Papers by Abdelmajid Jemni
International Journal of Advanced Research, 2016
In this paper, we proposed an approach to understand the mechanism of gas adsorption in a micropo... more In this paper, we proposed an approach to understand the mechanism of gas adsorption in a microporous solid. This approach is deduced from the concept of flow; the flow of the quantity of material which crosses a closed surface is proportional to the potential adsorbate-adsorbent interaction. For this first study, we used two couples; activated carbon AC35 with ethanol and acetone at the same temperature 30 ° C, in order to over complicate the issue for this first approach. Our study of the adsorption potential as a function of the pore radius allowed us to show that there are two types of interaction forces. The first type active, as in the case of adsorption in micropores and mesopores, and the second is active, as for the macropores and side surfaces of the grains. These findings justify the existence of two models: the Dubinin-Astakov (filling volume), and the Brunauer, Emmet and Teller (adsorption layer). Adsorption follows three steps, the micropore filling will occur the first followed by the filling of mesopores and the macropores and finally the surface adsorption corresponds to the side surface of the microporous solid grains. The order in which the filling pore has allowed us to establish the link between the time parameter and the pore radius Copy Right, IJAR, 2016,. All rights reserved.
Special topics & reviews in porous media, 2012
Comfort is one of the most important attributes of textiles used in clothing. Clothing comfort is... more Comfort is one of the most important attributes of textiles used in clothing. Clothing comfort is influenced by (i) fabric factors viz. fiber conductivity, fabric parameters, air contained within the fabric etc; (ii) environment factors viz. temperature, humidity and wind speed; and (iii) human factors viz. color, fashion, psychology of the wearer, etc. Thermal properties of clothing are one of the most important aspects of clothing comfort. Many studies have been conducted to analyze the relationship between various fabric parameters and comfort properties by using statistical methods . However, the statistical methods used have some limitations. One of the most common problems faced in statistical modeling is the non-linear relationship of different fabric parameters with thermal comfort properties. Furthermore, most of the fabric parameters which directly influence the thermal properties such as thickness, fabric weight, porosity, etc. are related to each other and are derived from basic fabric specifications such as yarn linear density, thread spacing, etc and hence it is difficult to study the effect of one parameter without changing the other. Therefore a sys-tem is required which can predict the thermal parameters of the fabric by considering the collective influence of all the fabric parameters at the same time. This is where artificial neural network can be effectively put to use. Artificial neural network (ANN) has proved useful for many prediction-related problems in textiles such as the prediction of characteristics of textiles; identification, classification and analysis of defects; process optimization; and marketing and planning [5-7, 11, 15]. Researchers have already tried to use neural networks to predict various comfort-related properties such as human sensory perceptions and overall comfort index [8-10, 12, 16]. 1 In this paper artificial neural network is used to predict the steady-state thermal resistance and maximum instantaneous heat transfer Q max of a fabric when the fabric weaving and construction parameters are given as inputs. Two different network architectures were studied. In one case, the
Springer Proceedings in Materials, 2022
Fibers and Polymers, 2015
Today numerous consumers consider thermal comfort to be one of the most significant attributes wh... more Today numerous consumers consider thermal comfort to be one of the most significant attributes when purchasing textile and apparel products, so there is a need to develop a model able to simulate objectively the consumers’ perception. The global thermal comfort of stretch knitted fabrics is a multi-criteria phenomenon that requires the satisfaction of several properties at the same time. In this paper, we used the desirability functions to evaluate the satisfaction degree of global thermal comfort. Statistical method was used to investigate the interrelationship among knit thermo-physical properties, and group them into factors. Two models of artificial neural network (general and special) have been set up to predict the global thermal comfort from structural parameters (inputs) of knitted fabrics made from pure yarn cotton (cellulose) and viscose (regenerated cellulose) fibers and plated knitted with elasthane (Lycra) fibers. A virtual leave one out approach dealing with over fitting phenomenon and allowing the selection of the optimal neural network architecture was used. By combining the strengths of statistics and fuzzy logic (data reduction and information summation) also a neural network (self-learning ability), hybrid model was developed to simulate the consumer thermal comfort perception. After that, ANN model is inverted. With a required output value and some input parameters it is possible to calculate the unknown optimum input parameter. Finally, this forecasting can help industrials to anticipate the consumer’s taste. Thus, they can adjust the knitting production parameter to reach the desired global thermal comfort to satisfy this consumer.
