• International journal of advanced smart convergence
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• 제7권4호
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• pp.84-91
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• 2018

In this paper, we simulated three different HV systems and analyzed of each vacuum characteristics by VacCAD modelling. In each of modelled vacuum systems, selection of chamber materials, combination of rough pump with high vacuum pump and conductance of roughing line (diameter and length) were proposed as system variables. In the modelling of chamber materials, the pumping times to ultimate pressures of different chamber materials (stainless steel, aluminum) were compared by the variations of chamber volume. In this model, the effects of outgassing dependent on the chamber materials was also simulated and aluminum was estimated to optimum chamber materials. It was also obtained that modelling of vane and roots pump with diffusion pump and diameter, length of $50{\times}250$ [mm]roughing line were characterized as optimum variables to reach the ultimate pressure of 10E-7 [mbar] most effectively. Optimum design factors for vacuum characteristics of modelled vacuum system were achieved by VacCAD simulations. Feasibility of VacCAD as vacuum simulator was verified and applications of VacCAD expected to be increased to fields in vacuum needed.

• International journal of advanced smart convergence
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• 제11권4호
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• pp.88-95
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• 2022

Vacuum simulation is associated with the prediction and calculation of how materials, pumps and systems will perform using mathematical equations. In this investigation, three different high vacuum systems were simulated and estimated with each vacuum characteristics by VacTran simulator. In each of modelled vacuum systems, selection of gas loads into vessel, combination of rough and high vacuum pumps and dimension of conductance elements were proposed as system variables. In pump station model, the pumping speed to pressures by the combination of root pump was analyzed under the variations of vessel volume. In this study, the effects of outgassing dependent on vessel materials was also simulated and aluminum vessel was estimated to optimum materials. It was obtained from the modelling with diffusion pump that the diameter, length of 50×250[mm]roughing line was characterized as optimum variables to reach the ultimate pressure of 10E-7[torr]. Optimum design factors for vacuum characteristics of modelled vacuum system were achieved by VacTran simulator. Feasibility of VacTran as vacuum simulator was verified and applications of VacTran in high tech process expected to be increased.

• 한국수소및신에너지학회논문집
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• 제33권1호
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• pp.85-94
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• 2022

To detect anomaly signs of thermal runaway in advance, this study analyzed the signals from various sensors installed in lithium-ion batteries. The thermal runaway mechanism was analyzed, and measurement variables for anomalies of a battery cell were surface temperature, strain, and gas concentration. The changes and characteristics of three variables during the thermal runaway process were analyzed under the abuse environment: the overheat and the overcharge. In experiment, the thermal runaway of the battery proceeded in the initial developing stage, the outgassing stage, and the ignition stage. Analysis from the measured data indicated that the suitable variable to detect all stages of thermal runaway is the surface temperature of the battery, and surface strain is alternative.

• 유기물자원화
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• 제18권1호
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• pp.66-72
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• 2010

본 연구는 경기도 A지역 자원회수시설에서 연소온도의 변화에 따른 NOx, SOx, CO, HCL, DUST의 발생변화와 보일러 배출가스 온도, 보일러 출구산소 농도, 반건식 반응탑 출구온도, 촉매탑온도, 배출가스 온도의 변화를 분석하였다. SOx, CO, Hcl, DUST는 자원회수시설 내의 연소온도가 상승함에 따라 거의 5 ppm 미만의 일정한 값을 유지한 반면 NOx 는 40 ppm에서 70 ppm으로 증가하는 추세였다. 한편 보일러 배출가스 온도와 촉매탑 온도는 일정치를 유지하였으나 보일러 출구의 산소농도는 조금씩 감소하는 결과를 나타내었다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 추계학술발표대회
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• pp.18.1-18.1
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• 2011

