Annealing and diffusion processes in thin film CdS/Cu2S solar cells

Diffusion of copper during post-fabrication annealing of CdS/Cu₂S thin film solar cells was studied by Auger electron spectroscopy. Depth profiles of the constituent element concentrations indicate that, for samples annealed in air, a deep penetration of copper into the cadmium sulphide layer occurs together with a significant out-diffusion of cadmium. In contrast, the copper penetration which results from vacuum or hydrogen annealing treatment is substantially less and no out-diffusion of cadmium is observed for annealing temperatures up to 400°C.     

A hybrid algorithm for scheduling scientific workflows in IaaS cloud with deadline constraint

The Journal of Supercomputing - Scientific workflows are used to process large amounts of data and perform complex analyses; thus, they require powerful computing resources to produce the desired...     

A step forward in studying the compact genetic algorithm

The compact Genetic Algorithm (cGA) is an Estimation of Distribution Algorithm that generates offspring population according to the estimated probabilistic model of the parent population instead of using traditional recombination and mutation operators. The cGA only needs a small amount of memory; therefore, it may be quite useful in memory-constrained applications. This paper introduces a theoretical framework for studying the cGA from the convergence point of view in which, we model the cGA by a Markov process and approximate its behavior using an Ordinary Differential Equation (ODE). Then, we prove that the corresponding ODE converges to local optima and stays there. Consequently, we conclude that the cGA will converge to the local optima of the function to be optimized.     

Design techniques for fault-tolerant systolic arrays

A systematic approach of designing fault-tolerant systolic architectures is proposed in this paper. In this approach, redundant computations are introduced at the algorithmic level by deriving three versions of a given algorithm. Fault-tolerant systolic array is constructed by merging the corresponding systolic array of the three versions of the algorithm. The merging method attempts to obtain the fault-tolerant systolic array at minimal cost in terms of area and speed. It is based on rescheduling input data, rearranging data flow, and increasing the utilization of the array cells. The resulting design can detect and tolerate all single permanent and temporary faults and the majority of the multiple fault patterns with high probability.     

Editorial: Special Issue on High Performace Distributed Computing

The Journal of Supercomputing -     

Numerical study of elliptical cracks in cylinders with a thickness transition

The paper deals with elliptical cracks in a cylinder with a thickness transition. This structure is an assembly of two cylinders of thickness t and t₂ (t<t₂). In the transition zone, the thickness varies linearly. The purpose is to check whether tabulated data used for SIF calculations in a cylinder of uniform thickness t can be used for the cylinder with a thickness transition. A comparative study is made on the effect of a crack in a cylinder with a thickness transition and in a uniform thickness cylinder. Loads considered are pure tensile stress and bending moment. A numerical analysis was performed considering elastic behaviour at the crack tip. A crack mesh was designed and validated for 3D models. The results show that SIF calculations in the transition assuming a uniform thickness cylinder are conservative but not precise. The comparative study shows that the cylinder with a thickness transition is more vulnerable to a defect.     

Optimized Growth of Heteroepitaxial (111) NiFe2O4 Thin Films on (0001) Sapphire with Two In‐Plane Variants via Chemical Solution Deposition

(111)‐oriented epitaxial thin films of nickel ferrite (NFO) are grown on c‐plane sapphire [α‐Al₂O₃(0001)] substrates using a chemical solution deposition technique. The processing conditions, including pyrolysis and annealing temperatures, are varied to achieve a film that shows maximum texture and epitaxy. It is shown that increasing the pyrolysis temperature to 400°C and decreasing the annealing temperature to 750°C for 10 min result in the highest degree of texture in the films. Lower film thickness also leads to a higher degree of texture. Microstructural studies confirm an in‐plane epitaxial relationship between the (111) NFO film and the (0001) Al₂O₃ substrate in two variants, [110]_NFO || or .     

Vapour-deposited CdS films and their dependence on the source material

An investigation has been made of the conditions required for the formation of vapour-deposited CdS thin films with reproducible characteristics suitable for use in photovoltaic solar cells. Cathodoluminescence spectroscopy has been used to provide information on differences in composition between the deposited films and the source material from which they were produced, and particular consideration has been given to the influence of the source material structure and stoichiometry on the electrical properties of the resultant films. Under identical deposition conditions, four different high-purity sources were shown to produce films with very different electrical characteristics, but by selecting appropriate deposition conditions (substrate temperature and deposition rate) it was found that each material was capable of generating films with the required characteristics.     

Miniature endoscope for simultaneous optical coherence tomography and laser-induced fluorescence measurement

We have designed a multimodality system that combines optical coherence tomography (OCT) and laser-induced fluorescence (LIF) in a 2.0-mm-diameter endoscopic package. OCT provides approximately 18-microm resolution cross-sectional structural information over a 6-mm field. LIF spectra are collected sequentially at submillimeter resolution across the same field and provide histochemical information about the tissue. We present the use of a rod prism to reduce the asymmetry in the OCT beam caused by a cylindrical window. The endoscope has been applied to investigate mouse colon cancer in vivo.