Multilevel inverters offer many well-known advantages for use in high-voltage and high-power applications, but they are also well suited for low-power applications. A single phase inverter is developed in this paper to deliver power from a residential-scale system of Photovoltaic panels to the utility grid. The single-stage inverter implements a novel control technique for the reversing voltage topology to produce a stepped output waveform. This approach increases the granularity of control over the PV systems, modularizing key components of the inverter and allowing the inverter to extract the maximum power from the systems. The adaptive controller minimizes harmonic distortion in its output and controls the level of reactive power injected to the grid. A computer model of the controller is designed and tested in the MATLAB program Simulink to assess the performance of the controller. To validate the results, the performance of the proposed inverter is compared to that of a comparable voltage-sourced inverter.

This bachelor thesis was composed by the initiative of a large aluminium profile producer in southern Sweden. Together, the authors and the company analyzed and mapped the current production flow of a selected item. The lead time and total output for a selected article was determined in order to examine the possibility of reducing the amount of tied up capital and related costs. Findings showed that reducing tied up capital and associated costs could be done through adjustment of production layout, production efficiency as well as alterations of produced quantities. By combining these three proposals for improvement, an overall recommendation for future course of action for the company was composed. / Bakgrund: Det problem som utgör grunden för uppsatsen är förankrat i ProfilGruppens osäkerhet gällande vart i en artikels flödesväg kapitalbindning uppstår. Flödesvägar anses kunna ha onödiga delprocesser, samtidigt som använd lager- samt produktionskvantitet inte är teoretiskt förankrad. Potentiellt skulle kapitalbindning och kapitalkostnad kunna reduceras genom analys av dessa aspekter.   Syfte: Uppsatsens syfte är att utreda förbättringsmöjligheter i termer av reducerad kapitalbindning och kapitalkostnad inom en typartikels flödesväg.   Metod: Studien följer en kombination av de kvalitativa och kvantitativa forskningsstrategierna. Arbetet präglas av ett positivistiskt synsätt, eftersom målet är att nå en kvantitativ reduktion av företagets kostnader. Samtidigt är uppsatsen en fallstudie, en design tätt kopplad till kvalitativ forskning. Studien utmärks av ett ständig förhållande till teoretisk relevans, i syfte att kunna applicera genomförd analys på andra företag försatta i liknande situation.    Slutsats: Forskningens resultat visar att tre av de fyra analyserade förbättringsförslagen är av intresse att implementera i företagets verksamhet. Genom att kombinera samtliga förslag till en sammanställd rekommendation presenteras en övergripande framtida handlingsplan för ProfilGruppen att vidta.

A single-phase grid connected transformerless photovoltaic (PV) inverter for residential application is presented. The inverter is derived from a boost cascaded with buck converter along with a line frequency unfolding circuit. Due to its novel operating modes, high efficiency can be achieved because there is only one switch operating at high frequency at a time, and the converter allows the use of power MOSFET and ultra-fast reverse recovery diode. This dissertation begins with theoretical analysis and modeling of this boost-buck converter based inverter. And the model indicates small boost inductance will leads to increase the resonant pole frequency and decrease the peak of Q, which help the system be controlled easier and more stable. Thus, interleaved multiple phases structure is proposed to have small equivalent inductance, meanwhile the ripple can be decreased, and the inductor size can be reduced as well. A two-phase interleaved inverter is then designed accordingly. The double-carrier modulation method is proposed based on the inverter's operation mode. The duty cycle for buck switch is always one if the inverter is running in boost mode. And the duty cycle for boost switches are always zero if the inverter is running in buck mode. Because of this, the carrier for boost mode is stacked on the top of the carrier for buck mode, as a result, there is no need to compare the input and output voltage to decide which mode the inverter should operate in. And the inverter operates smoothly between these two modes. Based on similar concept, three advanced modulation methods are proposed. One of them can help further improve the efficiency, and one of them can help increase the bandwidth and gain, and the last one takes the advantage of both. Based on similar concept, another three dual-mode double-carrier based SPWM inverters are proposed. With both step-up and step-down functions, this type of inverter can achieve high efficiency in a wide range because only one switch operates at the PWM frequency at a time. Finally, the simulation and experiment results are shown to verify the concept and the tested CEC (California Energy Commission) efficiency is 97.4%. It performs up to 2% more efficiently better than the conventional solution. / Ph. D.

