Modeling Group

@article{yakoubi_1678,

title = {Analysis of a time--discrete scheme for the Navier-Stokes/Allen-Cahn model},

author = {Driss Yakoubi and Jean Deteix and Gerard Lionel Ndetchoua Kouamoa},

url = {https://www.sciencedirect.com/science/article/pii/S0022247X20309793?via%3Dihub},

year  = {2021},

date = {2021-04-01},

journal = {Journal Of Mathematical Analysis And Applications},

volume = {496},

number = {2},

pages = {124816},

abstract = {This paper address the existence and uniqueness, in suitable functional spaces, of the solution of a non linear system of equations originating from the implicit time discretization of the coupled unsteady Navier-Stokes and Allen-Cahn equations. This result is based on the convergence analysis of an original stabilized fixed point algorithm, from which we also get a maximum principle. Numerical experiments are performed to illustrate the influence of the implicit formulation in comparison to a simpler approach based on a semi-explicit time scheme.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{bobbia_1684,

title = {Extreme quantile regression in proportional tail framework},

author = {Benjamin Bobbia and Clément Dombry and Davit Varron},

url = {http://rmi.ge/transactions/TRMI-volumes/175-1/175-1.htm},

year  = {2021},

date = {2021-04-01},

journal = {Transactions of A. Razmadze Mathematical Institute, In press},

volume = {175},

number = {1},

pages = {13-32},

abstract = {We revisit the model of heteroscedastic extremes initially introduced by Einmahl et al. (JRSSB, 2016) to describe the evolution of a non stationary sequence whose extremes evolve over time and adapt it into a general extreme quantile regression framework. We provide estimates for the extreme value index and the integrated skedasis function and prove their asymptotic normality. Our results are quite similar to those developed for heteroscedastic extremes but with a different proof approach emphasizing coupling arguments. We also propose a pointwise estimator of the skedasis function and a Weissman estimator of the conditional extreme quantile and prove the asymptotic normality of both estimators.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{chablat_1789,

title = {Workspace analysis in the design parameter space of a 2-dof spherical parallel mechanism for a prescribed workspace: Application to the otologic surgery},

author = {Damien Charles Chablat and Guillaume Michel and Philippe Bordure and Swaminath Venkateswaran and Ranjhan Jha},

url = {https://www.sciencedirect.com/science/article/pii/S0094114X20304419},

year  = {2021},

date = {2021-03-01},

journal = {Mechanism And Machine Theory},

volume = {157},

number = {3},

pages = {104224},

abstract = {During Otologic surgery, and more broadly during microsurgery, the surgeon encounters several difficulties due to the confined spaces and micro-manipulations. The purpose of the paper is to design a robot with a prescribed regular workspace shape to handle an endoscope to assist the Otologic surgery. A spherical parallel mechanism with two degrees of freedom is analysed in its design parameter space. This mechanism is composed of three legs (2USP-U) to connect the base to a moving platform connected to a double parallelogram to create a remote center of motion (RCM). Its kinematic properties, i.e. the singularity locus and the number of direct kinematic solutions, are investigated. For some design parameters, non-singular assembly modes changing trajectories may exist and have to be investigated inside the prescribed regular workspace shape. Two sets of design parameters are presented with their advantages and disadvantages.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{ben_abdallah_1269,

title = {Molecular weight influence on shape memory effect of shape memory polymer blend ( poly(caprolactone)/styrene-butadiene-styrene )},

author = {Abir Ben Abdallah and Fehmi Gamaoun and Achraf Kallel and Abbas Tcharkhtchi},

