507 research outputs found
Power and spectrally efficient M-ARY QAM schemes for future mobile satellite communications
An effective method to compensate nonlinear phase distortion caused by the mobile amplifier is proposed. As a first step towards the future use of spectrally efficient modulation schemes for mobile satellite applications, we have investigated effects of nonlinearities and the phase compensation method on 16-QAM. The new method provides about 2 dB savings in power for 16-QAM operation with cost effective amplifiers near saturation and thereby promising use of spectrally efficient linear modulation schemes for future mobile satellite applications
Introduction to geostatistics
Geographical Information System (GIS) is a technological tool used to describe and
characterize spatially referenced geographical information for the purpose of visualizing,
querying and analyzing. The tool enables capturing, storing, analyzing, sharing, displaying
and modelling of spatial data maintained with in single database. Making decision based
on geography is basics to human thinking and spatial analysis using GIS enable people to
combine information from many independent sources and derive entirely new layers of
information that are more accurate and reliable in decision making. Spatial analysis involves
study of phenomenon that varies with time and space
Estimation of imprints of the bounce in loop quantum cosmology on the bispectra of cosmic microwave background
Primordial non-Gaussianity has set strong constraints on models of the early
universe. Studies have shown that Loop Quantum Cosmology (LQC), which is an
attempt to extend inflationary scenario to planck scales, leads to a strongly
scale dependent and oscillatory non-Gaussianity. In particular, the
non-Gaussianity function generated in LQC,
though similar to that generated during slow roll inflation at small scales, is
highly scale dependent and oscillatory at long wavelengths. In this work, we
investigate the imprints of such a primordial bispectrum in the bispectrum of
Cosmic Microwave Background (CMB). Inspired by earlier works, we propose an
analytical template for the primordial bispectrum in LQC. We write the template
as a sum of strongly scale dependent and oscillatory part, which captures the
contribution due to the bounce, and a part which captures the scale invariant
behaviour similar to that of slow roll. We then compute the reduced bispectra
of temperature and electric polarisation and their three-point
cross-correlations corresponding to these two parts. We show that the
contribution from the bounce to the reduced bispectrum is negligible compared
to that from the scale-independent part. Thus, we conclude that the CMB
bispectra generated in LQC will be similar to that generated in slow roll
inflation. We conclude with a discussion of our results and its implications to
LQC.Comment: v1:17 pages, 8 figures; v2: 23 pages, 9 figures, improved template of
bispectrum, new subsections added, version accepted for publication in JCA
‘Eastern’ Common Swift Apus apus pekinensis in the Lakshadweep Archipelago, with identification notes on juvenile birds
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Techno-Economic Analysis of Hybrid Layered Manufacturing
Subtractive manufacturing (CNC machining) has high quality of geometric and
material properties but is slow, costly and infeasible in some cases; additive
manufacturing (RP) is just the opposite. Total automation and hence speed is
achieved in RP by compromising on quality. Hybrid Layered Manufacturing
(HLM) developed at IIT Bombay combines the best features of both these
approaches. It uses arc welding for building near-net shapes which are finish
machined to final dimensions. High speed of HLM surpasses all other processes
for tool making by eliminating NC programming and rough machining. The
techno-economic viability of HLM process has been proved through a real life
case study. Time and cost of tool making using HLM promises to be substantially
lower than that of CNC machining and other RP methods. Interestingly, the
material cost in HLM was also found to be lower. HLM is a cheaper retrofitment
to any 3 or 5 axis CNC milling machine or machining center.Mechanical Engineerin
Cooling through parametric modulations and phase-preserving quantum measurements
We propose a cooling protocol that uses phase-preserving quantum measurements
and phase-dependent modulations of the trapping potential at parametric
resonance to cool a quantum oscillator to near its quantum-mechanical
ground-state. The sequential measurements and feedback provide a definite phase
reference and stabilize the oscillator in the long-time limit. The protocol is
robust against moderate amounts of dissipation and phase errors in the feedback
loop. Our work has implications for the cooling of mechanical resonators and
the integration of quantum refrigerators into quantum circuits.Comment: 18 pages, of which 6 are the main text and the remainder supplemental
material, 6 figure
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