2,173 research outputs found
Experimentally Attainable Optimal Pulse Shapes Obtained with the Aid of Genetic Algorithms
We propose a methodology to design optimal pulses for achieving quantum
optimal control on molecular systems. Our approach constrains pulse shapes to
linear combinations of a fixed number of experimentally relevant pulse
functions. Quantum optimal control is obtained by maximizing a multi-target
fitness function with genetic algorithms. As a first application of the
methodology we generated an optimal pulse that successfully maximized the yield
on a selected dissociation channel of a diatomic molecule. Our pulse is
obtained as a linear combination of linearly chirped pulse functions. Data
recorded along the evolution of the genetic algorithm contained important
information regarding the interplay between radiative and diabatic processes.
We performed a principal component analysis on these data to retrieve the most
relevant processes along the optimal path. Our proposed methodology could be
useful for performing quantum optimal control on more complex systems by
employing a wider variety of pulse shape functions.Comment: 7 pages, 6 figure
Valoración de proyectos de energía térmica bajo condiciones de incertidumbre a través de opciones reales.
Este trabajo valora una planta a base de carbón para la generación de energía térmica en un país latinoamericano considerando sus opciones reales. El trabajo presenta, en primer lugar, el comportamiento probabilístico de cada una de las variables que afectan la viabilidad financiera del proyecto. Para ello, se proponen modelos ARIMAGARCH que permiten pronosticar las medias y la volatilidad de las variables que determinan el flujo de caja. Debido a la alta volatilidad en los precios de la energía y al incremento del precio internacional del carbón en los últimos años, se espera que estos proyectos no sean viables financieramente. Sin embargo, al considerar las opciones reales de expansión, de abandono y de continuar puede dar como resultado escenarios en los cuales esta tecnología sea competitiva. Los resultados obtenidos sugieren disminución de los riesgos de pérdida e incremento del valor del proyecto
Valoración del riesgo financiero (CFAR) en las EPS a través de opciones reales: una aplicación al nivel de atención IV
El número de pacientes tratados por insuficiencia renal en Colombia es cadavez mayor; por esta razón conocer los costos asociados a esta enfermedad es unanecesidad manifiesta de las Entidades Promotoras de Salud con el fin de garantizarla estabilidad del Sistema de Seguridad Social en Salud. Este trabajo evalúa financieramente,mediante opciones reales, la posibilidad de hacer un trasplante de riñónen un paciente bajo tratamiento de insuficiencia renal y el Flujo de Caja en Riesgoal tener en cuenta esta opción. Se encontró que al hacer un análisis periódico delos costos asociados a continuar con el tratamiento, existen casos en los que es máseficiente hacer el trasplante, disminuyendo el valor presente de las erogaciones delpaciente, mejorando el flujo de caja en riesgo y controlando los gastos futuros de laentidad que lo atiende
Global patterns and drivers of ecosystem functioning in rivers and riparian zones
River ecosystems receive and process vast quantities of terrestrial organic carbon, the fate of which depends strongly on microbial activity. Variation in and controls of processing rates, however, are poorly characterized at the global scale. In response, we used a peer-sourced research network and a highly standardized carbon processing assay to conduct a global-scale field experiment in greater than 1000 river and riparian sites. We found that Earth’s biomes have distinct carbon processing signatures. Slow processing is evident across latitudes, whereas rapid rates are restricted to lower latitudes. Both the mean rate and variability decline with latitude, suggesting temperature constraints toward the poles and greater roles for other environmental drivers (e.g., nutrient loading) toward the equator. These results and data set the stage for unprecedented “next-generation biomonitoring” by establishing baselines to help quantify environmental impacts to the functioning of ecosystems at a global scale
Introducción al problema de la erosión litoral en Urabá (sector Arboletes - Turbo), Costa Caribe Colombiana
Introduction to littoral erosion problem in Urabá (Arboletes-Turbo area) Colombian Caribbean coast. Shoreline retreat has been the net dominant historical trend along the 145 km-length littoral between Arboletes and Turbo (Southern Caribbean of Colombia). For the last four decades, there were identified in this littoral shoreline retreats of about 50-100m in several places (Uveros, Damaquiel, Zapata, Turbo) and a maximun of 1.6 km in the Punta Rey-Arboletes area, where land losses were of 4.5 k m2, at exceptional rates of 40m/year. The synthesis of the available information suggest that the general “susceptibility” to erosion between Arboletes and Turbo could be related primarily to relative sea level rise, associated to tectonic movements as well as to the effects of mud diapirism and hydroisostacy. In the more critical areas (Arboletes, Turbo), the natural erosive trends were accelerated by anthropic actions, including river diversion (Turbo), beach mining, and inadequate (or total absense) practices for controlling residual and natural waters. Up to August 2000, there were invested about Col 10.000 millones. Con muy pocas excepciones, los espolones perpendiculares a las playas no han recuperado arenas y más bien se han convertido en generadores de nuevos problemas en los sectores adyacentes. A corto plazo, la erosión litoral entre Arboletes y Turbo es causada tanto por factores marinos como por procesos de erosión subaérea y es función en buena parte de las litologías poco resistentes de las terrazas y acantilados, compuestos en su mayoría por lodolitas fracturadas y meteorizadas (con buzamientos o planos de debilidad inclinados hacia el mar) y por sedimentos finos no consolidados, fácilmente licuables: ambas condiciones facilitan la ocurrencia de deslizamientos, caídas de rocas y flujos de lodo que determinan retrocesos rápidos (3 a 4 metros) del contorno litoral, sobre todo en los primeros 15 días de la transición verano-invierno (abril) y durante los “mares de leva” (periodos de oleajes fuertes). El caso de la erosión litoral entre Turbo y Arboletes ilustra claramente cómo las tendencias erosivas naturales pueden intensificarse fuertemente por intervenciones humanas (incluyendo las defensas ingenieriles) y la necesidad urgente de coordinar esfuerzos para controlar o mitigar con eficiencia las pérdidas de terrenos litorales
