| 1. |
- Alfredsson, Lars-Inge, 1964-
(författare)
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VLSI Architectures and Arithmetic Operations with Application to the Fermat Number Transform
- 1996
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The properties of arithmetic operations in Fermat integer quotient rings 2m+1, where m = 2t, are investigated. The arithmetic operations considered are mainly those involved in the computation of the Fermat number transform. We consider some ways of representing the binary coded integers in such rings and investigate VLSI architectures for arithmetic operations, with respect to the different element representations. The VLSI architectures are mutually compared with respect to area (A) and time (T) complexity and area-time performance (AT2). The VLSI model chosen is a linears witch-level RC model.In the polar representation, the nonzero elements of a field are represented by the powers of a primitive element of the field. In the thesis we particularly investigate the properties of arithmetic operations and their corresponding VLSI architectureswith respect to the polar representation of the elements of Fermat prime fields. Somenew results regarding the applicability of the Fermat number transform when usingthe polar representation are also presented.
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| 2. |
- Almeida, Rosimary, 1960-
(författare)
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Severity of illness versus severity of disease : definitions and applications
- 1996
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Outcome assessment should consist of two basic steps - "selection of a meaningful outcome" and "determination of what caused the outcome". The latter step requires comparisons, and therefore information about the initial status of the patients. Severity ratings attempt to group patients with similar initial status so that outcome comparisons are meaningful. They are consequently an essential ingredient in outcome assessment.This thesis aims at expanding the knowledge about outcome measurement focusing on the severity of a case with regard to definitions and applications of severity measures. Further, theoretical knowledge is integrated with practical needs for outcome assessment and methodology is developed for modelling the use of resources and interpreting the association between different severity measures.As with illness and disease, severity of illness and severity of disease are interchangeable terms in medical literature. Based on a holistic theory of health, these terms were differentiated. Severity of a case was described by two basic components - severity of disease and severity of illness. Essentially, severity of illness concerns suffering and disability, and severity of disease concerns risk of death, risk of suffering and risk of disability. These definitions were the core of a set of criteria for classifying severity measures or outcome measures.The role of a disease severity score in explaining resources use (e.g., intensity of technology utilization and length of hospital stay) in a neonatal intensive care unit was investigated. A disease severity score based on the death risk of the initial diagnosis was found to be an indicator of intensity of therapeutic technology together with gestational age and Apgar score. However, it does not show statistical significance to explain length of stay, which was explained by intensity of diagnostic technology and birthweight.The demand for patient classification systems (standard systems to describe a patient's condition) on a national and local level was investigated. There is little experience in the use of these systems, but at the same time there is a demand from the nurse managers for standard measures of a patient's need for care.There is still little knowledge about the association between severity of illness and severity of disease. This association was studied for patients with ulcerative colitis using data analysis techniques for dimension reduction such as cluster analysis, homogeneity analysis and non linear principal components analysis. A non linear relationship between illness and disease severity measures was found. The overall clinical judgement of disease activity was more related to illness patterns than symptoms or endoscopy and laboratory findings. In addition, the two measures of illness severity (Sickness Impact Profile and Rating Form for Inflammatory Bowel Disease Patient Concerns) were found to represent complementary information about a patient's illness experience. This illustrates the importance of conceptual knowledge in the selection process of an illness measure for outcome evaluations. These findings also reinforce the need for the development of systems to support interpretation of these kinds of complex associations, as traditional statistics have been shown to be of limited value under these circumstances.
