• 한국전기전자재료학회논문지
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• 제37권4호
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• pp.400-406
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• 2024

Next-generation wide-bandgap semiconductors such as SiC, GaN, and Ga2O3 are being considered as potential replacements for current silicon-based power devices due to their high mobility, larger size, and production of high-quality wafers at a moderate cost. In this study, we investigate the gradual modulation of chemical composition in multi-stacked metal oxide semiconductor thin films to enhance the performance and bias stability of thin-film transistors (TFTs). It demonstrates that adjusting the Ga ratio in the indium gallium oxide (IGO) semiconductor allows for precise control over the threshold voltage and enhances device stability. Moreover, employing multiple deposition techniques addresses the inherent limitations of solution-processed amorphous oxide semiconductor TFTs by mitigating porosity induced by solvent evaporation. It is anticipated that solution-processed indium gallium oxide (IGO) semiconductors, with a Ga ratio exceeding 50%, can be utilized in the production of oxide semiconductors with wide band gaps. These materials hold promise for power electronic applications necessitating high voltage and current capabilities.

• 한국조경학회지
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• 제30권4호
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• pp.37-46
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• 2002

The main purpose of this research is to discuss the urban heat island which will be caused by urbanization, especially by the construction of new town on a wide green zone. Over the last ten years, five new towns have been developed around the Seoul metropolitan area. However these new towns become bedroom communities and create traffic problems between Seoul and its surrounding areas because of an increase in population and a lack of roads and other infrastructures. The construction of another such new town is under consideration in the Pan-gyo area. But it is important that Pan-gyo remains a wide green zone. Many studies show that green space can play an important role in improving urban eco-meteorological, ameliorative capability and air hygiene. The objective of this study is to analyze the urban heat islands of Bund-Dang Si which was constructed in 1996 and of the Pan-Gyo area planned as new town. To investigate the local thermal environment and its negative effects caused by change of the land use type and urbanization we used LANDSAT TM images for extraction of urban surface temperature according to change of land use over 15 years. These data were analyzed together with digital land use and topographic data. As a study result, we found that the thermal island of this area from 1985 to 1999 rapidly increased with a difference of mean temperature of more than 12'E. Before construction of Bun-Dang Si the temperature of this area was the same as the forest, but during the new town construction in 1991, an urban heat island developed. The temperature of forest with a size of over 50% of the investigation area was lowest, which leads us to conclude that the forest cools the urban and its surroundings. The mean temperature of the residential and commercial area is more than +4.5$^{\circ}C$ higher then forest, so this method of land use is the main factor increasing the urban heat island. Urban heat islands and green space play an important role in urban wind systems, i.e. Thermal Induced Air Exchange and Structural Wind Circulation, because of their special properties with regard to energy balance between constructed urban and land. The skill to allocate land use types in urban areas is a very important planning device to reduce air pollution and induce the fresh cold air from green space. An urban climatic experiment featuring a numerical wind simulation study to show the air corridor will be published in a following research paper.

• Ocean and Polar Research
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• 제27권1호
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• pp.15-24
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• 2005

In order to investigate the structures and dynamics of phytoplankton communities, each physicochemical environmental factor, species composition, standing crop, and dominant species were examined in the marine ranching ground of Tongyeong coastal waters from April to October, 2000. During the studies, mean water temperature and salinity were $18.8^{\circ}C$ and 33.1 psu, respectively. DO, SS and transparency varied from 5.43 to 11.39 mg/l, 14.6 to 32.4mg/l and 3.5 to 9.0m, respectively. Light intensities varied from 0.02 to $966{\mu}E/m^2/s$, which decreased with depth. $NH_4-N,\;NO_3-N,\;NO_2-N,\;PO_4-P,\;and\;SiO_2-Si$ were fluctuated from 0.059 to 0.332 mg/l, 0.040 to 0.800 mg/l, 0.001 to 0.468 mg/l, 2.3 to $143.0{\mu}g/l$, and 0.007 to 0.600 mg/l, respectively. chlorophyll a concentrations were fluctuated from 0.7 to $8.9{\mu}g/l$. Among 130 taxa of phytoplankton communities observed. diatoms occupied more than 81.54% of the total species, and the others were dinoflagellates and silicoflagellates. Phytoplankton standing crops ranged from $4.6{\times}10^4\;to\;2.6{\times}10^6cells/l$. In October, the standing crops were at bloom level showing more than $10^6cells/lat$ all stations. Dominant species changed by month and station. Leptocylindrus danicus occupied 59.84% in April and 22.03% in June. Pseudo-nitzschia pungens in August and Chaetoceros socialis and Skeletonema costatum in October were predominant species. In order to investigate factors influencing the total phytoplankton standing crops the correlations between the standing crops of diatoms, dinoflagellates, all phytoplanktons occurred and environmental factors were calculated using a multiple regression analysis. The coefficient of determination $(R^2)$ for total standing crops was 0.63 which explained 63% of variance and that of $R^2$ for diatom was 0.82. In statistical analysis, the results showed that the environmental factors influencing the size of the communities were predominantly water temperature, salinity and silicate.

