Moduli spaces of parabolic U(p,q)U(p,q)-Higgs bundles

Using the $L^2$-norm of the Higgs field as a Morse function, we count the number of connected components of the moduli space of parabolic $U(p,q)$-Higgs bundles over a Riemann surface with a finite number of marked points, under certain genericity conditions on the parabolic structure. This space is homeomorphic to the moduli space of representations of the fundamental group of the punctured surface in $U(p,q)$, with fixed compact holonomy classes around the marked points. We apply our results to the study of representations of the fundamental group of elliptic surfaces of general type.Comment: 46 pages, no figures. Corrected typos, added remarks. To appear in "Quarterly Journal of Mathematics

La industrialización chilena del siglo XX como proyecto de transformación

El artículo desarrolla una mirada amplia, desde una perspectiva económico-polí- tica, sobre la industrialización chilena del siglo XX. En primer lugar, se presenta una breve reseña de los antecedentes históricos que precedieron a la llamada industrialización protegida. En segundo lugar, se aborda el proceso político y económico que llevó al compromiso del Estado con este proyecto. En tercer lugar, se mencionan las principales políticas utilizadas para realizar el proyecto, las líneas centrales de los debates respectivos y algunos resultados. En cuarto lugar se toma nota de las críticas más relevantes y los intentos de reformas en los años 1960. Finalmente, se evalúa desde una perspectiva más amplia y crítica, el carácter de la visión de país que impulsó la industrialización y el debate reciente, en el con- texto del neo-liberalismo y la globalización.Palabras claves: Industrialización, Chile, siglo XX.AbstractThis article provides an overview of Chilean industrialization during the twentieth century, based on a political economy approach. First, a brief overview of the historical antecedents that preceded the so-called protected industrialization is provided. Secondly, the article deals with the economic and political process that led to the state’s engagement with this project. Third, the main policies used to undertake this project are mentioned, as well as the core debates around them, and some results are provided. Fourth, the main criticisms and attempts of reforms during the 1960s are highlighted. Finally, the nature of the country’s vision that pushed for industrialization is assessed from a wide and critical point of view, linking it with current debates embodied within the context of neoliberalism and globalization.Keywords: Industrialization, Chile, twentieth century

Is undergraduate programme accreditation influenced by educational public policy quality indicators? An exploratory study of the Chilean Higher Education quality assurance system

In Chile, as well as in most of Latin America, public policies for higher education have recently adopted a focus on quality assurance and accreditation systems. Uncertainty, however, still exists in terms of the quality assurance consistency in the current Chilean accreditation system, especially in terms of the relation between public policy quality indicators for higher education and their relation to accreditation outcomes. Therefore, the aim of this study was to make a first explorative attempt to investigate the relationships between these indicators and the results of undergraduate programme accreditation. We hypothesised that the public policy quality indicators of first-year drop-out rate, employment at graduation and ratio of actual to expected time to graduation would be strongly correlated to undergraduate programme accreditation as well as largely explaining its accreditation-year variance. By means of correlation and multiple regression analyses, we found small-sized associations, being first-year drop-out the only significant predictor of programme accreditation, explaining a 9.4% of its variance. These results raise questions regarding the consistency between the aims of public policy for higher education and the current accreditation system. This study should be of value to policy makers, managers and curriculum developers in terms of this initial analysis of the consistency between quality indicators and the accreditation system. Further research is necessary to make a systematic and in-depth assessment of the impact of quality assurance mechanisms to provide better rationale for making important decisions such as when defining the characteristics of the accrediting institutions as well as for establishing effective ways to achieve the proposed public policy objectives

Contributions on spectral control for the asymmetrical full bridge multilevel inverter

