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  • 1.
    Alami, Jones
    Linköping University, Department of Physics, Measurement Technology, Biology and Chemistry. Linköping University, The Institute of Technology.
    Plasma characterisation in high power pulsed magnetron sputtering2003Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this thesis, plasma parameters including plasma and floating potentials, electron energy distribution function (EEDF) plasma density and electron temperature are studied in a high power pulsed magnetron (HPPM) discharge at different Argon (Ar) gas pressures and different magnetron powers. It is reported that the EEDF during and shortly after the pulse can be represented by a bi-Maxwellian distribution indicating two energy groups of electrons.

    Furthermore, we report on the variation of the plasma parameters and electron energy distribution function with gas pressure in the pressure range 0.5-20 mtorr. At a high pressure (> 10 mTorr) two density peaks are present, the second of which occurs hundreds of microseconds after the pulse is switched off. It shows that the second peaks occurrence depends on the target material used as well as the chamber pressure and the magnetron power. It is found that the electron density is very high (up to 1019 m-3, during the whole of the measured 2000 µs, indicating the importance of the second density peak in maintaining the high plasma density.

    Measurements on the electron temperature show that this does not exceed 3 eV while the pulse is on, and that it is no more than 0.5 after the pulse is off. A movie is constructed using Langmuir probe measurements data, showing the temporal evolution of the plasma at 20 mTorr argon pressure and 11 J pulse energy. Analysis shows the existence of a magnetic trap underneath the center of the target. Furthermore, the electron flux in the substrate vicinity 10 - 12 cm from the target is found to be homogeneous. Ti thin films are grown along the sidewalls of a hole, 1 cm2 in area and 2 cm in depth, using both de magnetron and HPPM sputtering. Secondary electron microscopy shows that the film grown by de magnetron sputtering shows clear columnar growth, while a dense and flat film was produced using the HPPM sputtering technique.

  • 2.
    Albrektsson, Jörgen
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Optimisation of Off-Road Transport Missions2018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Mines, construction sites, road construction and quarries are examples of applications where construction equipment are used. In a production chain consisting of several construction machines working together, the work needs to be optimised and coordinated to achieve an environmental friendly, energy efficient and productive production. Recent rapid development within positioning services, telematics and human machine interfaces (HMI) opens up for control of individual machines and optimisation of transport missions where several construction machines co-operate.

    The production chain on a work site can be split up in different sub-tasks of which some can be transport missions. Taking off in a transport mission where one wheel loader ("loader" hereinafter) and two articulated haulers ("haulers" hereinafter) co-operate to transport material at a set production rate [ton/h], a method for fuel optimal control is developed. On the mission level, optimal cycle times for individual sub-tasks such as wheel loader loading, hauler transport and hauler return, are established through the usage of Pareto fronts.

    The haulers Pareto fronts are built through the development of a Dynamic Programming (DP) algorithm that trades fuel consumption versus cycle time for a road stretch by means of a time penalty constant. Through varying the time penalty constant n number of times, discrete fuel consumption - cycle time values can be achieved, forming the Pareto front. At a later stage, the same DP algorithm is used to generate fuel optimal vehicle speed and gear trajectories that are used as control signals for the haulers. Input to the DP algorithm is the distance to be travelled, road inclination, rolling resistance coefficient and a max speed limit to avoid unrealistic optimisation results.

    Thus, a method to describe the road and detect the road related data is needed to enable the optimisation. A map module is built utilising an extended Kalman Filter, Rauch-Tung-Striebel smoother and sensor fusion to merge data and estimate parameters not observable by sensors. The map module uses a model of the vehicle, sensor signals from a GPS or GNSS sensor and machine sensors to establish a map of the road.

    The wheel loader Pareto front is based on data developed in previous research combined with Volvo in-house data. The developed optimisation algorithms are implemented on a PC and in an interactive computer tablet based system. A human machine interface is created for the tablet, guiding the operators to follow the optimal control signals, which is speed for the haulers and cycle time for the loader. To evaluate the performance of the system it is tested in real working conditions.

    The contributions develop algorithms, set up a demo mission control system and carry out experiments. Altogether rendering in a platform that can be used as a base for a future design of an off-road transport mission control system.

    List of papers
    1. Road estimation and fuel optimal control of an off-road vehicle
    Open this publication in new window or tab >>Road estimation and fuel optimal control of an off-road vehicle
    2017 (English)In: Proceedings of the 3rd International Conference on Vehicle Technology and Intelligent Transport Systems, SciTePress, 2017, p. 58-67Conference paper, Published paper (Refereed)
    Place, publisher, year, edition, pages
    SciTePress, 2017
    National Category
    Control Engineering
    Identifiers
    urn:nbn:se:liu:diva-142731 (URN)10.5220/0006247200580067 (DOI)978-989-758-242-4 (ISBN)
    Conference
    3rd International Conference on Vehicle Technology and Intelligent Transport Systems, VEHITS 2017, April 22-24, 2017, in Porto, Portugal
    Available from: 2018-04-03 Created: 2018-04-03 Last updated: 2018-11-22
    2. Fuel Optimal Control of an Articulated Hauler Utilising a Human Machine Interface
    Open this publication in new window or tab >>Fuel Optimal Control of an Articulated Hauler Utilising a Human Machine Interface
    2019 (English)In: Smart Cities, Green Technologies, and Intelligent Transport Systems / [ed] Donnellan, Brian; Klein, Cornel; Helfert, Markus; Gusikhin, Oleg; Pascoal, António, Springer International Publishing , 2019, p. 190-208Conference paper, Published paper (Refereed)
    Abstract [en]

    Utilising optimal control presents an opportunity to increase the fuel efficiency in an off-road transport mission conducted by an articulated hauler. A human machine interface (HMI) instructing the hauler operator to follow the fuel optimal vehicle speed trajectory has been developed and tested in real working conditions. The HMI implementation includes a Dynamic Programming based method to calculate the optimal vehicle speed and gear shift trajectories. Input to the optimisation algorithm is road related data such as distance, road inclination and rolling resistance. The road related data is estimated in a map module utilising an Extended Kalman Filter (EKF), a Rauch-Tung-Striebel smoother and a data fusion algorithm. Two test modes were compared: (1) The hauler operator tried to follow the optimal vehicle speed trajectory as presented in the HMI and (2) the operator was given a constant target speed to follow. The objective of the second test mode is to achieve an approximately equal cycle time as for the optimally controlled transport mission, hence, with similar productivity. A small fuel efficiency improvement was found when the human machine interface was used.

    Place, publisher, year, edition, pages
    Springer International Publishing, 2019
    Series
    Communications in Computer and Information Science book series (CCIS), ISSN 1865-0929, E-ISSN 1865-0937 ; 921
    Keywords
    Off-road, Construction equipment, Human machine interface, Optimal control, Dynamic programming, Kalman filters
    National Category
    Vehicle Engineering
    Identifiers
    urn:nbn:se:liu:diva-153311 (URN)10.1007/978-3-030-02907-4_10 (DOI)978-3-030-02906-7 (ISBN)978-3-030-02907-4 (ISBN)
    Conference
    6th International Conference, SMARTGREENS 2017 and Third International Conference, VEHITS 2017, Porto, Portugal, April 22–24, 2017
    Available from: 2018-12-12 Created: 2018-12-12 Last updated: 2018-12-12
    3. Fuel optimal control of an off-road transport mission
    Open this publication in new window or tab >>Fuel optimal control of an off-road transport mission
    2018 (English)In: 2018 IEEE International Conference on Industrial Technology (ICIT), 2018, p. 175-180Conference paper, Published paper (Refereed)
    National Category
    Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:liu:diva-151856 (URN)10.1109/ICIT.2018.8352172 (DOI)978-1-5090-5949-2 (ISBN)
    Conference
    2018 IEEE International Conference on Industrial Technology (ICIT), 19-22 Feb.,Lyon, France
    Available from: 2018-10-06 Created: 2018-10-06 Last updated: 2018-11-22
  • 3.
    Allström, Andreas
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Highway Traffic State Estimation and Short-term Prediction2016Licentiate thesis, monograph (Other academic)
    Abstract [en]

    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.

  • 4.
    Almroth, Per
    Linköping University, Department of Mechanical Engineering. Linköping University, The Institute of Technology.
    Constitutive modeling of a nickel base superalloy: with a focus on gas turbine applications2003Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    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.

  • 5.
    Almén, Lisbeth
    Linköping University, Department of Electrical Engineering. Linköping University, The Institute of Technology.
    Reducing the effects of driver distraction: a comparison of distraction alerts on driver attention2003Licentiate thesis, monograph (Other academic)
    Abstract [en]

    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.

  • 6.
    Al-Shujary, Ahmed
    Linköping University, Department of Mathematics, Mathematics and Applied Mathematics. Linköping University, Faculty of Science & Engineering.
    Kähler-Poisson Algebras2018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The focus of this thesis is to introduce the concept of Kähler-Poisson algebras as analogues of algebras of smooth functions on Kähler manifolds. We first give here a review of the geometry of Kähler manifolds and Lie-Rinehart algebras. After that we give the definition and basic properties of Kähler-Poisson algebras. It is then shown that the Kähler type condition has consequences that allow for an identification of geometric objects in the algebra which share several properties with their classical counterparts. Furthermore, we introduce a concept of morphism between Kähler-Poisson algebras and show its consequences. Detailed examples are provided in order to illustrate the novel concepts.

  • 7.
    Alvbrant, Joakim
    Linköping University, Department of Electrical Engineering, Integrated Circuits and Systems. Linköping University, Faculty of Science & Engineering.
    A study on emerging electronics for systems accepting soft errors2016Licentiate thesis, monograph (Other academic)
    Abstract [en]

    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.

  • 8.
    Alvehus, Johan
    Linköping University, Department of Computer and Information Science. Linköping University, The Institute of Technology.
    Mötets metaforer: en studie av berättelser om möten1999Licentiate thesis, monograph (Other academic)
    Abstract [en]

    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.

  • 9.
    Andersson, Anders
    Linköping University, Department of Computer and Information Science. Linköping University, Faculty of Science & Engineering. Swedish National Road and Transport Research Institute (VTI), Linköping, Sweden.
    Extensions for Distributed Moving Base Driving Simulators2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Modern vehicles are complex systems. Different design stages for such a complex system include evaluation using models and submodels, hardware-in-the-loop systems and complete vehicles. Once a vehicle is delivered to the market evaluation continues by the public. One kind of tool that can be used during many stages of a vehicle lifecycle is driving simulators.

    The use of driving simulators with a human driver is commonly focused on driver behavior. In a high fidelity moving base driving simulator it is possible to provide realistic and repetitive driving situations using distinctive features such as: physical modelling of driven vehicle, a moving base, a physical cabin interface and an audio and visual representation of the driving environment. A desired but difficult goal to achieve using a moving base driving simulator is to have behavioral validity. In other words, \A driver in a moving base driving simulator should have the same driving behavior as he or she would have during the same driving task in a real vehicle.".

    In this thesis the focus is on high fidelity moving base driving simulators. The main target is to improve the behavior validity or to maintain behavior validity while adding complexity to the simulator. One main assumption in this thesis is that systems closer to the final product provide better accuracy and are perceived better if properly integrated. Thus, the approach in this thesis is to try to ease incorporation of such systems using combinations of the methods hardware-in-the-loop and distributed simulation. Hardware-in-the-loop is a method where hardware is interfaced into a software controlled environment/simulation. Distributed simulation is a method where parts of a simulation at physically different locations are connected together. For some simulator laboratories distributed simulation is the only feasible option since some hardware cannot be moved in an easy way.

