• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.100-100
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• 2011

2004년 일본의 Hosono 그룹에 의해 처음 발표된 이래로, amorphous gallium-indium-zinc oxide (a-GIZO) thin film transistors (TFTs)는 높은 이동도와 뛰어난 전기적, 광학적 특성에 의해 큰 주목을 받고 있다. 또한 넓은 밴드갭을 가지므로 가시광 영역에서 투명한 특성을 보이고, 플라스틱 기판 위에서 구부러지는 성질에 의해 플랫 패널 디스플레이나 능동 유기 발광 소자(AM-OLED), 투명 디스플레이에 응용될 뿐만 아니라, 일반적인 Poly-Si TFT에 비해 백플레인의 대면적화에 유리하다는 장점이 있다. 최근에는 Y2O3나 ZrO2 등의 high-k 물질을 gate insulator로 이용하여 높은 캐패시턴스를 유지함과 동시에 낮은 구동 전압과 빠른 스위칭 특성을 가지는 a-GIZO TFT의 연구 결과가 보고되었다. 하지만 투명 디스플레이 소자 제작을 위해 플라스틱이나 유리 기판을 사용할 경우, 기판 특성상 공정 온도에 제약이 따르고(약 $300^{\circ}C$ 이하), 이를 극복하기 위한 부가적인 기술이 필수적이다. 본 연구에서는 p-type Si을 back gate로 하는 Inverted-staggered 구조의 a-GIZO TFT소자를 제작 하였다. p-type Si (100) 기판위에 RF magnetron sputtering을 이용하여 Gate insulator를 증착하고, 같은 방법으로 채널층인 a-GIZO를 70 nm 증착하였다. a-GIZO를 증착하기 위한 sputtering 조건으로는 100W의 RF power와 6 mTorr의 working pressure, 30 sccm Ar 분위기에서 증착하였다. 소스/드레인 전극은 e-beam evaporation을 이용하여 Al을 150 nm 증착하였다. 채널 폭은 80 um 이고, 채널 길이는 각각 20 um, 10 um, 5 um, 2 um이다. 마지막으로 Furnace를 이용하여 N2 분위기에서 $500^{\circ}C$로 30분간 후속 열처리를 실시한 후에, 전기적 특성을 분석하였다.

• Journal of Korean Society for Atmospheric Environment
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• v.26 no.6
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• pp.666-682
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• 2010

The forecasting system for Today's and Tomorrow's PM10 was developed based on the statistical model and the forecasting was performed at 9 AM to predict Today's 24 hour average PM10 concentration and at 5 PM to predict Tomorrow's 24 hour average PM10. The Today's forecasting model was operated based on measured air quality and meteorological data while Tomorrow's model was run by monitored data as well as the meteorological data calculated from the weather forecasting model such as MM5 (Mesoscale Meteorological Model version 5). The observed air quality data at ambient air quality monitoring stations as well as measured and forecasted meteorological data were reviewed to find the relationship with target PM10 concentrations by the regression analysis. The PM concentration, wind speed, precipitation rate, mixing height and dew-point deficit temperature were major variables to determine the level of PM10 and the wind direction at 500 hpa height was also a good indicator to identify the influence of long-range transport from other countries. The neural network, regression model, and decision tree method were used as the forecasting models to predict the class of a comprehensive air quality index and the final forecasting index was determined by the most frequent index among the three model's predicted indexes. The accuracy, false alarm rate, and probability of detection in Tomorrow's model were 72.4%, 0.0%, and 42.9% while those in Today's model were 80.8%, 12.5%, and 77.8%, respectively. The statistical model had the limitation to predict the rapid changing PM10 concentration by long-range transport from the outside of Korea and in this case the chemical transport model would be an alternative method.

