L'observation du milieu interstellaire est très importante aux fréquences mm / (sub) mm / Thz pour comprendre comment se forment les étoiles et les planètes. De telles observations dépendent des récepteurs hétérodynes. Ces instruments atteignent une résolution spectrale très élevée en convertissant un signal haute fréquence à une fréquence plus basse. Dans un récepteur hétérodyne, le signal collecté est superposé sur un signal artificiel, bien connu, monochromatique, généré par l'oscillateur local (OL), donc ce signal artificiel est plus-ou-moins la fréquence du signal du ciel. Le mélangeur produit le signal de la fréquence du battement. Cette fréquence est équivalente à la différence entre le OL et la fréquence du signal du ciel. Ainsi, le signal du ciel est traduit à une fréquence plus basse, pour qu'il soit facile à amplifier et détecter. Habituellement, les récepteurs hétérodynes ont seulement un pixel spatial avec de nombreux canaux en fréquences. Notre objectif est de développer des réseaux de centaines de pixels. Pour faire cela, certains composants de l'hétérodyne doivent être repensés radicalement, tels que l'antenne de réception et le diviseur de faisceau OL. En effet, l'antenne réceptrice est généralement constituée d'une antenne à double fentes sur une lentille, ou d'une antenne cornet. Par contre, ces antennes ne sont pas les meilleurs choix pour des réseaux de nombreux pixels car elles doivent être usinées et montées individuellement. Au lieu de cela, il est commode de développer des structures planaires qui peuvent être facilement produites toutes ensembles. En particulier, nous avons conçu et simulé des réseaux d'antennes patch, de réseaux de transmission, et de plaques de zone. Le réseau d'antennes patch consiste d'un réseau de patchs métalliques reliés par une ligne microruban et séparés du plan de masse par un substrat diélectrique. Cette configuration profite du facteur du réseau pour réduire la largeur de faisceau du signal collecté. Cependant, nos simulations nous montrent que la bande RF des réseaux d'antennes patch est étroite. Pour cette raison, nous avons analysé la possibilité d'utiliser une autre solution : le réseau de transmission. C'est un réseau de plusieurs cellules qui déphase une onde afin de transformer son front de phase de forme planaire en forme sphérique. Le but de la matrice de transmission est de focaliser le faisceau collecté vers une antenne et mélangeur à double fentes. La thés démontre qu'un effet de focalisation satisfaisant est atteint sur une ligne. Nous avons fabriqué un tel réseau de transmission et l'avons testé en laboratoire. En raison des petites dimensions de quelques millimètres, ces tests sont difficiles à réaliser. Au sein de l'erreur de mesure, la conception et les simulations sont cohérentes. Une troisième option (d'une lentille planaire) a été étudiée dans la thèse : la plaque de zone. C'est un type particulier de réseau de transmission qui ne présente que deux déphasages de 0 ° et 180 °. Le plaque de zone focalise bien, mais est peu efficace. La dernière partie de la thèse introduit un type de diviseur de faisceau particulier qui permet une division du faisceau du signal OL vers un réseau de quatre mélangeurs très serrés. Diviser le faisceau avec des angles suffisamment petits est très difficile avec les réseaux de Fourier et Dammann classiques. Pour cette raison la méthode que nous avons proposée pour concevoir un tel diviseur est très novatrice. En effet, il permet la formation de motifs de faisceaux de forme arbitraire, qui ne sont pas limités par les ordres de diffraction. Les simulations montrent des efficacités allant jusqu'à 80% qui sont très bonnes en comparaison avec les réseaux classiques. En résumé, dans cette thèse, j'ai essayé plusieurs moyens radicalement différents pour simplifier les récepteurs hétérodynes et ouvrir la voie aux grandes matrices hétérodynes avec des centaines de pixels. / The observation of the interstellar medium is very important at mm/(sub)mm/THz frequencies to understand how stars and planets form. Generally such observations rely on heterodyne receivers. These are instruments that achieve very high spectral resolution by down converting a high frequency signal towards a lower frequency one. In a heterodyne receiver the incoming signal is superimposed onto an artificial, well-known, monochromatic signal generated by the local oscillator (LO), chosen to be close to the frequency of the sky signal. The mixer produces the beat frequency signal. It has a frequency equivalent to the difference between the LO and sky signal frequency. Thus the sky signal is translated to a lower frequency, and it is easier to amplify and detect. Usually heterodyne receivers have only one spatial pixel with many frequency channels. Some prototypes have been realized recently with few pixels. Our objective is to develop arrays of hundreds of pixels. In order to do that, some components which compose the heterodyne receiver must be radically rethought, such as the receiving antenna and the LO beam divider.Indeed the receiving antenna generally consists of a double slot antenna on a lens, or a horn antenna. Such antennas are not the best choice for arrays of many pixels since they have to be machined and mounted individually. Instead it is convenient to develop planar structures which can be easily produced in bulk in a single process. In particular we designed and simulated arrays of patch antennas, transmit-arrays and zone plates. The array of patch antennas consists of an array of metallic patches connected via a microstrip line and separated from the ground plane by a dielectric substrate. This configuration takes advantage of the array factor to reduce the beamwidth of the incoming signal in place of the lens. However our simulations showed the array of patch antennas to be quite narrowband for a general purpose application, and quite difficult to realize. For this reason we also analyzed the possibility to use another solution such as the transmit-array. It is an array of several cells which provide a certain phase shift to an incoming wave in order to transform its phase front from planar to spherical. The purpose of the transmit-array is to focus the incoming beam towards a double slot antenna and a mixer placed below it. The simulations showed that a good focusing effect can be reached on a line. We fabricated such a transmit-array and tested it in the laboratory. Because of the small dimensions of a few millimeters these tests are difficult to carry out. Within the measurement error design and simulations are consistent. A third option of a planar lens was studied in the thesis: the zone plate. This is a particular kind of transmit-array which presents only two phase shift of 0° and 180°. The zone plates focus well, but are unfortunately not very efficient.The final part of the thesis introduces a particular kind of beam divider which allows beam splitting of the LO signal towards an array of four very closely packed mixers. To split the beam with such small relative angles is very difficult with the classical Fourier and Dammann grating, for this reason the method we proposed to design such a beam divider is very innovative. Indeed it allows the forming of arbitrary shaped beam patterns, which are not limited by the diffraction orders. Simulations show efficiencies up to 80% which are very good in comparison with classical gratings.In summary in this thesis I have tried several radically different approaches to simplify heterodyne receivers and made a first step towards for large heterodyne arrays with hundreds of pixels.

