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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Kostymbyxa utan sidsöm : En studie kring borttagningens påverkan hos en kostymbyxas sidsöm

Lamti, Sandra January 2018 (has links)
Det mest vanliga idag är att kostymbyxor har två sidsömmar eftersom den har en stor vikt för plaggets passforms och komfort. Om dessa inte existerar måste byxans innerbensöm inrymma all passform vilket gör det problematiskt då byxan ska sitta nära kroppen. Studien är ett samarbete med ett svenskt modeföretag som vill skapa en effektivare konfektionslösning rörande borttagningen av en figurnära kostymbyxas sidsöm.   Uppsatsen använder sig av företagets mest sålda vara för revidering, tillsammans med jämförelse av litteratur och en marknadsundersökning. Andra metoder som används i undersökningen är avprovning på intern provmodell som bedömts visuellt och via ett avprovningsprotokoll men också tabeller i form av krav- och måttlistor.   Genom att applicera mönsterkonstruktionen på tyg i olika vinklar i förhållande till tygets trådrak har olika resultat påvisats. Resultatet visar bättre passform vid en trådrak parallellt med varpriktningen. Det visar sig även finnas ett samband med materialets draperingsförmåga, det mjukare materialet i studien ger ett finare fall. Medan 45° trådrak från varpriktningen visade ett resultat som hade passformsbrister. / The most common things today is that suit pants have two side-seams because it's of great importance to achieve the desired fit and comfort of the garment. Without the side-seams, the inside leg seam would have to involve all fits, which makes it problematic considering the garment is supposed to stay tight to the body.  The study is a collaboration with a Swedish fashion company that wants to creat a more effective clothing solution for removal of a figurative suit pants side-seams.   The essay uses the company’s best-selling product for revise, along with comparing of literature and one market research. Other methods used in the survey are tests on an internal test model, assessed visually and through a test protocol, but also test charts in regard to requirements and measurements.   By applying the pattern to the fabric at different grainlines, different results have been shown. The results shows better fit at grainline parallel to the warp direction. It also turns out that there is a connection with the draping ability of the material, the softer material in the study gives a finer drape. While 45° grainline from the warp direction showed a result that had lack of fit.
32

Metodologia de detecção de trajetória de soldagem baseada em visão computacional

Bauernfeind, Omar Alejandro January 2017 (has links)
Em geral, um problema importante em um sistema de soldagem robotizado, ou com manipuladores automáticos, é a necessidade de uma trajetória ser reprogramada quando a forma ou a posição das peças mudam. Como solução a esse problema é proposto um método que utiliza técnicas de visão computacional, para assim detectar a trajetória de soldagem em juntas de topo. O método deve ser dinâmico permitindo a identificação de juntas de topo com cantos não próximos, linhas não retas e tamanhos diferentes entre as peças, assim como apresentar robustez contra variáveis desfavoráveis do ambiente industrial como riscos nas peças ou no fundo e mudanças de luminosidade. A trajetória é detectada baseando-se na linha de bordas da imagem global e adicionalmente trabalha-se sobre duas características da linha de solda: distância quase constante entre linhas paralelas e pixels de linha de solda com menor intensidade de luminosidade que as bordas. Uma etapa é proposta para robustez do método sobre linha de bordas descontinuas e possíveis erros em ponto inicial e final de solda. O trabalho proposto é validado com distintas configurações de junta de topo, como com cantos de peças não coincidentes, linha de solda não reta e diferentes orientações de peças. Os pontos da trajetória de solda obtidos são comparados com uma linha de solda considerada ideal, resultando em uma média e desvio padrão geral inferiores à um valor de 0,5 mm. Uma validação experimental é realizada com uma solda executada por um robô industrial seguindo os pontos de solda detectados, com os resultados demostrando que o método efetivamente pode definir uma trajetória de solda para aplicações industriais robotizadas. / In general, one of the most important problems in a robotic welding system, or in automatic manipulations, is the requirement of a path trajectory to be reprogramed when the shape or the position of the welding pieces are changed. In order to detect the welding seam in butt joints, a method that makes use of computational vision techniques is proposed. The method needs to be dynamic against variation in the configuration of the pieces, so as curved or not straight seam lines, not coincident corners; beside of that, it must to present robustness against unfavorable variables of the industrial environment, so as scratches in the pieces or illumination changes. Two features of the welding line are taken into account to develop the method: almost constant distance between parallel seam lines and darker pixels in the center of the seam than in the borders. Moreover a robustness step is proposed over two weaknesses of the method: discontinuities in the edges of the welding line and possible errors in the location of the start and end welding points. The validation step of the method involves different configuration of butt joints, as pieces without corner being coincident, not straight welding line and different orientations. The points of the welding seam detected by the method, are compared against a set of welding points considered as an ideal set of points, getting as results a mean and standard deviation lower than ± 0.5 mm. An experimental test is carried out by an industrial robot that welds two pieces following the welding line points, with the results showing that the method can effectively define a welding trajectory for industrial robotics applications.
33

