| 1. |
- Azizoğlu, Yağız, 1986-
(författare)
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Modeling of Cold Pilgering of Tubes
- 2017
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Cold pilgering is a challenging tube forming process in terms of modeling due to the complexity in kinematic of tools, friction condition and material behavior. The process development has mostly been based on simple formulas and costly full-scale tryouts. The aim in this study is to develop validated Finite element models of cold pilgering to increase the understanding of influence of the process parameters on the produced tubes.In the course of this thesis, three-dimensional mechanical and thermo-mechanical Finite element models of cold pilgering were developed. The commercial code MSC.Marc was used in the simulations. General 3D models are needed to be able to capture asymmetric deformation in cold pilgering. It was found that tool deflections together with elastic deformation of roll dies have considerable influence on the rolling force. Furthermore, the strain rate and temperature effects on the response of the material and thereby on the rolling force were evaluated.
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| 2. |
- Loukil, Mohamed Sahbi, 1984-
(författare)
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Microcracking in fiber composites and degradation of thermo-elastic properties of laminates
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The macroscopic failure of composite laminates subjected to tensile increasing load is preceded by initiation and evolution of several microdamage modes. The most common damage mode and the one examined in this thesis is intralaminar cracking in layers. Due to this kind of microdamage the laminate undergoes stiffness reduction when loaded in tension. For example, the elastic modulus in the loading direction and the corresponding Poisson’s ratio will decrease.The degradation of the elastic properties of these materials is caused by reduced stress in the damaged layer which is mainly due to two parameters: crack opening displacement (COD) and crack sliding displacement (CSD). At fixed applied load these parameters depend on the properties of the damaged and surrounding layers, on layer orientation and on thickness. When the number of cracks per unit length is high (high crack density in the layer) the COD and CSD are reduced because of to crack interaction.The main objective of the first paper is to investigate the effect of crack interaction on COD using FEM and to describe the identified dependence on crack density in a simple and accurate form by introducing an interaction function dependent on crack density. This interaction function together with COD of non-interactive crack gives accurate predictions of the damaged laminate thermo-elastic properties. The application of this function to more complex laminate lay-ups is demonstrated. All these calculations are performed assuming that cracks are equidistant.However, the crack distribution in the damaged layer is very non-uniform, especially in the initial stage of multiple cracking. In the second paper, the earlier developed model for general symmetric laminates is generalized to account for non-uniform crack distribution. This model is used to calculate the axial modulus of cross-ply laminates with cracks in internal and surface layers. In parametric analysis the COD and CSD are calculated using FEM, considering the smallest versus the average crack spacing ratio as non-uniformity parameter. It is shown that assuming uniform distribution we obtain lower bond to elastic modulus. A “double-periodic” approach presented to calculate the COD of a crack in a non-uniform case as the average of two solutions for periodic crack systems is very accurate for cracks in internal layers, whereas for high crack density in surface layers it underestimates the modulus reduction.In the third paper, the thermo-elastic constants of damaged laminates were calculated using shear lag models and variational models in a general calculation approach (GLOB-LOC) for symmetric laminates with transverse cracks in 90° layer. The comparison of these two models with FEM was presented for cross-ply and quasi-isotropic laminates.
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| 3. |
- Bäckström, Ingela, 1963-
(författare)
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Quality Management for Sustainable Health : Methodologies, Values and Practices taken from Swedish Organizations
- 2006
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In many Western countries today, not least in Sweden, there are a lot of organizations that have great problems with sickness absence. The costs connected to the high rates of sickness absence have also risen to alarming levels. Healthy co-workers and healthy organizations are obvious goals for many leaders, but this is not always so easy to establish. Work practices and leadership that are beneficial to co-worker health are thus vital to identify. Studies have shown relationships between company-wide implementation of quality programs and improved co-worker satisfaction along with low co-worker turn over; in other words, co-worker health along with improved customer satisfaction and financial results. Despite the great problems concerning sickness absence, there are organizations that have been awarded prizes for excellence in leadership, internal partnership, working environment, and profitability. The overall purposes of the research described in this thesis are to examine and describe how management and leadership can establish sustainable health among the co-workers and examine how the leadership for sustainable health is related to Quality Management. The in-depth purpose is to examine which aspects within the values derived from the quality movement are those that primarily influence the co-workers’ perceived health. The results presented can be described in three parts and are results from four case studies carried out in five different organizations. Three of the organizations have received awards for establishing good working environment, good financial results, and low sick leaves among their co-workers; the fourth received an award for the successful implementation of quality programs. The first part consists of results from case studies in three different organizations and describes how organizations can work to achieve sustainable health among their co-workers, with practical examples. The results are methodologies, values and organizational structure, which it is considered possible for other organizations to adopt in their efforts to achieve good working conditions resulting in fewer sick leaves. The second part is an attempt to investigate if leadership for sustainable health is related to Quality Management. Methodologies, leadership values, organizational structure, and general values found in organizations which have achieved sustainable health are analyzed in the light of Deming’s 14 points, and a correlation is indicated. There is also correlation found between the TQM values and the co-workers’ perception of their health. The third part examines which of the aspects within the values grown from the quality movement are those that influence the co-workers perceived health. The results show significant correlation between the values and the co-workers’ perception of their health. Aspects found within the value “Top management commitment” were named; Empathy, Presence and Communication, Integrity, and Continuity. Within the value “Let everybody be committed” the aspects; Development, Influence and Being informed were found. These aspects are described in more detail and also in one model per value. The result implies that the TQM values; “Top management commitment”, “Improve continuously” “Let everybody be Committed” and “Focus on customers” are important for achieving healthy organizations and sustainable health among co-workers.
