| 1. |
- Larsson, Carina, 1969-
(författare)
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Communicating performance measures : Supporting continuous improvement in manufacturing companies
- 2017
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Manufacturing enterprises are a key driver of economic growth (Eurostat, 2016). Implementing continuous improvement (CI) is commonly used to increase competitiveness (Hyland et al., 2007), but despite the well-known theory of CI, many manufacturing companies fail in implementing it (Bhasin, 2012; Nordin et al., 2012; Tiwari et al., 2007).An identified critical success factor in CI implementation is the evaluation of performance, including the performance evaluation system itself, the linkage between targets at different company levels, and continual evaluation of performance (Bakås et al., 2011; Scherrer-Rathje et al., 2009; Ukko et al., 2009). Another critical success factor in CI implementation is the communication of performance measures (Bakås et al., 2011; Ukko et al., 2009).This research explores the communication of performance measures. The aim is to support CI by improving the communication of performance measures, and to this end, this thesis concentrates on identifying the main challenges in the communication of performance measures supporting CI. The research scope is manufacturing companies in general, and manufacturing SMEs in particular. The relevant literature concerning the communication of performance measures in manufacturing companies is identified and summarized. Also, current practice is explored, focusing on how performance measures are communicated in manufacturing companies, and whether and how the communication supports CI. This has been done to identify divergences between current practice and theory. Finally, theory and empirical findings are synthesized to identify some of the main challenges to be addressed in order to succeed in CI.The main task is to support CI efforts in manufacturing SMEs, eliminating the identified divergences in the communication of performance measures by adapting these measures to these manufacturing SMEs. These challenges can be summarized as follows: - using both financial performance measures as well as objective and subjective, non-financial performance measures - aligning performance measures with strategy and targets - integrating all performance measure communication, as related to both daily performance and CI, in the same communication loop. - forming two-way communication channels between managers and operators - aligning oral and written communication channels - exploring how information systems can facilitate the communication of performance measures - using and optimizing the visual communication of performance measures
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| 2. |
- Mai, Anh, 1986-
(författare)
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Organizing for efficiency : Essays on merger policies, independence of authorities, and technology diffusion
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Institutions are fundamentally sets of rules in a society that help create stability. Organizations are groups of people who may share the same goal. Changes in organizations and institutions will have large effects on the performance of economies. This thesis explores empirical aspects concerning two elements of institutional and organizational design: economic regulations and independent regulatory authorities (IRAs).Essay 1 studies the impact of the 2004 EU merger policy reform on how mergers are reviewed by the European Commission. The EU policy appears to have softened after the reform for unilateral mergers and this may suggest an improvement of merger policy efficiency.Essay 2 compares the merger enforcements in the EU and the US. Our approach is to decompose the differences into policy effects and casemix effects. The EU policy has significantly changed after its 2004 reform. Overall, the results show a convergence between the two policies for dominance mergers after the EU policy reform.Essay 3 constructs an independence index for 109 European IRAs in six different sectors: competition, energy, financial markets, pharmaceuticals, food safety, and telecom. Factor analysis suggests that the heads of the agencies are mostly constrained by four factors: collegial bodies, the judicial system, politics and scope of tasks, and resources.Essay 4 explores a correlation between independence of regulatory authorities and corruption. We find that the authorities in corrupt countries to a large extent rely on collegial bodies but are less tightly controlled by the judicial system, compared with those in “clean” countries.Essay 5 studies the impact of regulation on broadband diffusion speed. The results imply that a strict local loop unbundling policy appears to slow the diffusion speed of fixed broadband. In contrast, a procompetition policy that aims to promote entry has a significant positive impact on the diffusion speed of mobile broadband.
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| 3. |
- Persson, Mats, 1967-
(författare)
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The Construction of Support and Opposition : A Study of an Attempted Higher Education Merger
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This study focuses on support and opposition in an attempted merger between three Norwegian university colleges. The university colleges that took part in the merger process were Buskerud University College, Vestfold University College and Østfold University College, all three located in the south-east part of Norway. The study takes its point of departure in the fact that the merger process was terminated before a decision to merge was reached. It aims to describe the two discourses of support and opposition, and explain change in discursive practices from support to opposition.The thesis is divided into three parts. In the first part the conceptual framework used in the analysis is presented, as well as the area of mergers in higher education and methodological aspects. Four conceptual pairs are used to analyse the merger process; support/opposition, idea/operationalisation, outwards/inwards and modern/traditional. The second part is constructed as a play with acts presenting the merger process in a chronological order where the conceptual pairs are used to describe and explain discursive practices. The third and final part focuses on general insights into the construction of support and opposition in the terminated merger process.The study shows that the use of different discursive practices evolved into antagonism between the three university colleges leading to the termination of the merger process. Supporting the idea to merge in order to achieve university status was not enough to support the merger if the operationalisation of how the merger process was to be conducted, and how the merged organisation was to be constructed led to a disadvantageous power position. In addition, discursive practices of support and opposition were conditioned by discourses of the education market and academic drift.
