Study of electron heat transport in LHD and TJ-II

The magnetically confined plasmas study is one of the most promising research fields in the present days due to the high perspectives of unlimited and clean energy that fusion has generated. In this framework, the stellarator devices play a significant role because of, unlike in the tokamak case, their continuum working regime, which will be an essential feature of the future fusion commercial reactor.Heat transport studies in stellarator devices are completely necessary since the main plasma properties (and therefore, the total fusion power generated) are absolutely dependent. Nowadays, the largest stellarator in the world is the Large Helical Device (LHD). There is also a stellarator device is Spain, TJ-II, which is located in the installations of CIEMAT in Madrid. In this thesis, turbulent and conductive heat transport is studied in both devices with the aim of comparing its formation and suppression. First of all, collisional transport, i.e. neoclassical transport, which is caused by the particle collisions, is studied by means of a new transport model implemented in the transport code PRETOR-Stellarator. This model is able to calculate heat diffusivities as well as the neoclassical electric field with reasonable accuracy without spending as much computational time as in the Monte Carlo techniques. It is deduced from the results that, for both TJ-II and LHD, neoclassical transport may be quite important in plasmas with low density and high temperatures, although higher levels of neoclassical transport are obtained in TJ-II. Both devices share the feature that in low collisional plasmas, a high positive neoclassical electric field with a high shear appears in the plasma core. This electric field can be responsible of the suppression of the turbulence heat transport.Some new turbulent heat transport models have been added to PRETOR-Stellarator in order to study this kind of transport. Both, LHD and TJ-II, share a common heat transport in the confinement region (plasma core), called drift wave electromagnetic transport, and which is due to the fluctuations of the magnetic field. Outside this region, turbulent heat transport in LHD has similar characteristic to that in tokamaks, whereas in TJ-II, turbulent transport is maintained.Turbulent heat transport reduction is a major issue in fusion research, since the capability of producing commercial fusion energy depends strongly on the low levels of turbulence of the plasma. The appearance of a neoclassical electric field in the plasma core and its interaction with turbulent transport has been studied. It is shown that this electric field is able to generate a rotation in the plasma which is able to suppress turbulent transport to neoclassical levels when density is low enough. These plasmas are called to have an internal transport barrier and have stepped electron temperature profiles with hollow electron density profiles. Another important phenomenon related with electron heat transport is non-local transport, which can not be studied within the general diffusive framework that is used to study turbulent transport in plasmas. The non-local transport is caused by the interaction of long distant parts of the plasma. In this thesis, a new model for this type of transport, which is based on the convolution over a kernel of the neoclassical transport, has been proposed to explain this phenomenon. It has been shown that this model is able to simulate the main characteristics of this transport, e.g. fast pulses propagation, ballistic transport or the growing of the turbulence levels close to the axis of the device. All these phenomena have been observed in LHD and TJ-II. Finally, once electron heat transport in stellarators has been clarified, a comparison of the designs of the future commercial reactor based on both, stellarators and tokamaks, has been carried out. A stellarator commercial reactor, based on the design of the LHD, would have a 15.5 m major radius, 2.5 m minor radius, with a continuum working regime based on low temperatures and high densities. Main energy sinks are due to conductive-convective heat losses and radiation losses (in a 95% from Bremmstrahlung radiation). The fact that it has such a large major radius makes this design expensive and difficult to build. A tokamak fusion reactor would be smaller, however, the high temperatures achieved make cyclotron radiation losses to be very high, and a wall with a high reflection coefficient seems to be necessary.L'estudi de les propietats dels plasmes confinats magnèticament esta esdevenint un dels temes primordials de recerca degut a les prometedores perspectives (de netedat i ampli abast) que l'energia produïda per fusió nuclear està fomentant. Es dins d'aquest context on l'estudi dels dispositius de confinament magnètic de tipus stellarator juguen un paper molt important, ja que un reactor de fusió basat en aquest concepte podria tenir (al contrari dels tokamaks) un mode de funcionament continu i no polsat.L'estudi del transport de calor en el dispositius de fusió per confinament magnètic de tipus stellarator és totalment necessari, ja que les propietats del plasma (i per tant de l'energia produïda per fusió) en depenen completament. Actualment, el stellarator més gran del món es troba al Japó i es diu Large Helical Device (LHD), mentre que a Espanya, el stellarator TJ-II es troba a les instal·lacions del CIEMAT a Madrid. En aquesta tesi, s'estudien ambdós dispositius per tal de determinar de que depèn que aparegui o que desaparegui el transport de calor turbulent en aquests dispositius, i si hi ha algun tipus de punt en comú.En primer lloc, s'analitza el transport de calor colisional (degut a la col·lisió de les partícules que formen el plasma) mitjançant la introducció d'un model de transport colisional (anomenat neoclàssic) al codi de transport PRETOR-Stellarator. Aquest model es capaç de calcular magnituds físiques tal com difusivitats i camps elèctrics neoclàssics però sense consumir tant de temps com a d'altres tècniques que utilitzen mètodes de Monte Carlo. Dels resultats es desprèn que el transport neoclàssic, tant al TJ-II com al LHD, pot ser important, en plasmes amb baixa densitat i temperatures grans. Ambdós dispositius comparteixen la característica de que apareix, en aquests casos, un gran camp elèctric al centre del plasma que pot ser fa que el transport turbulent disminueixi. Mitjançant la introducció de diferents models pel transport turbulent a PRETOR-Stellarator, s'estudia el transport turbulent als dos dispositius. De l'anàlisi es dedueix que ambdós dispositius poden compartir el mateix tipus de transport (anomenat electromagnètic) i que es degut a les variacions locals del camp magnètic. Tanmateix, fora de la zona central, el LHD té un tipus de transport semblant al que existeix al tokamak JET (Joint European Torus), mentre que el TJ-II continua amb el transport electromagnètic.La reducció del transport turbulent prèviament estudiat és un tema capdal ja que permetria un millor confinament del plasma. S'ha estudiat com el camp elèctric format al centre del plasma pot generar un rotació que disminueix el transport turbulent tant al LHD com al TJ-II. Aquests plasmes es diuen que tenen una barrera interna del transport que redueix el transport turbulent a valors neoclàssics sempre que la densitat sigui prou baixa.Un altre fenomen lligat al transport molt important és el transport no local, que es degut a les correlacions entre parts llunyanes del plasma i que no es pot entendre dintre del context del transport difusió que se sol emprar per a estudiar el plasmes confinats. En el marc d'aquesta tesi s'ha dissenyat un model de transport no local per mitjà d'una convolució sobre el transport neoclàssic. Amb aquest model s'ha aconseguit reproduir molts del efectes no locals que apareixen als plasmes (com ara la ràpida propagació de fenòmens turbulents o la propagació de fronts turbulents que mantenen una forma d'ona ), i que s'han descrit tant al LHD com al TJ-II.Finalment es realitza una comparació entre els dissenys dels reactors de fusió basats en stellarators i tokamaks. Un reactor de fusió stellarator tindria un radi major de 15.5 m i treballaria en mode continu amb alta densitat i baixa temperatura. Les pèrdues d'energia més importants serien, en aquest cas, degudes a la convenció i conducció dins del plasma. El fet que tingui una grandària tan gran el faria molt car de construir. En el cas dels tokamaks, la seva grandària seria més petita, però les pèrdues per radiació ciclotró serien molt grans (degut al règim d'alta temperatura i baixa densitat) i el disseny d'una paret del reactor amb un coeficient de reflexió molt gran fora totalment necessari.Postprint (published version

