• Journal of the Korean Society of Marine Environment & Safety
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• v.30 no.2
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• pp.226-232
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• 2024

During scuba diving in Korea, accidents involving bodies being struck by the ship propeller when entering and exiting the water, repeatedly occur every year. In response to the need to reduce accidents and implement safety management measures, Korea has established regulations for the installation and management of propeller guards. However, owing to the absence of clear production regulations in domestic laws and regulations, the installation standards are ambiguous, and the inspection items are limited to the appearance and fixation status. As a result, the safety of divers in propeller accidents is not guaranteed. Therefore, this study was conducted to specify the current legal requirements for the installation and inspection of propeller guards. To achieve this goal, we conducted a thorough analysis of the current state of domestic and foreign propeller guards and the legal factors pertaining to safety standards. Based on this analysis, we identified specific areas for improvement and proposed a plan to enhance the system for installation and inspection. The installation standards for propeller guards were clearly outlined in terms of the lattice size and material. Additionally, inspection standards were proposed for appearance, fixation, and material condition, along with clear indicators for assessing them.

• Journal of the Society of Disaster Information
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• v.20 no.3
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• pp.549-562
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• 2024

Purpose: In this study, numerical analysis was conducted to verify the vibration reduction effect of installing vibration barriers under various installation conditions to mitigate train-induced vibrations from the GTX. Method: To identify the factors influencing vibration reduction among the installation conditions, the stiffness ratio of the filling material and the installation depth of the barrier were varied. Result: The study results indicated that using ductile filling materials provided superior vibration reduction compared to hard filling materials. The vibration reduction effect was found to be more significant when the stiffness ratio between the ground and the filling material was closer to zero. Additionally, the deeper the installation depth of the barrier, the better the vibration reduction effect. Conversely, if the barrier was installed too shallowly, vibration at the measurement point was amplified. Conclusion: The optimal installation condition for vibration reduction was found to be a stiffness ratio of 0.08 and an installation depth of 15 meters, resulting in a vibration reduction rate of 60.34% at a measurement point 10 meters away from the vibration source.

• Journal of Bio-Environment Control
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• v.32 no.4
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• pp.377-383
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• 2023

The effects of exogenous sodium nitroprusside (SNP, nitric oxide donor) on the growth, yield, photosynthetic characteristics, and antioxidant enzyme activity of kimchi cabbage (Brassica rapa L. subsp. pekinensis (Lour.) Hanelt) was studied under the low temperature conditions. Kimchi cabbages were treated with SNP of three concentrations (7.5, 15, 30 mg·L^-1) for three times at four-day intervals and exposed to low temperature (16/7℃) stress for seven days. SNP treatment induced increases of net photosynthetic rate (Pn), stomatal conductance (Gs), intracellular CO₂ concentration (Ci) and transpiration rate (Tr) under the stress condition with the highest level after the third treatment. The contents of malondialdehyde (MDA) and H₂O₂ were significantly lower in the treatment of SNP compared to the non-treated control. The activity of ascorbate peroxidase (APX), catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD), increased in treated plants by up to 38, 187, 24 and 175%, respectively compared to the non-treated control. SNP-treated and untreated plants had similar growth characteristics. Compared to the control group, SNP-treatment increased fresh weight and leaf area by 5%. Overall, our findings suggest that the application of sodium nitroprusside to the leaves contributes to reducing physiological damage and enhancing the activities of antioxidant enzymes, thereby improving low temperature stress tolerance in kimchi cabbage.

• Journal of Bio-Environment Control
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• v.32 no.4
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• pp.353-358
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• 2023

This study aimed to investigate the growth and phenol content changes of basil (Ocimum basilicum L.) under five different light intensities and photoperiods, maintaining the same Daily Light Integral (DLI) conditions in a plant factory. Basil seeds were sown on a rockwool medium for four weeks and then transplanted. To maintain a DLI 17mol·m^-2·d^-1, light intensity and photoperiod were set at 16h-295, 18h-260, 20h-235, 22h-215, and 24h-200μmol·m^-2·s^-1 and cultivated for four weeks. The harvested results showed that basil plant height, number of lateral branches, and leaf number tended to decrease from the 16h-295 treatment to the 24h-200 treatment. Shoot fresh weight, dry weight, leaf area, leaf width, and leaf length were significantly higher in the 18 h-260 treatment. The total phenolic contents in the 18h-260 treatment was significantly higher by 51.3%, 172.7%, 111%, and 119.7% compared to the 16h-295, 20h-235, 22h-215, and 24h-200 treatments, respectively. Therefore, it is anticipated that cultivating basil under the condition of 18h-260 treatment could yield enhanced growth quality and an increase in total phenolic contents.

