检索结果-内蒙古大学图书馆

BPS2025 - Simulations of deformation-dependent signaling at the plasma membrane and the nuclear envelope

Biophysical Journal 2025年第3期124卷 143a-143a页

作者： Emmet A. Francis Einollah Sarikhani Vrund Patel Dhivya P. Meganathan Marie E. Rognes Zeinab Jahed Padmini Rangamani Department of Pharmacology University of California San Diego La Jolla CA USA Department of Nanoengineering University of California San Diego La Jolla CA USA Department of Numerical Analysis and Scientific Computing Simula Research Laboratory Oslo Norway

来源：评论

学校读者我要写书评

暂无评论

OPTIMIZATION OF HOPF BIFURCATION POINTS

arXiv

引用

arXiv 2022年

作者： Boullé, Nicolas Farrell, Patrick E. Rognes, Marie E. Isaac Newton Institute for Mathematical Sciences University of Cambridge CB3 0EH United Kingdom Mathematical Institute University of Oxford OxfordOX2 6GG United Kingdom Department of Scientific Computing and Numerical Analysis Simula Research Laboratory Oslo Norway Department of Mathematics University of Bergen Bergen Norway

We introduce a numerical technique for controlling the location and stability properties of Hopf bifurcations in dynamical systems. The algorithm consists of solving an optimization problem constrained by an extended system of nonlinear partial differential equations that characterizes Hopf bifurcation points. The flexibility and robustness of the method allows us to advance or delay a Hopf bifurcation to a target value of the bifurcation parameter, as well as controlling the oscillation frequency with respect to a parameter of the system or the shape of the domain on which solutions are defined. numerical applications are presented in systems arising from biology and fluid dynamics, such as the FitzHugh-Nagumo model, Ginzburg-Landau equation, Rayleigh-Bénard convection problem, and Navier-Stokes equations, where the control of the location and oscillation frequency of periodic solutions is of high *** Codes 65P30, 65P40, 37M20, 65K10, 49M41 Copyright © 2022, The Authors. All rights reserved.

关键词： Hopf bifurcation

来源：评论

学校读者我要写书评

暂无评论

How quantum and evolutionary algorithms can help each other: two examples

arXiv

引用

arXiv 2024年

作者： Bhandari, Shailendra Nichele, Stefano Denysov, Sergiy Lind, Pedro G. Department of Computer Science OsloMet - Oslo Metropolitan University P.O. Box 4 St. Olavs plass OsloN-0130 Norway OsloMet Artificial Intelligence Lab Pilestredet 52 OsloN-0166 Norway NordSTAR - Nordic Center for Sustainable and Trustworthy AI Research Pilestredet 52 OsloN-0166 Norway Department of Computer Science and Communication Østfold University College B R A Veien 4 HaldenN-1757 Norway Simula Research Laboratory Numerical Analysis and Scientific Computing Oslo0164 Norway

We investigate the potential of bio-inspired evolutionary algorithms for designing quantum circuits with specific goals, focusing on two particular tasks. The first one is motivated by the ideas of Artificial Life that are used to reproduce stochastic cellular automata with given rules. We test the robustness of quantum implementations of the cellular automata for different numbers of quantum gates The second task deals with the sampling of quantum circuits that generate highly entangled quantum states, which constitute an important resource for quantum computing. In particular, an evolutionary algorithm is employed to optimize circuits with respect to a fitness function defined with the Mayer-Wallach entanglement measure. We demonstrate that, by balancing the mutation rate between exploration and exploitation, we can find entangling quantum circuits for up to five qubits. We also discuss the trade-off between the number of gates in quantum circuits and the computational costs of finding the gate arrangements leading to a strongly entangled state. Our findings provide additional insight into the trade-off between the complexity of a circuit and its performance, which is an important factor in the design of quantum circuits. © 2024, CC BY.