The construction industry is moving towards an increasingly industrial production and one step towards this is to use prefabricated rebar cages. A new concept is being tested where tied rebar cages are produced on the construction site by industrial robots. The industrial robots produce the rebar cages based on a geometric model and when finished they are lifted to the casting site with the help of a crane. In order for this concept to become an efficient process, it must already be possible to evaluate the stability of the rebar cages in the early design phase to be able to efficiently determine whether it is possible to lift the rebar cages to the casting site after production. The scope of this thesis is to investigate what is required to create a numerical model with help of data from a geometric model in an efficient way in order to determine whether a rebar cage can be lifted. This thesis is limited to one specific rebar cage that has already been created in the CADprogram Tekla Structures by the contractor Skanska Sweden AB. The process of what is required when creating a numerical model with data from a geometric model is limited between the analysis software LUSAS Bridge and the CAD software Tekla Structures. To be able to determine what is required in order to create a numerical model with data from a geometric model in the analysis software LUSAS Bridge in an efficient way a survey was performed. The survey includes the necessary steps to create a numerical model of a tied rebar cage from a geometric model and the problems that occurs along the way to get an efficient process. In order to determine if the geometric model of the rebar cage is liftable a linear analysis was created in the analysis software LUSAS Bridge. The analysis was created with data from the geometric model created in Tekla Structures and with experimental results from a study where tied connection strength and stiffness were evaluated. The analysis was created to simulate a rebar cage for a bridge foundation in scale 1:2 that is lifted in four lifting points. The lifting points in this analysis is modeled as supports while the rebar cage is subjected to an acceleration force to simulate a lift. The analysis is performed in two parts, first when the tied connections have full stiffness capacity and the second part when the stiffness is decreased to be able to evaluate what happens to the stability of the rebar cage. In order to determine if the rebar cage is liftable two conditions are looked at, (1) stress in rebars and (2) forces in the joint elements. The results from the study show that in order to create a numerical model of a tied rebar cage in an efficient way some improvements must be done in the analysis software LUSAS Bridge. The most time-consuming process when creating a numerical model of a tied rebar cage are the connections. In order to create these tied connections in an efficient way some new functions must be created in LUSAS Bridge where the software can generate different types of tied connections. The results from the analysis show that the stress in the rebars at the lifting points is the criterion that is most critical when the rebar cage is lifted. The maximum stress reached 356 MPa with the utilization rate of 81,9% when the connection stiffness has full capacity. When the connection stiffness was adjusted, it was also shown here that the stress was the criterion that is most critical. The analysis for 50% connection stiffness capacity showed a maximum stress of 402 MPa with the utilization rate of 92,4%, this shows an increase of 10,5% of the utilization rate when the IV  connection stiffness is decreased with 50%. Based on these results, it can be stated that the rebar cage can be lifted if four lifting points are used. It can also be seen from the results that the stiffness in the connections has a very small impact on the behavior of the cage and therefore the placement of the rebars contributes more to the stability. / Byggindustrin går mot ett allt mer industriellt byggande och ett steg på vägen är att använda sig av prefabricerade armeringskorgar. Ett nytt koncept håller på att undersökas där man vill framställa najade armeringskorgar på byggarbetsplatsen med hjälp av industrirobotar. Industrirobotarna bygger armeringskorgarna utifrån en geometrisk modell för att sedan lyftas till gjutplatsen med hjälp av en kran. För att detta koncept ska bli en effektiv process måste man redan i projekteringsfasen kunna utvärdera armeringskorgarnas lyftbarhet för att kunna avgöra om det går att lyfta armeringskorgarna till gjutplatsen efter att de är färdigmonterade. Examensarbetets syfte är att undersöka vad som krävs för att ska skapa en numerisk modell med hjälp av data från en geometrisk modell på ett effektivt sätt för att sedan kunna avgöra om en armeringskorg går att lyfta. Denna studie är avgränsad till enbart en typ av armeringskorg som redan är skapad i CADprogrammet Tekla Structures av entreprenören Skanska Sverige