Kernel Multivariate Analysis Framework for Supervised Subspace Learning: A Tutorial on Linear and Kernel Multivariate Methods

Feature extraction and dimensionality reduction are important tasks in many fields of science dealing with signal processing and analysis. The relevance of these techniques is increasing as current sensory devices are developed with ever higher resolution, and problems involving multimodal data sources become more common. A plethora of feature extraction methods are available in the literature collectively grouped under the field of Multivariate Analysis (MVA). This paper provides a uniform treatment of several methods: Principal Component Analysis (PCA), Partial Least Squares (PLS), Canonical Correlation Analysis (CCA) and Orthonormalized PLS (OPLS), as well as their non-linear extensions derived by means of the theory of reproducing kernel Hilbert spaces. We also review their connections to other methods for classification and statistical dependence estimation, and introduce some recent developments to deal with the extreme cases of large-scale and low-sized problems. To illustrate the wide applicability of these methods in both classification and regression problems, we analyze their performance in a benchmark of publicly available data sets, and pay special attention to specific real applications involving audio processing for music genre prediction and hyperspectral satellite images for Earth and climate monitoring

An explanatory and predictive PLS-SEM approach to the relationship between organizational culture,organizational performance and customer loyalty: The case of health clubs

Purpose This study aims to analyze the impact and predictive capacity of organizational culture on both customer loyalty and organizational performance in health clubs using data from managers and customers of health clubs in Spain. Design/methodology/approach A total of 101 managers were asked to measure organizational culture and organizational performance and 2,931 customers were asked to indicate their customer loyalty. The proposed hypotheses were tested and their predictability assessed through PLS-SEM. A composite concept was adopted to analyze the relationships between the different constructs and their indicators. Findings The findings suggest that organizational culture has a positive relationship with both customer loyalty and organizational performance. The four main dimensions of organizational culture that influence this relationship are, in order of significance, organizational presence, formalization, atmosphere and service-equipment. The authors’ model has a very good predictive power for both dependent variables. Originality/value Customer loyalty is an aspect of health clubs that can be improved. This study highlights the importance of creating a strong organizational culture in health clubs, as it enhances and predicts customer loyalty and organizational performance. Its predictability has already been tested with samples of managers and customers, with the analysis being performed from the perspective of the organization’s management and customer perceptions. This study also contributes to the field of sport management, using a predictive PLS-SEM techniqu

The perceived quality, value and satisfaction of a sports club. The prospect of parents and adult athletes