关键词： Quantum computers

来源：评论

学校读者我要写书评

暂无评论

Fast uncertainty quantification of tracer distribution in the brain interstitial fluid with multilevel and quasi Monte Carlo

arXiv

引用

arXiv 2020年

作者： Croci, Matteo Vinje, Vegard Rognes, Marie E. Mathematical Institute University of Oxford Oxford United Kingdom Department for Numerical Analysis and Scientific Computing Simula Research Laboratory Lysaker Norway

Efficient uncertainty quantification algorithms are key to understand the propagation of uncertainty - from uncertain input parameters to uncertain output quantities - in high resolution mathematical models of brain physiology. Advanced Monte Carlo methods such as quasi Monte Carlo (QMC) and multilevel Monte Carlo (MLMC) have the potential to dramatically improve upon standard Monte Carlo (MC) methods, but their applicability and performance in biomedical applications is underexplored. In this paper, we design and apply QMC and MLMC methods to quantify uncertainty in a convection-diffusion model of tracer transport within the brain. We show that QMC outperforms standard MC simulations when the number of random inputs is small. MLMC considerably outperforms both QMC and standard MC methods and should therefore be preferred for brain transport models. Copyright © 2020, The Authors. All rights reserved.

关键词： Finite element method

来源：评论

学校读者我要写书评

暂无评论

Application of a dispersive wave hydro-sediment-morphodynamic model in the Ria Formosa lagoon

arXiv

引用

arXiv 2022年

作者： Kazhyken, Kazbek Valseth, Eirik Videman, Juha Dawson, Clint Oden Institute for Computational Engineering and Sciences The University of Texas at Austin AustinTX78712 United States CAMGSD Departamento de Matemática Universidade de Lisboa Lisbon1049-001 Portugal Department of Data Science The Norwegian University of Life Sciences Ås1433 Norway Department of Numerical Analysis and Scientific Computing Simula Research Laboratory Oslo0164 Norway

Results of an application of a dispersive wave hydro-sediment-morphodynamic model in the western circulation cell of the Ria Formosa lagoon located in the Algarve region of the southern Portugal are presented. This area of interest has a couple of features that complicate the application of the dispersive wave model: (1) the area has a complex irregular geometry with a number of barrier islands that separate the lagoon from the Atlantic Ocean, artificial and naturally occurring tidal inlets, and a number of curling channels inside the lagoon that interconnect the inlets and serve as waterways between the lagoon settlements;(2) the tidal range in the area can reach up to 3.5 m;therefore, the terrain inside the lagoon is characterized by vast salt marshes and tidal flats, and the wetting-drying process is a key component of any hydrodynamic simulation in this area. A model representation of the area has been developed by generating an unstructured finite element mesh of the circulation cell, and collecting data on parameters that characterize the tidal waves in the area, and bottom friction and sediment transport models used in the simulations. The results of the simulations indicate that the dispersive wave model can be applied in coastal areas with nontrivial underlying physical processes, and complex irregular geometries. Moreover, the dispersive term of the model is capable of capturing additional flow characteristics that are otherwise not present in hydrodynamic simulations that involve the nonlinear shallow water equations;and these additional flow features can, in their turn, affect the resulting sediment transport and bed morphodynamic process simulations. Copyright © 2022, The Authors. All rights reserved.

关键词： Equations of motion

来源：评论

学校读者我要写书评

暂无评论

Efficacy of reduced order source terms for a coupled wave-circulation model in the Gulf of Mexico

arXiv

引用

arXiv 2023年

作者： Loveland, Mark Meixner, Jessica Valseth, Eirik Dawson, Clint Oden Institute for Computational Engineering and Sciences University of Texas at Austin Oden Institute for Computational Engineering and Sciences The University of Texas at Austin 201 E. 24th St. AustinTX78712 United States College ParkMD United States The Department of Data Science The Norwegian University of Life Science Drøbakveien 31 Ås1433 Norway Department of Scientific Computing and Numerical Analysis Simula Research Laboratory Kristian Augusts gate 23 Oslo0164 Norway

