Showing papers by "Indian Institute of Technology Guwahati published in 2000"

Highly regular, modular, and cascadable design of cellular automata-based pattern classifier

Abstract: This paper enumerates a new approach to the solution of classification problems based on the properties of Additive Cellular Automata. Classification problem plays a major role in various fields of computer science, such as grouping of the records in database systems, detection of faults in VLSI circuits, image processing, and so on. The state-transition graph of Non-group Cellular Automata (CA) consists of a set of disjoint trees rooted at some cyclic states of unit cycle length - thus forming a natural classifier. First a scheme of classifying the patterns distributed into only two classes has been dealt with. This has been further extended for solution of the multiclass classification problem. The Multiclass Classifier saves on an average 34% of memory as compared to the straight-forward approach storing directly the class of each pattern. A regular, modular, and cascadable hardware implementation of the classifier has been presented which is highly suitable for VLSI realization. The design has been specified in Verilog and verified for functional correctness.

Copper(II)-catalyzed reactions of activated aromatics.

Abstract: The catalytic reaction of cis-bisglycinato copper(II) monohydrate in the presence of hydrogen peroxide leads to hydroxylation of phenol to give catechol and hydroquinone (1:1.2 ratio) in good yield. 2,6-Dimethylphenol can be hydroxylated by hydrogen peroxide and a catalytic amount of cis-bisglycinato copper(II) monohydrate to give an aggregate of 1,4-dihydroxy-2,6-dimethylbenzene and 2,6-dimethylphenol. A similar reaction of o-cresol gives 2,5-dihydroxytoluene. The reactivity of cis-bisglycinato copper(II) monohydrate in hydrogen peroxide with o-cresol is 4.5 times faster than that of a similar reaction by trans-bisglycinato copper(II) monohydrate. A catalytic reaction of cis-bisglycinato copper(II) monohydrate with aniline in aqueous hydrogen peroxide gives polyanilines in the form of pernigraniline with different amounts of Cu(OH)2 attached to them. The two major components of polyanilines obtained have Mn values of 1040 and 1500, respectively. Resistance of films of these polyanilines increases with te...

Flexural fatigue characteristics of asphalt concrete with crumb rubber

Abstract: The paper describes an investigation on fatigue of Asphalt Concrete modified by addition of crumb rubber as a pan of aggregates. Flexural fatigue tests on Asphalt Concrete and Rubber Modified Asphalt Concrete conducted at 20. 25 and 30°C under constant strain mode indicated that the fatigue life of Rubber Modified Asphalt Concrete is significantly higher than that of the plain Asphalt Concrete. Design charts are presented to show that the pavement with Rubber Modified Asphalt Concrete requires a lower design thickness.

Error estimates for semidiscrete Galerkin approximation to a time dependent parabolic integro-differential equation with nonsmooth data

Abstract: In this paper, an attempt has been made to carry over known results for the finite element Galerkin method for a time dependent parabolic equation with nonsmooth initial data to an integro-differential equation of parabolic type. More precisely, for the homogeneous problem a standard energy technique in conjunction with a duality argument is used to obtain an L2-error estimate of order \(\) for the semidiscrete solution when the given initial function is only in L2. Further, for the nonhomogeneous case with zero initial condition, an error estimate of order \(\) uniformly in time is proved, provided that the nonhomogeneous term is in L∞(L2). The present paper provides a complete answer to an open problem posed on p. 106 of the book Finite Element Methods for Integro-differential Equations by Chen and Shih.

Application of Fuzzy Set Theory in the Scheduling of a Tandem Cold-Rolling Mill

Abstract: In a tandem cold-rolling mill, a strip is successively reduced in gauge at each stand as it passes through the mill. The optimal scheduling of a tandem mill is an important but difficult task. In this work, a scheduling problem is considered as an optimization problem which minimizes the total specific power and satisfies certain constraints. Since the material properties and friction coefficient are not known precisely, they are treated as fuzzy numbers. The fuzzy set theory is applied to find out an optimum drafting pattern. The methodology is illustrated by means of a few examples. It is observed that the schedule in which the maximum reduction is achieved in the first pass results in minimum specific power; however, its reliability is poor. Optimization using fuzzy set theory provides a solution which meets the twin requirements of high reliability and minimum power.

