DSpace Collection:
http://hdl.handle.net/2117/3920
2015-05-27T08:04:37ZEstructuras A-infinito en la opérada de cactus
http://hdl.handle.net/2117/22097
Title: Estructuras A-infinito en la opérada de cactus
Authors: Gálvez Carrillo, Maria Immaculada; Lombardi, Leandro; Tonks, Andrew
Abstract: Diversas versiones de la opérada de cactus inicialmente definida por Voronov han sido estudiadas. Es conocida su equivalencia débil con la opérada de pequeños discos. Se conoce pues que la opérada de cactus admite una acción de la opérada de Gerstenhaber salvo homotopía. En este proyecto, nuestro objetivo es obtener una realización explícita de dicha acción. Por el momento, hemos construido una acción explícita de la opérada A8 en la opérada de cactus, que presentamos en este pósterOn computing flat outputs through Goursat normal form
http://hdl.handle.net/2117/27990
Title: On computing flat outputs through Goursat normal form
Authors: Franch Bullich, Jaume; Manzanera, Ana; Valero, Gemma
Abstract: This paper is devoted to computation of flat outputs by means of the Goursat normal form of the Pfaffian system associated to any control system in state space form. The algorithm explained here consists in three steps: i) Transformation of the system into its Pfaffian equivalent. ii) Computation of the Goursat normal form for the Pfaffian system. iii) Rewriting of the state space equations in the new variables. At this stage, a feedback law simplifies the equations and, therefore, the flat outputs can be easily computed. As an example, the algorithm is applied to a system consisting in a car with expanding wheels. Point to point trajectories are obtained thanks to the property of differential flatness. The paper also includes a control law that minimizes errors in the initial conditions.2015-05-20T17:10:42ZA methodology to assess ionospheric models for GNSS
http://hdl.handle.net/2117/27981
Title: A methodology to assess ionospheric models for GNSS
Authors: Rovira Garcia, Adrià; Juan Zornoza, José Miguel; Sanz Subirana, Jaume; González Casado, Guillermo; Ibáñez Segura, Marcos - Deimos2015-05-20T12:32:18ZNovel ionospheric activity indicator specifically tailored for GNSS users
http://hdl.handle.net/2117/27928
Title: Novel ionospheric activity indicator specifically tailored for GNSS users
Authors: Sanz Subirana, Jaume; Juan Zornoza, José Miguel; González Casado, Guillermo; Prieto Cerdeira, Roberto; Schlüter, S.; Orús Pérez, Raul
Abstract: This work introduces a novel ionospheric activity indicator useful for identifying disturbed periods affecting performance for GNSS users, at regional level. This indicator is based in the “Along Arc TEC Rate (AATR) and can be easily computed from GNSS data. The AATR indicator has been assessed over more than one Solar Cycle (2002-2013) involving 140 receivers distributed world-wide. Results show that it is well correlated with the ionospheric activity and, unlike other global indicators linked to the geomagnetic activity (i.e. DST, Ap), it is sensitive to regional behaviour the ionosphere and identifies specific effects on GNSS users. Moreover from a devoted analysis of EGNOS performances in different ionospheric conditions, it follows that the AATR indicator is able to predict SBAS user availability anomalies linked to the ionosphere. The AATR indicator has been chosen as the metric to characterise the ionosphere operational conditions in the frame of EGNOS activities. This indicator has been also proposed for joint analysis in the International SBAS-Ionosphere Working Group.2015-05-15T08:41:11ZDecomposing almost complete graphs by random trees
http://hdl.handle.net/2117/27908
Title: Decomposing almost complete graphs by random trees
Authors: Lladó Sánchez, Ana M.
