On the optimaL response of q-vortex

Wingtip vortices represent a hazard for the stability of the following airplane in airport highways. These flows have been usually modeled as swirling jets/wakes, which are known to be highly unstable and susceptible to breakdown at high Reynolds numbers for certain flow conditions, but different to the ones present in real flying airplanes. A very recent study based on Direct Numerical Simulations (DNS) shows that a large variety of helical responses can be excited and amplified when a harmonic inlet forcing is imposed. In this work, the optimal response of q-vortex (both axial vorticity and axial velocity can be modeled by a Gaussian profile) is studied by considering the time-harmonically forced problem with a certain frequency ω. We first reproduce Guo and Sun’s results for the Lamb-Oseen vortex (no axial flow) to validate our numerical code. In the axisymmetric case m = 0, the system response is the largest when the input frequency is null. The axial flow has a weak influence in the response for any axial velocity intensity. We also consider helical perturbations |m| = 1. These perturbations are excited through a resonance mechanism at moderate and large wavelengths as it is shown in Figure 1. In addition, Figure 2 shows that the frequency at which the optimal gain is obtained is not a continuous function of the axial wavenumber k. At smaller wavelengths, large response is excited by steady forcing. Regarding the axial flow, the unstable response is the largest when the axial velocity intensity, 1/q, is near to zero. For perturbations with higher azimuthal wavenumbers |m| > 1, the magnitudes of the response are smaller than those for helical modes. In order to establish an alternative validation, DNS has been carried out by using a pseudospectral Fourier formulation finding a very good agreement.

Heat fluxes between the Guadalquivir river and the Gulf of Cádiz Continental Shelf

An 18-year time series of daily sea surface temperature of Gulf of Cadiz and an 18-month time series of temperature collected in the vicinity of the Guadalquivir estuary mouth have been analyzed to investigate the heat exchange between the estuary and the adjacent continental shelf. The first time identifies a continental shelf area where seasonal thermal oscillation signal (amplitudes and phase) changes abruptly. In order to explain this anomaly, the second data set allows a description of thermal fluctuations in a wide range of frequencies and an estimation of the upstream heat budget of the Guadalquivir estuary. Results show that high frequency thermal signal, diurnal and semidiurnal, and water flux signal through Guadalquivir mouth, mainly semidiurnal, apparently interact randomly to give a small exchange of thermal energy at high frequency. There is no trace, at the estuary's mouth, of daily heat exchanges with intertidal mudflats probably because it tends to cancel on daily time scales. Results also show that fluctuations of estimated air-sea fluxes force fluctuations of temperature in a quite homogeneous estuarine, with a delay of 20 days. The along-channel thermal energy gradient reaches magnitudes of 300-400 J m-4 near the mouth during the summer and winter and drives the estuary-shelf exchange of thermal energy at seasonal scale. Particularly, the thermal heat imported by the estuary from the shelf area during late fall-winter-early spring of 2008/2009 is balanced by the thermal heat that the estuary exports to the shelf area during late spring-summer of 2008. In summary, Guadalquivir river removes/imports excess of thermal energy towards/from the continental shelf seasonally, as a mechanism to accommodate excess of heat from one side respect to the other side.

