| 31. |
- Allström, Andreas
(författare)
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Highway Traffic State Estimation and Short-term Prediction
- 2016
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Traffic congestion is increasing in almost all large cities, leading to a number of negative effects such as pollution and delays. However, building new roads is not a feasible solution. Instead, the use of the existing road network has to be optimized, together with a shift towards more sustainable transport modes. In order to achieve this there are several challenges that needs to be addressed. One challenge is the ability to provide accurate information about the current and future traffic state. This information is an essential input to the traffic management center and can be used to influence the choices made by the travelers. Accurate information about the traffic state on highways, where the potential to manage and control the traffic in general is very high, would be of great significance for the traffic managers. It would help the traffic managers to take action before the system reaches congestion and limit the effects of it. At the same time, the collection of traffic data is slowly shifting from fixed sensors to more probe based data collection. This requires an adaptation and further development of the traditional traffic models in order for them to handle and take advantage of the characteristics of all types of data, not just data from the traditionally used fixed sensors.The objective of this thesis is to contribute to the development and implementation of a model for estimation and prediction of the current and future traffic state and to facilitate an adaptation of the model to the conditions of the highway in Stockholm. The model used is a version of the Cell Transmission Model (CTM-v) where the velocity is used as the state variable. Thus, together with an Ensemble Kalman Filter (EnKF) it can be used to fuse different types of point speed measurements. The model is developed to run in real-time for a large network. Furthermore, a two-stage process used to calibrate the model is implemented. The results from the calibration and validation show that once the model is calibrated, the estimated travel times corresponds well with the ground truth travel times collected from Bluetooth sensors.In order to produce accurate short-term predictions for various networks and conditions it is vital to combine different methods. We have implemented and evaluated a hybrid prediction approach that assimilates parametric and non-parametric short-term traffic state prediction. To predict mainline sensor data we use a neural network, while the CTM-v is ran forward in time in order to predict future traffic states. The results show that both the hybrid approach and the CTM-v prediction without the additional predicted mainline sensor data is superior to a naïve prediction method for longer prediction horizons.
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| 32. |
- Almén, Lisbeth
(författare)
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Reducing the effects of driver distraction : a comparison of distraction alerts on driver attention
- 2003
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- With the advancement of technology the traffic environment is becoming increasingly complex. Not only is there an increase in the number of in-vehicle displays and systems that are installed or brought into the car, there is also an increasing number of vehicles as well as other road users and messages on the road. All these factors have a potential of causing the driver to become distracted. Since a major contributor to traffic accidents today is driver distraction it is becoming increasingly important to understand how to mitigate the effects associated with distraction.The overall aim of this thesis is to investigate what effects the use of a distraction alert into the car has on driver attention.The thesis is based on three experimental studies, in which the topic of driver distraction and how it can be reduced is central. Two of the studies were performed in a simulated driving environment in which two different distraction alerts were tested and compared. The Kansei study was performed to acquire knowledge and input for the second simulator study.The studies show that it is rather difficult to make a driver distracted on demand with an artificial distracter. They further show that the used method needs to be developed before a potential distraction alert can be recommended.
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| 33. |
- Almroth, Per, 1975-
(författare)
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Constitutive modeling of a nickel base superalloy : with a focus on gas turbine applications
- 2003
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Gas turbines are used where large amounts of energy is needed, typically as engines in aircraft, ferries and power plants. From an efficiency point of view it is desirable to increase the service temperature as much as possible. One of the limiting factors is then the maximum allowable metal temperatures in the turbine stages, primarily in the blades of the first stage, that are exposed to the highest gas temperatures. Specially designed materials are used to cape with these severe conditions, such as the nickel base superalloy IN792. In order to be able to design the components for higher temperatures and tighter tolerances, a detailed understanding and computational models of the material behaviour is needed.The models presented in this work have been developed with the objective of being physically well motivated, and with the intention of avoiding excessive numbers of parameters. The influence of the parameters should also be as easy as possible to interpret. The models are to describe the the behaviour of IN792, under conditions typically found for a gas turbine blade. Specifically the high- and intermediate- temperature isothermal modelling of IN792 have been addressed.One main issue when characterising the material and calibrating the models is the use of relevant tests, that are representative of component conditions. Therefore isothermal tests with an eye on the typical environment of a turbine blade have been planned and performed.Using numerical optimization techniques the material parameters for the isothermal behaviour of IN792 at 650°C and 850°C have been estimated. The good overall calibration results for these specific temperatures, using the presented modeling concept and nonstandard constitutive tests, suggests that the model can describe the behaviour of IN792 in gas turbine hot part applications.
