• Applied Chemistry for Engineering
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• v.33 no.2
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• pp.159-165
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• 2022

To enhance the photocatalytic activities of WO₃ photocatalysts, fluorine doping was performed to induce the oxygen vacancies. Both plasma and direct vaper fluorination were carried out for fluorine doping, and photocatalytic activities were examined by using methylene blue dye. Oxygen vacancies of the plasma and direct vaper fluorinated WO₃ photocatalysts were measured to be 14.65 and 18.59%, which increased to about 23 and 56% at pristine WO₃ photocatalysts. The degradation efficiency of methylene blue was also determined about 1.7 and 3.4 times higher than pristine WO₃ photocatalysts, respectively, depending on oxygen vacancies increased. In addition, it was confirmed that the bandgap process energy decreased from 2.95 eV to 2.64 and 2.45 eV after fluorine doping. From this result, it is considered that the direct vaper fluorination has an advantage for increasing the photocatalytic activities of WO₃ compared to that of the plasma fluorination.

• The Journal of the Convergence on Culture Technology
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• v.8 no.5
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• pp.697-703
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• 2022

Due to the recent economic downturn caused by Covid-19 and the unstable international situation, many investors are choosing the derivatives market as a means of investment. However, the derivatives market has a greater risk than the stock market, and research on the market of market participants is insufficient. Recently, with the development of artificial intelligence, machine learning has been widely used in the derivatives market. In this paper, reinforcement learning, one of the machine learning techniques, is applied to analyze the scalping technique that trades futures in minutes. The data set consists of 21 attributes using the closing price, moving average line, and Bollinger band indicators of 1 minute and 3 minute data for 6 months by selecting 4 products among futures products traded at trading firm. In the experiment, DNN artificial neural network model and three reinforcement learning algorithms, namely, DQN (Deep Q-Network), A2C (Advantage Actor Critic), and A3C (Asynchronous A2C) were used, and they were trained and verified through learning data set and test data set. For scalping, the agent chooses one of the actions of buying and selling, and the ratio of the portfolio value according to the action result is rewarded. Experiment results show that the energy sector products such as Heating Oil and Crude Oil yield relatively high cumulative returns compared to the index sector products such as Mini Russell 2000 and Hang Seng Index.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.4
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• pp.351-361
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• 2023

The purpose of this paper is to help those who research and develop solar cells in university laboratories and industrial sites understand the most basic and important quantum efficiency measurement and analysis method in analyzing solar cell performance. Starting with the definition of quantum efficiency, we calculate the theoretical current density according to the band gap of the solar cell material from the solar spectrum, along with a detailed introduction to the measurement and analysis methods, and measure and analyze the theoretical current density and quantum efficiency. We discuss in depth how to analyze the performance of solar cells through Quantum efficiency measurement and analysis of solar cells is a very useful method that can give intuition to solar cell performance analysis as it can analyze solar cells according to depth (front emitter, bulk, rear surface). Students and researchers who study solar cells with a deep understanding of theoretical current density and quantum efficiency measurement analysis are expected to use it as a basis for analyzing solar cell performance.

• Clinical and Experimental Pediatrics
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• v.49 no.9
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• pp.946-951
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• 2006

Purpose : The purpose of this study was to demonstrate the effectiveness of combined exercise for 12 weeks on the adiponectin and obesity related variables in overweight and obese children. Methods : Eighteen children in 5th grade in a certain elementary school in Busan were recruited. They were all overweight or obese children(more than 85 percentile in body mass index). Nine children in the experimental group were given exercises consisting of walking and band resistant training for 12 weeks. Auxological data(including height, weight and body fat mass) and laboratory data (fasting blood sugar, insulin, adiponectin) were checked at baseline and at the 1 week, and at the 4 weeks and 12 weeks stages of their exercise program. Insulin resistance and sensitivity were evaluated indirectly using HOMA index and QUICKI index. Results : Adiponectin gradually decreased until the 4 weeks point and gradually increased thereafter to the starting level at the 12 weeks stage. Body weight, body mass index(BMI) and HOMA index significantly decreased more at the 1 week, 4 weeks, and 12 weeks stages in the experimental group than in the control group. Body fat mass significantly decreased at 12 weeks. The change of insulin was significantly correlated with changes of body weight and BMI. But there was no correlation between changes of adiponectin and changes of insulin. Conclusion : Exercise seems to effect the adiponectin concentration. And it might be assumed that exercise increases the adiponectin concentration if it is continued for long time(may be more than 12 weeks). More studies may be necessary to draw that conclusion.