FLOOD RISK ASSESSMENT UNDER HISTORICAL AND PREDICTED LAND USE CHANGE USING CONTINUOUS HYDROLOGIC MODELING

Current procedures for flood risk estimation assume flood distributions are stationary over time, meaning annual maximum flood (AMF) series are not affected by climatic variation, land use/land cover (LULC) change, or management practices. Thus, changes in LULC and climate are generally not accounted for in policy and design related to flood risk/control, and historical flood events are deemed representative of future flood risk. These assumptions need to be re-evaluated, however, as climate change and anthropogenic activities have been observed to have large impacts on flood risk in many areas. In particular, understanding the effects of LULC change is essential to the study and understanding of global environmental change and the consequent hydrologic responses. The research presented herein provides possible causation for observed nonstationarity in AMF series with respect to changes in LULC, as well as a means to assess the degree to which future LULC change will impact flood risk. Four watersheds in the Midwest, Northeastern, and Central United States were studied to determine flood risk associated with historical and future projected LULC change. Historical single framed aerial images dating back to the mid-1950s were used along with Geographic Information Systems (GIS) and remote sensing models (SPRING and ERDAS) to create historical land use maps. The Forecasting Scenarios of Future Land Use Change (FORE-SCE) model was applied to generate future LULC maps annually from 2006 to 2100 for the conterminous U.S. based on the four IPCC-SRES future emission scenario conditions. These land use maps were input into previously calibrated Soil and Water Assessment Tool (SWAT) models for two case study watersheds. In order to isolate effects of LULC change, the only variable parameter was the Runoff Curve Number associated with the land use layer. All simulations were run with daily climate data from 1978-1999, consistent with the 'base' model which employed the 1992 NLCD to represent 'current' conditions. Output daily maximum flows were converted to instantaneous AMF series and were subsequently modeled using a Log-Pearson Type 3 (LP3) distribution to evaluate flood risk. Analysis of the progression of LULC change over the historic period and associated SWAT outputs revealed that AMF magnitudes tend to increase over time in response to increasing degrees of urbanization. This is consistent with positive trends in the AMF series identified in previous studies, although there are difficulties identifying correlations between LULC change and identified change points due to large time gaps in the generated historical LULC maps, mainly caused by unavailability of sufficient quality historic aerial imagery. Similarly, increases in the mean and median AMF magnitude were observed in response to future LULC change projections, with the tails of the distributions remaining reasonably constant. FORE-SCE scenario A2 was found to have the most dramatic impact on AMF series, consistent with more extreme projections of population growth, demands for growing energy sources, agricultural land, and urban expansion, while AMF outputs based on scenario B2 showed little changes for the future as the focus is on environmental conservation and regional solutions to environmental issues.

Feasibility study and flow scheduling optimization of a multi-product pipeline system

The first goal of this study is to analyse a real-world multiproduct onshore pipeline system in order to verify its hydraulic configuration and operational feasibility by constructing a simulation model step by step from its elementary building blocks that permits to copy the operation of the real system as precisely as possible. The second goal is to develop this simulation model into a user-friendly tool that one could use to find an “optimal” or “best” product batch schedule for a one year time period. Such a batch schedule could change dynamically as perturbations occur during operation that influence the behaviour of the entire system. The result of the simulation, the ‘best’ batch schedule is the one that minimizes the operational costs in the system. The costs involved in the simulation are inventory costs, interface costs, pumping costs, and penalty costs assigned to any unforeseen situations. The key factor to determine the performance of the simulation model is the way time is represented. In our model an event based discrete time representation is selected as most appropriate for our purposes. This means that the time horizon is divided into intervals of unequal lengths based on events that change the state of the system. These events are the arrival/departure of the tanker ships, the openings and closures of loading/unloading valves of storage tanks at both terminals, and the arrivals/departures of trains/trucks at the Delivery Terminal. In the feasibility study we analyse the system’s operational performance with different Head Terminal storage capacity configurations. For these alternative configurations we evaluated the effect of different tanker ship delay magnitudes on the number of critical events and product interfaces generated, on the duration of pipeline stoppages, the satisfaction of the product demand and on the operative costs. Based on the results and the bottlenecks identified, we propose modifications in the original setup.

Regulation of bone marrow stem cells through oscillatory shear stresses - A heart valve tissue engineering perspective

