Theory of dislocation tunneling through a pinning point

We have calculated the transition rate for a string unpinning from a point barrier, using a truncated parabolic potential. In this approximation, it was shown that the result for this N-dimensional system has the one-dimensional form R=ν_effexp (−ΔU/kT_eff), where ν_eff is an effective frequency, ΔU the barrier height, T_eff the effective temperature. There is a crossover temperature T* separating the high temperature classical behavior from the low temperature quantum rate and given by T*=ω_eff/2k. The effective temperature is given by the actual temperature above T*, while below it, is given by the ground state energy, calculated using the effective frequency. The important point is that if one knows the transition rate at high T, then the crossover temperature and the low T transition rate may be calculated. The effective frequency has been calculated for dislocations in the classical regime: ν_eff0.26 (U₀/Gb³) ν_D, where U₀ is the binding energy with a pinning atom, G the shear modulus, b the Burgers vector, and ν_D is the Debye frequency. The predicted crossover temperature of a few tenths Kelvin for an Al crystal is in good agreement with our recent experimental results.     

Risk assessment of airborne fine particles and nanoparticles

Pulmonary health effects of fine particles and nanoparticles are overviewed in this paper, mainly based on the researches conducting in our laboratory. For the hazard assessment, we exposed rats to aerosolized asbestos-substitutes or nanoparticles aerosols (nickel oxide and titanium dioxide), and examined the biological and pathological effects of the particle on lung, a major target organ for the particles, and cytokines which are related to inflammation, fibrosis and carcinogenesis in the lung. It is essential to perform comprehensive evaluation of the toxicity of poorly soluble powder samples using the precise characterization data and exposure methods, such as single instillation or aerosol inhalation.     

Reaction of thiobarbituric acid with saturated aldehydes

The reaction of thiobarbituric acid (TBA) with saturated aldehydes, i.e., 1-butanal, 1-hexanal and 1-heptanal, produced a 455-nm yellow and a 532-nm red pigment. Formation of the pigments depended on the reaction conditions. The yellow pigment was unstable in the presence of excess amounts of the saturated aldehydes. The red pigment was formed only when the reaction was performed at a TBA/aldehyde ratio of 1∶1 in aqueous acetic acid. Formation of the yellow and red pigments required molecular oxygen. The colorless adducts, intermediates for the yellow and the red pigments, were isolated from the reaction mixtures. Aldol condensation and dehydration of 2 mol of the saturated aldehydes initially gave the α,β-unsaturated aldehydes, which in turn reacted with TBA to form the colorless adducts, pyranopyrimidine derivatives. The adducts were then converted into the yellow and red pigments under aerobic conditions.     

Detection of back-side pit on a ferrous plate by magnetic flux leakage method with analyzing magnetic field vector

We have developed a magnetic flux leakage (MFL) system using magnetic resistive (MR) sensors for detecting two dimensional magnetic field components, and an induction coil that generates low magnetic field strengths and extremely low frequencies. The signal at each scanned measurement point (i) was divided by the signal strength M_mes,i and phase α_i by a lock-in amplifier. Using the strength M_mes,i and phase α_i, we calculated the imaginary part of the signal using the common phase β. By optimization of the common phase β to the imaginary part, the analyzed scanning data curve was shown to be effective in estimating the size (depth and diameter) of back-side pits on a ferrous plate. Comparing the two dimensional magnetic field components of leakage, the imaginary part of the y-component parallel to the induced magnetic field was found to be suitable for detecting the back-side pits.     

High-velocity impact experiment of aluminum foam sample using powder gun

Porous materials such as aluminum foam have been investigated for possible use as impact shock absorbers in transportation aeronautic applications. However, the response of aluminum foam during impacts at high velocities of more than 100 m/s is not yet fully understood. A high-velocity impact experiment was therefore carried out to clarify impact shock absorption properties of aluminum foam. A one-stage powder gun was used to accelerate an aluminum foam sample to impact a rigid wall. Velocity and deformation of the aluminum foam sample during impact was studied using a digital high-speed video camera, while the pressure wave in the aluminum foam sample was measured using a PVDF gauge. The experimental observations revealed uneven collapse of the aluminum foam sample structure during high speed impact with a general stress plateau effect, typical for cellular material structures when subjected to quasi-static loading.     

