• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.558-567
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• 2011

One of the main objectives of noise control act is to define and ensure application and respect of noise exposure limits. Most advanced countries have prepared a legal framework for noise limits either by national laws, ordinances or municipal by-laws. A large number of advaced countries have adopted the $L_{eq}$ index for the main sources of noise (road, railway, industry). The exception is aircraft noise for which regulatory practice is highly disparate. These differences in the indices adopted, the periods and areas to which regulations apply, definitions of measurement conditions and ways in which noise levels are calculated make it difficult to compare the current advanced countries standards. This study presents the current noise abatement policy of the advanced countries and proposes the improvement of the current noise abatement policy of Korea to catch up with it of the advanced countries.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.05a
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• pp.202-203
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• 2018

Chemistry and microstructure of steel reinforcement bars play an important role to control the corrosion in concrete environments. In present study, we have chosen two different microstructure of steel rebars produced from companies and assessed their corrosion characteristics in simulated concrete pore (SCP) solution with prolonged exposure periods. Hot rolled steel rebar showed more corrosion resistance compare to thermo-mechanically treated (TMT) one. The growth of passive is greater in hot rolled (A) than TMT (B) due to orientation of microstructure. TMT steel rebar exhibit distorted microstructure with many micro cells which enhances the galvanic coupling and induce the deterioration while on the other hand hot rolled rebars exhibit fine grain boundary which responsible in growth of uniform, adherent and protective passive film resultant improved impedance was observed.

• Nuclear Engineering and Technology
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• v.55 no.1
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• pp.45-51
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• 2023

During the operation of a nuclear power plant (NPP), the waste reactor vessel closure head (RVCH) that is replaced owing to design or manufacturing defects is buried in a designated area or temporarily stored in a radiation shielding facility within the NPP. In such cases, storing it for extended periods proves a challenge owing to space constraints in the power plant and a safety risk associated with radiation exposure; therefore, dismantling it quickly and safely is crucial. However, not much research has been done on the dismantling of the RVCH in an operational power plant. This study proposes a dismantling process based on the radioactive contamination level measured for the Kori #1 RVCH, which is currently being discarded and stored, and examines the decontamination and cutting according to this process. In addition, the amount of secondary waste and dismantling cost are evaluated, and the dismantling effect of the reactor closure head is analyzed.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.06a
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• pp.83-84
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• 2020

In present study, we have deposited the Zinc coating using arc thermal spray and plasma arc spray processes onto the steel substrate and durability of the deposited coating was evaluated. The bond adhesion result shows that plasma arc sprayed Zn coating exhibited higher in its value compared to arc thermal spray. SEM shows that Zn coating deposited by plasma arc process is more compact, less porous and adherent compare to arc spray process. The corrosion resistance properties are evaluated in artificial ocean water solution with exposure periods. EIS results show that total impedance at 0.01 Hz of plasma arc sprayed coating is higher than arc thermal spray owing to the compact and less porous morphology. It is concluded that plasma arc sprayed Zn coating is better than arc thermal spray process.

• Asian-Australasian Journal of Animal Sciences
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• v.15 no.6
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• pp.859-865
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• 2002

The aim of this research was to clarify the direct effects of a hot environment on ruminal motility in sheep fed twice a day. In the first experiment, in order to equalize variable factors excluding the ambient temperature between the thermoneutral environment ($23^{\circ}C$, relative humidity 80%) and the hot environment ($32^{\circ}C$, relative humidity 80%), sheep were fed equal amounts of the same quality feed twice a day. The sheep were allowed free access to water for the duration of the two one-hour feeding periods (10:00 am-11:00 am, 5:00 pm-6:00 pm). On the fourth day after exposure to the hot environment, the frequency and strength of ruminal contractions were continuously recorded between 9:30 am and 11:00 pm. Prior to the exposure to a hot environment the frequency and strength of ruminal contractions were recorded in a thermoneutral environment during the period 9:30 am-11:00 pm. In the second experiment, in order to maintain the stomach content of the sheep at equal levels in both environments, the sheep were fed equal amounts of the same quality feed twice a day. Following the completion of the two one-hour feeding periods, a fixed amount of warm water was infused into the rumen. Rumen motility was then recorded during the same period as for the first experiment (9:30 am-11:00 pm). In the first experiment, when the frequency of ruminal contractions prior to (24, 24 frequency/15 min), during (48, 47 frequency/min) and after (22, 19 frequency/min) both the morning and afternoon feeding in a hot environment was compared with the values from the thermoneutral environment (20, 22; 50, 50; 21, 20 frequency/min), there was found to be no difference. However, the strength of ruminal contractions after morning and afternoon feeding (3.7, 3.1 mm Hg) in the hot environment decreased significantly in comparison with the thermoneutral environment (4.3, 3.8 mm Hg). In the second experiment, the frequency of ruminal contractions in the hot environment was not significantly different from that in the thermoneutral environment. The strength of ruminal contractions after ruminal infusion of warm water in the hot environment (morning: 4.6, afternoon: 4.5 mm Hg) was significantly lower than that in the thermoneutral environment (morning: 5.6, afternoon: 5.0 mm Hg). The results suggest that a hot environment acts directly on the strength of ruminal contractions in sheep fed twice a day rather than on the frequency.