url = {https://onlinelibrary.wiley.com/doi/10.1002/app.49761},

year  = {2021},

date = {2021-02-01},

journal = {Journal Of Applied Polymer Science},

volume = {138},

number = {5},

pages = {49761},

abstract = {The shape memory effect (SME) does not only concern the macroscopic structure. It concerns also the polymer structure at morphological, macromolecular, and molecular scales. This effect may depend on different physicochemical properties like morphology heterogeneity, chain rigidity, steric hindrance, chain polarity, free volume, cross-linking or entanglement density, molecular shape and weight, and so on. Hence, finding the relationship between the SME and these properties is very important. This can help to obtain the knowledge about the phenomenon origin and mechanism. One of the basic polymer properties, which can have direct SME, may be the molecular weight (Mw). The question here is: If the Mw of a shape memory polymer (SMP) changes, for different reasons like degradation, what will be the effect of this change on its SME. In order to answer to this question, the investigation is focused on an SMP blend of 40% poly(?-caprolactone) (PCL) and 60% styrene-butadiene-styrene (SBS). Then, enzymatic hydrolysis is performed on this blend to change its Mw. It is shown that this change is only related to the variation in the Mw of PCL. After that, different samples with a distinct average Mw are prepared and characterized by various experimental methods. Shape memory tests are performed on these blends, and the recovery rate (Rr) for each of them is determined. It is found that when Mw of PCL decreases, its degree of crystallinity, its glass transition, and its melting temperatures, corresponding to the PCL phase, increase. However, the elongation at break of the blend declines with the reduction in Mw. The tests show that the alteration in the blend's Mw influences its SME. Indeed, Rr of the (PCL/SBS) mixture drops with the decrease in Mw of PCL.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pouradier_duteil_1268,

title = {Kinetic approach to the collective dynamics of the rock paper scissors binary game},

author = {Nastassia Pouradier Duteil and Francesco Salvarani},

url = {https://www.sciencedirect.com/science/article/pii/S0096300320304549#!},

year  = {2021},

date = {2021-01-01},

journal = {Applied Mathematics And Computation},

volume = {388},

pages = {125496},

abstract = {This article studies the kinetic dynamics of the rock-paper-scissors binary game. We first prove existence and uniqueness of the solution of the kinetic equation and subsequently we prove the rigorous derivation of the quasi-invariant limit for two meaningful choices of the domain of definition of the independent variables. We notice that the domain of definition of the problem plays a crucial role and heavily influences the behavior of the solution. The rigorous proof of the relaxation limit does not need the use of entropy estimates for ensuring compactness.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{zhang_1406,

title = {Failure prediction of magnesium alloys based on improved CDM model},

author = {Kai Zhang and Houssem Badreddine and Naila Hfaiedh and Khemais Saanouni and Jianlin Liu},

url = {https://www.sciencedirect.com/science/article/abs/pii/S0020768321000214?via%3Dihub},

year  = {2021},

date = {2021-01-01},

journal = {International Journal Of Solids And Structures},

volume = {217-218},

pages = {155-177},

abstract = {The aim of this contribution is to improve the behavior and failure prediction accuracy for magnesium alloy sheet forming simulation by using advanced fully coupled Continuum Damage Mechanics (CDM) model. Starting from known fully coupled constitutive equations at large inelastic (plastic or viscoplastic) strains, three aspects are enhanced on the CDM model developed by Saanouni (2012). The first one concerns the accurate description of tension-compression asymmetry in yielding and hardening of magnesium alloys induced by combined slip and twinning deformations. The second concerns introducing the stress state dependence in damage evolution to improve the fracture prediction under various loading paths. The third deals with temperature and strain rate (viscosity) effects for metal forming processes at elevated temperatures. The improved fully coupled constitutive equations were implemented into finite element code ABAQUS/Explicit via user subroutine VUMAT including the specific local integration scheme to compute the state variables at each quadrature point. Various kinds of tensile tests at different temperatures and strain rates are used to determine the material parameters, and the complete identification procedure is given in details. As validation, the improved model is applied to simulate the three-point bending and circular cup deep drawing tests, the predicted results show good agreements with the experimental observations.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{ouaddi_1582,

title = {Passive piezomagnetic monitoring of structures subjected to in-service cyclic loading: Application to the detection of fatigue crack initiation and propagation},

author = {Achraf Ouaddi and Olivier Hubert and Jader Furtado and Song He},

url = {https://doi.org/10.1063/9.0000195},

year  = {2021},

date = {2021-01-01},

journal = {Aip Advances},

volume = {11},

number = {1},

pages = {015344},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{vanaei_2092,

title = {Multi-scale damage analysis and fatigue behavior of PLA manufactured by fused deposition modeling (FDM)},

author = {Hamidreza Vanaei and Mohammadali Shirinbayani and Saeedeh Vanaei and Joseph Fitoussi and Sofiane Khelladi and Abbas Tcharkhtchi},

url = {https://doi.org/10.1108/RPJ-11-2019-0300},

year  = {2021},

date = {2021-01-01},

journal = {Rapid Prototyping Journal},

volume = {27},

number = {2},

pages = {371-378},

abstract = {Purpose



Fused deposition modeling (FDM) draws particular attention due to its ability to fabricate components directly from a CAD data; however, the mechanical properties of the produced pieces are limited. This paper aims to present the experimental aspect of multi-scale damage analysis and fatigue behavior of polylactic acid (PLA) manufactured by FDM. The main purpose of this paper is to analyze the effect of extruder temperature during the process, loading amplitude, and frequency on fatigue behavior.

