• 한국강구조학회 논문집
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• 제8권3호통권28호
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• pp.3-11
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• 1996

To investigate the effect of fatigue crack growth due to the surface residual stress, it is measured the residual stress distribution by x-ray diffraction at the crack tip each constant crack growth in the notch specimens, and quantitively assessed the effect of crack closure caused to the distribution of compressive stress at the crack tip from evaluating crack openning stress using the finite element analysis. It is concluded that the degree of the residual stress distribution at the crack tip is decreased with increasing the crack length. From the fact that it is similar to the crack openning stress ratio, it is found that the compressive residual stress distribution and size is related to the crack closure effect and surface residual stress field with propagating crack in the notch specimens depends on the stress intensity factor range at the crack tip.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 ITC-CSCC -2
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• pp.673-676
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• 2000

Adaptive Fourier analysis of sinusoidal signals in noise is of essential importance in many engineering fields. So far, many adaptive algorithms have been developed for this purpose. In particular, a filter bank based algorithm called constrained notch Fourier transform of its cost-efficiency and easily controllable performance. However, its performance deteriorates when the signal frequencies are not uniformly spaced. This paper proposes, at first, a new structure for the CNFT, referred to as modified CNFT (MCNFT), to compensate the performance degeneration of the CNFT for noisy sinusoidal signals with non-uniformly spaced frequencies. Next, a detailed performance analysis for the MCNFT is conducted. Closed form expression of steady-state mean square error (MSE) for the discrete Fourier coefficients (DFCs) is derived. Extensive simulations are presented to demonstrate the improved performance of the MCNFT and the validity of the analytical results.

• 전기학회논문지
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• 제61권1호
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• pp.64-69
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• 2012

In this paper, the optimal design of notch and barrier was carried out in order to improve characteristics of constant torque with minimizing the cogging torque occurred by teeth and slot structure. Optimized design was carried out by design of experiment and various characteristics including torque were studied by finite element method(FEM). In addition, in order to verify resonance frequency, natural frequency of the stator was analyzed by modal analysis.

• 한국인터넷방송통신학회논문지
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• 제23권5호
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• pp.103-108
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• 2023

본 논문에서는 미사일의 눈 역할을 하는 탐색기에 적용할 수 있는 AESA 안테나의 성능 고도화 연구를 진행하고 실제 측정을 통해 안테나 성능을 검증하였다. AESA 안테나 설계 시에는 필연적으로 발생하는 복사소자 간의 상호간섭 영향으로 송신 시 능동반사계수의 최적화를 고려해야하며, 탐색기의 공간 제한을 극복할 수 있는 소형/경량화가 적용된 복사소자의 선정이 중요한 설계 고려 사항이다. 이에 탐색기용 AESA 구조에 적용하기 위한 배열안테나 연구를 통해 전기적 성능 및 Low-profile 구조 측면에서 최적화가 필요하다. 본 논문에서 설계하고 측정한 복사소자는 일반적인 비발디 안테나의 성능을 고도화시키면서 Low-profile 구조를 만족할 수 있는 Step Flared Notch(SFN)를 설계하였다. 본 논문을 통해 SFN은 일반적인 비발디 안테나와 동일하게 광대역 특성을 가지며 AESA 안테나에 필요한 특성들이 최적화 된 특성을 보유함을 확인 할 수 있었다. 시뮬레이션을 통해 최적화 된 구조는 실제 프로토타입 안테나 제작을 통해 패턴 특성과 능동반사계수 특성을 확인하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 G
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• pp.3286-3288
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• 1999

The electrostatically actuated test structure was presented to measure the micro mechanical characteristics of micromaterials as thin films forming the microactuators. The test structure was fabricated by the surface micromachining processes and driven by the electrostatic force, In order to measure the fracture toughness, the sharp notch in the test structure was introduced by the etching process. On the basis of the beam bending theory, the elastic modulus was measured by using the microcantilevr beam and the mechanical displacement, curvature and deflection curve under the electrostatic force was evaluated by using the electrostatic structure.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1997년도 특별강연 및 춘계학술발표 개요집
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• pp.107-111
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• 1997

In this paper distribution of welding residual stress on the double fillet welded joint which exits and not exits root gap, i.e. full penetration and partial penetration is investigated by two dimensional cunduct and thermal elasto-plastic analysis. And stress distribution on notch-tip of the structure where welding residual stress regarded as initial stress and then external load is added is also investigated.

