bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simulating mechanical systems with frictional contact using a nonsmooth generalized‐alpha method
Authors: Capobianco Giuseppe , Harsch Jonas , Eugster Simon R. , Leine Remco I. 
Published: December 2021

AbstractIn this paper, we introduce a nonsmooth generalized‐alpha method for the simulation of mechanical systems with frictional contact. In many engineering applications, such systems are composed of rigid and flexible bodies, which are interconnected by joints and can come into contact with each other or their surroundings. Prominent examples are automotive, wind turbine, and robotic systems. It is known from structural mechanics applications, that generalized‐alpha schemes perform well for flexible multibody systems without contacts. This motivated the development of nonsmooth generalized‐alpha methods for the simulation of mechanical systems with frictional contacts [2, 3, 5]. Typically, the Gear‐Gupta‐Leimkuhler approach is used to stabilize the unilateral constraint, such that numerical penetration of the contact bodies can be avoided ‐ a big issue of the most popular time‐stepping schemes such as Moreau's scheme. The nonsmooth generalized‐alpha method presented in this paper is derived in [2] and in contrast to [3,5] accounts for set‐valued Coulomb‐type friction on both velocity and acceleration level. Finally, we validate the method using a guided flexible hopper as a benchmark mechanical system.
Investigating Schmidt number effects in turbulent electroconvection using one‐dimensional turbulence
Authors: Klein Marten , Schmidt Heiko 
Published: December 2021

AbstractTurbulent electroconvection denotes a fluctuating multiphysical flow in which hydrodynamics and electrokinetics interact on multiple scales. The dynamical processes at work are entangled down to the molecular‐diffusive scales that are determined by the Schmidt (Sc) and Reynolds (Re) number. Turbulence properties are generally nonuniversal which leads to high numerical resolution requirements. We address the numerical challenges associated with accuracy and feasibility by utilizing a stochastic one‐dimensional turbulence (ODT) model. Here, ODT is applied to turbulent Couette flow of dilute electrolytes as canonical problem for turbulent electroconvection. For Sc ⩾ O(10), ODT predicts an increase of the skin friction drag due to electrohydrodynamically (EHD) enhanced small‐scale eddy production once the flow is sufficiently turbulent.
Cryosuction‐induced fracturing in multiphase porous materials: Numerical modeling and experimental validation
Authors: Heider Yousef , Sweidan Abdel Hassan , Markert Bernd 
Published: December 2021

AbstractWhether naturally‐ or artificially‐induced due to human activities, decreasing or increasing the suction in multiphase‐fluid‐saturated porous materials can lead to enormous changes in their thermo‐hydromechanical properties. In this, both the mathematical description and the numerical modeling of the coupled problem present a challenging task. The following contribution considers the instance related to micro‐cryosuction‐induced fractures, which can be observed in saturated and unsaturated porous materials under freezing conditions. This research focuses on continuum porous media mechanics extended by a diffusive phase‐field fracture method. For the cryosuction‐induced fractures in saturated porous media, the water freezing is treated as a phase‐change process. This is modeled using a phase‐field approach, in which the thermal energy derives the phase change and, thus, leads to the occurrence of micro‐cryosuction due to the formation of the ice phase.
An efficient solver for a Cosserat rod of non‐constant width applied to a problem of fluid‐structure interaction
Authors: Schoppmann Karl , Löhrer Bastian , Tschisgale Silvio , Fröhlich Jochen , de Langre Emmanuel 
Published: December 2021

AbstractThe paper addresses a fluid‐structure problem involving a trapezoidal ribbon which undergoes large static reconfiguration, yielding a drag force independent of the velocity over a sizable velocity range. With experimental reference data on shape and drag available in the literature, the paper reports on Large Eddy Simulations of the configuration providing ample information on the surrounding transitional flow field and the distribution of forces along the structure. To obtain these results, a new implementation of a Cosserat solver was developed permitting non‐constant properties along the structure.
Efficient numerical treatment of a gradient damage model for materials undergoing large deformations
Authors: Riesselmann Johannes , Junker Philipp , Balzani Daniel 
Published: December 2021

