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Optimal Control of a Frictional Contact Problem

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Acta Mathematicae Applicatae Sinica 2015年第4期31卷 991-1000页

作者： Arezki TOUZALINE Laboratoire de Systèmes Dynamiques Faculté de MathématiquesUSTHB

We consider a mathematical model which describes a contact between a deformable body and a foundation. The contact is bilateral and modelled with Tresca＇s friction law. The goal of this paper is to study an optimal control problem which consists of leading the stress tensor as close as possible to a given target, by acting with a control on the boundary of the body. We state an optimal control problem which admits at least one solution. We also introduce the regularized control problem for which we study the convergence when the regularization parameter tends to zero. Finally, an optimally condition is established for this problem.

关键词： optimal control of variational inequalities elastic materials Tresca's friction, weak solution

Induced Surface Austenitic-Martensitic Transition by Mechanical Deformation in Mn *** of Surface Properties

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Journal of Iron and Steel Research International 2011年第S1期18卷 223-227页

作者： Boutarek-Zaourar Nama Mansour Samir Amara Sif Eddine usthb FGMGPBP 32 EL ALIA BAB EZZOUARALGER usthb FCBP 32 EL ALIA BAB EZZOUARALGER

For a lot of applications in the mechanical industry,both attractive and mechanical properties of materials and wear resistance are *** such a combination is achieved only by performing surface *** aim of this investigation is the consolidation of 12% Mn steel surface by treatment of *** show by optical and scanning electron microscopy,X ray diffraction,X ray spectrometry analysis and also by the realization of micro hardness,the effect of this kind of treatment on the mechanical and structural stability of the surface *** of many obtained results,we distinguish the clear surface consolidation induced by a modification of surface zone crystalline *** mechanical deformation causes the transformation from an austenitic structure to the martensitic structure.

关键词： phase transition Mn steel mechanical deformation surface properties impact treatment

Soliton excitations in a polariton condensate with defects

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Chinese Physics B 2018年第1期27卷 278-283页

作者： Abderahim Mahmoud Belounis Salem Kessal SNIRM Laboratory Faculty of Physics Universite des Sciences et de la Technologie Houari Boumediene (USTHB)

To study soliton excitations in a polariton condensate with defects, we use the Gross-Pitaevskii equation and its hydrodynamic form. An extra term is added to take into account the non-equilibrium nature of the polariton condensate and the presence of defects. The reductive perturbation method transforms these hydrodynamic equations into a modified Korteweg-de Vries equation in the long wavelength limit. We linearize this equation and study the soliton linear excitations. We give an analytic expression of traveling excitations using the variation of constants method. In the more general form, we show numerically that the excitations are oscillations simultaneously hut in an opposite way. i.e., the amplitude and the width of the dark soliton oscillate

关键词： solitons polariton condensates reductive perturbation method

Texture evolution in AZ91 alloy after hot rolling and annealing

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Transactions of Nonferrous Metals Society of China 2013年第8期23卷 2215-2221页

作者： B.ALILI H.AZZEDDINE K.ABIB D.BRADAI Faculty of Physics USTHB

A commercial AZ91 magnesium alloy with a random initial texture was subjected to homogenization heat treatment （solution annealing） at 450 ℃. This resulted in the appearance of a weak triple （0001）-（10]-0）-（1120） fibber texture. After hot rolling at 400 ℃, the deformation texture was typically （0001） basal with splitting of the basal poles in the rolling direction. After annealing at 450℃ for 36 h, the annealing texture was the retained deformation texture with more homogeneous distribution of poles around the ideal basal orientation. There was no trace of abnormal grain growth.

关键词： AZ91 alloy texture hot rolling recrystallization

Strength Pareto fitness assignment for pseudo-relevance feedback： application to MEDLINE

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Frontiers of Computer Science 2018年第1期12卷 163-176页

作者： Ilyes KHENNAK Habiba DRIAS Laboratory for Research in Artificial Intelligence Computer Science Department University of Sciences and Technology Houari Boumediene (USTHB) Algiers 16111 Algeria

Because of users＇ growing utilization of unclear and imprecise keywords when characterizing their informa- tion need, it has become necessary to expand their original search queries with additional words that best capture their actual intent. The selection of the terms that are suitable for use as additional words is in general dependent on the degree of relatedness between each candidate expansion term and the query keywords. In this paper, we propose two criteria for evaluating the degree of relatedness between a candidate expansion word and the query keywords：（1） co-occurrence frequency, where more importance is attributed to terms oc- curring in the largest possible number of documents where the query keywords appear; （2） proximity, where more im- portance is assigned to terms having a short distance from the query terms within documents. We also employ the strength Pareto fitness assignment in order to satisfy both criteria si- multaneously. The results of our numerical experiments on MEDLINE, the online medical information database, show that the proposed approach significantly enhances the re- trieval performance as compared to the baseline.