AB. Processen som krävs för att skapa en numerisk modell med hjälp av en geometrisk modell är begränsad till analysprogrammet LUSAS Bridge och CAD-programmet Tekla Structures. För att kunna avgöra vad som krävs för att skapa en numerisk modell med hjälp av en geometrisk modell i analysprogrammet LUSAS Bridge utfördes en kartläggning. Kartläggningen omfattar de steg som krävs för att skapa en numerisk modell av en najad armeringskorg från en geometrisk modell och de svårigheter som finns längs vägen. För att kunna avgöra om den geometriska modellen av armeringskorgen är lyftbar skapades en linjär Finita Element Analys i analysprogrammet LUSAS Bridge. Analysen är skapad med hjälp av data från den geometriska modellen från Tekla Structures samt testresultat från en tidigare studie där man har provat hållfastheten och styvheten hos najade knutpunkter. Analysen är skapad för att efterlikna en armeringskorg till ett brofundament i skala 1:2 som lyfts i fyra punkter. Lyftpunkterna i denna analys är simulerade som stöd medan armeringskorgen utsätts för en accelerationskraft för att efterlikna ett lyft. Analysen utförs i två delar, en när de najade knutpunkterna har full styvhet och den andra när styvhet för knutpunkterna minskar. Detta för att se hur styvheten i knutpunkterna påverkar stabiliteten i armeringskorgen. Armeringskorgens lyftbarhet bedöms av två olika kriterier (1) spänning i armeringsjärnen och (2) krafter i knutpunkterna. Resultaten från studien visar att för att kunna skapa en numeriskmodell av en najad armeringskorg på ett effektivt sätt måste en del förbättringar göras i analysprogrammet LUSAS Bridge. Den process som är mest tidskrävande är när man skapar de najade knutpunkterna för armeringskorgen. För att det ska gå att genomföra detta på ett effektivt sätt måste en ny funktion skapas i LUSAS Bridge där programmet kan generera olika typer av knutpunkter automatiskt. Resultaten från analysen visade att spänningen av armeringsjärnen vid lyftpunkterna är det kriterium som är mest kritisk när armeringskorgen utsätts för lyft. Den maximala spänningen uppgick till 356 MPa med en utnyttjandegrad på 81,9% för armeringskorgen med full styvhet. När styvheten justerades visades det även här att spänningen är det kriterium som är mest kritiskt. Analysen för 50% styvhet visade en maximal spänning på 402 MPa med en utnyttjande grad på 92,4%, detta visar en ökning på 10,5% av utnyttjandegraden när styvheten halveras. VI  Utifrån dessa resultat kan man konstatera att armeringskorgen går att lyfta om man använder fyra lyftpunkter. Man kan även utifrån resultaten se att en minskning av styvheten i knutpunkterna har en liten påverkar på armeringskorgens lyftbarhet och istället är det placeringen av armeringsjärnen som har störst betydelse.

[ES] Hoy en día, la arquitectura moderna está orientada principalmente al empleo eficiente de materiales tecnológicos y sostenibles, la tecnificación del proceso de diseño, proyecto y construcción, y la búsqueda de soluciones muy ligeras. Estas ideas se reflejan en las estructuras flexo-activas, que recientemente han atraído considerable atención como nuevo paradigma para construir estructuras ligeras, tanto en el ámbito de la investigación como en la práctica. El término "flexión activa" hace referencia a una categoría de estructuras en las que la flexión se emplea en el proceso de configuración de su forma. Los sistemas estructurales flexo-activos incluyen barras o láminas incurvadas cuya geometría es el resultado de su deformación elástica desde una configuración inicial recta o plana. Hasta el momento, el número de realizaciones es limitado; se trata sobre todo de aplicaciones experimentales con funcionalidad arquitectónica o artística. La obtención de la configuración de equilibrio es una de las principales dificultades que aparecen en la fase de concepción, debido precisamente a la no linealidad de la respuesta estructural de las barras activas, así como a la posible interacción con otros elementos estructurales como membranas o cables, que trabajan por forma, y cuya geometría no se puede fijar de modo arbitrario. Los métodos computaciones de determinación de forma para estructuras flexo-activas incluyen modelos de elementos finitos con cables virtuales no lineales que se acortan hasta alcanzar la configuración final, o algoritmos de relajación dinámica que consideran las variables que caracterizan la deformación de las barras activas. Esta tesis doctoral tiene por objeto proporcionar un análisis en profundidad de la aplicabilidad del principio de flexión activa al diseño de estructuras ligeras, en particular a los puentes peatonales. Para ello, la investigación se aborda desde tres puntos de vista: a) modelización computacional; b) eficiencia estructural; c) diseño y construcción. En primer lugar, se lleva a cabo una revisión de la bibliografía existente, haciendo hincapié en los trabajos previos en el diseño de pasarelas con flexión activa. En el campo de la modelización computacional, se desarrolla