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Roy, Rinto, Alexander Tessler, Cecilia Surace et Marco Gherlone. « Shape Sensing of Plate Structures Using the Inverse Finite Element Method : Investigation of Efficient Strain–Sensor Patterns ». Sensors 20, no 24 (9 décembre 2020) : 7049. http://dx.doi.org/10.3390/s20247049.
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Methods for real-time reconstruction of structural displacements using measured strain data is an area of active research due to its potential application for Structural Health Monitoring (SHM) and morphing structure control. The inverse Finite Element Method (iFEM) has been shown to be well suited for the full-field reconstruction of displacements, strains, and stresses of structures instrumented with discrete or continuous strain sensors. In practical applications, where the available number of sensors may be limited, the number and sensor positions constitute the key parameters. Understanding changes in the reconstruction quality with respect to sensor position is generally difficult and is the aim of the present work. This paper attempts to supplement the current iFEM modeling knowledge through a rigorous evaluation of several strain–sensor patterns for shape sensing of a rectangular plate. Line plots along various sections of the plate are used to assess the reconstruction quality near and far away from strain sensors, and the nodal displacements are studied as the sensor density increases. The numerical results clearly demonstrate the effectiveness of the strain sensors distributed along the plate boundary for reconstructing relatively simple displacement patterns, and highlight the potential of cross-diagonal strain–sensor patterns to improve the displacement reconstruction of more complex deformation patterns.
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Benca, Emir, Ivan Zderic, Jan Caspar, Kenneth van Knegsel, Lena Hirtler, Boyko Gueorguiev, Harald Widhalm, Reinhard Windhager et Peter Varga. « On Measuring Implant Fixation Stability in ACL Reconstruction ». Sensors 21, no 19 (6 octobre 2021) : 6632. http://dx.doi.org/10.3390/s21196632.
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Numerous methods and devices are available for implant fixation in anterior cruciate ligament (ACL) reconstruction. Biomechanical data indicate high variability in fixation stability across different devices. This study aims to provide a better insight into measuring the structural characteristics and mechanical behavior of ACL implant fixations. Fourteen human tibial specimens with reconstructed ACLs were subjected to progressively increasing dynamic loading until failure. The motions of the tibia, the proximal and distal graft ends, as well as the testing frame and actuator, were continuously recorded via a motion tracking system. Significantly higher displacements of the machine actuator (1.0 mm at graft slippage onset, and 12.2 mm at ultimate load) were measured compared to the displacements of the proximal (0.8 and 4.3 mm, respectively) and distal graft (0.1 and 3.4 mm, respectively) ends. The displacements measured at different sites showed significant correlations. The provided data suggest significant and systematic inaccuracies in the stiffness and slippage of the fixation when using machine displacement, as commonly reported in the literature. The assessment of the distal graft displacement excludes the artifactual graft elongation, and most accurately reflects the graft slippage onset indicating clinical failure. Considering the high displacement at the ultimate load, the ultimate load could be used as a standardized variable to compare different fixation methods. However, the ultimate load alone is not sufficient to qualitatively describe fixation stability.
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Le Hanneur, Malo, Andrew Thoreson, Damien Delgrande, Thibault Lafosse, Jean-David Werthel, Philippe Hardy et Bassem Elhassan. « Biomechanical Comparison of Anatomic and Extra-Anatomic Reconstruction Techniques Using Local Grafts for Chronic Instability of the Acromioclavicular Joint ». American Journal of Sports Medicine 46, no 8 (10 mai 2018) : 1927–35. http://dx.doi.org/10.1177/0363546518770603.
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Background: Anatomic reconstruction techniques are increasingly used to address cases of acromioclavicular (AC) joint chronic instability. These usually involve an additional surgical site for autograft harvesting or an allograft. Purpose: To describe a triple-bundle (TB) anatomic reconstruction using on-site autografts, the semiconjoint tendon (SCT) and the coracoacromial ligament (CAL), and compare its primary stability to the native AC joint ligamentous complex and to a modified Weaver-Dunn (WD) reconstruction. Study Design: Controlled laboratory study. Methods: Intact AC joints of 12 paired cadaveric shoulders were tested for anterior, posterior, and superior translations under cyclic loading with a servo-hydraulic testing system. One shoulder from each pair was randomly assigned to the TB group, where 2 SCT strips were used to reconstruct the coracoclavicular ligaments while the distal end of the CAL was transferred to the distal extremity of the clavicle to reconstruct the AC ligaments; the other shoulder received a modified WD reconstruction. After reconstruction, the same translational testing was performed, with an additional load-to-failure test in the superior direction. Results: In both the TB and the WD groups, no significant differences were found before and after reconstruction in terms of joint displacements after cyclic loading, in all 3 directions. Compared with the WD reconstruction, the TB repair resulted in significantly lower displacements in both the anterior (ie, 2.59 ± 1.08 mm, P = .011) and posterior (ie, 10.17 ± 6.24 mm, P = .014) directions, but not in the superior direction. No significant differences were observed between the 2 reconstructions during the load-to-failure testing, except for the displacement to failure, which was significantly smaller (ie, 5.34 ± 2.97 mm) in the WD group ( P = .037). Conclusion: Anterior, posterior, and superior displacements after an anatomic reconstruction of the AC joint complex using the SCT and CAL as graft material were similar to those of native AC joints and significantly smaller in the axial plane than those of AC joints after a WD repair. Clinical Relevance: An anatomic reconstruction is achievable using the CAL and the SCT as on-site graft materials, providing satisfactory initial stability and thereby allowing earlier mobilization.
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Peng, Zhenrui, Kangli Dong et Hong Yin. « A Modal-Based Kalman Filter Approach and OSP Method for Structural Response Reconstruction ». Shock and Vibration 2019 (16 juin 2019) : 1–15. http://dx.doi.org/10.1155/2019/5475686.
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The objective of the work is experimental validation and optimal experimental design for structural response reconstruction. A modal-based Kalman filter approach based on excitation identification Kalman filter is proposed for response reconstruction and excitation estimation of structures by using noisy acceleration and strain measurements. Firstly, different filters are introduced and discussed. Secondly, to avoid single type sensors, a displacement reconstruction based on modal method is introduced into the proposed approach. Thirdly, the backward sequential algorithm is given to obtain the optimal sensor locations. It is shown that the proposed method can avoid the divergency in the estimated process of excitation and displacements as a result of incomplete measurements. Reasonable estimates of strains, displacements, velocities, accelerations, and excitations of structures can be accomplished with few acceleration sensors and strain gauges.
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Esposito, Marco, Massimiliano Mattone et Marco Gherlone. « Experimental Shape Sensing and Load Identification on a Stiffened Panel : A Comparative Study ». Sensors 22, no 3 (29 janvier 2022) : 1064. http://dx.doi.org/10.3390/s22031064.
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The monitoring of loads and displacements during service life is proving to be crucial for developing a modern Structural Health Monitoring framework. The continuous monitoring of these physical quantities can provide fundamental information on the actual health status of the structure and can accurately guide pro-active condition-based maintenance operations, thus reducing the maintenance costs and extending the service life of the monitored structures. Pushed by these needs and by the simultaneous development in the field of strain sensing technologies, several displacement reconstruction and load identification methods have been developed that are based on discrete strain measurements. Among the different formulations, the inverse Finite Element Method (iFEM), the Modal Method (MM) and the 2-step method, the latter being the only one able to also compute the loads together with the displacements, have emerged as the most accurate and reliable ones. In this paper, the formulation of the three methods is summarized in order to set the numerical framework for a comparative study. The three methods are tested on the reconstruction of the external load and of the displacement field of a stiffened aluminium plate starting from experimentally measured strains. A fibre optic sensing system has been used to measure surface strains and an optimization procedure has been performed to provide the best fibre pattern, based on five lines running along the stiffeners’ direction and with a back-to-back measuring scheme. Additional sensors are used to measure the applied force and the plate’s deflection in some locations. The comparison of the results obtained by each method proves the extreme accuracy and reliability of the iFEM in the reconstruction of the deformed shape of the panel. On the other hand, the Modal Method leads to a good reconstruction of the displacements, but also exhibits a sensitivity to the choice of the modes considered for the specific application. Finally, the 2-step approach is able to correctly identify the loads and to reconstruct the displacements with an accuracy that depends on the modeling of the experimental setup.
