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Core/Shell Structure of Ferroelectric (Ba0.94Ca0.06)TiO3 Grains
Yoshihiro Iwahori,Hiroshi Tanaka,Masaki Takata,Yoshihiro Terado,Chikako Moriyoshi,Yoshihiro Kuroiwa 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.2
The crystal structure of ferroelectric (Ba0.94Ca0.06)TiO3 (BCT) with small grains on an average of 1-μm in size has been investigated by using high-energy synchrotron-radiation powder-diffraction. A core/shell structure model, in which the grain consists of a core with tetragonal symmetry covered all over with a thin tetragonal shell with low tetragonality, is proposed and provides a markedly contrast with the core/shell structure of pure BaTiO3, which is generally known to have a shell with cubic symmetry. The higher permittivity of BCT is attributed to the characteristic shell structure with tetragonal symmetry. A change in the chemical bonding nature of BCT on the ferroelectric phase transition is clearly demonstrated in the electron charge density map. The crystal structure of ferroelectric (Ba0.94Ca0.06)TiO3 (BCT) with small grains on an average of 1-μm in size has been investigated by using high-energy synchrotron-radiation powder-diffraction. A core/shell structure model, in which the grain consists of a core with tetragonal symmetry covered all over with a thin tetragonal shell with low tetragonality, is proposed and provides a markedly contrast with the core/shell structure of pure BaTiO3, which is generally known to have a shell with cubic symmetry. The higher permittivity of BCT is attributed to the characteristic shell structure with tetragonal symmetry. A change in the chemical bonding nature of BCT on the ferroelectric phase transition is clearly demonstrated in the electron charge density map.
Yoshihiro Kikuchi(Yoshihiro Kikuchi),Takehiko Tode(Takehiko Tode),Junko Hirata(Junko Hirata),Hideyuki Nakata(Hideyuki Nakata),Tsunekazu Kita(Tsunekazu Kita) 고려인삼학회 2003 Journal of Ginseng Research Vol.27 No.3
The aim of this study is to evaluate clinical usefulness of Korean red ginseng (RG) on various postmenopausal syndromes. Total plasminogen inhibitor-1 (tPAI-1) in peripheral blood from 9 postmenopausal women with climacteric syndromes (CS) was measured before and 3 months after treatment with daily oral administrat i on of 6g RG and that from 8 postmenopausal women without any CS was also measured as healthy controls. Blood samples were collected in the early morning on the bed-rest. Psychological conditions of postmenopausal women with CS were measured before and 3 months after treatment with RG using simplified menopausal index (SMI). In addition, OKETSU (blood stagnation) syndrome scores and KI deficiency (generalized energy stagnation) scores proposed by Terasawa et al., were recorded before and 3months after treatment with RG in postmenopausal women with CS and in healthy postmenopausal women. OKETSU syndrome scores and tPAI-1 levels in postmenopausal patients with CS were significantly (P<0.001 and<br/> P<0.01) higher than those in healthy postmenopausal women without CS. Similarly, SMI scores and KI deficiency scores in postmenopausal patients with CS were about three-fold higher than those without any CS. When RG was administered for 3 months, KI deficiency scores and OKETSU scores as well as SMI scores declined around the levels of healthy postmenopausal women. Although tPAI-1 levels significantly (P<0.05) decreased after treatment with RG, those did not reach the levels of healthy postmenopausal women. Clinical usefulness of administration of RG to postmenopausal women with CS was confirmed from evaluation not only by modern medicine but also by traditional KAMPO medicine.
Charge Density Distribution of PbHfO3 in Antiferroelectric Phase
Yoshihiro Terado,Yoshihiro Kuroiwa,Chikako Moriyoshi,Hitoshi Kawaji,Tooru Atake 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.2I
Electron charge density distributions of PbHfO3 in the antiferroelectric phase with an orthorhombic structure have been revealed by analyzing the high-energy synchrotron-radiation powder diffraction data using the maximum entropy method/Rietveld method. The covalent bonding natures of both the Pb-O and Hf-O bonds are clearly visualized at 100 K. The formation of Pb-O electron orbital hybridization is a new finding which characterizes the antiferroelectric phase, whereas Pb is ionic in the paraelectric phase with a cubic structure.
Yoshihiro Sugi,Yukio Hasegawa,Hiroshi Tamada,Kenichi Komura,Yoshihiro Kubota,김종호 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.2
Isopropylation of naphthalene (NP) was examined over H-mordenite (MOR), H-Y zeolite (FAU), and HBeta zeolite (BEA) in order to elucidate roles of isopropylnaphthalene (IPN) isomers during the catalysis. 2-IPN was the predominant isomer over MOR and works as a precursor for the selective formation of β,β-DIPN, particularly, 2,6-DIPN. In contrast, 1-IPN was predominant (with 2-IPN as a minor isomer) over FAU and BEA at low temperatures;dialkylation accompanied by the consumption of 1- and 2-IPN led to predominant formation of α,α- and α,β-DIPN. The formation of β,β-DIPN from 2-IPN was enhanced at higher temperatures. Bulky transition states of 1-IPN in IPN isomers and α,α- and α,β-DIPN among DIPN isomers were hindered by the interaction with MOR channels, resulting in the selective formation of β,β-DIPN, particularly 2,6-DIPN through the less bulky 2-IPN. FAU and BEA allow the formation of α,α- and α,β-DIPN from both of 1- and 2-IPN isomers because their channels are too large to exclude bulky transition states. The catalysis over FAU and BEA occurred under kinetic control at lower temperatures, and thermodynamic control also participates at higher temperatures.
