• Journal of The Geomorphological Association of Korea
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• v.23 no.1
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• pp.117-128
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• 2016

High resolution aerial photographs and digital elevation models for Bangpo beach using UAV were generated in this study to analyze the thematic and geometric characteristics of coastal features. Based on 728 aerial images acquired on September 10, 2016 by the UAV, a image mosaic at 2.2 cm spatial resolution and a digital elevation model at 4.4 cm spatial resolution were developed. This study found out that Bangpo beach consisted of intertidal zone and supratidal zone. The intertidal zone can be subdivided into lower part and upper part with distinctive geomorphological characteristics. While the lower part included sand bars and ripple marks along the coastline, the cusps and sand dunes were the major coastal features of the upper part. Part of the intertidal zone was occupied by shore platform with average slope of 0.9 degree containing various sizes of gravels. The supratidal zone slanted toward ocean with berms on the surface with an interval of 15 m. These coastal features indicated the flow intensity towards to the land and tidal effect. It validated that the UAV application in coastal research was very effective analyzing to examine coastal processes.

• Journal of Soil and Groundwater Environment
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• v.26 no.3
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• pp.1-13
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• 2021

Groundwater monitoring is commonly practiced with real-time sensors placed in several depth spots in aquifer. However, this method only provides monitoring data at the point where the sensors are installed. In this study, we developed a vertical line monitoring system (VLMS) that can provide continuous data of groundwater parameters along the vertical depth. The device was installed in a well located on the coast of the eastern part of Jeju island to monitor electrical conductivity, temperature, salinity, pH, dissolved oxygen, and oxidation-reduction potential over approximately 3 months from September 11 to December 3, 2020. The results indicated that the groundwater levels fluctuated with the tidal change of seawater level, and the upper and lower boundaries of the freshwater and saltwater zone in the groundwater were located at below 16 m and 36 m of mean sea level, respectively. There was a large variation in EC values during the high tide and temperature change was the greatest during flow tide. Although further investigation is needed for improvement of the device to obtain more accurate and reliable data, the device has a potential utility to provide fundamental data to understand the seawater intrusion and transport mechanisms in coastal aquifers.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.19-19
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• 2020

한강 하구는 매우 다이나믹한 공간이다. 서해의 조석변화가 한강과 임진강에 영향을 미치는 동시에 한강과 임진강의 영향이 조석에도 영향을 미친다. 한강과 임진강의 유량은 서로에게도 영향을 미친다. 결과적으로 한강, 임진강, 조석이 서로 밀접하게 영향을 미치는 곳이 한강 하구이다. 그러나 지금까지 군사적인 문제로 인해 한강 하구에 대한 조사나 분석은 많이 이루어질 수 없었다. 그로인해 하구의 수리적인 영향이 정확하게 분석되지 못하였다. 본 연구에서는 한강 하구의 흐름 모의 결과를 바탕으로 조석변화의 특성을 분석하였다. 또한 신곡수중보 주위의 흐름 조사 결과를 바탕으로 하구에서 발생하는 조석 변화의 영향도 분석하였다. 한강 본류의 경우 평상시 조석이 영향을 미치는 범위는 잠실수중보 직하류까지이다. 한강 본류에 계획홍수량이 흐르는 경우 한강대교 지점에는 조석의 영향이 나타나지 않으며, 약 10,000cms 이상의 홍수량에서는 조석영향이 거의 나타나지 않는 것으로 분석되었다. 임진강의 경우에도 계획 홍수량이 흐를 경우 조석이 영향을 미치는 범위는 하구부 일정 구간에 한정된다. 한강 하구부에서 홍수시 조석의 영향으로 인해 홍수위가 상승될 수 있는 경우는 제한적이라고 할 수 있다. 임진강의 유량은 한강의 조석변화에도 영향을 미친다. 임진강에 평상시 유량이 흐르는 경우와 홍수량이 흐르는 경우에 나타나는 한강의 조석영향 범위 및 크기는 다르다. 반대로 한강의 유량은 임진강의 흐름에도 영향을 미치게 된다. 이와 같은 상호간의 영향은 매우 밀접하게 발생하게 된다. 한강 하구부에 설치되어 있는 신곡수중보는 조석의 변화에 큰 영향을 미치고 있다. 조석으로 인해 발생하는 수위의 변화가 수중보로 인해 줄어들게 되어 이 지점을 기준으로 수위차가 발생하게 된다. 만조시에는 수중보를 월류하는 흐름이 발생하는데 상류방향의 유속이 빠르게 나타난다. 수심방향의 유속변화도 크게 나타나는데 상류 및 하류 방향의 유속이 시간과 장소에 따라 매우 다양하고 복잡하게 나타나게 된다. 한강 하구부의 수리현상은 매우 복잡하지만 지금까지 조사되거나 분석되지 못한 것이 사실이다. 하구부의 지속가능한 관리를 위해서는 의사결정을 할 수 있는 기초자료와 분석 결과가 매우 중요하다. 본 연구의 결과는 한강 하구 조사와 분석을 위해 활용될 수 있으리라 기대된다.

