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Littérature scientifique sur le sujet « Incremental variational approach »

Auteur : Grafiati

Publié le 23 février 2024

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Articles de revues sur le sujet "Incremental variational approach"

Balzani, Daniel, et Thomas Schmidt. « Relaxed incremental variational approach for damage in arteries ». PAMM 15, n^o 1 (octobre 2015) : 81–82. http://dx.doi.org/10.1002/pamm.201510031.

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Huang, Y., A. Abou-Chakra Guéry et J. F. Shao. « Incremental variational approach for time dependent deformation in clayey rock ». International Journal of Plasticity 64 (janvier 2015) : 88–103. http://dx.doi.org/10.1016/j.ijplas.2014.07.003.

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Veerse, F., et J. N. Thepaut. « Multiple-truncation incremental approach for four-dimensional variational data assimilation ». Quarterly Journal of the Royal Meteorological Society 124, n^o 550 (juillet 1998) : 1889–908. http://dx.doi.org/10.1002/qj.49712455006.

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Dimitrov, S., et E. Schnack. « Variational approach for strain-driven, incremental homogenization of inelastic solids ». PAMM 5, n^o 1 (décembre 2005) : 329–30. http://dx.doi.org/10.1002/pamm.200510141.

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Fletcher, Steven J., et Andrew S. Jones. « Multiplicative and Additive Incremental Variational Data Assimilation for Mixed Lognormal–Gaussian Errors ». Monthly Weather Review 142, n^o 7 (27 juin 2014) : 2521–44. http://dx.doi.org/10.1175/mwr-d-13-00136.1.

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Abstract An advance that made Gaussian-based three- and four-dimensional variational data assimilation (3D- and 4DVAR, respectively) operationally viable for numerical weather prediction was the introduction of the incremental formulation. This reduces the computational costs of the variational methods by searching for a small increment to a background state whose evolution is approximately linear. In this paper, incremental formulations for 3D- and 4DVAR with lognormal and mixed lognormal–Gaussian-distributed background and observation errors are presented. As the lognormal distribution has geometric properties, a geometric version for the tangent linear model (TLM) is proven that enables the linearization of the observational component of the cost functions with respect to a geometric increment. This is combined with the additive TLM for the mixed distribution–based cost function. Results using the mixed incremental scheme with the Lorenz’63 model are presented for different observational error variances, observation set sizes, and assimilation window lengths. It is shown that for sparse accurate observations the scheme has a relative error of ±0.5% for an assimilation window of 100 time steps. This improves to ±0.3% with more frequent observations. The distributions of the analysis errors are presented that appear to approximate a lognormal distribution with a mode at 1, which, given that the background and observational errors are unbiased in Gaussian space, shows that the scheme is approximating a mode and not a median. The mixed approach is also compared against a Gaussian-only incremental scheme where it is shown that as the z-component observational errors become more lognormal, the mixed approach appears to be more accurate than the Gaussian approach.

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Ye, Fei, et Adrian G. Bors. « Continual Variational Autoencoder via Continual Generative Knowledge Distillation ». Proceedings of the AAAI Conference on Artificial Intelligence 37, n^o 9 (26 juin 2023) : 10918–26. http://dx.doi.org/10.1609/aaai.v37i9.26294.

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Humans and other living beings have the ability of short and long-term memorization during their entire lifespan. However, most existing Continual Learning (CL) methods can only account for short-term information when training on infinite streams of data. In this paper, we develop a new unsupervised continual learning framework consisting of two memory systems using Variational Autoencoders (VAEs). We develop a Short-Term Memory (STM), and a parameterised scalable memory implemented by a Teacher model aiming to preserve the long-term information. To incrementally enrich the Teacher's knowledge during training, we propose the Knowledge Incremental Assimilation Mechanism (KIAM), which evaluates the knowledge similarity between the STM and the already accumulated information as signals to expand the Teacher's capacity. Then we train a VAE as a Student module and propose a new Knowledge Distillation (KD) approach that gradually transfers generative knowledge from the Teacher to the Student module. To ensure the quality and diversity of knowledge in KD, we propose a new expert pruning approach that selectively removes the Teacher's redundant parameters, associated with unnecessary experts which have learnt overlapping information with other experts. This mechanism further reduces the complexity of the Teacher's module while ensuring the diversity of knowledge for the KD procedure. We show theoretically and empirically that the proposed framework can train a statistically diversified Teacher module for continual VAE learning which is applicable to learning infinite data streams.

