A Memetic Algorithm for staff scheduling problem in airport security service

The staff scheduling problem is widely studied in Operational Research. Various surveys are available in the literature dealing with this problem which concerns various objectives and various constraints. In this article, we present a staff scheduling problem in airport security service. First, a modeling of the problem, and a representation of solutions are shown. The problem is solved in three steps, days-off scheduling, shift scheduling, and staff assignment. We focus on the last step, by providing a Memetic Algorithm (MA) which merged an Evolutionary Algorithm and Local Search techniques. We propose a chromosome encoding, a crossover operator and a combined neighborhood function, specially dedicated to this staff assignment problem. Besides providing better solutions than software currently used, this algorithm provides up to 50% of improvement from initial feasible solutions.     

Recent Advances in Boron Nitride Nanotubes and Nanosheets

Herein the recent experiments performed by the authors on fabricated multi-walled BN nanotubes and monoatomic BN graphene-like nanosheets are reviewed. The results are presented in several sections, namely: (i) method for high-yield synthesis of thin, defect-free BN nanotubes of only a few-layers, with external diameters below 10 nm; (ii) verification of BN nanotube piezoelectrical behavior and its electrically-induced thermal decomposition under combined resistive heating and electrical charging in a transmission electron microscope; (iii) the first direct measurements of the true tensile strength and Young’s modulus of BN nanotubes, using newly developed nanotensile tests inside an electron microscope; the measured values were found to be ∼30 GPa and ∼900 GPa, respectively; and (iv) diverse kinetic processes taking place within the prepared monoatomic BN sheets (so-called “white graphenes”) affiliated with intensive knock-on B and N atom displacements under high energy electron beam irradiation in an aberration-corrected medium-voltage high-resolution transmission electron microscope.     

Dissolution mechanism of 316L in lead–bismuth eutectic at 500 °C

In the frame of the Accelerator Driven System (ADS) cooled by liquid lead–bismuth eutectic (LBE), the austenitic stainless steel 316L is considered as a possible structural material for the reactor. However, the corrosion of 316L in this liquid alloy environment can be substantial, especially when a dissolution process occurs. In order to understand the dissolution process and to obtain a modelling of the 316L corrosion rate by LBE, an experimental dissolution kinetics of 316L is carried out in stagnant LBE at 500 °C up to 3000 h. A Ni preferential dissolution of the 316L is observed, leading to the formation of a ferritic layer at the 316L surface. A discussion on the various steps occurring in dissolution process leads to the conclusion that only the Ni dissolution reaction rate can control the 316L dissolution kinetics. The dissolution reaction rate constant, k_d, calculated from this study experimental points is equal to 4.2 × 10⁻¹¹ mol cm⁻² s⁻¹.     

Reduced graphene oxide

This paper describes a novel approach to the preparation of reduced graphene oxide and its dispersions in organic solvents. Graphite oxide, graphene oxide, and reduced graphene oxide have been prepared and characterized by a variety of physicochemical techniques.     

Microdeformation mechanisms in rubber toughened PMMA and PMMA-based copolymers

The classical method of toughening polymethylmethacrylate (PMMA) is to incorporate composite rubber particles into the homopolymer matrix. This approach has been extended in the present work by (i) combining rubber toughening with chemical modification of the matrix or (ii) introduction of the rubber modifier via PMMA-b-polybutylacrylate (PBA)-b-PMMA triblock copolymers. Significant improvements in fracture toughness at low speeds were observed in notched compact tension tests when the ductility of the rubber toughened PMMA matrix was improved by copolymerization, and comparable levels of toughness were achieved in the block copolymers. However, both types of material showed a transition to more brittle behavior at impact speeds, associated with increased localization of the crack tip deformation. Physical interpretations for this behavior and the scope for further optimization of the fracture response are discussed.     

The Microstructure,Texture and Mechanical Properties of Friction Stir Welded Aluminum Alloy

Russian Journal of Non-Ferrous Metals - The microstructure and texture of 7075-T6 FSW weld with optimal parameters are investigated using optical microscopy, electron back scatter diffraction and...     

Polyethersulfone containing sulfonimide groups as proton exchange membrane fuel cells

In this publication a new synthesis approach of polyethersulfone containing sulfonimide groups (SI-PES), by chemical modification of sulfonated polyethersulfone (S-PES), was developed. The synthesis protocol was optimized in order to turn all the sulfonic function into sulfonimide. The effect of replacing arylsulfonic acid function with a more acidic one, i.e. aryl trifluoromethanesulfonimide, was evaluated through thermal, dynamic mechanical analysis, water uptake and conductivity. For similar ionic exchange capacity (IEC), i.e. 1.8 H⁺/dm³, at 60 °C and 95% relative humidity, the conductivity of SI-PSF is 9.5 mS/cm while that of S-PSF is only 3.5 mS/cm. However, at 60 °C the water uptake is 3 times higher for SI-PSF membranes as compare with S-PSF. An important change is observed in the slope of the conductivity and water uptake plots of SI-PES membranes, at different temperatures, depending of IEC. This could be explained by an important change in membrane morphology.     

Beyond Intercalation‐Based Li‐Ion Batteries: The State of the Art and Challenges of Electrode Materials Reacting Through Conversion Reactions (Adv. Mater. 35/2010)

Despite the imminent commercial introduction of Li‐ion batteries in electric drive vehicles and their proposed use as enablers of smart grids based on renewable energy technologies, an intensive quest for new electrode materials that bring about improvements in energy density, cycle life, cost, and safety is still underway. This Progress Report highlights the recent developments and the future prospects of the use of phases that react through conversion reactions as both positive and negative electrode materials in Li‐ion batteries. By moving beyond classical intercalation reactions, a variety of low cost compounds with gravimetric specific capacities that are two‐to‐five times larger than those attained with currently used materials, such as graphite and LiCoO₂, can be achieved. Nonetheless, several factors currently handicap the applicability of electrode materials entailing conversion reactions. These factors, together with the scientific breakthroughs that are necessary to fully assess the practicality of this concept, are reviewed in this report.     

Practical Solvent‐Free Ruthenium Trichloride‐Mediated Benzannulation Approach to Fused Functionalized Arenes

The solvent‐ and ligand‐free [2+2+2] ruthenium‐promoted cycloaddition of α,ω‐diynes and alkynes provides a facile and efficient strategy for the synthesis of substituted benzene‐derived systems. The search for the optimal reaction conditions revealed the unprecedented catalytic activity of ruthenium trichloride for benzannulation reactions and this atom‐economical process allowed the synthesis of fused arenes including dihydrobenzofurans, isoindolines, indanes in good to high yields. This practical protocol also gave rise to the preparation of pentasubstituted aromatic derivatives and was applied to the one‐gram scale synthesis of a functionalized heterocycle.