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Crystal engineering and characterization of a structure-H ionic clathrate hydrate
Shin, Kyuchul,Moudrakovski, Igor L.,Udachin, Konstantin A.,Ratcliffe, Christopher I.,Ripmeester, John A. National Research Council 2015 Canadian journal of chemistry Vol.93 No.8
<P> Ionic hydrates are known to form numerous clathrate structures in which either the cations or anions sit in cages and the counterions are incorporated into the water framework. Due to the inclusion of the ionic species, such ionic clathrate hydrates not only show many peculiar features such as metal ion encagement and superoxide ion generation, but also exhibit notable physicochemical properties such as outstanding ionic conductivity and thermal stability. Thus, the ionic clathrate hydrates are considered for their potential applicability in various fields, including those that involve solid electrolytes, gas sensors, and energy storage. In this study, we report the design, synthesis, and characterization of the first ionic clathrate hydrate of the hexagonal structure-H (Str.H) crystal type. Diethyl-dimethyl-ammonium hydroxide hydrate was synthesized with CH4 and Xe as help gases, and the crystal structure was identified by powder X-ray diffraction analysis. Further confirmation of the formation of Str.H was obtained from Raman spectroscopy and <SUP>13</SUP>C, <SUP>129</SUP>Xe, and <SUP>2</SUP>H solid-state NMR spectroscopy. From <SUP>13</SUP>C NMR and ab initio calculations, it was shown that the quaternary ion occupies the large cage of Str.H with a conformation different from that in solution, due to constraints imposed by the dimensions of the cage. The H deficiency introduced by substitution of OH<SUP>-</SUP> for a water molecule appears, from <SUP>129</SUP>Xe NMR, to be disordered over the framework, and, from <SUP>2</SUP>H NMR, to substantially increase the rate of reorientational mobility of the D atoms in the framework, over that observed for a Str.I hydrate and for ice. The Str.H hydrates are commonly more stable than other structures, thus the present findings on the ionic Str.H clathrate hydrate may offer a new approach for improving the stability of ionic clathrate hydrates for their practical application. </P>
Structural identification of DClO4 clathrate hydrates: Neutron powder diffraction analysis
Kyuchul Shin,Minjun Cha,Wonhee Lee,Huen Lee 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.5
Acid clathrate hydrates which do not contain hydrogen fluoride impurities are believed to include several vacancy sites in the host lattice for protonation of the framework. In this work, the crystal structures of a DClO4· 5.5D2O solid at various temperatures were identified by the direct space method and Rietveld refinement of the neutron powder diffraction patterns. A position change of vacancy sites accompanying the shift of ClO4 − guest ions in the 51262 cavity toward the center of the cavity from the edge of the hexagonal face was observed at about 180 K, and this phenomenon is expected to result in weakened host proton-guest anion interactions and to induce a phase transition related to the proton conduction behavior of the DClO4 clathrate. The present findings explain the proton dynamics of the hydrogen fluoride-free acid clathrate hydrates and provide a better understanding of the nature of guest-host interactions occurring on ion-doped hydrate materials.
Discrete Magnetic Patterns of Nonionic and Ionic Clathrate Hydrates
Shin, Kyuchul,Cha, Minjun,Choi, Sukjeong,Dho, Joonghoe,Lee, Huen American Chemical Society 2008 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.130 No.51
<P>In this communication, the charge transfer phenomenon from ionic host lattice to nonionic guest molecule was observed by magnetization and Raman spectroscopy measurements for nonionic and ionic clathrate hydrates. The present findings on the magnetic property of nonionic guest molecules in ionic hydrate might provide important information on the unrevealed nature of host-guest interaction in ionic hydrate systems. The charge transfer occurring between ionic host and nonionic guest molecules will open up interesting application fields for ionized hydrate complexes and activated secondary guest molecules.</P>
Direct observation of atomic hydrogen generated from the water framework of clathrate hydrates
Shin, Kyuchul,Cha, Minjun,Kim, Hyungjun,Jung, Yousung,Kang, Young Soo,Lee, Huen Royal Society of Chemistry 2011 Chemical communications Vol.47 No.2
<P>We demonstrate that the N<SUB>2</SUB>-induced ionic hydrate system can be a solution to produce the hydrogen radical from water without direct energy sources such as H<SUB>2</SUB> and CH<SUB>4</SUB>.</P> <P>Graphic Abstract</P><P>We demonstrate that the N<SUB>2</SUB>-induced ionic hydrate system can be a solution to produce the hydrogen radical from water without direct energy sources. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0cc02616f'> </P>
Shin, Kyuchul,Cha, Minjun,Lee, Wonhee,Seo, Yutaek,Lee, Huen American Chemical Society 2014 The Journal of Physical Chemistry Part C Vol.118 No.28
<P>The unique host–guest interactions of ionic clathrate hydrates, as distinct from those of other nonionic clathrate hydrates, need to be investigated to understand their inherent physicochemical features, but direct observation of ionic host geometry has not yet been attempted. In this study, we first report the distortions of the water–water connection in the charged cages caused by orbital mixing between a paramagnetic guest and an ion-doped host, and by electrostatic repulsion between the cationic host and guest via the direct observation with using synchrotron high-resolution powder diffraction analysis. The present findings well explain the mechanisms of unique phenomena occurring in ionic clathrate hydrates with paramagnetic guests.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2014/jpccck.2014.118.issue-28/jp504656x/production/images/medium/jp-2014-04656x_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp504656x'>ACS Electronic Supporting Info</A></P>
