• 한국진공학회지
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• 제8권4B호
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• pp.497-506
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• 1999

Carbon has been widely used for the material of plasma facing components in fusion experiment devices like a tokamak, because carbon has good thermal and mechanical properties. However carbon gas a relatively high ougassing rate. Therefore the amount and the surface area of the carbon material used in the vessel will determine the background pressure of the vacuum vessel. In this experiment influences of carbon on the vacuum performance was investigated by measuring chamber pressure, ougassing rater and gas spectrum of carbon fiber composite (CFC) samples in various situations, pumping out, chamber baking, carbon heating (250~$500^{\circ}C$), exposure to atmosphere for maintenance of in-vessel components, etc., occurring routinely during tokamak operations.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.368-373
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• 2001

A major concern on high-energy centrifugal pump is the potential for interaction of two-phase flow phenomena with mechanical response of the pumping elements. The other concern is the pressure pulsations created from trailing edge of the impeller blade and flow separation and recirculation at partial load in centrifugal pumps. These interactions generating between rotor and casing cause dynamic pulsation on pump and exciting pipeline vibration. The higher severity responses, the more lead to failure of pump and system components. Finally, it cause severe axial vibration of single stage pump due to the hydraulic instability in flow condition below BEP.

• 한국안전학회지
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• 제30권1호
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• pp.47-51
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• 2015

In the study, a new non-open cut tunnel steel pipe method using slot hole has been developed. As is overcomes shortcomings of conventional methods, it is applied to the field. The main concept of the new method is the steel pipe pumping system with slot holes which, by means of formation slot holes between each steel pipe, applied to the magnitude of the relaxed earth pressure caused by excavation to the ground to prevent ground displacement. The stability of the support members and effect of displacement control of the new method were verified through several ways as numerical analysis and site test. The new method was applied to the construction of a 11.5m wide, 7.4m high and 50m long section that passes side subway and large buildings in inner city. By applying the new method, tunnel construction was successfully completed in 6 months. It decreases the construction period to 30% compared to that of conventional methods, and ground was almost negligible.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 봄 학술논문 발표대회
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• pp.191-192
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• 2023

In recent years, the use of high-strength grout has gained popularity in offshore wind power generation complexes for facility foundations and bridges. These marine wind farms require support for horizontal loads from wind and waves. To ensure the strength of the grout produced in environments similar to the actual placing site, this study investigated the curing of high-strength grout discharged through pump pressure in various environments, and examined the difference in strength according to different variables. Compressive strength measurements revealed that the core specimen collected from the bottom (3cm) and uppermost (50cm) of the specimen exhibited lower strength compared to other height specimens, while the core specimen obtained from the corner exhibited lower strength compared to the center. These findings suggest that the strength difference between the center and the corner is more pronounced when curing at low temperatures. This effect is greater than the strength reduction that typically occurs during low-temperature curing, and thus, necessitates careful attention in similar construction environments.

• 한국진공학회지
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• 제22권5호
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• pp.225-230
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• 2013

크라이오펌프는 응축과 흡착을 통해 기체를 배기하므로 극저온 표면 온도와 증기압이 배기성능에 큰 영향을 미친다. 어느 부분의 온도가 어중간하면 한번 응축했던 기체분자가 방출과 재응축 또는 재흡착을 반복하여 진공용기 압력이 어느 선 이하로 떨어지지 않고 심한 요동을 나타낸다. 어떤 기체나 특정 온도 범위에서 이런 불안정성이 나타날 수 있지만 크라이오펌프를 많이 사용하는 스퍼터 장치의 공정기체인 알곤을 배기할 때 불안정성이 발생하는 것은 좋지 않다. 본 논문에서는 알곤 회복시간 측정실험을 수행하면서 크라이오펌프의 알곤 불안정성의 원인과 대책을 분석했다.

