Artículos de revistas: "Piecewise sources"

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Koldovský, Zbyněk, Jiří Málek, Petr Tichavský, Yannick Deville y Shahram Hosseini. "Blind separation of piecewise stationary non-Gaussian sources". Signal Processing 89, n.º 12 (diciembre de 2009): 2570–84. http://dx.doi.org/10.1016/j.sigpro.2009.04.021.

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Melyukov, Valery y Evgeny A. Marinin. "Controlled Process of Crystallization in Weld Pool". Materials Science Forum 1037 (6 de julio de 2021): 258–63. http://dx.doi.org/10.4028/www.scientific.net/msf.1037.258.

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In this report the problem of control of solidification crack formation in welded plates is considered. In this problem the welding source is determined in dependence on the preset configuration and curvature of the rear part weld pool. A double ellipsoid model of weld pool with preset semi-axes may be used for the first approximation of preset weld pool configuration. It is an inverse problem which may be more efficiently solved as optimal control problem. The Function of welding source as a controlling function obtained in the result of solution is determined in a class of piecewise continuous functions which is more common class and the continuous-smooth functions are special partial case of common class. Recent methods of optimal control which use for solution of optimal control problems require to present the controlling functions in class of piecewise constant functions. Laser influence, electron beam, plasma, arc and submerged arc are the welding sources with high concentrated energy. A mathematical models of these welding sources may be introduced in class of piecewise continuous function with an efficient accuracy.

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3

Shamir, G. I. y N. Merhav. "Low-complexity sequential lossless coding for piecewise-stationary memoryless sources". IEEE Transactions on Information Theory 45, n.º 5 (julio de 1999): 1498–519. http://dx.doi.org/10.1109/18.771150.

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4

TADEUSIEWICZ, MICHAL y KRZYSZTOF GŁOWIENKA. "A CONTRACTION ALGORITHM FOR FINDING ALL THE DC SOLUTIONS OF PIECEWISE-LINEAR CIRCUITS". Journal of Circuits, Systems and Computers 04, n.º 03 (septiembre de 1994): 319–36. http://dx.doi.org/10.1142/s0218126694000193.

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An efficient algorithm for finding all the DC solutions of a broad class of piecewise-linear circuits, having hybrid representation, is described in this paper. Circuits belonging to this class can include electronic devices modelled by linear resistors, linear controlled sources, piecewise-linear two terminal resistors and independent sources. The algorithm is based on the idea of successive division and contraction of the solution domain. Two contraction methods are developed that result in a high rate of convergence of the computation process. Numerical examples and comparison analyses show the efficiency of this algorithm.

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5

Cottereau, Benoit, Karim Jerbi y Sylvain Baillet. "Multiresolution imaging of MEG cortical sources using an explicit piecewise model". NeuroImage 38, n.º 3 (noviembre de 2007): 439–51. http://dx.doi.org/10.1016/j.neuroimage.2007.07.046.

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6

Deleforge, Antoine, Florence Forbes y Radu Horaud. "Acoustic Space Learning for Sound-Source Separation and Localization on Binaural Manifolds". International Journal of Neural Systems 25, n.º 01 (6 de enero de 2015): 1440003. http://dx.doi.org/10.1142/s0129065714400036.

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In this paper, we address the problems of modeling the acoustic space generated by a full-spectrum sound source and using the learned model for the localization and separation of multiple sources that simultaneously emit sparse-spectrum sounds. We lay theoretical and methodological grounds in order to introduce the binaural manifold paradigm. We perform an in-depth study of the latent low-dimensional structure of the high-dimensional interaural spectral data, based on a corpus recorded with a human-like audiomotor robot head. A nonlinear dimensionality reduction technique is used to show that these data lie on a two-dimensional (2D) smooth manifold parameterized by the motor states of the listener, or equivalently, the sound-source directions. We propose a probabilistic piecewise affine mapping model (PPAM) specifically designed to deal with high-dimensional data exhibiting an intrinsic piecewise linear structure. We derive a closed-form expectation-maximization (EM) procedure for estimating the model parameters, followed by Bayes inversion for obtaining the full posterior density function of a sound-source direction. We extend this solution to deal with missing data and redundancy in real-world spectrograms, and hence for 2D localization of natural sound sources such as speech. We further generalize the model to the challenging case of multiple sound sources and we propose a variational EM framework. The associated algorithm, referred to as variational EM for source separation and localization (VESSL) yields a Bayesian estimation of the 2D locations and time-frequency masks of all the sources. Comparisons of the proposed approach with several existing methods reveal that the combination of acoustic-space learning with Bayesian inference enables our method to outperform state-of-the-art methods.

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7

Mastepanenko, M. A., S. N. Bondar, Sh Zh Gabrielyan y A. V. Ivashina. "Approximation Piecewise Stabilization of the Thermal Voltage Coefficient of Reference Voltage Sources". Russian Electrical Engineering 91, n.º 7 (julio de 2020): 433–39. http://dx.doi.org/10.3103/s106837122007010x.

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8

Merhav, N. "On the minimum description length principle for sources with piecewise constant parameters". IEEE Transactions on Information Theory 39, n.º 6 (1993): 1962–67. http://dx.doi.org/10.1109/18.265504.

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9

Suko, Tota, Toshiyasu Matsushima y Shigeichi Hirasawa. "Asymptotic property of universal lossless coding for independent piecewise identically distributed sources". Journal of Discrete Mathematical Sciences and Cryptography 13, n.º 4 (agosto de 2010): 383–91. http://dx.doi.org/10.1080/09720529.2010.10698301.

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10

Shamir, Gil I. y Daniel J. Costello. "On the redundancy of universal lossless coding for general piecewise stationary sources". Communications in Information and Systems 1, n.º 3 (2001): 305–32. http://dx.doi.org/10.4310/cis.2001.v1.n3.a4.