Las topologías de circuitos inversores multinivel pueden trabajar a tensiones y potencias mayores que las alcanzadas por convertidores convencionales de dos niveles. Además, la conversión multinivel reduce la distorsión armónica de las variables de salida y en algunos casos, a pesar del aumento de elementos de conmutación, también reduce las pérdidas de conversión al incrementarse el número de niveles. La reducción de distorsión alcanzada por el número de niveles puede aprovecharse para reducir las pérdidas de conmutación disminuyendo la frecuencia de las señales portadoras. Para reducir aún más esta frecuencia sin degradar el espectro, nosotros controlamos las pendientes de las portadoras triangulares. Primero se han desarrollado dos modelos analíticos para predecir el espectro del voltage de salida, dependiendo de: el índice de modulación MA, la razón de distribución de voltaje K de las fuentes de alimentación , y las cuatro pendientes de las portadoras{r1, r2, r3, r4}. El primer modelo considera el Muestreo Natural y se basa en Series Dobles de Fourier (SDF) mientras que el segundo modelo, utiliza la Serie Sencilla de Fourier (SSF) introduciendo el concepto de Muestreo Pseudo-Natural, una aproximación digital de la modulación natural. Ambos modelos son programados en Matlab, verificados con Pspice y validados con un prototipo experimental que contiene un modulador digital implementado con DSP.La concordancia entre las modulaciones natural y pseudo-natural, asi como entre sus respectivos modelos, es aprovechada por un algorítmo genético (AG) donde la THD es la función costo a reducir. Después de varios ensayos y de sintonizar el AG, se genera una matriz que contiene conjuntos de portadoras optimizadas dentro un rango específico de las variables {MA,K} y es probada con un segundo prototipo en lazo cerrado. Un lazo lento digital modifica las portadoras creadas por un dsPIC en modulaciones PWM; estas son demoduladas y sus amplitudes corregidas por un lazo de acción anticipada. Estas portadoras se comparan con una referencia sinusoidal que a su vez es modificada por variables de estado, generando finalmente la modulación multinivel en lazo cerrado. Los resultados finales demuestran la fiabilidad de la reducción de armónicos usando la programación de las pendientes de las portadoras. Palabras claves: inversor multinivel, PWM, distorsión armónica, modelo espectral, pendiente de portadora, conjunto de portadoras, distribución de niveles, Serie Doble de Fourier, Serie Simple de Fourier, muestreo natural, muestreo regular, muestreo pseudo-natural , Algoritmos Genéticos.Multilevel inverter (MI) topologies can work at higher voltage and higher power than conventional two-level converters. In addition, multilevel conversion reduces the output variables harmonic distortion and, sometimes, in spite of the devices-count increment, the conversion losses can also decrease by increasing the number of levels. The harmonic distortion reduction achieved by increasing the number of levels, can be used to further reducing the switching losses by decreasing the inverter carrier frequencies. To reduce even more the switching frequency without degrading output spectrum, we control the triangular carrier waveforms slopes. First, to achieve this target, two analytical models have been created in order to predict the inverter output voltage spectrum, depending on diverse parameters: the amplitude modulation index MA, the voltage distribution K of the inverter input sources, and the four carrier slopes {r1, r2, r3, r4}. The first model considers Natural Sampling and is based on Double Fourier Series (DFS) whereas the second model based on Simple Fourier Series (SFS), introduces the concept of Pseudo-Natural Sampling, as a digital approximation of the natural modulation. Both models are programmed in Matlab, verified with Pspice simulations and validated with a first experimental prototype with a DSP digital modulator.The good agreement between natural and pseudo-natural modulations, as well as their respective DFS and SFS models, is exploited by a Genetic Algorithm (GA) application where THD is the cost function to minimize. After testing and properly tuning the GA, a framework matrix containing the optimized carriers set for a specific range of variables {MA,K} is generated and then, tested with a second, closed-loop prototype. A slow digital loop modifies the carrier slopes created by dsPIC microcontroller as PWM modulations, whose amplitude, once demodulated, are affected by a feed-forward loop. These carriers, compared with a sinusoidal reference, state-feedback modified, generate finally the closed-loop multilevel modulation. The final results demonstrates the feasibility of harmonic reduction by means of carrier slopes programming. Keywords: multilevel inverter, PWM, harmonic distortion, spectral modeling, carrier slope, carriers set, level distribution, Double Fourier Series, Simple Fourier Series, natural sampling, regular sampling, pseudo-natural sampling, Genetic Algorithms

High cycle fatigue of ARMCO iron severely deformed by ECAP

The high-cycle fatigue behavior of ARMCO iron severely deformed by Equal Channel Angular Pressing (ECAP) at room temperature through route Bc until 8 passes, with an average grain size of ~365 nm, was studied and compared with the same material in the annealed state with an average grain size of ~72 µm. The fatigue limit of the 8 passes ECAPed sample increased with respect to the annealed material by more than 250% rising from 274 MPa to 717 MPa. Striations and dimpled relief were observed on the fracture surfaces of the fatigued ultrafine and coarse grain fatigue samples. The microstructure was characterized by Electron Backscattered Diffraction (EBSD) before and after the fatigue tests and it was observed in both samples an increment in the fraction of Low Angle Grain Boundaries (LAGB) at high number of cycles to failure. A texture analysis for the materials after the fatigue failure was done. This study shown a preferential orientation towards the ¿ fiber for both conditions.Peer ReviewedPostprint (author's final draft

Multiple Order Dual-Band Active Ring Filters with Composite Right/Left Handed Cells

In this paper, a novel dual-band active filter topology is presented. The non-linear phase response of a composite right/left-handed cell is used to achieve the desired dual-band performance. Additionally, the proposed structure based on coupled ring resonators yields a very compact solution in which high-order implementations can be easily obtained by cascading multiple rings. The theoretical principles of this type of filters are analyzed in detail. Finally, three prototypes based on first-, second- and third-order structures validate the feasibility of this type of filters. Good agreement between simulations and measurements has been achieved