• 제목/요약/키워드: nonlinear scaling

검색결과 122건 처리시간 0.027초

균일한 외압을 받는 원환보강 원통구조의 비선형 좌굴 특성 (Nonlinear Buckling Characteristics of Ring-stiffened Circular Cylinders under Uniform External Pressure)

  • 안당;김수영;신성철;정보영;구윤회
    • 한국해양공학회지
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    • 제26권2호
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    • pp.79-84
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    • 2012
  • This study aimed to analyze the nonlinear buckling of ring-stiffened circular cylinders under uniform external pressure, e.g. hydrostatic pressure, considering material nonlinearity and initial imperfection. In the present study, we analyzed the collapse pressure of pressure vessels using ANSYS Workbench, which is a framework of finite element methods. First, linear buckling analysis is performed to find collapse modes of the model. Second, scaling the first mode shape with small factor, geometric model is pre-deformed. And then, by analyzing the nonlinear buckling of the pre-deformed shape, the collapse pressure is estimated. To verify the validity of the analyses, we compared the results with Ross' experimental results. Finally, we applied it to ring-stiffened circular cylindrical shell of the pressure hull of a small submarine.

MINIMIZATION OF EXTENDED QUADRATIC FUNCTIONS WITH INEXACT LINE SEARCHES

  • Moghrabi, Issam A.R.
    • Journal of the Korean Society for Industrial and Applied Mathematics
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    • 제9권1호
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    • pp.55-61
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    • 2005
  • A Conjugate Gradient algorithm for unconstrained minimization is proposed which is invariant to a nonlinear scaling of a strictly convex quadratic function and which generates mutually conjugate directions for extended quadratic functions. It is derived for inexact line searches and for general functions. It compares favourably in numerical tests (over eight test functions and dimensionality up to 1000) with the Dixon (1975) algorithm on which this new algorithm is based.

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혼합 유전알고리즘을 이용한 비선형 최적화문제의 효율적 해법

  • 윤영수;이상용
    • 한국산업정보학회논문지
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    • 제1권1호
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    • pp.63-85
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    • 1996
  • This paper describes the applications of genetic algorithm to nonlinear constrained optimization problems. Genetic algorithms are combinatorial in nature, and therefore are computationally suitable for treating continuous and idstrete integer design variables. For several problems , the conventional genetic algorithms are ill-defined , which comes from the application of penalty function , encoding and decoding methods, fitness scaling, and premature convergence of solution. Thus, we develope a hybrid genetic algorithm to resolve these problems and present two examples to demonstrate the effectiveness of the methodology developed in this paper.

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시스템 식별을 위한 웨이브릿 이론 연구 (A Study of Wavelet Theory for System Identifications)

  • 김동옥;이영석;권재철;서보혁
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 1998년도 하계학술대회 논문집 B
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    • pp.635-637
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    • 1998
  • Based on wavelet theory, the new notion of wavelet networks is proposed as alternative to feedforward neural networks for approximating arbitrary nonlinear functions. An algorithm presented in this paper trains coefficients of wavelet. i.e., translations and scaling., and then learns weights with the wavelet coefficients. And experimental results are reported.

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Joint stress based deflection limits for transmission line towers

  • Gayathri, B.;Ramalingam, Raghavan
    • Steel and Composite Structures
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    • 제26권1호
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    • pp.45-53
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    • 2018
  • Experimental investigations have revealed significant mismatches between analytical estimates and experimentally measured deflections of transmission towers. These are attributed to bolt slip and joint flexibility. This study focuses on effects of joint flexibility on tower deflections and proposes criterions for permissible deflection limits based on the stresses in joints. The objective has been framed given that guidelines are not available in the codes of practices for transmission towers with regard to the permissible limits of deflection. The analysis procedure is geometric and material nonlinear with consideration of joint flexibility in the form of extension or contraction of the cover plates. The deflections due to bolt slip are included in the study by scaling up the deflections obtained from analysis by a factor. Using the results of the analysis, deflection limits for the towers are proposed by limiting the stresses in the joints. The obtained limits are then applied to a new full scale tower to demonstrate the application of the current study.

