Using Virtual Reality in the teaching of manufacturing processes with material removal in CNC Machine-Tools

This paper presents a methodology for the incorporation of a Virtual Reality development applied to the teaching of manufacturing processes, namely the group of machining processes in numerical control of machine tools. The paper shows how it is possible to supplement the teaching practice through virtual machine-tools whose operation is similar to the 'real' machines while eliminating the risks of use for both users and the machines.

A data-globe and immersive virtual reality environment for upper limb rehabilitation after spinal cord injury

While a number of virtual data-gloves have been used in stroke, there is little evidence about their use in spinal cord injury (SCI). A pilot clinical experience with nine SCI subjects was performed comparing two groups: one carried out a virtual rehabilitation training based on the use of a data glove, CyberTouch combined with traditional rehabilitation, during 30 minutes a day twice a week along two weeks; while the other made only conventional rehabilitation. Furthermore, two functional indexes were developed in order to assess the patient���s performance of the sessions: normalized trajectory lengths and repeatability. While differences between groups were not statistically significant, the data-glove group seemed to obtain better results in the muscle balance and functional parameters, and in the dexterity, coordination and fine grip tests. Related to the indexes that we implemented, normalized trajectory lengths and repeatability, every patient showed an improvement in at least one of the indexes, either along Y-axis trajectory or Z-axis trajectory. This study might be a step in investigating new ways of treatments and objective measures in order to obtain more accurate data about the patient���s evolution, allowing the clinicians to develop rehabilitation treatments, adapted to the abilities and needs of the patients.

Tecnolog��a de registro y reproducci��n sonora para entornos de realidad virtual

Este proyecto de fin de carrera tiene como objetivo obtener una visi��n detallada de los sistemas y tecnolog��as de grabaci��n y reproducci��n utilizadas para aplicaciones de audio 3D y entornos de realidad virtual, analizando las diferentes alternativas existentes, su funcionamiento, caracter��sticas, detalles t��cnicos y sus ��mbitos de aplicaci��n. Como punto de partida se estudiar�� la teor��a psicoac��stica y la localizaci��n de fuentes sonoras en el espacio, base para el estudio de los sistemas de audio 3D. Se estudiar�� tanto la espacializaci��n sonora en un espacio real y la espacializaci��n virtual (simulaci��n mediante procesado de informaci��n de la localizaci��n de fuentes sonoras), en los que intervienen algunos fen��menos ac��sticos y psicoac��sticos como ITD, o diferencia de tiempo que existe entre una se��al ac��stica que llega a los pabellones auditivos, la ILD, o diferencia de intensidad o amplitud que hay entre la se��al que llega a los pabellones auditivos y la localizaci��n espacial mediante otra serie de mecanismos biaurales. Tras una visi��n general de la teor��a psicoac��stica y la espacializaci��n sonora, se analizar��n con detalle los elementos de grabaci��n y reproducci��n existentes para audio 3D. Concretamente, a lo largo del proyecto se profundizar�� en el funcionamiento del sistema est��reo, caracterizado por el posicionamiento sonoro mediante la utilizaci��n de dos canales; del sistema biaural, caracterizado por reconstruir campos sonoros mediante el uso de las HRTF; de los sistemas multicanal, detallando gran parte de las alternativas y configuraciones existentes; del sistema Ambiophonics, caracterizado por implementar filtros de cruce; del sistema Ambisonics, y sus diferentes formatos y t��cnicas de codificaci��n y decodificaci��n; y del sistema Wavefield Synthesis, caracterizado por recrear ambientes sonoros en grandes espacios. ABSTRACT This project aims to get a detailed view of recording and reproducing systems and technologies used to 3D audio applications and virtual reality environments, analyzing the different alternatives available, their functioning, features, technical details and their different scopes of applications. As a starting point, will be studied the psychoacoustic theory and the localization of sound sources in space, basis for the 3D audio study. Will be studied both the spacialization of sound sources in real space as virtual spatialization of sound sources (simulation by information processing of localization of sound sources), in which involves some acoustic and psychoacoustic phenomena like ITD (or the Interaural time difference), the ILD, (or the Interaural Level Difference) and spatial localization by another set of binaural mechanisms. After a general overview of the psychoacoustics theory and the sound spatialization, will be analyzed in detail existing methods of recording and reproducing for 3D audio. Specifically, during the project will analyze the characteristics of the stereo systems, characterized by sound positioning using two channels; the binaural systems, characterized by reconstructing sound fields by using the HRTF; the multichannel systems, detailing many of the existing alternatives and configurations; the Ambiophonics system, which is characterized by implementing crosstalk elimination techniques; the Ambiosonics system, and its various formats and encoding and decoding techniques; and the Wavefield Synthesis system, characterized by recreate soundscapes in large spaces.

