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1

Parametric Optimization for Producing Semi-Solid A383 Alloy using Cooling Slope Casting Process

Rao M. S., Khandelwal Himandshu, Kumar M., Kumar A.

Archives of Foundry Engineering

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2023

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Vol. 23, iss. 1

43--52

EN

Cooling slope casting is a simple technique to produce semi-solid feedstock with a non-dendritic structure. The cooling slope technique depends on various parameters like slope length, slope angle, pouring temperature etc, that has been investigated in the present study. This work presents an extensive study to comprehend the combined effect of slope angle, slope length, pouring temperature, on hardness and microstructure of A383 alloy. Response Surface Methodology was adopted for design of experiments with varying process parameters i.e. slope angle between 15o to 60o, slope length between 400 to 700 mm, and pouring temperature between 560 oC to 600 oC. The response factor hardness was analysed using ANOVA to understand the effect of input parameters and their interactions. The hardness was found to be increasing with increased slope length and pouring temperature; and decreased with slope angle. The empirical relation for response with parameters were established using the regression analysis and are incorporated in an optimization model. The optimum hardness with non-dendritic structure of A383 alloy was obtained at 27o slope angle, 596.5 mm slope length and 596 oC pouring temperature. The results were successfully verified by confirmation experiment, which shows around 2% deviation from the predicted hardness (87.11 BHN).

2

Kernel function based regression approaches for estimating the oxygen transfer performance of plunging hollow jet aerator

Kumar M., Tiwari N. K., Ranjan S.

Journal of Achievements in Materials and Manufacturing Engineering

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2019

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Vol. 95, nr 2

74--84

EN

Purpose: To evaluate the capability of various kernels employed with support vector regression (SVR) and Gaussian process regression (GPR) techniques in estimating the volumetric oxygen transfer coefficient of plunging hollow jets. Design/methodology/approach: In this study, a data set of 81 observations is acquired from laboratory experiments of hollow jets plunging on the surface of water in the tank. The jet variables: jet velocity, jet thickness, jet length, and water depth are varied accordingly and the values of volumetric oxygen transfer coefficient is computed. An empirical relationship expressing the oxygenation performance of plunging hollow jet aerator in terms of jet variables is formulated using multiple nonlinear regression. The performance of this nonlinear relationship is compared with various kernel function based SVR and GPR models. Models developed with the training data set (51 observations) are checked on testing data set (24 observations) for performance comparison. Sensitivity analysis is carried out to examine the influence of jet variables in effecting the oxygen transfer capabilities of plunging hollow jet aerator. Findings: The overall comparison of kernels yielded good estimation performance of Radial Basis Function kernel (RBF) and Pearson VII Function kernel (PUK) using the SVR technique which is followed by nonlinear regression, and other kernel function based regression models. Research limitations/implications: The results of the study pertaining to the performance of kernels are based on the current experimental conditions and the estimation potential of the regression models may fluctuate beyond the selection of current data range due to datadependant learning of the soft computing models. Practical implications: Volumetric oxygen transfer coefficient of plunging hollow jets can be predicted precisely using SVR model by employing RBF as kernel function as compared to empirical correlation and other kernel function based regression models. Originality/value: The comparative analysis of kernel functions is conducted in this study. In previous studies, the predictive modelling approaches are implemented in simulating the aeration properties of cylindrical solid jets only, while this paper simulates the volumetric oxygen transfer coefficient of diverging hollow jets with the jet variables by utilizing polynomial, normalized polynomial, PUK, and RBF kernels in SVR and GPR.

3

Color image encryption using singular value decomposition in discrete cosine Stockwell transform domain

Vaish A., Kumar M.

Optica Applicata

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2018

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Vol. 48, nr 1

25--38

EN

In this paper, an image encryption technique using singular value decomposition (SVD) and discrete cosine Stockwell transform (DCST) is proposed. The original source image is encrypted using bands of DCST along with the SVD decomposed images. The number of bands in DCST, parameters used to mask the singular values, the way of permutation used to shuffle the values of SVD transformed images and the way of arrangement of SVD matrices are used as encryption keys. It is necessary to have correct knowledge of all the keys along with their respective values, for correct decryption of encrypted images. The robustness and the quality measurement of proposed work are analyzed by comparing it with some existing works.

