• 한국강구조학회 논문집
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• 제14권6호
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• pp.711-720
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• 2002

본 연구에서는 곡선교에서 주행차량에 의한 동적 응답을 보다 정밀하게 구현할 수 있는 3차원 해석 모형을 개발하였다. 원심력에 의한 차량의 롤링운동에 따른 차량의 쏠림현상을 구현하여 곡선교의 대표적인 응답특성인 편경사와 곡률반경에 따른 동적응답과 받침의 변화에 따른 동적 응답 특성을 규명하였으며, 2가지 지점조건에 대하여 주행차량에 의한 곡선교의 동적 특성을 비교 분석하였다. 또한 이와 함께 곡선교에서 어떤 파라미터가 하중 분배에 가장 효율적인가를 비교 분석하였다. 동적해석결과 받침이 외측에 배치된 경우가 중앙에 배치된 경우보다 더 유리하게 분석되었으며, 여러 가지 조건에 따라 하중분배 특성이 다르게 나타남을 알 수 있었다.

• 한국도로학회논문집
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• 제7권4호
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• pp.185-202
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• 2005

본 연구에서는 현장 실험 조성의 제약을 극복하기 위해 3차원 가상현실(virtual reality)로 설계중인 도로를 모델링한 후, 피실험자가 Eye camera가 장착된 차량 시뮬레이터 (driving simulator)에 탑승하고 주행하면서 운전자가 행하는 선형변화에 대한 동적 반응 및 운전자의 시각행태에 대한 데이터를 획득하였다 본 실험에 적용된 차량시뮬레이터의 그래픽 모듈은 동역학 해석 모듈에 의해 얻어진 데이터를 기초로 하여 운동재현기와 가상환경의 일치감들 최대로 함으로써 피실험자로 하여금 차량시뮬레이터의 비현실성 및 부작용을 최소화하도록 하였다. 또한, Eye camera는 기존의 여타 장비와는 달리 운전자가 헬멧이나 렌즈 등 어떠한 부착장치도 착용하지 않고 실험할 수 있는 FaceLAB을 사용함으로써 운전자의 자연스러운 시각행태를 아무런 데이터 손실없이 획득하였다. 본 연구에서는 조사된 데이터를 바탕으로 도로 안전성을 평가하기 위해 차량 시뮬레이터, Eye camera방법을 통해 설계시 도로 기하구조 변화에 따라 운전자가 느끼는 안전성의 변화를 파악함으로써 도로 기하구조 조건과 안전성의 상관성을 명확하게 규명하고 이를 통해 운전자가 도로 주행시 편안하고 쾌적한 주행을 보장받을 수 있는 도로를 설계 단계에서부터 평가할 수 있는 방법을 제시하려고 한다.

• Radiation Oncology Journal
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• 제35권1호
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• pp.65-70
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• 2017

Purpose: To evaluate the utility of implanted surgical clips for detecting interfractional errors in the treatment of hepatobiliary and pancreatic cancer with postoperative radiotherapy (PORT). Methods and Materials: Twenty patients had been treated with PORT for locally advanced hepatobiliary or pancreatic cancer, from November 2014 to April 2016. Patients underwent computed tomography simulation and were treated in expiratory breathing phase. During treatment, orthogonal kilovoltage (kV) imaging was taken twice a week, and isocenter shifts were made to match bony anatomy. The difference in position of clips between kV images and digitally reconstructed radiographs was determined. Clips were consist of 3 proximal clips (clip_p, ${\leq}2cm$) and 3 distal clips (clip_d, >2 cm), which were classified according to distance from treatment center. The interfractional displacements of clips were measured in the superior-inferior (SI), anterior-posterior (AP), and right-left (RL) directions. Results: The translocation of clip was well correlated with diaphragm movement in 90.4% (190/210) of all images. The clip position errors greater than 5 mm were observed in 26.0% in SI, 1.8% in AP, and 5.4% in RL directions, respectively. Moreover, the clip position errors greater than 10 mm were observed in 1.9% in SI, 0.2% in AP, and 0.2% in RL directions, despite respiratory control. Conclusion: Quantitative analysis of surgical clip displacement reflect respiratory motion, setup errors and postoperative change of intraabdominal organ position. Furthermore, position of clips is distinguished easily in verification images. The identification of the surgical clip position may lead to a significant improvement in the accuracy of upper abdominal radiation therapy.

