Browsing by Author "Nayak, J."

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3,4-Dimethoxybenzaldehydethiosemicarbazone as corrosion inhibitor for aged 18 Ni 250 grade maraging steel in 0.5 M sulfuric acid
(2011) Poornima, T.; Nayak, J.; Nityananda Shetty, A.N.
The corrosion inhibition of the aged 18 Ni 250 grade maraging steel in 0.5 M sulfuric acid by 3,4-dimethoxybenzaldehydethiosemicarbazone(DMBTSC) has been investigated by potentiodynamic polarization and electrochemical impedance spectroscopy(EIS) techniques. The inhibition efficiency increased with the increase in inhibitor concentration and decreased with the increase in temperature. Polarization curves indicated mixed type inhibition behavior affecting both cathodic and anodic corrosion currents. The thermodynamic parameters of corrosion and adsorption processes were evaluated. The adsorption of DMBTSC on the aged maraging steel surface was found to obey the Langmuir adsorption isotherm model, and the calculated Gibb's free energy values confirm the spontaneous adsorption. The results obtained by the two techniques were in good agreement. © 2010 Springer Science+Business Media B.V.
3-Ethyl-4-amino-5-mercapto-1,2,4-triazole as a corrosion inhibitor for 6061/Al-15 vol% SiCp composite in a sodium hydroxide solution
(2011) Kumari, P.D.R.; Nayak, J.; Nityananda Shetty, A.N.
The inhibition efficiency of 3-ethyl-4-amino-5-mercapto-1,2,4-triazole (EAMT) on the corrosion of 6061/Al-15 vol% SiCp composite in different concentrations of sodium hydroxide solution has been investigated in the 30-50°C temperature range using Tafel and electrochemical impedance spectroscopic techniques. The inhibitor efficiency depends on the concentration of the inhibitor, concentration of the corrosive media, and temperature. The inhibition was assumed to occur through adsorption of the inhibitor molecule on the metal surface. The adsorption of the inhibitor on the metal surface is found to obey Langmuir adsorption isotherm. Thermodynamic parameters for the adsorption processes were determined from the experimental data. Copyright © Taylor &Francis Group, LLC.
3-ethyl-4-amino-5-mercapto-1,2,4-triazole as corrosion inhibitor for 6061-alloy in sodium hydroxide solution
(2011) Reena Kumari, P.D.; Nayak, J.; Nityananda Shetty, A.N.
The inhibition action of 3-ethyl-4-amino-5-mercapto-1,2,4-triazole (EAMT) on the corrosion of 6061-Al alloy in different concentrations of aqueous sodium hydroxide solution has been investigated at different temperatures, using potentiodynamic polarization and electrochemical impedance spectroscopic techniques. The surface morphology of the metal surface was investigated by scanning electron microscopy (SEM). The experimental results showed that the presence of EAMT in sodium hydroxide solution decreases the corrosion rates and the corrosion current densities (icorr), and increases the charge transfer resistance (Rp). It was found that the inhibitor efficiency depends on the concentration of the inhibitor, concentration of the corrosive media and temperature. The inhibition was assumed to occur through adsorption of the inhibitor molecule on the metal surface. The adsorption of the inhibitor on the metal surface is found to obey Langmuir adsorption isotherm. EAMT acts as a mixed inhibitor. Thermodynamic parameters for the adsorption processes were determined from the experimental data. The results obtained from both the techniques are in good agreement.
3-Methyl-4-amino-5-mercapto-1,2,4-triazole as corrosion inhibitor for 6061 Al alloy in 0.5 M sodium hydroxide solution
(Springer New York LLC barbara.b.bertram@gsk.com, 2011) Kumari, P.D.R.; Nayak, J.; Nityananda Shetty, A.N.
3-Methyl-4-amino-5-mercapto-1,2,4-triazole (MAMT) was synthesized, and its inhibition action on the corrosion of 6061 Al alloy in 0.5 M sodium hydroxide was investigated by means of potentiodynamic polarization and electrochemical impedance spectroscopy techniques. The effect of inhibitor concentration, temperature, and concentration of the corrosion medium on the inhibitor action was investigated. The surface morphology of the metal surface was investigated by scanning electron microscopy (SEM). The inhibition efficiency increased with the increase in the concentration of the inhibitor, but decreased with the increase in temperature. Both thermodynamic and kinetic parameters were calculated and discussed. The adsorption of MAMT on the base alloy was found to be through physisorption, obeying Langmuir's adsorption isotherm. The results obtained from both the techniques were in good agreement with each other. © 2011 ACA and OCCA.