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| 4. |
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| 5. |
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| 6. |
- Rundquist, Jonas, 1964-
(författare)
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Outsourcing of New Product Development - A decision framework
- 2007
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The focus of this thesis is the outsourcing of activities in the New Product Development (NPD) process. Outsourcing of NPD refers to the outsourcing of development activities for the developing of new products (goods and/or service), where all or just the innovative part of the NPD process is purchased externally based on a contract with organizational units separate from the outsourcing firm. This definition implies that (A) the activity should be an innovative part of the NPD process, (B) the activity should have previously been conducted internally, and (C) the activity should be purchased under a contractual agreement between the organizations.This thesis focuses on the outsourcing of NPD in medium sized firms. Although the framework is probably also useful for small and large firms, the three empirical studies in the thesis explored samples of medium sized firms. NPD is a knowledge intensive activity that requires the ability to handle uncertainties and is very dependent on the individuals involved in the process. In this way it differs from production, which (especially when producing standard items on a large scale) is easier to control, monitor and to evaluate the costs. Therefore, some considerations connected to knowledge acquisition and uncertainty needs to be addressed.A literature review reveals that research on outsourcing often focuses on A) Large firms and B) outsourcing of production activities. In addition, research on NPD usually involves large firms, despite the fact that the interest in product development in small and medium sized firms has grown rapidly in recent years. Since outsourcing of NPD is a method frequently used to access competence, and reduce costs and/or uncertainty, it seems motivated to study the outsourcing of NPD in medium sized firms.The thesis presents a decision framework that is based on three empirical studies (two survey studies and one case study) and a theoretical framework. The theoretical framework presented in the thesis is commonly used to understand outsourcing questions in general. In the present thesis the framework is applied in the specific situation of outsourcing a knowledge intensive activity (such as NPD) in the context of medium sized firms. Transactions cost, resource based, resource dependency, knowledge based, agency cost, and institutional theories are revisited in the thesis.Outsourcing can lead to advantages in form of lower costs, access to knowledge or other resources, as well as access to markets, but it can also result in a knowledge drain, lower motivation among in-house staff, or an increased level of dependency on external organizations. Therefore the decision to outsource is not always a good one, and the pros and cons must be carefully evaluated. The result of the thesis is a decision framework that maps factors affecting the decisions that need to be made when outsourcing NPD. The implications can be of value to the outsourcing firm as well as to the potential outsourcing partner. The framework has been presented to the firms in the studies and thus has already proved its value to some extent.The framework will also be used for the design of the studies that will hopefully take me towards my PhD degree, including a new survey study as well as a case study focusing on knowledge integration.