• Solar Energy
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• v.18 no.3
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• pp.197-203
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• 1998

A 5 ton/day pilot scale two-phase anaerobic digester was constructed and tasted to treat Korean food wastes in Anyang city. The process was developed based on 3 years of lab-scale experimental results on am optimim treatment method for the recovery of biogas and humus. Problems related to food waste are ever Increasing quantity among municipal solid wastes(MSW) and high moisture and salt contents. Thus our food waste produces large amounts of leachate and bed odor in landfill sites which are being exhausted. The easily degradable presorted food waste was efficiently treated in the two-phase anaerobic digestion process. The waste contained in plastic bags was shredded and then screened for the removal of inert material such as fabrics and plastics, and subsequently put into the two-stage reactors. Heavy and light inerts such as bones, shells, spoons and plastic pieces were again removed by gravity differences. The residual organic component was effectively hydrolyzed and acidified in the first reactor with 5 days space time at pH of about 6.5. The second, methanization reactor part of which is filled with anaerobic fillters, converted the acids into methane with pH between 7.4 to 7.8. The space time for the second reactor was 15 days. The effluent from the second reactor was recycled to the first reactor to provide alkalinities. The process showed stable steady state operation with the maximum organic rate of 7.9 $kgVS/m^3day$ and the volatile solid reduction efficiency of about 70%. The total of 3.6 tons presorted MSW containing 2.9 tons of food organic was treated to produce about $230m^3$ of biogas with 70% of methane and 80kg humus. This process is extended to full scale treating 15 tons of food waste a day in Euiwang city and the produced biogas is utilized for the heating/cooling of adjacent buildings.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1277-1279
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• 1994

In the structure of ZnO/nip-SiC: H/metal substrate amorphous silicon (a-Si:H) solar cells, the effects of inserting a rear textured ZnO in the p-SiC:H/metal interface and a graded bandgap buffer layer in the i/p-SiC:H have been analysed by computer simulation. The incident light was taken to have an intensity of $100mW/cm^2$(AM-1). The thickness of the a-Si:H n, ${\delta}$-doped a-SiC:H p, and buffer layers was assumed to be $200{\AA},\;66{\AA}$, and $80{\AA}$, respectively. The scattering coefficients of the front and back ZnO were taken to be 0.2 and 0.7, respectively. Inserting the rear buffer layer significantly increases the open circuit voltage($V_{oc}$) due to reduction of the i/p interface recombination rate. The use of textured ZnO markedly improves collection efficiency in the long wavelengths( above ${\sim}550nm$ ) by back scattering and light confinement effects, resulting in dramatic enhancement of the short circuit current density($J_{sc}$). By using the rear buffer and textured ZnO, the i-layer thickness of the ceil for obtaining the maximum efficiency becomes thinner(${\sim}2500{\AA}$). From these results, it is concluded that the use of textured ZnO and buffer layer at the backside of the ceil is very effective for enhancing the conversion efficiency and reducing the degradation of a-Si:H pin-type solar cells.

• KIEAE Journal
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• v.9 no.6
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• pp.73-80
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• 2009

The purpose of this paper is to suggest rules and regulations about a bike parking facility, With the objective of expanding bike parking facilities for the comfort of bikers. In Korea, the requirements to establish the facility comply with several regulations like laws for the encouragement of bike usages, rules and regulations for the encouragement of bike usages, regulations of Gyeonggi Regional Corporation rules and Korea National Housing Corporation(Korea Land and Housing Corporation) and requirements for the approval of green buildings. Such rules regulate the number of parking spots depending on the number of nearby houses and the size of a parking facility. Amongst the foreign regulations about the facility is 'obligatory regulations for the establishment of a bike parking facility' in Japan. In the United States, all states apply rules about the bike facility to determine the number of bike parking spots in accordance with the number of car parking spots. Comparing Korean rules regarding the bike parking facility with those of foreign governments will give a good insight into the current situation of Korean regulations. In order to investigate the current usage of bikes, 30 houses in Goyang city, 35 schools, 16 retails shops and 20 medical centers were researched. Thereafter, a correlation test between the size of buildings and the number of bike parking spots was carried out. The result of the test indicates that there is a lack of space for bike parking. It is recommended that the bike parking facility be installed with a convenient access to a building in order to increase the rate of bike usages.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.4
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• pp.303-309
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• 2020

