65,514 research outputs found
On the Distribution of the Sum of n Non-Identically Distributed Uniform Random Variables
The distribution of the sum of independent identically distributed uniform
random variables is well-known. However, it is sometimes necessary to analyze
data which have been drawn from different uniform distributions. By inverting
the characteristic function, we derive explicit formulae for the distribution
of the sum of n non-identically distributed uniform random variables in both
the continuous and the discrete case. The results, though involved, have a
certain elegance. As examples, we derive from our general formulae some special
cases which have appeared in the literature.Comment: 20 page
Fe and N self-diffusion in non-magnetic Fe:N
Fe and N self-diffusion in non-magnetic FeN has been studied using neutron
reflectivity. The isotope labelled multilayers, FeN/57Fe:N and Fe:N/Fe:15N were
prepared using magnetron sputtering. It was remarkable to observe that N
diffusion was slower compared to Fe while the atomic size of Fe is larger
compared to N. An attempt has been made to understand the diffusion of Fe and N
in non-magnetic Fe:N
Understanding the effects of geometry and rotation on pulsar intensity profiles
We have developed a method to compute the possible distribution of radio
emission regions in a typical pulsar magnetosphere, taking into account the
viewing geometry and rotational effects of the neutron star. Our method can
estimate the emission altitude and the radius of curvature of particle
trajectory as a function of rotation phase for a given inclination angle,
impact angle, spin-period, Lorentz factor, field line constant and the
observation frequency. Further, using curvature radiation as the basic emission
mechanism, we simulate the radio intensity profiles that would be observed from
a given distribution of emission regions, for different values of radio
frequency and Lorentz factor. We show clearly that rotation effects can
introduce significant asymmetries into the observed radio profiles. We
investigate the dependency of profile features on various pulsar parameters. We
find that the radiation from a given ring of field lines can be seen over a
large range of pulse longitudes, originating at different altitudes, with
varying spectral intensity. Preferred heights of emission along discrete sets
of field lines are required to reproduce realistic pulsar profiles, and we
illustrate this for a known pulsar. Finally, we show how our model provides
feasible explanations for the origin of core emission, and also for one-sided
cones which have been observed in some pulsars.Comment: 21 pages, 11 figures, accepted for publication in MNRA
Aharonov-Bohm effect in the presence of evanescent modes
It is known that differential magnetoconductance of a normal metal loop
connected to reservoirs by ideal wires is always negative when an electron
travels as an evanescent modes in the loop. This is in contrast to the fact
that the magnetoconductance for propagating modes is very sensitive to small
changes in geometric details and the Fermi energy and moreover it can be
positive as well as negative. Here we explore the role of impurities in the
leads in determining the magnetoconductance of the loop. We find that the
change in magnetoconductance is negative and can be made large provided the
impurities do not create resonant states in the systems. This theoretical
finding may play an useful role in quantum switch operations.Comment: 9 figures available on reques
Surfactant induced smooth and symmetric interfaces in Cu/Co multilayers
In this work we studied Ag surfactant induced growth of Cu/Co multilayers.
The Cu/Co multilayers were deposited using Ag surfactant by ion beam sputtering
technique. It was found that Ag surfactant balances the asymmetry between the
surface free energy of Cu and Co. As a result, the Co-on-Cu and Cu-on-Co
interfaces become sharp and symmetric and thereby improve the thermal stability
of the multilayer. On the basis of obtained results, a mechanism leading to
symmetric and stable interfaces in Cu/Co multilayers is discussed.Comment: 7 Pages, 7 Figure
Socioeconomic impact and farmers' assessment of Nile tilapia (Oreochromis niloticus) culture in Bangladesh
The book reports on the socioeconomic study made on tilapia culture in seasonal ponds/ditches in Bangladesh. Results show that the simple technology, requiring very low labor input, is economically viable and brings other benefits.Tilapia culture, Sociological aspects, Cost benefit analysis, Aquaculture techniques, Bangladesh, Oreochromis niloticus
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