• 한국과학교육학회지
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• 제25권5호
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• pp.583-594
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• 2005

이 연구에서는 진자에 대한 중학생들의 개념을 조사하고 그네를 타는 근운동 체험으로 불일치 자료를 제시하고 인지갈등 정도 및 개념변화를 살펴보았다. 다수의 학생들은 단진자에 작용하는 합력에 대해 진자 운동의 양 끝 주변에서는 운동궤도를 따라 표현하며 중심 부근에서는 힘이 없다고 하였다. 그 이유를 설명할 때 많이 고려하는 힘의 종류는 중력,운동방향으로의 힘, 그리고 장력이었다. 모든 학생들이 관찰 결과가 자신들의 예상과 다르다는 것을 인정하고 활동을 매우 즐거워하였지만 인지갈등 정도는 그다지 높지 않았다. 인지갈등 요소별로 보면 '흥미'가 가장 높았으며, '불안'이 현저하게 낮았다. 직후 사후 검사와 지연 사후 검사에서 대부분의 학생들이 관찰했던 합력의 방향은 잘 기억하게 되었으나 그 이유를 잘 이해하고 옳게 진술한 학생은 소수였다.

• 제어로봇시스템학회논문지
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• 제8권5호
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• pp.363-372
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• 2002

In ship operation, the roll motions can seriously degrade the performance of mechanical and personnel effectiveness. So many studies for the roll stabilization system design have been performed and good results have been achieved. In many studies, the stabilizing fins are used. Recently rudders, which have been extensively modified, have been used exclusively to stabilize the roll. But, in the roll stabilization control system, the control performance is very sensitive to the ship speed. So, we can see that it is important to consider the ship speed in the rudder roll control system design. The gain-scheduling control technique is very useful in the control problem incorporating time varying parameters which can be measured in real time. Based on this fact, in this paper we examine the;$H_{\infty}$-Gain Scheduling control design technique. Therefore, we assume that a parameter, the ship speed which can be estimated in real time, is varying and apply the gain-scheduling control technique to design the course keeping and anti-rolling control system far a ship. In this control system, the controller dynamics is adjusted in real-time according to time-varying plant parameters. The simulation result shows that the proposed control strategy is shown to be useful for cases when the ship speed is varying and robust to disturbances like wind and wave.

• 대한기계학회논문집
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• 제14권6호
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• pp.1408-1416
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• 1990

본 연구에서는 과도 연성 열탄성문제의 해를 구할때 사용되는 직접시간적분방 법과 Laplace 변환방법은 상호 장 단점을 가지고 있다. 각 방법들의 장단점은 서로 배타적이므로 서로의 장점을 살리는 수치방법이 필요하다. 그런데, 대부분의 과도 열탄성문제는 급격한 온도변화로 인한 물체의 변형에 관심이 있기때문에 이 형태의 문 제를 효율적으로 다루는 데 주안점을 두고 본 연구를 수행하였다. 유도된 유한요소 방정식은 결국 열탄성 지배 방정식 중 열전달방정식인 에너지보존식은 Gurtin의 범함 수로부터 유도된 원래의 형태를 사용하나 수치적 안정성(numerical stability)을 보장 하기 위하여 운동방정식은 시간에 대한 2차미분 형태로 수정하였다. 에너지보존식은 시간에 대한 합성적분(convolution)형태로 표현되므로 온도의 시간미분항이 소거되므 로 경계에서의 급격한 온도변화로 인한 수치 해석적 문제점은 간단히 해결된다. 그 러므로, 제안된 수치해법은 직접시간적분방법의 일종이나 결과식인 유한요소방정식은 기존의 문헌들과 상당한 차이가 있다. 과도 연성 열탄성해석을 위한 새로운 근사수 치해법의 장점을 이론적으로 설명하기보다 수치계산면에서의 안전성, 정확성 및 효율 성이 있음을 증명하기 위하여 이미 발표된 문헌들에서 다룬 예제를 선정하여 해석결과 를 비교하였다.

