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Modeling and numerical analysis of granite rock specimen under mechanical loading and fire

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岩石力学与工程学报 2015年第1期34卷 101-108页

作者： Luc Leroy Ngueyep.Mambou Joseph Ndop jean-marie bienvenu ndjaka Laboratory of Sciences Material Department of PhysicsFaculty of ScienceUniversity of Yaoundé Department of Mine Mineral Processing and EnvironmentSchool of Geology and Mining EngineeringUniversity of Ngaoundéré Douala Institute of Technology

The effect of ISO 834 fire on the mechanical properties of granite rock specimen submitted to uniaxial loading is numerically investigated. Based on Newton's second law, the rate-equation model of granite rock specimen under mechanical load and fire is established. The effect of heat treatment on the mechanical performance of granite is analyzed at the center and the ends of specimen. At the free end of granite rock specimen, it is shown that from 20 C to 500 C, the internal stress and internal strain are weak; whereas above 500 C, they start to increase rapidly, announcing the imminent collapse. At the center of specimen, the analysis of the internal stress and internal strain reveals that the fi re reduces the mechanical performance of granite signi fi cantly. Moreover, it is found that after 3 min of exposure to fi re,the mechanical energy necessary to fragment the granite can be reduced up to 80%.

关键词： Granite rock specimen High temperature Internal stress Internal strain ISO 834 fire

Displacements, Strains, and Stresses Investigations in an Inhomogeneous Rotating Hollow Cylinder Made of Functionally Graded Materials under an Axisymmetric Radial Loading

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World Journal of Mechanics 2018年第3期8卷 59-72页

作者： Elise Rose Atangana Nkene Luc Leroy Mambou Ngueyep Joseph Ndop Emma Sandring Djiokeng jean-marie bienvenu ndjaka Department of Physics Faculty of Sciences University of Douala Douala Cameroon Douala Institute of Technology Douala Cameroon Laboratory of Material Sciences Department of Physics Faculty of Sciences University of Yaoundé 1 Yaoundé Cameroon Department of Mine Mineral Processing and Environment School of Geology and Mining Engineering University of Ngaoundéré Meiganga Cameroon

In this paper, an analytical and numerical study of strain fields, stress fields and displacements in a rotating hollow cylinder, whose walls were completely made in Functionally Graded Materials (FGM), was conducted. We have considered the rotating hollow cylinder submitted to an asymmetric radial loading. It is assumed that, because of the functional graduation of the material, the mechanical properties such as Young elastic modulus and the density varies in the radial direction, in accordance with a the power law function. The inhomogeneity parameter was selected between -1 and 1. On the basis of the second law of Newton, Hooke’s law and the strain-stress relationship, we established the differential equation which governs the equilibrium for a rotating hollow cylinder. We found the analytical solution and compared to the numerical solution obtained by using the shooting method and the fourth order Runge-Kutta algorithm. The analytical and numerical results lead to the conclusion that the magnitude of the tangential stresses is greater than that of the radial stresses. The changes due to the graduation of FGM does not produce consistent variations in the distribution of radial stresses, but strongly affects the distribution of tangential stresses. The tangential stresses, tangential strains and displacements are much higher at the inner surface of the cylinder wall. The internal radial pressure intensely affects the radial stresses and the radial strain.

关键词： Functionally Graded Materials Radial Stresses Tangential Stresses Cylinder Wall

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

Density Results in Sobolev Spaces Whose Elements Vanish on a Part of the Boundary

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Chinese Annals of Mathematics,Series B 2011年第6期32卷 823-846页

作者： jean-marie Emmanuel BERNARD Laboratoire Analyse et Probabitilités Université d'Evry val d'Essonne23 Boulevard de France91037 EVRYFrance

This paper is devoted to the study of the subspace of Wm＇＂ of functions that vanish on a part γ0 of the boundary. The author gives a crucial estimate of the Poincare constant in balls centered on the boundary of γ0. Then, the convolution-translation method, a variant of the standard mollifier technique, can be used to prove the density of smooth functions that vanish in a neighborhood of γ0, in this subspace. The result is first proved for m = 1, then generalized to the case where m 〉 1, in any dimension, in the framework of Lipschitz-continuous domain. However, as may be expected, it is needed to make additional assumptions on the boundary of γ0, namely that it is locally the graph of some Lipschitz-continuous function.

