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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.
1

Submillimetre astronomy

Eve, W. D. January 1981 (has links)
No description available.
2

Ancient astronomy

Middleton, Stephen Douglas January 1910 (has links)
No description available.
3

Ancient astronomy

Middleton, Stephen Douglas January 1910 (has links)
No description available.
4

AIRBORNE INFRARED ASTRONOMY

AUMANN, HARTMUT HANS-GEORG January 1970 (has links)
No description available.
5

RFI mitigation in radio astronomy

Thompson, Nicholas Christopher 04 1900 (has links)
Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Technical advances in electromagnetics, signal processing and processing power have led to a significant increase in sensitivity and accuracy in radio telescopes. With this increase in sensitivity, radio frequency interference (RFI) has become a much larger problem. The notable growth in wireless communication as well as self generated RFI has further escalated this problem. In order to utilise the full capabilities of modern radio telescopes, RFI mitigation is required on the captured signals. With the enormous data rates of modern radio telescopes, managing RFI has become increasingly difficult, and in order to utilise the full captured radio spectrum, more accurate RFI mitigation strategies will be necessary. The use of different RFI mitigation strategies is studied in the form of online and offline techniques. This includes Spectral Kurtosis, Spectral Flatness and the Var/SumThreshold method. The special case for RFI mitigation in timing pulsars will also be studied. These techniques are well known in the radio astronomy community; here, spectral kurtosis and spectral flatness will be implemented on the raw data as well as the post correlated data. System speed and accuracy will be the deciding factors when testing these methods as possible solutions to this problem. / AFRIKAANSE OPSOMMING: ‘n Toename in die sensitiwiteit van hedendagse radioteleskope kan toegedra word aan die tegniese bevordering in elktromagnetika en seinverwerking. Die toename in sensitiwiteit het egter tot die gevolg dat radiofrekwensiesteuring ‘n groter rol speel in hedendaagse radioteleskope. Die groei in die gebruik van radioverbindings asook die gevolge van self gei¨nduseerde radiofrekwensiesteuring dra ook verder by tot hierdie probleem. Radiofrekwensiesteuring matiging word toegepas op die opgevangde seine, om sodoende gebruik te maak van die volle kapasiteit van moderne radioteleskope. Die bestuur van radiofrekwensiesteuring word bemoeilik deur die groot hoeveelheid intydse data van die radioteleskope. Meer akurate radiofrekwensiesteuring matigingstegnieke word vereis om die bandwydte ten volle te hanteer. Daar word op ‘n aantal verskillende matingstegnieke gefokus. Hierdie tegenieke kan in twee kategorieë verdeel word, naamlik aanlyn- en aflyntegenieke. Onderafdelings van hierdie kategorieë sluit in: spektrale kurtose, spektrale matheid en “Var/SumThreshold”. Daar word ook na ‘n spesiale geval van radiofrekwensiesteuring matiging gekyk, in die opmeeting van tydsberekening-pulsars. Alhoewel hierdie tegnieke bekend is in die radioastronomie gemeenskap, word spektrale kurtose en spektrale matheid egter toegepas op die rou data sowel as postgekorreleerde data. Daar sal op stelsel spoed en akuratheid gefokus word, om vas te stel of hierdie metodes wel moontlike oplossings bied tot die probleem bespreek.
6

Spectroscopic mode identification in a sample of non-radially pulsating stars : a thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Astronomy at the University of Canterbury /

Wright, Duncan John. January 2008 (has links)
Thesis (Ph. D.)--University of Canterbury, 2008. / Typescript (photocopy). Includes bibliographical references (p. 190-195). Also available via the World Wide Web.
7

Analysis of three close eclipsing binary systems : BP Velorum, V392 Carinae and V752 Centauri : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Science, University of Canterbury /

Schumacher, Hana Josephine. January 2008 (has links)
Thesis (M. Sc.)--University of Canterbury, 2008. / Typescript (photocopy). Includes bibliographical references (p. 66-68).
8

