Effect of weld tip geometry on ultrasonic welding of A6061 aluminium alloy

The authors ultrasonically welded A6061 aluminium alloy sheet using two types of weld tips with different contact face geometries, and investigated the effect of the weld tip on the performance and interface structure of the welds. One type of tip has a cylindrical contact face without knurl, which is called a C-tip in this study. The other type of tip has a flat contact face with knurl, which is a called K-tip in this study. The following main results were obtained.

The strength of the joints welded using the C-tip was higher than that welded using the K-tip and the fluctuation in joint strength with the C-tip was smaller. The C-tip could stably produce the higher strength joint. Using the K-tip, the knurl indentations were made on the workpiece surface due to the pyramidal projections on the weld tip, and the indentation size expanded with welding time, resulting in the deterioration of the joint property. On the other hand, the indentation made on a workpiece surface by using the C-tip showed a distinctive shape like an ellipse, elongated perpendicular to the ultrasonic vibration, and the indentation grew with welding time.

Using the K-tip, unbonded regions remained at the weld interface due to the concavity on the weld tip face. In the cross-sectional structure parallel to the workpiece width of the joint welded using the C-type tip, a distinctive feature was observed that the faying surface of the anvil workpiece was mixed with that of the sonotrode workpiece by intense plastic deformation and a horn-like protuberance intruding into the sonotrode workpiece was formed at the periphery of the welded area.     

Novel Synthesis Method of Hydroxyapatite Whiskers by Hydrolysis of alpha-Tricalcium Phosphate in Mixtures of Water and Organic Solvent

A novel and simple nonhydrothermal method was developed for synthesizing hydroxyapatite whiskers under mild conditions. Hydroxyapatite whiskers were synthesized by the hydrolysis of alpha-tricalcium phosphate at 80°C and atmospheric pressure. The effect of aliphatic alcohols on the transformation of alpha-tricalcium phosphate to hydroxyapatite in water-alcohol systems was examined. When the hydroxyapatite was characterized by XRD and TEM observation, its morphology and size were found to vary with the specific alcohol used during hydrolysis. The effect of reaction time on hydrolysis of alpha-tricalcium phosphate to hydroxyapatite also was studied.     

Identification of system characteristics of a power system with time series data. Identification of frequency fluctuation characteristics of a small‐scale isolated system

Understanding actual characteristics of a power system with recorded time series data is of great importance, for example, in improving the performance of the system. Although system identification is a well‐known technique to achieve this goal, its applicability to a certain system should be examined for the particular case because its accuracy highly depends on the inherent characteristics of the system. While many papers have discussed application of a system identification technique to a power system, few papers have examined its applicability to the actual data of a power system. This paper presents a new system identification method to estimate characteristics of a power system while using output of intermittent generators or fluctuating loads as an external disturbance. The method employs cross spectra and coherence as a key factor in the identification; it estimates a transfer function of a power system, contribution of observed disturbance to total disturbance, and so on. The method is applied to time series data of two model systems: simulation results and measured data of an isolated power system with diesel generators. The study gives satisfactory results; implication on the accuracy of the method is discussed through the sample studies. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(3): 36–45, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20051     

Effect of boron concentration in Y2O3:(Eu,B) phosphor on luminescence property

Y₂O₃:(Eu,B) red phosphor was obtained by a thermal decomposition technique of a mixture of yttrium–ethylenediaminetetraacetic acid (Y–EDTA), Eu–EDTA and boric acid. The doping ratio of boron, [B]/([Y]C[Eu]), in the starting material was varied from 0 to 1. The properties of morphology, crystallization behavior, metal composition and photoluminescence of resulting Y₂O₃:(Eu,B) powder were examined. The Y₂O₃:(Eu,B) powder had spherical shape with a diameter of 1–5 mm with some hollows on the surface. No secondary cohesive particles were seen. X-ray diffractometry revealed that although the crystallinity of powder was improved with addition of small amounts of boron, it decreased with excess amounts of boron. Several peaks indexed as the impurity phases of Y₃BO₆ and YBO₃ were observed on the samples obtained under condition of excess amounts of boron. The photoluminescence intensity observed at 611 nm was dependent upon crystallinity of the sample.     

Spontaneous emission from a three-level atom embedded in anisotropic photonic band gap structures

Abstract

We investigate spontaneous emissions from a three-level atom embedded in realistic anisotropic photonic band gap structures, where the band edge is assumed to be midway between the two upper levels of the atom. In the anisotropic model, the atom-field interaction is reduced to be smaller than that in the ideal isotropic model, which results in the reduction of suppression and oscillation effects in the spontaneous emission; however, we demonstrate that the suppression is strongly enhanced even in the anisotropic model by expanding the detuning between the upper level and the band edge, while the oscillation is greatly reduced. This demonstration is carried out by calculating the atomic state vector for a wide range of the detuning. Using the state vector, the atom-field interaction is studied for two field parts, a localized part and a propagating part, separately. For the localized part, the atom-field interaction is enhanced by expanding the detuning, in spite of the anisotropy, which leads to a strong suppression effect, while for the propagating part, the atom-field interaction is reduced, which leads to a weak oscillation effect. This result is relevant to strong memory effects with high-speed switching, which are attractive properties for a qubit.     

Cranberry extract suppresses interleukin-8 secretion from stomach cells stimulated by Helicobacter pylori in every clinically separated strain but inhibits growth in part of the strains

It is known that cranberry inhibits the growth of Helicobacter pylori (HP). In human stomach, HP basically induces chronic inflammation by stimulating stomach cells to secrete interleukin (IL)-8 and other inflammatory cytokines, and causes stomach cancer, etc. The aim of this study was to investigate the inhibiting effects of cranberry on HP growth and IL-8 secretion from stomach cells induced by HP, using clinically separated HP strains. HP growth in liquid culture and on-plate culture was evaluated by titration after 2-day incubation and by agar dilution technique, respectively. For IL-8 experiments, MKN-45, a stomach cancer cell line, was incubated with HP for 24 h and IL-8 in the medium was assayed by ELISA. Cranberry suppressed growth of the bacteria only in six of the 27 strains. Meanwhile, it suppressed IL-8 secretion in all the strains. The results may suggest a possible role of cranberry in prevention of stomach cancer by reducing gastric inflammation.     

Breast Cancer Detection Using an Ultrashort-Pulse Radar System in Synthetic Breast Phantom Model

Using ultrashort-pulse radar with compact vivaldi antennas,the simulation experiment of breast cancer detection has been performed in a synthetic breast phantom.Two metallic balls with 9 mm and 6 mm in diameter are used as tumors in our experiment.The image reconstructions of the breast models with tumors using reflection data have been presented by a confocal microwave imaging technique.The method can be used for a pulse compression technique to reflected waves for clear image formation.