Evolutionary algorithms in dynamic environments

The file attached to this record is the author's final peer reviewed version.Evolutionary algorithms (EAs) are widely and often used for solving stationary optimization problems where the fitness landscape or objective function does not change during the course of computation. However, the environments of real world optimization problems may fluctuate or change sharply. If the optimization problem is dynamic, the goal is no longer to find the extrema, but to track their progression through the search space as closely as possible. All kinds of approaches that have been proposed to make EAs suitable for the dynamic environments are surveyed, such as increasing diversity, maintaining diversity, memory based approaches, multi-population approaches and so on

VASCULAR CHANGES IN TYPE 2 DIABETES MELLITUS: APPLICATION TO RESTENOSIS AFTER STENTING

Stents used to decrease cardiovascular risk in patients with type 2 diabetes mellitus (T2DM) are prone to increased rates of restenosis. The mechanisms are incompletely elucidated, but low wall shear stress (WSS) and altered intracellular signaling likely contribute. We tested the hypothesis that neointimal hyperplasia (NH) after bare-metal stenting is due to vascular remodeling (enhanced formation of advanced glycation end-products (AGEs), increased downstream vascular resistance (DVR), and decreased WSS), and that decreasing AGEs with ALT-711 (Alagebrium) mitigates this response. Stents were implanted into the abdominal aorta of Zucker lean (ZL), obese (ZO), and diabetic (ZD) rats. After 21 days, the stented region was sectioned for NH quantification or casted and imaged for regional estimation of WSS and local intrastrut WSS by computational fluid dynamics. The thoracic and abdominal aorta, carotid, iliac, femoral and arterioles in cremaster muscle were harvested to detect AGEs related collagen cross-linking, and protein expression including transforming growth factor beta (TGFβ) and receptor for AGE (RAGE). A trend toward elevated DVR was observed, whereas blood flow (BF) and intrastrut TAWSS were significantly decreased in ZD compared to ZL and ZO rats (eg. TAWSS: 14.5 ± 1.9 vs 30.6 ± 1.6 and 25.4 ± 2.2 dyn/cm2, respectively; mean±SEM P\u3c0.05). Intrastrut NH was increased in ZO but not ZD rats. ALT-711 reduced DVR in ZD rats (15.6±2.5x105 to 8.39±0.6x105 dyn∙s/cm5), while decreasing NH (ZL: 7.7±1.0 to 4.3±0.9%; ZO: 12.0±1.5 to 4.9±0.8%; ZD: 9.4±0.7 to 3.7±0.4%) and causing similar regional TAWSS results in all groups. AGEs related collagen cross-linking was elevated in the arterioles of ZD rats, but alleviated by ALT-711. No consistent differences in RAGE or TGFβ expression were observed in treated versus untreated rats. Remodeling of the distal vasculature appears to play an important role in modulating WSS in T2DM, but WSS alone does not predict NH response as observed under normoglycemia. ALT-711 led to similar values for AGEs related arteriolar collagen cross-linking, BF through the stent, and regional WSS, while decreasing NH in all rats. Although TGFβ and RAGE expression did not appear to be modified by ALT-711, other intracellular signaling pathways remain to be explored

Conformal perturbations of dirac operators and general Kastler-Kalau-Walze type theorems for even dimensional manifolds with boundary

In this paper, we establish the proof of general Kastler-Kalau-Walze type theorems for conformal perturbations of dirac Operators on even dimensional compact manifolds with (respectively without) boundary.Comment: arXiv admin note: substantial text overlap with arXiv:2310.09775; text overlap with arXiv:2111.1503

Development of direct and indirect III-V on Si growth for solar cell applications

