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In situ(α-Al_2O_3+ZrB_2)/Al composites with network distribution fabricated by reaction hot pressing

International Journal of Minerals,Metallurgy and Materials 2015年第10期22卷 1092-1100页

作者： El Oualid Mokhnache Gui-song Wang Lin Geng Kaveendran Balasubramaniam Abdelkhalek Henniche noureddine ramdani School of Materials Science and Engineering Harbin Institute of Technology Polymer Materials Research Center Harbin Engineering University

In situ（α-Al2O3+ZrB2）/Al composites with network distribution were fabricated using low-energy ball milling and reaction hot pressing. Differential thermal analysis（DTA） was used to study the reaction mechanisms in the Al–Zr O2–B system. X-ray diffraction（XRD） and scanning electron microscopy（SEM） in conjunction with energy-dispersive X-ray spectroscopy（EDX） were used to investigate the composite phases, morphology, and microstructure of the composites. The effect of matrix network size on the microstructure and mechanical properties was investigated. The results show that the optimum sintering parameters to complete reactions in the Al–Zr O2–B system are 850°C and 60 min. In situ-synthesized α-Al2O3 and Zr B2 particles are dispersed uniformly around Al particles, forming a network microstructure; the diameters of the α-Al2O3 and Zr B2 particles are approximately 1–3 μm. When the size of Al powder increases from 60–110 μm to 150–300 μm, the overall surface contact between Al powders and reactants decreases, thereby increasing the local volume fraction of reinforcements from 12% to 21%. This increase of the local volume leads to a significant increase in microhardness of the in situ（α-Al2O3–Zr B2）/Al composites from Hv 163 to Hv 251.

关键词： metal matrix composites network distribution sinte

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The rise of diabetes prevalence in the Arab region

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Open Journal of Epidemiology 2012年第2期2卷 55-60页

作者： Abdesslam Boutayeb Mohamed E. N. Lamlili Wiam Boutayeb Abdellatif Maamri Abderrahim Ziyyat noureddine ramdani Department of Biology Faculty of Science University Mohamed Ier Oujda Morocco Health Career Training Institute & Faculty of Sciences Oujda Morocco Laboratory of Stochastic and Determinstic Modelling & Research Unit Associated to CNRST Faculty of Sciences University Mo-hamed Ier Oujda Morocco.

Introduction: Arab populations have many similarities and dissimilarities. They share culture, language and religion but they are also subject to economic, political and social differences. The purpose of this study is to understand the causes of the rising trend of diabetes prevalence in order to suggest efficient actions susceptible to reduce the burden of diabetes in the Arab world. Method: We use principal component analysis to illustrate similarities and differences between Arab countries according to four variables: 1) the prevalence of diabetes, 2) impaired glucose tolerance (IGT), 3) diabetes related deaths and 4) diabetes related expenditure per person. A linear regression is also used to study the correlation between human development index and diabetes prevalence. Results: Arab countries are mainly classified into three groups according to the diabetes comparative prevalence (high, medium and low) but other differences are seen in terms of diabetes-related mortality and diabetes related expenditure per person. We also investigate the correlation between the human development index (HDI) and diabetes comparative prevalence (R = 0.81). Conclusion: The alarming rising trend of diabetes prevalence in the Arab region constitutes a real challenge for heath decision makers. In order to alleviate the burden of diabetes, preventive strategies are needed, based essentially on sensitization for a more healthy diet with regular exercise but health authorities are also asked to provide populations with heath- care and early diagnosis to avoid the high burden caused by complications of diabetes.

关键词： Arab Region Diabetes Prevalence Transition Human Development Regression Principal Component Analysis

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