bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural Optimisation Using Parametrised Level Set Methods and Extended Finite Element Method
Authors: Wohlgemuth Felix , Barthold Franz‐Joseph 
Published: December 2018

AbstractIn the framework of level‐set‐based optimisation, several approaches to solve bi‐material and topological problems have been developed. In this study a combined concept of different approaches is introduced, joining together a parametrised geometry description with superellipses or b‐splines and a modified approach for the extended finite element method within an optimisation setup of topological and shape iterations introduced by Allaire [1]. The parametrisation with geometric figures or splines allows us to reduce the number of design variables to a minimum whereas we hold up a sufficient precision in the geometry description. Moreover it simplifies the shape derivatives as we gain an implicit description for the moving interfaces. In order to solve the boundary value problem of structural mechanics, we introduce a modified extended finite element approach which uses a sub‐meshing technique that enables us to keep existing strategies from homogeneous structures and transform them onto a discontinuous material using enriched shape functions provided by the standard extended finite element method. Shape sensitivities are evaluated on the sub‐elements and extrapolated to the element nodes. The topological derivative as developed by Novotny [4] is evaluated and prescribes the initiation of new discontinuities as inclusions or holes.
Simultaneous Registration of Image Sequences – a novel singular value based images similarity measure
Authors: Brehmer Kai , Wacker Benjamin , Modersitzki Jan 
Published: December 2018

AbstractThe comparison of images is an important task in image processing. For a comparison of two images, a variety of measures has been suggested. However, applications such as dynamic imaging or serial sectioning provide a series of many images to be compared. When these images are to be registered, the standard approach is to sequentially align the j‐th image with respect to its neighbours and sweep with respect to j. One of the disadvantages is that information is distributed only locally. We introduce an alternative so‐called SqN approach. SqN is based on the Schatten‐q‐norm of the image sequence gradients, i.e. rank information of image gradients of the whole image sequence. With this approach, information is transported globally. Our experiments show that SqN gives at least comparable registration results to standard distance measures but its computation is about six times faster.
Investigating the effect of Nano‐silica on the depth of water penetration in concrete used in seawater: Case study of Caspian Sea
Authors: Arasteh Khoshbin Omolbanin , Ricken Tim 
Published: December 2018

AbstractOne of the requirements of concrete structures is functional continuity whatever for it is required to be resistance in a particular period. Water during cementing process leads to hydration causing concrete hardness, whereas after hardening of concrete in most cases damages it's structure and properties. Dams, waveguides, docks and oil platforms in the seawater are subject to gradual erosion, which is very slow but measurable. Seawater due to the properties of sulfate, acid and alkali is a significant threat to concrete durability. Reducing the water absorption into the concrete body is the primary step to address the concrete erosion. Changing the concrete characteristics is an approach to increase concrete density and decrease its porosity leading to erosion reduction. Adding fine‐grained such as Nano derivatives can fill the void space within the concrete and reducing seawater absorption. In this research, we study the effect of Nano‐silica with 1% and 5% replacement ratios instead of cement on compressive strength and water penetration depth for concrete in environments of the Caspian Sea.
Evaluation of the Reduced Order Models for Thermoelastodynamic Response of Geometrically Nonlinear Finite Element Models
Authors: Karamooz Mahdiabadi Morteza , De Crescenzo Francesco , Meyer Christian H. , Rixen Daniel J. 
Published: December 2018

AbstractThis work deals with model order reduction of geometric nonlinear FE models under thermal loads. The nonlinear reduced order model (NLROM) is developed in a non‐intrusive approach. Namely, the NLROM can be constructed in any FE package which has the ability to solve nonlinear static problems, without requiring to deal with the governing equations of the full‐order model in closed form. The identification of the nonlinear stiffness tensors as well as thermal induced terms can be performed using either force based or displacement based estimation techniques. The Implicit Condensation (IC) method properly develops the NLROM for transverse displacement and has been also extended to approximate the in‐plane motion, which is called Implicit Condensation and Expansion (ICE). Here, ICE is extended for the thermoelastodynamic problem to accurately approximate the in‐plane motion in the presence of temperature fields.
Model‐based geometry reconstruction of quantum dots from TEM
Authors: Maltsi Anieza , Koprucki Thomas , Niermann Tore , Streckenbach Timo , Tabelow Karsten , Polzehl Jörg 
Published: December 2018

