Articles de revues : « Direction Reconstruction »

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Wang, Linyuan, Ailong Cai, Hanming Zhang, Bin Yan, Lei Li et Guoen Hu. « Distributed Reconstruction via Alternating Direction Method ». Computational and Mathematical Methods in Medicine 2013 (2013) : 1–7. http://dx.doi.org/10.1155/2013/418747.

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With the development of compressive sensing theory, image reconstruction from few-view projections has received considerable research attentions in the field of computed tomography (CT). Total-variation- (TV-) based CT image reconstruction has been shown to be experimentally capable of producing accurate reconstructions from sparse-view data. In this study, a distributed reconstruction algorithm based on TV minimization has been developed. This algorithm is very simple as it uses the alternating direction method. The proposed method can accelerate the alternating direction total variation minimization (ADTVM) algorithm without losing accuracy.

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Wang, Lin Yuan, Ai Long Cai, Bin Yan, Lei Li, Han Ming Zhang et Guoen Hu. « Inexact Distributed Reconstruction via Alternating Direction Method ». Applied Mechanics and Materials 511-512 (février 2014) : 417–20. http://dx.doi.org/10.4028/www.scientific.net/amm.511-512.417.

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Total variation (TV)-based CT image reconstruction has been shown to be experimentally capable of producing accurate reconstructions from sparse-view data. In this study, an inexact distributed reconstruction algorithm based on TV minimization has been developed. The algorithm is relatively simple as it uses the inexact alternating direction method, which involves linearization and proximal points techniques. The outstanding acceleration factor is achieved as the algorithm distributes the data and computation to individual nodes. Experimental results demonstrate that the proposed method can accelerate the alternating direction total variation minimization (ADTVM) algorithm with very little accuracy loss.

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Anderson, M. D., F. Baron et M. C. Bentz. « TLDR : time lag/delay reconstructor ». Monthly Notices of the Royal Astronomical Society 505, n^o 2 (19 mai 2021) : 2903–12. http://dx.doi.org/10.1093/mnras/stab1394.

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ABSTRACT We present the time lag/delay reconstructor (TLDR), an algorithm for reconstructing velocity delay maps in the maximum a posteriori framework for reverberation mapping. Reverberation mapping is a tomographical method for studying the kinematics and geometry of the broad-line region of active galactic nuclei at high spatial resolution. Leveraging modern image reconstruction techniques, including total variation and compressed sensing, TLDR applies multiple regularization schemes to reconstruct velocity delay maps using the alternating direction method of multipliers. Along with the detailed description of the TLDR algorithm we present test reconstructions from TLDR applied to synthetic reverberation mapping spectra as well as a preliminary reconstruction of the Hβ feature of Arp 151 from the 2008 Lick Active Galactic Nuclei Monitoring Project.

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Després, Bruno, et Frédéric Lagoutière. « Genuinely Multi-Dimensional Non-Dissipative Finite-Volume Schemes for Transport ». International Journal of Applied Mathematics and Computer Science 17, n^o 3 (1 octobre 2007) : 321–28. http://dx.doi.org/10.2478/v10006-007-0026-z.

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Genuinely Multi-Dimensional Non-Dissipative Finite-Volume Schemes for TransportWe develop a new multidimensional finite-volume algorithm for transport equations. This algorithm is both stable and non-dissipative. It is based on a reconstruction of the discrete solution inside each cell at every time step. The proposed reconstruction, which is genuinely multidimensional, allows recovering sharp profiles in both the direction of the transport velocity and the transverse direction. It constitutes an extension of the one-dimensional reconstructions analyzed in (Lagoutière, 2005; Lagoutière, 2006).

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ZHANG, XIAODONG, SHIRA L. BROSCHAT et PATRICK J. FLYNN. « A NUMERICAL STUDY OF CONJUGATE GRADIENT DIRECTIONS FOR AN ULTRASOUND INVERSE PROBLEM ». Journal of Computational Acoustics 12, n^o 04 (décembre 2004) : 587–604. http://dx.doi.org/10.1142/s0218396x04002377.

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In ultrasound inverse problems, the integral equation can be nonlinear, ill-posed, and computationally expensive. One approach to solving such problems is the conjugate gradient (CG) method. A key parameter in the CG method is the conjugate gradient direction. In this paper, we investigate the CG directions proposed by Polyak et al. (PPR), Hestenes and Stiefel (HS), Fletcher and Reeves (FR), Dai and Yuan (YD), and the two-parameter family generalization proposed by Nazareth (TPF). Each direction is applied to three test cases with different contrasts and phase shifts. Test case 1 has low contrast with a phase shift of 0.2π. Reconstruction of the object is obtained for all directions. The performances of the PPR, HS, YD, and TPF directions are comparable, while the FR direction gives the poorest performance. Test case 2 has medium contrast with a phase shift of 0.75π. Reconstruction is obtained for all but the FR direction. The PPR, HS, YD, and TPF directions have similar mean square error; the YD direction takes the least amount of CPU time. Test case 3 has the highest contrast with a phase shift of 1.003π. Only the YD direction gives reasonably accurate results.

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Mannella, C. A., M. Marko, K. Buttle, P. Penczek, A. Leith et J. Frank. « Tomographic reconstruction of mitochondria ». Proceedings, annual meeting, Electron Microscopy Society of America 53 (13 août 1995) : 740–41. http://dx.doi.org/10.1017/s0424820100140075.

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During oxidative phosphorylation, free energy of substrate oxidation is used to generate electrochemical gradients across the mitochondrial inner membrane. Full understanding of this process requires knowing the pathways for internal diffusion of ions and metabolites inside the organelle. This, in turn, requires detailed information about the organization of the membranes that compartmentalize the mitochondrion and the distribution of transport proteins (proton pumps, ion channels, metabolite carriers) on these membranes.We have undertaken the study of the compartmentation of rat-liver mitochondria (conventionally fixed and plastic-embedded) using electron microscopic tomography. Reconstructions of isolated mitochondria have been computed using projection images collected on the Albany high-voltage electron microscope from sections (0.5-1-μm thick) tilted around one axis over +/− 70° at 2° increments. A problem encountered with this approach is the directional loss of resolution due to the “missing wedge” of information in Fourier space in the direction parallel to the tilt axis. To overcome this problem, we have developed an alignment algorithm that allows projections collected over two or more tilting directions to be used in the same modified back-projection calculation.

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Barbieri, Riccardo, Felix M. Töpfer, Joram Soch, Carsten Bogler et John-Dylan Haynes. « Reconstruction of motion direction from fMRI data ». Journal of Vision 20, n^o 11 (20 octobre 2020) : 1274. http://dx.doi.org/10.1167/jov.20.11.1274.

