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Structural and electron charge density studies of a nonlinear optical compound 4,4 di-methyl amino cyano biphenyl

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Chinese Physics B 2014年第1期23卷 312-317页

作者： Naima Boubegra, Abdelkader Chouaih, Mokhtaria Drissi and Fodil Hamzaoui achouaih@*** []laboratoire de Technologie et Proprits du Solide (LTPS) Universit Abdelhamid Ibn Badis de Mostaganem 27000 Mostaganem Algeria

The 4,4 dimethyl amino cyano biphenyl crystal (DMACB) is characterized by its nonlinear activity. The intra molecular charge transfer of this molecule results mainly from the electronic transmission of the electro-acceptor (cyano) and electro-donor (di-methyl-amino) groups. An accurate electron density distribution around the molecule has been calculated based on a high-resolution X-ray diffraction study. The data were collected at 123 K using graphite-monochromated Mo K α radiation to sin(β)/λ = 1.24 Å−1. The integrated intensities of 13796 reflections were measured and reduced to 6501 independent reflections with I ≥ 3σ(I). The crystal structure was refined using the experimental model of Hansen and Coppens (1978). The crystal structure has been validated and deposited at the Cambridge Crystallographic Data Centre with the deposition number CCDC 876507. In this article, we present the thermal motion and the structural analysis obtained from the least-square refinement based on F2 and the electron density distribution obtained from the multipolar model. [ABSTRACT FROM AUTHOR]

关键词： ELECTRON density X-ray diffraction CRYSTAL structure STRUCTURAL analysis (Science) CARRIER density (Semiconductors)

Recent advances in development of vertical-cavity based short pulse source at 1.55 μm

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Frontiers of Optoelectronics 2014年第1期7卷 1-19页

作者： Zhuang ZHAO Sophie BOUCHOULE Jean-Christophe HARMAND Gilles PATRIARCHE Guy AUBIN Jean-Louis OUDAR laboratoire de Photonique et de Nanostructures (LPN) CNRS Marcoussis France

This paper reviews and discusses recent developments in passively mode-locked vertical external cavity surface emitting lasers （ML-VECSELs） for short pulse generation at 1.55 gin. After comparing ML- VECSELs to other options for short pulse generation, we reviewed the results of ML-VECSELs operating at telecommunication wavelength and point out the chal- lenges in achieving sub-picosecond operation from a ML- VECSEL at 1.55 gm. We described our recent work in the VECSELs and semiconductor saturable absorber mirrors （SESAMs）, their structure design, optimization and characterization, with the goal of moving the pulse width from picosecond to sub-picosecond.

关键词： semiconductor laser vertical external cavitysurface emitting laser (VECSEL) indium phosphide heatdissipation saturable absorber mirror mode-locking

Tribological Behavior of CoCr28Mo/CoCr28Mo Pair in the Presence of Bio-lubrication

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Journal of Bionic Engineering 2018年第4期15卷 703-712页

作者： Manel Guezmil Walid Bensalah Salah Mezlini laboratoire de Genie Mecanique (LGM) ENIM Rue Ibn Eljazzar 5019 Monastir University Tunisia

The tribological behavior of the CoCr28Mo/CoCr28Mo pair was studied using pin-on-disc tribometer. Four bio-lubricants were re- tained including pure sesame oil, nigella oil, physiological solution （0.9% NaC1） and Hyalgan. Hyalgan is a sodium hyaluronate （20 mg/2 mL） pharmaceutical intra-articular injection used, in this study, as a reference. The Coefficient of Friction （CoF） and wear rate （K） of CoCr28Mo were computed after tribological tests. The tribological efficiency of vegetable oils with regard to their chemical compo- sition and structure was compared to Hyalgan. It is found that, the use of vegetable oils enhanced significantly the tribological behavior of CoCr28Mo/CoCr28Mo pair. The obtained results were correlated to the chemical structure of vegetable oils namely the Unsaturations Number （UN） of fatty acids constituting the oil. Microscopic and chemical characterization of CoCr28Mo pins and discs were conducted and the wear mechanism was discussed.

关键词： CoCr alloy friction coefficient wear resistance oil lubrication

Structure of Channel Flows with Surface Mounted Ribs

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Journal of Thermal Science 2004年第3期13卷 213-219页

作者： Gérard J. POITRAS Laurent-Emmanuel BRIZZI Yves GAGNON Université de Moncton Moncton (NB) CanadaLaboratoire d'études aérodynamiques Université de Poitiers 86960 Futuroscope FranceUniversité de Moncton Edmundston (NB) Canada

The flow inside a channel with surface mounted ribs is studied by numerical simulation and experimental flow visualization. Both the geometry with one rib and the geometry with two ribs, placed perpendicular to the flow, are studied, with particular emphasis on the effect of the variation of the distance between the ribs on the structure of the flow. Results show that, for Reynolds number flows of 400 and 1000 (based on the uniform incoming velocity and the height of the ribs), the flow reattaches between the ribs when they are separated by distances of 12h (h being the height of the ribs) and 6h, respectively. In this respect, however, the numerical results for the Reynolds number flow of 1000 are in contradiction with published results.

关键词： vortex methods flow visualization channel flows ribs.

