| 1. |
- Stenlund, Jörgen, 1959-
(författare)
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Travelling through time : Students’ interpretation of evolutionary time in dynamic visualizations
- 2019
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Evolutionary knowledge is important to understand and address contemporary challenges such as loss of biodiversity, climate change and antibiotic resistance. An important aspect that is considered to be a threshold concept in teaching and learning about evolution is the time it involves. The history of evolution comprises several scales of magnitude, some of which are far from direct human experience and therefore difficult to understand. One way of addressing this issue is to use dynamic visualizations that represent time, for example, to facilitate teaching and learning about evolution.This thesis investigates how students’ comprehension of evolution and evolutionary time can be facilitated by visualizations in educational settings. Two different dynamic visualizations were investigated. In paper I different temporal versions of a spatio-temporal animation depicting hominin evolution were explored. The temporal information was expressed as one or several timelines along which an animated cursor moved, indicating the rate of time. Two variables, the number of timelines with different scales, and the mode of the default animated time rate (either constant throughout the animation or decreasing as the animation progressed), were combined to give four different time representations. The temporal aspects investigated were undergraduate students' ability to find events at specific times, comprehend order, comprehend concurrent events, comprehend the length of time intervals, and their ability to compare the lengths of time intervals.In paper II, perceptions and comprehension of temporal aspects in an interactive, multi-touch tabletop application, DeepTree, were investigated. This application depicts the tree of life. The focus was on the interactive aspects, especially how the zooming feature was perceived, but also on any misinterpretations associated with the interaction. The same temporal aspects listed for paper I were also implicitly investigated.The findings indicate that handling the problem of large differences in scale by altering the rate of time in the visualization can facilitate perception of certain temporal aspects while, at the same time, can hinder a correct comprehension of other temporal aspects. Findings concerning DeepTree indicate that the level of interactions varies among users, and that the zooming feature is perceived in two ways, either as a movement in time or as a movement in the metaphorical tree. Several misinterpretations were observed, for example the assumption that the zooming time in the tree corresponds to real time, that there is an implicit coherent timeline along the y-axis of the tree, and that more nodes along a branch corresponds to a longer time.The research reported in this thesis supports the claim that careful choice, and informed use of visualizations matters, and that different visualizations are best suited for different educational purposes
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| 2. |
- Žitinski Elías, Paula, 1987-
(författare)
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Halftoning for Multi-Channel Printing : Algorithm Development, Implementation and Verification
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A seemingly straightforward way to enhance the quality of printed images is to increase the number of colorants, beyond the four traditionally used, in multi-channel printing. Potential improvements to reproduced images include: increased colour accuracy, enhanced colour smoothness and reduced image graininess. Nevertheless, numerous challenges exist, one of them being the implementation of halftoning algorithms, which transform the original image into a binary one that is reproducible by the printing system. This thesis concerns the development, implementation and verification of halftoning algorithms suitable for an increased number of colorants in multi-channel printing.The first focus in this thesis is on the implementation of an amplitude modulated (AM) halftoning method for seven-channel printing utilizing CMYKRGB colorants. The proposed AM halftoning method utilizes non-orthogonal halftone screens instead of orthogonal ones (dots), thus enabling a wider angle range for the channels that makes possible to accommodate multi-channel impressions. The performance of the non-orthogonal halftoning method was evaluated by computational simulation of channel misregistration for 1600 different scenarios and assessment of printed orthogonal and non-orthogonal patches. The simulated and printed results demonstrate that the proposed halftoning method utilizing non-orthogonal screens shows no visible moiré and produces smaller colour shifts in case of misregistration when compared to orthogonal halftoning.However, the layer thickness of the combined colorants is not controlled by the aforementioned multi-channel AM halftoning approach. Therefore, the second focus in this thesis concerns the adjustment and implementation of a multilevel halftoning algorithm for achromatic and chromatic inks. In this algorithm, a channel is processed so that it can be printed using multiple inks of same hue value, achieving a single ink layer. Here, the thresholds for ink separation and dot gain compensation pose an interesting challenge. Since dot gain originates from the interaction between a specific ink and specific paper, compensating the original image for multilevel halftoning means expressing the dot gain of multiple inks in terms of the nominal coverage of a single ink. The applicability of the proposed multilevel halftoning workflow is demonstrated using multiple inks while avoiding dot-on-dot placement and accounting for dot gain. The results also show that the multilevel halftoned image is visually improved in terms of graininess and detailenhancement when compared to a bi-level halftoned image.
