• 한국진공학회지
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• 제6권1호
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• pp.1-8
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• 1997

SUS 316 합금의 노출 조건에 따른 오염 과정과 구조를 x-ray photoelectron spectroscopy실험을 통해 보았다. SUS표면에 부착된 오염 물질은 주로 metal-oxide, metal-H-oxide, CO, COH, 그리고 CxHy임을 보았다. 오염 물질의 층별 형성 구조는 $C_xH_y$/CO(COH)/metal-H-oxide/metal-oxide가 SUS합금 위에 있는 형태이다. 오염 과정은 주로 금속 구성물의 산화와 $C_xH_y$의 흡착과정 두 가지에 의해서 이루어지는 것을 볼 수 있 었다. 초고진공 환경에서는, 오염은 주로 산화층 형성에 의한 것으로 노출 시간이 증가함에 따라 산화층의 두께가 계속 증가하였다. 고진공 또는 높은 압력 환경에서는 노출 초기에 대 부분의 산화층이 형성되고, 노출 시간의 증가에 대해서는 주로 $C_xH_y$에 의한 오염이 계속 증 가하였다. 스테인레스 표면 안에 깊이 분포하고 있는 metal-oxide의 농도는 지수형으로 감 소하는 형태의 분포를 가지며 그 두께는 대기 노출된 시료의 경우 광전자의 평균자유행로 규모로 형성되는 것을 보았고, 특히 Fe-oside가 Cr-oxide를 덮고 있는 표면 편석 현상이 보 였다.

• 대기
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• 제21권1호
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• pp.85-93
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• 2011

UK Met Office Unified Model (UM) is a grid model applicable for both global and regional model configurations. The Met Office has developed a 4D-Var data assimilation system, which was implemented in the global forecast system on 5 October 2004. In an effort to improve its Numerical Weather Prediction (NWP) system, Korea Meteorological Administration (KMA) has adopted the UM system since 2008. The aim of this study is to provide the basic information on the effects of satellite data assimilation on UM performance by conducting global satellite data denial experiments. Advanced Tiros Operational Vertical Sounder (ATOVS), Infrared Atmospheric Sounding Interferometer (IASI), Special Sensor Microwave Imager Sounder (SSMIS) data, Global Positioning System Radio Occultation (GPSRO) data, Air Craft (CRAFT) data, Atmospheric Infrared Sounder (AIRS) data were assimilated in the UM global system. The contributions of assimilation of each kind of satellite data to improvements in UM performance were evaluated using analysis data of basic variables; geopotential height at 500 hPa, wind speed and temperature at 850 hPa and mean sea level pressure. The statistical verification using Root Mean Square Error (RMSE) showed that most of the satellite data have positive impacts on UM global analysis and forecasts.

• 한국전기전자재료학회논문지
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• 제13권4호
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• pp.349-358
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• 2000

Fabrication and Characterization of Bi$_{2}$/Sr$_{2}$/CaCu$_{2}$/O$_{8}$(Bi2212) superconductor thick films were fabricated successfully on C tapes by liquid reaction between Cu-free precursors of Bi$_{x}$/SrCaO/$_{y}$(x=1.2-2) and Cu tapes. Cu-free Bi-Sr-Ca-O powder mixtures were screen-printed on Cu tapes and heat-treated at 850-87$0^{\circ}C$ for several minutes in air oxygen nitrogen and low oxygen pressure. In order to obtain the optimum heat-treatment condition we studied the effect of the precursor composition the printing thickness and the heat-treatment atmosphere on the superconducting properties of Bi2212 films and the reaction mechanism. Microstructures and phases of thick films were analyzed by films and the reaction mechanism. Microstructures and phases of thick films were analyzed by optical microscope and XRD. The electric properties of superonducting films were examined by the four probe method. At heat-treatment temperature the thick films were in a partially molten state by liquid reaction between CuO of the oxidized copper tape and the precursors which were printed on Cu tapes. During the heat-treatment procedure Bi2212 superconducting particle nucleate and grow in preferred orientations.ons.s.

