• Journal of Environmental Health Sciences
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• v.36 no.5
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• pp.402-410
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• 2010

The objectives of this study were to evaluate the air quality surrounding an indoor swimming pool, to estimate the cancer risk based on the airborne exposure to trihalomethanes (THMs), and to examine the ventilation efficiency by Computational Fluid Dynamics (CFD). Chlorine and THMs were measured poolside, and in the staff room and reception area. The indoor swimming pool was modeled using the Airpak program, with ventilation drawings and actual survey data. Temperature, flow and mean age of the air were analyzed. Levels of chlorine poolside, and in the staff room, and reception area were $203\;{\mu}g/m^3$, $5\;{\mu}g/m^3$, and $10\;{\mu}g/m^3$, respectively. Chloroform was the dominant THM in all sampling sites and mean concentrations were $16.30\;{\mu}g/m^3$, $0.51\;{\mu}g/m^3$, and $0.06\;{\mu}g/m^3$ poolside, in the staff room and reception area, respectively. Bromodichloromethane and Dibromochloromethane levels were respectively estimated as $10.3\;{\mu}g/m^3$ and $1.7\;{\mu}g/m^3$ poolside, $1.3\;{\mu}g/m^3$ and $0.1\;{\mu}g/m^3$ in the staff room, and were not detected in the reception area. The cancer risks from inhalation exposure to THMs were estimated between $3.37{\times}10^{-7}$ and $1.84{\times}10^{-5}$. A short circulation phenomenon was observed from the supply air vents to the exhaust air vents located in the ceiling. A high temperature layer was formed within one meter of the ceiling, and a low temperature layer was formed under this layer due to the low velocity and high temperature of the supply air, and the improper locations of the supply air vents and exhaust air vents. The stagnation was evident at the above adult pool and the mean age of the air was 22 minutes. Disinfection by-products in the indoor swimming pool were present in higher concentrations than in the outdoor air. In order to increase the removal of pollutants, adjustment was required of the supply air volume and the supply/exhaust position.

• Membrane Journal
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• v.13 no.2
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• pp.65-72
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• 2003

This study was focused on the investigation of filtration characteristics of membrane-coupled fermentor system for dissolved organics recovery from liquid organic sludge. On the filterability of MF over the range of $0.1{\sim}5 {\mu}m,$ the magnitude of total membrane resistance ($R_t$) is ranged as follows in the order; $0.1 {\mu}m>0.2{\mu}m>0.5 >1{\mu}m>2{\mu}m>5{\mu}m$. The cake layer resistance ($R_c$) occupied about 68~88% of total resistance with fermented sludge. Permeation flux decline was mainly attributed to the $R_c$, which was formed by a strong deposition from physico-chemical interactions of solids on membrane surface. Higher suspended solids (SS) concentration of suspension caused lower permeation flux. However, there was not a proportion relation beyond a certain SS concentration. The cross-flow velocity on the membrane surface was faster, which resulted in the higher permeation flux and also more efficient with low trans membrane pressure (TMP) in viewpoint of energy efficiency. The appropriate pH of suspension was over the range of 5.0~6.0 for dissolved organics recovery as well as the permeation flux. It is possible f3r bacteria to be separated perfectly with $0.1{\mu}m\; and \;0.2{\mu}m$ membrane pore size. Based on experimental results, most appropriate membrane pore size for the recovery is believed to around $1{\mu}m$.

• Korean Journal of Clinical Laboratory Science
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• v.50 no.4
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• pp.477-483
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• 2018

Transcranial doppler is a non-invasive method that measures the blood flow velocity and the direction of cerebral blood vessels through the doppler principle. The pulsatility index is an index for measuring the transcranial doppler that reflects the distal vascular resistance and is used as an index for the presence and diffusion of cerebral small vessel diseases. The purpose of this study was to evaluate the risk factors affecting the basilar artery pulsatility index in ischemic stroke patients. From January 2014 to May 2015, 422 patients were selected by measuring the transcranial doppler pulsatility index, considering their basilar artery pulsatility index. Univariate analysis was performed using the basilar artery pulsatility index as a dependent variable. Multiple regression analysis was performed considering the factors affecting the pulsatility index as variables. Univariate analysis revealed age, presence of hypertension, presence of diabetes mellitus, presence of hyperlipidemia, and hematocrit (P<0.1) as factors. Multiple regression analysis showed statistically significant results with age (P<0.001), presence of diabetes (P=0.004), and presence of hyperlipidemia (P=0.041). The risk factors affecting the basilar artery pulsatility index of transcranial doppler were age, diabetes, and hyperlipidemia. Further research will be needed to increase the cerebral pulsatility index as a surrogate marker of the elderly, diabetes, and hyperlipidemia.

