• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 춘계학술대회 논문집
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• pp.340-346
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• 2013

This paper describes a helicopter vibration induced by main rotor in forward flight. The hub loads in the fixed frame, which are dominant source of helicopter vibration, are obtained by multi-blade summation of rotating blades loadings. The components of 3/rev, 4/rev, and 5/rev blades loadings are transmitted by blades to 4/rev hub loads in the fixed frame. The vertical vibrations of helicopter at pilot seat and copilot seat are calculated through rigid body transfer functions considering airframe to be rigid body. The blades are assumed to be elastic and undergo the flap, lag, and torsion motion and free wake aerodynamic model is used to calculate the precise blade loadings in the analysis. The 4/rev vertical vibration responses are analyzed from rotating blade loadings and fixed hub loadings.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.120-124
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• 2003

NVH issue at idle condition is one of the major concerns of Passenger and Commercial Vehicle including Sports Utility Vehicle Especially steering wheel vibration at idle condition is a very complex problem and affected by firing frequency of the engine, stiffness of a steering wheel system and the body to which the steering wheel system is attached. To avoid vibration mode coupling between each system of a vehicle, experimental and analytical method has been used at the pre-prototype stage. The resonance frequency of the body and the frame has been decoupled by CAE and the resonance frequency of steering wheel system has been set in between the 1st bending frequency of body and frame. These Results has been used as design guidelines tot the prototype drawing stage. The experimental verification of tile modified pre-prototype vehicle shows good results of the vibration mode decouple. Modal test of prototype vehicle also confirms the vibration mode decouple between each system.

• 한국군사과학기술학회지
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• 제22권5호
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• pp.590-598
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• 2019

Aerial photographs taken by an image sensor fixed on a flight body, e.g. without a gimbal, are generally distorted according to its attitude, altitude and angle of view in flight. This can result in a significant difficulty of analyzing geometric information which should be integrated for numerous still frames. In this study, a simulation method of observation performance that uses geometric relationships between navigation data and image data is suggested, and this method is shown to be very useful for easily examining the integrated information such as the total range of photography, the time of target acquisition, etc.

• 한국전산구조공학회논문집
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• 제26권1호
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• pp.9-17
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• 2013

본 연구에서는 고층 전단벽-골조 구조시스템의 효율적인 해석모델을 제안하였다. 전단벽-골조구조시스템은 휨거동하는 전단벽과 전단거동하는 골조로 구성된다. 그리고 전단벽-골조구조시스템의 변형형상은 골조와 전단벽의 상호작용으로 결정된다. 효율적인 해석모델에서는 이러한 거동특성을 반영되어야 하므로 골조와 전단벽을 분리하여 동적인 거동특성을 반영할 필요가 있다. 본 연구에서는 벽체부와 골조부를 분리하기 위하여 T형 강체를 전단벽의 위치에 대체하는 방법을 사용하였다. 분리한 벽체부와 골조부 각각의 등가모델을 구성한 후 결합시키는 방법으로 고층 전단벽-골조구조시스템의 등가모델을 완성하였다. 제안한 등가모델의 정확성과 효율성을 검증하기 위하여 고층의 전단벽-골조 구조물의 시간이력해석을 수행하였고, 그 결과 제안한 등가모델이 해석시간과 컴퓨터 메모리를 현저하게 줄이면서도 정확한 결과를 도출하였다.

• 한국HCI학회:학술대회논문집
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• 한국HCI학회 2008년도 학술대회 1부
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• pp.439-444
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• 2008

추상적인 매개공간을 예제모션들로 표본추출(sampling)하고, 그것들을 보간하여 주어진 입력 매개변수(parametrs)와 대응되는 블렌딩 가중치(blend weights)를 계산하는 블렌딩 기반의 매개화된 합성기법은 뛰어난 제어력과 효율성 때문에 널리 쓰이고 있다. 그러나 보다 세부적인 모션 제어를 위해 매개공간의 차원을 증가시킬수록, 표본추출을 위해 필요한 예제모션의 수가 기하급수적으로 늘어나게 된다. 본 논문은 상체모션과 하체모션의 분리된 생성 및 제어를 위해 두 개의 매개공간(parameter spaces)을 사용하는 방법론을 제안한다. 즉, 매 애니메이션 프레임마다 각 매개공간으로부터 두 개의 바탕프레임(source frames)이 추출되면, 하나로부터의 상체를 다른 하나의 하체에 접합(splicing)하여 실시간으로 목적모션을 생성한다. 이를 통해 사용자가 입력한 상체제약과 하체제약을 모두 만족하는 모션을 생성할 수 있을 뿐만 아니라 매개공간의 차원 복잡도에서 기인하는 문제를 해결할 수 있다. 본 논문을 통해, 우리는 두 개의 매개화된 모션공간으로부터 시간적 상호관계가 고려된 모션을 생성하기 위한 새로운 시간왜곡(time-warping)기법을 제안한다. 또한 상체의 공간적 특성을 기반으로 예제모션들을 매개화할 경우, 접합되는 하체에 따라 변경되는 예제모션들의 매개변수를 빠르게 근사하기 위한 기법을 소개한다.

