• Journal of Ocean Engineering and Technology
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• v.30 no.4
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• pp.327-333
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• 2016

Reinforced concrete structures have found wide usage in land and maritime applications. However, the corrosion of reinforced concrete has been recognized as a serious problem from economic and safety standpoints. In previous studies, the corrosion behavior of the inner steel bar embedded in mortar (W/C: 0.4, 0.5) was investigated using electrochemical methods. In this study, multiple mortar test specimens (W/C: 0.6) with six different cover thicknesses were prepared and immersed in flowing seawater for five years. Subsequently, equations related to the cover thickness, period of immersion, and corrosion characteristics of the embedded steel bar were evaluated using electrochemical methods. Prior to immersion, the corrosion potentials indicated an increase with increasing cover thickness, and after five years, all corrosion potentials demonstrated a trend in the positive direction irrespective of the cover thickness. However, the relationships between the corrosion potential and cover thickness were not in complete agreement. Furthermore, after five years, all of the corrosion potentials indicated values that were nobler compared to those obtained prior to immersion, and their corrosion current densities also decreased compared to their values obtained prior to immersion. It was considered that the embedded steel bar was easily corroded because of the aggression of water, dissolved oxygen, and chloride ions; a higher W/C ratio also assisted the corrosion process. The corrosive products deposited on the surface of the steel bar for five years cast a resistance polarizing effect shifting the corrosion potential in the nobler direction. Consequently, it was considered that the W/C ratio of 0.6 showed nearly same results as those of W/C of 0.4 and 0.5. Therefore, the corrosion potential as well as various parameters such as the cover thickness, period of immersion, and W/C ratio must be considered at once for a more accurate evaluation of the corrosion property of reinforced steel exposed to marine environment for a long period.

• Journal of Animal Environmental Science
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• v.16 no.3
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• pp.205-215
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• 2010

Geothermal heat pump system (GHPS) is an energy-efficient technology that use the relatively constant and renewable energy stored in the earth to provide heating and cooling. With the aim of using GHPS as a heating source, it's possibilities of application in farrowing house were examined by measuring environmental assessment and sow's performance. A total of 96 sows were assigned to 2 pig housings (GHPS and conventional housing) with 48 for four weeks in winter season. During the experimental period, indoor maximum temperature in GHPS-housing was measured up to $26.7^{\circ}C$, average temperature could maintain $21.2^{\circ}C$. The mean value of dust levels and $CO_2$, $NH_3$ and $H_2S$ gas emissions were decreased in GHPS-housing compare with those of conventional housing. Litter size, birth weight, parity and weaning weight did not differ between housings. However, feed intake of sow in GHPS-housing was lower than that of conventional housing. In energy consumption for heating, electric power consumption increased in GHPS-housing than the conventional housing, a 2,250 kwh increase, whereas there is no fuel usage for heater in GHPS-housing. Amount of ground water circulated for heating in cold weather for earth heat exchanger was 8.4-12.9 ton per day. In conclusion, GHPS may have environmental benefits and effectiveness of heating in farrowing housing and affect the performance in sows.

• Journal of the Korean Society of Radiology
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• v.10 no.8
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• pp.597-602
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• 2016

Recent clinical field utilizes the aluminium filter in order to reduce the low-energy photons. However, the usage of the filter can cause adverse effect on the image quality because of the scattered dose that is generated by X-ray hardening phenomenon. Further, usage of filter with improper thickness can be a reason of dose creep phenomenon where unnecessary exposure is generated towards the patient. In this study, the author evaluated the RMS and the RSD analysis in order to have a quantitative evaluation for the effect of forward scattering dose by the filter on the image. as a result of the study, the FSR and the RSD was increased together with the increasing of thickness of the filter. In this study the RSD means the standard deviation of the mean value is relatively size. It can be understood that the signal-to-noise ratio decreases when the average value is taken as a signal and the standard deviation is judged as a noise. The signal-to-noise ratio can understanding as index of resolution at image. Based on these findings, it was quantitatively verified that there is a correlation of the image quality with the FSR by using an additional filter. The results, a 2.5 mmAl which is as recommended by NCRP in the tube voltage of 70 kVp or more showed the 14.6% on the RSD when the filter was not in used. these results are considered able to be utilized as basic data for the study about the filter to improve the quality of the image.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.7
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• pp.848-857
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• 2018

Recently, around the world, active development of new renewable energy sources including solar power, waves, and fuel cells, etc. has taken place. Particularly, floating offshore wind farms have been developed for saving costs through large scale production, using high-quality wind power and minimizing noise damage in the ocean area. The development of floating wind farms requires an evaluation of the Maritime Safety Audit Scheme under the Maritime Safety Act in Korea. Floating wind farms shall be assessed by applying the line and area concept for systematic development, management and utilization of specified sea water. The development of appropriate evaluation methods and standards is also required. In this study, proper standards for marine traffic surveys and assessments were established and a systemic treatment was studied for assessing marine spatial area. First, a marine traffic data collector using AIS or radar was designed to conduct marine traffic surveys. In addition, assessment methods were proposed such as historical tracks, traffic density and marine traffic pattern analysis applying the line and area concept. Marine traffic density can be evaluated by spatial and temporal means, with an adjusted grid-cell scale. Marine traffic pattern analysis was proposed for assessing ship movement patterns for transit or work in sea areas. Finally, conceptual design of a Marine Traffic and Safety Assessment Solution (MaTSAS) was competed that can be analyzed automatically to collect and assess the marine traffic data. It could be possible to minimize inaccurate estimation due to human errors such as data omission or misprints through automated and systematic collection, analysis and retrieval of marine traffic data. This study could provides reliable assessment results, reflecting the line and area concept, according to sea area usage.

• Journal of radiological science and technology
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• v.40 no.1
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• pp.41-47
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• 2017

Considering that the X-ray apron used in the department of radiology is also used in the department of nuclear medicine, the study aimed to analyze the shielding rate of the apron according to types of radioisotopes, thus ${\gamma}$ ray energy, to investigate the protective effects. The radioisotopes used in the experiment were the top 5 nuclides in usage statistics $^{99m}Tc$, $^{18}F$, $^{131}I$, $^{123}I$, and $^{201}Tl$, and the aprons were lead equivalent 0.35 mmPb aprons currently under use in the department of nuclear medicine. As a result of experiments, average shielding rates of aprons were $^{99m}Tc$ 31.59%, $^{201}Tl$ 68.42%, and $^{123}I$ 76.63%. When using an apron, the shielding rate of $^{131}I$ actually resulted in average dose rate increase of 33.72%, and $^{18}F$ showed an average shielding rate of -0.315%, showing there was almost no shielding effect. As a result, the radioisotopes with higher shielding rate of apron was in the descending order of $^{123}I$, $^{201}Tl$, $^{99m}Tc$, $^{18}F$, $^{131}I$. Currently, aprons used in the nuclear medicine laboratory are general X-ray aprons, and it is thought that it is not appropriate for nuclear medicine environment that utilizes ${\gamma}$ rays. Therefore, development of nuclear medicine exclusive aprons suitable for the characteristics of radioisotopes is required in consideration of effective radiation protection and work efficiency of radiation workers.