• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.9 s.252
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• pp.913-920
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• 2006

Three-dimensional flow and aerodynamic loss in the tip-leakage flow region of a high-turning first-stage turbine rotor blade with a squealer tip have been measured with a straight miniature five-hole probe for the tip gap-to-chord ratio, h/c, of 2.0%. This squealer tip has a indent-to-chord ratio, $h/{st}/c$, of 5.5%. The results are compared with those for a plane tip $(h_{st}/c=0.0%)$. The squealer tip tends to reduce the mass flow through the tip gap and to suppress the development of the tip-leakage vortex. Therefore, it delivers lower aerodynamic loss in the near-tip region than the plane tip does. At the mid-span, however, the aerodynamic loss has nearly the same value for the two different tips.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.12
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• pp.77-87
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• 1993

PMOSFETs were studied on the effect of Hot-Carrier induced drain leakage current (Gate-Induced-Drain-Leakage). The result turned out that change in Vgl(drain voltage where 1pA/$\mu$m of drain leadage current flows) was largest in the Channel-Hot-Hole(CHH) injection condition and next was in dynamic stress and was smallest in electron trapping (Igmax) condition under various stress conditions. It was analyzed that if electron trapping occurrs in the overlap region of gate and drain(G/D), it reduces GIDL current due to increment of flat-band voltage(Vfb) and if CHH is injected, interface states(Nit) were generated and it increases GIDL current due to band-to-defect-tunneling(BTDT). Especially, under dynamic stress it was confirmed that increase in GIDL current will be high when electron injection was small and CHH injection was large. Therefore as applying to real circuit, low drain voltage GIDL(BTDT) was enhaced as large as CHH Region under various operating voltage, and it will affect the reliablity of the circuit.

• The KSFM Journal of Fluid Machinery
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• v.7 no.5 s.26
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• pp.36-42
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• 2004

The effect of tip clearance height on the three-dimensional flow and aerodynamic loss in the wake region of a high-turning turbine rotor cascade has been investigated with a miniature cone-type five-hole probe. Distributions of velocity magnitude, secondary velocity vectors, and total-pressure loss coefficient are presented for three tip gap-to-span ratios of h/s = 0.0, 0.5 and 1.0 percent. The result shows that with the increment of h/s, tip leakage vortex tends to be intensified and aerodynamic loss due to the leakage vortex is increased as well. In the case of h/s = 1.0 percent, aerodynamic loss in the tip-leakage flow region is found dominant in comparison with that in the passage vortex region. With increasing h/s, mass-averaged secondary loss coefficient has a greater portion in the mass-averaged total-pressure loss coefficient.

• Transactions on Electrical and Electronic Materials
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• v.18 no.4
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• pp.225-228
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• 2017

In this study, zinc tin oxide (ZTO) films were prepared on indium tin oxide (ITO) glasses and annealed at different temperatures under vacuum to investigate the correlation between the Ohmic/Schottky contacts, electrical properties, and bonding structures with respect to the annealing temperatures. The ZTO film annealed at $150^{\circ}C$ exhibited an amorphous structure because of the electron-hole recombination effect, and the current of the ZTO film annealed at $150^{\circ}C$ was less than that of the other films because of the potential barrier effect at the Schottky contact. The drift current as charge carriers was similar to the leakage current in a transparent thin-film device, but the diffusion current related to the Schottky barrier leads to the decrease in the leakage current. The direction of the diffusion current was opposite to that of the drift current resulting in a two-fold enhancement of the cut-off effect of leakage drift current due to the diffusion current, and improved performance of the device with the Schottky barrier. Hence, the thin film with an amorphous structure easily becomes a Schottky contact.

• Progress in Superconductivity and Cryogenics
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• v.25 no.1
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• pp.6-10
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• 2023

2 K superfluid helium cryogenic system is the crucial component of many large accelerators. When the cryogenic system is operating at 2K@3129Pa, many room-temperature parts are connected to superfluid helium via tubes. Air Leakage in these connections may lead to air contamination of the cryogenic system. Air contamination may cause equipment failure in cryogenic systems and, in extreme cases, render the entire accelerator system inoperable. Helium guard is a technique that guards against air contamination of these sub-atmospheric pressure connections in 2 K superfluid helium cryogenic system. This paper introduces a typical 2 K cryogenic distribution design for large accelerators, and make risk analysis of air contamination. Finally, the analysis of specific leakage points and detailed engineering design are presented, which may be used as a reference when designing of a 2 K superfluid helium cryogenic distribution system.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2002.11a
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• pp.43-48
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• 2002

