Energy-based model of a solar-powered pumped-hydro storage system

This document presents a port-Hamiltonian model of a pumped-hydro storage system, using Photo Voltaic energy as the primary source. MATLAB simulation results show that the model is functional under ideal conditions of constant solar radiation. It also graphically demonstrate the relationship between input solar power and the accumulation of energy at the upper reservoir. This work is a fundamental step towards a tool for the analysis and design of optimized and fully automated system

La importancia del valor de marca en los clubs de fútbol = The importance of brand equity in footbal clubs

Dada la importancia del fútbol en la actualidad, se hace un estudio de su componente principal, los clubs de fútbol. Durante este texto se exponen las principales fuentes de ingresos y gastos que influyen en la valoración financiera de estos. Sin embargo, el punto central de este trabajo es la valoración de la marca de los clubs de fútbol desde el punto de vista del consumidor. Las teorías de medición del valor de marca de Aaker y Keller son la base sobre la que se realiza tanto el análisis de este valor como el caso práctico. La marca de un club de fútbol tiene un papel protagonista en el valor real de estos, de hecho, se expone como un análisis meramente centrado en la capacidad financiera no define el valor real de un club. Este valor de marca radica en una serie de dimensiones que deberían ser potenciadas por los departamentos de marketing de las entidades futbolísticas. Además, el caso práctico realizado proyecta la importancia que los aficionados a este deporte perciben en determinados aspectos y que son clave para establecer relaciones consistentes entre club y seguidor

Interactions between geomorphology and production chain of 2 high-quality coffee in Costa Rica

High-altitude coffee has an international reputation due to its high quality, especially in countries with a long production history like Costa Rica. Specific geographical characteristics determine the regions where high-altitude coffee can be cultivated. Over the last two decades, new production conditions have promoted the growth of smallholder coffee farms in the Upper Buenavista Catchment (UBC) in the South of Costa Rica. To understand this phenomenon's process, we ini-tially performed a detailed geomorphological mapping of the high-elevation production sites in the UBC. Then, we used remote sensing to determine the coffee land cover (2005, 2012, and 2018) to compare their landforms. Furthermore, we analyzed the production-processing-market chain that has promoted coffee plantations since 2005. Our results show that coffee farmers chose more unstable and erosive areas with short-term production prospects to cultivate premium-prices coffee. Moreover, farmers have changed their role in the coffee sector, evolving from small pro-ducers to entrepreneurs with specialized knowledge. These actions may reduce economic risks and improve the household incomes of smallholder coffee producers. However, limited research has been done along the tropics about the relationships between landforms, socioeconomic drivers, and high-altitude coffee yield. Therefore, our results are essential to present geomor-phology and applied geography as baselines in land use planning for agricultural landscapes.UCR::Vicerrectoría de Docencia::Ciencias Sociales::Facultad de Ciencias Sociales::Escuela de Geografí

Axis Dorsal Laminotomy for Excision of a Meningioma in a Dog

Background: Surgical access to the spinal cord at the level of C2 vertebra presents technical limitations, due to anatomical particularities in this region. The ventral slot technique does not allow space for the removal of dorsolateral masses. The axis hemilaminectomy technique provides limited access to the dorsal aspect of spinal cord and there is a risk of damaging the vertebral arteries. The axis dorsal laminotomy technique allows good access to spinal cord and preserves the atlantoaxial and nuchal ligaments, however few papers describe this technique. The objective of this paper is to report the axis dorsal laminotomy performed in a dog with a meningioma at this level.Case: An 11-year-old male, Maltese dog, was presented with a 15-day history of progressive weakness, intense cervical pain and difficulty in locomotion of the four limbs. He was being treated with painkillers without improvement. On clinical examination, the physiological parameters were normal. Neurological examination showed tetraparesis with the syndrome localized in the cranial cervical region. The main differential diagnoses were intervertebral disc disease, neoplasia, inflammatory or infectious disease. Computed tomography was performed and the evaluation of images allowed the visualization of an intradural-extramedullary neoplastic process, promoting important spinal compression, with approximate dimensions of the lesion 0.70 cm high x 0.67 cm wide x 0.78 cm long, with apparent involvement of the meninges, with a more lateralized location on the left, with meningioma being the main differential diagnosis. Thus, exploratory surgery, through the technique of dorsal laminotomy of the axis was performed. After the removal of the mass, the spinous process was repositioned in its anatomical location and fixed with 0.6 mm steel cerclage wire that was passed through the holes made in the dorsal lamina of the axis. After the surgery a neck brace was kept for 45 days. According to the histological changes observed, the neoplasm was classified as grade one meningothelial meningioma. The patient showed gradual improvement and started walking again 4 days after the surgery, staying well and without pain for 5 months, when there was a recurrence of the neoplasia.Discussion: Surgical access to the cervical region in question is limited due to the presence of complex ligamentous structures, vascular network and the anatomical features of the first and second cervical vertebrae. Thus, the dorsal axis laminotomy technique was used. The approach allowed good visualization of the spinal canal as well as the preservation of the atlantoaxial ligament, maintaining atlantoaxial stability. Through histopathological analysis, the neoplasm was classified as grade I meningothelial, which is considered a benign meningioma, but its behavior is considered malignant due to the compression of the spinal cord and the impossibility of removal with surgical margins, as recommended for oncological surgeries. The patient's survival after surgical treatment is in accordance with that described by other authors which varies from 2.2 to 47 months. Radiotherapy seems to improve the prognosis, but this therapeutic modality is not easily available in the country. There is also insufficient information on the use of chemotherapy for this type of neoplasia, or on the relationship between tumor graduation and survival. The surgery was proposed in order to confirm the suspicion, decompress the spinal cord and collect material for biopsy; the technique performed is feasible and no intraoperative complications have occurred

