Multi-layer study of wave propagation in sunspots

We analyze the propagation of waves in sunspots from the photosphere to the chromosphere using time series of co-spatial Ca II H intensity spectra (including its line blends) and polarimetric spectra of Si I 10827 and the He I 10830 multiplet. From the Doppler shifts of these lines we retrieve the variation of the velocity along the line-of-sight at several heights. Phase spectra are used to obtain the relation between the oscillatory signals. Our analysis reveals standing waves at frequencies lower than 4 mHz and a continuous propagation of waves at higher frequencies, which steepen into shocks in the chromosphere when approaching the formation height of the Ca II H core. The observed non-linearities are weaker in Ca II H than in He I lines. Our analysis suggests that the Ca II H core forms at a lower height than the He I 10830 line: a time delay of about 20 s is measured between the Doppler signal detected at both wavelengths. We fit a model of linear slow magnetoacoustic wave propagation in a stratified atmosphere with radiative losses according to Newton's cooling law to the phase spectra and derive the difference in the formation height of the spectral lines. We show that the linear model describes well the wave propagation up to the formation height of Ca II H, where non-linearities start to become very important.Comment: Accepted by The Astrophysical Journa

Light propagation control by finite-size effects in photonic crystals

We exhibit the strong influence on light propagation of the finite size in photonic band-gap material. We show that light emission can be controlled by the symmetry group of the boundary of the finite device. These results lead simply to important practical applications.Comment: 5 pages, 4 figures, Revte

Application of demand flow technology to cable assembly production line

Includes bibliographical references

The Hanle and Zeeman Effects in Solar Spicules: A Novel Diagnostic Window on Chromospheric Magnetism

An attractive diagnostic tool for investigating the magnetism of the solar chromosphere is the observation and theoretical modeling of the Hanle and Zeeman effects in spicules, as shown in this letter for the first time. Here we report on spectropolarimetric observations of solar chromospheric spicules in the He I 10830 \AA multiplet and on their theoretical modeling accounting for radiative transfer effects. We find that the magnetic field in the observed (quiet Sun) spicular material at a height of about 2000 km above the visible solar surface has a strength of the order of 10 G and is inclined by approximately $35^{\circ}$ with respect to the local vertical direction. Our empirical finding based on full Stokes-vector spectropolarimetry should be taken into account in future magnetohydrodynamical simulations of spicules.Comment: 12 pages and 2 figure

Efficient light coupling from integrated single-mode waveguides to supercollimating photonic crystals on silicon-on-insulator platforms

We propose a practical and efficient solution for the coupling of light from integrated single-mode waveguides to supercollimating planar photonic crystals on conventional silicon-on-insulator platforms. The device consists of a rib waveguide, designed to sustain spatially extended single-modes and matched to a supercollimating photonic crystal, which has been truncated at its boundary to improve impedance matching between the two photonic components. Three-dimensional simulations show transmission efficiencies up to 96 % and reflections below 0.2 % at wavelengths close to 1.55 microns. This approach constitutes a significant step toward the integration of supercollimating structures on photonic chips.Comment: 11 pages, 4 figure

REDUCED-SCALE STUDY OF LIQUID FUEL STORAGE TANK FIRE USING FIRE DYNAMICS SIMULATOR

Most of the accidents that occur in liquid fuel storage tank parks are caused by fire. This paper presents a numerical study using Large Eddy Simulation through Fire Dynamics Simulator (FDS) for the simulation of liquid fuel (ethanol) storage tanks at different scales (real-scale 1:1, and reduced- scales, 1:2, 1:4, 1:8). This paper proposes correlations for flame height, and temperature profile and radiative heat flux profile in the region adjacent to the tanks. Correlations have as inputs the diameters of the tanks in real- and reduced-scale, temperature profiles and radiative heat flux profiles for a reduced-scale tank simulation, and then provide as outputs flame height and temperature profiles and radiative heat flux profiles for the tank in real- scale. Percentage errors of the correlations found in this study are lower than 2.0% and 0.6% for the maximum radiative heat flux and maximum temperature, respectively