3-Methyl-4-amino-5-mercapto-1,2,4-triazole as corrosion inhibitor for 6061/Al-15 (vol-%) sic(p) composite in 0.5M sodium hydroxide solution
(2011) Kumari, P.D.R.; Nayak, J.; Nityananda Shetty, A.N.
3-Methyl-4-amino-5-mercapto-1,2,4-triazole (MAMT) was investigated for its inhibition action on the corrosion of 6061/Al - 15 (vol-%) SiC(p) composite in 0.5M sodium hydroxide solution at different temperatures by potentiodynamic polarization and electrochemical impedance spectroscopic techniques. The effect of inhibitor concentration, temperature and concentration of the corrosion medium on the inhibitor action was investigated. The inhibition efficiency increased with the increase in the concentration of inhibitor but decreased with the increase in temperature. Both thermodynamic and activation parameters were calculated and discussed. The adsorption of MAMT on the composite was found to be through physisorption obeying Langmuir's adsorption isotherm.
Adsorption and inhibitor action of 4-(N,N-dimethylamino) benzaldehyde thiosemicarbazone on 6061 Al/SiC composite and its base alloy in sulfuric acid medium
(2011) Geetha, G.M.; Nayak, J.; Nityananda Shetty, A.N.
The inhibitive action of 4-(N,N-dimethylamino)benzaldehyde thiosemicarbazone (DMABT) on the corrosion behavior of 6061 Al -15 vol. pct. SiC(p) composite and its base alloy was studied at different temperatures in sulfuric acid medium containing varying concentrations of it, using Tafel extrapolation technique and AC impedance spectroscopy (EIS). Results showed that DMABT was an effective inhibitor, showing inhibition efficiency of 70% in 0.5 M sulfuric acid. The adsorption of DMABT on both the composite and base alloy was found to be through physisorption obeying Langmuir adsorption isotherm. The thermodynamic parameters such as free energy of adsorption and activation parameters were calculated. © Taylor & Francis Group, LLC.
Analysis of speech has become a popular non-invasive tool for assessing the speech abnormalities. Acoustic nature of the abnormal speech gives relevant information about the type of disorder in the speech production system. These signals are essentially non-stationary; may contain indicators of current disease, or even warnings about impending diseases. The indicators may be present at all times or may occur at random -:during certain intervals of the day. However, to study and pinpoint abnormalities in voluminous data collected over several hours is strenuous and time consuming. Therefore, computer based analytical tools for in-depth study and classification of data over daylong intervals can be very useful in diagnostics. This paper deals with the classification of certain diseases using artificial neural network, and then analyzed. This analysis is carried out using continuous wavelet transformation patterns. The results for various types of subjects discussed in detail and it is evident that the classifier presented in this paper has a remarkable efficiency in the range of 80-85% of accuracy. © 2005 Elsevier SAS. All rights reserved.
(Classification and analysis of speech abnormalities) Nayak, J.; Subbanna Bhat, P.; Acharya, A.U.; Aithal, U.V.
2005
AR modeling of heart rate signals
(2004) Nayak, J.; Bhat, P.S.; Rajendra, A.U.; Niranjan, U.C.; Sing, O.W.
The electrocardiogram (ECG) is a representative signal containing information about the condition of the heart. The shape and size of the P-QRS-T wave, the time intervals between its various peaks etc may contain useful information about the nature of disease afflicting the heart. However, the human observer can not directly monitor these subtle details. Besides, since bio-signals are highly subjective, the symptoms may appear at random in the time scale. Therefore, the heart rate variability signal is used as the base signal for the highly useful in diagnostics. This paper deals with the analysis of eight cardiac abnormalities using Auto Regressive (AR), modeling technique. The results are tabulated below for specific example. � 2004 IEEE.
AR modeling of heart rate signals
(Institute of Electrical and Electronics Engineers Inc., 2004) Nayak, J.; Subbanna Bhat, P.; Acharya, A.U.; Niranjan, U.C.; Sing, O.W.
