7,073 research outputs found
Recommended from our members
Thaan Vuzha Nilam Tharisu: the land without a farmer becomes barren
This report forms a part of the international research project on policy and sustainable agriculture, Policies that Work for Sustainable Agriculture and Regenerated Rural Economies. The report details the findings of one of the constituent studies, undertaken by an Indian NGO, the Society for People's Education and Economic Change (SPEECH). The Importance of this project is that it concentrated on rainfed rather than irrigated agriculture - i.e. the sharp end of rural development in India, and that the focus was very much on the micro-level, looking at policy as seen from the ground. One of the recurring themes throughout the research was the importance of appreciating people as individuals, and in this spirit some of the personal qualities of the research team are shared. The research covers events in sites in the Virudhunagar district of Tamilnadu: Tiruchuli Panchayat Union and the Villur chain of tanks. This is an essentially rural area, where the need for sustainable forms of agriculture and rural livelihoods is clear. The political landscape is fractured and complex (§2.3), and the officials with the responsibility of implementing policy face significant obstacles and disincentives in doing so in response to the needs of local communities
Conditions for the Quantum to Classical Transition: Trajectories vs. Phase Space Distributions
We contrast two sets of conditions that govern the transition in which
classical dynamics emerges from the evolution of a quantum system. The first
was derived by considering the trajectories seen by an observer (dubbed the
``strong'' transition) [Bhattacharya, et al., Phys. Rev. Lett. 85: 4852
(2000)], and the second by considering phase-space densities (the ``weak''
transition) [Greenbaum, et al., Chaos 15, 033302 (2005)]. On the face of it
these conditions appear rather different. We show, however, that in the
semiclassical regime, in which the action of the system is large compared to
, and the measurement noise is small, they both offer an essentially
equivalent local picture. Within this regime, the weak conditions dominate
while in the opposite regime where the action is not much larger than Planck's
constant, the strong conditions dominate.Comment: 8 pages, 2 eps figure
Parameter scaling in the decoherent quantum-classical transition for chaotic systems
The quantum to classical transition has been shown to depend on a number of
parameters. Key among these are a scale length for the action, , a
measure of the coupling between a system and its environment, , and, for
chaotic systems, the classical Lyapunov exponent, . We propose
computing a measure, reflecting the proximity of quantum and classical
evolutions, as a multivariate function of and searching for
transformations that collapse this hyper-surface into a function of a composite
parameter . We report results
for the quantum Cat Map, showing extremely accurate scaling behavior over a
wide range of parameters and suggest that, in general, the technique may be
effective in constructing universality classes in this transition.Comment: Submitte
Quantized Orbits and Resonant Transport
A tight binding representation of the kicked Harper model is used to obtain
an integrable semiclassical Hamiltonian consisting of degenerate "quantized"
orbits. New orbits appear when renormalized Harper parameters cross integer
multiples of . Commensurability relations between the orbit frequencies
are shown to correlate with the emergence of accelerator modes in the classical
phase space of the original kicked problem. The signature of this resonant
transport is seen in both classical and quantum behavior. An important feature
of our analysis is the emergence of a natural scaling relating classical and
quantum couplings which is necessary for establishing correspondence.Comment: REVTEX document - 8 pages + 3 postscript figures. Submitted to
Phys.Rev.Let
Frequency reconfigurable antennas for cognitive radio applications: a review
Wireless communication systems undergo tremendous growth these days and devices able to operate in a number of frequencybandsarehighlydemanded. Reconfiguration in antenna characteristic striggered the evolution of antennas that can workin multiple frequency, pattern or polarization environment.The frequency reconfigurable antennas thuse mergedarewell suited in Cognitive Radios which take part in the effective utilization of unused bands of frequencies by continuously interacting with the RF environment. Thus, Cognitive Radios enhancetheutilization of frequency spectrum and establish reliable communication. The most recent research works carried out in the arena of Frequency Reconfigurable Antennas for Cognitive Radio applications are reviewed and summed up in this paper to present the attributes and categorization. Four techniques adopted to attain frequency reconfiguration are extensively compared in this paper to find the advantages and constraints of each methodology. The applications of the works reviewed here are not only limited to Cognitive radios, but extended to a number of wireless communication services like, WLAN, WiMAX, et
Persistent patterns and multifractality in fluid mixing
Persistent patterns in periodically driven dynamics have been reported in a wide variety of contexts ranging from table-top and ocean-scale fluid mixing systems to the weak quantum-classical transition in open Hamiltonian systems. We illustrate a common framework for the emergence of these patterns by considering a simple measure of structure maintenance provided by the average radius of the scalar distribution in transform space. Within this framework, scaling laws related to both the formation and persistence of patterns in phase space are presented. Further, preliminary results linking the scaling exponents associated with the persistent patterns to the multifractal nature of the advective phase-space geometry are shown
Time Evolution Of Cyclotron Line of Her X-1; A Detailed StatisticalAnalysis Including New ASTROSAT Data
The cyclotron line feature in the X-ray spectrum of the accretion powered
pulsar Her X-1 has been observed and monitored for over three decades. The line
energy exhibited a slow secular decline over the period 1995-2014, with a
possible (not confirmed) indication of a reversal thereafter. Recent works have
shown that the temporal evolution of the line energy may be modelled as a
flattening after an earlier decrease until MJD 55400 (. In this work,
we present the results of ASTROSAT observations in the context of earlier data
and offer a common interpretation through a detailed study of temporal and flux
dependence. We find that the variation of the line energy does not support an
upward trend but is consistent with the reported flattening after an earlier
decrease until MJD .Comment: Accepted in MNRA
Parametrized tests of post-Newtonian theory using Advanced LIGO and Einstein Telescope
General relativity has very specific predictions for the gravitational
waveforms from inspiralling compact binaries obtained using the post-Newtonian
(PN) approximation. We investigate the extent to which the measurement of the
PN coefficients, possible with the second generation gravitationalwave
detectors such as the Advanced Laser Interferometer Gravitational-Wave
Observatory (LIGO) and the third generation gravitational-wave detectors such
as the Einstein Telescope (ET), could be used to test post-Newtonian theory and
to put bounds on a subclass of parametrized-post-Einstein theories which differ
from general relativity in a parametrized sense. We demonstrate this
possibility by employing the best inspiralling waveform model for nonspinning
compact binaries which is 3.5PN accurate in phase and 3PN in amplitude. Within
the class of theories considered, Advanced LIGO can test the theory at 1.5PN
and thus the leading tail term. Future observations of stellar mass black hole
binaries by ET can test the consistency between the various PN coefficients in
the gravitational-wave phasing over the mass range of 11-44 Msun. The choice of
the lower frequency cut off is important for testing post-Newtonian theory
using the ET. The bias in the test arising from the assumption of nonspinning
binaries is indicated.Comment: 18 pages, 11 figures, Matches with the published versio
- …