Evaluaci��n y tratamiento basados en realidad virtual de la negligencia espacial unilateral: an��lisis del estado de la cuesti��n y demostraci��n de enfoques alternativos

En el siguiente trabajo se presenta en primer lugar de forma detallada la enfermedad denominada negligencia espacial unilateral (s��ntomas, tipos, causas, evaluaci��n y tratamientos) para proporcionar una mejor comprensi��n del principal objetivo del estudio, que es el an��lisis de las soluciones virtuales, existentes en la literatura, aplicadas al tratamiento de esta enfermedad, incluy��ndose una amplia descripci��n de cada estudio encontrado sobre el tema. A continuaci��n, se han realizado tres implementaciones en realidad virtual de tres t��cnicas cl��sicas de rehabilitaci��n llevadas a cabo en un entorno virtual, que son la estimulaci��n optocin��tica, eye patching, y adaptaci��n prism��tica y se ha desarrollado una aplicaci��n 3D para evaluar el grado y tipo de negligencia sufrida por los pacientes. Que de forma conjunta, constituyen un primer paso hacia un enfoque alternativo para el tratamiento de la enfermedad, m��s personalizado y eficaz. Por ��ltimo, en las conclusiones, se analizan las principales ventajas y desventajas encontradas en el uso de estas tecnolog��as aplicadas a la enfermedad y los trabajos futuros que pueden derivar de este trabajo.---ABSTRACT---The following work starts by presenting in detail a disease called unilateral spatial neglect (symptoms, types, causes, assessment and treatment) to provide the background for this study's main objective, which is the analysis of the virtual solutions existing in the literature for the treatment of this disease. The document includes an extensive description of the previous work found in this topic. Afterwards, three implementations of three classical rehabilitation techniques were performed in virtual reality: optokinetic stimulation, eye patching and prism adaptation, as a proof-of-concept, and a 3D application was implemented to assess the degree and type of negligence suffered by patients. Altogether, they constitute a first step towards an alternative approach for the treatment of disease, more personalized and effective. Finally, the conclusions analyze the main advantages and disadvantages encountered in the use of these technologies when applied to this disease and suggest future work.

Restauraci��n virtual del patrimonio sonoro. Aplicaci��n al antiguo rito hisp��nico

Una de las aplicaciones m��s interesantes de las tecnolog��as de Realidad Ac��stica Virtual es la posibilidad de recuperar el patrimonio cultural del sonido de los recintos hist��ricos que se han perdido o cuyas caracter��sticas se han modificado a lo largo de los siglos. En este trabajo, las tecnolog��as de realidad ac��stica virtual se utilizan para tratar de reconstruir virtualmente el sonido producido en las actividades lit��rgicas del antiguo rito hisp��nico. Bajo este nombre se conoce a la liturgia que celebraban los cristianos de la pen��nsula ib��rica hasta su prohibici��n, en favor del culto romano, a mediados del siglo XI. El rito hisp��nico -tambi��n conocido como rito visig��tico-moz��rabe- es una de las manifestaciones culturales m��s interesantes de la Alta Edad Media en occidente. Se trata de un patrimonio cultural desaparecido, tanto desde el punto de vista de las se��ales sonoras que lo integraban -ya que la mayor��a de las melod��as que conformaban el rito se han perdido- como desde el punto de vista de los espacios en los que se desarrollaba, debido a que las iglesias conservadas de la ��poca han experimentado modificaciones a lo largo de los siglos que alteran sus condiciones ac��sticas con respecto a las que ten��an en el periodo de vigencia de esta liturgia. Para llevar a cabo este proyecto, se han realizado modelos ac��sticos digitales de un grupo representativo de iglesias prerrom��nicas de la Pen��nsula Ib��rica en su estado primitivo. Se ha procurado que las iglesias seleccionadas representen la variedad de comportamientos ac��sticos esperables en este tipo de edificios. Con este objetivo, se han elegido cinco iglesias prerrom��nicas que presentan diferencias sustanciales en los par��metros que, a priori, van a influir en mayor manera a su comportamiento ac��stico: el volumen del recinto, la forma de la planta y el tipo de cubierta. El proceso de creaci��n de los modelos ac��sticos digitales de las iglesias se ha dividido en dos fases: en la primera se han creado modelos de los edificios en su estado actual, que se han validado a partir de los datos obtenidos en mediciones ac��sticas realizadas in situ; a partir de los modelos validados de las iglesias en su estado actual, en la segunda fase se han generado los modelos ac��sticos digitales correspondientes al estado primitivo de las mismas, modificando los modelos anteriores de acuerdo con las hip��tesis de reconstrucci��n propuestas en las investigaciones arqueol��gicas m��s recientes. Se han realizado grabaciones en c��mara anecoica de una serie de piezas del repertorio original del canto moz��rabe. Las grabaciones se han llevado a cabo con un array esf��rico compuesto por 32 micr��fonos, con objeto de obtener informaci��n sobre la directividad de la emisi��n sonora de los cantantes, que se aplicar�� en las auralizaciones. Finalmente, se han realizado diversas auralizaciones, teniendo en cuenta diferentes configuraciones lit��rgicas que eran usuales en este rito. ABSTRACT One of the most interesting applications of the Acoustic Virtual Reality technologies is the possibility to recover the cultural heritage of the sound of the historical sites that have been lost or whose characteristics have been modified through time. In this work, Acoustic Virtual Reality technologies are used to try to reconstruct virtually the sound produced in the liturgical activities of the Hispanic Rite. This is the name given to the liturgy celebrated by Christians of the Iberian Peninsula prior to the introduction of the Roman cult in the mid-eleventh century. The Hispanic Rite (also known as Visigothic or Mozarabic rite) is one of the most interesting cultural manifestations of the Middle Ages. It is a lost cultural heritage, both from the point of view of the sound signals that were used since the majority of the melodies that conformed the rite have been lost, and from the point of view of the spaces in which this liturgy was celebrated, because the churches preserved from that era have changed over the centuries altering its acoustic conditions respect to which they were in the period in which this liturgy was in effect. To carry out this project, acoustic models of a representative group of the pre-Romanesque churches in the Iberian Peninsula have been made in his primitive state. To select the sample of buildings to study, efforts have been made to ensure that the selected churches were representative of the range of expected acoustic behaviors in this type of buildings. Five churches have been selected, showing differences in the parameters that have the greatest influence on their acoustic behavior: the enclosure volume, the shape of the floor plan and the type of roof. The process of creating digital acoustic models of the churches has been divided into two phases. In the first phase acoustic models of the churches in its current state have been created. These models have been validated with the data obtained from in situ acoustic measurements. From the validated models of churches in its current state, in the second phase, changes in the acoustic models have been performed in order to represent the primitive state of the churches, according to the historical reconstruction hypothesis that have been proposed in the most recent archaeological investigations. Anechoic recordings of a series of pieces of the original Mozarabic Chant repertoire have been recorded. The recordings were made with a spherical array composed of 32 microphones, in order to obtain information on the directivity of the sound emission of the singers. These directivity data will be used to simulate the directional radiation of the sound sources in the auralizations. Finally, auralizations were produced corresponding to different liturgical configurations which were common in this rite.