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| 7. |
- Charles, Corinne, 1979-
(författare)
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Modelling microstructure evolution of weld deposited Ti-6Al-4V
- 2008
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The microstructure and consequently the mechanical properties of titanium alloys are highly dependent on the temperature history endured by the material. The manufacturing process of metal deposition induces repetitive cooling and heating in the material determining a specific microstructure. The presented study is devoted to developing and implementing a microstructure model for Ti-6Al-4V intended to be coupled to a thermo- mechanical model of the metal deposition process.Microstructural analysis of the metal deposited samples was first performed to understand the formed microstructure. A set of representative parameters for microstructure modelling were then selected as representative for the known impact of Ti-6Al-4V microstructure on mechanical properties. Evolution equations for these parameters were implemented for thermal finite element analysis of the process. Six representative state variables are modelled: the phase volume fraction of total alpha, beta, Widmanstätten alpha, grain boundary alpha, martensite alpha, and the alpha lath thickness. Heating, cooling and repeated re-heating involved in the process of metal deposition are taken into account in the model. The phase transformations were modelled based on a diffusionnal theory described by a Johnson-Mehl-Avrami formulation, as well as diffusionless transformations for the martensite alpha formation and the beta reformation during reheating. The Arrhenius equation is applied as a simplification to model temperature dependent alpha lath size calculation. Grain growth is not included in the present formulation, but would have to be added for capturing alpha lath coarsening during long term heat treatment.The temperature history during robotised tungsten inert gas deposition welding is simulated together with the microstructure. The implementation of the model handles well the complex cyclic thermal loading from the metal deposition process. A particular banded structure observed in the metal deposited microstructure is partially explained using the proposed microstructure model. It is concluded that although qualitatively interesting results have been achieved, further calibration testing over a wider range of temperature histories must be performed to improve the transformation kinetic parameters for reliable quantitative predictions of the microstructure.
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| 8. |
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| 9. |
- Larsson, Tobias
(författare)
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Effective development of dynamic systems : a structured approach
- 1999
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This licentiate thesis deals with effective simulation of multibody dynamic systems in the product development process. Previous work to make simulation more effective has concentrated on developing faster calculation methods. Instead, this approach is to make the process of multibody dynamics simulation more effective by structuring of products, simulation models and their usage. Efforts have been made to clarify how computer tools are used in product development in industry today. Insight into the two domains of product development and multibody dynamics is given. These domains have traditionally been separated but the introduction of concurrent engineering and faster computers puts new demands on the integration of computer support and analysis in the development process. A proposal for performing the multibody dynamics methodology in a modular way in the product development process is given based on the performed work.
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| 10. |
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| 11. |
- Lilja, Johan
(författare)
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Quality practice and customer value: strengthening the ideal linkage
- 2005
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Quality management is continuously evolving and the progression so far is frequently described in terms of four stages. According to these descriptions, Total Quality Management (TQM) constitutes the currently highest level, or fourth stage, of quality management. Despite the divergence of views on what constitutes TQM, it is commonly described as a number of diverse activities, here designated as quality practice, performed to display and embody a certain set of values. One of these values, acknowledged as central to TQM, is to focus on the customers. This value basically implies that a TQM organization should adapt its operations to what creates value for its customers. Hence, there is ideally a strong linkage between the application of quality practice and the creation of customer value. In a wider perspective, this linkage fundamentally determines the vital contribution of quality practice to competitiveness. However, this linkage has so far been given poor attention among quality researchers. Furthermore, differences of opinions exist regarding its strength. It has for instance been argued that quality practices commonly included in TQM lack a linkage to customer value, decrease the competitiveness of the organization in which they are implemented, and hinder the organization’s ability to create customer value. The aim of this thesis is accordingly to examine the ideal linkage between quality practice and customer value in order to increase its strength. In accordance to the idea of continuous improvement, the aim is to improve the reflection of the value ‘focus on the customers’ in quality practice. The research process described in this thesis has started by examining and developing the current theoretical foundation and models of TQM concerning customer value, in terms of the theory of attractive quality. Furthermore, an affective conceptualization of customer value has been used as a basis for an initial examination of the ideal linkage. Among the presented results it is indicated that quality practice, including the measures currently used to capture customer perceptions, is more or less restricted to negative motivations of external customers. Negative motivations basically stem from the customers strive to avoid and reduce negative emotional states. The linkage to positive