30 research outputs found
Spatio-temporal analysis through remote sensing and GIS in Moscow region, Russia
Spatio-temporal analysis is a process for city development with growing population and economy for better implementation of planning policies with advance technology. In this research work, three dates (1995, 2005 & 2016) satellite images were used to mapping and monitoring of Moscow region, Russia. This study focuses on the further classification of the study area into different categories on the basis of use and association by implementing a rule-based classification system on remotely sensed data. This research provides useful and up-to-date information to local land use planners, managers and policy-makers to step up towards sustainable development in Moscow region, Russia.This data work is financially supported by the Russian Scientific Foundation (RSF), grant no. 14-31-00014 “Establishment of a Laboratory of Advanced Technology for Earth Remote Sensing”
Mapping and evaluating urban density patterns in Moscow, Russia
The defense of the notion of ‘compact city’ as a strategy to reduce urban sprawl to support greater utilization of existing infrastructure and services in more compact areas and to improve the connectivity of employment hubs is actively discussed in urban research. Using the urban residential density as a surrogate measure for urban compactness, this paper empirically examines a cadaster database that contains details of every property with a view of capturing changes in urban residential density patterns across Moscow using geospatial techniques. The policy of densification in chase of a more compact city has produced mixed results. Findings of this study signal that the urban densities across the buffer zones around Moscow city are significantly different. The Landsat images from 1995, 2005 and 2016 are classified based on the maximum likelihood to expand the land use/cover maps and identify the land cover. Then, the area coverage for all the land use/cover types at different points in time is combined with the distance from the city center. After that, urbanization densities from the city center toward the outskirts for every 1-km distance from 1 to 60 km are calculated. The city density on the distance of 1 to 35 km is found to be very high in the years 1995 to 2016. As usual, the population, traffic conditions, industrialization and government policy are the major factors that influenced the urban expansion.This work was financially supported by the Russian Science Foundation (RSF), grant no. 14-31-00014 “Establishment of a Laboratory of Advanced Technology for Earth Remote Sensing”
A review of food security and flood risk dynamics in central dry zone area of Myanmar
The Central Dry Zone area of Myanmar is the most water stressed and one of the most food insecure regions in the country. Agriculture is the most important economic sector in Myanmar as it is essential for national food security and a major source of livelihood. The adverse effects of climate change are believed to be a major constraint to food insecurity and flood risk. This paper gives a structured overview of the current scientific knowledge available and reveals the relevance of this information with regard to food security and flood risk dynamics in central dry zone area of Myanmar.This work is financially supported by the Russian Scientific Foundation (RSF), grant no. 14-31-00014 “Establishment of a Laboratory of Advanced Technology for Earth Remote Sensing”
Land use/cover change detection through remote sensing and GIS techniques: a case study of Astrakhan, Russia
The present study illustrates the spatial-temporal dynamics of Land use/cover change in Astrakhan city, Russia. Landsat satellite imageries of three different time periods of 2000, 2007 and 2015 were acquired by earth explorer website and quantify the changes in the Astrakhan. In this study maximum-likelihood supervised classification along with post-classification change detection was applied to satellite images for 2000, 2007 and 2015 in order to map land use/cover changes. The land use/cover study was classified into five major class’s viz. agriculture, bare-land, settlements, vegetation and water body. The classification results were then further refined using ancillary data, visual interpretation and expert knowledge of the area along with GIS. After post-classification change detection a change image form the cross-tabulations were generated. The result shows extensive vegetation degradation and water logging in different parts of the study area
Microscopic nonequilibrium theory of double-barrier Josephson junctions
We study nonequilibrium charge transport in a double-barrier Josephson
junction, including nonstationary phenomena, using the time-dependent
quasiclassical Keldysh Green's function formalism. We supplement the kinetic
equations by appropriate time-dependent boundary conditions and solve the
time-dependent problem in a number of regimes. From the solutions,
current-voltage characteristics are derived. It is understood why the
quasiparticle current can show excess current as well as deficit current and
how the subgap conductance behaves as function of junction parameters. A
time-dependent nonequilibrium contribution to the distribution function is
found to cause a non-zero averaged supercurrent even in the presence of an
applied voltage. Energy relaxation due to inelastic scattering in the
interlayer has a prominent role in determining the transport properties of
double-barrier junctions. Actual inelastic scattering parameters are derived
from experiments. It is shown as an application of the microscopic model, how
the nature of the intrinsic shunt in double-barrier junctions can be explained
in terms of energy relaxation and the opening of Andreev channels.Comment: Accepted for Phys. Rev.