Since the basement building like the communication hole and etc. is built under the ground where it is pressed by the water, the leakage happens due to the dried-shrinking crack, the sinking crack, the creation of the work-joint of the building and etc. caused by the character of the material and construction way of the reinforced concrete building. Especially, a lot of repair for the leakage cannot help but being taken in temporary way without any noticeable countermeasure. Therefore, this kind of repair is socially criticized many times that this is defective construction even if this costs a lot. The fundamental reason of the above mentioned symptoms can be found in the creation of the work-joint caused by the character of the concrete building, the limitation of the physical performance of the existing water-proof and repair material, the limitation of the construction, the limitation of the physical sustaining performance of the concrete building, the limitation(heat-injury, deterioration) of the constancy of the durability caused by aging and etc. Therefore, in this study, we would like to present the better understanding on the water-proof seal relating to the application at the spot and its test evaluation related data since the necessity of the establishment of the quality control standard and the performance testing way on the relevant water-proof seal is rising a lot to regulate the water-proof technology and the leakage repair technology in accordance with the growth of the demand on the facility.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.6
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• pp.825-833
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• 2018

In this study, one calculated the range of damage to the combustion characteristics according to the composition of LNG and the size of leaking holes, and analyzed the damage effect in case of leakage accidents caused by pipe damage in the re-gasification process for the LNG supply system. In order to confirm the combustion characteristics according to LNG composition, there was no significant difference in the result of risk analysis by LNG-producing areas. However, the higher the methane content of the components, the lower the risk of flash fire, hazardous areas of overpressure due to explosion, and thermal radiation damage caused by jet fire. In addition, one investigated the effect of leakage, holes, and ruptures on the risk range and explosions according to the size of the pipe-leakage hole. Also, the influence of overpressure and the range of damage from radiant heat could be predicted. One confirmed the effect of LNG composition and pipe-leakage size on fire and explosion.

• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.3
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• pp.181-187
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• 2016

A thermal power plant has a heat exchanger tube to collect and convert the heat generated from the high temperature and pressure steam to energy, but the tubes are arranged in a complex manner. In the event that a leakage occurs in any of these tubes, the high-pressure steam leaks out and may cause the neighboring tubes to rupture. This leakage can finally stop power generation, and hence there is a dire need to establish a suitable technology capable of detecting tube leaks at an early stage even before it occurs. As shown in this paper, by applying acoustic emission (AE) technology in existing boiler tube leak detection equipment (BTLD), we developed a system that detects these leakages early enough and generates an alarm at an early stage to necessitate action; the developed system works better that the existing system used to detect fine leakages. We verified the usability of the system in a 560MW-class thermal power plant boiler by conducting leak tests by simulating leakages from a variety of hole sizes (ⵁ2, ⵁ5, ⵁ10 mm). Results show that while the existing fine leakage detection system does not detect fine leakages of ⵁ2 mm and ⵁ5 mm, the newly developed system could detect leakages early enough and generate an alarm at an early stage, and it is possible to increase the signal to more than 18 dB.

• Journal of computational fluids engineering
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• v.21 no.2
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• pp.99-105
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• 2016

The present study has been carried out to analyze the flow characteristics with geometric shape and control conditions in subsea by-pass valve. The function of by-pass valve is to prevent reverse flow. In this study, the static analysis has been perform for analyzing fluid flow in open state. In order to consider the turbulent effect, the standard ${\kappa}-{\varepsilon}$ model was used. A variety of parametric studies, such as by-pass valve type or size, volume flow rate, leakage hole size, leakage hole position, block type, block shape, were performed. The pressure difference across the valve in the model broadened the flow channel cross-sectional area was greater than the base model for the same operating conditions. As the pipe diameter in the block decreases the pressure difference is greatly increased. The pressure difference according to block shape such as edge type and round was almost negligible. For the same Reynolds number the pressure difference was little changed according to the size of the valve.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.11
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• pp.7-13
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• 2004

Experimental results are presented for the degradation of 3 nm-thick gate oxide under -2.5V $\leq$ V$_{g}$ $\leq$-4.0V stress and 10$0^{\circ}C$ conditions using P and NMOSFETs that are annealed with hydrogen or deuterium gas at high-pressure (5 atm). The degradation mechanisms are highly dependent on stress conditions. For low gate voltage, hole-trapping is found to dominate the reliability of gate oxide both in P and NMOSFETs. With increasing gate voltage to V$_{g}$ =-4.0V, the degradation becomes dominated by electron-trapping in NMOSFETs, however, the generation rate of "hot" hole was very low, because most of tunneling electrons experienced the phonon scattering before impact ionization at the Si interface. Statistical parameter variations as well as the gate leakage current depend on and are improved by high-pressure deuterium annealing, compared to corresponding hydrogen annealing. We therefore suggest that deuterium is effective in suppressing the generation of traps within the gate oxide. Our results therefore prove that hydrogen related processes are at the origin of the investigated oxide degradation.gradation.