Abstract: An old conjecture of Ringel states that every tree with m edges decom- poses the complete graph K 2 m +1 . A more general version of the Ringel’s conjecture says that every tree with m edges decomposes K rm +1 for each r = 2 provided that r and m + 1 are not both odd. The best lower bound for the order of a complete graph decomposed by a given tree with m edge is O ( m 3 ). We show that asymptotically almost surely a random tree with m edges and p = 2 m + 1 is a prime decomposes the complete graph minus one edge K 3 p - e . We also show that, for every prime of the form 2 km + 1 a random tree with m edges asymptotically almost surely decomposes the graph K 2 km +1 (3) obtained from the complete graph by replacing each vertex by the complement of a triangle.2015-05-13T11:30:43ZIntegrated tool for the acoustic assessment and monitoring of marine activities and operations
http://hdl.handle.net/2117/27907
Title: Integrated tool for the acoustic assessment and monitoring of marine activities and operations
Authors: Moura, André; Lopes, Diogo; Cruz, Erica; Hospital Bravo, Raúl; Sarrate Ramos, Josep; Díez, Pedro2015-05-13T10:32:57ZCaracterizaciones combinatorias y algebraicas de grafos distancia-regulares
http://hdl.handle.net/2117/27894
Title: Caracterizaciones combinatorias y algebraicas de grafos distancia-regulares
Authors: Fiol Mora, Miquel Àngel
Abstract: Los grafos distancia-regulares aparecen a menudo en el estudio de es-
tructuras matemáticas con un alto grado de simetría y/o regularidad. Un ejemplo bien conocido de tales grafos son los esqueletos de los sólidos platónicos. Desde que fueron propuestos por Norman Biggs, los grafos distancia-regulares han sido caracterizados por numerosos resultados, tanto de carácter combinatorio como algebraico. Como ejemplo del primer caso, sabemos que un grafo es distancia-regular si, y sólo si, el número de caminos de una longitud dada entre dos vértices sólo depende de la distancia entre dichos vértices. En esta charla se van a presentar y comparar las diferentes caracterizaciones conocidas, tanto las más clásicas como las que han sido recientemente descubiertas por el conferenciante y algunos de sus colaboradores. Entre las últimas, cabe destacar el que ya es conocido en la literatura com el `teorema del exceso espectral’. Este resultado puede considerarse como una caracterización casi-espectral, y afirma que un grafo es distancia-regular si, y sólo si, su exceso espectral (una cantidad calculable a partir de su matriz de adyacencia) es igual a su exceso medio (el número medio de vértices a distancia máxima de cada vértice).2015-05-12T11:41:00ZAn interlacing approach for bounding the sum of Laplacian eigenvalues of graphs
http://hdl.handle.net/2117/27893
Title: An interlacing approach for bounding the sum of Laplacian eigenvalues of graphs
Authors: Abiad, Aida; Fiol Mora, Miquel Àngel; Haemers, Willem H.; Perarnau Llobet, Guillem
Abstract: We apply eigenvalue interlacing techniques for obtaining lower and upper
bounds for the sums of Laplacian eigenvalues of graphs, and characterize equality.
