as potential bioindicators from the first sampling period dataset, and four of these species were again consistently identified from the second sampling period. Furthermore, abundance of the bioindicators had significantly declined with increasing grazing pressure, but positively correlated with four habitat variables (i.e. heights of shrub, herb and grass, and cover of shrub). These findings suggest that those consistently identified four species represent suite of reliable bioindicators that can successfully be used for monitoring of changes in habitat structure in the site. Recommendations on how to apply these findings for ecological monitoring are provided.","PeriodicalId":18948,"journal":{"name":"Momona Ethiopian Journal of Science","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2019-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.4314/mejs.v11i2.2","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43970890","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Kafta-Sheraro National Park (KSNP) is one of the most important protected areas in Ethiopia and provides a number of important ecological and hydrological benefits to the local people. However, the park is under immense pressure as a result of a rapidly increasing human population that resulted from a voluntary resettlement program launched by the government in 2003. Using satellite imageries taken in the years 2003, 2009 and 2015, this study examined patterns of changes in land use/cover throughout the park over a 12 year period (2003 to 2015), during which human population pressure is known to have increased over time and changes in government policies were taken place. The results showed that, over the period of 12 years, wood land experienced the most changeover the study period, with a loss of cover of 862.3 km 2 (i.e. from 77.8% coverage of the total park area in 2003 to 38.0% in 2015) at annual rate of 79.3 km 2 ). Conversely, the other land cover types showed increasing pattern, particularly, bush land and agricultural land were increasing at a rate of 44.96 and 18.90 km 2 per year, respectively. Overall, the rate of land cover change was higher during the first period (2003 to 2009) compared with the second period (2009 to 2015) for all land use and land cover types, except grass land, suggesting that human impacts were higher following the resettlement program in 2003 and then slowed down following establishment of the park in 2007. The major causes of land cover change in the area were settlement and population expansion, cultivation, fire, mining and grazing. We suggest that better effective park protection systems should be in place to mitigate and restore habitats.
Kafta-Sheraro国家公园(KSNP)是埃塞俄比亚最重要的保护区之一，为当地人民提供了许多重要的生态和水文效益。然而，由于2003年政府发起的自愿重新安置计划导致人口迅速增加，公园面临着巨大的压力。利用2003年、2009年和2015年拍摄的卫星图像，本研究检查了整个公园在12年期间(2003年至2015年)土地利用/覆盖的变化模式，在此期间，已知人口压力随着时间的推移而增加，政府政策也发生了变化。结果表明:在12年的研究期间，林地变化最大，覆盖面积减少862.3 km2(即从2003年占公园总面积的77.8%减少到2015年的38.0%)，年减少率为79.3 km2。相反，其他土地覆被类型均呈增加趋势，其中灌木林和农用地的年增长率分别为44.96和18.90 km 2。总体而言，除草地外，所有土地利用和土地覆盖类型的土地覆被变化速率在第一期(2003 - 2009年)高于第二期(2009 - 2015年)，表明人类活动的影响在2003年实施移民安置计划后更高，在2007年建立公园后有所减缓。导致该地区土地覆被变化的主要原因是定居和人口扩张、耕作、火灾、采矿和放牧。我们建议建立更有效的公园保护系统，以减轻和恢复栖息地。
{"title":"Dynamics of Land Use and Land Cover in the Kafta-Sheraro National Park, NW Ethiopia: Patterns, Causes and Management Implications","authors":"A. Zenebe, A. Addisu","doi":"10.4314/mejs.v11i2.5","DOIUrl":"https://doi.org/10.4314/mejs.v11i2.5","url":null,"abstract":"Kafta-Sheraro National Park (KSNP) is one of the most important protected areas in Ethiopia and provides a number of important ecological and hydrological benefits to the local people. However, the park is under immense pressure as a result of a rapidly increasing human population that resulted from a voluntary resettlement program launched by the government in 2003. Using satellite imageries taken in the years 2003, 2009 and 2015, this study examined patterns of changes in land use/cover throughout the park over a 12 year period (2003 to 2015), during which human population pressure is known to have increased over time and changes in government policies were taken place. The results showed that, over the period of 12 years, wood land experienced the most changeover the study period, with a loss of cover of 862.3 km 2 (i.e. from 77.8% coverage of the total park area in 2003 to 38.0% in 2015) at annual rate of 79.3 km 2 ). Conversely, the other land cover types showed increasing pattern, particularly, bush land and agricultural land were increasing at a rate of 44.96 and 18.90 km 2 per year, respectively. Overall, the rate of land cover change was higher during the first period (2003 to 2009) compared with the second period (2009 to 2015) for all land use and land cover types, except grass land, suggesting that human impacts were higher following the resettlement program in 2003 and then slowed down following establishment of the park in 2007. The major causes of land cover change in the area were settlement and population expansion, cultivation, fire, mining and grazing. We suggest that better effective park protection systems should be in place to mitigate and restore habitats.","PeriodicalId":18948,"journal":{"name":"Momona Ethiopian Journal of Science","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2019-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.4314/mejs.v11i2.5","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47842713","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Landslides are one of the natural threats that often result in great loss of life and destruction of property in Ethiopia. One of the areas that is affected by landslides of different types and sizes is the Tarmaber district in the rift margin in the central part of Ethiopia. Keeping in view the cause and effect relationship and mitigation, Analytical Hierarchy Process (AHP) approach is used in the present case to understand the possible causes for landslides. Based on AHP, landslide susceptibility map is produced for Tarmaber using field survey data, remote sensing data, and geographic information system tools. The factors considered in the present case that can influence landslides are lithology, proximity to fault, land use, proximity to drainage, slope gradient, aspect and elevation. The results are validated with the inventory of landslide occurrences. The landslide susceptibility index (LSI) is calculated using the weighted -linear combination (WLC) technique based on the assigned weight and rating given by the AHP method. The accuracy of the results verified using the existing landslide locations is about 88.6%.The landslide susceptibility zonation map has identified our classes/zones: very high (29%), high (44%), moderate (20.0%) and low (7%). Keywords: Landslide susceptibility; Analytical Hierarchy Process (AHP); Tarmaber; Ethiopia.
