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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.
51

Chasing the Night: Understanding the Value of Enthusiasts in Dark Sky Tourism : An exploratory study

Lindén, Stephanie, Talp, Arvid January 2024 (has links)
In the academic field of tourism, a relatively new type of tourism called Dark Sky Tourism is emerging. In this touristic field, there is a lack of studies focused on the individual tourist perspective. Therefore, this paper explores the perceived values of Dark Sky Tourism (DST). This study uses a deductive exploratory approach to understand the characteristics of DST in the context of experience value and perceived value and to connect it with two different value typologies. The data were collected through a netnographic research method by analyzing five different social media platforms. Subsequently, thematic analysis was utilized to analyze the data. The analysis resulted in five correspondent themes that were relevant throughout all of the collected data. These themes are as follows: (1) Aesthetic Significance, (2) Therapeutic Experiences, (3) Exploration and Curiosity, (4) Low-budget Appeal, and finally, (5) Nature and Heritage. The results of this study provide a holistic picture of what DST is all about and what individual Dark Sky Tourists value in DST. Future potential DST destinations can use this study to understand how to build an optimal DST experience.
52

Active Lateral Secondary Suspension in a High-Speed Train to Improve Ride Comfort

Orvnäs, Anneli January 2009 (has links)
<p>Active secondary suspension in trains has been studied for a number of years, showing promising improvements in ride comfort. However, due to relatively high implementation and maintenance costs, active technology is not being used in service operation to a large extent. The objective of this study is to develop an active lateral secondary suspension concept that offers good ride comfort improvements and enables centring of the carbody above the bogies when negotiating curves at unbalanced speed. Simultaneously, the active suspension concept should be a cost-effective solution for future series production. The thesis consists of an introductory part and three appended papers.</p><p>The introductory part describes the concept of active secondary suspension together with different actuator types and control methods. Further, the present simulation model and applied comfort evaluation methods are presented. The introductory part also comprises a summary of the appended papers, an evaluation of track forces and suggestions for further work.</p><p>Paper A presents the initial development of an active lateral secondary suspension concept based on sky-hook damping in order to improve vehicle dynamic performance, particularly on straight tracks. Furthermore, a Hold-Off-Device (HOD) function has been included in the suspension concept in order to centre the carbody above the bogies in curves and hence avoid bumpstop contact. Preparatory simulations as well as the subsequent on-track tests in the summer of 2007 showed that the active suspension provides improved passenger ride comfort and has significant potential to be a cost-effective solution for future implementation.</p><p>In Paper B, measurement results from on-track tests performed in 2008 are presented. The active secondary suspension concept was slightly modified compared to the one presented in the first paper. One modification was the implementation of a gyroscope in order to enable detection of transition curves and to switch off the dynamic damping in these sections. Ride comfort in the actively suspended carbody was significantly improved compared to that in the passively suspended car. The satisfactory results led to implementation of the active suspension system in long-term tests in service operation in the beginning of 2009.</p><p>In Paper C, a quarter-car model in MATLAB has been used to investigate a more advanced control algorithm: <em>H</em><sub>∞</sub> instead of sky-hook. <em>H</em><sub>∞</sub> control provides more flexibility in the design process due to the possibility to control several parameters. In particular, this is done by applying weight functions to selected signals in the system. When comparing the two control strategies through simulations, the results show that <em>H</em><sub>∞</sub> control generates similar carbody accelerations at the same control force as sky-hook; however, the relative displacement displacement is somewhat lower.</p>
53

Population Structure of Yarrow's Spiny Lizard, Sceloporus jarrovii, and its Malarial Parasite, Plasmodium chiricahuae

Kaplan, Matthew Ezra January 2011 (has links)
Estimates from radiocarbon-dated packrat middens indicate that the high elevation woodland communities of the Madrean Sky Islands were continuous as recently as 8,000 to 12,000 years ago. A number of population studies on a diverse collection of taxa have investigated the extent to which the Madrean Sky Island system has limited gene flow among mountain ranges. The results of several of these studies indicate that population divergences may be more ancient than the Holocene. Yarrow’s spiny lizards, Sceloporus jarrovii, were sampled from eight sites representing seven mountain ranges. The populations of S. jarrovii are host to the malarial parasite, Plasmodium chiricahuae. DNA sequences from the lizards and their malarial parasites were used to reconstruct the evolutionary relationships and estimate the ages of the populations for both host and parasite. The findings of these analyses indicate that the sky island populations of S. jarrovii have been isolated for hundreds of thousands of years and did not experience gene flow during the last woodland expansion. In contrast, the results indicate that the malarial infection occurred more recently, possibly during the Holocene woodland expansion. In addition, the prevalence of the malarial infection was compared to multiple attributes of the lizards. This analysis revealed a negative relationship between the genetic diversity of the lizard populations and the prevalence of infection. Furthermore, lizard populations with lower prevalence of infection have a lower frequency of multiclonal infections.
54

