| 1. |
- Abbasi, Maisam
(författare)
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Themes and challenges in developing sustainable supply chains
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Sustainable development is one of the greatest global challenges facing human beings in the 21st century. In order to tackle sustainability related problems, several global, European, and national targets for 2050 have been set. The transition of supply chains activities towards sustainability targets calls for designing new strategies and continuously identifying and tackling the challenges that can hinder the operationalization of such strategies. The purpose of this research was to explore and classify themes and challenges in developing sustainable supply chains activities in general, and freight transport and urban distribution in particular. Three research questions were defined followed by defining the scientific assumptions and research strategies. Three research studies were then designed and carried out to find trustworthy and authentic answers to the corresponding research questions. However, research design, data collection, and data analysis were mixed and overlapping as they were not completely sequentially carried out. Data were collected by triangulation of different research methods, namely, literature review, content analysis, and semi-structured interviews. Analysis of the data was guided by principles of content analysis, discourse analysis, analytic induction, and grounded theory. Synthesis of the analyzed data resulted in the emergence of categories of themes and challenges, the development of hypotheses, and further discussion. In total, five categories of themes were identified for making supply chains environmentally sustainable, fifteen for making freight transport sustainable, and eight for making urban freight distribution sustainable. Five categories of challenges were identified for making supply chains environmentally sustainable, five for making freight transport sustainable, and seven for making urban freight distribution sustainable. All the themes and challenges were then synthesized to determine the patterns of their association. Five major themes in developing sustainable supply chains emerged, namely, increasing sustainability awareness, closing the loop of supply chains, making supply chains energy-efficient, making supply chains environmentally responsible, and managerial issues. Five major challenges in developing sustainable supply chains emerged, namely, change of behavior, costs, implementation, corporate governance, and antagonistic effects and paradoxical conflicts. As the nature of supply chains and the challenges identified in developing them sustainably is complex, a complexity theory perspective was considered beneficial for dealing with them. Such a perspective can enable us to: take a more holistic view of available sustainability-oriented strategies and activities; analyze the antagonistic effects of strategies and activities on each other; recognize conflicts of a paradoxical character that exist in supply chains; analyze the changes influencing and influenced by the strategies and activities; appreciate enough diversity and freedom among the sub-systems rather than too much simplification of them; design and redesign the transition paths for different types of supply chains. A complexity theory perspective can also be beneficial when governing a transformative transition of supply chains towards sustainability targets. Lessons are suggested in the discussion chapter that may help policy and decision makers in designing the future strategies and in tackling the challenges. The themes identified can be beneficial for increasing the absorptive capacity of industries, practitioners, and policy makers while they design innovative strategies for transitions towards sustainability targets. The identified challenges can also be beneficial for reducing the inertia and uncertainties against operationalization of sustainable development in practice.
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| 2. |
- Abdul Hamid, Akram
(författare)
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Method for evaluation of renovation measures with regards to moisture and emission loads : Based on risk assessments
- 2017
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Renovating the European building stock has for almost two decades been a matter of importance. For Sweden, it is important to renovate its multifamily buildings in order to achieve a reduced energy use, but also because renovation is needed due to building materials and services reaching (or having passed) the end of their life span. In order to renovate properly, renovation measures must be implemented correctly to avoid negative impact on the building materials and the indoor environment. For this purpose, renovation measures need to be evaluated with regards to moisture and emission loads, and the risks related to these. This thesis has developed a realistically applicable method for this type of evaluation, called RememberL, and tests RememberL on two renovation measures as case studies. Through laboratory tests, in-field measurements, building performance simulations, hygrothermal simulations and surveys, the renovation measures are evaluated according to the methodology. RememberL thereby yields useful results for understanding the impact that these methods have on building materials and the indoor environment and vice versa. Furthermore, through the application of RememberL on these case studies, it is further developed to a method that proves flexible through several alternatives.
