Este estudio ha tenido como objetivo principal la comprensión del proceso de aprendizaje de las ciencias experimentales en la educación infantil con niños de 5-6 años de edad. El proceso de aprendizaje se ha estudiado considerando las teorías del cambio conceptual y la construcción de modelos científicos precursores (MCP) en un contexto dialógico de instrucción. Para tal efecto, el estudio abordó dos estudios de casos: el fenómeno de flotación y hundimiento de los cuerpos y la caracterización de seres vivos. El MCP de flotación se caracterizó considerando propiedades relevantes de los objetos relacionadas con la densidad (peso, tamaño, hueco o lleno). EL MCP de ser vivo se caracterizó en base a propiedades biológicas tales como utilización de energía (nutrición, movimiento, excresión, respiración), crecimiento y desarrollo, y reproducción. Los estudios exploratorios se llevaron a cabo con un grupo de 25 niños en tres fases: pre-test, proceso de instrucción y post-test. El cambio conceptual se evaluó considerando las diferencias entre los pre-tests y los post-test en base a los modelos de Chi et al. (1994) y Thagard (1992), y la perspectiva contextual de Printich et al., (1993).Por otra parte, se analizaron las interacciones verbales para caracterizar los tipos de conversaciones que tuvieron lugar entre los niños y la docente durante el proceso de instrucción, y su incidencia en la promoción del cambio conceptual. Los resultados mostraron que los niños presentaron diferentes patrones de cambio conceptual dando lugar a diferentes patrones de aprendizaje y éstos, a su vez, a la construcción de los modelos científicos precursores de flotación y ser vivo propuestos. En el caso de flotación los cambios fueron principalmente epistemológicos en los cuales la mayoría de los niños enriquecieron su comprensión del fenómeno permitiéndoles construir el modelo precursor formulado. En el caso de seres vivos los cambios fueron epistemológicos y ontológicos con un enriquecimiento y una reestructuración de su comprensión, y de esta forma, también la mayoría de ellos construyeron el modelo precursor de ser vivo. Por otra parte, las interacciones verbales entre la docente y los niños mostraron evidencia de los diversos recursos que utilizaron los niños para enriquecer y reestructurar su conocimiento y que la mediación de la docente fue fundamental en este proceso. La perspectiva didáctica basada en la visión socioconstructivista del aprendizaje, la valoración del aprendizaje como cambio conceptual y la estrategia de instrucción basada en la modelización, mostró ser adecuada para comprender los procesos de aprendizaje en el aula. / This study had as main objective the understanding of experimental science learning in early childhood education with children aged 5-6 years old. The learning process has been studied considering the theories of conceptual change and the construction of scientific models precursors (MCPs) in a dialogic instruction. To that end, the study dealt with two case studies: the phenomenon of floating and sinking and the characterization of living things. MCP flotation considered relevant properties of objects related to the density (weight, size, hollow or full), and the MCP of living was based on biological properties such as utilization of energy (nutrition, movement, excretion, respiration), growth and development, and reproduction. Exploratory studies were conducted with a group of 25 children in three phases: pre-test, instructional process and post-test. Conceptual change was evaluated considering the differences between the pre-tests and post-test based on the model Chi et al. (1994) and Thagard (1992), and the contextual perspective of Printich et al. (1993). Moreover, verbal interactions were analyzed to characterize the types of conversations that occurred among children and teacher during the instructional process, and its impact on the promotion of conceptual change.Results showed that children had different patterns of conceptual change leading to different patterns of learning and, in turn, the construction of the scientific precursor models proposed. In the case of flotation, changes were mostly epistemological in which the majority of children enriched their understanding of the phenomenon by allowing the construction of the precursor model formulated. In the case of living things changes were epistemological and ontological leading children enrich and restructure their understanding, and so most of them also built the forerunner model of living thing. Moreover, the verbal interactions between teachers and children showed evidence of various resources used by children to enhance and restructure their knowledge and that the mediation of the teacher was crucial in this process. The educational perspective based on the socio-constructivist perspective, assessment of learning as conceptual change and strategy-based instruction in modelling, showed to be adequate for understanding the processes of learning in the classroom.

