14,245 research outputs found
Tracking the US Business Cycle With a Singular Spectrum Analysis
The monitoring of economic developments is an exercise of considerable importance forpolicy makers, namely, central banks and fiscal authorities as well as for other economic agents such as financial intermediaries, firms and households. However, the assessment of the business cycle is not an easy endeavor as the cyclical component is not an observable variable. In this paper we resort to singular spectrum analysis in order to disentangle the US GDP into several underlying components of interest. The business cycle indicator yielded through this method is shown to bear a resemblance with band-pass filtered output. As the end-of-sample behavior is typically a thorny issue in business cycle assessment, a real-time estimation exercise is here conducted to assess the reliability of the several filters. The obtained results suggest that the business cycle indicator proposed herein possesses a better revision performance than other filters commonly applied in the literature.
Extended Hamiltonian systems in multisymplectic field theories
We consider Hamiltonian systems in first-order multisymplectic field
theories. We review the properties of Hamiltonian systems in the so-called
restricted multimomentum bundle, including the variational principle which
leads to the Hamiltonian field equations. In an analogous way to how these
systems are defined in the so-called extended (symplectic) formulation of
non-autonomous mechanics, we introduce Hamiltonian systems in the extended
multimomentum bundle. The geometric properties of these systems are studied,
the Hamiltonian equations are analyzed using integrable multivector fields, the
corresponding variational principle is also stated, and the relation between
the extended and the restricted Hamiltonian systems is established. All these
properties are also adapted to certain kinds of submanifolds of the
multimomentum bundles in order to cover the case of almost-regular field
theories.Comment: 36 pp. The introduction and the abstract have been rewritten. New
references are added and some little mistakes are corrected. The title has
been slightly modifie
Games on Cellular Spaces: How Mobility Affects Equilibrium
In this work we propose a new model for spatial games. We present a definition of mobility in terms of the satisfaction an agent has with its spatial location. Agents compete for space through a non-cooperative game by using mixed strategies. We are particularly interested in studyig the relation between Nash equilibrium and the winner strategy of a given model with mobility, and how the mobility can affect the results. The experiments show that mobility is an important variable concerning spatial games. When we change parameters that affect mobility, it may lead to the success of strategies away from Nash equilibrium.Spatial Games, Agent-Based Modelling, Mobility, Satisfaction, Chicken Game, Nash Equilibrium
Effect of stress and/or field annealing on the magnetic behavior of the „Co77Si13.5B9.5…90Fe7Nb3 amorphous alloy
Variations of coercive field, induced magnetic anisotropy, and saturation magnetostriction constant
in sCo77Si13.5B9.5d90Fe7Nb3 amorphous ribbons submitted to stress and/or axial magnetic-field
annealing are reported. The annealing was carried out by using the Joule-heating effect saverage
temperature values of the sample corresponding to the intensity of the electrical current were 273,
378, 409, and 445 °Cd and the applied stress and axial magnetic field during the thermal treatments
were 500 MPa and 750 A/m, respectively. As a result of these treatments, a uniaxial in-plane
magnetic anisotropy, which affects drastically the soft magnetic character of the samples, was
developed.Ministerio de Ciencia y TecnologÃa de España-MAT2001-0082-C04-0
Spin States Protected from Intrinsic Electron-Phonon-Coupling Reaching 100 ns Lifetime at Room Temperature in MoSe
We present time-resolved Kerr rotation measurements, showing spin lifetimes
of over 100 ns at room temperature in monolayer MoSe. These long lifetimes
are accompanied by an intriguing temperature dependence of the Kerr amplitude,
which increases with temperature up to 50 K and then abruptly switches sign.
Using ab initio simulations we explain the latter behavior in terms of the
intrinsic electron-phonon coupling and the activation of transitions to
secondary valleys. The phonon-assisted scattering of the photo-excited
electron-hole pairs prepares a valley spin polarization within the first few ps
after laser excitation. The sign of the total valley magnetization, and thus
the Kerr amplitude, switches as a function of temperature, as conduction and
valence band states exhibit different phonon-mediated inter-valley scattering
rates. However, the electron-phonon scattering on the ps time scale does not
provide an explanation for the long spin lifetimes. Hence, we deduce that the
initial spin polarization must be transferred into spin states which are
protected from the intrinsic electron-phonon coupling, and are most likely
resident charge carriers which are not part of the itinerant valence or
conduction band states.Comment: 18 pages, 17 figure
Recovery of substrates and macro-benthos after fishing trials with a new Portuguese clam dredge
The effect of dredging on bottom structure was assessed, to estimate the damage inflicted on the benthic macrofauna left on the dredge path and to evaluate aggregations of scavengers within the track. Sediment
suspended during dredging rapidly resettled both on sand and sandy-mud bottoms. Dredge tracks were deeper on sandy-mud sediments and persisted longer than in sandy sediments. The disappearance of tracks in both sediment types depended both on current strength and wave action. Damage and mortality induced by dredging on the macrobenthic animals left on the dredge path was relatively low. Post-fishing diver observations showed that damaged animals left on the dredge path rapidly attracted scavengers, mainly Ophiura albida. Immediately after the tow ophiuras reached densities 8 times greater in the track
region than in the background. However, they dispersed again rapidly because only few damaged fauna were available on the dredge tracks. Undamaged or slightly damaged shellfish started to rebury immediately
after escaping from the dredge
Lifecycle Assessment of Different Constructive Solutions in Aggressive Maritime Environments - Application to the Viaduct of the Oil Terminal of the Port of Leixões
The maritime environment is one of the most aggressive for infrastructures. This type of exposure
affects severely the durability of any infrastructure, if proper preventive measures are not taken
into account.
In the construction of new structures one of the most important factors to take into account is the
ratio cost / durability. This way, it is intended to make a study of two different structural solutions,
as well as an analysis of their life cycles, for the viaduct of the oil tanker terminal of port of Leixões, in Portugal, since the current structure has reached the end of its life cycle after 50 years.
It will be then designed a solution of precast and pre-stressed reinforced concrete beams with a reinforced concrete slab, and another solution with steel beams with a reinforced concrete slab.
The new structure will be designed according to current regulations, which are developed in a way
that such structures should reach a service life of 100 years.
It is expected that this study will be able to
provide a solution that is economically viable for the
replacement of the viaduct, and where it is possible to reach the expected life time of 100 years
with the lowest possible cost(undefined)info:eu-repo/semantics/publishedVersio
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