Combining finite learning automata with GSAT for the satisfiability problem

A large number of problems that occur in knowledge-representation, learning, very large scale integration technology (VLSI-design), and other areas of artificial intelligence, are essentially satisfiability problems. The satisfiability problem refers to the task of finding a satisfying assignment that makes a Boolean expression evaluate to True. The growing need for more efficient and scalable algorithms has led to the development of a large number of SAT solvers. This paper reports the first approach that combines finite learning automata with the greedy satisfiability algorithm (GSAT). In brief, we introduce a new algorithm that integrates finite learning automata and traditional GSAT used with random walk. Furthermore, we present a detailed comparative analysis of the new algorithm's performance, using a benchmark set containing randomized and structured problems from various domains.     

Computer and network security risk management: theory,challenges, and countermeasures

The need to secure information systems and networked infrastructures is now commonplace in most enterprises. The use of novel communication technologies has became a crucial factor that can considerably improve or affect productivity. This is essentially due to the importance of the information transmitted across communication networks and stored in servers. As a consequence, strong ties are being built between security and the enterprise business activity. Risk management, which is the discipline that deals with this aspect, integrates a litany of architectures, techniques, and models that are described in this paper. A global view is proposed to the reader through a presentation of the research activity that has been directed towards this field. Copyright © 2005 John Wiley & Sons, Ltd.     

Etude de l'influence du mode d'anodisation sur la cinétique de croissance des films d'alumine en milieu acide sulfurique

The kinetics of growth of Al₂O₃ oxide films made by anode oxidation of ALuminium 1050A with two anodization techniques has been investigatedan compared. The first technique is the classical method based on continuous tension during the complete electrlysis duration, and the second one is the modern method ofpulsed tensions, whcih consists of periodically imposing to the material two anodc tensions E₁ and E₂ (E₁ > E₂) during time T₁ and T₂ until the end on anodization. We have shown that the second technique allows the fabrication of films more rapidly for the same electrolysis duraton. Energy and electrolysis time are saved, making it attractive from an economical viewpoint. This advantage arises from the positive effect of excess heat disiption gathered during the imposition of tension, E₁, when E₂ is imposed thereafter (recovery effect). The logging of in situ transient responses in the case of pulsed anodization is a significant asset to explain the growth film kinetics obtained with this method.     

Heat capacities of both PMMA stereomers: Comparison between atomistic simulation and experimental data

The domains of time and space generally covered by full atomistic simulation (AS) to represent the glass transition temperature, T_g, are very small. Physical interpretations of the phenomena occurring at this transition are inevitably limited. To specifically address such limitation, behavior of the heat capacity that accounts for the freezing of the degrees of freedom as temperature is decreased, is investigated. The selected polymer is poly(methyl methacrylate) since it offers the opportunity to exhibit a different T_g according to the tacticity of its chain. AS and experimental data are thus compared to a theoretical model that takes into account three contributions to the leap in the heat capacity occurring at T_g. The comparison discloses that an excellent agreement is obtained between simulated and experimental contributions from vibrations and free volume. However, from an AS viewpoint changes in the conformation weakly contribute to this leap. Despite this discrepancy local contributions to the glass transition as predicted by atomistic simulation, are sufficient to determine T_g.     

Factorial design of experiment (DOE) for parametric exergetic investigation of a steam methane reforming process for hydrogen production

Hydrogen is expected to play a significant role in future energy systems. The efficient production of hydrogen at a minimum cost and in an environmentally acceptable manner is crucial for the development of a hydrogen-including economy. The exergy analysis is a powerful tool to quantify sustainable development potential. An important aspect of sustainable development is minimizing irreversibility. The purpose of this study is to perform the exergy analysis of a steam methane reforming (SMR) process for hydrogen production. As a first step, an exergy analysis of an existing process is shown to be an efficient tool to critically examine the process energy use and to test for possible savings in primary energy consumption. The results of this investigation prove that the exergetic efficiency of the SMR process is 65.47%, and the majority of destroyed exergy is localized in the reformer with a 65.81% contribution to the whole process destroyed exergy. Next, an exergetic parametric study of the SMR has been carried out with a factorial design of experiment (DOE) method. The influence of the reformer operating temperature and pressure and of the steam to carbon ratio (S/C) on the process exergetic efficiency has been studied. A second-order polynomial mathematical model has been obtained through correlating the exergetic efficiencies with the reformer operating parameters. The results of this study show that the rational choice of these parameters can improve the process exergetic performance.     

