338 research outputs found
Application of remote monitoring and ground-based sensing in pastoralism
The development and implementation of an innovative system applying digital aerospace technologies in pastoralism constitute one of the current trends in agricultural development designed to solve numerous problems associated with soil fertility restoration in grazing pastures. Here, a promising line of research is to explore the feasibility of using satellite systems for an overall nutrient yield assessment per hectare of grazing land. The present article describes a comprehensive approach to the optimization of pastoralism that is based on remote methods for assessing pasture fertility using unmanned aerial vehicles (UAVs) and artificial Earth satellites. An analysis of existing methodological approaches reveals that the formalization of prediction processes is complicated by the lack of a theoretical basis for creating appropriate model-algorithmic support. The data on vegetation index dynamics and the nutritional values of forage plants obtained by interpreting imagery from a UAV camera and the multispectral cameras of a satellite service, as well as data from a portable handheld nitrogen sensor, were compared with the actual nutritional values of pasture plants. The study results provide a means to optimize the grouping of grazing animals, taking into account the actual possibility of achieving an increase in live weight. The provided findings indicate the possibility of achieving an additional 11.06% increase in daily live weight gain in young sheep (Jalgin Merino) when keeping them in pasture areas having a vegetation index of at least 0.5. Remote monitoring based on satellite service allows more efficient use of pastures. Study shows a positive relationship between remote sensing NDVI and feed nutritional value. Animal grazing optimization provides an additional 11.06% increase in live weight gain
Essential self-adjointness of magnetic Schr\"odinger operators on locally finite graphs
We give sufficient conditions for essential self-adjointness of magnetic
Schr\"odinger operators on locally finite graphs. Two of the main theorems of
the present paper generalize recent results of Torki-Hamza.Comment: 14 pages; The present version differs from the original version as
follows: the ordering of presentation has been modified in several places,
more details have been provided in several places, some notations have been
changed, two examples have been added, and several new references have been
inserted. The final version of this preprint will appear in Integral
Equations and Operator Theor
Numerical study of oil spill in the Patos lagoon under flood and ebb conditions
Facing great obstacles to eradicate environmental hazards generated by oil spills, it is crucial to establish actions against such accidents. In this context, the focus of this study is to analyze oil spills at the harbor region of Rio Grande, Rio Grande do Sul. The Easy Coupling Oil System (ECOS) model was used to model the oil spills under different environmental conditions simulated by the hydrodynamic model Telemac-3D, with the intention to identify the main forces controlling the movement of the oil slicks over a year of averaged hydrodynamic conditions from 2003 to 2015. The computational domain comprises the Patos Lagoon, the harbor area of Rio Grande and the Southern Brazilian Shelf. For the oil spill simulations, eight distinct events were defined considering both flood and ebb conditions in the estuarine region of the Patos Lagoon. The oil spill simulations showed that, in ebb conditions, the oil slick movement is mainly ruled by the currents, moving towards the outflow. After a few hours, the wind action makes the slick move towards the margins of the waterway. In flood conditions, on the other hand, the oil slick drifts to the interior of the estuary, following the dominant currents and the local winds
TEMPORAL VARIABILITY OF LONGITUDINAL SEDIMENT TRANSPORT ON THE BRAZILIAN CONTINENTAL SHELF
The sediment transported along the coast can alter the existing balance in certain environments, causing or accelerating erosive processes, and resulting in economic and environmental damages. In this way, predicting changes in the coastal zone and understanding the beach processes is an essential source of information for the elaboration of coastal management plans. In this context, the present work aims to estimate the alongshore sediment transport (LST) in several sectors of the Brazilian Coast, identifying the annual average and the predominant transport. This study was conducted for the period between the years 1979 and 2015, using computational modeling to investigate the behavior of the waves, and empirical formulas to calculate the LST rates. In addition, the temporal variability was investigated through the wavelet analysis. The results showed a great diversity in the wave climate behavior along the Brazilian Coast, presenting a good correlation in terms of magnitude between the estimation of LST and past studies in the different sectors analyzed. The place where transport has become pronounced understands the sector between Alagoas and Rio Grande do Norte states, while the opposite was observed in the Southern part of Bahia. The wavelet analysis showed that the spectrum of LST time series has a significant amount of energy for processes with a seasonal and annual variability, indicating that the northern regions of Brazil are most affected by the interannual processes. In this sense, informations along the Brazilian coast are presented, that may be considered in future projects, involving the sustainable management of the coastal zones
Observation of narrow baryon resonance decaying into in pA-interactions at with SVD-2 setup
SVD-2 experiment data have been analyzed to search for an exotic baryon
state, the -baryon, in a decay mode at on IHEP
accelerator. The reaction with a limited multiplicity was
used in the analysis. The invariant mass spectrum shows a resonant
structure with and . The statistical significance of this peak was estimated to be of . The mass and width of the resonance is compatible with the recently
reported - baryon with positive strangeness which was predicted as an
exotic pentaquark () baryon state. The total cross section for
production in pN-interactions for was estimated to be
and no essential deviation from A-dependence for inelastic
events was found.Comment: 8 pages, 7 figures, To be submitted to Yadernaya Fizika. v3-v5 - Some
references added, minor typos correcte
Influence of s-d interfacial scattering on the magnetoresistance of magnetic tunnel junctions
We propose the two-band s-d model to describe theoretically a diffuse regime
of the spin-dependent electron transport in magnetic tunnel junctions (MTJ's)
of the form F/O/F where F's are 3d transition metal ferromagnetic layers and O
is the insulating spacer. We aim to explain the strong interface sensitivity of
the tunneling properties of MTJ's and investigate the influence of electron
scattering at the nonideal interfaces on the degradation of the TMR magnitude.
