• Journal of Korea Water Resources Association
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• v.51 no.1
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• pp.61-70
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• 2018

This study examined how to determine the optimal sediment level in dam reservoir for efficient plan and operation of dam. Currently, Korea is applying a horizontally accumulated method for sediment level estimation for the safety design of dam and so the method estimated relatively higher level than others. However, the sediment level of dam reservoir should be accurately estimated because it is an important factor in assessing life cycle of a dam. The sediment level in dam reservoir can be determined by SED-2D model linked with RMA-2, horizontally accumulated method, area increment method, and empirical area reduction method. The estimated sediment level from each method was compared with the observed sediment level measured in 2007 in Imha dam reservoir, Korea and then the optimal method was determined. Also, the future sediment level was predicted by each method for the future trend analysis of sediment level. As the results, the most accurate sediment level was estimated by the empirical area reduction method and the future trend of sediment level variation followed the past trend. Therefore, we have found that the empirical area reduction method is a proper one for more accurate estimation of sediment level and it can be validated by the results from a numerical model of SED-2D linked with RMA-2 model.

• Journal of Internet Computing and Services
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• v.9 no.3
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• pp.69-77
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• 2008

An algorithm for tracking the trace of structured light is proposed to obtain depth information accurately. The technique is based on the fact that the pixel location of light in an image has a unique association with the object depth. However, sometimes the projected light is dim or invisible due to the absorption and reflection on the surface of the object. A dynamic programming approach is proposed to solve such a problem. In this paper, necessary mathematics for implementing the algorithm is presented and the projected laser light is tracked utilizing a dynamic programming technique. Advantage is that the trace remains integrity while many parts of the laser beam are dim or invisible. Experimental results as well as the 3-D restoration are reported.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.9
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• pp.1007-1013
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• 2011

Because of their high flexibility and durability, multilayer bellows are manufactured for use in commercial vehicles, while single-layer bellows are manufactured for use in passenger vehicles. A study based on the finite element method (FEM) and shape optimization for the single-layer bellows has been actively performed; however, until now, a study based on the FEM has rarely been performed for the multilayer bellows with gaps between the layers. This paper presents a finite-element modeling scheme for the multilayer bellows to improve simulation reliability during the evaluation of stress and flexibility. For performing shape optimization for the multilayer bellows, DOE (design of experiment) and the Kriging metamodel followed by the D-optimal method are used.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.327-332
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• 2001

An experimental design technique is developed for estimating the moments of system response functions. It is easy to implement and provides accurate results compared with other traditional methods. It is based on the work of Taguchi, later improved by D'Errico and Zaino. The existing experimental techniques, however, is applicable only for normally distributed cases. In this article the three-level Taguchi method is extended to obtain optimum choice for levels and weights to handle nonnormal distributions. A systematic procedure for reliability analysis is then proposed by using the Pearson system and the narrow system reliability bounds. Illustrative examples including a tolerance optimization problem are shown very accurate comparing with those by Monte-Carlo simulations and the first-order reliability method.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.4
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• pp.174-178
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• 2008

Nano-crystalline slaked lime was synthesized using design of experiment. In order to synthesize slaked lime, calcium chloride $(CaCl_2)$ and urea were used as starting materials. Calcium chloride solution and urea solution were mixed and heated in vessel that calcium carbonate was precipitated during heating. Precipitates were filtered, washed several times using D.I.water and ethanol and finally dried in oven. Slaked lime $(Ca(OH)_2)$ has been fabricated by the hydration of calcined $CaCO_3$. Design of experiment (Taguchi method) was used to optimize parameter, to minimize noise factors of experiment and to statistically analyze the results. Slaked lime having about 50 nm in optimized crystallite size could be obtained by calcination of $CaCO_3$ at $1000^{\circ}C$ for 0.5 h and hydration with D.I water containing ethanol and oxalic acid.

• Proceedings of the KWS Conference
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• 2010.05a
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• pp.77-77
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• 2010

본 연구에서는 Sn-3.0Ag-0.5Cu (SAC305) 무연솔더의 최적 인쇄성을 위한 PCB 및 마스크설계, 스크린프린팅 공정변수의 최적값을 실험계획법을 통해 평가하였다. 사용된 칩은 가로 0.4mm 세로 0.2mm의 0402 MLCC칩이며, 사용된 시험보드는 OSP 표면처리된 PCB이었다. 인쇄성을 판단하기 위한 공정인자는 금속마스크 두께, 마스크홀 크기, 패드크기 및 모양, 인쇄각도, 인쇄속도, 판분리속도이었다. ANOVA분석을 통해 주인자를 파악하였으며, 인쇄성에 영향을 미치는 주인자는 마스크두께와 인쇄각도임이 확인되었다. 그 후 중심 합성법을 이용하여 인쇄성 최적 조건을 확인하였다. 결과로 나타난 등고선/표면도를 통해, 마스크두께가 작을 때에는 인쇄각도가 작아야 높은 인쇄성을 갖으며, 또한 마스크 두께가 클 경우에는 인쇄각도가 커야 높은 인쇄성을 가짐을 알 수 있었다. 추가실험을 통해서 인쇄성 표면도의 정확도를 확인하였으며, 실험값은 표면도에서 표시된 인쇄성값과 비슷함을 알 수 있었다. 또한, 인쇄성이 낮은 영역과 높은 영역에서 접합강도값을 측정하였으며, 인쇄성이 좋은 영역에서 접합강도도 높음을 알 수 있었다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.4 s.235
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• pp.460-468
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• 2005