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| 3. |
- Alvandpour, Atila, 1960-
(författare)
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Power Estimation and Low Power CMOS Circuit Techniques
- 1999
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The increasing power consumption due to the high integration rate of VLSI digital CMOS circuits has become a major concern. Many important design issues and parameters are strongly dependent on the power dissipation and the accuracy of its estimated value during the design exploration. Among these issues we identify particularly the operation time per battery pack, the computational capacity and performance of the mobile electronic products, as well as more general aspects such as circuit reliability, cost for packaging and power supplies. In this thesis, some issues on power estimation and development of low-power circuit techniques, aimed for medium and high speed operations, are addressed.The complex impact of Miller capacitance on power and performance of digital CMOS circuits is investigated. Significant enhancements in characterization and modeling of the Miller effects compared to the existing conclusions, which are based on simplified rules, are achieved.A novel estimation technique for the relatively involved average short-circuit power consumption has been developed. Compared to the existing, time-consuming technique, the proposed technique provides a fast estimation with a reasonable accuracy, and has a potential to be used for real measurement.A significant portion of the total power consumption in VLSI circuits is due to the capacitance of the interconnections, however, estimating the interconnect length and its RC property at early stages in a large-scale top-down design flow is a hard task. Existing, simplified interconnection length estimation techniques are unacceptably inaccurate and unable to give a useful feedback during the design verification and simulation.A new design-sensitive interconnection length estimation technique and a corresponding algorithm has been developed. The technique has the unique quality to estimate the length of each interconnection separately, and therefore detects and localizes most of the potentially long interconnects. The result of the estimation can directly be used to add the important RC properties of the interconnects to the power estimators or circuit simulators, consequently yielding a significant increase in estimation accuracy.An investigation on generic low-power circuit techniques aimed for main-stream design styles has been made and various suggestions are proposed. The result has later been used to adapt the design of cell libraries to low power requirements.High fan-in dynamic gates can result in lower power consumption, fewer logic levels and very compact layout. Two major disadvantages, which reduce the practical use of such wide gates, are the relatively long propagation delay and the large leakage currents, which are due to the increasing subthreshold current in today's and future submicron devices. For speeding up the wide gates, new and simple sensing elements are proposed, which results in faster gates and lower power consumption compared to the alternative solutions. The issues related to large subthreshold leakage currents is also addressed and a leakage-tolerant multi-phase keeper circuit is presented. The new keeper holds the dynamic output of the wide domino gates statically, with a greater driving strength than that in the conventional solution. Furthermore, an increase in robustness is achieved without any significant delay penalty.Large capacitive loads resulting from long on-chip interconnects and the corresponding driver-receiver circuits can consume a significant portion of the total power consumption of a CMOS chip. A low-power, high-speed and robust driver-receiver circuit is proposed. The new bus architecture utilizes a precharge-to-low interconnect and a fast and simple level converter as receiver, which together reduce the power consumption up to 70% below that of a conventional precharged bus architecture without any delay penalty.
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| 4. |
- Andersson, Dick
(författare)
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Conformational Studies of Protein Structure and Dynamics
- 1999
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The protein folding problem is one of the most important issues to be solved in the field of molecular biology. The subject of this thesis mainly deals with various aspects of the folding process.In Paper I, near-UV CD kinetic measurements on mutants, in which one tryptophan (Trp) residue had been replaced, were performed to probe the development of asymmetric environments around specific Trp residues during the refolding of human carbonic anhydrase II (HCA II). The development of the individual (Trp) CD spectra during refolding was obtained by subtracting the CD spectrum of the mutant lacking one Trp from that of HCA II at different time points. The same method was used for the particular Trp residues to obtain the kinetic CD traces monitored at a specific wavelength (270 nm). Three Trp residues were analyzed, each probing different structural regions of the native structure. The investigated Trp residues develop their native CD bands at different rates, showing that formation of native-like tertiary structure is occurring with varying rates indifferent regions of the protein.The same approach was applied to the extracellular domain of human tissue factor (sTF), which contains four Trp residues (Paper II). The individual Trp CD spectra showed that all four residues contributed to the CD spectrum in almost the entire wavelength region investigated, including the far-UV region. This leads to uncertain predictions of the amounts of various types of secondary structure. Accordingly, the best prediction of secondary sTF structure content was achieved using a hypothetical Trp-free CD spectrum. The kinetic refolding results suggest that the compact asymmetric environments of the individual Trp residues in sTF are formed simultaneously, leading to the conclusion that the native tertiary structure of the whole protein is formed in a cooperative manner.In Paper III, the role of the metal ion cofactor for the refolding of bovine carbonic anhydrase II (BCA II) was studied from the molten globule to the native state. Refolding was possible to achieve by mere addition of the metal ion to the apomolten-globule, because the apoenzyme was less stable than the holoenzyme. The cofactor-effected refolding can be summarized as follows: 1) initially, the metal ion binds to the molten globule; 2) compaction of the metal-binding site region is then induced by the metal ion binding; 3) a functioning active center is formed; 4) finally, the native tertiary structure is generated in the outer parts of the protein.In paper IV the aim was to determine the nature of the tetramer contact of human extracellular superoxide dismutase (hEC-SOD). We chose a strategy in which we mapped the subunit interaction interface by studying effects of twelve different mutations in the N-terminal domain fused to HCA II. The results show that the hydrophobic side of a predicted amphiphatic a-helix (formed by residues 14-32) in the N-terminal domain is essential for the subunit interaction.
