SNR enhancement of quasi-distributed weak acoustic signal detection by elastomers and MMF integrated Φ-OTDR.

We have proposed and demonstrated a weak acoustic signal detection technology based on phase-sensitive optical time-domain reflectometry (Φ-OTDR). Non-contact acoustic signals transmitting through air gap between the sound source and the receiver are difficult to detect due to fast attenuation. In order to improve the detection ability of non-contact weak acoustic signals, we demonstrate that multi-mode fiber (MMF) is a better solution than single-mode fiber (SMF) benefiting from its larger core and higher Rayleigh backscattering (RBS) capture coefficient. The frequency signal-to-noise ratio (SNR) has been enhanced by 9.26 dB. Then, with the help of 3D printing technology, elastomers have been designed to further enhance the detection ability due to the high-sensitive response to acoustic signals. Compared with the previous reported "I" type elastomer, the location and frequency SNR enhancement caused by our new proposed "n" type elastomer are 8.39 dB and 11.02 dB in SMF based system. The values are further improved to 10.51 dB and 13.38 dB in MMF and "n" type elastomer integrated system. And a phase-pressure sensitivity of -94.62 dB re rad/µPa has been achieved at 2.5 kHz. This non-contact weak acoustic signal detection technique has great application potential in the quasi-distributed partial discharge (PD) detection of smart grid.

Measuring factors affecting grip strength in a Taiwan Chinese population and a comparison with consolidated norms.

We inquire whether assessment of an individual's upper limb function may be improved by using specific regional norms rather than consolidated global norms. Grip strengths were measured in a sample of 482 adults across Taiwan, and compared with consolidated norms. To ensure comparable conditions, our procedures were those recommended by the American Society of Hand Therapists (ASHT). Overall the mean grip strength of our sample was significantly (male 25%, female 27%) lower than consolidated norms derived from largely Caucasian populations. We investigated variables that might relate to this divergence. Results of ANOVA and stepwise multiple regression analysis showed that gender, age and palm length were effective predictors in grip strength. A regression equation was derived. When other variables were matched, palm length appeared an important discriminating factor. Further anthropometric and socio-economic factors also need investigation. Specific regional norms should provide more accuracy for ergonomists and health workers assessing an individual's upper limb function, and may avoid errors in appraisal. This paper suggests grip strength values for Taiwan.