Artykuły w czasopismach: „Parallel Smoothers”

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Xie, Dexuan. "Analysis of a Class of Parallel Multigrid Smoothers". BIT Numerical Mathematics 44, nr 4 (grudzień 2004): 813–28. http://dx.doi.org/10.1007/s10543-004-3830-y.

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Yang, Xiang, i Rajat Mittal. "Efficient relaxed-Jacobi smoothers for multigrid on parallel computers". Journal of Computational Physics 332 (marzec 2017): 135–42. http://dx.doi.org/10.1016/j.jcp.2016.12.010.

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Poddar, Shashi, i John L. Crassidis. "Adaptive Lag Smoother for State Estimation". Sensors 22, nr 14 (15.07.2022): 5310. http://dx.doi.org/10.3390/s22145310.

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Fixed-lag smoothing has been used across different disciplines for offline analysis in many applications. With rising computational power and parallel processing architectures, fixed-lag smoothers are increasingly integrated into online processing system with small delays. This delay is directly related to the lag-length used in system design, which needs to be chosen appropriately. In this work, an adaptive approach is devised to choose an appropriate lag-length that provides a good trade-off between accuracy and computational requirements. The analysis shown in this paper for the error dynamics of the fixed-lag smoother over the lags helps in understanding its saturation over increasing lags. In order to provide the empirical results, simulations are carried out over a second-order Newtonian system, single-axis attitude estimation, Van der Pol’s oscillator, and three-axis attitude estimation. The simulation results demonstrate the performance achieved with an adaptive-lag smoother as compared to a fixed-lag smoother with very high lag-length.

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CIEGIS, R., F. GASPAR i C. RODRIGO. "On The Parallel Multiblock Geometric Multigrid Algorithm". Computational Methods in Applied Mathematics 8, nr 3 (2008): 223–36. http://dx.doi.org/10.2478/cmam-2008-0016.

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Abstract The application of a parallel multiblock geometric multigrid is consid-ered. It is applied to solve a two-dimensional poroelastic model. This system of PDEs is approximated by a special stabilized monotone finite-difference scheme. The obtained system of linear algebraic equations is solved by a multigrid method, when a domain is partitioned into structured blocks. A new strategy for the solution of the discrete problem on the coarsest grid is proposed and the efficiency of the obtained algorithm is investigated. The geometrical structure of the sequential multigrid method is used to develop a parallel version of the multigrid algorithm. The convergence properties of several smoothers are investigated and some computational results are presented.

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Axelsson, O. "Analysis of incomplete matrix factorizations as multigrid smoothers for vector and parallel computers". Applied Mathematics and Computation 19, nr 1-4 (lipiec 1986): 3–22. http://dx.doi.org/10.1016/0096-3003(86)90094-9.

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John, Volker, i Lutz Tobiska. "Numerical performance of smoothers in coupled multigrid methods for the parallel solution of the incompressible Navier-Stokes equations". International Journal for Numerical Methods in Fluids 33, nr 4 (2000): 453–73. http://dx.doi.org/10.1002/1097-0363(20000630)33:4<453::aid-fld15>3.0.co;2-0.

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Holmes, Steven J., Peter J. Wright i Robert J. Fryer. "Evidence from survey data for regional variability in cod dynamics in the North Sea and West of Scotland". ICES Journal of Marine Science 65, nr 2 (25.01.2008): 206–15. http://dx.doi.org/10.1093/icesjms/fsm192.

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Abstract Holmes, S. J., Wright, P. J., and Fryer, R. J. 2008. Evidence from survey data for regional variability in cod dynamics in the North Sea and West of Scotland. – ICES Journal of Marine Science, 65: 206–215. Although cod (Gadus morhua) in the North Sea and ICES Division VIa are assessed as single units, recent research suggests that the stocks consist of reproductively isolated subpopulations within a metapopulation. We investigate whether temporal trends in stock indicators are asynchronous across subpopulations, which would support the metapopulation hypothesis. First quarter trawl survey data for the years 1983–2005 were aggregated into putative areas of high spawner fidelity (three in VIa, seven in the North Sea) to obtain indices of spawning–stock biomass (SSB) and recruitment (numbers-at-age 1). Asynchrony was investigated by fitting a smoother to the data for each of the ten spawning areas and testing whether the smoothers were parallel. Trends in SSB differed between spawning areas in both VIa and the North Sea. In VIa, SSB collapsed in the most southwesterly area, but remained more constant elsewhere. In the North Sea, there was a general decline in SSB, but areas thought to contain resident inshore populations showed more rapid declines than those in adjacent offshore areas. Recruitment results offered less support for a metapopulation, although recruitment in the southern North Sea declined rapidly before any trend was seen for the North Sea as a whole.

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Gräbel, Jens, Bruno Lang i Peer Ueberholz. "Performance Optimization for the Parallel Gauss-Seidel Smoother". PAMM 5, nr 1 (grudzień 2005): 831–32. http://dx.doi.org/10.1002/pamm.200510387.

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Soanca, Andrada, Alexandra Roman, Andreea Ciurea, Iulia Cristina Micu, Andrei Picos i Sofia Iozon (Ene). "The evaluation of root surface modifications after different subgingival mechanical instrumentation techniques – an in vitro study". Romanian Journal of Stomatology 69, nr 1 (31.03.2023): 43–49. http://dx.doi.org/10.37897/rjs.2023.1.8.

