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基于异态相干沸腾的狭窄受限空间内沸腾传热强化研究

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基于异态相干沸腾的狭窄受限空间内沸腾传热强化研究

作者：马亚（Omisanya mayowa ibrahim）天津大学

学位级别：硕士

沸腾换热能够在较小的温差下传输极大的热流密度。与其他换热方式相比,在同等换热量的下,节省设备尺寸,减轻质量,节省空间。因此沸腾换热经常被应用在石油化工,热力发电,汽车空调和电子设备等工业领域。沸腾换热特性可以通过沸腾曲线爱... 详细信息

沸腾换热能够在较小的温差下传输极大的热流密度。与其他换热方式相比,在同等换热量的下,节省设备尺寸,减轻质量,节省空间。因此沸腾换热经常被应用在石油化工,热力发电,汽车空调和电子设备等工业领域。沸腾换热特性可以通过沸腾曲线爱描述。在1934年,Nukiyama等获得了第一条沸腾曲线,根据饱和沸腾曲线过热度变化,可将饱和沸腾过程分为四个阶段:自然对流阶段、核态沸腾阶段、过渡沸腾阶段和膜态沸腾阶段。对于核态沸腾阶段,当壁面过热度满足起始沸腾条件时,传热进入核态沸腾阶段。在起始沸腾点之后,加热表面开始出现汽泡。随着热流密度增加,汽泡核心数目不断增多。表面汽泡逐渐变大直至在浮力作用下脱离壁面,同时带走大量热量。由于汽泡运动对液体产生了剧烈扰动,所以加热面处热传递十分强烈。因而核态沸腾阶段是非常高效的传热阶段。孤立核态沸腾阶段和充分发展核态沸腾阶段的区别在于:处于孤立核态沸腾阶段时,沸腾表面汽泡生长和脱离相互独立;而充分发展核态沸腾阶段,沸腾表面汽泡生成和脱离更剧烈,从而大量汽泡快速从表面脱离后相互干扰,发生合并从而生成汽块或汽柱。随着热流密度不断增加,壁面过热度将出现急剧增大,传热性能突然发生恶化,这个转折点所对应的热流密度就是临界热流密度(critical heat flux,简称CHF)。当热流密度大于CHF时,传热机制变为膜态沸腾阶段,此时大量汽泡在加热壁面剧烈干扰和合并使得加热壁面表面形成一层蒸汽薄膜,由于加热壁面蒸汽薄膜会产生极大热阻,将恶化表面传热性能,造成加热表面的温度突然升高。因此在实际应用中,为了防止加热壁面被烧坏,应尽量避免膜态沸腾阶段。然而在大多数沸腾应用中,系统需要在低于相应临界热流密度下工作,沸腾的工程应用主要集中于核态沸腾区。因此为了保持设备在安全的温度区间运行,提升沸腾传热的CHF时非常必要的。由于CHF产生的机理是传热表面的绝大部分区域被蒸汽所覆盖,润湿区域仅出现在传热面的边缘处,液体向传热面供给十分困难。基于上述机理,通过传热面不间断的液体供给会促进CHF的提升。目前广泛应用于提升CHF的方法为表面改性技术,包括应用结构化表面,多空涂层表面,亲疏水分布表面以及纳米流体来提升CHF。表面改性技术提升CHF主要归因于增大传热面积,增加气化核心,改变润湿特性和毛细作用的影响。但是其提升效果极大的依赖于传热面表面特性。因此开发一种不依赖于传热面比表面特性而能提升CHF的方法尤为重要。之前的研究表明,微小空间内沸腾换热干涸状态下传热面的绝大部分区域被气泡覆盖,仅在传热面入口附近存在液体往复移动产生的润湿区域。基于上述现象,本研究设计了一种不依改变靠表面特性,而是调整内部构造提升沸腾传热CHF的传热块,即导热性交替分布型传热块。在传热过程中,传热块的不同区域处于不同温度状态,实现了核态沸腾和膜态沸腾状态在整个传热面共存。在不同沸腾状态边界处润湿和干涸状态的非稳定的交替出现,从而达到促进蒸发并强化传热的目的。异态沸腾传热块分布示意图。图1(a)为传热块内部结构示意图。传热块是利用电火花放电技术在紫铜传热块上穿出不同尺寸的矩形孔,并在孔内插入低导热材料制成。沸腾过程中,传热面出现区域性高低温交替分布,不同沸腾状态存在于不同温度区域。如图1(b)所示,在高导热材料区域上方,沸腾机制是膜态沸腾,传热表面被气膜所覆盖;低导热材料区域上方,沸腾机制是核态沸腾,传热表面被液膜所覆盖。另外,在不同沸腾状态的交界处,非稳态的润湿和干涸状态交替出现。伴随着气泡的运动,低导热材料区域上方的液膜移动到高导热性能材料上方,进而保持了整个传热表面的润湿特性。本实验中具体采用的传热面的结构参数如表1所示。本研究以去离子水作为工作流体,运用异态相干沸腾来实现狭窄空间内沸腾换热临界热流密度(CHF)的提升。该方法是基于在传热表面附近布置两种不同热导率的材料形成导热性的不均匀分布,进而沸腾过程中不同的沸腾模式在传热表面形成,通过不同沸腾模式之间的相互作用使得CHF提升。同时研究了材料宽度、间隙尺寸、表面尺寸对沸腾换热临界热流密度(CHF)的影响。实验条件如表2所示。具体结论如下1、与均匀传热面相比,导热性交替分布传热面的沸腾传热特性得到明显提升。对于传热系数,当传热面底部加载在相同的热流密度时,由于导热性材料的存在,热流量集中在高导热性材料区域,因此在较低的热流密度条件下核态沸腾就会发生。因此,导热性交替分布传热面在较低的避免过热度下核态沸腾发生,故其传热性能好于均匀分布传热面。对于CHF,由于高低导热性材料在传热块内部交替分布,沸腾过程中不同的沸腾模型在传热面上共存。在高热流密度区域,膜态沸腾和核态沸腾分布出现在传热面高导热材料区域和低导热材料区域,传热面上呈现了干涸区域和润湿区域的交替分布。利用气液交界面非稳态的周期性移动,促进液体向干涸区域的供

