Eiji Sakagami

Sound radiation from a double-leaf elastic plate with a point force excitation: effect of an interior panel on the structure-borne sound radiation

Abstract The sound radiation from a double-leaf elastic plate subjected to a point force excitation is investigated theoretically, to gain a fundamental insight into the sound radiation from an interior panel of a double-leaf structure in buildings. The effects of the interior panel on the sound radiation, which show a negative effect at low frequencies due to the mass–air–mass resonance, are discussed in detail. The theory is validated experimentally. As a measure of the efficiency of the interior leaf in reducing noise radiation, the radiation reduction is defined in this study, and it is found useful for predicting the sound radiation due to the structure-borne sound in building elements. Parametric studies through theoretical results are made to clarify the effects of the parameters of the sound radiation system, and to gain a fundamental insight into the control of structure-borne noise radiation. It is shown that it is difficult to reduce the radiated sound power by an interior panel alone, even if its mass is increased.

Magnetic Properties of YBa2(Cu1-xFex)3Oy

The static magnetic susceptibility of YBa 2 (Cu 1- x Fe x ) 3 O y in the normal state was measured for both slowly cooled superconducting specimens and quenched semiconductor-like specimens. The susceptibility is found to be expressed by the sum of the Curie-Weiss term and a temperature-independent paramagnetic term, χ 0 , for both types of specimen. The Curie constant and χ 0 increase with an increasing iron concentration. No anomaly showing magnetic ordering was observed.

The Meissner Effect of the Small Single Crystals of Ba2YCu2.89O6.80

Single crystals of Ba2YCu2.89O6.80 compound responsible for superconductivity were prepared in average size of several hundred microns. The Meissner effect of these single crystals was measured. The crystal structure and the deficiency of oxygen and copper of this specimen have been determined by X-ray diffraction method.

Anomalous Resistivity in Ba-Y-Cu-O Systems

Anomalous temperature dependence of the resistivity was observed in Ba-Y-Cu-O systems whose starting composition is different from the Ba, Y, Cu ratio of 2:1:3. It may be attributed to an occurrence of partial superconductivity with higher transition temperature than 90 K, or a semiconductor-metal transition.

Superconductivity in Exchange-Enhanced Paramagnetic Compound Ti0.5+xCo0.5- x

TiCo, a d-band metal, is known to be an exchange-enhanced itinerant paramagnet. We measured the dc susceptibility of polycrystalline Ti 0.5+ x Co 0.5- x with small x over the temperature range of 1.7 to 300 K. In order to study superconductivity, the ac susceptibility of this compound was also measured down to 14 mK. We observed superconductivity in this system, whose superconducting transition temperature was approximately 35 mK for Ti 0.510 Co 0.490 .