motivations of the external customers is seemingly much weaker or even absent. The indicated focus can be seen as a reflection of early theories of motivation emphasizing negative motivations as the governing principle. Modern theories emphasize, however, both negative and positive motivations. The sole emphasis on negative motivations indicated in current quality practice would imply that external customers prefer to exist in a state of boring neutrality. A dual emphasis recognizes that while our customers want to minimize pain and disappointment, they want to maximize pleasure as well, to make life interesting and stimulating. An extension of quality practice, including the use of multiple output measures, is suggested to increasing the reflection of this duality of customer value in TQM. As a foundation for such an extension, a two-dimensional perspective on the mechanisms involved in the strong positive emotional state associated with attractive quality elements has been proposed. The proposed perspective points at two separate mechanisms in terms of the satisfaction of high-level needs and latent needs
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| 12. |
- Wingstedt, Johnny
(författare)
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Narrative music : towards an understanding of musical narrative functions in multimedia
- 2005
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- As the computer screen is replacing the book as the dominant medium for communication (Kress, 2003), questions about how meaning is constituted by the multimodal interaction of different media (including music) is becoming increasingly important in contemporary research of pedagogy, sociology and media studies. The overall aim with this licentiate thesis is to explore musical narrative functions as they appear in multimedia such as film and computer games. The thesis is based on three publications. Publication 1 proposes a classification of musical narrative functions, with 6 narrative classes(the Emotive, Informative, Descriptive, Guiding, Temporal and Rhetorical classes) and 11 categories. The relational interplay of music with contextual factors is emphasized. Publication 2 describes the design of a software tool, REMUPP (Relations Between Musical Parameters and Perceived Properties), to be used for experimental studies of musical expression. REMUPP is used for real time alteration of musical expression, by the manipulation of musical parameters such as tempo, harmony, rhythm, articulation, etc. Publication 3 describes a quasi-experiment using REMUPP, where a group of young participants (12-13 years old) were given the task of adapting musical expression - by manipulating 7 parameters - to make it fit 3 visual scenes shown on a computer screen. They also answered a questionnaire asking about their musical backgrounds and habits of listening to music, watching movies and playing computer games. Numerical data from the manipulations were analyzed statistically with regards to the preferred values of the musical parameters in relation to the different visual scenes. The results indicated awareness and knowledge about codes and conventions of musical narrative functions, and were to some degree affected by the participants' gender, musical backgrounds and media habits.
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| 13. |
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| 14. |
- Kuzmin, Leonid, 1958-
(författare)
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Investigation of the most essential factors influencing ski glide
- 2006
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- There are many different parameters of a ski running surface (material, roughness, hydrophobicity, etc.). All the parameters have an influence on ski glide, some more and some less. Furthermore, some parameters with only minor relevance are commonly declared as critical, while truly critical parameters, as far as we know, never been investigated. In this thesis, we try to identify and structure the different stages of ski running surface preparation. In our experiments, we have applied well-established, commonly used treatments parallel with alternative preparations. The unexpected result of our experiments is that the treatments commonly used today are not as good as alternative treatments, namely; stone grinding and glide wax application are far from an optimal ski treatment if minimising friction over a given distance is the major goal.
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| 15. |
- Köhler, Veronica, 1974-
(författare)
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Co-Creators of Scope of Action : An exploration of the dynamic relationship between people, IT, and work in a nursing context
- 2006
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Information Technology (IT) is today widespread in our work places, in our spare time and in our society overall. Implementations of IT in organizations come with high expectations on effectiveness, revenue, smoother work processes and so on. However, this simplified view on IT ignores the fact that it is the IT usage rather than the IT artifact per se that in the end decides the effect of an implementation of IT. Although the IT artifact certainly has been designed to support certain tasks and processes, the success or failure of the Information System (IS) in the end depends on the individuals' actions, which ultimately depend on their perceptions and interpretations of the IS. Thus, when technology is being implemented and becomes an IS in use, it becomes a part of work, and as such more of a social system than a technological one.The actual result of a design process does not solely consist of things or artifacts, but above all changed action patterns for the users. From this follows that we must consider design of artifacts as something more than merely the constructing of actual objects with functions and properties that are easily measured. Rather, a large part of all design activities has to do with design of conceivable social milieus, not artifacts. Thus, design may be defined as the suggesting and establishing of scope of action. The concept scope of action aims at describing the fact that the design of, and consequently the implementation of, a specific IT artifact always aims at creating a certain scope of action; some actions are made easier, others are made more difficult or even impossible. This scope of action has to some extent been deliberately