Metodologia de detecção de trajetória de soldagem baseada em visão computacional

Bauernfeind, Omar Alejandro January 2017 (has links)
Em geral, um problema importante em um sistema de soldagem robotizado, ou com manipuladores automáticos, é a necessidade de uma trajetória ser reprogramada quando a forma ou a posição das peças mudam. Como solução a esse problema é proposto um método que utiliza técnicas de visão computacional, para assim detectar a trajetória de soldagem em juntas de topo. O método deve ser dinâmico permitindo a identificação de juntas de topo com cantos não próximos, linhas não retas e tamanhos diferentes entre as peças, assim como apresentar robustez contra variáveis desfavoráveis do ambiente industrial como riscos nas peças ou no fundo e mudanças de luminosidade. A trajetória é detectada baseando-se na linha de bordas da imagem global e adicionalmente trabalha-se sobre duas características da linha de solda: distância quase constante entre linhas paralelas e pixels de linha de solda com menor intensidade de luminosidade que as bordas. Uma etapa é proposta para robustez do método sobre linha de bordas descontinuas e possíveis erros em ponto inicial e final de solda. O trabalho proposto é validado com distintas configurações de junta de topo, como com cantos de peças não coincidentes, linha de solda não reta e diferentes orientações de peças. Os pontos da trajetória de solda obtidos são comparados com uma linha de solda considerada ideal, resultando em uma média e desvio padrão geral inferiores à um valor de 0,5 mm. Uma validação experimental é realizada com uma solda executada por um robô industrial seguindo os pontos de solda detectados, com os resultados demostrando que o método efetivamente pode definir uma trajetória de solda para aplicações industriais robotizadas. / In general, one of the most important problems in a robotic welding system, or in automatic manipulations, is the requirement of a path trajectory to be reprogramed when the shape or the position of the welding pieces are changed. In order to detect the welding seam in butt joints, a method that makes use of computational vision techniques is proposed. The method needs to be dynamic against variation in the configuration of the pieces, so as curved or not straight seam lines, not coincident corners; beside of that, it must to present robustness against unfavorable variables of the industrial environment, so as scratches in the pieces or illumination changes. Two features of the welding line are taken into account to develop the method: almost constant distance between parallel seam lines and darker pixels in the center of the seam than in the borders. Moreover a robustness step is proposed over two weaknesses of the method: discontinuities in the edges of the welding line and possible errors in the location of the start and end welding points. The validation step of the method involves different configuration of butt joints, as pieces without corner being coincident, not straight welding line and different orientations. The points of the welding seam detected by the method, are compared against a set of welding points considered as an ideal set of points, getting as results a mean and standard deviation lower than ± 0.5 mm. An experimental test is carried out by an industrial robot that welds two pieces following the welding line points, with the results showing that the method can effectively define a welding trajectory for industrial robotics applications.
34