• 동력기계공학회지
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• 제12권1호
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• pp.13-19
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• 2008

In this study, a variable induction and exhaust system is applied to turbocharged diesel engine to improve the volumetric efficiency, especially, in a low and transient engine speed range where much of the pollutant matters are expelled out. The volumetric efficiency is known as one of the most important factor which affects significantly engine performance, fuel economy and further emission and noise level. As the torque increase with the engine speed up, the gas flow in an exhaust pipe become pulsating and then has an effect on boost up capacity of air charging into the cylinder and expelling capacity to atmosphere simultaneously. But at a low and idling speed, the pulsation effect was not so significant. Accordingly, resonator was employed to compensate their loss. The variable induction system consists of the secondary pipe, resonator, intercooler, and torque variance were examined with extended operating conditions. In the mean time, for interpretation and well understanding for the phenomena of wave action that arising during intake and exhaust process between turbocharger and variable intake system, the concept of the combined supercharging was introduced. Some of results are depicted which deal with a pressure history during valve events of induction process. Consequently, by the governing of these phase and amplitude of pulsating wave, it enables us to estimate and evaluate for the intake system performance and also, designing stage of the system layout.

• 한국군사과학기술학회지
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• 제15권2호
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• pp.208-214
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• 2012

The spectral radiance received by a remote sensor is consisted of the self-emitted component directly from the target surface, the reflected component of the solar irradiance at the target surface, and the scattered component by the atmosphere without ever reaching the object surface. In general, the self-emitted component is the most important part in the infrared signatures from the target. We measured the solar irradiation, sky irradiation, air temperature, wind velocity, wind direction, relative humidity, and atmospheric pressure together with the surface temperatures of rectangular parallelepiped targets. The measured diurnal surface temperature variations on the three different rectangular parallelepiped targets constructed by the steel, aluminum and bakelite are obtained at the same time intervals. The measured surface temperature results show that the top surface temperature of bakelite recorded up tp $7.6^{\circ}C$ higher than that of aluminium and $6.1^{\circ}C$ higher than that of steel at 11 AM on the sunny condition. A complete set of measured data including the surface temperature of rectangular parallelepiped targets together with the detailed weather information can be a valuable reference for future study.

• 한국재료학회지
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• 제2권5호
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• pp.360-365
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• 1992

Ga 첨가효과 및 Sputter 제조조건이 전기적 특성에 미치는 영향을 고찰하기 위해 ZnO분말과 G$a_2O_3$분말을 소결하여 타겟트를 제조하여 Sputter법으로 유리기판에 Ga-doped ZnO 다결정박막을 제조하였다. RF 전력밀도, 아르곤 개스압력 및 Ga 함유량등을 최적화한 후 제조한 투명한 Ga-doped ZnO 박막의 비저항은 1$0^{-3}$ohm-cm이며, undoped 및 Ga-doped ZnO 박막의 전자농도는 각 $10^{18}$, $10^{21}$/c$m^2$이였다. 공기와 질소분위기에서 열처리를 행하였을 때 Ga-doped ZnO 박막의 비저항은 $10^{2}$ order 증가하였다. 가시광영역의 투과율은 80% 이상이였으며, Ga 함유량이 증가하면 optical band gap도 넓어졌다.

• 대기
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• 제29권2호
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• pp.115-129
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• 2019

Surface winds over the ocean influence not only the climate change through air-sea interactions but the coastal erosion through the changes in wave height and direction. Thus, demands on a reliable projection of future changes in surface winds have been increasing in various fields. For the future projections, climate models have been widely used and, as a priori, their simulations of surface wind are required to be evaluated. In this study, we evaluate the climatological mean surface winds over the Korean Waters simulated by five regional climate models participating in Coordinated Regional Climate Downscaling Experiment (CORDEX) for East Asia (EA), an international regional climate model inter-comparison project. Compared with the ERA-interim reanalysis data, the CORDEX-EA models, except for HadGEM3-RA, produce stronger wind both in summer and winter. The HadGEM3-RA underestimates the wind speed and inadequately simulate the spatial distribution especially in summer. This summer wind error appears to be coincident with mean sea-level pressure in the North Pacific. For wind direction, all of the CORDEX-EA models simulate the well-known seasonal reversal of surface wind similar to the ERA-interim. Our results suggest that especially in summer, large-scale atmospheric circulation, downscaled by regional models with spectral nudging, significantly affect the regional surface wind on its pattern and strength.

