• Ecology and Resilient Infrastructure
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• v.9 no.3
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• pp.131-140
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• 2022

The magnitude and frequency of extreme floods are increasing owing to the effects of climate change. Therefore, multipurpose flood management techniques incorporating nature-based solutions have been introduced to mitigate the limitations of flood management and river design methods relying on existing observation data. Nature-based solutions to prepare for such extreme flooding events include ways to retreat the embankment, expand the floodplain, and reduce flood damage. To apply these technologies, adopting appropriate location selection methods based on various evaluation factors, such as flood damage reduction effects, sustainable ecological environments, river connectivity, and physical channel structure enhancements, should be prioritized. Therefore, in this study, the optimal location for implementing the multipurpose floodplain construction project was determined by selecting the location of the floodplain expansion with objectivity in the river waterfront area upstream of Daecheong Dam to downstream of Yongdam Dam. Through the final location determination, the Dongdaeje and Jeogokje sections were included in the optimal location considering both flood damage reduction and water environment improvement.

• The Journal of the Acoustical Society of Korea
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• v.42 no.1
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• pp.25-31
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• 2023

In order to estimate the radial speed of an underwater object so-called target with active sonar, Continuous Wave (CW) pulse is generally used, but if a target is slow and at near distance, it is not easy to estimate the radial velocity of the target due to acoustic reverberation in the ocean. In 2017, Wang et al. utilized broadband signal of two Hyperbolic Frequency Modulation (HFM) pulses, which is known as a doppler-invariant pulse, with equal frequency band and in opposite sweep directions to overcome this problem and successfully estimate the radial speed of slow-moving nearby target. They demonstrated the estimation of the radial velocity with computer simulation using the parameters of two HFM starting time differences and receiving times. However, for it uses two HFM pulses with equal frequency, cross-correlation between the two pulses negatively affect the detection performance. To mitigate this cross-correlation effect, we suggest using two different band HFM with the opposite sweep directions. In this paper, a method of radial velocity estimation is derived and simulated using two HFM pulses with the pulse length of 1 second and bandwidth of 400 Hz. Applying the suggested method, the radial velocity was estimated with approximately 6 % of relative error in the simulation.

• Korean Journal of Ecology and Environment
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• v.55 no.4
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• pp.320-329
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• 2022

Urban areas in watersheds increase the impervious surface, and agricultural areas deteriorate the water quality of rivers due to the use of fertilizers. As such, anthropogenic land use affects the type, intensity and quantity of land use and is closely related to the amount of substances and nutrients discharged to nearby streams. Riparian vegetation reduce the concentration of pollutants entering the watershed and mitigate the negative impacts of land use on rivers. This study analyzes the data through correlation analysis and regression analysis through point data measured twice a year in spring and autumn in 21 selected damaged tributary rivers within the Han River area, and then uses a structural equation model to determine the area land use. In the negative impact on water quality, the mitigation effect of riparian vegetation was estimated. As a result of the correlation analysis, the correlation between the agricultural area and water quality was stronger than that of the urban area, and the area ratio of riparian vegetation showed a negative correlation with water quality. As a result of the regression analysis, it was found that agricultural areas had a negative effect on water quality in all models, but the results were not statistically significant in the case of urban areas. As a result of the model estimated through the structural equation, BOD, COD, TN, and TP showed a mitigation effect due to the accumulation effect of river water quality through riparian vegetation in agricultural areas, but the effect of riparian vegetation through riparian vegetation was found in urban areas. There was no These results were interpreted as having a fairly low distribution rate in urban areas, and in the case of the study area, there was no impact due to riparian forests due to the form of scattered and distributed settlements rather than high-density urbanized areas. The results of this study were judged to be unreasonable to generalize by analyzing the rivers where most of the agricultural areas are distributed, and a follow-up to establish a structural equation model by expanding the watershed variables in urban areas and encompassing the variables of various factors affecting water quality research is required.

