• Ocean Systems Engineering
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• 제4권2호
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• pp.117-136
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• 2014

The increased interest in the design of energy efficient ships post IMO regulation on enforcing EEDI has encouraged researchers to reevaluate the numerical methods in predicting important hull design parameters. The prediction of added resistance and stability of ships in the rough sea environment dictates selection of ship hulls. A 3D panel method based on Green function is developed for vessel motion prediction. The effects of parametric instability are also investigated using the Volterra series approach to model the hydrostatic variation due to ship motions. The added resistance is calculated using the near field pressure integration method.

• International journal of advanced smart convergence
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• 제9권1호
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• pp.193-201
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• 2020

The main objective of this study is to investigate the impact of additional modalities on the performance of emotion recognition using speech, facial expression and physiological measurements. In order to compare different approaches, we designed a feature-based recognition system as a benchmark which carries out linear supervised classification followed by the leave-one-out cross-validation. For the classification of four emotions, it turned out that bimodal fusion in our experiment improves recognition accuracy of unimodal approach, while the performance of trimodal fusion varies strongly depending on the individual. Furthermore, we experienced extremely high disparity between single class recognition rates, while we could not observe a best performing single modality in our experiment. Based on these observations, we developed a novel fusion method, called parametric decision fusion (PDF), which lies in building emotion-specific classifiers and exploits advantage of a parametrized decision process. By using the PDF scheme we achieved 16% improvement in accuracy of subject-dependent recognition and 10% for subject-independent recognition compared to the best unimodal results.

• 한국신뢰성학회지:신뢰성응용연구
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• 제11권1호
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• pp.43-57
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• 2011

In the paper, we consider two-dimensional warranty policy with failure times and repair times. The failure times are considered within the warranty period and the repair times are considered within the repair time limit. Under the renewable warranty policy and non-renewable warranty policy, we consider the number of warranty services in the censored area by warranty period and repair time limit to conduct warranty cost analysis. We investigate the field data to check their dependency and implement our proposed approaches to conduct warranty cost analysis using the parametric methods. Numerical examples are discussed to demonstrate the applicability of the methodologies and results based on the proposed approach in the paper.

• 한국CDE학회논문집
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• 제3권4호
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• pp.293-303
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• 1998

The objective of this study is to develop a PC level freeform surface modeling system which explicitly represents information of part geometry. Surface modeler uses nonuniform rational B-spline (NURBS) function with nonuniform knot vector for the flexible modeling work. The results of this study are as follows. 1) By implementation surface modeler through applying representation scheme proposed to represent free-form surface explicity, the technical foundation to develop free-from surface modeling system using parametric method. 2) Besides the role to model geometric shape of a surface, geometric modeler is developed to model arbitrary geometric shape. By doing this, the availability of the modeling system is improved. Geometric modeler can be utilized application fields such as collision test of tool and fixture, and tool path generation for NC machine tool.

• Steel and Composite Structures
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• 제28권1호
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• pp.25-37
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• 2018

For the first time, the parametric instability characteristics of tow-steered variable stiffness composite laminated (VSCL) cylindrical panels is investigated using B-spline finite strip method (FSM). The panel is considered containing geometrical defects including cutout and delamination. The material properties are assumed to vary along the panel axial length of any lamina according to a linear fiber-orientation variation. A uniformly distributed inplane longitudinal loading varies harmoni-cally with time is considered. The instability load frequency regions corresponding to the assumed in-plane parametric load-ing is derived using the Bolotin's first order approximation through an energy approach. In order to demonstrate the capabili-ties of the developed formulation in predicting stability behavior of the thin-walled VSCL structures, some representative results are obtained and compared with those in the literature wherever available. It is shown that the B-spline FSM is a proper tool for extracting the stability boundaries of perforated delaminated VSCL panels.

• 산업공학
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• 제8권3호
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• pp.133-139
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• 1995

Free from curves and surfaces are frequently used in designing engineering products such as car, ship, airplane, and hosing of electronic households. In many aspect, it is very nice to use the cutter radius compensation function of CNC controller when contour machining a 2-dimensional curve. However, if the 2D curve is a parametric spline, it is not easy to apply the cutter radius compensation function of CNC controller to the NC data obtained from many commercial CAM system. This is mainly due to the error magnification effect when offsetting line segments with inevitable round-off error at their vertices. Proposed in this paper is an approach to contour machining a 2D parametric spline while using cutter radius compensation. Some implementation results are included.

