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Numerical Simulation of Unsteady Friction in Transient Two-Phase Flow with Godunov Method

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Journal of Water Resource and Protection 2013年第11期5卷 1048-1058页

作者： samba Bousso Musandji Fuamba Department of CGME Polytechnique Montreal Succursale Centre Ville Montréal Canada Department of Civil Geological and Mining Engineering (CGME) Polytechnique Montreal Succursale Centre Ville Montréal Canada

Most numerical transient flow models that consider dynamic friction employ a finite differences approach or the method of characteristics. These models assume a single fluid (water only) with constant density and pressure wave velocity. But when transient flow modeling attempts to integrate the presence of air, which produces a variable density and pressure-wave velocity, the resolution scheme becomes increasingly complex. Techniques such as finite volumes are often used to improve the quality of results because of their conservative form. This paper focuses on a resolution technique for unsteady friction using the Godunov approach in a finite volume method employing single-equivalent twophase flow equations. The unsteady friction component is determined by taking into account local and convective instantaneous accelerations and the sign of both convective acceleration and velocity values. The approach is used to reproduce a set of transient flow experiments reported in the literature, and good agreement between simulated and experimental results is found.

关键词： Finite Volume Godunov Method Transient Flow Two Phase Flow Unsteady Friction

Minimum and Maximum Temperature Trends in Congo-Brazzaville: 1932-2010

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Atmospheric and Climate Sciences 2014年第3期4卷 404-430页

作者： Gaston samba Dominique Nganga Centre de Recherches et d’études sur l’Environnement (CR2E) Université Marien Ngouabi Brazzaville République du Congo

Maximum and minimum temperatures time series of Congo-Brazzaville are analyzed for trend and discontinuities over the period 1932 to 2010. Temperatures series show an irregular increase. A total of 8 synoptic stations show positive trends in their annual mean maximum temperature series, and 7 of them are significant, with higher trends for urban stations. Annual mean minimum temperature showed 6 stations having positive trends. This increase is in relation with observations at regional scale. However, the differences are observed between large towns (Brazzaville and Pointe-Noire), and small or rural towns (Dolisie, Sibiti, Impfondo, Djambala). Trends in diurnal temperature range (DTR) are large positive trends in maximum temperature that are mainly observed in cities. The curve of DTR shows a decreasing trend which indicates the increasing of minimum temperatures. The effects of urbanization on temperature trends are investigated. Most stations regarded as urban stations are still useful for trend analysis;being situated on the suburban of the studied cities, they are therefore, not substantially influenced by the urban heat island.

关键词： Congo Republic Temperatures Maximum and Minimum Temperature Trends

Adaptation of Root Crop Farming System to Climate Change in Ikwerre Local Government Area of Rivers State, Nigeria

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American Journal of Climate Change 2017年第1期6卷 40-51页

作者： Vincent Ezikornwor Weli samba Bajie Department of Geography and Environmental Management Faculty of Social Sciences University of Port Harcourt Port Harcourt Nigeria Deputy Ombudsman Banjul Gambia

This study examined adaptation of root crop farming system to climate change in Ikwerre Local Government Area of Rivers state, Nigeria. Seven towns were selected based on a population of five thousand and above from which one hundred and ninety-one respondents were randomly chosen. Sixty-six years’ data on climatic variables of rainfall, temperature and relative humidity were obtained from Nigeria Meteorological Agency between 1950-2015. Analyses were carried out using simple proportion for qualitative variables while mean and standard deviation were used in analyzing the qualitative variable. Similarly, the triangulation method involving qualitative and quantitative components in data generation was used. Results showed that, there had been a steady but gradual increase in the mean annual minimum and maximum temperatures over the study period of thirty years. The overall mean rainfall computed was 191.1 mm. In general, there was a shift increase in both rainfall and temperature during the period under study. The respondents attributed crop failure (100%), reduced crop yield (100%), increase incidence of pest and diseases (100%) and delay in planting period (100%) as direct effects of climate change. A steady trend in relative humidity of (84.3%) was recorded and the mean annual wind speed computed was 67.9 knots. The adapted strategies include delay planting period, crop diversification 100%, cultivation of early maturing crops such as maize, vegetables, intercropped with the root crops and changes in the time of farm operations (99.4%) as well as a change in the planting period and changing farm location (98.9%). The latter will in addition to other benefits reduce the incidences of pest and diseases that may be attracted to the same field if continuously cultivated with the same crops. An implementable policy of accessibility of finance to the real farmers is seriously advocated.

