• Journal of Korean Society of Coastal and Ocean Engineers
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• v.34 no.4
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• pp.128-134
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• 2022

Nakdong river estuary is being operated with the goal of expanding the period of seawater inflow from this year to 2022 every month and creating a brackish water area within 15 km of the upstream of the river bank. In this study, the deep learning algorithm Long Short-Term Memory (LSTM) was applied to predict the salinity of the Nakdong Bridge (about 5 km upstream of the river bank) for the purpose of rapid decision making for the target brackish water zone and prevention of salt water damage. Input data were constructed to reflect the temporal and spatial characteristics of the Nakdong River estuary, such as the amount of discharge from Changnyeong and Hamanbo, and an optimal model was constructed in consideration of the hydraulic characteristics of the Nakdong River Estuary by changing the degree according to the sequence length. For prediction accuracy, statistical analysis was performed using the coefficient of determination (R-squred) and RMSE (root mean square error). When the sequence length was 12, the R-squred 0.997 and RMSE 0.122 were the highest, and the prior prediction time showed a high degree of R-squred 0.93 or more until the 12-hour interval.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.6
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• pp.148-156
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• 2022

Although most domestic concrete structures are simultaneously exposed to freeze-thaw and chloride environments, concrete durability in the field is evaluated by each single action, and the evaluation of chloride-caused damage of concrete requires additional indoor experimental analysis of chloride contents by coring samples from structures in the field. However, in Korea, policies to strengthen facility maintenance, such as 「Special Act on the Safety Control and Maintenance of Establishments」 and 「Framework Act on Sustainable Infrastructure Management」, have been established and implemented since 2018 and facilities subject to safety inspection management by the government and local governments increases, the effective simplification technology for the inspection and diagnosis of concrete structure is needed. Therefore, this study attempted to evaluate the possibility of determining the acceleration chloride penetration of freeze-thaw damaged concrete by using the surface rebound value. For this purpose, concrete specimens already having freeze-thaw damage by exposure to the freeze-thaw acceleration environment were immersed in chloride water. After that, the acceleration relationship of chloride penetration according to freeze-thaw damage was analyzed using the amount of chloride contents in concrete.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.6
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• pp.23-32
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• 2022

Although PSCB girder bridges account for 4% of the bridges in use on highways, they do not account for much, but 98% of PSCB girder bridges are 1^st type and 2^nd type of bridge. Also, the total length of the PSCB girder bridge is 16% (192km) of the total length of the highway bridge. Thus, the PSCB girder bridge can be one of the bridge types where maintenance is important. In order to analyze the damage types of PSCB girder bridges, a detailed analysis was conducted by selecting 62 places (477 spans) precision safety diagnosis reports considering ratio of the construction method and snow removal environment exposure class. Analysis of report and a field investigation was conducted, and as a result, most of the causes of deterioration damage were caused by rainwater (salt water) flowing into the bridge pavement soaking in between the top flange and the interface. After concrete slab deteriorate occurred then bridge pavement cracking and breaking increased and exfoliation of concrete occurred by corrosion and expansion of the reinforcing bars occurred. In addition, the cause of cracks in the longitudinal direction on the bottom of the top flange is considered to be cracks caused by restrained drying shrinkage. In conclusion, for reasonable maintenance considering the characteristics of PSCB girder bridges, it should be suggested in the design aspect that restrained drying shrinkage crack on top flange. Also, it is believed that differentiated maintenance method should be proposed according to snow removal environment exposure class.

• Microbiology and Biotechnology Letters
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• v.50 no.4
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• pp.557-562
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• 2022

In this study we evaluated biohydrogen production potential as operational parameters (substrate, salt concentration, and temperature) using eight inoculum sources. While the volumetric biohydrogen production rate was significantly affected by temperature and inoculum sources, substrate and salt concentration did not have a significant effect on the biohydrogen production. Mesophilic temperature (37℃) was also found more appropriate for the hydrogen production than thermophilic temperature (50℃). Rate, while the eight inoculum sources, anaerobic digestion sludge exhibited the fastest biohydrogen production. The maximum production rate from anaerobic digestion sludge was 2,729 and 1,385 ml-H₂·l^-1·d^-1 at mesophilic and thermophilic temperature, respectively.