Adaptation of machining toolpath to distorted geometries: application to remove a constant thickness on rough casting prosthesis

This study proposes a method to adapt the geometry of the toolpath to a specified target. In the case study presented, the geometrical target is to remove a constant thickness on the rough workpiece. This case is normally present in the polishing of the femoral component of knee prostheses. In fact, an operator carries out these operations manually. The aim of this study is to contribute to the automation of prosthesis production, notably, in the preparation of surface polishing. The proposed method can deform and adapt a toolpath to ensure the required geometry of the machined surface. The proposed toolpath deformation method is composed of three steps: alignment, toolpath deformation, and toolpath smoothing. Alignment between the measured surface of the roughcast prostheses and the nominal toolpath is carried out by an Iterative Closest Point (ICP) algorithm. The principle of this algorithm is to find the optimal rigid transformation to readjust the toolpath on the measured surface. Subsequently, the toolpath is deformed to remove the constant thickness of the roughcast prostheses. Next, to increase the machined quality, a smoothing stage is carried out on the obtained toolpath. Experimental tests on industrial prostheses geometry are conducted to validate the effectiveness of this method.     

Physical and chemical characterization of adsorbed protein onto gold electrode functionalized with Tunisian coral and nacre

Bone substitutes are more and more used in bone surgery because of their biologic safety, clinic efficiency and facility to synthesize. Bone substitutes with active osteogenic properties, associating biomaterials with organic macromolecule components of the extracellular matrix (protein, GAG) are recommended. Nevertheless, we should have a simple technique to control interactions between proteins and the material. Natural coral and nacre have been found to be impressive bone graft substitutes. In this work, we characterize nacre and coral powder using energy dispersive X-ray analysis (EDX). We used electrochemical impedance spectroscopy (EIS) and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy to evaluate bovine serum albumin (BSA) as model protein, adsorbed to these biomaterial surfaces. In order to understand the nacre/coral-protein interfacial compatibility, it is necessary to investigate the wettability.     

Antioxidative activities of some peptides isolated from hydrolyzed potato protein extract

Three peptides (5A, 5C and 6C), purified from potato protein hydrolysate fractions, possessed antioxidative activities. Isolation and purification were carried out using gel permeation chromatography and successive reverse-phase HPLC. These three peptide fractions were sequenced and identified as Phe-Gly-Glu-Arg, Phe-Asp-Arg-Arg and Phe-Gly-Glu-Arg-Arg, respectively. The fractions 5A, 5C and 6C inhibited linoleic acid oxidation by 55.3%, 58.5% and 61.7% using β-carotene decolorization assay system, while the inhibition ratio was 32.1%, 93.0% and 93.4% in the ferric thiocyanate assay system, respectively. The peptide fractions 5A, 5C and 6C also repressed lipid oxidation by 24.2%, 14.7% and 26.4% in the erythrocyte membrane ghost assay system, respectively. Oral administration of 100 mg/kg of body weight of the chemically synthesized peptides, 5A, 5C and 6C to rats (male Wistar) 30 min prior to ethanol injection reduced ethanol-induced gastric mucosal damage by 67.9%, 57.0% and 60.3%, respectively. Conclusively, these peptides have shown real potent antioxidative activities and could further be investigated for potential use as food additives.     

Hydrogen solid storage: First-principles study of ZrNiH3

The ZrNiH₃ compound is a good candidate for hydrogen storage. In this work we used the first-principles calculation to study this compound. The crystal structures, the electronic properties and the optimization of the internal parameters are treated by the FP-LAPW method implanted in the WIEN2K code. The enthalpies of the dehydrogenation of the ZrNiH₃ compound are calculated. We found that the enthalpy is about −42.89 kJ/mol H, greater but similar to the experimental value of −34.3 kJ/mol H. Potential reasons for this discrepancy are discussed.