| 1. |
- Kaufmann, Thomas, et al.
(författare)
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Recent developments of the meshless radial point interpolation method for time-domain electromagnetics
- 2012
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Ingår i: International Journal of Numerical Modelling: Electronic Networks, Devices and Fields. - : Wiley. - 0894-3370 .- 1099-1204. ; 25:5-6, s. 468-489
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Forskningsöversikt (refereegranskat)abstract
- Meshless methods are a promising new field in computational electromagnetics. Instead of relying on an explicit mesh topology, a numerical solution is computed on an unstructured set of collocation nodes. This allows to model fine geometrical details with high accuracy and facilitates the adaptation of node distributions for optimization or refinement purposes. The radial point interpolation method (RPIM) is a meshless method based on radial basis functions. In this paper, the current state of the RPIM in electromagnetics is reviewed. The localized RPIM scheme is summarized, and the interpolation accuracy is discussed in dependence of important parameters. A time-domain implementation is presented, and important time iteration aspects are reviewed. New formulations for perfectly matched layers and waveguide ports are introduced. An unconditionally stable RPIM scheme is summarized, and its advantages for hybridization with the classical RPIM scheme are discussed in a practical example. The capabilities of an adaptive time-domain refinement strategy based on the experiences on a frequency-domain solver are discussed.
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| 2. |
- Lamers, Jules, 1986
(författare)
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The Functional Method for the Domain-Wall Partition Function
- 2018
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Ingår i: Symmetry, Integrability and Geometry - Methods and Applications. - 1815-0659. ; 14
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Forskningsöversikt (refereegranskat)abstract
- We review the (algebraic-)functional method devised by Galleas and further developed by Galleas and the author. We first explain the method using the simplest example: the computation of the partition function for the six-vertex model with domain-wall boundary conditions. At the heart of the method lies a linear functional equation for the partition function. After deriving this equation we outline its analysis. The result is a closed expression in the form of a symmetrized sum - or, equivalently, multiple-integral formula - that can be rewritten to recover Izergin's determinant. Special attention is paid to the relation with other approaches. In particular we show that the Korepin-Izergin approach can be recovered within the functional method. We comment on the functional method's range of applicability, and review how it is adapted to the technically more involved example of the elliptic solid-on-solid model with domain walls and a reflecting end. We present a new formula for the partition function of the latter, which was expressed as a determinant by Tsuchiya-Filali-Kitanine. Our result takes the form of a 'crossing-symmetrized' sum with 2(L) terms featuring the elliptic domain-wall partition function, which appears to be new also in the limiting case of the six-vertex model. Further taking the rational limit we recover the expression obtained by Frassek using the boundary perimeter Bethe ansatz.
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| 3. |
- de Graaf, Albert A, et al.
(författare)
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Nutritional systems biology modeling: from molecular mechanisms to physiology.
- 2009
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Ingår i: PLoS computational biology. - : Public Library of Science (PLoS). - 1553-7358 .- 1553-734X. ; 5:11
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Forskningsöversikt (refereegranskat)abstract
- The use of computational modeling and simulation has increased in many biological fields, but despite their potential these techniques are only marginally applied in nutritional sciences. Nevertheless, recent applications of modeling have been instrumental in answering important nutritional questions from the cellular up to the physiological levels. Capturing the complexity of today's important nutritional research questions poses a challenge for modeling to become truly integrative in the consideration and interpretation of experimental data at widely differing scales of space and time. In this review, we discuss a selection of available modeling approaches and applications relevant for nutrition. We then put these models into perspective by categorizing them according to their space and time domain. Through this categorization process, we identified a dearth of models that consider processes occurring between the microscopic and macroscopic scale. We propose a "middle-out" strategy to develop the required full-scale, multilevel computational models. Exhaustive and accurate phenotyping, the use of the virtual patient concept, and the development of biomarkers from "-omics" signatures are identified as key elements of a successful systems biology modeling approach in nutrition research--one that integrates physiological mechanisms and data at multiple space and time scales.
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| 4. |
- Travaglini, Gabriele, et al.