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| 34. |
- Alvbrant, Joakim, 1973-
(författare)
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A study on emerging electronics for systems accepting soft errors
- 2016
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Moore’s law has until today mostly relied on shrinkage of the size of the devices inintegrated circuits. However, soon the granularity of the atoms will set a limit together with increased error probability of the devices. How can Moore’s law continue in thefuture? To overcome the increased error rate, we need to introduce redundancy. Applyingmethods from biology may be a way forward, using some of the strategies that transformsan egg into a fetus, but with electronic cells.A redundant system is less sensitive to failing components. We define electronic clayas a massive redundancy system of interchangeable and unified subsystems. We show how a mean voter, which is simpler than a majority voter, impact a redundant systemand how optimization can be formalized to minimize the impact of failing subsystems.The performance at given yield can be estimated with a first order model, without the need for Monte-Carlo simulations. The methods are applied and verified on a redundant finite-impulse response filter.The elementary circuit behavior of the memristor, ”the missing circuit element”, is investigated for fundamental understanding and how it can be used in applications. Different available simulation models are presented and the linear drift model is simulated with Joglekar-Wolf and Biolek window functions. Driven by a sinusoidal current, the memristor is a frequency dependent component with a cut-off frequency. The memristor can be densely packed and used in structures that both stores and compute in the same circuit, as neurons do. Surrounding circuit has to affect (write) and react (read) to the memristor with the same two terminals.We looked at artificial neural network for pattern recognition, but also for self organization in electronic cell array. Finally we look at wireless sensor network and how such system can adopt to the environment. This is also a massive redundant clay-like system.Future electronic systems will be massively redundant and adaptive. Moore’s law will continue, not based on shrinking device sizes, but on cheaper, numerous, unified and interchangeable subsystems.
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| 35. |
- Alvehus, Johan, 1973-
(författare)
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Mötets metaforer : en studie av berättelser om möten
- 1999
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Although meetings are, for most, an important part of the daily routine, they are easily disregarded. When viewed as a form of interaction, meetings become more problematic. While the form of interaction is important for the interpretation of content, it also opens up possibilities for manipulation.The purpose of this study is to contribute to an increased understanding of the possibilities for constructing the form of interaction in meetings. This has been achieved through a study of narratives on meetings, here in terms of normative management literature.The literature on meeting management offers distinct views on how meetings supposedly function. These views can be expressed in terms of two metaphors: meetings as organisms and meetings as machines. Metaphors serve to both highlight and conceal certain aspects of a phenomenon. The organism metaphor highlights the homogeneity and dynamics of meetings. In contrast, the machine metaphor helps explain how meetings work, as well as how they can be measured and evaluated.Different metaphors are often portrayed as either totally distinct from, or directly related to each other. However, the literature on managing meetings reveals that the organism and machine metaphors are both related and discrete. Accordingly, the dialectics of highlighting and concealing aspects of a phenomenon must be complemented by the dialectics between the metaphors. The latter can be expressed in terms of links that integrate the metaphors, as well as links that separate the metaphors and define differences between them. In the literature these links emerge as options for action, i.e., alternatives for enacting a particular metaphor using specific techniques. Accordingly, certain techniques provide options for choosing the form of interaction. However, meetings in themselves can also be viewed as a kind of information technology in the same way as e-mail or videoconferencing technology. Normative statements, e.g. the literature on managing meetings, are important clues for the analysis of how different forms of social action can be designed.In studying interaction and communication, an analysis of conscious attempts to design or influence situations should be considered. Such analysis is facilitated by working with a refined concept of form-the double dialectics of form/content and form/form-along with the concept of techniques.