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Schmidt, Thomas, et Daniel Balzani. « Relaxed incremental variational approach for the modeling of damage-induced stress hysteresis in arterial walls ». Journal of the Mechanical Behavior of Biomedical Materials 58 (mai 2016) : 149–62. http://dx.doi.org/10.1016/j.jmbbm.2015.08.005.

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Günther, Christina, Philipp Junker et Klaus Hackl. « A variational viscosity-limit approach to the evolution of microstructures in finite crystal plasticity ». Proceedings of the Royal Society A : Mathematical, Physical and Engineering Sciences 471, n^o 2180 (août 2015) : 20150110. http://dx.doi.org/10.1098/rspa.2015.0110.

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A micromechanical model for finite single crystal plasticity was introduced by Kochmann & Hackl (2011 Contin. Mech. Thermodyn. 23, 63–85 ( doi:10.1007/s00161-010-0714-5 )). This model is based on thermodynamic variational principles and leads to a non-convex variational problem. Based on the Lagrange functional, an incremental strategy was outlined to model the time-continuous evolution of a first-order laminate microstructure. Although this model provides interesting results on the material point level, owing to the global minimization in the evolution equations, the calculation time and numerical instabilities may cause problems when applying this model to macroscopic specimens. In this paper, a smooth transition zone between the laminates is introduced to avoid global minimization, which makes the numerical calculations cumbersome compared with the model in Kochmann & Hackl. By introducing a smooth viscous transition zone, the dissipation potential and its numerical treatment have to be adapted. We outline rate-dependent time-evolution equations for the internal variables based on variational techniques and show as first examples single-slip shear and tension/compression tests.

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Pethe, Rohit, Thomas Heuzé et Laurent Stainier. « Variational h-adaption for coupled thermomechanical problems ». Engineering Computations 37, n^o 4 (25 novembre 2019) : 1261–90. http://dx.doi.org/10.1108/ec-05-2019-0243.

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Purpose The purpose of this paper is to present a variational mesh h-adaption approach for strongly coupled thermomechanical problems. Design/methodology/approach The mesh is adapted by local subdivision controlled by an energy criterion. Thermal and thermomechanical problems are of interest here. In particular, steady and transient purely thermal problems, transient strongly coupled thermoelasticity and thermoplasticity problems are investigated. Findings Different test cases are performed to test the robustness of the algorithm for the problems listed above. It is found that a better cost-effectiveness can be obtained with that approach compared to a uniform refining procedure. Because the algorithm is based on a set of tolerance parameters, parametric analyses and a study of their respective influence on the mesh adaption are carried out. This detailed analysis is performed on unidimensional problems, and a final example is provided in two dimensions. Originality/value This work presents an original approach for independent h-adaption of a mechanical and a thermal mesh in strongly coupled problems, based on an incremental variational formulation. The approach does not rely on (or attempt to provide) error estimation in the classical sense. It could merely be considered to provide an error indicator. Instead, it provides a practical methodology to adapt the mesh on the basis of the variational structure of the underlying mathematical problem.

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Hernández-Sanjaime, Rocío, Martín González, Antonio Peñalver et Jose J. López-Espín. « Estimating Simultaneous Equation Models through an Entropy-Based Incremental Variational Bayes Learning Algorithm ». Entropy 23, n^o 4 (24 mars 2021) : 384. http://dx.doi.org/10.3390/e23040384.

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The presence of unaccounted heterogeneity in simultaneous equation models (SEMs) is frequently problematic in many real-life applications. Under the usual assumption of homogeneity, the model can be seriously misspecified, and it can potentially induce an important bias in the parameter estimates. This paper focuses on SEMs in which data are heterogeneous and tend to form clustering structures in the endogenous-variable dataset. Because the identification of different clusters is not straightforward, a two-step strategy that first forms groups among the endogenous observations and then uses the standard simultaneous equation scheme is provided. Methodologically, the proposed approach is based on a variational Bayes learning algorithm and does not need to be executed for varying numbers of groups in order to identify the one that adequately fits the data. We describe the statistical theory, evaluate the performance of the suggested algorithm by using simulated data, and apply the two-step method to a macroeconomic problem.

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Thèses sur le sujet "Incremental variational approach"

Vernier, Patricia. « Homogenization of composite materials with fractional viscoelastic constituents ». Electronic Thesis or Diss., Sorbonne université, 2023. http://www.theses.fr/2023SORUS552.

