Showing papers by "Indian Institute of Technology Guwahati published in 2001"

Multireservoir Modeling with Dynamic Programming and Neural Networks

Abstract: For optimal multireservoir operation, a dynamic programming-based neural network model is developed in this study. In the suggested model, multireservoir operating rules are derived using a feedforward neural network from the results of three state variables' dynamic programming algorithm. The training of the neural network is done using a supervised learning approach with the back-propagation algorithm. A multireservoir system called the Parambikulam Aliyar Project system is used for this study. The performance of the new multireservoir model is compared with (1) the regression-based approach used for deriving the multireservoir operating rules from optimization results; and (2) the single-reservoir dynamic programming-neural network model approach. The multireservoir model based on the dynamic programming-neural network algorithm gives improved performance in this study.

Fully compact higher-order computation of steady-state natural convection in a square cavity.

Abstract: The flow in a thermally driven square cavity with adiabatic top and bottom walls and differentially heated vertical walls for a wide range of Rayleigh numbers (10(3)< or =Ra< or =10(7)) has been computed with a fourth-order accurate higher-order compact scheme, which was used earlier only for the stream-function vorticity (psi-omega) form of the two-dimensional steady-state Navier-Stokes equations. The boundary conditions used are also compact and of identical accuracy. In particular, a compact fourth-order accurate Neumann boundary condition has been developed for temperature at the adiabatic walls. The treatment of the derivative source term is also compact and has been done in such a way as to give fourth-order accuracy and easy assimilation with the solution procedure. As the discretization for the psi-omega formulation, boundary conditions, and source term treatment are all fourth-order accurate, highly accurate solutions are obtained on relatively coarser grids. Unlike other compact solution procedure in literature for this physical configuration, the present method is fully compact and fully higher-order accurate. Also, use of conjugate gradient and hybrid biconjugate gradient stabilized algorithms to solve the symmetric and nonsymmetric algebraic systems at every outer iteration, ensures good convergence behavior of the method even at higher Rayleigh numbers.

Raman spectra of CdS nanocrystals in Nafion: longitudinal optical and confined acoustic phonon modes

Abstract: Quantum confinement effects on the longitudinal optical and acoustic phonons in CdS nanocrystals in the strongly confined regime in the polymer matrix Nafion are studied using Raman spectroscopy. The LO-phonon modes show size-dependent asymmetric broadening though the broadening and asymmetry are less than those predicted by the phonon confinement models. Two types of confined acoustic modes corresponding to n =1, l =0 and n =1, l =2 spheroidal vibrations are observed. Softening of the spheroidal modes is observed in the strongly confined regime.

Peroxometal-mediated environmentally favorable route to brominating agents and protocols for bromination of organics

Abstract: Higher-valent transition metals react with H 2O2 to form peroxometallates, thereby activating the coordinated peroxide. Based on the reaction profiles of peroxometal species, environmentally acceptable newer syntheses of tetrabutylammonium tribromide (TBATB), Bu4NBr3, cetyltrimethylammonium tribromide (CTMATB), cetyl(Me)3NBr3, and tetraethyl- ammonium tribromide (TEATB), Et4NBr3, have been developed from the reactions of the corresponding quaternary ammonium bromides with H2O2 and a catalytic amount of vanadi- um(V) or molybdenum(VI). Other transition metals capable of activating peroxide give sim- ilar results. The quaternary ammonium tribromides (QATBs) thus produced, especially TBATB and CTMATB, very efficiently act as clean and selective brominating agents for a variety of organic substrates. Very facile bromination of organic substrates, including aro- matics, is also possible by tetrabutylammonium bromide (TBAB) Bu4NBr, either promoted by V2O5-H2O2 or catalyzed by MoO4 2- -H2O2. The scope of the protocols has been under- scored, and the relevance to green chemistry has been highlighted.

Low power state assignment and flipflop selection for finite state machine synthesis: a genetic algorithmic approach

Abstract: Current renewed emphasis for more aggressive logic designs with lesser area, delay, and power demands exploration of alternative avenues that could lead to better designs, albeit at the higher cost of computation. The author explores the avenue of genetic algorithm for a holistic view for synthesis of finite state machine (FSM) targeting power reduction by incorporating both state assignment and sequential element selection. Exhaustive experimentation performed on a large suite of benchmarks has established the fact that this tool results in state encodings with on average 46.08% reduction in power requirement over NOVA, without any significant increase in the number of product terms. The effectiveness of judicious flipflop selection has been demonstrated by showing that the approach with all D-flipflops as the sequential element requires 33.78% more power than the approach with a choice of D and T flipflop types. Moreover, as compared to the technique presented in LPSA, the algorithm presented here requires 38.96% less power when using a mix of D and T flipflops. The quality of the solution obtained and the high rate of convergence have established the effectiveness of the genetic algorithm in solving this particular NP-complete problem. Further, the inherent parallelism of genetic algorithm makes the proposed scheme ideal for solving the problem in a multiprocessor environment.

