Manufacturing of Aluminum Matrix Composites Reinforced with Iron Oxide (Fe3O4) Nanoparticles: Microstructural and Mechanical Properties

The purpose of this paper is to demonstrate the low-cost manufacturing of aluminum matrix composites reinforced with nano iron oxide as light and efficient materials for engineering applications. It is very desirable to use reinforced aluminum matrix composites in structural applications (automotive, aeronautical, etc.) because of their outstanding stiffness-to-weight and strength-to-weight ratios. In modern industry, it is increasingly important to develop new composites as alternative materials to fabricate multifunctional pieces. Detailed information is presented on the manufacturing process of this composite, and a preliminary study was performed on the cryogenic-cycling behavior to evaluate the interface between the matrix and the reinforcement. Microindentation tests were carried out to evaluate the micromechanical properties of these materials; a simple and practical finite element model is proposed to predict certain parameters related to the composition of the composite.     

Fault tolerance for highly available internet services: concepts, approaches, and issues

Fault-tolerant frameworks provide highly available services by means of fault detection and fault recovery mechanisms. These frameworks need to meet different constraints related to the fault model strength, performance, and resource consumption. One of the factors that led to this work is the observation that current fault-tolerant frameworks are not always adapted to existing Internet services. In fact, most of the proposed frameworks are not transport-level- or session-level-aware, although the concerned services range from regular services like HTTP and FTP to more recent Internet services such as multimodal conferencing and voice over IP. In this work we give a comprehensive overview of fault tolerance concepts, approaches, and issues. We show how the redundancy of application servers can be invested to ensure efficient failover of Internet services when the legitimate processing server goes down.     

Computer-aided diagnosis systems: a comparative study of classical machine learning versus deep learning-based approaches

Knowledge and Information Systems - The diagnostic phase of the treatment process is essential for patient guidance and follow-up. The accuracy and effectiveness of this phase can determine the...     

Low-cost adsorbents for a dye uptake from contaminated water modeling of adsorption isotherms: The Langmuir,Freundlich and Elovich models

The adsorption of organic molecule to clay minerals has been reported by several investigators. Bentonite, which is made homoionics by mono-, di- and trivalent cations was used to remove the dye, an organic molecule (Quinalizarin) used to dye cotton. Equilibrium data were obtained by the batch technique. The results show the largest adsorption capacity of the homoionic bentonite; the saturation level was reached, the high adsorption capacity (79 meq/100 g), close to the cation exchange capacity of the synthesized bentonite (89 meq/100 g), indicates a strong interaction between the dye molecule and the adsorbent. Adsorption onto the clay was essentially immediate and correlated with the cation exchange-capacity (CEC). The type of exchangeable cations indicate that adsorption was primarily to the negatively charged sites on the clay. The amount of the adsorbed color was found to be a function of the type of exchangeable cations; it drops off in the following order: Bent-Al³⁺ > bent-NH⁴⁺ > bent-Na⁺ > bent-Fe³⁺ > bent-Li⁺ > bent-Ca²⁺ > bent-Mg²⁺ > bent-K⁺. The Langmuir, Freundlich and Elovitch models were employed to examine the equilibrium adsorption data. In all cases, the results show that all adsorption systems could be adequately fitted by these three models. It is seen that the linear fit is fairly good for these three models, the correlation coefficients R ² was found to be equal to 0.9 in approximately all cases. The article is published in the original.     

Integrated production,statistical process control,and maintenance policy for unreliable manufacturing systems

The objective of this paper is to develop an integrated approach for the joint control of production, maintenance and quality for batch manufacturing systems. We consider such systems that are subject to degradation which is at the origin of the production of defective units. The quality control of lots produced is performed using an ‘x-bar’ control chart. This graphical tool will allow estimating the quality of the batch being produced and possibly undertake perfect preventive or corrective maintenance actions on the production system. A buffer stock is built to maintain continuity of supply during maintenance actions. The incurred total cost includes setup cost, inventory costs, the cost of unused products, maintenance costs and quality costs. Decision variables include the buffer stock size, the sample size, the sampling interval, the surveillance and the control limits of the control chart. Numerical experiments and sensitivity analyses are provided to evaluate the effectiveness of the proposed control policy and the robustness of the solving approach.     

