Hassen Trabelsi

Titanium dioxide mediated photo-degradation of methyl orange by ultraviolet light

The photo-degradation of an aqueous solution containing the azo dye methyl orange (MO) is reported. Disappearance of color and substrate together with decreases in chemical oxygen demand (COD) and total organic carbon (TOC) content were observed. The effects of some auxiliary dyeing additives were also evaluated. The photo-decomposition followed pseudo-first-order kinetics. Some by-products and their photo-degradation pathways were identified. In addition, the toxicity and phytotoxicity of some by-products were tested using the earthworm (Eisenia andrei) avoidance test and the Bromus ramosus seed germination test. High sensitivity of E. andrei towards soil wetted with MO solution was observed, and germination of B. ramosus seeds was inhibited by MO solution, while no effects were seen for the same solution after photocatalytic oxidation.

Solar Photocatalytic Decolorization and Degradation of Methyl Orange Using Supported TiO2

Abstract The photocatalytic degradation of Methyl orange has been investigated on dynamic solar pilot plant using nonwoven fibers coated with TiO2 as photocatalyst. The operational parameters, such as initial dye concentration and pH, were studied. Disappearance of color and substrate together with decreases in chemical oxygen demand (COD) and total organic carbon (TOC) content were observed. The photo-decomposition followed pseudo-firstorder kinetics. In addition, the toxicity of some by-products was tested using the earthworm (Eisenia andrei) avoidance test. High sensitivity of E. andrei towards soil wetted with MO solution was observed, while no effects were seen for the same solution after photocatalytic oxidation.

CSP approach and interval computation for the coupling between static and dynamic requirements in the preliminary design of a compression spring

In this study, a new design approach based on an interval computation method and the constraint satisfaction problem technique (CSP approach) was discussed. It has been applied in the design of a compression spring, implemented in the vehicle suspension system. A design process is proposed and compared with what is done in conventional design. IT allows making static and dynamic sizing in one step. In fact, with the CSP, static and dynamic requirements can be coupled in the same step of sizing. In the CSP all requirements imposed can be integrated from the beginning. So it avoids falling on the loop “design-simulate-back to the initial step in case of failure”. In this study, the design parameters values of the compression spring generated by the CSP verify all requirements and the resulting simulation of the system behaviour respects all constraints required. The results obtained in this study affirmed that the suggested method is valid and potentially useful to the size dynamic system and can be applied easily and effectively.

Effectiveness of an interval computation approach to the dynamic simulation of a MacPherson Suspension system

In this paper, a new design approach based on methods by intervals adapted to the integration of a simulation step at the earliest stage of preliminary design for dynamic systems is proposed. The general idea consists in using the interval computation method to make a simulation by intervals in order to minimize the number of simulations. These intervals represent the domains of possible values for the design parameters of the system. So the parameterized model of system is solved by interval. This avoids launching n simulations with n values for each design parameter. The proposed method is evaluated by several tests on a scalable numerical example. It has been applied to solve parameterized differential equations of a Macpherson suspension system and study its dynamic behavior. The dynamic model of the MacPherson suspension is nonlinear but linearisable. It was transformed into a parameterized state equation by intervals. The solution to this state equation is given in the form of a matrix exponential. Three digital implementations of exponential have been tested to obtain convergent results. Simulations results are presented and discussed.

Passive and active acoustic properties of a diaphragm at low Mach number: Experimental procedure and numerical simulation

In this paper a low noise flow duct facility that performs a multimodal characterization of the passive and active acoustic properties of obstacles in the aero-acoustic conditions of an automotive air conditioning system is presented. The experimental procedure is made of two steps. In the first one the passive data, i.e. the multimodal scattering matrix, is measured with a multi-sources method. In the second step the outgoing modal pressure spectra radiated upstream and downstream by the flow obstacle interaction source is achieved. A numerical simulation of the experiment based on a 3D-Finite Element Method is developed. A very good agreement between the theoretical and experimental results of the no flow scattering matrix of a diaphragm is found. The effect of the flow on the scattering matrix is shown before performing the measurement of the aero-acoustic source characteristics of the diaphragm.

Application of the CSP Approach and the Interval Computation for the Optimal Sizing of a Compression Spring

In this present study a new design approach based on intervals calculation method and Constraint Satisfaction Problem technique «CSP approach» was discussed. It has been applied in the design of a compression spring implemented in vehicle suspension system. Compared to what is done in conventionally design, the design process proposed avoid to go through two stages of sizing (static and dynamic of design steps), since with the CSP, static and dynamic requirements can beings coupled in the same step of sizing. Also it avoids falling on the loop design-simulate-back to the initial step in case of failure, as in the CSP all requirements imposed can be integrated from the beginning. Therefore the design parameters values of the compression spring generated by CSP verify all requirements imposed and the results simulation of the system behavior are always success and respect all constraints required. The general idea of the design process proposed consists to express the design variables by interval, integrate all different types of constraints imposed before simulation step and finally to solve the problem by CSP approach. The intervals generated by CSP represent the domains of possible values u200bu200bfor the design variables of the system which satisfy the requirements imposed. The results obtained in this work affirmed that the suggested method is valid.

Reliability Based Design Optimization of Shape Memory Alloy

“Smart Materials” become more and more used due to their physical properties compared to other materials. Shape memory alloys (SMA) could be classified as one of them. Such material is characterized by the ability to remember its original shape after deformation. SMA provides high structural performance. However, this kind of material increases the cost of structures. Thus, optimization techniques have been applied in order to obtain minimum the volume structure. As SMA requires a global optimization tool, the evolutionary algorithms such as particle swarm optimization (PSO) is well suited. In deterministic optimization, the uncertainties of the system parameters are not taken into consideration. As a result, the optimal design obtained does not ensure the target reliability level. Thus, reliability based design optimization (RBDO) method was applied to provide an enhanced design. However, classical RBDO leads to high computational time. So, the purpose of this paper is to optimize SMA structure taking into consideration uncertainties in the structural dimensions. Therefore, a proposed RBDO methodology based on safety factors derived from Karush Kuhn Tucker (KKT) methodology coupled with PSO is developed. Compared to deterministic optimization, the proposed method guarantees the target reliability level of the structure but requires little extra computational effort.