Single-fiber grid for improved spatial resolution in distributed fiber optic sensor.

The spatial resolution of an optical-fiber-based Raman distributed temperature sensor is limited by the pulse width of the laser used. We discuss a methodology of increasing spatial resolution by using a single-fiber grid. Spatial resolution improvement of up to 10 times is demonstrated.

Nondestructive characterization of musical pillars of Mahamandapam of Vitthala Temple at Hampi, India.

This paper presents the first scientific investigation on the musical pillars of the Vitthala Temple at Hampi, India. The solid stone columns in these pillars produce audible sound, when struck with a finger. Systematic investigations on the acoustic characteristics of the musical pillars of mahamandapam (great stage) of the Vitthala Temple have been carried out. The 11 most popular pillars that produce sounds of specific musical instruments are considered for the investigations. The sound produced from these 11 most popular musical pillars was recorded systematically and different nondestructive testing techniques such as low frequency ultrasonic testing, impact echo testing, and in situ metallography were employed on the musical columns of these pillars. The peak frequencies in the amplitude spectrum of the sound produced from various columns in these pillars are correlated with the dimensional measurements and ultrasonic velocity determined using impact echo technique. The peak frequencies obtained experimentally have been found to have excellent correlation with the calculated flexural frequencies based on the dimensional measurements and ultrasonic velocities of the columns.