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作者： GAJI AMEENA abba（阿米娜）中国石油大学(北京)

学位级别：硕士

Severe slugging is a transient and unsteady flow regime that occurs in offshore flowlines-riser production systems,most prevalently on aged oil fields which are proned to heavier oil deposits,low flow rates and the peculiar nature of the unevenness of the seabed *** phenomenon is characterized with pressure fluctuations and instabilities of the flow *** behaviour of this flow regime poses a threat on the structural integrity,reliability and safety of the offshore production facilities due to its fatigue loading behaviour and damage of the material *** researchers in China and abroad have made contributions towards describing the dynamic behavior of pipeline-riser structures induced by severe slug ***,due to the complicated nature of severe slugging,no study has fully understood the dynamic behavior of steel lazy-wave risers induced by a full-staged severe slug flow which this research draws its originality *** is therefore in the interest of the offshore oil and gas industry to improve and optimize the fatigue design of deepwater riser structures by including the fatigue loads from severe *** study presents the numerical modelling and simulation of the interaction between the full-staged severe slug flow and the dynamic behavior and stress impact of a steel lazy-wave *** fluid analysis,structural analysis and the FSI coupling were carried out using FLUENT,ABAQUS and Mp CCI software programs,*** two-phase flow system is modelled with a comingling flow of water and air with liquid and gas velocities of 0.382m/s and 1.37m/s *** 2D steel lazy-wave riser was modelled with material properties of API Grade X-65 steel with an inner diameter of 0.05 m,outer diameter of 0.075 m,pipe length of 1.8m and a pipe inclination of-5 *** uniform meshes with wall refinement were used to generate15,599 mesh elements for the fluid *** volume of fluid(VOF)model,kepsilon turbulence

关键词： Severe slugging steel flexible riser fluid-structure interaction Abaqus MpCCI

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Antimotility effects of extracts and fractions of Eastern Nigeria mistletoe(Loranthus micranthus Linn)

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Asian Pacific Journal of Tropical Medicine 2012年第7期5卷 556-560页

作者： Patience O Osadebe Chika C abba Matthias O Agbo Department of Pharmaceutical and Medicinal Chemistry University of NigeriaNsukkaEnugu StateNigeria

Objective:To evaluate the antimotility activity of Eastern Nigerian mistletoe[Loranthus micranthus（***） Linn]parasitic on six different host trees *** nitida,Persia americana,Kola accuminata,Irvingia gabonensis,Citrus simensis and Pentacletra macrophylla （***）.Methods:The antimotility of the methanol extracts and solvent fractions were evaluated in castor oil induced diarrheoa in ***:The methanol extracts（200 mg/kg, i.p.） inhibited defeacation significantly（P 5 exhibited inhibitory activity which was comparable to loperamide（73.3%）. Conclusions:The methanol extract of L micranthus parasitic on *** exhibits higher antimotility activity that other *** solvent fractions could serve as source of novel antimotility agents.

关键词： Loranthus micranthus Fractination Gastrointestinal transit Atropine

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Modeling the impact of quarantine during an outbreak of Ebola virus disease

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Infectious Disease Modelling 2019年第1期4卷 12-27页

作者： Attila Dénes abba B.Gumel Bolyai Institute University of SzegedAradi vertanúk tere 1.Szeged H-6720Hungary School of Mathematical and Statistical Sciences Arizona State UniversityTempeAZ 85287-1804USA Other affliation:Department of Mathematics and Applied Mathematics University of PretoriaPretoria 0002South Africa

The quarantine of people suspected of being exposed to an infectious agent is one of the most basic public health measure that has historically been used to combat the spread of communicable diseases in human *** study presents a new deterministic model for assessing the population-level impact of the quarantine of individuals suspected of being exposed to disease on the spread of the 2014e2015 outbreaks of Ebola viral *** is assumed that quarantine is imperfect(i.e.,individuals can acquire infection during quarantine).In the absence of quarantine,the model is shown to exhibit global dynamics with respect to the disease-free and its unique endemic equilibrium when a certain epidemiological threshold(denoted byR 0)is either less than or greater than ***,unlike the full model with imperfect quarantine(which is known to exhibit the phenomenon of backward bifurcation),the version of the model with no quarantine does not undergo a backward *** data relevant to the 2014e2015 Ebola transmission dynamics in the three West African countries(Guinea,Liberia and Sierra Leone),uncertainty analysis of the model show that,although the current level and effectiveness of quarantine can lead to significant reduction in disease burden,they fail to bring the associated quarantine reproduction number(R Q0)to a value less than unity(which is needed to make effective disease control or elimination feasible).This reduction of R Q0 is,however,very possible with a modest increase in quarantine rate and *** is further shown,via sensitivity analysis,that the parameters related to the effectiveness of quarantine(namely the parameter associated with the reduction in infectiousness of infected quarantined individuals and the contact rate during quarantine)are the main drivers of the disease transmission ***,this study shows that the singular implementation of a quarantine intervention strategy can lead to the effective control or

