abstract: The universe since its formation 13.7 billion years ago has undergone many changes. It began with expanding and cooling down to a temperature low enough for formation of atoms of neutral Hydrogen and Helium gas. Stronger gravitational pull in certain regions caused some regions to be denser and hotter than others. These regions kept getting denser and hotter until they had centers hot enough to burn the hydrogen and form the first stars, which ended the Dark Ages. These stars did not live long and underwent violent explosions. These explosions and the photons from the stars caused the hydrogen gas around them to ionize. This went on until all the hydrogen gas in the universe was ionized. This period is known as Epoch Of Reionization. Studying the Epoch Of Reionization will help understand the formation of these early stars, the timeline of the reionization and the formation of the stars and galaxies as we know them today. Studying the radiations from the 21cm line in neutral hydrogen, redshifted to below 200MHz can help determine details such as velocity, density and temperature of these early stars and the media around them. The EDGES program is one of the many programs that aim to study the Epoch of Reionization. It is a ground-based project deployed in Murchison Radio-Astronomy Observatory in Western Australia. At ground level the Radio Frequency Interference from the ionosphere and various man-made transmitters in the same frequency range as the EDGES receiver make measurements, receiver design and extraction of useful data from received signals difficult. Putting the receiver in space can help majorly escape the RFI. The EDGES In Space is a proposed project that aims at designing a receiver similar to the EDGES receiver but for a cubesat. This thesis aims at designing a prototype receiver that is similar in architecture to the EDGES low band receiver (50-100MHz) but is significantly smaller in size (small enough to fit on a PCB for a cubesat) while keeping in mind different considerations that affect circuit performance in space. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2019

This project is about the asymmetry of time. The main source of discontent for physicists and philosophers alike is that even though in every physical theory we developed and/or discovered for explaining how the universe functions, the laws are time reversal invariant; there seems to be a very genuine asymmetry between the past and the future. The aim of this project is to examine several attempts to solve this friction between the laws of physics and the asymmetry and provide a new proposal that makes use of modern cosmology. In the recent history of physics and in contemporary philosophy of science there have been several attempts to explain the asymmetry of time and reconcile this asymmetry with time reversal invariant physical laws. David Albert developed one of the most recent attempts at solving the problem in Time and Chance (2000). Albert claims that there is a conclusive solution to the problem of asymmetry of time: namely, combining the laws of mechanics with several novel concepts that he introduces, the most important of which is what he calls "the past hypothesis". Eric Winsberg developed another modern attempt to solve the problem of the asymmetry of time. Winsberg combines Hans Reichenbach's branch systems proposal with a "framework" view of laws to solve the problem. Although this version of the branch systems proposal overcomes several problems associated with Reichenbach's original construction of the proposal, certain aspects of it are still open to critique. Following a brief introduction, my chapters include 1) a history of the problem of the asymmetry of time, in which I provide a historical overview of the issues particularly discussed by Boltzmann and his interlocutors, 2) a detailed evaluation of David Albert's account of the asymmetry of time, where he argues that we can solve all the problems if we use a combination of laws of physics and the past hypothesis, 3) a detailed overview of Eric Winsberg's account that depends a specific way of looking at the laws of physics--the framework view, and 4) my account, which attempts to solve the problem of the asymmetry of time, making extensive use of the developments on modern cosmology, specifically regarding the inflationary mechanism. I claim that if we take into account recent developments in modern cosmology and proposals for laws for initial conditions, then we cannot maintain the metaphysical status of the past hypothesis in Albert's project. Specifically, I argue that in order for a theory to make use of initial conditions of the universe, it has to include a set of laws from modern cosmology pertaining to that initial condition. I defend the position that inflation can supply the source of asymmetry when supported by the aggregate view of laws, which I introduce in the last chapter. The explanation of the asymmetry of time requires the use of dynamical equations from modern cosmology that would produce the boundary conditions. The boundary condition produced in this way would fill in for the source of the asymmetry of time. Consequently, I argue that the explanation of the asymmetry of time is encoded in the laws of modern cosmology.

