4,974 research outputs found
Recovery of Vanadium Pentoxide from Vanadium Bearing Titaniferrous Magnetites Projected Pilot Plant Studies
The treatment of vanadium bearing ores for the recovery
of vanadium pentoxide is not new to India. A plant capable of producing 250 lbs. of vanadium pentoxide per day was set up at Jamshedpur during World War II by the Tata Iron & Steel Co. Ltd., but as the demand of ferro-vanadium decreased considerably after the war, the plant had to be shut down. A company was also set up for the extraction of vanadium at Rairangpur during World War II and it is reported that the plant went-into production in September,
1945 and stopped work in April 1946 and has since been lying idle.Various reasons, viz., high cost of production, lack of demand etc. have been assigned for closing down the plant. With the country's industrial development and the establishment of'"the alloy and tool steel industry, as envisaged in the 3rd Five Year Plan, it is anticipated that the demand of ferro-vanadium will increase consid-erably
Machine-Vision Aids for Improved Flight Operations
The development of machine vision based pilot aids to help reduce night approach and landing accidents is explored. The techniques developed are motivated by the desire to use the available information sources for navigation such as the airport lighting layout, attitude sensors and Global Positioning System to derive more precise aircraft position and orientation information. The fact that airport lighting geometry is known and that images of airport lighting can be acquired by the camera, has lead to the synthesis of machine vision based algorithms for runway relative aircraft position and orientation estimation. The main contribution of this research is the synthesis of seven navigation algorithms based on two broad families of solutions. The first family of solution methods consists of techniques that reconstruct the airport lighting layout from the camera image and then estimate the aircraft position components by comparing the reconstructed lighting layout geometry with the known model of the airport lighting layout geometry. The second family of methods comprises techniques that synthesize the image of the airport lighting layout using a camera model and estimate the aircraft position and orientation by comparing this image with the actual image of the airport lighting acquired by the camera. Algorithms 1 through 4 belong to the first family of solutions while Algorithms 5 through 7 belong to the second family of solutions. Algorithms 1 and 2 are parameter optimization methods, Algorithms 3 and 4 are feature correspondence methods and Algorithms 5 through 7 are Kalman filter centered algorithms. Results of computer simulation are presented to demonstrate the performance of all the seven algorithms developed
Numerical Diagonalisation Study of the Trimer Deposition-Evaporation Model in One Dimension
We study the model of deposition-evaporation of trimers on a line recently
introduced by Barma, Grynberg and Stinchcombe. The stochastic matrix of the
model can be written in the form of the Hamiltonian of a quantum spin-1/2 chain
with three-spin couplings given by H= \sum\displaylimits_i [(1 -
\sigma_i^-\sigma_{i+1}^-\sigma_{i+2}^-) \sigma_i^+\sigma_{i+1}^+\sigma_{i+2}^+
+ h.c]. We study by exact numerical diagonalization of the variation of
the gap in the eigenvalue spectrum with the system size for rings of size up to
30. For the sector corresponding to the initial condition in which all sites
are empty, we find that the gap vanishes as where the gap exponent
is approximately . This model is equivalent to an interfacial
roughening model where the dynamical variables at each site are matrices. From
our estimate for the gap exponent we conclude that the model belongs to a new
universality class, distinct from that studied by Kardar, Parisi and Zhang.Comment: 11 pages, 2 figures (included
Broadband Passive Sonar Signal Simulation in Shallow Ocean
The broadband plane wave model is valid only in the far-field of a point source under free-field propagating conditions. However the acoustics in ocean is characterized by multi-modal acoustic propagation due to its top-bottom limited boundary conditions. The effect of multi-modal field is to alter the source spectrum while the effect of dispersion is to modify the pulse shape. Moreover the use of a plane wave beamformer in a multi-modal field leads to a bias in the bearing estimates. These effects are highly dependant on the environment parameters and have important ramifications for target localization and classification in an ocean waveguide. We propose a more realistic simulator which essentially models these effects and therefore serves to provide test signals for first hand verification of signal processing algorithms to be developed for such scenarios. This model is to be understood as a better model than the naïve plane wave model which is entirely oblivious of even the gross features such as wave propagation in an oceanic waveguide. The channel parameter so estimated from the present simulation can be convolved with the radiated noise spectra of the source to generate the passive sonar signal.Defence Science Journal, 2011, 61(4), pp.370-376, DOI:http://dx.doi.org/10.14429/dsj.61.8
