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Study of industrially applied methods for verification, validation and uncertainty quantification of simulator models

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International Journal of Modeling, Simulation, and Scientific Computing 2015年第2期6卷 56-84页

作者： magnus Eek Sogol Kharrazi Hampus Gavel Johan Olvander Saab Aeronautics Linkoping SE-58188Sweden Swedish National Road and Transport Research Institute(VTI)Linkoping SE-58195Sweden Linkoping University Linkoping SE-58183Sweden

To better utilize the potential of system simulation models and simulators,industrially applicable methods for Verification,Validation and Uncertainty Quantification(VV&UQ)are *** paper presents an exploratory case study of VV&UQ techniques applied on models integrated in aircraft system simulators at Saab Aeronautics and in driving simulators at the Swedish National Road and Transport Research Institute(VTI).Results show that a large number of Verification and Validation(V&V)techniques are applied,some of which are promising for further development and use in simulator credibility *** the application of UQ,a large gap between academia and this part of industry has been identified,and simplified methods are *** applicability of the NASA Credibility Assessment Scale(CAS)at the studied organizations is also evaluated and it can be concluded that the CAS is considered to be a usable tool for achieving a uniform level of V&V for all models included in a simulator,although its implementation at the studied organizations requires tailoring and coordination.

关键词： Simulator credibility simulation model verification validation uncertainty quantification V&V VV&UQ NASA Credibility Assessment Scale

Continuous-time proportional-integral distributed optimisation for networked systems

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Journal of Control and Decision 2014年第3期1卷 191-213页

作者： Greg Droge Hiroaki Kawashima magnus B.Egerstedt School of Electrical and Computer Engineering Georgia Institute of TechnologyAtlantaGAUSA Graduate School of Informatics Kyoto UniversityKyotoJapan

In this paper,we explore the relationship between dual decomposition and the consensusbased method for distributed *** relationship is developed by examining the similarities between the two approaches and their relationship to gradient-based constrained *** formulating each algorithm in continuous-time,it is seen that both approaches use a gradient method for optimisation with one using a proportional control term and the other using an integral control term to drive the system to the constraint ***,a significant contribution of this paper is to combine these methods to develop a continuous-time proportional-integral distributed optimisation ***,we establish convergence using Lyapunov stability techniques and utilising properties from the network structure of the multi-agent system.

关键词： distributed optimisation multi-agent control networked systems

Particle Collisions in a Lumped Particle Model

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Communications in Computational Physics 2011年第9期10卷 823-843页

作者： Omar al-Khayat Are magnus Bruaset Hans Petter Langtangen Computational Geosciences CBCSimula Research LaboratoryP.O.Box 134NO-1325 LysakerNorway Department of Informatics University of OsloP.O.Box 1080BlindernNO-0316 OsloNorway Center for Biomedical Computing Simula Research LaboratoryP.O.Box 134NO-1325 LysakerNorway

This paper presents an extension of the lumped particle model in[1]to include the effects of particle *** lumped particle model is a flexible framework for the modeling of particle laden flows,that takes into account fundamental features,including advection,diffusion and dispersion of the *** this paper,we transform a binary collision model and concepts from kinetic theory into a collision procedure for the lumped particle *** apply this new collision procedure to investigate numerically the role of particle collisions in the hindered settling *** hindered settling effect is characterized by an increase in the effective drag coefficient CD that influences each particle in the *** coefficient is given by CD=(1−φ)−nC∗D,whereφis the volume fraction of particles,C∗D is the drag coefficient for a single particle,and n≃4.67 for creeping *** obtain an approximation for CD/C∗D by calculating the effective work done by collisions,and comparing that to the work done by the drag *** our numerical experiments,we observe a minimal value of n=***,by allowing high energy dissipation,an approximation for the classical value for creeping flow,n=4.7,is *** also obtain high values for n,up to n=6.5,which is consistent with recent physical experiments on the sedimentation of sand grains.

关键词： Lumped particle model particle collision hindered settling

A Lumped Particle Modeling Framework for Simulating Particle Transport in Fluids

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Communications in Computational Physics 2010年第6期8卷 115-142页

This paper presents a lumped particle model for simulating a large number of *** lumped particle model is a flexible framework in modeling particle flows,embodying fundamental features that are intrinsic in particle laden flow,including advection,diffusion and *** this paper,the particles obey a simplified version of the Bassinet-Boussinesq-Oseen equation for a single spherical ***,instead of tracking the individual dynamics of each particle,a weighted spatial averaging procedure is used where the external forces are applied to a“lump”of particles,from which an average position and velocity is *** temporal evolution of the particles is computed by partitioning the lumped particle into smaller entities,which are then transported throughout the physical *** smaller entities recombine into new particle lumps at their target *** particles prone to the effects of Brownian motion or similar phenomena,a symmetric spreading of the particles is included as *** experiments show that the lumped particle model reproduces the effects of Brownian diffusion and uniform particle transport by a fluid and *** late time scale diffusive nature of particle motion is also reproduced.

