13,605 research outputs found
Comparison between Windowed FFT and Hilbert-Huang Transform for Analyzing Time Series with Poissonian Fluctuations: A Case Study
Hilbert-Huang Transform (HHT) is a novel data analysis technique for
nonlinear and non-stationary data. We present a time-frequency analysis of both
simulated light curves and an X-ray burst from the X-ray burster 4U 1702-429
with both the HHT and the Windowed Fast Fourier Transform (WFFT) methods. Our
results show that the HHT method has failed in all cases for light curves with
Poissonian fluctuations which are typical for all photon counting instruments
used in astronomy, whereas the WFFT method can sensitively detect the periodic
signals in the presence of Poissonian fluctuations; the only drawback of the
WFFT method is that it cannot detect sharp frequency variations accurately.Comment: 10 pages, 12 figure
Studies on the leptocephali of Bombay waters V. A few other Leptocephali
Leptocephali belonging to the family Murrenidre arc very common in Indian coastal waters as judged by the relatively large member of varieties recorded so far. Including the present form 14 varieties of murrenid leptocephali and 1 murrenid preleptocephalinc stage have been recorded from
both the coasts of India
Flux dependent 1.5 MeV self-ion beam induced sputtering from Gold nanostructured thin films
We discuss four important aspects of 1.5 MeV Au2+ ion-induced flux dependent
sputtering from gold nanostrcutures (of an average size 7.6 nm and height 6.9
nm) that are deposited on silicon substrates: (a) Au sputtering yield at the
ion flux of 6.3x10^12 ions cm-2 s-1 is found to be 312 atoms/ion which is about
five times the sputtering yield reported earlier under identical irradiation
conditions at a lower beam flux of 10^9 ions cm-2 s-1, (b) the sputtered yield
increases with increasing flux at lower fluence and reduces at higher fluence
(1.0x10^15 ions cm-2) for nanostructured thin films while the sputtering yield
increases with increasing flux and fluence for thick films (27.5 nm Au
deposited on Si) (c) Size distribution of sputtered particles has been found to
vary with the incident beam flux showing a bimodal distribution at higher flux
and (d) the decay exponent obtained from the size distributions of sputtered
particles showed an inverse power law dependence ranging from 1.5 to 2.5 as a
function of incident beam flux. The exponent values have been compared with
existing theoretical models to understand the underlying mechanism. The role of
wafer temperature associated with the beam flux has been invoked for a
qualitative understanding of the sputtering results in both the nanostructured
thin films and thick films.Comment: 25 pages, 5 figures, 1 table To be Appeared in J. Phys. D: Appl. Phy
Unimpeded permeation of water through helium-leak-tight graphene-based membranes
Permeation through nanometer pores is important in the design of materials
for filtration and separation techniques and because of unusual fundamental
behavior arising at the molecular scale. We found that submicron-thick
membranes made from graphene oxide can be completely impermeable to liquids,
vapors and gases, including helium, but allow unimpeded permeation of water
(H2O permeates through the membranes at least 10^10 times faster than He). We
attribute these seemingly incompatible observations to a low-friction flow of a
monolayer of water through two dimensional capillaries formed by closely spaced
graphene sheets. Diffusion of other molecules is blocked by reversible
narrowing of the capillaries in low humidity and/or by their clogging with
water
Survey on the idle capacity of fish processing (freezing) plants in India - 2. East coast
The extent of idle capacity in the fish processing (freezing) plants in the east coast of India estimated by stratified random sampling and the factors responsible for the same are reported. The estimates of idle capacity of fish processing plants in the east coast for the years 1978 and 1979 were respectively 75.9% and 72.5% on the basis of 250 working days per annum and double shift per day. The percentage errors of estimates worked out to 6.9 for 1978 and 4.7 for 1979. The corresponding figures were worked out on the basis of 200 working days also. Substantial under-utilisation of plants in all the maritime states in the east coast accounted mainly to non-availability of raw material, high cost of production, shortage of power, scarcity of ice and potable water during peak season and frequent labour troubles
Prawn and fish culture for increased yields
Although culture of marine fish
and shell fish in one form or the
other has been in existence in different
parts of the world from ancient
times, yet its progress h as been rather
slow till a couple of decades ago.
Over the years, accent has been on
exploitation of the readily available
natural stocks from seas rather than
on culture operations
Color Skyrmions in the Quark-Gluon Plasma
We consider the general formulation of nonabelian fluid dynamics based on
symmetry considerations. We point out that, quite generally, this admits
solitonic excitations which are the color analog of skyrmions. Some general
properties of the solitons are discussed.Comment: LaTeX, 13 pages, references adde
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