Showing papers by "Indian Institute of Technology Bombay published in 1998"
TL;DR: This paper presents a complementary and simple method to make a point forecast of waves in real time sense based on the current observation of waves at a site that incorporates the technique of neural networks.
287 citations
TL;DR: Dynamics, within the CMP across 1990 and 1995, are investigated through the comparison of the words, co-word pairs and structurally equivalent blocks and the results are projected using multi-dimensional scaling.
Abstract: The present study investigates the use of co-word analysis method to understand the micro structure of a research speciality. This study is done in the area of Condensed Matter Physics (CMP) taking two time-periods, 1990 and 1995. Based on concurrent set of journals occurring in the subject heading list of CMP in these two time-periods, a database is created after downloading articles present in these journals from the INSPEC database. Using words extracted from the titles from the created database, suitable co-word pairs are constructed. These words, and co-word pairs are explored further to understand their linkages with each other through network analysis methods. Dynamics, within the CMP across 1990 and 1995, are investigated through the comparison of the words, co-word pairs and structurally equivalent blocks. The results are projected using multi-dimensional scaling. The important conclusions of this study are discussed.
128 citations
100 citations
26 Aug 1998
TL;DR: This work makes use of large and candidate itemsets and their counts in the older database, and scans the increment to find which rules continue to prevail and which ones fail in the merged database, to find new rules for the incremental and updated database.
Abstract: The association rules represent an important class of knowledge that can be discovered from data warehouses Current research efforts are focused on inventing efficient ways of discovering these rules from large databases As databases grow, the discovered rules need to be verified and new rules need to be added to the knowledge base Since mining afresh every time the database grows is inefficient, algorithms for incremental mining are being investigated Their primary aim is to avoid or minimize scans of the older database by using the intermediate data constructed during the earlier mining We present one such algorithm We make use of large and candidate itemsets and their counts in the older database, and scan the increment to find which rules continue to prevail and which ones fail in the merged database We are also able to find new rules for the incremental and updated database The algorithm is adaptive in nature, as it infers the nature of the increment and avoids altogether if possible, multiple scans of the incremental database Another salient feature is that it does not need multiple scans of the older database We also indicate some results on its performance against synthetic data
87 citations
TL;DR: Real-time forecasting of stream flows during storms provides an essential input to operational flood management and the technique of neural networks was applied to model it.
Abstract: Real-time forecasting of stream flows during storms provides an essential input to operational flood management. This work is usually very complex owing to the uncertain and unpredictable nature of the underlying phenomena. The technique of neural networks therefore was applied to model it. Forecasting of flood values during storms with a lead time of one and more hours was made using a selected sequence of past flood values observed at a specific location. Training of the network was done with the help of three alternative methods, viz., error backpropagation, conjugate gradient, and cascade correlation. Resulting flood forecasts were found to be satisfactory-especially when warning time was the least.
70 citations
TL;DR: The delivery of liposome-incorporated retinoids to the blood has been studied and it is found that these systems reduce blood viscosity and cause less lysis of red blood cells than retinoid compounds not complexed in liposomes.
66 citations
02 Jun 1998
TL;DR: A grayvalue structure tensor provides knowledge about a local grayvalue variation that can be used to devise a spatiotemporally adaptive optic flow estimation process, which substantially simplifies the analysis of remaining effects which easily jeopardize a ‘naive’ segmentation approach.
Abstract: A grayvalue structure tensor provides knowledge about a local grayvalue variation. This knowledge can be used to devise a spatiotemporally adaptive optic flow estimation process. Such an adaptive estimation lowers the level at which the resulting optic flow (OF) field is disturbed by noise and estimation artefacts. This in turn substantially simplifies the analysis of remaining — often subtle — effects which easily jeopardize a ‘naive’ segmentation approach. Appropriate treatment of such effects eventually results in a basically simple, but nevertheless surprisingly robust segmentation approach. Various stages of this approach are illustrated by examples for the extraction of moving vehicle images from a digitized road intersection video-sequence.
