• Journal of Power Electronics
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• v.14 no.2
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• pp.302-314
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• 2014

Due to advancements in power electronics and inverter topologies, the current controlled multilevel voltage-source pulse width modulated (PWM) inverter is usually preferred for accurate control, quick response and high dynamic performance. A multilevel topology approach is found to be best suited for overcoming many problems arising from the use of high power converters. This paper presents a comprehensive review and comparative study of several current control (CC) techniques for multilevel inverters with a special emphasis on various approaches of the hysteresis current controller. Since the hysteresis CC technique poses a problem of variable switching frequency, a ramp-comparator controller and a predictive controller to attain constant switching frequency are described along with its quantitative comparison. Furthermore, various methods have been reviewed to achieve hysteresis current control PWM with constant switching frequency operation. This paper complies various guidelines to choose a particular method suitable for application at a given power level, switching frequency and dynamic response.

• Journal of Power Electronics
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• v.9 no.6
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• pp.949-959
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• 2009

This paper presents a systematic investigation of the fault-mode behaviors of matrix converter systems. Knowledge about converter behaviors after fault occurrence is important from the standpoint of reliable system design, protection and fault-tolerant control. Converter behaviors have been, in detail, examined with both qualitative and quantitative approaches for key fault types, such as switch open-circuited faults and switch short-circuited faults. Investigating the fault-mode behaviors of matrix converters reveals that converter operation with switch short-circuited faults leads to overvoltage stresses as well as overcurrent stresses on other healthy switching components. On the other hand, switch open-circuited faults only result in overvoltage to other switching components. This study can be used to predict fault-mode converter behaviors and determine additional stresses on remaining power circuit components under fault-mode operations.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2003.11a
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• pp.233-236
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• 2003

Redesign of business processes still attracts a lot of interest. There have been a variety of quantitative approaches to analyze of business process. However, to examine and determine the quality-focused characteristics of the business process, a qualitative approach should be deployed. This paper introduces a qualitative approach process analysis, especially adopted the concept of the emotional engineering which is used in the area of the product design. To analyze the qualitative aspect of the business process, the emotional adjectives for the business process are used. The proposed methodology enables to determine which of business process is better or not in a more intuitive way.

• Korean Management Science Review
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• v.32 no.1
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• pp.133-145
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• 2015

Motion picture industry in Korea has been growing constantly and aroused various kinds of research attention. Particularly, the introduction of official box-office database service brought quantitative studies. However, approaches based on diffusion models have been rarely found with domestic film markets. In addition to the fundamental statistical review on Korea and US film markets, we applied a diffusion model to daily box-office revenue. Unlike conventional preference of Gamma distribution on the film markets, estimation results proved that BMIC can also explain the trend of daily revenue successfully. The comparison with BMIC showed that there is a distinctive difference in diffusion patterns of Korea and US film markets. Generally, word-of-mouth effect appeared more significant in Korea.

• Journal of Korean Society for Quality Management
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• v.30 no.3
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• pp.38-52
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• 2002

This paper is concerned with the analysis of structural equation model(SEM) with the ordinal data such as Likert scale. The SEM is misused when the arbitrary scores allocated to the Likert scale are treated as quantitative data. The underlying distribution approaches have been studied to solve this problem, and the partial least squares(PLS) Is also tried. In this paper the quantification methods for the Likert scale are proposed to analyze the SEM. We assume that the Likert scale is an observation of the interval of the continuous underlying distribution, and the respondents have their own patterns in the response of some questions. Normal and beta distributions as the response patterns are considered to quantify the Likert scale. To compare the efficiency of the proposed method the bootstrap simulations are tried.

• IE interfaces
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• v.14 no.3
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• pp.310-317
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• 2001

The purpose of this study is to investigate and to develop a decision support system for supporting the outworn facility replacement analysis in shipbuilding. This paper also provides an information system which can be effectively applied to various criteria in decision making. The modelbase of decision support system uses the concepts of the analytic hierarchy process along with an appropriate scoring methods. The AHP represents an improvement over other well-known scoring approaches since the criteria weights of priorities established by the AHP are not based on arbitrary scales, but use a ratio scale for human judgements. The proposed methodology in this research enables the decision maker to evaluate the investment alternatives based on qualitative data and quantitative data in a systematic way.

• Proceedings of the Korea Society for Simulation Conference
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• 2001.10a
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• pp.13-19
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• 2001

Unlike that of most management science methodologies, the focus in systems thinking is not on \\\"solving\\\" problems or seeking an optimal solution. Conventional problem solving does not explicitly consider the context of the problem. This implies that the \\\"hospital financial management problem\\\" could be neatly isolated from its environmental and external factors. System thinking and system archetypes, in contrast, acknowledges the messiness of the world and views a problem in the context of its environment. This is one reason why qualitative variables play an important role in system thinking, as these variables represent conditions or phenomena that cannot be measured or accounted in a strictly quantitative approaches. In this paper we present specific healthcare system archetypes which consider such external influences in the healthcare industry in Australia and observe their behavior over time. behavior over time.

• Journal of Construction Engineering and Project Management
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• v.3 no.3
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• pp.42-48
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• 2013

Construction industry is considered as the most hazardous industry due to its unique nature. Safety and quality management are essential to control hazards and improve success in project implementation. This paper focuses on evaluating the crucial factors influencing safety and quality management in construction projects. In order to achieve this, the qualitative and quantitative approaches were used for data collection. The findings of this study reveal the crucial safety factors as management commitment, safety awareness of top management practices/ procedures/ reviews, and errors in judgement or carelessness. Project supervision, employee involvement/ altitude, and expertise knowledge/ training were considered as the crucial quality factors influencing safety and quality management. The study shows that safety and quality issues cannot be overlooked therefore proper implementation is paramount to achieve project success.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1997.10a
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• pp.247-251
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• 1997

FCM(Fuzzy Cognitive Map) is a fuzzy signed directed graph for representing causal reasoning which has fuzziness between causal concepts. Authors have already proposed FCM-based fault diagnostic scheme and verified its usefulness. However, the previously proposed scheme has the problem of lower diagnostic resolution as in the case of other qualitative approaches. In order to improve the diagnostic resolution, a concept of fuzzy number is introduced into the basic FCM-based fault diagnostic algorithm. By incorporation the fuzzy number into fault FCM models, quantitative information such as the transfer gain between the state variables can be effectively utilized for better diagnostic resolution. Furthermore, an enhanced TAM(Temporal Associative Memory) recall procedure and modified and modified pattern matching scheme are also proposed.

• Journal of the Korean Institute of Telematics and Electronics
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• v.25 no.1
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• pp.49-55
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• 1988

To provide a quantitative parameter of evaluating diagnosis of the liver diseases accurately, the ultrasonic attenuation coefficient was estimated from liver phantoms, 15 normal human livers and 30 liver disease patients. Two kind of phantoms(No.1: 1552m/s, No.2: 1562m/s) which have velocity (1560m/s) similar to that in human liver were constructed and their ultrasonic attenuation coefficients were determined. In this paper the spectral-shift approach and spectral-difference approach were used for estimating ultrasonic attenuation coefficient, \ulcornerdB/Cm.MHz). These two approaches were utilized to esitmate for 15 normal humans without any liver disease and 30 liver disease patients. The results indicate that the two types of phantoms produce the value of near the suggested value of 0.5 and the attenuation coefficients of hepatoma, normal liver, corrhosis, fatty liver and hepatitis show decreasing value in order named, suggesting that the present study can be of clinical value incorrelating the estimated attenuation coefficidents with the liver diseases.