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Zhang, Qing, Xing Fu, Zhiguo Sun et Liang Ren. « A Smart Multi-Rate Data Fusion Method for Displacement Reconstruction of Beam Structures ». Sensors 22, no 9 (20 avril 2022) : 3167. http://dx.doi.org/10.3390/s22093167.
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Dynamic displacement plays an essential role in structural health monitoring. To overcome the shortcomings of displacement measured directly, such as installation difficulty of monitoring devices, this paper proposes a smart reconstruction method, which can realize real-time intelligent online reconstruction of structural displacement. Unlike the existing approaches, the proposed algorithm combines the improved mode superposition methods that is suitable for complex beam structures with the Kalman filtering approach using acceleration and strain data. The effectiveness of the proposed multi-rate data fusion method for dynamic displacement reconstruction is demonstrated by both numerical simulation and model vibration experiment. Parametric analysis shows that the reconstruction error is only 5% when the noise signal to noise ratio is 5 dB, illustrating that the proposed algorithm has excellent anti-noise performance. The results also indicate that both the high-frequency and low-frequency components of the dynamic displacements can be accurately reconstructed through the proposed method, which has good robustness.
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Xu, Hao, Qi Zhou, Lei Yang, Minjing Liu, Dongyue Gao, Zhanjun Wu et Maosen Cao. « Reconstruction of full-field complex deformed shapes of thin-walled special-section beam structures based on in situ strain measurement ». Advances in Structural Engineering 23, no 15 (4 juillet 2020) : 3335–50. http://dx.doi.org/10.1177/1369433220937156.
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This study proposed a method capable of reconstructing complex deformations of thin-walled special-section beam structures subjected to highly coupled loading cases, in terms of the combination of tension/compression, biaxial bending, and warping torsion. The complex beam deformation was decoupled, depending on axial strain measurement strategy on beam surface, and leads to reconstructed full-field displacements (deformed shapes) as the linear superposition of deformations subject to individual loading types. Full-filed strain/stress distributions can then be derived based on the reconstructed displacements. Particular efforts were focused on reconstructing beam deformation subject to warping torsion, where both rotations angles and warping displacements across the beam cross-section and along the beam length were identified precisely. As a proof-of-concept validation, the effectiveness of the method was examined using finite element analysis, where the deformed shape of a thin-walled hat-section beam under the coupling between uniaxial bending and warping torsion was reconstructed., Experiments were conducted subsequently to reconstruct deformation of an aluminum hat-section beam using distributed optical fiber sensors for the measurement of axial strains on the beam surface. The reconstructed full-field deformed shapes of the beam were compared with the three-dimensional displacement signals captured using a non-contact digital image correlation system. The effectiveness of the proposed methodology for complex deformation reconstruction is possible to be extended to a variety of thin-walled beam-type structures which are typical in civil and aerospace engineering, showing potential contributions in fields such as on-line structural health monitoring and active structural control.
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Xu, Libo, Feifei Zhao, Jingli Du et Hong Bao. « Two-Step Calibration Method for Inverse Finite Element with Small Sample Features ». Sensors 20, no 16 (16 août 2020) : 4602. http://dx.doi.org/10.3390/s20164602.
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When the inverse finite element method (inverse FEM) is used to reconstruct the deformation field of a multi-element structure with strain measurements, strain measurement errors can lower the reconstruction accuracy of the deformation field. Furthermore, the calibration ability of a self-structuring fuzzy network (SSFN) is weak when few strain samples are used to train the SSFN. To solve this problem, a novel two-step calibration method for improving the reconstruction accuracy of the inverse FEM method is proposed in this paper. Initially, the errors derived from measured displacements and reconstructed displacements are distributed to the degrees of freedom (DOFs) of nodes. Then, the DOFs of nodes are used as knots, in order to produce non-uniform rational B-spline (NURBS) curves, such that the sample size employed to train the SSFN can be enriched. Next, the SSFN model is used to determine the relationship between the measured strain and the DOFs of the end nodes. A loading deformation experiment using a three-element structure demonstrates that the proposed algorithm can significantly improve the accuracy of reconstruction displacement.
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Kashani, Hany, Graham Wright, Ali Ursani, Garry Liu, Masoud Hashemi et Narinder Paul. « Restricting motion effects in CT coronary angiography ». British Journal of Radiology 92, no 1103 (novembre 2019) : 20190384. http://dx.doi.org/10.1259/bjr.20190384.
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Objective: Evaluation of coronary CT image blur using multi segment reconstruction algorithm. Methods: Cardiac motion was simulated in a Catphan. CT coronary angiography was performed using 320 × 0.5 mm detector array and 275 ms gantry rotation. 1, 2 and 3 segment reconstruction algorithm, three heart rates (60, 80 and 100bpm), two peak displacements (4, 8 mm) and three cardiac phases (55, 35, 75%) were used. Wilcoxon test compared image blur from the different reconstruction algorithms. Results: Image blur for 1, 2 and 3 segments in: 60 bpm, 75% R–R interval and 8 mm peak displacement: 0.714, 0.588, 0.571 mm (1.18, 0.6, 0.4 mm displacement) 80 bpm, 35% R–R interval and 8 mm peak displacement: 0.869, 0.606, 0.606 mm (1.57, 0.79,0.52 mm displacement) 100 bpm, 35% R–R interval and 4 mm peak displacement: 0.645, 0.588, 0.571 mm (0.98, 0.49, 0.33 mm displacement). The median image blur overall for 1 and 2 segments was 0.714 mm and 0.588 mm respectively (p < 0.0001). Conclusion: Two-segment reconstruction significantly reduces image blur. Advances in knowledge: Multisegment reconstruction algorithms during CT coronary angiography are a useful method to reduce image blur, improve visualization of the coronary artery wall and help the early detection of the plaque.
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Moulton, M. J., L. L. Creswell, S. W. Downing, R. L. Actis, B. A. Szabo, M. W. Vannier et M. K. Pasque. « Spline surface interpolation for calculating 3-D ventricular strains from MRI tissue tagging ». American Journal of Physiology-Heart and Circulatory Physiology 270, no 1 (1 janvier 1996) : H281—H297. http://dx.doi.org/10.1152/ajpheart.1996.270.1.h281.
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A method is developed and validated for approximating continuous smooth distributions of finite strains in the ventricles from the deformations of magnetic resonance imaging (MRI) tissue tagging "tag lines" or "tag surfaces." Tag lines and intersections of orthogonal tag lines are determined using a semiautomated algorithm. Three-dimensional (3-D) reconstruction of the displacement field on tag surfaces is performed using two orthogonal sets of MRI images and employing spline surface interpolation. The 3-D regional ventricular wall strains are computed from an initial reference image to a deformed image in diastole or systole by defining a mapping or transformation of space between the two states. The resultant mapping is termed the measurement analysis solution and is defined by determining a set of coefficients for the approximating functions that best fit the measured tag surface displacements. Validation of the method is performed by simulating tag line or surface deformations with a finite element (FE) elasticity solution of the heart and incorporating the measured root-mean-square (rms) errors of tag line detection into the simulations. The FE-computed strains are compared with strains calculated by the proposed procedure. The average difference between two-dimensional (2-D) FE-computed strains and strains calculated by the measurement analysis was 0.022 +/- 0.009 or 14.2 +/- 3.6% of the average FE elasticity strain solution. The 3-D displacement reconstruction errors averaged 0.087 +/- 0.002 mm or 2.4 +/- 0.1% of the average FE solution, and 3-D strain fitting errors averaged 0.024 +/- 0.011 or 15.9 +/- 2.8% of the average 3-D FE elasticity solution. When the rms errors in tag line detection were included in the 2-D simulations, the agreement between FE solution and fitted solution was 24.7% for the 2-D simulations and 19.2% for the 3-D simulations. We conclude that the 3-D displacements of MRI tag lines may be reconstructed accurately; however, the strain solution magnifies the small errors in locating tag lines and reconstructing 3-D displacements.
