bluuebunny/crossref_metadata_2025 huggingface dataset:
Multiphasic modelling of thrombus formation and growth based on the Theory of Porous Media
Authors: Gupta Ishan , Schanz Martin
Published: May 2023

Aortic dissection (AD) has a high mortality rate. 40% of the people with Type B Aortic Dissection do not live for more than a month. The prognosis of Aortic Dissection is quite challenging leading to an interest in computational methods to help with the decision‐making process for the treatment. The Theory of Porous Media (TPM) provides an excellent framework to describe the multiphasic structure of the thrombus. The whole aggregate is divided into solid, liquid and nutrient constituents. We assume the constituents to be materially incompressible, the whole aggregate to be fully saturated and under isothermal conditions. The balance equations of the constituents have coupling terms, also known as production terms, which take care of the interactions between the different phases. The volume fractions define the constituents. Therefore, the regions with thrombus are determined using the solid volume fraction. Darcy's law describes the flow of fluid in the porous media. We present the set of equations and a numerical example for thrombosis in Type B Aortic Dissection. We implement the equations in PANDAS, a finite element package designed to solve strongly coupled multiphase porous media problems.
A Novel Energy and Momentum Consistent Mixed Formulation for Coupled Nonlinear Electro‐Thermo‐Elastodynamics
Authors: Zähringer Felix , Franke Marlon , Betsch Peter
Published: May 2023

In the present contribution, a novel mixed formulation aimed at the energy‐momentum consistent simulation of coupled nonlinear electro‐thermo‐elastodynamic systems, in particular dielectric elastomer actuators, is proposed. It is essentially based on a mixed framework for elastodynamics in the case of polyconvex stored energy functions. In accordance with this framework, the properties of the rediscovered tensor cross product are exploited in a first step to derive a mixed formulation via a Hu‐Washizu type extension of the stored energy function. Afterwards, the corresponding strong form is derived and supplemented with the (initial) boundary value problems of thermodynamics and electrostatics. By additionally choosing an appropriate polyconvexity‐inspired energy density function, this procedure leads to a fully coupled electro‐thermo‐elastodynamic formulation that benefits from the properties of the underlying mixed framework.

Furthermore, an energy‐momentum consistent time integration scheme is proposed for the novel framework, where discrete derivatives in the sense of Gonzalez are employed. The formulation is second‐order accurate and stable even for large time step sizes. Eventually, the performance of the novel formulation is illustrated in a numerical example.
Numerical simulation of the thermal wave induced by a moving interfacial heat source with respect to Christov–Cattaneo's equation
Authors: Feike Marvin C. , Mundt Christian
Published: May 2023

The hyperbolic wave equation of heat conduction with respect to Christov's formulation is utilized with the Streamline‐ Upwind‐Petrov‐Galerkin method in space and the Θ, Houbolt, linear acceleration, Wilson‐Θ and Newmark methods in time. The derivation of this equation and its matrix formulation are shown. A 2D transient finite element simulation of a generic asperity with an infinite line heat source in an interface, either as a heat flux density q̇ or temperature distribution T, is performed for Math = [0.5; 1.0]. A sensitivity study is presented for the mentioned numerical schemes. The temperature jump in the solution is interpreted as an indicator for a thermal shock.
The Numerical Assembly Technique for arbitrary planar beam structures based on an improved homogeneous solution
Authors: Kramer Thomas , Gfrerer Michael Helmut
Published: May 2023

The Numerical Assembly Technique (NAT) is extended to investigate arbitrary planar frame structures with a focus on the computation of natural frequencies. This allows us to obtain highly accurate results without resorting to spatial discretization. To this end, we systematically introduce a frame structure as a set of nodes, beams, bearings, springs, and external loads and formulate the corresponding boundary and coupling conditions. As the underlying homogeneous solution of the governing equations, we use a novel approach recently presented in the literature. This greatly improves the numerical stability and allows the stable computation of very high natural frequencies accurately. We show this improvement by investigating the condition number of the system matrix and also by the use of variable precision arithmetic.
Using Mixed Precision in Low‐Synchronization Reorthogonalized Block Classical Gram‐Schmidt
Authors: Oktay Eda , Carson Erin
Published: May 2023

Mixed precision hardware has recently become commercially available, and more than 25% of the supercomputers in the TOP500 list now have mixed precision capabilities. Using lower precision in algorithms can be beneficial in terms of reducing both computation and communication costs. There are many current efforts towards developing mixed precision numerical linear algebra algorithms, which can lead to speedups in real applications. Motivated by this, we aim to further the state‐of‐the‐art in developing and analyzing mixed precision variants of iterative methods. In iterative methods based on Krylov subspaces, the orthogonal basis is generated by Arnoldi or Lanczos methods or their variants. In long recurrence methods such as GMRES, one needs to use an explicit orthogonalization scheme such as Gram‐Schmidt to orthonormalize the vectors generated.

Krylov subspace methods, such as GMRES, are typically communication‐bound on modern machines; the runtime is usually dominated by the cost of global synchronizations which are required for the necessary orthogonalization. This has motivated the development of various algorithmic variants which attempt to reduce the communication cost while maintaining a stable algorithm. Recent work has focused on the development of low‐synchronization block variants of Gram‐Schmidt orthogonalization, which, when used within communication‐avoiding (s‐step) or block variants of GMRES, can reduce the number of global synchronizations to one per block.

