• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권8호
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• pp.545-550
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• 2000

This paper presents design and analysis of an HID lamp ballast for a fast turn on characteristics and stable operation. It produces a high open circuit voltage for the ignition and it is controlled to supply effectively the power required to shorten the warm-up period after the breakdown. The lamp modeling by empirical data is presented. It is very effective in the designing of the control loop in the steady-state operating region. A stable operation of the lamp power regulation in the steady state is achieved, which is crucial for the long life time and constant light output. Stability analysis of the system is performed and the results are verified through various simulation results and the hardware experiments.

• The Korean Journal of Ceramics
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• 제2권2호
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• pp.111-113
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• 1996

Dielectric properties at microwave frequency region of the five-layered compound $Ba_5Nb_4O_{15}$ prepared by the conventional solid state reaction method were investigated. $Ba_5Nb_4O_{15}$ has excellent microwave dielectric characteristics; ${\varepsilon}_r$=38, Q=7500 at 10 GHz, and ${\tau}_l$=+50 ppm/K. Since this compound has a high dielectric constant, high Q and sufficiently stable characteristics, it is useful for the applications at microwave frequencies.

• KEPCO Journal on Electric Power and Energy
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• 제1권1호
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• pp.93-97
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• 2015

The combustion tests for Korean anthracite-bituminous coal blend were carried out in the 200 MW utility boiler. The burning characteristics of the blend were studied with a thermogravimetric analyzer (TGA). From the observation of TGA burning profiles, it was found that the presence of bituminous coal in the blend appeared to enhance the reactivity of anthracite in the higher temperature region, indicating certain interactions between the two coals. The plant test showed the boiler operation was reasonably stable with somewhat poor combustion efficiency, and some modification of the combustion environment in the furnace is necessitate for the further stable plant operation.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집
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• pp.308-311
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• 2001

Bi-2212 and Bi-2223 thin films are prepared by IBS(ion beam sputtering) technique. Three phases of Bi-2201, Bi-2212 and Bi-2223 appear as stable ones in spite of the conditions for thin film fabrication of Bi-2212 and Bi-2223 compositions, depending on substrate temperature($T_{sub}$) and ozone pressure(PO$_3$). It is found out that these phases show similar $T_{sub}$ and PO$_3$ dependence, and that the stable regions of these phases are limited within very narrow temperature.

• Macromolecular Research
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• 제17권3호
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• pp.163-167
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• 2009

This study presents a microfluidic method for the production of monodisperse poly(ethylene glycol) (PEG) microspheres using continuous droplet formation and in situ photopolymerization in microfluidic devices. We investigated the flow patterns for the stable formation of droplets using capillary number and the flow rate of the hexade-cane phase. Under the stable region, the resulting microspheres showed narrow size distribution having a coefficient of variation (CV) of below 1.8%. The size of microspheres ($45{\sim}95{\mu}m$) could be easily controlled by changing the interfacial tension between the two immiscible phases and the flow rates of the dispersed or continuous phase.

• Bulletin of the Korean Chemical Society
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• 제7권3호
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• pp.224-228
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• 1986

A nonlinear theory is presented for the fluctuations of intermediates in the Brusselator near the critical point caused by diffusion. The method used is the two time scaling method different from the conventional method in the sense that a slight nonlinear effect is included in the initial time region where the linear approximation is conventionally valid. The result obtained by the nonlinear theory shows that fluctuations close to the critical point approach the value of a stable steady state or deviate infinitely from an unstable steady state, as time goes to infinity, while the linear theory gives approximately time-independent fluctuations. A brief discussion is given for the correlation at a time between fluctuating intermediates when the system approaches a stable steady state.