This study proposes a crack identification algorithm to analyze the surface condition of porcelain insulators and to efficiently visualize cracks. The proposed image processing algorithm for crack identification consists of two primary steps. In the first step, the brightness is eliminated by converting the image to the lab color space. Then, the background is removed by the K-means clustering method. After that, the optimum image treatment is applied using morphological image processing and median filtering to remove unnecessary noise, such as blobs. In the second step, the preprocessed image is converted to grayscale, and any cracks present in the image are identified. Next, the region properties, such as the number of pixels and the ratio of the major to the minor axis, are used to separate the cracks from the noise. Using this image processing algorithm, the precision of crack identification for all the sample images was approximately 80%, and the F1 score was approximately 70. Thus, this method can be helpful for efficient crack monitoring.

• Journal of the Korean Electrochemical Society
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• v.23 no.2
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• pp.25-38
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• 2020

Photoelectrochemical water splitting has been considered as the most promising technology for generating hydrogen energy. Transition metal dichalcogenide (TMD) compounds have currently attracted tremendous attention due to their outstanding ability towards the catalytic water-splitting hydrogen evolution reaction (HER). Herein, we report the synthesis method of various transition metal dichalcogenide including MoS₂, MoSe₂, WS₂, and WSe₂ nanosheets as excellent catalysts for solar-driven photoelectrochemical (PEC) hydrogen evolution. Photocathodes were fabricated by growing the nanosheets directly onto Si nanowire (NW) arrays, with a thickness of 20 nm. The metal ion layers were formed by soaking the metal chloride ethanol solution and subsequent sulfurization or selenization produced the transition metal chalcogenide. They all exhibit excellent PEC performance in 0.5 M H₂SO₄; the photocurrent reaches to 20 mA cm^-2 (at 0 V vs. RHE) and the onset potential is 0.2 V under AM1.5 condition. The quantum efficiency of hydrogen generation is avg. 90%. The stability of MoS₂ and MoSe₂ is 90% for 3h, which is higher than that (80%) of WS₂ and WSe₂. Detailed structure analysis using X-ray photoelectron spectroscopy for before/after HER reveals that the Si-WS₂ and Si-WSe₂ experience more oxidation of Si NWs than Si-MoS₂ and Si-MoSe₂. This can be explained by the less protection of Si NW surface by their flake shape morphology. The high catalytic activity of TMDs should be the main cause of this enhanced PEC performance, promising efficient water-splitting Si-based PEC cells.

• Sleep Medicine and Psychophysiology
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• v.21 no.2
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• pp.80-84
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• 2014

Introduction: Sleep has numerous important physiological and cognitive functions that may be particularly important to elite athletes. Sleep deprivation can have significant effects on athletic performance. However, there are few published data related to the amount of sleep obtained by elite athletes. We investigated sleep patterns of Korean women golfers using sleep-related questionnaires. Methods: For this study, 98 Korean university women golfers and 46 age- and sex-matched controls were recruited. All subjects were asked to complete the self-administered sleep questionnaire consisting of questions about habitual sleep patterns (sleep onset time, sleep latency, awakening time in the morning, day time napping time), exercise habits, Epworth Sleepiness Scale (ESS), Insomnia Severity Index (ISS), Pittsburgh Sleep Quality Index (PSQI), validation of the Perceived Stress Scale (PSS), and Beck Anxiety Inventory (BAI). Results: The sleep onset time was significantly earlier (pm 23 : $05{\pm}00$ : 52 and 00 : $14{\pm}00$ : 51 ; t = 5.287, p < 0.001), the waking time was later (am 07 : $21{\pm}01$ : 09 and 6 : $35{\pm}00$ : 32; t = -2.715, p = 0.008), the weekday total sleep time was greater ($417.77{\pm}78.18$ minute and $351.52{\pm}77.83$ minute ; t = 4.406, p = 0.001), and the daytime nap time was greater ($77.73{\pm}41.28$ minute and $20.22{\pm}33.03$ minute ; t = 7.623, p < 0.001) in the golf athletes compared to the controls. The PSQI scores were significantly lower, but estimated sleep latency and ESS, ISS, PSS, and BAI scores were not different among the two groups. Conclusion: This study suggests that Korean university women golfers have good sleep patterns resulting in no difference in sleep-related stress compared to age- and sex-matched control students.

