Letteratura scientifica selezionata sul tema "Suitable parameterization"
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Articoli di riviste sul tema "Suitable parameterization"
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Mechem, David B., e Yefim L. Kogan. "A Bulk Parameterization of Giant CCN". Journal of the Atmospheric Sciences 65, n. 7 (1 luglio 2008): 2458–66. http://dx.doi.org/10.1175/2007jas2502.1.
Testo completoAbstract (sommario):
Abstract A parameterization for giant cloud condensation nuclei (GCCN), suitable for use in bulk microphysical models, has been developed that uses precise representations of the condensational growth of aerosol particles in the subcloud layer. The formulation employs an observationally based GCCN distribution function and directly observable parameters of GCCN, such as concentration and the shape of the aerosol spectra. The parameterization couples naturally to parameterizations of sea salt flux from the ocean surface. The behavior of the GCCN parameterization in a large eddy simulation (LES) framework is consistent with simulations employing explicit, size-resolving microphysical methods. The parameterization properly represents the sensitivity of cloud, drizzle, turbulence, and radiative properties to changes in GCCN concentration for polluted and clean background CCN environments.
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Ming, Yi, V. Ramaswamy, Leo J. Donner e Vaughan T. J. Phillips. "A New Parameterization of Cloud Droplet Activation Applicable to General Circulation Models". Journal of the Atmospheric Sciences 63, n. 4 (1 aprile 2006): 1348–56. http://dx.doi.org/10.1175/jas3686.1.
Testo completoAbstract (sommario):
Abstract A new parameterization is proposed to link the droplet number concentration to the size distribution and chemical composition of aerosol and updraft velocity. Except for an empirical assumption of droplet growth, the parameterization is formulated almost entirely on first principles to allow for satisfactory performance under a variety of conditions. For a series of updraft velocity ranging from 0.03 to 10.0 m s−1, the droplet number concentrations predicted with the parameterization are in good agreement with the detailed parcel model simulations with an average error of −4 ± 26% (one standard deviation). The accuracy is comparable to or better than some existing parameterizations. The parameterization is able to account for the effects of droplet surface tension and mass accommodation coefficient on activation without adjusting the empirical parameter. These desirable attributes make the parameterization suitable for being used in the prognostic determination of the cloud droplet number concentration in general circulation models (GCMs).
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Sun, Difu, Junqiang Song, Xiaoyong Li, Kaijun Ren e Hongze Leng. "A Novel Sea Surface Roughness Parameterization Based on Wave State and Sea Foam". Journal of Marine Science and Engineering 9, n. 3 (25 febbraio 2021): 246. http://dx.doi.org/10.3390/jmse9030246.
Testo completoAbstract (sommario):
A wave state related sea surface roughness parameterization scheme that takes into account the impact of sea foam is proposed in this study. Using eight observational datasets, the performances of two most widely used wave state related parameterizations are examined under various wave conditions. Based on the different performances of two wave state related parameterizations under different wave state, and by introducing the effect of sea foam, a new sea surface roughness parameterization suitable for low to extreme wind conditions is proposed. The behaviors of drag coefficient predicted by the proposed parameterization match the field and laboratory measurements well. It is shown that the drag coefficient increases with the increasing wind speed under low and moderate wind speed conditions, and then decreases with increasing wind speed, due to the effect of sea foam under high wind speed conditions. The maximum values of the drag coefficient are reached when the 10 m wind speeds are in the range of 30–35 m/s.
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Alexias, Pavlos, e Kyriakos C. Giannakoglou. "Shape Optimization of a Two-Fluid Mixing Device Using Continuous Adjoint". Fluids 5, n. 1 (8 gennaio 2020): 11. http://dx.doi.org/10.3390/fluids5010011.
Testo completoAbstract (sommario):
In this paper, the continuous adjoint method is used for the optimization of a static mixing device. The CFD model used is suitable for the flow simulation of the two miscible fluids that enter the device. The formulation of the adjoint equations, which allow the computation of the sensitivity derivatives is briefly demonstrated. A detailed analysis of the geometry parameterization is presented and a set of different parameterization scenarios are investigated. In detail, two different parameterizations are combined into a two-stage optimization algorithm which targets maximum mixture uniformity at the exit of the mixer and minimum total pressure losses. All parameterizations are in conformity with specific manufacturability constraints of the final shape. The non-dominated front of optimal solutions is obtained by using the weighted sum of the two objective functions and executing a set of optimization runs. The effectiveness of the proposed synthetic parameterization schemes is assessed and discussed in detail. Finally, a reduced length mixer is optimized to study the impact of the length of the tube on the device’s performance.
