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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.
21

New and Improved Methods to Characterize, Classify, and Estimate Daily Sky Conditions for Solar Energy Applications

Kang, Byung O. 29 April 2014 (has links)
Firstly, this dissertation proposes a new characterization and classification method for daily sky conditions by using the daily sky clearness index (KD) and the daily probability of persistence (POP-KD) that can be derived from ground-based irradiance measurement data. Quality of daily solar irradiance is characterized by a newly proposed parameter, POP-KD. This characterized daily quality is varying and uncertain at the middle level of the quantity, but high and more certain at very high and low quantity levels. In addition, the proposed characterization method shows interesting results for KD and POP-KD: a statistical consistency for multiple years and similarity for their seasonal trends. The classification results also indicate an existence of dominant classes, and transitions between the dominant classes are significant for all locations. This dissertation also generates annual synthetic sequences of KD and POP-KD using a Markov approach. The generated sequences show statistical similarities with observed sequences. Secondly, this dissertation proposes methodologies to estimate day-ahead solar irradiance using the National Weather Service (NWS) sky cover forecast. For model development, this paper splits up a direct estimation process from the sky cover forecast to solar irradiance into two stages: forecast verification and cloud-to-irradiance conversion. Uncertainty for each stage and for the overall estimation process is quantified. NWS forecast uncertainty (about 20%) is identified as the main source of uncertainty for the overall process. In addition, verification of the sky cover forecast shows approximately 20% overestimated bias at days with a high irradiance level. Thus, the NWS sky cover forecast needs to be adjusted based on the type of day. This dissertation also proposes a conversion equation relating daily quantity of cloud information and daily quantity of solar irradiance. The proposed conversion equation achieves accuracy with simplicity. Five day-ahead solar irradiance quantity estimation methods are proposed in this dissertation. The proposed methods incorporate different schemes for dealing with the bias discovered in the cloud forecast. The observed data are regularly found within the 95% confidence intervals of the estimated values. Estimation results demonstrate the effectiveness of the conditional adjustment schemes at different irradiance levels. Lastly, this dissertation proposes a methodology to estimate day-ahead solar irradiance using fluctuation information of the NWS sky cover forecast. POP-KD was used as a parameter for the quality of daily solar irradiance. POP-KD efficiently represents the quality of daily solar irradiance. In addition, POP-KD indicates the probability that solar irradiance variability is within the ramp rates of common generators in power systems at a certain photovoltaic penetration level. This dissertation also proposes a new equation for the conversion from cloud fluctuation information to daily quality of surface solar irradiance. The proposed equation achieves accuracy. The proposed day-ahead solar irradiance quality estimation method is based on fluctuation information provided by the NWS sky cover forecast. This method uses a normalization approach to relate fluctuation of cloud forecast and fluctuation of cloud observation. The observed data are regularly found within the 95% CIs of the estimated values. / Ph. D.
22

The relationship between sky view factor and the brightness of the night sky

Törmänen, Samuel January 2024 (has links)
Light pollution is a problem that affects both living creatures as well as the perception of the night sky. As artificial lighting becomes more affordable and energy efficient, more and more lights are being used, further increasing the light pollution produced by us humans where cities with larger populations experience the largest amount of light pollution. There is however a knowledge gap in the field of light pollution regarding the possibility of a relationship between sky view factor and the brightness of the night sky. This study attempts to reduce that knowledge gap. By using cameras to take photos in different locations, the brightness of the night sky can be compared and together with the sky view factor of each location in can be determined if there exist such a relationship. Based on the results of this study, trends suggesting that this relationship exists emerges, however not to the extent that any definite conclusions can be drawn without further studies.
23