    Results presented in this thesis show that a complete vehicle or hardware-in-the-loop test laboratory can successfully be connected to a moving base driving simulator. Further, it is demonstrated that using a framework for distributed simulation eases communication and integration due to standardized interfaces. One identified potential problem is complexity in interface wrappers when integrating hardware-in-the-loop in a distributed simulation framework. From this aspect, it is important to consider the model design and the intersections between software and hardware models. Another important issue discussed is the increased delay in overhead time when using a framework for distributed simulation.

    List of papers
    1. Vehicle Powertrain Test Bench Co-Simulation with a Moving Base Simulator Using a Pedal Robot
    Open this publication in new window or tab >>Vehicle Powertrain Test Bench Co-Simulation with a Moving Base Simulator Using a Pedal Robot
    2013 (English)In: SAE International Journal of Passenger Cars - Electronic and Electrical Systems, ISSN 1946-4614, E-ISSN 1946-4622, Vol. 6, no 1, p. 169-179Article in journal (Refereed) Published
    Abstract [en]

    To evaluate driver perception of a vehicle powertrain a moving base simulator is a well-established technique. We are connecting the moving base simulator Sim III, at the Swedish National Road and Transport Research Institute with a newly built chassis dynamometer at Vehicular Systems, Linköping University. The purpose of the effort is to enhance fidelity of moving base simulators by letting drivers experience an actual powertrain. At the same time technicians are given a new tool for evaluating powertrain solutions in a controlled environment. As a first step the vehicle model from the chassis dynamometer system has been implemented in Sim III. Interfacing software was developed and an optical fiber covering the physical distance of 500 m between the facilities is used to connect the systems. Further, a pedal robot has been developed that uses two linear actuators pressing the accelerator and brake pedals. The pedal robot uses feedback loops on accelerator position or brake cylinder pressure and is controlled via an UDP interface. Results from running the complete setup showed expected functionality and we are successful in performing a driving mission based on real road topography data. Vehicle acceleration and general driving feel was perceived as realistic by the test subjects while braking still needs improvements. The pedal robot construction enables use of a large set of cars available on the market and except for mounting the brake pressure sensor the time to switch vehicle is approximately 30 minutes.

    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-92215 (URN)10.4271/2013-01-0410 (DOI)
    Available from: 2013-05-08 Created: 2013-05-08 Last updated: 2019-04-28Bibliographically approved
    2. Models for Distributed Real-Time Simulation in a Vehicle Co-Simulator Setup
    Open this publication in new window or tab >>Models for Distributed Real-Time Simulation in a Vehicle Co-Simulator Setup
    2013 (English)In: Proceedings of the 5th International Workshop on Equation-Based Object-Oriented Modeling Languages and Tools; April 19, University of Nottingham, Nottingham, UK / [ed] Henrik Nilsson, Linköping: Linköping University Electronic Press, 2013, Vol. 84, p. 131-139Conference paper, Published paper (Refereed)
    Abstract [en]

    A car model in Modelica has been developed to be used in a new setup for distributed real-time simulation where a moving base car simulator is connected with a real car in a chassis dynamometer via a 500m fiber optic communication link. The new co-simulator set-up can be used in a number of configurations where hardware in the loop can be interchanged with software in the loop. The models presented in this paper are the basic blocks chosen for modeling the system in the context of a distributed real-time simulation; estimating parameters for the powertrain model; the choice of numeric solver; and the interaction with the solver for real-time properties.

    Place, publisher, year, edition, pages
    Linköping: Linköping University Electronic Press, 2013
    Series
    Linköping Electronic Conference Proceedings, ISSN 1650-3686, E-ISSN 1650-3740 ; 84
    Keywords
    Modelica; real-time; distributed; communications link
    National Category
    Computer Systems
    Identifiers
    urn:nbn:se:liu:diva-118994 (URN)978-91-7519-621-3 (ISBN)978-91-7519-617-6 (ISBN)
    Conference
    The 5th International Workshop on Equation-Based Object-Oriented Modeling Languages and Tools, April 19, University of Nottingham, Nottingham; UK
    Available from: 2015-06-05 Created: 2015-06-05 Last updated: 2019-04-28Bibliographically approved
    3. A Driving Simulation Platform using Distributed Vehicle Simulators and HLA
    Open this publication in new window or tab >>A Driving Simulation Platform using Distributed Vehicle Simulators and HLA
    Show others...
    2015 (English)In: Proceedings of the DSC 2015 Europe: Driving Simulation Conference & Exhibition / [ed] Heinrich Bülthoff, Andras Kemeny and Paolo Pretto, 2015, p. 123-130Conference paper, Published paper (Refereed)
    Abstract [en]

    Modern vehicles are complex systems consisting of an increasing large multitude of components that operate together. While functional verification on individual components is important, it is also important to test components within a driving environment, both from a functional perspective and from a driver perspective. One proven way for testing is vehicle simulators and in this work the main goals have been to increase flexibility and scalability by introducing a distributed driving simulator platform.

    As an example, consider a workflow where a developer can go from a desktop simulation to an intermediate driving simulator to a high fidelity driving simulator with Hardware-In-the-Loop systems close to a finished vehicle in an easy way. To accomplish this, a distributed simulation architecture was designed and implemented that divides a driving simulator environment into four major entities with well-defined interfaces, using HLA as the method of communication. This platform was evaluated on two aspects, flexibility/scalability and timing performance. Results show that increased flexibility and scalability was achieved when using a distributed simulation platform. It is also shown that latency was only slightly increased when using HLA.

    Keywords
    Test, Vehicle, Engine, Performance, Simulator (driving), Computer
    National Category
    Computer Systems
    Research subject
    90 Road: Vehicles and vehicle technology, 911 Road: Components of the vehicle; 90 Road: Vehicles and vehicle technology, 96 Road: Vehicle operating and management
    Identifiers
    urn:nbn:se:liu:diva-136153 (URN)9783981309935 (ISBN)
    Conference
    Driving Simulation Conference 2015. 16-18 september 2015, Tübingen, Germany
    Available from: 2016-01-11 Created: 2017-03-31 Last updated: 2019-04-28Bibliographically approved
  • 10.
    Andersson, Annica
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Chemical and electronic structure of electroluminescent materials and interfaces in polymer-LEDs2000Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    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.

  • 11.
    Andersson, Håkan
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    A Co-Simulation Approach for Hydraulic Percussion Units2018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This Licentiate of Engineering thesis concerns modelling and simulation of hydraulic percussion units. These units are often found in equipment for breaking or drilling in rock and concrete, and are also often driven by oil hydraulics, in which complex fluid-structure couplings are essential for their operation.

    Current methodologies used today when developing hydraulic percussion units are based on decoupled analyses, which are not correctly capturing the important coupled mechanisms. Hence, an efficient method for coupled simulations is of high importance, since these mechanisms are critical for the function of these units. Therefore, a co-simulation approach between a 1D system simulation model representing the fluid system and a structural 3D FE-model is proposed.

    This approach is presented in detail, implemented for two well-known simulation tools and evaluated for a simple but relevant model. The Hopsan simulation tool was used for the fluid system and the FE-simulation software LS-DYNA was used for the structural mechanics simulation. The co-simulation interface was implemented using the Functional Mock-up Interface-standard.

    The approach was further developed to also incorporate multiple components for coupled simulations. This was considered necessary when models for the real application are to be developed. The use of two components for co-simulation was successfully evaluated for two models, one using the simple rigid body representation, and a second where linear elastic representations of the structural material were implemented.

    An experimental validation of the co-simulation approach applied to an existing hydraulic hammer was performed. Experiments on the hydraulic hammer were performed using an in-house test rig, and responses were registered at four different running conditions. The co-simulation model was developed using the same approach as before. The corresponding running conditions were simulated and the responses were successfully validated against the experiments. A parameter study was also performed involving two design parameters with the objective to evaluate the effects of a parameter change.

    This thesis consists of two parts, where Part I gives an introduction to the application, the simulation method and the implementation, while Part II consists of three papers from this project.

    List of papers
    1. A co-simulation method for system-level simulation of fluid-structure couplings in hydraulic percussion units
    Open this publication in new window or tab >>A co-simulation method for system-level simulation of fluid-structure couplings in hydraulic percussion units
    Show others...
    2017 (English)In: Engineering with Computers, ISSN 0177-0667, E-ISSN 1435-5663, Vol. 33, no 2, p. 317-333Article in journal (Refereed) Published
    Abstract [en]

    This paper addresses a co-simulation method for fluid power driven machinery equipment, i.e. oil hydraulic machinery. In these types of machinery, the fluid-structure interaction affects the end-product performance to a large extent, hence an efficient co-simulation method is of high importance. The proposed method is based on a 1D system model representing the fluid components of the hydraulic machinery, within which structural 3D Finite Element (FE) models can be incorporated for detailed simulation of specific sub-models or complete structural assemblies. This means that the fluid system simulation will get a more accurate structural response, and that the structural simulation will get more correct fluid loads at every time step, compared to decoupled analysis. Global system parameters such as fluid flow, performance and efficiency can be evaluated from the 1D system model simulation results. From the 3D FE-models, it is possible to evaluate displacements, stresses and strains to be used in stress analysis, fatigue evaluation, acoustic analysis, etc. The method has been implemented using two well-known simulation tools for fluid power system simulations and FE-simulations, respectively, where the interface between the tools is realised by use of the Functional Mock-up Interface standard. A simple but relevant model is used to validate the method.

    Place, publisher, year, edition, pages
    SPRINGER, 2017
    Keywords
    Co-simulation; Fluid-structure coupling; System simulation; Functional mock-up interface; Fluid power machinery; Transmission line modelling
    National Category
    Computer Systems
    Identifiers
    urn:nbn:se:liu:diva-136875 (URN)10.1007/s00366-016-0476-8 (DOI)000398468100012 ()
    Note

    Funding Agencies|Atlas Copco Construction Tools

    Available from: 2017-04-30 Created: 2017-04-30 Last updated: 2018-09-11
    2. System level co-simulation of a control valve and hydraulic cylinder circuit in a hydraulic percussion unit
    Open this publication in new window or tab >>System level co-simulation of a control valve and hydraulic cylinder circuit in a hydraulic percussion unit
    Show others...
    2017 (English)In: Proceedings of 15:th Scandinavian International Conference on Fluid Power, June 7-9, 2017, Linköping, Sweden / [ed] Petter Krus, Liselott Ericson and Magnus Sethson, Linköping: Linköping University Electronic Press, 2017, Vol. 144, p. 225-235Conference paper, Published paper (Refereed)
    Abstract [en]

    In this study a previously developed co-simulation method that is based on a 1D system model representing the fluid components of a hydraulic machinery, within which structural 3D Finite Element (FE) models can be incorporated for detailed simulation of specific sub-models or complete structural assemblies, is further developed. The fluid system model consists of ordinary differential equation sub-models that are computationally very inexpensive, but still represents the fluid dynamics very well. The co-simulation method has been shown to work very well for a simple model representing a hydraulic driven machinery. A more complex model was set up in this work, in which two cylinders in the hydraulic circuit were evaluated. Such type of models, including both the main piston and control valves, are necessary as they represent the real application to a further extent than the simple model, of only one cylinder. Two models have been developed and evaluated, from the simple rigid body representation of the structural mechanics model, to the more complex model using linear elastic representation. The 3D FE-model facilitates evaluation of displacements, stresses, and strains on a local level of the model. The results can be utilised for fatigue assessment, wear analysis and for predictions of noise radiation.