In this work, we focus on the block variant of low‐synchronization classical Gram‐Schmidt with reorthogonalization, which we call BCGSI+LS. We demonstrate that the loss of orthogonality produced by this orthogonalization scheme can exceed O(u)κ(𝒳), where u is the unit roundoff and κ(𝒳) is the condition number of the matrix to be orthogonalized, and thus we can not in general expect this to result in a backward stable block GMRES implementation. We then develop a mixed precision variant of this algorithm, called BCGSI+LS‐MP, which uses higher precision in certain parts of the computation. We demonstrate experimentally that for a number of challenging test problems, our mixed precision variant successfully maintains a loss of orthogonality below O(u)κ(𝒳). This indicates that we can achieve a backward stable block GMRES algorithm that requires only one synchronization per iteration.
Oscillatory solutions to problems in fluid mechanics: Analysis and numerics
Authors: Feireisl Eduard
Published: May 2023

Approximate solutions to models of perfect (inviscid) fluid flows may develop oscillations when approaching the limit problem. Anticipating that these oscillations represent, in fact, the behavior of real fluids in the inviscid limit we discuss several possibilities how to identify them and effectively visualize by means of numerical methods.
Pressure‐robust and conforming discretization of the Stokes equations on anisotropic meshes
Authors: Kempf Volker
Published: May 2023

Pressure‐robust discretizations for incompressible flows have been in the focus of research for the past years. Many publications construct exactly divergence‐free methods or use a reconstruction approach [13] for existing methods like the Crouzeix–Raviart element in order to achieve pressure‐robustness. To the best of our knowledge, except for our recent publications [3, 4], all those articles impose a condition on the shape‐regularity of the mesh, and the two mentioned papers that allow for anisotropic elements use a non‐conforming velocity approximation. Based on the classical Bernardi–Raugel element we provide a conforming pressure‐robust discretization using the reconstruction approach on anisotropic meshes. Numerical examples support the theory.
The skeleton equation method for acoustic transmission problems with varying coefficients
Authors: Florian Francesco , Hiptmair Ralf , Sauter Stefan
Published: May 2023

In this paper we describe the skeleton equation method, to transform a three‐dimensional acoustic transmission problem with variable coefficients and mixed boundary conditions to a non‐local equation on a two‐dimensional skeleton, without relying on an explicit knowledge of Green's function. This is achieved introducing and analyzing abstract layer potentials as solutions of auxiliary coercive full space transmission problems; they satisfy jump conditions across domain interfaces. The novelty in this paper is that we reduce acoustic scattering problems with possible variable coefficients to boundary integral equation on the domain skeleton, and we prove frequency exlicit continuity and coercivity estimates. The resulting equations are stated in a form such that standard boundary element methods can be applied for the discretization.
Sampling‐based model order reduction for stochastic differential equations driven by fractional Brownian motion
Authors: Jamshidi Nahid , Redmann Martin
Published: May 2023

In this paper, we study large‐scale linear fractional stochastic systems representing, e.g., spatially discretized stochastic partial differential equations (SPDEs) driven by fractional Brownian motion (fBm) with Hurst parameter H > ½. Such equations are more realistic in modeling real‐world phenomena in comparison to frameworks not capturing memory effects. To the best of our knowledge, dimension reduction schemes for such settings have not been studied so far.

In this work, we investigate empirical reduced order methods that are either based on snapshots (e.g. proper orthogonal decomposition) or on approximated Gramians. In each case, dominant subspaces are learned from data. Such model reduction techniques are introduced and analyzed for stochastic systems with fractional noise and later applied to spatially discretized SPDEs driven by fBm in order to reduce the computational cost arising from both the high dimension of the considered stochastic system and a large number of required Monte Carlo runs.

We validate our proposed techniques with numerical experiments for some large‐scale stochastic differential equations driven by fBm.
Efficient model‐correction based reliability analysis of uncertain dynamical systems
Authors: Hirzinger Benjamin , Nackenhorst Udo
Published: May 2023

In this contribution, a model‐correction‐based strategy is applied for efficient reliability analysis of uncertain dynamical systems based on a low‐fidelity (LF) model whose outcomes are corrected in a probabilistic sense to represent the more realistic outcomes of the high‐fidelity (HF) model. In the model‐correction approach utilized, the LF model is calibrated to the HF model close to the so‐called most probable point (MPP) in standard normal space, which allows a more realistic assessment of the considered complex dynamical system. Since only few expensive limit state function evaluations of the HF model are required, an efficient reliability analysis is enabled. In an application example, the LF model describes an existing single span railway bridge modelled as simply supported Euler‐Bernoulli beam subjected to moving single forces representing the axle loads of a moving train. The HF modelling approach accounts for the bridge‐train interaction by modelling the passing train as mass‐spring‐damper (MSD) system, however increasing the computational effort of the limit state function evaluations. The failure probabilities evaluated with the model‐correction approach are contrasted and discussed with the failure probabilities of the sophisticated bridge‐train interaction model. It is shown that the model‐correction‐based approach provides reliable failure probability prediction of the HF model while leading to a significant reduction in computational effort.
Energy‐Momentum‐Entropy consistent time integration of dissipative thermomechanical systems in an extended framework of GENERIC
Authors: Valdes y Beck Vanessa , Betsch Peter
Published: May 2023

