• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.5
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• pp.538-544
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• 2013

In this study, cavitation characteristics of a thermal spray coating were evaluated in order to improve durability and cavitation resistance. For a coating material, a Ni-based self-fluxing alloy was thermal-sprayed over a ALBC3 alloy substrate and subsequently modified by heat treatment.The resulted self-fluxing coating layer had relatively high hardness compared to the base material, and thus would be expected to exhibit good durability. However, the cavitation characteristics were deteriorated due to the intrinsic porous structure of the coating. Therefore, it is essential to optimize heat treatment condition during thermal spraying coating process for self-fluxing alloy, and in this research the increase in heat treatment temperature is thought to increase the fluidity of B and Si in the self-fluxing alloy and to remove pores or defects, leading to the characteristics enhancement.

• Journal of the Society of Naval Architects of Korea
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• v.52 no.2
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• pp.104-109
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• 2015

The Korea Research Institute of Ships & Ocean Engineering (KRISO) has an ice tank to make a test environment similar to the real ice in the polar sea in order to carry out model tests. One of the most important task of the ice tank is to generate the model ice to have similar material properties as sea ice. The primary properties of sea ice which influence the ice performance of ice breakers and ice-strengthened vessels traveling in the polar sea are ice thickness, flexural strength, density, modulus of elasticity and crystal structure etc. Among them, since the density of model ice influences the buoyance resistance of ice for the ship model, the accurate measurement of ice density should be used to obtain the accurate analysis results from the model test. In this paper, some existing methods to measure the density of model ice are reviewed and a new one is proposed to measure it accurately and easily as possible. In this study, the measuring system including an UTM and several measuring devices was established to obtain the model ice density. Polyethylene and ice specimens are used for a series of repeatable measurement tests. From the results, it was recognized that both of the displacement method and the weight/weight methods gave the stable and favorable tendency.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.2
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• pp.88-93
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• 2005

To develop a 100 hp high temperature superconducting(HTS) motor with high efficiency first in Korea, we fabricated a HTS field winding and test. HTS field winding is composed of sixteen HTS race track shaped coils wound with stainless steel-reinforced Bi-2223 tape conductor by react and wind fabrication method. Nomex paper was used for electrical insulation. Each of four magnet pole assemblies was constructed with four double pancake sub-coils, mechanically stacked and electrically in series. Four magnet assemblies were fixed on an aluminum support structure to make effective heat transfer. The Critical current (Ic) was 41.5A at 77K and self field. However the lowest Ic value of sub-coils was 35A. Joule heat generated by each joints between sub-coils was lower than 1mW at 77K and 34A. And Joule heat generated by the joints between field coils was lower than 10mW at 77K and 34A. Joule heat of the whole field winding was 1W at 77K and 32A. And so, the lowest Ic value of sub-coils was more important than Joule heats generated by all joints. The operating current must be lower than the lowest Ic of all the sub-coils. In this paper, design, construction and testing of HTS field winding, Joule heat generated by the joints, and operating current were discussed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.5 s.120
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• pp.530-538
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• 2007

An inductor library for efficient low cost RFIC design has been developed based on a standard digital 0.18 ${\mu}m$ CMOS process. The developed library provides four structural variations that are most popular in RFIC design; standard spiral structure, patterned ground shield(PGS) structure to enhance quality factor, stacked structure to enable high inductance values in a given silicon area, multilayer structure to lower series resistance. Electromagnetic simulation, equivalent circuit, and parameter extraction processes have been verified based on measurement results. The extensive measurement and simulation results of the inductor library can be a great asset for low cost RFIC design and development.

• Microbiology and Biotechnology Letters
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• v.10 no.4
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• pp.289-295
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• 1982

Streptomyces bobili (YS-40) isolated from soil was tested that it had drug resistance against penicillin, cephalosporin series antibiotics and other antibiotics in the previous paper. The treatment of Streptomyces bobili, (YS-40) with ethidium bromide (EtBr), acriflavine and sodium dodecyl sulfate. (SDS) resulted in the elimination of R-plasmid from the host strain. Minimum growth inhibitory concentrations (MIC) of Hg, Ag, penicillin-G, ampicillin, chloramphenicol, oxytetracycline, streptomycin and kanamycin were found to be 15, 10, > 3, 000, > 100, > 1, 000, > 100, < 5 and < 5$\mu\textrm{g}$/$m\ell$ respectively. Among the curing agents, EtBr was proved to be the most powerful compound for the elimination of R-plasmid in the strain and the elimination rate with EtBr(10$\mu\textrm{g}$/$m\ell$) was about 98%. Optimal pH to. the elimination of R-plasmid was pH 7.0 and the R-plasmid in the cells incubated for 24 hrs was proved to be eliminated most effectively. Aerial mass color, soluble pigment formation and reverse side color were reported to be often the plasmid associated characteristics of the R-plasmid bearing bacteria. But these characteristics of the uncured and cured Streptomyces bobili, (YS-40) showed no changes in the most of the pigment formation media tested in this work.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.11 no.2
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• pp.189-194
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• 2018