Design/methodology/approach



Three specific case studies were analyzed and compared with spool material for understanding the effect of bonding formation: single printed filament, two printed filaments and three printed filaments. Specific experiments of quasi-static tensile tests coupled with microstructure observations are performed to multi-scale damage analysis. A strong variation of fatigue strength as a function of the loading amplitude, frequency and extruder temperature is also presented.



Findings



The obtained experimental results show the first observed damage phenomenon corresponds to the inter-layer bonding of the filament interface at the stress value of 40?MPa. For instance, fatigue lifetime clearly depends on the extruder temperature and the loading frequency. Moreover, when the frequency is 80?Hz, the coupling effect of thermal and mechanical fatigue causes self-heating which decreases the fatigue lifetime.

Originality/value



This paper comprises useful data regarding the mechanical behavior and fatigue lifetime of FDM made PLA specimens. In fact, it evaluates the effect of process parameters (extruder temperature) based on the nature of FDM that is classified as a thermally-driven process.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{maarouf_1679,

title = {Analysis of backward Euler/spectral discretization for an evolutionary mass and heat transfer in porous medium},

author = {Sarra Maarouf and Driss Yakoubi},

url = {https://www.sciencedirect.com/science/article/pii/S0022247X20305898?via%3Dihub},

year  = {2020},

date = {2020-12-01},

journal = {Journal Of Mathematical Analysis And Applications},

volume = {492},

number = {1},

pages = {124427},

abstract = {This paper presents the unsteady Darcy's equations coupled with two nonlinear reaction-diffusion equations, namely this system describes the mass concentration and heat transfer in porous media. The existence and uniqueness of the solution are established for both the variational formulation problem and for its discrete one obtained using spectral discretization. Optimal a priori estimates are given using the Brezzi-Rappaz-Raviart theorem. We conclude by some numerical tests which are in agreement with our theoretical results.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{vanaei_1959,

title = {An Overview on Materials and Techniques in 3D Bioprinting Toward Biomedical Application},

author = {Saeedeh Vanaei and Mohammad Salemizadeh Parizi and Shohreh Vanaei and Fatemeh Salemizadehparizi and Hamidreza Vanaei},

url = {https://doi.org/10.1016/j.engreg.2020.12.001},

year  = {2020},

date = {2020-12-01},

journal = {Engineered Regeneration},

volume = {2},

pages = {1-18},

abstract = {Three-dimensional (3D) bioprinting, an additive manufacturing based technique of biomaterials fabrication, is an innovative and auspicious strategy in medical and pharmaceutical fields. The ability of producing regenerative tissues and organs has made this technology a pioneer to the creation of artificial multi-cellular tissues/organs. A broad variety of biomaterials is currently being utilized in 3D bioprinting as well as multiple techniques employed by researchers. In this review, we demonstrate the most common and novel biomaterials in 3D bioprinting technology further with introducing the related techniques that are commonly taking into account by researchers. In addition, an attempt has been accomplished to hand over the most relevant application of 3D bioprinting techniques such as tissue regeneration, cancer investigations, etc. by presenting the most important works. The main aim of this review paper is to emphasis on strengths and limitations of existence biomaterials and 3D bioprinting techniques in order to carry out a comparison through them.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{bernard_1413,

title = {Optimal Estimate of the Spectral Gap for the Degenerate Goldstein-Taylor Model},

author = {Etienne Bernard and Francesco Salvarani},

url = {https://link.springer.com/article/10.1007/s10955-020-02631-y},

year  = {2020},

date = {2020-11-01},

journal = {Journal Of Statistical Physics},

volume = {181},

pages = {1470-1471},

abstract = {x},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{benmesbah_1563,

title = {Methane Hydrate Formation and Dissociation in Sand Media: Effect of Water Saturation, Gas Flowrate and Particle Size},

author = {Fatima Benmesbah and Livio Ruffine and Pascal Clain and Véronique Osswald and Olivia Fandino and Laurence Fournaison and Anthony Delahaye},