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| 3. |
- Erlandsson, Fredrik
(författare)
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On social interaction metrics : social network crawling based on interestingness
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- With the high use of online social networks we are entering the era of big data. With limited resources it is important to evaluate and prioritize interesting data. This thesis addresses the following aspects of social network analysis: efficient data collection, social interaction evaluation and user privacy concerns. It is possible to collect data from online social networks via their open APIs. However, a systematic and efficient collection of online social networks data is still challenging. To improve the quality of the data collection process, prioritizing methods are statistically evaluated. Results suggest that the collection time can be reduced by up to 48% by prioritizing the collection of posts. Evaluation of social interactions also require data that covers all the interactions in a given domain. This has previously been hard to do, but the proposed crawler is capable of extracting all social interactions from a given page. With the extracted data it is for instance possible to illustrate indirect interactions between different users that do not necessarily have to be connected. Methods using the same data to identify and cluster different opinions in online communities have been developed. These methods are evaluated with the too Linguistic Inquiry and Word Count. The privacy of the content produced; and the users’ private information provided on social networks is important to protect. Users must be aware of the consequence of posting in online social networks in terms of privacy. Methods to protect user privacy are presented. The proposed crawler in this thesis has, over the period of 20 months, collected over 38 million posts from public pages on Facebook covering: 4 billion likes and 340 million comments from over 280 million users. The performed data collection yielded one of the largest research dataset of social interactions on Facebook today, enabling qualitative research in form of social network analysis.
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| 4. |
- Helmholz, Hannes, 1990
(författare)
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Binaural Rendering of Spherical Microphone Array Signals
- 2021
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The presentation of extended reality for consumer and professional applications requires major advancements in the capture and reproduction of its auditory component to provide a plausible listening experience. A spatial representation of the acoustic environment needs to be considered to allow for movement within or an interaction with the augmented or virtual reality. This thesis focuses on the application of capturing a real-world acoustic environment by means of a spherical microphone array with the subsequent head-tracked binaural reproduction to a single listener via headphones. The introduction establishes the fundamental concepts and relevant terminology for non-experts of the field. Furthermore, the specific challenges of the method due to spatial oversampling the sound field as well as physical limitations and imperfections of the microphone array are presented to the reader. The first objective of this thesis was to develop a software in the Python programming language, which is capable of performing all required computations for the acoustic rendering of the captured signals in real-time. The implemented processing pipeline was made publicly available under an open-source license. Secondly, specific parameters of the microphone array hardware as well as the rendering software that are required for a perceptually high reproduction quality have been identified and investigated by means of multiple user studies. Lastly, the results provide insights into how unwanted additive noise components in the captured microphone signals from different spherical array configurations contribute to the reproduced ear signals.
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| 5. |
- Murmann, Patrick
(författare)
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Towards Usable Transparency via Individualisation
- 2019
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The General Data Protection Regulation grants data subjects the legal rights of transparency and intervenability. Ex post transparency provides users of data services with insight into how their personal data have been processed, and potentially clarifies what consequences will or may arise due to the processing of their data. Technological artefacts, ex post transparency-enhancing tools (TETs) convey such information to data subjects, provided the TETs are designed to suit the predisposition of their audience. Despite being a prerequisite for transparency, however, many of the TETs available to date lack usability in that their capabilities do not reflect the needs of their final users.The objective of this thesis is therefore to systematically apply the concept of human-centred design to ascertain design principles that demonstrably lead to the implementation of a TET that facilitates ex post transparency and supports intervenability. To this end, we classify the state of the art of usable ex post TETs published in the literature and discuss the gaps therein. Contextualising our findings in the domain of fitness tracking, we investigate to what extent individualisation can help accommodate the needs of users of online mobile health services. We introduce the notion of privacy notifications as a means to inform data subjects about incidences worthy of their attention and examine how far privacy personas reflect the preferences of distinctive groups of recipients. We suggest a catalogue of design guidelines that can serve as a basis for specifying context-sensitive requirements for the implementation of a TET that leverages privacy notifications to facilitate ex post transparency, and which also serve as criteria for the evaluation of a future prototype.