• 한국습지학회지
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• 제20권1호
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• pp.35-42
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• 2018

본 연구에서는 도심구간 하천의 수생식물을 대상으로 흐름에 대한 대응양상 판단 및 식재영역 결정을 목표로 하였다. 수생식물로서 달뿌리풀, 갈대, 물억새, 개여뀌 및 고마리를 선정하고 흐름의 유속과 수심 및 식생의 성장도에 대하여 대응 분석하여 상기 수생식물의 식재영역을 결정하였다. 수생식물의 대응은 일반적으로 흐름에 대하여 안정, 회복, 훼손 및 유실로 구분되었다. 현지 조사 결과 수생식물의 회복과 훼손 정도는 식생의 휘어짐 각도를 기준으로 대략 $30^{\circ}{\sim}50^{\circ}$의 범위에서 구분되었다. 식생은 달뿌리풀, 갈대, 물억새, 개여뀌 순으로 흐름에 대한 대응력이 컸다. 달뿌리풀은 뿌리의 강한 고착력으로 수심이 0.9 m에서 유속 1.5 m/s까지 대응력이 강했다. 갈대는 수심 1.0 m와 유속 0.9 m/s 범위 내에서 흐름에 대응 가능하였다. 물억새는 대체적으로 수심 1.0 m와 유속 0.6 m/s 이하가 식재 가능 영역으로 제한된 식재 범위를 나타내었다. 개여뀌나 고마리는 흐름에 대한 대응력이 보다 약하며, 수심이 1.0 m를 넘는 경우 유속이 조금만 커져도 생존이 어려웠다. 상기 결과를 이용하여 수생식물 각 수종별 식재영역을 제시하였다.

• 한국경제지리학회지
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• 제6권1호
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• pp.145-170
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• 2003

본 연구는 충청북도를 사례로 대학교육기회의 확대가 이루어진 이후에 지역노동시장의 변화 특성과 지방의 고등학교 졸업생들에서 나타나는 대학진학행동의 특징을 밝힘으로써 지방에 있어서 대학교육기회확대가 갖는 의미를 탐구하고자 했다. 대학교육기회의 양적 팽창이 이루어지면서 충청북도의 노동시장에 있어서 대졸 취업자의 직종 하향이동이 심화되고 있으며, 이에 대한 반작용으로 대학진학행동에서 충청북도를 이탈하여 보다 상위 중심지로 또는 핵심지역으로 이탈하려는 경향이 점차 두드러지고 있는 것으로 분석되었다. 특히 이 과정에서 도를 단위로 하는 취학권이 약화되고 있음이 밝혀졌다.

• Journal of Information Technology Applications and Management
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• 제30권1호
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• pp.33-52
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• 2023

This study observes the difference in the actual regional ripple effect of the decrease in admission resources due to the decrease in school age population, which has been weak in empirical studies, and how much the decrease in competition rate by department nationwide provides a significant shock to the decrease in enrollment rate in the population unit. An empirical quantitative analysis was attempted. As a result of applying the panel-tobit regression model, a clear gap was confirmed in the decrease in the registration rate due to the decrease in the competition rate both nationally and in the provinces, and in particular, a highly significant relationship was derived with the decrease in the recruitment rate. In particular, the sensitivity of the risk of unrecruitment due to a decrease in competition rate was the highest in the Jeolla region (0.499), followed by the Gangwon region (0.475) and the Gyeongsang region (0.471), and the metropolitan region (0.158) was confirmed to be the most stable. This suggests that the gap in insufficient funding has gradually widened by region over the past 10 years, and that the shock wave becomes more pronounced in the provinces farther away from the metropolitan area. Based on this study, if we deviate from the standardized application of university development policies for the metropolitan area and regional universities, and present a customized higher education strategy for each region, it will be an opportunity to prevent local extinction due to a decrease in the school-age population and achieve coexistence with higher education institutions and regions at the same time.

• Journal of Mechanical Science and Technology
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• 제20권9호
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• pp.1449-1458
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• 2006

Controlled Auto-ignition (CAI) combustion processes can be broadly divided between a CAI process that is applied to four-cycle engines and a CAI process that is applied to two-cycle engines. The former process is generally referred to as Homogeneous Charge Compression Ignition (HCCI) combustion and the later process as Active Thermo-Atmosphere Combustion (ATAC) The region of stable engine operation differs greatly between these two processes, and it is thought that the elucidation of their differences and similarities could provide useful information for expanding the operation region of HCCI combustion. In this research, the same two-cycle engine was operated under both the ATAC and HCCI combustion processes to compare their respective combustion characteristics. The results indicated that the ignition timing was less likely to change in the ATAC process in relation to changes in the fuel octane number than it was in the HCCI combustion process.