url = {https://www.mdpi.com/1996-1073/13/19/5200},

year  = {2020},

date = {2020-10-01},

journal = {Energies},

volume = {13},

number = {19},

pages = {5200},

abstract = {Assessing the influence of key parameters governing the formation of hydrates and determining the capacity of the latter to store gaseous molecules is needed to improve our understanding of the role of natural gas hydrates in the oceanic methane cycle. Such knowledge will also support the development of new industrial processes and technologies such as those related to thermal energy storage. In this study, high-pressure laboratory methane hydrate formation and dissociation experiments were carried out in a sandy matrix at a temperature around 276.65 K. Methane was continuously injected at constant flowrate to allow hydrate formation over the course of the injection step. The influence of water saturation, methane injection flowrate and particle size on hydrate formation kinetics and methane storage capacity were investigated. Six water saturations (10.8%, 21.6%, 33%, 43.9%, 55% and 66.3%), three gas flowrates (29, 58 and 78 mLn min?1) and three classes of particle size (80-140, 315-450 and 80-450 µm) were tested, and the resulting data were tabulated. Overall, the measured induction time obtained at 53-57% water saturation has an average value of 58 ± 14 min minutes with clear discrepancies that express the stochastic nature of hydrate nucleation, and/or results from the heterogeneity in the porosity and permeability fields of the sandy core due to heterogeneous particles. Besides, the results emphasize a clear link between the gas injection flowrate and the induction time whatever the particle size and water saturation. An increase in the gas flowrate from 29 to 78 mLn min-1 is accompanied by a decrease in the induction time up to 100 min (i.e., 77% decrease). However, such clear behaviour is less conspicuous when varying either the particle size or the water saturation. Likewise, the volume of hydrate-bound methane increases with increasing water saturation. This study showed that water is not totally converted into hydrates and most of the calculated conversion ratios are around 74-84%, with the lowest value of 49.5% conversion at 54% of water saturation and the highest values of 97.8% for the lowest water saturation (10.8%). Comparison with similar experiments in the literature is also carried out herein.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{vanaei_2096,

title = {A comparative in-process monitoring of temperature profile in fused filament fabrication},

author = {Hamidreza Vanaei and Deligant Michael and Mohammadali Shirinbayani and Raissi Kaddour and Joseph Fitoussi and Sofiane Khelladi and Abbas Tcharkhtchi},

url = {https://doi.org/10.1002/pen.25555},

year  = {2020},

date = {2020-10-01},

journal = {Polymer Engineering And Science},

volume = {61},

number = {1},

pages = {68-76},

abstract = {Fused filament fabrication (FFF), an additive manufacturing technique, is used to produce prototypes and a gradually more important processing route to get final products. Due to the layer-by-layer deposition mechanism involved, bonding between adjacent layers is controlled by the thermal energy of the material being printed. Thus, it is strongly in conjunction with the temperature development of the filaments during the deposition sequence. This study gives out an in-process set-up enabling to record temperature profile of two adjacent filaments or a sequence of deposition in various locations during FFF process. The main characteristic of the presented procedure is the possibility of obtaining a global temperature profile resulted from an IR-camera; parallel to those recorded using a K-type thermocouple. Needless to say that a K-type thermocouple accurately records the local temperature at the interface of adjacent filaments. Conversely, an IR-camera signifies the temperature profile on the captured surface. The obtained results showed that there is a remarkable difference between the cooling rate and re-heating peaks. The primary outcome of this study is the consideration of results accuracy and the possibility of working on optimization of the obtained temperature profile. Altogether it helps optimize inter-layer strength while assessing the temperature evolution.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{zhang_1270,

title = {Enhanced CDM model accounting of stress triaxiality and Lode angle for ductile damage prediction in metal forming},

author = {Kai Zhang and Houssem Badreddine and Naila Hfaiedh and Khemais Saanouni and Jianlin Liu},

url = {https://journals.sagepub.com/doi/full/10.1177/1056789520958045},

year  = {2020},

date = {2020-09-01},

journal = {International Journal Of Damage Mechanics},

volume = {30},

number = {2},

pages = {260-282},

abstract = {This paper deals with the prediction of ductile damage based on CDM approach fully coupled with advanced elastoplastic constitutive equations. This fully coupled damage model is developed based on the total energy equivalence assumption under the thermodynamics of irreversible processes framework with state variables. In this model, the damage evolution is enhanced by accounting for both stress triaxiality and Lode angle. The proposed constitutive equations are implemented into Finite Element (FE) code ABAQUS/Explicit through a user material subroutine (VUMAT). The material parameters are determined by the hybrid experimental-numerical method using various tensile and shear tests. Validation of the proposed model has been done using different tests of two aluminum alloys (Al6061-T6 and Al6014-T4). Through comparisons of numerical simulations with experimental results for different loading paths, the predictive capabilities of the proposed model have been shown. The model is found to be able to capture the initiation as well as propagation of macro-crack in sheet and bulk metals during their forming processes},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{charles_1518,

