Showing papers by "Indian Institute of Technology Guwahati published in 2002"
TL;DR: A new method of synthesis of an Au nanoparticle-conductive polyaniline composite is reported by using H2O2 both for reduction of HAuCl4 and polymerization of aniline in the same aqueous medium, with electrical conductivity measured to be two orders of magnitude higher than the polymer itself.
207 citations
TL;DR: In this article, a class of higher order compact (HOC) schemes with weighted time discretization for the two-dimensional unsteady convection-diffusion equation with variable convection coefficients was developed.
Abstract: A class of higher order compact (HOC) schemes has been developed with weighted time discretization for the two-dimensional unsteady convection-diffusion equation with variable convection coefficients. The schemes are second or lower order accurate in time depending on the choice of the weighted average parameter μ and fourth order accurate in space. For 0.5 ≤ μ ≤ 1, the schemes are unconditionally stable. Unlike usual HOC schemes, these schemes are capable of using a grid aspect ratio other than unity. They efficiently capture both transient and steady solutions of linear and nonlinear convection-diffusion equations with Dirichlet as well as Neumann boundary condition. They are applied to one linear convection-diffusion problem and three flows of varying complexities governed by the two-dimensional incompressible Navier-Stokes equations
160 citations
TL;DR: A comprehensive review on polyphenolic compounds is presented in this paper, focusing on the structural and functional implications on the regiochemistry as well as on the stereochemistry of oligomeric polyphenols.
Abstract: A comprehensive review on the polyphenolic compounds is presented. The emphasis is placed on the structural and functional implications on the regiochemistry as well as on the stereochemistry of oligomeric polyphenols. A correlation between the natural polyphenolic compounds and the synthetic ones is highlighted by making a general classification of polyphenolic compounds. The uses and applications of polyphenolic compounds are discussed in detail.
123 citations
TL;DR: Chemoselective acetalization of an aldehyde in the presence of ketone, unsymmetrical acetal formation, shorter reaction times, mild reaction conditions, the stability of acid-sensitive protecting groups, high efficiencies, facile isolation of the desired products, and the catalytic nature of the reagent make the present methodology a practical alternative.
Abstract: Acyclic and cyclic acetals of various carbonyl compounds were obtained in excellent yields under a mild reaction condition in the presence of trialkyl orthoformate and a catalytic amount of tetrabutylammonium tribromide (TBATB) in absolute alcohol. Chemoselective acetalization of an aldehyde in the presence of ketone, unsymmetrical acetal formation, shorter reaction times, mild reaction conditions, the stability of acid-sensitive protecting groups, high efficiencies, facile isolation of the desired products, and the catalytic nature of the reagent make the present methodology a practical alternative.
117 citations
TL;DR: In this paper, a collapsed dimension method was used to solve the combined conduction-radiation problem using a gray planar absorbing, emitting and anisotropically scattering medium, where non-dimensional medium temperature and heat flux distributions were found for various values of boundary temperature, optical thickness, boundary emissivity and conductionradiation parameter.
44 citations
TL;DR: In this article, the free vibration behavior of rotating blades modeled as laminated composite, hollow (single celled) boxed beams is investigated, and a geometrically nonlinear structural model incorporating a number of non- classical effects such as anisotropy, heterogeneity, transverse shear flexibility, and warping inhibition is developed.
42 citations
TL;DR: Both cyclic and acyclic acetals were deprotected to give the corresponding aldehydes in acetonitrile, and are transformed to methyl esters in methanol, on treatment with a catalytic quantity of V2O5 and H2O2 under identical conditions acid sensitive alcohol protecting groups, such as tetrahydropyranyl and tert-butyldimethylsilyl ethers, were cleaved regenerating the corresponding alcohols.
40 citations
TL;DR: In this article, the role of copper complexes to delineate structure reactivity correlation to perform selective oxidative transformations is discussed, and the recent developments on various copper catalysed as well as stoichiometric organic oxidative reactions involving copper complexes are discussed.
Abstract: Copper containing enzymes are indispensable for their ability to act as oxygen carrier and oxidation reactions of different substrates. The recent developments on various copper catalysed as well as stoichiometric organic oxidative reactions involving copper complexes are discussed. The emphasis is put on the state of art on the role of copper complexes to delineate structure reactivity correlation to perform selective oxidative transformations.
