Sub-structural Niching in Estimation of Distribution Algorithms

We propose a sub-structural niching method that fully exploits the problem decomposition capability of linkage-learning methods such as the estimation of distribution algorithms and concentrate on maintaining diversity at the sub-structural level. The proposed method consists of three key components: (1) Problem decomposition and sub-structure identification, (2) sub-structure fitness estimation, and (3) sub-structural niche preservation. The sub-structural niching method is compared to restricted tournament selection (RTS)--a niching method used in hierarchical Bayesian optimization algorithm--with special emphasis on sustained preservation of multiple global solutions of a class of boundedly-difficult, additively-separable multimodal problems. The results show that sub-structural niching successfully maintains multiple global optima over large number of generations and does so with significantly less population than RTS. Additionally, the market share of each of the niche is much closer to the expected level in sub-structural niching when compared to RTS

Effect of Rare Earth Oxides (Y2O3, Nd2O3) on Oxidation Kinetics of Al-Li base alloy

The oxidation of Al-Li base alloy containing small amounts of rare earth (RE) oxides such as Y2O3 and  d2O3 particles has been studied at temperatures between 300°Cand 550°C. The lithium is selectively oxidized in Al-Li alloys and the parabolic rate constants for the growth of the resulting oxides layer Li2O, LiAl5O8, Li2CO3 and Li5AlO4 are about an order of magnitude higher than those for growth of oxides on alloy (Al-Li) with RE oxides. Alloys used in this study were prepared by melting and casting in a permanent steel mould under controlled atmosphere. It was found that 0.2%Y2O3 containing alloys possess the lowest oxidation rate and show great improvements in oxidation resistance compared to the base alloy. Oxides found on base alloy are subjected to cracking and spalling during thermal shock at high temperature i.e. 500°Cand 550°C. Identification of oxidation kinetics was carried out by using weight gain measurements while scanning electron microscopy (SEM) and x-ray diffraction analysis were used for microstructural morphologies and phase identification of the oxide scales. The weight gain measurement results suggest that the oxidation kinetic of all studied alloys follows the parabolic law in most experimental tests under the different temperatures except at 300°C oxidation kinetic follows almost a logarithmic rate law

Parallel Nonbinary LDPC Decoding on GPU

Nonbinary Low-Density Parity-Check (LDPC) codes are a class of error-correcting codes constructed over the Galois field GF(q) for q > 2. As extensions of binary LDPC codes, nonbinary LDPC codes can provide better error-correcting performance when the code length is short or moderate, but at a cost of higher decoding complexity. This paper proposes a massively parallel implementation of a nonbinary LDPC decoding accelerator based on a graphics processing unit (GPU) to achieve both great flexibility and scalability. The implementation maps the Min-Max decoding algorithm to GPU’s massively parallel architecture. We highlight the methodology to partition the decoding task to a heterogeneous platform consisting of the CPU and GPU. The experimental results show that our GPUbased implementation can achieve high throughput while still providing great flexibility and scalability.National Science Foundation (NSF

Dual guidance in evolutionary multi-objective optimization by localization

In this paper, we propose a framework using local models for multi-objective optimization to guide the search heuristic in both the decision and objective spaces. The localization is built using a limited number of adaptive spheres in the decision space. These spheres are usually guided, using some direction information, in the decision space towards the areas with non-dominated solutions. We use a second mechanism to adjust the spheres to specialize on different parts of the Pareto front using the guided dominance technique in the objective space. With this dual guidance, we can easily guide spheres towards different parts of the Pareto front while also exploring the decision space efficiently

Flammability action of tires material after adding flame inhibitor

Magnesium hydroxide was used as flame inhibitor to increased flame resistance for tires .Magnesium hydroxide was adding with (5%,10%) weight percents to rubber master batch of tire and then exposed the resulting material to a flame generated from gas torch with (10 mm) exposure distance . Method of measuring the surface temperature opposite to the flame was used to determine the heat transferred through tire material. The results were obtained shows enhanced flame resistance for tire by added magnesium hydroxide and this resistance increased by increasing hydroxide Percentage

Study of Corrosion Behavior of Metal Matrix Composite Based on Al-Alloy (7020) Prepared by Atomization

An experimental procedure has been fully formulated and carried out toprepare composite material of an aluminum (alloy 7020) matrix reinforced by Al2O3 particles with weight percentages of 5%, 7% and 10% and its particle size of (+53-75)μm using molten metal atomization technique. These experiments involve the preparation of aluminum matrix composite (AMCS) materials and study their Corrosion resistance in 3.5% solution of NaCl at temperature degrees 30˚C, 38˚C and 45˚C using various testing techniques. These include electrochemical corrosion and optical microscopy .The corrosion rate was found to increase as the temperature was nominally raised from 30˚C to 38˚C and 45˚C for the 10%wt of alumina in atomized AMCS samples in 3.5% NaCl solution. At a temperature of 30˚C the corrosion rate was found to rise with increasing percentages of Al2O3 particles for 5%, 7% and 10% atomized samples. This is due to galvanic corrosion between the matrix and the second phases (MgAl2O4) and (MgO) in microstructure of AMCS. Optical microscope showed a profound appearance of general corrosion in all microstructural area and grain boundaries

A STUDY EFFECT OF SOME VARIABLES IN TIG SPOT WELDING FOR (ALUMINUM – MAGNESIUM) ALLOY

The present work investigates the effect of some of the variables in spot tungsten inert gas shielded welding (TIG Spot) for (Aluminum-Magnesium) alloy type(5052-O) which is non–heat treatable alloy for its wide industrial uses and applications in field of welding technology. TIG Spot welding was performed by using tungsten electrode (EWTh2)of diameter (3.2mm) and DC current with direct polarity (DCSP) at constant shielded gas flow rate (15litre/min). The welded specimens were tested by using the Instron machine to determine the maximum shear force (shear strength ) of spot welded and to define the optimum conditions of spot welding variables in relation to the weld current, weld time and arc length of welding to produce an acceptable weld. The metallurgical changes of the weld zone and heat affected zone were studied under optimum conditions of welding. It has been shown that the increase in the welding current and welding time tends to increase the maximum shear force and it reaches maximum value and then decreases with high currents and long times. The maximum shear force was 2.4KN at welding current of (90) Amp , welding time ( 7)sec and arc length (1.6mm ) for 1mm thickness. It was also found that the highest value of hardness ( 53.5 Hv) was at the center of the spot welded and decreases gradually from the center of the weld spot towards the base metal