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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.
61

Studie možností využití Teslovy turbíny jako zdroj energie / Study of the possibility of using Tesla's turbine as a source of energy

Šedina, Martin January 2020 (has links)
The master thesis deals with the currently used types of water turbines and next part of the thesis deals with the theory of Tesla turbine. The theoretical part discusses water wheels, water turbines with their types and models which are described in the work. The thesis also discusses the construction of the Tesla turbine, its possibilities of using, inside principles and information about Tesla´s patent. The practical part contains the design of the Tesla turbine with modifications for increasing efficiency. The thesis describes production and assembly of turbine and the technology used for production of the turbine. There is also described how the turbine was measured and there are results of measurements of the turbine.
62

Akumulace elektrické energie pro zdroj s nestabilní produkcí / Accumulation of electricity for a source with unstable production

Petrenec, Jan January 2020 (has links)
This diploma thesis deals with possibilities of accumulation of electricity generated by renewable sources with unstable production. Several goals were set by an assignment of this thesis. Within a research, current trends of the accumulation are presented in detail on examples of specific representatives with their technical parameters and economic possibilities. Further, an unstable source of electricity – the wind farm of three power plants Multibrid 5000 with all its parameters and operational details is defined for purposes of individual designs of accumulation systems. Firstly, the detailed design of an advanced compressed air energy storage (A-CAES) is realized. It includes a thermodynamic calculation of chosen components, their partial technical solutions, a financial evaluation of investment and a determination of theoretical payback period. Furthermore, the design for accumulators Tesla Powerpack is realized. It contains a calculation of individual system parameters, a financial evaluation of investment and a determination of theoretical payback period. Last part of the thesis is dedicated to a comparison and an evaluation of the achieved results of both realized methods of the electricity accumulation. In the end, A-CAES is chosen as more perspective variation.
63

Entwicklung eines 7 Tesla-MRT-Algorithmus zur farbkodierten Volumetrie der Mamillarkörper in vivo bei Bipolarer Störung – eine Pilotstudie

Freund, Nora 03 June 2017 (has links)
Involviert in Netzwerke für das episodische Gedächtnis sowie als Bestandteil des Hypothalamus und des limbischen Systems stellen sich die im Zwischenhirn gelegenen Mamillarkörper als Zielstruktur im Kontext affektiver Störungen dar. Bislang waren die Mamillarkörper diesbezüglich lediglich in einer postmortem durchgeführten Studie Gegenstand der Forschung; es liegen keine Untersuchungen mit Hilfe der 7 Tesla-Magnetresonanztomografie vor. Um diese neuen Möglichkeiten der in vivo-Volumetrie im Submillimeterbereich auszuschöpfen, wurde auf Grundlage einer farbkodierten Darstellung ein detaillierter Algorithmus entwickelt, der sich als Hauptergebnis der vorliegenden Arbeit als hoch reliabel erwies. In der vorliegenden Pilotstudie wurde darüber hinaus das Mamillarkörper-Volumen von 14 Patientinnen und Patienten mit einer Bipolaren Störung und 20 gesunden Kontrollpersonen anhand von hochaufgelösten T1-gewichteten MRT-Bildern bestimmt. Ein signifikanter Unterschied zwischen den beiden Gruppen konnte nicht nachgewiesen werden, ebenso kein Unterschied zwischen den Geschlechtern. Es konnte gezeigt werden, dass das Volumen der Mamillarkörper signifikant invers mit dem Alter der ProbandInnen korreliert. Des Weiteren wurde eine signifikante positive Korrelation mit dem Gesamthirnvolumen der ProbandInnen festgestellt. Krankheitsschwere und Episodenzahl hingegen hatten keinen Einfluss auf das Mamillarkörper-Volumen. Die Ergebnisse dieser Pilotstudie sollten anhand einer größeren Stichprobe überprüft werden.
64

Non-contrast-enhanced hepatic MR arteriography with balanced steady-state free-precession and time spatial labeling inversion pulse: optimization of the inversion time at 3 Tesla / balanced SSFP法とTime-SLIP法を併用した肝動脈の非造影MR angiography:3テスラMR装置における撮像条件の最適化

