• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.341-341
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• 2012

Recently, oxide semi-conductor materials have been investigated as promising candidates replacing a-Si:H and poly-Si semiconductor because they have some advantages of a room-temperature process, low-cost, high performance and various applications in flexible and transparent electronics. Particularly, amorphous indium-gallium-zinc-oxide (a-IGZO) is an interesting semiconductor material for use in flexible thin film transistor (TFT) fabrication due to the high carrier mobility and low deposition temperatures. In this work, we demonstrated improvement of flexibility in IGZO TFTs, which were fabricated on polyimide (PI) substrate. At first, a thin poly-4vinyl phenol (PVP) layer was spin coated on PI substrate for making a smooth surface up to 0.3 nm, which was required to form high quality active layer. Then, Ni gate electrode of 100 nm was deposited on the bare PVP layer by e-beam evaporator using a shadow mask. The PVP and $Al_2O_3$ layers with different thicknesses were used for organic/inorganic multi gate dielectric, which were formed by spin coater and atomic layer deposition (ALD), respectively, at $200^{\circ}C$. 70 nm IGZO semiconductor layer and 70 nm Al source/drain electrodes were respectively deposited by RF magnetron sputter and thermal evaporator using shadow masks. Then, IGZO layer was annealed on a hotplate at $200^{\circ}C$ for 1 hour. Standard electrical characteristics of transistors were measured by a semiconductor parameter analyzer at room temperature in the dark and performance of devices then was also evaluated under static and dynamic mechanical deformation. The IGZO TFTs incorporating hybrid gate dielectrics showed a high flexibility compared to the device with single structural gate dielectrics. The effects of mechanical deformation on the TFT characteristics will be discussed in detail.

• Journal of Electrical Engineering and Technology
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• 제10권4호
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• pp.1621-1625
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• 2015

Power quality has always been a concern of power engineers. Certainly an argument can be successfully made that most parts of power engineering have the ultimate objective to improve power quality. AC motors were widely used in industrial and domestic applications. Generally, AC motors were of two types: Induction and Synchronous motors. In motor many parameters like different load cycling, switching, working in hot weather and unbalances creates harmonics which creates major reasons for temperature rise of the motors. Due to high peak value of voltage, harmonics can weaken insulation in cables, windings and capacitors and different electronic components. Higher value of harmonics increase the motor current and decrease the power factor which will reduce the life time of the motor and increase the overall rating of all electrical equipments. Harmonics reduction of all the motors in India will save more power. Coating of windings of the motor with nano fillers will reduce the amount of harmonics in the motor. Based on the previous project works, actions were taken to use the enamel filled with various nano fillers for the coating of the windings of the different AC motors. Ball mill method was used to convert the micro particles of Al₂O₃, SiO₂, TiO₂, ZrO₂ and ZnO into nano particles. SEM, TEM and XRD were used to augment the particle size of the powder. The synthesized nano powders were mixed with the enamel by using ultrasonic vibrator. Then the enamel mixed with the nano fillers was coated to the windings of the several AC motors. Harmonics were measured in terms of various indices like THD, VHD, CHD and DIN by using Harmonic analyzer. There are many other measures and indices to describe power quality, but none is applicable in all cases and in many instances, these indices may hide more than they show. Sometimes power quality indices were used as a basis of comparison and standardization. The efficiency of the motors was increased by 5 – 10 %. The thermal withstanding capacity of the motor was increased by 5º to 15º C. The harmonics of the motors were reduced by 10 – 50%.

