| 1. |
- Persson, Anna
(författare)
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Knitted Circuits for Visual and Tactile Interactive Expressions
- 2009
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- As computational technology and new materials are entering the world of textiles, our view on the textile material is challenged; the areas of textile design and interaction design start to merge. Designing interactive textiles means communicating new expressional forms through textile material. This thesis aim to contribute to the exploration of designing interactive knitted textiles with focus on linking interactive properties, especially visual and tactile, to different ways of expressing them. Design examples and experiments presented are meant to show new possibilities for designing textile material able to change structure, colour and temperature in different ways in response to environmental stimuli. As a way of presenting, and reflecting on, these interactive properties, a notion of expression diagrams is introduced.
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| 2. |
- Bengtsson, Jerker
(författare)
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Efficient implementation of stream applications on processor arrays
- 2006
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis concludes work conducted on exploring the usage of parallel and reconfigurable processor architectures in industrial high-performance embedded systems. This kind of systems has by tradition been built using a mix of digital signal processors and custom made hardware. Digital signal processors provide full functional felxibility, but at the cost of lower performance. Custom made hardware can be optimized for specific functions for high performance, but at the cost of inflexibility and high development costs. A desire is to combine flexibility and performance using commercial hardware, without trading too much of performance for flexibility.Parallel and reconfigurable architectures provide a flexible computing space constituting processing elements that are coupled through configurable communication structures. Architectures designed with less complex processing elements render a high degree of utilizable parallelism at the cost of having to use a portion of the pocessing elements for control functions. In the thesis it is shown that it is possible to utilize this kind of architecture to achieve high performance efficiency, despite the fact that a large fraction of PEs are required to implement control-oriented portions in a fairly complex algorithm.A major problem is that architectures of this kind expose a very complex programming abstraction for compilers and programmers. The approach taken in this work is a domain-specific stream processing model which provides means to express application-specific dataflows and computations in terms of streams. An extensive application study comprising the baseband processing in radio base stations has been used to define sufficient data types, operators and language construct. Furthermore, to support industrial requirements on portability to different architectures, it must be possible to express parallelism and characteristic computations without exposing of hardware details in the source code.To be able to prototype and set up experiments with stream processing languages an experimental programming framework has been developed. A first prototype language with specific primitive types, operators and stream constructs has been implemented in order to elaborate with baseband programming. It is demonstrated how these types and operators can be used to express machine-independent bit field and other fine-grained data parallel computations. Furthermore, the language has been designed with constructs for efficient and flexible programming of reconfiguration of distributed function parameters.
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| 3. |
- Bilstrup, Urban, 1971-
(författare)
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Design Space Exploration of Wireless Multihop Networks
- 2005
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis explores the feasible design space of wireless multihop networks and identifies fundamental design parameters. In the process of exploring it is important to ignore all details and instead take a holistic view. This means that all protocol details are overseen, all details of radio wave propagation models are overseen and the system is modelled strictly on an architectural level. From a theoretical information perspective, there is a limit to the capacity that a certain bandwidth and a certain signal-to-noise ratio at the receiver can provide. This limit is approximated as a volume in the time-frequency-space domain. A single transmission is represented as an occupied volume in this domain. A wireless multihop network covers a spatial area, and the question is how multiple numbers of transmission volumes can be fit into a given limited spatial area. This volume fitting should be done in order to maximize the overall performance or to trade available resources to favour a specific characteristic in the wireless multihop network. The volume model is used for the design space exploration of a wireless multihop network. It is argued that the fault tolerance and the energy gain achieved in a multihop topology are its strength as compared to a single-hop architecture. It is further shown that the energy gain is achieved at the expense of delay and a greater end-to-end error probability. This indicates that these parameters must be very carefully balanced in order to gain in the global overall performance perspective. It can further be concluded that the overall spatial capacity is increased as a result of the spatial channel reuse in a multihop topology. On the other hand, it is also shown that the multihop topology introduces a rather stringent geometrical capacity limitation when the number of nodes of a wireless multihop network is increased. The dynamics (e.g. node mobility, changing radio channels etc.) of a large scale wireless multihop network is also a limiting factor. The nodes’ mobility creates a knowledge horizon beyond which very little can be known about the present network topology.
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| 4. |
- Gustafsson, Marie
(författare)
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Design, Development, and Adoption of Ontology-Driven Clinical Software
- 2006
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis addresses how ontology-driven applications can be designed and developed to support distributed clinical knowledge management in oral medicine, where geographically dispersed practitioners need to share practical clinical knowledge. A step in developing tools for knowledge management is representing knowledge in a machine-processable and sharable manner. We investigate the use of the World Wide Web Consortium's recommendations of the Web Ontology Language (OWL) and Resource Description Framework (RDF) to describe clinical knowledge in oral medicine. The MedView project, a cooperation between clinicians in oral medicine and computer scientists, provides a basis for this work. Limitations of MedView's original knowledge model are identified, together with a list of requirements for a new model.In this new model, OWL and RDF are used for representing examination templates, value lists, aggregates of values, and individual examination records. Further, we give a description of how the ISO/IEC 15288 system life cycle processes can be used to structure the ontology development process. To support distributed knowledge management in oral medicine, an online community for sharing and discussing difficult and interesting cases was built, which uses OWL and RDF for representing examinations, users, meetings, news, and case meta-data. OWL and RDF were found to support the requirements of making ontology reuse possible, and different language versions and meta-data are more easily represented than in the original model. One of the requirements not readily provided for is capturing interactions between different parts of templates, for which the Semantic Web Rule Language could be used. In practice, we found it hard to find ontologies to reuse. Further, there are differing opinions on the appropriate use of constructs, and OWL doesn't directly provide the expected validation facilities. Also, we found a lack of guidance for developing OWL ontologies at different levels of sophistication.
