Artículos de revistas: "Stereoscopic digital image correlation"

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MOLINA VIEDMA, ANGEL JESUS, LUIS FELIPE SESE, ELÍAS LOPEZ ALBA y FRANCISCO ALBERTO DIAZ GARRIDO. "INTEGRATION OF DIGITAL IMAGE CORRELATION AND THERMOELASTICITY FOR EXPERIMENTAL ANALYSYS OF OPERATIONAL MODAL SHAPES". DYNA 99, n.º 4 (1 de julio de 2024): 410–16. http://dx.doi.org/10.52152/d11078.

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Full-field optical techniques provide valuable information for the analysis of mode shapes thanks to their high density of measurement points, providing very detailed maps, in a noninvasive way that avoids alterations of the dynamic behaviour of the specimen. Digital image correlation and thermoelastic stress analysis are two of the most interesting ones. The first provides displacement fields that can be three-dimensional if a calibrated stereoscopic system is used. The second uses a thermographic camera to determine the stress invariant. Given the complementary nature of these magnitudes, this study deals with the integration of the displacement and stress fields by means of a calibrated set of a stereoscopic system and a thermographic camera which, through spatial triangulation, allow the association of the measurements to the same spatial point on the specimen. For this purpose, typical laboratory setups have been carried out for the characterisation of operational modal shapes of resonances. The integration has allowed a more accurate interpretation of the behaviour of the specimen, identifying the regions with the highest mechanical stress. This shows the advantages of integration compared to the isolated analysis of displacement and/or stress measurements that are usually carried out and proves the potential for the development of optical techniques at a scientific and industrial level, opening up new avenues of study.

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Cheng, Wei-Han y Hsin-Haou Huang. "Image-Based Hidden Damage Detection Method: Combining Stereo Digital Image Correlation and Finite Element Model Updating". Sensors 24, n.º 15 (25 de julio de 2024): 4844. http://dx.doi.org/10.3390/s24154844.

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Maintenance and damage detection of structures are crucial for ensuring their safe usage and longevity. However, damage hidden beneath the surface can easily go unnoticed during inspection and assessment processes. This study proposes a detection method based on image techniques to detect and assess internal structural damage, breaking the limitation of traditional image methods that only analyze the structure’s surface. The proposed method combines full-field response on the structure’s surface with finite element model updating to reconstruct the structural model, using the reconstructed model to detect and assess hidden structural damage. Initially, numerical experiments are conducted to generate known damaged areas and parameter distributions. Data from these experiments are used to update the finite element model, establish and validate the proposed model updating method, and assess its accuracy in evaluating hidden damage, achieving an accuracy rate of 90%. Furthermore, discussions on more complex damage scenarios are carried out through numerical experiments to demonstrate the feasibility and applicability of the proposed method in reconstructing different forms of damage. Ultimately, this study utilizes stereoscopic digital imaging techniques to acquire full-field information on surfaces, and applies the proposed method to reconstruct the structure, enabling the detection and assessment of hidden damage with an accuracy rate of 86%.

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Barranco-Gutiérrez, Alejandro-Israel, José-Alfredo Padilla-Medina, Francisco J. Perez-Pinal, Juan Prado-Olivares, Saúl Martínez-Díaz y Oscar-Octavio Gutiérrez-Frías. "New Four Points Initialization for Digital Image Correlation in Metal-Sheet Strain Measurements". Applied Sciences 9, n.º 8 (24 de abril de 2019): 1691. http://dx.doi.org/10.3390/app9081691.

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Nowadays, the deformation measurement in metal sheets is important for industries such as the automotive and aerospace industries during its mechanical stamping processes. In this sense, Digital Image Correlation (DIC) has become the most relevant measurement technique in the field of experimental mechanics. This is mainly due to its versatility and low-cost compared with other techniques. However, traditionally, DIC global image registration implemented in software, such as MATLAB 2018, did not find the complete perspective transformation needed successfully and with high precision, because those algorithms use an image registration of the type “afine” or “similarity”, based on a 2D information. Therefore, in this paper, a DIC initialization method is presented to estimate the surface deformation of metal sheets used in the bodywork automotive industry. The method starts with the 3D points reconstruction from a stereoscopic digital camera system. Due to the problem complexity, it is first proposed that the user indicates four points, belonging to reference marks of a “Circle grid”. Following this, an automatic search is performed among the nearby marks, as far as one desires to reconstruct it. After this, the local DIC is used to verify that those are the correct marks. The results show reliability by reason of the high coincidence of marks in experimental cases. We also consider that the quality of mark stamping, lighting, and the initial conditions also contribute to trustworthy effects.

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Kim, Dong Hak, Jeong Hyun Lee, Ho Dong Kim y Ki Ju Kang. "An Experimental Measurement of Toughness Locus for a Ductile Material". Key Engineering Materials 297-300 (noviembre de 2005): 2410–15. http://dx.doi.org/10.4028/www.scientific.net/kem.297-300.2410.

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A toughness locus Jc-Q for a ductile steel, SA106 Grade C used in the main steam piping of nuclear power plants, has been experimentally evaluated. Along with the standard fracture test procedure for J-R curve, Q as the second parameter governing stress triaxiality nearby the crack tip is measured from the displacements nearby the side necking which occurs near the crack tip on the lateral surface of a fracture specimen. The displacements nearby the side necking are measured from the digital images taken during the fracture experiment based on Stereoscopic Digital Photography (SDP) and high resolution Digital Image Correlation (DIC) software. The crack length is monitored by Direct Current Potential Drop (DCPD) method and the J-R curve is determined according to ASTM standard E1737-96. The effects of crack length, specimen geometry and thickness of specimen are studied, which are included in the toughness locus Jc-Q.

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Paolillo, Gerardo y Tommaso Astarita. "PaIRS-UniNa: A Robust And Accurate Free Tool For Digital Particle Image Velocimetry And Optical Camera Calibration". Proceedings of the International Symposium on the Application of Laser and Imaging Techniques to Fluid Mechanics 21 (8 de julio de 2024): 1–9. http://dx.doi.org/10.55037/lxlaser.21st.120.