AbstractIn this contribution we present a gradient damage formulation (cf. [1]) for hyperelastic materials undergoing large deformations, which is based on the small strain formulation of [2]. Through discretizing the gradient extended damage field with the neighbored element method the damage update can be performed at the element level. Although local update iterations remain present, the global system of equations goes without any additional degrees of freedom compared to purely elastic computations. Furthermore, in the case of severely damaged material, an element erosion based stabilization technique is considered. Computing efficiency and numerical robustness is demonstrated in several numerical examples.
Predictive modeling and simulation of silica aerogels by using aggregation algorithms
Authors: Abdusalamov Rasul , Pandit Prakul , Itskov Mikhail , Milow Barbara , Rege Ameya 
Published: December 2021

AbstractSilica aerogels are highly porous solids with very low densities and thermal conductivities. Their high porosity results in a fractal morphology which has a strong influence on their mechanical properties. The geometric structure of silica aerogels can be described by diffusion‐limited cluster‐cluster aggregation (DLCA) models.In this work, the DLCA method is implemented to model silica aerogel networks and investigate the influence of different input parameters, as for example, varying particle sizes on their fractal properties. The resulting model networks are characterized for their fractal properties and compared with the small angle X‐ray scattering (SAXS) results of silica aerogels. Furthermore, their mechanical properties are simulated using the finite element method. There, the effect of varying densities on their mechanical properties is examined. In addition, an artificial neural network (ANN) is trained based on the input parameters of the DLCA algorithm to predict the fractal properties of the silica aerogel model. By inverting the ANN it is possible to identify the necessary inputs to generate desired fractal morphologies with specific mechanical properties.
On the computation of physically realizable generalized flat inputs for nonlinear single‐output systems from a geometric point of view
Authors: Fritzsche Klemens , Guo Yuhang , Röbenack Klaus 
Published: December 2021

AbstractPhysical realizability is a structural property of (classical) flat inputs for state space systems which originate from higher order differential equations. These state space systems contain a derivative array, i.e., an integrator chain. Flat input injections into this array, however, structurally prevents from the reversal of the order reduction. Using a generalized flat input definition, we demonstrate how physical realizability can be achieved.
Applications of the asymptotic homogenization to materials with periodic and non‐periodic micro structures
Authors: Sheshenin Sergey , Artamonova Nina , Klementyev Petr 
Published: December 2021

AbstractThe first part of the paper presents the application of the asymptotic homogenization for determining the effective elastic and elasto‐plastic properties and stress concentrations in the B4C/2024Al composite using 3D x‐ray images of the internal structure. For comparison, calculations were performed for a dispersed composite with an aluminum matrix, in which boron carbide inclusions were simulated by ellipsoids. The elasto‐plastic behavior of the real structure of the B4C/2024Al composite was investigated in computational experiments on uniform compression, uniaxial tension, and a combination of pure shear and uniform compression. The calculation results were compared with experimental data. The second study concerns the application of asymptotic homogenization to metamaterials. Metamaterials may have unusual behaviour such as tension–bending coupling or tension–torsion coupling. Most metamaterials have a periodic structure in Cartesian coordinates. We studied tension‐compression‐shear coupling provided by the metamaterial using second order asymptotic representation.
Geometrically and physically nonlinear coupled consolidation problem
Authors: Artamonova Nina , Sheshenin Sergey 
Published: December 2021

AbstractConsolidation is the process of soil compaction under load as water is squeezed out of a porous medium [1]. A physically and geometrically nonlinear formulation of the consolidation problem is developed. The developed nonlinear consolidation model is applied to simulate hyperelastic deformation of a biological material saturated with blood or plasma and elastoplastic deformation of porous water‐saturated soil.
Estimating divergence‐free flows via neural networks
Authors: Kabanov Dmitry I. , Espath Luis , Kiessling Jonas , Tempone Raul F. 
Published: December 2021

