• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2007년도 정기 학술대회 논문집
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• pp.283-288
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• 2007

This paper presents an analytical prediction of Nonlinear characteristics of prestressed concrete bridges by strengthened of externally tendon considering the work sequence, using beam-column element based on flexibility method and tendon element. The beam-column element was developed with reinforced concrete material nonlinearities which are based on the smeared crack concept. The fiber hysteresis rule of beam-column element is derived from the uniaxial constitutive relations of concrete and reinforcing steel fibers. The tendon element represent the bonded tendon and unbonded tendon behaviors. Beam-column element and tendon element was be subroutine A computer program, named RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology), for the analysis of RC and PSC structures was used. The proposed numerical method for prestressed concrete structures by strengthened of externally tendon is verified by comparison with reliable experimental results.

• 대한기계학회논문집A
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• 제20권3호
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• pp.968-977
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• 1996

The linear/nonlinear vibration response of the rotating hybrid cylindrical shell with simply supported boundary condition is studied. The Ritz-Galerkin method is applied to obtain the nonlinear frequency equation, which excludes in-plane and rotatory inertia but includes bending stretching coupling terms. The bifurcation phenomena for the linear frequency and the frequency ratio(nonlinear/linear frequency ratio) are presented. The hybrid cylindrical shells are composed of composite(GFRP, CFRP) metal(aluminium, steel) with symmetric and antisymmetric stacking sequence. The effects of the Coriolis and centrifugal force are considered The results also present the effects of length-to- radies ratio, radius-to-thickness ratio, the circumferential wave number, the stacking sequence, the material property, the initial excitation amplitude and the rotating speed. The present linear frequency results are compared with those of the available literature.

• 한국전자통신학회논문지
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• 제15권1호
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• pp.179-184
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• 2020

랜덤성이 우수한 의사난수열 생성기로 알려진 셀룰라 오토마타(Cellular automata, CA)는 그 응용분야가 매우 다양하다. Cho 등은 긴 주기의 비선형 수열을 생성하기 위하여 CA기반의 수축수열 생성기를 설계하였다. 또한, 카오스 캣맵은 초기 조건에 대한 민감성과 예측 불가능한 특성을 가지는 복잡한 비선형 동역학계로 많은 연구자들에 의하여 연구되어 왔다. 본 논문에서는 높은 보안성을 위하여 최대 주기를 갖는 CA기반의 수축 생성기로 생성한 비선형 수열과 3차원 카오스 캣맵을 이용한 새로운 영상 암호화 방법을 제안한다.

• Journal of Power Electronics
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• 제17권3호
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• pp.716-724
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• 2017

The output voltage of an off-grid inverter is influenced by load current, and the voltage harmonics especially the 5th and 7th are increased with nonlinear loads. In this paper, to attenuate the output voltage harmonics of off-grid inverters with nonlinear loads nearby, a load current feedforward is proposed. It is introduced to a voltage control loop based on the Positive and Negative Sequence Harmonic Regulator (PNSHR) compensation to modify the output impedance at selective frequencies. The parameters of the PNSHR are revised with the output impedance of the off-grid inverter, which minimizes the output impedance of the off-grid inverter. Experimental results verify the proposed method, showing that the output voltage harmonics caused by nonlinear loads can be effectively suppressed.

• 한국전자통신학회논문지
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• 제17권2호
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• pp.357-364
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• 2022

의사난수 생성기(PRNG)는 많은 양의 난수가 필요할 때 사용되는 프로그램이다. 대칭 키 암호시스템에서 대칭 키를 생성, 공개 키 암호나 디지털 서명에서 공개 키 쌍의 생성, 일회용 패드로 패딩에 사용되는 열을 생성하는 데 사용한다. 다양한 과학 분야에서 비선형 동역학계를 구체적으로 표현하는데 유용한 셀룰라 오토마타(CA)는 이산적이고 추상적인 계산 시스템으로 하드웨어 구현이 가능하여 암호시스템에서 키를 생성하는 PRNG로 응용되고 있다. 본 논문에서는 이웃 셀의 반경을 2로 증가한 5-이웃 CA를 이용하여 비선형 수열을 효과적으로 생성할 수 있는 프로그램 가능한 5-이웃 CA기반의 PRNG를 합성하는 알고리즘을 제안한다.

