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作者： habimana jean willy（威利）华南理工大学

学位级别：硕士

金属玻璃是一种具有特殊性质的新材料，它是通过控制合金冷却过程从而避免结晶形核来获得的。然而，到目前为止，精确控制合金熔体的冷却过程非常困难，金属玻璃形成理论也不完善。人们根据一些经验准则来提高获得块体金属玻璃（BMG）... 详细信息

金属玻璃是一种具有特殊性质的新材料，它是通过控制合金冷却过程从而避免结晶形核来获得的。然而，到目前为止，精确控制合金熔体的冷却过程非常困难，金属玻璃形成理论也不完善。人们根据一些经验准则来提高获得块体金属玻璃（BMG）的机会，但是经验准则并不能保证BMG的形成。特别是，这些经验准则对于不同的合金体系起着不同的作用。所以目前很难精确预测同时具有高玻璃形成能力（GFA）和良好材料性能的合金成分。研究GFA表征的科学工作者通过考虑金属玻璃形成的动力学行为和热力学行为，提出了不同的GFA判据。研究发现，其中一些判据与实验观察到的结果存在明显偏差。因此，认识和了解GFA判据并运用这些判据来预测不同合金系的GFA十分重要，特别是对于那些具有高的或低的GFA的合金体系。本论文的目的是通过评价几种典型的GFA参数，获得最简单、可靠的GFA判据，研究Fe基合金中产生不寻常GFA的原因，同时利用理论计算和试验研究相结合，针对一类具体的硬磁Nd-Y-Fe-B-M合金，在保证高性能的同时优化其玻璃形成能力。本文首先通过基于合金特征温度的GFA判据与GFA之间的相互关系来详细分析它们的准确性。这些判据包括β, θ, γ, γm, γc和ω，而描述GFA的主要目标参数包括临界冷却速率（Rc）和临界尺寸（Zmax），其中Rc是最准确的GFA测量方法，而Zmax是应用最多的参数。本文分析研究了九种不同的合金体系的Rc-GFA判据和Zmax-GFA判据相互关系，获得了不同判据用于预测GFA的可靠性。其次，本文通过热分析法和组成元素的物理性质计算来获得定义结晶过程动力学和热力学行为的参数，研究了铁基合金的GFA及玻璃形成机制。最后，针对特定的Nd-Y-Fe-B-M硬磁合金，本文采用Rc目标函数进行GFA非线性优化，获得了既具有高性能又具有高GFA的合金成分。研究发现，在几种主要的判据中，β判据存在缺点，而θ, γ, γm, γc和ω判据展现与Rc或Zmax几乎相同的相关度，并且当数据发生变化时仍然展现相同的相关稳定性。不过当选用Zmax作为GFA测量方法则得到较小的R2值。此外，GFA判据-Zmax之间的相关度分布主要依赖于所研究的合金系。对于某些合金系，这种相关度完全是随机分布的，意味着用实验获得的非晶棒材的最大临界尺寸所定义的特征温度基判据来预测包括铁、锆基在内的某些合金系的GFA仍然存在问题。对于铁基合金，通过动力学和热力学参数估算所得的Rc与文献中提及的实验测量值Rc非常吻合。同时也发现，在铁基合金中，具有高熔化焓ΔHm的合金成分可以在没有高过冷度的条件下获得金属玻璃。高玻璃形成能力合金系中观察到的大的β参数（Turnbul理论的参数）和高的ΔHm值表明，这类合金系的玻璃形成过程主要由抑制形核长大所控制。通过对硬磁合金FeMoYBNd和FeNbYBNd的GFA非线性优化，获得了具有高GFA的合金成分。优化结果与现有的实验结果一致。研究发现，具有提高合金GFA能力的元素（如Y）在替代Fe时对合金系的影响结果由合金的其他组成元素决定。添加元素也有可能会对合金GFA产生负面作用。对于给定B、Nd含量的Fe-Mo-Y-B-Nd和Fe-Nb-Y-B-Nd合金系，Y元素有一个优化合金GFA的最佳值。为了在2-6%范围内寻找Y元素的最佳值，Fe-Mo-Y-B-Nd和Fe-Nb-Y-B-Nd合金系中B/Nd的比率分别假定在21.5%/6.5%和22.2%/5.8%（Fe+Mo或者Fe+Nb的含量固定在68%）。同时发现，在高稀土Nd含量的成分中，相对于Fe-Mo-Y-B-Nd合金系，Fe-Nb-Y-B-Nd合金系更有可能获得具有良好GFA的成分。最后，论文通过实验研究部分证实了理论分析结果。选取理论模型预测的既具有高的磁性能又具有高的GFA的4种合金成分，通过快速凝固技术（包括熔体快淬和喷铸）制备了Fe-Mo-Y-B-Nd合金。XRD分析表明，实验成功地获得了直径2.3mm的大块金属玻璃非晶棒材。结果显示，理论模型可以很好地预测合金系的玻璃形成能力。通过后续热处理工艺优化，有望在这些高稀土含量的块体材料中获得高的硬磁性能。论文工作为纳米复合稀土永磁的成分设计和直接铸造制备提供了新的思路。