Production of butyl acetate ester by lipase from novel strain of Rhizopus oryzae

A new lipase preparation from Rhizopus oryzae was used to catalyze the esterification reaction between acetic acid and butanol to produce butyl acetate ester (pineapple flavor). This flavor compound can be used in food, cosmetic and pharmaceutical industries. Only 3% of butyl acetate was obtained when free lipase was used in the synthesis containing only the substrates. In contrast, the conversion yield reached 25% when immobilized lipase was used under the same conditions. The synthesis of butyl acetate catalyzed by immobilized lipase in nonconventional media was optimized. A maximum conversion yield of 60% in a solvent-free system was obtained under the following conditions: amount of immobilized lipase, 500 IU; amount of initially added water, 45%; acetic acid/butanol molar ratio, 1:1; and in incubation temperature, 37 degrees C. Immobilized lipase could be repeatedly used for three cycles without a decrease in synthesis activity. The production of butyl acetate esters by immobilized R. oryzae lipase was also studied in the presence of organic solvents. Compared with a solvent-free system, the synthesis activity was improved in the presence of heptane and hexane with conversion yields of 80% and 76%, respectively. However, solvent-free systems tend to purify more easily the products without any toxicity and inflammability problems.     

The equivalence of two classical list scheduling algorithms for dependent typed tasks with release dates,due dates and precedence delays

We consider a finite set of unit time execution tasks with release dates, due dates and precedence delays. The machines are partitioned into k classes. Each task requires one machine from a fixed class to be executed. The problem is the existence of a feasible schedule. This general problem is known to be \(\mathcal {NP}\)-complete; many studies were devoted to the determination of polynomial time algorithms for some special subcases, most of them based on a particular list schedule. The Garey–Johnson and Leung–Palem–Pnueli algorithms (respectively GJ and LPP in short) are both improving the due dates to build a priority list. They are modifying them using necessary conditions until a fixed point is reached. The present paper shows that these two algorithms are different implementations of the same generic one. The main consequence is that all the results valid for GJ algorithm are also for LPP and vice versa.     

Critical factors affecting the photovoltaic characteristic and comparative study between two maximum power point tracking algorithms

This paper presents the characterization and the modeling of the electric characteristics of currentvoltage and power–voltage of the photovoltaic (PV) panels. The philosophy behind digital simulation of solar energy systems is that experiments which normally should be done on real systems under high assembling costs can be done numerically in a short time on a computer, thus saving time and investments. The electric parameters of PV cells and the optimal electric quantities of PV panels have been analyzed (voltage and power) according to the meteorological variations (Temperature, solar irradiation …). The obtained results show that the diode parameters of the PV cells depend on solar irradiation: the current saturation increases with solar irradiation. This induces a decrease of the optimal voltage with solar irradiation; when the solar irradiation varies from 600 W/m² to 1000 W/m². By taking into consideration all the modeling results, the electric behavior of the cells association in parallels or in series, as well as the aging of a PV panel have been analyzed. Moreover, a comparative study between two types of MPPT techniques that are used in photovoltaic systems to extract the maximum power have been introduced which are Perturb and Observe (P &O) and Incremental Conductance (INC).     

Self-oscillations in field emission nanowire mechanical resonators: a nanometric dc-ac conversion

We report the observation of self-oscillations in a bottom-up nanoelectromechanical system (NEMS) during field emission driven by a constant applied voltage. An electromechanical model is explored that explains the phenomenon and that can be directly used to develop integrated devices. In this first study, we have already achieved approximately 50% dc/ac (direct to alternating current) conversion. Electrical self-oscillations in NEMS open up a new path for the development of high-speed, autonomous nanoresonators and signal generators and show that field emission (FE) is a powerful tool for building new nanocomponents.