Persistence at the onset of spatiotemporal intermittency in coupled map lattices
We study persistence in coupled circle map lattices at the onset of
spatiotemporal intermittency, an onset which marks a continuous transition, in
the universality class of directed percolation, to a unique absorbing state. We
obtain a local persistence exponent of theta_l = 1.49 +- 0.02 at this
transition, a value which closely matches values for theta_l obtained in
stochastic models of directed percolation. This result constitutes suggestive
evidence for the universality of persistence exponents at the directed
percolation transition. Given that many experimental systems are modelled
accurately by coupled map lattices, experimental measurements of this
persistence exponent may be feasible.Comment: 7 pages, Latex, 6 Postscript figures, Europhysics Letters (to appear
The Irreducible String and an Infinity of Additional Constants of Motion in a Deposition-Evaporation Model on a Line
We study a model of stochastic deposition-evaporation with recombination, of
three species of dimers on a line. This model is a generalization of the model
recently introduced by Barma {\it et. al.} (1993 {\it Phys. Rev. Lett.} {\bf
70} 1033) to states per site. It has an infinite number of constants
of motion, in addition to the infinity of conservation laws of the original
model which are encoded as the conservation of the irreducible string. We
determine the number of dynamically disconnected sectors and their sizes in
this model exactly. Using the additional symmetry we construct a class of exact
eigenvectors of the stochastic matrix. The autocorrelation function decays with
different powers of in different sectors. We find that the spatial
correlation function has an algebraic decay with exponent 3/2, in the sector
corresponding to the initial state in which all sites are in the same state.
The dynamical exponent is nontrivial in this sector, and we estimate it
numerically by exact diagonalization of the stochastic matrix for small sizes.
We find that in this case .Comment: Some minor errors in the first version has been correcte
Capillary deformations of bendable films
We address the partial wetting of liquid drops on ultrathin solid sheets resting on a deformable foundation. Considering the membrane limit of sheets that can relax compression through wrinkling at negligible energetic cost, we revisit the classical theory for the contact of liquid drops on solids. Our calculations and experiments show that the liquid-solid-vapor contact angle is modified from the Young angle, even though the elastic bulk modulus (E) of the sheet is so large that the ratio between the surface tension γ and E is of molecular size. This finding establishes a new type of “soft capillarity” that stems from the bendability of thin elastic bodies rather than from material softness. We also show that the size of the wrinkle pattern that emerges in the sheet is fully predictable, thus resolving a puzzle noticed in several previous attempts to model “drop-on-a-floating-sheet” experiments, and enabling a reliable usage of this setup for the metrology of ultrathin films
The Glass Transition and Liquid-Gas Spinodal Boundaries of Metastable Liquids
A liquid can exist under conditions of thermodynamic stability or
metastability within boundaries defined by the liquid-gas spinodal and the
glass transition line. The relationship between these boundaries has been
investigated previously using computer simulations, the energy landscape
formalism, and simplified model calculations. We calculate these stability
boundaries semi-analytically for a model glass forming liquid, employing
accurate liquid state theory and a first-principles approach to the glass
transition. These boundaries intersect at a finite temperature, consistent with
previous simulation-based studies.Comment: Minor text revisions. Fig.s 4, 5 update
The Nature of the Activity in Hickson Compact Groups of Galaxies
We present the results of the spectral classification of the 82 brightest
galaxies in a sample of 17 compact groups. We verify that the AGNs are
preferentially located in the most early-type and luminous galaxies of the
groups, as is usually observed in the field. But these AGNs also appear to be
systematically concentrated towards the central parts of the groups. Our
observations suggest a correlation between activity types, morphologies and
densities of galaxies in the compact groups. This is consistent with a scenario
in which galaxies of compact groups evolve by interacting with their
environment and are currently in a quiet phase of their activityComment: 22 pages, LaTeX (aasms4.sty) + 7 figures; accepted for publication in
the Astrophysical Journa
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