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This contribution presents PaIRS-UniNa (PArticle Image Reconstruction Software – University of Naples “Federico II”), a free software application designed to perform digital particle image velocimetry (PIV). PaIRS-UniNa relies on a powerful C library designed for speed, robustness and accuracy, and a user-friendly graphical interface (Figure 1) running in Python environment on all operating systems, including Windows, Linux and MacOS. At the current stage, it features modules to perform two-component (2C) PIV, stereoscopic PIV and optical camera calibration for multi-camera systems. The processing of PIV and stereoscopic PIV data is based on an iterative image deformation method, which can be customized by the user varying different parameters in such a way to find the best compromise between accuracy and computational speed. These parameters include the size, shape and number of interrogation windows, the number of process iterations and the type of interpolating functions for both image deformation and displacement interpolation (such as bilinear, bicubic, methods based on simplexes or the FFT shift theorem and B-splines of varying orders). Additionally, it is possible to select a range of weighting windows for cross-correlation estimation and velocity field filtering, including rectangular, Blackman, Gaussian, Harris, Hann windows, among others, and several vector validation strategies for outlier detection and replacement. Such a level of customization enables to effectively adjust the modulation transfer function of the PIV process to meet specific application requirements. For the stereoscopic PIV process two different approaches are possible: mapping, which involves applying PIV to de-warped images for 2D-2C displacement fields, and warping, which applies PIV to raw images and combine 3C reconstruction and image dewarping in a single subsequent step. In order to accurately estimate the laser sheet plane location and correct errors due to misalignment and inaccurate displacement vector positions, a disparity correction procedure is also available. The calibration module (CalVi) supports accurate calibration with the camera models mostly used in the PIV community: polynomials, rational functions and the pinhole camera model. Moreover, it supports the integration of the pinhole camera model with a refractive correction model for cylindrical geometries and camera calibration procedures working with unknown positions and orientations of the calibration target. In such a way, the target may be moved by hand without losing accuracy in comparison with a conventional calibration, in which the target is displaced with the aid of translational and rotational stages and knowledge of the target positions is strictly required. Already used in numerous experimental studies by the Experimental Thermo-Fluid Dynamics group of University of Naples “Federico II” and international collaborating groups, PaIRS-UniNa offers a rapid and effective free alternative to commercial PIV software for research and industrial use.

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Molina-Viedma, Ángel J., Elías López-Alba, Luis Felipe-Sesé y Francisco A. Díaz. "Operational Deflection Shape Extraction from Broadband Events of an Aircraft Component Using 3D-DIC in Magnified Images". Shock and Vibration 2019 (9 de abril de 2019): 1–9. http://dx.doi.org/10.1155/2019/4039862.

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Recently, many works have shown the capabilities of noninterferometric optical techniques, such as digital image correlation, to characterise modal behaviour. They provide a global insight into the structure or component behaviour which implies massive spatial information, unaffordable by traditional sensor instrumentation. Moreover, phase-based motion magnification (PMM) is a methodology which, based on a sequence of images, magnifies a periodic motion encoded in phase time-domain signals of the complex steerable pyramid filters employed to decompose the images. It provides a powerful tool to interpret deformation. However, the interpretation is just qualitative and should be avoided if out-plane motion is recorded as only one camera is employed. To overcome this issue, 3D digital image correlation (3D-DIC) has been linked with PMM to provide measurements from stereoscopic sets of images, providing full-field displacement maps to magnified images. In this work, the combination of PMM and 3D-DIC has been employed to evaluate the modal behaviour of an aircraft cabin under random excitation. The study was focused on the passenger window area due to its significance to the structural integrity as a discontinuity of the peel. Operational deflection shapes at different resonances were characterised by magnifying a single resonance in the spectrum and then measuring with 3D-DIC. These measurements were validated with those obtained in forced normal mode tests. Motion and displacement videos improved the understanding of the identified resonance deformation. Actually, a relevant behaviour was noticed in the window’s frame, a quite narrow area where using traditional sensors would not provide such a detailed 3D information.

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Felipe-Sesé, Luis, Ángel Molina-Viedma, Elías López-Alba y Francisco Díaz. "RGB Colour Encoding Improvement for Three-Dimensional Shapes and Displacement Measurement Using the Integration of Fringe Projection and Digital Image Correlation". Sensors 18, n.º 9 (17 de septiembre de 2018): 3130. http://dx.doi.org/10.3390/s18093130.

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Three-dimensional digital image correlation (3D-DIC) has become the most popular full-field optical technique for measuring 3D shapes and displacements in experimental mechanics. The integration of fringe projection (FP) and two-dimensional digital image correlation (FP + DIC) has been recently established as an intelligent low-cost alternative to 3D-DIC, overcoming the drawbacks of a stereoscopic system. Its experimentation is based on the colour encoding of the characterized fringe and speckle patterns required for FP and DIC implementation, respectively. In the present work, innovations in experimentation using FP + DIC for more accurate results are presented. Specifically, they are based on the improvement of the colour pattern encoding. To achieve this, in this work, a multisensor camera and/or laser structural illumination were employed. Both alternatives are analysed and evaluated. Results show that improvements both in three-dimensional and in-plane displacement are obtained with the proposed alternatives. Nonetheless, multisensor high-speed cameras are uncommon, and laser structural illumination is established as an important improvement when low uncertainty is required for 2D-displacement measurement. Hence, the uncertainty has been demonstrated to be reduced by up to 50% compared with results obtained in previous experimental approaches of FP + DIC.

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Vetter, Sebastian y Gunnar Siedler. "Automated 3D-Objectdocumentation on the Base of an Image Set". Geoinformatics FCE CTU 6 (21 de diciembre de 2011): 370–75. http://dx.doi.org/10.14311/gi.6.46.

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Digital stereo-photogrammetry allows users an automatic evaluation of the spatial dimension and the surface texture of objects. The integration of image analysis techniques simplifies the automation of evaluation of large image sets and offers a high accuracy [1]. Due to the substantial similarities of stereoscopic image pairs, correlation techniques provide measurements of subpixel precision for corresponding image points. With the help of an automated point search algorithm in image sets identical points are used to associate pairs of images to stereo models and group them. The found identical points in all images are basis for calculation of the relative orientation of each stereo model as well as defining the relation of neighboured stereo models. By using proper filter strategies incorrect points are removed and the relative orientation of the stereo model can be made automatically. With the help of 3D-reference points or distances at the object or a defined distance of camera basis the stereo model is orientated absolute. An adapted expansion- and matching algorithm offers the possibility to scan the object surface automatically. The result is a three dimensional point cloud; the scan resolution depends on image quality. With the integration of the iterative closest point- algorithm (ICP) these partial point clouds are fitted to a total point cloud. In this way, 3D-reference points are not necessary. With the help of the implemented triangulation algorithm a digital surface models (DSM) can be created. The texturing can be made automatically by the usage of the images that were used for scanning the object surface. It is possible to texture the surface model directly or to generate orthophotos automatically. By using of calibrated digital SLR cameras with full frame sensor a high accuracy can be reached. A big advantage is the possibility to control the accuracy and quality of the 3d-objectdocumentation with the resolution of the images. The procedure described here is implemented in software Metigo 3D.

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Jayyosi, C., K. Bruyère-Garnier y M. Coret. "Geometry of an inflated membrane in elliptic bulge tests: Evaluation of an ellipsoidal shape approximation by stereoscopic digital image correlation measurements". Medical Engineering & Physics 48 (octubre de 2017): 150–57. http://dx.doi.org/10.1016/j.medengphy.2017.06.020.

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Alizzio, Damiano, Marco Bonfanti, Guido Garozzo, Fabio Lo Savio, Roberto Montanini y Antonino Quattrocchi. "Comparison between 3D-reconstruction optical methods applied to bulge-tests through a feed-forward neural network". ACTA IMEKO 10, n.º 4 (30 de diciembre de 2021): 194. http://dx.doi.org/10.21014/acta_imeko.v10i4.1156.

