| 1. |
- De Angelis, Hernán, 1974-
(författare)
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Palaeo-ice streams in the north-eastern Laurentide Ice Sheet
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis presents a palaeoglaciological study aimed to determine the location, geometry and temporal evolution of palaeo-ice streams of the north-easternmost Laurentide Ice Sheet. The work was accomplished through the geomorphological interpretation of satellite imagery over 3.19 x 106 km2 of the Canadian Arctic, using a glaciological inversion scheme. Ice streams were active in this region during most of the time between the Last Glacial Maximum and the last deglaciation. A web of ice streams and inter-ice stream areas existed. Three major ice stream networks are identified: the M'Clintock Channel, Gulf of Boothia – Lancaster Sound and Hudson Strait. The M'Clintock Channel bears the most complex landform record, comprising three generations of palaeo-ice streams. Their location was weakly controlled by the subglacial topography and their geometry was determined by frozen-bed portions of the ice sheet, thus providing evidence for pure ice streams in the Laurentide Ice Sheet. In contrast, the more pronounced relief of the Gulf of Boothia – Lancaster Sound corridor supported topographically controlled ice streams. The landform record on emerged land along Hudson Strait is insufficient to support the existence of ice streams. It is therefore proposed that ice streams were constrained within the deep parts of the strait while flanked by cold-based zones on the margins. Small transient ice streams on Baffin and Prince of Wales islands drained local remnant ice caps during the collapse of the ice sheet. Analysis of the controls on the location and flow of palaeo-ice streams suggests that the interaction between the subglacial topography and thermal state of the substrate plays a more fundamental role than the geology. It is concluded that the behaviour of ice streams cannot be explained in terms of environmental controls alone, but the complex dynamics of ice stream shear margins and onset zones must be considered.
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| 2. |
- Goodfellow, Bradley W., 1971-
(författare)
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Relict non-glacial surfaces and autochthonous blockfields in the northern Swedish mountains
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Relict non-glacial surfaces occur in many formerly glaciated landscapes, where they represent areas that have escaped significant glacial modification. Frequently distinguished by blockfield mantles, relict non-glacial surfaces are important archives of long-term weathering and landscape evolution processes. The aim of this thesis is to examine the distribution, weathering, ages, and formation of relict non-glacial surfaces in the northern Swedish mountains. Mapping of surfaces from aerial photographs and analysis in a GIS revealed five types of relict non-glacial surfaces that reflect differences in surface process types or rates according to elevation, gradient, and bedrock lithology. Clast characteristics and fine matrix granulometry, chemistry, and mineralogy reveal minimal chemical weathering of the blockfields. Terrestrial cosmogenic nuclides were measured in quartz samples from two blockfield-mantled summits and a numerical ice sheet model was applied to account for periods of surface burial beneath ice sheets and nuclide production rate changes attributable to glacial isostasy. Total surface histories for each summit are almost certainly, but not unequivocally, confined to the Quaternary. Maximum modelled erosion rates are as low as 4.0 mm/kyr, which is likely to be near the low extreme for relict non-glacial surfaces in this landscape. The blockfields of the northern Swedish mountains are Quaternary features formed through subsurface physical weathering processes. While there is no need to appeal to Neogene chemical weathering to explain blockfield origins, these surfaces have remained continuously regolith-mantled and non-glacial since their inception. Polygenetic surface histories are therefore indicated, where the large-scale surface morphologies are potentially older than their regolith mantles.