Considerando a forte relação entre a Astronomia e a Física, a pesquisa apresentada propõe focalizar uma atividade de ensino que, partindo da observação do céu, com motivação para compreendê-lo, indo além da admiração e do deslumbramento, leve à elaboração de conceitos da Física escolar. A pesquisa trata de investigar uma forma de desenvolver o conceito de energia partindo de uma observação astronômica, onde os aprendizes são participantes ativos no processo da sua aprendizagem. Foi desenvolvida uma sequência didática e aplicada a alunos do Ensino Médio de uma escola pública de São Paulo. O objetivo era motivar os alunos a observar um fenômeno celeste, as crateras lunares, para construir o conceito de energia mecânica, num processo com as etapas de: observação, obtenção de dados pertinentes e adequados, levantamento de hipóteses e verificação num experimento controlado no laboratório escolar. Todas as atividades foram registradas em áudio ou vídeo e, com base nas transcrições, foi realizada uma análise textual discursiva. A análise permitiu qualificar as observações sob diferentes aspectos, bem como revelar as concepções expressas na tentativa de modelar, no laboratório escolar, uma possível causa das crateras observadas. Em todo o trabalho foi notável o papel fundamental do professor como mediador; a atenção para acompanhar a argumentação dos alunos e orientar as atividades parece ter garantido resultados de aprendizagem. A teoria de Vigotski foi considerada para interpretar os resultados sobre a construção de conceitos. Como resultados foram obtidas categorias sobre como se dão as observações realizadas pelos alunos, saindo de uma Observação Primária, evoluindo até uma Observação Qualificada. E também quais as relações que se estabelecem ao investigar um problema para que o conceito de energia mecânica crie significado para o aluno, Relações entre as grandezas e o conceito, até a Relação de Terceiro Grau, entre conceito e fenômeno. / In view of the strong relationship between Astronomy and Physics the proposed research aims to focus on a teaching activity that starts from the sky observation with an understanding motivation that lies beyond admiration and bewilderment and that may lead to the elaboration of school Physics concepts. The research deals with the investigation of a way of developping the concept of energy, starting from astronomical observations where students take active part in their learning process. A didactic sequence was elaborated and applied to secondary school students at a São Paulo public school. The objective was to motivate students to observe a celestial phenomenom, namely lunar craters, in order to build up the concept of mechanical energy in a process with the following steps: observation, obtention of related and adequate data, possible hypothesis and verification with a school laboratory controlled experiment. All activities were recorded in audio or video and with the aid of transcriptions a textual discursive analysis was effected. This analysis enabled a qualification of observations under several points of view as well as disclosing conceptions that were expressed in an atempt to model, in the school laboratory, a possible cause for the observed craters. The role played by the teacher during the whole process was essential as a moderator; his attention to follow the students argumentation and drive activities seems to have secured learning results. Vigotski theory was considered for interpreting results respect to construction of concepts. As results were obtained classes of observations made by the students, leaving a Primary Observation, evolving into a Qualified Observation. And what are the relationships that are established to investigate a problem that the mechanical energy concept create meaning to the student, relations between quantities and the concept, to the third degree of relationship, between concept and phenomenon.

