Shinde V.,ENSTA ParisTech |
Longatte E.,ENSTA ParisTech |
Baj F.,ENSTA ParisTech |
Hoarau Y.,ICUBE |
Braza M.,CNRS Institute of Fluid Mechanics of Toulouse
Journal of Computational Physics | Year: 2016
Galerkin projection of the Navier-Stokes equations on Proper Orthogonal Decomposition (POD) basis is predominantly used for model reduction in fluid dynamics. The robustness for changing operating conditions, numerical stability in long-term transient behavior and the pressure-term consideration are generally the main concerns of the Galerkin Reduced-Order Models (ROM). In this article, we present a novel procedure to construct an off-reference solution state by using an interpolated POD reduced basis. A linear interpolation of the POD reduced basis is performed by using two reference solution states. The POD basis functions are optimal in capturing the averaged flow energy. The energy dominant POD modes and corresponding base flow are interpolated according to the change in operating parameter. The solution state is readily built without performing the Galerkin projection of the Navier-Stokes equations on the reduced POD space modes as well as the following time-integration of the resulted Ordinary Differential Equations (ODE) to obtain the POD time coefficients. The proposed interpolation based approach is thus immune from the numerical issues associated with a standard POD-Galerkin ROM. In addition, a posteriori error estimate and a stability analysis of the obtained ROM solution are formulated. A detailed case study of the flow past a cylinder at low Reynolds numbers is considered for the demonstration of proposed method. The ROM results show good agreement with the high fidelity numerical flow simulation. © 2015 Elsevier Inc.
Salzenstein F.,ICube |
Montgomery P.,ICube |
Boudraa A.O.,Ecole Navale
Optics Express | Year: 2014
In this work, a new method for surface extraction in white light scanning interferometry (WLSI) is introduced. The proposed extraction scheme is based on the Teager-Kaiser energy operator and its extended versions. This non-linear class of operators is helpful to extract the local instantaneous envelope and frequency of any narrow band AM-FM signal. Namely, the combination of the envelope and frequency information, allows effective surface extraction by an iterative re-estimation of the phase in association with a new correlation technique, based on a recent TK crossenergy operator. Through the experiments, it is shown that the proposed method produces substantially effective results in term of surface extraction compared to the peak fringe scanning technique, the five step phase shifting algorithm and the continuous wavelet transform based method. In addition, the results obtained show the robustness of the proposed method to noise and to the fluctuations of the carrier frequency. © 2014 Optical Society of America.
Garci M.,ICube |
Kammerer J.-B.,ICube |
THERMINIC 2014 - 20th International Workshop on Thermal Investigations of ICs and Systems, Proceedings | Year: 2014
Through mechanical coupling, thermal effects can lead to drift in circuits' electrical performances, as well as integrated circuits reliability issues. It is thus necessary to consider thermal, mechanical and electrical effects all together in a self-consistent manner, This work focuses on the electro-thermo-mechanical simulation of integrated circuits in the target of ICs reliability monitoring from the early design stages. An electro-thermo-mechanical simulation tool was developed using the Cadence® environment and the Spectre® simulator. The simulation principle is based on the direct simulation approach with a mixed compact and finite elements modelling. Three networks, i.e. the electrical, the thermal and the mechanical networks, are directly generated, coupled then simulated using a single simulator, i.e. Spectre®. This paper discusses our networks modelling approaches. The way the three networks are coupled and simulated is described. The thermo-mechanical model is validated through simulation results, compared with results obtained using COMSOL® A first thermo-mechanical simulation of a simple integrated circuit featuring a power device is presented. © 2014 IEEE.
Kopp J.-B.,ICube |
Schmittbuhl J.,Ecole et Observatoire des science de la Terre |
Lin J.,ICube |
13th International Conference on Fracture 2013, ICF 2013 | Year: 2013
For rapid crack propagations, two kinds of material behavior have been observed. Typically, most materials show an increase of the fracture energy with the crack tip velocity. However, there do exist a few materials for which the fracture energy tends to decrease with the velocity [1, 2]. They are viscoplastic blend materials like polymers such as rubber toughened polymethylmethacrylate (RT-PMMA). For these materials, crack tips are seen to propagate at the same velocity whatever the loading rate is (or strain energy release rate). This critical velocity has been shown to be the crack branching velocity, at least at a macroscopic scale. Our study shows that the classical approach which considers that the amount of created surface during the propagation can be approximated as the sample thickness multiplied by the crack length is not appropriate. Indeed, this study shows that the exact fracture surface roughness has to be included in the amount of created surface in order to establish an intrinsic material fracture energy GID. As the fracture surface roughness depends on the scale at which the sample is observed, a self-affine model widely used for fracture surfaces is introduced [3, 4]. This statistical geometrical model of the fracture surface with two parameters, a Hurst exponent and a topothesy is shown to be effective and provides a better estimate of the intrinsic surface fracture energy. Copyright © (2013) by International Conference on Fracture.