关键词： Particle modeling framework particle transport lumped particle model

From file to factory: Innovative design solutions for multi-storey timber buildings applied to project Zembla in Kalmar, Sweden

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Frontiers of Architectural Research 2019年第1期8卷 1-16页

作者： Alex Kaiser magnus Larsson Ulf Arne Girhammar Division of Wood Science and Engineering Lulea University of Technology 931 87 Skelleftea Sweden Former Lulea University of Technology Sweden

A "file-to-factory" process of computer technology is a way to both maximise efficiency throughout the building process, in crease a buildi ng's performance, and be able to add interesting architectural possibilities throughout the design phase. The authors investigate a novel approach that produces a set of building trajectories rather than a set of buildings, yet yields a series of build-able examples of those trajectories. This paper evaluates how this series of stacked multi-storey timber buildings can be both incorporated within a file-to-factory process, and give rise to creating new innovative solutions throughout the entire design and manufacturing process. This process is applied to a real Swedish project called Zembla. It redefines the notion of sprawl, turning it into a progressive tactics for linking the dty fabric to rural areas. It is a postsustainable file-to-factory-produced timber ground-scraper;soaring above ground and water, suggesting a new way of making city-sized buildings for the future. A plug-in grid-shell structure is designed to contain a minimal amount of timber elements, beams make up the lattice, cross-laminated panels add structural support, surfaces come together to form the living capsules. Having the structure undulate across the topography and touching the ground in as few places as possible uses the dichotomy between landscape and urbanism, bringing the city to the people living in less densified areas. Each living unit is customised to its topological conditions within the grid.

关键词： Multi-storey timber buildings File-to-factory Modular systems Grid shells Slotting Living capsules

High resolution strain mapping of a single axially heterostructured nanowire using scanning X-ray diffraction

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Nano Research 2020年第9期13卷 2460-2468页

作者： Susanna Hammarberg Vilgaile Dagyte Lert Chayanun Megan O.Hill Alexander Wyke Alexander Bjorling Ulf Johansson Sebastian Kalbfleisch magnus Heurlin Lincoln J.Lauhon magnus T.Borgstrom Jesper Wallentin Synchrotron Radiation Research and NanoLund Lund UniversityBox 118Lund 22100Sweden Solid State Physics and NanoLund Lund UniversityBox 118Lund 22100Sweden Department of Materials Science and Engineering Northwestern UniversityEvanstonIllinois 60208USA MAX IV Laboratory Lund UniversityBox 118Lund 22100Sweden

Axially heterostructured nanowires are a promising platform for next generation electronic and optoelectronic *** based on theoretical modeling have predicted more complex strain distributions and increased critical layer thicknesses than in thin films,due to lateral strain relaxation at the surface,but the understanding of the growth and strain distributions in these complex structures is hampered by the lack of high-resolution characterization ***,we demonstrate strain mapping of an axially segmented GalnP-lnP 190 nm diameter nanowire heterostructure using scanning X-ray *** systematically investigate the strain distribution and lattice tilt in three different segment lengths from 45 to 170 nm,obtaining strain maps with about 10^-4 relative strain *** experiments were performed using the 90 nm diameter nanofocus at the NanoMAX beamline,taking advantage of the high coherent flux from the first diffraction limited storage ring MAX *** experimental results are in good agreement with a full simulation of the experiment based on a three-dimensional(3D)finite element *** largest segments show a complex profile,where the lateral strain relaxation at the surface leads to a dome-shaped strain distribution from the mismatched interfaces,and a change from tensile to compressive strain within a single *** lattice tilt maps show a cross-shaped profile with excellent qualitative and quantitative agreement with the *** contrast,the shortest measured InP segment is almost fully adapted to the surrounding GalnP segments.

