Resonating strings have shown promise in a variety of applications including micron-scale mass and temperature sensors. We present microchannel string resonators (MSRs) which have resonance frequency modulated by the internal gauge pressure of silicon nitride microchannels sitting atop the strings. We present an analytical model to predict the pressure sensitivity (Hz/kPa) of the first resonance frequency as well as experimental results for three identical MSRs. While the highest experimental sensitivity of one of the resonators is 5.19 Hz/kPa (0.5 Hz/mbar), the analytical model suggests sensitivity could increase by two orders of magnitude if the microchannels are fabricated at nanometer scale with a length of 10 μm, a channel width of 600 nm, and a channel thickness of 50 nm. The average pressure resolution of the sensors is 0.4 kPa. These results are for a calibrated range of pressure from 50 kPa to 100 kPa (500 mbar to 1000 mbar). However, the analytical model shows that resonance frequency is a linear function of pressure over a range of several MPa, suggesting that the microchannel resonators could have a pressure sensing range (dynamic range) suitable for many applications.

No abstract

Gas turbine engine efficiency, safety, and life cycle cost are directly influenced by the durability and performance of the turbine hot section. Numerous advances have been applied to improve the capabilities of turbines including new structural materials, innovative thermal barrier coatings, and advanced heat transfer techniques; however, improved designs are still dependent on accurate knowledge of true turbine environmental conditions during operation. In conjunction with ongoing advances in physics-based modeling, physical measurement of actual turbine conditions remains a necessity. The Small CAESAR project supports the demonstration and maturation of advanced components, including sensors, under the VAATE program. Sporian Microsystems provided smart pressure/temperature sensor suite probes for testing under Small CAESAR. These probes survived in situ conditions in three engine locations: compressor discharge, high pressure turbine inlet and low pressure turbine inlet, in a test designed to demonstrate TRL 6. Nomenclature% = Percent °C = Degree Celsius °F = Degree Fahrenheit A = Amp BNC = Bayonet Neill-Concelman CAESAR = Component and Engine Structural Assessment Research CAD = Computer Aided Design DC = Direct Current DEC = Distributed Engine Control DECWG = Distributed Engine Controls Working Group DIRCT = Distributed Intelligent Robust Controls Technologies EGT = Exhaust Gas Temperature ERA = Environmentally Responsible Aviation FADEC = Full Authority Digital Engine Control

The authors describe the use of matrices in thick lens theory. Complicated optical systems may then be dealt with simply at sixth form level.