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| 5. |
- Andersson, Håkan
(författare)
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Error-Correcting Codes Based on Chaotic Dynamical Systems
- 1998
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This dissertation treats a novel class of error-correcting codes based on chaotic dynamical systems. The codes are defined over a continuous alphabet whereas the information that is to be transmitted belongs to a discrete set of symbols. Simple expressions can be given for the encoders, and the codewords can be described by a parity-check relation. However, the most interesting approach is to view the codewords as orbits of iterated dynamical systems described by integer matrices.Under some rather natural assumptions, the codes are shown to be group codes. The minimum distance is proved to be well-defined and strictly greater than zero. An algorithm for calculating it is also given. Initially, no robust sliding-window encoder inverses exist, but this deficiency is remedied by the introduction of fractal signal sets. The problem of catastrophic encoders is also solved by the introduction of these totally disconnected signal sets.Decoding strategies are discussed, and it is shown why the Viterbi algorithm does not work in higher dimensions for this type of codes. So-called list decoding emerges as a good alternative and its merits are considered. Simulations and comparisons with binary antipodal signaling are performed. The setting of the work is in two dimensions. However, the strength of this code construction is that it easily generalizes to higher dimensions.
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| 6. |
- Andersson, Maria, 1965-
(författare)
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Cooperation in local electricity markets : modelling of technical measures
- 1997
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis presents a system analysis for co-operation in local electricity markets including distributors and customers. The purpose of co-operation is to minimise the system cost of local markets by introducing system measures, such as end-use measures and municipal co-generation plants. Co-operation will strengthen the position of local markets in the national as well as future international electricity markets. With end-use measures local markets will achieve flexibility, additional reserve capacity and ability to avoid sudden large costs for peak loads. Biomass-fired cogeneration plants can become of great importance in an international market. In Sweden there is a simultaneous demand for electricity and district heating, many local markets already include district heating systems and there are major forest areas which can contribute with renewable fuel. The system analysis is partly based on the simulation model (INDSIM) and the linear programming model (MODEST). The simulation model has been further developed (STRATO) to include calculation of system costs. Shadow price analysis has been developed in order to study incentives for system measures. Calculation procedures have been developed that describe cooperation between distributor and customer. Six case studies of a selection of real, existing local markets in Sweden are presented. The studies show the potential economical effects of co-operation measured by system costs and shadow prices. Co-operation has been considered between demand- and supply-side, electricity- and district heating systems and also between different time periods. In a typical local market with 90 000 inhabitants, if end use measures are introduced without cooperation the system cost of the distributor will increase by 14 million SEK for a time period of 25 years. If instead end-use measures are introduced in co-operation, together with a biomass-fired cogeneration plant, the system cost of the local market will be reduced by 444 million SEK. Furthermore, the use of biomass in the local market is increased from 36 to 72 % while the use of oil is decreased from 34 to 1%. Another case study of another local market (50 000 inhabitants) shows that end-use measures will reduce the system cost (excluding investment costs) of an industry by 50 % corresponding to 1.3 million SEK for one year. The end-use measures imply reduced power demand during peak load periods in the local market and increased power demand during non- peak load periods.
