1,423 research outputs found
Determination of the chromospheric quiet network element area index and its variation during 2008-2011
Generally it has been considered that the plages and sunspots are the main
contributors to the solar irradiance. There are small scale structures on the
sun with intermediate magnetic fields that could also contribute to the solar
irradiance. It has not yet been quantified how much of these small scale
structures contribute to the solar irradiance and how much it varies over the
solar cycle.
In this paper, we used Ca II K images obtained from the telescope installed
at Kodaikanal observatory. We report a method to separate the network elements
from the background structure and plage regions. We compute the changes in the
network element area index during the minimum phase of solar cycle and part of
the ascending phase of cycle 24. The measured area occupied by the network
elements is about 30% and plages less than 1% of the solar disk during the
observation period from February 2008-2011. During the extended period of
minimum activity it is observed that the network element area index decreases
by about 7% compared to the area occupied by the network elements in 2008. A
long term study of network element area index is required to understand the
variations over the solar cycle.Comment: 12 pages, 9 Figures, Accepted for publication in RA
Mitigating the source-side channel vulnerability by characterization of photon statistics
Quantum key distribution (QKD) theoretically offers unconditional security.
Unfortunately, the gap between theory and practice threatens side-channel
attacks on practical QKD systems. Many well-known QKD protocols use weak
coherent laser pulses to encode the quantum information. These sources differ
from ideal single photon sources and follow Poisson statistics. Many protocols,
such as decoy state and coincidence detection protocols, rely on monitoring the
photon statistics to detect any information leakage. The accurate measurement
and characterization of photon statistics enable the detection of adversarial
attacks and the estimation of secure key rates, strengthening the overall
security of the QKD system. We have rigorously characterized our source to
estimate the mean photon number employing multiple detectors for comparison
against measurements made with a single detector. Furthermore, we have also
studied intensity fluctuations to help identify and mitigate any potential
information leakage due to state preparation flaws. We aim to bridge the gap
between theory and practice to achieve information-theoretic security.Comment: Comments and suggestions are welcome
Indian Journal of Animal Science: a scientometric assessment and application of Lotka's Law (2015-2020)
This paper analyse the scientometric attributes of the publications that appeared in the Indian Journal of Animal Science, a scientific journal in animal breeding, physiology, nutrition, dairying, animal production and fisheries, etc. from 2015 to 2020. The bibliographic records of publications were retrieved from the Web of Science database and retrieved 1720 research papers. The collected data were analysed by using Web of Science and biblioshiny software. The results revealed that the maximum number of research papers were published during the year 2020 and also received maximum citations in the same year. The research contribution also followed the Lotka’s Law and found that the maximum contribution was given by the researchers of ICAR - Indian Veterinary Research Institute, Bareilly and the highest research publications were from India
Quantum key distribution with multiphoton pulses: An advantage
In this article, we introduce a quantum key distribution protocol for the
line of sight channels based on coincidence measurements. We present a
proof-of-concept implementation of our protocol. We show that using coincidence
measurements to monitor multi-photon pulses results in a higher secure key rate
over longer distances for such channels. This key rate is higher than popular
implementations of quantum key distribution protocol based on BB84, for
example, the GLLP analysis [Quant. Info. Comput. \textbf{4}, 325 (2004)]. In
the experiment, we could generate around more key bits per signal pulse
as compared to the GLLP analysis of BB84 protocol with similar parameters and
equal value of mean photon number.Comment: 12 pages, 4 figures and 3 tables. Final accepted version (Accepted
for publication in OSA Continuum
COVID-19 lockdown induced changes in NO2 levels across India observed by multi-satellite and surface observations
© Author(s) 2021. This work is distributed under the Creative Commons Attribution 4.0 License.We have estimated the spatial changes in NO 2levels over different regions of India during the COVID-19 lockdown (25 March-3 May 2020) using the satellite-based tropospheric column NO 2observed by the Ozone Monitoring Instrument (OMI) and the Tropospheric Monitoring Instrument (TROPOMI), as well as surface NO 2concentrations obtained from the Central Pollution Control Board (CPCB) monitoring network. A substantial reduction in NO 2levels was observed across India during the lockdown compared to the same period during previous business-as-usual years, except for some regions that were influenced by anomalous fires in 2020. The reduction (negative change) over the urban agglomerations was substantial (~20 %-40 %) and directly proportional to the urban size and population density. Rural regions across India also experienced lower NO 2values by ~15 %-25 %. Localised enhancements in NO 2associated with isolated emission increase scattered across India were also detected. Observed percentage changes in satellite and surface observations were consistent across most regions and cities, but the surface observations were subject to larger variability depending on their proximity to the local emission sources. Observations also indicate NO 2enhancements of up to~25%during the lockdown associated with fire emissions over the north-east of India and some parts of the central regions. In addition, the cities located near the large fire emission sources show much smaller NO 2reduction than other urban areas as the decrease at the surface was masked by enhancement in NO 2due to the transport of the fire emissions.Peer reviewedFinal Published versio
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