• 자원환경지질
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• 제44권5호
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• pp.373-386
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• 2011

옥천변성대의 대표적인 우라늄 광화대인 괴산군 덕평리 일대의 흑색점판암과 이에 협재하는 함우라늄 탄질점판암을 상호 구분하여 이들에 대한 지구화학적 연구를 수행함으로써 우라늄 광상의 생성환경에 대해 고찰하였다. 희토류원소 함량은 탄칠점판암이 평균 254 ppm로서 혹색점판암(169 ppm) 보다 높고, 표준시료로 표준화한 결과 탄질시료의 Eu이 현저히 부화되어 나타난다. 산화환원지시원소에 해당하는 원소들의 경우 V, Cr, Co, Ni, Mo, 및 U 등이 흑색점판암에 비해 탄질점판암에서 현저히 부화되어 있는데, 특히, V은 흑색점판암에 비해 24배, Mo은 62배, U은 60배 가량 높게 산출된다. 이 밖에 백금족원소의 경우 Pd와 Pt가 탄질점판암에서 높은 함량을 나타낸다. 정의 Eu 이상을 비롯해 표준 해수기원 셰일에 비해 현저히 부화된 상기 원소들의 산출은 이들이 단순한 해수로부터 침전된 것이 아닌 고온의 환원환경인 해저열수활동과 관련된 퇴적환경에서 생성되었음을 시사한다. 넓은 조성변화를 나타내는 주성분 원소비 ($SiO_2/Al_2O_3$: 3.98~11.88, $Al_2O_3/Na_2O$: 25.6~139.06, $K_2O/Na_2O$: 6.80~46.85)도 퇴적물의 근원암이 퇴적암과 화성암이 혼재되었을 가능성을 나타내며, 또한 황의 함량이 흑색점판암에서 평균 0.6 wt.%인 반면, 탄질점판 암에서는 2.6 wt.%로 높게 나타나는 것은 탄질점판암이 황을 다량 포함하는 열수환경의 영향을 받았음을 보여준다. 이와 같은 지화학적 특징은 옥천변성대와 지구조적으로 대비되며 퇴적분기성 기원으로 알려진 남중국형 백금족광상(Mo-Ni-Zn-PGE)의 생성환경과도 유사한 특징이다. 이상으로 보아 덕평려 일대 우라늄광화작용은 해저열수활동의 영향을 받고 산소가 결핍된 유기물이 풍부한 퇴적분지에서 형성된 것으로 해석된다.

• 한국전기전자재료학회논문지
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• 제32권5호
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• pp.371-375
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• 2019

Developing a thin-film transistor with characteristics such as a large area, high mobility, and high reliability are key elements required for the next generation on displays. In this paper, we have investigated the research trends related to improving the reliability of oxide-semiconductor-based thin-film transistors, which are the primary focus of study in the field of optical displays. It has been reported that thermal treatment in a high-pressure oxygen atmosphere reduces the threshold voltage shift from -7.1 V to -1.9 V under NBIS. Additionally, a device with a $SiO_2/Si_3N_4$ dual-structure has a lower threshold voltage (-0.82 V) under NBIS than a single-gate-insulator-based device (-11.6 V). The dual channel structure with different oxygen partial pressures was also confirmed to have a stable threshold voltage under NBIS. These can be considered for further study to improve the NBIS problem.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권2호
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• pp.1561-1564
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• 2007

$Tb^{3+}-activated$ green-emitting $(Y,Gd)Ga_3(BO_3)_4$ phosphor has been investigated. The main absorption was in the $120{\sim}238$ nm and exhibited a green emission with the 545 nm and several peaks due to inner shell transition of $Tb^{3+}$ ion. With the optimized $Tb^{3+}$ concentrations, the maximum emission brightness was 90% of the $Zn_2SiO_4$:Mn phosphor.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.956-959
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• 2001

In die and mould industry, major material such as cemented carbide is broadly used for increasing the life time and decreasing the cost. It is also required the development for the skills of wire-cut electrical discharge machining(WEDM), but the WEDMed surface was found to be worst due to the attached components of wire. Precision machining method like lapping is necessary for obtaining high quality surface. The lapping compound such as Al2O3 and SiC and cast iron lap can be used for lapping process. The components of Cu and Zn were found WEDMed surface of the specimen. As the result, the low quality of precision was obtained and the heat damage layer of the specimen was occurred. The value of surface hardness was deteriorated, and therefore finish process was required.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2015년도 제46회 하계학술대회
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• pp.1149-1150
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• 2015