• Korean Journal of Remote Sensing
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• v.36 no.5_1
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• pp.679-692
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• 2020

We coupled a CFD model to the WRF-Chem model (WRF-CFD model) and investigated the characteristics of flows and carbon monoxide (CO) distributions in a building-congested district. We validated the simulated results against the measured wind speeds, wind directions, and CO concentrations. The WRF-Chem model simulated the winds from southwesterly to southeasterly, overestimating the measured wind speeds. The statistical validation showed that the WRF-CFD model simulated the measured wind speeds more realistically than the WRF-Chem model. The WRF-Chem model significantly underestimated the measured CO concentrations, and the WRF-CFD model improved the CO concentration prediction. Based on the statistical validation results, the WRF-CFD model improved the performance in predicting the CO concentrations by taking complicatedly distributed buildings and mobiles sources of CO into account. At 04 KST on May 22, there was a downdraft around the AQMS, and airflow with a relatively low CO concentration was advected from the upper layer. Resultantly, the CO concentration was lower at the AQMS than the surrounding area. At 15 KST on May 22, there was an updraft around the AQMS. This resulted in a slightly higher CO concentration than the surroundings. The WRF-CFD model transported CO emitted from the mobile sources to the AQMS measurement altitude, well reproducing the measured CO concentration. At 18 KST on May 22, the WRF-CFD model simulated high CO concentrations because of high CO emission, broad updraft area, and an increase in turbulent diffusion cause by wind-shear increase near the ground.

• Korean Journal of Optics and Photonics
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• v.13 no.3
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• pp.197-203
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• 2002

The TiO$_2$ coating solutions were synthesized with different concentrations (T1-0.7N, T2-2.0N) of hydrochloric acid used as catalyst. and TiO$_2$ thin films were prepared by sol-gel dip coating. Their structural and optical properties were examined as a function of calcination temperature. XRD results showed that T1 thin films calcined at 400~80$0^{\circ}C$ had the anatase phase, while those calcined at 100$0^{\circ}C$ had the rutile phase. T2 thin films calcined at 40$0^{\circ}C$ and $600^{\circ}C$ had the anatase phase, with the rutile phase for calcination at 80$0^{\circ}C$. Crystallinity of T2 thin films was superior to that of T1 thin films. The crystallite size of TiO$_2$ thin films increased with increasing calcination temperature, and the crystallite size of anatase phase in T2 thin films was larger than that in T1 thin films, but the crystallite size of rutile phase in T2 thin films was smaller. The surface morphology of the films showed that the films were formed more densely in the rutile phase than in the anatase phase, this phenomenon appeared conspicuously in T2 thin films. The transmittance of the samples with thin films on quartz glass calcined at 100$0^{\circ}C$ was significantly reduced at wavelength range about 300-700 nm due to the increased absorption originating from the change of crystallite phase and composition of the films and the scattering effect originating from increasing crystallite size. The refractive index of TiO$_2$ thin films increased, and hence the film thickness as well as the porosity of TiO$_2$ thin films decreased with increasing calcination temperature. Furthermore, the refractive index of T2 thin films was higher than T1 thin films, and porosity of T2 films was lower.

