• Journal of Korean Society for Geospatial Information Science
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• v.16 no.1
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• pp.83-93
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• 2008

The topographic effect is one of the most important component in the solution of the geodetic boundary value problem (geodetic BVP). Therefore, topographic effect should be considered properly for developing the precise geoid model, especially for the area where contains many mountains like Korea. The selection of gravity reduction method in the context of the precise geoid determination depends on the magnitude of its indirect effect, the smoothness and magnitude of the reduced gravity anomalies, and their related geophysical interpretation. In this study, Korean digital elevation model with 100m resolution was constructed and topographic effect was calculated by three reduction methods as like Helmert condensation method and RTM method and Airy-isostatic reduction method. Through the analysis of computation results, we can find that RTM reduction method is the best optimal method and the results shows that gravity anomaly and indirect effect of geoidal height are $0.660{\pm}13.009mGal$, $-0.004{\pm}0.131m$ respectively and it is the most gentle slow of the three methods. Through this study, it was found that the RTM method is better suitable for calculating topographic effect precisely in context of precise geoid determination in Korea than other reduction methods.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.1205-1208
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• 1996

This paper proposes balanced model reduction of non-minimum phase plant. The algorithm presented in this paper is to convert high-order non-minimum phase plant into low-oder minimum phase plant using balanced model reduction. Balanced model reduction requires the error bound that Hankel singular value produces. This algorithm shows the tolerance that admits the method of this paper.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.2
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• pp.396-406
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• 2007

In this paper, we proposed development of improved model reduction and design of hierarchical controller using reduction model. The model reduction is considered that it is the transient response and the steady-state response through the use of nyquist curve. The hierarchical controller selected tuning of PID controller to ensure specified gain and phase margin and hybrid smith-predictor fuzzy controller using reduction model. Simulation examples are given to show the better performance of the proposed method than conventional methods.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.5
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• pp.34-38
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• 2011

The shorter the electric power line is, the less its cost becomes. In this paper, the Steiner tree is applied to find the shortest path of the electric power line to obtain resultant cost reduction. Up to 18.3[%] of length reduction can be expected compared to conventional method when the lines are connected through the Steiner points, which also can result in appreciable cost reduction.

• Wind and Structures
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• v.31 no.5
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• pp.473-482
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• 2020

The first-order method for estimating the extreme wind pressure on building envelopes with consideration of the directionality of wind speed and wind pressure is improved to enhance its computational efficiency. In this improved method, the result is obtained directly from the empirical distribution of a random selection of annual maximum wind pressure samples generated by a Monte Carlo method, rather than from the previously utilized extreme wind pressure probability distribution. A discussion of the relationship between the first- and full-order methods indicates that when extreme wind pressures in a non-typhoon climate with a high return period are estimated with consideration of directionality, using the relatively simple first-order method instead of the computationally intensive full-order method is reasonable. The validation of this reasonableness is equivalent to validating two assumptions to improve its computational efficiency: 1) The result obtained by the full-order method is conservative when the extreme wind pressure events among different sectors are independent. 2) The result obtained by the first-order method for a high return period is not significantly affected when the extreme wind speeds among the different sectors are assumed to be independent. These two assumptions are validated by examples in different regions and theoretical derivation.

• Archives of Craniofacial Surgery
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• v.10 no.2
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• pp.76-80
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• 2009

Purpose: Zygoma is a major portion of the midfacial skeleton, forms the malar prominence and the three adjacent bony articulations. Zygoma fracture is a very common in facial trauma. Open reduction and rigid fixation of displaced zygoma fractures are necessary to avoid immediate and delayed facial asymmetry and depression. However, it is possible to happen the complications related to the plates and screws. So, we planned to treat the 24 patients of Group II, III, IV zygoma fractures with precise reduction and non-fixation method via intraoral approach. Methods: From August, 2006, to August, 2009, we treated 24 cases of zygoma fracture with reduction and non-fixation methods. Before the surgery, we choose the patients who could be treated with this method among the Group II, III, IV patients. Results: No patients in this study had postoperative complications such as displacement of bony fragments, facial depression and asymmetry, malocclusion, hypoesthesia. Satisfactory aesthetic and functional results can be obtained. Conclusion: In the treatment of the zygoma fracture, it is possible to treat with precise reduction and non-fixation method. The greatest advantage is to decrease the operative time, no need to wide dissection, no complications related to the plates and screws. For the using of this method, it is necessary to choose the adequate patients through the preoperative planning.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.8 no.6
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• pp.46-54
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• 2009

This study deals with the effects on the accident reduction according to the installation of RLC (red light cameras). The objective is to analyze the effects on the accident reduction using EB (Empirical Bayes) method. In pursuing the above, the study uses the 728 accident data occurred at the 28 intersections which RLC are installed. The main results are as follows. First, the effects of accident reduction were analyzed to be 20.74% by simple before-after study method. Second, the safety performance functions (SPF) were developed by the Poisson and negative binominal regression models, and since the over-dispersion parameter was close to zero, Poisson model was evaluated to be more appropriate than the negative binominal model. Also, the Poisson model was analyzed to be statistically significant because its ${\rho}^2$ value was 0.409. Finally, the results of analysis using an EB method showed that the accidents were reduced by range from 3.89 to 29.23%.

• Ocean and Polar Research
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• v.42 no.4
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• pp.293-301
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• 2020

Blades of tidal stream turbines have to sustain many different loads during operation in the underwater environment, so securing their structural safety is a key issue. In this study, we focused on periodic loads due to wave orbital motion and propose a load reduction method with a blade design. The flap of an airplane wing is a well-known structure designed to increase lift, and it can also change the load distribution on the wing through deflection. For this reason, we adopted a passive flap structure for the load reduction and investigated its effectiveness by an analytical method based on the blade element moment theory. Flap torsional stiffness required for the design of the passive flap can be obtained by calculating the flap moment based on the analytic method. Comparison between a flapped and a fixed blade showed the effect of the flap on load reduction in a high amplitude wave condition.

• Proceedings of the Optical Society of Korea Conference
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• 1998.08a
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• pp.210-211
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• 1998

• Journal of Korean Society for Quality Management
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• v.44 no.3
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• pp.473-486
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• 2016

Purpose: Although the price reduction policy is established for military supplies, it is more focused on general military items. Therefore, it is hard to apply the current price reduction policy directly to the major weapon system. The purpose of this study is to develop an evaluation model which generates appropriate outputs for price reduction of military supplies. Methods: To improve the current policy, we first analyze the relevant policies of price reduction of similar organizations. We gather the opinions of related organization through survey including DAPA, Logistics Command, DTaQ and Defense industry companies. Then, we develop a price reduction model based on the analytic hierarchical process(AHP) method to find out important factors for price reduction. Results: The results of AHP analysis show that the important factors when applying price reduction of military supplies. From the analysis, the proposed method effectively generates the amounts of price reduction for the nonconformance items. Conclusion: The results of this research will be used as guidelines to improve military supplies policy of price reduction.