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Search Results: 1 - 10 of 532032 matches for " M. P. Chakravarthy "
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Inhibition Behaviour of Some Isonicotinic Acid Hydrazides on the Corrosion of Mild Steel in Hydrochloric Acid Solution
M. P. Chakravarthy,K. N. Mohana
International Journal of Corrosion , 2013, DOI: 10.1155/2013/854781
Abstract: New corrosion inhibitors, namely, isonicotinic acid (1H-indol-3-yl-methylene)hydrazide (INIMH) and isonicotinic acid (1H-pyrrol-2-yl-methylene)hydrazide (INPMH), have been synthesized, and their inhibitive characteristics for the corrosion of mild steel in 0.5?M HCl were investigated by mass loss and electrochemical techniques. The structures of the synthesized compounds were confirmed using spectral studies. Potentiodynamic polarization studies revealed that the investigated inhibitors are of mixed type. Various thermodynamic parameters were evaluated. Langmuir adsorption isotherm was found to be the best description for both inhibitors. FTIR spectra, energy dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM) were performed to characterize the passive film on the metal surface. 1. Introduction Mild steel is the most important engineering material particularly for structural, instrumental, industrial, and automobile applications. Corrosion problem occurs in these industries and can cause disastrous damage to metal and alloy structures causing economic consequences in terms of repair, replacement, and product losses. Pickling is a treatment on metallic surfaces in order to remove tightly adherent oxide films, stains, rust, or scale resulting from hot forming, heat treating, welding, and other high temperature operations [1]. The two acids commonly used in pickling are hydrochloric acid or sulphuric acid or it may be a combination of acids and may also contain nitric or hydrofluoric acids. Once the acid is rinsed out, the freshly cleaned steel will be very prone to oxidation (corrode) unless we apply a corrosion inhibitor of some type [2]. Therefore, a wide variety of corrosion inhibitors ranging from rare earth elements [3, 4] to organic compounds [5–8] have been used. The use of inhibitors is one of the practical methods for preventing corrosion of mild steel especially in acid media [9]. Inhibitors protect the metal by adsorbing on the surface and retard metal corrosion in aggressive environment. Selection of an appropriate inhibitor for specific environment and metal is of great importance. Generally, the heterocyclic organic compounds having higher basicity and electron density on the heteroatoms like oxygen, nitrogen, and sulphur have a tendency to resist corrosion [10, 11]. It has been known that efficient inhibitors should possess plentiful pi-electrons and unshared electron pairs on either nitrogen atoms or sulfur atoms of the inhibitors to the d-orbital of iron. The adsorption characteristics of organic molecules are also
Adsorption and Corrosion Inhibition Characteristics of Some Nicotinamide Derivatives on Mild Steel in Hydrochloric Acid Solution
M. P. Chakravarthy,K. N. Mohana
ISRN Corrosion , 2014, DOI: 10.1155/2014/687276
Abstract: The present investigation includes the study of corrosion inhibition effect of N-(1H-Indol-3-ylmethylene)-nicotinamide (IMN) and N-(3,4,5-trimethoxy-benzylidene)-nicotinamide (TMN) on mild steel in 0.5?M HCl by mass loss and electrochemical measurements. The obtained results showed that inhibition efficiency increased with the increasing concentration of inhibitors and decreased with increase in temperature and immersion time. Potentiodynamic polarization curves indicate that both IMN and TMN were acting as mixed type of inhibitors. Langmuir adsorption isotherm model was employed to determine the equilibrium of adsorption for inhibiting process in both inhibitors. Nyquist plots revealed that, as the concentration of the inhibitors increases, double layer capacitance ( ) and corrosion current ( ) decreases, while polarization resistance ( ) increases. Various thermodynamic parameters for the adsorption of inhibitors on mild steel were computed and discussed. The passive film formed on the metal surface was characterized by FTIR, EDX, and SEM. 1. Introduction Mild steel (MS) is cheap, strong, stiff, and widely used engineering material because of its good mechanical properties. It is the most important structural material exposed to outdoor conditions especially in acidic media [1] where corrosion is considerably more severe. Because of the general aggressiveness of acid solutions, inhibitors are commonly used to reduce the corrosive attack on metallic materials [2, 3]. Therefore, selection of an appropriate inhibitor ranging from rare earth elements [4] to organic compounds [5–8] for specific environment and metal is of great importance. In other words, the efficiency of these compounds is attributed to their steric factors, functional groups, lone pairs of electrons present on the hetero atoms, and pi-orbital character of donating electrons which determine the type of interaction between organic molecules and the metallic surfaces. The presence of corrosion inhibitors in a little amount blocks the corrosion sites and enhances the adsorption process, thereby increasing the life time of the metallic materials [9, 10]. A review of the literature reveals that the applicability of organic compounds as corrosion inhibitors for MS in acidic media has been recognized for a long time. A large number of organic compounds, particularly those containing nitrogen, oxygen, or sulphur in a conjugated system, are known to be applied as inhibitors to control acid corrosion of iron and steel. The inhibition process has been shown to occur via inhibitor adsorption, and
Comparative studies of different control strategies for shunt active filter
M. Chakravarthy,P. M. Sarma,S. N. Saxena
Journal of Engineering and Applied Sciences , 2011,
Abstract: Shunt Active power filter reduces the harmonics by injecting a current into the system proportional to the reference signal. Various strategies for effecting this are studied and compared. It is shown that PID control scheme yields better results.
