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Study on α-cluster levels in non-4n nuclei using low-energy RI beams
Yamaguchi, H,Kahl, D,Hayakawa, S,Sakaguchi, Y,Abe, K,Nakao, T,Suhara, T,Iwasa, N,Kim, A,Kim, D H,Cha, S M,Kwag, M S,Lee, J H,Lee, E J,Chae, K Y,Wakabayashi, Y,Imai, N,Kitamura, N,Lee, P,Moon, J Y,Lee, IOP Publishing 2017 Journal of physics. Conference series Vol.863 No.-
Experimental investigation of a linear-chain structure in the nucleus <sup>14</sup>C
Yamaguchi, H.,Kahl, D.,Hayakawa, S.,Sakaguchi, Y.,Abe, K.,Nakao, T.,Suhara, T.,Iwasa, N.,Kim, A.,Kim, D.H.,Cha, S.M.,Kwag, M.S.,Lee, J.H.,Lee, E.J.,Chae, K.Y.,Wakabayashi, Y.,Imai, N.,Kitamura, N.,Lee North-Holland Pub. Co 2017 Physics letters. Section B Vol.766 No.-
It is a well-known fact that a cluster of nucleons can be formed in the interior of an atomic nucleus, and such clusters may occupy molecular-like orbitals, showing characteristics similar to normal molecules consisting of atoms. Chemical molecules having a linear alignment are commonly seen in nature, such as carbon dioxide. A similar linear alignment of the nuclear clusters, referred to as linear-chain cluster state (LCCS), has been studied since the 1950s, however, up to now there is no clear experimental evidence demonstrating the existence of such a state. Recently, it was proposed that an excess of neutrons may offer just such a stabilizing mechanism, revitalizing interest in the nuclear LCCS, specifically with predictions for their emergence in neutron-rich carbon isotopes. Here we present the experimental observation of α-cluster states in the radioactive <SUP>14</SUP>C nucleus. Using the Be10+α resonant scattering method with a radioactive beam, we observed a series of levels which completely agree with theoretically predicted levels having an explicit linear-chain cluster configuration. We regard this as the first strong indication of the linear-chain clustered nucleus.
김아람,N. H. Lee,I. S. Hahn,J. S. Yoo,M. H. Han,S. Kubono,H. Yamaguchi,S. Hayakawa,Y. Wakabayashi,D. Binh,H. Hashimoto,T. Kawabata,D. Kahl,Y. Kurihara,Y. K. Kwon,T. Teranishi,S. Kato,T. Komatsubara,B. Gu 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.1
For the study of astrophysically important states in 18Ne, the 14O(α, α)14O cross section was measured in inverse kinematics using a radioactive 14O beam. This reaction was investigated for properties of resonant states of 18Ne for determining the 14O(α, p)17F reaction rate, which is one of the most important reactions for understanding the breakout mechanism from the Hot CNO cycle to the rp-process. Alpha-induced elastic scattering on 14O was performed using the lowenergy radioactive ion (RI) beam separator at the Center for Nuclear Study (CNS) in the RIKEN Accelerator Research Facility. The energy range Ex = 7.2 ∽ 13.1 MeV of 18Ne was scanned with the thick target method. Recoiled alpha particles were measured with Si dE-E telescopes. Spins and widths of three resonances at Ex = 8.6, 9.22, and 10.06 MeV were calculated using the R-matrix analysis, and a new state of 18Ne at Ex = 12.0 MeV was found in this experiment.
Astrophysically Important 26Si States Studied with the 28Si(4He,6He)26Si Reaction
Y. K. Kwon,이춘식,J. Y. Moon,J. H. Lee,J. Y. Kim,M. K. Cheoun,S. Kubono,H. Yamaguchi,J. J. He,A. Saito,Y. Wakabayashi,H. Fujikawa,G. Amadio,N. Iwasa,K. Inafuku,L. H. Khiem,M. Tanaka,Y. Fuchi,A. A. Chen,S 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.2
The emission of a 1.809-MeV γ-ray from the first excited state of 26Mg, followed by β-decay of 26Al in its ground state (denoted as 26Alg.s.), has been identied by several gamma-ray telescopes. To resolve the controversy over the possible sources of the observational 1.809-MeV γ-rays, one needs accurate knowledge of the production rate of 26Alg.s.. The 25Al(p,γ)26Si reaction is one of the most important astrophysical reactions to be investigated, but its rate is uncertain due to the lack of level information on 26Si above the proton threshold (Qpγ = 5.518 MeV). Illiadis et al. suggested that the 25Al(p,γ)26Si reaction should be dominated by a 3+ unnatural parity state at Ex = 5970 keV. Recent studies proposed several states as candidates for the 3+ states. However, the spin-parity assignments for these states are still uncertain. In the present work, we measured the 28Si(4He,6He)26Si reaction at 120 MeV to confirm the unnatural parity states just above the proton threshold. The measurement was performed with the high-resolution particle analyzer at the Center for Nuclear Study, University of Tokyo. We observed a total of 22 excited states in 26Si. The 7018-keV level, which was only observed by Bardayan et al. with the 28Si(p; t)26Si reaction, was confirmed in our measurement. Among the candidates of unnatural parity states at Ex = 5678, 5916, and 5945 keV, the 5918-keV state was only observed within the error of the excitation energy. A new state at Ex = 6101 keV was also identified.