AbstractWe apply neural networks to the problem of estimating divergence‐free velocity flows from given sparse observations. Following the modern trend of combining data and models in physics‐informed neural networks, we reconstruct the velocity flow by training a neural network in such a manner that the network not only matches the observations but also approximately satisfies the divergence‐free condition. The assumption is that the balance between the two terms allows to obtain the model that has better prediction performance than a usual data‐driven neural network. We apply this approach to the reconstruction of truly divergence‐free flow from the noiseless synthetic data and to the reconstruction of wind velocity fields over Sweden.
Kolmogorov's similarity hypotheses application in research of the turbulent swirl flows in pipe generated by the various axial fan geometries
Authors: Čantrak Ðorđe S. , Janković Novica Z. , Nedeljković Miloš S. 
Published: December 2021

AbstractKolmogorov has formulated his two hypotheses of similarity in 1941 considering local‐isotropic turbulence, and later has refined his theory [1, 2]. In this paper are discussed three turbulent swirl flows generated by the three various axial fan types in‐built in the pipe. The spectral characteristics of the generated turbulent swirl flows are determined on the basis on the LDA (laser Doppler anemometry) experimental data for the circumferential velocity. In the inertial subranges these curves have the same tangent and obey the “‐ 5/3” Kolmogorov law. It is shown that in the generated turbulent swirl flows occur eddies of various scales, encompassing very wide spectra of wave numbers, i.e. frequencies.
Virtual testing of as‐designed additively manufactured lattice structures
Authors: Gebhardt Ulrike , Kästner Markus , Gustmann Tobias , Hufenbach Julia Kristin , Kühn Uta , Hirsch Franz , Berner Matthias 
Published: December 2021

AbstractLattice structures and their characterization are much discussed in current research. The complex manufacturing process of laser powder bed fusion with its repeated melting and remelting of metallic powder influences the resulting material properties.Within this contribution the influence of process parameters on the overall behaviour of lattice structure compression test specimens is inherently described within the material model which is derived from tensile tests of additively manufactured material test specimens. The simulation of the lattice structures is performed with an isotropic elastic‐plastic material model on the as‐designed geometry, neglecting all geometric deviations caused by the manufacturing process. The comparison to compression experiments on the same, additively manufactured geometry, shows surprisingly good agreement. The potential of this approach is evaluated on compression tests with as‐built test specimens as well as test specimens which were heat treated after manufacturing.
A Modified Minibatch Sampling Method for Parameter Estimation in Hidden Markov Models using Stochastic Variational Bayes
Authors: Majumder Reetam , Gobbert Matthias K. , Neerchal Nagaraj K. 
Published: December 2021

AbstractParameter estimation using stochastic variatonal Bayes (SVB) under a mean field assumption can be carried out by sampling a single data point at each iteration of the optimization algorithm. However, when latent variables are dependent like in hidden Markov models (HMM), a larger sample is required at each iteration to capture that dependence. We describe a minibatch sampling procedure for HMMs where the emission process can be segmented into independent and identically distributed blocks. Instead of sampling a block and using all elements within it, we divide the block into subgroups and sample subgroups from different blocks using simple random sampling with replacement. Simulation results are provided for an HMM for precipitation data, where each block of 90 days represents 3 months of wet season data. SVB based on the proposed sampling method is shown to provide parameter estimates comparable with existing methods.
Efficient monolithic solution of FE2 problems
Authors: Lange Nils , Hütter Geralf , Abendroth Martin , Kiefer Bjoern 
Published: December 2021

AbstractThe concurrent FE2‐method is a very powerful and flexible computational tool for multi‐scale problems. However the computational effort is very high. The conventional, staggered (“nested Newton”) solution scheme solves the microscopic problem iteratively within each macroscopic Newton‐Raphson (NR) iteration, although the macroscopic deformation gradients as boundary conditions at the micro scale are only estimates. In this contribution a monolithic FE2scheme is proposed, solving the displacements of both scales in a common NR loop, which proved being faster by saving expansive micro‐scale iterations.
Computational modelling of compressible cementitious composite materials
Authors: Iskhakov Tagir , Timothy Jithender J. , Meschke Günther 
Published: December 2021

