Showing papers by "Indian Institute of Technology Kharagpur published in 2008"
TL;DR: Use of cheaper raw materials and efficient biological hydrogen production processes will surely make them more competitive with the conventional H2 generation processes in near future.
643 citations
TL;DR: In this paper, the authors delineate the prospects and potentials of biohydrogen as a renewable energy resource and present a review of the potential of bio-hydrogen in the future.
587 citations
18 Aug 2008
TL;DR: It is found that links tend to be created by users who already have many links, that users tend to respond to incoming links by creating links back to the source, and that users link to other users who are already close in the network.
Abstract: Online social networking sites like MySpace, Orkut, and Flickr are among the most popular sites on the Web and continue to experience dramatic growth in their user population. The popularity of these sites offers a unique opportunity to study the dynamics of social networks at scale. Having a proper understanding of how online social networks grow can provide insights into the network structure, allow predictions of future growth, and enable simulation of systems on networks of arbitrary size. However, to date, most empirical studies have focused on static network snapshots rather than growth dynamics.In this paper, we collect and examine detailed growth data from the Flickr online social network, focusing on the ways in which new links are formed. Our study makes two contributions. First, we collect detailed data covering three months of growth, encompassing 950,143 new users and over 9.7 million new links, and we make this data available to the research community. Second, we use a first-principles approach to investigate the link formation process. In short, we find that links tend to be created by users who already have many links, that users tend to respond to incoming links by creating links back to the source, and that users link to other users who are already close in the network.
439 citations
TL;DR: This paper model the sequence of operations in credit card transaction processing using a hidden Markov model (HMM) and shows how it can be used for the detection of frauds and compares it with other techniques available in the literature.
Abstract: Due to a rapid advancement in the electronic commerce technology, the use of credit cards has dramatically increased. As credit card becomes the most popular mode of payment for both online as well as regular purchase, cases of fraud associated with it are also rising. In this paper, we model the sequence of operations in credit card transaction processing using a hidden Markov model (HMM) and show how it can be used for the detection of frauds. An HMM is initially trained with the normal behavior of a cardholder. If an incoming credit card transaction is not accepted by the trained HMM with sufficiently high probability, it is considered to be fraudulent. At the same time, we try to ensure that genuine transactions are not rejected. We present detailed experimental results to show the effectiveness of our approach and compare it with other techniques available in the literature.
430 citations
TL;DR: A review of published literatures on experimental and mathematical studies on bread baking during the last two decades is presented in this paper, where experimental and simulative studies on profiling of temperature, moisture content, pore volume, expansion ratio during baking are also reviewed.
363 citations
TL;DR: In this article, the effect of various PZT/CFO configurations having three, five, and nine layers has been systematically investigated by impedance and modulus spectroscopy, and the results showed evidence of three types of conduction process at elevated temperature: (i) low frequency $(l1\phantom{\rule{0.3em}{0ex}}\mathrm{MHz}$ and (ii) midfrequency conductivity $(l10\phantastic{\rule} 0.