un novedoso método numérico de determinación de forma para estructuras flexo-activas basado en el modelo geométricamente exacto para piezas alargadas (también conocido como la teoría de vigas de Reissner-Simó). Distintos ejemplos numéricos han sido reproducidos para mostrar la exactitud del método. La parte de la investigación relacionada con el análisis de la eficiencia estructural se centra en el comportamiento del sistema flexo-activo propuesto en esta tesis para el diseño de estructuras ligeras: el arco flexo-activo arriostrado (o atirantado). Se trata de un arco plano compuesto por una barra flexible y continuo que se activa por la acción de los cables principales que tiran de ambos extremos de la varilla, y de los puntales o cables secundarios que desvían el cable principal y actúan en ciertas secciones transversales. La parte computacional-analítica se completa con el desarrollo de un procedimiento numérico basado en algoritmos genéticos, con el fin de obtener configuraciones estructurales eficientes. La tesis finaliza con el diseño, fabricación y montaje de una pasarela flexo-activa hecha con tubos PRFV utilizando este tipo estructural, realizada en el laboratorio de modelos de la Universitat Politècnica de València. / [CA] Hui dia, l'arquitectura moderna està orientada principalment a l'ús eficient de materials tecnològics i sostenibles, la tecnificació del procés de disseny, projecte i construcció, i la cerca de solucions molt lleugeres. Aquestes idees es reflecteixen en les estructures flexo-actives, que recentment han atret considerable atenció com a nou paradigma per a construir estructures lleugeres, tant en l'àmbit de la investigació com en la pràctica. El terme "flexió activa" fa referència a una categoria d'estructures en les quals la flexió s'empra en el procés de configuració de la seua forma. Els sistemes estructurals flexo-actius inclouen barres o làmines incorbades, la geometria de les quals és el resultat de la seua deformació elàstica des d'una configuració inicial recta o plana. Fins al moment, el nombre de realitzacions és limitat; es tracta sobretot d'aplicacions experimentals amb funcionalitat arquitectònica o artística. L'obtenció de la configuració d'equilibri és una de les principals dificultats que apareixen en la fase de concepció, degut precisament a la no linealitat de la resposta estructural de les barres actives, així com a la possible interacció amb altres elements estructurals com a membranes o cables, que treballen per forma, i la geometria de la qual no es pot fixar de manera arbitrària. Els mètodes computacions de determinació de forma per a estructures flexo-actives inclouen models d'elements finits amb cables virtuals no lineals que s'escurcen fins a aconseguir la configuració final, o algorismes de relaxació dinàmica que consideren les variables que caracteritzen la deformació de les barres actives. Aquesta tesi doctoral té per objecte proporcionar una anàlisi en profunditat de l'aplicabilitat del principi de flexió activa al disseny d'estructures lleugeres, en particular als ponts per als vianants. Per a això, la investigació s'aborda des de tres punts de vista: a) modelització computacional; b) eficiència estructural; c) disseny i construcció. En primer lloc, es duu a terme una revisió de la bibliografia existent, amb recalcament en els treballs previs en el disseny de passarel·les amb flexió activa. En el camp de la modelització computacional, es desenvolupa un nou mètode numèric de determinació de forma per a estructures flexo-actives basat en el model geomètricament exacte per a peces allargades (també conegut com la teoria de bigues de Reissner-Simó). Diferents exemples numèrics han sigut reproduïts per a mostrar l'exactitud del mètode. La part de la investigació relacionada amb l'anàlisi de l'eficiència estructural se centra en el comportament del sistema flexo-actiu proposat en aquesta tesi doctoral per al disseny d'estructures lleugeres: l' arc flexo-actiu esbiaixat (o lligat). Es tracta d'un arc pla compost per un membre flexible i continu que s'activa per l'acció dels cables principals que tiren de tots dos extrems de la vareta, i dels puntals o cables secundaris que desvien el cable principal i actuen en certa secció transversal de la vareta. La part computacional-analítica es completa amb el desenvolupament d'un procediment numèric basat en algorismes de tipus genètic, amb la finalitat d'obtindre configuracions estructurals eficients. La tesi finalitza amb el disseny, fabricació i muntatge d'una passarel·la flexo-activa feta amb tubs PRFV utilitzant aquest tipus estructural, realitzada en el laboratori de models de la Universitat Politècnica de València. / [EN] Nowadays, modern architecture is focused on the search of efficient uses of technological and sustainable materials, high-tech concept-design-erection processes and the possibility to produce lightweight solutions with maximum elegance in shape. These ideas are reflected on bending-active structures, which recently