• Journal of Korean Society of Industrial and Systems Engineering
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• v.6 no.9
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• pp.35-38
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• 1983

In this paper major subject is to investigate the measurement errors affecting on the determination of observation numbers, which are required for work measurement, to set up the standard work time. The main consider is, however, with clarification of the differences between measurement errors in case of cycle operation being observed based on the continuous and the work elements observation.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.8
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• pp.151-161
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• 2013

An active power factor correction (PFC) circuit is presented which employs a newly proposed input voltage sensor-less control technique operated in continuous conduction mode (CCM) and critical conduction mode (CRM). The conventional PFC circuit with input voltage sensor-less control technique degrades the power factor (PF) under the light load condition due to DCM operation. In the proposed PFC circuit, the switching frequency is basically 70KHz in CCM operation. In light load condition, however, the PFC circuit operates in CRM and the switching frequency is increased up to 200KHz. So CCM/CRM operation of the PFC circuit alleviates the decreasing of the PF in light load condition. The proposed PFC controller IC has been implemented in a $0.35{\mu}m$ BCDMOS process and a 240W PFC prototype is built. Experimental results shows the PF of the proposed PFC circuit is improved up to 10% from the one employing the conventional CCM/DCM dual mode control technique. Also, the PF is improved up to 4% in the light load condition of the IEC 61000-3-2 Class D specifications.

• Resources Recycling
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• v.33 no.2
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• pp.46-53
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• 2024

The residual heat and high CaO content present in the slag remaining in the ladle after the completion of continuous casting in the electric arc furnace (EAF) steelmaking process have been utilized to reduce power consumption and lime usage in the ladle furnace (LF) process. However, if the timing of such processes does not align with the LF and continuous casting operations, the recycling rate will decrease. To increase the slag recycling rate, the effect of ladle slag recycling methods, specifically pouring ladle slag into the slag pot in advance for subsequent recycling, on LF operations was analyzed. The slag liquefaction rate was calculated using the thermodynamic program Factsage 8.3 for ladle molten slag recycling methods. By applying each of the 10 heats operations for the ladle slag recycling methods, the desulfurization ability and LF operation performance were compared. It was found that when slag was immediately recycled into the ladle after continuous casting was completed, power consumption decreased by 0.3 MWh, LF operation time was shortened by 1.2 minutes, and the desulfurization rate increased by 5.8%.

• Journal of Electrical Engineering and Technology
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• v.3 no.2
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• pp.243-253
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• 2008

This paper deals with the analysis, design, and implementation of a single phase AC-DC Zeta converter with high frequency transformer isolation and power factor correction(PFC) in two modes of operation, discontinuous current mode of operation(DCM), and continuous current mode of operation(CCM). A Digital Signal Processor(DSP) based implementation is carried out for validation of the Zeta converter developed design in discontinuous mode of operation. A comparison of both modes of operation is presented for a 1kW power rating from the point of view of steady state and dynamic behavior, power quality, simplicity, control technique, device rating, and converter size. The experimental results of a developed prototype of Zeta converter are presented for validation of the developed design. It is observed that CCM is most suitable for higher power applications where it requires some complex control and sensing of the additional variables.

• Journal of Service Research and Studies
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• v.6 no.4
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• pp.35-45
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• 2016

This study derives the critical success factors through discussion of expert group in operation stage of ERP system that is suggested by the prior study. Relative importance of the derived critical success factors are analyzed using Analytic Hierarchy Process(AHP). In the first layer of the hierarchy, organizational/ human resource factors are appeared to be the most important factors. In the second layer of the hierarchy, CEO support is evaluated as the most important success factor considering the weight of the 1st layer of the hierarchy followed by process optimization, change management, support of the operation department, and maintenance of process innovation organization. This study suggests that, in order to maximize the introducing effect, continuous support and attention of management is not the only requirement. Proper change management to handle the internal environment change caused by the introduction of the ERP system, support of operation department dedicated to ERP system, and separate department for continuous innovation of process are also required.