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Madi, Raneem, Gerrit Huibert de Rooij, Henrike Mielenz e Juliane Mai. "Parametric soil water retention models: a critical evaluation of expressions for the full moisture range". Hydrology and Earth System Sciences 22, n. 2 (12 febbraio 2018): 1193–219. http://dx.doi.org/10.5194/hess-22-1193-2018.
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Abstract. Few parametric expressions for the soil water retention curve are suitable for dry conditions. Furthermore, expressions for the soil hydraulic conductivity curves associated with parametric retention functions can behave unrealistically near saturation. We developed a general criterion for water retention parameterizations that ensures physically plausible conductivity curves. Only 3 of the 18 tested parameterizations met this criterion without restrictions on the parameters of a popular conductivity curve parameterization. A fourth required one parameter to be fixed. We estimated parameters by shuffled complex evolution (SCE) with the objective function tailored to various observation methods used to obtain retention curve data. We fitted the four parameterizations with physically plausible conductivities as well as the most widely used parameterization. The performance of the resulting 12 combinations of retention and conductivity curves was assessed in a numerical study with 751 days of semiarid atmospheric forcing applied to unvegetated, uniform, 1 m freely draining columns for four textures. Choosing different parameterizations had a minor effect on evaporation, but cumulative bottom fluxes varied by up to an order of magnitude between them. This highlights the need for a careful selection of the soil hydraulic parameterization that ideally does not only rely on goodness of fit to static soil water retention data but also on hydraulic conductivity measurements. Parameter fits for 21 soils showed that extrapolations into the dry range of the retention curve often became physically more realistic when the parameterization had a logarithmic dry branch, particularly in fine-textured soils where high residual water contents would otherwise be fitted.
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Hernández-Rivera, Efraín, Souma Chowdhury, Shawn P. Coleman, Payam Ghassemi e Mark A. Tschopp. "Integrating exploratory data analytics into ReaxFF parameterization". MRS Communications 8, n. 03 (settembre 2018): 1300–1310. http://dx.doi.org/10.1557/mrc.2018.155.
Testo completoAbstract (sommario):
We present a systematic approach to refine hyperdimensional interatomic potentials, which is showcased on the ReaxFF formulation. The objective of this research is to utilize the relationship between interatomic potential input variables and objective responses (e.g., cohesive energy) to identify and explore suitable parameterizations for the boron carbide (B–C) system. Through statistical data analytics, ReaxFF's parametric complexity was overcome via dimensional reduction (55 parameters) while retaining enough degrees of freedom to capture most of the variability in responses. Two potentials were identified which improved on an existing parameterization for the objective set if interest, showcasing the framework's capabilities.
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Ratkowsky, D. A. "A suitable parameterization of the Michaelis-Menten enzyme reaction". Biochemical Journal 240, n. 2 (1 dicembre 1986): 357–60. http://dx.doi.org/10.1042/bj2400357.
Testo completoAbstract (sommario):
It is shown here that a suitable form for estimation and inference using the Michaelis-Menten [(1913) Biochem Z. 49, 333-369] model for simple enzymic reactions is one in which the two parameters appear in the denominator of the equation. In this form, convergence to the least-squares estimates using the Gauss-Newton method [see Kennedy & Gentle (1980) Statistical Computing, Marcel Dekker, New York] is virtually ensured, or, as the model in this form is a member of the class of ‘generalized linear models’, it may be fitted by packages such as those of Rothamsted Experimental Station [(1977) GENSTAT (A General Statistical Program), Rothamsted Experimental Station, Harpenden] and the Numerical Algorithms Group [(1978) GLIM (Generalised Linear Interactive Modeling), Numerical Algorithms Group, Oxford]. Furthermore, the parameters-in-denominator principle is readily extended to more complicated catalytic models. With all parameters in the denominator, the least-squares estimators are close to being unbiased and normally distributed, whereas severe bias and non-normality may result from use of the standard formulations.
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Njuki, Sammy M., Chris M. Mannaerts e Zhongbo Su. "Accounting for Turbulence-Induced Canopy Heat Transfer in the Simulation of Sensible Heat Flux in SEBS Model". Remote Sensing 15, n. 6 (14 marzo 2023): 1578. http://dx.doi.org/10.3390/rs15061578.