Abstract: The electrical properties of ferroelectric $\mathrm{Pb}(\mathrm{Zr},\mathrm{Ti}){\mathrm{O}}_{3}$ (PZT) and ferromagnetic $\mathrm{Co}{\mathrm{Fe}}_{2}{\mathrm{O}}_{4}$ (CFO) thin film multilayers (MLs) fabricated by pulsed laser deposition technique has been studied by impedance and modulus spectroscopy. The effect of various PZT/CFO configurations having three, five, and nine layers has been systematically investigated. The transmission electron microscopy images revealed that the ML structures were at least partially diffused near the interface. Diffraction patterns indicate clear PZT and CFO crystal structures in the interior and at the interface of the ML structure. Room temperature micro-Raman spectra indicate separate PZT and CFO phases in ML structure without any impurity phase. We studied frequency and temperature dependencies of impedance, electric modulus, and ac conductivity of ML thin films in the ranges of $100\phantom{\rule{0.3em}{0ex}}\mathrm{Hz}\char21{}1\phantom{\rule{0.3em}{0ex}}\mathrm{MHz}$ and $200\char21{}650\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, respectively. We observed two distinct electrical responses in all the investigated ML films at low temperature $(l400\phantom{\rule{0.3em}{0ex}}\mathrm{K})$ and at elevated temperature $(g400\phantom{\rule{0.3em}{0ex}}\mathrm{K})$. We attributed these contributions to the grain effects at low temperature and grain boundary effects at high temperature. We explained this electrical behavior by Maxwell-Wagner-type contributions arising from the interfacial charge at the interface of the ML structure. Master modulus spectra indicate that the magnitude of grain boundary compared to grain becomes more prominent with the increase in the number of layer. The frequency dependent conductivity results well fitted with the double power law, $\ensuremath{\sigma}(\ensuremath{\omega})=\ensuremath{\sigma}(0)+{A}_{1}{\ensuremath{\omega}}^{{n}_{1}}+{A}_{2}{\ensuremath{\omega}}^{{n}_{2}}$, and the results showed evidence of three types of conduction process at elevated temperature: (i) low frequency $(l1\phantom{\rule{0.3em}{0ex}}\mathrm{kHz})$ conductivity is due to long-range ordering (frequency independent), (ii) midfrequency conductivity $(l10\phantom{\rule{0.3em}{0ex}}\mathrm{kHz})$ may be due to the short-range hopping, and (iii) high frequency $(l1\phantom{\rule{0.3em}{0ex}}\mathrm{MHz})$ conduction is due to the localized relaxation hopping mechanism.
338 citations
TL;DR: The unique formation of the MRAC with the instantaneous and steady-state reactive power completely eliminates the requirement of any flux estimation in the process of computation, so the method is less sensitive to integrator-related problems like drift and saturation.
Abstract: In this paper, a detailed study on the model reference adaptive controller (MRAC) utilizing the reactive power is presented for the online estimation of rotor resistance to maintain proper flux orientation in an indirect vector controlled induction motor drive. Selection of reactive power as the functional candidate in the MRAC automatically makes the system immune to the variation of stator resistance. Moreover, the unique formation of the MRAC with the instantaneous and steady-state reactive power completely eliminates the requirement of any flux estimation in the process of computation. Thus, the method is less sensitive to integrator-related problems like drift and saturation (requiring no integration). This also makes the estimation at or near zero speed quite accurate. Adding flux estimators to the MRAC, a speed sensorless scheme is developed. Simulation and experimental results have been presented to confirm the effectiveness of the technique.
331 citations
TL;DR: A genetic algorithm (GA) based fuzzy multi-objective approach for determining the optimum values of fixed and switched shunt capacitors to improve the voltage profile and maximize the net savings in a radial distribution system is presented.
329 citations
TL;DR: Sericin promotes proliferation of cells when used as a constituent of cell culture in serum-free media, and supports cell adhesion and proliferation when used in pure form and/or blended in matrices.
321 citations
TL;DR: The objective is to isolate the biologically active fraction of the lipopeptide biosurfactant produced by a marine Bacillus circulans and study its antimicrobial potentials.
Abstract: Aims: To isolate the biologically active fraction of the lipopeptide biosurfactant produced by a marine Bacillus circulans and study its antimicrobial potentials.
