Toshiro Tanaka

Crystal-Originated Singularities on Si Wafer Surface after SC1 Cleaning

It is clarified that a new type of singularity is formed on Si wafer surface by the Standard Cleaning 1 (SC1) of the RCA cleaning process. Such singularities are perceived by laser particle counters as small particles on wafers. It is shown that the singularities correspond to small shallow pits caused by the etching effect of the SC1 cleaning solution. The origin of the pits is presumed to be some kind of defect in the melt-grown crystals.

Simultaneous measurement of the phase and group velocities of Lamb waves in a laser-generation based imaging method.

This paper describes a novel approach to the simultaneous measurement of the phase and group velocities of Lamb waves based on images of their propagation. The laser-generation based imaging method was first introduced to obtain images of Lamb wave propagation. The time series of snapshot images is used to make a position-time diagram, and the velocities can be estimated based on the slopes of the position curves. Thus, the phase and group velocities can be obtained by measuring the phase advance and energy flow of the Lamb wave, respectively. Details of the principle of simultaneous measurement are presented herein. Experimental verification was also performed in the range of 0.2-3.0 MHz-mm using aluminum plates. The average errors between experiment and theory in the phase and group velocities were 3.31% and 5.68%, respectively.

Experimental Investigation of Mode Conversions of the T(0,1) Mode Guided Wave Propagating in an Elbow Pipe

Mode conversions from the fundamental torsional guided wave mode, T(0,1), to the higher-order torsional modes, T(1,1), T(2,1), T(3,1), and T(4,1), at a welded elbow pipe were experimentally investigated in a wide frequency range from 30 to 80 kHz. One ring-shaped transducer system was used as the transmitter and another as the receiver. Both systems consist of eight circumferentially located piezoelectric transducer elements. A novel method for a preferential detection of the torsional modes was proposed on the basis of the circumferential wave structures of the modes, which was utilized for investigations of mode conversions. Dispersion relations of the converted modes in frequency ranges from 30 to 80 kHz were also experimentally investigated, which agreed very well with those of the theoretical calculations.

Punchthrough Probability of Josephson Logic Gates

The operating speed of Josephson logic gates is restricted by the punchthrough phenomenon, which has a probabilistic nature. The punchthrough probability for identical operating speeds varies according to the type of gate. This paper reports a study of the punchthrough probability for two-junction interferometers and resistor-coupled gates. With the interferometers, the punchthrough probability is predicted from the equation of motion for the center of the phase of the two junctions. With the resistor-coupled gates, the punchthrough probability is calculated by taking into account the dumping effect produced by the resistors of the gates. The predictions are confirmed by computer simulation.

System design to improve running-form with motion-capture

In this paper, we propose a system to help learners improve the running form by the motion-capture system. We can capture the running form along with the time processing by this system. The system assumes the ideal running form that keeps the stable style. An ideal form is given by an expert. The system detects and represents the difference between learners form and pre-defined ideal form. In order for that, the system compares the current form with an ideal form that is represented by three-dimensional values. In our system, an ideal running-form is previously defined. The system also presents an advice of improving the running-form for learners.

Highly Sensitive Detection of Defects in Piping Using Multireflecting Guided Wave Energy Trapping Method

A multireflecting guided wave energy trapping (MGET) method has been developed for the highly sensitive detection of defects in a pipe using a guided wave. The MGET method enhances the amplitude of a defect signal using two wave reflectors. In the MGET method, the two reflectors are set at both ends of a region of piping to be inspected, and a guided wave is generated, which propagates in the region of inspection. With this setup, multireflection can be observed between the two reflectors. If a defect exists in the region, the amplitude of the defect signal increases owing to the increase in the number of reflections at the reflectors because n combinations of multiple propagation paths having the same path length exist in the defect signal after n reflections. Details of the principle of the MGET method and its experimental verification are reported. The sensitivity of the MGET method is about 10 times higher than that of the conventional guided wave method. The efficiency of the method is quantitatively discussed by considering a simple mathematical model together with the experimental results.

The influence of fluorine addition on the crystal structure and electrical properties of a YBa2Cu3O7−δ oxide superconductor

The influence on crystal structure and electrical properties of fluorine ions replacing oxygen ions in the YBa2Cu3O7-δ lattice is observed by mixing BaF2 powder and calcining at 1193 K. Within a small limit, the increase of BaF2 addition gives a sharp rise to the lattice constant of the c-axis while excess addition over the limit causes almost no change in the lattice constant. This suggests that BaF2 dissolves in solid solution with the minute solubility limit which is estimated to be around x=0.15 in the form of YBa2Cu3O7-δFx. The zero-resistivity transition temperature is the highest at x=0.10.