关键词：沸腾换热异态相干沸腾临界热流密度提升狭窄空间非均匀热导结构

Selected Aspects of Camel Immune System and Immune Responses

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Open Journal of Veterinary medicine 2021年第6期11卷 177-211页

作者： Saeed Y. Al Ramadan Kazem T. Al-mohammed Salem ibrahim H. Alshubaith Ahmed m. Al-Ali Salah Abohelaika mohammed S. moqbel Ahmed m. Alluwaimi Department of Anatomy College of Veterinary Medicine King Faisal University Al-Ahsaa Saudi Arabia Animal Resources management Ministry of Environment Water and Agriculture Al-Ahsaa Saudi Arabia Environmental Health Department Al-Ahsaa Municipality Al-Ahsa Saudi Arabia Central biotechnology Laboratory Veterinary Teaching Hospital College of Veterinary Medicine King Faisal University Al-Ahsaa Saudi Arabia Clinical Pharmacology Department Qatif Central Hospital Ministry of Health Saudi Arabia Department of microbiology and Parasitology College of Veterinary Medicine King Faisal University Al-Ahsaa Saudi Arabia

The camel economy is of considerable importance for arid countries. In the last decade, studies about camel immune system and immune responses have recorded increasing interest. However, drawing a comprehensive picture of the camel immune system remains far from reached. A major part of this review is to cover the studies of the primary and secondary immune organs and the markers of the camel immune cells and certain lymphoid tissues. At the same time, immune responses to different diseases and the nature of effective immunity were included, with an emphasis on the most important zoonotic diseases in camels such as MERS CoV;brucellosis. New findings on the diversity mechanisms of camel immunoglobulin genes were addressed. However, detail of the mechanism of MHC-restricted cellular immunity and the mechanism of B lymphocyte activation in camels await further attention. Interestingly, the gross and the histological structure of the lymphoid tissues of the camel’s thymus, tonsils, and peyer’s patches have indicated significant differences from other animals in terms of structure and function. The most peculiar CD expression, such as LPAM-I, MAdCAM-1 and CX3CR1, in certain camel cells and tissues refers to possible extraordinary mechanisms of immune hemostasis in camel in mily:"">comparison to other ruminants. The widely applied immunodiagnostic techniques to control camel diseases and to assist in improving the camel resistance were considered. Extensive studies of the camel immune system were greatly hampered by lack of specific reagents to camel markers and low funds in the field of camel i

