said elkoun - Academia.edu (original) (raw)

Papers by said elkoun

Research paper thumbnail of Recent progress in the accelerated aging and lifetime prediction of elastomers : A review

Polymer Degradation and Stability

Research paper thumbnail of Morphology and crystallization behaviour of polyhydroxyalkanoates-based blends and composites: A review

Biochemical Engineering Journal

Research paper thumbnail of Élaboration D'Un Absorbant Acoustique À Partir De Panic Érigé, via Le Développement De La Méthode Des Matrices De Transfert en Parallèle

Research paper thumbnail of Recent highlights on the parallel transfer matrix method (P-TMM)

Recently, an extension of the transfer matrix method (TMM) to calculate absorption coefficient an... more Recently, an extension of the transfer matrix method (TMM) to calculate absorption coefficient and transmission loss of acoustic systems in parallel (one next to each other and not one after the other) has been published [1]. This method (P-TMM) is based on the continuity of flow and pressure on each side of the stack. To comply with these constraints, assumptions must be set: there is only plane waves that propagate, no exchange is allowed between the elements of the stack, the stack is smaller than the wavelength. Further progress has been made. Firstly, a comparison with the method of the sum of admittances (ASM) [2] will be presented. Then, a further extension of the P-TMM will be introduced for stacks where each component is not isolated from each other : discretized P-TMM. the diffusion effect is taken into account in the P-TMM approach.

Research paper thumbnail of Transmission loss of a sound insulating panel made from charged recyclable thermoplastic

This article aims at investigating the sound insulation property of composites made of recyclable... more This article aims at investigating the sound insulation property of composites made of recyclable thermoplastic charged with heavy particles. Polyethylene (PE) is the most used thermoplastic polymer worldwide. Behind this generic name lies several types of PE, where linear low density polyethylene (LLDPE) is the most common one. Metal particles are often used to improve the electrical properties of materials. However Young modulus increases too. Subsequently, and in order to reduce composites rigidity, samples microstructure was modified by subjected all composites to a special procedure. Then, Young modulus was again reevaluated. Buoyancy method was used to assess the composites density. In this work, it was shown that the sound insulation properties of a material made of recyclable thermoplastic can be assessed by the rigidity to density ratio, and, enhanced by reducing this ratio.

Research paper thumbnail of Assessment of acoustic properties of different recycled polymer-based materials for road work sound barrier walls application

Research paper thumbnail of Transfer matrix modeling and numerical verification of locally reacting acoustic mosaics

Research paper thumbnail of Comparison between parallel transfer matrix method and admittance sum method

The Journal of the Acoustical Society of America, 2014

A transfer matrix method to predict absorption coefficient and transmission loss of parallel asse... more A transfer matrix method to predict absorption coefficient and transmission loss of parallel assemblies of materials which can be expressed by a 2 × 2 transfer matrix was published recently. However, the usual method based on the sum of admittances is largely used to predict also surface admittance of parallel assemblies. This paper aims to highlight differences between both methods through three examples on a parallel assembly backed by (1) a rigid wall, (2) an air cavity, and (3) an anechoic termination.

Research paper thumbnail of Transfer matrix method applied to the parallel assembly of sound absorbing materials

The Journal of the Acoustical Society of America, 2013

The transfer matrix method (TMM) is used conventionally to predict the acoustic properties of lat... more The transfer matrix method (TMM) is used conventionally to predict the acoustic properties of laterally infinite homogeneous layers assembled in series to form a multilayer. In this work, a parallel assembly process of transfer matrices is used to model heterogeneous materials such as patchworks, acoustic mosaics, or a collection of acoustic elements in parallel. In this method, it is assumed that each parallel element can be modeled by a 2 × 2 transfer matrix, and no diffusion exists between elements. The resulting transfer matrix of the parallel assembly is also a 2 × 2 matrix that can be assembled in series with the classical TMM. The method is validated by comparison with finite element (FE) simulations and acoustical tube measurements on different parallel/series configurations at normal and oblique incidence. The comparisons are in terms of sound absorption coefficient and transmission loss on experimental and simulated data and published data, notably published data on a para...

Research paper thumbnail of Plastic deformation of polyethylene and ethylene copolymers: Part I Homogeneous crystal slip and molecular mobility

Journal of Materials Science, 1998

The plastic behaviour of polyethylene and ethylene copolymers is studied under uniaxial tensile t... more The plastic behaviour of polyethylene and ethylene copolymers is studied under uniaxial tensile testing with particular attention to the development of plastic instability. Heterogeneous crystal slip is suggested to take place when homogeneous crystal slip either is not allowed at the temperature and strain rate of the experiment or is exhausted owing to extension of the chain folds. The chain unfolding concomitant to the fragmentation of the crystalline lamellae is suspected to have a low strain hardening that is responsible for the phenomenon. Partial screw dislocations with a shorter Burgers vector than in the case of homogeneous slip are proposed to become operative because of the activation of 90°chain twists in the crystalline stems. Dissociation of dislocations into partials involves stacking faults in the orthorhombic structure that may turn into monoclinic structure through a martensitic-like transformation. Crystal slip is likely to concentrate in these faulty regions owing to the reduced molecular interactions and lower density. Two types of correspondence of the transformed monoclinic phase with the parent orthorhombic structure are observed. The modification of the chain-folding macroconformation as a function of the crystallinity of the materials is suspected to influence the transformation shear mode.