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Objectives. The aim of this in vitro study was to observe through scanning electron microscopy (SEM) the surface morphology of root samples treated with different mechanical instrumentation methods and the additional application of a nano-colloidal silver-based antiseptic solution. Material and methods. Root samples were prepared from extracted molars and divided in four groups: group 1 of samples was instrumented with Gracey curette (7/8), group 2 of samples was instrumented with ultrasonic tip 1S, group 3 of samples was instrumented with ultrasonic tips 1S plus H4R/L, group 4 of samples was treated with ultrasonic tips 1S plus H4R/L and application of the silver-based antiseptic solution. All samples were then subjected to SEM examination. Outcomes. Group 1 of samples presented a smoother surface compared to the samples in the other groups. Group 2, 3 and 4 displayed superficial grooves parallel to the direction of action of the ultrasonic tip. In group 3 and 4, root planning with tip H4R/L did not ameliorate the smoothness of the surface. The smear layer was present, regardless the instrumentation method. In group 4, the additional application of the antiseptic solution did not influence the surface morphology or the amount of smear layer. Conclusions. Gracey curettes created a smoother radicular surface compared to ultrasonic tips. Smear layer was obvious on the radicular surfaces, no matter the instrumentation method. The application of the silver-based antiseptic solution had no additional impact on surface morphology.

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Wang, Zhaojie, Feifeng Zheng i Ming Liu. "Identical Parallel Machine Scheduling Considering Workload Smoothness Index". Applied Sciences 13, nr 15 (28.07.2023): 8720. http://dx.doi.org/10.3390/app13158720.

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Workload balance is significant in the manufacturing industry. However, on the one hand, some existing specific criteria cannot achieve the minimization workload imbalance of parallel machines. On the other hand, there are few algorithms in existing studies that can effectively solve the parallel machine scheduling problem with the objective of minimizing workload imbalance. Inspired by this, we investigate an identical parallel machine scheduling problem with the objective of the minimum workload smoothness index. We first establish a mathematical model for the considered problem and then linearize its objective function. We prove the NP-hardness of the problem by reducing the PARTITION problem to it, and we provide both the upper bound and lower bound of the studied problem. An efficient genetic algorithm and an improved list scheduling algorithm are also proposed to efficiently address the considered problem. The numerical results demonstrate the effectiveness of the proposed methods.

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Carbonari, Luca, Luca Bruzzone i Massimo Callegari. "Impedance Control of a Spherical Parallel Platform". International Journal of Intelligent Mechatronics and Robotics 1, nr 1 (styczeń 2011): 40–60. http://dx.doi.org/10.4018/ijimr.2011010103.

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This article describes the impedance control of an in-parallel actuated orientation platform. The algorithm is based on a representation of platform orientation which exploits the equivalent axis of rotation: this approach is more intuitive and easier to visualize than conventional methods based on Cardan or Euler angles. Moreover, since for small angular displacements the Mozzi’s axis lies very close to angular velocity, impedance control algorithms based on such representation provides better performances and smoother motions. Results of numerical simulations and experimental tests are shown and commented with reference to the spherical parallel machine.

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Nakasato, Naohito, Masao Mori i Ken'ichi Nomoto. "Smoothed Particle Hydrodynamics with GRAPE and Parallel Virtual Machine". Astrophysical Journal 484, nr 2 (sierpień 1997): 608–17. http://dx.doi.org/10.1086/304352.

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Anderson, A. J. "A parallel implementation of a smoothed adaptive deconvolution filter". Journal of Microcomputer Applications 15, nr 2 (kwiecień 1992): 157–68. http://dx.doi.org/10.1016/0745-7138(92)90057-c.

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Huang, X., K. Hu, X. Ling, Y. Zhang, Z. Lu i G. Zhou. "GLOBAL PATCH MATCHING". ISPRS Annals of Photogrammetry, Remote Sensing and Spatial Information Sciences IV-2/W4 (13.09.2017): 227–34. http://dx.doi.org/10.5194/isprs-annals-iv-2-w4-227-2017.

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This paper introduces a novel global patch matching method that focuses on how to remove fronto-parallel bias and obtain continuous smooth surfaces with assuming that the scenes covered by stereos are piecewise continuous. Firstly, simple linear iterative cluster method (SLIC) is used to segment the base image into a series of patches. Then, a global energy function, which consists of a data term and a smoothness term, is built on the patches. The data term is the second-order Taylor expansion of correlation coefficients, and the smoothness term is built by combing connectivity constraints and the coplanarity constraints are combined to construct the smoothness term. Finally, the global energy function can be built by combining the data term and the smoothness term. We rewrite the global energy function in a quadratic matrix function, and use least square methods to obtain the optimal solution. Experiments on Adirondack stereo and Motorcycle stereo of Middlebury benchmark show that the proposed method can remove fronto-parallel bias effectively, and produce continuous smooth surfaces.

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Kashi, Aditya, Syam Vangara, Siva Nadarajah i Patrice Castonguay. "Asynchronous fine-grain parallel implicit smoother in multigrid solvers for compressible flow". Computers & Fluids 198 (luty 2020): 104255. http://dx.doi.org/10.1016/j.compfluid.2019.104255.

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Fryer, Christopher L., Gabriel Rockefeller i Michael S. Warren. "SNSPH: A Parallel Three‐dimensional Smoothed Particle Radiation Hydrodynamics Code". Astrophysical Journal 643, nr 1 (20.05.2006): 292–305. http://dx.doi.org/10.1086/501493.

