This dissertation is devoted to the groups generated by automata. The first part of the dissertation deals with L-presentations for such groups. We describe the sufficient condition for an essentially free automaton group to have an L-presentation. We also find the L-presentation for several other groups generated by three-state automata, and we describe the defining relations in the Grigorchuk groups G_w. In case when the sequence w is almost periodic these relations provide an L-presentation for the group G_w. We also describe defining relations in the series of groups which contain Grigorchuk-Erschler group and the group of iterated monodromies of the polynomial z^2 + i. The second part of the dissertation considers groups generated by 3-state automata over the alphabet of 2 letters and 2-state automata over the 3-letter alphabet. We continue the classification work started by the research group at Texas A&M University ([BGK+07a, BGK+07b]) and further reduce the number of pairwise nonisomorphic groups generated by 3-state automata over the 2-letter alphabet. We also study the groups generated by 2-state automata over the 3-letter alphabet and obtain a number of classification results for this class of group.

Sound waves are highly conductive in the ocean; therefore, they are used in underwater detection and signal transmission. During these applications, we may receive some signals, such as radiated noise, self-noise, reverberation noise, target noise, and ambient noise. These signals are influential in the application of underwater acoustics, so many people study underwater noise and create numerous mathematical and physical models in order to improve the applications. According to the past researches, ambient noise is the most complicated one among all the other underwater noise. Until now, there are still some unknown factors in the ambient noise study, many of which are too intricate to be modulated. Accordingly, it is very important to know more about the ambient noise for the enhancing of the quality of underwater communication and detection, which is the reason why people keep researching on ambient noise. Among all kinds of ambient noise, wind-generated noise is not only loud in volume, but also wide in frequency scale, which makes it the most detectable noise during sound detection. In order to understand wind-generated noise, we have compiled past papers first to look for the correlation between physical mechanisms and models of mathematics. In addition, we have constructed a measuring system for underwater sound in the ocean and another measuring system for wind on land. Data from the two measuring system were analyzed by statistics. One of the correlations between wind and ambient noise is that the stronger wind appears, the louder ambient noise is generated. But wind does not always generate ambient noise; it has to be strong enough to generate ambient noise. However, even when the wind is strong enough, ambient noise is not generated immediately, but with a delay. By analyzing the data, we have not only proved the credibility of the data from the old researches, but also presented a method of statistics for analyzing the wind delay effect, and the minimum velocities of wind which generates ambient noise.

The fiber-optic microampere current sensor used two metal-coated single mode optical fibers to detect the current when it pass through the coated part which existing a thermal resistance effect.When the optical fiber experience temperature change,variation of the phase shift would be incurred by the change of refractive index and geometric structure of the fiber.Then we can observe the phase amplitude to know the input current.Besides we combine the all-fiber Michelson interferometer with the Faraday rotator mirror to build up a polarization-insensitive structure.Final using the phase-generated carrier technique(PGC) to stabilize demodulate the phase signal.

