• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.5
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• pp.424-432
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• 2011

Shape parameters and design variables for a centrifugal compressor impeller were investigated for optimizing a centrifugal compressor. In order to compare the performance of an optimized impeller with the performance of the original impeller, an already tested impeller was chosen and design variables for optimization were selected. The meridional shapes at the shroud and at the hub were re-designed using the Bezier curve. The camber-lines of the impeller blade at the hub and at the tip were also expressed by the Bezier curve. The shape curves for impeller could be expressed using 6-8 control points. Among them, eight control points which have strong effect to the shape can be selected as design variables for optimization. Therefore, any impeller which is expressed by data points for its shape can be optimized using few design variables.

• Journal of the Optical Society of Korea
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• v.8 no.3
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• pp.99-103
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• 2004

This paper describes the optimal design of an AWG spectrum to meet various specifications and improve some physical parameters. The objective function is the norm of the difference between design parameters and target values. To obtain the design parameters, the Fourier model is employed and the design variables arc spacing of array waveguide, width of array waveguide, optical path difference, and focal length. The (1+1) Evolution Strategy is employed as the optimization tool. The optimization procedure is applied to a 16-channel AWG and the optimized design variables will considerably improve the system performance.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04b
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• pp.719-724
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• 1998

It is proposed in this paper to develop the rational mix design system of High-strength concrete which is adjusted in the domestic circumstances. 1) Collect a lots of data in order to introduce the optimum mix design which has relation among material variables which compose High-strength concrete and run by using SAS (Statistical analysis system) which is one of multivariate statistical analysis method. 2) Select the important material variables for mix design of High-strength concrete by major component analysis and propose the standard range of each material variable along the target strengths. From the results of this study, it was proposed the range of proper material variables in domestic circumstance, which are W/C, S/A, air and admixture amounts, etc, at the target strengths for concrete kind. Also it was developed the optimum mix design program of High-strength concrete according to target strength and size of aggregate and made mix design ease in domestic construction site.

• Journal of Ocean Engineering and Technology
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• v.21 no.2 s.75
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• pp.75-80
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• 2007

The design variables for structural systems, in most practical designs, are chosen from a list of discrete values, which are commercially available sizing. This paper presents the application of Genetic Algorithms for determining the optimum design for two-dimensional structures with discrete and pseudocontinuous design variables. Genetic Algorithms are heuristic search algorithms and are effective tools for finding global solutions for discrete optimization. In this paper, Genetic Algorithms are used as the method of Elitism and penalty parameters, in order to improve fitness in the reproduction process. Examples in this paper include: 10 bar planar truss and 1 bay 8-story frame. Truss with discrete and pseudoucontinuous design variables and steel frame with W-sections are used for the design of discrete optimization.

• IE interfaces
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• v.18 no.4
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• pp.465-476
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• 2005

Evolutionary operation is a useful tool for improving full-scale manufacturing process by systematically changing the levels of the process variables without jeopardizing the product. This paper presents a system design for the evolutionary operation software called 'evolutionary optimizer'. Evolutionary optimizer consists of four modules: factorial design, many variables, mixture, and mean/dispersion. Context diagram, data flow diagram and entity-relationship modelling are used to systematically design the evolutionary optimizer system.

• Steel and Composite Structures
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• v.29 no.1
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• pp.67-75
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• 2018

High performance concrete (HPC) depends on various parameters such as the type of cement, aggregate and water reducer amount. Generally, the ready concrete company in various regions according to the requirements and costs, mix design of concrete as well as type of cement, aggregates, and, amount of other components will vary as a result of moment decisions or dynamic optimization, though the ideal conditions will be more applicable for the design of mix proportion of concrete. This study aimed to apply dynamic optimization for mix design of HPC; consequently, the objective function, decision variables, input and output variables and constraints are defined and also the proposed dynamic optimization model is validated by experimental results. Results indicate that dynamic optimization objective function can be defined in such a way that the compressive strength or performance of all constraints is simultaneously examined, so changing any of the variables at each step of the process input and output data changes the dynamic of the process which makes concrete mix design formidable.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1203-1208
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• 2009

In this paper, the flow characteristics of the mixed-flow pump impellers and diffusers were numerically predicted by commercial CFD software and DOE(design of experiments). We also discussed how to improve the performance of the mixed-flow pump by designing the impeller and diffuser in the mixed-flow pump. Geometric design variables were defined by the vane plane development which indicates the blade-angle distributions and length of the impeller and the diffusers. Firstly, the design optimization of the defined impeller geometric variables has been done. After that, the flow characteristics were analyzed in the point of incidence angle at the diffuser leading edge for the optimized impeller. Then design of the defined diffuser shape variables has been performed. The reason for the performance improvement was discussed by examining the flow characteristics through the diffuser.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11a
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• pp.52-57
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• 2001

In this paper, the optimum designs of air-bearing surface(ABS) are achieved effectively by using reduced basis concept which can reduce the number of design variables although the design space is distended. Generally, the optimization method is more effective than the trial and error. However, the efficiency of the former is largely dependent on the number of the design variables. In order to reduce the number of design variables and increase the efficiency, reduced basis concept is applied. We can define the desired design as a linear combination of basis designs using this concept. From this optimization method with reduced basis concept, we easily obtain the optimum designs of ABS whose target flying heights are 25, 20, 15 nm.

• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.4
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• pp.59-71
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• 1994

A multi-polynomial method is proposed to synthesize DRRD cam profiles. A cam lift duration s divided into 10 sections, each of them is expressed by a polynomial equation. 12 design variables are extracted from the cam profile displacement, velocity, and acceleration curves. Because all the design variables have physical meanings which are familiar to most cam designers, it is easy to imagine a profile shape from the design variables. The design envelope of the method is wide enough to be used in DRRD automotive cam designs. Polydyne cams, widely used in automotive engines, are included into the envelope. Unlike Polydyne cams, the method provides capability of wide velocity factor variations, which gives much flexibility in flat-faced tappet design. Area factor of profiles designed by the method can be increased 5-10% compared to those of Polydyne cams without increasing acceleration factor. The method is especially useful for cam profile optimizations.

• The KSFM Journal of Fluid Machinery
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• v.12 no.4
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• pp.44-53
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• 2009

Numerical design optimization of a fan-shaped hole for film-cooling has been carried out to improve film-cooling effectiveness by combining a three-dimensional Reynolds-averaged Navier-Stokes analysis with the radial basis neural network method, a well known surrogate modeling technique for optimization. The injection angle of hole, lateral expansion angle of hole and ratio of length-to-diameter of the hole are chosen as design variables and spatially averaged film-cooling effectiveness is considered as an objective function which is to be maximized. Twenty training points are obtained by Latin Hypercube sampling for three design variables. Sequential quadratic programming is used to search for the optimal point from the constructed surrogate. The film-cooling effectiveness has been successfully improved by the optimization with increased value of all design variables as compared to the reference geometry.