Heart valve disease occurs in adults as well as in pediatric population due to age-related changes, rheumatic fever, infection or congenital condition. Current treatment options are limited to mechanical heart valve (MHV) or bio-prosthetic heart valve (BHV) replacements. Lifelong anti-coagulant medication in case of MHV and calcification, durability in case of BHV are major setbacks for both treatments. Lack of somatic growth of these implants require multiple surgical interventions in case of pediatric patients. Advent of stem cell research and regenerative therapy propose an alternative and potential tissue engineered heart valves (TEHV) treatment approach to treat this life threatening condition. TEHV has the potential to promote tissue growth by replacing and regenerating a functional native valve. Hemodynamics play a crucial role in heart valve tissue formation and sustained performance. The focus of this study was to understand the role of physiological shear stress and flexure effects on de novo HV tissue formation as well as resulting gene and protein expression. A bioreactor system was used to generate physiological shear stress and cyclic flexure. Human bone marrow mesenchymal stem cell derived tissue constructs were exposed to native valve-like physiological condition. Responses of these tissue constructs to the valve-relevant stress states along with gene and protein expression were investigated after 22 days of tissue culture. We conclude that the combination of steady flow and cyclic flexure helps support engineered tissue formation by the co-existence of both OSS and appreciable shear stress magnitudes, and potentially augment valvular gene and protein expression when both parameters are in the physiological range. ^

Movement effects on the flow physics and nutrient delivery in engineered valvular tissues

Mechanical conditioning has been shown to promote tissue formation in a wide variety of tissue engineering efforts. However the underlying mechanisms by which external mechanical stimuli regulate cells and tissues are not known. This is particularly relevant in the area of heart valve tissue engineering (HVTE) owing to the intense hemodynamic environments that surround native valves. Some studies suggest that oscillatory shear stress (OSS) caused by steady flow and scaffold flexure play a critical role in engineered tissue formation derived from bone marrow derived stem cells (BMSCs). In addition, scaffold flexure may enhance nutrient (e.g. oxygen, glucose) transport. In this study, we computationally quantified the i) magnitude of fluid-induced shear stresses; ii) the extent of temporal fluid oscillations in the flow field using the oscillatory shear index (OSI) parameter, and iii) glucose and oxygen mass transport profiles. Noting that sample cyclic flexure induces a high degree of oscillatory shear stress (OSS), we incorporated moving boundary computational fluid dynamic simulations of samples housed within a bioreactor to consider the effects of: 1) no flow, no flexure (control group), 2) steady flow-alone, 3) cyclic flexure-alone and 4) combined steady flow and cyclic flexure environments. We also coupled a diffusion and convention mass transport equation to the simulated system. We found that the coexistence of both OSS and appreciable shear stress magnitudes, described by the newly introduced parameter OSI-:τ: explained the high levels of engineered collagen previously observed from combining cyclic flexure and steady flow states. On the other hand, each of these metrics on its own showed no association. This finding suggests that cyclic flexure and steady flow synergistically promote engineered heart valve tissue production via OSS, so long as the oscillations are accompanied by a critical magnitude of shear stress. In addition, our simulations showed that mass transport of glucose and oxygen is enhanced by sample movement at low sample porosities, but did not play a role in highly porous scaffolds. Preliminary in-house in vitro experiments showed that cell proliferation and phenotype is enhanced in OSI-:τ: environments.^

Las sociedades cooperativas y sociedades laborales como motor de desarrollo económico y social: Análisis de su impacto socioeconómico en la región de Andalucía

El objetivo de este trabajo es analizar la importancia de las Sociedades Cooperativas y Sociedades Laborales en Andalucía y su contribución a la Economía Social en España. El rol que están asumiendo estas organizaciones empresariales de la Economía Social en la actual situación de crisis económica hace destacar aún más sus funciones social y económica, manteniéndose plena su vigencia como modelos empresariales de desarrollo económico sostenible y solidario. Con este fin, se realiza un análisis de la creación de Cooperativas y Sociedades Laborales en la región de Andalucía, y mediante la observación de las principales magnitudes económicas y sociales, se tratará de poner de manifiesto su papel fundamental en la generación de valor, mostrando cómo el desarrollo de estas figuras empresariales supone un volumen de negocio y empleo satisfactorio, especialmente en tiempos de crisis. En otras palabras, este estudio trata de mostrar la creciente importancia de las Sociedades Cooperativas y Sociedades Laborales, destacando su relevancia económica y social.