36 citations
TL;DR: In this article, a-SiGe:H thin films and n-i-p solar cells for GeH 4 /Si 2 H 6 ratio varying from 1.37 to 1.84 eV were investigated.
Abstract: We report our systematic studies on a-SiGe:H thin films and n-i-p solar cells for GeH 4 /Si 2 H 6 ratio varying from 1.43 to 0. This results in a variation of band gap from 1.37 to 1.84 eV. The FTIR studies show that the total hydrogen content in these films decreases as Ge content increases. For Ge rich films, the hydrogen also goes in to Ge-H mode. I V measurements on n-i-p solar cells with i-layer having different Ge content show that as Ge content increase, Short circuit current (J sc ) increases, whereas open circuit voltage (V oc ). fill factor (FF) and conversion efficiency (η) decrease. For Ge rich films, J sc does not significantly increase after GeH 4 /Si 2 H 6 ratio increases beyond 0.72; however V oc , FF and η decrease drastically. The quantum efficiency (QE) measurements in the subgap absorption range show that band gap and Urbach slope of the i-layer can very well be estimated in the devices.
32 citations
TL;DR: This paper is on the development of an educational tool, based on freeware, for the introduction of various Web-related aspects of remote instrumentation, with an important ingredient for handling multiple clients through a scheduling strategy that uses semaphores.
Abstract: With the growth of the Internet, an interesting possibility is that of performing research, development, and collaborative experimentation unlimited by physical location. The focus of this paper is on the development of an educational tool, based on freeware, for the introduction of various Web-related aspects of remote instrumentation. An important ingredient of the system is a mechanism for handling multiple clients through a scheduling strategy that uses semaphores. Other features include provisions for multiple-instrument access and output of the data acquired in textual and graphical forms. The approach is cost-effective, and the solution is suitable for a variety of platforms. Experiments using two instruments, namely a digital multimeter and a thermocouple unit, are reported.
30 citations
TL;DR: A neural network model was designed and trained to predict the steady-state performance of a UASB reactor treating high-strength (unrefined sugar based) wastewater and provided important insights into key variables that were responsible for influencing the working of the U ASB reactor under varying input conditions.
Abstract: Up-flow anaerobic sludge blanket (UASB) reactors are being used with increasing regularity all over the world, especially in India, for a variety of wastewater treatment operations. Consequently, there is a need to develop methodologies enabling one to determine UASB reactor performance, not only for designing more efficient UASB reactors but also for predicting the performance of existing reactors under various conditions of influent wastewater flows and characteristics. This work explores the feasibility of application of an artificial neural network-based model for simulating the performance of an existing UASB reactor. Accordingly, a neural network model was designed and trained to predict the steady-state performance of a UASB reactor treating high-strength (unrefined sugar based) wastewater. The model inputs were organic loading rate, hydraulic retention time, and influent bicarbonate alkalinity. The output variables were one or more of the following, effluent substrate concentration (Se), reactor bicarbonate alkalinity, reactor pH, reactor volatile fatty acid concentration, average gas production rate, and percent methane content of the gas. Training of the neural network model was achieved using a large amount of experimentally obtained reactor performance data from the reactor mentioned above as the training set. Training was followed by validation using independent sets of performance data obtained from the same UASB reactor. Subsequently, simulations were performed using the validated neural network model to determine the impact of changes in parameters like influent chemical oxygen demand (COD) concentration and hydraulic retention time on the reactor performance. Simulation results thus obtained were carefully analyzed based on qualitative understanding of UASB process and were found to provide important insights into key variables that were responsible for influencing the working of the UASB reactor under varying input conditions. © 2002 John Wiley & Sons, Inc. Biotechnol Bioeng 77: 806–814, 2002; DOI 10.1002/bit.10168
TL;DR: In this paper, a technique of lithography in thin polyaniline film formed at the air-water interface, by simultaneous chemical and photochemical polymerization of aniline, was reported.
Abstract: We report here a new technique of lithography in thin polyaniline film formed at the air-water interface, by simultaneous chemical and photochemical polymerization of aniline. A solution of aniline in acidic KBrO 3 / KBr polymerized to form thin film at the air-water interface. When the polymerization was carried out in the presence of light at the interface, a macroscopic pattern could be seen formed on the film in the shape and size of the incident light beam. A desirable shape of the pattern could be achieved by using appropriate optical mask. The lithographic pattern could be imprinted using incident light of wavelength in the range of 320-650 nm. Observation under optical microscope revealed that nucleation pattern of polymer growth was absent in the area of the polymer film grown in the presence of light that otherwise was present in the film formed in dark. FTIR spectra of polymer films grown in light and dark were the same.
