1. Articles in category: NDE/NDT

    1-24 of 479 1 2 3 4 ... 18 19 20 »
    1. In Situ Detection of Interfacial Flow Instabilities in Polymer Co-Extrusion Using Optical Coherence Tomography and Ultrasonic Techniques

      In Situ Detection of Interfacial Flow Instabilities in Polymer Co-Extrusion Using Optical Coherence Tomography and Ultrasonic Techniques

      Co-extrusion is a widely used processing technique for combining various polymers with different properties into a tailored multilayer product. Individual melt streams are combined in a die to form the desired shape. Under certain conditions, interfacial flow instabilities are observed; however, fundamental knowledge about their onset and about critical conditions in science and industry is scarce. Since reliable identification of interfacial co-extrusion flow instabilities is essential for successful operation, this work presents in situ measurement approaches using a novel co-extrusion demonstrator die, which is fed by two separate melt streams that form a well-controlled two-layer co-extrusion polymer melt flow. An ...

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    2. Research partnership develops 10 second high-throughput technology to detect counterfeit documents

      Research partnership develops 10 second high-throughput technology to detect counterfeit documents

      Fraudulent identity documents are an ever-evolving challenge, particularly at international border crossings. To increase their resilience to counterfeiting, many security features have been added to identification documents over the last decade. However, due to the efficiency of organised crime, the threat of individuals crossing the borders using fraudulent documents remains high. Now, a research partnership between foster+freeman and the University of Kent has developed a new, a non-destructive, high-throughput analysis technique to counter this threat. By repurposing a medical technology known as OCT (optical coherence tomography), the research group were able to rapidly distinguish the difference between legitimate and ...

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    3. In situ process monitoring and automated multi-parameter evaluation using optical coherence tomography during extrusion-based bioprinting

      In situ process monitoring and automated multi-parameter evaluation using optical coherence tomography during extrusion-based bioprinting

      In three-dimensional (3D) bioprinting, errors during the printing process leads to lower structural fidelity, and the desired structural and functional performances cannot be fully satisfied. Process monitoring with high-speed imaging techniques is helpful for identifying material deposition errors. 3D reconstruction of printed objects enables comprehensive evaluation of structural characteristics, with wide-field full-depth imaging being necessary for large objects. In this study, we demonstrate 3D extrusion-based bioprinter-associated optical coherence tomography (3D P-OCT) to achieve high-speed, wide-field and full-depth imaging, and provide in situ process monitoring and comprehensive evaluation for 3D bioprinting . In 3D P-OCT, a wide field was achieved with a ...

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    4. Optical coherence tomography-surveilled laser ablation using multifunctional catheter and 355-nm optical pulses

      Optical coherence tomography-surveilled laser ablation using multifunctional catheter and 355-nm optical pulses

      An optical coherence tomography (OCT)-monitored laser ablation system is presented in this study. The laser ablation subsystem is constructed using the third harmonic output of a Nd:YAG laser source operating at a 355-nm optical wavelength with a single pulse energy greater than 160 mJ and a 1–10 Hz tunable repetition rate. The imaging subsystem is a typical M-mode swept-source OCT system. Moreover, a type of all-fiber multifunctional integrated catheter is demonstrated. The ablation catheter consists of a fiber bundle including 41 multi-mode fibers with an outer diameter of 0.9 mm. A forward-viewing OCT imaging probe is ...

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    5. Laser beam welding of geometric figures using OCT seam tracking

      Laser beam welding of geometric figures using OCT seam tracking

      A measuring device for monitoring a laser welding process that is connectable to a machining device for machining a workpiece by a high-energy processing beam that is displaceable on the workpiece along a main machining path that corresponds to a contour of a closed geometric figure. The measuring device includes an optical coherence tomography unit having a measuring beam source for generating an optical measuring beam that is displaceable on the workpiece by at least one movable deflection unit. The optical measuring beam is displaceable on the workpiece along a first discrete measuring line, along a second discrete measuring line ...

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    6. Phase-sensitive optical coherence tomography for non-contact monitoring photocuring process

      Phase-sensitive optical coherence tomography for non-contact monitoring photocuring process

      A method combining phase-contrast technique and spectral-domain optical coherence tomography (OCT) has been recently proposed for visualizing curing behaviors inside polymers (2020 Appl. Phys. Lett. 116 054103). Here, based on the method, a non-contact and highly-sensitive optical sensor is further developed to monitor the photocuring process of light-cured polymers. Compared with the existing method, the proposed optical sensor features two distinct advantages: (a) the sensor uses a point-detection OCT, rather than a line-field OCT, to capture the interference signal, which significantly improves its practicability and the measuring speed; (b) the sensor can simultaneously monitor the shrinkage strains and refractive index ...

