Aerogels with gradients in density have been produced in experiments, as part of an effort to develop materials that will be used in outer space to capture particles traveling at high speeds for the STARDUST mission.

Spectrometers are used for applications such as chemical analysis, remote sensing, environmental measuring, and optical measurements. Most spectrometers utilize prisms and gratings, where the dispersion of light depends upon the angle and rotation of the grating. But gratings and other moving parts are...

A paper summarizes a continuing program of vibro-acoustic testing of two aircraft fuselage structures: (1) a 12-ft (3.7-m)-long generic aluminum test-bed cylinder that contains stiffening rings and stringers and (2) the 40-ft (12.2-m)-long fuselage of a 10-passenger turboprop airplane, made of...

Advances in time gating of ultrasonic signals in scanning acoustic microscopes have been proposed to enable detailed nondestructive examination of bonds and other interfaces deep within the interiors of such micromachined objects as high-density integrated electronic circuits and...

A method of in situ chemical analysis by use of small, simple, robust sensors has been proposed. The basis for the proposal is the discovery that chemical reactions emit acoustic waves, and that characteristic frequency spectra are associated with specific reactions. The acoustic frequencies...

A small, robust, lightweight, low-power-consumption instrumentation system has been proposed for determining the kinetic energies, masses, and other parameters of wind-borne particles. Originally intended for use in future exploration of Mars, the system might also prove useful on Earth for...