This leads to generalizations of, and variations on theorems by Grone, and Grone &
Merris. As a consequence we obtain inequalities involving bounds for some well-known
parameters of a graph, such as edge-connectivity, and the isoperimetric number.2015-05-12T11:31:57ZUso del e-portafolio en la formación: el e-portafolio integral
http://hdl.handle.net/2117/27850
Title: Uso del e-portafolio en la formación: el e-portafolio integral
Authors: Domínguez García, Santiago; García Planas, María Isabel; Palau, Ramon; Taberna Torres, Judit
Abstract: : The use of e-portfolio is becoming common in the learning and assessment of students. This is due to the need of teachers to enhance student autonomy making them to reflect on the process of learning. Lately, we have worked with different software, facilitating its generation and use. In this paper, the recent experience in the use of e-portfolio at the Universitat Politècnica de Catalunya and Universitat Rovira i Virgili are set.2015-05-08T12:11:09ZNatural configurations for formation flying around triangular libration points for the elliptic and the bicircular problem in the earth-moon system
http://hdl.handle.net/2117/27848
Title: Natural configurations for formation flying around triangular libration points for the elliptic and the bicircular problem in the earth-moon system
Authors: Salazar, Francisco; Winter, O. C.; Macau, E.E.N.; Masdemont Soler, Josep; Gómez Muntané, Gerard
Abstract: The concept of Satellite Formation Flying (SFF) means to have two or more satellites in orbit such that their
relative positions remain constant or obeying a certain dynamical configuration along the trajectory. This concept
involves the control over the coordinated motion of a group of satellites, with the goal of maintaining a specific
geometric space configuration between the elements of the cluster. Assume a constellation of satellites is flying close
a given nominal trajectory around L
4
or L
5
in the Earth-Moon system, in such a way that, there is some freedom in
the selection of the geometry of the constellation. We are interested in avoiding large variations of the mutual
distances between spacecraft. In this case, previous studies about triangular libration points have determined the
existence of regions of zero and minimum relative radial acceleration with respect to the nominal trajectory that
prevent from the expansion or contraction of the constellation. Similarly, these studies have also shown the existence
of regions of maximum relative radial acceleration with respect to the nominal trajectory that produce a larger
expansion and contraction of the constellation. However, these studies only considered the gravitational force of the
Earth and the Moon using as approximation the Circular Restricted Three Body Problem (CRTBP). Although the
CRTBP model is a good approximation for the dynamics of spacecraft in the Earth-Moon system, the stability of
constellations flying around L4 and L5 is strongly a
ff
ected when the primary orbit eccentricity and perturbations
from the sun (gravity and light pressure) are considered. As consequence, the previous studies show that, using the
CRTBP model, the fuel consumption to maintain the geometry of the constellation computed by the residual
acceleration is practically zero. In this manner, the goal of this work is the study and analysis of the best regions to
place a constellation that is flying close a given nominal trajectory around L
4
or L
5
, involving a linear approximation
of the equations of motion relative to the periodic orbits around triangular libration points and taking into account the
Moon’s eccentricity and perturbations from the Sun. This model is not only more realistic for practical engineering
applications but permits to determine more accurately the fuel consumption to maintain the geometry of the
constellation2015-05-08T12:08:39ZConfinement of spacecraft swarms in J2-perturbed orbits about the earth
http://hdl.handle.net/2117/27845
Title: Confinement of spacecraft swarms in J2-perturbed orbits about the earth
Authors: García-Taberner, Laura; Masdemont Soler, Josep
Abstract: There have been studies of the reliability of a swarm
[3], based on nano-satellites, that give a study for the num-
ber of satellites that can be working as a period of time,
with good results for a 5-10 anys time step.
The strategies to control the swarm are based in three
main concepts. The first one studies the global movement
of the swarm as the ones that we can find in nature [5],
where each of the spacecraft has behavior depending on
the position and velocity of closest neighbors. The sec-
ond one are the strategies that include the provision of
collision-free orbits for long periods of time[1]. Finally
,
there is the strategy to keep the relative distance between
spacecraft [2].
