• International Journal of CAD/CAM
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• 제6권1호
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• pp.29-40
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• 2006

The paper presents an optimization system which integrates a parametric design tool, 3D diffraction-radiation analysis and hydrodynamic performance assessment based on short and long term wave statistics. Controlled by formal optimization strategies the system is able to design offshore structure hulls with superior seakeeping qualities. The parametric modeling tool enables the designer to specify the geometric characteristics of the design from displacement over principal dimensions down to local shape properties. The computer generates the hull form and passes it on to the hydrodynamic analysis, which computes response amplitude operators (RAOs) for forces and motions. Combining the RAOs with short and long-term wave statistics provides a realistic assessment of the quality of the design. The optimization algorithm changes selected shape parameters in order to minimize forces and motions, thus increasing availability and safety of the system. Constraints ensure that only feasible designs with sufficient stability in operation and survival condition are generated. As an example the optimization study of a semisubmersible is discussed. It illustrates how offshore structures can be optimized for a specific target area of operation.

• 품질경영학회지
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• 제22권4호
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• pp.59-78
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• 1994

In some observational studies, we have often random censoring model. However, the data available may be partially observable censored data consisting of the observed failure times and only those nonfailure times which are subject to follow up. In this paper, we present an extension of the problem of partially parametric estimation of the survival function to such partially observable censored data. The proposed estimator treats the observed failure times nonparametrically and uses a parametric model only for those nonfailure times which are subject to follow-up. We discuss the motivation and construction of the proposed estimator and investigate the limiting properties of the proposed estimator such as asymptotic normality. Also, when the assumed parametric model is exponential, the asymptotic variance of the estimator is obtained. Furthermore, an example is given to compare the proposed estimator with the modified Kaplan Meier(MKM) estimator. From the results, it is shown that the relative efficiency of the proposed estimator is higher than that of the MKM estimator in the follow-up study with increasing time.

• International Journal of Costume and Fashion
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• 제15권2호
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• pp.63-77
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• 2015

By means of statistical analysis and module concept, this paper investigated the current situation of high school girl's uniform and put forward its improved design and database establishment. Combined with the survey data, the future design direction and trend of the high school girls' uniform were proposed. By using modular design concept, the uniform is divided into five modules, and a style database has been built. Meanwhile, the parametric pattern database has been completed by using garment CAD system, based on the style database above, which has 42,336 possibilities to assemble a pair of school uniform. Combining with digital sewing techniques and by using computerized embroidery machine, the personalized design of high school girl's summer uniform has been realized. And two simulated case have been given for examples to prove its feasibility. The idea of modular design and parametric design method proposed in this study offer references for establishing the modular design database and parametric pattern database for other types of school uniform and are of relatively high practical and theoretical value.

• 한국생산제조학회지
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• 제24권1호
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• pp.110-116
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• 2015

This study investigates the whirling stability of a rotating shaft-disk system under parametric excitation using periodically varying torque. The equations of motion were derived using a lumped-mass model, and the Floquet method was employed to find the effects of torque fluctuation, internal and external damping, and rotational speed on whirling stability. Results indicated that the effect of torque fluctuation was considerable on the instability around resonance, but minimal on supercritical instability. Stability diagrams were sensitive to the parametric excitation frequency; critical torque decreased upon increasing excitation frequency, with faster response convergence or divergence. In addition, internal and external damping had a considerable effect on unstable regions, and reduced the effects of the parametric excitation frequency on critical torque and speed. Results obtained from the Floquet approach were in good agreement with those obtained by numerical integration, except for some cases with Floquet multipliers very close to unity.