• Tunnel and Underground Space
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• v.33 no.5
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• pp.299-311
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• 2023

Continuous excavation technologies are developed to improve the excavation rate of shield TBM. Continuous excavation is a technology that provides thrust to segments, excluding being installed one, to reduce tunneling downtime. This paper investigated the prior technology related to continuous excavation segments. The main technology was classified into helical segment, honeycomb segment, and conventional segment methods. The helical segment method has not been applied in actual construction yet, and the honeycomb segment method has not succeeded in commercialization. The continuous excavation method using conventional segments has been successfully demonstrated. The thrust force and operation method of the thrust jacks for the semi-continuous technology were analyzed. Continuous excavation TBM research is also progressing in Korea, and through the analysis of successful cases, the need to develop independent continuous excavation methods has been identified.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.66 no.4
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• pp.169-176
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• 2017

This paper presents research on low-voltage microgrids to maintain a continuous power supply to critical loads on grid-connected islands in Korea. The low-voltage microgrids of this paper focused on that changes public office buildings into uninterrupted microgrids by autonomous operation. For this, a microgrid controller (MGC) and a power conditioning system (PCS) that allow a seamless transfer between grid-connected and grid-isolated operation are proposed. The proposed PCS operates with a silicon controlled rectifier (SCR) switch and employs a simple structure. It supplies power continuously without operators through a coordinated operation between MGC and PCS. In addition, proposed MG has a schedule operation for minimizing electricity charges and provides ancillary services that enable the utilization of resources according to the operation purpose of utility distribution networks. To demonstrate the uninterrupted low-voltage microgrid proposed in this study, a microgrid was implemented and tested in a public office building in Anjwa Island, Jeollanam-do in Korea. A seamless, autonomous operation history, despite system disturbances, was obtained through a long-term demonstration of operation. The results showed that the proposed microgrid technology can be used to achieve energy resilience in grid-connected island areas.

• Journal of Intelligence and Information Systems
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• v.14 no.3
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• pp.25-39
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• 2008

The objective of this study is to forecast the operational continuous ability using Artificial Neural Networks in battalion defensive operation for the commander decision making support. The forecasting of the combat result is one of the most complex issue in military science. However, it is difficult to formulate a mathematical model to evaluate the combat power of a battalion in defensive operation since there are so many parameters and high temporal and spatial variability among variables. So in this study, we used company combat power level data in Battalion Command in Battle Training as input data and used Feed-Forward Multilayer Perceptrons(MLP) and General Regression Neural Network (GRNN) to evaluate operational continuous ability. The results show 82.62%, 85.48% of forecasting ability in spite of non-linear interactions among variables. We think that GRNN is a suitable technique for real-time commander's decision making and evaluation of the commitment priority of troops in reserve.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.125-130
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• 2001

A existing design method of PSC girder bridges, according to total service loads, stress required tendon force at a time. Because this design method increases beam depth, design of long span is difficult. However, As UC girder stressing at difficult loading stages reduces sectional depth of PSC girder, both design and operation of long span bridges is possible. so, this study analyzes the effect of design parameter (Girder Strength, Girder Spacing, Span Length, Joint Strength) on the beam depth of IPC girder continuous bridges, and shows sectional depth of UC girder for design of long span bridges. According to analysis, when a continuous bridges of same length span is at strength of joint over strength of girder of 600kg/$cm^{2}$, a change of beam depth is observed and when a continuous bridges of different span length is at strength of joint below strength of girder of 600kg/$cm^{2}$, a change of beam depth is observed. In two case, a change of beam depth is mostly observed over strength of girder of 350kg/$cm^{2}$ according to analysis of deflection data, a continuous bridges of IPC girder is nearly satisfied.

• The Korean Journal of Pain
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• v.9 no.2
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• pp.363-367
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• 1996

Background: Recently postoperative pain control with continuous epidural analgesia has been increased. This study aimes to evaluate backpain following continuous epidural analgesia by pressure threshold meter (algometer). Methods: After informed consent, 50 ASA physical status I or II patients undergoing elective gynecologic surgery were selected. After placing epidural catheter, patients received morphine 0.05mg/kg with 0.25% bupivacaine 5 ml followed by continuous infusion of 0.125% bupivacaine 100 ml with morphine 4 mg for 48 hours. backpain was measured by pressure algometer over lumbar paraspinalis at the L4 level, 5 and 7 cm from the midline on preoperative, operation day, 1st, 2nd, 3rd, and 4th postoperative days. Results: Postoperative mean pressure thresholds of were higher than preoperative value (p<0.05). Conclusion: The continuous epidural analgesia dose not provide or aggravate postoperative backpain, but it must be evaluated for long term follow-up.