Intelligent maximum power tracking control of a PMSG wind energy conversion system

A comparative control study for a maximum power tracking strategy of variable speed wind turbine is provided. The system consists of a direct drive permanent magnet synchronous generator (PMSG) and an uncontrolled rectifier followed by a DC/DC switch‐mode step down converter connected to a DC load. The buck converter is used to catch the maximum power from the wind by generating an efficient duty cycle. Distinct Maximum Power Point Tracking (MPPT) algorithms are analyzed and compared: a classical Proportional‐Integral controller (PI) and two based Fuzzy Logic Controllers (FLC), including a conventional Fuzzy‐PI and an Adaptive FLC‐PI. The main aim of the presented study is to develop an advanced control scheme for wind generators to ensure a high level operating of the system and a maximum power extraction from the wind. This is achieved by analyzing the behavior of the system under fluctuating wind conditions employing Matlab Simpower Systems tool. Simulation results confirm that the Adaptive FLC‐PI controller algorithm has better performances in terms of dynamic response and efficiency especially in comparison with the ones of a PI controller under variable wind speed.     

Towards the Development of Small‐Molecule MO25 Binders as Potential Indirect SPAK/OSR1 Kinase Inhibitors

The binding of the scaffolding protein MO25 to SPAK and OSR1 protein kinases, which regulate ion homeostasis, causes increases of up to 100‐fold in their catalytic activity. Various animal models have shown that the inhibition of SPAK and OSR1 lowers blood pressure, and so here we present a new indirect approach to inhibiting SPAK and OSR1 kinases by targeting their protein partner MO25. To explore this approach, we developed a fluorescent polarisation assay and used it in screening of a small in‐house library of ≈4000 compounds. This led to the identification of one compound—HK01—as the first small‐molecule inhibitor of the MO25‐dependent activation of SPAK and OSR1 in vitro. Our data confirm the feasibility of targeting this protein–protein interaction by small‐molecule compounds and highlights their potential to modulate ion co‐transporters and thus cellular electrolyte balance.     

Numerical and experimental study of dryer in forced convection

A numerical simulation model is developed to predict the forced convection performance of a dryer. This model takes into account the shrinkage phenomenon of the products during the drying process. The experimental results of the potato drying are obtained in climatic conditions similar to conditions found in natural open‐air drying when the dryer is fed by air heated by a solar air flat plate collector. After a study of the influence of parameters of the drying air on the product during the drying process, we expose the experimental results and compare them with those calculated by the theoretical model. Copyright © 2001 John Wiley & Sons, Ltd.     

Bond-slip law and short tie behavior without main cracks

The aim of this paper is to study the reinforced concrete short tie-rods behavior using the adhesion-slip curve shape between steel and concrete adopted by the European Concrete Committee. We are interested here in short tie-rods without main cracks for which we calculate and measure the maximum mobilization state of steel-concrete adhesion, and beyond the decrease mode of this bond. For this, tests of short tie-rods, with different high adhesion rebar diameters have been carried out. To characterize the first phase of the adhesion-slip behavior law (τ?g), pull out tests have been carried out with the same concrete, the same reinforcement and the same cross-section such as the tie-rod tests, with a proposed method to estimate the adhesion peak and the corresponding slip. For this adhesion peak value, slightly underestimated by the conventional curve of the European Concrete Committee, a new expression is suggested. A numerical model with theoretical relations of the behavior of such tie-rods is proposed. The comparison of this model with the obtained test curves of the short tie-rods shows a suitable approach. Also, we deduce that the steel (coated with concrete) fictitious module slope is even higher than the percentage of reinforcement is low. These results may help to understand the tie-rods behavior generally, in the phase of cracks stabilization, during which the tie-rod is composed of short tie-rods without main cracks.     

Simulation of a new concept of an indirect solar dryer equipped with offset rectangular plate fin absorber‐plate

A simulation code was developed to predict the indirect solar dryer performance of the thin beds of discs of potato, subjected to time‐varying air conditions. Two mathematical models are developed separately; the first allows the determination of the thermal performances of the solar collector with offset rectangular plate fin absorber‐plate and the second, allows to determine the kinetics of drying for the data input of the air at the exit of the collector. The latter takes into account calorific losses through the walls of the dryer and shrinkage of discs. Experimental results of the solar dryer thermal performances, using sunlight in Valenciennes (in the North of France), will be compared with the results obtained by the theoretical model suggested. Copyright © 2005 John Wiley & Sons, Ltd.     

Epoxidation of Ethylene by Silver Oxide (Ag<Subscript>2</Subscript>O) Cluster: A Density Functional Theory Study

Abstract  

Density functional theory (DFT) calculations were employed to study epoxidation of ethylene on a [Ag₁₄O₉] cluster model representing silver oxide (001) surface. Theoretical results obtained in this study showed that formation paths of acetaldehyde and vinyl alcohol have higher activation barriers than that of ethylene oxide formation path on silver oxide (35 and 35 vs. 20 kcal/mol). Formation of the ethylene oxometallocycle intermediate is found to have a low probability on Ag₂O(001) surface. The essential reason for this may be lower basicity of surface oxygen atom on silver oxide surface and the absence of a surface vacancy position to activate ethylene. Adsorbed EO is formed on Ag₂O surface cluster without an activation barrier. The activation barriers of the rate-limiting steps for the production of EO mechanisms (via ethyleneoxy and non-activated paths, 20 vs. 14 kcal/mol) are in relatively good agreement with the experimental activation energy values (14, 17 and 22 kcal/mol) reported for EO formation on silver catalyst.