Machine learning approach to recognize ventricular arrhythmias using VMD based features

The occurrence of life-threatening ventricular arrhythmias (VAs) such as Ventricular tachycardia (VT) and Ventricular fibrillation (VF) leads to sudden cardiac death which requires detection at an early stage. The main aim of this work is to develop an automated system using machine learning tool for accurate prediction of VAs that may reduce the mortality rate. In this paper, a novel method using variational mode decomposition (VMD) based features and C4.5 classifier for detection of ventricular arrhythmias is presented. The VMD model was used to decompose the electrocardiography (ECG) signals to extract useful informative features. The method was tested for ECG signals obtained from PhysioNet database. Two standard databases i.e. CUDB (Creighton University Ventricular Tachyarrhythmia Database) and VFDB (MIT-BIH Malignant Ventricular Ectopy Database) were considered for this work. A set of time–frequency features were extracted and ranked by the gain ratio attribute evaluation method. The ranked features are subjected to support vector machine (SVM) and C4.5 classifier for classification of normal, VT and VF classes. The best detection was obtained with sensitivity of 97.97%, specificity of 99.15%, and accuracy of 99.18% for C4.5 classifier with a 5 s data analysis window. These results were better than SVM classifier result having an average accuracy of 86.87%. Hence, the proposed method demonstrates the efficiency in detecting the life-threatening VAs and can serve as an assistive tool to clinicians in the diagnosis process.

     

Dual-Layer Oxidation-Protective Plasma-Sprayed SiC-ZrB<Subscript>2</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-Carbon Nanotube Coating on Graphite

Graphite is used in high-temperature gas-cooled reactors because of its outstanding irradiation performance and corrosion resistance. To restrict its high-temperature (>873 K) oxidation, atmospheric-plasma-sprayed SiC-ZrB₂-Al₂O₃-carbon nanotube (CNT) dual-layer coating was deposited on graphite substrate in this work. The effect of each layer was isolated by processing each component of the coating via spark plasma sintering followed by isothermal kinetic studies. Based on isothermal analysis and the presence of high residual thermal stress in the oxide scale, degradation appeared to be more severe in composites reinforced with CNTs. To avoid the complexity of analysis of composites, the high-temperature activation energy for oxidation was calculated for the single-phase materials only, yielding values of 11.8, 20.5, 43.5, and 4.5 kJ/mol for graphite, SiC, ZrB₂, and CNT, respectively, with increased thermal stability for ZrB₂ and SiC. These results were then used to evaluate the oxidation rate for the composites analytically. This study has broad implications for wider use of dual-layer (SiC-ZrB₂/Al₂O₃) coatings for protecting graphite crucibles even at temperatures above 1073 K.     

Adsorption effect of Zn+2 and Co+2 on the antibacterial properties of SiC-porcelain ceramics

This investigation reports the adsorption effect of Cobalt and Zinc ions on the antibacterial properties of Silicon Carbide (SiC) added fired Porcelain based ceramics against Escherichia coli and Staphylococcus aureus. Incorporation of SiC in porcelain composition shows decrease in bulk density and increase in apparent porosity gradually upto 15 weight percent addition. The bulk density and apparent porosity of 15 wt% SiC added porcelain are 2.01 g/cm³ and 24.03%, respectively. Phase and microstructural charecterization reveals that fine grained interlocked mullite network with little unconverted quartz and carborandum are uniformly distributed in the microstructure. Co⁺² and Zn⁺² adsorption on exposed surface is calculated to be ~0.42 mg/cm² and Inductively coupled mass plasma spectroscopy (ICP-MS) shows that 1641.41 ppm of Co⁺² and 1936.37 ppm of Zn⁺² are leached in water from adsorbed surface. This is the first report where, transition metal specific antibacterial efficacy of SiC added porcelain-based ceramics are investigated. This report reveals that both Co⁺² and Zn⁺² adsorption results in antibacterial efficacy against E coli and S aureus and Co⁺² adsorption is superior to (zone of inhibition is ~1.3 cm more depending on bacteria and sample specifications) Zn⁺² adsorption.     