• Korean Chemical Engineering Research
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• 제43권6호
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• pp.675-682
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• 2005

불화실리콘산($H_2SiF_6$)과 질산알루미늄의 혼합 수용액을 주형으로 사용되는 $C_{16}TMABr$(cethyltrimethylaminonium bromide)용액에 첨가하여 불화실리콘산의 hydrolysis 반응에 의해서 메조포러스 분자체(Al-MMS)를 합성하였다. 합성된 분자체를 분석한 결과 비표면적이 $981m^2/g$이고, 기공 크기가 $39{\AA}$ 부근에서 균일함을 보이는 메조포러스 분자체가 합성되었으며, $NH_3$-TPD 결과 산의 세기가 크지 않음을 알 수 있었다. 합성된 담체가 납사분해 잔사유에 포함되어 있는 방향족 화합물의 수소화 반응에 대한 촉매 담체로써 적용 가능한가를 조사하기 위해서 Pt 및 Pd의 금속 성분을 담지시킨 후, 납사 분해 잔사유에 많이 포함되어 있는 방향족 화합물인 나프탈렌을 모델화합물로 정하고 나프탈렌의 수소화 반응에 대한 온도별 전환율, 반응속도 상수, 활성화 에너지를 조사하였다. 또한, 다른 메조포러스 담체와 상용담체를 이용하여 촉매를 제조한 후 같은 방법으로 비교하였다. 그 결과 PtPd/Al-MMS 촉매가 우수한 탈방향족 활성과 황저항성을 나타내었으며, 다른 메조포러스 담체 및 상용 담체와 비교한 결과 활성이 우수하게 나타났다. 실제 납사분해 잔사유의 일종인 PGO(pyrolized gas oil)를 원료로 실험해 본 결과 활성이 우수하게 나타났으며 Pd/Al-MMS 촉매는 납사분해 잔사유에 포함된 방향족 화합물의 수소화 촉매로써 응용 가능성을 보였다.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2002년도 제3회 최신 분말제품 응용기술 Workshop
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• pp.25-37
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• 2002