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| 6. |
- Andersson, Karl
(författare)
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On access network selection models in heterogeneous networking environments
- 2008
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis proposes and evaluates architectures and algorithms for access network selection in heterogeneous networking environments. The ultimate goal is to select the best access network at any time taking a number of constraints into account including user requirements and network characteristics. The proposed architecture enables global roaming between access networks within an operator's domain, as well as across operators without any changes in the data and control plane of the access networks being required. Also, the proposed architecture includes an algorithm for measuring performance of access networks that can be used on a number of access technologies being wired or wireless. The proposed access network selection algorithm also has an end-to-end perspective giving a network performance indication of user traffic being communicated. The contributions of this thesis include an implementation of a simulation model in OPNET Modeler, a proposal of a metric at the network layer for heterogeneous access networks, an implementation of a real-world prototype, a study of multimedia applications on perceived quality of service, an access network selection algorithm for highly mobile users and vehicular networks, and an extension of the mentioned access network selection algorithm to support cross-layer decision making taking application layer and datalink layer metrics into account.
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| 7. |
- Boytsov, Andrey
(författare)
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Context reasoning, context prediction and proactive adaptation in pervasive computing systems
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The paradigm of pervasive computing aims to integrate the computing technologies in a graceful and transparent manner, and make computing solutions available anywhere and at any time. Different aspects of pervasive computing, like smart homes, smart offices, social networks, micromarketing applications, PDAs, etc. are becoming a part of everyday life. Context of pervasive computing system is any piece of information that can be of possible interest to the system. Context often includes location, time, activity, surroundings, etc. One of the core features of pervasive computing systems is context awareness – the ability to use context information to the benefit of the system. The thesis proposes a set of context prediction and situation prediction methods on top of enhanced situation awareness mechanisms. Being aware of the future context enables a pervasive computing system to choose the most efficient strategies to achieve its stated objectives and therefore a timely response to the upcoming situation can be provided. This thesis focuses on the challenges of context prediction, but in order to become really efficient and useful, context prediction approaches need to be gracefully integrated with different other aspects of reasoning about the context. This thesis proposes a novel integrated approach for proactively working with context information. In order to become efficient, context prediction should be complemented with proper acting on predicted context, i.e. proactive adaptation. The majority of current approaches to proactive adaptation solves context prediction and proactive adaptation problems in sequence. This thesis identifies the shortcomings of that approach, and proposes an alternative solution based on reinforcement learning techniques. The concept of situation provides useful generalization of context data and allows eliciting the most important information from the context. The thesis proposes, justifies and evaluates improved situation modeling methods that allow covering broader range of real-life situations of interest and efficiently reason about situation relationships. The context model defines the pervasive computing system’s understanding of its internal and external environments, and determines the input for context prediction solutions. This thesis proposes novel methods for formal verification of context and situation models that can help to build more reliable and dependable pervasive computing systems and avoid the inconsistent context awareness, situation awareness and context prediction results. The architecture of pervasive computing system integrates all the aspects of context reasoning and governs the interaction and collaboration between different context processing mechanisms. This thesis proposes, justifies and evaluates the architectural support for context prediction methods. The novel architectural solutions allow encapsulating various practical issues and challenges of pervasive computing systems and handling them on low levels of context processing, therefore, supporting the efforts for efficient context prediction and proactive adaptation.