De la transformación a la bancarización de las cajas de ahorros españolas: un análisis de los resultados perseguidos

Esta investigación tiene su origen en el proceso de reordenación que ha acontecido en el sector bancario español. Dicha reestructuración se ha llevado a cabo para tratar de reducir las dudas sobre la viabilidad de las entidades bancarias a medio y largo plazo y así poder restituir de nuevo la confianza en el sector. Aunque la crisis económico-financiera ha afectado a todo el sector bancario, ha sido el subsector de las cajas de ahorros el que ha experimentado la mayor transformación mediante fusiones, absorciones y a través de Sistemas Institucionales de Protección –SIP-, y el que se ha visto sometido al denominado proceso de bancarización. Considerando lo anterior, la presente investigación se centra en el estudio de las cajas de ahorros para trata de comprobar si dicha transformación y consiguiente proceso de bancarización ha permitido que se satisfagan los objetivos perseguidos con la reordenación bancaria. Para ello, se analiza la evolución de magnitudes económico-financieras relevantes para el sector bancario durante el período comprendido entre 1999 y 2012. Los resultados sugieren que no todas las cajas de ahorros han visto mejorados sus ratios de eficiencia, solvencia, brecha financiera y obra social, lo que indica que aún queda bastante por hacer para lograr solventar los problemas que afectan al sector estudiado.

Los centros especiales de empleo en Castilla y León, 2007-2013: efectos de la crisis en función de la personalidad jurídica que adoptan

Este trabajo surge con el propósito de realizar un estudio, económico-financiero, sobre los Centros Especiales de Empleo localizados en Castilla y León, a partir de una clasificación en función de la personalidad jurídica que adoptan y comprobar cómo les puede afectar la crisis económica iniciada a finales de 2007. Se analizan diferentes partidas recogidas en sus estados financieros y se comparan los resultados del análisis con los obtenidos en años anteriores, periodo 2007-2013, al objeto de mostrar una perspectiva más amplia de su tamaño, desarrollo, crecimiento y comportamiento. Para ello se utilizan las siguientes magnitudes económicas: activo total, cifra de negocios y resultados. Se compara la variable empleo con las subvenciones recibidas por los Centros poniendo de manifiesto como la crisis sí les afecta en función de la personalidad jurídica que adoptan, siendo las entidades más perjudicadas las asociaciones y personas físicas, pudiendo incluso ocasionar su desaparición. Además se introduce la cuenta de reversión para los Centros, que mide qué porcentaje de las ayudas públicas recibidas es devuelto a la sociedad.

Modelo de gestión financiera basado en la optimización de las necesidades operativas de fondos: el caso de las empresas farmacéuticas en España

Este trabajo de investigación pretende poner de manifiesto la necesidad de gestionar de forma adecuada la tesorería que genera el ciclo de explotación de la empresa. Esta teso-rería es garantía de continuidad de la empresa, porque permite disponer de liquidez y obtener financiación a partir de la optimización de los elementos del negocio, especial-mente, en situaciones de crisis, con estancamiento o caída de las cifras de negocio, con recortes en el gasto público que afectan a la cadena de valor, con limitaciones al acceso al crédito externo, con socios y accionistas que buscan rentabilidad para sus inversiones sin tener que realizar nuevas aportaciones. Síntesis Para gestionar de forma adecuada la tesorería que genera el ciclo de explotación, es ne-cesario disponer de un modelo de optimización de las Necesidades Operativas de Fon-dos (NOF). Ante la ausencia de este tipo de modelos, este trabajo de investigación pre-tende construir y probar uno, como herramienta automatizada que simule y mida el im-pacto que tiene la inversión en las NOF sobre la solvencia, la rentabilidad y el valor de una empresa, para corregir un problema de indisponibilidad o de insuficiencia de liqui-dez. Para construir el modelo, se ha elegido Excel como software informático soporte. A partir de este software, se ha planteado la construcción del modelo siguiendo los si-guientes pasos: 1. Automatización del paso de los estados financieros contables a unos estados finan-cieros funcionales a partir la utilización de plantillas de toma de datos que permitan identificar y cuantificar las NOF. 2. Diseño de unas plantillas de simulación con alternativas generadoras de impactos sobre los estados financieros. Estas alternativas incluyen tanto elementos sin coste explícito como elementos con dicho coste. 3. Emisión automática de informes comparativos de la posición de la empresa antes y después de los impactos simulados sobre los estados financieros, para analizar la si-tuación de la misma en términos de equilibrio financiero, de solvencia, de rentabili-dad y de valor generado, incluyendo ratios que relacionan distintas magnitudes y permiten observar la gestión y la eficiencia operativa..

