Efficient error estimation and adaptive meshing method for boundary element analysis

This paper describes a new and efficient error estimator by using the Direct Regular Method and h or h-r adaptive meshing for BEM analysis. This posteriori error estimator correctly indicates the discretization errors on each element. Based on the error distribution, and the adaptive meshing is generated automatically. The accuracy and convergence of this method are demonstrated by the numerical results on the stress concentration problem and the crack problem.     

Characterization of vacuum-annealed TiNb2O7 as high potential anode material for lithium-ion battery

Electrochemical properties of mixed titanium-niobium oxide TiNb₂O₇ (TNO) synthesized via vacuum annealing as high potential anode material for lithium-ion batteries were investigated. Crystal structure, size, and morphology are nearly independent of the annealing atmosphere for starting materials but the color of vacuum-annealed TNO (TNO-V) is dark blue while white for the air-annealed one (TNO-A). X-ray photoelectron spectroscopy analysis also indicated that Ti⁴⁺ and Nb⁵⁺ in TNO are partially reduced into Ti³⁺ and Nb⁴⁺ due to the introduction of oxygen vacancy. Electronic conductivity for TNO-V was around 10⁻³ S cm⁻¹ at room temperature and much higher than that for TNO-A (=10⁻¹¹ S cm⁻¹). In electrochemical testing, both TNO-A and TNO-V electrodes showed reversible capacity of 260-270 mAh g⁻¹ at low current density of 0.5 mA cm⁻², while at higher current density of 5.0 mA cm⁻², TNO-V electrode retained higher reversible capacity of 140 mAh g⁻¹ than that for TNO-A electrode (=80 mAh g⁻¹). The enhancement of intrinsic electronic conductivity greatly contributes to improve the rate performance of TNO.     

In situ IR-RAS investigation of corrosion of tin in air containing H_2O, NO_2 and SO_2 at room temperature

In order to obtain a fundamental understanding of the corrosion behavior of tin in atmosphere, in situ IR-RAS (infrared reflection absorption spectroscopy) measurements were performed on tin in humid air containing SO2 and NO2 at room temperature. Time-resolved in situ IR spectra in air of 90% RH (relative humidity) containing 1×10-5-2.2×10-5 SO2 suggested that the tin oxide layers worked as a protective film and no significant corrosion occurred. The corrosion products in air of 80%-90% RH containing 1×10-5-2.2×10-5 NO2 were SnO2, SnO, nitrate and hyponitrite. The synergistic effect of SO2 and NO2 on corrosion of tin was not observed in air of 90% RH containing 0.84×10-6 SO2 and 1.8×10-6 NO2.     

Analysis of eddy currents in laminated silicon steel sheets of permanent magnet‐type MRI by 3d finite element method using multinode technique

We developed a method, called the multinode technique, that can take into account any electrical isolation of conductors using the multinodes of the electric scalar potentials. The eddy currents in the laminated silicon steel sheets can be calculated using this method without the mesh of the interlaminar air gap. It is quantitatively clarified that the eddy currents in the laminated silicon steel sheets in a permanent magnet‐type MRI system have effects on the time variations of the flux distributions. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 156(1): 61–69, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20208     

Characteristics of microwave plasma induced by lasers and sparks

Characteristics of the plasma light source of microwave (MW) plus laser-induced breakdown spectroscopy (LIBS) or spark-induced breakdown spectroscopy (SIBS) were studied. The plasma was initially generated by laser- or spark-induced breakdown as a plasma seed. A plasma volume was then grown and sustained by MWs in air. This MW plasma had a long lifetime, large volume, strong emission intensity, and high stability with time. These characteristics are suitable for applications in the molecular analysis of gases such as OH or N(2). Because the plasma properties did not depend on laser or spark plasma seeds, the resulting plasma was easily controllable by the input power and duration of the MWs. Therefore, a significant improvement was achieved in the spectral intensity and signal-to-noise ratio. For example, the peak intensity of the Pb spectra of LIBS increased 15 times, and that of SIBS increased 880 times without increases in their background noise. A MW-enhanced plasma light source could be used to make the total system smaller and cheaper than a conventional LIBS system, which would be useful for real-time and in situ analysis of gas molecules in, for example, food processing, medical applications, chemical exposure, and gas turbine or automobile air-to-fuel ratio and exhaust gas measurement.     