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11

Simpson, David John Warwick y Rachel Kuske. "The influence of localized randomness on regular grazing bifurcations with applications to impacting dynamics". Journal of Vibration and Control 24, n.º 2 (12 de abril de 2016): 407–26. http://dx.doi.org/10.1177/1077546316642054.

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This paper concerns stochastic perturbations of piecewise-smooth ODE systems relevant for vibro-impacting dynamics, where impact events constitute the primary source of randomness. Such systems are characterized by the existence of switching manifolds that divide the phase space into regions where the system is smooth. The initiation of impacts is captured by a grazing bifurcation, at which a periodic orbit describing motion without impacts develops a tangential intersection with a switching manifold. Oscillatory dynamics near regular grazing bifurcations are described by piecewise-smooth maps involving a square-root singularity, known as Nordmark maps. We consider three scenarios where colored noise only affects impacting dynamics, and derive three two-dimensional stochastic Nordmark maps with the noise appearing in different nonlinear or multiplicative ways, depending on the source of the noise. Consequently the stochastic dynamics differs between the three noise sources, and is fundamentally different to that of a Nordmark map with additive noise. This critical dependence on the nature of the noise is illustrated with a prototypical one-degree-of-freedom impact oscillator.

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12

Jeong, D. G. y J. D. Gibson. "Uniform and piecewise uniform lattice vector quantization for memoryless Gaussian and Laplacian sources". IEEE Transactions on Information Theory 39, n.º 3 (mayo de 1993): 786–804. http://dx.doi.org/10.1109/18.256488.

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13

Fraguela Collar, Andres, Jose Jacobo Oliveros Oliveros, Maria Monserrat Morin Castillo y Jose Julio Conde Mones. "Identification of piecewise constant sources in non-homogeneous media based on boundary measurements". Applied Mathematical Modelling 39, n.º 23-24 (diciembre de 2015): 7697–717. http://dx.doi.org/10.1016/j.apm.2015.04.026.

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14

Pandey, Animesh y Anurag Gupta. "Topological Defects and Metric Anomalies as Sources of Incompatibility for Piecewise Smooth Strain Fields". Journal of Elasticity 139, n.º 2 (4 de octubre de 2019): 237–67. http://dx.doi.org/10.1007/s10659-019-09750-y.

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15

Potthast, Roland. "A new non-iterative singular sources method for the reconstruction of piecewise constant media." Numerische Mathematik 98, n.º 4 (18 de agosto de 2004): 703–30. http://dx.doi.org/10.1007/s00211-004-0524-y.

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16

NAGARAJ, NITHIN. "HUFFMAN CODING AS A NONLINEAR DYNAMICAL SYSTEM". International Journal of Bifurcation and Chaos 21, n.º 06 (junio de 2011): 1727–36. http://dx.doi.org/10.1142/s0218127411029392.

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In this paper, source coding or data compression is viewed as a measurement problem. Given a measurement device with fewer states than the observable of a stochastic source, how can one capture their essential information? We propose modeling stochastic sources as piecewise-linear discrete chaotic dynamical systems known as Generalized Luröth Series (GLS) which has its roots in Georg Cantor's work in 1869. These GLS are special maps with the property that their Lyapunov exponent is equal to the Shannon's entropy of the source (up to a constant of proportionality). By successively approximating the source with GLS having fewer states (with the nearest Lyapunov exponent), we derive a binary coding algorithm which turns out to be a rediscovery of Huffman coding, the popular lossless compression algorithm used in the JPEG international standard for still image compression.

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17

Yang, Ying y Benzhuo Lu. "An Error Analysis for the Finite Element Approximation to the Steady-State Poisson-Nernst-Planck Equations". Advances in Applied Mathematics and Mechanics 5, n.º 1 (febrero de 2013): 113–30. http://dx.doi.org/10.4208/aamm.11-m11184.

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AbstractPoisson-Nernst-Planck equations are a coupled system of nonlinear partial differential equations consisting of the Nernst-Planck equation and the electrostatic Poisson equation with delta distribution sources, which describe the electrodiffusion of ions in a solvated biomolecular system. In this paper, some error bounds for a piecewise finite element approximation to this problem are derived. Several numerical examples including biomolecular problems are shown to support our analysis.

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18

Kuliev, Samir. "SYNTHESIS OF ZONAL CONTROL OF LUMPED SOURCES FOR THE HEAT CONDUCTION PROCESS". Azerbaijan Journal of High Performance Computing 3, n.º 2 (29 de diciembre de 2020): 207–22. http://dx.doi.org/10.32010/26166127.2020.3.2.207.222.

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The paper studies the problem of synthesis of control of lumped sources for an object with distributed parameters based on discrete observation of the phase state at specific object points. We propose an approach in which the whole phase space at the observed points is preliminarily divided in some way into given subsets (zones). The synthesized controls are selected from the class of piecewise-constant functions, and their current values are determined by a subset of the phase space containing the population of current states of the object at the observed points, at which controls take constant values. Such synthesized controls are called zonal. We give a numerical technique for obtaining optimal values of zonal controls using efficient first-order optimization methods. To this purpose, we derive formulas for the gradient of the objective function in the space of zonal controls.

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19

Peng, Y., K. von Salzen y J. Li. "Simulation of mineral dust aerosol with Piecewise Log-normal Approximation (PLA) in CanAM4-PAM". Atmospheric Chemistry and Physics 12, n.º 15 (1 de agosto de 2012): 6891–914. http://dx.doi.org/10.5194/acp-12-6891-2012.

