• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2515-2518
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• 2008

The vacuum interrupter (VI) is widely used in medium-voltage switching circuits due to its abilities and advantages as an environmental friendly circuit breaker. An understanding of the vacuum arc flow phenomena is very important for improving the performance of vacuum interrupter. In order to 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 the thermal flow fields, simultaneously. In this study, we have investigated arc plasma constriction phenomena and an effect of AMF on the arc plasma with the high-current vacuum arcs for the cup-type AMF electrode by using a commercial finite element analysis (FEA) package, ANSYS. The simulation results applied with various AMFs and constant Joule heat generation show that strong axial magnetic field (AMF) permits the arc to be maintained in a diffused mode to a high-current vacuum arc. However, further studies are required on the two-way coupling method and radiation model for arc plasma in order to accomplish the advanced analysis method.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.480-481
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• 2012

LED (Light Emitting Diode)는 친환경적이며 고수명 등의 여러 장점을 가지고 있어서 액정디스플레이의 광원으로 널리 사용되고 있다. 그러나 LED 제품을 제조하기 위해서는 칩, 패키지, 모듈, 시스템으로 구성된 4단계의 복잡한 제조공정을 거쳐야 하므로 가격이 높은 단점이 있다. 이를 개선하기 위해서 패키지, 모듈, 시스템의 3단계의 공정을 하나로 통합한 hybrid LED package(HLP) 개념이 제시되었다. HLP는 LED chip을 PCB에 직접 실장한 뒤 초정밀 가공 및 성형 기술을 활용하여 일체형 광학패턴을 인가함으로써 공정을 단순화하면서도 광효율을 향상시킬 수 있다. 이에 본 연구에서는 다구찌 실험계획법을 사용하여 디스플레이에서 중요시되는 휘도를 높일 수 있는 일체형광학패턴 형상 최적화를 실시하였으며, 최적화된 일체형 광학패턴을 제조하기 위한 초정밀 가공 및 성형기술을 개발하였다. 최적화 결과 높이 25um, 꼭지각 90도의 음각형태의 사각피라미드 패턴이 최적형상으로 결정되었으며, 패턴이 없을 때와 비교하여 휘도가 약 32.3% 높아지는 것으로 나타났다. 이러한 일체형 광학패턴을 제품으로 구현하기 위하여 초정밀 절삭기술을 활용하여 마스터 금형을 제작하였다. 최종적으로 사출성형을 통해 일체형 광학패턴을 제작하게 되는데 이때 사출기 내부 공기흐름 및 진공도를 최적화함으로써 패턴 내부에 불필요한 기포가 발생하지 않도록 하는데 성공하였다. 이를 통해 생산성이 높은 사출성형으로 HLP 제품을 양산할 수 있는 가능성을 확인하였고, 추후에는 실제 제품을 제작하는 연구를 수행할 예정이다.

• Land and Housing Review
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• v.11 no.3
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• pp.61-68
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• 2020

Advanced glazing systems with excellent heat transmission values (Ug-Value) have been developed to reduce the energy consumption and the greenhouse gas emission. This study proposes a triple glazing system consisting of gaps with a vacuum and a carbon dioxide gas layer which is one of greenhouse gases. As a fundamental stage, this study is focused on calculating the optimal glazing thickness and the Ug-Value via a computer simulation, Therm & Window package. As the results, it was presented that the optimal thickness of the proposed triple glazing system is 22.2 mm, and the Ug-Value is 0.273 W/㎡·K. If this glazing system is to be applied to buildings, it could not only reduce building energy consumption but could also contribute to the treatment of carbon dioxide gas which is one of greenhouse gases.

• Journal of the Korean Vacuum Society
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• v.13 no.3
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• pp.127-131
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• 2004

Package reliability test was conducted to investigate the effect of solder composition on the ball fatigue strength for BGA (Ball Grid Array) packaging. The test pieces are assembled using eutectic composition 63Sn/37Pb, 62Sn/36Pb/2Ag, and 63Sn/34.4Pb/2Ag/0.5Sb solder after pre-conditioning at MRT Lv 3 (Moisture Resistance Test Level) and then conducted under T/C (Temperature Cycle test). For each case, the ball shear strength was obtained and micro structure photos were taken. SEM (scanning electron microscope) and EDX (Energy Dispersive X-ray) were used to the analyze failure mechanism. The growth rate of Au-Sn intermetallic compound in Sn63Pb34.5Ag2Sb0.5 solder was slow when compared to 63Sn/37Pb solder and 62Sn/36Pb/2Ag solder. The degradation of shear strength of solder balls caused by solder composition was discussed.

