• KIEE International Transactions on Electrophysics and Applications
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• v.5C no.4
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• pp.145-151
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• 2005

The synthetic breaking test method was developed to evaluate the breaking performance of ultra high-voltage circuit breaker and made up of two independent circuits; current source circuit and voltage source circuit. In application of this test method, it is necessary to extend the arc of the test breaker. So, the new re-ignition system using VTGS (Vacuum Triggered Gap-Switch) was constructed to improve the efficiency and reliability of this test. In this re-ignition system, VTGS operates in high vacuum state of $5{\time}10^{17}$torr and control system consists of the triggering device and the air M-G (Motor-Generator). This re-ignition system showed the operating characteristics, such as delay time ($t_d$) and jitter time ($t_j$ not exceeding 5us and 1us respectively, and had the operating voltage of $25\~150kVdc$ at the gap distance of 24mm.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.04b
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• pp.121-123
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• 2002

Fast response characteristics of twisted nematic liquid crystal display (TN-LCD) cell with different nematic liquid crystals (NLCs) and cell gap on a rubbed polyimide (PI) surface were studied. High transmittance and fast response time of the TN-LCD on the rubbed PI surface were achieved by using high birefringence ($\Delta$ n) and low cell gap. It is considered that the transmittance and response time of the TN-LCD on the rubbed PI surface decreased as $\Delta$ nd decrease.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2000.02a
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• pp.35-38
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• 2000

A preliminary design of gas-gp thermal switch is presented to reduce the cooldown time of superconducting system conduction-cooled by a two-stage refrigerator without liquid cryogens. The switch connects thermally the first and the second stages (ON) to take advantage of the larger refrigeration capacity at the first stage during the beginning period. After the cryogenic temperature is reached, the switch should isolate thermally the two stages (OFF) in order to reduce the heat leak to the cold end. In this paper, a new concept for the performance index is introduced to evaluate the reduction of the cooldown time and the increase of the cooling load at the same time. In addition, the design of a gas-gap switch is discussed as a closed container of several staggered concentric tubes filled with gas, which is frozen at low temperatures for the shut-off of heat without any mechanical actuation. Some of the detailed features in the design is quantitative investigated by the gas convection model in the continuum or the rarefied gas region.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.514-517
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• 2002

We investigated response characteristics of twisted nematic (TN) cell with different nematic liquid crystals (NLCs) and cell gap d on a rubbed polyimide (PI) surface. High transmittance and fast response time of the TN cell on the rubbed PI surface were achieved by using high birefringence (${\Delta}n$) and low cell gap d. The response time of TN cell on the rubbed PI surface was measured 5.1 ms. The transmittance and response time of the TN cell on the rubbed PI surface decreased with decreasing ${\Delta}nd$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.9
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• pp.808-811
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• 2002

We investigated response characteristics of twisted nematic (TN) cell with different nematic liquid crystals (NLCs) and cell gap d on a rubbed polyimide (PI) surface. High transmittance and fast response time of the TN cell on the rubbed PI surface were achieved by using high birefringence (Δn) and low cell gap d. The response time of TN cell on the rubbed PI surface was measured 5.1 ms. The transmittance and response time of the TN cell on the rubbed PI surface decreased with decreasing Δnd.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.498-501
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• 2003

We investigated response characteristics of twisted nematic (TN) cell with different nematic liquid crystals (NLCs) and cell gap d on a rubbed polyimide (PI) surface. High transmittance and fast response time of the TN cell on the rubbed PI surface were achieved by using high birefringence (${\Delta}n$) and low cell gap d. The transmittance and response time of the TN cell on the rubbed PI surface decreased with decreasing ${\Delta}nd$. The fast response time of TN cell using high birefringence with ${\Delta}nd=0.363$ on the rubbed PI surface was measured 5.1 ms.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.27 no.5
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• pp.428-434
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• 2001

After miniplate fixation of mandibular angle fractures, fracture line stability during functional loading was evaluated. Using panoramic radiographs, 15 mandibular angle fracture patients who were treated by open reduction and one miniplate fixation along the external oblique ridge, were evaluated at postoperative 1, 4 and 8 weeks. At each time, 2 radiographs were taken: one taken during maximum biting of hardened silicone sheet on the affected side molar area and the other on the non-affected side. The distraction gap of inferior border of mandible at each time and each side was measured and these data were analysed statistically with clinical findings. The differences of inferior border distraction gap during hardened silicone sheet biting on the affected side molar area and on the non-affected side molar area at 4 week radiographs were smaller than those of 1 week's except one case. At 8 week's radiographs, the fracture lines were so stabilized that it was almost impossible to find the gap differences except one case and there were increased radiopacity along the entire fracture lines. Clinically, bony union was confirmed in all cases during plate removal performed at postoperative 6 month. By statistical analysis(paired t-test), the inferior border distraction gap during biting of hardened silicone sheet on the affected side was significantly reduced during 1 and 4 week interval(p<0.01). The differences of inferior border distraction gap during biting on the affected side molar area and on the non-affected side molar area were also significantly reduced at 1 and 4 week interval(p<0.01). But the inferior border distraction(compression) gap during non-affected side biting was not significantly changed. From these findings, it could be concluded that fracture line stability during functional loading after one miniplate fixation of mandibular angle fractures stems mainly from reduction of inferior border distraction gap during affected side biting on time interval. According to these radiographic and clinical findings, the clinical superiority of one miniplate fixation technique in mandibular angle fracture treatment could be confirmed.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.257-260
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• 2002

This study is intended is to analyze the blocking performance with variation of the gap of bar and kinds of metal lath for construction joint when placing concrete. According to the results, passing ratio of concrete increases with increase of vibrating time. In the case of W/C 50%, when blocking concrete with bar of D10 and D20 which the gap of bar is below 200mm, or metal lath, passing ratio of concrete is below 10%, so blocking performance is favorable. In the case of W/B 30%, while concrete does not flow out without vibration at slump 21mm, concrete flows out at some degree before vibration at slump flow 65mm and then, as 5 seconds passes after first vibration, final passing ratio shows about 85~90%. When blocking concrete by bar D10 of the gap 20mm, bar D20 of the gap 10mm and metal lath, it is thought that concrete can be blocked effectively because final passing ratio is below 10%.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.10
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• pp.1038-1044
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• 2009

In this study, vibrations of an electric motor are analyzed when the motor has the interaction between mechanical and electromagnetic behaviors. For this vibration analysis a 3-phase 8-pole brushless DC motor is selected. Vibrations of the motor are influenced by coupled electromechanical characteristics. The variation of air-gap induced by vibration has an influence on the inductance of the motor coil. To analyze dynamic characteristics of the rotor, we studied inductance by the variation of an air-gap. After obtaining the kinetic, potential and magnetic energies for the motor, the equations of motion are derived by using Lagrange's equation. By applying the Newmark time integration method to the equations, the dynamic responses for the displacements and currents are computed.

• Current Optics and Photonics
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• v.3 no.6
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• pp.566-570
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• 2019

To investigate dependence of the sensitivity of THz metamaterials on the position of target dielectric materials, we functionalized the metamaterial gap with an adhesive polymer. A shift in resonance frequency occurs when polystyrene microbeads are deposited in the gap of the metamaterial's metal resonator pattern, while little change is observed when they are deposited on other areas of the metasurface. A two-dimensional mapping of the sensitivity, with a grid size of 1 ㎛, is obtained from a finite-difference time-domain simulation: The frequency shift is displayed as a function of the position of a target dielectric cube. The resulting sensitivity distribution clearly reveals the crucial role of the gap in sensing with metamaterials, which is consistent with the electric field distribution near the gap.