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| 4. |
- Zou, Yiming, 1985-
(författare)
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The Effect of Various Dopants on Diamond Growth : A Combined Experimental & Theoretical Approach
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Diamond is a unique material with many exceptional properties. It has therefore been proven to be an important material for many applications. Moreover, the introduction of dopant species into the gas phase during the CVD growth process has been shown to strongly influence not only the properties and morphology of diamond, but also the growth rate. The purpose with the theoretical part of the present study has been to support and explain the experimental observations regarding the effect of various dopants (nitrogen, phosphorous, sulphur, and boron) on the diamond growth rate. Commonly observed H-terminated diamond surfaces [(111), (110) and (100)-2×1], were thereby carefully investigated using density functional theory under periodic boundary conditions. Based on the assumption that the hydrogen abstraction reaction is the growth rate-limiting step, both the thermodynamic and kinetic aspects of the diamond growth process were found to be severely affected by various dopants. More specifically, the results showed that nitrogen and phosphorous dopants (positioned within the 2nd, 3rd or 4th carbon layer) will cause an enhancement in the growth rate (as compared with non-doped situations). On the other hand, any growth rate improvement does only occur when positioning boron in the 2nd, and sulphur in the 4th, atomic carbon layer. With boron, and sulphur, positioned within the other atomic carbon layers, the growth rates were observed to decrease. In addition, the main purpose with the experimental part of the present study has been to investigate the effect of one specific dopant precursor (TMB) on the boron-doped diamond growth process. The result has shown that the increasing mass flow of TMB will not affect the mechanism of the HFCVD growth process of boron doped diamond. However, a linear boron carrier concentration in the diamond film vs. mass flow rate of TMB was observed.
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| 5. |
- da Silva, Joakim, et al.
(författare)
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Resolution characterization of a silicon-based, photon-counting computed tomography prototype capable of patient scanning
- 2019
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Ingår i: Journal of Medical Imaging. - USA : SPIE - International Society for Optical Engineering. - 2329-4302 .- 2329-4310. ; 6:4
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Tidskriftsartikel (refereegranskat)abstract
- Photon-counting detectors are expected to bring a range of improvements to patient imaging with x-ray computed tomography (CT). One is higher spatial resolution. We demonstrate the resolution obtained using a commercial CT scanner where the original energy-integrating detector has been replaced by a single-slice, silicon-based, photon-counting detector. This prototype constitutes the first full-field-of-view silicon-based CT scanner capable of patient scanning. First, the pixel response function and focal spot profile are measured and, combining the two, the system modulation transfer function is calculated. Second, the prototype is used to scan a resolution phantom and a skull phantom. The resolution images are compared to images from a state-of-the-art CT scanner. The comparison shows that for the prototype 19 lp∕cm are detectable with the same clarity as 14 lp∕cm on the reference scanner at equal dose and reconstruction grid, with more line pairs visible with increasing dose and decreasing image pixel size. The high spatial resolution remains evident in the anatomy of the skull phantom and is comparable to that of other photon-counting CT prototypes present in the literature. We conclude that the deep silicon-based detector used in our study could provide improved spatial resolution in patient imaging without increasing the x-ray dose.
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| 6. |
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| 7. |
- Lindh, Magnus, 1973-
(författare)
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Evolution of Plants : a mathematical perspective
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The Earth harbors around 300 000 plant species. The rich and complex environment provided by plants is considered a key factor for the extraordinary diversity of the terrestrial fauna by, for example, providing food and shelter. This thesis contributes to the understanding of these questions by investigating how the interplay of physiology, demography, and evolution gives rise to variation and diversity in fundamental plant traits. This will help us answer questions such as: How has this amazing diversity of plant species emerged? Which mechanisms maintain diversity? How are plant strategies and plant diversity influenced by variations in the environment?A plant faces multiple problems to survive and reproduce successfully. These problems can be modeled by considering traits, trade-offs and a fitness measure. For example: How to maximize growth rate, while maximizing structural stability? I will investigate four plant models in order to understand the function of plants, and mechanisms promoting diversity. Paper I: We study how annual plants with and without growth constraints should optimize their flowering time when productivity or season length changes. With a dynamic ontogenetic growth model and optimal control theory we prove that a bang-bang reproductive control is optimal under constrained growth and constant mortality rate. We find that growth constraints can flip the direction of optimal phenological response for increasing productivity. The reason is that the growth rate of vegetative mass saturates at high productivity and therefore it is better to flower earlier and take advantage of a longer reproductive period. If season length extends equally both in the beginning and the end of the season, growth constraints control the direction of the optimal response as well. Our theory can help explaining phenological patterns along productivity gradients, and can be linked to empirical observations made on a calendar scale.Paper II: We introduce a new measure of tree crown-rise efficiency based on the loss of biomass of the tree during growth. The more mass the tree looses during growth, the less crown-rise efficient it is. Top-heavy shapes loose more biomass than bottom-heavy shapes. Light-use efficiency is defined as the mean light assimilation of the leaves in the crown times the ratio of leaf mass and total mass. We then study the trade-off between light-use efficiency to crown-rise efficiency for tree crown shapes. We