No-vision walking is supported in the central nervous system (CNS) by a spatial updating process. This process involves the iterative updating of a mental representation of the environment using estimates of distance traveled gleaned from locomotive kinematic activity. An effective means of examining the online regulation of this process is a continuous pointing task, which requires performers to walk along a straight-line forward trajectory while keeping their right arm straight and index finger fixated on a stationary ground-level target beside the walking path. In the current thesis, no-vision continuous pointing was examined in typically calibrated and recalibrated perceptual-motor states. Shoulder and trunk joint angles provided the basis for perceptual measures that reflected spatial updating performance and kinematic measures that reflected its underlying CNS online regulation. In the typically calibrated conditions, no-vision walking demonstrated a slight perceptual underestimation of distance traveled (Study 1). In the recalibrated conditions, no-vision walking demonstrated: a) perceptual underestimation and overestimation following adaptation periods involving walking with low and high visual gains, respectively (Study 2); and b) partial recalibration following exposures to vision and arm gains (Study 3). The latter was suggested as being impacted by task specific changes in CNS multisensory integration resulting from the development of a robust task prior and/or the altering of sensory cue weights. Importantly, this thesis used a novel trajectory parsing procedure to quantify discrete CNS perceptual updating units in the shoulder plane of elevation trajectory. The starts and ends of these updating units were consistently timed to the late left-to-early right foot swing phase of the step-cycle, regardless of perceptual-motor state. This was suggested to reflect perceptual units that were purposely timed, but indirectly mapped, to this kinematic event. The perceptual differences in Studies 1 and 2 were at least partially reflected in these units. / Thesis / Doctor of Philosophy (PhD) / It is well understood that humans can effectively walk without vision to environmental locations up to 15 metres away. However, less is known about how these walking movements are controlled during the course of forward progression. This thesis fills this knowledge gap using a task that requires participants to walk forward along a straight path while keeping their right index finger pointed toward a ground-level target beside the walking path. The patterns of arm movements performed during this task are indicative of the control strategies used by the performer to mentally update their positions in space. One of the key contributions of this work is showing that humans perform this mental updating in a repetitive manner, and that these repetitions are consistently linked to early forward movements of the right leg. This pattern is maintained when walking without vision is performed in a variety of different contexts.

Distal pointing is the interaction style defined by directly pointing at targets from a distance. It follows a laser pointer metaphor and the position of the cursor is determined by the intersection of a vector extending the pointing device with the display surface. Distal pointing as a basic interaction style poses several challenges for the user, mainly because of the lack of precision humans have when using it. The focus of this thesis is to understand and improve distal pointing, making it a viable interaction metaphor to be used in a wide variety of applications. We achieve this by proposing and validating a predictive model of distal pointing that is inspired by Fitts' law, but which contains some unique features. The difficulty of a distal pointing task is best described by the angular size of the target and the angular distance that the cursor needs to go across to reach the target from the input device perspective. The practical impact of this is that the user's relative position to the target should be taken into account. Based on the model we derived, we proposed a set of design guidelines for high-precision distal pointing techniques. The main guideline from the model is that increasing the target size is much more important than reducing the distance to the target. In order to improve distal pointing, we followed the model guidelines and designed interaction techniques that aim at improving the precision of distal pointing tasks. Absolute and Relative Mapping (ARM) distal pointing increases precision by offering the user a toggle which changes the control/display (CD) ratio such that a large movement of the input device is mapped to a small movement of the cursor. Dynamic Control Display Ratio (DyCoDiR) automatically increases distal pointing precision, as the user needs it. DyCoDiR takes into account the user distance to the interaction area and the speed at which the user moves the input device to dynamically calculate an increased CD ratio, making the action more precise the steadier the user tries to be. We performed an evaluation of ARM and DyCoDiR comparing them to basic distal pointing in a realistic context. In this experiment, we also provided variations of the techniques which increased the visual perception of targets through zooming in the area around the cursor when precision was needed. Results from the study show that ARM and DyCoDiR are significantly faster and more accurate than basic distal pointing with tasks that require very high precision. We analyzed user navigation strategies and found that the high precision techniques afford users to remain stationary while performing interactions. However, we also found that individual differences have a strong impact on the decision to walk or not, and that, sometimes, is more important than the technique affordance. We provided a validation for the distal pointing model through the analysis of expected difficulty of distal pointing tasks in light of each technique tested. We propose selection by progressive refinement, a new design concept for distal pointing selection techniques, whose goal is to offer the ability to achieve near perfect accuracy in selection at very cluttered environments. The idea of selection by progressive refinement is to gradually eliminate possible targets from the set of selectable objects until only one object is available for selection. We implemented SQUAD, a selection by progressive refinement distal pointing technique, and performed a controlled experiment comparing it to basic distal pointing. We found that there is a clear tradeoff between immediate selections that require high precision and selections by progressive refinement which always require low precision. We validated the model by fitting the distal pointing data and proposed a new model, which has a linear growth in time, for SQUAD selection. / Ph. D.

