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Vol 2 - Issue 1

Uncertainties and Reliability of Multiphysical Systems

List of Articles

An equivalent isotropic approximation for reliability-based design of mini-plate fixation used in fractured mandibles

The objective of this work is to assess the reliability level of mini-plate fixation following surgical operation. A 3-dimensional finite element model is developed in order to study the negative effect due to the stabilization of the fracture. Since muscles can be cut or harmed during surgery and consequentially cannot operate at its maximum capacity, there is a strong need to introduce loading uncertainties in order to obtain reliable designs. Several scenarios (or modes) may lead to failure. The first important failure scenario is the von Mises stress of all components which presents the fracture indicators. The bone structure possesses anisotropic behaviors. An optimized yield stress/elasticity modulus formulation is integrated using an equivalent isotropic approximation in order to reduce the computing time. The second failure scenario is the contact pressure which should not exceed a maximum pressure pain threshold. The last failure mode is the relative displacement (gap) between two fracture surfaces which should not exceed a prescribed value in order to obtain rapid bone healing. A reliability algorithm is next developed to identify the single and multiple failure mode cases. The different results are carried out considering a clinical case of a male patient of 28 years of age.

Experimental characterization of hydroforming

The shaping by the hydroforming process involves several complex phenomena and presents several types of non-linearities (geometric, material, etc.). The development of a hydroforming operation requires a lot of tests to accurately determine the optimal production loads and to obtain a part without defects. When testing the hydroforming of the sheet is limited by the curve of the deformation in the center of the piece in view of the mounting of realization. This work consists in carrying out experimental hydroforming tests of the sheets in order to determine the load to be applied with the chosen thickness.

Modeling and numerical simulation of hydroforming

The hydroforming process is strong in its technological advantages; it is nonetheless true that a good control of this process is vital for its development. In an increasingly competitive industrial environment, automakers are reducing design time and the cost of developing new products and processes such as hydroforming. The numerical simulation has now become an essential tool to meet these needs by reducing the number of tests, tooling costs and design time. Necking, breaking and wrinkling are the main failure modes that cause the systematic rejection of parts. Therefore, improving the prediction of appearance of these defects during the simulation is in the direction of better control of the process. In this article, we present a theoretical study and a numerical simulation of the process and we compare the results.

An aerodynamic Study of wind turbine blade

Present paper aims to numerically simulate an aerodynamic flow around a wind turbine blade. So two simulations are performed using ANSYS CFX; first, a section of a wind turbine blade subjected to an air flow, using three different turbulence models under a variety of angles of attack in order to choose the appropriate model. And then, using this model in a 3-D simulation of a wind turbine blade to expose these aerodynamic performances in complex CFD domains.

Metaheuristic for the RBDO of the brasure’s joints of an electronic board

In the majority of mechatronic devices, thermal fatigue of solder joints is a mechanism causing failure of the solder joints. This type of failure is the main cause that the lifetime of embedded mechatronics systems is often related. This paper presents a finite element simulation of themechanical behavior of solder joints in an electronic board as well as the application of the CMAES optimization method to increase the reliability of joints. This method is the best evolutionary method for continuous parametric optimization. In particular, she was the winner of the stochastic methods (other ES, but also PSO, Differential Evolution, and other EDAs)[8]. A model of finite element simulation is developed, this model intends to analyze the sequence of failure events in mechatronic devices. In this article, this numerical model is used to estimate the number of fatigue life cycles by modeling the most stressed solder joints, and then the proposed CMAES optimization method is performed to overcome the disadvantage of geometric complexity (difficulty application of gradient methods) of mechatronic components. Numerical results show the increasing of the fatigue life cycle of mechatronic devices.

Mathematical error‐correction modeling of the liquidity of the stock market. Application: Impact of Market Structure and Institutional Savings on the Capital Market

A mathematical model is estimated from the significant variables (after the elimination of the low influencing variables) and from dummy variables introduced to correct some cyclical events that impact the ordinary correlations of the variables. There may be several stationary linear combinations between built-in variables of order one. In Johansen’s method, the cointegration space is determined by estimating an autoregressive model. We will use the liquidity ratio as a proxy for the liquidity of the Moroccan stock market, to estimate the indicators and the factors that determine its variability in the short and long run. The appropriate econometric method would be to estimate a vector error correction model (VECM) that has the property of determining the long and short term relationships between variables.

