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Search Results: 1 - 10 of 1564 matches for " Yuji Muro "
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Anisotropic Electronic Structure of the Kondo Semiconductor CeFe2Al10 Studied by Optical Conductivity
Shin-ichi Kimura,Yuji Muro,Toshiro Takabatake
Physics , 2010, DOI: 10.1143/JPSJ.80.033702
Abstract: We report temperature-dependent polarized optical conductivity [$\sigma(\omega)$] spectra of CeFe$_2$Al$_{10}$, which is a reference material for CeRu$_2$Al$_{10}$ and CeOs$_2$Al$_{10}$ with an anomalous magnetic transition at 28 K. The $\sigma(\omega)$ spectrum along the b-axis differs greatly from that in the $ac$-plane, indicating that this material has an anisotropic electronic structure. At low temperatures, in all axes, a shoulder structure due to the optical transition across the hybridization gap between the conduction band and the localized $4f$ states, namely $c$-$f$ hybridization, appears at 55 meV. However, the gap opening temperature and the temperature of appearance of the quasiparticle Drude weight are strongly anisotropic indicating the anisotropic Kondo temperature. The strong anisotropic nature in both electronic structure and Kondo temperature is considered to be relevant the anomalous magnetic phase transition in CeRu$_2$Al$_{10}$ and CeOs$_2$Al$_{10}$.
Country-Specific Dynamic Optimal Capital Income Tax Rate  [PDF]
Kazunobu Muro
Theoretical Economics Letters (TEL) , 2012, DOI: 10.4236/tel.2012.23045
Abstract: The empirical tax rate on capital income ranges between 0.4 and 0.6 in OECD countries. This paper presents the optimal taxation problem in an one-sector dynamic general equilibrium model where the government is confronted with fiscal constraint (the ratio of government expenditure to GDP is exogenously given) while households and firms do not recognize the fiscal constraint. We derive analytically the positive optimal tax rates on capital income. Under the fiscal constraint, the optimal tax rate on capital income depends on the discount rate, the rate of capital depreciation, and the ratio of government spending to GDP. Our model can generate the country-specific optimal tax rate on capital income (0.2 to 0.4). Thus, this paper insists that the empirical data of tax rates in OECD countries are higher than the results predicted by our model.
Relation between $c$-$f$ hybridization and magnetic ordering in CeRu$_2$Al$_{10}$: An optical conductivity study of Ce(Ru$_{1-x}$Rh$_x$)$_2$Al$_{10}$ ($x\leq0.05$)
Shin-ichi Kimura,Hiroshi Tanida,Masafumi Sera,Yuji Muro,Toshiro Takabatake,Takashi Nishioka,Masahiro Matsumura,Riki Kobayashi
Physics , 2015, DOI: 10.1103/PhysRevB.91.241120
Abstract: A Kondo semiconductor CeRu$_2$Al$_{10}$ with an orthorhombic crystal structure shows an unusual antiferromagnetic ordering at rather high temperature $T_0$ of 27.3 K, which is lower than the Kondo temperature $T_{\rm K}\sim$ 60 K. In optical conductivity [$\sigma(\omega)$] spectra that directly reflect electronic structure, the $c$-$f$ hybridization gap between the conduction and $4f$ states is observed at around 40 meV along the three principal axes. However, an additional peak at around 20 meV appears only along the $b$ axis. With increasing $x$ to 0.05 in Ce(Ru$_{1-x}$Rh$_x$)$_2$Al$_{10}$, the $T_0$ decreases slightly from 27.3 K to 24 K, but the direction of the magnetic moment changes from the $c$ axis to the $a$ axis. Thereby, the $c$-$f$ hybridization gap in the $\sigma(\omega)$ spectra is strongly suppressed, but the intensity of the 20-meV peak remains as strong as for $x=0$. These results suggest that the change of the magnetic moment direction originates from the decreasing of the $c$-$f$ hybridization intensity. The magnetic ordering temperature $T_0$ is not directly related to the $c$-$f$ hybridization but is related to the charge excitation at 20 meV observed along the $b$ axis.
On the Generalization of Hilbert’s 17th Problem and Pythagorean Fields  [PDF]
Yuji Shimizuike
Advances in Pure Mathematics (APM) , 2013, DOI: 10.4236/apm.2013.37A001

The notion of preordering, which is a generalization of the notion of ordering, has been introduced by Serre. On the other hand, the notion of round quadratic forms has been introduced by Witt. Based on these ideas, it is here shown that 1) a field F is formally real n-pythagorean iff the nth radical, RnF is a preordering (Theorem 2), and 2) a field F is n-pythagorean iff for any n-fold Pfister form ρ. There exists an odd integer l(>1) such that l×ρ is a round quadratic form (Theorem 8). By considering upper bounds for the number of squares on Pfister’s interpretation, these results finally lead to the main result (Theorem 10) such that the generalization of pythagorean fields coincides with the generalization of Hilbert’s 17th Problem.

Observation of Environmental Stress Cracking in Polymethylmethacrylate by Using the Chemiluminescence Method  [PDF]
Yuji Higuchi
Materials Sciences and Applications (MSA) , 2015, DOI: 10.4236/msa.2015.611107
Abstract: Polymethylmethacrylate (PMMA) is highly regarded for its transparency, and is used in such products as cameras and Video Tape Recorders as plastic lenses to take advantage of its excellent optical properties. Also, it is used in numerous other industrial fields like automobile lamp lenses, billboards, and lighting equipment. The phenomenon of environmental stress cracking is known to occur in PMMA due to ethanol, and there are cases when this may become a factor which causes damage of molded products. In the present paper, upon close observation by using the method of chemiluminescence in order to elucidate the mechanism by which this environmental stress cracking occurs, we report that we are able to capture the formation of a radical at the moment of cracking.