关键词： Root Crop Climate Change Adaptation Farming System and Crop Failure

Analysis of Water Pipeline Breaks

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World Journal of Engineering and Technology 2016年第2期4卷 220-227页

作者： Chris samba Malick Baldeh Kenneth Tuffour Facility Solution Technology Inc. BaKau Gambia

This study explores the arrivals of water pipeline break failures. The aim is to assist the facility manager in the decision making process. Based on characteristics of the data set ranging from 2011 to 2014, two steps of analysis were presented in the paper. This first step is the analysis of partially complete data set (2011 data). The 2-sample KS test is adopted to check the similarity between this data set and the entire data set with no underlying distribution implied. In order to conduct the reliability analysis, the Weibull distribution is adopted to evaluate the data. For annual data set, the 2-parameter Weibull distribution fits data sets pretty well. The shape parameters are a little greater than 1, indicating a slightly increasing arrival rate of such failures. For the entire data set, the 3-parameter Weibull tends to fit the data better than the 2-parameter Weibull. The shape parameter is well above 1, indicating an increasing arrival rate of the failures. To eliminate the impact of missing points for the 2011 data set, data from 2012 to 2014 were also considered as a new set, the Weibull distribution generated a decent fitting. The shape parameter is a little greater than 1. Therefore, there is a slightly increasing arrival rate of those pipeline failures. Results from this study provide decision makers valuable information in terms of whether additional efforts shall be made to enhance the system’s performance in order to reduce the failure rate.

关键词： Water Pipeline Break 2-Sample KS Test Reliability Analysis Weibull Distribution Shape Parameter

Impact of Living Donor Liver Transplantation on COVID-19 Clinical Outcomes from a Quaternary Care Centre in Delhi

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Journal of Clinical and Translational Hepatology 2022年第4期10卷 770-777页

作者： Imtiakum Jamir Niteen Kumar Gaurav Sood Ashish George Pankaj Lohia samba Siva Rao Pasupuleti Amrish Sahney Manav Wadhawan Ajay Kumar Abhideep Chaudhary Department of HPB Surgery and Liver Transplantation BLK Super Speciality HospitalNew DelhiIndia Department of Critical Care BLK Super Speciality HospitalNew DelhiIndia Department of Statistics Mizoram University(A Central University)Pachhunga University College CampusAizawlMizoramIndia Institute of Digestive and Liver Diseases BLK Super Speciality HospitalNew DelhiIndia

Background and Aims:The anticipated fear of serious out-comes in coronavirus infected liver transplant recipients led to disruption of transplant services *** aim of our study was to analyze COVID-19 severity in transplant recipients and to compare the difference of COVID-19 clinical outcomes in early(1 year)post-transplant ***:41 post-living donor liver transplant recipients with COVID-19 infection were studied retrospectively from 1st April 2020 to 28th February ***:The median age was 49.00 years with a male preponderance(80.49%).Fif-teen patients had infection within 1 year of transplant and 26 were infected after 1 year of *** overall median interval between transplantation and COVID-19 diagnosis was 816.00 *** and malaise were the common presenting *** most common associated comorbidities were diabetes mellitus(65.85%)and hypertension(46.34%).The severity of illness was mild in 28(68.29%),moderate in 4(9.76%),severe in 6(14.63%)and critical in 3(7.32%).To identify associated risk factors,we divided our patients into less severe and more severe *** for lymphopenia,there was no worsening of total bilirubin,transaminases,al-kaline phosphatase,and gamma-glutamyl transferase in the more severe ***(19.51%)patients required inten-sive care unit admission and three(7.32%)died,while none suffered graft *** recipients with early *** post-transplant COVID-19 infection,there were similar outcomes in terms of severity of COVID-19 illness,intensive care unit care need,requirement of respiratory support,and ***:Living donor liver transplantation can be per-formed during the COVID-19 pandemic without the fear of poor recipient outcome in cases of unfortunate contraction of severe acute respiratory syndrome coronavirus-2.