Mathematical optimization of time series. Cleaning financial series of calendar and seasonal effects ‐Moroccan financial market‐

The construction of the national calendar allows the optimization and the production of the seasonally adjusted series, thus significantly improving the quality of the models used to obtain reliable, legible, and interpretable indicators. Series decomposition improves the quality of regressions by isolating irregular, seasonal, and time-sensitive effects that can bias the modeled relationships. We will analyze the series of variables explored using the Demetra + software [1] to better refine our estimates. The exploratory analysis of the data used should make it possible to
summarize the distribution of each series and the relationships between variables whose characteristics might require measurement and unit transformations (or recoding). Outliers, for example, are likely to influence the results of a statistical model. This treatment will capture the influential values before modeling the correlations between the variables being estimated.

Evolution of the crystallite size of Erbium Tetrapolyphosphate with heat treatment or oxidation

Our study focuses on the influence of the oxidation temperature on the crystallite size, oxidation kinetics and mechanisms associated with the oxidation of Erbium Tetrapolyphosphate (TPE). We compared the evolution of the crystallographic morphology of the TPE powder subjected to a heat treatment at high temperature between 200 ° C and 1100 ° C. The evolution of the crystallite size of the powder was demonstrated by X-rays diffraction. The structural units of phosphate-based glass were assessed from Raman spectra as TPE; the results show the decomposition of powder in the
temperature range of 850° -1100°C. Er3+ absorption spectra were measured in the range of 400-800 nm. Optical bandgap (Eg) were determined using Tauc’s relationship for direct transitions.

High photocatalytic activity of hydroxyapatite biodegradable semiconductor for solar panels and environment protection

Incorporating metal ions into a calcium hydroxyapatite structure is a successful pathway to increase their physical, chemical and biological properties. The calcium hydroxyapatite was obtained by solid state method at high temperature, using CaCO3 and (NH4)2HPO4 as sources of calcium and phosphorus. Metal ion (M2+ = Mn2+, Co2+, Ni2+, Cu2+) incorporation was carried out by dint of grinding and high temperature effect for remove all impurity. Hydroxyapatite (HAP) powders doped with metal ions were characterized by uv-visible spectroscopy analysis to evaluate the photocatalytic activity of all samples of hydroxyapatite. The result shows the high photocatalytic activity of all HAP powders.

Methodolgy and optimization of the electrical energy in a gas turbine power station

Energy Dependence in Morocco is about 93.3%, which makes the price of kWh tightly linked to fluctuations in oil prices. This paper focuses on improving the energy efficiency of an auxiliary gas turbine 315 MW station of Kenitra city in Morocco as example. The main goal of this study is to calculate the cost of kWh and try to reduce it by developing proposals and solutions to optimize energy, operational conditions and performance of the station. In this regard, a functionally planned cutting of the station to calculate the cost per kWh based on the cost of consumption of each station. Then, we mathematically modeled the equations that result .This will allow to analyze consumption auxiliary energy of the station and consequently to identify the most energy installations consumption.

Modeling of isobaric vapor-liquid equilibrium for binary systems of methanol, ethanol and water

The present work exposes a thermodynamic framework of the modeling of the vapor liquidequilibrium for the three binary systems composed of methanol-water, methanol-ethanol and ethanol-cyclohexane at 101.3 kPa. The experimental data were correlated using the extended UNIQUAC model. The deviations between the calculated and experimental vapor-phase compositions, liquid-phase compositions and bubble point temperatures have been determined. To improve the accuracy of the proposed model we determine the deviations between the calculated and experimental values with respect to all variables (i.e.vapor-phase compositions, liquid-phase compositions and bubble point temperatures). The calculated results of methanol-water,, methanol-ethanol and ethanol-cyclohexane mixtures are compared with experimental data presented in literature showing minimum of deviations.

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