Photo-acoustic spectroscopy (PAS) has been successfully applied to detect various gases and chemicals due to its high selectivity and sensitivity. However, the performance of the conventional acoustic sensors prohibits the application of PAS for harsh environment gas species real-time monitoring. By replacing conventional acoustic sensors, such as microphone and piezo-transducers, with a high-temperature Fiber Bragg Grating (FBG) vibration sensor, we developed a fiber-optic PAS sensing system that can be used in high-temperature and high-pressure harsh environments for gas species identification and concentration measurement. A resonant acoustic chamber is designed, and FBG vibration sensor is embedded in the molybdenum membrane. An OPO laser is used for spectrum scanning. Preliminary test on water vapor has been conducted, and the result is analyzed. This sensing technology can be adapted into harsh environments, such as Integrated Gasification Combined Cycle (IGCC) power plant, and provide on-line real-time monitoring of gases species, such as CO, H2O, and O2. Presently, our FBG-based vibration sensor
can withstand the high temperature up to 800°C.
Dynamic response characteristics of silica fiber long-period grating with a modified cladding, composed of
∼10-100 nm nanoparticle palladium oxides thin film material prepared by a magnetron sputtering
technique, have been investigated at several elevated temperatures with a 2%H2/98%N2 mixing gas
concentration. The fiber cladding modified grating, without cladding chemical etching process,
demonstrates 540 pm per 1% H2 sensitivity, a better than 1sec response times at 160oC, respectively. The
thermal responses of the prototype have demonstrated increased dynamic wavelength shift while reducing
response time simultaneously. The observed thermal dependence of the prototype could be attributed to a
combined effect of thermal dependent hydrogen atoms diffusion rate and hydrogen atoms solubility.
Integrated Gasification Combined Cycle (IGCC) power plants have great potential for future clean-coal power generation. Today, the quality of coal is measured by sampling coal using various offline methods, and the syn-gas composition is determined by taking samples downstream of the gasifier and measured by gas chromatograph (GC). Laser induced plasma technology has demonstrated high sensitivity for elementary detection. The capability of free space transmission and focusing of laser beam makes laser induced plasma a unique technology for online compositional analysis in coal gasification environment and optimization control.
It is very critical to develop sensor that can operate in high temperature and chemically harsh environments. Sapphire (Al2O3) material, which possesses a melting point of 2050°C and a wide transmission wavelength region as high as ~3.5μm, has been demonstrated to be an ideal candidate for high temperature fiber-based environmental sensing applications. Under harsh environment, the performance of conventional blackbody radiation based sapphire fiber high temperature sensor could be easily affected due to the lack of cladding. In this paper, a fiber-optic temperature sensor with a single-crystal sapphire fiber as the light guide and a high temperature ceramic coating as the sensing element as well as the protection layer was presented. The radiance emitted from the ceramic coating is used to measure the temperature, and it is transmitted to optical receiver through the sapphire fiber. This ceramic coating greatly improved the stability and dynamical range of pyrometer. Preliminary experimental results demonstrated that the sensor is very promising for measuring ultra-high temperature up to 1900°C in the harsh environment.
Dielectric properties of Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals grown by a modified Bridgman method are investigated under strong, high frequency (>100 kHz) AC field. It is found that there is a phase transition due to the applied AC field, which may be due to the following reasons: (1) strong AC field quickly switches the polarization directions of domains that heats up the crystal due to the friction of domain change; (2) phase transition happens because of the increase of the temperature. Comparing with conventional heating techniques, AC field induced phase transition is a quicker more effective way. Experimental results confirm the increase of d33 and the change of transmittance under strong AC field.
In this paper, a unique non-contact, minimum invasive technique for the assessment of mechanical properties of single cardiac myocyte is presented. The assessment process includes following major steps: (1) attach a micro magnetic bead to the cell to be measured, (2) measure the contractile performance of the cell under the different magnetic field loading, (3) calculate mechanical loading force, and (4) derive the contractile force from the measured contraction data under different magnetic field loading.
In this paper, electro-optic properties of 0.67Pb(Mg1/3Nb2/3)03-0.33PbTiO3 (PMN-33%PT) single crystals under proper AC bias are reported. It is found that PMN-33%PT has an extremely large linear electro-optic coefficient, r33 ~9800 pm/V under proper AC bias. Besides this huge electro-optic coefficient, PMN-33%PT crystals also have very good optical quality and the random scatterings caused by the multiple domains can be totally removed by the AC bias. Furthermore, unlike KTN, PMN-PT has a much higher phase transition temperature (~175°C), which is sufficiently away from the room temperature so that a good thermal stability can be achieved. The combinations of giant electro-optic coefficient, good optical quality, and high thermal stability may make PMN-33%PT the best electro-optic material among all electro-optic crystals developed so far, which could revolutionize applications of electro-optic crystals to telecommunications, medical imaging, et al. This research may also help to understand the mechanism underlying the ultrahigh performance of this new generation of single crystal materials (e.g., PZN-PT, PMN-PT) via the interaction between crystal internal structures and external AC electric field, which may stimulate further interest in the fundamental theory of ferroelectrices under changing electric field that could direct improving the quality of existing ferroelectric crystals and developing new ferroelectric crystals.