• Proceedings of the KSME Conference
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• 2001.06a
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• pp.945-950
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• 2001

Vacuum interrupters that is used in various switchgear components such as circuit breakers, distribution switches, contactors, etc. spreads the arc uniformly over the surface of the contacts. The electrode of vacuum interrupters is used sintered Cu-Cr material satisfied with good electrical and mechanical characteristics. Because the closing velocity is 1-3m/s, the deformation of the material of electrodes depends on the strain rate and the dynamic behavior of the sintered Cu-Cr material is a key to investigate the impact characteristics of the electrodes. The dynamic response of the material at the high strain-rate is obtained from the split Hopkinson pressure bar test using cylinder type specimens. Experimental results from both quasi-static and dynamic compressive tests with the split Hopkinson pressure bar apparatus are interpolated to construct the Johnson-Cook equation as the constitutive relation that should be applied to simulation of the dynamic behavior of electrodes. To evaluate impact characteristic of a vacuum interrupter, simulation is carried out with five parameters such as initial velocity, added mass of a movable electrode, wipe spring constant, initial offset of a wipe spring and virtual fixed spring constant.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.5
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• pp.924-931
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• 2002

Vacuum interrupters in order to be used in various switch-gear components such as circuit breakers, distribution switches, contactors, etc. spread the arc uniformly over the surface of the contacts. The electrodes of vacuum interrupters are made of sinter-forged Cu-Cr materials for good electrical and mechanical characteristics. Since the closing velocity is 1-2m/s and impact deformation of the electrode depends on the strain rate at that velocity, the dynamic behavior of the sinter-forged Cu-Cr is a key to investigate the impact characteristics of the electrodes. The dynamic response of the material at the high strain rate is obtained from the split Hopkinson pressure bar test using disc-type specimens. Experimental results from both quasi-static and dynamic compressive tests are Interpolated to construct the Johnson-Cook model as the constitutive relation that should be applied to simulation of the dynamic behavior of the electrodes. The impact characteristics of a vacuum interrupter are investigated with computer simulations by changing the value of five parameters such as the initial velocity of a movable electrode, the added mass of a movable electrode, the wipe spring constant, initial offset of a wipe spring and the virtual fixed spring constant.

• Food Science and Preservation
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• v.24 no.4
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• pp.497-504
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• 2017

The aim of this study was to investigate the characteristics of paprika dried by various methods. Moisture content of dried paprika was higher in vacuum freeze-dried red paprika (DRP) (11.85%) than in vacuum freeze-drying of osmotic dried red paprika in sugar (RPS), vacuum freeze-drying of osmotic dried red paprika in fructose (RPF) and vacuum freeze-drying of osmotic dried red paprika in corn syrup (RPCS). Carbohydrate content of DRP was the lowest among the dried groups, but fat, protein, and ash contents were the highest in DRP. The pH of paprika was the highest in RPF (5.34), while it was the lowest in DRP (5.05). Reducing sugar and sugar contents of RPF were 28.59 g/100 g and $5.03^{\circ}Brix$, respectively, which are the highest level among the groups. All color values in inside of paprika were the highest in RPCS, while in outside of paprika, L value is the highest in RPCS, and the value of a, b were the highest in RPS. Regarding the texture characteristics of paprika, strongness, hardness, adhesiveness, chewiness and brittleness were the highest in RPS (p<0.05).

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.8
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• pp.94-101
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• 2005

The silent discharge type ozonizer with three electrodes(central electrode, internal electrode, and external electrode) and one discharge gap(discharge gap between internal electrode and external electrode) has been designed and manufactured. It is a silent discharge type ozonizer for which the AC high frequency voltages applied to the central electrode within vacuum discharge tube and the internal electrode for which the external electrode is a ground Ozone is generated by silent discharge in discharge gap. At the moment, discharge characteristics and ozone generation characteristics were investigated in accordance with vacuum of discharge tube, frequency of AC power source, discharge power of ozonizer, and quantity of supplied oxygen gas. In consequence, ozone characteristics proportional to vacuum of discharge tube and frequency of AC power source. The maximum value of ozone can be obtained 7,700[ppm], 460[mg/h] and 70[g/kwh].

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.24 no.1
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• pp.17-26
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• 2018

This study aimed to investigate the effects of vacuum packaging on the quality characteristics of frozen Tteokgalbi made from spent laying hen meat and mechanically deboned chicken meat (MDCM). The samples were prepared with different levels of added MDCM; C (0%), T1 (20%), T2 (40%), and T3 (60%). The samples were allocated for microbiological and physico-chemical analyses after 0, 45, and 90 days at $-18^{\circ}C$, with or without vacuum packaging. After 90 days of storage, the values of volatile basic nitrogen were significantly lower in the vacuum packaged samples compared to the non-vacuum samples, irrespective of the added levels of MDCM (p<0.05). Sensory results at day 0 of storage showed that the texture scores of C and T1 samples were significantly higher than those of T2 and T3, while the flavor scores were the lowest for the T3 samples (p<0.05). In addition, with increased storage duration, the texture and flavor attributes of the vacuum-packaged samples were found to be higher than those of non-vacuum samples. In general, the vacuum-packaged samples tended to show superior physico-chemical quality characteristics compared to the non-vacuum samples, when the storage time was extended up to 90 days.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.200.1-200.1
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• 2016