An investigation of the propagation characteristics of a single frequency mid-latitude NVIS radio channel

Burgess, Samuel J. January 1999 (has links)
No description available.
55

The Sky in Our Mouths

Tyler, William Aldon 08 1900 (has links)
I believe that poetry has survived for thousands of years because it provides people with a transpersonal connection that they can't find elsewhere. I look for poetry that is more than an emotional expression, more than witty word play, and more than an interesting observation. I want poetry to give me that inspirational spark, that glimpse into a world beyond my own. Poems that succeed in doing this force me into a perspective that I haven't previously imagined by yoking together two or more seemingly disparate elements. This tension between the old elements and the new link between them creates energy for the poem. This poetic nexus contributes to the transpersonal experience that I seek.
56

In Pursuit of Women Scientists: Using Science Plays to Promote Women Entering STEM Disciplines

Hartman, Danielle 01 January 2016 (has links)
Higher education currently seeks to increase female enrollment in STEM. Women face many challenges attempting to breach this male dominated arena with misconceptions, gender stereotypes, and few female role models. With the recent trend in higher education to encourage more women to enter the STEM disciplines and K-12 schools cutting funding for arts programs, theatre may be losing its value in the education system. The value of interdisciplinary studies is beginning to be forgotten during the grade school years as school boards battle budget cuts, but we can remind society of it through science plays. Theatre artists use other disciplines such as psychology, history, and science to enhance their work, but I argue that theatre can also help promote the needs of other disciplines. Science plays have become increasingly popular over the last two and a half decades and have done much for theatre. Science plays can assist in addressing the issues facing women attempting to enter STEM disciplines. The majority of science plays feature historical people and can therefore provide the much needed role models and address the other issues and misconceptions. To do this, science plays featuring women should target middle and high school girls as well as their teachers, parents, and guidance counselors who often discourage girls from pursing STEM interests.
57

Determining the observer’s velocity using radio continuum surveys

Randriamiarinarivo, Nandrianina January 2019 (has links)
>Magister Scientiae - MSc / In the standard (‘concordance’) model of Cosmology, there is a fundamental assumption that the Universe is statistically isotropic and homogeneous on large scales, known as the Cosmological Principle. The Cosmological Principle requires that the dipole anisotropy apparent in the CMB should also be observed in galaxy number counts if this signal occurs due to the aberration and Doppler effects from our peculiar motion. This thesis will investigate the accuracy with which the cosmic kinematic dipole can be determined by comparing real data from NRAO VLA Sky Survey (NVSS) catalog with the simulated sky maps following its specifications. The mock maps are generated using FLASK code which assumes a lognormal distribution for the radio count density field from z=0 to z =4 and taking as an entry an angular power spectrum from CAMB which assumed a flat ΛCDM cosmology and a redshift distribution. After analising the kinematic dipole, we turn to the analysis of statistical isotropy in the catalog. We used ANalysis Of Variance (ANOVA) test on patches in the sky of different radii as one of the statistical tools for the analysis. We found that as we go to a higher radius for the patches, we have a better agreement between the theory and the observation as expected. We also saw that the more we are rigorous on the rejection criteria, the smaller is the discrepancy between the observed and simulated number count distribution in the sky. We found an optimum choice of 25◦ as patch size, and if the accepted patches have a maximum of 30% of their pixels masked. Therefore, we find that the NVSS data agrees with the fundamental assumption of statistical isotropy at angular scales > 20◦.
58