In this study, hafnium was doped into aluminum zinc oxide (AZO) films were deposited on glass and Si substrates at room temperature via co-sputtering by varying the electric power applied to the Hf target. The properties of deposited Hf-doped AZO films, such as crystalline structure, optical transmittance, and band gap were analyzed using various methods such as X-ray diffraction (XRD) and UV/visible spectrophotometer. The experimental results confirmed that the abovementioned properties of Hf-AZO films strongly depended on the Hf sputtering power.

• 자원환경지질
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• 제30권5호
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• pp.417-431
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• 1997

Characteristics of sedimentary rocks and enrichment of toxic elements in shale and coal from the Chungnam coal field were investigated based upon geochemistry of major, trace and rare earth elements. Shale and coal of the area are interbedded along the Traissic to the Jurassic Daedong Supergroup, which can be subdivided into grey shale, black shale and coal. The coal had been mined, however all the mines are abandonded due to the economic problems. The shale and coal are characterized by relatively low contents of $SiO_2$, and $Al_2O_3$ and high levels of loss-on-ignition (LOI), CaO and $Na_2O$ in comparison with the North American Shale Composite (NASC). Light rare earth elements (La, Ce, Yb and Lu) are highly enriched with the coal. Ratios of $Al_2O_3/Na_2O$ and $K_2O/Na_2O$ in shale and coal range from 30.0 to 351.8 and from 4.2 to 106.8, which have partly negative correlations against $SiO_2/Al_2O_3$ (1.24 to 6.06), respectively. Those are suggested that controls of mineral compositions in shale and coal can be due to substitution and migration of those elements by diagenesis and metamorphism. Shale and coal of the area may be deposited in terrestrial basin deduced from high C/S (39 to 895) and variable composition of organic carbon (0.39 to 18.40 wt.%) and low contents of reduced sulfur (0.01 to 0.05 wt.%). These shale and coal were originated from the high grade metamorphic and/or igneous rocks, and the rare earth elements of those rocks are slightly influenced with diagenesis and metamorphism on the basis of $Al_2O_3$ versus La, La against Ce, Zr versus Yb, the ratios of La/Ce (0.38 to 0.85) and Th/U (3.6 to 14.6). Characteristics of trace and rare earth elements as Co/Th (0.07 to 0.86), La/Sc (0.31 to 11.05), Se/Th (0.28 to 1.06), V/Ni (1.14 to 3.97), Cr/V (1.4 to 28.3), Ni/Co (2.12 to 8.00) and Zr/Hf (22.6~45.1) in the shale and coal argue for inefficient mixing of the simple source lithologies during sedimentation. These rocks also show much variation in $La_N/Yb_N$ (1.36 to 21.68), Th/Yb (3.5 to 20.0) and La/Th (0.31 to 7.89), and their origin is explained by derivation from a mixture of mainly acidic igneous and metamorphic rocks. Average concentrations in the shale and coal are As=7.2 and 7.5, Ba=913 and 974, Cr=500 and 145, Cu=20 and 26, Ni=38 and 35, Pb=30 and 36, and Zn=77 and 92 ppm, respectively, which are similar to those in the NASC. Average enrichment indices for major elements in the shale (0.79) and coal (0.77) are lower than those in the NASC. In addition, average enrichment index for rare earth elements in coal (2.39) is enriched rather than the shale (1.55). On the basis of the NASC, concentrations of minor and/or environmental toxic elements in the shale and coal were depleted of all the elements examined, excepting Cr, Pb, Rb and Th. Average enrichment indices of trace and/or potentially toxic elements (As, Cr, Cu, Ni, Pb, U and Zn) are 1.23 to 1.24 for shale and 1.06 to 1.22 for coal, respectively.

