21,476 research outputs found
Anti-correlated hard X-ray time lags in Galactic black hole sources
We investigate the accretion disk geometry in Galactic black hole sources by
measuring the time delay between soft and hard X-ray emissions. Similar to the
recent discoveries of anti-correlated hard X-ray time lags in Cyg X-3 and GRS
1915+105, we find that the hard X-rays are anti-correlated with soft X-rays
with a significant lag in another source: XTE J1550-564. We also find the
existence of pivoting in the model independent X-ray spectrum during these
observations. We investigate time-resolved X-ray spectral parameters and find
that the variation in these parameters is consistent with the idea of a
truncated accretion disk. The QPO frequency, which is a measure of the size of
truncated accretion disk, too changes indicating that the geometric size of the
hard X-ray emitting region changes along with the spectral pivoting and soft
X-ray flux. Similar kind of delay is also noticed in 4U 1630-47.Comment: 14 pages, 7 figures, accepted for publication in Ap
Theoretical studies on tone noise from a ducted fan rotor
The method of computing radiated noise from a ducted rotor due to inflow distortion and turbulence are examined. Analytical investigations include an appropriate description of sources, the cut-off conditions imposed on the modal propagation of the pressure waves in the annular duct, and reflections at the upstream end of the duct. Far field sound pressure levels at blade passing frequency due to acoustic radiation from a small scale low speed fan are computed. Theoretical predictions are in reasonable agreement with experimental measurements
Groundwater externalities of surface irrigation transfers under National River Linking Project: Polavaram – Vijayawada link
River basin managementRiver basin developmentDevelopment projectsWater transferIrrigation canalsGroundwater irrigationTube well irrigationRiceSurface irrigationCrop managementSoil salinityWaterlogging
Electrical and Magnetic behaviour of PrFeAsO0.8F0.2 superconductor
The superconducting and ground state samples of PrFeAsO0.8F0.2 and PrFeAsO
have been synthesised via easy and versatile single step solid state reaction
route. X-ray & Reitveld refine parameters of the synthesised samples are in
good agreement to the earlier reported value of the structure. The ground state
of the pristine compound (PrFeAsO) exhibited a metallic like step in
resistivity below 150K followed by another step at 12K. The former is
associated with the spin density wave (SDW) like ordering of Fe spins and later
to the anomalous magnetic ordering for Pr moments. Both the resistivity
anomalies are absent in case of superconducting PrFeAsO0.8F0.2 sample. Detailed
high field (up to 12Tesla) electrical and magnetization measurements are
carried out for superconducting PrFeAsO0.8F0.2 sample. The PrFeAsO0.8F0.2
exhibited superconducting onset (Tconset) at around 47K with Tc({\rho} =0) at
38K. Though the Tconset remains nearly invariant, the Tc({\rho} =0) is
decreased with applied field, and the same is around 23K under applied field of
12Tesla. The upper critical field (Hc2) is estimated from the Ginzburg Landau
equation (GL) fitting, which is found to be ~ 182Tesla. Critical current
density (Jc) being calculated from high field isothermal magnetization (MH)
loops with the help of Beans critical state model, is found to be of the order
of 103 A/cm2. Summarily, the superconductivity characterization of single step
synthesised PrFeAsO0.8F0.2 superconductor is presented.Comment: 15 Pages Text + Fig
Some experiences with the viscous-inviscid interaction approach
Methods for simulating compressible viscous flow using the viscid-inviscid interaction approach are described. The formulations presented range from the more familiar full-potential/boundary-layer interaction schemes to a method for coupling Euler/Navier-Stokes and boundary-layer algorithms. An effort is made to describe the advantages and disadvantages of each formulation. Sample results are presented which illustrate the applicability of the methods
Density and ultrasonic velocity measurements in hexyloxybenzylidene phenylazoaniline
The temperature variation of density and ultrasonic velocity of the liquid crystal hexyloxybenzylidene phenylazoaniline are reported. The density across the smectic A-smectic B transition is more predominant than the other transitions. The density variation with temperature and the calculated thermal expansion coefficients suggest that the transitions isotropic liquid-nematic, nematic-smectic A and smectic A-smectic B are of first order. Anomalous behaviour of ultrasonic velocity is observed across the isotropic liquid-nematic transition and prominent dips in velocity are observed at the nematic-smectic A and smectic A-smectic B transitions. The adiabatic compressibility (βad) Rao number (Ra) and molar compressibility (B) are estimated using the experimental density and ultrasonic velocity
A unified data flow model for fault tolerant computers
The Dataflow Simulation System (DFSS) at USL was used as the medium on which a functional simulaton of sIFT was produced. DFSS is written in PL/I and is supported by MULTICS. Within the simulation, all the interprocessor communication, fault simulation, system state data, and monitoring were implemented in dataflow and supported directly by DFSS. The actual processor level computation was carried out by the SIFT code in PASCAL. The interface between DFSS in PL/I and the SIFT code in PASCAL was supported under a mechanism in DFSS called a Node Realization Module (NRM)
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