A detailed study of auroral fragments

Dreyer, Joshua January 2019 (has links)
Aurora occurs in various shapes, one of which is the hitherto unreported phenomenon of auroral fragments. For three periods of occurrence of these fragments their properties were studied in detail during this master’s thesis, using mainly ground-based instrumentation located near Longyearbyen on Svalbard, Norway. A base dataset was constructed from 103 all-sky camera images, manually marking 305 fragments for further analysis. This thesis reports and describes the fragment observations during the observed events, including the auroral and geomagnetic context. Fragments generally seem to fall into two categories, the first being singular, apparently randomly distributed fragments, and the second being periodic fragments that occur in groups with a regular spacing close to auroral arcs. A typical fragment has a small horizontal size below 20 km, a short lifetime of less than a minute and shows no field-aligned extent in the emission. The fragments appear mainly west of zenith (73%) during the three observation nights, whereas their north-south distribution is symmetric around the zenith. Almost all of them exhibit westward drift, the estimated speed for one of the fragments passing the field of view of ASK is ∼1 km/s. A spectral signature can be seen in the green auroral wavelength of O at 557.7 nm and red emission line of N2 at 673.0 nm, but no emission enhancement was observed in the blue wavelengths. One fragment passing the EISCAT Svalbard radar’s field of view shows a local ion temperature increase in a small altitude range of ∼15 km, whereas there is no visible increase in electron density. This could be explained by fragment generation due to locally strong horizontal electric fields. A potential mechanism for this might be electric fields of atmospheric waves superposing with the converging electric fields of auroral arcs created by particle precipitation and the corresponding field-aligned currents. The resulting field would be perpendicular to the magnetic field and the auroral arcs, leading to wave-like density variations of excited plasma close to the arcs. Further study is required to verify this hypothesis and improve the understanding of fragment properties determined from the limited dataset used for this thesis.
59

Novos métodos de estimação de ruído de fundo de céu aplicados à missão CoRoT. / New methods for estimating sky background noise applied to the CoRoT mission.

Coelho, Luciana Guidon 11 April 2012 (has links)
O satélite franco-europeu com participação brasileira, CoRoT (Convention, Rotation and planetary Transits), faz parte de uma missão espacial dedicada à sismologia estelar e à busca por exoplanetas. Para a descoberta de exoplanetas, o objetivo é detectar a ocultação temporária da estrela ao redor da qual orbita o planeta em questão, ou seja, detectar um trânsito planetário que pode ser traduzido por uma diminuição tênue do fluxo de fótons estelar coletado pelos CCDs do fotômetro. Existem alguns ruídos e diversas fontes de luz que atingem os CCDs e que não são provenientes das estrelas em estudo. Tais ruídos e fontes de luz geram uma iluminação chamada de fundo de céu nos CCDs que é não homogênea e que precisa ser corrigida antes do início da exploração científica dos dados obtidos nas observações do satélite. A correção de fundo de céu é um procedimento padrão na redução de dados fotométricos, e consiste na subtração do nível médio de fundo de céu das medições fotométricas de uma estrela. Para a determinação do fundo de céu o CoRoT utiliza um conjunto de janelas de fundo de céu. Este trabalho propõem métodos alternativos para a alocação destas janelas de fundo de céu e estimação do ruído de fundo de céu para o canal de exoplanetas do satélite CoRoT. São apresentados dois novos métodos de alocação de janelas e são testados diversos métodos de estimação de ruído de fundo de céu. Os testes realizados neste trabalho sugerem fortemente a utilização do método chamado k-min para a alocação de janelas e do método mediana e 5 vizinhos para a estimação de ruído de fundo de céu. O método k-min procura alocar as janelas de maneira homogênea e em locais de mínimo de uma imagem do céu observado pelo satélite e o método mediana e 5 vizinhos estima o ruído de fundo de céu a partir da mediana de todas as janelas de fundo de céu com nível DC corrigido pela mediana das cinco janelas vizinhas mais próximas. / The French-European satellite with Brazilian participation, CoRoT (Convention, Rotation and planetary Transits), is part of a space mission dedicated to stellar seismology and exoplanets search. Both scientific programs are based on a high-precision photometry and require long-term uninterrupted observations. The satellite uses stellar photometry from images captured on CCD (charged coupled devices), known as photometry by mask. For the discovery of exoplanets, the goal is to detect the temporary hiding of the star which around orbits the planet in question, that is, to detect a planetary transit, which can be translated by a slight decrease in the stellar photon flux collected by the CCDs of the photometer. There are some noise and various sources of light that reaches the CCD and are not from the stars under study. Such noise and light sources produce a light called \"sky background\" in CCDs that is not homogeneous and that must be corrected before the scientific exploration of the data obtained from satellite observations. The sky background correction is a standard procedure in the reduction of photometric data. It consists in subtracting the average level of sky background of photometric measurements of a star. To determine the sky background noise, CoRoT uses a set of sky background windows and this work proposes alternative methods for allocating these windows and for estimating the sky background noise to the CoRoT exoplanet channel. Here are present two new methods of windows allocation and are tested several methods of estimating the sky background noise. Tests conducted in this study strongly suggest the use of the method called k-min for windows allocation and the method \"median and 5 neighbors\" to the estimation of sky background noise. The k-min method tries to allocate windows homogeneously and in minimum locals of image of the sky observed by the satellite, and the method \"median and 5 neighbors estimates the sky background noise by the median of all background windows with DC level corrected by the median of the five nearest neighbors.
60

