• 대한원격탐사학회지
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• 제12권2호
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• pp.126-138
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• 1996

1995년 늦가을인 11월 6일에서 8일 사이에 우리나라로부터 동해상으로 이동하면서 폭발적으로 발달한 저기압을 종관자료와 위성영상자료를 사용하여 분석하였다. 이 저기압은 중국북부에서 이동하여 한반도 국경 부근에서 경압성 구름(Baroclinic Leaf Cloud)으로 형태를 띠었고 동해상에서 컴마형(Comma) 구름으로 발달하였으며, 다시 저기압 최성기에 동반되는 Lambda형 구름으로 발달하였다. 여러 과학자들이 동해선풍에 대한 이동과 발달에 대한 수치모사에 따른 예보를 할 때 이런 저기압의 큰 경압성, 수증기의 지속적인 유입, 그리고 따뜻한 해양상으로 한파의 내습이 보편적으로 고려되는 것 들이다. 저기압의 중심기압이 24시간 내에 40hPa 이상 하강하는 이런 저기압은 겨울철에는 종종 강한 바람과 폭우나 폭설을 동반하곤 한다. 위의기간 중 12시간 연속적인 위성영상과 기상변수의 분석에 의하면 이 저기압과 관련하여 해면기압과 500hPa 기압고도의 중심은 기상위성의 합성된 강조적의영상을 사용하여 동쪽으로 이동한 전형적인 모습을 잘 묘사하고 있다. 열대성저기압의 강도와 중심기압을 가진 이런 저기압에 동반된 강풍은 60놋트로 북아메리카의 저기압폭탄이나 대서양 폭풍과 유사하게 하루에 44hpa나 중심기압이 떨어졌다.

• 항공우주시스템공학회지
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• 제14권3호
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• pp.42-50
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• 2020

우주용 적외선 센서의 탑재 교정용 흑체 시스템은 궤도상에서 센서 출력특성 교정을 위해 다양한 기준온도에서 한정된 개수의 온도센서로부터 고정밀의 대표표면온도 추정이 가능해야 한다. 본 논문에서 제안된 흑체 시스템은 흑체 가열 후 잔열 수송을 위한 히트파이프를 흑체 후면 중앙의 일체형 플랜지에 결합하는 방식을 적용하였다. 따라서 흑체 표면온도구배 최소화와 함께 원형 대칭 형태의 온도구배를 얻을 수 있어 표면온도 추정이 용이하면서도 발사 및 궤도환경에서 하중이 가해지더라도 안정적인 히트파이프 접속부를 갖도록 하며, 복수의 히트파이프 적용에 따른 Fail Safe 설계가 가능하도록 한다. 또한 온도센서 부착작업이 용이하도록 센서를 흑체 외부 표면에 적용하더라도 높은 정확도로 표면온도 추정이 가능하다. 본 논문에서 제안된 흑체 시스템의 설계 유효성 입증을 위해 궤도 열해석을 수행하였으며, 해석결과를 기반으로 온도센서 개수 및 위치에 따른 대표표면온도 추정을 실시하였다.

• Nuclear Engineering and Technology
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• 제54권11호
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• pp.4102-4110
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• 2022

Aiming at high-power and long-pulse operation up to 1000 s, some improvements have been made for both 2.45 GHz and 4.6 GHz lower hybrid (LH) systems during the recent 5 years. At first, the guard limiters of the LH antennas with graphite tiles were upgraded to tungsten, the most promising material for plasma facing components in nuclear fusion devices. These new guard limiters can operate at a peak power density of 12.9 MW/m². Strong hot spots were usually observed on the old graphite limiters when 4.6 GHz system operated with power >2.0 MW [B. N. Wan et al., Nucl. Fusion 57 (2017) 102019], leading to a reduction of the maximum power capability. With the new limiters, 4.6 GHz LH system, the main current drive (CD) and electron heating tool for EAST, can be operated with power >2.5 MW routinely. Long-pulse operation up to 100 s with 4.6 GHz LH power of 2.4 MW was achieved in 2021 and the maximal temperature on the guard limiters measured by an infrared (IR) camera was about 540 ℃, much below the permissible value of tungsten material (~1200 ℃). A discharge with a duration of 1056 s was achieved and the 4.6 GHz LH energy injected into the plasma was up to 1.05 GJ. Secondly, the fully-active-multijunction (FAM) launcher of 2.45 GHz system was upgraded to a passive-active-multijunction (PAM), for which the density of optimum coupling was relatively low (below the cut-off value). Good coupling with reflection coefficient ~3% has been achieved with plasma-antenna distance up to 11 cm for the new PAM. Finally, in order to eliminate the effect of ion cyclotron range of frequencies (ICRF) wave on 4.6 GHz LH wave coupling, the location of the ICRF launcher was changed to a port that is located 157.5° toroidally from the 4.6 GHz LH system and is not magnetically connected.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권10호
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• pp.710-715
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• 1999

