Saint-Sauveur-en-Rue, France
Saint-Sauveur-en-Rue, France

Time filter

Source Type

Chaussemier M.,EPF College of Engineering | Pourmohtasham E.,EPF College of Engineering | Gelus D.,Groupe SEB | Pecoul N.,Groupe SEB | And 4 more authors.
Desalination | Year: 2015

The formation of calcium carbonate in water has some important implications in geoscience researches, ocean chemistry studies, CO2 emission issues and biology. In industry, the scaling phenomenon may cause technical problems such as reduction of heat transfer efficiency in cooling systems and obstruction of pipes.The use of chemicals which act as antiscalant is a common approach in the control of scale deposition. However, inorganic nitrogen and phosphorous compounds are involved in eutrophication process. Therefore, it is of prime importance to find alternative solutions, i.e. green inhibitors of scale formation. This last decade, several new scale inhibitors, that are more ecological compared with conventional inhibitors, have been reported in the literature. Plant extracts have been also recently used as new green antiscalants. Indeed, as they can be easily extracted and are environmentally friendly, they represent an interesting alternative source of "natural" organic molecules.In this review, a focus of some green antiscalants derived from petrochemicals has been reported. Then the efforts done those last years to obtain green inhibitors, either by using "natural" organic molecules or extracted from plants were summarized. Such green inhibitors might be used in various technical areas, i.e. energy, water, food and beverages industries. © 2014 Elsevier B.V.


Park H.,Cergy-Pontoise University | Park H.,Yeungnam University | Ruellan M.,Cergy-Pontoise University | Martaj N.,EPF College of Engineering | And 2 more authors.
Energy and Buildings | Year: 2013

This work proposes a generic thermal model of electrical appliances in order to evaluate the influence of their thermal gain on low energy buildings. To this purpose, home electrical appliances are firstly classified into four categories according to thermal and electrical points of view. A generic physically driven thermal model is then established based on the first thermodynamics principle. In order to analyze the relevance of the proposed generic model applied to practical cases, the corresponding ARX and ARMAX models are firstly derived. Then, an identification method based on the least square approach is applied to these models in order to get the corresponding parameters. Finally, the parameters of the generic model are calculated and the model is implemented in Matlab/Simulink®. The case of a refrigerator is studied in order to illustrate the proposed approach. The matching between the measurements on the actual system and the results of simulation based on the identified generic model of the appliance validate the proposed approach. © 2013 Elsevier B.V. All rights reserved.


Chen J.,MINES ParisTech Center of materials | Madi Y.,MINES ParisTech Center of materials | Madi Y.,EPF College of Engineering | Morgeneyer T.F.,MINES ParisTech Center of materials | Besson J.,MINES ParisTech Center of materials
Computational Materials Science | Year: 2011

Plasticity and fracture mechanisms of a 2198 Al-Cu-Li thin sheet alloy having a thickness equal to 6 mm are investigated. Two heat treatments are studied: T351 and T851. Mechanical tests are carried out on flat specimens including smooth tensile samples and U-notched specimens. Test data are used to identify the parameters of constitutive equations describing plastic anisotropy. The microscopic fracture surfaces of the different specimens are observed using scanning electron microscopy. Smooth and notched samples exhibit a slant fracture surface. Two microscopic fracture mechanisms are identified: fibrous fracture involving grain boundary decohesion and dimple fracture. Observed fracture modes depend on specimen geometry (notches increase stress triaxiality and favor dimple fracture) but also on loading direction. Loading along the rolling direction leads to predominant fibrous fracture. Reducing sheet thickness to 2 mm also favors fibrous fracture. Finally a localization indicator based on Rice's analysis of bifurcation is used to analyse finite element simulations and predict observed fracture plane orientations. © 2010 Elsevier B.V. All rights reserved.