Novos métodos de estimação de ruído de fundo de céu aplicados à missão CoRoT. / New methods for estimating sky background noise applied to the CoRoT mission.

Luciana Guidon Coelho 11 April 2012 (has links)
O satélite franco-europeu com participação brasileira, CoRoT (Convention, Rotation and planetary Transits), faz parte de uma missão espacial dedicada à sismologia estelar e à busca por exoplanetas. Para a descoberta de exoplanetas, o objetivo é detectar a ocultação temporária da estrela ao redor da qual orbita o planeta em questão, ou seja, detectar um trânsito planetário que pode ser traduzido por uma diminuição tênue do fluxo de fótons estelar coletado pelos CCDs do fotômetro. Existem alguns ruídos e diversas fontes de luz que atingem os CCDs e que não são provenientes das estrelas em estudo. Tais ruídos e fontes de luz geram uma iluminação chamada de fundo de céu nos CCDs que é não homogênea e que precisa ser corrigida antes do início da exploração científica dos dados obtidos nas observações do satélite. A correção de fundo de céu é um procedimento padrão na redução de dados fotométricos, e consiste na subtração do nível médio de fundo de céu das medições fotométricas de uma estrela. Para a determinação do fundo de céu o CoRoT utiliza um conjunto de janelas de fundo de céu. Este trabalho propõem métodos alternativos para a alocação destas janelas de fundo de céu e estimação do ruído de fundo de céu para o canal de exoplanetas do satélite CoRoT. São apresentados dois novos métodos de alocação de janelas e são testados diversos métodos de estimação de ruído de fundo de céu. Os testes realizados neste trabalho sugerem fortemente a utilização do método chamado k-min para a alocação de janelas e do método mediana e 5 vizinhos para a estimação de ruído de fundo de céu. O método k-min procura alocar as janelas de maneira homogênea e em locais de mínimo de uma imagem do céu observado pelo satélite e o método mediana e 5 vizinhos estima o ruído de fundo de céu a partir da mediana de todas as janelas de fundo de céu com nível DC corrigido pela mediana das cinco janelas vizinhas mais próximas. / The French-European satellite with Brazilian participation, CoRoT (Convention, Rotation and planetary Transits), is part of a space mission dedicated to stellar seismology and exoplanets search. Both scientific programs are based on a high-precision photometry and require long-term uninterrupted observations. The satellite uses stellar photometry from images captured on CCD (charged coupled devices), known as photometry by mask. For the discovery of exoplanets, the goal is to detect the temporary hiding of the star which around orbits the planet in question, that is, to detect a planetary transit, which can be translated by a slight decrease in the stellar photon flux collected by the CCDs of the photometer. There are some noise and various sources of light that reaches the CCD and are not from the stars under study. Such noise and light sources produce a light called \"sky background\" in CCDs that is not homogeneous and that must be corrected before the scientific exploration of the data obtained from satellite observations. The sky background correction is a standard procedure in the reduction of photometric data. It consists in subtracting the average level of sky background of photometric measurements of a star. To determine the sky background noise, CoRoT uses a set of sky background windows and this work proposes alternative methods for allocating these windows and for estimating the sky background noise to the CoRoT exoplanet channel. Here are present two new methods of windows allocation and are tested several methods of estimating the sky background noise. Tests conducted in this study strongly suggest the use of the method called k-min for windows allocation and the method \"median and 5 neighbors\" to the estimation of sky background noise. The k-min method tries to allocate windows homogeneously and in minimum locals of image of the sky observed by the satellite, and the method \"median and 5 neighbors estimates the sky background noise by the median of all background windows with DC level corrected by the median of the five nearest neighbors.

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