• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.1
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• pp.39-47
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• 2005

In this paper, a method of station keeping strategy using relative orbital motion and numerical optimization technique is presented for geostationary spacecraft. Relative position vector with respect to an ideal geostationary orbit is generated using high precision orbit propagation, and compressed in terms of polynomial and trigonometric function. Then this relative orbit model is combined with optimization scheme to propose a very efficient and flexible method of station keeping planning. Proper selection of objective and constraint functions for optimization can yield a variety of station keeping methods improved over the classical ones. Results from the nonlinear simulation have been shown to support such concept.

• Journal of the Korean Data and Information Science Society
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• v.12 no.2
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• pp.1-10
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• 2001

Neural networks we increasingly being seen as an addition to the statistics toolkit which should be considered alongside both classical and modern statistical methods. Neural networks are usually useful for classification and function estimation. In this paper we concentrate on function estimation using neural networks with weight decay factor The use of weight decay seems both to help the optimization process and to avoid overfitting. In this type of neural networks, the problem to decide the number of hidden nodes, weight decay parameter and iteration number of learning is very important. It is called the optimization of weight decay neural networks. In this paper we propose a automatic optimization based on genetic algorithms. Moreover, we compare the weight decay neural network automatically learned according to automatic optimization with ordinary neural network, projection pursuit regression and support vector machines.

• International Commerce and Information Review
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• v.13 no.1
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• pp.3-28
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• 2011

Recently marketing methods of small and medium exporting firms have changed from internet marketing using homepage, or e-catalogs, to search engine marketing. However, there is no specific proof of search engine marketing effectiveness. Therefore the purpose of this research is to explore marketing performance of search engine marketing(SEM) based on search engine optimization. In order to build an optimal SEM strategy, quantitative data are collected from the Google-analytics such as homepage visits, page views, and traffic source for three years. At the same time, this study has carried out a survey to measure the qualitative effectiveness. The result of this quantitative study suggests that the existing carryover effects and lag effects would be maintained through search engine optimization. Meanwhile, the qualitative survey shows that satisfaction and awareness of homepage have been improved after search engine optimization. This can support logically increase of homepage visiting ratio of quantitative analysis. Also exporting companies know very well, that traffic and page views have increased after search engine optimization.

• Korean Journal of Construction Engineering and Management
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• v.15 no.4
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• pp.95-106
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• 2014

The outer surfaces of free form buildings contain panels with two-directional curvatures. To construct these panels, complex geometric surfaces should be divided into forms and sizes that can be manufactured and constructed efficiently. Because the bigger the curvatures of these panel, the more expensive the construction costs, these complex curvatures should go through optimal process of reinterpretation to minimize the curved surfaces with complex two-directional curvatures, which is called panel optimization. Small construction and design companies have trouble in calculating even rough estimate and cannot adjust expected construction cost of the panels based on comparison of design alternatives in conjunction with panel optimization process due to lack of knowledge and experience. This study conducts the research that can support designers' cost decision-making in the design stage of the free form buildings with respect to the panel optimization process. A 3D commercial application specialized to modeling free form shapes is used for the purpose.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.4B
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• pp.178-185
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• 2005

NEMO basic support is a solution that provides network mobility in the Internet topology. Yet, when multiple mobile networks are nested, this basic solution suffers ken pinball-routing and a severe routing overhead. Therefore, several solutions for route optimization in a nested mobile network have already been suggested by the IETF NEMO WG. However, the current paper proposes Regional Information-based Route Optimization (RIRO) in which mobile routers maintain a Nested Router List (NRL) to obtain next-hop information, and packets are transmitted with a new routing header called an RIRO Routing Header (RIRO-RH). We showed that RIRO had the minimum packet overhead that remained constant, irrespective of how deep the mobile network was nested, in comparison with two earlier proposed schemes - Reverse Routing Header (RRH) and Bi-directional tunnel between HA and Top-Level mobile router (BHT).