Les experiències prèvies en l'àmbit dels magatzems de dades (o data warehouse), mostren que l'esquema multidimensional del data warehouse ha de ser fruit d'un enfocament híbrid; això és, una proposta que consideri tant els requeriments d'usuari com les fonts de dades durant el procés de disseny.Com a qualsevol altre sistema, els requeriments són necessaris per garantir que el sistema desenvolupat satisfà les necessitats de l'usuari. A més, essent aquest un procés de reenginyeria, les fonts de dades s'han de tenir en compte per: (i) garantir que el magatzem de dades resultant pot ésser poblat amb dades de l'organització, i, a més, (ii) descobrir capacitats d'anàlisis no evidents o no conegudes per l'usuari.Actualment, a la literatura s'han presentat diversos mètodes per donar suport al procés de modelatge del magatzem de dades. No obstant això, les propostes basades en un anàlisi dels requeriments assumeixen que aquestos són exhaustius, i no consideren que pot haver-hi informació rellevant amagada a les fonts de dades. Contràriament, les propostes basades en un anàlisi exhaustiu de les fonts de dades maximitzen aquest enfocament, i proposen tot el coneixement multidimensional que es pot derivar des de les fonts de dades i, conseqüentment, generen massa resultats. En aquest escenari, l'automatització del disseny del magatzem de dades és essencial per evitar que tot el pes de la tasca recaigui en el dissenyador (d'aquesta forma, no hem de confiar únicament en la seva habilitat i coneixement per aplicar el mètode de disseny elegit). A més, l'automatització de la tasca allibera al dissenyador del sempre complex i costós anàlisi de les fonts de dades (que pot arribar a ser inviable per grans fonts de dades).Avui dia, els mètodes automatitzables analitzen en detall les fonts de dades i passen per alt els requeriments. En canvi, els mètodes basats en l'anàlisi dels requeriments no consideren l'automatització del procés, ja que treballen amb requeriments expressats en llenguatges d'alt nivell que un ordenador no pot manegar. Aquesta mateixa situació es dona en els mètodes híbrids actual, que proposen un enfocament seqüencial, on l'anàlisi de les dades es complementa amb l'anàlisi dels requeriments, ja que totes dues tasques pateixen els mateixos problemes que els enfocament purs.En aquesta tesi proposem dos mètodes per donar suport a la tasca de modelatge del magatzem de dades: MDBE (Multidimensional Design Based on Examples) and AMDO (Automating the Multidimensional Design from Ontologies). Totes dues consideren els requeriments i les fonts de dades per portar a terme la tasca de modelatge i a més, van ser pensades per superar les limitacions dels enfocaments actuals.1. MDBE segueix un enfocament clàssic, en el que els requeriments d'usuari són coneguts d'avantmà. Aquest mètode es beneficia del coneixement capturat a les fonts de dades, però guia el procés des dels requeriments i, conseqüentment, és capaç de treballar sobre fonts de dades semànticament pobres. És a dir, explotant el fet que amb uns requeriments de qualitat, podem superar els inconvenients de disposar de fonts de dades que no capturen apropiadament el nostre domini de treball.2. A diferència d'MDBE, AMDO assumeix un escenari on es disposa de fonts de dades semànticament riques. Per aquest motiu, dirigeix el procés de modelatge des de les fonts de dades, i empra els requeriments per donar forma i adaptar els resultats generats a les necessitats de l'usuari. En aquest context, a diferència de l'anterior, unes fonts de dades semànticament riques esmorteeixen el fet de no tenir clars els requeriments d'usuari d'avantmà.Cal notar que els nostres mètodes estableixen un marc de treball combinat que es pot emprar per decidir, donat un escenari concret, quin enfocament és més adient. Per exemple, no es pot seguir el mateix enfocament en un escenari on els requeriments són ben coneguts d'avantmà i en un escenari on aquestos encara no estan clars (un cas recorrent d'aquesta situació és quan l'usuari no té clares les capacitats d'anàlisi del seu propi sistema). De fet, disposar d'uns bons requeriments d'avantmà esmorteeix la necessitat de disposar de fonts de dades semànticament riques, mentre que a l'inversa, si disposem de fonts de dades que capturen adequadament el nostre domini de treball, els requeriments no són necessaris d'avantmà. Per aquests motius, en aquesta tesi aportem un marc de treball combinat que cobreix tots els possibles escenaris que podem trobar durant la tasca de modelatge del magatzem de dades. / Previous experiences in the data warehouse field have shown that the data warehouse multidimensional conceptual schema must be derived from a hybrid approach: i.e., by considering both the end-user requirements and the data sources, as first-class citizens. Like in any other system, requirements