Synthesis and characterization of CdS nanocrystals in a perfluorinated ionomer (Nafion)

Abstract: CdS nanocrystals having mean diameters in the range 1.4–6 nm are synthesised in the polymer matrix Nafion. X-ray diffraction (XRD) patterns of the samples show broadened peaks corresponding to the cubic phase of CdS. A detailed analysis of the XRD profiles using a profile fitting and separation programme (PROFIT) revealed the broadening to be arising from the size effects. The mean diameters of the nanocrystals are determined from the full width at half maxima (FWHM) of the XRD peaks.

Cellular automata-based recursive pseudoexhaustive test pattern generator

Abstract: This paper presents a recursive technique for generation of pseudoexhaustive test patterns. The scheme is optimal in the sense that the first 2/sup k/ vectors cover all adjacent k-bit spaces exhaustively. It requires substantially less hardware than the existing methods and utilizes the regular, modular, and cascadable structure of local neighborhood Cellular Automata (CA), which is ideally suited for VLSI implementation. In terms of XOR gates, this approach outperforms earlier methods by 15 to 50 percent. Moreover, test effectiveness and hardware requirements have been established analytically, rather than by simple simulation and logic minimization.

Oxidative oligomerisation of 1,4-diaminobenzene by copper and cobalt catalysts

Abstract: The reaction of cis -bisglycinatocopper(II) monohydrate in hydrogen peroxide with 1,4-diaminobenzene gives N–N-bonded oligomer I . Oligomer I contains a free radical with an ESR signal at 3180 G. The oligomer also contains copper(II) ion, with a strong ESR absorption at 3165 G. The oligomer has the property of a thermoelectric switch. A similar oligomerisation reaction of 1,4-diaminobenzene with Co(DAM) 7 Cl 4 (where DAM is diacetylmonoxime) also gives an N–N-bonded oligomer which also has a radical. This oligomer also has the property of a thermoelectric switch.

Simultaneous measurement of flowing fluid layer and film thickness of a soap bubble using a UV−visible spectrophotometer

Abstract: In this Letter we report a method for observing Marangoni convection driven fluid flow, in various soap bubble systems, using a UV−visible spectrophotometer. We also report time-dependent simultaneous measurement of the thickness of the fluid layer and thickness of the bubble film. The measurement is based on earlier reports1,2 of time-dependent monitoring of film thickness in a soap bubble by observing the interference maxima and minima occurring in the UV−visible region of wavelength. In the present case the interference maxima and minima due to the upward fluid flow appeared superimposed on those due to film thickness. Our observations suggest that the fluid layer thickness remains nearly constant for both vertical and horizontal bubbles even though the film thickness changes with time. The observed values of the fluid layer thickness are about 6.94 ± 0.15 μm for the vertical bubble and about 4.75 ± 0.09 μm for the horizontal bubble. Also, the intensity of the interference peaks due to Marangoni convec...

The oligomer of 1,6-naphthalenediol as a support in oxidative reactions of cis-bisglycinato copper(II) and hydrogenperoxide

Abstract: Oxidative oligomerization of 1,6-naphthalenediol by cis-bisglycinato copper(II)monohydrate with hydrogenperoxide gives C–O bonded oligomer. Further reactivity of this oligomer with hydrogen peroxide and organic substrate shows improvement in the yield of oxidative and hydrolytic reactions. For example the oligomer along with cis-bisglycinato copper(II) catalyses hydrolytic reaction of benzamide to benzoic acid.

Patterning Design in Color at the Submicron Scale

Abstract: We demonstrate the generation of patterns on overhead projector paper (OHP) and glass slides with the dimension at the submicron scale and in various colors. We have used the commercially available permanent marker pen to write lines on the surface of OHPs and glass slides and transferred the patterns of a compact disk (CD) onto the line. Observation under an optical microscope exhibited various color patterns on the film as per the design of the mold. When the mold was pressed twice on the same parent line in perpendicular geometry, cross patterns could be observed.

Relay feedback and wavelet based estimation of plant model parameters

Abstract: The paper presents a relay feedback and wavelet based method for the estimation of completely unknown processes for autotune purposes. From a single symmetrical relay feedback analysis a set of general expressions are presented for on-line process identification. Using these expressions the exact parameters of open loop stable and unstable first order plus time delay (FOPDT) and second order plus time delay (SOPDT) transfer function models may be obtained from simple measurements made on the limit cycle. However, noise in limit cycle output results in inaccurate estimate of the process model parameters. This paper proposes an effective mother wavelet for tracking the critical points of a noisy output signal. Further, using the wavelets based noise reduction it has been shown how accurate measurements can be made on the noisy limit cycle signal. Simulation studies illustrate the value of the proposed identification method.