Testo completoAbstract (sommario):
Surface turbulent heat fluxes are crucial for monitoring drought, heat waves, urban heat islands, agricultural water management, and other hydrological applications. Energy Balance Models (EBMs) are widely used to simulate surface heat fluxes from a combination of remote sensing-derived variables and meteorological data. Single-source EBMs, in particular, are preferred in mapping surface turbulent heat fluxes due to their relative simplicity. However, most single-source EBMs suffer from uncertainties inherent to the parameter kB−1, which is used to account for differences in the source of heat and the sink of momentum when representing aerodynamic resistance in single-source EBMs. For instance, the parameterization of kB−1 in the commonly used single-source Surface Energy Balance System (SEBS) model uses a constant value of the foliage heat transfer coefficient (Ct), in the parameterization of the vegetation component of kB−1 (kBv−1). Thus, SEBS ignores the effect of turbulence on canopy heat transfer. As a result, SEBS has been found to greatly underestimate sensible heat flux in tall forest canopies, where turbulence is a key contributor to canopy heat transfer. This study presents a revised parameterization of kBv−1 for the SEBS model. A physically based formulation of Ct, which considers the effect of turbulence on Ct, is used in deriving the revised parameterization. Simulation results across 15 eddy covariance (EC) flux tower sites show that the revised parameterization significantly reduces the underestimation of sensible heat flux compared to the original parameterization under tall forest canopies. The revised parameterization is relatively simple and does not require additional information on canopy structure compared to some more complex parameterizations proposed in the literature. As such, the revised parameterization is suitable for mapping surface turbulent heat fluxes, especially under tall forest canopies.
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Gholami, Yaser, Romain Brossier, Stéphane Operto, Alessandra Ribodetti e Jean Virieux. "Which parameterization is suitable for acoustic vertical transverse isotropic full waveform inversion? Part 1: Sensitivity and trade-off analysis". GEOPHYSICS 78, n. 2 (1 marzo 2013): R81—R105. http://dx.doi.org/10.1190/geo2012-0204.1.
Testo completoAbstract (sommario):
In most geologic environments, accounting for anisotropy is necessary to perform acoustic full waveform inversion (FWI) of wide-azimuth and wide-aperture seismic data because of the potential dependence of wave speeds on the direction of the wave propagation. In the framework of multiparameter FWI, the subsurface parameterization controls the influence of the different parameter classes on the modeled seismic data as a function of the scattering angle and hence the resolution with which the parameters can be reconstructed and the potential trade-off between different parameters. We have evaluated a numerical procedure based on computation of the scattering patterns of the different parameters to assess the sensitivity of the seismic data to different parameterizations of vertical transverse isotropic media in the acoustic approximation. Among the different categories we have tested, a monoparametric FWI was found for imaging one wave speed with a broad wavenumber content, keeping the Thomsen parameters fixed, which have a small influence on the data relative to the wave speed. This raises the question of the initial information required in the background models of the Thomsen parameters to perform reliable monoparameter FWI. Alternatively, simultaneously inverting the horizontal and vertical wave speeds introduces limited trade-off effects because these wave speeds have significant influence on the data for distinct ranges of scattering angles, while the influence of the Thomsen parameter [Formula: see text] remains weak. With such parameterization, the short-to-intermediate wavelengths of the vertical velocity are updated from the short-to-intermediate scattering angles, while the long-to-intermediate wavelengths of the horizontal velocity are updated from the wide-to-intermediate scattering angles. We concluded that the choice of the subsurface parameterization can be driven by the acquisition geometry, which controls the scattering-angle coverage and hence the resolving power of FWI, and by the accuracy of the available initial FWI models.
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Boutle, I. A., J. E. J. Eyre e A. P. Lock. "Seamless Stratocumulus Simulation across the Turbulent Gray Zone". Monthly Weather Review 142, n. 4 (27 marzo 2014): 1655–68. http://dx.doi.org/10.1175/mwr-d-13-00229.1.
Testo completoAbstract (sommario):
Abstract A pragmatic approach for representing partially resolved turbulence in numerical weather prediction models is introduced and tested. The method blends a conventional boundary layer parameterization, suitable for large grid lengths, with a subgrid turbulence scheme suitable for large-eddy simulation. The key parameter for blending the schemes is the ratio of grid length to boundary layer depth. The new parameterization is combined with a scale-aware microphysical parameterization and tested on a case study forecast of stratocumulus evolution. Simulations at a range of model grid lengths between 1 km and 100 m are compared to aircraft observations. The improved microphysical representation removes the correlation between precipitation rate and model grid length, while the new turbulence parameterization improves the transition from unresolved to resolved turbulence as grid length is reduced.
Tesi sul tema "Suitable parameterization"
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Bahari, Mustapha. "Transport optimal pour la génération de maillage et le r-raffinement". Electronic Thesis or Diss., Université Côte d'Azur, 2024. http://www.theses.fr/2024COAZ5032.