From sensorimotor dependencies to perceptual practices: making enactivism social
Proponents of enactivism should be interested in exploring what notion of action best captures the type of action-perception link that the view proposes, such that it covers all the aspects in which our doings constitute and are constituted by our perceiving. This article proposes and defends the thesis that the notion of sensorimotor dependencies is insufficient to account for the reality of human perception, and that the central enactive notion should be that of perceptual practices. Sensorimotor enactivism is insufficient because it has no traction on socially dependent perceptions, which are essential to the role and significance of perception in our lives. Since the social dimension is a central desideratum in a theory of human perception, enactivism needs a notion that accounts for such an aspect. This article sketches the main features of the Wittgenstein-inspired notion of perceptual practices as the central notion to understand perception. Perception, I claim, is properly understood as woven into a type of social practices that includes food, dance, dress, music, etc. More specifically, perceptual practices are the enactment of culturally structured, normatively rich techniques of commerce of meaningful multi- and inter-modal perceptible material. I argue that perceptual practices explain three central features of socially dependent perception: attentional focus, aspects’ saliency, and modal-specific harmony-like relations
Liquefaction Evaluations at the Savannah River Site. A Case History
Over the past decade, liquefaction assessments have been performed for many existing and planned critical facilities at the Department of Energy’s Savannah River Site (SRS). The assessments incorporated site-specific Cyclic Resistance Ratio (CRR) and Ks with the use of the cone penetration test (CPT). The SRS-specific CRR and Ks were developed from laboratory testing of carefully collected samples. Test results show SRS soils have increased liquefaction resistance of two to three times when compared to standard literature for Holocene-age deposits. This increase in strength can be attributed to many factors such as aging and overconsolidation. The purpose of this paper is to discuss liquefaction methodologies used at the SRS. Specifically, 1) use of the CPT and correlations of CPT-derived results with that of high-quality undisturbed samples; 2) aging; and 3) Ks vertical confining stress factor
Técnicas de lógica difusa en la predicción de índices de mercados de valores: una revisión de literatura.
El pronóstico de índices de mercados de valores es una tarea importante en ingeniería financiera, porque es una información necesaria para la toma de decisiones. Este estudio tiene como objetivo evaluar el estado del arte en el progreso del pronóstico del mercado de valores, usando metodologías basadas en sistemas de inferencia borrosa y redes neuronales neuro-difusas, enfatizando el caso del Índice General de la Bolsa de Colombia (IGBC). Se empleó la revisión sistemática de literatura para responder cuatro preguntas de investigación. Existe una tendencia importante sobre el uso de las metodologías basadas en inferencia difusa para predecir los índices de los mercados de valores, explicada por la precisión del pronóstico en comparación con otras metodologías tradicionales. La mayoría de las investigaciones se enfocan en metodologías de “series de tiempo difusas” y ANFIS, pero, hay otras aproximaciones prometedoras que no han sido evaluadas aún. Existe un vacío de investigación en el caso del mercado accionario colombiano
Combined beach - inner shelf erosion in short and medium term (Maspalomas, Canary Islands)
The analysis of the accurate topo-bathymetric digital elevation model (DEM), the cartography of the submarine sedimentary cover and the monitoring of short (seasonal) and medium-term (2000-2009) morphological changes have permitted depicting the erosional trend in the short and medium-term of the Maspalomas sedimentary system. Short-term analysis showed intense sedimentary fluxes between the beaches and the inner shelf, and sedimentary exchanges with other sectors of the inner shelf, while the steep slope inner shelf fronting La Bajeta cape was identified as a sink area. In the medium-term the sediment budget showed high erosion of the supratidal and intertidal sectors of the beaches due to storm waves in the 2005-2006 winter, followed by accretion over the next four years, but which did not reach the initial sedimentary state. The inner shelf and subtidal sector of the beaches showed negative budgets in the short and medium-term. Interannual variability of the wave and wind regimes determines decadal beach erosion-accretion cycles, while long-term climatic change, evidenced at the study area by a decrease of trade winds and NE wave intensity in 2005, is expected to produce a possible increase of erosion at the El Inglés inner shelf and consequently a decrease in sediment inputs to the El Inglés beach and Maspalomas dune field. Finally, the influence of the geological heritage is depicted by the Fataga gully’s control of the present coastal morphology, and by the island relief control of the wind, waves and current directions in the study area
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