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The mechanical behaviour of rubber-like materials can be investigated through numerous techniques that differ from each other in costs, execution times and parameters described. Bulge test method proved helpful for hyperelastic membranes under plane and equibiaxial stress state. In the present study, bulge tests in force control were carried out on SBR 20% CB-filled specimens. 3D reconstructions of the dome were achieved through two different stereoscopic techniques, the epipolar geometry and the Digital Image Correlation. Through a Feed-Forward Neural Network (FFNN), these reconstructions were compared with the measurements by a laser triangulation sensor taken as reference. 3D-DIC reconstruction was found to be more accurate. Indeed, bias errors of the 3D-DIC and epipolar techniques with respect to the relative reference values, under creep condition, were 0.53 mm and 0.87 mm, respectively.<br /><br />

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Ioli, F., E. Bruno, D. Calzolari, M. Galbiati, A. Mannocchi, P. Manzoni, M. Martini et al. "A REPLICABLE OPEN-SOURCE MULTI-CAMERA SYSTEM FOR LOW-COST 4D GLACIER MONITORING". International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLVIII-M-1-2023 (21 de abril de 2023): 137–44. http://dx.doi.org/10.5194/isprs-archives-xlviii-m-1-2023-137-2023.

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Abstract. Image-based monitoring has emerged as a prevalent technique for sensing mountain environments. Monoscopic time-lapse cameras, which rely on digital image correlation to quantify glacier motion, have limitations due to the need for a Digital Elevation Model for deriving 3D flow velocity fields. Multi-camera systems overcome this limitation, as they allow for a 3D reconstruction of the scene. This paper presents a replicable low-cost stereoscopic system designed for 4D glacier monitoring. The system consists of independent and autonomous units, built from off-the-shelves components, such as a DSLR camera, an Arduino microcontroller, and a Raspberry Pi Zero, reducing costs compared to pre-built time-lapse cameras. The units are energetically self-sufficient and resistant to harsh alpine conditions. The system was successfully tested for more than a year to monitor the northwest terminus of the Belvedere Glacier (Italian Alps). Daily stereo-pairs acquired were processed with Structure-from-Motion to derive 3D point clouds of the glacier terminus and estimate glacier retreat and ice volume loss. By combining the information about ice volume loss with ablation estimates and ice flow velocity information, e.g., derived from monoscopic-camera time series, a multi-camera system enables a comprehensive understanding of sub-seasonal glacier dynamics.

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Ahn, Y. J., M. A. Eitner, S. Rafati, M. N. Musta, J. Sirohi y N. T. Clemens. "Experimental Investigation of Fluid-Structure Interaction in Mach 2 Flow Using Simultaneous High-Speed PIV and DIC". Proceedings of the International Symposium on the Application of Laser and Imaging Techniques to Fluid Mechanics 20 (11 de julio de 2022): 1–18. http://dx.doi.org/10.55037/lxlaser.20th.224.

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The fluid-structure interaction (FSI) of a compliant panel under a compression-ramp-induced shock-wave/boundary-layer interaction (SBLI) has been studied in Mach 2 flow. Simultaneous high-speed measurements of the velocity field and the panel displacement were conducted using 50 kHz particle image velocimetry (PIV) and 5 kHz stereoscopic digital image correlation (DIC). The mean effect of the panel displacement has been evaluated by monitoring the change in velocity profiles along the streamwise direction (x), upstream of the separated flow region. Streamwise (u) velocity near the panel surface has been shown to change its magnitude in response to the wall shape. Furthermore, the strong cross-correlation between fluctuations of the wall-normal panel displacement and the transverse (v) velocity can be explained by the flow remaining tangent to the wall surface as the panel deforms. This latter result is consistent with the panel motion being sufficiently low frequency compared to flow convective time scales that the flow is quasi-steady. In addition, assessment of the correlation between the separation shock position and panel displacement seems to suggest that when the panel is bulged down (concave up) at the downstream end of the panel, a larger separated flow is generated and the shock moves upstream. This observation remains speculative, but is consistent with the flow undergoing greater compression for the bulged down case.

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Giorgio, I., P. Harrison, F. dell'Isola, J. Alsayednoor y E. Turco. "Wrinkling in engineering fabrics: a comparison between two different comprehensive modelling approaches". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 474, n.º 2216 (agosto de 2018): 20180063. http://dx.doi.org/10.1098/rspa.2018.0063.

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We consider two ‘comprehensive’ modelling approaches for engineering fabrics. We distinguish the two approaches using the terms ‘semi-discrete’ and ‘continuum’, reflecting their natures. We demonstrate a fitting procedure, used to identify the constitutive parameters of the continuum model from predictions of the semi-discrete model, the parameters of which are in turn fitted to experimental data. We, then, check the effectiveness of the continuum model by verifying the correspondence between semi-discrete and continuum model predictions using test cases not previously used in the identification process. Predictions of both modelling approaches are compared against full-field experimental kinematic data, obtained using stereoscopic digital image correlation techniques, and also with measured force data. Being a reduced order model and being implemented in an implicit rather than an explicit finite-element code, the continuum model requires significantly less computational power than the semi-discrete model and could therefore be used to more efficiently explore the mechanical response of engineering fabrics.

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Atoui, Oussama, Azer Maazoun, Aldjabar Aminou, Bachir Belkassem, Lincy Pyl y David Lecompte. "Dynamic Behavior of Aluminum Plates Subjected to Sequential Fragment Impact and Blast Loading: An Experimental Study". Applied Sciences 13, n.º 6 (10 de marzo de 2023): 3542. http://dx.doi.org/10.3390/app13063542.

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This paper presents a study on the dynamic behavior of thin aluminum plates subjected to consecutive fragment impact and blast loading. To this end, two separate experimental setups are used. In the first setup, 2 mm thick aluminum plates EN-AW-1050A-H24 were subjected to the ballistic impact of fragment-simulating projectiles (FSPs). Experiments were carried out for FSP calibers of 7.62 mm and 12.7 mm considering both single impact and triple impacts with variations in the spacing of the impact locations. The out-of-plane displacement and in-plane strain fields were measured using digital image correlation (DIC) coupled to a pair of high-speed cameras in a stereoscopic setup. In the second setup, a subsequent blast loading was applied to the perforated plates using an explosive-driven shock tube (EDST). After the plates are perforated, the strain field around the holes depended on the caliber, the impact orientation of the FSP, and the distance between the impact locations. When the blast loading was applied, cracks tended to appear in areas of strain concentration between the perforated holes. It was found that the relative distance between the holes significantly influences the target’s response mode.

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Flora, Harpaul S., Neil Woodhouse, Stuart Robson y Mohan Adiseshiah. "Micromovements at the Aortic Aneurysm Neck Measured during Open Surgery with Close-Range Photogrammetry: Implications for Aortic Endografts". Journal of Endovascular Therapy 8, n.º 5 (octubre de 2001): 511–20. http://dx.doi.org/10.1177/152660280100800514.

