• Journal of Electrical Engineering and Technology
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• v.9 no.5
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• pp.1527-1536
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• 2014

This paper investigates the optimal values of turn-on and turn-off angles, and ratio of flux linkage at turn-off angle and peak phase current positions of optimal control for accomplishing maximum output power in an 8/6 Switched Reluctance Generator (8/6 SRG). Phase current waveform is analyzed to determine optimal excitation angles (optimal turn-on and turn-off angles) of the SRG for maximum output power which is applied from a nonlinear magnetization curve in terms of control variables (dc bus voltage, shaft speed, and excitation angles). The optimal excitation angles in single pulse mode of operation are proposed via the analytical model. Simulated and experimental results have verified the accuracy of the analytical model.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.6 s.123
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• pp.553-559
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• 2007

In this study, based on the results from the sinusoidal base excitation analyses of a single degree of freedom system with a tuned mass damper (TMD), it is verified that optimal friction force can improve the performance of a TMD like a linear viscous damper which has been usually used in general TMD. The magnitude of the optimal friction increases with increasing mass ratio of the TMD and decreases with increasing structural damping. Particularly, it is observed that the optimized friction force gives better control performance than the optimized viscous damping of the TMD. However, because the performance of the TMD considerably deteriorates when the friction force increases over the optimal value, it is required to keep the friction force from exceeding the optimal value.

• Journal of applied mathematics & informatics
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• v.4 no.2
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• pp.469-476
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• 1997

In this paper we present a random number generation method which is one of the rejection methods, To accelerate ratio-of-uniform method we use an efficiency variable γ. After finding the optimal value of γwith respect to interesting distribution with pro-portional density random numbers can be generated in acceleration.

• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.675-677
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• 2005

This study proposes a fuzzy classification using EM algorithm. For cluster validation, this approach iteratively estimates the class-parameters in the fuzzy training for the sample classes and continuously computes the log-likelihood ratio of two consecutive class-numbers. The maximum ratio rule is applied to determine the optimal number of classes.

• Journal of the Korean Society for Library and Information Science
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• v.38 no.1
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• pp.35-50
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• 2004

This study evaluated the applicability of the static hierarchic clustering model to clustering query results in OPAC. Two clustering methods(Between Average Linkage(BAL) and Complete Linkage(CL)) and two similarity coefficients(Dice and Jaccard) were tested on the query results retrieved from 16 title-based keyword searchings. The precision of optimal dusters was improved more than 100% compared with title-word searching. There was no difference between similarity coefficients but clustering methods in optimal cluster effectiveness. CL method is better in precision ratio but BAL is better in recall ratio at the optimal top-level and bottom-level clusters. However the differences are not significant except higher recall ratio of BAL at the top-level duster. Small number of clusters and long chain of hierarchy for optimal cluster resulted from BAL could not be desirable and efficient.

• Environmental Engineering Research
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• v.19 no.1
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• pp.9-14
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• 2014

Fenton reaction with zerovalent iron (ZVI) and $Fe^{2+}$ ions was studied to treat pharmaceutical wastewaters (PhWW) including antibiotics and non-biodegradable organics. Incremental biodegradability was assessed by monitoring biochemical oxygen demand (BOD) changes during Fenton reaction. Original undiluted wastewater samples were used as collected from the pharmaceutical factory. Experiments were carried out to obtain optimal conditions for Fenton reaction under different $H_2O_2$ and ion salts (ZVI and $Fe^{2+}$) concentrations. The optimal ratio and dosage of $H_2O_2$/ZVI were 5 and 25/5 g/L (mass basis), respectively. Also, the optimal ratio and dosage of $H_2O_2/Fe^{2+}$ ions were 5 and 35/7 g/L (mass basis), respectively. Under optimized conditions, the chemical oxygen demand (COD) removal efficiency by ZVI was 23% better than the treatment with $Fe^{2+}$ ion. The reaction time was 45 min for ZVI and shorter than 60 min for $Fe^{2+}$ ion. The COD and total organic carbon (TOC) were decreased, but BOD was increased under the optimal conditions of $H_2O_2$/ZVI = 25/5 g/L, because organic compounds were converted into biodegradable intermediates in the early steps of the reaction. The BOD/TOC ratio was increased, but reverse-wise, the COD/TOC was decreased because of generated intermediates. The biodegradability was increased about 9.8 times (BOD/TOC basis), after treatment with ZVI. The combination of chemical and biological processes seems an interesting combination for treating PhWW.

