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American Journal of Computational Mathematics 2014年第2期4卷 73-86页

作者： alemayehu shiferaw Ramesh Chand Mittal Department of Mathematics Indian Institute of Technology Roorkee India

In this work, by extending the method of Hockney into three dimensions, the Poisson’s equation in cylindrical coordinates system with the Dirichlet’s boundary conditions in a portion of a cylinder for is solved directly. The Poisson equation is approximated by fourth-order finite differences and the resulting large algebraic system of linear equations is treated systematically in order to get a block tri-diagonal system. The accuracy of this method is tested for some Poisson’s equations with known analytical solutions and the numerical results obtained show that the method produces accurate results.

关键词： Poisson’s Equation Tri-Diagonal Matrix Fourth-Order Finite Difference Approximation Hockney’s Method Thomas Algorithm

An Efficient Direct Method to Solve the Three Dimensional Poisson’s Equation

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American Journal of Computational Mathematics 2011年第4期1卷 285-293页

作者： alemayehu shiferaw Ramesh Chand Mittal 不详

In this work, the three dimensional Poisson’s equation in Cartesian coordinates with the Dirichlet’s boundary conditions in a cube is solved directly, by extending the method of Hockney. The Poisson equation is approximated by 19-points and 27-points fourth order finite difference approximation schemes and the resulting large algebraic system of linear equations is treated systematically in order to get a block tri-diagonal system. The efficiency of this method is tested for some Poisson’s equations with known analytical solutions and the numerical results obtained show that the method produces accurate results. It is shown that 19-point formula produces comparable results with 27-point formula, though computational efforts are more in 27-point formula.

关键词： Poisson’s Equation Finite Difference Method Tri-diagonal Matrix Hockney’s Method Thomas Algorithm

Numerical Solution of the Coupled Viscous Burgers’ Equation Using Differential Quadrature Method Based on Fourier Expansion Basis

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Applied Mathematics 2018年第7期9卷 821-835页

作者： Masho Jima alemayehu shiferaw Ali Tsegaye Department of Mathematics Jimma University Jimma Ethiopia

The differential quadrature method based on Fourier expansion basis is applied in this work to solve coupled viscous Burgers’ equation with appropriate initial and boundary conditions. In the first step for the given problem we have discretized the interval and replaced the differential equation by the Differential quadrature method based on Fourier expansion basis to obtain a system of ordinary differential equation (ODE) then we implement the numerical scheme by computer programing and perform numerical solution. Finally the validation of the present scheme is demonstrated by numerical example and compared with some existing numerical methods in literature. The method is analyzed for stability and convergence. It is found that the proposed numerical scheme produces a good result as compared to other researcher’s result and even generates a value at the nodes or mesh points that the results have not seen yet.

关键词： Differential Quadrature Method Fourier Expansion Coupled Viscous Coupled Viscous Burgers’ Equation Initial and Boundary Conditions

Fast Finite Difference Solutions of the Three Dimensional Poisson’s Equation in Cylindrical Coordinates

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American Journal of Computational Mathematics 2013年第4期3卷 356-361页

作者： alemayehu shiferaw R. C. Mittal Department of Mathematics Indian Institute of Technology Roorkee India

In this work, the three-dimensional Poisson’s equation in cylindrical coordinates system with the Dirichlet’s boundary conditions in a portion of a cylinder for is solved directly, by extending the method of Hockney. The Poisson equation is approximated by second-order finite differences and the resulting large algebraic system of linear equations is treated systematically in order to get a block tri-diagonal system. The accuracy of this method is tested for some Poisson’s equations with known analytical solutions and the numerical results obtained show that the method produces accurate results.

关键词： Poisson’s Equation Hockney’s Method Thomas Algorithm

Co-dynamics of COVID-19 and TB with COVID-19 vaccination and exogenous reinfection for TB:An optimal control application

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Infectious Disease Modelling 2023年第2期8卷 574-602页

作者： Zenebe shiferaw Kifle Legesse Lemecha Obsu Department of Mathematics Adama Science and Technology UniversityAdamaEthiopia