Den utveckling som internet har genomgått har bidragit till att en rad förändringar har skett. Det innehåll som finns på internet har ändrats och skapas numer av dess användare lika mycket som av företag och organisationer. Det har skett en utökning av plattformar där användarna kan kommunicera och interagera med varandra och dela med sig av personliga åsikter och erfarenheter på ett enkelt sätt. Vi är dessutom mer kritiska till vad som skrivs på internet och reflekterar över vad som är pålitlig information eller inte, samtidigt som vi som turister och konsumenter bryr oss om och påverkas av vad andra tycker och tänker. Inom turismnäringen har TripAdvisor blivit en viktig plattform för denna form av informationsskapande och spridande. TripAdvisor är en arena där resenärer och turismverksamheter möts.   Syftet med uppsatsen är att kartlägga vad som skrivs på TripAdvisor och hur hotellverksamheter påverkas och arbetar med dessa omdömen, detta utifrån en studie av tre hotell i Karlstad. Uppsatsens syfte konkretiseras genom tre frågeställningar: Hur sker ryktesspridning via internet, så kallad e-WoM, inom hotellnäringen?, Hur ser hotellets arbete med omdömena ut? och Vilken påverkan har e-WoM för hotellen?. Detta undersöks genom kvalitativ metod i form av en textanalys av innehållet i TripAdvisor omdömen samt genom intervjuer med representanter från de tre hotellen. Uppsatsens teoretiska utgångspunkter berör user-generated content, elektronisk ryktesspridning, relations- och kommunikationsaspekter.   Studien har kommit fram till att innehållet i omdömena inte skiljer sig åt i någon större utsträckning gällande de tre hotellen. Hotellens arbete med TripAdvisor ser olika ut, två av hotellen arbetar aktivt med omdömena och det tredje saknar helt ett arbetssätt. Omdömenas påverkan är närvarande i hotellens arbete ur både positiv och negativ aspekt, här handlar det om förbättringsmöjligheter samt negativ publicitet. Att TripAdvisor omdömen fungerar som en viktig informationskälla och starkt påverkar potentiella gäster är något som framkommit tydligt under studiens gång.

Estimates of the economic impact generated by tourism events can vary greatly depending on the methodologies used to conduct an analysis. This professional report will attempt to establish a standardized methodology for estimating the economic impact created by demand shocks to the economy resulting from event generated tourism visitation and spending with the final deliverable being a state-level input-output model for Texas. A review of state-level input-output models created for Michigan and Georgia in addition to a hypothetical scenario based on the 1996 Atlanta Olympics will illustrate the importance of assumptions in input-output analysis and lead to a discussion regarding some elements of hosting an event and increasing tourism that cannot be captured through this method. The report concludes by briefly examining considerations that should be made before applying the Texas model, the potential for future improvements, and finally the viability of recruiting events as an economic development strategy. / text

Interferometry with computer generated holograms (CGH) has evolved to be a standard technology for optical testing and metrology. By controlling the phase of the diffracted light, CGHs are capable of generating reference wavefronts of any desired shape, which allows using of interferometers for measuring complex aspheric surfaces. Fabrication errors in CGHs, however, cause phase errors in the diffracted wavefront, which directly affects the accuracy and validity of the interferometric measurements. Therefore, CGH fabrication errors must be either calibrated or budgeted. This dissertation is a continuation and expansion of the analysis and calibration of the wavefront errors caused by CGH in optical testing. I will focus on two types of error: encoding error and etching variation induced errors. In Topic one, the analysis of wavefront error introduced by encoding the CGH is discussed. The fabrication of CGH by e-beam or laser writing machine specifically requires using polygon segments to approximate the continuously smooth fringe pattern of an ideal CGH. Wavefront phase errors introduced in this process depend on the size of the polygon segments and the shape of the fringes. We propose a method for estimating the wavefront error and its spatial frequency, allowing optimization of the polygon sizes for required measurement accuracy. This method is validated with both computer simulation and direct measurements from an interferometer. In Topics two, we present a new device, the Diffractive Optics Calibrator (DOC), for measuring etching parameters, such as duty-cycle and etching depth, for CGH. The system scans the CGH with a collimated laser beam, and collects the far field diffraction pattern with a CCD array. The relative intensities of the various orders of diffraction are used to fit the phase shift from etching and the duty cycle of the binary pattern. The system is capable of measuring variations that cause 1 nm peak-to-valley (P-V) phase errors. The device will be used primarily for quality control of the CGHs. DOC is also capable of generating an induced phase error map for calibration. Such calibration is essential for measuring freeform aspheric surfaces with 1 nm root-mean-square (RMS) accuracy.