Kawahara, Seiya 24 November 2017 (has links)
京都大学 / 0048 / 新制・論文博士 / 博士(医学) / 乙第13133号 / 論医博第2137号 / 新制||医||1024(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 溝脇 尚志, 教授 妹尾 浩, 教授 鈴木 実 / 学位規則第4条第2項該当 / Doctor of Medical Science / Kyoto University / DFAM
65

Modelling cortical laminae with 7T magnetic resonance imaging

Wähnert, Miriam 28 January 2015 (has links) (PDF)
To fully understand how the brain works, it is necessary to relate the brain’s function to its anatomy. Cortical anatomy is subject-specific. It is character- ized by the thickness and number of intracortical layers, which differ from one cortical area to the next. Each cortical area fulfills a certain function. With magnetic res- onance imaging (MRI) it is possible to study structure and function in-vivo within the same subject. The resolution of ultra-high field MRI at 7T allows to resolve intracortical anatomy. This opens the possibility to relate cortical function of a sub- ject to its corresponding individual structural area, which is one of the main goals of neuroimaging. To parcellate the cortex based on its intracortical structure in-vivo, firstly, im- ages have to be quantitative and homogeneous so that they can be processed fully- automatically. Moreover, the resolution has to be high enough to resolve intracortical layers. Therefore, the in-vivo MR images acquired for this work are quantitative T1 maps at 0.5 mm isotropic resolution. Secondly, computational tools are needed to analyze the cortex observer-independ- ently. The most recent tools designed for this task are presented in this thesis. They comprise the segmentation of the cortex, and the construction of a novel equi-volume coordinate system of cortical depth. The equi-volume model is not restricted to in- vivo data, but is used on ultra-high resolution post-mortem data from MRI as well. It could also be used on 3D volumes reconstructed from 2D histological stains. An equi-volume coordinate system yields firstly intracortical surfaces that follow anatomical layers all along the cortex, even within areas that are severely folded where previous models fail. MR intensities can be mapped onto these equi-volume surfaces to identify the location and size of some structural areas. Surfaces com- puted with previous coordinate systems are shown to cross into different anatomical layers, and therefore also show artefactual patterns. Secondly, with the coordinate system one can compute cortical traverses perpendicularly to the intracortical sur- faces. Sampling intensities along equi-volume traverses results in cortical profiles that reflect an anatomical layer pattern, which is specific to every structural area. It is shown that profiles constructed with previous coordinate systems of cortical depth disguise the anatomical layer pattern or even show a wrong pattern. In contrast to equi-volume profiles these profiles from previous models are not suited to analyze the cortex observer-independently, and hence can not be used for automatic delineations of cortical areas. Equi-volume profiles from four different structural areas are presented. These pro- files show area-specific shapes that are to a certain degree preserved across subjects. Finally, the profiles are used to classify primary areas observer-independently.
66