AbstractThe reconstruction of geometric properties of semiconductor quantum dots (QDs) from imaging of bulk‐like samples (thickness 100‐300 nm) by transmission electron microscopy (TEM) is a difficult problem. A direct reconstruction by solving the tomography problem is not feasible due to the limited image resolution (0.5‐1 nm), the highly nonlinear behavior of the dynamic electron scattering, nonlocal effects due to strain and strong stochastic influences due to uncertainties in the experiment. We present a mathematical model for the numerical simulation of TEM images. This includes elasticity theory to obtain the strain profile coupled with the Darwin‐Howie‐Whelan equations, describing the propagation of the electron wave through the sample. Furthermore, we introduce a novel concept for 3D model‐based geometry reconstruction of QDs from TEM images. The approach includes a geometric model for the QD configuration in real space, a database of simulated TEM images and a statistical procedure for the estimation of the geometric properties and the classification of QD types.
Analysis of pullout behavior of single steel fibers embedded in concrete using phase‐field modeling
Authors: Pise Mangesh , Brands Dominik , Gebuhr Gregor , Schröder Jörg , Anders Steffen 
Published: December 2018

AbstractIn this contribution, a constitutive framework of elasto‐plastic phase‐field model for fracture is applied to simulation of pullout test of single steel fiber embedded in concretes and compare it to the experimental results. For the description of the mechanical behavior the Drucker‐Prager plasticity model is used. The aim is to examine the pullout behavior of a single steel fiber and its influence on the overall material behavior. Therefore, the mechanical behavior of concrete is studied in experimental single fiber pullout test. The predictive capability of the above mentioned model is analyzed in detail by simulating a single fiber pullout test and compared against the experimental data.
Hyperelastic material modeling of graphene based on density functional calculations
Authors: Shirazian Farzad , Ghaffari Reza , Hu Ming , Sauer Roger A. 
Published: December 2018

AbstractA new parameter set for the graphene material model of [1] is obtained. The material model is anisotropic hyperelastic and calibrated by a trial data set generated by density functional theory (DFT). The DFT experiments are one pure dilatation test and two uniaxial stretch tests along the armchair and zigzag directions. The strain energy is computed from ab‐initio simulations and used to calibrate the parameters of the hyperelastic model. The strain energy and stresses from the new parameter set are calculated and verified with the results of [1].
Adjoint shape optimization for fluid‐structure interaction
Authors: Heners Jan Ph. , Radtke Lars , Düster Alexander , Hinze Michael 
Published: December 2018

AbstractA partitioned approach for the solution of the adjoint associated to the coupled system of time‐dependent fluid‐structure interaction is presented. Allowing for an efficient computation of both sensitivity and gradient distributions relying on the adjoint method, an optimization strategy based on the steepest descent algorithm is applied. The performance of the developed shape optimization process improving flow conditions and related cost functionals is demonstrated by application to ducted flow situations and common fluid dynamic design tasks considering the interaction between fluid loads and structural deformations. Both physical capability and feasibility are discussed in terms of theoretical and numerical aspects in order to evaluate the efficiency of the realized optimal control process.
Experimental and numerical characterisation of fibre‐metal‐elastomer laminates by using DMA regarding its damping behaviour
Authors: Sessner Vincent , Liebig Wilfried V. , Kärger Luise , Weidenmann Kay A. 
Published: December 2018

