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Distribution of tropospheric amplitude scintillation on Ku Band earth-space link over a tropical station

Ashidi Ayodeji Gabriel, Ojo Joseph Sunday, Ajewole Moses Oludare, Adediji Adekunle Titus

Acta Geophysica

2022

Vol. 70, no 1

415--427

This work utilized three years of measured satellite radio beacons to examine the statistical and temporal characteristics of tropospheric scintillation intensity and amplitude on the earth-space link over Akure, Southwest Nigeria (7.17 °N, 5.18 °E, 358 m). The signal measurement from Eutelsat W4/W7 satellite was taken between January 2016 and December 2018. The instrument used is Tektronix Y400 NetTek spectrum analyzer at a sampling rate of 1-s, downlink frequency 12.254 GHz, and path elevation of 036°E. Analysis involving cumulative distribution and probability density functions was performed over seven sampling intervals for characterizing the distribution of scintillation phenomenon on an annual and sub-annual basis. The results show scintillation intensity (σχ) to be well approximated by lognormal, Gamma, and generalized extreme value (GEV) distributions, while scintillation amplitude (χ) was suitably described by Gaussian distribution model. Also, as the sampling interval increased, the accuracy of the distribution models decreased. Analysis of mean and standard deviation equally revealed that scintillation intensities measured over longer intervals are less variable. Finally, a two-part exponential model developed for scintillation intensity prediction performed well as indicated by a least R2 value of 0.97 just as highest sum of square error (SSE) and root-mean-square error (RMSE) values of 0.192 and 0.087, respectively, were returned for both the goodness of ft and goodness of validation tests.

Statistical analysis for modeling ship operation processes in ports

Özkan Emin Deniz, Koçer Umay Uzunoğlu, Nas Selçuk

Zeszyty Naukowe Akademii Morskiej w Szczecinie

2020

nr 62 (134)

71--79

The proper selection of statistical distributions is important for modeling port operations using simulations or queuing theory. The aim of this study was to determine the appropriate statistical distributions for modeling random processes related to ship operations in ports, including ship arrivals, berthing maneuver processes, service processes, and unberthing maneuver processes. A literature review was performed on the statistical distributions used in these random processes. In addition, the port data on ship operations gathered from three different ports in Turkey were examined. Goodness of fit tests were conducted to determine the appropriate distribution for each process.