• Journal of Korean Society of Water and Wastewater
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• v.31 no.5
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• pp.459-469
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• 2017

A real scale leakage test facility was developed to study the leak signal characteristics of water supply pipelines, and then leak tests were carried out. The facility was designed to overcome the limited experimental circumstances of domestic water supply pipeline experimental facilities. The length of the pipeline, which was installed as a straight line, is 280m. Six pipes were installed on a 70m interval with different pipe material and diameters that are DCIP(D200, D150, D100, D80), PE(D75) and PVC(D75).The intensity of the leakage is adjusted by changing the size of the leak hole and the opening rate of ball valve. Various pressure conditions were simulated using a pressure reducing valve.To minimize external noise sources which, deteriorate the quality of measured leak signal, the facility was built at a quiet area, where traffic and water consumption by customers is relatively rare. In addition, the usage of electric equipment was minimized to block out noise and the facility was operated using manual mode. From the experimental results of measured leakage signal at the facility, it was found that the signal intensity weakened and the signal of high frequency band attenuated as the distance from the water leakage point increased.

• Journal of the Korean Ceramic Society
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• v.34 no.8
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• pp.803-810
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• 1997

Ba0.5Sr0.5TiO3 thin films were deposited by RF magnetron sputliring method in order to clarify the anneal condition and doping effect on loakage current Nb and Al were selected as electron donor and acceptor dopants respectively, in the BST films because they have been known to have nearly same ionic radii as Ti and thought to substitute Ti sites to influence the charge carrier and the acceptor state adjacent to the gram boundary. BST thin films prepared in-situ at elevated temperature showed selatively high leakage current density and low breakdown voltage. In order to achieve smooth surface and to improve electrical properties, BST thin films were deposited at room temperature and annealed at elevated temperature. Post-annealed BST thin films showed smoother surface morphology and lower leakage current density than in-situ prepared thin films. The leakage current density of Al doped thin films was measured to be around 10-8A/cm2, which is much lower than those of undoped and Nb doped BST films. The result clearly demonstrates that higher Schottky barrier and lower mobile charge carrier concentration achieved by annealing in the oxygen atmosphere and by Al doping are desirable for reducing leakage current density in BST thin films.

• Journal of the Korean Institute of Gas
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• v.17 no.3
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• pp.14-19
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• 2013

This paper presents an experimental study on the safety of a valve for a special gas cylinder. The test valves that were randomly dismantled from the special gas cylinder were experimented on the gas leakage and operation safeties. The crack, wear and deformation of the valve body, screw thread, safety disk, vent hole, stem and handle components that may affect to the gas leakage safety of a used valve were not found in this experimental study. A painted handle of a valve was partly stripped from the coated surface, and the surface of PT screw of a used valve body was rusted. But, these paint and rust problems do not affected to the gas leakage safety of used valves. And there was no gas leakage in the dismantled valve, and the permanent deformation and partial scars of a valve stem and O-rings were observed on the rubbing surfaces. Thus, the valve seat and O-rings are recommended to be replaced for a gas leakage safety of a dismantled valve. And it is necessary to repair and inspect handle fastening forces for a safe opening and closing operations of a valve.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.145-145
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• 2015

처음 유기물의 인광 발견 이후 Host-dopant 시스템을 이용하여 Emission layer(EML)을 Co-deopsition 하는 방법으로 주로 인광 유기 발광 다이오드를 제작 하였다. [1] co-deposition을 이용해 만든 유기 발광 다이오드에 많은 장점이 있지만, 반대로 소자를 제작하는데 있어서는 많은 문제점을 가지고 있다. [2-4] 이러한 문제점을 개선하기 위하여 co-deposition 대신 non-doped Multi Quantum Well(MQW) 구조를 사용하여 doping 하지 않는 방법을 이용하는 논문들이 보고 되고 있다. Hole, electron, exciton이 MQW 구조를 지나면서, dopant well 안에 갇히게 되고, 그 안에서 다른 layer 간에 energy transfer와, hole-electron leakage가 줄어 들어, 더 효율적인 유기 발광 다이오드를 만들 수 있게 된다. [5-7] 이 연구에서는 CBP를 Potential Barrier로 사용하고, Ir(ppy)3 (Green dopant), Ir(btp)2 (Red dopant) 를 각각 Potential Well로 사용하였고, 두께는 CBP 9nm, dopant 1nm로 하였다. 이러한 소자를 만들고 dopant를 3개의 well에 적당히 배치하여, 각 well에서의 실험적인 발광 량 과, EML 안에서의 발광 mechanism 그리고 각 potential barrier를 줄여가며 dexter, forster에 의한 energy transfer에 대하여 알 수 있었다.