• Korean Chemical Engineering Research
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• v.55 no.1
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• pp.93-98
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• 2017

This experiment investigated characteristic changes in a $Cu_2ZnSnS_4$(CZTS) solar cell by applying a $Zn(O_x,S_{1-x})$ butter layer with various compositions on the upper side of the absorber layer. Among the four single layers such as $Zn(O_{0.76},S_{0.24})$, $Zn(O_{0.56},S_{0.44})$, $Zn(O_{0.33},S_{0.67})$, and $Zn(O_{0.17},S_{0.83})$, the $Zn(O_{0.76},S_{0.24})$ buffer layer was applied to the device due to its bandgap structure for suppressing electron-hole recombination. In the application of the $Zn(O_{0.76},S_{0.24})$ buffer layer to the device, the buffer layer in the device showed the composition of $Zn(O_{0.7},S_{0.3})$ because S diffused into the buffer layer from the absorber layer. The $Zn(O_{0.7},S_{0.3})$ buffer layer, having a lower energy level ($E_V$) than a CdS buffer layer, improved the $J_{SC}$ and $V_{OC}$ characteristics of the CZTS solar cell because the $Zn(O_{0.7},S_{0.3})$ buffer layer effectively suppressed electron-hole recombination. A substitution of the CdS buffer layer by the $Zn(O_{0.7},S_{0.3})$ buffer layer improved the efficiency of the CZTS solar cell from 2.75% to 4.86%.

• The Korean Journal of Food And Nutrition
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• v.20 no.1
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• pp.79-87
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• 2007

An evaluation of the influence of nutritional health camp for in obese elementary students was assessed. Anthropometric measurement, 24-hour recall of dietary intake, MMTIC(Murphy-Meisgeier Type Indicator for Children) and questionnaire response(nutritional knowledge, nutritional attitude, and self-satisfaction) was documented in 43 obese elementary students(29 boys and 14 girls). The mean age of the elementary students was 11.2 years. The mean height, body weight and obesity index was 144.7 cm, 55.4 kg and 41.0% in boys, and 136.1 cm, 45.2 kg, 40.0% in girls. The mean energy intake was 1,522.4 kcal in boys and 1,494.9 kcal in girls. The subjects taking less than estimated average requirement(EAR) for vitamin ${B_2}$, folate, vitamin C and calcium was over 70%. A considerable number of students(65.1%) showed U band(undetermined character). The students demonstrated a propensity towards increased average nutritional knowledge and self-satisfaction after attending the nutritional health camp. In addition, a significant increase in average nutritional attitude was observed(p<0.001). The results of this study suggest that nutritional health camp positively influenced the nutritional attitude of elementary students.

• Journal of the Korean Vacuum Society
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• v.17 no.4
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• pp.359-364
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• 2008

We have investigated optical and structural properties of $Al_{0.3}Ga_{0.7}N$/GaN and $Al_{0.3}Ga_{0.7}N/GaN/Al_{0.15}Ga_{0.85}N/GaN$ heterostructures (HSs) grown by metal-organic chemical vapor deposition, by means of Hall measurement, high-resolution X-ray diffraction, and temperature- and excitation power-dependent photoluminescence (PL) spectroscopy. A strong GaN band edge emission and its longitudinal optical phonon replicas were observed for all the samples. At 10 K, a 2DEG-related PL peak located at ${\sim}\;3.445\;eV$ was observed for $Al_{0.3}Ga_{0.7}N$/GaN HS, while two 2DEG peaks at ${\sim}\;3.42$ and ${\sim}\;3.445\;eV$ were observed for $Al_{0.3}Ga_{0.7}N/GaN/Al_{0.15}Ga_{0.85}N/GaN$ HS due to the additional $Al_{0.15}Ga_{0.85}N$ layers. Moreover, the emission intensity of the 2DEG peak was higher in $Al_{0.3}Ga_{0.7}N/GaN/Al_{0.15}Ga_{0.85}N/GaN$ HS than in $Al_{0.3}Ga_{0.7}N$/GaN HS probably due to an effective confinement of the photo-excited holes by the additional $Al_{0.15}Ga_{0.85}N$ layers. The 2DEG-related emission intensity decreased with increasing temperature and disappeared at temperatures above 150 K. To investigate the origin of the new 2DEG peaks, the energy-band structure for multiple AlGaN/GaN HSs were simulated and compared with the experimental data. As a result, the observed high- and low-energy peaks of 2DEG can be attributed to the spatially-separated 2DEG emissions formed at different AlGaN/GaN heterointerfaces.

• 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 ($100mA/cm^2$).