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    7. Optical Coherence Tomography Applied to Non-Destructive Seed Coat Thickness Measurement

      Optical Coherence Tomography Applied to Non-Destructive Seed Coat Thickness Measurement

      Background: Seed coat thickness is a parameter of interest in lentil breeding and processing. Methods described in the literature are destructive and time consuming, limiting the usefulness of this seed characteristic in breeding or grading. In this study, a low-cost optical coherence tomography (OCT) system (OQ Labscope 2.0 from Lumedica, Inc., Durham, NC USA) was used to non-destructively measure lentil seed coat thicknesses. These measurements were compared to destructive measurements obtained via optical microscopy of cross-sectioned seeds. Results: Measurements from the two methods were comparable with consistent trends in thickness and population separability among the five lentil accessions used ...

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      Mentions: Lumedica
    8. Full-field optical coherence tomography using tunable-path-difference source for three-dimensional multi-layered imaging with enhanced signal-to-noise ratio

      Full-field optical coherence tomography using tunable-path-difference source for three-dimensional multi-layered imaging with enhanced signal-to-noise ratio

      We demonstrate a novel scheme for a full-field optical coherence tomography (FF-OCT) system using a tunable-path-difference source (TPDS). Recently, the comb-spacing-swept source (CSWS) method, including TPDS, has been successfully applied to improve the stability of three-dimensional (3D) time-domain (TD)-FF-OCT imaging by eliminating the mechanical scanning of the reference path, which has been the main source of undesirable noise in general TD-OCT. However, CSWS-OCT has the drawback of a degraded signal-to-noise ratio (SNR) from a duplicated interferometer structure. In this study, we improve the configuration of the TPDS so that it can be connected directly to the measurement interferometer, including ...

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    9. Non-Destructive Subsurface Inspection of Marine and Protective Coatings Using Near- and Mid-Infrared Optical Coherence Tomography

      Non-Destructive Subsurface Inspection of Marine and Protective Coatings Using Near- and Mid-Infrared Optical Coherence Tomography

      Near- and mid-infrared optical coherence tomography (OCT) is evaluated as a non-destructive and non-contact reflection imaging modality for inspection of industrial and marine coatings. Near-infrared OCT was used to obtain high-resolution images (~6/2 µm lateral/axial) of hidden subsurface cracks and defects in a resin base coating, which had been exposed to high pressure and high temperature to study coating degradation in hostile environments. Mid-infrared OCT was employed for high-resolution (~15/8.5 µm lateral/axial) subsurface inspection of highly scattering marine coatings, demonstrating monitoring of wet film thickness and particle dispersion during curing of a 210 µm layer ...

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    10. Layered viscoelastic properties of granular biofilms

      Layered viscoelastic properties of granular biofilms

      Granular biofilms are dense spherical complex biological systems composed mainly of multi-microbial cells, water, and extracellular polymeric substances (EPS). They facilitate efficient purification and settling of activated sludge in wastewater treatment processes . The viscoelastic properties of these complex biofilm systems are important characteristics that control their growth and dictate how they respond to hydrodynamic forces and chemical stimuli. However, the viscoelastic properties of granular biofilms are poorly understood. In this paper, we study granular biofilms' viscoelastic properties using optical coherence elastography (OCE), a nondestructive method that integrates optical coherence tomography (OCT) with elastic wave propagation . While quantitative viscoelastic characterization of ...

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    11. The Effect of Thermocycling on Interfacial Bonding Stability of Self-Etch Adhesives: OCT Study

      The Effect of Thermocycling on Interfacial Bonding Stability of Self-Etch Adhesives: OCT Study

      Objective: The aim of this study was to monitor the behavior of interfacial gaps formed under different bonded polymeric restorations before and after thermocycling (TC), using swept-source optical coherence tomography (SS-OCT) and confirming the obtained findings with confocal laser scanning microscopy (CLSM). Materials and methods: Cylindrical class I cavities were prepared in twenty noncarious human premolar teeth (1.5 mm depth × 3.5 mm diameter) and divided randomly into two groups: TS and SN, according to the adhesive system ( n = 10). In the TS group, one-step self-etch adhesive Clearfil Tri-S Bond Plus (Kuraray Noritake Dental, Japan) was used, followed by ...

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    12. Microstructural changes in rice (Oryza sativa L.) leaves under varying low pH levels: a swept-source optical coherence tomography approach

      Microstructural changes in rice (Oryza sativa L.) leaves under varying low pH levels: a swept-source optical coherence tomography approach

      Soil acidification has shown detrimental effects on rice plants that lead to decreased rice production. In the present study, we aim to study the microstructural changes in rice leaves under acidic stress through swept-source optical coherence tomography (SS-OCT). To achieve this, rice seeds were germinated, subsequently these germinated seedlings were further grown under varying pH conditions for 14 d. Growth in root and shoot of plants and chlorophyll content of leaf samples were studied at varying pH levels. Similarly, acidic stress treated rice leaves were also subjected to SS-OCT image analysis revealing several features present in the layers of leaves ...