Image reconstruction in radio astronomy with non-coplanar synthesis arrays

Goodrick, Lee 03 1900 (has links)
Thesis (MEng)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Traditional radio astronomy imaging techniques assume that the interferometric array is coplanar, with a small field of view, and that the two-dimensional Fourier relationship between brightness and visibility remains valid, allowing the Fast Fourier Transform to be used. In practice, to acquire more accurate data, the non-coplanar baseline effects need to be incorporated, as small height variations in the array plane introduces the w spatial frequency component. This component adds an additional phase shift to the incoming signals. There are two approaches to account for the non-coplanar baseline effects: either the full three-dimensional brightness and visibility model can be used to reconstruct an image, or the non-coplanar effects can be removed, reducing the three dimensional relationship to that of the two-dimensional one. This thesis describes and implements the w-projection and w-stacking algorithms. The aim of these algorithms is to account for the phase error introduced by non-coplanar synthesis arrays configurations, making the recovered visibilities more true to the actual brightness distribution model. This is done by reducing the 3D visibilities to a 2D visibility model. The algorithms also have the added benefit of wide-field imaging, although w-stacking supports a wider field of view at the cost of more FFT bin support. For w-projection, the w-term is accounted for in the visibility domain by convolving it out of the problem with a convolution kernel, allowing the use of the two-dimensional Fast Fourier Transform. Similarly, the w-Stacking algorithm applies a phase correction in the image domain to image layers to produce an intensity model that accounts for the non-coplanar baseline effects. This project considers the KAT7 array for simulation and analysis of the limitations and advantages of both the algorithms. Additionally, a variant of the Högbom CLEAN algorithm was used which employs contour trimming for extended source emission flagging. The CLEAN algorithm is an iterative two-dimensional deconvolution method that can further improve image fidelity by removing the effects of the point spread function which can obscure source data. / AFRIKAANSE OPSOMMING: Tradisionele beeldvormingstegnieke in radio-astronomie aanvaar dat die interferometriese skikking samevlakkig is. Dit beteken dat die twee-dimensionele Fourier verhouding tussen helderheid en sigbaarheid geldig bly en dat die Vinnige Fourier Transform aangewend kan word. Klein hoogtevariasies in die skikkingsvlak bring die w-ruimtelike frekwensiekomponent mee, wat ’n faseverskuiwing in die inkomende seine tot gevolg het. Dus, in praktyk, moet die bydrae van die nie-samevlakkige basislyneffekte in ag geneem word om sodoende die akkuraatheid van die data te verhoog. Twee benaderings kan gevolg word om die nie-samevlakkige basislyneffekte in ag te neem: Metodes wat die volle drie dimensionele helderheid en sigbaarheidsmodel gebruik kan toegepas word om ’n beeld te herbou, andersins kan die nie-samevlakkige effekte verwyder word om sodoende die drie-dimensionele verhouding te verminder tot ’n twee-dimensionele verhouding. Hierdie tesis beskryf en implementeer die ‘w-projeksie’ en ‘w-stapel’ algoritmes. Die doel van hierdie algoritmes is om die fasefout wat deur nie-samevlakkige sinteseskikkingskonfigurasies veroorsaak word, reg te stel. Hierdie regstelling maak die herwinde sigbaarheid van die beeld meer getrou aan die werklike helderheidsverspreidingsmodel. ’n Bykomende voordeel van die algoritmes is beeldvorming van wye-veld ruimtewaarnemings. In ‘w-projection’ word die w-term in die sigbaarheidsdomein in ag geneem deur die ruimtelike frekwensiekomponent met behulp van ’n konvolusiekern vanuit die probleem te verwyder. Die twee-dimensionele Vinnige Fourier Transform kan gevolglik toegepas word. Soortgelyk hieraan, wend die ‘w-Stacking’ algoritme ’n fasekorreksie aan tot ’n reeks beeldlae, om sodoende ’n beeld te verkry wat die nie-samevlakkige basislyneffekte in ag neem. Die KAT7 teleskoop is gebruik in die simulasie en analiese van die tekortkominge en voordele van beide algoritmes. ’n Hibriede weergawe van die Högbom CLEAN algoritme is bykomend oorweeg. Hierdie algoritme is ’n iteratiewe twee-dimensionele dekonvolusiemetode wat die betroubaarheid van beelde verbeter deur die verskansingseffek van puntverspreidingsfunksies te verwyder. Verder gebruik die Högbom CLEAN algoritme kontoersnoeiing om uitgebreide bron-emisies te identifiseer.
9

Culprit and victim management RFI environment for a radio astronomy site

Van der Merwe, Carel 03 1900 (has links)
Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: A methodology is developed to manage the large number of RFI Culprits on a new Radio Telescope location such as the South African site being developed in the Karoo, both during construction and ongoing operations. The requirement for RFI control is presented, with brief reference to the more traditional methods used by other Radio Telescope observatories. The new approach is then presented, based on methods used in the engineering field of Logistic Engineering. Three case studies are used to illustrate how the approach can be applied. Finally, recommendations are made on how the approach can be implemented for new Radio Telescope projects. / AFRIKAANSE OPSOMMING: ‘n Metodolgie word ontwikkel vir die beheer van die groot aantal Radiofrekwensiesteurings oortreders by ‘n nuwe Radio Teleskoop terrein, soos die Suid Afrikaanse terrein wat huidiglik in die Karoo ontwikkel word. Die metodolgie geld beide gedurende konstruksie en gedurende bedryf. Die behoefte vir RFS beheer word aangebied, met kortlikse melding van die meer tradisionele metodes wat ander Radio Teleskoop Sterrewagte gebruik. ‘n Nuwe aanslag, gebaseer op die metodolgieë van Logistieke Ingenieurswese, word dan aangebied. Drie gevallestudies wys hoe hierdie nuwe aanslag toegepas kan word. Laastens word aanbevelings gemaak om hierdie nuwe aanslag met nuwe Radio Teleskoop projekte te implimenteer.
10

Legitimating Astronomy

Howard, Graham Unknown Date (has links)
Science is usually justified in terms of its utilitarian attributes. Modern professional astronomy has no obvious utilitarian rationale, yet it receives considerable resources to carry on its work. Concepts from the sociology of science and political sociology can be used to help explain this apparent puzzle. The means by which astronomy succeeds in procuring resources can be seen in terms of a process of legitimation. Professional astronomy justifies and explains itself to specific audiences, ensuring that funding agencies will see astronomy as worthy of support. Several activities are suggested as legitimation practices. The mechanics of funding are discussed, followed by a description of modern professional astronomy as a 'big science'. Boundary work and popularisation are examined as important legitimation practices. Boundary work constructs a path for astronomy that legitimises it by allying the field to successful sciences such as physics, and distancing it from other activities such as ufology and astrology. Astronomy is popular with the public, and this popularity gives rise to a groundswell of support, and is used to promote astronomy as educating a public that will support science in general. The professional structures of astronomy serve to mark out astronomers as an elite scientific group, with an esoteric knowledge that includes high levels of mathematics. Astronomers' specialist technical skills can be of use in a variety of situations, but the scientific and mathematical knowledge itself also contributes to successful legitimation. It is concluded that the primary rationale for the funding of astronomy is humanistic rather than utilitarian.

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