AbstractHybrid carbon fibre‐elastomer‐metal laminates consist of alternating layers of carbon fibre reinforced plastics, elastomer layers and aluminium sheets. These laminates offer great potential for a lightweight structural material with adjustable damping properties. The material damping is strongly influenced by the viscoelastic properties of the elastomer layers which damp by the principle of constrained layer damping when the laminate is vibrated. In this study the material damping was experimentally characterised by three point bending dynamic mechanical analysis (DMA). In this regard, HyCEML specimens were tested on different frequencies and temperatures. The loss factor, storage‐ and loss modulus were measured to characterise the damping over the temperature and the frequency range. Time‐temperature superposition was applied to determine the damping characteristics at higher and lower frequencies. The experimental results were compared to numerical studies on the basis of a characterisation of the single constituents. A test setup with a cantilever beam under free vibration was chosen for the comparison of experimental and numerical results. Detailed multi‐layer finite element models were generated offering high flexibility in terms of type and number of finite elements especially in the direction of laminate thickness. For this purpose, existing material models were used to investigate the influence of each component on the system's damping behaviour. The damping in the free vibration experiments was determined with the logarithmic decrement at the free end. Also the numerically and experimentally determined first eigenfrequencies were compared. It could be shown that the laminate damping is strongly dependent on the glass transitions of both the carbon‐fibre reinforced plastics and the elastomers. The numerically determined first eigenfrequency matched the experimental with a deviation of 10 %, the logarithmic decrement of the experimental results was more than 50 % higher. The damping behaviour of the HyCEM laminate, however, is underestimated by the numerical investigation, since nonlinear viscoelastic effects are not yet considered.
Geometry‐Inspired Control of the Brockett‐Integrator in Cylindrical Coordinates
Authors: Knoll Carsten , Xue Yifan , Röbenack Klaus 
Published: December 2018

AbstractThe so‐called Brockett‐Integrator is a famous control system. On the one hand it has a very simple structure (second order polynomial, three state components, two affine inputs, no drift) and fulfills the Lie‐Algebra‐Rank‐Condition for (strong) local accessibility. Nevertheless, it has the challenging control property, that it does not admit a continuously differentiable control law, which stabilizes the origin.In this contribution we consider the system in cylindrical coordinates. If the first time derivatives of the radius and the orientation are chosen as the new inputs, the transformed system dynamics is even simpler (in terms of expression length) than in usual Cartesian form. Moreover, the system can be decomposed into two subsystems and a differentially flat output can be easily read off. Based on this partially decoupled system dynamics we formulate a simple three‐staged control law which drives the system into the origin by aiming for a minimal arc length in the (original) state space.
The effect of magnetic field advection on turbulent magnetohydrodynamic flow in a square duct
Authors: Bandaru Vinodh , Boeck Thomas , Schumacher Jörg 
Published: December 2018

AbstractIn the field of magnetohydrodynamics, turbulent duct flows in a transverse magnetic field are of considerable interest. Their velocity fields exhibit electromagnetic boundary layers and anisotropy due to damping of turbulent fluctuations by the Lorentz force. The weak induced magnetic field is slaved to the velocity field (quasistatic limit) in laboratory experiments since the magnetic Reynolds number is small. Here we consider flow conditions with finite magnetic Reynolds number in direct numerical simulations, whereby the full induction equation needs to be solved. The modification of the imposed transverse field by the flow and other differences to the quasistatic results are briefly discussed.
Retarded potentials for wave propagation in elastic trusses
Authors: Pölz Dominik , Gfrerer Michael , Schanz Martin 
Published: December 2018

AbstractA space‐time boundary element method for the dynamic simulation of simplified elastic truss systems is proposed. The considered truss systems consist of elastic rods whose dynamic behaviour is governed solely by the 1D wave equation. By using time domain boundary integral equations the problem reduces to the nodes of the truss system and therefore no spatial discretization is necessary. The discretization employs an adaptive mesh refinement scheme enabling the accurate resolution of non‐smooth solutions.
Investigation of the network topology of vitreous silica during cyclic tensile loading
Authors: Bamer Franz , Ebrahem Firaz , Markert Bernd 
Published: December 2018