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| 7. |
- Axelsson, Jakob
(författare)
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Analysis and Synthesis of Heterogeneous Real-Time Systems
- 1997
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- During the development of a real-time system the main goal is to find an implementation that satisfies the specified timing constraints. Often, it is most cost-effective to use a heterogeneous solution based on a mixture of different microprocessors and application-specific integrated circuits. There is however a lack of techniques to handle the development of heterogeneously implemented systems, and this thesis therefore presents a novel approach inspired by research in the area of hardware/software codesign. The behaviour of the entire system is specified in a high-level, homogeneous description, independently of how different parts will later be implemented, and a thorough design space exploration is performed at the system level using automatic or semi-automatic synthesis tools which operate on virtual prototypes of the implementation.The objective of the synthesis is to find the least costly implementation which meets all timing constraints, and in order to predict these characteristics of the final system, different analysis methods are needed. The thesis presents an intrinsic analysis which estimates the hardware resource usage of individual tasks, and an extrinsic analysis for determining the effects of resource sharing between several concurrent tasks. The latter is similar to the fixed-priority schedulability analysis used for single-processor systems, but extended to heterogeneous architectures. Since these analysis procedures are applied early in the design process, there are always some discrepancies between the estimated data and the actual characteristics of the final system, and constructive ways of dealing with these inaccuracies are therefore also presented.Several synthesis algorithms are proposed for different aspects of the design. The hardware architecture is assembled from a component library using heuristic search techniques, and three alternative algorithms are evaluated in the thesis. The optimal partitioning of the functionality on an architecture is found using a branch-and-bound algorithm. Finally, a fixed-priority scheduler is instantiated by assigning priorities to the concurrent tasks of the behaviour. Together, the proposed analysis and synthesis methods provide a solid basis for systematic engineering of heterogeneous real-time systems.
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| 8. |
- Bachinger, Thomas
(författare)
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Multisensor arrays : for bioprocess monitoring
- 1999
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Bioprocess engineering, the technology that is focused on the exploitation of the metabolic potential of biological agents, has attracted growing interest throughout the past 50 years from both scientific and industrial communities. The products that have been brought to market range from pharmaceuticals and enzymes to food products and vitamins. The quality of human life has been improved through these efforts in many ways.Despite a strong research effort and the fact that microbial transformations often reach yields close to the theoretical maximum. many bioprocesses still operate at relatively low yields. One of the obstacles in effective operation is the extraction of useful information from the bioprocess. Sensors that acquire real-time information about the cells' state and their interaction with the environment in the bioreactor are seldom available. Hence, the implementation of sophisticated process control is prevented.In this thesis a new approach of non-invasive on-line bioprocess monitoring is evaluated. Chemical multisensor arrays (i.e. electronic noses) are used to extract information from the composition of volatiles emitted from the cell culture. The focus is on two specific areas: (i) monitoring of key variables in the bioreactor environment and (ii) monitoring of cell states and physiological events. The overall concern is, besides the increase of yield and reproducibility, the safety operation of bioprocesses.To cover a comprehensive area of modern bioprocessing, several organisms are investigated under different modes of operation in laboratory- and production scale processes. In repeated batch cultivations of recombinant Escherichia coli it is shown that an electronic nose can monitor biomass and specific growth rate with high accuracy. Glucose and ethanol concentration are monitored in batch cultivations of Saccharomyces cerevisiae. Bioproduct monitoring is presented in production-scale mammalian cell cultivation. The concentration of a therapeutic protein is monitored on-line in this long-term bioprocess thereby also outlining the stability of the sensor technique.In production-scale mammalian cell culture it is possible to follow cell transition states and monitor the reproducibility of the process. The physiological state of the cell population is revealed in laboratory-scale cultivations. It is shown that microbial contamination can be identified earlier than with conventional methods. Finally, the metabolic burden imposed on bacterial cells through strong overexpression of recombinant protein is monitored in fed-batch cultivation.