Modelling ecological cognitive rehabilitation therapies for building virtual environments in brain injury

Brain Injury (BI) has become one of the most common causes of neurological disability in developed countries. Cognitive disorders result in a loss of independence and patients? quality of life. Cognitive rehabilitation aims to promote patients? skills to achieve their highest degree of personal autonomy. New technologies such as virtual reality or interactive video allow developing rehabilitation therapies based on reproducible Activities of Daily Living (ADLs), increasing the ecological validity of the therapy. However, the lack of frameworks to formalize and represent the definition of this kind of therapies can be a barrier for widespread use of interactive virtual environments in clinical routine.

Metadata Visualization of Cultural Heritage Information within a Collaborative Environment

Cultural content on the Web is available in various domains (cultural objects, datasets, geospatial data, moving images, scholarly texts and visual resources), concerns various topics, is written in different languages, targeted to both laymen and experts, and provided by different communities (libraries, archives museums and information industry) and individuals (Figure 1). The integration of information technologies and cultural heritage content on the Web is expected to have an impact on everyday life from the point of view of institutions, communities and individuals. In particular, collaborative environment scan recreate 3D navigable worlds that can offer new insights into our cultural heritage (Chan 2007). However, the main barrier is to find and relate cultural heritage information by end-users of cultural contents, as well as by organisations and communities managing and producing them. In this paper, we explore several visualisation techniques for supporting cultural interfaces, where the role of metadata is essential for supporting the search and communication among end-users (Figure 2). A conceptual framework was developed to integrate the data, purpose, technology, impact, and form components of a collaborative environment, Our preliminary results show that collaborative environments can help with cultural heritage information sharing and communication tasks because of the way in which they provide a visual context to end-users. They can be regarded as distributed virtual reality systems that offer graphically realised, potentially infinite, digital information landscapes. Moreover, collaborative environments also provide a new way of interaction between an end-user and a cultural heritage data set. Finally, the visualisation of metadata of a dataset plays an important role in helping end-users in their search for heritage contents on the Web.

IDT-3D: Identification and tracking in controlled environments using a 3D unified user interface

Identification and tracking of objects in specific environments such as harbors or security areas is a matter of great importance nowadays. With this purpose, numerous systems based on different technologies have been developed, resulting in a great amount of gathered data displayed through a variety of interfaces. Such amount of information has to be evaluated by human operators in order to take the correct decisions, sometimes under highly critical situations demanding both speed and accuracy. In order to face this problem we describe IDT-3D, a platform for identification and tracking of vessels in a harbour environment able to represent fused information in real time using a Virtual Reality application. The effectiveness of using IDT-3D as an integrated surveillance system is currently under evaluation. Preliminary results point to a significant decrease in the times of reaction and decision making of operators facing up a critical situation. Although the current application focus of IDT-3D is quite specific, the results of this research could be extended to the identification and tracking of targets in other controlled environments of interest as coastlines, borders or even urban areas.

Fast Correction of Tiled Display Systems on Planar Surfaces

A method for fast colour and geometric correction of a tiled display system is presented in this paper. Such kind of displays are a common choice for virtual reality applications and simulators, where a high resolution image is required. They are the cheapest and more flexible alternative for large image generation but they require a precise geometric and colour correction. The purpose of the proposed method is to correct the projection system as fast as possible so in case the system needs to be recalibrated it doesn���t interfere with the normal operation of the simulator or virtual reality application. This technique makes use of a single conventional webcam for both geometric and photometric correction. Some previous assumptions are made, like planar projection surface and negligibleintra-projector colour variation and black-offset levels. If these assumptions hold true, geometric and photometric seamlessness can be achievedfor this kind of display systems. The method described in this paper is scalable for an undefined number of projectors and completely automatic.

