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This paper intends to give a code about
atmospheric propagation effects affecting terahertz (THz) communication system.
The main focus is on attenuation caused by atmospheric gases with the radiation
transmission theory and the empirical continuum absorption based on the HITRAN
database. Theoretical aspects about them are presented, emphasizing on those
which deserve special attention as frequency increases. Laboratory measurements
of the absorption spectra of laboratory air and major atmospheric gases mixed
with water vapor in the 250 - 350 GHz frequency range at atmospheric pressure
and room temperature on a basis of backward wave oscillators (BWOs) are
obtained. The results of experiments are compared with the calculations. It is
found that the water vapor transmittance is greater than the calculation. Data
of these measurements agree with the results of analysis of atmospheric spectra
with in statistical accuracy of experiments. Accurate measurements are also
needed for further studies of the physics of the molecules and their interactions.
The investigation makes it significant for enhancing accuracy of models of
radiation propagation in the atmosphere.
Fatigue has negative impacts on the general
working population as well as on seafarers. In order to study seafarers’ fatigue,
a questionnaire-base survey was conducted to gain information about potential
risk factors for fatigue and construct indexes indicating fatigue. The study
applies T-test to compare strata of seafarers to analyse work and sleep patterns
in global seafaring. Qualitative analysis are also employed to explore the
impacts of fatigue on seafarer’s occupational health and safety.