Energy‐Momentum‐Entropy (EME) time‐stepping schemes are distinguished by their numerical stable and robust behaviour, which stems from their ability to preserve the structure of the underlying system. In the context of closed dissipative thermomechanical systems, they are energy‐ and momentum‐preserving as well as entropy‐producing. In order to illustrate the qualification of the GENERIC framework for the design of EME integrators, a thermoviscoelastic double pendulum is chosen as discrete model problem to which the discrete gradient operator due to Gonzalez [1] is applied. The acronym GENERIC pertains to ‘General Equation for Non‐Equilibrium Reversible Irreversible Coupling’ and provides by design a thermodynamic admissible mathematical framework for the evolution equations of dissipative thermomechanic systems. This contribution enlightens the incorporation of constraints in the GENERIC formalism and the necessity of a Lyapunov function as stability criterion.
On the influence of the probabilistic microstructural characteristics of glass fiber‐reinforced composites on the wave propagation in GLARE
Authors: Rauter Natalie , Weber Wolfgang E.
Published: May 2023

In an attempt to reduce the crack propagation speed in structures made of fiber‐reinforced composites metal layers are added to the laminate forming a new group of materials, so‐called fiber metal laminates. GLARE, a combination of glass fiber‐reinforced polymer and aluminum, is well‐known and frequently used in the aeronautical industry. One major drawback of such materials is their susceptibility to impact damage, which is not detectable by visual inspections. Hence, an adequate structural health monitoring technique to detect interlaminar damage like delaminations is essential for components made from fiber metal laminates. One approach here is the use of guided ultrasonic waves because they travel long distances without substantial damping and cover the whole thickness of thin‐walled structures. However, the probabilistic microstructure causes a continuous mode conversion in wave guides made from fiber‐reinforced composites. This significantly influences the signal processing and as a consequence, the interpretation of captured time signals. This phenomenon is induced by the random spatial distribution of the fibers in the matrix material, leading to an ongoing excitation of new wave modes within the propagating S0 wave mode. In this research, the effect is studied for the wave propagation in GLARE 3/2‐0.4. Therefore, the spatial distribution of the transverse YOUNG's modulus for the glass fiber‐reinforced layers is represented by homogeneous second‐order GAUSSian random fields. Afterwards, the propagation of the guided ultrasonic wave is simulated numerically. The results reveal that the continuous mode conversion is not only observable within the glass fiber‐reinforced polymer layers but also at the top and bottom surface and hence, within the isotropic layers. This holds for the wave propagation both in and perpendicular to the fiber orientation of the glass fiber‐reinforced polymer layers.
Numerical relaxation limit and outgoing edges in a central scheme for networked conservation laws
Authors: Kolbe Niklas
Published: May 2023

A recently introduced scheme for networked conservation laws is analyzed in various experiments. The scheme makes use of a novel relaxation approach that governs the coupling conditions of the network and does not require a solution of the Riemann problem at the nodes. We numerically compare the dynamics of the solution obtained by the scheme to solutions obtained using a classical coupling condition. In particular, we investigate the case of two outgoing edges in the Lighthill–Whitham–Richards model of traffic flow and in the Buckley–Leverett model of two phase flow. Moreover, we numerically study the asymptotic preserving property of the scheme by comparing it to its preliminary form before the relaxation limit in a 1‐to‐1 network.
A data‐driven solver scheme for inelastic problems
Authors: Prume Erik , Stainier Laurent , Ortiz Michael , Reese Stefanie
Published: May 2023

We review the data‐driven computing paradigm for inelastic problems. We extend an efficient graph search algorithm for the data search by thermodynamic constraints and a rate independent history parametrization based on the mechanical work increment. In addition, we propose a strategy how to use commercial solvers in the framework. Finally, we demonstrate the proposed method with a numerical example featuring 2‐d continuum plasticity.
Development of a FEM tool to calculate the dispersion curves of 2D phononic structures
Authors: Nies Christopher , Mellmann Marius , Ankay Benjamin , Zhang Chuanzeng
Published: May 2023

The control and manipulation of acoustic and elastic waves is an important research topic in engineering sciences. In acoustics, an adequate combination of different materials can contribute to an efficient and broadband sound isolation. The realization of a vibration‐free environment for high‐precision mechanical systems in laboratories and measuring environments is also desirable in many practical cases. Therefore, advanced materials and structures with outstanding acoustic and elastodynamic properties are of great importance in engineering applications. In this paper, a numerical tool based on the finite element method (FEM) is developed for computing the dispersion relations or band structures of two‐dimensional (2D) phononic crystals (PCs) composed of an elastic matrix and periodically distributed cylindrical inclusions.
A two‐dimensional analysis of the influence of delamination on the wave propagation in a fiber metal laminate
Authors: Nikiema Wendwoga Fulgence , Rauter Natalie , Lammering Rolf
Published: May 2023