Testo completoAbstract (sommario):
Dans cette thèse, nous développons des solveurs rapides et des procédures de génération de maillage adaptatif basés sur le transport optimal dans le contexte de l'Analyse Isogéométrique, en utilisant les B-Splines comme base des éléments finis. Notre approche garantit la construction d'une bijection, abordant ainsi un défi majeur de l'Analyse Isogéométrique. Nous utilisons des éléments finis standard pour résoudre l'équation de Monge-Ampère. Cependant, une analyse de cette approche montre des limitations significatives, notamment lorsqu'elle est confrontée à des variations importantes au voisinage de la frontière. Pour surmonter ce défi, nous dérivons une nouvelle formulation utilisant une discrétisation B-Splines compatible basée sur la suite de DeRham. De plus, nous introduisons de nouveaux solveurs rapides utilisant la méthode de diagonalisation rapide pour aborder efficacement cette question.Nous proposons une variété de tests et d'applications pour illustrer la performance et l'efficacité de notre approche. Celles-ci incluent des tests utilisant des solutions construites de l'équation de Monge-Ampère ainsi que des fonctions de densité analytiques. De plus, nous appliquons notre solveur à des problèmes elliptiques et à des problèmes dépendant du temps, en relevant des défis tels que l'obtention d'une précision élevée, la capture précise des interfaces, et la réduction efficace des oscillations.Finalement, la paramétrisation B-spline de presque toutes les géométries présentées repose sur les informations donnnées par le bord, utilisant une nouvelle approche basée sur le transport optimalIn this thesis, we develop fast solvers and adaptive mesh generation procedures based on the Optimal Transport using B-Splines Finite Elements within the Isogeometric Analysis framework. Our approach ensures the construction of a bijection mapping, addressing a major challenge in Isogeometric Analysis.Initially, we employ standard B-Splines Finite Elements to solve the Monge-Ampère Equation. However, an analysis of this approach reveals significant limitations, particularly when confronted with high variations near the boundary. To overcome this challenge, we derive a new formulation utilizing compatible B-Splines discretization based on a discrete DeRham sequence. Furthermore, we introduce new fast solvers using the Fast Diagonalization method to address this issue effectively.We provide various tests and applications to demonstrate the performance and efficiency of our novel approach. These include testing our approach using manufactured solutions of the Monge-Ampère equation and employing analytical density functions. Additionally, we apply our solver to elliptic problems and time-dependent problems, addressing challenges such as achieving higher accuracy, accurately capturing sharp interfaces, and effectively reducing oscillations.Finally, the parameterization of nearly all presented geometries relies on CAD-boundary information, employing a novel approach based on optimal transport
Capitoli di libri sul tema "Suitable parameterization"
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Cheng, Yougan, Ronny Straube, Abed E. Alnaif, Lu Huang, Tarek A. Leil e Brian J. Schmidt. "Virtual Populations for Quantitative Systems Pharmacology Models". In Methods in Molecular Biology, 129–79. New York, NY: Springer US, 2022. http://dx.doi.org/10.1007/978-1-0716-2265-0_8.
Testo completoAbstract (sommario):
AbstractQuantitative systems pharmacology (QSP) places an emphasis on dynamic systems modeling, incorporating considerations from systems biology modeling and pharmacodynamics. The goal of QSP is often to quantitatively predict the effects of clinical therapeutics, their combinations, and their doses on clinical biomarkers and endpoints. In order to achieve this goal, strategies for incorporating clinical data into model calibration are critical. Virtual population (VPop) approaches facilitate model calibration while faced with challenges encountered in QSP model application, including modeling a breadth of clinical therapies, biomarkers, endpoints, utilizing data of varying structure and source, capturing observed clinical variability, and simulating with models that may require more substantial computational time and resources than often found in pharmacometrics applications. VPops are frequently developed in a process that may involve parameterization of isolated pathway models, integration into a larger QSP model, incorporation of clinical data, calibration, and quantitative validation that the model with the accompanying, calibrated VPop is suitable to address the intended question or help with the intended decision. Here, we introduce previous strategies for developing VPops in the context of a variety of therapeutic and safety areas: metabolic disorders, drug-induced liver injury, autoimmune diseases, and cancer. We introduce methodological considerations, prior work for sensitivity analysis and VPop algorithm design, and potential areas for future advancement. Finally, we give a more detailed application example of a VPop calibration algorithm that illustrates recent progress and many of the methodological considerations. In conclusion, although methodologies have varied, VPop strategies have been successfully applied to give valid clinical insights and predictions with the assistance of carefully defined and designed calibration and validation strategies. While a uniform VPop approach for all potential QSP applications may be challenging given the heterogeneity in use considerations, we anticipate continued innovation will help to drive VPop application for more challenging cases of greater scale while developing new rigorous methodologies and metrics.
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Davies, S., K. J. Packer, A. Baruya e A. I. Grant. "Enhanced information recovery in spectroscopy using the maximum entropy method". In Maximum Entropy in Action, 73–108. Oxford University PressOxford, 1991. http://dx.doi.org/10.1093/oso/9780198539414.003.0004.