Proposta para a estimativa da resistência à compressão uniaxial in situ de camadas de carvão com a utilização de geofísica / Methodology to estimate the in situ uniaxial compressive strength of coal seams based on geophysical data

Clovis Gonzatti 08 February 2008 (has links)
A arte de dimensionar pilares em minas subterrâneas de carvão tem sido objeto de pesquisa há mais de 100 anos no mundo inteiro. A maioria dos métodos de dimensionamento de pilares para a lavra segundo o método \"câmara e pilares\" se vale de parâmetros de resistência e geométricos das camadas de carvão. A resistência in situ da camada de carvão (S1) é um desses parâmetros. No Brasil, na Bacia Carbonífera Sul-Catarinense, uma nova camada de carvão, a Bonito, passou a ser minerada em volume considerável a partir da década de 1990. A sua resistência in situ ainda hoje é uma incógnita. Tendo como campo experimental a camada de carvão Bonito presente na mina Fontanella, no município de Treviso - SC, foram desenvolvidos diferentes estudos de laboratório e em subsolo, visando à caracterização mecânica, estrutural e geofísica dessa camada. Adicionalmente, foram realizadas investigações sobre uma segunda camada de carvão, a Irapuá, já relativamente conhecida, presente em outras duas minas na mesma bacia carbonífera. Os estudos realizados serviram de base para a proposição de uma nova metodologia para a estimativa da resistência à compressão uniaxial in situ de camadas de carvão (S1), levando em consideração a resistência de laboratório e informações geofísicas de laboratório e in situ. Com o uso da nova metodologia, são propostos valores de resistência à compressão uniaxial in situ da camada de carvão Bonito, para diferentes condições geológico-estruturais observadas na mina Fontanella, e para a camada Irapuá, nas minas Morozini Norte e Santa Augusta Norte. / Researchers in all over the world have spent a lot of time in developing techniques for pillar design in coal underground mines that use room and pillar method. Almost all the available methods are based on strength and geometric parameters of the coal seam. One of the most important is the coal seam in situ strength (S1). In Brazil, at Sul-Catarinense Carboniferous basin, a new coal seam (Bonito seam) is being mined since the last decade. Many instability problems have occured during mining. The coal seam strength is not very well known so far. Using the Bonito seam present at Fontanella mine in Treviso - SC, different studies were performed in laboratory and in situ. In adition, another coal seam, Irapuá, was also studied. The compilation of data at different sites was used to propose a new approach to estimates of the in situ uniaxial compressive strength of coal seams (S1) using three parameters. The uniaxial compressive strength and compressional wave ultra sonic velocity are determined in laboratory using small samples, while seismic velocity is measured in large scale conditions directly at the coal seam in situ. Using the new approach, values for in situ strength at Fontanella mine are proposed and also for two mines at Irapuá coal seam, Morozini Norte and Santa Augusta Norte.
35

Development of a real-time ultrasonic sensing system for automated and robotic welding

Siores, E. January 1988 (has links)
The implementation of robotic technology into welding processes is made difficult by the inherent process variables of part location, fit up, orientation and repeatability. Considering these aspects, to ensure weld reproducibility consistency and quality, advanced adaptive control techniques are essential. These involve not only the development of adequate sensors for seam tracking and joint recognition but also developments of overall machines with a level of artificial intelligence sufficient for automated welding. The development of such a prototype system which utilizes a manipulator arm, ultrasonic sensors and a transistorised welding power source is outlined. This system incorporates three essential aspects. It locates and tracks the welding seam ensuring correct positioning of the welding head relatively to the joint preparation. Additionally, it monitors the joint profile of the molten weld pool and modifies the relevant heat input parameters ensuring consistent penetration, joint filling and acceptable weld bead shape. Finally, it makes use of both the above information to reconstruct three-dimensional images of the weld pool silhouettes providing in-process inspection capabilities of the welded joints. Welding process control strategies have been incorporated into the system based on quantitative relationships between input parameters and weld bead shape configuration allowing real-time decisions to be made during the process of welding, without the need for operation intervention.
36