guarantee that the system devised meets the end-user necessities. In addition, since the data warehouse design task is a reengineering process, it must consider the underlying data sources of the organization: (i) to guarantee that the data warehouse must be populated from data available within the organization, and (ii) to allow the end-user discover unknown additional analysis capabilities.Currently, several methods for supporting the data warehouse modeling task have been provided. However, they suffer from some significant drawbacks. In short, requirement-driven approaches assume that requirements are exhaustive (and therefore, do not consider the data sources to contain alternative interesting evidences of analysis), whereas data-driven approaches (i.e., those leading the design task from a thorough analysis of the data sources) rely on discovering as much multidimensional knowledge as possible from the data sources. As a consequence, data-driven approaches generate too many results, which mislead the user. Furthermore, the design task automation is essential in this scenario, as it removes the dependency on an expert's ability to properly apply the method chosen, and the need to analyze the data sources, which is a tedious and timeconsuming task (which can be unfeasible when working with large databases). In this sense, current automatable methods follow a data-driven approach, whereas current requirement-driven approaches overlook the process automation, since they tend to work with requirements at a high level of abstraction. Indeed, this scenario is repeated regarding data-driven and requirement-driven stages within current hybrid approaches, which suffer from the same drawbacks than pure data-driven or requirement-driven approaches.In this thesis we introduce two different approaches for automating the multidimensional design of the data warehouse: MDBE (Multidimensional Design Based on Examples) and AMDO (Automating the Multidimensional Design from Ontologies). Both approaches were devised to overcome the limitations from which current approaches suffer. Importantly, our approaches consider opposite initial assumptions, but both consider the end-user requirements and the data sources as first-class citizens.1. MDBE follows a classical approach, in which the end-user requirements are well-known beforehand. This approach benefits from the knowledge captured in the data sources, but guides the design task according to requirements and consequently, it is able to work and handle semantically poorer data sources. In other words, providing high-quality end-user requirements, we can guide the process from the knowledge they contain, and overcome the fact of disposing of bad quality (from a semantical point of view) data sources.2. AMDO, as counterpart, assumes a scenario in which the data sources available are semantically richer. Thus, the approach proposed is guided by a thorough analysis of the data sources, which is properly adapted to shape the output result according to the end-user requirements. In this context, disposing of high-quality data sources, we can overcome the fact of lacking of expressive end-user requirements.Importantly, our methods establish a combined and comprehensive framework that can be used to decide, according to the inputs provided in each scenario, which is the best approach to follow. For example, we cannot follow the same approach in a scenario where the end-user requirements are clear and well-known, and in a scenario in which the end-user requirements are not evident or cannot be easily elicited (e.g., this may happen when the users are not aware of the analysis capabilities of their own sources). Interestingly, the need to dispose of requirements beforehand is smoothed by the fact of having semantically rich data sources. In lack of that, requirements gain relevance to extract the multidimensional knowledge from the sources.So that, we claim to provide two approaches whose combination turns up to be exhaustive with regard to the scenarios discussed in the literature

The present thesis is aimed at analyzing the concept of quality and at dis-cussing, in a unified manner, its role not only in operations management but also in strategic thinking. It criticizes the widespread view that quality is meeting the client’s needs and expectations in such a way that the gap between perceptions and expectations is minimized. Essentially it develops a systematic proposal in order to understand the concept on the intui-tive basis that quality is tantamount to how well something works for a given purpose. The analysis is based on the fact that anytime that the quality concept is used there are actors that carry out an action with the help of a means—thus quality is a particular sort of means-ends fitness. Roughly speaking, the quality