• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.8
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• pp.1055-1061
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• 2018

Recently, due to the rapid development of electric vehicle and energy storage system, it is emphasized for battery management system to be needed and to be improved. BMS carries out various movement for optimization the use of the energy and safe use of secondary battery, these movement of BMS start at high wattage shunt fixed resistor which performs a function for detecting current among the BMS components. In addition, for the safe operation of secondary battery, the reliability of current voltage variation detected from shunt should be secured, and for corresponding characteristics, the quality of Temperature coefficient of resistance for BMS shunt and the quality of Thermo electromotive force all must be excellent. For these reasons, this study comes up with the stabilization plan for thermo electromotive force and temperature coefficient of resistance of BMS shunt resistor which is key to secondary battery operation.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.339-342
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• 2010

Doosan Heavy Industries & Construction Co., Ltd. constructed a gas turbine engine test cell to verify operating characteristics and design parameters of 5MW class gas turbine engine for power generation under developing. Engine test cell was designed to satisfy critical requirements to scrutinize all performance parameters of the engine with safe and reliability in accordance with design specification. As the test cell developed can effectively reproduce engine operation conditions covering from start-up to maximum power condition, it can be utilized to make a continuing design improvement of the engine based on practical test data at full stretch. Moreover, it is expected to be serviceable to develop derivative engines and be utilized to put them into serial production and contribute to a competitiveness reenforcement as a gas turbine engine manufacturer.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.854-860
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• 2004

"Research and Development of Melt-Growth Composite (MGC) Ultra High Efficiency Gas Turbine System Technology" program has been started in JFY2001. The main objective of the program is to establish basic component technologies to apply MGC material to an efficient gas turbine system successfully. It is known that MGC material maintains its mechanical strength at room temperature up to about 2000 K, which is ideal for the high temperature gas turbine. The purposes of the present study are to develop the cooling structure of the gas turbine combustor liner where MGC material is applied as the heat shield panel, also to develop the low NOx combustion system for a 1970 K (1700 deg.C) class gas turbine combustor. To start with, basic heat transfer characteristics were investigated by one-dimensional calculation and heat transfer experiment for the cooling structure. Axially staged configuration and fuel preparation were investigated by CFD calculation and experiments for the low NOx combustor.

• Journal of Korean Society of Transportation
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• v.7 no.2
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• pp.89-111
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• 1989

This study concentrates on a basic investigation research related to some of parameters to be used for the analysis of capacity and the level of service for signalized intersections. The parameters to be studied are ideal saturation flow rate, large vehicle's passenger car equivalent(PCE) ane the lane utilization factors of through and left turn vehicles. The field data were collected at six intersections in Seoul using video cameras so as to reflect conditions in urban areas. In this study discharge headway based on a rear bumper of each vehicle was used and all the parameters were estimated using a regression technique. The findings of this research are as follows : 1. The saturation headway and saturation flow rate on a single lane with the lane width of 3.1m are 1.652 seconds and 2,180 pcphgpl. It was found that the frist 5 vehicles in the queue experience some start-up lost time. 2. It was confirmed that the new method adopted for the estimate of large vehicle's PCE gives larger PCE values than those derived from the method commonly used. 3. For the estimate of lane utilization factors of through and left turn vehicles, a relationship was established and the corresponding formulas were developed.

• Journal of IKEEE
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• v.23 no.2
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• pp.622-627
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• 2019

This paper propose an initial rotor position detection method for sensorless operation of a single-phase permanent magnet synchronous motor(SP-PMSM) with asymmetric air-gap. In general, the sensorless control based on back-emf estimation is difficult to estimate the back-emf at the zero and low speed regions. For this reason, an open loop start-up technique is indispensable, and it is also necessary to detect the initial position of the rotor in order to rotate in a certain direction. In this paper, we propose a method to detect rotor polarity by adding offset voltage to high frequency voltage signal based on the magnetic characteristics of SP-PMSM. The validity and usefulness of the proposed algorithm are verified through several experimental results.