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    13. Biometric Identification with 3D Fingerprints Acquired Through Optical Coherence Tomography

      Biometric Identification with 3D Fingerprints Acquired Through Optical Coherence Tomography

      —A method to obtain epidermal and dermal 3D fingerprints from high-resolution images acquired using Optical Coherence Tomography (OCT) is proposed. This method addresses limitations of current 3D reconstruction techniques such as depth and resolution variations, sensitivity to low illumination and poor contrast. The availability of these fingerprints made possible the creation of new identification techniques that benefit from the rich information available in 3D. We propose a 3D fingerprint matching process based on KH maps, which are 2D representations of curvature types extracted by computing the Gaussian and mean curvatures from a region of interest around minutiae.The matching strategy ...

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    14. Optical scanning for industrial metrology

      Optical scanning for industrial metrology

      An approach to improving optical scanning increases the strength of optical reflection from the build material during fabrication. In some examples, the approach makes use of an additive (or a combination of multiple additives) that increases the received signal strength and/or improves the received signal-to-noise ratio in optical scanning for industrial metrology. Elements not naturally present in the material are introduced in the additives in order to increase fluorescence, scattering or luminescence. Such additives may include one or more of: small molecules, polymers, peptides, proteins, metal or semiconductive nanoparticles, and silicate nanoparticles.

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      Mentions: Inkbit
    15. Time-encoded mid-infrared Fourier-domain optical coherence tomography

      Time-encoded mid-infrared Fourier-domain optical coherence tomography

      In this contribution, we report on a technically simple approach to high-resolution and sensitive spectral-domain OCT imaging in the mid-infrared range. The proposed OCT system employs an InF 3 supercontinuum source; for detection, a time-encoded spectrometer based on a single InAsSb point detector is used. The developed spectrometer enables structural imaging in the spectral range from around 3140 nm to 4190 nm with a characterised sensitivity above 80 dB and an axial resolution below 8 μm. The capabilities of the system are exhibited for imaging of porous ceramic samples and transition-stage green parts fabricated using an emerging method of lithography-based ...

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      Mentions: RECENDT
    16. Feasibility Study of Detecting Plum’s Early Mechanical Injury Based on Optical Coherence Tomography and Cell Morphological Parameters

      Feasibility Study of Detecting Plum’s Early Mechanical Injury Based on Optical Coherence Tomography and Cell Morphological Parameters

      Mechanical injury, which is hardly observed by naked eyes and machine vision technique if the epidermis of the plum is not ruptured, tends to be the main cause of the shorten shelf life and decay of plums. For the purpose of non-destructive discriminate the mechanical injury, this study proposes to apply optical coherence tomography (OCT) to conduct 3D observation to plum’s subcutaneous tissues, and to automatically compute the tissues’ morphological parameters. The OCT image processing consists of image denoising, binarization, cell segmentation, region selection, and calculation of cell morphological parameters. Afterwards, mechanical injury can be detected based on the ...

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    17. Depth-independent internal fingerprint based on optical coherence tomography

      Depth-independent internal fingerprint based on optical coherence tomography

      Optical coherence tomography (OCT) was used for imaging three-dimensional fingerprint to overcome the effects of different skin states and fake fingerprint. However, the OCT-based fingerprint features depend on the depth of fingertip skin which is still challenging for biometric recognition and encryption. In this work, we presented a new approach of maximum intensity projection (MIP) image of the epidermal-dermal junction (DEJ) to extract the internal fingerprint that is independent of the depth of fingertip skin. To begin with, the surface and DEJ were segmented based on the deep learning algorithm. Then the internal fingerprint was extracted by the MIP image ...

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    18. Use of optical coherence tomography and light microscopy for characterisation of mechanical properties and cellular level responses of ‘Centurion’ blueberries during weight loss

      Use of optical coherence tomography and light microscopy for characterisation of mechanical properties and cellular level responses of ‘Centurion’ blueberries during weight loss

      Postharvest blueberry softening hinders consumer acceptance and correlates with high moisture loss during storage. Such textural variations have been attributed to factors such as turgor, cell wall modifications and other microstructural changes in the outer cell layers of the fruit. This paper investigates the impact of moisture loss on blueberry quality, as well as the structure and/or function relationships associated with fruit mechanical properties during postharvest using an integrated physical and novel microstructural approach. Four different weight loss conditions [62%, 76%, 93% and 98% relative humidity (RH)] at 5.7 °C were evaluated over a three-week postharvest storage period ...

