Temperature Dependence of Electrical and Thermal Conductivities of an Epoxy-Based Isotropic Conductive Adhesive

The temperature dependence of the transport properties, including electrical and thermal conductivities, of a practical isotropic conductive adhesive (ICA) including an epoxy-based binder was investigated in order to comprehensively evaluate the physical changes induced during exposure to elevated temperatures. The ICA specimens were cured and post-annealed under various conditions in order to clarify the effect of curing state of the adhesive binder on the electrical resistivity. The electrical resistivity at ambient temperature tends to decrease with increasing curing temperature, even if the samples exhibit full conversion. In addition, an annealing effect, resulting in a deviation from a linear relationship in the temperature dependence of resistivity, can be induced during the heating process experienced during resistivity measurements. However, the ICA specimens exhibited similar values for the temperature coefficient of resistivity (TCR), regardless of the curing and post-annealing conditions in the temperature range where the annealing effect is rarely induced, although the thermal history of the specimens significantly influences the absolute values of electrical resistivity. The temperature dependence of the thermal conductivity is almost accounted for by the decrease in the contribution of conducting electrons in the temperature range below the glass-transition temperature, T _g.     

Calculation and uncertainty evaluation of conductance of a precise orifice for orifice-flow method

For the realization of an accurate vacuum standard by the orifice-flow method in high and ultra-high vacuum, it is important to determine the conductance of an orifice accurately. Since the shape of the edge of the orifice significantly influences the conductance, a new orifice with thin tapered edge was designed and fabricated to measure its dimension and shape precisely with microscopy techniques.The area of the aperture was determined with the relative standard uncertainty, u_r, of 0.011% from the diameter measurement. The transmission probability, W, was estimated with u_r of 0.039% using a Monte Carlo calculation from the geometry. Influences of a deviation from cosine distribution of incident molecules due to the geometry of a vacuum chamber and the specular reflection at the orifice edge on the value of W were also discussed.As a result, the conductance was calculated with u_r of 0.041%. The main source of the uncertainty was that of W and originated from its geometry, which verifies that the measurement of orifice edge is important for the accurate evaluation of the conductance.     

Proposal of a Hamming distance detector using neuron MOS transistors

A neuron MOS transistor has been proposed which operates more “intelligently” than a conventional MOS transistor. In this paper, we propose a Hamming distance detector with a large noise margin using the neuron MOS transistors. The proposed circuit accepts two bitstreams to be compared in parallel, and makes it possible to determine if the two bitstreams are identical (“exact match”) or if the Hamming distance between the two bitstreams is within a certain range (“near match”). Moreover, the “acceptable” range of the Hamming distance (in the case of “near match”) can be soft‐programmed. The operating characteristics of the circuit are also analyzed in detail. Furthermore, these analyses are fully confirmed by simulation using the circuit analysis program HSPICE. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 155(1): 44–51, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20223     

The Durability of the Enantio-Differentiating Ability of a Tartaric Acid–NaBr-Modified Reduced Nickel Catalyst Pre-Modified in Tetrahydrofuran

The enantio-differentiating hydrogenation of methyl acetoacetate was carried out over a (R,R)-tartaric acid–NaBr-modified reduced Ni catalyst. The reduced Ni was pre-modified in a tetrahydrofuran solution of tartaric acid and NaBr at atmospheric pressure or at a high hydrogen pressure. The enantio-differentiating ability of 70–90% was maintained during 40 runs over the reduced nickel catalyst pre-modified at 9 MPa hydrogen and 373 K. The results indicated that the durability of a high enantio-differentiating ability of an in-situ-modified catalyst would be attributed to the modification conditions at the high hydrogen pressure of 9 MPa and the high temperature of 373 K in the autoclave.     