AbstractIn this paper, we present visco‐plastic effects of vitreous silica. By introducing a stepwise loading‐relaxation procedure, we evaluate a quasi‐static hysteresis and observe permanent plastic deformation. The investigation of the medium‐range order of the sample at various deformation states provides new insights into the changes of the atomistic arrangements caused by the plastification.
Parametric model order reduction applied to thin‐walled structures modified by acoustic black holes
Authors: Rodríguez Sánchez Raúl , Miksch Matthias , Müller Gerhard 
Published: December 2018

AbstractIn thin walled structures a smooth reduction of the thickness results in a decreasing propagation speed and an increasing amplitude of the bending wave. Acoustic black holes (ABH) make use of this modulation to enhance the energy dissipation in the vicinity of the ABH. Modifying a thin walled structure with ABH can significantly influence the energy distribution in the structure. For large systems those investigations become computationally expensive. This contribution investigates the influence of the geometric parameter that defines the design of an ABH by using Model Order Reduction (MOR). Several numerical models are evaluated to assess the dependency between the geometric design parameters of the thickness variation and the energy distribution in the structure, the computational time and the quality of the approximation are compared with the solution obtained using the corresponding full‐scale FE model.
A mixed extended finite element formulation for the simulation of cracks in nearly incompressible materials
Authors: Loehnert Stefan 
Published: December 2018

AbstractA low order mixed extended finite element for the simulation of cracks in nearly incompressible materials is presented. The finite element is based on a classical Q1P0 formulation in 3D including enrichment functions and corresponding degrees of freedom to account for the discontinuity in the displacement field. In addition, in the mixed formulation the volumetric stress field is enriched as well. The additional degrees of freedom can be eliminated on element level. The superior convergence behaviour of the presented formulation especially for nearly incompressible material behaviour is demonstrated by means of examples from linear elastic fracture mechanics.
On a Multi‐Scale and Multi‐Phase Model of Paracetamol‐induced Hepatotoxicity for Human Liver
Authors: Lambers Lena , Waschinsky Navina , Ricken Tim 
Published: December 2018

AbstractMore than 650 Million people worldwide suffer from a certain kind of liver disease. One of the most common disease is the non‐alcoholic fatty liver disease (NAFLD) which affects about 20‐30 % of the population in industrial countries. During a NAFLD fat is stored in liver cells causing tissue growth which impacts blood perfusion inside the liver. The liver is responsible for detoxification of drugs and toxins, e.g. the pain killer Paracetamol. However high dosages of toxic metabolites can harm the liver. The detoxification is perfusion‐dependent, due to the substances transported by the blood flow. To understand and predict the processes during a liver disease, we have developed a computational model using a multi‐scale and multi‐phase function‐perfusion approach basend on the Theory of Porous Media (TPM).
3‐D Numerical Simulation and Analysis of the Flow Pattern in the Shot Sleeve of the Cold Chamber HPDC Process
Authors: Laouar Roudouane 
Published: December 2018

AbstractThis work presents a 3d‐numerical study of the flow of molten metal in the shot sleeve of a horizontal high‐pressure die casting machine. The analysis of the flow pattern caused by the filling and the plunger motion can be of help in reducing porosity in manufactured parts caused by air entrapment. A particular attention has been paid to the flow and temperature field below the filling hole. The used numerical model is based on the conservation equations of mass, momentum and energy, and describes the free surface using the volume‐of‐fluid method.
Design and Optimization of Large‐Deformation Compliant Mechanisms
Authors: Humer Alexander 
Published: December 2018

AbstractAs compared to conventional mechanisms, compliant mechanisms exploit flexible deformation rather than rigid‐body motion of its components. The key advantage of jointless or monolithic structures lies in the absence of relative motion between the links. Besides the reduction in parts required to perform a task, compliant mechanisms typically show little friction, if any, and do not require lubrication to minimize wear. On the downside, design and synthesis of compliant mechanisms become much more involved than in rigid‐body linkages. In particular, optimization of compliant mechanisms relying on (sub‐)structures subjected to large flexible deformation is a challenging task, in which diverse aspects need to be considered. First and foremost, kinematic analysis of compliant mechanisms usually requires geometric non‐linearities to be accounted for. Further, limitations in actuation forces and torques impose constraints on the design. