• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1999년도 봄 학술발표회 논문집
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• pp.321-326
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• 1999

In this study, fatigue crack propagation problem of plate under multi-axial loading is mainly considered To analyze this special problem, recently developed technique called EFGM(Element-Free Galerkin Method), one of the Meshfree Methods, and general fatigue crack growth raw herein Paris law are used Using the Implemented scheme, paths of fatigue cracks by constant-amplitude load fluctuation and multiple-crack growth behavior are examined. The failure mechanism of steel plate due to crack propagation is studied. As a result, an algorithm that treats multiple fatigue crack problems is proposed. A numerical example shows that the prediction of growing paths can be achieved successfully and efficiently by proposed algorithm.

• 한국사이버테러정보전학회:학술대회논문집
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• 한국사이버테러정보전학회 2004년도 제1회 춘계학술발표대회
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• pp.181-185
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• 2004

최근에 피해가 보고되고 있는 인터넷 웜은 최초발생 후 단 며칠 만에 전 세계적인 피해를 입히고 있다. 이들 웜들은 메일을 비롯한 기타 여러 가지 경로를 통해 스스로 복제하는 성질을 이용하여 매우 빠른 속도로 전파가 가능하다. 하지만 이를 제대로 막을 수 있는 수단은 마련되지 못하고 있다. 따라서, 인터넷 웜으로부터 네트워크 자산을 보호하기 위해, 체계화되고 자동화된 방지 메카니즘의 인터넷 웜 분야의 연구가 필요하다 이에, 본 논문에서는 인터넷 일의 확산과 방어 모델을 기술하고자 한다.

• 대한전기학회논문지:시스템및제어부문D
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• 제53권10호
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• pp.690-696
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• 2004

This paper is proposed a hybrid intelligent controller based on the vector controlled surface permanent magnet synchronous motor(SPMSM) drive system. The hybrid combination of neural network and fuzzy control will produce a powerful representation flexibility and numerical processing capability. Also, this paper is proposed speed control of SPMSM using neural network-fuzzy(NNF) control and speed estimation using artificial neural network(ANN) Controller. The back propagation neural network technique is used to provide a real time adaptive estimation of the motor speed. The error between the desired state variable and the actual one is back-propagated to adjust the rotor speed, so that the actual state variable will coincide with the desired one. The back propagation mechanism is easy to derive and the estimated speed tracks precisely the actual motor speed. This paper is proposed the theoretical analysis as well as the simulation results to verify the effectiveness of the new method.

• 한국정밀공학회지
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• 제20권9호
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• pp.166-172
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• 2003

Vibration and Noise of air conditioner are entirely determined by compressor vibration. Compressor vibration transmitted to the enclosure of air conditioner or pipes connected compressor with heat exchanger. Enclosure generate(noise and vibration. Therefore, the analysis of compressor vibration analysis is considered significant technical issue. For the reduction of vibration of compressor, it is necessary to grasp correctly vibration transmission paths and excitation sources in the compressor shell. Because, shell ( Surface of compressor ) shows whole vibration characteristic of compressor mechanism. In this paper, vibration intensity was applied to measure vibration energy flow on the shell .From this technique, it is possible to catch the path of vibration propagation along the one cycle and the location of vibration energy sources may change with time on the shell.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.973-978
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• 2001

Noise reduction has become a major issue of the manufacturing industry. This paper describes the reduction of noise and vibration of rotary compressors. Empirical design for the present strap of the accumulator has been considered to be sufficient for the constraint of the accumulator resonance modes without thorough study. Recently, however, some researchers found out that the accumulator contributes considerably to the sound propagation. In this paper, the contribution of accumulator to the noise propagation is investigated through sound measuring experiments by checking the directivity of the noise. And, experimental modal analysis results show that frequencies of some resonance modes of the accumulator coincide with the highest peaks on sound spectrum. To demonstrate the reason for those resonance modes, a finite element analysis is conducted. Normal mode analysis of the finite element model of the rotary compressor shows the mechanism of the accumulator resonance modes.