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Ranjit, B., V. A. Tolpekin et A. Stein. « MULTIPLE-POINT GEOSTATISTICS TO DERIVE MISSING SURFACE DISPLACEMENT VALUES OF A GLACIER INFERRED FROM DINSAR ». ISPRS Annals of Photogrammetry, Remote Sensing and Spatial Information Sciences IV-2/W5 (29 mai 2019) : 631–38. http://dx.doi.org/10.5194/isprs-annals-iv-2-w5-631-2019.
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<p><strong>Abstract.</strong> Glacier displacements play a vital role in the monitoring and understanding of glacier dynamics. Glacier displacement fields are typically retrieved from pre- and post-event SAR images using DInSAR. The glacier displacement map produced by DInSAR contains missing values due to decorrelation of the SAR images. This study demonstrates the utility of direct sampling—a well-established multiple-point geostatistics method—for deriving those missing values. Univariate and bivariate implementations of direct sampling are employed. In the univariate implementation, missing values are derived in single displacement map, whereas in bivariate implementation gaps in two displacement maps are filled simultaneously. Evaluation is carried out by artificially generated missing values on the displacement map of different shapes and sizes at different locations with known values. Imposed missing values are then reconstructed and compared with the original values. Reconstruction results of both implementations were compared with ordinary kriging using qualitative and quantitative measures. The study shows that with an increase in the size of such discontinuities, ordinary kriging predictions deteriorate significantly, whereas only slight decrease in reconstruction accuracy is observed for direct sampling. The results of both implementations are similar with the univariate implementation performing slightly better over bivariate implementation because the information from ancillary data is only partly complementary for bivariate reconstructions. Direct sampling performed better than ordinary kriging with accuracy below the DInSAR detection limit. This study concludes that multiple-point geostatistics is an effective method for deriving missing values in DInSAR derived displacement maps. Direct sampling based reconstruction is fast and straightforward to implement.</p>
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Ogushi, Matsuoka, Defilippi et Pasquali. « Improvement of Persistent Scatterer Interferometry to Detect Large Non-Linear Displacements with the 2π Ambiguity by a Non-Parametric Approach ». Remote Sensing 11, no 21 (23 octobre 2019) : 2467. http://dx.doi.org/10.3390/rs11212467.
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Persistent scatterer interferometry (PSI) is commonly applied to monitor surface displacements with millimetric precision. However, this technique still has trouble estimating non-linear displacements because the algorithm is designed for the slow and linear displacements. Additionally, there is a variety of non-linear displacement types, and finding an appropriate displacement model for PSI is still assumed to be a fairly large task. In this paper, the conventional PSI technique is extended using a non-parametric non-linear approach (NN-PSI), and the performance of the extended method is investigated by simulations and actual observation data processing with TerraSAR-X. In the simulation, non-linear displacements are modeled by the magnitudes and periods of the displacement, and the evaluation of NN-PSI is conducted. According to the simulation results, the maximum magnitude of the displacement that can be estimated by NN-PSI is two and a half times the magnitude of the SAR sensor’s wavelength (2.5λ that is roughly equivalent to 8 cm for X-band, 14 cm for C-band, and 60 cm for L-band), and the period of the displacement is about three months. However, this displacement cannot be reconstructed by the conventional PSI due to the limitation, known as the 2π displacement ambiguity. The result of the observation data processing shows that a large displacement with the 2π ambiguity can be estimated by NN-PSI as the simulation results show, but the conventional PSI cannot reconstruct it. In addition, a different approach, Small BAseline Subset (SBAS), is applied to the same data to ensure the accuracy of results, and the correlation between NN-PSI and SBAS is 0.95, while that between the conventional PSI and SBAS is –0.66. It is concluded that NN-PSI enables the reconstruction of non-linear displacements by the non-parametric approach and the expansion of applications to measure surface displacements that could not be measured due to the limitations of the traditional PSI methods.
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Nowak, Edward, et Waldemar Odziemczyk. « Control network reliability reconstruction for Zatonie dam ». Reports on Geodesy and Geoinformatics 105, no 1 (1 juin 2018) : 1–5. http://dx.doi.org/10.2478/rgg-2018-0001.
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Abstract Absolute horizontal displacements are an important element of dam safety level assessment. Appropriate design of measurement network is a prerequisite for the acquisition of displacement values that meet the reliability requirements. A network of this kind, apart from ensuring the required precision of displacement determination, should be characterised by reliability allowing for elimination of gross errors in the results of geodetic surveys. This study aims to propose a method to improve reliability characteristic of surveying network used for horizontal displacement identification in Zatonie dam. The desired effect (increase in the network’s reliability) is obtained by the authors in two stages. The first stage concerns expansion of the existing network by addition of three free stations. As the obtained effect did not prove to be satisfactory, in the second stage so called observation accuracy harmonisation was carried out, which optimally utilises the reliability potential of the measurement construction. In order to successfully carry out the harmonisation, a modification to the procedure’s algorithm had to be introduced. A design of a network ensuring detection of a gross error in any given observation was obtained as the result of the performed actions.
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Reilly, Megan, Kurosh Darvish, Soroush Assari, John Cole et Eric Gokcen. « Plantar Plate Reconstruction for Stage IV Plantar Plate Tear Using Flexor Tendon Tenodesis ». Foot & ; Ankle Orthopaedics 3, no 3 (1 juillet 2018) : 2473011418S0039. http://dx.doi.org/10.1177/2473011418s00399.
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Category: Lesser Toes Introduction/Purpose: Outcomes of the surgical treatment of dislocated lesser toes have improved significantly over the past few years due to the development of techniques to repair plantar plate tears through a dorsal incision. However, treatment of stage 4 tears with no reparable plantar plate can be challenging. The current treatment involves flexor to extensor tendon transfer, requiring multiple incisions and surgical time. An alternative approach is presented, using the same modern techniques of plantar plate repair, but reconstructing the plantar plate using a flexor tendon tenodesis to the plantar base of the proximal phalanx. Methods: Four fresh frozen cadaver foot and ankle specimens were used to determine the stability of this new technique. A simulated Lachman’s test was performed on the 2nd, 3 rd, and 4th metatarsophalangeal joints utilizing a force measurement instrument with displacement control on specimens with an intact plantar plate, an excised plantar plate, and following a flexor tenodesis reconstruction. Results: The intact plantar plate force was 9.0+2.6kN for 2 mm displacement, and following excision of the plantar plate, the force reduced to 1.3+0.4kN. The flexor tenodesis reconstruction improved the force to 6.0+1.9kN. Conclusion: Plantar plate reconstruction with a flexor tenodesis to the proximal phalanx resulted in stability equal to 53% of the intact plantar plate, for the shear displacements between 2 to 6 mm. This procedure may be an alternative treatment option in patients with Stage 4 irreparable plantar plate tears.
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EL-MASRI, SOUHEIL. « Displacements and Reconstruction : The Case of West Beirut - Lebanon ». Disasters 13, no 4 (décembre 1989) : 334–44. http://dx.doi.org/10.1111/j.1467-7717.1989.tb00727.x.
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Thedy, John, Kuo-Wei Liao, Chun-Chieh Tseng et Chia-Ming Liu. « Bridge Health Monitoring via Displacement Reconstruction-Based NB-IoT Technology ». Applied Sciences 10, no 24 (11 décembre 2020) : 8878. http://dx.doi.org/10.3390/app10248878.
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An aged bridge’s performance is affected by degradation and becomes one of the major concerns in maintenance. A preliminary, simple and workable procedure of bridge damage detection is required to minimize maintenance costs. In the past, frequency is one of the most common indicators to detect damage occurrence. Recent research found that using frequency as a health indicator still has room to improve. Alternatively, dynamic displacement is used as an indicator in the current study. These dynamic displacements are reconstructed based on measured acceleration records from micro electro mechanical system (MEMS) sensors. The Newmark-beta method with Windows is proposed to acquire the reconstructed displacements of considered bridges. To demonstrate the accuracy and applicability of the proposed approach, three different experiments are carried out; (i) A small scale bridge with the implementation of MEMS acceleration sensors; (ii) a numerical complex finite element method (FEM) bridge model; (iii) an actual bridge with the implementation of MEMS acceleration sensors and narrow bandwidth Internet of things (NB-IoT) technology. The first experiment shows that the proposed method can successfully identify the difference between damaged/undamaged bridges and determine damage location. The second experiment indicates that the proposed method is able to identify the difference between stiffened/unstiffened bridges. The last experiment shows the applicability of the proposed method on an actual bridge health monitoring project.