Methods and Results: The marine isolate B. circulans was cultivated in glucose mineral salts medium and the crude biosurfactant was isolated by chemical isolation method. The crude biosurfactants were solvent extracted with methanol and the methanol extract was subjected to reverse phase high-performance liquid chromatography (HPLC). The crude biosurfactants resolved into six major fractions in HPLC. The sixth HPLC fraction eluting at a retention time of 27·3 min showed the maximum surface tension-reducing property and reduced the surface tension of water from 72 mNm−1 to 28 mNm−1. Only this fraction was found to posses bioactivity and showed a pronounced antimicrobial action against a panel of Gram-positive and Gram-negative pathogenic and semi-pathogenic micro-organisms including a few multidrug-resistant (MDR) pathogenic clinical isolates. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of this antimicrobial fraction of the biosurfactant were determined for these test organisms. The biosurfactant was found to be active against Gram-negative bacteria such as Proteus vulgaris and Alcaligens faecalis at a concentration as low as 10 μg ml−1. The biosurfactant was also active against methicillin-resistant Staphylococcus aureus (MRSA) and other MDR pathogenic strains. The chemical identity of this bioactive biosurfactant fraction was determined by post chromatographic detection using thin layer chromatography (TLC) and also by Fourier transform infrared (FTIR) spectroscopy. The antimicrobial HPLC fraction resolved as a single spot on TLC and showed positive reaction with ninhydrin, iodine and rhodamine-B reagents, indicating its lipopeptide nature. IR absorption by this fraction also showed similar and overlapping patterns with that of other lipopeptide biosurfactants such as surfactin and lichenysin, proving this biosurfactant fraction to be a lipopeptide. The biosurfactant did not show any haemolytic activity when tested on blood agar plates, unlike the lipopeptide biosurfactant surfactin produced by Bacillus subtilis.
Conclusions: The biosurfactant produced by marine B. circulans had a potent antimicrobial activity against Gram-positive and Gram-negative pathogenic and semi-pathogenic microbial strains including MDR strains. Only one of the HPLC fractions of the crude biosurfactants was responsible for its antimicrobial action. The antimicrobial lipopeptide biosurfactant fraction was also found to be nonhaemolytic in nature.
Significance and impact of the study: This work presents a nonhaemolytic lipopeptide biosurfactant produced by a marine micro-organism possessing a pronounced antimicrobial action against a wide range of bacteria. There is a high demand for new antimicrobial agents because of the increased resistance shown by pathogenic micro-organisms against the existing antimicrobial drugs. This study provides an insight into the search of new bioactive molecules from marine micro-organisms.
319 citations
TL;DR: The GNEE electrode has been successfully used for the simultaneous detection of As(III), Cu(II), and Hg(II) at sub-part-per-billion level without any interference for the first time.
Abstract: Simultaneous electrochemical detection of As(III), Hg(II), and Cu(II) using a highly sensitive platform based on gold nanoelectrode ensembles (GNEEs) is described. GNEEs were grown by colloidal chemical approach on thiol-functionalized sol—gel derived three-dimensional silicate network preassembled on a polycrystalline gold (Au) electrode. GNEEs on the silicate network have been characterized by field emission scanning electron microscopy, X-ray diffraction, diffuse reflectance spectroscopy, and electrochemical measurements. Square wave anodic stripping voltammetry (SWASV) has been used for the detection of As(III) and Hg(II) without any interference from Cu(II) at the potentials of 0.06 and 0.53 V, respectively. The GNEE electrode is highly sensitive, and it shows linear response for As(III) and Hg(II) up to 15 ppb. The detection limit (signal-to-noise ratio = 4) of the GNEE electrode toward As(III) and Hg(II) is 0.02 ppb, which is well below the guideline value given by the World Health Organization (WH...
TL;DR: In this paper, the performance of Ricardo E6 engine using biodiesel obtained from mahua oil (B100) and its blend with high speed diesel (HSD) at varying compression ratio (CR), injection timing (IT), and engine loading (L) has been presented.
TL;DR: Acetic acid was found to be superior to formic acid for the in situ cottonseed oil epoxidation and was possible to obtain up to 78% relative conversion to oxirane with very lessOxirane cleavage by in situ technique.
TL;DR: A fuzzy clustering-based particle swarm (FCPSO) algorithm has been proposed to solve the highly constrained EED problem involving conflicting objectives and was able to provide a satisfactory compromise solution in almost all the trials, validating the efficacy and applicability of the proposed approach over the real-world multiobjective optimization problems.