• Korean Journal of Culture and Social Issue
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• v.28 no.4
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• pp.529-553
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• 2022

The present study aimed to examine the mediation effect of identity development between perceived parental academic achievement pressure (PPAAP) and mental health. Specifically, we examined whether the relation between PPAAP and mental health is mediated by the positive or negative aspects of identity development. Participants were 110 Korean college students. They completed online self-report questionnaires that included PPAAP, identity development, personal well-being, and depression. We found that PPAAP was negatively related to personal well-being and positively related to depression. Moreover, the relation between PPAAP and mental health was mediated only by the negative aspects of identity development. In other words, PPAAP was related to the negative aspects of identity development, which, in turn, was negatively associated with mental health. This study contributes to the literature in that it proposed identity development as a mediator between PPAAP and mental health and found that the negative, not positive, aspects of identity development mediated the relation. We suggest that institutional interventions that help develop identity can be an effective way to mitigate the negative impacts of PPAAP on mental health of children living in the highly competitive Korean society. Limitations and future research directions are also discussed.

• Journal of Food Hygiene and Safety
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• v.38 no.4
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• pp.193-201
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• 2023

Antimicrobials in human medicine are classified by The World Health Organization (WHO) into three groups: critically important antimicrobials (CIA), highly important antimicrobials (HIA), and important antimicrobials (IA). CIA are antibiotic classes that satisfy two main criteria: that they are the sole or the only available limited therapeutic option to effectively treat severe bacterial infections in humans (Criterion 1), and infections where bacteria are transmitted to humans from non-human sources or have the potential to acquire resistance genes from non-human sources (Criterion 2). WHO emphasizes the need for cautious and responsible use of the CIA to mitigate risk and safeguard human health. Specific antimicrobials within the CIA with a high priority for management are reclassified as "highest priority critically important antimicrobials (HP-CIA)" and include the 3^rd generation of cephalosporins and the next generation of macrolides, quinolones, glycopeptides, and polymyxins. The CIA list is the scientific basis for risk assessment and risk management policies that warrant using antimicrobials to reduce antimicrobial resistance in several countries. In addition, the CIA list ensures food safety in the food industry, including for the popular food chain companies McDonald's and KFC. The continuous update of the CIA list reflects the advancement in research and emerging future challenges. Thus, active and deliberate evaluation of antimicrobial resistance and the construction of a list that reflects the specific circumstances of a country are essential to safeguarding food security.

• Journal of the Korean Electrochemical Society
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• v.26 no.3
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• pp.35-41
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• 2023

The carbon-coated silicon monoxide (c-SiO_x), which is a negative electrode active material for lithium-ion batteries (LIBs), has a limited cycle performance due to severe volume changes during cycles, despite its high specific capacity. In particular, the significant volume change of the active material can deform the electrode structure and easily damage the electron transfer pathway. To improve performance and mitigate electrode damage caused by volume changes, we replaced parts of the carbon black conducting agent with carbon nanotubes (CNTs) having a linear shape. The content of the entire conductive material in the electrode was fixed at 10% by mass, and the relative content of CNTs ranged from 0% to 25% by mass to prepare electrodes and evaluate electrochemical performance. As the CNT content in the electrode increased, both cycle life and rate capability improved. Even a small amount of CNT can significantly improve the electrochemical performance of a c-SiO_x negative electrode with large volume changes. Furthermore, dispersing CNTs effectively can lead to achieving the equivalent performance with a reduced quantity of CNTs.

• Journal of Life Science
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• v.33 no.8
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• pp.639-650
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• 2023

The levels of harmful components in aerosols from heated tobacco products (HTPs) have been reported to be significantly lower than in cigarette smoke. However, it remains unclear whether the use of HTPs can mitigate the cardiovascular risks associated with cigarette smoking (CS). The objective of this study was to investigate the effects of a short-term switch from CS to HTP use on cardiac autonomic regulation (CAR). Seven healthy male smokers completed an open-label, randomized, cross-over trial consisting of five days of CS, use of three different HTPs (IQOS use, IQ; lil SOLID use, LS; lil HYBRID use, LH), or non-smoking (NS). Each session was separated by a one-week washout period, and levels of exhaled carbon monoxide (CO) and carboxyhemoglobin (COHb), systolic (SBP) and diastolic blood pressure (DBP), and heart rate variability (HRV) reflecting CAR were assessed before use of the product assigned to each session and at 24, 48, 72, 96, and 120 hr after use. Levels of exhaled CO and COHb were statistically significantly reduced only during NS. There were no statistical changes in SBP and DBP within any session. However, in HRV spectral analysis, log-transformed high frequency (lnHF) increased statistically significantly in IQ, LS, and NS, respectively. Normalized HF (HFnu) was significantly increased in NS and LH, respectively. lnHF and HFnu showed significant interaction effects. The findings of this study suggest that a short-term switch to HTPs instead of CS may lead to different distribution patterns of CAR, primarily driven by enhanced cardiac vagal tone.