关键词： Camel CX3CR1 Heavy Chain Antibody mERS-CoV Peyer’s Patches

Assessment of Genetic Relationship and Application of Computational Algorithm to Assess Functionality of Non-Synonymous Substitutions in DQA2 Gene of Cattle, Sheep and Goats

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Open Journal of Genetics 2015年第4期5卷 145-158页

作者： Steven b. Ugbo Abdulmojeed Yakubu Jude N. Omeje bwaseh S. bibinu ibrahim S. musa Joseph O. Egahi N. I. Dim Department of Animal breeding and Physiology University of Agriculture Makurdi Nigeria Department of Animal Science Faculty of Agriculture Nasarawa State University Keffi Shabu-Lafia Campus Lafia Nigeria Department of Veterinary medicine and Surgery University of Abuja Abuja Nigeria

The major histocompatibility complex (mHC) is a fundamental part of the immune system in nearly all vertebrates. DQA2 is a member of the mHC complex and an important candidate gene involved in susceptibility/resistance to various diseases. Therefore, the present study aimed at investigating computationally molecular genetic variation of DQA2 gene of cattle, sheep and goats especially on its evolution and differentiation within and among species as well as the attendant effects of the polymorphism on the function of DQA2 gene. A total of thirty three DQA2 nucleotide sequences comprising cattle (10), sheep (12) and goats (11) were retrieved from the Genbank. Forty seven amino acid substitutions of the wild type alleles located in the putative peptide coding region of caprine DQA2 alleles were obtained from the alignment of deduced amino acid sequences of goats. Out of these, eleven amino acid substitutions (H14L, H14R, L34m, E35L, G56S, G56R, 161V, A62E, D69Q, T72N and T72G) were returned neutral;an indication that they did not impair protein function. The Expected Accuracy (EA) ranged from 53% - 87%. For sheep, sixteen amino acid substitutions (A11P, A11T, A11G, A11m, L14S, L14T, V27L, V27S, G35S, S46T, D55E, L57T, L57A, L57G, K65Q and V68I) appeared beneficial while the rest forty seven appeared harmful (EA ranged from 53% - 93%). Twenty four amino acid substitutions did not impair the function of protein while seventy seven substitutions appeared to have a negative effect on the function of protein of cattle (EA ranged from 53% - 94%). The phylogeny based on nucleotide and amino acid sequences of DQA2 gene revealed the close relatedness of the caprine, ovine and bovine species. The present knowledge would be relevant for performing further genotype-phenotype research as well as pharmacogenetics studies in order to show association between caprine, ovine and bovine DQA2 allelic variation and the clinical progression of infectious diseases especially in a developing

关键词： DQA2 Genetic Relationship Amino Acid Substitution Phylogeny Ruminants

Long-Term mortality of Children with Congenital Heart Disease Admitted to the Departmental University Hospital of borgou/Alibori from 2011 to 2022

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World Journal of Cardiovascular Diseases 2024年第3期14卷 166-186页

