A Modified Particle Swarm Optimizer for the Coordination of Directional Overcurrent Relays

The coordination of directional overcurrent relays (DOCR) is treated in this paper using particle swarm optimization (PSO), a recently proposed optimizer that utilizes the swarm behavior in searching for an optimum. PSO gained a lot of interest for its simplicity, robustness, and easy implementation. The problem of setting DOCR is a highly constrained optimization problem that has been stated and solved as a linear programming (LP) problem. To deal with such constraints a modification to the standard PSO algorithm is introduced. Three case studies are presented, and the results are compared to those of LP technique to demonstrate the effectiveness of the proposed methodology.     

Optimization of municipal solid waste leaching test procedure: assessment of the part of hydrosoluble organic compounds

Despite national recycling campaigns, the amount of municipal solid waste (MSW) to be treated remains very important in France with almost 39% of the waste produced going to landfills. Therefore with the increasing concern over sustainable development and energy valorization, it seems essential to optimize current treatment methods and develop new preparation techniques of the waste. Nevertheless an important first step to take into account is to evaluate the waste using a different method than biogas production. In this perspective, the leaching test (LT) could be used as a tool to evaluate the ability of a waste to mobilize organic and mineral compounds. This research aims at optimizing a leaching test protocol mainly adapted to organic waste in order to be used on MSW to assess the fractions of both fast and slow mobilized organic matter. Several leaching tests have thus been implemented, optimized and compared in terms of accessible organic matter in the waste. Results have shown that the test conditions have a great influence on the mobilization of pollutants. The duration of the test affects mainly the quantity and quality of organic molecules extracted. The renewal of the eluent does not properly simulate the conditions of a landfill. The results would be used to assess the performance and the efficiency of new ways of waste pretreatment.     

Prediction of skin temperature of externally water cooled pipes under intense fires

A multiphase, multimode heat transfer numerical model was used to estimate the maximum skin temperature of a stagnant water‐filled pipe structure subject to an intense flame. This transient two‐dimensional mathematical model takes into account conduction, convection and radiation as well as evaporation of cooling water. Results have been obtained based on practical data and experimental field findings. The cooling water film that surrounds the pipe structure attacked by the flames, can originate from fire‐fighting water hoses or from a sprinkler water system. Two different values of water film thickness of 3 and 5 mm are analysed. The simulation results indicate that the main parameter which controls the pipe skin temperature, is the water film thickness covering the pipe. Indeed the maximum steel pipe skin temperature drops from 175.5 to 108.8°C when the water film thickness is increased from 3 to 5 mm for the 20 inch‐water‐filled pipes. However the water presence inside the pipe has negligible effect on the pipe skin temperature. Copyright © 2004 John Wiley & Sons, Ltd.     

New relations between the Schur-Cohn-Fujiwara and Nour Eldinstability criteria

The authors demonstrate relationships between two different stability criteria, including reduced-order versions of these criteria. Modifications of the criteria can also be used for root counting. The various matrices whose signatures are the key to obtaining root distributions are related by congruency transformations with triangular structure, implying that the sign patterns of the leading principal minors are identical     

Iterative simplex-finite difference method for the characterizationof optical waveguides

A new method is presented for reconstructing smooth refractive index profiles of optical waveguides from measured effective indexes. It is based on the semivectorial finite difference method to solve the polarized wave equation for a given refractive index profile. An iterative simplex algorithm is used to find the best refractive index parameters that give, as a solution, effective indexes close to the measured ones. The method is applied successfully to Ag⁺-Na ⁺ ion-exchanged glass slab waveguides and to diffused Mg/Ti:LiNbO₃ slab waveguides. Dopant concentration profiles are obtained by using secondary ion mass spectrometry. The relationship between the refractive index change and the dopant concentration is determined for both cases. The iterative simplex algorithm-finite difference method (ISA-FDM) is compared to other index profile reconstruction methods, and the advantages with respect to WKB-based methods are pointed out     

Lignocellulose–polymer composite. I

Bagasse grinded to different mesh sizes was used for the production of lignocellulose polymer composites. Samples of different polymer loads were prepared from crude-grafted bagasse with polymethyl methacrylate. A sodium bisulfite–soda lime glass system was used as an initiator for the grafting reaction. The properties of the resulting composites have been found to be affected by both the polymer load and the mesh size of the ground bagase. Grafting in the absence of soda lime glass from the initiator system was successful, and the properties of the composite produced from the prepared samples differed greatly from those containing glass. Other oxides, namely, copper (cupric) oxide and iron (ferric) oxide, were used in replacing glass in the initiator system. Some of the properties of the composite containing the latter were deteriorated. A composite from the true-grafted sample (homopolymer free) showed improvement in some of the properties, while the others deteriorated. Composites prepared from impregnated bagasse with polymer or homopolymer behaved differently in their properties and from those from crude-grafted samples, depending on the mesh size of the ground bagasse they are made from.     

Dielectric investigation of the molecular dynamics of blends (II): polymers with dissimilar molecular architecture (PS/TMPC blend)

The molecular dynamics of polystyrene/tetramethyl polycarbonate (PS/TMPC) blends were investigated using dielectric spectroscopy in the frequency and temperature ranges 10^?2?10⁷ Hz and 50–220°C, respectively. Blends with different compositions, namely 12.5, 25, 50, 75 and 87.5 wt% PS/TMPC were found to be compatible over the entire composition range and showed one glass relaxation process corresponding with the transition observed by calorimetric measurements. It was found that neither the kinetics or the distribution of relaxation times of the local process observed in pure TMPC were affected by blending. This fact implies that the local environment of the segments is not changed upon blending. Furthermore, these blends showed that the blending of TMPC with weakly polar polystyrene does not cause any change in the dipolar interaction of the TMPC segments, so that the relaxation strength varies linearly with composition. It is concluded that the polymeric chains of the TMPC and PS are not mixed at a segmental level, but at a higher structural level lying somewhere between segmental and molecular. This conclusion is in good agreement with that obtained in the case of blends composed of polymers with similar molecular architecture.