• Journal of Welding and Joining
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• 제13권1호
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• pp.89-102
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• 1995

The evaluation of reheat cracking susceptibility in CrMoV turbine rotor steel was performed using thermally simulated heat affected zones. The examinations were carried out in terms of microstructural characterization, microhardness measurement and a Charpy type notch opening three point bend test. It was found that reheat cracking susceptibility increased as the peak temperature increased. This effect was due to the combined effects of the carbide dissolution and unrestricted grain growth at 1350.deg. C peak temperature. Reheat cracking susceptibility was estimated based on microhardness measurement and prior austenite grain size. It was established that for this particular material, reheat cracking in coarse grained heat affected zone can be eliminated if the microhardness is below about 360DPH and the grain size is below about 30.mu.m. It is evident that reheat cracking susceptibility can be eliminated or reduced by carefully controlling the welding parameters such that a refined structure is produced in the coarse grained heat affected zone.

• 한국전자파학회논문지
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• 제14권2호
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• pp.111-118
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• 2003

넛치 안테나는 진행파형 안테나로서 공진형 안테나에 비해 광대역 특성과 넓은 빔 폭을 가지므로 광대역 위상 배열 안테나의 복사 소자로 사용되어진다. 본 논문에서는 단일 복사 소자의 해석으로 무한 배열 안테나를 모의할 수 있는 도파관 시뮬레이터를 이용하여 3 : 1 이상의 주파수 대역과 $\pm$45$^{\circ}$의 빔 조향 범위를 만족하는 광대역 E-평면 넛치 위상 배열 안테나를 설계하였다. 설계된 단일 소자의 등가회로 모델링을 통해 단일 소자와 무한 배열소자에서의 임피던스 특성을 비교하였으며, 설계된 결과를 이용하여 1$\times$9배열 E-평면 넛치 위상 배열 안테나 전체를 해석하였다. 이때 구해진 안테나간 상호 결합 계수를 이용하여 각 소자의 빔 조향 각도에 따른 능동 반사 계수를 구하였으며, 능동 소자 패턴을 통해 빔 조향에 따른 이득의 변화를 살펴보았다.

• 한국정보전자통신기술학회논문지
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• 제3권2호
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• pp.25-30
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• 2010

본 논문에서는 사각 분리형 링 공진기를 기본으로 하는 새로운 노치형 공진기를 제안한다. 이 공진기와 마이크로 스트립 선로가 결합된 R-SRR구조에 대해 전기적인 특성을 시뮬레이션과 측정 결과를 비교하여 나타내었다. 제안된 구조의 공진 특성으로 부터 등가회로를 나타내었고, 공진기의 구조에서 셀의 간격, 셀 사이즈, 셀의 개수 등의 변화에 대한 공진기의 공진 특성의 변화를 나타내었다. 구조적 변수 중에서 셀의 크기 요소가 공진 주파수의 가장 큰 변화 요인이다. 본 연구의 결과는 주파수 가변 대역통과 필터 설계 및 전압 제어 발진기 등의 설계에 활용할 수 있다.

• Structural Engineering and Mechanics
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• 제44권2호
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• pp.239-255
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• 2012

This work presents a contribution to understand the inverted trussed beams behavior. The system has a main beam and struts with rectangular cross section associated to a wire rope enlaced to the main beam. It is an unpublished system with the advantage of easy positioning of the wire rope, once it is a continuous and connected by turnbuckles. It is a system that can be used as support for concrete formworks or for rehabilitation wooden beams proposal. The enlacement of the cable demands a small notch at the top of the cross section and a cross pin at the bottom. Six inverted trussed beams were tested, with spans of 180 cm with cables diameter of 1/4". Additionally, four simple beams without any external steel cable were also tested with material from the same lot of wood, allowing a comparison in rupture. The results showed capacity gain of around 60% compared to a simple beam. Once the wire rope characteristics and anchoring are very important for structure response, some improvement suggestions for the efficiency of the cables are also presented.