A novel strategy to test core based designs

Abstract: This paper proposes a novel technique for testing core based system-on-a-chip (SOC), targeting to reduce the test application time as well as the test hardware. The proposed work is to be done in two parts: (i) Core Level and (ii) Interconnect Level. To date, many authors have studied the problem of testing core-based systems, but not much work exists on testing the cores and the interconnects together. Also proposed is an efficient test access design to reduce test cost by minimising test application time. Test access is a major challenge for testing of core-based system-on-a-chip designs. Several issues related to the Test Access Mechanism (TAM) design such as assignment of cores to test buses, optimal number of buses required, distribution of test data bandwidth between several buses have been handled in this paper. In doing so, the testing time has been found to be drastically reduced at the cost of some extra test hardware.

Tuning of controllers for integrating time delay processes

Abstract: Presents an identification method and a simple control strategy for open loop integrating processes with time delay. From a symmetrical relay test the open-loop integrating process model transfer function is estimated. A control strategy involving an inner loop in the feedback path and a proportional integral controller in the feedforward path is proposed. The inner feedback loop with a controller plays an important role in stabilizing the integrating processes. Then the PI controller in the outer loop is designed to control the stabilized process efficiently. Simple tuning formulae interims of the estimated process model parameters have been derived for the controllers based on user-specified gain and phase margins. A comparison of the performances of the proposed design settings with those given by earlier workers is presented.

Visible spectroscopic observation of controlled fluid flow up along a soap bubble film from a pool of solution

Abstract: In this paper we report the demonstration of controlled fluid movement up along a soap bubble film from a solution on which the bubble floats. The control is achieved by controlling the gradient in surfactant concentration present in the bubble film and the solution below. We monitored the fluid flow by following the time-dependent visible absorption spectrum of a Rhodamine dye in the film that moved from the solution to the film due to fluid flow. Our observations suggest that an initial surfactant concentration gradient between the film and the solution (the solution having higher concentration) induces upward flow of fluid. Increase in the concentration gradient increases the rate of flow. No fluid flow was observed when the concentration gradient was zero or lower. In addition, our observation indicates that the upward movement of fluid occurs in concurrence with drainage of the film.

3,5‐Dimethylpyrazolium Fluorochromate(VI), C5H8N2H[CrO3F], (DmpzHFC): A Convenient New Reagent for Oxidation of Organic Substrates.

Abstract: A new chromium(VI) reagent, 3,5-dimethylpyrazolium fluorochromate, C 5 H 8 N 2 H[CrO 3 F] (DmpzHFC), has been developed by reacting dmpz with CrO 3 and aqueous HF for the selective oxidation of primary, secondary and allylic alcohols to the corresponding carbonyl compounds, polycyclic hydrocarbons to cyclic ketones and allylic Δ 5 -steroids to the corresponding α,β-unsaturated ketones.

Peroxometal-Mediated Environmentally Favorable Route to Brominating Agents and Protocols for Bromination of Organics

Abstract: Higher-valent transition metals react with H 2O2 to form peroxometallates, thereby activating the coordinated peroxide. Based on the reaction profiles of peroxometal species, environmentally acceptable newer syntheses of tetrabutylammonium tribromide (TBATB), Bu4NBr3, cetyltrimethylammonium tribromide (CTMATB), cetyl(Me)3NBr3, and tetraethyl- ammonium tribromide (TEATB), Et4NBr3, have been developed from the reactions of the corresponding quaternary ammonium bromides with H2O2 and a catalytic amount of vanadi- um(V) or molybdenum(VI). Other transition metals capable of activating peroxide give sim- ilar results. The quaternary ammonium tribromides (QATBs) thus produced, especially TBATB and CTMATB, very efficiently act as clean and selective brominating agents for a variety of organic substrates. Very facile bromination of organic substrates, including aro- matics, is also possible by tetrabutylammonium bromide (TBAB) Bu4NBr, either promoted by V2O5-H2O2 or catalyzed by MoO4 2- -H2O2. The scope of the protocols has been under- scored, and the relevance to green chemistry has been highlighted.

Tetrabutylammonium Tribromide (TBATB)—MeOH: An Efficient Chemoselective Reagent for the Cleavage of tert‐Butyldimethylsilyl (TBDMS) Ethers.

