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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

Predicted and measured arrival rates of meteors over forward-scatter links.

Mawrey, Robert Stanley. January 1991 (has links)
Investigations into currently accepted methods of modelling variations in the arrival rate of meteors over forward-scatter meteor links have revealed some shortcomings. In these investigations, particular emphasis is placed on the work of Rudie due to its current acceptance in the literature. The non-uniform radiant distribution of meteors measured by Davies and modelled by Rudie, is critically examined and predictions using these models are compared with measured results taken over two forward-scatter links in the Southern Hemisphere. A new, alternative method of including the effect of non-uniform radiant distributions on the predicted arrival rate of meteors is given. The method used by Rudie to model Davies' measured radiant distribution is shown to be unnecessarily complicated and a simpler alternative is given. Furthermore, Rudie's distribution is shown not to be derived from a particular set of Davies' results as implied by Rudie. Other non-uniform distributions of meteors are also investigated. Comparisons between monthly-averaged daily cycles of measured and predicted arrival rates of meteors for a midpath and an endpath meteor link are used to reveal the validity and limitations of the published distributions. A new graphical method is used to aid in determining the validity and limitations of the non-uniform distributions. Discrepancies in the published predicted and measured annual variations in the arrival rate of meteors are investigated. Contrary to recently published information, predicted annual variations in the arrival rate of meteors for meteor radiants close to the ecliptic are shown to be comparable to measured results. / Thesis (Ph.D.)-University of Natal, Durban, 1991.
2

An adaptive protocol for use over meteor scatter channels.

Spann, Michael Dwight. January 1987 (has links)
Modem technology has revived interest in the once popular area of meteor scatter communications. Meteor scatter systems offer reliable communications in the 500 to 2000 km range all day, every day. Recent advances in microprocessor technology have made meteor scatter communications a viable and cost effective method of providing modest data rate communications. A return to the basic fundamentals has revealed characteristics of meteor scatter propagation that can be used to optimize the protocols for a meteor scatter link. The duration of an underdense trail is bounded when its initial amplitude is known. The upper bound of the duration is determined by maximizing the classical underdense model. The lower bound is determined by considering the volume of sky utilized. The duration distribution between these bounds is computed and compared to measured values. The duration distribution is then used to specify a fixed data rate, frame adaptive protocol which more efficaciously utilizes underdense trails, in the half duplex environment, than a non-adaptive protocol. The performance of these protocols is verified by modeling. / Thesis (Ph.D.)-University of Natal, Durban, 1987.

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