• Tuberculosis and Respiratory Diseases
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• v.43 no.2
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• pp.201-209
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• 1996

Background : Auto-PEEP which develops when expiratory lung emptying is not finished until the beginning of next inspiration is frequently found in patients on mechanical ventilation. Its presence imposes increased risk of barotrauma and hypotension, as well as increased work of breathing (WOB) by adding inspiratory threshold load and/or adversely affecting to inspiratory trigger sensitivity. The aim of this study is to evaluate the relationship of auto-PEEP with WOB and to evaluate the effect of PEEP applied by ventilator (external PEEP) on WOB in patients with auto-PEEP. Method : 15 patients, who required mechanical ventilation for management of acute respiratory failure, were studied. First, the differences in WOB and other indices of respiratory mechanics were examined between 7 patients with auto-PEEP and 8 patients without auto-PEEP. Then, we applied the 3 cm $H_2O$ of external PEEP to patients with auto-PEEP and evaluated its effects on lung mechanics as well as WOB. Indices of respiratory mechanics including tidal volume ($V_T$), repiratory rate, minute ventilation ($V_E$), peak inspiratory flow rate (PIFR), peak expiratory flow rate (PEFR), peak inspiratory pressure (PIP), $T_I/T_{TOT}$, auto-PEEP, dynamic compliance of lung (Cdyn), expiratory airway resistance (RAWe), mean airway resistance (RAWm), $p_{0.1}$, work of breathing performed by patient (WOB), and pressure-time product (PTP) were obtained by CP-100 Pulmonary Monitor (Bicore, USA). The values were expressed as mean $\pm$ SEM (standard error of mean). Results : 1) Comparison of WOB and other indices of respiratory mechanics in patients with and without auto-PEEP : There was significant increase in WOB ($l.71{\pm}0.24$ vs $0.50{\pm}0.19\;J/L$, p=0.007), PTP ($317{\pm}70$ vs $98{\pm}36\;cm$ $H_2O{\cdot}sec/min$, p=0.023), RAWe ($35.6{\pm}5.7$ vs $18.2{\pm}2.3\;cm$ H2O/L/sec, p=0.023), RAWm ($28.8{\pm}2.5$ vs $11.9{\pm}2.0cm$ H2O/L/sec, p=0.001) and $P_{0.1}$ ($6.2{\pm}1.0$ vs 2.9+0.6 cm H2O, p=0.021) in patients with auto-PEEP compared to patients without auto-PEEP. The differences of other indices including $V_T$, PEFR, $V_E$ and $T_I/T_{TOT}$ showed no significance. 2) Effect of 3 cm $H_2O$ external PEEP on respiratory mechanics in patients with auto-PEEP : When 3 cm $H_2O$ of external PEEP was applied, there were significant decrease in WOB ($1.71{\pm}0.24$ vs $1.20{\pm}0.21\;J/L$, p=0.021) and PTP ($317{\pm}70$ vs $231{\pm}55\;cm$ $H_2O{\cdot}sec/min$, p=0.038). RAWm showed a tendency to decrease ($28.8{\pm}2.5$ vs $23.9{\pm}2.1\;cm$ $H_2O$, p=0.051). But PIP was increased with application of 3 cm $H_2O$ of external PEEP ($16{\pm}2$ vs $22{\pm}3\;cm$ $H_2O$, p=0.008). $V_T$, $V_E$, PEFR, $T_I/T_{TOT}$ and Cdyn did not change significantly. Conclusion : The presence of auto-PEEP in mechanically ventilated patients was accompanied with increased WOB performed by patient, and this WOB was decreased by 3 cm $H_2O$ of externally applied PEEP. But, with 3 cm $H_2O$ of external PEEP, increased PIP was noted, implying the importance of close monitoring of the airway pressure during application of external PEEP.

