• 한국운동역학회지
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• 제13권3호
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• pp.1-14
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• 2003

This study was conducted to investigate the principles and motions for increasing the jumping height of Fosbury Flop. The subjects were three male jumpers who were former Korean national team players. Their jumping motions were analyzed using the DLT method of three-dimensional cinematography. The conclusions were as follows. 1. The horizontal velocity of approach run and decreasing of this velocity during the take off phase were increased as the jumping height was increased. Therefore, in order to increase the jumping height, the horizontal velocity of approachrun should be increased and decreased properly during the take-off phase. The average height of the analyzed Dials was 2.15m. The average horizontal velocity of approachrun was 7.49m/s and decreased to 4.16m/s at the instance of take-off. 2. The vertical velocity of the center of gravity was increased as the ascending height of the center of gravity during the take-off phase was increased. Therefore, the center of gravity at the instant of touch down should be lowered. This could be possible by increasing the length of the last stride and the backward lean angle of the body. The average length of the last stride was 111.1% of the standing height, the average height of the center of gravity was 46.6% of the standing height and the average backward lean angle of the body was 40.3 degrees.

• 대한토목학회논문집
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• 제34권3호
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• pp.723-728
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• 2014

세굴방지를 위하여 설치하는 해안구조물의 쇄파효과를 검증하기 위하여 수리조파실험이 실시된다. 하지만 수리조파실험을 실시하기 위해서 사용되는 실험 장치와 해안구조물의 제작에 많은 비용과 시간이 소요된다. 수치해석모델과 수리조파실험의 해석결과를 비교하여 검증하면, 수치모델을 활용하여 쇄파효과를 예측할 수 있고 실험 장치와 해안구조물 제작에 소요되는 비용과 시간을 절약할 수 있다. 본 연구에서는 다면체 사석 구조물을 대상으로 수치해석결과와 수리조파실험 결과의 처오름 및 처내림 높이 비교분석을 수행하였고 해석적 모의 조파실험 모델링 기법을 검증하였다. 또한, 사용한 수치해석 접근 방법을 활용하여 사석의 부피비와 마찰면적을 변화시켜 쇄파효과를 예측하였다.

• Advances in pediatric surgery
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• 제14권1호
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• pp.67-74
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• 2008

The usefulness of totally implantable central venous port for long-term intravenous infusion is widely accepted in children. Usually the catheters are placed through the internal or external jugular vein. In case of jugular vein cut-down, two separate incisions are needed for catheter and port respectively. Patients also feel uncomfortable as the catheter run through the neck. However these disadvantages can be overcome by using the cephalic vein (CV). We reviewed our experiences on CV cut-down for totally implantable central venous port in children. From January 2002 to December 2006, 201 patients (M:F=127:74) underwent 218 central venous port insertions. Mean age at operation was 5.9 years (2 months - 19 years). Indications included chemotherapy (N=167), long-term intravenous antibiotics infusion (N=36), and total parenteral nutrition (N=15). CV was selected preferentially. The incision includes the deltopectoral triangle laterally, and both the CV cut-down and port insertion were achieved with a single incision. The number of insertion through external, internal jugular vein, and CV was 77, 66 and 75, respectively. The median age, height and body weight were higher in CV cut-down group. The youngest age for CV cut-down was 8 months, the shortest height was 69 cm and the smallest body weight was 5.9 kg. Of 118 trials of CV cut-down, cut-down was successful in 75 cases (63.6 %). CV was absent in 10 cases(8.4 %) and CV was sacrificed after catheter tip malposition in 10 cases (8.4 %). There was only one complication, in which the catheter was inserted into the minute branch of subclavian artery. The CV cut-down method for totally implantable central venous port was safe and feasible in selected groups of patients in children. In addition, preservation of jugular vein and a more favorable cosmetic effect are other benefits of CV cut-down.

• 한국방재학회 논문집
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• 제8권4호
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• pp.135-143
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• 2008

