Modeling and stability analysis of tethered kites at high altitudes

A systematic analysis of the role played by several physical mechanisms in the longitudinal stability of a tethered kite is presented. A simple model, which artificially constrains the pitch motion of the kite and approximates the tether by a massless and rigid bar, is improved progressively to include the kite pitch motion as well as the tether inertia, flexibility, wind load, and elasticity. The models are presented as compact sets of ordinary differential equations without algebraic constraints, which are explicitly eliminated by making an extensive use of Lagrangian mechanics. The contributions of each physical mechanism on kite stability are investigated separately, and a tradeoff between the complexity and computational costs of the models against their accuracy and reliability is carried out. The wind load on the tether is identified as a key effect stabilizing the steady state of the kites. The optimal bridle design and tether length selections to compute the kite ceiling are discussed.This work was supported by Fundación BBVA under the Convocatoria 2015 de Ayudas BBVA a Investigadores y Creadores Culturales grant no. IN[15]_TIC_ING_0313. G. Sánchez-Arriaga was supported by the Ministerio de Economía y Competitividad of Spain (grant no. RYC-2014-15357)Publicad

Unstable manifold, Conley index and fixed points of flows

We study dynamical and topological properties of the unstable manifold of isolated invariant compacta of flows. We show that some parts of the unstable manifold admit sections carrying a considerable amount of information. These sections enable the construction of parallelizable structures which facilitate the study of the flow. From this fact, many nice consequences are derived, specially in the case of plane continua. For instance, we give an easy method of calculation of the Conley index provided we have some knowledge of the unstable manifold and, as a consequence, a relation between the Brouwer degree and the unstable manifold is established for smooth vector fields. We study the dynamics of non-saddle sets, properties of existence or non-existence of fixed points of flows and conditions under which attractors are fixed points, Morse decompositions, preservation of topological properties by continuation and classify the bifurcations taking place at a critical point

Spaces of approximative maps. II

The authors study the space A\sp*(X,Y) of all approximative maps f=\{f\sb k: X\to Y\} between compact subsets X, Y of the Hilbert cube. The topology of this space is given by the pseudometric d\sp*(\underline f,\underline g)=\inf \{\sup \{dist(f\sb k,g\sb k)\vert $k\ge k'\}\vert$ $k'=1,2,...\}$. They show that approximative maps from the same path component of A\sp*(X,Y) induce the same shape morphism, but the converse implication does not hold. They also consider several classes of approximative maps which form closed subsets of A\sp*(X,Y).Depto. de Álgebra, Geometría y TopologíaFac. de Ciencias MatemáticasTRUEpu

On mathematical aspects of exact nonlinear rotational water waves

This thesis addresses various theoretical questions regarding exact nonlinear solutions to the geophysical governing equations which are explicit in the Lagrangian framework. Such solutions are scarce, being Gerstner’s wave the only-known explicit and exact solution of the nonlinear two-dimensional periodic gravity wave problem with a non-flat free surface under constant density. This remarkable solution was extended by Pollard to an incompressible vertically-stratified fluid in a rotating system. More recently, exact and explicit solutions of the nonlinear governing equations for geophysical water waves, describing several physical scenarios, have been derived. A thorough analysis of these solutions is conducted in this thesis. From a mathematical point of view, the Lagrangian flow map defining a flow motion needs to satisfy certain conditions. It is proven in Chapters 2 and 6 that this is the case for the equatorially-trapped, non-hydrostatic internal water waves [14] and for the generalisation of Pollard’s solution [26], respectively. An advantage of some of these explicit solutions is that they are able to accommodate currents, leading to more complicated and interesting flows. This is shown in Chapter 3 where a new solution of the f-plane approximation of the geophysical equations is constructed. This solution incorporates both a constant current in the zonal direction and a transverse current in the meridional direction. The study of this solution and of other internal water waves is further developed in Chapter 4. Relevant mean flow properties are provided, establishing a relation between Eulerian and Lagrangian quantities. Furthermore, the effects of the vorticity present in these flows are compared with those of the better-known irrotational case. In addition, Chapter 5 examines the robustness of these solutions in terms of the hydrodynamic stability. This is done for the internal wave discussed in Chapter 2 and the solution of the modified β-plane approximation equations [61] by applying the short-wavelength instability method. An important aspect of the flows studied throughout this work is that they exhibit vorticity. This is further analysed in the Eulerian framework in Chapter 7 within the context of small-amplitude two-dimensional steady periodic gravity water waves propagating over a flat bed. A dispersion relation for waves with two layers of different vorticity is derived and the existence of such waves is discussed

