• 산업경영시스템학회지
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• 제35권2호
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• pp.16-20
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• 2012

The purpose of this thesis is to develop a performance rating training tool for the time and motion study. It is widely recognized that rating training tools based on films were made several decades ago and introduced to Korea. However, to the best of our knowledge, those films are not used for rating training in Korea any more. Furthermore, although rating is still important method for the efficient operational management study, it is briefly mentioned without any training or exercise. In this paper, we propose a simple rating training tool based on Excel with VBA. The mottoes of our development are the ease of acquisition and trainees' motivation. Test results show that trainees can obtain the concept of rating and the ability of accurate and consistent rating as they play a computer game sitting in front of the personal computer.

• International Journal of Naval Architecture and Ocean Engineering
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• 제13권1호
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• pp.367-378
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• 2021

This paper develops a dynamic regression model to quantify the contribution of key external factors to operational energy efficiency of ships. On this basis, kernel density estimation is applied to explore distribution patterns of fluctuations in operational performance. An empirical analysis based on these methods show that distribution of fluctuations in Energy Efficiency Operational Indicator (EEOI) is leptokurtic and fat tailed, rather than a normal one. Around 85% of fluctuations in EEOI can be jointly explained by capacity utilization and sailing speed, while the rest depend on other external factors largely beyond control. The variations in capacity utilization and sailing speed cannot be fully passed on to the energy efficiency performance of ships, due to complex interactions between various external factors. The application of the methods is demonstrated, showing a potential approach to develop a rating mechanism for use in the legally binding framework on operational energy efficiency of ships.

• 한국초전도ㆍ저온공학회논문지
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• 제5권1호
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• pp.103-106
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• 2003

The short circuit current problem is one of the operational problems that need to be solved by power system engineers in Korea. It is an important issue in the Seoul metropolitan area especially because of highly meshed configuration. Currently, it is regulated by changing 154 kV system configuration from loop connection to radial system, by splitting of the bus where load balance can be achieved, and by upgrading circuit breaker rating. A development project for 154 kV/2 KA SFCL application to 154 kV transmission system after 2010 is proceeding. In this paper, a feasibility study of superconducting fault current limiter (SFCL) is carried out in Seoul metropolitan area to find out the effects of its application and feasibility. This study shows that it can reduce fault current considerably, and as it can minimize the upgrading of circuit breaker rating, the economic potential of SFCL is evaluated positively.

• 전력전자학회논문지
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• 제19권5호
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• pp.391-398
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• 2014

This paper presents a resonant step-down DC/DC converter to reduce the voltage stresses of a 3-phase inverter module under the three-phase AC utility line condition. Under this condition, a conventional 3-phase inverter module suffers from high voltage stresses as a result of the high rectified DC link voltage; hence, a high-cost high-voltage-rating inverter module must be used. However, using the proposed converter, a low-cost low-voltage-rating inverter module may be adopted to drive the motor even under the 3-phase AC line condition. The proposed converter, which can be realized with small size inductor and low-voltage-rating semiconductor devices, operates at a high-efficiency mode because of the zero-current switching operations of all the semiconductor devices. The operational principles are explained and a design example is provided in the study. Experimental results demonstrate the validity of the proposed converter.

• 전력전자학회논문지
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• 제18권2호
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• pp.169-177
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• 2013

This paper proposes a new configuration of bidirectional intelligent semiconductor transformer with rating of 1.9kV/127V, 2kVA. The proposed transformer consists of high-voltage high-frequency AC-DC rectifier, and low-voltage DC-DC and DC-AC converters. The operational feasibility of proposed transformer was verified by computer simulation with PSCAD/EMTDC software. Based on the simulation results, a hardware prototype with rating of 1.9kV/127V, 2kVA was built and tested in the lab to confirm the feasibility of hardware implementation. Using three units of this transformer, a 3-phase transformer with rating of 3.3kV/220V, 6kVA can be built.

• Journal of Electrical Engineering and Technology
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• 제3권3호
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• pp.391-400
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• 2008

Multi-pulse topology of converters using elementary six-pulse GTO - VSC (gate turn off based voltage source converter) operated under fundamental frequency switching (FFS) control is widely adopted in high power rating static synchronous compensators (STATCOM). Practically, a 48-pulse ($6{\times}8$ pulse) configuration is used with the phase angle control algorithm employing proportional and integral (PI) control methodology. These kinds of controllers, for example the ${\pm}80MVAR$ compensator at Inuyama switching station, KEPCO, Japan, employs two stages of magnetics viz. intermediate transformers (as many as VSCs) and a main coupling transformer to minimize harmonics distortion in the line and to achieve a desired operational efficiency. The magnetic circuit needs altogether nine transformers of which eight are phase shifting transformers (PST) used in the intermediate stage, each rating equal to or more than one eighth of the compensator rating, and the other one is the main coupling transformer having a power rating equal to that of the compensator. In this paper, a two-level 48-pulse ${\pm}100MVAR$ STATCOM is proposed where eight, six-pulse GTO-VSC are employed and magnetics is simplified to single-stage using four transformers of which three are PSTs and the other is a normal transformer. Thus, it reduces the magnetics to half of the value needed in the commercially available compensator. By adopting the simple PI-controllers, the model is simulated in a MATLAB environment by SimPowerSystems toolbox for voltage regulation in the transmission system. The simulation results show that the THD levels in line voltage and current are well below the limiting values specified in the IEEE Std 519-1992 for harmonic control in electrical power systems. The controller performance is observed reasonably well during capacitive and inductive modes of operation.

