Journal Articles
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Item Review on physical and chemical properties of low and high-temperature polymer electrolyte membrane fuel cell (PEFC) sealants(Elsevier Ltd, 2022) Kumar, V.; Koorata, P.K.; Shinde, U.; Padavu, P.; George, S.C.Sealants (or gaskets) play an exceptional role in the efficient functioning of polymer electrolyte membrane fuel cells (PEFCs). They prevent leakage of reactant gases and coolants from the perimeter of cell. Also, they circumvent the direct mixing of reactant gases in the active region of the PEFC. Sealants ensure electrical insulation, preventing a short circuit between anode and cathode of the PEFCs. Sealants enhance the safety, thereby improving the functional performance of the PEFCs. In addition, the sealants have functional requirements that contain excellent physical and chemical properties to withstand the working conditions of PEFCs. Hence, the physical and chemical properties of the sealants are crucial for improving the sealing capability as well as the performance of PEFC. In this article, properties such as weight loss, indentation load, elastic modulus, hardness, hysteresis loss, chemical composition and chemical structure of well-known PEFC sealants are reviewed. These PEFC sealants are classified into low-temperature PEFC (LT-PEFC) and high-temperature PEFC (HT-PEFC) sealants, depending on the operational temperature. The polymeric materials such as silicone rubber, fluoroelastomers (FKM), ethylene propylene diene monomer (EPDM) rubber, polytetrafluoroethylene (PTFE) rubber, etc. are found to be suitable sealant materials for PEFCs. © 2022 Elsevier LtdItem Hydrodynamic performance characteristics of semicircular breakwater—wave run-up and run-down(2010) Hegde, A.V.; Ganesh, C.; Kumar, V.Breakwaters are structures protecting a shore area, harbor, anchorage, or a basin from the fury of ocean waves. They create calm waters and give protection for safe mooring, operating and handling of ships, and provide protection to harbor facilities. Semicircular breakwaters are becoming increasingly popular these days, as they have high stability against the action of waves. The paper explains the physical model studies to evaluate the wave run-up (Rd/Hi) and wave run-down (Rd/Hi) on semicircular breakwater model for various incident wave heights H, wave periods T, water depths d and spacing (S) to diameter (D) ratios of perforations (S/D). It is found that relative wave run-up increases with the increase in wave steepness (Hi/gT2) and relative run-down decreases with the increase in wave steepness. Relative wave run-up and wave run-down values increase with the increase in depth parameter (d/gT2). The relative run-up and run-down values decrease with increasing perforations (decreasing S/D values) in breakwater. © 2010 Taylor & Francis Group, LLC.Item Equilibrium and kinetic study for the removal of malachite green using activated carbon prepared from Borassus flabellofer male flower(2010) JagadeeshBabu, P.E.; Kumar, V.; Visvanathan, R.Activated carbon was prepared from dried Borassus flabellofer male flower and batch adsorption experiments were conducted to study its potential to remove malachite green (MG) dye. The process was further optimized by studying the operating variables like initial pH of the stock solution, activation temperature, initial dye concentration, adsorbent loading and contact time. The optimized pH and activation temperatures were found to be 7.55 and 450.C respectively, where further analysis was made using these optimal variables. Linear, Freundlich and Langmuir isotherms were studied and it was found that the Langmuir isotherms have the highest correlation coefficients compared to the others. Further, the sorption kinetics were analysed using pseudo-first-order and pseudo-second-order kinetic models. The data showed that the second-order equation was the more appropriate, which indicate that the intra-particle diffusion is the rate limiting factor. © 2009 Curtin University of Technology and John Wiley & Sons, Ltd.Item Synthesis, structural analysis and solvatochromic behaviour of 4,6-bis (4-butoxyphenyl)-2-methoxynicotinonitrile mesogen(2013) Ahipa, T.N.; Kumar, V.; Vasudeva Adhikari, A.V.In this communication, we report the synthesis and characterisation of a new luminescent liquid crystalline material, 4,6-bis (4-butoxyphenyl)-2-methoxynicotinonitrile (3). We have confirmed its structure by Fourier transform infrared and 1H nuclear magnetic resonance spectroscopy, elemental analysis and X-ray single crystal diffraction studies. The newly synthesised compound crystallises in a monoclinic system with the space group C2/c and its cell parameters are found to be a = 25.181(4) Å, b = 15.651(4)Å, c = 12.703(19) Å, V = 4880.4 (16) Å, Z = 8. The results indicate that the presence of weak CH... O and CH... N hydrogen bonding as short-range intermolecular interactions are responsible for the formation of its crystal assembly. The measured torsion angle shows the existence of a distorted structure for the molecule wherein 4-butoxyphenylene ring substituent at the fourth position of the central pyridine ring forms a torsion angle ?