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Redistribution and magnitude of stresses around horse shoe and circular excavations opened in anisotropic rock

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International Journal of Mining Science and Technology 2015年第4期25卷 615-621页

作者： Mambou Ngueyep luc Leroy Ndop Joseph Ndjaka Jean-Marie Bienvenu Laboratory of Material Sciences Department of Physics Faculty of Sciences University of Yaoundé 1 Department of Mine Mineral Processing and Environment School of Geology and Mining Engineering University of Ngaoundéré Douala Institute of Technology

In this paper numerical analysis of underground structures, taking account the transverse isotropy system of rocks, was done using CAST 3M code by varying the shape of excavation and the coefficient of earth pressure k. Numerical results reveal that the anisotropy behavior, the shape of hole and the coefficient of earth pressure k have significant influence to the mining induced stress field and rock deformations which directly control the stability of underground excavation design. The magnitude of horizontal stress obtained for the horse shoe shape excavation(25.2 MPa for k = 1; 52.7 MPa for k = 2)is lower than the magnitude obtained for circular hole(26.4 MPa for k = 1; 59.5 MPa for k = 2).Therefore, we have concluded that the horse shoe shape offers the best stability and the best design for engineer. The anisotropy system presented by rock mass can also influence the redistribution of stresses around hole opened. Numerical results have revealed that the magnitude of redistribution of horizontal stresses obtained for transverse isotropic rock(12.1 MPa for k = 0.5; 25.2 MPa for k = 1 and52.7 MPa for k = 2) is less than those obtained in the case of isotropic rock(27.6 MPa for k = 1;48.6 MPa for k = 2 and 90.81 MPa for k = 2). The more the rock has the anisotropic behavior, the more the mass of rock around the tunnel is stable.

关键词： Horse shoe excavation Stress Strain Transverse isotropy Finite element

Phase control of ellipsometric interferometer for nanometric positioning system

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Science China(Technological Sciences) 2011年第12期54卷 3424-3430页

作者： XU SuAn CHASSAGNE luc TOPCU Suat ZHONG ShaoJun HUANG YanYan College of Mechanical and Electrical Engineering China Jiliang University Hangzhou 310018 China LISV University of Versailles Saint-Quentin Versailles cedex 78035 France

Development in industry is asking for improved resolution and higher accuracy in dimensional metrology. In this paper,we proposed a control displacement method based on a polarization ellipsometirc interferometer and phase-locked loop technique. The proposed principle was set up. The experimental results of step and step displacements with a step value of 5 nm were presented. We also analyzed the resolution,the potential minimal displacement of the established system. The results show that the position error induced by the ellipticty deviation of the light beam becomes negligible thanks to our signal processing circuit with high-order filter. This method could be useful for many applications in nano dimensional metrology and semiconductor industry.

关键词： ellipsometric interferometer phase locked loop nanometric position control displacement monitoring

Offering Adequate Pedagogical Progression via Mobile Equipments——Experiment of a French Engineering School

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开放教育研究 2006年第1期12卷 59-62页

作者： Jean-luc Koning Grenoble National Institute of Technology France

Students may enter our 5-year engineering school in France at two levels; first and third year. However, due to their quite different backgrounds (this is especially true for third year students) , we need to provide newcomers with a 6-week training period during which they follow classes in the fields where they particularly feel weak. Unfortunately, depending on the student' s background, this is not always possible to bring him/her to the expected level. Another aspect one needs to mention is that these students may not have the same weaknesses in a given field. However, for economical reasons, those classes follow a uniform program as it is not feasible to provide a customised progression. In this paper we discuss how to redesign a mathematics course so as to offer tailored exercise sequencing. Groups of 20 students could then draw their exercises from an intranet database according to their previously completed work, try to solve it by themselves, request additional hints and even ask for some direct help from the teacher. Such a database is currently under development. If it turns out several students stumble against the same difficulty the teacher could show the whole class room how to solve it using the digital projector. This project goes one step further than our initial mobile education project (2003 - 2004 ). Until recently, we had used the equipment in a unique direction, from the instructor toward the students. Here, in this new project we are focusing on the whole loop in order to offer a more adequate (personalized) pedagogical progression ; from the student to the teacher (when the tablet PCs are monitored by the teacher) , and back toward the students (when a direct help is provided by the teacher).

