• Korean Journal of Agricultural and Forest Meteorology
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• v.11 no.4
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• pp.192-205
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• 2009

The unexpected wind over the Mt. Hwawang on 9 February 2009 was deadly when many spectators were watching a traditional event to burn dried grasses and the fire went out of control due to the wind. We analyzed the fatal wind based on wind flow simulations over a digitized complex terrain of the mountain with a localized heating area using a three dimensional computational fluid dynamics model, CFD_NIMR_SNU (Computational Fluid Dynamics_National Institute of Meteorological Research_Seoul National University). Three levels of fire intensity were simulated: no fire, $300^{\circ}C$ and $600^{\circ}C$ of surface temperature at the site on fire. The surface heat accelerated vertical wind speed by as much as $0.7\;m\;s^{-1}$ (for $300^{\circ}C$) and $1.1\;m\;s^{-1}$ (for $600^{\circ}C$) at the center of the fire. Turbulent kinetic energy was increased by the heat itself and by the increased mechanical force, which in turn was generated by the thermal convection. The heating together with the complex terrain and strong boundary wind induced the unexpected high wind conditions with turbulence at the mountain. The CFD_NIMR_SNU model provided valuable analysis data to understand the consequences of the fatal mountain fire. It is suggested that the place of fire was calm at the time of the fire setting due to the elevated terrain of the windward side. The suppression of wind was easily reversed when there was fire, which caused updraft of hot air by the fire and the strong boundary wind. The strong boundary wind in conjunction with the fire event caused the strong turbulence, resulting in many fire casualties. The model can be utilized in turbulence forecasting over a small area due to surface fire in conjunction with a mesoscale weather model to help fire prevention at the field.

• Journal of agricultural medicine and community health
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• v.40 no.2
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• pp.53-61
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• 2015

Objectives: An outbreak of food poisoning occurred among the baseball club students at a high school in Ulsan city in 2014. An epidemiological investigation was carried out to examine the infection source and the transmission route of pathogen, and to prevent a recurrence. Methods: A questionnaire survey was conducted for 26 male students and 2 food handlers. Rectal swabs were examined in 7 students and the 2 food handlers, and an environmental investigation was performed. A retrospective cohort study was used to evaluate the association between risk factors and disease. Results: The attack rate was 35.7% (10 persons/28 persons) from June 9 to 14, and Enterotoxigenic E. coli ST/LT was isolated from 7 among 28 persons. The study revealed that no food was a significant risk factor for the outbreak. There were no connection between environmental factors and the outbreak. Conclusions: The major risk factors for this outbreak were presumed to be the contaminated ice cube and ice making machines and eating ice cube from the machines. More strict personal and environmental hygiene need to be enforced to prevent such outbreaks.

• Korean Chemical Engineering Research
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• v.55 no.2
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• pp.201-213
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• 2017

Water is removed from crude oil containing water by using oil separator. This study aims to develop a three-dimensional (3D) Eulerian computational fluid dynamics (CFD) model to predict the separation efficiency of air-water-oil separator. In the incompressible, isothermal and unsteady-state CFD model, air is defined as continuous phase, and water and oil are given as dispersed phase. The momentum equation includes the drag force, lift force and resistance force of porous media. The standard k-${\varepsilon}$ model is used for turbulence flow. The exit pressures of water and oil play an important role in determining the liquid level of the oil separator. The exit pressures were identified to be 6.3 kPa and 5.1 kPa for water and oil, respectively, to keep a liquid level of 25 cm at a normal operating condition. The time evolution of volume fractions of air, water and oil was investigated. The settling velocities of water and oil along the longitudinal separator distance were analyzed, when the oil separator reached a steady-state. The oil separation efficiency obtained from the CFD model was 99.85%, which agreed well with experimental data. The relatively simple CFD model can be used for the modification of oil separator structure and finding optimal operating conditions.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.7
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• pp.922-930
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• 2020