Fiber-optic Sagnac interferometer for the observation of Berry’s topological phase

Abstract: Few experiments have been reported for the observation of Berry’s phase for the photon. This may be due to the difficulty of configuring suitable experiments. We start by repeating previous work on the observation of the optical activity of a helically wound fiber coil in the transmissive mode, but then we go on to demonstrate that when the light is reflected back through the same coil from a mirrored surface, it cancels this optical activity. We also report on a new experimental configuration in which a helical fiber coil is built into the loop of a Sagnac interferometer. The changes in Berry’s phase acquired by the two counterpropagating beams can be varied by stretching the coil with the result that fringes are produced at the output. One of the major benefits of this experimental setup is that it enables observations of Berry’s phase to be made for light in any state of polarization.

Fiber-optic tunable loop mirror using Berry’s geometric phase

Abstract: A method is presented for constructing a fiber-optic loop mirror whose reflectivity is tunable even though a fixed-ratio directional coupler is used. The tunability is polarization and wavelength independent and depends only on the geometry of the fiber-tuning element. This loop mirror can be used to transfer energy from one channel to another in a controllable way. We experimentally demonstrate the tunable reflectivity and present some experimental investigations.

Cobalt(II) diacetylmonoxime complex-catalysed oxidative coupling reactions of few aromatic compounds

Abstract: Catalytic amount of a diacetylmonoxime cobalt(II) chloride complex [A] along with hydrogen peroxide reacts with toluene to give benzylalcohol, benzaldehyde and trace amount of p-cresol and o-cresol. Similar catalytic reaction of aniline gives C–N-bonded oligomer having Mn and Mw of 1256 and 1892, respectively. Mass spectra determined by MALDI suggests the polyaniline to have highest mass from 14 units of aniline with CoCl2 unit attached at the end. The oligomer thus formed have semiconducting properties. Similar reaction of phenol with cobalt(II) diacetylmonoxime (Co–DAM) complex in the presence of hydrogen peroxide gives C–O-bonded polyphenol. The reaction of 2-aminophenol with [A] and hydrogen peroxide leads to aggregate that has property of irreversible thermoelectric sensor. ESR suggests this property to originate from free radical present in the aggregate. Substituted aniline such as 2,4-dimethoxyaniline can also form low molecular aggregate from similar reaction that has semiconducting property in the range of 35°C–180°C.

Distribution of critical current density on Bi-110 K superconductor from AC susceptibility study

Abstract: AC susceptibility as a function of ac field amplitude was measured on a cylindrical sample of 110 K phase of Bi–Sr–Ca–Cu–O system at different temperatures. The sample was prepared by the uniaxial press sintering technique. The susceptibility data were analysed in terms of the Bean critical state model and by taking into account the statistical distribution of intergrain critical current density in the sample. The experimental data could be fitted well to the above model. From the analysis, the volume fraction of intergranular superconductor and the distribution of critical current density at different temperatures were determined.

Automatic tuning of the modified Smith predictor controllers

Abstract: A simple relay feedback automatic tuning method is proposed for the modified Smith predictor, to provide a controller for stable, unstable and integrating processes with long dead time. A single asymmetrical relay feedback test is used to obtain a reduced order process model in terms of a second order dynamics plus dead time model. Very simple but straightforward tuning formulae are derived for the controllers which have a simple relationship with the plant model parameters. Thus the plant model blocks in the Smith predictor structure, as well as all the controllers are designed from a single asymmetrical relay test. Excellent performance of the auto-tuned Smith predictor has been substantiated by simulations.

Hydroquinone aggregates as a thermoelectric switch

Abstract: The reaction of cis-bis-glycinato copper(II) monohydrate with hydroquinone in the presence of hydrogen peroxide leads to copper(II)-containing hydrogen bonded aggregates having the properties of a thermoelectric switch in the region of 42 to 160°C. The ESR shows evidence of a change in coordination around the copper centre during the conductivity change of the switch. A similar reaction of hydroquinone with copper(II) acetate monohydrate and hydrogen peroxide leads to an aggregate having such a property from room temperature to 130°C. The reaction of hydroquinone with tertiary butyl hydroperoxide in the presence of a catalytic amount of cis-bis-glycinato copper(II) monohydrate gives quinhydrone that possesses semiconducting properties above 100°C. The quinhydrone thus prepared on doping with cis-bis-glycinato copper(II) monohydrate shows the properties of a thermoelectric switch.