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| 9. |
- Bellgran, Monica
(författare)
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Systematic Design of Assembly Systems : Preconditions and Design Process Planning
- 1998
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Efficient assembly systems are necessary to the success of industrial companies where assembly is a strategic core activity. Each assembly system is the result of a unique design process where the available resources and options are utilised in order to suit the specific preconditions of the company and the situation. Designing assembly systems in a systematic way based on a pre-defined structure is advantageous as it improves the chances of achieving the best possible assembly system in a shorter time.In this thesis, a model for analysis of assembly system design is presented, based on the synthesis of empirical findings and a theoretical framework. The analysis model consists of contextual aspects (part 1 ). It further includes an analysis of aspects important to the design process planning activities related to how they should be managed and structured (part 2). The analysis model finally emphasises the design process (part 3) involving preparatory design aspects, and aspects relevant for the design specification activities, i.e. the creation, evaluation and selection of the assembly system proposal.In order to improve the way an assembly system is designed in practice, a method supporting the planning of this design process is also developed. This method development strategy highlights the necessity of the system designers making relevant adaptations by selecting from the pre-defined method structure. The method is presented in a modular form based on a tree structure. In part, the method identifies activities concerning design process management. However, the main part of the method includes the presentation of preparatory design activities and design specification activities.In total, the method comprises eight phases that are further subdivided on two more levels of detail. Besides structuring these design activities, the method also includes parameters that are important when designing assembly systems.
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| 10. |
- Bengtsson, Per
(författare)
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Microstructural, Residual Stress, and Thermal Shock Studies of Plasma Sprayed ZrO2-Based Thermal Barrier Coatings
- 1997
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Thermal barrier coatings (TBCs), with a thickness of 0.4 mm, are today extensively used on the hot parts of both stationary and flying jet engines. The purpose of the TBC is to protect the underlying material from high temperatures and severe thennal shock. To increase the efficiency of a jet engine, higher turbine inlet temperatures and higher pressure ratios are sought. Consequently, materials with increased insulating properties will be required and a way to achieve this is to use thicker coatings. However, standard production procedures of thick TBCs (> 1 mm) result in coatings with an insufficient thernal shock life. The aim of this work is to develop a thick thermal barrier coating withan acceptable thernal shock life.In the present thesis, parts of the microstructure, the residual stress state, and their correlation to process parameters in thick thermal barrier coatings are described. Further, an optimised coating structure is developed to increase the thermal shock resistance of a burner can, coated with a 1.8 mm thick TBC. The studied thermal barrier coatings, plasma sprayed onto a nickel-based substrate material, consist of a bond coating and a top coating. The bond coating material is an MCrAlY alloy and the top coating material is made of Zr02, partially stabilised with 8 wt.% Y203. The spraying of the coatings is perforned at Volvo Aero Corporation. Residual stresses in the samples were measured with a layer removal technique and the stresses were compared to modelled stresses from a finite element model.Tensile stresses in the order of 150 MPa were measured in the bond coating, after the bond coating deposition. These stresses remained after the spraying of the top coating, where low stresses varying from -15 to 10 MPa were found, dependent on spraying conditions. The low stresses were a result of stress relaxation by microcrack formation. The compressive top coating stresses were found in samples where the substrate temperature was high at the end of the topcoating spraying. This gave a large temperature difference when cooling to room temperature, and due to different thermal expansion coefficients between the substrate and the top coating, more compressive stresses resulted. Good agreement between modelled and measured residual stresses was obtained. Columnar grains were found in the solidified droplets (splats) of the top coating. Between the splats, horizontally oriented delaminations were found. Top coatings sprayed at a high substrate temperature or a high passage thickness showed the columnar grains to extend through the thickness of each lamella. This decreased the density of horizontal delaminations. The density of vertical microcracks was also found to decrease as the substrate temperature increased. This was confirmed from the modelling, where the top coating inelastic strain showed the same behaviour.Also, a segmentation crack network was found in top coatings sprayed with a high substrate temperature or a high passage thickness. The thermal shock performance of a burner can containing a 1.8 mm thick segmented top coating was compared to a can sprayed according to standard procedures. Within 35 thernal shock cycles, the standard burner can contained cracks which were considered to be unsafe for the integrity of the can. No such cracks were found in the segmented structure after 1000 cycles.The study shows that thick thermal barrier coatings on real components can be used in jet engines provided that the correct structure is chosen.
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