Briere V.,EPF College of Engineering | Briere V.,University of Pittsburgh | Harries K.A.,University of Pittsburgh | Kasan J.,HDR | Hager C.,University of Pittsburgh
Construction and Building Materials | Year: 2013

In prestressed concrete elements, bond between pretensioned strands and the surrounding concrete is attributed to adhesion, mechanical interlock and the friction and 'wedge-action' attributable to radial expansion of the strand following release. The latter effect is referred to as the Hoyer effect and is the subject of this paper. The Hoyer effect contributes primarily to the transfer of the initial prestressing force to the concrete thereby affecting the transfer length. The transfer of large prestressing forces, particularly at an early concrete age, can lead to local cracking associated with bursting stresses or splitting associated with transfer of the strand force through bond. An analysis of embedded strand behavior based on fundamental principles of mechanics clearly demonstrates the importance of strand dilation characteristics in the development of concrete stresses and therefore the transfer of prestressing forces. An experimental program demonstrates that the dilation of seven wire strand is affected by not only the Poisson's ratio for steel but also the 'tightening' of the helical wires and effects of bearing between these wires. The resulting dilation of a seven wire strand is larger than Poisson's ratio for steel and is found to be a function of strand diameter. A discussion of design code provisions for prestressing strand transfer length is included. North American practice, while conservative, does not explicitly address the mechanics of stress transfer. Improvement in this regard could result in more efficient prestressed concrete structures. European practice, on the other hand, appears to reasonably capture the Hoyer effect. © 2012 Elsevier Ltd. All rights reserved.


Cheng C.Z.,Hefei University of Technology | Cheng C.Z.,EPF College of Engineering | Cheng C.Z.,CNRS Pascal Institute | Niu Z.R.,Hefei University of Technology | And 2 more authors.
International Journal of Fracture | Year: 2012

The traditional brittle fracture criteria for V-notched structures are established on the base of the singular stress field at a V-notch tip where only two singular stress terms are adopted. The non-singular stress terms also play a significant role in determining the stress and strain fields around a V-notch tip, which in turn could affect the fracture character of V-notched structures predicted by the fracture mechanics criteria. In this paper, the effect of the non-singular stress on the brittle fracture properties for the V-notch problem is discussed. Firstly, the stress field around a V-notch tip is described by the Williams asymptotic expansions. At the same time, the stress field far from the V-notch tip is modeled by the conventional boundary element method since there is no stress singularity. By the combination of the Williams asymptotic expansions and the boundary integral equations, the complete stress field at a V-notch tip including several non-singular stress terms can be obtained. Then, three different brittle fracture criteria are introduced to predict the critical loading and initial crack propagation direction of V-notched structures under mixed-mode loading. Comparing with the existed experimental results, it can be found that the degree of accuracy of the predicted results when taking into account the non-singular stress terms is much higher than the predicted ones neglecting the non-singular stress. © 2012 Springer Science+Business Media B.V.


Cheng C.Z.,Hefei University of Technology | Cheng C.Z.,EPF College of Engineering | Niu Z.R.,Hefei University of Technology | Recho N.,EPF College of Engineering | And 3 more authors.
Computers and Structures | Year: 2011

The stress computational accuracy of internal points by conventional boundary element method becomes more and more deteriorate as the points approach to the boundary due to the nearly singular integrals including nearly strong singularity and hyper-singularity. For calculating the boundary stress, a natural boundary integral equation in which the boundary variables are the displacements, tractions and natural boundary variables was established in the authors' previous work. Herein, a natural stress boundary integral equation (NSBIE) is further proposed by introducing the natural variables to analyze the stress field of interior points. There are only nearly strong singular integrals in the NSBIE, i.e., the singularity is reduced by one order. The regularization algorithm proposed by the authors is taken over to deal with these singular integrals. Consequently, the NSBIE can analyze the stress field closer to the boundary. Numerical examples demonstrated that two orders of magnitude improvement in reducing the approaching degree can be achieved by NSBIE compared to the conventional one when the near boundary stress field is evaluated. Furthermore, this new way is extended to the multi-domain elasticity problem to calculate the stress field near the boundary and interface. © 2011 Elsevier Ltd. All rights reserved.


Cogranne R.,University of Technology of Troyes | Zitzmann C.,EPF College of Engineering | Retraint F.,University of Technology of Troyes | Nikiforov I.V.,University of Technology of Troyes | And 2 more authors.
Signal Processing | Year: 2014

This paper proposes a novel methodology to detect data hidden in the least significant bits of a natural image. The goal is twofold: first, the methodology aims at proposing a test specifically designed for natural images, to this end an original model of images is presented, and, second, the statistical properties of the designed test, probability of false alarm and power function, should be predictable. The problem of hidden data detection is set in the framework of hypothesis testing theory. When inspected image parameters are known, the Likelihood Ratio Test (LRT) is designed and its statistical performance is analytically established. In practice, unknown image parameters have to be estimated. The proposed model of natural images is used to estimate unknown parameters accurately and to design a Generalized Likelihood Ratio Test (GLRT). Finally, the statistical properties of the proposed GLRT are analytically established which permits us, first, to guarantee a prescribed false-alarm probability and, second, to show that the GLRT is almost as powerful as the optimal LRT. Numerical results on natural image databases and comparison with prior art steganalyzers show the relevance of theoretical findings. © 2014 Elsevier B.V. All rights reserved.


