5,273 research outputs found
Crystals for Demazure Modules of Classical Affine Lie Algebras
We study, in the path realization, crystals for Demazure modules of affine
Lie algebras of types . We find a special sequence of
affine Weyl group elements for the selected perfect crystal, and show if the
highest weight is l\La_0, the Demazure crystal has a remarkably simple
structure.Comment: Latex, 28 page
A Resource Based Stage-Structured Fishery Model With Selective Harvesting of Mature Species
In this paper we have considered a model in which revenue is generated from fishing and the growth of the fish depends upon the plankton which in turn follows a logistic law of growth. Here the fish population has two stages, a juvenile stage and a mature stage and we consider the harvesting of the mature fish species. Stability and permanence of the system are discussed. Maximum sustainable yield, maximum economic yield and optimal sustainable yield are obtained and different tax policies are discussed to achieve the reference points
Fluctuation Cumulant Behavior for the Field-Pulse Induced Magnetisation-Reversal Transition in Ising Models
The universality class of the dynamic magnetisation-reversal transition,
induced by a competing field pulse, in an Ising model on a square lattice,
below its static ordering temperature, is studied here using Monte Carlo
simulations. Fourth order cumulant of the order parameter distribution is
studied for different system sizes around the phase boundary region. The
crossing point of the cumulant (for different system sizes) gives the
transition point and the value of the cumulant at the transition point
indicates the universality class of the transition. The cumulant value at the
crossing point for low temperature and pulse width range is observed to be
significantly less than that for the static transition in the same
two-dimensional Ising model. The finite size scaling behaviour in this range
also indicates a higher correlation length exponent value. For higher
temperature and pulse width range, the transition seems to fall in a mean-field
like universality class.Comment: 5 pages, 8 eps figures, thoroughly revised manuscript with new
figures, accepted in Phys. Rev. E (2003
Preparation and Structural Characterization of ZnSe Thin Films by X-Ray Diffraction Technique
Microstructural changes induced by ternary additions in a hypo-eutectic titanium-silicon alloy
Hypo-eutectic Ti-6.5 wt % Si alloy modified by separate additions of misch metal and low surface tension elements (Na, Sr, Se and Bi) has been examined by microscopic study and thermal analysis. Addition of third element led to modification of microstructure with apparently no significant enhancement of tensile ductility, with the exception of bismuth. Bismuth enhanced the ductility of the alloy by a factor of two and elastic-plastic fracture toughness to 9 MPa m-½ from a value of almost zero. The improved ductility of bismuth modified alloy is attributed to the reduced interconnectivity of the eutectic suicide, absence of significant suicide precipitation in the eutectic region and increase in the volume fraction of uniformly distributed dendrites. These changes are accompanied by a decrease in the temperature of eutectic solidification
On the evaluation of stability of rare earth oxides as face coats for investment casting of titanium
Attempts have been made to evaluate the thermal stability of rare earth oxide face coats against liquid titanium. Determination of microhardness profiles and concentration profiles of oxygen and metallic constituents of oxide in investment cast titanium rods has allowed gradation of relative stability of rare earth oxides. The relative stability of evaluated oxides in the order of increasing stability follows the sequence CeO2 → ZrO2 → Gd2O3 → didymium oxide → Sm2O3 → Nd2O3 → Y2O3. The grading does not follow the free energy data of the formation of these oxides. A better correlation with the experimental observations is obtained when the solubility of the metallic species in titanium is also taken into consideration
Characterization of a deep-depletion 4K x 4K CCD Detector System designed for ADFOSC
We present the characterization of the CCD system developed for the ADFOSC
instrument on the 3.6m Devasthal Optical Telescope (DOT). We describe various
experiments performed to tune the CCD controller parameters to obtain optimum
performance in single and four-port readout modes. Different methodologies
employed for characterizing the performance parameters of the CCD, including
bias stability, noise, defects, linearity, and gain, are described here. The
CCD has grade-0 characteristics at temperatures close to its nominal operating
temperature of C. The overall system is linear with a regression
coefficient of 0.9999, readout noise of 6 electrons, and a gain value close to
unity. We demonstrate a method to calculate the dark signal using the gradient
in the bias frames at lower temperatures. Using the optimized setting, we
verify the performance of the CCD detector system on-sky using the ADFOSC
instrument mounted on the 3.6m DOT. Some science targets were observed to
evaluate the detector's performance in both imaging and spectroscopic modes.Comment: Accepted for publication in JATIS, SPI
Authors' reply re: Laparoscopic ablation or excision with helium thermal coagulator versus electrodiathermy for the treatment of mild-to-moderate endometriosis: randomised controlled trial.
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