• 대한조선학회논문집
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• 제52권3호
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• pp.187-197
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• 2015

This study aims the development of a semi-analytic method for the parametric roll of large containerships advancing in longitudinal waves. A 1.5 Degree-of-Freedom(DOF) model is proposed to account the change of transverse stability induced by wave elevations and vertical motions (heave and pitch). By approximating the nonlinearity of restoring moment at large heel angles, the magnitude of roll amplitude is predicted as well as susceptibility check for parametric roll occurrence. In order to increase the accuracy of the prediction, the relationship between righting arm(GZ) and metacentric height(GM) is examined in the presence of incident waves, and then a new formula is proposed. Based on the linear approximation of the mean and first harmonic component of GM, the equation of parametric roll in irregular wave excitations is introduced, and the computational results of the proposed model are validated by comparing those of weakly nonlinear simulation based on an impulse-response-function method combined with strip theory. The present semi-analytic doesn’ t require heavy computational effort, so that it is very efficient particularly when numerous sea conditions for the analysis of parametric roll should be considered.

• Communications for Statistical Applications and Methods
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• 제26권5호
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• pp.519-526
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• 2019

Response dimension reduction in a sufficient dimension reduction (SDR) context has been widely ignored until Yoo and Cook (Computational Statistics and Data Analysis, 53, 334-343, 2008) founded theories for it and developed an estimation approach. Recent research in SDR shows that a semi-parametric approach can outperform conventional non-parametric SDR methods. Yoo (Statistics: A Journal of Theoretical and Applied Statistics, 52, 409-425, 2018) developed a semi-parametric approach for response reduction in Yoo and Cook (2008) context, and Yoo (Journal of the Korean Statistical Society, 2019) completes the semi-parametric approach by proposing an unstructured method. This paper theoretically discusses and provides insightful remarks on three versions of semi-parametric approaches that can be useful for statistical practitioners. It is also possible to avoid numerical instability by presenting the results for an orthogonal transformation of the response variables.

• Asian Pacific Journal of Cancer Prevention
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• 제16권18호
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• pp.8567-8571
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• 2016

Background: The Cox model is known as one of the most frequently-used methods for analyzing survival data. However, in some situations parametric methods may provide better estimates. In this study, a Weibull parametric model was employed to assess possible prognostic factors that may affect the survival of patients with breast cancer. Materials and Methods: We studied 438 patients with breast cancer who visited and were treated at the Cancer Research Center in Shahid Beheshti University of Medical Sciences during 1992 to 2012; the patients were followed up until October 2014. Patients or family members were contacted via telephone calls to confirm whether they were still alive. Clinical, pathological, and biological variables as potential prognostic factors were entered in univariate and multivariate analyses. The log-rank test and the Weibull parametric model with a forward approach, respectively, were used for univariate and multivariate analyses. All analyses were performed using STATA version 11. A P-value lower than 0.05 was defined as significant. Results: On univariate analysis, age at diagnosis, level of education, type of surgery, lymph node status, tumor size, stage, histologic grade, estrogen receptor, progesterone receptor, and lymphovascular invasion had a statistically significant effect on survival time. On multivariate analysis, lymph node status, stage, histologic grade, and lymphovascular invasion were statistically significant. The one-year overall survival rate was 98%. Conclusions: Based on these data and using Weibull parametric model with a forward approach, we found out that patients with lymphovascular invasion were at 2.13 times greater risk of death due to breast cancer.

• 한국건설관리학회:학술대회논문집
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• 한국건설관리학회 2008년도 정기학술발표대회 논문집
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• pp.207-211
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• 2008

국내 건설산업은 급격한 시장변화와 경쟁심화의 과정을 겪으면서 프로젝트 초기 단계의 예산 집행 및 관리의 중요성이 증가하고 있다. 설계 완료 이후의 단계에서 조정 가능한 비용은 20%에 불과하기 때문에, 프로젝트 초기 단계에서 중요한 의사결정이 이루어진다. 하지만 초기 단계에서의 의사결정은 설계정보가 확정되지 않고, 정보가 한정되는 등 불확실성 하에서 이루어진다. 이에 따라, 본 연구는 프로젝트 초기 단계의 정확한 비용 예측을 목적으로 parametric method를 사용하여 공사비 예측 방법을 제안하였다. Parametric method를 이용한 공사비 예측 방법은 프로젝트 초기단계에 사용하기에 적합하며, 특히 신속하게 공사비 예측을 할 수 있다는 장점을 지닌다. 국내 아파트 9개 단지 $11{\sim}15$층 규모의 총 84개동 공공아파트 실적자료를 분석하여 공사비와 영향요인간 상관관계 분석을 실시하였다. 다중공선성 문제를 야기하는 변수를 제거한 후, 다중회귀분석을 통하여 공사비 예측 관계식을 도출하였다.

• 산업진흥연구
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• 제7권4호
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• pp.1-8
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• 2022

우리 주위를 살펴보면 한 번 사용하고 버리는 일회용품이 많다. 폭죽이나 탄약과 같은 일회용품이 대표적인데 이들 일회용품은 제조 후 한 동안 저장되어 있다가 필요한 때 사용하고 나면 폐기처분하게 된다. 하지만 이런 일회용품은 일반 운영장비와 달리 신뢰성평가가 제대로 이루어지지 못했다. 이에 본 연구에서는 일회용품 중에서 탄약에 대한 저장탄약신뢰성프로그램을 통해 탄약의 경우 신뢰성 확보를 위해 정부에서 어떤 일을 하는지 먼저 살펴본다. 이어서 통계분석적인 측면에서 탄약과 같은 일회용품에 대한 신뢰성분석 방안으로 어떤 것이 있는지 알아본다. 구체적으로 통계학에서 로트의 품질수준을 파악하는 샘플링검사를 활용하여 일정한 시기에 생산된 탄약에 대한 신뢰성의 수준을 파악할 수 있다. 본 연구에서는 KS Q0001인 계수규준형 1회 샘플링검사표를 이용할 수 있음으로 보여준다. 다음으로 탄약의 저장신뢰도를 파악할 수 있는 방법으로 비모수적인 방법과 모수적인 방법을 소개한다. 비모수적인 방법중에서 특히 Kaplan-Meier 방법은 중도중단데이터가 포함된 경우에도 활용될 수 있다. 마지막으로 모수적인 방법 중에는 신뢰성분석에 많이 활용되는 와이블분포가 탄약의 저장신뢰도를 파악하는 데에도 활용될 수 있다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2007년도 추계학술대회 논문집
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• pp.569-570
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• 2007

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2009년도 춘계학술대회 논문집
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• pp.163-164
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• 2009

• East Asian mathematical journal
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• 제25권1호
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• pp.45-53
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• 2009

In this paper, by using the technique of the resolvent operators, we study the behaviour and sensitivity analysis of the solutions set for a class of parametric completely generalized nonlinear variational inclusions with set-valued mappings.

• 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.

• 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.