    Place, publisher, year, edition, pages
    Linköping: Linköping University Electronic Press, 2017
    Series
    Linköping Electronic Conference Proceedings, ISSN 1650-3686, E-ISSN 1650-3740 ; 144
    Keywords
    Co-simulation, Fluid-structure coupling, System simulation, Functional mockup interface, Fluid power machinery, Transmission line modelling
    National Category
    Applied Mechanics Vehicle Engineering Control Engineering
    Identifiers
    urn:nbn:se:liu:diva-151015 (URN)10.3384/ecp17144225 (DOI)9789176853696 (ISBN)
    Conference
    15th Scandinavian International Conference on Fluid Power, June 7-9, 2017, Linköping, Sweden
    Available from: 2018-09-11 Created: 2018-09-11 Last updated: 2018-09-11Bibliographically approved
  • 12.
    Andersson, Ingemar
    Linköping University, Department of Electrical Engineering. Linköping University, The Institute of Technology.
    Cylinder pressure and ionization current modeling for spark ignited engines2002Licentiate thesis, monograph (Other academic)
  • 13.
    Andersson, Jon M.
    Linköping University, Department of Physics, Measurement Technology, Biology and Chemistry. Linköping University, The Institute of Technology.
    Low-temperature growth of alumina2004Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Physical phenomena related to the growth of alumina, A12O3, are investigated by experiments and ab initio calculations. Alumina is a well studied material with applications in a variety of areas, due to its many beneficial properties. For example, the α and κ phases are widely used as wear-resistant coatings due to their hardness and thermal stability, while, e.g., the γ and θ phases find applications as catalysts or catalyst supports, since they have large surface areas.

    Alumina growth at low temperatures usually results in one of the metastable phases. These are involved in transition sequences, which all irreversibly end in the transformation to the thermodynamically stable α phase at about 1050°C. Thus, the metastable aluminas can be grown at low temperatures but cannot be used in high temperature applications, while formation of the stable α phase typically require high temperatures, prohibiting the use of temperature sensitive substrates.

    In the experimental part of this work, single-phase α-alumina thin films were grown at temperatures down to 280°C. This was achieved by pre-depositing a chromia template layer, which is shown to promote formation of α-alumina. The results demonstrate that low-temperature α-alumina growth is possible once initial nucleation has occurred.

    In the second part of this work, the effect of additives on the phase stability of α- and θ-alumina is investigated by density functional theory calculations. The studied alumina dopants are 5 at.% of Cr, Mo, Co, or As, which substitute for Al in the lattices, and 5 at.% of N or S, substituting for O. We predict that most tested dopants tend to reverse the stability between α- and θ-alumina, so that, e.g., Mo-doping makes the θ phase energetically favored. The exception is Co, which instead gives a slight increase in the relative stability of the α phase. The stability of some of these compounds is also studied by calculating their energies of formation from their constituents, i.e., related dopant oxides, pure metals, and molecules. The results show that the Cr-, Mo-, and Co-doped aluminas are higher in energy than phase separations into pure alumina and other phases, containing the dopants. Thus, the doped aluminas seem to be metastable and will most likely phase separate at high temperatures.

  • 14.
    Andersson, K. Ola
    Linköping University, Department of Electrical Engineering. Linköping University, The Institute of Technology.
    Studies on performance limitations in CMOS DACs2002Licentiate thesis, monograph (Other academic)
    Abstract [en]

    The digital-to-analog converter (DAC) is a bottle neck in broadband communication systems. High update rates are required in combination with high accuracy. In this work, we study factors that limit the performance of current-steering DACs, focusing on the linearity properties of DACs for telecommunication applications like digital subscriber lines (DSL).

    There are many different sources of nonlinear behavior in current-steering DACs. Static errors dominate the low-frequency behavior, whereas the high-frequency behavior is dominated by dynamic errors. The static errors are mainly caused by mismatch between components and finite output resistance in the current sources. The dynamic nonlinearity caused by parasitic capacitance in transistors and wires is of special interest in this work. Two closely related types of models of this dynamic nonlinearity were developed.

    The linearity requirements on the converters for high-speed telecommunication applications can be hard to meet using a straightforward approach. Various methods for improving the linearity of DACs are studied in this work. Some of the methods, like dynamic element matching (DEM) and a novel differential DAC architecture, rely on redundant coding to improve the linearity. Two methods utilizing models of the dynamic nonlinearity caused by the parasitic capacitance in the current sources were also developed. One of the methods utilizes a feedback similar to delta-sigma modulation to spectrally shape the distortion. The other method is a type of predistortion where the input is modified in order to yield an improved output that is closer to the desired output, compared with using the original input.

    CMOS technology is popular for implementation of integrated circuits. Two main advantages of CMOS, compared with, e.g., bipolar technology, is low cost and the possibility of designing circuits with relatively low power consumption.

    CMOS is also the preferred technology for implementing large systems on a single chip with both analog and digital blocks. Three different current-steering CMOS DACs were developed in this work, and are presented in the thesis. Measurement results show close resemblance with the simulation results obtained from the developed models.

  • 15.
    Andersson, Lars Mattias
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Topics in color measurement2004Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Color characterizations of printing situations are essential for a correct color reproduction. To obtain a good color characterization, knowledge about the substrate, the printing process and the printer function are all of great importance. In this thesis, methods for color characterization of printing situations are proposed and the problems associated with the transfer of color characterization methods from spectrophotometers to flatbed scanners are extensively studied. All methods have been developed with bearing on digital printing technologies, although they can be applied to any printing system. Special emphasis has been put on the influence of paper properties in printing situations and image capturing of printed substrates.

  • 16.
    Andersson, Olov
    Linköping University, Department of Computer and Information Science, Artificial Intelligence and Integrated Computer Systems. Linköping University, Faculty of Science & Engineering.
    Methods for Scalable and Safe Robot Learning2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Robots are increasingly expected to go beyond controlled environments in laboratories and factories, to enter real-world public spaces and homes. However, robot behavior is still usually engineered for narrowly defined scenarios. To manually encode robot behavior that works within complex real world environments, such as busy work places or cluttered homes, can be a daunting task. In addition, such robots may require a high degree of autonomy to be practical, which imposes stringent requirements on safety and robustness. \setlength{\parindent}{2em}\setlength{\parskip}{0em}The aim of this thesis is to examine methods for automatically learning safe robot behavior, lowering the costs of synthesizing behavior for complex real-world situations. To avoid task-specific assumptions, we approach this from a data-driven machine learning perspective. The strength of machine learning is its generality, given sufficient data it can learn to approximate any task. However, being embodied agents in the real-world, robots pose a number of difficulties for machine learning. These include real-time requirements with limited computational resources, the cost and effort of operating and collecting data with real robots, as well as safety issues for both the robot and human bystanders.While machine learning is general by nature, overcoming the difficulties with real-world robots outlined above remains a challenge. In this thesis we look for a middle ground on robot learning, leveraging the strengths of both data-driven machine learning, as well as engineering techniques from robotics and control. This includes combing data-driven world models with fast techniques for planning motions under safety constraints, using machine learning to generalize such techniques to problems with high uncertainty, as well as using machine learning to find computationally efficient approximations for use on small embedded systems.We demonstrate such behavior synthesis techniques with real robots, solving a class of difficult dynamic collision avoidance problems under uncertainty, such as induced by the presence of humans without prior coordination. Initially using online planning offloaded to a desktop CPU, and ultimately as a deep neural network policy embedded on board a 7 quadcopter.

    List of papers
    1. Model-Based Reinforcement Learning in Continuous Environments Using Real-Time Constrained Optimization
    Open this publication in new window or tab >>Model-Based Reinforcement Learning in Continuous Environments Using Real-Time Constrained Optimization
    2015 (English)In: Proceedings of the Twenty-Ninth AAAI Conference on Artificial Intelligence (AAAI) / [ed] Blai Bonet and Sven Koenig, AAAI Press, 2015, p. 2497-2503Conference paper, Published paper (Refereed)
    Abstract [en]

    Reinforcement learning for robot control tasks in continuous environments is a challenging problem due to the dimensionality of the state and action spaces, time and resource costs for learning with a real robot as well as constraints imposed for its safe operation. In this paper we propose a model-based reinforcement learning approach for continuous environments with constraints. The approach combines model-based reinforcement learning with recent advances in approximate optimal control. This results in a bounded-rationality agent that makes decisions in real-time by efficiently solving a sequence of constrained optimization problems on learned sparse Gaussian process models. Such a combination has several advantages. No high-dimensional policy needs to be computed or stored while the learning problem often reduces to a set of lower-dimensional models of the dynamics. In addition, hard constraints can easily be included and objectives can also be changed in real-time to allow for multiple or dynamic tasks. The efficacy of the approach is demonstrated on both an extended cart pole domain and a challenging quadcopter navigation task using real data.

    Place, publisher, year, edition, pages
    AAAI Press, 2015
    Keywords
    Reinforcement Learning, Gaussian Processes, Optimization, Robotics
    National Category
    Computer Sciences Computer Vision and Robotics (Autonomous Systems)
    Identifiers
    urn:nbn:se:liu:diva-113385 (URN)978-1-57735-698-1 (ISBN)
    Conference
    Twenty-Ninth AAAI Conference on Artificial Intelligence (AAAI), January 25-30, 2015, Austin, Texas, USA.
    Funder
    Linnaeus research environment CADICSeLLIIT - The Linköping‐Lund Initiative on IT and Mobile CommunicationsSwedish Foundation for Strategic Research VINNOVAEU, FP7, Seventh Framework Programme
    Available from: 2015-01-16 Created: 2015-01-16 Last updated: 2018-01-11Bibliographically approved
    2. Model-Predictive Control with Stochastic Collision Avoidance using Bayesian Policy Optimization
    Open this publication in new window or tab >>Model-Predictive Control with Stochastic Collision Avoidance using Bayesian Policy Optimization
    2016 (English)In: IEEE International Conference on Robotics and Automation (ICRA), 2016, Institute of Electrical and Electronics Engineers (IEEE), 2016, p. 4597-4604Conference paper, Published paper (Refereed)
    Abstract [en]

    Robots are increasingly expected to move out of the controlled environment of research labs and into populated streets and workplaces. Collision avoidance in such cluttered and dynamic environments is of increasing importance as robots gain more autonomy. However, efficient avoidance is fundamentally difficult since computing safe trajectories may require considering both dynamics and uncertainty. While heuristics are often used in practice, we take a holistic stochastic trajectory optimization perspective that merges both collision avoidance and control. We examine dynamic obstacles moving without prior coordination, like pedestrians or vehicles. We find that common stochastic simplifications lead to poor approximations when obstacle behavior is difficult to predict. We instead compute efficient approximations by drawing upon techniques from machine learning. We propose to combine policy search with model-predictive control. This allows us to use recent fast constrained model-predictive control solvers, while gaining the stochastic properties of policy-based methods. We exploit recent advances in Bayesian optimization to efficiently solve the resulting probabilistically-constrained policy optimization problems. Finally, we present a real-time implementation of an obstacle avoiding controller for a quadcopter. We demonstrate the results in simulation as well as with real flight experiments.

