• Economic and Environmental Geology
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• v.57 no.2
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• pp.243-251
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• 2024

In this study, a surface geological survey was first conducted to investigate aggregate resources in the Yeongam area of Jeollanam-do, and a drilling survey was conducted in the lower part of the surface, which was difficult to identify through a surface geological survey, to determine the spatial distribution of aggregates. Drilling sites were selected considering the topographical development and Quaternary alluvium characteristics of the study area, and river aggregate drilling surveys were conducted at a total of 5 points and land aggregate drilling surveys were conducted at a total of 28 points. Borehole core sediments were classified into seven sedimentary units to determine whether they could be used as aggregates, and optically stimulated luminescence dating was performed on representative boreholes to measure the depositional period for each sedimentary unit. As a result of the study, most of the Yeongam area had a very wide river basin, so it was estimated that there would be a large amount of aggregate, but the amount of aggregate was evaluated to be very small compared to other cities and counties. Most of the unconsolidated sedimentary layers in the Yeongam area are composed of blue-grey marine clay with a vertical thickness of more than 10 m. The sand-gravel layer corresponding to the aggregate section is distributed in the lower part of the marine clay, thinly covering the bedrock weathering zone. This is because the amount of aggregates themselves is small and most of the aggregates are distributed at a depth of 10 m below the surface, which is currently difficult to develop, so the possibility of developing aggregates is evaluated to be very low. As a result of dating, it can be seen that the blue-grey marine clay layer is an intertidal sedimentary layer formed as the sea level rose rapidly about 10,000 years ago. The deposition process continued from 10,000 years ago to the present, and as a result, a very thick clay layer was deposited. This clay layer was formed very dominantly for about 6,000 to 8,000 years, and the sand-gravel layer in the section where aggregates deposited in the Pleistocene period can exist was measured to have been deposited at about 13.0 to 19.0 ka, and about 50 ka, showing that it was deposited as paleo-fluvial deposits before the marine transgression process.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.29 no.1
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• pp.56-76
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• 2024

We for the first time made a successful longest continuous sectional observation in the East Sea by an underwater glider during 95 days from September 18 to December 21 2020 in the Korea along the 106 Line (129.1 °E ~ 131.5 °E at 37.9 °N) of the regular shipboard measurements by the National Institute of Fishery Science (NIFS) and obtained twelve hydrographic sections with high spatiotemporal resolution. The glider was deployed at 129.1 °E in September 18 and conducted 88-days flight from September 19 to December 15 2020, yielding twelve hydrographic sections, and then recovered at 129.2 °E in December 21 after the last 6 days virtual mooring operation. During the total traveled distance of 2550 km, the estimated deviation from the predetermined zonal path had an average RMS distance of 262 m. Based on these high-resolution long-term glider measurements, we conducted a comparative study with the bi-monthly NIFS measurements in terms of spatial and temporal resolutions, and found distinguished features. One is that spatial features of sub-mesoscale such as sub-mesoscale frontal structure and intensified thermocline were detected only in the glider measurements, mainly due to glider's high spatial resolution. The other is the detection of intramonthly variations from the weekly time series of temperature and salinity, which were extracted from glider's continuous sections. Lastly, there were deviations and bias in measurements from both platforms. We argued these deviations in terms of the time scale of variation, the spatial scale of fixed-point observation, and the calibration status of CTD devices of both platforms.

• Korean Journal of Environment and Ecology
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• v.38 no.1
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• pp.55-66
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• 2024