AbstractThe integrity of tunnel structures deployed in difficult geological conditions such as expansive soils can be improved by incorporating compressible layers in the tunnel lining. Such compressible lining materials can be obtained by embedding weak inclusions (Expanded polystyrene, Expanded glass beads, Air voids) into a cement paste material. The material properties of these individual constituents as well as their geometry affect the overall material behaviour of such cementitious composites. Design of the compressible tunnel lining for specific geological conditions can be improved by choosing optimal characteristics of the composite constituents. This procedure can be enhanced by using a simulation based data driven framework. For compaction simulation of the cementitious composite, a multiscale voxel based model is proposed. To account for the influence of the composite microstructure, the model is enhanced by continuum micromechanics.
Another Hilbert inequality and critically separated interpolation nodes
Authors: Kunis Stefan , Rolfes Julian 
Published: December 2021

AbstractAbstract: Estimates on the condition number of Vandermonde matrices have implications on several algorithms ranging from polynomial interpolation to sparse super resolution in fluorescence microscopy. Classically, the situation is studied for monomials on real intervals, the complex unit disk, and the complex unit circle. Except for roots of unity and well separated nodes on the unit circle, the condition number grows strongly with increasing polynomial degree. Here, we show that the condition number of the Vandermonde matrix for a particular instance of critically separated nodes on the complex unit circle grows logarithmically with the polynomial degree. The proof is based on a variant of Hilbert's inequality with remainder term.
Consideration of the crystallization heat in the crystallization simulation of semi‐crystalline thermoplastics
Authors: Horn Tobias Daniel , Wulf Hans , Ihlemann Jörn 
Published: December 2021

AbstractModerate cooling rates form a spherulite structure when semi‐crystalline thermoplastics are cooled from quiescent melt. In a simulation of the spherulite structure evolution, both the crystallization kinetics and the temperature development must be taken into account. In this paper, the consideration of the crystallization heat in the simulation of the temperature development is demonstrated using polybutylene terephthalate. It is shown, that the consideration of the crystallization heat is necessary in order to calculate the correct evolution of spherulite structure.
Stochastic segmentation on images with uncertain data
Authors: Theilen Elin , Preusser Tobias 
Published: December 2021

AbstractThe present work considers a stochastic segmentation method on images in the presence of noise within a PDE‐based image processing framework. Classical methods are not able to capture the error propagation of uncertain estimated input data and their impact on the final segmentation result, which can be of great importance for clinical decisions. Therefore, an intrusive generalized polynomial chaos (gPC) expansion for a stochastic level‐set based geodesic active contours method is proposed. Employing an operator splitting and a stochastic Galerkin projection a deterministic and symmetric non‐linear hyperbolic system can be obtained, which can be treated using common numerical methods.
Stochastic Modeling of a Lifted Methane/Air Jet Flame with Detailed Chemistry
Authors: Starick Tommy , Lignell David O. , Schmidt Heiko 
Published: December 2021

AbstractThis preliminary numerical study investigates a lifted methane/air jet flame in a vitiated coflow by means of the One‐Dimensional Turbulence (ODT) model. In the considered Cabra Burner configuration [Combust. Flame 143 491‐506 (2005)], a jet flame issues from a central nozzle into a vitiated coflow of hot combustion products from lean premixed hydrogen/air flames. ODT is a map‐based model for turbulent flow simulations which uses a stochastic formulation for the turbulent advection. The diffusion and reaction effects along the one‐dimensional domain are considered by temporally advancing deterministic evolution equations. ODT simulations are performed with a representation of the methane/air chemistry by a reduced 19‐species mechanism with 15 reactions and a detailed 53‐species mechanism with 325 reactions. In this work, we present centerline profile of temperature and species concentrations obtained from ODT simulations using a cylindrical ODT‐formulation. Additionally, two‐dimensional renderings of the temperature distribution are shown. Although the simulation of reactive jet configurations by means of ODT is not novel, the complex stabilization region depending on the flow conditions represents a challenge for the model. Considering the reduced order of the model, ODT is able to predict the flow characteristics and reasonably matches the existing experimental data.
Finite element analysis of a 2D cantilever on a noisy intermediate‐scale quantum computer
Authors: Mielke André , Ricken Tim 
Published: December 2021