• Journal of The Korean Society of Agricultural Engineers
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• v.61 no.4
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• pp.11-22
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• 2019

The objective of this study was to improve the cross-sectional area and height estimation method using stream width. Stream water levels should be calculated together to simulate inundation of agricultural land. However, cross-sectional survey data of small rural rivers are insufficient. The previous study has developed regression equations between the width and the cross-sectional area and between the width and the height of stream cross-section, but can not be applied to a wide range of stream widths. In this study, cross-sectional survey data of 6 streams (Doowol, Chungmi, Jiseok, Gam, Wonpyeong, and Bokha stream) were collected and divided into upstream, midstream and downstream considering the locations of cross-sections. The regression equations were estimated using the complete data. $R^2$ between the stream width and cross-sectional area was 0.96, and $R^2$ between width and height was 0.81. The regression equations were also estimated using divided data for upstream, midstream and downstream considering the locations of cross-sections. The range of $R^2$ between the stream width and cross-sectional area was 0.86 - 0.91, and the range of $R^2$ between width and height was 0.79 ? 0.92. As a result of estimating the cross-sections of 6 rivers using the regression equations, the regression equations considering the locations of cross-sections showed better performance both in the cross-sectional area and height estimation than the regression equations estimated using the complete data. Hydrologic Engineering Center - River Analysis System (HEC-RAS) was used to simulate the flood stage analysis of the estimated and the measured cross-sections for 50-year, 100-year, and 200-year frequency floods. As a result of flood stage analysis, the regression equations considering the locations of cross-sections also showed better performance than the regression equations estimated using the complete data. Future research would be needed to consider the factors affecting the cross-sectional shape such as river slope and average flow velocity. This study can be useful for inundation simulation of agricultural land adjacent to an unmeasured stream.

• Journal of Korean Society of Disaster and Security
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• v.15 no.3
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• pp.41-46
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• 2022

Recently, the scale of flood damage occurring in urban areas is increasing due to climate change and urbanization, so various flooding analysis techniques are needed. In the Sadangcheon Stream basin, which has been continuously flooded since 2010, a basic plan for improving drainage was established using XP-SWMM and measures to prevent flooding were proposed. However, in the process of inundation analysis, the analysis considering the city's buildings was not conducted, resulting in a problem that the degree of flooding damage tends to be overestimated. Therefore, in this study, XP-SWMM was used to compare and analyze cases where buildings were not considered and designated as inactive areas. As a result of the study, it was analyzed if the building was not considered, the flood damaged area was 271,100 m² and the depth of submersion was 0.15 m, and if the building was considered inactive area, the flood damaged area was 172,900 m² and the depth of submersion was 0.32 m that it is under-estimated about 36% and an flow velocity around the building increased from 1.62 m/s to 1.83 m/s about 1.12 times.

• The Journal of Korean Medicine
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• v.44 no.4
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• pp.87-103
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• 2023

