• Journal of Korean Institute of Industrial Engineers
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• v.7 no.1
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• pp.21-31
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• 1981

This paper develops a short term forecasting model for household electric power consumption in Seoul, which can be used for the effective planning and control of utility management. The model developed is based on exponentially weighted moving average model and incorporates monthly average temperature as an exogeneous factor so as to enhance its forecasting accuracy. The model is empirically compared with the Winters' three parameter model which is widely used in practice and the Box-Jenkins model known to be one of the most accurate short term forecasting techniques. The result indicates that the developed hybrid exponential model is better in terms of accuracy measured by average forecast error, mean squared error, and autocorrelated error.

• Korean Management Science Review
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• v.29 no.1
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• pp.33-56
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• 2012

Domestic LCD TV market is composed of two groups of products produced by major firms and small and medium enterprises. The major companies make the price relatively high, but the other makes lower in the same sizes. The model of the low price products does not make consumers choice when they choose LCD TV. This makes the questions of capability between difference price products. The reason above mentioned, the firms that include group of comparatively lower price, are worried about not increasing sale because of prejudice. This study is to find any interrelationship and evaluate the efficiency between the products using performance, exterior and brand power of product. In order to do this, a hybrid AHP/DEA evaluation model for comparison/valuation of LCD TV products is developed. The proposed process is; first, to derive hierarchy structure of LCD TV evaluation criteria using axiomatic design, second, to calculate the score of each LCD TV product through AHP analysis including weight calculation of evaluation criteria, and last, to evaluate the efficiency of LCD TV product by applying DEA by defining product scores as output and prices as input. It concludes that the high price products shows good efficiency, but there are some products with good exterior and brand power, not performance, also presenting good efficiency.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.5
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• pp.143-147
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• 2011

Operating points of a fuel cell system (FCS) can be shifted to its high-efficiency region by hybridization in a fuel cell hybrid vehicle (FCHV), so the hydrogen can be saved. In this paper, the hydrogen consumption of an FCHV is compared to that of a fuel cell vehicle (FCV). A power management strategy is applied to the FCHV and the related simulation is carried out. The concept of equivalent hydrogen consumption is introduced in order to consider the effect of the difference between initial and final battery SOC on the total hydrogen consumption.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.1010-1014
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• 2002

A new type actuator has been designed and investigated to overcome thermal problems in slim optical disc drive which is adopted in mobile storage devices. Recently, in optical storage device technical trends, the size of optical disc drives is slimmer to adopt notebook computer and the spindle rotate velocity is faster to achieve high transfer rate and the power of actuator is higher to perform tilting, etc. However, these trends of optical disc drives tend to raise the environment temperature of drives, actuator power and parts temperature. Moreover, it is more difficult to remove the heat inside a drive and the temperature of an actuator increases and drive slims. As a result, increase of surface temperature of actuator body caused that second resonance of an actuator moves down to a lower frequency band and the performance of optical parts also deteriorates. Especially objective lens, coil and magnet of the actuator parts are easily damaged. To manage these thermal problems, in this paper an actuator with a hybrid blade, which is composed of vectra which has low thermal conductivity and magnesium which has high thermal conductivity, has been suggested and verified. Despite the high temperature environment, the proposed actuator showed good dynamic performance.

• Smart Structures and Systems
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• v.22 no.2
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• pp.139-150
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• 2018

A variable electromotive-force generator (VEG), which is a modified generator with an adjustable overlap between the rotor and the stator, is proposed to expand the operational range of a regular generator through a simple and robust active control strategy. It has a broad range of applications in hybrid vehicles, wind turbines, water turbines, and similar technologies. A mathematical model of the VEG is developed, and a novel prototype is designed and fabricated. The performance of the VEG with an active control system, which adjusts the overlap ratio based on the desired output power at different rotor speeds for a specific application, is theoretically and experimentally studied. The results show that reducing the overlap between the rotor and the stator of the generator results in reduced torque loss of the generator and an increased rotational speed of the generator rotor. A VEG can improve the fuel efficiency of hybrid vehicles; it can also expand operational ranges of wind turbines and water turbines and harness more power.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.11
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• pp.1603-1611
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• 2021