    Place, publisher, year, edition, pages
    Institute of Electrical and Electronics Engineers (IEEE), 2016
    Series
    Proceedings of IEEE International Conference on Robotics and Automation, ISSN 1050-4729
    Keywords
    Robot Learning, Collision Avoidance, Robotics, Bayesian Optimization, Model Predictive Control
    National Category
    Robotics Computer Sciences
    Identifiers
    urn:nbn:se:liu:diva-126769 (URN)10.1109/ICRA.2016.7487661 (DOI)000389516203138 ()
    Conference
    IEEE International Conference on Robotics and Automation (ICRA), 2016, Stockholm, May 16-21
    Projects
    CADICSELLIITNFFP6CUASSHERPA
    Funder
    Linnaeus research environment CADICSELLIIT - The Linköping‐Lund Initiative on IT and Mobile CommunicationsEU, FP7, Seventh Framework ProgrammeSwedish Foundation for Strategic Research
    Available from: 2016-04-04 Created: 2016-04-04 Last updated: 2018-01-10Bibliographically approved
    3. Deep Learning Quadcopter Control via Risk-Aware Active Learning
    Open this publication in new window or tab >>Deep Learning Quadcopter Control via Risk-Aware Active Learning
    2017 (English)In: Proceedings of The Thirty-first AAAI Conference on Artificial Intelligence (AAAI) / [ed] Satinder Singh and Shaul Markovitch, AAAI Press, 2017, Vol. 5, p. 3812-3818Conference paper, Published paper (Refereed)
    Abstract [en]

    Modern optimization-based approaches to control increasingly allow automatic generation of complex behavior from only a model and an objective. Recent years has seen growing interest in fast solvers to also allow real-time operation on robots, but the computational cost of such trajectory optimization remains prohibitive for many applications. In this paper we examine a novel deep neural network approximation and validate it on a safe navigation problem with a real nano-quadcopter. As the risk of costly failures is a major concern with real robots, we propose a risk-aware resampling technique. Contrary to prior work this active learning approach is easy to use with existing solvers for trajectory optimization, as well as deep learning. We demonstrate the efficacy of the approach on a difficult collision avoidance problem with non-cooperative moving obstacles. Our findings indicate that the resulting neural network approximations are least 50 times faster than the trajectory optimizer while still satisfying the safety requirements. We demonstrate the potential of the approach by implementing a synthesized deep neural network policy on the nano-quadcopter microcontroller.

    Place, publisher, year, edition, pages
    AAAI Press, 2017
    Series
    Proceedings of the AAAI Conference on Artificial Intelligence, ISSN 2159-5399, E-ISSN 2374-3468 ; 5
    National Category
    Computer Vision and Robotics (Autonomous Systems) Computer Sciences
    Identifiers
    urn:nbn:se:liu:diva-132800 (URN)978-1-57735-784-1 (ISBN)
    Conference
    Thirty-First AAAI Conference on Artificial Intelligence (AAAI), 2017, San Francisco, February 4–9.
    Projects
    ELLIITCADICSNFFP6SYMBICLOUDCUGS
    Funder
    Linnaeus research environment CADICSELLIIT - The Linköping‐Lund Initiative on IT and Mobile CommunicationsEU, FP7, Seventh Framework ProgrammeCUGS (National Graduate School in Computer Science)Swedish Foundation for Strategic Research
    Available from: 2016-11-25 Created: 2016-11-25 Last updated: 2018-01-13Bibliographically approved
  • 17.
    Andersson, Theresa
    Linköping University, Department of Physics, Measurement Technology, Biology and Chemistry. Linköping University, The Institute of Technology.
    Molecular recognition of proteins by functionalized folded polypeptide receptors2004Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis describes the design, synthesis and characterization of synthetic receptor molecules for the recognition and binding of proteins with applications in bioseparation and biosensing. A 42-residue polypeptide, designed to fold into a helix-loop-helix motif and dimerize in solution to form a four-helix bundle, was used as the scaffold. In the first part of the thesis it was functionalized by the incorporation of three substituents at the side chains of lysine residues. A library of 343 receptors was created and screened for affinity towards the human IgG fab fragment using SPR technology. The scaffold was reacted in a stepwise and combinatorial procedure with seven active esters in a pH controlled site-selective acylation reaction to form amides at the side chains of three lysine residues. Four receptor candidates were found to have 0.1 mM affinities and were selected for further investigation.

    Both the unfunctionalized scaffold and the four selected receptors were found to bind well also to HCA II and the molecular interactions with this target protein were studied in detail. NMR studies of their interactions with 15N-labeled HCA II revealed that the peptides bound to a hydrophobic patch near the active site cleft, and SPR studies of modified receptor polypeptides led to the conclusion that mainly hydrophobic interactions were involved in binding.

    In the second part of the thesis two scaffolds were functionalized with a benzenesulfonamide ligand linked to the scaffold by a series of aliphatic spacers of varying length. Benzenesulfonamide is a known inhibitor of HCA II with a dissociation constant of 1.5 µM and it was found that the overall affinity of the functionalized peptide was enhanced by increasing the length of the ligand spacer due to cooperativity between the scaffold and the ligand in the binding to HCA II. The receptor with a seven methylene group spacer bound HCA II with a dissociation constant of 4 n M. It was also shown that the sequence of the scaffold polypeptide strongly affected the overall affinity of the peptide conjugate for the target protein.

  • 18.
    Andersson, Tobias
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    The flight perturbation problem: operational aircraft rescheduling2001Licentiate thesis, monograph (Other academic)
    Abstract [en]

    When there is a perturbation in a carefully planned flight schedule, e.g. an aircraft breakdown, it is important to minimize the negative consequences of this disturbance. In this thesis, a model and a number of solution strategies for the Flight Perturbation Problem is presented. Based on a connection network, a mixed integer multicommodity flow model with side constraints is developed. Cancellations, delays and aircraft swaps, both within the same fleet and between different aircraft types, are used to take care of the perturbation. The model also assures that the schedule returns to normal within a certain time.

    Six different solution strategies arc used to solve the model; the first based on a Lagrangian relaxation of the mixed integer multicommodity flow model. Four strategies are based on Dantzig-Wolfe decomposition and in two of them all feasible points are generated by a tree search algorithm before the master problem is solved, while the other two are column generation based. The last strategy is based on the metaheuristic tabu search.

    The computational tests with real problem data show that the Dantzig-Wolfe based strategies and the tabu search strategy arc very promising, and especially the tabu search strategies could be used in a real problem application that could provide airlines with solutions to complex perturbation problems.

  • 19.
    Andersson, Torbjörn
    Linköping University, Department of Management and Engineering, Machine Design. Linköping University, Faculty of Science & Engineering.
    Aesthetic Flexibility: Modularity of Visual Form in Product Portfolios and Branded Products2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The increase in competition amongst companies that produce complex or large product portfolios has created a need to utilise modularity strategies not only to flexibly manage technical complexity in a costeffective manner but also for visual appearance. This research aims to understand how the visual appearance of products is affected by modular product development strategies. Specifically, the aim is to understand how such strategies induce constraints and generate possibilities for management of visual appearance in the design process.

    Five studies have been conducted during the course of this licentiate thesis. Two were conducted with professionals and students in design, while the remaining three are theoretical studies based on findings in the literature, theory building, and experimental research. The goal has been to investigate how designers work when they are put to the task of changing and developing the designs of complex products that are part of a portfolio. The challenge has been to study what suitable strategies exist that manage complex products and product brands, then investigate how these influence designers’ practices.

    The first study examined how coherence towards a product category influences the design of new products. The outcome of the study was a method to explore visual coherence and diversity in the appearance of a product category.

    The remaining four studies investigated how modularity, brand management and the redesign of product portfolios influence a design process. The second study described a design phenomenon known as aesthetic flexibility, which was further explored in studies three and five. The outcome from these studies was a proposal for four aesthetic flexibility strategies.

    The fourth study investigated in what way portfolio extension strategies found in brand management and design research are related, and how such strategies influence aesthetic flexibility. The results from study four were illustrated as a model.

    The main contribution of this work is the phenomenon of ‘aesthetic flexibility’, which helps understand the factors that influence designers when working with branded modular products. Understanding visual flexibility serves as a starting point in further investigations of how different development strategies affect the possibilities for visual product design.

    The findings of this work serve to illustrate and explain a complex and multi-facetted design phenomenon which many designers manage more or less intuitively today, thus advancing academics’, teachers’ and professional designers’ understanding of the field.

    List of papers
    1. Aesthetic Flexibility in the Management of Visual Product Branding
    Open this publication in new window or tab >>Aesthetic Flexibility in the Management of Visual Product Branding
    2015 (English)In: Procedia Manufacturing, ISSN 2351-9789, Vol. 3, p. 2191-2198Article in journal (Refereed) Published
    Abstract [en]

    This paper will investigate the strategic design decision-making of an in-house designer in a company with a large product portfolio, with respect to how designers plan for future visual alterations of the product. In-house designers have to think strategically about the creation of recognition and differentiation through design because they influence the company’s overall strategies. Therefore, while balancing aesthetic and semiotic qualities of the product, designers have to consider current as well as future needs for recognition and product differentiation. The ability to do so is affected by cost and brand positioning strategy. An exploratory study was setup to investigate what design strategies could be found in an industrial design team employed by a company. The study exposed how in-house designers could strategically incorporate aesthetic flexibility in product parts in order to create opportunities for faster facelifts or redesigns. The importance of managing carry-over details in larger product portfolios was also discovered. To carry over parts from different products is an important way for a company to save money, development time and at the same time increase brand recognition through repetition. Carry-over can be an aid to enhance visual recognition, but it can also be a hindrance when the designer needs to create differencing design values. Most products have a lifespan before they need to be updated or redesigned, which depends on the competition in a product segment. This makes it extra important for designers to have an understanding of when to incorporate carry-over details and when not to. A model was created to describe how carry-over details, design cues and aesthetic flexibility could be managed in a product portfolio. The model is based on Rune Monö’s works and brand management literature, with an emphasis on the brand positioning framework of Point of Difference, Point of Parity and brand extension by Keller et al.