of a means is its capability to improve the expected conse-quences of the action. The analysis shows under which conditions this conclusion can be understood in terms of multi-attribute preference orderings under uncertainty—some ideas from decision theory, which are required in order to do that, are presented. In short, whether the expected consequences improve or not depends on an assumed preference ordering that has to be correct given the actors’ circumstances and purposes—but it may be distinct from the actual preferences of many individual actors. Quality is neither subjective (it does not change depending on the psychological processes of any particular individual) nor objective (in a sense, it depends on action and cognition), but it is relative to a given set of reference preferences. Some conditions apply to what it counts as a means, how it relates to an end, which attributes are relevant to assess consequences, or which reference preferences are well-formed. In particular, I discuss to which kind of means the concept is properly applied. As a complement, a basic model of means-ends relationships (built on several properties of Boolean functions) is presented. At a slightly more technical level, it shows relevant insights, but strictly speaking it is not required in order to understand the rest of the thesis. Quality appears in management under two interrelated forms: (a) or-ganizations’ interventions in the quality of what they use and provide and (b) organizations’ initiatives to compete through quality. (a) The basic structure behind quality management is examined under the lens of the quality concept’s analysis. The following issues are dis-cussed: setting quality criteria, product design, process design, onsite planning, onsite control, standardization, product improvement, process improvement and rethinking reference preferences. (b) The role of quality on competitive advantage and sustainable profit-ability depends on how quality relates to entry barriers. I show different ways in which quality can interact (if it does) with product differentiation, experience effects, scope economies, reputation, capital requirements, access to distribution channels, switching costs, legal barriers or scale economies. The strength of quality as a driver of profitability is dis-cussed—the conclusion is that it is not easy to build sustainable competitive advantages on the basis of quality alone and that its complementary role in competition has several aspects that are needed to be taken into account. Finally, the particular example of how the quality concept works in re-lation to information flows is treated in some detail. Information flows are processes that move information from the firm’s inner or outer environ-ment to actions. Decisive factors of its quality (basically, information asymmetries and coherence) are discussed. Two actual case studies are presented. The example of information flows is aimed at showing the mo-tivation for a general analysis of the quality concept beyond sloganlike statements about clients, products, perceptions and expectations. / La tesis tiene como objetivo analizar el concepto de calidad y discutir de forma unificada su papel tanto en la dirección de operaciones como en el pensamiento estratégico. El trabajo argumenta en contra de la opinión generalizada de que la calidad es satisfacer las necesidades y expectativas del cliente de tal manera que la diferencia entre percepciones y expectativas se reduzca. Se desarrolla una propuesta sistemática con el fin de entender el concepto sobre la base intuitiva de que la calidad se relaciona con lo bien que funcionan las cosas para un fin determinado. El análisis se basa en el hecho de que cualquier uso del concepto de calidad supone que hay actores que realizan una acción con la ayuda de un medio. En consecuencia, la calidad es un tipo particular de relación entre medios y fines. En términos generales, la calidad de un medio es su capacidad para mejorar las consecuencias esperadas de la acción. El análisis muestra cómo ésta conclusión puede entenderse en términos de preferencias multiatributo bajo condiciones de incertidumbre. Que las consecuencias sean mejores o no depende de suponer una relación de preferencias que debe ser correcta dados los propósitos y circunstancias de los actores, pero que puede ser distinta de las preferencias reales de muchos actores individuales. La calidad no es subjetiva (no cambia en función de los procesos psicológicos de un individuo en particular) ni objetiva (en cierto sentido, depende de la acción y la cognición), sino que es relativa a ciertas preferencias de referencia. En la tesis se estudia qué se considera un medio, cómo se relaciona con un fin, qué atributos son relevantes, cuándo las preferencias de referencia están bien formadas, y a qué