A single particle Hamiltonian for electro-magnetic properties of graphene nanoribbons
Lee, H.,Wakabayashi, K.,Son, Y.W.,Miyamoto, Y. Pergamon Press ; Elsevier Science Ltd 2012 Carbon Vol.50 No.10
Graphene zigzag edges are known to show the spin polarized ferromagnetic states, which are well described by the mean field treatment of Hubbard model. The parameter of onsite Coulomb interaction U is estimated to be comparable to the kinetic hopping parameter t so as to fit the electronic band structures obtained by the spin-polarized density functional theory (DFT). In this paper, we propose a simple way to transfer the electronic band structures obtained by DFT onto the mean-field Hubbard Hamiltonian by adopting site-dependent U parameter, which is taken as the decaying function from the edge. This approach is applicable to both anti-ferromagnetic and ferromagnetic states between two edges of graphene nanoribbons and will serve to perform the further large-scale simulation of electro-magnetic transport properties of graphene-based nanodevices.
Effectiveness of Minimal Quantity Lubrication in Machining Processes
S. SUDA,H. YOKOTA,I. INASAKI,T. WAKABAYASHI 한국트라이볼로지학회 2002 한국트라이볼로지학회 학술대회 Vol.2002 No.10
A minimal quantity lubrication (MQL) machining is able to achieve both functions of cooling and lubrication with an extremely low quantity of a cutting fluid and a large amount of air blow. Using a biodegradable ester oil, turning tests were carried out to evaluate the effectiveness of the MQL system. It was found that the performance of MQL cutting was equivalent to, or better than, that of conventional cutting, because the MQL system tends to prevent the heat damage of the tool tip and, if an effective lubricant such as a particular polyol ester is applied to the system, it can avoid the extensive transfer of workpiece materials on to the tool surface.
Gunji, Takao,Wakabayashi, Ryo H.,Noh, Seung Hyo,Han, Byungchan,Matsumoto, Futoshi,DiSalvo, Francis J.,Abruñ,a, Hé,ctor D. Elsevier 2018 ELECTROCHIMICA ACTA Vol.283 No.-
<P><B>Abstract</B></P> <P>We present an investigation of the alloying effects of 3d transition metals with palladium, and on their activity towards the oxygen reduction reaction (ORR) in alkaline media, as well as the durability of the electrocatalysts over time. Bimetallic Pd-<I>M</I> (<I>M</I> = Fe, Co and Ni) nanoparticles (NPs) were prepared by an impregnation method followed by reduction under forming gas and a subsequent annealing treatment. In order to enhance the catalytic activity towards the ORR, the bimetallic Pd-<I>M</I> nanoparticles were electrochemically dealloyed. The dealloyed Pd-<I>M</I> nanoparticles had a core-shell structure with a Pd<SUB>3</SUB> <I>M</I>-core and a Pd-shell about 1 nm in thickness. The core-shell materials exhibited higher electrocatalytic activity towards the ORR, and longer-term durability when compared to pure Pd.</P>
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
K. Tahara,Y. Fukuda,G. Wakabayashi,H. Ban,Y. Morimoto,M. Yoshioka,K. Kiyohara,Y. Koba,H. Iwamoto,Y. Uozumi,N. Matsufuji 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
We measured proton-production double differential cross sections (DDXs) by 290 MeV/u carbon beams on carbon, copper, lead targets at forward angles. The proton energies were measured with the spectrometer which consisted of GSO(Ce) crystals and plastic scintillators. The measured DDXs were compared with the calculated ones with PHITS code. The simulation results generally agreed with the measured ones. The measured results will be useful as the benchmark of existing simulation codes and for the future improvements.