Refinement criteria for global illumination using convex funcions

In several computer graphics areas, a refinement criterion is often needed to decide whether to go on or to stop sampling a signal. When the sampled values are homogeneous enough, we assume that they represent the signal fairly well and we do not need further refinement, otherwise more samples are required, possibly with adaptive subdivision of the domain. For this purpose, a criterion which is very sensitive to variability is necessary. In this paper, we present a family of discrimination measures, the f-divergences, meeting this requirement. These convex functions have been well studied and successfully applied to image processing and several areas of engineering. Two applications to global illumination are shown: oracles for hierarchical radiosity and criteria for adaptive refinement in ray-tracing. We obtain significantly better results than with classic criteria, showing that f-divergences are worth further investigation in computer graphics. Also a discrimination measure based on entropy of the samples for refinement in ray-tracing is introduced. The recursive decomposition of entropy provides us with a natural method to deal with the adaptive subdivision of the sampling region

SIGFRUT: aplicación web para el diseño de plantaciones e instalaciones agrícolas

The SIGFRUT project is set within what we could call GIS applications in a web environment. (The acronym GIS is SIG in Spanish). We are all familiar with Internet map servers or IMS, with which we can visualize different thematic layers, check their attributes and, in the best cases, consult a data base, selecting and visualizing the elements that meet the required conditions. Nevertheless, these types of applications are basically simple map viewers and do not have any more functional features than the classic tools of visualization and consultation.(...)

LOCALITZA: una herramienta SIG para resolver problemas de localización óptima

LOCALITZA software is a tool that increases GIS applications possibilities to analyze and solve optimal facility location problems. This system, that it is being migrated from Delphi to Python, allows to evaluate how existing facility supply covers the demand. ON the other hand, it includes the resolution of an elevated number of classic location-allocation models and, in some cases, includes new models

Una aproximación empírica a la comunicación desde la teoría de los actos de habla de Searle

This work considers communicative intention as the basis for rhe analysis of rhe communicative phenomenon in natural contexts. It also aims to reconcile the traditions that analyse human communication today. The convergence with the referential-ecological approach (Boada and Forns, 1989; 1997) has dealt with a number of important problems that the classic referential approach was unable to address. Its system of categories includes new variables, in addition to the classic referential variables. The cornmunicative intention is taken into account, albeit implicitly. Using a conciliatory approach, the study aims to study the intentional dimension in greater depth. The speech act theory (Searle, 1969; 1975) is used to categorize the cornrnunicative exchanges arnong a sarnple of 28 individuals and presents a certain complirnentariety with data from other traditions

Multilevel multitrait-multimethod model: application to the measurement of egocentered social networks

Our goal in this paper is to assess reliability and validity of egocentered network data using multilevel analysis (Muthen, 1989, Hox, 1993) under the multitrait-multimethod approach. The confirmatory factor analysis model for multitrait-multimethod data (Werts & Linn, 1970; Andrews, 1984) is used for our analyses. In this study we reanalyse a part of data of another study (Kogovšek et al., 2002) done on a representative sample of the inhabitants of Ljubljana. The traits used in our article are the name interpreters. We consider egocentered network data as hierarchical; therefore a multilevel analysis is required. We use Muthen's partial maximum likelihood approach, called pseudobalanced solution (Muthen, 1989, 1990, 1994) which produces estimations close to maximum likelihood for large ego sample sizes (Hox & Mass, 2001). Several analyses will be done in order to compare this multilevel analysis to classic methods of analysis such as the ones made in Kogovšek et al. (2002), who analysed the data only at group (ego) level considering averages of all alters within the ego. We show that some of the results obtained by classic methods are biased and that multilevel analysis provides more detailed information that much enriches the interpretation of reliability and validity of hierarchical data. Within and between-ego reliabilities and validities and other related quality measures are defined, computed and interpreted