During hurricanes, coupled wave-circulation models are critical tools for public safety. The standard approach is to use a high fidelity circulation model coupled with a wave model that uses the most advanced source terms. As a result, the models can be computationally expensive and so this study investigates the potential consequences of using simplified (reduced order) source terms within the wave model component of the coupled wave-circulation model. The trade-off between run time and accuracy with respect to observations is quantified for a set of two storms that impacted the Gulf of Mexico, Hurricane Ike and Hurricane Ida. Water surface elevations as well as wave statistics (significant wave height, peak period, and mean wave direction) are compared to observations. The usage of the reduced order source terms yielded significant savings in computational cost. Additionally, relatively low amounts of additional error with respect to observations during the simulations with reduced order source terms are observed in our computational experiments. However, large changes in global model outputs of the wave statistics were observed based on the choice of source terms particularly near the track of each hurricane. © 2023, CC BY.

关键词： Hurricanes

来源：评论

学校读者我要写书评

暂无评论

WAVEx: Stabilized Finite Elements for Spectral Wind Wave Models Using FEniCSx

arXiv

引用

arXiv 2023年

作者： Loveland, Mark Valseth, Eirik Meixner, Jessica Dawson, Clint Oden Institute for Computational Engineering and Sciences University of Texas at Austin 201 E. 24th St. AustinTX78712 United States The Department of Data Science The Norwegian University of Life Science Drøbakveien 31 Ås1433 Norway Department of Scientific Computing and Numerical Analysis Simula Research Laboratory Kristian Augusts gate 23 Oslo0164 Norway NWS NCEP EMC 830 University Research Court College ParkMD20740 United States

The prediction of the wind wave spectrum of the ocean using numerical models are an important tool for researchers, engineers, and communities living in coastal areas. The governing equation of the wind wave models, the Wave Action Balance Equation, presents unique challenges for implementing reliable numerical models because it is highly advective, highly nonlinear and high dimensional. Historically, most operational models have utilized finite difference methods, others have used finite volume methods but relatively few attempts at using finite element methods. In this work, we seek to fill this gap by investigating several different finite element discretizations of the Wave Action Balance Equation. The methods, which include streamline upwind Petrov-Galerkin (SUPG), least squares, and discontinuous Galerkin, are implemented and convergence properties are examined for some simplified 2-D test cases. Then, a new spectral wind wave model, WAVEx, is formulated and implemented for the full problem setting. WAVEx uses continuous finite elements along with SUPG stabilization in geographic/spectral space that allows for fully unstructured triangular meshes in both geographic and spectral space. For propagation in time, a second order fully implicit finite difference method is used. When source terms are active, a second order operator splitting scheme is used to linearize the problem. In the splitting scheme, propagation is solved using the implicit method and the nonlinear source terms are treated explicitly. Several test cases, including analytic tests and laboratory experiments, are demonstrated and results are compared to analytic solutions, observations, as well as output from another model that is used operationally. © 2023, CC BY.

关键词： Python

来源：评论

学校读者我要写书评

暂无评论

U-NET BASED PREDICTION OF CEREBROSPINAL FLUID DISTRIBUTION AND VENTRICULAR REFLUX GRADING

arXiv

引用

arXiv 2024年

作者： Rieff, Melanie Holzberger, Fabian Lapina, Oksana Ringstad, Geir Valnes, Lars Magnus Warsza, Bogna Eide, Per Kristian Mardal, Kent André Wohlmuth, Barbara Department of Mathematics School of Computation Information and Technology Technical University of Munich Garching Germany Department of Radiology Oslo University Hospital Rikshospitalet Oslo Norway Department of Neurosurgery Oslo University Hospital Rikshospitalet Oslo Norway Department of Geriatrics and Internal Medicine Sorlandet Hospital Arendal Norway KG Jebsen Centre for Brain Fluid Research Institute of Clinical Medicine Faculty of Medicine University of Oslo Oslo Norway Institute of Clinical Medicine Faculty of Medicine University of Oslo Oslo Norway Department of Mathematics University of Oslo Oslo Norway Department of Numerical Analysis and Scientific Computing Simula Research Laboratory Oslo Norway

