Nanoscale resolution interrogation scheme for simultaneous static and dynamic fiber Bragg grating strain sensing

A combined interrogation and signal processing technique which facilitates high-speed simultaneous static and dynamic strain demodulation of multiplexed fiber Bragg grating sensors is described. The scheme integrates passive, interferometric wavelength-demodulation and fast optical switching between wavelength division multiplexer channels with signal extraction via a software lock-in amplifier and fast Fourier transform. Static and dynamic strain measurements with noise floors of 1 nanostrain and 10 nanostrain/sqrt(Hz), between 5 mHz and 2 kHz were obtained. An inverse analysis applied to a cantilever beam set up was used to characterise and verify strain measurements using finite element modeling. By providing distributed measurements of both ultahigh-resolution static and dynamic strain, the proposed scheme will facilitate advanced structural health monitoring

An Analysis of Common Music Production Elements From the 1980s: Highlighting the Musical Influences of Michael Jackson, Prince, and Madonna

This production paper analyzes the impact the music technology used in the music productions of Michael Jackson, Prince and Madonna has had on today\u27s music. The history and application of music technologies such as the Yamaha DX7 and LinnDrum are discussed at length. The music of the 1980s era played a significant role in inspiring how music sounds in the 2020s decade, and the music production elements used by Michael Jackson, Prince and Madonna can still be heard toda

High-speed interferometric FBG interrogator with dynamic and absolute wavelength measurement capability

A passive, interferometric wavelength demodulation technique has been extended to measure the absolute wavelengths of a multiplexed array of fiber Bragg grating sensors. The scheme retains its original strain resolution of 10 nε/√{Hz}. A proof-of-concept interrogation system was able to determine the absolute wavelength of Bragg peaks to within 20 pm (17 με). Static and dynamic Bragg grating strains were accurately demodulated in both absolute and relative wavelength measurement modes. This demonstration indicates that interferometric techniques are able to provide absolute, static and dynamic measurements of strain within a single platform

Solid-state interferometric interrogator and multiplexer for high-speed dynamic and absolute FBG wavelength measurement

We present a solid-state FBG array interrogator and multiplexer capable of determining absolute FBG wavelengths and of providing high-speed, high-resolution static and dynamic measurements. Using a described procedure, deployable on multiplexing passive-interferometric schemes, the system is able to determine initial sensor wavelengths and thereafter track wavelength changes with interferometric resolution. The scheme allows high-resolution interrogation of FBG sensor arrays to be applied to many industrial applications, where previously the lack of combined absolute and quasi-static wavelength measurement precluded the use of interferometric techniques. Using a preliminary laboratory embodiment, we demonstrate a wavelength determination accuracy of <0.3 nm and a measurement resolution of 10 fm/√Hz, and propose pathways to improved performance and miniaturisation

Mechanical strength of silica fiber splices after exposure to extreme temperatures

By using a combination of type-I and regenerated gratings, the mechanical strength of optical fiber splices after exposure to temperatures over 1300 C was characterized. Splice strength was found to decrease with temperature with a secondorder polynomial dependence after exposure to environments hotter than 500 C. Splices exposed to temperatures above 1300 C were 80% more fragile than non-exposed splices. The lack of optical attenuation and the narrowing distribution of breaking strengths for higher temperatures suggest surface damage mechanisms, such as hydrolysis, play a key role in weakening post-heating and that damage mechanisms dominate over strengthening induced by crack melting

Optical fibre sensors for monitoring prestressed concrete structures in nuclear power plants

This thesis was previously held under moratorium from 20th November and 20th November 2015.Lifetime extensions of nuclear fission reactors in the UK are required to satisfy growing demands for electrical power. Many of these reactors are nearing the end of their original design life, so the continued structural integrity, particularly of the reactors' prestressed concrete pressure vessels and containments is of prime concern. Currently, a lift-off inspection of a 1 % random sample of prestressing tendons is performed at 18 month to 5 year intervals to ensure adequate prestress is present in these structures, but the extended life times are making higher resolution, more frequent and in-depth monitoring techniques more desirable. In this thesis, a method of instrumenting prestressing strands with optical fibre Bragg grating strain sensors is outlined. An all-metal encapsulation and bonding technique is developed to ensure sensor reliability under the radioactive and high-stress environments of fission reactors. This 'smart strand' is complemented by a specially developed interrogation scheme capable of continuously and automatically monitoring static and dynamic nanoscale changes in Bragg grating strain. High-resolution interrogation was achieved by extending an interferrometric demodulation technique into the static measurement regime. By modulating the strain sensitivity using a fast optical switch, strain signals could be recovered independently of noise sources using various signal processing algorithms. The application of this technology could augment the continued monitoring of concrete vessel integrity, reducing both the risks and costs associated with performing lift-off measurements in the current and next generation of nuclear reactors.Lifetime extensions of nuclear fission reactors in the UK are required to satisfy growing demands for electrical power. Many of these reactors are nearing the end of their original design life, so the continued structural integrity, particularly of the reactors' prestressed concrete pressure vessels and containments is of prime concern. Currently, a lift-off inspection of a 1 % random sample of prestressing tendons is performed at 18 month to 5 year intervals to ensure adequate prestress is present in these structures, but the extended life times are making higher resolution, more frequent and in-depth monitoring techniques more desirable. In this thesis, a method of instrumenting prestressing strands with optical fibre Bragg grating strain sensors is outlined. An all-metal encapsulation and bonding technique is developed to ensure sensor reliability under the radioactive and high-stress environments of fission reactors. This 'smart strand' is complemented by a specially developed interrogation scheme capable of continuously and automatically monitoring static and dynamic nanoscale changes in Bragg grating strain. High-resolution interrogation was achieved by extending an interferrometric demodulation technique into the static measurement regime. By modulating the strain sensitivity using a fast optical switch, strain signals could be recovered independently of noise sources using various signal processing algorithms. The application of this technology could augment the continued monitoring of concrete vessel integrity, reducing both the risks and costs associated with performing lift-off measurements in the current and next generation of nuclear reactors

