All temperature sensors or sensor systems previously developed have one common feature-–the sensors are part of electrically closed circuits and electrical connections are used to form the closed circuits. Using existing frameworks for designing, powering and interrogating sensors, any damage that ruptures the circuit can render the sensor non-functional. In many damage events, it is necessary to identify that the damage has occurred and also continue the measurement. In this paper we report a new temperature sensing method that uses a recently developed technique for designing, powering and interrogating sensors developed at NASA. In lieu of sensors being a collection of components assembled using electrical connections, the open-circuit sensors are patterns of electrically conductive material that can store electric fields and magnetic fields without electrical connections. These sensors are powered using oscillating magnetic fields and respond with their own electric and magnetic fields whose signatures provide temperature information. Because no electrical connections are used, there is no point on the sensor that if damaged renders the sensor non-functional. Damage to the sensor simply shifts the sensor's frequency range, allowing it to continue measurement while damaged. Temperature-sensitive dielectric material is placed within the sensor's responding electric field to modulate the sensor's resonant frequency. Temperature sensitivity and functional temperature range are dependent upon the temperature-sensitive material used and how it is placed within sensor's responding electric field. The principle and design strategies of the open-circuit temperature sensors are discussed and experimental results are presented.

This paper presents a new method for on-line monitoring of the liquid level and water content of brake fluid using an enclosed reference probe as the capacitive sensing part. The probe has an enclosed cavity at the end which is designed to hold fresh brake fluid as an on-line reference. Three capacitances formed by four electrodes are used for the liquid level, water content and reference measurement and form the mutual calibrating output functions of the sensing probe. The liquid level measurement is calibrated to the permittivity changes by the capacitance for water content measurement. At the same time, the water content measurement is calibrated to temperature changes and variety of fluids by the capacitance of the reference measurement. Therefore, once the permittivity characteristics of brake fluids are experimentally modeled, the proposed method has a self-calibration ability to influence factors including temperature, water content (to liquid level measurement) and variety of brake fluids without an additional sensor supported by database as in conventional intelligent sensor systems. The design and implementation method are discussed with a prototype probe developed and tested. The permittivity characteristics of brake fluid samples are discussed. The calibration method and errors analysis are presented. The method presents a different way to construct a smart sensor which is useful in brake fluid condition monitoring and also other liquid measurement applications.

The geopolymerization process is an appropriate way of disposing of municipal solid waste incineration fly ash (MSWIFA), and possesses the advantages of immobilizing the heavy metals and making full use of its pozzolanic properties in manufacturing green, cementitious materials. In this study, coal fly ash (FA) and metakaolin (MK) were used to prepare a geopolymer composite, with MK partially replaced by different proportions of MSWIFA through the alkali-activation method. The microstructure and hydration mechanism of the geopolymer composites containing MSWIFA were investigated through mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM), and Fourier transform-infrared spectroscopy (FT-IR) tests; and the immobilization effect of the geopolymer paste on heavy metal ions was explored through inductively coupled plasma-atomic emission spectrometry (ICP-AES). The MIP analysis showed that the addition of MFARR had an overall degrading effect on the pore structure of the matrix. When the content of MSWIFA reached the maximum of 35%, the porosity and average pore diameter increased by 25% and 16%, respectively, corresponding to the case without MSWIFA. However, the pore size distribution exhibited an improving trend when the MFARR was increased from 15% to 25%. The SEM images revealed that the integrity of the micromorphology of the geopolymer mortar became weaker after adding MSWIFA. When the MSWIFA content was increased to 35%, the microstructural compactness decreased and more pores and microcracks appeared in the matrix. The FT-IR pattern study suggested that all the geopolymer composites had a similar internal structure, consisting of O-H, C-O, Si-O-Si, and Si-O-Al. The main component of the geopolymer paste hydrated at 28 d remained dominated by calcium silica-aluminate (C-A-S-H), when the MSWIFA ranged from 0% to 35%. Finally, the ICP-AES results showed that the leaching concentrations of the geopolymer paste of J-40 at 28 d for Cd, Cr, Cu, Pb, and Zn met the requirements of Chinese standards.

Composite materials are increasingly used in modern aircraft for reducing weight, improving fuel efficiency, and enhancing the overall design, performance, and manufacturability of airborne vehicles. Materials such as fiberglass reinforced composites (FRC) and carbon-fiber-reinforced polymers (CFRP) are being used to great advantage in airframes, wings, engine nacelles, turbine blades, fairings, fuselage and empennage structures, control surfaces and coverings. However, the potential damage from the direct and indirect effects of lightning strikes is of increased concern to aircraft designers and operators. When a lightning strike occurs, the points of attachment and detachment on the aircraft surface must be found by visual inspection, and then assessed for damage by maintenance personnel to ensure continued safe flight operations. In this paper, a new method and system for aircraft in-situ damage detection and diagnosis are presented = distance vector t = time δ = skin depth µ, µ r = permeability and relative permeability σ = conductivity ω = angular frequency of the signal

A novel multifunctional distributed optical fiber sensor basing on fiber attenuation is proposed to measure ambient temperature and distributed pressure. The sensor is composed of two fibers, the first fiber is used to sense pressure and temperature value while the second fiber is for position information and pressure indication. Distributed sensing is realized based on the attenuation of the second fiber. Pressure position is determined by the outputs of the second fiber. The sensor works at the time-sharing model to realize the multifunctional sensing purpose with the second fiber working as indication. The prototype model of the sensor is developed and tested. The effectiveness of sensor is conformed by experimental results. The proposed sensor presents a novel method for distributed optical fiber sensor.