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Journal articles on the topic 'Explicit filtering LES'

Author: Grafiati

Published: 6 September 2023

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1

Azadani, L. N., and A. E. Staples. "Large-Eddy Simulation of Turbulent Barotropic Flows in Spectral Space on a Sphere." Journal of the Atmospheric Sciences 72, no. 5 (May 1, 2015): 1727–42. http://dx.doi.org/10.1175/jas-d-14-0183.1.

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Abstract Numerical simulations of atmospheric circulation models are limited by their finite spatial resolution, so large-eddy simulation (LES) is a preferred approach to study these models. In LES, a low-pass filter is applied to the flow field to separate the large- and small-scale motions. In implicitly filtered LES, the computational mesh and discretization schemes are considered to be the low-pass filter, while in the explicitly filtered LES approach, the filtering procedure is separated from the grid and discretization operators and allows for better control of the numerical errors. The aim of this paper is to study and compare implicitly filtered and explicitly filtered LES of atmospheric circulation models in spectral space. To achieve this goal, the results of implicitly filtered and explicitly filtered LES of a barotropic atmosphere circulation model on a sphere in spectral space are presented and compared with the results obtained from direct numerical simulation (DNS). Different numerical experiments are performed to investigate the efficiency of explicit filtering over implicit filtering under different dissipation terms and rotation rates. The study shows that explicit filtering increases the accuracy of the computations and improves the results, particularly where the location of coherent structures is concerned, a topic of particular importance in LES of atmospheric flows for climate and weather applications.

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2

Shaked, U., and E. Soroka. "Explicit solution to the unstable stationary filtering problem." IEEE Transactions on Automatic Control 31, no. 2 (February 1986): 185–89. http://dx.doi.org/10.1109/tac.1986.1104216.

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3

Wang, Wenyuan. "Generalized explicit schemes for coherence-enhancing diffusion filtering." Optical Engineering 47, no. 1 (2008): 017003. http://dx.doi.org/10.1117/1.2829765.

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4

Bose, Sanjeeb T., Parviz Moin, and Donghyun You. "Grid-independent large-eddy simulation using explicit filtering." Physics of Fluids 22, no. 10 (October 2010): 105103. http://dx.doi.org/10.1063/1.3485774.

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5

Fang, Xiaonan, Miao Wang, Ariel Shamir, and Shi‐Min Hu. "Learning Explicit Smoothing Kernels for Joint Image Filtering." Computer Graphics Forum 38, no. 7 (October 2019): 181–90. http://dx.doi.org/10.1111/cgf.13827.

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6

Dabrowska, Anita, and John Gough. "Quantum Trajectories for Squeezed Input Processes: Explicit Solutions." Open Systems & Information Dynamics 23, no. 01 (March 2016): 1650004. http://dx.doi.org/10.1142/s1230161216500049.

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We consider the quantum (trajectories) filtering equation for the case when the system is driven by Bose field inputs prepared in an arbitrary non-zero mean Gaussian state. The a posteriori evolution of the system is conditioned by the results of a single or double homodyne measurements. The system interacting with the Bose field is a single cavity mode taken initially in a Gaussian state. We show explicit solutions using the method of characteristic functions to the filtering equations exploiting the linear Gaussian nature of the problem.

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7

ECER, A., N. GOPALASWAMY, H. U. AKAY, and Y. P. CHIEN. "Digital Filtering Techniques for Parallel Computation of Explicit Schemes." International Journal of Computational Fluid Dynamics 13, no. 3 (January 2000): 211–22. http://dx.doi.org/10.1080/10618560008940899.

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8

Cuzzola, Francesco A., and Augusto Ferrante. "Explicit formulas for LMI-based H2 filtering and deconvolution." Automatica 37, no. 9 (September 2001): 1443–49. http://dx.doi.org/10.1016/s0005-1098(01)00077-2.

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9

Mathew, Joseph, Holger Foysi, and Rainer Friedrich. "A new approach to LES based on explicit filtering." International Journal of Heat and Fluid Flow 27, no. 4 (August 2006): 594–602. http://dx.doi.org/10.1016/j.ijheatfluidflow.2006.02.007.

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10

De Stefano, Giuliano, and Oleg V. Vasilyev. "Wavelet-based adaptive large-eddy simulation with explicit filtering." Journal of Computational Physics 238 (April 2013): 240–54. http://dx.doi.org/10.1016/j.jcp.2012.09.030.

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11

Zhong, Jiang, Yi Feng Cheng, and Shi Tao Deng. "Web Recommendation Based on Unified Collaborative Filtering." Advanced Materials Research 219-220 (March 2011): 887–91. http://dx.doi.org/10.4028/www.scientific.net/amr.219-220.887.