• Journal of Embryo Transfer
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• v.28 no.3
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• pp.177-184
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• 2013

The objective of this study was to analyze the accuracy of estrus detection of heat detector and analysis of estrus behavior (mounting and mounted), and the evaluation of conditions required for improving reproductive efficiency in Holstein dairy cows fitted with a estrous detector. The heat detection system consists of estrous detector based on wireless sensor and an electric bulletin board displayed estrus behavior data. When cow mounting other cows, the accuracy of estrus behavior displayed an electric bulletin board were 87.5% (mounting other cows only), 100% (mounting other cows but not standing), 80.0% (mounting other cows with standing for 1~4 seconds), 90.0% (mounting other cows but not standing for 1~4 seconds), 80% (mounting other cows with standing for more than 5 seconds) and 90.0% (mounting other cows but not standing for more than 5 seconds). When cow mounted other cows, the accuracy of estrus behavior displayed an electric bulletin board were 100% (mounted other cows but not standing), 100% (mounted other cows with standing for 1~4 seconds), 100% (mounted other cows but not standing for 1~4 seconds) and 100% (mounted other cows with standing for more than 5 seconds). Circadian distribution of first observed in estrus were 59.1% (am 8~pm 6) and 40.9% (pm 6~am 8). Distribution for the number of estrus behavior were 40.9% (less than 3 times), 36.4% (4~6 times) and 22.7% (more than 4 times). The conception rates relative to interval from first estrus behavior to insemination for estrus periods were 23.1% (less than 11 hours) and 55.6% (12~20 hours).

• Applied Chemistry for Engineering
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• v.22 no.1
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• pp.15-20
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• 2011

Poly[2,3-dimethyl-5,8-dithiophene-2-yl-quinoxaline-alt-9,9-dihexyl-9H-fluorene] (PFTQT) and poly[2,3-dimethyl-5,8-dithiophen-2-yl-quinoxaline-alt-10-hexyl-10H-phenothiazine (PPTTQT) based on 2,3-dimethyl-5,8-dithiophen-2-yl-quinoxaline weresynthesized by Suzuki coupling reaction. All polymers were soluble in common organic solvents such as chloroform, chlorobenzene, o-dichlorobenzene, tetrahydrofuran (THF) and toluene. The maximum absorption wavelength and band gap of PFTQT were 440 nm and 2.30 eV, and PPTTQT were 445 nm and 2.23 eV, respectively. The HOMO and LUMO energy level of PFTQT were -6.05 and -3.75 eV, and PPTTQT were -5,89 and -3.66 eV, respectively. The organic photovoltaic devices based on the blend of polymer and PCBM (1 : 2 by weight ratio) were fabricated. Efficiencies of devices were 0.24% (PFTQT) and 0.16% (PPTTQT), respectively. The short circuit current density ($J_{sc}$), fill factor (FF), and open circuit voltage ($V_{oc}$) of the device with PFTQT were $0.97mA/cm^2$, 29% and 0.86 V, and the device based on PPTTQT were $0.80mA/cm^2$, 28% and 0.71 V, 31% and 0.71 V, respectively, under air mass (AM) 1.5 G and 1 sun condition ($100mA/cm^2$).