A compensation method for the end effect of a linear induction motor

For the end effect of a linear induction motor (LIM), the authors propose a new concept that the end effect can be compensated for only by the supply of secondary current synchronized with the current of the LIM in front of the entry end of the LIM, without considering the flux density distribution in the LIM primary region. As a concrete method to supply the secondary current in front of the LIM, the authors propose the rotator with rare‐earth‐type permanent magnets which has a strong flux density without ohmic loss, and does not cause the power factor problem even for the influence of end effect. The results of analytical study on the numerical example of LIM designed for subways are as follows. This method can make the flux density and thrust density distribution in the LIM primary region almost entirely agree with those of the case without end effects. This method can compensate for the thrust, power factor, and efficiency of the LIM at the rated speed to coincide with the characteristics without end effect. There is no problem in the slip characteristic curves of the LIM with the compensator, although the compensator only rotates synchronizing with the frequency of the LIM. The effect of compensation becomes large in the lower slip. The force to rotate the compensator is very small in the suitable design. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 143(3): 58–67, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10132     

Preparation Conditions and Morphology of Superconducting Fine Particles in the Bi-Ca-Sr-Cu-O System Prepared by Spray Pyrolysis

The morphology and crystalline phases of superconducting fine particles with a composition of Bi₂Ca₁Sr₂Cu₂O_x were studied in terms of preparation conditions, using an aerosol flow reactor with varying temperature profiles: constant, increasing, and humped temperature distributions. The temperature profile in the reactor was found to affect greatly the morphology of the superconducting particles produced. The humped distribution with maximum temperatures over 900°C provided solid particles consisting mainly of the 80 K phase, when other preparation conditions were optimized. This finding indicates the possibility of controlling the morphology, as well as the crystalline phases, of superconducting particles by spray pyrolysis.     

Deposition of Si-DLC film and its microstructural, tribological and corrosion properties

Silicon-incorporated diamond-like carbon (Si-DLC) films were deposited using a bipolar-type plasma based ion implantation and deposition technique, and the effects of Si-incorporation on the microstructural, tribological, anti-corrosion and lubricant bonding properties of the Si-DLC films were investigated. The analysis of Raman spectroscopy exhibited that the sp³ bonds in the DLC film increase due to Si addition. XPS analysis revealed that a thick oxide layer exists on the Si-DLC film surfaces. These explain the high lubricant bonding properties of the Si-DLC films compared to that of the Si-free DLC films. The silicon oxide layer on the Si-DLC film and the transferred silicon oxide layer on the steel ball prevents from the metal/DLC contact between the Si-DLC film and steel ball when sliding, which results in a low friction. Incorporation of Si in DLC films led to significant improvements in the corrosion resistance due to low internal stress and thick insulating oxide layer.     

An efficient method to compute closest loadability limit in power systems

A closest loadability limit (CLL) is considered as a most reliable index in the assessment and enhancement of voltage stability of a power system. Two kinds of methods, the iterative method and the direct N‐R method, have been proposed so far, but the computation of CLL is known to be troublesome. The former method is quite time‐consuming and its convergence is sometimes distributed due to the existence of multiple local CLLs, while the latter method is hardly useful unless a very accurate initial condition is available. This paper proposes a new method to compute a CLL, consisting of three stages of computations. The first stage is to obtain a rough initial estimate of a CLL, where multiple local CLLs can be approximated by the multiple load flow solutions. The initial estimate is refined by the second stage computation based on a method similar to the conventional iterative method. The third stage is to obtain a direct solution by mean of the N‐R method. The effectiveness of the proposed method is demonstrated using IEEE 14, 30, 57, and 118 bus test systems. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 140(1): 57–67, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.1171     

Ir-base refractory superalloys for ultra-high temperatures

The microstructure and compression strengths of Ir-15 at. pct X (X=Ti, Ta, Nb, Hf, Zr, or V) binary alloys at temperatures between room temperature and 1800 °C were investigated to evaluate the potential of these alloys for ultra-high-temperature use. The fcc and L1₂ two-phase structures of these alloys were examined by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The strengths of the Ir-Ta, -Nb, -Hf, and -Zr alloys were above 800 MPa at temperatures up to 1200 °C and about 200 MPa at 1800 °C. The strengths of these alloys under 1000 °C are equivalent to or higher than those of the commercially used Ni-base superalloys, MAR-M247 and CMSX-10. The Nb concentration dependence of strength was investigated using a series of Ir-Nb alloys with Nb concentrations from 0 to 25 at. pct. It was found that the Ir-base alloys were strengthened by L1₂ precipitation hardening. The potential of the Ir-base alloys for ultra-high temperature use is discussed.