Conceptual framework for the design, implementation and validation of psychomotor skills��� assessment systems in minimally invasive surgery

Las t��cnicas de cirug��a de m��nima invasi��n (CMI) se est��n consolidando hoy en d��a como alternativa a la cirug��a tradicional, debido a sus numerosos beneficios para los pacientes. Este cambio de paradigma implica que los cirujanos deben aprender una serie de habilidades distintas de aquellas requeridas en cirug��a abierta. El entrenamiento y evaluaci��n de estas habilidades se ha convertido en una de las mayores preocupaciones en los programas de formaci��n de cirujanos, debido en gran parte a la presi��n de una sociedad que exige cirujanos bien preparados y una reducci��n en el n��mero de errores m��dicos. Por tanto, se est�� prestando especial atenci��n a la definici��n de nuevos programas que permitan el entrenamiento y la evaluaci��n de las habilidades psicomotoras en entornos seguros antes de que los nuevos cirujanos puedan operar sobre pacientes reales. Para tal fin, hospitales y centros de formaci��n est��n gradualmente incorporando instalaciones de entrenamiento donde los residentes puedan practicar y aprender sin riesgos. Es cada vez m��s com��n que estos laboratorios dispongan de simuladores virtuales o simuladores f��sicos capaces de registrar los movimientos del instrumental de cada residente. Estos simuladores ofrecen una gran variedad de tareas de entrenamiento y evaluaci��n, as�� como la posibilidad de obtener informaci��n objetiva de los ejercicios. Los diferentes estudios de validaci��n llevados a cabo dan muestra de su utilidad; pese a todo, los niveles de evidencia presentados son en muchas ocasiones insuficientes. Lo que es m��s importante, no existe un consenso claro a la hora de definir qu�� m��tricas son m��s ��tiles para caracterizar la pericia quir��rgica. El objetivo de esta tesis doctoral es dise��ar y validar un marco de trabajo conceptual para la definici��n y validaci��n de entornos para la evaluaci��n de habilidades en CMI, en base a un modelo en tres fases: pedag��gica (tareas y m��tricas a emplear), tecnol��gica (tecnolog��as de adquisici��n de m��tricas) y anal��tica (interpretaci��n de la competencia en base a las m��tricas). Para tal fin, se describe la implementaci��n pr��ctica de un entorno basado en (1) un sistema de seguimiento de instrumental fundamentado en el an��lisis del v��deo laparosc��pico; y (2) la determinaci��n de la pericia en base a m��tricas de movimiento del instrumental. Para la fase pedag��gica se dise���� e implement�� un conjunto de tareas para la evaluaci��n de habilidades psicomotoras b��sicas, as�� como una serie de m��tricas de movimiento. La validaci��n de construcci��n llevada a cabo sobre ellas mostr�� buenos resultados para tiempo, camino recorrido, profundidad, velocidad media, aceleraci��n media, econom��a de ��rea y econom��a de volumen. Adicionalmente, los resultados obtenidos en la validaci��n de apariencia fueron en general positivos en todos los grupos considerados (noveles, residentes, expertos). Para la fase tecnol��gica, se introdujo el EVA Tracking System, una soluci��n para el seguimiento del instrumental quir��rgico basado en el an��lisis del v��deo endosc��pico. La precisi��n del sistema se evalu�� a 16,33ppRMS para el seguimiento 2D de la herramienta en la imagen; y a 13mmRMS para el seguimiento espacial de la misma. La validaci��n de construcci��n con una de las tareas de evaluaci��n mostr�� buenos resultados para tiempo, camino recorrido, profundidad, velocidad media, aceleraci��n media, econom��a de ��rea y econom��a de volumen. La validaci��n concurrente con el TrEndo�� Tracking System por su parte present�� valores altos de correlaci��n para 8 de las 9 m��tricas analizadas. Finalmente, para la fase anal��tica se compar�� el comportamiento de tres clasificadores supervisados a la hora de determinar autom��ticamente la pericia quir��rgica en base a la informaci��n de movimiento del instrumental, basados en aproximaciones lineales (an��lisis lineal discriminante, LDA), no lineales (m��quinas de soporte vectorial, SVM) y difusas (sistemas adaptativos de inferencia neurodifusa, ANFIS). Los resultados muestran que en media SVM presenta un comportamiento ligeramente superior: 78,2% frente a los 71% y 71,7% obtenidos por ANFIS y LDA respectivamente. Sin embargo las diferencias estad��sticas medidas entre los tres no fueron demostradas significativas. En general, esta tesis doctoral corrobora las hip��tesis de investigaci��n postuladas relativas a la definici��n de sistemas de evaluaci��n de habilidades para cirug��a de m��nima invasi��n, a la utilidad del an��lisis de v��deo como fuente de informaci��n y a la importancia de la informaci��n de movimiento de instrumental a la hora de caracterizar la pericia quir��rgica. Bas��ndose en estos cimientos, se han de abrir nuevos campos de investigaci��n que contribuyan a la definici��n de programas de formaci��n estructurados y objetivos, que puedan garantizar la acreditaci��n de cirujanos sobradamente preparados y promocionen la seguridad del paciente en el quir��fano. Abstract Minimally invasive surgery (MIS) techniques have become a standard in many surgical sub-specialties, due to their many benefits for patients. However, this shift in paradigm implies that surgeons must acquire a complete different set of skills than those normally attributed to open surgery. Training and assessment of these skills has become a major concern in surgical learning programmes, especially considering the social demand for better-prepared professionals and for the decrease of medical errors. Therefore, much effort is being put in the definition of structured MIS learning programmes, where practice with real patients in the operating room (OR) can be delayed until the resident can attest for a minimum level of psychomotor competence. To this end, skills��� laboratory settings are being introduced in hospitals and training centres where residents may practice and be assessed on their psychomotor skills. Technological advances in the field of tracking technologies and virtual reality (VR) have enabled the creation of new learning systems such as VR simulators or enhanced box trainers. These systems offer a wide range of tasks, as well as the capability of registering objective data on the trainees��� performance. Validation studies give proof of their usefulness; however, levels of evidence reported are in many cases low. More importantly, there is still no clear consensus on topics such as the optimal metrics that must be used to assess competence, the validity of VR simulation, the portability of tracking technologies into real surgeries (for advanced assessment) or the degree to which the skills measured and obtained in laboratory environments transfer to the OR. The purpose of this PhD is to design and validate a conceptual framework for the definition and validation of MIS assessment environments based on a three-pillared model defining three main stages: pedagogical (tasks and metrics to employ), technological (metric acquisition technologies) and analytical (interpretation of competence based on metrics). To this end, a practical implementation of the framework is presented, focused on (1) a video-based tracking system and (2) the determination of surgical competence based on the laparoscopic instruments��� motionrelated data. The pedagogical stage���s results led to the design and implementation of a set of basic tasks for MIS psychomotor skills��� assessment, as well as the definition of motion analysis parameters (MAPs) to measure performance on said tasks. Validation yielded good construct results for parameters such as time, path length, depth, average speed, average acceleration, economy of area and economy of volume. Additionally, face validation results showed positive acceptance on behalf of the experts, residents and novices. For the technological stage the EVA Tracking System is introduced. EVA provides a solution for tracking laparoscopic instruments from the analysis of the monoscopic video image. Accuracy tests for the system are presented, which yielded an average RMSE of 16.33pp for 2D tracking of the instrument on the image and of 13mm for 3D spatial tracking. A validation experiment was conducted using one of the tasks and the most relevant MAPs. Construct validation showed significant differences for time, path length, depth, average speed, average acceleration, economy of area and economy of volume; especially between novices and residents/experts. More importantly, concurrent validation with the TrEndo�� Tracking System presented high correlation values (>0.7) for 8 of the 9 MAPs proposed. Finally, the analytical stage allowed comparing the performance of three different supervised classification strategies in the determination of surgical competence based on motion-related information. The three classifiers were based on linear (linear discriminant analysis, LDA), non-linear (support vector machines, SVM) and fuzzy (adaptive neuro fuzzy inference systems, ANFIS) approaches. Results for SVM show slightly better performance than the other two classifiers: on average, accuracy for LDA, SVM and ANFIS was of 71.7%, 78.2% and 71% respectively. However, when confronted, no statistical significance was found between any of the three. Overall, this PhD corroborates the investigated research hypotheses regarding the definition of MIS assessment systems, the use of endoscopic video analysis as the main source of information and the relevance of motion analysis in the determination of surgical competence. New research fields in the training and assessment of MIS surgeons can be proposed based on these foundations, in order to contribute to the definition of structured and objective learning programmes that guarantee the accreditation of well-prepared professionals and the promotion of patient safety in the OR.