Shin, Kyuchul,Cha, Minjun,Lee, Wonhee,Kim, Hyungjun,Jung, Yousung,Dho, Joonghoe,Kim, Jinkwon,Lee, Huen American Chemical Society 2011 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.133 No.50
<P>Clathrate hydrates are a highly prospective material in energy and environmental fields, but the inherent nature of inclusion phenomena occurring in the stacked water cages has not been completely resolved yet. Investigating the magnetism of guest molecules is a new experimental approach in clathrate hydrate research to open the possibility of icy magnetic applications as a novel material as well as to understand the unrevealed host-guest interactions in icy inclusion compounds. In this study, we observed an indirect spin coupling between encaged dioxygen molecules via a nonmagnetic water framework through the measurement of guest magnetization. This spin coupling is reminiscent of superexchange coupling between magnetic ions through intervening oxygens in antiferromagnetic oxides, such as MnO and CoO. Theoretical calculations revealed that OH(-) incorporated in the framework induced the mixing of perpendicular π* orbitals of two distant dioxygens and that ammonia doping into the hydrate cage leads to a longer lifetime of that orientation.</P>
Thermal Expansivity of Ionic Clathrate Hydrates Including Gaseous Guest Molecules
Shin, Kyuchul,Lee, Wonhee,Cha, Minjun,Koh, Dong-Yeun,Choi, Yong Nam,Lee, Heeju,Son, Bae Soon,Lee, Seongsu,Lee, Huen American Chemical Society 2011 The Journal of physical chemistry B Vol.115 No.5
<P>Although thermal expansion is a key factor in relation to the host−guest interaction of clathrate hydrates, few studies have investigated the thermal behavior of ionic clathrate hydrates. The existence of ionic species in these hydrates creates a unique host−guest interaction compared to that of nonionic clathrate hydrates. It was revealed that X-ray diffraction cannot be used for research of tetramethylammonium hydroxide clathrate hydrates due to damage of the cations by the X-ray, which results in abnormal thermal expansion of the ionic clathrate hydrates. Hence, in the present work, the thermal expansivities of binary sII Me<SUB>4</SUB>NOD·16D<SUB>2</SUB>O and sI DClO<SUB>4</SUB>·5.5D<SUB>2</SUB>O were measured by neutron powder diffraction (NPD) in order to shed light on their thermal behavior. General correlations for the thermal behaviors of given structures were established and lattice expansions depending on the guests were compared between ionic and nonionic clathrate hydrates. The peculiar change in the thermal expansivity of binary DClO<SUB>4</SUB>·5.5D<SUB>2</SUB>O was also considered in relation to the host−guest configuration.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpcbfk/2011/jpcbfk.2011.115.issue-5/jp110737q/production/images/medium/jp-2010-10737q_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp110737q'>ACS Electronic Supporting Info</A></P>
지능형 드라이브 IC를 이용한 전자 트로틀 제어 시스템 개발
신규철(Kyuchul Shin),천동필(Dong pil Chun),이우택(Wootaik Lee) 한국자동차공학회 2005 한국자동차공학회 Symposium Vol.- No.-
This paper presents an electronic throttle controller(ETC) using Intelligent Driver IC. ETC is a DC servo system that controls the throttle plate precisely. The conventional motor controller needs both a microcontroller and the external device such as motor driver IC , communication IC, and signal interface IC. An intelligent Driver IC integrates a microcontroller and external devices into a single chip. It is easy to install the intelligent IC in ETC or other DC servo systems. The microcontroller of intelligent Driver IC is a low cost microcontroller which has no floating-point calculation capability and low computing speed. Therefore ETC has a simple and compact control algorithm. The control algorithm of ETC is a modified proportional and integral control. ETC has nonlinear static friction which is caused by the mechanical structure of ETC. This nonlinear friction is overcome by the proportional controller which has a gain scheduling method. The integral controller is designed not only to minimize the steady state error, but also to avoid the windup effect. The experimental result shows a good performance.
한국인 영어학습자와 영어원어민이 발화한 영어 약화모음에 관한 연구
신승훈(Shin Seung-Hoon),윤남희(Yoon Nam-Hee),윤규철(Yoon Kyuchul) 한국음성학회 2011 말소리와 음성과학 Vol.3 No.4
Flemming and Johnson (2007) claim that there is a fundamental distinction between the mid central vowel [?] and the high central vowel [?] in that [?] occurs in an unstressed word-final position while [?] appears elsewhere. Compared to English counterparts, Korean [?] and [?] are full vowels and they have phonemic contrast. The purpose of this paper is to explore the acoustic quality of two English reduced vowels produced by Korean learners and native speakers of English in terms of their two formant frequencies. Sixteen Korean learners of English and six native speakers of English produced four types of English words and two types of Korean words with different phonological and morphological patterns. The results show that Korean learners of English produced the two reduced vowels of English and their Korean counterparts differently in Korean and English words.