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| 3. |
- Holmgren, Johan, 1977-
(författare)
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Studies in Local Public Transport Demand
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis consists of four papers where the overall purpose is to contribute to the understanding of how local public transport demand is affected by different factors. An underlying theme running trough the thesis is the two-way relationship between public transport demand and the service level caused by the fact that capacity and quality are joint products.In Paper I the relationship between public transport demand and the service level (in terms of vehicle-kilometres) is investigated using panel data from Swedish counties. A Granger causality test is performed in order to test if the level of service cause public transport demand or if demand cause service level, or if they cause each other. It is found that demand and service cause each other, which is to say that there is a two-way relationship between them.In Paper II elasticity estimates for local public transport demand from previous research are summarised and the variation in results is analysed using meta-regression. The variation is explained by model specification, type of data used and origin of data.In Paper III a demand function for local public transport is estimated using panel data from Swedish counties. Instrument variable estimation is used in order to avoid the problem of a two-way relationship between demand and service level (vehicle-kilometres). Demand elasticities with respect to public transport fare, price of petrol, vehicle-kilometres and car ownership are found to be -0.4, 0.34, 0.55, and -1.37. After also taking the effects of income on car ownership into account, it is found that the total effect of income on public transport demand is close to zero.In Paper IV it is found that the strong increase in public transport demand in the town of Linköping between 1946 and 1983, in addition to fare, vehicle-kilometres and car ownership, can be explained by the rapid increase in female labour force participation and the expansion of the city’s outer areas. The city expansion is thought to have increased average trip distance and thereby reduced the number of trips that could be made walking or by bicycle. After 1983, female labour force participation decreased slightly and the expansion of the areas in question has stopped. Without these positive forces to counterbalance the rising levels of car ownership bus trips per capita has fallen by 71%. The effects of a policy change, including peak-load pricing, straighter bus routes, smaller bus size and staggered school hours, is analysed. It is found that the proposed changes would increase public transport travel by 42 % compared to present policy.
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| 4. |
- Jansson, Johan, 1978
(författare)
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Automated Computational Modeling
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is part of the FEniCS project of Automation of Computational Mathematical Modeling (ACMM) as the modern manifestation of the basic principle of science:formulating mathematical equations (modeling) and solving equations (computation). The vision of FEniCS is to set a new standard towards the goals of generality, efficiency, and simplicity, concerning mathematical methodology, implementation, and application.ACMM includes the key steps of Automation of (a) discretization of differential equations,(b) solution of discrete systems, (c) error control of discrete solutions, (d) optimizationand (e) modeling. FEniCS is based on adaptive finite element methods (FEM) [1]. This thesis presents the following examples of Automated Computational Modeling asconcrete realizations of ACMM with main focus on (a)-(c): MG: Multi-adaptive Galerkin ODE-solver: This part concerns the automation of (a1) discretization in time by the MG implementation of the multi-adaptive ODE-solver mcG(q)/mdG(q) formulated in the thesis ([9]) by Anders Logg, based on Galerkin's method with continuous/discontinuous piecewise polynomial approximation in time of degree q with different time steps for different components, automati- cally determined by a posteriori error estimation. MG realizes automation of (a1) by Galerkin's method, (b) by fixed-point or Newton's method, and (c) by a posteriori error estimation using duality. MG is the first general multi-adaptive ODE-solver with automatic error control based on duality. MG has potentially a very vast range of applicability. MG may also be run in mono-adaptive form with the same time step for all components, eliminating the over-head required for multi-adaptivity. For bench-mark problems with different time scales, we demonstrate substantial performance gains with MG, as compared to mono-adaptive solvers. MG is joint work with Anders Logg. Ko: Solid mechanics solver: This part includes the automation of (a2) discretization in space of a general continuum model for solid mechanics with elasto-visco-plastic materials and large displacements, rotations and deformations. When coupled with MG for time-discretization this gives the solid mechanics solver Ko realizing (a) and (b) with (c) in progress. Ko is based on an updated Lagrangian formulation where equilibrium and constitutive equations are expressed on the current deformed configuration. Ko is the first automated solid mechanics solver and the range of possible applications is very large. We show that the performance of Ko is comparable to that of a mass-spring solver, which is the industry standard for performance-intensive solid mechanics simulations [8]. Ko demonstrates the general capability and potential of FEniCS. DOLFIN as a PSE: We present the FEniCS tool chain, and in particular DOLFIN, as a general and automated problem solving environment (PSE). DOLFIN realizes the overall concept of automated computational modeling by taking a PDE in mathematical notation as input and automatically discretizing and computing the solution by the FEM with full efficiency, including automated time discretization of time dependent PDE with the ODE solver. This is joint work with Johan Hoffman, Anders Logg and Garth Wells. Automated Modeling: We present a case study of automated modeling (e) in a model problem with a fast and a slow time scale. By resolving the fast time scale for a short period of time an effective coefficient is determined by optimization, which allows simulation of the slow time scale over long time. This is joint work with Claes Johnson and Anders Logg.
