| 61. |
- Sundqvist, Erik, 1985-
(författare)
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Towards systematic improvement work in project-based organizations : An efficiency and effectiveness perspective
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Project-based organizations (PBOs) have adopted projects as a primary tool for carrying out most of their operations. By doing so, the PBO operates mainly on two organizational levels, the project level and the organizational level. For these organizations, improving project management (PM) performance is central for the survival of the organization, since PM is considered both a strategic competence and a source of competitive advantage for delivering customer value. For PBOs, prioritizing efficiency has often been described as a short-term focus meeting time and budget targets. The need to shift focus toward value creation in PM is suggested to be of importance to succeed in delivering value to customers. Project performance, and the separate but interlinked concept of project success, can be described using the two concepts of efficiency—doing things right—and effectiveness—doing the right things. However, although commonly used within the field of quality management, the application of these two concepts in the PM literature and practice has proven to be unclear which has implications on organizational improvement.It is through the two concepts, efficiency and effectiveness, that systematic improvement work in PBOs can be understood. This thesis addresses the need for influences from other research fields, by approaching improvement work in PBOs from a quality management perspective. More specifically, the purpose is to advance our understanding of how PBOs can work systematically toward improvements, from an efficiency and effectiveness perspective. This is done by exploring challenges related to improvement work in a PBO operating as a subsidiary to the Swedish minerals group LKAB. In order to do this case study research has been used, including a combination of data collection methods: including semi-structured interviews, participant observations, and document analysis. Case study findings have continually been compared to theory in order to reach conclusions.The findings indicate that an organizational-level improvement process is missing, and that PBOs need to link such a process to project-level processes, in order to work toward improvements. Applying an efficiency and effectiveness perspective further clarifies the division of practice and responsibility between PBO and the client. Further, it is suggested that the role of the project manager as an improvement agent in PBOs should be formalized and clarified, in order to support learning and organizational-level improvement. Finally, the need to clarify and manage what constitutes value and value creation among stakeholders in projects is emphasized, in order to support both efficiency and effectiveness in project work.The thesis contributes to the literature by discussing the prerequisites for PBOs to work toward improvements, and by approaching project management from a quality management perspective. From a managerial perspective the thesis emphasizes the importance of clarifying responsibilities regarding project value creation, as current practice seem to promote a separation of responsibility, in which the PBO is responsible for aspects of efficiency, and the customer is responsible for aspects of effectiveness.
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| 62. |
- Sundqvist, Jesper
(författare)
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Aspects of Heat Flow in Laser Processing of Metals
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Since the laser was invented in 1960, its use in manufacturing industry has been growing rapidly. Laser processing of metals is based on the flow of heat that is generated by the absorbed laser beam. One outstanding aspect of laser beams is high precision along with high controllability of energy transfer, which includes creative techniques of shaping the beam and in turn the process. The thesis presents six Papers A-F on different metal processing techniques, namely welding, hardening and cutting, the latter combined with additive manufacturing. For each respective technique it was studied how desired properties can be optimized by controlled use of the laser beam and in turn of the temperature field. Addressing their different complexity of the heat transfer, various theoretical and experimental analysis methods were applied.Laser beam welding is usually conducted with standard beam shapes, i.e. Gaussian or top-hat like, which is not always optimal for the process. Identification of an optimised weld pool shape or temperature cycle could increase the quality of welded products or even enable new applications. Papers A and B aim to increase the knowledge for non-standard beam shapes, particularly for single-pulse conduction mode welding. Paper A presents an investigation on an industrial application where a C-shaped weld joint is desired. The sensitivity to and optimization of different C-shaped beam irradiation profiles is discussed. The analysis is mainly carried out by applying Finite Element Analysis, FEA, to calculate the heat conduction