Ethanol internal reforming in solid oxide fuel cells: A path toward high performance metal-supported cells for vehicular applications

Internal reforming of ethanol fuel was investigated on high-performance metal-supported solid oxide fuel cells (MS-SOFCs) with infiltrated catalysts. The hydrogen concentration and internal reforming effects were evaluated systematically with different fuels including: hydrogen, simulated reformate, anhydrous ethanol, ethanol water blend, and hydrogen-nitrogen mixtures. A simple infiltration of Ni reforming catalyst into 40 vol% Ni-Sm0.20Ce0.80O2-δ (Ni-SDCN40) and fuel-side metal support leads to complete internal reforming, as confirmed by comparison to simulated reformate. The performance difference between hydrogen and fully-reformed ethanol is attributed entirely to decrease in hydrogen concentration. High peak power density was achieved for a range of conditions, for example 1.0 W cm−2 at 650 °C in ethanol-water blend, and 1.4 W cm−2 at 700 °C in anhydrous ethanol fuel. Initial durability tests with ethanol-water blend show promising stability for 100 h at 700 °C and 0.7 V. Carbon is not deposited in the Ni-SDCN40 anode during operation

Construction of a Versatile Ultra-Low Temperature Scanning Tunneling Microscope

We constructed a dilution-refrigerator (DR) based ultra-low temperature scanning tunneling microscope (ULT-STM) which works at temperatures down to 30 mK, in magnetic fields up to 6 T and in ultrahigh vacuum (UHV). Besides these extreme operation conditions, this STM has several unique features not available in other DR based ULT-STMs. One can load STM tips as well as samples with clean surfaces prepared in a UHV environment to an STM head keeping low temperature and UHV conditions. After then, the system can be cooled back to near the base temperature within 3 hours. Due to these capabilities, it has a variety of applications not only for cleavable materials but also for almost all conducting materials. The present ULT-STM has also an exceptionally high stability in the presence of magnetic field and even during field sweep. We describe details of its design, performance and applications for low temperature physics.Comment: 6 pages, 9 figures. accepted for publication in Rev. Sci. Instru

Neutrino Magnetic Moments and Minimal Supersymmetric SO(10) Model

We examine supersymmetric contributions to transition magnetic moments of Majorana neutrinos. We first give the general formula for it. In concrete evaluations, informations of neutrino mass matrix elements including CP phases are necessary. Using unambiguously determined neutrino mass matrices in recently proposed minimal supersymmetric SO(10) model, the transition magnetic moments are calculated. The resultant neutrino magnetic moments are found to be roughly an order of magnitude larger than those calculated in the standard model extended to incorporate the see-saw mechanism.Comment: 8 pages, 4 figures, the version to be published in International Journal of Modern Physics

On the Mott glass in the one-dimensional half-filled charge density waves

We study the effect of impurity pinning on a one-dimensional half-filled electron system, which is expressed in terms of a phase Hamiltonian with the charge degree of freedom. Within the classical treatment, the pinned state is examined numerically. The Mott glass, which has been pointed out by Orignac et al. [Phys. Rev. Lett 83 (1999) 2378], appears in the intermediate region where the impurity potential competes with the commensurate potential. Such a state is verified by calculating the soliton formation energy, the local restoring force around the pinned state and the optical conductivity.Comment: 13 pages, 5 figures, to be published in J. Phys. Soc. Jpn. 72 No.11 (2003

One-Particle Excitation of the Two-Dimensional Hubbard Model

The real part of the self-energy of interacting two-dimensional electrons has been calculated in the t-matrix approximation. It is shown that the forward scattering results in an anomalous term leading to the vanishing renormalization factor of the one-particle Green function, which is a non-perturbative effect of the interaction U. The present result is a microscopic demonstration of the claim by Anderson based on the conventional many-body theory. The effect of the damping of the interacting electrons, which has been ignored in reaching above conclusion, has been briefly discussed.Comment: 7 pages, LaTeX, 1 figure, uses jpsj.sty, to be published in J. Phys. Soc. Jpn. 66 No. 3 (1997

Low-Temperature Scaling Regime of Random Ferromagnetic-Antiferromagnetic Spin Chains

Using the Continuous Time Quantum Monte Carlo Loop algorithm, we calculate the temperature dependence of the uniform susceptibility, and the specific heat of a spin-1/2 chain with random antiferromagnetic and ferromagnetic couplings, down to very low temperatures. Our data show a consistent scaling behavior in both quantities and support strongly the conjecture drawn from the approximative real-space renormalization group treatment. A statistical analysis scheme is developed which will be useful for the search scaling behavior in numerical and experimental data of random spin chains.Comment: 4 pages and 3 figure

Ground State Spin Structure of Strongly Interacting Disordered 1D Hubbard Model

We study the influence of on-site disorder on the magnetic properties of the ground state of the infinite U 1D Hubbard model. We find that the ground state is not ferromagnetic. This is analyzed in terms of the algebraic structure of the spin dependence of the Hamiltonian. A simple explanation is derived for the 1/N periodicity in the persistent current for this model.Comment: 3 pages, no figure

Impurity Effects on Quantum Depinning of Commensurate Charge Density Waves

We investigate quantum depinning of the one-dimensional (1D) commensurate charge-density wave (CDW) in the presence of one impurity theoretically. Quantum tunneling rate below but close to the threshold field is calculated at absolute zero temperature by use of the phase Hamiltonian within the WKB approximation. We show that the impurity can induce localized fluctuation and enhance the quantum depinning. The electric field dependence of the tunneling rate in the presence of the impurity is different from that in its absence.Comment: 14 pages with 13 figures. Submitted to J. Phys. Soc. Jp

Theoretical Study of Friction: A Case of One-Dimensional Clean Surfaces

A new method has been proposed to evaluate the frictional force in the stationary state. This method is applied to the 1-dimensional model of clean surfaces. The kinetic frictional force is seen to depend on velocity in general, but the dependence becomes weaker as the maximum static frictional force increases and in the limiting case the kinetic friction gets only weakly dependent on velocity as described by one of the laws of friction. It is also shown that there is a phase transition between state with vanishing maximum static frictional force and that with finite one. The role of randomness at the interface and the relation to the impurity pinning of the sliding Charge-Density-Wave are discussed. to appear in Phys.Rev.B. abstract only. Full text is available upon request. E-mail: [email protected]: 2 pages, Plain TEX, OUCMT-94-