• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1322-1327
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• 2005

This paper presents a single-stage ZVT full-bridge AC/DC converter for aerospace applications. The detailed operating principle and design consideration of this soft-switched converter are analyzed and described. The proposed circuit topology and control scheme are proposed to exhibit optimum performances (i.e. high power factor, high efficiency, ring-free and low EMI features). A laboratory prototype, 500W 5V/100A AC/DC converter was implemented. The simulation and experimental waveforms verify the feasibility of the proposed design.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.10
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• pp.875-880
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• 2008

In this paper, we deal with the TLP evaluation results for GGNMOS in ESD protection device of conventional CMOS process. An evaluation parameter for GGNMOS is that repeatability evaluation for reference device($W/L=50\;{\mu}m1.0\;{\mu}m$) and following factors for design as gate width, number of finger, present or not for N+ gurad -ring, space of N-field region to contact and present or not for NLDD layer. The result of repeatability was showed uniformity of lower than 1 %. The result for design factor evaluation was ; 1) gate width leading to increase It2, 2) An increase o( finger number was raised current capability(It2), and 3) present of N+ gurad-ring was more effective than not them for current sink. Finally we suggest the optimized design conditions for GGNMOS in evaluated factor as ESD protection device of conventional CMOS process.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.5
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• pp.134-142
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• 1994

An upper bound elemental technique (UBET) is applied to predict variations of neutral plane and optimal position of the initial billet for rib-wep shaped ring forging. In the analysis, the neutral plane position and velocity fields are determined by minimizing the total power consump- tion with respect to chosen parameters. The degree of die-cavity filling by initial billet-position and the variations of neutral plane by friction condition are investigated. Experiments have been carried out with pure plasticine billets at room temperature. The theoretical predictions of the forging load and the flow pattern are in good agrement with the experimental results.

• Fibers and Polymers
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• v.5 no.4
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• pp.275-279
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• 2004

Yarn tension is a key factor that affects the efficiency of a ring spinning system. In this paper, a specially constructed rig, which can rotate a yam at a high speed without inserting any real twist into the yarn, was used to simulate a ring spinning process. Yarn tension was measured at the guide-eye during the simulated spinning of different yarns at various balloon heights and with varying yarn length in the balloon. The effect of balloon shape, yarn hairiness and thickness, and yam rotating speed, on the measured yarn tension, was examined. The results indicate that the collapse of balloon shape from single loop to double loop, or from double loop to triple etc, lead to sudden reduction in yarn tension. Under otherwise identical conditions, a longer length of yarn in the balloon gives a lower yarn tension at the guide-eye. In addition, thicker yarns and/or more hairy yarns generate a higher tension in the yarn, due to the increased air drag acting on the thicker or more hairy yarns.

• Journal of Korean Ophthalmic Optics Society
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• v.4 no.2
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• pp.45-49
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• 1999

The second harmonic, wavelength is 397nm, of the continuous wave diode laser, whose maximum power is 35mW, was generated in $LiIO_3$ crystals in a ring enhancement cavity. 5mm- and 10mm-long crystals cut $43.21^{\circ}$ for optic axis were used in this experiment. Both surfaces of those were anti-reflection coated for 794nm. In case the crystal was inserted into the cavity, the condition of separation between two concave mirrors for the optimum mode matching was found. The conversion efficiency of second harmonic generation was increased by the resonant enhancement of pumping power in the ring enhancement cavity, and the frequency of diode laser was locked to that of the counter-propagation mode generated from the surface of crystal. When the pumping power was 28 mW, the infrared buildup factor was about 45 without the crystal, and 14 with the crystal due to the transmission loss of crystal. The maximum second harmonic powers of $1.5{\mu}W$ and $6.6{\mu}W$ were obtained, and corresponding conversion efficiencies were $(6.584{\pm}0.56){\times}10^{-3}$%, $2.6{\pm}0.21){\times}10%{-2}$% in 5mm- and 10mm-long $LiIO_3$, respectively.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.1031-1033
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• 2006