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Liu, Xinwu, et Lihong Huang. « Poissonian image reconstruction using alternating direction algorithm ». Journal of Electronic Imaging 22, n^o 3 (12 août 2013) : 033007. http://dx.doi.org/10.1117/1.jei.22.3.033007.

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Varga, László, Péter Balázs et Antal Nagy. « Direction-dependency of binary tomographic reconstruction algorithms ». Graphical Models 73, n^o 6 (novembre 2011) : 365–75. http://dx.doi.org/10.1016/j.gmod.2011.06.006.

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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, n^o 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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Palacci, Patrick. « Papillae reconstruction : clinical considerations ». Faculty Dental Journal 3, n^o 1 (janvier 2012) : 8–19. http://dx.doi.org/10.1308/204268512x13207759526210.

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Implant restorations in the anterior maxilla are challenging, especially when treating patients with a high lip line and a lack of available tissue. These patients will exhibit large and unsightly dark embrasures reminiscent of severe gingival recession. The action of augmenting or regenerating soft tissue is more difficult to perform in the coronal direction than in other directions. Unfortunately, there is usually a need to replace lost tissue in the coronal dimension. Today’s dental implantology is not only focused on function but also aesthetics. Papilla reconstruction or preservation is a key factor for a successful aesthetic outcome.

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Yan, Hai Xia, et Yan Jun Liu. « Adaptive Dual Conjudate Gradient Projection Algorithm for Compressed Sensing Image Reconstruction ». Applied Mechanics and Materials 347-350 (août 2013) : 2600–2604. http://dx.doi.org/10.4028/www.scientific.net/amm.347-350.2600.

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In order to improve the quality of noise signals reconstruction method, an algorithm of adaptive dual gradient projection for sparse reconstruction of compressed sensing theory is proposed. In ADGPSR algorithm, the pursuit direction is updated in two conjudate directions, the better original signals estimated value is computed by conjudate coefficient. Thus the reconstruction quality is improved. Experiment results show that, compared with the GPSR algorithm, the ADGPSR algorithm improves the signals reconstruction accuracy, improves PSNR of reconstruction signals, and exhibits higher robustness under different noise intensities.

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Ruttimann, U. E. « Computer-Based Reconstruction and Temporal Subtraction of Radiographs ». Advances in Dental Research 1, n^o 1 (décembre 1987) : 72–79. http://dx.doi.org/10.1177/08959374870010011601.

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The most important physical parameter limiting the diagnostic performance achieved with radiographic images is the signal-to-noise ratio (SNR). In most dental applications, the normal anatomical structures contribute to a background pattern in the image that is limiting the SNR attainable. Hence, the projection direction of radiographs is a fundamental determinant of the SNR. The acquisition of a basis set of projection images obtained from a plurality of spatially registered sampling directions permits the reconstruction of any desired slice lying within a limited volume by tomosynthesis. Alternatively, the multi-projection strategy permits synthesis of any arbitrary radiographic image whose projection direction lies within the cone spanned by the basis projection directions. This feature can be used to synthesize a desired image at the proper projection angle required for meaningful subtraction from a previously obtained radiograph, and thus to suppress anatomy-related background variations.

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VESELOVSKAYA, Elizaveta. « WHAT DID OUR ANCESTORS LOOK LIKE ? OR, THE CAPABILITIES OF ANTHROPOLOGICAL RECONSTRUCTION ». LIFE OF THE EARTH 43, n^o 3 (25 août 2021) : 347–60. http://dx.doi.org/10.29003/m2439.0514-7468.2020_43_3/347-360.

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Anthropological Reconstruction Laboratory of the Center for Physical Anthropology, Institute of Ethnology and Anthropology RAS. The article relates the current state of the M.M. Gerasimov Laboratory of Anthropological Reconstruction of the Center for Physical Anthropology, Institute of Ethnology and Anthropology, Russian Academy of Sciences. Emphasizing the role of the founder of the method of face reconstruction from the skull, the author discusses the latest improvements to this method. The data bank on the thickness of the facial integument in representatives of various ethnic groups, and the accumulated experience with regard to the relationships between facial features and the underlying structures of the skull, made it possible to create a program of craniofacial correspondence ‘The Algorithm of Appearance’, which significantly improves the process of reconstructing in vivo appearance based on the skull. The visual reconstruction of the appearance is supplemented by an anthropological description of the lifetime appearance, in terms of the ‘verbal portrait’ used in forensic science. A description of a unique collection of more than 300 sculptural and graphic portraits made on the basis of the skulls of ancient people and historical figures is given. Based on the examples of specific projects, the possibilities of anthropological reconstruction for solving applied and theoretical problems of science are shown. The reconstruction of the appearance of soldiers killed in the Second World War is the key patriotic direction of the Laboratory s work. Based on the results of these reconstructions, several fi were identifi Th Laboratory is currently at work on reconstructing the lifetime appearance of A.V. Suvorov on the basis of a death mask.

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Yan, Hai Xia, Yan Jun Liu et Yu Ming Sun. « Medical Image Compressed Sensing Reconstruction ». Applied Mechanics and Materials 556-562 (mai 2014) : 4835–38. http://dx.doi.org/10.4028/www.scientific.net/amm.556-562.4835.

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In order to improve the speed of compressed sensing image reconstruction algorithm, a two step rapid gradient projection for sparse reconstruction in medical image reconstruction is proposed. in traditional gradient projection for sparse reconstruction algorithm, the searching direction is alternate between the negative gradient direction when the direction is ill, the searching speed is slow. Now we search with two step gradient projection, the speed is increased when meets the ill-condition. Compared with the original GPSR algorithm, the TSGPSR algorithm not only accelerate the speed of operation, but also improves the accuracy of the reconstruction. and exhibits higher robustness under different noise intensities.

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Kynkäänniemi, Tuomas, Osku Kemppinen, Ari-Matti Harri et Walter Schmidt. « Wind reconstruction algorithm for Viking Lander 1 ». Geoscientific Instrumentation, Methods and Data Systems 6, n^o 1 (22 juin 2017) : 217–29. http://dx.doi.org/10.5194/gi-6-217-2017.

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Abstract. The wind measurement sensors of Viking Lander 1 (VL1) were only fully operational for the first 45 sols of the mission. We have developed an algorithm for reconstructing the wind measurement data after the wind measurement sensor failures. The algorithm for wind reconstruction enables the processing of wind data during the complete VL1 mission. The heater element of the quadrant sensor, which provided auxiliary measurement for wind direction, failed during the 45th sol of the VL1 mission. Additionally, one of the wind sensors of VL1 broke down during sol 378. Regardless of the failures, it was still possible to reconstruct the wind measurement data, because the failed components of the sensors did not prevent the determination of the wind direction and speed, as some of the components of the wind measurement setup remained intact for the complete mission. This article concentrates on presenting the wind reconstruction algorithm and methods for validating the operation of the algorithm. The algorithm enables the reconstruction of wind measurements for the complete VL1 mission. The amount of available sols is extended from 350 to 2245 sols.