Effect of Zn and Co doping on antibacterial efficacy and cytocompatibility of spark plasma sintered hydroxyapatite

Hydroxyapatite [Hap, Ca₁₀(PO₄)₆(OH)₂] is one of the most preferred bioceramic material for orthopedic implants and coatings due to its stoichiometric similarities with human hard tissues. However, foreign body implantation inside human body sometimes leads to bacterial film formation over the implant surface causing the implant failure, thereby needing a revision surgery. This study attempts to select the better dopant between zinc (Zn) and cobalt (Co) as per the antibacterial efficacy when doped in Hap. To prepare antibacterial transition-metal-doped Hap, Zn and Co are doped in Hap as per the chemical formula Ca_10−x M_x(PO₄)₆(OH)₂, (M = Zn or Co and x = 0.24) to improve antibacterial efficacy. Phase and microstructural characterization by Rietveld refinement, scanning electron microscopy (SEM), and Fourier transformation infrared spectroscopy (FT-IR) confirms the doping. Evaluation of antibacterial activity against E coli reveals that both Zn- and Co-doped Hap shows antibacterial property with the latter being more effective (zone of inhibition ~3 mm more) for the same level of doping. Inductively coupled plasma-mass spectrometry confirms the presence of ~676 ppb Co⁺² and ~303 ppb Zn⁺² after leaching. In addition, cytotoxicity assay with NIH3T3 cell line reveals cytocompatibility of both the compositions with either dopant. The effect of spark plasma sintering on densification and mechanical properties of Co-doped Hap is investigated for the first time and compared with Hap with the same level of Zn doping. It appears that Co-doped Hap attains higher densification (~7% more) and fracture toughness (~2 times better) as compared to that of Zn-doped counterpart (densification: 86% and fracture toughness: 0.75 ± 0.12 MPa √m). Thus, this study suggests that Co- and Zn-doped Hap are promising candidates for bone tissue engineering with improved antibacterial properties and in addition, Co-doped Hap can attain higher density and offer better fracture toughness than that of Hap doped with Zn.     

Parallel architecture for accelerating affine transform in high-speed imaging systems

Affine transform is widely used in the high speed image processing systems. This transform plays an important role in various high speed applications like Optical quadrature microscopy (OQM), image stabilisation in digital camera and image registration etc. In these applications, transformations of image consume most of the execution time. Hence, for high speed imaging systems, acceleration of Affine transform is very much sought for. In this paper, the pipelined architecture implementation of a proposed inherent parallel algorithm for Affine transform has been presented. The acceleration of the image transformation will help in reducing the processing time of high speed imaging systems. The architecture is mapped in Field programmable gate array (FPGA) and the result shows that the proposed algorithm is almost 4 times faster than the conventional algorithm while retaining the image quality. Using the proposed algorithm, an image of size 1,920 × 1,080 can be transformed with a frame rate of 540 frames per second and the multiplane image synthesis for image stabilisation on the same digital image can be performed with a frame rate of 65 fps.     

Effect of TiC Reinforcement on Densification,Structural Evolution and High-Temperature Oxidation Behaviour of ZrB2-20 vol pct SiC Composite

Metallurgical and Materials Transactions A - This study aims to develop a novel TiC-doped ZrB2-SiC-TiC composite with enhanced sinterability, densification, phase and microstructural stability and...     

A review on high entropy silicides and silicates: Fundamental aspects,synthesis, properties

Metal silicides and silicates belong to the silicon-based non-oxide and oxide ceramics family with exceptional properties. Silicides face fatal oxidation at low temperatures and intrinsic brittleness, whereas silicates face instability in phase at high temperatures which restricts its usage in vast engineering applications. Hence, the ceramic community introduced the concept of high entropy in metal silicides and silicates. Since 2019, high entropy silicides and silicates, a multicomponent system, have created new avenues for materials discovery and design. High entropy silicides displayed elevated properties than the traditional silicides aiming its applications in microelectronic, high-temperature oxidation resistance coatings, and structural materials. Similarly, high entropy silicates displayed improved properties than the traditional silicates making them the most promising materials for environmental and thermal barrier coating applications for hot section components in gas turbines. The review focuses on specific case studies to emphasize the latest research and developments in high entropy silicides and silicates. Synthesis approaches employed in developing high entropy silicides and silicates and their structural and microstructural outcomes are addressed. The possible application is predicted based on the overview of the properties explored to date. The review concludes with future possibilities offered by the high entropy silicides and silicates.