作者： Serge Hugues mahougnon Dohou Nicolas Hamondji Amegan Ahmad ibrahim Gérard médétinmè Kpanidja Chabi Olaniran Alphonse biaou Houétondji Léopold Codjo Cardiology Teaching and Research Unit (CHUD-b/A) Faculty of Medicine University of Parakou Parakou Benin É cole de Sant&#233 Publique de l&#8217Universit&#233 de Montr&#233al (ESPUM) Montr&#233al Qu&#233bec Canada Paediatrics and medical Genetics Teaching and Research Unit (CHUD-b/A) Faculty of Medicine University of Parakou Parakou Benin Regional Institute of Public Health University of Abomey-Calavi Cotonou Benin Cardiology Department Faculty of Health Sciences University of Abomey-Calavi Cotonou Benin

background: Congenital heart disease is a public health issue due to its incidence and mortality rate. The aim of this study was to investigate the long-term mortality of children with congenital heart disease admitted to the Departmental University Hospital of borgou/Alibori (CHUD-b/A) from 2011 to 2022. methods: This descriptive longitudinal study with analytical aims covered 11 years (April 1, 2011 to December 31, 2022). It consisted of a review of the records of children under 15 years of age with echocardiographically confirmed congenital heart disease. This was followed by an interview with the parents to assess the children’s current condition. Data were entered using Kobocollect software and analyzed using R Studio 4.2.2. software. Results: A total of 143 complete files were retained. The median age at diagnosis was 14 months (IIQ: Q1 = 4;Q3 = 60) with a range of 2 days and 175 months, and the sex-ratio (m/F) was 0.96. Left-to-right shunts were the most frequent cardiopathy group (62.9%). Only 35 children (24.5%) benefited from restorative treatment. The mortality rate was 31.5%. median survival under the maximum bias assumption was 114 months and 216 months under the assumption of minimum bias. Survival was significantly better in children with right-to-left shunts (p = 0.0049) under the assumption of minimum bias. The death risk factors were: age at diagnosis less than 12 months (aHR = 7.58;95% CI = 3.36 - 17.24;p Conclusion: The long-term mortality of congenital heart disease is high and favoured by the absence of restorative treatment. Local correction of congenital heart disease and medical follow-up will help to reduce this mortality.

关键词： Congenital Heart Disease Long-Term mortality Parakou Risk Factors

Vibrational Spectroscopic Investigations, Electronic Properties, molecular Structure and Quantum mechanical Study of an Antifolate Drug: Pyrimethamine

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Computational Chemistry 2022年第4期10卷 157-185页

作者： Pélagie manwal A mekoung bel Youssouf G. mountessou maraf b. mbah martin Signe Auguste Abouem A Zintchem Charles P. N. Nanseu ibrahim N. mbouombouo Department of Inorganic Chemistry Faculty of Science University of Yaoundé I Yaoundé Cameroon Computational Chemistry Laboratory Department of Chemistry Higher Teacher Training College University of Yaoundé I Yaoundé Cameroon

The computational modelling supported by experimental results can explain the molecular structure, vibrational assignments, reactive sites and several structural properties. In this context, the spectroscopic (FT-IR, FT-Raman and NmR) analysis, electronic properties (HOmO and LUmO energies) and molecular structure of pyrimethamine (Pyr) were investigated by density functional theory (DFT) method associated with three levels of theory viz., b3LYP, mN15 and wb97XD with 6-311++G(d,p) and def2TZVPP as basis sets, respectively in the Gaussian 16 programs. The 1H and 13C NmR chemical shifts were calculated with a gauge-independent atomic orbital (GIAO) approach by also applying the same levels of theory and basis sets. All experimental results were compared with theoretical data. Although the results revealed high degrees of correlation between the theoretical and experimental values for spectroscopic properties using the three methods. Furthermore, the atomic and natural charges, energy band gap and chemical reactivity were determined, while the frontier molecular orbital (FmO) and molecular electrostatic potential (mEP) surfaces were plotted to explain the reactive nature of the title molecule.

