Analyse théorique et caractérisation expérimentale ďune jonction Y intégrée utilisée comme capteur de déplacement

The coherent coupling of radiation modes in symmetric single-mode Y-junction excited by a single mode fiber is studied in this work. Using the bpm (beam propagation method) we find that the power splitting between the two outputs of the junction depends strongly on the fiber displacement with respect to the junction axis of symmetry. A GaAs/GaAlAs single mode junction is tested and the experimental measurements show a splitting ratio as high as 12 dB that could not be explained if the radiation field is neglected. The experimental results confirm the theoretical predictions that take into account the propagation of radiation modes in the structure. These results propose the structure to be used as an integrated optical displacement sensor with a sensitivity in the order of 5 dB/μm and a dynamic range within 4 to 5 μm.     

Study of Heat Effect on the Composition of Dunes Sand of Ouargla (Algeria) Using XRD and FTIR

The spectra of x-ray diffraction (XRD) and infrared spectroscopy (FTIR) shows that the dunes sand of Ouargla’s region consists naturally of crystalline structures of α-quartz and gypsum, as well as other uncrystallized compounds with low concentrations like kaolinite and hematite, in addition to some organic compounds. The sand heating process at temperatures between 200 and 1200 °C affects its composition. By heating at 200 °C crystalline phases of anhydrite and bassanite appear due to the continuing loss of water from the gypsum. All the gypsum transforms into anhydrite, and the kaolinite transforms into metakaolin because of the breaking of the OH bond, producing water vapor by heating in the range of 400–800 °C. The heating at 1000 °C disassembles the kaolinite into aluminium-silicon and cristobalite, and leads to the emergence of a new crystalline phase related to wollastonite resulting from the start of a reaction between the anhydride and the quartz. Heating at 1200 °C leads to the disappearance of all the anhydrite because of its interaction with the quartz, producing the wollastonite and the release of sulfur dioxide SO₂ and oxygen O₂, in addition to the increase of the cristobalite proportion because of the disintegration of all the kaolinite into mullite and cristobalite, or the transformation of quartz phase into cristobalite. Also occuring is an interaction between the hematite and the quartz producing the ferrosilite characterized by its green color.     

超静定型钢桁架满应力设计中压杆稳定许用应力的简便算法

压杆稳定许用应力的计算,是超静定型钢桁架满应力设计的技术关键,迄今未很好解决。在离散变量连续化处理的基础上,导出了各种截面型钢压杆在每次迭代计算中稳定许用应力的通用计算公式,该公式形式简单,极易在程序中实现,供结构设计工作者参考。     

Numerical analysis of the crack growth path in the cement mantle of the reconstructed acetabulum

In this study, we use the finite element method to analyze the propagation's path of the crack in the orthopedic cement of the total hip replacement. In fact, a small python statement was incorporated with the Abaqus software to do in loop the following operations: extracting the crack propagation direction from the previous study using the maximal circumferential stresses criterion, drawing the new path, meshing and calculating again (stresses and fracture parameters). The loop is broken when the user's desired crack length is reached (number of propagations) or the value of the mode I stress intensity factor is negative. Results show that the crack propagation's path can be influenced by human body posture. The existing of a cavity in the vicinity of the crack can change its propagation path or can absolutely attract it enough to meet it. Crack can propagate in the outward direction (toward the acetabulum bone) and cannot propagate in the opposite direction, the mode I stress intensity factor increases with the crack length and that of mode II vanishes.     

Relation between structure and mechanical properties (elastoplastic and fracture behavior) of hybrid organic–inorganic coating

The mechanical properties of various inorganic organic films were studied and compared in order to investigate the relation between structural modifications and the mechanical behavior. Films were prepared by a sol–gel process and spin-coated on silicon substrate. The organic–inorganic hybrid is composed of a mixture of colloidal silica and organosiloxane precursors. The functionality of the organosiloxane and the nature of its organic part have been modified to obtain a structural change. Mechanical properties were studied using nanoindentation. Analysis of the strength evolution as a function of depth of indentation shows the layer hardness and elastic modulus. Moreover, coating and interface toughness and residual stresses were determined by a time resolved study of energy dissipation during indentation. The structural changes were determined using liquid and solid ²⁹Si NMR spectroscopy. Quantity of partially and fully condensed species in the deposited sol and final solid are discussed in relation to the mechanical properties.     

Definition of requirements for accessing multilingual information opinions

Multimedia Tools and Applications - In this paper, we will present a study concerning the understanding of the needs of people using Internet in order to access to multilingual information. In...     

Chromatic Classification of Ouargla (Algeria) Dunes Sand: Determination of Main Compositions and Color Causes,by Using XRD,FTIR and XRF

In the present work, a manually chromatic classification of Ouargla dunes sand has been carried out. According to its visual color, eight chromatic types of sand have been obtained: transparent (yellow, orange and red), and opaque (white, milky, gray, black and red). According to the main chemical compositions of sand, both XRD and FTIR have divided the chromatically sorted sand into three groups: quartzite (transparent samples), calcareous (milky, gray and black opaque samples) and calcareous quartzite (white and red opaque samples), without possibility of distinguishing between the sorted samples. FTIR spectroscopy has shown all functional groups and vibration modes in these samples. XRF spectroscopy has shown that sand grain colors are closely related to the main compositions as well as the impurities. It has also been shown that transparent samples contain more than 92 % of quartz (SiO ₂). The redness of transparent samples is proportional to iron (Fe) impurities. It has also been shown that milky, gray and black opaque samples contain more than 55 % of calcium oxide (CaO). The milky color is due to magnesium (Mg) and sulfur (S), whereas the blackness is due to iron (Fe) and manganese (Mn). Both white and red opaque samples contain approximately equal concentrations of quartz and calcite, whilst the redness refers to the high concentration of iron (Fe), whereas the whiteness is due to the presence of magnesium (Mg).     

Optimization of cleaning schedulesin heat exchanger networkssubject to fouling

Many heat exchanger networks in continuous processes are subject to fouling, which causes significant losses in efficiency over time. This paper addresses the problem posed in scheduling cleaning operations in order to maintain optimal operation in such networks. A mixed integer nonlinear programming modelis presented and is solved using the Outer Approximation/Extended Relaxation algorithm. The methodology is demonstrated via case studies using fouling rates obtained from plant data studies. Both linear and asymptotic fouling behaviors are considered. The challenges posed by the nonconvexity of the problem in finding a global optimum are discussed.     

Numerical study of the influence of diesel post injection and exhaust gas expansion on the thermal cycle of an automobile engine

This study deals with the development of a numerical tool developed to analyze the thermomanagement of the heat rejection from the fuel combustion in the case of a four cylinder 2 L – 110 HP direct injection Diesel engine. It is composed of two main elements: the first one simulates all the phenomena linked to the combustion, the second one is about thermal exchanges in the heart of the engine. We only deal with the first one here.The combustion study is based on two aspects: the consideration of multi injection (the pilot injection, the main injection and the post injection) and the simulation of compressible flows through the exhaust valves.This model allows us to predict the combustion chamber energy balance (heat fluxes, mechanical work) and the fuel consumption with an experimental tolerance within 3%. Engine tests have been made at the laboratory to validate this result.Fuel consumption calculation is linked to the accurate estimation of the exhaust gas flow and temperature. The main interest of this method is that it takes into account the sonic blockage at the exhaust valve opening.This work has also allowed to precise the post injection importance during the engine temperature rise. The increase in thermal rejects is used to accelerate the warm up of the different engine fluids.