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Cette thèse porte sur la prédiction des propriétés mécaniques effectives de matériaux hétérogènes composés de constituants viscoélastiques fractional, au moyen d'une approche incrémentale variationnelle. Nous appliquons la méthode Effective Internal Variable (EIV) développée par Lahellec and Suquet (2007), particulièrement attrayante pour le traitement de comportements viscoélastiques (Tressou et al., 2016). Contrairement aux méthodes d'homogénéisation communément utilisées qui reposent sur le principe de correspondance et pour lesquelles les fluctuations des champs ne sont pas accessibles, cette approche incrémentale permet de calculer les propriétés effectives dans le domaine direct au moyen des méthodes variationalles de Ponte Castañeda (1991 et 2002) qui prennent en compte les seconds-moments des champs mécaniques. La méthode EIV s'inscrit dans le cadre des Matériaux Standards Généralisés (MSG), dans lequel le comportement des matériaux dissipatifs est décrit par deux potentiels thermodynamiques convexes. Nous considérons des constituants viscoélastiques fractionnaires, dont la loi constitutive est décrite par des équations différentielles linéaires avec des dérivées fractionnaires. En accord avec des observations expérimentales, ce formalisme prend en compte des effets de mémoire longue à travers la superposition de plusieurs temps caractéristiques (Caputo et Mainardi, 1971). La distribution de ces derniers est donnée explicitement par l'expression du spectre en loi puissance. Les potentiels thermodynamiques des matériaux viscoélastiques fractionnaires sont définis en cohérence avec le cadre des MSG. Cette cohérence s'appuie sur l'interprétation rhéologique de l'élément fractionnaire comme un Maxwell généralisé (Lion, 1997). Ainsi, nous tirons parti de l'extension de la méthode EIV à plusieurs variables internes développée par Tressou et al. (2023) afin d'homogénéiser des matériaux composites contenant des constituants viscoélastiques fractionnaires. De plus, les temps caractéristiques sont adéquatement choisis à partir de la discrétisation du spectre. Cette discrétisation est réalisée avec la procédure de Papoulia et al. (2010), basée sur une méthode des trapèzes améliorée. Plus précisément, nous appliquons cette méthode à la fonction de Mittag-Leffler impliquée dans la définition des spectres de relaxation. Nous abordons deux problèmes hétérogènes différents au moyen de la méthode EIV. Nous considérons d'abord un composite de type matrice-inclusions sous chargement harmonique, pour lequel nous rencontrons des difficultés numériques. Nous évaluons ensuite la méthode EIV sur un polycristal de glace soumis à un essai de fluage
This PhD thesis deals with the prediction of the mechanical effective properties of composite materials with linear fractional viscoelastic constituents by means of an incremental variational approach. We make use of the Effective Internal Variable (EIV) method developed by Lahellec and Suquet (2007), which is particularly attractive for viscoelasticity (Tressou et al., 2016). Contrary to the common homogenization methods that rely on the correspondence principle and where the fluctuations are not accessible, this incremental method evaluates the effective properties into the direct domain through the variational methods of Ponte Castañeda (1991 and 2002) that take into account the second-moments of the fields. The EIV method is based on the Generalized Standard Materials framework, in which the dissipative materials are described by means of two convex thermodynamic potentials. We consider local fractional viscoelastic constituents, of which the constitutive behaviours follow linear differential equations with fractional derivative operators. In accordance with experimental observations, this formalism takes into account long-memory effects through the superposition of several characteristic times (Caputo and Mainardi, 1971). Their distribution is provided by the explicit expression of the spectrum as a power law. The potentials of fractional viscoelastic constituents are consistently defined in the GSM framework through the rheological interpretation of the fractional damping element as a generalized Maxwell model (Lion, 1997). Therefore, we take advantage of the extension of the EIV method to several internal variables, developed by Tressou et al. (2023) for the homogenization of composites with local fractional viscoelastic behaviours. Besides, the characteristic times are appropriately chosen by discretizing the spectrum. This is done using the midpoint-based procedure developed by Papoulia et al. (2010). More specifically, we apply their method to the Mittag-Leffler function involved in the definition of the relaxation spectrum. We use the EIV method to tackle two different heterogeneous problems. We consider a matrix-inclusion composite under harmonic loading, for which we come accros numerical issues. We then evaluate the EIV method for a polycrystal subject to a monotonous creep loading

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Chapitres de livres sur le sujet "Incremental variational approach"

Zeng, Anping, Tianrui Li, Junbo Zhang et Dun Liu. « An Incremental Approach for Updating Approximations of Rough Fuzzy Sets under the Variation of the Object Set ». Dans Rough Sets and Current Trends in Computing, 36–45. Berlin, Heidelberg : Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-642-32115-3_4.