title = {Mathematical and numerical study of a dusty Knudsen gas mixture},

author = {Frédérique Charles and Francesco Salvarani},

url = {https://link.springer.com/article/10.1007/s10440-019-00277-x},

year  = {2020},

date = {2020-08-01},

journal = {Acta Applicandae Mathematicae},

volume = {168},

number = {1},

pages = {17-31},

abstract = {We consider a mixture composed of a gas and dust particles in a very rarefied setting. Whereas the dust particles are individually described, the surrounding gas is treated as a Knudsen gas, in such a way that interactions occur only between gas particles and dust by means of diffuse reflection phenomena. After introducing the model, we prove the existence and the uniqueness of the solution and provide a numerical strategy for the study of the equations. At the numerical level, we focus our attention on the phenomenon of energy transfer between the gas and the moving dust particles.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{vanaei_2091,

title = {Experimental study of PLA thermal behavior during fused filament fabrication},

author = {Hamidreza Vanaei and Mohammadali Shirinbayani and Sidonie Fernandes Costa and Fernando Moura Duarte and José António Covas and Deligant Michael and Sofiane Khelladi and Abbas Tcharkhtchi},

url = {https://doi.org/10.1002/app.49747},

year  = {2020},

date = {2020-08-01},

journal = {Journal Of Applied Polymer Science},

volume = {138},

number = {4},

pages = {49747},

abstract = {Fused filament fabrication (FFF) is an additive manufacturing technique that is used to produce prototypes and a gradually more important processing route to obtain final products. Due to the layer-by-layer deposition mechanism involved, bonding between adjacent layers is controlled by the thermal energy of the material being printed, which strongly depends on the temperature development of the filaments during the deposition sequence. This study reports experimental measurements of filament temperature during deposition. These temperature profiles were compared to the predictions made by a previously developed model. The two sets of data showed good agreement, particularly concerning the occurrence of reheating peaks when new filaments are deposited onto previously deposited ones. The developed experimental technique is shown to demonstrate its sensitivity to changing operating conditions, namely platform temperature and deposition velocity. The data generated can be valuable to predict more accurately the bond quality achieved in FFF parts.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{vanaei_2090,

title = {Toward the understanding of temperature effect on bonding strength, dimensions and geometry of 3D-printed parts},

author = {Hamidreza Vanaei and Raissi Kaddour and Deligant Michael and Mohammadali Shirinbayani and Joseph Fitoussi and Sofiane Khelladi and Abbas Tcharkhtchi},

url = {https://doi.org/10.1007/s10853-020-05057-9},

year  = {2020},

date = {2020-07-01},

journal = {Journal Of Materials Science},

volume = {55},

number = {0},

pages = {14677-14689},

abstract = {Fused filament fabrication (FFF), which is an additive manufacturing technique, opens alternative possibilities for complex geometries fabrication. However, its use in functional products is limited due to anisotropic strength issues. Indeed, the strength of FFF fabricated parts across successive layers in the build direction (Z direction) can be significantly lower than the strength in X-Y directions. This strength weakness has been attributed to poor bonding between printed layers. This bonding depends on the temperature of the current layer being deposited?at melting temperature (Tm)?and the temperature of the previously deposited layer. It is assumed that depositing a layer at Tm on a layer at temperature around crystallization temperature (Tc) would enable higher material crystallinity and thus better bonding between previous and present layers. On the contrary, if the previous layer temperature is below Tc, material crystallinity will be low and bonding strength weak. This paper aims at studying the significant effect of temperature difference (?T) between previous and current deposited layers temperatures on (1) inter-layers bonding strength improvement and (2) part dimensions, geometry and structure stability. A 23% increase in the inter-layers bonding strength for previous layer temperature slightly higher than Tc reported here confirms the above assumption and offers a first solution toward the increase in inter-layers bonding strength in FFF.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{hamroun_1169,

title = {Existence of large solutions to the Landau-Lifshitz-Bloch equation},

author = {Djamila Hamroun and Kamel Hamdache},

url = {https://www.intlpress.com/site/pub/pages/journals/items/cms/_home/acceptedpapers/index.php},

