Dynamics in the centre manifold around equilibrium points in periodically perturbed three-body problems

A new application of the parameterization method is pre- sented to compute invariant manifolds about the equilib- rium points of Periodically Perturbed Three-Body Problems ( PPTBP ). These techniques are applied to obtain high-order semi-numerical approximations of the center manifolds abo ut the points L 1 , 2 of the Sun-perturbed Earth-Moon Quasi- Bicicular Problem ( QBCP ), which is a particular case of PPTBP . The quality of these approximations is compared with results obtained using equivalents of previous normal form procedures. Then, the parameterization is used to ini- tialize the computation of Poincaré maps, which allow to get a qualitative description of the periodically-perturb ed dynamics near the equilibrium pointsPostprint (published version

A computational model for estimating the performance of flat plane low concentration systems

The implementation of PV systems is one of the feasible alternatives to meet the energy supply in communities far from the conventional electric grid. Several studies have shown that a flat plane concentrator can produce better electrical behaviour in a PV system, due to the reduction of the effective panel surface needed for the operation of the system. As the cost of a PV system is strongly conditioned by the cost of the PV panels, it can lead to an increase of the PV market. This work describes the computational model developed to represent the concentration pattern over a collector, generated by a flat plane reflector. A useful 3D representation of the system has been programmed to visualize the concentration system. The computational model was developed in Mathematica Programming Language Environment. The simulation tool created shows that Mathematica is a quick and powerful tool to represent the low-concentrating photovoltaic systems

Acquiring Spanish at the Interfaces: An Integrative Approach to the L2 Acquisition of Psych-Verbs

This dissertation provides a comprehensive analysis of the L2 acquisition of Spanish psych-verbs (e.g. gustar `to like') across four different proficiency levels. In particular, psych-verbs constitute a testing ground for the predictions of the Interface Hypothesis (Sorace and Filiaci, 2006; Tsimpli, Sorace, Heycok & Filiaci, 2004; Sorace, Serratrice, Filiaci & Baldo, 2009; inter alia), one of the most influential theories in current generative second language acquisition. Its main claim is that properties that hinge on external interfaces (i.e. those that require the interaction between a linguistic module and a cognitive module) are more problematic for learners than those that do not hinge on that interface (i.e. internal interfaces/narrow syntax). In order to assess the empirical adequacy of the IH, this project encompasses five experiments that test different syntactic properties of psych predicates as well as phenomena that belong to both internal and external interfaces. The results of this study indicate that clitic and verb agreement is the most problematic aspect of psych-verb acquisition in accordance with the previous literarture in the field (e.g. Montrul, 1998, 2001). As for the issue of interfaces, this project is only partially consistent with the proposals of the IH. Whereas external interfaces present a certain level of difficulty for some groups of L2 learners, the low-proficiency participants are sensitive to pragmatic factors in spite of their lack of mastery of the morphosyntax of these constructions. Thus, external interfaces are problematic for L2ers but not more so than internal interfaces. Additionally it is not a necessary condition that syntax will precede the understanding of pragmatic phenomena. Instead, pragmatics can come for free in L2 acquisition while the learner still struggles with the target syntactic templates. Because of these inconsistencies with the IH, I turned to a more articulated model, the Integrative Model of Bilingual Acquisition (Pires & Rothman, 2011), that accounts for the differences between native and non-native speakers by resorting to the interplay of a series of factors (i.e. formal complexity, L1-L2 parameter mapping, processing resources and primary linguistic data). I argue that this more sophisticated model not only is able to more successfully account for the patterns found in this dissertation but it is also a more integrated explanation for the intricacies of the acquisition process.Doctor of Philosoph

Evaluating the Sensitivity of Face Presentation Attack Detection Techniques to Images of Varying Resolutions

In the last decades, emerging techniques for face Presentation Attack Detection (PAD) have reported a remarkable performance to detect attack presentations whose attack type and capture conditions are known a priori. However, the generalisation capability of PAD approaches shows a considerable deterioration to detect unknown attacks. In order to tackle those generalisation issues, several PAD techniques have focused on the detection of homogeneous features from known attacks to detect unknown Presentation Attack Instruments without taking into account how some intrinsic image properties such as the image resolution or biometric quality could impact their detection performance. In this work, we carry out a thorough analysis of the sensitivity of several texture descriptors which shows how the use of images with varying resolutions for training leads to a high decrease on the attack detection performance