Marine accidents involving fishing boats, caused by a loss of stability, have been increasing over the last decade. One of the main reasons for these accidents is a sudden wind attacks. In this regard, the wind loads acting on the ship hull need to be estimated accurately for safety assessments of the motion and maneuverability of the ship. Therefore, this study aims to develop a computational model for the inlet boundary condition and to numerically estimate the wind load acting on a fishing boat. In particular, wind loads acting on a fishing boat at the wind speed profile boundary condition were compared with the numerical results obtained under uniform wind speed. The wind loads were estimated at intervals of 15° over the range of 0° to 180°, and i.e., a total of 13 cases. Furthermore, a numerical mesh model was developed based on the results of the mesh dependency test. The numerical analysis was performed using the RANS-based commercial solver STAR-CCM+ (ver. 13.06) with the k-ω turbulent model in the steady state. The wind loads for surge, sway, and heave motions were reduced by 39.5 %, 41.6 %, and 46.1 % and roll, pitch, and yaw motions were 48.2 %, 50.6 %, and 36.5 %, respectively, as compared with the values under uniform wind speed. It was confirmed that the developed inlet boundary condition describing the wind speed gradient with respect to height features higher accuracy than the boundary condition of uniform wind speed. The insights obtained in this study can be useful for the development of a numerical computation method for ships.

• Journal of Korean Orthopaedic Sports Medicine
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• v.2 no.1
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• pp.62-70
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• 2003

Purpose: We examined the kinematics and kinetics of the shoulder in youth baseball pitchers in light of the mechanisms of development of little league shoulder and humeral retrotorsion. Materials and Methods: The joint kinematics and the net force and torque acting on the humerus were calculated in fourteen youth pitchers throwing in a simulated game. Results: The major force component acting on the humerus was a tensile force of 378$\pm$81 N that peaked just after ball release. The predominant torque on the humerus was an external rotation torque about the long axis of the humerus. This torque reached a peak value of 35.3$\pm$6.7 Nm about 73$\%$through the pitching motion. This torque is approximately 66$\%$ of the torque required to fracture of the adult humerus. Conclusions: The direction of the humeral torque was consistent with the development of increased humeral retrotorsion in the throwing arm. Shear stress arising from the high torque during the late cocking phase likely leads to deformation the relatively weak proximal humeral epiphysis. The external rotation torque applied to the humerus during the pitch also agrees with the proposed mechanism for development little league shoulder, which has been hypothesized to be due to rotational stresses acting on the epiphysis during the throwing motion.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.40 no.3
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• pp.214-224
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• 2004

A large cage system for the purpose of fishes farming in the open sea was influenced by various forces from the ocean environment. The deformation of the cage by these forces affects the safety of the cage itself, as well as that of the cultivated creatures. In this research, theoretical model was established to analyzing dynamic movement influenced by current for cage. Also, to increase the accuracy of calculations, the reduction ratio of flow speed acquired using the flume tank experiment. Applying the reduction ratio of flow speed to the numerical calculation, the calculation values were compared with the measured values in the flume tank experiment using cage model. The results were as follows ; 1. When the flow speed of the flume tank is fixed, the decrease of the velocity of flow which is passed the upper panel side is proportion to the increase of porosity ratio of netting. 2. When the porosity ratio is fixed, the increase of the velocity of flow which is passed the upper panel side is proportion to the increase of velocity of flow. 3. When the porosity ratio and the flow speed of the flume tank are fixed, the decrease of the velocity of flow which is passed the upper panel side is proportion to the increase of attack angle. 4. As a result of comparison between the underwater shape by simulation which is applying the reduction ratio of flow speed from the experiment using plane netting and that by model experiment, it was found out that the result of the simulation was very close to that of model gear within ${\pm}$ 5 % error range.

• Korean Journal of Applied Biomechanics
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• v.19 no.1
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• pp.159-166
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• 2009

The purpose of this study was to develop and automatic gait event detection algorithm using single accelerometer which is attached at the top of the shoe. The sinal vector magnitude and anterior-posterior(x-axis) directional component of accelerometer were used to detect heel strike(HS) and toe off(TO), respectively. To evaluate proposed algorithm, gait event timing was compared with that by force plate and kinematic data. In experiment, 7 subjects performed 10 trials level walking with 3 different walking conditions such as fast, preferred & slow walking. An accelerometer, force plate and 3D motion capture system were used during experiment. Gait event by force plate was used as reference timing. Results showed that gait event by accelerometer is similar to that by force plate. The distribution of differences were spread about $22.33{\pm}17.45m$ for HS and $26.82{\pm}14.78m$ for To and most error was existed consistently prior to 20ms. The difference between gait event by kinematic data and developed algorithm was small. Thus it can be concluded that developed algorithm can be used during outdoor walking experiment. Further study is necessary to extract gait spatial variables by removing gravity factor.