• 한국전자파학회논문지
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• 제15권10호
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• pp.996-1004
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• 2004

1차원 클러스터 기반의 시퀀스 등화기(1-D CBSE)는 시퀀스 등화기(MLSE)가 갖는 계산상의 복잡성을 효율적으로 해결하고 비선형 채널에서의 뛰어난 성능 개선을 가져온다. 본 논문에서는 다중 경로 페이딩 채널 추정에 대응하는 1-D CBSE의 클러스터 중심을 추정하기 위한 향상된 훈련 시퀀스 구성 기법을 제안하였다. 새로이 제안된 등화기는 기존의 방식에서 갖는 문제점을 해결하고, 보다 짧은 길이의 훈련 시퀀스를 이용함으로써 대역폭 효율을 증대시키는 향상된 결과를 가져왔다. 제안된 알고리즘의 우수성은, 기존의 방법과 제안된 최적의 훈련시퀀스를 적용한 1-D클러스터 기반의 새로운 중심 추정을 통한 방법을 비교를 통하여 보였다. 특히, 컴퓨터 시뮬레이션에 의한 심볼 에러율(SER)에 기반을 둔 비교 분석을 통하여 살펴보았다.

• Smart Structures and Systems
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• 제31권2호
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• pp.113-130
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• 2023

Hybrid simulation (HS) has attracted community attention in recent years as an efficient and effective experimental technique for structural performance evaluation in size-limited laboratories. Traditional hybrid simulations usually take deterministic properties for their numerical substructures therefore could not account for inherent uncertainties within the engineering structures to provide probabilistic performance assessment. Reliable structural performance evaluation, therefore, calls for stochastic hybrid simulation (SHS) to explicitly account for substructure uncertainties. The experimental design of SHS is explored in this study to account for uncertainties within analytical substructures. Both computational simulation and laboratory experiments are conducted to evaluate the pseudo-random Sobol sequence for the experimental design of SHS. Meta-modeling through polynomial chaos expansion (PCE) is established from a computational simulation of a nonlinear single-degree-of-freedom (SDOF) structure to evaluate the influence of nonlinear behavior and ground motions uncertainties. A series of hybrid simulations are further conducted in the laboratory to validate the findings from computational analysis. It is shown that the Sobol sequence provides a good starting point for the experimental design of stochastic hybrid simulation. However, nonlinear structural behavior involving stiffness and strength degradation could significantly increase the number of hybrid simulations to acquire accurate statistical estimation for the structural response of interests. Compared with the statistical moments calculated directly from hybrid simulations in the laboratory, the meta-model through PCE gives more accurate estimation, therefore, providing a more effective way for uncertainty quantification.

• 한국자동차공학회논문집
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• 제7권9호
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• pp.119-130
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• 1999

This paper deals buckling behavior of laminated composite cylindrical shells subjected to combination of axial compression and torison. Linear and nonlinear finite element analysis are carried out . the influence of load type, load ratio, fiber orientation angle, stacking sequence, and intial imperfect on buckling behavior is discussed.

• 대한수학회보
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• 제39권2호
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• pp.269-276
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• 2002

Let E be a real Banach space. Let T : E longrightarrow E be a map with F(T) : = { x $\in$ E : Tx = x} $\neq$ 0 and satisfying the accretive-type condition $\lambda\$\mid$x-Tx\$\mid$^2$, for all $x\inE,\;x^*\inf(T)\;and\;\lambda >0$. We prove some necessary and sufficient conditions for the convergence of the Mann iterative sequence to a fixed point of T.

• 대한수학회보
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• 제42권1호
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• pp.17-22
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• 2005

The generalized quasilinearization technique has been employed to obtain a sequence of approximate solutions converging monotonically and rapidly to a solution of the nonlinear Neumann boundary value problem.