• Journal of Navigation and Port Research
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• v.48 no.1
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• pp.17-26
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• 2024

Port distripark can activate more functions. It is adjacent to a port. However, domestic port distripark is still limited to support port because of the shortage of infrastructure facilities, government policy, and investment. Therefore, this study tried to investigate the operation status of domestic port distripark and derive policy implications by conducting DEA analysis and productivity analysis based on internal data of each port distripark. As a result of Data Envelopment analysis, it was found that the west port distripark of Gwangwang and the northern port distripark of Incheon were efficient in the warehouse industry while the northern port distripark of Incheon and the Ulsan 1 port distripark were efficient in the manufacturing industry. In addition, in the case of foreign investment productivity, the west side port distripark of Gwangyang and the stage 1 port distripark of Pyeongtaek Dangjin were found to be higher than the others. In the case of facility investment productivity, the port distripark on the west side of Gwangyang and the north side of Incheon had the highest productivity. Lastly, in the case of labor productivity, the north side of Incheon and Busan ungdong port distripark showed the highest productivity. These results imply that it is important to review handling item when picking up enterprises in the port distripark for enhancing efficiency, foreign investment, and facility investment. The number of employees is not directly affecting the productivity improvement.

• Journal of Environmental Health Sciences
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• v.50 no.1
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• pp.16-24
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• 2024

Background: Indoor PM_2.5 concentrations in residential houses can be affected by various factors depending on the season. This is because not only do the climate characteristics depend on the season, but the activity patterns of occupants are also different. Objectives: The purpose of this study is to compare factors affecting indoor PM_2.5 concentrations in apartments and detached houses in Daegu according to seasonal changes. Methods: This study included 20 households in Daegu, South Korea. The study was conducted during the summer (from July 10 to August 10, 2023) and the autumn (from September 11 to October 9, 2023). A sensor-based instrument for PM_2.5 levels was installed in the living room of each residence, and measurements were taken continuously for 24 hours at intervals of one minute during the measurement period. Based on the air quality monitoring system data in Daegu, outdoor PM_2.5 concentrations were estimated using ordinary kriging (OK) in Python. In addition, the indoor activities of the occupants were investigated using a time-activity pattern diary. The affecting factors of indoor PM_2.5 concentration were analyzed using multiple regression analysis. Results: Indoor and outdoor PM_2.5 concentrations of the residences during summer were 15.27±11.09 ㎍/m³ and 11.52±7.56 ㎍/m³, respectively. Indoor and outdoor PM_2.5 concentrations during autumn were 13.82±9.61 ㎍/m³ and 9.57±5.50 ㎍/m³, respectively. The PM_2.5 concentrations were higher in summer compared to autumn both indoors and outdoors. The primary factor affecting indoor PM_2.5 concentration in summer was occupant activity. On the other hand, during the autumn season, the primary affecting factor was outdoor PM_2.5 concentration. Conclusions: Indoor PM_2.5 concentration in residential houses is affected by occupant activity such as the inflow of outdoor PM_2.5 concentration, cooking, and cleaning, as found in previous studies. However, it was revealed that there were differences depending on the season.

• Membrane Journal
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• v.34 no.1
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• pp.70-78
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• 2024

A photo-crosslinked anion exchange membrane (AEM) based on quaternary-aminated polyacrylates was developed for reverse electrodialysis (RED). Although reverse electrodialysis is a clean and renewable energy generation system, the low power output and high membrane cost are serious obstacles to its commercialization. Cross-linked AEMs without any polymer supporters were fabricated through photo-crosslinking between polymer-typed acrylates with anion conducting groups, in particular, polymer-typed acrylates were synthesized based on engineering plastic with outstanding mechanical and chemical property. The fabricated membranes showed outstanding physical, chemical, and electrochemical properties. The area resistance of the fabricated membranes (CQAPPOA-20, CQAPPOA-35, and CQAPPOA-50) were ~50% lower than that of AMV (2.6 Ω cm²). Moreover, the transport number of CQAPPOA-35 wase comparable to that of AMV, despite the thin thickness (40 ㎛) of the fabricated membranes. The RED stack with the CQAPPOA-35 membrane provided an excellent maximum power density of 2.327 W m^-2 at a flow rate of 100 mL min^-1, which is 15% higher than that (2.026 W m^-2) of the RED stack with the AMV membrane. Considering easy fabrication process by UV photo-crosslinking and outstanding RED stack properties, the CQAPPOA-35 membrane is a promising candidate for REDs.

