• 한국지진공학회논문집
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• 제13권3호
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• pp.29-38
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• 2009

지진 발생시 교량 상판 연결부의 상대변위로 레일에 발생하는 부가응력으로 인한 레일의 좌굴과 파손은 열차의 탈선을 유발할 수 있다. 교량의 지진응답 증가에 영향을 미치는 지반의 탈선취약요소와 교량의 구조적인 요소를 고려하여 고속철도교량 장대레일의 지진응답을 평가하였다. 연약층이 있는 지반, 상하역전형 지반과 같은 지반 탈선취약요소를 고려하기 위해서 지반을 평행층상지반으로 모델링하여 부지효과가 고려된 자유장운동을 구하고 이를 입력지진으로 사용하였다. 교각 높이나 적용 도상을 변화시키면서 구조적 특성이 레일의 지진응답에 미치는 영향을 분석하였다.

• 대한조선학회지
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• 제12권1호
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• pp.47-58
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• 1975

The effect of the bow shape on the ship motion response among longitudinal regular waves, is investigated employing the strip theory. The two dimensional hydrodynamic forces such as added mass and damping are calculated by the integral equation method for arbitrary sections. Nine ship models are selected for investigation. They are U, UV and V bow ship forms of different block coefficient of 0.6, 0.7 and 0.8 with constant after body. The heave amplitude of the V bow ship is smaller than that of the U bow ship in the whole range of wave length except extremely short wave as were stated by the earlier investigators. This results holds also in the case of bow vertical motions such as vertical relative displacement, velocity and acceralation. As to the pitch amplitudes, the V bow ship gives smaller value in long waves but larger value in short waves. However, heave and pitch phase angles are practically not influenced by the form of the fore body sections. In the bow motions, a little difference in phase angle is appeared in the vicinity of the wave which has same ship length. With respect to the wave exiting force and moment unfovourable effects could be expected in V bow ships. And these tendency hold also in the wave bending moment.

• 대한조선학회논문집
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• 제35권1호
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• pp.32-39
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• 1998

잠수된 원형실린더의 대진폭운동에 대한 수치해석이 제시된다. 방법은 포텐셜이론에 근간을 두고 정현파중에서 2차원 운동은 초기치 문제로 귀결된다. 완전한 비선형자유표면 조건은 수치 계산영역에서 적용되고, 비선형 수치해는 수치계산의 임의의 가정된 경계를 따라 외부영역에서의 선형해로서 부과된다. 잠수된 원형실린더의 대진폭운동의 계산은 직접적으로 시간영역에서 시뮬레이션된다. 계산결과로 부터 물체와 유체입자의 상호 운동은 부양운동과 표류운동에 중요한 효과를 준다.

• 대한방사선기술학회지:방사선기술과학
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• 제20권2호
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• pp.56-62
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• 1997

To evaluated the image quality and the patient exposure for the chest radiography, its fundamental imaging properties were investigated. The basic imaging properties were evaluated by measuring characteristic curves, relative speeds, average gradient, and patient exposure dose. The image qualities were evaluated by using a rotating meter. It was found that the film gradient of SRO750/SRH system was 3.13 and that of SRO750/HR-C30 was 1.77. The ratio of SRO1000/TMH to FS/RP-1 was 1 to 18.2. It was possible to visualize the static image when the exposure time was less than 2.5 msec in patient that had respiratory excessive motion, heart beat and natural physical motion, and less than 8.5 msec in normal. The ratio of medical exposure dose compared with our method was 1 to 25 in the routine chest radiography and maximum was 1 to 70. In estimation of the image quality in same cases, we found that the image of SRO1000/SRH and TMH of super sensitive systems was the same results. We found that these super sensitive screen-film systems were available for the chest radiography considering the relationship between the image quality and patient exposure.

• 대한조선학회논문집
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• 제59권6호
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• pp.338-344
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• 2022

Roll moment usually is ignored when analyzing the maneuverability of surface ships. However, it is well known that the influence of roll moment on maneuverability is significant for ships with small metacentric height such as container ships, passenger ships, etc. In this study, a pure roll test is performed to determine the hydrodynamic derivatives with respect to roll motion as added mass and damping. The target ship is an autonomous surface ship designed to carry containers with a small drift and large freeboard. The commercial code of STAR CCM+ software is applied as a specialized tool in naval hydrodynamic based on RANS equation for simulating the pure roll of the ship. The numerical uncertainty analysis is conducted to verify the numerical accuracy. By distinguishing the in-phase and out-of-phase from hydrodynamic forces and moments due to roll motion, added mass derivatives and damping derivatives relative to roll angular velocity are obtained.

• 로봇학회논문지
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• 제17권3호
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• pp.288-295
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• 2022

This study shows a system identification method of a balancing loading device for a stair climbing delivery robot. The balancing loading device is designed as a 2-axes gimbal structure and is interpreted as two independent pendulum structures for simplifying. The loading device's properties such as mass, moment of inertia, and position of the center of gravity are changeable for luggage. The system identification process of the loading device is required, and the controller should be optimized for the system in real-time. In this study, the system identification method is based on least squares method to estimate the unknown parameters of the loading device's dynamic equation. It estimates the unknown parameters by calculating them that minimize the error function between the real system's motion and the estimated system's motion. This study improves the accuracy of parameter estimation using a null space solution. The null space solution can produce the correct parameters by adjusting the parameter's relative sizes. The proposed system identification method is verified by the simulation to determine how close the estimated unknown parameters are to the real parameters.