63 citations
TL;DR: The observed distribution and periodicity of labeled residues reinforce the conclusion that the M4 segments are organized as transmembrane α-helices with a common “face” of each helix in contact with lipid.
61 citations
TL;DR: The training algorithm of cascade correlation involved the lowest training time and hence is found to be more suitable for adaptive training purpose and hence the approach may look more attractive to apply.
Abstract: Prediction of tides at a subordinate station located in the interior of an estuary or a bay is normally done by applying an empirical correction factor to observations at some standard or reference station. This paper presents an objective way to do so with the help of the neural network technique. In complex field conditions this approach may look more attractive to apply. Prediction of high water and low water levels as well as that o fcontinuous tidal curves is made at three different locations. The networks involved are trained using alternative training algorithms. Testing of the networks indicated satisfactory reproduction of actual observations. This was further confirmed by a high value of the accompanying correlation coefficient. Such a correlation was better than the one obtained through use of the statistical linear regression model. The training algorithm of cascade correlation involved the lowest training time and hence is found to be more suitable for adaptive training purpose.
61 citations
Journal Article•
TL;DR: Red cell rigidity is an important hemorheological parameter determining the passage of erythrocyte through narrow capillaries and the reduction of blood viscosity under high shear rates, and cholesterol levels have been found to consistently cause a simultaneous increase in RBC rigidity.
Abstract: Red cell rigidity is an important hemorheological parameter determining the passage of erythrocyte through narrow capillaries and the reduction of blood viscosity under high shear rates. The changes in red cell rigidity in various diseases of altered blood flow - hypertension (HT), diabetes mellitus (DM), myocardial infarction (MI) and cerebrovascular accidents (CVA), using equal sample sizes of 25 each, have been analysed in this paper. One of the essential elements of red cell rigidity is the structural and functional properties of erythrocyte membrane which, in turn, is determined by the membrane biochemistry. Since cholesterol-rich erythrocytes have increased rigidity, the serum cholesterol and triglycerides levels have been monitored in order to detect the extent to which they affect red cell rigidity. No significant change in red cell rigidity have been found in CVA. RBC rigidity is found to be significantly increased in the other diseases. Significant increase in triglyceride levels have been found in all the diseases studied. Cholesterol levels were significantly increased in all diseases except CVA. Hence, increased cholesterol levels have been found to consistently cause a simultaneous increase in RBC rigidity. Triglycerides levels, on the other hand, have not shown a consistent change with changes in RBC rigidity, but have been shown to be a more sensitive marker for early detection of diseased status.
61 citations
TL;DR: In this article, a second-order splitting method is applied to a KdV-like Rosenau equation in one space variable and an orthogonal cubic spline collocation procedure is employed to approximate the resulting system.
Abstract: A second-order splitting method is applied to a KdV-like Rosenau equation in one space variable. Then an orthogonal cubic spline collocation procedure is employed to approximate the resulting system. This semidiscrete method yields a system of differential algebraic equations (DAEs) of index 1. Error estimates in L2 and L∞ norms have been obtained for the semidiscrete approximations. For the temporal discretization, the time integrator RADAU5 is used for the resulting system. Some numerical experiments have been conducted to validate the theoretical results and to confirm the qualitative behaviors of the Rosenau equation. Finally, orthogonal cubic spline collocation method is directly applied to BBM (Benjamin-Bona-Mahony) and BBMB (Benjamin-Bona-Mahony-Burgers) equations and the well-known decay estimates are demonstrated for the computed solution.
TL;DR: A polynomial-time algorithm is presented that directly checks for solvability of a useful class of aggregation constraints, where the reduction-based approach does not lead to efficient checks forsolvability.
TL;DR: In this paper, the existence of the broken pseudospin symmetry was investigated based on the relativistic mean field (RMF) approach, and the quasidegenerate pseudo-spin doublets were confirmed to exist near the Fermi surface for both spherical and deformed nuclei.