The electrocardiogram (ECG) is a representative signal containing information about the condition of the heart. The shape and size of the P-QRS-T wave, the time intervals between its various peaks etc may contain useful information about the nature of disease afflicting the heart. However, the human observer can not directly monitor these subtle details. Besides, since bio-signals are highly subjective, the symptoms may appear at random in the time scale. Therefore, the heart rate variability signal is used as the base signal for the highly useful in diagnostics. This paper deals with the analysis of eight cardiac abnormalities using Auto Regressive (AR), modeling technique. The results are tabulated below for specific example. Â© 2004 IEEE.
Automated identification of diabetic retinopathy stages using digital fundus images
(2008) Nayak, J.; Subbanna Bhat, P.S.; Acharya, R.; Lim, C.M.; Kagathi, M.
Diabetic retinopathy (DR) is caused by damage to the small blood vessels of the retina in the posterior part of the eye of the diabetic patient. The main stages of diabetic retinopathy are non-proliferate diabetes retinopathy (NPDR) and proliferate diabetes retinopathy (PDR). The retinal fundus photographs are widely used in the diagnosis and treatment of various eye diseases in clinics. It is also one of the main resources for mass screening of diabetic retinopathy. In this work, we have proposed a computer-based approach for the detection of diabetic retinopathy stage using fundus images. Image preprocessing, morphological processing techniques and texture analysis methods are applied on the fundus images to detect the features such as area of hard exudates, area of the blood vessels and the contrast. Our protocol uses total of 140 subjects consisting of two stages of DR and normal. Our extracted features are statistically significant (p<0.0001) with distinct mean±SD as shown in Table 1. These features are then used as an input to the artificial neural network (ANN) for an automatic classification. The detection results are validated by comparing it with expert ophthalmologists. We demonstrated a classification accuracy of 93%, sensitivity of 90% and specificity of 100%. © 2007 Springer Science+Business Media, LLC.
Automatic identification of diabetic maculopathy stages using fundus images
(2009) Nayak, J.; Subbanna Bhat, P.S.; Acharya, R.
Diabetes mellitus is a major cause of visual impairment and blindness. Twenty years after the onset of diabetes, almost all patients with type 1 diabetes and over 60% of patients with type 2 diabetes will have some degree of retinopathy. Prolonged diabetes retinopathy leads to maculopathy, which impairs the normal vision depending on the severity of damage of the macula. This paper presents a computer-based intelligent system for the identification of clinically significant maculopathy, non-clinically significant maculopathy and normal fundus eye images. Features are extracted from these raw fundus images which are then fed to the classifier. Our protocol uses feed-forward architecture in an artificial neural network classifier for classification of different stages. Three different kinds of eye disease conditions were tested in 350 subjects. We demonstrated a sensitivity of more than 95% for these classifiers with a specificity of 100%, and results are very promising. Our systems are ready to run clinically on large amounts of datasets. © 2009 Informa Healthcare USA, Inc.
Background. Digital watermarking is a technique of hiding specific identification data for copyright authentication. This technique is adapted here for interleaving patient information with medical images, to reduce storage and transmission overheads. Methods. The patient information is encrypted before interleaving with images to ensure greater security. The bio-signals are compressed and subsequently interleaved with the image. This interleaving is carried out in the spatial domain and Frequency domain. The performance of interleaving in the spatial, Discrete Fourier Transform (DFT), Discrete Cosine Transform (DCT) and Discrete Wavelet Transform (DWT) coefficients is studied. Differential pulse code modulation (DPCM) is employed for data compression as well as encryption and results are tabulated for a specific example. Results. It can be seen from results, the process does not affect the picture quality. This is attributed to the fact that the change in LSB of a pixel changes its brightness by 1 part in 256. Spatial and DFT domain interleaving gave very less %NRMSE as compared to DCT and DWT domain. Conclusion. The Results show that spatial domain the interleaving, the %NRMSE was less than 0.25% for 8-bit encoded pixel intensity. Among the frequency domain interleaving methods, DFT was found to be very efficient. © 2004 Nayak et al, licensee BioMed Central Ltd.
(Simultaneous storage of medical images in the spatial and frequency domain: A comparative study) Nayak, J.; Subbanna Bhat, P.; Acharya, A.U.; Niranjan, U.C.
2004
Benzimidazole as corrosion inhibitor for heat treated 6061 Al- SiCp composite in acetic acid
(2015) Chacko, M.; Nayak, J.
