No description available.

No description available.

Yes / The goal of this study was to investigate the reference frames used in perceptual encoding and storage of visual motion information. In our experiments, observers viewed multiple moving objects and reported the direction of motion of a randomly selected item. Using a vector-decomposition technique, we computed performance during smooth pursuit with respect to a spatiotopic (nonretinotopic) and to a retinotopic component and compared them with performance during fixation, which served as the baseline. For the stimulus encoding stage, which precedes memory, we found that the reference frame depends on the stimulus set size. For a single moving target, the spatiotopic reference frame had the most significant contribution with some additional contribution from the retinotopic reference frame. When the number of items increased (Set Sizes 3 to 7), the spatiotopic reference frame was able to account for the performance. Finally, when the number of items became larger than 7, the distinction between reference frames vanished. We interpret this finding as a switch to a more abstract nonmetric encoding of motion direction. We found that the retinotopic reference frame was not used in memory. Taken together with other studies, our results suggest that, whereas a retinotopic reference frame may be employed for controlling eye movements, perception and memory use primarily nonretinotopic reference frames. Furthermore, the use of nonretinotopic reference frames appears to be capacity limited. In the case of complex stimuli, the visual system may use perceptual grouping in order to simplify the complexity of stimuli or resort to a nonmetric abstract coding of motion information.

The quality of hatchery conditions significantly impacts the hatchling health. An insight into the spatiotemporal distribution of environmental factors like temperature, ventilation, humidity, and CO2 within an incubator can be the key to reduce the pathogen spread. The objective of this study is to develop an efficient computational fluid dynamics model to predict thermo-fluid and scalar transport over an incubation period using high performance computing systems. Various modeling approaches for grid generation, inflow conditions, fan and heater modeling, and scalar transport are evaluated to identify cost effective numerical models and allow long time simulations with reliable data. The model is validated using in-house experimental measurements, showing reasonable agreement in predicting environmental conditions. Parametric studies explore the effects of fan speed and rotation direction on moisture and CO2 accumulation. Particle transport simulations provide insights into potential pathogen spread. This research demonstrates CFD's potential to provide a better understanding of complex biological systems by offering detailed understanding of spatiotemporal gradients within an incubator.

Die Verknüpfung von geodätischen Raumtechniken wie GNSS, DORIS, SLR oder VLBI zur Ableitung eines geodätischen Referenzrahmens wie dem ITRF gelingt erst durch sogenannte Kolokationsstationen. Die geometrischen Beziehungen zwischen den betriebenen Raumtechniken sind dabei aus präzisen lokalen Vermessungen abzuleiten. Es wird ein Konzept zur automatisierten Bestimmung des IVS-Referenzpunktes am TWIN Radioteleskop Wettzell vorgestellt. Erste Untersuchungsergebnisse werden präsentiert.

Le modèle de nutation de référence (MHB2000) et le repère céleste international (ICRF2) ont été établis en 2000 et en 2009 respectivement. Les observations VLBI s’étant accumulées depuis, ce sont autant de nouvelles données permettant d’affiner la nutation et de mieux caractériser l’instabilité des radiosources constituant le repère céleste. L’allongement des données disponibles révèle des défauts dans la nutation de référence comme des fluctuations dans la position des radiosources. Il importe donc de réajuster les termes de nutation, tout en évaluant l’impact de l’instabilité du repère de référence céleste sur celle-ci. Dans un premier temps, nous déterminons des corrections significatives des termes de nutation du modèle MHB2000 jusqu'à 50 micro-seconde d'arc sur la base des séries opérationnelles de l'IVS. Nous en évaluons aussi l'incertitude. Notre intérêt s’est focalisé sur la nutation libre du noyau et un terme spectralement proche, le terme annuel rétrograde. Nous tentons de caractériser leur variabilité multi-annuelle, en amplitude, phase et fréquence, malgré la corrélation qui les affecte.Dans un second temps, nous avons étudié la stabilité du repère céleste par une étude approfondie des sources susceptibles de définir ce repère. De telles sources sont sélectionnées par analyse de variance d'Allan de leurs déplacements astrométriques. Cette analyse donne la « couleur » du bruit aléatoire qui affecte leurs positions en fonction des différentes échelles de temps correspondant à 30 ans d’observations VLBI. Plus précisément, nous sélectionnons les radiosources présentant un bruit blanc. Il en résulte que sur 123 sources parmi celles choisies pour l'ICRF2 en 2009, seules 40 respectent ce critère de stabilité sur la période 1985-2016. Ce nombre est insuffisant pour construire un repère céleste stable et des compromis sont nécessaires. Enfin, la propagation des erreurs des positions des radiosources sur la nutation a été caractérisée, expliquant le bruit anormalement grands de certaines séries de nutation diffusées par l'IVS. / The reference nutation model (MHB2000) and the International Celestial Reference Frame (ICRF2) was established in 2000 and 2009 respectively. VLBI observations are being accumulated since and these are all new data to refine the nutation and better characterize the instability of radio sources constituting the celestial frame. The lengthening of the available data reveals defects in the reference wobble and fluctuations in the position of radio sources.It is important to adjust the nutation terms while assessing the impact of the instability of the celestial reference frame on it. Initially, we obtain significant corrections in terms of nutation model MHB2000 up to 50 micro-seconds of degree on the basis of IVS operational nutation time series. We also evaluate their uncertainty. Our interest is focused on the the free core nutation and a term closed in frequency, the retrograde annual term. We try to characterize the multi-annual variability, on amplitude, phase and period, despite correlation that affects both terms.Secondly, we study the stability of the celestial reference frame by a comprehensive study of the potential sources to define the frame. Such defining sources are selected by analysis using Allan variance of their astrometric displacements. This analysis gives the "color" of the random noise that affects positions based on different time scales corresponding to 30 years of VLBI observations. Specifically, we select radio sources with white noise. It follows that on 123 sources from those chosen for ICRF2 in 2009, only 40 meet this criterion of stability over the period 1985-2016. This number is too small to build a new celestial reference frame and compromises are necessary. Finally, errors propagation of radio position on nutation has been characterized, explaining the noise unusually large of some nutation time series diffused by the IVS.

