Intrinsic microwave dielectric loss of lanthanum aluminate

The intrinsic dielectric properties of LaAlO? were investigated to understand the microwave properties of several materials containing LaAlO?. In this study, LaAlO? single crystals were prepared by the Czochralski method. The temperature dependence of the dielectric properties and neutron inelastic scattering of the single crystals were measured. From these data, the intrinsic dielectric properties were evaluated and it was found that the dielectric loss of the LaAlO? includes two types of dielectric loss. One is a phonon absorption-related loss and the other is a component of the loss arising from Debye- type orientation polarization. The latter affects the room temperature dielectric loss in materials containing LaAlO?. The present study suggests that avoiding this polarization loss is an important goal in decreasing the total dielectric loss.     

Fabrication and evaluation of a novel cathode-supported honeycomb SOFC stack

A novel solid oxide fuel cell (SOFC) stack based on a cathode-supported honeycomb SOFC single unit, capable of generating high volumetric power density, was fabricated. Facile connection of the honeycomb single units is achieved using a metal interconnect with a gastight conductive paste. The honeycomb single unit is designed to use the outer honeycomb face and the anode layer on the honeycomb edge face as the current collection paths for the cathode and anode sides, respectively. Current is conducted between the cathode of a single unit and the anode of an adjacent single unit through the metallic interconnect. A two-unit stack exhibited an open circuit voltage of approximately 2 V and twice the power of a single unit at 600 °C under wet H₂ fuel flow. The volumetric power density of the honeycomb SOFC stack at 600 °C was calculated to be approximately 0.6 W/cm³.     

Crystal Structure of Metastable Tetragonal Zirconia up to 1473 K

The crystal structure of metastable tetragonal zirconia prepared via the alkoxide method has been investigated at temperatures up to 1473 K, to clarify the similarity between this metastable phase and the tetragonal phase at high temperature. The lattice constants, tetragonality, oxygen shift parameter, and equivalent isotropic thermal parameter of the metastable tetragonal phase are proportional to the temperature. These parameters, when extrapolated to the high-temperature range, are very similar to those of the high-temperature tetragonal phase. Present results indicate that the structure of the metastable tetragonal phase is the same as that of the high-temperature tetragonal phase.     

Surface acoustic wave based sensors employing ionic liquid for hydrogen sulfide gas detection

This paper describes a new type hydrogen sulfide (H₂S) gas sensor using ionic liquid (IL). In this sensor, a reservoir for the IL was integrated on a surface acoustic wave (SAW) resonator. The IL serves as an absorber for H₂S gas. Mass change due to this absorption is detected as shift in the resonant frequency. In this study, we fabricated and demonstrated the sensor using the lithium niobate (LiNbO₃) SAW resonator with the resonant frequency of 38 MHz. The integrated reservoir was filled by the IL 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]-[PF₆]). As an experimental result, we observed the linear correlation between the frequency-shift and the exposure time of the sensor to the H₂S gas.     

Temperature Dependence of the Raman Spectrum in Lithium Oxide Single Crystal

Temperature dependence of the Raman spectrum of lithium oxide single crystal has been measured over a temperature range of 80 to 1073 K. The frequency shift and the line width of the Raman spectrum in lithium oxide were about 531 and 4.5 cm^-1 at 80 K, respectively. At 1073 K, the frequency shift and the line width attained the values of 464 and 112 cm^-1, respectively. The strong temperature dependence of the frequency shift and line width was compared with data from some crystals with a fluorite structure.     

Sintering of fibrous barium titanate powder compacts with preferred orientation

The sintering of fibrous BaTiO₃ powder particles was investigated. Special emphasis was given to the role of particle orientation in the compact on densification and microstructure development. Compacts were made by dry-pressing. During the initial stage of sintering, the fibrous particles rearranged and bundles of particles were formed. The volume of pores between bundles of particles decreased on further heating. Grain growth started when the sintered density reached ca. 56% of the theoretical density. Higher temperatures of sintering increased the degree of the crystal axis orientation. Thus, highly orientated sintered bodies with high densities were prepared by heating at 1500 °C.     

Submodular fractional programming for balanced clustering

We address the balanced clustering problem where cluster sizes are regularized with submodular functions. The objective function for balanced clustering is a submodular fractional function, i.e., the ratio of two submodular functions, and thus includes the well-known ratio cuts as special cases. In this paper, we present a novel algorithm for minimizing this objective function (submodular fractional programming) using recent submodular optimization techniques. The main idea is to utilize an algorithm to minimize the difference of two submodular functions, combined with the discrete Newton method. Thus, it can be applied to the objective function involving any submodular functions in both the numerator and the denominator, which enables us to design flexible clustering setups. We also give theoretical analysis on the algorithm, and evaluate the performance through comparative experiments with conventional algorithms by artificial and real datasets.     

Practical Reliability and Maintainability Analysis Tool for an Open Source Cloud Computing

We focus on a cloud computing environment by using open source softwares such as OpenStack and Eucalyptus because of the unification management of data and low cost. A cloud computing is attracting attention as a network service to share the computing resources, that is, networks, servers, storage, applications, and services. We propose jump diffusion models based on stochastic differential equations in order to consider the interesting aspect of the provisioning process. Especially, the reliability and maintainability analysis tool for cloud computing is developed in this paper. Also, we analyze actual data to show numerical illustrations of application of the software analysis tool considering the characteristics of cloud computing. Copyright © 2015 John Wiley & Sons, Ltd.     

Electrochemical investigation of uranium β-diketonates for all-uranium redox flow battery

The redox flow battery using uranium as the negative and the positive active materials in polar aprotic solvents was proposed. In order to establish the guiding principle for the uranium compounds as the active materials, the investigation of uranium β-diketonate complexes was conducted on (i) the solubility of active materials, (ii) the electrode reaction of U(VI) and U(IV) β-diketonate complexes and (iii) the estimation of the open circuit voltage of the battery. The solubilities of higher than 0.8 mol dm⁻³ of U(VI) complexes and higher than 0.4 mol dm⁻³ of a U(IV) complex were obtained in the solvents. The electrode reactions of U(pta)₄, UO₂(dpm)₂, UO₂(fod)₂ and UO₂(pta)₂ were first studied and the redox potentials of uranium β-diketonates were thermodynamically discussed. The open circuit voltage is estimated more than 1 V by using Hacac or Hdpm. The larger open circuit voltage is expected when a ligand with the larger basicity is used.     

Quantitative analysis for reaction between epoxidized natural rubber and poly (L‐lactide) through 1H‐NMR spectroscopy

Reaction between epoxidized natural rubber and poly(L ‐lactide) (PLLA) was investigated quantitatively in terms of conversion of the epoxidized natural rubber. The epoxidized natural rubber was prepared by epoxidation of high ammonia natural rubber (HA‐NR) or deproteinized natural rubber (DPNR) with peracetic acid followed by depolymerization with ammonium persulfate. The resulting liquid HA‐NR having epoxy group (LENR) or liquid DPNR having epoxy group (LEDPNR) were subjected to heating at 473 K for 20 min, after blending with PLLA. The products were characterized through morphology observation, DSC measurement, and ¹H‐NMR spectroscopy. The conversions of the rubbers were estimated from intensity ratio of signals in ¹H‐NMR spectrum for the products after removing unreacted rubber with toluene. Difference in the estimated conversion between the LENR/PLLA and LEDPNR/PLLA blends was interpreted in relation to proteins present in the rubber. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010