Abstract: Economic dispatch is a highly constrained optimization problem encompassing interaction among decision variables. Environmental concerns that arise due to the operation of fossil fuel fired electric generators, transforms the classical problem into multiobjective environmental/economic dispatch (EED). In this paper, a fuzzy clustering-based particle swarm (FCPSO) algorithm has been proposed to solve the highly constrained EED problem involving conflicting objectives. FCPSO uses an external repository to preserve nondominated particles found along the search process. The proposed fuzzy clustering technique, manages the size of the repository within limits without destroying the characteristics of the Pareto front. Niching mechanism has been incorporated to direct the particles towards lesser explored regions of the Pareto front. To avoid entrapment into local optima and enhance the exploratory capability of the particles, a self-adaptive mutation operator has been proposed. In addition, the algorithm incorporates a fuzzy-based feedback mechanism and iteratively uses the information to determine the compromise solution. The algorithm's performance has been examined over the standard IEEE 30 bus six-generator test system, whereby it generated a uniformly distributed Pareto front whose optimality has been authenticated by benchmarking against the epsiv -constraint method. Results also revealed that the proposed approach obtained high-quality solutions and was able to provide a satisfactory compromise solution in almost all the trials, thereby validating the efficacy and applicability of the proposed approach over the real-world multiobjective optimization problems.
TL;DR: The underlying basic principles and processes involved in existing fluoride removal technologies are highlighted so as to catalyze further research in this area and highlight the lack of concise conceptual reviews in defluoridation research.
Abstract: Water is precious to us, as it supports every spheres of human life. The increasing reports on pollution of this “sacred resource” from different sources show our scant regard to this pivotal issue. People in more than 35 nations across the globe face issues of excess fluoride in drinking water, the intensity and severity of which varies with the environmental settings in terms of their geographical and economical status. It has been observed that very few proven sustainable options are available for fluoride removal, especially in developing countries, where the impact of the issue is highly intense. Though the considerable amount of research undertaken worldwide has thrown up many technologies, each having its own advantages and limitations, a lasting solution is still at large. The coagulation and adsorption/ion-exchange processes are the most widely opted defluoridation techniques practiced in fluoride-endemic areas. The Nalgonda technique and adsorption by bone char, or a combination of both, have be...
TL;DR: In this paper, an Al-7Si alloy reinforced with in situ TiB 2 particles was synthesized successfully by using salt reaction route and the in situ composites have shown significant improvement in mechanical properties in comparison to the base alloy.
TL;DR: In this paper, the authors report the mechanical, morphological, water absorption, thermal conductivity, and thermal behavior of rigid polyurethane foam varying with the density, which controls the foam architecture.
Abstract: Density is an important parameter that influences the properties and performances of rigid polyurethane foam (PUF). Rigid PUF with different densities were prepared by varying the amount of distilled water as blowing agent. This investigation reports the mechanical, morphological, water absorption, thermal conductivity, and thermal behavior of rigid PUF varying with the density, which controls the foam architecture. The density of the PUF decreased from 116 to 42 kg/m3 with an increase in the amount of water from 0.1 to 3.0 parts per hundred polyol by weight (phr), respectively. It was found that the mechanical properties of the PUFs changed with the foam density. The results of water absorption of the PUFs showed that water absorption increased with decrease in density, due to increase in the cell size and decrease in the cell-wall thickness. The thermal conductivity measurements showed that the thermal conductivity decreased with increase in density. It was due to the decrease in cell size. The thermal analysis of the PUFs shows that the glass transition temperature increases with the decrease in foam density, but the thermal stability decreases with the decrease in foam density. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
21 Apr 2008
TL;DR: A hybridization of collaborative filtering and content based recommendation system where attributes used for content based recommendations are assigned weights depending on their importance to users.
Abstract: We propose a hybridization of collaborative filtering and content based recommendation system. Attributes used for content based recommendations are assigned weights depending on their importance to users. The weight values are estimated from a set of linear regression equations obtained from a social network graph which captures human judgment about similarity of items.