关键词：法国移动学习设备工程院校开放教育教学方法

Mass Screening Using Antigenic and Molecular Diagnostic Tests of COVID-19 in Bangui at the Beginning of the Second Wave in July 2021

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Journal of Tuberculosis Research 2024年第1期12卷 1-12页

作者： Clotaire Donatien Rafaï Marie-Roseline Darnycka Belizaire Pierre Somse Wilfrid Sylvain Nambei Ernest Lango-Yaya Oscar Senzongo luc Salva Hereidebona Ulrich Jeffrey Kotemossoua Rabbi Mermoz Senekian Simon Pounguinza Christian-Diamant Mossoro-Kpinde Alain Le Faou Jean De Dieu Longo François-Xavier Mbopi-Keou Gérard Grésenguet Boniface Koffi National Laboratory of Clinical Biology and Public Health Bangui Central African Republic Faculty of Health Sciences University of Bangui Bangui Central African Republic World Health Organization Bangui Central African Republic Ministry of Health and Population Bangui Central African Republic Faculty of Medicine Maieutic and Health Sciences University of Lorraine Pole Brabois Santé Nancy France Faculty of Medicine and Biomedical Sciences University of Yaounde I Yaounde Cameroun

Objective: COVID-19 surveillance was established as early as March 2020 in the Central African Republic (CAR), after the WHO statement relating to the identification of several cases outside China. However, given the non-performing molecular biology technical platform in many developing countries in sub-Saharan Africa, the second wave promised to be surprising and formidable. In this context, a mass survey was launched in Bangui to determine the prevalence of COVID-19. Patients and Methods: From March 18 to April 2, 2021, a mass screening campaign took place in tourist places, companies and the main hospital infrastructures. Nasopharyngeal swab samples were collected from participants with and without symptoms of Influenza-like illness (ILI) and stored in VTM tubes. The Ag (COVID-19) and RT-PCR tests were carried out in Bangui at the LNBCSP. The sequencing of RT-PCR SARS-CoV-2 positives was carried out at the INRB. Results: We included 1480 participants of whom 33 (2.23%) were SARS-COV-2 positive, of whom 24 were male and 9 female. This sex difference was statistically significant (p = 0.012) as the sex ratio M/F was 1.09. Sampling sites located in the 1st arrondissement were the most prolific (p = 0.006) and were sequenced. In addition to the analysis of the 33 samples from the predefined sites under study, 17 control sequences from the provinces generated during the same period are added. We detected 2 Variants Of Concern (VOC) including the predominant B.1.620 (43.86%) followed by B.1.1.7 or Alpha (5.10%). Conclusion: The study showed the importance of surveillance and the availability of means of diagnosis of COVID-19. The identified risk factors were sex and sampling site. This study has shown the importance of setting up sentinel sites for COVID-19 surveillance in all regions of the country and the appropriate use of the anti-COVID-19 vaccine.

关键词： COVID-19 Variants Central African Republic

Existence and Uniqueness to a Fully Nonlinear Version of the Loewner–Nirenberg Problem Dedicated to Celebrate the Sixtieth Anniversary of USTC

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Communications in Mathematics and Statistics 2018年第3期6卷 269-288页

作者： María del Mar González YanYan Li luc Nguyen Departamento de Matemáticas Universidad Autónoma de MadridCampus de Cantoblanco28049 MadridSpain Department of Mathematics Hill CenterBusch CampusRutgers University110 Frelinghuysen RoadPiscatawayNJ 08854USA Mathematical Institute and St Edmund Hall University of OxfordAndrew Wiles BuildingRadcliffe Observatory QuarterWoodstock RoadOxford OX26GGUK

We consider the problem of finding on a given Euclidean domainof dimension n≥3 a complete conformally flat metric whose Schouten curvature A satisfies some equations of the form f(λ(−A))=*** generalizes a problem considered by Loewner and Nirenberg for the scalar *** prove the existence and uniqueness of such metric when the boundary δΩ is a smooth bounded hypersurface(of codimension one).When δΩ contains a compact smooth submanifold ∑ of higher codimension with δΩ\∑ being compact,we also give a‘sharp’condition for the divergence to infinity of the conformal factor near ∑ in terms of the codimension.

关键词： Fully nonlinear Loewner-Nirenberg problem Singular fully nonlinear Yamabe metrics Conformal invariance

Minimal Lagrangian submanifolds of the complex hyperquadric

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Science China Mathematics 2020年第8期63卷 1441-1462页

作者： Haizhong Li Hui Ma Joeri Van der Veken luc Vrancken Xianfeng Wang Department of Mathematical Sciences Tsinghua UniversityBeijing 100084China Department of Mathematics KU LeuvenLeuven 3001Belgium Institut des Sciences et Techniques de Valenciennes Universite Polytechnique Hauts-de-FranceCampus du Mont HouyValenciennes 59313France School of Mathematical Sciences and LPMC Nankai UniversityTianjin 300071China Mathematical Sciences Institute Australian National UniversityCanberraACT 2601Australia

We introduce a structural approach to study Lagrangian submanifolds of the complex hyperquadric in arbitrary dimension by using its family of non-integrable almost product *** particular,we define local angle functions encoding the geometry of the Lagrangian submanifold at *** prove that these functions are constant in the special case that the Lagrangian immersion is the Gauss map of an isoparametric hypersurface of a sphere and give the relation with the constant principal curvatures of the *** also use our techniques to classify all minimal Lagrangian submanifolds of the complex hyperquadric which have constant sectional curvatures and all minimal Lagrangian submanifolds for which all local angle functions,respectively all but one,coincide.