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Abstract. A new size-resolved dust scheme based on the numerical method of piecewise log-normal approximation (PLA) was developed and implemented in the fourth generation of the Canadian Atmospheric Global Climate Model with the PLA Aerosol Model (CanAM4-PAM). The total simulated annual global dust emission is 2500 Tg yr−1, and the dust mass load is 19.3 Tg for year 2000. Both are consistent with estimates from other models. Results from simulations are compared with multiple surface measurements near and away from dust source regions, validating the generation, transport and deposition of dust in the model. Most discrepancies between model results and surface measurements are due to unresolved aerosol processes. Biases in long-range transport are also contributing. Radiative properties of dust aerosol are derived from approximated parameters in two size modes using Mie theory. The simulated aerosol optical depth (AOD) is compared with satellite and surface remote sensing measurements and shows general agreement in terms of the dust distribution around sources. The model yields a dust AOD of 0.042 and dust aerosol direct radiative forcing (ADRF) of −1.24 W m−2 respectively, which show good consistency with model estimates from other studies.

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20

Gramfort, Alexandre, Théodore Papadopoulo, Emmanuel Olivi y Maureen Clerc. "Forward Field Computation with OpenMEEG". Computational Intelligence and Neuroscience 2011 (2011): 1–13. http://dx.doi.org/10.1155/2011/923703.

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To recover the sources giving rise to electro- and magnetoencephalography in individual measurements, realistic physiological modeling is required, and accurate numerical solutions must be computed. We present OpenMEEG, which solves the electromagnetic forward problem in the quasistatic regime, for head models with piecewise constant conductivity. The core of OpenMEEG consists of the symmetric Boundary Element Method, which is based on an extended Green Representation theorem. OpenMEEG is able to provide lead fields for four different electromagnetic forward problems: Electroencephalography (EEG), Magnetoencephalography (MEG), Electrical Impedance Tomography (EIT), and intracranial electric potentials (IPs). OpenMEEG is open source and multiplatform. It can be used from Python and Matlab in conjunction with toolboxes that solve the inverse problem; its integration within FieldTrip is operational since release 2.0.

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21

Costello, D. J. y G. I. Shamir. "Asymptotically optimal low-complexity sequential lossless coding for piecewise-stationary memoryless sources .I. The regular case". IEEE Transactions on Information Theory 46, n.º 7 (2000): 2444–67. http://dx.doi.org/10.1109/18.887857.

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22

Gachkevich, O. R. y M. G. Gachkevich. "Optimal heating of a piecewise-homogeneous cylindrical glass shell by the surrounding medium and heat sources". Journal of Mathematical Sciences 96, n.º 1 (agosto de 1999): 2935–39. http://dx.doi.org/10.1007/bf02169010.

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23

Aleksandrov, An A., M. N. Zakharov y M. S. Kuts. "Optimization of Industrial Complex Power Supply by Means of Renewable Energy Sources". Herald of the Bauman Moscow State Technical University. Series Mechanical Engineering, n.º 1 (136) (marzo de 2021): 85–102. http://dx.doi.org/10.18698/0236-3941-2021-1-85-102.

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The usage of renewable energy sources and energy storage devices allows an enterprise to reduce its electricity supply costs. Significant savings can be achieved only in the case of a well-organized system of managing energy flows of the enterprise and electricity consumption. The puprpose of the study was to analyze the existing storage devices and renewable energy sources, and on the basis of the analysis, introduce an approach to organizing energy supply of the enterprise based on the usage of storage devices and renewable energy sources. The approach introduced implies the electricity purchase schedule curve optimization to minimize the total costs. The purchase schedule curve optimization for the case of energy storage usage is an ill-posed problem. Within the framework of solving the problem, the form of the curve was formalized to a piecewise constant function, which made it possible to solve it by applying multi-criteria optimization based on a modified method of directed random search. We analyzed a model case, for which an optimal purchase schedule curve was obtained using storage devices and solar panels, and the achievable economic effect from their use was graphed. The maximum value of operational costs, which makes the usage of energy storage and renewable energy source efficient, was found

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LI, JIANPING, JICHUANG FENG y JIANMING CHEN. "A PIECEWISE-DEFINED SEVERITY DISTRIBUTION-BASED LOSS DISTRIBUTION APPROACH TO ESTIMATE OPERATIONAL RISK: EVIDENCE FROM CHINESE NATIONAL COMMERCIAL BANKS". International Journal of Information Technology & Decision Making 08, n.º 04 (diciembre de 2009): 727–47. http://dx.doi.org/10.1142/s0219622009003727.

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Following the Basel II Accord, with the increased focus on operational risk as an aspect distinct from credit and market risk, quantification of operational risk has been a major challenge for banks. This paper analyzes implications of the advanced measurement approach to estimate the operational risk. When modeling the severity of losses in a realistic manner, our preliminary tests indicate that classic distributions are unable to fit the entire range of operational risk data samples (collected from public information sources) well. Then, we propose a piecewise-defined severity distribution (PSD) that combines a parameter form for ordinary losses and a generalized Pareto distribution (GPD) for large losses, and estimate operational risk by the loss distribution approach (LDA) with Monte Carlo simulation. We compare the operational risk measured with piecewise-defined severity distribution based LDA (PSD-LDA) with those obtained from the basic indicator approach (BIA), and the ratios of operational risk regulatory capital of some major international banks with those of Chinese commercial banks. The empirical results reveal the rationality and promise of application of the PSD-LDA for Chinese national commercial banks.

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Versteeg, Hendrik K., Jonathan C. Henson y Weeratunge Malalasekera. "An Adaptive Angular Quadrature for the Discrete Transfer Method Based on Error Estimation". Journal of Heat Transfer 125, n.º 2 (21 de marzo de 2003): 301–11. http://dx.doi.org/10.1115/1.1560148.