[C(4), C(3), C(10), C(19)] of 40.55°. Its liquid crystalline behaviour was investigated with the aid of polarised optical microscopy and differential scanning calorimetry. The study reveals that the compound displays a broad nematic phase in the range of 78-112°C. Further, solution phase optical studies indicate that it is a blue light emitter in different non-polar and polar organic solvents at a concentration of 10-5M. © 2013 Copyright Taylor and Francis Group, LLC.Item Identification and characterization of novel indole based small molecules as anticancer agents through SIRT1 inhibition(2013) Panathur, N.; Udayakumar, U.; Koushik, P.V.; Alvala, M.; Yogeeswari, P.; Sriram, D.; Kumar, V.In our pursuit to develop new potential anticancer leads, we designed a combination of structural units of indole and substituted triazole; and a library of 1-{1-methyl-2-[4-phenyl-5-(propan-2-ylsulfanyl)-4H-1,2,4-triazol-3- yl]-1H-indol-3-yl}methanamine derivatives was synthesized and characterized. Cytotoxic evaluations of these molecules over a panel of three human cancer cell lines were carried out. Few molecules exhibited potent growth inhibitory action against the treated cancer cell lines at lower micro molar concentration. An in vitro assay investigation of these active compounds using recombinant human SIRT1 enzyme showed that one of the compounds (IT-14) inhibited the deacetylation activity of the enzyme. The in vivo study of IT-14 exemplified its promising action by reducing the prostate weight to the body weight ratio in prostate hyperplasia animal models. A remarkable decrease in the disruption of histoarchitecture of the prostate tissues isolated from IT-14 treated animal compared to that of the positive control was observed. The molecular interactions with SIRT1 enzyme were also supported by molecular docking simulations. Hence this compound can act as a lead molecule to treat prostatic hyperplasia. © 2013 Elsevier Masson SAS. All rights reserved.Item Application of ISM technique for analysis of the procurement related attributes in JIT supply chain management(Inderscience Publishers, 2014) Mishra, O.P.; Kumar, V.; Garg, D.The fierce competition in selling a product has made us have to think differently. The supply chain is one issue in front of each production firm to compete with another and to get privilege of another. The excellence of the supply chain is possible only when the product is of the best quality while being cost competitive. The reduction of the production cost has become the focus point in reducing the overall cost of the supply chain. This paper focuses JIT procurement process in the SC to cut one the overall costs. To estimate the factors affecting the JIT procurement (JP) we have recognised the important attributes from the literatures. A questionnaire-based survey was carried out to give the ranking of the attributes found from literature and then an interpretative structural model (ISM) is prepared to link the levels of importance of the JP attributes among themselves. On the basis of levels of the attributes managerial staff are suggested to focus on the particular issues to make the JP successful, therefore making the JIT supply chain management successful even in the worst scenario. Copyright © 2014 Inderscience Enterprises Ltd.Item New columnar liquid crystal materials based on luminescent 2-methoxy-3-cyanopyridines(Springer New York LLC journals@springer-sbm.com, 2014) Ahipa, T.N.; Kumar, V.; Vasudeva Adhikari, A.V.A new series of donor-acceptor-donor (D-A-D) type luminescent mesogens carrying 2-methoxy-3-cyanopyridine as a central core linked with variable alkoxy chain lengths (m = 6 and 8) as terminal substituents was synthesized and characterized using spectral methods. The newly synthesized molecules were subjected to single-crystal X-ray diffraction (SCXRD), powder X-ray diffraction (PXRD), differential scanning calorimetric (DSC), polarizing optical microscopy (POM), and fluorescence emission studies in order to ascertain their mesogenic and photophysical properties. The SCXRD data on 4a and 4b reveal that the presence of short intermolecular contacts, viz. C-H···N, C-H···O, C-H···?, and ?