In the past historians have used the works of Honorius Augustodunensis to answer the question of who he was. In doing this the intellectual importance of his work has often been overlooked. Honorius was one of the most popular writers of the early twelfth century, and his most popular work was the Imago Mundi. The purpose of this study is to examine the work and its historical context and to furnish an English translation of the complete text. The present work looks at each book of the Imago Mundi and its sources to develop a concept of Honorius' writing style and his methods. It also examines twelfth-century manuscripts of the Imago Mundi and their houses of origin to construct a reason for the work's popularity, both in Honorius' own time and for centuries after.

Bibliography: leaves 100-106. Studies different models of "quintessence", in particular, a quintessence arising from an ultra-light pseudo Nambu-Goldstone boson. Overviews dynamical properties for these models using phase-space analyses to study attractor and tracker solutions. Studies high-redshift type Ia supernovae constraints on these models. Studies the impact of a simple phenomenological model for supernovae luminosity evolution on the PNGB models and the potentials of a future supernovae data set to discriminate the PNGB models over the other quintessence models. Studies gravitational lensing statistics of high luminosity quasars upon the quintessence models.

A land ethic within the built enviroment was examined from the perspective of the surveying community in New Zealand. The research followed a structure of context, interpretation and application; used legal analysis; and, sampled the ideologies of iwi liason officers, consultant surveyors, and local authorities. Context involved asking why a land ethic was being debated, by focusing on the current level of environmental thought, and on the actions of the International Federation of Surveyors (FIG) and the New Zealand Institute of Surveyors (NZIS). Some findings are: that terms such as sustainable management and nature are ambiguous cultural constructs; and, that the adoptation of an environmental policy by the NZIS continues to be a tortuous process. Interpretation involved asking what constituted a New Zealand ethic, by putting such an ethic into perspective in relation to ecophilosophy, and by searching for a contemporary sense of kaitiakitanga. Some findings are: that restraint and humility are requirements in any moral theory of nature; that kaitiakitanga is not dependent on title to land; and, that iwi liason officers are divided as to how kaitiakitanga applied to the built environment. Application involved suggesting how a land ethic could be invoked in the built environment, through the provision of green space in the form of local purpose reserves. Some findings are: that surveyors regard reserves as being significantly less vital to a community�s well-being than engineered services; and, that local authorities are not generally aware that reserve policies might have to be linked to municipal open space strategies. The broad conclusions are: that regardless of the environment that now exists, surveyors will be required to make moral choices about the environment that is sought; that a land ethic will not necessarily provide rational prescriptions directing action towards land; and, that there is inherent tension between land tenure, land use and a land ethic. Suggested avenues for further research include a comparative analysis of other landed professions; the empowerment of women within any land ethic; and, the use of content analysis as an alternative methodology.

Bibliography: leaves 100-106. / v, 107 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Studies different models of "quintessence", in particular, a quintessence arising from an ultra-light pseudo Nambu-Goldstone boson. Overviews dynamical properties for these models using phase-space analyses to study attractor and tracker solutions. Studies high-redshift type Ia supernovae constraints on these models. Studies the impact of a simple phenomenological model for supernovae luminosity evolution on the PNGB models and the potentials of a future supernovae data set to discriminate the PNGB models over the other quintessence models. Studies gravitational lensing statistics of high luminosity quasars upon the quintessence models. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physics and Mathematical Physics, 2001