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Kataoka, T., H. Moritomo, S. Omokawa, A. Iida, T. Wada et M. Aoki. « Palmar reconstruction of the triangular fibrocartilage complex for instability of the distal radioulnar joint : a biomechanical study ». Journal of Hand Surgery (European Volume) 38, no 5 (3 octobre 2012) : 515–22. http://dx.doi.org/10.1177/1753193412461743.
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We developed a new triangular fibrocartilage complex reconstruction technique for distal radioulnar joint instability in which the palmar portion of the triangular fibrocartilage complex was predominantly reconstructed, and evaluated whether such reconstruction can restore stability of the distal radioulnar joint in seven fresh cadaver upper extremities. Distal radioulnar joint instability was induced by cutting all soft-tissue stabilizers around the distal ulna. Using a palmar approach, a palmaris longus tendon graft was sutured to the remnant of the palmar radioulnar and ulnocarpal ligaments. The graft was then passed through a bone tunnel created at the fovea and was sutured. Loads were applied to the radius, and dorsopalmar displacements of the radius relative to the ulna were measured using an electromagnetic tracking device in neutral rotation, 60° supination and 60° pronation. We compared the dorsopalmar displacements before sectioning, before reconstruction and after reconstruction. Dorsopalmar instability produced by sectioning significantly improved in all forearm positions after reconstruction.
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Zhang, Qi, et Xiang Yuan Zheng. « Walsh Transform and Empirical Mode Decomposition Applied to Reconstruction of Velocity and Displacement from Seismic Acceleration Measurement ». Applied Sciences 10, no 10 (19 mai 2020) : 3509. http://dx.doi.org/10.3390/app10103509.
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This paper focuses on reconstruction of dynamic velocity and displacement from seismic acceleration signal. For conventional time-domain approaches or frequency-domain approaches, due to initial values and non-negligible noise in the acceleration signal, drift and deviation in velocity and displacement are inevitable. To deal with this deficiency, this paper develops a Walsh transform and Empirical Mode Decomposition (EMD)-based integral algorithm, or WATEBI in short. In the WATEBI algorithm, the Walsh transform is employed to realize vibration signal reconstruction. Next, the EMD method is used to eliminate the residual in the reconstructed signal. Finally, the trend term in velocity and displacement is removed by linear least-squares fit. This algorithm can be straightforwardly implemented by an ordinary computer. Reconstructed displacements and velocities from vibration of a simulated single-degree-of-freedom system and two-site measured ground motions in earthquakes validated the robustness and adaptiveness of this algorithm. It can be also applied to many other areas, like mechanical engineering and ocean engineering.
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Krug, Randall G., Elizabeth A. Bradley et Jamie J. Van Gompel. « An Assessment of Globe Position Dynamics following Transcranial Lateral and Superior Orbital Wall Resections without Rigid Reconstruction : A Case Series of 55 Patients ». Journal of Neurological Surgery Part B : Skull Base 81, no 03 (21 mai 2019) : 244–50. http://dx.doi.org/10.1055/s-0039-1688773.
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Background There is no consensus exists regarding which reconstructive approach, if any, should be used after performing transcranial lateral orbital wall resections. Rigid reconstruction is often done to prevent enophthalmos; however, it is not clear if this is a risk with extensive orbital wall resections for transcranial surgery. Objective To assess globe position dynamics in patients that underwent transcranial lateral and superior orbital wall resections without rigid reconstruction to determine if enophthalmos is a significant risk. Methods Preoperative (PO) and postoperative data were retrospectively collected from the electronic medical records of 55 adult patients undergoing lateral and superior orbital wall resections as part of a skull base approach. The globe positions were assessed radiologically at all available time points and used to track relative globe displacements over time. Results An evaluation of PO variables identified a relationship between maximum lesion diameters and globe positions dynamics. The composition of globe position presentations in the population remained relatively stable over time, with only 1 out of 55 patients (1.81%) developing postoperative enophthalmos. An assessment of mean globe displacements revealed improvements in the patients presenting with PO exophthalmos, and stability in the patients presenting with normal PO globe positions. Conclusions Excellent results in long-term postoperative globe position dynamics can be achieved without the use of rigid reconstruction after transcranial lateral and superior orbital wall resections, regardless of the PO globe positioning.
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Labonté, G. « Neural network reconstruction of fluid flows from tracer-particle displacements ». Experiments in Fluids 30, no 4 (4 avril 2001) : 399–409. http://dx.doi.org/10.1007/s003480000217.
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Kowalski, Mateusz, Piotr Kaczmarek, Rafał Kabaciński, Mieszko Matuszczak, Kamil Tranbowicz et Robert Sobkowiak. « A simultaneous localization and tracking method for a worm tracking system ». International Journal of Applied Mathematics and Computer Science 24, no 3 (1 septembre 2014) : 599–609. http://dx.doi.org/10.2478/amcs-2014-0043.
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Abstract The idea of worm tracking refers to the path analysis of Caenorhabditis elegans nematodes and is an important tool in neurobiology which helps to describe their behavior. Knowledge about nematode behavior can be applied as a model to study the physiological addiction process or other nervous system processes in animals and humans. Tracking is performed by using a special manipulator positioning a microscope with a camera over a dish with an observed individual. In the paper, the accuracy of a nematode’s trajectory reconstruction is investigated. Special attention is paid to analyzing errors that occurred during the microscope displacements. Two sources of errors in the trajectory reconstruction are shown. One is due to the difficulty in accurately measuring the microscope shift, the other is due to a nematode displacement during the microscope movement. A new method that increases path reconstruction accuracy based only on the registered sequence of images is proposed. The method Simultaneously Localizes And Tracks (SLAT) the nematodes, and is robust to the positioning system displacement errors. The proposed method predicts the nematode position by using NonParametric Regression (NPR). In addition, two other methods of the SLAT problem are implemented to evaluate the NPR method. The first consists in ignoring the nematode displacement during microscope movement, and the second is based on a Kalman filter. The results suggest that the SLAT method based on nonparametric regression gives the most promising results and decreases the error of trajectory reconstruction by 25% compared with reconstruction based on data from the positioning system
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Nowak, Klaudia. « A Village Remembered : Reconstruction of the Lemko Cultural Space from Before the Displacement using the Example of Bartne Village ». Rocznik Ruskiej Bursy 17 (26 décembre 2021) : 151–82. http://dx.doi.org/10.12797/rrb.17.2021.17.06.
Texte intégralRésumé :
A Village Remembered. Reconstruction of the Lemko Cultural Space from Before the Displacement on the Example of Bartne Village
Tragic events of the middle of the 20th century, which were massive displacements of Lemkos to the western territories, led to irreversible spatial changes in the whole Lemkovyna. This destruction of space was a multi- stage process which progressed from the 1940s to the present day. In the material context, places such as the village of Bartne described in the article were almost completely destroyed, and the people living there and creating it were displaced. Based on oral narratives of contemporary inhabitants of Bartne, the article attempts to reconstruct the cultural space of Bartne from before the displacement.
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Aglyamov, Salavat R., Andrei R. Skovoroda, Hua Xie, Kang Kim, Jonathan M. Rubin, Matthew O'Donnell, Thomas W. Wakefield, Daniel Myers et Stanislav Y. Emelianov. « Model-Based Reconstructive Elasticity Imaging Using Ultrasound ». International Journal of Biomedical Imaging 2007 (2007) : 1–11. http://dx.doi.org/10.1155/2007/35830.