The motivation for this thesis was the need for further development of multibody dynamics simulation packages focused on detailed contact analysis. The thesis makes contributions in three different areas: Part I summarizes the equations, algorithms and design decisions necessary for dynamics simulation of flexible bodies with moving contacts. The assumed general shape function approach is presented. Additionally, the described technique enables studies of the residual stress release during grinding of flexible bodies. The proposed set of mode shapes was also successfully applied for modeling of heat flow. Part II is motivated by the need to reduce the computation time. The availability of the new cost-efficient multiprocessor computers triggered the development of the presented hybrid parallelization framework. The framework is designed to be easily portable and can be implemented without any system level coding or compiler modifications. Part III is motivated by the need for inter-operation with other simulation tools. A co-simulation framework based on the Transmission Line Modeling (TLM) technology was developed. The framework enables integration of several different simulation components into a single time-domain simulation. The framework has been used for connecting MSC.ADAMS and SKF BEAST simulation models. Throughout the thesis the approach was to present a practitioner roadmap. The detailed description of the theoretical results relevant for a real software implementation is put in focus. The software design decisions are discussed and the results of real industrial simulations are presented. This work has been supported by SKF, SSF/ProViking, ECSEL, KK-stiftelsen.

Les transferts de technologie sont des contrats de vente de grands systèmes (transport, énergie, défense) qui rassemblent de la fourniture de biens matériels et un ensemble de biens immatériels que sont la documentation, l'assistance technique et la formation. Cette dernière occupe aujourd'hui une place centrale dans ces grands contrats et les ingénieurs des grandes entreprises en charge de ces transferts deviennent formateurs. Dans le cadre de cette activité de formation, la vente de technologie s'accompagne de différentes tensions dont nous faisons l'hypothèse qu'ils se cristallisent sous forme de dilemmes d'activités. D'abord, un dilemme industriel opposant les logiques de vente de la technologie à celles de protection de la technologie. Ensuite un dilemme professionnel confrontant la fonction de formateur avec celle d'ingénieur. Pour faire face à cette situation les ingénieurs construisent un sens différent dans la finalité de leur action. A partir des entretiens réalisés, différentes constructions de sens apparaissent et montrent une grande hétérogénéité dans les réponses des ingénieurs face à cette mission de formation occasionnelle. Ces réponses conduisent vers des redéfinitions individuelles des buts et objectifs de la formation, et in fine des contrats de transferts de technologie. La formation à la construction d'un ethos de formateur occasionnel dans le cadre des transferts de technologie constitue ici une réflexion originale sur une activité peu étudiée et en plein développement. / Technology transfers are contracts related to the sale of large, complex systems (in the fields of transport, energy-supply, defence, etc.) that combine the delivery of material goods and a variety of immaterial products such as documentation, technical assistance and training. Training nowadays is a key feature in such high-end contracts and the engineers in charge of these transfers in large companies are becoming trainers. However, the sale of technology comes with various tensions that develop into dilemmas for the trainer. On the one hand, an industrial dilemma arises from the opposition between the sale of technology and the protection of that same technology. On the other hand, a professional dilemma results from the clash between two functions: that of the trainer and that of the engineer.To overcome these difficulties, engineers construct a meaning of their own, in line with the perceived purpose of their action. Based on the interviews conducted, different constructions of meaning are identified and show significant heterogeneity in the responses of the engineers faced with this occasional training mission. These responses lead to individual redefinitions of the aims of the training scheme, as well as of the technology transfer contracts. Providing guidance in the construction of an ethos of the occasional trainer in the domain of technology transfers provides the opportunity for an original exploration of an activity that is only starting to attract the academic attention it deserves.