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Purpose: To describe the motion of abdominal aortic aneurysm (AAA) as a first step toward determining if stent-graft migration may be due to propulsive movements at the neck. Method: In an initial laboratory validation test, a silicone AAA model was imaged with a stereo-pair configuration of calibrated digital cameras using retro-reflective and ink dot surface targets. This technique was then applied to 4 aneurysm necks imaged at open surgery. In each case the paired images were measured and analyzed to produce sequences of accurate three-dimensional (3-D) surface models of the anterior aspect of the aortic neck. Engineering techniques were used to visualize and identify differences between the generated surfaces, allowing changes in shape of the aortic wall to be determined. Results: The correlation between stereoscopic digital imaging with electronic caliper measurements of linear dimensions was accurate, irrespective of the type of surface targets used ( r2 = 0.98). The AAA neck demonstrated complex 3-D movements that ranged from 1.0 to 1.5 mm in the radial direction to 0.6 to 1.0 mm along the longitudinal axis, with a 0.44 to 0.59-mm rotational component (p < 0.05). Conclusions: This pilot study raises questions about the validity of accepted models of arterial wall movements and compliance in which rotation has not been described. The technique used to measure dynamic neck morphology appears promising as a means to further define the mechanical parameters of the human aorta, which may assist in designing stent-grafts.

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Warsitzka, Michael, Prokop Závada, Fabian Jähne-Klingberg y Piotr Krzywiec. "Contribution of gravity gliding in salt-bearing rift basins – a new experimental setup for simulating salt tectonics under the influence of sub-salt extension and tilting". Solid Earth 12, n.º 8 (30 de agosto de 2021): 1987–2020. http://dx.doi.org/10.5194/se-12-1987-2021.

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Abstract. Basin-scale salt flow and the evolution of salt structures in rift basins is mainly driven by sub- and supra-salt faulting and sedimentary loading. Crustal extension is often accompanied and followed by thermal subsidence leading to tilting of the graben flanks, which might induce an additional basinward-directed driver for salt tectonics. We designed a new experimental analogue apparatus capable of integrating the processes of sub-salt graben extension and tilting of the flanks, such that the overlapping effects on the deformation of a viscous substratum and the brittle overburden can be simulated. The presented experimental study was performed to demonstrate the main functionality of the experimental procedure and setup, demonstrating the main differences in structural evolution between conditions of pure extension, pure tilting, and extension combined with tilting. Digital image correlation of top-view stereoscopic images was applied to reveal the 3D displacement and strain patterns. The results of these experiments suggest that in salt basins affected by sub-salt extension and flank inclination, the salt flow and downward movement of overburden affects the entire flanks of the basin. Supra-salt extension occurring close to the graben centre is overprinted by the downward movement; i.e. the amount of extension is reduced or extensional faults zones are shortened. At the basin margins, thin-skinned extensional faults developed as a result of gravity gliding. A comparison with natural examples reveals that such fault zones can also be observed at the margins of many salt-bearing rift basins indicating that gravity gliding played a role in these basins.

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Żurada, Anna, Jerzy St Gielecki, R. Shane Tubbs, Marios Loukas, Agnieszka Żurada-Zielińska, Wojciech Maksymowicz, Dariusz Nowak y Aaron A. Cohen-Gadol. "Three-Dimensional Morphometry of the A1 Segment of the Anterior Cerebral Artery With Neurosurgical Relevance". Neurosurgery 67, n.º 6 (1 de diciembre de 2010): 1768–82. http://dx.doi.org/10.1227/neu.0b013e3181fa7fcb.

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Abstract BACKGROUND: Despite research in the anatomical sciences for the last 200 years, some structures of the human body remain controversial or incompletely described. One of these structures is the A1 segment of the anterior cerebral artery (ACA). OBJECTIVE: To analyze the A1 segment of the ACA using novel stereoscopic methods because the 3-dimensional morphometry of the ACA is important to neurosurgeons. METHODS: A digital-image computer-based system was used to analyze the A1 segment of 230 ACAs derived from computed tomography. Data analysis included the inner diameter, length, and volume and calculation of A1 symmetry, hypoplasia, and deviation, and tortuosity indexes. RESULTS: Hypoplasia of the A1 segment was found in 0.87% and only on the right sides, whereas asymmetry was found in 42.6% and was more common in female patients. Right A1 segments tended to be longer in male patients, and this reached significance. Also of significance was the correlation of an increased length with age. Right A1 segments tended to have greater volumes, and this was significant in a comparison of male and female patients. Tortuosity indexes tended to be greater for left sides, but deviation indexes tended to be greater on the right sides. CONCLUSION: Morphometric data of the A1 segment of the ACA as analyzed in the present study may be of utility to the neurosurgeon. Right A1 segments tend to be more tortuous, more deviated, longer, and narrower than left A1 segments.

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Yu, Tianyu, Wenjian Ni, Zhiyu Zhang, Qinhuo Liu y Guoqing Sun. "Regional Sampling of Forest Canopy Covers Using UAV Visible Stereoscopic Imagery for Assessment of Satellite-Based Products in Northeast China". Journal of Remote Sensing 2022 (10 de enero de 2022): 1–14. http://dx.doi.org/10.34133/2022/9806802.

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Canopy cover is an important parameter affecting forest succession, carbon fluxes, and wildlife habitats. Several global maps with different spatial resolutions have been produced based on satellite images, but facing the deficiency of reliable references for accuracy assessments. The rapid development of unmanned aerial vehicle (UAV) equipped with consumer-grade camera enables the acquisition of high-resolution images at low cost, which provides the research community a promising tool to collect reference data. However, it is still a challenge to distinguish tree crowns and understory green vegetation based on the UAV-based true color images (RGB) due to the limited spectral information. In addition, the canopy height model (CHM) derived from photogrammetric point clouds has also been used to identify tree crowns but limited by the unavailability of understory terrain elevations. This study proposed a simple method to distinguish tree crowns and understories based on UAV visible images, which was referred to as BAMOS for convenience. The central idea of the BAMOS was the synergy of spectral information from digital orthophoto map (DOM) and structural information from digital surface model (DSM). Samples of canopy covers were produced by applying the BAMOS method on the UAV images collected at 77 sites with a size of about 1.0 km2 across Daxing’anling forested area in northeast of China. Results showed that canopy cover extracted by the BAMOS method was highly correlated to visually interpreted ones with correlation coefficient (r) of 0.96 and root mean square error (RMSE) of 5.7%. Then, the UAV-based canopy covers served as references for assessment of satellite-based maps, including MOD44B Version 6 Vegetation Continuous Fields (MODIS VCF), maps developed by the Global Land Cover Facility (GLCF) and by the Global Land Analysis and Discovery laboratory (GLAD). Results showed that both GLAD and GLCF canopy covers could capture the dominant spatial patterns, but GLAD canopy cover tended to miss scattered trees in highly heterogeneous areas, and GLCF failed to capture non-tree areas. Most important of all, obvious underestimations with RMSE about 20% were easily observed in all satellite-based maps, although the temporal inconsistency with references might have some contributions.

