• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.2 no.2
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• pp.64-70
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• 1988

In many applications of inverter system, it is desirable to obtain an AC output voltage with variable frequency and amplitude. For the variable-speed AC motor drive, the system is one major area of application for the variable-frequency inverter. V ariable~voltage variable-frequency sinusoidal output in three-phase inverter is possible by employing the techniques developed. In this paper, the technique of particular harmonics elimination(PHE) in three-phase PWM inverter-output waveforms is introduced. The required switching patterns are determind on personal computer. Results are stored in look-up table in EPROM and used to control the switching of the inverter devices. The experimental results indicate that the loss in an induction motor is minimized to a degree by using this algorithm. The proposed PWM pattern is effective not only to the induction motor but also to the other electromagnetic machine such as Voltage Regulator, UPS.

• Journal of Korean Society for Quality Management
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• v.39 no.2
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• pp.244-255
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• 2011

In this study, we try to evaluate the efficiency of the photonics industry using a data envelopment analysis(DEA) model. We first develope four stage procedures for selecting proper input and output variables which consist of selecting the first candidate variables from literature survey, selecting the second candidate variables through experts' discussion, measuring the partial efficiency of the selected variables based on Tofallis' profiling, and clustering some variables through the rank correlation analysis of partial efficiency proposed by Min and Kim(l998). With this procedure, we select 4 input variables(capital, number of employee, R&D cost, operating cost) and 2 output variables(sales, growth of sales) and then utilize CCR and BCC model to measure efficiencies of 26 photonics companies in Gwangju. Moreover, we perform the reference group analysis to figure out what causes inefficiencies and to provide the desirable values for input and output variables at which inefficient photonics companies become efficient. Finally, we classify 26 photonics companies into three groups such as optical communications, optical applications, and optical sources, and perform the Kruskal-Wallis test to check if there exist some differences between efficiencies of three groups.

• Computers and Concrete
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• v.30 no.3
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• pp.225-236
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• 2022

In this article, Multi-Gene Genetic Programming (MGGP) is proposed for the estimation of the compressive strength of concrete. MGGP is known to be a powerful algorithm able to find a relationship between certain input space features and a desired output vector. With respect to most conventional machine learning algorithms, which are often used as "black boxes" that do not provide a mathematical formulation of the output-input relationship, MGGP is able to identify a closed-form formula for the input-output relationship. In the study presented in this article, MGPP was used to predict the compressive strength of plain concrete, concrete with fly ash, and concrete with furnace slag. A formula was extracted for each mixture and the performance and the accuracy of the predictions were compared to the results of Artificial Neural Network (ANN) and Extreme Learning Machine (ELM) algorithms, which are conventional and well-established machine learning techniques. The results of the study showed that MGGP can achieve a desirable performance, as the coefficients of determination for plain concrete, concrete with ash, and concrete with slag from the testing phase were equal to 0.928, 0.906, 0.890, respectively. In addition, it was found that MGGP outperforms ELM in all cases and its' accuracy is slightly less than ANN's accuracy. However, MGGP models are practical and easy-to-use since they extract closed-form formulas that may be implemented and used for the prediction of compressive strength.

• Journal of the Korean Institute of Intelligent Systems
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• v.7 no.4
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• pp.58-64
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• 1997

FLC(Fuzzy Logic Controller) is stronger to the disturbance than a classical controller and its overshoot of the intialized value is excellent. In case an unknown process or the mathematical modeling of a complicated system is impossible, a fit control quantity can be acquired by the Fuzzy inference. But FLC can not converge correctly to the desirable value because the FLC's output value by the size of the quantization level of the Fuzzy variable always has a minor error. There are many ways to eliminate the minor error, but I will suggest GA-FLC and EP-FLC Hybrid controller which csombines FLC with GA(Genetic Algorithm) and EP(Evo1ution Programming). In this paper, the output characteristics of this Hybrid controller will be compared and analyzed with those of FLC, it will he showed that this Hybrid controller converge correctly to the desirable value without any error, and !he convergence speed performance of these two kinds of Hyhrid controller also will be compared.

• Journal of the Korea Society of Computer and Information
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• v.11 no.1 s.39
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• pp.157-165
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• 2006

This paper proposes a new output-buffered multicast ATM switch with tandem crosspoints switching fabric, named the MTCOS(Multicast Tandem Crosspoint Output-buffered Switch). The MTCOS consists of multiple simple crosspoint switch fabrics, named TCSF(Tandem Crosspoint Switch Fabric) , and concentrated output buffers for efficient multicasting. The TCSF resolves the cell delay deviation problem which the self-routing crossbar switches inherently have. Further, it offers multiple concurrent pathes from one input to multiple output ports. It also provides multi-channel switching by easy software configuration and has several desirable characteristics such as scalability, high Performance, and modularity. A shared traffic concentration and output queuing strategies of the MTCOS results in lower cell loss as well as lower cell delay time over a wide range of multicast traffic. Furthermore, it has lower hardware complexity than that of the SCOQ and Knockout multicast switch to achieve the same Knockout concentration rate as the conventional switches. It is shown that the proposed switch can be easily applied to design high performance for any multicast traffic by analytic analysis and computer simulation.

• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.1
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• pp.46-53
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• 2009

A new zero-current switching LLC resonant post-regulator for multi-output power system is proposed in this paper. A conventional LLC resonant converter employs extra non-isolated DC/DC converters to obtain tight-regulated multi-slave output voltages. Therefore, it has several serious problems such as a poor efficiency and high cost of production. The proposed post-regulator features low voltage and current stress across the output rectifier diodes and power switches. Moreover, the proposed post-regulator requires only one power switch instead of the bulky and expensive non-isolated DC/DC converter. Therefore, it features a simple structure and lower cost. Especially, since the proposed post-regulator can ensure the ZCS of all power switches, it has very desirable advantages such as more improved EMI characteristics and reduced switching losses. Finally, to confirm the operation, validity, and features of the proposed circuit, experimental results from a proposed zero-current LLC resonant post-regulator are presented.

• The Transactions of the Korean Institute of Power Electronics
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• v.13 no.6
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• pp.439-446
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• 2008

The medium power system for the recent electronic products that can perform the multi-function requires various multi-output, high-efficiency and low cost characteristics. To cope with these critical issues, a new high-efficiency and cost-effective multi-output LLC resonant converter is proposed in this paper. The proposed converter requires only 1 power switch instead of the bulky and expensive non-isolated DC/DC converter. Therefore, it features a simple structure, lower cost and high-efficiency. Especially, since the proposed converter can ensure the ZVS or ZCS of all power switches, it has very desirable advantages such as more improved EMI characteristics and reduced switching losses. Finally, to confirm the operation, validity, and features of the proposed circuit, experimental results from a SMPS prototype for 42" FHD PDP TV are presented.

• Journal of the Economic Geographical Society of Korea
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• v.13 no.3
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• pp.457-469
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• 2010

The study aims to estimate interregional trade coefficient of service industry using the gravity model. The gravity model has been widely used for prediction of the level of human interaction between two regions which is positively related to attraction of them and negatively related to the distance between them. To apply the gravity model for explaining the interregional trade flow of service industry, the choice of proper proxy variables which represent a dependent variable and independent variables is most important. However, the literature shows that there are few studies on this issue. Four models concerned to the choice of proxy variables are considered. Finally, this paper employs the least-squares regression analysis to test the model's goodness-of-fit, and suggests the most appropriate model based on the result from the analysis. The result shows that the interregional trade of service industry in regional input-output table developed by The Bank of Korea is desirable as a dependent variable, the service industry output of export region, the population of import region, and the spatial distance between regions are desirable as independent variables.

• Journal of Chest Surgery
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• v.23 no.1
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• pp.32-40
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• 1990

Surgical correction of congenital cardiac defects in infants and children with an elevated pulmonary arterial pressure or pulmonary vascular resistance carries a significant early postoperative mortality. And accurate assessments of cardiac output is critically important in these patients. From April 1988 through September 1989, serial measurements of cardiac index, ratio of pulmonary-systemic systolic pressure, ratio of pulmonary-systemic resistance, central venous pressure, left atrial pressure, and urine output during the first 48 hours after the cardiac operation were made in 30 congenital cardiac defects associated with pulmonary hypertension. Cardiac index showed significant increase only after 24 hour postoperatively and this low cardiac performance in the early postoperative period should be considered when postoperative management is being planned in the risky patients. There were no variables which showed any significant correlation with cardiac index. In 12 cases[40%], pulmonary hypertensive crisis developed during the 48 hours postoperatively, and they were treated with full sedation, hyperventilation with 100 % 0y and pulmonary vasodilator infusion. In all patient with preoperative pulmonary hypertension, surgical placement of a pulmonary artery catheter is desirable to allow prompt diagnosis of pulmonary hypertensive crisis and to monitor subsequent therapy.

• 한국정보통신설비학회:학술대회논문집
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• 2007.08a
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• pp.390-393
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• 2007

The reliability as well as the power capability of the UPS system can be increased by replacing a single UPS unit with multiple small UPS units in parallel, resulting in a so-called module UPS. This module UPS system allows that a new module can be added or replaced while maintaining power to loads, which is a hot-swappable operation. In addition, it has desirable features such as ease of output power expandability, convenience of maintenance and repair, and high reliability. To realize the module UPS, load sharing without interconnection among parallel connecting modules as well as a small scale and lightweight topology is necessary. The frequency and voltage droop method is applied to parallel operation control to achieve load sharing. 5kVA modules are designed and implemented to confirm the effectiveness of the proposed approaches. Experimental results show that the module UPS system has a high power factor, a low distortion of output voltage and input current, hot-swappable operations and good load sharing characteristics.