{"title":"GIS-based Landslide Susceptibility Evaluation Using Analytical Hierarchy Process (AHP) Approach: The Case of Tarmaber District, Ethiopia","authors":"A. Abay, G. Barbieri, Kifle Woldearegay","doi":"10.4314/MEJS.V11I1.2","DOIUrl":"https://doi.org/10.4314/MEJS.V11I1.2","url":null,"abstract":"Landslides are one of the natural threats that often result in great loss of life and destruction of property in Ethiopia. One of the areas that is affected by landslides of different types and sizes is the Tarmaber district in the rift margin in the central part of Ethiopia. Keeping in view the cause and effect relationship and mitigation, Analytical Hierarchy Process (AHP) approach is used in the present case to understand the possible causes for landslides. Based on AHP, landslide susceptibility map is produced for Tarmaber using field survey data, remote sensing data, and geographic information system tools. The factors considered in the present case that can influence landslides are lithology, proximity to fault, land use, proximity to drainage, slope gradient, aspect and elevation. The results are validated with the inventory of landslide occurrences. The landslide susceptibility index (LSI) is calculated using the weighted -linear combination (WLC) technique based on the assigned weight and rating given by the AHP method. The accuracy of the results verified using the existing landslide locations is about 88.6%.The landslide susceptibility zonation map has identified our classes/zones: very high (29%), high (44%), moderate (20.0%) and low (7%). Keywords: Landslide susceptibility; Analytical Hierarchy Process (AHP); Tarmaber; Ethiopia.","PeriodicalId":18948,"journal":{"name":"Momona Ethiopian Journal of Science","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2019-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.4314/MEJS.V11I1.2","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42456841","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The study area, upper Bilate catchment, is strongly dependent on groundwater like other rural catchments in the country. The main objective of this work is to quantify the amount of groundwater recharge in upper Bilate catchment. Recharge was estimated using physically based distributed recharge model called WetSpass. As input to the model precipitation, potential evapotranspiration, temperature and wind speed were estimated using data collected from meteorological stations located within the catchment and nearby areas. The physical environmental data including land use, soil type, and groundwater depth were collected from field and existing maps. Slope and topography map were generated from Shuttle Radar Topographic Mission elevation data. Using the model the mean annual recharge of the catchment was found to be 9.4 % of the precipitation whereas the direct runoff was found to be 20 % of the precipitation. The study area is characterized by lower groundwater recharge relative to surface runoff due to the effect of impermeable soils, morphology of the land and land use/land cover of the study area. The western and northern parts of the area are identified as recharging zone and the central and southern part are discharge zone. The groundwater recharge zoning map was validated using base flow separation method and also compared with previous groundwater recharge works of the study area. This study revealed that the groundwater recharge estimation using WetSpass model is reasonable and useful for quantification of annual groundwater recharge with spatial and seasonal variation and also capable in the identification of groundwater recharge zones in the area under study. Keywords: Runoff; Evapotranspiration; Groundwater; WetSpass; Bilate catchment; Ethiopia.
