• 대한기계학회논문집
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• 제13권2호
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• pp.221-228
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• 1989

본 연구에서는 가상균열진전법과 수정 J-적분식을 연계하여 사용할 수 있는 유한요소 프로그램을 개발하고, 이 프로그램을 기존 결과가 있는 2상재료에 적응하여 타당성을 검토한 후, 다상재료의 경우에도 확장하였고, 실제 상변태가 발생하는 중수(heavy water)형 원자로 압력관(pressure tube)의 균열해석에 적용하여 보았다.

• 한국전자파학회논문지
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• 제14권7호
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• pp.769-776
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• 2003

본 논문은 경계적분법과 세그멘테이션 기법을 이용하여 광대역 주파수 및 광 조향각 범위에서 빔조향이 가능한 마이크로스트립 로트만 렌즈의 해석 및 설계를 제안하고 있다. 렌즈 각 포트간의 모든 상호결합과 다중반사 및 선로간 불연속 특성이 해석에 포함되었다. 등간격 포트 설계를 통해 광조향각 범위에서 배열포트의 출력 리플을 억제하는 구조를 구현하였다. 12 입력 12 출력의 각 포트에 지수함수 테이퍼를 적용하여 임피던스 정합 및 포트간 상호결합을 해석하고 최적화하였다. 제작된 렌즈는 측정결과 6~18 GHz의 광대역 주파수 범위와 $\pm$53$^{\circ}$의 조향각 범위에 대해 $\pm$1.8 dB 이하의 삽입손실 편차와 1$^{\circ}$이하의 조향 정확도를 가지며, 해석결과 와도 잘 일치함을 확인하였다.

• 한국전자파학회논문지
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• 제13권5호
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• pp.500-506
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• 2002

본 논문에서는 광대역 주파수 범위에서 동작하며 광각 빔 조향이 가능하고 반복 제작이 용이한 간단한 구조의 전자전장비용 소형 마이크로스트립 로트만 렌즈를 제안하였다. 렌즈를 2차원의 평행판 회로로 모델링한 후 둘레 전체에 대해 경계적분을 수행하고 8개의 빔포트와 8개의 배열포트 간 전달계수를 구하였으며, 제작된 렌즈의 회로망 측정결과와 잘 일치하는 결과를 얻었다. 선형배열안테나로 급전된 다중빔 패턴을 예측하여 제작렌즈가 3:1의 주파수 대역에 걸쳐 $\pm$65$^{\circ}$ 이상의 광각 빔 스캔과 $\pm$5 dB 이하의 삽입손실 편차를 가짐을 확인하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.729-732
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• 2003

The K-R design curve is an engineering method of linear-elastic fracture analysis under plane-stress loading conditions. By the way, linear-elastic fracture mechanics (LEFM) is valid only as long as nonlinear material deformation is confined to a small region surrounding the crack tip. Like general steels, it is virtually impossible to characterize the fracture behavior with LEFM, in many materials. Critical values of J contour integral or crack tip opening displacement (CTOD) give nearly size independent measures of fracture toughness, even for relatively large amounts of crack tip plasticity. Furthermore, the crack tip opening displacement is the only parameter that can be directly measured in the fracture test. On the other. the crack tip opening angle (CTOA) test is similar to CTOD experimentally. Moreover, the test is easier to measure the fracture toughness than other method. The shape of the CTOA curve depends on material fracture behavior and, on the opening configuration of the cracked structure. CTOA parameter describes crack tip conditions in elastic-plastic materials, and it can be used as a fracture criterion effectively. In this paper, CTOA test is performed for steel JS-SS400 hot-rolled thin plates under plane-stress loading conditions. Special experimental apparatuses are used to prevent specimens from buckling and to measure crack tip opening angle for thin compact tension (CT) specimens.

• 대한수학회논문집
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• 제28권4호
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• pp.783-797
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• 2013

Recently, Liu et al. [Bilateral generating functions for the Chan-Chyan-Srivastava polynomials and the generalized Lauricella function, Integral Transform Spec. Funct. 23 (2012), no. 7, 539-549] investigated, in several interesting papers, some various families of bilateral generating functions involving the Chan-Chyan-Srivastava polynomials. The aim of this present paper is to obtain some bilateral generating functions involving the Chan-Chyan-Sriavastava polynomials and three general classes of multivariable polynomials introduced earlier by Srivastava in [A contour integral involving Fox's H-function, Indian J. Math. 14 (1972), 1-6], [A multilinear generating function for the Konhauser sets of biorthogonal polynomials suggested by the Laguerre polynomials, Pacific J. Math. 117 (1985), 183-191] and by Kaano$\breve{g}$lu and $\ddot{O}$zarslan in [Two-sided generating functions for certain class of r-variable polynomials, Mathematical and Computer Modelling 54 (2011), 625-631]. Special cases involving the (Srivastava-Daoust) generalized Lauricella functions are also given.