assume that the total tree mass is constant, and a constant vertical light gradient represent the shading from a surrounding forest. We find large differences in crown shapes at intermediate vertical light gradient, when both self-shading and mean-field shading are important, suggesting light-use vs crown-rise efficiency as a new trade-off that can explain tree diversity. Our crown-rise efficiency measure could easily be integrated into existing forest models.Paper III: We extend an evolutionary tree crown model, where trees with different heights compete for light, with drought-induced mortality rates depending on ground-water availability and the depth of an optional taproot. The model does not include competition for ground water. Our model explains how ground-water availability can shape plant communities, when taproot and non-taproot strategies can coexist, and when only one of these strategies can persist. We investigate how emerging plant diversity varies with water table depth, soil water gradient and drought-induced mortality rate. The taproot enables plants to reach deep water, thus reducing mortality, but also carries a construction cost, thus inducing a trade-off. We find that taproots maintain plant diversity under increasing drought mortality, and that taproots evolve when groundwater is accessible at low depths. There are no viable strategies at high drought mortality and deep water table. Red Queen evolutionary dynamics appear at intermediate drought mortality in mixed communities with and without taproots, as the community never reaches a final evolutionarily stable composition.Paper IV: We extend a size-structured plant model, with self-shading and two evolving traits, crown top-heaviness and crown width-to-height ratio. The model allows us to identify salient trade-offs for the crown shape. The most important trade-off for top-heaviness is light-use efficiency vs crownrise efficiency, and the most important trade-off for width-to-height ratio is self-shading vs branch costs. We find that when the two traits coevolve; the outcome is a single common evolutionarily stable strategy (ESS), far away from the highest net primary production (NPP). When only sun angle is decreasing with increasing latitude both the crown width-to-height ratio and crown top-heaviness decrease. However, when light response in addition to the sun angle decreases with increasing latitude, the crown width-to-height ratio is nearly invariant of latitude except at low site productivity when the ratio decreases with latitude. Top-heaviness is always decreasing with increasing latitude. Finally, we find that crown top-heaviness increases with the NPP or leaf-area index (LAI) at ESS, but crown width-to-height ratio is maximal at an intermediate NPP or LAI.
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| 8. |
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| 9. |
- Persson, Mats, 1987-
(författare)
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Spectral Computed Tomography with a Photon-Counting Silicon-Strip Detector
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Computed tomography (CT) is a widely used medical imaging modality. By rotating an x-ray tube and an x-ray detector around the patient, a CT scanner is able to measure the x-ray transmission from all directions and form an image of the patient’s interior. CT scanners in clinical use today all use energy-integrating detectors, which measure the total incident energy for each measurement interval. A photon-counting detector, on the other hand, counts the number of incoming photons and can in addition measure the energy of each photon by comparing it to a number of energy thresholds. Using photon- counting detectors in computed tomography could lead to improved signal-to-noise ratio, higher spatial resolution and improved spectral imaging which allows better visualization of contrast agents and more reliable quantitative measurements. In this Thesis, the feasibility of using a photon-counting silicon-strip detector for CT is investigated. In the first part of the Thesis, the necessary performance requirements on such a detector is investigated in two different areas: the detector element homogeneity and the capability of handling high photon fluence rates. A metric of inhomogeneity is proposed and used in a simulation study to evaluate different inhomogeneity compensation methods. Also, the photon fluence rate incident on the detector in a scanner in clinical use today is investigated for different patient sizes through dose rate measurements together with simulations of transmission through patient im- ages. In the second part, a prototype detector module is used to demonstrate new applications enabled by the energy resolution of the detector. The ability to generate material-specific images of contrast agents with iodine and gadolinium is demonstrated. Furthermore, it is shown theoretically and ex- perimentally that interfaces in the image can be visualized by imaging the so-called nonlinear partial volume effect. The results suggest that the studied silicon-strip detector is a promising candidate for photon-counting CT.
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| 10. |
- Persson, Mats, 1987-, et al.
(författare)
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Subpixel x-ray imaging with an energy-resolving detector
- 2018
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Ingår i: Journal of Medical Imaging. - : SPIE - International Society for Optical Engineering. - 2329-4302 .- 2329-4310. ; 5:1
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Tidskriftsartikel (refereegranskat)abstract
- The detector pixel size can be a severe limitation in x-ray imaging of fine details in the human body. We demonstrate a method of using spectral x-ray measurements to image the spatial distribution of the linear attenuation coefficient on a length scale smaller than one pixel, based on the fact that interfaces parallel to the x-ray beam have a unique spectral response, which distinguishes them from homogeneous materials. We evaluate the method in a simulation study by simulating projection imaging of the border of an iodine insert with 200 mg/ml I in a soft tissue phantom. The results show that the projected iodine profile can be recovered with an RMS resolution of 5% to 34% of the pixel size, using an ideal energy-resolving detector. We also validate this method in an experimental study by imaging an iodine insert in a polyethylene phantom using a photon-counting silicon-strip detector. The results show that abrupt and gradual transitions can be distinguished based on the transmitted x-ray spectrum, in good agreement with simulations. The demonstrated method may potentially be used for improving visualization of blood vessel boundaries, e.g., in acute stroke care.
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