Les estimations des mouvements de soi provenant des signaux vestibulaires contribuent à la planification et l’exécution des mouvements volontaires du bras lorsque le corps se déplace. Cependant, comme les senseurs vestibulaires sont fixés à la tête alors que le bras est fixé au corps, les signaux vestibulaires doivent être transformés d’un système de référence centré sur la tête à un système centré sur le corps pour pouvoir contribuer de façon appropriée au contrôle moteur du bras. Le but premier de ce travail était d’étudier l’évidence d’une telle transformation. La stimulation galvanique vestibulaire (SGV) a été utilisée pour activer les afférences vestibulaires et simuler une rotation autour d’un axe naso-occipital fixe pendant que des sujets humains faisaient des mouvements du bras dans le plan horizontal, avec la tête dans différentes orientations. Une transformation des signaux vestibulaires implique que la SVG devrait simuler une rotation autour d’un axe horizontal lorsque la tête est droite et autour d’un axe vertical lorsque la tête est en flexion antérieure. La SGV devrait ainsi perturber les mouvements du bras en fonction de l’orientation de la tête. Nos résultats démontrent que les signaux vestibulaires contribuant aux mouvements d’atteinte sont effectivement transformés en un système de référence centrée sur le corps. Le deuxième but de ce travail était d’explorer les mécanismes utilisant ces signaux vestibulaires transformés. En comparant les effets de la SGV appliquée avant ou pendant les mouvements d’atteinte nous avons montré que les signaux vestibulaires transformés contribuent à des mécanismes de compensation distincts durant la planification des mouvements d’atteinte comparativement à l’exécution. / Vestibular signals provide self-motion estimates that contribute to the planning and execution of voluntary reaching movements during body motion. However, because the vestibular sensors are fixed in the head whereas the arm is fixed to the trunk vestibular signals must be transformed from a head-centered to a body-centered reference frame to contribute appropriately to limb motor control. The first goal of the current work was to investigate the evidence for such a transformation. To do so we used galvanic vestibular stimulation (GVS) to selectively activate vestibular afferents and simulate rotation about a fixed roughly naso-occipital axis as human subjects performed reaching movements with the head in different orientations. If vestibular signals that contribute to reaching are transformed to body-centered coordinates, then with the head upright GVS should simulate mainly tilt about an earth-horizontal axis (roll), whereas with the head pitched forward the same stimulus should simulate rotation about an earth-vertical axis (yaw). We therefore predicted that GVS should perturb horizontal-plane reach trajectories in a head-orientation dependent manner. Our results demonstrate that vestibular signals which contribute to reaching are indeed transformed to a body-centered reference frame. The second goal of this work was to explore the mechanisms that use these transformed vestibular signals. By comparing the effect of GVS applied during versus prior to reaching we also provide evidence that transformed vestibular signals contribute to distinct compensation mechanisms for body motion during reach planning versus execution.

This master thesis presents an overview of psychological and neurological the- ories and research of human navigation, how it works, what systems it con- sists of and what external information it requires to operate. I present several experiments administered in virtual environment which tested the process of accessing two discrete spatial reference frames: allocentric landmark-centred and object-centred. The research tries to answer whether these reference frames interface during the learning phase and whether their access is sim- ultaneous or sequential. Data from my experiment are partially concordant with previous research and imply that the two representations exist inde- pendent of each other. Subjects tend to manifest longer reaction times during the spatial task when they need to change the reference frames in order to provide a correct answer. But the data also suggest that the switch from the object-centred reference frame does not occur prior to the task itself, which is conflicting with previous studies. Possible explanations are discussed. keywords: human navigation, switching, environmental representations, object- centred reference frame, virtual reality 1