• 한국소음진동공학회논문집
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• 제16권7호
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• pp.704-711
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• 2006

Vibration test on MAST(multi axial simulation table) system has several advantage over one-axial vibration test that could simulate 6-DOF, 3-axial translation and 3-axial moment, at the same time. Since field vibration motion can be fully represented with 6-DOF, multi-axial vibration test on vehicle component is widely conducted in technical leading companies to make sure its fatigue performance in vibration environment. On the way to fulfill the process, editing technique of obtained field data is key issue to success a reliable vibration testing with MAST system. Since the original signals are not only too large to fulfill it directly, but all of the measured data is not guarantee its convergency on generating its driving files, editing technique of the original signals are highly required to make some events that should meet the equal fatigue damage on the target component In this paper, key technique on editing a field data feasible for MAST system is described based on energy method in vibration fatigue. To explain its technique explicitly, author first introduced a process on field data acquisition of two vehicle component and then, representing events are produced to keep up with the editing strategy about a energy method. In the final chapter, a time information regarding a vibration test on MAST system is derived from the energy data which is critical information to perform a vibration test.

• 한국운동역학회지
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• 제20권3호
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• pp.267-275
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• 2010

The purpose of this study was to investigate the effects of balance ability improvement exercise program which applied to the elderly people for increasing balance, stability and range of motion. Ten elderly people and ten university students were recruited as the subjects. Kinematic data were collected by seven real-time infrared cameras while subjects walk stair descent as a pre-test. Korean folk dance exercise program was applied to the elderly for 12 weeks. Same experiment on stair descent walk was performed as post-test. Results indicated that CM movement and selected joint angle patterns of elderly group after treatment changed to the similar patterns of young group. However, ankle joint angle and vertical GRF of elderly group after treatment also increased compared to those of the elderly group before treatment. This might be explained by the fact that elderly used a different walking strategy which maximize support base for increasing stability. Overall, these results indicated that the exercise treatment may affect to adapt and improve the gait pattern of stair descent of elderly people.

• Smart Structures and Systems
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• 제18권5호
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• pp.955-982
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• 2016

Recent studies integrating vibration control and structural health monitoring (SHM) use control devices and control algorithms to enable system identification and damage detection. In this study real-time SHM is used to enhance structural vibration control and reduce damage. A newly proposed control algorithm, including integrated real-time SHM and semi-active control strategy, is presented to mitigate both damage and seismic response of the main structure under strong seismic ground motion. The semi-active independently variable stiffness (SAIVS) device is used as semi-active control device in this investigation. The proper stiffness of SAIVS device is obtained using a new developed semi-active control algorithm based on real-time damage tracking of structure by damage detection algorithm based on identified system Markov parameters (DDA/ISMP) method. A three bay five story steel braced frame structure, which is equipped with one SAIVS device at each story, is employed to illustrate the efficiency of the proposed algorithm. The obtained results show that the proposed control algorithm could significantly decrease damage in most parts of the structure. Also, the dynamic response of the structure is effectively reduced by using the proposed control algorithm during four strong earthquakes. In comparison to passive on and off cases, the results demonstrate that the performance of the proposed control algorithm in decreasing both damage and dynamic responses of structure is significantly enhanced than the passive cases. Furthermore, from the energy consumption point of view the maximum and the cumulative control force in the proposed control algorithm is less than the passive-on case, considerably.

• 대한기계학회논문집A
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• 제37권6호
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• pp.731-738
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• 2013

본 논문은 6 륜 독립구동/독립조향 차량의 독립 스티어-바이-와이어 장치의 고장 안전 주행 제어방법을 제시하였다. 조향부 고장 휠의 횡방향 타이어 힘이 차량 선회 운동에 저항력으로 작용할 수 있으므로, 이를 줄이기 위하여 본 고장 안전 주행 제어 알고리즘은 조향부 고장 휠에 높은 슬립률이 발생하도록 토크 입력을 가한다. 고슬립으로 인한 조향부 고장 휠의 종방향 타이어 힘 증가를 고려하기 위하여 종방향 타이어 힘을 추정하여 고장나지 않은 휠의 구동력 최적 분배에 구속 조건에 포함시킨다. 개루프 조향 및 폐루프 조향 시뮬레이션 결과 조향부 고장이 발생한 차량의 주행시 고장을 고려하지 않은 최적 구동력 분배 제어에 비하여 본 알고리즘 적용시 차량의 주행 성능이 보정됨을 확인하였다.

