• Korean Journal of Agricultural Science
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• v.39 no.4
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• pp.515-523
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• 2012

Recent development and enlargement of reclaimed lands along the sea shores required to explore alternatives to existing crops, which are suitable to grow well and to declare higher profits. The objectives of this study were to investigate yield-related parameters for development of new leafy vegetables, and to screen some candidates among New Zealand spinach genotypes which were collected in Korea. Initially all the collected genotypes were grown for 7 weeks in a greenhouse of the experiment field in Chungnam National University, and then transplanted into the field to measure morphological or physiological parameters (plant height, branch number, stem diameter, chlorophyll content, and maximum canopy diameter), and yield-related parameters (leaf number, leaf length, leaf width, fresh weight and dry weight). Those parameters were quantitatively measured at 1, 5 or 9 weeks after transplanting (WAT). Parameters exhibiting statistically significant difference among the accessions were plant height, branch number, maximum canopy diameter, chlorophyll content, and leaf length. In contrast to highly correlated parameters with fresh and dry weight obtained in salt-affected soil in the earlier report, fresh weight was correlated significantly with leaf length (r=0.72), leaf width (r=0.64), and canopy diameter(r=0.66), while dry weight was correlated significantly with plant height (r=0.46), leaf length (r=0.72), leaf width (r=0.73), fresh weight (r=0.79), chlorophyll content (r=0.47), and canopy diameter (r=0.87). Based on the significantly correlated with yield parameters, the candidate accessions which were ranked in top statistical groups include CNU06A01, CNU06A13, CNU06A26, CNU06A35, CNU06A38, and CNU06A55. In order to be cultivated in reclaimed lands, it is necessary to screen out salt tolerant accessions among the above high-yielding genotypes.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.11 no.1
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• pp.56-67
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• 1999

It is desired to use a domestically manufactured ocean data buoy for the long-term operational ocean monitoring. The ocean data buoy manufacturing technology was introduced through the research cooperation with the Qingkong University of Taiwan. The introduced ocean data buoy system was further expanded and improved for more efficient application for the marine environmental monitoring in Korea. The size of the ocean data buoy is 2.5 m in diameter, which is smaller compared to the NOAA's 3.0 m discus buoy to allow easy land transportation and ocean deployment as well. From the dynamic response test of the buoy carried out numerically, it was shown that the measurement of waves with period greater than 4 seconds is acceptable. The measurement and control system of the data buoy were improved to increase the number of measuring parameters, to reduce power consumption and to enhance better data analysis and management. Each component of the improved data buoy system was described in detail in this paper. Water quality sensors of water temperature, salinity, DO, pH and turbidity were added to the system in addition to the marine meteorological sensors of wind speed and direction, air temperature, humidity, air pressure and wave. Inmarsat satellite communication system is used for the real-time data telemetry from the buoy deployed offshore. A field performance test of the improved and domestically manufactured buoy was carried out for a month at the open sea off Pohang together with DatawelI's Wave-rider buoy to compare the wave data. The results of the test were satisfactory.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.3
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• pp.226-235
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• 2011

Field measurements of the winds and waves were carried out for one year at multiple locations inside and outside of the Pohang New Harbor in order to clarify the reason of downtimes frequently occurring at most of the harbor quays and to establish an efficient countermeasure. In addition, the downtime records of the quays and precipitation data provided by Korea Meteorological Agency were acquired for mutual comparison and comprehensive analysis of the cause of downtimes. Except the influence of precipitation, it was found that the downtimes occurred when the height of waves entering into the harbor incurred by either one of swell, wind seas, or mixture of both, exceeded a threshold. The seiche whose period ranges from 5 to 80 minutes, which was suspected as a possible cause of the downtimes, is shown to have no direct relation with the downtimes. Meanwhile, the height of far-infra-gravity waves whose period ranges between 0.5 and 3 minutes, propagating to the harbor mouth forced by short period waves, showed almost proportional relationship with the height of short period waves. Based on the result of this study, it is concluded that the downtime problems of Pohang New Harbor can be greatly improved by effectively preventing the entrance of short period waves such as swell or wind seas.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.10
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• pp.125-132
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• 2019

Because the water exposed to shock waves caused by an underwater explosion cannot withstand the appreciable tension induced by the change in both pressure and velocity, the surrounding water is cavitated. This cavitating water changes the transferring circumstance of the shock loading. Three phenomena contribute to hull-plate damage; initial shock loading and its interaction with the hull plate, local cavitation, and local cavitation closure then shock reloading. Because the main concern of this paper is local cavitation due to a near-field underwater explosion, the water surface and the waves reflected from the sea bottom were not considered. A set of governing equations for the structure and the fluid were derived. A simple one-dimensional infinite plate problem was considered to verify this uncoupled solution approach compared with the analytic solution, which is well known in this area of interest. The uncoupled solution approach herein would be useful for obtaining a relatively high level of accuracy despite its simplicity and high computational efficiency compared to the conventional coupled method. This paper will help improve the understanding of fluid-structure interaction phenomena and provide a schematic explanation of the practical problem.

