• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.394-396
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• 1999

ADD has developed a special BLDCM(brushless d.c. motor) that has small size and high power density. The model of BLDCM is like that of advanced nation. Design, production and test carried out by ADD and HYOSUNG Corp.. We simulated back EMF of phase, inductance of line and eddy current loss of rotor after we tested the motor at 80 Kw. According to analysis we have established the performance of 100Kw power recently. There are the same results that we designed.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.455-457
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• 2008

본 논문에서는 2상 SPMSM을 이용하여 이동로봇의 이동 및 정지를 담당하는 일체형 엑츄에이터를 제작하였다. 이 일체형 엑츄에이터는 동기모터, 브레이크, 드라이브의 조합으로 이루어지며 이동로봇 등에 있어서 동작 및 성능을 좌우하는 구동장치의 핵심부품으로써 이동로봇의 품질 및 성능을 좌우한다고 할 수 있다. 그리하여 이 일체형 엑츄에이터의 핵심부품인 2상 SPMSM과 이를 제어하기 위한 구동장치에 대한 제어시스템을 제안하고 이를 시뮬레이션과 실험을 통해 검증하였다.

• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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• pp.464-467
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• 2010

Ice accretion on aircraft surface in icing condition induces external shape changes that may result in a hazard factor for aircraft safety. In case of aircraft main wing with high lift equipment, ice accretion is observed around leading edge and flap. During the design phase, location of ice accretion and associated aerodynamic characteristics must be investigated. In this study, icing effects on aerodynamic characteristics of the main wing section of KC-100 aircraft are investigated using an Eulerian-based FENSAP-ICE code in various icing conditions.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.863-864
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• 2009

• Bulletin of the Korean Chemical Society
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• v.24 no.3
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• pp.274-278
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• 2003

New banana-shaped achiral compounds, 1,3-phenylene bis [4-{4-(alkenyloxy) phenyliminomethyl}benzoate]s were synthesized by varying the length of alkenyl group; their ferroelectric properties are described. The smectic mesophases, including a switchable chiral smectic C $(Sm\;C^*)$ phase, were characterized by differential scanning calorimetry, polarizing optical microscopy and triangular wave method. The presence of vinyl groups at the terminals of linear side wings in the banana-shaped achiral molecules containing Schiff's base mesogen induced a decrease in melting temperature and formation of the switchable $(Sm\;C^*)$ phase in the melt. The smectic phases having the octenyloxy group such as $(CH_2)_6CH=CH_2$ showed ferroelctric switching, and their values of spontaneous polarization on reversal of an applied electric field were 120 nC/cm² (X=H) and 225 nC/ cm² (X=F), respectively. We could obtain ferroelectric phases by controlling the number of carbon atom in alkenyloxy chain of a bent-core molecule.

• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.5
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• pp.463-470
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• 2006

This paper deals with a new 3-phase power quality disturbance generator. The proposed generator can provide phase jump as well as voltage sag, swell, outage, unbalance, and over and under voltage. The operating principle of the generator is described in each mode of disturbance. The magnitude of the phase jump is analysed and it is found that the magnitude is the function of the turn-ratios of the transformers consisting the generator. The scheme has simple structure compared with the conventional one, and the major components of the proposed scheme are SCR thyristor and transformer, which guarantees high reliability and cost-effective implementation of the generator. Furthermore, high efficiency can be obtained because there is no PWM switching of the semiconductor devices, and it is easy to control the system. Simulations are carried out to confirm the operation in each disturbance mode, and experiments has been done with 5kVA power rating. The usefulness of the proposed scheme is verified through simulation and experimental results. It is expected that the scheme can be applied to the performance test of the custom power devices such as UPS, DVR, DSTATCOM, and SSTS with cost-effective system.

