• Journal of the Korean Institute of Gas
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• v.27 no.2
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• pp.71-78
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• 2023

In general, electric submersible pumps (ESPs), which have an average life of 1.0 to 1.5 years, experience a decrease in performance and a reduction in life of the pump depending on oil and gas reservoir characteristics and operating conditions in wells. As the result, the failure of ESP causes high well workover costs due to retrieval and installation, and additional costs due to shut down. In this study, a flow loop system was designed and established to predict the life of ESP in long­term operation of oil and gas wells, and the life cycle data of ESP from the time of installation to the time of failure was acquired and analyzed. Among the data acquired from the system, flow rate, inlet and outlet temperature and pressure, and the data of the vibrator installed on the outside of ESP were analyzed, and then the performance status according to long-term operation was classified into five stages: normal, advice I, advice II, maintenance, and failed. Through the experiments, it was found that there was a difference in the data trend by stage during the long­term operation of the ESP, and then the condition of the ESP was diagnosed and the failure of the pump was predicted according to the operating time. The results derived from this study can be used to develop a failure prediction program and data analysis algorithm for monitoring the condition of ESPs operated in oil and gas wells.

• Composites Research
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• v.36 no.3
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• pp.186-192
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• 2023

Recently, in the field of railway vehicles, interest in the use of composite materials for weight reduction and transportation efficiency is increasing. Accordingly, research and commercialization development to apply composite materials to various vehicle parts are being actively conducted, and evaluation is conducted centering on post-measurement such as mechanical performance evaluation of finished products to verify quality when composite materials are applied. However, the analysis of heat and stress generated during the molding process of composite materials, which are factors that greatly affect manufacturing quality, is insufficient. Therefore, in this study, in order to verify the molding quality of composite parts for railway vehicles, the molding quality analysis was conducted for the two types of composite interior panels (laminate panel and sandwich panel) that are most actively used. To this end, temperature and strain changes were monitored during the molding process by using an FBG fiber optic sensor, which is easy to apply to the inside of the composite, and the residual strain value generated after molding was completed was measured. As a result, it was confirmed that overheating and excessive residual stress did not occur, thereby verifying the excellent molding quality of the composite interior panel for railway vehicles.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.4A
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• pp.391-398
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• 2010

The fire performance of RC slabs with half-depth precast panel after exposure to the ISO-834 fire standard without loading has been experimentally investigated. During heating, according to the ISO 834 fire curve, concrete spalling was observed for concrete without PP(polypropylene) fibers. No spalling occurred when heating concrete containing PP fibers. The maximum temperature of RC slabs with PP fibers with half-depth precast panel was lower than that of concrete without PP fibers. The ultimate load after cooling of the RC slabs that were not loaded during the furnace tests was evaluated by means of 3 points bending tests. The ultimate load of the RC slabs without PP fibers showed a considerable reduction (around 32.5%) of the ultimate load after cooling if compared with of RC slabs with PP fibers. The ultimate load of the RC slabs with half-depth precast panel with PP fibers is higher than that of a full-depth RC slabs with PP fibers. Also, the addition of PP fibers and the use of half-depth precast panel improve fire resistance.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.4
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• pp.349-354
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• 2023

This study wa s conducted a s pa rt of ma ximizing the use of ca rbon dioxide by a pplying CCU(Ca rbon Ca pture, Utiliza tion) a mong technologies for reducing CO₂ in the cement industry. In a carbon dioxide curing environment, changes in carbonation depth and changes in basic physical properties by age due to the mixing of carbonation reaction accelerators were usually targeted at Portland cement paste. In addition, in order to check the fixed amount of CO₂ in the concrete field, a thermal analysis method was applied to evaluate CaCO₃ decarbonization at high temperatures. As a result of the evaluation, it was confirmed that the carbonation depth in the cured body significantly increased due to the incorporation of CRA in the carbonation depth diffusion performance. In addition, it was confirmed that the weight reduction rate increased by 23.8 % and 40.77 %, respectively, compared to Plain, in the order of curing conditions for constant temperature and humidity and curing conditions for carbonation chambers, so it was confirmed that the amount of excellent CaCO₃ produced by the addition of CRA increased as the concentration of CO₂ increased.

