• 한국정밀공학회지
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• 제26권3호
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• pp.40-46
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• 2009

Toroidally-wound brushless direct-current (BLOC) machines are compact, highly efficient, and can work across a large magnetic gap. For these reasons, they have been used in pumps, flywheel energy storage systems and left ventricular assist devices among others. The common feature of these systems is a spinning rotor supported by a set of (either mechanical or magnetic) bearings. From the view point of dynamics, it is desirable to increase the first critical speed of the rotor so that it can run at a higher operating speed. The first critical speed of the rotor is determined by the radial stiffnesses of the bearings and the rotor mass. The motor also affects the first critical speed if the rotor is displaced from the rotating center. In this paper, we analytically derive the flux density distribution in a toroidally-wound BLOC machine and also derive the negative stiffness of the motor, based on the assumption that the rotor displacement perturbs the flux density distribution linearly. The estimated negative stiffness is validated by finite element analyses.

• 대한수의학회지
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• 제33권1호
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• pp.171-178
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• 1993

The present study was carried out to investigate the developmental potency to blastocyst after freezing and thawing of nuclear transplanted 2-cell embryos. The nuclei from 2-, 4- and 8-cell mouse embryos were transferred into enucleated 2-cell embryos, and the reconstituted embryos were submitted to direct current(DC) pulse at output voltage of 2.0 kV/cm for $100{\mu}$ sec to induce cell fusion. The recovery rate and developmental potency to blastocyst after freezing and thawing of nuclear transplanted 2-cell embryos was investigated. 1. The recovery rate of nuclear transplanted 2-cell embryos in normal morphology after freezing and thawing was significantly higher in rapid freezing(DMSO 4.5M) than in slow cooling(p<0.01). 2. When the recovered embryos in normal morphology were cultured in vitro, there were no significant differences in the developmental potency to blastocyst between the freezing methods and the concentrations of cryoprotectant. In summary, these experiments have proved that rapid freezing method(DMSO 4.5M) is effective in nuclear transplanted 2-cell mouse embryos. If improved micromanipulation techniques and freezing are combined, nuclear transplantation technique will contribute to the improvement of productivity in livestock animals.

• 열처리공학회지
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• 제30권4호
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• pp.151-155
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• 2017

The ZTO single layer and ZTO/Ag/ZTO tri-layer films were deposited on glass substrates by using the radio frequency (RF) and direct current (DC) magnetron sputtering and then rapid thermal annealed (RTA) in a low pressure condition for 10 minutes at 150 and $300^{\circ}C$, respectively. As deposited tri-layer films show the 81.7% of visible transmittance and $4.88{\times}10^{-5}{\Omega}cm$ of electrical resistivity, while the films annealed at $300^{\circ}C$ show the increased visible transmittance of 82.8%. The electrical resistivity also decreased as low as $3.64{\times}10^{-5}{\Omega}cm$. From the observed results, it is concluded that rapid thermal annealing (RTA) is an attractive post-deposition process to optimize the opto-elecrtical properties of ZTO/Ag/ZTO tri-layer films for the various display applications.

• 전기학회논문지
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• 제67권11호
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• pp.1408-1414
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• 2018

Recently, as a solution to the problem of maintaining system reliability, stability, and quality occurring worldwide, such as activation of smart grid and recognition of super grid and rapid grid interconnection of renewable energy sources HVDC(High Voltage Direct Current) will appear on the front of the electric power system. These concepts are also very important concepts in HVDC systems. When the HVDC system is linked to the existing power system, it is composed of AC/DC/AC conversion device, and these conversion devices are composed of many thyristors. These parts(Devices) are connected in a complicated manner, and they belong to the one with a higher failure rate. However, the problem of establishing the concept of failure rate of HVDC parts directly linked to economic efficiency and the understanding accompanying it are still insufficient. Therefore, in this paper, we establish the meaning of reliability in power system and try to develop a model to analyze and verify the failure rate data of HVDC based on this.