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| 5. |
- Jansson, Johan, 1973-
(författare)
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Car(ing) for our environment? : Consumer eco-innovation adoption and curtailment behaviors: The case of the alternative fuel vehicle.
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Determinants influencing consumer eco-innovation adoption and green curtailment behaviors in a travel context are at the center of this thesis. Previous research on green consumer behavior has uncovered that internalized personal attitudinal factors such as values, beliefs, and norms are influential in determining mainly non-consumption and post-purchase behaviors. This thesis extends the understanding of a moral basis of green consumer behavior by exploring the influences of attitudinal factors on both car curtailment behaviors, and on consumer adoption of a high involvement eco-innovation – the alternative fuel vehicle. The integrated influences of innovation specific characteristics, car habits, knowledge and social norms, are also examined. Furthermore, differences between AFV adopters and non-adopters are explored, and the notion of consumers performing purchase and curtailment behaviors for different reasons is utilized in the development of nuanced profiles of three distinct consumer groups. Four studies, which build on two quantitative data collections on adopters and non-adopters of AFVs in Sweden, are included in this thesis.In the first study, similarities and differences among adopters and non-adopters of AFVs, and the effects of attitudinal factors (values, beliefs, and norms), knowledge, and sociodemographics on the adoption decision are analyzed. The results show that knowledge and personal norms are strong predictors of AFV adoption and that the VBN theory is applicable in this context. The main implication from the study is that high-involvement green purchase decisions, such as eco-innovation adoption, can be viewed as morally based.In the second study, a set of determinants influencing both curtailment of car use and willingness to adopt a less environmentally harmful vehicle are analyzed. Biospheric values, personal proenvironmental norms, and car habit strength are found to influence both types of behaviors in different ways. The main implication from this study is that green purchase decisions and curtailment behaviors within a specific context are determined by partly different factors but personal norm is a strong predictor of both types of behaviors.The third study extends the findings from the previous one in segmenting consumers on curtailment behaviors and proenvironmental purchases. Three distinct types of consumers emerge from the data. The Non-greens are found to exhibit the lowest levels of green attitudes and behaviors, and the strongest car habits. The Curtailers are distinguished by performing primarily reductionist behaviors, and by being the most willing to reduce negative environmental impact of car use. The Ecovators are found to be the most inclined to purchase eco-innovations and also display the greenest values. The study shows that green consumers are a heterogeneous group that can be separated on the basis of green curtailment behaviors and proenvironmental purchase decisions, and that there seems to be no inherent contradiction in being an early adopter of new green technology (such as the AFV) and also having high levels of proenvironmental values, beliefs, and norms.In the final study, innovation specific characteristics and consumer innovativeness factors are integrated with normative and attitudinal determinants influencing AFV adoption. The results show that personal and social norms, consumer novelty seeking, and four perceived innovation characteristics influence the adoption decision. Differences between AFV adopters’ and non-adopters’ ratings of AFV specific attributes are also analyzed. The contribution of this study is the integration of VBN theory and the DOI framework and the empirical conclusion that eco-innovations need to deliver on both traditional and proenvironmental attributes in order to be perceived as attractive by consumers.In sum, this thesis demonstrates the importance of proenvironmental personal norms for consumer adoption of a high involvement eco-innovation such as the AFV.