• Korean Journal of Ecology and Environment
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• v.56 no.4
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• pp.375-383
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• 2023

To determine the cause of the population decline in Gobiobotia naktongensis, substrate preference and burying behaviour were investigated in this study. In general, the species was shown to prefer a substrate size of 1 mm or less, depending on the flow. In addition, the burying depth varied according to the size of the fish and increased with a decrease in water temperature. Our findings showed that the main cause of the population reduction was the physical changes in the substrate structure due to the dams or barrages construction. Notably, the accumulation of silt and mud in the substrate upon the formation of an upstream lentic water region for structural construction and bed armouring caused by scouring and reduced downstream inflow of fine sediment were deterministic in the fish habitat changes, causing problems in burying. As sand substrate structure is critical for the survival and inhabitation of psammophilous species, efficient strategies should be developed with proper habitat management to reduce the anthropogenic damage

• Economic and Environmental Geology
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• v.56 no.6
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• pp.675-695
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• 2023

The tracksite of dinosaurs and pterosaurs in Sanbuk-dong of Gunsan is the largest early Cretaceous dinosaur footprint fossil site in Korea, and all the footprints are important evidence indicating that large ornithopod and theropod dinosaurs inhabited the Korean peninsula during the early Cretaceous. The Sanbuk-dong site was covered with waterproof sheet in an outdoor environment until the installation of a protective enclosure in 2021. As a result, various factors such as shear force, load reduction, temperature and humidity fluctuations, acid rain, salinity and microorganisms have complexly interacted in the substrate of fossils, exacerbating the damage to footprints. For 159 footprints in 12 trackways among the footprints found in the site, the damage types were classified in detail and the level of each damage was assessed. The damages were classified into 6 types through the classification of deterioration degree of individual footprints. As a result of ultrasonic physical property evaluation on the surface of the fossil site, most of these footprints are in the completely weathered (CW) stage. Furthermore, various weathering patterns were observed in the study area, and surface contaminants were analyzed along the stratigraphy. Although the patterns of freshness and contaminants varied at different points within the fossil site, the chemical compositions were similar. Based on the results, an efficient conservation management system for dinosaur footprint fossils was established, and a conservation treatment type for each footprint was proposed.

• Korean Journal of Mineralogy and Petrology
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• v.36 no.4
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• pp.221-232
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• 2023

Carbon neutrality requires carbon dioxide reduction technology and alternative green energy sources. Palygorskite is a clay mineral with a ribbon structure and possess a large surface area due to the nanoscale pore size. The clay mineral has been proposed as a potential material to capture carbon dioxide (CO₂) and possibly to store eco-friendly hydrogen gas (H2). We report our preliminary results of grand canonical Monte Carlo (GCMC) simulations that investigated the adsorption isotherms and mechanisms of CO₂ and H₂ into palygorskite nanopores at room temperature. As the chemical potential of gas increased, the adsorbed amount of CO₂ or H₂ within the palygorskite nanopores increased. Compared to CO₂, injection of H₂ into palygorskite required higher energy. The mean squared displacement within palygorskite nanopores was much higher for H₂ than for CO₂, which is consistent with experiments. Our simulations found that CO₂ molecules were arranged in a row in the nanopores, while H₂ molecules showed highly disordered arrangement. This simulation method is promising for finding Earth materials suitable for CO₂ capture and H₂ storage and also expected to contribute to fundamental understanding of fluid-mineral interactions in the geological underground.