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Holmes, Steven J., Colin P. Millar, Robert J. Fryer i Peter J. Wright. "Gadoid dynamics: differing perceptions when contrasting stock vs. population trends and its implications to management". ICES Journal of Marine Science 71, nr 6 (15.05.2014): 1433–42. http://dx.doi.org/10.1093/icesjms/fsu075.

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Recent research suggests that ICES stock definitions for cod, haddock, and whiting of “west of Scotland” and “North Sea”, do not reflect underlying population structures. As population responses to different vital rates and local pressures would be expected to lead to asynchrony in dynamics, we examined trends in local spawning-stock biomass (SSB) among putative subpopulations of the three species. Delineation of subpopulation boundaries around spawning time was made based on genetic, tagging, and otolith microchemistry studies together with density distributions of species based on research vessel survey data. Subpopulation specific indices of SSB were derived using numbers-at-age and maturity observations from the same research vessel data and asynchrony was assessed by fitting a smoother to log SSB for each subpopulation and testing whether the smooths were parallel. Results for cod support the hypothesis of distinct inshore and larger offshore subpopulations and for whiting for northern and southern North Sea subpopulations with a boundary associated with the 50 m depth contour. In haddock, no difference in SSB trends between the North Sea and west of Scotland was found. For cod and whiting, subpopulation SSB trends differed substantially within current stock assessment units, implying reported stock-based SSB time-series have masked underlying subpopulation trends.

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Wang, Pinqiang, Mengbin Zhu, Yan Chen i Weimin Zhang. "Implicit Equal-Weights Variational Particle Smoother". Atmosphere 11, nr 4 (30.03.2020): 338. http://dx.doi.org/10.3390/atmos11040338.

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Under the motivation of the great success of four-dimensional variational (4D-Var) data assimilation methods and the advantages of ensemble methods (e.g., Ensemble Kalman Filters and Particle Filters) in numerical weather prediction systems, we introduce the implicit equal-weights particle filter scheme in the weak constraint 4D-Var framework which avoids the filter degeneracy through implicit sampling in high-dimensional situations. The new variational particle smoother (varPS) method has been tested and explored using the Lorenz96 model with dimensions N x = 40 , N x = 100 , N x = 250 , and N x = 400 . The results show that the new varPS method does not suffer from the curse of dimensionality by construction and the root mean square error (RMSE) in the new varPS is comparable with the ensemble 4D-Var method. As a combination of the implicit equal-weights particle filter and weak constraint 4D-Var, the new method improves the RMSE compared with the implicit equal-weights particle filter and LETKF (local ensemble transformed Kalman filter) methods and enlarges the ensemble spread compared with ensemble 4D-Var scheme. To overcome the difficulty of the implicit equal-weights particle filter in real geophysical application, the posterior error covariance matrix is estimated using a limited ensemble and can be calculated in parallel. In general, this new varPS performs slightly better in ensemble quality (the balance between the RMSE and ensemble spread) than the ensemble 4D-Var and has the potential to be applied into real geophysical systems.

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Jenkins, David R. "Differential contrast enhancement of digital image information by PC-based massively parallel processing". Proceedings, annual meeting, Electron Microscopy Society of America 52 (1994): 516–17. http://dx.doi.org/10.1017/s0424820100170311.

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Digital images represent two-dimensional intensity maps which characterize the spacial x/y distribution of contrast information. Often, small detail contrasts are visaully unrecognizable due to the prevalence of large contrast components which, inversely proportional to their extent, compress the intensity range of the detail contrasts. A new “pixel-accurate intensity processing” (PAIP) technology provides unrestricted access to and display of all detail information contained in digital images independent of content, size and depth (8-16 bit). It offers an exciting new way for objective and exhaustive digital image evaluation in near-real-time.We developed a PC-based massively parallel processing workstation (PiXision) for fast, artifact free differential contrast extraction utilizing the PAIP technology. Information extraction and enhancement requires only a few digital processing steps (Fig. 1): 1. The original image is smoothed with pixelaccurate precision within a significant intensity range (IRS) using the PAIP technology; 2. The smoothed image may additionally be subtracted from the original generating a detail image; 3. Finally, the smoothed or detail images are linearly scaled to 8-bit providing full visual intensity range. The basic software routine “smoolhens” an image to any significant intensity range without spacial artifacts, using a variable automatically adjusting local mask for pixel averaging.

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Mandel, J., E. Bergou, S. Gürol, S. Gratton i I. Kasanický. "Hybrid Levenberg–Marquardt and weak-constraint ensemble Kalman smoother method". Nonlinear Processes in Geophysics 23, nr 2 (11.03.2016): 59–73. http://dx.doi.org/10.5194/npg-23-59-2016.

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Abstract. The ensemble Kalman smoother (EnKS) is used as a linear least-squares solver in the Gauss–Newton method for the large nonlinear least-squares system in incremental 4DVAR. The ensemble approach is naturally parallel over the ensemble members and no tangent or adjoint operators are needed. Furthermore, adding a regularization term results in replacing the Gauss–Newton method, which may diverge, by the Levenberg–Marquardt method, which is known to be convergent. The regularization is implemented efficiently as an additional observation in the EnKS. The method is illustrated on the Lorenz 63 model and a two-level quasi-geostrophic model.