Tesla Valve for Hydrogen Decompression : Fluid Dynamic Analysis

Bäckman, Elias, Willén, Mathilda January 2019 (has links)
Människans påverkan på växthuseffekten har under de senaste åren varit en mycket aktuell fråga. Det är många olika faktorer som bidrar till ett negativt avtryck på miljön, där ett stort bidrag kommer från sektorn bilindustri. Majoriteten av dagens bilar drivs på fossila bränslen som genererar skadande utsläpp på miljön. Att hitta nya alternativa bränslen som är förnyelsebara och energivänliga som kan ersätta de fossila skulle kunna leda till ett signifikant minskat avtryck på klimat och miljö. Att använda väte som bränsle och i synnerhet att driva fordonet på vätgas är ett av de alternativen då avgivna utsläpp endast består av vatten och varm luft, förutsatt att man använder sig av förnybar energi vid framställning av vätgasen. I bränsletanken återfinns ett högt tryck hos vätgasdrivna bilar, detta för att mer bränsle ska kunna förvaras och därmed öka antal mil möjliga att köra på en tank. Ett tryckfall är nödvändigt för att förse bränslecellen med vätgas vid rätt tryck, och för att uppnå högst möjliga verkningsgrad. Teslaventilen har inga rörliga delar vilket medför ett brett spektrum av applikationer i industriella situationer på grund av dess uthållighetsegenskaper. För att kunna kategorisera prestandan och uppnå optimal effekt krävs förståelse om ventilens geometriska uppbyggnad. Med rätt geometri på Tesla-ventilens olika strukturparametrar kan man uppnå ett högt tryckfall, med andra ord en hög prestanda. I denna studie har tre olika geometriska parametrar hos Tesla-ventilen undersökts för att kunna dra slutsatser och etablera deras optimala värden för bästa prestanda. Parametrarna som varit av intresse är innerradien på kurvan av Tesla-ventilen, avståndet mellan flera sammankopplade ventiler och tvärsnittets utformning. Resultaten erhölls genom numeriska metoder av Computational Fluid Dynamics simuleringar i programmet ANSYS Fluent. Resultat visade att en liten innerradie och ett längre avstånd mellan flera sammankopplade ventiler gav upphov till högre tryckfall. Tvärsnitten som undersöktes var rektangulärt och cirkulärt, där det cirkulära visade en bättre förmåga av att effektivt sänka trycket hos fluiden. Slutsatser som drogs var att cirkulärt tvärsnitt var att föredra och att en liten innerradie och ett stort avstånd mellan ventiler optimerar prestandan hos Tesla-ventiler. / 在过去的几年里,人类对温室效应的影响一直是社会舆论中一个突出和争论的主 题。对环境造成负面影响的因素有很多,汽车便是其中之一。如今,大多数汽车依靠 化石燃料驱动,在这个过程中会造成有毒物质的排放。因此,对可再生与环境友好的 替代燃料的研究重要性愈发突出。氢,(更具体地说,氢气),由于燃烧产物只有 水,成为了一种可选的替代燃料。 在氢燃料汽车的储氢罐中,往往设置高压以提高氢气储量并增加里程数。而为了 保证燃料电池高效运行,在储氢罐和燃料电池之间必须采取减压手段,这也使高效降 压成为了氢燃料汽车研究领域中的一个长期需求。特斯拉阀在没有活动部件的情况 下,允许流体沿一个方向流动,并限制其往相反方向流动。该概念在工业环境中具备 广泛的应用潜力,而理解特斯拉阀(的工作机理)对于表征设备性能非常重要。采用 最优几何形状的特斯拉阀,可以实现高压降,换言之高性能。 本研究对特斯拉阀的三种结构参数进行了调查,得出了使特斯拉阀降压性能达到 最优时的参数值。所研究的三种参数分别是内部曲线半径,多级特斯拉阀中的阀间距 以及阀门的横截面。为了获得结果,使用计算流体动力学软件 ANSYS Fluent 进行了数 值模拟。结果表明,与较大的半径相比,较小的内部曲线半径产生更高的压降。随着 多级特斯拉阀的阀间距增大,阀门降压性能提高。对横截面的研究中,比较了矩形截 面和圆形截面的特斯拉阀的降压性能,发现圆形截面的特斯拉阀降压性能更优。本研 究的最终结论是(在特斯拉阀设计中采用)圆形横截面,小的内部曲线半径和大的阀 间距可以提高装置性能。 / The last couple of years, the footprint of humankind on the greenhouse effect has been a highlighted and debated topic. There are many contributing factors to the negative impacts on the environment, one of them being the sector of automobile. Today, most cars are driven on fossil fuel energy which produces toxic emissions. The search for replaceable alternative fuels is hence of importance and keys of demands are renewable energy and energy-friendly resources. Hydrogen as a fuel, in particular the hydrogen gas, is one of the options considering the only residues to be water and hot air, provided that the energy used in the hydrogen production comes from renewable sources. In the storage tank of cars fueled by hydrogen gas, a high pressure is set due to its advantages of opportunities of more storage and thus increased mileage of the tank. A decompression process is necessary to supply the fuel cell with hydrogen gas at the right pressure, and thus achieve highest possible degree of efficiency. The concept offers a wide set of application opportunities in industrial situations and understanding the valve is important for characterizing the performance on the device. Given correct and optimal geometry on the Tesla valve, a high pressure-drop could be achieved, in other words a high performance. In this study three geometric parameters were investigated in order to conclude their ideal value for optimizing the performance. The parameters of interest were the inner curve radius, the valveto-valve distance in a multi-stage Tesla valve and the cross-section of the valve. In order to obtain the results, a numerical study was conducted using simulations in a Computational Fluid Dynamics program, ANSYS Fluent. The results denoted that a small inner curve radius yielded the highest pressure-drop when comparing to larger radius’. The performance was enhanced with a large valveto-valve distance of the multi-stage Tesla valves and the findings of the cross-sections, which were chosen to be rectangular and circular of interest, displayed a superior performance for the circular cross-sections. Conclusions were drawn that circular cross-section is to prefer and that a small inner curve radius and large valve-to-valve distance yield an enhanced performance of the device.
67