• International Union of Geodesy and Geophysics Korean Journal of Geophysical Research
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• 제25권1호
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• pp.47-56
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• 1997

We present a theoretical study on how the plasmasphere responses to the sudden impulses in the magnetosphere. A mechanism on how Pi 2 pulsations are excited in the magnetosphere is also proposed. When impulsive disturbances associated with the substorm onset are assumed in the magnetotail, their propagation toward the sunward direction is investigated with a wave equation. The propagation speed undergoes serious variations owing to the existence of the plasmasphere, which results in various reflection and tunneling of traveling disturbances at the plasmapause. In order to examine the effect of the plasmapause on initial impulsive disturbances, we analytically solve the wave equation based on the model of reasonable Alfven speed profile. The exact solution shows that virtual resonant states exist inside the plasmaspheric cavity. We obtain the result that these unique modes strongly persist for arbitrary incoming impulses from the source in the magnetotail, which quantitatively corresponds to the signature of PI 2 pulsations.

• 항공우주시스템공학회지
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• 제1권1호
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• pp.45-52
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• 2007

This paper analyzed the extension effects of fatigue life and the application of pre-indentation in aircraft structural material such as aluminum alloys. The test specimen used the thin sheet of aluminum alloy with a single-edged notch. The experiments were conducted after making the pre-crack under a constant amplitude loading. As the fatigue life extension technique, the pre-indentation making an indent on the predicted path of crack propagation was applied. The work presented here discussed about a proper mathematical relation between crack growth rate and the range of stress intensity factor and about the generalization of crack growth mechanism with large retardation effect. A technique to enhance the applicability of pre-indentation if also mentioned.

• Journal of Advanced Marine Engineering and Technology
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• 제9권2호
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• pp.153-158
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• 1985

The dependence of the corrosion potential on the stress corrosion cracking of 304 austenitic stainless steel was inspected by using the specimen of constant displacement type under the environment of 42% $MgCl_2$ boiled solution. The relationship of the corrosion potential to the intermittent propagation behaviour in stress corrosion cracking was cleared. As the results, a possible model of stress corrosion cracking of 304 austenitic stainless steel in $MgCl_2$ boiled solution was presented on the basis of the Film Rupture Model. This model is specified by the following process. Rupturing of passive film at notch tip .rarw. Dissolution of metal ion and formation of tunnel .rarw. Initiation of microcrack .rarw. Propagation of main crack .rarw. Recreation of passive film at new crack surface.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.182-187
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• 2000

The application of fracture mechanics have traditionally concentrated on cracks leaded by tensile stresses, and growing under an opening or mode I mechanism. However, many cases of failures occur from growth of cracks subjected to mixed mode loading. Several criteria have been proposed regarding the crack growth direction under mixed mode loadings. This paper is aimed at prediction of fatigue crack growth behaviour under mixed mode(I+II) in two dimensional branched type precrack. In this paper, the maximum tangential stress(MTS) criterion was used to predict crack growth direction. Not only experiment but also finite element analysis(FEA) was carried out. The theoretical predictions were compared with experimental results in this paper

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.695-700
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• 2008

Artificial neural network (ANN) has been extensively used in areas of nonlinear system modeling, analysis and design applications. Basically, ANN has its distinct capabilities of implementing system identification and/or function approximation using a number of input/output patterns that can be obtained via numerical and/or experimental manners. The paper describes a role of ANN, especially a back-propagation neural network (BPN) in the context of engineering analysis, design and optimization. Fundamental mechanism of BPN is briefly summarized in terms of training procedure and function approximation. The BPN based causality analysis (CA) is further discussed to realize the problem decomposition in the context of multidisciplinary design optimization. Such CA is also applied to quantitatively evaluate the uncoupled or decoupled design matrix in the context of axiomatic design with the independence axiom.