Structural Health Monitoring (SHM) of composite materials using Guided Ultrasonic Wave (GUW) represent a central research topic with a large range of application fields. One major concern in this context is the detection of hidden inter‐laminar damage such as delaminations in composites, as these cannot be detected by visual inspection [1]. Fiber Metal Laminate (FML) consist of different layers of metal (e.g. steel) and Fiber Reinforced Polymer (FRP) stacked on top of each other and belong to a new type of material system that has been insufficiently explored in the context of damage detection using GUW. Following the objective of damage detection using GUW, two dimensional numerical simulations of the wave propagation in FML composed of layers made from steel and Carbon Fiber Reinforced Polymer (CFRP) are conducted. In order to properly identify and describe the different phenomena occurring when the GUW encounter a delamination three kind of numerical models were considered: undamaged plate, damaged plate with symmetrically and off‐center placed delamination. As far as the modeling of delaminations, the present work is restricted to a zero‐thickness‐delamination generated by de‐merging nodes at the interface of the layers. Mode‐selective excitation (fundamental symmetric and anti‐symmetric mode wave) of the models was then applied and the B‐scan representations of the in‐plane and out‐of‐plane displacement fields were generated and compared. Effects such as reflection, transmission and mode conversion of the main wave are observed and analyzed. Thus, a singular phenomenon as the trapped mode wave can be clearly observed and interpreted.
On the Systematic Construction of Lyapunov Functions for Polynomial Systems
Authors: Natkowski Lars , Gerbet Daniel , Röbenack Klaus
Published: May 2023

Lyapunov functions are a widely used tool to evaluate stability properties of nonlinear dynamical systems' equilibria. In this paper quantifier elimination is used to construct Lyapunov functions for polynomial systems from a parametric ansatz. Because the existing algorithms for quantifier elimination are inherently computationally expensive, a strategy is to simplify the quantifier elimination problem beforehand. A method is presented that may help simplifying the problem of finding suitable Lyapunov functions by deriving easier to evaluate necessary conditions. Finally, the introduced method is applied to an example system to show local asymptotic stability of an equilibrium point by constructing a Lyapunov function.
DoD Stabilization of linear hyperbolic PDEs on general cut‐cell meshes
Authors: Birke Gunnar , Engwer Christian , May Sandra , Streitbürger Florian
Published: May 2023

Standard numerical methods for hyperbolic PDEs require for stability a CFL‐condition which implies that the time step size depends on the size of the elements of the mesh. On cut‐cell meshes, elements can become arbitrarily small and thus the time step size cannot take the size of small cut‐cells into account but has to be chosen based on the background mesh elements.

A remedy for this is the so called DoD (domain of dependence) stabilization for which several favorable theoretical and numerical properties have been shown in one and two space dimensions [4, 9]. Up to now the method is restricted to stabilization of cut‐cells with exactly one inflow and one outflow face, i.e. triangular cut‐cells with a no‐flow face (see [4]).

We extend the DoD stabilization to cut‐cells with multiple in‐ and outflow faces by properly considering the flow distribution inside the cut‐cell. We further prove L2‐stability for the semi‐discrete formulation in space and present numerical results to validate the proposed extension.
Modeling and numerical simulation of flow processes of wood‐polymer composites
Authors: Liese Fabian , Wünsch Olaf
Published: May 2023

The combination of natural fibers and polymers is finding expanding application in a range of industrial branches, and knowledge of the material behavior is essential for further improving the products and the processing procedure. In this work, the material behavior of wood‐polymer composites (WPC) will be modeled and numerical simulations will be used to investigate the flow behavior. By means of rheological measurements, a shear thinning flow behavior of the composite can be determined, which is also often taken into account in the numerical simulation of WPC processing tools. Increasing shear viscosity and a formation of a yield point with increasing wood content can be observed. However, in addition to the shear‐dominant deformation states, noticeable strain deformations also occur due to cross‐sectional changes. In order to experimentally investigate and model the behavior of WPC under strain, this work involves measurements on hyperbolic dies in which a uniaxial strain state is present and extensional viscosity can be derived from this. Different boundary conditions such as noSlip, navierSlip and full slip are investigated in the simulations. In addition, during the extrusion of WPC, wall shear stresses of about 0.1 MPa and above can be observed. Measurements in a high‐pressure capillary rheometer allow the wall slip velocity to be measured as a function of the wall shear stress at different wood contents. The wall slip behavior is modeled and taken into account accordingly as a boundary condition in the numerical simulations using OpenFOAM [8].
A Reinforcement Learning Based Slope Limiter for Second‐Order Finite Volume Schemes
Authors: Schwarz Anna , Keim Jens , Chiocchetti Simone , Beck Andrea
Published: May 2023