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| 6. |
- Jansson, Johan, 1975-
(författare)
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Digester modelling for diagnostics and control
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis will show the possibility for the development and use of an on-line model for application to continuous digesters for pulp production. The model is developed by using a program called Dymola (Dynamic Modeling Laboratory). What makes the Dymola software so well suited is that the program solves equations simultaneously. The model is a further development from the Purdue model [Bhartiya et al, 2003]. The main difference between this model and the Purdue model however, is the dynamics in the model. The dynamics are very important when you use the model for control purposes because the cooking process has long dead and retention times. The main purpose of this model is to use it for the advanced control of continuous digesters as well as giving the operators a better understanding of what happens in the cooking process when changes are made. The model will also be used for diagnostic purposes. Advanced control in this case is Model Predicted Control (MPC). The MPC will control the quality of the pulp “kappa” number and the chemical consumption during digestion. This thesis describes the model and results are shown for applications of on-line diagnosis in three pulp mills in South Africa. Real time process data from the pulp mills is fed into the model and a simulation is performed. Thereafter, the results from the simulation are compared to the actual measured data for a number of key variables. By comparing the simulation results to the real process data and following the trends of the deviations between the two, different types of faults and upsets can be detected in both the process and sensors.
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| 7. |
- Jansson, Johan, 1974-
(författare)
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Internetbranschen i Stockholms innerstad : En studie av agglomerationsfördelar, sociala nätverksrelationer och informationsflöden
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals with questions concerning spatial agglomeration of economic activities. The object of study is the Internet industry in central Stockholm. Through the use of statistical data and an interview study the Internet industry is described, measured, and analyzed through theories concerning agglomerations, social network relations, and knowledge and information flows. These theories are interpreted through five agglomeration themes related to the role of customers, subcontractors and partners, competitors, financing, and labour market, respec-tively.The research has recognized the importance of proximity to create and maintain social networks, and to spread information and knowledge, especially tacit knowledge. The thesis also shows how social networks, and information and knowledge flows have an essential role in all the five agglomeration themes that are analyzed. The results of this analysis show that the proximity to customers is the most important factor for the location of the Internet indus-try. Also, the local labour market and access to suppliers and partners are important factors. Competitors and rivals have a role to play when it comes to the diffusion of knowledge and information, although its importance as a location factor is hard to estimate. The analysis of the firms’ financing demonstrate that this factor hardly has been of crucial importance for the location of the Internet industry, but access to (venture) capital might have been of indirect importance for the location and the pace of the development of the Internet industry.
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| 8. |
- Mattsson, Johan, 1971-
(författare)
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Pointing, Placing, Touching : Physical Manipulation and Coordination Techniques for Interactive Meeting Spaces
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the design and study of dedicated ubiquitous computing environments, efforts to enhance and support co-located collaborative activities and work have been a particular focus. In his vision of ubiquitous computing, Mark Weiser foresees a new era of computing, one that closes and follows on from the era of Personal Computing (Post Desktop). The vision involves simultaneous computations facilitated by a number of technical resources (services and artifacts) available in the environment. Ubiquitous Computing also draws on the perspective of embodied interaction: that our overall physical and social interaction, and the design of artifacts supporting interaction with people, places, and the environment, are two different perspectives sharing a common goal. This thesis addresses three critical aspects of interactive meeting spaces: Multi-device selection, Multi-device setup, and Multi-device direct manipulation. To do so, physical interaction techniques have been designed that make more visible the critical and central co-located manipulation and coordination actions in interactive meeting spaces. The tree designed physical interaction techniques, that have been developed and investigated are: the iwand, a pointing technique; the Magic Bowl, a placing technique; and Physical Cursors, a touching technique. In evaluation of the interaction techniques, addressed five problems that originated in observations during the development of interactive meeting spaces. How to: 1) identify and manipulate a physical object in order to select and control a particular service; 2) support the control of complementary combinations of services through physical manipulation; 3) capture, store and recall a preset group of services; 4) maintain and reuse presets, to preserve the prerequisite for a scene, under continually changing circumstances; and 5) design ways to manipulate physical widgets to enable a social protocol for coordination as an alternative to individual (invisible) manipulation? A tentative design pattern language developed, along with “sharing control”, a further developed sample of a design pattern, which applies to physical manipulations in interactive meeting spaces. Additionally, principles are described for conducting long-term studies of living-laboratory observations and for revisiting central design decisions. The principles and design patterns are drawn from designed interaction techniques and from the design and deployment of interactive meeting spaces.