Some applications of carbon nanotubes (CNTs) as field emitters, such as x-ray tubes and microwave amplifiers, require high current emission from a small emitter area. To emit the high current density, CNT emitters should be optimally fabricated in terms of material properties and morphological aspects including high crystallinity, aspect ratio, distribution density, height uniformity, adhesion on a substrate, low outgassing rate during electron emission in vacuum, etc. In particular, adhesion of emitters on the substrate is one of the most important parameters to be secured for high current field emission from CNTs. So, we attempted a novel approach to improve the adhesion of CNT emitters by incorporating metal oxide layers between CNT emitters. In our previous study, CNT emitters were fabricated on a metal mesh by filtrating the aqueous suspensions containing both highly crystalline thin multiwalled CNTs and thick entangled multiwalled CNTs. However, the adhesion of CNT film was not enough to produce a high emission current for an extended period of time even after adopting the metal mesh as a fixing substrate of the CNT film. While a high current was emitted, some part of the film was shown to delaminate. In order to strengthen the CNT networks, cobalt-nickel oxides were incorporated into the film. After coating the oxide layer, the CNT tips seemed to be more strongly adhered on the CNT bush. Without the oxide layer, the field emission voltage-current curve moved fast to a high voltage side as increasing the number of voltage sweeps. With the cobalt-nickel oxide incorporated, however, the curve does not move after the second voltage sweep. Such improvement of emission properties seemed to be attributed to stronger adhesion of the CNT film which was imparted by the cobalt-nickel oxide layer between CNT networks. Observed after field emission for an extended period of time, the CNT film with the oxide layer showed less damage on the surface caused by high current emission.

• 한국진공학회지
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• 제6권4호
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• pp.308-313
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• 1997

Capacitance Diaphragm Gauge(CDG)를 전달표준기로 사용하여 한국과 영국의 저진 공표준의 국제비교를 수행한 결과 양국 표준기에서 교정한 CDG의 압력비의 차이는 0.05% 이었다. 또한 두 개의 Spinning Rotor Gauge(SRG)를 이용하여 한국과 일본이 고진공표준의 국제비교를 수행한 결과 양국 표준기에서 교정한 SRG의 accommodation coefficient($sigma$)의 차이가 0.4% 이내이었다. CDG와 SRG를 이용한 한국과 영국의 저진공표준기 및 한국과 일 본의 고진공표준기의 국제비교 결과 CDG 및 SRG 자체의 고유오차범위 이내에서 결과가 일치함을 확인할 수 있었다.

• Journal of Korean Society for Atmospheric Environment
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• 제18권E1호
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• pp.29-36
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• 2002

The selective catalytic reduction (SCR) reaction of promoter catalysts was investigated in this study. A pure anatase type of TiO$_2$ was used as support. Activation measurement of prepared catalysts was practiced on a fixed reactor packing by the glass bead after filling up catalysts in 1/4 inch stainless tube. The reaction temperature was measured by K-type thermocouple and catalyst was heated by electric furnace. The standard compositions of the simulated flue gas mixture in this study were as follows: NO 1,780ppm, NH$_3$1,780ppm, $O_2$1% and $N_2$ as balance gas. In this study, gas analyzer was used to measure the outgassing gas. Catalyst bed was handled for 1hr at 45$0^{\circ}C$, and the reactivity of the various catalyst was determined in a wide temperature range. Conversion of NH$_3$/NO ratio and of $O_2$ concentration was practiced at 1,1.5 and 2, respectively. The respective space velocity were as follows . 10,000, 15,000 and 17,000 hr-1. It was found that the maximum conversion temperature range was in a 5$0^{\circ}C$. It was also found toi be very sensitive at space velocity, $O_2$ concentration, and NH$_3$/NO ratio. We also noticed that the maximum conversion temperature of (W, Mo, Sn) -V$_2$O$_{5}$/TiO$_2$ catalysts was broad. Specially WO$_3$-V$_2$O$_{5}$TiO$_2$2 catalyst appeared nearly 100% conversion at not only above 30$0^{\circ}C$ ut also below 25$0^{\circ}C$. At over 30$0^{\circ}C$, NH$_3$ oxidation decreased with decrease of surface excess oxygen. In addition, WO$_3$-V$_2$O$_{5}$TiO$_2$ catalyst did not appear to affect space velocity, $O_2$ concentration, and NH$_3$/NO ratio.ratio.