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    19. OCT Capillary Depth Measurement in Copper Micro Welding Using Green Lasers

      OCT Capillary Depth Measurement in Copper Micro Welding Using Green Lasers

      The transition of the powertrain from combustion to electric systems increases the demand for reliable copper connections. For such applications, laser welding has become a key technology. Due to the complexity of laser welding, especially at micro welding with small weld seam dimensions and short process times, reliable in-line process monitoring has proven to be difficult. By using a green laser with a wavelength of λ = 515 nm, the welding process of copper benefits from an increased absorption, resulting in a shallow and stable deep penetration welding process. This opens up new possibilities for the process monitoring. In this contribution, the ...

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    20. Image processing based detection of the fibre orientation during depth-controlled laser ablation of CFRP monitored by optical coherence tomography

      Image processing based detection of the fibre orientation during depth-controlled laser ablation of CFRP monitored by optical coherence tomography

      Layer-accurate and precisely stepped removal of damaged areas is required for the repairing process of parts made of carbon fibre-reinforced plastic (CFRP) to obtain a high bonding strength of the repair plies in the rebuilding process. Conventional techniques are characterized by a high degree of manual labour and mechanical load of the processed part. Here, a novel laser-based and controlled approach for automated and layer-accurate removal of damaged areas is presented. In-line depth measurements by optical coherence tomography during nanosecond laser ablation enable depth-controlled homogeneous material removal with minimum damage <10 μm and low surface roughness in the range of ...

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    21. Inpainting for Saturation Artifacts in Optical Coherence Tomography using Dictionary-based Sparse Representation

      Inpainting for Saturation Artifacts in Optical Coherence Tomography using Dictionary-based Sparse Representation

      Saturation artifacts in optical coherence tomography (OCT) occur when received signal exceeds the dynamic range of spectrometer. Saturation artifact shows a streaking pattern and could impact the quality of OCT images, leading to inaccurate medical diagnosis. In this paper, we automatically localize saturation artifacts and propose an artifact correction method via inpainting. We adopt a dictionary-based sparse representation scheme for inpainting. Experimental results demonstrate that, in both case of synthetic artifacts and real artifacts, our method outperforms interpolation method and Euler's elastica method in both qualitative and quantitative results. The generic dictionary offers similar image quality when applied to ...

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    22. Study on cocoonase, sericin, and degumming of silk cocoon: computational and experimental

      Study on cocoonase, sericin, and degumming of silk cocoon: computational and experimental

      Cocoonase is a proteolytic enzyme that helps in dissolving the silk cocoon shell and exit of silk moth. Chemicals like anhydrous Na2CO3, Marseille soap, soda, ethylene diamine and tartaric acid-based degumming of silk cocoon shell have been in practice. During this process, solubility of sericin protein increased resulting in the release of sericin from the fibroin protein of the silk. However, this process diminishes natural color and softness of the silk. Cocoonase enzyme digests the sericin protein of silk at the anterior portion of the cocoon without disturbing the silk fibroin. However, no thorough characterization of cocoonase ...

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      Mentions: UCSF
    23. Material-specific imaging of nanolayers using extreme ultraviolet coherence tomography

      Material-specific imaging of nanolayers using extreme ultraviolet coherence tomography

      Scientific and technological progress depend substantially on the ability to image on the nanoscale. In order to investigate complex, functional, nanoscopic structures like, e.g., semiconductor devices, multilayer optics, or stacks of 2D materials, the imaging techniques not only have to provide images but should also provide quantitative information. We report the material-specific characterization of nanoscopic buried structures with extreme ultraviolet coherence tomography. The method is demonstrated at a laser-driven broadband extreme ultraviolet radiation source, based on high-harmonic generation. We show that, besides nanoscopic axial resolution, the spectral reflectivity of all layers in a sample can be obtained using algorithmic ...

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    24. Recent progress of nondestructive techniques for fruits damage inspection: a review

      Recent progress of nondestructive techniques for fruits damage inspection: a review

      In the process of growing, harvesting, and storage, fruits are vulnerable to mechanical damage , microbial infections, and other types of damage , which not only reduce the quality of fruits , increase the risk of fungal infections, in turn greatly affect food safety, but also sharply reduce economic benefits. Hence, it is essential to identify damaged fruits in time. Rapid and nondestructive detection of fruits damage is in great demand. In this paper, the latest research progresses on the detection of fruits damage by nondestructive techniques , including visible/near-infrared spectroscopy, chlorophyll fluorescence techniques , computer vision, multispectral and hyperspectral imaging, structured-illumination reflectance imaging ...

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