Abstract: Based on the relativistic mean field (RMF) approach the existence of the broken pseudospin symmetry is investigated. Both spherical RMF and constrained deformed RMF calculations are carried out employing realistic Lagrangian parameters for spherical and for deformed sample nuclei. The quasidegenerate pseudospin doublets are confirmed to exist near the Fermi surface for both spherical and deformed nuclei.
01 Jan 1998
TL;DR: The risk-sensitive filter as mentioned in this paper differs from a conditional mean estimator (Kalman filter) and is either risk-prone or risk-averse depending on the sign of a scalar thetas that appears in the cost function.
Abstract: Algorithms for risk-sensitive filters have been developed in literature and connections to H∞ filtering also established. The risk-sensitive filter differs from a conditional mean estimator (Kalman filter) and is either risk-prone or risk-averse depending on the sign of a scalar thetas that appears in the cost function. The RS filter exhibits many interesting properties. Statistical properties, parameter estimation and explicit bounds of estimation for these filters are presented in the paper.
TL;DR: It is shown that both types of system properties are expressible in FNLOG and may be verified by logical deduction, and also hold for the corresponding behavior specification.
Abstract: The task of designing large real-time reactive systems, which interact continuously with their environment and exhibit concurrency properties, is a challenging one. The authors explore the utility of a combination of behavior and function specification languages in specifying such systems and verifying their properties. An existing specification language, statecharts, is used to specify the behavior of real-time reactive systems, while a new logic-based language called FNLOG (based on first-order predicate calculus and temporal logic) is designed to express the system functions over real time. Two types of system properties, intrinsic and structural, are proposed. It is shown that both types of system properties are expressible in FNLOG and may be verified by logical deduction, and also hold for the corresponding behavior specification.
TL;DR: The effect of nitrogen on the weld cladding of 904L filler metal towards microstructure and electrochemical corrosion was investigated in this paper, where the initial addition of nitrogen to the shielding gas was found to decrease the pitting resistance of the clad as compared to that obtained without nitrogen addition.
TL;DR: In this paper, a second-order splitting method is applied to the Kuramoto-Sivashinsky equation and then an orthogonal cubic spline collocation procedure is employed to the approximate resulting system.
Abstract: In this paper, a second-order splitting method is applied to the Kuramoto-Sivashinsky equation and then an orthogonal cubic spline collocation procedure is employed to the approximate resulting system. This semidiscrete method yields a system of differential algebraic equations (DAEs) of index 1. Error estimates in L 2 and L c¢ norms are obtained for the semidiscrete approximation. For the time discretization, the time integrator RADAU5 is used. The results of numerical experiments are presented to validate the theoretical findings.
TL;DR: A single neuron control scheme for suppression of wing rock of slender delta wings is presented and the robustness of the scheme is demonstrated by the suppression of the wing rock at various initial conditions and different angles of attack.
Abstract: Wing rock is a highly nonlinear phenomenon in which the aircraft undergoes limit cycle roll oscillations at high angles of attack. A single neuron control scheme for suppression of wing rock of slender delta wings is presented. The effectiveness of the control scheme is demonstrated through software simulation and real-time control experiments in a wind tunnel on a 80/spl deg/ swept back wing. The suppression of the limit cycle is achieved in presence of control saturation. The robustness of the scheme is demonstrated by the suppression of the wing rock at various initial conditions and different angles of attack.
TL;DR: In this article, a package of simulation models has been developed to study the hydrological processes controlling runoff and to predict flow hydrographs in the Indian arid zone.
Abstract: A package of simulation models has been developed to study the hydrological processes controlling runoff and to predict flow hydrographs in the Indian arid zone. The models describe rainfall-runoff in the upland phase and the interaction between runoff and transmission losses in the channel phase, so as to derive the drainage basin outflow hydrograph. In the upland phase the rising limb of the hydrograph is predicted through a regression model and the recession through a conceptual analogue of discharge from a single leaky reservoir. The leaky reservoir is described by a continuity equation and by discharge-stage and storage-stage relationships at the outlet. In the channel phase the governing equations for movement of a flood wave subjected to the transmission losses are simplified through a time averaging process to develop an ordinary differential equation describing transmission losses as a function of distance, inflow, channel width, time parameters of flow and effective hydraulic conductivi...