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Web usage mining technique is widely used for Web recommendation, which customizes Web content to user-preferred style. Traditional techniques of Web usage mining can only discover usage pattern explicitly. In order to employ the users’ feature and web pages’ attributes to get more accuracy recommendation, we propose a unified collaborative filtering model for web recommendation which combined the latent and external features of users and web page through back propagation neural networks. In the algorithm, we employ Probabilistic Latent Semantic Analysis (PLSA) method to get latent features. The main advantages of this technique over standard memory-based methods are the higher accuracy, constant time prediction, and an explicit and compact model representation. The preliminary experimental evaluation shows that substantial improvements in accuracy over existing methods can be obtained.

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12

Dev, Ashwani, and George A. McMechan. "Spatial antialias filtering in the slowness-frequency domain." GEOPHYSICS 74, no. 2 (March 2009): V35—V42. http://dx.doi.org/10.1190/1.3052115.

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A rigorous, explicit spatial antialias filter is designed and applied to spatially coarsely sampled seismic data by removing all energy above the first Nyquist wavenumber, and aliased energy that is folded back across the Nyquist, in the horizontal slowness-frequency domain. The spatial filtering in the slowness-frequency domain is explicit, free from any event linearity assumption, and does not require any interpolation. The spatially aliased energy is dispersive, and present at small and large slownesses. Comparison of the output data after antialias spatial filtering, with output data after conventional antialias frequency filtering, shows that the filter removes the spatially aliased frequencies selectively at each slowness; antialias low-pass frequency filtering under- or overcorrects for spatial aliasing at all slownesses. A seismic gather can be spatially dealiased only at the expense of wavelet spectral changes; dealiasing and preservation of amplitude variations with offset are not simultaneously possible.

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13

Lin, Hong-Dar, Huan-Hua Tsai, Chou-Hsien Lin, and Hung-Tso Chang. "Optical Panel Inspection Using Explicit Band Gaussian Filtering Methods in Discrete Cosine Domain." Sensors 23, no. 3 (February 3, 2023): 1737. http://dx.doi.org/10.3390/s23031737.

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Capacitive touch panels (CTPs) have the merits of being waterproof, antifouling, scratch resistant, and capable of rapid response, making them more popular in various touch electronic products. However, the CTP has a multilayer structure, and the background is a directional texture. The inspection work is more difficult when the defect area is small and occurs in the textured background. This study focused mainly on the automated defect inspection of CTPs with structural texture on the surface, using the spectral attributes of the discrete cosine transform (DCT) with the proposed three-way double-band Gaussian filtering (3W-DBGF) method. With consideration to the bandwidth and angle of the high-energy region combined with the characteristics of band filtering, threshold filtering, and Gaussian distribution filtering, the frequency values with higher energy are removed, and after reversal to the spatial space, the textured background can be weakened and the defects enhanced. Finally, we use simple statistics to set binarization threshold limits that can accurately separate defects from the background. The detection outcomes showed that the flaw detection rate of the DCT-based 3W-DBGF approach was 94.21%, the false-positive rate of the normal area was 1.97%, and the correct classification rate was 98.04%.

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14

Sallam, Rouhia, M. Hussien, and Hamdy Mousa. "Collaborative Filtering Using Explicit and Implicit Ratings for Arabic Dataset." IJCI. International Journal of Computers and Information 8, no. 2 (December 1, 2021): 17–25. http://dx.doi.org/10.21608/ijci.2021.207735.

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15

Spachmann, H., R. Schuhmann, S. Setzer, and T. Weiland. "Explicit temporal integrators for low-pass filtering of FDTD signals." IEEE Antennas and Wireless Propagation Letters 1 (2002): 150–53. http://dx.doi.org/10.1109/lawp.2002.807571.

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16

Nouri, N. M., S. Yekani Motlagh, E. Yasari, and N. Mobadersany. "Investigation of the explicit cutoff filtering in Large Eddy Simulation." Progress in Computational Fluid Dynamics, An International Journal 12, no. 1 (2012): 1. http://dx.doi.org/10.1504/pcfd.2012.044849.

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17

Tuia, Devis, Jordi Munoz-Mari, Jose Luis Rojo-Alvarez, Manel Martinez-Ramon, and Gustavo Camps-Valls. "Explicit Recursive and Adaptive Filtering in Reproducing Kernel Hilbert Spaces." IEEE Transactions on Neural Networks and Learning Systems 25, no. 7 (July 2014): 1413–19. http://dx.doi.org/10.1109/tnnls.2013.2293871.

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18

Kleptsyna, M. L., and A. Le Breton. "Optimal linear filtering of general multidimensional Gaussian processes and its application to Laplace transforms of quadratic functionals." Journal of Applied Mathematics and Stochastic Analysis 14, no. 3 (January 1, 2001): 215–26. http://dx.doi.org/10.1155/s104895330100017x.

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The optimal filtering problem for multidimensional continuous possibly non-Markovian, Gaussian processes, observed through a linear channel driven by a Brownian motion, is revisited. Explicit Volterra type filtering equations involving the covariance function of the filtered process are derived both for the conditional mean and for the covariance of the filtering error. The solution of the filtering problem is applied to obtain a Cameron-Martin type formula for Laplace transforms of a quadratic functional of the process. Particular cases for which the results can be further elaborated are investigated.