Hyperbolic equations admit discontinuities in the solution and thus adequate and physically sound numerical schemes are necessary for their discretization. Second‐order finite volume schemes are a popular choice for the discretization of hyperbolic problems due to their simplicity. Despite the numerous advantages of higher‐order schemes in smooth regions, they fail at strong discontinuities. Crucial for the accurate and stable simulation of flow problems with discontinuities is the adequate and reliable limiting of the reconstructed slopes. Numerous limiters have been developed to handle this task. However, they are too dissipative in smooth regions or require empirical parameters which are globally defined and test case specific. Therefore, this paper aims to develop a new slope limiter based on deep learning and reinforcement learning techniques. For this, the proposed limiter is based on several admissibility constraints: positivity of the solution and a relaxed discrete maximum principle. This approach enables a slope limiter which is independent of a manually specified global parameter while providing an optimal slope with respect to the defined admissibility constraints. The new limiter is applied to several well‐known shock tube problems, which illustrates its broad applicability and the potential of reinforcement learning in numerics.
Patient‐specific simulation of brain tumour growth and regression
Authors: Suditsch Marlon , Ricken Tim , Wagner Arndt
Published: May 2023

The medical relevance of brain tumours is characterised by its locally invasive and destructive growth. With a high mortality rate combined with a short remaining life expectancy, brain tumours are identified as highly malignant. A continuum‐mechanical model for the description of the governing processes of growth and regression is derived in the framework of the Theory of Porous Media (TPM). The model is based on medical multi‐modal magnetic resonance imaging (MRI) scans, which represent the gold standard in diagnosis. The multi‐phase model is described mathematically via strongly coupled partial differential equations. This set of governing equations is transformed into their weak formulation and is solved with the software package FEniCS. A proof‐of‐concept simulation based on one patient geometry and tumour pathology shows the relevant processes of tumour growth and the results are discussed.
Analysis of the remote laser cutting process induced damage in carbon fibre reinforced polymers
Authors: Schmidt Benjamin , Husert Markus , Hollmer Katharina , Zimmermann Martina , Kästner Markus
Published: May 2023

In machining technologies for fibre reinforced polymers, remote laser cutting plays a special role as it can minimize the drawbacks of conventional laser cutting methods, in particular thermally induced damage such as charred edges and matrix evaporation. In this contribution, a thermal simulation model for the remote laser cutting process is presented. With the aim of a universally applicable model that works independently of the selected carbon fibres, matrix system, and fibre content, the effective thermal material parameters are calculated with a rule of mixture from the microscopic parameters for fibre, matrix, and process gas. The evaporation of matrix and fibre material is modelled with phase transitions. The moving laser spot is modelled with a Gaussian distribution as a heat input on the upper side. The emerging process gas is assumed to absorb a part of the laser power according to the Lambert‐Beer law.
On the numerical treatment of heat sources in laser beam welding processes
Authors: Hartwig Philipp , Scheunemann Lisa , Schröder Jörg
Published: May 2023

Laser beam welding is a contact free fusion technique which has gained importance during the last years due to rising need for automatization in industrial processes. However, a well‐known problem is the formation of solidification cracks in the rear region of the melting pool. In order to investigate the formation of solidification cracks which is highly dependent on the chemical composition, the welding speed, weld beam intensity and the resulting temperature gradient in the material, the modeling of the laser beam as a heat source plays a prominent role. In order to investigate heat sources in laser beam welding, this contribution compares two methods, the Goldak model and a second model that mimics the region of the melt pool with the idea of an isothermal region. Suitable boundary value problems to show the differences of the methods are demonstrated.
Computational challenges in mixed‐dimensional beam/solid coupling
Authors: Firmbach Max , Steinbrecher Ivo , Popp Alexander , Mayr Matthias
Published: May 2023

The simulation of mixed‐dimensional couplings poses a variety of computational challenges in order to enable accurate modeling and efficient solution of problems in science, engineering and biomedicine. In this contribution, we study computational challenges and bottlenecks in the mixed‐dimensional modeling of coupled beam/solid systems and discuss possible remedies to allow large‐scale computations of applications in structural engineering. In particular, we address questions of memory consumption in geometric search operations, partitioning for computations on parallel clusters and performance of the linear solver by suitable preconditioning techniques.
Adaptive strategies based on equilibration for the Biot equations
Authors: Bertrand Fleurianne , Brodbeck Maximilian
Published: May 2023

The hypercircle theorem leads to a posteriori error estimates for the three‐field variational formulation of the Biot problem involving displacements, total pressure and fluid pressure. Based thereon, adaptive strategies can be constructed. In particular, the error estimator is derived on the basis of Hdiv‐conforming reconstructions of stress and flux approximations while the symmetry of the reconstructed stress is allowed to be satisfied only weakly. The reconstructions can therefore be performed locally on a set of vertex patches. The local nature of the reconstruction leads to two different possible adaptive strategies. In this paper, we review these two different adaptive strategies for the Biot problem. Numerical experiments underline the differences between the two strategies.
Consistent Euler‐Bernoulli beam theory in gradient elasticity: Two equivalent formulations of a simple constitutive law
Authors: Üngör Özer , Broese Carsten , Müller Ralf , Sideris Stergios-Alexandros , Tsakmakis Charalampos
Published: May 2023