Abstract: TBDMS, THP, and DMT ethers are efficiently deprotected with tetrabutylammonium tribromide in methanol. The apparent order of stability of different protecting group is phenolic TBDMS > 1° OTBDPS > 2° OTBDMS > 2° OTHP > 1° OTHP > 1° OTBDMS > 1° ODMT. TBDMS ether has been cleaved selectively in the presence of isopropylidine, Bn, Ac, Bz, THP, and TBDPS groups. This method is high yielding, fast, clean, safe, cost-effective, and therefore most suitable for practical organic synthesis.

Palladium(II) Catalysed Silicon-Oxygen Bond Formation Versus Rearrangement Reactions

Abstract: Phenylsilane and diphenylsilane undergoes rearrangement reactions by palladium catalysts such as Pd(TMEDA)Cl2, Pd(TEEDA)Cl2, [Pd(PPh3)]2Cl2 (where TMEDA = tetramethylethylenediamine, TEEDA = tetraethylethylenediamine) at room temperature. However, the reductive Si-O bond forming reaction can be performed on hydrosilanes through competitive paths. The reactions of phenylsilane and quinonic compounds are catlaysed by Pd(TMEDA)Cl2 (such as 1,4-benzoquinone, 1,4-napthoquinone) to give siloxanes, backbone of these siloxanes which contains rearranged phenylsilane units. The thin films of such oligomers has plot of resistance vs temperature profile resembling semiconductor.

Oxidative oligomerisation of 2-naphthol by cis-bis(glycinato)copper(II)

Abstract: The reaction of 2-naphthol with tert-butylhydroperoxide by cis-bis(glycinato)copper(II) oligomerises 2-naphthol. One of the isolated tetramer A contains a tert-butyloxy group. Similar reaction of 2-naphthol with hydrogen peroxide in the presence of cis-bis(glycinato)copper(II) oligomerises 2-naphthol gives tetramer through hydroxylative oligomerisation. The oligomers are bound to oxo-bridged copper cores to give B and C. These oligomers exhibit thermal sensing property. The oligomer (B) converts benzamide to benzoic acid, as well as catalyses oxidation of aromatic aldehydes such as benzaldehyde to corresponding acids.

Benzyl alcohol-ammonia (1:1) cluster structure investigated by combined IR-UV double resonance spectroscopy in jet andab initio calculation

Abstract: Laser-induced fluorescence excitation and IR-UV double resonance spectroscopy have been used to determine the hydrogen-bonded structure of benzyl alcohol-ammonia (1:1) cluster in a jet-cooled molecular beam. In addition,ab initio quantum chemical calculations have been performed at HF/6-31G and HF/6-31G(d,p) levels for different ground state equilibrium structures of the cluster to correlate the calculated OH and NH frequencies and their intensities with experimental results. The broad red-shifted OH-stretching mode in the IR-UV double resonance spectrum suggests strong hydrogen bonding between the hydroxyl hydrogen and the lone pair of the ammonia nitrogen. The position and intensity distribution of the calculated NH and OH modes for the minimum-energy gauche form at HF/6-31G level have better correlation with the experimental results compared to other calculated ground state equilibrium conformers. These results lead to the conclusion that the minimum energy gauche form of the cluster is populated in the jet-cooled condition.

Features preserving filters using fuzzy Kohonen clustering network in detection of impulse noise

Abstract: It is always advisable to apply filtering only on corrupted pixels of images leaving untouched the uncorrupted ones to preserve image features and to avoid blurring effects. We present an algorithm which can detect the corrupted pixels in texture images. It uses a fuzzy Kohonen clustering network that integrates with the fuzzy c-means (FCM) model utilizing the updating strategies of the first and the learning rate of the second.

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.

Silicon-oxygen-bonded oligomers having thermoelectric switching properties

Abstract: The electrical properties of siloxane oligomers prepared from the reaction of 1,4-naphthalenediol or 1,4-naphthoquinone with diphenylsilane using different palladium catalysts, such as PdCl2, Pd(TMEDA)Cl2, Pd(TEEDA)Cl2 (where TMEDA = N,N′-tetramethylethylenediamine, TEEDA = N,N′-tetraethylethylenediamine), are dependent on the catalyst. Thermoelectric switching properties can be obtained from the siloxane prepared from the coupling reaction of diphenylsilane with 1,4-naphthoquinone or 1,4-naphthalenediol using Pd(TMEDA)Cl2 as catalyst. Copyright © 2001 John Wiley & Sons, Ltd.

On the entropy and spectral radius of finite-state machines

Abstract: A large class of discrete-event processes are modelled using finite-state machines and regular languages. Here we address the problems of spectral radius and entropy of a finite state machine and show that the entropy of a system is upper bounded by its event set.