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Abstract The maximum entropy method for the reliable extraction of information from spectroscopic data is outlined. Examples are shown from Raman and nuclear magnetic resonance spectroscopies, with particular reference to the selection and parameterization of suitable lineshape functions for deconvolution. An account is also given of our experiences with a proposed definition of the entropy function different from the usual form.
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Klemm, Lisa, Daniela Thaller, Claudia Flohrer, Anastasiia Walenta, Dieter Ullrich e Hendrik Hellmers. "Intra-Technique Combination of VLBI Intensives and Rapid Data to Improve the Temporal Regularity and Continuity of the UT1-UTC Series". In International Association of Geodesy Symposia. Berlin, Heidelberg: Springer Berlin Heidelberg, 2023. http://dx.doi.org/10.1007/1345_2023_235.
Testo completoAbstract (sommario):
AbstractThe difference UT1-UTC is the most variable quantity among the Earth Orientation Parameters (EOP) with significant unpredictable variation. It can be measured only with the quasi-space-fixed technique VLBI. The IVS organizes two different VLBI observation campaigns: The bi-weekly 24-hour Rapid campaigns and the daily 1-hour Intensive sessions. As a result, two independent UT1-UTC time series are estimated and published as official IVS EOP-S and EOP-I products. These have different strengths and weaknesses in terms of continuity and accuracy, but both are characterized by irregular temporal resolution. We present the current activities of BKG towards a combined processing of VLBI Intensive and Rapid data in one common adjustment. In this way, we unify the strengths of both sessions and generate a UT1-UTC time series characterized by a daily, continuous and temporally regular resolution, e.g., at 12:00 UTC. We achieved a significant improvement in accuracy of 35% lower WRMS values compared to the regular session-wise Intensive-only solution. By using a continuous EOP parameterization, the accuracy is almost at a constant level and less dependent on the irregularity of the VLBI observation period. The processing is based on homogenized, datum-free NEQs which allow a rigorous combination on the normal equation level instead of the observation level. Based on the improved combination method, we intend to set up a new operational VLBI EOP product at BKG. Its characteristics make it suitable as an input for EOP prediction algorithms.
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Taylor, F. W. "Climate observations by remote sensing". In Elementary Climate Physics, 130–59. Oxford University PressOxford, 2005. http://dx.doi.org/10.1093/oso/9780198567332.003.0009.
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Abstract Progress with understanding any aspect of the Earth as a physical system, in particular the environmental effects of climate change, depends critically on our ability to design and carry out suitable programmes of measurements. Theory and modelling alone cannot improve our understanding of the physics on which predictions rely, and only relevant data of high quality can test and improve specific models and parameterizations. By developing suitable instruments, we can explore and understand the physical processes in the atmosphere and oceans at the same time as we monitor the climate system for variations and secular change.
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Lcucari, Valentina, e Guido Consonni. "Compatible Priors for Causal Bayesian Networks". In Bayesian Statistics 7, 597–606. Oxford University PressOxford, 2003. http://dx.doi.org/10.1093/oso/9780198526155.003.0040.
Testo completoAbstract (sommario):
Abstract We consider discrete causal DAG-models (or Bayesian Networks) wherein the ordering of the variables is fixed across model structures. Given a prior on the parameter space of a model we describe a method for deriving a compatible prior on the parameter space of a submodel. This allows to generate automatically compatible priors for model parameters starting from a single prior relative to the largest entertained model. Our method makes use of a general procedure for constructing compatible priors for causal DAG- models, named reference conditioning, which is invariant within a suitable class of re-parameterizations and is model intrinsic. We show that if the generating prior satisfies global parameter independence, so does the compatible prior; in addition, prior modularity holds. Further results are obtained when the starting prior is product Dirichlet. A simple illustration of the methodology, and comparisons with alternative methods, are presented.
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Feferman, Solomon, John W. Dawson, Stephen C. Kleene, Gregory H. Moore, Robert M. Solovay e Jean van Heijenoort. "Introductory note to 1999b, c, d, g and h". In Kurt GöDel Collected Works Volume I, 272–75. Oxford University PressNew York, NY, 2001. http://dx.doi.org/10.1093/oso/9780195147209.003.0055.
