MONOTONICITY PROPERTIES FOR A SINGLE SERVER QUEUE WITH CLASSICAL RETRIAL POLICY AND SERVICE INTERRUPTIONS

MOHAMED BOUALEM,MOULOUD CHERFAOUI,DJAMIL AISSANI 장전수학회 2016 Proceedings of the Jangjeon mathematical society Vol.19 No.2

The purpose of this study is to introduce a new analytical approach namely, a qualitative analysis, which is another field of own right to establish insensitive stochastic bounds on some performance measures of a single server queue with classical retrial policy and service interruptions by using the monotonicity and comparability approach relative to the convex ordering. More precisely, we study the conditions of comparability of certain performance measures, namely the probability of number of external customers entering during a service period, the conditions of monotonicity of transition operator of embedded Markov chain and the conditions to compare the stationary distributions. Numerical studies are performed to support the theoretical obtained results.

Influence of porosity on the behavior of cement orthopaedic of total hip prosthesis

Ali, Benouis,Boualem, Serier,Smail, Benbarek Techno-Press 2015 Biomaterials and biomedical engineering Vol.2 No.4

This paper presents three-dimensional finite element method analyses of the distribution of equivalents stress of Von Mises. Induced around a cavity located in the bone cement polymethylmethacrylate (PMMA). The presences and effect of its position in the cement was demonstrated, thus on the stress level and distribution. The porosity interaction depending on their positions, and their orientations on the interdistances their mechanical behaviour of bone cement effects were analysed. The obtained results show that micro-porosity located in the proximal and distal zone of the prosthesis is subject to higher stress field. We show that the breaking strain of the cement is largely taken when the cement, containing the porosities very close adjacent to each other.

Effects of Foundation Soil Stiffness on the 3-D Modal Characteristics and Seismic Response of a Highway Bridge

Mouloud Ouanani,Boualem Tiliouine 대한토목학회 2015 KSCE JOURNAL OF CIVIL ENGINEERING Vol.19 No.4

This paper presents the main results of an investigation into the influence of foundation soil stiffness on the modal characteristics and seismic response of a highway bridge with spread foundations. A sensitivity study including six types of soil profiles is first performed to examine the effects of foundation soil stiffness on critical dynamic response parameters of the bridge. 3-D modal characteristics of lateral, vertical, longitudinal and torsional vibrations modes are identified and compared for various soil and rock conditions. The study is then extended to estimate the time history nonlinear seismic response of coupled foundation soil-bridge models utilizing an extension of the Fast Nonlinear Analysis (FNA) algorithm. Two different approaches for modeling soil foundation interaction are considered: a PGA consistent linear soil model and an advanced non linear soil model. Results show, among others, the major influence of soil flexibility effects on the modal characteristics and seismic response behavior of the bridge. Moreover, the results illustrate clearly the importance of soil nonlinearity on coupled foundation soil-bridge response. It follows, from a design perspective, that analytical models used for the seismic analysis of bridge structures should explicitly consider the effects of soil-structure interaction including nonlinear soil behavior.

Influence of porosity on the behavior of cement orthopaedic of total hip prosthesis

Ali, Benouis,Boualem, Serier,Smail, Benbarek Techno-Press 2015 Biomaterials and Biomechanics in Bioengineering Vol.2 No.4

This paper presents three-dimensional finite element method analyses of the distribution of equivalents stress of Von Mises. Induced around a cavity located in the bone cement polymethylmethacrylate (PMMA). The presences and effect of its position in the cement was demonstrated, thus on the stress level and distribution. The porosity interaction depending on their positions, and their orientations on the interdistances their mechanical behaviour of bone cement effects were analysed. The obtained results show that micro-porosity located in the proximal and distal zone of the prosthesis is subject to higher stress field. We show that the breaking strain of the cement is largely taken when the cement, containing the porosities very close adjacent to each other.

New optimization method of patch shape to improve the effectiveness of cracked plates repair

Mohamed S. Bouchiba,Boualem Serier 국제구조공학회 2016 Structural Engineering and Mechanics, An Int'l Jou Vol.58 No.2

An optimization method of patch shape was developed in this study, in order to improve repair of cracked plates. It aimed to minimize three objectives: stress intensity factor, patch volume and shear stresses in the adhesive film. The choice of these objectives ensures improving crack repair, gaining mass and enhancing the adhesion durability between the fractured plate and the composite patch. This was a multi-objective optimization combined with Finite elements calculations to find out the best distribution of patch height with respect to its width. The implementation of the method identified families of optimal shapes with specific geometric features around the crack tip and at the horizontal end of the patch. Considerable mass gain was achieved while improving the repair efficiency and keeping the adhesive shear stress at low levels.

Effect of cavity-defects interaction on the mechanical behavior of the bone cement

Zouambi, Leila,Serier, Boualem,Benamara, Nabil Techno-Press 2014 Advances in materials research Vol.3 No.1

The presence of cavities in the bone cement has a great importance for the transport of antibiotics, but its existence in this material can lead to its weakening by notch effect. The aim of this study allows providing a physical interpretation to the cavities interconnection by cracks observed experimentally. The most important stress of Von Mises is localized at the cement/bone interface near the free edge which is the seat of stress concentration. The presence and interaction of cavities in this site concentrate, by notch effect, stresses which tend to the tensile fracture stress of Bone cement.