Las smart cities latinas. Factores que impiden su desarrollo

Technologies have evolved in a vertiginous way throughout the world; the use of ICTs has become widespread in such a way that today practically every human being on the planet has access to some type of technology with internet interconnection, from smartphones to integrated systems of neural networks that have revolutionized the conception of what was understood as technology. In recent decades the name of Smart cities has emerged, which respond to new proposals to create or transform cities into smart cities. The objective of this research is to know what are the main characteristics that define this type of cities and above all to know what are the factors that affect and prevent their development in Latin America, the research is carried out under the methodological approach of bibliographic documentary type. . And among the most relevant findings is the fact that, paradoxically, smartcities not only respond to the fact that they are cities with a high incidence of technology, but rather are linked to the fact that their citizens are immersed in consolidated processes such as recycling and under a new governance approach, and to a certain extent citizens can access new trends in technology.Las tecnologías han evolucionado de una manera vertiginosa en el mundo entero, el uso de las TIC’s se ha masificado de tal manera que hoy en día prácticamente todo ser humano en el planeta tiene acceso a algún tipo de tecnología con interconexión a internet, desde los smartphones hasta sistemas integrados de redes neuronales que han revolucionado la concepción de lo que se entendía como tecnología. En estas últimas décadas surge el nombre de las Smart cities, las cuales responden a las nuevas propuestas de crear o transformas las ciudades en ciudades inteligentes. El objetivo de la presente investigación es conocer cuáles son las características principales que definen este tipo de ciudades y sobre todo conocer cuáles son los factores que inciden e impiden su desarrollo en américa latina, la investigación se realiza bajo el enfoque de metodológico de tipo documental bibliográfico. Y entre los hallazgos más relevantes se encuentran el hecho de que paradójicamente las smartcities no solo responden al hecho de que sean ciudades con alta incidencia en tecnologías, sino más bien están ligados a que sus ciudadanos estén inmersos en procesos consolidados como el reciclaje y bajo un enfoque de nueva gobernanza, y en cierta medida los ciudadanos puedan accesar a las nuevas tendencias en tecnologías

Current-Sensorless Control Strategy for the MPPT of a PV Cell:An Energy-Based Approach

A novel energy-based modelling and control strategy is developed and implemented to solve the maximum power point tracking problem when a photovoltaic cell array is connected to consumption loads. A mathematical model that contains key characteristic parameters of an energy converter stage connected to a photovoltaic cell array is proposed and recast using the port-Hamiltonian framework. The system consists of input-output power port pairs and storage and dissipating elements. Then, a current-sensorless control loop for a maximum power point tracking is designed, acting over the energy converter stage and following an interconnection and damping assignment passivity-based strategy. The performance of the proposed strategy is compared to a (classical) sliding mode control law. Our energy-based strategy is implemented in a hardware platform with a sampling rate of 122 Hz, resulting in lower dynamic power consumption compared to other maximum power point tracking control strategies. Numerical simulations and experimental results validate the performance of the proposed energy-based modelling and the novel control law approach

A Reversible Hydropump–Turbine System

Water-pumped storage systems have become an ideal alternative to regulate the intermittent power delivered by renewable energy sources. For small-scale operations, a type of centrifugal pump coupled to asynchronous machines represents an adequate solution due to their techno-economic feasibility in addition to their ability to operate as reversible systems. This work provides a novel port-Hamiltonian modelling approach to an integrated reversible hydropump–turbine system, that can be switched from motor pump to turbine-generator by employing a conventional hydraulic switch. Our modelling strategy provides a clear physical interpretation of the energy flow from the mechanical to electrical domains. Then, the model was built with multi-domain storing and dissipating elements and the interconnection of well-defined input–output port pairs. The system’s internal energy, i.e., Hamiltonian function, can be exploited for energy-shaping control strategies. The performance of our modelling approach is validated via numerical simulations

Geometric Aspects of the Dipolar Interaction in Lattices of Small Particles

The hysteresis curves of systems composed of small interacting magnetic particles, regularly placed on stacked layers, are obtained with Monte Carlo simulations. The remanence as a function of temperature, in interacting systems, presents a peak that separates two different magnetic states. At low temperatures, small values of remanence are a consequence of antiferromagnetic order due to the dipolar interaction. At higher values of temperature the increase of the component normal to the lattice plane is responsible for the small values of remanence. The effect of the number of layers, coordination number and distance between particles are investigated.Comment: 5 pages, 7 figure