The Change in Self-Esteem among Middle School Students in Japan, 1989-2002  [PDF]
Yuji Ogihara
Psychology (PSYCH) , 2016, DOI: 10.4236/psych.2016.711136
Abstract: This paper examined temporal changes in self-esteem among middle school students in Japan from 1989 to 2002. Previous research showed that self-esteem decreased among middle school students between 1999 and 2006. However, it was unclear whether such a decrease was also present in other periods of time. To obtain a better understanding of how people adapt to socio-economic environments, it is important to gain a more comprehensive view of such long-term cultural/social changes. Therefore, to supplement the findings of the existing research on changes in self-esteem, we analyzed large-sample time-series data collected in Japan in 1989 and 2002. We found that middle schoolers’ self-esteem decreased from 1989 to 2002, consistent with previous research. Thus, our study extends the previous research by presenting additional data showing the decrease in self-esteem in Japan.
Rheological Behavior of Nanosilica Suspensions in Poly(Ethylene Oxide) Solutions with Sodium Chloride  [PDF]
Yuji Hirose
Materials Sciences and Applications (MSA) , 2017, DOI: 10.4236/msa.2017.85022
Abstract: Suspensions of silica nanoparticles showed shear-thickening profiles under steady shear conditions up on addition of a small amount of poly(ethylene oxide) (PEO). The suspensions turned into gels upon shaking and their fluidity was recovered several minutes after resting. We studied the rheological properties of these shake gels with small amounts of sodium chloride (NaCl). Gelation occurred at lower shear rates upon addition of small amounts of NaCl. In addition, the time taken by the gelated samples to recover their original viscosity increased with the increasing NaCl content. The weakened repulsive interactions between the silica particles upon NaCl addition lead to particles in closer proximity, and three-dimensional networks of PEO chains are easily formed as the electric double layer of the particles becomes thinner.
Orbital Phase Theory and the Diastereoselectivity of Some Organic Reactions  [PDF]
Yuji Naruse
Journal of Materials Science and Chemical Engineering (MSCE) , 2018, DOI: 10.4236/msce.2018.67005
The orbital phase refers to the relationship between orbitals that originates from their wave character. We show here that the orbital phase essentially determines the diastereoselectivity of the following three organic reactions. 1) Torquoselectivity of the electrocyclicring-opening reaction of 3-substituted cyclobutenes; 2) Contradictory torquoselectivity of the retro-Nazarov reaction; 3) Diastereoselectivity in electrophilic addition to substituted ethylenes.
Electronic Structure of Noncentrosymmetric Superconductor Li$_2$(Pd$_x$Pt$_{1-x}$3)B Studied by Photoemission Spectroscopy
Rikiya Yoshida,Hiroyuki Okazaki,Mitsutoshi Tajima,Takayuki Muro,Izumi Hase,Kozo Okada,Hiroyuki Takeya,Kazuto Hirata,Masaaki Hirai,Yuji Muraoka,Takayoshi Yokoya
Physics , 2008, DOI: 10.1143/JPSJ.77.104701
Abstract: We have performed x-ray photoemission spectroscopy on the system of noncentrosymmetric superconductor, Li$_2$(Pd$_x$Pt$_{1-x}$3)B. For Li$_2$Pt$_3$B, we found 2 major peaks with 2 other weak components, and the band calculations were in agreement with the observation. The assignment of valence band features using the calculated partial density of states determined that Pt 5d and B 2p contribute to the density of states at the Fermi level. The effect of antisymmetric spin-orbit coupling on the band structure might have been probed, and the analysis on the effect of Pt incorporation into the system indicates the smooth evolution of electronic structures. We presented the measurements of core levels (Pd 3d, Pt 4f, and B 1s) and discussed the chemical bonding states and electronic structures from them.
Optical study of charge instability in CeRu2Al10 in comparison with CeOs2Al10 and CeFe2Al10
Shin-ichi Kimura,Takuya Iizuka,Hidetoshi Miyazaki,Tetsuya Hajiri,Masaharu Matsunami,Tatsuya Mori,Akinori Irizawa,Yuji Muro,Junpei Kajino,Toshiro Takabatake
Physics , 2011, DOI: 10.1103/PhysRevB.84.165125
Abstract: The anisotropic electronic structure responsible for the antiferromagnetic transition in CeRu$_2$Al$_{10}$ at the unusually high temperature of $T_0$ = 28 K was studied using optical conductivity spectra, Ce 3d X-ray photoemission spectra, and band calculation. It was found that the electronic structure in the $ac$ plane is that of a Kondo semiconductor, whereas that along the b axis has a nesting below 32 K (slightly higher than $T_0$). These characteristics are the same as those of CeOs$_2$Al$_{10}$ [S. Kimura {\it et al.}, Phys. Rev. Lett. 106, 056404 (2011).]. The $c$-$f$ hybridization intensities between the conduction and $4f$ electrons of CeRu$_2$Al$_{10}$ and CeOs$_2$Al$_{10}$ are weaker than that of CeFe$_2$Al$_{10}$, showing no magnetic ordering. These results suggest that the electronic structure with one-dimensional weak $c$-$f$ hybridization along the b axis combined with two-dimensional strong hybridization in the $ac$ plane causes charge-density wave (CDW) instability, and the CDW state then induces magnetic ordering.
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