tipo de medios tiene sentido aplicar el concepto. Como complemento, se presenta un modelo simple (construido a partir de propiedades de las funciones booleanas) sobre relaciones medios-fines. El concepto de calidad aparece en la gestión bajo dos formas interrelacionadas: (a) las actividades de las organizaciones para intervenir en la calidad de lo que utilizan y proporcionan, y (b) las iniciativas para competir a través de la calidad. (a) Las actividades básicas de la gestión de la calidad se examinan bajo la perspectiva del análisis del concepto: definición de criterios de calidad, diseño de productos, diseño de procesos, planificación operativa, control, estandarización, mejora del producto, mejora de procesos, y redefinición de las preferencias de referencia. (b) El papel de la calidad en la rentabilidad y la ventaja competitiva sostenibles depende de cómo la calidad se relaciona con las barreras de entrada. El trabajo trata diferentes formas en que la calidad puede interactuar con la diferenciación del producto, los efectos de aprendizaje, las economías de alcance, la reputación, los requisitos de capital, el acceso a canales de distribución, los efectos red, las barreras legales o las economías de escala. Se argumenta que no es fácil de construir ventajas competitivas sostenibles solamente sobre la base de la calidad; su papel complementario en otras estrategias competitivas tiene varios aspectos a considerar. Por último, se trata el ejemplo concreto de la calidad de los flujos de información (procesos que mueven información desde el entorno hasta las decisiones para modificarlo). Se estudian, y se ilustran mediante dos casos reales, los factores decisivos de su calidad: la coherencia y las asimetrías en la información. El ejemplo de la información tiene por objetivo mostrar la necesidad de un análisis del concepto de calidad más allá de exhortaciones sobre clientes, productos, percepciones y expectativas. / L’objectiu de la tesi és analitzar el concepte de qualitat i discutir de forma unificada el seu paper tant en la direcció d'operacions com en el pensament estratègic. El treball argumenta en contra de l'opinió generalitzada de que la qualitat consisteix en satisfer les necessitats i expectatives del client de manera que la diferència entre percepcions i expectatives es redueixi. Es desenvolupa una proposta sistemàtica per tal d'entendre el concepte sobre la base intuïtiva de que la qualitat es relaciona amb com de bé funcionen les coses per una finalitat determinada. L'anàlisi es basa en el fet que qualsevol ús del concepte de qualitat suposa que hi ha actors que realitzen una acció amb l'ajuda d'un mitjà. En conseqüència, la qualitat és un tipus particular de relació entre mitjans i fins. En termes generals, la qualitat d'un mitjà és la seva capacitat per millorar les conseqüències esperades de l'acció. L'anàlisi mostra com aquesta conclusió es pot entendre en termes de preferències multiatribut sota condicions d'incertesa. Que les conseqüències siguin millors o no depèn de suposar una relació de preferències que ha de ser correcta donats els propòsits i circumstàncies dels actors, però que pot ser diferent de les preferències reals de molts actors individuals. La qualitat no és subjectiva (no canvia en funció dels processos psicològics d'un individu en particular) ni objectiva (en certa manera, depèn de l'acció i la cognició), sinó que és relativa a certes preferències de referència. En la tesi s'estudia què es considera un mitjà, com es relaciona amb un fi, quins atributs són rellevants, quan les preferències de referència estan ben formades, i a quin tipus de mitjans té sentit aplicar el concepte. Com a complement, es presenta un model simple (construït a partir de propietats de les funcions booleanes) sobre les relacions entre mitjans i fins. El concepte de qualitat apareix en la gestió sota dues formes interrelacionades: (a) les activitats de les organitzacions per intervenir en la qualitat d’allò que fan servir i proporcionen, i (b) les iniciatives per competir a través de la qualitat. (a) Les activitats bàsiques de la gestió de la qualitat s'examinen sota la perspectiva de l'anàlisi del concepte: definició de criteris de qualitat, disseny de productes, disseny de processos, planificació operativa, control, estandardització, millora del producte, millora de processos , i redefinició de les preferències de referència. (b) El paper de la qualitat en la rendibilitat i l'avantatge competitiu sostenibles depèn de com la qualitat es relaciona amb les barreres d'entrada. El treball tracta diferents formes en les que la qualitat pot interactuar amb la diferenciació del producte, els efectes d'aprenentatge, les economies d'abast, la reputació, els requisits de capital, l'accés a canals de distribució, els efectes xarxa, les barreres legals o les economies d'escala. S'argumenta que no és fàcil construir avantatges competitius sostenibles només sobre la base de la qualitat; el seu paper complementari en altres estratègies competitives té diversos aspectes a considerar. Finalment, es tracta l'exemple concret de la qualitat dels fluxos d'informació (processos que mouen informació des de l'entorn fins a les decisions per modificar). S'estudien, i s'il•lustren mitjançant dos casos reals, els factors decisius de la seva qualitat: la coherència i les asimetries en la informació. L'exemple de la informació té per objectiu mostrar la necessitat d'una anàlisi del concepte de qualitat més enllà d’exhortacions sobre clients, productes, percepcions i expectatives.