• Journal of Bio-Environment Control
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• v.33 no.2
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• pp.107-113
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• 2024

For efficient soil water management in open fields, the proper use of soil moisture sensors is a prerequisite. Particularly in open-field environments like orchards with extensive root systems, the appropriate positioning of sensors is very important. The present study was conducted to identify the optimal placement of soil moisture sensors by assessing changes in soil water potential across various positions within orchard field soils after installing tensiometers. In apple and Asian pear orchards located in two regions of Korea, nine soil water potential sensors (TEROS 21, METER Group) were installed at distances of 20, 40, and 60 cm from the tree trunk and depths of 10, 20, and 30 cm from the soil surface, and monitored the soil water potential changes over two years. Results indicated that the positions closer to the tree trunk and the soil surface exhibited more pronounced changes in soil water potential. The greatest magnitude of change in soil water potential was observed at a distance of 20 cm and a depth of 10 cm, suggesting this position as the most suitable for soil moisture sensor installation. However, variations in the degree and pattern of changes in soil water potential were noted across sensor positions due to root system growth over time. Therefore, periodic observation and adjustments in sensor placement would be advisable to accurately monitor the soil moisture condition in long-term crops such as fruit trees in open fields.

• Applied Chemistry for Engineering
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• v.21 no.2
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• pp.169-173
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• 2010

Many salts have the ability to attract and remove water vapor from the surrounding environment. The ability of each salt to remove water vapor is based on the flow rate and temperature of air in surrounding. The objective of this study was toinvestigate the humid control characteristics in air-water system by using a desiccants. The aim is to asses the influence of three parameters on the humid control process which are air volume rate, air temperature and desiccant amount. Humidity control materials which consist of K (potassium) or Na (sodium) have been synthesized by the aqueous process. The humidity control properties of materials have been also investigated. Experiment results are as following. Thermal characteristics of desiccants showed similar properties regardless of processing condition. The experiments were examined by using artificial air-water system (humidity : 70~93%, air volume rate : $0.22{\sim}0.69m^3/s$). The results showed that the Na-type desiccant was an effective material. It was found that dew point increased with air volume rate, and the humidity change in humid control process was depended on desiccants amount.

• Corrosion Science and Technology
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• v.4 no.4
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• pp.155-163
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• 2005

Heavy duty coating are required to have minimum durable period of 15 years under average usage environment because these paints are coated with purpose of anti-corrosion, antifouling, plastering etc. Onto steel structures constructed upon land and sea and other ferrous structures of electric power generation plants, electricity transmission towers, large structures of various plants, etc. Therefore we tried to estimate heavy duty coating longevity through reliability evaluation method and used combined cyclic anti-conrrosion test method composed of drying, moisturizing and salt spray as for accelerated life test to estimate longevity. Accelerated life test hours to heavy duty coating of first grade (with longevity not less than 15 years) specification may be obtained from troubleless test hours $t_n=\frac{B_p}{n^{1/\beta}}\left[\frac{1n(1-CL)}{1n(1-p)} \right]^{1/\beta}=19.671$ (yr) where shape parameter $\beta=1.1$, confidence level CL=80 %, warranty life $B_{10}=15$ yr and sampling size n=10 (2 sets). Because acceleration factor {AF} found by accelerated test is 41.7, accelerated life test hours required may be represented about 4,132 hr so that if this amount of hours is converted to number of cycles(6 hr/cycle) of complex cycle corrosion resistance test then the amount is tantamount about 690 cycles. That means if there does not occur trouble failure (with defect factor sum not more than 20) during when there is performed 690 cycles of combined cyclic anti-corrosion test to heavy duty coating specimen then it signifies that there can be warranted longevity $B_{10}$ of 15 yr under condition of confidence level CL=80 %.