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Siebert, T., E. Hack, G. Lampeas, E. A. Patterson y K. Splitthof. "Uncertainty Quantification for DIC Displacement Measurements in Industrial Environments". Experimental Techniques 45, n.º 5 (16 de febrero de 2021): 685–94. http://dx.doi.org/10.1007/s40799-021-00447-3.

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AbstractBackground: most methods of uncertainty quantification for digital image correlation are orientated towards the research environment and it remains difficult to quantify all of the uncertainty introduced along the measurement chain in an industrial environment. This gap in capability can become critical when physical tests are required for certification purposes. Objective: To develop and demonstrate an uncertainty quantification method that was independent of a specific DIC system, easily integrated with the measurement workflow, applicable at the measurement location and capable of capturing the contributions from all sources of uncertainty. Methods: an elegant new method utilises the calibration target, commonly used with DIC systems to evaluate their intrinsic and extrinsic parameters, through reference measurements before and after relative motion between the measurement system and the object of interest. The method is described and demonstrated for quantifying the field of uncertainty associated with maps of displacement and deformation in a large-scale industrial component. Results: The fields of uncertainty associated with measurements, using stereoscopic DIC, of x-, y- and z- displacement components during a compression buckling test on an aircraft fuselage panel are presented. The derived uncertainty has independently been corroborated along one axis by moving a calibrated translation stage. Conclusions: A new method has been proposed that allows the quantification of the fields of uncertainty arising from all sources when DIC measurements are performed on a large-scale object of interest in an industrial environment. The method requires no additional equipment and can be readily included in the workflow of a measurement campaign.

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Achbab, E., R. Lambarki, H. Rhinane y D. Saifaoui. "ESTIMATION OF PHOTOVOLTAIC POTENTIAL AT THE URBAN LEVEL FROM 3D CITY MODEL (SOLAR CADASTER): CASE OF CASABLANCA CITY, MOROCCO". International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLVI-4/W3-2021 (10 de enero de 2022): 9–16. http://dx.doi.org/10.5194/isprs-archives-xlvi-4-w3-2021-9-2022.

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Abstract. Nowadays, the use of solar energy in buildings, especially photovoltaic energy, has undergone a great evolution in the world, thanks to various technological advances and to incentive programs. Related to this topic, the solar cadaster is an important interactive tool to predict the solar potential in an urban environment. The main objective of this research work is to estimate the photovoltaic energy potential of roofs based on aerial photogrammetry and GIS processing. The location chosen for the study is the Maarif district located in the city of Casablanca in order to raise awareness of the public and decision makers to this energy potential through a geoportal that will be developed for this purpose. The tool proposed in this research work makes it possible to evaluate the solar irradiation on a part of the territory of Casablanca with a sufficiently satisfactory precision and reliability, this thanks to the precise reconstruction of the territory in 3D urban model called digital surface model (DSM) at 50 cm resolution by techniques known as photogrammetry which makes it possible to carry out measurements extracted from a stereoscopic pairs, by using the parallax and the correlation between the digital images taken from various points of view. The analysis was used on the basis of specific algorithms and several factors including geographical location, shade, tilt, orientation, roof accessibility and topography which are the main factors influencing the productivity of solar panels.

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DiCecco, Sante, Kenneth Cheong, Farinaz Khameneh, Zhi Deng, Michael Worswick y Cliff Butcher. "Formability Characterization Using Curvature and Strain-Rate-Based Limit Strain Detection Methods Applied to Marciniak, Nakazima, and Stretch-Bend Tests". Metals 14, n.º 10 (12 de octubre de 2024): 1164. http://dx.doi.org/10.3390/met14101164.

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Despite advancements in the characterization of forming limit curves (FLCs) with the development of stereoscopic digital image correlation (DIC), there is still uncertainty in the accuracy of the limit strains, especially in forming operations with out-of-plane bending. The ISO12004-2:2008 standard offers a standardized approach to FLC determination but is not without limitations and is not always applicable to new materials and forming processes (e.g., warm forming, hot stamping). In the present work, a physically based limit strain detection technique is developed, termed the Enhanced Curvature Method (ECM), based on the sheet surface curvature evolution at the onset of necking in sheet formability testing. The ECM is applied to the characterization of 1.1 mm AA5182-O sheet using Marciniak, Nakazima, and stretch–bend characterization tests, and its limit strains are compared with those from the linear best-fit (LBF) local strain-rate approach and the ISO-12004 standard. The ECM considers the physical nature of necking in sheet forming with the aid of thresholds defined in terms of an imperfection metric analogous to the well-known Marciniak–Kuczynski (MK) imperfection factor. By quantifying the evolution of necking, FLCs of different safety margins can be readily generated, enabling a more intuitive selection for the factor of safety. For lower and upper ECM thresholds, the Marciniak plane strain limiting strain was determined to lie between 0.173 and 0.198, respectively, which is comparable to the analytical prediction of 0.194 and in general agreement with the published literature for AA5182-O. Similar plane strain limits were obtained using the ISO and LBF methods with values of 0.188 and 0.208, respectively. The same rankings in limit strain values between methods were observed for plane strain loading in Nakazima and stretch–bend tests.

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22

Aminou, Aldjabar, Mohamed Ben Rhouma, Bachir Belkassem, Hamza Ousji, Lincy Pyl y David Lecompte. "Experimental and Numerical Evaluation of Calcium-Silicate-Based Mineral Foam for Blast Mitigation". Applied Sciences 14, n.º 21 (22 de octubre de 2024): 9656. http://dx.doi.org/10.3390/app14219656.

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Cellular materials such as aluminum and polyurethane foams are recognized for their effectiveness in energy absorption. They commonly serve as crushable cores in sacrificial cladding for blast mitigation purposes. This study delves into the effectiveness of autoclaved aerated concrete (AAC), a lightweight, porous material known for its energy-absorbing properties as a crushable core in sacrificial cladding. The experimental set-up features a rigid frame made of steel measuring 1000 × 1000 × 15 mm3 with a central square opening (300 × 300 mm2) holding a 2 mm thick aluminum plate representing the structure. The dynamic response of the aluminum plate is captured using two high-speed cameras arranged in a stereoscopic configuration. Three-dimensional digital image correlation is used to compute the transient deformation fields. Blast loading is achieved by detonating 20 g of C4 explosive set at 250 mm from the plate’s center. The study assesses the mineral foam’s absorption capacity by comparing out-of-plane displacement and mean permanent deformation of the aluminum plate with and without the protective solution. Six foam configurations (A to F) are tested experimentally and numerically, varying in the foam’s free space for expansion relative to its total volume. Results show positive protective effects, with configuration F reducing maximum deflection by at least 30% and configuration C by up to 70%. Foam configuration influences energy dissipation, with an optimal lateral surface-to-volume ratio (ζ) enhancing protective effects, although excessive ζ leads to non-uniform foam crushing. To address the influence of front skin deformability, a non-deformable front skin has been adopted. The latter demonstrates an increased effectiveness of the sacrificial cladding, particularly for ζ values above the optimal value obtained when using a deformable front skin. Notably, using a non-deformable front skin increases maximum deflection reduction and foam energy absorption by up to approximately 30%.