Semi-online neural-Q_leaming for real-time robot learning

Reinforcement learning (RL) is a very suitable technique for robot learning, as it can learn in unknown environments and in real-time computation. The main difficulties in adapting classic RL algorithms to robotic systems are the generalization problem and the correct observation of the Markovian state. This paper attempts to solve the generalization problem by proposing the semi-online neural-Q_learning algorithm (SONQL). The algorithm uses the classic Q_learning technique with two modifications. First, a neural network (NN) approximates the Q_function allowing the use of continuous states and actions. Second, a database of the most representative learning samples accelerates and stabilizes the convergence. The term semi-online is referred to the fact that the algorithm uses the current but also past learning samples. However, the algorithm is able to learn in real-time while the robot is interacting with the environment. The paper shows simulated results with the "mountain-car" benchmark and, also, real results with an underwater robot in a target following behavior

A new approach to real time traffic sign recognition based on colour information

The automatic interpretation of conventional traffic signs is very complex and time consuming. The paper concerns an automatic warning system for driving assistance. It does not interpret the standard traffic signs on the roadside; the proposal is to incorporate into the existing signs another type of traffic sign whose information will be more easily interpreted by a processor. The type of information to be added is profuse and therefore the most important object is the robustness of the system. The basic proposal of this new philosophy is that the co-pilot system for automatic warning and driving assistance can interpret with greater ease the information contained in the new sign, whilst the human driver only has to interpret the "classic" sign. One of the codings that has been tested with good results and which seems to us easy to implement is that which has a rectangular shape and 4 vertical bars of different colours. The size of these signs is equivalent to the size of the conventional signs (approximately 0.4 m2). The colour information from the sign can be easily interpreted by the proposed processor and the interpretation is much easier and quicker than the information shown by the pictographs of the classic signs

Necessary and sufficient conditions for robust stability using modal intervals

In this paper, robustness of parametric systems is analyzed using a new approach to interval mathematics called Modal Interval Analysis. Modal Intervals are an interval extension that, instead of classic intervals, recovers some of the properties required by a numerical system. Modal Interval Analysis not only simplifies the computation of interval functions but allows semantic interpretation of their results. Necessary, sufficient and, in some cases, necessary and sufficient conditions for robust performance are presented

Medical image registration based on random line sampling

One of the key aspects in 3D-image registration is the computation of the joint intensity histogram. We propose a new approach to compute this histogram using uniformly distributed random lines to sample stochastically the overlapping volume between two 3D-images. The intensity values are captured from the lines at evenly spaced positions, taking an initial random offset different for each line. This method provides us with an accurate, robust and fast mutual information-based registration. The interpolation effects are drastically reduced, due to the stochastic nature of the line generation, and the alignment process is also accelerated. The results obtained show a better performance of the introduced method than the classic computation of the joint histogram

Viewpoint-Based Ambient Occlusion

We've developed a new ambient occlusion technique based on an information-theoretic framework. Essentially, our method computes a weighted visibility from each object polygon to all viewpoints; we then use these visibility values to obtain the information associated with each polygon. So, just as a viewpoint has information about the model's polygons, the polygons gather information on the viewpoints. We therefore have two measures associated with an information channel defined by the set of viewpoints as input and the object's polygons as output, or vice versa. From this polygonal information, we obtain an occlusion map that serves as a classic ambient occlusion technique. Our approach also offers additional applications, including an importance-based viewpoint-selection guide, and a means of enhancing object features and producing nonphotorealistic object visualizations

Cartografías simbólicas para la cultura y el desarrollo

El presente trabajo tiene como punto de partida la convicción que es necesario explorar nuevos marcos teóricos y metodológicos para la producción de conocimiento sobre las múltiples relaciones de la cultura con el desarrollo. Para tal efecto revisa la naturaleza polisémica del concepto cultura, su tratamiento por las ciencias sociales y la economía y su concepción actual como explicación última de toda actividad humana. Subraya la necesidad de generar un conocimiento propio del campo cultural que adopte renovadas concepciones y bases epistemológicas provenientes de las artes y las humanidades que privilegian lo intuitivo, lo individual frente a lo colectivo. La revisión de fuentes provenientes de la filosofía permite una lectura y un enfoque reformado de la naturaleza de la cultura que cuestiona la clásica concepción antropológica que reduce lo religioso a una expresión cultural. Los argumentos presentados exponen que en toda forma cultural está implícita una particular cosmovisión, una visión de la vida; una valoración del mundo que se conecta con el significado último de la existencia humana que es de naturaleza religiosa. Todas las comunidades culturales tienen en su haber una serie de prácticas, tradiciones, usos, costumbres, expresiones creativas que dan cuenta de una identidad particular y que son registradas a través de mapeos culturales y sistemas de información. El texto hace referencias a políticas y programas culturales sobre cultura y desarrollo en la región centroamericana