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Mandel, J., E. Bergou, S. Gürol i S. Gratton. "Hybrid Levenberg–Marquardt and weak constraint ensemble Kalman smoother method". Nonlinear Processes in Geophysics Discussions 2, nr 3 (26.05.2015): 865–902. http://dx.doi.org/10.5194/npgd-2-865-2015.

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Abstract. We propose to use the ensemble Kalman smoother (EnKS) as the linear least squares solver in the Gauss–Newton method for the large nonlinear least squares in incremental 4DVAR. The ensemble approach is naturally parallel over the ensemble members and no tangent or adjoint operators are needed. Further, adding a regularization term results in replacing the Gauss–Newton method, which may diverge, by the Levenberg–Marquardt method, which is known to be convergent. The regularization is implemented efficiently as an additional observation in the EnKS. The method is illustrated on the Lorenz 63 and the two-level quasi-geostrophic model problems.

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Fu, Lin, Zhe Ji, Xiangyu Y. Hu i Nikolaus A. Adams. "Parallel fast-neighbor-searching and communication strategy for particle-based methods". Engineering Computations 36, nr 3 (8.04.2019): 899–929. http://dx.doi.org/10.1108/ec-05-2018-0226.

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Purpose This paper aims to develop a parallel fast neighbor search method and communication strategy for particle-based methods with adaptive smoothing-length on distributed-memory computing systems. Design/methodology/approach With a multi-resolution-based hierarchical data structure, the parallel neighbor search method is developed to detect and construct ghost buffer particles, i.e. neighboring particles on remote processor nodes. To migrate ghost buffer particles among processor nodes, an undirected graph is established to characterize the sparse data communication relation and is dynamically recomposed. By the introduction of an edge coloring algorithm from graph theory, the complex sparse data exchange can be accomplished within optimized frequency. For each communication substep, only efficient nonblocking point-to-point communication is involved. Findings Two demonstration scenarios are considered: fluid dynamics based on smoothed-particle hydrodynamics with adaptive smoothing-length and a recently proposed physics-motivated partitioning method [Fu et al., JCP 341 (2017): 447-473]. Several new concepts are introduced to recast the partitioning method into a parallel version. A set of numerical experiments is conducted to demonstrate the performance and potential of the proposed parallel algorithms. Originality/value The proposed methods are simple to implement in large-scale parallel environment and can handle particle simulations with arbitrarily varying smoothing-lengths. The implemented smoothed-particle hydrodynamics solver has good parallel performance, suggesting the potential for other scientific applications.

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Roth, L., i H. Mayer. "REDUCTION OF THE FRONTO-PARALLEL BIAS FOR WIDE-BASELINE SEMI-GLOBAL MATCHING". ISPRS Annals of Photogrammetry, Remote Sensing and Spatial Information Sciences IV-2/W5 (29.05.2019): 69–76. http://dx.doi.org/10.5194/isprs-annals-iv-2-w5-69-2019.

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<p><strong>Abstract.</strong> Semi-Global Matching (SGM) is a widely-used technique for dense image matching that is popular because of its accuracy and speed. While it works well for textured scenes, it can fail on slanted surfaces particularly in wide-baseline configurations due to the so-called fronto-parallel bias. In this paper, we propose an extension of SGM that utilizes image warping to reduce the fronto-parallel bias in the data term, based on estimating dominant slanted planes. The latter are also used as surface priors improving the smoothness term. Our proposed method calculates disparity maps for each dominant slanted plane and fuses them to obtain the final disparity map. We have quantitatively evaluated our approach outperforming SGM and SGM-P on synthetic data and demonstrate its potential on real data by qualitative results. In this way, we underscore the need to tackle the fronto-parallel bias in particular for wide-baseline configurations in both the data term and the smoothness term of SGM.</p>

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Vu, Trieu Minh, Reza Moezzi, Jindrich Cyrus, Jaroslav Hlava i Michal Petru. "Parallel Hybrid Electric Vehicle Modelling and Model Predictive Control". Applied Sciences 11, nr 22 (12.11.2021): 10668. http://dx.doi.org/10.3390/app112210668.

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This paper presents the modelling and calculations for a hybrid electric vehicle (HEV) in parallel configuration, including a main electrical driving motor (EM), an internal combustion engine (ICE), and a starter/generator motor. The modelling equations of the HEV include vehicle acceleration and jerk, so that simulations can investigate the vehicle drivability and comfortability with different control parameters. A model predictive control (MPC) scheme with softened constraints for this HEV is developed. The new MPC with softened constraints shows its superiority over the MPC with hard constraints as it provides a faster setpoint tracking and smoother clutch engagement. The conversion of some hard constraints into softened constraints can improve the MPC stability and robustness. The MPC with softened constraints can maintain the system stability, while the MPC with hard constraints becomes unstable if some input constraints lead to the violation of output constraints.

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Loiseau, Julien, Hyun Lim, Mark Alexander Kaltenborn, Oleg Korobkin, Christopher M. Mauney, Irina Sagert, Wesley P. Even i Benjamin K. Bergen. "FleCSPH: The next generation FleCSIble parallel computational infrastructure for smoothed particle hydrodynamics". SoftwareX 12 (lipiec 2020): 100602. http://dx.doi.org/10.1016/j.softx.2020.100602.