Self-sensing alkali-activated materials : a review

Alkali-activated materials are an emerging technology that can serve as an alternative solution to ordinary Portland cement. Due to their alkaline nature, these materials are inherently more electrically conductive than ordinary Portland cement, and have therefore seen numerous applications as sensors and self-sensing materials. This review outlines the current state-of-the-art in strain, temperature and moisture sensors that have been developed using alkali activated materials. Sensor fabrication methods, electrical conductivity mechanisms, and comparisons with self-sensing ordinary Portland cements are all outlined to highlight best practice and propose future directions for research

Iconicity in English and Spanish and its relation to lexical category and age of acquisition

Signed languages exhibit iconicity (resemblance between form and meaning) across their vocabulary, and many non-Indo-European spoken languages feature sizable classes of iconic words known as ideophones. In comparison, Indo-European languages like English and Spanish are believed to be arbitrary outside of a small number of onomatopoeic words. In three experiments with English and two with Spanish, we asked native speakers to rate the iconicity of ~600 words from the English and Spanish MacArthur-Bates Communicative Developmental Inventories. We found that iconicity in the words of both languages varied in a theoretically meaningful way with lexical category. In both languages, adjectives were rated as more iconic than nouns and function words, and corresponding to typological differences between English and Spanish in verb semantics, English verbs were rated as relatively iconic compared to Spanish verbs. We also found that both languages exhibited a negative relationship between iconicity ratings and age of acquisition. Words learned earlier tended to be more iconic, suggesting that iconicity in early vocabulary may aid word learning. Altogether these findings show that iconicity is a graded quality that pervades vocabularies of even the most “arbitrary” spoken languages. The findings provide compelling evidence that iconicity is an important property of all languages, signed and spoken, including Indo-European languages

Hybrid optical-fibre/geopolymer sensors for structural health monitoring of concrete structures

In this work, we demonstrate hybrid optical-fibre/geopolymer sensors for monitoring temperature, uniaxial strain and biaxial strain in concrete structures. The hybrid sensors detect these measurands via changes in geopolymer electrical impedance, and via optical wavelength measurements of embedded fibre Bragg gratings. Electrical and optical measurements were both facilitated by metal-coated optical fibres, which provided the hybrid sensors with a single, shared physical path for both voltage and wavelength signals. The embedded fibre sensors revealed that geopolymer specimens undergo 2.7 mε of shrinkage after one week of curing at 42 °C. After curing, an axial 2 mε compression of the uniaxial hybrid sensor led to impedance and wavelength shifts of 7 × 10−2 and −2 × 10−4 respectively. The typical strain resolution in the uniaxial sensor was 100 με. The biaxial sensor was applied to the side of a concrete cylinder, which was then placed under 0.6 mε of axial, compressive strain. Fractional shifts in impedance and wavelength, used to monitor axial and circumferential strain, were 3 × 10−2 and 4 × 10−5 respectively. The biaxial sensor’s strain resolution was approximately 10 με in both directions. Due to several design flaws, the uniaxial hybrid sensor was unable to accurately measure ambient temperature changes. The biaxial sensor, however, successfully monitored local temperature changes with 0.5 °C resolution

Smart cements : repairs and sensors for concrete assets

Smart cements offer a unique opportunity to unify our approach to the remote monitoring and repair of concrete assets. Here, we present our latest progress in manufacturing and testing smart cement sensor-repairs based on fly ash geopolymers — a novel class of cement-like binders that cure to a strong, chemically resistant, electrically conductive shell. Since chloride and moisture are two of the leading causes of degradation of reinforced concrete, we are proposing a technology that is able to monitor chloride ingress into concretes at different levels of moisture. The main task of the work was to manufacture geopolymer binders for concrete specimens, and to cure them at ambient temperatures. We have studied how practical considerations, such as the concrete substrate’s maturity, can affect how or whether smart cements can be applied, thus understanding the main limitations of the technology. By using electrical impedance measurements, we aim to demonstrate that geopolymer skin layers can provide high resolution monitoring of chloride contamination at different levels of moisture. Here we present results which show that smart cements are sensitive to changes in humidity of the surrounding environment. Our goal is to develop a robust and field-worthy technology which unifies civil monitoring and maintenance. This goal is of key national importance to the US and many countries within Europe, who now face an ageing population of reinforced concrete bridges, tunnels and support structures