Silicon–oxygen bonding on diphenylsilane through palladium(II)-catalysed reactions

Abstract: The reactions of phenols with diphenylsilane are catalysed by palladium(II) catalysts such as Pd(TMEDA)Cl2 (TMEDA = tetramethylethylenediamine), Pd(DEED)Cl2 (DEED = N,N′-diethylethylenediamine), Pd(TEEDA)Cl2 (TEEDA = N,N′-tetraethylethylenediamine) or PdCl2 to form hydrated silanols with molecular formula Ph2Si(OR)OH·nH2O (when R = C6H5, n = 3; when R = p-CH3C6H4 or o-CH3C6H4, n = 1). The reaction of hydroquinone with diphenylsilane in the presence of catalytic amounts of Pd(TMEDA)Cl2 forms an Si–O-bonded hydrated aggregate of composition [(C6H5)2Si(OC6H4O).0.5H20]n. p-Benzoquinone reacted with diphenylsilane in the presence of a catalytic amount of Pd(TMEDA)Cl2 and the reaction proceeded via a multiple pathway involving quinhydrone as an intermediate charge-transfer complex which reacted further with diphenylsilane to give a linear siloxane. Copyright ­© 2000 John Wiley & Sons, Ltd.

Teaching computer graphics and robotics using symbolic computation software

Abstract: An approach to teaching undergraduate courses in computer graphics and robotics is presented. Objects in two and three dimensions of various shapes are involved in the study of graphics and robotics. The representation and manipulation of these objects constitute important topics of discussion in these courses. Students will evince keen interest in learning the material if instructors supplement classroom lectures with demonstrations and homework assignments using a symbolic computing program for solving problems. In this article, it is shown how Maple can be used for solving a wide range of problems arising in robotics and graphics, each with different requirements in terms of the software tools required. Fast prototype development, concept illustration, and graphical solution verification are facilitated by the use of a symbolic computing system such as Maple, and these cannot be accomplished with the same ease using traditional programming languages such as C or FORTRAN. © 2000 John Wiley & Sons, Inc. Comput Appl Eng Educ 8: 18–30, 2000

Robustness analysis of uncertain, nonlinear systems

Abstract: Based on the notion of positively invariant tubes, we present a simple and novel methodology for quantitative analysis of uncertain nonlinear systems described by a parametrized family of ordinary differential equations with uncertain initial values Both the uncertain parameters and the sets they take values in are allowed to be piecewise continuous in time The proposed methodology can be used to verify and generate pointwise in time upper bounds on the worst-case deviation of the actual system state from a nominal state trajectory This is useful in verifying limits on the worst-case state behaviour and in the estimation of the worst-case transient response and steady state error Two examples demonstrate that this methodology compares favourably with alternative techniques like simulation and Lyapunov-like analysis with regard to computational speed and tractability A third example shows that the proposed method can improve upon one of the best known bounds on the solutions of linear systems The fourth example involving speed control of a PM synchronous motor highlights the method's potential in the synthesis of robust nonlinear controllers

Use of k−ε−γ Model to Predict Intermittency in Turbulent Boundary-Layers

Abstract: The intermittency profile in the turbulent flat-plate zero pressure-gradient boundary-layer and a thick axisymmetric boundary-layer has been computed using the Reynolds-averaged k-e-γ model, where k denotes turbulent kinetic energy, e its rate of dissipation, and γ intermittency. The Reynolds-averaged model is simpler compared to the conditional model used in the literature. The dissipation equation of the Reynolds-averaged model is modified to account for the effect of entrainment. It has been shown that the model correctly predicts the observed intermittency of the flows.

Synthesis, characterisation and physicochemical properties of polyphenols prepared by cobalt(II) catalysed oxidative polymerisation

Abstract: The catalytic reaction of Co 2 (DAM) 7 Cl 4 with phenolic compounds such as phenol, p -cresol, o -cresol, m -cresol etc. in the presence of hydrogen peroxide gave C–O bonded oligomers ( 1–4 ). The oligomers were characterised by NMR, IR, elemental analysis. The M n values of 1–4 were 3417, 3494, 3438 and 3550, respectively. The oligomers contain OH end groups. The oligomer 1 has resistance profile such that it increases to 50°C and then falls exponentially in the region of 50 to 170°C. The resistance of 2 and 4 are similar to semiconductor in the range of 30–180°C. The oligomer 3 has a resistance profile such that it decreases from 30 to 100°C and then increases from 100 to 140°C and once again falls in the region of 140–200°C. The oligomer 4 has an esr signal at 3220 G and shows the presence of a free radical. The intensity of this signal increases ten times upon heating to 90°C.

Efficient Design of ENCA Based Cipher System

Abstract: This paper presents two simple, secure block ciphering schemes designed based on the group properties of the Extended Neighbourhood Cellular Automata (ENCA). The encipherment and decipherment procedures of the schemes follow the similar protocols. Due to the nonlinear ENCA operations and many-to-many mapping among the plaintext and ciphertext characters, the measure of strength of the proposed scheme against intrusion can be found to be comparable with the existing schemes. There are further scopes to improve the complexity by increasing the size of the message block as well as the CAs. The simplified logic structure makes the schemes more significant from the implementation point of view.