Design of multi-homing architecture for mobile hosts

Kiani, Adnan K. January 2009 (has links)
This thesis proposes a new multi-homing mobile architecture for future heterogeneous network environment. First, a new multi-homed mobile architecture called Multi Network Switching enabled Mobile IPv6 (MNS-MIP6) is proposed which enables a Mobile Node (MN) having multiple communication paths between itself and its Correspondent Node (CN) to take full advantage of being multi-homed. Multiple communication paths exist because MN, CN, or both are simultaneously attached to multiple access networks. A new sub layer is introduced within IP layer of the host’s protocol stack. A context is established between the MN and the CN. Through this context, additional IP addresses are exchanged between the two. Our MNS-MIP6 architecture allows one communication to smoothly switch from one interface/communication path to another. This switch remains transparent to other layers above IP. Second, to make communication more reliable in multi-homed mobile environments, a new failure detection and recovery mechanism called Mobile Reach ability Protocol (M-REAP) is designed within the proposed MNS-MIP6 architecture. The analysis shows that our new mechanism makes communication more reliable than the existing failure detection and recovery procedures in multi-homed mobile environments. Third, a new network selection mechanism is introduced in the proposed architecture which enables a multi-homed MN to choose the network best suited for particular application traffic. A Policy Engine is defined which takes parameters from iv the available networks, compares them according to application profiles and user preferences, and chooses the best network. The results show that in multi-homed mobile environment, load can be shared among different networks/interfaces through our proposed load sharing mechanism. Fourth, a seamless handover procedure is introduced in the system which enables multi-homed MN to seamlessly roam in a heterogeneous network environment. Layer 2 triggers are defined which assist in handover process. When Signal to Noise Ratio (SNR) on a currently used active interface becomes low, a switch is made to a different active interface. We show through mathematical and simulation analysis that our proposed scheme outperforms the existing popular handover management enhancement scheme in MIPv6 networks namely Fast Handover for MIPv6 (FMIPv6). Finally, a mechanism is introduced to allow legacy hosts to communicate with MNS-MIP6 MNs and gain the benefits of reliability, load sharing and seamless handover. The mechanism involves introducing middle boxes in CN’s network. These boxes are called Proxy-MNS boxes. Context is established between the middle boxes and a multi-homed MN.
37

Image-Based Micro-Scale Modeling of Flow in Porous Media

Riasi, Mohammad Sadegh January 2019 (has links)
No description available.
38

Konstrukce multifunkčního obráběcího centra / Design of multi-functional machining centre

Gruník, Jan January 2011 (has links)
This work deals with the construction and describes a detailed calculation of a machine frame of the shaft-turning lathe and 2D axis passes including the underpass according to the chosen initial parameters. The information contained in this work is not only of theoretical knowledge, but it should also serve for the practical use as a guide for the frames construction. The work also contains a background research on the topic, the model frame, the frame strength analysis, optimization of the frame, 2D axis, calculation, design and implementation of the underpass and the whole assembly. A suggestion for the future procedure and optimizing of the existing structure is found in this work as well.
39

Investigation of decommissioned reactor pressure vessels of the nuclear power plant Greifswald