• Structural Engineering and Mechanics
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• 제13권2호
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• pp.135-154
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• 2002

This paper presents the convected material frame approach to study the nonlinear behavior of inelastic frame structures. The convected material frame approach is a modification of the co-rotational approximation by incorporating an adaptive convected material frame in the basic definition of the displacement vector and strain tensor. In the formulation, each discrete element is associated with a local coordinate system that rotates and translates with the element. For each load increment, the corresponding strain-displacement and nodal force-stress relationships are defined in the updated local coordinates, and based on the updated element geometry. The rigid body motion and deformation displacements are decoupled for each increment. This modified approach incorporates the geometrical nonlinearities through the continuous updating of the material frame geometry. A generalized nonlinear function is used to derive the inelastic constitutive relation and the kinematic hardening is considered. The equation of motion is integrated by an explicit procedure and it involves only vector assemblage and vector storage in the analysis by assuming a lumped mass matrix of diagonal form. Several numerical examples are demonstrated in close agreement with the solutions obtained by the ANSYS code. Numerical studies show that the proposed approach is capable of investigating large deflection of inelastic planar structures and providing an excellent numerical performance.

• 한국자동차공학회논문집
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• 제10권1호
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• pp.216-233
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• 2002

Due to the environmental problems of fuel consumption and vehicle emission, etc., automotive makers are trying to reduce the weight of vehicles. The most effective way to reduce a vehicle weight is to use lighter materials, such as aluminum and plastics. Aluminum Intensive Vehicle(AIV) has many advantages in the aspects of weight reduction, body stiffness and model change. So, most of automotive manufacturers are attempting to develop AIV using Aluminum Space Frame(ASF). The weight of AIV can be generally reduced to about 30% than that of conventional steel vehicle without the loss of impact energy absorbing capability. And the body stiffness of AIV is higher than that of conventional steel monocoque body. In this study, Aluminum Intensive Vehicle is developed and analyzed on the basis of steel monocoque body. The energy absorbing characteristics of aluminum extrusion components are investigated from the test and simulation results. The crush and crash characteristics of AIV based on the FMVSS 208 regulations are evaluated in comparison with steel monocoque. Using these results, the design concepts of the effective energy absorbing members and the design guide line to improve crashworthiness for AIV are suggested.

• 한국인터넷방송통신학회논문지
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• 제11권6호
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• pp.49-56
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• 2011

오늘날 자전거는 레저용으로 각 회사에서 다양화되고 있다. 각 자전거 메이커로부터 다품종의 자전거가 판매되고 있지만, 구매자가 그 중에서 자신의 신체에 적합한 자전거의 정보를 얻는 것은 쉬운 것은 아니다. 따라서 대부분 구매자의 신체치수를 이용하여 자전거를 구매하고 있다. 이와 같은 방법을 이용하는 것은 표준 신체치수에 의하여 자전거의 치수를 결정하는 방법이다. 그러나 이 방법에 의하여 자전거를 구입하였을 경우 구매자의 신체에 적합한 자전거라고 볼 수가 없다. 본 연구에서는 구매자가 직접 본인의 신체에 맞도록 최적 설계시스템을 조절하여 자전거를 설계한다. 그리고 퍼지제어기를 이용한 주행 시험 장치에서 주행시험을 한다. 그 결과를 이용하여 구매자의 신체에 적합한 자전거인가를 판단할 수 있는 최적 자전거 설계시스템을 연구한 것이다.

• 한국기계가공학회지
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• 제17권4호
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• pp.55-63
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• 2018

In recent years, with the growing interest in electric vehicles, the development of a Neighborhood Electronic Vehicle (NEV) made for urban driving is accelerating. Existing NEVs are set to ~0.3 - 0.35 with more emphasis on performance rather than minimizing air resistance. In this paper, a NEV with a streamlined car body is proposed. The shape of dolphins and sharks was applied to the car body to minimize the air resistance generated when driving. Also, the performance of the vehicle was estimated by calculating the traction force and the roll couple, etc. To check the drag coefficient of the car body, finite element analysis software (COMSOL Multiphysics) was used. The frame of the vehicle is divided into the forward and the rear parts. Carbon pipe is used for the frame by MIG welding. The car body of the vehicle was fabricated by forming carbon fiber. This study confirmed the general possibility of using NEVs through driving experiments.

• International Journal of Naval Architecture and Ocean Engineering
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• 제6권4호
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• pp.1024-1040
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• 2014

The theoretical background and a numerical solution procedure for a time domain hydroelastic code are presented in this paper. The code combines a VOF-based free surface flow solver with a flexible body motion solver where the body linear elastic deformation is described by a modal superposition of dry mode shapes expressed in a local floating frame of reference. These mode shapes can be obtained from any finite element code. The floating frame undergoes a pseudo rigid-body motion which allows for a large rigid body translation and rotation and fully preserves the coupling with the local structural deformation. The formulation relies on the ability of the flow solver to provide the total fluid action on the body including e.g. the viscous forces, hydrostatic and hydrodynamic forces, slamming forces and the fluid damping. A numerical simulation of a flexible barge is provided and compared to experiments to show that the VOF-based flow solver has this ability and the code has the potential to predict the global hydroelastic responses accurately.