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| 3. |
- Abrahamsson, Cristian
(författare)
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Elevengagemang ur ett NO-lärarperspektiv : Hur lärare uppfattar elevers engagemang och dess betydelse för lärarrollen och undervisningen
- 2019
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- AbstractThis essay focuses on teachers' perspective on student engagement and aims to highlight the connection between student engagement, teaching and content matter. It investigates how teachers interpret the concept of student engagement and what consequences their interpretation have for themselves, their teaching and their students. It also examines how teachers perceive the relationship between student engagement and the content of science teaching. The study is based on a theoretical view on engagement as a context-dependent, multi-dimensional concept that includes other concepts such as interest and motivation. Engagement is a concept often used when describing a desirable quality of school students. In research, the concept has been linked to students' outcome and lack of engagment as a precursor for drop-out from school behaviour. Many studies about engagement focus on how the concept is to be defined and measured and how engagement is influenced by its context, often described with other concepts such as attitude, interest and motivation. These studies often have a student-oriented perspective with questionnaires or self-assessments.Two methods for data collecting has been used. First, a three-stage Delphi survey distributed to 39 Swedish expert science teachers and second, four focus group interviews with a total of 21 science teachers teaching in Swedish upper primary school. The results show that teachers in the studies had no problem to use the concept of engagement even though they did not have a clear definition of what it stands for. They link engagement to motivation and interest and often interpret students’ feelings or behaviours as engagement, whereas evidence of cognitive strategies often go unnoticed. The teachers emphasize that their teaching in terms of strategies, methods and relations to studens is of great importance to students' engagement rather than content matter, itself. The major conclusions concern the relation between teaching and student engagement. Teachers can create engagement by using interesting aspects of the content or by linking it to students' own experiences. They see students' engagement as a confirmation of their own ability and the quality of their work. Their interpretation of the students' responses will then influence the form and content of teaching as student engagement is considered important. The results imply that engagement has a role to play as a concept teachers can use when they want to discuss science teaching and students' learning. This requires that teachers gain a deeper understanding of all dimensions of student engagement in view of the major influence student engagement has on the teacher and thereby the teaching. Then teachers’ knowledge about how to create engagement in science can be used as a means of increasing students’ learning, not for engagement as a goal for the teaching itself.
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| 4. |
- Afzali Far, Behrouz
(författare)
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Analytical and Parametric Study of Damped Vibrations in Gough-Stewart Platforms
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This work establishes a comprehensive and fully parametric model for the damped vibrations of Gough-Stewart Platforms (GSPs) at symmetric configurations. It is noteworthy that in the literature a complete solution to this problem has not been presented. This work has been carried out in three stages which are the subjects of Papers I, II and III. After the industrial stage of the work which is reflected in Paper I, we have generalized the problem and established a fully parametric model of the damped vibrations of GSPs in Paper II and finally extended the model by taking inertia of the struts into consideration in Paper III. The final model is parametrically developed in terms of all the design variables of the system and can be directly employed for the analysis, optimization and control of GSPs. In this work, we parametrically formulate the kinematic equations which are eventually obtained in the form of a Jacobian matrix. The focus of this work is on the Cartesian-space formulation in which Bryant angles, due to their advantages over Euler angles, are chosen to represent the orientation of the platform. The equations of motion are formulated and linearized based on a Lagrangian dynamics approach where Rayleigh axial damping of the struts is introduced to the system. Inertia, stiffness and damping matrices are parametrically formulated. By introducing the inertia of the struts, the inertia matrix turned out to be quite complicated to formulate. Interestingly, despite its apparent symmetrical geometry, the equivalent inertia matrix is obtained as a non-diagonal matrix. The eigenvectors and damped eigenfrequencies of the system are then parametrically established. In addition, the decoupled vibrations are analytically investigated where it is shown that the consideration of strut inertia may lead to significant changes of the decoupled conditions. Finally, for a reference GSP, the vibrational behavior with respect to different design variables are systematically studied.