Full duplex voice communication handsets over single carrier frequency

Abstract: A new technique for realization of two-way voice communication over a single carrier frequency as an improvement over the usual walky-talky type, simplex handsets, which are very widely used for civil as well as for military applications, is proposed. The challenge lies in providing cost-effective, full-duplex digital voice communication handsets, conserving the bandwidth at the same time.

Local heat transfer distribution in a rib roughened rotating square duct with ribs on two opposite surfaces

Abstract: An experimental investigation has been carried out to study the local heat transfer distribution in a square channel rotating about an axis normal to the free-stream direction in the presence of rib turbulators. The ribs are configured in a symmetric arrangement on two opposite surfaces with a rib angle of 90” to the mainstream flow. Experiments have been carried out for pitch-to-rib height ratios of 5 and 10 for a constant rib height-tohydraulic diameter ratio of 0.1. Experiments have been conducted for Reynolds numbers varying from 23000 to 41000 with the rotation number varying from 0 0.38 with water as the working medium. The test section in which the ribs are placed on the leading and trailing surfaces is considered as the base case (Orientation angle = O”, Coriolis force vector normal to the ribbed surfaces). The channel is turned in steps of 30” to vary the orientation angle from 0” to 90”. At all orientation angles other than zero, the heat transfer observed in case of pitch-to-rib height ratio of 5 is comparatively highter than that of a pitch-to-rib height ratio of 10. Hence, the pitch-to-rib height ratio of 10 configuration that is most preferred for the stationary case no longer appears to yield high heat transfer in the presence of rotation. Nomenclature A Area of cross section of copper cylinder ( m2 ) CP Specific heat of water ( kJ / kg K ) D Channel hydraulic diameter ( m ) e Rib height (m) h Heat transfer coefficient ( W / m2 K ) kf Thermal conductivity of water (W/m K) I Length of the copper cylinder ( m ) Nu(st) Nusselt number under stationary conditions Nu(rot) Nusselt number under conditions of rotation *Assistant Professor, Department of Mechanical Engineering **Associate Professor, Department of Mechanical Engineering Copyright

Modified collapsed dimension method for radiative heat transfer problems

Abstract: Introduction C OLLAPSED dimensionmethod (CDM) is one of the ray tracing methods used for the solution of radiative transfer problems. Development of this method is partly based on the works of Shih and Chen1 and Shih and Ren2 on the discretized intensity method. Some light on the method was thrown by Blank. Subsequent developmentof the method was made by Blank andMishra.4 Detailed description of this method is available in Ref. 5. In CDM, three-dimensionalradiative information is mapped into a two-dimensionalsolutionplane in terms of effective intensity (EI) andoptical thicknesscoefŽ cient (OTC). Thus, unlikeothermethods, analysis and computations in this method are performed in a twodimensional solution plane instead of three-dimensionalspace. CDMhas beenused for the solutionof radiativetransferproblems with highaccuracy.4;5 Thismethodhasbeenfoundtowork for awide rangeof optical thickness (very low to high optical thickness). Furthermore, CDM has also been found to work well for the conjugate mode heat transfer problems. In CDM, for determinationof heat  ux and temperature information, at each point of interest EIs have to be integrated over planar angle in the solutionplane.Theseangularintegrationsareperformed by dividing the planar angle into intervals of equal sizes. In each subinterval, EI is assumed isotropic. Hence, for higher accuracy, CDM requiresmore EIs and, thus, higher computational time. In the presentwork,with the objectiveofmakingCDMmore economical, the method is modiŽ ed. In the modiŽ ed CDM (MCDM), angular integrations of the EIs are performed differently. The discretizationand integrationsperformed in thismethod originatefrom the concept of the discrete ordinate method (DOM). Here, the planar angle is divided into a Ž nite number of subintervals according to the number of Gaussian quadraturepoints considered.Hence, in MCDM, angular subintervals are unequal and instead of considering average values of interval, the weighted mean corresponding to the Gauss points is considered. With this, the method becomes more realistic, and it derives computational efŽ ciency with a more realistic representationof the radiative transfer process. In the present work, improvements in MCDM over CDM are tested by solving radiative transfer problems in oneand twodimensional Cartesian enclosures with gray and homogeneous, absorbing, emitting, and anisotropically scattering medium. Both radiative and nonradiative equilibrium situations are considered. MCDM and CDM results are compared with results from the exact method and DOM.