Local Search Methods for the Optimal Winner Determination Problem in Combinatorial Auctions

In this paper, both stochastic local search (SLS) and tabu search (TS) are studied for the optimal winner determination problem (WDP) in combinatorial auctions. The proposed methods are evaluated on various benchmark problems, and compared with the hybrid simulated annealing (SAGII), the memetic algorithms (MA) and Casanova. The computational experiments show that the SLS provides competitive results and finds solutions of a higher quality than TS and Casanova methods.     

Angular dependence of the critical current density and the temperature scaling of the flux pinning force in YBCO thin film

In this paper, the critical current J_c(Θ) have been investigated as a function of magnetic-field angle Θ. Θ is the angle between the c-axis and the applied magnetic field direction. This investigation concerned three temperature values (60?K, 78?K and 81?K). The normalized pinning force f_p versus the normalized magnetic field h was also studied (f_p?=?F_p / F_pmax and h?=?H / H_max). The F_p expression was determined based on the Kramer model.The studied sample was a single crystal of YBaCuO thin film deposited by the ablation laser method on the surface (100) of a SrTiO₃ substrate.The results of this work show the existence of point core pinning of the normal centers in the low field regime and the occurrence of the flux creep in high field regime.     

Kinetics and mechanism of the oxidation of iodide by diaquote- trakis(2,2′-bipyridine)-μ-oxodiruthenium(III) ion in acid medium

Transition Metal Chemistry - The kinetics of the oxidation of iodide by diaquotetrakis-(2,2-bipyridine)-μ-oxodiruthenium(III), [Ru2O]4+, were studied in aqueous perchloric acid at...     

Synthesis and characterization of new heptacyclic helicenes

New helically chiral substituted heptacyclic systems have been prepared from a simple phenanthrene building block in good yields and purity, via a four-step sequence involving palladium-catalysed Heck coupling and oxidative photocyclization. X-ray crystal structure analysis indicated that the conformation resembled that of the unsubstituted heptahelicene. The optical properties of these heptacyclic helicenes were investigated and show interesting behaviour.     

Facile synthesis of TMS-protected trifluoromethylated alcohols using trifluoromethyltrimethylsilane (TMSCF3) and various nucleophilic catalysts in DMF

Organofluorine compounds are becoming increasingly important in different fields, such as material science, agro chemistry, and the pharmaceutical industry. Nucleophilic trifluoromethylation is one of the widely used methods to incorporate a trifluoromethyl moiety into organic molecules. We have carried out extensive studies to develop varieties of easily accessible nucleophilic catalysts to promote such reactions. TMS-protected trifluoromethylated alcohols were prepared from both aldehydes and ketones in excellent yields using catalytic amount of amine N-oxide. Carbonate and phosphate salts also showed efficient catalytic activity toward this reaction. These reactions were highly solvent dependent, and DMF was found to be the most suitable one among the various solvents studied. All these reactions proceeded under very mild conditions, giving clean products and avoiding the use of any fluoride initiators or expensive catalysts, and extremely water-free conditions. The mechanism for the reaction is discussed in detail. DFT calculations were performed on the possible reaction intermediates using the Gaussian 03 program at B3LYP/6-311+G* level to support the proposed mechanism.