关键词： COVID-19 SARS-CoV-2 Living donor liver transplantation,LDLT Mortality Perioperative

The Influence of Climate Factors on the Stability of Infrastructures: Case of Forest Ecosystem in Southern Cameroon

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International Journal of Geosciences 2015年第12期6卷 1317-1322页

作者： Philemon Zo’o Zame Philippe samba Assomo University of Yaounde I Yaoundé Cameroon

The southern forest ecosystem of Cameroon extends from latitude 2° to 6°N and from 10° to 16°E. In order to investigate about the influence of climate factors on the infrastructures, the main parameters of local climate of that ecosystem have been evaluated. The results show that, the factors are stable and have a common trend. But, the abundance of precipitations;the important hydrographic network and the presence of dense forest appear as the majors climatic constraints that may be taken in account to ensure the stability of the infrastructures in forest ecosystem.

关键词： Forest Ecosystem Climate Factors Stability Infrastructures Cameroon

塞拉利昂内战（1991-2002）对西非国家经济共同体（ECOWAS）的影响

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塞拉利昂内战（1991-2002）对西非国家经济共同体（ECOWAS）的影响

作者： SHEBORA samba KAMARA 吉林大学

学位级别：硕士

本文标题为“塞拉利昂内战(1991-2002)对西非国家经济共同体(ECOWAS)的影响”。本文试图探索单个成员国的情况如何影响洲际组织的发展。1991年至2002年发生的塞拉利昂内战影响到了西非国家经济共同体(ECOWAS)的进一步发展。本文所研究... 详细信息

本文标题为“塞拉利昂内战(1991-2002)对西非国家经济共同体(ECOWAS)的影响”。本文试图探索单个成员国的情况如何影响洲际组织的发展。1991年至2002年发生的塞拉利昂内战影响到了西非国家经济共同体(ECOWAS)的进一步发展。本文所研究的西非国家经济共同体包括建立机构以及在组织内建立体制框架等多个方面,这将有利于推动地区协调,进而推动实现该地区经济一体化的重要发展目标。正是该组织的快速发展吸引力一系列机构的加入才使其拥有了现在的规模。本文优先探讨了1999年通过的安全架构指导议定书,因为它所表现出的内涵与塞拉利昂内战的经验息息相关。考虑到冲突的性质以及塞拉利昂是西非国家经济共同体成员国这一事实,塞拉利昂的内部冲突是西非国家经济共同体关注重点关注的问题。本文的论点是:国家间组织的成员国,特别是像塞拉利昂这样出现具有破坏性的内部冲突的成员国,可能会改变或至少扩大国家间组织的功能和作用。这种情况下,在西非国家经济共同体中纳入或采用安全协议便为这种观点提供了证据,因为在这之前,该组织的运作中并没有明确定义的安全协议。塞拉利昂是非洲西海岸一个人口约7000000的国家。这个国家灾难频发,包括内战、山体滑坡、埃博拉病毒等多种类型。所有的这些情况都令其它国家和国际组织,特别是塞拉利昂参与的洲际组织感到不安,所以这些组织别无选择,只能在必要时进行干预。但在所有这些努力中,西非国家经济共同体因为在内战中的起到的作用而得到人们最高的认可。塞拉利昂内战始于1991年,共持续了11年,直到2002年正式宣布结束。内战带来的结果是毁灭性的,并且极难由地方当局自行解决。西非国家经济共同体(ECOWAS)成立于1975年,旨在加强西非各国之间的经济融合,塞拉利昂在内战种及内战结束后得到了多个国家和国际组织的帮助,包括西非国家经济共同体中的成员国。尽管西非国家经济共同体在结束冲突方面发挥了作用,但战争也通过激发组织的安全性对组织的运作产生了影响。本文的理论框架侧重于分析跨国体系、战争与和平、制度化、全球化与国际关系理论,本文着眼于对上述国际关系理论进行更广泛的解释,探讨学者特别是现实主义和自由主义学者在该领域所持有的看法,从而在两大理论之间建立联系。在这种情况下对国家、跨国组织与战争、制度化及国际关系理论的政治解释进行研究,以具体探讨西非国家经济共同体安全框架的实体化及其与塞拉利昂之间内战的联系。然而由于这是对这一主题研究的一种新方法,所以相关的文献比较有限,因此本文的文献综述主要围绕两个关键变量:(i)战争与国家间组织;(ii)西非国家经济共同体功能范围的扩大以及在塞拉利昂内战中发挥的作用。本文在收集和分析数据时遵循过程追踪方法,这将有助于产生有用的数据和令人满意的结果。这项研究的主要发现是,“在西非国家经济共同体范围内通过安全议程的进程,受到了塞拉利昂内战的影响”。塞拉利昂内战属于区域问题,它对西非国家经济共同体的行动产生了巨大影响,特别是在增加部队维持稳定以及在西非国家经济共同体的运作中建立安全架构方面。因此,内战给我们的启示之一就是应该改变或扩大洲际组织的范围。同时,它也启示我们国家仍然是现实主义者认为的国际关系中最重要的角色,但不同于自由主义者的观点,国际组织也非常重要,任何国家都不能将自己与其他国家隔离开来。直到现在塞拉利昂仍然很感谢西非国家经济共同体作为对于内战的成功干预,这也进一步证实,在涉及国家、国际组织和战争时,现实主义和自由主义者的观念存在着共同点。本文的结论是,塞拉利昂的内战是一个重要的事件,它实际上推动了西非国家经济共同体功能范围的扩大。在战争之前,西非国家经济共同体并没有制定完善的安全议程,但在1999年战争的最后阶段,这一议定书被采纳并且已经制度化。这并不是巧合,它反映的是这样一种机制对维持国家经济利益的重要性,因为战争证明缺乏安全保障可能会破坏地区组织的长远利益。