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| 36. |
- Amadori, Kristian, 1976-
(författare)
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On Aircraft Conceptual Design : A Framework for Knowledge Based Engineering and Design Optimization
- 2008
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis presents a design framework where analytical tools are linked together and operated from an efficient system level interface. The application field is aircraft conceptual design. Particular attention has been paid to CAD system integration and design optimization.Aircraft design is an inherently multidisciplinary process. The goal is to search for the design that, in the best of possible ways, fulfills the requirements. It is therefore desirable to be able to effectively investigate and analyze solutions from a variety of points of view, weighting together the results and gathering a general figure of merit. At the same time, increasing competition on a global market forces to shorten the design process and to reduce costs. Thus a system that allows a tight and efficient integration of different disciplines and improving data flow and storage plays a key role.Integrating a CAD system to the framework is of central relevance. The geometrical model includes most of the information; specific data, required to carry out particular analysis, can be extracted from it. This is possible adopting parametric associative models that are controlled from a spreadsheet user interface. Strategies for building CAD models with a very high degree of flexibility are presented. Not only the external shape can be changed, but also the internal structure can be completely modified. Structural elements can be added or removed, and their position and shaping changed.In this work the design of an Unmanned Aerial Vehicle is used as test case for comparing three different optimization algorithms. The presented framework is also used for automatically design Micro Aerial Vehicles, starting from a short list of requirements and ending with a physical prototype produced by a rapid prototyping machine.
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| 37. |
- Ammenberg, Jonas
(författare)
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How do standardised environmental management systems affect environmental performance and business?
- 2001
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis aims to increase the understanding of what a standardised environmental management system (EMS) is, can be, and is not. The EMS infrastructure, i.e. the standards for EMSs and corresponding systems for their application, is analysed to find out how"ft affects the environmental efforts of companies. Furthermore, the topic of how standardised EMSs fit small and medium-sized enterprises (SMEs) is discussed. A special EMS solution used by a group of SMEs is examined to clarify how this model has affected the environmental efforts and business of these enterprises.The thesis is based on three studies. Firstly, external environmental auditors were interviewed. Secondly, the environmental reviews for the group of SMEs were studied. This study also involved a literature review on how to measure environmental performance. Thirdly, the environmental co-ordinators working at the mentioned small enterprises were interviewed.It can be concluded that it is too early to draw any general conclusions on how standardised EMSs affect environmental performance. How ISO 14001 is interpreted and applied is largely left to companies and external environmental auditors. In practise, 14001's requirement concerning continual improvement is often restricted to a few environmental aspects and does not say anything about the total environmental impact. Furthermore, there is an inconsistency in the standard text and its implementation concerning which criteria are approved when assessing environmental aspects. Some auditors allow the inclusion of criteria regarding economy and quality, etc. To ensure the credibility of ISO 14001, the standard and the systems for its application should be improved.The EMS model studied seems to be a cost-effective solution for SMEs that removes the most important barriers for EMS implementation and maintenance at small firms. Also, it appears to have led to significant environmental improvements.
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| 38. |
- Anderson, Kristin, 1977-
(författare)
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Tree Structures in Broadcast Encryption
- 2005
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The need for broadcast encryption arises when a sender wishes to securely distribute messages to varying subsets of receivers, using a broadcast channel, for instance in a pay-TV scenario. This is done by selecting subsets of users and giving all users in the same subset a common decryption key. The subsets will in general be overlapping so that each user belongs to many subsets and has several different decryption keys. When the sender wants to send a message to some users, the message is encrypted using keys that those users have. In this thesis we describe some broadcast encryption schemes that have been proposed in the literature. We focus on stateless schemes which do not require receivers to update their decryption keys after the initial keys have been received; particularly we concentrate on the Subset Difference (SD) scheme.We consider the effects that the logical placement of the receivers in the tree structure used by the SD scheme has on the number of required transmissions for each message. Bounds for the number of required transmissions are derived based on the adjacency of receivers in the tree structure. The tree structure itself is also studied, also resulting in bounds on the number of required transmissions based on the placement of the users in the tree structure.By allowing a slight discrepancy between the set of receivers that the sender intends to send to and the set of receivers that actually can decrypt the message, we can reduce the cost in number of transmissions per message. We use the concept of distortion to quantify the discrepancy and develop three simple algorithms to illustrate how the cost and distortion are related.
