Data compression approach for long-term monitoring of pavement structures

Pavement structures are designed to withstand continuous damage during their design life. Damage starts as soon as the pavement is open to traffic and increases with time. If maintenance activities are not considered in the initial design or considered but not applied during the service life, damage will grow to a point where rehabilitation may be the only and most expensive option left. In order to monitor the evolution of damage and its severity in pavement structures, a novel data compression approach based on cumulative measurements from a piezoelectric sensor is presented in this paper. Specifically, the piezoelectric sensor uses a thin film of polyvinylidene fluoride to sense the energy produced by the micro deformation generated due to the application of traffic loads. Epoxy solution has been used to encapsulate the membrane providing hardness and flexibility to withstand the high-loads and the high-temperatures during construction of the asphalt layer. The piezoelectric sensors have been exposed to three months of loading (approximately 1.0 million loads of 65 kN) at the French Institute of Science and Technology for Transport, Development and Networks (IFSTTAR) fatigue carrousel. Notably, the sensors survived the construction and testing. Reference measurements were made with a commercial conventional strain gauge specifically designed for measurements in hot mix asphalt layers. Results from the carrousel successfully demonstrate that the novel approach can be considered as a good indicator of damage progression, thus alleviating the need to measure strains in pavement for the purpose of damage tracking

Validation of a Novel Sensing Approach for Continuous Pavement Monitoring Using Full-Scale APT Testing

The objective of this paper is to present a novel approach for the continuous monitoring of pavement condition through the use of combined piezoelectric sensing and novel condition-based interpretation methods. The performance of the developed approach is validated for the detection of bottom-up fatigue cracking through full-scale accelerated pavement testing (APT). The innovative piezoelectric sensors are installed at the bottom of a thin 102 mm (4 in.) asphalt layer. The structure is then loaded until failure (up to 1 million loading cycles in this study). The condition-based approach, used in this work, does not rely on stain measurements and allows users to bypass the need for any structural or finite-element models. Instead, the data compression approach relies on variations in strain energy harvested by smart sensors to track changes in material and structural conditions. Falling weight deflectometer (FWD) measurements and visual inspections were used to validate the observations from the sensing system. The results in this paper present a first large-scale validation in pavement structures for a piezopowered sensing system combined with a new response-only based approach for data reduction and interpretation. The proposed data analysis method has demonstrated a very early detection capability compared to classical inspection methods, which unveils a huge potential for improved pavement monitoring

Lipid characterization of Eryngium maritimum seeds grown in Tunisia

Fatty acid, triacylglycerol, phospholipid, tocol and sterol compositions of E. maritimum seeds collected from plants grown in ten different Tunisian littoral locations were determined. Constitutes from different locations are significantly different. Seeds presented high oil content, ranging from ca. 22% to 34% on a dry weight basis, and were characterized by a constant fatty acid profile among the growing locations. Gas chromatographic analysis revealed an important level of unsaturated fatty acids (ca. 90% of total fatty acid content), with a prevalence of oleic (ca. 63%) and linoleic (ca. 25%) acids. Results obtained by GC-FID showed that the carbon number (CN) values of the TAGs in all samples were 50 (1.5%), 52 (25.6%) and 54 (73%). Phosphatidylcholine was the most common phospholipid, accounting for more than 60% of the total content, followed by phosphatidic acid (about 30%). Different tocols concentration was reported in seeds with \u3b2-tocotrienol as the most abundant one in all samples. Stigmasterol was the most abundant sterol in all seeds, representing nearly 70% of the total content, followed by \u3b2-sitosterol and \u3947-sitosterol. In all, the findings of this work highlight the valuable levels of minor constituents from Eryngium maritimum storage lipids which can be therefore a prospective source of useful natural bioactive molecules that may replace synthetic antioxidants

Ellipsometric investigation of porous silicon layers for the design of a DBR

Porous silicon layers (PSL) were fabricated by electrochemical etching and investigated by spectroscopic ellipsometry (SE) in the energy range 0.6−5 eV. Within the effective medium approximation (EMA) and through an optical model consisting of a mixture of void and crystalline silicon (cSi), we were able to determine the porosity (void concentration) and the thicknesses of the PSL. The PSL were divided into several sublayers in order to obtain the best agreement between measured and simulated spectra. Once the etching parameters have been controlled and by choosing the appropriate conditions, it was possible to design a distributed Bragg reflector (DBR) with a high reflectivity band centered at 800 nm. This DBR consists on stacks of alternate PSL having two different refractive indices