• 한국콘텐츠학회논문지
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• 제15권12호
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• pp.285-293
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• 2015

본 연구는 요양병원 의사 및 간호 인력 대상으로 차등등급에 따른 의료서비스 질 향상 및 만족도, 병원운영성과에 대하여 어떻게 인지하고 있는지를 파악함으로써 차등등급제도가 효율적으로 운영되기 위한 기초자료를 제공하기 위하여 수행되었다. 본 연구의 결과는 다음과 같다. 의사 등급과 간호 인력 등급에 따른 차이분석을 위해 독립표본t검증을 실시한 결과, 의사2등급에서 환자권리향상과 경영 효율성이 높다는 것을 알 수 있었고, 간호 인력 2등급에서 환자안전향상, 진료향상, 환자권리향상이 높다는 것을 확인하였다. 의사 및 간호 인력 등급에 따른 차이분석을 위해 ANOVA분석을 실시한 결과, 환자안전향상, 병원재정, 병원위상에서는 의사 1, 간호 인력 2등급에서, 환자권리향상 및 자기계발에서는 의사 2, 간호 인력 1등급에서 높다는 것을 확인하였다. 전반적으로 의사, 간호 인력의 등급은 높지만, 1등급과 2등급 간의 차이는 각 부문 별로 상이한 결과가 나와 향후 요양병원 차등등급제의 의사 및 간호 인력 1, 2등급 간의 산정기준 개편을 고려할 필요가 있을 것이다.

• Journal of Biosystems Engineering
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• 제35권2호
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• pp.69-76
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• 2010

This study was conducted to develop an index of fuel consumption to rate agricultural tractors by their fuel efficiencies. The fuel consumption index consisted of two components: basic and operational indexes. The basic index is to consider an average amount of fuel consumed by engine when it transmits 20 and 100% of the rated power. The operational index is to consider the fuel consumed by tractor for typical field operations: plowing, rotavating, and the remains. The equations and procedures to obtain these indexes were proposed. The method and fuel consumption rate to classify tractors into 5 grades were also proposed. The best 15% of the tractor models were rated as the first grade, 20% as the second grade, 30% as the third grade, 20% as the fourth grade, and 15% as the fifth grade in order of fuel efficiency. Using the fuel consumption index, the classification was conducted on 143 tractor models tested at the National Institute of Agricultural Engineering from 2000 to 2007. The proposed 5-grade system of classification using the fuel consumption index could be used to rate the fuel efficiency of 20-100 kW tractor models produced over past 10 years in Korea.

• 한국디지털정책학회:학술대회논문집
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• 한국디지털정책학회 2004년도 춘계학술대회
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• pp.195-204
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• 2004

Due to growth of diversified media, content screening is the definite procedures. The procedures of screening varies from country by country in various reasons. Therefore, reason of conducting such study is to compare & contrast screening process by countries. In order to clarify definition of terms that measures screening, "censorship" means "legislative filtering process prior to public appearance". In contrary "Rating and/or Classification" is defined opposite of it. After defining these terms, Screening is dignified into two distinctive measures, which are "legislative intereference" and "voluntary notification". Those two measures are again sub-categorized into eight distinctive operational definition. Utilizing those distinctive measures, our study has concluded as US, Japan and some laissez-faire countries use "voluntary notification" systems but in contrast China and Brunei use "legislative filtering" system.? Korea and Australia uses unique combination of both system. In order for Korea to adopt "voluntary notification system", legislative intereference must be weaken and develop strong "voluntary notification" system.

• 전기학회논문지
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• 제61권9호
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• pp.1221-1225
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• 2012

This paper describes CSC(Current Sourced Converters)-based HVDC operational strategy for voltage stability enhancement in the power system. In case of CSC-based HVDC system, rectifier and inverter consume reactive power up to about 60% of converter rating. Therefore, CSC-based HVDC is basically not useful system for voltage stability even if AC filters and shunt capacitors are attached. But, If the particular power system condition is fulfilled, CSC-based HVDC also can be the rapid reactive power source for voltage stability enhancement using a cooperative control with converter and AC filters/Shunt Capacitors. In this paper, the cooperative control algorithm is presented and simulated to ${\pm}80kV$ 60MW HVDC system in Jeju island.