关键词： information retrieval query expansion pseudo-relevance feedback proximity multi-objective optimization,Pareto dominance MEDLINE

Improved shape from shading without initial information

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Frontiers of Computer Science 2017年第2期11卷 320-331页

作者： Lyes ABADA Saliha AOUAT Laboratory of Research in Artificial Intelligence Department of Computer ScienceUniversity of Sciences and Technology Houari Boumediene (USTHB) Algiers 16111 Algeria

The number of constraints imposed on the sur- face, the light source, the camera model and in particular the initial information makes shape from shading （SFS） very dif- ficult for real applications. There are a considerable number of approaches which require an initial data about the 3D ob- ject such as boundary conditions （BC）. However, it is difficult to obtain these information for each point of the object Edge in the image, thus the application of these approaches is lim- ited. This paper shows an improvement of the Global View method proposed by Zhu and Shi [1]. The main improvement is that we make the resolution done automatically without any additional information on the 3D object. The method in- volves four steps. The first step is to determine the singular curves and the relationship between them. In the second step, we generate the global graph, determine the sub-graphs, and determine the partial and global configuration. The proposed method to determine the convexity and the concavity of the singular curves is applied in the third step. Finally, we apply the Fast-Marching method to reconstruct the 3D object. Our approach is successfully tested on some synthetic and real im- ages. Also, the obtained results are compared and discussed with some previous methods.

关键词： shape from shading SFS image formation equation level-set graphs theory 3D reconstruction.

Grain growth in AZ31 alloy after uniaxial compression

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Transactions of Nonferrous Metals Society of China 2010年第12期20卷 2215-2222页

作者： S.ABDESSAMEUD H.AZZEDDINE B.ALILI D.BRADAI Laboratoire Faculty of PhysicsUniversity of Sciences and Technology Houari Boumediene(USTHB)BP32El-Alia Bab EzzouarAlgiers 16111Algeria

The grain growth morphology,kinetics and texture change after uniaxial compression at 430 ℃ of an extruded AZ31 alloy were *** samples were loaded following two routes insuring two initial textures of the samples with compression direction parallel and normal to the extrusion *** both initial textures,a stable grain size is attained upon isothermal annealing and the grain growth kinetics can be described by:dn= dRn+kt with an n value of around *** annealing texture with grown grains is a retained hot deformation texture without emerging or strengthening other *** grain growth is not observed for annealing time up to 10 000 h at 450℃.

关键词： AZ31 magnesium alloy uniaxial compression annealing grain growth texture

Influence of isovector pairing and particle-number projection effects on spectroscopic factors for one-pair like-particle transfer reactions in proton-rich even-even nuclei

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Chinese Physics C 2018年第4期42卷 171-187页

作者： Y.Benbouzid N.H.Allal M.Fellah M.R.Oudih Laboratoire de Physique Theorique-Faculte de Physique-usthb BP32 El-Alia16111 Bab-EzzouarAlgerAlgeria

Isovector neutron-proton（np） pairing and particle-number fluctuation effects on the spectroscopic factors（SF） corresponding to one-pair like-particle transfer reactions in proton-rich even-even nuclei are studied. With this aim, expressions of the SF corresponding to two-neutron stripping and two-proton pick-up reactions, which take into account the isovector np pairing effect, are established within the generalized BCS approach, using a schematic definition proposed by Chasman. Expressions of the same SF which strictly conserve the particle number are also established within the Sharp-BCS（SBCS） discrete projection method. In both cases, it is shown that these expressions generalize those obtained when only the pairing between like particles is considered. First, the formalism is tested within the Richardson schematic model. Second, it is applied to study even-even proton-rich nuclei using the single-particle energies of a Woods-Saxon mean-field. In both cases, it is shown that the np pairing effect and the particle-number projection effect on the SF values are important, particularly in N =Z nuclei, and must then be taken into account.

关键词： neutron-proton pairing particle-number fluctuations spectroscopic factor

Shear reinforcement effect of reinforced concrete tie-columns on the lateral resistance of confined masonry walls

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Earthquake Engineering and Engineering Vibration 2016年第2期15卷 313-324页

作者： Samir Bouhedja Abdelkrim Bourzam Ahmed Boukhaled Ammar Nechnech University of Sciences and Technology Houari Boumediene(USTHB)Faculty of Civil EngineeringLaboratory of EnvironmentWaterGeomechanics and Structures(LEEGO)BP 32 El AliaBab EzzouarAlgiers16111Algeria University of Sciences and Technology Houari Boumediene(USTHB)Faculty of Civil EngineeringLaboratory of Built Environment Research(LBE)BP 32 El AliaBab EzzouarAlgiers16111Algeria

Tie-columns improve significantly the lateral resistance of masonry bearing walls against persistent, transient and accidental loads. The research work described herein has been carried out to assess the lateral resistance of confined masonry walls, where contribution of the masonry panel is evaluated according to material mechanics and tie-columns effect is estimated by a proposed analytical formulation based on a model reported on previously. This approach takes into account the effect of dowel support on the reaction of its adjacent shear reinforcement： the conditions for the various contributions of transverse reinforcements are better defined following a clear evaluation of the participation ratio of these reinforcements. Lateral resistances of confined masonry walls measured in full-scale tests and gleaned from the literature are compared and checked with resistances calculated using the present approach.

关键词： reinforcement columns confined reinforced walls Shear formulation panel participation herein