attracted considerable attention as a new paradigm to build lightweight structures both in research and practice. The concept 'active bending' refers to a category of structures in which bending is used in the process of shape configuration. Bending-active structural systems include curved rods or shells which have been elastically bent from an initial straight or plane configuration. As of now, the number of realisations is limited; they are mostly experimental ones, with architectural or artistic nature. Form finding of the equilibrium configuration is one of the main difficulties during the conceptual phase, due to the non-linearity of the structural response of the active members, and also to the interaction with other form-active structural elements as membranes or cables, whose geometry cannot be prescribed in advance. Computational form-finding methods for bending-active structures include finite element models with non-linear virtual links that are shortened to reach the final form, or dynamic relaxation (explicit) algorithms to cope with the variables describing the response of the active members. This PhD thesis aims to provide an indepth analysis on the applicability of the active bending principle to the design of lightweight structures, in particular pedestrian bridges. For that purpose, the work is carried out from three points of view: (a) computational modelling and simulation; (b) structural performance and efficiency; (c) design and construction. First of all, a literature review on the topic and a overview of realisations in the fied of bending-active footbridges is provided. In the field of computational modelling, a novel form-finding method based on the geometrically exact rod model (or Reissner-Simo beam theory) is implemented. Numerical examples are also given to show the accuracy of the method. The part of the work related to the analysis of the structural performance and efficiency is focused on the bending-active configuration proposed in this PhD thesis for designing lightweight structures: the bending-active braced (or tied) arch. This is a simple planar arch composed of a continuous flexible member that is activated by the action of main cables pulling at both ends of the rod, and secondary struts or cables that deviate the main cable and act at certain cross-section of the rod. The computational-analytical part is completed with the development of a numerical procedure based on genetic algorithms to obtain efficient structural configurations. The thesis ends with the design, fabrication and assembling of a bending-active short footbridge made of GFRP tubes using this structural type, held in the laboratory of concept models of the Polytechnic University of Valencia. / The author has had the opportunity to join the research project: Sistemas estructuras flexo-activos- Concepción, desarrollo y análisis de nuevos prototipos (FLEXACT - grant BIA2105-69330- P) / Bessini Muñoz, JG. (2021). Form-finding and Performance of Bending-active Structures. Proposals of Application to Lightweight Braced Arches [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/165575

MScEng / Thesis (MScEng (Electrical and Electronic Engineering))--Univerity of Stellenbosch, 2009. / ENGLISH ABSTRACT: As the number of distributed generation units connected to a distribution network increase, the possibility of island formation increases. An island is formed when distributed generation units continue to energize local loads within a section of the grid, which has been disconnected from the main distribution network. These islands pose significant danger to maintenance personnel as well as to members of the public. In this study, an investigation is done into various anti-islanding methods. The modes of operation of these methods are discussed, as well as their strengths and weaknesses. The slip-mode frequency shift method and the Sandia voltage shift method, in combination with over/under voltage and frequency protection, are simulated and tested to confirm their functionality. The results obtained show that it is possible to prevent distributed generation units from energizing local loads when the grid is disconnected. / AFRIKAANSE OPSOMMING: Die moontlike toekomstige toename in die aantal verspreide generasie eenhede gekoppel aan die verspreidings netwerk, verhoog die moontlikheid van eiland vorming. ‘n Eiland word gevorm wanneer verspreide generasie eenhede energie aan lokale laste voorsien nadat die netwerk ontkoppel is. Dit hou groot gevaar in vir onderhouds personeel asook vir die publiek. In die tesis word ‘n studie gedoen oor die verskillende metodes om die vorming van ongewensde eilande te voorkom. Die glipmode-frekwensieskuif metode en die Sandia spanningskuif metode word gekombineer met die oor/onder spanning en frekwensie beskerming metodes. Die kombinasie van metodes word dan gesimuleer en eksperimenteel getoets. Die verkrygde resultate toon dat dit moontlik is om die vorming van ongewensde eilande effektief te voorkom.