year  = {2020},

date = {2020-05-14},

journal = {Communications In Mathematical Sciences},

volume = {18},

number = {2},

pages = {487-513},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{vanaei_2087,

title = {Influence of process parameters on thermal and mechanical properties of polylactic acid fabricated by fused filament fabrication},

author = {Hamidreza Vanaei and Mohammadali Shirinbayani and Deligant Michael and Raissi Kaddour and Fitoussi Joseph and Sofiane Khelladi and Abbas Tcharkhtchi},

url = {https://doi.org/10.1002/pen.25419},

year  = {2020},

date = {2020-05-01},

journal = {Polymer Engineering And Science},

volume = {60},

number = {8},

pages = {1822-1831},

abstract = {Fused filament fabrication is considered one of the most used processes in additive manufacturing rapid prototypes out of polymeric material. Poor strength of the deposited layers is still one of the main critical problems in this process, which affects the mechanical properties of the final parts. To improve the mechanical strength, investigation into various process parameters must be considered. In this article, the influence of different process parameters has been experimentally investigated by means of physicochemical and mechanical characterizations. Special attention was given to the thermal aspect. In that respect, the in situ measurement of temperature profile during deposition indicated that several parameters affect the cooling rate of material and consequently have an influence on the final parts. It was found that the influence of increasing the extruder temperature is more significant in comparison with other process parameters.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{hamdache_606,

title = {Weak Solutions to Unsteady and Steady Models of Conductive Magnetic Fluids},

author = {Kamel Hamdache and Djamila Hamroun},

url = {https://link.springer.com/article/10.1007%2Fs00245-018-9505-x},

year  = {2020},

date = {2020-04-01},

journal = {Applied Mathematics And Optimization},

volume = {81},

pages = {479-509},

abstract = {We study a nonlinear coupling system of partial differential equations describing the dynamic of a magnetic fluid with internal rotations. The present mathematical model generalizes those discussed previously in the literature since actually the fluid is electrically conducting inducing additional nonlinearities in the problem and the dynamics of the magnetic field is described by the quasi-static Maxwell equations instead of the usual magnetostatic ones. We prove existence of weak solutions with finite energy first for the unsteady problem then for the steady one.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{plasman_1680,

title = {A projection scheme for Navier--Stokes with  variable viscosity and natural boundary condition},

author = {Ludovic Plasman and Jean Deteix and Driss Yakoubi},

url = {https://onlinelibrary.wiley.com/doi/10.1002/fld.4851},

year  = {2020},

date = {2020-04-01},

journal = {International Journal for Numerical Methods in Fluids},

volume = {92},

number = {12},

pages = {1845-1865},

abstract = {Combiningthe Navier-Stokes systems with Neumann (or natural) boundary condition to characterize a fluid flow is frequent. The popular projection (or pressure

correction) methods inspired by Chorin and Temam are not well adapted to such boundary condition, which translate in loss of accuracy. If some alternative projection methods have been proposed to reduce the accuracy loss due to the Neumann condition in case of Newtonian fluids, little has been pro-

posed for generalized Newtonian fluids. In this work, we propose two methods

derived from the incremental pressure correction projection that can be used

for fluids with inhomogeneous or variable viscosity with natural boundary condition. Both time and space accuracy of the methods will be illustrated using a manufactured solution.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{mula_1514,

title = {Homogenization in the energy variable for a neutron transport model.},

author = {Olga Mula and Francesco Salvarani and Harsha Hutridurga},

url = {https://content.iospress.com/articles/asymptotic-analysis/asy191544},

year  = {2020},

date = {2020-03-01},

journal = {Asymptotic Analysis},

volume = {117},

number = {1-2},

pages = {1-25},

abstract = {This article addresses the homogenization of linear Boltzmann equation when the optical parameters are highly heterogeneous in the energy variable. We employ the method of two-scale convergence to arrive at the homogenization result. In doing so, we show the induction of a memory effect in the homogenization limit. We also provide some numerical experiments to illustrate our results. In the Appendix, we treat a related case of the harmonic oscillator.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{anwasia_1125,

title = {On the Maxwell- Stefan diffusion limit for reactive mixture of polyatomic gases in non-isothermal setting},

author = {Benjamin Anwasia and Marzia Bisi and Ana Jacinta Soares and Francesco Salvarani},

