Absbact -Terrestrial links operating at frequencies higher than IO GHz suffers degradation due to rain. Various researches have been conducted to study rain-induced degradations such as rain attenuation. Apart from rain attenuation, rain fade is also a major factor affecting the performance of a terrestrial microwave link. This paper therefore, seeks to investigate the impacts of rain fade to the performance of terrestrial microwave links. In this paper, rain fade slope and rain fade depth are investigated and analyzed. The superposition of rain attenuation and rain fade is also investigated. Signal fall time and recovery time are also major concern n this paper. All the analysis leads to understanding on the impacts of rain fade on the performance and reliability of microwave terrestrial links lntrodnctionFor terrestrial microwave links operating at frequencies higher than 10 GHz, rain-induced degradations are significant. Major degradations caused by rain that affect the reliability and availability of terrestrial links are rain attenuation and rain fade. In researches to determine rain attenuation. receive signal of a terrestrial link is sampled to an integration time of one minute [I-31. Besides attenuation, rain fade is another major factor affecting the performance of microwave links. Rain fade is the dynamic fluctuation of receive signal due to inhomogeneities of the signal path, ranging from a few seconds to a few minutes. Rain fade provides additional information on understanding the characteristics of rain-induced degradations.0-7803-8129-7/03/$17.00 02003 IEEE.The next section briefs on the research experimental setup. Then, the following section reports on results and analysis. The analysis is focused on rain fade slope and rain fade depth. Besides that, the relationship between fade slope to fall time and recovery time is discussed. The additional impact due to superposition of fade depth and attenuated signal is also discussed.
Machines operators expose to excessive noise in the workplace that may lead to hearing damage. This study investigates construction machine operators noise exposure levels for eight hours or time weighting averages (TWAs), relationship TWA with machine noise emission level, the practices of using hearing protection devices (HPDs) and working in a closed machine cab. Heavy and non-heavy machine operators at five construction sites involved with excavation and piling activities were selected and measured by using dosimeters. 68% of operators were exposed to TWA of 85 dBA and 18% of the operators exceeded the permissible limit. 40% of operators work inside a closed machine cab, 18% wear earplugs and only 16% practiced both. Both operators of heavy machines (except excavators) and dump trucks are exposed to TWA > 90 dBA if they work in open machine cabs. The TWAs were found well correlated (r=0.41) with the machine noise emission, which ranged between 84 dBA to 125 dBA. Furthermore, this study proposes the type of HPD for the operators of typical machine to minimise the risk of hearing loss.
This study aims to evaluate noise exposure and prevalence of hearing loss among typical road construction workers. Personal noise dosimeter was used to obtain the noise exposure profile of heavy equipment operators that are working on various stages; road work, trade work and pavement work. Symptoms of hearing loss among workers were observed through interview session. It was a degradation in human hearing ability. Workers with symptoms of hearing loss may have problem in understanding speech or conversation. There are 73 construction workers that were evaluated, 60 of them are machine’s operators, 7 are site supervisors and 6 are premix workers. The results show that in road works stage there are 6.9% workers exposed to action level ≥85 dBA and 1.4% workers exposed to noise ≥90 dBA. 4.1% workers from trade work and 13.7% workers from pavement work were exposed to noise ≥85 dBA. There are 5.48% of workers from pavement work exposed to hazard level of noise with only 2.74% of worker used Hearing Protection Devices (HPD). There is a prevalence of symptoms of hearing loss among workers with 45% of workers from road works, 32% from trade works and 23% from pavement stage. These exposed workers suggested to have an audiometric testing program annually in order to identify deterioration in their hearing ability as early as possible.
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