Thesis (M.S.)--Ohio University, June, 2004. / Title from PDF t.p. Includes bibliographical references (p. 94-95)

Thesis (Ph.D.)--Ohio University, November, 2004. / Title from PDF t.p. Includes bibliographical references (p. 132-146)

Diss.--Marburg--Philipps Universität, 1990. / Bibliogr. p. 275-287.

Thesis (M.S.)--Boston University

Decameter radiation was first observed from Jupiter by Burke and Franklin (JGR 60, 213, 1955). In 1964 Bigg (Nature, 203, 1008, (1964)) found that 1o exerted a profound effect on the radiation. The majority of the early theories to explain the origin of the decameter emissions, attributed the radiation to an emission process occurring at or near the electron gyrofrequency or the plasma frequency. Intro., p. 1. The majority of the early theories to explain the origin of the decameter emissions, attributed the radiation to an emission process occurring at or near the electron gyrofrequency or the plasma frequency (for a review see eg. Warwick, Space Sci. Rev. &" 841 (1967)). More recent work centred around the question of how 10 modulates the emission (see the article of Carr and Gulkis (Annual Review of Astronomy and Astrophysics Vol 8 (1970)) for a detailed review).

[pt] Este trabalho apresenta o desenvolvimento de uma estratégia de controle de erro híbrida baseada em correção de erro (FEC- Forward Error Correction) e protocolo de retransmissão (ARQ-Automatic Repeat Request) para uma Rede de Pacote Via Rádio (PRNET- Packet Radio Network). O controle de erro tem como objetivo garantir a integridade dos dados e manter o desempenho do sistema dentro de níveis aceitáveis em termos de confiabilidade e throughput (vazão). Também forma implementados os protocolos correspondentes às camadas de Enlace e Rede segundo a padronização OSI/ISO. / [en] This work presents the development of a hybrid error- control strategy for a Packet Radio Network (PRNT) based on error correction (FEC) and a retransmission protocol (ARQ). The error control is intended to assure data integrity and to maintain an acceptable system performance in terms of reliability and throughput. The OSI/ISO Link and Network layers were also implemented.

Seminario para optar a la Licenciatura en Comunicación Social / Este trabajo ha pretendido determinar la pertinencia cultural que la oferta informativa de los medios periodísticos nacionales presenta para los habitantes de la Región de Magallanes y Antártica Chilena, entendiendo como pertinencia cultural la manifestación de elementos sustantivos -en forma y contenido- que interpelan espontáneamente el modo de ser intrínseco de los sujetos que comparten una identidad. En la base, se encuentra la pregunta acerca del modo y rango en que los medios de comunicación nacionales están respondiendo a las necesidades de información de quienes no viven en Santiago y de cómo están participando en la preservación una homogenización artificial de la chilenidad en desmedro de la diversidad cultural del país. Debido a que el objetivo planteado sólo puede abordarse adecuadamente, mediante un estudio de orden cualitativo - ya que hablamos de consumo cultural e identidad- nos inscribimos en el enfoque epistemológico constructivista y utilizamos la técnica de los grupos de discusión. Analizamos los distintos relatos, desde las perspectivas de los hábitos informativos, preferencias por medios regionales o nacionales, necesidad y valoración de la información, modos en que se representa a la región magallánica en los medios nacionales, elementos culturales de la oferta noticiosa que comparten y se consideran propios. El resultado es significativo. Los magallánicos hacen una crítica profunda a los medios periodísticos nacionales, su calidad, contenidos y función social. A la vez, con excepción de escasos temas de orden político, económico y social, la información les resulta ajena, sin interés y culturalmente amenazante para el futuro del país.