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19

Bazarov, T. O., M. A. Senko, A. N. Dorozhkin, D. D. Starykh, O. E. Nanii, and V. N. Treshchikov. "Symbol rate limitation due to optical filtering." Laser Physics Letters 19, no. 7 (May 19, 2022): 075101. http://dx.doi.org/10.1088/1612-202x/ac6b45.

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Abstract Explicit expressions for the dependence of signal-to-noise ratio on the optical filter bandwidth and its slope have been obtained. The resulting expressions were confirmed experimentally. The dependencies of critical symbol rate on two parameters, namely the bandwidth and roll-off factor, were studied both for the case of one and several filters.

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20

Leijdekker, Vincent, and Peter Spreij. "EXPLICIT COMPUTATIONS FOR A FILTERING PROBLEM WITH POINT PROCESS OBSERVATIONS WITH APPLICATIONS TO CREDIT RISK." Probability in the Engineering and Informational Sciences 25, no. 3 (May 17, 2011): 393–418. http://dx.doi.org/10.1017/s0269964811000076.

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We consider the filtering problem for a doubly stochastic Poisson or Cox process, where the intensity follows the Cox–Ingersoll–Ross model. In this article we assume that the Brownian motion, which drives the intensity, is not observed. Using filtering theory for point process observations, we first derive the dynamics for the intensity and its moment-generating function, given the observations of the Cox process. A transformation of the dynamics of the conditional moment-generating function allows us to solve in closed form the filtering problem, between the jumps of the Cox process as well as at the jumps, which constitutes the main contribution of the article. Assuming that the initial distribution of the intensity is of the Gamma type, we obtain an explicit solution to the filtering problem for all t>0. We conclude the article with the observation that the resulting conditional moment-generating function at time t, after Nt jumps, corresponds to a mixture of Nt+1 Gamma distributions. Currently, the model that we analyze has become popular in credit risk modeling, where one uses the intensity-based approach for the modeling of default times of one or more companies. In this approach, the default times are defined as the jump times of a Cox process. In such a model, one only has access to observations of the Cox process, and thus filtering comes in as a natural technique in credit risk modeling.

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21

CECI, C., A. GERARDI, and P. TARDELLI. "AN ESTIMATE OF THE APPROXIMATION ERROR IN THE FILTERING OF A DISCRETE JUMP PROCESS." Mathematical Models and Methods in Applied Sciences 11, no. 02 (March 2001): 181–98. http://dx.doi.org/10.1142/s0218202501000830.

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This paper deals with the filtering of a discrete Markov jump process when only the total number of jumps is observed. By using the recursive structure of the filtering equation, a technique to approximate the filter with a finite-dimensional filter is presented. An explicit bound for the approximation error, both almost surely and in L1, is given.

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22

Germano, M. "Turbulence: the filtering approach." Journal of Fluid Mechanics 238 (May 1992): 325–36. http://dx.doi.org/10.1017/s0022112092001733.

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Explicit or implicit filtered representations of chaotic fields like spectral cut-offs or numerical discretizations are commonly used in the study of turbulence and particularly in the so-called large-eddy simulations. Peculiar to these representations is that they are produced by different filtering operators at different levels of resolution, and they can be hierarchically organized in terms of a characteristic parameter like a grid length or a spectral truncation mode. Unfortunately, in the case of a general implicit or explicit filtering operator the Reynolds rules of the mean are no longer valid, and the classical analysis of the turbulence in terms of mean values and fluctuations is not so simple.In this paper a new operatorial approach to the study of turbulence based on the general algebraic properties of the filtered representations of a turbulence field at different levels is presented. The main results of this analysis are the averaging invariance of the filtered Navier—Stokes equations in terms of the generalized central moments, and an algebraic identity that relates the turbulent stresses at different levels. The statistical approach uses the idea of a decomposition in mean values and fluctuations, and the original turbulent field is seen as the sum of different contributions. On the other hand this operatorial approach is based on the comparison of different representations of the turbulent field at different levels, and, in the opinion of the author, it is particularly fitted to study the similarity between the turbulence at different filtering levels. The best field of application of this approach is the numerical large-eddy simulation of turbulent flows where the large scale of the turbulent field is captured and the residual small scale is modelled. It is natural to define and to extract from the resolved field the resolved turbulence and to use the information that it contains to adapt the subgrid model to the real turbulent field. Following these ideas the application of this approach to the large-eddy simulation of the turbulent flow has been produced (Germano et al. 1991). It consists in a dynamic subgrid-scale eddy viscosity model that samples the resolved scale and uses this information to adjust locally the Smagorinsky constant to the local turbulence.

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23

Calvia, Alessandro. "Stochastic filtering and optimal control of pure jump Markov processes with noise-free partial observation." ESAIM: Control, Optimisation and Calculus of Variations 26 (2020): 25. http://dx.doi.org/10.1051/cocv/2019020.

