• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.970-972
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• 2011

The vacuum chamber pressure was investigated according to the second throat exhaust diffuser entrance diameter. The sizes of diffuser entrance were changed three cases, and each case was computed by using CFD. Also in order to relatively compare the vacuum chamber pressure the Euler equation was adopted. According to the results, as the size of diffuser entrance was increased it was observed that the vacuum chamber pressure was decreased.

• Advances in Computational Design
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• v.5 no.3
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• pp.261-276
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• 2020

The reasonable layout of vacuum cleaner can effectively improve the collection efficiency of iron filings generated in the process of steel production. Therefore, in this study, the CFD-DEM coupling model and two-fluid model are used to calculate the iron filings collection efficiency of vacuum cleaner with different inclination/cross-sectional area, pressure drop and inlet angle. The results are as follows: The CFD-DEM coupling method can truly reflect the motion mode of iron filings in pneumatic conveying. Considering the instability and the decline of the growth rate of iron filings collection efficiency caused by high pressure drop, the layout of 75° inclination is suggested, and the optimal pressure drop is 100Pa. The optimal simulation results based on two-fluid model show that when the inlet angle and pressure drop are in the range of 45°~65° and 70Pa~100Pa, larger mass flow rate of iron filings can be obtained. It is hoped that the simulation results can offer some suggestion to the layout of vacuum cleaner in the rolling mill.

• Solar Energy
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• v.17 no.4
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• pp.67-74
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• 1997

The electrochromic $WO_3$ thin films were prepared by using the electron beam deposition technique. The influences of vacuum pressure were examined in terms of the surface morphology and the electrochromic properties of films. From the results, the electrochromic behavior of electron beam deposited films strongly depends on the vacuum pressure during deposition. The film prepared under a vacuum pressure of $5{\times}10^4$ mbar was found to be rather stable when subjected to the repeated coloring and bleaching cycles in an aqueous acid electrolyte of 1M $H_2SO_4$. It was also found that the degraded film by repeated cycling in the aqueous acid solution changed the grain shape of film surface.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.247-254
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• 2000

The base pressure of vacuum vessel of the KSTAR (Korea Superconducting Tokamak Advanced Research) Tokamak is to be a ultra high vacuum, $10^{-6}{\sim}10^{-7}Pa$, to produce clean plasma with low impurity containments. For this purpose, the KSTAR vacuum vessel and plasma facing components need to be baked up to at least $250^{\circ}C,\;350^{\circ}C$ respectively, within 24 hours by hot nitrogen gas from a separate baking/cooling line system to remove impurities from the plasma-material interaction surfaces before plasma operation. Here by applying the implicit numerical method to the heat balance equations of the system, overall temperature distributions of the KSTAR vacuum vessel and plasma facing components are obtained during the whole baking process. The model for 2-dimensional baking analysis are segmented into 9 imaginary sectors corresponding to each plasma facing component and has up-down symmetry. Under the resulting combined loads including dead weight, baking gas pressure, vacuum pressure and thermal loads, thermal stresses in the vacuum vessel during bakeout are calculated by using the ANSYS code. It is found that the vacuum vessel and its supports are structurally rigid based on the thermal stress analyses.

• Journal of Powder Materials
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• v.1 no.2
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• pp.159-166
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• 1994

The variation of the microstructures and the mechanical properties with varying vacuum hot pressing temperature and pressure was investigated in PyM processed 20 vol%) SiCw/ 2124Al composites. As increasing the vacuum hot pressing temperature, the aspect ratio of whiskers and density of composites increased due to the softening of 2124Al matrix with the increased amount of liquid phase. The tensile strength of composite increased with increasing vacuum hot pressing temperature up to $570^{\circ}C$ and became saturated above $570^{\circ}C$, To attain the high densification of composites above 99%, the vacuum hot pressing pressure was needed to be above 70 MPa. However, the higher vacuum hot pressing pressure above 70 MPa was not effective to increase the tensile strength due to the reduced aspect ratio of SiC whiskers from damage of whiskers during vacuum hot pressing. A phenomenological equation to predict the tensile strength of $SiC_w$/2124AI composite was proposed as a function including two microstructural parameters, i.e. density of composites and aspect ratio of whiskers. The tensile strength of $SiC_w$/2124AI were found more sensitive to the porosity than other P/M materials due to the higher stress concentration and reduced load transfer efficiency by the pores locating at whisker/matrix interfaces.