• Journal of Korean Society of Steel Construction
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• v.10 no.3 s.36
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• pp.487-495
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• 1998

Recently, the space truss has been attracted by many designers because of their ability to support significant loads with a minimum material. And it is relatively flexible to design the configuration of structures. This paper presents a volume optimization for the space truss on the basis of result evaluated from nonlinear analysis. The optimization of the truss is done by nonlinear optimum GINO(General Interactive Nonlinear Optimizer) program. The objective function considered is the volume of the steel bars. The constraints for optimum design are the design limits, such as the axial force strength, maximum slenderness, minimum thickness, allowable deflection and ratio of the external diameter to thickness of the circular tube bars.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.2
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• pp.406-414
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• 2002

A new approach, referred to as a successive zooming genetic algorithm (SZGA), is Proposed for identifying a global solution for continuous optimization problems. In order to improve the local fine-tuning capability of GA, we introduced a new method whereby the search space is zoomed around the design point with the best fitness per 100 generation. Furthermore, the reliability of the optimized solution is determined based on the theory of probability. To demonstrate the superiority of the proposed algorithm, a simple genetic algorithm, micro genetic algorithm, and the proposed algorithm were tested as regards for the minimization of a multiminima function as well as simple functions. The results confirmed that the proposed SZGA significantly improved the ability of the algorithm to identify a precise global minimum. As an example of structural optimization, the SZGA was applied to the optimal location of support points for weight minimization in the radial gate of a dam structure. The proposed algorithm identified a more exact optimum value than the standard genetic algorithms.

• Journal of Radiation Protection and Research
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• v.19 no.2
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• pp.99-107
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• 1994

This study aims to introduce a prescriptive methodology to comprehensively support the analysis of decision process by the use of Saaty's Analytical Hierarchy Process for the optimization of radiation protection. The analytical Hierarchy Process for the optimization of radiation protection. The analytical process for the problem of selecting options among given protection alternatives is illustrated with the data of the uranium mine example in ICRP Publ. 55. This technique, unlike other conventional selection method, is considered to provide a useful tool for the protection manager with respect to its ease of use and simplification in the choice of optimal alternative associated with radiological protection.

• Journal of the Korean Data and Information Science Society
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• v.20 no.5
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• pp.829-835
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• 2009

Parameter design is an approach to reducing performance variation of quality characteristic value in products and processes. Taguchi has used the signal-to-noise ratio to achieve the appropriate set of operating conditions where variability around target is low in the Taguchi parameter design. However, there are difficulties in practical application, such as complexity and nonlinear relationships among quality characteristics and control factors (design factors), and interactions occurred among control factors. Neural networks have a learning capability and model free characteristics. There characteristics support neural networks as a competitive tool in processing multivariable input-output implementation. In this paper we propose a substantially simpler optimization procedure for parameter design using neural network. An example is illustrated to compare the difference between the Taguchi method and neural network method.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.1 s.244
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• pp.87-94
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• 2006

This paper presents the hydrodynamic design and performance analysis method for a miniaturized centrifugal blood pump using three-dimensional computational fluid dynamics (CFD) code. In order to obtain the hydraulically high efficient configuration of a miniaturized centrifugal blood pump for cardiopulmonary circulation, a well-established commercial CFD code was incorporated considering detailed flow dynamic phenomena in the blood pump system. A prototype of centrifugal blood pump developed by the present design and analysis method has been tested in the mock circulatory system. Predicted results by the CFD code agree very well with in vitro hydraulic performance data for a centrifugal blood pump over the entire operating conditions. Preliminary in vivo animal testing has also been conducted to demonstrate the hemodynamic feasibility for use of centrifugal blood pump as a mechanical circulatory support. A miniaturized centrifugal blood pump developed by the hydraulic design optimization and performance prediction method presented herein shows the possibility of a good candidate for intra and extracorporeal cardiopulmonary circulation pump in the near future.