While naturalistic theories have come to dominate the philosophical landscape, there is still little consensus on what “naturalism” means. I trace the origins of contemporary naturalism to a view, called the “fundamental naturalistic impulse,” that originates in Quine’s turn against Carnap and which I take to be necessary for naturalism. In light of this impulse, some “substantively naturalistic” theories are examined: a weak version of non-supernaturalism, Railton’s a posteriori reduction of moral terms, and “Canberra plan” conceptual analyses of moral property terms. I suggest that if we take the fundamental naturalistic impulse seriously, then there is no need to differentiate substantive versions of naturalism over and above methodological versions. Substantive thesis in ontology or semantics can be had on account of one’s methodological commitments. This not only cuts against the distinction between methodological and substantive naturalisms, but also demonstrates just how far method can reach.

This is a thesis which contributes to research in two different fields: theoretical physics and physics education research. The common link between these two research areas is that both involve explorations of abstract physics and mathematical representations, but from different perspectives. The first part of this thesis is situated in theoretical physics. Here a cosmological scenario is explored where a de Sitter phase is replaced with a phase described with a scale factor a(t) ~ tq, where 1/3<1. This scenario could be viewed as an inflationary toy model, and is shown to open up the possibility of an information paradox. This potential paradox is resolved even in the worst case scenario by showing that the time scales involved for such a paradox to occur is of the order of magnitude of the recurrence time for the de Sitter space. The second part of this thesis is situated in physics education research. A number of learning situations that are experienced as abstract by students are explored: probability in one dimensional quantum tunnelling; the mindsets that students adopt towards understanding physics equations used in typical teaching scenarios; and what students focus on when presented with physics equations. The results for the quantum scattering study are four phenomenographic categories of description, for the mind sets study, six epistemological components of mindsets and for the focus on physics equations study, three foci creating five levels of increasing complexity of ways of experiencing physics equations.  Pedagogical implications of these results are discussed.

This thesis deals with the development of a Conceptual Design Tool for unmanned helicopters, so called VTOL UAVs. The goal of the Design Tool is: • Quick results • Good accuracy • Easy to use The two first points of the goal are actually more or less dependent on each other. In almost all cases a high accuracy gives a slow calculator and vice versa. In order to fulfill the goal a compromise between calculation accuracy and calculation time needs to be done. To make the Design Tool an easy to use program a graphical user interface is used. The graphical user interface allows the user to systematically work his way thru the program from a fictive mission to a complete design of a helicopter. The pre-requirements on the user have been eliminated to a minimum, but for the advanced user the possibilities to create more specific and complex helicopters are good. In order to develop a Conceptual Design Tool the entire helicopter needs to be seen as a complete system. To see the helicopter as a system all of the sub parts of a helicopter need to be studied. The sub parts will be compared against each other and some will be higher prioritized than other. The outline of this thesis is that it is possible to make a user friendly Conceptual Design Tool for VTOL UAVs. The design procedure in the Design Tool is relatively simple and the time from start to a complete concept is relatively short. It will also be shown that the calculation results have a good agreement with real world flight test data.

