• 대한기계학회논문집
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• 제19권4호
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• pp.1051-1061
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• 1995

In order perform leak-before-break design of nuclear piping systems and integrity evaluation of reactor vessels, full stress-strain (.sigma. - .epsilon.) curves and fracture resistance (J-R) curves are required. However it is time-consuming and expensive to obtain J-R curves experimentally. The objective of this paper is to develop two methods for J-R curve prediction. In the first method, elastic-plastic finite element analyses for a series of crack length / specimen width ratio were performed. Accordingly the load versus load line displacement (P .delta.) curve corresponding to the fracture strain is obtained and the J-R curve based on the generalized locus method is obtained. In the second method, the correlation between .sigma.-.epsilon. curves and J-R curves was statistically analyzed and an empirical equation to predict the J-R curve from the .sigma.-.epsilon. test result is proposed. A good correlation between the predicted results based on the proposed methods and the experimental ones is obtained.

• 한국해양공학회지
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• 제7권1호
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• pp.25-32
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• 1993

In composite materials, the fracture perpendicular to the fiber direction usually shows a non-linear behavior accompannying blunting and plastic deformation around the crack tip. In this study, the fracture thoughness in random short fiber SMC composite material and Carbon/Epoxy composite material is estimated by the A.M.(Area Method) and the G.L.M.(Generalized Locus Method) which can determine a stable total energy release rate(G$_T$) not only in highly elghly elastic material but also in highly non-linear materials.

• Journal of Power Electronics
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• 제16권5호
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• pp.1939-1949
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• 2016

This paper presents an alternative frequency adaptive grid synchronization technique named HDN-FLL, which can accurately extract the fundamental positive- and negative-sequence components and interested harmonics in adverse three-phase grid voltage. The HDN-FLL is based on the harmonic decoupling network (HDN) consisting of multiple first order complex vector filters (FOCVF) with a frequency-locked loop (FLL), which makes the system frequency adaptive. The stability of the proposed FLL is strictly verified to be global asymptotically stable. In addition, the linearization and parameters tuning of the FLL is also discussed. The structure of the HDN has been widely used as a prefilter in grid synchronization techniques. However, the stability of the general HDN is seldom discussed. In this paper, the transfer function expression of the general HDN is deduced and its stability is verified by the root locus method. To show the advantages of the HDN-FLL, a simulation comparison with other gird synchronization methods is carried out. Experimental results verify the excellent performance of the proposed synchronization method.

• 대한기계학회논문집
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• 제19권2호
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• pp.391-401
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• 1995

Several tests of the Double Cantilever Beam(DCB) were carried out for influence of the fiber orientation on the Mode I of the interlaminar fracture behavior in the Carbon/Epoxy composites. The interlaminar fracture toughness of Mode I was estimated based on the energy release rate of Mode I, $G_{I}$. The fracture toughness at crack initiation, $G_{IC}$, increases from type A to type E. The fracture toughness, $G_{IR}$ , is almost constant macroscopically for type A and type E when crack propagates. $G_{IR}$ for types B, C, D increases rapidly at the beginning of the crack growth then it decreases gradually. The fracture surface observation by SEM was also obtained the same results. Consequently the influence of the fiber orientation on the Mode I Interlaminar fracture behavior was made clear.ear.

• 한국조리학회지
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• 제18권4호
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• pp.100-117
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• 2012

본 연구의 목적은 일선 호텔직원들의 개인자원으로서 핵심자기평가(자아존중감, 일반화된 자아효능감, 통제위치 및 정서적 안정성), 직무스트레스 요인으로서 고객언어폭력(직무스트레스 요인)과 직무결과로서 이직의도 간의 구조관계를 분석하는 것이었다. 자료는 부산시내에 소재하는 10개의 특급호텔에 근무하는 일선직원들을 표본으로 하여 자기기입식 조사법에 의하여 수집되었다. 총 405부의 설문지가 최종 분석에 이용되었다. 본 연구는 연구모형과 연구가설들을 검증하기 위하여 구조방정식모형분석을 적용하였다. 가설화된 것처럼, 분석결과는 핵심자기평가가 고객언어폭력에 대한 지각과 이직의도를 경감시키는 것을 보여주었다. 고객언어폭력은 이직의도를 증폭시킨다는 결과를 보여주었다. 마지막으로, 실무적 시사점을 논의하였으며, 본 연구의 한계점을 제시하였고 향후 연구방향을 제안하였다.