• Korean Journal of Materials Research
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• v.15 no.2
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• pp.93-96
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• 2005

The arc melting was employed to prepare undoped $CoSb_3$ compounds and their thermoelectric properties were investigated. Specimen annealed at $400^{\circ}C$ for 24 hrs showed sound microstructure. However, considerable voids and cracks were found after annealing at above $500^{\circ}C$. It seems to be attributed to the phase dissociation and thermal expansion due to phase transitions during annealing and cooling. Single phase $\delta-CoSb_3$ was successfully obtained by annealing at $400^{\circ}C$ for 24 hrs. In the case of increasing annealing temperature, phase decompositions occurred. Undoped $CoSb_3$ showed p-type conduction and intrinsic semiconducting behavior at all temperatures examined. Thermoelectric properties were remarkably improved by annealing and they were closely related to phase transitions.

• Journal of Sensor Science and Technology
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• v.25 no.1
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• pp.20-26
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• 2016

The bioelectrical impedance (BI) for the young and the elderly was measured using bioelectrical impedance spectroscopy (BIS). First, while applying a current of $600{\mu}A$ to the foot and hand, BI was measured at 50 frequencies ranging from 5 to 1000 kHz. The BI for young subjects was considerably lower than that for old subjects since young subjects have more lean mass (hydration). The prediction marker was 0.74 for young subjects and 0.78 for old subjects. Second, a Cole-Cole diagram was obtained for young subjects and old subjects, indicating the different characteristic frequencies. At 50 kHz, the average phase angle was $7.8^{\circ}$ for young subjects whereas that was $6.1^{\circ}$ for old subjects. Third, BIVA was analyzed for young subjects and old subjects. The vector length was 210.89 [${\Omega}/m$] for young subjects and 326.12 [${\Omega}/m$] for old subjects. At 50 kHz, the resistance (R/H) and the reactance ($X_C/H$) divided by height were 208.94 [${\Omega}/m$] and 28.68 [${\Omega}/m$] for young subject, and 324.33 [${\Omega}/m$] and 34.09 [${\Omega}/m$] for old subjects.

• Progress in Superconductivity and Cryogenics
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• v.21 no.1
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• pp.18-24
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• 2019

This study was carried out to investigate the effect of milling of boron (B), which is one of raw materials of $MgB_2$, on the critical current density ($J_c$) of $MgB_2$. B powder used in this study is semi-amorphous B (Pavezyum, Turkey, 97% purity, 1 micron). The size of B powder was reduced by planetary milling using $ZrO_2$ balls (a diameter of 2 mm). The B powder and balls with a ratio of 1:20 were charged in a ceramic jar and then the jar was filled with toluene. The milling time was varied from 0 to 8 h. The milled B powders were mixed with Mg powder in the composition of (Mg+2B), and the powder mixtures were uniaxially pressed at 3 tons. The powder compacts were heat-treated at $700^{\circ}C$ for 1 h in flowing argon gas. Powder X-ray diffraction and FWHM (Full width at half maximum) were used to analyze the phase formation and crystallinity of $MgB_2$. The superconducting transition temperature ($T_c$) and $J_c$ of $MgB_2$ were measured using a magnetic property measurement system (MPMS). It was found that $B_2O_3$ was formed by B milling and the subsequent drying process, and the volume fraction of $B_2O_3$ increased as milling time increased. The $T_c$ of $MgB_2$ decreased with increasing milling time, which was explained in terms of the decreased volume fraction of $MgB_2$, the line broadening of $MgB_2$ peaks and the formation of $B_2O_3$. The $J_c$ at 5 K increased with increasing milling time. The $J_c$ increase is more remarkable at the magnetic field higher than 3 T. The $J_c$ at 5 K and 4 T was the highest as $4.37{\times}10^4A/cm^2$ when milling time was 2 h. The $J_c$ at 20 K also increased with increasing milling time. However, The $J_c$ of the samples with the prolonged milling for 6 and 8 h were lower than that of the non-milled sample.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.1059-1060
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• 2012