Viehrig, Hans-Werner, Altstadt, Eberhard, Houska, Mario, Mueller, Gudrun, Ulbricht, Andreas, Konheiser, Joerg, Valo, Matti 05 June 2018 (has links)
The investigation of reactor pressure vessel (RPV) material from the decommissioned Greifswald nuclear power plant representing the first generation of Russian-type WWER-440/V-230 reactors offers the opportunity to evaluate the real toughness response. The Greifswald RPVs of 4 units represent different material conditions as follows: • Irradiated (Unit 4), • irradiated and recovery annealed (Units 2 and 3), and • irradiated, recovery annealed and re-irradiated (Unit1). The recovery annealing of the RPV was performed at a temperature of 475° for about 152 hours and included a region covering ±0.70 m above and below the core beltline welding seam. Material samples of a diameter of 119 mm called trepans were extracted from the RPV walls. The research program is focused on the characterisation of the RPV steels (base and weld metal) across the thickness of the RPV wall. This report presents test results measured on the trepans from the beltline welding seam No. SN0.1.4. and forged base metal ring No. 0.3.1. of the Units 1 2 and 4 RPVs. The key part of the testing is focussed on the determination of the reference temperature T0 of the Master Curve (MC) approach following the ASTM standard E1921 to determine the facture toughness, and how it degrades under neutron irradiation and is recovered by thermal annealing. Other than that the mentioned test results include Charpy-V and tensile test results. Following results have been determined: • The mitigation of the neutron embrittlement of the weld and base metal by recovery annealing could be confirmed. • KJc values of the weld metals generally followed the course of the MC though with a large scatter. • There was a large variation in the T0 values evaluated across the thickness of the multilayered welding seams. • The T0 measured on T-S oriented SE(B) specimens from different thickness locations of the welding seams strongly depended on the intrinsic structure along the crack front. • The reference temperature RT0 determined according to the “Unified Procedure for Lifetime Assessment of Components and Piping in WWER NPPs - VERLIFE” and the fracture toughness lower bound curve based thereon are applicable on the investigated weld metals. • A strong scatter of the fracture toughness KJc values of the recovery annealed and re-irradiated and the irradiated base metal of Unit 1 and 4, respectively is observed with clearly more than 2% of the values below the MC for 2% fracture probability. The application of the multimodal MC-based approach was more suitable and described the temperature dependence of the KJc values in a satisfactory manner. • It was demonstrated that T0 evaluated according to the SINTAP MC extension represented the brittle fraction of the data sets and is therefore suitable for the nonhomogeneous base metal. • The efficiency of the large-scale thermal annealing of the Greifswald WWER 440/V230 Unit 1 and 2 RPVs could be confirmed.
40

Inductive measurement of narrow gaps for high precision welding of square butt joints

Svenman, Edvard January 2016 (has links)
A recent method in aero engine production is to fabricate components from smaller pieces, rather than machining them from large castings. This has made laser beam welding popular, offering high precision with low heat input and distortion, but also high productivity. At the same time, the demand for automation of production has increased, to ensure high quality and consistent results. In turn, the need for sensors to monitor and control the laser welding process is increasing. In laser beam welding without filler material, the gap between the parts to be joined must be narrow. Optical sensors are often used to measure the gap, but with precise machining, it may become so narrow that it is difficult to detect, with the risk of welding in the wrong position. This kind of problems can cause severe welding defects, where the parts are only partially joined without any visible indication. This thesis proposes the use of an inductive sensor with coils on either side of the gap. Inducing currents into the metal, such a sensor can detect even gaps that are not visible. The new feature of the proposal is based on using the complex response of each coil separately to measure the distance and height on both sides of the gap, rather than an imbalance from the absolute voltage of each coil related to gap position. This extra information allows measurement of gap width and misalignment as well as position, and decreases the influence from gap misalignment to the position measurement. The sensor needs to be calibrated with a certain gap width and height alignment. In real use,these will vary, causing the sensor to be less accurate. Using initial estimates ofthe gap parameters from the basic sensor, a model of the response can be used to estimate the measurement error of each coil, which in turn can be used for compensation to improve the measurement of the gap properties.The properties of the new method have been examined experimentally, using a precise traverse mechanism to record single coil responses in a working range around a variable dimension gap, and then using these responses to simulate a two coil probe. In most cases errors in the measurement of weld gap position and dimensions are within 0.1 mm.The probe is designed to be mounted close to the parts to be welded, and will work in a range of about 1 mm to each side and height above the plates. This is an improvement over previous inductive sensors, that needed to be guided to the mid of the gap by a servo mechanism.

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