Journal of the Textile Institute, 2013
ABSTRACT In this paper, a computer-aided system for designing knit stretch materials is presented... more ABSTRACT In this paper, a computer-aided system for designing knit stretch materials is presented. It allows designers to optimize the structure of knit stretch materials according to the functional properties. This system aims at modeling the relation between functional properties (outputs) and structural parameters (inputs) of knitted fabrics. Thirteen features characterizing knit structures and operating parameters were taken as input parameters of the artificial neural networks (ANNs). These parameters were preselected according to their possible influence on the outputs which were the elongation, growth, and elastic recovery. In order to reduce the complexity of the models, an original fuzzy logic-based method was proposed to select the most relevant parameters which were taken as input variables of the ANNs. The selection procedure of structural parameters allows designers to focus on the most relevant parameters in order to conduct production experiments related to the new product. Then, two types of model are set up by utilizing multilayer feed forward neural networks, which take into account the generality and the specificity of the product families, respectively. The presented models have been validated with the use of experimental data concerning several families of knitted fabrics.
Green energy and technology, Sep 19, 2022
Energy Sources, Part A: Recovery, Utilization, and Environmental Effects
Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2021
Medical Engineering & Physics, 2012
A numerical model was developed to predict the dynamics of a solid particle in a poststenotic blo... more A numerical model was developed to predict the dynamics of a solid particle in a poststenotic blood vessel region. The flow through a 3D axisymmetric stenosis with 75% reduction in cross-section area was considered for inlet Reynolds numbers of 500 and 1000, which corresponds to typical values for the blood flow in human large arteries. Spherical particles were injected in the flow from the stenosis and tracked using the Discrete Phase Model (DPM) based on a Lagrangian approach. Within the scope of the development of ultrasound thrombolysis methods, the hydrodynamical forces predicted were used to evaluate the residence time of the particle and the minimal ultrasonic intensity required to keep it in the treatment region. For particle sizes larger than 400 μm, the intensity required appeared to be compatible with extracorporeal therapeutic ultrasound.
International Journal of Nonlinear Sciences and Numerical Simulation, Aug 18, 2022
This study numerically investigates the two-dimensional natural convection in a square enclosure ... more This study numerically investigates the two-dimensional natural convection in a square enclosure with an isothermal diamond elliptic array at Rayleigh numbers of 104≤ Ra ≤ 107. Three cases are considered, i.e., case 1 where two pairs of circular heating bodies are used inside the cavity, one is placed on the vertical centerline (VC) of the cavity and the other on the horizontal centerline (HC), case 2 where one pair of horizontal elliptic heating bodies is placed on the VC of the cavity and the other on the HC and case 3 where the horizontal elliptic heating bodies are replaced by vertical elliptic heating bodies. Numerical simulation was carried out based on the mesoscopic approach (LBM). The effects of the horizontally and vertically heated arrays were investigated. We demonstrate that, only when the Rayleigh number increases to Ra = 107, the numerical solutions reach an unsteady state for all cases. The transition of the flow regime from the unsteady state to the steady state depends on the variation in the ratio of the elliptical cylinder.