The fossil record of star formation from galaxy spectra

Panter, Ben January 2005 (has links)
In this thesis I present work using the MOPED algorithm to extract in a non-parametric fashion star formation histories and galaxy masses from the spectra of galaxies in the Sloan Digital Sky Survey. The recovered parameters for all galaxies are combined to give insight into the processes of star and galaxy formation on both individual galaxy and cosmic scales. The MOPED algorithm allows use of the entire spectral range, rather than concentrating on specific features, and can be used to estimate the complete star formation history without prior assumptions about its form. By combining the star formation histories of 96,545 galaxies in the redshift range 0 < z < 0:34 the cosmic star formation rate is determined from the present day to z ~ 6. The results show that the peak of star formation occurred at z ~ 0:6, and that 26% of the mass of stars in the present-day Universe was formed at z ~ 2. The average metallicity rises from Z/Z= 0:44 at high redshift to a peak of 0:8 at z ~ 1 before declining to a level around 0.25 atthe present day. Although the peak in star formation is more recent than previously thought, the sample used includes galaxies with a range of masses not accessible to traditional studies, down to a limit of L ~ 2 x 10-3L*. By cutting the sample into ranges of mass it can be seen that the redshift at which starformation activity peaks is an essentially monotonically increasing function of final stellar mass. The time of the peak in star formation ranges from z > 2 for the highest mass galaxies (MS < 1012M) to z ~ 0:2 for the lowest (MS < 1010M). A typical L* galaxy appears to have its peak at around z » 0:8. These differences in star formation with mass reconcile the redshift of the peak found in this work with the previous estimates, generally deep surveys only probe the SFR of galaxies with MS < ML*. The stellar mass calculated using the reconstructed spectra eliminates contamination from either emission lines or AGN components. Using these masses it is possible to construct the mass function for the stellar mass component of galaxies which give excellent agreement with previous works, but extend their range by more than two decades in mass to 10 7.5 < Ms/h-2M < 1012. I present both a standard Schechter fit and a fit modified to include an extra, high-mass contribution, possibly from cluster cD galaxies. The Schechter fit parameters are phi* = (7:8 +/- 0:1) £ 10-3h3Mpc-3, M* = (7.64 +/- 0.09) x 10*10h-2M and alpha = -1.159 +/- 0.008. The sample also yields an estimate for the contribution from baryons in stars to the critical density of omega b*h = (2.39+/-0.08)x10-3, in good agreement with other indicators. No evolution of the mass function in the redshift range 0:05 < z < 0:34 is apparent, indicating that almost all stars were already formed at z » 0:34 with little or no star formation activity since then and that the evolution seen in the luminosity function must be largely due to stellar fading. The star formation history can be interpreted as a measure of how gas was transformed into stars as a function of time and stellar mass: the Baryonic Conversion Tree (BCT). There is a clear correlation between early star formation activity and present-day stellar mass: the more massive galaxies have formed about 80% of their stars at z > 1, while for the less massive ones the value is only about 20%. Comparing the BCT to the dark matter merger tree indicates that star formation efficiency at z > 1 had to be high (as much as 10%) in galaxies with present-day stellar mass larger than 2 x 10*11M, if this early star formation occurred in the main progenitor. The LCDM paradigm can accommodate a large number of red objects; it is the high efficiency in the conversion from gas to stars that needs to be explained. On the other hand, in galaxies with present-day stellar mass less than 10*11M, efficient star formation seems to have been triggered at z ~ 0:2. This work shows that there is a characteristic mass (M » 10*10M) for feedback efficiency (or lack of star formation). For galaxies with masses lower than this, feedback (or star formation suppression) is very efficient while for higher masses it is not. The BCT, determined here for the first time, should be an important observable with which to confront theoretical models of galaxy formation.
24

Cosmological parameter estimation with QUaD CMB polarization and temperature experiment

Memari, Yasin January 2009 (has links)
In this thesis we examine the theoretical origin and statistical features of the Cosmic Microwave Background radiation. We particularly focus on the CMB power spectra and cosmological parameter estimation from QUaD CMB experiment data in order to derive implications for the concordance cosmological model. In chapter 4 we present a detailed parameter estimation analysis of the combined polarization and temperature power spectra from the second and third season observations of the QUaD experiment. QUaD has for the first time detected multiple acoustic peaks in the polarization spectrum, allowing meaningful parameter analyses from the polarization data alone. In a standard 6-parameter ACDM parameter estimation analysis we find the QUaD TT power spectrum to be in very good agreement with previous results. However, the QUaD polarization data shows some tension with ACDM model. The origin of this 1−2σ tension remains unclear, and may point to new physics, residual systematics or simple random chance. Combining polarization and temperature data we find an acceptable fit, and show that our results are dominated by the polarization signal. We combine QUaD with the five-year data from the WMAP satellite and the SDSS Luminous Red Galaxies 4th data release power spectrum, and extend our analysis to constrain the tensor-to-scalar ratio and the primordial isocurvature perturbations. Our analysis sets a benchmark for future polarization experiments. In chapter 5 we outline and test a new semi-analytical approach for the estimation of the pseudo- temperature and polarization CMB power spectra for experiments with incomplete sky coverage. We propose a method for constructing the mode-mode coupling matrices which connect the temperature and polarization pseudo-Cℓ’s to the unbiased all-sky bandpowers in the flat sky approximation. We apply this method to the apodization masks of the QUaD CMB experiment and we show that the true underlying bandpowers can be reconstructed from the simulated QUaD-like pseudo-Cℓ’s to high precision. We further investigate the possibility of extending the proposed analytical flat sky approach to the exact calculation of the PCL covariance matrices over a large range of multipoles and we find that the numerical calculation is extremely computationally expensive. The flat sky pseudo-Cℓ and covariances methods presented in this chapter are still work in progress and require more testing.
25