Microanalyses on the RuO2 Particle–Glass Matrix Interface in Thick-Film Resistors with Piezoresistive Effects

The piezoresistive mechanisms of composite thick films based on RuO₂ particles and both calcium-borosilicate and bismuth-borosilicate glass matrices were investigated by chemical and electrical microanalyses. The resistor based on bismuth-borosilicate glass showed higher sensitivity than that based on calcium-borosilicate glass. It was confirmed that the diffusion of ruthenium into glass affects the binding state of RuO₂ at the interface of the glass. Furthermore, an intermediate resistive layer is detected around the RuO₂ particle. These results suggest that the piezoresistive effect is related to a change in the electrical conductivity of the interfacial reaction layer caused by the diffusion of ruthenium into glass.     

CVCF inverter based on nonlinear control of instantaneous active and reactive power and its operation characteristics

This paper describes a direct‐power‐controlled CVCF inverter and presents its experimentally examined operation characteristics. The most important feature of this strategy is the direct selection of the switching states of the CVCF inverter to restrict errors between the feedback and command values of active and reactive power. In addition, this paper presents a theoretical analysis of the relationship between the instantaneous power and the switching state, which is essential for deriving a switching‐state table for the controller. The feasibility of the proposed method was verified through several computer simulations and experimental tests using a 2.0‐kVA prototype setup. The output voltages were confirmed to be stable sinusoidal waveforms with a total harmonic distortion of 1.13% under nonlinear load conditions. Excellent voltage balance was achieved by the proposed strategy even under unbalanced load conditions. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 174(3): 62–69, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21023     

Maximum‐power‐point tracking method of photovoltaic power system using a single transducer

This paper describes a novel strategy of maximum‐power‐point tracking for photovoltaic power generation systems. A unique feature of this method is the capacity to see the maximum power point using only a single transducer, that is, a Hall‐effect CT or an isolation amplifier. Output power of the photovoltaic can be estimated with an average value and ripple amplitude of the detected reactor current or the capacitor voltage. A conventional hill‐climbing method is employed to seek the maximum power point, using the output power estimated with only the current or voltage transducer. In this paper, not only a theoretical aspect of the proposed method is discussed, but also experimental results are presented to prove the feasibility of the method. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 160(1): 79– 86, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20275     

Signal control by successive updating of control parameters based on prediction of traffic flow

In traditional coordinated traffic signal control on an urban road network, the following two problems occur. First, the conventional method involves a time lag between traffic measurement and signal control. Second, an abrupt switching of control parameters throws the traffic flow into disorder. This paper proposes a new approach to avoid these problems. We increase the frequency of switching. The control parameters are switched as frequently as every two cycles. At the time of switching, minor variations of the ongoing plan are generated. For each variation of plan, traffic delay at each intersection is predicted based on measured traffic data at upstream detectors. Then the plan minimizing the delay is chosen to be the control parameters in the next cycle. In order to evaluate the validity of this approach, experiments were carried out using a traffic simulator. The experiments indicate that the proposed method reduces the queue length significantly, compared with the conventional method. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 161(3): 49–57, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20391     

Difference in the detection limits of flaws in the depths of multi-layered and continuous aluminum plates using low-frequency eddy current testing

We examined the difference in the detection limits of flaws in the depths of multi-layered and continuous aluminum plates using low-frequency eddy current testing. The detection limits were measured by using a magneto-resistive sensor. Comparing the frequency of an applied magnetic field, the detection limit at 50 Hz is deeper than that at 1 kHz. Comparing the sample structure, the detection limit in the multi-layered samples is deeper than that in the continuous samples. These results are likely due to the differences in the skin depth and conductivity of the sample.