Conditional compositional biplots: theory and application

The biplot has proved to be a powerful descriptive and analytical tool in many areas of applications of statistics. For compositional data the necessary theoretical adaptation has been provided, with illustrative applications, by Aitchison (1990) and Aitchison and Greenacre (2002). These papers were restricted to the interpretation of simple compositional data sets. In many situations the problem has to be described in some form of conditional modelling. For example, in a clinical trial where interest is in how patients’ steroid metabolite compositions may change as a result of different treatment regimes, interest is in relating the compositions after treatment to the compositions before treatment and the nature of the treatments applied. To study this through a biplot technique requires the development of some form of conditional compositional biplot. This is the purpose of this paper. We choose as a motivating application an analysis of the 1992 US President ial Election, where interest may be in how the three-part composition, the percentage division among the three candidates - Bush, Clinton and Perot - of the presidential vote in each state, depends on the ethnic composition and on the urban-rural composition of the state. The methodology of conditional compositional biplots is first developed and a detailed interpretation of the 1992 US Presidential Election provided. We use a second application involving the conditional variability of tektite mineral compositions with respect to major oxide compositions to demonstrate some hazards of simplistic interpretation of biplots. Finally we conjecture on further possible applications of conditional compositional biplots

On optimal computation of MPLS label binding for multipoint-to-point connections

Most network operators have considered reducing Label Switched Routers (LSR) label spaces (i.e. the number of labels that can be used) as a means of simplifying management of underlaying Virtual Private Networks (VPNs) and, hence, reducing operational expenditure (OPEX). This letter discusses the problem of reducing the label spaces in Multiprotocol Label Switched (MPLS) networks using label merging - better known as MultiPoint-to-Point (MP2P) connections. Because of its origins in IP, MP2P connections have been considered to have tree- shapes with Label Switched Paths (LSP) as branches. Due to this fact, previous works by many authors affirm that the problem of minimizing the label space using MP2P in MPLS - the Merging Problem - cannot be solved optimally with a polynomial algorithm (NP-complete), since it involves a hard- decision problem. However, in this letter, the Merging Problem is analyzed, from the perspective of MPLS, and it is deduced that tree-shapes in MP2P connections are irrelevant. By overriding this tree-shape consideration, it is possible to perform label merging in polynomial time. Based on how MPLS signaling works, this letter proposes an algorithm to compute the minimum number of labels using label merging: the Full Label Merging algorithm. As conclusion, we reclassify the Merging Problem as Polynomial-solvable, instead of NP-complete. In addition, simulation experiments confirm that without the tree-branch selection problem, more labels can be reduced

Application for fault location in electrical power distribution systems

Fault location has been studied deeply for transmission lines due to its importance in power systems. Nowadays the problem of fault location on distribution systems is receiving special attention mainly because of the power quality regulations. In this context, this paper presents an application software developed in Matlabtrade that automatically calculates the location of a fault in a distribution power system, starting from voltages and currents measured at the line terminal and the model of the distribution power system data. The application is based on a N-ary tree structure, which is suitable to be used in this application due to the highly branched and the non- homogeneity nature of the distribution systems, and has been developed for single-phase, two-phase, two-phase-to-ground, and three-phase faults. The implemented application is tested by using fault data in a real electrical distribution power system

Fronts from complex two-dimensional dispersal kernels: theory and application to Reid's paradox

Bimodal dispersal probability distributions with characteristic distances differing by several orders of magnitude have been derived and favorably compared to observations by Nathan [Nature (London) 418, 409 (2002)]. For such bimodal kernels, we show that two-dimensional molecular dynamics computer simulations are unable to yield accurate front speeds. Analytically, the usual continuous-space random walks (CSRWs) are applied to two dimensions. We also introduce discrete-space random walks and use them to check the CSRW results (because of the inefficiency of the numerical simulations). The physical results reported are shown to predict front speeds high enough to possibly explain Reid's paradox of rapid tree migration. We also show that, for a time-ordered evolution equation, fronts are always slower in two dimensions than in one dimension and that this difference is important both for unimodal and for bimodal kernels

Counterpoise-corrected geometries and harmonic frequencies of N-body clusters: application to (HF)n (n=3,4)