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The ray effect is a serious problem in radiative heat transfer computations. Continuously varying radiation fields are approximated numerically by sampling a limited number of angular directions. The discrete transfer method (DTM) is a conceptually simple technique suitable for general-purpose calculations of thermal radiation in complex geometries. Over the years a large variety of quadratures based on fixed ray firing patterns has been suggested for use in conjunction with the DTM. Arguably, in absence of a comprehensive error analysis, the efficacy of all these quadratures has only been proved for limited collections of radiation problems. Recently, sharp error bounds for the heat flux integral in the DTM have been established for irradiation distributions of three different continuity classes: smooth fields, fields with discontinuous angular derivatives and piecewise constant fields. The resulting error formulas have paved the way for a new adaptive quadrature strategy. Results are presented of its application to an idealized jet flame and to radiative exchanges inside a cube-shaped enclosure, along with brief comments on the viability of this approach in general-purpose CFD/radiation computations. In this paper, the following capabilities of the new adaptive angular quadrature are demonstrated: Evaluation of DTM heat flux integrals to a pre-specified tolerance for any intensity distribution; Excellent accuracy with very low ray numbers for irradiation due to small view factor sources; and Good heat flux estimates for piecewise constant sources, provided that the starting mesh is selected carefully.

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26

Jekosch, Simon y Ennes Sarradj. "An Extension of the Virtual Rotating Array Method Using Arbitrary Microphone Configurations for the Localization of Rotating Sound Sources". Acoustics 2, n.º 2 (15 de mayo de 2020): 330–42. http://dx.doi.org/10.3390/acoustics2020019.

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The characterization of rotating aeroacoustic sources using microphone array methods has been proven to be a useful tool. One technique to identify rotating sources is the virtual rotating array method. The method interpolates the pressure time data signals between the microphones in a stationary array to compensate the motion of the rotating sources. One major drawback of the method is the requirement of ring array geometries that are centred around the rotating axis. This contribution extends the virtual rotating array method to arbitrary microphone configurations. Two different ways to interpolate the time signals between the microphone locations are proposed. The first method constructs a mesh between the microphone positions using Delaunay-triangulation and interpolates over the mesh faces using piecewise linear functions. The second one is a meshless technique which is based on radial basis function interpolation. The methods are tested on synthetic array data from a benchmark test case as well as on experimental data obtained with a spiral array and a five-bladed fan.

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27

Ruotoistenmäki, Tapio. "The gravity anomaly of two‐dimensional sources with continuous density distribution and bounded by continuous surfaces". GEOPHYSICS 57, n.º 4 (abril de 1992): 623–28. http://dx.doi.org/10.1190/1.1443274.

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The gravity anomaly of a complicated two‐dimensional (2-D) source having arbitrary surfaces and density varying in either horizontal or vertical direction is calculated using a combination of closed form solutions and numerical integration. The surfaces and density can be defined by continuous or piecewise continuous two‐dimensional functions in the integration interval. For example, the anomalies for intrusions or folded sedimentary units, having an arbitrary density in the horizontal direction and a polynomial density distribution in the vertical direction, can be calculated using surfaces represented by functions of the horizontal dimension. When modeling dipping layered intrusions or sedimentary beds the surfaces are represented by functions of the vertical dimension in which case the density can be an arbitrary function of depth and a polynome function of horizontal coordinate. The accuracy of the method is defined by the user. The method gives simple and general equations to calculate anomalies of complicated sources which have no closed form solution, thus reducing the number of algorithms needed in interpretation programs.

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28

Aida-zade, Kamil Rajab y Yegana R. Ashrafova. "Optimal Control Problems of Sources in Distributed Systems on the Classes of Impulsive, Piecewise Constant and Heaviside Functions". Journal of Automation and Information Sciences 43, n.º 5 (2011): 64–82. http://dx.doi.org/10.1615/jautomatinfscien.v43.i5.60.

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Gachkevich, A. R. y N. G. Gachkevich. "Optimal heating of the atmosphere around piecewise-homogeneous shells of revolution in the presence of internal heat sources". International Applied Mechanics 31, n.º 11 (noviembre de 1995): 911–16. http://dx.doi.org/10.1007/bf00847431.

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30

Tien, Meng-Hsuan y Kiran D’Souza. "Method for controlling vibration by exploiting piecewise-linear nonlinearity in energy harvesters". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 476, n.º 2233 (enero de 2020): 20190491. http://dx.doi.org/10.1098/rspa.2019.0491.

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Vibration energy is becoming a significant alternative solution for energy generation. Recently, a great deal of research has been conducted on how to harvest energy from vibration sources ranging from ocean waves to human motion to microsystems. In this paper, a theoretical model of a piecewise-linear (PWL) nonlinear vibration harvester that has potential applications in variety of fields is proposed and numerically investigated. This new technique enables automatic frequency tunability in the energy harvester by controlling the gap size in the PWL oscillator so that it is able to adapt to changes in excitations. To optimize the performance of the proposed system, a control method combining the response prediction, signal measurement and gap adjustment mechanism is proposed in this paper. This new energy harvester not only overcomes the limitation of traditional linear energy harvesters that can only provide the maximum power generation efficiency over a narrow frequency range but also improves the performance of current nonlinear energy harvesters that are not as efficient as linear energy harvesters at resonance. The proposed system is demonstrated in several case studies to illustrate its effectiveness for a number of different excitations.

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31

Gjerde, Ingeborg G., Kundan Kumar, Jan M. Nordbotten y Barbara Wohlmuth. "Splitting method for elliptic equations with line sources". ESAIM: Mathematical Modelling and Numerical Analysis 53, n.º 5 (septiembre de 2019): 1715–39. http://dx.doi.org/10.1051/m2an/2019027.

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In this paper, we study the mathematical structure and numerical approximation of elliptic problems posed in a (3D) domain Ω when the right-hand side is a (1D) line source Λ. The analysis and approximation of such problems is known to be non-standard as the line source causes the solution to be singular. Our main result is a splitting theorem for the solution; we show that the solution admits a split into an explicit, low regularity term capturing the singularity, and a high-regularity correction term w being the solution of a suitable elliptic equation. The splitting theorem states the mathematical structure of the solution; in particular, we find that the solution has anisotropic regularity. More precisely, the solution fails to belong to H1 in the neighbourhood of Λ, but exhibits piecewise H2-regularity parallel to Λ. The splitting theorem can further be used to formulate a numerical method in which the solution is approximated via its correction function w. This recasts the problem as a 3D elliptic problem with a 3D right-hand side belonging to L2, a problem for which the discretizations and solvers are readily available. Moreover, as w enjoys higher regularity than the full solution, this improves the approximation properties of the numerical method. We consider here the Galerkin finite element method, and show that the singularity subtraction then recovers optimal convergence rates on uniform meshes, i.e., without needing to refine the mesh around each line segment. The numerical method presented in this paper is therefore well-suited for applications involving a large number of line segments. We illustrate this by treating a dataset (consisting of ~3000 line segments) describing the vascular system of the brain.