지난 수십년간 전 세계적으로 지진해일로 인해 수많은 피해가 발생하였으며 특히, 2004년 발생한 수마트라 지진해일로 인해 우리나라에서도 지진해일에 대한 관심이 높아지고 있다. 우리나라는 과거 1983년 동해 중부 지진해일과 1993년 북해도 남서외해 지진해일로 인해 동해안에 비교적 큰 피해를 입었으며, 앞으로도 동해안에는 지진해일에 의한 피해가 발생할 가능성이 높다. 따라서 동해안에 위치해 있는 주요항에 대한 지진해일 피해 예측이 반드시 필요한 실정이다. 본 연구에서는 동해안의 주요항 중 하나인 포항신항에 대해서 지진해일 최대 처오름높이 및 최저 처내림높이를 계산하였으며, 모두 세 가지 지진해일에 대해 수치모의를 하였다. 포항신항에는 배후 공업단지가 발달해 있어 지진해일에 의한 범람이 발생하면 큰 피해가 발생할 수 있으며, 배후 공업단지에 필요한 냉각수를 취수하는 취수구에서 지진해일에 의한 처내림현상으로 인해 취수가 중단되면 공장 가동이 중단되는 피해가 발생할 수 있다. 따라서 수치모의는 처오름높이에 의한 범람여부 및 처내림높이에 의한 취수구에서의 취수 가능여부에 초점을 맞추어 수행하였다. 검토 결과 포항신항은 전반적으로 지진해일에 안전한 것으로 나타났으나 가장 큰 규모의 지진해일에 대해서는 피해를 입는 것으로 나타났다. 그러므로 이에 대한 적절한 방재대책을 마련할 필요가 있다.

• 해양환경안전학회지
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• 제21권5호
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• pp.591-598
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• 2015

본 연구에서는 태풍 나크리에 의한 해운대 해수욕장의 쇄파대 수리특성을 SWASH 모형을 이용하여 분석하였다. 국립해양조사원에서 제공하는 파랑관측자료를 바탕으로 태풍 나크리 내습 시의 대표파를 선정하였다. 수치모형에서 입사파는 JONSWAP Spectrum에 의한 불규칙파로 선정하였다. SWASH 모형에 의해 산정된 해빈류 패턴은 현지관측자료와 비교하였으며 수치모형에서 산정된 최대소상고는 비디오 모니터링 자료 및 경험식과 비교하였다. 최대소상고의 위치는 비디오 모니터링 자료에 나타난 파흔을 이용하여 유추하였으며 태풍 NAKRI(1412) 내습 시 S 계열의 파랑이 지배적으로 작용하였으며 동백섬측에서 미포측으로 연안류가, 해운대 해수욕장 중앙부근에서 이안류가 발생하였다. SWASH 모형을 이용하여 산정한 최대소상고(1.15 m)는 비디오 모니터링 자료(1.26 m)와 유사한 경향성을 나타냈으며 Stockdon et al.에 의해 제시된 경험식(1.33m)과 비교적 유사하게 나타났다.

• Geomechanics and Engineering
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• 제30권6호
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• pp.539-549
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• 2022

Accidental anchor drop can cause disturbances to seabed materials and pose significant threats to the safety and serviceability of submarine structures such as pipelines. In this study, a series of anchor drop tests was carried out to investigate the penetration mechanism of a Hall anchor in sand and clay. A special anchor drop apparatus was designed to model the inflight drop of a Hall anchor. Results indicate that Coriolis acceleration was the primary cause of large horizontal offsets in sand, and earth gravity had negligible impact on the lateral movement of dropped anchors. The indued final horizontal offset was shown to increase with the elevated drop height of an anchor, and the existence of water can slow down the landing velocity of an anchor. It is also observed that water conditions had a significant effect on the influence zone caused by anchors. The vertical influence depth was over 5 m, and the influence radius was more than 3 m if the anchor had a drop height of 25 m in dry sand. In comparison, the vertical influence depth and radius reduced to less than 3 m and 2 m, respectively, when the anchor was released from 10 m height and fell into the seabed with a water depth of 15 m. It is also found that the dynamically penetrating anchors could significantly influence the earth pressure in clay. There is a non-linear increase in the measured penetration depth with kinematic energy, and the resulted maximum earth pressure increased dramatically with an increase in kinematic energy. Results from centrifuge model tests in this study provide useful insights into the penetration mechanism of a dropped anchor, which provides valuable data for design and planning of future submarine structures.

• 한국운동역학회지
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• 제15권3호
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• pp.133-142
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• 2005

The purpose of this study was to compare of the kinematic variables from takeoff preparation to takeoff used by long jumpers who recorded over 8meters in 2002 Busan Asian Game and 2003 Daegu Universiade and 2001 national championship. The kinematic characteristics from the last three stride to takeoff at the takeoff board were analyzed such as velocities, heights and angles. The conclusion were as follows; In order to record over 8meters the national long jumpers should have under 5cm height variation at the penultimate stride of the run-up. In the approach phase the horizontal velocity of the jumpers should reach to 10m/s in touchdown at takeoff board The vertical velocity must have 3.75m/s simultaneously in order to record 8meters. The jumpers need to continue talent of the horizontal velocity in touchdown at takeoff board and require jumping power of the takeoff leg at takeoff board The appropriate body variation range ratio between takeoff and touchdown should be 1.2 vs 1 and the trunk angle at touch down on the board should be close to the erect posture for higher body flight.