The generalized Kubo formalism and the Green's functions method were used to
calculate the conductance of the system. The vertex corrections to the
conductivity were found with the use of "ladder" approximation combined with
the coherent-potential approximation (CPA) that allowed to consider the case of
strong electron scattering. It is shown that the Ward identity is satisfied in
the framework of this approximation that provides the necessary condition for a
conservation of a tunneling current. Based on the known results of ab-initio
calculations of the TMR for ballistic junctions, we assume that exchange split
quasi-free s-like electrons with the density of states being greater for the
majority spin sub-band give the main contribution to the TMR effect. We show
that, due to interfacial inter-band scattering, the TMR can be substantially
reduced even down to zero value. This is related to the fact that delocalized
quasi-free electrons can scatter into the strongly localized d sub-band with
the density of states at the Fermi energy being larger for minority spins
compared to majority spins. It is also shown that spin-flip electron scattering
on the surface magnons within the interface leads to a further decrease of the
TMR at finite temperature.Comment: REVTeX4, 20 pages, 9 figures, 1 table, submitted to Phys.Rev.B; In
Version 2 the text is substantially improved, the main results and
conclusions left the sam
Block bond-order potential as a convergent moments-based method
The theory of a novel bond-order potential, which is based on the block
Lanczos algorithm, is presented within an orthogonal tight-binding
representation. The block scheme handles automatically the very different
character of sigma and pi bonds by introducing block elements, which produces
rapid convergence of the energies and forces within insulators, semiconductors,
metals, and molecules. The method gives the first convergent results for
vacancies in semiconductors using a moments-based method with a low number of
moments. Our use of the Lanczos basis simplifies the calculations of the band
energy and forces, which allows the application of the method to the molecular
dynamics simulations of large systems. As an illustration of this convergent
O(N) method we apply the block bond-order potential to the large scale
simulation of the deformation of a carbon nanotube.Comment: revtex, 43 pages, 11 figures, submitted to Phys. Rev.
A dynamical systems approach to the tilted Bianchi models of solvable type
We use a dynamical systems approach to analyse the tilting spatially
homogeneous Bianchi models of solvable type (e.g., types VI and VII)
with a perfect fluid and a linear barotropic -law equation of state. In
particular, we study the late-time behaviour of tilted Bianchi models, with an
emphasis on the existence of equilibrium points and their stability properties.
We briefly discuss the tilting Bianchi type V models and the late-time
asymptotic behaviour of irrotational Bianchi VII models. We prove the
important result that for non-inflationary Bianchi type VII models vacuum
plane-wave solutions are the only future attracting equilibrium points in the
Bianchi type VII invariant set. We then investigate the dynamics close to
the plane-wave solutions in more detail, and discover some new features that
arise in the dynamical behaviour of Bianchi cosmologies with the inclusion of
tilt. We point out that in a tiny open set of parameter space in the type IV
model (the loophole) there exists closed curves which act as attracting limit
cycles. More interestingly, in the Bianchi type VII models there is a
bifurcation in which a set of equilibrium points turn into closed orbits. There
is a region in which both sets of closed curves coexist, and it appears that
for the type VII models in this region the solution curves approach a
compact surface which is topologically a torus.Comment: 29 page
Giant Flare in SGR 1806-20 and Its Compton Reflection from the Moon
We analyze the data obtained when the Konus-Wind gamma-ray spectrometer
detected a giant flare in SGR 1806-20 on December 27, 2004. The flare is
similar in appearance to the two known flares in SGR 0526-66 and SGR 1900+14
while exceeding them significantly in intensity. The enormous X-ray and
gamma-ray flux in the narrow initial pulse of the flare leads to almost
instantaneous deep saturation of the gamma-ray detectors, ruling out the
possibility of directly measuring the intensity, time profile, and energy
spectrum of the initial pulse. In this situation, the detection of an
attenuated signal of Compton back-scattering of the initial pulse emission by
the Moon with the Helicon gamma-ray spectrometer onboard the Coronas-F
satellite was an extremely favorable circumstance. Analysis of this signal has
yielded the most reliable temporal, energy, and spectral characteristics of the
pulse. The temporal and spectral characteristics of the pulsating flare tail
have been determined from Konus-Wind data. Its soft spectra have been found to
contain also a hard power-law component extending to 10 MeV. A weak afterglow
of SGR 1806-20 decaying over several hours is traceable up to 1 MeV. We also
consider the overall picture of activity of SGR 1806-20 in the emission of
recurrent bursts before and after the giant flare.Comment: 29 pages including 18 figures; to appear in Astronomy Letters, 2007,
33, p 1-1
Asymptotics of Eigenvalues and Eigenfunctions for the Laplace Operator in a Domain with Oscillating Boundary. Multiple Eigenvalue Case
We study the asymptotic behavior of the solutions of a spectral problem for
the Laplacian in a domain with rapidly oscillating boundary. We consider the
case where the eigenvalue of the limit problem is multiple. We construct the
leading terms of the asymptotic expansions for the eigenelements and verify the
asymptotics
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