Yasuo Hirose

Measurement method of VHF elastic vibrations by optical fiber interferometric sensing

A measurement method is presented for elastic vibration modes with extremely small vibration amplitudes in the very high frequency (VHF) range. The measurement system is an optical fiber interferometric sensor, which detects optical phase modulations caused by the elastic vibrations being tested to give the vibration amplitudes. Extensive use of recent optical fiber technology along with a signal processing technique enables the authors to achieve detailed measurements of vibration amplitudes as small as 0.1 A at frequencies as high as nearly 150 MHz.<<ETX>>

Evaluation of nonlinear elastic coefficient causing frequency shifts in AT-cut resonators

The authors describe an experimental evaluation scheme of the fourth order nonlinear elastic constant of quartz C/sub 6666/ using AT-cut resonators. The evaluation has been made from measured quadratic frequency changes against excitation currents and actual vibration amplitude distributions of thickness-shear vibrations measured by an optical fiber vibration sensor. More reasonable estimates of C/sub 6666/ were obtained compared with those previously reported which vary considerably from each other.<<ETX>>

The design of phoneme grouping for coarse phoneme recognition

Automatic speech recognition for real-world applications such as a robot should deal with speech under noisy environments. This paper presents coarse phoneme recognition which uses a phoneme group instead of a phoneme as a unit of speech recognition for such a real-world application. In coarse phoneme recognition, the design of the phoneme group is crucial. We, thus, introduce two types of phoneme groups - exclusive and overlapping phoneme groups, and evaluate coarse phoneme recognition with these two phoneme grouping methods under various kinds of noise conditions. The experimental results show that our proposed overlapping phoneme grouping improves the correct phoneme inclusion rate by 20 points on average.

Method of Measuring VHF Elastic Vibration Modes by Optical Sensing

This paper describes an optical measurement method of elastic vibration modes with extremely small vibration amplitudes in the very high frequency (VHF) range. The measurement system is an optical fibre interferometric sensor, in which optical phase modulations caused by elastic vibrations under study are detected and processed to give the vibration amplitudes. Extensive use of recent optical fibre technology and a signal processing technique enabled us to achieve detailed measurements of vibration modes with amplitudes as small as 0.1 A at frequencies as high as 150 MHz.

Optical Fibre Sensing System For Three Dimensional Vibration Measurements

This paper describes a novel optical fibre sensing system for three dimensional small mechanical vibration measurements with significantly improved performances over the existing ones. The minimum detectable vibration displacements are on the order of 0.1-0.01 A at frequencies up to 30 MHz.