Thesis. 1975. B.S.--Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science. / Includes bibliographical references. / by George Fawcett, Jr. / B.S.

Thesis. 1976. B.S.--Massachusetts Institute of Technology. Dept. of Mechanical Engineering. / Microfiche copy available in Archives and Engineering. / Includes bibliographical references. / by Joseph B. Hamilton. / B.S.

<div>Two new Kolsky bar techniques were developed to address a lack of capability in existing torsion Kolsky bar experiments. The side-impact torsion Kolsky bar provides for controllable duration, amplitude, and shape of the incident torsion wave, allowing for more ideal conditions during dynamic torsion experiments. The technique provides an ideal platform to study dynamic friction as well as dynamic shear of a material. The technique makes use of soft pulse shapers to convert longitudinal loading into torsional loading. The technique also brought forth a secondary technique to allow combined dynamic compression and dynamic torsion for soft materials. The combined loading was applied to study both shear properties and the friction behavior of a</div><div>particle composite, which was imaged using x-ray phase contrast imaging. The same composite was studied with different surface conditions on the side-impact torsion Kolsky bar to discover the differences in behavior brought about by the choice of manufacturing method. The composite showed different friction behavior to metallic</div><div>materials, and exhibited much more shear deformation during the experiment. The composite was also prone to surface evolution, leading to complex friction behavior.</div>

Orientador: Cláudio Luiz Carvalho / Banca: Fernanda Catia Bozelli / Banca: Hermes Adolfo de Aquino / Resumo: De acordo com pesquisas em ensino de ciências, nos últimos tempos, os alunos de forma geral, não compreendem e não desenvolvem as tarefas sobre os conceitos básicos de ciências, como por exemplo, relacionar um tema de Física com os acontecimentos rotineiros do dia a dia, assim como relacioná-lo com a Química ou Geografia. Uma possível hipótese está no fato de que o ambiente escolar frequentado pelos alunos, atualmente, está desconexo com os interesses e curiosidades que eles possuem em aprender. Estes interesses estão ligados apenas a conceitos imediatistas. Esta geração de alunos que está se moldando é conhecida como "geração tecnológica". As simples experimentações em si realizadas em salas de aulas não refletem no real aprendizado para que os alunos desenvolvam competências e habilidades na elaboração de saberes científico. Os conteúdos são apenas direcionados para cumprir currículos em espaços de tempo cada vez mais reduzidos. Pela fundamentação teórica de David Ausubel, que relaciona a questão de materiais representativos e significativos no processo de ensino aprendizagem, foi proposta, nesta pesquisa, a discussão dos conceitos de Astronomia, em formatos de oficinas, na qual os alunos foram incentivados a criar o próprio conhecimento de forma construtivista por meio da metodologia mediadora na relação com os outros saberes como a Matemática, Geografia, História, Física incentivando a interdisciplinaridade. Os resultados obtidos nas oficinas foram gravados e transformado... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In agreement of recent science education research, recently, in general, students cannot understand and also can not develop their stuff about basic science concepts, such as make the relationship between Physics and something that happen day-by-day either relation with chemistry or geography. A possible hypothesis can be the fact of the scholar ambient could be disconnected from the interest and curiosities that they should be to learn. These interests are connected just only with immediatist concepts. The students generation that is coming is called "Technological generation". The experiments did in classroom have not been enough to improve their scientific skills. The subjects are just specifically used to fulfill curricula in a short period of time (and this time have been reduced constantly or periodically or frequently). By the theoretical basis of David Ausubel, that related representative and significative materials in the teaching/ learnt process was proposed, in this Project, the discussion of about Astronomy concepts using workshop format, In which students were encouraged to create their own knowledge in a constructivist way through the mediator methodology in relation to other knowledge such as Mathematics, Geography, History, Physics encouraging interdisciplinarity. The results obtained in the workshops were recorded and transformed in media material that it can be shared in web. This material is being used for reference source and studies, providing free access... (Complete abstract click electronic access below) / Mestre