Interferometry with computer generated holograms (CGH) has evolved to be a standard technology for optical testing and metrology. By controlling the phase of the diffracted light, CGHs are capable of generating reference wavefronts of any desired shape, which allows using of interferometers for measuring complex aspheric surfaces. Fabrication errors in CGHs, however, cause phase errors in the diffracted wavefront, which directly affects the accuracy and validity of the interferometric measurements. Therefore, CGH fabrication errors must be either calibrated or budgeted. This dissertation is a continuation and expansion of the analysis and calibration of the wavefront errors caused by CGH in optical testing. I will focus on two types of error: encoding error and etching variation induced errors. In Topic one, the analysis of wavefront error introduced by encoding the CGH is discussed. The fabrication of CGH by e-beam or laser writing machine specifically requires using polygon segments to approximate the continuously smooth fringe pattern of an ideal CGH. Wavefront phase errors introduced in this process depend on the size of the polygon segments and the shape of the fringes. We propose a method for estimating the wavefront error and its spatial frequency, allowing optimization of the polygon sizes for required measurement accuracy. This method is validated with both computer simulation and direct measurements from an interferometer. In Topics two, we present a new device, the Diffractive Optics Calibrator (DOC), for measuring etching parameters, such as duty-cycle and etching depth, for CGH. The system scans the CGH with a collimated laser beam, and collects the far field diffraction pattern with a CCD array. The relative intensities of the various orders of diffraction are used to fit the phase shift from etching and the duty cycle of the binary pattern. The system is capable of measuring variations that cause 1 nm peak-to-valley (P-V) phase errors. The device will be used primarily for quality control of the CGHs. DOC is also capable of generating an induced phase error map for calibration. Such calibration is essential for measuring freeform aspheric surfaces with 1 nm root-mean-square (RMS) accuracy.

As techniques for manufacturing and metrology advance, optical systems are being designed with more complexity than ever before. Given these prescriptions, alignment and calibration can be a limiting factor in their final performance. Computer generated holograms (CGHs) have several unique properties that make them powerful tools for meeting these demanding tolerances. This work will present three novel methods for alignment and calibration of optical systems using computer generated holograms. Alignment methods using CGHs require that the optical wavefront created by the CGH be related to a mechanical datum to locate it space. An overview of existing methods is provided as background, then two new alignment methods are discussed in detail. In the first method, the CGH contact Ball Alignment Tool (CBAT) is used to align a ball or sphere mounted retroreflector (SMR) to a Fresnel zone plate pattern with micron level accuracy. The ball is bonded directly onto the CGH substrate and provides permanent, accurate registration between the optical wavefront and a mechanical reference to locate the CGH in space. A prototype CBAT was built and used to align and bond an SMR to a CGH. In the second method, CGH references are used to align axi-symmetric optics in four degrees of freedom with low uncertainty and real time feedback. The CGHs create simultaneous 3D optical references where the zero order reflection sets tilt and the first diffracted order sets centration. The flexibility of the CGH design can be used to accommodate a wide variety of optical systems and maximize sensitivity to misalignments. A 2-CGH prototype system was aligned multiplied times and the alignment uncertainty was quantified and compared to an error model. Finally, an enhanced calibration method is presented. It uses multiple perturbed measurements of a master sphere to improve the calibration of CGH-based Fizeau interferometers ultimately measuring aspheric test surfaces. The improvement in the calibration is a function of the interferometer error and the aspheric departure of the desired test surface. This calibration is most effective at reducing coma and trefoil from figure error or misalignments of the interferometer components. The enhanced calibration can reduce overall measurement uncertainty or allow the budgeted error contribution from another source to be increased. A single set of sphere measurements can be used to calculate calibration maps for closely related aspheres, including segmented primary mirrors for telescopes. A parametric model is developed and compared to the simulated calibration of a case study interferometer.

Thesis (M.A.)--Texas State University--San Marcos, 2008. / Vita. Includes bibliographical references (leaves 69-74). Also available on microfilm.

Thesis (M.A.)--University of Alberta, 2009. / Title from PDF file main screen (viewed on Mar. 31, 2010). A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master Arts, [Department of] Humanities Computing, University of Alberta. Includes bibliographical references.