• 대한지하수환경학회지
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• 제5권3호
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• pp.129-140
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• 1998

이 연구는 오염원이 산재해 있는 농촌지역으로 아산지역을, 그리고 공업단지와 주거지역이 위치한 공단지역으로 구로구지역을 연구대상지역으로 선정하여 공단지역과 농촌지역 지하수의 물리.화학적 특성과 오염 양상을 조사하였다. 또한 지하수의 효율적인 이용과 적절한 관리를 위해 지리정보시스템을 구축하고 이를 이용하여 지하수오염과 잠재점오염원의 공간적인 관련성을 규명하였다. 아산지역 지하수는 Ca-HCO$_3$유형의 지하수이며 SiO$_2$와 HCO$_3$함량비가 높은 특징을 보여 물-암석 반응이 지하수 성분을 지배하는 가장 큰 요인임을 보여준다. 구로구지역 지하수는 Ca-HCO$_3$유형의 지하수이며 Cl, NO$_3$및 SO$_4$등 오염물질이 부화되고 SiO$_2$에 비해 Ca 함량비가 더 높게 나타나는 등 다양한 오염원에 의한 영향을 반영하고있다. 아산지역에서는 37.5%(총 40개 중 15개)의 지하수 시료에서 NO$_3$,SO$_4$및 Zn의 함량이 먹는 물 수질 기준을 초과하는 오염현상이 조사되었으며, 대부분이 NO$_3$의 오염이었다. 축산농가 및 공장에 대해 오염영향범위를 조사하기 위해 버퍼링 분석을 실시한 결과 l00 m 거리에 걸쳐 오염의 영향이 미치고 있어 공장 및 축산농가가 지하수 오염의 직접적인 원인임을 확인하였다. 구로구지역에서는 64.7%(총 51개 중 33개)의 지하수 시료에서 NO$_3$, Cl, SO$_4$, Fe 및 Zn의 함량이 음용수 수질기준을 초과하는 오염현상이 확인되었다. NO$_3$오염은 50 m 이상의 심부지하수에서도 관찰되어 이미 심각한 오염현상이 진행되었음을 보여주었다. Cl 오염은 구로동 지역의 50 m 이하 천부지하수에서 관찰되었으나 구로동의 구로공단지역에서는 먹는 물 수질기준 이하의 낮은 함량을 보였다. 구로동지역은 70%, 고척동지역은 42%, 궁동지역은 14%의 지하수 시료에서 오염물질이 먹는 물 수질기준을 초과하는 오염현상이 조사되었다.

• 한국약용작물학회지
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• 제2권2호
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• pp.162-167
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• 1994

국내에서 자생하고 있는 광릉쥐오줌풀 및 넓은잎 쥐오줌풀의 지하부에서 지방산, 무기성분 및 휘발성 유기산의 조성을 분석한 결과는 다음과 같다. 1. 광릉 및 넓은잎 쥐오줌플의 조지방질 함량은 $3.7{\sim}4.5%$ 범위 이었고 지방산은 총11종이 동정되었는데 그중 특히 양적으로 많이 함유되어있는 linoleic acid, linolenic acid 및 palmitic acid 등은 산지에 따라 함량차이가 큰 경향을 보였다. 2. 희분함량은 $4.3{\sim}6.3%$ 이었고 무기성분중 많이 검출된 성분으로는 조규소$(SiO_2)$를 위시하여 K, Na, Ca, Mg, Al, Fe, Mn, Zn등 이었으며, Na, Fe, Zn 및 Cu 는 산지에 따라 함량차이가 큰 경향을 보였다. 3. 광릉 쥐오줌풀로 부터 분리한 산성분획으로 부터 40종의 성분을 확인하였으며 그중 dimethoxy-2-propenoic acid, 3, 4-dimethoxy benzoic acid, 4-methoxy phenyl-2-propenoic acid 이외에도 3-methyl butanoic acid(isovaleric acid), 3-methyl pentanoic acid, 2-methyl butanoic acid 등 branched-chain fatty acid 류가 양적으로 많이 검출되었다.