This study conducted a survey to investigate the characteristics of fish communities and the inhabiting status of endangered species in the Byekgye Stream, Korea from April to September 2020. A total of 3,415 fish of 9 families and 31 species were collected from 7 survey stations during the survey period. The dominant species was Zacco koreanus (relative abundance of 31.2%), and the subdominant species was Z. platypus (15.0%), followed by Pungtungia herzi (11.7%), Acheilognathus yamatsutae (5.4%), A. lanceolata intermedia (4.8%), Rhinogobius brunneus (4.4%), and Pseudopungtungia tenuicorpa (4.3%). Among the fish species collected, 19 (61.3%) were identified as Korean endemic species, and two cold-water fish species sensitive to climate change (Rhynchocypris kumgangensis and Cottus koreanus) were collected. Four species were designated as class II endangered wildlife by the Ministry of Environment: A. signifer, P. tenuicorpa, Rhodeus pseudosericeus, and C. koreanus. A. signifer and P. tenuicorpa mainly inhabited the mid to lower streams, R. pseudosericeus in the midstream, and R. pseudosericeus in the upstream. P. tenuicorpa inhabited in large numbers, and estimating the age by total length-frequency distribution in July, the total length of the 26-35 mm group was estimated as 0 years old, the 54-75 mm group as 1 year old, 82-97 mm group as 2 years old, 104-109 mm group as 3 years or older. The cluster analysis showed that the dominance index decreased from upstream to downstream, but the diversity, evenness, and richness index increased. The water quality of Byekgye Stream was evaluated as good overall since the river health (fish assessment index, FAI) using fish was evaluated as excellent (5 stations) and good (2 stations). Byekgye Stream has relatively well-preserved habitats, but conservation measures are required as habitats are disturbed by river repair work in some parts of the midstream and downstream areas where many endangered species inhabit.

• Journal of Food Hygiene and Safety
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• v.39 no.2
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• pp.95-101
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• 2024

In this study, we investigated the migration level of items specified in the Korean Standards and Specifications for Utensils, Containers, and Packages (Ministry of Food and Drug Safety Notification) for 50 utensils and hygiene products made of biodegradable resins. Our results revealed that one Polylactide (PLA) baby tableware contained 20 mg/L in consumption of potassium permanganate, exceeding the standard of 10 mg/L or less. In all other samples, formaldehyde, lead (Pb), and arsenic (As) levels could be considered very safe and remained below the standard. Moreover, we tested the PLA baby tablewares (n = 21) for migration into a food simulant (4% v/v acetic acid) upon repeated elution at 100℃ for 30 min or UV irradiation for 2 h. We detected increased formaldehyde and As amounts at the repeated 100℃ treatment for 30 min compared to those upon repeated UV irradiation. However, the migration level was markedly low under both conditions. Furthermore, the Estimated Daily Intake (EDI) calculated on an infant-to-child basis from the formaldehyde and As migration at 100℃ for 30 min in the PLA sample was at the maximum value, i.e., 6.0×10^-4 mg/kg b.w./day and 1.3×10^-1 ㎍/kg b.w./day, corresponding to 0.40% and 10.42% of the Tolerable Daily Intake (TDI, 0.15 mg/kg b.w./day) and Provisional Tolerable Weekly Intake (PTWI, 9.0 ㎍/kg b.w./week), respectively. Therefore, in this study, we confirmed that biodegradable synthetic resins are safe to use for food.

• Journal of the Korean Society of Radiology
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• v.82 no.6
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• pp.1505-1523
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• 2021

Purpose Although chest CT has been discussed as a first-line test for coronavirus disease 2019 (COVID-19), little research has explored the implications of CT exposure in the population. To review chest CT protocols and radiation doses in COVID-19 publications and explore the number needed to diagnose (NND) and the number needed to predict (NNP) if CT is used as a first-line test. Materials and Methods We searched nine highly cited radiology journals to identify studies discussing the CT-based diagnosis of COVID-19 pneumonia. Study-level information on the CT protocol and radiation dose was collected, and the doses were compared with each national diagnostic reference level (DRL). The NND and NNP, which depends on the test positive rate (TPR), were calculated, given a CT sensitivity of 94% (95% confidence interval [CI]: 91%-96%) and specificity of 37% (95% CI: 26%-50%), and applied to the early outbreak in Wuhan, New York, and Italy. Results From 86 studies, the CT protocol and radiation dose were reported in 81 (94.2%) and 17 studies (19.8%), respectively. Low-dose chest CT was used more than twice as often as standard-dose chest CT (39.5% vs.18.6%), while the remaining studies (44.2%) did not provide relevant information. The radiation doses were lower than the national DRLs in 15 of the 17 studies (88.2%) that reported doses. The NND was 3.2 scans (95% CI: 2.2-6.0). The NNPs at TPRs of 50%, 25%, 10%, and 5% were 2.2, 3.6, 8.0, 15.5 scans, respectively. In Wuhan, 35418 (TPR, 58%; 95% CI: 27710-56755) to 44840 (TPR, 38%; 95% CI: 35161-68164) individuals were estimated to have undergone CT examinations to diagnose 17365 patients. During the early surge in New York and Italy, daily NNDs changed up to 5.4 and 10.9 times, respectively, within 10 weeks. Conclusion Low-dose CT protocols were described in less than half of COVID-19 publications, and radiation doses were frequently lacking. The number of populations involved in a first-line diagnostic CT test could vary dynamically according to daily TPR; therefore, caution is required in future planning.