극치자료계열의 Scaling 특성과 Bayesian GLM Model을 이용한 지역빈도해석 (A Bayesian GLM Model Based Regional Frequency Analysis Using Scaling Properties of Extreme Rainfalls)

  • 김진영;권현한;이병석
    • 대한토목학회논문집
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    • 제37권1호
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    • pp.29-41
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    • 2017
  • 확률강수량 산정은 하천관리, 수공구조물 설계 및 위험도 분석에 있어 중요한 기초적인 자료 중 하나이다. 실무에서는 대표지속시간에 대해서 지점빈도해석을 통해 확률강수량을 추정하고 이를 지속시간에 대해서 회귀분석을 실시하여 IDF (intensity-duration-frequency) 곡선을 작성한다. 이들 IDF곡선을 활용하여 기타 지속시간에 대해서는 내삽 또는 외삽으로 보간 하여 확률강수량 추정이 이루어지고 있다. 우리나라의 경우 상대적으로 자료 연한이 짧은 점을 고려한다면, 보다 정확하고 신뢰성 있는 확률강수량 산정 기법의 필요성이 대두되고 있다. 이러한 이유로 본 연구에서는 Bayesian GLM 모형을 통하여 자료의 확률분포 매개변수의 Scaling 특성을 고려할 수 있는 지역빈도해석 모형을 개발하였다. 모형 적용결과 개별지점에서 효과적인 매개변수 추정뿐만 아니라, 유역전체의 특성을 대표하는 매개변수 추정이 가능하였다. 본 연구결과를 통해 도출된 IDF 곡선은 향후 다양한 수자원분야의 기초자료로 활용될 수 있을 것으로 기대되며, 미계측유역 또는 지속시간별 자료가 불충분한 지역에 대해서도 활용이 가능할 것으로 판단된다.

Ultrasonic waves in a single walled armchair carbon nanotube resting on nonlinear foundation subjected to thermal and in plane magnetic fields

  • Selvamani, Rajendran;Jayan, M. Mahaveer Sree;Ebrahimi, Farzad
    • Coupled systems mechanics
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    • 제10권1호
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    • pp.39-60
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    • 2021
  • The present paper is concerned with the study of nonlinear ultrasonic waves in a magneto thermo (MT) elastic armchair single-walled carbon nanotube (ASWCNT) resting on polymer matrix. The analytical formulation is developed based on Eringen's nonlocal elasticity theory to account small scale effect. After developing the formal solution of the mathematical model consisting of partial differential equations, the frequency equations have been analyzed numerically by using the nonlinear foundations supported by Winkler-Pasternak model. The solution is obtained by ultrasonic wave dispersion relations. Parametric work is carried out to scrutinize the influence of the non local scaling, magneto-mechanical loadings, foundation parameters, various boundary condition and length on the dimensionless frequency of nanotube. It is noticed that the boundary conditions, nonlocal parameter, and tube geometrical parameters have significant effects on dimensionless frequency of nano tubes. The results presented in this study can provide mechanism for the study and design of the nano devices like component of nano oscillators, micro wave absorbing, nano-electron technology and nano-electro- magneto-mechanical systems (NEMMS) that make use of the wave propagation properties of armchair single-walled carbon nanotubes embedded on polymer matrix.

SEMICLASSICAL ASYMPTOTICS OF INFINITELY MANY SOLUTIONS FOR THE INFINITE CASE OF A NONLINEAR SCHRÖDINGER EQUATION WITH CRITICAL FREQUENCY