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| 5. |
- Ahlström, Johan
(författare)
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Corrosion of steel in concrete at various moisture and chloride levels
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- About 7000 concrete bridges in Sweden were built before 1965. The annual cost for maintenance of these bridges is about 0.6% of their total value. The cooling water tunnels at Swedish nuclear power plants have been exposed to seawater for about 30-40 years. The maintenance cost for these tunnels has been evaluated to be about one billion Swedish kronor. It is important to evaluate the risk of corrosion for these types of structures and due to the relatively their old age, corrosion of steel in concrete might be an increasing problem in the future. Generally, corrosion of steel in concrete is induced by either carbonation or by chlorides. Carbonation means that carbon dioxide in air reacts with calcium within the concrete. This means that the pH of the concrete is decreasing and the steel start to corrode. Chloride induced corrosion means that chlorides are transported through the concrete to the steel and the corrosion rate can then increase significantly. It has been proposed in the literature that a certain chloride threshold level exist where an initiation of a significantly high corrosion rate occur. For decades, researchers have been trying to determine this chloride threshold level and the results scatter to a large extent. This is probably due to many different experimental setups and different properties of the used steel and concrete. One important factor to consider is the moisture condition of the concrete. It is generally accepted that the corrosion rate of the steel is low in dry concrete due to high resistivity. For very wet concrete, the corrosion rate is also low due to slow transportation rate of oxygen to the steel surface. At an intermediate moisture condition, the corrosion rate is high due to relatively low resistivity and high transportation rate of oxygen. In the present study, samples made of steel cast in chloride containing mortar were exposed to different moisture conditions. The moisture condition was either static at a certain relative humidity or dynamic where the relative humidity was cycling between 75% and 100%. The lowest chloride concentration which caused initiation of corrosion was 1% Cl by mass of cement and was measured for samples exposed to 97% RH. At higher or lower moisture conditions than 97% RH, the corrosion rate was lower. For samples exposed to dynamic moisture conditions, the lowest chloride concentration which initiates corrosion was measured to be 0.6% Cl by mass of cement. Based on these results it was suggested that the chloride threshold level is lower than 1% Cl by mass of cement for samples exposed to static moisture conditions and even lower chloride concentration can initiate corrosion in dynamic moisture conditions. The present study also assessed the corrosion properties of steel in a cooling water tunnel. The corrosion potential was measured during one year and it was found that the steel in concrete was in an electrical connection with water pumps made of stainless steel and in contact with sacrificial anodes. The connection with the pumps increased the corrosion potential and the connection with the sacrificial anodes decreased the corrosion potential. To assess if there is an increased risk of galvanic corrosion due to the connection with the pumps, a complementary study was made to measure potentials where the corrosion increase significantly. The results suggested that it is not likely that the steel in the tunnel suffer of galvanic corrosion, due to that the measured corrosion potentials in the tunnel was lower than the measured potentials in the complementary study.