Aiding the Pilot in Flight Control Fault Detection

Chiecchio, Jerome Jose Andres 21 January 2005 (has links)
Three flight simulator experiments examined how a health monitoring system may aid pilots in detecting flight control faults. The first experiment introduced an unexpected fault in the flight control system during an approach to a fictitious airport. The second experiment used a factorial design of (1) presence ?? notof a Fault Meter display and (2) presence ?? not ?? an Alerting System, which could have one or two phased alerts. In half the runs, a fault was triggered at some point, and pilot response was recorded. The next experiment comprised one flight in which pilots were given a false alarm by these systems, testing for automation bias. No consistent pilot response was found to the faults, with pilots sometimes successfully landing the aircraft, sometimes immediately or eventually initiating a go-around, and sometimes loosing aircraft control and crashing. The pilots were not able to identify the fault in 11% of the cases. Tunnel tracking error increased following the faults and the false alarm, suggesting it may be both a manifestation of attempts to diagnose a fault and a cue to pilots of a problem. Finally, the triggering of a false alarm showed the existence of automation bias induced after a small number of interactions with the HMS.
26

Pilgrimage to the Night Sky

Hosein, Vincent 12 January 2015 (has links)
The purpose of the Pilgrimage to the Night Sky is to encourage a self driven journey of rediscovering the beauty and simple pleasure of looking up and seeing a star-filled sky. The goal is to create two sites in the landscape that will act as the starting points to this pilgrimage by showcasing the stars in the night sky and will nurture the curiosity of those who have an interest in the heavens. A progression approach is meant to be experienced while on this journey, with the first stage of the pilgrimage taking place in Assiniboine Forest. The second stage of the pilgrimage takes place ten minutes south of the city at Glenlea Observatory which hosts an exponential increase of stars in the night sky. The practicum concludes with an assortment of resources people can use to continue their pilgrimage and search for their darkest night sky.
27

O VI absorbers in SDSS spectra

Frank, Stephan, January 2008 (has links)
Thesis (Ph. D.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 195-199).
28

Satellite monitoring of current and historical development patterns in Big Sky, Montana 1990-2005 /

Campos, Natalie Monique. January 2008 (has links) (PDF)
Thesis (MS )--Montana State University--Bozeman, 2008. / Typescript. Chairperson, Graduate Committee: Rick L. Lawrence. Includes bibliographical references (leaves 71-77).
29

Microwave observations of the Southern sky from the TopHat experiment : the cosmic microwave background and the Magellanic clouds /

Bezaire, Jeffery J. January 2003 (has links)
Thesis (Ph. D.)--University of Chicago, Dept. of Physics, June 2003. / Includes bibliographical references. Also available on the Internet.
30

Vers le ciel : Le ciel peint au Pakistan et en Occident comme enjeu épistémologique majeur / Towards the sky : The sky painted in Pakistan and in the West like their epistemological issues.

Umar, Sophiya 18 October 2013 (has links)
La thèse s’appuie sur une comparaison approfondie entre la peinture pakistanaise et la peinture occidentale. Cette dernière se caractérise le plus souvent par des genres (portraits, paysages…) des motifs, souvent exécutés à l’huile à la manière européenne classique. Dans la peinture occidentale (principalement la production française, anglaise et américaine à partir du XIXe siècle) la thèse explore une véritable sémantique du ciel.Notre propre production picturale se situant de manière complexe à mi-chemin entre les deux cultures, définit ainsi une sorte de jeu dans un entre-deux riche de sens.Il s’agit donc de décrire cet interstice avec précision, de développer les rapports poétiques et philosophiques que nous entretenons avec le ciel par notre propre pratique de la peinture et d’évaluer la nature exacte des paradigmes culturels qui sont désormais les nôtres.Bien entendu, s’agissant d’une thèse en arts plastiques, sont étroitement mêlées, réflexions historiques, critiques, esthétiques, la création proprement dite d’œuvres picturales ainsi que leur interprétation. / This thesis is based on a deep comparative study between Pakistani paintings and the Western paintings. The paintings in Pakistan are often characterized by genres (portraits, landscapes...), patterns, executed in oil in resemblance with classical European style. In Western paintings (mostly French productions, American and English from the nineteenth century), the thesis explores a true semantics of the sky in paintings.Our own pictorial production, located in a halfway between the two cultures, defines a kind of game in a wide sense.It is therefore to describe this interstice with precision, and develop our poetic and philosophical relationship by our own practice of paintings, relating to the subject of sky. We evaluate the exact nature of the cultural paradigms, which are now ours.Of course, as it is the thesis in the domain of fine-arts, it is intertwined, with historical reflections, criticism, and aesthetics, with addition to the actual creation of painting work and their interpretations which is also a part of this research work.

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