• 열처리공학회지
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• 제28권6호
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• pp.296-299
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• 2015

$In_2O_3/Ti$ bi-layered films were deposited on glass substrate at room temperature with radio frequency (RF) and direct current (DC) magnetron sputtering to consider the effect of Ti buffer layer on the electrical and optical properties. In a comparison of figure of merit, $In_2O_3$ 90 nm/Ti 10 nm thin films show the higher opto-electrical performance of $3.0{\times}10^{-4}{\Omega}^{-1}$ than that of the $In_2O_3$ single layer films ($2.6{\times}10^{-4}{\Omega}^{-1}$). From the observed results, it is supposed that the $In_2O_3\;90nm/TiO_2$ 10 nm bi-layered films may be an alternative candidate for transparent electrode in a transparent thin film transistor device.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권2호
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• pp.1632-1635
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• 2007

We developed a novel growth method of CNTs on metal substrate for device applications, deposited by a triode direct current plasma enhanced chemical vapor deposition (dc-PECVD). With resist-assisted patterning (RAP) method, we had grown CNTs on metal substrate, which were strongly bonded with metal substrate.

• Transactions on Electrical and Electronic Materials
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• 제17권2호
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• pp.121-124
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• 2016

ZnSnO₃ (ZTO)/Ag/ ZnSnO₃ (ZTO) trilayer films were prepared on glass substrates by radio frequency (RF) and direct current (DC) magnetron sputtering. The electrical resistivity and optical transmittance of the films were investigated as a function of the Ag interlayer thickness. ZTO films with a 15 nm thick Ag interlayer show the highest average visible transmittance (83.2%) in the visible range. In this study, the highest figure of merit (2.1×10⁻² Ω cm) is obtained with the ZTO 50 nm/Ag 15 nm/ZTO 50 nm films. The enhanced optical and electrical properties of ZTO films with a 15 nm thick Ag interlayer are attributed to the crystallization of the Ag interlayer, as supported by the distinct XRD pattern of the Ag (111) peaks. From the observed results, higher optical and electrical performance of the ZTO film with a 15 nm thick Ag interlayer seems to make a promising alternative to conventional transparent conductive ITO films.

• 한국결정성장학회지
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• 제23권1호
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• pp.27-30
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• 2013

Catalyst-free graphene nano-sheets without substrates have been synthesized using fullerene and a high direct current (dc) pulse in the spark plasma sintering (SPS) process. Graphene nano-sheets were synthesized directly in the gas phase of carbon atoms which are generated from fullerene at a temperature of $600^{\circ}C$. Characterization has been carried out by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), Raman spectroscopy (Raman), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD).

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집
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• pp.334-337
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• 2002

The Quantum Hall Resistance(QHR) device which consists of GaAs/AlGaAs heterojunction structure is used for the realization of QHR Standard based on QHE. In order to characterize electrical contact resistances and dissipations of the device, it is slowly cooled down for eliminating thermal shock and unwanted noise. Then, the two properties are measured under 1.5 K and 5.15 T. Contact resistances are all within 1.2 Ω and longitudinal resistivities are all within 1 mΩ up to DC 90${\mu}$A. The results mean the device is operated well to realize the QHR Standard. To confirm it, the QHR Standard having the device is compared using a direct current comparator bridge with a 1 Ω resistance standard which the calibrated value is known from QHR standards maintained by other countries. The difference between them is agreed well within measurement uncertainty. It is thus considered that the properties of the device is estimated well and has good performance.

• JSTS:Journal of Semiconductor Technology and Science
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• 제15권5호
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• pp.554-562
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• 2015

This paper presents the design and analysis of gate-recessed AlGaN/GaN Fin-type Field-Effect Transistor (FinFET). The three-dimensional (3-D) technology computer-aided design (TCAD) simulations were performed to analyze the direct-current (DC) and radio-frequency (RF) characteristics for AlGaN/GaN FinFETs. The fin width ($W_{fin}$) and the height of GaN layer ($H_{GaN}$) are the design parameters used to improve the electrical performances of gate-recessed AlGaN/GaN FinFET.