• 소성∙가공
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• 제13권7호
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• pp.594-599
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• 2004

In the sheet metal forming operations, the strain measurement of sheet panel is an essential work which provides the formability information needed in die design, process design, and product inspection. To measure efficiently complex geometry strains, the 3-dimensional automative strain measurement system, which theoretically has a high accuracy but practically has about 3～5％ strain error, is often used. For eliminating the strain error resulted in measuring the strains of formed panels using an automated strain measurement system, the position error calibration method is suggested, which computes accurate strains using the grids with accurate nodal coordinates. The accurate nodal coordinates are calculated by adding the nodal coordinates measured by the measurement system and the position error found using the multiple regression method as a function of the main error parameters obtained from the analysis of strain error in a standard cube. For the verification, the strain distributions of square and dome cups obtained from the position error calibration method are compared with those provided by the finite element analysis and ASAME.

• Plant Resources
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• 제1권1호
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• pp.22-25
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• 1998

To establish direct multipropagation through organogenesis from nodal explants of Anoectochilus formosanus Hayata, the nodes were cultured on LS medium containing various concentrations of 6-benzyladenine(BA). High plant regeneration and adventitious bud formation were obtained from supplemented with 4.0mg/l of BA. Plant height was promoted by adding 0.3% activated charcoal. Plantlet regeneration capacity from nodes was depended on nodal parts on the stem, upper position was the best comparing with intermediate and lower.

• 대한기계학회논문집A
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• 제29권4호
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• pp.534-539
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• 2005

Nodal displacements are referred to the initial configuration in the total Lagrangian formulation and to the last converged configuration in the updated Lagrangian furmulation. This research proposes a relative nodal displacement method to represent the position and orientation for a node in truss structures. Since the proposed method measures the relative nodal displacements relative to its adjacent nodal reference frame, they are still small for a truss structure undergoing large deformations for the small size elements. As a consequence, element formulations developed under the small deformation assumption are still valid for structures undergoing large deformations, which significantly simplifies the equations of equilibrium. A structural system is represented by a graph to systematically develop the governing equations of equilibrium for general systems. A node and an element are represented by a node and an edge in graph representation, respectively. Closed loops are opened to form a spanning tree by cutting edges. Two computational sequences are defined in the graph representation. One is the forward path sequence that is used to recover the Cartesian nodal displacements from relative nodal displacement sand traverses a graph from the base node towards the terminal nodes. The other is the backward path sequence that is used to recover the nodal forces in the relative coordinate system from the known nodal forces in the absolute coordinate system and traverses from the terminal nodes towards the base node. One open loop and one closed loop structure undergoing large deformations are analyzed to demonstrate the efficiency and validity of the proposed method.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.788-791
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• 2005

Nodal displacements are referred to the Initial configuration in the total Lagrangian formulation and to the last converged configuration in the updated Lagrangian formulation. This research proposes a relative nodal displacement method to represent the position and orientation for a node in truss structures. Since the proposed method measures the relative nodal displacements relative to its adjacent nodal reference frame, they are still small for a truss structure undergoing large deformations for the small size elements. As a consequence, element formulations developed under the small deformation assumption are still valid fer structures undergoing large deformations, which significantly simplifies the equations of equilibrium. A structural system is represented by a graph to systematically develop the governing equations of equilibrium for general systems. A node and an element are represented by a node and an edge in graph representation, respectively. Closed loops are opened to form a spanning tree by cutting edges. Two computational sequences are defined in the graph representation. One is the forward path sequence that is used to recover the Cartesian nodal displacements from relative nodal displacements and traverses a graph from the base node towards the terminal nodes. The other is the backward path sequence that is used to recover the nodal forces in the relative coordinate system from the known nodal forces in the absolute coordinate system and traverses from the terminal nodes towards the base node. One closed loop structure undergoing large deformations is analyzed to demonstrate the efficiency and validity of the proposed method.

• 소음진동
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• 제8권4호
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• pp.623-631
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• 1998

The free vibration analyses of the isotropic and composite(CFRP, GFRP) rectangular plates with point supports at the free edge and middle position are performed. The natural frequencies and nodal patterns of plates with point supports are experimentally determined by impact testing using an impact hammer. To compare and verify these experimental results, the finite element analysis is also carried out. The effect of the point support position, the number of point supports, and the anisotropic parameters on the natural frequencies and nodal patterns of cantilevered rectangular plates are investigated.

• Journal of Plant Biotechnology
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• 제5권2호
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• pp.115-119
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• 2003

To determine the appropriate concentrations of nutrients and growth regulators for shoot proliferation and root initiation, several rose hybrid tea cultivars were cultured. Cultured shoot tips and lateral buds from different cultivars proliferated multiple shoots on Murashige and Skoog (MS) medium supplemented with 0 to 4 mg/L BA and 0 to 0.05 mg/L NAA. The ability of the explants to proliferate shoots and initiate roots was affected by genotype, the nodal position of explant, the strength of MS basal medium and growth regulators used. The buds nearest the apex exhibited the slowest rate of development. Most cultivars had the highest shoot proliferation when cultured on MS medium with 2 mg/L BA and 0.01 mg/L NAA, but the degree varied by cultivars. Root development was enhanced by lowering the concentration of MS salts.

