• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.2
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• pp.370-376
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• 2022

Smart ships related studies are being conducted in various fields owing to the development of technology, and an engine room patrol robot that can patrol the unmanned engine room is one such study. A patrol robot moves around the engine room based on the information learned through artificial intelligence and checks the machine normality and occurrence of abnormalities such as water leakage, oil leakage, and fire. Study on engine room patrol robots is mainly conducted on machine detection using artificial intelligence, however study on movement and control is insufficient. This causes a problem in that even if a patrol robot detects an object, there is no way to move to the detected object. To secure maneuverability to quickly identify the presence of abnormality in the engine room, this study experimented with whether a patrol robot can determine the shortest path by applying the A* algorithm. Data were obtained by driving a small car equipped with LiDAR in the ship engine room and creating a map by mapping the obtained data with SLAM(Simultaneous Localization And Mapping). The starting point and arrival point of the patrol robot were set on the map, and the A* algorithm was applied to determine whether the shortest path from the starting point to the arrival point was found. Simulation confirmed that the shortest route was well searched while avoiding obstacles from the starting point to the arrival point on the map. Applying this to the engine room patrol robot is believed to help improve ship safety.

• Journal of Environmental Impact Assessment
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• v.31 no.4
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• pp.241-249
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• 2022

Humans and wild birds coexist in cities, where habitat fragmentation due to urbanization threatens the habitat and movement of birds. In this study, in order to identify landscape features associated with wild bird collide, we characterized landscape composition within a 500 m radius and points of wild bird carcasses in Suwon-city, South Korea. Dead birds were identified as having a Normalized Difference Vegetation Index (NDVI) of 0.3, Normalized Difference Built-up Index (NDBI) of -0.05, and Normalized Difference Water Index (NDWI) of -0.16 at the points of collide. And there were NDVI of 0.34, NDBI of -0.01, NDWI of -0.18, building height of 13.8 m, and soundproof wall length of 227.3 m within a radius of 500 m. Land cover type was dominated by grassland, used area, and bare land. In particular, the edges of urbanized areas, where apartments bordered forests, reservoirs, and golf courses, were identified as high-risk spaces. In order to minimize bird mortality risk in urban environments, the impact of changes to a vertical landscape should be reviewed from an environmental impact assessment approach. In addition, a preventive management plan that considers the temporal and spatial features that wild animals can safely avoid and adapt to in urbanized spaces should be prepared.

• Journal of the Korean Society of Radiology
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• v.16 no.5
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• pp.603-609
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• 2022

The dose distribution in the human body was evaluated and analyzed through dosimetry data using water phantom, ionization chamber and simulated by Monte Carlo simulation for ^99mTc and ¹⁸F sources, which are frequently used in the nuclear medicine in this study. As a result of this study, it was found that the dose decreased exponentially as the distance from the radioisotope increased, and it particularly showed a tendency to decrease sharply when the radioisotope was separated by 5 cm. It means that a large amount of dose is delivered to an organ located within 4 cm of source's movement path when a source uptake in the human body. Numerically, it was formed in the rage of 0.16 to 2.16 pC/min for ^99mTc and 0.49 to 9.29 pC/min for ¹⁸F. In addition, the energy transfer coefficient calculated using the result was found to be similar to the measured value and the simulation value in the range of 0.240 to 0.260. Especially, when the measured data and the simulation value were compared, there was a difference is within 2%, so the reliability of the data was secured. In this study, the distribution of radiation generated from a source was calculated to quantitatively evaluate the internal dose by radioisotopes. It presented reliable results through comparative analysis of the measurement value and simulation value. Above all, it has a great significance to the point that it was presented by directly measuring the distribution of radiation in the human body.

• Journal of People, Plants, and Environment
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• v.23 no.2
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• pp.211-220
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• 2020