Debido al interés por conocer la percepción de los servicios deportivos, este estudio tiene los objetivos de evaluar la calidad percibida, valor y satisfacción de los padres de deportistas y, deportistas adultos de un club deportivo de baloncesto y, examinar la relación entre dichas variables. La muestra se compuso de 112 usuarios (33 mujeres y 79 hombres) de un club deportivo de baloncesto, realizándose en primer lugar un análisis de los descriptivos, análisis factorial exploratorio, análisis de la varianza y finalmente un estudio de regresiones lineales. Los resultados arrojan un instrumento fiable y válido compuesto de cinco dimensiones (actividad, instalación, material, personal y comunicación), donde las dimensiones de actividad y personal fueron las mejor valoradas. Finalmente, tras el análisis de regresiones lineales, se encontró una relación significativa de la calidad percibida y el valor percibido, concretamente de las dimensiones actividad y personal. Además se estableció relación significativa entre el valor percibido y la satisfacción.Due to the interest in knowing the perception of sports services, this study has the objective to assess the perceived quality, value and satisfaction of sports club basketball parents and adult athletes, and to examine the relationship between these variables. Sample was composed by 112 users (33 women and 79 men) of a basketball sport club, being realized first an analysis descriptive, second an exploratory factorial analysis, an analysis of variance and finally linear regressions. Results show a reliable and valid instrument composed by five dimensions (activity, facilities, material, staff and communication) where the activity and staff dimensions were the best rated. At last before linear regressions’ study, a significant relationship was found between perceived quality and perceived value, especially in activity and personal dimensions. Also a relationship between perceived value and satisfaction was established

Programas y servicios para personas mayores en centros de fitness de Sevilla

La práctica de actividad física por parte de las personas mayores, es cada vez más una práctica habitual en este grupo de población. Así las empresas de servicios deportivos, ofertan programas específicos y desarrollan actividades con el fin de mejorar la calidad de vida de esta población. Uno de los lugares donde se ofertan estas actividades, son los centros de fitness privados (CFP), y cada vez más, se pueden ver usuarios mayores realizando ejercicios en maquinaria de última generación, y realizando actividades con material sofisticado. Nuestro estudio refleja la realidad de 45 CFP del municipio de Sevilla, en relación a las cuotas y actividades específicas ofertadas para los mayores en los propios centros. Del mismo modo, pone de manifiesto la situación de esta oferta en relación a los distritos censales de Sevilla. En la investigación se pudo comprobar, como la mayoría de los centros testados no tenían una oferta específica de actividades para mayores

Fidelización de usuarios mayores en centros de fitness: gestión de clientes por programas de actividad física

Los centros de fitness, son hoy en día lugares donde los socios realizan actividad física «controlada», donde mejoran su estado físico y mental, incluso en donde se socializan con otros socios de todas las edades. Estos centros, han sido normalmente gestionados por personas sin formación en la materia y con el único interés de tener socios, sin tener en cuenta la repercusión a largo plazo. Este interés, sumado a problemas de gestión del centro, y a problemas personales de los socios, ha propiciado que existan altas tasas de deserción en este tipo de centros indoor, con la consecuente elevación de los gastos en marketing, no obteniendo así, una rentabilidad sostenible. Proponemos, un programa de actividad física con el que se podría mejorar estas tasas de fidelización, siendo el punto central de la gestión de los centros de hoy en día, la satisfacción y la lealtad a los centros de fitnes

La historia y evolución del fitness

Mankind has always maintained the mentality of vitality since its existence. Fitness was used to survive through hunting and gathering required by living conditions in ancient times, the movement arising from competition during the cold war period was seen as a propaganda tool in certain periods, and today as a mass sport that prioritizes muscle, beauty and aesthetics used commercially. In the modern world, fitness, which is done with external appearance and aesthetic concerns, has a very old history. This article will highlight historical events and influential individuals who shaped the history of fitness, from primitive man to the founding of the modern fitness movement. For this reason, the history of fitness in the research; In societies, body culture, primitive people and fitness, before and after the industrial revolution, between certain years (1920-1990), were gathered under the titles of today's fitness. As a result, fitness, which developed as a result of physical culture in the 20th century, has a large market in the world.Desde su existencia, la humanidad siempre ha mantenido la mentalidad de vitalidad. En la antigüedad, las condiciones de vida exigían que el fitness se utilizara para sobrevivir a través de la caza y la recolección, durante la guerra fría se vio como una herramienta de propaganda, y hoy en día como un deporte de masas usado comercialmente que prioriza la musculatura, la belleza y la estética. En el mundo moderno, el fitness, que se realiza con fines estéticos, tiene una historia muy antigua. Este artículo muestra los acontecimientos históricos y las personas influyentes que dieron forma a la historia del fitness, desde el hombre primitivo hasta la fundación del movimiento moderno del fitness. Por esta razón, el trabajo se estructura en la cultura corporal en las sociedades, los pueblos primitivos la revolución agrícola y el fitness, antes y después de la revolución industrial (1920-1990), y el fitness actual. En definitiva, el fitness que se desarrolló como resultado de la cultura física en el siglo XX, tiene un gran mercado global