AbstractQuantum computing is a promising new computing paradigm that may yield both significant speedup over classical algorithms as well as new ways to think about problems and finding novel solution algorithms. While large‐scale error‐corrected quantum computers are still under development, a selection of noisy intermediate‐scale quantum processing units is readily made available by some companies via cloud access. Despite the lack of error correction, these units can be used to test established quantum algorithms on custom problem setups. Here, we solve the finite element problem of a two‐dimensional cantilever, completely fixed on one side and loaded on the opposite side, on a 15‐qubit QPU from IBM.
Infinite‐horizon optimal control – Asymptotics and dissipativity
Authors: Faulwasser Timm , Kellett Christopher M. 
Published: December 2021

AbstractThis note discusses the interplay between dissipativity and the asymptotics of continuous‐time infinite‐horizon optimal control problems. We focus on the results on convergence of optimal primal solutions derived in [6]. Moreover, we present a result on the attractivity of the infinite‐horizon optimal adjoint trajectories, which is closely related to transversality conditions for infinite‐horizon optimal control problems. Proofs and further results can be found in [6].
Preparation and properties of polyaniline‐silver composite by glucose reduction
Authors: Han Zhuowei , Liu Qi , Zhao Hui , Shi Yujing , Liu Yinuo , Chen Jianbo 
Published: December 2021

AbstractIn this article, an environmentally friendly and simple one‐pot synthesis method to prepare polyaniline‐silver composite materials is presented by using glucose as the reducing agent. The structure and morphology of the composites are confirmed and characterized by UV–visible spectroscopy, Fourier transform‐infrared spectroscopy, X‐ray diffraction, thermogravimetric analysis, and scanning electron microscopy (SEM). Based on the SEM micrographs, the polyaniline‐silver composites with typical morphology of intercalated nanoflowers are synthesized for the first time. In addition, the electrical conductivity, oxidation resistance, and antibacterial property of the composites are enhanced compared with those of polyaniline. This study is expected to provide insights and opportunities for improving the preparation methods and conditions of polyaniline‐silver composites.
The genome of the endangered Macadamia jansenii displays little diversity but represents an important genetic resource for plant breeding
Authors: Sharma Priyanka , Murigneux Valentine , Haimovitz Jasmine , Nock Catherine J. , Tian Wei , Kharabian Masouleh Ardashir , Topp Bruce , Alam Mobashwer , Furtado Agnelo , Henry Robert J. 
Published: December 2021

AbstractMacadamia, a recently domesticated expanding nut crop in the tropical and subtropical regions of the world, is one of the most economically important genera in the diverse and widely adapted Proteaceae family. All four species of Macadamia are rare in the wild with the most recently discovered, M. jansenii, being endangered. The M. jansenii genome has been used as a model for testing sequencing methods using a wide range of long read sequencing techniques. Here, we report a chromosome level genome assembly, generated using a combination of Pacific Biosciences sequencing and Hi‐C, comprising 14 pseudo‐molecules, with a N50 of 52 Mb and a total genome assembly size of 758 Mb of which 56% is repetitive. Completeness assessment revealed that the assembly covered −97.1% of the conserved single copy genes. Annotation predicted 31,591 protein coding genes and allowed the characterization of genes encoding biosynthesis of cyanogenic glycosides, fatty acid metabolism, and anti‐microbial proteins. Re‐sequencing of seven other genotypes confirmed low diversity and low heterozygosity within this endangered species. Important morphological characteristics of this species such as small tree size and high kernel recovery suggest that M. jansenii is an important source of these commercial traits for breeding. As a member of a small group of families that are sister to the core eudicots, this high‐quality genome also provides a key resource for evolutionary and comparative genomics studies.