• Progress in Superconductivity and Cryogenics
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• v.25 no.4
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• pp.32-39
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• 2023

One of the main problems faced in developing India's first HTS power cable was that of shrinkage in length of the double-walled vacuum-insulated cryostat. The shrinkage was due to the evacuation of the annular vacuum space which results in a shorter working cable length. This work reports experimentally observed contraction during evacuation and analyses corrugated pipes/bellows which house the cable core of HTS cables. The effect of corrugation geometry including length, corrugation pitch and depth, diameters of corrugated pipes and thicknesses of pipes is studied numerically to realize the degree of shrinkage due to vacuum as well as chill down. Finally, necessary length compensation and associated cost is determined to tackle the shrinkage issue.

• Geomechanics and Engineering
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• v.24 no.2
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• pp.129-141
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• 2021

The vacuum preloading method has been used in many countries for soil improvement and land reclamation. However, the treatment time is long and the improvement effect is poor for the straight-line vacuum preloading method. To alleviate such problems, a novel combined air booster and straight-line vacuum preloading method for shallow ground treatment is proposed in this study. Two types of traditional vacuum preloading and combined air booster and straight-line vacuum preloading tests were conducted and monitored in the field. In both tests, the depth of prefabricated vertical drains (PVDs) is 4.5m, the distance between PVDs is 0.8m, and the vacuum preloading time is 60 days. The prominent difference between the two methods is when the preloading time is 45 days, the injection pressure of 250 kPa is adopted for combined air booster and straight-line vacuum preloading test to inject air into the ground. Based on the monitoring data, this paper systematically studied the mechanical parameters, hydraulic conductivity, pore water pressure, settlement and subsoil bearing capacity, as determined by the vane shear strength, to demonstrate that the air-pressurizing system can improve the consolidation. The consolidation time decreased by 15 days, the pore water pressure decreased to 60.49%, and the settlement and vane shear strengths increased by 45.31% and 6.29%, respectively, at the surface. These results demonstrate the validity of the combined air booster and straight-line vacuum preloading method. Compared with the traditional vacuum preloading, the combined air booster and straight-line vacuum preloading method has better reinforcement effect. In addition, an estimation method for evaluating the average degree of consolidation and an empirical formula for evaluating the subsoil bearing capacity are proposed to assist in engineering decision making.

• Journal of the Korean Vacuum Society
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• v.4 no.S2
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• pp.95-99
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• 1995

keV ion beam irradiatin for surface modification and thin film growth have been discussed. keV ion beam irradiation in reactive gas environment has been developed for improving wettability of polymer, and for enhancing adhesion to metal film, and adventages of the method have been reviewed. An epitaxial Cu film on Si(100) substrate has been grown by ionized cluster beam and changes of crystallinity and surface roughness have been discussed. Stoichiometric $SnO_2$ films on Si(100) and glass have been grown by a hybrid ion beam Deposition(2 metal ion sources+1 gas ion source), and nonstoichiometric $SnO_2$ films are controlled by various deposition conditions in the HIB. Surface modification for polymer by kev ion irradiation have been developed. Wetting angle of water to PC has been changed from 68 degree to 49 degree with $Ar^+$ irradiation and to 8 degree with $Ar^+$ irradiation and the oxygen environment. Change of surface phenomena in a keV ion beam and characteristics of the grown films are suggested.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.10a
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• pp.293-298
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• 1999

To make use of various switches, relays, and control instruments, a connector (jack) is used to link the battery (power) and operating units. A connector must have precision as well as solidity to control the power in a car. To improve productivity, we researched and developed a connector molding by adapting vacuum system and we've made it possible to minimize the incomplete molding and weld-line. As a result, good quality can be warranted with less costs.

• Applied Biological Chemistry
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• v.44 no.2
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• pp.81-87
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• 2001

Oyster jeot-gal were prepared in the form of salt-fermented oyster and oyster in soy sauce tentatively and used for investigation the retarding effect of its fermentation in a vacuum from the physicochemical and microbiological points of view. $_PH$ value decreased slightly but amino-N (AN) and volatile basic nitrogen (VBN) increased inversely during the fermentation periods. AN contents were greater in vacuum fermentation than in non-vacuum, whereas VBN were greater in non-vacuum. Total viable cell counts were similar to trend of gentle decrement after increment to some degree but showed higher in non vacuum than in vacuum. In vacuum product, total amino acid contents increased with the elapse of fermentation days or in time of reduction those were higher than in non-vacuum. On the results of chemical analysis, it showed that fermentation was delayed in vacuum and that vacuum fermentation was effective for the shelf-life extension of jeot-gal.

