Characteristics of the optical resonator composed of the nonlinear directional coupler

This paper describes a simple method of analysis of an optical resonator composed of a nonlinear directional coupler. Assuming the coupler is made in semiconductor‐doped glass by the K⁺‐ion diffused technique, the transmission and reflection characteristics are calculated and demonstrated. The parameter dependence of the bistability appearing in the transmitted and reflected light is also presented. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(3): 1–10, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20036     

Intergranular stress corrosion cracking behavior of niobium-added Type 308 stainless steel weld overlay metal in a simulated BWR environment

Type 308 stainless steel weld metal as an internal cladding of reactor pressure vessels for boiling water reactors is subject to postweld heat treatment during fabrication and can suffer sensitization depending on carbon and ferrite contents. This sensitization can be avoided by using niobium-added Type 308 weld metal (specified as Type 308 NbL) which was developed for one-layer overlay welding application. In the present study, stress corrosion cracking (SCC) behavior of heat-treated Types 308 and 308NbL weld metals in oxygenated high temperature pure water was evaluated by slow strain rate test and U-bend tests with and without crevice. Every test showed that Type 308NbL weld metals were highly resistant to SCC compared to ordinary Type 308 weld metals. In single U-bend test, one-layer overlay weld metals of Type 308NbL produced by electroslag welding process using wide strip electrodes were crack free over 23,000 h. The U-bend test data of ordinary Type 308 weld metals were successfully analyzed by an SCC reaction model. Using this analysis, the SCC life margin for Type 308NbL over ordinary Type 308 weld metals, expressed as a ratio of respective times to SCC initiation, was estimated to be about 36.     

Intergranular stress corrosion cracking behavior of types 308 and 316 stainless steel weld metals in a simulated boiling water reactor environment

The sensitization behavior of types 308 and 316 stainless steel weld metals as internal overlays for reactor pressure vessels (RPVs) was studied with respect to the effects of postweld heat treatment (PWHT) at about 600 °C during RPV fabrication and low-temperature aging during operation. For the study, a criterion for the rate of intergranular corrosion (IGC) for detecting the susceptibility to intergranular stress corrosion cracking (IGSCC) in high-temperature oxygenated pure water was established by quantitatively evaluating the results from a modified ASTM A262E test. A criterion for expecting satisfactory resistance to IGSCC was found to be an IGC rate of about 1 μm/h. Type 308 weld metal can be sensitized as indicated by an IGC rate >1 μm/h, and can be healed, as indicated by an IGC rate <1 μm/h, depending on the length of PWHT. However, this healed weld metal can be resensitized by exposing it to 500 °C×24 h; in this condition, it shows a relatively high susceptibility to IGSCC. On the contrary, type 316 weld metal was almost immune to sensitization under the same heat treatments. By transmission electron microscopy (TEM), its excellent resistance was attributable to carbon fixation by molybdenum carbide precipitation within ferrite phases during PWHT. Reheat embrittlement of type 316 weld metal was also examined.     

Conjugate Heat Transfer Analysis of Film Cooling Flows

The objective of this study is to evaluate the potential of various grids to satisfactorily simulate the development of a cooling film, using a coupled computation that takes into account the full geometry. Detailed computations of a single row of 30 degrees round holes on a flat plate are presented for blowing ratios of 0.764,1.01 and 1.54. The simulation results are compared well with experimental data. The two-layer model gave more accurate results but consumed much more computational time than the standard wall functions. The k-e turbulence model with wall functions with appropriate values of y is suitable for practical use. The results show the importance of the conjugate calculation for accurately describing the influence of the heat transfer within the cooling film.     

Novel charge neutralization techniques applicable to wide current range of FIB processing in FIB-SEM combined system

FIB-induced charging is one of the most critical issues for achieving successful circuit modifications of LSI. We have developed novel charge neutralization techniques applicable to a wide current range (from pico to nanoampere-order) of FIB processing in a FIB-SEM combined system. The method utilizes a 500 eV focused electron beam instead of an electron shower, and also a combination of microprobing and FIB-assisted deposition to make a current path from FIB processing point to the grounded microprobe. The effects of our techniques on charge neutralization capability were investigated using electrically erasable-programmable read-only memory devices and n-MOS transistors. For the low FIB current condition of less than 500 pA, it is found that the focused electron beam prevents threshold voltage shifts of both irradiated and neighboring transistors, and that the ratio of electron to ion beam currents is a key parameter to achieving effective charge neutralization. We also demonstrated that the combined method of microprobing and FIB-assisted deposition prevents parameter shifts of transistors even for high-current (nanoampere-order) FIB irradiation. Moreover, we evaluated the upper-limit resistance of the current path formed by FIB-assisted carbon deposition to prevent charging induced by a given FIB current.     