Backgrounds and objectives: Cardiotonic Pills^® (CP) are used for vascular diseases such as coronary diseases, atherosclerosis, and cerebral infarction. This study aimed to determine the transient effects of CP on cerebrovascular CO₂ reactivity (CVR) and erythrocyte deformability in normal subjects. Methods: This study had a crossover design and included 10 participants who were randomly allocated to 2 groups. The experimental group was given CP with water, while the control group was given only water. CVR was measured by hyperventilation-induced CVR of the middle cerebral artery (MCA) using transcranial Doppler (TCD). Erythrocyte deformability was measured using a Rheoscan-D microfluidic ektacytometer. All measurements were performed prior to and 1, 2, and 3 hours after CP or water administration. Blood pressure and heart rate were also measured before and after administration. Results: CP significantly improved CVR 3 hours after administration in the experimental group compared to the control group (p = 0.042). The corrected blood flow velocity at partial pressure of end-tidal carbon dioxide (PETCO₂) = 40mmHg (CV40) was also significantly improved 2 and 3 hours after administration in the CP group compared to the control group (p = 0.036 and p = 0.021, respectively). CP significantly improved erythrocyte deformability 3 hours after administration in the experimental group compared to the control group (p = 0.027). Mean heart rate and mean blood pressure showed no change. Conclusions: This study demonstrated that CP increases CVR and erythrocyte deformability. These results suggested that CP improves cerebral microcirculation which provide evidence for the future use of CP for prevention of ischemic stroke and neurodegenerative diseases.

• Korean Journal of Agricultural and Forest Meteorology
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• v.5 no.2
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• pp.70-80
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• 2003

We report the first direct measurement of $CO_2$ flux over Kwangneung broadleaf deciduous forest, one of the tower flux sites in KoFlux network. Eddy covariance system was installed on a 30 m tower along with other meteorological instruments from June to August in 2002. Although the study site was non-ideal (with valley-like terrain), turbulence characteristics from limited wind directions (i.e., 90$\pm$45$^{\circ}$) was not significantly different from those obtained at simple, homogeneous terrains with an ideal fetch. Despite very low rate of data retrieval, preliminary results from our analysis are encouraging and worthy of further investigation. Ignoring the role of advection terms, the averaged net ecosystem exchange (NEE) of $CO_2$ ranged from -1.2 to 0.7 mg m$^{-2}$ s$^{-1}$ from June to August in 2002. The effect of weak turbulence on nocturnal NEE was examined in terms of friction velocity (u*) along with the estimation of storage term. The effect of low uf u* NEE was obvious with a threshold value of about 0.2 m s$^{-1}$ . The contribution of storage term to nocturnal NEE was insignificant; suggesting that the $CO_2$ stored within the forest canopy at night was probably removed by the drainage flow along the hilly terrain. This could be also an artifact of uncertainty in calculations of storage term based on a single-level concentration. The hyperbolic light response curves explained ＞80% of variation in the observed NEE, indicating that $CO_2$ exchange at the site was notably light-dependent. Such a relationship can be used effectively in filling up the missing gaps in NEE data through the season. Finally, a simple scaling analysis based on a linear flow model suggested that advection might play a significant role in NEE evaluation at this site.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.24 no.2
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• pp.351-373
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• 2019

The cold eddies around the Ulleung Basin in the East Sea were identified from satellite altimeter sea level data using the Winding-Angle method from 1993 to 2015. Among the cold eddies, the Dokdo Cold Eddies (DCEs), which were formed at the first meandering trough of the East Korea Warm Current (EKWC) and were pinched off to the southwest from the eastward flow, were classified and their migration patterns were analyzed. The vertical structures of water temperature, salinity, and flow velocity near the DCE center were also examined using numerical simulation and observation data provided by the Hybrid Coordinate Ocean Model and the National Institute of Fisheries Science, respectively. A total of 112 DCEs were generated for 23 years. Of these, 39 DCEs migrated westward and arrived off the east coast of Korea. The average travel distance was 250.9 km, the average lifespan was 93 days, and the average travel speed was 3.5 cm/s. The other 73 DCEs had moved to the east or had hovered around the generated location until they disappeared. At 50-100 m depth under the DCE, water temperature and salinity (T < $5^{\circ}C$, S < 34.1) were lower than those of ambient water and isotherms made a dome shape. Current faster than 10 cm/s circulates counterclockwise from the surface to 300 m depth at 38 km away from the center of DCE. After the EKWC separates from the coast, it flows eastward and starts to meander near Ulleungdo. The first trough of the meander in the east of Ulleungdo is pushed deep into the southwest and forms a cold eddy (DCE), which is shed from the meander in the south of Ulleungdo. While a DCE moves westward, it circumvents the Ulleung Warm Eddy (UWE) clockwise and follows U shape path toward the east coast of Korea. When the DCE arrives near the coast, the EKWC separates from the coast at the south of DCE and circumvents the DCE. As the DCE near the coast weakens and extinguishes about 30 days later after the arrival, the EKWC flows northward along the coast recovering its original path. The DCE steadily transports heat and salt from the north to the south, which helps to form a cold water region in the southwest of the Ulleung Basin and brings positive vorticity to change the separation latitude and path of the EKWC. Some of the DCEs moving to the west were merged into a coastal cold eddy to form a wide cold water region in the west of Ulleung Basin and to create a elongated anticlockwise circulation, which separated the UWE in the north from the EKWC in the south.