• Korean Journal of Applied Biomechanics
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• v.19 no.1
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• pp.99-106
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• 2009

The purpose of this study was to determine whether hormone levels change knee laxity in healthy females. Twenty three healthy females were recruited for the study. Serum estradiol and progesterone levels were recorded three times during the subjects' menstrual cycles. The first measurements were taken between day 3 and 7 of the follicular phase and the second data collection coincided with ovulation, 24 to 48 hours after the estrogen surge detected by an ovulation predictor kits. Based on a 28 day cycle, the third data collection occurred approximately 7 days later during the luteal phase. Knee joint laxity was recorded at the same intervals with a KT 2000 arthometer. Hormone levels and phases were compared to passive knee joint laxity with multiple regression analysis. Estradiol and progesterone levels differed significantly across the three tests. Knee joint laxity increased during ovulation. Based on a multiple regression analysis, estradiol and progesterone levels predicts 77.9% to 80.9% of the laxity at 20lb and 30lb loads. An antagonistic relationship between estradiol and progesterone was found when testing for knee laxity. Serum hormone levels have moderate power in predicting knee joint laxity. Individual hormonal profiling in female athletes would allow researchers to access the structural properties of the ACL, such as the laxity which may provide beneficial information to understand female ACL injury mechanism in sports activity.

• Korean Journal of Applied Biomechanics
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• v.15 no.3
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• pp.71-78
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• 2005

The purpose of this research was to conduct an analysis on the factors that determine the distance at the time of target swing based on the use of late hitting of outstanding college golfers to verify the difference between late hitting and the distance that target increases in regular swing and the distance. Then, this research conducts an analysis on the correlation between club head velocity, ball velocity, launch angle, back spin, meet ratio and distance that become kinematics variables at the time of target swing. To attain the above mentioned purpose, 25 outstanding college players with average experience and handicap of 6 years and 5, respectively, were targeted Comparative analysis on two swing that target increase in regular and the distance was conducted by used driver. When it pertained to two types of swing. analysis system comprised of an analytical software called the Science Eye of the Bridgestone and peripheries was used to define the relationship between variables of club head velocity, ball velocity, launch angle, back spin, meet ratio that become kinematics variables. As for the method of processing data pertaining to the factors that determine the distance, differences of distance by the type of swing was verified by using independent T-test that leveraged SPSS 120 statistics program. Moreover, level of correlation between variables that contribute to the increase in distance through relation of correlation, and analysis of tendencies was conducted to analyze tendency of non-distance to increase in accordance to the increase of each variable. Key results produced through this experiment are as follows: 1. Artificial late hitting for increased non-distance that targets skilled players had effect on increased the distance(p<. 05). 2 The drive distance is correlated with each measured variable that is positive correlation to ball velocity, club head velocity, meet ratio and relation of back spin and launch angle are negative correlation. ball velocity and club head velocity are very high correlated with drive distance(p<.01), back spin and distance are negative correlation(p<.01). 3. Among each measured variable increasing the club velocity is the most contribution, and ball velocity and meet ratio and the increasing launch angle and back spin is negative effect for increasing distance.