Tungsten coatings on the graphite (CX-2320) were successfully deposited using the vacuum plasma spraying (VPS) method. An optimum coating procedure was developed and coating thicknesses of $409{\mu}m$ (without an interlayer) and $378{\mu}m$ (with an interlayer) were obtained with no cracks and no signs of delamination. The mechanical characteristics and microstructure of the tungsten coating layers were investigated using a Vickers hardness tester, FE-SEM, EDS, and XRD. The effect of a titanium interlayer on the properties of the tungsten coating was investigated. It was shown that the titanium interlayer prevented the diffusion of carbon to the tungsten layer, thereby suppressing the formation of tungsten carbide. Vickers hardness data yielded values that were 62.5 ~ 80.46% of those for bulk tungsten, indicating that tungsten coatings on graphite can be utilized as a plasma-facing material. High heat flux tests were performed by using thermal plasma with a maximum flux of $10MW/^2$. Vickers hardness after the heat flux test is performed to see a change in the mechanical properties. The formationof a tungsten carbide and the effect of the titanium interlayer for the diffusion barrier are investigated by using energy dispersion spectroscopy (EDS).

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.479-482
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• 2008

In order to more closely examine the vacuum arc phenomena, it is necessary to predict the magnetohydrodynamic (MHD) characteristics by the multidisciplinary numerical modeling, which is coupled with the electromagnetic and hydrodynamic fields, simultaneously. In this study, the thermal-fluid characteristics of high current vacuum arcs were calculated by a commercial multiphysics package, ANSYS, in order to obtain Joule heat, Lorentz force and the interactions with flow variables. We assumed the diffused-mode arc within an AMF vacuum interrupter. It was found with four different currents that the temperature distributions on the anode surface are diffused uniformly without concentration in 7kA for both types (cup and coil-type). But the arc plasma transition and an increase of thermal flux density for increasing the applied current have caused the change of temperature distributions on the anode surface. We should need further studies on the two-way coupling method and radiation model for arc plasmas in order to accomplish the advanced analysis method for multiphysics.

• Progress in Superconductivity and Cryogenics
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• v.8 no.3
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• pp.45-48
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• 2006

The conduction-cooled HTS SMES is operated in cryogenic and high vacuum condition. Thus. Insulation design at cryogenic temperature and high vacuum is a key and an important element that should be established to accomplish compact design is a big advantage of HTS SMES. However, the behaviors of insulators for cryogenic conditions in vacuum are virtually unknown. Therefore, active research and development of insulation concerning application of the conduction cooled HTS SMES was needed. In this study, the insulation characteristics at experimented high vacuum and cryogenic similar to running condition of SMES system. Also, investigated about insulation characteristics of suitable some materials to insulator for conduction-cooled HTS SMES. As these results. the basis data was obtained for insulation materials selection and insulation design for development of 600kJ class conduction-cooled HTS SMES.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.3
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• pp.88-97
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• 2009

The vacuum die casting techniques can diminish the porosity of products and provide better surface appearance by the ordinary high pressure die casting process. The vacuum system can also reduce the cold laps in the die casting process and minimize the overflow pockets of the die. The vacuum system does not need high pressures to die cast compared to the ordinary die casting process, and so enables die casting of large parts for a given machine size. Parts made by the vacuum system have higher strength and more elongation than parts made by the ordinary die casting systems. In this paper, we designed and produced the Magnesium seat frames using the vacuum die casting processes. The new Magnesium seat frame was designed to satisfy safety regulations. Some safety test procedures of the seat frame were simulated by the finite element method. We obtained 10% weight reduction by design modification of seat frames compared to the current model. Flow simulations were carried out to minimize the trial and error in producing the parts. The die casted parts using vacuum systems resulted in better mechanical characteristics and no defects compared to those without vacuum systems.

• The Korean Journal of Food And Nutrition
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• v.11 no.5
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• pp.536-541
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• 1998

This study was carried out to investigate the changes of characteristics of myofibrillar protein for the vacuum chilled, the air frozen or the rechilled Holstein beef loin. The vacuum chilled beef was stored at 1$^{\circ}C$ and the air frozen beef was stored at -20$^{\circ}C$ for 60 days. The rechilled beef was restored for 3 days at 1$^{\circ}C$ by using the vacuum chilled or the air frozen beef. Myofibrillar protein extractability, 30,000 dalton component content and Mg-ATP ase activity for the vacuum chilled beef were higher than those of the air frozen beef. Each parameters increased significantly for the vacuum chilled beef after the 20 days storage, but there was no significant difference for the vacuum chilled beef after the 20 days storage, but there was no significant difference for the air frozen beef during the 60 days storage. By the rechilling process, myofibrillar protein extractability of the vacuum chilled and the frozen beef were not significant difference. The 30,000 dalton component of the vacuum chilled beef was showed not significant increment by rechilling, but the frozen beef was showed significant increment by rechilling. The Mg-ATPase activity of myofibrillar protein of the vacuum chilled beef was not changes by rechilling, but the frozen beef after the 20 days storage was significant increment by rechilling.