6061 Al-SiCpcomposite was solutionizedat 350 �C for 30 minutes and water quenched. It was then underaged at 140 �C (T6 treatment). The aging behaviour of the composite was studied using Rockwell B hardness measurement. Corrosion behaviour of the underaged sample was studied in different concentrations of acetic acid and at different temperatures. Benzimidazole at different concentrations was used for the inhibition studies. Inhibition efficiency of benzimidazole was calculated for different experimental conditions. Thermodynamic parameters were found out which suggested benzimidazole is an efficient inhibitor and it adsorbed on to the surface of composite by mixed adsorption where chemisorption is predominant. � Published under licence by IOP Publishing Ltd.
Benzimidazole as corrosion inhibitor for heat treated 6061 Al- SiCp composite in acetic acid
(Institute of Physics Publishing helen.craven@iop.org, 2015) Chacko, M.; Nayak, J.
6061 Al-SiCpcomposite was solutionizedat 350 Â°C for 30 minutes and water quenched. It was then underaged at 140 Â°C (T6 treatment). The aging behaviour of the composite was studied using Rockwell B hardness measurement. Corrosion behaviour of the underaged sample was studied in different concentrations of acetic acid and at different temperatures. Benzimidazole at different concentrations was used for the inhibition studies. Inhibition efficiency of benzimidazole was calculated for different experimental conditions. Thermodynamic parameters were found out which suggested benzimidazole is an efficient inhibitor and it adsorbed on to the surface of composite by mixed adsorption where chemisorption is predominant. Â© Published under licence by IOP Publishing Ltd.
Compositionally Modulated Multilayered Zn-Co Deposits for Better Corrosion Resistance
(Springer, 2020) Bhat, R.S.; Venkatakrishna, K.; Nayak, J.; Hegde, A.C.
Zn-Co compositionally modulated multilayer alloy (CMMA) deposits have been developed onto mild steel using single bath technique. Multilayer alloy coatings have been galvanostatically produced using square current pulses. The switched cathode current density and number of layers have been designed for improved corrosion resistance. Experimental data revealed that multilayer coating with 120 layers at 10/30 mA/cm2 demonstrated ~ 125 times higher resistance to corrosion than monolayer alloy coating of the same thickness. The improved corrosion resistance of multilayer coatings is due to small changes in the wt.% cobalt, leading to change in the phase structure of deposit in alternate layers. The defects and failures occurring in a single layer in the deposition process are covered by the alternatively deposited coating layers. Therefore, the direction of the corrosive agent is extended or blocked. Further, the better corrosion resistances afforded by Zn-Co CMMA coatings were explained through changes in electronic properties at the interface, supported by Mott-Schottky’s plot. However, the decrease of corrosion resistance at a high degree of layering is attributed to the less relaxation time for redistribution of solutes in the diffusion layer, during plating. Potentiodynamic polarization and electrochemical impedance data showed its good protection ability. The enhanced corrosion resistance of multilayered deposits is due to small change in cobalt content, leading to alter the phase structure of the alternate-layers of the deposits. The structural morphology and the topographical structure of the coating were analyzed by scanning electron microscopy and atomic force microscopy. Evaluation of the chemical composition of the alloy coatings was carried out by x-ray photoelectron spectroscopy. © 2020, ASM International.
Computer-based identification of cataract and cataract surgery efficacy using optical images
(2009) Nayak, J.; Subbanna Bhat, P.S.; Acharya, R.; Faust, O.; Min, L.C.
The eyes are complex sensory organs, they are designed to capture images under varying light conditions. Eye disorders, such as cataract, among the elderly are a major health problem. Cataract is a painless clouding of the eye lens which develops over a long period of time. During this time, the eyesight gradually worsens. It can eventually lead to blindness and, is common in older people. In fact, about a third of people over 65 have cataracts in one or both eyes. In this paper, we made use of two types of classifiers for identification of normal, cataract (early and developed stage), and post-cataract eyes using features extracted from optical images. These classifiers are artificial neural network and support vector machine. A database of 174 subjects, using the cross-validation strategy, is used to test the effectiveness of both classifiers. We demonstrate a sensitivity of more than 90% for both of these classifiers. Furthermore, they have a specificity of 100% and, as such, the results obtained are very promising. The proposed feature extraction and classification systems are ready clinically to run on a large amount of data sets. © 2009 World Scientific Publishing Company.
Corrosion aspects of Al and Mg based composites
(Elsevier, 2025) Bhole, K.B.; Arya, S.B.; Nayak, J.
