• International Journal of Ocean System Engineering
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• 제4권1호
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• pp.19-28
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• 2014

The tension leg platform (TLP) is a vertically moored structure with excess buoyancy. The TLP is regarded as moored structure in horizontal plan, while inherit stiffness of fixed platform in vertical plane. In this paper, a numerical study using modified Morison equation was carried out in the time domain to investigate the influence of nonlinearities due to hydrodynamic forces and the coupling effect between surge, sway, heave, roll, pitch and yaw degrees of freedom on the dynamic behavior of TLP's. The stiffness of the TLP was derived from a combination of hydrostatic restoring forces and restoring forces due to cables and the nonlinear equations of motion were solved utilizing Newmark's beta integration scheme. The effect of tethers length and wave characteristics such as wave period and wave height on the response of TLP's was evaluated. Only uni-directional waves in the surge direction was considered in the analysis. It was found that for short wave periods (i.e. 10 sec.), the surge response consisted of small amplitude oscillations about a displaced position that is significantly dependent on tether length, wave height; whereas for longer wave periods, the surge response showed high amplitude oscillations about that is significantly dependent on tether length.

• Advances in nano research
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• 제4권3호
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• pp.197-228
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• 2016

In the present study, thermo-electro-mechanical vibration characteristics of functionally graded piezoelectric (FGP) Timoshenko nanobeams subjected to in-plane thermal loads and applied electric voltage are carried out by presenting a Navier type solution for the first time. Three kinds of thermal loading, namely, uniform, linear and non-linear temperature rises through the thickness direction are considered. Thermo-electro-mechanical properties of FGP nanobeam are supposed to vary smoothly and continuously throughout the thickness based on power-law model. Eringen's nonlocal elasticity theory is exploited to describe the size dependency of nanobeam. Using Hamilton's principle, the nonlocal equations of motion together with corresponding boundary conditions based on Timoshenko beam theory are obtained for the free vibration analysis of graded piezoelectric nanobeams including size effect and they are solved applying analytical solution. According to the numerical results, it is revealed that the proposed modeling can provide accurate frequency results of the FGP nanobeams as compared to some cases in the literature. In following a parametric study is accompanied to examine the effects of several parameters such as various temperature distributions, external electric voltage, power-law index, nonlocal parameter and mode number on the natural frequencies of the size-dependent FGP nanobeams in detail. It is found that the small scale effect and thermo-electrical loading have a significant effect on natural frequencies of FGP nanobeams.

• 대한기계학회논문집A
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• 제36권11호
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• pp.1427-1432
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• 2012

풍력터빈이 점차 대형화 되면서 로터 직경도 점차 커지고 있다. 로터 블레이드는 윈드시어와 타워교란 효과로부터 기계적 하중을 받게 된다. 이러한 기계적 하중은 풍력터빈의 수명을 단축시킨다. 따라서, 풍력터빈의 크기가 커짐에 따라 기계적 하중 완화를 위한 풍력터빈 제어 시스템 설계가 중요하다. 본 논문에서는 로터 블레이드의 기계적 하중 저감을 위한 개별 피치 제어에 대해 소개하고 IPC 성능 검증을 위해 시뮬레이션을 통하여 논의한다.

• Wind and Structures
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• 제20권2호
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• pp.191-211
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• 2015

Several frameworks for the dynamic analysis of wind-vehicle-bridge systems were presented in the past decade to study the safety or ride comfort of road vehicles as they pass through bridges under crosswinds. The wind loads on the vehicles were generally formed based on the aerodynamic parameters of the stationary vehicles on the ground, and the wind loads for the pure bridge decks without the effects of road vehicles. And very few studies were carried out to explore the dynamic effects of the aerodynamic interference between road vehicles and bridge decks, particularly for the moving road vehicles. In this study, the aerodynamic parameters for both the moving road vehicle and the deck considering the mutually-affected aerodynamic effects are formulized firstly. And the corresponding wind loads on the road vehicle-bridge system are obtained. Then a refined analytical framework of the WVB system incorporating the resultant wind loads, a driver model, and the road roughness in plane to fully consider the lateral motion of the road vehicle under crosswinds is proposed. It is shown that obvious lateral and yaw motions of the road vehicle occur. For the selected single road vehicle passing a long span bridge, slight effects are caused by the aerodynamic interference between the moving vehicle and deck on the dynamic responses of the system.