Nowadays most integrated circuits are built using the bulk CMOS technology, but it has much difficulty in further reduction of the power consumption and die size. As a super low-power technology to solve such problems, the SOI technology attracts great attention recently. In this paper, the study results of the temperature dependency of the hot carrier effects in the n-channel MOSFETs fabricated on the thin SOI substrate were discussed. In spite that the devices employed the LDD structure, the hot carrier effects were more serious than expected due to the high series resistance between the channel region and the substrate contact to the ground, and were found to be less serious for the higher temperature with the more phonon scattering in the channel region, which resulted in reducing the hot electron generation.

• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.1
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• pp.72-81
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• 2009

This paper presents quasi-resonant type high power factor ac power supply for atmospheric pressure plasma cleaning system adopting three phase PFC boost converter and it's control method. The presented ac power supply consists of single phase H-bridge inverter, step-up transformer for generating high voltage and three phase PFC boost converter for high power factor on source utility. Unlikely to the traditional LC resonant converter, the propose one has an inductor inside only. A single resonant takes place through the inside inductor and the capacitor from the plasma load modeled into two series capacitor and one resistance. The quasi-resonant can be achieved by cutting the switching signal when the load current decrease to zero. To obtain power control ability, the propose converter controlled by two control schemes. One is the changing output pulse period scheme in the manner of PFM(Pulse Frequency Modulation) control. On the other, to provide more higher power to load, the DC rail voltage is directly controlled by the 3-phase PFC boost converter. The significant merits of the proposed converter are the uniform power providing capability for high quality plasma generation and low reactive power in AC and DC side. The proposed work is verified through digital simulation and experimental implementation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.6
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• pp.367-371
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• 2018

1,200 V class junction barrier schottky (JBS) diodes and schottky barrier diodes (SBD) were simultaneously fabricated on the same 4H-SiC wafer. The resulting diodes were characterized at temperatures from room temperature to 473 K and subsequently compared in terms of their respective I-V characteristics. The parameters deduced from the observed I-V measurements, including ideality factor and series resistance, indicate that, as the temperature increases, the threshold voltage decreases whereas the ideality factor and barrier height increase. As JBS diodes have both Schottky and PN junction structures, the proper depletion layer thickness, $R_{on}$, and electron mobility values must be determined in order to produce diodes with an effective barrier height. The comparison results showed that the JBS diodes exhibit a larger effective barrier height compared to the SBDs.

• Journal of Navigation and Port Research
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• v.37 no.2
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• pp.137-142
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• 2013

The displacement Deep-V catamaran concept was developed in Newcastle University(UNEW) through development of the systematic Deep-V catamaran series. One of the most important Deep-V catamaran launched to date is Newcastle University's own multi-purpose research vessel, The Princess Royal. The vessel was launched in 2011 and enhanced the Deep-V catamaran concept further with the successful adoption of a novel anti-slamming bulbous bow and tunnel stern for improved efficiency. It was however identified that the vessel has substantial amount of dynamic trim that limited the visibility of the captain. The dynamic trim also increased the wave-making resistance thereby preventing the vessel from attaining its maximum speed in certain sea states. This paper therefore presents the application of devices such as Trim Tabs, Interceptors, Transom Wedges and Integrated Transom Wedges-Tabs to control the dynamic trim and improvement of fuel efficiency of the vessel. All of these energy saving devices were fitted into a model for tests in Newcastle University's Towing Tank. Model test verification confirmed that the optimum appendage was the interceptors, they produced a 5% power saving and 1.2 degree trim reduction at 15 knots, and investigations of full scale trials will be scheduled with and without application of device to compare the improvement of performance.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.481-481
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• 2007

This work describes the effect of the number of roll pressing and the composition of carbon black on the electric and mechanical properties of carbon-PTFE electrode, in which composition is MSP 20 : carbon black: PTFE = 95-x : x : 5 wt.%. It was found that the best electric and mechanical properties were obtained in sheet electrode roll-pressed for about 15 times and in sheet electrode, in which composition is MSP 20 : carbon black: PTFE = 80 : 15 : 5 wt.%. These behaviors could be explained by the network structure of PTFE fibrils and conducting paths linked with carbon blacks, respectively. On the other hand, cell capacitor using the sheet electrode with 15 wt.% of carbon black attached on aluminum current collector with the electric conductive adhesive, in composition is carbon black : CMC = 70 : 30 wt.%, has exhibited the best rate capability in the current range of $0.5mA/cm^2$ $100mA/cm^2$ and the lowest equivalent series resistance.