12 Aug 2002
TL;DR: It is shown that caching of routes in AODV can lead to significant reduction in routing and MAC load as well as in delay in delivering the packet as compared to A ODV without much compromise in terms of packet delivery fraction.
Abstract: Ad hoc networks are characterized by multihop wireless connectivity, frequently changing network topology and the need for efficient dynamic routing protocols. Recent comparative studies between Ad hoc on demand routing protocols like Ad hoc On demand Distance Vector routing (AODV) and Dynamic Source Routing (DSR) (the two on demand routing protocols for Ad hoc networks) have shown that AODV performs better than DSR for high mobility cases but faces the problem of high routing and MAC load as compared to DSR. This is because DSR resort to aggressive use of caching of routes while AODV does not. In this paper, we have incorporated caching of routes in AODV with the aim to reduce the routing and MAC load of AODV without changing the basic structure of the protocol. A detailed simulation model with MAC and physical layer models is used to study the effect of caching of routes in AODV and to compare its performance with AODV without cache and DSR. We show that caching of routes in AODV can lead to significant reduction in routing and MAC load as well as in delay in delivering the packet as compared to AODV without much compromise in terms of packet delivery fraction.
TL;DR: The analysis in the present paper improves upon the earlier results of Baker and Dougalis under the minimum smoothness assumptions of Rauch for a purely second‐order hyperbolic equation with quadrature.
Abstract: In this article, the effect of numerical quadrature on the finite element Galerkin approximations to the solution of hyperbolic equations has been studied. Both semidiscrete and fully discrete schemes are analyzed and optimal estimates are derived in the L∞(H1), L∞(L2) norms, whereas quasi-optimal estimate is derived in the L∞(L∞) norm using energy methods. The analysis in the present paper improves upon the earlier results of Baker and Dougalis [SIAM J Numer Anal 13 (1976), pp 577–598] under the minimum smoothness assumptions of Rauch [SIAM J Numer Anal 22 (1985), pp 245–249] for a purely second-order hyperbolic equation with quadrature. © 2002 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 18: 537–559, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/num.10022
TL;DR: A general formulation for analysis of sound field in a uniform flow duct lined with bulk-reacting sound-absorbing material is presented, which can be used as guidelines for the acoustic design of silencers, air-conditioning ducts, industrial fans, and other similar applications.
Abstract: A general formulation for analysis of sound field in a uniform flow duct lined with bulk-reacting sound-absorbing material is presented here. Presented theoretical model predicts the rate of attenuation for symmetric as well as asymmetric modes in rectangular duct lined with loosely bound (bulk-reacting) sound-absorbing material, which allows acoustic propagation through the lining. The nature of attenuation in rectangular ducts lined on two and four sides with and without mean flow is discussed. Computed results are compared with published theoretical and experimental results. The presented model can be used as guidelines for the acoustic design of silencers, air-conditioning ducts, industrial fans, and other similar applications.
TL;DR: In this article, the dc electrical conduction in xV 2 O 5 20SnO (80 - x)TeO 2 (18 mol% < x < 50 mol%) glasses has been studied in the temperature range from 100 to 480 K.
Abstract: The dc electrical conduction in xV 2 O 5 20SnO (80 - x)TeO 2 (18 mol% < x < 50 mol%) glasses has been studied in the temperature range from 100 to 480 K. Glasses with x < 20 exhibited p-type conduction whereas the rest show n-type conduction. All the glass compositions exhibited a crossover from variable range hopping (VRH) to small polaron hopping (SPH) conduction at a characteristic temperature well below room temperature. The low temperature dc conduction mechanism in these glasses has been analysed using Mott's approach. Mott parameter analysis gave values for the density of states at the Fermi level N(E F ) between 1.42 × 10 26 m -3 eV -1 and 15.0 x 10 26 m -3 eV -1 at 230 K. The disorder energy W d was found to be varying between 0.02 and 0.03 eV. N(E F ), the average hopping distance R VRH and the VRH-SPH transition temperature T R exhibit an interesting composition dependence, which is interpreted in terms of the majority charge carrier reversal (MCCR) phenomenon occurring in these glasses.