designed, but these changes may on the other hand also be undesired and not predicted in advance. The complexity of this phenomenon is great and hard to grasp in advance. However, this does not mean that we can allow ourselves to ignore exploring this phenomenon more deeply. On the contrary, with a usage perspective on IS success or failure, scope of action becomes very important.Although the term scope of action may seem a rather intuitive concept, we need more concrete knowledge about its character in order to be able to understand IT usage, both when designing a new IT artifact and when studying or evaluating IT. Thus, our intuitive understanding of the concept needs to be complemented with theory on the ‘constituents’ and effects of this phenomenon. For this purpose, in this thesis nurses’ use of the Electronic Patient record (EPR) is being explored in order to gain an empirically derived understanding of the character of scope of action.The research findings highlight the emergent character of scope of action. It is obvious that an individual’s scope of action is not being created on one occasion, and above all not only by the IT artifact. Various co- creators such as the IT artifact, the usage and the social context create and re-create scope of action. Also, how the individual interprets and understands the IT artifact in IT usage will influence her scope of action. This since sensemaking and learning processes on both a personal and organizational level take place that are co-creators of the individual’s scope of action, at the same time as the individual’s knowledge and previous sensemaking and learning influences her use of the IT artifact.Thus, reasoning, thinking, learning, and the IT artifact co-evolve over time in adaptation and appropriation processes. This means that IT as a mediational means constitutes an important co-creator of scope of action. From this also follows that work integrated learning is an important co- creator of scope of action when using IT in a work setting, at the same time as work integrated learning is being influenced by the individual’s scope of action.Finally, in order to understand how scope of action emerges in use, merely focusing on structures is insufficient. Scope of action emerges as a product of interplay between complex processes involving artifacts, usage and context. This means that the user’s scope of action is co-created by both static structures as well as dynamic processes relating to the IT artifact, the organization, and the work practice. Thus, the IT artifact, and subsequently scope of action, must be must be understood in relation to the multi-aspectual context of which it is a part instead of merely in relation to the properties of the IT artifact per se.
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| 16. |
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| 17. |
- Aalipour, Mojgan
(författare)
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Human Factors Approach for Maintenance Improvement
- 2015
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The purpose of this research work is to explore and describe human factors affectingmaintenance execution. To achieve the purpose of this study, the influencing factors have been identified using a literature survey. They have been categorized into four main groups namely organizational, workplace, job and individual factors. The Analytical Hierarchy Process (AHP) method is employed on data questionnaires to rank the priority of the factors. The interrelationships between these factors have been recognized by theInterpretive Structural Modelling (ISM) model. In the present case studies, MICMAC1analysis technique is also implemented for identifying the driving, dependent, linkage and autonomous factors. The data was collected through a questionnaire survey involving the participation of 16 and 25 maintenance staff and 10 mining experts in Swedish and Iranian mines, respectively. Within the study, it has been identified that the temperature, work layout, tools design and tools availability are the most important factors in both mines related to these categories. However, the significant factors in the organizational and individual categories are different in the selected mines. The effect of workplace factors on the maintainability of mining equipment is discussed and thereafter a methodology for maintainability management in the design and operation phases is developed. In the thirdcase study HEART2 is applied to estimate the probability of human error occurring duringmaintenance execution in an Iranian cable company. This research supports maintenance management to gain knowledge of human factors that affect maintenance execution. Further, this understanding could be useful in the development of strategies to improve the execution of maintenance.Keywords: Human Factors, Maintenance Management, Human Reliability, HumanPerformance, AHP, ISM, MICMAC, HEART
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| 18. |
- Aas, Gro Hanne
(författare)
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Kvinneforskningspolitiske (pr)øvelser
- 1999
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Målsettingen for licentiatuppsatsen er å analysere nordisk kvinneforsknings formuleringer av forskningspolitiske felter, problemstillinger og utfordringer, og gjennom kontakt og diskusjon bidra til samarbeid, diskusjoner og offentlighet om forskingspolitikk i kvinneforskning. Arbeidet har tatt utgangspunkt i relativt nytt materiale fra Danmark, Norge og Sverige. I kap. 1 presenteres prosjektet, problemstillinger og materiale. Kapitlene 2-6 består av innledninger og artikler holdt eller skrevet i løpet av de to senaste åren. Diskusjoner om kjønn og akademia står i fokus i kap. 2 - "Universities have politics". I kap. 3, artikkelen "Gamle og nye drømmer", diskuteres et kvinneforskningspolitiske intervensjonsprosjekt som blev utført for en del år tilbake, og det antydes noen nye omdreiningspunkter for et slikt arbeid. Enkelte perspektiver utdypes i kap. 4, "Kvinneforskningens samfunnskontrakt", hvor termen "kvinneperspektiv" som forskningspolitisk term granskas krtitiskt. De to siste kapitlene tar utgangspunkt i den norske forskningsmeldingen som kom våren 1999. Ut fra tre lesestrategier forsøkes det leses muligheter for kvinneforskningspolitiske strategier. Det ses også på innholdet i regjeringens forskningspolitiske verdidebatt, og det diskuteres mulige intervensjoner i denne ut fra feministiske vitenskaps- og teknologistudier.
