Development of a virtual Couette rheometer for aerated granular material

A novel rheometer to study the behavior of granular materials in an aerated bed of particles has been developed. The device, called the aerated bed virtual Couette rheometer, is shown to be able to measure the shear stresses in the quasi-static and in the intermediate flow regimes. To validate the instrument, a Newtonian fluid of known viscosity was first sheared. The device was then used for measuring the shear stress of nonaerated glass beads with three -3D printed cells of different sizes to validate the optimal radial position, r*, where both shear rate and shear stress are independent of the cell radius. The results for the nonaerated glass beads displayed Coulomb behavior. The same behavior was observed when the bed was aerated. These experiments also showed that for a fixed shear rate the shear stress decreases as the aeration velocity, U. increases.     

Electrooxidation of Diacetone -L-Sorbose (DAS) into Diacetone-2-Keto-L-Gulonic acid (DAG) at nickel electrodes

The oxidation of diacetone-L-sorbose (DAS) into diacetone-2-keto-L-gulonic acid (DAG) is a step in the synthesis of vitamin C. This oxidation was carried out electrochemically in a stirred cell with the redox couple Ni (OH)₂/β-NiOOH as an electrochemical mediator. The anode was made of a current collector (nickel foam or platinized-titanium) and of a suspension of Ni(OH)₂ in KOH aqueous media. The mediated electrooxidation of DAS was achieved by the Ni(OH)₂β-NiOOH couple in solution which was regenerated at the current collector. This process required a two-compartment reactor but afforded high yields of chemical conversion: we obtained 96% with a 48% faradaic yield. Previous works dealing with DAS electrooxidation to DAG on nickel anode are reviewed hereafter.     

The Influence of Heat Treatment on Structural and Mechanical Properties of the Tool Steel

Metallurgist - The present research work aims to study the heat treatment effect on the structural and mechanical properties of the tool steel AISI D2. The steel has undergone a double treatment....     

Mathematical programming models for scheduling in a CPU/FPGA architecture with heterogeneous communication delays

This paper deals with the mathematical modelling of a scheduling problem in a heterogeneous CPU/FPGA architecture with heterogeneous communication delays in order to minimize the makespan, \(C_{max}\). This study was motivated by the quality of the available solvers for Mixed Integer Program. The proposed model includes the communication delay constraints in a heterogeneous case, depending on both tasks and computing units. These constraints are linearized without adding any extra variables and the obtained linear model is reduced to speed-up the solving with CPLEX up to 60 times. Computational results show that the proposed model is promising. For an average sized problem of up to 50 tasks and five computing units the solving time under CPLEX is a few seconds.     

An efficient artificial bee colony algorithm with application to nonlinear predictive control

In this paper a constrained nonlinear predictive control algorithm, that uses the artificial bee colony (ABC) algorithm to solve the optimization problem, is proposed. The main objective is to derive a simple and efficient control algorithm that can solve the nonlinear constrained optimization problem with minimal computational time. Indeed, a modified version, enhancing the exploring and the exploitation capabilities, of the ABC algorithm is proposed and used to design a nonlinear constrained predictive controller. This version allows addressing the premature and the slow convergence drawbacks of the standard ABC algorithm, using a modified search equation, a well-known organized distribution mechanism for the initial population and a new equation for the limit parameter. A convergence statistical analysis of the proposed algorithm, using some well-known benchmark functions is presented and compared with several other variants of the ABC algorithm. To demonstrate the efficiency of the proposed algorithm in solving engineering problems, the constrained nonlinear predictive control of the model of a Multi-Input Multi-Output industrial boiler is considered. The control performances of the proposed ABC algorithm-based controller are also compared to those obtained using some variants of the ABC algorithms.     

Formal Methods Based Synthesis of Single Event Transient Tolerant Combinational Circuits

Recent radiation ground testing campaigns of digital designs have demonstrated that the probability for Single Event Transient (SET) propagation is increasing in advanced technologies. This paper presents a hierarchical reliability-aware synthesis framework to design combinational circuits at gate level with minimal area overhead. This framework starts by estimating the vulnerability of the circuit to SETs. This is done by modeling the SET propagation as a Satisfiability problem by utilizing Satisfiability Modulo Theories (SMTs). An all-solution SMT solver is adapted to estimate the soft error rate due to SETs. Different strategies to mitigate SETs are integrated in the proposed framework to selectively harden vulnerable nodes in the design. Both logical and temporal masking factors of the target circuit are improved to harden sensitive paths or sub-circuits, whose SET propagation probability is relatively high. This process is repeated until the desired soft error rate is achieved or a given area overhead constraint is met. The proposed framework was implemented on different combinational designs. The reliability of a circuit can be improved by 64% with less than 20% area overhead.     