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| 5. |
- Nilsson, Björn, 1965-
(författare)
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Towards energy efficient protocols for active RFID
- 2007
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The absence of a global standard is a bottleneck when using Radio Frequency Identification (RFID) technology. This thesis explores data communication protocols for Active-RFID regarding their energy efficiency and how they can be suited to fit a large variety of applications.The use of Radio Frequency Identification systems (RFID) is growing rapidly. Today mostly "passive" RFID systems are used because no onboard energy source is needed on the transponders. However, "active" RFID technology, with onboard power sources in the transponders, gives a range of opportunities not possible with passive systems. Besides that Active RFID offers longer working distance between RFID-reader and tag than passive RFID, this also enables the tags to do sensor measurements, calculations and storage even when no RFID-reader is in the vicinity of the tags.To obtain energy efficiency in an Active RFID system the data communication protocol to be used should be carefully designed with energy optimization in mind. This thesis describes how energy consumption can be calculated, to be used in protocol definition, and how evaluation of protocols in this respect can be made. The performance of such a new protocol, in terms of energy efficiency, aggregated throughput, delay, and number of air collisions is evaluated and compared to an existing, commercially available protocol for Active RFID, as well as the IEEE standard 802.15.4 (used e.g. in the Zigbee medium-access layer). Simulations show that, by acknowledging the payload and using deep sleep mode on the tag, the lifetime of a tag is increased.For all types of protocols using an air channel for transmitting and receiving information it is obvious that the utilization of the channel is maximized when no collisions occur. To avoid and minimize collisions in the air interface it is possible to listen to the channel (carrier sense) and know its status. Knowing that the channel is occupied should result in a back-off and a later retry, instead of persistently listening to the channel which would require constant energy consumption. We further study the effect on tag energy cost and packet delay incurred by some typical back-off algorithms (constant, linear, and exponential) used in a contention based CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) protocols for Active RFID communication. The study shows that by selecting the proper back-off algorithm coefficients (based on the number of tags), i.e. the initial contention window size and back-off interval coefficient, the tag energy consumption and read-out delays can be significantly lowered.
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| 6. |
- Kunert, Kristina, 1976
(författare)
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Fibre-Optic AWG Networks Supporting Real-Time Communication in High-Performance Embedded Systems
- 2008
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- High-performance embedded systems communicating heterogeneous traffic with high bandwidth and strict timing requirements are in need of more efficient communication solutions. This thesis proposes two multi-wavelength passive optical networks able to meet these demands. The networks are based upon a single-hop star topology with an Arrayed Waveguide Grating (AWG) placed in the centre. The intended application areas for the two networks are short range embedded communication systems like System Area Networks (SANs) and router architectures with electronic queuing. The AWG’s attractive property of spatial wavelength reuse, as well as the combination of fixed-tuned and tuneable transceivers in the end nodes, enables simultaneous control and data traffic transmission. This, in turn, makes it possible to support heterogeneous traffic with both hard and soft real-time constraints.Additionally, two Medium Access Control (MAC) protocols, one for each network solution, are developed. Traffic scheduling is centrally controlled by a node, the protocol processor, residing together with the AWG in a hub. All nodes use Earliest Deadline First (EDF) scheduling and communicate with the protocol processor through physical control channels. A case study, including simulations, in the field of Radar Signal Processing (RSP) and simulations using periodic real-time traffic are conducted for the two application areas respectively, showing very good results. Further, a deterministic real-time analysis is conducted to provide throughput and delay guarantees for hard real-time traffic and an increase in guaranteed traffic is achieved through an analysis of existing traffic dependencies in a multichannel network. Simulation results incorporating the traffic dependency analysis indicate a considerable increase in the possible guaranteed throughput of hard real-time traffic.
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| 7. |
- Agelis, Sacki
(författare)
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Reconfigurable Optical Interconnection Networks for High-Performance Embedded
- 2005
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In embedded computer and communication system the capacity demand for interconnection networks is increasing continuously in order to achieve high-performance systems. Recent breakthroughs show that by using reconfigurability inside a single chip substantial performance gains can be added. However, in this thesis the focus is on system level reconfigurability (between chips or modules) and the performance gains that potentially can be achieved by having support for runtime reconfigurability on the system level.This thesis addresses the field of runtime system level reconfigurability with the use of optics in switches and routers for data- and telecommunications, and in multi-processor systems used for embedded signal processing. Several reconfigurable systems for switching and routing with support to adapt for asymmetric traffic patterns are proposed and compared to identify how design choices affect flexibility, performance etc. The proposed solutions are characterized by their multistage optical interconnection networks with reconfigurable shuffle patterns, where the reconfigurability is provided by micro-optical-electrical mechanical systems. More specifically, application-specific bottlenecks can be resolved by reconfiguring the interconnection network according to the current application demands. The benefits of the architectural solutions are confirmed by simulations that clearly show that the architectures can achieve high performance for both symmetric application characteristics and for several classes of asymmetric application characteristics. The final architectural solution is characterized by electronic packet-switches interconnected through an optical backplane, which is reconfigurable. Moreover, the thesis presents how several signal processing applications can be mapped to run concurrently in a time-shared scheme on a single reconfigurable multi-processor system that has high flexibility to adapt for the application currently at hand. The interconnection network is then adapted (reconfigured) according to the demands of the currently executed application in each time instance. The analysis shows that it is feasible to build such a system with today’s components.
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