• Journal of Korean Neurosurgical Society
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• 제52권5호
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• pp.435-440
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• 2012

Objective : The purpose of this study is to find the optimal stiffness and volume of bone cement and their biomechanical effects on the adjacent vertebrae to determine a better strategy for conducting vertebroplasty. Methods : A three-dimensional finite-element model of a functional spinal unit was developed using computed tomography scans of a normal motion segment, comprising the T11, T12 and L1 vertebrae. Volumes of bone cement, with appropriate mechanical properties, were inserted into the trabecular core of the T12 vertebra. Parametric studies were done by varying the volume and stiffness of the bone cement. Results : When the bone cement filling volume reached 30% of the volume of a vertebral body, the level of stiffness was restored to that of normal bone, and when higher bone cement exceeded 30% of the volume, the result was stiffness in excess of that of normal bone. When the bone cement volume was varied, local stress in the bony structures (cortical shell, trabecular bone and endplate) of each vertebra monotonically increased. Low-modulus bone cement has the effect of reducing strain in the augmented body, but only in cases of relatively high volumes of bone cement (>50%). Furthermore, varying the stiffness of bone cement has a negligible effect on the stress distribution of vertebral bodies. Conclusion : The volume of cement was considered to be the most important determinant in endplate fracture. Changing the stiffness of bone cement has a negligible effect on the stress distribution of vertebral bodies.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.764-769
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• 2006

Vibration test on MAST(multi axial simulation table) system has several advantage over one-axial vibration test that could simulate 6-DOF, 3-axial translation and 3-axial moment, at the same time. Since field vibration motion can be fully represented with 6-DOF, multi-axial vibration test on vehicle component is widely conducted in technical leading companies to make sure its fatigue performance in vibration environment. On the way to fulfill the process, editing technique of obtained field data is key issue to success a reliable vibration testing with MAST system. Since the original signals are not only too large to fulfill it directly, but all of the measured data is not guarantee its convergency on generating its driving files, editing technique of the original signals are highly required to make some events that should meet the equal fatigue damage on the target component In this paper, key technique on editing a field data feasible for MAST system is described based on energy method in vibration fatigue. To explain its technique explicitly, author first introduced a process on field data acquisition of two vehicle component and then, representing events are produced to keep up with the editing strategy about a energy method. In the final chapter, a time information regarding a vibration test on MAST system is derived from the energy data which is critical information to perform a vibration test.

• 과학교육연구지
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• 제42권2호
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• pp.120-131
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• 2018

본 연구의 목적은 구르는 물체에 작용하는 마찰력에 대한 과학 영재 학생들의 이해의 특징을 살펴보고, 이로부터 도출할 수 있는 교수 학습법적인 시사점은 무엇인지 살펴보는 것이었다. 이를 위해 수도권 소재 과학영재학교에서 고급물리학을 수강하는 3학년 학생 48명을 연구 참여자로 하여 구르는 물체에 작용하는 마찰력에 대한 세 가지 문항을 개인별로 풀어보게 하고, 이후 조별 토론을 실시하였다. 연구 결과 학생들의 응답은 규칙형, 비규칙형, 계산형의 세 유형으로 나눌 수 있었으며, 비규칙형으로 분류되는 학생들이 가장 많았다. 이중 규칙형의 학생들은 마찰력과 관련한 규칙을 활용하여 구르는 물체에 작용하는 마찰력에 대해 추론하는데 어려움을 겪고 있었다. 연구자는 접촉면에서의 상대 운동을 강조하는 전략과 더불어 마찰력에 대한 규칙을 사용하지 않고도 마찰력의 방향을 제대로 추론하도록 가르친다면 학생들이 마찰력에 대한 깊은 이해에 도달할 수 있을 것이라고 생각한다.