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We consider an infinite horizon optimal control problem for a pure jump Markov process X, taking values in a complete and separable metric space I, with noise-free partial observation. The observation process is defined as Yt = h(Xt), t ≥ 0, where h is a given map defined on I. The observation is noise-free in the sense that the only source of randomness is the process X itself. The aim is to minimize a discounted cost functional. In the first part of the paper we write down an explicit filtering equation and characterize the filtering process as a Piecewise Deterministic Process. In the second part, after transforming the original control problem with partial observation into one with complete observation (the separated problem) using filtering equations, we prove the equivalence of the original and separated problems through an explicit formula linking their respective value functions. The value function of the separated problem is also characterized as the unique fixed point of a suitably defined contraction mapping.

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24

Wu, Yuqing, and Isao Noda. "Extension of Quadrature Orthogonal Signal Corrected Two-Dimensional (QOSC 2D) Correlation Spectroscopy I: Principal Component Analysis Based QOSC 2D." Applied Spectroscopy 61, no. 10 (October 2007): 1040–44. http://dx.doi.org/10.1366/000370207782217761.

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The present study proposes a new quadrature orthogonal signal correlation (QOSC) filtering method based on principal component analysis (PCA). The external perturbation variable vector typically used in the QOSC operation is replaced with a matrix consisting of the spectral data principal components (PCs) and their quadrature counterparts obtained by using the discrete Hilbert–Noda transformation. Thus, QOSC operation can be carried out for a dataset without the explicit knowledge of the external variables information. The PCA-based QOSC filtering can be most effectively applied to two-dimensional (2D) correlation analysis. The performance of this filtering operation on the simulated spectra data set with the interference of strong random noise demonstrated that the PCA-based QOSC filtering not only eliminates the influence of signals that are unrelated to the final target but also preserves the out-of-phase information in the data matrix essential for asynchronous correlation analysis. The result of 2D correlation analysis has also demonstrated that essentially only one principal component is necessary for PCA-based QOSC to perform well. Although the present PCA-based QOSC filtering scheme is not as powerful as that based on the explicit knowledge of the external variable vector, it still can significantly improve the quality of 2D correlation spectra and enables OSC 2D to deal with the problems of losing the quadrature (or out-of-phase) information. In particular, it opens a way to perform QOSC for the spectral dataset without external variables information. The proposed approach should have wide applications in 2D correlation analysis of spectra driven by multiplicative effects in complicated systems in biological, pharmaceutical, and agriculture fields, and so on, where the explicit nature of the external perturbation cannot always be known.

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25

BOGEY, C., and C. BAILLY. "Turbulence and energy budget in a self-preserving round jet: direct evaluation using large eddy simulation." Journal of Fluid Mechanics 627 (May 25, 2009): 129–60. http://dx.doi.org/10.1017/s0022112009005801.

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An axisymmetric jet at a diameter-based Reynolds number of 1.1 × 104 is computed by a large eddy simulation (LES) in order to investigate its self-similarity region. The LES combines low-dissipation numerical schemes and explicit filtering of the flow variables to relax energy through the smaller scales discretized. The computational domain extends up to 150 jet radii in the downstream direction, which is found to be large enough to discretize a part of this region. Turbulence in the self-preserving jet is characterized by evaluating explicitly from the LES fields the second- and third-order moments of velocity, the pressure–velocity correlations as well as the budgets for the turbulent kinetic energy and for its components. Reference solutions are thus obtained. They agree well with the experimental data given by Panchapakesan & Lumley (J. Fluid Mech., vol. 246, 1963, p. 197) for a jet at the same Reynolds number. The distance required to achieve self-similarity in the LES, around 120 radii from the inflow, is particularly similar to that in the experiment. The discrepancies observed with respect to the data provided by Panchapakesan & Lumley and by Hussein, Capp & George (J. Fluid Mech., vol. 258, 1994, p. 31) for a jet at a higher Reynolds number, specially regarding the turbulence diffusion and the dissipation, are discussed. They appear largely resulting from the approximations made in the experiments to estimate the quantities that cannot be measured with accuracy. The role of the pressure terms in the energy redistribution is also clarified by the LES. Moreover, the turbulent energy budget is calculated in the jet from an equation derived from the filtered compressible Navier–Stokes equations, which includes the dissipation due to the explicit filtering. This has allowed us to assess the behaviour of the LES approach based on relaxation filtering (LES-RF) from the contributions of filtering and viscosity to energy dissipation. The filtering activity is particularly shown to adjust by itself to the grid and flow properties.

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26

Shaked, Uri. "Explicit solution to the singular discrete-time stationary linear filtering problem." IEEE Transactions on Automatic Control 30, no. 1 (January 1985): 34–47. http://dx.doi.org/10.1109/tac.1985.1103784.

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27

Mathew, Joseph, Richard Lechner, Holger Foysi, Joern Sesterhenn, and Rainer Friedrich. "An explicit filtering method for large eddy simulation of compressible flows." Physics of Fluids 15, no. 8 (August 2003): 2279–89. http://dx.doi.org/10.1063/1.1586271.