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| 6. |
- Alce, Günter
(författare)
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Prototyping Methods for Augmented Reality Interaction
- 2015
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The age of wearable technology devices is upon us. These devices are available in many different form factors including head-mounted displays (HMDs), smartwatches and wristbands. They enable access to information at a glance. They are intended to always be ‘‘on’’, to always be acting and to always be sensing the surrounding environment in order to offer a better interface to the real world. A technology suitable for these kinds of user interfaces (UIs) is augmented reality (AR) due to its ability to merge real and virtual objects. It can be difficult and time consuming to prototype and evaluate this new design space due to components that are undeveloped or not sufficiently advanced. To overcome this dilemma and focus on the design and evaluation of new user interfaces instead, it is essential to be able to quickly simulate undeveloped components of a system to enable the collection of valuable feedback from potential users. The aim of the research presented in this thesis was to develop and evaluate two methods that can be used for prototyping AR interaction. The thesis is based on the four attached papers. Paper 1 presents a Wizard of Oz tool called WozARd and the set of tools it offers. The WozARd device allows the test leader to control the visual, tactile and auditive output that is presented to the test participant. WozARd is also suitable for use in an AR environment where images are overlaid on the smartphone’s camera view or on glasses. The main features that were identified as necessary for simulating AR functionality were: presentation of media such as images, video and sound; navigation and location based triggering; automatically taking photos; capability to log test results; notifications; and the integration of the Sony SmartWatch for interaction possibilities. The study described in Paper 2 is an initial investigation of the capability of the WozARd method to simulate a believable illusion of a real working AR city tour. A user study was carried out by collecting and analyzing qualitative and quantitative data from 21 participants who performed the AR city tour using the WozARd with a HMD and smartwatch. The data analysis focused on seven categories that can have a potential impact on how the WozARd method is perceived by participants: precision, relevance, responsiveness, technical stability, visual fidelity, general user experience, and human operator performance. Overall, the results seem to indicate that the participants perceived the simulated AR city tour as a relatively realistic experience despite a certain degree of technical instability and human operator mistakes. Paper 3 presents a proposed method, called IVAR (Immersive Virtual AR), for prototyping wearable AR interaction in a virtual environment (VE). IVAR was developed in an iterative design process that resulted in a testable setup in terms of hardware and software. Additionally, a basic pilot experiment was conducted to explore what it means to collect quantitative and qualitative data with the proposed prototyping method. The main contribution is that IVAR shows potential to become a useful wearable AR prototyping method, but that several challenges remain before meaningful data can be produced in controlled experiments. In particular, tracking technology needs to improve, both with regards to intrusiveness and precision. The goal of Paper 4 was to apply IVAR to evaluate the four interaction concepts from Paper 3: two for device discovery and two for device interaction implemented in a virtual environment. The four interaction concepts were compared in a controlled experiment. Overall, the results indicate that the proposed interaction concepts were found natural and easy to use. Overall, the research presented in this thesis found the two prototyping methods, the WozARd and the IVAR method, to be useful for prototyping AR interaction but several challenges remain before meaningful data can be produced in controlled experiments. WozARd is flexible in terms of being easy to add new UI, and is sufficiently stable for prototyping an ecosystem of wearable technology devices in outdoor environments, but it relies on a well-trained wizard operator. IVAR is suitable for simulations of more complex scenarios, e.g. since registration and tracking easily can be simulated. However, it has the disadvantage of being static, since users need to sit down and their movements are somewhat limited because they are connected to a computer with cables.
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| 7. |
- Alfranseder, Emanuel
(författare)
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Essays in Financial Economics
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Chapter 1 develops a framework to investigate the impact of the financial crisis starting in 2007 and employs an extended GARCH model to test for spillover and contagion effects originating from the financial sector. We find that the financial crisis affects financially distressed firms more heavily than non-distressed firms. Financial constraints do not play an equally crucial role during the crisis. Overall, the analysis shows that the financial sector affects the returns of non-financial firms during the crisis. We find little evidence that the turbulence in the financial sector expressed in terms of volatility fully encroaches upon non-financial firms. Chapter 2 introduces a model aiming to explain the equity premium puzzle. Consumers exhibit both pessimism and doubt. Consumers are pessimistic if their beliefs about the dividend are a translation of the objective dividend by an independent and identically distributed normal random variable with negative mean. Consumers exhibit doubt if their beliefs are a translation of the objective dividend by an independent and identically distributed normal random variable with mean zero. A cross-sectional empirical study using the SHARE database explores the differences between various European countries in terms of pessimism and doubt and tests the theoretical model empirically.