Población, precios y renta de la tierra en Toledo, siglos XVI-XVII

La coyuntura vivida por la población rural en Castilla la Nueva durante la Edad Moderna no ha gozado de una producción historiográfica abundante. Las investigaciones sobre devenir del mundo agrario en este territorio tan vasto e importante del centro peninsular vivieron su apogeo hace varias décadas. No obstante, las contribuciones de los últimos años, relacionadas con la reconstrucción de magnitudes económicas y demográficas en varias zonas de la región, están resultando muy sugestivas. Toledo fue una de las ciudades castellanas más pobladas e importantes a comienzos de la Edad Moderna, y su catedral era la sede de una de las más poderosas archidiócesis de los reinos hispánicos. La citada urbe, como el resto de Castilla, conoció una fase expansiva en el siglo XVI y sufrió una depresión en el siglo XVII. La bibliografía general sobre la Ciudad Imperial y su territorio circundante en esta época es muy extensa, pero relativamente escasa en cuanto a estudios socioeconómicos de larga duración. El principal cometido de esta investigación es reconstruir y analizar la evolución de tres magnitudes coyunturales muy significativas en el Toledo moderno: la población, el coste de la vida y la renta de la tierra. La explotación de las fuentes eclesiásticas y civiles toledanas permite establecer varios objetivos concretos: 1) estudiar el movimiento de la población en la provincia toledana entre los siglos XVI y XIX a través de censos y registros bautismales; 2) construir un índice de precios para la ciudad de Toledo entre 1521 y 1650, que servirá como indicador de la evolución del nivel de vida de los toledanos y como deflactor de las magnitudes expresadas en términos corrientes; y 3) examinar los contratos agrarios y la trayectoria de la renta de la tierra entre 1521 y 1650, a partir de una muestra representativa de posesiones rurales de la catedral toledana. El balance demográfico en la provincia de Toledo fue especialmente pobre entre finales del siglo XVI y mediados del siglo XIX. La tendencia fue positiva en el Quinientos, pero la recuperación posterior al declive del Seiscientos fue exasperante; hasta la segunda mitad del siglo XVIII no se sobrepasarían los niveles máximos de finales del siglo XVI. Torrijos-­‐‑La Sagra-­‐‑ Toledo y La Mancha, comarcas entonces densamente pobladas y con buena dotación de recursos agrarios, participaron más en la fase depresiva. Por su parte, Talavera y La Jara-­‐‑Montes, tuvieron un papel más destacado en la recuperación posterior...

Stability and smoothness improvements for an underactuated biped with a tail

In this work we present an important improvement in our model of biped mechanism that allows the elevation in a stable form of the system's feet during the execution of trajectories. This improvement allows for simpler trajectory planning and also facilitates the reduction of losses in the collision between the feet and the ground. On the other hand, we add to the design phase the study of the displacement of the Zero Moment Point, as well as the variation of the normal component of the ground reaction force during the motion of the system. Consideration of the above mentioned magnitudes in the design phase allows us to design the necessary support area of the system. These magnitudes will be used as a smoothness criterion of the ground contact to facilitate the selection of robot parameters and trajectories.