Ingeniería Tisular del hueso y el cartílago empleando células mesenquimales estromales y biomateriales

Programa Oficial de Doutoramento en Ciencias da Saúde. 5007V01[Resumo]A artrose (OA) é a patoloxía reumática máis prevalente e, na actualidade, non existe un tratamento efectivo. Unha das causas deste trastorno é o desenvolvemento secundario tras unha lesión na cartilaxe hialina articular ou no óso subcondral. A Enxeñería Tisular (IT) osteocondral, utilizando células e soportes, xurdiu como unha terapia prometedora. O obxectivo deste estudo foi determinar o potencial de reparación das células mesenquimais estromais (CMEs), en combinación con diferentes tipos de soportes, para o seu uso na IT osteocondral. En primeiro lugar, illáronse e caracterizáronse CMEs, obtidas de medula ósea humana e ovina, e de células similares a CMEs (CSMEs), diferenciadas a partir de células pluripotentes inducidas (iPS). En segundo lugar, estudouse a capacidade de diferenciación condroxénica das CMEs humanas, cultivadas en diferentes soportes de coláxeno (Col). Tamén, testouse a capacidade de diferenciación osteoxénica das CMEs ovinas, cultivadas sobre soportes de Col I e β fosfato tricálcico (β-FTC). Por último, analizouse a capacidade de reparación das CMEs, cultivadas en soportes de Col, nun modelo de lesión de cartilaxe in vitro. Os resultados confirman a identidade das CMEs e a súa capacidade de formar neotecidos condroxénicos e osteoxénicos sobre biomateriais de Col. A presenza de proteoglicans (PGs) na composición dos soportes mellora o fenotipo condroxénico do tecido cartilaxinoso neoformado e a reparación de lesións na cartilaxe hialina, nun modelo in vitro. O uso dos constructos, formados polas CMEs e biomateriais de Col, resulta prometedor para a reparación de lesións osteocondrais.[Resumen]La artrosis (OA) es la patología reumática más prevalente y, actualmente, no existe un tratamiento efectivo. Una de las causas de la enfermedad es su desarrollo secundario tras una lesión en el cartílago hialino articular o en el hueso subcondral. La Ingeniería Tisular (IT) osteocondral, utilizando células y soportes, ha surgido como una terapia prometedora. El objetivo de este estudio fue determinar el potencial de reparación de las células mesenquimales estromales (CMEs), en combinación con diferentes tipos de soportes, para su uso en la IT osteocondral. En primer lugar, se aislaron y caracterizaron CMEs, obtenidas de médula ósea humana y ovina, y de células similares a CMEs (CSMEs), diferenciadas a partir de células pluripotentes inducidas (iPS). En segundo lugar, se estudió la capacidad de diferenciación condrogénica de las CMEs humanas, cultivadas en diferentes soportes de colágeno (Col). También, se testó la capacidad de diferenciación osteogénica de las CMEs ovinas, cultivadas sobre soportes de Col I y β fosfato tricálcico (β-FTC). Por último, se analizó la capacidad de reparación de las CMEs, cultivadas en soportes de Col, en un modelo de lesión de cartílago in vitro. Los resultados confirman la identidad de las CMEs y su capacidad de formar neotejidos condrogénicos y osteogénicos sobre biomateriales de Col. La presencia de proteoglicanos (PGs) en la composición de los soportes mejora el fenotipo del tejido cartilaginoso neoformado y la reparación de lesiones en el cartílago hialino, en un modelo in vitro. El uso de los constructos, formados por las CMEs y biomateriales de Col, resulta prometedor para la reparación de lesiones osteocondrales.[Abstract]Osteoarthritis (OA) is the most prevalent rheumatic disorder and currently, there is no effective treatment to treat it. Lesions in the articular hyaline cartilage or in the subchondral bone may lead secondarily to OA. Osteochondral Tissue Engineering (IT) using cells and scaffolds has emerged as a promising therapy. The aim of this study was to determine the repair potential of mesenchymal stromal cells (CMEs) combined with different types of scaffolds, and their usefulness in osteochondral IT. First, CMEs from human and ovine bone marrow and, from induced plutipotent stem cells (iPS) were isolated and characterized. Secondly, chondrogenic differentiation capacity of human CMEs on collagen (Col) scaffolds was studied. Also, osteogenic differentiation capacity of ovine CMEs on Col I and β tricalcium phosphate (β-FTC) was tested. Finally, the repair capacity of CMEs cultured on Col scaffolds in an in vitro cartilage lesion model was assessed. Results confirmed the CMEs identity and their capacity to form chondrogenic and osteogenic neotissues, when cultured on Col scaffolds. The addition of proteoglycans (PGs) to the scaffold composition improves the phenotype of neoformed cartilaginous tissue and the repair capacity in the in vitro hyaline cartilage lesion model. The use of CMEs and Col scaffolds for engineered tissue constructs is a promising approach for osteochondral lesions repair

