A hybrid GA and PSO optimized approach for heart-disease prediction based on random forest

Multimedia Tools and Applications - Nowadays, heart diseases are significantly contributing to deaths all over the world. Thus, heart-disease prediction has garnered considerable attention in the...     

Vapour side corrosion in a ME desalination plant at Jebel Dhana

Jebel Dhana, from the Abu Dhabi Water and Electricity Authority (ADWEA), operates two 2 MGD multi-effect thermo-compression distillers commissioned in 1996. Tube failures were first reported approximately 16 months after commissioning. The initial tube failures were from the upper rows, but more recent failures were apparently randomly distributed throughout the tube bundle. Ten tubes were removed and their corrosion morphology was examined macroscopically and microscopically. The corrosion products were analysed by X-ray, EDAX, and EPMA techniques. The copper nickel alloy tubes were found to have suffered from vapour side corrosion; however, there was no sign of any copper oxide deposition, as has often been seen in failed tubes from MSF distillers. The failures took two forms: corrosion fatigue cracking, and pitting corrosion. The corrosion fatigue was in the form of a circumferential crack at a flat portion of the tube in the centre of a tube span. It was believed that the flat surface had developed as a result of fretting against a neighbouring tube, and had been worn away to the point of failure. Unfortunately, the position of the tubes in the tube bundle had not been identified during their removal, but it is suspected that the damaged tube had been in the top row, with the flattened portion directly below one of the two vapour inlet pipes. The other tubes sampled showed pitting corrosion. Some of the pitting had perforated the tube walls whilst others showed pitting on the outer surface only. Some of the pits contained corrosion products whilst others were free of them. This pitting corrosion is attributed to the formation of carbonic acid in the presence of oxygen (air). A weak acid is formed due to the dissolution of CO₂ in the condensing water vapour. The gas concentration varies within the tube bundle, due to the vapour phase, allowing the gas concentration to increase in specific areas of the tube bundle, causing the non-uniformity of attack. There was no immediate tie-up between the pitting corrosion and the two steam inlet pipes due to the unknown position of the sampled tubes within the tube bundle. It is recommended that the oxygen level be reduced by ensuring that the distiller vessels are as air-tight as possible, thus reducing the tendency towards pitting corrosion.     

Intelligent methodologies for cardiac sound signals analysis and characterization in cepstrum and time-scale domains

Biometric authentication is the process that allows an individual to be identified based on a set of unique biological features data. In this study, we present different experiments to use the cardiac sound signals (phonocardiogram “PCG”) as a biometric authentication trait. We have applied different features extraction approaches and different classification techniques to use the PCG as a biometric trait. Through all experiments, data acquisition is based on collecting the cardiac sounds from HSCT-11 and PASCAL CHSC2011 datasets, while preprocessing is concerned with de-noising of cardiac sounds using multiresolution-decomposition and multiresolution-reconstruction (MDR-MRR). The de-noised signal is then segmented based on frame-windowing and Shanon energy (SE) methods. For feature extraction, Cepstral (Cp) domain (based on mel-frequency) and time-scale (T-S) domain (based on Wavelet Transform) features are extracted from the de-noised signal after segmentation. The features, extracted from the Cp-domain and the T-S domain, are fed to four different classifiers: Artificial neural networks (ANN), support vector machine (SVM), random forest (RF) and K-nearest neighbor (KNN). The performance of the classifications is assessed based on the k-fold cross validation. The computation complexity of the feature extraction domains is expressed using the Big-O measurements. The T-S features are superior to PCG heart signals in terms of the classification accuracy. The experiments' results give the highest classification accuracy with lowest computation complexity for RF in the Cp domain and SVM and ANN in the T-S domain.     

Hybrid intelligent techniques for MRI brain images classification

This paper presents a hybrid technique for the classification of the magnetic resonance images (MRI). The proposed hybrid technique consists of three stages, namely, feature extraction, dimensionality reduction, and classification. In the first stage, we have obtained the features related to MRI images using discrete wavelet transformation (DWT). In the second stage, the features of magnetic resonance images have been reduced, using principal component analysis (PCA), to the more essential features. In the classification stage, two classifiers have been developed. The first classifier based on feed forward back-propagation artificial neural network (FP-ANN) and the second classifier is based on k-nearest neighbor (k-NN). The classifiers have been used to classify subjects as normal or abnormal MRI human images. A classification with a success of 97% and 98% has been obtained by FP-ANN and k-NN, respectively. This result shows that the proposed technique is robust and effective compared with other recent work.     

The oxidation behaviour of cobalt-base alloys containing dispersed oxides formed by internal oxidation

CoCr alloys containing a dispersed oxide phase have been produced by internally oxidizing alloys to which 1 wt % of a reactive element—Hf, Ti or Zr—has been added. Internal oxidation was carried out in a sealed quartz capsule containing a 50/50 powder mixture of CrCr₂O₃, or X-40-Cr₂O₃. The alloys produced in this way show all the beneficial characteristics demonstrated by similar alloys made by other techniques: (a) a continuous protective Cr₂O₃ scale is established at a chromium level of 10%, considerably below that required (approximately 25%) in the absence of a dispersoid; (b) a reduction in the growth rate of the Cr₂O₃ compared to particle-free alloys, particularly at high temperatures, and (c) greatly improved adhesion of the protective scale to the substrate. The beneficial effects appear to be independent of the composition of the dispersoid, and also its distribution. Oxidation of the CoCr-1 Hf, Zr or Ti alloys without pre-treatment produces scales characteristic of the chromium content of a corresponding binary alloy, indicating that some internal oxidation treatment is necessary and it is not sufficient to rely on the internal oxides formed during normal oxidation.     

