.

.

La stéréovision multi-vues consiste à retrouver la forme des objets à partir de plusieurs images prises de différents points de vue connus. Ceci est un problème inverse où on cherche la cause (l'objet) alors qu'on observe l'effet (les images). Sous une optique bayésienne, la solution serait une reconstruction qui reproduise au mieux les images observées tout en restant plausible a priori. Dans cette thèse, nous présentons des modèles et des méthodes permettant de minimiser la différence entre les images observées et les images obtenues par le rendu de la reconstruction. Pour ceci, il est nécessaire de tenir compte des occultations qui on lieu lors du rendu. Le résultat principal de la thése est le calcul de la dérivée de l'erreur de reprojection par rapport aux variations de surface qui tiens en compte les changements de visibilité lors que la surface se déforme.

This thesis presents a series of studies to explore and understand the design of eyes-free interfaces for mobile devices. The motivation is to devise a holistic design concept that is based on the WIMP paradigm and is adapted to the requirements of mobile user interaction. It is proposed that audio is a very efficient and effective modality for use in an eyes-free mobile interface. Methods to transfer the WIMP paradigm to eyes-free interfaces are proposed and evaluated. Guidelines for the implementation of the paradigm are given and – by means of an example – a holistic design concept is proposed. This thesis begins with an introduction to and critical reflection of re- currently important themes and research methods from the disciplines of psychoacoustics, psychology, and presence research. An overview of related work is given, paying particular attention to the use of interface metaphors in mobile eyes-free interfaces. The notion of distance is discussed as a method to prioritise, structure, and manage attention in eyes-free interfaces. Practical issues arising from sources becoming inaudible with increasing distance can be addressed by proposing a method modeled on echo location. This method was compared to verbally coded distance information and proved useful for identifying the closest of several objects, while verbally coded distance infor- mation was found to be more efficient for identifying the precise distance of an object. The knowledge gained from the study can contribute to improv- ing other applications, such as GPS based navigation. Furthermore, the issue of gaining an overview of accessible objects by means of sound was exam- ined. The results showed that a minimum of 200 ms between adjacent sound samples should be adhered to. Based on these findings, both earcons and synthesized speech are recommendable, although speech has the advantage of being more flexible and easier to learn. Monophonic reproduction yields comparable results to spatial reproduction. However, spatial reproduction has the additional benefit of indicating an item’s position. These results are transferable and generally relevant for the use of audio in HCI. Tactile interaction techniques were explored as a means to interact with an auditory interface and were found to be both effective and enjoyable. One of the more general observations was that 2D and 3D gestures were intuitively used by participants, who transferred their knowledge of established gestures to auditory interfaces. It was also found that participants often used 2D ges- tures to select an item and proceeded to manipulate it with a 3D gesture. The results suggest the use of a small gesture set with reversible gestures for do/undo-type actions, which was further explored in a follow up study. It could be shown that simple 3D gestures are a viable way of manipulating spatialized sound sources in a complex 3D auditory display. While the main contribution of this thesis lies in the area of HCI, pre- viously unresearched issues from adjacent disciplines that impact the user experience of auditory interfaces have been addressed. It was found that regular, predictable movement patterns in 3D audio spaces cause symptoms of simulator sickness. However, these were found to be minor and only oc- curred under extreme conditions. Additionally, the influence of the audio reproduction method on the perception of presence, social presence, and realism was examined. It was found that both stereophonic and binaural reproduction have advantages over monophonic sound reproduction: stereo- phonic sound increases the perception of social presence while binaural sound increases the feeling of being present in a virtual environment. The results are important contributions insofar as one of the main applications of mobile devices is voice based communication; it is reasonable to assume that there will be an increase in real-time voice based social and cooperative networking applications. This thesis concludes with a conceptual design of a system called “Foogue”, which uses the results of the previous experiments as the basis of an eyes-free interface that utilizes spatial audio and gesture input.

This item is not the definitive copy. Please use the following citation when referencing this material: Dillon and Vaughan (1997) It's the journey and the destination: Shape and the emergent property of genre in digital documents. New Review of Multimedia and Hypermedia, 3, 91-106. Introduction: To anyone versed in the literature on hypermedia, it is clear that the last 10 yearsâ worth of research on usability since Conklinâ s (1987) seminal article has largely been ignored by web designers. Surfing web sites even casually will likely expose a user to screens of badly formatted text, superfluous graphics, mixed fonts, unreadable color combinations, and dangling or dead links. While the issue of knowledge transfer between research disciplines and design practice is fraught with problems and is a fascinating topic in and of itself (see e.g., Klein and Eason, 1993), this is not the focus of the present paper. Instead we wish to extend work that started with the birth of hypertext systems and continues to demand attention in these days of free-for-all web design: the evaluation of user behaviour in electronic space. Specifically, this paper will extend the analysis of â user navigationâ to the evaluation of user behaviour in web environments.