COVID-19 and Tuberculosis(TB)are among the major global public health problems and diseases with major socioeconomic impacts.The dynamics of these diseases are spread throughout the world with clinical similarities which makes them difficult to be mitigated.In this study,we formulate and analyze a mathematical model containing several epidemiological characteristics of the co-dynamics of COVID-19 and TB.Sufficient conditions are derived for the stability of both COVID-19 and TB sub-models equilibria.Under certain conditions,the TB sub-model could undergo the phenomenon of backward bifurcation whenever its associated reproduction number is less than one.The equilibria of the full TBCOVID-19 model are locally asymptotically stable,but not globally,due to the possible occurrence of backward bifurcation.The incorporation of exogenous reinfection into our model causes effects by allowing the occurrence of backward bifurcation for the basic reproduction number R_(0)η*).The analytical results show that reducing R_(0)<1 may not be sufficient to eliminate the disease from the community.The optimal control strategies were proposed to minimize the disease burden and related costs.The existence of optimal controls and their characterization are established using Pontryagin's Minimum Principle.Moreover,different numerical simulations of the control induced model are carried out to observe the effects of the control strategies.It reveals the usefulness of the optimization strategies in reducing COVID-19 infection and the co-infection of both diseases in the community.

关键词： COVID-19 Co-infection Exogenous reinfection Basic reproduction number Bifurcation Optimal control

Variable screening in multivariate linear regression with high-dimensional covariates

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Statistical Theory and Related Fields 2022年第3期6卷 241-253页

作者： shiferaw B.Bizuayehu Lu Li Jin Xu School of Statistics East China Normal UniversityShanghaiPeople’s Republic of China School of Mathematical Sciences Shanghai Jiao Tong UniversityShanghaiPeople’s Republic of China Key Laboratory of Advanced Theory and Application in Statistics and Data Science-MOE East China Normal UniversityShanghaiPeople’s Republic of China

We propose two variable selection methods in multivariate linear regression with highdimensional covariates.The first method uses a multiple correlation coefficient to fast reduce the dimension of the relevant predictors to a moderate or low level.The second method extends the univariate forward regression of Wang[(2009).Forward regression for ultra-high dimensional variable screening.Journal of the American Statistical Association,104(488),1512–1524.https://***/10.1198/jasa.***.tm08516]in a unified way such that the variable selection and model estimation can be obtained simultaneously.We establish the sure screening property for both methods.Simulation and real data applications are presented to show the finite sample performance of the proposed methods in comparison with some naive method.

关键词： Dimension reduction forward regression multiple correlation coefficient multivariate regression variable selection

A comparative assessment on regeneration status of indigenous woody plants in Eucalyptus grandis plantation and adjacent natural forest

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Journal of Forestry Research 2009年第1期20卷 31-36页

作者： shiferaw Alem Tadesse Woldemariam Ethiopian Institute of Agricultural Research Forestry Research Center P.O. Box 30708 Addis Ababa Ethiopia Addis Ababa University Department of Biology Education P.O.Box 1176 Addis Ababa Ethiopia

差异，密度和在桉树类下面的自然地改革的木本植物的种类作文宏大种植园和邻近的自然森林被调查并且比较。二十个阴谋，与 20 m ×的一个区域为各个的 20 m， E 在两个被建立。宏大独立地是种植园和邻近的自然森林。在每个阴谋，种类名... 详细信息

差异，密度和在桉树类下面的自然地改革的木本植物的种类作文宏大种植园和邻近的自然森林被调查并且比较。二十个阴谋，与 20 m ×的一个区域为各个的 20 m， E 在两个被建立。宏大独立地是种植园和邻近的自然森林。在每个阴谋，种类名字，丰富，直径和高度被记录。幼苗的数字在五次要情节被收集(在每个主要阴谋以内的 4 m 2) 。在种植园的 46 种类的一个总数，和自然森林里的 52 种类，它属于 36 个家庭被记录。种类(H′) 的差异在种植园是 2.19 并且 2.74 在自然森林里。密度在故事下面，木本植物在自然森林里是在种植园和 4122 stems/ha 的 3842 stems/ha。自然森林和种植园里的幼苗的密度分别地是 8101 stems/ha 和 4151 stems/ha。木质的种类作文的高类似在自然森林和种植园之间被发现。E。宏大种植园被发现比另外的在下面木质的种类以一个好一些的方法赞成 Millitia ferruginia 和 Coffea 阿拉伯咖啡的新生和生长。

关键词：自然森林自然再生种植园木质物种差异

Genetic Variation for Grain Yield and Yield Related Traits in Tef [<i>Eragrostis tef</i>(Zucc.)Trotter] under Moisture Stress and Non-Stress Environments

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American Journal of Plant Sciences 2012年第8期3卷 1041-1046页