• Journal of the Korean Society of Safety
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• v.31 no.3
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• pp.42-46
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• 2016

In LCD Display or semiconductor manufacturing processes, the anti-static technology of glass substrates and wafers becomes one of the most difficult issues which influence the yield of the semiconductor manufacturing. In order to overcome the problems of wafer surface contamination various issues such as ionization in decompressed vacuum and inactive gas(i.e. $N_2$ gas, Ar gas, etc.) environment should be considered. Soft X ray radiation is adequate in air and $O_2$ gas at atmospheric pressure while UV radiation is effective in $N_2$ gas Ar gas and at reduced pressure. At this point of view, the "vacuum ultraviolet ray ionization" is one of the most suitable methods for static elimination. The vacuum ultraviolet can be categorized according to a short wavelength whose value is from 100nm to 200nm. this is also called as an Extreme Ultraviolet. Most of these vacuum ultraviolet is absorbed in various substances including the air in the atmosphere. It is absorbed substances become to transit or expose the electrons, then the ionization is initially activated. In this study, static eliminator based on the vacuum ultraviolet ray under the above mentioned environment was tested and the results show how the ionization performance based on vacuum ultraviolet ray can be optimized. These vacuum ultraviolet ray performs better in extreme atmosphere than an ordinary atmospheric environment. Neutralization capability, therefore, shows its maximum value at $10^{-1}{\sim}10^{-3}$ Torr pressure level, and than starts degrading as pressure is gradually reduced. Neutralization capability at this peak point is higher than that at reduced pressure about $10^4$ times on the atmospheric pressure and by about $10^3$ times on the inactive gas. The introductions of these technology make it possible to perfectly overcome problems caused by static electricity and to manufacture ULSI devices and LCD with high reliability.

• Journal of Korean Vacuum Science & Technology
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• v.7 no.1
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• pp.1-7
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• 2003

The pressure distributions in the test stand built for developing KSTAR NBI ion sources were obtained using a network system composed of conductance elements modeling the ion source, the neutralizer, and other beam line components. The allowable regime was defined on the coordinates of the gas supply rate to the ion source and the neutralizer, considering the proper conditions of the three critical parameters, the ion source pressure for good arc discharge, the pressure integral in the neutralizer for sufficient neutralization, and the chamber pressure for minimum neutral beam loss. The neutral beam evolution along the path from the ion source extraction grid to the calorimeter through the neutralizer, the bending magnet and the vacuum chamber was estimated for typical pressure distributions.

• Journal of the Korean Vacuum Society
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• v.8 no.3B
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• pp.333-339
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• 1999

$RuO_2$ thin films were prepared with various deposition conditions by rf magnetron sputtering. The films were annealed in vacuum, air, and air-vacuum, after that, the structural and electrical properties of the films were investigated. As the substrate temperature increases, the preferred orientation of the films changes from (101) to (200), and the grain size increases; especially, at $500^{\circ}C$, the size considerably increases. The preferred orientation of the films changes from (200) to (101) and the roughness of surface increase with the increase in oxygen partial pressure. The lowest value of resistivity of $RuO_2$ we prepared is $1.5\times 10^{-5}\Omega\codt\textrm{cm}$ at the conditions of $400^{\circ}C$ and 10% of oxygen partial pressure. After the processes of annealing, the films deposited at $400^{\circ}C$ and a oxygen partial pressure of 10% were relatively stable. The films deposited at $500^{\circ}C$ have denser structure and smoother surface when the films are annealed in vacuum after annealing in air.

• Journal of Information Display
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• v.9 no.4
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• pp.15-20
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• 2008

A DC-magnetron inline sputter was established, and the influence of the base pressure on the structural characteristics of the ITO thin films was studied. When the inline sputter system was established and operated for ITO sputtering, its initial vacuum level did not go below $5\times10^{-6}$ torr. The vacuum leak test was conducted by measuring t he elapsed time until the vacuum level reached $1\times10^{-6}$ torr. The base pressure was successfully maintained at $1\times10^{-6}$ torr for 900 min, and the uniformity of the ITO film that had been deposited at this pressure significantly improved.

• Journal of the Korean Vacuum Society
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• v.21 no.1
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• pp.1-5
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• 2012

The measurement device of internal pressures of small components sealed hermetically was developed. The internal pressure of a sample measured with this device was 43.151 kPa, and the expanded uncertainty ($\kappa$=2) was 741 Pa. The resultant measurement ability of internal pressures in small vacuum components, which had been almost impossible previously, shows the possibility of internal vacuum detection of hermetically sealed parts.