Learning curves of basic laparoscopic psychomotor skills in SINERGIA VR simulator

Purpose: Surgical simulators are currently essential within any laparoscopic training program because they provide a low-stakes, reproducible and reliable environment to acquire basic skills. The purpose of this study is to determine the training learning curve based on different metrics corresponding to five tasks included in SINERGIA laparoscopic virtual reality simulator. Methods: Thirty medical students without surgical experience participated in the study. Five tasks of SINERGIA were included: Coordination, Navigation, Navigation and touch, Accurate grasping and Coordinated pulling. Each participant was trained in SINERGIA. This training consisted of eight sessions (R1���R8) of the five mentioned tasks and was carried out in two consecutive days with four sessions per day. A statistical analysis was made, and the results of R1, R4 and R8 were pair-wise compared with Wilcoxon signed-rank test. Significance is considered at P value <0.005. Results: In total, 84.38% of the metrics provided by SINERGIA and included in this study show significant differences when comparing R1 and R8. Metrics are mostly improved in the first session of training (75.00% when R1 and R4 are compared vs. 37.50% when R4 and R8 are compared). In tasks Coordination and Navigation and touch, all metrics are improved. On the other hand, Navigation just improves 60% of the analyzed metrics. Most learning curves show an improvement with better results in the fulfillment of the different tasks. Conclusions: Learning curves of metrics that assess the basic psychomotor laparoscopic skills acquired in SINERGIA virtual reality simulator show a faster learning rate during the first part of the training. Nevertheless, eight repetitions of the tasks are not enough to acquire all psychomotor skills that can be trained in SINERGIA. Therefore, and based on these results together with previous works, SINERGIA could be used as training tool with a properly designed training program.