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Elasticity imaging is a reconstructive imaging technique where tissue motion in response to mechanical excitation is measured using modern imaging systems, and the estimated displacements are then used to reconstruct the spatial distribution of Young's modulus. Here we present an ultrasound elasticity imaging method that utilizes the model-based technique for Young's modulus reconstruction. Based on the geometry of the imaged object, only one axial component of the strain tensor is used. The numerical implementation of the method is highly efficient because the reconstruction is based on an analytic solution of the forward elastic problem. The model-based approach is illustrated using two potential clinical applications: differentiation of liver hemangioma and staging of deep venous thrombosis. Overall, these studies demonstrate that model-based reconstructive elasticity imaging can be used in applications where the geometry of the object and the surrounding tissue is somewhat known and certain assumptions about the pathology can be made.
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Wang, Fanwen, Hui Zhang, Fei Dai, Weibo Chen, Chengyan Wang et He Wang. « MAGnitude-Image-to-Complex K-space (MAGIC-K) Net : A Data Augmentation Network for Image Reconstruction ». Diagnostics 11, no 10 (19 octobre 2021) : 1935. http://dx.doi.org/10.3390/diagnostics11101935.
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Deep learning has demonstrated superior performance in image reconstruction compared to most conventional iterative algorithms. However, their effectiveness and generalization capability are highly dependent on the sample size and diversity of the training data. Deep learning-based reconstruction requires multi-coil raw k-space data, which are not collected by routine scans. On the other hand, large amounts of magnitude images are readily available in hospitals. Hence, we proposed the MAGnitude Images to Complex K-space (MAGIC-K) Net to generate multi-coil k-space data from existing magnitude images and a limited number of required raw k-space data to facilitate the reconstruction. Compared to some basic data augmentation methods applying global intensity and displacement transformations to the source images, the MAGIC-K Net can generate more realistic intensity variations and displacements from pairs of anatomical Digital Imaging and Communications in Medicine (DICOM) images. The reconstruction performance was validated in 30 healthy volunteers and 6 patients with different types of tumors. The experimental results demonstrated that the high-resolution Diffusion Weighted Image (DWI) reconstruction benefited from the proposed augmentation method. The MAGIC-K Net enabled the deep learning network to reconstruct images with superior performance in both healthy and tumor patients, qualitatively and quantitatively.
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Dastjerdi, Maryam Mehdizadeh, Ali Fallah et Saeid Rashidi. « Efficient Sensitivity Based Reconstruction Technique to Accomplish Breast Hyperelastic Elastography ». BioMed Research International 2018 (25 novembre 2018) : 1–16. http://dx.doi.org/10.1155/2018/3438470.
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Hyperelastic models have been acknowledged as constitutive equations which reliably model the nonlinear behaviors observed from soft tissues under various loading conditions. Among them, the Mooney-Rivlin, Yeoh, and polynomial models have been proved capable of accurately modeling responses of breast tissues to applied compressions. Hyperelastic elastography technique takes advantage of the disparities between hyperelastic parameters of varied tissues and the change in hyperelastic parameters in pathological processes. The precise reconstruction of hyperelastic parameters of a completely unknown pathology in the breast in a noninvasive and nondestructive way using the ultrasound elastography has been scrutinized in this paper. In the ultrasound elastography, tissue displacement field is extracted from radio frequency signals or images recorded using the ultrasound medical imaging system; hence the exact displacement field might not be obtained. Our results indicate that the parameters estimated by manipulating the iterative sensitivity-matrix based method converge to tissue’s real hyperelastic parameters providing appropriate parameters are assigned to the hypothetical hyperelastic and regularization parameters. Iterative methods have therefore been proposed to compute proper hypothetical hyperelastic and regularization parameters. Accurate estimates of hyperelastic parameters of obscure breast pathology have been achieved even from imprecise measurements of displacements induced in the tissue by the ramp excitation.
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Atefi Monfared, Kamelia, et Leo Rothenburg. « Ground surface displacements and tilt monitoring for reconstruction of reservoir deformations ». International Journal of Rock Mechanics and Mining Sciences 48, no 7 (octobre 2011) : 1113–22. http://dx.doi.org/10.1016/j.ijrmms.2011.07.003.
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Titz, Alexandra. « Geographies of Doing Nothing–Internal Displacement and Practices of Post-Disaster Recovery in Urban Areas of the Kathmandu Valley, Nepal ». Social Sciences 10, no 3 (22 mars 2021) : 110. http://dx.doi.org/10.3390/socsci10030110.
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Disaster-related internal displacement is on the rise in many countries and is increasingly becoming an urban phenomenon. For many people, as in the case of the earthquake disaster 2015 in Nepal, protracted or multiple disaster displacements are a lived reality. While the drivers of displacement are relatively well understood, significant uncertainties remain regarding the factors that trigger prolonged or secondary displacement and impede ending of displacement or achieving durable solutions. The purpose of this article is to illustrate and theorise the discourse of reconstruction and return that shapes experiences, strategies, and policies in order to gain a better understanding of the obstacles to pursuing durable solutions that are still shaping the reality of life for urban internally displaced people (IDPs) in Kathmandu Valley. I use the concepts of ‘fields of practice’ and ‘disaster justice’ to provide insights into the theorisation of the links between social inequality, structural forms of governance, and the reconstruction process itself. Findings demonstrate that the application of these concepts has great potential to expand our understanding of ‘realities of life’ and practices of IDPs, and thus contribute to a more differentiated evidence base for the development and implementation of appropriate disaster risk reduction policies and practices.
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Mikhailov, Valentin, Еlena Kiseleva, Pavel Dmitriev, Vasily Golubev, Ekaterina Smolyaninova et Elena Timoshkina. « On Reconstruction of the Three Displacement Vector Components from SAR LOS Displacements for Oil and Gas Producing Fields ». Procedia Technology 16 (2014) : 385–93. http://dx.doi.org/10.1016/j.protcy.2014.10.104.
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Hong, Yun Hwa, Se Gun Lee et Hae Sung Lee. « Design of the FEM-FIR filter for displacement reconstruction using accelerations and displacements measured at different sampling rates ». Mechanical Systems and Signal Processing 38, no 2 (juillet 2013) : 460–81. http://dx.doi.org/10.1016/j.ymssp.2013.02.007.
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NEMENKO, A. V., et M. M. NIKITIN. « LINEAR RECONSTRUCTION OF THE CONTROLLED OBJECT POSITION ». Fundamental and Applied Problems of Engineering and Technology 4, no 2 (2020) : 136–40. http://dx.doi.org/10.33979/2073-7408-2020-342-4-2-136-140.
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We consider the method of non-contact measurement of the displacements of a controlled structure using its scanning by radiation of the optical range with fixing the point of reception of reflected radiation. We show that when coordinating the position of the receiving and transmitting blocks, a high sensitivity of the method is achieved. For the practical application of the method, the installation of a receiving and transmitting unit and a mirror technological site at a controlled facility is required.
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de Lange, A., R. Huiskes et J. M. G. Kauer. « Effects of Data Smoothing on the Reconstruction of Helical Axis Parameters in Human Joint Kinematics ». Journal of Biomechanical Engineering 112, no 2 (1 mai 1990) : 107–13. http://dx.doi.org/10.1115/1.2891160.
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In biomechanical joint-motion analyses, the continuous motion to be studied is often approximated by a sequence of finite displacements, and the Finite Helical Axis (FHA) or “screw axis” for each displacement is estimated from position measurements on a number of anatomical or artificial landmarks. When FHA parameters are directly determined from raw (noisy) displacement data, both the position and the direction of the FHA are ill-determined, in particular when the sequential displacement steps are small. This implies, that under certain conditions, the continuous pathways of joint motions cannot be adequately described. The purpose of the present experimental study is to investigate the applicability of smoothing (or filtering) techniques, in those cases where FHA parameters are ill-determined. Two different quintic-spline smoothing methods were used to analyze the motion data obtained with Roentgenstereophotogrammetry in two experiments. One concerning carpal motions in a wrist-joint specimen, and one relative to a kinematic laboratory model, in which the axis positions are a priori known. The smoothed and nonsmoothed FHA parameter errors were compared. The influences of the number of samples and the size of the sampling interval (displacement step) were investigated, as were the effects of equidistant and nonequidistant sampling conditions and noise invariance.