关键词： Density results Boundary value problems Sobolev spaces

Multiplexing technology for in vitro diagnosis of pathogens： the key contribution of phosphorus dendrimers

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Science China Materials 2018年第11期61卷 1454-1461页

作者： jean Pierre Majoral jean marie Francois Richard Fabre Alice Senescau Serge Mignani Anne-marie Caminade Laboratoire de Chimie de Coordination du CNRS 31077 Toulouse Cedex 4France LCC-CNRS Universit6 de Toulouse CNRSToulouseFrance Dendris 31670 LabegeFrance LISBP UMR CNRS 5504 INRA 79231077 Toulouse Cedex 04France Universite Paris Descartes PRES Sorbonne Paris Cite CNRS-UMR 860Laboratoire de Chimie et de Biochimie Pharmacologiques et Toxicolgique75006 ParisFrance

After the microbiology based on Pasteur's method and polymerase chain reaction(PCR), the diagnosis company named Dendris has proposed a third-generation of diagnosis enabling the search of a broad range of pathogens with strong sensitivity and specificity. This extraordinary profile was possible thanks to the use of phosphorus dendrimers for which various techniques of deposition on a given support were investigated and described and analyzed in this report.

关键词： phosphorus dendrimers diagnosis DNA arrays multiplexing technology

Effects of indole-3-butyric acid and age of stem cuttings on root morphology,growth,and survival of Cornus sericea

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Journal of Forestry Research 2023年第2期34卷 433-440页

作者： Sahari Inoue Chibuzo Ilogu jean-marie Sobze Northern Alberta Institute of Technology Centre for Boreal ResearchPeace RiverAB T8S 1R2Canada Fine Phenotyping Lab Crop Health and ProtectionHarpenden AL52JQUK

Red osier dogwood(Cornus sericea L.),widely distributed throughout North America,is essential for wildlife,thus *** is recommended for reclamation or revegetation of sites disturbed by oil and gas extraction because it tolerates a wide range of soil types and high pH *** germination of this species is extremely difficult with long stratification requirements and poor germination,cuttings facilitate *** this study,to develop techniques to propagate the species from stem cuttings,four concentrations of indole-3-butyric acid(IBA)and two cutting ages previous year’s growth(PYG)and current year’s growth(CYG)were investigated for survival and *** 4 months,survival rate,height growth,and shoot biomass from PYG cuttings were enhanced with IB *** contrast,IB A did not affect these parameters in CYG *** morphology was significantly affected by IB A concentration and cutting ***,at higher concentrations,increased root surface and *** root surface area and length of PYG cuttings were increased,which may facilitate the absorption of essential resources and consequently increase *** results indicate that increasing the concentration of IB A may be an effective way to have better plant survival and growth of previous year’s cuttings in red osier dogwood.

关键词： Vegetative propagation IBA Chronological age Cornus sericea L. Survival rate

Density and Strength of Mortar Made with the Mixture of Wood Ash, Crushed Gneiss and River Sand as Fine Aggregate

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Journal of Materials Science and Chemical Engineering 2018年第4期6卷 109-120页

作者： Mambou Ngueyep Luc Leroy Keyangue Tchouata Jules Hermann Atangana Nkene Elise Rose Ndop Joseph Fotseu Miyo Christian Dupont ndjaka jean-marie bienvenu Laboratory of Material Sciences Department of Physics Faculty of Sciences University of Yaoundé 1 Yaoundé Cameroon School of Geology and Mining Engineering University of Ngaoundéré Meiganga Cameroon Douala Institute of Technology Douala Cameroon Department of Physics Faculty of Sciences University of Douala Douala Cameroon