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| 39. |
- Andersson, Ann-Christine
(författare)
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Practice-based Improvements in Healthcare
- 2010
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A central problem for the healthcare sector today is how to manage change and improvements. In recent decades the county councils in Sweden have started various improvement initiatives and programs in order to improve their healthcare services. The improvement program of the Kalmar county council, which constitutes the empirical context for this thesis, is one of those initiatives.The purpose of this thesis is to contribute to a broader understanding of large-scale improvement program in a healthcare setting. This is done by analyzing practitioner’s improvement ideas, describing participants in the improvement projects, revising and testing a survey to measure the development of improvement ideas and describing the improvement program from a theoretical perspective. The theoretical change model used looks at change from two opposing directions in six dimensions; Goals, Leadership, Focus, Process, Reward system and Use of consultants.The aims of the county council improvement program are to become a learning organization, disseminate improvement methodologies and implement continuous quality improvements in the organization. All healthcare administrations and departments in the county council were invited to apply for funds to accomplish improvement projects. Another initiative invited staff teams to work with improvement ideas in a program with support from facilitators, using the breakthrough methodology. Now almost all ongoing developments, improvements, patient safety projects, manager and leader development initiatives are put together under the county council improvement program umbrella.In the appended papers both qualitative and quantitative research approach were used. The first study (paper I) analyzed which types of improvement projects practitioners are engaged in using qualitative content analysis. Five main categories were identified: Organizational Process; Evidence and Quality; Competence Development; Process Technology; and Proactive Patient Work. Most common was a focus on organizational changes and process, while least frequent was proactive patient work. Besides these areas of focus, almost all aimed to increase patient safety and increase effectiveness and availability.Paper II described the participants in two of the initiatives, the categorized improvement projects in paper I and the team members in the methodology guided improvement programs. Strong professions like physicians and nurses were well represented, but other staff groups were not as active. Managers were responsible for a majority of the projects. The gender perspective reflected the overall mix of employees in the county council.Paper III described a revision and test of a Minnesota Innovation Survey (MIS) that will be used to follow and measure how quality improvement ideas develop and improve over time. Descriptive statistics were presented. The respondents were satisfied with their work and what they had accomplished. The most common comment was about time, not having enough time to work with the improvement idea and the difficulty of finding time because of regular tasks. This was the first test of the revised survey and the high use of the answer alternative “Do not know” showed that the survey did not fit the context very well in its present version.Trying to connect the county council improvement program and the initiatives studied in papers I and II with the change model gave rise to some considerations. The county council improvement program has an effort to combine organizational changes and a culture that encourages continuous improvements. Top-down and bottom-up management approaches are used, through setting out strategies from above and at the same time encouraging practitioners to improve their day-to-day work. Whether this will be a successful way to implement and achieve a continuous improvement culture in the whole organization is one of the main issues remaining to find out in further studies.
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| 40. |
- Andersson, Annica
(författare)
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Chemical and electronic structure of electroluminescent materials and interfaces in polymer-LEDs
- 2000
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Following the discovery that conjugated polymers can be used as the emitting layer in light emitting devices, extensive studies on these materials have been carried out. In a few years, due to the development of new materials and an increasing knowledge of the underlying chemistry and physics, the performance has improved a lot. One of the important factors that determine the performance of the devices is the chemistry upon interface formation. In the simplest single-layer device there are two interfaces, the interface between the conjugated polymer and the anode and cathode respectively. This thesis deals to a large extent with investigations of the chemical and electronic structure at these interfaces by means of X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). The first chapters give a short introduction to conjugated polymers, polymer LEDs and photoelectron spectroscopy on conjugated material. The following three chapters provide some background information in the subject areas of the papers with some references to closely related studies. The first paper compares the device performance characteristics upon using two different anodes, indium tin oxide (ITO) and fluorine tin oxide (FTO). The second and third papers report on chemical interactions between the ITO-anode and the precursor polymer of PPV, one of the most frequently used conjugated polymers. The fourth and final paper reports on the early stage of interface formation between two different metal atoms (lithium and sodium), and a conjugated molecule.
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