Imagerie des couches corticales par résonance magnétique à 7 teslas / Imaging cortical layers with magnetic resonance at 7 teslas

Leprince, Yann 11 February 2015 (has links)
Cette thèse présente le développement d’une méthodologie qui permet d’analyser la structure en couches du cortex cérébral, en utilisant l’imagerie par résonance magnétique en champ intense (IRM à 7 teslas). Alors que l’architecture corticale est traditionnellement étudiée par imagerie microscopique de coupes de tissu post-mortem, l’utilisation d’une technique non invasive telle que l’IRM permet d’envisager d’étudier la lamination corticale in vivo, et ainsi de dépasser les atlas architecturaux classiques comme celui de Brodmann.Deux approches ont été utilisées pour l’acquisition d’images à haute résolution. La première, développée pour l’imagerie in vivo, utilise une reconstruction super-résolue à partir de coupes épaisses acquises dans différentes géométries. La seconde, basée sur une séquence tridimensionnelle optimisée pour l’imagerie post-mortem, a permis l’acquisition d’images de pièces anatomiques.La contribution principale de cette thèse réside dans le développement d’un couple de méthodes permettant d’extraire automatiquement, en chaque point du cortex, un profil caractérisant son architecture en couches. Pour permettre l’extraction robuste de ces profils, un modèle original de l’influence de la courbure corticale a été développé et implémenté.Ces méthodes ont été testées et validées sur plusieurs pièces anatomiques. Ce travail permet d’envisager la caractérisation de l’architecture des aires corticales, voire leur délimitation automatique, en utilisant l’IRM en champ intense. / This thesis presents the development of a methodology for the analysis of the layered structure of the cerebral cortex, using high-field magnetic resonance imaging (7-tesla MRI). While cortical layers are traditionally studied using microscopic imaging of post-mortem tissue slices, the use a non-invasive technique such as MRI will enable in vivo studies, and thus allow new approaches beyond the use of classical architectural atlases such as Brodmann's.Two imaging methodologies have been used to acquire high-resolution images. First, a method based on super-resolution reconstruction from thick slices acquired in different geometries was developed for in vivo imaging. Second, a three-dimensional imaging sequence optimized for post-mortem tissue allowed imaging excised brain specimen.The main contribution of this thesis consists of a pair of methods that perform an automatic extraction of cortical profiles, which characterize the laminar architecture at any cortical location. In order to allow robust extraction of these profiles, an original model of the influence of cortical curvature was developed and implemented.These methods were tested and validated on multiple brain specimen. This work allows envisaging an automatic microarchitectural characterization of cortical areas, and even architectural parcellation, using high-field MRI.
68

Tuned and asynchronous stencil kernels for CPU/GPU systems

Venkatasubramanian, Sundaresan 18 May 2009 (has links)
We describe heterogeneous multi-CPU and multi-GPU implementations of Jacobi's iterative method for the 2-D Poisson equation on a structured grid, in both single- and double-precision. Properly tuned, our best implementation achieves 98% of the empirical streaming GPU bandwidth (66% of peak) on a NVIDIA C1060. Motivated to find a still faster implementation, we further consider "wildly asynchronous" implementations that can reduce or even eliminate the synchronization bottleneck between iterations. In these versions, which are based on the principle of a chaotic relaxation (Chazan and Miranker, 1969), we simply remove or delay synchronization between iterations, thereby potentially trading off more flops (via more iterations to converge) for a higher degree of asynchronous parallelism. Our relaxed-synchronization implementations on a GPU can be 1.2-2.5x faster than our best synchronized GPU implementation while achieving the same accuracy. Looking forward, this result suggests research on similarly "fast-and-loose" algorithms in the coming era of increasingly massive concurrency and relatively high synchronization or communication costs.
69