• Korean Journal of Radiology
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• v.21 no.4
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• pp.431-441
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• 2020

Objective: To compare the diagnostic performance and interobserver variability of strain ratio obtained from one or two regions of interest (ROI) on breast elastography. Materials and Methods: From April to May 2016, 140 breast masses in 140 patients who underwent conventional ultrasonography (US) with strain elastography followed by US-guided biopsy were evaluated. Three experienced breast radiologists reviewed recorded US and elastography images, measured strain ratios, and categorized them according to the American College of Radiology breast imaging reporting and data system lexicon. Strain ratio was obtained using the 1-ROI method (one ROI drawn on the target mass), and the 2-ROI method (one ROI in the target mass and another in reference fat tissue). The diagnostic performance of the three radiologists among datasets and optimal cut-off values for strain ratios were evaluated. Interobserver variability of strain ratio for each ROI method was assessed using intraclass correlation coefficient values, Bland-Altman plots, and coefficients of variation. Results: Compared to US alone, US combined with the strain ratio measured using either ROI method significantly improved specificity, positive predictive value, accuracy, and area under the receiver operating characteristic curve (AUC) (all p values < 0.05). Strain ratio obtained using the 1-ROI method showed higher interobserver agreement between the three radiologists without a significant difference in AUC for differentiating breast cancer when the optimal strain ratio cut-off value was used, compared with the 2-ROI method (AUC: 0.788 vs. 0.783, 0.693 vs. 0.715, and 0.691 vs. 0.686, respectively, all p values > 0.05). Conclusion: Strain ratios obtained using the 1-ROI method showed higher interobserver agreement without a significant difference in AUC, compared to those obtained using the 2-ROI method. Considering that the 1-ROI method can reduce performers' efforts, it could have an important role in improving the diagnostic performance of breast US by enabling consistent management of breast lesions.

• Korean Journal of Ecology and Environment
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• v.34 no.1 s.93
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• pp.9-19
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• 2001

contrasting monsoon between 1993 and 1994 produced an interannual difference in hydrology. Theoretical water residence time (TWRT) in monsoon 1993 averaged 27 d, which was>3 months shorter compared to the TWRT in monsoon 1994. A dominant physical process influencing thermal stratification, water movement, and mixing regime was an interflow current in 1993. During summer 1993, river water plunged to mid-lake (location 27 km) and passed through the 10${\sim}$20m stratum of the reservoir, resulting in an isolation of epilimnetic lake water from advected river water. The interflow disrupted thermal stratification and produced a meta-hypolimnetic warming of >4$^{\circ}C$ downlake, thereby increased a mixing depth (>13 m). In contrast, during monsoon 1994 density currents were not observed and strong thermal stratification occurred in the entire reservoir, resulting in > 2 fold greater thermal resistance (8.2${\times}10^{5}$ erg)compared to 1993 (4.0${\times}10^{5}$ erg). This reservoir was identified as a typical warm monomictic reservoir which showed one mixis during early winter. The timing of overturn, however, differed between the two years as a result of distinct contrast in TWRT and thermal regime; overturn in 1993 occured about one month earlier relative to that in 1994. Hypolimnetic warming was predictable in this system; the variation in discharge accounted (Y = 4.35-0.06X+0.10X$^{2}$, p<0.0001)for 98% of the interannual variation in hypolimnetic temperature. Overall data suggest that thermal stability, the timing of fall overturn, and water residence time in this system are primarily regulated by the intensity of monsoon.

• Journal of the Korean earth science society
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• v.36 no.2
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• pp.139-157
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• 2015

We investigated the relative errors of satellite-observed Surface Skin Temperature (SST) data caused by sea ice in the northern hemispheric ocean ($30-90^{\circ}N$) during April 16-24, 2003-2014 by intercomparing MODerate Resolution Imaging Spectroradiometer (MODIS) Ice Surface Temperature (IST) data with two types of Atmospheric Infrared Sounder (AIRS) SST data including one with the AIRS/Advanced Microwave Sounding Unit-A (AMSU) and the other with 'AIRS only'. The MODIS temperatures, compared to the AIRS/AMSU, were systematically up to ~1.6 K high near the sea ice boundaries but up to ~2 K low in the sea ice regions. The main reason of the difference of skin temperatures is that the MODIS algorithm used infrared channels for the sea ice detection (i.e., surface classification), while microwave channels were additionally utilized in the AIRS/AMSU. The 'AIRS only' algorithm has been developed from NASA's Goddard Space Flight Center (NASA/GSFC) to prepare for the degradation of AMSU-A by revising part of the AIRS/AMSU algorithm. The SST of 'AIRS only' compared to AIRS/AMSU showed a bias of 0.13 K with RMSE of 0.55 K over the $30-90^{\circ}N$ region. The difference between AIRS/AMSU and 'AIRS only' was larger over the sea ice boundary than in other regions because the 'AIRS only' algorithm utilized the GCM temperature product (NOAA Global Forecast System) over seasonally-varying frozen oceans instead of the AMSU microwave data. Three kinds of the skin temperatures consistently showed significant warming trends ($0.23-0.28Kyr^{-1}$) in the latitude band of $70-80^{\circ}N$. The systematic disagreement among the skin temperatures could affect the discrepancies of their trends in the same direction of either warming or cooling.

