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First-principles study of the new potential photovoltaic absorber:Cu_2MgSnS_4 compound

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Chinese Physics B 2017年第7期26卷 294-304页

作者： Belmorsli Bekki Kadda Amara Mohammed El Keurti laboratoire d'étude physico-chimique Université Dr.Moulay Tahar de Saida

The structural, electronic, optical, and elastic properties of Cu_2MgSnS_4 in four crystalline phases（wurtzite-stannite（WS）, stannite（ST）, kesterite（KS）, and primitive-mixed Cu Au（PMCA）） are investigated using density functional theory（dFT） in the framework of the full potential linearized augmented plane wave plus local-orbitals（FP-LAPW＋lo） method within the generalized gradient approximation based on the Perdew 2008 functional（GGA-PBEsol）. For each phase, the structural parameters, bulk modulus, and its pressure derivative are calculated. The relative stability of these phases is also discussed. In addition, the elastic constants have been calculated in order to investigate the mechanical stability of all phases. Moreover, the anisotropy factor, shear modulus, Young＇s modulus, Lame＇s coefficient, and Poisson＇s ratio have been estimated from the calculated single crystalline elastic constants. For the band structure, the density of states and optical properties of the exchange and correlation effects are treated by the Tran-Blaha modified Becke-Johnson potential to give a better description of the band-gap energies and optical spectra. The obtained results are compared with available experimental data and to other theoretical calculations.

关键词： quaternary chalcogenide semiconductor elastic constants electronic properties optical properties

Adjustment of the annual cycle to climatic change in a long-lived migratory bird species

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Current Zoology 2009年第2期55卷 92-101页

作者： A. P. MФLLER E. FLENSTEd-JENSEN W. MARdAL3 laboratoire d'ecologie Systématique et EvolutionCNRS UMR 8079Université Paris-SudBatiment 362F-91405 Orsay CedexFrance Cypresvej 1 DK-9700 BrФnderslevDenmark Legindvej 102 SФnderhDK-7752 SnedstedDenmark

Climate change has advanced the phenology of many organisms. Migratory animals face particular problems because climate change in the breeding and the wintering range may be asynchronous, preventing rapid response to changing conditions. Advancement in timing of spring migration may have carry-over effects to other parts of the annual cycle, simply because advancement of one event in the annual cycle also advances subsequent events, gradually causing a general shift in the timing of the entire annual cycle. Such a phenotypic shift could generate accumulating effects over the years for individuals, but also across generations. Here we test this novel hypothesis of phenotypic response to climate change by using long-term data on the Arctic tern Sterna paradisaea. Mean breeding date advanced by almost three weeks during the last 70 years. Annual arrival date at the breeding grounds during a period of 47 years was predicted by environmental conditions in the winter quarters in the Southern Ocean near the Antarctic and by mean breeding date the previous year. Annual mean breeding date was only marginally determined by timing of arrival the current year, but to a larger extent by arrival date and breeding date the previous year. Learning affected arrival date as shown by a positive correlation between arrival date in year （i ＋ 1） relative to breeding date in year （i） and the selective advantage of early breeding in year （i）. This provides a mechanism for changes in arrival date being adjusted to changing environmental conditions. This study suggests that adaptation to changing climatic conditions can be achieved through learning from year to year

关键词： Arctic tern Arrival date Climate change Migration Southern Oscillation Sterna paradisaea

Topological Studies of Three-dimensional Flows in a High Pressure Compressor Stator Blade Row without and with Boundary Layer Aspiration

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Chinese Journal of Aeronautics 2011年第5期24卷 541-549页

作者： Ankit SACHdEVA Francis LEBOEUF laboratoire de Mécanique des Fluides et d'Acoustique Ecole Centrale de Lyon

This paper presents a numerical study of the flow topologies of three-dimensional （3d） flows in a high pressure compressor stator blade row without and with boundary layer aspiration on the hub wall. The stator blade is representative of the first stage operating under transonic inlet conditions and the blade design encourages development of highly complex 3d flows. The blade has a small tip clearance. The computational fluid dynamics （CFd） studies show progressive increase of hub corner stall with the increase in incidence. Aspiration is implemented on the hub wall via a slot in the comer between the hub wall and the suction surface. The CFd studies show aspiration to be sensitive to the suction flow rate; lower rate leads to very complex flow struc- tures and increased level of losses whereas higher rate renders aspiration effective for control of hub comer separation. The flow topologies are studied by trace of skin friction lines on the walls. The nature of flow can be explained by the topological rules of closed separation. Furthermore, a deeper analysis is done for a particular case with advanced criterion to test the non-degeneracy of critical points in the flow field.