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| 8. |
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| 9. |
- Alhelfi, Ali Kadhim Hadi
(författare)
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On Bubble Dynamics in Acoustic Cavitation
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Nyligen har mycket uppmärksamhet ägnats åt studier rörande ickelinjära oscillationer av sfäriska gasbubblor i pulserande tryckfält. Denna lic-avhandlning syftar till att utöka kunskapen kring kavitationsfenomenet. I detta arbete undersöks olika modeller och en förbättrad numerisk modell har utvecklats för att analysera akustiska kavitationsfenomen. Resultaten från den utvecklade modellen innefattar bildande och kollaps av enstaka gasbubblor i en vätska under inverkan av ultraljud som en funktion av tiden. Modellen valideras och jämförs för tre huvudfall. Dessa fall är: enhetligt tryck och temperatur inne i bubblan, enhetligt tryck och varierande temperatur inne i bubblan, samt varierande tryck och temperatur inne i bubblan. För fall 2 och fall 3 tas hänsyn både till värmeöverföringen inne i bubblan och till den omgivande vätskan. Olika grundläggande egenskaper hos oscillerande bubblor i ett ultraljud akustiskt fält såsom tryck, temperatur, densitet, hastighet och acceleration inne i bubblan under påverkan av tidsberoende ljudtryck har undersökts och resultaten för varje enskilt fall jämförs med motsvarande experimentella data. De numeriskt beräknade resultaten visar att antagandet om ett enhetligt tryck och temperatur inuti bubblan predikterar ett samband mellan radien och tiden som avviker starkt från de uppmätta värdena. Vidare visades det att för att prediktera de extrema tillstånd som förknippas med en kollaps måste bubblans dynamik ta hänsyn både till tryckgradienten och värmeöverföringen inne i bubblan samt över bubblans yta.
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| 10. |
- Alic, Vedad
(författare)
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Numerical Methods for Conceptual Structural Design
- 2016
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Conceptual design is the first phase in the design process in which all the requirements and design objectives are synthesized into conceptual alternatives. In practice today, major decisions regarding the buildings geometry, massing, and overall form are usually made during the first phase. Considering structural performance requirements during conceptual design enhances interdisciplinary interaction, and creates a visual link between form and numeric performance evaluations, reducing work on poorly performing solutions. To include structural performance in conceptual design requires, amongst other things, the availability of tools such as simulation software, suitable for conceptual studies.The aim of the research is to develop new efficient methods and procedures for supporting an interactive and iterative design process that includes engineering aspects. By integrating engineering knowledge and physical aspects in the developed tools, a more efficient and betteradapted design process can be obtained. Modeling tools for conceptual studies should encourage creativity and be capable of interactively modifying the model in a sketch-like fashion once it has been created. Supporting an interactive and iterative design process, requires new interaction models and numerical approaches in the tools used.The research has focused on two different areas, were the first is related to conceptual studies for reducing ground borne wave propagations in an urban scale. A tool is developed for simulating forms with masses placed on top of soil in an urban scale and studying the resulting effect that the forms have on the propagating waves. The tool uses the finite element method and studies the vibration reduction effects in the frequency domain. Paper A presents the tool and draws some conclusions related to the levels of vibration reduction for various patterns, showing that some patterns are effective in mitigating the incoming vibrations. The approach in the tool makes it possible to obtain results in minutes, allowing the user to generate many alternative proposals quickly, and act as an aid in brainstorming sessions.Papers B and C focus on a recent extension of the finite element method, called isogeometric analysis. The implementation of isogeometric analysis with membrane elements for form finding of efficient shapes for shells is presented. The dynamic relaxation method is used for finding the static solutions. The method is employed directly on design geometry, which is described by non-uniform rational b-splines (NURBS), without the need for any further discretization. Paper B investigates various selections of mass and damping for the dynamic relaxation method with NURBS based membrane elements. The results are used to implement two plug-ins for the computer aided design applications Rhinoceros 3D and Grasshopper 3D, of which the former is presented in paper C. The method describes form found geometries well with very few elements and can be used to explore different efficient shapes for shells very rapidly and directly in design software, and is thus suited for design explorations.
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