• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.8
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• pp.763-771
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• 2011

An optimization procedure for the design of a ventilation axial-flow fan is presented in this paper. Flow analyses of the preliminary fan are performed by solving three-dimensional Reynolds-averaged Navier-Stokes equations via a finite-volume solver with the shear-stress transport turbulence model as a turbulence closure. Three variables, the hub-to-tip ratio and the stagger angles at the mid and tip spans, are selected for the optimization. The Latin-hypercube sampling method as a design-of-experiments technique is used to generate twenty-five design points within the design space. and the weighted average surrogate models, WTA1, WTA2, and WTA3, are applied for find optimal designs. The results show that the efficiency is considerably enhanced.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.4
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• pp.407-416
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• 2007

Fuel spray nozzle has a critical effect on combustion characteristics. Mass flow rate and SMD(sauter mean diameter) were selected as design variables by using the experiment data of various types of duplex fuel nozzles for the swirl atomizers. The sensitivity of each design variable on the mass flow rate and SMD was analyzed and the uniformity of mass flow rate was investigated through the shape optimization of duel-orifice-type swirl atomizers. The design variables that have a little effect on the optimum design were excluded using the DOE(design of experiments) method, which enabled the optimization of sensitive design variables on mass flow rate and limit tolerance. The SMD of the research spray nozzle that was used in this study was found to be most similar to that of the calculation results using the Jasuja's SMD relationship. This study showed the specific characteristics of duel orifice type swirl atomizers and the optimization of these kinds of nozzle. This study provided the optimization design of mass flow rate and its allowable tolerance.

• Journal of Korea Water Resources Association
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• v.36 no.2
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• pp.143-152
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• 2003

This paper suggests the improvement of the Sumjinkang for the estimation of areal averages of heavy rainfall events based on the optimal network and three existing networks. The problem consists of minimizing an objective function which includes both the accuracy of the areal mean estimation as expressed by the Kriging variance and the economic cost of the data collection. The wellknown geostatistical variance-reduction method is used in combination with SATS which is an algorithm of minimization. At the first stage, two kinds of optimal solutions are obtained by two trade-off coefficients. One of them is a optimal solution, the other is an alternative. At the second stage, a quasi optimal network and a quasi alternative are suggested so that the existing raingages near to the selected optimal raingages are included in the two solutions instead of gages of new gages.

• Journal of Korea Water Resources Association
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• v.56 no.12
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• pp.969-980
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• 2023

Since the 2000s, ensemble streamflow prediction (ESP) has been actively utilized in South Korea, primarily for hydrological forecasting purposes. Despite its notable success in hydrological forecasting, the original objective of enhancing water resources system management has been relatively overlooked. Consequently, this study aims to demonstrate the utility of ESP in water resources management by creating a simple hypothetical exercise for dam operators and applying it to actual multi-purpose dams in South Korea. The hypothetical exercise showed that even when the means of ESP are identical, different costs can result from varying standard deviations. Subsequently, using sampling stochastic dynamic programming (SSDP) and considering the capacity-inflow ratio (CIR), optimal release patterns were derived for Soyang Dam (CIR = 1.345) and Chungju Dam (CIR = 0.563) based on types W and P. For this analysis, Type W was defined with standard deviation equal to the mean inflow, and Type P with standard deviation ten times of the mean inflow. Simulated operations were conducted from 2020 to 2022 using the derived optimal releases. The results indicate that in the case of Dam Chungju, more aggressive optimal release patterns were derived under types with smaller standard deviations, and the simulated operations demonstrated satisfactory outcomes. Similarly, Soyang Dam exhibited similar results in terms of optimal release, but there was no significant difference in the simulation between types W and P due to its large CIR. Ultimately, this study highlights that even with the same mean values, the standard deviation of ESP impacts optimal release patterns and outcomes in simulation. Additionally, it underscores that systems with smaller CIRs are more sensitive to such uncertainties. Based on these findings, there is potential for improvements in South Korea's current operational practices, which rely solely on single representative values for water resources management.