A conceptual design of a miniature vegetation cutter for use in minefields in southern Lebanon has been developed and the authors have evaluated its mechanical properties focusing on the stress in welded joints using the CAD software Pro/Engineer Wildfire 4.0. The conceptual design has been developed in the field in close cooperation with field staff from MAG Lebanon. The requirements from the field specify that the cutter should have a cutting range of 80 cm, be equipped with adjustable covers, weigh less than 200 kg, be fitted to a commercial hydraulic excavator, and have the ability to cut vegetation, bushes and small trees including (olive) trees with a diameter up to 10 cm. The miniature cutter is to be manufactured in the field and fitted to a commercial hydraulic ex­cava­tor (Caterpillar 301.6C). It consists of a rotor on which eight cutting blades, alternatively chains, are attached in a helix formation. The cutter is protected by adjustable covers. When in operation, the rotor spins at 750 revolutions per minute whereby the blades cut through the shrubs and bushes in the cutter’s path. The blades are mounted in a T-shape on arms, which are fastened to the rotor by a pin joint between two brackets (each) on the rotor. Blades and arms are to be welded together, as are the brackets to the rotor. These welded joints are the primary focus of the report. 3D CAD models have been created and analysed in PTC Pro/Engineer Wildfire 4.0 to ascertain that the stress in the joints will not exceed the yield strength of the weld consumables, which should be 500 MPa. Ideally, the stress in the joints would be half the yield strength. Type of bearings and a hydraulic motor have been selected for the cutter. Based on the specifica­tions of the hydraulic motor an approximation of the forces acting on the weld joints in the case of an accidental stop (e.g. collision with a rock) has been calculated, and entered into the CAD software. Also, an approximation of the size (diameter) of branches the cutter would be able to tear apart in the case of branches getting stuck has been calculated and shown to be about 14.6 mm. Based on this, it is estimated that the cutter should be used only in areas where the shrubbery is of 20-30 mm in diameter, maximum. Considering this, and the relative light weight of the cutter, it is not likely that the cutter will be able to cut through the larger olive trees as requested, but it is considered that the tool still could be a valuable asset for mine clearing in Lebanon. In order to cut through thicker trees, it would be necessary to increase the power supply to the cutting system as well as the sturdiness of the cutting parts. Finding the required power and technical solutions for this demands further research which does not fit within the time frame for this report. A preliminary weight approximation shows that the cutter will weigh roughly 170 kg, which falls below the limit of 200 kg and leaving some room for the bearings to be added. The results from the stress analyses show that the stress in the welded joints falls well below the yield limit of 500 MPa, but not below 250 MPa. Still, the stress in all the welded joints is shown to be less than 300 MPa or at 40 % of the limit, which may still be acceptable. The end user will have to decide whether this is an acceptable safety margin before manufacturing the cutter and if it is not, measures will need to be taken to reinforce the weld joints and try to minimise the stress concentration in them.

Identifying the detrimental effect of environmental factors and subsystem interactions are one of themost challenging aspects of early hazard assessment in the design of complex safety critical systems.Therefore, a complete understanding of potential failure effects before the catastrophe happens is a verydifficult task. The thesis proposes a model-based hazard analysis procedure for early identification ofpotential safety issues caused by unexpected environmental factors and subsystem interactions within acomplex safety critical system. The proposed methodology maps hazard and vulnerability modes tospecific components in the system and analyzes the hazard propagation paths for risk control andprotection strategies. The main advantage of the proposed method is the ability to provide the designerswith means to use low-fidelity, high level models to identify hazardous interactions. Using thistechnique, designers can examine the collective impacts of environmental and subsystem risks onoverall system during early stages of design and develop a hazard mitigation strategy.