Analysis of an optical resonator formed by a pair of specially shaped axicons

We propose a design for an optical resonator suited to using large-bore active media. The resonator consists of a pair of waxicons, so we call it a "wwaxicon optical resonator." The resonator is considered a conventional (solid) resonator surrounded by coaxial annular resonators. A numerical simulation of the resonator designed for use in a commercial CO2 laser is performed. It is found that parasitic oscillation modes can be suppressed by the use of an spatial-frequency filter. The resonator exhibits oscillation in the TEM*01 transverse mode and produces twice as much output power as a sevenfold multipass stable optical resonator.     

Phase Separation in Sol–Gel Process of Alkoxide-Derived Silica-Zirconia in the Presence of Polyethylene Oxide

Phase separation in a sol–gel process of SiO₂–ZrO₂ in the presence of polyethylene oxide is investigated. An amorphous gel with interconnected macroporous morphology is obtained when phase separation and sol–gel transition concur to fix a transitional structure of spinodal decomposition. Macropore size, together with connectivity of the pores and gel skeleton, can be controlled precisely by selecting an appropriate starting composition for preparation at a zirconium content ≤11.7 mol%. The macroporous gel retains additional mesopores <4 nm and exhibits typical bimodal pore size distribution. The addition of ZrO₂ in SiO₂ improves the thermal stability of both macroporous and mesoporous structures.     

Excited states and optical properties entirely from first principles: Extended FLAPW method and its graphical user interface

This review serves to explain in some detail the nature and unique treatment of optical properties entirely from first-principles within the powerful FLAPW code and its accompanying sophisticated GUI. One unique feature of the method and its code is the viewing and printing of the various calculated optical properties – Im (eps), Re (eps), N, K, R, EELS and alpha – in the same way as the band structure, charge and spin densities and the density of states were done in the previous version of the FLAPW code. Another unique feature is the ability to calculate the optical properties in several modes, with the LDA and/or the model GW and the sX-LDA approaches (each with and without the inclusion of spin-orbit coupling). The code is also designed to carry out accurate calculations of the optical properties of dilutely doped semiconductors employing several dilute limit simulation tools: these include k-mesh refinement around a certain k-point within a given radius, edge refinement (which refines the tetrahedra around the Fermi energy to get an accurate absorption edge), a further k-mesh refinement to take account the user-specified (or calculated) Fermi level that reflects the dopant or defect concentration, simulation of temperature effects with the Fermi-Dirac statistics, etc. This revised version was published online in June 2006 with corrections to the Cover Date.     

Secure Service and Network Framework for Mobile Ethernet

Secure cellular data services have become more popular in the Japanese market. These services are based on 2G/3G cellular networks and are expected to move into the next-generation wireless networks, called Beyond 3G. In the Beyond 3G, wireless communication available at a user's location is selected based on the type of the service. The user downloads an application from one wireless network and executes it on another. Beyond 3G expects core and wireless operators and allows to plug-in new wireless access. A security model that can accommodate these requirements needs to be sufficiently flexible for end users to utilize with ease. In this paper, we explain the Mobile Ethernet architecture for all IP networks in terms of the Beyond 3G. We discuss usage scenario/operator models and identify entities for the security model. We separate a mobile device into a personal identity card (PIC) containing cryptographic information and a wireless communications device that offers security and flexibility. We propose a self-delegation protocol for device authentication and use a delegated credential for unified network- and service-level authentication. We also propose proactive handover authentication using the security context between different types of wireless access, such as Third Generation Partnership Project (3GPP) and WLAN, so that the secure end-to-end communication channels established by service software on the TCP/IP are not terminated. Lastly, we raise security issues regarding the next-generation platform.