• Korean Journal of Plant Resources
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• v.27 no.2
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• pp.155-173
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• 2014

The habitats characteristics of Exochorda serratifolia were investigated to compile basic data for conservation and restoration. Natural habitats were located at an altitude of 1 m to 624 m above sea level with angles of inclination ranging from 2 degrees to 81 degrees. A total of 248 vascular plant taxa were identified from 37 quadrats in 16 habitats. The importance value of Exochorda serratifolia is 18.70%, and 5 highly ranked species such as Rhododendron mucronulatum (3.79%), Abelia tyaihyoni (3.27%), Euonymus alatus for. ciliatodentatus, Quercus mongolica (3.23%), and Indigofera kirilowii (2.97%) are considered to be an affinity with Exochorda serratifolia in their habitats. Species diversity was 1.03, dominance and evenness were found to be 0.15 and 0.85, respectively. Average field capacity was 24.19%, the organic matter was 8.21%, pH was 5.52, and available phosphorus was $7.71{\mu}g/g$. Correlation coefficients analysis based on environmental factors, vegetation, and soil analysis shows that the coverage of Exochorda serratifolia is correlated with field capacity and available phosphorus.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.2
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• pp.28-36
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• 2022

As port structures are exposed to various extreme external loads such as wind (typhoons), sea waves, or collision with ships; it is important to evaluate the structural safety periodically. To monitor the port structure, especially the rubber fender, a fender segmentation system using a vision sensor and deep learning method has been proposed in this study. For fender segmentation, a new deep learning network that improves the encoder-decoder framework with the receptive field block convolution module inspired by the eccentric function of the human visual system into the DenseNet format has been proposed. In order to train the network, various fender images such as BP, V, cell, cylindrical, and tire-types have been collected, and the images are augmented by applying four augmentation methods such as elastic distortion, horizontal flip, color jitter, and affine transforms. The proposed algorithm has been trained and verified with the collected various types of fender images, and the performance results showed that the system precisely segmented in real time with high IoU rate (84%) and F1 score (90%) in comparison with the conventional segmentation model, VGG16 with U-net. The trained network has been applied to the real images taken at one port in Republic of Korea, and found that the fenders are segmented with high accuracy even with a small dataset.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.35 no.1
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• pp.13-21
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• 2023

As problems such as difficulties in securing stable energy resources and global warming due to the emission of greenhouse gases due to the use of fossil fuels have emerged, interest in the development of renewable energy is increasing. Since the tidal phenomenon has a regularity that occurs regularly with a certain period, it is possible to predict accurately in advance, which has a advantage in terms of energy recovery. Therefore, various methods have been devised to utilize the tide as an energy source. Tidal power using barrages is a representative method that is widely operated, but the promotion of tidal power generation projects is being delayed or stopped due to the decrease in the level of water in the tidal basin, changes in water quality and in the ecosystem. In this study, a field experiment was conducted to develop and verify the performance of a tidal power device applicable to sea areas where dykes are already installed. As a result of carrying out four cases of experiments using two water tanks, pipe lines, open channels, weirs, and water turbine and generator, the possibility of developing a power generation system capable of 10 kW output or more and 60% efficiency or more was confirmed. These research results can be used for small-scale tidal power by utilizing the existing dykes.

• The Journal of the Convergence on Culture Technology
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• v.9 no.6
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• pp.25-31
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• 2023

The dispute over the Northern Limit Line in the West Sea has been sharply opposed since the U.N. commander set it in August 1953 with the aim of preventing accidental armed conflict between the two Koreas in the waters of the Korean Peninsula. In 2022, for the first time since the division, North Korea made a missile provocation beyond the NLL. The purpose of this study is to identify how the research on the NLL, which is under way by North Korea's actual provocation, has been conducted and to suggest a direction to proceed. This study examined the trend of research using a total of five academic information DBs, including RISS and Scholar, focusing on academic papers studied on NLL from 1998 to 2023. As a result of examining the current status of each year, field, and research method, significant differences in research volume were identified according to the government's relationship with North Korea, and the research field had the most introduction of the concept of NLL and historical background, confirming the need to expand to more diverse fields to have international legal justification and justification for the NLL, considering the changing international environment according to the logic of power. In terms of final research methods, most of them were literature studies, so the need for quantitative research using interviews, surveys, and big data was also found. It is hoped that the analysis results of this paper will play a positive role in setting the research direction for the international response of the NLL in the future amid the interests of the international political environment that is still ongoing.