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Fan, Wei, Chunlin He, Anping Zeng et Ke Lin. « An Incremental Approach Based on Hierarchical Classification in Multikernel Fuzzy Rough Sets Under the Variation of Object Set ». Dans Intelligent Computing Methodologies, 3–17. Cham : Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-13832-4_1.

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Subercaseaux, Bernardo, et Marijn J. H. Heule. « The Packing Chromatic Number of the Infinite Square Grid is 15 ». Dans Tools and Algorithms for the Construction and Analysis of Systems, 389–406. Cham : Springer Nature Switzerland, 2023. http://dx.doi.org/10.1007/978-3-031-30823-9_20.

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AbstractA packing k-coloring is a natural variation on the standard notion of graph k-coloring, where vertices are assigned numbers from $$\{1, \ldots , k\}$$ { 1 , … , k } , and any two vertices assigned a common color $$c \in \{1, \ldots , k\}$$ c ∈ { 1 , … , k } need to be at a distance greater than c (as opposed to 1, in standard graph colorings). Despite a sequence of incremental work, determining the packing chromatic number of the infinite square grid has remained an open problem since its introduction in 2002. We culminate the search by proving this number to be 15. We achieve this result by improving the best-known method for this problem by roughly two orders of magnitude. The most important technique to boost performance is a novel, surprisingly effective propositional encoding for packing colorings. Additionally, we developed an alternative symmetry breaking method. Since both new techniques are more complex than existing techniques for this problem, a verified approach is required to trust them. We include both techniques in a proof of unsatisfiability, reducing the trusted core to the correctness of the direct encoding.

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De Nicolao, G., et R. Scattolini. « Properties of MBPC Algorithms ». Dans Advances in Model-Based Predictive Control, 103–69. Oxford University PressOxford, 1994. http://dx.doi.org/10.1093/oso/9780198562924.003.0002.

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Abstract This paper deals with the stability properties of predictive control with terminal constraints on the output and input variables. Specifically, in predictive control with terminal constraints on the controlled variable is forced to match a reference value over a given intraval at the end of the pred1ct1on horizon, while the control variable is allowed to have a restricted number of projected control variations. Both the classical receding horizon approach, where only the first projected control increment _is applied, and the so-called intervalwise receding horizon strategy, where a number of future control increments are effectively applied, are considered. A preliminary investigation of the robustness properties of receding horizon control is performed by exploiting its strict relations with infinite horizon Linear Quadratic control.

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Müller, Peter, Giovanni Parmigiani et Kenneth Rice. « FDR and Bayesian Multiple Comparisons Rules ». Dans Bayesian Statistics 8, 359–80. Oxford University PressOxford, 2007. http://dx.doi.org/10.1093/oso/9780199214655.003.0014.

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Abstract We discuss Bayesian approaches to multiple comparison problems, using a decision theoretic perspective to critically compare competing approaches. We set up decision problems that lead to the use of FDR-based rules and generalizations. Alternative definitions of the probability model and the utility function lead to different rules and problem-specific adjustments. Using a loss function that controls realized FDR we derive an optimal Bayes rule that is a variation of the Benjamini and Hochberg (1995) procedure. The cutoff is based on increments in ordered posterior probabilities instead of ordered p-values. Throughout the discussion we take a Bayesian perspective. In particular, we focus on conditional expected FDR, conditional on the data. Variations of the probability model include explicit modeling for dependence. Variations of the utility function include weighting by the extent of a true negative and accounting for the impact in the final decision.

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« Partitioning of Hysteresis Loops and Life Relations ». Dans Fatigue and Durability of Metals at High Temperatures, 83–109. ASM International, 2009. http://dx.doi.org/10.31399/asm.tb.fdmht.t52060083.

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Abstract This chapter compares and contrasts empirical approaches for partitioning hysteresis loops and predicting creep-fatigue life. The first part of the chapter presents experimental partitioning methods, explaining how they can be used to partition any loading cycle into its basic strain-range components. The methods covered include rapid cycling between peak stress extremes, half-cycle rapid loading and unloading, and variations of the incremental step-stress approach. The methods are then compared based on their ability to predict creep-fatigue life. The chapter goes on from there to describe how fatigue life can be estimated from ductility measurements when cyclic data are unavailable or are likely to change. It also explains how cyclic life is influenced by the time-dependent nature of creep-plasticity and the physical and metallurgical effects of environmental exposure.

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Yang, Seung-Eun, Kwang-Hyun Park et Zeungnam Bien. « Gesture Spotting Using Fuzzy Garbage Model and User Adaptation ». Dans Contemporary Theory and Pragmatic Approaches in Fuzzy Computing Utilization, 120–38. IGI Global, 2013. http://dx.doi.org/10.4018/978-1-4666-1870-1.ch009.