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Rudenko, S. S., D. G. Koliushko et O. V. Kashcheyev. « DETERMINATION OF DIRECTION TO RECONSTRUCTION OF GROUNDING SYSTEM ». Electrical Engineering & ; Electromechanics, n^o 2 (29 avril 2017) : 57–61. http://dx.doi.org/10.20998/2074-272x.2017.2.09.

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Di Marco, Alessandro, Enrico Costa, Fabio Muleri, Paolo Soffitta, Sergio Fabiani, Fabio La Monaca, John Rankin et al. « A Weighted Analysis to Improve the X-Ray Polarization Sensitivity of the Imaging X-ray Polarimetry Explorer ». Astronomical Journal 163, n^o 4 (15 mars 2022) : 170. http://dx.doi.org/10.3847/1538-3881/ac51c9.

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Abstract Imaging X-ray Polarimetry Explorer (IXPE) is a Small Explorer mission that was launched at the end of 2021 to measure the polarization of X-ray emission from tens of astronomical sources. Its focal-plane detectors are based on the Gas Pixel Detector, which measures the polarization by imaging photoelectron tracks in a gas mixture and reconstructing their initial directions. The quality of the single track, and then the capability of correctly determining the original direction of the photoelectron, depends on many factors, e.g., whether the photoelectron is emitted at low or high inclination with respect to the collection plane or the occurrence of a large Coulomb scattering close to the generation point. The reconstruction algorithm used by IXPE to obtain the photoelectron emission direction also calculates several properties of the shape of the tracks that characterize the process. In this paper we compare several such properties and identify the best one to weight each track on the basis of the reconstruction accuracy. We demonstrate that significant improvement in sensitivity can be achieved with this approach and for this reason it will be the baseline for IXPE data analysis.

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Yan, Hai Xia, et Yan Jun Liu. « Research of Adaptive Gradient Projection Algorithm on Remote Sensing Image Reconstruction ». Advanced Materials Research 765-767 (septembre 2013) : 572–75. http://dx.doi.org/10.4028/www.scientific.net/amr.765-767.572.

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In order to improve the low efficient and the noise effect of remote sensing image reconstruction, an algorithm of adaptive dual gradient projection for sparse reconstruction of compressed sensing theory is proposed. Point to the high frequency noise of remote sensing image, the ADGPSR algorithm pursuits the projection direction in two conjudate directions, thus the high frequency noise effect is overcame. Experiment results show that, compared with the GPSR algorithm, the ADGPSR algorithm on remote sensing image improves the signals reconstruction accuracy.

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Spang, Robert, Jonathan Egan, Philip Hanna, Aron Lechtig, Daniel Haber, Joseph P. DeAngelis, Ara Nazarian et Arun J. Ramappa. « Comparison of Patellofemoral Kinematics and Stability After Medial Patellofemoral Ligament and Medial Quadriceps Tendon–Femoral Ligament Reconstruction ». American Journal of Sports Medicine 48, n^o 9 (18 juin 2020) : 2252–59. http://dx.doi.org/10.1177/0363546520930703.

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Background: There is a lack of evidence regarding the optimum extensor-sided fixation method for medial patellofemoral ligament (MPFL) reconstruction. There is increased interest in avoiding patellar drilling via soft tissue–only fixation to the distal quadriceps, thus reconstructing the medial quadriceps tendon–femoral ligament (MQTFL). The biomechanical implications of differing extensor-sided fixation constructs remain unknown. Hypothesis: The null hypothesis was there would be no differences between traditional MPFL reconstruction and MQTFL reconstruction with respect to resistance to lateral translation, patellar position, or patellofemoral contact pressures. Study Design: Controlled laboratory study. Methods: Nine adult knee specimens were mounted on a jig that applied static, physiologic loads to the quadriceps tendons. Patellar position and orientation, knee flexion angle, and patellofemoral pressure were recorded at 8 different flexion angles between 0° and 110°. Additionally, a lateral patellar excursion test was conducted wherein a load was applied directly to the patella in the lateral direction with the knee at 30° of flexion and subjected to 2-N quadriceps loads. Testing was conducted under 4 conditions: intact, transected MPFL, MQTFL reconstruction, and MPFL reconstruction. For MQTFL reconstruction, the surgical technique established by Fulkerson was employed. For MPFL reconstruction, a traditional technique was utilized. Results: The patellar excursion test showed no significant difference between the MQTFL and intact states with respect to lateral translation. MPFL reconstruction led to significantly less lateral translation ( P < .05) than all other states. There were no significant differences between MPFL and MQTFL reconstructions with respect to peak patellofemoral contact pressure. MPFL and MQTFL reconstructions both resulted in increased internal rotation of the patella with the knee in full extension. Conclusion: Soft tissue-only extensor-sided fixation to the distal quadriceps (MQTFL) during patella stabilization appears to re-create native stability in this time 0 cadaver model. Fixation to the patella (MPFL) was associated with increased resistance to lateral translation. Clinical Relevance: Evolving anatomic knowledge and concern for patellar fracture has led to increased interest in MQTFL reconstruction. Both MQTFL and MPFL reconstructions restored patellofemoral stability to lateral translation without increasing contact pressures under appropriate graft tensioning, with MQTFL more closely restoring native resistance to lateral translation at the time of surgery.

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Dutt, Saurabh, et Vinod Kumar. « How anatomical is our tunnel ? A three dimensional CT evaluation of femoral tunnel in anatomic anteromedial single bundle anterior cruciate ligament reconstruction ». International Journal of Research in Orthopaedics 5, n^o 4 (27 juin 2019) : 656. http://dx.doi.org/10.18203/issn.2455-4510.intjresorthop20192679.