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Crespo, A. J. C., J. M. Domínguez, B. D. Rogers, M. Gómez-Gesteira, S. Longshaw, R. Canelas, R. Vacondio, A. Barreiro i O. García-Feal. "DualSPHysics: Open-source parallel CFD solver based on Smoothed Particle Hydrodynamics (SPH)". Computer Physics Communications 187 (luty 2015): 204–16. http://dx.doi.org/10.1016/j.cpc.2014.10.004.

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Plimpton, Steve, Steve Attaway, Bruce Hendrickson, Jeff Swegle, Courtenay Vaughan i David Gardner. "Parallel Transient Dynamics Simulations: Algorithms for Contact Detection and Smoothed Particle Hydrodynamics". Journal of Parallel and Distributed Computing 50, nr 1-2 (kwiecień 1998): 104–22. http://dx.doi.org/10.1006/jpdc.1998.1433.

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Jun, Zhou, Wang Qiong i Cheng Cheng. "Geomagnetic gradient bionic navigation based on the parallel approaching method". Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 233, nr 9 (10.08.2018): 3131–40. http://dx.doi.org/10.1177/0954410018793290.

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The priori geomagnetic map, which is difficult to obtain in practice, has a great effect on geomagnetic-aided navigation. In this paper, we propose a geomagnetic gradient bionic navigation method based on parallel approaching without a reference map. From the viewpoint of bionics, an objective function is developed to describe the convergence of geomagnetic navigation. According to the parallel approaching method, the radio equation of geomagnetic variation is proposed, and the heading angle is obtained by the least squares approximation method with geomagnetic gradient data. Simulation results show the proposed approach is able to navigate effectively without a magnetic priori map. Several experiments on different geomagnetic parameters are discussed, and a recommended method of parameter selection is presented. Our approach is also compared with the evolution method, and results in a more smoother and direct navigation path to the destination.

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Cochran, W. George, Joel H. Shapiro i David C. Ullrich. "Random Dirichlet Functions: Multipliers and Smoothness". Canadian Journal of Mathematics 45, nr 2 (1.04.1993): 255–68. http://dx.doi.org/10.4153/cjm-1993-012-6.

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AbstractWe show that if is a holomorphic function in the Dirichlet space of the unit disk, then almost all of its randomizations are multipliers of that space. This parallels a known result for lacunary power series, which also has a version for smoothness classes: every lacunary Dirichlet series lies in the Lipschitz class Lip1/2 of functions obeying a Lipschitz condition with exponent 1/2. However, unlike the lacunary situation, no corresponding “almost sure” Lipschitz result is possible for random series: we exhibit a Dirichlet function with norandomization in Lip1/2. We complement this result with a “best possible” sufficient condition for randomizations to belong almost surely to Lip1/2. Versions of our results hold for weighted Dirichlet spaces, and much of our work is carried out in this more general setting.

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Gao, Qun, Yan Jiang, Ke Peng i Lei Liu. "A Virtual Inertia Method for Stability Control of DC Distribution Systems with Parallel Converters". Energies 15, nr 22 (16.11.2022): 8581. http://dx.doi.org/10.3390/en15228581.

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DC distribution systems are a typical power electronic system with low inertia, low-rotational kinetic energy, and poor antidisturbance capability when loads fluctuate or parameters change. In this paper, a virtual inertia control with an additional first-order filtering link is proposed on the basis of P-Udc droop control. The results of the simulations and experiments verify that the additional inertia control reduces the voltage change rate and improves the system inertia by adjusting the virtual capacitance value on the DC side of the converter, which can achieve a smoother and more accurate voltage control and suppress the continuous voltage oscillation.

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Ni, Jinlu, Jiangping Mei i Weizhong Hu. "A hierarchical approach for rigid-body dynamics model simplification of a high-speed parallel robot by considering kinematics performance". Science Progress 104, nr 4 (październik 2021): 003685042110630. http://dx.doi.org/10.1177/00368504211063072.

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Considering the real-time control of a high-speed parallel robot, a concise and precise dynamics model is essential for the design of the dynamics controller. However, the complete rigid-body dynamics model of parallel robots is too complex for online calculation. Therefore, a hierarchical approach for dynamics model simplification, which considers the kinematics performance, is proposed in this paper. Firstly, considering the motion smoothness of the end-effector, trajectory planning based on the workspace discretization is carried out. Then, the effects of the trajectory parameters and acceleration types on the trajectory planning are discussed. But for the fifth-order and seventh-order B-spline acceleration types, the trajectory will generate excessive deformation after trajectory planning. Therefore, a comprehensive index that considers both the motion smoothness and trajectory deformation is proposed. Finally, the dynamics model simplification method based on the combined mass distribution coefficients is studied. Results show that the hierarchical approach can guarantee both the excellent kinematics performance of the parallel robot and the accuracy of the simplified dynamics model under different trajectory parameters and acceleration types. Meanwhile, the method proposed in the paper can be applied to the design of the dynamics controller to enhance the robot's performance.

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Mei, Jiangping, Fan Zhang, Jiawei Zang, Yanqin Zhao i Han Yan. "Trajectory optimization of the 6-degrees-of-freedom high-speed parallel robot based on B-spline curve". Science Progress 103, nr 1 (10.10.2019): 003685041988011. http://dx.doi.org/10.1177/0036850419880115.

