• Journal of the Society of Naval Architects of Korea
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• v.36 no.2
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• pp.121-134
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• 1999

In this paper, a ship calculation program is developed, which prof[nuts hydrostatics and volume calculation intact and damage stability and hull variation. Hull form and compartment geometry are expressed with NURBS curve wire-frame model. Hydrostatics and volume calculation are performed directly with the intersection method between section geometry and 3D planar surface. Equilibrium ship position is calculated with hydrostatic equilibrium equation which is linearized by 1st order Taylor series expansion sequentially. The developed program shows more accurate results and easy uses than the latter.

• Annual Conference on Human and Language Technology
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• 1992.10a
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• pp.581-590
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• 1992

고품위 입출력 장치의 급속한 발달과 전자 출판 시스템의 출현은 더 다양한 서체를 요구하게 되었다. 컴퓨터에서 사용되고 있는 한글 서체는 명조, 고딕체를 제외하고는 주로 장식용 폰트를 만들어 사용하고 있다. 본 논문에서는 Cubic B-Spline 곡선을 이용하여 다양한 필기체 폰트를 구현하였고, 필기체가 가지는 특성(날림의 정도, 글자의 기울이기 정도, 각 음소의 크기, 각 글자의 크기의 균일성 등)에 따라 인자를 부여하여 개별화되고 사실적인 폰트를 생성하였다. 각 인자의 조합은 암호화되어 각 개인의 폰트로 부여된다. 즉, 개인의 고유 폰트는 폰트 암호(password)로 부여되고, 제어인자는 폰트암호의 해쉬값에 의해 선택되며, 사용자들로부터 이 제어인자들을 숨기게 되면 각 사용자들의 폰트는 유일하고, 안전하게 되므로, 일정정도의 안정성이 보장된다고 보여진다. 그리고 본 연구에서 구현된 폰트는 한글 필기체 문자인식의 정도를 측정하는 다양한 데이타를 제공하는 데에도 의미가 있다.

• Journal of the Society of Naval Architects of Korea
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• v.46 no.3
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• pp.232-248
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• 2009

Numerical methodology to solve ship springing problem, which is basically fluid-structure interaction problem, was explored in this study. Solution of this hydroelasticity problem was sought by coupling higher order B-spline Rankine panel method and finite element method in time domain, each of which is introduced for fluid and structure domain respectively. Even though varieties of different combinations in terms of numerical scheme are possible and have been tried by many researchers to solve the problem, no systematic study regarding the characteristics of each scheme has been done so far. Here, extensive case studies have been done on the numerical schemes especially focusing on the iteration method, FE analysis of beam-like structure, handling of forward speed problem and so on. Two different iteration scheme, Newton style one and fixed point iteration, were tried in this study and results were compared between the two. For the solution of the FE-based equation of motion, direct integration and modal superposition method were compared with each other from the viewpoint of its efficiency and accuracy. Finally, calculation of second derivative of basis potential, which is difficult to obtain with accuracy within grid-based method like BEM was discussed.

• Journal of Ocean Engineering and Technology
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• v.27 no.2
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• pp.1-7
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• 2013

This paper aims at contributing to the field of ship design by introducing new systematic variation methods for ship hull forms. Hull form design is generally carried out in two stages. The first is the global variation considering the sectional area curve. Because the geometric properties of a sectional area curve have a decisive effect on the global hydrodynamic properties of ships, the design of a sectional area curve that satisfies various global design conditions, e.g., the displacement, longitudinal center of buoyancy, etc., is important in the initial hull form design stage. The second stage involves the local design of section forms. Section forms affect the local hydrodynamic properties, e.g., the local pressure in the fore- and aftbody. This paper deals with a new method for the systematic variation of sectional area curves. The longitudinal volume distribution of a ship depends on the sectional area curve, which can geometrically be controlled using parametric variation and a variation that uses the modification function. Based on these methods, we suggest a more generalized method in connection with the derivation of the lines for a new design compared to those for similar ships. This is the so-called the volumetric balanced variation (VOB) method for ship forms using a B-spline modification function and an optimization technique. In this paper the global geometric properties of hull forms are totally controlled by the form parameters. We describe the new method and some application examples in detail.

• International Journal of CAD/CAM
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• v.7 no.1
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• pp.31-40
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• 2007

Reverse engineering of reliefs aims to turn an existing relief superimposed on an underlying surface into a geometric model which may be applied to a different base surface. Steps in this process include segmenting the relief from the background, and describing it as an offset height field relative to the underlying surface. We have previously considered relief segmentation using a geometric snake. Here, we show how to use this initial segmentation to estimate the background surface lying under the relief, which can be used (i) to refine the segmentation and (ii) to express the relief as an offset field. Our approach fits a B-spline surface patch to the measured background data surrounding the relief, while tension terms ensure this background surface smoothly continues underneath the relief where there are no measured background data points to fit. After making an initial estimate of relief offset height everywhere within the patch, we use a support vector machine to refine the segmentation. Tests demonstrate that this approach can accurately model the background surface where it underlies the relief, providing more accurate segmentation, as well as relief height field estimation. In particular, this approach provides significant improvements for relief concavities with narrow mouths and can segment reliefs with small internal holes.