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32

Kim, Jihye, Seongjun Park, Heegang Kim y Myoung Souk Yeo. "Emission characterization of size-resolved particles in a pre-school classroom in relation to children’s activities". Indoor and Built Environment 28, n.º 5 (2 de mayo de 2017): 659–76. http://dx.doi.org/10.1177/1420326x17707565.

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The objective of this study was to investigate the effect of children’s daily activity patterns on the size-resolved indoor particles in a pre-school classroom, qualitatively and quantitatively. Real-time particle number size distribution data in conjunction with activity were collected experimentally in a pre-school classroom during two seasons: late spring and early winter. We divided daily activities into six groups: Arrival, Large Group, Small Group, Naptime, Dismissal and Unoccupied. The concentration variation forms of coarse particles were compared qualitatively among activity groups. The results indicated that noteworthy coarse particle concentration variations were observed during each activity group. These variations were caused by four factors: presence/absence of children, variation in the number of children, activity intensity and presence of sources. The emission rates were estimated to quantify the impact of activities. Time series emission rates were deduced from the piecewise-constant inputs and outputs model. The piecewise-constant emission rates were averaged for sequential parts to reduce noise and ensure daily repeated peaks were not missed. The sequential part-constant emission rates were consistent with previously described particle number concentration variation results and the predicted indoor particle number concentration data with sequential part-constant emission rates agreed well with measured data.

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Tan, Shengmin, Xu Wang y Chuanwen Jiang. "Optimal Scheduling of Hydro–PV–Wind Hybrid System Considering CHP and BESS Coordination". Applied Sciences 9, n.º 5 (2 de marzo de 2019): 892. http://dx.doi.org/10.3390/app9050892.

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Coordination of a hydropower, combined heat and power (CHP), and battery energy storage system (BESS) with multiple renewable energy sources (RES) can effectively reduce the adverse effects of large-scale renewable energy integration in power systems. This paper proposes a concept of a renewable-based hybrid energy system and puts forward an optimal scheduling model of this system, taking into account the cost of operation and risk. An optimization method is proposed based on Latin hypercube sampling, scene reduction, and piecewise linearization. Firstly, a large number of samples were generated with the Latin hypercube sampling method according to the uncertainties, including the renewable resources availability, the load demand, and the risk aversion coefficients, and the generated samples were reduced with a scene reduction method. Secondly, the piecewise linearization method was applied to convert nonlinear constraints into linear to obtain the best results of each scene. Finally, the performance of the proposed model and method was evaluated based on case studies with real-life data. Results showed that the renewable-based hybrid system can not only reduce the intermittent and volatility of renewable resources but also ensure the smooth of tie-line power as much as possible. The proposed model and method are universal, feasible, and effective.

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34

Chernokozhin, Evgeny V. y Amir Boag. "Method of Generalized Debye Sources for the Analysis of Electromagnetic Scattering by Perfectly Conducting Bodies With Piecewise Smooth Boundaries". IEEE Transactions on Antennas and Propagation 61, n.º 4 (abril de 2013): 2108–15. http://dx.doi.org/10.1109/tap.2012.2233456.

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35

Prytkov, Sergei V. y Alexei V. Syromyasov. "Calculation of Light Distribution of a Conventionally Point Light Source in an Arbitrarily Oriented Coordinate System". Volume 28, Number 2, 2020, n.º 02-2020 (abril de 2020): 106–12. http://dx.doi.org/10.33383/2019-015.

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The article reviews calculation of total light distribution of several light sources (LS), which are differently oriented in space with their locations conventionally 1 being the same. It is proposed that luminous intensity curves (photometric body) of LSs are described in IESNA format (or in the format of tables, which is basically the same). Two methods of solving the problem are proposed. The first one is related to preliminary trigonometric interpolation of luminous intensity curves for each LS performed by means of discrete Fourier transformation (DFT). The second one is based on piecewise-linear interpolation of this curves using Delaunay triangulation. Both methods may be implemented by means of popular mathematic software (such as Wolfram Mathematica or Octave) and their applicability is confirmed experimentally.

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Cheung, C. W. y G. J. Hancock. "Wind tunnel interference on unsteady two-dimensional aerofoil motions in low speed flows". Aeronautical Journal 92, n.º 913 (marzo de 1988): 115–21. http://dx.doi.org/10.1017/s0001924000022016.

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Summary The aerodynamic characteristics of two-dimensional transient aerofoil motions in low-speed flows in a wind tunnel with either closed wall or open (jet) walls, including the effect of a downstream closed wall diffuser, have been investigated. The mathematical formulation for the aerofoil and its unsteady wake is based on linear theory and is solved by a piecewise linear vorticity method; the wall boundaries are represented by distributions of sources. Numerical calculations have been made for various values of tunnel height to chord ratio. Interference effects on the rate of build up of lift to a steady state following a step change in incidence can be large, especially for open jet tunnels.

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37

Dumbrava, Virgil, George Cristian Lazaroiu, Gabriel Bazacliu y Dario Zaninelli. "Demand response power system optimization in presence of renewable energy sources". Proceedings of the International Conference on Business Excellence 11, n.º 1 (1 de julio de 2017): 218–26. http://dx.doi.org/10.1515/picbe-2017-0023.