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Thanks to the rapid advancement of human-computer interaction technologies it is becoming easier for the elderly and/or people with disabilities to operate various electrical systems. Operation of home appliances by using a set of predefined hand gestures is an example. However, hand gesture recognition may fail when the predefined command gestures are similar to some ordinary but meaningless behaviors of the user. This paper uses a gesture spotting method to recognize a designated gesture from other similar gestures. A fuzzy garbage model is proposed to provide a variable reference value to determine whether the user’s gesture is the command gesture or not. Further, the authors propose two-stage user adaptation to enhance recognition performance: that is, off-line (batch) adaptation for inter-person variation and on-line (incremental) adaptation for intra-person variation. For implementation of the two-stage adaptation method, a genetic algorithm (GA) and the steepest descent method are adopted for each stage. Experimental results were obtained for 5 different users with left and up command gestures.

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Calvert, Julia. « Introduction to the Politics of Investment Treaties ». Dans The Politics of Investment Treaties in Latin America, 1–27. Oxford University PressOxford, 2022. http://dx.doi.org/10.1093/oso/9780198870890.003.0001.

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Abstract The introductory chapter contextualizes the book and lays out the central research questions. It first examines the legitimacy crisis engulfing international investment law and the different reform preferences being debated in national, regional, and multilateral circles. Variation in governments’ reform preferences cannot be reduced to different experiences with the costs of investment treaties. Most governments have adopted incremental reforms in their IIA programmes, but beyond this the picture is more complicated. Some governments that considered banning ISDS never lost an ISDS case. Other governments heavily targeted by investor claims defend the status quo. Variation in reform preferences therefore raise important questions about what erodes and what sustains the authority of investment rules over time. Why do some governments frequently targeted by investor claims continue to deepen their treaty commitments while others reform them? Why do governments that support strong investment protections continue to attract investor claims? The chapter connects these questions to political shifts in Latin America, where governments have become increasingly divided in their approach toward stringent investment protections. The chapter also expounds upon the study’s research design, the importance of prior beliefs in guiding reform preferences, and its comparative focus on reform preferences in Peru, Ecuador, and Argentina.

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Weber, Wendell W. « Predictive Biology ». Dans Pharmacogenetics, 338–88. Oxford University PressNew York, NY, 2008. http://dx.doi.org/10.1093/oso/9780195341515.003.0011.

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Abstract After its emergence as a discipline akin to both pharmacology and genetics, pharmacogenetics focused on determining the relationships between variations in single genes and variations in the response of individuals to drugs and other exogenous substances. The intent of pioneer investigators was firmly rooted in learning how human responsiveness to these agents was linked to the molecular processes of cells and tissues. After biologists deciphered the mechanisms by which cells read information encoded in the human genome and invented genomics technologies, the switch from pharmacogenetics to pharmacogenomics began, bringing about dramatic changes in the pace and scope of pharmacogenetics from the mid-1980s to the present time. Going from genetics to genomics resulted in a flood of new gene discoveries and new approaches to the identification of drug susceptibility loci; applications of genomics principles led to the discovery of many gene-based drug targets and to incremental advances in the development of new therapeutic agents. Today, the composition and function of hundreds or thousands of human genes spanning large fractions of the genome in many individuals and populations can be examined efficiently as a result ot advances in high-throughput genomic technologies combined with new methods to store, access, and analyze genomic data. A plethora of conferences, workshops, and educational programs focusing on a wide variety of themes helped everyone keep pace, while academic and industrial scientists, including many whose skills and immediate interests lay outside biology, lent their expertise to pharmacogenomic initiatives.

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Mayer, Helmut. « An Integrated Approach To Forward Modeling Carbonate Platform Development ». Dans Computers in Geology - 25 Years of Progress. Oxford University Press, 1994. http://dx.doi.org/10.1093/oso/9780195085938.003.0019.

