How Can Environment Influence Ultra-Long Radio Propagation?

2018 ◽  
Vol 7 (2.23) ◽  
pp. 479
Author(s):  
M S. Mikhailov ◽  
A A. Volkova ◽  
V A. Permyakov
Keyword(s):  
Small Deviation ◽  
Sea Surface ◽  
Radio Propagation ◽  
Radio Link ◽  
Sea Waves ◽  
Evaporation Duct ◽  
Optimal Excitation ◽  
Vertical Variations ◽  
Elevated Surface ◽  
Transmitting Antenna

Even a small deviation of the environmental parameter can lead to significant changes in the propagation over long distances. The article investigates the radio propagation above the sea, taking into account the distortion of the refractive index caused by evaporation. This feature of the troposphere is called the evaporation duct. The radio propagation over-the-horizon in the evaporation duct is possible. The conditions for optimal excitation of the evaporation duct by a highly directional antenna are studied. The main factors influencing the range of the radio link are studied, such as the height of the transmitting antenna and attenuation in air and in hydrometeors and diffraction at sea waves. Also, the effect of vertical variations the evaporation duct on radio propagation is considered. In addition, elevated-surface duct may appear over the sea surface separately or together with the evaporation duct. The effect of an elevated surface and mixed ducts on the radio propagation is considered. The radio propagation is calculated by the parabolic equation method. 

scholarly journals STUDY OF EFFICIENCY OF APPLICATION OF DIFFERENT ANTENNAS FOR THE RECEIVING OF SPECIAL INFORMATION FROM THE SATELLITES TYPE OF CUBESAT FOR REMOTE SENSING OF THE EARTH

2018 ◽  
Vol 2 (48) ◽  
pp. 154-157
Author(s):  
O. V. Kalvatynsky
Keyword(s):  
Remote Sensing ◽  
Patch Antenna ◽  
Error Probability ◽  
Directional Pattern ◽  
Radio Link ◽  
Target Information ◽  
Helical Antenna ◽  
Special Information ◽  
Different Diameters ◽  
Transmitting Antenna

The subject matter of the article is the radio links of the target information of the space remote sensing systems (Earth remote sensing) from spacecraft of the CUBESAT type. The aim is to study the effectiveness of receiving antennas of different diameters (5 and 12 m), namely, changing the information receiving zone. The goal: to develop a mathematical for determining the minimum reception angles of the target information, taking into account the directional pattern and the flaps of the maximum of the diagram from the direction to the receiving station. Determine the minimum angles of the receiving location of the target information with a given error probability per bit of information (< 10-7) under the condition of different types of on-board transmitting antennas and receive antennas of different diameters. The methods used are: synthesis, mathematical modeling and graphical analysis of the results obtained. The following results are obtained. When using a transmitting helical antenna, the minimum reception angles with a given error probability per bit of information < 10-7 are less by 100 than using a patch antenna. But the value of signal to noise ratio (S/N) when using a helical antenna is dominated by a patch antenna at elevation angles greater than 640, subject to rotation in the direction of the receiving station. When using reflectors with a diameter of 5 m, it is possible to receive information with a specified error probability only for elevation angles greater than 23.50. Thus, the use of reflectors with a diameter of 12 m will significantly increase the possibilities for surveying the Earth's surface due to a longer session of receiving special information. Conclusions. Analysis of the technical characteristics of modern on-board components of spacecraft like CUBESAT has demonstrated the promise of using such spacecraft for environmental monitoring. The study of the CUBESAT satellite radio link was carried out taking into account the directional pattern of the on-board transmitting antenna of the target radio link, using a mathematical model created by the author. Using a patch antenna in comparison with a helix antenna makes it possible to extend the information receiving area with specified quality indicators by 100 by the elevation angle. Comparison of receiving stations with an antenna diameter of 5 and 12 m indicates the prospects of using reflectors of antenna systems with a diameter of 12 m, which are in Ukraine. The use of ground antennas with a reflector diameter of 12 m will allow receiving special information at minimum elevation angles of 120 under the conditions of the calculations (orbit height, on-board transmitter power, data transfer speed).