(författare)
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The SAGEX review on scattering amplitudes
- 2022
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Ingår i: Journal of Physics A. - : IOP Publishing. - 1751-8113 .- 1751-8121. ; 55:44
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Forskningsöversikt (refereegranskat)abstract
- This is an introduction to, and invitation to read, a series of review articles on scattering amplitudes in gauge theory, gravity, and superstring theory. Our aim is to provide an overview of the field, from basic aspects to a selection of current (2022) research and developments.
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| 5. |
- Kirchner, Nina, et al.
(författare)
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Shallow ice approximation, second order shallow ice approximation, and full Stokes models : A discussion of their roles in palaeo-ice sheet modelling and development
- 2016
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 135, s. 103-114
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Forskningsöversikt (refereegranskat)abstract
- Full Stokes ice sheet models provide the most accurate description of ice sheet flow, and can therefore be used to reduce existing uncertainties in predicting the contribution of ice sheets to future sea level rise on centennial time-scales. The level of accuracy at which millennial time-scale palaeo-ice sheet simulations resolve ice sheet flow lags the standards set by Full Stokes models, especially, when Shallow Ice Approximation (SIA) models are used. Most models used in paleo-ice sheet modeling were developed at a time when computer power was very limited, and rely on several assumptions. At the time there was no means of verifying the assumptions by other than mathematical arguments. However, with the computer power and refined Full Stokes models available today, it is possible to test these assumptions numerically. In this paper, we review (Ahlkrona et al., 2013a) where such tests were performed and inaccuracies in commonly used arguments were found. We also summarize (Ahlkrona et al., 2013b) where the implications of the inaccurate assumptions are analyzed for two paleo-models - the SIA and the SOSIA. We review these works without resorting to mathematical detail, in order to make them accessible to a wider audience with a general interest in palaeo-ice sheet modelling. Specifically, we discuss two implications of relevance for palaeo-ice sheet modelling. First, classical SIA models are less accurate than assumed in their original derivation. Secondly, and contrary to previous recommendations, the SOSIA model is ruled out as a practicable tool for palaeo-ice sheet simulations. We conclude with an outlook concerning the new Ice Sheet Coupled Approximation Level (ISCAL) method presented in Ahlkrona et al. (2016), that has the potential to match the accuracy standards of full Stokes model on palaeo-timescales of tens of thousands of years, and to become an alternative to hybrid models currently used in palaeo-ice sheet modelling. The method is applied to an ice sheet covering Svalbard.
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| 6. |
- Tavana, Madjid, et al.
(författare)
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A systematic review of the soft computing methods shaping the future of the metaverse
- 2024
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Ingår i: Applied Soft Computing. - 1568-4946. ; 150
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Forskningsöversikt (refereegranskat)abstract
- The metaverse is an emerging technology with the potential to revolutionize our interactions with digital environments. Soft computing presents exciting opportunities in shaping this immersive virtual world. This paper provides a systematic review of the research on soft computing methods in the metaverse, highlighting the interdisciplinary nature of the field and the need for coordination to shape its future. The systematic literature review conducted in this article identifies the contributors and domains in soft computing, emphasizing the need for new developments and joint applications in soft computing and the metaverse. The study categorizes soft computing techniques into five classes - machine learning, fuzzy systems, evolutionary computing, probability analysis, and mixed/hybrid methods - contributing to the emerging metaverse-related research and development. We propose a decision framework for selecting the most suitable soft computing method to assist researchers and developers in methodically assessing the alternative methods. The findings provide a roadmap and opportunities for soft computing models and applications shaping the future of the metaverse. This article can serve as a useful reference for researchers, practitioners, and policymakers working in soft computing and the metaverse.
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| 7. |
- Borén, Jan, 1963, et al.
(författare)
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Kinetic Studies to Investigate Lipoprotein Metabolism.