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Oliveira, Jorge, José Xavier, Fábio Pereira, José Morais et Marcelo de Moura. « Direct Evaluation of Mixed Mode I+II Cohesive Laws of Wood by Coupling MMB Test with DIC ». Materials 14, no 2 (14 janvier 2021) : 374. http://dx.doi.org/10.3390/ma14020374.
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Governing cohesive laws in mixed mode I+II loading of Pinus pinaster Ait. are directly identified by coupling the mixed mode bending test with full-field displacements measured at the crack tip by Digital Image Correlation (DIC). A sequence of mixed mode ratios is studied. The proposed data reduction relies on: (i) the compliance-based beam method for evaluating strain energy release rate; (ii) the local measurement of displacements to compute the crack tip opening displacement; and (iii) an uncoupled approach for the reconstruction of the cohesive laws and its mode I and mode II components. Quantitative parameters are extracted from the set of cohesive laws components in function of the global phase angle. Linear functions were adjusted to reflect the observed trends and the pure modes (I and II) fracture parameters were estimated by extrapolation. Results show that the obtained assessments agree with previous experimental measurements addressing pure modes (I and II) loadings on this wood species, which reveals the appropriateness of the proposed methodology to evaluate the cohesive law under mixed mode loading and its components.
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Li, Tengteng, Maosen Cao, Jianle Li, Lei Yang, Hao Xu et Zhanjun Wu. « Structural Damage Identification Based on Integrated Utilization of Inverse Finite Element Method and Pseudo-Excitation Approach ». Sensors 21, no 2 (16 janvier 2021) : 606. http://dx.doi.org/10.3390/s21020606.
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The attempt to integrate the applications of conventional structural deformation reconstruction strategies and vibration-based damage identification methods is made in this study, where, more specifically, the inverse finite element method (iFEM) and pseudo-excitation approach (PE) are combined for the first time, to give rise to a novel structural health monitoring (SHM) framework showing various advantages, particularly in aspects of enhanced adaptability and robustness. As the key component of the method, the inverse finite element method (iFEM) enables precise reconstruction of vibration displacements based on measured dynamic strains, which, as compared to displacement measurement, is much more adaptable to existing on-board SHM systems in engineering practice. The PE, on the other hand, is applied subsequently, relying on the reconstructed displacements for the identification of structural damage. Delamination zones in a carbon fibre reinforced plastic (CFRP) laminate are identified using the developed method. As demonstrated by the damage detection results, the iFEM-PE method possesses apparently improved accuracy and significantly enhanced noise immunity compared to the original PE approach depending on displacement measurement. Extensive parametric study is conducted to discuss the influence of a variety of factors on the effectiveness and accuracy of damage identification, including the influence of damage size and position, measurement density, sensor layout, vibration frequency and noise level. It is found that different factors are highly correlated and thus should be considered comprehensively to achieve optimal detection results. The application of the iFEM-PE method is extended to better adapt to the structural operational state, where multiple groups of vibration responses within a wide frequency band are used. Hybrid data fusion is applied to process the damage index (DI) constructed based on the multiple responses, leading to detection results capable of indicating delamination positions precisely.
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Chesne, S., C. Pezerat et J. L. Guyader. « Identification of Boundary Forces in Beams From Measured Displacements ». Journal of Vibration and Acoustics 128, no 6 (19 janvier 2006) : 757–71. http://dx.doi.org/10.1115/1.2202171.
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This paper deals with shear force and bending moment identification in a beam from measured displacement. The proposed approach, using the weak form of the equation of motion, is based on the extraction of shear force or bending moment from integral equation and choice of test functions, associated to each boundary quantity of interest. After the theorical description, numerical simulation results are shown in order to clarify limits of the method and to stress its self-regularization. Two experimentations are described, showing very good accuracy of shear force and bending moment reconstruction in comparison with direct measurements.
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Kruschke, Oliver. « Holographic interferometric microscope with conjugate reconstruction for measurement of three-dimensional displacements ». Optical Engineering 34, no 4 (1 avril 1995) : 1122. http://dx.doi.org/10.1117/12.196520.
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Petrescu, Horia Alexandru, Daniel Vlasceanu, Stefan Dan Pastrama et Lucian Gheorghe Gruionu. « Numerical Analysis for Determining the Displacements of a Lung Tumor ». Key Engineering Materials 638 (mars 2015) : 177–82. http://dx.doi.org/10.4028/www.scientific.net/kem.638.177.
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In this paper, a numerical analysis is undertaken in order to establish the three dimensional linear displacementsof tumors located inside the lung. In this way, the position of the tumor can be emphasized in various stages of the breathing process, helping thus the healthcare professionals both in surgical operations and in performing transbronchial biopsy. First, a geometrical model of the lung and airways was achieved with a 3D reconstruction program using CT scan images. The model was then imported in the ANSYS finite element software, which was used to perform the numerical simulations. The breathing process was simulated by applying external pressure on the surfaces of the lung. The values of this pressure were chosen as to correspond to the inspiration phase of the breathing process. Finally, conclusions are drawn regarding the values of the displacement of the nodules during breathing.
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Fernandes, N. M., B. D. L. Pinto, L. O. B. Almeida, J. F. W. Slaets et R. Köberle. « Recording from Two Neurons : Second-Order Stimulus Reconstruction from Spike Trains and Population Coding ». Neural Computation 22, no 10 (octobre 2010) : 2537–57. http://dx.doi.org/10.1162/neco_a_00016.
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We study the reconstruction of visual stimuli from spike trains, representing the reconstructed stimulus by a Volterra series up to second order. We illustrate this procedure in a prominent example of spiking neurons, recording simultaneously from the two H1 neurons located in the lobula plate of the fly Chrysomya megacephala. The fly views two types of stimuli, corresponding to rotational and translational displacements. Second-order reconstructions require the manipulation of potentially very large matrices, which obstructs the use of this approach when there are many neurons. We avoid the computation and inversion of these matrices using a convenient set of basis functions to expand our variables in. This requires approximating the spike train four-point functions by combinations of two-point functions similar to relations, which would be true for gaussian stochastic processes. In our test case, this approximation does not reduce the quality of the reconstruction. The overall contribution to stimulus reconstruction of the second-order kernels, measured by the mean squared error, is only about 5% of the first-order contribution. Yet at specific stimulus-dependent instants, the addition of second-order kernels represents up to 100% improvement, but only for rotational stimuli. We present a perturbative scheme to facilitate the application of our method to weakly correlated neurons.
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Лейер, Дарья, Сергей Маций, Sergey Maciy, Екатерина Безуглова et Ekaterina Bezuglova. « Monitoring and Modeling of Landslide Processes on the Example of the City of Sochi ». Construction and Architecture 1, no 1 (1 mai 2013) : 54–61. http://dx.doi.org/10.12737/342.
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ssible designing of reinforcement constructions. Yet some problems in simulation of landslide situation do occur. Options for using different soil models and calculation schemes are being analyzed on the example of protective structures construction for railway tunnel in the city of Sochi region. Simulation of landslide slope condition is carried out using geotechnical software Plaxis considering different soil models (Linear Elastic и Mohr-Coulomb) and «reconstruction» of structures displacements. The value of retaining wall displacement alongside landslide slope as well as retaining walls sections inner movement is being estimated by results of complex monitoring. Recent developments were causing threat to the safety of building and construction works continuation at the railway and also to the normal operation of structures lower down the slope.
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Klockiewicz, Zbyszko, Grzegorz Ślaski et Hubert Pikosz. « The method of kinematic excitation reconstruction based on measured suspension dynamic responses – experimental verification ». IOP Conference Series : Materials Science and Engineering 1199, no 1 (1 novembre 2021) : 012083. http://dx.doi.org/10.1088/1757-899x/1199/1/012083.
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Abstract The paper presents the method of kinematic road excitation reconstruction based on measured suspension dynamic responses and its reconstruction with use of estimated displacements of unsprung mass as a preliminary approximation of kinematic excitation and tracking control system with a PID controller that allows for faithful reconstruction of unsprung mass accelerations and, in turn, kinematic excitations. The authors performed an experimental verification of the method with use of one axle car trailer and measurements of road profile and acquiring signals of suspension dynamics responses. The signal processing methodology and obtained results are presented for random and determined excitations. The necessary requirements to use the method effectively were defined and its limitations were listed.