Os galpões de concreto pré-moldado, formados por pórticos atirantados, são muito utilizados, no Brasil. Porém, para o projeto dessas estruturas, a bibliografia é limitada. Além disso, vários critérios de projeto são adaptados dos relativos a estruturas de concreto moldado no local e de múltiplos pavimentos. O objetivo deste trabalho é contribuir para a análise desse tipo de estrutura, introduzindo conceitos que dificilmente são considerados na prática, tais como: rigidez da ligação viga-pilar, análise não-linear física e geométrica, deformação excessiva e fluência. A pesquisa foi desenvolvida por meio de análises estruturais, usando modelos de galpões comuns na prática. Cada conceito citado anteriormente foi analisado em exemplos. A rigidez da ligação viga-pilar foi avaliada com base no parâmetro de restrição à rotação, \'alfa\'R. A não-linearidade física (NLF) do concreto foi considerada pelo método de Branson. Para a não-linearidade geométrica (NLG), foram utilizados os parâmetros \'alfa\' e o processo P.\'delta\'. A deformação excessiva, incluindo a fluência, foi discutida tendo em conta os aspectos normativos. Constatou-se que a ligação viga-pilar pode ter comportamento semi-rígido em alguns casos, mas, se corretamente dimensionada, apresenta, de fato, comportamento rígido. A consideração da NLF apresentou resultados melhores que a análise elástica linear, sendo possível, para o exemplo estudado, utilizar um coeficiente redutor de inércia igual a 0,5, para as vigas e para os pilares do pórtico. Concluiu-se, também, que a consideração da NLG deve ser feita sistematicamente para esse tipo de estrutura, uma vez que alguns exemplos apresentaram acréscimos de momentos superiores a 10% e \'alfa\' > \'alfa\' lim. Além disso, observou-se que a verificação do estado limite de deformação excessiva (ELS-DEF) pode ser determinante na escolha das seções transversais do pórtico, sendo obrigatória a consideração da fluência. Nesse sentido, o presente trabalho contribui para a literatura técnica sobre a análise estrutural dos galpões atirantados, auxiliando projetistas no cálculo dessas estruturas e servindo de referência nos cursos sobre esse assunto. / Sheds of precast concrete formed by tied portal frames are widely used in Brazil. However, there are few works on the design of these structures. In addition, several design criteria are adapted from those relative to the structures of cast in place concrete and multi-storey buildings. The objective of this work is to contribute to the analysis of this type of structure, introducing concepts that are hardly seen in practice, such as: rigidity of beam-column connection, physics and geometric nonlinear analysis, excessive deformation, and creep. The research was developed by mean of structural analysis, using models of sheds common in practice. Each concept previously mentioned was analyzed in examples. The stiffness of the beam-column connection was evaluated with base on the restriction parameter of the rotation, \'alfa\'R. The physics non-linearity (PNL) of concrete was considered by the method of Branson. For the geometric non-linearity (GNL) the parameter \'alfa\' and the process P.\'delta\' were used. The excessive deformation including creep was discussed taking in account the aspects of brazilian codes. It was found that the beam-column connection may have semi-rigid behavior in some cases, but, if properly designed, it has in fact rigid behavior. The consideration of the PNL had better results than the linear elastic analysis, and, for the sample studied, was possible to use a reduction coefficient of inertia equal to 0.5 for the beams and columns of the portal frame. It was also concluded that the consideration of GNL should be done systematically for this type of structure, since as some examples showed increase of moments above 10% and \'alfa\' > \'alfa\' lim. Furthermore, it was observed that the verification of deflection serviceability can be decisive in the choice of the portal frame cross sections, being obligatory the consideration of creep. In this sense, the present work contributes to the technical literature on the structural analysis of the tied portal frame sheds, helping engineers in the design of these structures and serving as reference in courses about this subject.