Diferenciación "in vitro" de células madre aisladas de médula ósea humana sobre biomateriales de colágeno

Objetivos. El objetivo de este estudio ha sido evaluar la idoneidad de diferentes biomateriales de colágeno como posibles soportes de ingeniería tisular, para el tratamiento de lesiones cartilaginosas. Metodología. Se aislaron células madre mesenquimales de la médula ósea humana (CMMs-MOh), de varios donantes, y se expandieron in vitro. Tras obtener un número suficiente de células, se formó un conjunto celular y se sembró sobre los biomateriales, con un medio de estimulación de la diferenciación condrogénica. Tras 30 días de estimulación se testó el crecimiento y diferenciación mediante microscopía electrónica, técnicas histológicas, técnicas inmunohistoquímicas y biología celular. Resultados. Todos los biomateriales presentaron crecimiento y proliferación celular. En todos los biomateriales tuvo lugar diferenciación condrogénica de las CMM-MOh, en mayor o menor medida. Conclusiones. Todos los biomateriales permitieron el crecimiento y proliferación de las CMMs-MOh, pero sólo en el biomaterial C1C2HS se observó formación de tejido con características similares a cartílago. Futuros estudios permitirán determinar si éste biomaterial es adecuado para la reparación de cartílago articular.Traballo fin de mestrado (UDC.FCS). Asistencia e investigación sanitaria. Especialidade en fundamentos de investigación biomédica. Curso 2011/201

Initial orbit determination methods for track-to-track association

The detection and identification of Resident Space Objects (RSOs) from survey tracks requires robust and efficient orbit determination methods for the association of observations of the same RSO. Both Initial Orbit Determination (IOD) and Orbit Determination (OD) methods perform the orbital estimation in which the association of tracks relies. The choice of proper IOD and OD methods is essential for the whole data association, since they are in charge of providing the estimation required to evaluate the figure of merit of the association. In this paper, we review the state of the art and propose a novel method that does not require initialisation, accounts for measurement noise and provides a full estimation (i.e., state vector and covariance) from an arbitrary number of optical observations. To do so, a boundary value problem is formulated to find a pair of ranges leading to a minimum residuals of the observations. The proposed methods are compared against classical alternatives simulated in scenarios representative of the current space debris environment.This project has received funding from the "Comunidad de Madrid" under "Ayudas destinadas a la realización de doctorados industriales" program (project IND2017/TIC7700). Besides, the authors would like to acknowledge the contributions from Alfredo Miguel Antón Sácnchez, Pablo García Sánchez and Adrián Díez Martín from GMV for their support, review and advice

Track-to-track association methodology for operational surveillance scenarios with radar observations

