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 z∼1z \sim 1. II. Stellar content of quiescent galaxies within the dust-corrected stellar mass−-colour and the UVJUVJ colour−-colour 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 mass$-$colour and $UVJ$ colour$-$colour diagrams corrected for extinction up to $z\sim1$. 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 $UVJ$ 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 $UVJ$ diagrams are typically contaminated by a $\sim20$% fraction of DSF galaxies. A significant part of the galaxies in the green valley are actually obscured star-forming galaxies ($\sim30-65$%). 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 mass$-$colour and $UVJ$ colour$-$colour 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