• 한국운동역학회지
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• 제16권2호
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• pp.25-35
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• 2006

The purpose of this study was to investigate the shock attenuation mechanisms while varying the loads in a backpack during drop landing. Ten subjects (age: $22.8{\pm}3.6$, height: $173.5{\pm}4.3$, weight: $70.4{\pm}5.2$) performed drop landing under five varying loads (0, 5kg. 10kg. 20kg. 30kg). By employing two cameras (Sony VX2100) the following kinematic variables (phase time, joint rotational angle and velocity of ankle, knee and hip) were calculated by applying 2D motion analysis. Additional data, i.e. max vertical ground force (VGRF) and acceleration, was acquired by using two AMTI Force plates and a Noraxon Inline Accelerometer Sensor. Through analysing the power spectrum density (PSD), drop landing patterns were classified into four groups and each group was discovered to have a different shock attenuation mechanism. The first pattern that appeared at landing was that the right leg absorbed most of the shock attenuation. The second pattern to appear was that subject quickly transferred the load from the right leg to the left leg as quickly as possible. Thus, this illustrated that two shock attenuation mechanisms occurred during drop landing under varying load conditions.

• 한국전문물리치료학회지
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• 제14권3호
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• pp.23-31
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• 2007

The purpose of this study was to determine the influence of high-heeled shoes on walking of obese women as it was already proven an extrinsic factor of knee osteoarthritis in women with normal weight. In this study the aimed therefore in particular was to utilize high-heeled shoes in proving it's causal influence on knee osteoarthritis by measuring the angle and torque of the knee joint. Fifteen obese women (BMI>25 $kg/m^2$) were measured in their twenties. Each angle and torque of their knee joints during walking on 6.5 cm high-heeled shoes and with a bare feet, were compared with each other and analyzed with a 3D motion analysis system. There was no significant difference in walking speed, cadence and stride length between the two conditions. However, there was a significant increase in a double limb support time and the stance phase when walking on high-heeled shoes as when walking with bare feet. The peak knee flexion angle and peak knee varus torque was higher when walking on high-heeled shoes than with bare feet. On the contrary, the peak knee flexion angle in the swing phase was not statistically different. The prolongation of peak knee varus torque was also proven. There was a significant increase in peak knee varus torque in the initial and last stance phases during walking on high-heeled shoes as compared to walking on bare feet. Through the above results, it was proven that when obese women walked on high-heeled shoes, rather than with bare feet, peak knee flexor and varus torque increased along with the changes of the in knee joint angle. Therefore, the influence of high-heeled shoes might be a significant intrinsic factor in knee osteoarthritis of obese women.

• Smart Structures and Systems
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• 제12권3_4호
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• pp.363-379
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• 2013

Dynamic displacement of structures is an important index for in-service structural condition and behavior assessment, but accurate measurement of structural displacement for large-scale civil structures such as long-span bridges still remains as a challenging task. In this paper, a vision-based dynamic displacement measurement system with the use of digital image processing technology is developed, which is featured by its distinctive characteristics in non-contact, long-distance, and high-precision structural displacement measurement. The hardware of this system is mainly composed of a high-resolution industrial CCD (charge-coupled-device) digital camera and an extended-range zoom lens. Through continuously tracing and identifying a target on the structure, the structural displacement is derived through cross-correlation analysis between the predefined pattern and the captured digital images with the aid of a pattern matching algorithm. To validate the developed system, MTS tests of sinusoidal motions under different vibration frequencies and amplitudes and shaking table tests with different excitations (the El-Centro earthquake wave and a sinusoidal motion) are carried out. Additionally, in-situ verification experiments are performed to measure the mid-span vertical displacement of the suspension Tsing Ma Bridge in the operational condition and the cable-stayed Stonecutters Bridge during loading tests. The obtained results show that the developed system exhibits an excellent capability in real-time measurement of structural displacement and can serve as a good complement to the traditional sensors.

• 천문학회보
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• 제44권1호
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• pp.65-65
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• 2019

Near-Earth objects consist of a mixture of bodies originated from outer solar system and main asteroidal belt, which are recognized as comets and near-Earth asteroids. In principal, they have orbits distinguishable by their orbital elements. It is, however, that some comets are recognized as asteroids because they could have lost the most of volatile materials in their subsurface layers. Due to their asteroidal appearances, it has been challenging to discriminate such dormant comets from a list of known asteroids. Here we propose to utilize polarimetric technique for finding such dormant comets. We thus conducted a polarimetric observations of three candidates of dormant comet nuclei, (331471) 1984 QY1, (3552) Don Quixote and (944) Hidalgo, by using the 1.6-m Pirka Telescope at the Nayoro observatory (operated by Hokkaido University, Japan). We selected these asteroids in comet-like orbits (ACOs) based on the orbital elements (i.e., the Tisserand parameter with respect to Jupiter TJ < 3). We found that 1984 QY1 has a polarimetric albedo (geometric albedo determined via polarimetry) pV = 0.16 +/- 0.06 while both Don Quixote and Hidalgo have Rc-band polarimetric albedos pR < 0.05. In accordance with the polarimetric result together with a dynamical analysis, we surmised that 1984 QY1 could be an S-type asteroid evolved into the current orbit via 3:1 mean motion resonance with Jupiter. On the contrary, the previous spectroscopic studies indicated that Don Quixote and Hidalgo are classified into D-type taxonomic group, which are typical of comet nuclei. In this presentation, we will introduce our polarimetric observations of ACOs and emphasize that polarimetry is powerful for discriminating the asteroidal and cometary origins.