4

Automated diagnosis of atrial fibrillation ECG signals using entropy features extracted from flexible analytic wavelet transform

Kumar M., Pachori R. B., Rajendra Acharya U.

Biocybernetics and Biomedical Engineering

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2018

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Vol. 38, no. 3

564--573

EN

Atrial fibrillation (AF) is the most common type of sustained arrhythmia. The electrocardiogram (ECG) signals are widely used to diagnose the AF. Automated diagnosis of AF can aid the clinicians to make a more accurate diagnosis. Hence, in this work, we have proposed a decision support system for AF using a novel nonlinear approach based on flexible analytic wavelet transform (FAWT). First, we have extracted 1000 ECG samples from the long duration ECG signals. Then, log energy entropy (LEE), and permutation entropy (PEn) are computed from the sub-band signals obtained using FAWT. The LEE and PEn features are extracted from different frequency bands of FAWT.We have found that LEE features showed better classification results as compared to PEn. The LEE features obtained maximum accuracy, sensitivity, and specificity of 96.84%, 95.8%, and 97.6% respectively with random forest (RF) classifier. Our system can be deployed in hospitals to assist cardiac physicians in their diagnosis.

5

Prediction of indoor radon/thoron concentration in a model room from exhalation rates of building materials for different ventilation rates

Kumar M., Sharma N., Sarin A.

Acta Geophysica

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2018

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Vol. 66, no. 5

1249--1255

EN

Studies have confirmed that elevated levels of radon/thoron in the human–environments can substantially increase the risk of lung cancer in general population. The building materials are the second largest contributors to indoor radon/thoron after soil and bedrock beneath dwellings. In present investigation, the exhalation rates of radon/thoron from different building materials samples have been analysed using active technique. Radon/thoron concentrations in a model room have been predicted based on the exhalation rates from walls, floor and roof. The indoor concentrations show significant variations depending upon the ventilation rate and type of building materials used.

6

An analytical approach for transmission expansion planning with generation variations

Kumar M., Kaur R.

Transactions on Environment and Electrical Engineering

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2017

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Vol. 2, No. 2

72--79

EN

Today, the transmission expansion planning for an existing power system under different constraints, is one of the major challenge for power engineers. There are several reasons; one of the reasons is rapid growth in load and inadequate capacity addition. Hence, it is important and essential to implement an algorithm for the transmission expansion which works well and have a good feasibility under certain assumptions and available constraints. Transmission expansion planning used in proposed paper works on an analytical algorithm which has been implemented for specific load condition with variations in generation. For that purpose, an economical factor has been measured that considers economical aspects of the line to be added for expansion. The prescribed analytical approach is also implemented for its feasibility check on a practical case study system.

7

Efficient classes of ratio-cum-product estimators of population mean in stratified random sampling

Vishwakarma G. K., Kumar M.

Probability and Mathematical Statistics

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2016

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Vol. 36, Fasc. 2

267--278

EN

In this paper, classes of separate and combined ratio-product estimators are proposed for estimating the finite population mean in stratified random sampling. The expressions for biases and mean squared errors (MSEs) of the proposed classes are derived to the first order of approximation. It is also verified that the proposed classes of estimators, under their optimum conditions, are equivalent to the separate regression estimator. The proposed classes of estimators are compared with the other existing estimators by using the MSE criterion, and the conditions under which the proposed classes perform better are obtained. Theoretical results are validated with the help of an empirical study.

8

Synthesis, investigation on structural and electrical properties of cobalt doped Mn–Zn ferrite nanocrystalline powders

Bhuvaneswari M., Sendhilnathan S., Kumar M., Tamilarasan R., Giridharan N. V.

Materials Science Poland

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2016

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Vol. 34, No. 2

344--353

EN

Synthesis of CoxMnyZnyFe2O4 (x = 0.1, 0.5, 0.9 and y = 0.45, 0.25, 0.05) nanocrystalline powders was done by chemical co-precipitation method. The crystal structure was determined by using X-ray diffraction (XRD) studies. The crystallite size and lattice parameters were calculated from the XRD data. The XRD results revealed that the crystallite size of the nanocrystalline powder was found to decrease from 37 nm to 28 nm with the substitution of cobalt. The effect of cobalt ions on the crystallization process, the lattice parameters and electrical properties of Mn–Zn ferrites has been also investigated. The AC conductivity increased with an increase in frequency but it decreased with an increase in cobalt content. The complex impedance analysis of the data showed that the resistive and capacitive properties of the Co–Mn–Zn ferrite are predominant due to the fact that the processes are associated with the grains and grain boundaries. The dielectric constant and dielectric loss dependence on doping level and frequency at room temperature were also studied.