    Place, publisher, year, edition, pages
    Elsevier, 2015
    Keywords
    Strategic Design Decisions, Brand extension, Visual recognition, Product management, In-house designers, Carry-over
    National Category
    Production Engineering, Human Work Science and Ergonomics
    Identifiers
    urn:nbn:se:liu:diva-129547 (URN)10.1016/j.promfg.2015.07.360 (DOI)000383740302042 ()
    Conference
    6th International Conference on Applied Human Factors and Ergonomics (AHFE 2015) and the Affiliated Conferences, AHFE 2015, 26–30 July 2015Las Vegas, United States
    Available from: 2016-06-21 Created: 2016-06-21 Last updated: 2016-12-06Bibliographically approved
  • 20.
    Andreasson, Daniel
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, The Institute of Technology.
    Slack-time aware dynamic routing schemes for on-chip networks2007Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Network-on-Chip (NoC) is a new on-chip communication paradigm for future IP-core based System-on-Chip (SoC), designed to remove a number of limitations of today-s on-chip interconnect solutions. A Nointerconnects cores by means of a packet switched micro-network, which improves scalability and reusability, resulting in a shorter time to market. A typical NoC will be running many applications concurrently, which results in shared network capacity between different kinds of traffic flows. Due to the diverse characteristic of applications, some traffic flows will require real-time communication guarantees while others are tolerant to even some loss of data. In order to provide different levels of Quality-of-Service (QoS) for traffic flows, the communication traffic is separated into different service classes. Traffic in NoC is typically classified into two service classes: the guaranteed throughput (GT) and the best-effort (BE) service class. The GT class offers strict QoS guarantees by setting up a virtual path with reserved bandwidth between the source (GT-producer) and destination (GT-consumer), called a GT-path. The BE class offers no strict QoS guarantees, but tries to efficiently use any network capacity which may become available from the GT traffic. The GT traffic may not fully utilize its bandwidth reservation if its communication volume varies, leading to time intervals where there is no GT traffic using the bandwidth reservation. These intervals are referred to as slack-time. If the slack can not be used this leads to unnecessarily reduced performance of BE traffic, since a part of the available network capacity becomes blocked. This thesis deals with methods to efficiently use the slack-time for BE traffic. The contributions include three new dynamic schemes for slack distribution in NoC. First, a scheme to inform the routers of a GT-path about available slack is evaluated. The GT-producer plans its traffic using a special playout buffer and issues control packets containing the actual amount of slack-time available. The results show that this scheme leads to decreased latency, jitter and packet drops for BE traffic. Secondly, an extension to this scheme is evaluated, where slack is distributed among multiple GT-paths (slack distribution in space). This opens up the possibility to balance the QoS of BE traffic flows which overlap with the GT-paths. Thirdly, a scheme to distribute slack among the links of a GT-path (slack distribution in time) is proposed. In this approach, arriving GT-packets, at a certain router along the GT-path, can wait for a maximum defined amount of time. During this time, any waiting BE traffic in the buffers can be forwarded over the GT-path. The results confirm that this is especially important during high BE-traffic load, where this technique decreases the jitter of BE traffic considerably.    

  • 21.
    Antoni, Marc
    Linköping University, Department of Mechanical Engineering, Quality Technology and Management. Linköping University, The Institute of Technology.
    Inter-project learning: a quality perspective2000Licentiate thesis, monograph (Other academic)
    Abstract [en]

    The development of most sectors in Western economies goes towards a more flexible, project-oriented way of doing business. However, the vast majority of projects exceed their planned budget in terms of time, financial resources and other resources. In companies, which organize work in the form of projects, reinventions of the wheel can also often be observed. One reason for problems of project management is learning deficiencies. Most projects have repetitive components, which make an institutionalization of them useful. However, any formalization should be seen in a balanced relation to the renewal potential of projects.

    The research presented in this thesis aims to gain insight into enabling factors of Inter-Project Learning. This aim is pursued via theoretical literature studies and the study of organizations. The thesis consists of a frame and four papers covering different aspects of Inter-Project Learning. The areas discussed in the frame and the papers are Project Management, Profound Knowledge. Organizational Learning and Process Management.

    In the literature it was found that Inter-Project Learning is usually not planned for, which is supported by empirical evidence. Inter-Project Learning activities partly gave the impression of being seen as pleasant side effects. A central challenge for Inter-Project Learning is the understanding and perception of time in projects, since members of a temporary organization have partly other goals than members of the permanent parental organization. Deming's concept of Profound Knowledge was found to be one useful way of achieving a better understanding of the problems surrounding Inter-Project Learning.

    Experience from projects can be preserved in a process organization supporting Inter-Project Learning. However, it was found that the relation between both project and process organization, as well as between project manager and process owner, in practice is often unclear, which can lead to problems.

    Furthermore. a distinction of forms supporting Inter-Project Learning in codification and personalization forms was found to be convenient. These should not be understood as mutually exclusive approaches, but rather as a choice of emphasis. Empirical data suggest that the choice of emphasis is not a static one, but can shift over time.

    Apart of the findings have been combined in a tentative model for Inter­Project Learning, which shall function as a basis for further discussion. improvement and research.

  • 22.
    Aresu, Emanuela
    Linköping University, Department of Mechanical Engineering, Fluid and Mechanical Engineering Systems. Linköping University, The Institute of Technology.
    Design process management for successful assembly systems2001Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Assembly system design is an important task for a manufacturing company regardless of the nature of its existing assembly activities. However, unlike the product development process, the process of designing assembly systems has not been emphasised.

    The research presented in this thesis aims at identifying and structuring the performance of assembly systems and their design processes, and proposing a framework for identifying important relationships between the results of specific design projects and influencing factors in the field of the design process. These objectives have been accomplished through theoretical and empirical studies. The empirical studies were carried out in the form of an interview study at 15 companies and three case studies at Swedish manufacturing companies both aimed at describing and analysing companies' assembly systems as well as their assembly system design processes.

    A number of characteristics of successful assembly systems have been identified and classified according to the system theory. They have then been structured in a model where the mentioned characteristics have been classified into nine groups indicating the performance of the assembly system. Assembly system performance is represented from a higher level of abstraction by assembly strategy, to a lower level of abstraction by quality, lead time and delivery precision, flexibility, cost and productivity of the assembly system.

    The assembly system design processes have also been investigated and analysed empirically, showing that structured methods are seldom used in the assembly system design process, but mainly experience and knowledge of system designers is utilised. Although larger companies worked more systematically, no specific method for the design of assembly system has been found. The performance of the assembly system design process has been identified and presented in a model with nine performance indicators into three levels, from a higher level of abstraction (design process strategy) to a lower level of abs traction (quality, lead time and delivery precision, flexibility, cost and productivity).

    From the two performance models, an approach to a matrix linking design factors to the design project results has been developed. Examples of the design factors have been given based on research studies in the field of product development, and on the theoretical and empirical studies presented in this thesis. The matrix described is an approach to a tool for the support of production managers and system designers in order to design successful assembly systems.

  • 23.
    Armakavicius, Nerijus
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Study of novel electronic materials by mid-infrared and terahertz optical Hall effect2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Development of silicon based electronics have revolutionized our every day life during the last three decades. Nowadays Si based devices operate close to their theoretical limits that is becoming a bottleneck for further progress. In particular, for the growing field of high frequency and high power electronics, Si cannot offer the required properties. Development of materials capable of providing high current densities, carrier mobilities and high breakdown fields is crucial for a progress in state of the art electronics.

    Epitaxial graphene grown on semi-insulating silicon carbide substrates has a high potential to be integrated in the current planar device technologies. High electron mobilities and sheet carrier densities make graphene extremely attractive for high frequency analog applications. One of the remaining challenges is the interaction of epitaxial graphene with the substrate. Typically, much lower free charge carrier mobilities, compared to free standing graphene, and doping, due to charge transfer from the substrate, is reported. Thus, a good understanding of the intrinsic free charge carriers properties and the factors affecting them is very important for further development of epitaxial graphene.

    III-group nitrides have been extensively studied and already have proven their high efficiency as light sources for short wavelengths. High carrier mobilities and breakdown electric fields were demonstrated for III-group nitrides, making them attractive for high frequency and high power applications. Currently, In-rich InGaN alloys and AlGaN/GaN high electron mobility structures are of high interest for the research community due to open fundamental questions.

    Electrical characterization techniques, commonly used for the determination of free charge carrier properties, require good ohmic and Schottky contacts, which in certain cases can be difficult to achieve. Access to electrical properties of buried conductive channels in multilayered structures requires modification of samples and good knowledge of the electrical properties of all electrical contact within the structure. Moreover, the use of electrical contacts to electrically characterize two-dimensional electronic materials, such as graphene, can alter their intrinsic properties. Furthermore, the determination of effective mass parameters commonly employs cyclotron resonance and Shubnikov-de Haas oscillations measurements, which require long scattering times of free charge carriers, high magnetic fields and low temperatures.

    The optical Hall effect is an external magnetic field induced optical anisotropy in  conductive layers due to the motion of the free charge carriers under the influence of the Lorentz force, and is equivalent to the electrical Hall effect at optical frequencies. The optical Hall effect can be measured by generalized ellipsometry and provides a powerful method for the determination of free charge carrier properties in a non-destructive and contactless manner. In principle, a single optical Hall effect measurement can provide quantitative information about free charge carrier types, concentrations, mobilities and effective mass parameters at temperatures ranging from few kelvins to room temperature and above. Further, it was demonstrated that for transparent samples, a backside cavity can be employed to enhance the optical Hall effect.

    Measurement of the optical Hall effect by generalized ellipsometry is an indirect technique requiring subsequent data analysis. Parameterized optical models are fitted to match experimentally measured ellipsometric data by varying physically significant parameters. Analysis of the optical response of samples, containing free charge carriers, employing optical models based on the classical Drude model, which is augmented with an external magnetic field contribution, provide access to the free charge carrier properties.

    The main research results of the graduate studies presented in this licentiate thesis are summarized in the five scientific papers.

    Paper I. Description of the custom-built terahertz frequency-domain spectroscopic ellipsometer at Linköping University. The terahertz ellipsometer capabilities are demonstrated by an accurate determination of the isotropic and anisotropic refractive indices of silicon and m-plane sapphire, respectively. Further, terahertz optical Hall effect measurements of an AlGaN/GaN high electron mobility structures were employed to extract the two-dimensional electron gas sheet density, mobility and effective mass parameters. Last, in-situ optical Hall effect measurement on epitaxial graphene in a gas cell with controllable environment, were used to study the effects of environmental doping on the mobility and carrier concentration.

    Paper II. Presents terahertz cavity-enhanced optical Hall measurements of the monolayer and multilayer epitaxial graphene on semi-insulating 4H-SiC (0001) substrates. The data analysis revealed p-type doping for monolayer graphene with a carrier density in the low 1012 cm−2 range and a carrier mobility of 1550 cm2/V·s. For the multilayer epitaxial graphene, n-type doping with a carrier density in the low 1013 cm−2 range, a mobility of 470 cm2/V·s and an effective mass of (0.14 ± 0.03) m0 were extracted. The measurements demonstrate that cavity-enhanced optical Hall effect measurements can be applied to study electronic properties of two-dimensional materials.

    Paper III. Terahertz cavity-enhanced optical Hall effect measurements are employed to study anisotropic transport in as-grown monolayer, quasi free-standing monolayer and quasi free-standing bilayer epitaxial graphene on semi-insulating 4H-SiC (0001) substrates. The data analysis revealed a strong anisotropy in the carrier mobilities of the quasi freestanding bilayer graphene. The anisotropy is demonstrated to be induced by carriers scattering at the step edges of the SiC, by showing that the mobility is higher along the step than across them. The scattering mechanism is discussed based on the results of the optical Hall effect, low-energy electron microscopy, low-energy electron diffraction and Raman measurements.

    Paper IV. Mid-infrared spectroscopic ellipsometry and mid-infrared optical Hall effect measurements are employed to determine the electron effective mass in an In0.33Ga0.67N epitaxial layer. The data analysis reveals slightly anisotropic effective mass and carrier mobility parameters together with the optical phonon frequencies and broadenings.

    Paper V. Terahertz cavity-enhanced optical Hall measurements are employed to study the free charge carrier properties in a set of AlGaN/GaN high electron mobility structures with modified interfaces. The results show that the interface structure has a significant effect on the free charge carrier mobility and that the sample with a sharp interface between an AlGaN barrier and a GaN buffer layers exhibits a record mobility of 2332±73 cm2/V·s. The determined effective mass parameters showed an increase compared to the GaN value, that is attributed the the penetration of the electron wavefunction into the AlGaN barrier layer.