A study was conducted on the methods of basis set superposition error (BSSE)-free geometry optimization and frequency calculations in clusters larger than a dimer. In particular, three different counterpoise schemes were critically examined. It was shown that the counterpoise-corrected supermolecule energy can be easily obtained in all the cases by using the many-body partitioning of energy

La presión laboral tendenciosa (Mobbing)

El trabajo de investigación surge en el año 2001, ante la necesidad de hacer frente a una nueva realidad jurídica, el mobbing. Para ello fue decisivo el estudio de lo publicado (básicamente de ramas ajenas al Derecho) pero sobre todo las entrevistas con las víctimas de mobbing y sus asociaciones; este extremo, unido a la ausencia de un tratamiento internacional, obligó a un camino autodidacta para definir mobbing jurídicamente. La Tesis define mobbing como la presión laboral tendente a la autoeliminación de un trabajador mediante su denigración (presión laboral tendenciosa), y con ello por primera vez se tiene una definición de mobbing en línea y media, con plena validez jurídica, que es susceptible de ser memorizada y por lo tanto divulgada, para corregir el problema. El denominado "concepto uniformado de mobbing" recalca la denigración como mecanismo frente a los tratos degradantes y recalca la autoeliminación como finalidad de un comportamiento doloso. El trabajo aporta fórmulas para deslindar casos de mobbing de otras figuras próximas, y en este sentido debe citarse "la regla del 9" para saber si hay mobbing; en sede de estadísticas se critican metodológicamente muchas de ellas presentadas hasta el momento y se aporta alguna en sede de Tribunales; pero sobre todo se advierte de los riesgos jurídicos de una previsible regulación específica antimobbing, mediante el examen de las distintas definiciones que se han esgrimido hasta el momento. La segunda parte de la Tesis profundiza sobre el grado de sensibilización de nuestro ordenamiento jurídico y Tribunales, a cuyo fin se ha trabajado con más de un centernar y medio de sentencias dictadas sobre la materia, y por supuesto la totalidad de las recogidas en las bases de datos de las editoriales. El análisis sirve para apreciar la bondad de la sistemática aquí defendida, poniendo en evidencia errores, y contradicciones. La Tesis advierte que la presión laboral tendenciosa más allá de vulnerar el derecho constitucional al trabajo, o los derechos fundamentales a la integridad moral y el honor, es una transgresión a todo un "espíritu constitucional", y en este sentido se analiza con detalle tanto la posibilidad de recurrir en amparo, como el derecho a la indemnidad para quien se enfrenta a esta situación. Advirtiendo de las ventajas de efectuar esta reacción mediante la modalidad procesal de tutela de los derechos fundamentales, se analiza la recurrida acción del art.50 ET, donde se realizan aportaciones sugerentes como el plazo prescripción o la "doctrina de los antecedentes", y se otorgan respuestas a las preguntas sobre obligación de seguir trabajando y ejecución provisional. En sede de acciones de Seguridad Social, la Tesis distingue entre la incapacidad temporal y permanente (depresiones) y la muerte y supervivencia, aportándose sobre la primera la técnica denominada "interpretación en tres niveles" y descartando la posibilidad de considerar accidente de trabajo el suicidio tras un mobbing por imperativo legal, pero aportando un sucedáneo bastante razonable como es el accidente no laboral. Junto a ello se razona por la viabilidad del recargo del art.123 LGSS. Civilmente, la Tesis se posiciona de "lege ferenda" por reconducir este tipo de acciones resarcitorias del daño psíquico y moral al orden civil, por una mayor explicación sobre el origen del quantum, pero sobre todo considera inadmisible la STS 11-3-04, y ello por una pluralidad de argumentos, pero sobre todo por cuanto viene a autorizar "de facto" este tipo de conductas. La posibilidad de accionar administrativamente frente a este riesgo psicosocial se analiza en un doble terreno, la empresa y la Administración. Si bien el cauce sobre el primero tiene algunos meandros que se desbelan, la situación es radicalmente frustrante en la Administración -donde se encuentra el mayor caldo de cultivo del mobbing- , y ello por el RD 707/2002, pero todavía en mayor medida por el Criterio Técnico 34/2003 mediante el cual la interpretación del Director General de la Inspección de Trabajo y Seguridad Social ha venido tácitamente a derogar parcialmente la Ley de Prevención de Riesgos Laborales para la Administración. En materia penal, la Tesis se decanta "a priori" por dos tipos penales, los delitos contra los derechos de los trabajadores, y el delito de trato degradante; sin embargo, en la práctica sólo este segundo es el camino que puede alcanzar buen puerto. Finalmente se realiza un estudio detallado de la Ley 62/2003, ley que se divulgó como reguladora del acoso moral, y que después se defiende como un avance frente al mobbing. La Tesis advierte que no es cierto ni lo uno, ni lo otro, habiendo creado un "espejismo legal" que puede perjudicar a las víctimas de mobbing, además de no servir su estructura para una futura regulación explícita antimobbing.