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Wagner, Emilio, Pablo Wagner, Daniel Baumfeld, Tiago Baumfeld, Marcelo Prado et Caio Nery. « Biomechanical Evaluation of a Novel Lisfranc Injury Cadaveric Model Using Supination and Pronation Testing ». Foot & ; Ankle Orthopaedics 4, no 4 (1 octobre 2019) : 2473011419S0043. http://dx.doi.org/10.1177/2473011419s00430.
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Category: Basic Sciences/Biologics, Sports, Trauma Introduction/Purpose: Lisfranc joint injuries occur due to direct or indirect trauma, where twisting forces are applied. Cadaveric models have been used to evaluate injury patterns and fixation methods, but a frequent limitation has been historically the small amount of joint displacement after injury, which hinders a correct evaluation of the damage degree and reconstruction effectiveness. Our hypothesis was that adding pronation and supination motion to a cadaveric model would produce reliable and measurable joint displacements. Methods: 24 fresh frozen lower leg cadaveric specimens were utilized. The medial (C1), intermediate (C2) cuneiforms, first (M1) and second (M2) metatarsal bones were marked. A complete ligament injury was performed between C1-C2 and C1-M2 in 12 specimens (Group 1), and between C1-C2, C1-M2, C1-M1 and C2-M2 in 12 matched specimens (Group 2). Supination and pronation motion of the forefoot relative to the hindfoot was obtained through internal and external rotation of the tíbia, using an Instrom machine. A 3D Digitizer was used to measure distances between the bones already mentioned. Results: Distance C1-C2 increased 3 mm after ligament injury with supination motion (p<0.05). Distance C1-M2 increased 4 mm after ligament injury with pronation motion (p<0.05). Distances between C1-M1 and C2-M2 only changed in Group 2, increasing 3 mm and 2 mm respectively (p<0.05). Conclusion: Pronation and supination motion of the forefoot relative to the hindfoot produces measurable joint displacements in a cadaveric Lisfranc injury model. We believe this new method for testing cadaveric lisfranc injuries will allow a better understanding of injury patterns and repair or reconstruction techniques.
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Scaioni, M., J. Crippa, L. Longoni, M. Papini et L. Zanzi. « IMAGE-BASED RECONSTRUCTION AND ANALYSIS OF DYNAMIC SCENES IN A LANDSLIDE SIMULATION FACILITY ». ISPRS Annals of Photogrammetry, Remote Sensing and Spatial Information Sciences IV-5/W1 (13 décembre 2017) : 63–70. http://dx.doi.org/10.5194/isprs-annals-iv-5-w1-63-2017.
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The application of image processing and photogrammetric techniques to dynamic reconstruction of landslide simulations in a scaled-down facility is described. Simulations are also used here for active-learning purpose: students are helped understand how physical processes happen and which kinds of observations may be obtained from a sensor network. In particular, the use of digital images to obtain multi-temporal information is presented. On one side, using a multi-view sensor set up based on four synchronized GoPro 4 Black<sup>®</sup> cameras, a 4D (3D spatial position and time) reconstruction of the dynamic scene is obtained through the composition of several 3D models obtained from dense image matching. The final textured 4D model allows one to revisit in dynamic and interactive mode a completed experiment at any time. On the other side, a digital image correlation (DIC) technique has been used to track surface point displacements from the image sequence obtained from the camera in front of the simulation facility. While the 4D model may provide a qualitative description and documentation of the experiment running, DIC analysis output quantitative information such as local point displacements and velocities, to be related to physical processes and to other observations. All the hardware and software equipment adopted for the photogrammetric reconstruction has been based on low-cost and open-source solutions.
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Lu, Ping, et David J. Smith. « Reconstructions and Dynamic Processes on CdTe Surfaces Studied by UHV High-Resolution Electron Microscopy ». Proceedings, annual meeting, Electron Microscopy Society of America 48, no 1 (12 août 1990) : 310–11. http://dx.doi.org/10.1017/s0424820100180306.
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Surface profile imaging at resolutions of better than 2Å is highly suitable for studies of surface structures and reactions. In the case of semiconductor materials, the main challenge is to prepare surfaces free of any contamination. The technique has previously been used to study surface reconstructions of Si and CdTe. In our previous observations, clean surfaces of CdTe were obtained by careful control of the incident electron beam within a JEM-4000EX high resolution electron microscope with a pressure of 10-7 torr. In the present study, observations of reconstructions and dynamic phenomena on CdTe surfaces were carried out with a Phillips-430ST, modified for Ultra-High Vacuum in the vicinity of the specimen and equipped with an in situ heating facility. The base vacuum in the region of the sample could usually reach ∼3×l0-9 torr after baking the microscope column at ∼120°C for 36 hours. The CdTe specimen was prepared by cutting a large single crystal into 3mm discs in a [110] direction, then mechanically polishing to a thickness of ∼20 microns, and finally ion milling to perforation.When viewed along a [110] projection, the CdTe sample was found to be dominated by clean or nearly clean (111) and (110) surfaces(with amorphous materials less than 5Å) whilst the (001) surface was usually very short and rough. A completely clean surface was obtained by in situ annealing of the crystal to about 200°. The (110) surface was then found to be reconstructed with a very characteristic chevron appearance in the manner described previously. Long and flat CdTe(OOl) surfaces were obtained by insitu annealing of the crystal at ∼510°C at which temperature edges of the crystal started to gradually sublime. Characterization of the surface structure was then possible when the crystal was cooled back down to temperatures below about 300°C. It was found that the (001) surface had a (2×1) reconstruction at temperatures below about 200°C which transformed reversibly into a (3×1) reconstruction over the approximate temperature range of 200°C<T<300°C. Figures la and lb show the (2×1) and (3×1) reconstructed (001) surfaces, viewed along the [110] projection, which were recorded at temperatures of 140°C and 240°C respectively. Structural models for the (2×1) and (3×1) reconstructions, obtained directly on the basis of the experimental images, are shown in Figs.2a and 2b respectively. The (2×1) reconstruction involves a 1/2 monolayer of Cd vacancies and a very large inward contraction of the remaining Cd surface atoms, which then displace the second layer of Te atoms as indicated. This model is similar to that proposed by Chadi for the Ga-rich (2×1) reconstructed GaAs(100) surface. The (3×1) reconstruction involves both the formation of surface dimers and the presence of vacancies at the surface. Every third atomic-pair is missing along the [1,-1,0] direction, and the remaining two atom pairs at the surface form the surface dimer. Although the (3×1) reconstruction has a larger number of electrons in dangling bonds, a surface with vacancies can be relaxed to reduce the strain energy due to the surface dimers. The directions of the atomic displacements away from the ideal dimer positions are indicated in the figure. Relatively large atomic displacements for several layers into the bulk are clearly visible in experimental images, as seen in Fig.lb. Further details of the surface reconstructions can be found elsewhere.
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Wang, Rui, Bin Xu, Lei Wu et Honggang Xu. « Long-term outcomes after arthroscopic single-bundle reconstruction of the posterior cruciate ligament : A 7-year follow-up study ». Journal of International Medical Research 46, no 2 (27 septembre 2017) : 865–72. http://dx.doi.org/10.1177/0300060517722243.
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Objective Arthroscopy is the most popular technique in posterior cruciate ligament (PCL) reconstruction surgery. However, no consensus on long-term outcomes after arthroscopic PCL reconstruction has been reached. This study was performed to evaluate the long-term outcomes after arthroscopic autologous hamstring or allogeneic tendon single-bundle reconstruction of the PCL. Methods Fifty-eight patients who underwent arthroscopic PCL reconstruction in Anhui, China from 2007 to 2009 were included. The follow-up period ranged from 56 to 83 months. During the follow-up, the Lysholm knee score and Tegner activity score were used to assess knee function. The KT-2000 arthrometer (MEDmetric Corp., San Diego, CA, USA) was used to assess the stability of the reconstructed PCL. Results The mean Lysholm score, mean Tegner score, and mean forward and backward displacements were not significantly different between the final follow-up and 1 year after the surgery. Additionally, no significant differences were observed in any of the above-mentioned parameters between autologous and allogeneic reconstruction at the final follow-up. Conclusion Both autologous and allogeneic reconstruction had few complications and satisfactory long-term outcomes.