• 한국해양공학회지
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• 제35권3호
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• pp.173-182
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• 2021

The maneuvering performance of a ship on the actual sea is very different from that in calm water due to wave-induced motion. Enhancement of a ship's maneuverability in waves at the design stage is an important way to ensure that the ship navigates safely. This paper focuses on the maneuvering prediction of a Russian trawler in wind and irregular waves. First, a unified seakeeping and maneuvering analysis of a Russian trawler is proposed. The hydrodynamic forces acting on the hull in calm water were estimated using empirical formulas based on a database containing information on several fishing vessels. A simulation of the standard maneuvering of the Russian trawler was conducted in calm water, which was checked using the International Maritime Organization (IMO) standards for ship maneuvering. Second, a unified model of seakeeping and maneuvering that considers the effect of wind and waves is proposed. The wave forces were estimated by a three-dimensional (3D) panel program (ANSYS-AQWA) and used as a database when simulating the ship maneuvering in wind and irregular waves. The wind forces and moments acting on the Russian trawler are estimated using empirical formulas based on a database of wind-tunnel test results. Third, standard maneuvering of a Russian trawler was conducted in various directions under wind and irregular wave conditions. Finally, the influence of wind and wave directions on the drifting distance and drifting angle of the ship as it turns in a circle was found. North wind has a dominant influence on the turning trajectory of the trawler.

• 한국운동역학회지
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• 제32권2호
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• pp.49-55
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• 2022

Objective: This study aims to verify the front squat motions using by two different surfaces, thereby elucidating the grounds for effective training environment that can minimize the risk of injury. Method: Total of 10 healthy male crossfit athletes were recruited for this study (age: 32.30 ± 3.05 yrs., height: 173.70 ± 5.12 cm, body mass: 82.40 ± 6.31 kg, 1RM: 160 ± 13.80 kg). All participants are those who know how to do front squats well with more than five years of crossfit athlete experience. All participants have sufficient experience in front squats on two types of surface which are soft surface (SS) and hard surface (HS). In each surface, participant perform 10reps of the front squat with 80% of the pre-measured 1RM. A 3-dimensional motion analysis with 8 infrared cameras and 2 channels of EMG was performed in this study. Paired sample t-test was used for statistical verification between two surfaces. The significant level was set at α=.05. Results: The significantly decreased rectus femoris muscle activation was found in SS compared with that of HS on phase 1 (p<.05). Also, ROM of ankle joint was significantly increased in the SS compare with that of HS on phase 1 (p<.05). The muscle activity ratio of gluteus maximus/rectus femoris showed a significant difference only in SS compared with that of HS on phase 1 (p<.05). Conclusion: In conclusion, Korean crossfit boxes should consider the use of hard surface, which has a relatively less risk of injury than soft surface, in selecting flooring materials. For the Crossfit athletes, they are also considered appropriate to train on a relatively hard surface.

• 한국운동역학회지
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• 제18권2호
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• pp.85-94
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• 2008

본 연구의 목적은 3명의 우수 골프선수를 대상으로 아이언 클럽(3, 6, 9번)의 스윙 동작을 3차원적으로 비교 분석하고, 이의 분석에 따른 요인들을 정량적으로 제시하여 선수 및 일반 골퍼들이 바람직한 아이언 스윙 동작을 배우는데 기초자료를 제공하는데 있다. 3차원 영상분석을 실시하여 다음과 같은 결론을 도출하였다. 1. 각 클럽별로 전체 스윙 시간에는 큰 차이를 보이지 않았으며, 각 국면별 시간도 거의 유사하게 나타났다. 2. 각 클럽별로 어드레스와 임팩트시 머리위치 변화는 차이가 없었다. 3. 클럽의 길이에 따른 차이를 제외하면 각 클럽별로 오른 무릎관절 각도변화는 유사하게 나타났다. 4. 각 클럽별로 고관절의 회전각도 변화는 약간의 차이가 나타났다. 5. 각 클럽별로 어드레스와 임팩트 동작시 어깨관절의 회전각도와 동일하게 만들어 주어 스윙의 정확도를 높이고, 탑스윙시 어깨회전 각도를 $90^{\circ}$이상 유지하여 스윙의 회전력을 높이는 것으로 나타났다. 6. 클럽이 짧을수록 상체전경 각도가 약간의 차이로 커지는 것으로 나타났으며 어드레스와 탑스윙, 임팩트 동작시상체전경 각도가 $30-36^{\circ}$의 형태를 유지하면서 스윙을 하였다.