Research paper thumbnail of Plastic Deformation of Polyethylene Studied by Infrared Dichroism

Applied Spectroscopy, 1999

Infrared dichroism m easurements have been carried out to investigate the plastic deformation m e... more Infrared dichroism m easurements have been carried out to investigate the plastic deformation m ech anisms of homogeneous and heterogeneous ethylene copolymers issued from the metallocene and the Ziegler± Natta catalyses, respectively. The two copolymers having the same density display signi® cantly different plastic behavior that should result from different m ech anisms of crystal slip. Such mechanisms are analyzed on the basis of the m ain crystal slip system s (100)[001] and (010)[001] having the higher shear com pliances. Attention is focused on the Schmid factor, S, of the slip planes, which is the ratio of the resolved shear stress acting on each slip plane to the applied tensile stress. From the orientation functions of the three crystallographic axes of the orthorhombic unit cell, the Schmid factor of the two slip systems is determ ined as a function of plastic strain. The heterogeneous copolymer exhibits somewhat higher data for the (010)[001] slip, which suggest a preferred activation of this system during the yielding stage. In contrast, the homogeneous copolymer displays close values for the two slip systems, indicating that plastic¯ow is m ore likely governed by a combined activation of the two slip systems, and with eventual cross slip owing to the comm on [001] slip direction.

Research paper thumbnail of Single stage purification of flax, hemp, and milkweed stem and their physical and morphological properties

International Journal of Polymer Analysis and Characterization, 2017

ABSTRACT Agriculture biomass is an alternative possible solution for the extraction of cellulose,... more ABSTRACT Agriculture biomass is an alternative possible solution for the extraction of cellulose, compared to the classical soft and hard wood. However, the valorization of cellulose is challenging for the researchers as it involves multiple steps. In the present study, the raw fibers of flax, hemp, and milkweed stem fibers were purified in single step using hydrogen peroxide in water. By this method authors successfully extracted the purified cellulose fibers without damaging the fiber length. The purified fibers were characterized to understand the thermal, functional, crystalline, and morphological properties by thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The FTIR results showed the effective removal of lignin and significant improvement in thermal stability was observed by TGA. Evidently, the SEM results showed significant improvement in the morphology compared to that of the raw fibers. XRD results showed that the treatment does not affect the crystallinity of the fibers.

Research paper thumbnail of Recent progress in the accelerated aging and lifetime prediction of elastomers : A review

Polymer Degradation and Stability

Research paper thumbnail of Morphology and crystallization behaviour of polyhydroxyalkanoates-based blends and composites: A review

Biochemical Engineering Journal

Research paper thumbnail of Élaboration D'Un Absorbant Acoustique À Partir De Panic Érigé, via Le Développement De La Méthode Des Matrices De Transfert en Parallèle

Research paper thumbnail of Recent highlights on the parallel transfer matrix method (P-TMM)

Recently, an extension of the transfer matrix method (TMM) to calculate absorption coefficient an... more Recently, an extension of the transfer matrix method (TMM) to calculate absorption coefficient and transmission loss of acoustic systems in parallel (one next to each other and not one after the other) has been published [1]. This method (P-TMM) is based on the continuity of flow and pressure on each side of the stack. To comply with these constraints, assumptions must be set: there is only plane waves that propagate, no exchange is allowed between the elements of the stack, the stack is smaller than the wavelength. Further progress has been made. Firstly, a comparison with the method of the sum of admittances (ASM) [2] will be presented. Then, a further extension of the P-TMM will be introduced for stacks where each component is not isolated from each other : discretized P-TMM. the diffusion effect is taken into account in the P-TMM approach.

Research paper thumbnail of Transmission loss of a sound insulating panel made from charged recyclable thermoplastic

This article aims at investigating the sound insulation property of composites made of recyclable... more This article aims at investigating the sound insulation property of composites made of recyclable thermoplastic charged with heavy particles. Polyethylene (PE) is the most used thermoplastic polymer worldwide. Behind this generic name lies several types of PE, where linear low density polyethylene (LLDPE) is the most common one. Metal particles are often used to improve the electrical properties of materials. However Young modulus increases too. Subsequently, and in order to reduce composites rigidity, samples microstructure was modified by subjected all composites to a special procedure. Then, Young modulus was again reevaluated. Buoyancy method was used to assess the composites density. In this work, it was shown that the sound insulation properties of a material made of recyclable thermoplastic can be assessed by the rigidity to density ratio, and, enhanced by reducing this ratio.