No description available.

Webcasts are an emerging technology enabled by the expanding availability and capacity of the World Wide Web. This has led to an increase in the number of lectures and academic presentations being broadcast over the Internet. Ideally, repositories of such webcasts would be used in the same manner as libraries: users could search for, retrieve, or browse through textual information. However, one major obstacle prevents webcast archives from becoming the digital equivalent of traditional libraries: information is mainly transmitted and stored in spoken form. Despite voice being currently present in all webcasts, users do not benefit from it beyond simple playback. My goal has been to exploit this information-rich resource and improve webcast users' experience in browsing and searching for specific information. I achieve this by combining research in Human-Computer Interaction and Automatic Speech Recognition that would ultimately see text transcripts of lectures being integrated into webcast archives. In this dissertation, I show that the usefulness of automatically-generated transcripts of webcast lectures can be improved by speech recognition techniques specifically addressed at increasing the accuracy of webcast transcriptions, and the development of an interactive collaborative interface that facilitates users' contributions to machine-generated transcripts. I first investigate the user needs for transcription accuracy in webcast archives and show that users' performance and transcript quality perception is affected by the Word Error Rate (WER). A WER equal to or less than 25% is acceptable for use in webcast archives. As current Automatic Speech Recognition (ASR) systems can only deliver, in realistic lecture conditions, WERs of around 45-50%, I propose and evaluate a webcast system extension that engages users to collaborate in a wiki manner on editing imperfect ASR transcripts. My research on ASR focuses on reducing the WER for lectures by making use of available external knowledge sources, such as documents on the World Wide Web and lecture slides, to better model the conversational and the topic-specific styles of lectures. I show that this approach results in relative WER reductions of 11%. Further ASR improvements are proposed that combine the research on language modelling with aspects of collaborative transcript editing. Extracting information about the most frequent ASR errors from user-edited partial transcripts, and attempting to correct such errors when they occur in the remaining transcripts, can lead to an additional 10 to 18% relative reduction in lecture WER.

With the increasing demand for online learning, well-designed computer online learning resources are indispensable. User interfaces evaluation has become a critical quality attribute of interactive software intended to meet the requirements of the user groups. It is this aspect of adaptations that make them critical for the study of evaluation of user interfaces. This study describes a preliminary evaluation of the user interface design of a new online learning resource (Open Learning System). The main objectives of the study are to investigate the effect of the interaction on the user (usability, efficiency, effectiveness and satisfaction), to assess the extent of the system (resource) functionality and to identify specific problems in the design (aspects of design that cause unexpected results or confusion). This will form part of iterative design and testing process of the new interface, which seeks to evaluate the success of the interface within the framework of the fundamental HCI principles under guidelines of the constructivists learning approach. The Open Learning System (OLS) is grounded on the constructivist-based learning approach. The underlying philosophy of the system assumes when learners are engaged in a social learning context, they actively construct knowledge, therefore the resource is considered as a tool to support learning and not an end in itself. By so doing it is geared to provide greater access to information, support Computer-Mediated Communication (CMC) using tools such as e-mail, chat and discussion foruI? and creating context for learners' work and peer review. A theoretical framework for evaluating the OLS was developed and proposed which comprised of the constructivist epistemology, Rich Environment for Active Learning (REAL), the User Centred Design (UCD) approach and the Human Computer Interface (HCI) design principles. This integrated theoretical framework has been referred to as 'Designing-by-Constructivism' model. The study investigates the use of the OLS by two sets of users: staff members (module creators) and learners (module consumers). In view of the fact that the data collected is qualitative, the approach assumes the use of semi-structured questionnaires, evaluation matrix and interviews. The information/feedback gathered will assist the developers to do preliminary reviews. The study will also be useful to academics pursuing more HCI issues or those with an interest in developing learning resources. The main elements of the 'Designing-by-Constructivism' model were present in the resource. The results analysis indicates that the resource supports collaborative learning and the use of authentic activities in learning. This serves as an intrinsic motivation to most of the users. The results also show a high degree of user satisfaction and appreciation of OLS resource. Largely, the participants are satisfied that the overall OLS design met their needs. The major contribution being, "OLS is interactive and user friendly". However, some users have expressed the desire to have more tools incorporated into the resource, while others have expressed concern about difficulties in logging into the system. / Thesis (M.Sc.)-University of Natal, Durban, 2003.