Mozarabic Chant anechoic recordings for auralization purposes

The Hispanic Rite is the liturgy celebrated by Christians of the Iberian Peninsula before the imposition of the Roman Rite in the mid-eleventh century. As in other early Christian liturgies, music was the core of the Hispanic Rite. This music, known as Mozarabic Chant is one of the richest musical repertoires of the Middle Ages. Currently, a research project is underway involving the restoration of the Hispanic Rite sound, using techniques of acoustic virtual reality. The project aims to perform the auralization of the sound of Mozarabic Chant in his primitive environment, that is, taking into account the acoustic characteristics of the pre-Romanesque churches in their original state. For this purpose, anechoic recordings were made for a number of musical pieces representative of the Mozarabic Chant repertoire. In total eight (8) musical pieces have been recorded and interpreted, each of one, by six (6) different singers. The recordings were made using a spherical array composed by 32 microphones. This paper describes the more relevant aspects related to the recorded musical material, the technical specifications and installation details of the recording equipment, the data processing, and a summary of the results.

Experimental Prototype Merging Stereo Panoramic Video and Interactive 3D Content in a 5-sided CAVETM

Immersion and interaction have been identified as key factors influencing the quality of experience in stereoscopic video systems. An experimental prototype designed to explore the influence of these factors in 3D video applications is described here1. The focus is on the real-time insertion algorithm of new 3D models into the original video streams. Using this algorithm, our prototype is aimed to explore a new interaction paradigm ? similar to the augmented reality approach ? with 3D video applications.

Metodolog��a para el desarrollo de un sistema de visualizaci��n multi-proyector con caracter��sticas crom��ticas uniformes

Los sistemas de proyecci��n multi-proyector han adquirido gran popularidad en los ��ltimos a��os para su uso en un amplio rango de aplicaciones como sistemas de realidad virtual, simuladores y visualizaci��n de datos. Esto es debido a que normalmente estas aplicaciones necesitan representar sus datos a muy alta resoluci��n y a lo largo de una gran superficie. Este tipo de sistemas de proyecci��n son baratos en comparaci��n con las resoluciones que pueden conseguir, se pueden configurar para proyectar sobre pr��cticamente cualquier tipo de superficie, sea cual sea su forma, y son f��cilmente escalables. Sin embargo, para hacer que este tipo de sistemas generen una imagen sin discontinuidades geom��tricas o colorim��tricas requieren de un ajuste preciso. En la presente tesis se analizan en detalle todos los problemas a los que hay que enfrentarse a la hora de dise��ar y calibrar un sistema de proyecci��n de este tipo y se propone una metodolog��a con una serie de optimizaciones para hacer el ajuste de estos sistemas m��s sencillo y r��pido. Los resultados de esta metodolog��a se muestran aplicados a la salida gr��fica de un simulador de entrenamiento. Multi-projector display systems have gained high popularity over the past years for its use in a wide range of applications such as virtual reality systems, simulators or data visualization where a high resolution image over a large projection surface is required. Such systems are cheap for the resolutions they can provide, can be configured to project images on almost any kind of screen shapes and are easily scalable, but in order to provide a seamless image with no photometric discontinuities they require a precise geometric and colour correction. In this thesis, we analyze all the problems that have to be faced in order to design and calibrate a multi-projector display. We propose a calibration methodology with some optimizations that make the adjustment of this kind of displays easier and faster. The results of the implementation of this methodology on a training simulator are presented and discussed