• 한국입자에어로졸학회지
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• 제9권3호
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• pp.149-161
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• 2013

Experiments on photochemical reactions of purified air alone in an indoor smog chamber were carried out after flushing Teflon bags with purified air for many hours in order to check the level of contamination on the chamber wall. Ozone concentrations were linearly increased from <4 ppb up to about 8 ppb with irradiation time for four hours. Outgassing of NOx from the chamber wall was found to be less than 1 ppb. New ultrafine particles were formed and grown up to about 70 nm during the photochemical reactions, and then total number and mass concentrations of particles were increased from <10 particles/$cm^3$ up to about 4,000 particles/$cm^3$ and $1.3{\mu}g/m^3$, respectively. The wall conditions of these Teflon bags flushed with purified air might not severly affect the chamber experimental results for photochemical reactions of polluted urban ambient air. The difference of gaseous species between two chambers was 2.4 ppb of ozone at most, indicating that the wall cleaning performance of two chambers was nearly similar.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.353-353
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• 2008

Carbon nanotubes (CNTs) are attractive for field emitter because of their outstanding electrical, mechanical, and chemical properties. Several applications using CNTs as field emitters have been demonstrated such as field emission display (FED), backlight unit (BLU), and X-ray source. In this study, we fabricated a CNT cathode using transparent ultra-thin CNT film. First, CNT aqueous solution was prepared by ultrasonically dispersing purified single-walled carbon nanotubes (SWCNTs) in deionized water with sodium dodecyl sulfate (SDS). To obtain the CNT film, the CNT solution in a milliliter or even several tens of micro-litters was deposited onto a porous alumina membrane through vacuum filtration process. Thereafter, the alumina membrane was solvated by the 3 M NaOH solution and the floating CNT film was easily transferred to an indium-tin-oxide (ITO) glass substrate of $0.5\times0.5cm^2$ with a film mask. The transmittance of as-prepared ultra-thin CNT films measured by UV-Vis spectrophotometer was 68~97%, depending on the amount of CNTs dispersed in an aqueous solution. Roller activation, which is a essential process to improve the field emission characteristics of CNT films, increased the UV-Vis transmittance up to 93~98%. This study presents SEM morphology of CNT emitters and their field emission properties according to the concentration of CNTs in an aqueous solutions. Since the ultra-thin CNT emitters prepared from the solutions show a high peak current density of field emission comparable to that of the paste-base CNT emitters and do not contain outgassing sources such as organic binders, they are considered to be very promising for small-size-but-high-end applications including X-ray sources and microwave power amplifiers.

• Journal of Electrical Engineering and Technology
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• 제7권6호
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• pp.959-964
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• 2012

Internal pressure of vacuum interrupter (VI) is one of the most important parameters in VI operation and may increase due to the outgassing from the materials inside VI or gas permeation through metal flange or ceramic vessel. The increase of the pressure above a certain level leads to the failures of switching or insulation. Therefore, an effective pressure check of VI is essential and an analysis of partial discharge (PD) characteristics is an effective monitoring method to identify the degree of the internal pressure of VI. This paper introduces a research work on monitoring the internal pressure of VI by analyzing PDs which were measured using a capacitive PD coupler. The authors have developed cost effective capacitive coupler based on the ceramic material that has an excellent insulation properties and the main component of the capacitive coupler is made by SrTiO3. Detectable internal pressure range and distinguishability of the internal pressure of VI were investigated. From the PD tests results, the internal pressure range, from $10^{-2}$ torr to 500 torr, can be monitored by PD measurements using the capacitive coupler and PD inception voltage (PDIV) follows the Paschen's law. In addition, rise time of PD pulse at 13.2kV decreases with the increase of the internal pressure of VI.