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Transmittance and Extinction Coefficient of Sea and Well-Water in Mombasa County, Kenya

100%
Mogunde C., Mosiori C. O.
Path of Science
|
2018
|
vol. 4
|
issue 10
3001-3005
EN
Using a laser transmitter in the range of 200 nm to 1200 nm, transmittance and total extinction coefficients were determined for two different but close related optical media which are ocean water and shallow well water in Mombasa County, in Kenya. The results were interpreted using Lambert–Beer’s law as applied for very small ranges of concentrations. It was established that the total extinction coefficients for two forms of water showed linearity with values of total extinction coefficients found to be µt = 7.734 (g/ml)-1 mm-1 and µt = 127.6 mm-1 at a wavelength of 638 nm for ocean water and shallow well water respectively.
2
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Noise reduction at the shooting range by means of level-dependent hearing protectors

100%
Młyński R., Kozłowski E.
Medycyna Pracy
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2019
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vol. 70
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issue 3
265-273
EN
Background The aim of the tests was to establish the possibilities of reducing impulse noise by using level-dependent hearing protectors at a shooting range. The tests included 9 models of level-dependent earmuffs and 2 models of level-dependent earplugs. They were conducted in the presence of impulse noise generated by 7 types of firearms (pistols, a submachine gun, rifles, a shotgun). Material and Methods The tests were conducted at an outdoor shooting range, using an acoustic test fixture that meets the requirements of the ANSI/ASA S12.42-2010 standard. Noise parameters were established for the noise reaching the microphones installed in the ear simulators of the acoustic test fixture: uncovered and protected by the tested hearing protectors. Results All 11 tested level-dependent hearing protectors allow to satisfactorily (below the exposure limit values) reduce the C-weighted peak sound pressure level and A-weighted maximum sound pressure level parameters of noise produced during shots from the 7 types of firearms included in the study. Moreover, in the most unfavorable case, the permissible number of impulses due to the value of the A-weighted noise exposure level normalized to an 8-h working day parameter exceeds 5000 per day. Conclusions Level-dependent hearing protectors constitute the appropriate means to protect the hearing of people at a shooting range, while maintaining the functionality of these protection devices to transmit speech signals. Med Pr. 2019;70(3):265–73
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Analiza tłumienia prędkości fali podłuŜnej w elemencie Ŝelbetowym z zarysowaniem

67%
TEODORCZYK M.
Edukacja-Technika-Informatyka
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2012
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vol. 3
|
issue 1
303-308
PL
W pracy przedstawiono wpływ zarysowania na prędkość podłużnych fal akustycznych w elemencie żelbetowym pod obciążeniem. Badania przeprowadzono na belce o wymiarach 120 × 300 × 6300 mm wykonanej w zakładzie prefabrykacji. Pokazano, iż powstawaniu rys towarzyszy spadek prędkości propagacji fal nawet o ponad 50%. Analiza prędkości rozchodzenia się podłużnych fal akustycznych w elementach pod obciążeniem jest perspektywą opracowania metody nieniszczącej oceny stanu technicznego konstrukcji betonowych. Efektem pomiaru jest spadek prędkości fal do pewnego poziomu degradacji materiału.
EN
This paper presents effect of cracks formation on the velocity of longitudinal acoustic waves in reinforced concrete element under load. Experiments were carried out on 120 × 300 × 6300 mm prefabricated beams. It was found, that formation of cracks causes attenuation of elastic wave (acoustic) velocity of over 50%. Hence, analysis of the elastic wave velocity can be used for structures diagnosis. Research will be carried out to develop non-destructive method for evaluation of technical state of reinforced concrete structures, which is based on the of longitudinal wave velocity.
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