From introduction: Jupiter is the largest planet in the solar system. Its distance from the Sun is five times that of the Earth and its mass is nearly two and a half times that of all the other planets added together. Jupiter turns about its own axis rather rapidly, once in just under ten hours, and it completes one revolution about the Sun in just under twelve years. Thus Earth has to pass almost directly between the Sun and Jupiter once every thirteen months. When this happens Jupiter is said to be in "opposition", as its position is then opposite to that of the Sun, when viewed from Earth. Around this time the planet will be most favourably placed for observations, as it is at its closest to Earth and up in the sky for a large part of the night. During the day observations on radio frequencies are more difficult, as the Sun is a source of great interference. Besides being an emitter of thermal electromagnetic radiation, as one would expect, Jupiter also emits two kinds of non-thermal radiation, one in the decimetre wavelength range and the other in the decametre wavelength range. A large number of scientists have worked on the problems of decimetre and decametre radiation. This thesis deals with some aspects of decametre radiation.

This thesis describes the results of an investigation of the physical properties of the Gum Nebula. For this investigation a radio continuum map of the region was made at 2326 MHz and resolution ⅓° with the HartRAO antenna. This map was used to generate spectral index images and an infrared to radio flux density ratio (IRR) image. The latter image shows that the IRR of the nebula is in the range 20 to 250, identifying it as an old SNR. Several spectral index images of this region were generated using two different methods, one based on the isolation of the nebula from its background radiation, the other based on TT-plots (Turtle et al., 1962). The two methods yield similar results, which show that the nebula has a thermal shell with a non-thermal region in its interior. Below the galactic plane the thermal region dominates and above the plane the nonthermal region. These results suggest a model of an old SNR with an H II region shell. Spectral line observations of hydrogen recombination lines and hydroxyl (OH) were made with the HartRAO and the Mopra telescopes. The detection of hydrogen recombination lines at four positions in the thermal regions of the nebula give electron temperatures and emission measures in the ranges 4000 to 6000 K and 220 to 460 pc.cm⁻⁶ respectively. The turbulent velocities are of the order of 20 km/s. A search for shocked OH lines at 1667 MHz and 1720 MHz in the Gum Nebula gave results that were negative, but numerous unshocked 1667 MHz OH lines were detected. The latter were used in a test for an expansion of the nebula. The most plausible fit to the data gives an expansion centre at l = 260.5°, b = -2.5° and at a distance of 0.7 kpc from us. The front face angular radius and expansion velocity are 10.5° and 16 km/s respectively. The back face angular radius and expansion velocity are 8.50 and 7 km/s respectively.

This thesis describes the investigation carried out on the propagation of radio pulses of frequency 4.73 Mc/s between Grahamstown and Durban. The thesis is divided into two sections - A and B. Section A consists of two chapters. The introductory chapter gives a brief account of how the existence of the ionosphere came to be known. Then follows a description of the different layers of ionization and a review of the theories that have been propounded on the formation of these layers. Chapter 2 deals with the apparatus which includes the transmitter in Grahamstown and the receiving apparatus in Durban. The receiving apparatus comprises: i) a superheterodyne receiver whose gain was high (between 130 and 140 dbs); (ii) a time delay calibrator which could measure time differences of 100 μsec fairly accurately; (iii) a 310 A Tektronix oscilloscope; (iv) a continuously running 35 mm recording camera. Section B is made up of three chapters and is concerned with the actual analysis of the data recorded. The theory of propagation of radio waves in the ionosphere is discussed in Chapter 3. The effects of the magnetic field are neglected since it is found that the error introduced would not make the results unacceptable. Chapter 4 contains the analysis of the data recorded. One summer day and one winter day are discussed in detail in order to obtain the pattern of the diurnal variations for both summer and winter. Some interesting phenomena are also dealt with. An attempt to do ray tracing was successful and the paths followed by a Pedersen and a lower ray from Grahamstown to Durban have been drawn. New topics for further research are discussed in Chapter 5. There are two appendices. Appendix I gives the time delays of all the pulses recorded and their possible identifications. An overall picture of the propagation via the various layers throughout the day (both for summer and for winter is presented in Appendix II.