• International journal of advanced smart convergence
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• v.8 no.4
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• pp.200-206
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• 2019

In this study, we compared the VacCAD and VacSim^(Multi), commercial vacuum simulators, to verify the advantages of VacCAD's efficiency. It was emphasized on immediacy and simplicity of simulation modelling, and characteristics of the pump combinations, pumping down curves, and vacuum materials. First, usability of simulation mechanism was estimated through the modeling schematics and obtained simulation results of each employed simulator were compared to evaluate the applicability in practice. Simulation reliability of each simulator was also probed by comparing the pumping characteristics of commercially available high vacuum systems. In addition, the degree of tolerances on VacCAD was also investigated through pumping down analysis considering outgassing effect due to chamber material variations. The higher effectiveness and expediency of VacCAD than VacSim^(Multi) has been presented, and it was expected that the utilization of VacCAD in vacuum applications to be increased.

• Journal of Powder Materials
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• v.5 no.4
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• pp.293-298
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• 1998

In all larger hardmetal workshops furnaces for dewaxing, vacuum sintering or vacuum and overpressure sintering are today's standard. The furnace technology is well established. Equipment specifications such as operating overpressure, determine sintering cost, product quality, safety and reliability of the furnace and ultimately influence the competitiveness of the hard metal procucer in the global market. Essential furnace requirements are an efficient utilization of the furnace, an environmental friendly dewaxing system, high temperature uniformity, metallurgical treatment with process gases, as well as reduced cooling time by means of rapid cooling. Examples of reduced sintering costs are described achieved using a new design of vacuum sintering furnace with an improved rapid cooling device, cooling times are reduced by up to 45%. Additionally, a cost comparison of two different designs of vacuum overpressure sintering furnaces are included.

• Journal of the Semiconductor & Display Technology
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• v.4 no.3 s.12
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• pp.23-27
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• 2005

The effects of the base vacuum level on a plasma display panel (PDP) produced by the vacuum in-line sealing technology were investigated. The main equipment of the vacuum in-line sealing process consists of the sealing chamber, pumping systems for evacuating, mass flow controller for introducing the plasma gases, and other measuring systems. During the sealing process, the impurity gases were fully evacuated and the panel was prevented from the adsorption of impurity gases. As a result, the brightness increased as the impurity gas density decreased, so we found that the vacuum in-line sealing process was more efficient technology an the conventional sealing process.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.9
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• pp.1159-1164
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• 2018

Vacuum circuit breakers(VCB) are widely used for current interruption of high-voltage inductive loads such as induction motors. This VCB can be chopped off before the current zero due to its high arc-extinguishing capability. One of the outstanding features of VCB is that it can cut off high frequency re-ignition current more than other circuit breakers. If the transient recovery voltage generated in the arc extinguishing is higher than the dielectric strength of the circuit breaker, a re-ignition phenomenon occurs. The surge voltage of the re-ignition is very high in magnitude and the steepness of the waveform is so severe that it can act as a high electrical stress on the winding. If the high frequency current of one phase affects the other two phases when the re-ignition occurs, it may cause a high surge voltage due to the virtual current chopping. If the magnitude of the voltage allowed in the motor winding is high or the waveform level is too severe, it may lead to insulation breakdown. Therefore, it is necessary to reduce the voltage to within a certain range. In this study, we briefly explain the various phenomena at the time of interruption, analyzed the magnitude of the dielectric strength and the transient recovery voltage at the simultaneous three-phase interruption that can give the greatest influence to the inductive load, proposed a method to reduce the impact.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.669-672
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• 1992

The increasing application of Vacuum Circuit-Breakers (VCB) on utility and industrial systems has prompted and detailed investigation of vacuum switching surge mechanisms and protections. This paper arranges arc-extinguishing principles of magnetic field in vacuum in order to disperse rapidly arc generated from vacuum contacts on switching VCR and plans establishment of protection means to protect high-voltage motor against surge voltage magnitude and transient voltage rate of rise

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.100-100
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• 2010

Because of power consumption increase, global wanning, and limitation of installation, not only high reliability and interruption capability but also compact and light power apparatuses are needed. To improve the insulation performance, the high E field concentration phenomena was considered. Breakdown mechanism in vacuum is different from that in other insulation materials. therefore, It is necessary to understand the electric field distribution and insulation characteristics. This paper discusses the simulation and LI(light impulse) test of the shield of outside vacuum interrupter As a result, FEM simulation and LI test show that improve distribution of electrical field and equi-potential line. due to external shield. in this case, outside shield induced electric field of triple junction point.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.49 no.5
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• pp.415-418
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• 2004

The effects of sonication and vacuum infiltration on transformation efficiency was investigated by using immature embryos of Korean wheat as explants. Two Agrobacterium tumefaciens strains, KYRT1 and EHA105, carrying pCAMBIA 1305.1 were used. Transformation efficiency was demonstrated by the detection of $\beta-glucu-ronidase$ (GUS) activity. GUS expression showed clear difference among Korean wheat cultivars. Geurumil showed higher GUS expression efficiency $79.1\%$ compared with other cultivars. The effects of the duration of vacuum infiltration and sonication treatment showed a tendency high GUS expression efficiency by their combination. In comparison with other Agrobacterium strains, KYRT1 showed high efficiency in most Korean cultivars.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.1313-1316
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• 2006

Demands of high volume dry vacuum pumps on the domestic semiconductor and LCD industries are rapidly increasing as the size of wafers and LCD is increasing. This study introduces a new experimental setup for testing the reliability of vacuum pumps. The test system was designed to measure the acoustic pressure and mechanical vibration levels simultaneously. It is shown that the test system enables the analysis and evaluation of the performance of dry pumps under the different gas-load conditions. Detailed experimental result are shown to enable us to examine the characteristics and performance of dry pumps.

• Food Science and Preservation
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• v.3 no.1
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• pp.55-60
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• 1996

To obtain the basic data on precooling effects for establishment the suitable postharvest handling technique or method of keeping high quality of vegetalble corn, the sweet, supersweet and waxy corn, (Danok #2, Cocktail #86 and Chalok #1), being mainly consumed as vegetables in Korea, were precooled with ice or vacuum cooling method immediately after harvest. The vacuum cooling was the most effective for the field heat removal of vegetable corn. It took only 30 min. at 4 to 5 torr of cold chamber pressure of vacuum precooler to lower the corn temperature from 30 to 2$^{\circ}C$. The ice cooling was also thought to be a useful precooling method with relatively short cooling time of 6 hrs. The vegetable corn treated with vacuum or ice cooling showed low and stable respiration rates of 25.5 to 43.5 CO2 mg/kg/hr. when stored at 0∼2$^{\circ}C$ while the samples stored at room temperature (20∼25$^{\circ}C$) without precooling were as high as 64.1 to 245 CO, mg/kg/hr.

• Journal of the Korean Vacuum Society
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• v.10 no.1
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• pp.9-15
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• 2001

The total pressure and partial pressure of small cavity for flat panel display have been successfully measured by using an ultra-high vacuum chamber with mass spectrometer. The total pressure in the panel was in the range of $10^{-6}$ Torr and the major partial pressure affecting increase in total pressure were those of Ar, $CH_4$and He. The baking temperature during evacuation process was very important for high-vacuum package, the total pressure and partial pressure of $CH_4$ were decreased as the increase of baking temperature.