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Kiryong Kim,Dongsul Shin,Jong-Pil Lee,Tae-Jin Kim,Dong-Wook Yoo,Hee-Je Kim 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
This paper proposes a control strategy for grid interactive Power Conditioning System (PCS) which has a feedforward voltage control based on grid frequency detection. The PCS should supply the power to the critical load, regardless of the grid condition. In order to provide the power to the critical load continuously, the PCS should operate two modes. One is Grid-Connected mode and the other is Stand-Alone mode. It is important to know the grid condition to decide operation modes. This paper proposes a control method based on the grid frequency to detect the grid condition and consists of a current controller and a feedforward voltage controller. The grid frequency detection is able to reduce the grid fault detection time and a feedforward voltage controller helps voltage regulation fast. This proposed control strategy is verified by the simulation and experimental results.
Analysis of Tritium Compounds in Consumer Goods Using High Precision Gas Mass Spectrometry
Jeong Eun Kim,Min Jun Kim,Bong Gi Kim,Jin Bok Lee,Jin Seog Kim,Sang Ho Lim,Kiryong Hong 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.1
Some consumer goods containing radioactive substances are in circulation and used in everyday life. In accordance with the Nuclear Safety Act, consumer goods with radioactivity are regulated. However, since most consumer goods distributed in Korea have no information that can confirm the amount of radiation, it is necessary to analyze the radiation for safety regulation. Among these consumer goods, GTLS (Gaseous Tritium Light Source) contains gaseous tritium (tritium, written as 3H or T), which is a radioactive material. The gaseous composition ratio in GTLS was analyzed using a precision gas mass spectrometer (Thermo Fisher, model MAT 271). As a result of GTLS analysis, the H2, HD or H3 +(T) or 3He, HT or D2 or He, DT, and T2, which correspond to the mass-to-charge ratio (m/z) 2 to 6 and the air components were detected. In addition, substances corresponding to m/z=24 and m/z=21 were also detected. These were compared with pure CH4 and those fragmentation patterns. The ratios of CT4 (m/z = 24) to CT3 (m/z = 21) and CH4 (m/z = 16) to CH3 (m/z = 15) were compared and they agree within the measurement uncertainty. We also performed additional experiments to separate the water component in the GTLS samples, considering the possibility that the m/z = 21 to m/z = 24 region is tritium compounds based on H2O. Despite the removal of the water components, peaks were detected at m/z=21 and m/z=24. Therefore, we confirmed that the component of m/z = 24 in the GTLS sample was CT4.
Kiryong Kim,Dongsul Shin,Jaecheol Lee,Jong-Pil Lee,Dong-Wook Yoo,Hee-Je Kim 전력전자학회 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.4
This paper proposes a control strategy based on the frequency detection method, comprising a current control and a feed-forward voltage control loop, is proposed for grid-interactive power conditioning systems (PCS). For continuous provision of power to critical loads, PCS should be able to check grid outages instantaneously. Hence, proposed in the present paper are a frequency detection method for detecting abnormal grid conditions and a controller, which consists of a current controller and a feedforward voltage controller, for different operation modes. The frequency detection method can detect abnormal grid conditions accurately and quickly. The controller which has current and voltage control loops rapidly helps in load voltage regulation when grid fault occurs by changing reference and control modes. The proposed seamless transfer control strategy is confirmed by experimental results.
Kim, Joonghan,Hong, Kiryong,Kim, Hyun Kook,Lee, Yoon Sup,Kim, Tae Kyu American Chemical Society 2013 Journal of chemical theory and computation Vol.9 No.2
<P>The relativistic effects are essential for a complete understanding of the reactions involving heavy transition metal cations with hydrocarbons. Despite this, spin–orbit coupling (SOC) <I>along</I> the reaction pathway is rarely considered. In this work, we demonstrate an unusual SOC on the chemical reactivity of a reaction of Os<SUP>+</SUP> with methyl fluoride (CH<SUB>3</SUB>F) using density functional theory (DFT), high-level ab initio, and spin–orbit multiconfigurational ab initio methods. With the inclusion of the SO effect in the relevant potential energy surfaces (PESs), C–H bond activation by an Os<SUP>+</SUP> cation occurs readily <I>via</I> almost barrierless (about 2 kcal/mol) PESs of the SO coupled ground state. In contrast, a substantial reaction barrier was observed for C–F bond activation. The calculated results are in line with recent systematic experimental findings for reactions of transition metal cations with CH<SUB>3</SUB>F. These results show that the SO effect can facilitate specific bond activation in chemical reactions associated with catalytic transition metal cations.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jctcce/2013/jctcce.2013.9.issue-2/ct301041u/production/images/medium/ct-2012-01041u_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ct301041u'>ACS Electronic Supporting Info</A></P>
Kim, Jeongho,Kim, Kyung Hwan,Oang, Key Young,Lee, Jae Hyuk,Hong, Kiryong,Cho, Hana,Huse, Nils,Schoenlein, Robert W.,Kim, Tae Kyu,Ihee, Hyotcherl The Royal Society of Chemistry 2016 Chemical communications Vol.52 No.19
<P>Characterization of transient molecular structures formed during chemical and biological processes is essential for understanding their mechanisms and functions. Over the last decade, time-resolved X-ray liquidography (TRXL) and time-resolved X-ray absorption spectroscopy (TRXAS) have emerged as powerful techniques for molecular and electronic structural analysis of photoinduced reactions in the solution phase. Both techniques make use of a pump-probe scheme that consists of (1) an optical pump pulse to initiate a photoinduced process and (2) an X-ray probe pulse to monitor changes in the molecular structure as a function of time delay between pump and probe pulses. TRXL is sensitive to changes in the global molecular structure and therefore can be used to elucidate structural changes of reacting solute molecules as well as the collective response of solvent molecules. On the other hand, TRXAS can be used to probe changes in both local geometrical and electronic structures of specific X-ray-absorbing atoms due to the element-specific nature of core-level transitions. These techniques are complementary to each other and a combination of the two methods will enhance the capability of accurately obtaining structural changes induced by photoexcitation. Here we review the principles of TRXL and TRXAS and present recent application examples of the two methods for studying chemical and biological processes in solution. Furthermore, we briefly discuss the prospect of using X-ray free electron lasers for the two techniques, which will allow us to keep track of structural dynamics on femtosecond time scales in various solution-phase molecular reactions.</P>