• 대기
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• 제31권1호
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• pp.29-43
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• 2021

In this study, two-step statistical approach including Principal Component Analysis (PCA) and Multiple Linear Regression (MLR) was employed, and main meteorological factors explaining the high-PM2.5 episodes were identified in two regions: Seoul and Busan. We first performed PCA to isolate the Principal Component (PC) that is linear combination of the meteorological variables observed at two levels: surface and 850 hPa level. The employed variables at surface are: temperature (T2m), wind speed, sea level pressure, south-north and west-east wind component and those at 850 hPa upper level variables are: south-north (v850) and west-east (u850) wind component and vertical stability. Secondly we carried out MLR analysis and verified the relationships between PM2.5 daily mean concentration and meteorological PCs. Our two-step statistical approach revealed that in Seoul, dominant factors for influencing the high PM2.5 days are mainly composed of upper wind characteristics in winter including positive u850 and negative v850, indicating that continental (or Siberian) anticyclone had a strong influence. In Busan, however, the dominant factors in explanaining in high PM2.5 concentrations were associated with high T2m and negative u850 in summer. This is suggesting that marine anticyclone had a considerable effect on Busan's high PM2.5 with high temperature which is relevant to the vigorous photochemical secondary generation. Our results of both differences and similarities between two regions derived from only statistical approaches imply the high-PM2.5 episodes in Korea show their own unique characteristics and seasonality which are mostly explainable by two layer (surface and upper) mesoscale meteorological variables.

• 전기전자학회논문지
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• 제27권3호
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• pp.225-233
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• 2023

본 논문은 해양사고 시 인체 인양정보를 모니터링하는 시스템을 구현한다. 모니터링 시스템은 수중환경 정보를 송신하는 인양기구제어기를 통하여 초음파 통신을 수행하며, 수상에서는 관제센터 또는 모선까지 10 km내 GPS 정보를 제공하기 위해 LoRa 통신을 수행한다. 수중 인양제어기는 공압 센서, 자이로 센서 및 온도센서 정보를 전송한다. 수중조건은 수심 10m 마다 수압 1기압씩 높아지고, 기구의 공기양은 육상에 비해서 1/2씩 줄어드는 환경에서 60 kg 수중 마네킹을 모델을 사용한다. 인양기구 SMB(Surface Marker Buoy)에 38g의 CO2 카트리지 1개를 사용하여 10 sec 이내에 수면 상승 조건을 기반으로 인양기구 출수 시험을 한다. 수중 통신은 수심 40m에서 100m까지 2,400bps 초음파 센서를 이용하여 데이터 전송환경을 구성한다. 모니터링 신호는 수심, 수온, 방향각 등을 수면 위의 구조요원에게 제공함으로써 인양작업자의 안전과 안전한 인체 구조를 목표로 한다.

• 청정기술
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• 제29권2호
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• pp.126-134
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• 2023

직접촉매분해기술은 반도체 및 디스플레이 산업에서 아산화질소(N₂O)의 배출을 완화할 수 있는 유망한 기술이다. 본 연구는 7대 온실가스 중에 하나인 N₂O 직접촉매분해를 위한 γ-Al₂O₃ 촉매에 관한 것이다. 실험에 사용한 γ-Al₂O₃ 촉매는 뵘석 분말을 사용하여 압출 성형하여 제조하였으며, 반응은 직경 약 5 mm 크기로 분쇄한 촉매를 직경 25.4 mm (1인치) 반응기를 사용하여 수행하였다. N₂O 농도는 약 1%가 되도록 공급하였으며, 온도는 550-750 ℃, 압력은 상압, GHSV는 1800-2000 h-1에서 촉매반응 특성을 확인하였다. 분위기 가스로는 질소, 공기 그리고 공기+수분을 공급하여 N₂O 분해 특성과 산소의 영향 및 스팀의 영향을 확인하였다. 촉매 내구성은 N₂ 분위기에서 수행하였는데, 700 ℃에서 350 시간 동안 연속 운전을 통해 확인하였다. 실험결과 불활성 분위기(N₂)일 경우 700 ℃에서 N₂O 분해율이 100%에 가까운 수준까지 도달함을 확인하였고, 공기와 수분을 공급할 경우 분해율이 낮아짐을 확인하였다. 내구성 실험 결과 350 시간동안 촉매성능저하는 없었다. 따라서 뵘석 분말로 제조한 γ-Al₂O₃ 촉매는 N₂O 분해 특성에 우수할 뿐만 아니라 내구성 또한 우수하여 전자 산업을 비롯하여 질산제조공정 등 산소와 수분이 존재하는 경우에도 적용 가능할 것으로 기대한다.