In-line measurements of below-the-surface food deformation during drying with an interference-based optical fiber strain sensor

Strain, deformation and temperature measurements constitute the most interesting parameters to be monitored in smart structures. White-light interferometry offers these performances even for long-term measurements. Based on the Michelson interferometer, a fiber optic localized strain sensor and multiplexing strain-sensing techniques are demonstrated in this paper. Related problem about the spatial division limitation of fiber optic sensors is discussed. Finally, application examples such as cable strain measuring of cable-stayed bridge model, inside strain measurements for concrete specimens and temperature monitoring are also given.

Optical strain sensors [optical fiber strain (OFS] based on optical frequency domain reflection (OFDR) are an optical sensor with great application value and the ability to achieve distributed detection. However, both the external ambient temperature and the strain contribute to the frequency shift of the Rayleigh scattering spectrum in the optical fiber during the measurement. This means that the problem of temperature compensation (TC) must be considered when detecting strain in the environment with temperature field, especially in high-temperature environment. In this article, a method of double-wire-based single optical fiber was proposed to aim at this problem, which makes one single fiber have two functions of TC and strain sensing at the same time. The contact strain sensing experiment was carried out on the conventional standard single-mode fiber (SMF)-128 polyimide-coated (PI) distributed OFS sensor (DOFSS) under high-temperature conditions (0 °C–300 °C). The TC for the strain measurement of optical fiber sensor-based OFDR was effectively realized by performing data fusion operation on the measurement results of TC and strain sensing, and the relationship between the temperature change rate and the compensation error rate (ER) was obtained. In addition, the noncontact fiber stretching sensing experiment under ultrahigh-temperature (50 °C–600 °C) conditions was carried out for the first time, which further verified the effectiveness of the method for the compensation of the fiber strain measurement error. Feasibility especially provides a simple and effective method for the application of strain measurement technology in high-temperature environment.

In the present study, real-time measurement of internal and residual strains in GFRP laminates with an optical fiber strain sensor was performed in an autoclave molding. An Extrinsic Fabry-Perot Interferometric (EFPI) type optical fiber strain sensor was embedded into prepreg sheets before the molding. The ion viscosity and the temperature of the epoxy resin matrix were also measured simultaneously with the internal strain measurement. The results of the experiments showed that the internal and residual strain of GFRP laminates during the molding could be monitored by the optical fiber sensor embedded in the parallel direction to the reinforcing fibers. It was also found that the circumstances around the embedded optical fiber strain sensor should be taken into account for the interpretation of the measured internal and residual strain.

Polyphenols accumulation effects on surface color variation in apple slices hot air drying process

By employing headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS), this study displayed the compositional changes in volatile organic compounds (VOCs) in Tricholoma matsutake samples subjected to hot-air drying (HAD) and vacuum freeze-drying (VFD) processes from their fresh samples. A total of 99 VOCs were detected, including 2 acids, 10 aldehydes, 10 alcohols, 13 esters, 12 ketones, 24 alkanes, 14 olefins, 7 aromatic hydrocarbons, and 7 heterocyclic compounds. Notably, the drying process led to a decrease in most alcohols and aldehydes, but an increase in esters, ketones, acids, alkanes, olefins, aromatic, and heterocyclic compounds. Venn diagram (Venn), principal component analysis (PCA), and partial least squares-discriminant analysis (PLS-DA) analyses enabled an easy and rapid distinction between the VOC profiles of T. matsutake subjected to different drying methods. Among the identified VOCs, 30 were designated as marker VOCs indicative of the employed drying process. And the VFD method was more capable of preserving the VOCs of fresh T. matsutake samples than the HAD method. Benzaldehyde, 1-Octen-3-ol, 3-Octanol, and (E)-2-Octen-1-ol were identified as markers for FRESH T. matsutake. Conversely, (E)-3-Hexene, lavender lactone, and α-Pinene were associated with VFD T. matsutake. For HAD T. matsutake, olefins, pyrazine, and esters, particularly ocimene, 2,5-Dimethyl-pyrazine, and methyl cinnamate, significantly contributed to its particularities. The results from this present study can provide a practical guidance for the quality and flavor control of volatile organic compounds in preciously fungal fruiting bodies by using drying processes.

