Showing papers by "Indian Institute of Technology Bombay published in 1991"

Pulsed electrogeneration of bubbles for electroflotation

Abstract: Fine bubbles of the size required for many processes such as electroflotation can be generated by electrolysis. A large number of factors such as electrode material, electrode surface/morphological properties, pH and current density affect the gas bubble size distribution. This work is aimed at studies on the effect of interrupted current (pulsed) electrolysis on the generation of gas bubbles. A microcomputer-controlled current source designed to generate the required pulses is described along with typical results obtained with this system. It was observed that a decrease in duty cycle at a given pH and average current density causes an increase in fine sized bubbles and concomitant increase in bubble flux. A mechanism based on local potential gradients is proposed to explain this phenomenon.

Determining optical flow for irregular domains by minimizing quadratic functionals of a certain class

Abstract: Snyder (1989) has recently classified all smoothness terms which involve first-order derivatives of the flowfield u(x, t) and of the image grey-value function g(x, t). The physically plausible smoothness terms belonging to this class are known from the work of Horn and Schunck (1981) and Nagel (1987). In this paper we discuss the possibilities of approximating the solutions to the minimization problems of Horn & Schunk (1981) and Nagel (1987). In particular, it is shown that these solutions exist, are unique, and depend continuously on the input data. These properties make it possible, while taking into consideration arbitrary models of the grey-value function, to approximate efficiently the (weak) solutions of the associated boundary-value problems in irregularly shaped domains (with a “sufficiently smooth” boundary) using finite elements. Experiments with image sequences from synthetic as well as outdoor scenes show how the orientation dependency of the smoothness term in Nagel's approach influences the results.

Algorithmic characterization of vehicle trajectories from image sequences by motion verbs

Abstract: Images of vehicles which move in traffic scenes recorded by a stationary camera have been detected and tracked without operator intervention. The resulting vehicle trajectories were projected from the image plane onto the street plane. A suitable system internal representation of about 90 German motion verbs was then exploited in order to automatically characterize trajectory segments in terms of natural language concepts. A multiresolution approach for feature matching has been developed which is robust enough to track vehicle images across hundreds of frames, despite considerable variations in size and projected velocity. Results from experiments with image sequences from real-world traffic scenes are presented. >

Practical adaption of the global optimization algorithm of Morel and Renvoise

Abstract: This paper discusses some issues in practical adaptation of the MorelRenvoise algorithm for global optimization by suppression of partial redundancies [41. Drechsler and Stadel [31 propose placement of empty blocks along edges in the program flow graph to eliminate some practical difficulties in using the Morel-Renvoise algorithm. The possibility of edge placement was mentioned by Morel and Renvoise in the original paper [4]. Dhamdhere [11 has previously discussed the technique of edge placement of expressions. Sorkin [51 comments on a possible adverse impact of the edge blocks on the running time of the algorithm and proposes consideration of edge blocks only to hold expressions moved out of loops. However, this fear is unfounded since edge blocks are only conceptional and do not participate in the iterations of the solution process [1]. Further, edge placement is a general technique for the elimination of partial redundancies in a program; its application need not be restricted to the optimization of loops.

Multicomponent batch distillation column design

Abstract: We are presenting a short-cut method for design of multicomponent batch distillation columns, operating under variable reflux and constant reflux conditions. The method is essentially a modification of the short-cut method widely used in the design of continuous multicomponent columns. The technique has been tested for both binary and multicomponent systems

Geology, Petrography and Systematic Stratigraphy of Pre-Ariyalur Sequence in Tiruchirapaui District, Tamil Nadu, India

Abstract: A new litho unit-Terani Formation is proposed. The lower part of the Uttatur Formation is found to be homotaxially equivalent to the Dalmiapuram Formation. A new geological map based on these units is presented.

A k-step predictive scheme for speed control of diesel driven power-plants

Abstract: An adaptive speed control scheme for diesel prime-movers is presented. Diesel prime-movers are characterized by nonlinear, time-varying parameters, including a nonlinear input dead-time variation that introduces an unknown delay between the injection of fuel and the production of engine torque. Such plants are difficult to control by conventional proportional-integral (PI) controllers. It is shown that by assuming the existence of an additional system time-constant, an explicit estimate of the plant parameters and dead-time can be obtained. The algorithm converges quickly. The resulting predictor can then be used to set up a k-step-ahead predictive controller. Studies are presented to compare the performance of the adaptive scheme to that of a fixed, tuned PI controller. The algorithm is shown to be flexible enough to operate under a wide range of droop settings, and equally applicable to various operating conditions. >

Application of artificial neural network in protective relaying of transmission lines