• Geomechanics and Engineering
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• v.37 no.6
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• pp.599-614
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• 2024

To evaluate the safety status of deteriorated segments in a submarine shield tunnel during its service life, a seepage model was established based on a cross-sea shield tunnel project. This model was used to study the migration patterns of erosive ions within the shield segments. Based on these laws, the degree of deterioration of the segments was determined. Using the derived analytical solution, the internal forces within the segments were calculated. Lastly, by applying the formula for calculating safety factors, the variation trends in the safety factors of segments with different degrees of deterioration were obtained. The findings demonstrate that corrosive seawater presents the evolution characteristics of continuous seepage from the outside to the inside of the tunnel. The nearby seepage field shows locally concentrated characteristics when there is leakage at the joint, which causes the seepage field's depth and scope to significantly increase. The chlorine ion content decreases gradually with the increase of the distance from the outer surface of the tunnel. The penetration of erosion ions in the segment is facilitated by the presence of water pressure. The ion content of the entire ring segment lining structure is related in the following order: vault < haunch < springing. The difference in the segment's rate of increase in chlorine ion content decreases as service time increases. Based on the analytical solution calculation, the segment's safety factor drops more when the joint leaks than when its intact, and the change rate between the two states exhibits a general downward trend. The safety factor shows a similar change rule at different water depths and continuously decreases at the same segment position as the water depth increases. The three phases of "sudden drop-rise-stability" are represented by a "spoon-shaped" change rule on the safety factor's change curve. The issue of the poor applicability of indicators in earlier studies is resolved by the analytical solution, which only requires determining the loss degree of the segment lining's effective bearing thickness to calculate the safety factor of any cross-section of the shield tunnel. The analytical solution's computation results, however, have some safety margins and are cautious. The process of establishing the evaluation model indicates that the secondary lining made of molded concrete can also have its safety status assessed using the analytical solution. It is very important for the safe operation of the tunnel and the safety of people's property and has a wide range of applications.

• 한국해양학회지
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• v.30 no.6
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• pp.550-564
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• 1995

The temporal and spatial characteristics of wind fields over the neighbouring seas of the Korean peninsula are investigated using 10-years daily wind data during 1978${\sim}$1987 which have been spatially smoothed and low-pass filtered. Long term annual and monthly means are examined for synoptic patterns and spectral analyses are made for temporal variability and spatial coherence. Spatial patterns of the annual mean wind stress and curl have a strong resemblance with those of monthly means during the winter season. Two outstanding periodicities are observed at 1 and 2 cycles per year. The synoptic winds over the study area are highly coherent at both the annual and semi-annual periodicities. However, each basin has its own characteristic spatial pattern. For instance, the prevailing wind during the winter season is northerIy over the northern East Sea (ES), Yellow Sea (YS), and northern East China Sea (ECS), while it is northwesterly over the southern ES and northesterly over the northern ES and southern ECS. At the same time, the wind stress curl is positive over the northern ES and southern ECS, while it is negative over the southern ES, YS and northern ECS. On the other hand, the wind field during the summer season, with its strength being much reduced, is completely different from that during the winter season, and frequent passage of tropical storms provokes large temporal variability over ECS. One remarkable point is that the annual cycle, dominated by the Siberian High, tends to propagate from northeast to southwest, i.e., from northern 25 toward southern ES, YS and ECS, while the semi-annual cycle propagates in the opposite direction, from southwest to northeast. The semi-annual periodicity may reflect development of extratropical cyclones in spring and fall which frequently cross the Korean peninsula. In higher frequencies, there are no dominant periodicities, but local winds over YS and ES are highly correlated for frequencies larger than 0.1 cycles per day and phase difference increases linearly with frequency. This linear increase of phase corresponds to phase speed of 550 and 730 km/d at 0.1 and 0.3 cpd, respectively, The phase speed is apparently coincident with moving speed of extratropical cyclones across the Korean peninsula in the west-east direction.