url = {https://www.aimsciences.org/article/doi/10.3934/krm.2020003},

year  = {2020},

date = {2020-02-01},

journal = {Kinetic And Related Models},

volume = {13},

number = {1},

pages = {63-95},

abstract = {In this article we deduce a mathematical model of Maxwell-Stefan type for a reactive mixture of polyatomic gases with a continuous structure of internal energy. The equations of the model are derived in the diffusive limit of a kinetic system of Boltzmann equations for the considered mixture, in the general non-isothermal setting. The asymptotic analysis of the kinetic system is performed under a reactive-diffusive scaling for which mechanical collisions are dominant with respect to chemical reactions. The resulting system couples the Maxwell-Stefan equations for the diffusive fluxes with the evolution equations for the number densities of the chemical species and the evolution equation for the temperature of the mixture. The production terms due to the chemical reaction and the Maxwell-Stefan diffusion coefficients are moreover obtained in terms of general collision kernels and parameters of the kinetic model.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{hamdache_995,

title = {Asymptotics behaviours for the Landau-Lifshitz-Bloch equation},

author = {Kamel Hamdache and Djamila Hamroun},

url = {https://dergipark.org.tr/tr/pub/atnaa/issue/49323/512065},

year  = {2019},

date = {2019-12-01},

journal = {Advances in the Theory of Nonlinear Analysis and its Applications},

volume = {3},

number = {3},

pages = {174-191},

abstract = {The Landau-Lifshitz-Bloch (LLB) equation is an interpolation between Bloch equation valid for high temperatures and Landau-Lifshitz equation valid for low temperatures. Conversely in this paper, we discuss the behaviours of the solutions of (LLB) equation both as the temperature goes to infinity or 0. Surprisingly in the first case, the behaviour depends also on the scaling of the damping parameter   and the volume exchange parameter a. Three cases are considered and accordingly we get either a linear stationary equation, Bloch equation or Stokes equation. As for the small temperature behaviour, d and a being independent of the temperature, we show that the limit of (LLB) equation is Landau-Lifshitz-Gilbert equation.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{ben_abdallah_992,

title = {Enzymatic Hydrolysis of Poly (Caprolactone) and its Blend with Styrene-Butadiene-Styrene (40% PCL/60% SBS)},

author = {Abir Ben Abdallah and Achraf Kallel and Fehmi Gamaoun and Abbas Tcharkhtchi},

url = {https://link.springer.com/article/10.1007%2Fs10924-019-01522-y},

year  = {2019},

date = {2019-11-01},

journal = {Journal Of Polymers And The Environment},

volume = {27},

pages = {2341-2351},

abstract = {In this study, we aim to evaluate the effect of enzymatic hydrolysis on aliphatic polyester and on its shape memory blend. Therefore, the hydrolysis of poly (?-caprolactone) (PCL) and of its shape memory polymer (SMP) blend [40% PCL/60% styrene-butadiene-styrene (SBS)] in a solution containing an Amano lipase from pseudomonas fluorescence and a phosphate buffered saline (PBS), is achieved. An appropriate characterization helps to better understand the behaviour of these polymers. So, the properties of these materials prior and after hydrolytic degradation are investigated. When they are submitted to enzymatic hydrolysis, the physico-chemical and mechanical properties of PCL and its blend (PCL/SBS) change. PCL undergoes a significant decrease in weight during enzymatic hydrolysis. Yet, blending PCL with SBS considerably reduces its degradation rate in terms of weight drop, compared with pure PCL. The enzymatic hydrolysis causes chains splitting, which rises their mobility and facilitates their reorientation. Consequently, for PCL and its blend, the degree of crystallinity Xc rises during hydrolytic degradation, which confirms that the amorphous regions of PCL are more susceptible to hydrolysis. Besides, this continuous rise in crystallinity causes the augmentation of PCL and its blend melting, crystallization and glass transition temperatures. Moreover, the PCL brittleness increases, and the blend ductility decreases with the enzymatic hydrolysis time. For both, PCL and its blend, the young modulus displays two opposite effects; it goes up due the growth of crystallinity, but at the end of hydrolysis, its value goes down because of weight loss.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nguyen_1496,

title = {Role of the Crystal Lattice Structure in Predicting Fracture Toughness},