Previous work shows evidence that cerebrospinal fluid (CSF) plays a crucial role in brain waste clearance processes, and that altered flow patterns are associated with various diseases of the central nervous system. In this study, we investigate the potential of deep learning to predict the distribution in human brain of a gadolinium-based CSF contrast agent (tracer) administered intrathecal. For this, T1-weighted magnetic resonance imaging (MRI) scans taken at multiple time points before and after intrathecal injection were utilized. We propose a U-net-based supervised learning model to predict pixel-wise signal increases at their peak after 24 hours. Its performance is evaluated based on different tracer distribution stages provided during training, including predictions from baseline scans taken before injection. Our findings indicate that using imaging data from just the first two hours post-injection for training yields tracer flow predictions comparable to those trained with additional later-stage scans. The model was further validated by comparing ventricular reflux gradings provided by neuroradiologists, and inter-rater grading among medical experts and the model showed excellent agreement. Our results demonstrate the potential of deep learning-based methods for CSF flow prediction, suggesting that fewer MRI scans could be sufficient for clinical analysis, which might significantly improve clinical efficiency, patient well-being, and lower healthcare costs. Copyright © 2024, The Authors. All rights reserved.

关键词： Cerebrospinal fluid

来源：评论

学校读者我要写书评

暂无评论

POLYLLA: Polygonal meshing algorithm based on terminal-edge regions

arXiv

引用

arXiv 2022年

作者： Salinas, Sergio Hitschfeld-Kahler, Nancy Ortiz-Bernardin, Alejandro Si, Hang Department of Computer Sciences Universidad de Chile Av. Beauchef 851 RM Santiago8370456 Chile Computational and Applied Mechanics Laboratory Department of Mechanical Engineering Universidad de Chile Av. Beauchef 851 RM Santiago8370456 Chile Numerical Mathematics and Scientific Computing Weierstrass Institute for Applied Analysis and Stochastics Mohrenstr. 39 Berlin Berlin10117 Germany

This paper presents an algorithm to generate a new kind of polygonal mesh obtained from triangulations. Each polygon is built from a terminal-edge region surrounded by edges that are not the longest-edge of any of the two triangles that share them. The algorithm is termed Polylla and is divided into three phases. The first phase consists of labeling each edge of the input triangulation according to its size;the second phase builds polygons (simple or not) from terminal-edges regions using the label system;and the third phase transforms each non simple polygon into simple ones. The final mesh contains polygons with convex and non convex shape. Since Voronoi based meshes are currently the most used polygonal meshes, we compare some geometric properties of our meshes against constrained Voronoi meshes. Several experiments were run to compare the shape and size of polygons, the number of final mesh points and polygons. For the same input, Polylla meshes contain less polygons than Voronoi meshes, and the algorithm is simpler and faster than the algorithm to generate constrained Voronoi meshes. Finally, we have validated Polylla meshes by solving the Laplace equation on an L-shaped domain using the Virtual Element Method (VEM). We show that the numerical performance of the VEM using Polylla meshes and Voronoi meshes is similar. Copyright © 2022, The Authors. All rights reserved.

关键词： Mesh generation

来源：评论

学校读者我要写书评

暂无评论

Author Correction: Spatial modeling algorithms for reactions and transport in biological cells

NATURE COMPUTATIONAL SCIENCE

引用

NATURE COMPUTATIONAL SCIENCE 2025年第2期5卷 185-185页

作者： Francis, Emmet A. Laughlin, Justin G. Dokken, Jorgen S. Finsberg, Henrik N. T. Lee, Christopher T. Rognes, Marie E. Rangamani, Padmini Department of Pharmacology University of California San Diego School of Medicine La Jolla CA USA Department of Mechanical and Aerospace Engineering University of California San Diego La Jolla CA USA Computational Engineering Division Lawrence Livermore National Laboratory Livermore CA USA Department of Molecular Biology University of California San Diego La Jolla CA USA Department of Numerical Analysis and Scientific Computing Simula Research Laboratory Oslo Norway K. G. Jebsen Centre for Brain Fluid Research University of Oslo Oslo Norway Department of Computational Physiology Simula Research Laboratory Oslo Norway

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：