• Journal of the Korean Applied Science and Technology
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• v.40 no.4
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• pp.674-684
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• 2023

The purpose of this study was to investigate the effect of acute listening to music on the cardiovascular reactivity to sympathoexcitation. In this crossover design study, 15 healthy adults(23.1±1.94(yrs) were randomized to either (1)acute listen to the subject's preferred music for 30 minutes and (2)sat as a time control by an experiment coordinator. After completing each trial, the cold pressor test(CPT) was conducted. Heart rate(HR) and blood pressure(BP) were measured for 4 times at baseline, during and after the CPT. Heart rate variability(HRV) were measured for 3 times at baseline, prior and after the CPT. HR and BP increased during the CPT in both trial and returned to baseline after CPT(time effect, p < .001). After CPT, brachial systolic BP reactivity to the CPT was attenuated in listening to music trial compared to control trial(p = . 008). As a result of heart rate variability(HRV), the difference values between the baseline and prior to the CPT showed a significant increase in standard deviation of the NN intervals(SDNN), total power(TP) and high frequency(HF) only in the music trial (p = .001, p = .002, p = .011). The difference value between prior to and after the CPT did not show significance. But compared with the control trial, the music trial was confirmed that SDNN, TP and HF were more activated. Therefore, listening to music alleviated anxiety and tension before the CPT, and it is estimated that it had a favorable effect on stability after the CPT. This findings showed that listening to music may have a positive effect on brachial systolic BP and HRV to sympathoexcitation.

• The Journal of Engineering Geology
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• v.34 no.2
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• pp.229-248
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• 2024

This investigated the hydrogeochemical and isotopic characteristics of geothermal waters, groundwaters, and surface waters in Dongrae-gu, Busan, South Korea, in order to determine the origins of the salinity components in the geothermal waters, and their formation mechanisms and heat sources The geothermal waters are Na-Cl-type, distinct from surrounding groundwaters (Na-HCO₃^- and, Ca-HCO₃^- (SO₄, Cl)-type) and surface waters (Ca-HCO₃(SO₄, Cl)-type). This indicates the geothermal waters formed at depth as compared with the groundwaters. δ¹⁸O and δD values of the geothermal waters are relatively depleted as compared with the groundwaters, due to altitude effects and deep circulation of the geothermal waters. Helium and neon isotope ratios (³ He/⁴He and, ⁴He/²⁰Ne) of the geothermal waters plot on a single mixing line between mantle (³He = 3.76~4.01%) and crust (⁴He = 95.99~96.24 %), indirectly suggesting that the heat source is due to the decay of radioactive elements in rocks. The geothermal reservoir temperatures were calculated using the silica-enthalpy and Giggenbach models, yielding values of 82~130℃, and the depth of the geothermal reservoir is estimated to be 1.7~2.9 km below the surface. The correlation between Cl/Na and Cl/HCO₃ for the Dongrae geothermal waters requires the input of salty water. The supply of saline composition is interpreted due to the dissolution of residual paleo-seawater.