The main contribution of this paper is the adapta-
tion of a methodology proposed for reconfigurations of
spacecraft [6] to swarms, taking into account that the
higher complexity of the problem needs some adjuste-
ments. These adjustements are based on the strategies of
swarms in nature (there are only reconfigurations based
on the neighbour states). The statement of the problem
is to calculate the cost to maintain the spacecraft of the
swarm for a year in a sphere of radius
R
for a year, avoid-
ing collisions and minimizing the fuel usage2015-05-08T11:40:27ZInputs received from Ionospheric research groups on activities related with RT global electron content determination
http://hdl.handle.net/2117/27837
Title: Inputs received from Ionospheric research groups on activities related with RT global electron content determination
Authors: Hernández Pajares, Manuel2015-05-08T10:13:24ZEnvironmental management tools supporting decisions in basins with mining activities
http://hdl.handle.net/2117/27789
Title: Environmental management tools supporting decisions in basins with mining activities
Authors: Pérez Foguet, Agustí; Yacoub, Cristina; Miralles Esteban, Núria; Giné Garriga, Ricard
Abstract: The socio - environmental conflicts related to water quality and quantity associated with mining in the Andean region is cause for concern. There is a role for scientific data an d social participation in mining related conflicts and the evolution to an ecosystem approach in water management, however few academic studies can be found which assess the environmental problems in the region and proposing methodologies adapted to mining contexts. The Jequetepeque river basin, located in Northern Peru, was chosen for action - research carried out from 2006 - 2011 and included a sequence of projects involving different local stakeholders (government, universities, NGOs). The application of hyd rological modeling, “smart” environmental monitoring and the use of aggregated indices on raw data for management is evaluated. The approach facilitates innovative work in the water sector, while partners that participate gain knowledge and capacities to take informed decisions related to mining and water resource management.2015-05-06T12:48:32ZTowards an optimal overall description of electron density information gathered during GNSS satellite occultations
http://hdl.handle.net/2117/27780
Title: Towards an optimal overall description of electron density information gathered during GNSS satellite occultations
Authors: Olivares Pulido, Germán; Hernández Pajares, Manuel; Limberger, Marco; García Rigo, Alberto; Aragón-Angel, Angela; Schmidt, Michael; Hugentobler, U
Abstract: The purpose of this work is to characterize the performance of different interpolation methods in order to build a global model of ionospheric free electron density, directly derived from the inversions of GNSS occultation data. Indeed, the occultation of GNSS satellites, observed from dual-frequency L-band receivers onboard Low Earth Orbiters (LEOs) is providing valuable ionospheric data since the first mission (GPS/MET) in 1995. This is an excellent scenario to derive, in a simple and precise way, the almost instantaneous distribution of ionospheric electron density in a region of few thousands of kilometers from each occultation event. This can be done, for instance, applying the Improved Abel Transform Inversion technique proposed during the last decade by the UPC authors. In such approach the horizontal gradient of the electron density is taken from the Vertical Total Electron Content gradient as proxy. This assumption increases the accuracy of the electron density retrieval, compared with the Classical Abel Transform Inversion, which assumes spherical symmetry in the occultation region. The availability of numerous occultation events (up to 2000 per day during the full availability of the FORMOSAT-3/COSMIC LEO constellation) enables the execution of studies on the feasibility of simple but accurate ways to interpolate such fields of electron density values, given by each occultation, in an overall electron density model2015-05-06T11:02:57ZUPC contributions to GNSS monitoring of ionosphere in the frame of the IGS Iono-WG
http://hdl.handle.net/2117/27771
Title: UPC contributions to GNSS monitoring of ionosphere in the frame of the IGS Iono-WG
Authors: García Rigo, Alberto; Hernández Pajares, Manuel; Orús Pérez, Raul
Abstract: UPC has been acting as Ionosphere Associate Analysis Center (IAAC) from the beginning of the IGS Iono-WG activities on 1st June, 1998, providing multiple products on GNSS monitoring of ionosphere and also assuming its chairmanship for 5 years (2002 to 2007), as the result of the common work of the co-authors of this presentation.
The recently formed UPC-IonSAT research group has not only continued providing rapid, final and 2-days ahead predicted Global Ionospheric Maps (GIMs) at 2-hour time resolution in IONEX format labelled UPCG, UPRG and U2PG respectively) but also real time GIMs (labelled URTG) and 15-minute and 1-hour time resolution GIMs considering rapid latencies (labelled UQRG and UHRG, respectively).
Such products have been generated using the TOMION SW for ionospheric modelling and precise positioning. TOMION has evolved from 1998 until nowadays in order to provide the above-mentioned recent products but also to improve the performance of the previously existing ones. This also has led to a reprocessing campaign. It is also worth mentioning that an improved Kriging interpolation technique, combined with the global tomographic modelling ([Orús et al., 2005 and Hernández-Pajares et al.1999]) has recently enabled a boost in the performance for all existing products.2015-05-06T10:21:33Z