Scanning laser wave recorder with registration of “instantaneous” sea surface profiles

2021 ◽  
Author(s):  
V.V. Sterlyadkin ◽  
K.V. Kulikovsky ◽  
A.V. Kuzmin ◽  
E.A. Sharkov ◽  
M.V. Likhacheva
Keyword(s):  
Spatial Scales ◽  
Wind Waves ◽  
Single Point ◽  
Video Recording ◽  
Surface Profile ◽  
Weather Conditions ◽  
Sea Surface ◽  
Sea Waves ◽  
Wide Range ◽  
Wave Recorder

AbstractA direct optical method for measuring the “instantaneous” profile of the sea surface with an accuracy of 1 mm and a spatial resolution of 3 mm is described. Surface profile measurements can be carried out on spatial scales from units of millimeters to units of meters with an averaging time of 10−4 s. The method is based on the synchronization of the beginning of scanning a laser beam over the sea surface and the beginning of recording the radiation scattered on the surface onto the video camera matrix. The heights of all points of the profile are brought to a single point in time, which makes it possible to obtain “instantaneous” profiles of the sea surface with the frequency of video recording. The measurement technique and data processing algorithm are described. The errors of the method are substantiated. The results of field measurements of the parameters of sea waves are presented: amplitude spectra, distribution of slopes at various spatial averaging scales. The applied version of the wave recorder did not allow recording capillary oscillations, but with some modernization it will be possible. The method is completely remote, does not distort the properties of the surface, is not affected by wind, waves and sea currents, it allows you to measure the proportion of foam on the surface. The possibility of applying the proposed method at any time of the day and in a wide range of weather conditions has been experimentally proved.

Multipath Channel Model for Radio Propagation over Sea Surface

2016 ◽  
Vol 90 (1) ◽  
pp. 245-257 ◽  
Author(s):  
Fang Huang ◽  
Xuefei Liao ◽  
Yong Bai
Keyword(s):  
Channel Model ◽  
Multipath Channel ◽  
Sea Surface ◽  
Radio Propagation

Numerical Modeling of the Oil Spill Trajectory and Real-Time Tracking Using Intelligent Swarm Robots

2013 ◽  
Vol 446-447 ◽  
pp. 1261-1265 ◽  
Author(s):  
Mohsen Pashna ◽  
Rubiyah Yusof ◽  
Zool H. Ismail
Keyword(s):  
Numerical Modeling ◽  
Numerical Model ◽  
Crude Oil ◽  
Oil Spill ◽  
Water Surface ◽  
Sea Surface ◽  
Sea Waves ◽  
Robot Locomotion ◽  
Swarm Robots ◽  
Real Time Tracking

An oil spill is discharge of fluid petroleum such as crude oil or its by-product derivations such as diesel and gasoline on the water surface. In this paper, a numerical model of the oil spill has been introduced as a simulation of releasing oil on the sea surface. Meantime, the influence of sea waves and wind has been considered and shown. Moreover, a swarm of robots is engaged in order to track the spreading boundaries of the slicked oil, so that a novel schedule of robot locomotion is presented, based on the online sharing information in the flock network. Therefore, the swarm of robots tracks the oil spill margins intelligently and successfully.

The directional spectrum of ocean waves, and processes of wave generation

1962 ◽  
Vol 265 (1322) ◽  
pp. 286-315 ◽  
Keyword(s):  
Pressure Fluctuations ◽  
Wave Spectrum ◽  
Ocean Waves ◽  
Wave Generation ◽  
Air Pressure ◽  
Sea Surface ◽  
Shear Instability ◽  
Main Stage ◽  
Sea Waves ◽  
Directional Spectrum

This paper describes some recent observations of the directional spectrum of sea waves and of air pressure fluctuations at the sea surface, and discusses their implications for theories of wave generation. The angular spread of the wave energy in the generating area is found to be comparable with the ‘resonance angle’ sec -1 ( σU/g ) ( σ = wave frequency, U = wind speed) but lies slightly below it in the middle range of frequencies. The best fit to the directional spectrum F ( σ, ɸ ) is shown to be a cosine-power law: F ( σ, ɸ ) ∝ cos 2s (1/2 ɸ ), where s decreases as σ in ­ creases. At the higher frequencies the total spectrum satisfies the equilibrium law: F ( σ ) ∝ σ -5 . The initial stages of wave generation are attributed to turbulence in the air stream, and the main stage of growth to the shear instability mechanism described by Miles. At the highest frequencies the form of the spectrum suggests that wave breaking plays a predominant part, as proposed by Phillips. The broadening of the angular distribution at the highest frequencies may also be due partly to third-order ‘resonant’ interactions among components of the wave spectrum . The air-pressure fluctuations are nearly in phase with the vertical displacement of the sea surface (over most of the frequency range) and are consistent with the shear-flow model proposed by Miles. The turbulent component of the air pressure is much smaller than was previously supposed.