Young adults in rural tourism areas

This thesis examines how tourism affects conditions for young adults in rural areas. Such a study lies at the intersection of research about tourism impacts, adult transition, and rural areas. The aim is to examine how largescale tourism affects the opportunities for young adults living in rural areas; their perception of place and the perceived opportunities and obstacles that tourism provides. The thesis utilizes a mixed method approach. A quantitative study based on micro-data on individuals identifies the patterns and magnitudes of the mechanisms by which tourism affects population change among young adults. Interview methods are used in the case study area, Sälen, to investigate these mechanisms in depth. Finally, the rural–urban dichotomy is explored in a conceptual study that asks how tourism affects the perception of a local village as either rural or urban. Young inhabitants in rural areas are rarely considered in tourism research; therefore, the main contribution of this thesis is that it illuminates how tourism affects conditions for young adults in rural areas. The thesis reveals a substantial impact on the adult transition, mainly due to easier access to the labor market and a good supply of jobs during the high season. Further, the large number of people passing through creates flows of opportunities to make friends, get a job, or just meet people. All of these factors contribute to high mobility in these places, and to the perception of them as places where things happen. The high mobility in Sälen implies that fixed migrant categories (such as stayers and leavers) are largely insufficient. The tourism environment creates a space that is always under construction and continually producing new social relations mainly perceived as opportunities. Conceptualizing this as a modern rurality is a way to move beyond the often implicit notions of urban as modern and rural as traditional.

Características preferidas por hombres y mujeres que buscan pareja estable de su mismo sexo

Las preferencias en elección de pareja de hombres y mujeres interesados en establecer relaciones a largo plazo con personas de su mismo sexo biológico ha sido un tema de interés para el análisis evolucionista, ya que existe debate frente a los resultados de las investigaciones y los planteamientos de las teorías de inversión parental y estrategias sexuales. Con el objetivo de identificar qué características son preferidas por hombres y mujeres interesados en establecer una relación a largo plazo con personas de su mismo sexo biológico y contribuir a esta discusión, se llevó a cabo un estudio descriptivo en el que analizamos el contenido de 732 perfiles de hombres y mujeres (H=491; M=241) que buscaban una relación estable con parejas de su mismo sexo biológico. Las categorías analizadas fueron: edad, atractivo físico (apariencia, contextura, estatura y peso), estatus socioeconómico (situación laboral, nivel educativo y zona de residencia buscada), estado civil, número de hijos y hábitos saludables (fumar y beber). Los resultados encontrados muestran que los hombres presentan rangos amplios en las características deseadas en una pareja (edad=16.87; estatura=11.37; peso=15.23) y además buscan personas menores a la edad ofrecida (M=-4.17 años). En las mujeres se encontró que los rangos son más restringidos (edad=13.85; estatura=9.83; peso=12.77) y además prefieren parejas mayores (M=2.89 años). A nivel general, se evidencia que los resultados encontrados en la mayoría de las variables podrían indicar congruencia con los planteamientos de la teoría de inversión parental y estrategias sexuales; sin embargo, en otras variables los resultados no son claros.

ACTIVIDAD SISMICA DE CARACTER SUPERFICIAL REGISTRADA POR LA RED SISMOGRÁFICA DEL OVSICORI-UNA EN LA HOJA DE SAN JOSE 1:200.000 ENTRE ABRIL 1984 - JULIO 1988

Este trabajo es el resultado del análisis de la información existente, registrada por el OVSICORI-UNA para la región del Valle Central de Costa Rica (Hoja San José, escala 1:200.000).  Históricamente el Valle Central ha sufrido por la acción de varios terremotos.  Entre los más dañinos podemos citar el de Cartago de 1841, el de Fraijanes de 1888, el de Cartago de 1910, el de Sarchí de 1912, el de Patillos de 1952 y el de los del Bajos del Toro en 1955.  Esta actividad asociada a fallas de carácter superficial (z 15 km) y con magnitudes moderadas mb 6.5, muy probablemente se volverá a presentar en el futuro, en igual forma en que se han visto afectada la ciudad de San Salvador en la hermana república de El Salvador.  Es, por lo tanto, de vital importancia investigar conocer y evaluar la existencia de las fallas que han ocasionado dichos terremotos.