Cheng C.,Hefei University of Technology | Cheng X.,Anhui Economic and Management Institute | Niu Z.,Hefei University of Technology | Recho N.,EPF College of Engineering | Recho N.,CNRS Pascal Institute
European Journal of Mechanics, A/Solids | Year: 2016

Due to the material or geometrical discontinuities, the stress, electric displacement and magnetic induction may become theoretically infinite and singular at the vertexes of magneto-electro-elastic (MEE) V-notches, where the mechanical failure or dielectric breakdown may initiate from. Based on the assumption of the asymptotic expansions of the physical fields near the vertex, the characteristic differential equations with respect to the singularity order are derived from the equilibrium equations and Maxwell equations. After a set of variable replacement, these non-linear differential equations are transformed into the linear ones. The traditional iterative method for solving the transcendental equation is avoided. The mechanical, electric and magnetic boundary conditions together with interfacial continuity conditions are also expressed by the combination of the singularity order and characteristic angular functions. The singularity characteristic analyses for MEE V-notches are transformed into a problem of solving characteristic ordinary differential equations with variable coefficients. The singularity orders and characteristic angular functions can be derived by introducing the interpolating matrix method to solve the established characteristic equations. Herein, the singularities for the in-plane and anti-plane MEE V-notches are respectively investigated. The influence of the poling direction on the singularities of MEE V-notches is discussed. The role of the volume fraction of the BaTiO3 inclusions on the singularities of MEE V-notches is studied. The obtained results can be used to design MEE products for reducing the singularity induced by the V-notch. © 2015 Elsevier Masson SAS. All rights reserved.


Cheng C.,Hefei University of Technology | Cheng C.,EPF College of Engineering | Niu Z.,Hefei University of Technology | Recho N.,EPF College of Engineering | And 2 more authors.
Fatigue and Fracture of Engineering Materials and Structures | Year: 2013

A coupled model resulting from the boundary element method and eigen-analysis is proposed in this paper to analyse the stress field at crack tip. This new combine method can yield several terms of the non-singular stress in the Williams asymptotic expansion. Then the maximum circumferential stress (MCS) criterion taken the non-singular stress into account is introduced to predict the brittle fracture of cracked structures. Two earlier experiments are re-examined by the present numerical method and the role of the non-singular stress in the brittle fracture is investigated. Results show that if more terms of non-singular stress are taken into account, the predicted crack propagation direction and the critical loading by MCS criterion are much closer to the existing experimental results, especially for dominating mode II loading conditions. Moreover, numerical results manifest that Williams series expansion can describe the stress field further from the crack tip if more non-singular stress terms are adopted. © 2012 Wiley Publishing Ltd.


Cheng C.Z.,Hefei University of Technology | Cheng C.Z.,EPF College of Engineering | Cheng C.Z.,University Blaise Pascal | Recho N.,EPF College of Engineering | And 2 more authors.
Nuclear Engineering and Design | Year: 2012

The complete elasticity stress field at a crack tip region can be presented by the sum of the singular stress and several non-singular stress terms according to the Williams asymptotic expansion theory. The non-singular stress has a non-negligible influence on the prediction of the crack extension direction and crack growth rate under the fatigue loading. A novel method combining the boundary element method and the singularity characteristic analysis is proposed here to evaluate the complete stress field at a crack tip region. In this new method, any non-singular stress term in the Williams series expansion can be evaluated according to the computational accuracy requirement. Then, a modified Paris law is introduced to predict the crack propagation under the mixed-mode loading for exploring the influence of the non-singular stress on the fatigue life duration. By comparing with the existed experimental results, the predicted crack fatigue life when the non-singular stress is taken into consideration is more accurate than the predicted ones only considering the singular stress. © 2012 Elsevier B.V. All rights reserved.

Loading EPF College of Engineering collaborators
Loading EPF College of Engineering collaborators