    List of papers
    1. Cavity-enhanced optical Hall effect in epitaxial graphene detected at terahertz frequencies
    Open this publication in new window or tab >>Cavity-enhanced optical Hall effect in epitaxial graphene detected at terahertz frequencies
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    2017 (English)In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 421, p. 357-360Article in journal (Refereed) Published
    Abstract [en]

    Cavity-enhanced optical Hall effect at terahertz (THz) frequencies is employed to determine the free charge carrier properties in epitaxial graphene (EG) with different number of layers grown by high-temperature sublimation on 4H-SiC(0001). We find that one monolayer (ML) EG possesses p-type conductivity with a free hole concentration in the low 1012 cmᅵᅵᅵ2 range and a free hole mobility parameter as high as 1550 cm2/Vs. We also find that 6 ML EG shows n-type doping behavior with a much lower free electron mobility parameter of 470 cm2/Vs and an order of magnitude higher free electron density in the low 1013 cmᅵᅵᅵ2 range. The observed differences are discussed. The cavity-enhanced THz optical Hall effect is demonstrated to be an excellent tool for contactless access to the type of free charge carriers and their properties in two-dimensional materials such as EG.

    Place, publisher, year, edition, pages
    Elsevier, 2017
    Keywords
    THz optical Hall effect, Epitaxial graphene, Free charge carrier properties
    National Category
    Physical Sciences Condensed Matter Physics Atom and Molecular Physics and Optics Ceramics
    Identifiers
    urn:nbn:se:liu:diva-132407 (URN)10.1016/j.apsusc.2016.10.023 (DOI)000408756700015 ()
    Note

    Funding agencies: Swedish Research Council (VR) [2013-5580]; Swedish Governmental Agency for Innovation Systems (VINNOVA) under the VINNMER international qualification program [2011-03486, 2014-04712]; Swedish foundation for strategic research (SSF) [FFL12-0181, RIF14-055]

    Available from: 2016-11-09 Created: 2016-11-09 Last updated: 2019-03-05Bibliographically approved
    2. Properties of two-dimensional electron gas in AlGaN/GaN HEMT structures determined by cavity-enhanced THz optical Hall effect
    Open this publication in new window or tab >>Properties of two-dimensional electron gas in AlGaN/GaN HEMT structures determined by cavity-enhanced THz optical Hall effect
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    2016 (English)In: Physica Status Solidi C-Current Topics in Solid State Physics, Vol 13 No 5-6, Wiley-VCH Verlagsgesellschaft, 2016, Vol. 13, no 5-6, p. 369-373Conference paper, Published paper (Refereed)
    Abstract [en]

    In this work we employ terahertz (THz) ellipsometry to determine two-dimensional electron gas (2DEG) density, mobility and effective mass in AlGaN/GaN high electron mobility transistor structures grown on 4H-SiC substrates. The effect of the GaN interface exposure to low-flow-rate trimethylaluminum (TMA) on the 2DEG properties is studied. The 2DEG effective mass and sheet density are determined tobe in the range of 0.30-0.32m0 and 4.3-5.5×1012 cm–2, respectively. The 2DEG effective mass parameters are found to be higher than the bulk effective mass of GaN, which is discussed in view of 2DEG confinement. It is shown that exposure to TMA flow improves the 2DEG mobility from 2000 cm2/Vs to values above 2200 cm2/Vs. A record mobility of 2332±61 cm2/Vs is determined for the sample with GaN interface exposed to TMA for 30 s. This improvement in mobility is suggested to be due to AlGaN/GaN interface sharpening causing the reduction of interface roughness scattering of electrons in the 2DEG.

    Place, publisher, year, edition, pages
    Wiley-VCH Verlagsgesellschaft, 2016
    Series
    Physica Status Solidi C-Current Topics in Solid State Physics, ISSN 1862-6351
    Keywords
    AlGaN/GaN HEMTs, THz ellipsometry, 2DEG properties, THz optical Hall effect
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-133135 (URN)10.1002/pssc.201510214 (DOI)000387957200045 ()
    Conference
    11th International Conference on Nitride Semiconductors (ICNS), Beijing, China, August 30-September 4. 2015
    Available from: 2016-12-12 Created: 2016-12-09 Last updated: 2019-03-05Bibliographically approved
  • 24.
    Aron, Frédéric
    et al.
    Linköping University, Department of Electrical Engineering. Linköping University, The Institute of Technology.
    Dubreuil, Thierry
    Linköping University, Department of Electrical Engineering. Linköping University, The Institute of Technology.
    A design approach for DSP integrated circuits1993Licentiate thesis, monograph (Other academic)
    Abstract [en]

    This thesis presents a design approach for digital signal processing integrated circuits. In the first part, we present the different steps of DSP integrated circuit design. Then, we discuss the various methods used at each level and propose a well structured methodology for layout design.

    In the second part, the implementation of a tool responding to the requirements issued from part one is discussed. We introduce the object-oriented paradigm used and discuss the expected benefits. The emphasis is there on the application of the theoretical requirements and their mapping into object-oriented structures.

  • 25.
    Asami-Johansson, Yukiko
    Linköping University, Department of Mathematics. Linköping University, Faculty of Educational Sciences.
    Designing Mathematics Lessons Using Japanese Problem Solving Oriented Lesson Structure: A Swedish case study2015Licentiate thesis, monograph (Other academic)
    Abstract [en]

    This licentiate thesis is concerned with applying the Japanese problem solving oriented (PSO) teaching approach to Swedish mathematics classrooms. The overall aim of my research project is to describe and investigate the viability of PSO as design tool for teaching mathematics. The PSO approach is a variation of a more general Japanese teaching paradigm referred to as “structured problem solving”. These teaching methods aim to stimulate the process of students’ mathematical thinking and have their focus on enhancing the students’ attitudes towards engaging in mathematical activities. The empirical data are collected using interviews, observations and video recordings over a period of nine months, following two Swedish lower secondary school classes. Chevallard’s anthropological framework is used to analyse which mathematical knowledge is exposed in the original Japanese lesson plans and in the lessons observed in the classrooms. In addition, Brousseau’s framework of learning mathematics is applied to analyse the perception of individual students and particular situations in the classroom.

    The results show that the PSO based lesson plans induce a complex body of mathematical knowledge, where different areas of mathematics are linked. It is found that the discrepancy between the Japanese and Swedish curriculum cause some limitations for the adaptation of the lesson plans, especially in the area of Geometry. Four distinct aspects of the PSO approach supporting the teaching of mathematics are presented.

  • 26.
    Askenäs, Linda
    Linköping University, Department of Computer and Information Science. Linköping University, The Institute of Technology.
    Affärssystemet: en studie om teknikens aktiva och passiva roll i en organisation2000Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Denna studie handlar om användning av affärssystem och hur det påverkar organiseringen i ett företag. Studien är retrospektiv och omfattar en tidsperiod på ett decennium och den är gjord på ett ABB bolag. Fokus har varit på divisionens interna verksamhet och de på förändringar som skett under tiden. Studien aktualiserar vikten av att se användningen av ett affärssystem som en del av organiseringsprocessen. I organiseringsprocessen möts individer, struktur och teknik i ett dualistiskt samspel. Utfallet bestäms utifrån vilken av individen, strukturen eller tekniken som just då har drivkraften. I empirin har det framkommit fem olika mönster för hur detta möte sker, där tekniken erhåller olika grad av aktiv eller passiv påverkan. Dessa mönster har studerats och tolkats utifrån metaforiska begrepp, där tekniken har setts som en aktör i organiseringsprocessen. Beroende på hur individer förhåller sig till och hanterar affärssystemet tilldelas det olika roller i organisationen. Den mest aktiva rollen är manipulatör rollen, där affärssystemet påverkar individerna mot deras egna intressen. Byråkratrollen påverkar organisationen genom att den upprätthåller strukturen såsom individerna har beslutat. Konsultrollen har inte en lika aktiv påverkan på individerna, utan möjliggör snarare olika arbetssätt för individerna. En mer passiv roll tilldelas affärssystemet i rollen som administratör, där affärssystemet enbart administrerar informationen åt individerna. Den mest passiva påverkan från affärssystemet är då det inte används alls, i permittentrollen. Att framgångsrikt använda sig av ett affärssystem innebär att individerna aktivt och medvetet tilldelar tekniken en roll. För att kunna göra det behövs en förståelse för hur individerna upplever användningen och hur användningen av tekniken överensstämmer med strukturen.

  • 27.
    Axelsson, Caroline
    Linköping University, Department of Electrical Engineering. Linköping University, The Institute of Technology.
    Direct Fourier methods in 3D-reconstruction from cone-beam data1994Licentiate thesis, monograph (Other academic)
    Abstract [en]

    The problem of 3D-reconstruction is encountered in both medical and industrial applications of X-ray tomography. It would seem natural to recover volume data by just repeating 2D-reconstructions slice-by-slice. However, 2D fan-beam exposure is wasting most of the photons on the collimator and such a procedure is inefficient in terms of data acquisition. Fast scanning with acceptable signal-to-noise ratio requires cone-beam exposure.

    A method able to utilize a complete set of projections complying with Tuy's condition was proposed by Grangeat. His method is mathematically exact and consists of two distinct phases. In phase 1 cone-beam projection data are used to produce the derivative of the Radon transform. In phase 2, after interpolation, the Radon transform data are used to reconstruct the three-dimensional object function.

    To a large extent our method is an extension of the Grangeat method. Our aim is to reduce the computational complexity, i.e. to produce a faster method. The most taxing procedure during phase 1 is computation of line-integrals in the detector plane. By applying the direct Fourier method in reverse for this computation, we reduce the complexity of phase 1 from O(N4 ) to O(N3logN). Phase 2 can be performed either as a straight 3D-reconstruction or as a sequence of two 2D-reconstructions in vertical and horizontal planes, respectively. Direct Fourier methods can be applied for the 2D- and for the 3D-reconstruction, which reduces the complexity of phase 2 from O(N4) to O(N31ogN) as well. In both cases, linogram techniques are applied.

    For 3D-reconstruction the inversion formula contains the second derivative filter instead of the well-known ramp-filter employed in the 2D-case. The derivative filter is more well-behaved than the 2D ramp-filter. This implies that less zeropadding is necessary which brings about a further reduction of the computational efforts.

    The method has been verified by experiments on simulated data. The image quality is satisfactory and independent of cone-beam angles. For a 5123 volume we estimate that our method is ten times faster than Grangeat's method.

  • 28.
    Backlund, Göran
    Linköping University, Department of Mechanical Engineering. Linköping University, The Institute of Technology. Combitech Systems AB, Linköping, Sweden.
    The effects of modeling requirements in early phases of buyer-supplier relations2000Licentiate thesis, monograph (Other academic)
    Abstract [en]

    This work is an attempt to attack waste of resources during development of embedded systems. Modern systems, in aircraft or automobiles, constantly grow in complexity and also become more integrated. The task of specifying system requirements really shows how crippled the human mind is when we try to master the complexity by the use of natural language. In order to clearly resolve the requirements, other methods need to be employed.

    Focus on system requirements means focus on the early phases of systems development. It is particularly crucial to clearly understand the requirements in collaborative development, since the system requirement specification usually is a part of the contractual agreement. The research questions are: How shall models be used in collaborative systems development? What is the effect of using models?