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Abstract This paper optimizes the price-based demand response of a large customer in a power system with stochastic production and classical fuel-supplied power plants. The implemented method of optimization, under uncertainty, is helpful to model both the utility functions for the consumers and their technical limitations. The consumers exposed to price-based demand can reduce their cost for electricity procurement by modifying their behavior, possibly shifting their consumption during the day to periods with low electricity prices. The demand is considered elastic to electricity price if the consumer is willing and capable to buy various amounts of energy at different price levels, the demand function being represented as purchasing bidding blocks. The demand response is seen also by the scientific literature as a possible source of the needed flexibility of modern power systems, while the flexibility of conventional generation technologies is restricted by technical constraints, such as ramp rates. This paper shows how wind power generation affects short term operation of the electricity system. Fluctuations in the amount of wind power fed into the grid require, without storage capacities, compensating changes in the output of flexible generators or in the consumers’ behavior. In the presented case study, we show the minimization of the overall costs in presence of stochastic wind power production. For highlighting the variability degree of production from renewable sources, four scenarios of production were formulated, with different probabilities of occurrence. The contribution brought by the paper is represented by the optimization model for demand-response of a large customer in a power system with fossil fueled generators and intermittent renewable energy sources. The consumer can reduce the power system costs by modifying his demand. The demand function is represented as purchasing bidding blocks for the possible price forecasted realizations. The consumer benefit function is modelled as a piecewise linear function.

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Gu, Zhi Peng y Jiang Zeng. "Model of Metal Halide Lamps and Harmonic Analysis Based on PSCAD/EMTDC". Applied Mechanics and Materials 392 (septiembre de 2013): 469–74. http://dx.doi.org/10.4028/www.scientific.net/amm.392.469.

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Metal halide lamp (MH) is widely used in stadium lighting because of its significant advantages. But this high-intensity gas discharge lamp circuit contains the arcand such negative resistance characteristics lead to harmonic current. In addition, electronic ballasts of MH with rectifier circuit and inverter also produced a large number of electrical harmonics, becoming the main harmonic sources. In this paper, piecewise linearization method is used to establish the electrical model of 2500W metal halide lamp and a three-level model of electronic ballasts with the PSCAD/EMTDC. This paper analyzed the grid side harmonic current when the model is running. Comparing the simulation results to the measured data of Shenzhen Universiade venues lighting circuit, we can verify the accuracy of the model.

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Arkani‐Hamed, J. y W. J. Hinze. "Limitations of the long‐wavelength components of the North American magnetic anomaly map". GEOPHYSICS 55, n.º 12 (diciembre de 1990): 1577–88. http://dx.doi.org/10.1190/1.1442809.

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The magnetic anomaly map of North America and its related data set provide the opportunity not only to view the obvious short‐wavelength anomalies (<300 km) in a continental context, but to isolate and analyze the longer wavelength anomalies. However, care must be used in analyzing the longer wavelengths because of the effects of noncrustal sources on these anomalies. Inversion of the anomalies into lateral variations of crustal magnetization suggests that the long‐wavelength anomalies (>2600 km) are strongly affected by core field components that have not been completely removed from the North American data set. Furthermore, the piecewise matching of the magnetic anomalies of adjacent survey areas in the map compilation has contaminated the intermediate wavelength anomalies (300–2600 km).

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40

Shishov, V. I. "Interstellar Scintillation and Clouds of the Interstellar Turbulent Plasma". International Astronomical Union Colloquium 182 (2001): 163–69. http://dx.doi.org/10.1017/s0252921100000907.

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AbstractData on interstellar diffraction and refraction scintillation of pulsars are analyzed. Comparison between theory and the observational data shows that two types of spectra for electron density fluctuations are realized in the interstellar medium: pure power law and piecewise with a break. The distribution of turbulent plasma in the Galaxy has a three component structure. Component A is diffuse and it is distributed outside of the spiral arms of the Galaxy. Component BI is cloudy and associated with Galactic arms. Component BII is extremely nonuniform and associated with HII regions and supernova remnants. The origin of the interstellar plasma turbulence is considered, and possible sources of turbulent energy are discussed. The contribution of supernova bursts in the interstellar gas ionization and generation of turbulence are analyzed among other factors.

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41

Lyrintzis, A. S. "Review: The Use of Kirchhoff’s Method in Computational Aeroacoustics". Journal of Fluids Engineering 116, n.º 4 (1 de diciembre de 1994): 665–76. http://dx.doi.org/10.1115/1.2911834.

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A comprehensive review of the use of Kirchhoff’s method in computational aeroacoustics is given. Kirchhoff’s integral formulation allows radiating sound to be evaluated based on quantities on an arbitrary control surface S if the wave equation is assumed outside. The control surface S is assumed to include all the nonlinear flow effects and noise sources. Thus only surface integrals are needed for the calculation of the far-field sound. A numerical CFD method can be used for the evaluation of the flow-field solution in the near-field and thus on surface S. Kirchhoff’s integral formulation has been extended to an arbitrary, moving, deformable piecewise-continuous surface. The available Kirchhoff formulations are reviewed and various aeroacoustic applications are given. The relative merits of Kirchhoff’s method are also discussed.

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42

De Silva, H. N., D. S. Tustin, W. M. Cashmore, C. J. Stanley, G. Lupton y S. J. McArtney. "Fruit Fresh Mass—Diameter Relationship for `Royal Gala' Apple across Seasons and among Fruit Production Regions of New Zealand". HortScience 32, n.º 7 (diciembre de 1997): 1169–73. http://dx.doi.org/10.21273/hortsci.32.7.1169.

