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No description available.

No description available.

Ocean wave as a renewable energy source possesses great potential for solving the world energy crisis and benefit human beings. The total theoretical potential wave power on the ocean-facing coastlines of the world is around 30,000 TWh, although cannot all be adopted for generating electricity, the amount of the power can be absorbed still can occupy a large portion of the world's total energy consumption. However, multiple reasons have stopped the ocean wave energy from being widely adopted, and among those reasons, the most important one is immature of the Power Take-off (PTO) technology. In this dissertation, a self-reactive two-body wave energy point absorber that is embedded with a novel PTO using the unique mechanism of Mechanical Motion Rectifier (MMR) is investigated through design, analysis and testing to improve the energy harvesting efficiency and the reliability of the PTO. The MMR mechanism can transfer the reciprocated bi-directional movement of the ocean wave into unidirectional rotation of the generator. As a result, this mechanism brings in two advantages towards the PTO. The first advantage it possess is that the alternating stress of the PTO is changed into normal stress, hence the reliability of the components are expected to be improved significantly. The other advantage it brings in is a unique phenomenon of engagement and disengagement during the operation, which lead to a piecewise nonlinear dynamic property of the PTO. This nonlinearity of the PTO can contribute to an expanded frequency domain bandwidth and better efficiency, which are verified through both numerical simulation and in-lab experiment. During the in-lab test, the prototyped PTO achieved energy transfer efficiency as high as 81.2%, and over 40% of efficiency improvement compared with the traditional non-MMR PTO under low-speed condition, proving the previously proposed advantage. Through a more comprehensive study, the MMR PTO is further characterized and a refined dynamic model. The refined model can accurately predict the dynamic response of the PTO. The major factors that can influence the performance of the MMR PTO, which are the inertia of the PTO, the damping coefficient, and the excitation frequency, are explored through analysis and experiment comprehensively. The results show that the increase on the inertia of the PTO and excitation frequency, and decrease on the damping coefficient can lead to a longer disengagement of the PTO and can be expressed analytically. Besides the research on the PTO, the body structure of the point absorber is analyzed. Due to the low-frequency of the ocean wave excitation, usually a very large body dimension for the floating buoy of the point absorber is desired to match with that frequency. To solve this issue, a self-reactive two-body structure is designed where an additional frequency between the two interactive bodies are added to match the ocean wave frequency by adopting an additional reactive submerged body. The self-reactive two-body structure is tested in a wave to compare with the single body design. The results show that the two-body structure can successfully achieve the frequency matching function, and it can improve more than 50% of total power absorption compared with the single body design. / Doctor of Philosophy / Ocean wave as a renewable energy source possesses great potential for solving the world energy crisis and benefit human beings. The total theoretical potential wave power on the ocean-facing coastlines of the world is around 30,000 TWh, although impossible to be all transferred into electricity, the amount of the power can be absorbed still can cover a large portion of the world's total energy consumption. However, multiple reasons have stopped the ocean wave energy from being widely adopted, and among those reasons, the most important one is immature of the Power Take-off (PTO) technology. In this dissertation, a novel two body wave energy converter with a PTO using the unique mechanism of Mechanical Motion Rectifier (MMR) is investigated through design, analysis, and testing. To improve the energy harvesting efficiency and the reliability of the PTO, the dissertation induced a mechanical PTO that uses MMR mechanism which can transfer the reciprocated bi-directional movement of the ocean wave into unidirectional rotation of the generator. This mechanism brings in a unique phenomenon of engagement and disengagement and a piecewise nonlinear dynamic property into the PTO. Through a comprehensive study, the MMR PTO is further characterized and a refined dynamic model that can accurately predict the dynamic response of the PTO is established. The major factors that can influence the performance of the MMR PTO are explored and discussed both analytically and experimentally. Moreover, as it has been theoretically hypothesis that using a two-body structure for designing the point absorbers can help it to achieve a frequency tuning effect for it to better match with the excitation frequency of the ocean wave, it lacks experimental verification. In this dissertation, a scaled two-body point absorber prototype is developed and put into a wave tank to compare with the single body structure. The test results show that through the use of two-body structure and by designing the mass ratio between the two bodies properly, the point absorber can successfully match the excitation frequency of the wave. The highest power capture width ratio (CWR) achieved during the test is 58.7%, which exceeds the results of similar prototypes, proving the advantage of the proposed design.

This thesis regards the design process of a test rig for a new type of clutch. To save excessive fuel losses in heavy vehicles, a dog clutch has been designed with elastic engagement to lower peak torque. Currently, there is no way of testing this clutch. The purpose of this thesis is therefore to design a test rig that allows physical testing of this newly developed clutch. The thesis describes how suitable tests/measurements are found to indicate clutch functionality. By following a design process, these tests/measurements are incorporated in a test rig design. Initially, requirements were set. With these requirements, concepts have been generated. After some reviewing and improving, one final concept has been chosen. This concept has been designed using separate subsystems. When integrating these subsystems, a final design is realised. The final design measures the axial positions of components inside the clutch. It also measures torque and speed of the input and output. This all while having a variable input speed, engagement force, output braking torque, and output rotational inertia. The test rig is suitable for long-term testing to test wear of the different clutch components. Advice on future works has been given to the company based on the achieved results.