• 대한조선학회지
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• 제21권3호
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• pp.27-34
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• 1984

When a ship is travelling in following seas, the encounter frequency is reduced to be very low. In that case broaching phenomenon is most likely to occur, and it may be due to wave exciting forces acting on ships. It is thought that the wave exciting forces acting on ships in following seas almost consist of two components. One is hydrostatic force due to Froude-Krylov hypothesis, and the other is hydrodynamic lift force due to orbital motion of water particles below the wave surface. In the present paper, the emphasis is laid upon wave exciting sway force, yaw moment and roll moment acting on ships in following seas. The authers take the case that the component of ship speed in the direction of wave propagation is equal to the wave celerity, i.e., the encounter frequency is zero. Hydrostatic force components are calculated by line integral method on Lewis form plane, and hydrodynamic lift components are calculated by lifting surface theory. Furthermore captive model tests are carried out in regular following waves generated by means of a wave making board. Through the comparison between calculated and measured values, it is confirmed that the wave exciting forces acting on ships in following seas can be predicted in terms of present method to a certain extent.

• Clinical and Experimental Pediatrics
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• 제49권5호
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• pp.570-573
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• 2006

대요근은 12번 흉추의 외연면에서 5번 요추까지의 외연면에 걸쳐 기시하여 대퇴골의 소전자에 부착되는 근육으로 고관절의 굴곡에 관여한다. 이는 후복막 기관으로 여러 혈관에서 풍부한 혈류 공급을 받으며, S자 결장, 공장, 충수 돌기, 요관, 대동맥, 신장, 췌장, 척추, 림프선 등 여러 장기와 인접하고 있어 감염의 호발 부위가 된다. 그러나, 요근 농양 발생시, 그 증상이 비특이적이고 건강한 소아에서 드물게 발병하는 이유로 고관절 질환으로 혼돈되기도 하여, 진단과 치료가 지연되는 예가 많다. 저자들은 평소 건강하던 14세 남아가 침대에서 떨어져 경한 우측 둔부 좌상을 입은 이후, 우측 둔부 통증과 발열 및 보행 불능을 호소하여 고관절 이상을 의심해 시행한 자기 공명 영상에서 우연히 우측 요근내 농양을 발견해 항생제 치료를 시행하였던 증례를 경험하였기에 보고하는 바이다.

• 한국항공우주학회지
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• 제41권3호
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• pp.210-216
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• 2013

풍력터빈이 점차 대형화 되면서 로터 직경도 점차 커지고 있다. 로터 블레이드는 윈드시어와 타워 교란 효과로부터 기계적 하중을 받게 된다. 이러한 기계적 하중은 풍력터빈의 수명을 단축시킨다. 풍력터빈의 크기가 커짐에 따라 기계적 하중 완화를 위한 풍력터빈 제어 시스템 설계가 중요하다. 본 논문에서는 로터 블레이드의 기계적 하중 저감을 위한 천이영역에서의 개별 피치 제어에 대해 소개하고 IPC 성능 검증을 위해 시뮬레이션을 통하여 논의한다.

• 한국콘텐츠학회논문지
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• 제9권9호
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• pp.97-104
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• 2009

본 논문은 고차원 얼굴 모션 캡처 데이터를 선형 및 비선형 투영 기법에 각각 적용하고, 이를 2차원 평면으로 투영하기 위한 최적의 방법론에 대한 것이다. 본 방법의 핵심 요소는 프레임 단위의 고차원 얼굴 표정 데이터를 선형 투영 기법인 PCA와 비선형 투영 기법인 Isomap, MDS, CCA, Sammon's Mapping, LLE 등에 적용하고 이를 저차원 공간에 분포시키는 방법론 및 그 결과를 비교 분석하는 것이다. 이를 위해서는 먼저 기존의 고차원 얼굴 표정 프레임 데이터들 사이의 거리를 구하고, 선형 및 비선형 투영 기법들을 적용한 상태에서 기존의 데이터들 사이의 거리 관계를 유지하면서 저차원인 2차원 평면 공간에 분포시키는 것이다. 그리고 2차원 공간에 분포된 얼굴 표정 데이터가 원형 데이터와 비교 했을 때, 최적의 상태로 프레임 데이터들 사이의 거리 관계를 유지하고 있는 투영 기법을 찾는다. 결국 본 논문에서는 고차원 얼굴 표정 데이터를 저차원 공간에 투영하기 위한 선형 및 비선형 투영 기법들을 비교 분석하고, 각각에서 최적의 투영 기법을 찾아낸다.