关键词：玻璃形成能力大块非晶金属临界冷却速率临界尺寸优化铁基合金

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Overview of finite elements simulation of temperature profile to estimate properties of materials 3D-printed by laser powder-bed fusion

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Chinese Physics B 2020年第4期29卷 98-109页

作者： habimana jean willy Xinwei Li Yong Hao Tan Zhe Chen Mehmet Cagirici Ramadan Borayek Tun Seng Herng Chun Yee Aaron Ong Chaojiang Li Jun Ding Department of Materials Science and Engineering Faculty of EngineeringNational University of Singapore9 Engineering Drive 1Singapore 117576Singapore

Laser powder bed fusion(LPBF),like many other additive manufacturing techniques,offers flexibility in design expected to become a disruption to the manufacturing *** current cost of LPBF process does not favor a try-anderror way of research,which makes modelling and simulation a field of superior importance in that area of *** this work,various methods used to overcome challenges in modeling at different levels of approximation of LPBF process are *** efforts made towards a reliable and computationally effective model to simulate LPBF process using finite element(FE)codes are presented.A combination of ray-tracing technique,the solution of the radiation transfer equation and absorption measurements has been used to establish an analytical equation,which gives a more accurate approximation of laser energy deposition in powder-substrate *** this new analytical energy deposition model is used in in FE simulation,with other physics carefully set,it enables us to get reliable cooling curves and melt track morphology that agree well with experimental *** use of more computationally effective approximation,without explicit topological changes,allows to simulate wider geometries and longer scanning time leading to many applications in real engineering *** applications are herein presented including:prediction of printing quality through the simulated overlapping of consecutive melt tracks,simulation of LPBF of a mixture of materials and estimation of martensite inclusion in printed steel.

关键词： selective laser melting powder bed fusion finite element modeling laser absorption

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Enhancing laccase stability and activity for dyes decolorization using ZIF-8@MWCNT nanocomposite

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Chinese Journal of Chemical Engineering 2022年第8期35卷 66-75页

作者： Pascal habimana Yanjun Jiang Jing Gao jean Bernard Ndayambaje Osama M.Darwesh jean Pierre Mwizerwa Xiaobing Zheng Li Ma School of Chemical Engineering and Technology Hebei University of TechnologyTianjin 300130China University of Rwanda College of Science and Technology3900 KigaliRwanda Department of Agricultural Microbiology National Research CentreCairo 12622Egypt College of Mechatronics and Control Engineering Shenzhen UniversityShenzhen 518060China

The continuous use of chemical dyes in various industries,and their discharge into industrial effluents,results in severe problems to human life and water *** have the ability to decolorize dyes and toxic chemicals in industrial effluents as green *** possible industrial applications have been limited by poor reusability,low stability,and loss of free laccase *** this research,lac-case was immobilized on zeolitic imidazolate framework coated multi-walled carbon nanotubes(Laccase@ZIF-8@MWCNTs)via metal affinity adsorption to develop an easy separable and stable *** optimum reaction conditions for immobilized laccase are at a pH of 3.0 and a temperature of 60℃.The immobilized laccase was enhanced in storage and thermal *** results indicated that Laccase@ZIF-8@MWCNTs still maintained 68%of its original activity after 10 times of repeated *** importantly,the biocatalytic system was applied for decolorization of different dyes(20 mg·L^(-1))without a mediator,and up to 97.4%for Eriochrome black T and 95.6%Acid red 88 was achieved in 25 *** with these properties may be used in a variety of environmental and industrial applications.