• 대한조선학회논문집
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• 제53권5호
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• pp.388-399
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• 2016

A motion analysis of an underwater towed cable is a complex task due to its nonlinear nature of the problem. The major source of the nonlinearity of the underwater cable analysis is that the motion of the cable involves large rigid-body motion. This large rigid-body motion makes difficult to use standard displacement-based finite element method. In this paper, the authors apply recently developed nodal position-based finite element method which can deal with the geometric nonlinearity due to the large rigid-body motion. In order to enhance the stability of the large-scale nonlinear cable motion simulation, an efficient time-integration scheme is proposed, namely predictor/multi-corrector Newmark scheme. Three different predictors are introduced, and the best predictor in terms of stability and robustness for impulsive cable motion analysis is proposed. As a result, the nonlinear motion of underwater cable is predicted in a very efficient manner compared to the classical finite element of finite difference methods. The efficacy of the method is demonstrated with several test cases, involving static and dynamic motion of a single cable element, and also under water towed cable composed of multiple cable elements.

• 방송공학회논문지
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• 제14권3호
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• pp.322-331
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• 2009

본 논문은 윤곽선 기반 메쉬 최적화를 이용한 스테레오 영상의 효율적인 데이터 표현 방법을 제안한다. 스테레오 영상에 대한 메쉬 기반 2차원 워핑은 주로 제어점 선택과 선택된 제어점들의 시차 정보 추정 성능에 의존한다. 따라서 제안된 방법은 제어점 선택을 위하여 강한 윤곽선과 객체의 경계선만으로 구성된 특징 지도를 생성하고 이를 기반으로 격자형 메쉬를 생성한다. 또한, 지역단위로 2차원 워핑을 수행하며 목적영상과의 오차를 최소로 하는 제어점의 위치를 반복적으로 추정하게 된다. 최적화된 제어점 위치를 찾기 위한 반복적 2차원 워핑 과정은 많은 계산 시간을 요구하기 때문에 이를 개선하기 위하여 입력된 스테레오 영상은 수평 시차만 존재하고 최적의 제어점 위치는 객체의 경계선을 포함한 윤곽선 위에 존재함을 가정한다. 따라서 제안한 윤곽선 기반 워핑 방법은 수평선 위에 윤곽선만을 따라 반복적으로 최적화된 제어점 위치를 탐색한다. 본 논문의 실험에서는 스테레오 영상에 대하여 제어점 수에 따른 신호에 대한 잡음비(PSNR)를 측정하여 기존 방법과 제안한 방법의 품질을 비교 하였다. 뿐만 아니라 최적의 메쉬 생성을 위한 수행시간을 비교하여 평가하였다. 실험 결과를 통하여 제안한 방법은 적은 수의 제어점을 이용하여 품질의 저하를 줄이고 빠르게 최적의 메쉬를 생성함으로써 효율적인 스테레오 영상 표현 방법을 제공하였다.

• 비파괴검사학회지
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• 제28권2호
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• pp.131-136
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• 2008

정재초음파를 이용하면 유체에 잠겨 있거나 유체를 따라서 흐르는 미세 입자의 조작이 가능하다. 정재초음파 장이 입자에 힘을 작용하여 입자를 음압마디 또는 반음압마디로 이동시킨다. 본 연구에서는 정재초음파의 주파수를 조정함으로써 유동 중 미세 입자의 위치를 제어하는 방법을 제안하고자 한다. 이를 위해 먼저 수침형 초음파 트랜스듀서를 이용하여 폭 수 밀리미터의 미세 채널을 가지는 정재초음파 발생시스템을 구성하였다. 제안한 발생시스템을 이용하여 주파수 2 MHz부터 2.5 MHz까지 영역에서 정재초음파 장을 발생시키고, 물을 따라 흐르는 수 마이크로미터 내외의 탄화규소 입자가 음압 마디로 잘 이동함을 확인하였다. 이때, 미세 채널의 폭과 주파수가 입자의 거동에 미치는 영향을 관찰하였으며, 주파수가 미세입자의 이동 위치를 결정하는 중요한 파라미터임을 확인하였다. 결과적으로, 초음파의 주파수를 조정함으로써 입자의 이동 위치를 제어할 수 있음을 실험을 통해 확인하였으며 최대 범위는 약 261 마이크로미터이다. 본 연구로부터 유체내의 입자 조작에 있어서 정재초음파의 다양한 응용 가능성을 확인할 수 있었다.

• 한국소음진동공학회논문집
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• 제12권7호
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• pp.534-541
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• 2002

Vibration and sound characteristics of King Song-Dok Bell are ivesigated. Natural frequencies. vibration modes and beat period of the bell are precisely measured. The effect of striking position and the position of nodal lines on the beat characteristics is examined. It is first found that the beat characteristics are quote different according to the position on the bell surface and clear beat is periodically generated on the circumference. It turns out that in King Song-Dok Bell, Dangjwa(the present striking position) is located at the position which makes a beat in the first vibration mode, as welt as it produces very clear beat In the second vibration mode.