Corrosion is a significant concern in various industries, particularly in applications where metal components are exposed to aggressive environments. Aluminum (Al) and magnesium (Mg) are lightweight metals that find extensive use in aerospace, automotive, and structural applications. However, their susceptibility to corrosion limits their widespread adoption in certain conditions. Metal matrix composites (MMCs) have emerged as a promising solution to enhance the corrosion resistance of these metals while maintaining their desirable mechanical properties. The corrosion resistance of pure Al and Mg is often compromised in harsh environments due to galvanic coupling, electrolyte exposure, and chemical reactions. MMCs, where metal works as a matrix while reinforced by ceramic or hard metallic phases, offer a unique property to tailor a required mechanical property along with suitable corrosion resistance. However, it is challenging to control as well as enhance resistance to corrosion in various corrosive environments. The development of advanced metal matrix composites with tailored corrosion resistance profiles holds the key to expanding the application range of Al and Mg in diverse industries, ensuring their longevity and reliability in corrosive environments. A range of electrochemical techniques, including open circuit potential, electrochemical impedance spectroscopy, and polarization resistance test, highlighting their applications are discussed. © 2026 Elsevier Inc. All rights reserved..
CORROSION BEHAVIOR OF 18% Ni M250 GRADE MARAGING STEEL UNDER WELD-AGED CONDITION IN SULFURIC ACID MEDIUM
(2012) Sanatkumar, B.S.; Nayak, J.; Nityananda Shetty, A.N.
The corrosion behavior of 18% Ni M250 grade maraging steel under weld-aged condition was investigated in sulfuric acid medium of different concentrations (0.1-2 M) at different temperatures (30°-60°C). Electrochemical measurements were carried out using the potentiodynamic polarization technique and electrochemical impedance spectroscopy (EIS). The results showed an increase in the corrosion rate with the increases in temperature as well with increase in the concentration of the corrosion medium. The results obtained from the Tafel extrapolation technique and electrochemical impedance spectroscopy were in good agreement. Activation parameters were evaluated using the Arrhenius equation and transition state equation. The surface morphology of the corroded specimen was compared with that of the un-corroded sample by using scanning electron microscopy (SEM). © 2012 Copyright Taylor and Francis Group, LLC.
Corrosion behavior of 6061/Al-15 vol. pct. SiC(p) composite and the base alloy in sodium hydroxide solution
(Elsevier B.V., 2016) Reena Kumari, P.D.; Nayak, J.; Nityananda Shetty, A.
The corrosion behavior of 6061/Al-15 vol. pct. SiC(p) composite and 6061 Al base alloy was investigated in a sodium hydroxide solution. The electrochemical parameters were derived from potentiodynamic polarization and electrochemical impedance spectroscopic (EIS) techniques. The results showed that the corrosion resistance of the composite was lower than that of the base alloy in selected corrosion media. The corrosion rates of both the composite and the base alloy increased with the increase in the concentration of sodium hydroxide and also with the increase in temperature. The surface morphology of the metal surface was investigated using scanning electron microscope (SEM). Activation energy was evaluated using Arrhenius equation, and enthalpy of activation and entropy of activation values were calculated using transition state equation. © 2012
Corrosion behaviour of 6061 Al - 15vol. Pct. SiC composite and its base alloy in a mixture of 1:1 Hydrochloric and sulphuric acid medium
(2009) Geetha, G.M.; Nayak, J.; Nityananda Shetty, A.N.
Silicon carbide particulate - reinforced aluminum (SiCp-Al) composites possess a unique combination of high specific strength, high elastic modulus, good wear resistance and good thermal stability than the corresponding non-reinforced matrix alloy systems. These composites are potential structural material for aerospace and automotive applications. The corrosion characteristics of 6061 Al/SiCp composite and the base alloy were experimentally assessed. The corrosion test was carried out at different temperatures in 1:1 mixture of hydrochloric acid and sulphuric acid at a concentration range of 0.01 to 1N for each of the acid, as corrosion media using Tafel extrapolation technique and Electrochemical impedance spectroscopy (EIS). The results obtained from Tafel extrapolation technique and Electrochemical impedance spectroscopy were in good agreement. The results showed an increase in the corrosion rate with increases in temperature as well as the increase in the concentration of the corrosion media. The thermodynamic parameters like energy of activation were calculated using Arrhenius theory equation and, enthalpy of activation and entropy of activation were calculated using transition state theory equation. © 2009 by ESG.