• 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 Association of Geographic Information Studies
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• v.2 no.2
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• pp.27-44
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• 1999

Digital maps produced in Korea are various in scale and include a lot of geographic and attribute data. In this study, it is argued that, to reduce the production cost and the difficulties for renewal, it is necessary to establish the already nationally drawn 1:5,000 scale digital maps as the base maps and simplify them as much as the TIGER files in the U.S. The comprehensive data included in the digital maps in Korea are mostly land use information, which are supposed to be established separately from the digital maps. The land use information system could be maintained and updated cheaply and frequently at the local government level. In response to common needs, the land use information could be imported to GIS and used for analyses. As technologies and societies changes, the Census questions and methodologies should be changed for better uses. Along with GIS, the Census would be developed and processed more reliably and efficiently. Also, it is recommended for Korean government to develop the Census Tract and Block Group system. Current Eup, Myon, Dong as basic units for Census information may not be useful or effective for micro level urban analyses and public service planning activities because of their large population and land areas. It is recommended that optimum population of a Census Tract be 5,000 and a Block Groups 1,500, and one Census Tract includes 1~9 Block Groups. It is recommend that Census Tract and Block Group boundary lines be decided flexibly in light of population, physical features, socio-economic attributes, and tradition. For urban analyses using GIS, socio-economic census data, city government's information such as parcel data and building permit data, survey data, and satellite image data could also be used. The existence of Census Tracts and Block Groups as well as GIS could help for the data and methods to be useful for urban analyses and public service provisions.

• Journal of the Korean Society of Food Science and Nutrition
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• v.38 no.7
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• pp.832-838
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• 2009

The inhibitory effects of solvent extracts from dried beet (Beta vulgaris) on $H_2O_2$-induced oxidative stress in cell systems and on the growth of cancer cell lines (HT-29 human colon cancer and AGS human gastric adenocarcinoma cells) were investigated. Inhibitory effects of acetone with methylene chloride (A+M) and methanol (MeOH) extracts on the growth of HT-29 and AGS cancer cells increased in a dose dependent manner (p<0.05). The inhibitory effect was more significant on the growth of AGS cells and A+M extracts had a higher inhibitory effect compared to MeOH extracts. The treatments of hexane, 85% aq. methanol, butanol and water fractions significantly inhibited the growth of both cancer cells (p<0.05). Among fractions, hexane and 85% aq. methanol fractions showed higher inhibitory effects. In order to determine the protective effect on $H_2O_2$-induced oxidative stress, DCHF-DA (dichlorodihydrofluorescin diacetate) assay was conducted. The A+M and MeOH extracts of dried beet appeared to significantly reduce the levels of intracellular (ROS) with dose responses. Among the fractions, 85% methanol fractions showed a higher protective effect on production of lipid peroxides. These results indicate that the intake of dried beet may improve oxidative stress in cell and reduce cancer risk.

• Progress in Medical Physics
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• v.20 no.4
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• pp.269-276
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• 2009

Radiation treatment techniques using photon beam such as three-dimensional conformal radiation therapy (3D-CRT) as well as intensity modulated radiotherapy treatment (IMRT) demand accurate dose calculation in order to increase target coverage and spare healthy tissue. Both jaw collimator and multi-leaf collimators (MLCs) for photon beams have been used to achieve such goals. In the Pinnacle3 treatment planning system (TPS), which we are using in our clinics, a set of model parameters like jaw collimator transmission factor (JTF) and MLC transmission factor (MLCTF) are determined from the measured data because it is using a model-based photon dose algorithm. However, model parameters obtained by this auto-modeling process can be different from those by direct measurement, which can have a dosimetric effect on the dose distribution. In this paper we estimated JTF and MLCTF obtained by the auto-modeling process in the Pinnacle3 TPS. At first, we obtained JTF and MLCTF by direct measurement, which were the ratio of the output at the reference depth under the closed jaw collimator (MLCs for MLCTF) to that at the same depth with the field size $10{\times}10\;cm^2$ in the water phantom. And then JTF and MLCTF were also obtained by auto-modeling process. And we evaluated the dose difference through phantom and patient study in the 3D-CRT plan. For direct measurement, JTF was 0.001966 for 6 MV and 0.002971 for 10 MV, and MLCTF was 0.01657 for 6 MV and 0.01925 for 10 MV. On the other hand, for auto-modeling process, JTF was 0.001983 for 6 MV and 0.010431 for 10 MV, and MLCTF was 0.00188 for 6 MV and 0.00453 for 10 MV. JTF and MLCTF by direct measurement were very different from those by auto-modeling process and even more reasonable considering each beam quality of 6 MV and 10 MV. These different parameters affect the dose in the low-dose region. Since the wrong estimation of JTF and MLCTF can lead some dosimetric error, comparison of direct measurement and auto-modeling of JTF and MLCTF would be helpful during the beam commissioning.