The main purpose of this paper is to study the feasibility of using wood bottom ash to partially replace natural fine aggregate or crushed gneiss sand in the manufacturing of mortars. The experiment uses wood ash as fine aggregates, which passes through 5 mm sieve, in proportions of 5%, 10%, 15%, 20% and 25% by weight to replace partially river sand and crushed gneiss, and the both sand of the same size as the aggregate respectively. Experimental results show that density of mortar and the compressive strength of mortar decrease globally with the increase in wood ash content. At 56 days, and for all replacements with wood ash, compressive strengths values of mortar obtained with the mixture of wood ash and river sand is greater than 20 MPa, which is not the case for mortar made with crushed gneiss and wood ash. Moreover, for 5% of replacement with wood ash, compressive strengths of mortar obtained with the mixture of wood ash and river sand and the mixture of wood ash and crushed gneiss are respectively 37 MPa and 32 MPa at 56 days. These values satisfied the strength requirements. Hence, 5% replacement of crushed gneiss with wood ash is suggested and could be benefit for mortar. In addition, the replacement of sand by wood ash is preferable with river sand which contains fewer fines than crushed gneiss. The compressive strength of mortar with 25% wood ash + river sand could be suitable.

关键词： Wood Bottom Ash River Sand Crushed Gneiss Mortar Compressive Strength Density

Environmental photocatalysis:Perspectives for China

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Science China Chemistry 2010年第9期53卷 1831-1843页

作者： HERRMANN jean marie Institut de Recherches sur la Catalyse et l'Environnement de Lyon UMR 5256 CNRS/Université Lyon1 2 Av.Albert Einstein 69626 Villeurbanne Cedex

Photocatalysis is based on the double aptitude of the photocatalyst(essentially titania) to simultaneously adsorb reactants and absorb efficient *** photocatalysis is able to be efficient in Fine,"Green" and Environmental *** induces mild oxidations in the absence of water by generating active neutral atomic O* *** instance,the oxidation of 4-tert-butyl-toluene is 100% selective in *** water treatment,many toxic inorganic ions are oxidized in their harmless upper oxidized *** elimination of organic pollutants is the main field of water photocatalytic *** of aliphatic and aromatic pollutants are totally mineralized into CO2 and innocuous inorganic *** complex molecules,such as pesticides(herbicides,insecticides,fungicides,etc.) or dyes,are totally *** example of green chemistry is the total degradation of dyes in water,in particular for the azo-dyes,with 100% selective degradation of -N=N-azo-groups into *** is also active in the "bio-world" by killing bacteria(***,streptococcus,etc.) in water without *** pollutants can also be destroyed,especially all the VOC's(volatile organic compounds),providing certain air humidity enabling titania to produce cracking OH* *** chemical engineering reasons,the photocatalyst has to be fixed on a photo-inert *** these conditions,UV-irradiated titania-based photocatalysis could be applied to the elimination of air pollutants,VOC's,solvents,odors,chemicals,*** treatment has to be associated with water and solid waste treatment because of *** is conducted by covering water treatment ponds or lagunas by rafts on which large sheets of Ahlstrom paper are deposited,supporting titania associated with activated ***,virus AH5N2,a model virus close to H5N1,responsible for the avian flu could be totally *** is directly connected wi

关键词： photocatalysis green chemistry environmental chemistry air pollutants water pollutants solar energy China

Synthesis of a novel macrocyclic ligand containing bipyridine units

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Chinese Journal of Chemistry 2000年第3期18卷 384-387页

作者：何永炳 LEHN jean-marie Department of Chemistry Wuhan University Wuhan Hubei 430072 China

The 6-hydroxymethyl-6'-tetrahydropyranyloxymethyl-2, 2'-bipyridine (2) was synthesized by the reaction of 6,6'-dihydroxymethyl-2, 2'-bipyridine (1) with 3, 4-dihydroxypyran (DHP). ***-6'-iodomethyl-2, 2'-bipyridine (5) was obtained from mesylate and iodizating reaction of compound 2. The coupling of 2 and 5 followed by hydrolysis gave bis(6'-hydroxymethyl-2, 2'-bipyridine-6-methyl) ether (7). The macrocyclic ligand 8 was obtained by treating 7 and 6, 6'-dibromethyl-2, 2'-bipyridine. The synthetic conditions of the intermediate 2 and macocyclic ligand 8 were discussed.

关键词： azacrown ether bipyridine derivative macrocyclic ligand