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Measurement-based Static Load Modeling Using the PMU data Installed on the University Load
Sangwook Han,Jihun Kim,Byongjun Lee,Hwachang Song,Hongrae Kim,Jeong-hoon Shin,Tae-kyun Kim 대한전기학회 2012 Journal of Electrical Engineering & Technology Vol.7 No.5
Load modeling has a significant influence on power system analysis and control. In recent years, measurement-based load modeling has been widely practiced. In the load modeling algorithm, the model structure is determined and the parameters of the established model are estimated. For parameter estimation, least-squares optimization method is applied. The model parameters are estimated so that the error between the measured values and the predicted values is to be minimized. By introducing sliding window concept, on-line load modeling method can be performed which reflects the dynamic behaviors of loads in real-time. For the purpose of data acquisition, the measurement system including PMU is implemented in university level. In this paper, case studies are performed using real PMU data from Korea Univ. and Seoul National University of Science and Technology. The performances of modeling real and reactive power behaviors using exponential and ZIP load model are evaluated.
Han, Sangwook,Hwang, Taewoo,Oh, Ilyeong,Choi, Moonseok,Moon, Young Hoon Elsevier 2018 Journal of materials processing technology Vol.256 No.-
<P>A tailor-rolled blank is a semi-finished part that can be used to produce stamping parts with continuous thickness variations. This study investigates a cold manufacturing process to fabricate a TRB with variable thickness variations in both the longitudinal and latitudinal directions. The effect of the rolling process on the characteristics of the transition zone and the deformation behaviors of the blanks were investigated using various processing conditions. The dimensional variations at the transition zones were analyzed based on the cross-sectional thickness profiles of the formed blanks. The results show that manufacturing such a TRB requires an extra process to reduce dimensional instabilities caused by superimposed transition zones in both directions. To manufacture sound blanks with acceptable dimensions, this study proposes a trial method that uses blanks with circular and square holes instead of solid blank.</P>
Han, Gill Sang,Yun, Yeonghun,Kim, Min Hee,Han, Se-Hoon,Jung, Hyun Suk,Lee, Sangwook Elsevier 2018 Materials letters Vol.228 No.-
<P><B>Abstract</B></P> <P>In this study, we report the effects of Na<SUP>+</SUP> diffusion into TiO<SUB>2</SUB> during thermal annealing on TiO<SUB>2</SUB> photocatalysis. After annealing at 500 °C for 1 h, the photoactivity of colloidal sol-based crystalline TiO<SUB>2</SUB> is almost similar regardless of substrates. Interestingly, after the annealing the photoactivity of polymeric sol-based amorphous TiO<SUB>2</SUB> thin film on soda lime glass (SLG) is significantly reduced compared to that on quartz. We observed that Na<SUP>+</SUP> does not easily bond with TiOTi in crystalline TiO<SUB>2</SUB>, while large amount of TiONa bonds are formed in the amorphous TiO<SUB>2</SUB> on SLG during crystallization at 500 °C. Our results suggest that the control of TiO<SUB>2</SUB> photoactivity has applications in improving photo-stability of various optoelectronic devices.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Crystalline TiO<SUB>2</SUB> on SLG exhibits similar photoactivity with that on quartz, after annealing. </LI> <LI> Amorphous TiO<SUB>2</SUB> on SLG exhibits lower photoactivity than that on quartz, after annealing. </LI> <LI> Na<SUP>+</SUP> does not easily bond with TiOTi in crystalline TiO<SUB>2</SUB>. </LI> <LI> TiONa bonds are formed in amorphous TiO<SUB>2</SUB> on SLG during crystallization. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
( Sangwook Han ),( Donghyuk Kim ),( Seongrae Kim ),( Jongmyoung Kim ),( Dalyong Mun ),( Koichi Morita ),( Wonho Kim ) 한국고무학회 2021 엘라스토머 및 콤포지트 Vol.56 No.1
The vulcanizate structure of silica-filled compounds is affected by the filler-rubber interaction (FRI) due to the silica-rubber coupling reaction and the chemical crosslink density (CCD) of the matrix rubber. In this study, the vulcanizate structure changes of silica-filled compounds according to the silane and sulfur variation were quantitatively analyzed using the Flory-Rehner and Kraus equations. In efficiency vulcanization (EV) conditions with low sulfur content, FRI increased when the bis-[3-(triethoxysilyl)propyl]tetrasulfide (TESPT) content increased, and the CCD clearly decreased. By contrast, in semi-EV conditions with high sulfur content, as TESPT content increased, the FRI increased the same way EV conditions, but the CCD was unchanged. Based on these results, it was confirmed that FRI of the silica-filled compounds increased as TESPT content increased, but CCD decreased or retained similar values according to the vulcanization system, indicating that the formation reaction of FRI was preferred over CCD.
Real Time Wide Area Voltage Stability Index in the Korean Metropolitan Area
Sangwook Han,Byongjun Lee,Sangtae Kim,Younghwan Moon 대한전기학회 2009 Journal of Electrical Engineering & Technology Vol.4 No.4
Through the development of phasor measurement units (PMU), various aspects of power system dynamic behavior could be monitored and diagnosed. Monitoring dynamic voltage stability has become one of the achievements we can obtain from PMUs. It is very important to select the most appropriate method for the Korea Electric Power Corporation (KEPCO) system since there are many voltage stability indices. In this paper, we propose an advanced WAVI (Wide Area Voltage Stability) that is well suited for the purposes of monitoring the dynamic voltage stability of KEPCO’s PMU installation plan. The salient features of the proposed index are: i) it uses only PMU measurements without coupling with EMS data; ii) it is computationally unburdened and can be applied to real-time situations. The proposed index is applied to the KEPCO test system and the results show that it successfully predicts voltage instability through comparative studies.
Taxonomic Review of the Genus Hemicrepidius Germar 1839 (Coleoptera: Elateridae) in Korea
Taeman Han,Hae Chul Park,Young Bo Lee,Sangwook Park,Seunghwan Lee 한국응용곤충학회 2012 한국응용곤충학회 학술대회논문집 Vol.2012 No.10
We reviewed the Korean species belonging to the genus Hemicrepidius. Of the previously recorded five species, the specimens known as H. (s. str.) secessus secessus (Candèze, 1873) are confirmed as the misidentification of H. oblongus (Solsky, 1870). The status of H. (s. str.) secessus hallaensis Kishii 2002 is suggested to be raised to species level. We also propose three new species, H. (s. str.) sp1 nov., H. (s. str.) sp2 nov., H. (Miwacrepidius) sp1 nov. from Korea. In Hemicrepidius sensu strito, molecular approaches based on the species recognized from Korea, Russia, and Japan using COI and 16S rRNA genes strongly support that all Korean species and the Russian specimens of H. oblongus are clustered into a monophyletic group, whereas Japanese species might be early and independently divided from the former.