• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.238-242
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• 2004

The paper describes an automatic frequency control current-fed inverter for forging applications. The IGBT in series with diodes as its switching devices in the inverter circuit which is of full-bridge type. The operating frequency is automatically tracked to maintain a small constant leading phase angle when load parameters change. The load voltage is controlled to protect the switches. The output power can be adjusted by varying the input current from phase controlled rectifiers which is a part of current source. The system has been operated at 15-17 kHz. The output power transferred to the load is 1,595 watts. It can heat the steel work pieces with 15 mm diameter and 120 mm long from room temperature to approximately 1100 $^{\circ}C$ within 20 seconds with 0.97 leading power factor on the input side.

• Journal of Korea Technology Innovation Society
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• v.1 no.3
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• pp.402-418
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• 1998

This study attempts to analysis of the 1'ole and B/C(Benefict/Cost)of National Supported Supercomputing Center in process of the promotion for informatization in Korea. ETRI Supercomputing Center, as National Supported Supercomputing Center, was established in 1967 as a laboratory of KIST(Korea Institute of Science and Technology). ETRI Supercomputer Center have acted a leading role as National HPCC(High Performance Computing and Communication) in Korea. The result of B/C analysis of En Supercomputer Center showed that it is twenty times benefit as many as cost for the last 30 years. As soon as possible, it was Suggested that ETRI Supercomputer Center must be developed as National Supercomputing Center(NSC).

• Journal of Electrical Engineering and Technology
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• v.13 no.3
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• pp.1317-1325
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• 2018

A generator-grid coupling calculation model is established to study the leading-phase operational capability of a 770 MW jumbo hydro-generator in a Chinese ultra-mega hydropower station. The static and dynamic stability of the generator are analyzed and calculated to obtain stability limits under leading-phase operating conditions. Three-dimensional (3D) time-varying nonlinear moving electromagnetic and temperature field models of the generator end-region are also established and used to determine the magnetic field, loss, and temperature of the end-region under the leading-phase operating condition. The simulation results agree with data measured from the actual 770 MW hydro-generator. This paper provides reliable reference data for the leading-phase operation of a jumbo hydro-generator, which will help to improve in the design and manufacture of future hydro-generators.

• 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.

• Photonics industry news
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• s.60
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• pp.68-70
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• 2010

• The monthly packaging world
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• s.231
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• pp.63-73
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• 2012

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.35 no.3
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• pp.277-283
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• 1999

For the purpose of leading horse mackerel Trachurus japonicus schools, mackerel Scomber japonicus schools and arrow squid Todarodes pacificus schools, which migrate to the Cheju coast and are caught by the set-net, to the set-net by attracting lamps, we made five attracting lamps and took a practical experiment in the Gwiduk and Dongbuk set-net fishing ground. In the set-net with two bag-nets, we compared the amount of catch of both bag-nets by the means of switching on and off the each attracting lamps in order, switching off the attracting lamps in order which had been switched on and moving an attracting lamp.In the bag-net with an attracting lamp, horse mackerel, mackerel and arrow squid were caught the most, on the other hand, yellow tail Seriola quinqueradiata, striped mullet Mugil cephalus were caught in large quantities in the bag-net without attracting lamp. File fish Stephanolepis cirrhifer, Dusky spinefoot Siganus fuscescens were caught evenly in both bag-nets regardless of an attracting lamp.This result indicates that the amount of horse mackerel, mackerel, arrow squid can be increased by the use of attracting lamps in the set-net fishing method.

• Journal of the Korea Institute of Military Science and Technology
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• v.4 no.2
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• pp.215-224
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• 2001

An experimental investigation was conducted on the interaction of vortices over a delta wing with the leading edge extension for three angles of attack($16^{\circ},\; 24^{\circ} \;and\; 28^{\circ}$) at Reynolds number of $1.76{\times}10^6.$ The experimental data included total pressure contours and velocity vectors using 5-hole probe measurements. Constant total pressure coefficient contours show the LEX vortex moves downward and outboard, while the wing vortex exhibited an inboard and upward migration. At near the trailing edge, these vortices reveal a direct interaction between the wing and LEX vortex, featuring a coiling of vortex cores about each other. The combined effect of the interaction of these two vortices and proximity to the wing surface results in the increase of the suction peak. This is in contrast to the result obtained on the delta wing alone configuration, where the effect of the vortex breakdown was manifested. The interaction of the wing and LEX vortices is more pronounced at higher AOA.

• Wind and Structures
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• v.31 no.3
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• pp.185-196
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• 2020

A method to reduce the wind pressure at the leading edge of a noise barrier was investigated by gradually lowering the height of a member added to the end of the noise barrier. The shape of the lowered height of the added member was defined by its length and slope, and the optimal variable was determined in wind tunnel testing via the boundary-layer wind profile. The goal of the optimal shape was to reduce the wind pressure at the leading edge of the noise barrier to the level suggested in the Eurocode and to maintain the base-bending moment of the added member at the same level as the noise-barrier section. Using parametric wind tunnel investigation, an added member with a slope of 1:2 that protruded 1.2 times the height of the noise barrier was proposed. This added member is expected to simplify, or at least minimize, the types of column members required to equidistantly support both added members and noise barriers, which should thereby improve the safety and construction convenience of noise-barrier structures.

• Journal of the Korea Institute of Military Science and Technology
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• v.15 no.5
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• pp.550-556
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• 2012

In this study, a series of ballistic experiments have been performed to investigate the protection mechanism of some inert reactive cassettes against shaped charge jet. Three kinds of material were tested as a core material of the inert cassettes, i.e. one of rubber materials, a high modulus and high strength composite material used for ballistic protection and a mixture of energetic materials. Parameters such as deformation of the cassettes, occurrence time of jet distortion, leading jet length and residual penetration depth were investigated from the experiments and they were compared to each other quantitatively according to the jet incidence angles. The results show that the increment of cassette deformation caused jet distortion to occur early and jet distortion brought decrease of the length of leading jet. Then the decrease of the length of leading jet accompanied the decrease of residual penetration depth.