TL;DR: The integrated maintenance scheduling system presented in this paper takes into consideration device and system-specific data in order to coordinate the maintenance activities for constrained maintenance schedules and supports the maintenance engineer to coordinate maintenance activities more effectively.
Abstract: In electrical energy systems, an essential part of their operation costs results from maintenance activities. Many applications discussing the task of reducing maintenance expenditure mainly aim at developing diagnostic techniques in order to avoid unnecessary maintenance activities. However, maintenance scheduling can only be done effectively if the condition of the whole power system is taken into account and system-specific aspects are considered besides device-specific information. The integrated maintenance scheduling system presented in this paper takes into consideration device and system-specific data in order to coordinate the maintenance activities for constrained maintenance schedules. Since, despite the restrictions, many different schedules can be generated, they are evaluated in order to find an optimal schedule concerning economic and utility dependent criteria. For this task, methods of evolutionary strategies and fuzzy decision theory are applied. In this way, the presented scheduling system supports the maintenance engineer to coordinate maintenance activities more effectively.
TL;DR: In this article, the authors present estimates of the regional lung deposition of polycyclic aromatic hydrocarbons (PAH) associated with a typical multimodal urban aerosol and examine the effect of varying size distribution characteristics on lung deposition.
Abstract: Recent epidemiological evidence of associations between increased mortality and ambient particle concentrations suggests that ultrafine particles (smaller than 1 mum diameter) and their constituents are potentially significant contributors because of their enhanced toxicity and their potential for greater lung penetration. Measurements of size distributions of potentially carcinogenic polycyclic aromatic hydrocarbons (PAH) in urban aerosols show their predominance in ultrafine and fine modes centered about 70 and 700 nm. In this article we present estimates of the regional lung deposition of PAH associated with a typical multimodal urban aerosol and examine the effect of varying size distribution characteristics on lung deposition. Size-dependent deposition fractions, from a deterministic calculation using deposition probabilities in a lung anatomical model, have been combined with the fraction of aerosol or PAH mass present in each particle size range and integrated over the entire size range to obtain t...
TL;DR: This paper presents a meta-modelling framework for neural net-based AdaptiveLinear Quadratic Control and some examples of how this framework has been implemented in the real-time environment.
Abstract: References 1Joshi, S. M., Control of Large Flexible Space Structures, Springer– Verlag, Berlin, 1989, pp. 24–26. 2Lin, C. L., “Robust Control of Flexible Structures Using Residual Mode Filters,” Journal of Guidance, Control, and Dynamics, Vol. 16, No. 5, 1993, pp. 973–977. 3Lin, C. L., and Chen, B. S., “Robust Observer-Based Control of Large Flexible Structures,” Journal of Dynamic Systems, Measurement, and Control, Vol. 116, Dec. 1994, pp. 713–722. 4Sun, J., and Ioannou, P., “Robust Adaptive LQ Control Schemes,” IEEE Transaction on Automatic Control, Vol. AC-37, No. 1, 1992, pp. 100–106. 5Wang, J., “Recurrent Neural Networks for Solving Linear Matrix Equations,”Computers andMathematicswith Applications, Vol. 26, No. 9, 1993, pp. 23–34. 6Leon, S. J., Linear Algebra with Applications, Macmillan, New York, 1994, pp. 347–355. 7Lin, C. L., “Neural Net-Based AdaptiveLinear Quadratic Control,”Proceedings of the 1997 IEEE International Symposium on Intelligent Control, Istanbul, Turkey, 1997, pp. 187–192. 8Czajkowski, E. A., and Preumont, A., “Spillover Stabilization and DecentralizedModalControlofLarge Space Structures,”AIAAPaper 87-0903, 1987.
TL;DR: In this paper, an extended risk-sensitive filter (ERSF) is used to estimate the motion parameters of an object recursively from a sequence of monocular images and the effect of varying the risk factor /spl theta/ on the estimation error is examined.