关键词： Electronic Property NmR Pyrimethamine Vibrational Spectrum

Aqueous extract of Corchorus olitorius decreases cytotoxicityof aflatoxin b1 and fumonisin b1 in H4IIE-luc cells

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Hepatoma Research 2015年第1期1卷 75-85页

作者： mohamed I.m.ibrahim Rialet Pieters Sekena H.Abdel-Aziem Anna m.van der Walt Cornelius C.bezuidenhout John P.Giesy mosaad A.Abdel-Wahhab Department of Food Toxicology and Contaminants National Research CentreDokkiCairo 12622Egypt Unit of Environmental Sciences and management North-West UniversityPrivate Bag X6001Potchefstroom 2520South Africa Department of Cell biology National Research CentreDokkiCairo 12622Egypt Department of Veterinary biomedical Sciences and Toxicology Centre University of SaskatchewanSaskatoonSaskatchewan S7N 5B4Canada Department of Zoology and Center for Integrative ToxicologyMichigan State UniversityEast LansingMI 48824USA Department of biology and Chemistry and State Key Laboratory in marine Pollution City University of Hong KongKowloonHong KongChina School of biological Sciences University of Hong KongHong KongChina State Key Laboratory of Pollution Control and Resource Reuse School of the EnvironmentNanjing UniversityNanjing 210093JiangsuChina Department of biology Hong Kong Baptist UniversityHong KongChina

Aim:Afl atoxin b1(AFb1)and fumonisin b1(Fb1)are important food-borne ***-contamination of foodstuffs with these two mycotoxins is well-known and has been implicated in a possible development of hepatocellular carcinoma in humans living in regions of the world where exposures to these mycotoxins in grain are *** aim of the current study was to evaluate the potential protective effects of an aqueous extract of Cochorus olitorius(***,moroheiya)against cytotoxicity of AFb1 and/or Fb1 in H4IIE-luc rat hepatoma cells,using assays to measure cell viability and disruption of DNA *** this transactivation assay was originally developed to specifi cally respond to aryl hydrocarbon agonists,this cell line was used because of its hepatic ***:H4IIE-luc cells were incubated with different concentrations of AFb1 and/or Fb1 for 24 and 48 h with or without aqueous extract of ***:both mycotoxins decreased cell viability and increased DNA *** was more pronounced when cells were exposed simultaneously to AFb1 and ***:Aqueous extract of *** protected cells against cytotoxicity of *** contains a water-soluble,natural chemo-preventative agent for cancer that should be isolated and identifi ed.

关键词： Anticancer cytotoxicity DNA liver moroheiya mycotoxins

Digestive fungal flora in asymptomatic subjects in bobo-Dioulasso,burkina Faso

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Asian Pacific Journal of Tropical biomedicine 2014年第8期4卷 659-662页

作者： bamba Sanata Ouédraogo Abdoul Salam Sangaré ibrahim Zida Adama Cissé mamoudou Karou D.Simplice Simpore Jacques Guiguemdé T.Robert Hennequin Christophe Department of Parasitology-mycology University Hospital Sanou SouroBobo-DioulassoBurkina Faso Department of Parasitology-mycology Higher Institute of Health SciencesPolytechnic University of Bobo-DioulassoBurkina Faso Department of bacteriology-Virology Higher Institute of Health SciencesPolytechnic University of Bobo-DioulassoBurkina Faso Faculty of Health Sciences University of OuagadougouBurkina Faso biomolecular Research Center Pietro Annigoni(CERbA/LAbIOGENE) OuagadougouBurkina Faso Service of Parasitology-mycology Saint Antoine de Paris HospitalFrance

Objective::To identify Candida species in asymptomatic subjects in bobo-Dioulasso(burkina Faso) by the matrix—assisted laser desortption ionization—time of flight mass ***:A cross-sectional study was conducted from January to February 2013 in bohoDioulasso to coiled fecal and urine specimens from voluntary *** strains were isolated on Sabouraud dextrose agar and analyzed using matrix—assisted laser desorption ionisation—time-of—flight mass ***:A total of 135 samples including stools(78.5%,106/135) and urine(21.5%,29/135) were *** results revealed that fecal specimens contained mainly Candida krusei(***)(42.5%) followed by Candida albicans(29.3%),Candida glabrata(18.0%) and Candida tropicalis(***)(4.7%).***(34.6%) was also found to be the most frequently identified in urine samples followed by Candida albicans(27.0%).***(15.4%) and Candida parapsilosis,However,uncommon species such as Candida *** *** norvegensis,Candida *** lusitaniae and Candida robusta were also identified from fecal and urines ***:This study noted the emergence of species such as ***,Candida glabrata,Candida parapsiolosis,***,Candida nivariensis,Candida norvegensis,and *** is an imperative to take into account the existence of these species in the therapeutic management of patients in bobo—Dioulasso.