Adsorption and surface properties of silica with transformer insulating oils

The presence of polar species in transformer insulating oil may cause degradation and electric discharges in the power transformer. Such oil polar fraction can originate either from the neat oil and/or from its oxidative degradation in the power transformer. The aim of this study is to examine the relation between the insulating oil and the electrical properties of its polar fraction in order to predict eventual failure in the power transformer.We investigate at ambient temperature the adsorption of the polar fractions of various transformers insulating oils (a new and two used oils) from the neat oils onto silica particles. The adsorbed amount was higher for the used oils as compared to the new one. Infrared spectra of the polar fraction indicate the presence of hydroxyl, aromatic and carboxyl functional groups that are found in the asphaltenes compounds. Microelectrophoresis study of the oil polar fraction covered silica particles gives negatively charged oil polar fraction. Such oil surface charge depends on the pH and results from the ionisation of the oil acidic surface groups. Finally, we obtain a good correlation between the amount of the oil polar fraction and the magnitude of the zeta potential at the water/oil-silica interface.     

Smartphone-based colorimetric determination of sulfadiazine and sulfasalazine in pharmaceutical and veterinary formulations

A novel, simple, accurate, and low-cost colorimetric device based on an Android smartphone was developed for sulfonamide determination. A software program was developed to be used for analyzing the samples. Various parameters for digital colorimetric detection were investigated and optimized, such as the volume of the sample drop, the type of sample holder, the distance from the mobile phone camera to the sample holder, and the effect of ambient light. From the optimized conditions, a calibration curve was created by the intensity of blue channel for sulfonamides for the concentration range of 0.5–2.5?µg?mL^?1 with good linearity and a regression coefficient (R²) of 0.996. The results obtained by the smartphone method were compared with a spectrophotometric procedure at the 95% confidence level (n?=?3). Both methods correlated well with a regression coefficient (R²) of 0.997. The limit of detection of both methods was equal to 0.11?µg?mL^?1. The developed smartphone system was successfully used for the determination of sulfonamides in pharmaceutical and veterinary formulations with recoveries of 102 and 98.7%, respectively. The developed method provides good accuracy (relative error <5%) and precision (relative standard deviation <7%) and offers simple, convenient, rapid, and inexpensive determination of sulfonamides.     

Modelling end of life phase of the complex products: the case of end of life aircraft

There are different approaches to modelling the products at the End of Life (EOL), including closed loop approach, the ladder of lansink and material flow. The sustainability principles and the complexity of the products may affect the choice of modelling type. The life cycle costs, several subsystems and the interaction between design features, construction, technology, suppliers and legislation affect the degree of complexity of the products. Hence, developing appropriate strategies are required for modelling EOL phase of the complex products. This article presents strategies for modelling EOL phase of complex products considering sustainability tools, EOL phase models and the characteristics of these products. An ingenerated approach is proposed to address the four essential aspects of the complex product at the EOL: operational, tactical, strategic and sustainability. The case of aircraft at the EOL is presented to highlight the application of the proposed approach.     

Bi-objective optimization of maintenance scheduling for power systems

Enhance the quality of energy production in power generating stations and reducing its cost have become of paramount importance. One of the methods to reach that goal is by minimizing the maintenance scheduling time. For this purpose, a new competitive mechanism, based on a modified genetic algorithm (MGA), has been proposed to perform the preventive maintenance (PM) scheduling. Firstly, a mono-objective optimization (makespan) has implemented, and the results were quite good. Secondly, and in order to benefit from the waste time, a bi-objective optimization was developed to find a trade-off between makespan and training time of operators. Finally, the MGA-based maintenance scheduling was tested on a hybrid renewable power system (HRPS), that uses photovoltaic modules and a fuel cell (PV/FC) as sources and the telecommunication platform as load, the obtained results have proved the high efficiency of the proposed MGA-based maintenance scheduling.