As IMO environmental regulations are tightened, the need to establish a system that can reduce emissions is increasing, and for this purpose, various power control management systems have been studied and implemented as a new energy management system for ships. In this study, we design a control process through modeling for Bi-Directional Converter (BDC) application with bi-directional power flow to link batteries, which are energy storage devices, to conventional generator power systems, and propose mechanisms for batteries optimized for varying loads. This work models MATLAB/Simulink as a BDC and simulates current control and state of charge (SOC) optimization at the time of charging and discharging batteries according to load scenarios. Through this, the battery, power, and load were interlocked so that the generator operated on board could be operated in the optimal operation range, and power control management was performed to enable the generator to operate in the high fuel efficiency range.

• Proceedings of the KIPE Conference
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• 2003.07b
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• pp.740-744
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• 2003

The development of electric vehicle has been accelerated by the recent 'California Initiative' which has required increasing proportions of new vehicle in Los Angeles area to be ZEV(Zero Emission Vehicles) But, because skill of battery is feeble, ZEV regulation was postponed but that is by CO2 restriction and environmental pollution problem the latest because do development require. In the electric vehicle and hybrid electric vehicle, the battery ECU(Battery Management System, BMS) is very important and an essential equipment. The accurate state of charge(SOC) is required for the battery for hybrid electric vehicles. This paper proposes SOC algorithm for the HEV based on the terminal voltage. Also, designed and analyzed battery ECU to apply on HEV.

• Journal of Advanced Navigation Technology
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• v.19 no.3
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• pp.250-256
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• 2015

Digital load is increasing suddenly for various reasons, such as easy control and management. Accordingly, a consumption pattern of load is becoming DC. However, the power supply is supplied by AC power. The load power supply substantially needs DC power. AC power has to be converted to DC power. Renewable energy sources like solar, wind and fuel cells are DC power generation, but the transfer needs to through by AC power, thus DC power has to be converted to AC power. Resultantly, a multi-stage conversion loss is constantly increasing. The power distribution system of DC-based is required for effective use of these energy sources. This requires a DC load, as well as is necessary to develop DC breaker. This study is expect for system and equipment for reliable DC power distribution through the study of the arc extinguish technology for direct current a hybrid arc extinguishing technology with permanent magnets technology.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.9
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• pp.833-841
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• 2016

The 200 W electrically powered unmanned aerial vehicle, which is studied in this research, uses solar cells, a fuel cell and batteries as the main power source simultaneously. The output of each power source performs power control for each power source by the active power control method so that an adequate capacity of the battery could be maintained while limiting the maximum output of the fuel cell. The output variation for each power source under the active power control method was identified through an integrated ground test. In addition, the effect of limiting the maximum output of the fuel cell on the output variation of the entire system was experimentally identified, and it was confirmed that the adequate maximum output value of the fuel cell for preventing the overdischarge of six series-connected, small size batteries for fuel cell systems is 150 W.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.719-728
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• 2015

This paper presents the results of field tests on Voltage Management System (VMS) using hybrid voltage control, which utilizes coordinated controls of various reactive power resources such as generators, FACTS and switched shunt devices to regulate the pilot bus voltage in a voltage control area. It also includes the results of performance test on RTDS-based test bed in order to validate the VMS before installing it in Jeju power system. The main purpose of the system is adequately to regulate the reactive power reserve of key generators in a normal condition with coordination of discrete shunt devices such as condensers and reactors so that the reserves can avoid voltage collapse in emergency state in Jeju system. Field tests in the automatic mode of VMS operation are included in steady-states and transient states. Finally, by the successful operation of VMS in Jeju power system, the VMS is proved to effectively control system voltage profiles in steady-state condition, increase system MVAR reserves and improve system reliability for pre- and post-contingency.