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| 19. |
- Abdikalikova, Zamira
(författare)
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Embedding theorems for spaces with multiweighted derivatives
- 2007
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This Licentiate Thesis consists of four chapters, which deal with a new Sobolev type function space called the space with multiweighted derivatives. This space is a generalization of the usual one dimensional Sobolev space. Chapter 1 is an introduction, where, in particular, the importance to study function spaces with weights is discussed and motivated. In Chapter 2 we consider and analyze some results of L. D. Kudryavtsev, where he investigated one dimensional Sobolev spaces. Moreover, in this chapter we present and prove analogous results by B. L. Baidel'dinov for generalized Sobolev spaces. These results are crucially for the proofs of the main results of this Licentiate Thesis. In Chapter 3 we prove some embedding theorems for these new generalized Sobolev spaces. The main results of Kudryavtsev and Baidel'dinov about characterization of the behavior of functions at a singularity take place in weak degeneration of spaces. However, with the help of our new embedding theorems we can extend these results to the case of strong degeneration. In Chapter 4 we prove some new estimates for each function in a Tchebychev system. In order to be able to study also compactness of the embeddings from Chapter 3 such estimates are crucial. I plan to study this question in detail in my further PhD studies.
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| 20. |
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| 21. |
- Abid, Nosheen, 1993-
(författare)
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Deep Learning for Geo-referenced Data : Case Study: Earth Observation
- 2021
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The thesis focuses on machine learning methods for Earth Observation (EO) data, more specifically, remote sensing data acquired by satellites and drones. EO plays a vital role in monitoring the Earth’s surface and modelling climate change to take necessary precautionary measures. Initially, these efforts were dominated by methods relying on handcrafted features and expert knowledge. The recent advances of machine learning methods, however, have also led to successful applications in EO. This thesis explores supervised and unsupervised approaches of Deep Learning (DL) to monitor natural resources of water bodies and forests. The first study of this thesis introduces an Unsupervised Curriculum Learning (UCL) method based on widely-used DL models to classify water resources from RGB remote sensing imagery. In traditional settings, human experts labeled images to train the deep models which is costly and time-consuming. UCL, instead, can learn the features progressively in an unsupervised fashion from the data, reducing the exhausting efforts of labeling. Three datasets of varying resolution are used to evaluate UCL and show its effectiveness: SAT-6, EuroSAT, and PakSAT. UCL outperforms the supervised methods in domain adaptation, which demonstrates the effectiveness of the proposed algorithm. The subsequent study is an extension of UCL for the multispectral imagery of Australian wildfires. This study has used multispectral Sentinel-2 imagery to create the dataset for the forest fires ravaging Australia in late 2019 and early 2020. 12 out of the 13 spectral bands of Sentinel-2 are concatenated in a way to make them suitable as a three-channel input to the unsupervised architecture. The unsupervised model then classified the patches as either burnt or not burnt. This work attains 87% F1-Score mapping the burnt regions of Australia, demonstrating the effectiveness of the proposed method. The main contributions of this work are (i) the creation of two datasets using Sentinel-2 Imagery, PakSAT dataset and Australian Forest Fire dataset; (ii) the introduction of UCL that learns the features progressively without the need of labelled data; and (iii) experimentation on relevant datasets for water body and forest fire classification. This work focuses on patch-level classification which could in future be expanded to pixel-based classification. Moreover, the methods proposed in this study can be extended to the multi-class classification of aerial imagery. Further possible future directions include the combination of geo-referenced meteorological and remotely sensed image data to explore proposed methods. Lastly, the proposed method can also be adapted to other domains involving multi-spectral and multi-modal input, such as, historical documents analysis, forgery detection in documents, and Natural Language Processing (NLP) classification tasks.