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28

Ma, Xiao, Hongwei Lu, Zaobin Gan, and Jiangfeng Zeng. "An explicit trust and distrust clustering based collaborative filtering recommendation approach." Electronic Commerce Research and Applications 25 (September 2017): 29–39. http://dx.doi.org/10.1016/j.elerap.2017.06.005.

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29

Bertels, A., B. Kober, A. Rittler, and A. Kempf. "Large-Eddy Simulation of Sandia Flame D with Efficient Explicit Filtering." Flow, Turbulence and Combustion 102, no. 4 (April 2019): 887–907. http://dx.doi.org/10.1007/s10494-018-9997-0.

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Margrave, Gary F., Hugh D. Geiger, Saleh M. Al-Saleh, and Michael P. Lamoureux. "Improving explicit seismic depth migration with a stabilizing Wiener filter and spatial resampling." GEOPHYSICS 71, no. 3 (May 2006): S111—S120. http://dx.doi.org/10.1190/1.2196034.

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We present a new approach to the design and implementation of explicit wavefield extrapolation for seismic depth migration in the space-frequency domain. Instability of the wavefield extrapolation operator is addressed by splitting the operator into two parts, one to control phase accuracy and a second to improve stability. The first partial operator is simply a windowed version of the exact operator for a half step. The second partial operator is designed, using the Wiener filter method, as a band-limited, least-squares inverse of the first. The final wavefield extrapolation operator for a full step is formed as a convolution of the first partial operator with the complex conjugate of the second. This resulting wavefield extrapolation operator can be designed to have any desired length and is generally more stable and more accurate than a simple windowed operator of similar length. Additional stability is gained by reducing the amount of evanescent filtering and by spatially downsampling the lower temporal frequencies. The amount of evanescent filtering is controlled by building two operator tables, one corresponding to significant evanescent filtering and the other to very little evanescent filtering. During the wavefield extrapolation process, most steps are taken with the second table while the first is invoked only for roughly every tenth step. Also, the data are divided into frequency partitions that are optimally resampled in the spatial coordinates to further enhance the performance of the extrapolation operator. Lower frequencies are downsampled to a larger spatial sample size. Testing of the algorithm shows accurate, high-angle impulse responses and run times comparable to the phase shift method of time migration. Images from trial depth migrations of the Marmousi model show very high resolution.

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31

Jiang, Xiaolei, Li Zhang, Ran Zhang, Hongxia Yin, and Zhenchang Wang. "Explicit Filtering Based Low-Dose Differential Phase Reconstruction Algorithm with the Grating Interferometry." Computational and Mathematical Methods in Medicine 2015 (2015): 1–7. http://dx.doi.org/10.1155/2015/623236.

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X-ray grating interferometry offers a novel framework for the study of weakly absorbing samples. Three kinds of information, that is, the attenuation, differential phase contrast (DPC), and dark-field images, can be obtained after a single scanning, providing additional and complementary information to the conventional attenuation image. Phase shifts of X-rays are measured by the DPC method; hence, DPC-CT reconstructs refraction indexes rather than attenuation coefficients. In this work, we propose an explicit filtering based low-dose differential phase reconstruction algorithm, which enables reconstruction from reduced scanning without artifacts. The algorithm adopts a differential algebraic reconstruction technique (DART) with the explicit filtering based sparse regularization rather than the commonly used total variation (TV) method. Both the numerical simulation and the biological sample experiment demonstrate the feasibility of the proposed algorithm.

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Gietzmann, Miles B., and Adam J. Ostaszewski. "The sound of silence: equilibrium filtering and optimal censoring in financial markets." Advances in Applied Probability 48, A (July 2016): 119–44. http://dx.doi.org/10.1017/apr.2016.45.

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AbstractFollowing the approach of standard filtering theory, we analyse investor valuation of firms, when these are modelled as geometric-Brownian state processes that are privately and partially observed, at random (Poisson) times, by agents. Tasked with disclosing forecast values, agents are able purposefully to withhold their observations; explicit filtering formulae are derived for downgrading the valuations in the absence of disclosures. The analysis is conducted for both a solitary firm andmco-dependent firms.

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Shi, Wenchuan, Liejun Wang, and Jiwei Qin. "User Embedding for Rating Prediction in SVD++-Based Collaborative Filtering." Symmetry 12, no. 1 (January 7, 2020): 121. http://dx.doi.org/10.3390/sym12010121.

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The collaborative filtering algorithm based on the singular value decomposition plus plus (SVD++) model employs the linear interactions between the latent features of users and items to predict the rating in the recommendation systems. Aiming to further enrich the user model with explicit feedback, this paper proposes a user embedding model for rating prediction in SVD++-based collaborative filtering, named UE-SVD++. We exploit the user potential explicit feedback from the rating data and construct the user embedding matrix by the proposed user-wise mutual information values. In addition, the user embedding matrix is added to the existing user bias and implicit parameters in the SVD++ to increase the accuracy of the user modeling. Through extensive studies on four different datasets, we found that the rating prediction performance of the UE-SVD++ model is improved compared with other models, and the proposed model’s evaluation indicators root-mean-square error (RMSE) and mean absolute error (MAE) are decreased by 1.002–2.110% and 1.182–1.742%, respectively.

