• 한국통신학회논문지
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• 제34권11B호
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• pp.1272-1282
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• 2009

본 논문은 태그간 메쉬 네트워킹 방법과 네트워크 간섭을 해결하기 위한 RFID 태그간 메쉬 네트워킹을 위한 듀얼 라디오 태그 시스템 의 구현을 설명한다. 최근 항만 또는 물류창고에서 상품 선적 및 보관 등의 정보를 자동화 하기 위해 RFID 전자태그가 부착된 컨테이너, 팔레트의 이용이 확대되고 있다. 그러나 RFID 시스템은 항만이나 물류창고에 산재되어 있는 금속성 물체 등으로 인해 리더와 태그간의 통신을 방해하는 음영지역이 발생한다. 본 논문에서 제안한 통신 음영지역 문제점 해결하기 위한 방법은 다음과 같다. 리더와 태그간의 직접 통신이 가능한 지역은 ISO/IEC 18000-7 표준에 따라 433MHz 주파수 대역에서 통신하고 리더와 태그간의 통신이 불가능한 음영지역이나 리더의 통신 범위를 벗어난 지역에서는 IEEE 802.15.4 표준에 따라 2.4GHz 주파수 대역에서 태그간 메쉬 네트워킹을 이용하여 통신한다. 이 방법을 적용한 통신방식은 리더와 태그간 통신에서 존재하는 통신 음영지역의 해소에 큰 도움을 줄 수 있고, 리더를 추가로 설치하는 방식보다 설치비용 절감 효과를 기대할 수 있다. 그리고 네트워크 인프라가 갖추어져 있지 않은 곳에서도 태그간 메쉬 네트워킹을 이용하여 쉽고, 빠르고, 경제적으로 네트워크 인프라를 구축할 수 있다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.202-207
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• 2004

An elastic-plastic finite element analysis of fatigue crack closure is performed for plane strain conditions. The stabilization behavior of crack opening level and the effect of mesh size on the crack opening stress are investigated. In order to obtain a stabilized crack opening level for plane strain conditions, the crack must be advanced through approximately four times the initial monotonic plastic zone. The crack opening load tends to increase with the decrease of mesh size. The mesh size nearly equal to the theoretical plane strain cyclic plastic zone size may provide reasonable numerical results comparable with experimental crack opening data. The crack opening behavior is influenced by the crack growth increment and discontinuous opening behavior is observed. A procedure to predict the most appropriate mesh size for different stress ratio is suggested. Crack opening loads predicted by the FE analysis based on the procedure suggested resulted in good agreement with experimental ones within the error of 5 %. Effect of the distance behind the crack tip on the crack opening load determined by the ASTM compliance offset method based on the load-displacement relation and by the rotational offset method based on the load-differential displacement relation is investigated. Optimal gage location and method to determine the crack opening load is suggested.

• 디지털산업정보학회논문지
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• 제5권4호
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• pp.1-9
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• 2009

It establishes the nonlinear optics material recently on solid-state laser output side and from the infrared ray until is early has in the ultraviolet rays and the wavelength of broadband there makes be a possibility of getting the laser light which and in processing and measuring field it is widely used. Consequently, it used the pulse reiteration law from origination and nine as the fundamental wave direct plan it produced. intense it affixed the nonlinear optics material (KTP) in pulsed light and it got the green light. When inflicting a same energy in respectively reiteration mesh, intense interrelation of pulse light output and green light output between. It analyzed the conversion ratio which it follows in the mesh.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 추계학술대회 초록집
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• pp.178.2-178.2
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• 2010

The wind turbine gearbox is important rotating part to transmit torque from turbine blade to generator. Generally, gear shaft which rotates causes vibration by influence of stiffness and mass with gear shaft. Root cause of this vibration source is well known to gear transmission error that is decided from gear tooth property. Transmission error excites a gear, and makes excitation force that is vibrated shaft. This vibration of shaft is transmitted to gearbox housing through gearbox bearing. If the resonance about which the natural frequency of the gearbox accords with shaft exciting frequency occurs, a wind turbine can lead to failure. The gearbox for wind turbine should be considered influence of vibration as well as the fatigue life and its performance by such reason. The cause to vibration should be closely examined to reduce influence of such vibration. In this paper, the cause of the vibration which occurs by a gearbox is closely examined and the method which can reduce the vibration which occurred is shown. It is compared with vibration test outcome of a 3MW gearbox for verification of the method shown by this paper.

• Journal of Mechanical Science and Technology
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• 제18권2호
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• pp.253-261
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• 2004

A simple and effective filtering method to control the member size of an optimized structure is proposed for topology optimization. In the present approach, the original objective sensitivities are replaced with their relative values evaluated within a filtering area. By adjusting the size of the filtering area, the member size of an optimized structure or the level of its topological complexity can be controlled even within a given finite element mesh. In contrast to the checkerboard-free filter, the present filter focuses on high-frequency components of the sensitivities. Since the present filtering method does not add a penalty term to the objective function nor require additional constraints, it is not only efficient but also simple to implement. Mean compliance minimization and eigenfrequency maximization problems are considered to verify the effectiveness of the present approach.

• 한국전산구조공학회논문집
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• 제35권6호
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• pp.343-349
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• 2022

본 논문에서는 구조물이 다중 구조물로 연결되는 경우 연결부의 조인트 위치를 기존의 위상최적설계 기법을 활용해 설계하는 기법을 개발하였다. 조인트는 길이가 0이고 강성이 매우 강한 스프링으로 모델링되었으며, 조인트는 유한요소 메시 형상과 무관하게 이동할 수 있도록 모델링되었다. 최적화 과정에서 조인트가 서로 뭉치는 현상을 방지하기 위해 조인트 최소거리 조건을 추가해 조인트간의 최소거리가 확보된 설계를 얻었다. 최적설계 시 목적함수로는 전체 구조물의 compliance 값이 사용되었으며, 조인트 최소거리 조건에 따른 결과를 비교하기 위해 2개의 수치예제를 해석하였다. 위상최적설계 결과 조인트 최소거리 조건의 변화에 따라 조인트 및 구조물의 최적 형상을 얻을 수 있었다.

• Steel and Composite Structures
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• 제37권6호
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• pp.663-678
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• 2020

This paper proposes a novel topology optimization method generating multiple materials for external linear plane crack structures based on the combination of IsoGeometric Analysis (IGA) and eXtended Finite Element Method (X-FEM). A so-called eXtended IsoGeometric Analysis (X-IGA) is derived for a mechanical description of a strong discontinuity state's continuous boundaries through the inherited special properties of X-FEM. In X-IGA, control points and patches play the same role with nodes and sub-domains in the finite element method. While being similar to X-FEM, enrichment functions are added to finite element approximation without any mesh generation. The geometry of structures based on basic functions of Non-Uniform Rational B-Splines (NURBS) provides accurate and reliable results. Moreover, the basis function to define the geometry becomes a systematic p-refinement to control the field approximation order without altering the geometry or its parameterization. The accuracy of analytical solutions of X-IGA for the crack problem, which is superior to a conventional X-FEM, guarantees the reliability of the optimal multi-material retrofitting against external cracks through using topology optimization. Topology optimization is applied to the minimal compliance design of two-dimensional plane linear cracked structures retrofitted by multiple distinct materials to prevent the propagation of the present crack pattern. The alternating active-phase algorithm with optimality criteria-based algorithms is employed to update design variables of element densities. Numerical results under different lengths, positions, and angles of given cracks verify the proposed method's efficiency and feasibility in using X-IGA compared to a conventional X-FEM.