The Future of Energy Storage : Investment Evaluations Regarding Energy Storage Systems Connected to PV Systems / Framtidens Energilagring : Investeringsberäkningar för energilagringssystem anslutna till PV-system

Lindberg, Oskar, Högström, Emil, Falkenberg, Oskar January 2017 (has links)
An ever-decreasing cost of photovoltaics (PV) combined with generous installation subsidies lead to a growth of PV systems in Sweden. A large-scale penetration of PV power would make Energy Storage Systems (ESS) interesting for providing back-up storage, enabling flexibility and regulating intermittence. ESS represents a vital link between electrical supply and demand, and moreover a critical feature for increasing the use and attractiveness of renewable and intermittent energy sources. The purpose of this study is to do a quantitative analysis examining the most beneficial way to store electricity from PV regarding investment cost, life span, capacity and pay-off time. The study object is Valsätraskolan, a school in Uppsala with an existing PV system. The thesis shows that Lithium-ion batteries are the best prospected battery type but still not an economically profitable investment. With the current grid- and battery prices the most suitable battery solution has a pay-off time of 125 years. If the school would extend their PV system to cover all preferable roof areas, the pay-off time would be 48 years. If ESS are to become attractive from a financial point of view, the grid prices would have to increase and the cost for ESS decrease substantially.
70

Grafisk identitet i en tid av förändring. Hur uttrycks stora fordonstillverkares eco-branding i förhållande till paradigmskiftet mot krav på hållbar utveckling?

Wilhelm, Ewe January 2018 (has links)
I mitt arbete ämnar jag besvara frågan “Hur uttrycks stora fordonstillverkares eco-branding i förhållande till paradigmskiftet mot krav på hållbar utveckling?”. Syftet är att undersöka svårigheterna och balansgången med eco-branding inom fordonsindustrin. Detta görs utifrån en branding-studie av tre stora fordonstillverkares användning av eco-branding, ihop med mina egna erfarenheter av ett liknande designprojekt. Grafisk identitet och visuell kommunikation studeras utifrån el och hybridbilarna BMW i3, Tesla Model S och Toyota Prius. Positionering av företagen inom området kopplas till teori om hållbar utveckling, eco-branding och greenwashing för att diskutera krav på transparens och företagens upplevda legitimitet och trovärdighet. Det framkommer att de olika företagen brandar sig på olika sätt, med olika grad av eco-branding. Något som beror mycket på vilka värderingar och historia företaget och dess varumärke har. Även om det är en balansgång mellan greenwashing och trovärdighet, så kan alla ses ha olika styrkor; samt svagheter att förbättra för ökad transparens eller trovärdighet. En slutsats är dock att eco-branding börjar bli mer trovärdig och att greenwashing-trenden generellt börjat mattas av. Gemensamt för alla aktörer är att framtidsvisionen är det centrala i varumärkesbyggandet. Dock har konventionella fordonstillverkare svårare förutsättningar att förhålla sig till paradigmskiftet än nyare aktörer. / In this essay I aim to answer the question “How is the eco-branding of large automotive companies expressed, in relation to the paradigm shift towards demands for sustainability?”. The purpose is to examine the difficulties and balancing of eco-branding within the automotive industry. This is done through a comparative analysis of three large automotive companies and their use of eco-branding, together with my own experience from a similar design project. Corporate identity and visual communication is studied through the electric and hybrid cars BMW i3, Tesla Model S and Toyota Prius. The positioning of the brands within the field is linked to theory on sustainable development, eco-branding and greenwashing; to discuss demands for transparency and the brands perceived legitimacy and credibility. It is revealed that the different companies brand themselves in relatively different ways, with different degrees of eco-branding.This depends on the values and history of the company and it’s brand. Even though there is a balancing between greenwashing and credibility, they all have different strengths, as well as areas for improvement to increase company transparency and authenticity. A conclusion is however that eco-branding is becoming more credible and the trend of greenwashing is generally started to slightly diminish. It is revealed that future vision plays a central part in all of the brands. However conventional companies are shown to have significantly more difficulties in positioning themselves within the paradigmshift compared to newer actors.

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