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34

Wang, Xiao Bin, and Qing Jun Wang. "Study on Personalized Recommendation Technology of Digital TV Programs." Applied Mechanics and Materials 347-350 (August 2013): 3035–38. http://dx.doi.org/10.4028/www.scientific.net/amm.347-350.3035.

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This paper aims at one of key technologies in digital television development ---intelligent personalized recommendation technology of digital TV programs for study. This paper proposes to take advantage of ample TV-Anytime to describe metadata so as to perform specific plans of guide service for TV programs based on TV-Anytime metadata specification. It combines technology such as data mining and artificial intelligence etc with a view of building a personalized TV program recommendation system on the framework of the multi-agent. Besides, a hybrid algorithm with content filtering and collaborative filtering based on the systematical recommendation algorithm has been put forward. In order to overcome the deficiencies of traditional collaborative filtering algorithm which relies on users explicit evaluation, the paper represents an improved algorithm with the footing of content collaborative filtering.

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35

Chow, Fotini Katopodes, Robert L. Street, Ming Xue, and Joel H. Ferziger. "Explicit Filtering and Reconstruction Turbulence Modeling for Large-Eddy Simulation of Neutral Boundary Layer Flow." Journal of the Atmospheric Sciences 62, no. 7 (July 1, 2005): 2058–77. http://dx.doi.org/10.1175/jas3456.1.

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Abstract Standard turbulence closures for large-eddy simulations of atmospheric flow based on finite-difference or finite-volume codes use eddy-viscosity models and hence ignore the contribution of the resolved subfilter-scale stresses. These eddy-viscosity closures are unable to produce the expected logarithmic region near the surface in neutral boundary layer flows. Here, explicit filtering and reconstruction are used to improve the representation of the resolvable subfilter-scale (RSFS) stresses, and a dynamic eddy-viscosity model is used for the subgrid-scale (SGS) stresses. Combining reconstruction and eddy-viscosity models yields a sophisticated (and higher order) version of the well-known mixed model of Bardina et al.; the explicit filtering and reconstruction procedures clearly delineate the contribution of the RSFS and SGS motions. A near-wall stress model is implemented to supplement the turbulence models and account for the stress induced by filtering near a solid boundary as well as the effect of the large grid aspect ratio. Results for neutral boundary layer flow over a rough wall using the combined dynamic reconstruction model and the near-wall stress model show excellent agreement with similarity theory logarithmic velocity profiles, a significant improvement over standard eddy-viscosity closures. Stress profiles also exhibit the expected pattern with increased reconstruction level.

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36

KITANO, Yuya, and Akihiko NAKAYAMA. "Large-Eddy Simulation of High Reynolds Number Cannel Flow applying Explicit Filtering." PROCEEDINGS OF HYDRAULIC ENGINEERING 52 (2008): 1021–26. http://dx.doi.org/10.2208/prohe.52.1021.

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37

Yau, S. S. T., and Yuen-Tai Lai. "Explicit solution of DMZ equation in nonlinear filtering via solution of ODEs." IEEE Transactions on Automatic Control 48, no. 3 (March 2003): 505–8. http://dx.doi.org/10.1109/tac.2003.809169.

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Ghiasi, Zia, Jonathan Komperda, Dongru Li, Ahmad Peyvan, David Nicholls, and Farzad Mashayek. "Modal explicit filtering for large eddy simulation in discontinuous spectral element method." Journal of Computational Physics: X 3 (June 2019): 100024. http://dx.doi.org/10.1016/j.jcpx.2019.100024.

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Li, Zhenbo, and Shuqian Zhu. "Delay-DependentH∞Filtering for Singular Time-Delay Systems." Discrete Dynamics in Nature and Society 2011 (2011): 1–20. http://dx.doi.org/10.1155/2011/760878.

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This paper deals with the problem of delay-dependentH∞filtering for singular time-delay systems. First, a new delay-dependent condition which guarantees that the filter error system has a prescribedH∞performanceγis given in terms of linear matrix inequalities (LMIs). Then, the sufficient condition is obtained for the existence of theH∞filter, and the explicit expression for the desiredH∞filter is presented by using LMIs and the cone complementarity linearization iterative algorithm. A numerical example is provided to illustrate the effectiveness of the proposed method.

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Mahmoud, Magdi S., Alaeddin K. Jaradat, and Abdel Wahid Saif. "Gain Scheduled Filtering Design for Parameter Varying System." International Journal of System Dynamics Applications 1, no. 2 (April 2012): 80–95. http://dx.doi.org/10.4018/ijsda.2012040106.

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In this paper, the problem of gain-scheduled H8 filter design for a class of parameter-varying systems with time-varying delays is discussed. An improved stability and H8-performance condition of the augmented system is developed. A sufficient existence condition of a desired gain-scheduled H8 filter is derived and expressed in terms of feasibility testing of linear matrix inequalities (LMIs) and explicit expressions of the filter gains are provided. Numerical simulations are presented to demonstrate the effectiveness of the proposed design method.