关键词： strain mapping nanowire heterostructure X-ray diffraction(XRD) MAX IV finite element modeling

Modelling of temperature and strain rate dependent behaviour of pearlitic steel in block braked railway wheels

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Railway Engineering Science 2021年第4期29卷 362-378页

作者： Ali Esmaeili Johan Ahlstrom magnus Ekh Dimitrios Nikas Tore Vernersson CHARMEC/Department of Industrial and Materials Science Chalmers University of TechnologyGothenburgSweden Now at Department of Engineering and Physics Karlstad UniversityKarlstadSweden CHARMEC/Department of Mechanics and Maritime Sciences Chalmers University of TechnologyGothenburgSweden

Block braked railway wheels are subjected to thermal and rolling contact *** thermal loading results in high temperatures and thermal stresses which cause slow time dependent processes such as creep,relaxation and static recovery of the wheel *** the same time,the rolling contact loading implies a very fast mechanical load *** paper is focused on material modeling of pearlitic steel for a wide range of loading rates at elevated *** starting point is a viscoplasticity model including nonlinear isotropic and kinematic *** Delobelle overstress function is employed to capture strain rate dependent response of the *** model also includes static recovery of the hardening to capture slower viscous(diffusion dominated)behaviour of the *** for the pearlitic wheel steel ER7 in terms of cyclic strain-controlled uniaxial tests with hold-time,uniaxial ratchetting tests including rapid cycles and biaxial cyclic tests with tension/compression and torsion are used to calibrate the material *** experiments were performed under isothermal conditions at different *** the ratchetting tests,higher loading rates are obtained and these have been used to calibrate the high strain rate response of the viscoplasticity *** paper is concluded with a numerical example of a block braked wheel where the importance of accounting for the viscoplasticity in modelling is highlighted.

关键词： Block braking High temperatures Pearlitic steel Railway wheels Viscoplasticity

Core-shell particles of C-doped CdS and graphene: A noble metal-free approach for efficient photocatalytic H_(2) generation

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Green Energy & Environment 2020年第4期5卷 461-472页

作者： Muhammad Zubair Estelle Marie M.Vanhaecke Ingeborg-Helene Svenum magnus RФnning Jia Yang Department of Chemical Engineering Norwegian University of Science and Technology(NTNU)Sem Sælands vei 4TrondheimNO7491Norway SINTEF Industry P.O.Box 4760 TorgardenTrondheimNO7465Norway

To achieve efficient photocatalytic H_(2) generation from water using earth-abundant and cost-effective materials,a simple synthesis method for carbon-doped CdS particles wrapped with graphene(C-doped CdS@G)is *** doping effect and the application of graphene as cocatalyst for CdS is studied for photocatalytic H_(2) *** most active sample consists of CdS and graphene(CdS-0.15G)exhibits promising photocatalytic activity,producing 3.12 mmol g^-(1) h^-(1) of H_(2) under simulated solar light which is^4.6 times superior than pure CdS nanoparticles giving an apparent quantum efficiency(AQY)of 11.7%.The enhanced photocatalytic activity for H_(2) generation is associated to the narrowing of the bandgap,enhanced light absorption,fast interfacial charge transfer,and higher carrier density(N_(D))in C-doped CdS@G *** is achieved by C doping in CdS nanoparticles and the formation of a graphene shell over the C-doped CdS *** stability test,the spent catalysts sample was also characterized to investigate the nanostructure.

关键词： C-doped CdS@G Core-shell nanostructure Photocatalytic H2 generation Graphene Carbon doping in CdS Bandgap narrowing

Diffusivity-limited q-space trajectory imaging

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Magnetic Resonance Letters 2023年第2期3卷 187-196,I0005页

作者： Deneb Boito magnus Herberthson Tom Dela Haije Ida Blystad Evren Ozarslan Department of Biomedical Engineering Campus USLinkoping UniversityLinkopingSE-58183.Sweden Center for Medical Image Science and Visualization Linkoping UniversityLinkopingSE-58183Sweden Department of Mathematics Linkoping UniversityLinkopingSE-58183Sweden Department of Computer Science University of CopenhagenCopenhagenDK-2300Denmark Department of Radiology in Linkoping and Department of Health Medicine and Caring SciencesLinkoping UniversityLinkopingSE-58183Sweden

Q-space trajectory imaging(QTI)allows non-invasive estimation of microstructural features of heterogeneous porous media via diffusion magnetic resonance imaging performed with generalised gradient waveforms.A recently proposed constrained estimation framework,called QTI+,improved QTI's resilience to noise and data sparsity,thus increasing the reliability of the method by enforcing relevant positivity *** this work we consider expanding the set of constraints to be applied during the fitting of the QTI *** show that the additional conditions,which introduce an upper bound on the diffusivity values,further improve the retrieved parameters on a publicly available human brain dataset as well as on data acquired from healthy volunteers using a scanner-ready protocol.

关键词： Diffusion Diffusion MRI q-space trajectory imaging QTI Microstructure Microscopic anisotropy QTI+ Constrained