• Journal of Korea Foundry Society
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• v.27 no.4
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• pp.153-158
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• 2007

Molten metal flow in vacuum die casting was characterized by a numerical analysis. The VOF method was used to simulate the filling behaviors of molten metal during filling process. The various vacuum degrees of no vacuum(760 mmHg), 650, 500, 250 and 60mmHg were artificially applied in cavity. And the filling behaviors of molten metal with the applied vacuum conditions were simulated and compared with those of experiment. The results showed that molten metal was partially filled into cavity when vacuum was applied and the filling length of molten metal in cavity was increased with increasing applied reduced pressure in cavity. Also, the simulated filling behaviors of molten metal were apparently similar to those of experiment, indicating the numerical analysis developed in this study was highly effective. Through the result of fluid flow simulation, both relation equations of filling length and filling velocity with the variation of pressure conditions in cavity were calculated respectively and the internal gas contents of casting was significantly reduced by the modification of vacuum gate system.

• The Korean Journal of Food And Nutrition
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• v.16 no.4
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• pp.353-358
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• 2003

Low salt-fermented product of alaska pollack roe were prepared tentatively and also discussed the retarding effect of fermentation period by vacuum. The results were as follows. The moisture content, pH and salinity decreased slightly, but the contents of VBN and total amino acids increased gradually during fermentation regardless of ripening types. pH and salinity showed little difference with ripening types, but moisture content was a little lower and the contents of VBN was some higher in non vacuum than those in vacuum, whereas total amino acid contents were greater in vacuum. In addition, total viable cell count were similar to trend of gentle decrement after increment to some degree but were higher in non vacuum than those in vacuum. Judging from the results of physicochemical analysis, it was showed that fermentation delayed in vacuum therefore it was considered that vacuum fermentation can be effective on shelf-life extension of jeot-gal.

• Journal of Plant Biotechnology
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• v.48 no.4
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• pp.271-277
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• 2021

The present study aimed to assess and compare the quality characteristics and antioxidant activities of apple juice and blueberry juice at hourly intervals over a period of time based on the presence or absence of vacuum blending (0 and 800 hPa) using a household blender. Measurement of the dissolved oxygen content revealed that the removal rates of dissolved oxygen were approximately 83% and 86% in the apple and blueberry juice samples, respectively, after vacuum blending. Moreover, compared with general blending, there was little change in the antioxidant property and degree of browning over time with vacuum blending. Furthermore, hourly assessments revealed that the decrease in the polyphenol and flavonoid contents in the apple and blueberry juice samples was significantly lesser with vacuum blending for 3, 6, and 12 h than with general blending. Assessment of the change in ferric reducing antioxidant power (FRAP) activity over time revealed that the rate of decrease in FRAP activity over time was lower with vacuum blending than with general blending for both juice samples. ABTS and DPPH radical scavenging assays performed to determine the change in free radical scavenging activity revealed inhibitory activity at 0, 3, 6, and 12 h and confirmed that vacuum blending resulted in long-lasting antioxidant activities in both apple and blueberry juice samples. Taken together, the present results confirmed that vacuum blending is associated with superior quality maintenance and antioxidant properties in comparison with general blending.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.4 no.3
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• pp.183-188
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• 2003

Non-molding and welding line happen by the assembly of gas at the connector terminal. There is not good phenomenon of burr by increasing the over injection pressure, the temperatures of die and resin to prevent from them. Therefore, the connector mold to apply the vacuum molding system is developed in this study. The vacuum pressure is controlled systematically with the optimum conditions in the important ingredients of injection molding that are the temperatures of melting resin and die and cooling condition. The badness in charging is cleared by making a vacuum to non-charging part of the deep bottom part of each cavity. And the vacuum system to reduce the cycle time is applied as the study envelopment of molding work. So, the good product and the productivity improvement can be obtained in this study.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.1
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• pp.129-138
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• 2001

This study examined the effects of the annealing heat treatments on the mechanical properties of the Invar(Fe-36%Ni Alloy) materials. Invar materials were annealed at various temperatures range 900~120$0^{\circ}C$ in vacuum(10-4Torr) and hydrogen atmospheres. And annealing conditions were changed by cooling rate and holding time at 110$0^{\circ}C$. The grain size of rolled Invar materials was very fine but those of annealed Invar materials at 900~120$0^{\circ}C$ in vacuum and hydrogen atmosphere increased with increasing annealing temperature. The micro-vickers hardness values of annealed Invar materials were decreased about 15% that of the rolled Invar materials, regardless of the various of annealing temperatures, atmosphere(vacuum, hydrogen) and annealing conditions. The tensile strength and yield strength of annealed Invar materials at 900~120$0^{\circ}C$ in vacuum and hydrogen atmosphere were decreased 10.0~14.4% and 34.6~39.1% those of the rolled Invar materials, respectively. The strength ratio(tensile strength/ yield strength) of annealed Invar materials was improved to 1.7~1.8 from the value of 1.2~1.3 of rolled Invar materials. The degree of spring back of annealed Invar materials was about 50% of the rolled Invar materials, regardless of the various of annealing temperatures, atmosphere(vacuum, hydrogen) and annealing conditions.