• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2006.10a
• /
• pp.137-138
• /
• 2006

• Proceedings of the Korean Vacuum Society Conference
• /
• 2008.08a
• /
• pp.279-279
• /
• 2008

• Journal of the Korean Society for Precision Engineering
• /
• v.25 no.12
• /
• pp.132-138
• /
• 2008

Recently, mastering processes for high density optical disc such as Blu-ray disc rely on electron beams, which are operable in only vacuum. In the mastering process, one of the most important tasks is to design precision stages for providing precise positioning of the works with respect to the source in a high vacuum environment. In this paper, we have developed a precision rotation table usable in the electron beam mastering. The rotation table adopted air bearings for a high positioning repeatability and velocity stability. The air leakage from the air bearings has been minimized by employing the differential exhaust scheme using three steps of air drain. The design parameters such as diameters of exhaust lines, seal lengths, and pumping speeds were decided according to the optimization method using genetic algorithm. The performance on the vacuum level of the rotation table was evaluated experimentally and theoretically. The results indicate that a vacuum level of $10^{-4}$ Pa is achieved with operation of air bearings in a vacuum chamber, which is sufficient for the electron beam mastering.

• Journal of Power System Engineering
• /
• v.17 no.3
• /
• pp.17-22
• /
• 2013

Diesel particulate filter has been adopted in new vehicle with diesel engine. Since the flow of exhaust gas was clogged as particulate matters were deposited in the filter, it have bad effects on a fuel consumption and power. It was investigated that a particulate filtering system with vacuum pump in the exhaust gas line could be free from clogging in previous research. In this study, the effects of water injection and position of inlet port in filtering system on reducing in particulate matter were investigated. It was noticed that particulate matter were decreased remarkable by water injection and moving the position of inlet port.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.12 no.4
• /
• pp.16-23
• /
• 2008

Theoretical and numerical approaches were conducted in order to study supersonic exhaust diffusers to simulate high altitude performance of rockets on the ground. A physical model of concern includes a rocket motor, vacuum chamber, and diffuser, which have axisymmetric configurations. An analysis was conducted to investigate operation characteristics of supersonic exhaust diffusers from a flow-development point of view. Emphasis was placed on theoretical formulation to predict the starting pressure of diffusers, the effect of the vacuum chamber size, and the minimum starting pressure of the rocket motor to start the diffuser.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2007.11a
• /
• pp.431-432
• /
• 2007

• Particle and aerosol research
• /
• v.11 no.4
• /
• pp.93-98
• /
• 2015

Particles which generated from plasma enhanced chemical vapor deposition (PECVD) during thin film deposition process can affect to the process yield. By using light extinction method, ISPM can measure particles in the large-diameter pipe (${\leq}300mm$). In our research, in-situ particle monitor (ISPM) sensor was installed at the 300 mm diameter exhaust-line to count the particles in each size. In-house flange for mounting the transmitting and receiving parts of ISPM was carefully designed and installed at a certain point of exhaust line where no plasma light affect to the light extinction measurement. Measurement results of trend changes on particle count in each size can confirm that ISPM is suitable for real-time monitoring of vacuum process.

• Vacuum Magazine
• /
• v.2 no.1
• /
• pp.31-34
• /
• 2015

This article introduces fundamentals of self-diagnosis and predictive (or preventive) maintenance technologies for dry vacuum pumps. The state variables of dry pumps are addressed, such as the pump and motor body temperatures, consumption currents of main and booster pumps, mechanical vibration, and exhaust pressure, etc. The adaptive parametric models of the state variables of the dry pump are exploited to provide dramatic reduction of data size and computation time for self-diagnosis. Two indicators, the Hotelling's $T^2$ and the sum of squares residuals (Q), are illustrated to be quite effective and successful in diagnosing dry pumps used in the semiconductor processes.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2012.05a
• /
• pp.475-478
• /
• 2012

In this study, preliminary design of a high-altitude test facility (HATF) was performed to simulate the high-altitude environment using a rocket engine that liquid oxygen and kerosene were used as the propellant. Experimental facility consists of vacuum chamber, supersonic exhaust diffuser, heat exchanger, ejector and gas generator. The vacuum chamber was simulated and maintained high-altitude environmental pressure by supersonic exhaust diffuser. Combustion gas of the rocket engine was cooled by water at heat exchanger after that the mixed gas was emitted to the air by ejector. The ejector which was operated by the steam generator using 75% ethanol and liquid oxygen as propellants and water for steam maintains a vacuum condition.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2009.08a
• /
• pp.275-275
• /
• 2009