  • Aguas-Barreno, Ariel;Cevallos-Chavez, Jordy;Mayorga-Zambrano, Juan;Medina-Espinosa, Leonardo
    • 대한수학회보
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    • 제59권1호
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    • pp.241-263
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    • 2022
  • We consider a nonlinear Schrödinger equation with critical frequency, (P𝜀) : 𝜀2∆v(x) - V(x)v(x) + |v(x)|p-1v(x) = 0, x ∈ ℝN, and v(x) → 0 as |x| → +∞, for the infinite case as described by Byeon and Wang. Critical means that 0 ≤ V ∈ C(ℝN) verifies Ƶ = {V = 0} ≠ ∅. Infinite means that Ƶ = {x0} and that, grossly speaking, the potential V decays at an exponential rate as x → x0. For the semiclassical limit, 𝜀 → 0, the infinite case has a characteristic limit problem, (Pinf) : ∆u(x)-P(x)u(x) + |u(x)|p-1u(x) = 0, x ∈ Ω, with u(x) = 0 as x ∈ Ω, where Ω ⊆ ℝN is a smooth bounded strictly star-shaped region related to the potential V. We prove the existence of an infinite number of solutions for both the original and the limit problem via a Ljusternik-Schnirelman scheme for even functionals. Fixed a topological level k we show that vk,𝜀, a solution of (P𝜀), subconverges, up to a scaling, to a corresponding solution of (Pinf ), and that vk,𝜀 exponentially decays out of Ω. Finally, uniform estimates on ∂Ω for scaled solutions of (P𝜀) are obtained.

준정적 충돌해석을 통한 선박충돌방공호의 방호능력평가 (A Protection Capacity Evaluation of Vessel Protective Structures by Quasi-Static Collision Analysis)

  • 이계희
    • 한국전산구조공학회논문집
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    • 제24권6호
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    • pp.691-697
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    • 2011
  • 본 연구에서는 방호공의 최대방호능력을 산정하기 위하여 선박충돌방호공과 선박을 수치적으로 모델링하고 준정적해석으로 충돌해석을 수행하였다. 방호공은 구조물의 비선형 거동과 지반의 지지효과 및 인발을 고려하여 모델링되었다. 충돌선박은 비선형거동이 집중되는 선수부분을 정밀하게 모델링하고 효율적인 해석을 위해 mass scaling기법을 사용하였다. 동일한 해석모델에 대하여 동적해석을 추가적으로 수행하여 두 해석방법의 차이점과 효율성을 평가하였다. 선박과 방호공의 에너지소산곡선을 바탕으로 충돌선박이 교량하부구조에 충돌력을 전달되는 시점을 추정하고, 이를 바탕으로 대상선박의 최대충돌허용속도를 산정하였다. 이러한 추정방법이 방호공의 에너지소산한계를 명확히 판단할 수 있어 공학적으로 효율적인 산정방법임을 보였다.

Comparison of different post-processing techniques in real-time forecast skill improvement

  • Jabbari, Aida;Bae, Deg-Hyo
    • 한국수자원학회:학술대회논문집
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    • 한국수자원학회 2018년도 학술발표회
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    • pp.150-150
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    • 2018
  • The Numerical Weather Prediction (NWP) models provide information for weather forecasts. The highly nonlinear and complex interactions in the atmosphere are simplified in meteorological models through approximations and parameterization. Therefore, the simplifications may lead to biases and errors in model results. Although the models have improved over time, the biased outputs of these models are still a matter of concern in meteorological and hydrological studies. Thus, bias removal is an essential step prior to using outputs of atmospheric models. The main idea of statistical bias correction methods is to develop a statistical relationship between modeled and observed variables over the same historical period. The Model Output Statistics (MOS) would be desirable to better match the real time forecast data with observation records. Statistical post-processing methods relate model outputs to the observed values at the sites of interest. In this study three methods are used to remove the possible biases of the real-time outputs of the Weather Research and Forecast (WRF) model in Imjin basin (North and South Korea). The post-processing techniques include the Linear Regression (LR), Linear Scaling (LS) and Power Scaling (PS) methods. The MOS techniques used in this study include three main steps: preprocessing of the historical data in training set, development of the equations, and application of the equations for the validation set. The expected results show the accuracy improvement of the real-time forecast data before and after bias correction. The comparison of the different methods will clarify the best method for the purpose of the forecast skill enhancement in a real-time case study.

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