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According to the problem that the existing high-speed parallel robot cannot satisfy the operation requirements of non-planar industrial production line, a 6-degrees-of-freedom high-speed parallel robot is proposed to carry out the kinematic and dynamic analyses. Combining with the door-type trajectory commonly used by the parallel robot, it adopts 3-, 5-, and 7-time B-spline curve motion law to conduct the trajectory planning in operation space. Taking the average cumulative effect of joint jerky as the optimization target, a trajectory optimization method is proposed to improve the smoothness of robot end-effector motion with the selected motion law. Furthermore, to solve the deformation problem of the horizontal motion stage of the trajectory, a mapping model between the control point subset of B-spline and the motion point subset of trajectory is established. Based on the main diagonally dominant characteristic of the coefficient matrix, the trajectory deformation evaluation index is constructed to optimize the smoothness and minimum deformation of the robot motion trajectory. Finally, compared to without the optimization, the maximum robot joint jerk decreases by 69.4% and 72.3%, respectively, and the maximum torque decreases by 51.4% and 38.9%, respectively, under a suitable trajectory deformation.

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Chen, Qing Lin, i Qi Lin. "Analysis on Metamorphic of the Cable-Driven Parallel Mechanism in Wind Tunnel Test". Applied Mechanics and Materials 336-338 (lipiec 2013): 1196–203. http://dx.doi.org/10.4028/www.scientific.net/amm.336-338.1196.

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The workspace is limited in the fixed parameters of cable-driven parallel mechanism and interference often happens between cables and surfaces of actuator. The fundamental basis of metamorphic mechanisms is addressed in accordance with the design, kinematics and dynamics, as well as the compliant metamorphic mechanisms. Metamorphic structure was applied to the cable-driven parallel mechanism. The more adaptive metamorphic mechanism is the full mobile hinge, which provided whole workspace of the frame. Through adding the adaptive hinge, the workspace was extended. The new methods of distant to detect interference between cables and faces of actuator was discussed and applied to a 6 DOF cable-driven parallel mechanism. Comparing with other methods of calculation of interference, it showed more accurate and provided a function to metamorphic control. The volume of interference was coherent and the force of cable was smoother to control when testing the high angle of attack.

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Casagrande, Angelo, Pénélope Leyland i Luca Formaggia. "Parallel Mesh Adaptive Techniques for Complex Flow Simulation: Geometry Conservation". Modelling and Simulation in Engineering 2012 (2012): 1–13. http://dx.doi.org/10.1155/2012/495935.

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Dynamic mesh adaptation on unstructured grids, by localised refinement and derefinement, is a very efficient tool for enhancing solution accuracy and optimising computational time. One of the major drawbacks, however, resides in the projection of the new nodes created, during the refinement process, onto the boundary surfaces. This can be addressed by the introduction of a library capable of handling geometric properties given by a CAD (computer-aided design) description. This is of particular interest also to enhance the adaptation module when the mesh is being smoothed, and hence moved, to then reproject it onto the surface of the exact geometry.

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Lind, Steven J., Benedict D. Rogers i Peter K. Stansby. "Review of smoothed particle hydrodynamics: towards converged Lagrangian flow modelling". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 476, nr 2241 (wrzesień 2020): 20190801. http://dx.doi.org/10.1098/rspa.2019.0801.

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This paper presents a review of the progress of smoothed particle hydrodynamics (SPH) towards high-order converged simulations. As a mesh-free Lagrangian method suitable for complex flows with interfaces and multiple phases, SPH has developed considerably in the past decade. While original applications were in astrophysics, early engineering applications showed the versatility and robustness of the method without emphasis on accuracy and convergence. The early method was of weakly compressible form resulting in noisy pressures due to spurious pressure waves. This was effectively removed in the incompressible (divergence-free) form which followed; since then the weakly compressible form has been advanced, reducing pressure noise. Now numerical convergence studies are standard. While the method is computationally demanding on conventional processors, it is well suited to parallel processing on massively parallel computing and graphics processing units. Applications are diverse and encompass wave–structure interaction, geophysical flows due to landslides, nuclear sludge flows, welding, gearbox flows and many others. In the state of the art, convergence is typically between the first- and second-order theoretical limits. Recent advances are improving convergence to fourth order (and higher) and these will also be outlined. This can be necessary to resolve multi-scale aspects of turbulent flow.

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sci, global. "Parallel Smoothed Aggregation Multilevel Schwarz Preconditioned Newton-Krylov Algorithms for Poisson-Boltzmann Problems". Numerical Mathematics: Theory, Methods and Applications 13, nr 3 (czerwiec 2020): 745–69. http://dx.doi.org/10.4208/nmtma.oa-2019-0174.

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Vanaverbeke, S., R. Keppens, S. Poedts i H. Boffin. "GRADSPH: A parallel smoothed particle hydrodynamics code for self-gravitating astrophysical fluid dynamics". Computer Physics Communications 180, nr 7 (lipiec 2009): 1164–82. http://dx.doi.org/10.1016/j.cpc.2008.12.041.

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Nishiura, Daisuke, Mikito Furuichi i Hide Sakaguchi. "Computational performance of a smoothed particle hydrodynamics simulation for shared-memory parallel computing". Computer Physics Communications 194 (wrzesień 2015): 18–32. http://dx.doi.org/10.1016/j.cpc.2015.04.006.

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Dvinskikh, Darina, i Alexander Gasnikov. "Decentralized and parallel primal and dual accelerated methods for stochastic convex programming problems". Journal of Inverse and Ill-posed Problems 29, nr 3 (22.01.2021): 385–405. http://dx.doi.org/10.1515/jiip-2020-0068.