• 대한물리치료과학회지
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• 제10권1호
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• pp.90-101
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• 2003

Gait analysis can provide a better understanding of how the alignment of the lower limb and foot can contribute to force observed at the knee. Anatomic and mechanical factors that affect loading in the knee pint can contribute to pathologic change seen at the knee in degenerative pint disease and should be considered in treatment plan. The purpose of this study is to present the gait analysis data and to determine whether there is any relationships between alignment of the lower limb, foot progression angle and knee pint moments in elderly healthy women with 3-dimensional motion analyzer. The results were as follows; 1. Cadence showed 114.8 steps/min, gait speed showed 1.05 m/s, time per a stride showed 1.06 sec, time per a step showed 0.53 sec, single-supporting phase was 0.41 sec, double-supporting phase was 0.24 sec, stride length was 1.04 m, Step length was 0.56 m. 2. According to the parameters of kinematics, the maximal knee flexion angle through swing phase showed left $46.82^{\circ}$, right $40.19^{\circ}$ and the maximal knee extension angle showed left $-1.32^{\circ}$, right $2.01^{\circ}$. knee varus showed left $26.90^{\circ}$, right $30.93^{\circ}$. 3. Moment, one of kinetic parameters of knee pint the maximal flexion moment showed left 0.363. Nm/kg, right 0.464 Nm/kg and maximal extension moment showed left 0.389 Nm/kg, right 0.463 Nm/kg. The maximal. adduction moment showed left 0.332 Nm/kg, right 0.379 Nm/kg and the maximal internal rotatory moment showed left 0.13 Nm/kg, right 0.140 Nm/kg. 4. On sagittal plane, the maximal power of knee joint showed left 0.571 J/kg, right 0.629 J/kg. On coronal plane, the maximal power of knee joint showed left 0.11 J/kg, right 0.12 J/kg. On transverse plane, the maximal power of knee joint showed left 0.058 J/kg, right 0.072 J/kg. 5. The subject who had varus alignment of the lower extremity had statistically higher in knee adduction moment in mid stance phase. 6. The subject who had large foot progression angle had statistically lower in knee adduction moment in late stance phase. A relationship was observed between the alignment of the lower extremity and the adduction moment of the knee joint during stance phase. Hence, we need some research to figure, out the change of adduction moment according to the sort of knee joint osteoarthritis and the normal geriatrics as well. And we also require more effective, specific therapeutic program by making use of those background of researches.

• 대한조선학회논문집
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• 제59권6호
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• pp.423-431
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• 2022

In this paper, the results of Planar Motion Mechanism (PMM) test for a 1/15 scaled model of the MARIN Joubert BB2 submarine is dealt with to derive the maneuvering coefficients for surface condition. For the depth of surface navigation, the top of the sail was exposed 0.46 m above the water surface in the model scale, and it corresponds to 6.9 m in the full scale. The resistance and self-propulsion tests were conducted, and the model's self-propulsion point was obtained for 1.328 m/s, which corresponded to 10 knots in the full scale. The maneuvering tests were performed at the model's self-propulsion point, and the maneuvering coefficients were obtained. Based on the maneuvering coefficients, a turning simulation was performed for starboard 30 degree of stern fins. The straight-line stability and control effectiveness in the horizontal plane were analyzed using the maneuvering coefficients and compared with the appropriate range. For the analysis of the neutral fin angle of the X-type stern fin, the stern fin test with drift angles was carried out. As a result, the flow straightening effect at lower and upper parts of the stern fin was discussed.