Modelizaci��n de los Procesos de Cristalizaci��n en Poliolefinas

���Por lo tanto, la cristalizaci��n de pol��meros se supone, y en las teor��as se describe a menudo, como un proceso de m��ltiples pasos con muchos aspectos f��sico-qu��micos y estructurales influyendo en ��l. Debido a la propia estructura de la cadena, es f��cil entender que un proceso que es termodin��micamente forzado a aumentar su ordenamiento local, se vea obstaculizado geom��tricamente y, por tanto, no puede conducirse a un estado de equilibrio final. Como resultado, se forman habitualmente estructuras de no equilibrio con diferentes caracter��sticas dependiendo de la temperatura, presi��n, cizallamiento y otros par��metros f��sico-qu��micos del sistema���. Estas palabras, pronunciadas recientemente por el profesor Bernhard Wunderlich, uno de los mas relevantes fisico-quimicos que han abordado en las ultimas d��cadas el estudio del estado f��sico de las macromol��culas, adelantan lo que de alguna manera se explicita en esta memoria y constituyen el ���leitmotiv��� de este trabajo de tesis. El mecanismo de la cristalizaci��n de pol��meros esta aun bajo debate en la comunidad de la f��sica de pol��meros y la mayor��a de los abordajes experimentales se explican a trav��s de la teor��a LH. Esta teor��a cl��sica debida a Lauritzen y Hoffman (LH), y que es una generalizaci��n de la teor��a de cristalizaci��n de una mol��cula peque��a desde la fase de vapor, describe satisfactoriamente muchas observaciones experimentales aunque esta lejos de explicar el complejo fen��meno de la cristalizaci��n de pol��meros. De hecho, la formulaci��n original de esta teor��a en el National Bureau of Standards, a comienzos de la d��cada de los 70, sufri�� varias reformulaciones importantes a lo largo de la d��cada de los 80, buscando su adaptaci��n a los hallazgos experimentales. As�� naci�� el r��gimen III de cristalizaci��n que posibilita la creacion de nichos moleculares en la superficie y que dio pie al paradigma ofrecido por Sadler y col., para justificar los experimentos que se obtenian por ���scattering��� de neutrones y otras t��cnicas como la t��cnica de ���droplets��� o enfriamiento rapido. Por encima de todo, el gran ��xito de la teor��a radica en que explica la dependencia inversa entre el tama��o del plegado molecular y el subenfriamiento, definido este ultimo como el intervalo de temperatura que media entre la temperatura de equilibrio y la temperatura de cristalizaci��n. El problema concreto que aborda esta tesis es el estudio de los procesos de ordenamiento de poliolefinas con distinto grado de ramificacion mediante simulaciones num��ricas. Los copolimeros estudiados en esta tesis se consideran materiales modelo de gran homogeneidad molecular desde el punto de vista de la distribuci��n de tama��os y de ramificaciones en la cadena polim��rica. Se eligieron estas poliolefinas debido al gran interes experimental en conocer el cambio en las propiedades fisicas de los materiales dependiendo del tipo y cantidad de comonomero utilizado. Adem��s, son modelos sobre los que existen una ingente cantidad de informaci��n experimental, que es algo que preocupa siempre al crear una realidad virtual como es la simulaci��n. La experiencia en el grupo Biophym es que los resultados de simulaci��n deben de tener siempre un correlato mas o menos pr��ximo experimental y ese argumento se maneja a lo largo de esta memoria. Emp��ricamente, se conoce muy bien que las propiedades f��sicas de las poliolefinas, en suma dependen del tipo y de la cantidad de ramificaciones que presenta el material polim��rico. Sin embargo, tal como se ha explicado no existen modelos te��ricos adecuados que expliquen los mecanismos subyacentes de los efectos de las ramas. La memoria de este trabajo es amplia por la complejidad del tema. Se inicia con una extensa introducci��n sobre los conceptos b��sicos de una macromolecula que son relevantes para entender el contenido del resto de la memoria. Se definen los conceptos de macromolecula flexible, distribuciones y momentos, y su comportamiento en disoluci��n y fundido con los correspondientes parametros caracteristicos. Se pone especial ��nfasis en el concepto de ���entanglement��� o enmaranamiento por considerarse clave a la hora de tratar macromol��culas con una longitud superior a la longitud critica de enmaranamiento. Finaliza esta introducci��n con una rese��a sobre el estado del arte en la simulaci��n de los procesos de cristalizaci��n. En un segundo capitulo del trabajo se expone detalladamente la metodolog��a usada en cada grupo de casos. En el primer capitulo de resultados, se discuten los estudios de simulaci��n en disoluci��n diluida para sistemas lineales y ramificados de cadena ��nica. Este caso mas simple depende claramente del potencial de torsi��n elegido tal como se discute a lo largo del texto. La formaci��n de los n��cleos ���babys��� propuestos por Muthukumar parece que son consecuencia del potencial de torsi��n, ya que este facilita los estados de torsi��n mas estables. As�� que se propone el an��lisis de otros potenciales que son igualmente utilizados y los resultados obtenidos sobre la cristalizaci��n, discutidos en consecuencia. Seguidamente, en un segundo capitulo de resultados se estudian moleculas de alcanos de cadena larga lineales y ramificados en un fundido por simulaciones atomisticas como un modelo de polietileno. Los resultados atomisticos pese a ser de gran detalle no logran captar en su totalidad los efectos experimentales que se observan en los fundidos subenfriados en su etapa previa al estado ordenado. Por esta razon se discuten en los cap��tulos 3 y 4 de resultados sistemas de cadenas cortas y largas utilizando dos modelos de grano grueso (CG-PVA y CG-PE). El modelo CG-PE se desarrollo durante la tesis. El uso de modelos de grano grueso garantiza una mayor eficiencia computacional con respecto a los modelos atom��sticos y son suficientes para mostrar los fen��menos a la escala relevante para la cristalizaci��n. En todos estos estudios mencionados se sigue la evoluci��n de los procesos de ordenamiento y de fusi��n en simulaciones de relajaci��n isoterma y no isoterma. Como resultado de los modelos de simulaci��n, se han evaluado distintas propiedades fisicas como la longitud de segmento ordenado, la cristalinidad, temperaturas de fusion/cristalizacion, etc., lo que permite una comparaci��n con los resultados experimentales. Se demuestra claramente que los sistemas ramificados retrasan y dificultan el orden de la cadena polim��rica y por tanto, las regiones cristalinas ordenadas decrecen al crecer las ramas. Como una conclusi��n general parece mostrarse una tendencia a la formaci��n de estructuras localmente ordenadas que crecen como bloques para completar el espacio de cristalizaci��n que puede alcanzarse a una temperatura y a una escala de tiempo determinada. Finalmente hay que se��alar que los efectos observados, estan en concordancia con otros resultados