Os galpões de concreto pré-moldado, formados por pórticos atirantados, são muito utilizados, no Brasil. Porém, para o projeto dessas estruturas, a bibliografia é limitada. Além disso, vários critérios de projeto são adaptados dos relativos a estruturas de concreto moldado no local e de múltiplos pavimentos. O objetivo deste trabalho é contribuir para a análise desse tipo de estrutura, introduzindo conceitos que dificilmente são considerados na prática, tais como: rigidez da ligação viga-pilar, análise não-linear física e geométrica, deformação excessiva e fluência. A pesquisa foi desenvolvida por meio de análises estruturais, usando modelos de galpões comuns na prática. Cada conceito citado anteriormente foi analisado em exemplos. A rigidez da ligação viga-pilar foi avaliada com base no parâmetro de restrição à rotação, \'alfa\'R. A não-linearidade física (NLF) do concreto foi considerada pelo método de Branson. Para a não-linearidade geométrica (NLG), foram utilizados os parâmetros \'alfa\' e o processo P.\'delta\'. A deformação excessiva, incluindo a fluência, foi discutida tendo em conta os aspectos normativos. Constatou-se que a ligação viga-pilar pode ter comportamento semi-rígido em alguns casos, mas, se corretamente dimensionada, apresenta, de fato, comportamento rígido. A consideração da NLF apresentou resultados melhores que a análise elástica linear, sendo possível, para o exemplo estudado, utilizar um coeficiente redutor de inércia igual a 0,5, para as vigas e para os pilares do pórtico. Concluiu-se, também, que a consideração da NLG deve ser feita sistematicamente para esse tipo de estrutura, uma vez que alguns exemplos apresentaram acréscimos de momentos superiores a 10% e \'alfa\' > \'alfa\' lim. Além disso, observou-se que a verificação do estado limite de deformação excessiva (ELS-DEF) pode ser determinante na escolha das seções transversais do pórtico, sendo obrigatória a consideração da fluência. Nesse sentido, o presente trabalho contribui para a literatura técnica sobre a análise estrutural dos galpões atirantados, auxiliando projetistas no cálculo dessas estruturas e servindo de referência nos cursos sobre esse assunto. / Sheds of precast concrete formed by tied portal frames are widely used in Brazil. However, there are few works on the design of these structures. In addition, several design criteria are adapted from those relative to the structures of cast in place concrete and multi-storey buildings. The objective of this work is to contribute to the analysis of this type of structure, introducing concepts that are hardly seen in practice, such as: rigidity of beam-column connection, physics and geometric nonlinear analysis, excessive deformation, and creep. The research was developed by mean of structural analysis, using models of sheds common in practice. Each concept previously mentioned was analyzed in examples. The stiffness of the beam-column connection was evaluated with base on the restriction parameter of the rotation, \'alfa\'R. The physics non-linearity (PNL) of concrete was considered by the method of Branson. For the geometric non-linearity (GNL) the parameter \'alfa\' and the process P.\'delta\' were used. The excessive deformation including creep was discussed taking in account the aspects of brazilian codes. It was found that the beam-column connection may have semi-rigid behavior in some cases, but, if properly designed, it has in fact rigid behavior. The consideration of the PNL had better results than the linear elastic analysis, and, for the sample studied, was possible to use a reduction coefficient of inertia equal to 0.5 for the beams and columns of the portal frame. It was also concluded that the consideration of GNL should be done systematically for this type of structure, since as some examples showed increase of moments above 10% and \'alfa\' > \'alfa\' lim. Furthermore, it was observed that the verification of deflection serviceability can be decisive in the choice of the portal frame cross sections, being obligatory the consideration of creep. In this sense, the present work contributes to the technical literature on the structural analysis of the tied portal frame sheds, helping engineers in the design of these structures and serving as reference in courses about this subject.

