Tatsuya Fujimoto

Unconventional Superconductivity and Electron Correlations in the Cobalt Oxyhydrate Na0:35CoO2 yH2O from Nuclear Quadrupole Resonance

We report a careful 59Co nuclear quadrupolar resonance measurement on the recently discovered cobalt oxyhydrate Na0.35CoO2.yH(2)O superconductor from T=40 K down to 0.2 K. We find that in the normal state the spin-lattice relaxation rate 1/T(1) follows a Curie-Weiss type temperature (T) variation, 1/T(1)T=C/(T-theta), with theta=-42 K, suggesting two-dimensional antiferromagnetic spin correlations. Below T(c)=3.9 K, 1/T(1) decreases with no coherence peak and follows a T(n) dependence with n approximately 2.2 down to approximately 2.0 K but crosses over to a 1/T(1) proportional to T variation below T=1.4 K, which suggests non-s-wave superconductivity. The data in the superconducting state are most consistent with the existence of line nodes in the gap function.

Evolution of local magnetic state in SmRu4P12 probed by muon spin relaxation

We performed muon spin relaxation measurements on randomly aligned single-crystalline samples of SmRu 4 P 12 down to 0.02 K to investigate static and dynamical magnetic properties in low fields. Th...

Effect of small amounts of hydrogen introduced reductively into coal on its hydroliquefaction

Abstract Kairan, Miike and Akabira bituminous coals were reductively hydrogenated by treatment with metallic sodium in liquid ammonia or with molten potassium in refluxing THF, followed by hydrogenation with methanol. These pretreatments added some hydrogen to aromatic rings and cleaved some CO and/or CC bonds connecting the structural units of the coal. Hydroliquefaction at 425 °C in tetralin was enhanced by this pretreatment, with in some cases a reduction in the total hydrogen consumed. For Akabira coal, liquefaction was also performed at 450 °C. Hydrogen introduced into the coal markedly affected both conversion and product distribution, especially in the early stages of liquefaction. This can be partly explained in terms of the shuttling effect of hydrogen added to aromatic rings, stabilizing the reactive coal fragments in the initial stages of the reaction.

Hydroliquefaction of subbituminous coal: effectiveness of pretreatment by organic reduction with Na or K

Abstract Hydroliquefaction of subbituminous Taiheiyo coal, without any pretreatment and after organic reduction, was carried out in the presence of tetralin using fine iron powder as catalyst. Two pretreatment procedures were used (A) reduction of coal with Na in liquid ammonia solution and (B) treatment with K in refluxing THF. Samples of treated coal with well-dispersed iron powder were prepared by co-reduction of coal coated with FeBr 2 using both procedures. Non-catalytic liquefaction of coal treated by A showed double the yield of hexane-solubles compared with that from liquefaction of the original coal while non-catalytic liquefaction of the coal treated by B roughly tripled the hexane-solubles yield and consumed the same amount of hydrogen. The presence of iron powder increased hexane-solubles by 5 wt% while increasing benzene-solubles by 13 wt% compared with non-catalytic liquefaction of treated coal by procedure B. The coals prepared by co-reduction (A and B) showed highest conversion (73 and 77%) along with highest yield of HS (38 and 43%). This significant effect on hydroliquefaction could be correlated with a slight increase of hydrogen atoms added to coal organic materials and the loosening of clusters of aromatic sheets.

Development and control of a novel cylindrical IPM linear vernier motor for compliant robot actuation

We have been studying small sized direct-drive electromagnetic linear actuators and their control method. These actuators were able to emulate the viscoelastic characteristics of the human muscle by PD position control to respond to external forces flexibly. However, their thrust force was not enough in order to apply to legs and shoulders of robots. In this paper, we present a novel small cylindrical linear vernier motor for artificial muscle of humanoid robots. First, the structure and operating principle of the proposed linear vernier motor are described. Then, the thrust and detent force of the motor are shown by 2D finite element analysis and measurement on a prototype. As the result, the validity of the simulation is discussed. Finally, the effect of the position controller with the disturbance observer on reduction of detent force and deviation between target and actual mover position is clarified.

Unconventional Superconductivity and Electron Correlations in the Cobalt Oxyhydrate [Formula presented] from Nuclear Quadrupole Resonance

We report a careful 59Co nuclear quadrupolar resonance measurement on the recently discovered cobalt oxyhydrate Na0.35CoO2.yH(2)O superconductor from T=40 K down to 0.2 K. We find that in the normal state the spin-lattice relaxation rate 1/T(1) follows a Curie-Weiss type temperature (T) variation, 1/T(1)T=C/(T-theta), with theta=-42 K, suggesting two-dimensional antiferromagnetic spin correlations. Below T(c)=3.9 K, 1/T(1) decreases with no coherence peak and follows a T(n) dependence with n approximately 2.2 down to approximately 2.0 K but crosses over to a 1/T(1) proportional to T variation below T=1.4 K, which suggests non-s-wave superconductivity. The data in the superconducting state are most consistent with the existence of line nodes in the gap function.

Unconventional Superconductivity and Electron Correlations in Cobalt Oxyhydrate Na

We report a careful 59Co nuclear quadrupolar resonance measurement on the recently discovered cobalt oxyhydrate Na0.35CoO2.yH(2)O superconductor from T=40 K down to 0.2 K. We find that in the normal state the spin-lattice relaxation rate 1/T(1) follows a Curie-Weiss type temperature (T) variation, 1/T(1)T=C/(T-theta), with theta=-42 K, suggesting two-dimensional antiferromagnetic spin correlations. Below T(c)=3.9 K, 1/T(1) decreases with no coherence peak and follows a T(n) dependence with n approximately 2.2 down to approximately 2.0 K but crosses over to a 1/T(1) proportional to T variation below T=1.4 K, which suggests non-s-wave superconductivity. The data in the superconducting state are most consistent with the existence of line nodes in the gap function.

_{0.35}

We report magnetic field ( H ) effect on the unconventional magnetism in LiNiO 2 that consists of a spin-1/2 triangular (TRI) lattice through the 7 Li nuclear spin lattice relaxation (1/ T 1 ) and NMR intensity measurements. Instead of a ferromagnetic (FM) ground state expected from the FM-Weiss constant, a marginal ordered state emerges below T M ∼20 K, evidenced from the wipe-out effect of 7 Li-NMR signal and the divergent behavior of 1/ T 1 towards T M . The existence of the strong antiferromagnetic (AF) interaction along with the FM one is concluded to lead to a magnetically frustrated state at low temperatures and its AF exchange constant J AF is estimated to be about -20 K. This marginal ordered state due to the frustration of the antiferro-orbital order is found to be suppressed by applying H exceeding 10 T, revealing an orbital exchange constant J °∼-10 K. In the paramagnetic regime at high temperatures, the system behaves like an assembly of local moments with an exchange frequency ω ex ∼11 K, co...