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Abstract We introduce primal and dual stochastic gradient oracle methods for decentralized convex optimization problems. Both for primal and dual oracles, the proposed methods are optimal in terms of the number of communication steps. However, for all classes of the objective, the optimality in terms of the number of oracle calls per node takes place only up to a logarithmic factor and the notion of smoothness. By using mini-batching technique, we show that the proposed methods with stochastic oracle can be additionally parallelized at each node. The considered algorithms can be applied to many data science problems and inverse problems.

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40

Yaskin, Vladyslav. "An Extension of Polynomial Integrability to Dual Quermassintegrals". International Mathematics Research Notices 2020, nr 13 (19.06.2018): 3978–90. http://dx.doi.org/10.1093/imrn/rny152.

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Abstract A bounded domain $K$ is called polynomially integrable if its parallel section function $V_{n-1}(K\cap \{\xi ^\perp +t\xi \})$ is a polynomial of $t$ (on its support) for every $\xi $. A complete characterization of such domains was given recently. Here we obtain a generalization of these results in the setting of dual quermassintegrals. We also address the associated smoothness issues.

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41

Evstigneev, N. M., F. S. Zaitsev i O. I. Ryabkov. "High-performance parallel algorithms based on smoothed particles hydrodynamics for solving continuum mechanics problems". Doklady Mathematics 90, nr 3 (listopad 2014): 773–77. http://dx.doi.org/10.1134/s1064562414060258.

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Li, Shenhong, Xiongwu Xiao, Bingxuan Guo i Lin Zhang. "A Novel OpenMVS-Based Texture Reconstruction Method Based on the Fully Automatic Plane Segmentation for 3D Mesh Models". Remote Sensing 12, nr 23 (28.11.2020): 3908. http://dx.doi.org/10.3390/rs12233908.

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The Markov Random Field (MRF) energy function, constructed by existing OpenMVS-based 3D texture reconstruction algorithms, considers only the image label of the adjacent triangle face for the smoothness term and ignores the planar-structure information of the model. As a result, the generated texture charts results have too many fragments, leading to a serious local miscut and color discontinuity between texture charts. This paper fully utilizes the planar structure information of the mesh model and the visual information of the 3D triangle face on the image and proposes an improved, faster, and high-quality texture chart generation method based on the texture chart generation algorithm of the OpenMVS. This methodology of the proposed approach is as follows: (1) The visual quality on different visual images of each triangle face is scored using the visual information of the triangle face on each image in the mesh model. (2) A fully automatic Variational Shape Approximation (VSA) plane segmentation algorithm is used to segment the blocked 3D mesh models. The proposed fully automatic VSA-based plane segmentation algorithm is suitable for multi-threaded parallel processing, which solves the VSA framework needed to manually set the number of planes and the low computational efficiency in a large scene model. (3) The visual quality of the triangle face on different visual images is used as the data term, and the image label of adjective triangle and result of plane segmentation are utilized as the smoothness term to construct the MRF energy function. (4) An image label is assigned to each triangle by the minimizing energy function. A texture chart is generated by clustering the topologically-adjacent triangle faces with the same image label, and the jagged boundaries of the texture chart are smoothed. Three sets of data of different types were used for quantitative and qualitative evaluation. Compared with the original OpenMVS texture chart generation method, the experiments show that the proposed approach significantly reduces the number of texture charts, significantly improves miscuts and color differences between texture charts, and highly boosts the efficiency of VSA plane segmentation algorithm and OpenMVS texture reconstruction.

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Dao, M. H., H. Xu, E. S. Chan i P. Tkalich. "Numerical modelling of extreme waves by Smoothed Particle Hydrodynamics". Natural Hazards and Earth System Sciences 11, nr 2 (11.02.2011): 419–29. http://dx.doi.org/10.5194/nhess-11-419-2011.

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Abstract. The impact of extreme/rogue waves can lead to serious damage of vessels as well as marine and coastal structures. Such extreme waves in deep water are characterized by steep wave fronts and an energetic wave crest. The process of wave breaking is highly complex and, apart from the general knowledge that impact loadings are highly impulsive, the dynamics of the breaking and impact are still poorly understood. Using an advanced numerical method, the Smoothed Particle Hydrodynamics enhanced with parallel computing is able to reproduce well the extreme waves and their breaking process. Once the waves and their breaking process are modelled successfully, the dynamics of the breaking and the characteristics of their impact on offshore structures could be studied. The computational methodology and numerical results are presented in this paper.

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He, Enyi, i Shihao Yin. "Tooth profile design of a novel helical gear mechanism with improved geometry for a parallel shaft transmission". Mechanical Sciences 13, nr 2 (16.12.2022): 1011–18. http://dx.doi.org/10.5194/ms-13-1011-2022.

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Abstract. Based on the space curve meshing equation, a novel helical gear mechanism with improved geometry is presented. First, equations of the theoretical contact curves were derived based on the space curve meshing theory. Then, tooth surfaces with a concave–convex meshing form were constructed, depending on the contact curves. The tooth profiles were improved as the theoretical contact curves were corrected by predestining the designed transmission errors. The effect of the center distance error on the transmission errors was studied, and the effects of gear modifications on transmission errors and maximum contact stresses were also investigated. The results show that the transmission error curves of the improved gear drive become much smoother. Maximum contact stresses of the improved gear drive are decreased synchronously.