Numerical simulations of conversion to Alfven waves in sunspots

We study the conversion of fast magneto-acoustic waves to Alfven waves by means of 2.5D numerical simulations in a sunspot-like magnetic configuration. A fast, essentially acoustic, wave of a given frequency and wave number is generated below the surface and propagates upward though the Alfven/acoustic equipartition layer where it splits into upgoing slow (acoustic) and fast (magnetic) waves. The fast wave quickly reflects off the steep Alfven speed gradient, but around and above this reflection height it partially converts to Alfven waves, depending on the local relative inclinations of the background magnetic field and the wavevector. To measure the efficiency of this conversion to Alfven waves we calculate acoustic and magnetic energy fluxes. The particular amplitude and phase relations between the magnetic field and velocity oscillations help us to demonstrate that the waves produced are indeed Alfven waves. We find that the conversion to Alfven waves is particularly important for strongly inclined fields like those existing in sunspot penumbrae. Equally important is the magnetic field orientation with respect to the vertical plane of wave propagation, which we refer to as "field azimuth". For field azimuth less than 90 degrees the generated Alfven waves continue upwards, but above 90 degrees downgoing Alfven waves are preferentially produced. This yields negative Alfven energy flux for azimuths between 90 and 180 degrees. Alfven energy fluxes may be comparable to or exceed acoustic fluxes, depending upon geometry, though computational exigencies limit their magnitude in our simulations.Comment: Accepted for publication in Ap

Ratemaking of dependent risks

We start by describing how, in some cases, we can use variance-related premium principles in ratemaking, when the claim numbers and individual claim amounts are independent. We use quasi-likelihood generalized linear models, under the assumption that the variance function is a power function of the mean of the underlying random variable. We extend this approach to the cases where the claim numbers are correlated. Some alternatives to deal with dependent risks are presented, taking explicitly into account overdispersion. We present regression models covering the bivariate Poisson, the generalized bivariate negative binomial and the bivariate Poisson–Laguerre polynomial, which nest the bivariate negative binomial. We apply these models to a portfolio of the Portuguese insurance company Tranquilidade and compare the results obtained.info:eu-repo/semantics/publishedVersio

Development of a Standard Methodology for Documenting Processes in an Organization

The application of process management in our country has been extended throughout the last decade; improvement in management, high performance levels, reduction of operation times, optimization of resources and obtaining of quality certifications are among the main reasons why both public and private organizations seek to implement it. However, despite being an implicit activity within the change of management model to the process approach and even the improvement of the functional administrative model, the documentation of processes becomes an uncomfortable, complex and time-consuming task that often generates nervousness and distrust in workers. Diversity of criteria and the lack of an adequate methodology with effective tools makes it difficult to achieve the expected results. This article presents in detail the steps, their sequence and instruments used that allow an organization to raise the information of its processes and document them. As a result of different research projects developed over several years, the methodology of process mapping allowed for the documentation of all the activities of different administrative units of the Escuela Superior Politécnica de Chimborazo and not only to comply with the laws and regulations but also to improve their management. In the last application, it contributed to the development of the documentary structure of a quality management system that allowed an academic unit to achieve international quality certification. Keywords: management, processes, process documentation, process manual. Resumen Escuela Superior Politécnica de Chimborazo, Riobamba, Ecuador *E-mail: [email protected] La aplicación de la gestión de procesos en nuestro país se ha ido extendiendo a lo largo de la última década; mejoras en la gestión, altos niveles de rendimiento, reducción de tiempos de operaciones, optimización de recursos y obtenciones de certificaciones de calidad son entre otros los principales motivos por los cuales organizaciones tanto públicas como privadas buscan implementarla. Sin embargo y a pesar de ser una actividad implícita dentro del cambio de modelo de gestión hacia el enfoque de procesos e incluso del mejoramiento del modelo administrativo funcional, la documentación de los procesos se convierte en una labor incomoda, compleja y con un alto consumo de tiempo que suele generar nerviosismo y desconfianza en los trabajadores. Diversidad de criterios y la falta de una metodología adecuada con instrumentos eficaces complica cumplir los resultados esperados. El presente artículo presenta a detalle los pasos, su secuencia e instrumentos utilizados que le permiten a una organización levantar la información de sus procesos y documentarlos. Resultado de diferentes proyectos de investigación desarrollados a los largo de varios años, la metodología de levantamiento de procesos permitió documentar todas las actividades de distintas unidades administrativas de la Escuela Superior Politécnica de Chimborazo y no solo cumplir lo establecido el leyes y reglamentos sino también mejorar su gestión, en la última aplicación contribuyó a elaborar la estructura documental de un sistema de gestión de la calidad que logró que una unidad académica alcance una certificación internacional de calidad. Palabras claves: gestión, procesos, documentación de procesos, manual de procesos