• The Journal of Engineering Geology
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• v.26 no.1
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• pp.117-128
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• 2016

Chemical reaction tests were performed to assess the properties of hardened specimens of cement pastes (KS-1 Portland and Class G) exposed to supercritical CO₂ for 1, 10, and 100 days. After exposure, the samples' measured permeability and strength were compared with values measured for pristine samples. The pristine cements had permeabilities of 0.009~0.025 mD, which increased by one order of magnitude after 100 days of exposure (to 0.11~0.29 mD). The enhancement of permeability is attributed to the stress release experienced by the samples after removal from the pressure vessel after exposure. Despite its enhancement, the measured permeability mostly remained lower than the API (American Petroleum Institute) recommended maximum value of 0.2 mD. The degradation of the cement samples due to exposure to supercritical CO₂ led to a layer of altered material advancing inwards from the sample edges. The Vickers hardness in the altered zone was much higher than that in the unaltered zone, possibly owing to the increase in density and the decrease in porosity due to the carbonation that occurred in the altered zone. Hardness close to the edge within the altered zone was found to have decreased significantly, which is attributed to the conversion of C-S-H into less-strong amorphous silica.

• Environmental Analysis Health and Toxicology
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• v.24 no.3
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• pp.241-249
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• 2009

Heavy metal contaminants on the aquatic environment are of interest because they can have severe effects on economy and public health. Recently, the studies for monitoring of heavy metals try to do on aquatic system to assess safety and health of ecosystem by heavy metals. Thus, biological responses were investigated on Korean fairy shrimp Branchinella kugenumaensis exposed to cadmium (Cd) or copper (Cu) for long-periods (30 days). The survival rate decreased significantly (p<0.05) on B. kugenumaensis exposed to Cd and Cu at all concentrations. Especially, the highest decrease was observed at the relatively high concentration of Cd and Cu (p<0.01) and the response by Cd exposure was at dose-dependent. The growth rates were also decreased significantly (p<0.05) on B. kugenumaensis exposed to Cd and Cu for at all concentrations. Then, the reproduction rate, numbering cyst, was decreased significantly (p<0.01) on B. kugenumaensis after Cd or Cu exposures. Long exposure of the relatively high concentration Cd and Cu can have severe effects on the reproduction, while exposures of Cd and Cu can not have effects on sex ratios of B. kugenumaensis. Additionally, asymmetric telson deformity was only observed after Cd exposure. Therefore, these results suggest that B. kugenumaensis is a sensitive bio-indicator of heavy metal exposure and these biological responses of B. kugenumaensis give important information for long-term monitoring on aquatic ecosystem.

• Korean Journal of Environmental Biology
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• v.21 no.1
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• pp.36-41
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• 2003

In order to estimate chornic toxicity of copper in the juvenile oliver flounder, Paralichthys olivaceus, experiments were investigated the effects of long term sublethal copper exposure on survival rate, metabolic rate, feed efficiency and growth rate. Oliver flounder were exposed for 6 weeks to four different sublethal copper concentration (50, 80, 180, 320 $\mu\textrm{g}$ $L^{-1}$). Survival rate of them significantly affected above 180 $\mu\textrm{g}$ $L^{-1}$, and reduced for increase exposure periods and concentrations. Copper exposure to 180 and 320 $\mu\textrm{g}$ $L^{-1}$ significantly decreased metabolic rate in olive flounder. Exposure to waterborne copper concentrations as high as 80 $\mu\textrm{g}$ $L^{-1}$ resulted in significantly reduced feed efficiency and growth rate. From these results, it could be concluded that the high level of 80 $\mu\textrm{g}$ $L^{-1}$ copper concentration in the bottom water would curtail production of the olive flounder in coastal area.

