• Journal of the Society of Naval Architects of Korea
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• v.36 no.3
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• pp.50-59
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• 1999

This paper is concerned on the generation of an optimal section of wing in ground effect by a SQP method which is one of nonlinear optimization techniques. A potential panel method is used for the flow analysis and the ground effect is taken into account by an image method. The numerical method is first verified by an inverse problem where a shape of wing section is sought for the prescribed pressure distribution. The purpose of the present paper is to generate a wing section which can give a maximum lift subjected to the design constraints including the height stability which is important in the WIG design. The effect of the tail wing is also included.

• Journal of the Society of Naval Architects of Korea
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• v.37 no.4
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• pp.11-18
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• 2000

This paper is concerned with the generation of an optimal forward hull form by a nonlinear programming method. A Rankine source panel method based on the inviscid and potential flow approximation is employed to calculate the wave-making resistance and SQP method is also used for the optimization. The hull form is represented by a spline function. The forward hull form of a minimum wave resistance with the given design constraints is generated. In addition, the forward hull form of a minimum total resistance by considering the frictional resistance together with an empirical form factor is produced and compared with the former result.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.6
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• pp.751-759
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• 2007

We have developed several methods for the optimization problem having large-scale and highly nonlinear system. First, step by step method in optimization process was employed to improve the convergence. In addition, techniques of furnishing good initial guesses for analysis using sensitivity information acquired from optimization iteration, and of manipulating analysis/optimization convergency criterion motivated from simultaneous technique were used. We applied them to flow control problem and verified their efficiency and robustness. However, they are based on quasi-Newton method that approximate the Hessian matrix using exact first derivatives. However solution of the Navier-Stokes equations are very cost, so we want to improve the efficiency of the optimization algorithm as much as possible. Thus we develop a true Newton method that uses exact Hessian matrix. And we apply that to the three-dimensional problem of flow around a sphere. This problem is certainly intractable with existing methods for optimal flow control. However, we can attack such problems with the methods that we developed previously and true Newton method.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.11
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• pp.1049-1059
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• 2010

This paper treats the aerodynamic optimization of the blade planform for helicopters. The blade shapes, which should be determined during the threedimensional aerodynamic configuration design step, are defined and are parameterized using the B$\acute{e}$zier curves. This research focuses on the design approaches generally adopted by industries and or research institutes using their own experiences and know-hows for the parameterization and for the definition of design constraints. The hover figure of merit and the equivalent lift-to-drag ratio for the forward flight are used to define the objective function. The resultant nonlinear programming (NLP) problem is solved using the sequential quadratic programming (SQP) method. The applications show the present method can design the important planform shapes such as the airfoil distribution, twist and chord variations in the efficient manner.

• The Journal of the Acoustical Society of Korea
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• v.22 no.8
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• pp.637-644
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• 2003

In this study, with the FEM we analyzed the variation of the resonance frequency, bandwidth, and sound pressure of the Tonpilz transducer in relation to its design variables. Through statistical multiple regression analysis of the results, we derived functional forms of the resonance frequency, bandwidth, and sound pressure in terms of the design variables. By applying the constrained optimization technique, SQP-PD, to the derived function, we determined the optimal structure of the transducer that could provide the highest sound pressure level at the resonance frequency of 30,000 Hz and having the -3 dB bandwidth more than 10%, The validity of the optimized results was confirmed through comparison of the optimal performance with that of the FEA. The optimal design method proposed could reflect all the cross-coupled effects of multiple structural variables, and could determine the detailed geometry of the transducer with great efficiency and rapidity.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.5
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• pp.661-669
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• 2007

Eyer since the Prandtl's experiment in 1934 and X-21 airjet test in 1950 both attempting to reduce drag, it was found that controlling the velocities of surface for extremely fast-moving object in the air through suction or injection was highly effective and active method. To obtain the right amount of suction or injection, however, repetitive trial-and error parameter test has been still used up to now. This study started from an attempt to decide optimal amount of suction and injection of incompressible Navier-Stokes by employing optimization techniques. However, optimization with traditional methods are very limited, especially when Reynolds number gets high and many unexpected variables emerges. In earlier study, we have proposed an algorithm to solve this problem by using step by step method in analysis and introducing SQP method in optimization. In this study, we propose more effective and robust algorithm and techniques in solving flow optimization problem.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.31 no.4
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• pp.183-190
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• 2018

This paper presents optimization of the main spar of Human-Powered Aircraft (HPA) wing. Mass minimization was attempted, while considering large torsional deformation of the beam. Sequential Quadratic Programming (SQP) method was adopted as a relevant tool to conduct structural optimization algorithm. An inner diameter and ply thicknesses of the main spar were selected as the design variables. The objective function includes factors such as mass minimization, constant tip bending displacement, and constant tip twist of the beam. For estimation of bending and torsional deformation, the geometrically exact beam model, which is appropriate for large deflection, was adopted. Properties of the cross sectional area which the geometrically exact beam model requires were obtained by Variational Asymptotic Beam Sectional Analysis (VABS), which is a cross sectional analysis program. As a result, maintaining tip bending displacement and tip twist within 1.45%, optimal design that accomplished 7.88% of the mass reduction was acquired. By the stress and strain recovery, structural integrity of the optimal design and validity of the present optimization procedure were authenticated.

• Magazine of the Korean Society of Agricultural Engineers
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• v.36 no.2
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• pp.111-122
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• 1994

In this study, an algorithm which can be applied to the optimum design of simple steel plate girders was developed, and efficient optimization strategies for the solution of algorithm were found out. The optimum design algorithm consists of 3-levels of optimization. In the first and second levels of optimization, the absolute maximum bending moment and shearing force are extracted and in the third level of optimization, the optimum cross section of steel plate girder is determined. For the optimum design of cross section, the objective function is formulated as the total area of cross section and constraints are derived in consideration of the various stresses and the minimum dimension of flange and web based on the part of steel bridge in the Korea standard code of road bridge. Sequential unconstrained minimization technique using the exterior penalty function method(SUMT-EP), sequential linear programming(SLP) and sequential quadratic programming (SQP) are proved to be efficient and robust strategies for the optimum design of simple plate girder cross section. From the reliable point of view, SLP is the most efficient and robust strategy and SQP is the most efficient one from the viewpoint of converguency and computing time.

• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.4
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• pp.217-224
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• 2003

The objective of this paper is to suggest the technique of program to perform structural optimization design after reliability analysis to consider the uncertainties of structural reponses. AFOSM method is used for reliability analysis then, structural optimization design is developed for 10-bar truss and 3 span 10 stories planar frame model is subject to reliability indices and probability of failure by reliability analysis. SQP method is used for optimization design method, this method has many attractions. As a result of analyzing with having and not having constraints and uncertainty, the minimum weight of truss and planar frame increased respectively 20.92% and average 8.08%.

• Journal of KIISE:Computer Systems and Theory
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• v.34 no.3
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• pp.124-131
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• 2007

Research field on crowd animation can be classified into two major categories. One is to offer realism of the crowd motion and the other is to improve speed of the animation. For the last decade, a lot of research on realism and behavior of crowd have been presented. But lately, research on improving speed seems like more interesting. Therefore, in this paper, we conducted an experiment to analyze what is the main bottleneck of crowd animation. As the result, we find out one of the most important bottleneck is the number of joints transformed in each animation frame. In order to resolve this problem we propose a novel level-of-detail technique 'motion level-of-detail', which is a joint-reduction technique operated in the pre-processing time. We used a non-linear optimization, SQP (sequential quadric programming), to generate the low detailed motions.