• Journal of the Korean Institute of Landscape Architecture
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• v.35 no.2 s.121
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• pp.1-12
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• 2007

근래 한국에서도 대표적 공공공간인 공원의 조성 및 관리와 관련하여 파트너십에 대한 관심이 일고 있다. 주민들이 만들어가는 공원, 다양한 힘의 역학구조 속에서 공공성 유지, 지속 가능한 사회 구현에 도움이 될 것이라는 전망 때문이다. 이에 본 연구에서는 추후 한국에서의 실천과 제도정비에 도움이 될 수 있도록, 영국에서는 어떻게 정책적으로 파트너쉽을 유도하는지 그리고 커뮤니티는 이를 어떻게 수용하여 자신들의 사례를 만들어 가는가를 살펴보았다. 사례연구에 있어서는 질적 연구방법을 택했으며, 분석보다는 사례가 갖는 내러티브(narratives)를 다층적으로 서술하는데 초점을 두었다. 이것은 거대 내러티브가 사라지고 있는 현대 사회에서 일반적 원칙보다는 개별 사례의 구체성을 밝히는 것이 보다 중요하다는 일부 사회학 연구자들의 견해를 수용한 것이다. 더욱이, 주민참여 관련 사례는 지역특성과 주민의 영향을 많이 받기 때문에 이러한 연구방법이 유용할 것이다. 더불어, 이러한 방식은 자못 추상적 이해에 그칠 외국 사례를 보다 구체적으로 이해하는데 적합할 것이다. 연구결과에 있어, 먼저 영국에서는 지방의제21(LA21)이 지방정부의 서비스에 대한 근본적 태도와 체계를 바꾸는데 기여했다는 것을 알 수 있었다. 일례로, 뉴캐슬(Newcastle upon Tyne)시는 직접 서비스를 제공하기 보다는 주민들의 참여를 촉진하고 도와주는 방향으로 역할을 전환하고 있었다. 그리고 다양한 자금지원체계는 직접적으로 파트너십을 독려하고 있었다. 영국 뉴캐슬(Newcastle upon Tyne) 웨이브리 파크(Waverley Park) 사례를 살펴본 바에 따르면, 파트너십에 대한 지방정부의 태도가 성공적 파트너십에 있어 중요한 요소임을 확인할 수 있었다. 이 사례에서는 프렌즈그룹 이외, 커뮤니티 외부의 비영리 단체가 참여하지 않았는데, 이는 지방정부가 적극적으로 주민들의 참여를 촉구하고 도왔기 때문이다. 이외, 커뮤니티의 구성원과 공무원들의 개인적 역할도 중요하다는 것을 알 수 있었다. 중앙정부는 단지 자금뿐만이 아니라 다양한 사례에서 축적한 정보를 커뮤니티에 지원하고 전 과정을 모니터링 하고 있었는데, 간접적 참여라고 할 수 있다. 앞에서 언급했듯이, 본 연구는 영국에서의 파트너십과 관련된 제도, 그리고 제도가 구체적 현실에서 작동되면서 나타나는 특수성을 살펴보는 데 주력했다. 그런데 사례 연구에서 발견한 특수성을 한국에서의 시사점으로 명시하는 것은 한계가 있을 수 있다. 그래서 시사점은, 제도적 차원에서 한국과 영국을 비교하여 간략하게 제시했다. 첫째, 지방의제 21의 수용 방식이다. 한국의 지방정부 또한 지방의제 21을 실천하기 위해 협의회 등을 설치하였지만 행정 시스템을 전반적으로 변화시키고 있는 영국과는 차이점이 있다. 둘째, 공원과 녹지에 대한 지원금이 제공될 때, 지역주민의 동의를 요구하는 것은 커뮤니티의 참여를 독려하고 주인의식을 갖도록 하는데 효과적이라는 것도 시사점이 될 수 있다. 한국에서도 녹색복권 등 세원 이외의 자금이 공원 및 녹지 공간에 투입되고 있으나 주민들이 직접 이를 이용하도록 되어 있지는 않다. 즉, 커뮤니티의 참여와 관련되어 쓰이고 있지는 않다. 세 번째는, 커뮤니티와 공원과의 관계로 공원 설계와 관리에 있어서 영국에서는 커뮤니티가 직접 고객(client)으로서 역할을 하고 있었다. 한국에서도 계획 및 설계 과정에 주민을 참여시키는 경우가 있으나 의견청취 정도에 머물고 있고, 몇몇 시민단체를 중심으로 시민들이 직접 공원 관리에 참여하는 경우도 있으나 운동(movement)차원에 머물고 있을 뿐 이를 위한 제도적, 법적 토대가 구축되어 있지는 않다.