TL;DR: In this paper, a quasi-three-dimensional computer model and its validation with experimental results of the thermal transport processes in the metering section of a single-screw plasticating extruder are presented.
10 Dec 2002
TL;DR: An algorithm and its associated architecture have been proposed for parallel compensation of the scale factor for the radix-4 CORDIC algorithm in the rotation mode, which reduces the latency from n to (n/2)+3, at the cost of a reasonable increase in hardware complexity.
Abstract: Although the full radix-4 CORDIC algorithm is efficient compared to the standard radix-2 version, the scale-factor overhead causes its improvement to be limited. In this work, an algorithm and its associated architecture have been proposed for parallel compensation of the scale factor for the radix-4 CORDIC algorithm in the rotation mode. The proposed method, which makes no prior assumptions about the elementary angles of rotation, reduces the latency from n to (n/2)+3, where n is the precision length in bits, at the cost of a reasonable increase in hardware complexity. The architecture presented relates to the redundant signed-digit number system. The architecture has been modelled in VHDL and simulated to establish its functional validity.
13 Dec 2002
TL;DR: Strategies involved in the implementation of a spell checker for Assamese, the official language or the North Eastern Indian State of Assam are described.
Abstract: Spell checkers form a vital ingredient of text processors, character recognition systems, dictionary search engines, language processing software and similar tools. Although considerable work has been done in the area for English and related languages, the Indian language scenario presents a relatively more complex and uphill task. This paper describes strategies involved in the implementation of a spell checker for Assamese, the official language or the North Eastern Indian State of Assam.
TL;DR: In order to arrive at proper decisions at various stages of the design, the concepts of fuzzy sets and priority decision tables were employed.
TL;DR: In this article, aldimines, aldoximes and aldehydes can be converted to the corresponding carboxylic acid on reaction with catalytic amount of cis-bisglycinato copper(II) monohydrtae in the presence of a copper-II catalyst.
Abstract: Aromatic aldimines, aldoximes and aldehydes can be converted to the corresponding carboxylic acid on reaction with catalytic amount of cis-bisglycinato copper(II) monohydrtae in the presence of copper(II) catalyst. The reactions are facilitated by addition of polyaniline as support. In the case of aldimines, evidences on participation of self-generated polyaniline is observed. The mechanistic aspect involving an oxy radical attached to copper(II) is presented with ESR evidence.
10 Dec 2002
TL;DR: The authors propose an efficient pipelined parallel architecture for the one-dimensional hierarchical search (1DHS) block-matching algorithm that is efficient in terms of both speed and hardware cost.
Abstract: The realisation of a real-time video-coding system calls for a dedicated motion-estimation architecture. Whereas all the existing motion-estimation architectures offer either computational speed or hardware simplicity, in this paper, the authors propose an efficient pipelined parallel architecture for the one-dimensional hierarchical search (1DHS) block-matching algorithm that is efficient in terms of both speed and hardware cost. The architecture exploits the advantageous features of the 1DHS algorithm and makes use of an intelligent memory configuration to achieve high speed while keeping the hardware complexity low. The architecture also makes use of a data-reuse technique, thereby reducing the number of external memory accesses. The proposed architecture has been modelled in VHDL and simulated to establish its functional validity.
TL;DR: In this paper, measurements of X-ray diffraction (XRD) at room temperature and temperature variation of dc electrical resistivity down to 20 K were carried out and a strong correlation between Mn-O-Mn bond angles and Tc of metal-insulator (M-I) transition was found.
Abstract: Electron-doped (Ba1−xLax)MnO3 compounds were prepared for x=0−0.5. Measurements of X-ray diffraction (XRD) at room temperature and temperature variation of dc electrical resistivity down to 20 K were carried out. Samples with x=0.2–0.5 exhibit metal-insulator (M-I) transition. The maximum M-I transition temperature (Tc) of 289 K was observed for 30% of La doping (x=0.3). XRD patterns of these samples (x=0.2−0.5) were analyzed using Rietveld refinement. These samples are found to be mostly in single-phase form with orthorhombic symmetry (space group Pbnm). We have found strong correlation between Mn-O-Mn bond angles and Tc of M-I transition. The resistivity data below Tc could be fitted to the expression ρ=ρ1+ρ2T2 and this shows that double exchange interaction plays a major role even in Mn4+-rich compound. Above Tc the resistivity data were fitted to variable range hopping and small polaron models.