9

Offline handwritten pre-segmented character recognition of Gurmukhi script

Kumar M., Jindal M. K., Sharma R. K., Jindal S. J.

Machine Graphics and Vision

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2016

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Vol. 25, No. 1/4

45--55

EN

In this paper, we have proposed a feature extraction technique for recognition of segmented handwritten characters of Gurmukhi script. The experiments have been performed with 7000 specimens of segmented offline handwritten Gurmukhi characters collected from 200 different writers. We have considered the set of 35 basic characters of the Gurmukhi script and have proposed the feature extraction technique based on boundary extents of the character image. PCA based feature selection technique has also been implemented in this work to reduce the dimension of data. We have used k-NN, SVM and MLP classifiers. SVM has been used with four different kernels. In this work, we have achieved maximum recognition accuracy of 93.8% for the 35-class problem when SVM with RBF kernel and 5-fold cross validation technique were employed.

10

Inventory models with multiple production and remanufacturing batches under shortages

Singh S. R., Sharma S., Kumar M.

Control and Cybernetics

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2016

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Vol. 45, no. 3

385--416

EN

Owing to the ecological requirements and regulations, an enormous concern is being paid to the product re-processing. In the established literature, researchers considered that the remanufactured items are as good as the new ones. Yet, such an assumption is not convenient, as in many real situations the recycled products are considered by the customers to be of secondary quality. Further, the classical studies mainly addressed the inventory models without shortages, and this is not applicable in many practical business situations. This paper extends the reverse logistics inventory models with ﬁnite production and remanufacturing rate along with the assumption that newly produced and repaired (remanufactured) objects are not of same characteristics. Shortages are allowed and numerous stock-out cases are discussed. The collected used items are remanufactured (repaired) and non-repaired products are disposed oﬀ. The proposed models are illustrated with some numerical examples and their results are discussed.

11

Biosorption of aniline blue from aqueous solution using a novel biosorbent Zizyphus oenoplia seeds: Modeling studies

Kumar M., Elangovan G, Tamilarasan R, Vijayakumar G., Mukeshkumar P. C., Sendhilnathan S.

Polish Journal of Chemical Technology

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2015

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Vol. 17, nr 3

70--77

EN

This article presents the feasibility for the removal of Aniline Blue dye (AB dye) from aqueous solution using a low cost biosorbent material Zizyphus oenoplia seeds. In this study, a batch mode experiments of the adsorption process were carried out as a function of pH, contact time, concentration of dye, adsorbent dosage and temperature. The experimental data were fitted with Freundlich and Langmuir isotherm equations. The feasibility of the isotherm was evaluated with dimensionless separation factor (RL). The kinetic data of sorption process are evaluated by using pseudo-first order and pseudo-second order equations. The mode of diffusion process was evaluated with intra-particle diffusion model. The thermodynamic parameters like change in enthalpy (ΔHº); change in entropy (ΔSº) and Gibbs free energy change (ΔGº) were calculated using Van’t Hoff plot. The biosorbent material was characterized with Fourier Transform Infrared (FTIR) spectroscopy and the morphology was identified with Scanning Electron Microscope (SEM) in before and after adsorption of AB dye.

12

Structural and optical properties of SnO2-Al2O3 nanocomposite synthesized via sol-gel route

Mishra N. K., Kumar C., Kumar A., Kumar M., Chaudhary P., Singh R.

Materials Science Poland

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2015

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Vol. 33, No. 4

714--718

EN

A nanocomposite of 0.5SnO2-0.5Al2 O3 has been synthesized using a sol-gel route. Structural and optical properties of the nanocomposite have been discussed in detail. Powder X-ray diffraction and scanning electron microscopy with energy-dispersive X-ray diffraction spectroscopy confirm the phase purity and the particle size of the 0.5SnO2-0.5Al2 O3 nanocomposite (13 to 15 nm). The scanning electron microscopy also confirms the porosity in the sample, useful in sensing applications. The FT-IR analysis confirms the presence of physical interaction between SnO2 and Al2 O3 due to the slight shifting and broadening of characteristic bands. The UV-Vis analysis confirms the semiconducting nature because of direct transition of electrons into the 0.5SnO2-0.5Al2 O3 nanocomposites.