关键词： Ebola virus disease Quarantine Global dynamics

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Evaluation of p53 codon 72 polymorphism in adenocarcinomas of the colon and rectum in La Plata, Argentina

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World Journal of Gastroenterology 2006年第9期12卷 1426-1429页

作者： Luis Orlando Pérez Martin Carlos abba Fernando Noel Dulout Carlos Daniel Golijow Centro de Investigaciones en Genética Básica y Aplicada Facultad de Ciencias Veterinarias Universidad Nacional de La PlataCalle 60 y 118 S/NB 1900 AVWLa PlataArgentina

AIM： To evaluate the potential association between p53 codon 72 polymorphism and sporadic colorectal adenocarcinoma development, and human papillornavirus （HPV） infection. METHODS： One-hundred and nine controls and 53 patients with colon cancer from the city of La Plata, Argentina were analyzed, p53 codon 72 genotypes and HPV infection were identified using allele-specific polymerase chain reaction and nested polymerase chain reaction, respectively. RESULTS： The differences in the distribution ofp53 codon 72 polymorphisrn between the cases and controls were statistically significant. The arginine allele had a prevalence of 0.65 in controls and 0.77 in cases. The corresponding odds ratio for the homozygous arginine genotype was 2.08 （95% CI, 1.06-4.05; P〈0.05）. Lack of association was found between ,053 polymorphism and HPV infection in the set of adenocarcinomas. CONCLUSION： The findings of the present study indicate that p53 codon 72 arginine homozygous genotype may represent a genetic predisposing factor for colon cancer development. However, further studies are needed in order to elucidate the role of p53 codon 72 polymorphism in colorectal cancer.

关键词： p53 codon 72 polymorphism Human papillomavirus, Colorectal cancer

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The Impact of Oil Exportation on Economic Growth in Nigeria 2000-2016

The Impact of Oil Exportation on Economic Growth in Nigeria ...

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作者： Souleymane abba K Nafissatou 浙江工商大学

学位级别：硕士

The main objective of this paper is to study and measure the impact of oil exportation on economic growth in Nigeria by using advancement model multiple regression model to check the relationship between the oil export of Nigeria and Nigeria GDP using annual data covering the years 2000-2016,the source of the data is the Central Bank of Nigeria（CBN）and world bank *** research focuses on the impacts of oil exports on the economic growth in *** one of the most developing countries in Africa,Nigeria GDP is mainly based on the export of oil and *** addition,the research are applied to test the hypothesis of economic growth strategy led by *** research is based on the following hypothesis to test the correlation between the variable there is positive effects of oil exportation to RGDP in Nigeria,There is a decrease of RGDP when oil exportation in mediate by inflation,there are a short run or long run relationship between RGDP and oil exportation,A granger causality exists between RGDP and the independent ***,this research aims at studying the impact of oil export on ***,the relationship of oil export for Nigeria is a major *** the research tried to find out the extent and importance of oil exports on the trade,investment,*** achieving this research,there will be an attempt to investigate the positive and negative influence of oil exports in Nigeria in terms on economic sustainability and ***,in views of this,we tried to research on how oil exports sector have contributed to economic growth in Nigeria *** can be concluded that oil industry in Nigeria has an positive and important role on the GDP in *** economy globally depends on this sector with 16%of the total *** industry is playing a significant part in progress of the *** is the basic revenue sources of Nigeria *** government has taken advantage from opportunities produced by increa

关键词： Oil export Economic growth RGDP multiple regressionmodel

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Mathematical analysis of a model for zoonotic visceral leishmaniasis

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Infectious Disease Modelling 2017年第4期2卷 455-474页

作者： Nafiu Hussaini Kamaldeen Okuneye abba B.Gumel Department of Mathematical Sciences Bayero University KanoP.M.B.3011KanoNigeria School of Mathematical and Statistical Sciences Arizona State UniversityTempeAZ 85287USA

