• Title, Summary, Keyword: parametric study

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FE Model Based Parametric Study Support System

  • Jang, Beom-Seon
    • Journal of Ship and Ocean Technology
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    • v.12 no.4
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    • pp.7-19
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    • 2008
  • In preliminary ship design, a parametric study is a more realistic way to explore design space and analyze design problem than an optimization technique due to time-consuming computational work or a difficulty in incorporating all constraints into the optimization formulation. In the parametric study, feasible alternatives are examined in various aspects; the best one can be selected. Among the aspects, the strength assessment by FE analysis is an essential process in the ship design. This paper proposes a system to facilitate a parametric study for FE model based on design of experiment (DOE). It works on a FE pre-processor environment and assists a user to define a parametric study by interacting with FE model. It also provides an interface module with a FE solver in order to control the input file and extract predefined FE results from the output file. Based on the proposed system, a better understating and a better design are expected to be achieved.

A parametric study on fatigue of a top-tensioned riser subjected to vortex-induced vibrations

  • Kim, Do Kyun;Wong, Eileen Wee Chin;Lekkala, Mala Konda Reddy
    • Structural Monitoring and Maintenance
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    • v.6 no.4
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    • pp.365-387
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    • 2019
  • This study aims to provide useful information on the fatigue assessment of a top-tensioned riser (TTR) subjected to vortex-induced vibration (VIV) by performing parametric study. The effects of principal design parameters, i.e., riser diameter, wall thickness, water depth (related to riser length), top tension, current velocity, and shear rate (or shear profile of current) are investigated. To prepare the base model of TTR for parametric studies, three (3) riser modelling techniques in the OrcaFlex were investigated and validated against a reference model by Knardahl (2012). The selected riser model was used to perform parametric studies to investigate the effects of design parameters on the VIV fatigue damage of TTR. From the obtained comparison results of VIV analysis, it was demonstrated that a model with a single line model ending at the lower flex joint (LFJ) and pinned connection with finite rotation stiffness to simulate the LFJ properties at the bottom end of the line model produced acceptable prediction. Moreover, it was suitable for VIV analysis purposes. Findings from parametric studies showed that VIV fatigue damage increased with increasing current velocity, riser outer diameter and water depth, and decreased with increasing shear rate and top tension of riser. With regard to the effects of wall thickness, it was not significant to VIV fatigue damage of TTR. The detailed outcomes were documented with parametric study results.

Parametric Body Model Generation for Garment Drape Simulation

  • Kim, Sungmin;Park, Chang-Kyu
    • Fibers and Polymers
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    • v.5 no.1
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    • pp.12-18
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    • 2004
  • A parametric body model generation system has been developed. Using various mathematic and geometric algorithms of this system, a three-dimensionally scanned human body can be converted into a resizable body model. Once a parametric body model is formed, its size and shape can be modified instantaneously by providing appropriate anthropometric data. To facilitate the subsequent pattern arrangement process for garment drape simulation, a bounding box generation algorithm has been developed in this study. Also the model can be converted into a set of parametric surfaces that it can also be used for three-dimensional garment pattern design system.

Study on Numerical Sensitivity and Uncertainty in the Analysis of Parametric Roll (파라메트릭 횡동요 수치해석의 민감도 및 불확실성에 대한 연구)

  • Park, Dong-Min;Kim, Tae-Young;Kim, Yong-Hwan
    • Journal of the Society of Naval Architects of Korea
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    • v.49 no.1
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    • pp.60-67
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    • 2012
  • This study considers the numerical analysis on parametric roll for container ships. As a method of numerical simulation, an impulse-response-function approach is applied in time domain. A systematic study is carried out for the parametric roll of two container ships, particularly observing the sensitivity of computational results to some parameters which can affect the analysis of parametric roll. The parameters to be considered are metacentric height (GM), simulation time window, and the discretization of wave spectrum. Based on the result of parametric roll simulation, numerical sensitivity and uncertainty in computational analysis are discussed.

Parametric pitch instability investigation of Deep Draft Semi-submersible platform in irregular waves

  • Mao, Huan;Yang, Hezhen
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.8 no.1
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    • pp.13-21
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    • 2016
  • Parametric pitch instability of a Deep Draft Semi-submersible platform (DDS) is investigated in irregular waves. Parametric pitch is a form of parametric instability, which occurs when parameters of a system vary with time and the variation satisfies a certain condition. In previous studies, analyzing of parametric instability is mainly limited to regular waves, whereas the realistic sea conditions are irregular waves. Besides, parametric instability also occurs in irregular waves in some experiments. This study predicts parametric pitch of a Deep Draft Semi-submersible platform in irregular waves. Heave motion of DDS is simulated by wave spectrum and response amplitude operator (RAO). Then Hill equation for DDS pitch motion in irregular waves is derived based on linear-wave theory. By using Bubnov-Galerkin approach to solve Hill equation, the corresponding stability chart is obtained. The differences between regular-waves stability chart and irregular-waves stability chart are compared. Then the sensitivity of wave parameters on DDS parametric pitch in irregular waves is discussed. Based on the discussion, some suggestions for the DDS design are proposed to avoid parametric pitch by choosing appropriate parameters. The results indicate that it's important and necessary to predict DDS parametric pitch in irregular waves during design process.