    The framework of reference for this work is the product development process, collaborative development and requirements analysis. The standard systems development processes are studied and their importance, apart from providing an orderly way of conducting development and establishing a common terminology, is the fact that they are needed as a tool for measuring organizational efficiency. Largely due to complexity, outsourcing of systems development is common in the aircraft industry - the buyer cannot have all required competence in-house. Consequently, parts of the development work is outsourced to suppliers who share risk, and this collaborative development leads to close relations between buyer and supplier. The airworthiness certification process is a contributing factor; it is not easy to change suppliers. The collaborative development relies on commercial contracts where the system requirements are a central part. This motivates focus on the requirements analysis phase; well understood and communicated requirements are a prerequisite for a successful collaborative development project.

    It is also a part of the lean philosophy - always attack waste of resources - to bring in the supplier early, and to focus on the early phases. Good requirements must have specific characteristics, hut if we try to specify complex systems in natural language, the sheer number of requirements represent complexity that limits the overview, and characteristics like completeness, consistency and unambiguity are often violated. Therefore, formal methods are needed for specification since they force the engineers to state the required functionality exactly. There are formalisms available, like Statecharts or ROOMcharts, that can capture the functional behavior of a complex system, and offer testing of the specification since the resulting model is executable.

    Management is responsible for process improvements, hut often lack tools for decision support; justification for investment in a process change. There have, until recently, not existed any tools for simulation of process improvement, for highly iterative processes. Design Structure Matrix is a method used in this work that actually can simulate such processes.

    The use of requirement models in collaborative systems development, and the resulting effect, is studied in two cases. These cases are subprojects in the Gripen fighter program at Saab AB, where two other organizations are suppliers to the projects. One case represents a situation before introduction of modeling requirements, and the other case represents the after situation, since modeling is already a natural way of working in that case. Modeling was tested in one of the cases, within the framework of this study. The results are positive, from both cases, and are summarized as recommendations to future projects. The results prove the current text-based requirement specifications to be inadequate and to cause problems later in systems development.

    Model integration efforts, prior to this work as well as efforts executed in this work, are summed up and result in recommendations to future projects.

    A method for simulating the effects of process improvement was tested on one of the cases. The Design Structure Matrix (DSM) method was applied to a collaborative systems development process, which was derived from interviews in the case studies. The process change studied was the introduction of requirements modeling, and the result was a substantial reduction of total project time. This result was corroborated by study­ ing problem reports in that project, since many of the detected problems were of the kind that they probably had been detected early through modeling of functional requirements. The other case, which early adopted a model-based approach, actually found some design errors, and due to their early detection the result was a reduction of project time. However, it is difficult to account for the problems "that never occurred", since many of them were avoided very early in the project, prior to any problem reporting having been established.

    Finally, a "Digital Mock-Up" room, which is a concept for model-based design currently applied to airframe development, is recommended for carrying over to the systems and software engineering areas. In such rooms the systems development teams can meet around requirements models, performance models, etc. and actually make the models the foundation and design base of their decisions and engineering work.

  • 29.
    Bakoglidis, Konstantinos D.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Low Friction and Wear Resistant Carbon Nitride Thin Films for Rolling Components Grown by Magnetron Sputtering2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The scope of this licentiate thesis is the investigation of carbon based thin films suitable for rolling components, especially roller bearings. Carbon and carbon nitride are materials with advantageous tribological properties and high resiliency. Such materials are required in order to withstand the demanding conditions of bearing operation, such as high loads and corrosive environments. A fundamental condition for coated bearings is that the deposition temperature must be striktly limited. Thus, carbon nitride (CNx) thin films were synthesized here at low temperature of 150 oC by different reactive magnetron sputtering techniques, which are mid-frequency magnetron sputtering (MFMS), direct current magnetron sputtering (DCMS), and high power impulse magnetron sputtering (HiPIMS). While DCMS is a very well studied technique for carbon based films, MFMS and HiPIMS are relatively new sputtering techniques for carbon, and especially CNx depositions. Using different magnetron sputtering techniques, different ionization conditions prevail in the chamber during each process and influence the obtained film properties at a great extent. It was found that bias duty cycles and the amount of working gas ions are key parameters and affect the morphology and microstructure as well as the mechanical response of the films. Moreover, different bias voltages, from 20 V up to 120 V were applied during the processes in order to investigate the changes that the different ion energies induce in the film structure.

    The structural, mechanical and tribological properties of CNx films are also presented in this licentiate thesis. The morphology of CNx films strongly depends on both the deposition technique and ion energy. The special configuration of MFMS mode produces highly homogeneous and dense films even from low applied bias voltages, while in HiPIMS mode high bias voltages above 100 V must be applied in order to produce films with similar structural characteristics. DCMS is also proven as a good technique for homogeneous and dense films. Low bias voltages do not favor  homogeneous structures, thus at 20 V all techniques produced films with columnar structures with intercolumnar voids. High bias voltages influence the N incorporation in the films, with the appearance of re-sputtering of N-containing species and a promotion of sp2 bonding configurations with increasing ion energy. Nevertheless, the different deposition mode influences the sp2 content in different ways, with only MFMS showing a clear increase of sp2 content with increasing bias voltage and HiPIMS showing relatively constant sp2 content. The morphology and microstructure of the CNx films affects their mechanical response, with higher ion energies producing harder films. A dependency of hardness and elastic modulus with increasing ion energy was obtained, where for all deposition modes, hardness and elastic modulus increase linearly with increasing bias voltage. Films with hardness as high as 25 GPa were synthesized by MFMS at 120 V , while the softer film yielded a hardness of 7 GPa and was deposited by HiPIMS at 20 V . The elastic recovery of the films differs with increasing ion energies, presenting a correlation with the C sp2 bond content. The highest elastic recovery of 90% was extracted for the film deposited by MFMS at 120 V and is a value similar to the elastic recovery obtained for FL-CNx films. All films developed compressive residual stresses, depending also on the ion energies and the deposition mode used. It is demonstrated that the induced stresses in the films increase when denser and more homogeneous film morphologies are obtained and with higher Ar intercalcation. Low friction coefficients were obtained for all films between 0.05 and 0.07, although the deposition conditions are not detrimental for the development of friction coefficient. The wear resistance of the films was found to be dependent on the morphology and to some extent on the microstructure of the films. Harder, denser, and more homogeneous films have higher wear resistance. Especially, CNx films deposited by MFMS at 120 V present no wear.

    The tribological characteristics of the surface of the films were also investigated at nanoscale by a new reciprocal wear test. In this wear test, the recording of the track profile is performed in between consecutive test cycles, eliminating also thermal drift. The very low wear of the films deposited by MFMS at 100 V and 120 V revealed that during the wear test a phase transformation on the surface may take place, possibly graphitization. It is also demonstrated the way that the surface characteristics, such as asperities and roughness affects the tribological measurements. Attention is also turned to the presence of large asperities on the film surface and the way they affect the obtained average friction coefficient and tribological measured data.

    List of papers
    1. Low-temperature growth of low friction wear-resistant amorphous carbon nitride thin films by mid-frequency, high power impulse, and direct current magnetron sputtering
    Open this publication in new window or tab >>Low-temperature growth of low friction wear-resistant amorphous carbon nitride thin films by mid-frequency, high power impulse, and direct current magnetron sputtering
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    2015 (English)In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 33, no 5, article id 05E112Article in journal (Refereed) Published
    Abstract [en]

    Amorphous carbon nitride (a-CNx) thin films were deposited on steel AISI52100 and Si(001) substrates using mid-frequency magnetron sputtering (MFMS) with an MF bias voltage, high power impulse magnetron sputtering (HiPIMS) with a synchronized HiPIMS bias voltage, and direct current magnetron sputtering (DCMS) with a DC bias voltage. The films were deposited at a low substrate temperature of 150 °C and a N2/Ar flow ratio of 0.16 at the total pressure of 400 mPa. The negative bias voltage (Vs) was varied from 20 V to 120 V in each of the three deposition modes. The microstructure of the films was characterized by high-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED), while the film morphology was investigated by scanning electron microscopy (SEM). All films possessed amorphous microstructure with clearly developed columns extending throughout the entire film thickness. Layers grown with the lowest substrate bias of 20 V exhibited pronounced intercolumnar porosity, independent of the technique used. Voids closed and dense films formed at Vs ≥ 60 V, Vs ≥ 100 V and Vs = 120 V for MFMS, DCMS and HiPIMS, respectively. X-ray photoelectron spectroscopy (XPS) revealed that the nitrogen-to-carbon ratio, N/C, of the films ranged between 0.2 and 0.24. Elastic recoil detection analysis (ERDA) showed that Ar content varied between 0 and 0.8 at% and increases as a function of Vs for all deposition techniques. All films exhibited compressive residual stress, σ, which depends on the growth method; HiPIMS produces the least stressed films with stress between – 0.4 and – 1.2 GPa for all Vs values, while for CNx films deposited by MFMS σ = – 4.2 GPa. Nanoindentation showed a significant increase in film hardness and reduced elastic modulus with increasing Vs for all techniques. The harder films were produced by MFMS with hardness as high as 25 GPa. Low friction coefficients, between 0.05 and 0.06, were recorded for all films. Furthermore, CNx films produced by MFMS and DCMS at Vs = 100 V and 120 V presented a high wear resistance with wear coefficients of k ≤ 2.3 x 10-5 mm3/Nm.

    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-118343 (URN)10.1116/1.4923275 (DOI)000361229000012 ()
    Note

    On the day of the defence date the status of this article was Manuscript.

    Available from: 2015-05-27 Created: 2015-05-27 Last updated: 2017-12-04Bibliographically approved
    2. Nanotribological properties of wear resistant a-CNx thin films deposited by mid-frequency magnetron sputtering
    Open this publication in new window or tab >>Nanotribological properties of wear resistant a-CNx thin films deposited by mid-frequency magnetron sputtering
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    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    The nanotribological properties of amorphous carbon nitride (a-CNx) thin films deposited with mid-frequency magnetron sputtering (MFMS) were investigated at the nanoscale using an in-situ technique in a Hysitron Triboindenter TI 950. The friction coefficient, wear rate, track roughness, and the track profiles were recorded as a function of the number of linear reciprocal cycles, revealing the manner that the nanotribological and surface properties change during the wear test. The surface composition of  the films was evaluated by x-ray photoelectron spectroscopy (XPS). The friction coefficient ranges between 0.05 – 0.07, while the wear coefficient ranges from 9.4 x 10-8 up to 1.5 x 10-4 mm3/Nm. Debris particles and surface modifications characterize the friction and lubrication behavior in the track. The friction and main lubrication mechanism on the modified surface changes after the removal of debris particles, while this change appears at different cycle for each CNx film depending on the substrate bias voltage. Films grown at higher bias are modified earlier than films grown at lower bias. The wear behavior can be divided into two, track roughnessdependent, regimes; (1) films with track roughness > 1 nm showed wear with obvious tracks and (2) the films with roughness < 1 nm showed negative wear at the nanometer scale with a volume of material projected in the area of the wear track. This material volume is believed to be result of a surface modification, where the molar volume of the modified surface is larger than the molar volume of the surface before the wear test.