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The forward model presented here is designed to simulate stratigraphic and geometric development of carbonate platforms. Starting from an initial basement geometry, the effects of a number of key variables on water depth are combined for each time increment. This procedure is repeated in an iterative fashion for subsequent time steps. The variables considered include subsidence, carbonate production, sediment redistribution, compaction, isostatic compensation, and eustatic sea-level change. Time- or depth-dependent functions are developed for these variables. Free parameters in these functions allow fitting to realistic magnitudes. A sample simulation demonstrates the characteristics of the model and indicates its usefulness in case studies and predictions. In recent years a number of studies on the modeling of sediment accumulation in various basin settings has been published. Most of them are concerned with clastic basin fill or do not discriminate lithologies (e.g., Turcotte and Kenyon, 1984; Kenyon and Turcotte, 1985; Tetzlaff, 1986; Bitzer and Harbaugh, 1987; Flemings and Jordan, 1987, 1989; Tetzlaff and Harbaugh, 1989; Jervey, 1989), while only few focus on mixed clastic/carbonate systems (e.g., Aigner et al., 1989; Lawrence et al., 1990) or carbonate platforms (e.g., Lerche et al., 1987; Bice, 1988; Demicco and Spencer, 1989; Scaturo et al., 1989). Sediment accumulation and distribution on a carbonate platform and the adjacent slope represent a highly complex system of numerous interdependent factors which in concert determine the development of the stratigraphy and geometry of the platform. The goal of this study is to develop a model that yields a "best compromise" between two principal targets: representation of all important variables in geologically reasonable functional relationships on the one hand, and simplicity on the other. Forward modeling of sedimentary systems serves to simulate the stratigraphic and geometric evolution of the system, dependent on variations in the input parameters. The purpose of this approach is to establish the critical variables and parameters which dominate the system and to produce a geologically reasonable generic stratigraphic pattern. The next step then would be to use the model to reproduce known patterns of actual modern or ancient sedimentary systems (inverse modeling).

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Actes de conférences sur le sujet "Incremental variational approach"

Geuzaine, Christophe, Laurent Stainier et Francois Henrotte. « Energy-Consistent Finite Element Modelling of Ferromagnetic Hysteresis ». Dans ASME 2012 11th Biennial Conference on Engineering Systems Design and Analysis. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/esda2012-82050.

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In this article we propose a macroscopic model for ferromagnetic hysteresis that is well-suited for finite element implementation. The model is readily vectorial and relies on a consistent thermodynamic formulation. In particular, the stored magnetic energy and the dissipated energy are known at all times, and not solely after the completion of closed hysteresis loops as is usually the case. The obtained incremental formulation is variationally consistent, i.e., all internal variables follow from the minimization of a thermodynamic potential. This variational approach is directly inspired from the kinematic hardening theory of plasticity, which opens the door for novel energy-consistent coupled mechanical/electromagnetic models.

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Gu, Xiaojun, Wael Zaki, Ziad Moumni et Weihong Zhang. « Implementation of the Large Time Increment Method for the Simulation of Pseudoelastic Shape Memory Alloys ». Dans ASME 2015 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/smasis2015-8923.

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The paper presents a numerical implementation of the Large Time Increment (LaTIn) method for the integration of the ZM model [1] for SMAs in the pseudoelastic range. LaTIn was initially proposed as an alternative to the conventional incremental approach for the integration of nonlinear constitutive models [2]. It is adapted here for the simulation of pseudoelastic SMA behavior and is shown to be especially useful in situations where the phase transformation process presents little to no hardening. In these situations, a slight stress variation during a load increment can result in large variation of the volume fraction of martensite within a representative volume element of the SMA. This can lead to difficulty in numerical convergence if the incremental method is used. LaTIn involves two stages: in the first stage a solution satisfying the conditions of static equilibrium is obtained for each load increment without considering the consistency with the phase transformation conditions, then in the second stage consistent increments of the local state variables are determined for the entire loading path. The two stages take place sequentially, in contrast to the incremental method that requires satisfying the global equilibrium and local consistency conditions simultaneously at a given load increment before proceeding to the next. The numerical integration algorithm consists of the following steps: 1. Division of the loading path into a finite number of increments, 2. Solution for all the load increments of the static equilibrium problem in which the local consistency conditions are relaxed, 3. Update of the state variables in accordance with the consistency conditions for all the load increments. Steps 2 and 3 are repeated until a solution is reached that satisfies simultaneously the equilibrium and consistency requirements. An algorithm is presented for the implicit integration of the time-discrete equations. The algorithm is used for finite element simulations using Abaqus, in which the model is implemented by means of a user material subroutine. The simulation results are discussed in comparison with those obtained using conventional step-by-step incremental integration.

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Kiefer, Björn, Karsten Buckmann, Thorsten Bartel et Andreas Menzel. « Modeling of Single Crystal Magnetostriction Based on Numerical Energy Relaxation Techniques ». Dans ASME 2014 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/smasis2014-7436.