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Calzolari, Antonella, Patrick Florchinger, and Giovanna Nappo. "Nonlinear Filtering for Markov Systems with Delayed Observations." International Journal of Applied Mathematics and Computer Science 19, no. 1 (March 1, 2009): 49–58. http://dx.doi.org/10.2478/v10006-009-0004-8.

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Nonlinear Filtering for Markov Systems with Delayed ObservationsThis paper deals with nonlinear filtering problems with delays, i. e., we consider a system (X, Y), which can be represented by means of a system (X, Ŷ), in the sense thatYt= Ŷa(t), wherea(t)is a delayed time transformation. We start withXbeing a Markov process, and then study Markovian systems, not necessarily diffusive, with correlated noises. The interest is focused on the existence of explicit representations of the corresponding filters as functionals depending on the observed trajectory. Various assumptions on the functiona(t)are considered.

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Aggoun, Lakhdar, Mohamed Al-Lawati, and W. P. Malcolm. "Filtering and M-ary Detection of Markov Modulated Mean Reverting Model." Sultan Qaboos University Journal for Science [SQUJS] 15 (December 1, 2010): 87. http://dx.doi.org/10.24200/squjs.vol15iss0pp87-100.

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In an earlier paper we developed a stochastic model incorporating a double-Markov modulated mean-reversion model. The model is based on an explicit discretisation of the corresponding continuous time dynamics. Here we discuss parameter estimation via the technique of M-ary detection.

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Yang, Chang, Xing Hua Li, and Xue Guang Zhou. "Tacit Extraction for Keyword in Chinese." Applied Mechanics and Materials 58-60 (June 2011): 1415–20. http://dx.doi.org/10.4028/www.scientific.net/amm.58-60.1415.

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The present Extraction for Keyword in Chinese (EKC for short) is merely directed against explicit keywords or prototype keywords, and has not take into account those tacit keywords distorted by network hackers with the method of active jamming in Chinese. For this purpose, with the help of M. Polanyi’s theory of tacit knowledge, this paper presents a new approach for the tacit EKC (TEKC for short), which can improve the ratio of precision and recall for information filtering. Based on the TEKC, the paper presents a set of classifications of how to distort the explicit keywords and the solutions to calculate the tacit distortion of those tacit keywords. Furthermore, 4 algorithms were designed, including in picture tacit, textspeak tacit, fake paleography tacit and character tacit, which can extract the tacit keywords in text but traditional EKC could not. Owing to the increased number of extracted keywords, the recall of keywords raised and the precision of information filtering improved. Experiments show that the classification of tacit keywords in Chinese, the calculation of tacit distortion and the algorithms to tacit extract the keywords in Chinese, etc can effectively improve the performance of EKC and raise the recall of web filtering algorithms based on TEKC.

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Ye, Hong Ling, Ning Chen, Pei Ze Shao, and Yun Kang Sui. "Topological Optimization of Plate Subjected to Linear Buckling Constraints Based on Independent Continuous Mapping Method." Applied Mechanics and Materials 602-605 (August 2014): 139–43. http://dx.doi.org/10.4028/www.scientific.net/amm.602-605.139.

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In this paper, a model of topology optimization for the lightest plate structures with linear buckling constraints is constructed based on Independent, Continuous and Mapping (ICM) method. Exponential function is adopted as filtering function of the element weight, the element stiffness matrix and the element geometric stiffness matrix. Based on the Taylor expansion and the filtering function, the buckling constraints were approximately expressed as explicit functions. The optimization model was translated into a dual programming and solved by the sequence second-order programming. Two numerical examples show that this method is validity and efficient.

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Wang, Yufeng, Jerry M. Harris, Min Bai, Omar M. Saad, Liuqing Yang, and Yangkang Chen. "An explicit stabilization scheme for Q-compensated reverse time migration." GEOPHYSICS 87, no. 3 (April 18, 2022): F25—F40. http://dx.doi.org/10.1190/geo2021-0134.1.

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Attenuation compensation in prestack depth migration typically requires nonphysical frequency-dependent energy amplification, which may lead to numerical instability. An explicit stabilization approach is developed for seismic [Formula: see text] compensation after deriving the [Formula: see text]-space Green’s function of the compensated constant-[Formula: see text] wave equation, which has decoupled fractional Laplacians. At high wavenumbers, as time increases, the time propagator of [Formula: see text]-space Green’s function increases exponentially. Therefore, an exponential window function is introduced to stabilize the exponentially divergent time propagator. Unlike the conventional low-pass filtering approach in the frequency or wavenumber domain, the proposed method assumes that the exponent of the chosen window is a power function of the wavenumber magnitude, which only involves explicit stabilization terms in the time-space domain. An explicit stabilization form helps to perform seismic data [Formula: see text] compensation more conveniently. We outline the basic structure of the proposed approach with explicit stabilization and highlight some numerical details using compute unified device architexture-based implementations. The strong scaling analysis justifies the good performance of the developed code package in terms of computational efficiency and scalability. In addition, we further analyze the optimal scheme parameter selection and the influence of parameters on filtering performance. The proposed [Formula: see text]-compensated reverse time migration is applied on the Marmousi model and synthetic and real crosswell examples to verify its feasibility and numerical stability.