Genetic algorithm and wavelet hybrid scheme for ECG signal denoising

This paper introduces an effective hybrid scheme for the denoising of electrocardiogram (ECG) signals corrupted by non-stationary noises using genetic algorithm (GA) and wavelet transform (WT). We first applied a wavelet denoising in noise reduction of multi-channel high resolution ECG signals. In particular, the influence of the selection of wavelet function and the choice of decomposition level on efficiency of denoising process was considered. Selection of a suitable wavelet denoising parameters is critical for the success of ECG signal filtration in wavelet domain. Therefore, in our noise elimination method the genetic algorithm has been used to select the optimal wavelet denoising parameters which lead to maximize the filtration performance. The efficiency performance of our scheme is evaluated using percentage root mean square difference (PRD) and signal to noise ratio (SNR). The experimental results show that the introduced hybrid scheme using GA has obtain better performance than the other reported wavelet thresholding algorithms as well as the quality of the denoising ECG signal is more suitable for the clinical diagnosis.     

The oxidation of cobalt—tungsten alloys

The oxidation behaviour of CoCrW alloys containing from 0–25%Cr and up to 30%W in oxygen at 900–1100°C has been studied. In CoW alloys there is a slight reduction in the oxidation rate as the tungsten content is increased, hwoever this is much mor emarked in Co15CrW alloys. Tungsten has little effect in Co25CrW alloys. On the binary alloys and CoCrW alloys which do not form Cr₂O₃, the scale has two layers: an outer, tungsten-free layer of columnar-grained CoO, and an inner layer of CoO containing CoWO₄ precipitates together with CoCr₂O₄ particles in the ternary alloys. The relative thicknesses of the two layers and the distribution of the constituents in the inner layer depends in temperature and alloy composition. The CoWO₄ and CoCr₂O₄ particles appear to be responsible for the reduction in oxidation rate by a blocking mechanism in the inner layer. There is some evidence to suggest that tungsten additions to Co?25%Cr alloys assist the exclusive formation of Cr₂O₃.     

Effect of carbon on the sulphidation of cobalt-tantalum alloys

The sulphidation of cobalt-tantalum-carbon alloys containing 10 and 15 wt% Ta and carbon in the range 0–1 wt%, was carried out in H₂-H₂S mixture containing 10% by volume H₂S. The reaction kinetics at 800–1000°C were followed thermo-gravimetrically and the scale products examined in detail using metallographic and X-ray diffraction techniques. In these sulphidation conditions (10% H₂S – 90% H₂) addition of 10 and 15% Ta to cobalt was unable to suppress the formation of liquid cobalt-rich sulphides; consequently, very rapid rates of alloy consumption were attained. Decreasing the temperature resulted in the distribution of the tantalum sulphides in a fine scale. Transport of cobalt through the inner layer was sufficiently rapid to form an outer, molten sulphide layer. The inability of tantalum-rich sulphides to develop into a continuous layer appears to be responsible for the disappointing effect of tantalum on the sulphidation resistance. Increasing carbon contents in the alloy increase the sulphidation rate, but the increase is not very dramatic.     

Sulfidation and sulfidation-oxidation of nickel- and cobalt-base alloys containing dispersions of stable oxides

The presence of a fine dispersion of a stable oxide is known to have a beneficial effect on the oxidation resistance of nickel- and cobalt-base heat-resisting alloys. This paper presents some preliminary experimental results relating to the hot-corrosion resistance of these alloys. Alloys forming Cr ₂O₃ scales appear to be resistant to oxidation when coated with sodium sulfate, whereas an alloy normally forming an Al ₂O₃ scale suffers accelerated attack. During sulfidation some of the alloys suffer an accelerated degradation, with sulfur penetrating rapidly along what appear to be grain boundaries. The same effect is noted in sulfidation-oxidation experiments, when the Cr ₂O₃-forming alloys suffer accelerated oxidation, the effect of the dispersoid being apparently removed. An Al ₂O₃-forming alloy resists this form of attack well. The sodium sulfate-coated test is probably a good guide to the behavior under weakly corroding conditions, whereas the sulfidation-oxidation test may give a better indication of the behavior under highly aggressive conditions.     

Effect of presulfidation on the oxidation behavior of Co-based alloys. Part I. Presulfidation at sulfur partial pressures above the dissociation pressure of cobalt sulfide

The effects of presulfidation in H₂-H₂S atmospheres of sulfur activity sufficient to form cobalt and chromium sulfides on the oxidation rates of Co-Cr binary alloys containing 0–25 wt.% Cr and Co-25 wt.% Cr alloys containing 0–2 wt.% C have been investigated. Presulfidation increases the oxidation rate, but the effect is not very dramatic. Carbon additions to the Co-25 wt.% Cr alloy progressively increase the oxidation rate, but not to as great an extent as a simple model based on the reduction of the chromium activity in the alloy. Sulfur released from the preformed sulfides by oxidation diffuses into the alloy precipitating fresh sulfides, there appears to be no outward diffusion of sulfur through the oxide scale. These internal sulfides have a liquid-like morphology in cobalt-base alloys when the oxidation is carried out at 1000°C, as compared to 800°C in corresponding nickel-base alloys. When the sulfide layer produced during the presulfidation is thin, so that oxidation destroys the continuous sulfide layer, the subsequent scale morphologies after oxidation exhibit many features similar to samples subjected to hot corrosion in environments containing sodium sulfate.