作者： Wondewosen shiferaw alemayehu Balcha Hussen Mohammed Department of Plant and Horticultural Sciences Hawassa University Hawassa Ethiopia Jinka Agricultural Research Centre South Agricultural Research Institute Hawassa Ethiopia School of Agricultural Science Dilla University Dilla Ethiopia

Tef [Eragrostis tef (Zucc.)Trotter] is an ancient and major cereal crop in Ethiopia. Increasing tef grain yield partly requires developing cultivars that are adapted to drought stress environment. An experiment was carried out using 18 tef genotypes grown during September to December, 2010, under two water supply environments (stress during grain filling period, and non-stress) to identify genetic variation, heritability and correlations of grain yield and yield related traits. Broad-sense heritability values under respective stress and non-stress environments were grain yield (g/m2) 0.80 and 0.89, total biomass (g/m2) 0.89 and 0.73, harvest index 0.69 and 0.79, panicle weight (g/plant) 0.93 and 0.92, and seed weight (g/plant) 0.96 and 0.86. The correlations of grain yield under respective stress and non-stress environments were total biomass rp = 0.64, rg = 0.70, and rp = 0.48, rg = 0.56, harvest index rp = 0.70, rg = 0.64, and rp = 0.87, rg = 0.90, panicle weight rp = 0.98, rg = 1.00, and rp = 0.96, rg = 1.00, and seed weight/plant rp = 0.98, rg = 1.00, and rp = 0.90, rg = 1.00. The present experiment showed that either grain yield per se, or seed weight/plant could be used to improve grain yield under stress and non-stress environments.

关键词： Variability Broad-Sense Heritability Correlations Moisture Stress Eragrostis tef

Optimizing Tax Services to Improve the Business Environment in Ethiopia

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Belt and Road Initiative Tax Journal 2023年第1期4卷 71-74页

作者： Yoseph shiferaw Hundessa Revenues Federal Democratic Republic of Ethiopia

This article sets out framework for measures which have been taken by the Government of Ethiopia to optimize tax services in Ethiopia.A set of measures among others which potentially influence taxpayer services such as legislation changes,information technology modernization,introducing compliance risk management and standard taxpayers’services are explicitly discussed.

关键词： Tax service Business environment Fiscal incentive Tax transformation

Malaria helminth co-infections and their contribution for aneamia in febrile patients attending Azzezo health center,Gondar,Northwest Ethiopia:a cross sectional study

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Asian Pacific Journal of Tropical Medicine 2012年第10期5卷 803-809页

作者： Abebe Alemu Yitayal shiferaw Aklilu Ambachew Halima Hamid School of Biomedical and Laboratory Sciences.College of Medicine and Health Sciences University of GondarGondarEthiopia

Objective:To assess the prevalence of malaria helminth co-infections and their contribution for aneamia in febrile patients attending Azzezo health center,Gondar,Northwest Ethiopia. Methods:A cross section study was conducted among febrile patients attending Azezo health center from February-March 30,2011.Convenient sampling technique was used to select 384 individuals.Both capillary blood and stool were collected.Giemsa stained thick and thin blood film were prepared for identification of Plasmodium species and stool sample was examined by direct wet mount and formalin-ether concentration technique for detection of intestinal helminthes parasites.Haemoglobin concentration was determined using a portable haemoglobin spectrophotometer,Hemocue Hb 201 analyzer.Results:Out of 384 febrile patients examined for malaria parasites,44(11.5%) individuals were positive for malaria parasites,of which Plasmodium vivax accounted for 75.0%(33),Plasmodium falciparum for 20.5%(9| infectious,whereas two person (4.5%) had mixed species infection.Prevalence of malaria was higher in males(28) when compared with prevalence in females(16).More than half(207,53.9%) of study participants had one or more infection.Prevalence was slightly higher in females(109,52.7%) than in males(98,47.3%).About helminths,Ascaris lumbricoides was the predominant isolate(62.1%) followed by hookworms(18.4%). Only 22 participants were co-infected with malaria parasite and helminths and co-infection with Ascaris lumbricoides was predominant(45.0%).The prevalence of anemia was 10.9%and co-infection with Plasmodium and helminth parasites was significantly associated with(P<0.000 1) higher aneamia prevalence compared to individuals without any infection.Conclusions: Prevalence of malaria and soil transmitted helminths is high and the disease is still major health problem in the study area.Hence,simultaneous combat against the two parasitic infections is very crucial to improve health of the affected communities in economically developing countries.

关键词： Malaria Helminth Aneamia Febrile