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| 22. |
- Abiri, Olufunminiyi
(författare)
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Simplifications of non-local damage models
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Ductile fracture presents challenges with respect to material modelling and numerical simulations of localization. The strain and damage localization may be unwanted as it indicates a failure in the process or, as in the case of machining and cutting, a wanted phenomenon to be controlled. The latter requires a higher accuracy regarding the modelling of the underlying coupled plastic and fracturing/damage behaviour of the material, metal in the current context as well as the robustness of the simulation procedure. The focus of this thesis is on efficient and reliable finite element solution of the localization problem through the non-local damage model. The non-local damage model extends the standard continuum mechanics theory by using non-local continuum theory in order to achieve mesh independent results when simulating fracture or shear localization. In this work, the non-local damage model and its various simplifications are evaluated in an in-house finite element code developed using Matlab™. The accuracy, robustness, efficiency and costs of the models are investigated and also compared to a general multi-length scale finite element formulation. A numerical study versus published data is used to demonstrate the validity of the model. The explicit non-local damage variant will be implemented in a commercial finite element code for use in machining simulation
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| 23. |
- Adolfsson, Daniel
(författare)
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Steelmaking slags as raw material for sulphoaluminate belite cement
- 2007
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The present work was undertaken as part of the research in the Minerals and Metals Recycling research centre, MiMeR. The course of the thesis is attributed to metallurgical slags from the steelmaking industry and the possible use of such by-products as raw material for sulphoaluminate belite cement (SAB). Implementing steel slags into the production of cement could contribute to the steel industry's possibility of increasing the recirculation. In addition to the previous objective, the introduction of slag into the cement manufacturing can also facilitate the reduction of carbon dioxide emissions as well as lowering the overall energy consumption during the manufacturing. The reason for this is that the SAB system enables the reduction of the lime saturation factor (LSF) which in turn implies that less limestone is needed in the raw meal. Additionally, the firing temperature can be reduced by about 100-150°C, since dicalcium silicate and sulphoaluminate are formed already at approximately 1200-1250°C. In any event, one should remember that this is not intended to be a final solution for the recycling of slag, nor a replacement for already accepted cement materials. A number of applications currently exist where ordinary Portland cement (OPC) is used, but in cases where the OPC could be replaced with other type of cements, e.g. SAB cement, the possibility of using residues material in cement applications is increased. Considering the clinker covered within this work, possible applications are those where slow hydraulic properties are suitable. The behaviour of high temperature reactions of tested mixtures was investigated using thermogravimetric analysis coupled with a quadrupole mass spectrometer. Mineralogical observations were carried out with x-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The results proved that steelmaking slags have the potential to work as raw material, since sulphoaluminate along with polymorphs of dicalcium silicate and ferrite phases were detected after firing at 1200 ºC in an air atmosphere. The hydraulic properties of the specimens were analysed through conduction calorimetry, XRD, differential scanning calorimetry (DSC) as was the mechanical strength of the specimens when hydrated for 2 and 28 days. The compressive strength was in accordance with that suggested in the literature for slow hardening SAB cement. Both mixtures tested behaved the same with regard to heat development as well as the amount of AFt formed during the first 24 hours of the hydration.
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| 24. |
- Aguilar, Wilson
(författare)
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Study of the Synthesis of ZSM-5 from Inexpensive Raw Materials
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- ZSM-5 is an aluminosilicate with high silica ratio with suitable properties for catalysis, ion exchange, adsorption and membrane applications. ZSM-5 is usually produced industrially from concentrated systems in which there is formation of an amorphous gel phase. Typical syntheses of ZSM-5 require sources of silicon and aluminium, a mineralizer and an organic molecule as so-called templating agent. The silicon and aluminum sources widely used for the synthesis are pure reagent chemicals and in particular quaternary ammonium compounds like tetrapropyl ammonium hydroxides (TPA-OH), are employed as templating agents. Unfortunately, these compounds are rather expensive. Demand for inexpensive sources of aluminosilicates for the synthesis of ZSM-5 has increased during the last two decades. Natural raw materials such as kaolin clay and diatomaceous earth (diatomite) are two potential inexpensive sources of silica and alumina. Moreover, the molecule n-butylamine (NBA) has been reported as a low-cost templating agent to replace the quaternary ammonium compounds. The aim of this work was to show for the first time that leached metakaolinite or diatomite in combination with sodium hydroxide and n-butylamine could be used as inexpensive raw materials for the synthesis of ZSM-5 without using an additional source of silica. After synthesis optimization, both sources of aluminosilicate were found to behave differently during the course of synthesis and led to slightly different products. The chemical composition of the raw materials and the products were determined using inductively coupled plasma-sector field mass spectrometry (ICP-SFMS). Crystallinity was examined by X-ray