author = {Thuy Nguyen and Daniel Bonamy},

url = {https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.123.205503},

year  = {2019},

date = {2019-11-01},

journal = {Physical Review Letters},

volume = {123},

number = {20},

pages = {205503},

abstract = {We examine the atomistic scale dependence of a material's resistance to failure by numerical simulations and analytical analysis in electrical analogs of brittle crystals. We show that fracture toughness depends on the lattice geometry in a way incompatible with Griffith's relationship between fracture and free surface energy. Its value finds its origin in the matching between the continuum displacement field at the engineering scale, and the discrete nature of solids at the atomic scale. The generic asymptotic form taken by this field near the crack tip provides a solution for this matching, and subsequently a way to predict toughness from the atomistic parameters with application to graphene},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{yakoubi_1683,

title = {An adaptive discontinuous Galerkin method for very stiff systems of ordinary differential equations},

author = {Driss Yakoubi and André Fortin},

url = {https://www.sciencedirect.com/science/article/pii/S0096300319302875?via%3Dihub},

year  = {2019},

date = {2019-10-01},

journal = {Applied Mathematics And Computation},

volume = {358},

pages = {330-347},

abstract = {We present a discontinuous Galerkin (DG) method for the numerical solution of stiff systems of ordinary differential equations (ODEs). We use a standard DG variational formulation with polynomials of degree k in each time interval. We show that the method is A-stable for every k. We then introduce a hierarchical Legendre finite element basis and we show that a whole family of approximations can be obtained simply by truncating the last p degrees of freedom from the computed solution. We show that these approximations converge to order in L2-norm and to order in supremum norm. We then show how this can be used to control the error and the time step length. We present numerical examples of solutions on very stiff problems and on stiff problems with very long time integration where the time step length can vary on many orders of magnitude.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{yakoubi_1681,

title = {Shear rate projection schemes for non--Newtonian fluids},

author = {Driss Yakoubi and Jean Deteix},

url = {https://www.sciencedirect.com/science/article/pii/S0045782519303469?via%3Dihub},

year  = {2019},

date = {2019-09-01},

journal = {Computer Methods In Applied Mechanics And Engineering},

volume = {354},

number = {1},

pages = {620-636},

abstract = {The operator splitting approach applied to the Navier-Stokes equations gave rise to various numerical methods for the simulations of the dynamics of fluids. The separate work of Chorin and Temam on this subject gave birth to the so-called projection methods. The most basic of those schemes, the incremental and non-incremental variant (see Guermond et al. 2006) induce an artificial Neumann boundary condition on the pressure. The so-called rotational incremental pressure-correction scheme proposed by Timmermans et al. (1996) gives a consistent equation for the pressure in case of a Newtonian fluids with homogeneous viscosity. In this work we propose a family of projection methods for generalized Newtonian fluids based on an extension of the rotational projection scheme. Called shear rate projections, these methods produce consistent pressure when applied to generalized Newtonian fluids. Accuracy of the methods will be illustrated using a manufactured solution. Numerical experiments for the flow past a cylinder, with a Carreau rheological model, will also be presented},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{kallel_891,

title = {Study of bonding formation between the filaments of PLA in FFF process},

author = {Achraf Kallel and Imade Koutiri and Elham Babaeitorkamani and Alireza Khavandi and Morteza Tamizifar and Mohammadali Shirinbayani and Abbas Tcharkhtchi},

url = {https://www.hanser-elibrary.com/doi/10.3139/217.3718},

year  = {2019},

date = {2019-08-01},

journal = {International Polymer Processing},

volume = {34},

number = {4},

pages = {434-444},

abstract = {Fused filament fabrication (FFF) is an additive manufacturing (AM) process that provides physical objects commonly used for modeling, prototyping and production application. The major drawback of this process is poor mechanical property due to the porous structure of final parts. This process requires careful management of coalescence phenomenon. In this paper, the major influencing factors during the FFF process of poly(lactic acid) (PLA) were investigated experimentally and with a numerical model. It has been shown that the polymer temperature has a significant effect on rheological behavior of PLA especially on adhesion of the filaments. An experimental set-up has been placed in the machine to have the cyclic temperature of the filament. A variation of the polymer temperature influences process parameters such as feed rate, temperature of nozzle and temperature of the platform. The results showed that the amount of polymeric coalescence (neck growth) rises when increasing the feed rate, the nozzle temperature, and the platform temperature. A model to predict the neck growth is proposed. It predicts a lower amount of neck growth value than obtained with experimentally. This difference has been explained as the effect of other phenomena, such as polymer relaxation time, pressure of the nozzle and especially cyclic temperature which is not taken into account in the model.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}