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This paper presents an energy relaxation-based approach for the modeling of single crystalline magnetic shape memory alloy response under general two-dimensional magneto-mechanical loading. It relies on concepts of energy relaxation in the context of non-convex free energy landscapes whose wells define preferred states of straining and magnetization. The constrained theory of magnetoelasticity developed by DeSimone and James [1] forms the basis for the model development. The key features that characterize the extended approach are (i) dissipative effects, accounted for in an incremental variational setting, and (ii) finite magnetocrystalline anisotropy energy. In this manner, important additional response features, e.g. the hysteretic nature, the linear magnetization response in the pre-variant reorientation regime, and the stress dependence of the maximum field induced strain, can be captured, which are prohibited by the inherent assumptions of the constrained theory. The enhanced modeling capabilities of the extended approach are demonstrated by several representative response simulations and comparison to experimental results taken from literature. These examples particularly focus on the response of single crystals under cyclic magnetic field loading at constant stress, and cyclic mechanical loading at constant magnetic field.

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Nadkarni, Prajit, et Narendra Varma Dasararaju. « Visually Similar Products Retrieval for Shopsy ». Dans International Conference on Signal Processing and Vision. Academy and Industry Research Collaboration Center (AIRCC), 2022. http://dx.doi.org/10.5121/csit.2022.122203.

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Visual search is of great assistance in reseller commerce, especially for non-tech savvy users with affinity towards regional languages. Product attributes available in e-commerce have potential for building better visual search systems [2, 20, 29]. We design a visual search system for reseller commerce using a multi-task learning approach and address challenges like image compression, cropping, etc, faced in reseller commerce. Our model consists of three tasks: attribute classification, triplet ranking and variational autoencoder (VAE). We introduce an offline triplet mining technique which utilizes information from multiple attributes to capture relative order within data. This technique displays better performance compared to traditional triplet mining [27] baseline. We compare and report incremental gain achieved by our unified multi-task model over each individual task separately. The efsfectiveness of our method is demonstrated using in-house dataset of images from the Lifestyle business-unit of Flipkart. To efficiently retrieve images in production, we use Approximate Nearest Neighbor (ANN) index.

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Antaluca, Eduard, Daniel Ne´lias et Spiridon Cretu. « A Three-Dimensional Friction Model for Elastic-Plastic Contact With Tangential Loading : Application to Dented Surfaces ». Dans ASME/STLE 2004 International Joint Tribology Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/trib2004-64331.

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A three-dimensional numerical model based on a semi-analytical method in the framework of small strains and small displacements with respect of Hertz’s hypotheses is presented for solving an elastic-plastic dented contact with friction. The calculation of surface deformations and pressure distribution, which is the most time consuming step during the elastic-plastic algorithm, is obtained using a method based on a variational principle with a Fast Fourier Transform (FFT) and a Conjugate Gradient Method (CGM). The method is fast enough to allow investigating the effect of a small size surface defect, here a debris denting, on the subsurface elastic-plastic stress state, requiring a fine mesh with around 106 surface grid points. Further, the FFT approach is also involved in the calculation of internal stress state. The plasticity model is based on an incremental load and Von Mises yield criterion. The effects of the contact pressure distribution and residual strain on the geometry of the contacting surfaces yield from the Betti’s reciprocal theorem with initial strain. The code is used to compute a few smooth and dented contacts, with several types of contact interfaces conditions, including frictionless and Coulomb friction. The effects of surface dents and friction on the contact pressure and subsurface stress field are presented and discussed.

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Grimm, Tyler J., Ihab Ragai et John T. Roth. « Utilization of Wavy Toolpath in Single-Point Incremental Forming ». Dans ASME 2018 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/imece2018-86885.

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Incremental forming (IF) is a sheet material forming method which utilizes a hemispherically tipped tool to form material. The tool is typically CNC controlled along a path which outlines the contours of the final geometry. The most common toolpaths used during forming are the spiral and step-down paths. Few variations of these toolpaths currently exist. A novel toolpathing strategy is proposed herein. This toolpath forms a wave-like path in order to mimic the effects of vibration-assisted tooling; however, with much greater control. A variation of this strategy in which the tool does not lose contact with the surface of the part throughout its path was tested. This method has been found to be an effective approach for improving the surface variability of the final part.

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Sagar, Abhinandan, Caneon Kurien et Mayank Mittal. « Impact of Hydrogen Energy Fractions on Cycle-to-Cycle Variations in Biogas-Fueled Spark Ignition Engine ». Dans Automotive Technical Papers. 400 Commonwealth Drive, Warrendale, PA, United States : SAE International, 2023. http://dx.doi.org/10.4271/2023-01-5075.