关键词： high pressure compressor flow topologies three-dimensional flows boundary layer aspiration tip clearance

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

Study of Several Impinging Jets

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Journal of Thermal Science 2000年第3期9卷 217-223页

作者： L.-Emmanuel BRIZZI Anthony BERNARd J.-Louis BOUSGARBIES Eva dORIGNAC J. -Jacques VULLIERME (laboratoire d’Etudes Aerodynamiques (UMR 6609), Boulevard 3, Teleport 2, BP 179, 86960 FUTUROSCOPE Cedex. France. laboratoire de Mecanique de Lille (URA 1441 laboratoire d’Etudes Aérodynamiques (UMR 6609) Futuroscope Cedex France laboratoire de Mécanique de Lille (URA 1441) Villeneuve D’Ascq Cedex France laboratoire d’Etudes Thermiques ENSMA Futuroscope Cedex France

Impinging jets are frequently adapted for cooling overheated parts. With the film cooling technique, this process improves thermal exchanges between walls and fluid. However if many works have concerned only the thermal aspect of this problem [1], its dynamic field has been rarely studied especially for multiple impingements. As the two phenomena cannot be totally dissociated, we have undertaken the aerodynamic and thermal study of jets impinging on a plane wall. Various techniques have been used as visualizations (spreading over method, LASER sheet visualizations), LdA measurements to propose a topology schema of the flow and infrared thermography.

关键词： impinging jets heat transfer LdA visualization infrared thermography.

Theoretical prediction of structural,electronic and optical properties of quaternary alloy Zn_(1-x)Be_xS_ySe_(1-y)

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Chinese Physics B 2012年第3期21卷 321-327页

作者： Hacini K Meradji H Ghemid S El Haj Hassan F laboratoire LPR D'epartement de PhysiqueFaculté des SciencesUniversité de Annaba laboratoire de physique des Matériaux Faculté des SciencesUniversité Libanaise

Within density functional theory based on the full potentiM-linearized augmented plane wave method, we carry out the first-principles calculation of the structural, electronic, and optical properties of the zinc blende quaternary alloy Zn1-xBexSySe1-y. The Perdew-Burke-Ernzerhof generaized gradient approximation based on the optimization of total energy and the Engel-Vosko generalized gradient approximation based on the optimization of the corresponding potential are used. Our investigation on the effect of the composition on lattice constants, bulk modulus, band gap, optical dielectric constant, and refractive index shows a non-linear dependence. The energy gap Eg（x, y） has been determined over the entire compositions x and y. In addition, the energy band gap of the technologically important quaternary alloy Znl-xBexSySe1-y in conditions of being lattice matched to ZnS substrate has been investigated. It is noteworthy that the present work is the first theoretical study of the quaternary alloy of interest.

关键词： density functional theory full potential-linearized augmented plane wave method qua-ternary alloy lattice-matched substrate

Coherent Structures Generated by a Circular Jet Issuing into a Cross Laminar Boundary Layer

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Journal of Thermal Science 1997年第2期6卷 81-85页

作者： L. E. Brizzi J. L. Bousgarbiès E. Foucault laboratoire d’Etudes Aérodynamiques URA 191 Poitiers France laboratoire d’Etudes Aérodynamiques URA 191 (ESIP) Poitiers France

Visualisations by LASER topographies and velocity measurements by LdV have allowed the study of the fiow resulting from the illteraction between a circular jet and a cross boundary layer. This type of fiow is dominated by the presence of many complex vortices that come from the recombining of the vorticity created in the injection tube and that created aIong the chamber floor.

关键词： jet vortical structures cross-flow boundary layer

Prediction model for the diffusion length in silicon-based solar cells

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Journal of Semiconductors 2009年第7期30卷 3-6页

作者： Cheknane A Benouaz T laboratoire d'Etude et dveloppement des Matriaux Semiconducteurs et dilectrques Universit Amar Telidji de Laghouat laboratoire de Modlisation UniversitAbou BakarBelkaid de Tlemcen Algrie

A novel approach to compute diffusion lengths in solar cells is presented. Thus, a simulation is done; it aims to give computational support to the general development of a neural networks （NNs）, which is a very powerful predictive modelling technique used to predict the diffusion length in mono-crystalline silicon solar cells. Furthermore, the computation of the diffusion length and the comparison with measurement data, using the infrared injection method, are presented and discussed.

关键词： diffusion length minority-cartier lifetime infrared injection solar cell prediction modelling