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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.
11

Non-linear model fitting for the measurement of thin films and surface topography

Yoshino, Hirokazu January 2017 (has links)
Inspection of optical components is essential to assure the quality and performance of optical systems. Evaluation of optical components includes metrology measurements of surface topography. It also requires optical measurements including refractive index, thin film thickness, reflectivity and transmission. The dispersion characteristics of optical constants including refractive index are also required. Hence, various instruments are used to make these measurements in research laboratories and for quality assurance. Clearly, it would be a significant advantage and cost saving if a technique was developed that could combine surface metrology with optical measurements. {Coherence Scanning Interferometry} (CSI) (also referred to as {Scanning White Light Interferometry} (SWLI)) has been used widely to measure surface topography with sub-nanometre vertical resolution. One of the benefits of the CSI is that the technique is non-contacting and hence non-destructive. Thus the test surfaces are not affected by the measurement using a CSI instrument whereas damage to the surfaces can occur when using traditional contact methods such as stylus profilometry. However use of CSI is geometrically limited to small areas ($\lesssim 10 \times 10$ mm) with gentle slopes ($\lesssim \ang{40}$) because of the numerical aperture of objective lens whereas stylus profilometry works well with larger areas and higher slopes due to the range of motion of the gauge and the traverse unit. Since the CSI technique is optical and involves light reflection and interference it is possible to extend the technique for the measurement of the thickness of transparent films, the roughness of surfaces buried beneath thin films or interfacial surfaces. It may also be used to determine spectral complex refractive index. This thesis provides an analytical framework of new methods to obtain complex refractive index in a visible light domain and interfacial surface roughness (ISR). It also provides experimental verification of these new capabilities using actual thin film model systems. The original Helical Complex Field (HCF) function theory is presented followed by its existing extensions that enable determination of complex refractive index and interfacial surface roughness. Further theoretical extensions of the HCF theory are also provided: A novel theory to determine the refractive index of a (semi-)transparent film is developed to address the constraint of the current HCF theory that restricted its use to opaque materials; Another novel theory is provided to measure ISR with noise compensation, which avoids erroneous surface roughness caused by the numerical optimisation affected by the existence of noise. The effectiveness of the ISR measurement with noise compensation has been verified using a number of computer simulations. Stylus profilometry is a well established method to provide a profile and has been used extensively as a 'reference' for other techniques. It normally provides a profile on which the roughness and the waviness are computed. Extension of the stylus profilometry technique to areal measurement of asymmetrical surfaces, namely raster scan measurement, requires a system to include error compensation between each traverse. The system errors and the random errors need to be separately understood particular when the measurement of a surface with nanometre-order accuracy is required. In this thesis a mathematical model to locate a stylus tip considering five mechanical errors occurring in a common raster scan profilometer is provided. Based on the model, the simulator which provides an areal measurement of a sphere was developed. The simulator clarified the relationship between the Zernike coefficients obtained from the form residual and the size of the errors in the form of partial derivatives of Zernike coefficients with respect to the errors. This provides theoretical support to the empirical knowledge of the relationship between the coefficients and the errors. Furthermore, a method to determine the size of errors directly from Zernike coefficients is proposed supported by simulations. Some of the error parameters were accurately determined avoiding iterative computation with this method whereas the errors are currently being determined by iterative computation.
12

Development and evaluation of a 6DOF interface to be used in a medical application / Utveckling och utvärdering av ett 6DOF gränssnitt för användning i en medicinsk tillämpning

Larsson, Ulrica, Pettersson, Johanna January 2002 (has links)
This thesis was performed at the research centre CINECA in Bologna, Italy. An interface with six degrees of freedom, 6DOF, to be used in a virtual environ- ment for the positioning of medical components was developed in co-operation with IOR, one of the most important orthopaedic hospitals in Italy. The main reason for doing this was to find out whether or not a virtual en-viron-ment and 6DOF interaction could make the pre-operative planning of an ope-ration more efficient compared to other techniques. Is it easy to posi-tion an object using stereovision and a 6DOF tracker tool? Further-more, the interface might also be used in other applications and areas in the future. Described is the development of an interaction class especially constructed for the use of a tracking tool called a stylus pen. This tool takes advantage of all 6DOF, i.e. it recognises movements in the x, y and z directions and likewise the orientation of the tool around the three axis. Moreover, an application which uses the interaction class was created in order to evaluate its usefulness. The application enables the user to load, save and position objects within a virtual environment. The result of this evaluation is then described and discussed. In the evaluations it was shown that the stylus pen with 6DOF is an intuitive in-ter-action tool which works well for positioning. The stereovision also seems to further improve the users ability to position objects. However, the created interaction class needs to be further developed before itcan be implemented in a pre-operative planning tool.
13

Style and interpretation in the seven keyboard toccatas of J.S. Bach, BWV 910-916