Monitoring road pavement performance through a novel data processing approach, accelerated pavement test results

This research presents a novel performance-based interpretation method for continuous monitoring of pavement condition through the use of piezoelectric sensors. The objective of this study is to validate the compressed cumulative loading event approach, implemented in a previously developed piezoelectric sensor, for detecting subsurface fatigue cracking through full-scale accelerated pavement testing. A piezo-electric film of polyvinylidene fluoride is used to harvest the microstrain energy induced by the traffic loading at the surface. Epoxy is used to protect the sensor following a H-shape packaging. Piezoelectric sensors were exposed to approximately 1.0 million load repetitions between November 2017 and February 2018 at the IFSTTAR carrousel in Nantes, France. Reference strain measurements were recorded with two types of commercial strain gauge. Results from the full-scale test have successfully validated the novel approach for detecting subsurface cracking in asphalt concrete pavements. Finally, the piezoelectric sensors were able to detect damage progression and severity through the number of open threshold levels

Strain effects of InP/Si and InP/porous Si studied by spectroscopic ellipsometry

In this work, we study the optical interband transitions of InP on silicon (InP/Si) and on porous silicon (InP/PSi) substrates grown by molecular beam epitaxy (MBE). Spectroscopic ellipsometry for photon energies from 2 to 5 eV is used to determine the InP/Si and InP/PSi complex refractive index and thickness. Bruggeman effective medium approximation (EMA) associated to the Cauchy model are used to model the experimental ellipsometric data. We have found that the E1 and E1 + $\Delta _{1}$ transition energies of InP/Si and InP/PSi shift to low energies compared to bulk InP. This effect is interpreted as a result of the strain relaxation of the InP layers grown respectively on Si and porous Si substrates

Comparison and Modeling of Commercial Supercapacitors via Standardized Potentiostatic Electrochemical Impedance Spectroscopy

The main scope of the study is the characterization of the capacitive and resistive behavior of two supercapacitor cells and one hybrid supercapacitor available on the market, through potentiostatic electrochemical impedance spectroscopy (PEIS). The PEIS tests were performed by applying to all cells the same voltage perturbation in the same frequency range. In a first phase, the instrumentation used for the acquisitions was optimized, with particular care to the connections between the potentiostat and the supercapacitor cell. The Nyquist diagrams obtained for each sample are compared and capacitance/frequency graphs are deduced. The technological differences between various devices are then discussed in relation to the results. The characterization of the sample cells and the collected data are used to propose the corresponding models conceived for circuit simulation. These models are based on simple electronic components available in the standard circuit simulation software tools

Catalytic properties of a highly thermoactive polygalacturonase from the mesophilic fungus Penicillium occitanis and use in juice clarification

A new polygalacturonase (PG1) is purified to homogeneity from the hyper-pectinolytic mutant (CT1) of Penicillium occitanis by using two chromatographic steps. The purified PGI exhibited a very high specific activity toward PGA, namely 57533.2 U/mg of protein and a high optimal temperature, 70 degrees C. In our knowledge, it is one of the highest temperature optima described till now, even among those reported for thermophilic fungi; recalling here that our fungus is a mesophilic one. The N-terminal sequence was almost identical to that deduced from the previously cloned pga1 gene. The mass spectrometry analysis of PG1 further confirmed its belonging to the pga1 gene. As the peptide sequence of the pga1 bears the signature of endopolygalacturonases, we brought in this work evidences that it belongs to enzymes that hydrolyze pectin by endo-fashion. Indeed, during the hydrolysis of polygalacturonic acid by PG1, the viscosity drops very quickly while reducing sugars were released very slowly. In addition, thin layer chromatography showed that mainly oligosaccharides were released from PGA, namely tetra and trigalacturonic acids. The purified PGI was able to enhance the clarification of citrus juice. Considering all these properties, this novel fungal would be an interesting biocatalyst for future application in fruit and vegetable transformation. (C) 2016 Elsevier B.V. All rights reserved