Natural frequencies of composite beams with a variable fiber volume fraction including rotary inertia and shear deformation

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Applied Mathematics and Mechanics(English Edition) 2009年第6期30卷 717-726页

作者： Y. Bedjilili A. Tounsi H. M. Berrabah I. Mechab E. A. Adda Bedia S. Benaissa Université de Tlemcen Faculté des Sciences de l'ingénieurDépartement de Génie MécaniqueAlgérie laboratoire des Matériaux et Hydrologie Université de Sidi Bel AbbesAlgérie laboratoire de Mathématiques Université de Sidi Bel AbbesAlgérie

The present study is concerned with the vibration analysis of symmetric composite beams with a variable fiber volume fraction through thickness. First-order shear deformation and rotary inertia have been included in the analysis. The solution procedure is applicable to arbitrary boundary conditions. Continuous gradation of the fiber volume fraction is modeled in the form of an m-th power polynomial of the coordinate axis in the thickness direction of the beam. By varying the fiber volume fraction within the symmetric composite beam to create a functionally graded material （FGM）, certain vibration characteristics are affected. Results are presented to demonstrate the effects of shear deformation, fiber volume fraction, and boundary conditions on the natural frequencies and mode shapes of composite beams.

关键词： free vibration functionally graded materials first-order shear deformationtheory

Surface Effects on Wannier Excitons in Superlattices:Monte Carlo Simulation

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Chinese Physics Letters 2002年第8期19卷 1164-1167页

作者： K. Afif, A. Benyoussef and J. Diouri laboratoire de Magnetisme Faculte des Sciences Groupe d"Electronique et de Physique du Solide Faculte des Science

Using a Monte Carlo quadrature, we calculate by a variational method the binding energy Eb of Wannier excitons in N-period m-CdMnTe/n-CdTe superlattices, including or not including the step discontinuity in the potential barrier at the interface, and with varying N as well as well width. The calculation is performed in the framework of the effective mass approximation for both heavy-hole and light-hole excitons. The degree of exciton localization dependence on these parameters is accurately illustrated.

关键词： Monte Carlo methods

Auto-correlation Effects on the sp^3-d Exchange Interaction in Cd1-x MnxTe/CdTe Multilayers

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Chinese Physics Letters 2002年第11期19卷 1679-1682页

作者： K. Afif, A. Benyoussef and J. Diouri laboratoire de Magnetisme Faculte des Sciences Groupe d"Electronique et de Physique du Solide Faculte des Sciences

Band offsets and total energy of Wannier excitons in multilayers are affected by dimensional and auto-correlation effects, and sp^3-d coupling is consequently modified. Thus, the calculation of the Zeeman splitting in the quantum wells has to take into account these effects, especially when the mismatch cannot be disregarded. In this work, the theoretical study of these combined effects has been performed for Cd1-xMnxTe/CdTe multilayers embedded by Cd1-yZnyTe as the substrate (or the buffer) on one side and as a cladding layer on the other side. This sample allows us to highlight the role played by the substrate (buffer) and the growth direction on the Zeeman splitting in such multilayers

关键词： Multilayers

Complex dynamics of an archetypal self-excited SD oscillator driven by moving belt friction

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Chinese Physics B 2016年第1期25卷 480-488页

作者：李志新曹庆杰 Léger Alain School of Astronautics Harbin Institute of Technology laboratoire de Mécanique et d'Acoustique CNRS

We propose an archetypal self-excited system driven by moving belt friction, which is constructed with the smooth and discontinuous （SD） oscillator proposed by the Cao et al. and the classical moving belt. The moving belt friction is modeled as the Coulomb friction to formulate the mathematical model of the proposed self-excited SD oscillator. The equilibrium states of the unperturbed system are obtained to show the complex equilibrium bifurcations. Phase portraits are depicted to present the hyperbolic structure transition, the multiple stick regions, and the friction-induced asymmetry phenomena. The numerical simulations are carried out to demonstrate the friction-induced vibration of multiple stick-slip phenomena and the stick-slip chaos in the perturbed self-excited system. The results presented here provide an opportunity for us to get insight into the mechanism of the complex friction-induced nonlinear dynamics in mechanical engineering and geography.

关键词： self-excited smooth and discontinuous (SD) oscillator multiple stick regions friction-inducedasymmetry stick-slip chaos

Physico-chemical and mechanical properties of Ti_3SiC_2-based materials elaborated from SiC/Ti by reactive spark plasma sintering

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Journal of Advanced Ceramics 2019年第1期8卷 47-61页

作者： Faten TURKI Houyem ABdeRRAZAK Frédéric SCHOENSTEIN Florent TêTARD Mohieddine ABdeLLAOUI Noureddine JOUINI laboratoire des Matériaux Utiles Institut National de Recherche et d’Analyse Physico-chimique laboratoire de Sciences des Procédés et Matériaux Université Paris 13 Sorbonne Paris Cité CNRS

In this paper, the synthesis of Ti_3 SiC_2 from SiC/Ti powder using reactive spark plasma sintering(R-SPS) in the temperature range of 1300-1400 ℃ is reported. The results show that the purity of Ti_3 SiC_2 is improved up to 75 wt% when the holding time is increased from 10 to 20 min at1400 ℃. The thermodynamic and experimental results indicate that Ti_3 SiC_2 formation takes place via the reaction of a pre-formed TiC phase with the silicides, formed from the eutectic *** analysis of mechanical behaviour indicates that samples with higher percentage of secondary phases exhibit higher microhardness and better resistance compared to the near single phase Ti_3 SiC_2.

关键词： Ti3SiC2 reactive spark plasma sintering(R-SPS) density mechanical properties