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Background: ACL reconstruction has become a common orthopaedic procedure. The anatomy and biomechanics of ACL have been one of the most researched and debated topics in the orthopaedic literature. This has implication on the surgical procedure too with shift from traditional transtibial to more anatomic anteromedial ACL reconstruction. Anteromedial technique results in more anatomic femoral tunnel with graft positioned at the native insertion site. The tunnel position is crucial for better outcome after ACL reconstruction. The purpose of the study was to ascertain the femoral tunnel position made by anatomic single bundle reconstruction with the help of three dimensional computer tomography.Methods: A prospective case series involving thirty patients with ACL tear who underwent anteromedial single bundle ACL reconstruction. Computer tomography scans were performed on thirty knees that underwent single bundle anteromedial ACL reconstruction. Three dimensional models were created and the data was analyzed according to coordinate system method. Femoral tunnel position was measured in proximal to distal and posterior to anterior directions. This data was compared with the already published reference data on anatomical tunnel position.Results: Femoral tunnel centre on the medial wall of lateral femoral condyle was located at 35±9% in the posterior to anterior direction. In the proximal to distal direction, the tunnel was placed at 30±12%. Femoral tunnel was placed anteriorly as compared to anatomic anteromedial and posterolateral tunnel position. There was no significant difference in tunnel position in proximal to distal direction.Conclusions: Femoral tunnel centre on the medial wall of lateral femoral condyle was located at 35±9% in the posterior to anterior direction. In the proximal to distal direction, the tunnel was placed at 30±12%. Femoral tunnel was placed anteriorly as compared to anatomic anteromedial and posterolateral tunnel position. There was no significant difference in tunnel position in proximal to distal direction.

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Yuan, Yongfeng, et Kuanquan Wang. « A Mixed Gauss and Directional Distance Filter for Fiber Direction Tracking ». International Journal of Image and Graphics 14, n^o 01n02 (janvier 2014) : 1450001. http://dx.doi.org/10.1142/s0219467814500016.

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Fiber directional tracking through diffusion tensor magnetic resonance imaging (DT-MRI) is a promising research field in visualization and computer graphics and is widely applied in the reconstruction of fiber orientation and the structure of biological tissues. The filter technique used to blur noise in data is of critical importance for fiber directional tracking, particularly because existing tracking methods are very sensitive to impulsive noise. In this paper, a mixed filter of the 3D Gauss and directional distance filter (GDDF) is proposed to suppress noises in corrupted vector fields. Simulation results and objective evaluation of vector datasets demonstrate that GDDF not only possesses the capability of noise attenuation but also preserves vector directions. By validating the simulated vector data against experimental heart data, it is also shown that the GDDF is an effective and stable preprocessing method that accurately reconstructs fiber orientation.

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Liu, Jianguo, Ze Chen et Huiming Zhang. « Study on Safety Guarantee Measures for the Same-direction Separated Subgrade Section ». Highlights in Science, Engineering and Technology 18 (13 novembre 2022) : 48–51. http://dx.doi.org/10.54097/hset.v18i.2566.

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In the reconstruction and expansion of the expressway, due to factors such as resource utilization of original roads, economic applicability, adaptation to local conditions, and construction organization, the method of reconstruction and expansion and widening is restricted. The widening method of half-width utilization of the original road and half-width newly built in the same direction is adopted, forming the separated subgrade section in the same direction. Based on the implementation plans of different expressway reconstruction and expansion projects, this paper analyzes and studies the characteristics of the same-direction separated subgrade section, from the aspects of the safety guarantee principle, the design of safety facilities, and the same-direction separated subgrade section with interchanges. The reasonable measures safety protection was proposed to promote the smooth flow of expressway traffic and improve driving safety. It is of certain guiding significance for the design of safety facilities in the same-direction separated subgrade section of expressway reconstruction and expansion projects.

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Lu, Xinmiao, Cunfang Yang, Qiong Wu, Jiaxu Wang, Yuhan Wei, Liyu Zhang, Dongyuan Li et Lanfei Zhao. « Improved Reconstruction Algorithm of Wireless Sensor Network Based on BFGS Quasi-Newton Method ». Electronics 12, n^o 6 (7 mars 2023) : 1267. http://dx.doi.org/10.3390/electronics12061267.

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Aiming at the problems of low reconstruction rate and poor reconstruction precision when reconstructing sparse signals in wireless sensor networks, a sparse signal reconstruction algorithm based on the Limit-Broyden-Fletcher-Goldfarb-Shanno (L-BFGS) quasi-Newton method is proposed. The L-BFGS quasi-Newton method uses a two-loop recursion algorithm to find the descent direction dk directly by calculating the step difference between m adjacent iteration points, and a matrix Hk approximating the inverse of the Hessian matrix is constructed. It solves the disadvantages of BFGS requiring the calculation and storage of Hk, reduces the algorithm complexity, and improves the reconstruction rate. Finally, the experimental results show that the L-BFGS quasi-Newton method has good experimental results for solving the problem of sparse signal reconstruction in wireless sensor networks.

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Yan, Hai Xia, et Yan Jun Liu. « Improved Gradient Projection Algorithm for Compressed Sensing ». Applied Mechanics and Materials 543-547 (mars 2014) : 2623–26. http://dx.doi.org/10.4028/www.scientific.net/amm.543-547.2623.

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In order to improve efficient of compressed sensing image reconstruction, an improved gradient projection algorithm of compressed sensing theory is proposed. In improved Gradient Projection algorithm, the pursuit direction is updated by search at negative gradient direction, thus the gradient direction is a single direction, because the traditional gradient projection algorithm searching at alternating searching method ,the efficient of gradient projection algorithm is higher than the traditional gradient projection algorithm, Experiment results show that, compared with the GPSR algorithm, the IGPSR algorithm improves the signals reconstruction accuracy, improves PSNR of reconstruction signals, and exhibits higher robustness under different noise intensities.

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Tominaga, Shoji, Keita Hirai et Takahiko Horiuchi. « Appearance Reconstruction of Fluorescent Objects Based on Reference Geometric Factors ». Color and Imaging Conference 2019, n^o 1 (21 octobre 2019) : 393–98. http://dx.doi.org/10.2352/issn.2169-2629.2019.27.70.

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An approach is proposed for the reliable appearance reconstruction of fluorescent objects under arbitrary conditions of material and illuminant based on reference geometric factors. First, a large set of spectral images is acquired from a variety of scenes of fluorescent objects paired with a mutual illumination effect under different conditions. The target fluorescent object is constructed using a cube and a flat plate supporting it, and is subsequently illuminated using a directional light source. We produce many target objects of the same size with different fluorescent materials and observe them under different illumination conditions. The observed spectral images are subsequently decomposed into five components, combining the spectral functions and geometric factors. The reference geometric factors are independent of the material, illuminant, and illumination direction change; instead, they are only dependent on object geometries. A reliable estimation method of reference geometric factors is presented using the whole spectral images observed under various conditions. Further, we propose an algorithm for reconstructing a realistic appearance including mutual illumination effect under arbitrary conditions of material, illuminant, and illumination direction. Finally, the reliability of the proposed approach is examined experimentally.