• Journal of Korea Water Resources Association
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• v.57 no.6
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• pp.421-435
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• 2024

In April 2023, a wildfire broke out in Gangneung located in the east coast region due to the influence of the Yanggang-local wind. In this study, GIS-based RUSLE(Revised Universal Soil Loss Equation) and SEMMA (Soil Erosion Model for Mountain Areas) were used to evaluate the erosion rate due to vegetation recovery in a small watershed of the Gangneung WUI(Wildland-Urban Interface) fire. The small watershed of WUI fire has a low altitude range of 10-30 m and the average slope of 10.0±7.4° which corresponds to a gentle slope. The soil texture was loamy sand with a high organic content and the deep soil depth. As herbaceous layer regenerated profusely in the gully after the wildfire, the NDVI (Normalized Difference Vegetation Index) reached a maximum of 0.55. Simulation results of erosion rates showed that RUSLE ranged from 0.07-94.9 t/ha/storm and SEMMA ranged from 0.24-83.6 t/ha/storm. RUSLE overestimated the average erosion rate by 1.19-1.48 times compared to SEMMA. The erosion rates were estimated to be high in the middle slope where burned pine trees were widely distributed and the slope was steep and to be relatively low in the hollow below the gully where herbaceous layer recovers rapidly. SEMMA showed a rapid increase in erosion sensitivity under at certain vegetation covers with NDVI below 0.25 (Ic = 0.35) on post-fire hillslopes. Gentle slopes with high organic content and rapid recovery of natural vegetation had relatively low erosion rate compared to steep slopes. As subsequent infrastructure and human damages due to sediment disaster by heavy rain is anticipated in WUI fire areas, the research results may be used as basic data for targeted management and decision making on the implementation of emergency treatment after the wildfire.

• Journal of the Microelectronics and Packaging Society
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• v.31 no.1
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• pp.16-22
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• 2024

Along with the high interest in electric vehicles and new renewable energy, there is a growing demand to apply lithium-ion batteries in the construction equipment industry. The capacity of heavy construction equipment that performs various tasks at construction sites is rapidly decreasing. Therefore, it is essential to accurately predict the state of batteries such as SOC (State of Charge) and SOH (State of Health). In this paper, the errors between actual electrochemical measurement data and estimated data were compared using the Dual Extended Kalman Filter (DEKF) algorithm that can estimate SOC and SOH at the same time. The prediction of battery charge state was analyzed by measuring OCV at SOC 5% intervals under 0.2C-rate conditions after the battery cell was fully charged, and the degradation state of the battery was predicted after 50 cycles of aging tests under various C-rate (0.2, 0.3, 0.5, 1.0, 1.5C rate) conditions. It was confirmed that the SOC and SOH estimation errors using DEKF tended to increase as the C-rate increased. It was confirmed that the SOC estimation using DEKF showed less than 6% at 0.2, 0.5, and 1C-rate. In addition, it was confirmed that the SOH estimation results showed good performance within the maximum error of 1.0% and 1.3% at 0.2 and 0.3C-rate, respectively. Also, it was confirmed that the estimation error also increased from 1.5% to 2% as the C-rate increased from 0.5 to 1.5C-rate. However, this result shows that all SOH estimation results using DEKF were excellent within about 2%.

• Clean Technology
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• v.30 no.1
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• pp.37-46
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• 2024

Environmental problems caused by plastic waste have been continuously growing around the world, and plastic waste is increasing even faster after COVID-19. In particular, PP and PE account for more than half of all plastic production, and the amount of waste from these two materials is at a serious level. As a result, researchers are searching for an alternative method to plastic recycling, and plastic pyrolysis is one such alternative. In this paper, a numerical study was conducted on the pyrolysis behavior of non-condensable gas to predict the chemical reaction behavior of the pyrolysis gas. Based on gas products estimated from preceding literature, the behavior of non-condensable gas was analyzed according to temperature and residence time. Numerical analysis showed that as the temperature and residence time increased, the production of H₂ and heavy hydrocarbons increased through the conversion of the non-condensable gas, and at the same time, the CH₄ and C₆H₆ species decreased by participating in the reaction. In addition, analysis of the production rate showed that the decomposition reaction of C₂H₄ was the dominant reaction for H₂ generation. Also, it was found that more H₂ was produced by PE with higher C₂H₄ contents. As a future work, an experiment is needed to confirm how to increase the conversion rate of H₂ and carbon in plastics through the various operating conditions derived from this study's numerical analysis results.