Abstract: In this paper, an extended risk-sensitive filter (ERSF) is used to estimate the motion parameters of an object recursively from a sequence of monocular images. The effect of varying the risk factor /spl theta/ on the estimation error is examined. The performance of the filter is compared with the extended Kalman filter (EKF) and the theoretical Cramer-Rao lower bound. When the risk factor /spl theta/ and the uncertainty in the measurement noise are large, the initial estimation error of the ERSF is less than that of the corresponding EKF The ERSF is also found to converge to the steady state value of the error faster than the EKF. In situations when the uncertainty in the initial estimate is large and the EKF diverges, the ERSF converges with small errors. In confirmation with the theory, as /spl theta/ tends to zero, the behavior of the ERSF is the same as that of the EKF.
TL;DR: In this article, it was shown that the convolution of two symmetric unimodal distributions on R is unimmodal, and that symmetrization of a non-negative random variable with its tail probability is also a symmetric random variable.
30 Nov 1998-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, two recent ideas for understanding and modeling the development of cube recrystallization texture in rolled and plane strain deformed aluminum and copper have been tested by experimental studies.
Abstract: Two recent ideas for understanding and modeling the development of cube recrystallization texture in rolled and plane strain deformed aluminum and copper have been tested by experimental studies. The ideas are: (i) the concept called either ‘orientation pinning’ or ‘variant inhibition’—the inhibition of the growth of recrystallized grains by contact with regions in the deformed material with similar orientation, and (ii) the simple model, αC = NCdR/λC, for predicting the frequency of recrystallized cube grains based on nucleation from closely spaced deformed cube bands inherited from pre-existing cube grains. λC is the mean spacing between deformed cube bands,dR is the thickness of the recrystallized grains, both measured in the normal direction, ND, and NC is the number of cube grains per cube band in a linear traverse in ND. Detailed experimental results by orientation imaging microscopy have confirmed the importance of orientation pinning in preventing the development of the majority deformation texture components in warm deformed aluminum since here dR > λV, the inter-variant spacing of the rolling texture variants. In the same material cold rolled to an equivalent strain, retained rolling texture developed since, after cold rolling,dR
04 Jan 1998
TL;DR: The performance of the proposed MAP-MRF based scheme for simultaneous recovery of the depth and the focused image of a scene from two defocused images is found to be better than that of existing window-based techniques.
Abstract: A MAP-MRF based scheme is proposed for simultaneous recovery of the depth and the focused image of a scene from two defocused images. The space-variant blur parameter and the focused image of the scene are both modeled as MRFs and their MAP estimates are obtained using simulated annealing. The performance of the proposed scheme is tested on synthetic as well as real data and the estimates of the depth are found to be better than that of existing window-based techniques.
TL;DR: In this article, a circular microstrip antenna has been modified by shorting along the zero field to yield shorted semi-circular and 90° sectoral microstrip antennas.
Abstract: A circular microstrip antenna has been modified by shorting along the zero field to yield shorted semi-circular and 90° sectoral microstrip antennas. Experimental results on these antennas are presented. The shorted 90° sectoral antenna results in a size reduction of four times without any significant change in performance. The area is further reduced by partially shorting one of the edges of the 90° sectoral antenna.
TL;DR: In this article, the thermal properties, electrical conductivity and vibrational spectra of PEO based electrolyte membranes of various compositions, x PEO(1− x )[LiCF 3 SO 3 /Dibutyl phthalate], where x varies from 0.17 to 0.84 were prepared by solution casting.
TL;DR: In this article, large amplitude limit cycles were described in terms of primary Hopf secondary fold bifurcation pairs, and the mechanism responsible for such limit cycles is non linear damping.
TL;DR: This contribution slightly extends the first approach and combines it with the second in order to demonstrate that consequent exploitation of model knowledge will lead to robust tracking results even for complex driving manoeuvres, significant occlusions, low contrast and small vehicle images.