Most producing companies aim to reduce tied up capital, which is meant to increase inventory turnover. In this study, an EMS (Electronic manufacturing service) -company, a contract manufacturer, will be studied. The company does not own the products themselves, but is a service company that manufactures to customers. The business has a problem that existed for a long period of time, they have a low inventory turnover among their component inventory. The company therefore wants to increase its inventory turnover in order to reduce its tied-up capital. The aim is to develop knowledge about supplier and customer relationships that affect the stock turnover rate in component stocks. In order to make calculations, it is profitable for the company to order materials multiple times for increased inventory turnover or fewer times to keep down the order cost. Case study is based on qualitative data in the form of interviews and observations. A large part of this study is also based on quantitative data from the company's MRP (material requirements planning) system. The literature is based on articles that deals with key concepts such as EOQ (economic order quantity), customer and supplier relationships. The conclusion of this study suggests that the company should use EOQ to reduce overall order cost while reducing the tied-up capital.

Arbetet har utförts vid Tekniska Högskolan i Jönköping där en studie har genomförts i samarbete med Kitron AB som är ett elektroniktillverkande företag. Kitron strävar efter att reducera kapitalbindningen för att vara kostnadseffektiva och därmed hålla hög konkurrenskraft. Studiens syfte var att identifiera de aspekter som påverkar företagets kapitalbindning och ta fram åtgärdsförslag för att minska kapitalbindningen som orsakas av materialflödet för ett av Kitrons kundprogram inom medicinteknik. Olika metoder användes för att samla in data gällande materialflödet. För att finna åtgärder analyserades materialflödet utifrån insamlad teori och genomförd värdeflödesanalys. Studien resulterade i identifiering av ett antal aspekter som påverkar kapitalbindningen och utifrån de togs åtgärder fram. De rekommenderade åtgärderna grundas i teori om Lean production. Åtgärdsförslagen bidrar till att effektivisera materialflödet och minimera den totala ledtiden för att reducera kapitalbindningen. Ett effektivare materialflöde kan uppnås genom att producera enligt principerna inom just in time och minimera slöseri. God samverkan med de kunder och leverantörer som påverkar materialflödet är också önskvärt. Den produktstruktur som Kitron utgår ifrån kan även anpassas efter produktionen för att minimera produktionsledtiden. Sammanfattningsvis krävs en kortare ledtid för att reducera kapitalbindningen inom det studerade kundprogrammet. Med hjälp av en del av de presenterade åtgärdsförslagen skapades ett idealt materialflöde som innebar reducering av produktionsledtiden med 15,5 dagar. Detta skulle medföra en reducering av kapitalbindningen med ungefär 454 000 kronor. / This project has been carried out at Jönköping University of Technology. The study has been executed in collaboration with the electronics manufacturing company, Kitron AB. Kitron aims to reduce the capital tied up to be cost efficient and improve the competitiveness. The purpose with this study was to identify the aspects that affect the company´s capital tied up and also find solutions to reduce the capital tied up caused by the material flow. A case study was executed at the company where the study was delimited to one specific customer of Kitron that make biomedical technology. Different methods were being used to gather data which has later been analyzed based on the theoretical framework. To find the solutions and identify the material flow an analyze was executed from theoretical aspects and a value stream map.  The study resulted in identification of several aspects that affect the capital tied up. From these aspects, solutions were found. The recommended solutions are based on theory about lean production. The solutions contribute to a more efficient material flow and help reduce the total lead time to enable a lower capital tied up. A more efficient material flow can be achieved by producing according to the principles of just in time and by reducing waste. It is preferable to cooperate with customers and suppliers that affect the material flow to improve it. The product structure can be arranged differently to enable a shorter production lead time. In conclusion, a shorter lead time is necessary to reduce the capital tied up concerning the studied customer. An ideal material flow was created by using some of the suggested solutions, which resulted in a shorter production lead time by 15,5 days. This would also contribute to a reduction of the capital tied up with 454 000 SEK.