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Yan, Hai Xia, et Yan Jun Liu. « Rapid Gradient Projection Algorithm for Image Reconstruction ». Applied Mechanics and Materials 530-531 (février 2014) : 443–46. http://dx.doi.org/10.4028/www.scientific.net/amm.530-531.443.

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In order to improve the speed of compressed sensing image reconstruction algorithm, a rapid gradient projection algorithm for image reconstruction is proposed. In traditional Gradient Projection algorithm, the pursuit direction is alternating, in rapid gradient projection algorithm, we use the Newton's method to calculate the gradient descent direction, thus the constraints conditions of gradient projection is satisfied. And the target function is updated in each iteration computing. The effect of approximation matrix to target function is reduced. The iteration computing times is reduced, because the algorithm works in accurate search direction. Experiment results show that, compared with the GPSR algorithm, the RGPSR algorithm improves the signals reconstruction accuracy, improves PSNR of reconstruction signals, and exhibits higher robustness under different noise intensities.

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Heintzmann, R., G. Kreth et C. Cremer. « Reconstruction of Axial Tomographic High Resolution Data from Confocal Fluorescence Microscopy : A Method for Improving 3D FISH Images ». Analytical Cellular Pathology 20, n^o 1 (2000) : 7–15. http://dx.doi.org/10.1155/2000/459351.

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Fluorescent confocal laser scanning microscopy allows an improved imaging of microscopic objects in three dimensions. However, the resolution along the axial direction is three times worse than the resolution in lateral directions. A method to overcome this axial limitation is tilting the object under the microscope, in a way that the direction of the optical axis points into different directions relative to the sample. A new technique for a simultaneous reconstruction from a number of such axial tomographic confocal data sets was developed and used for high resolution reconstruction of 3D‐data both from experimental and virtual microscopic data sets. The reconstructed images have a highly improved 3D resolution, which is comparable to the lateral resolution of a single deconvolved data set. Axial tomographic imaging in combination with simultaneous data reconstruction also opens the possibility for a more precise quantification of 3D data. The color images of this publication can be accessed from http://www.esacp.org/acp/2000/20‐1/heintzmann.htm. At this web address an interactive 3D viewer is additionally provided for browsing the 3D data. This java applet displays three orthogonal slices of the data set which are dynamically updated by user mouse clicks or keystrokes.

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Tang, Ling, Hong Song et Lian Jun Hu. « Blind Separation of Coherent Signals Based on Toeplitz Matrix Reconstruction ». Applied Mechanics and Materials 135-136 (octobre 2011) : 331–35. http://dx.doi.org/10.4028/www.scientific.net/amm.135-136.331.

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A new blind beamforming algorithm for separating and estimating coherent signals arriving at an antenna array is proposed in this paper. This algorithm is implemented through arranging the received data’s correlation function of each array element and reference array element (the first array element), to form the Hermitian Toeplitz matrix first. Then through the singular value decomposition of the matrix the signal subspace and noise subspace can be get, in order to achieve the direction vector of coherent sources to beamform, which can separate the independent signals from different directions effectively without knowing the transcendent knowledge of the signals. The new approach can estimate the coherent signals’ direction-of-arrival(DOA) on the basis of separation, and has good performance under the low SNR. The simulation results show that the proposed method is effective．

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Wang, Linyuan, Ailong Cai, Hongkui Liu, Hanming Zhang, Bin Yan, Lei Li et Guoen Hu. « Column distribution reconstruction algorithm via the alternating direction method ». Optik 126, n^o 9-10 (mai 2015) : 1006–11. http://dx.doi.org/10.1016/j.ijleo.2015.02.041.

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Park, Yunjung, et Seungeun Lee. « Exploring the Direction of Reconstruction Based on Dewey theory ». Journal of Curriculum Integration 17, n^o 1 (28 février 2023) : 53–73. http://dx.doi.org/10.35304/jci.17.1.03.

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Cai, Ai Long, Lin Yuan Wang, Lei Li, Bin Yan, Xing Wei, Yong Zhang et Jian Xin Li. « GPU Based Cone Beam Computed Tomography Reconstruction by the Inexact Alternating Direction Method ». Applied Mechanics and Materials 519-520 (février 2014) : 651–54. http://dx.doi.org/10.4028/www.scientific.net/amm.519-520.651.

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GPU based sparse reconstruction shows great significance in cone beam computed tomography (CBCT). This paper proposes a GPU based efficient algorithm for sparse view CBCT reconstruction. The reconstruction problem is converted to a constrained optimization using total variation minimization. The alternating direction method is adopted to solve it efficiently. Furthermore, a linearized proximity and FFT techniques are used for improving computation efficiency. To tackle with the most time consumption of forward and backward projection operation, the GPU hardware acceleration is utilized. The simulation experiments indicate that the new method is able to realize high accuracy reconstruction for CBCT with high speed.

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Li, Fangda, Ankit Manerikar, Tanmay Prakash et Avinash C. Kak. « A Splitting-Based Iterative Algorithm for GPU-Accelerated Statistical Dual-Energy X-Ray CT Reconstruction ». Electronic Imaging 2020, n^o 14 (26 janvier 2020) : 6–1. http://dx.doi.org/10.2352/issn.2470-1173.2020.14.coimg-a14.

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When dealing with material classification in baggage at airports, Dual-Energy Computed Tomography (DECT) allows characterization of any given material with coefficients based on two attenuative effects: Compton scattering and photoelectric absorption. However, straightforward projection-domain decomposition methods for this characterization often yield poor reconstructions due to the high dynamic range of material properties encountered in an actual luggage scan. Hence, for better reconstruction quality under a timing constraint, we propose a splitting-based, GPU-accelerated, statistical DECT reconstruction algorithm. Compared to prior art, our main contribution lies in the significant acceleration made possible by separating reconstruction and decomposition within an Alternating Direction Method of Multipliers (ADMM) framework. Experimental results, on both synthetic and real-world baggage phantoms, demonstrate a significant reduction in time required for convergence.

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Shegelski, M. MR, M. B. Whitwick et R. Holenstein. « Multiple vs. single scattering in low energy electron holography ». Canadian Journal of Physics 79, n^o 1 (1 janvier 2001) : 17–28. http://dx.doi.org/10.1139/p01-024.