Testo completoAbstract (sommario):
Abstract In addition to the many important logical results on which Gödel reported in Karl Menger’s Ergebnisse eines mathematischen Kolloquiums at the University of Vienna, there are five lesser known ones on geometry. In fact, Gödel had taken courses with Menger, and these notes are best seen within the framework of a program for reforming and purifying differential and projective geometry developed by Menger in the colloquium. In order to free the notion of “curvature” from “the complicated conceptual machinery” (Menger 1952) of classical differential geometry, in particular from coordinates, parameterizations and differentiability assumptions, Menger proposed to study suitable n-tuples of points in compact convex metric spaces. The triangle inequality implies the existence of three points in the Euclidean plane isometric to any triple of points in such a space, and their curvature is taken to be the reciprocal of the radius of the circle circumscribed around them. Menger then defined the curvature at a point of a curve in his space as the number from which the curvature of any three sufficiently close isometric points in the Euclidean plane differs arbitrarily little. Several results were based on this definition as well as on modifications of it by Franz Alt and by Gödel himself (Alt 1933). For surfaces the problem of curvature is more ambiguous and difficult. One now considers quadruples of points in Menger’s spaces; but points isometric to them may not exist at all in Euclidean space, and even when they do exist, the reciprocal of the radius of their circumscribed sphere is of no particular significance for the problem of curvature. Gödel (1993b) shows, however, in answer to a question of Laura Klanfer, that this reciprocal can be used to prove that, if an isometric Euclidean quadruple exists and is non-coplanar, then the metric quadruple is isometric, under the geodesic metric, to four points of a metricized sphere of suitable radius.
Atti di convegni sul tema "Suitable parameterization"
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Lee, Chen-Han, Lingyun Lu, Jon Dym e Guangyan Yin. "Shape Preserving Global Parameterization for CAD/CAM/CAE". In ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-60274.
Testo completoAbstract (sommario):
CAD/CAM/CAE applications often deal with open or closed shells of faces (surfaces). Each face has it’s own 2-D parameter space that may not be rectangular. In many applications we need to merge the individual parameter spaces into a single global parameter space that resembles the model shape in the 3-D physical space. In this paper, we present a method of building such shape-preserving global parameterization (of a shell of faces) that is suitable for CAD/CAM/CAE applications.
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Naets, Frank, Gert H. K. Heirman e Wim Desmet. "A Novel Approach to Real-Time Flexible Multibody Simulation: Sub-System Global Modal Parameterization". In ASME 2011 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/detc2011-47187.
Testo completoAbstract (sommario):
This paper introduces a novel model reduction technique, namely Sub-System Global Modal Parameterization (SS-GMP), for real-time simulation of flexible multibody systems. In the past, other system-level model reduction techniques have been proposed for this purpose, but these were limited in applicability due to the large storage requirements for systems with many rigid degrees-of-freedom (DOFs). However, in the SS-GMP approach, the motion of a mechanism is split up into a global motion and a relative motion of the (sub-)system. The relative motion is then reduced according to the Global Modal Parameterization, which is a model reduction procedure suitable for closed chain flexible multibody systems. In combination with suitable explicit solvers, the SS-GMP approach enables (hard) real-time simulations due to the strong reduction in the number of DOFs and the conversion of a system of differential-algebraic equations into a system of ordinary differential equations. The proposed approach is validated numerically with a quarter-car model. This fully flexible mechanism is simulated faster than real-time on a regular PC with the SS-GMP approach while providing accurate results.
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Yu, Junjie, e Behnam Jafarpour. "Deep Learning-Based Disentangled Parametrization for Model Calibration Under Multiple Geologic Scenarios". In SPE Reservoir Simulation Conference. SPE, 2023. http://dx.doi.org/10.2118/212177-ms.
Testo completoAbstract (sommario):
Abstract Parametrization is widely used to improve the solution of ill-posed subsurface flow model calibration problems. Traditional low-dimensional parameterization methods consist of spatial and transform-domain methods with well-established mathematical properties that are mostly amenable to interpretation. More recent deep learning-based parametrization approaches exhibit strong performance in representing complex geological patterns but lack interpretability, making them less suitable for systematic updates based on expert knowledge. We present a disentangled parameterization approach with variational autoencoder (VAE) architecture to enable improved representation of complex spatial patterns and provide some degree of interpretability by allowing certain spatial features and attributes of a property map to be controlled by a single latent variable (generative factor), while remaining relatively invariant to changes in other latent factors. The existence of disentangled latent variables brings extra controllability to incorporate expert knowledge in making updates to the model. We explore two different approaches to achieve disentangled parameterization. In the first approach, we use β-VAE to learn disentangled factors in unsupervised learning manner, while in the second approach we apply the conditional VAE to represent discrete disentangled factors through supervised learning. By encoding the geologic scenarios into discrete latent codes, the parameterization enables automated scenario selection during inverse modeling and assisted updates on the spatial maps by experts. We present preliminary results using a single-phase pumping test example to show how model calibration can benefit from the proposed disentangled parameterization.
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Ćurković, Milan, e Damir Vučina. "PARAMETERIZATION OF COMPLEX CULTURAL HERITAGE SHAPES FOR ONLINE VIEWING AND INTERACTIVE PRESENTATION AND PROCESSING". In ARQUEOLÓGICA 2.0 - 8th International Congress on Archaeology, Computer Graphics, Cultural Heritage and Innovation. Valencia: Universitat Politècnica València, 2016. http://dx.doi.org/10.4995/arqueologica8.2016.3510.