Free vibration of symmetrically laminated quasi-isotropic super-elliptical thin plates

  • Altunsaray, Erkin
    • Steel and Composite Structures
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    • v.29 no.4
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    • pp.493-508
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    • 2018
  • Free vibration analysis of super-elliptical composite thin plates was investigated. Plate is formed by symmetrical quasi-isotropic laminates. Rayleigh-Ritz method was used for parametric analysis based on the governing differential equations of Classical Laminated Plate Theory (CLPT). Simply supported and clamped boundary conditions at the periphery of plates were considered. Parametric study was performed for the effect of different lamination type, aspect ratio, thickness and super-elliptical power on natural frequencies. Convergence study and validation of isotropic case were achieved. A number of design parameters like different dimensions, structure systems, panel sizes, panel thicknesses, lamination sequences, boundary conditions and loading conditions must be considered in the production of composite ships. The number of possible combinations practically may be so high that a parametric study should be carried out in order to determine the optimum design parameters rapidly during the preliminary design stage. The use of Rayleigh-Ritz method could make this parametric study possible. Thereby it might be decreasing the consumption of time, material and labor. Certain results for some different super-elliptical powers presented in tabulated form in Appendix for designers as well.

A Study on the Effects of Exitation Voltage Waveforms on the Performances of Parametric Transformer (여자전압의 파형에 따른 Parametric Transformer의 특성)

  • Woo, Jung-In;Jung, Kee-Wha
    • Proceedings of the KIEE Conference
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    • pp.706-709
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    • 1992
  • This paper deals with the operation of a parametric transformer through the normalization of system equations. Based on these equations, the effects of excitation voltage waveforms on the performances of the parametric transformer are analyzed.

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Directional Characteristics of Parametric Loudspeakers in Near-field (파라메트릭 스피커의 근접음장 방향성 특성연구)

  • Ju, Hyeong-Sick;Kim, Yang-Hann
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.545-550
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    • 2005
  • A parametric loudspeaker is a device to generate highly directional sound using ultrasounds. The parametric loudspeaker could be used to focus sound in a limited space, so it is important to study the characteristics of the parametric loudspeaker in near-field. Mechanism of the audible sound generation in the parametric loudspeaker is explained by nonlinear interaction of the ultrasounds and is modeled as KZK equation, the nonlinear wave equation which contains attenuation, nonlinearity and diffraction. To measure the directional characteristics of the parametric loudspeaker precisely, a method to reduce the spurious signal which taints the measured signal was invented. With the method, directivity patterns of the parametric loudspeaker were measured and compared to the approximated solution and piston sources.

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Parametric Empirical Bayes Estimators with Item-Censored Data

  • Choi, Dal-Woo
    • Journal of the Korean Data and Information Science Society
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    • v.8 no.2
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    • pp.261-270
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    • 1997
  • This paper is proposed the parametric empirical Bayes(EB) confidence intervals which corrects the deficiencies in the naive EB confidence intervals of the scale parameter in the Weibull distribution under item-censoring scheme. In this case, the bootstrap EB confidence intervals are obtained by the parametric bootstrap introduced by Laird and Louis(1987). The comparisons among the bootstrap and the naive EB confidence intervals through Monte Carlo study are also presented.

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Study on novel hierarchical parametric stereo coding method for Multichannel audio signal (멀티채널 오디오 신호의 계층적 코딩이 가능한 파라메트릭 스테레오 코딩 방법에 대한 연구)

  • Moon, Han-Gil
    • Proceedings of the IEEK Conference
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    • pp.875-876
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    • 2008
  • Parametric stereo coding is a technique to efficiently code a stereo audio signal as a monaural signal plus small amount of parametric overhead to describe the stereo image. The stereo properties are analyzed, encoded, and reinstated in a decoder according to spatial psycho-acoustical principles. However, coding of multichannel audio signal using parametric stereo still requires considerable bit-rate. In this paper, enhanced parametric stereo coding for multichannel audio signal is proposed.

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