- 2012
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Ingår i: Journal of internal medicine. - : Wiley. - 1365-2796 .- 0954-6820. ; 271:2, s. 166-173
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Forskningsöversikt (refereegranskat)abstract
- To develop novel strategies for prevention and treatment of dyslipidaemia, it is essential to understand the pathophysiology of dyslipoproteinaemia in humans. Lipoprotein metabolism is a complex system in which abnormal concentrations of various lipoprotein particles can result from alterations in their rates of production, conversion and/or catabolism. Traditional methods that measure plasma lipoprotein concentrations only provide static estimates of lipoprotein metabolism and hence limited mechanistic information. By contrast, the use of tracers labelled with stable isotopes and mathematical modelling provides a powerful tool for probing lipid and lipoprotein kinetics in vivo and furthering understanding of the pathogenesis of dyslipoproteinaemia.
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| 8. |
- Athanasopoulos, George, et al.
(författare)
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Forecast reconciliation : A review
- 2024
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Ingår i: International Journal of Forecasting. - : Elsevier. - 0169-2070 .- 1872-8200. ; 40:2, s. 430-456
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Forskningsöversikt (refereegranskat)abstract
- Collections of time series formed via aggregation are prevalent in many fields. These are commonly referred to as hierarchical time series and may be constructed cross-sectionally across different variables, temporally by aggregating a single series at different frequencies, or even generalised beyond aggregation as time series that respect linear constraints. When forecasting such time series, a desirable condition is for forecasts to be coherent: to respect the constraints. The past decades have seen substantial growth in this field with the development of reconciliation methods that ensure coherent forecasts and improve forecast accuracy. This paper serves as a comprehensive review of forecast reconciliation and an entry point for researchers and practitioners dealing with hierarchical time series. The scope of the article includes perspectives on forecast reconciliation from machine learning, Bayesian statistics and probabilistic forecasting, as well as applications in economics, energy, tourism, retail demand and demography.
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| 9. |
- Ames, Ellery, 1984, et al.
(författare)
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Stationary solutions of the axially symmetric Einstein-Vlasov system: present status and open problems
- 2024
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Ingår i: CLASSICAL AND QUANTUM GRAVITY. - 0264-9381 .- 1361-6382. ; 41:7
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Forskningsöversikt (refereegranskat)abstract
- The purpose of this work is to review the status about stationary solutions of the axially symmetric Einstein-Vlasov system with a focus on open problems of both analytical and numerical nature. For the latter we emphasize that the code used to construct stationary solutions in Ames et al (2016 Class. Quantum Grav. 33 155008; 2019 Phys. Rev. D 99 024012) is open source, see Ames and Logg (2023 J. Open Source Softw. 8 5979). In the analytical setting the open problems include establishing methods for proving existence of axisymmetric stationary solutions which are far from spherically symmetric, both in the general case and for certain special classes of solutions pointed out in the text. In the numerical setting there are intriguing properties of highly relativistic solutions that demand further attention, such as whether a sequence of such stationary solutions can approach a Kerr black hole, or if they necessarily approach the thin ring limit reminiscent of cosmic strings. The question of whether stationary solutions include states with thin-disk like morphologies as seen in many galaxies is also open. Finally, there are opportunities to extend this research to new settings such as the case of massless particles and coupled black hole-matter systems. We believe that some of the open problems highlighted here are of central importance for the understanding of nature.
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| 10. |
- Khan, Muhammad Saif Ullah, et al.
(författare)
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Three-Dimensional Reconstruction from a Single RGB Image Using Deep Learning: A Review
- 2022
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Ingår i: Journal of Imaging. - : MDPI. - 2313-433X. ; 8:9
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Forskningsöversikt (refereegranskat)abstract
- Performing 3D reconstruction from a single 2D input is a challenging problem that is trending in literature. Until recently, it was an ill-posed optimization problem, but with the advent of learning-based methods, the performance of 3D reconstruction has also significantly improved. Infinitely many different 3D objects can be projected onto the same 2D plane, which makes the reconstruction task very difficult. It is even more difficult for objects with complex deformations or no textures. This paper serves as a review of recent literature on 3D reconstruction from a single view, with a focus on deep learning methods from 2018 to 2021. Due to the lack of standard datasets or 3D shape representation methods, it is hard to compare all reviewed methods directly. However, this paper reviews different approaches for reconstructing 3D shapes as depth maps, surface normals, point clouds, and meshes; along with various loss functions and metrics used to train and evaluate these methods.
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