The purpose of this work is to develop a high-efficiency air cleaning system for air pollutants such as particulate and gaseous state in indoor environments. In order to enhance a removal efficiency of gaseous state pollutants, we suggested that pulsed discharge plasma be combined with $TiO_2$ photocatalyst (photocatalytic plasma air cleaning unit). We investigated experimentally the basic characteristics of photocatalytic plasma air cleaning unit and measured air pollutants removal efficiency. The wavelength of light radiated from pulsed discharge plasma under the atmospheric condition was 310~380nm. Its energy is enough to excite the $TiO_2$ photocatalyst and it makes a photochemical reaction in the surface of $TiO_2$ photocatalyst. The removal quantity of trimethylamine$((CH_3)_3N)\; was\; 130mg/m^34 which is twice quantity of pulsed discharge plasma without $TiO_2$ phtocatalyst unit. From the result of gas analysis using FT-IR, nitric oxide was not detected and trimethylamine was decomposed to $H_2O\; and \;CO_2$. And trimethylamine removal efficiency was 95%. These experimental results indicate that photocatalytic plasma air cleaning unit is a potential method in removing the pollutants.

• 대한화학회지
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• 제33권2호
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• pp.156-163
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• 1989

사염화탄소 용액중에서 thiopropionamide(TPA)와 N,N-dimethylalkylamides(DMF, DMA, DMP)간의 수소결합에 관한 열역학적 상수를 구하기 위하여 TPA의 근적외선 영역의 흡수띠 중에서 $ν_a+amide II$조합띠를 사용하여 5${\sim}$55$^{\circ}C$ 범위에서 실험하였다. TPA 단위체와 수소결합을 하고 있는 TPA의 혼합 흡수띠를 Lorentzian-Gaussian product function을 사용하여 개개의 띠로 분리하였다. 컴퓨터로 분해하여 얻은 개개의 흡수띠의 면적을 사용하여 단위체 및 1 : 1 복합체의 농도를 계산하였고 이로부터 평형상수를 구하였다. 열역학적 상수들은 온도의존 흡수띠를 분석하여 구하였다. TPA와 DMF, DMA 및 DMP간의 1 : 1 복합체의 ${\Delta}$$H^{\circ}$는 각각 -12.5, -13.5, -14.1kJ/mol이었고.${\Delta}$$S^{\circ}$는 각각 -15.2, -17.9, -22.3kJ/mol${\cdot}$deg이었다.

• 한국재료학회지
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• 제22권6호
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• pp.321-327
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• 2012

The production of functional activated carbon materials starting from inexpensive natural precursors using environmentally friendly and economically effective processes has attracted much attention in the areas of material science and technology. In particular, the use of plant biomass to produce functional carbonaceous materials has attracted a great deal of attention in various aspects. In this study the preparation of activated carbon has been attempted from rice husks via a chemical activation-assisted microwave system. The rice husks were milled via attrition milling with aluminum balls, and then carbonized under purified $N_2$. The operational parameters including the activation agents, chemical impregnation weight ratio of the calcined rice husk to KOH (1:1, 1:2 and 1:4), microwave power heating within irradiation time (3-5 min), and the second activation process on the adsorption capability were investigated. Experimental results were investigated using XRD, FT-IR, and SEM. It was found that the BET surface area of activated carbons irrespective of the activation agent resulted in surface area. The activated carbons prepared by microwave heating with an activation process have higher surface area and larger average pore size than those prepared by activation without microwave heating when the ratio with KOH solution was the same. The activation time using microwave heating and the chemical impregnation ratio with KOH solution were varied to determine the optimal method for obtaining high surface area activated carbon (1505 $m^2$/g).

• 한국재료학회지
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• 제22권6호
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• pp.275-279
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• 2012

(3-mercaptopropyl)trimethoxysilane (MPTMS) was used as a silylation agent, and modified silica nanoparticles were prepared by solution polymerization. 2.0 g of silica nanoparticles, 150 ml of toluene, and 20 ml of MPTMS were put into a 300 ml flask, and these mixtures were dispersed with ultrasonic vibration for 60 min. 0.2 g of hydroquinone as an inhibitor and 1 to 2 drops of 2,6-dimethylpyridine as a catalyst were added into the mixture. The mixture was then stirred with a magnetic stirrer for 8 hrs. at room temperature. After the reaction, the mixture was centrifuged for 1 hr. at 6000rpm. After precipitation, 150 ml of ethanol was added, and ultrasonic vibration was applied for 30 min. After the ultrasonic vibration, centrifugation was carried out again for 1 hr. at 6000rpm. Organo-modification of silica nanoparticles with a ${\gamma}$-methacryloxypropyl functional group was successfully achieved by solution polymerization in the ethanol solution. The characteristics of the ${\gamma}$-mercaptopropyl modified silica nanoparticles (MPSN) were examined using X-ray photoelectron spectroscopy (XPS, THERMO VG SCIENTIFIC, MultiLab 2000), a laser scattering system (LSS, TOPCON Co., GLS-1000), Fourier transform infrared spectroscopy (FTIR, JASCO INTERNATIONL CO., FT/IR-4200), scanning electron microscopy (SEM, HITACHI, S-2400), an elemental analysis (EA, Elementar, Vario macro/micro) and a thermogravimetric analysis (TGA, Perkin Elmer, TGA 7, Pyris 1). From the analysis results, the content of the methacryloxypropyl group was 0.98 mmol/g and the conversion rate of acrylamide monomer was 93%. SEM analysis results showed that the organo-modification of ultra-fine particles effectively prevented their agglomeration and improved their dispensability.