The most important industrial application of gamma radiation in characterizing green compacts is the determination of the density. Examples are given where this method is applied in manufacturing technical components in powder metallurgy. The requirements imposed by modern quality management systems and operation by the workforce in industrial production are described. The accuracy of measurement achieved with this method is demonstrated and a comparison is given with other test methods to measure the density. The advantages and limitations of gamma ray densitometry are outlined. The gamma ray densitometer measures the attenuation of gamma radiation penetrating the test parts (Fig. 1). As the capability of compacts to absorb this type of radiation depends on their density, the attenuation of gamma radiation can serve as a measure of the density. The volume of the part being tested is defined by the size of the aperture screeniing out the radiation. It is a channel with the cross section of the aperture whose length is the height of the test part. The intensity of the radiation identified by the detector is the quantity used to determine the material density. Gamma ray densitometry can equally be performed on green compacts as well as on sintered components. Neither special preparation of test parts nor skilled personnel is required to perform the measurement; neither liquids nor other harmful substances are involved. When parts are exhibiting local density variations, which is normally the case in powder compaction, sectional densities can be determined in different parts of the sample without cutting it into pieces. The test is non-destructive, i.e. the parts can still be used after the measurement and do not have to be scrapped. The measurement is controlled by a special PC based software. All results are available for further processing by in-house quality documentation and supervision of measurements. Tool setting for multi-level components can be much improved by using this test method. When a densitometer is installed on the press shop floor, it can be operated by the tool setter himself. Then he can return to the press and immediately implement the corrections. Transfer of sample parts to the lab for density testing can be eliminated and results for the correction of tool settings are more readily available. This helps to reduce the time required for tool setting and clearly improves the productivity of powder presses. The range of materials where this method can be successfully applied covers almost the entire periodic system of the elements. It reaches from the light elements such as graphite via light metals (AI, Mg, Li, Ti) and their alloys, ceramics ($AI_20_3$, SiC, Si_3N_4, $Zr0_2$, ...), magnetic materials (hard and soft ferrites, AlNiCo, Nd-Fe-B, ...), metals including iron and alloy steels, Cu, Ni and Co based alloys to refractory and heavy metals (W, Mo, ...) as well as hardmetals. The gamma radiation required for the measurement is generated by radioactive sources which are produced by nuclear technology. These nuclear materials are safely encapsulated in stainless steel capsules so that no radioactive material can escape from the protective shielding container. The gamma ray densitometer is subject to the strict regulations for the use of radioactive materials. The radiation shield is so effective that there is no elevation of the natural radiation level outside the instrument. Personal dosimetry by the operating personnel is not required. Even in case of malfunction, loss of power and incorrect operation, the escape of gamma radiation from the instrument is positively prevented.

• 한국재료학회지
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• 제6권7호
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• pp.723-732
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• 1996

ICB 공정으로 선행 증착한 Cu Seeding 층이 이후의 CVD 공정으로 증착하는 최종의 Cu 박막의 기계적 전기적 특성에 미치는 영향을 고찰하였고, seening을 하지 않은 CVD-Cu 박막과의 특성을 비교하였다. seeding 층을 형성한 경우의 CVD-Cu 박막에 있어서 증착 속도가 증가하였으며, grain 크기의 균일성도 향상되는 경향을 보였다. 증착된 Cu 박막은 seening에 무관하게 모두 FCC 우선배향인 (111)의 결정배향을 나타냈으며, seeding 우에 성정된 박막의 경우 $I_{111}/I_{200}$비가 향상되었다.$ 180^{\circ}C$의 동일 조건하에서 증착하는 경우 $40\AA$ seeding층 위에 성장한 박막의 전기비저항이 $2.42\mu$$\Omega$.cm로 낮은 값을 나타내었으며, 130$\AA$ seeding 경우는 오히려 전기비저항이 증가하는 경향을 나타내었다. Cu 박막의 접착력은 seeding층의 두께가 $0\AA$에서 $130\AA$으 증가함에 따라 21N에서 27N 으로 향상되었다.

• Journal of Applied Biological Chemistry
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• 제66권
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• pp.477-483
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• 2023

잇꽃을 80% MeOH 수용액으로 추출하고, 얻어진 추출물을 EtOAc, n-BuOH 및 물로 용매 분획 하였다. 이 중 n-BuOH 분획으로부터 silica gel (SiO₂), octadecyl silica gel (ODS) column chromatography, 및 Prep-LC로 정제하여 4종의 화합물을 분리하였다. Nuclear magnetic resornance, mass spectroscopy 및 infrarad spectroscopy 등의 스펙트럼 데이터를 통해 화합물의 화학구조를 astragalin (1), isoquercetin (2), nicotiflorin (3), 그리고 rutin (4) 로 동정하였다. 본 연구를 통해 잇꽃 추출물, 용매 분획물 및 모든 분리 화합물의 alloxan에 의해 손상된 zebrafish 유충 췌도 보호 효과를 평가하기 위한 실험을 수행하였다. EtOAc (CTE), n-BuOH (CTB) 및 H₂O (CTW) 분획 모두 통계 유의적으로 우수한 항당뇨 효능을 확인하였으며, 분리된 화합물 1-4로 처리된 췌도 크기는 알록산 유도군 대비 각각 87.0, 88.5, 88.7, 및 89.3% 로 유의적으로 증가했다. 분리된 4종의 화합물 중 nicotiflorin은 6.752 mg/추출물(g)으로 높은 함량을 나타내었다. 이 결과를 통해 잇꽃 유래 화합물은 항당뇨 소재의 기능 지표성분으로서 활용 가능성을 확인하였다.