Cement & Concrete Composites, 2020
Chemical Engineering Science, Apr 1, 2022
HAL (Le Centre pour la Communication Scientifique Directe), May 29, 2007
HAL (Le Centre pour la Communication Scientifique Directe), 2008
Over the last few years, natural fiber-based hybrid polymers have been widely used to increase th... more Over the last few years, natural fiber-based hybrid polymers have been widely used to increase the biodegradability and costeffectiveness of the products in many industrial applications, such as automobile construction industries. Adding filler materials provides enhanced wear properties and thermal behaviors of composites. Kenaf fiber has better strength and stiffness, and it has been used as reinforcement in polymer composites. Silicon carbide as filler material in composites modifies the mechanical properties and thermal behaviors. The present research analyzes the thermal characteristics of silicon carbide/kenaf fiber-reinforced epoxy composites with various weight percentages. Six different composite specimens were fabricated at varying weight percentages of silicon carbide. The specimens were subjected to various thermal tests, such as heat deflection temperature (HDT), coefficient of thermal expansion (CTE), thermal conductivity (TC), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The findings could serve to expand the range of application for SiC/kenaf fiberreinforced composite, which may have better thermal stability, better performance, and lower thermal expansion than the other regularly used natural fiber-reinforced composites.
International Journal of Hydrogen Energy, 2017
2019 Advances in Science and Engineering Technology International Conferences (ASET), Mar 1, 2019
Special thanks also to colleagues Aline Kirsten and Caroline Bedin for performing the night elect... more Special thanks also to colleagues Aline Kirsten and Caroline Bedin for performing the night electroluminescence measurements used in this work, and to Ernesto Moscardini for the cleaning of PV systems and performing of I-V curve measurements to quantify the soiling shown in this thesis. I would like to extend my sincere gratitude to colleagues Marília Braga and Trajano Viana for the many discussions on the extensive amount of results stemming from this project, co-authoring of scientific articles, and revision of this thesis. I also would like to express my gratitude to Rafael Campos for prolonged nights of data processing, interpretation of results and co-authorship of articles. To Dr. Gilberto Figueiredo for the insights of low-cost electroluminescence that were used in this study. To the members of the evaluation committee, I express my gratefulness in taking your time to read this thesis, and for your invaluable suggestions for the overall enrichment of my thesis. I would like to acknowledge Prof. Hans Helmut Zürn and Prof. Helena Flavia Naspolini, for having given me guidance and support during all these years since my early beginning at UFSC. A special thanks to my friend Juan Debali for the professional ABNT formatting, and to all my friends who helped and contributed to making this happen. To my four mothers (Maristela, Marise, Marlene and Marli*) for all the support, dedication, affection, and for teaching me the important values in life. To my friend, and beloved wife Kamila for all the partnership, understanding and joy of the past days and of many others that will still come. "O otimista é um tolo. O pessimista, um chato. Bom mesmo é ser um realista esperançoso" Ariano Suassuna. Palavras-chave: Energia solar fotovoltaica. Desempenho de sistemas fotovoltaicos. Coeficiente de desempenho. PID. Sobreirradiância.
International Journal of Hydrogen Energy, May 1, 2003
To analyse heat and mass transfer in a metal–hydrogen reactor, the hypothesis that disregards the... more To analyse heat and mass transfer in a metal–hydrogen reactor, the hypothesis that disregards the radiative heat transfer in the reactor, is typically used. In this paper, we take into account the radiative heat transfer and we test the validity of this hypothesis in the case of the LaNi5 and in the case of the magnesium. A theoretical model is
International journal of mechanical engineering and robotics research, 2017
A pseudo three dimensional numerical analysis is presented for simulation of cylindrical heat pip... more A pseudo three dimensional numerical analysis is presented for simulation of cylindrical heat pipe using the Lattice Boltzmann method. The analysis includes the heat conduction in the wall and liquid-wick regions as well as the vapor region. Comparisons between the present model and previous numerical results showed very good agreement. The estimations of the liquid and vapor velocity profiles and temperature distributions are also presented and discussed. It is shown that the vapor flow field remains nearly symmetrical about the heat pipe centerline. Numerical results under different working conditions are presented, which provide guidance for the heat pipe design.
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Papers by Abdelmajid Jemni