Application situation of optical fiber strain sensor used in bridge structure state monitoring is detailed introduced in this paper, two bridges which optical fiber strain sensor is adopted in construction stage stress monitoring and long-time stress monitoring in our country are introduced as example. According to the theoretical analysis of structures, the strain monitoring locations are selected. The composite technology between optical fiber strain sensor and concrete is researched. The installation technology and protect method between optical fiber strain sensor and steel girder are extracted, and advanced acquisition software is explored. Finally, the application foreground of optical fiber strain sensor is discussed. The research result indicates that the optical fiber strain sensor is extraordinary suitable for state monitoring of bridge structure because it has the merits of light structure and reliable performance.

Application situation of optical fiber strain sensor used in bridge structure state monitoring is detailed introduced in this paper, two bridges which optical fiber strain sensor is adopted in construction stage stress monitoring and long-time stress monitoring in our country are introduced as example. According to the theoretical analysis of structures, the strain monitoring locations are selected. The composite technology between optical fiber strain sensor and concrete is researched. The installation technology and protect method between optical fiber strain sensor and steel girder are extracted, and advanced acquisition software is explored. Finally, the application foreground of optical fiber strain sensor is discussed. The research result indicates that the optical fiber strain sensor is extraordinary suitable for state monitoring of bridge structure because it has the merits of light structure and reliable performance.

In this paper, a two-step hot air and microwave drying method was used to dry Porphyra, and the drying process was optimized. Taking the total drying time of Porphyra, the contents of protein and total sugar in dried Porphyra as indexes, the optimal drying process was obtained by using central composite design, model fitting by either quadratic polynomial or neural network, and genetic algorithm optimization. The results showed that the total drying time for sequential hot air drying(first) and microwave drying(later) was shorter than that for sequential microwave drying and hot air drying. In the case of sequential hot air drying(first) and microwave drying(later), the total drying time required to reduce the moisture content to 0.1 g/g DM was the shortest (62.5±1.4 min), if the hot air drying temperature and time were 65 ℃ and 1 h, and the subsequent microwave power was 400 W. Comparing the contents of protein and total sugar in dried Porphyra obtained under the optimal process conditions of the two drying methods, the quality of dried Porphyra obtained by sequential hot air drying(first) and microwave drying(later) was better than sequential microwave drying(first) and hot air drying(later). A highest protein content of 68.82±1.46 mg/g DM was obtained, when the hot air drying temperature and time were 48 ℃ and 3 h, and the subsequent microwave power was 240 W. Moreover, if the samples were first air dried at 65 ℃ for 2 h and then microwave processed at 240 W to the end, the total sugar content was the highest (124.72±7.17 mg/g DM). Generally, the sequential hot air drying(first) and microwave drying(later) would be suitable for the dehydration of Porphyra in terms of drying time and product quality.

Study of reliability of fibre Bragg grating fibre optic strain sensors for field-test applications

In this article, a novel compact optical diffraction strain sensor using medium density grating foil is presented. The grating, generally with a frequency of 300–500 lines/mm attached on the surface of a specimen, is illuminated by a focused laser beam. The centroids of diffracted beam spots from the grating are automatically determined with two position-sensitive detector sensors connected to a personal computer. The shift of second-order diffracted beam spots due to the specimen deformation is then detected. The influences of noise sources and system geometry on system performances, such as sensitivity, spatial resolution, strain range, and measurement linearity are discussed. Strain sensitivity of 1.3 microstrain can be achieved. The spatial resolution for strain measurement of 0.4 mm is attainable. The system can be used for continuous measurement and for both static and dynamic tests.