One of the largest product categories within all the electronic products is portable ­computers, also known as notebooks, is slowly replacing stationary computers and is ­predicted to be the mainstream choice in the near future. But the current state of ­notebook shows these products are not accommodated for an effective large scale ­recycling process. As the notebooks are becoming more compact, its inner ­structures have become more complicated. Permanently fastening methods, multi-material ­compositions and many other factors contribute to an ineffective, expensive and tedious recycling process. The goal of the project treated in this report was to investigate the possibilities of a simplified structure adapted for an effective disassembly and recycling process. And to develop a conceptual notebook adapted for the stated purpose. The project resulted in a conceptual notebook named Sixten with an enhanced and ­simplified inner structure. All permanently fastening methods was replaced by ­detachable locking and securing devices. The number of tools required for dismantling was reduced, as the usage of screws. The variation of materials used in the notebook, with ­electrical components apart, is low. These materials, ABS plastics and aluminum were chosen based on their recyclable and processing possibilities. But also because of the durability and desired mechanical properties the structure required. The limited number of materials used in Sixten makes it environmentally beneficial since every material ­requires its own specific recycling process, and by reducing the number of materials energy can be saved on using only a few recycling methods. Sixten fulfills the principals of design for disassembly as a notebook that is easy to ­disassemble in comparison with notebooks on the market today. The disassembly time has been reduced, from the 45 minutes which may be required to fully disassemble a conventional notebook, down to an estimated disassembly time of 6 minutes, which is the time Sixten requires. It is in this short disassembly time where the economic benefits of Sixten lie.

Tidigare forskning visar att bråk är ett område där många elever har problem. Syftet med den här studien är att studera gymnasieelevers matematiska kunskaper i multiplikation och division av bråk. Elevernas kunskaper studerades utifrån en konstruktivistisk syn på kunskap och med procedurell och konceptuell kunskap som analysverktyg. 61 elever från kursen Matematik A har löst totalt 10 uppgifter med multiplikation och division av bråk. 7 av eleverna intervjuades dessutom för att få en bättre uppfattning om deras kunskaper. Elevernas kunskaper kategoriserades sedan utifrån procedurella- och konceptuella kvaliteter. Resultatet visar att eleverna främst använder algoritmer för att lösa uppgifterna men även andra strategier som till exempel att skriva bråken som decimaler förekommer. Elevernas kunskap i multiplikation och division av bråk är av procedurell karaktär med fokus på att komma ihåg algoritmer för att lösa uppgifterna. Elevernas konceptuella kunskaper i bråkräkning är överlag inte lika utvecklade. Det framkommer genom att eleverna visar på svårigheter att lösa uppgifter i vissa sammanhang, bristande förståelse för betydelsen av beräkningarna och för varför de olika algoritmerna fungerar. / Earlier researches show that fraction is an area where many students have problems. The aim with this essay is to study upper secondary school students’ mathematical knowledge in multiplication and division of fraction. The students’ knowledge will be studied from a constructivistic perspective of knowledge and with procedural and conceptual knowledge as an instrument for the analysis. 61 students from the course Matematik A have solved totally 10 mathematical problems with multiplication and division of fraction. 7 of the students were furthermore interviewed to get a better understanding of their knowledge. The students’ knowledge were then categorized from procedurally and conceptually qualities. The result shows that the students primarily use algorithms to solve the problems but also other strategies as example to write the fraction as decimals occur. The students’ knowledge in multiplication and division of fraction is of procedural character with focus on remembering the algorithms for the different types of problems. The students conceptually knowledge in fraction arithmetic is overall not fully developed. It comes out by the students difficulties to solve problems in certain context, deficient understanding of the meaning of the calculations and why the different algorithms work.