关键词： Metal-organic framework Zeolitic imidazolate framework Reusability and stability Immobilized laccase Dye decolorization

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Decomposition and decoupling analysis of carbon dioxide emissions in African countries during 1984–2014

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Journal of Environmental Sciences 2021年第4期33卷 85-98页

作者： Claudien habimana Simbi Jianyi Lin Dewei Yang jean Claude Ndayishimiye Yang Liu Huimei Li Lingxing Xu Weijing Ma Key Lab of Urban Environment and Health Institute of Urban EnvironmentChinese Academy of SciencesXiamen 361021China University of Chinese Academy of Sciences Beijing 100049China School of Geographical Sciences Southwest UniversityChongqing 400715China Faculty of Geography University of MarburgMarburg 35032Germany

The potential for mitigating climate change is growing worldwide,with an increasing emphasis on reducing CO_(2)emissions and minimising the impact on the *** continent is faced with the unique challenge of climate change whilst coping with extreme poverty,explosive population growth and economic ***_(2)emission patterns in Africa are analysed in this study to understand primary CO_(2)sources and underlying driving forces *** are examined using gravity model,logarithmic mean divisia index and Tapio's decoupling indicator of CO_(2)emissions from economic development in 20 selected African countries during *** reveal that CO_(2)emissions increased by 2.11%(453.73 million ton)over the research *** centre for African CO_(2)emissions had shifted towards the northeast *** and economic growth were primary driving forces of CO_(2)*** structure and emission efficiency effects partially offset the growth of CO_(2)*** economic growth effect was an offset factor in central African countries and Zimbabwe due to political instability and economic *** structure and emission efficiency were insufficient to decouple economic development from CO_(2)emissions and relieve the pressure of population explosion on CO_(2)emissions in ***,future efforts in reducing CO_(2)emissions should focus on scaleup energy-efficient technologies,renewable energy update,emission pricing and long-term green development towards sustainable development goals by 2030.

关键词： CO_(2)emissions Decoupling Driving forces Logarithmic mean divisia index method Patterns Africa

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火山灰材料在道路工程路基改良中的应用研究 ——以东非卢旺达穆桑兹地区为例

火山灰材料在道路工程路基改良中的应用研究 ——以东非卢旺达穆...

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作者： habimana jean PIERRE 绍兴文理学院

学位级别：硕士

土壤是道路建设系统的重要组成部分,因此有必要提高土壤路基材料的强度和稳定性,以获得足够的承载力来支撑车辆荷载。总体而言,本文的研究重点是在道路工业中使用火山材料改善土壤路基,以东非卢旺达的Musanze地区为例,Musanze是该地区... 详细信息

土壤是道路建设系统的重要组成部分,因此有必要提高土壤路基材料的强度和稳定性,以获得足够的承载力来支撑车辆荷载。总体而言,本文的研究重点是在道路工业中使用火山材料改善土壤路基,以东非卢旺达的Musanze地区为例,Musanze是该地区存在的材料之一。穆桑泽区是卢旺达通过其火山在可持续发展方面进展迅速的城市之一,这些火山呈现不同的喷发时间。事实上,这项研究的目的是制定火山喷发后在道路工业中使用这些火山材料的计划,并设计改善土壤路基所需的可能参数。该项目是由于该地区土壤路基和未使用火山材料的承载力不稳定而提出的,这些材料可作为保持这些火山材料稳定的关键,以满足用作路基的技术要求。该项目也有助于提高我们如何通过使用火山材料使用不同技术改善土壤路基的知识,并有助于熟悉不同的土壤测试,如加州承载比（CBR）、粒度分布和普氏测试,尤其是压实。结果表明,原始土样的最大干密度为1.616g/cm,混合火山物质的原始土样最大干密度达1.866g/cm,高于仅原始土样。使用火山材料稳定土壤后,由于火山材料含有47.9%的二氧化硅,可以吸收土壤中多余的水分,导致原生土壤的塑性指数值下降。可以看出,土为软粘土,塑性指数约为10.1%,属于高液限粘土（CH）,质量属于中等至较差的高塑性路基。土壤路基中火山物质混合物对天然土壤强度的影响可以从未烘焙条件下的CBR测试结果中看出,在14天的养护时间内,与火山物质混合的每一种土壤变化都可以看出,20%的火山物质增加到原始土壤,导致CBR值从14.5%增加到16.8%。添加一定比例的火山物质可以提高土壤的承载力,也可以提高土壤凝聚力。为了实现这一目标,将收集数据并进行分析。首先,将使用Arc GIS软件和Cova Dis获得地形数据,以确定采样地点;第二,还将进行岩土工程测试;第三,还将绘制和解释测试样本的结果。这些数据的分析将使用微软Excel和工程软件等计算机程序进行。