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23

DiCecco, S., M. Di Ciano, C. Butcher y M. Worswick. "Effect of Initial Temper on the Warm Forming Characteristics of a High Strength 7000-series Al-Zn-Mg-Cu Alloy". IOP Conference Series: Materials Science and Engineering 1238, n.º 1 (1 de mayo de 2022): 012087. http://dx.doi.org/10.1088/1757-899x/1238/1/012087.

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Abstract In this work, the formability of a developmental 7000-series copper containing aluminium alloy was assessed at room temperature (RT), 150°C, 175°C and 200°C in pre-aged (PA), peak-aged (T6) and overaged (T76) tempers using Nakazima tests with stereoscopic digital image correlation (DIC) strain measurement. The limit strains were identified using a novel curvature-based approach to detect the formation of an acute neck. The tensile mechanical properties in these warm forming processing routes were characterized with and without a paint bake cycle. Finally, a thermo-mechanical tensile simulator was used to evaluate the constitutive response of the PA and T76 tempers as a function of strain-rate and time at 175°C. Formability results found the selected PA temper to have a good room temperature formability and a mild positive response to the selected warm-forming cycles. The T6 and T76 tempers both exhibited increases in formability in response to warm forming. The PA temper had a significant positive response to short-duration warm forming and subsequent paint baking, with the yield strength increasing from 420 MPa to 512 MPa following this thermal cycle. For the T6 temper, the warm-forming cycle showed a trend characteristic of retrogression and re-aging, with the warm-forming cycle dropping the yield strength from 566 MPa to 534 MPa and the subsequent paint-bake re-aging to 554 MPa. The effect of aging during pre-heating prior to warm forming on the warm constitutive response of the PA and T76 tempers was also investigated. Both tempers exhibited rather different aging responses to short-duration thermal cycles. In the PA temper, this manifested as an increase in at-temperature yield strength and loss of hardening rate. In contrast, the T76 temper exhibited a drop in strength since this temper is already over-aged prior to warm forming. Both the PA and T76 tempers showed comparable at-temperature strain-rate sensitivity.

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24

Seehaus, Thorsten, Veniamin I. Morgenshtern, Fabian Hübner, Eberhard Bänsch y Matthias H. Braun. "Novel Techniques for Void Filling in Glacier Elevation Change Data Sets". Remote Sensing 12, n.º 23 (29 de noviembre de 2020): 3917. http://dx.doi.org/10.3390/rs12233917.

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The increasing availability of digital elevation models (DEMs) facilitates the monitoring of glacier mass balances on local and regional scales. Geodetic glacier mass balances are obtained by differentiating DEMs. However, these computations are usually affected by voids in the derived elevation change data sets. Different approaches, using spatial statistics or interpolation techniques, were developed to account for these voids in glacier mass balance estimations. In this study, we apply novel void filling techniques, which are typically used for the reconstruction and retouche of images and photos, for the first time on elevation change maps. We selected 6210 km2 of glacier area in southeast Alaska, USA, covered by two void-free DEMs as the study site to test different inpainting methods. Different artificially voided setups were generated using manually defined voids and a correlation mask based on stereoscopic processing of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) acquisition. Three “novel” (Telea, Navier–Stokes and shearlet) as well as three “classical” (bilinear interpolation, local and global hypsometric methods) void filling approaches for glacier elevation data sets were implemented and evaluated. The hypsometric approaches showed, in general, the worst performance, leading to high average and local offsets. Telea and Navier–Stokes void filling showed an overall stable and reasonable quality. The best results are obtained for shearlet and bilinear void filling, if certain criteria are met. Considering also computational costs and feasibility, we recommend using the bilinear void filling method in glacier volume change analyses. Moreover, we propose and validate a formula to estimate the uncertainties caused by void filling in glacier volume change computations. The formula is transferable to other study sites, where no ground truth data on the void areas exist, and leads to higher accuracy of the error estimates on void-filled areas. In the spirit of reproducible research, we publish a software repository with the implementation of the novel void filling algorithms and the code reproducing the statistical analysis of the data, along with the data sets themselves.

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25

Kasuga, Hideo y Nobuki Fuse. "Stereoscopic image conversion for multi-layer digital illustrations". Journal of the Society for Art and Science 15, n.º 2 (15 de junio de 2016): 66–74. http://dx.doi.org/10.3756/artsci.15.66.

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McCormick, Nick y Jerry Lord. "Digital Image Correlation". Materials Today 13, n.º 12 (diciembre de 2010): 52–54. http://dx.doi.org/10.1016/s1369-7021(10)70235-2.

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27

Wilson, Anthony J., Bianca C. Chin, Vivian M. Hsu, Michael N. Mirzabeigi y Ivona Percec. "Digital Image Correlation". Plastic and Reconstructive Surgery 135, n.º 5 (mayo de 2015): 869e—876e. http://dx.doi.org/10.1097/prs.0000000000001224.

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28

Zhou, Wujie, Gangyi Jiang, Mei Yu, Zhongpeng Wang, Zongju Peng y Feng Shao. "Reduced reference stereoscopic image quality assessment using digital watermarking". Computers & Electrical Engineering 40, n.º 8 (noviembre de 2014): 104–16. http://dx.doi.org/10.1016/j.compeleceng.2014.06.007.

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29

Lee, Yoon-Hyuk, Hyun-Jun Choi, Dong-Wook Kim y Young-Ho Seo. "Arbitrary Viewpoint/Disparity Stereoscopic Image Generation from a Digital Hologram". Journal of Broadcast Engineering 19, n.º 6 (30 de noviembre de 2014): 854–65. http://dx.doi.org/10.5909/jbe.2014.19.6.854.

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30

Yi, Faliu y Inkyu Moon. "Automatic calculation of tree diameter from stereoscopic image pairs using digital image processing". Applied Optics 51, n.º 18 (15 de junio de 2012): 4120. http://dx.doi.org/10.1364/ao.51.004120.

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31

Khaja, Abdul Aziz y Wael A. Samad. "Hybrid Digital Image Correlation". Journal of Engineering Mechanics 146, n.º 4 (abril de 2020): 04020009. http://dx.doi.org/10.1061/(asce)em.1943-7889.0001726.

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32

Xie, Huimin y Yilan Kang. "Digital image correlation technique". Optics and Lasers in Engineering 65 (febrero de 2015): 1–2. http://dx.doi.org/10.1016/j.optlaseng.2014.07.010.

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Balogh, Attila, Mark C. Preul, Mark Schornak, Michael Hickman y Robert F. Spetzler. "Intraoperative stereoscopic QuickTime Virtual Reality". Journal of Neurosurgery 100, n.º 4 (abril de 2004): 591–96. http://dx.doi.org/10.3171/jns.2004.100.4.0591.

