High‐frequency forward scatter and propagation experiments in the Delaware Bay

1998 ◽  
Vol 104 (3) ◽  
pp. 1748-1748
Author(s):  
Wenkai Qin ◽  
Mohsen Badiey ◽  
Randy Zagar ◽  
Jeff Simmen
Keyword(s):  
High Frequency ◽  
Delaware Bay ◽  
Forward Scatter

A Disturbing Factor in Very High Frequency Communications Via Ionospheric Forward Scatter

Nature ◽  
1956 ◽  
Vol 178 (4545) ◽  
pp. 1280-1283 ◽  
Author(s):  
D. A. CROW ◽  
F. A. KITCHEN ◽  
G. A. ISTED ◽  
G. MILLINGTON
Keyword(s):  
High Frequency ◽  
Very High Frequency ◽  
Disturbing Factor ◽  
Forward Scatter ◽  
Very High

High‐frequency reciprocal transmission experiments in the Delaware Bay: Focus on the direct path

1998 ◽  
Vol 104 (3) ◽  
pp. 1748-1748
Author(s):  
Joe R. Zagar ◽  
Mohsen Bradiey ◽  
Wenkai Qin ◽  
Jeff Simmen
Keyword(s):  
High Frequency ◽  
Delaware Bay ◽  
Direct Path

scholarly journals Clutter Distribution Analysis of A Tropical Foliage Clutter for Different Profiles Based on FSR Micro-Sensor Network

2018 ◽  
Vol 7 (3.7) ◽  
pp. 72
Author(s):  
Nur Alia Zulkifli ◽  
N E. Abd Rashid ◽  
Z I. Khan ◽  
N N. Ismail ◽  
R S. A. Raja Abdullah ◽  
...  
Keyword(s):  
High Frequency ◽  
Free Space ◽  
Distribution Model ◽  
Distribution Analysis ◽  
Distribution Models ◽  
Very High Frequency ◽  
Forward Scatter ◽  
Micro Sensor ◽  
Log Normal ◽  
Very High

Comparison of four different clutter profiles (border, seaside, free space and forest) using Forward Scatter Radar (FSR), which operates in Ultra-High and Very High Frequency (UHF and VHF) bands, is analyzed in this paper. Clutter levels ranging from low, medium, strong and very strong on each profile were studied. Based on the standard deviation of each clutter profile, border suits the best profile as the strongest clutter profile amidst seaside and free space, while the forest is determined as the lowest clutter profile. Subsequently, the characteristics of the clutter are investigated and compared based on the five distribution models (Log-Normal, Log-Logistic, Gamma, Weibull and Nakagami).  The parameters of the five distributions are evaluated using Root Mean Square Error (RMSE) in order to prove that the distribution model fits best to the clutter data. It can be concluded that Gamma distribution is the best distribution model for all cases of frequency bands and profiles.  

STATISTICAL ANALYSIS FOR TERENGGANU FORWARD SCATTER RADAR SEASIDE CLUTTER

2016 ◽  
Vol 78 (5-7) ◽  
Author(s):  
Nor Najwa Ismail ◽  
Nur Emileen Abd Rashid ◽  
Zuhani Ismail Khan
Keyword(s):  
Statistical Analysis ◽  
Weibull Distribution ◽  
High Frequency ◽  
Goodness Of Fit ◽  
Distribution Model ◽  
Logistic Distribution ◽  
Distribution Models ◽  
Very High Frequency ◽  
Forward Scatter ◽  
Scatter Radar

