First principles study of structural,electronic and optical properties of AgSbS2

In this work, we study the structural, electronic and optical properties of AgSbS₂, using full-potential linearized augmented plane wave and the pseudopotential plane wave scheme in the frame of generalized gradient approximation. Features such as the lattice constant, bulk modulus and its pressure derivative are reported. Our results suggest a phase transition from AF-IIb phase to rocksalt (B1) phase under high pressure. The calculated band structure and density of states show that the material under load has an indirect energy band gap X→(LГ) for AF-IIb phase (semiconductor) and a negative band gap W→(ГX) for B1 phase (semimetal). The optical properties are analyzed and the origin of some peaks in the spectra is discussed. Besides, the dielectric function, refractive index and extinction coefficient for radiation up to 14 eV have also been reported and discussed.     

Contribution to the declination of the dependability requirements using a three-dimensional decomposition of complex systems

The declination of the dependability requirements of the complex systems is one of the most critical processes of systems conception as well as systems engineering. We consider that these dependability requirements must be globally considered at the complete system level if they are to be respected before being allocated on the components of the system. Our approach is based on a three-dimensional decomposition model of the system whose purpose is to describe the way in which the system operates in order to deduce its dysfunction that serves as a basic support for the declination of the dependability requirements. The proposed method is applied to a nitric acid cooling system before being introduced into a chemical reactor.     

Conduction electrons bound to magneto-donors and magneto-acceptors in GaAs/GaAlAs quantum wells

Interband photoluminescence from asymmetric modulation-doped GaAs---GaAlAs quantum wells in the presence of a magnetic field has been investigated. The free-carrier Landau level excitations as well as transitions between magneto-donor and free hole states have been observed. Experiments with tilted magnetic field provide strong evidence for the existence of conduction electrons bound to ionized magneto-acceptors, characterized by discrete energies above the conduction band Landau levels. The observations are compared with the theory.     

PtRu Colloid Nanoparticles for CO Oxidation in Microfabricated Reactors

The catalytic activity of PtRu colloid nanoparticles for CO oxidation is investigated in microfabricated reactors. The measured catalytic performance describes a volcano curve as a function of the Pt/Ru ratio. The apparent activation energies for the different alloy catalysts are between 21 and 117 kJ/mol, which agree well with literature. The size distribution of the colloid nanoparticles is determined from STM and TEM, from which an average size of the colloid nanoparticles of 2.2±0.5 nm is determined.     

Equal Size Clusters to Reduce Congestion in Wireless Multimedia Sensor Networks

Wireless Multimedia Sensor Networks (WMSNs) are a particular instance of Wireless Sensor Networks that support the transmission of multimedia data such as video, image or sound. Those multimedia data should be delivered with a variety of predefined levels of Quality of Service swhich imposes the development of specific routing protocols. In this paper, we propose a new routing protocol based on clustering, that balances the number of nodes in clusters, called Equal Size Clusters to reduce Congestion in WMSNs. We seek to balance the number of members in each cluster in order to reduce intra-cluster congestion and reduce the number of congested cluster-heads. Therefore, we propose a novel metric called Maximum Cluster-heads Utilization Ratio (MCUR) that indicates the largest number of members assigned to a cluster-head to ensure a reliable transmission of multimedia data. Simulation results indicate that our proposed scheme outperforms other protocols proposed in the literature in terms of MCUR, number of cluster-heads and energy consumed.     

Photocatalytic hydrogen evolution over CuCrO2

We have been studying the technical feasibility of a photochemical H₂ evolution based on a dispersion of CuCrO₂ powder in aqueous electrolytes containing various reducing agents (S²⁻, and ). The title oxide combines a fair resistance to corrosion with an optimal band gap E_g of 1.32 eV. The intercalation of a small amount of oxygen should be accompanied by a partial oxidation of Cu⁺ into Cu²⁺ implying a p-type semiconductivity. The S²⁻ oxidation inhibits the photocorrosion and the H₂ evolution increases parallel to polysulfides formation. Most of H₂ is produced when p-CuCrO₂ is connected to n-Cu₂O formed in situ. H₂ liberation proceeds mostly on CuCrO₂ while the oxidation of S²⁻ takes place over Cu₂O surface and the hetero system Cu₂O/CuCrO₂ is optimized with respect to some physical parameters. The photoactivity is dependent on preparation conditions and lowering the synthesis temperature through nitrate route leads to an increase in specific surface area S_sp. The photoelectrochemical H₂ production is a multistep process where the rate determining step is the arrival of electrons at the interface because of their low mobility. Prolonged irradiation (>80 min) leads to a pronounced decrease of the photoactivity; the tendency toward saturation is due to the undesired back reduction of polysulfides in a closed system and to their strong absorption in the visible region (λ_max = 520 nm).     