Characterization of structure of single particles from various automobile engines under steady-state conditions

The effective density ρ_eff of particles emitted from various types of automobile engines was measured using a differential mobility analyzer (DMA)–aerosol particle mass analyzer method, and their morphology was investigated via transmission electron microscopy analysis. The measured exhaust particles were particles emitted from diesel engines (DEs), gasoline direct injection spark ignition (DISI) engines, gasoline port fuel injection (PFI) engines, and liquefied petroleum gas (LPG) engines. ρ_eff and the morphology of the particles were measured after classification with the DMA, and six electrical mobility diameters D_m ranging from 30 to 300 nm were selected. ρ_eff was found to decrease as D_m increased for all particles. A morphological study showed that DE and DISI particles were mainly agglomerates and PFI and LPG particles were mainly nonagglomerates. Numbers and diameters of the primary particles in the agglomerates showed no systematic differences between DE and DISI particles at a given D_m. Rather, the primary particle diameter d_p increased with increasing D_m of the agglomerates; the empirical relationship between the two diameters was found to be d_p = 8.498ln(D_m) – 12.781 for DE and DISI particles. The core (elemental carbon) diameters in the primary particles of the DE particles increased as D_m increased and were estimated to range from 8.5 nm for D_m = 70 nm to 22.1 nm for D_m = 300 nm. Although the primary particle diameter and core diameter depend on D_m, the organic coating (shell) thickness, which ranged from 5.1 to 7.4 nm, was found to be independent of D_m.

Copyright © 2016 American Association for Aerosol Research     

Sulfidation properties of Cr23C6 at 1073 K in H2S-H2 atmospheres of 103.5−10−6 Pa sulfur pressure

The sulfidation behavior of chromium carbide, Cr₂₃C₆, was investigated in H₂S-H₂ gas mixtures over a sulfur partial pressure range of 10^3.5–10^–6 Pa at 1073 K using thermogravimetry, optical and scanning electron microscopy, X-ray diffraction analysis, and electron-probe microanalysis. The kinetics were rapid for short time periods and followed a linear rate law at low sulfur pressures, whereas sulfidation tends to obey a parabolic rate law at high pressures. Sulfidation rates decreased with increasing carbon content in the carbide. Surface morphologies could be divided into three groups: (I) at high sulfur pressures, petal-like. crystals (Cr₂S₃); (II) at intermediate pressures, a twinlike structure (Cr₃S₄); (III) and at low pressures, a flat surface with numerous hexagonal pits (Cr_1–xS). The scale consisted of two distinct layers: an external scale with a single or multilayer structure and an inner scale with a mixture of Cr_1–xS, Cr₃C₂, and Cr₇C₃. These higher carbides, Cr₃C₂ and Cr₇C₃, may be formed by the sulfidation-carburization of Cr₂₃C₆. Pt-marker experiments indicated that the external scale grew by chromium diffusion and that sulfur migration played an important role in the growth of the inner scale.     

Airflow produced by dielectric barrier discharge between asymmetric parallel rod electrodes

We observed a novel type of airflow produced by an atmospheric rf discharge between asymmetric parallel rod electrodes. The electrodes were a bare metal rod 1 mm in diameter and a glass-coated metal rod 3.2 mm in diameter. The thrust, measured by a pendulum, increased with discharge input power.     

High‐pressure synthesis of a 12CaO·7Al2O3–12SrO·7Al2O3 solid solution

Solid solutions of 12CaO·7Al₂O₃ (C12A7) and 12SrO·7Al₂O₃ (S12A7) crystals were synthesized under high pressure. X‐ray diffraction patterns revealed that the lattice constants of the synthesized samples depend linearly on the compositional ratio of C12A7 and S12A7. Electron‐probe X‐ray microanalyses show that the chemical compositions of the crystals are represented by xC12A7·(1?x)S12A7 (0<x<1). These results indicate that the variation in the lattice constants is originated from a difference in the ionic radii of Ca²⁺ and Sr²⁺ ions. From impedance measurements, it was found that S12A7 has the highest conductivity (~1 × 10^?3 Scm^?1 at 550°C) among the solid solutions in the C12A7–S12A7 system.