• 대한수의학회지
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• 제47권2호
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• pp.259-263
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• 2007

The choice of input distribution in quantitative risk assessments modeling is of great importance to get unbiased overall estimates, although it is difficult to characterize them in situations where data available are too sparse or small. The present study is particularly concerned with accommodation of uncertainties commonly encountered in the practice of modeling. The authors applied parametric and non-parametric bootstrap simulation methods which consist of re-sampling with replacement, in together with the classical Student-t statistics based on the normal distribution. The implications of these methods were demonstrated through an empirical analysis of trade volume from the amount of chicken and pork meat imported to Korea during the period of 1998-2005. The results of bootstrap method were comparable to the classical techniques, indicating that bootstrap can be an alternative approach in a specific context of trade volume. We also illustrated on what extent the bias corrected and accelerated non-parametric bootstrap method produces different estimate of interest, as compared by non-parametric bootstrap method.

• Journal of the Korean Data and Information Science Society
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• 제27권5호
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• pp.1389-1397
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• 2016

Semi-parametric frailty model with nonparametric baseline hazards has been widely used for the analyses of clustered survival-time data. The frailty models can be fitted via an auxiliary Poisson hierarchical generalized linear model (HGLM). For the inferences of the frailty model marginal likelihood, which gives MLE, is often used. The marginal likelihood is usually obtained by integrating out random effects, but it often requires an intractable integration. In this paper, we propose to obtain the MLE via Laplace approximation using a Poisson HGLM approach for semi-parametric frailty model. The proposed HGLM approach uses hierarchical-likelihood (h-likelihood), which avoids integration itself. The proposed method is illustrated using a numerical study.

• Structural Engineering and Mechanics
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• 제40권5호
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• pp.705-718
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• 2011

The aim of the investigation described in this paper is to study the nonlinear parametric vibrations and stability of a simply-supported viscoelastic beam with an intra-span spring. Taking into account a time-dependent tension inside the beam as the main source of parametric excitations, as well as employing a two-parameter rheological model, the equations of motion are derived using Newton's second law of motion. These equations are then solved via a perturbation technique which yields approximate analytical expressions for the frequency-response curves. Regarding the main parametric resonance case, the local stability of limit cycles is analyzed. Moreover, some numerical examples are provided in the last section.

• 한국조명전기설비학회지:조명전기설비
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• 제7권1호
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• pp.37-45
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• 1993

파라메트릭 발전을 이용한 전력변환장치로서, 파라메트릭 변압기의 동작원리를 설명한다. 이 기기의 수학적인 모델을 유도하여 기기의 출력측에 발진이 발생하는 영역을 구하고, 이 영역내에서의 각 특성을 시뮬레이션에 의해 살펴봄으로서 정성적 및 정량적 해석을 시도하였다. 그밖에도 기기가 주파수변환기나 연파기로서 동작함도 보여준다.

• 한국자동차공학회논문집
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• 제24권5호
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• pp.612-617
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• 2016

A motorcycle frame is a structure that endures the load and retains durability under various driving environments. A motorcycle has been developed with a diverse utility range, and its design has always been expanded to the newly created concept based on advanced engineering technologies. In this study, a compact motorcycle frame is considered to perform parametric studies that can enhance the stiffness of a frame with computational simulation. Finite element analysis is used to compare the deformation and stiffness of a base model and four case-models with three design-change-parameters. The parametric studies are analyzed to provide available methods that can be expected in the industrial fields of engineering design for a motorcycle frame.

• 응용통계연구
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• 제27권3호
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• pp.461-473
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• 2014

꼬리가 두꺼운 분포의 고분위수에 대한 신뢰구간을 연구하였다. 통계량의 극한 분포에 근거한 점근적 방법과 붓스트랩 방법을 같이 고려하였다. 이 두 방법에 모수적, 비모수적, 준모수적 기법을 각각 적용할 수 있는데, 전체 11가지 신뢰구간의 성능을 실제신뢰수준과 길이로 비교하였다. 모의실험 결과 준모수적이면서 점근적인 신뢰구간과 축량을 이용하는 준모수적 붓스트랩 신뢰구간이 실제신뢰수준의 기준에서 안정된 성능을 보인다는 것을 알 수 있었다.