The classical Euler‐Bernoulli beam theory in elastostatic is known to be inconsistent, since the equilibrium equations are not satisfied in local form. Recently, it has been shown that the theory will become consistent if one assumes elastic anisotropy subject to internal constraints. This is shown to be true even for a simple gradient elasticity law. Normally, beam bending is considered as one‐dimensional problem. We summarise in the present paper the results of a previous work concerning two well‐known one‐dimensional formulations of Euler‐Bernoulli beam and gradient elastic material behaviour. The two formulations appear to be different because the functional of internal forces includes the cross‐sectional area of the beam in one but not in the other. It is shown that the two one‐dimensional formulations can be derived as special cases of a three‐dimensional simple gradient elasticity model and that they are equivalent to each other.
Gaussian fluctuations around limit measures of generalized SQG point vortices
Authors: Geldhauser Carina , Romito Marco
Published: May 2023

We report on recent results on generalized surface quasi‐geostropic point vortex models. The statistical physics of these models is particularly interesting, as their mean‐field limit is a steady solution of the gSQG PDE. We present a central limit theorem‐type result for gSQG point votex models and make a comparison with results for Euler point vortex models.
Repulsion dynamics for uniform Pareto front approximation in multi‐objective optimization problems
Authors: Borghi Giacomo
Published: May 2023

Scalarization allows to solve a multi‐objective optimization problem by solving many single‐objective sub‐problems, uniquely determined by some parameters. In this work, several adaptive strategies to select such parameters are proposed in order to obtain a uniform approximation of the Pareto front. This is done by introducing a heuristic dynamics where the parameters interact through a binary repulsive potential. The approach aims to minimize the associated energy potential which is used to quantify the diversity of the computed solutions. A stochastic component is also added to overcome non‐optimal energy configurations. Numerical experiments show the validity of the proposed approach for bi‐ and tri‐objectives problems with different Pareto front geometries.
Experiments and Modelling of the Load Capacity of Green Wood
Authors: Loske Simon , Muench Ingo
Published: May 2023

The material properties of green wood in the shaft of vital trees differ significantly from the generally known material properties of technically processed, dried wood. Furthermore, completely different residual stresses and fracture mechanisms are present in the natural full cross‐section [1]. The properties also depend on the tree species. Our work focuses on green wood from european beech (Fagus sylvatica). A large number of experiments on small test specimens of green wood are known from [2]. We present both, experiments on small and large‐scaled specimens. Latter are bending test on trunks with full cross‐section. Combining results and considering micro‐mechanical properties of cellular wood components [3], a computational model is fitted to our experimental results. This aspect influences the fracture resistance of a tree and should be representable in a computational model. This is particularly important in order to better assess the risk of building on vital trees.
Vibration and damping analysis of cantilever sandwich plates with viscoelastic core using zig‐zag theory
Authors: Gao Yingshan , Zhang Shunqi , Ma Songyun , Markert Bernd
Published: May 2023

In the present work, an FE formulation using the zig‐zag hypothesis is developed for cantilever sandwich plates with viscoelastic care layer. Both viscoelastic and elastic layers of sandwich structures are considered based on the first‐order shear deformation theory to achieve higher accuracy. The FE simulation is validated by a frequency and loss factor analysis of sandwich plate. Furthermore, the damping characteristics and transient response of the cantilever sandwich plates are systematically studied.
Numerical modeling of reactive flow in porous media at the pore scale
Authors: Toktaliev Pavel , Iliev Oleg
Published: May 2023

Different numerical algorithms for the solution of a class of unsteady convection‐diffusion‐reaction (CDR) equations are presented and compared in this paper. The fully implicit in time discretizations are usually preferred because they are unconditionally stable for linear problems. However, when implicit discretization is used for nonlinear problems, iterations over the nonlinearity have to be performed. Picard (simple linearization) or Newton's methods can be used for this purpose. An alternative to the fully implicit discretization is fractional time‐step methods, e.g. splitting with respect to physicochemical processes. The study of the latter class of discretization is especially interesting in the case when only the reactive term contains nonlinearity, while the convection and diffusion operators are linear. The CDR models used to describe processes in catalytic filters belong to this class. Numerical experiments for CDR equation with controllable stiffness of reaction term for different transport regimes, which are described by Peclet and Damkohler numbers are demonstrated and analyzed.
Stability in mechanics and dynamics; a brief historical tour from Newton to modern tools, including Riemannian structures and entropy
Authors: Gunesch Roland
Published: May 2023

This article presents some historical developments in the theory of stability in mechanics from a dynamical systems point of view, focusing on mathematical methods from the earliest developments (Newton) and explaining some classical and some recent methods used, including Riemannian structures, entropy and notions of stability in dynamics.
Mechanical, thermal, and electrical properties of amine‐ and non‐functionalized reduced graphene oxide/epoxy carbon fiber‐reinforced polymers
Authors: Ackermann Annika C. , Demleitner Martin , Guhathakurta Jajnabalkya , Carosella Stefan , Ruckdäschel Holger , Simon Sven , Fox Bronwyn L. , Middendorf Peter
Published: May 2023