tanto teoricos/simulacion como experimentales discutidos a lo largo de esta memoria. Su resumen se muestra en un capitulo de conclusiones y l��neas futuras de investigaci��n que se abren como consecuencia de esta memoria. Hay que mencionar que el ritmo de investigaci��n se ha acentuado notablemente en el ultimo ano de trabajo, en parte debido a las ventajas notables obtenidas por el uso de la metodolog��a de grano grueso que pese a ser muy importante para esta memoria no repercute f��cilmente en trabajos publicables. Todo ello justifica que gran parte de los resultados esten en fase de publicaci��n. Abstract ���Polymer crystallization is therefore assumed, and in theories often described, to be a multi step process with many influencing aspects. Because of the chain structure, it is easy to understand that a process which is thermodynamically forced to increase local ordering but is geometrically hindered cannot proceed into a final equilibrium state. As a result, nonequilibrium structures with different characteristics are usually formed, which depend on temperature, pressure, shearing and other parameters���. These words, recently written by Professor Bernhard Wunderlich, one of the most prominent researchers in polymer physics, put somehow in value the "leitmotiv "of this thesis. The crystallization mechanism of polymers is still under debate in the physics community and most of the experimental findings are still explained by invoking the LH theory. This classical theory, which was initially formulated by Lauritzen and Hoffman (LH), is indeed a generalization of the crystallization theory for small molecules from the vapor phase. Even though it describes satisfactorily many experimental observations, it is far from explaining the complex phenomenon of polymer crystallization. This theory was firstly devised in the early 70s at the National Bureau of Standards. It was successively reformulated along the 80s to fit the experimental findings. Thus, the crystallization regime III was introduced into the theory in order to explain the results found in neutron scattering, droplet or quenching experiments. This concept defines the roughness of the crystallization surface leading to the paradigm proposed by Sadler et al. The great success of this theory is the ability to explain the inverse dependence of the molecular folding size on the supercooling, the latter defined as the temperature interval between the equilibrium temperature and the crystallization temperature. The main scope of this thesis is the study of ordering processes in polyolefins with different degree of branching by using computer simulations. The copolymers studied along this work are considered materials of high molecular homogeneity, from the point of view of both size and branching distributions of the polymer chain. These polyolefins were selected due to the great interest to understand their structure��� property relationships. It is important to note that there is a vast amount of experimental data concerning these materials, which is essential to create a virtual reality as is the simulation. The Biophym research group has a wide experience in the correlation between simulation data and experimental results, being this idea highly alive along this work. Empirically, it is well-known that the physical properties of the polyolefins depend on the type and amount of branches presented in the polymeric material. However, there are not suitable models to explain the underlying mechanisms associated to branching. This report is extensive due to the complexity of the topic under study. It begins with a general introduction to the basics concepts of macromolecular physics. This chapter is relevant to understand the content of the present document. Some concepts are defined along this section, among others the flexibility of macromolecules, size distributions and moments, and the behavior in solution and melt along with their corresponding characteristic parameters. Special emphasis is placed on the concept of "entanglement" which is a key item when dealing with macromolecules having a molecular size greater than the critical entanglement length. The introduction finishes with a review of the state of art on the simulation of crystallization processes. The second chapter of the thesis describes, in detail, the computational methodology used in each study. In the first results section, we discuss the simulation studies in dilute solution for linear and short chain branched single chain models. The simplest case is clearly dependent on the selected torsion potential as it is discussed throughout the text. For example, the formation of baby nuclei proposed by Mutukhumar seems to result from the effects of the torsion potential. Thus, we propose the analysis of other torsion potentials that are also used by other research groups. The results obtained on crystallization processes are accordingly discussed. Then, in a second results section, we study linear and branched long-chain alkane molecules in a melt by atomistic simulations as a polyethylene-like model. In spite of the great detail given by atomistic simulations, they are not able to fully capture the experimental facts observed in supercooled melts, in particular the pre-ordered states. For this reason, we discuss short and long chains systems using two coarse-grained models (CG-PVA and CG-PE) in section 3 and 4 of chapter 2. The CG-PE model was developed during the thesis. The use of coarse-grained models ensures greater computational efficiency with respect to atomistic models and is enough to show the relevant scale phenomena for crystallization. In all the analysis we follow the evolution of the ordering and melting processes by both isothermal and non isothermal simulations. During this thesis we have obtained different physical properties such as stem length, crystallinity, melting/crystallization temperatures, and so on. We show that branches in the chains cause a delay in the crystallization and hinder the ordering of the polymer chain. Therefore, crystalline regions decrease in size as branching increases. As a general conclusion, it seems that there is a tendency in the macromolecular systems to form ordered structures, which can grown locally as blocks, occupying the crystallization space at a given temperature and time scale. Finally it should be noted that the observed effects are consistent with both, other theoretical/simulation and experimental results. The summary is provided in the conclusions chapter along with future research lines that open as result of this report. It should be mentioned that the research work has speeded up markedly in the last year, in part because of the remarkable benefits obtained by the use of coarse-grained methodology that despite being very important for this thesis work, is not easily publishable by itself. All this justify that most of the results are still in the publication phase.