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Jaewan Im,Sanghun Lee,Insol Jo,Jeong Won Kang,Jeong Won Kang 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.107 No.-
This study investigated the use of ionic liquids such as 1-butyl-3-methylimidazolium chloride, 4-butyl-4-methyl morpholinium chloride, 1-butyl-1-methylpiperidinium chloride, and 1,3-dimethylimidazoliummethylphosphite to dissolve cellulose, hemicellulose, and lignin biomass, as alternatives to highly toxicorganic solvents. The biomass treated with the ionic liquids is characterized by scanning electron microscopy,X-ray diffraction, thermogravimetric analysis, and Fourier-transform infrared spectroscopy. The Xraydiffraction results revealed that most of the biomass treated with ionic liquids had low crystallinityafter treatment with the ionic liquids. Thermogravimetric analysis confirmed that the pyrolysis temperatureof the biomass treated with the ionic liquid decreased. However, it was found that the pyrolysistemperature of the biomass was increased again after the ionic liquid was washed with an antisolvent. This result was interpreted using Fourier-transform infrared spectroscopy to show that the O–H hydrogenbonding of cellulose was restored. The experimental results from this study can help provide a betterunderstanding of the biomass regeneration mechanism of ionic liquids and increase the applicability ofbiomass in various fields.
JaeWan Choi,Hyun-Soo Seol,Ju Lee 대한전기학회 2018 Journal of Electrical Engineering & Technology Vol.13 No.2
In this paper, interior permanent magnet synchronous motor (IPMSM) design for sensorless drive, considering magnetic neutral point shift according to magnetic saturation, has been proposed. Sensorless control was divided into a method based on inductance and a method based on back induced voltage. Because induced voltage is very small at zero or low speed, error in rotor initial position estimation may occur. Using the ratio of saliency addresses this problem. When using highfrequency injections at low speed, the rotor’s initial position is estimated at the smallest portion of the inductance. IPMSM has the minimum inductance at the d-axis. However, if magnetic saturation leads to magnetic neutral point variation, following the load current change, there is a change in the minimum point of inductance. In this case, it can lead to failure of initial rotor position estimation. As a result, it is essential that the blocking design has an inductance minimum point shift. As such, in this study, an IPMSM design method, by blocking magnetic neutral point change, has been proposed. After determining the inductance profile based on the finite element analysis (FEA), the results of proposed method were verified.
Comprehensive Asset Pricing Tests in the Korean Stock Market
Jaewan Bae,Jangkoo Kang,Jun Park 한국재무학회 2023 한국재무학회 학술대회 Vol.2023 No.11
We examine the empirical performance in the Korean stock market of three new asset pricing factor models: the Stambaugh–Yuan (2017) mispricing factor model, the Daniel et al. (2020) three-factor model, and the Hou et al. (2021) q5-factor model. We find that all factors in these factor models have significantly positive risk premiums and are not explained by the Fama– French six-factor model. Compared to other prevalent models, the q5 model shows the highest maximum Sharpe ratio, mainly due to its profitability and expected growth factors. Further, the q5 model exhibits superior performance in explaining the returns of 97 anomaly portfolios in the Korean market.
Frequency Control of Converter Fed Micro-grid for Flexible Frequency Operation
Jaewan Suh,Dong-Hee Yoon,Yoon-Sung Cho,Gilsoo Jang 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
Recently, uncertainty in power system increase rapidly. On the other hand, the new construction of power plant or transmission line runs into opposition by the resistance of the local people. And those makes the power system operation more difficult. Because of those challenges new methodologies are required to gain the flexibility of the power grids. Flexible frequency operation provides customized frequency through BTB HVDC, overall system is operated in relaxed frequency regulation. In this operation, sensitive loads which need high quality electric power are operated as micro-grid by BTB HVDC. This paper presents control of converter which connect microgrid to power system in flexible frequency operation. In test system, main power system is operated in flexible frequency regulation and micro gird is operated in high quality frequency. Simulation result shows contribution of proposed control strategy for main-grid frequency control in flexible operation.
Jaewan Kim,Heung-Ryoul Noh 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.76 No.6
We present analytical solutions for the second-order correlation function [g(2)(τ)] for light scattered from a two-level atom driven by laser light with arbitrary detuning and the Rabi frequency. By solving the optical Bloch equations for a two-level atom, we obtain analytical solutions for the populations that are subsequently used for calculating g(2)(τ). We also obtain g(2)(τ) for special cases, such as zero detuning or weak laser intensity, directly from the general analytical solutions for g(2)(τ).