The measurement of ionospheric absorption using extraterrestrial radio waves

Introduction: The discovery by Jansky in 1932 of the presence of radio waves incident upon the earth from outer space has led to several new methods of studying the earth's upper atmosphere. This report describes the manner in which these extraterrestrial radio waves may be used to measure the radio absorption characteristics of the ionosphere. It opens with a brief discussion of the theory of ionospheric absorption; this is followed by a description of the basic principles involved in this new technique. Two different types of equipment which may be used for this type of absorption measurement are then discussed. The report concludes with a brief summary of three types of ionospheric absorption phenomena which have been studied at various latitudes with such equipments.Introduction – Section I Summary of Theory of Ionospheric Absorption – Section II Extraterrestrial Radio Waves and Ionospheric Absorption – Section III The Measurement of Ionospheric Absorption Using Extraterrestrial Radio Waves : With a simple receiver ; The continually self-calibrating system ; Some additional points – Section IV Some Experimental Observations of Ionospheric Absorption Using Extraterrestrial Radio Waves – BibliographyYe

An approach to valuing ponds within farming systems for aquaculture

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Even circuits of prescribed clockwise parity

We show that a graph has an orientation under which every circuit of even length is clockwise odd if and only if the graph contains no subgraph which is, after the contraction of at most one circuit of odd length, an even subdivision of K_{2,3}. In fact we give a more general characterisation of graphs that have an orientation under which every even circuit has a prescribed clockwise parity. This problem was motivated by the study of Pfaffian graphs, which are the graphs that have an orientation under which every alternating circuit is clockwise odd. Their significance is that they are precisely the graphs to which Kasteleyn's powerful method for enumerating perfect matchings may be applied

Experiment Luxembourg

The earlier orbits and ephemerides for the Soviet satellites were not sufficiently accurate to be very useful in making observations in Alaska. Extrapolations from our own observations gave better predictions. This merely pointed out the fact that rough observations of meridian transits at high latitudes will give better values of the inclination of the orbit than precision observations at low latitudes. Hence, it was decided to observe visually the meridian transits estimating the altitude by noting the position with respect to the stars or using crude alidade measurements. The times of the earlier observations were observed on a watch or clock and the clock correction obtained from WWV. Later the times were determined with the aid of stop watches, taking time intervals from WWV signals. This rather meager program of optical observations of the Soviet satellites was undertaken to give supplementary data for use of the radio observations, and particularly to assist in the prediction of position of the satellite so that the 61-foot radar of Stanford Research Institute could be set accurately enough to observe it (the beam width at the half-power points is about 3°). This report contains primarily the visual observations made at the Geophysical Institute by various members of the staff, and a series of observations by Olaf Halverson at Nome, Alaska. In addition there is a short discussion of the geometry of the trajectory, the illumination of a circumpolar satellite, and a note on the evaluation of Brouwer's moment factors.The research reported In this document has been sponsored by the Geophysics Research Directorate of the Air Force Cambridge Research Center* Air Research and Development Command, under Contract AF 19(604)-3880.List of Figures -- Introduction -- Present knowledge of the electron densities and collision frequencies in the D region of the ionosphere. -- The theory of radio wave interaction. -- The outline of the planned experiment. -- Some comments about the planned experiment. Some comments about gyrointeraction. -- Conclusion -- Acknowledgements -- ReferencesYe

Task A, Analysis of C-W Data, Final Report

The object of this investigation is to obtain additional information concerning the effects of aurora on high frequency radio signals which is essential to a complete understanding of new modes of propagation that have tactical and strategic applications.Signal Corps Contract No. DA-36-039-SC-71137 Department of the Army Project No. 3-99-03-022 Signal Corps Project No. 182BLIST OF FIGURES -- [SECTION I] PURPOSE -- [SECTION II] ABSTRACT -- [SECTION III] PUBLICATIONS. LECTURES, REPORTS AND CONFERENCES -- [SECTION IV] FACTUAL DATA : 1. Signal Outage Time on Short Paths and Blackouts Compared for Years of High and Low Solar Activity. ; 2. Study of Possible Relations between Transmission over Long Paths and Ionospheric,Magnetic and Solar Phenomena. ; 3. Study of Fluctuation Indices. ; 4. Effects of Ionospheric Absorption and Irregularities on 4 Mc/s Short Path Transmission. ; 5. F2 Region Parameters at College for the Period June 1941 Through December 1956. ; 6. Tables of Monthly Medians Signal Strength June 1949-December 1950 and January 1954-October 1955. -- [SECTION V] OVERALL CONCLUSIONS -- [SECTION VI] RECOMMENDATIONS -- [SECTION VII] PERSONNELYe

Technology and growth: an overview

Technology ; Economic development

Dynamic FOV visible light communications receiver for dense optical networks

This study explores how the field-of-view (FOV) of a visible light communications (VLCs) receiver can be manipulated to realise the best signal-to-noise ratio (SNR) while supporting device mobility and optimal access point (AP) selection. The authors propose a dynamic FOV receiver that changes its aperture according to receiver velocity, location, and device orientation. The D-FOV technique is evaluated through modelling, analysis, and experimentation in an indoor environment comprised of 15 VLC APs. The proposed approach is also realised as an algorithm that is studied through analysis and simulation. The results of the study indicate the efficacy of the approach including a 3X increase in predicted SNR over static FOV approaches based on measured received signal strength in the testbed. Additionally, the collected data reveal that D-FOV increases effectiveness in the presence of noise. Finally, the study describes the tradeoffs among the number of VLC sources, FOV, user device velocity, and SNR as a performance metric.Accepted manuscrip