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A number of mass—diameter equations were compared for their potential use in indirect measurement of fruit masses of `Royal Gala' apple (Malus ×domestica). The fruit fresh-mass—diameter relationship changed with time during the season, hence no single function fitted the data well. Smooth piecewise functions that assume different relationships for intervening segments of a curve bounded by knots on the x-axis are particularly useful for modeling such data. The curve is said to be smooth because the first derivative of the function is continuous on the interval, including the knots. Two such equations, a three-parameter piecewise power function and a five-parameter spline exponential function, provided good fits to data. For both equations, the estimated mean bias on individual fruit predictions was within 5% of predicted mass over the two validating data sets. As for the precision conditional on no bias, a sample size of 20 fruit gave standard errors within 2.5% of mean predicted mass. These precisions are adequate to meet the industry requirements for monitoring fruit mass through the growing season. There was evidence of a seasonal difference in the estimated bias, but we were unable to confirm that this variation resulted from seasonal differences in fruit shape. Application of these two equations to data from other regions suggested that divergence from the estimated functional form may in fact be greater under increasingly different climatic conditions. Hence, further investigations to identify possible sources of these differences are necessary before the proposed equations can be applied across climatically different regions.

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43

Zhao, Yinghao, Hesong Hu, Lunhua Bai, Mengxiong Tang, Hang Chen y Dingli Su. "Fragility Analyses of Bridge Structures Using the Logarithmic Piecewise Function-Based Probabilistic Seismic Demand Model". Sustainability 13, n.º 14 (13 de julio de 2021): 7814. http://dx.doi.org/10.3390/su13147814.

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Seismic fragility analysis is an efficient method to evaluate the structural failure probability during earthquake events. Among the existing fragility analysis methods, the probabilistic seismic demand model (PSDM) and the joint probabilistic seismic demand model (JPSDM) are generally used to compute the component and system fragility, respectively. However, the statistical significance behind the parameters related to the current PSDM and JPSDM are not comparable. Aside from that, when calculating the system fragility, the Monte Carlo sampling (MCS) method is time-consuming. To solve the two flaws, in this paper, the logarithm piecewise functions were used to generate the PSDM and the JPSDM, and the MCS was replaced by the univariate conditioning approximation (UCA) method. The concepts and application procedures of the proposed fragility analysis methods were elaborated first. Then, the UCA method was illustrated in detail. Finally, fragility curves of a steel arch truss case study bridge were generated by the proposed method. The research results indicate the following: (1) the proposed methods unify the data sources and statistical significance of the parameters used in the PSDM and the JPSDM; (2) the logarithmic piecewise function-based PSDM sensitively reflects the changing trend of the component’s demand with the fluctuation of the seismic intensity measure; (3) under transverse seismic waves, major injuries happen on the side bearings of the bridge, while slight damage may occur on each pier, and as the seismic intensity measure increases, the side bearings are more likely to be damaged; (4) for the severe damage and the absolute damage of the studied bridge, the system fragility curves are closer to the upper failure bounds; and (5) compared with the MSC method, the accuracy of the UCA method can be guaranteed with less calculation time.

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44

Lascola, Robert, Patrick E. O’Rourke y Edward A. Kyser. "A Piecewise Local Partial Least Squares (PLS) Method for the Quantitative Analysis of Plutonium Nitrate Solutions". Applied Spectroscopy 71, n.º 12 (5 de octubre de 2017): 2579–94. http://dx.doi.org/10.1177/0003702817734000.

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We have developed a piecewise local (PL) partial least squares (PLS) analysis method for total plutonium measurements by absorption spectroscopy in nitric acid-based nuclear material processing streams. Instead of using a single PLS model that covers all expected solution conditions, the method selects one of several local models based on an assessment of solution absorbance, acidity, and Pu oxidation state distribution. The local models match the global model for accuracy against the calibration set, but were observed in several instances to be more robust to variations associated with measurements in the process. The improvements are attributed to the relative parsimony of the local models. Not all of the sources of spectral variation are uniformly present at each part of the calibration range. Thus, the global model is locally overfitting and susceptible to increased variance when presented with new samples. A second set of models quantifies the relative concentrations of Pu(III), (IV), and (VI). Standards containing a mixture of these species were not at equilibrium due to a disproportionation reaction. Therefore, a separate principal component analysis is used to estimate of the concentrations of the individual oxidation states in these standards in the absence of independent confirmatory analysis. The PL analysis approach is generalizable to other systems where the analysis of chemically complicated systems can be aided by rational division of the overall range of solution conditions into simpler sub-regions.

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45

Stoyanov, Ludmil, Ivan Bachev, Zahari Zarkov, Vladimir Lazarov y Gilles Notton. "Multivariate Analysis of a Wind–PV-Based Water Pumping Hybrid System for Irrigation Purposes". Energies 14, n.º 11 (31 de mayo de 2021): 3231. http://dx.doi.org/10.3390/en14113231.

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The Green Deal and increased nutritional needs are driving factors in human activities nowadays. Agriculture is an essential economic sector that can profit from the application of renewable energy sources by the assimilation of off-grid, arid and barren terrains. Power supplied by hybrid systems for water pumping is a solution for overcoming the stochastic character of the renewable energy sources. This paper presents a sizing methodology for a hybrid system with wind and PV generation and water tank storage, based on the consideration of the entire energy conversion chain with energy models and a one-year operation simulation. The PV generator is modeled using a reduced Durisch’s model, while for the wind generator a piecewise interpolation is used. The methodology is applied for sites in Bulgaria with specific agricultural crops and meteorological data. Combinations of PV (different technologies) and wind (different types) generators and water tank capacities are considered and discussed. The combinations are compared on the basis of three criteria: the investment cost, the satisfaction of crop requirements and system oversizing. The possibility for the introduction of battery storage is also examined. The results show some trends in the hybrid system sizing and the possibility to apply the proposed methodology for various sites, generators and crops.

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46

Han, Houde, Min Tang y Wenjun Ying. "Two Uniform Tailored Finite Point Schemes for the Two Dimensional Discrete Ordinates Transport Equations with Boundary and Interface Layers". Communications in Computational Physics 15, n.º 3 (marzo de 2014): 797–826. http://dx.doi.org/10.4208/cicp.130413.010813a.

