Infiltration and Top Seed Growth-Textured YBCO Bulks With Multiple Holes

The recently reported hole-patterned YBa₂Cu₃O _y (Y123) bulks with improved superconducting properties are highly interesting from material quality and application variety points of view. It is well known that the core of plain bulk superconductors needs to be fully oxygenated and some defects like cracks, pores, and voids must be suppressed in order that the material can trap a high magnetic field or carry a high current density. To minimize the above defects, we have used a combination of standard superconducting ceramic processing and an infiltration technique to prepare regularly perforated YBa₂Cu₃O _y (Y123) bulk superconductors. This process leads to negligible shrinkage upon annealing and a uniform distribution of Y211 inclusions. Texture was evidenced by neutron pole figure measurements. Flux mapping was used to verify the superconducting homogeneity of the samples and to investigate the field-trapping ability. In addition, the textured drilled samples were reinforced using resin or metal impregnation and the influence of the different processing steps on the hardness of the materials has been investigated.     

HColonies: a new hybrid metaheuristic for medical data classification

Medical data feature a number of characteristics that make their classification a complex task. Yet, the societal significance of the subject and the computational challenge it presents has caused the classification of medical datasets to be a popular research area. A new hybrid metaheuristic is presented for the classification task of medical datasets. The hybrid ant–bee colonies (HColonies) consists of two phases: an ant colony optimization (ACO) phase and an artificial bee colony (ABC) phase. The food sources of ABC are initialized into decision lists, constructed during the ACO phase using different subsets of the training data. The task of the ABC is to optimize the obtained decision lists. New variants of the ABC operators are proposed to suit the classification task. Results on a number of benchmark, real-world medical datasets show the usefulness of the proposed approach. Classification models obtained feature good predictive accuracy and relatively small model size.     

Circle-criterion Based Nonlinear Observer Design for Sensorless Induction Motor Control

This paper deals with the design of a nonlinear observer for sensorless induction motor control. Based upon the circle criterion approach, a nonlinear observer is designed to estimate pertinent but unmeasurable state variables of the considered induction machine for sensorless control purpose. The observer gain matrices are computed as a solution of linear matrix inequalities(LMI) that ensure the stability conditions of the state observer error dynamics in the sense of Lyapunov concepts. Measured and estimated state variables can be exploited to perform a state feedback control of the machine system. The simulation results are presented to illustrate the effectiveness of the proposed approach for nonlinear observer design.     

A PSO and a Tabu search heuristics for the assembly scheduling problem of the two-stage distributed database application

The assembly flowshop scheduling problem has been addressed recently in the literature. There are many problems that can be modeled as assembly flowshop scheduling problems including queries scheduling on distributed database systems and computer manufacturing. The problem has been addressed with respect to either makespan or total completion time criterion in the literature. In this paper, we address the problem with respect to a due date-based performance measure, i.e., maximum lateness. We formulate the problem and obtain a dominance relation. Moreover, we propose three heuristics for the problem: particle swarm optimization (PSO), Tabu search, and EDD. PSO has been used in the areas of function optimization, artificial neural network training, and fuzzy system control in the literature. In this paper, we show how it can be used for scheduling problems. We have conducted extensive computational experiments to compare the three heuristics along with a random solution. The computational analysis indicates that Tabu outperforms the others for the case when the due dates range is relatively wide. It also indicates that the PSO significantly outperforms the others for difficult problems, i.e., tight due dates. Moreover, for difficult problems, the developed dominance relation helps reduce error by 65%.     

A CAD tool for an array of differential oscillators coupled through a broadband network

A new expression of the equations describing the locked states of two oscillators coupled through a resistor is presented in this article. This theory has led to the elaboration of a CAD tool which provides, in a short simulation time, the frequency locking region of two coupled differential oscillators. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.     

Influence of secondary source technologies and energy management strategies on Energy Storage System sizing for fuel cell electric vehicles

Fuel cell electric vehicles (FCEVs) have some limitation which make them less competitor to thermal ones and delay their commercialization. The most important problems as the range, the durability and the cost depend directly on the energy storage problematic issues. In this context, this work presents an optimal sizing methodology for an Energy Storage System (ESS) composed by a fuel cell and an assistant source to supply a lightweight vehicle with 700 km driving range. Firstly, a comparative study between single and hybrid source is carried out to show the benefits of hybridization according to the range in terms of weight, cost and fuel consumption. Moreover, in order to improve the hybrid source characteristics, three technologies of the secondary source are tested and evaluated to be chosen for hybridization with fuel cell system purposes. Furthermore, the influence of three Energy Management Strategies (EMSs) on ESS sizing is studied where an optimal strategy provides the most favorable dimensions of the hybrid system. Simulation results give us the best technology needed for hybridization and allow us adopting the optimal management strategy to design the hybrid source. Finally, in order to show the influence of the driving cycles on the ESS design, a comparison study using the New European Driving Cycle “NEDC” and the Assessment and Reliability of Transport Emission Models Inventory Systems (ARTEMIS) confirms that there is a slow influence of the driving cycle on the ESS sizes.     

Effects of material thickness and processing method on poly(lactic-co-glycolic acid) degradation and mechanical performance

In this study, the effects of material thickness and processing method on the degradation rate and the changes in the mechanical properties of poly(lactic-co-glycolic acid) material during simulated physiological degradation were investigated. Two types of poly(lactic-co-glycolic acid) materials were considered: 0.12?mm solvent-cast films and 1?mm compression-moulded plates. The experimental results presented in this study were compared to the experimental results of Shirazi et al. (Acta Biomaterialia 10(11):4695–703, 2014) for 0.25?mm solvent-cast films. These experimental observations were used to validate the computational modelling predictions of Shirazi et al. (J Mech Behav Biomed Mater 54: 48–59, 2016) on critical diffusion length scale and also to refine the model parameters. The specific material processing methods considered here did not have a significant effect on the degradation rate and the changes in mechanical properties during degradation; however, they influenced the initial molecular weight and they determined the stiffness and hardness of the poly(lactic-co-glycolic acid) material. The experimental observations strongly supported the computational modelling predictions that showed no significant difference in the degradation rate and the changes in the elastic modulus of poly(lactic-co-glycolic acid) films for thicknesses larger than 100?μm.