In this study, in order to solve these problems, a new type of electronic ballast, which is composed of rectifier, active power factor corrector, series resonant half bridge inverter and piezoelectric transformer, was proposed for driving T5 fluorescent lamp. Driving of piezoelectric transformer was carried out with input region for the ring electrode and output region for the dot electrode. A 35W (T5) fluorescent lamp was successfully driven by the fabricated ballast with piezoelectric transformer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.423-426
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• 2000

The 3-D $31.5$\times$31.5$\times$2.5mm$^3$model of contour vibration mode piezoelectric transformer with Pb($Ni_{1/2}$$W_{1/2}$)$O_3$-Pb(Zr,Ti)$O_3$ ceramics was simulated by ANSYS according to the dot size 17, 18, 19, 20, 21 $mm\phi$ and analyzed the results. The mechanical quality factor of the 3-D model was decreased with the dot size and increased as 2605 at 20 $mm\phi$ and after then decreased again. The output voltage of that sample was 74123 [V] and the maximum stress of the dot electrode at that sample was 288[$10^7$N/$m^2$] and the maximum displacement of the ring electrode at that sample was 128 [$\mu\textrm{m}$].

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.414-419
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• 2009

Good control of thermal energy helps to increase characteristics and eliminate defects of large cast-forged part, such as large sized forged shell. Thermal energy control is a important factor. We have studied about forging process and after heat treatment process by FEM simulation. There are three ways of process. Changes of temperature and microstructure for forged shell were predicted according to temperature declination in large cast-forged product. So we will be able to choose the proper time from heat treatment conditions by FEM simulation.

• The Journal of Internal Korean Medicine
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• v.33 no.1
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• pp.26-38
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• 2012

Objectives : The aim of this study was to investigate the effect of partial pyloric obstruction on body weight, gastric juice, gastric surface area and gastric edema in normal intact and/or vagotomized rats. Methods : Partial pyloric obstruction was performed by wrapping a non-absorbable rubber ring (D:6 mm, W:4 mm, T:1 mm) around the 1st portion of the duodenum. Vagotomy was performed by resecting the branches around the esophagogastric junction. Pre-post body weight differential, fasting gastric juice volume, gastric surface area and gastric edema were measured at 8 weeks and 20 weeks. For the effect of pyloric reperfusion the rubber ring was removed after 8 weeks and then an additional 12 weeks of observation was performed to the end of the 20-week experimental period. Results : In the initial 8 weeks observation, the effect of pylorus obstruction and/or vagotomy was significantly remarkable in the pylorus obstructed and vagotomized group; slowdown of weight gain, increase of fasting gastric juice volume, dilatation of gastric surface area and severe gastric edema were shown. In the remaining 12 weeks observation, the effect of reperfusion was significantly remarkable in the ring-removed antral dilated group; recovery of weight gain, decrease of gastric surface area and decrease of gastric edema were shown. However, gastric juice volume was not significantly different from the other group. Conclusions : Partial pyloric obstruction plays a aggravating role and the vagus nerve plays a protective role in body weight, gastric juice, gastric surface area, and gastric edema. Furthermore, pyloric valve dysfunction as an aggravating factor strengthened in defect of the vagus nerve. These results suggest that patients with both functional pyloric outlet obstruction and hypofunction of vagus nerve need to be diagnosed in good time and treated properly.

• Progress in Medical Physics
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• v.9 no.1
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• pp.29-35
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• 1998

There has been necessity of an air free ionization chamber using the gold-crystal-aluminium plates, henceforth called the crystal chamber. The crystal chamber formed of parallel plates is very small in size and has more response for absorbed dose of therapeutic radiation beams. The gold plate on the crystal facing the photon and electron beam acts as an intensifier of signals and crystal plate as an ionization medium respectively. Both the copper guard ring and the aluminum collecting electrode are connected to an electrometer. Using high energy photon (6, 15 MV) and electron (9, 12, 15, 18 MeV) beams, the responses of the crystal chamber are evaluated against a PTW Farmer-type chamber at a field size of 10${\times}$10cm$^2$ and 100 cm SSD. The responses of crystal chamber for therapeutic radiation electron and photon beams are greater in magnitude by several order than Farmer. The crystal chamber has good linearity without correction factor C$\_$t,p/ with respect to the signals, a reading reproduction with good accuracy and precision less than 0.5%, and has other useful functions in measuring radiation beams.