关键词： Candida mass spectrometry matrix—assisted laser desorption ionization—time of flight boboDioulasso

Effects of model Structural Complexity and Data Pre-Processing on Artificial Neural Network (ANN) Forecast Performance for Hydrological Process modelling

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Open Journal of modern Hydrology 2021年第1期11卷 1-18页

作者： martins Yusuf Otache John Jiya musa ibrahim Abayomi Kuti mustapha mohammed Lydia Ezekiel Pam Department of Agricultural & bioresources Engineering Federal University of Technology Minna Nigeria Raw materials Research and Development Council Abuja Nigeria

The choice of a particular Artificial Neural Network (ANN) structure is a seemingly difficult task;worthy of relevance is that there is no systematic way for establishing a suitable architecture. In view of this, the study looked at the effects of ANN structural complexity and data pre-processing regime on its forecast performance. To address this aim, two ANN structural configurations: b>1) Single-hidden layer, b>andb> 2) Double-hidden layerb> feed-forward back propagation network were employed. Results obtained revealed generally that: a) ANN comprised of double hidden layers tends to be less robust and converges with less accuracy than its single-hidden layer counterpart under identical situations;b) for a univariate time series, phase-space reconstruction using embedding dimension which is based on dynamical systems theory is an effective way for determining the appropriate number of ANN input neurons, and c) data pre-processing via the scaling approach excessively limits the output range of the transfer function. In specific terms considering extreme flow prediction capability on the basis of effective correlation: Percent maximum and minimum correlation coefficient (b>Rb>maxb>%b> and b>Rb>

关键词： Streamflow Neural Network Phase-Space Optimisation Algorithm

Clinical and Therapeutic Aspects of Giant Fibroids at the Hôpital du mali about 30 Cases

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Open Journal of Obstetrics and Gynecology 2020年第6期10卷 778-789页

作者： mamadou b. Coulibaly Alassane Traore mody A. Camara Abdrahamane Togo Adama Sangaré Issa Ongoiba Kalba Timbine Amadou Sidibé Apérou Guindo Niani mounkoro ibrahim Teguete Youssouf Traore moustaphe Toure Service of Gynecology of the Hopital du mali Bamako Mali Service of medical Imaging of the Hopital du mali Bamako Mali Service of Anesthesia and Resuscitation of the Hopital du mali Bamako Mali Service of Gynecology-Obstetrics of Gabriel TOURE Teaching Hospital Bamako Mali

The fibroids affect 20% to 25% of women of reproductive age and are 3 to 9 times more common in black women. We’ll talk about giant fibroids (GFs) when uterine height reaches or exceeds the navel. We have initiated this study in order to report the epidemioclinical and therapeutic aspects of giant fibroids at the Hopital du Mali. A descriptive retro-prospective study, conducted in the service of gynecology of the Hopital du Mali from November 2017 to December 2018 were included in this study, any patients, regardless of their age, having developed a fibroid, the uterin e height of the patient reaching or exceeding the umbilicus on physical examination and who were on surgical treatment. We had collected 30 cases of GFs out of the 92 patients who had undergone myomectomies, with a frequency of 32.60%. The age group 25 - 29 years accounted for 46.6% with an average age of 35 years. Housewives represented 50% and nulligravida made up 33% of our patients. Desire to become pregnant was the main reason for consultation in 34.4% of cases. The uterine height was between 25 and 29 cm on physical examination in 46.66% of cases. Myomectomy was performed in 76.64% and hysterectomy in 23.3% of cases. The size of the nuclei after surgery was over 25 cm in 48.66% of our patients. b>Conclusionb>mily:Verdana;">: The giant fibroid (GF) is a common cause of myomectomy. The treatment is either hysterectomy or myomectomy and

关键词： Giant Fibroma Care Surgery Hôpital du mali