4,119 research outputs found
TIROS 1- Camera Attitude Data, Analysis of Location Errors, and Derivation of Correction for Calibration
Tiros i, camera attitude data, analysis of location errors, and derivation of correction for calibratio
Neutron monitors and muon detectors for solar modulation studies: 2. time series
The level of solar modulation at different times (related to the solar
activity) is a central question of solar and galactic cosmic-ray physics. In
the first paper of this series, we have established a correspondence between
the uncertainties on ground-based detectors count rates and the parameter
(modulation level in the force-field approximation) reconstructed from
these count rates. In this second paper, we detail a procedure to obtain a
reference time series from neutron monitor data. We show that we can
have an unbiased and accurate reconstruction (). We also discuss the potential of Bonner spheres spectrometers and muon
detectors to provide time series. Two by-products of this calculation
are updated values for the cosmic-ray database and a web interface to
retrieve and plot from the 50's to today
(\url{http://lpsc.in2p3.fr/crdb}).Comment: 15 pages, 5 figures, 2 tables. AdSR, in press. Web interface to get
modulation parameter phi(t): new tab in http://lpsc.in2p3.fr/crd
Geometrically constrained magnetic wall
The structure and properties of a geometrically constrained magnetic wall in
a constriction separating two wider regions are investigated theoretically.
They are shown to differconsiderably from those of an unconstrained wall, so
that the geometrically constrained magnetic wall truly constitutes a new kind
of magnetic wall, besides the well known Bloch and Neel walls. In particular,
the width of a constrained wall cann become very small if the characteristic
length of the constriction is small, as is actually the case in an atomic point
contact. This provides a simple, natural explanation for the large
magnetoresistance observed in ferromagnetic atomic point contacts.Comment: RevTeX, 4 pages, 4 eps figures; v2: revised version; v3: ref. adde
Bargaining Power and Value Sharing in Distribution Networks: A Cooperative Game Theory Approach
This paper illustrates a methodology for analyzing bargaining games on network markets, by means of numerical models that can be calibrated with real data. Economic incentives to join or to expand a network depend on how the network surplus is being distributed, which in turn depends on a variety of factors: position of each agent (e.g., a country) in a specific network, its reliability in the cooperation scheme (e.g., geo-political stability), existence of market distortions and availability of outside options (e.g., alternative energy sources). This study is aimed at presenting a game theory methodology that can be applied to real world cases, having the potential to shed light on several political economy issues.
The methodology is presented and illustrated with application to a fictitious network structure. The method is based on a two-stage pro- cess: first, a network optimization model is used to generate payoff values under different coalitions and network structures; a second model is subsequently employed to identify cooperative game solutions. Any change in the network structure entails both a variation in the overall welfare level and in the distribution of surplus among agents, as it affects their relative bargaining power. Therefore, expected costs and benefits, at the aggregate as well as at the individual level, can be compared to assess the economic viability of any investment in network infrastructure. A number of model variants and extensions are also considered: changing demand, exogenous instability factors, market distortions, externalities and outside options
Sawja: Static Analysis Workshop for Java
Static analysis is a powerful technique for automatic verification of
programs but raises major engineering challenges when developing a full-fledged
analyzer for a realistic language such as Java. This paper describes the Sawja
library: a static analysis framework fully compliant with Java 6 which provides
OCaml modules for efficiently manipulating Java bytecode programs. We present
the main features of the library, including (i) efficient functional
data-structures for representing program with implicit sharing and lazy
parsing, (ii) an intermediate stack-less representation, and (iii) fast
computation and manipulation of complete programs
Influence of topography and Co domain walls on the magnetization reversal of the FeNi layer in FeNi/AlO/Co magnetic tunnel junctions
We have studied the magnetization reversal dynamics of FeNi/AlO/Co
magnetic tunnel junctions deposited on step-bunched Si substrates using
magneto-optical Kerr effect and time-resolved x-ray photoelectron emission
microscopy combined with x-ray magnetic circular dichroism (XMCD-PEEM).
Different reversal mechanisms have been found depending on the substrate miscut
angle. Larger terraces (smaller miscut angles) lead to a higher nucleation
density and stronger domain wall pinning. The width of domain walls with
respect to the size of the terraces seems to play an important role in the
reversal. We used the element selectivity of XMCD-PEEM to reveal the strong
influence of the stray field of domain walls in the hard magnetic layer on the
magnetic switching of the soft magnetic layer.Comment: 8 Pages, 7 Figure
Spin Transfer Torque for Continuously Variable Magnetization
We report quantum and semi-classical calculations of spin current and
spin-transfer torque in a free-electron Stoner model for systems where the
magnetization varies continuously in one dimension.Analytic results are
obtained for an infinite spin spiral and numerical results are obtained for
realistic domain wall profiles. The adiabatic limit describes conduction
electron spins that follow the sum of the exchange field and an effective,
velocity-dependent field produced by the gradient of the magnetization in the
wall. Non-adiabatic effects arise for short domain walls but their magnitude
decreases exponentially as the wall width increases. Our results cast doubt on
the existence of a recently proposed non-adiabatic contribution to the
spin-transfer torque due to spin flip scattering.Comment: 11 pages, 9 figure
Theory of magnetic domains in uniaxial thin films
For uniaxial easy axis films, properties of magnetic domains are usually
described within the Kittel model, which assumes that domain walls are much
thinner than the domains. In this work we present a simple model that includes
a proper description of the magnetostatic energy of domains and domain walls
and also takes into account the interaction between both surfaces of the film.
Our model describes the behavior of domain and wall widths as a function of
film thickness, and is especially well suited for the strong stripe phase. We
prove the existence of a critical value of magneto-crystalline anisotropy above
which stripe domains exist for any film thickness and justify our model by
comparison with exact results. The model is in good agreement with experimental
data for hcp cobalt.Comment: 15 pages, 7 figure
Magnetic relaxation of exchange biased (Pt/Co) multilayers studied by time-resolved Kerr microscopy
Magnetization relaxation of exchange biased (Pt/Co)5/Pt/IrMn multilayers with
perpendicular anisotropy was investigated by time-resolved Kerr microscopy.
Magnetization reversal occurs by nucleation and domain wall propagation for
both descending and ascending applied fields, but a much larger nucleation
density is observed for the descending branch, where the field is applied
antiparallel to the exchange bias field direction. These results can be
explained by taking into account the presence of local inhomogeneities of the
exchange bias field.Comment: To appear in Physical Review B (October 2005
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