The isopropylation of biphenyl over H-mordenite - Roles of 3- and 4-isopropylbiphenyls
Yoshihiro Sugi,Chokkalingam Anand,Tomonori Sugimura,Kenichi Komura,Yoshihiro Kubota,Jong Ho Kim,Gon Seo,Ajayan Vinu 한국화학공학회 2013 Korean Journal of Chemical Engineering Vol.30 No.5
The isopropylation of biphenyl (BP) and 3- and 4-isopropylbiphenyls (3- and 4-IPBPs) was examined over H-mordenites (MOR) to elucidate the mechanism of shape-selective formation of 4,4'-diisopropylbiphenyl (4,4'-DIPB). The isopropylation of BP occurred predominantly to form 4-isopropylbiphenyl (4-IPBP) from BP and 4,4'-DIPB from 4-IPBP. However, 3-IPBP, a minor isomer from BP, cannot participate effectively in the formation of 3,4'-DIPB due to steric restriction of its isopropyl moiety with MOR channels. Selective formation of 4,4'-DIPB was observed at low to moderate temperatures: 225-275 oC. However, the selectivities for 4,4'-DIPB were decreased at high temperatures,300-350 oC under propene pressure, 0.8MPa, by the isomerization of 4,4'-DIPB at external acid sites. The isomerization of 4,4'-DIPB occurred under low propene pressure even at 250 oC. The roles of 3- and 4-IPBPs in the formation of DIPB isomers were examined in the isopropylation of their mixtures. 4-IPBP was consumed much faster than 3-IPBP in all cases examined. 4-IPBP was an exclusive precursor to DIPB isomers, particularly 4,4'-DIPB. 4,4'-DIPB was also found as a predominant isomer in encapsulated products at all conditions examined. These results show that 4-IPBP can preferentially establish active transition state with propene and acid site in MOR channels, resulting in selective formation of 4,4'-DIPB. It is concluded that the isopropylation of BP over MOR occurs through reactant selectivity mechanism and restricted transition state mechanism, but not through product selectivity mechanism.
해외 리포트 - 고감도.고속 분자 Imaging 기술의 전망
Takiguchi, Yoshihiro 한국광학기기산업협회 2009 光學世界 Vol.121 No.-
보다 높은 공간분해능과 광검출능을 가지면서 분자의 고속 시간 응답 또는 거동 관측을 할 수 있는 Imaging 장치는 여러 가지 Nanotechnology를 포함한 요소기술의 진보에 따라 매일 새로워지고 있다. 그 중에서 분자관측에 의해 비로서 분명해지는 생체활동의 해명, 의료적으로 중요한 새로운 지견, 신규 유기재료 개발 등이 가능하게 되었으며, 얼마나 요소기술을 미묘하게 조합해 갈 것인지가 중요한 점이다. 이것은 분자관측을 목표로 하는 연구자뿐 아니라 이들 장치를 개발하는 기술자 또는 기업의 제휴가 필요하다는 것을 말한다. 이후에는 이들 연구자나 장치 제조사를 연결하여 상세한 대응을 하는 사업도 중요해질 것이다. 본고는 <광기술컨텍트 2009년 1월호>에 게재된 Takiguchi Yoshihiro 교수(Hikari Sangyo Sosei(광산업창성(光産業創成))대학원대학)의 기고문을 발췌, 번역한 것이다.
Development for Flaking Life Improvement of Planetary Gear Set
Yoshihiro SUGIYAMA,Sangki KIM,Joonho SONG 한국자동차공학회 2014 한국자동차공학회 학술대회 및 전시회 Vol.2014 No.11
As a shift mechanism of automatic transmission for vehicles, planetary gear set is generally used. It is necessary to suppress skew due to cause of the thrust washer wear and the pinion shaft flaking by skew phenomenon occurred full type roller bearing which supports the planetary gear. In this study, it is focused to radial clearance of needle bearing and rigidity of carrier to examine the inhibitor effect of skew phenomenon for the pinion shaft faking. It is possible to be improved life of flaking by increasing the carrier rigidity and reducing needle bearing clearance.
Interaction between ultrafine ceria particles and glycine
Yoshihiro Hirata,Hisanori Shimazu,Hideyuki Takahashi,Soichiro Sameshima 한양대학교 세라믹연구소 2004 Journal of Ceramic Processing Research Vol.5 No.1
An ultrafine ceria powder of 15 nm equivalent spherical particle diameter was dispersed at 2 vol% solid in aqueous solutions with and without glycine (H2NCH2COOH) of 0.05-5.0 mass% against ceria. The addition of glycine increased the zeta potential of the ceria toward positive values in acidic suspensions. The phase separation of ceria suspensions due to the decreased repulsive energy with decreasing particle size, was suppressed by the steric stabilization effect of the adsorbed glycine. No significant influence of the glycine addition on the zeta potential and phase separation of the basic suspension was measured.