关键词：国家间组织西非国家经济共同体内战功能范围

Linear and Nonlinear Stokes Waves Theory: Numerical Hydrodynamic and Energy Studies

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Open Journal of Fluid Dynamics 2023年第1期13卷 61-79页

作者： Alpha Malick Ndiaye Fadel Diop samba Dia Cheikh Mbow Laboratoire de Mécanique des Fluides et Transferts Département de Physique Faculté des Sciences et Techniques Université Cheikh Anta Diop (UCAD) Dakar Sénégal

The increase of wave energy in electricity production is an objective shared by many countries to meet growing demand and global warming. To analyze devices capable of converting the energy of sea waves into electrical energy, it is important to master the various theories of gravity waves and generation. We will in our work consider a numerical waves tank for an amplitude A=0.5, a wavelength λ=0.25 , an average height He=10 and a Froude number fixed at 1 × 105. Numerical wave channel analysis is used to reproduce the natural phenomenon of wave propagation in an experimental model. Wave makers are usually used to generate waves in the channel. In theory, the influence of an incident wave can be considered, as in the case of our study. In this study, the evolution of the hydrodynamic parameters and the energy transported in one wavelength can be determined by calculation. A change of variable will be done in this work to facilitate the writing of the boundary conditions at the free surface and at the bottom. The nonlinear Stokes theory will be studied in this case in order to provide hydrodynamic solutions through the Navier-Stokes equations to finally deduce the energetic results. To do this, the finite difference method will be used for the hydrodynamic results such as the velocity potential and the free surface elevation and the trapezium method of Newton for the energetic results. Thus, we will determine the energetic potential according to the decrease in the slope of the tank. To do this, we will take as values of beta representing the inverse of the slope of the tank, β=100, β=105, β=110 and β=105. .

关键词： Waves Tank Energy Waves Gravity Waves Navier-Stokes Numerical Nonlinear Stokes Theory

Poisson Process and Its Application to the Storm Water Overflows

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Computational Water, Energy, and Environmental Engineering 2016年第2期5卷 47-53页

作者： Malick Baldeh Chris samba Kenneth Tuffour Assane Boya Facility Solution Technology Inc. Bakau The Gambia Gaston Berger University Saint-Louis Senegal

The homogenous Poisson process is often used to describe the event arrivals. Such Poisson process has been applied in various areas. This study focuses on the arrival pattern of storm water overflows. A set of overflow data was obtained from the storm water pipeline of a municipality. The aim is to verify the overflow arrival pattern and check whether the Poisson process can be applied. The adopted method is the analysis over the inter-arrival times. The exponential distribution test is conducted on the annual data set as well as the entire data set. The results show that all data sets follow the exponential distribution. With the verification of Poisson process, specific examples are also given to show how the Poisson process properties can be used in the management of storm water pipeline management. For other data that are featured with various heterogeneities, the homogenous Poisson process might not be able to be verified and used. Under such circumstances, non-homogenous survival model can be used to simulate the arrival process.

关键词： Storm Water Overflow Poisson Process Exponential Distribution Weibull Distribution