• Journal of Navigation and Port Research
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• v.47 no.4
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• pp.256-270
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• 2023

In this study, a sliding mode (SM) controller for dynamic positioning (DP) was specifically designed for a turret connection operation of a ship or an offshore structure in which an arbitrary point on the structure could be controlled as the motion center instead of the center of mass. The SM controller allows control of the arbitrary point and provides capability to manage uncertainties in the dynamics of ships and offshore structures, external forces caused by unknown changing marine environments, and transient performance of DP systems. The Jacobian matrix included in kinematic equations of the controlled object was modified to design the SM controller to control based on an arbitrary point of ships or offshore structures. To ensure robustness of the controller, the Lyapunov stability theory was applied in the design of the SM controller. In general, for robustness in DP control, gain scheduling based on a proportional-derivative (PD) control algorithm is employed. However, finding appropriate gains for gain scheduling complicates the application of DP systems. Therefore, in this study, the SM control algorithm was considered to mitigate the complexity of the DP controller for ships and offshore structures. To validate the proposed SM control algorithm, time-domain simulations were conducted and utilized to evaluate the performance of the control algorithm. The effectiveness of the proposed SM controller was assessed by comparing simulation results with results of a conventional PD control algorithm applied in DP control.

• Land and Housing Review
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• v.14 no.3
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• pp.17-36
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• 2023

This research aims to investigate the socio-demographic, financial, and housing statuses of young married couples in Chonsei housing and to analyze the determinants of their residential environment quality and housing expenditure in four districts - Seoul and Gyeonggi-Incheon Area(GIA) of the Seoul Metropolitan Area(SMA), and metropolises and non-metropolises of non-SMA. From the 2020 Korean Housing Survey(KHS), this cross-sectional analysis examined a sample of 691 households, and the findings revealed that most were headed by college-educated, salaried male workers aged 31 years old. While childless dual-earner couples were common in Seoul, single-income families of three were prevalent in non-SMA. The financial status of the couples in Seoul was a lot better than in the other three areas, particularly much higher in Chonsei deposit and total asset value. Further, many lived in a three-bedroom apartment unit sized 60m² and bigger, using a Chonsei loan. Regardless of areas, almost all the households spent a very low portion of their living expenses and income on housing costs. However, dual-earner families positively increased borrowing capacity, which improves the household's financial position that is likely to lead to equity increment in a volatile asset market in the long run. The statistical results indicated that residential environment assessment was influenced by neighborhood quality and housing expenditure was affected by housing size in Seoul, urban amenities in GIA and householder's gender in non-metropolises. Thus, this research proposes that strong measures be considered to mitigate housing inequality embedded in geographical and socio-economic disparities.

• Korean Chemical Engineering Research
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• v.61 no.1
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• pp.62-67
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• 2023

Due to the prolonged impact of COVID-19, the demand for Information Technology (IT) products is increasing, and their production facilities are expanded. Consequently, the use of harmful and dangerous chemicals are increased, the risk of fire(s) and explosion(s) is also elevated. In order to mitigate these risks, the government sets standards, such as KS C IEC 60079-10-1, and manages explosion-prone hazardous facilities where flammable substances are manufactured, used, and handled. However, using the standards of KS, it is difficult to predict the actual possibility of an explosion in a facility, because ventilation (an important factor) is not considered when setting up a hazardous work environment. In this study, the SEMI S6, Tracer Gas Test was applied to the chemical vapor deposition (CVD) facility, a major part of the display industry, to evaluate ventilation performance and to confirm the possibility of creating a less explosive environment. Based on the results, it was confirmed that the ventilation performance in the assumed scenarios met the standards stipulated in SEMI S6, along with supporting the possibility of creating a less explosive working condition. Therefore, it is recommended to use the prediction tool using engineering techniques, as well as KS standards, in such hazardous environments to prevent accidents and/or reduce economic burden following accidents.