Zoonotic visceral leishmaniasis(ZVL),caused by the protozoan parasite Leishmania infantum and transmitted to humans and reservoirhosts by female sandflies,is endemic inmany parts of the world(notably in Africa,Asia and the Mediterranean).This study presents a new mathematical model for assessing the transmission dynamics of ZVL in human and non-human animal reservoir *** model undergoes the usual phenomenon of backward bifurcation exhibited by similar vector-borne disease transmission *** the absence of such phenomenon(which is shown to arise due to the disease-induced mortality in the host populations),the nontrivial disease-free equilibrium of the model is shown to be globallyasymptotically stable when the associated reproduction number of the model is less than *** case and demographic data relevant to ZVL dynamics in Arac atubamunicipality of Brazil,it is shown,for the default case when systemic insecticide-based drugs are not used to treat infected reservoir hosts,that the associated reproduction number of the model (ℛ0) ranges from 0.3 to 1.4,with a mean of ℛ0=0:***,when the effect of such drug treatment is explicitly incorporated in the model(i.e.,accounting for the additional larval and sandfly mortality,following feeding on the treated reservoirs),the range ofℛ0 decreases toℛ02∈[0.1,0.6],with a mean ofℛ0=0:35(this significantly increases the prospect of the effective control or eliminationof the disease).Thus,ZVL transmissionmodels(in communities where such treatment strategy is implemented)that do not explicitly incorporate the effect of such treatmentmay be over-estimating the disease burden(asmeasured in terms ofℛ0)in the *** is shown thatℛ0 ismore sensitive to increases in sandflylifespanthan thatof the animal reservoir(so,a strategy that focuses on reducing sandflies,rather than the animal reservoir(e.g.,via culling),may be more effective in reducing ZVL burden in the community).Further sensitivity analysi

关键词： Leishmania infantum Zoonotic visceral leishmaniasis(ZVL) Reproduction number Stability Backward bifurcation

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Will vaccine-derived protective immunity curtail COVID-19 variants in the US?

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Infectious Disease Modelling 2021年第1期6卷 1110-1134页

作者： Marina Mancuso Steffen E.Eikenberry abba B.Gumel Arizona State University School of Mathematical and Statistical SciencesTempeAZ85287USA Department of Mathematics and Applied Mathematics University of PretoriaPretoria0002South Africa

Multiple effective vaccines are currently being deployed to combat the COVID-19 pandemic,and are viewed as the major factor in marked reductions of disease burden in regions with moderate to high vaccination *** effectiveness of COVID-19 vaccination programs is,however,significantly threatened by the emergence of new SARS-COV-2 variants that,in addition to being more transmissible than the wild-type(original)strain,may at least partially evade existing vaccines.A two-strain(one wildtype,one variant)and two-group(vaccinated or otherwise)mechanistic mathematical model is designed and used to assess the impact of the vaccine-induced cross-protective efficacy on the spread the COVID-19 pandemic in the United *** analysis of the model shows that,in the absence of any co-circulating SARS-CoV-2 variant,the vaccine-derived herd immunity threshold needed to eliminate the wild-type strain can be achieved if 59%of the US population is fully-vaccinated with either the Pfizer or Moderna *** threshold increases to 76%if the wild-type strain is co-circulating with the Alpha variant(a SARS-CoV-2 variant that is 56%more transmissible than the wild-type strain).If the wild-type strain is co-circulating with the Delta variant(which is estimated to be 100%more transmissible than the wild-type strain),up to 82%of the US population needs to be vaccinated with either of the aforementioned vaccines to achieve the vaccine-derived herd *** sensitivity analysis of the model reveal the following four parameters as the most influential in driving the value of the reproduction number of the variant strain(hence,COVID-19 dynamics)in the US:(a)the infectiousness of the co-circulating SARS-CoV-2 variant,(b)the proportion of individuals fully vaccinated(using Pfizer or Moderna vaccine)against the wild-type strain,(c)the cross-protective efficacy the vaccines offer against the variant strain and(d)the modification parameter accounting for the reduced infectio

关键词： COVID-19 Vaccine Wild-type Variant Reproduction number Herd immunity

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Petrogenesis and Tectonic Implications of Peralkaline A-Type Granites and Syenites from the Suizhou-Zaoyang Region,Central China

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Journal of Earth Science 2018年第5期29卷 1181-1202页

作者： Hafizullah abba Ahmed Changqian Ma Lianxun Wang Ladislav A.Palinkas Musa Bala Girei Yuxiang Zhu Mukhtar Habib State Key Laboratory of Geological Processes and Mineral Resources School of Earth SciencesChina University of GeosciencesWuhan 430074China Department of Geology Modibbo Adama University of TechnologyYola P.M.B.2076Nigeria Institute of Mineralogy and Petrology Faculty of SciencesUniversity of ZagrebZagreb HR-10000Croatia Department of Geology Faculty of Earth and Environmental SciencesBayero UniversityKanoNigeria Department of Mineral and Petroleum Resources Engineering Kaduna PolytechnicKadunaNigeria