scholarly journals Optimization of 3D Trajectory of the Vehicle with Dynamic Principle of Maintaining According to the Criterion of Minimum Average True Geometric Altitude

2020 ◽  
Vol 3 (3) ◽  
Keyword(s):  
Sea Surface ◽  
Vehicle Body ◽  
Sea Waves ◽  
Sea State ◽  
General Direction ◽  
Air Cushion ◽  
Simulation Results ◽  
Drag Ratio ◽  
Lift To Drag Ratio ◽  
Aerodynamic Quality

The paper proposes to minimize the altitude of a low-flying vehicle near the waved sea surface due to the desire to lay a trajectory in smooth maneuvers mainly over the troughs of sea waves. The approach to the wave hollow is carried out by comparing the measurements of two radar altimeters and deviating the course by a certain amount in the direction of the altimeter, which showed higher altitude. The change in altitude is due to the property of self-stabilization of the vehicle and vertical maneuvers. The effectiveness of the proposed algorithm was evaluated by computer simulation of the movement of a light highly maneuverable vehicle under conditions of 6 sea state number. The simulation results showed the possibility of reducing the altitude from 3.0 to 2.35 meters and increasing the aerodynamic quality (lift-to-drag ratio) of the winged vehicle by 20%. It was also found that the greatest efficiency of minimizing altitude is achieved with the reference heading of the vehicle perpendicular to the general direction of sea wave’s propagation. The modeling did not take into account the influence of wind disturbances and accidental touches of the sea surface by the vehicle body, as well as the punching of the sea surface by air cushion. Consideration of these factors will be the direction of further research.

scholarly journals Paleoceanography and dinoflagellate cyst stratigraphy across the Lower–Middle Pleistocene Subseries (Calabrian–Chibanian Stage) boundary at the Chiba composite section, Japan

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Eseroghene J. Balota ◽  
Martin J. Head ◽  
Makoto Okada ◽  
Yusuke Suganuma ◽  
Yuki Haneda
Keyword(s):  
Kuroshio Extension ◽  
Sea Surface ◽  
Middle Pleistocene ◽  
Dinoflagellate Cyst ◽  
Extension System ◽  
Composite Section ◽  
Pacific Margin ◽  
Stratotype Section ◽  
Elevated Surface ◽  
The Kuroshio

AbstractA dinoflagellate cyst record from the highly resolved Chiba composite section in Japan has been used to reconstruct sea-surface paleoceanographic changes across the Lower–Middle Pleistocene Subseries (Calabrian–Chibanian Stage) boundary at the global stratotype, constituting the first detailed study of this microfossil group from the Pleistocene of the Japanese Pacific margin. Cold, subarctic water masses from 794.2 ka gave way to warming and rapid retreat of the Subpolar Front at 789.3 ka, ~ 2000 years before the end of Marine Isotope Stage (MIS) 20. Throughout the fully interglacial conditions of MIS 19c, assemblages are consistent with warm sea surface temperatures but also reveal instability and latitudinal shifts in the Kuroshio Extension system. The abrupt dominance of Protoceratium reticulatum cysts between 772.9 and 770.4 ka (MIS 19b) registers the influence of cooler, mixed, nutrient-rich waters of the Kuroshio–Oyashio Interfrontal Zone resulting from a southward shift of the Kuroshio Extension. Its onset at 772.9 ka serves as a local ecostratigraphic marker for the Chibanian Stage Global Boundary Stratotype Section and Point (GSSP) which occurs just 1.15 m (= 1300 years) below it. An interval from 770.1 ka to the top of the examined succession at 765.8 ka (MIS 19a) represents warm, presumably stratified but still nutrient-elevated surface waters, indicating a northward shift of the Kuroshio Extension ~ 5 kyrs after the termination of full interglacial conditions on land.

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