The purpose of this study was to analyze the frequency and contents of horticultural activities in 696 individual activities listed in 11 teacher's guidebooks of Nuri Curriculum for 5-year-olds, and to find out the perceptions of horticultural activities in the formal curriculum. The target horticultural activities that were selected were those using natural objects like potted plants, water, wind, soil, stones, etc. as the topic or subject of activities, and those with different topics but are mentioning plants or natural objects as an example at least twice. The 150 selected horticultural activities were classified by life-based theme, activity type, activity domain, and medium. As a result of examining horticultural activities by life-based theme, there were 150 horticultural activities (21.55%): 40 in Spring, Summer, Autumn and Winter (5.75%), 34 in Animals, Plants, and Nature (4.89%), 22 in Environment and Life (3.16%), 19 in Our Country (2.73%), and nine in Our Neighborhood (1.29%), nine in Various Countries of the World (1.29%), four in Health and Safety (0.57%), four in Living tools (0.57%), four in Transportation (0.57%), three in Kindergarten and Friends (0.43%), two in Me and My Family (0.29%; χ²=130.427, p < .001). As a result of examining horticultural activities by activity type, there were 61 free choice activities (40.67%), 80 large and small group activities (53.33%), and nine outdoor play activities (6.00%), indicating that outdoor play was the fewest activity type (χ²=54.040, p < .001). The results of analyzing horticultural activities by activity domain showed that there were 25 in conversation (16.67%), 19 in science (12.50%), 14 in art (9.33%), 14 in cooking (9.33%), 10 in fairy tales (6.00%), nine in music (6.00%), eight in language (5.33%), eight in number operation (5.33%), eight in others (5.33%), six in children's plays (4.0%), six in games (4.0%), four in body and movement (2.67%), three in stacking (2.00%), three in roles (2.00%), three in rhythm (2.00%), two in children's poems (1.33%), two in field experience (1.33%) and one in outside play (0.67%; χ²=87.600, p < .001). As a result of examining the mediums used in the horticultural activities, 46 activities (30.67%) directly used plants as the mediums, 11 activities (7.33%) used soil such as stones, gravel, and earth as the mediums instead of plants, four activities (2.67%) used dry plants such as branches and dry leaves as the mediums, and 89 activities (59.33%) used videos, photos of plants, and pictures of plants as the mediums (χ²=121.307, p < .001).

• The Journal of Engineering Geology
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• v.33 no.1
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• pp.69-83
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• 2023

Forest fires increase the risk of subsequent soil erosion and mass movement in burned areas, even under rainfall conditions below landslide alert thresholds, by destroying plants and vegetation and causing changes to soil properties. These effects of forest fires can alter runoff in burned areas by altering soil composition, component minerals, soil water repellency, soil mass stability, and soil fabric. Heat from forest fires not only burns shallow organic matter and plants but also spreads below the surface, affecting soil constituents including minerals. This study analyzed X-ray diffraction and physical properties of topsoil and subsoil obtained from both burned and non-burned areas to identify the composition and distribution of clay minerals in the soil. Small amounts of mullite, analcite, and hematite were identified in burned soils. Vermiculite and mixed-layer illite/vermiculite (I/V) were found in topsoil samples from burned areas but not in those from non-burned areas. These findings show changes in soil mineral composition caused by forest fires. Expansive clay minerals increase the volume of soil during rainfall, degrading the structural stability of slopes. Clay minerals generated in soil in burned areas are therefore likely to affect the long-term stability of slopes in mountainous areas.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.35 no.4
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• pp.75-83
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• 2023

Apart from implementing hardware solutions like raising the crest freeboard of coastal structures to efficiently counter wave-overtopping, there is a simultaneous requirement for software-driven disaster mitigation strategies. These tactics involve the swift and accurate dissemination of wave-overtopping information to the inland regions of coastal zones, enabling the regulation of evacuation procedures and movement. In this study, a method was proposed to estimate wave-overtopping by utilizing the temporal variation of wave heights exceeding the structure's crown level, with the aim of developing an on-site wave measurement system for providing wave-overtopping information in the field. Laboratory model experiments were conducted on vertical seawall structures to measure wave-overtopping volumes and wave runup heights under different wave conditions and structural freeboard variations. By assuming that the velocity of water inundation on the top of the structure during wave-overtopping events is equivalent to the long-wave velocity, an overtopping discharge coefficient was introduced. This coefficient was utilized to estimate the rate of wave-overtopping based on the temporal changes in wave runup heights measured at the top of the structure. Upon reasonably calculating the overtopping discharge coefficient, it was verified that the estimation of wave-overtopping could be achieved solely based on the wave runup heights.

• Proceedings of the Korean Society of Developmental Biology Conference
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• 2003.10a
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• pp.72-72
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• 2003