This paper proposes a novel track-to-track association methodology able to detect and catalogue resident space objects (RSOs) from associations of uncorrelated tracks (UCTs) obtained by radar survey sensors. It is a multi-target multi-sensor algorithm approach able to associate data from surveillance sensors to detect and catalogue objects. The association methodology contains a series of steps, each of which reduces the complexity of the combinational problem. The main focus are real operational environments, in which brute-force approaches are computationally unaffordable. The hypotheses are scored in the measurement space by evaluating a figure of merit based on the residuals of the observations. This allows us to filter out most of the false hypotheses that would be present in brute-force approaches, as well as to distinguish between true and false hypotheses. The suitability of the proposed track-to-track association has been assessed with a simulated scenario representative of a real operational environment, corresponding to 2 weeks of radar survey data obtained by a single survey radar. The distribution and evolution of the hypotheses along the association process is analysed and typical association performance metrics are included. Most of the RSOs are detected and catalogued and only one false positive is obtained. Besides, the rate of false positives is kept low, most of them corresponding to particular cases or objects with high eccentricity or limited observability.Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. This project has received funding from the “Comunidad de Madrid” under “Ayudas destinadas a la realizacion doctorados industriales” program (project IND2017/TIC7700

Influencia de los estilos de aprendizaje en el rendimiento académico de los estudiantes de la facultad de odontología de la Universidad Nacional de la Amazonía Peruana 2021

The main objective of the study was to investigate whether learning styles (LE) influence academic performance (AR) of the Faculty of Dentistry of the National Amazonian University of Peru (FO-UNAP) 2021. Approach It was quantitative, non-experimental, descriptive and explanatory. The study sample was made up of all students who met the inclusion and exclusion criteria, 268 students, 125 men (46.6%) and 143 women, who were enrolled in the second semester of the FO-ONE P of the academic year (53.4%). I enrolled in 2021. Information was collected using data sheets. This included Kolb Learning Styles Inventory EA variables (convergence, divergence, assimilation, accommodation) and RA Cumulative Weighted Average (PPA) grades. ) (bad, average, good, excellent). The examined sample had a good RA of 56.0% (150 of 268), that is, grades between 14 and 16, and the main EA of the students converged at 45.1% (111 of 268). 36.6% of convergent EA students had good RA with grades 14-16 (p=0.000). All EAs (convergent, divergent, assimilative and adaptive) are associated with academic performance (p˂0.001). It is concluded that there is a significant relationship between EA and RA of the 2021 FO-UNAP students.El principal objetivo del estudio fue investigar si los estilos de aprendizaje (LE) influyen en el rendimiento académico (RA) de la Facultad de Odontología de la Universidad Nacional Amazónica del Perú (FO-UNAP) 2021. Enfoque Fue cuantitativo, no experimental, descriptivo y explicativo. La muestra del estudio estuvo compuesta por todos los estudiantes que cumplieron con los criterios de inclusión y exclusión, 268 estudiantes, 125 varones (46,6%) y 143 mujeres, que se encontraban matriculados en el segundo semestre de la FO-ONE P del año académico (53,4%). Me matriculé en 2021. La información se recopiló mediante hojas de datos. Esto incluyó las variables EA del Inventario de Estilos de Aprendizaje de Kolb (convergencia, divergencia, asimilación, acomodación) y notas del promedio ponderado acumulativo (PPA) de RA. (malo, regular, bueno, excelente). La muestra examinada tuvo una buena RA del 56,0% (150 de 268), es decir, grados entre 14 y 16, y la EA principal de los estudiantes convergió en el 45,1% (111 de 268). El 36,6% de los estudiantes de EA convergente tuvieron buena AR con grados 14-16 (p=0,000). Todas las EA (convergentes, divergentes, asimilativas y adaptativas) están asociadas con el rendimiento académico (p˂0,001). Se concluye que existe una relación significativa entre EA y RA de los estudiantes 2021 de FO-UNAP

Algunas propiedades de los compactos movibles.

Some properties of movable compacta are given in aonnection with quasi-dominación and likeness. The main result is the following : Let X,Y be two comnacta. If Y is movable and X-like then Y is quasi-dominated by X