Abstract: That the artificial neural network (ANN) can perform the pattern classification in excellent fashion is already established in the literature. The authors envisage the relay as a pattern classifying device. This opens a new dimension in relay philosophy which needs wide investigations. Keeping the microprocessor relay framework intact, the authors report the findings about the feasibility of using ANN in protection of transmission lines. The ADALINE model is explored for the application and is found to yield encouraging results. The input variables are quantified over the operating range which eases the arithmetics of the microprocessor. The training is performed in off-line mode and the converged weight matrix is stored for on-line use. >

A state-space approach to orthogonal digital filters

Abstract: An algorithm for designing multi-input multi-output (MIMO) orthogonal digital filters is developed using a state-space approach. The algorithm consists of three parts: (i) orthogonal embedding, (ii) transformation of the embedded orthogonal transition matrix to the alpha -extended upper Hessenberg form; and (iii) factorization of this new form into Givens (planar) rotations. Appropriately interconnecting the rotors leads to the pipelined orthogonal filter structure. As a consequence of the approach, for the single-input, single-output (SISO) case, an essentially orthogonal structure is obtained for the inverse filter; only one of the Givens rotors is replaced by a hyperbolic rotor. >

Performance analysis of total least squares methods in three-dimensional motion estimation

Abstract: An algorithm is presented to obtain the total least squares (TLS) estimates of the motion parameters of an object from range/stereo data or perspective views in a closed form. TLS estimates are suitable when data in both time frames are corrupted by noise, which is an appropriate model for motion analysis in practice. The robustness of different linear least squares methods is analyzed for the estimation of motion parameters against the sensor noise and possible mismatches in establishing object feature point correspondence. As the errors in point correspondence increase, the performance of an ordinary least squares (LS) estimator was found to deteriorate much faster than that of the TLS estimator. The Cramer-Rao lower bound (CRLB) of the error covariance matrix was derived for the TLS model under the assumption of uncorrelated additive Gaussian noise. The CRLB for the TLS model is shown to be always higher than that for the LS model. >

Flow of Newtonian fluid in non-uniform tubes with variable wall permeability with application to flow in renal tubules

Abstract: The hydrodynamical aspects of flow through proximal renal tubule have been investigated. Assuming renal fluid as Newtonian fluid, flow through diverging/converging tubes with variable wall permeability has been considered. Solutions have been obtained for approximate Navier-Stokes equations with boundary conditions which include a dynamic condition, i.e., leakage flux at the wall depends on variable wall permeability and transboundary pressure drop. Numerical solutions, using fourth order Runge-Kutta method, and approximate analytic solutions, using perturbation method, have been obtained. A comparison of the numerical solution with approximate analytic solution, shows a good agreement (difference less than 4%) between the two solutions for small values of |e|, a tube non-uniformity parameter. The velocity profiles at different positions along the axis, the axial distribution of wall shear stress, flow rate and leakage flux have been obtained. For a given value of wall permeability, in diverging (converging) tubes the fractional reabsorption FR is more (less) than its corresponding value in uniform tubes. Further, FR increases (decreases) as the wall permeability increases (decreases) as a linear function of axial distance. The results for flow with constant/variable permeability through uniform tubes and for flow through diverging/converging tubes with constant permeability can be obtained as special cases of this analysis. It is shown that by considering the divergent tube model with linear increase of wall permeability along the axis, an improvement of about 20% in total reabsorption can be achieved over the uniform tube model with constant wall permeability. It is concluded that the approach of using a dynamic boundary condition for leakage flux at the wall has an advantage over the method of prescribing the leakage flux at the wall for this physical problem. Using a set of data, relevant to a physiological situation, implications of the results on glomerular tubular balance have been briefly discussed.

A new parallel architecture for sparse matrix computation based on finite projective geometries

Abstract: No abstract available

CASNS—a heuristic algorithm for the nesting of irregular-shaped sheet-metal blanks

Abstract: This article reports on the design and implementation of a computer-aided sheet nesting system (CASNS) for the nesting of two-dimensional irregular-shaped sheet-metal blanks on a given sheet stock or coil stock. The system is designed by considering several constraints of sheet-metal stamping operations, such as bridge width and grain orientation, and design requirements such as maximising the strength of the part when subsequent bending is involved, minimisation of scrap, and economic justification for a single or multiple station operation. Through many practical case studies, the system proves its efficiency, effectiveness and usefulness.

Comparative study of spinodal decomposition in symmetric and asymmetric Cu-Ni-Cr alloys

Abstract: Spinodal decomposition in three alloys of nominal compositions 71Cu-27Ni-2Cr, 45Cu-45Ni-10Cr and 33Cu-52Ni-15Cr were studied by X-ray diffraction technique and transmission electron microscopy. It was found that the first and third alloys are asymmetric in nature while the second is symmetric. The symmetric alloy was found to decompose faster than the asymmetric ones. The asymmetry of the side bands was found to be related to the proportion of phases in the alloy. Electron microscopic studies revealed that during coarsening the major phase increases its connectivity by isolating the minor phase.