Virtuelle Realität (VR) wird seit Jahrzehnten in Industrie und Forschung sowie im Unterhaltungssektor genutzt. Dabei sind die verwendeten VR-Systeme meist nur auf einen Nutzer ausgelegt, wodurch es für andere Betrachter zu perspektivischen Verzerrungen kommt. Um mehreren Personen ein visuell gleichberechtigtes Nutzen des VR-Systems zu ermöglichen, muss jedem Nutzer eine individuelle Perspektive vermittelt werden. Es wird ein Klassifikationsschema vorgestellt, anhand dessen für verschiedene Interaktionsszenarien Anforderungen für eine derartige Hardwareumsetzung ableitbar sind. Um ausgewählte Aspekte der Mehrbenutzerinteraktionen zu untersuchen, wurde eine Prototypenplattform erstellt, mit der eine vielfältige Palette von Interaktionsszenarien für zwei Nutzer umgesetzt werden kann. Eine parallel zu dieser Arbeit entstandene mehrbenutzerfähige Powerwall und eine Erweiterung dieser zu einer L-Bench wurden genutzt, um mit zwei Studien ausgewählte Aspekte der Interaktion mehrerer Benutzer in VR empirisch zu untersuchen. Dazu wurden zwei Anwendungen kreiert: ein Puzzlespiel, welches eine Informationsasymmetrie zwischen den Nutzern simuliert, sowie ein Objekteinpassungsspiel, welches die Interaktion um eine körperliche Komponente erweitert. Mit diesen wurde untersucht, welche Sichtwechselmetapher zur Auflösung der Asymmetrie am besten geeignet ist.

Solid State Drives (SSD) blir idag allt vanligare som lagringsmedium och håller på att bli ett alternativ till magnetiska hårddiskar. Denna studie+ har undersökt hur man på bästa sätt kan utnjytta SSDer i en MySQL-databas. Undersökningen genomfördes med hjälp av experiment där prestandamätningar gjordes för att få en klar bild på i vilken konfiguration av SSDs som ger bäst prestanda i MySQL. Mätverktygen som användes var sql-bench och mysqlslap.   Resultaten visar att en databas på en enskild SSD presterar lika bra som en databas med  SSD-cache  under  majoriteten  av  mätningarna  och  visar  bättre  resultat  än resterande konfigurationerna som var en databas på hårddisk och transaktionsloggen på en SSD. / Solid State Drives (SSD) are now becoming  more common as storage and is about to  become  an  alternative  to  magnetic  disks.  This  report  studied  how  to  best  utilize SSDs in a MySQL database. This study was carried out using experiments in which performance benchmarks were made to get an accurate view on which configuration of  SSDs  that  gives  the  best  performance  in  MySQL.  The  benchmarks  where  made with sql-bench and mysqlslap.   The  results  indicate  that  a  database  using  only  SSD  storage  performs  equal  to  a database of solid-state cache under the majority of the tests and shows better results than the remaining configurations that include a database on a single hard drive and a configuration with the transaction log on a SSD.

Virtuelle Realität (VR) wird seit Jahrzehnten in Industrie und Forschung sowie im Unterhaltungssektor genutzt. Dabei sind die verwendeten VR-Systeme meist nur auf einen Nutzer ausgelegt, wodurch es für andere Betrachter zu perspektivischen Verzerrungen kommt. Um mehreren Personen ein visuell gleichberechtigtes Nutzen des VR-Systems zu ermöglichen, muss jedem Nutzer eine individuelle Perspektive vermittelt werden. Es wird ein Klassifikationsschema vorgestellt, anhand dessen für verschiedene Interaktionsszenarien Anforderungen für eine derartige Hardwareumsetzung ableitbar sind. Um ausgewählte Aspekte der Mehrbenutzerinteraktionen zu untersuchen, wurde eine Prototypenplattform erstellt, mit der eine vielfältige Palette von Interaktionsszenarien für zwei Nutzer umgesetzt werden kann. Eine parallel zu dieser Arbeit entstandene mehrbenutzerfähige Powerwall und eine Erweiterung dieser zu einer L-Bench wurden genutzt, um mit zwei Studien ausgewählte Aspekte der Interaktion mehrerer Benutzer in VR empirisch zu untersuchen. Dazu wurden zwei Anwendungen kreiert: ein Puzzlespiel, welches eine Informationsasymmetrie zwischen den Nutzern simuliert, sowie ein Objekteinpassungsspiel, welches die Interaktion um eine körperliche Komponente erweitert. Mit diesen wurde untersucht, welche Sichtwechselmetapher zur Auflösung der Asymmetrie am besten geeignet ist.

No description available.

The GMT-Consortium Large Earth Finder (G-CLEF) is an echelle spectrograph with precision radial velocity (PRV) capability that will be a first light instrument for the Giant Magellan Telescope (GMT). G-CLEF has a PRV precision goal of 40 cm/sec (10 cm/s for multiple measurements) to enable detection of Earth-like exoplanets in the habitable zones of sun-like stars'. This precision is a primary driver of G-CLEF's structural design. Extreme stability is necessary to minimize image motions at the CCD detectors. Minute changes in temperature, pressure, and acceleration environments cause structural deformations, inducing image motions which degrade PRV precision. The instrument's structural design will ensure that the PRV goal is achieved under the environments G-CLEF will be subjected to as installed on the GMT azimuth platform, including: Millikelvin (0.001 K) thermal soaks and gradients 10 millibar changes in ambient pressure Changes in acceleration due to instrument tip/tilt and telescope slewing Carbon fiber/cyanate composite was selected for the optical bench structure in order to meet performance goals. Low coefficient of thermal expansion (C 1E) and high stiffness-to-weight are key features of the composite optical bench design. Manufacturability and serviceability of the instrument are also drivers of the design. In this paper, we discuss analyses leading to technical choices made to minimize G-CLEF's sensitivity to changing environments. Finite element analysis (FEA) and image motion sensitivity studies were conducted to determine PRV performance under operational environments. We discuss the design of the optical bench structure to optimize stiffness to -weight and minimize deformations due to inertial and pressure effects. We also discuss quasi-kinematic mounting of optical elements and assemblies, and optimization of these to ensure minimal image motion under thermal, pressure, and inertial loads expected during PRV observations.