The present study examined the possibility of cryopreservation of the D-shaped and umbo larvae of arkshell (Scapharca broughtonii), in terms of the survival rates after freezing and thawing. D-shaped and umbo larvae of arkshells were obtained from a shellfish farming on Yosu city. The average shell lengths were $93.3 \pm 10.1 \mu$m and $201.7 \pm 13.5 \mu$, respectively. Five cryoprotectants (CPAs), dimethyl sulfoxide (DMSO), glycerol, ethylene glycol (EG), propylene glycol (PG), and methanol, were tested at the concentrations of 1.5, 2.0 and 2.5 M. After larvae suspended in CPAs, cryoprotectants were loaded in 0.5 ml straws at a larval density of 50-100 larvae per straw, and epuilibrated for 10 and 20 minute at room temperature ($23^{\circ}C$), repectively. Straws were cooled at a rate of $1^{\circ}C$/min from $0^{\circ}C$ to $-12^{\circ}C$, held for 5 min at $-12^{\circ}C$, and then cooled at $2^{\circ}C$/min to $-35^{\circ}C$ and equilibrated for 5 min followed by plunging in liquid nitrogen. After storage in liquid nitrogen for 1 day, straws were thawed in a $30^{\circ}C$ water. As soon as straws were observed to melt, larvae were diluted with an equal volume of ASW and then washed twice with a large volume of ASW at an interval of 2 min to unload the CPAs. The results showed that after equilibration for 10 and 20 minute at room temperature, no larvae survived using methanol as CPAs, and it was observed that larval shells all open slightly, and larval flesh broke down and slopped over the shells. The highest survival rates (D-shaped larvae: 77.6%, umbo larvae: 59.3%) were obtained with 2M DMSO, and 1.5M glycerol yielded survival rates of 53.8% for D-shaped larvae and 37.5% for umbo larvae. The surviving D-shaped larvae showed active rotary motion and perfect membrane integrity and cytoplasmic normality, and the vigorous movement of veliger cilia was observed inside the closed shells. The breakdown of tissue occurred in the abnormal larvae, and the isolated cell often run out of shells.

• Journal of the Korean GEO-environmental Society
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• v.24 no.4
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• pp.23-29
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• 2023

Ground subsidence shows a mechanism in which the upper ground collapses due to the formation of a cavity due to the movement of soil particles in the ground due to the formation of a waterway because of damage to the water supply/sewer pipes. As a result, cavity is created in the ground and the upper ground is collapsing. Therefore, ground subsidence frequently occurs mainly in downtown areas where a large amount of underground facilities are buried. Accordingly, research to predict the risk of ground subsidence is continuously being conducted. This study tried to present a ground subsidence risk prediction model for two districts of ○○ city. After constructing a data set and performing preprocessing, using the property data of underground facilities in the target area (year of service, pipe diameter), density of underground facilities, and ground subsidence history data. By applying the dataset to the machine learning model, it is evaluated the reliability of the selected model and the importance of the influencing factors used in predicting the ground subsidence risk derived from the model is presented.

• Journal of The Geomorphological Association of Korea
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• v.28 no.3
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• pp.13-26
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• 2021

In mountain gully, channelized debris flow is an important phenomenon in the process of topographical change. Social infrastructure as roads may be damaged by channelized debris flows, but there has been little information about their occurrence and movement to prepare for the risk of the debris flow. Most of the channelized debris flows occur during heavy rains in mountainous valleys that are difficult to access, so there are not many field data. In this study, the topographical characteristics of the catchment, the rainfall and runoff related to the debris flow, the sedimentary pattern and the cross-sectional change of the channel bed, and the underflow velocity of the gravel bed have been investigated and analyzed in the Singi gully where the channelized debris flows occurred. In the catchment, there was almost no sediment runoff because the vegetation combine with the debris landforms and covered the surface. Therefore, the obvious cause of the channelized debris flows is the collapse of the slope and bed of the gully. Even if the gravel, cobbles, and boulders of the channel bed were lost by debris flow, the thalweg change due to debris flow may not be significant because they are supplied from the gully side slope normally. After the gabion structures were installed, the debris flow increased the thalweg change, bed erosion and side slope of the gully. Various sedimentary structures in the gully were classified according to the factors supporting the sedimentation. The hypsometric curve of the gully reflects the debris landforms and vegetation characteristics of the watershed and the sediment runoff due to debris flow, etc. The relationship between the flow velocity and the hydraulic gradient was non-linear under the condition that the porous medium with gully bed gravels is saturated with water. These results may be used as basic data for channelized debris flow research.

• Journal of the Korean GEO-environmental Society
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• v.25 no.6
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• pp.19-24
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• 2024

Urban densification has necessitated the development of subterranean spaces such as subway networks and underground tunnels to facilitate the dispersal and movement of populations. Development of these underground spaces requires excavation from the ground surface, which can induce groundwater flow and potentially lead to ground subsidence and sinkholes, damaging structures. To mitigate these risks, it is essential to model groundwater flow prior to construction, analyze its characteristics, and predict potential groundwater discharge during excavation. In this study, we collected meteorological, topographical, and soil conditions data for the city of ○○, where tunnel construction was planned. Using the Visual MODFLOW program, we modeled the groundwater flow. Excavation sections were set as drainage points to monitor groundwater discharge during the excavation process, and the effectiveness of seepage control measures was assessed. The model was validated by comparing measured groundwater levels with those predicted by the model, yielding a coefficient of determination of 0.87. Our findings indicate that groundwater discharge is most significant at the beginning of the excavation. Additionally, the presence of seepage barriers was found to reduce groundwater discharge by approximately 59%.