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| 9. |
- Olerud, Johan, 1977-
(författare)
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Role of Thrombospondin-1 in Endogenous and Transplanted Pancreatic Islets
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Type 1 diabetes mellitus is a severe life-long disease with a pronounced risk of developing secondary complications. One way to avoid the latter is to restore the fine tuning of blood glucose homeostasis by transplantation of pancreatic islets. However, isolated islets need to be properly engrafted and to re-establish a vascular network in order to regain function. Earlier studies have shown that pancreatic islets experimentally transplanted to e.g. the liver or the kidney become poorly revascularized. In the present thesis, mice deficient of the angiostatic factor thrombospondin-1 (TSP-1) were found to have an impaired beta-cell function. Development of this beta-cell dysfunction was prevented by treatment of TSP-1 deficient mice from birth with the TGFbeta-1 activating sequence of TSP-1. TSP-1 in islets was predominantly expressed in the endothelial cells. Isolated islet endothelial cells was observed to have a low proliferatory and migratory capacity towards angiogenic stimuli, but this could be reversed by neutralizing antibodies to the angiostatic factors alpha1-antitrypsin, endostatin or TSP-1. Transient downregulation of TSP-1 expression in mouse islet cells prior to transplantation improved graft revascularization, blood perfusion, oxygenation and function when evaluated one-month post-transplantation. The same result was achieved when islets or recipients of islets were pre-treated with the hormone prolactin one-month post-transplantation. The present study illustrates the importance of the angiostatic factor TSP-1 for islet beta-cell function and engraftment of islets following transplantation. Interference with TSP-1 can possibly be used to improve the results of clinical islet transplantation.
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| 10. |
- Olstam, Johan, 1979-
(författare)
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Simulation of Surrounding Vehicles in Driving Simulators
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Driving simulators and microscopic traffic simulation are important tools for making evaluations of driving and traffic. A driving simulator is de-signed to imitate real driving and is used to conduct experiments on driver behavior. Traffic simulation is commonly used to evaluate the quality of service of different infrastructure designs. This thesis considers a different application of traffic simulation, namely the simulation of surrounding vehicles in driving simulators.The surrounding traffic is one of several factors that influence a driver's mental load and ability to drive a vehicle. The representation of the surrounding vehicles in a driving simulator plays an important role in the striving to create an illusion of real driving. If the illusion of real driving is not good enough, there is an risk that drivers will behave differently than in real world driving, implying that the results and conclusions reached from simulations may not be transferable to real driving.This thesis has two main objectives. The first objective is to develop a model for generating and simulating autonomous surrounding vehicles in a driving simulator. The approach used by the model developed is to only simulate the closest area of the driving simulator vehicle. This area is divided into one inner region and two outer regions. Vehicles in the inner region are simulated according to a microscopic model which includes sub-models for driving behavior, while vehicles in the outer regions are updated according to a less time-consuming mesoscopic model.The second objective is to develop an algorithm for combining autonomous vehicles and controlled events. Driving simulators are often used to study situations that rarely occur in the real traffic system. In order to create the same situations for each subject, the behavior of the surrounding vehicles has traditionally been strictly controlled. This often leads to less realistic surrounding traffic. The algorithm developed makes it possible to use autonomous traffic between the predefined controlled situations, and thereby get both realistic traffc and controlled events. The model and the algorithm developed have been implemented and tested in the VTI driving simulator with promising results.
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