contributions, showing unexpected sensitivity in certain regimes. Paper B presents a semi-analytical model for fast calculation of the temperature field from different beam profiles. Examples include multi-spots or the misalignment sensitivity of Diffractive Optical Elements.In Paper C, for laser hardening of 11% Cr ferritic stainless steel the temperature field was studied to enable hardening. It was shown that single-track hardening without sensitisation could be achieved but overlapping tracks had a continuous network of ditched grain boundaries and is thereby at risk for sensitisation. The sensitised area is caused by a reheating cycle.The same mechanism for the same material was studied in Paper D when applying a recently developed drop deposition technique, where additive manufacturing is fed by laser cutting. The same reheating isotherm becomes critical, but here sensitisation tests show a discontinuous network of ditched grain boundaries in the added material. The solid heat-affected zone on the other hand has a continuous network of ditched grain boundaries, which implies a sensitisation risk. The continuous network is however not in contact with the surface. The tested parameters is thus not at risk for intergranular corrosion through sensitisation.For friction stir welding of dissimilar metals, Ti-6Al-4V with AISI 304L stainless steel, Paper E, the influence of a laser-induced preheating temperature field on the tool forces was investigated through numerical simulation. By suitable application of laser preheating, the forces acting on the tool can be substantially lowered, in a robust manner.The temperature field from seam welding induces a residual stress field. In Paper F, for continuous wave laser keyhole welding of high strength steel butt joints, a method is presented to identify the residual stress behaviour of laser welded sheets by measurement of the fatigue crack growth rate during testing, by deriving the crack acceleration. The analysis was confirmed by hole drilling tests and by FEA.The knowledge and methods of the above different experimental and theoretical studies complement each other. They contribute to further optimize certain aspects through laser-induced temperature fields, for different manufacturing techniques.
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| 63. |
- Sundström, Joel, 1988-
(författare)
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Studies of Transient and Pulsating flows with application to Hydropower
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The rotational motion of a hydraulic turbine runner makes pulsating flows ubiquitous in different locations of the machine. The cyclic loading thus induced may generate large pressure forces acting periodically on both stationary and rotating parts. In addition to the presence of pulsating flows in a turbine runner, transient flows are encountered at an increasingly higher rate due to the continual installation of intermittent sources of renewable energy, such as wind and solar power. To mitigate the imbalance that these unpredictable sources induce on the frequency of the electrical grid, hydropower turbines are enforced to regulate their power production, and consequently flow rate, thus leaving them to operate under transient conditions. In terms of wear and fatigue, a startup or shutdown of a hydraulic turbine corresponds to 10-20 hours of steady state operation at the design point. Transient operation of a hydraulic machine can, however, also be used in favour for measuring the discharge through the turbine using the pressure-time method. A better understanding of pulsating and transient flows thus has the potential both to mitigate problems associated with them, and to increase the accuracy with which the turbine flow rate can be measured; two great merits for the hydropower community. In light of this observation, the following work constitutes a fundamental investigation of transient and pulsating flows performed in a straight pipe.Studies have been performed experimentally using particle image velocimetry, hot-film anemometry, laser Doppler velocimetry and pressure sensors.A chief finding is that the time-development of the wall shear stress and near-wall turbulence fields exhibit significant similarity between transient and pulsating flows, despite the different conditions of the mean flow. Whereas the former is initiated from a statistically steady state, the latter is constantly subjected to a time-varying forcing. Both types of unsteady flows have previously been investigated in detail; however, any potential similarity between them has, largely, been unexplored. An important implication of this finding, then, is that knowledge acquired in one type of unsteady flow can be used, if not interchangeably, at least as a guidance for the expected behaviour in the other type of flow. An example is the development of unsteady turbulence models. Another important finding is that the frictional losses arising during the late stage of a pressure-time flow rate measurement can be accurately modelled using an analytical laminar formulation of the wall shear stress, despite the bulk of the flow being turbulent. The formulation of the wall shear stress has potential to be further improved by incorporating a damping-function.