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The theory of the low energy electron point source (LEEPS) microscope is presented in matrix form to account for multiple scattering. An iterative method is used to solve the matrix equation for the structure factor. An algorithm is developed for the storage and use of only the dominant elements of the structure matrix; this allows for the study of considerably large clusters. Examples of large clusters of atoms are studied to compare single scattering (SS) and multiple scattering (MS). A Kirchhoff-Helmholtz transform is used for the reconstruction. We report results where SS and MS give essentially the same reconstructions, and other results where SS and MS reconstructions are in severe disagreement. We find, for example, that SS and MS give virtually the same reconstruction along the optical axis for clusters that are "short" lateral to, but "long" in the direction of, the optical axis. In contrast, we also find that SS and MS give vastly different reconstructions lateral to the optical axis for clusters that are "wide" lateral to, and "thin" in the direction of, the optical axis. Some other results are also reported. Implications for further theoretical work, and for experimental LEEPS microscopy, are discussed. PACS No.: 61.14Nm

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Wang, Yuezong, Jiqiang Chen et Youfan Peng. « Surface Reconstruction of Microscale Objects Based on Grid-Patterned Structured-Light Measurements ». Microscopy and Microanalysis 28, n^o 1 (16 décembre 2021) : 152–72. http://dx.doi.org/10.1017/s1431927621013829.

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A structured-light projection system was designed for microscale objects with surface heights that ranged from tens to hundreds of microns. The system was composed of a universal projector and microscope system that supported editing the attributes of structured-light patterns in real-time and was capable of projecting microscale patterns. On this basis, reconstructing the metal surfaces of microscale objects based on grid patterns of structured light was investigated, the internal and external parameters of microscope vision and projection systems were calibrated, and an image algorithm for grid-node detection was designed. The results indicated that the proposed method successfully reconstructed the three-dimensional (3D) surface of microscale objects, and the reconstruction results were consistent with the original surfaces. With 95% confidence, the reconstruction precision in the X- and Y-directions was approximately ±4.0 μm and in the Z-direction was approximately ±7.5 μm. The designed system and the proposed method were suitable for 3D-shape measurement of microstructures in microscopic fields and can be adapted to meet a broader range of applications, as compared to current methods.

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Golyshkina, L. A. « Decoding Rhetoric : Theoretical and Methodological Substantiation of the Scientific Direction ». Nauchnyi dialog, n^o 5 (30 mai 2020) : 9–24. http://dx.doi.org/10.24224/2227-1295-2020-5-9-24.

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The theoretical and methodological substantiation of a new philological trend - decoding rhetoric, which is formed by synthesizing analytical rhetoric, cognitive science, semiotics, and text linguistics is presented in the article. Actual circumstances and factors that determine the possibility of highlighting the decoding rhetoric are indicated. A comparison of the style of decoding and decoding rhetoric is carried out. The concept of decoding rhetoric is described, its object and subject are formulated. The cognitive-communicative foundations of rhetorical decoding are considered. The concept of a rhetorical textotype as a cognitive landmark, or mental pattern programmed by the structure of a communicative act, is introduced. The rhetorical textotype as a model with the persuasive or acting potential of the text acts as a reference point for recognizing the producer's text-forming intention. Communicative-cognitive correlations are established that explain the essence of an effective text. Particular attention is paid to the rhetorical reconstruction of text formation as a research method. Rhetorical reconstruction as an analytical procedure allows to gradually consider the methods and means of verbalization of text formation strategies - inventive, dispositive and elocative. Rhetorical reconstruction acts as a tool for diagnosing the effectiveness of the text, and also identifies areas of its rhetorical risks. Areas of application of rhetorical reconstruction are indicated. The prospects of studying decoding rhetoric as a field of knowledge claiming its own linguo-ontological status are outlined.

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Tolkova, Irina, et Holger Klinck. « Source separation with an acoustic vector sensor for terrestrial bioacoustics ». Journal of the Acoustical Society of America 152, n^o 2 (août 2022) : 1123–34. http://dx.doi.org/10.1121/10.0013505.

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Passive acoustic monitoring is emerging as a low-cost, non-invasive methodology for automated species-level population surveys. However, systems for automating the detection and classification of vocalizations in complex soundscapes are significantly hindered by the overlap of calls and environmental noise. We propose addressing this challenge by utilizing an acoustic vector sensor to separate contributions from different sound sources. More specifically, we describe and implement an analytical pipeline consisting of (1) calculating direction-of-arrival, (2) decomposing the azimuth estimates into angular distributions for individual sources, and (3) numerically reconstructing source signals. Using both simulation and experimental recordings, we evaluate the accuracy of direction-of-arrival estimation through the active intensity method (AIM) against the baselines of white noise gain constraint beamforming (WNC) and multiple signal classification (MUSIC). Additionally, we demonstrate and compare source signal reconstruction with simple angular thresholding and a wrapped Gaussian mixture model. Overall, we show that AIM achieves higher performance than WNC and MUSIC, with a mean angular error of about 5°, robustness to environmental noise, flexible representation of multiple sources, and high fidelity in source signal reconstructions.

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Ivanyuk, V. G., B. P. Rusyn et R. Ya Kosarevych. « Development of 3D surface reconstruction by the images triad based on the Lambertian reflection model ». Information extraction and processing 2022, n^o 50 (19 décembre 2022) : 54–61. http://dx.doi.org/10.15407/vidbir2022.50.054.

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A method for reconstructing the surface of an object using on a series of images based on the Lambertian model of light reflection is proposed. The original images are obtained by the method of photography under natural lighting. The model parameters are determined by changing the position of the light source using additional shading and the stable position of the receiver. The series contains a triad of images obtained from different directions of illumination and a shaded image of the surface of the reconstruction object. In the first stage, the derived surfaces of the reconstruction object are reconstructed. The next step is the accumulation of derivatives and determination of the surface height of the reconstruction object. To simplify the complexity of the practical implementation of the 3D-reconstruction a pyramid layout is chosen. The photography of the triad of images of the pyramid is done before noon, at noon and in the afternoon. The information about the triad and the shadowed image of the pyramid surface enters the processing system, where the directions of the photograph lighting are first determined. The parameters of the lighting directions are determined based on data on the height of the Sun at its upper culmination on the day and the time of the photo shoot. The procedure for determining the elevation of the Sun on a particular day of the year has been implemented. Calculated lighting direction data and image information using the Lambertian model of light reflection are reconstructed into horizontal and vertical derivatives. As a result of the discrete accumulation of derivatives, the pyramid surface is reconstructed.

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Duijndam, A. J. W., M. A. Schonewille et C. O. H. Hindriks. « Reconstruction of band‐limited signals, irregularly sampled along one spatial direction ». GEOPHYSICS 64, n^o 2 (mars 1999) : 524–38. http://dx.doi.org/10.1190/1.1444559.