• Journal of Life Science
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• v.33 no.6
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• pp.481-489
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• 2023

The taste and quality of soy sauce, a fermented liquid condiment, is greatly influenced by microbial metabolism during fermentation. To investigate the microbiological characteristics of ganjang during the initial fermentation process, we prepared meju (fermented soybean) blocks fermented with starter cultures and solar salts and analyzed the microbial community quantitively using 16S rRNA gene profiling from ganjang that had been fermented over a five-week period. The ganjang samples were collected and analyzed after soaking for week one (1W), three (3W), and five (5W) weeks. We found that Halomonadaceae was significantly higher in the 1W group (89.83%) than the 3W and 5W groups (14.46%, and 13.78%, respectively). At a species level, Chromohalobacter beijerinckii and Chromohalobacter canadensis were the dominant species in the 1W group but several taxa such as Bacillus subtilis, Pediococcus acidilactici, and Enterococcus faecalis were more abundant in the 3W and 5W groups. Pearson correlation analysis of the relative abundance of the bacteria showed a negative correlation between Chromohalobacter and two bacterial genera Bacillus and Enterococcus. Beta-diversity showed a statistical distinction between the 1W and the 3W and 5W groups, while no significance was evident between the 3W and 5W groups. Linear discriminant effect size analysis was used to identify biomarkers and significant differences in the relative abundance of several halophilic bacteria, Bacillus sp. and lactic acid bacteria at 1W, 3W, and 5W, recpectively, which indicates the important role of the bacterial community at these time points.

• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.1
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• pp.82-89
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• 2024

Black ice is very difficult to recognize and reduces the friction of the road surface, causing automobile accidents. Since black ice is difficult to detect, there is a need for a system that identifies black ice in real time and warns the driver. Various studies have been conducted to prevent black ice on road surfaces, but there is a lack of research on systems that identify black ice in real time and warn drivers. In this paper, an real-time image-based analysis system was developed to identify the condition of asphalt road surface, which is widely used in Korea. For this purpose, a dataset was built for each asphalt road surface image, and then the road surface condition was identified as dry, wet, black ice, and snow using deep learning. In addition, temperature and humidity data measured on the actual road surface were used to finalize the road surface condition. When the road surface was determined to be black ice, the salt spray equipment installed on the road was automatically activated. The surface condition recognition system for the asphalt concrete pavement and black ice automatic prevention system developed in this study are expected to ensure safe driving and reduce the incidence of traffic accidents.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.11 no.1
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• pp.21-30
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• 2006

This study investigated the temperature-salinity spatio-temporal variability around the Ulleung-do Island (UI) by using CTD profiles obtained by the ARGO floats far the period of Oct.,2003 to Aug.,2005. The waterbody in the upper 700 m around the UI could be classified into five water masses, which is consistent to traditional water characteristics in the East Sea. In the upper surface layer, the temperature and salinity in fall season became even lower than those properties in the summer time. The East Sea Intermediate Water (ESIW) characterized by the salinity minimum layer shows the range of potential temperature between 1 to $5^{\circ}C$ and salinity lower than 34.06 psu. The ESIW lies approximately at 265 m depth with average thickness of 175 m. This thickness of the ESIW continues to be relatively uniform regardless of spatio-temporal space. However, the depth of the ESIW shows vertical variation influenced by the Ulleung warm eddy (UWE). Since the UWE lies in the upper layer, the Upper Portion of the Japan Sea Proper. Water (UPJSPW) is also affected to show the vertical variation. The influence extorted by the UWE reached down to 700 m depth in terms of temperature. The CTD profiles obtained with the high sampling rate by ARCO floats over two-year period provided with very useful and detailed informations in investigating the spatio-temporal variability In the study area.