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| 64. |
- Tabatabaei, Narges
(författare)
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Impact of Icing on Wind Turbines Aerodynamic
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Wind energy covered 11.6% of Europe electricity demand in 2017. Region with cold climates represent a strong potential for wind energy companies because of their sparse population and proper wind conditions. The global wind energy installations in cold climate regions is forecasted to reach a capacity of 186 GW by the end of 2020. But wind turbines installed in cold climate regions are prone to the risks of ice accumulation which affects their aerodynamics behavior, as well as the safety, and structural loads.The aerodynamic forces on wind turbine can be affected in two main ways: ice accretion changes the blade profile, and thus the flow path curvature, and the surface roughness. The importance of these two parameters depend on the ice type. The target ice type for this thesis is the smooth leading-edge glaze ice with horn shape. The aerodynamic consequences of the blade profile change because of the mentioned ice type are studied in detail. The findings of this thesis are classified in five main sections. The first section considers the methodology to model the performance of a wind turbine. The wake behind the turbine is also explored. Different aspects of the simulation methods with computational fluid dynamics using the Reynolds-averaged Navier-Stokes equations are investigated in both steady state and transient. In the second section, the time-dependent effects of icing are studied, exploring the moving vortices created by the irregularity of the ice and their frequencies and amplitudes. The main frequency modes of the flow dynamics were analyzed. In the third section, three-dimensional simulation of icing is implemented and the fluid flow arrangement through the rotor is investigated. Two well-recognized approaches are applied and compared, which are Blade Element Momentum (BEM) and CFD. An automated setup is programmed and launched to implement multiple CFD simulations to provide the aerodynamic data for structural analysis in the fourth section. The developed methodology is illustrated on a large-scale wind turbine. In section five, the effects of the uncertain level of ice-accretion is studied through an uncertainty quantification method. The aerodynamic losses are statistically discussed. Then, a scenario study is conducted according to the obtained polynomial chaos expansion, in which the probability distribution of wind power loss due to icing is inspected.The achievements of this thesis can be used in to design of a wind turbine which is supposed to work in a cold climate, as well as assess the economics of a predesigned wind turbine working in a cold region.
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| 65. |
- Thangavelu, Tharshini
(författare)
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Essays on Malnutrition, Savings and Preferences
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis consists of an introductory part and four self-contained papers addressing three different topics in economics, namely preferences, savings and malnutrition. In Paper I, an instrumental variable approach was employed to analyse how malnutrition affects children’s psychosocial abilities. The study looked specifically at children’s aspirations, self-esteem and self-efficacy. The children’s level of malnutrition was measured by the most commonly used measurement, namely the height-for-age Z score (HAZ). Young Lives panel data from Andhra Pradesh, India, as well as self-reported drought variables were employed as instruments to isolate the causal path. Consistent with previous evidence, the current study’s first-stage relationship showed a negative and statistically significant association between drought and children’s HAZ. The main result revealed that malnutrition had a negative impact on children’s self-efficacy, whereas it did not affect their aspirations or self-esteem. Furthermore, a robustness check showed gender differences in the effect of malnutrition on children’s psychosocial abilities. Thus, the self-efficacy of Indian boys was negatively affected by malnutrition, while that of girls was not. Because these results examine the consequences of malnutrition on children’s non-cognitive abilities, they contribute to a literature which, so far, has mainly focused on the consequences on their cognitive abilities. Also using the Young Lives data set, Paper II presents an investigation into children’s ability to catch up from earlier malnutrition. A comparison was specifically made between two cohorts of children born in 1994–95 and 2001–02, using their HAZ values when they were 8 (in 2002 and 2009, respectively) and then 12 years old (in 2006 and 2013, respectively). The objective was to study the differences between the two birth cohorts and the two age levels. In addition, the paper looked at determining the differences between various points on the distribution of HAZ values, using the quantile regression method. The result showed that the null hypothesis of a homogeneous catch-up effect along the entire distribution of HAZ could be rejected. Furthermore, the result suggested that less malnourished children had lower catch-up rates, whereas more malnourished children had higher ones. This evidence is also consistent with previous results, namely that, despite the economic growth that India has experienced and the hope that malnutrition would have declined as a result, children