Yes / Computer simulation is a powerful and convenient tool for the design and performance evaluation of free-space optical (FSO) communication systems. In this article, we present two simulation frameworks that incorporate not only the effects of atmospheric turbulence but also the impact of the angular fluctuations of the transmitter and receiver in FSO systems. In the first framework, the waveform of the optical signal is calculated sequentially from the transmitter to the receiver. Thus, it takes very long to run the simulation numerous times to obtain the statistical performance of the system. This is because the vast majority of simulation time is spent on the split-step beam propagation. In the second framework, we propose to isolate the beam propagation through atmospheric channel from the other effects. We compare the two frameworks in terms of accuracy and simulation time. We show that the second framework reduces the simulation time by more than a factor of 10 without sacrificing the accuracy under various conditions. / 10.13039/501100003725-National Research Foundation of Korea HR&D Center Funded by the Ministry of Science and ICT (Grant Number: 2022M1A3C2069728)

Der Einsatz großer, vertikaler Displays nimmt sowohl in Bereichen der Forschung als auch der Wirtschaft zu. Diese Displays eignen sich durch ihre Größe und Auflösung unter anderem für die Informationsvisualisierung. Es gibt bereits eine Menge von Forschungsarbeiten, welche die Interaktion mit großen, vertikalen Displays untersucht hat. Jedoch ist speziell die Bedienung Magischer Linsen auf großen Displaywänden weitgehend unbeachtet geblieben. Eine intuitive Interaktion mit Magischen Linsen auf einer Displaywand kann jedoch insbesondere in kollaborativen Szenarien große Vorteile bieten. Smartphones eignen sich durch ihre Portabilität zur Interaktion mit Displaywänden. Unter Verwendung von Mobilgeräten und einer hochauflösenden Displaywand wurden im Rahmen der vorliegenden Arbeit Interaktionskonzepte zur Steuerung und Parametrisierung Magischer Linsen entwickelt. Hierzu wurde eine Recherche des aktuellen Forschungsstandes betrieben und Anwendungsfälle für den Einsatz der Konzepte aufgestellt. Es wurde eine große Bandbreite von Interaktionskonzepten entwickelt, welche von lockeren bis zu fokussierten Interaktionen reichen. Für die Bedienung der Magischen Linsen wurden verschiedene Aktionen identifiziert, welche in einem Interaktionsablauf auftreten und durch die Konzepte zu unterstützen sind. Ein Teil der entwickelten Interaktionskonzepte wurde durch einen Prototypen implementiert und anhand von Beispieldatensätzen getestet. / The usage of large, vertical displays is increasing in felds of research as well as in the economy. Because of their size and resolution these displays are well suited for information visualization. There already are a number of publications which examine the interaction with large, vertical displays. Yet especially the operation of magic lenses on large display walls has been mostly ignored. An intuitive interaction with magic lenses on a large display may be espesially advantageous in collaborative scenarios. Smartphones are suited for interaction with display walls because of their portability. In this paper interaction concepts for operating and parametrizing magic lenses have been developed using mobile devices and a high resolution display wall. For this purpose the current state of research has been investigated and application scenarios for the use of the concepts have been constructed. A big amount of interaction concepts have been developed which range from casual to focused interactions. For the operation of magic lenses several actions have been identifed which occur in an interaction process and have to be adsressed by the concepts. Part of the developed interaction concepts have been implemented by a prototype and tested with sample data sets.

Der Einsatz großer, vertikaler Displays nimmt sowohl in Bereichen der Forschung als auch der Wirtschaft zu. Diese Displays eignen sich durch ihre Größe und Auflösung unter anderem für die Informationsvisualisierung. Es gibt bereits eine Menge von Forschungsarbeiten, welche die Interaktion mit großen, vertikalen Displays untersucht hat. Jedoch ist speziell die Bedienung Magischer Linsen auf großen Displaywänden weitgehend unbeachtet geblieben. Eine intuitive Interaktion mit Magischen Linsen auf einer Displaywand kann jedoch insbesondere in kollaborativen Szenarien große Vorteile bieten. Smartphones eignen sich durch ihre Portabilität zur Interaktion mit Displaywänden. Unter Verwendung von Mobilgeräten und einer hochauflösenden Displaywand wurden im Rahmen der vorliegenden Arbeit Interaktionskonzepte zur Steuerung und Parametrisierung Magischer Linsen entwickelt. Hierzu wurde eine Recherche des aktuellen Forschungsstandes betrieben und Anwendungsfälle für den Einsatz der Konzepte aufgestellt. Es wurde eine große Bandbreite von Interaktionskonzepten entwickelt, welche von lockeren bis zu fokussierten Interaktionen reichen. Für die Bedienung der Magischen Linsen wurden verschiedene Aktionen identifiziert, welche in einem Interaktionsablauf auftreten und durch die Konzepte zu unterstützen sind. Ein Teil der entwickelten Interaktionskonzepte wurde durch einen Prototypen implementiert und anhand von Beispieldatensätzen getestet. / The usage of large, vertical displays is increasing in felds of research as well as in the economy. Because of their size and resolution these displays are well suited for information visualization. There already are a number of publications which examine the interaction with large, vertical displays. Yet especially the operation of magic lenses on large display walls has been mostly ignored. An intuitive interaction with magic lenses on a large display may be espesially advantageous in collaborative scenarios. Smartphones are suited for interaction with display walls because of their portability. In this paper interaction concepts for operating and parametrizing magic lenses have been developed using mobile devices and a high resolution display wall. For this purpose the current state of research has been investigated and application scenarios for the use of the concepts have been constructed. A big amount of interaction concepts have been developed which range from casual to focused interactions. For the operation of magic lenses several actions have been identifed which occur in an interaction process and have to be adsressed by the concepts. Part of the developed interaction concepts have been implemented by a prototype and tested with sample data sets.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2005. / In this thesis, the maneuvering and orientation of an inspection/service satellite is investigated. This thesis will demonstrate a simplified satellite maneuver around another satellite (for docking purposes). This is illustrated with a cart on an air bearing table (frictionless environment) which simplifies the problem to two dimensions. A mathematical model of the system was designed and simulated (Matlab) for this maneuver. With the simulation, different strategies were considered to maneuver the cart in a circle around another object. The conclusion was made that approximating the circle with segments would conserve propellant. This strategy was implemented on the air bearing table.