• Journal of Ocean Engineering and Technology
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• v.20 no.3 s.70
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• pp.82-87
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• 2006

An approach to model a high-speed monohull vessel is introduced. The high-speed monohull form belonging to the category of multihull is drawing new attention, due to the rapidly growing trend of fast passenger ships and military purpose. Multihull forms are much thinner in their overall shape, compared to those of the conventional commercial vessels. Moreover, the parent hull forms are not readily obtainable when a new design is intended, which makes it hard to perform various technical calculations in terms of hull optimization, hydrodynamic computation, structural design, and so forth. In this paper, a parametric technique is used to design a high-speed hull form. To model a hull form, NURBS (Non Uniform Rational B-Spline) representation is used. The goal of research is to provide a fast and convenient tool to design an initial hull form with fewer parameters available in the early design stage. The technique employed in this paper will be applied to the design of multihull forms, such as catamaran, trimaran, and semi-swath.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.05a
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• pp.37-42
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• 2003

Fundamental Study for optimizing ship hull form using SQP(sequential quadratic programming) method in a resistance point of view is presented. The Wigley hull is used as an initial hull and numerical calculations are carried out according to various froude numbers. To obtain the ship resistance the wave resistance is evaluated by a Rankine source panel method with nonlinear free surface conditions and the ITTC 1957 friction line is used to predict the frictional resistance coefficient. The geometry of a hull surface is represented and modified by B-spline surface patch. The displacement and the waterplane transverse 2nd moment of inertia of the hull is fixed during the optimization process. And the shp design program called EzHULL is used to draw the lines of the optimized hull form to perform the model test.

• Journal of Ocean Engineering and Technology
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• v.22 no.2
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• pp.78-84
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• 2008

As a preliminary step to build a complete superyacht hull design program, the development of superyacht profile design system is introduced. The two-dimensional hull profile is decomposed into four local zones depending upon the functionality and connecting continuity of the profile. Characteristics of each zone are investigated and used to generate the model describing the geometric shape of zone using freeform curves. A set of design parameters is derived from the established geometric model. Generation and modification of a model are is by manipulating the chosen parameters. Four zones designed are integrated to form a final profile. An interactive design system performing all the modeling and modification processes is implemented using the graphic user interface system based an Microsoft Foundation Class and OpenCASCADE, a open graphic library. The shapes of the profiles generated by the developed design system are verified with those of built superyachts. The developed design system will be used for the construction of three-dimensional superyacht hull modeling system.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.213-217
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• 2008

This paper describes an application of centrifugal compressor optimization system, in which the blade profile of impeller is represented with NURBS(Non-Uniform Rational B-Spline) curve. A commercial CFD(Computational Fluid Dynamics) program named NUMECA fine/turbo was used to evaluate the performance of the whole centrifugal compressor flow passage including impeller and diffuser. The whole optimization design system was integrated based on iSIGHT, a commercial integration and optimization software, which provides a direct application of some optimization algorithms. To insure the practicability of optimization, the performance of centrifugal compressor under all condition was concerned during the optimizing process. That means a compositive object function considering the aerodynamic efficiency, pressure ratio and mass flow rate under different work condition was applied by using different weight number for different conditions. Using the optimization method described in this paper, an optimized design of the impeller blade of centrifugal compressor was obtained. Comparing to the original design, optimized design has a better performance not only under the design work condition, but also the off-design work condition including near stall and near choke condition.

• Structural Engineering and Mechanics
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• v.85 no.1
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• pp.119-133
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• 2023

Impact event is the key factor influencing the operational state of the mechanical equipment. Additionally, nonlinear factors existing in the complex mechanical equipment which are currently attracting more and more attention. Therefore, this paper proposes a novel hybrid-separate identification strategy to solve the force identification problem of the nonlinear structure under impact excitation. The 'hybrid' means that the identification strategy contains both l1-norm (sparse) and l2-norm regularization methods. The 'separate' means that the nonlinear response part only generated by nonlinear force needs to be separated from measured response. First, the state-of-the-art two-step iterative shrinkage/thresholding (TwIST) algorithm and sparse representation with the cubic B-spline function are developed to solve established normalized sparse regularization model to identify the accurate impact force and accurate peak value of the nonlinear force. Then, the identified impact force is substituted into the nonlinear response separation equation to obtain the nonlinear response part. Finally, a reduced transfer equation is established and solved by the classical Tikhonove regularization method to obtain the wave profile (variation trend) of the nonlinear force. Numerical and experimental identification results demonstrate that the novel hybrid-separate strategy can accurately and efficiently obtain the nonlinear force and impact force for the nonlinear structure.