abstract: This dissertation examines the efforts of the Carnegie Image Tube Committee (CITC), a group created by Vannevar Bush and composed of astronomers and physicists, who sought to develop a photoelectric imaging device, generally called an image tube, to aid astronomical observations. The Carnegie Institution of Washington’s Department of Terrestrial Magnetism coordinated the CITC, but the committee included members from observatories and laboratories across the United States. The CITC, which operated from 1954 to 1976, sought to replace direct photography as the primary means of astronomical imaging. Physicists, who gained training in electronics during World War II, led the early push for the development of image tubes in astronomy. Vannevar Bush’s concern for scientific prestige led him to form a committee to investigate image tube technology, and postwar federal funding for the sciences helped the CITC sustain development efforts for a decade. During those development years, the CITC acted as a mediator between the astronomical community and the image tube producers but failed to engage astronomers concerning various development paths, resulting in a user group without real buy-in on the final product. After a decade of development efforts, the CITC designed an image tube, which Radio Corporation of American manufactured, and, with additional funding from the National Science Foundation, the committee distributed to observatories around the world. While excited about the potential of electronic imaging, few astronomers used the Carnegie-developed device regularly. Although the CITC’s efforts did not result in an overwhelming adoption of image tubes by the astronomical community, examining the design, funding, production, and marketing of the Carnegie image tube shows the many and varied processes through which astronomers have acquired new tools. Astronomers’ use of the Carnegie image tube to acquire useful scientific data illustrates factors that contribute to astronomers’ adoption or non-adoption of those new tools. / Dissertation/Thesis / Doctoral Dissertation History and Philosophy of Science 2019

Obtaining a very high level of precision and sophistication in automated computer control is now available inexpensively from a variety of hardware and software sources. Applying this automated technology to an astronomical telescope broadens the scope of applications of the instrument, particularly in areas such as photo electrics, CCD imaging and remote control. The ultimate design goal of the UWS telescope was that of full roboticism, giving access of the facility to off campus clients both in Australia and overseas. The first phase towards full robotic control is automation of the required optical and mechanical parameters, providing precision targeting and object tracking. This thesis describes the mechanical aspects of the UWS telescope and the procedures and equipment involved in its automation, including the drive system, electro mechanical design and associated computer hardware and software. Sample performance test data shows that using a high percentage of inexpensive proprietary robotics components, a very sophisticated and accurate measuring device can be produced. / Master of Science (Hons.)

This thesis presents an engineering project measuring the effective wavelength of the CHARA Classic beam combiner on the CHARA Array. Knowing the actual effective wavelength of light observed is very important because that value is necessary for determining astrophysical parameters of stars. Currently, the value used for CHARA Classic data comes from a model of the system and is based on numbers published by the manufacturer of the filter; it is not derived from measurements done on the system directly. We use two data collection methods to observe standard stars of different spectral types and calculate the wavelength of light recorded by the instrument for each star. We find the best estimate of the effective wavelength for the CHARA Classic K′-band configuration to be 2.138±0.003μm, a 0.56% decrease from the previously adopted value of 2.150μm. Our result establishes the first estimate of the uncertainty in the effective wavelength.

published_or_final_version / Fine Arts / Master / Master of Philosophy