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45

Cromwell, D., A. G. P. Shaw, P. Challenor, R. E. Houseago-Stokes i R. Tokmakian. "Towards measuring the meridional overturning circulation from space". Ocean Science 3, nr 2 (14.05.2007): 223–28. http://dx.doi.org/10.5194/os-3-223-2007.

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Abstract. We present a step towards measuring the meridional overturning circulation (MOC), i.e. the full-depth water mass transport, in the North Atlantic using satellite data. Using the Parallel Ocean Climate Model, we simulate satellite observations of ocean bottom pressure and sea surface height (SSH) over the 20-year period from 1979–1998, and use a linear model to estimate the MOC. As much as 93.5% of the variability in the smoothed transport is thereby explained. This increases to 98% when SSH and bottom pressure are first smoothed. We present initial studies of predicting the time evolution of the MOC, with promising results. It should be stressed that this is an initial step only, and that to produce an actual working system for measuring the MOC from space would require considerable future work.

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46

Cromwell, D., A. G. P. Shaw, P. Challenor, R. Houseago-Stokes i R. Tokmakian. "Towards measuring the meridional overturning circulation from space". Ocean Science Discussions 3, nr 5 (6.10.2006): 1623–35. http://dx.doi.org/10.5194/osd-3-1623-2006.

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Abstract. We present a step towards measuring the meridional overturning circulation (MOC), i.e. the full-depth water mass transport, in the North Atlantic using satellite data. Using the Parallel Ocean Climate Model, we simulate satellite observations of ocean bottom pressure and sea surface height (SSH) over the 20-year period from 1979–1998, and use a linear model to estimate the MOC. As much as 93.5% of the variability in the smoothed transport is thereby explained. This increases to 98% when SSH and bottom pressure are first smoothed. We present initial studies of predicting the time evolution of the MOC, with promising results. It should be stressed that this is an initial step only, and that to produce an actual working system for measuring the MOC from space would require considerable future work.

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47

Nikolic, Nebojsa, Konstantin Popov, Zlatko Rakocevic, Dejan Djurovic, Miomir Pavlovic i Miodrag Stojanovic. "The structure of bright zinc coatings". Journal of the Serbian Chemical Society 65, nr 11 (2000): 819–27. http://dx.doi.org/10.2298/jsc0011819n.

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The structures of bright zinc coatings obtained from acid sulfate solutions in the presence of dextrin/salicyl aldehyde mixture were examined. It was shown by the STM technique that the surfaces of bright zinc coatings are covered by hexagonal zinc crystals, the tops of planes of which are flat and mutually parallel and which exhibit smoothness on the atomic level. X-Ray diffraction (XRD) analysis of the bright zinc coatings showed that the zinc crystallites are oriented in the (110) plane only.

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Koulouri, Alexandra. "Real-Time Ionospheric Imaging of S₄ Scintillation From Limited Data With Parallel Kalman Filters and Smoothness". IEEE Transactions on Geoscience and Remote Sensing 60 (2022): 1–12. http://dx.doi.org/10.1109/tgrs.2022.3140600.

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Shvachych G. G., Pobochii I. A., Barteniev H. M., Tkachenko O. G. i Tseluiko N. V. "NUMERICAL AND ANALYTICAL DIAGRAM OF A DISTRIBUTED SIMULATION OF DYNAMIC SYSTEMS". World Science 1, nr 3(43) (31.03.2019): 4–9. http://dx.doi.org/10.31435/rsglobal_ws/31032019/6397.

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The work is dedicated to the construction of numerical-analytical method of designing efficient algorithms for the solution of problems in economics and engineering. Using a priori information about the smoothness of the solution, great attention is paid to the construction of high-accuracy solutions. The proposed approach eliminates recurrent structure calculations unknown vectors decisions, which leads to the accumulation of rounding errors. Parallel form of the algorithm is the maximum, and therefore has the shortest possible time the implementation on parallel computing systems. Most conventional algorithms for solving these problems (sweep techniques, decomposition of the matrix into a product of two diagonal matrices, doubling, etc.) when multiple processors work typically no faster than if a single processor. The reason for this is substantial sequence computations of these algorithms.

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Yu, Junqi, Ruolin Li, Zengxi Feng, Anjun Zhao, Zirui Yu, Ziyan Ye i Junfeng Wang. "A Novel Parallel Ant Colony Optimization Algorithm for Warehouse Path Planning". Journal of Control Science and Engineering 2020 (1.08.2020): 1–12. http://dx.doi.org/10.1155/2020/5287189.

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In order to improve the working efficiency of automated guided vehicles (AGVs) and the processing efficiency of fulfilling orders in intelligent warehouses, a novel parallel ant colony optimization algorithm for warehouse path planning is proposed. Through the interaction of pheromones among multiple subcolonies, the coevolution of multiple subcolonies is realized and the operational capability of the algorithm is improved. Then, a multiobjective function with the object of the shortest path and the minimum number of turns of the AGV is established. And the path satisfying this objective function is obtained by the proposed algorithm. In addition, the path is further smoothed by reducing the number of intermediate nodes. The results show that the stability and convergence rate of the algorithm are faster and more stable, compared to other algorithms, in generating paths for different complexity maps. The smoothing treatment of the path significantly reduces the number of turns and the path length in the AGV driving process.

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