• Food Science and Preservation
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• v.30 no.1
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• pp.132-145
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• 2023

In this study, culture conditions were optimized to confirm the feasibility of Acetobacter pasteurianus as a starter for fermentation vinegar. Acetobacter pasteurianus strain can be used as a food ingredient. The optimal temperature and pH conditions of the selected Acetobacter pasteurianus SRCM101388 were 28℃ and pH 6.00, respectively. The response surface methodology (RSM) was used to optimize the composition of the medium, and Plackett-Burman design (PBD) was used to obtain the effective selection of culture medium, resulting in that glucose, sucrose, and yeast extract had the highest effect on increasing biomass. The optimal concentration, which was performed by central composite design (CCD), were determined to be 10.73 g/L of glucose, 3.98 g/L of sucrose, and 18.73 g/L of yeast extract, respectively. The optimal concentrations of trace elements for the production of biomass were found to be 1 g/L of ammonium sulfate, 0.5 g/L of magnesium sulfate, 2 g/L of sodium phosphate monobasic, 2 g/L of sodium phosphate dibasic, and the final optimized medium was pH 6.10. When incubated in a 5 L jar fermenter, the SRCM101388 strain showed a faster-dissolved oxygen (DO) reduction at a lower agitation rate (rpm), and it was able to grow even at reduced DO level when aeration was maintained. The amount of final biomass produced was 2.53±0.12×10⁹ CFU/mL (9.40±0.02 log CFU/mL) when incubated for 18 hours at 150 rpm, 0.5 vvm, pH 6.0, and 28℃.

• Food Science and Preservation
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• v.31 no.4
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• pp.601-611
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• 2024

The objective of this study was to integrate onion juice into traditional Korean soy sauce and to evaluate the sterilization conditions necessary for commercialization. As the sterilization temperature increased, pH decreased and titratable acidity increased. A reduction in °Brix was observed post-sterilization, from 37.37 °Brix in untreated soy sauce to 36.67-36.77 °Brix. In terms of chromaticity, the L value declined over the storage period while the a and b values increased. The quercetin component exhibited light sensitivity, with no significant difference observed in the sample on the 60th day. Neither Bacillus cereus nor Clostridium perfringens were detected, and the total bacterial count was comparable to that of commercially available soy sauce. This indicates that samples sterilized at 85℃ for 30 minutes fall within a safe quality range. Sensory evaluation revealed that samples sterilized at 85℃ for 30 minutes exhibited consistently high ratings.

• Journal of the Korean Society of Food Science and Nutrition
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• v.44 no.8
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• pp.1186-1193
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• 2015

This study was performed to investigate the changes in monacolin K content and antioxidant activities of Monascus-fermented brown rice with different germination temperatures and periods. Brown rice was germinated at 32, 35 and $37^{\circ}C$ for 1~4 days, after white rice (WB), brown rice (BR), and germinated brown rice (GBR) were fermented with M. pilosus 305-9 at $30^{\circ}C$ for 20 days. The redness, yellowness and Monascus pigments increased after germination. Total monacolin K content increased from 215.85 mg/kg of BR to 1,263.04 mg/kg of GBR ($32^{\circ}C$/1 day), whereas monacolin K content decreased with increase in germination period. Citrinin was not detected in any of the samples. Total polyphenol (TPC) and flavonoid contents (TFC) increased with increase in germination temperature and period, whereas electron donating ability (EDA) and total antioxidant activities (TAA) decreased due to reduction of Monascus pigment content. The TPC and TFC showed the highest values (13.80 mg/g and 1.30 mg/g, respectively) in GBR ($37^{\circ}C$/4 day), whereas EDA and TAA showed the highest values (22.16 mg Trolox equivalent/g and 62.27 mg ascorbic acid equivalent/g, respectively) in GBR ($32^{\circ}C$/1 day). These results indicated that the optimal germination temperature and period for increasing monacolin K content and antioxidant activities was found to be at $32^{\circ}C$ for 1 day. In addition, it was found that M. pilosus 305-9 was a useful strain for increasing monacolin K content without producing citrinin in functional foods and pharmaceutical industrial regions.