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<div class="section abstract"><div class="htmlview paragraph">The limitations related to the cost-effectiveness and technological feasibility of upgrading biogas to bio-methane for rural power generation applications have prompted researchers to explore alternative approaches for improving the quality of biogas fuel. This study focuses on evaluating the effect of hydrogen enrichment on combustion characteristics and cycle-to-cycle combustion variations in a single-cylinder spark ignition engine fueled with biogas (60% CH<sub>4</sub> and 40% CO<sub>2</sub>). The engine was run at a constant operating load of 6 Nm, with a compression ratio of 10:1 and an engine speed of 1500 rpm. To establish a baseline for comparison, engine characteristics were initially assessed using pure methane fuel. Subsequently, the share of hydrogen in the biogas fuel mixture was incrementally increased on the volumetric basis from 0% to 30% and experiments were performed to study the effects of these variations on combustion behavior. The statistical approach was adopted for analyzing cycle-to-cycle variations by considering 120 consecutive engine cycles. The results of this study showed that increasing the H<sub>2</sub> share from 0% to 30% in an SI engine powered by biogas improved the combustion characteristics (increment in peak in-cylinder pressure; reduction in COV<sub>IMEP</sub> from 9.9% to 1.7%; improvement in combustion phasing). With the addition of H<sub>2</sub>, flame propagation speed increased and combustion time decreased. Results indicated that hydrogen enrichment resulted in lower cycle-to-cycle variations (CCVs) of pressure and combustion-related parameters.</div></div>

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Grimm, Tyler J., Ihab Ragai et John T. Roth. « The Effects of Polarity and Current Path in Electrically Assisted Single Point Incremental Forming of 2024-T3 Aluminum ». Dans ASME 2017 12th International Manufacturing Science and Engineering Conference collocated with the JSME/ASME 2017 6th International Conference on Materials and Processing. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/msec2017-3037.

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Electrically assisted incremental sheet forming (EAIF) is a novel addition to the incremental forming (IF) method. One variation of this approach applies direct electrical current during forming. Many improvements over tradition IF can be seen by utilizing this method, to include greater part accuracy, reduced forming force, and greater formability. In order to maximize the effects of electrically assisted incremental forming, all parameters of the method must be investigated, including the polarity of the current passing through the part and the path that the applied current takes. The effects of altering these two parameters is the primary investigation in this research. It was determined that, in order to optimize springback reduction and formability during electrically assisted single point incremental forming, the tool should be assigned the positive electrode and the center of the workpiece should be assigned the negative electrode. Additionally, the mechanism behind the spalling effect inherent to EAIF is discussed.

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Jing, Yunge, et Tianrui Li. « A Matrix-Based Incremental Attribute Reduction Approach under Knowledge Granularity on the Variation of Attribute Set ». Dans 2015 10th International Conference on Intelligent Systems and Knowledge Engineering (ISKE). IEEE, 2015. http://dx.doi.org/10.1109/iske.2015.40.

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Zeng, Anping, Tianrui Li, Chuan Luo et Junbo Zhang. « An incremental approach for updating approximations of rough fuzzy set under the variation of attribute values ». Dans 2013 IEEE Symposium on Computational Intelligence in Dynamic and Uncertain Environments (CIDUE). IEEE, 2013. http://dx.doi.org/10.1109/cidue.2013.6595772.

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Rapports d'organisations sur le sujet "Incremental variational approach"

Ruvinsky, Alicia, Maria Seale, R. Salter et Natàlia Garcia-Reyero. An ontology for an epigenetics approach to prognostics and health management. Engineer Research and Development Center (U.S.), mars 2023. http://dx.doi.org/10.21079/11681/46632.

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Techniques in prognostics and health management have advanced considerably in the last few decades, enabled by breakthroughs in computational methods and supporting technologies. These predictive models, whether data-driven or physics-based, target the modeling of a system’s aggregate performance. As such, they generalize assumptions about the modelled system’s components, and are thus limited in their ability to represent individual components and the dynamic environmental factors that affect composite system health. To address this deficiency, we have developed an epigenetics-inspired knowledge representation for engineered system state that encompasses components and environmental factors. Epigenetics is concerned with explaining how environmental factors affect the expression of an organism’s genetic material. The field has derived important in-sights into the development and progression of disease states based on how environmental factors impact genetic material, causing variations in how a gene is expressed. The health of an engineered system is similarly influenced by its environment. A foundation for a new approach to prognostics based on epigenetics must begin by representing the entities and relationships of an engineered system from the perspective of epigenetics. This paper presents an ontology for an epigenetics-inspired representation of an engineered system. An ontology describing the epigenetics of an engineered system will enable the composition of a formal model and the incremental development of a more robust, causal reasoning system.

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