Hybrid Metamodeling/Metaheuristic Assisted Multi-Transmitters Placement Planning

With every passing day, the demand for data traffic is increasing, and this urges the research community not only to look for an alternating spectrum for communication but also urges radio frequency planners to use the existing spectrum efficiently. Cell sizes are shrinking with every upcoming communication generation, which makes base station placement planning even more complex and cumbersome. In order to make the next-generation cost-effective, it is important to design a network in such a way that it utilizes the minimum number of base stations while ensuring seamless coverage and quality of service. This paper aims at the development of a new simulation-based optimization approach using a hybrid metaheuristic and metamodel applied in a novel mathematical formulation of the multi-transmitter placement planning (MTPP) problem. We first develop a new mathematical programming model for MTPP that is flexible to design the locations for any number of transmitters. To solve this constrained optimization problem, we propose a hybrid approach using the radial basis function (RBF) metamodel to assist the particle swarm optimizer (PSO) by mitigating the associated computational burden of the optimization procedure. We evaluate the effectiveness and applicability of the proposed algorithm by simulating the MTPP model with two, three, four and five transmitters and estimating the Pareto front for optimal locations of transmitters. The quantitative results show that almost maximum signal coverage can be obtained with four transmitters; thus, it is not a wise idea to use higher number of transmitters in the model. Furthermore, the limitations and future works are discussed.     

Data mining with a simulated annealing based fuzzy classification system

In this paper, the use of simulated annealing (SA) metaheuristic for constructing a fuzzy classification system is presented. In several previous investigations, the capability of fuzzy systems to solve different kinds of problems has been demonstrated. Simulated annealing based fuzzy classification system (SAFCS), hybridizes the learning capability of SA metaheuristic with the approximate reasoning method of fuzzy systems. The objective of this paper is to illustrate the ability of SA to develop an accurate fuzzy classifier. The use of SA in classification is an attempt to effectively explore and exploit the large search space usually associated with classification problems, and find the optimum set of fuzzy if–then rules. The SAFCS would be capable to extract accurate fuzzy classification rules from input data sets, and applies them to classify new data instances in different predefined groups or classes. Experiments are performed with eight UCI data sets. The results indicate that the proposed SAFCS achieves competitive results in comparison with several well-known classification algorithms.     

A parallel algorithm for constrained two-staged two-dimensional cutting problems

In this paper, we solve the two-staged two-dimensional cutting problem using a parallel algorithm. The proposed approach combines two main features: beam search (BS) and strip generation solution procedures (SGSP). BS employs a truncated tree-search, where a selected subset of generated nodes are retuned for further search. SGSP, a constructive procedure, combines a (sub)set of strips for providing both partial lower and complementary upper bounds. The algorithm explores in parallel a subset of selected nodes following the master-slave paradigm. The master processor serves to guide the search-resolution and each slave processor develops its proper way, trying a global convergence. The aim of such an approach is to show how the parallelism is able to efficiently solve large-scale instances, by providing new solutions within a consistently reduced runtime. Extensive computational testing on instances, taken from the literature, shows the effectiveness of the proposed approach.     

Polyoxometalates/polymer composites for the photodegradation of bisphenol-A

Nowadays water scarcity represents a threat for human and living beings. Therefore, to satisfy the demands of people for clean and safe water, new technologies for wastewater treatment have been developed. Thus, photocatalysis has emerged as a green chemical approach for such treatment. In this context, new polyoxometalate (POM)/polymer composites with relevant photocatalytic properties have been developed via an easy and cheap photopolymerization process upon mild visible light irradiation at 405 nm. This fruitful association between POM and polymer allowed the obtention of shaped materials facile to collect and reuse at the end of the photocatalytic treatment avoiding then the usual time-consuming regeneration methods. The prepared photocomposites displayed excellent photocatalytic performance for the removal of bisphenol-A from water under different sources of irradiation. Hence, 100%, 88%, and 50% of this model compound were decomposed by the phosphomolybdic composite under just 90 min of UV lamp, solar and LED@375 nm irradiations, respectively. The effectiveness of these developed photocatalysts towards the degradation of other organic compounds, as well as the degradation mechanism based on the generation of highly reactive chemicals such as ^•OH radicals promoting the degradation were already reported. Bisphenol-A degradation pathway and the identification of the photoproducts were discussed using mass spectroscopy technique. Therefore, this paper highlighted the photocatalytic efficiency of the new manufactured materials for the photodegradation of the bisphenol-A, thus expanding their application fields, under different sources of irradiation and under pure solar irradiation which make their applications more interesting and less energy consuming.