III-V material solar cell on Si substrate has drawn a considerable amount of research interest due to the potential to deliver high energy conversion efficiency with reduced cost. However, challenges arise due to lattice constant mismatch and thermal expansion coefficient mismatch issue, as well as the anti-phase domain issue arising from polar on non-polar growth between III-V material and Si substrate. Two different approaches have been investigated in this work regarding crystalline III-V material integration on Si substrate. The first approach is to integrate III-V via virtual Ge. To this goal, growth procedures were developed for Migration Enhanced Epitaxy (MEE) initiation of GaAs deposition on offcut Ge substrate. Results showing that high temperature annealing prior to deposition plays a significant role on double atomic steps formation. Initiating the process at low temperature with group V material and applying low thermal energy group V material throughout the entire fabrication process improves the film quality. An alternative MEE initiation layer of AlAs was also investigated with results showing successful reduction of the surface roughness. The other approach applied strained layer superlattice (SLS) acting as a dislocation filter (DF) on the substrate has been demonstrated and analysed. InAlAs based SLSs were fabricated with As2 or As4 to investigate the impact of different As sources. Results indicate As2 can improve DF performance. A novel III-V alloy with high shear modulus and low band gap energy, GaAsSb, was identified by applying selection rules developed from a literature search. The performance of GaAsSb SLS DF was compared with InAlAs based SLS DFs. Calculated dislocation densities for all samples shows that the GaAsSb SLS DF has the best performance in threading dislocation reduction with ρ_TD=1.07×〖10〗^6 〖/cm〗^2 at sample surface. Finally, a comparison has been made between AlAs/GaAs distributed Bragg reflector (DBR) and chirped DBR (CDBR) for increasing optical absorption in the III-V solar cells. Results indicate CDBR is more reliable by minimizing the impact from incident angle issue while maintain the reflectance at high level. The results taken together suggest successful integration of III-V on Si is achievable for solar cell application

A memetic particle swarm optimisation algorithm for dynamic multi-modal optimisation problems

Copyright @ 2011 Taylor & Francis.Many real-world optimisation problems are both dynamic and multi-modal, which require an optimisation algorithm not only to find as many optima under a specific environment as possible, but also to track their moving trajectory over dynamic environments. To address this requirement, this article investigates a memetic computing approach based on particle swarm optimisation for dynamic multi-modal optimisation problems (DMMOPs). Within the framework of the proposed algorithm, a new speciation method is employed to locate and track multiple peaks and an adaptive local search method is also hybridised to accelerate the exploitation of species generated by the speciation method. In addition, a memory-based re-initialisation scheme is introduced into the proposed algorithm in order to further enhance its performance in dynamic multi-modal environments. Based on the moving peaks benchmark problems, experiments are carried out to investigate the performance of the proposed algorithm in comparison with several state-of-the-art algorithms taken from the literature. The experimental results show the efficiency of the proposed algorithm for DMMOPs.This work was supported by the Key Program of National Natural Science Foundation (NNSF) of China under Grant no. 70931001, the Funds for Creative Research Groups of China under Grant no. 71021061, the National Natural Science Foundation (NNSF) of China under Grant 71001018, Grant no. 61004121 and Grant no. 70801012 and the Fundamental Research Funds for the Central Universities Grant no. N090404020, the Engineering and Physical Sciences Research Council (EPSRC) of UK under Grant no. EP/E060722/01 and Grant EP/E060722/02, and the Hong Kong Polytechnic University under Grant G-YH60

Performance Analysis of Friction Stir Welded Lightweight Aluminum Alloy Sheet

The present research envisaged the performance analysis of a 1-mm thick 6061-T6 aluminum alloy sheet welded by the friction stir welding technique, using optical microscopy, micro-hardness measurement, a tensile test, a friction and wear test, and a salt spray corrosion test. It was found that the grain in the welded zone obtained was refined under each parameter. When the rotating speed of the tool was 15,000 rpm and the traveling speed of the tool was 300 mm·min-1, the tensile strength of the welded zone was highest, i.e. 74.8% of the base metal. Furthermore, the hardness distribution curve of the welded zone was of the 'W' type under each parameter, but the hardness value was lower than that of the base metal. The friction coefficient of the welded zone was lower than that of the base metal under each parameter, and the wear form was found to be mainly adhesive wear accompanied by abrasive wear. The welded zone and the base metal were subjected to salt spray corrosion after 12 hours under each parameter, which had a negative effect on the quality. However, after 12 hours of subsequent corrosion, the quality of each sample and the base material was not obvious