TL;DR: A novel algorithm is proposed for segmenting an image into multiple levels using its mean and variance, making use of the fact that a number of distributions tend towards Dirac delta function, peaking at the mean, in the limiting condition of vanishing variance.
TL;DR: In this article, the authors make a comprehensive review pertaining to fundamental studies on thermodynamic irreversibility and exergy analysis in the processes of combustion of gaseous, liquid and solid fuels.
TL;DR: The proposed technique, computationally more efficient than the spatial domain based method, is found to provide better enhancement compared to other compressed domain based approaches.
Abstract: This paper presents a new technique for color enhancement in the compressed domain. The proposed technique is simple but more effective than some of the existing techniques reported earlier. The novelty lies in this case in its treatment of the chromatic components, while previous techniques treated only the luminance component. The results of all previous techniques along with that of the proposed one are compared with respect to those obtained by applying a spatial domain color enhancement technique that appears to provide very good enhancement. The proposed technique, computationally more efficient than the spatial domain based method, is found to provide better enhancement compared to other compressed domain based approaches.
15 Feb 2008-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, a series of ferrite-bainite dual-phase (FBDP) steels containing wide variation of the harder constituents have been prepared from a low carbon Nb-micro-alloyed base material by suitable heat treatments.
Abstract: This investigation aims to examine structure–property relations of ferrite–bainite dual-phase (FBDP) steels and to compare these against that of ferrite–martensite dual-phase (FMDP) steels. For this purpose, a series of FBDP and FMDP steels containing wide variation (20–90%) of the harder constituents have been prepared from a low carbon Nb-micro-alloyed base material by suitable heat treatments. Hardness and tensile properties of the developed steels have been examined against the volume fraction of bainite or martensite. The nature of variation of the estimated mechanical properties such as hardness, yield and tensile strength, percentage elongation and strain-hardening exponent with the amount of the harder constituents of the FBDP and FMDP steels exhibits subtle to significant differences. These differences have been explained using the influence of the nature of the microstructural constituents and their mutual interactions. Low carbon FBDP steel with 60–70% bainite appears to possess excellent potential for structural applications.
TL;DR: In this paper, open-loop resonators loaded by shunt open stubs are proposed to design compact dual-band bandpass filters with improved out-of-band rejection characteristics.
Abstract: In this paper, open-loop resonators loaded by shunt open stubs are proposed to design compact dual-band bandpass filters with improved out-of-band rejection characteristics. The second passband of the dual-band filter is obtained by tuning higher resonant modes of the open-loop resonator by the stub length and position. A tapped-line input/output feed structure is used for external coupling. Required external coupling is obtained by adjusting the tapping position and dimension of the stub-loaded resonator. A lossless transmission line model is used to determine the resonance properties of the resonator and the external quality factor. Theoretical predictions are verified by the experimental results of three dual-band filters.
TL;DR: In this paper, the impact of Al2Cu and Ag2Al nanoparticle size and volume fraction on the effective thermal conductivity of water and ethylene glycol based nanofluid prepared by a two-stage process comprising mechanical alloying of appropriate Al-Cu and Al-Ag elemental powder blend followed by dispersing these nanoparticles (1 to 2 vol pct) in water and glycol with different particle sizes.
Abstract: Nanofluids, containing nanometric metallic or oxide particles, exhibit extraordinarily high thermal conductivity. It is reported that the identity (composition), amount (volume percent), size, and shape of nanoparticles largely determine the extent of this enhancement. In the present study, we have experimentally investigated the impact of Al2Cu and Ag2Al nanoparticle size and volume fraction on the effective thermal conductivity of water and ethylene glycol based nanofluid prepared by a two-stage process comprising mechanical alloying of appropriate Al-Cu and Al-Ag elemental powder blend followed by dispersing these nanoparticles (1 to 2 vol pct) in water and ethylene glycol with different particle sizes. The thermal conductivity ratio of nanofluid, measured using an indigenously developed thermal comparator device, shows a significant increase of up to 100 pct with only 1.5 vol pct nanoparticles of 30- to 40-nm average diameter. Furthermore, an analytical model shows that the interfacial layer significantly influences the effective thermal conductivity ratio of nanofluid for the comparable amount of nanoparticles.