13

Controllability of mixed Volterra–Fredholm type integrodifferential third order dispersion equations

Kumar M., Sukavanam N.

Journal of Applied Analysis

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2015

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Vol. 21, nr 1

1--7

EN

In this paper, we establish a result concerning the controllability of a mixed Volterra–Fredholm type integrodifferential third order dispersion equation. The result is obtained by using the theory of strongly continuous semigroups and the Banach fixed point theorem.

14

Modeling of experimental data for the adsorption of methyl orange from aqueous solution using a low cost activated carbon prepared from Prosopis juliflora

Kumar M., Tamilarasan R.

Polish Journal of Chemical Technology

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2013

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Vol. 15, nr 2

29--39

EN

This paper presents the feasibility for the removal of methyl orange (MO) dye from aqueous solution using an activated carbon prepared from Prosopis juliflora bark. Batch adsorption experiments were carried out as a function of pH, contact time, adsorbate concentration, adsorbent dosage and temperature. The commonly applicable isotherms namely Freundlich and Langmuir equations are used for the prediction of isotherm parameters. A comparison of linear least-square method and a trial-and-error non-linear method are examined in Freundlich and Langmuir (Four forms) isotherms. The nature of adsorption isotherm feasibility was evaluated with dimensionless separation factors (RL). The dynamics of adsorption process was analyzed with Lagergren’s Pseudo-first order and Pseudo-second order kinetic equations. Thermodynamic parameters like the change in enthalpy (ΔHo), change in entropy (ΔSo) and change in Gibbs free energy (ΔGo) were evaluated and ΔGo shows a negative value whereas ΔHo shows the positive value indicating that the adsorption process was spontaneous and endothermic in nature. The functional group characterization of the adsorbent was done using Fourier transform infrared spectroscopy (FTIR). The thermal stability of activated carbon was analyzed using Thermo gravimetric analysis (TGA) and Differential thermal analysis (DTA).

15

Study of Ni-20Cr coatings for high temperature applications - a review

Kumar M., Singh H., Singh N.

Archives of Metallurgy and Materials

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2013

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Vol. 58, iss. 2

523--528

EN

Hot corrosion is a serious problem in various high temperature applications. The thermal spray coatings provides possible solution to counter the problem of hot corrosion in high temperature environment and enhances the life of equipment. Ni-20Cr alloy compositions require long initiation time at which the hot corrosion process moves from the initiation stage to the propagation stage. In this review, the performance of Ni-Cr coatings by different investigators has been presented to understand the mechanism of hot corrosion under different environments.

PL

Wysokotemperaturowa korozja jest poważnym problemem w zastosowaniach wysokotemperaturowych. Możliwym rozwiązaniem problemu korozji w warunkach wysokiej temperatury poprzez zwiększenie żywotności urządzeń jest zastosowanie termicznych powłok natryskowych. Stopy o składzie Ni-20Cr wymagają długiego czasu inicjacji, po którym proces korozji wysokotemperaturowej z etapu inicjacji przechodzi do etapu propagacji. W tym przeglądzie zostały zaprezentowane badania zachowania powłok niklowo-chromowych wykonane przez różnych badaczy, żeby zrozumieć mechanizm korozji wysokotemperaturowej w warunkach różnych środowisk.

16

Electrical and optical properties of sol-gel derive ZnO: Al thin films

Sagar P., Kumar M., Mehra R. M.

Materials Science Poland

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2005

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Vol. 23, No. 3

685--696

EN

High quality sol-gel derived ZnO and ZnO: Al thin films were deposited on corning 7059 glass substrate by spin coating technique. The annealed films showed c-axis preferred orientation. The structural electrical and optical properties of the films were investigated as a function of Al concentration from 0 to 3.0 at%. A maximum conductivity of 18.86. omega-1*cm-1 with carrier concentration of 2.2 x 1024 m-3 was found for Al concentration of 0.8 at%. The conductivity is found to be activated type above 375 K and variable range hopping conduction is observed below room temperature. Various transport parameters such as average spacing between donors, effective Bohr radius, donor levels, Debye screening length and average grain size have been estimated. The increase in band gap with Al doping is explained in terms of Burstein Moss shift.