{"title":"Groundwater Recharge Estimation Using WetSpass Modeling in Upper Bilate Catchment, Southern Ethiopia","authors":"Bitsiet Dereje, D. Nedaw","doi":"10.4314/MEJS.V11I1.3","DOIUrl":"https://doi.org/10.4314/MEJS.V11I1.3","url":null,"abstract":"The study area, upper Bilate catchment, is strongly dependent on groundwater like other rural catchments in the country. The main objective of this work is to quantify the amount of groundwater recharge in upper Bilate catchment. Recharge was estimated using physically based distributed recharge model called WetSpass. As input to the model precipitation, potential evapotranspiration, temperature and wind speed were estimated using data collected from meteorological stations located within the catchment and nearby areas. The physical environmental data including land use, soil type, and groundwater depth were collected from field and existing maps. Slope and topography map were generated from Shuttle Radar Topographic Mission elevation data. Using the model the mean annual recharge of the catchment was found to be 9.4 % of the precipitation whereas the direct runoff was found to be 20 % of the precipitation. The study area is characterized by lower groundwater recharge relative to surface runoff due to the effect of impermeable soils, morphology of the land and land use/land cover of the study area. The western and northern parts of the area are identified as recharging zone and the central and southern part are discharge zone. The groundwater recharge zoning map was validated using base flow separation method and also compared with previous groundwater recharge works of the study area. This study revealed that the groundwater recharge estimation using WetSpass model is reasonable and useful for quantification of annual groundwater recharge with spatial and seasonal variation and also capable in the identification of groundwater recharge zones in the area under study. Keywords: Runoff; Evapotranspiration; Groundwater; WetSpass; Bilate catchment; Ethiopia.","PeriodicalId":18948,"journal":{"name":"Momona Ethiopian Journal of Science","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2019-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.4314/MEJS.V11I1.3","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41311516","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Erratum : “Reduced Tillage and Intercropping as a Means to Increase Yield and Financial Return in the Drylands of Tigray, Northern Ethiopia: A Case Study Under Rainfed and Irrigation Conditions”","authors":"The Editor","doi":"10.4314/mejs.v11i1.10","DOIUrl":"https://doi.org/10.4314/mejs.v11i1.10","url":null,"abstract":"","PeriodicalId":18948,"journal":{"name":"Momona Ethiopian Journal of Science","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2019-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.4314/mejs.v11i1.10","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43984739","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Today, many developing countries are using biomass as their primary energy supply. However, this energy affects the environment, health and safety of women and children. In addition, utilization of this energy using traditional cooking stoves is causing indoor air pollution and in turn health problems to millions of people. To overcome such problems, efforts are being made by researchers globally and are suggesting alternative safe energy sources. This paper demonstrates solar cooker with an integrated PCM thermal storage and heat transportation loop system suitable for high temperature applications. The system has designed to address Injera baking application. Injera, a fermented flat bread type, is the most common food type served three to four times a day in Ethiopia. Other countries like Eritrea, Somalia, Sudan and Yemen also use this food. The storage system has storing capacity of heat up to 250 0 C and it can retain this heat for about two days. The storage has coupled to a polar mounted concentrator, fixed receiver and used steam heat transfer fluid. The steam circulates naturally between the evaporator and condenser in a closed loop. The paper focuses on indirect charging, simultaneous charging-discharging and discharging of the stored heat for the purpose of Injera baking. The frying pan is a custom-made aluminum plate casted by embedding a 10mm coiled stainless steel steam pipe as heating element. The pan is 500mm in diameter and 30mm thick; and the fins are 20mm in diameter and 140mm long. The fins have immersed into a 20kg PCM, which is coupled to a 1.8m diameter parabolic dish collector. The solar fryer demonstrates Injera baking for average family size. Baking is tested from the stored heat, while storage is charging. A fully charged storage has supplied enough heat to baked average household Injera demands about 19Injeras and additional breads with the remaining heat. Keywords: Solar Injera baking; PCM charging; PCM storage; Solar Injera stove design; Solar cooking; Ethiopia.