Graphene and its related materials are increasingly applied in fiber‐reinforced polymers to tailor their material properties for high performance composites. Yet, the use of graphene derivatives that underwent a plasma functionalization process is not well understood. This study uses 1.50 wt.% of unfunctionalized (rGO) or plasma‐treated reduced graphene oxide with amine‐functionalities (frGO) in an epoxy matrix to prepare unidirectional pre‐impregnated carbon fibers. The material characteristics of the graphene‐modified carbon fiber‐reinforced polymers (g‐CFRP) are compared to the neat carbon fiber‐reinforced polymer (CFRP). Both g‐CFRP configurations exhibit a higher void content than the neat CFRP. No significant difference between the CFRP and the g‐CFRPs is observed with respect to the Young's modulus, glass transition temperature, storage modulus, specific heat capacity, thermal conductivity at room temperature, and in‐plane electrical conductivity. Yet, a reduction in ultimate tensile strength of up to −13% is noted. In addition, the apparent interlaminar shear strength and transverse electrical conductivity are increased by up to +12% for the rGO‐CFRP and +52% for the frGO‐CFRP. This knowledge will support the selection of additives for fiber‐reinforced polymers for, for example, lightning strike protection in aircrafts, sensory materials, electromagnetic interference shielding or heat transfer elements.
Effects of cyclic absorption–desorption of model fuels by aerospace‐grade carbon/epoxy composites
Authors: Harich Naoufal , Priddy Matthew W. , Lacy Thomas E. , Pittman Charles U. , Kundu Santanu
Published: May 2023

The aviation industry is in the process of using several alternative fuels sourced from renewable sources to decrease its impact on the environment. These alternative fuels are mostly comprised of aliphatic hydrocarbons and have low to no aromatic content. The Federal Aviation Administration (FAA) has approved several drop‐in fuels, in which alternative fuels are typically blended with conventional Jet A fuel. Because of blending, the drop‐in fuels consist of both aliphatic and aromatic components. To achieve a fundamental understanding of how individual aliphatic and aromatic components interact with the aerospace‐grade composites, we have considered four model fuels, three aliphatic with varying chain lengths and one aromatic. The absorption of these model fuels by composites in three absorption/desorption cycles was captured and compared to the conventional Jet A fuel. The equilibrium weight gain by the composites due to absorption was low but was different for each model fuel, and the trend could be validated using Hansen solubility parameters. The absorption of model fuels decreased the glass transition temperature of composites. The change in glass transition temperature was not significantly different between the model fuels and the conventional fuel. These results can be translated to alternative fuels, making them a possible substitute for Jet A in the aviation industry.
Immunoaffinity separation of miroestrol and deoxymiroestrol from Pueraria candollei var. mirifica (Airy Shaw & Suvat.) Niyomdham using fragment antigen‐binding antibody produced via Escherichia coli
Authors: Juengsanguanpornsuk Wipawee , Poopanee Nut , Krittanai Supaluk , Sakamoto Seiichi , Tanaka Hiroyuki , Putalun Waraporn , Yusakul Gorawit
Published: May 2023

Introduction

Miroestrol and deoxymiroestrol are potent phytoestrogens and are oestrogen markers of Pueraria candollei var. mirifica. However, purifying these compounds is difficult because they only exist in trace amounts.

Objectives

Active fragment antigen‐binding (Fab) antibodies were produced via Escherichia coli SHuffle® T7 and used to selectively separate these compounds.

Materials and methods

Two immunoaffinity separation approaches were developed, namely the immunoaffinity column (IAC) and a cell‐based method. Group‐specific Fab antibodies against miroestrol and deoxymiroestrol (anti‐MD Fab) were used as biological binding reagents for selective separation.

Results

The Fab‐based IAC effectively separated miroestrol and deoxymiroestrol (0.65 and 2.24 μg per 2 mL of resin, respectively) from P. mirifica root extract. When P. mirifica extract was added to E. coli cultures during Fab expression via a cell‐based method, the target compound accumulated in intracellular compartments and, thus, were separated from E. coli cells after the removal of other compounds. A yield of 1.07 μg of miroestrol per gram of cell pellet weight was obtained. Miroestrol and deoxymiroestrol were successfully purified from P. mirifica extract using anti‐MD Fab via the IAC and an intracellular cell‐based method.

Conclusion

The proposed methods can simplify the miroestrol and deoxymiroestrol extraction process and provide a basis for applications utilising recombinant antibodies to separate target compounds.
Functional characterization of a hypothetical protein (TTHA1873) from Thermus thermophilus
Authors: Iyyappan Yuvaraj , Dhayabaran Vaigundan , Elayappan Mohanapriya , Chaudhary Santosh Kumar , Palaniappan Chandrasekaran , Kanagaraj Sekar
Published: May 2023

Thermus thermophilus is an extremely thermophilic organism that thrives at a temperature of 65°C. T. thermophilus genome has ~2218 genes, out of which 66% (1482 genes) have been annotated, and the remaining 34% (736 genes) are assigned as hypothetical proteins. In this work, biochemical and biophysical experiments were performed to characterize the hypothetical protein TTHA1873 from T. thermophilus. The hypothetical protein TTHA1873 acts as a nuclease, which indiscreetly cuts methylated and non‐methylated DNA in divalent metal ions and relaxes the plasmid DNA in the presence of ATP. The chelation of metal ions with EDTA inhibits its activity. These results suggest that the hypothetical protein TTHA1873 would be a CRISPR‐associated protein with non‐specific DNase activity and ATP‐dependent DNA‐relaxing activity.
Virulence and transgenerational effects of Metarhizium anisopliae on Oxycarenus hyalinipennis
Authors: Shaukat Rana Farjad , Freed Shoaib , Ahmed Rizwan , Raza Mehtab , Naeem Afifa
Published: May 2023