• 한국재료학회지
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• 제12권10호
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• pp.814-819
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• 2002

TiN and TaN films as electrode materials of reactive sputtered $Ta_2$$O_{5}$ were prepared by sputtering to compare their thermal stabilities with $Ta_2$$O_{5}$ The microstructural change of $Ta_2$$O_{5}$ films with annealing was also investigated. As- deposited $Ta_2$$O_{5}$ film on $SiO_2$ was amorphous and annealing of 80$0^{\circ}C$ for 30 min made it transform to $\beta$-Ta$_2$O$_{5}$ crystalline which contains amorphous particles with the size of a few nm. Crystallization temperature of Ta$_2$Ta_2$$O_{5}$ on TaN is higher than that on TiN electrode. The interface between TaN and Ta$_2$O$_{5}$ maintained stably even after vacuum annealing up to $800^{\circ}C$ for 1 hr, but TiN interacted with $Ta_2$$_O{5}$ and so interdiffusion between TiN and $Ta_2$$O_{5}$ occurred by vacuum annealing of 80$0^{\circ}C$ for 1 hr. It indicates that TaN is thermally more stable with $Ta_2$$O_{5}$ than TiN.N.

• 한국재료학회지
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• 제17권1호
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• pp.31-36
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• 2007

Nanoimprint lithography (NIL) is a new lithographic method that offers a sub-10nm feature size, high throughput, and low cost. One of the most serious problems of NIL is the stiction between mold and resist. The antistiction layer coating is very effective to prevent this stiction and ensure the successful NIL results. In this paper, an antistiction layer was deposited by VSAM (vapor self assembly monolayer) method on silicon samples with FOTS (perfluoroctyltrichlorosilane) as a precursor for making an antistiction layer. A specially designed LPCVD (low pressure chemical vapor deposition) was used for this experiment. All experiments were achieved after removing the humidity. First, the evaporation test of FOTS was performed for checking the evaporation temperature at low pressure. FOTS was evaporated at 5 Tow and $110^{\circ}C$. In order to evaluate the temperature effect on antistiction layer, chamber temperature was changed from 50 to $170^{\circ}C$ with 0.1ml of FOTS for 1 minute. Good hydrophobicity of all samples was shown at about $110^{\circ}$ of contact angle and under $20^{\circ}$ of hysteresis. The surface energies of all samples calculated by Lewis acid/base theory was shown to be about 15mN/m. The deposited thicknesses of all samples measured by ellipsometry were almost 1nm that was similar value of the calculated molecular length. The surface roughness of all samples was not changed after deposition but the friction force showed relatively high values and deviations deposited at under $110^{\circ}$. Also the white circles were founded in LFM images under $110^{\circ}$. High friction forces were guessed based on this irregular deposition. The optimized VSAM process for FOTS was achieved at $170^{\circ}C$, 5 Torr for 1 hour. The hot embossing process with 4 inch Si mold was successfully achieved after VSAM deposition.

• Korean Chemical Engineering Research
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• 제53권4호
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• pp.425-430
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• 2015

고분자 복제방법을 이용하여 제조한 폼 형태의 다공성 탄화규소 표면에 수열 합성 방법을 적용하여 ZSM-5를 합성하였다. 다공성 탄화규소 표면으로부터 ZSM-5가 합성될 수 있도록 유도하기 위하여 합성단계에 앞서 탄화규소 표면에 산화 층을 형성하였다. 수열합성 반응은 산화처리 된 다공성 탄화규소와 TEOS, $Al(NO_3){\cdot}9H_2O$ 및 TPAOH를 원료로 사용하여 $150^{\circ}C$에서 7시간 진행하였다. XRD 및 SEM 분석을 통하여 $1{\sim}3{\mu}m$ 크기의 ZSM-5가 다공성 탄화규소 표면에 코팅되어 성장하였음을 확인하였다. BET 분석결과 ZSM-5 합성 후에 $10{\AA}$이하의 미세기공이 급격히 증가하였으며, 비표면적이 $0.83m^2/g$에서 $30.75m^2/g$으로 급격히 증가되었음을 알 수 있었다.