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SEUBERT, A., et K. HEINZ. « ITERATIVE IMAGE RECOVERY IN HOLOGRAPHIC LEED ». Surface Review and Letters 09, no 03n04 (juin 2002) : 1413–23. http://dx.doi.org/10.1142/s0218625x02003949.
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We report that the quality of atomic images reconstructed directly within the framework of holographic low energy electron diffraction can suffer from considerable atomic displacements. These are due to serious disturbances of the holographic object wave which exist when the object owns the same translational symmetry as the arrangement of beam splitters, for example when the latter induce a substrate reconstruction. We propose and test an iterative procedure for reducing these disturbances by a hybrid combination of the holographic reconstruction and some data fitting procedure. A reliable atomic image results after only a few iteration steps.
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Algar, Antonio, Esteban Codina et Javier Freire. « Bond Graph Simulation of Error Propagation in Position Estimation of a Hydraulic Cylinder Using Low Cost Accelerometers ». Energies 11, no 10 (29 septembre 2018) : 2603. http://dx.doi.org/10.3390/en11102603.
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The indirect calculation from acceleration of transversal displacement of the piston inside the body of a double effect linear hydraulic cylinder during its operating cycle is assessed. Currently an extensive effort exists in the improvement of the mechanical and electronic design of the highly sophisticated MEMS accelerometers. Nevertheless, the predictable presence of measurement errors in the current commercial accelerometers is the main origin of velocity and displacement measurement deviations during integration of the acceleration. A bond graph numerical simulation model of the electromechanical system has been developed in order to forecast the effect of several measurement errors in the use of low cost two axes accelerometers. The level of influence is assessed using quality indicators and visual signal evaluation, for both simulations and experimental results. The obtained displacements results are highly influenced by the diverse dynamic characteristics of each measuring axis. The small measuring errors of a simulated extremely high performance sensor generate only moderate effects in longitudinal displacement but deep deviations in the reconstruction of piston transversal movements. The bias error has been identified as the source of the higher deviations of displacement results; although, its consequences can be easily corrected.
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Aydın, Adem, Levent Uğur et Halil Atmaca. « The effect of anterolateral ligament integrity on the tibia displacement and reaction forces of anterior cruciate ligament ». Orthopaedic Journal of Sports Medicine 5, no 2_suppl2 (1 février 2017) : 2325967117S0010. http://dx.doi.org/10.1177/2325967117s00108.
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Objective: Recent studies focused on rotational instability and remained positive pivot test in patients with anterior cruciate ligament (ACL) reconstruction. Clinical, radiological and biomechanical studies showed the importance of the anterolateral ligament (ALL) integrity. ALL is one of the stabilization structures against the internal rotation of the tibia under forces which was associated with Segond fracture previously. Even some authors claimed that ACL failure and risk of re-rupture increased if only ACL reconstruction performed in patients with simultaneous ALL injury. The aim of the study is to evaluate the importance of ALL on knee biomechanics during anterior drawer test and internal rotation forces with different flexion angles in terms of reaction forces on ACL and the amount of tibia displacement via finite element analysis. Methods: Three dimensional (3D) solid model of knee joint and ALL injured models were constructed based on DICOM formatted computed tomography (CT) images. 0°, 15°,30°,45°,60°,75° and 90° flexion angles were applied respectively to reference models. Then varied anterior drawer and internal rotational forces were used to investigate the effect of ALL. ANSYS ®Version 17 was used in analyses and same boundary conditions were used in all models. Results: In critical analyzing the all results; medial displacement and the amount of anterior drawer distance were increased in all ALL injured models when compared with references. Therewithal the rotational displacements were increased by increasing the knee flexion angle and rotational torque. But, it was not a significant change in the amount of displacement between the models with respect to anteroposterior displacement when the anterior drawer force was increased. Conclusion: ALL particular has an important role in the stability of the internal rotation occurs against the force and with increased contribution rate to the knee joint stability by increasing the knee flexion angle. But the reaction forces were not affected by ALL integrity. So this study do not support the previous studies which suggest simultaneously reconstruction of both ligaments to avoid re rupture of ACL in cases with ALL injured.
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LIU, W., et K. A. R. MITCHELL. « AN INVESTIGATION OF STRUCTURAL DETAILS FOR THE ${\rm Cu}\left({110} \right) - \left( {\begin{array}{*{20}c} {\,\,\,2} 2 \\ { - 1} 1 \\\end{array}} \right)-{\rm P}$ RECONSTRUCTED SURFACE ». Surface Review and Letters 03, no 02 (avril 1996) : 1247–52. http://dx.doi.org/10.1142/s0218625x96002254.
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An exhaustive tensor LEED study for the half monolayer (ML) structure formed by P at the (110) surface of copper confirms the reconstruction reported earlier [Chem. Phys. 198, 235 (1995)]. All P atoms occupy identical six-coordinate sites; the reconstruction involves 0.25 ML of “added Cu” atoms at hollow sites, each bonded to two neighboring P atoms, which line up along the [Formula: see text] direction. Appreciable relaxations, both vertical and lateral, are identified for atoms in the first four layers. The new feature found here is that the displacements indicated by tensor LEED for individual atoms appear to follow trends that are broadly consistent with reasonable structural chemical principles.
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Sidelnik, A. « Determination of Fracture Tectonics of Rocks by Reconstruction of Stresses and Analysis of Displacements ». Procedia Structural Integrity 6 (2017) : 316–21. http://dx.doi.org/10.1016/j.prostr.2017.11.048.
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Smith, Ryan L., Annette Haworth, Vanessa Panettieri et Jeremy Millar. « Identification of Catheter Displacements in HDR Prostate Brachytherapy Using a ‘Shift Image’ Reconstruction Technique ». Brachytherapy 16, no 3 (mai 2017) : S106. http://dx.doi.org/10.1016/j.brachy.2017.04.204.
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Clapuyt, François, Veerle Vanacker, Fritz Schlunegger et Kristof Van Oost. « Unravelling earth flow dynamics with 3-D time series derived from UAV-SfM models ». Earth Surface Dynamics 5, no 4 (5 décembre 2017) : 791–806. http://dx.doi.org/10.5194/esurf-5-791-2017.
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Abstract. Accurately assessing geo-hazards and quantifying landslide risks in mountainous environments are gaining importance in the context of the ongoing global warming. For an in-depth understanding of slope failure mechanisms, accurate monitoring of the mass movement topography at high spatial and temporal resolutions remains essential. The choice of the acquisition framework for high-resolution topographic reconstructions will mainly result from the trade-off between the spatial resolution needed and the extent of the study area. Recent advances in the development of unmanned aerial vehicle (UAV)-based image acquisition combined with the structure-from-motion (SfM) algorithm for three-dimensional (3-D) reconstruction make the UAV-SfM framework a competitive alternative to other high-resolution topographic techniques. In this study, we aim at gaining in-depth knowledge of the Schimbrig earthflow located in the foothills of the Central Swiss Alps by monitoring ground surface displacements at very high spatial and temporal resolution using the efficiency of the UAV-SfM framework. We produced distinct topographic datasets for three acquisition dates between 2013 and 2015 in order to conduct a comprehensive 3-D analysis of the landslide. Therefore, we computed (1) the sediment budget of the hillslope, and (2) the horizontal and (3) the three-dimensional surface displacements. The multitemporal UAV-SfM based topographic reconstructions allowed us to quantify rates of sediment redistribution and surface movements. Our data show that the Schimbrig earthflow is very active, with mean annual horizontal displacement ranging between 6 and 9 m. Combination and careful interpretation of high-resolution topographic analyses reveal the internal mechanisms of the earthflow and its complex rotational structure. In addition to variation in horizontal surface movements through time, we interestingly showed that the configuration of nested rotational units changes through time. Although there are major changes in the internal structure of the earthflow in the 2013–2015 period, the sediment budget of the drainage basin is nearly in equilibrium. As a consequence, our data show that the time lag between sediment mobilization by landslides and enhanced sediment fluxes in the river network can be considerable.