关键词：道路工程路基土壤改良黏土火山灰

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Gestational Diabetes Mellitus and Its Associated Risk Factors in Pregnant Women at Selected Health Facilities in Kigali City, Rwanda

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Journal of Diabetes Mellitus 2016年第4期6卷 269-276页

作者： jean Baptsite Niyibizi Florien Safari jean Bosco Ahishakiye jean Bosco habimana Herbert Mapira Ngule Chrispus Mutuku Pan African University Institute of Sciences Technology and Innovation Nairobi Kenya Nyagatare Hospital Nyagatare Rwanda Rwinkwavu Hospital Kayonza Rwanda Gisenyi Hospital Rubavu Rwanda College of Medicine and Health Sciences University of Rwanda Kigali Rwanda Center for Traditional Medicine and Drugs Research Kenya Medical Research Institute Nairobi Kenya

Background: Gestational Diabetes Mellitus (GDM) is the most common complication of pregnancy that causes chronic hypertension, increased rate of cesarean delivery, fetal mortality and morbidity. Therefore, early diagnosis of GDM is vital to reduce maternal and fetal morbidity. Moreover, it can circumvent or procrastinate the onset of type 2 diabetes. Objectives: The main objective of this study was to determine the prevalence of GDM in pregnant women attending Kimironko, Kicukiro and Muhima Health Centres. The specific objectives were to determine the blood glucose during the second trimester in pregnant women aged between 21 and 45 years, to find out the frequencies of pregnant women presenting with GDM according to age and to assess some promising risk factors associated with GDM. Methods: A cross-sectional study was carried out at Kimironko, Kicukiro and Muhima Health centers using a sample size of 96 pregnant women. Blood glucose levels were measured using glucose oxidase method with a glucometer. Data were analyzed by using Microsoft Office Excel and SPSS version 20. Results: Out of 96 pregnant women who participated in the study, 8.3% were found to have GDM with the mean ± 2SD of 194.12 ± 25.53 mg/dl of their blood glucose results (Mean ± 2SD: A 95% level of confidence Intervals). The highest proportion of GDM was revealed in pregnant women aged between 26 - 30 years, representing a frequency of 5.2% whereas 2.1% of GDM was reflected in women aged between 21 - 25 years. The lowest proportion of GDM fell in age group of 31 - 35 years contributing to 1% of the total GDM. There were no cases of GDM in pregnant women in the 36 - 40 or 41 - 45 age groups. The mean ± 2SD of participant’s age groups was 27.12 ± 5.01 years. In addition, while obesity did not show to be associated with GDM, age and family history were found to be risk factors of GDM. Conclusion: The findings of this study revealed that the prevalence of GDM was 8.3% and the most affected pregnant women

关键词： Gestational Diabetes Mellitus (GDM) Prevalence Pregnancy Age Group Risk Factors

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Enhancing laccase stability and activity for dyes decolorization using ZIF-8@MWCNT nanocomposite

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中国化学工程学报（英文版） 2022年第8期

作者： Pascal habimana Yanjun Jiang Jing Gao jean Bernard Ndayambaje Osama M.Darwesh jean Pierre Mwizerwa Xiaobing Zheng Li Ma

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