TL;DR: In this paper, the authors deal with the delamination growth behavior of FRP composite laminates having two embedded delaminations at the interface under uniaxial and transverse loadings.
Abstract: This study deals with the delamination growth behaviour of FRP composite laminates having two embedded delaminations at the interface under uniaxial and transverse loadings. A full 3D FE analysis has been performed to calculate the interlaminar stresses at the interface responsible for delamination. The concept of fracture mechanics has been used to calculate the strain energy release rate components at the interface. Elliptical delaminations have been simulated to be present at the interface of two sublaminates each consisting of several plies, and the effect of the neighbouring delaminations on the other delamination has been studied under concentrated transverse loading as well as uniaxial tensile loading. Effects of delamination size, shape and the center distance between the two delaminations on individual strain energy release rate components have been evaluated to assess the delamination behaviour. It has been observed that the shape, size and the relative spacing of the two delaminations have a strong effect on the overlapping stress field, and the two delaminations grow in size to form a single delamination depending upon these parameters.
TL;DR: The response integrals of the almost Markovian-Galelian invariant test-field model (TFM) of Kraichnan, generalized to d dimensions, are analyzed and are found to be both ultraviolet and infrared finite in the range 0
Abstract: The response integrals of the almost Markovian-Galelian invariant test-field model (TFM) of Kraichnan, generalized to d dimensions, are analyzed They are found to be both ultraviolet and infrared finite in the range 0
TL;DR: The absorptions at 455 nm due to interaction with ammonium cation can be pushed back and forth to 525 nm by adding amine and acid, respectively showing the property of chemically driven reversible optical switching.
Abstract: Condensation of resorcinol with benzaldehyde in the presence of an acid gives an oligomeric product having a quinonic end group. The presence of the quinonic end group acts as a chromophore, and provides distinct visible absorptions at 450 and 475 nm. The oligomer interacts with different amines in a non-stoichiometric manner to give new absorptions at 525 nm. On addition of mineral acid, a new state can be generated having absorbance at 455 nm. This absorption can also be obtained from the interaction of an ammonium salt with the oligomer. The absorptions at 455 nm due to interaction with ammonium cation can be pushed back and forth to 525 nm by adding amine and acid, respectively showing the property of chemically driven reversible optical switching.
TL;DR: In this article, the nature of the methyl internal rotational barrier in thioacetaldehyde has been investigated by relaxation effect, natural bond orbital (NBO) analysis and Pauling exchange interactions.
Abstract: The nature of methyl internal rotational barrier in thioacetaldehyde has been investigated by relaxation effect, natural bond orbital (NBO) analysis and Pauling exchange interactions. The true experimental barrier can be obtained by considering fully relaxed rotation. Nuclear-electron attraction term is a barrier forming term in the fully relaxed rotation, but it appears as an antibarrier for rigid rotation. It is seen that during methyl rotation, the torsional mode is coupled with the aldehydic hydrogen out-of-plane wagging motion. Natural bond orbital analysis shows that the principal barrier forming term originates from the C-C bond. The lengthening of the C-C bond is explained by considering charge transfer interaction between several bonding and antibonding orbitals in the C-C bond region, which leads to higher bonding overlap for the eclipsed conformer compared to the staggered conformer. S-C(σ)/Cme-Hp and C-Hald/Cme-Hop interactions appear to be the main barrier-forming Pauling exchange terms but have less contribution to make to the barrier compared to the C-C bond interaction.
TL;DR: The thermal decomposition paths of pyridinium tetra chlorocopper(II) (A) differs from the anilinium-tetra chlorocpper (II)(B) (B) in the temperature range of 140-350°C as discussed by the authors.
16 Dec 2002
TL;DR: This paper proposes a fast watershed algorithm derived from Meyer's simulated flooding based algorithm for parallel processing adopted in conditional neighborhood comparisons for processing 3/spl times/3 pixels in one process.
Abstract: This paper proposes a fast watershed algorithm derived from Meyer's simulated flooding based algorithm The parallel processing adopted in conditional neighborhood comparisons for processing 3/spl times/3 pixels in one process leads to reduced computational complexity compared to Meyer's algorithm The proposed algorithm has been implemented in an Xilinx FPGA environment