• The Korean Journal of Physiology
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• v.15 no.1
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• pp.37-43
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• 1981

In the present study, an effort was directed to elucidate the effect of the physical training on the pulmonary function. Twenty-four male athletics major students who have undergone regular physical training for more than five years were randomly chosen as the athletic subjects, and 12 regular male students who have not been engaged in any form of regular physical exercise or training were chosen as the non-athletic subjects, and a comparison was made between the two groups. The following were mainly observed by spirometry for the study; respiratory rate, tidal volume, vital capacity, maximum voluntary ventilation(MVV), forced expiratory volume for 1 second$(FEV_1)$, percent $FEV_1$ to forced vital capacity$(FEV_1%)$, forced expiratory flow for initial 1 liter$(FEF_{0.2-1.2}L)$, and forced mid-expiratory flow$(FEF_{\;25-75}%)$. The results obtained are summarized as follow. 1) The respiratory rate, tidal volume, and vital capacity showed no significant difference between athletes and non-athletes. The MVV in athletes was significantly (p<0.01) increased to $148.1{\pm}3.1\;L/min$ comparing with $118.3{\pm}9.1\;L/min$ in non-athletes. 2) $FEV_1$ was $3.310{\pm}0.070\;L$ in athletes and $2.779{\pm}0.104$ in non-athletes; $FEV_1%\;83.63{\pm}1.29%$ in athletes and $75.33{\pm}1.75%$ in non-athletes, both showing significant(p<0.01) increase in athletes. 3) $FEF_{0.2-1.2}L$ was $297.1{\pm}13.5\;L/min in athletes and $222.7{\pm}15.0\;L/min$ in non-athletes; $FEF_{\;25-75}%$ was $3.543{\pm}0.109\;L/sec$ in non-athletes, both showing significant(p<0.01) increase in athletes. 4) Some discussions were made on these results. The lung volumes showed no significant difference between the two groups. But MVV, $FEV_1$, $FEV_1%$, $FEF_{0.2-1.2}L$ and $FEF_{25-75}%$ in athletes were significantly(p<0.01) higher than in non-athletes. It is therefore concluded that the athletes have more powerful respiratory muscles, or higher compliance of the lung and thorax than the non-athletes.

• Journal of Wetlands Research
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• v.21 no.2
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• pp.102-113
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• 2019

Slack-tide sampling was carried out at 6 stations at high and low tide for a tidal cycle during spring tide of the early summer (June) and summer (July, August) of 2016 to determine the difference of water quality according to tide in Masan Bay, Korea. The mixing regime of all the water quality components investigated was well explained through the correlation with SAL. In the early summer and summer, TURB, DSi and NNN which mainly flow into the bay from the streams and SS, COD, AMN and $H_2S$ which mainly indicate the internal sink and source materials have a property of conservative mixing and non-conservative mixing, respectively. The conservative mixing showed a good linear relationship of the water quality between high and low tide, and the non-conservative mixing showed a variation of different pattern each other. Factor analysis performed on the concentration difference data sets between high and low tide helped in identifying the principal latent variables for them. In early summer, multiple effects (tidal action, natural influx and internal sinks and sources etc.) acted in combination for the differences to be distributed evenly in four factors (VF1~4), since there were few allochthonous inputs as a low-water season. On the contrary, in summer, the parameters showing large concentration difference at ST-1 affected by stream water were concentrated in one factor (VF1) and clearly distinguished from the parameters affected by the internal sinks and sources. In fact, there is no estuary (bay) that always maintains steady state flow conditions. The mixing regime of an estuary might be changed at any time due to the change of flushing time, and furthermore the change of end-member conditions due to the internal sinks and sources makes the occurrence of concentration difference inevitable. Therefore, when investigating the water quality of the estuary, it is necessary to take a sampling method considering the tide to obtain average water quality data.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.9
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• pp.871-877
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• 2015

