• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.30-34
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• 2001

In the present study, we studied the method of predicting the on-design and on-design point performance of axial flow fan with adjustable pitch blades. With the change of stagger angle of axial flow fan with adjustable pitch blade, flow rate and pressure can be changed. Because of this merit adjustable pitch fans are used in many industrial facility. When changing stagger angle or estimating the performance at a wide range of off-design condition, incidence angle changes greatly as the flow rate changes. Therefore, the deviation angle at the blade exit is estimated by the correlation considering the effects of blade design, incidence angle variation. In the loss model, we used known pressure loss model for blade boundary layer and wake, secondary flow, endwall boundary layer and tip leakage flow. The results of modified deviation angle model and experiment were compared for the usefulness of the modified model.

• Proceedings of the IEEK Conference
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• 2002.07b
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• pp.1046-1049
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• 2002

In this paper, a sub-harmonic dual-gate FET mixer for IMT-2000 base-station was designed by using single-gate FET cascode structure and driven by the second order harmonic component of LO signal. The dual-gate FET mixer has the characteristic of high conversion gain and good isolation between ports. Sub-harmonic mixing is frequently used to extend RF bandwidth for fixed LO frequency or to make LO frequency lower. Furthermore, the LO-to-RF isolation characteristic of a sub-harmonic mixer is better than that of a fundamental mixer because the frequency separation between the RE and LO frequency is large. As RF power is -30dBm and LO power is 0dBm, the designed mixer shows the -47.17dBm LO-to-RF leakage power level, 10dB conversion gain, -0.5dBm OIP3, -10.5dBm IIP3 and -1dBm 1dB gain compression point.

• Proceedings of the IEEK Conference
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• 2003.07b
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• pp.667-670
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• 2003

Ni-silicide has low thermal stabiliy. This point is obstacle to apply NiSi to devices. So In this paper, we have studied for obtain thermal stability and analysis of dopant dependency of NiSi. And then we applied Ni-silicide to devices. To improvement of thermal stability, we deposit Ni70/Co10/Ni30/TiN100 to sample. Co midlayer is enhanced thermal stability of NiSi. Co/Ni/TiN, this structure show very difference between n-poly and p-poly in sheet resistance. But Ni/Co/Ni/TiN, structure show less difference. Also junction leakage is good.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.6 no.4
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• pp.28-35
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• 2007

Currently, most of all valves using at the semiconductor & LCD manufacturing process are packless type. Such valves are needed to have the functions to protect perfectly from the leakage of fluid by using bellows and diaphragm instead of the grand packing. But not only those valves made in Korea are not available at this point, but also advanced foreign manufacturers do not open enough their data on the basic technology. Otherwise although they open the data a little, they are almost data about stainless steel for pneumatic valves. In this paper, it was focused on the fluid valves for chemical & DI water based on the data of steel valves which are already using commercially. And also this study concentrated to collect the basic developing data of Eco-On/Off diaphragm valve by ourselves.

• Journal of Sensor Science and Technology
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• v.19 no.2
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• pp.67-86
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• 2010

Hydrogen is emerging as clean fuel and important industrial raw materials. The hydrogen gas is not sensed by the human olfactory system, But the combustion characteristics of hydrogen is that the ignition is very easy, the propagation speed of the flame is very fast and explosion limits is a wide range of 4 %~75 %. Therefore it is extremely in danger, and the need for its leakage detection technologies is especially important in places such as a production, transportation, storage and usage. The hydrogen sensors are classified with ceramic type, semiconductor type, optical type, electrochemical type and so on. Hydrogen sensors and their technologies are reviewed in detail for materials, fabrication process, sensing characteristics, good point and faults, and production and utilization of sensors be discussed.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2009.01a
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• pp.578-582
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• 2009

Computer-Generated Hologram (CGH) is generally made by Fourier Transform. CGH is made by an optical reconstruction. Computer-Generated Pseudo Hologram (CGPH) is made up Complex Hadamard Transform instead of CGH which is made by the Fourier Transform. CGPH differs from CGH in point of view the possibility of optical reconstruction. There is an advantage that it cannot be optical reconstruction, in other word, physical leakage of the confidential information is impossible. In this paper, a binary image was converted in Complex Hadamard Transform, and CGPH was made. Improvement of the reconstructed image from CGPH is done by error diffusion method and iterative method. The result that the reconstructed image is improved is shown.

• Tribology and Lubricants
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• v.29 no.3
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• pp.186-191
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• 2013

Hydraulic systems are used to transform mechanical energy into fluid energy and vice versa. They are widely applied in various industries; e.g., they are used in automobiles, public works, rockets, machine tools, heavy construction equipment, and airplanes. Hydraulic pumps are used to transform the energy in these systems. In this study, with the basic operation principles as a starting point, I attempted to clarify how the shape of a slipper affects the lubrication characteristics under practical conditions. A swashplate with a tilt angle of zero and capable of rotating motion was used, along with other devices. A slipper was located at 45 mm eccentricity from the center of the swashplate. The results of this experiment indicated that the shape of the bottom surface of a slipper affects the load capacity, leakage flow, and lubrication characteristics and that the slipper is one of the most important parts for improving the pump efficiency.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2014.11a
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• pp.98-99
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• 2014

질산산화법(nitric acid oxidation method)은 저온에서 안정적인 산화막을 형성하는 직접산화공정으로 azeotropic point(68 wt%)인 120도 이하의 온도에서 산화막을 형성한다. 120도에서 형성한 질산산화막은 CVD법으로 형성한 산화막 보다 낮은 누설전류밀도(leakage current density)를 나타낸다. 또한 질산의 농도가 증가함에 따라 형성한 산화막의 누설전류밀도가 감소하며, 이는 열산화법으로 형성한 산화막 보다 낮다. 질산산화의 낮은 누설전류밀도는 형성한 산화막의 높은 원자 밀도와 낮은 계면준위밀도에 의한 것으로 이 특성을 이용하여 게이트 절연막(gate insulator)과 태양전지의 passivation막으로 응용되고 있다.

• Nuclear Engineering and Technology
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• v.30 no.4
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• pp.377-385
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• 1998

Many nuclear power plants have experienced unscheduled shutdown due to the leakage of steam generator tubes. The leakages are normally due to the crack, possibly stress corrosion cracking (SCC) near the tube expansion at the top of tubesheet or at the tangential point of the row-1 U-bend region. The conventional eddy current technique, which makes use of a differential bobbin coil, has been found to be inadequate for the early detection of SCC. During the in-service inspection, therefore, it is a general practice that the rotating pancake coil (RPC) is used for detecting the cracks. Even in using RPC, however, it is difficult to determine the depth of the cracks quantitatively. This paper attempts to determine the detectability and sizing ability of RPC technique for axial or circumferential cracks at the tube expansion region. The simulated cracks with various dimensions were fabricated by electro-discharge machining (EDM) method. Experimental results are discussed with theoretical calculations.

• Journal of Korean Society of Water and Wastewater
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• v.24 no.5
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• pp.573-580
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• 2010

Average pressure in a pipe network is one of critical factors to estimate the flow distribution and to calculate UARL (Unavoidable Annual Real Losses) value in ILI (Infrastructure Leakage Index). While its collection period and measuring location are essential to obtain average pressure, their standard method have not been established so far. In this study, proper method including its procedure for data collection period and measuring point for average pressure were suggested using non-exceedance probability concept in the water distribution network.