Search

A new structure is proposed that is composed of reflector plated mounted in front and in back of the transducer at an angle of 45[degree], so that acoustic waves from front and back of the transducer are combined to form a single main beam. The analysis has shown that far field directivity has become sharper and acoustic pressure output is doubled.

Acoustic wave radiation is examined from cylindrical polyvinylidene fluoride (PVDF) film mounted inside a concentric wall with a small air gap. Results suggest that the radiation impedance is inversely proportional to the thickness of the air gap.

An innovative concept for design of an impedance-matching structure for air-coupled ultrasonic transducers is presented and discussed.

Cylindrical polyvinylidene fluoride (PVDF) film transducers, used for transmitting and receiving of 40KHz ultrasonic waves in air, are discussed. The focus is on the transducers' omni-directional polar response.

An innovative matching-layer design concept for narrowband continuous wave (CW) devices is described and discussed.

A new large-area polyvinylidene fluoride (PVDF) film air transducer, with a high power output and a sharp beam angle, is described. PVDF is formed into alternating concave and convex curved sections, producing a corrugation structure, with waves adding constructively to form a strong beam when corrugation height is approximately one-half of wavelength.

Two resonances have been observed in a curved PVDF air transducer. These are length extensional and flexural bending modes, and can be used to improve ultrasound performance.

A two-dimensional single-mode ditsributed feedback (DFB) laser is presented. The laser uses a perpendicular grating to broaden the width of narrow stripe lasersfor longitudinal and lateral mode applications. This grating is based on the threshold current gain and the couping constants for transverse electric and transverse magnetic modes. Analysis of this DFB laser indicates that the use ofcross grating could result in a single frequency operation of the device.

Abudefduf caudobimaculatus Okada and Ikeda 1939, having long been regarded as a junior synonym of Abudefduf vaigiensis (Quoy and Gaimard 1825), is herein redescribed as a valid species on the basis of the holotype and 77 additional specimens. Abudefduf caudobimaculatus can be distinguished from A. vaigiensis in having 11-13 (modally 12) dorsal-fin soft rays, 4 scale rows above the lateral line, 2½ scale rows between the middle of the spinous portion of the dorsal-fin base and lateral line, 3-4 (4) scale rows on the cheek, scales always present on the anteroventral region of the head, eleventh and last dorsal-fin spines and pectoral-fin length 15.5-18.4%, 17.1-20.6%, and 33.5-39.9% of SL, respectively, two black spots on the caudal-fin base, anteriormost bar descending to behind the pectoral-fin base, 0-1 tubed lateral-line scales on the fourth vertical bar, and third to seventh (usually fifth or sixth) dorsal-fin soft ray base at the anterior margin of the fourth vertical bar. Synonymies of A. vaigiensis are discussed with designations of lectotypes for Glyphisodon vaigiensis and Glyphisodon rahti. [ABSTRACT FROM AUTHOR]