• International Journal of Highway Engineering
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• v.13 no.3
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• pp.21-30
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• 2011

As well known, dowel bars are used to transfer traffic load acting on one edge to another edge of concrete slab in concrete pavement system. The dowel bars widely used in South Korea are round shape steel bar and they shows satisfactory performance under bending stress which is developed by repetitive traffic loading and environment loading. However, they are not invulnerable to erosion that may be caused by moisture from masonry joint or bottom of the pavement system. Especially, the erosion could rapidly progress with saline to prevent frost of snow in winter time. The problem under this circumstance is that the erosion not only drops strength of the steel dower bar but also comes with volume expansion of the steel dowel bar which can reduce load transferring efficiency of the steel dowel bar. To avoid this erosion problem in reasonable expenses, dowers bars with various materials are being developed. Fiber reinforced plastic(FRP) dower that is presented in this paper is suggested as an alternative of the steel dowel bar and it shows competitive resistance against erosion and tensile stress. The FRP dowel bar is developed in tube shape and is filled with high strength no shrinkage. Several slab thickness designs with the FRP dowel bars are performed by evaluating bearing stress between the dowel bar and concrete slab. To calculated the bearing stresses, theoretical formulation and finite element method(FEM) are utilized with material properties measured from laboratory tests. The results show that both FRP tube dowel bars with diameters of 32mm and 40mm satisfy bearing stress requirement for dowel bars. Also, with consideration that lean concrete is typical material to support concrete slab in South Korea, which means low load transfer efficiency and, therefore, low bearing stress, the FRP tube dowel bar can be used as a replacement of round shape steel bar.

• Journal of the Korean earth science society
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• v.27 no.4
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• pp.464-474
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• 2006

The paleoceanography since 14 ka was reconstructed based on the planktic foraminiferal assemblages of core sediments from the outer shelf of the Korea Strait. Planktic foraminifera in the core sediments can be divided into four assemblages: A, B, C, and D. Assemblage A consists mainly of Globigerinoides ruber group and Globigerinoides conglobatus with low abundance (less than 10%), indicating the tropical-subtropical water mass. Assemblage B is composed of Pulleniatina obliquiloculata and Neogloboquadrina dutertrei, the indicator of Kuroshio Current, and shows the aspect of the inflow of the Tsushima Current into the Korea Strait. Assemblage C yields polar-subpolar species, mainly Neogloboquadrina incompta and N. pachyderma. It decreases upward of the core. Assemblage D contains coastal water species such as Globigerina bulloides and G. quinqueloba. It is abundant in the lower to middle region of the core. From the analysis of distributions of each assemblage and the result of age datings in the core, it is suggested that the Korea Strait played a role of channelling the East China Sea and the East Sea after the LGM (ca. 14 ka). During this time, the coastal water, affected by fresh waters originated from the river systems of China and/ or the Korean Peninsula, flourished around the Korea Strait and theses coastal water might entered to the East Sea. Around 8.5 ka, the effect of the Tsushima Current started to strengthen in this region, and the present current system seems to be formed at about $7{\sim}6ka$.

• Journal of the Korean Society of Food Science and Nutrition
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• v.43 no.4
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• pp.550-556
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• 2014

Rice bran contains both excellent nutritional value and functional advantages. Its utilization is limited due to reducing texture and low storage. To satisfy various tastes, Bacillus spp. having high amylase and protease activities were selected. Using the strains, we made whole grain soybean Meju with a reduced manufacturing period by increasing the concentration of total nitrogen. We made soy sauces with mashing ratios of soy bean and rice bran at 10:0, 9:1, 7:3, and 5:5, and then compared their physiochemical properties. After 2 weeks of fermentation, the sugar content increased from 21~22% to 30~32%. However, pH and salinity showed no differences. At a ratio of 9:1, total nitrogen, amino nitrogen content, and total free amino acid contents were the highest at 1.62%, 652.52 mg%, and 8,804.03 mg/kg, respectively, compared to other mashing ratios of soy bean and rice bran. Especially, the contents of aspartic and glutamic acid, which increase delicate flavoring, were higher in our soy sauce compared to those of general traditional soy sauce and brewed soy sauce, which were 504.25 and 1,262.25 mg/kg, respectively. Serine and alanine, which are related to sweet taste, were present at 49.50 and 518.75 mg/kg, respectively, which were the highest among all mixing ratios, at a ratio of 9:1. Compared to general traditional soy sauce and brewed soy sauce, the contents of histamine and tyramine among biogenic amines decreased to 35.85 and 41.04 mg/kg, respectively. Finally, a soy bean and rice bran mixing ratio of 9:1 was determined to be the optimal mixing ratio in the sensory evaluation.