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Chen, Shuo, and Min Wu. "Attention Collaborative Autoencoder for Explicit Recommender Systems." Electronics 9, no. 10 (October 18, 2020): 1716. http://dx.doi.org/10.3390/electronics9101716.

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Recently, various deep learning-based models have been applied in the study of recommender systems. Some researches have combined the classic collaborative filtering method with deep learning frameworks in order to obtain more accurate recommendations. However, these models either add additional features, but still recommend in the original linear manner, or only extract the global latent factors of the rating matrices in a non-linear way without considering some local special relationships. In this paper, we propose a deep learning framework for explicit recommender systems, named Attention Collaborative Autoencoder (ACAE). Based on the denoising autoencoder, our model can extract the global latent factors in a non-linear fashion from the sparse rating matrices. In ACAE, attention units are introduced during back propagation, enabling discovering potential relationships between users and items in the neighborhood, which makes the model obtain better results in the rating prediction tasks. In addition, we propose how to optimize the training process of the model by proposing a new loss function. Experiments on two public datasets demonstrate the effectiveness of ACAE and its outperformance of competitive baselines.

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Patel, Sumit Kumar, and Joseph Mathew. "Shock Capturing in Large Eddy Simulations by Adaptive Filtering." Fluids 4, no. 3 (July 15, 2019): 132. http://dx.doi.org/10.3390/fluids4030132.

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A method for shock capturing by adaptive filtering for use with high-resolution, high-order schemes for Large Eddy Simulations (LES) is presented. The LES method used in all the examples here employs the Explicit Filtering approach and the spatial derivatives are obtained with sixth-order, compact, finite differences. The adaptation is to drop the order of the explicit filter to two at gridpoints where a shock is detected, and to then increase the order from 2 to 10 in steps at successive gridpoints away from the shock. The method is found to be effective in a series of tests of common inviscid 1D and 2D problems of shock propagation and propagation of waves through shocks. As a prelude to LES, the 3D Taylor–Green problem for the inviscid and a finite viscosity case were simulated. An assessment of the overall performance of the method for LES was carried out by simulating an underexpanded round jet at a Reynolds number of 6.09 million, based in centerline velocity and diameter at nozzle exit plane. Very close quantitative agreement was found for the development of centerline mean pressure when compared to experiment. Simulations on several increasingly finer grids showed a monotonic extension of the computed part of the inertial range, with little change to low frequency content. Amplitudes and locations of large changes in pressure through several cells were captured accurately. A similar performance was observed for LES of an impinging jet containing normal and curved shocks.

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Datta, Anindya, Joseph Mathew, and Santosh Hemchandra. "The explicit filtering method for large eddy simulations of a turbulent premixed flame." Combustion and Flame 237 (March 2022): 111862. http://dx.doi.org/10.1016/j.combustflame.2021.111862.

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49

Yi, Jing-Wen, Li Chai, and Jingxin Zhang. "Average Consensus by Graph Filtering: New Approach, Explicit Convergence Rate, and Optimal Design." IEEE Transactions on Automatic Control 65, no. 1 (January 2020): 191–206. http://dx.doi.org/10.1109/tac.2019.2907410.

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50

Klemp, Joseph B., William C. Skamarock, and Soyoung Ha. "Damping Acoustic Modes in Compressible Horizontally Explicit Vertically Implicit (HEVI) and Split-Explicit Time Integration Schemes." Monthly Weather Review 146, no. 6 (June 2018): 1911–23. http://dx.doi.org/10.1175/mwr-d-17-0384.1.

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Although the equations of motion for a compressible atmosphere accommodate acoustic waves, these modes typically play an insignificant role in atmospheric processes of physical interest. In numerically integrating the compressible equations, it is often beneficial to filter these acoustic modes to control acoustic noise and prevent its artificial growth. Here, a new technique is proposed for filtering the 3D divergence that may damp acoustic modes more effectively than filters previously implemented in numerical modes using horizontally explicit vertically implicit (HEVI) and split-explicit time integration schemes. With this approach, a divergence damping term is added as a final adjustment to the horizontal velocity at the new time level after completing the vertically implicit portion of the time step. In this manner, the divergence used in the filter term has exactly the same numerical form as that used in the discrete pressure equation. Analysis of the dispersion equation for this form of the filter documents its stability characteristics and confirms that it effectively damps acoustic modes with little artificial influence on the amplitude or propagation of the gravity wave modes that are of physical interest. Some specific aspects of the implementation of the filter in the Model for Prediction Across Scales (MPAS) are discussed, and results are presented to illustrate some of the beneficial aspects of suppressing acoustic noise.

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