{"title":"Numerical and experimental Analysis of Solar Injera Baking with a PCM Heat Storage","authors":"A. Tesfay, M. Kahsay, O. Nydal","doi":"10.4314/MEJS.V11I1.1","DOIUrl":"https://doi.org/10.4314/MEJS.V11I1.1","url":null,"abstract":"Today, many developing countries are using biomass as their primary energy supply. However, this energy affects the environment, health and safety of women and children. In addition, utilization of this energy using traditional cooking stoves is causing indoor air pollution and in turn health problems to millions of people. To overcome such problems, efforts are being made by researchers globally and are suggesting alternative safe energy sources. This paper demonstrates solar cooker with an integrated PCM thermal storage and heat transportation loop system suitable for high temperature applications. The system has designed to address Injera baking application. Injera, a fermented flat bread type, is the most common food type served three to four times a day in Ethiopia. Other countries like Eritrea, Somalia, Sudan and Yemen also use this food. The storage system has storing capacity of heat up to 250 0 C and it can retain this heat for about two days. The storage has coupled to a polar mounted concentrator, fixed receiver and used steam heat transfer fluid. The steam circulates naturally between the evaporator and condenser in a closed loop. The paper focuses on indirect charging, simultaneous charging-discharging and discharging of the stored heat for the purpose of Injera baking. The frying pan is a custom-made aluminum plate casted by embedding a 10mm coiled stainless steel steam pipe as heating element. The pan is 500mm in diameter and 30mm thick; and the fins are 20mm in diameter and 140mm long. The fins have immersed into a 20kg PCM, which is coupled to a 1.8m diameter parabolic dish collector. The solar fryer demonstrates Injera baking for average family size. Baking is tested from the stored heat, while storage is charging. A fully charged storage has supplied enough heat to baked average household Injera demands about 19Injeras and additional breads with the remaining heat. Keywords: Solar Injera baking; PCM charging; PCM storage; Solar Injera stove design; Solar cooking; Ethiopia.","PeriodicalId":18948,"journal":{"name":"Momona Ethiopian Journal of Science","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2019-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.4314/MEJS.V11I1.1","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43062242","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In Ethiopia, urban floods incidents are becoming a serious problem in recent years. They are mainly associated with poorly designed urban drainage system and land use planning. Combined to it, lack of early warning system and organized flood disaster mitigation measures at national and local level further increases the gravity of the problem. Adigrat is one of the north Ethiopian towns which is frequently attacked by these floods. To understand and address the issue, a study was conducted around Adigrat town with the aim to spatially delineate the flood hazard and risk with the help of geo-spatial and multi-criteria decision analysis (MCDA) tools. Baseline maps were developed using Landsat satellite images, DEM, aerial photographs, rainfall data and census population data. Different variables like slope, elevation, rainfall, water table, flow direction and flow accumulation, LULC, population density, building density and road density were considered for developing a model. After the data is collected and organized, Erdas Imagine and ArcGIS software were used to process and prepare the model, and finally weighted overlay model was adopted to stimulate the prototype. Each baseline maps was weighted against its impact since all factors have no the same importance. Accordingly, slope, LULC, elevations; and population density, flood hazard and LULC were found the most important factors. The flood risk areas are delineated based on flood hazard, LULC, population density, road and building density. The results indicate that the Kebeles03, 04 and 05 (center of the town) with flat slopes, low altitudes, more population and significant amount of built up area are found to be the most vulnerable for flood hazard. On the other hand, the Kebeles 01, 02 and 06 lying southwest and west of the study area are least affected by flood due to steep topography and high altitudes. It is suggested that similar type of inter-disciplinary studies are essential to minimize the damages and assure sustainable urban development. Keywords: Geo-spatial; Flood hazard; Flood risk; Vulnerability mapping; Adigrat town; Ethiopia
{"title":"Flood Hazard and Flood Risk Vulnerability Mapping Using Geo-Spatial and MCDA around Adigrat, Tigray Region, Northern Ethiopia","authors":"A. Nigusse, Okubay Gidey Adhanom","doi":"10.4314/MEJS.V11I1.6","DOIUrl":"https://doi.org/10.4314/MEJS.V11I1.6","url":null,"abstract":"In Ethiopia, urban floods incidents are becoming a serious problem in recent years. They are mainly associated with poorly designed urban drainage system and land use planning. Combined to it, lack of early warning system and organized flood disaster mitigation measures at national and local level further increases the gravity of the problem. Adigrat is one of the north Ethiopian towns which is frequently attacked by these floods. To understand and address the issue, a study was conducted around Adigrat town with the aim to spatially delineate the flood hazard and risk with the help of geo-spatial and multi-criteria decision analysis (MCDA) tools. Baseline maps were developed using Landsat satellite images, DEM, aerial photographs, rainfall data and census population data. Different variables like slope, elevation, rainfall, water table, flow direction and flow accumulation, LULC, population density, building density and road density were considered for developing a model. After the data is collected and organized, Erdas Imagine and ArcGIS software were used to process and prepare the model, and finally weighted overlay model was adopted to stimulate the prototype. Each baseline maps was weighted against its impact since all factors have no the same importance. Accordingly, slope, LULC, elevations; and population density, flood hazard and LULC were found the most important factors. The flood risk areas are delineated based on flood hazard, LULC, population density, road and building density. The results indicate that the Kebeles03, 04 and 05 (center of the town) with flat slopes, low altitudes, more population and significant amount of built up area are found to be the most vulnerable for flood hazard. On the other hand, the Kebeles 01, 02 and 06 lying southwest and west of the study area are least affected by flood due to steep topography and high altitudes. It is suggested that similar type of inter-disciplinary studies are essential to minimize the damages and assure sustainable urban development. Keywords: Geo-spatial; Flood hazard; Flood risk; Vulnerability mapping; Adigrat town; Ethiopia","PeriodicalId":18948,"journal":{"name":"Momona Ethiopian Journal of Science","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2019-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.4314/MEJS.V11I1.6","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43663898","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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