1,375 research outputs found
The credibility of the Venezuela crawling-band system
This paper studies the credibility of the Venezuela crawling-band exchange rate regime during the period July, 1996-February, 2002. We show that, introducing some modifications, the credibility analysis widely applied to target zone regimes can also be used in studying the credibility of crawling- band regimes. In analyzing the credibility of the Venezuela crawling band, first we use the so-called simple credibility tests developed by Svensson (1991). Additionally, we estimate the expected rate of realignment using the drift- adjustment method. Both the credibility tests and the drift-adjustment method give similar results, showing that the crawling-band system was highly credible during the period.crawling band exchange rate system, credibility, realignments
Construction Rehabilitation in Civil Engineering at bachelor degree level: A guideline course
ABSTRACT: In general terms, construction rehabilitation is not sufficiently studied worldwide in civil engineering schools. This article proposes an international guideline course on construction rehabilitation for civil engineering students at the bachelor degree level. As we live in an increasingly globalized world, the course aims to prepare students in the same basic concepts so the course content and its focus can be common for all civil engineering programs worldwide. Nevertheless, the course should be considered as a general guideline. At each university, special attention should be paid to the topics that are most common due to the varying construction practices, preservation laws and regulations, and legal jurisdiction governing the scope of practice in construction rehabilitation that exist in the region/country in which the university is located. Moreover, the guideline course should be focused on existing building types, both significant historic ones and those that make up the day-to-day rehabilitation market. To achieve this, the initial step of the methodology was the study and integration of the results obtained in a survey sent to lecturers at 89 universities in 30 countries around the world. Then, a preliminary grouping was done of topics that could be included in the course, preassigning a teaching time to each topic. Later, various renowned experts in the matter audited the tentative guideline course. Finally, based on their opinions and comments, the definitive guideline course was rewritten. Through this course, civil engineering students will improve their ability to recognize, analyze, diagnose, and solve problems that commonly appear in existing buildings, and they will increase their knowledge about maintaining and conserving them
Experimental ratchet effect in superconducting films with periodic arrays of asymmetric potentials
A vortex lattice ratchet effect has been investigated in Nb films grown on
arrays of nanometric Ni triangles, which induce periodic asymmetric pinning
potentials. The vortex lattice motion yields a net dc-voltage when an ac
driving current is applied to the sample and the vortex lattice moves through
the field of asymmetric potentials. This ratchet effect is studied taking into
account the array geometry, the temperature, the number of vortices per unit
cell of the array and the applied ac currents.Comment: 15 pages, figures include
Lattice effects and current reversal in superconducting ratchets
Competition between the vortex lattice and a lattice of asymmetric artificial
defects is shown to play a crucial role in ratchet experiments in
superconducting films. We present a novel and collective mechanism for current
reversal based on a reconfiguration of the vortex lattice. In contrast to
previous models of vortex current reversal, the mechanism is based on the
global response of the vortex lattice to external forces.Comment: 12 pages, 7 figure
Switchable collective pinning of flux quanta using magnetic vortex arrays
We constructed a superconducting/ferromagnetic hybrid system in which the
ordering of the pinning potential landscape for flux quanta can be manipulated.
Flux pinning is induced by an array of magnetic nanodots in the magnetic vortex
state, and controlled by the magnetic history. This allows switching on and off
the collective pinning of the flux-lattice. In addition, we observed
field-induced superconductivity that originates from the annihilation of flux
quanta induced by the stray fields from the magnetic vortices.Comment: PDF file 18 pages including 5 figures, accepted for publication in
Phys. Rev.
Photogalvanic current in artificial asymmetric nanostructures
We develop a theoretic description of the photogalvanic current induced by a
high frequency radiation in asymmetric nanostructures and show that it
describes well the results of numerical simulations. Our studies allow to
understand the origin of the electronic ratchet transport in such systems and
show that they can be used for creation of new types of detectors operating at
room temperature in a terahertz radiation range.Comment: 11 pages, 9 figs, EPJ latex styl
Desarrollo e implementación del curso de introducción a la física en la universidad autónoma de la ciudad de México (UACM)
El trabajo que ahora presentamos da cuenta del proceso de implementación del curso de Introducción a la Física que se imparte en la UACM basado en el trabajo del Physics Education Group de la Universidad de Washington. Éste se desarrolla desde un enfoque constructivista, con la intención de desarrollar conocimiento operativo y habilidades de pensamiento científico como elementos que pensamos pueden contrarrestar el fracaso usual en los cursos de física. Los resultados que se presentan en esta ponencia buscan dar evidencia de que la efectividad en el aprendizaje de la ciencia requiere del involucramiento mental activo y de la consideración del estado inicial real del estudiante, entre otras cosas; asimismo, se presenta un marco metodológico para implementar y evaluar actividades de aprendizaje bajo las mismas premisas
Stellar populations of galaxies in the ALHAMBRA survey up to . II. Stellar content of quiescent galaxies within the dust-corrected stellar masscolour and the colourcolour diagrams
Our aim is to determine the distribution of stellar population parameters
(extinction, age, metallicity, and star formation rate) of quiescent galaxies
within the rest-frame stellar masscolour and colourcolour diagrams
corrected for extinction up to . These novel diagrams reduce the
contamination in samples of quiescent galaxies owing to dust-reddened galaxies,
and they provide useful constraints on stellar population parameters. We set
constraints on the stellar population parameters of quiescent galaxies
combining the ALHAMBRA multi-filter photo-spectra with our SED-fitting code
MUFFIT, making use of composite stellar population models. The extinction
obtained by MUFFIT allowed us to remove dusty star-forming (DSF) galaxies from
the sample of red galaxies. The distributions of stellar population
parameters across these rest-frame diagrams are revealed after the dust
correction and are fitted by the LOESS method to reduce uncertainty effects.
Quiescent galaxy samples defined via classical diagrams are typically
contaminated by a % fraction of DSF galaxies. A significant part of the
galaxies in the green valley are actually obscured star-forming galaxies
(%). Consequently, the transition of galaxies from the blue cloud to
the red sequence, and hence the related mechanisms for quenching, seems to be
much more efficient and faster than previously reported. The rest-frame stellar
masscolour and colourcolour diagrams are useful for constraining
the age, metallicity, extinction, and star formation rate of quiescent galaxies
by only their redshift, rest-frame colours, and/or stellar mass. Dust
correction plays an important role in understanding how quiescent galaxies are
distributed in these diagrams and is key to performing a pure selection of
quiescent galaxies via intrinsic colours.Comment: (37 pages, 29 figures, accepted for publication in A&A
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