diffractometry (XRD), the morphology was studied by extreme-high-resolution scanning electron microscopy (XHR-SEM) and the specific surface area was estimated from nitrogen adsorption data by the BET method. The chemical composition of individual crystals was determined by energy dispersive spectrometry (EDS). Dealumination of the raw materials by acid leaching made it possible to reach appropriate SiO2/Al2O3 ratios and reduced the amount of impurities. The final ZSM-5 products had a SiO2/Al2O3 ratio in the range 20 – 40. The use of leached diatomite allowed reaching higher yield of ZSM-5 crystals within comparable synthesis times. However, low amounts of mordenite were formed, which was related to the high calcium content of diatomite. Another considerable advantage of diatomite over kaolin is that diatomite does not require heat treatment at high temperature to convert the kaolin to reactive metakaolin. Further characterization of the system by XHR-SEM and EDS at low voltage was carried out in order to understand the nucleation and early growth of the ZSM-5 zeolite crystals. The observations with unprecedented detail strongly suggest that nucleation and the succeeding growth occurs on the gel surface. The growth rates in the various crystallographic directions already at an early stage are such that the shape of the growing crystals resembles that of the final crystals. However, as the early growth is interface mediated, the growth rate along the gel particles is high and the gel particles will become partially embedded inside the growing crystals at an early stage. The Si and Al nutrients are probably transported along the solid/liquid interface and possibly through the liquid in the form of nanoparticles detaching from the gel. The organic template was initially contained in the liquid. However, it remains unclear at which stage the template becomes incorporated in the solid material. EDS at low voltage was also used to gain compositional information about the sodium/calcium ion exchanged products and extraneous phases when kaolin and Bolivian montmorillonite clay were used for the synthesis of zeolite A by alkali fusion. In order to evaluate the cation exchange capacity (CEC) of the synthesized zeolite, ICP-SFMS and EDS were compared. The EDS method used in this work resulted in (Na,Ca)/Al ratios in equivalent moles very close to 1.0 as expected and was therefore found more reliable than ICP-SFMS to measure cation exchange capacity for zeolite A. To summarize, the present work shows that it was possible to synthesize well-crystallized ZSM-5 zeolite from inexpensive raw materials such as leached metakaolin or leached diatomite, sodium hydroxide and n-butyl amine. Furthermore, the crystallization mechanism evidenced in this system might be more general and also apply for other concentrated systems, e.g. those using TPA as structure-directing. Finally, this work displays that EDS at low voltage can provide valuable local compositional information in the field of zeolite synthesis.
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| 25. |
- Ahmadi, Alireza
(författare)
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An assessment of operational consequences of failures to support aircraft scheduled maintenance program development
- 2007
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A majority of the direct and indirect maintenance costs in the life cycle of aircraft stems from the consequences of decisions taken during the initial maintenance program development. In particular, the preventive and corrective maintenance requirements, which greatly influence both the system availability and life cycle cost, need to be defined in order to perform only those preventive actions that are absolutely necessary and costeffective. Reliability-Centered Maintenance (RCM) is a systematic methodology used to identify the preventive maintenance tasks that are necessary to realize the inherent reliability of equipment at the lowest possible cost. Developing a scheduled maintenance program by means of RCM consists of identifying those preventive tasks which are both applicable (technically feasible) and effective (worth doing). An applicable maintenance task must satisfy the requirements of the type of failure to restore the item's initial performance capability. To be effective, a preventive maintenance task must lead to a reduced risk (or expected loss) of the consequence classes to a level which is acceptable to the user. In the design development phase, in order to identify the most cost effective solution, a design trade-off study is needed. This involves choosing the correct balance of the cost of consequences of failure and its correction, with their cost of prevention. However, during initial aircraft maintenance program development, lack of a methodology that supports the assessment of the operational consequences of failures has made the costeffectiveness analysis of maintenance tasks a challenging issue. This might reduce the accuracy of the analysis, which results in higher maintenance costs and may decreases the punctuality of operation, which ultimately increases the total aircraft life cycle cost. The purpose of this study is to develop a methodology for identifying different operational consequences and associated costs caused by aircraft system failure, in order to facilitate and enhance the capability of taking correct and efficient decisions when analyzing the cost-effectiveness of maintenance tasks. Some empirical studies of possible scenarios involving aircraft failures and their operational consequences for a commercial airline have been performed. Empirical data were extracted through document studies and interviews, guided by the application of an Event Tree Analysis (ETA). The analysis was performed together with experienced practitioners from both an aircraft manufacturer and commercial airlines, which contributed to a continuous verification of the outcomes of the study. Finally, the study has also estimated the associated cost of the identified operational consequences of failures. In order to quantify the operational consequences of failures, in the absence of adequate and reliable data, a methodology using pair-wise comparison technique has been applied to extract judgments of experts efficiently
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