Testo completoAbstract (sommario):
We have developed algorithms and programs capable of efficiently parameterizing complex cultural heritage shapes including texture, which significantly reduces the data-set size. This is potentially significant for online viewing and interactive presentation and processing. The proposed approach is based on Non-uniform rational B-splines (NURBS) mathematical model which is also by itself suitable for analysis, especially of different artistic techniques.
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Banerjee, Arijit, Nikhil Lakhkar, Shahi Riaz, Gamal Refai-Ahmed e Dereje Agonafer. "Multi-Objective Parameterization of Graphite Heat Spreader for Portable Systems Applications". In ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-42927.
Testo completoAbstract (sommario):
The advancement made in portable electronic systems has primarily been due to miniaturization of electronic systems. This in turn leads to an increase in power density which leads to higher temperatures and formation of hot spots. There is a temperature specification of system surfaces for human comfort (such as the surface close to a keyboard on laptops). Challenge in cooling portable devices is that there is not enough room to accommodate heat sinks. It is therefore important to have heat spreaders that can transfer the heat from critical devices to regions where cooling is available. Traditionally, copper has been the best heat spreader due to its high thermal conductivity. However, copper has a relatively high density and correspondingly high weight. Graphite is a suitable alternative. Recent advances in graphite technology have resulted in fairly high conductivity in the planar directions. In spite of these advances, the cost of graphite is an issue. In this paper, a multi-objective parameterization is utilized that considers weight and temperature distribution of the graphite heat spreader as objective parameters. The data is then compared to published data that utilizes graphite in a laptop.
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Đorđević, Milan, Milan Josifović, Milan Kosanović e Nikola Georgijević. "MODELOVANJE I ODREĐIVANJE PARAMETARA UPROŠĆENOG MODELA SINHRONOG GENERATORA ZA POTREBE PARAMETRIZACIJE MODELA REGULATORA NAPONA". In 35. Savetovanje Srpskog nacionalnog komiteta Međunarodnog saveta za velike električne mreže. Srpski nacionalni komitet Međunarodnog saveta za velike električne mreže CIGRE Srbija, 2023. http://dx.doi.org/10.46793/cigre35.0753dj.
Testo completoAbstract (sommario):
The dynamic model of a synchronous generator (SG) can be represented by a set of differential equations that describe the dynamics of electrical and mechanical subsystems of the machine. Such models are implemented and available in libraries of software tools for power systems’ dynamic processes modeling. However, the parameterization of these models requires a substantial set of machine parameters that is often not available. Verification of the model of automatic voltage regulator (AVR) is done based on results obtained through tests performed on SG at idle, by recording the response of the machine to a step change of stator voltage reference. The specific operating mode allows for reduction of complexity of SG model, and allows SG to be modeled with a first-order transfer function. Although simple, this model is very suitable for determination of AVR parameters. The small complexity of the proposed model lands itself suitable for efficient application of optimization algorithms in order to determine unknown parameters of the AVR transfer function. The paper will show the method for determination of parameters of the first order non-linear SG model, based on the SG’s measured response at open circuit test. The paper will also present the use of the proposed SG model for AVR parameterization.
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Hull, Patrick V., e Stephen Canfield. "Optimal Synthesis of Compliant Mechanisms Using Subdivision and Commercial FEA". In ASME 2004 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/detc2004-57497.
Testo completoAbstract (sommario):
The field of distributed-compliance mechanisms has seen significant work in developing suitable topology optimization tools for their design. These optimal design tools have grown out of the techniques of structural optimization. This paper will build on the previous work in topology optimization and compliant mechanism design by proposing an alternative design space parameterization through control points and adding another step to the process, that of subdivision. The control points assist a specific design to be represented as a solid model during the optimization process. The process of subdivision creates an additional number of control points that help smooth the surface (for example a C2 continuous surface depending on the method of subdivision chosen) creating a manufacturable design free of traditional numerical instabilities. Note that these additional control points do not add to the number of design parameters. This alternative parameterization and description as a solid model effectively and completely separates the design variables from the analysis variables during the optimization procedure. The motivation behind this work is to avoid several of the numerical instabilities that occur in topology optimization and to create an automated design tool from task definition to functional prototype created on a CNC or rapid-prototype machine. This paper will describe the complaint mechanism design process including subdivision and will demonstrate the procedure on several common examples.
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Becker, Malte, Sebastian Heppner, Raphael Alt, Tobias Kleinert e Katharina Schmitz. "Improving Fluid Power System Simulation Through an AAS-Based Simulation Framework". In ASME/BATH 2023 Symposium on Fluid Power and Motion Control. American Society of Mechanical Engineers, 2023. http://dx.doi.org/10.1115/fpmc2023-109807.
