• 한국초전도ㆍ저온공학회논문지
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• 제25권4호
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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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• 제24권2호
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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.

• 한국진공학회지
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• 제4권S2호
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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.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1999년도 추계학술대회 논문집 - 한국공작기계학회
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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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• 제44권2호
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• pp.81-87
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• 2001

굴을 대상으로 조미 양념 젓갈(salt-fermented oyster)과 전통적인 게장의 제조법을 이용한 젓갈 제품(oyster in soy sauce)으로 새로운 형태의 젓갈을 제조하여 각각 진공 및 무진공 상태로 저장하면서 숙성 형태별 숙성 기간에 따른 이화학적 성분의 변화를 살펴 보았다. 굴 젓갈에 있어서 pH는 숙성 기간이 경과함에 따라 점차 감소했으나, 아미노태 질소(AN)와 휘발성 염기 질소(VBN)는 반대로 증가하는 경향을 나타냈으며, 함량에 있어서는 AN의 경우 진공 숙성시에, VBN은 무진공 숙성시에 더 많은 것으로 나타났다. 총균수는 어느 정도 증가했다가 감소하는 경향은 비슷하나 진공 숙성에 비해 무진공 숙성시에 더 현저하였다. 총 구성 아미노산에 있어서는 숙성이 진행됨에 따라 진공의 경우 함량이 증가했거나 감소한 경우라도 무진공 숙성시에 비해 함량이 높은 것으로 나타났다. 이상의 결과를 종합해 볼 때,무진공 숙성시보다 진공 숙성시 숙성이 지연되는 것으로 보여지며, 숙성 지연으로 인한 젓갈의 품질 유지 기간의 연장에도 진공 숙성이 효과적이라고 사료되었다.

• 한국주조공학회지
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• 제27권4호
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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.

• 한국식품영양학회지
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• 제16권4호
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• pp.353-358
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• 2003

우리나라의 전통적인 젓갈류는 염도가 지나치게 높고 제조 방법이 단순하고 비위생적으로 생산되는 경우가 많아 고품질 젓갈 제품의 생산을 위해서는 새로운 공정 개발이 필요한 실정이다. 따라서 본 연구는 명란을 액 염지법으로 염도를 8%로 줄이고 진공 숙성기법으로 맛을 강화시켜 새로운 명란 젓갈을 제조하였다. 또한 저염 젓갈의 저장성을 높이기 위하여 진공 발효시켜 저장하면서 숙성 형태별 숙성 기간에 따른 이화학적 성분의 변화를 조사한 결과 명란 젓갈의 수분, pH 및 염도 변화는 숙성 기간이 경과함에 따라 큰 차이 없이 감소하는 경향이었고 수분은 무진공(상압) 숙성시에 약간 더 감소하는 것으로 나타났으며 휘발성 염기 질소(VBN) 및 구성 아미노산의 함량은 숙성형태에 상관없이 숙성이 진행됨에 따라 약간씩 증가하였고 VBN의 함량이 상압숙성에서 높은 경향이었고 총 구성아미노산은 진공 숙성시에 더 많게 나타났다. 총균수 역시 어느 정도 증가했다가 다소 감소하는 경향은 비슷하나 진공 숙성에 비해 상압 숙성시에 높았다. 이상의 결과로 볼 때, 명란젓갈의 숙성시 진공처리는 전반적인 젓갈의 숙성을 지연시켜주며 젓갈의 품질 유지 기간에도 효과적으로 나타났다.

• Journal of Plant Biotechnology
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• 제48권4호
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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.

• 한국산학기술학회논문지
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• 제4권3호
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• pp.183-188
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• 2003

본 연구는 Connector Mold의 Termina (리브)에 가스 모임으로 인한 미성형 및 웰드라인이 생성되어 이를 방지하기 위해 과다한 사출압력, 금형온도 및 수지온도를 높이므로 Burr둥의 불량현상이 발생하게된다. 따라서 연구에서는 진공성형시스템을 응용한 Connector Mold를 개발하기 위하여 사출성형의 중요한 인자가 되는 용융수지온도, 금형온도, 냉각조건을 최적 조건에서 진공압을 체계적으로 제어함으로 각 캐비티의 깊은 글 부분의 미충전 부분을 진공화 하여 충전불량을 해소하면서, 싸이클 시간을 단축시킬 수 있는 진공시스템을 연구개발 성형가공에 적용함으로 우수한 제품과 생산성 향상의 효과를 얻을 수 있다.

• 한국정밀공학회지
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• 제18권1호
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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.