Albarazanchi A.,University of Strasbourg |
Gerard P.,Icube |
Ambs P.,Upper Alsace University |
Meyrueis P.,University of Strasbourg
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2014
There is an increasing demand for optical elements having the functionalities of hybrid devices, such as the combination of a Fresnel lens and a diffraction grating. These new devices can be used in many applications, such as in optical spectrometers, optical precision measurement systems and diffractive optical systems for enhancing the efficiency of third generation photovoltaic solar cells. There is also a growing need for developments of a cost-effective technology to fabricate compact optical devices. Therefore the motivation of our project is to find a new model of the G-Fresnel (i.e. grating and Fresnel lens) taking into account the utilization of the electromagnetic theory for the rigorous analysis of its behavior. In this paper, a novel method is proposed and employed to design a G-Fresnel device that has only one structure layer with subwavelength features, and that focuses and separates different bands of light spectra in the same focal plane. The device performance has been studied through the use of rigorous electromagnetic theory, by using the Finite Difference Time Domain (FDTD) for the study of the near field and the Angular Spectrum Method (ASM) for the study of the propagation in the far field. The optimal design of the G-Fresnel profiles depends on the profile of the Fresnel lenses that minimize the longitude chromatic aberration, and also on the diffraction grating with high first order diffraction efficiency. The verification of the G-Fresnel model that we propose shows high diffraction efficiency and a good performance in separation for a broadband light spectrum. This promising G-Fresnel model could be used to increase the efficiency of third generation photovoltaic cells. © 2014 SPIE.
Rubbert L.,Ecole Polytechnique Federale de Lausanne |
Caro S.,École Centrale Nantes |
Gangloff J.,University of Strasbourg |
Journal of Mechanical Design, Transactions of the ASME | Year: 2014
The rigid-body replacement method is often used when designing a compliant mechanism. The stiffness of the compliant mechanism, one of its main properties, is then highly dependent on the initial choice of a rigid-body architecture. In this paper, we propose to enhance the efficiency of the synthesis method by focusing on the architecture selection. This selection is done by considering the required mobilities and parallel manipulators in singularity to achieve them. Kinematic singularities of parallel structures are indeed advantageously used to propose compliant mechanisms with interesting stiffness properties. The approach is first illustrated by an example, the design of a one degree of freedom compliant architecture. Then, the method is used to design a medical device where a compliant mechanism with three degrees of freedom is needed. The interest of the approach is outlined after application of the method. Copyright © 2014 by ASME.
Mamoghli S.,LGeCo |
Goepp V.,Icube |
Botta-Genoulaz V.,INSA Lyon
Enterprise Information Systems | Year: 2015
Enterprise Resource Planning (ERP) systems offer standard functionalities that have to be configured and customised by a specific company depending on its own requirements. A consistent alignment is therefore an essential success factor of ERP projects. To manage this alignment, an ‘Operational Model Based’ method is proposed. It is based on the design and the matching of models, and conforms to the modelling views and constructs of the ISO 19439 and 19440 enterprise-modelling standards. It is characterised by: (1) a predefined design and matching order of the models; (2) the formalisation, in terms of modelling constructs, of alignment and misalignment situations; and (3) their association with a set of decisions in order to mitigate the misalignment risk. Thus, a comprehensive understanding of the alignment management during ERP projects is given. Unlike existing methods, this one includes decisions related to the organisational changes an ERP system can induce, as well as criteria on which the best decision can be based. In this way, it provides effective support and guidance to companies implementing ERP systems, as the alignment process is detailed and structured. The method is applied on the ERP project of a Small and Medium Enterprise, showing that it can be used even in contexts where the ERP project expertise level is low. © 2015 Taylor & Francis
Goepp V.,ICube |
Petit M.,University of Namur
ICEIS 2013 - Proceedings of the 15th International Conference on Enterprise Information Systems | Year: 2013
The Strategic Alignment Model (SAM) remains one of the most relevant and cited models aiming at helping managers to achieve business/IT (Information Technology) alignment. Several alternative approaches extend or improve this model. A notable stream of research suggests applying Enterprise Architecture principles complementarily or independently to the SAM. We analyze these proposals and argue that they are sometimes fuzzy and hard to compare because they all use a specific structure or vocabulary making the objectivation of their strengths and weaknesses difficult. Some common vocabulary and concepts such as those of the ISO 15704 standard on Enterprise Reference Architectures and Methodologies are needed to make their comparison rigorous. We report on our ongoing research, using this standard to analyse the SAM.
Boisselier D.,IREPA LASER |
Sankare S.,IREPA LASER |
Physics Procedia | Year: 2014
The implementation of the continuous 5-axis configuration can extend the limits of the Laser Direct Metal Deposition (LDMD) processes, especially when the complexity of the parts to be built is growing. In order to follow the profile of a part, we use the orientation of its growth axis. Although 5-axis machining is well known nowadays, LDMD processes require a specific optimization that depends on many parameters. Unlike conventional machining, it has to be noted that the speed variation tool tip affects the stability of deposition. Thus, we have to smooth trajectories in order to provide fluid movements and also to ensure the stability of deposition. This article describes the method and results in the optimization of trajectories to build metallic parts with freeform. Optical sensors have been implemented in the focusing unit in order to follow the variations of the laser-powder-substrate interaction and also to detect the process instabilities. Thanks to the right use of a new and large 5 axis machine and specific setting trajectories, manufacturing parts in 5-axis, with no concession on the construction rate has been possible. © 2014 The Authors. Published by Elsevier B.V.
Petit M.,University of Namur |
Proceedings - CIE 45: 2015 International Conference on Computers and Industrial Engineering | Year: 2015
Business-IT alignment (BITA) is considered as a crucial challenge faced by enterprises. Several Enterprise-Architecture based solutions (that we call Enterprise Architecture Frameworks - EAFs for BITA) have been proposed in order to help to address this problem. However, currently, there is no systematic evaluation of EAFs to check if they are appropriate for BITA. In this paper, we propose a framework to help the evaluation of EAFs for BITA. The framework contains requirements coming from the ISO 15704 standard and some that we derive from the well-known Strategic Alignment Model of Henderson and Venkatraman. We then apply this evaluation framework to the de-facto standard EAF Archimate® proposed by the Open Group. The analysis allows us to identify a potential extension of Archimate® to make it more appropriate in a BITA context.