    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-118347 (URN)
    Available from: 2015-05-27 Created: 2015-05-27 Last updated: 2016-11-09Bibliographically approved
  • 30.
    Bartolini, Gabriel
    Linköping University, Department of Mathematics, Applied Mathematics. Linköping University, The Institute of Technology.
    On the Branch Loci of Moduli Spaces of Riemann Surfaces of Low Genera2009Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Compact Riemann surfaces of genus greater than 1 can be realized as quotient spaces of the hyperbolic plane by the action of Fuchsian groups. The Teichmüller space is the set of all complex structures of Riemann surfaces and the moduli space the set of conformal equivalence classes of Riemann surfaces. For genus greater than two the branch locus of the covering of the moduli space by the Teichmüller space can be identified wi the set of Riemann surfaces admitting non-trivial automorphisms. Here we give the orbifold structure of the branch locus of surfaces of genus 5 by studying the equisymmetric stratification of the branch locus. This gives the orbifold structure of the moduli space.

    We also show that the strata corresponding to surfaces with automorphisms of order 2 and 3 belong to the same connected component for every genus. Further we show that the branch locus is connected with the exception of one isolated point for genera 5 and 6, it is connected for genus 7 and it is connected with the exception of two isolated points for genus 8.

    List of papers
    1. On the connectedness of the branch locus of the moduli space of Riemann surfaces of low genus
    Open this publication in new window or tab >>On the connectedness of the branch locus of the moduli space of Riemann surfaces of low genus
    2012 (English)In: Proceedings of the American Mathematical Society, ISSN 0002-9939, E-ISSN 1088-6826, Vol. 140, no 1, p. 35-45Article in journal (Refereed) Published
    Abstract [en]

    Let be an integer and let , where denotes the moduli space of compact Riemann surfaces of genus . Using uniformization of Riemann surfaces by Fuchsian groups and the equisymmetric stratification of the branch locus of the moduli space, we prove that the subloci corresponding to Riemann surfaces with automorphism groups isomorphic to cyclic groups of order 2 and 3 belong to the same connected component. We also prove the connectedness of for and with the exception of the isolated points given by Kulkarni.

    Place, publisher, year, edition, pages
    American Mathematical Society, 2012
    Keywords
    Moduli spaces, Teichmüller modular group, automorphism group
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-73196 (URN)10.1090/S0002-9939-2011-10881-5 (DOI)000299596000004 ()
    Funder
    Swedish Research Council, 621-2007-6240
    Available from: 2011-12-21 Created: 2011-12-21 Last updated: 2018-09-01
  • 31.
    Bengtsson, Jens
    Linköping University, Department of Production Economics. Linköping University, The Institute of Technology.
    Essays on valuation of manufacturing flexibility: an option-pricing theory approach2000Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Flexibility in manufacturing operations is becoming increasingly more important to industrial firms due to e.g. increasing product demand volatility, internationalisation of markets and competition, and shorter product life cycles. Flexibility is hard to evaluate in the traditional way by discounting expected cash flow, but an accessible approach is to consider flexibility as real options and use option-pricing theory. The general purpose of this thesis is to analyse and increase the understanding of product-mix flexibility by using option pricing. Employing option pricing enables a number of flexibility related issues to be analysed. From a manufacturing point of view aspects such as the impact of capacity levels, degree of flexibility in the manufacturing process, and characteristics of product demand are analysed. From a financial point of view aspects such as the impact of correlation between product demand and the market portfolio, and the impact of mean-reverting processes are analysed. The manufacturing contexts are characterised by set-up costs, capacity constraints, and in the presence of several products.

  • 32.
    Bengtsson, Katarina
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Additive manufacturing methods and materials for electrokinetic systems2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Fabrication of miniaturized devices is usually time-consuming, costly, and the materials commonly used limit the structures that are possible to create. The techniques most often used to make microsystems involve multiple steps, where each step takes considerable time, and if only a few systems are to be made, the price per device becomes excessive. This thesis describes how a simple syringebased 3D-printer, in combination with an appropriate choice of materials, can reduce the delay between design and prototype and simplify fabrication of microsystems. This thesis suggest two types of materials that we propose be used in combination with 3D-printing to further develop microsystems for biology and biochemistry.

    Analytical applications in biology and biochemistry often contain electrodes, such as in gel electrophoresis. Faradaic (electrochemical) reactions have to occur at the metal electrodes to allow electron-to-ion transduction through an electrolyte-based system to drive a current when a potential is applied to the electrodes in an electrolyte-based system. These electrochemical reactions at the electrodes, such as water electrolysis, are usually problematic when miniaturizing devices and analytical systems. An alternative to metal electrodes can be electrochemicallyactive conducting polymers, e.g. poly(3,4-ethylenedioxythiophene) (PEDOT), which can be used to reduce electrolysis when driving a current through water-based systems. Paper 1 describes gel electrophoresis where the platinum electrodes were replaced with the conductive polymer PEDOT, without affecting the separation.

    Manufacturing and prototyping of microsystems can be simplified by using 3Dprinting in combination with a sacrificial material. A sacrificial template material can further simplify bottom-up manufacturing of more complicated forms such as protruding and overhanging structures. We showed in paper 2 that polyethylene glycol (PEG), in combination with a carbonate-based plasticizer, functions well as a 3D-printable sacrificial template material. PEG2000 with between 20 wt% and 30 wt% ethylene carbonate or propylene carbonate has properties advantageous for 3D-printing, such as shear-thinning rheology, mechanical and chemical stability, and easy dissolution in water.

    List of papers
    1. Conducting Polymer Electrodes for Gel Electrophoresis
    Open this publication in new window or tab >>Conducting Polymer Electrodes for Gel Electrophoresis
    2014 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 9, no 2, p. 0089416-Article in journal (Refereed) Published
    Abstract [en]

    In nearly all cases, electrophoresis in gels is driven via the electrolysis of water at the electrodes, where the process consumes water and produces electrochemical by-products. We have previously demonstrated that p-conjugated polymers such as poly(3,4-ethylenedioxythiophene) (PEDOT) can be placed between traditional metal electrodes and an electrolyte to mitigate electrolysis in liquid (capillary electroosmosis/electrophoresis) systems. In this report, we extend our previous result to gel electrophoresis, and show that electrodes containing PEDOT can be used with a commercial polyacrylamide gel electrophoresis system with minimal impact to the resulting gel image or the ionic transport measured during a separation.

    Place, publisher, year, edition, pages
    Public Library of Science, 2014
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-105901 (URN)10.1371/journal.pone.0089416 (DOI)000331711900141 ()
    Available from: 2014-04-14 Created: 2014-04-12 Last updated: 2017-12-05Bibliographically approved
    2. Plasticized polyethylene glycol as sacrificial support and template material for syringe-based 3D-printing
    Open this publication in new window or tab >>Plasticized polyethylene glycol as sacrificial support and template material for syringe-based 3D-printing
    2015 (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    Syringe-based 3D-printing is a powerful additive manufacturing method for fabricating short runs (small volumes) of components from multiple materials with a wide range of viscosities. However, objects that are hollow or not in complete contact with the printer’s stage are difficult to fabricate. Using a sacrificial template as a supporting layer enables bottom-up construction of complex structures. Template materials based on polyethylene glycol (PEG) plasticized with organic carbonates to tune their rheological (shear-thinning) and thermal (crystallization) properties have been evaluated, including results from rheometry, differential scanning calorimetry, dissolution rate, chemical compatibility with  polydimethylsiloxane (PDMS), and general functionality in a syringe-based 3D-printer. A family of such blends yields material that is easily printed, is stable over time, is soluble in water, and can support other materials and larger structures without collapsing. These mixtures are proposed for use with other extrudable or mouldable materials to enable 3D-printed devices with complex unsupported geometries.

    Keywords
    3D-Printing, polyethylene glycol, organic carbonates, sacrificial template, extrusion
    National Category
    Physical Sciences Physical Chemistry
    Identifiers
    urn:nbn:se:liu:diva-121250 (URN)
    Available from: 2015-09-10 Created: 2015-09-10 Last updated: 2015-09-10Bibliographically approved
  • 33.
    Berg, Amanda
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, Faculty of Science & Engineering. Termisk Systemteknik AB, Linköping, Sweden.
    Detection and Tracking in Thermal Infrared Imagery2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Thermal cameras have historically been of interest mainly for military applications. Increasing image quality and resolution combined with decreasing price and size during recent years have, however, opened up new application areas. They are now widely used for civilian applications, e.g., within industry, to search for missing persons, in automotive safety, as well as for medical applications. Thermal cameras are useful as soon as it is possible to measure a temperature difference. Compared to cameras operating in the visual spectrum, they are advantageous due to their ability to see in total darkness, robustness to illumination variations, and less intrusion on privacy.

    This thesis addresses the problem of detection and tracking in thermal infrared imagery. Visual detection and tracking of objects in video are research areas that have been and currently are subject to extensive research. Indications oftheir popularity are recent benchmarks such as the annual Visual Object Tracking (VOT) challenges, the Object Tracking Benchmarks, the series of workshops on Performance Evaluation of Tracking and Surveillance (PETS), and the workshops on Change Detection. Benchmark results indicate that detection and tracking are still challenging problems.

    A common belief is that detection and tracking in thermal infrared imagery is identical to detection and tracking in grayscale visual imagery. This thesis argues that the preceding allegation is not true. The characteristics of thermal infrared radiation and imagery pose certain challenges to image analysis algorithms. The thesis describes these characteristics and challenges as well as presents evaluation results confirming the hypothesis.

    Detection and tracking are often treated as two separate problems. However, some tracking methods, e.g. template-based tracking methods, base their tracking on repeated specific detections. They learn a model of the object that is adaptively updated. That is, detection and tracking are performed jointly. The thesis includes a template-based tracking method designed specifically for thermal infrared imagery, describes a thermal infrared dataset for evaluation of template-based tracking methods, and provides an overview of the first challenge on short-term,single-object tracking in thermal infrared video. Finally, two applications employing detection and tracking methods are presented.

    List of papers
    1. A Thermal Object Tracking Benchmark
    Open this publication in new window or tab >>A Thermal Object Tracking Benchmark
    2015 (English)Conference paper, Published paper (Refereed)
    Abstract [en]

    Short-term single-object (STSO) tracking in thermal images is a challenging problem relevant in a growing number of applications. In order to evaluate STSO tracking algorithms on visual imagery, there are de facto standard benchmarks. However, we argue that tracking in thermal imagery is different than in visual imagery, and that a separate benchmark is needed. The available thermal infrared datasets are few and the existing ones are not challenging for modern tracking algorithms. Therefore, we hereby propose a thermal infrared benchmark according to the Visual Object Tracking (VOT) protocol for evaluation of STSO tracking methods. The benchmark includes the new LTIR dataset containing 20 thermal image sequences which have been collected from multiple sources and annotated in the format used in the VOT Challenge. In addition, we show that the ranking of different tracking principles differ between the visual and thermal benchmarks, confirming the need for the new benchmark.

    Place, publisher, year, edition, pages
    IEEE, 2015
    National Category
    Computer Vision and Robotics (Autonomous Systems)
    Identifiers
    urn:nbn:se:liu:diva-121001 (URN)10.1109/AVSS.2015.7301772 (DOI)000380619700052 ()978-1-4673-7632-7 (ISBN)
    Conference
    12th IEEE International Conference on Advanced Video- and Signal-based Surveillance, Karlsruhe, Germany, August 25-28 2015
    Available from: 2015-09-02 Created: 2015-09-02 Last updated: 2019-10-23Bibliographically approved
    2. The Thermal Infrared Visual Object Tracking VOT-TIR2015 Challenge Results
    Open this publication in new window or tab >>The Thermal Infrared Visual Object Tracking VOT-TIR2015 Challenge Results