···? interactions, is responsible for their crystal packing. The measured torsion angle values indicate that molecules possess distorted non-planar structure. The DSC, POM, and PXRD studies confirm that all the molecules show thermotropic liquid crystalline behaviour and exhibit rectangular columnar phase. Further, their UV-visible and fluorescence spectral studies reveal that the target molecules are luminescent displaying a strong absorption band in the range of 335-340 nm and a blue fluorescence emission band in the range of 395-425 nm (both in solution and film state) with good fluorescence quantum yields (10-49 %). © 2014 Springer Science+Business Media New York.Item New luminescent 2-methoxy-6-(4-methoxy-phenyl)-4-p-tolyl-nicotinonitrile: Synthesis, crystal structure, DFT and photophysical studies(2014) Ahipa, T.N.; Kamath, P.R.; Kumar, V.; Vasudeva Adhikari, A.V.In the current communication, we report the synthesis, spectroscopic, crystal structure, DFT and photophysical studies of a new nicotinonitrile derivative, viz. 2-methoxy-6-(4-methoxy-phenyl)-4-p-tolyl-nicotinonitrile (2) as a potential blue light emitting material. The compound 2 was synthesized in good yield via a simple route. The acquired spectral and elemental analysis data were in consistent with the chemical structure of 2. The single crystal study further confirms its three dimensional structure, molecular shape, and nature of short contacts. Its DFT calculations reveal that compound 2 possesses a non-planar structure and its theoretical IR spectral data are found to be in accordance with experimental values. In addition, its UV-visible and fluorescence spectral measurements prove that the compound exhibits good absorption and fluorescence properties. Also, it shows positive solvatochromic effect when the solvent polarity was varied from non-polar to polar. © 2014 Elsevier B.V. All rights reserved.Item New 4-(2-(4-alkoxyphenyl)-6-methoxypyridin-4-yl)benzonitriles: Synthesis, liquid crystalline behavior and photo physical properties(Royal Society of Chemistry, 2014) Ahipa, T.N.; Kumar, V.; Shankar Rao, D.S.; Prasad, S.K.; Vasudeva Adhikari, A.V.A new series of luminescent 4-(2-(4-alkoxyphenyl)-6-methoxypyridin-4-yl) benzonitriles containing three ring systems, viz. methoxy pyridine, benzonitrile and alkoxy benzene with variable alkoxy chain length, with bent-core structures were synthesized as potential mesogens and characterized by spectral techniques. Their liquid crystalline behavior was investigated by polarizing optical microscopy (POM), differential scanning calorimetry (DSC) and variable temperature powder X-ray diffraction (PXRD) measurements. The study reveals that compounds with shorter chain lengths [i.e. m = 4] exclusively exhibit the nematic phase while compounds with longer chain lengths [i.e. m = 6-14 (only even)] show predominantly the orthorhombic columnar phase. Single crystal X-ray analysis of 4-(2-(4-butyloxy/octyloxyphenyl)-6-methoxypyridin-4-yl)benzonitriles reveals that they possess slightly non-planar unsymmetrical bent structures and their molecular packing consists of nonconventional H-bond interactions; it also explains the observed liquid crystalline phase. An optical study indicates that the title compounds are good blue emitting materials showing absorption and emission bands in the range 335-345 nm and 415-460 nm, respectively. An electrochemical study of 4-(2-(4-octyloxyphenyl)-6-methoxypyridin-4-yl) benzonitrile shows a band gap of 1.89 eV with HOMO and LUMO energy levels of -5.06 and -3.17 eV, respectively. Also, density functional theory (DFT) calculations confirm its optimized geometry, electronic absorption and frontier molecular orbital distributions. © the Partner Organisations 2014.Item Solving security issues in Docker using Stackelberg Games(Serials Publications serialspublications@vsnl.net, 2016) Sharath, N.; Kumar, V.; Chandrasekaran, K.Container technology has taken the world by storm and is replacing virtual machines rapidly. Docker is an open source tool that has implemented containers based on the linux ecosystem. Being lightweight and scalable, Docker has made data scaling very simple. Despite the obvious success of Dockerized applications, certain faults hold it back when it comes to usage in organizations that work with distributed teams. From a security standpoint, it is essential to be aware of scenarios that could cause the downfall of a company's entire network ecosystem with a single command. The study begins with a deep dive into Docker's code base and stress tests that have unearthed some more security issues. Taking into account one such issue related to networking in a multi-container environment gives rise to play on the trade off between efficiency of resource usage in a container, to its security. Using the backward induction technique of a stackelberg competition model, the efficiency of the distributed system can be made a function of its security and functionality. Solutions for both the scenarios where the attacker's type is known and unknown have been proposed using game theoretic approaches. A comparison on Machine Learning and Linear Programming based approaches give rise to the most optimal method for adopting a defense strategy in case of attacks in such distributed systems. © International Science Press.
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