关键词： minimal Lagrangian submanifolds the complex hyperquadric constant sectional curvature Gauss map isoparametric hypersurface

Electrical Conductivity and Current-Voltage Characteristics of Individual Conducting Polymer PEDOT Nanowires

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Chinese Physics Letters 2008年第9期25卷 3474-3477页

作者：龙云泽 DUVAIL Jean-luc 陈兆甲金爱子顾长志 College of Physics Science Qingdao University Qingdao 266071 Institut des Materiaux Jean Rouxel Universite de Nantes CNRS 44322 Nantes Prance Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing 100190

We report the current-voltage （Ⅰ-Ⅴ） characteristics and electrical conductivity of individual template-synthesized poly（3,4-ethylenedioxythiophene）（PEDOT） nanowires （190 ± 6 nm in diameter and δRT = 11.2 ± 2Ω^-1 cm^-1） over a wide temperature range from 300 to 10K. With lowering temperature, the Ⅰ - Ⅴ characteristics become nonlinear around 50K, and a clear Coulomb gap-like structure appears in the differential conductance （dI/dV） spectra. The temperature dependence of the resistance below 70 K follows In R α T^-1/2, which can be interpreted as Efros-Shklovskii hopping conduction in the presence of a Coulomb gap. In addition, the influences of measurement methods such as the applied bias voltage magnitude, the two-probe and four-probe techniques used in the resistance measurements are also reported and discussed.

关键词： FIELD-EFFECT TRANSISTORS JUNCTIONS Current--Voltage Characteristics

The control of soil polarization in Populus simonii and Quercus liaotungensis forests by forage litter on the Loess Plateau,P. R. China

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Journal of Forestry Research 2015年第3期26卷 687-695页

作者： Nhu Trung luc Zengwen Liu Yuanhao Bing Xiaoxi Zhang Thi Huong Nguyen Institute of Soil and Water Conservation Northwest A&F University Department of Agriculture and Rural Development of Lao Cai Lao Cai City 330100 Vietnam College of Natural Resources and Environment Northwest A&F University Key Laboratory of Plant Nutrition and the Agri-environment in Northwest China Ministry of Agriculture College of Forestry Northwest A&F University Department of Natural Resources and Environment of Lao Cai Lao Cai City 330100 Vietnam

Soil polarization in pure forest stands affects the stability and sustainable development of the ecosystem. The most effective approaches to the prevention of soil polarization may be the use of forage litter as fertilizer or the direct establishment of tree-grass communities. We investigated monospecific plantations of Populus simonii and Quercus liaotungensis. Such plantations have been established throughout the Loess Plateau of China. A 120-day decomposition incubation experiment with forest humus soil mixed with 7 common leguminous forage litterspecies was performed to study the uses of forage litter in controlling soil polarization in pure forests. The addition of forage litter of Astragalus adsurgens, Lespedeza bicolor, and Vicia viUosa to the soil of pure P. simonii forest clearly improved the soil quality, these forage species are suitable for planting with P. simonii, whereas Melilotus officinalis, Medicago sativa, and Onobrychis viciifolia litter produced obvious deterioration, thus these forages should not be planted with P. simonii. Coronilla varia litter showed no significant influence. The addition of forage litter of M. sativa to the soil of pure Q. liaotungensis forest clearly improved the soil quality, and C. varia and V. villosa also yielded improvements but were slightly less effective than M. sativa litter, these forages are suitable to be planted with Q. liaotungensis. However, L. bicolor showed obvious deterioration, followed by O. viciifolia and A. adsurgens, and M. officinalis had no significant influence. These spe- cies should not be planted with Q. liaotungensis.

关键词： Soil polarization Forage litter Populussimonii Quercus liaotungensis

Non-steroidal anti-inflammatory drugs(NSAIDs) and neuroprotection in the elderly a view from the mitochondria

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Neural Regeneration Research 2015年第9期10卷 1371-1372页

作者： María Calvo-Rodríguez lucía Nú?ez Carlos Villalobos Instituto de Biologíay Genética Molecular (IBGM) Consejo Superior de Investigaciones Científicas (CSIC) and Universidad de Valladolid

The most important risk factor for stroke and neurodegeneration is aging. In fact, survival after stroke diminishes largely with aging. In fact, recovery after brain artery occlusion is dramatically worsened by aging, even normal aging is associated with neuron damage and cognitive decline. Mechanisms involved in aging-related, cognitive decline and susceptibility to neuron damage in stroke and neurode- generation are largely unknown. One of the most important mech- anisms contributing to neural dysfunction and death is excitotox- icity. This process is based on the fact that the excessive glutamate receptor stimulation may lead to neuronal damage. This overstim- ulation may be due to increased concentration of glutamate, or the prolonged activation of receptors.

关键词： NSAIDs Non-steroidal anti-inflammatory drugs and neuroprotection in the elderly a view from the mitochondria view