in the younger cohort suffer from nutritional deficiencies similar to those experienced by the older cohort. Paper III sets out the replication of a study by Brune et al. (2016), who implemented a randomised control trial to understand Malawian tobacco farmers’ saving behaviour. The purpose of the intervention was to spur farmers to deposit some of their harvest income in order to relax the liquidity constraint at the beginning of the subsequent planting season. The intervention was implemented at the same time as the harvest period so that farmers’ saving behaviour could be studied closely. Offering a savings vehicle resulted in more inputs being purchased ahead of the next planting season, leading to higher yields and higher income from the next harvest. A further, and rather surprising, finding was that the extra money used to purchase inputs at the beginning of the next planting season was not from the post-harvest bank deposit: in fact, farmers withdrew most of the harvest income they had deposited well in advance of the next planting season. In this and other aspects, the results from the replication study support the findings of the original study. Finally, Paper IV describes a study on recreational anglers’ willingness to pay for improvements in the characteristics of fishing sites. The objective of the paper was twofold. The first objective was to explore the transferability of anglers’ responses between different angling sites, while the second objective was to estimate the welfare effects for anglers in respect of improvements in angling site characteristics. A choice experiment was used to capture transferability across the angling sites, and to examine anglers’ preferences for changes in angling conditions. A survey was conducted among anglers visiting two water bodies in northern Sweden. The findings showed that the anglers studied had highly heterogeneous preferences, which implies that policy interventions need to consider the specific characteristics of the angling groups they target.
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| 66. |
- Trublet, Mylene
(författare)
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Titanium(IV) Phosphates : The Next Generation of Wastewater Sorbents
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Treatment of industrial waters containing heavy metal ions is essential before being discharged into the environment. Consequently, European regulations have been established to control and limit the amount of heavy metals released. There is a need to develop efficient water treatment techniques that can remove contaminants with respect to these EU regulations.Ion-exchange is one of the processes that is being investigated due to fast kinetics, high treatment capacity and its ability to remove heavy metal ions present in trace amounts. Titanium phosphates (TiP) are a group of inorganic ion-exchangers that have demonstrated to be particularly selective towards transition metal ions in aqueous solutions. Two types of ion-exchange units are present in TiP material, which are –HPO4 and –H2PO4 groups. Their structural characteristic is highly dependent on the synthesis conditions, which include the source of titanium, temperature, reaction time and P2O5:TiO2 ratio. Most of the studies have been performed on amorphous TiP containing a mixture of both exchange units, with –HPO4 groups being predominant; as crystalline TiP and –H2PO4 based TiP are often obtained in difficult conditions, high temperature (up to 250 °C) and/or long reaction time (up to 30 days) and/or using autoclave. Despite promising properties depicted in batch conditions, very few data in continuous flow systems (fixed-bed columns) have been reported.In this work, amorphous TiP composed of entirely –H2PO4 ion-exchange units (TiP1) was synthesized at mild conditions using a TiOSO4 solution and HCl/deionized water as post-synthesis treatments. The sorbent was characterized using a range of techniques (solid-state 31P MAS NMR, Raman, XRD, TGA, BET, Elemental analysis, EXAFS and XANES,) and tested in batch and column set-ups towards single and multi-component waters. The chemical formula of TiP1 was established as TiO(OH)(H2PO4)·H2O and it was found that the synthesis of TiP1 was also dependent on the TiO2/H2SO4 content in the primary titanium solution.The material displayed a high maximum exchange capacity of ca. 6.4 meq.g-1, expressed as the sodium uptake. The actual ion-exchange capacity towards divalent metal ions was calculated to be ca. 3.4 meq.g-1 in batch condition and up to 4.1 meq.g-1 in fixed-bed column, which is to date the highest recorded for TiP materials. Kinetics of the exchange processes have been studied and the equilibrium was reached within 5-20 minutes. Modeling of the breakthrough curves was achieved using the Thomas model, indicating that the rate driving forces of the processes follow second-order reversible kinetics. The TiP1 sorbent has shown to maintain a high selectivity towards heavy metal ions in multi-component systems (including closed-mine waters) when column studies were performed. The sorption behavior of TiP1 in batch experiments correlates very well with data obtained in fixed-bed column conditions, confirming that prediction of the sorption behavior on the basis of batch data is conceivable.Another important aspect of this work also involves the mild syntheses of crystalline α-TiP, Ti(HPO4)·H2O, and LTP (Linked Titanium Phosphate) composed of α-TiP and TiP1, where the structural characteristics of these materials were investigated using solid-state NMR, XRD, TGA, EXAFS and XANES.