BACKGROUND

Insect pests cause major yield losses to Gossypium hirsutum, often requiring the use of chemical insecticides. To avoid human health, environmental and resistance problems, entomopathogenic fungi (EPF) can be used to control insect pests. In our study, the pathogenicity of Metarhizium anisopliae to Oxycarenus hyalinipennis was determined by the immersion method. Furthermore, the sublethal and lethal effects of M. anisopliae on the biological parameters of O. hyalinipennis were investigated by age‐stage, two‐sex life table software.

RESULTS

M. anisopliae infection was lethal to the fourth instar of O. hyalinipennis with LC50 values of 8.84 × 104 spores mL−1. The sublethal and lethal concentrations of M. anisopliae not only affected the parental generation (F0) but also the demographic parameters of the offspring of the filial generation (F1). Transgenerational results of F1 infected with M. anisopliae showed decreased net reproductive rate (R0), intrinsic rate of increase (r) and mean generation time (T) compared to those of the control group. The larval developmental duration significantly decreased to 15.52 and 19.02 days in the LC50 and LC20 groups, respectively, compared to 21.08 days in the control group. There was a noteworthy decline in mean fecundity in the LC50 and LC20 groups, i.e., 16.0 and 20.96 eggs, compared to 33.26 eggs in the control group. Adult longevity was likewise considerably reduced in the LC50 and LC20 treated groups.

CONCLUSION

The study showed that M. anisopliae can have an enduring impact on the biological parameters of O. hyalinipennis, which may enhance its use in eco‐friendly management programs. © 2023 Society of Chemical Industry.
Salidroside ameliorated the pulmonary inflammation induced by cigarette smoke via mitigating M1 macrophage polarization by JNK/c‐Jun
Authors: Feng Haoshen , Zhang Dan , Yin Yan , Kang Jian , Zheng Rui
Published: May 2023

Pulmonary inflammation induced by cigarette smoke (CS) promoted the development of chronic obstructive pulmonary disease (COPD), and macrophage polarization caused by CS modulated inflammatory response. Previous studies indicated that salidroside exerted therapeutic effects in COPD, but the anti‐inflammatory mechanisms were not clear. This study aimed to explore the effects and mechanisms of salidroside on macrophage polarization induced by CS. Wistar rats received passively CS exposure and were treated intraperitoneally with salidroside at a low, medium or high dose. Lung tissues were stained with hematoxylin–eosin. Emphysema and inflammatory scores were evaluated by histomorphology. Lung function, cytokines, and cell differential counts in BALF were detected. The macrophage polarization was determined by immunohistochemistry in lung tissues. Alveolar macrophages (AMs) were isolated and treated with cigarette smoke extract (CSE), salidroside or inhibitors of relative pathways. The polarization status was determined by qPCR, and the protein level was detected by Western blotting. CS exposure induced emphysema and lung function deterioration. The inflammatory scores, cytokines level and neutrophils counts were elevated after CS exposure. Salidroside treatment partly ameliorated above abnormal. CS exposure activated M1 and M2 polarization of AMs in vivo and in vitro, and salidroside mitigated M1 polarization induced by CS. CSE activated the JNK/c‐Jun in AMs and the M1 polarization of AMs was inhibited by the inhibitors of JNK and AP‐1. Salidroside treatment deactivated the JNK/c‐Jun, which indicated that salidroside mitigated the M1 polarization of AMs induced by CS via inhibiting JNK/c‐Jun. Salidroside treatment ameliorated the pulmonary inflammation and M1 polarization of AMs induced by CS, and the process might be mediated by the deactivation of JNK/c‐Jun.
A stochastic stability equation for unsteady turbulence in the stable boundary layer
Authors: Boyko Vyacheslav , Vercauteren Nikki
Published: May 2023

The atmospheric boundary layer is particularly challenging to model in conditions of stable stratification, which can be associated with intermittent or unsteady turbulence. We develop a modelling approach to represent unsteady mixing possibly associated with turbulence intermittency and with unresolved fluid motions, called sub‐mesoscale motions. This approach introduces a stochastic parametrisation by randomising the stability correction used in the classical Monin–Obhukov similarity theory. This randomisation alters the turbulent momentum diffusion and accounts for sporadic events that cause unsteady mixing. A data‐driven stability correction equation is developed, parametrised, and validated with the goal to be modular and easily combined with existing Reynolds‐averaged Navier–Stokes models. Field measurements are processed using a statistical model‐based clustering technique, which simultaneously models and classifies the non‐stationary stable boundary layer. The stochastic stability correction obtained includes the effect of the static stability of the flow on the resolved flow variables, and additionally includes random perturbations that account for localised intermittent bursts of turbulence. The approach is general and effectively accounts for the stochastic mixing effects of unresolved processes of possibly unknown origin.