The statistical analysis for Terengganu, Malaysia seaside clutter is presented in this paper. The measured clutter data were collected using a prototype of forward scatter radar (FSR) micro-sensor network with very high frequency (VHF) and ultra-high frequency (UHF) bands. Four categories of clutter strength were recorded during the measurements, which are low, medium, strong and very strong clutter. The classes were divided according to the wind speed occurred during the measurements period. The analysis is to determine the best-fit distribution model for the measured clutter data. Four types of distribution models are used in this analysis, which are Weibull, Gamma, Log-Logistic and Log-Normal distribution. One of the goodness of fit (GOF) tests called root mean square error (RMSE) is used to prove which distribution is a better fit to the probability distribution of the measured clutter data. The obtained results show that for 64 MHz with all clutter level strength, Weibull distribution provides better fit and records the lowest RMSE. Weibull distribution also fits best to the clutter data for low clutter of 151 MHz. However, for the rest of clutter level strength for 151 MHz, Gamma distribution is the best-fitted model with lowest RMSE values. Log-Logistic distribution proves to be the best fitted model to all clutter level strength of clutter data for 434 MHz with smallest RMSE values.

DEPENDENCE OF INTEGRATED DURATION OF METEOR ECHOES ON WAVELENGTH AND SENSITIVITY

1954 ◽  
Vol 32 (7) ◽  
pp. 450-467 ◽  
Author(s):  
D. W. R. McKinley
Keyword(s):  
Short Duration ◽  
High Frequency ◽  
Time Of Day ◽  
Very High Frequency ◽  
Forward Scatter ◽  
Long Duration ◽  
Meteor Trails ◽  
Cedar Rapids ◽  
Very High

The reflecting properties of short-duration and long-duration echoes from meteor trails are examined. For short-duration echoes only, the observed relation between relative numbers and durations of meteor echoes is independent of wavelength, the time of day, or the presence of a strong shower. Integrated duration times are determined from back-scatter experiments on 9.22 m., 5.35 m., and 2.83 m., and are found to vary with the 3.5th power of the wavelength, for either short- or long-duration echoes. The integrated echo power depends on the 6th power of the wavelength. The effect of changing the equipment sensitivity is considered. The data from the back-scatter observations are used to predict the integrated duration times in the forward-scatter case, and in particular, it is shown that the results of the Cedar Rapids – Sterling very-high-frequency experiment may be explained by meteoric reflections.

Performance of a high‐frequency acoustic forward‐scatter barrier in a dynamic coastal environment

2007 ◽  
Vol 121 (5) ◽  
pp. 3085-3086
Author(s):  
Karim G. Sabra ◽  
Stephane Conti ◽  
Philippe Roux ◽  
W. A. Kuperman ◽  
J. Mark Stevenson ◽  
...  
Keyword(s):  
High Frequency ◽  
Coastal Environment ◽  
Forward Scatter

The Microstructure of Steatite (Protoenstatite)

1985 ◽  
Vol 43 ◽  
pp. 236-237
Author(s):  
W. E. Lee ◽  
A. H. Heuer
Keyword(s):  
High Frequency ◽  
Glass Ceramics ◽  
Magnesium Silicate ◽  
Beam Current ◽  
Glassy Matrix ◽  
Angle Of Incidence ◽  
X Ray ◽  
Mechanical And Electrical Properties ◽  
Argon Ions ◽  
High Temperature Polymorph

IntroductionTraditional steatite ceramics, made by firing (vitrifying) hydrous magnesium silicate, have long been used as insulators for high frequency applications due to their excellent mechanical and electrical properties. Early x-ray and optical analysis of steatites showed that they were composed largely of protoenstatite (MgSiO3) in a glassy matrix. Recent studies of enstatite-containing glass ceramics have revived interest in the polymorphism of enstatite. Three polymorphs exist, two with orthorhombic and one with monoclinic symmetry (ortho, proto and clino enstatite, respectively). Steatite ceramics are of particular interest a they contain the normally unstable high-temperature polymorph, protoenstatite.Experimental3mm diameter discs cut from steatite rods (∼10” long and 0.5” dia.) were ground, polished, dimpled, and ion-thinned to electron transparency using 6KV Argon ions at a beam current of 1 x 10-3 A and a 12° angle of incidence. The discs were coated with carbon prior to TEM examination to minimize charging effects.

Sign in / Sign up

Export Citation Format

Share Document