An improved method for discovering link criticality in transport networks

Quantitatively assessing the importance or criticality of each link in a network is of practical value to operators, as that can help them to increase the network's resilience, provide more efficient services, or improve some other aspect of the service. Betweenness is a graph-theoretical measure of centrality that can be applied to communication networks to evaluate link importance. However, as we illustrate in this paper, the basic definition of betweenness centrality produces inaccurate estimations as it does not take into account some aspects relevant to networking, such as the heterogeneity in link capacity or the difference between node-pairs in their contribution to the total traffic. A new algorithm for discovering link centrality in transport networks is proposed in this paper. It requires only static or semi-static network and topology attributes, and yet produces estimations of good accuracy, as verified through extensive simulations. Its potential value is demonstrated by an example application. In the example, the simple shortest-path routing algorithm is improved in such a way that it outperforms other more advanced algorithms in terms of blocking ratio

Generalized Higher-Order Voronoi Diagrams on Polyhedral Surfaces

We present an algorithm for computing exact shortest paths, and consequently distances, from a generalized source (point, segment, polygonal chain or polygonal region) on a possibly non-convex polyhedral surface in which polygonal chain or polygon obstacles are allowed. We also present algorithms for computing discrete Voronoi diagrams of a set of generalized sites (points, segments, polygonal chains or polygons) on a polyhedral surface with obstacles. To obtain the discrete Voronoi diagrams our algorithms, exploiting hardware graphics capabilities, compute shortest path distances defined by the sites

Large-Scale Surface registration

The first part of this work presents an accurate analysis of the most relevant 3D registration techniques, including initial pose estimation, pairwise registration and multiview registration strategies. A new classification has been proposed, based on both the applications and the approach of the methods that have been discussed. The main contribution of this thesis is the proposal of a new 3D multiview registration strategy. The proposed approach detects revisited regions obtaining cycles of views that are used to reduce the inaccuracies that may exist in the final model due to error propagation. The method takes advantage of both global and local information of the registration process, using graph theory techniques in order correlate multiple views and minimize the propagated error by registering the views in an optimal way. The proposed method has been tested using both synthetic and real data, in order to show and study its behavior and demonstrate its reliability.

Molecular quantum similarity in QSAR: applications in computer-aided molecular design

La present tesi està centrada en l'ús de la Teoria de Semblança Quàntica per a calcular descriptors moleculars. Aquests descriptors s'utilitzen com a paràmetres estructurals per a derivar correlacions entre l'estructura i la funció o activitat experimental per a un conjunt de compostos. Els estudis de Relacions Quantitatives Estructura-Activitat són d'especial interès per al disseny racional de molècules assistit per ordinador i, en particular, per al disseny de fàrmacs. Aquesta memòria consta de quatre parts diferenciades. En els dos primers blocs es revisen els fonaments de la teoria de semblança quàntica, així com l'aproximació topològica basada en la teoria de grafs. Ambdues teories es fan servir per a calcular els descriptors moleculars. En el segon bloc, s'ha de remarcar la programació i implementació de programari per a calcular els anomenats índexs topològics de semblança quàntica. La tercera secció detalla les bases de les Relacions Quantitatives Estructura-Activitat i, finalment, el darrer apartat recull els resultats d'aplicació obtinguts per a diferents sistemes biològics.