Experimental and numerical prediction of the weakened zone of a ceramic bonded to a metal

Zaoui, Bouchra,Baghdadi, Mohammed,Mechab, Belaid,Serier, Boualem,Belhouari, Mohammed Techno-Press 2019 Advances in materials research Vol.8 No.4

In this study, a three-dimensional Finite Element Model has been developed to estimate the size of the weakened zone in a bi-material a ceramic bonded to metal. The calculations results were compared to those obtained using Scanning Electron Microscope (SEM). In the case of elastic-plastic behaviour of the structure, it has been shown that the simulation results are coherent with the experimental findings. This indicates that Finite Element modeling allows an accurate prediction and estimation of the weakening effect of residual stresses on the bonding interface of Alumina. The obtained results show us that the three-dimensional numerical simulation used by the Finite Element Method, allows a good prediction of the weakened zone extent of a ceramic, which is bonded with a metal.

Highly Ammonia Sensing Using Direct In Situ Electro-Deposited Polypyrrole-Dodecylbenzene Sulfonic Acid Film on ITO Coated Flexible Substrates

Fateh Merdj,Ahmed Mekki,Djamil Guettiche,Boualem Mettai,Zakaria Bekkar Djeloul Sayah,Zitouni Safidine,Abderrazak Abdi,Rachid Mahmoud,Mohamed M. Chehimi 한국고분자학회 2018 Macromolecular Research Vol.26 No.6

Air quality monitoring is of major concern as it is directly linked to public health. It requires the development of high sensitive devices with fast response towards hazardous gas and volatile compounds. Such performances depend on the nature and quality of deposition of the sensing layer. Herein, adherent polypyrroledodecylbenzene sulfonic acid (PPy–DBSA) films were deposited on a N-(3-trimethoxysilylpropyl) pyrrole modified ITO coated polyethylene teraphtalate (PET) flexible substrate by facile direct electrochemical oxidation of pyrrole in an aqueous solution of sulfonic acid. The obtained PPy-DBSA films were subjected to various characterization techniques such as, FTIR, Raman, SEM and conductivity measurements. Chemiresistive gas sensing tests have demonstrated selectivity and sensitivity of films toward ammonia vapors over the other vapors (nitrogen dioxide, carbon dioxide, hydrogen sulfide, acetone, methanol and ethanol) with higher response at 20 ppm, reasonably fast response time of 3 min and reaching detection limit of 3ppm. The response of the sensor can reasonably be related to the strong electrostatic interactions between vapor molecules and the dopant agents within PPy films. In comparison PPy- DBSA films prepared on pristine ITO/PET has exhibited lower response at 20 ppm of ammonia exposure, which highlights the role of surface modification and the contribution from the dopant agent nature for ammonia sensing. Moreover, chemiresistive response performances have been tested in the presence of humidity, under varied temperatures, and finally their behaviors were featured by an impedance spectroscopy in both presence and absence of gas. This work conclusively shows that the sensing performances are not only driven by the molecular interactions between the sensor and the analyte but also by the quality of deposition and adhesion of the former to the transducer. The latter feature can be controlled by appropriate chemical surface modification.

A new formulation of the J integral of bonded composite repair in aircraft structures

Nassim Serier,Belaïd Mechab,Rachid Mhamdia,Boualem Serier 국제구조공학회 2016 Structural Engineering and Mechanics, An Int'l Jou Vol.58 No.5

A three-dimensional finite element method is used for analysis of repairing cracks in plates with bonded composite patch in elastic and elastic plastic analysis. This study was performed in order to establish an analytical model of the J-integral for repair crack. This formulation of the J-integral to establish models of fatigue crack growth in repairing aircraft structures. The model was developed by interpolation of numerical results. The obtained results were compared with those calculated with the finite element method. It was found that our model gives a good agreement of the J-integral. The arrow shape reduces the J integral at the crack tip, which improves the repair efficiency.

Numerical analysis of crack propagation in cement PMMA: application of SED approach

Benouis Ali,Boulenouar Abdelkader,Benseddiq Noureddine,Serier Boualem 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.55 No.1

Finite element analysis (FEA) combined with the concepts of linear elastic fracture mechanics (LEFM) provides a practical and convenient means to study the fracture and crack growth of materials. In this paper, a numerical modeling of crack propagation in the cement mantle of the reconstructed acetabulum is presented. This work is based on the implementation of the displacement extrapolation method (DEM) and the strain energy density (SED) theory in a finite element code. At each crack increment length, the kinking angle is evaluated as a function of stress intensity factors (SIFs). In this paper, we analyzed the mechanical behavior of cracks initiated in the cement mantle by evaluating the SIFs. The effect of the defect on the crack propagation path was highlighted.