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Seismic signals are often irregularly sampled along spatial coordinates, leading to suboptimal processing and imaging results. Least squares estimation of Fourier components is used for the reconstruction of band‐limited seismic signals that are irregularly sampled along one spatial coordinate. A simple and efficient diagonal weighting scheme, based on the distance between the samples, takes the properties of the noise (signal outside the bandwidth) into account in an approximate sense. Diagonal stabilization based on the energies of the signal and the noise ensures robust estimation. Reconstruction for each temporal frequency component allows the specification of a varying spatial bandwidth dependent on the minimum apparent velocity. This parameterization improves the reconstruction capability for the lower temporal frequencies. In practical circumstances, the maximum size of the gaps in which the signal can be reconstructed is three times the (temporal frequency dependent) Nyquist interval. Reconstruction in the wavenumber domain allows a very efficient implementation of the algorithm, and takes a total number of operations a few times that of a 2-D fast Fourier transform corresponding to the size of the output data set. Quality control indicators of the reconstruction procedure can be computed which may also serve as decision criteria on in‐fill shooting during acquisition. The method can be applied to any subset of seismic data with one varying spatial coordinate. Applied along the cross‐line direction, it can be used to compute a 3-D stack with improved anti‐alias protection and less distortion of the signal within the bandwidth.

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Cai, Ailong, Linyuan Wang, Hanming Zhang, Bin Yan, Lei Li, Xiaoqi Xi, Min Guan et Jianxin Li. « 3D Alternating Direction TV-Based Cone-Beam CT Reconstruction with Efficient GPU Implementation ». Computational and Mathematical Methods in Medicine 2014 (2014) : 1–9. http://dx.doi.org/10.1155/2014/982695.

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Iterative image reconstruction (IIR) with sparsity-exploiting methods, such as total variation (TV) minimization, claims potentially large reductions in sampling requirements. However, the computation complexity becomes a heavy burden, especially in 3D reconstruction situations. In order to improve the performance for iterative reconstruction, an efficient IIR algorithm for cone-beam computed tomography (CBCT) with GPU implementation has been proposed in this paper. In the first place, an algorithm based on alternating direction total variation using local linearization and proximity technique is proposed for CBCT reconstruction. The applied proximal technique avoids the horrible pseudoinverse computation of big matrix which makes the proposed algorithm applicable and efficient for CBCT imaging. The iteration for this algorithm is simple but convergent. The simulation and real CT data reconstruction results indicate that the proposed algorithm is both fast and accurate. The GPU implementation shows an excellent acceleration ratio of more than 100 compared with CPU computation without losing numerical accuracy. The runtime for the new 3D algorithm is about 6.8 seconds per loop with the image size of256×256×256and 36 projections of the size of512×512.

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Li, Huaxin, et Jinxiao Pan. « Deflection Tomography Reconstruction Based on Diagonal Total Variation ». MATEC Web of Conferences 246 (2018) : 03022. http://dx.doi.org/10.1051/matecconf/201824603022.

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In view of the shortages of the reconstruction algorithm based on Total Variation (TV) minimum under the framework of measured field compressed sensing, we study the measured field sparse representation method and solving method of optimization equation, and propose the measured field reconstruction algorithms based on Diagonal Total Variation (DTV). When there is no obvious change in the reconstruction iteration of TV, gradient transformation of diagonal direction is introduced, the multi-directional information is used to obtain a more sparse representation of the measured field in the reconstruction. Under the condition of sparse projections, experimental results of this algorithm are demonstrated and compared with the results from the TV method. Comparisons show that this method can reconstruct high-quality measured field.

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Muiruri, Amos, Maina Maringa et Willie du Preez. « Crystallographic Texture Analysis of As-Built and Heat-Treated Ti6Al4V (ELI) Produced by Direct Metal Laser Sintering ». Crystals 10, n^o 8 (12 août 2020) : 699. http://dx.doi.org/10.3390/cryst10080699.

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This paper reports on an investigation of crystallographic texture of as-built and heat-treated Ti6Al4V (ELI) produced by direct metal laser sintering (DMLS). The texture analyses were conducted using electron backscatter diffraction (EBSD). The β-phase texture from the obtained EBSD data was ascertained based on a reconstruction method using the Automatic Reconstruction of Parent Grain for EBSD data (ARPGE) program. A significant improvement of the maximum intensity of the texture from the pole figure was also noted upon heat treatment. The as-built samples and samples heat-treated just below the α→β transformation temperature showed a stronger fibrous texture of the reconstructed β-grains with the ⟨100⟩ directions almost parallel to the build direction. The alignment of the fibrous texture in the build direction disappeared after heat treatment above the α→β-grain transformation temperature.

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Shiina, Takahiro, Takuto Maeda, Masayuki Kano, Aitaro Kato et Naoshi Hirata. « An Optimum 2D Seismic-Wavefield Reconstruction in Densely and Nonuniformly Distributed Stations : The Metropolitan Seismic Observation Network in Japan ». Seismological Research Letters 92, n^o 3 (3 février 2021) : 2015–27. http://dx.doi.org/10.1785/0220200196.

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Abstract We propose an optimization method for applying the seismic-wave gradiometry (SWG) method to a dense seismic station network consisting of nonuniformly distributed seismographs. As a nonuniformly distributed station array, we consider the station layout of the Metropolitan Seismic Observation Network (MeSO-net) operated in and around the Tokyo metropolitan area, Japan. In this study, thereby, we numerically investigate optimum shapes of weighting functions, which control the spatial weights of individual stations when estimating waveforms at any grid points in the SWG method, to reconstruct seismic wavefields propagating in the MeSO-net. The functions with isotropic spatial weights are found to be appropriate for wavefield reconstructions with seismic waves incoming from practically all directions, even for nonuniformly distributed stations. The reproducibility of the wavefields is greatly improved by changing the shapes of the spatial weights reflecting density of the stations. Further plausible wavefield reconstructions are made by considering the propagation directions of the seismic waves. In these cases, if the weight of a contribution for a wavefield reconstruction is larger at far stations with a direction perpendicular to the wave propagation direction, then the reproducibility of the waveforms is significantly increased. In addition, the spatial gradients of the amplitudes are well reproduced by the optimized SWG method even though the optimization only focused on the amplitudes. Therefore, our proposed optimization scheme can be used to accurately estimate seismic wavefields in a nonuniformly distributed station array. Actually, the weighting functions optimized in this study succeeded to reconstruct the seismic wavefield of a shallow crustal earthquake that occurred around the Tokyo metropolitan area, based on the observed seismograms obtained by the MeSO-net.

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Han, Xue Bing, et Zhao Jun Jiang. « An Improved Direction-of-Arrival Estimation Method Based on Sparse Reconstruction ». Applied Mechanics and Materials 263-266 (décembre 2012) : 135–38. http://dx.doi.org/10.4028/www.scientific.net/amm.263-266.135.