• KIPS Transactions on Software and Data Engineering
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• v.6 no.12
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• pp.565-572
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• 2017

Traditional method for time series analysis, autoregressive integrated moving average (ARIMA) allows to mine significant patterns from the past observations using autocorrelation and to forecast future sequences. However, Korean baseball games do not have regular intervals to analyze relationship among the past attendance observations. To address this issue, we propose artificial neural network (ANN) based attendance prediction model using various measures including performance, team characteristics and social influences. We optimized ANNs using grid search to construct optimal model for regression problem. The evaluation shows that the optimal and ensemble model outperform the baseline model, linear regression model.

• Communications for Statistical Applications and Methods
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• v.19 no.1
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• pp.107-115
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• 2012

Yoo and Cook (2007) developed an optimal sufficient dimension reduction methodology for the conditional mean in multivariate regression and it is known that their method is asymptotically optimal and its test statistic has a chi-squared distribution asymptotically under the null hypothesis. To check the effect of dimension used in estimation on regression coefficients and the explanatory power of the conditional mean model in multivariate regression, we applied their method to several simulated data sets with various dimensions. A small simulation study showed that it is quite helpful to search for an appropriate dimension for a given data set if we use the asymptotic test for the dimension as well as results from the estimation with several dimensions simultaneously.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2022.05a
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• pp.119-121
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• 2022

In this paper, we will make a model that finds optimal phase for each crossroad. When the traffic volume, traffic capacity, and the lane width of every direction is given for each crossroad, we aim to find the most efficient phase. We established an evaluation function that evaluates the efficiency of each phase using the values of the average waiting time in one direction, the average delay time, the standard deviation of the delay time, and the average delay time in each direction. The time allocation to optimize a phase pattern can be obtained by using the gradient decent method. Through this research, we hope to decrease the waiting time in transporation, thus improving the overall traffic condition in cities.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.14 no.6
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• pp.699-712
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• 1989

This paper describes a method of Korean speech synhes is using format VOCODER. The parameters of speech synthes is are a follows, 1) format F1, F2, and F3 by spectrum moment method and F4, F5 using the length of vocal tract. 2) pitch frequencies obtained by optimu, Comb method using AMDF. 3) short time average energy and short time mean amplitude. 4) The decision method of bandwidth reportd by Fant. 5) voicde/unvoiced discrimination using zerocrossing. 6) excitation wave reported by Rosenberg. 7) gaussian white noise. Synthesis results are in fairly good agreement with original speech.

• Applied Chemistry for Engineering
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• v.9 no.3
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• pp.394-398
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• 1998

An optimum synthetic condition was studied for the MCS used as a silicone monomer. The contact mixture was made from the four component catalyst system($CuCl/ZnCl_2/Sn/Cd$) and silicon particles. The contact mass was used for a series of experiments with methyl chloride, which were designed and done to explore the optimum condition for MCS synthesis by an experimental design method. The optimum temperature and MeCl flow rate, which were obtained using 50g contact mass at 60rpm and 1 atm, were in the range of $300-305^{\circ}C$ and of 70-80ccm. Also a continuous run was performed to confirm the conditions. The results showed that the average reaction rate and selectivity were 170(g-MCS/hr.kg-Si) and 0.05 respectively at 67% conversion of MeCl and 92% silicon utilization rate. Also the parameters of overall reaction rate equation and a total pressure were estimated on the basis of the results of the continuous run.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.621-622
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• 2015

최근 늘어나는 전력 수요에 따라, 세계적으로 전력에너지 절감을 통한 수요자원 확보 및 활용을 위한 부하 예측의 중요성이 증가하고 있다. 본 논문에서는, 수요관리용 전지전력저장시스템을 효율적으로 운영하고 계획하는데 필수적인 부하예측의 정확성을 높이기 위하여 이동평균법, 지수가중이동평균법, 최소자승법, 인공신경망 방법을 적용하였다. 시계열 데이터인 부하 데이터를 분석하여 최대부하일, 근무일, 토요일, 공휴일로 분류하였고, 각각의 방법으로 예측한 부하를 적용시켜 전기요금 절감을 목표로 하는 전지전력저장시스템의 최적 충 방전 운전계획을 세웠으며, 이를 이용하여 산출된 전기요금과 실제 전기요금을 비교 분석하였다.