Fracture mechanism characterization of cross-ply carbon-fiber composites using acoustic emission analysis

The sequence of microscopic fracture mechanisms in locally loaded cross-ply carbon-fiber composites was studied by analyzing acoustic emission (AE) signals in combination with the modal analysis of Lamb waves, using microscopic and ultrasonic examination of the specimen after load interruption. The first 70 AE events were analyzed, which were detected during the initial loading segment when the first sudden load drop and gradual load recovery were observed. Characteristics of the detected waves were compared with the S₀- and A₀-mode Lamb waves produced by a spot- or line-focused YAG laser. The internal damage progression of the composite specimen was determined to be the fiber fracture in the front lamina, transverse cracks in the mid-lamina, delamination and splitting.     

Estimation method for the light extraction efficiency of light-emitting elements with a rigorous grating diffraction theory

The light extraction efficiency of a light-emitting element with microstructured surface is analyzed with a rigorous grating diffraction theory. The grating theory reveals an improvement of extraction efficiency due to diffraction of light by the surface microstructure. The simulation results show that the improvement of extraction efficiency is due mainly to the reflected diffraction rather than to the transmitted diffraction. A part of total-internal-reflection light is diffracted into directions at less than the critical angle. Extraction efficiency is improved by multiple reflection and diffraction of light in a high-refractive-index layer. We propose a simple design method for an efficient surface microstructure from the viewpoint of reflected diffraction.     

Field evaluation of UHF radio propagation for an ITS safety system in an urban environment

Roadside-to-vehicle and vehicle-to-vehicle communication systems have been proposed as part of ITS development to help achieve vehicle safety and realize more secure road traffic environments. In this article we first introduce several typical applications and their radio range requirements for vehicle safety communication systems to clarify the technical point of view. Then we show some field experiment results in an urban area in Tokyo to investigate and verify the radio propagation characteristics and the quality of communications by using a wireless radio prototype system. Finally, we conclude that the current prototype system has potential to fulfill the radio range requirements of vehicle safety communications, but there are still lots of issues that need to be addressed.     

Collapse of micrometer-sized cavitation bubbles near a rigid boundary

The interaction of cavitation bubbles with a rigid boundary and its dependence on the distance between bubble and boundary is investigated experimentally. Individual cavitation bubbles, with a maximum radius of 150?μm, are generated by using pulsed high-intensity focused ultrasound. Observations are made with high-speed photography with framing rates of up to 200?million frames per second and exposure time of 5?ns, and the spatial resolution is in the order of a few micrometers. The significant parameter of this study is the non-dimensional stand-off parameter, γ, defined as the distance between the ultrasound focus and the rigid boundary scaled by the maximum bubble radius. Both the velocity of the liquid jet developed during bubble collapse and the maximum pressure of the shock wave emitted during bubble rebound show a minimum for γ?≈?1 and a constant value for γ?>?3. The maximum jet velocity is slightly smaller than the corresponding values obtained in the case of millimeter-sized bubbles and ranges from 80?m/s (at γ?≈?1) to 130?m/s (for γ?>?3). No jet formation was observed for γ?>?3. The shock wave pressure, measured at a distance of 5?mm from the emission center, ranges from 0.2?MPa (at γ?≈?1) to 0.65?MPa (for γ?>?3). These values are an order of magnitude smaller than those obtained in the case of millimeter-sized bubbles. The shock wave duration is almost independent of γ at a value of about 75?ns. For large γ values (γ?>?3), a large percentage of the bubble energy (up to 60?%) is transformed into the mechanical energy of the shock wave emitted during bubble rebound but, for γ?≈?1, the conversion efficiency decreases to 30?%. Independent of the relative distance between bubble and rigid boundary, the shock pressure decays proportionally to r ^?1 with increasing distance r from the emission center. The results are discussed with respect to cavitation damage and collateral effects in pulsed high-intensity focused ultrasound surgery.     

Electron microscopic observation on the parathyroid gland of the cardiomyopathic hamster (UM-X7.1 Syrian hamster).

The ultrastructure of the parathyroid gland (PTG) of the UM-X7.1 cardiomyopathic hamster (the UM-X7.1) was qualitatively and quantitatively compared with that of the normal hamster. In the UM-X7.1, the Golgi apparatus and rER were well developed compared with those of the control hamster. Morphometric analysis revealed that the mean values of the Golgi apparatus, rER and large vacuolar bodies were significantly greater in the UM-X7.1 than in the normal hamster and the mean value of lipid droplets was significantly less in the UM-X7.1 than in the normal hamster. Ultrastructurally, we consider that in the UM-X7.1, the synthesis and release of the parathyroid hormone may be activated by an excessive amount of circulating catecholamine, and the functional activity of the PTG may be higher than that in the normal hamster.     

Growth Mechanism of Monodispersed ZrO2 Particles

Monodispersed ZrO₂ seed particles which were prepared by hydrolysis of zirconium alkoxide solutions were allowed to grow by further addition of zirconium alkoxide and water under conditions in which new particles do not nucleate and grow. The particle growth mechanism is presumed to be a surface reaction in which the rate-determining step is a first-order polynuclearlayer growth mechanism. With this method of powder preparation, it is possible to precisely control the particle size, and it may be useful for applications in ceramic processing.     

Temperature dependence of high-frequency performance ofAlGaAs/InGaAs pseudomorphic HEMT's

High-frequency measurements of 1.5-μm gatelength AlGaAs/InGaAs pseudomorphic HEMTs have been performed at temperatures ranging from 77 to 463 K. A 28% increase and 27% decrease in f_T were observed by changing the temperature from 300 to 77 K and from 300 to 463 K, respectively. The effective saturation velocity evaluated from the total delay time, 1/2πf_T, versus reciprocal I_DS relation reveals almost the same temperature dependence as f_T. It is also shown that the temperature dependence is similar to that of calculated velocity at high electric fields but not to that at low fields. This suggests that the temperature dependence of the HEMT performance is determined by that of the saturation velocity in the channel     

cDNA cloning, tissue distribution, and subcellular localization of horseshoe crab big defensin

A full-length cDNA for horseshoe crab big defensin with a strong antimicrobial activity was obtained from a hemocyte cDNA library. The open reading frame of the cDNA coded for an NH2-terminal signal sequence followed by a propeptide and the mature big defensin. The propeptide is linked to the mature protein through an -Arg-X-Lys/Arg-Arg- motif, the processing site for Kex2-like proteases. Northern blot analysis revealed that big defensin is expressed in all the tissues tested, suggesting that big defensin plays an important role not only in hemocytes but also in other tissues for host defense. The subcellular localization, determined by immunocytochemistry at ultrastructural level, confirmed the previous findings obtained by biochemical analysis that big defensin locates in both small and large granules in hemocytes. Big defensin is the first example to demonstrate the existence of broad tissue distribution in horseshoe crab.