• International Journal of Fluid Machinery and Systems
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• v.6 no.1
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• pp.18-24
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• 2013

In order to apply the design method of diagonal flow fan based on axial flow design to the design of radial-outflow type diagonal flow fan which has lower specific speed of 600-700 [$min^{-1}$, $m^3/min$, m], radial-outflow type diagonal flow fan which specific speed was 670 [$min^{-1}$, $m^3/min$, m] was designed by a quasi three-dimensional design method. Experimental investigations were conducted by fan characteristics test, flow surveys by a five-hole probe and a hot wire probe. Fan characteristics test agreed well with the design values. In the flow survey at rotor outlet, the characteristic region was observed. Two flow phenomena are considered as the cause of the characteristic region, one is tip leakage vortex near rotor tip and another is pressure surface separation on the rotor blade.

• Proceedings of the KSR Conference
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• 2009.05b
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• pp.585-592
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• 2009

The performance of screw compressor depends on lots of design parameters of rotor profile, such as length of seal line, wrap angle, blow hole, suction and discharge port size, number of rotor lobe, etc. The optimum rotor profile makes it possible to increase the compression efficiency with low energy consumption, and to minimize the loss of power. In this research, a new rotor profile design and performance analysis are done by computer simulation. It is expected that the volumetric efficiency is improved because the internal leakage is reduced due to the minimization of blow hole and clearance, and the stiffness of rotors is increased due to the reduction of length to diameter ratio. Also, the specific power consumption will be secured for use ranging from low to high operation speed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.849-852
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• 2002

Recently, amorphous selenium is used as x-ray conversion material for flat-panel x-ray detector. In this paper, we investigated the effect of breakdown under high voltage and leakage current in PN-type multi-layer structure based on p-type a-Se and n-type conductive thin film. Experimental results show that the multi-layer based detector reduced leakage current because n-type CeO2 conductive layer prevent from hole injection into a-Se layer from collection electrode, Also, the breakdown voltage was improved by dielectric layer between a-Se and top electrode.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.7
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• pp.171-175
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• 1996

Gate insulator for Si field emitter is usually formed by e-beam evaporation. However, the evaported oxide requires densification for a stable process and a reduction of gate leakage which results from its Si-rich and nonstoicheiometric structure. In this study, we have developed the process technology able to densify the evaporated oxide in H$_{2}$O ambient. Using this process, we have fabricted thefield emitter array with 625 emitters per pixel, of which gate hole diameter is 1.4.mu.m, for the pixel, anode current of 14.3.mu.A was extracted at a gate bias of 100V and gate leakage was about 0.27% of the total emission current.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.161-164
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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/e, 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.

• International Journal of Fluid Machinery and Systems
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• v.1 no.1
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• pp.47-56
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• 2008

The flow behind the variable area nozzle which corresponds to the flow at the leading edge of the impeller was measured with a 3-hole yaw probe and calculated with CFD. Two nozzle throat-areas were investigated. One is the smallest and the other is the largest opening for the variable nozzle. Test results agreed with the calculated results qualitatively. The leakage flow through the tip clearance of the nozzle vane significantly affected the flow field downstream of the nozzle vane with the smallest opening. However, the effect on leakage flow on the flow field downstream of the nozzle vane with the largest opening was very weak and the effect of wake is dominant.