Analyses of flow and heat transfer characteristics and shape optimization of internally finned circular tubes have been performed for three-dimensional periodically fully developed turbulent flow and heat transfer. CFD and mathematical optimization are coupled in order to optimize the shape of heat exchanger. The design variables such as fin widths $(d_{1},\;d_{2})$ and fin height (h) are numerically optimized by minimizing the pressure loss and maximizing the heat transfer rate for limiting conditions of $d_{1}=0.2\~1.5\;mm,\;d_{2}=0.2\~1.5\;mm,$ and $h=0.2\~1.5mm$. Due to the periodic boundary conditions along main flow direction, the three layers of meshes are considered. The flow and thermal fields are predicted using the finite volume method and the optimization is carried out by means of the sequential quadratic programming (SQP) method which is widely used in the constrained nonlinear optimization problem.

• Journal of Korean Society of Transportation
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• v.23 no.7 s.85
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• pp.63-74
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• 2005

When we introduce the BRT systems, it is very important to decide the operating factors, such as bus-stop locations or headway. If the factors are inappropriate, unessential expenses for the operator and users of the bus line may be caused, and it leads increase of social total cost. So, it is necessary that we consider users' origin and destination of each bus line when we set location of bus-stops and the optimal headway. Meanwhile, Smart Card System was introduced of fare collection for the Public Transportation Reform in Seoul last year. This new card system makes it possible to store up the information about bus operating and passenger's trip link. With these substantial information. we can estimate bus-stop-based O-D table. So, in this thesis, it was studied a systematic methodology to find the optimal location and headway for skip-stop bus system (as a type of first step for BRT). The proposed methodology in this thesis is expected to be useful to effect analysis or setting operating factors for skip-stop bus system in each bus line.

• Radiation Oncology Journal
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• v.20 no.1
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• pp.24-33
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• 2002

Purpose : In order to improve dose homogeneity and to reduce acute toxicity in tangential whole breast radiotherapy, we evaluated two treatment techniques using multiple static fields or universal compensators. Materials and Methods : 1) Multistatic field technique : Using a three dimensional radiation treatment planning system, Adac Pinnacle 4.0, we accomplished a conventional wedged tangential plan. Examining the isodose distributions, a third field which blocked overdose regions was designed and an opposing field was created by using an automatic function of RTPS. Weighting of the beams was tuned until an ideal dose distribution was obtained. Another pair of beams were added when the dose homogeneity was not satisfactory. 2) Universal compensator technique : The breast shapes and sizes were obtained from the CT images of 20 patients who received whole breast radiation therapy at our institution. The data obtained were averaged and a pair of universal physical compensators were designed for the averaged data. DII (Dose Inhomogeneity Index : percentage volume of PTV outside $95\~105\%$ of the prescribed dose) $D_{max}$ (the maximum point dose in the PTV) and isodose distributions for each technique were compared. Results : The multistatic field technique was found to be superior to the conventional technique, reducing the mean value of DII by $14.6\%$ (p value<0.000) and the $D_{max}$ by $4.7\%$ (p value<0.000). The universal compensator was not significantly superior to the conventional technique since it decreased $D_{max}$ by $0.3\%$ (p value=0.867) and reduced DII by $3.7\%$ (p value=0.260). However, it decreased the value of DII by maximum $18\%$ when patients' breast shapes fitted in with the compensator geometry. Conclusion : The multistatic field technique is effective for improving dose homogeneity for whole breast radiation therapy and is applicable to all patients, whereas the use of universal compensators is effective only in patients whose breast shapes fit inwith the universal compensator geometry, and thus has limited applicability.

• The KIPS Transactions:PartD
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• v.13D no.6 s.109
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• pp.797-806
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• 2006

In the data warehouse environment, materialized views are typically used to support efficient query processing. Materialized views need to be updated when source data change. Since the update of the views need impose a significant overhead, it is essential to update the views efficiently. Though various view maintenance strategies have been discussed in the past, the efficient maintenance of SPJ materialized views has not been sufficiently investigated. In this paper, we propose an efficient incremental view maintenance method for SPJ materialized views that minimizes the total accesses to data sources. The proposed method finds an optimal view maintenance strategy using a dynamic programming algorithm. We also present various experimental results that shows the efficiency of our proposed method.