• 한국수자원학회논문집
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• 제36권3호
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• pp.399-411
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• 2003

Nash의 관측평균순간단위도의 신뢰구간을 결정하는 기법을 개발하였다. 이 방법은 두 매개변수를 Box-Cox 변환과 유역의 상사성관계식을 이용하여 이변수정규분포의 확률변수화하고 이들의 선형 상관관계를 이용한 통계적 추정과정과 더불어 parametric bootstrap 방법을 이용한 단위도의 신뢰구간 산정 등으로 구성된다. 또한 이 방법은 미계측유역에 대한 단위도 추정에도 이용이 가능한 특징을 갖고 있다. 위천유역에 대하여 제안된 방법을 적용한 결과 제시된 방법론은 단위도의 불확실성을 평가하고 그리고 미계측 유역에 대한 매개변수 추정에 있어서 적절한 대안임을 확인할 수 있었다.

• 한국CDE학회논문집
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• 제6권2호
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• pp.78-88
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• 2001

In order to adopt feature-based parametric modeling, CAD/CAM applications must have a geometric constraint solver that can handle a large set of geometric configurations efficiently and robustly. In this paper, we describe a graph constructive approach to solving geometric constraint problems. Usually, a graph constructive approach is efficient, however it has its limitation in scope; it cannot handle ruler-and-compass non-constructible configurations and under-constrained problems. To overcome these limitations. we propose an algorithm that isolates ruler-and-compass non-constructible configurations from ruler-and-compass constructible configurations and applies numerical calculation methods to solve them separately. This separation can maximize the efficiency and robustness of a geometric constraint solver. Moreover, the solver can handle under-constrained problems by classifying under-constrained subgraphs to simplified cases by applying classification rules. Then, it decides the calculating sequence of geometric entities in each classified case and calculates geometric entities by adding appropriate assumptions or constraints. By extending the clustering types and defining several rules, the proposed approach can overcome limitations of previous graph constructive approaches which makes it possible to develop an efficient and robust geometric constraint solver.

• Earthquakes and Structures
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• 제26권5호
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• pp.327-336
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• 2024

Evaluation of tunnel performance in seismic-prone areas demands efficient means of estimating performance at different hazard levels. The present study introduces an innovative push-over analysis approach which employs the standard earthquake spectrum to simulate the performance of a tunnel. The numerical simulation has taken into account the lining and surrounding rock to calculate the rock-tunnel interaction subjected to a static push-over displacement regime. Elastic perfectly plastic models for the lining and hardening strain rock medium were used to portray the development of plastic hinges, nonlinear deformation, and performance of the tunnel structure. Separately using a computational algorithm, the non-linear response spectrum was approximated from the average shear strain of the rock model. A NATM tunnel in Turkey was chosen for parametric study. A seismic performance curve and two performance thresholds are introduced that are based on the proposed nonlinear seismic static loading approach and the formation of plastic hinges. The tunnel model was also subjected to a harmonic excitation with a smooth response spectrum and different amplitudes in the fully-dynamic phase to assess the accuracy of the approach. The parametric study investigated the effects of the lining stiffness and capacity and soil stiffness on the seismic performance of the tunnel.

• 한국수자원학회논문집
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• 제44권2호
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• pp.125-134
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• 2011

이 논문은 비모수추정법에 의한 조건부가치측정법을 이용하여 부산시 가정용수 수질개선에 대한 지불의사액을 추정하는 것이다. 이와 같은 연구는 생활용수를 관리하는 정책입안자들에게 수질개선에 따른 경제적 편익의 정보를 제공하고, 부산시의 생활용수 개선사업을 수행여부나 수행규모를 결정하는데 있어서 유용한 정보와 시사점을 제공할 수 있다. 비모수추정법은 모수추정법에서 가정되는 모형분포의 적합도, 모형설정, 이분산 등의 가정과 검정이 필요 없을 뿐만 아니라 비교적 추정이 용이하고 보수적 추정을 할 수 있는 장점이 있다. 이 논문은 조건부가치측정법의 신뢰성과 타당성을 확보하기 위해서 층화된 무작위표본추출법에 의한 개인면접방법을 통하여 665개의 표본을 선정하였다. 추정결과 가정용수 수질개선에 대한 부산시 가구당 월 평균 지불의사액은 2009년 기준 3,190원에서 3,331원이고, 중앙값은 가구당 월 1,750원으로 추정되었다. 부산시민 전체의 가정용수 수질개선에 대한 연간 경제적 편익은 평균WTP를 적용할 경우 502억원, 중앙값 WTP를 적용할 경우 275억원으로 추산되었다. 이와 같은 연구결과는 상수도 수질정책의 시행여부를 결정하는 비용편익분석이나 다양한 생활용수 수질개선정책에 있어서 편익의 유용한 정보로 활용할 수 있다.