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| 67. |
- Womack, Jennifer L., 1960-
(författare)
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The Occupation of Caregiving : Moving Beyond Individualistic Perspectives
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The overall aim of this research was to illuminate and describe caregiving as an occupation, informed by perspectives from older adult care partners and occupational therapists. An additional aim was to integrate and inform study findings with theoretical constructs that inform occupational therapy practice through occupational science and public health perspectives. Although caregiving was the main construct under consideration, the specific focus was on care situations involving older adults.Study 1 considered the narratives of 3 older adult women serving as informal (unpaid) caregivers to friends and family members. All of the women were over the age of 65 and of varied racial/ethnic backgrounds. Data were elicited through story prompts embedded in repeated semi-structured interviews and analyzed using a storyboarding approach and poetic transcription.Study 2 was an ethnographic case study considering how care dyads take part in community mobility, a common instrumental activity of daily living, with a particular focus on how the caregiver supports the participation of the care recipient. 3 care dyads (6 participants) over the age of 65 were consented into the study. The researcher employed participant observation, field note journaling and semi-structured interviews followed by thematic qualitative analysis to illuminate strategies used by these care dyads to remain active in community mobility in the context of their care situation.Study 3 used a constructivist grounded theory approach to explore the perspectives of occupational therapists regarding their interactions with older adult caregivers. Repetitive focus groups with 11 occupational therapy practitioners, researcher memos and individual reflections from 2 additional participants provided multifaceted data that the researchers analyzed through several levels of coding to construct a grounded theory of occupational therapist-caregiver interactions.Study 4 consisted of secondary data analyses of a national survey of adult caregivers conducted in the United States in 2014-2015. Data specific to 482 caregivers age 65+ and older and their care recipients were extracted from the overall sample and considered in relationship to responses to questions regarding support received from healthcare providers. Descriptive and inferential statistical analyses were employed to develop a profile of older adult care situations and predict inquiries of support from healthcare providers based on care situation characteristics.Findings from the first two studies highlighted the relational nature of caregiving and an expanded view of the caregiver role. Study 1 also revealed that interactions with health care providers in positions of authority are often challenging and compel caregivers to act in ways they perceive as risky. Study 2 reinforced that caregivers act in ways that are influenced as much or more by the history of their relationships as by caregiving demands, and led to the explication of relational versus individual perspectives. These findings influenced the approaches used in studies 3 and 4, which focused on interactions between healthcare providers and older caregivers, specifically occupational therapists in study 3 and other healthcare professionals in study 4. Findings from study 3 resulted in a theoretical stance that occupational therapists are influenced by biomedical contexts to situate caregivers as paraprofessionals to help meet care recipient goals. This perpetuates an individualistic lens on caregiving, emphasizing the biomedical priorities of the patient over the priorities or support needs of the care situation. Support offered by healthcare providers in the form of inquiries about the needs of older caregivers was found in study 4 to be less than optimal, and appears not to be predicted by any characteristics of the care situation other than the living situation of the care recipient. In sum, individualistic perspectives fail to realize the occupational complexity of caregiving, and provide an opportunity to explore more collective paradigms when supporting older adult care situations.