Optimization of inverse reflector design

Aquesta tesi presenta un nou mètode pel disseny invers de reflectors. Ens hem centrat en tres temes principals: l’ús de fonts de llum reals i complexes, la definició d’un algoritme ràpid pel càlcul de la il•luminació del reflector, i la definició d’un algoritme d’optimització per trobar més eficientment el reflector desitjat. Les fonts de llum estan representades per models near-field, que es comprimeixen amb un error molt petit, fins i tot per fonts de llum amb milions de raigs i objectes a il•luminar molt propers. Llavors proposem un mètode ràpid per obtenir la distribució de la il•luminació d’un reflector i la seva comparació amb la il•luminació desitjada, i que treballa completament en la GPU. Finalment, proposem un nou mètode d’optimització global que permet trobar la solució en menys passos que molts altres mètodes d’optimització clàssics, i alhora evitant mínims locals.

La protección de los flujos masivos en el ordenamiento jurídico internacional y en el Derecho venezolano

En caso de desplazamiento masivo, resulta imposible determinar inmediatamente de manera individual los temores de persecución de las personas que integran el grupo. Precisamente, ante la realidad desconsoladora de la promoción de una protección internacional exclusivamente aplicable a un tipo de refugiados casi inexistente, la cada vez menos frecuente determinación en grupo y prima facie de refugiados, la proliferación de estatutos subsidiarios, el aumento del desplazamiento interno y las restricciones que imponen los Estados por motivo de seguridad nacional u orden público, se consideró que un estudio sobre la protección de los flujos masivos podría facilitar la obtención de una visión general del estado actual de la protección temporal y de las obligaciones que se han desarrollado para hacer frente a tales contingencias. A partir del planteamiento inicial de los retos y obstáculos legales que este fenómeno ha planteado para los Estados receptores y para la evolución del Derecho internacional de los refugiados y de la inexistencia de un régimen jurídico internacional universal que regule la protección de los flujos masivos, se ha elaborado una construcción doctrinal y práctica sobre la protección de esta situación en el Derecho internacional, sistematizando los distintos elementos que se han ido incorporando a esta protección colectiva. Se ha analizado la protección de los flujos masivos con el ánimo de dotar de rasgos positivos a un concepto que ha sido considerado como un avance negativo en el ámbito de la protección internacional. Y es que la protección temporal no tiene por qué reducir estándares de protección ni tampoco sustituir a la protección internacional clásica, que es la de los refugiados.

Assisted visual servoing by means of structured light

Aquesta tesi tracta sobre la combinació del control visual i la llum estructurada. El control visual clàssic assumeix que elements visuals poden ser fàcilment extrets de les imatges. Això fa que objectes d'aspecte uniforme o poc texturats no es puguin tenir en compte. En aquesta tesi proposem l'ús de la llum estructurada per dotar d'elements visuals als objectes independentment de la seva aparença. En primer lloc, es presenta un ampli estudi de la llum estructurada, el qual ens permet proposar un nou patró codificat que millora els existents. La resta de la tesi es concentra en el posicionament d'un robot dotat d'una càmara respecte diferents objectes, utilitzant la informació proveïda per la projecció de diferents patrons de llum. Dos configuracions han estat estudiades: quan el projector de llum es troba separat del robot, i quan el projector està embarcat en el robot juntament amb la càmara. Les tècniques proposades en la tesi estan avalades per un ampli estudi analític i validades per resultats experimentals.