TL;DR: Filippov's method - which has commonly been applied to mechanical switching systems - can be used fruitfully in power electronic circuits to achieve the same end by describing the behavior of the system during the switchings by combining this and the Floquet theory.
Abstract: To study the stability of a nominal cyclic steady state in power electronic converters, it is necessary to obtain a linearization around the periodic orbit. In many past studies, this was achieved by explicitly deriving the Poincare map that describes the evolution of the state from one clock instant to the next and then locally linearizing the map at the fixed point. However, in many converters, the map cannot be derived in closed form, and therefore this approach cannot directly be applied. Alternatively, the orbital stability can be worked out by studying the evolution of perturbations about a nominal periodic orbit, and some studies along this line have also been reported. In this paper, we show that Filippov's method - which has commonly been applied to mechanical switching systems - can be used fruitfully in power electronic circuits to achieve the same end by describing the behavior of the system during the switchings. By combining this and the Floquet theory, it is possible to describe the stability of power electronic converters. We demonstrate the method using the example of a voltage-mode-controlled buck converter operating in continuous conduction mode. We find that the stability of a converter is strongly dependent upon the so-called saltation matrix - the state transition matrix relating the state just after the switching to that just before. We show that the Filippov approach, especially the structure of the saltation matrix, offers some additional insights on issues related to the stability of the orbit, like the recent observation that coupling with spurious signals coming from the environment causes intermittent subharmonic windows. Based on this approach, we also propose a new controller that can significantly extend the parameter range for nominal period-1 operation.
TL;DR: The proposed method would be particularly advantageous over FDM in the manufacturing of thin, curved parts (shells) by reduction of stair-step effect, increase in strength and reduction in the number of layers.
Abstract: Extruder path generation for a new rapid prototyping technique named ''Curved Layer Fused Deposition Modeling'' (CLFDM) has been presented. The prototyping technique employs deposition of material in curved layers in contrast to flat layers as in Fused Deposition Modeling (FDM). The proposed method would be particularly advantageous over FDM in the manufacturing of thin, curved parts (shells) by reduction of stair-step effect, increase in strength and reduction in the number of layers. The criteria for the generation of tool paths for CLFDM are proper orientation of filaments and appropriate bonding between adjacent filaments in same layer and in successive layers.
TL;DR: Analysis by gas chromatography, high performance thin layer chromatography and Fourier transform infrared spectroscopy showed that the biosurfactant could effectively entrap and solubilize PAH.
TL;DR: In this paper, Yttrium (Y) modified nanocrystalline samples of BiFeO3 (BFO) were prepared by a metal ion ligand complex-based precursor-solution evaporation method.
Abstract: Yttrium (Y) modified nanocrystalline samples of BiFeO3 (BFO) were prepared by a metal ion ligand complex-based precursor-solution evaporation method. Partial substitution of Y (0–15%) at the Bi site results in structural change (rhombohedral to tetragonal) and single phase formation. With increasing Y concentration, enhancement in dielectric ordering, reduction in loss tangent and improvement in magnetic ordering in BFO were observed. Diffuse peaks in both permittivity and loss tangent were observed at 207 °C and 222 °C, respectively, for 15% substitution of Y. In all the Y substituted BFO samples, a switching behavior in low fields was observed in the field dependence of magnetization, even at room temperature, and this behavior was found to be improved with increasing Y concentration.
TL;DR: In this article, a polycrystalline sample of (Na0.5Bi 0.5)(Zr0.25Ti 0.75)O3 was prepared using a high-temperature solid-state reaction technique.
TL;DR: In this article, a C0 finite element formulation is used to carry out free vibration analysis of curved panels using a higher-order formulation, which includes Sanders' approximation for doubly curved shells considering the effects of rotary inertia and transverse shear.