Research paper thumbnail of Assessment of acoustic properties of different recycled polymer-based materials for road work sound barrier walls application

Research paper thumbnail of Transfer matrix modeling and numerical verification of locally reacting acoustic mosaics

Research paper thumbnail of Comparison between parallel transfer matrix method and admittance sum method

The Journal of the Acoustical Society of America, 2014

A transfer matrix method to predict absorption coefficient and transmission loss of parallel asse... more A transfer matrix method to predict absorption coefficient and transmission loss of parallel assemblies of materials which can be expressed by a 2 × 2 transfer matrix was published recently. However, the usual method based on the sum of admittances is largely used to predict also surface admittance of parallel assemblies. This paper aims to highlight differences between both methods through three examples on a parallel assembly backed by (1) a rigid wall, (2) an air cavity, and (3) an anechoic termination.

Research paper thumbnail of Transfer matrix method applied to the parallel assembly of sound absorbing materials

The Journal of the Acoustical Society of America, 2013

The transfer matrix method (TMM) is used conventionally to predict the acoustic properties of lat... more The transfer matrix method (TMM) is used conventionally to predict the acoustic properties of laterally infinite homogeneous layers assembled in series to form a multilayer. In this work, a parallel assembly process of transfer matrices is used to model heterogeneous materials such as patchworks, acoustic mosaics, or a collection of acoustic elements in parallel. In this method, it is assumed that each parallel element can be modeled by a 2 × 2 transfer matrix, and no diffusion exists between elements. The resulting transfer matrix of the parallel assembly is also a 2 × 2 matrix that can be assembled in series with the classical TMM. The method is validated by comparison with finite element (FE) simulations and acoustical tube measurements on different parallel/series configurations at normal and oblique incidence. The comparisons are in terms of sound absorption coefficient and transmission loss on experimental and simulated data and published data, notably published data on a para...

Research paper thumbnail of Plastic deformation of polyethylene and ethylene copolymers: Part I Homogeneous crystal slip and molecular mobility

Journal of Materials Science, 1998

The plastic behaviour of polyethylene and ethylene copolymers is studied under uniaxial tensile t... more The plastic behaviour of polyethylene and ethylene copolymers is studied under uniaxial tensile testing with particular attention to the development of plastic instability. Heterogeneous crystal slip is suggested to take place when homogeneous crystal slip either is not allowed at the temperature and strain rate of the experiment or is exhausted owing to extension of the chain folds. The chain unfolding concomitant to the fragmentation of the crystalline lamellae is suspected to have a low strain hardening that is responsible for the phenomenon. Partial screw dislocations with a shorter Burgers vector than in the case of homogeneous slip are proposed to become operative because of the activation of 90°chain twists in the crystalline stems. Dissociation of dislocations into partials involves stacking faults in the orthorhombic structure that may turn into monoclinic structure through a martensitic-like transformation. Crystal slip is likely to concentrate in these faulty regions owing to the reduced molecular interactions and lower density. Two types of correspondence of the transformed monoclinic phase with the parent orthorhombic structure are observed. The modification of the chain-folding macroconformation as a function of the crystallinity of the materials is suspected to influence the transformation shear mode.

Research paper thumbnail of Plastic Deformation of Polyethylene Studied by Infrared Dichroism

Applied Spectroscopy, 1999

Infrared dichroism m easurements have been carried out to investigate the plastic deformation m e... more Infrared dichroism m easurements have been carried out to investigate the plastic deformation m ech anisms of homogeneous and heterogeneous ethylene copolymers issued from the metallocene and the Ziegler± Natta catalyses, respectively. The two copolymers having the same density display signi® cantly different plastic behavior that should result from different m ech anisms of crystal slip. Such mechanisms are analyzed on the basis of the m ain crystal slip system s (100)[001] and (010)[001] having the higher shear com pliances. Attention is focused on the Schmid factor, S, of the slip planes, which is the ratio of the resolved shear stress acting on each slip plane to the applied tensile stress. From the orientation functions of the three crystallographic axes of the orthorhombic unit cell, the Schmid factor of the two slip systems is determ ined as a function of plastic strain. The heterogeneous copolymer exhibits somewhat higher data for the (010)[001] slip, which suggest a preferred activation of this system during the yielding stage. In contrast, the homogeneous copolymer displays close values for the two slip systems, indicating that plastic¯ow is m ore likely governed by a combined activation of the two slip systems, and with eventual cross slip owing to the comm on [001] slip direction.

Research paper thumbnail of Single stage purification of flax, hemp, and milkweed stem and their physical and morphological properties

International Journal of Polymer Analysis and Characterization, 2017

ABSTRACT Agriculture biomass is an alternative possible solution for the extraction of cellulose,... more ABSTRACT Agriculture biomass is an alternative possible solution for the extraction of cellulose, compared to the classical soft and hard wood. However, the valorization of cellulose is challenging for the researchers as it involves multiple steps. In the present study, the raw fibers of flax, hemp, and milkweed stem fibers were purified in single step using hydrogen peroxide in water. By this method authors successfully extracted the purified cellulose fibers without damaging the fiber length. The purified fibers were characterized to understand the thermal, functional, crystalline, and morphological properties by thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The FTIR results showed the effective removal of lignin and significant improvement in thermal stability was observed by TGA. Evidently, the SEM results showed significant improvement in the morphology compared to that of the raw fibers. XRD results showed that the treatment does not affect the crystallinity of the fibers.