• Korean Journal of Ecology and Environment
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• v.41 no.4
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• pp.441-448
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• 2008

The purpose of this study was to analyze chemical water quality, fish trophic guilds, tolerance indicators, and fish community conditions in the Gap Stream and to compare the stream conditions between the unimpacted site and impacted site. This study was conducted in the physically stable season (May 2008) to minimize physical impacts such as flow and hydrological disturbance, and applied the study in the Gap Stream with two sites of unimpacted upstream site (Unim-S), mainly surrounded by forested area and impacted site (Im-S), influenced by the wastewater disposal plants and industrial complex in the urban region. Chemical data analysis showed that the degree of organic matter pollution, based on BOD, and COD, was $2{\sim}3$ fold greater in the Im-S than the Unim-S, and that TP, as eutrophication indicators, was 4.7 fold greater in the Im-S. Also, $NH_3-N$ was in 8.2 fold greater in the Im-S ($6.25\;mg\;L^{-1}$) than the Unim-S ($0.76\;mg\;L^{-1}$), indicating a massive influence of wastewater from the disposal plant. Similar results were found in other chemical parameters. Thus, chemical impacts in the Im-S were evident, compared to the unimpacted site. Evaluations of tolerant indicator species indicated that sensitive species were dominant in the Unim-S (23.9%) and tolerant species were dominant (97.8%) in the Im-S. Condition factor (CF) was averaged 0.95 ($0.68{\sim}1.18$) in the Unim-S and 1.08 ($0.93{\sim}1.22$) in the Im-S. Fish community in the Unim-S and Im-S was categorized as Zacco-community and Hemibarbus-community, respectively, and the community diversity index (H') was significantly (p<0.05) higher in the Unim-S (0.810) than the Im-S (0.466). Overall, our results suggest that the comparison approach of various chemical and ecological indicators provide important information in identifying multiple stressors in the stream ecosystems.

• Journal of Aquaculture
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• v.21 no.4
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• pp.252-258
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• 2008

Gonadal development and reproductive cycle of the ark shell Scarpharca subcrenata were investigated by histological observations. Samples were collected monthly from March 2007 to February 2008 in the Yeoja Bay, Yeosu, Jeollanam-do, Korea. S. subcrenata was dioecious. The gonads consist of a number of oogenic follicle and acinus. Monthly changes in the gonad index reached a maximum in June and a minimum in September. Monthly changes in the condition index reached a maximum in April and a minimum in September. The reproductive cycle of this species can be divided into five successive stages: early active stage (January to April), late active stage (March to June), ripe stage (May to August), spent stage (July to September) and recovery and resting stage (September to March). The main spawning of S. subcrenata occurred in July and August in Yeoja Bay. The sex ratio of female to male was not significantly different from 1:1.

• Journal of the Korean Geographical Society
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• v.43 no.3
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• pp.312-323
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• 2008

The purpose of this paper is to analyze thermal sensation which is measured by human physioclimatic reactions in South Korea. Relationships between Temperature-Humidity Index(THI) and human thermal sensation scale are derived from a questionnaire, which investigates degree of volunteer's thermal sensation with respect to each biometeorological condition. Analyses of these empirical relationships make it possible to calculate thermal sensational indices and to classify bioclimatic types for individual weather stations based on long-term(1971-2000) averages of monthly temperature and humidity data. A generalized annual physioclimatic maps for each Annual Cumulative Thermal Sensation Index for the 68 stations are constructed to show men tend to feel in various areas. The Monthly thermal sensations are affected by latitude, altitude, orographic effects and systems of airmasses. The Annual Cumulative Thermal sensations are increasing towards northern areas and inland, and that the major factors are largely derived from cold stress in winter. The Annual Physioclimatic Types are grouped 8 climatic types(M, ES, M-ES, M-S, W-ES, C-ES, C-M, C-M-ES) according to climatic stress. Results of this study can be applied for evaluation of thermal environment in our daily activities, and for searching relevant sports training-sites, climatherapy etc.