• 한국정밀공학회지
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• 제30권12호
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• pp.1327-1333
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• 2013

Air bearings are widely used in precision stages because of low friction and high motion accuracy, however, they suffer from low stiffness in comparison with rolling bearings or hydrostatic bearings. So, several preloading methods using weight, magnet and vacuum force, and opposing pads have been used to increase the stiffness of the air bearings. In this paper, pressure distributions of the vacuum preloaded porous air bearings are calculated using the proposed method. And then, the load capacity and stiffness are analyzed. For the vacuum preloaded air bearings, the stiffness is increased owing to reduced bearing clearance by vacuum force. The simulation results indicate that variation of vacuum pressure with clearance in the vacuum pocket gives rise to low stiffness, so the vacuum pocket should be designed for pressure to be constantly maintained regardless of the bearing clearance by means of large effective pumping speed.

• 한국표면공학회지
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• 제33권2호
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• pp.69-76
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• 2000

The rf plasma chemical vapor deposition is a common method employed for diamond or amorphous carbon deposition. Diamond possesses the strongest bonding, as exemplified by a number of unique properties-extraordinary hardness, high thermal conductivity, and a high melting tempera tore. Therefore, it is very important to investigate the synthesis of semiconducting diamond and its use as semiconductor devices. An inductively coupled rf plasma CVD system for producing amorphous carbon films were developed. Uniform temperature and concentration profiles are requisites for the deposition of high quality large-area films. The system consists of rf matching network, deposition chamber, pumping lines for gas system. Gas mixtures with methane, and hydrogen have been used and Si (100) wafers used as a substrate. Amorphous carbon films were deposited with methane concentration of 1.5% at the process pressure of S torr~20 torr, and process temperature of about $750^{\circ}C$. The nucleation and growth of the amorphous carbon films have been characterized by several methods such as SEM and XRD.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 춘계학술대회 논문집
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• pp.787-790
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• 2012

In downtown, construction noise related claims are the most important issues. Sometimes noise related claims halt the construction process. Therefore, Introduction of noise reduction measures is common to construction process with a loud noise. This case is about concrete pouring for mat foundation of super tall building. Concrete pouring process using High Pressure Pumping machine causes high noise level in the vicinity of area. And large number of transit-mixer truck cause traffic congestion. This paper introduces effort and process to prevention of construction noise claims on massive scale concrete pouring.

• 한국전기전자재료학회논문지
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• 제11권8호
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• pp.607-612
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• 1998

RF HPCVD(Helicon Plasma Chemical Vapor Deposition) has been successfully constructed for diamond thin films. The system consists of plasma generation tube, deposition chamber, pumping lines for gas system. A mixture of $CH_4 and H_2$is used for reaction. Two thermocouples, a quartz tube surrounded by a RF antenna and a magnet, and a high temperature heater were set up in the deposition chamber. The process for the thin film diamond deposition has been carried put in a high vacuum system at a substrate temperature of $800^{\circ}C$, and pressure of 5 mtorr. It is also demonstrated. that the RF HPCVD system has advantages for controlling deposition parameters easily.

• 대한기계학회논문집B
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• 제24권8호
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• pp.1128-1138
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• 2000

Pumping action in ejector systems is generally achieved through the mixing of a high-velocity and high-energy stream with a lower-velocity and lower-energy stream within a duct. The design and performance evaluation of the ejector systems has developed as a combination of scale-model experiments, empiricism and theoretical analyses applicable only to very simplified configurations, because of the generic complexity of the flow phenomena. In order to predict the detailed performance characteristics of such systems, the flow phenomena throughout the operating regimes of the ejector system should be fully understood. This paper presents the computational results for the two-dimensional supersonic ejector system with a second throat. The numerical simulations are based on a fully implicit finite volume scheme of the compressible Reynolds-averaged Navier-Stokes equation in a domain that extends from the stagnation chamber to the diffuser exit. For a wide range of the operating pressure ratio the flow field inside the ejector system is investigated in detail. The results show that the supersonic ejector systems have an optimal throat area for the operating pressure ratio to be minimized.