21,115 research outputs found
Characteristic Variability Time Scales of Long Gamma-Ray Bursts
We determined the characteristic variability time scales (\Delta t_p) of 410
bright and long GRBs, by locating the peaks of their Power Density Spectra,
defined and calculated in the time domain. We found that the averaged
variability time scale decreases with the peak flux. This is consistent with
the time-dilation effect expected for the cosmological origin of GRBs. We also
found that the occurrence distribution of the characteristic variability time
scale shows bimodality, which might be interpreted as that the long GRB sample
is composed of two sub-classes with different variability time scales. However,
we found no difference for some other characteristics of these two sub-classes.Comment: 10 pages, 5 figures, corrected some typos and syntaxes, enlarged the
label fonts in fig.3 and fig.
Fish diseases in India, their causes and control measures - Winter school on recent advances in diagnosis and management of diseases in mariculture, 7th to 27th November 2002, Course Manual
In recent years intensive fish culture is being practiced in the brackishwater, coastal water and freshwater impoundments of India. Recent techniques of intensive and
super intensive fish culture involve high rates of stocking and supplementary feeding which has substantially enhanced the incidence of diseases in fishes in our countr
Asymptotically Optimal Load Balancing Topologies
We consider a system of servers inter-connected by some underlying graph
topology . Tasks arrive at the various servers as independent Poisson
processes of rate . Each incoming task is irrevocably assigned to
whichever server has the smallest number of tasks among the one where it
appears and its neighbors in . Tasks have unit-mean exponential service
times and leave the system upon service completion.
The above model has been extensively investigated in the case is a
clique. Since the servers are exchangeable in that case, the queue length
process is quite tractable, and it has been proved that for any ,
the fraction of servers with two or more tasks vanishes in the limit as . For an arbitrary graph , the lack of exchangeability severely
complicates the analysis, and the queue length process tends to be worse than
for a clique. Accordingly, a graph is said to be -optimal or
-optimal when the occupancy process on is equivalent to that on
a clique on an -scale or -scale, respectively.
We prove that if is an Erd\H{o}s-R\'enyi random graph with average
degree , then it is with high probability -optimal and
-optimal if and as , respectively. This demonstrates that optimality can
be maintained at -scale and -scale while reducing the number of
connections by nearly a factor and compared to a
clique, provided the topology is suitably random. It is further shown that if
contains bounded-degree nodes, then it cannot be -optimal.
In addition, we establish that an arbitrary graph is -optimal when its
minimum degree is , and may not be -optimal even when its minimum
degree is for any .Comment: A few relevant results from arXiv:1612.00723 are included for
convenienc
Scattering of Electron by Thomas-Fermi Potential
In this paper the elastic scatterriag cross-section of electrons by the
Thomas-Fermi potential as represented by the analytical forms due to Gombas and Tiets
has been calculated by the Born approximation method. Our results are in fair agreement
with those calculated with the exact numerical form of Thomas-Fermi potential. Further
comparison shows that the Gombas-Tietz form is a good as those of Rozental and Buchdahl
Ultrapure glass optical waveguide: Development in microgravity by the sol gel process
The sol-gel process for the preparation of homogeneous gels in three binary oxide systems was investigated. The glass forming ability of certain compositions in the selected oxide systems (SiO-GeO2, GeO2-PbO, and SiO2-TiO2) were studied based on their potential importance in the design of optical waveguide at longer wavelengths
Universality of Load Balancing Schemes on Diffusion Scale
We consider a system of parallel queues with identical exponential
service rates and a single dispatcher where tasks arrive as a Poisson process.
When a task arrives, the dispatcher always assigns it to an idle server, if
there is any, and to a server with the shortest queue among randomly
selected servers otherwise . This load balancing scheme
subsumes the so-called Join-the-Idle Queue (JIQ) policy and the
celebrated Join-the-Shortest Queue (JSQ) policy as two crucial
special cases. We develop a stochastic coupling construction to obtain the
diffusion limit of the queue process in the Halfin-Whitt heavy-traffic regime,
and establish that it does not depend on the value of , implying that
assigning tasks to idle servers is sufficient for diffusion level optimality
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