• Journal of the Korean Solar Energy Society
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• v.35 no.6
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• pp.51-60
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• 2015

In statutes on the promotion of distribution of new and renewable energy, which were revised in 2014, daylight system and fuel cell were added in addition to existing new and renewable energy sources. This study, therefore, aimed at setting up targets for the introduction of daylight system and analyzing the installation rate of new and renewable energy which can be provided by daylight system for the aggressive use of daylight system, thereby deducting the optimal combination ratio with other new and renewable energy sources. The results of the study are as follows. First, when a prism-shaped daylight system was installed to a round indoor gymnasium among domestic indoor gymnasiums, out of a supply obligations allotment rate of 15% of new and renewable energy, the rate of daylight system was basically set at 2.5%. Second, therefore, with daylight system coming first, the lacked supply obligations rate was taken up by solar photovoltaic, solar heat and geothermal heat. In addition, using the KRESS Program, economic, technical, environmental and complexity evaluations for the upper 5% was made, deducting the optimal ratio of the system. The results produced the following optimal combination ratios: solar photovoltaic (83.3%) in economic evaluation, solar heat (8.3%) and geothermal heat (75%) in technical evaluation, solar photovoltaic (83.3%) in environmental evaluation, and solar photovoltaic (83.3%, the same as in economic evaluation) in complexity evaluation.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.8
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• pp.439-447
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• 2009

Cogeneration system produces power as well as heat recovered from waste heat during power generation process. This system has higher energy efficiency than that of the power plant. In this study the optimal design for the cogeneration system with the increase of the capacity considering life cycle cost(LCC) analysis has been performed in the general facilities such as hotels and hospitals under the assumption of electricity cost of 95 won/kWh, the initial cost of cogeneration system of 1,500,000 won!kW and the value of 0.5${\sim}$1.0 in the ratio of heat to power. The optimal ratio of cogeneration capacity divided by average electricity load of facility was found out more than 0.5 in case of electricity cost with the increase of>30%, and the percentage of $CO_2$ reduction was about 9%. The most important factors in the economic analysis of cogeneration system was found out the electrity cost and the initial cost of cogeneration system. Also the ratio of heat to power at the value of>0.5 was not affected in the economy of cogeneration system, but was very important in the $CO_2$ reduction.

• Korean journal of food and cookery science
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• v.12 no.3
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• pp.331-338
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• 1996

The main aim of this study was to develop carrot soups with fishery products, which is improved from traditional gruel of Cheju island. For this the optimal procedure and ingredient mixing ratio for making basic carrot soup was determined through the instrumental measurement, the sensory evaluation and the nutrient analysis, and then the carrot-fishery soups were prepared by mixing the fishery products from Cheju island. The results were as follows: The optimal procedure for making basic carrot soup was to saute the sliced carrots and soaked rices with the sesame oil for 5 min, add the water, bring to a boil for 6 min, simmer for 15 min, then puree the soup. The optimal ingredient mixing ratio in the basic carrot soup was carrot 300 g: rice 45 g: water 900 $m\ell$: sesame oil 15 $m\ell$: salt 5 g. For preparing carrot-fishery soups were the optimal fishery products mixing ratio i) 30% tile fish or crab, ii) prawn, abalone, top shell, or ear shell 20%, iii) sea urchin 15%, iv) fusiform or gulf weed 5％. The order of sensory evaluation scores, on a 5-point scale, were sea urchin, crab > top shell, tile fish > abalone, ear shell > prawn > coral fish > fusiform, gulf weed. Nutrient composition analysis showed that vitamin A was 5 times higher in carrot soup than in pumpkin soup. Sensory evaluation scores show that carrot soup was prepared to pumpkin soup. A portion (200 g) of the soup would provide 144% of the recommended daily allowance of vitamin A. The results of this work indicate that an acceptable carrot-fishery soups of better nutritional and sensory values than pumpkin soup can be prepared.

• Asia-Pacific Journal of Business
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• v.14 no.1
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• pp.149-169
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• 2023

Purpose - The main purpose of this study is to develop the stress test model for Korean banks by exploring the optimal Monte Carlo simulation and BIS forecasting model. Design/methodology/approach - This study selects 15 Korean banks as sample financial firms and collects relevant 76 quarterly data for the period between year 2000 and 2018 from KRX(Korea Excange), Bank of Korea, and FnGuide. The Regression analysis, Unit-root test, and Monte Carlo simulation are hired to analyze the data. Findings - First, most of the sample banks failed to keep 8% BIS ratio for the adverse and severely Adverse Scenarios, implying that Korean banks must make every effort to realize better BIS ratios under adverse market conditions. Second, we suggest the better Monte Carlo simulation model for the Korean banks by finding that the more appropriate volatility should be different depending on variables rather than simple two-sigma which has been used in the previous studies. Third, we find that the stepwise regression model is better fitted than simple regression model in forecasting macro-economic variables for the BIS variables. Fourth, we find that, for the more robust and significant statistical results in designing stress tests, Korean banks are required to construct more valid time-series and cross-sectional data-base. Research implications or Originality - The above results all together show that the optimal volatility in designing optimal Monte Carlo simulation varies depending on the country, and many Korean banks fail to pass sress test under the adverse and severely adverse scenarios, implying that Korean banks need to make improvement in the BIS ratio.