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Object. The aim of this study was to acquire intraoperative images during neurosurgical procedures for later reconstruction into a stereoscopic image system (QuickTime Virtual Reality [QTVR]) that would improve visualization of complex neurosurgical procedures. Methods. A robotic microscope and digital cameras were used to acquire left and right image pairs during cranial surgery; a grid system facilitated image acquisition with the microscope. The surgeon determined a field of interest and a target or pivot point for image acquisition. Images were processed with commercially available software and hardware. Two-dimensional (2D) or interlaced left and right 2D images were reconstructed into a standard or stereoscopic QTVR format. Standard QTVR images were produced if stereoscopy was not needed. Intraoperative image sequences of regions of interest were captured in six patients. Relatively wide and deep dissections afford an opportunity for excellent QTVR production. Narrow or restricted surgical corridors can be reconstructed into the stereoscopic QTVR mode by using a keyhole mode of image acquisition. The stereoscopic effect is unimpressive with shallow or cortical surface dissections, which can be reconstructed into standard QTVR images. Conclusions. The QTVR system depicts multiple views of the same anatomy from different angles. By tilting, panning, or rotating the reconstructed images, the user can view a virtual three-dimensional tour of a neurosurgical dissection, with images acquired intraoperatively. The stereoscopic QTVR format provides depth to the montage. The system recreates the dissection environment almost completely and provides a superior anatomical frame of reference compared with the images captured by still or video photography in the operating room.

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34

Zheng, Wentao, Yoshiaki Shishikui, Yutaka Tanaka y Ichiro Yuyama. "Disparity estimation with hierarchical block correlation for stereoscopic image coding". Systems and Computers in Japan 28, n.º 6 (15 de junio de 1997): 1–9. http://dx.doi.org/10.1002/(sici)1520-684x(19970615)28:6<1::aid-scj1>3.0.co;2-f.

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35

Willert, Christian. "Stereoscopic digital particle image velocimetry for application in wind tunnel flows". Measurement Science and Technology 8, n.º 12 (1 de diciembre de 1997): 1465–79. http://dx.doi.org/10.1088/0957-0233/8/12/010.

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36

Żurada, Anna, Jerzy St. Gielecki, Jan Baron, JarosŁaw Zawiliński y Hanna Kozłowska. "Interactive 3D stereoscopic digital-image analysis of the basilar artery bifurcation". Clinical Anatomy 21, n.º 2 (2008): 127–37. http://dx.doi.org/10.1002/ca.20598.

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37

Yang, J. y K. Bhattacharya. "Combining Image Compression with Digital Image Correlation". Experimental Mechanics 59, n.º 5 (18 de enero de 2019): 629–42. http://dx.doi.org/10.1007/s11340-018-00459-y.

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38

Neggers, J., B. Blaysat, J. P. M. Hoefnagels y M. G. D. Geers. "On image gradients in digital image correlation". International Journal for Numerical Methods in Engineering 105, n.º 4 (14 de julio de 2015): 243–60. http://dx.doi.org/10.1002/nme.4971.

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39

Mao, Fangfang y Lei Zhao. "Panoramic Image Generation Technology for Full Digital Stereo 3D Reconstruction in Water Conservancy Surveying and Mapping Engineering". Mobile Information Systems 2022 (13 de agosto de 2022): 1–10. http://dx.doi.org/10.1155/2022/9718469.

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Due to the lack of image feature extraction in traditional panoramic image generation technology, the effect of 3D reconstruction of physical objects is poor. In this paper, fully digital stereoscopic 3D reconstruction technology is introduced in water conservancy surveying and mapping engineering to ensure complete panoramic image generation. Through in-depth analysis of the principle of 3D reconstruction technology and the database, the detailed water conservancy surveying and mapping engineering images are obtained, the feature vectors of the obtained panoramic images are matched, and the database is compared and positioned according to the matched position features. By using the initial position camera and calibration features, comparison and query are conducted with the image database, to remove the worthless confidence data, retain the outline of the object with reference value, obtain a fixed pose center point, and remove the overlapping area in the process of 3D reconstruction after calculating the outline of the image. Finally, the automatic generation of panoramic images is realized. Finally, the results of experimental analysis show that the panoramic image generation technology of the fully digital stereoscopic 3D reconstruction proposed in this paper has a relative accuracy of 49% compared with the traditional image generation method, and the effect of image generation is relatively good, which has a certain use value.

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40

Sjödahl, Mikael. "Gradient Correlation Functions in Digital Image Correlation". Applied Sciences 9, n.º 10 (24 de mayo de 2019): 2127. http://dx.doi.org/10.3390/app9102127.

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The performance of seven different correlation functions applied in Digital Image Correlation has been investigated using simulated and experimentally acquired laser speckle patterns. The correlation functions were constructed as combinations of the pure intensity correlation function, the gradient correlation function and the Hessian correlation function, respectively. It was found that the correlation function that was constructed as the product of all three pure correlation functions performed best for the small speckle sizes and large correlation values, respectively. The difference between the different functions disappeared as the speckle size increased and the correlation value dropped. On average, the random error of the combined correlation function was half that of the traditional intensity correlation function within the optimum region.

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41

Tomičevć, Zvonimir, François Hild y Stéphane Roux. "Mechanics-aided digital image correlation". Journal of Strain Analysis for Engineering Design 48, n.º 5 (11 de junio de 2013): 330–43. http://dx.doi.org/10.1177/0309324713482457.

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42

Shen, Huan, Peize Zhang y Xiang Shen. "Kernel based Digital Image Correlation". International Journal of Signal Processing, Image Processing and Pattern Recognition 8, n.º 3 (31 de marzo de 2015): 261–72. http://dx.doi.org/10.14257/ijsip.2015.8.3.24.

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43

Yang, J. y K. Bhattacharya. "Augmented Lagrangian Digital Image Correlation". Experimental Mechanics 59, n.º 2 (6 de diciembre de 2018): 187–205. http://dx.doi.org/10.1007/s11340-018-00457-0.

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44

Mudassar, Asloob Ahmad y Saira Butt. "Improved Digital Image Correlation method". Optics and Lasers in Engineering 87 (diciembre de 2016): 156–67. http://dx.doi.org/10.1016/j.optlaseng.2015.10.002.

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Curt, J., M. Capaldo, F. Hild y S. Roux. "Optimal digital color image correlation". Optics and Lasers in Engineering 127 (abril de 2020): 105896. http://dx.doi.org/10.1016/j.optlaseng.2019.105896.

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46

Wang, Hui Bai y Jian Feng Hou. "The Research of Digital Sandbox System". Advanced Materials Research 756-759 (septiembre de 2013): 1798–802. http://dx.doi.org/10.4028/www.scientific.net/amr.756-759.1798.