• 한국방재안전학회논문집
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• 제6권3호
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• pp.1-8
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• 2013

시간과 공간에 따라 변화하는 난류성분의 변동풍하중을 받는 고층건물의 경량화 및 연성화 현상은 고유진동수와 감쇠비를 적게함으로서 동적으로 매우 불리한 진동문제을 발생하게 되어, 변동풍하중을 받는 도심의 고층건물에 대한 동적해석의 중요성이 인식되고 있다. 본 논문에서는 돌풍과 같이 짧은 시간동안에 통계적 성질이 변화하는 변동풍하중을 나타내기 위하여 정상불규칙 풍하중에 시간에 따라 변화하는 결정적함수(A(t) = 1-exp($-{\beta}t$))를 곱하여 나타냈고, 이러한 변동풍하중을 받는 고층건물에 대한 평균류방향의 동적변위응답해석은 진동이론으로부터 Time-dependent Response Spectral Density함수를 나타냈고, 진동함수를 포함하여 나타내는 Time-dependent Response Spectral Density의 진동수영역에 대한 적분의 해로부터 동적응답을 해석적으로 구하기 위하여 Contour적분에서 Cauchy의 적분정리와 잔유치 정리(residue theorem)에 의한 잔유치 적분으로부터 해석함수를 구했다. 해석 예에서 본 논문에서 구한 해석함수와 기존의 수치해석방법에 따른 결과를 비교 검토했고, 고층건물의 동적 특성에 따른 해석결과도 비교 검토했다.

• 대한기계학회논문집A
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• 제27권11호
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• pp.1986-1996
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• 2003

Methodology based on the elastic-plastic fracture mechanics has been widely accepted in predicting the critical crack length(CCL) of pressure tubes of CANDU nuclear plants. A conservative estimate of CCL is obtained by employing the J-resistance curves measured with the specimens satisfying plane strain condition as suggested in the ASTM standard. Due to limited thickness of the pressure tubes the curved compact tension(CT) specimens taken out from tile pressure tube have been used in obtaining J-resistance curves. The curved CT specimen inevitably introduce slant fatigue crack during precracking. Hence, effect of specimen geometry and slant crack on J-resistance curve should be explored. In this study, the difference of J integral values between the standard CT specimens satisfying plane strain condition and the nonstandard curved CT with limited thickness (4.2mm) is estimated using finite element analysis. The fracture resistance curves of Zr-2.5Nb obtained previously by other authors are critically discussed. Various finite element analysis were conducted such as 2D analysis under plane stress and plane strain conditions and 3D analysis for flat CT, curved CT with straight crack and curved CT with slant crack front. J-integral values were determined by local contour integration near the crack tip, which was considered as accurate J-values. J value was also determined from the load versus load line displacement curve and the J estimation equation in the ASTM standard. Discrepancies between the two values were shown and suggestion was made for obtaining accurate J values from the load line displacement curves obtained by the curved CT specimens.

• Smart Structures and Systems
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• 제20권3호
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• pp.263-272
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• 2017

This paper presents the time response of a mixed vibration system with the viscous damping and the hysteretic damping. There are two ways to derive the time response of such a vibration system. One is an analytical method, using the contour integral of complex functions to compute the inverse Fourier transforms. The other is an approximate method in which the analytic functions derived by Hilbert transform are expressed in the state space representation, and only the effective eigenvalues are used to efficiently compute the transient response. The unit impulse responses of the two methods are compared and the change in the damping properties which depend on the viscous and hysteretic damping values is investigated. The results showed that the damping properties of a mixed damping vibration system do not present themselves as a linear combination of damping properties.

• 대한기계학회논문집
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• 제7권4호
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• pp.361-371
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• 1983

The turbulent structures of the free plane jet and two dimensional impinging jet are investigated experimentally. In order to get the two dimensional jet, the contour of the cubic equation suggested by Morel is used for a contracting nozzle. A linearized constant-temperature hot-wire anemometer is used for measurement. Mean velocities and turbulent intensities are measured along the centerline of the jet. Jet halp width spatial double velocity correlation coefficients and integral length scales are obtained. It is established that the free plane jet is truly self-preserving about 40 slot widths downstream of the nozzle. The experiments for the impinging jet are carried out at four different impingement wall locations within the self-preserving region of the free plane jet, and comparing the results with that of free plane jet, the mean velocity is changed in the region of 0.25H and turbulent intensities are affected in the region of 0.2H from the wall, respectively, where H means the distance between the nozzle exit and the wall.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1664-1665
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• 2011

This paper presents a derivation of the capacitance of a shielded microstrip line using the Finite Element Method (FEM). The first approach adopts a 2-D version of Gauss's theorem and an approximation of integral to finite differencing. In this case, the choice of a contour and the size of a mesh affects the validity of the capacitance. Next, the method for deriving the capacitance by using of energy relation is shown. Finally, the simulation results are compared to those of the commercial tool (COMSOL) adopted FEM.