• Journal of the Korean earth science society
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• v.38 no.1
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• pp.24-34
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• 2017

The westerly waves generation is described in the advanced earth science textbook used at high school as follows: as westerly wind approaches and blows over large mountains, the air flow shows wave motions in downwind side, which can be explained by the conservation of potential vorticity. However, there has been no case study showing the phenomena of the mesoscale westerly waves with observational data in the area of small mountains in Korea. And thus the wind speed and time persistency of westerly winds along with the width and length of mountains have never been studied to explain the generation of the westerly waves. As a first step, we assured the westerly waves generated in the downwind side of Sobaek mountains based on surface station wind data nearby. Furthermore, the critical or minimum wind velocity of the westerly wind over Sobaek mountains to generate the downwind wave were derived and calcuated tobe about $0.6m\;s^{-1}$ for Sobaek mountains, which means that the westerly waves could be generated in most cases of westerly blowing over the mountains. Using surface station data and 4-dimensional assimilation data of RDAPS (Regional Data Assimilation and Prediction System) provided by Korea Meteorological Agency, we also analyzed cases of westerly waves occurrence and life cycle in the downwind side of Sobaek mountains for a year of 2014. The westerly waves occurred in meso-${\beta}$ or -${\gamma}$ scales. The westerly waves generated by the mountains disappeared gradually with wind speed decreasing. The occurrence frequency of the vorticity with meso-${\beta}$ scale got to be higher when the stronger westerly wind blew. When we extended the spatial range of the analysis, phenomena of westerly waves were also observed in the downwind side of Yensan mountains in Northeastern China. Our current work will be a study material to help students understand the atmospheric phenomena perturbed by mountains.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.41 no.1
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• pp.17-26
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• 2005

There are several problems in the commercial pound net in the heavy tide ; the breaking and loss of net, steeply variation of net shape and decreasing of fishing efficiency, etc. In order to solve these problems, we introduced method of added sinker used to coastal cultivating cage of Japan and investigated the possibility of application to the Korean pound net. The results are obtained as follows; 1. In case of the upperward flow with fish court net, tension of the frame line was increased about 10${\sim}$25% than that of prototype according to the added sinker from 1.3gf to 5.2gf. The tension of A-type and B-type was similar to the case of the prototype, the tension of C-type and D-type was increased about 10${\sim}$15% than that of prototype. 2. The variation of deformed angle of fish court net was from 0$^{\circ}$ to 70$^{\circ}$ and that of the slope net was from 0$^{\circ}$ to 64$^{\circ}$ and that of the second bag net was from 0$^{\circ}$ to 46$^{\circ}$ and the depth of the second bag net was increased about 10% when the added sinker was changed from 1.3gf to 5.2gf. The depth of the first bag net and the second bag net were decreased about 50% than that of initial depth. 3. For the deformed angle of fish court net according to the attached point of the added sinker, A-type and B-type were decreased about 25% and 10% than the prototype, respectively. C-type was similar to the case of the prototype and D-type was increased about 15% than that of the prototype. The depth of slope net became deep in turn of A-type, B-type, C-type and D-type. For the depth of the second bag net, A-type, B-type, C-type and D-type were increased about 10${\sim}$15% than that of prototype. The depth of the slope net was changed from 0$^{\circ}$ to 63$^{\circ}$ and that of the second bag net was changed from 0${\sim}$44$^{\circ}$ according to the increase of velocity. 4. The optimal weight of added sinker was about 2.6${\sim}$3.6gf and the optimal attached point of added sinker was the case of C-type and D-type.