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| 8. |
- Brännström, Robert
(författare)
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Network-layer mobility in wireless ad hoc access networks
- 2005
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis proposes and discusses solutions to enable network-layer mobility in wireless ad hoc access networks. The deployment of wireless access networks has made them ubiquitous and current research strives to make them pervasive. Users having wireless access to wired IP networks and the Internet are driving the demand for mobile and heterogeneous solutions. To enable all kinds of mobility in heterogeneous All-IP networks there are many issues to be solved. This thesis focuses on network-layer mobility and connectivity of wireless multi-hop ad hoc networks to the Internet. In a wireless environment with overlapping service areas, mobile hosts need to select which gateway(s) to use to access the wireless infrastructure. The signal-to-noise ratio of an access point, which is part of a wireless LAN, does not reflect the number of attached hosts or the traffic between them. The throughput of the access point could be low while the signal is strong. At the same time an access point with weaker signal could allow higher throughput. In ad hoc routing, hop count is the most common metric and the selection of a route to a gateway is affected by the same utilization problem. This could lead to a situation where a short route is used by more hosts and performing worse than a longer route serving fewer hosts. This thesis proposes and discusses solutions to calculating network-layer metrics and using them in gateway selection and handover decisions. To enable connectivity of a mobile ad hoc network (MANET) to the Internet, a gateway must support the wired single-hop and wireless multi-hop approaches. To deploy network-layer mobility in a MANET, the Mobile IP protocol needs to be adapted for the multi-hop environment. A MANET enables connectivity to more than one gateway at a time and combined with multihoming it provides seamless handover between subnets. The gateway selection and handover decisions are complicated by the multihoming capabilities. This thesis proposes and discusses solutions to deploying multihomed mobility into MANETs and thereby handling multi-hop gateway discovery, registration of multiple gateways and tunneling to selected gateway(s). Traffic patterns in wired LANs generally follow the 80/20 ratio of Internet destined vs. local traffic. The same traffic patterns generally hold true for wireless hosts. Therefore it is important to maintain the route to the gateway for the Internet destined traffic. This thesis proposes and discusses a solution to maintaining gateway connectivity in MANETs by installing routes to gateways using advertisements. Deciding the locality of a peer and setting up the forwarding route differs between single-hop and multi-hop networks. In single-hop networks a source matches the destination prefix with its own to decide what forwarding policy to use. Local traffic is sent directly to the destination with the link- layer protocol while global traffic is forwarded to a default gateway. In multi-hop networks the ad hoc routing protocol finds the route to a destination either proactively or on-demand. This thesis proposes and discusses a solution to deciding on the mobile host destination locality in a MANET.
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| 9. |
- Drugge, Mikael
(författare)
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Wearable computer interaction issues in mediated human to human communication
- 2004
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis explores the use of wearable computers as mediators for human to human communication. The user of a wearable computer can deliver live video, audio and commentary from a remote location, allowing local participants to experience it and interact with people on the other side. In this way, knowledge and information can be shared over a distance, passing through the owner of the wearable computer who acts as a mediator. One of the main problems of today is that the virtual world offered by wearable computers can become too immersive, thereby distancing its user from interactions in the real world. At the same time, the very same immersion serves to let the user sense the remote participants as being there, accompanying and communicating through the virtual world. The key here is to get the proper balance between the real and the virtual worlds; remote participants should be able to experience a distant location through the user, while the user should similarly experience their company in the virtual world.
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| 10. |
- Elf, Stefan
(författare)
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Application semantics for cost-effective media distribution
- 2003
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Public use of the Internet increases as wideband connections become pervasive and applications suitable for media distribution grow popular. Group collaboration applications have attracted interest during recent years. Wireless connectivity and business applications also furthers a need for reliable communication protocols. Multicast is a driving force for new applications involving one-to-many as well as many-to-many user scenarios like lecturing, discussions, and collaborative work. In some applications guaranteed delivery of every packet is not crucial, while in other this is a requirement. Error handling in reliable protocols can present a substantial challenge already in a homogeneous environment. Including a plethora of end-user terminal types with widely varying resources it becomes even more challenging. Protocols and applications must therefore be able to handle receiver and network link heterogeneity. The thesis addresses some of the challenges facing the applications in this field, related to multicast and unicast alike. Although the obstacles each of them must overcome may differ, there are similarities with regards to possible solutions with respect to error handling or resource allocation. Error handling protocols are proactive or reactive. Proactive protocols transmit redundant information along with the original information, enabling the receivers to repair lost packets without feedback to the sender. Reactive protocols rely either on positive or negative feedback from the receivers in order to establish reliability. According to a definition of semantic reliability the reliability concept can be interpreted in terms of application semantics. It is proposed to view reliable multicast as a special case of semantically reliable multicast and to implement a dynamically configurable transport layer with an error-handling rule set that can be configured from the application or even from the sender in- session. It is also proposed to make use of the application's knowledge of specific semantics to improve on the recovery of lost packets, congestion handling, or resource allocation. The thesis also presents a bandwidth-sharing scheme for video in group collaboration using application semantics in the form of user hints. The presence of such events is made available to all senders via message passing between session members. As information relating to a user's interest in another user is conveyed, the sender may increase its use of resources on the expense of other senders. A scheme is proposed and a prototype implementation and experimental results are presented.
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