Mace, Abigail 14 March 2013 (has links)
The keyboard toccatas of J. S. Bach, BWV 910-916, present a formidable challenge of interpretation to the modern-day performer. These works contain some of the most unusual compositional techniques to be found in Bach’s output due to their use of an improvisatory, virtuosic style inherited from the seventeenth century. While pianists of today are trained to perform with perfect fidelity to the score, the treatises from the time of Bach point to a rhythmically free approach to the improvisatory features of these toccatas. The goal of this treatise is to explore how the historical tradition from which Bach’s toccatas emerged influenced their stylistic characteristics with the purpose of applying this information to create an informed performance by today’s interpreters. In this effort, this treatise focuses on several broad categories in the process of understanding the inspiration and, therefore, the interpretation of these works. These categories include the genesis of the toccata as a genre, the compositional techniques associated with the toccata, Bach's personal contribution to the genre, and the interpretation of Bach's toccatas specifically. / text
14

Konstrukce koncov©ho efektoru robota s monost­ automatick© vmÄny nstroje / Design of Robot end effector with automatic tool exchange

Jirges, Radek January 2020 (has links)
The goal of this thesis was to design an end effector for a small robot for testing of devices with a touchscreen. The effector has to communicate with the robot via serial interface and provide feedback about used downforce. Another requirement was possibility of automatic tool change. Measuring of downforce, signal processing, and communication with robot ensures custom electronics based on STM32 microprocessor and piezoresistive sensor. The mechanism of tool change was inspired by the system used with industrial robots but customized for this application. The result of this thesis is a functional prototype of a stylus for devices with a touchscreen which provides feedback about the downforce on display and possibility of automatic tool change. The main benefit of this solution is the possibility of changing the tool for the one with one or more styluses for testing gesture-based interface what is indispensable in these days.
15

Towards Topography Characterization of Additive Manufacturing Surfaces

Vedantha Krishna, Amogh January 2020 (has links)
Additive Manufacturing (AM) is on the verge of causing a downfall to conventional manufacturing with its huge potential in part manufacture. With an increase in demand for customized product, on-demand production and sustainable manufacturing, AM is gaining a great deal of attention from different industries in recent years. AM is redefining product design by revolutionizing how products are made. AM is extensively utilized in automotive, aerospace, medical and dental applications for its ability to produce intricate and lightweight structures. Despite their popularity, AM has not fully replaced traditional methods with one of the many reasons being inferior surface quality. Surface texture plays a crucial role in the functionality of a component and can cause serious problems to the manufactured parts if left untreated. Therefore, it is necessary to fully understand the surface behavior concerning the factors affecting it to establish control over the surface quality. The challenge with AM is that it generates surfaces that are different compared to conventional manufacturing techniques and varies with respect to different materials, geometries and process parameters. Therefore, AM surfaces often require novel characterization approaches to fully explain the manufacturing process. Most of the previously published work has been broadly based on two-dimensional parametric measurements. Some researchers have already addressed the AM surfaces with areal surface texture parameters but mostly used average parameters for characterization which is still distant from a full surface and functional interpretation. There has been a continual effort in improving the characterization of AM surfaces using different methods and one such effort is presented in this thesis. The primary focus of this thesis is to get a better understanding of AM surfaces to facilitate process control and optimization. For this purpose, the surface texture of Fused Deposition Modeling (FDM) and Laser-based Powder Bed Fusion of Metals (PBF-LB/M) have been characterized using various tools such as Power Spectral Density (PSD), Scale-sensitive fractal analysis based on area-scale relations, feature-based characterization and quantitative characterization by both profile and areal surface texture parameters. A methodology was developed using a Linear multiple regression and a combination of the above-mentioned characterization techniques to identify the most significant parameters for discriminating different surfaces and also to understand the manufacturing process. The results suggest that the developed approaches can be used as a guideline for AM users who are looking to optimize the process for gaining better surface quality and component functionality, as it works effectively in finding the significant parameters representing the unique signatures of the manufacturing process. Future work involves improving the accuracy of the results by implementing improved statistical models and testing other characterization methods to enhance the quality and function of the parts produced by the AM process.
16

Ultratenké polymerní filmy na pevných površích: studium fyzikálními metodami / Characterization of ultra-thin polymer films on solid substrates using different physical techniques

Pop-Georgievski, Ognen January 2013 (has links)
The presented doctoral research was aimed at preparation and characterization of ultra thin polymer films on solid substrates using different physical techniques. Each of these physical techniques probes selectively different characteristics of the films. While some of the techniques are strong in the predetermination of some unique properties of the layers, they might be limited and give no specific/conclusive information about some other important characteristics. Therefore, only the combination of the techniques provides a profound picture of the thickness, architecture, composition and functionality of the films/layers. This combined characterization approach elucidates in details the physical characteristics and the mechanisms responsible for the unique behavior of different polymer films/layers in the application that they are intended for. In the thesis, of particular interest were films of high biomedical, biotechnological and tissue engineering importance, such as: 1. poly(lactide) films formed by grafting "from-" a silanized alacrite thin films (L605 Co-based super alloy), 2. polydopamine (PDA) films that could serve as substrate independent mod- ification platform for further surface modification steps, 3. poly(ethylene oxide)films formed by "grafting to-" PDA modified surfaces, 4....

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