This work deals with provisioning of communication services via satellites for collectively mobile user groups in a heterogeneous network with several radio access technologies. The extended use of personalised user equipment beyond the coverage of one single terrestrial network by means of a satellite transport link, represents an increasingly important trend in mobile satellite communication. This trend is confirmed by the commercial introduction of broadband satellite communication to mobile terminals mounted on vehicles, trains, ships or aircraft. This work provides a consequent and structured approach for provisioning of services to broadband satellite terminals for mobile user groups and addresses: -- a systematic satellite communication system design process for collective mobile terminals; -- mobile satellite modelling at a wide range of frequencies, including current and potential frequencies; -- an optimised Pointing Acquisition and Tracking (PAT) system design including characterisation of moments for vehicle types of all mobile scenarios; -- a general hierarchical multi-service dimensioning methodology for collectively mobile user groups, including voice, data, and multimedia services; -- an aeronautical system dimensioning scheme with (capacity and handover) requirements analysis and evaluation of results for different satellite scenarios.

No description available.

[pt] Os satélites de um sistema de comunicações que opera numa determinada faixa de frequências utilizando satélites não-geoestacionários podem sofrer interferências indesejáveis provocadas por transmissores do Serviço Fixo Terrestre (SF) que operam nessa mesma faixa. Para o operador do sistema não geoestacionário é importante identificar quais as áreas da superfície da Terra que contêm os transmissores responsáveis por essas interferências indesejáveis, o que seria um primeiro passo na tentativa de resolver o problema através de negociações bilaterais com as estações transmissoras do SF envolvidas (coordenação). O presente trabalho apresenta a modelagem matemática do problema, e propõe que a identificação dessas áreas seja feita por meio da estimação das potências e apontamentos (ângulos de azimute e elevação) das antenas transmissoras do SF com base em medidas de potência tomadas nos diversos feixes de recepção de um satélite de teste. O trabalho analisa aspectos específicos do problema e propõe a utilização do Filtro de Kalman Estendido (EKF) para a estimação das potências e apontamentos das antenas transmissoras do SF. / [en] Satellites of a non-geostationary communication system may be victims of harmful interference produced by terrestrial fixed service (FS) transmitting stations operating in the same frequency band. It is important to the satellite system operator to identify the specific areas on Earth s surface containing the FS stations that are responsible for such interference. This would be a first step for solving the problem via bilateral coordination with each of the involved FS operators. This dissertation presents a mathematical model for the problem and proposes that the identification of these areas be made though the estimation of the transmitted power and the antenna pointing (azimuth and elevation angles) of the various FS stations, based on received power measurements taken on the beams of a test non-GSO satellite. This work also investigates the particular aspects of the problem and proposes the Extended Kalman Filter (EKF) as the algorithm for estimation.

While shopping in a retail store today the customers are often interacting with multiple sale channels when making a purchase. These channels can include in‑store terminals, the customers’ smartphone etc. This thesis looks at how physical mobile interaction can be implemented to enhance the experience when using different channels for a purchase. Physical mobile interaction is a way for a user to interact with real world objects using a mobile device. This thesis examines how some of these techniques can be used in a retail store using the customers’ own smartphone device. With todays smartphone market with several different operating systems available it is important to find find an implementation which suits the majority of the users. This paper details which technologies that are available to implement the physical mobile interaction on the major smartphone platforms. It also discusses important design decisions for it to work on these platforms. The paper concludes that it is possible to implement these techniques on todays major smartphone platforms. It also concludes that the best technology can not always be used because of limitations on one or more platforms.