• Asian-Australasian Journal of Animal Sciences
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• v.22 no.3
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• pp.328-335
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• 2009

This study was undertaken to investigate the influence of exposure and removal of four different cryoprotectants (CPAs) on the ATP content of cumulus cell-enclosed (COs) and cumulus cell-denuded (DOs) immature porcine oocytes. The in vitro nuclear maturation of the COs, exposed to and removed from the CPAs was also assessed. Both COs and DOs were exposed to 1.5 M concentrations of each CPA (ethylene glycol (EG); propylene glycol (PG); dimethyl-sulfoxide (DMSO); and glycerol (G)) for durations of 5, 15, and 30 minutes at room temperature ($23.5{\pm}1.5^{\circ}C$), and immersed in physiological saline supplemented with 20% (v/v) fetal bovine serum for 5 minutes ($39^{\circ}C$) to remove each CPA. Before, during and after exposure to each CPA, the ATP content of both the COs and the DOs was measured. After removal from each CPA an aliquot of the COs was matured for 44${\pm}$2 h, and their nuclear maturation rates were measured up to the metaphase stage of the second meiotic division (the M-II stage). The maturation rates up to the M-II stage were not significantly different between all the groups that were exposed to each CPA for 5 minutes. For 15 and 30 minute exposures, the maturation rates of the COs exposed to PG, DMSO and EG were almost the same as those of the control groups; however, the rates of G group exposed for 15 and 30 minutes were significantly lower (p<0.05) than the control group. These groups were also found to have a decrease in the ATP content of COs and DOs during and after exposure for the same periods (p<0.05). In addition, although the ATP contents of the COs after exposure to EG for any period were the same as the controls, the ATP content of the DOs exposed to EG for any period were significantly lower (p<0.05) than those of the controls. When the ATP content of the COs and DOs of each CPA were compared, the DOs exposed to PG were found to have a significantly greater level (p<0.05) than DOs exposed to G for any duration. In addition, the ATP content of DOs exposed to PG for 30 min and removal was also higher (p<0.05) than when exposed to DMSO for the same period. These findings indicate that PG may be a useful CPA for the cryopreservation of immature porcine oocytes.

• Asian-Australasian Journal of Animal Sciences
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• v.13 no.9
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• pp.1210-1218
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• 2000

Four experiments were conducted to evaluate the effect of temperature and humidity on biochemical indices of Arbor Acres broilers at different weeks of age. The alkaline phosphatase (AKP), acid phosphatase (ACP), lactic dehydrogenase (LD), creatine kinase (CK), plasma glucose (Glu), calcium (Ca), potassium (K), chloride (Cl), urea nitrogen (UN), uric acid (UA), plasma thyroxin (T4), triiodothyronine (T3) and insulin levels were determined in all the four experiments. In experiment 1, the plasma Glu, LD and CK levels were increased by heat exposure ($35{^{\circ}C}$ and 35, 60, or 85% RH, 2 h) and this effect was aggravated by longer exposure (24 h). No significant changes (p>0.05) were found in Ca concentration, activity of AKP and ACP. In experiment 2, temperature (10, 20, 30, $33{^{\circ}C}$) had significant effect on the levels of K, Cl, UN, UA levels and the activity of LD (p<0.01), but had no significant influence on the activity of CK (p>0.05). The UN, UK and LD levels were elevated by low temperature $(10{^{\circ}C})$ (p<0.01), Cl content was increased by high temperature ($(33{^{\circ}C})$ (p<0.01), and K level was decreased by high ($(33{^{\circ}C})$ or low $(10{^{\circ}C})$ temperature and increased by medium temperature $(30{^{\circ}C})$ (p<0.01). The humidity (35, 85% RH) only had significant effect on Cl concentration which was decreased by high humidity (p<0.01). In experiment 3, the result showed that only the LD and CK activity were significantly increased (p<0.01) by high temperature (7, 24, 28, $32{^{\circ}C}$) or high humidity (35, 85% RH). Temperature and humidity had no significant effect on K, Cl, UA, UN and Glu levels (p>0.05). In experiment 4 (24, 27, 30, $33{^{\circ}C}$; 30, 45, 60, 75, 90% RH), plasma T3 level was declined by high temperature $(33{^{\circ}C})$, and this phenomena disappeared in birds under high temperature and high humidity environment. T4 concentration in plasma was not affected by temperature (p>0.05), but was increased by high or low humidity (p<0.01). Neither temperature nor humidity had significant effect on plasma insulin concentration (p>0.05). The results of the four experiments suggested that broilers at different growth periods might have different thermal requirements and would response differently to heat exposure. The plasma biochemical indices themselves had big variation; the reaction of the indices to thermal exposure treatment differed with the age of broilers. The big variation of biochemical indices themselves might cover the response of indices to temperature and humidity treatments.