Background: Aloe vera has been used as a medicinal plant for several hundred years. Aloe vera gel is a rich source of certain bioactive polysaccharides which are essential for immune-therapic activities. Aloe vera gel is prone to bacterial activities which could reduce its storage life due to high water content (97-99%). Drying is the main operation for the dehydration of aloe vera gel but it could significantly affect the physicochemical and structural properties of dried aloe vera gel which in turn may alter its functionality. Individual drying processes like hot air and microwave drying, often fails to retain the quality of dried gel. Methods: Dehydration of aloe vera gel was performed using hot air, microwave-assisted, and hybriddrying processes towards the retention of its physicochemical and functional properties and, the statistical data analysis was performed by ANOVA to understand the effect of drying conditions on its quality. Results: Among all drying techniques, ‘centrifugation followed by freeze-drying’, and ‘centrifugation followed by hot air drying’ showed the highest carbohydrate and protein retention in dried aloe vera gel of 91.8, 82.3% and 90.9, 85.6%, respectively. Microwave input power did not alter the water retention capacity, but its higher value reduced both swelling property and fat adsorption capacity. However, all these functional properties gradually fell down with the increase in temperature of hot air drying. Conclusion: Carbohydrate, protein contents, and functional properties were sensitive to hot air drying temperature (>70 °C) and microwave power input in microwave-assisted drying (>160W). Retention of higher swelling and water retention capacity in hybrid techniques implied that the structural modification of the dried matrix was less affected. Keywords: Aloe vera gel, dehydration, hot air drying, microwave, hybrid drying techniques, functional properties.

NTE material employment in temperature resistive high sensitive fiber optic strain sensor development

A novel microwave pretreated hot air drying (PMt-HD) process for improving drying efficiency and drying quality of Z. bungeanum

Schisandra chinensis fruit is a famous tonic traditional Chinese medicine and healthy food. The chemical components of dried fruits may vary with the initial processing methods of fresh fruits. Therefore, in this study, the influence of drying was evaluated based on targeted metabolomics analysis. The ultrahigh performance liquid chromatography-triple quadrupole mass spectrometry (UPLC-QQQ-MS) was applied in determination of multicomponent including lignans, organic acids, and oligosaccharides. The fresh fruits of Schisandra chinensis were processed by natural drying in the sun, hot air drying and vacuum drying at different temperatures, and vacuum freeze drying, respectively. The contents of lignans, organic acids, and oligosaccharides in different fruit samples were quantified and statistically analyzed by partial least squares discriminant analysis (PLS-DA). The variation of totally 10 lignans, 5 organic acids, and 9 oligosaccharides with different drying process were compared. The results showed that the drying time of natural drying method was much longer than the other methods using instrument. For hot air and vacuum drying samples, most of lignans, organic acids, and oligosaccharides gradually decreased with the increase of temperature. And the appearance of fruit drying at higher temperature was dark red. At the same processing temperature, vacuum drying takes longer time than hot air drying. In addition, organic acid and oligosaccharide contents of vacuum freeze drying treated samples were higher than the other processed samples significantly. According to the targeted metabolomics analysis, the lignans, organic acids, and oligosaccharides markers were screened out for holistic quality evaluation of Schisandra chinensis fruits. In comprehensive consideration of multicomponent, drying time, fruit appearance and storage, and production feasibility, hot air drying at 50°C is more suitable for the process of Schisandra chinensis. The result is expected to provide a scientific basis for the selection of proper method for drying process of fresh Schisandra chinensis fruit.

Optical fibre sensors are being investigated since many years as candidates of choice for supporting structural health monitoring (SHM) in aerospace applications. Fibre Bragg grating (FBG) sensors, more specifically, can provide for accurate strain measurements and therefore return useful data about the mechanical strain state of the structure to which they are attached. This functionality can serve the detection of damage in an aircraft structure. However, very few solutions for protecting and bonding optical fibres to a state-of-the-art aircraft composite material have been reported. Most proof-of-principle demonstrations using optical fibre sensors for aerospace SHM-related applications reported in literature indeed rely on unpackaged fibre sensors bonded to isotropic metallic surfaces in a mostly unspecified manner. Neither the operation of the sensor, nor the adhesive material and bonding procedure are tested for their endurance against a full set of standardized in-flight conditions. In this work we propose a specialty coated FBG sensor and its permanent installation on aerospace-grade composite materials, and we demonstrate the compatibility with aerospace in-flight conditions. To do so we thoroughly evaluate the quality of the operation of the FBG sensor by correlating the reflection spectra of the installed sensors before and after exposure to a full set of realistic in-flight conditions. We also evaluate the difference in strain measured by the FBG, since any damage in the adhesive bond line would lead to strain release. The applied test conditions are based on aerospace standards and include temperature cycling, pressure cycling, exposure to humidity and hydraulic fluid and fatigue loading. We show that both the bond line and the quality of the sensor signal were negligibly affected by the applied environmental and mechanical loads representing in-flight conditions and therefore conclude that it can be considered for SHM of aerospace-grade composite materials.