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| 68. |
- Yang, Chen-Wei, 1987-
(författare)
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Cyber-Physical Engineering of Distributed Automation Systems in Energy Domain
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The main focus of this thesis is in the domain of Energy Systems, specifically in the engi-neering of modern Smart Grid (SG) automation systems. The SG has been categorizedas a Cyber-Physical System (CPS), a complex system which exhibits tight integration between the cyber and the physical processes and their interactions in a networked envi-ronment. The complexity and the computation of the automation system are expectedto increase with the promise of a ”smart” electric grid which is capable of self-healing, self-reconfiguration and become more resilient against cyber-attacks. These automation software systems require control strategies which are distributed in execution and requirevery tight integrations and interactions between various modular software and hardware components. As the automation system becomes more software intensive, we hypothesizethat existing design practices of developing the substation automation software system would struggle to cope with the distributed design challenges of the Smart Grid and they could be substantially enhanced by the application of model-driven design, distributed software architectures and semantic models.Model-driven engineering (MDE) is a software design paradigm that leverages the use of abstraction models at different stages of the design process for engineering complex software systems. MDE is widely used in the software engineering domain and it has proven to be effective when designing and maintaining large-scale software applications.One of the core tenants of MDE is model transformation and it is considered the heartand soul of MDE. The standard modelling language that is used for MDE in software engineering is the Unified Modelling Language (UML), which is a visual language with awide array of tool support. Despite its popularity in the software domain, UML models still have its limitations. In particular, the lack of uniformed semantics between its 13different visual diagrams and the lack of formal notations. In this thesis, we proposethe Cyber-Physical Engineering (CPE) framework, an MDE framework which combines semantic models and MDE based automatic model transformation in order to auto-generate both the automation control system and the simulation plant model from thephysical and functional specifications of CPS systems.All the scientific papers included in this thesis contributes towards the proposed Cyber-Physical Engineering methodology which includes MDE using semantic models, formal modelling of functional requirements and co-simulation testing of CPS systems.The contribution of the thesis is fivefold. Firstly, the thesis proposes the CPE frame-work, which is based on the use of semantic web modelling language where logical rea-soning can be applied to the models. The modelling language that is used is the Web Ontology Language (OWL), which is a declarative language with a strong formal foun-dation based on description logic. Secondly, the extended Semantic Web Rule Language(eSWRL) is introduced which defines the constructors that are necessary for model trans-forming OWL ontology models. The eSWRL transformation language is proposed to bean extension to the widely used ontology reasoning language Semantic Web Rule Lan-guage (SWRL) in order to address the limitations of monotonicity which restricts SWRLfrom transforming ontological models. Thirdly, the implementation of the underlying transformation engine of eSWRL in SWI Prolog. Fourthly, the formal modelling of func-tional requirements in ontology is proposed which investigates the viability of using nat-ural language based functional requirements to add control flow to the auto-generated automation control system. Lastly, an automated script based co-simulation environ-ment is shown to demonstrate how black-box validation can be performed to test theauto-generated automation control system.Finally, the thesis presents the resultant CPE framework for the modelling and genera-tion of distributed CPS automation software that leverages the use of semantic web OWL models. It is aimed to provide a top-down design approach of developing distributed con-trol software for CPS systems along with the simulation model of the physical plant. Inthis thesis, we demonstrate the development process of the CPE framework and throughcase study applications, how a semi-complete distributed automation software system in IEC 61499 can be automatically generated from substation specifications in IEC 61850 and natural language based functional requirements which provide the structure and thecontrol flow of the distributed automation software respectively. An eSWRL toolchainhas been developed to facilitate the various model transformation process of the CPE framework.
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