• 로봇학회논문지
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• 제18권3호
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• pp.285-292
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• 2023

Small-scale ground mobile robots can access confined spaces where people or larger robots are unable. As the scale of the robot decreases, the relative size of the environment increases; therefore, maintaining the mobility of the small-scale robot is required. However, small-scale robots have limitations in using a large number of high-performance actuators, powerful computational devices, and a power source. Insects can effectively navigate various terrains in nature with their legged motion. Discrete contact with the ground and the foot enables creatures to traverse irregular surfaces. Inspired by the leg motion of the insect, researchers have developed small-scale robots and they implemented swing and lifting motions of the leg by designing leg linkages that can be adapted to small-scale robots. In this paper, we propose a leg linkage design for insect-inspired small-scale ground mobile robots. To use minimal actuation and reduce the control complexity, we designed a 1-DOF 3-dimensional leg linkage that can generate a proper leg trajectory using one continuous rotational input. We analyzed the kinematics of the proposed leg linkage to investigate the effect of link parameters on the foot trajectory.

• Physical Therapy Rehabilitation Science
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• 제12권2호
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• pp.149-154
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• 2023

Objective: This study is designed to investigate the effect of ankle joint position on hip extensor muscle activity when bridging exercise in sagittal plane. Design: Cross-sectional study Methods: The subjects were recruited from 20 healthy adult men. The subjects performed three types of bridging exercises (normal bridging, ankle dorsiflexion bridging, ankle plantar flexion bridging) three times for five seconds with a rest of 15 seconds between measurements and two minutes of rest between each motion. The target muscles were the gluteus maximus, biceps femoris, soleus, and tibialis anterior. A surface electromyography was used to measure the muscle activity of these muscles. Results: The results show there was no statistically significant difference between the three types of exercise in the gluteus maximus muscle activity. However, the biceps femoris showed a significant difference between the three types of exercises (p<0.05). Conclusions: In conclusion, when the three different bridging exercises were performed by adding ankle motion to normal bridging exercise, there was a significant difference in the muscle activity of the gluteus maximus relative to the biceps femoris muscle activity in the order of the ankle dorsiflexion bridging, normal bridging, and ankle plantar flexion bridging exercise. Therefore, this could be an effective option for a bridging exercise if applied to patients with a weak gluteal muscle and shortening of the hamstring muscle in further studies.

• 한국음향학회지
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• 제28권4호
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• pp.336-342
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• 2009

일정한 주파수의 음향신호를 발생시키는 표적이 기동할 때 한 개의 고정된 센서에서 관측된 신호의 주파수는 시간에 따라 도플러 변이가 발생한다. 이러한 도플러 변이 현상을 이용한 기존의 CPA (Closest Point of Approach) 분석으로 센서 수신기에 표적이 최단거리로 근접했을 때의 시간, 거리, 속력 그리고 실제 신호의 중심주파수를 추정할 수 있다. 본 논문에서는 고정된 단일 센서 대신에 일정한 속도로 기동하는 배열센서 수신기에서 주파수뿐만 아니라 표적의 방위각을 관측하여 이로부터 표적의 실제 기동속도를 추정하는 기법을 제안한다. 그리고 제안한 기법의 성능검증을 위해 오차 분석 및 모의 실험을 수행하였다.

• 감성과학
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• 제23권3호
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• pp.63-78
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• 2020

사회적 상호작용에서 적절한 행동을 위해서는 사회인지적 정보 뿐 아니라 다양한 정서 정보의 처리 역시 중요하다. 정서의 처리과정은 자극의 속성 뿐 아니라 다양한 맥락과 외부 요인의 영향을 받는다. 본 연구는 정서처리에 영향을 미치는 요인들과 그 효과의 양상을 파악하기 위하여 생물형운동자극을 사용한 정서변별과제를 시행하였다. 첫 번째 과제에서는 분노, 행복, 또는 중립 정서를 지닌 단서자극과 함께 제시된 빨강, 초록, 흰색, 또는 노란색 중 하나의 색과 분노 또는 행복 정서를 지닌 표적자극을 비교하여, 단서자극에 비해 표적자극이 나타내는 정서를 판단하도록 하였다. 두 번째 과제에서는 정서 중립 자극만을 사용하여 색의 효과를 조사하였다. 실험 결과, 표적자극의 특정 색과 정서 간 연합이 관찰되었다. 즉, 빨간색은 분노정서, 초록색은 행복정서 처리를 촉진하는 것으로 보였다. 또한, 단서자극과 표적자극의 정서가 일치할 때 표적자극 정서의 변별 정확도가 높았으나, 빨간색과 분노정서가 조합된 조건에서는 단서자극 정서의 영향을 받지 않았다. 두 번째 과제에서는 표적자극의 색에 의해 착각적인 정서반응이 나타남을 관찰하였다. 본 연구를 통해 기존에 주로 사용된 얼굴자극이 아닌 생물형운동자극을 이용해 자극의 정서처리 과정에 영향을 미치는 맥락 및 색 요인의 효과를 구체적으로 확인하였으며, 가능한 후속연구 및 임상적 연구에 대해 논의하였다.