Testo completoAbstract (sommario):
Abstract This contribution introduces a simulation framework to significantly improve the simulation-based engineering process based on the Asset Administration Shell (AAS). The current simulation-based engineering process is characterized by long development times, high error susceptibility, and low availability of suitable simulation models. These deficits are addressed by seamlessly linking component data and encapsulated simulation models. Seamless linking is realized based on the AAS, a concept for realizing virtual representations of an asset [1]. The encapsulation enables better availability of simulation models in the engineering process by allowing stakeholders to exchange simulation models domain- and tool-independently. For this purpose, the Functional Mock-up Interface (FMI) is used, and coupling mechanisms for a component-based encapsulation of fluid power simulation models are presented. Based on the AAS, linking component data and encapsulated simulation models is realized to parameterize the simulation models and reduce the long development time and error susceptibility. Therefore, three functionalities have been developed based on the AAS data model. The first functionality allows searching and finding components or component simulation models from repositories of relevant stakeholders. As a result, individual components can be requested from specific component manufacturers during the development process. The second functionality enables domain- and tool-independent integration of simulation models into a simulation environment by using automatic parameterization or direct integration of encapsulated simulation models. Automatic parameterization reduces the time required and possible susceptibility to errors during manual parameterization, a task requiring integrating many different parameter sources. Finally, the third functionality enables bidirectional synchronization between field devices and component simulation models. As a result, the machine manufacturer can offer simulation model-based error support to the operator or assist the operator during commissioning. These functionalities result in a concept for a new AAS-based simulation framework, shown in this contribution. The concept is a solution for mentioned deficits in the simulation-based engineering process.
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Chen, Chao, e Johann Wurzenberger. "Parameterization of an Electrochemical Battery Model Using Impedance Spectroscopy in a Wide Range of Frequency". In WCX SAE World Congress Experience. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 2024. http://dx.doi.org/10.4271/2024-01-2194.
Testo completoAbstract (sommario):
<div class="section abstract"><div class="htmlview paragraph">The parameterization of the electrochemical pseudo-two-dimensional (P2D) model plays an important role as it determines the acceptance and application range of subsequent simulation studies. Electrochemical impedance spectroscopy (EIS) is commonly applied to characterize batteries and to obtain the exchange current density and the solid diffusion coefficient of a given electrode material. EIS measurements performed with frequencies ranging from 1 MHz down to 10 mHz typically do not cover clearly isolated solid state diffusion processes of lithium ions in positive or negative electrode materials. To extend the frequency range down to 10 μHz, the distribution function of relaxation times (DRT) is a promising analysis method. It can be applied to time-domain measurements where the battery is excited by a current pulse and relaxed for a certain period. By means of curve-fitting techniques, the pulse-relaxation measurement can be transferred in a function suitable for the DRT analysis, which is the basis for constructing additional low-frequency impedance points.</div><div class="htmlview paragraph">In this work, the EIS measured in the frequency domain and the simulated EIS derived from the time-domain measurement by the DRT method are combined to cover all electrochemical processes of the battery, especially the lithium-ion diffusion in the electrodes. The electrical equivalent circuit model (ECM) consisting of resistors, ZARC elements and Warburg elements in the frequency domain is applied to fit the EIS curve and identify the P2D model parameters. By investigating the intercalation processes using the distribution function of the differential capacity (DDC) technique, particles with different particle sizes are considered and their corresponding solid diffusion coefficients are identified by the established ECM. The consistency between time- and frequency-domain data is elaborated based on a model of a commercial automotive cell.</div></div>
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Reineke, Lea, Regina Schlegel e Sebastian Hein. "Influence Of Powder Packing Density On Binder Saturation And Wetting Behavior In Metal Binder Jetting". In Euro Powder Metallurgy 2023 Congress & Exhibition. EPMA, 2023. http://dx.doi.org/10.59499/ep235740488.
Testo completoAbstract (sommario):
Metal Binder Jetting (MBJ) has an increasing attention in additive manufacturing because of its serial production potential. Finding the most suitable parameterization in MBJ and develop pre-printing tests, can reduce the iteration stages in material-specific process development, which saves costs, effort as well as material resources and printing capacity. The powder binder interaction of five powders at different packing densities were determined and the wetting behaviors were compared. The equilibrium saturation, the wetting rate and the initial wetting time were analyzed. In order to understand the nature of the resulting porosity at low packing density, various samples were sintered and compared by micrographs. The results show that an increasing packing density decreases the initial wetting time, increases the equilibrium saturation and lowers the saturation rate. The relationship between wetting behavior and printing parameters, as well as the effect of drying must be investigated further in subsequent studies.