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AbstractThis paper presents two uniformly convergent numerical schemes for the two dimensional steady state discrete ordinates transport equation in the diffusive regime, which is valid up to the boundary and interface layers. A five-point node-centered and a four-point cell-centered tailored finite point schemes (TFPS) are introduced. The schemes first approximate the scattering coefficients and sources by piecewise constant functions and then use special solutions to the constant coefficient equation as local basis functions to formulate a discrete linear system. Numerically, both methods can not only capture the diffusion limit, but also exhibit uniform convergence in the diffusive regime, even with boundary layers. Numerical results show that the five-point scheme has first-order accuracy and the four-point scheme has second-order accuracy, uniformly with respect to the mean free path. Therefore a relatively coarse grid can be used to capture the two dimensional boundary and interface layers.

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47

Vuolo, Maria Raffaella, Laurent Menut y Hélène Chepfer. "Impact of Transport Schemes on Modeled Dust Concentrations". Journal of Atmospheric and Oceanic Technology 26, n.º 6 (1 de junio de 2009): 1135–43. http://dx.doi.org/10.1175/2008jtecha1197.1.

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Abstract A sensitivity study is performed with the CHIMERE-DUST chemistry transport model in order to evaluate the modeled mineral dust spread due to the horizontal transport scheme accuracy. Three different schemes are implemented in the model: the simple first-order UPWIND scheme, the second-order Van Leer scheme, and the third-order parabolic piecewise method (PPM) scheme. The results showed that a large part of the uncertainty in dust modeling may be due to the transport scheme only. Compared to the PPM scheme, it is shown that, over a large domain encompassing western Africa and the North Atlantic, a significant increase in the dust plume extension is locally diagnosed (+25% with Van Leer and +48% with UPWIND) and linked to a decrease in the dust maxima (−17% with Van Leer and −32% with UPWIND) to PPM. Far from the sources, hourly surface concentration differences may be up to 30 μg m−3 in Europe, highlighting the high uncertainty of dust modeling for air quality use.

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48

Alessandrini, Giovanni, Maarten V. De Hoop, Florian Faucher, Romina Gaburro y Eva Sincich. "Inverse problem for the Helmholtz equation with Cauchy data: reconstruction with conditional well-posedness driven iterative regularization". ESAIM: Mathematical Modelling and Numerical Analysis 53, n.º 3 (mayo de 2019): 1005–30. http://dx.doi.org/10.1051/m2an/2019009.

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In this paper, we study the performance of Full Waveform Inversion (FWI) from time-harmonic Cauchy data via conditional well-posedness driven iterative regularization. The Cauchy data can be obtained with dual sensors measuring the pressure and the normal velocity. We define a novel misfit functional which, adapted to the Cauchy data, allows the independent location of experimental and computational sources. The conditional well-posedness is obtained for a hierarchy of subspaces in which the inverse problem with partial data is Lipschitz stable. Here, these subspaces yield piecewise linear representations of the wave speed on given domain partitions. Domain partitions can be adaptively obtained through segmentation of the gradient. The domain partitions can be taken as a coarsening of an unstructured tetrahedral mesh associated with a finite element discretization of the Helmholtz equation. We illustrate the effectiveness of the iterative regularization through computational experiments with data in dimension three. In comparison with earlier work, the Cauchy data do not suffer from eigenfrequencies in the configurations.

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Baek, Hyoungsu, Henri Calandra y Laurent Demanet. "Velocity estimation via registration-guided least-squares inversion". GEOPHYSICS 79, n.º 2 (1 de marzo de 2014): R79—R89. http://dx.doi.org/10.1190/geo2013-0146.1.

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Least-squares (LS) acoustic-waveform inversion often suffers from a very narrow basin of attraction near the global minimum. To mitigate this problem, we evaluated an iterative inversion scheme in which the notion of proximity of two traces is not the usual LS distance, but instead it involves registration as in image processing. Observed data were matched to predicted waveforms via piecewise-polynomial warpings, obtained by solving a nonconvex optimization problem in a multiscale fashion from low to high frequencies. This multiscale process required defining low-frequency augmented signals to seed the frequency sweep at zero frequency. Custom adjoint sources were then defined from the warped waveforms. The new method, referred to as registration-guided least-squares, was successfully applied to a few scenarios of model velocity estimation in the transmission setting. We determined that the new method can converge to the correct model in situations in which conventional LS inversion suffers from cycle skipping and converges to a spurious model.

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50

Yang, Wei, Carlos Torres-Verdín, Junsheng Hou y Zhiyi (Ian) Zhang. "1D subsurface electromagnetic fields excited by energized steel casing". GEOPHYSICS 74, n.º 4 (julio de 2009): E159—E180. http://dx.doi.org/10.1190/1.3131382.

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We use numerical simulations to investigate the possibility of enabling steel-cased wells as galvanic sources to detect and quantify spatial variations of electrical conductivity in the subsurface. The study assumes a vertical steel-cased well that penetrates electrically anisotropic horizontal layers. Simulations include a steel-cased vertical well with a finite-length thin wire of piecewise-constant electric conductivity and magnetic permeability. The steel-cased well is energized at the surface or within the borehole at an arbitrary depth with an electrode connected to a current source of variable frequency. Electromagnetic (EM) fields excited by the energized steel-cased well are simulated with an integral-equation approach. Results confirm the accuracy of the simulations when benchmarked against the whole-space solution of EM fields excited by a vertical electric dipole. Additional simulations consider a wide range of frequencies and subsurface conductivity values for several transmitter-receiver configurations, including borehole-to-surface and crosswell. The distribution of electric current along the steel-cased well is sensitive to vertical variations of electric conductivity in the host rock. In addition, numerical simulations indicate that crosswell and borehole-to-surface receiver configurations could reliably estimate vertical variations of electric conductivity within radial distances of up to [Formula: see text] for frequencies below [Formula: see text] and for average host rock electric conductivities below [Formula: see text].

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