• 한국운동역학회지
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• 제15권4호
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• pp.143-151
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• 2005

This study was conducted to investigate the technical factors of Cuervo forward straight vaults with single twist, single and half twists, and double twists actually performed by three execellent male gymnasts participated in artistic gymnastics competition of 2003 summer Universiade in Daegu and the 85th National Sports Festival in Cheongju. To accomplish the research goals the Cuervo vaults of three gymnasts were filmed by using three digital camcorders set by 60 Hz, and data were collected through the DLT method of three dimensional cinematography. The kinematic and kinetic variables as each phasic time, CM displacement velocity, release angle inclination angle hip joint angle landing angle, average horse reaction force average moment arm average torque, whoe body's total remote local angular momentum were analyzed, so the following conclusions were reached. Generally to perform the better Cuervo vault, a gymnast should touch down on the board with the great horizontal velocity of the whole body through the fast run-up, and touch down on the horse by decreasing the horizontal displacement of the whole body during the preflight, so raise CM height gradually within a short horse contact time. He should increase the horse reaction force through checking the horizontal velocity of the whole body effectively and the inclination angular displacement of the handstand, if so he can have the large vertical velocity of the whole body. By using the acquired the velocity and the angular momentum of the whole body, he can vault himself higher and twist sufficiently, then he can get better if the body could be tilted by swinging both arms and perform the cat twist with a little flexions at hip joints. According to the above outcomes we can judge that the best athletes is LuBin, the better is YTY, and the next is JSM.

• Wind and Structures
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• 제35권5호
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• pp.309-322
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• 2022

Due to the complex terrain around high-speed railways, the windbreaks were established along different landforms, resulting in irregular windbreak transition regions between different subgrade infrastructures (flat ground, cutting, embankment, etc). In this paper, the effect of a windbreak transition on the wind flow around railways subjected to crosswinds was studied. Wind tunnel testing was conducted to study the wind speed change around a windbreak transition on flat ground with a uniform wind speed inflow, and the collected data were used to validate a numerical simulation based on a detached eddy simulation method. The validated numerical method was then used to investigate the effect of the windbreak transition from the flat ground to cutting (the "cutting" is a railway subgrade type formed by digging down from the original ground) for three different wind incidence angles of 90°, 75°, and 105°. The deterioration mechanism of the flow fields and the reasons behind the occurrence of the peak wind velocities were explained in detail. The results showed that for the windbreak transition on flat ground, the impact was small. For the transition from the flat ground to the cutting, the influence was relatively large. The significant increase in the wind speeds was due to the right-angle structure of the windbreak transition, which resulted in sudden changes of the wind velocity as well as the direction. In addition, the height mismatch in the transition region worsened the protective effect of a typical windbreak.

• 한국화재소방학회논문지
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• 제24권5호
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• pp.50-59
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• 2010

본 연구에서는 대구 D대학 기숙사 건물에 대해 2MW, 5MW 화재크기와 아트리움 방화셔터의 미설치 및 작동 경우의 4가지 화재시나리오를 구성하고, FDS(ver. 5.5.0)와 Pathfinder 2009 프로그램을 사용하여 화재 및 피난시뮬레이션을 수행하였다. 화재피난영향평가를 통하여 방화셔터와 배연구의 아트리움 제연 효과에 대한 성능을 확인하였고, 화재위험 및 피난안전을 분석하였다. 방화셔터의 작동은 연기 전파 방지에 큰 효과가 있지만, 상부 배연구를 통한 배연량이 불충분하여 방화셔터의 유무에 관계없이 연기층은 바닥으로부터 약 2m 지점까지 하강하고, 본 연구에서 설정한 연기층 한계 높이 이하가 되었다. 또 방화셔터 미설치, 5MW 화재크기의 경우, 온도보다 가시거리에 의한 화재위험 가능성이 더 크게 나타났고, 기숙사 중.상부 층의 계단실 피난여유시간은 약 5초 이내로 매우 작았다. 지상 1층 주출입구까지 전체 피난자의 순수 피난이동시간은 136초이다. 피난자의 더 안전한 피난을 위해 추가적인 보완조치가 필요하다고 사료된다.