A note on the dynamics around the L1,2 Lagrange points of the Earth-Moon system in a complete solar system model

The purpose of this paper is the study of the phase space around the collinear libration points L1 and L2 of the Earth–Moon system when the gravitational effects of the remaining bodies of the Solar System are taken into account. In the simplified model defined by the Circular Restricted Three Body Problem (CR3BP), the description of the phase space around these two points has already been done in the past, either using semi-analytical techniques1 or numerical ones.2 When using more realistic models of motion, the refinement of the different kinds of libration point orbits around both points (see G´omez et al.3) has some problems when the time interval used is large. These problems are more evident for the Earth–Moon L2 point due to a 1:2 resonance between the natural frequency of some halo orbits (!h) and the external frequency due to the perturbation of the Sun (!s); in fact !h ' 2!s for some orbits of the halo family of periodic orbits around this point. To analyse more closely this fact, Andreu4 introduced an intermediate model between the CR3BP and the restricted n-body problem, which is the so called Quasi-Bicircular Problem. It is a restricted four body problem in which the three primaries move following a “true” solution of the three body problem along orbits close to circular (the Earth and the Moon around their barycenter, and the Earth-Moon barycenter around the Sun). The description of the different types of orbits in the neighbourhood of L2 is also done in Reference 4 by means of the reduction of the Hamiltonian of the problem to the central manifold. The reduced Hamiltonian is then studied by means of Poincar´e maps at different energy levels.Postprint (published version

Capturing small asteroids into Sun-Earth Lagrangian points for mining purposes

The aim of this paper is to study the capture of small Near Earth Objects (NEOs) into the Sun-Earth L2 using low-thrust propulsion for mining or science purposes. As it is well known, the vicinity of these points is inside a net of dynamical channels suitable for the transport in the Earth-Moon neighborhood, so different final destinations from here could be easily considered. Asteroids with very small mass and not representing a potential hazard are analyzed. An initial pruning of asteroids is made, considering NEOs with stellar magnitude bigger than 28, which are the smallest available, and NEOs close to the Earth orbit with semi-major axis between 0.85-1.15. Due to the difficult determination of their physical properties, two methods to estimate the asteroid masses are conducted. A procedure to find the low-thrust optimization trajectories has been implemented. The initial seed is obtained integrating forward the equations of motion plus its conjugated equations expressed in cartesian coordinates and applying the Pontryagins maximum principle to obtain the optimal control with a switching function for the thrust. To refine the trajectory a 4 order Runge-Kutta shooting method has been used. The objective function in this study is the fuel consumption. Finally, the capable asteroids to get captured by a low-thrust engine have been listed indicating the main parameters.Postprint (published version

Estudio de la iluminación natural en la edificación

En la estación de radiación solar e iluminación de alta calidad del International Daylight Measurement Program (IDMP) en Madrid ubicada en la terraza norte de la E.T.S. de Arquitectura de la Universidad Politécnica de Madrid (40º 25’ N, 3º 41’ W) se está realizando un estudio conjunto entre profesores de la ETSAM y de la EUATM sobre la iluminación natural en la Edificación. Desde hace más de un año, se están midiendo iluminancias globales en superficies horizontales, en superficies verticales con las cuatro orientaciones (N, S, E y O) y en superficies inclinadas con distintos ángulos de inclinación mediante un domo semiesférico sobre el que se colocan los sensores fotométricos. Todas estas medidas para los tres tipos de cielo (despejado, parcialmente cubierto y cubierto). También se ha construido un modelo a escala de un local de la ETSAM con la finalidad de medir la iluminación natural simultáneamente en el local y en el modelo reducido. Una vez conocida la viabilidad del modelo se ha estudiado la iluminación natural que tendría dicho local, orientado al norte en la realidad, si estuviese orientado hacia el Sur, el Este o el Oeste. Con todo esto se han realizado varios trabajos de fin de máster del Máster en Técnicas y Sistemas de Edificación de la EUATM y se continúan realizando otros

Comment on "Identifying Molecular Orientation of Individual C₆₀ on a Si(111)-(7x7) Surface"

A Comment on the Letter by J. G. Hou, et al., Phys. Rev. Lett. 83, 3001 (1999)