Deep-sea equipment such as underwater robots and unmanned submersible vehicles, include various machine components and sensors, and it is important that their reliabilities be tested before use in the fields. This is necessary because they are affected by complex extreme-environment conditions, such as high pressures, extreme temperatures, and tidal forces that are present in the deep sea. We require test equipment that can conduct empirical tests in conditions that mimic these complex oceanic environments. In this study, we propose specifications that should be met, and a design plan for the primary components, which should limit their use to a maximum water pressure of 2.0 MPa, water temperature of $5{\sim}60^{\circ}C$, and a maximum flow velocity of 2 m/s. in work-in type underwater combined environment test equipment and. We present test system development procedures to verify the reliability of products and systems used in deep-sea environments.

• The korean journal of orthodontics
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• v.40 no.2
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• pp.66-76
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• 2010

Objective: Obstructive sleep apnea (OSA) is a common disorder which is characterized by a recurrence of entire or partial collapse of the pharyngeal airway during sleep. A given tidal volume must traverse the soft tissue tube structure of the upper airway, so the tendency for airway obstruction is influenced by the geometries of the duct and characteristics of the airflow in respect to fluid dynamics. Methods: Individualized 3D FEA models were reconstructed from pretreatment computerized tomogram images of three patients with obstructive sleep apnea. 3D computational fluid dynamics analysis was used to observe the effect of airway geometry on the flow velocity, negative pressure and pressure drop in the upper airway at an inspiration flow rate of 170, 200, and 230 ml/s per nostril. Results: In all 3 models, large airflow velocity and negative pressure were observed around the section of minimum area (SMA), the region which narrows around the velopharynx and oropharynx. The bigger the Out-A (outlet area)/ SMA-A (SMA area) ratio, the greater was the change in airflow velocity and negative pressure. Conclusions: Pressure drop meaning the difference between highest pressure at nostril and lowest pressure at SMA, is a good indicator for upper airway resistance which increased more as the airflow volume was increased.

• Journal of Soil and Groundwater Environment
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• v.14 no.6
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• pp.53-64
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• 2009

Wetlands can remove organic contaminants, metals and radionuclides from wastewater through various biogeochemical mechanisms. In this study, a mathematical model was developed for simulating the fate and transport of chemical species in marsh wetland sediments. The proposed model is a one-dimensional vertical saturated model which is incorporated advection, hydrodynamic dispersion, biodegradation, oxidative/reductive chemical reactions and the effects from external environments such as the growth of plants and the fluctuation of water level due to periodic tides. The tidal effects causes periodic changes of porewater flow in the sediments and the evapotranspiration and oxygen supply by plant roots affect the porewater flow and redox condition on in the rhizosphere along with seasonal variation. A series of numerical experiments under hypothetical conditions were performed for simulating the temporal and spatial distribution of chemical species of interests using the proposed model. The fate and transport of a trace metal pollutant, chromium, in marsh sediments were also simulated. Results of numerical simulations show that plant roots and tides significantly affect the chemical profiles of different electron acceptors, their reduced species and trace metals in marsh sediments.

• Journal of the Korean Association of Geographic Information Studies
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• v.11 no.4
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• pp.182-192
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• 2008

In oder to develop a decision supporting system for oil spill response, the prototype of pollution response support system which has integrated oil spill prediction system and pollution risk prediction system has developed for Incheon-Daesan area. Spill prediction system calculates oil spill aspects based on real-time wind data and real-time water flow and the residual volume of spilt oil and spread pattern are calculated considering the characteristic of spilt oil. In this study, real-time data is created from results of real-time meteorological forecasting model(National Institute of Environmental Research) using ftp, real-time tidal currents datasets are built using CHARRY(Current by Harmonic Response to the Reference Yardstick) model and real-time wind-driven currents are calculated applying the correlation function between wind and wind-driven currents. In order to model the feature which is spilt oil spreading according to real-time water flow is weathered, the decrease ratio by oil kinds was used. These real-time data and real-time prediction information have been integrated with ESI(Environmental Sensitivity Index) and response resources and then these are provided using GIS as a whole system to make the response strategy.