At large sporting events (LSEs), e.g. football matches and athletics events, the user experience has been shown to be highly variable (Nilsson, 2004; Nilsson et al. 2004). Reported problems include a lack of social interaction with fellow spectators, and insufficient relevant information on the events or the sporting action taking place (Nilsson, 2004; Nilsson et al. 2004; Esbjornsson et al. 2006; Jacucci et al. 2005). A possible solution is personalisation, making the mobile application adapt to the user, ensuring that only relevant information is retrieved and presented in a way that is suitable. This thesis is devoted to studying the user experience related to mobile personalization at LSEs. It aims to investigate how personalized mobile applications at LSEs can render the user experience more active and engaging in a contextually, socially and culturally relevant way. The thesis reviews different theoretical approaches to help to understand the concepts of interest e.g. personalization and user experience (Chapter 2). Research methods are also discussed including the challenge of adapting user-centred methods into the Chinese culture (Chapter 3). This thesis investigates the user experience of mobile personalization at LSEs by following the circle of user-centred research: It starts to consider user requirements and user experience at LSEs and derives the usage patterns that personalized mobile applications could usefully support (Chapter 4). Then it explores the relevant contextual factors at LSEs which could be used to prescribe the behaviour of a personalizable mobile application (Chapter 5). Next, it describes the user-centred process used to design personalizable interfaces for mobile applications used at LSEs. Four key elements of design are considered: content, conceptual, interaction and presentation design (Chapter 6). The final outputs of the design process were two personalized mobile prototypes for Chinese users at LSEs. These included versions based on either (1) user-initiated or (2) system-initiated personalisation. Finally it investigates the impact on user experience of mobile personalization at LSEs in two empirical studies (a field experiment and a lab-based experiment) with these prototypes (Chapters 7 and 8). Mobile personalization is shown to result in an enriched user experience across a range of activities that a spectator would undertake at a large sporting event. The thesis discusses primarily the effective design of mobile personalization, the design implications at LSEs, user experience design, and research methods for Chinese users (Chapter 9). In conclusion (Chapter 10), specific contributions and avenues for future work are highlighted.

Despite two decades of empirical studies focusing on programmers and the problems with programming, usability of textual programming languages is still hard to achieve. Its younger relation, visual programming languages (VPLs) also share the same problem of poor usability. This research explores and investigates the usability issues relating to VPLs in order to suggest a set of design principles that emphasise usability. The approach adopted focuses on issues arising from the interaction and communication between the human (programmers), the computer (user interface), and the program. Being exploratory in nature, this PhD reviews the literature as a starting point for stimulating and developing research questions and hypotheses that experimental studies were conducted to investigate. However, the literature alone cannot provide a fully comprehensive list of possible usability problems in VPLs so that design principles can be confidently recommended. A commercial VPL was, therefore, holistically evaluated and a comprehensive list of usability problems was obtained from the research. Six empirical studies employing both quantitative and qualitative methodology were undertaken as dictated by the nature of the research. Five of these were controlled experiments and one was qualitative-naturalistic. The experiments studied the effect of a programming paradigm and of representation of program flow on novices' performances. The results indicated superiority of control-flow programs in relation to data-flow programs; a control-flow preference among novices; and in addition that directional representation does not affect performance while traversal direction does - due to cognitive demands imposed upon programmers. Results of the qualitative study included a list of 145 usability problems and these were further categorised into ten problem areas. These findings were integrated with other analytical work based upon the review of the literature in a structured fashion to form a checklist and a set of design principles for VPLs that are empirically grounded and evaluated against existing research in the literature. Furthermore, an extended framework for Cognitive Dimensions of Notations is also discussed and proposed as an evaluation method for diagrammatic VPLs on the basis of the qualitative study. The above consists of the major findings and deliverables of this research. Nevertheless, there are several other findings identified on the basis of the substantial amount of data obtained in the series of experiments carried out, which have made a novel contribution to knowledge in the fields of Human-Computer Interaction, Psychology of Programming, and Visual Programming Languages.