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Digital sandbox is mainly the use of advanced computer technology, adding vivid images multimedia presentations and interactive features, such as 3D-3 dimensional animation and 3D model, combined with state-of-the-art optical imaging technology, on the basis of the existing traditional sandbox, to entertain visitors with dynamic visual effects, beautiful and multi-faceted show. The system for digital sandbox, the study of the generation and synthesis of the of holographic imaging surface image, with MAYA combined, quickly generate the image in all directions, and synthesis, resulting in a realistic three-dimensional scene; interactive virtual scene with speakers, through data gloves to control scene, to reach a wonderful stereoscopic display effect.

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47

Moreno Escobar, Jesús Jaime, Erika Yolanda Aguilar del Villar, Oswaldo Morales Matamoros y Liliana Chanona Hernández. "3D22MX: Performance Subjective Evaluation of 3D/Stereoscopic Image Processing and Analysis". Mathematics 11, n.º 1 (29 de diciembre de 2022): 171. http://dx.doi.org/10.3390/math11010171.

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This work is divided into three parts: (i) a methodology developed for building a 3D/ stereoscopic database, called 3D22MX, (ii) a software tool designed for degradation of 3D/stereoscopic images, and (iii) a psychophysical experiment carried out for a specific type of noise. The novelty of this work is to integrate these three parts precisely to provide not only professionals who design algorithms to estimate three-dimensional image quality but also those who wish to generate new image databases. For the development of the 3D/stereoscopic database, 15 indoor images and 5 outdoor ones were spatial-calibrated and lighted for different types of scenarios. Criteria calibration is different for indoor images with respect to outdoor images. The software tool to degrade 3D/stereoscopic images is designed from MatLab programming language since images captured in the first part are calculated for achieving several image degradation. Our program has ten different types of noises for degradation, such as white Gauss impulse, localvar, spatial correlation, salt & pepper, speckle, blur, contrast, jpeg, and j2k. Due to each type of noise containing up to five levels of degradation, in this proposal, a database of 20 images is required to design a tool for degrading and generating three-dimensional images ranging from all types of noise to yield psychophysical. Finally, there are applied specific criteria to carry out some psychophysical experiments with 3D/stereoscopic images. Moreover, we analyzed the methodology used to qualify and apply images to the j2k noise, explaining every degradation level for this noise.

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48

Khouri, Albert S., Bernard C. Szirth, Haytham I. Salti y Robert D. Fechtner. "DICOM transmission of simultaneous stereoscopic images of the optic nerve in patients with glaucoma". Journal of Telemedicine and Telecare 13, n.º 7 (1 de octubre de 2007): 337–40. http://dx.doi.org/10.1258/135763307782215389.

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We evaluated the Digital Imaging and Communications in Medicine (DICOM) standard for the transmission of stereoscopic images of the optic nerve. Digital optic nerve images were obtained from patients with glaucoma. Fifteen simultaneous stereo images from consecutive patients were analysed independently twice, in random order, by two glaucoma specialists to establish baseline values of vertical and horizontal cup-to-disc (CDV and CDH) ratios and image quality (1 = worst, 5 = best). Images were transmitted to a distant location and returned to the sending site using DICOM standards in both directions. The received images were reassessed again by the two glaucoma specialists. The image file size slightly increased for all received images (mean 2545 kByte) in comparison with the transmitted images (mean 2460 kByte). The mean baseline values for CDV, CDH and quality score were 0.66, 0.59 and 3.9, respectively. The corresponding mean values for the received images were 0.66, 0.62 and 3.73, respectively. The differences between transmitted and received images were not significant. Clinical interpretation of digital stereoscopic images of glaucomatous optic nerves appears to be unaffected by DICOM capture and transmission.

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49

Wurm, Reinhard E., Stephan Erbel, Isabel Schwenkert, Franz Gum, Daniel Agaoglu, Reinhard Schild, Lorenz Schlenger, Dirk Scheffler, Mario Brock y Volker Budach. "NOVALIS FRAMELESS IMAGE-GUIDED NONINVASIVE RADIOSURGERY". Neurosurgery 62, suppl_5 (1 de mayo de 2008): A11—A18. http://dx.doi.org/10.1227/01.neu.0000325932.34154.82.

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ABSTRACT OBJECTIVE To evaluate our initial experience with Novalis (BrainLAB, Heimstetten, Germany) frameless image-guided noninvasive radiosurgery. METHODS The system combines the dedicated Novalis linear accelerator with ExacTrac X-Ray 6D, an infrared camera and a kilovolt stereoscopic x-ray imaging system, a noninvasive mask system, and ExacTrac robotics for patient positioning in six degrees of freedom. Reference cranial skeletal structures are radiographically imaged and automatically fused to digital reconstructed radiographs calculated from the treatment planning computed tomographic scan to find the target position and accomplish automatic real-time tracking before and during radiosurgery. We present the acceptance testing and initial experience in 15 patients with 19 intracranial lesions treated between December 2005 and June 2006 at the Charité by frameless image-guided radiosurgery with doses between 12 and 20 Gy prescribed to the target-encompassing isodose. RESULTS Phantom tests showed an overall system accuracy of 1.04 ± 0.47 mm, with an average in-plane deviation of 0.02 ± 0.96 mm for the x-axis and 0.02 ± 0.70 mm for the y-axis. After infrared-guided patient setup of all patients, the overall average translational deviation determined by stereoscopic x-ray verification was 1.5 ± 1.3 mm, and the overall average rotational deviation was 1.0 ± 0.8 degree. The data used for radiosurgery, after stereoscopic x-ray verification and correction, demonstrated an overall average setup error of 0.31 ± 0.26 mm for translation and 0.26 ± 0.23 degree for rotation. CONCLUSION This initial evaluation demonstrates the system accuracy and feasibility of Novalis image-guided noninvasive radiosurgery for intracranial benign and malignant lesions.

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Atkinson, Devan y Thorsten Hermann Becker. "Stereo Digital Image Correlation in MATLAB". Applied Sciences 11, n.º 11 (26 de mayo de 2021): 4904. http://dx.doi.org/10.3390/app11114904.

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Digital Image Correlation (DIC) has found widespread use in measuring full-field displacements and deformations experienced by a body from images captured of it. Stereo-DIC has received significantly more attention than two-dimensional (2D) DIC since it can account for out-of-plane displacements. Although many aspects of Stereo-DIC that are shared in common with 2D DIC are well documented, there is a lack of resources that cover the theory of Stereo-DIC. Furthermore, publications which do detail aspects of the theory do not detail its implementation in practice. This literature gap makes it difficult for newcomers to the field of DIC to gain a deep understanding of the Stereo-DIC process, although this knowledge is necessary to contribute to the development of the field by either furthering its capabilities or adapting it for novel applications. This gap in literature acts as a barrier thereby limiting the development rate of Stereo-DIC. This paper attempts to address this by presenting the theory of a subset-based Stereo-DIC framework that is predominantly consistent with the current state-of-the-art. The framework is implemented in practice as a 202 line MATLAB code. Validation of the framework shows that it performs on par with well-established Stereo-DIC algorithms, indicating it is sufficiently reliable for practical use. Although the framework is designed to serve as an educational resource, its modularity and validation make it attractive as a means to further the capabilities of DIC.

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