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Nonlinear Fokker-Planck Equations on Curved Spacetime Surface and Its Applications
H Hara,N Ikeda 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.46 No.3
In order to investigate nonlinear and non-Markov processes, we propose solvable Fokker-Planck (FP) equations and a solvable stochastic dierential (SD) equation on a curved spacetime surface. The nonlinearity is described as a curvature of the surface on which the FP equations and the SD equation having memory eect are obtained by using fractional derivatives. The curved surface is given as a curvilinear coordinate system, expressed by using a parametric representation ~r = ~r(x; t) in three-dimensional Euclidian space. The curvilinear coordinates y and s are functions of the space coordinate x and time t, respectively. An interpretation of the nonlinearity is given as a virtual force determining the relationship of the physical spacetime to the curved spacetime. The stochastic dierential equation and the fractional derivatives are given on the curved spacetime surface.
Structural phase transitions and dielectric anomaly in YFe2O4-δ
Y. Horibe,K. Kishimoto,N. Ikeda,S. Mori 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.46 No.1
We examined structural changes related to charge ordering (CO) in the temperature window between 100 K and room temperature (RT) in YFe2O4 by transmission electron microscopy. Characteristic diuse scattering elongated along the [001] direction through the (1/3 1/3 0)-type reciprocal positions was found at RT, which is related to the microdomains due to the CO with a size of 10 { 20 nm. In addition, it was also found that the superlattice structures characterized by the (1/3 { 1/3 + 0)-type modulation vector, which should be due to the vacancy ordering,coexist with the microdomains due to the CO. On the other hand, in stoichimetric YFe2O4, we found temperature variations of the superlattice structures on warming from 100 K, which should be strongly related to the dielectric anomalies in YFe2O4.
Chris Sedgwick,STEPHEN SERJEANT,CHRIS PEARSON,I. Yamamura,S. Makiuti,N. Ikeda,Y. Fukuda,S. Oyabu,T. Koga,S. Amber,Glenn J. White 한국천문학회 2017 天文學論叢 Vol.32 No.1
We have identified 22 quasars in the AKARI far-infrared all-sky Bright Source Catalogue, using a matching radius of < 10 “, and excluding matches which are close to foreground extended sources or cirrus. We have confirmed a relation between quasar optical luminosity and far-infrared luminosity which was found in an earlier study. In addition, we have found that the 11 sources which are at redshift z > 1 are magnified with respect to the predicted far-infrared luminosity, and consider this may be due to gravitational lensing. If confirmed, this would provide a new way to identify lenses; if not, we may have identified an interesting new population of extreme starbursting quasars. %We are currently seeking spectroscopic confirmation of the redshifts and improved imaging for these sources.
박용구(Park, Y. G.),김주희(J.H. Kim),Ikeda Namiko(N.Ikeda),신동일(D.I. Shin) 한국차학회 2001 한국차학회지 Vol.7 No.1
It has been known that both Korean and Japanese wild tea were introduced from China around AD 800. However, the original population from which they were introduced was not confirmed, yet. We investigated the morphological and genetic variations using RAPD of Korean and Japanese wild tea plants and compared with their genetic differences based on the results. Twenty two superior individuals from 19 wild tea populations of Korea were selected and 19 superior cultivars of Japan were introduced for this study. Seeds collected from 6 wild populations of Korea were planted in Tea Experimental Station in Japan at 1994 and the progenies were compared with 6 year old Japanese wild tea seedlings. Characteristics of leaf morphology of Korean wild tea plants were similar to those of Chinese small leaf variety while Japanese wild tea revealed to be more tolerant to cold. Japanese cultivars have thick leaf that indicates a higher yield. Most conspicuous difference was seen in the flower structure which means a different breeding pattern in Korean and Japanese populations. RAPD results clearly demonstrated the difference between Korean and Japanese wild populations. From the results, we concluded that there are significant genetic differences between Korean and Japanese wild tea populations and, therefore, the original populations from which they were introduced are different.
Review and Prospect of Ferroelectricity and Magnetism in YMn2O5
Y. Noda,H. Kimura,I. Kagomiya,K. Kohn,N. Ikeda,S. Matumoto,T. Shobu,Y. Fukuda 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.IV
YMn2O5 undergoes ferroelectric successive phase transitions at 39 K and 19 K, in which a dielectric constant shows anomalies. Spontaneous polarization was also observed. Just above these ferroelectric phase transition temperatures, at 45 K, antiferromagnetic order occurs. Neutron elastic measurements and magnetic susceptibility measurements reveal that the ferroelectric phase transition at 39 K and 19 K occurs simultaneously with the change of magnetic ordering pattern. Review of experimental results and conjecture for the origin of spontaneous polarization are given.??
Lattice Modulation in YMn2O5 and TbMn2O5 Studied by Using Synchrotron Radiation X-rays
Yukio Noda,H Kimura,H Sawa,K Kohn,N Ikeda,S Kobayashi,Y Ishikawa,Y Kamada,Y Wakabayashi 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.2I
RMn2O5 (R = Y and rare earth) shows successive magnetic and ferroelectric phase transitions at about 45 K, 40 K, 39 K, 20 K and 10 K and is called a multiferroic compound. We have investigated the lattice modulation vectors (qL) of YMn2O5 and TbMn2O5 by using single crystal Synchrotron Radiation X-ray diraction and compared them with the magnetic propagation vectors (qM) studied by neutron diraction. The relation of the propagation vectors between magnetic materials and dielectrics is found to be qL = 2qM. A preliminary structure analysis of the atomic displacement pattern in the commensurate ferroelectric phase of TbMn2O5 is discussed.fb