Characterization of Performance of a 3D Printed Stirling Engine Through Analysis and Test

This thesis involves the fusion of two technologies, Stirling engines and additivemanufacturing. The project began by building a Stirling engine primarily out of 3D printed parts. Methods to measure the power output were designed and built with a combination of 3D printed and off the shelf parts. The Stirling engine was tested to see if there was a correlation to analysis results, and a regenerator was installed to determine the effect on performance for this relatively low temperature engine. Finally, variations in test operation and the use of heat sinks were used to find a combination that will allow the unit to run more reliably.One challenge of the 3D printed parts was the durability when subjected to heat and assembly loads, especially over multiple rebuilds. However, the convenience of 3Dprinting made it possible to print replacement parts easily. New designs and assemblies were also created as a part of the effort to develop a power measurement system.Power output was measured and corresponded to analysis predictions. Testing was conducted with a hot plate temperature of 349K (168 F) and a cold plate temperature of 308K (94 F), which corresponds to a Temperature Ratio of 1.13. Rate of rotation was 150 RPM, or 2.5 Hz. The net power output was measured to be 3.1mW. Adding that to the losses attributed to engine friction resulted in a gross power output of 17mW, which was close to the analysis prediction of 15mW. Regenerator testing showed that using a regenerator, on average, doubled the speed of rotation at the same temperature ratio. However, the regenerator was detrimental to long term operation because without active cooling, the cold plate was unable to dissipate the heat efficiently enough. Increasing the cold side heat transfer to ambient would be essential in increasing reliability. The addition of heatsinks to the cold side was tested to determine the effectiveness, with positive results. The heatsinks that were used in testing were also analyzed, and it was determined that the spacing was too narrow for optimum performance. For future designs, custom heatsinks could be used that maximize the natural convection of the cold side, or a method developed to provide active cooling

Problems in GPS Accuracy

Improving and predicting the accuracy of positioning estimates derived from the global positioning system (GPS) continues to be a problem of great interest. Dependable and accurate positioning is especially important for navigation applications such as the landing of commercial aircraft. This subject gives rise to many interesting and challenging mathematical problems. This dissertation investigates two such problems. The first problem involves the study of the relationship between positioning accuracy and satellite geometry configurations relative to a user\u27s position. In this work, accuracy is measured by so-called dilution of precision (DOP) terms. The DOP terms arise from the linear regression model used to estimate user position from GPS observables, and are directly related to user position errors. An analysis of the statistical properties explaining the behavior of the DOP terms is presented. The most accurate satellite geometries and worst configurations are given for some cases. The second problem involves finding methods for detecting and repairing cycle-slips in range delay data between a satellite and a receiver. The distance between a satellite and a receiver can be estimated by measuring the difference in the carrier frequency phase shift experienced between the satellite and receiver oscillators. Cycle-slips are discontinuities in the integer number of complete cycles in these data, and are caused by interruptions or degradations in the signal such as low signal to noise ratio, software failures, or physical obstruction of the signals. These slips propagate to errors in user positioning. Cycle-slip detection and repair are crucial to maintaining accurate positioning. Linear regression models and sequential hypothesis testing are used to model, detect, and repair cycle-slips. The effectiveness of these methods is studied using data obtained from ground-station receivers

Texture improvements in the high-temperature superconducting Bi₂Sr₂Ca₁Cu₂Ox̳/Ag system via surface energy driven grain alignment

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2005.In title on t.p., double-underscored "x" appears as subscript.Includes bibliographical references (leaf 40).The relation between processing, microstructure, and material property was investigated in the high-temperature superconducting Bi₂Sr₂Ca₁Cu₂Ox̳/Ag system. Experiments were based on a theoretical surface energy model proposing enhanced texture of the oxide at the Ag interface after melt-processing. Two classes of samples were processed and compared. Bi-2212 powder was deposited on a thin-foil Ag surface and was melt-processed to yield a 20 ± 10 micron-thick superconducting layer. A subset of these samples were processed with an additional Ag surface pneumatically pressed on top of the superconducting layer before heat treatment. Critical current density (...) measurements were performed in liquid helium and we obtained values ranging from 5,900-36,700 A/cm². A 3-6 fold increase in ..., for samples with the second Ag interface was observed. X-ray diffraction provided a technique for quantifying grain alignment via the Lotgering factor, and indicated samples with the upper Ag interface possess a higher degree of texturing. Our results support the interfacial energy model that a high degree of texture exists at the Ag surface, and provide clear evidence linking materials processing, superconducting grain alignment, and critical current density. Disparities observed in J for similarly processed samples were believed to be a consequence of local regions of alignment and the presence of impurities.by Mark E. Vodhanel.S.B

Time resolved chirp measurements of gain switched semiconductor laser using a polarization based optical differentiator

We present a novel implementation of the “phase reconstruction using optical ultra fast differentiation” (PROUD) technique and apply it to characterize the time resolved chirp of a gain switched semiconductor laser. The optical temporal differentiator is a fiber based polarization interferometer. The method provides a fast and simple recovery of the instantaneous frequency from two temporal intensity measurements, obtained by changing the spectral response of the interferometer. Pulses with different shapes and durations of hundreds of picoseconds are fully characterized in amplitude and phase. The technique is validated by comparing the measured pulse spectra with the reconstructed spectra obtained from the intensity and the recovered phase

Markkinaselvitys Suomessa asuvien maahanmuuttajien koulutustarpeista neljän ammattikorkeakoulun toimialoilla pääkaupunkiseudulla : Hera Competence -hanke

Hera Competence -markkinaselvityksen tarkoituksena oli etsiä vastauksia ”Minkälainen on neljän eri ammattikorkeakoulun alueella Suomessa asuvien maahanmuuttajien koulutustarve ammattikorkeakoulujen toimialoilla pääkaupunkiseudulla?”. Markkinaselvityksessä oli neljä näkökulmaa: maahanmuuttajat, työnantajat, ammattikorkeakoulut ja tukiorganisaatiot. Saatujen tulosten pohjalta tässä julkaisussa esitetään toimenpide-ehdotuksia,miten voitaisiin edistää maahanmuuttajienkoulutukseen hakeutumista, sisäänpääsyä, opintojen etenemistä ja työllistymistä. Hera Competence –markkinaselvitys on osa opetusja kulttuuriministeriön (OKM) rahoittamaa HERA Competence –hanketta. Hankkeen toteuttamisesta vastasivat Hämeen ammattikorkeakoulu (HAMK), Lahden ammattikorkeakoulu (Lamk), Laurea-ammattikorkeakoulu (Laurea) ja Metropolia Ammattikorkeakoulu