Coherent Charge Transport in Metallic Proximity Structures
We develop a detailed microscopic analysis of electron transport in normal
diffusive conductors in the presence of proximity induced superconducting
correlation. We calculated the linear conductance of the system, the profile of
the electric field and the densities of states. In the case of transparent
metallic boundaries the temperature dependent conductance has a non-monotoneous
``reentrant'' structure. We argue that this behavior is due to nonequilibrium
effects occuring in the normal metal in the presence of both superconducting
correlations and the electric field there. Low transparent tunnel barriers
suppress the nonequilibrium effects and destroy the reentrant behavior of the
conductance. If the wire contains a loop, the conductance shows Aharonov-Bohm
oscillations with the period as a function of the magnetic flux
inside the loop. The amplitude of these oscillations also demonstrates
the reentrant behavior vanishing at and decaying as at relatively
large temperatures. The latter behavior is due to low energy correlated
electrons which penetrate deep into the normal metal and ``feel'' the effect of
the magnetic flux . We point out that the density of states and thus the
``strengh'' of the proximity effect can be tuned by the value of the flux
inside the loop. Our results are fully consistent with recent experimental
findings.Comment: 16 pages RevTeX, 23 Postscript figures, submitted to Phys. Rev.
Manifestation of triplet superconductivity in superconductor-ferromagnet structures
We study proximity effects in a multilayered superconductor/ferromagnet (S/F)
structure with arbitrary relative directions of the magnetization . If
the magnetizations of different layers are collinear the superconducting
condensate function induced in the F layers has only a singlet component and a
triplet one with a zero projection of the total magnetic moment of the Cooper
pairs on the direction. In this case the condensate penetrates the F
layers over a short length determined by the exchange energy . If
the magnetizations are not collinear the triplet component has, in
addition to the zero projection, the projections . The latter component
is even in the momentum, odd in the Matsubara frequency and penetrates the F
layers over a long distance that increases with decreasing temperature and does
not depend on (spin-orbit interaction limits this length). If the thickness
of the F layers is much larger than , the Josephson coupling between
neighboring S layers is provided only by the triplet component, so that a new
type of superconductivity arises in the transverse direction of the structure.
The Josephson critical current is positive (negative) for the case of a
positive (negative) chirality of the vector . We demonstrate that this
type of the triplet condensate can be detected also by measuring the density of
states in F/S/F structures.Comment: 14 pages; 9 figures. Final version, to be published in Phys. Rev.
Nonequilibrium electron cooling by NIS tunnel junctions
We discuss the theoretical framework to describe quasiparticle electric and
heat currents in NIS tunnel junctions in the dirty limit. The approach is based
on quasiclassical Keldysh-Usadel equations. We apply this theory to diffusive
NIS'S tunnel junctions. Here N and S are respectively normal metal and
superconductor reservoirs, I is an insulator layer and S' is a nonequilibrium
superconducting lead. We calculate the quasiparticle electric and heat currents
in such structures and consider the effect of inelastic relaxation in the S'
lead. We find that in the absence of strong relaxation the electric current and
the cooling power for voltages are suppressed. The value of this
suppression scales with the diffusive transparency parameter. We ascribe this
suppression to the effect of backtunneling of nonequilibrium quasiparticles
into the normal metal.Comment: 12 pages, 6 figures, proceedings, to be published in JLT
Nonequilibrium Josephson effect in short-arm diffusive SNS interferometers
We study non-equilibrium Josephson effect and phase-dependent conductance in
three-terminal diffusive interferometers with short arms. We consider strong
proximity effect and investigate an interplay of dissipative and Josephson
currents co-existing within the same proximity region. In junctions with
transparent interfaces, the suppression of the Josephson current appears at
rather large voltage, , and the current vanishes at
. Josephson current inversion becomes possible in junctions with
resistive interfaces, where the inversion occurs within a finite interval of
the applied voltage. Due to the presence of considerably large and
phase-dependent injection current, the critical current measured in a current
biased junction does not coincide with the maximum Josephson current, and
remains finite when the true Josephson current is suppressed. The voltage
dependence of the conductance shows two pronounced peaks, at the bulk gap
energy, and at the proximity gap energy; the phase oscillation of the
conductance exhibits qualitatively different form at small voltage ,
and at large voltage .Comment: 11 pages, 9 figures, revised version, to be published in Phys. Rev.
Theory of charge transport in diffusive normal metal / conventional superconductor point contacts
Tunneling conductance in diffusive normal metal / insulator / s-wave
superconductor (DN/I/S) junctions is calculated for various situations by
changing the magnitudes of the resistance and Thouless energy in DN and the
transparency of the insulating barrier. The generalized boundary condition
introduced by Yu. Nazarov [Superlattices and Microstructures 25 1221 (1999)] is
applied, where the ballistic theory by Blonder Tinkham and Klapwijk (BTK) and
the diffusive theory by Volkov Zaitsev and Klapwijk based on the boundary
condition of Kupriyanov and Lukichev (KL) are naturally reproduced. It is shown
that the proximity effect can enhance (reduce) the tunneling conductance for
junctions with a low (high) transparency. A wide variety of dependencies of
tunneling conductance on voltage bias is demonstrated including a -shaped
gap like structure, a zero bias conductance peak (ZBCP) and a zero bias
conductance dip (ZBCD)