Comparison of Simultaneous Estimation of Cardiac Output by Four Techniques in Patients Undergoing Off-pump Coronary Artery Bypass Surgery- A Prospective Observational Study
Chakravarthy M,Patil T,Jayaprakash K,Kalligudd P
Annals of Cardiac Anaesthesia , 2007,
C. S. Dileep,M. M. M Abdoh,M. P. Chakravarthy,K. N. Mohana
Acta Crystallographica Section E , 2012, DOI: 10.1107/s1600536812039426
Abstract: In the title compound, C12H11N3OS, the dihedral angle between the pyridine and thiophene rings is 46.70 (9)° and the C—N—N—C torsion angle is 178.61 (15)°. In the crystal, inversion dimers linked by pairs of N—H...O hydrogen bonds generate R22(8) loops.
Supernumerary Fascicle of Abductor digiti minimi Muscle and Compression of Ulnar Nerve and Ulnar Artery: A Case Report
Thejodhar,P; Sampath,K. Madhyastha; Bhagath,Kumar, Potu; Sreedhar,V; Binod,K. T; Chakravarthy,M; Ramana,V; Satish,N;
International Journal of Morphology , 2007, DOI: 10.4067/S0717-95022007000400014
Abstract: the supernumerary fascicles of abductor digiti minimi muscle have been implicated in vascular and nerve compression. during routine dissection of an old male cadaver we observed an anomalous muscle was found to take it's origin from the antebrachial fascia and flexor retinaculum, traversed ulnar canal (guyon's) superficial to ulnar vessels and nerves to reach the proximal part of abductor digiti minimi. the anomaly is one of a kind. its course through guyon's canal could be a cause for guyon's canal syndrome. it was innervated by the ulnar nerve
Scaling Relationships for Input Energy in Electromagnetic Welding of Similar and Dissimilar Metals  [PDF]
S. V. Desai, Satendra Kumar, P. Satyamurthy, J. K. Chakravartty, D. P. Chakravarthy
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2010, DOI: 10.4236/jemaa.2010.29073
Abstract: In Electromagnetic Welding (EMW) process, the capacitive energy is the source of input energy. The tool that is used for welding comprises of an electromagnetic coil. The job piece to be welded is placed in close proximity with the coil. The welding is achieved by impact, when the colliding job pieces are accelerated towards each other by the Lorentz force. The electromagnetic and mechanical properties/ parameters of the equipment, tool and the job govern the overall welding process. We have described a procedure to calculate the capacitive input energies for jobs of different sizes. Data is given for welding of strips of aluminium, copper and S.S. in similar and dissimilar combinations. Since the EMW technique is used in limited applications, this type of data is not available. We have validated our model with some data available in the literature. It is hoped that, this information will help the designer, to select and standardize the system and process parameters.
A Probabilistic Approach for Authenticating Text or Graphical Passwords Using Back Propagation
ASN Chakravarthy,Prof. P S Avadhani
Computer Science , 2011,
Abstract: Password authentication is a common approach to the system security and it is also a very important procedure to gain access to user resources. In the conventional password authentication methods a server has to authenticate the legitimate user. In our proposed method users can freely choose their passwords from a defined character set or they can use a graphical image as password and that input will be normalized. Neural networks have been used recently for password authentication in order to overcome pitfall of traditional password authentication methods. In this paper we proposed a method for password authentication using alphanumeric password and graphical password. We used Back Propagation algorithm for both alphanumeric (Text) and graphical password by which the level of security can be enhanced. This paper along with test results show that converting user password in to Probabilistic values enhances the security of the system
A -out-of- reliability system with an unreliable server and phase type repairs and services: the policy
Srinivas R. Chakravarthy,A. Krishnamoorthy,P. V. Ushakumari
International Journal of Stochastic Analysis , 2001, DOI: 10.1155/s1048953301000326
Abstract: In this paper we study a k-out-of-n reliability system in which a single unreliable server maintains n identical components. The reliability system is studied under the (N,T) policy. An idle server takes a vacation for a random amount of time T and then attends to any failed component waiting in line upon completion of the vacation. The vacationing server is recalled instantaneously upon the failure of the Nth component. The failure times of the components are assumed to follow an exponential distribution. The server is subject to failure with failure times exponentially distributed. Repair times of the component, fixing times of the server, and vacationing times of the server are assumed to be of phase type. Using matrix-analytic methods we perform steady state analysis of this model. Time spent by a failed component in service, total time in the repair facility, vacation time of the server, non-vacation time of the server, and time until failure of the system are all shown to be of phase type. Several performance measures are evaluated. Illustrative numerical examples are presented.
An extended reinforcement learning model of basal ganglia to understand the contributions of serotonin and dopamine in risk-based decision making, reward prediction, and punishment learning
Pragathi P. Balasubramani,V. Srinivasa Chakravarthy,Ahmed A. Moustafa
Frontiers in Computational Neuroscience , 2014, DOI: 10.3389/fncom.2014.00047
Abstract: Although empirical and neural studies show that serotonin (5HT) plays many functional roles in the brain, prior computational models mostly focus on its role in behavioral inhibition. In this study, we present a model of risk based decision making in a modified Reinforcement Learning (RL)-framework. The model depicts the roles of dopamine (DA) and serotonin (5HT) in Basal Ganglia (BG). In this model, the DA signal is represented by the temporal difference error (δ), while the 5HT signal is represented by a parameter (α) that controls risk prediction error. This formulation that accommodates both 5HT and DA reconciles some of the diverse roles of 5HT particularly in connection with the BG system. We apply the model to different experimental paradigms used to study the role of 5HT: (1) Risk-sensitive decision making, where 5HT controls risk assessment, (2) Temporal reward prediction, where 5HT controls time-scale of reward prediction, and (3) Reward/Punishment sensitivity, in which the punishment prediction error depends on 5HT levels. Thus the proposed integrated RL model reconciles several existing theories of 5HT and DA in the BG.
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