• KDI Journal of Economic Policy
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• v.40 no.4
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• pp.23-45
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• 2018

The Korean government has provided various policy devices to boost technology transfers between academia and industry since the establishment of the Technology Transfer Promotion Act in 2000. Along with the enactment of the law, the Korean government mandated the establishment of a technology transfer office at national and public universities and encouraged technology transfer activities. Despite the quantitative expansion of technology transfer offices (TTOs), operational inefficiency was brought up. As a supplementary policy, the Korean government implemented a line of projects to support the labor and business expenses of leading TTOs. This research questions whether the project greatly affected the technical efficiency of TTOs. We analyze publicly available university panel data from 2007 to 2015 using a one-step stochastic frontier analysis. The results suggest that the program was marginally effective at shifting the technical efficiency distribution to the right on average, but it failed to maximize its impact by diversifying the policy means based on targets. The marginal effects of the program on technical efficiency differ according to the research capability and size of each school. We also compare technical efficiency against the licensing income at the start and end of the program. Technical efficiency increased for the leading TTOs, and both measures show improvements for unsupported TTOs. Our empirical results imply that diversifying the program for universities with different characteristics may have improved the effectiveness of the policy.

• Asia-Pacific Journal of Business
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• v.12 no.1
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• pp.101-120
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• 2021

Purpose - As the research of Chinese unicorn companies is still in early stages, this paper aims to investigate the factors that influence the success of Chinese IT unicorns. Design/methodology/approach - This study is conducted as a single case study and used various sources such as interviews, internal data, press releases, IR data, etc. to enhance the reliability and validity. Findings - First, the characteristics of the start-up team, social capital, and strategies as internal factors affect the success of unicorns. Among them, the more Guanxi in social capital factors, the greater the possibility of growing into an IT unicorn company. Second, the role of venture capital and geographical location have been identified that two factors affect the success of unicorns. In the role of venture capital, it has been confirmed that the world's top-level venture capital company or a company that has been invested by "BATJ" is more likely to grow into a unicorn company in China. Research implications or Originality - This paper distinguishes between internal and external factors to explain the factors that affect the growth of unicorn companies, which lays the foundation for future research, such as the exploration of the unicorns and the development of new variables.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.5
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• pp.425-430
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• 2022

A pumped storage power station is an important means to solve the problem of peak load regulation and ensures the safety of power grid operation. The doubly fed variable-speed pumped storage (DFVSPS) system adopts a doubly fed induction machine (DFIM) to replace the synchronous machine used in traditional pumped storage. The stator of DFIM is connected to the power grid, and the three-phase excitation windings are symmetrically distributed on the rotor. Excitation current is supplied by the converter. The active and reactive power of the unit can be quickly adjusted by adjusting the amplitude, frequency, and phase of the rotor-side voltage or current through the converter. Compared with a conventional pumped storage hydropower station (C-PSH), DFVSPS power stations have various operating modes and frequent start-up and shutdown. This study introduces the structure and principle of the DFVSPS unit. Mathematical models of the unit, including a model of DFIM, a model of the pump-turbine, and a model of the converter and its control, are established. Fast power control strategies are proposed for the unit model. A 300 MW model of the DFVSPS unit is established in MATLAB/Simulink, and the response characteristics in generating mode are examined.

• Journal of the Korean Institute of Gas
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• v.16 no.6
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• pp.17-22
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• 2012

In this study, characteristics of reforming process of Automotive LPG fuel using plasma reactor are investigated. Because plasma reformer technology has advantages of a fast start-up and wide fuel/oxidizer ratio of operation, and reactor size is smaller and more simple compared to typical combustor and catalytic reactor, plasma reforming is suitable to the on-board vehicle reformer. To evaluate the characteristics of the reforming process, parametric effect of $O_2$/C ratio, reactant flow rate and plasma power on the process were investigated. In the test of varying $O_2$/C ratio from partial oxidation stoichiometry to combustion stoichiometry, conversion of LPG was increased but selectivity of $H_2$ decreased. The optimum condition of $O_2$/C ratio for the highest $H_2$ yield was determined to be 0.8~0.9 for 20~50 lpm. The result can be a guide to map optimal condition of reforming process.

• The Korean Journal of Applied Statistics
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• v.27 no.7
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• pp.1207-1217
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• 2014

2011 Korean Economic Census is the first economic census in Korea, which contains text data on menus served by Korean-food restaurants as well as structured data on characteristics of restaurants including area, opening year and total sales. In this paper, we applied text mining to the text data and investigated statistical and technical issues and characteristics of Korean text mining. Pork belly roast was the most popular menu across provinces and/or restaurant types in year 2010, and the number of restaurants per 10000 people was especially high in Kangwon-do and Daejeon metropolitan city. Beef tartare and fried pork cutlet are popular menus in start-up restaurants while whole chicken soup and maeuntang (spicy fish stew) are in long-lived restaurants. These results can be used as a guideline for menu development to restaurant owners, and for government policy-making process that lead small restaurants to choose proper menus for successful business.