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In this paper, we account for efficient approach of direction-of-arrival estimation based on sparse reconstruction of sensor measurements with an overcomplete basis. MSD-FOCUSS ( MMV Synchronous Descending FOCal Underdetermined System Solver) algorithm is developed against to sparse reconstruction in multiple-measurement-vectors (MMV) system where noise perturbations exist in both the measurements and sensing matrix. The paper shows how sparse-signal model of DOA estimation is established and MSD-FOCUSS is derived, then the simulation results illustrate the advantage of MSD-FOCUSS when it is used to solve the problem of DOA estimation.

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Kim, Jae Gyoon, Kyoung Tak Kang et Joon Ho Wang. « Biomechanical Difference between Conventional Transtibial Single-Bundle and Anatomical Transportal Double-Bundle Anterior Cruciate Ligament Reconstruction Using Three-Dimensional Finite Element Model Analysis ». Journal of Clinical Medicine 10, n^o 8 (12 avril 2021) : 1625. http://dx.doi.org/10.3390/jcm10081625.

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The purpose of our study was to analyze the graft contact stress at the tunnel after transtibial single-bundle (SB) and transportal double-bundle (DB) anterior cruciate ligament (ACL) reconstruction. After transtibial SB (20 cases) and transportal DB (29 cases) ACL reconstruction, the three-dimensional image of each patient made by postoperative computed tomography was adjusted to the validation model of a normal knee and simulated SB and DB ACL reconstructions were created based on the average tunnel position and direction of each group. We also measured graft and contact stresses at the tunnel after a 134 N anterior load from 0° to 90° flexion. The graft and contact stresses became the greatest at 30° and 0° flexion, respectively. The total graft and contact stresses after DB ACL reconstruction were greater than those after SB ACL reconstruction from 0° to 30° and 0° to 90° knee flexion, respectively. However, the graft and contact stresses of each graft after DB ACL reconstruction were less than those after SB ACL reconstruction. In conclusion, the total graft and total contact stresses after DB ACL reconstruction are higher than those after SB ACL reconstruction from 0° to 30° and 0° to 90° knee flexion, respectively. However, the stresses of each graft after DB ACL reconstruction are about half of those after SB ACL reconstruction.

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Thiel, Andreas, Martin Greschner, Christian W. Eurich, Josef Ammermüller et Jutta Kretzberg. « Contribution of Individual Retinal Ganglion Cell Responses to Velocity and Acceleration Encoding ». Journal of Neurophysiology 98, n^o 4 (octobre 2007) : 2285–96. http://dx.doi.org/10.1152/jn.01342.2006.

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We investigate the capability of turtle retinal ganglion cell (RGC) ensembles to simultaneously encode multiple aspects of visual motion: speed, direction, and acceleration of moving patterns. Bayesian stimulus reconstruction reveals that the instantaneous firing rates of RGCs contain information about all of these stimulus properties. Stimulus velocity is mainly encoded by steady-state firing rates, whereas acceleration can be reconstructed from transient components in RGC activity induced by abrupt velocity changes. Therefore neurons in higher brain areas may in principle extract information about changing velocity from the instantaneous firing activity of RGCs, without the need to compare responses to present velocities to previous ones. However, reconstruction requires the estimation of a combined acceleration and velocity signal, indicating that RGC ensembles signal both properties simultaneously. In accordance with this conclusion, combined velocity/acceleration sensitivity enhances the similarity of artificial spike trains to experimental data by 50% compared with the case of pure velocity tuning. Decoding of motion direction in addition to speed and acceleration requires direction-sensitive cells, which generate higher firing rates for one of the motion directions and therefore show asymmetric velocity tuning. By dividing the entire ensemble of simultaneously recorded cells into one group of direction-sensitive cells and one group with symmetric tuning, we demonstrate that the population of direction-sensitive cells encodes a combination of motion speed, acceleration, and direction. However, estimation of velocity and acceleration is improved by including the larger group of RGC responses that are sensitive to speed but not to motion direction.

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Yan, Bin, Zhao Jin, Hanming Zhang, Lei Li et Ailong Cai. « NUFFT-Based Iterative Image Reconstruction via Alternating Direction Total Variation Minimization for Sparse-View CT ». Computational and Mathematical Methods in Medicine 2015 (2015) : 1–9. http://dx.doi.org/10.1155/2015/691021.

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Sparse-view imaging is a promising scanning method which can reduce the radiation dose in X-ray computed tomography (CT). Reconstruction algorithm for sparse-view imaging system is of significant importance. The adoption of the spatial iterative algorithm for CT image reconstruction has a low operation efficiency and high computation requirement. A novel Fourier-based iterative reconstruction technique that utilizes nonuniform fast Fourier transform is presented in this study along with the advanced total variation (TV) regularization for sparse-view CT. Combined with the alternating direction method, the proposed approach shows excellent efficiency and rapid convergence property. Numerical simulations and real data experiments are performed on a parallel beam CT. Experimental results validate that the proposed method has higher computational efficiency and better reconstruction quality than the conventional algorithms, such as simultaneous algebraic reconstruction technique using TV method and the alternating direction total variation minimization approach, with the same time duration. The proposed method appears to have extensive applications in X-ray CT imaging.

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Zhou, Bin, Dong-jun Ye, Wei Wei et Marcin Wozniak. « Alternating Direction Projections onto Convex Sets for Super-Resolution Image Reconstruction ». Information Technology And Control 49, n^o 1 (25 mars 2020) : 179–90. http://dx.doi.org/10.5755/j01.itc.49.1.24121.

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Image reconstruction is important in computer vision and many technologies have been presented to achieve better results. In this paper, gradient information is introduced to define new convex sets. A novel POCS-based model is proposed for super resolution reconstruction. The projection on the convex sets is alternative according to the gray value field and the gradient field. Then the local noise estimation is introduced to determine the threshold adaptively. The efficiency of our proposed model is verified by several numerical experiments. Experimental results show that, the PSNR and the SSIM can be both significantly improved by the proposed model.

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Aslan, Selin, Viktor Nikitin, Daniel J. Ching, Tekin Bicer, Sven Leyffer et Doğa Gürsoy. « Joint ptycho-tomography reconstruction through alternating direction method of multipliers ». Optics Express 27, n^o 6 (14 mars 2019) : 9128. http://dx.doi.org/10.1364/oe.27.009128.

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Maki, Atsuto. « Estimation of illuminant direction and surface reconstruction by Geotensity constraint ». Pattern Recognition Letters 21, n^o 13-14 (décembre 2000) : 1115–23. http://dx.doi.org/10.1016/s0167-8655(00)00072-6.

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