In this study, we present systematic petrological, geochemical, LA-ICP-MS zircon U-Pb ages and Nd isotopic data for the A-type granites and syenites from Suizhou-Zaoyang region. The results show that the peralkaline A-type granites and syenites were episodically emplaced in Suizhou-Zaoyang region between 450±3 and 441±7 Ma which corresponds to Late Ordovician and Early Silurian periods, respectively. Petrologically, the syenite-peralkaline granite association comprises of nephefine normative-syenite and alkaline granite in Guanzishan and quartz normative syenite and alkafine granite in Huangyangshan. The syenite-granite associations are ferroan to alkali in composition. They depict characteristics of typical OIB （oceanic island basalts） derived A-type granites in multi-elements primitive normalized diagram and Ybffa vs. Y/Nb as well as Ce/Nb vs. Y/Nb binary plots. Significant depletion in Ba, Sr, P, Ti and Eu indicates fractionation of feldspars, biotite, amphiboles and Ti-rich augite. The values of eNd（t） in Guanzishan nepheline syenite and alkaline granite are ＋1.81 and ＋2.26, respectively and the calculated two-stage model age for these rocks are 1 040 and 1 003 Ma, respectively. On the other hand, the Huangyangshan alkaline granite has eNd（t） values ranging from ＋2.61 to ＋3.46 and a relatively younger two-stage Nd model age values ranging from 906 to 975 Ma, respectively. Based on these data, we inferred that the Guanzishan nepheline syenites and granites were formed from fractional crystallization of OIB-like basic magmas derived from upweliing of metasomatized lithospheric mantle. The Huangyangshan quartz syenite and granite on the other hand, were formed from similar magmas through fractional crystallization with low input from the ancient crustal rocks. Typically, the rocks exhibit Al-type granite affinity and classified as within plate granites associated with the Ordovician crustal extension and the Silurian rifting.

关键词： Huangyangshan Guanzishan OIB derived A-type granites nepheline syenite alkaline granite South Qinling Suizhou-Zaoyang region.

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A construction of authentication codes with arbitration based on orthogonal spaces

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Journal of Harbin Institute of Technology(New Series) 2006年第2期13卷 134-140页

作者： BOUBACAR abba 游宏 Dept. of Mathematics Harbin Institute of Technology Harbin 150001 China

In this paper we give a new construction of authentication codes with arbitration using orthogonal spaces. Some parameters and the probabilities of successful attacks are computed.

关键词： Authentication codes with arbitration orthogonal spaces finite field

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Will an imperfect vaccine curtail the COVID-19 pandemic in the U.S.?

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Infectious Disease Modelling 2020年第1期5卷 510-524页

作者： Enahoro A.Iboi Calistus N.Ngonghala abba B.Gumel School of Mathematical and Statistical Sciences Arizona State UniversityTempeAZ85287USA Department of Mathematics University of FloridaGainesvilleFL32611USA Department of Mathematics and Applied Mathematics University of PretoriaPretoria0002South Africa Department of Mathematics Spelman CollegeAtlantaGeorgia30314USA

The novel coronavirus(COVID-19)that emerged from Wuhan city of China in late December 2019 continue to pose devastating public health and economic challenges across the *** the community-wide implementation of basic non-pharmaceutical intervention measures,such as social distancing,quarantine of suspected COVID-19 cases,isolation of confirmed cases,use of face masks in public,contact tracing and testing,have been quite effective in curtailing and mitigating the burden of the pandemic,it is universally believed that the use of a vaccine may be necessary to effectively curtail and eliminating COVID-19 in human *** study is based on the use of a mathematical model for assessing the impact of a hypothetical imperfect anti-COVID-19 vaccine on the control of COVID-19 in the United *** analytical expression for the minimum percentage of unvaccinated susceptible individuals needed to be vaccinated in order to achieve vaccine-induced community herd immunity is *** epidemiological consequence of the herd immunity threshold is that the disease can be effectively controlled or eliminated if the minimum herd immunity threshold is achieved in the *** of the model,using baseline parameter values obtained from fitting the model with COVID-19 mortality data for the U.S.,show that,for an anti-COVID-19 vaccine with an assumed protective efficacy of 80%,at least 82%of the susceptible US population need to be vaccinated to achieve the herd immunity *** prospect of COVID-19 elimination in the US,using the hypothetical vaccine,is greatly enhanced if the vaccination program is combined with other interventions,such as face mask usage and/or social *** combination of strategies significantly reduces the level of the vaccine-induced herd immunity threshold needed to eliminate the pandemic in the *** instance,the herd immunity threshold decreases to 72%if half of the US population regularly wears face masks in pu

关键词： COVID-19 SARS-CoV-2 Vaccination Social distancing Non-pharmaceutical intervention

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