• Korean Journal of Food Science and Technology
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• v.30 no.5
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• pp.1184-1188
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• 1998

Effects of gamma irradiation on pigments of beef was investigated by determination of the Hunter's color values and pigments such as myoglobin, metmyoglobin and oxymyoglobin after gamma irradiation up to 5 kGy in air or vacuum package for 7 days. 'L' and 'b' values increased but 'a' value decreased with the elapse of the storage period. But, 'L', 'a' and 'b' values of irradiated beef were lower than non-irradiated beef. Myoglobin decreased but oxymyoglobin and metmyoglobin increased with the elapse of the storage period. Myoglobin decreased but oxymyoglobin and metmyoglobin increased with gamma irradiation up to 5 kGy. In regard to packaging methods, vacuum package did not affect pigment of the beef as did air package.

• Food Science and Preservation
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• v.16 no.2
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• pp.166-171
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• 2009

The effects of vacuum precooling(VP) on the shelf-life of polyethylene film(PE) packaged King oyster mushrooms(Pleurotus eryngii) during storage at $-1^{\circ}C$ were investigated. VP was conducted below $0^{\circ}C$ in a $-1^{\circ}C$ cold chamber of 40 minutes, and mushrooms were stored for 30 days in batches of 1kg. The weight loss of the VP-treated mushroom was slightly lower than that of control. The $O_2$ concentrations of VP-treated mushroos, within 4 days of storage, were 2.44-14.50 %/kg-package/hr, thus higher than control values(2.01-8.19%/kg-package/hr). $CO_2$ generation of VP-treated mushrooms, again within 4 days of storage, was 0.47%/kg-package/hr, thus lower than that of controls(0.58%/kg-package/hr). The $CO_2/O_2$ ratio peaked on day 4 of storage in the control group, tbut no such peak was observed in VP-treated mushrooms. In the VP-treated fungi, lightness was higher, and redness and yellowness lower, than in controls, at all storage times.. In VP-treated mushrooms, strength, hardness and chewiness were significantly higher than in controls, but there were no significant differemces in springiness or cohesiveness. Softening and breakdown of under-cap wrinkles were observed in control mushrooms stored for 30 days, but occurred to a lesser extent in VP-treated fungi. Stipe reticulum tissue vessels in the 30 day-stored VP-treated mushrooms were relatively well-defined and clear, but were softer and diffuse in the control fungi. The results thus confirmed that VP after harvest enhanced mushroom shelf-life and PE packaging prolonged storage time. The data will have industrial applications.

• Journal of the Korean Society of Food Science and Nutrition
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• v.25 no.6
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• pp.932-936
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• 1996

Scallop, Pectinopecten yessoenis(Jay), cultivated in the cold east coast of Kwangwon region, Korea, is expected be to produced about 50, 000 tons in the year 2000. Scallop, first of all should be exuviated to process for new goods. In this study, vacuum and nitrogen packagings were applied to extend the shelf-life of exuviated scallop boiled with steam for 10 min. Vacuum and nitrogen packagings retarded the decrease in pH, whereas inhibited the production of $NH_2-N, $ VBN, TMA, and TBA of exuviated scallop stored at $5^{\circ}C.$ They also inhibited the microbial growth. But, there was no significant difference in the bacteriostatic effects between both packaging methods. The estimated shelf-lives of boiled and exuviated scallops for control, vacuum, and nitrogen packagings were about 30, 36, and 36 days, respectively.

• 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.

• JSTS:Journal of Semiconductor Technology and Science
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• v.14 no.6
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• pp.733-740
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• 2014

A resistive micro Pirani gauge using amorphous silicon (a-Si) thin membrane is proposed. The proposed Pirani gauge can be easily integrated with the other process-compatible membrane-type sensors, and can be applicable for in-situ vacuum monitoring inside the vacuum package without an additional process. The vacuum level is measured by the resistance changes of the membrane using the low noise correlated double sampling (CDS) capacitive trans-impedance amplifier (CTIA). The measured vacuum range of the Pirani gauge is 0.1 to 10 Torr. The sensitivity and non-linearity are measured to be 78 mV / Torr and 0.5% in the pressure range of 0.1 to 10 Torr. The output noise level is measured to be $268{\mu}V_{rms}$ in 0.5 Hz to 50 Hz, which is 41.2% smaller than conventional CTIA.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.4
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• pp.330-335
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• 2003

This paper reports the optimum structure of the vacuum packaged Porous poly-silicon Nano-Structured (PNS) emitter. The PNS layer was obtained by electrochemical etching process into polycrystalline silicon layer in a process controlled to anodizing condition. Current-voltage studies were carried out to optimize process condition of electron emission properties as a function of anodizing condition and top electrode thickness. Also, we measured in advance the electron emission properties as a function of substrate temperature because the vacuum packaged process was performed under the condition of high temperature ambient (430$^{\circ}C$). Auger Electron Spectrometer (AES) studies shows that Au as a top-electrode was diffused to PNS layer during temperature experiments. Thus, we optimized the thickness of top-electrode in order to make the vacuum package PNS emitter. As a result, the vacuum Packaged PNS emitter was successfully emitted by optimizing process.