• 마이크로전자및패키징학회지
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• 제23권2호
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• pp.73-78
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• 2016

집적회로(Integrated Circuit) 소자의 트랜지스터(transistor) 밀도 증가는 소자에서 발생하는 열 방출(heat dissipation)의 급격한 상승을 초래하여 열 문제를 발생시키고, 이는 소자의 성능과 열적 신뢰성에 영향을 크게 미친다. 열문제의 해결방안 중 본 연구에서는 냉매를 이용한 액체 냉각방법을 연구하였으며, 실리콘 웨이퍼에 관통실리콘비아(through Si via)와 마이크로 채널(microchannel)을 딥 반응성 이온 애칭(deep reactive ion etching)로 구현한 후 유리기판과 어노딕본딩을 통하여 액체 냉각 구조를 제작하였다. 제작된 마이크로 채널 위에 Ag, Cu 또는 Cr/Au/Cu bump를 스크린프린팅(screen printing) 방법으로 형성하였고, 범프의 유무를 통해 액체 냉각 전후의 냉각 모듈의 실리콘 표면온도의 변화를 적외선현미경으로 분석하였다. Cr/Au/Cu bump가 탑재된 액체 냉각 모듈의 경우 가열온도 $200^{\circ}C$에서 냉각 전후의 실리콘 표면 온도 차이는 약 $45.2^{\circ}C$이고, 전력밀도 감소는 약 $2.8W/cm^2$ 이었다.

• 천문학회보
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• 제40권1호
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• pp.60.1-60.1
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• 2015

High energy photons and mechanical energy produced by the process of star formation result in copious FIR molecular and atomic lines, which are important coolants of the system. Photons thermally or mechanically induced could dissociate water in the dense envelope to change relative abundances among the species of O, OH, and H2O. Here we analyze OH emission lines toward embedded young stellar objects (YSOs) observed as part of the Herschel open time key program, 'Dust, Ice, and Gas In Time (DIGIT)' in order to study the physical conditions of associated gas and the energy budget loaded on the OH line emission. According to our analysis of the Herschel/PACS spectra, OH emission peaks at the central spaxel in most of sources, but several sources show spatially extended emission structures. In the extended emission sources, the distribution of OH emission is correlated with that of [OI] emission and extended along the outflow directions. Considering the diversity of source properties, ratios between detected OH lines are relatively constant among sources. In addition, each OH line has strong correlation with bolometric luminosity. In order to determine the physical conditions of YSOs, we adopt several methods for the analysis of the OH lines: rotational diagram, non-LTE LVG analysis, and a 2-D PDR code. From the simple LVG analysis, we find that the thermal solution with the dense ( > $10^7cm^{-3}$) and warm ( ~ 100 K) OH gas reproduces the ratios of detected OH lines. However, our self-consistent PDR 2-D model, which can deal with the IR-pumping effect from the central protostar as well as the warm dust in situ, cannot fit the observational results, suggesting that an irradiated shock model is necessary for a better interpretation.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 추계학술대회 논문집
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• pp.112-112
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• 2009

In this study, the effect of a long post-deposition thermal annealing(600 and 1000 $^{\circ}C$) on the surface acoustic wave (SAW) properties of polycrystalline (poly) aluminum-nitride (AlN) thin films grown on a 3C-SiC buffer layer was investigates. The poly-AlN thin films with a (0002) preferred orientation were deposited on the substrates by using a pulsed reactive magnetron sputtering system. Experimental results show that the texture degree of AlN thin film was reduced along the increase in annealing temperature, which caused the decrease in the electromechanical coupling coefficient ($k^2$). The SAW velocity also was decreased slightly by the increase in root mean square (RMS) roughness over annealing temperature. However, the residual stress in films almost was not affect by thermal annealing process due to small lattice mismatch different and similar coefficient temperature expansion (CTE) between AlN and 3C-SiC. After the AlN film annealed at 1000 $^{\circ}C$, the insertion loss of an $IDT/AlN/3C-SiC/SiO_2/Si$ structure (-16.44 dB) was reduced by 8.79 dB in comparison with that of the as-deposited film (-25.23 dB). The improvement in the insertion loss of the film was fined according to the decrease in the grain size. The characteristics of AlN thin films were also evaluated using Fourier transform-infrared spectroscopy (FT-IR) spectra and X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM) images.