Cette thèse porte sur l'étude du rayonnement cosmique nucléaire chargé d'énergie comprise entre quelques centaines de MeV et 1~TeV. Celle-ci peut apporter des réponses à des questions aussi fondamentales que l'asymétrie entre matière et antimatière primordiales, la nature de la matière sombre ou la propagation du rayonnement cosmique. L'étude de ces phénomènes passe par la détection d'antimatière légère. Or l'interaction du rayonnement cosmique primaire au voisinage de la terre conduit à la production et au piégeage de particules secondaires, dont des noyaux légers d'antimatière. Ce travail vise à caractériser cette dernière composante de bruit physique pour des expériences ballons ou satellites. Ceci a été mené à bien grâce à une simulation Monte-Carlo tridimensionnelle prenant en compte de manière réaliste les interactions nucléaires. Cette étude montre en particulier l'importance du phénomène de piègeage magnétique et de l'interaction inélastique non-annihilante pour les particules présentes à 400~km d'altitude. La deuxième partie porte sur l'étude de l'imageur annulaire Cherenkov de l'expérience AMS qui permettra d'effectuer une séparation isotopique du rayonnement cosmique nucléaire chargé. La résolution en vélocité du détecteur a donc été étudiée lors de tests cosmiques et sous faisceau. Il en ressort que le détecteur est compris et que ses performances sont conformes aux attentes. Enfin, un travail de simulation prenant en compte le trigger et l'efficacité de détection d'AMS a été entrepris sur le rapport isotopique $^(10)$Be/$^(9)$Be qui montre les capacités d'AMS pour la contrainte des paramètres astrophysiques de propagation du rayonnement cosmique.

L'observatoire Pierre Auger vise à observer les évènements les plus violents de l'univers afin d'en découvrir les origines. Le premier site de cet observatoire, en cours de construction en Argentine, sera constitué de 1600 détecteurs au sol et de 4 télescopes d'observation de la fluorescence dans l'atmosphère. De par sa taille gigantesque, cet observatoire est le plus grand au monde. La présence d'eau en hiver sur une grande partie de la Pampa, et aussi, la grande surface rend l'accès difficile à la majorité des détecteurs. Les conditions difficiles d'environnement (variations thermiques, air salin et humidité) et la nécessité d'un fonctionnement permanent pendant 20 ans, imposent la recherche constante de la fiabilité à toutes les étapes du projet. Après une description nécessaire de l'ensemble de l'observatoire, ce mémoire décrit l'électronique des détecteurs de surface de l'observatoire Pierre Auger et les étapes de sa conception. La fiabilité constitue un problème prédominant de ce mémoire, en particulier en ce qui concerne :<ul><li>La recherche de la fiabilité optimale lors de la conception</li><li>L'évaluation de la fiabilité et la mise en place des stratégies de maintenance</li><li>La gestion de production (mise en place des procédures qualité, choix de l'entreprise, dossier de fabrication...) : de la qualité de production dépend la fiabilité du produit</li><li>Le déverminage qui permet d'éliminer les "défauts de jeunesse"</li><li>La mise au point des équipements de test</li><li>L'étude des performances des détecteurs, sa calibration et les méthodes de sélection des évènements. La bonne connaissance du fonctionnement des détecteurs constitue d'une part une approche système intéressante et d'autre part elle permet une identification rapide des défaillances</li><li>L'intégration, le suivi des cartes sur le terrain et la mise en place d'un retour d'expérience. L'expertise acquise peut profiter avantageusement à de futures expériences.</li></ul>

Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 197-204).

In the standard model of cosmology, the universe is currently dominated by dark energy in the form of the cosmological constant that drives the expansion to accelerate. While the cosmological constant hypothesis is consistent with all current data, models with dynamical behaviour of dark energy are still allowed by observations. Uncertainty also remains over whether the underlying assumption of a homogeneous and isotropic universe is valid, or if large-scale inhomogeneities in the matter distribution can be the cause of the apparent late-time acceleration.This thesis investigates inhomogeneous cosmological models in which dark energy clusters or where we live inside an underdense region in a matter-dominated universe. In both of these scenarios, we expect directional dependences in the redshift-luminosity distance relation of type Ia supernovae. Dynamical models of dark energy predict spatial variations in the dark energy density. Searches for angular correlated fluctuations in the supernova peak magnitudes, as expected if dark energy clusters, yield results consistent with no dark energy fluctuations. However, the current observational limits on the amount of correlation still allow for quite general dark energy clustering occurring in the linear regime. Inhomogeneous models where we live inside a large, local void in the matter density can possibly explain the apparent acceleration without invoking dark energy. This scenario is confronted with current cosmological distance measurements to put constraints on the size and depth of the void, as well as on our position within it. The model is found to explain the observations only if the void size is of the order of the visible universe and the observer is located very close to the center, in violation of the Copernican principle. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Accepted.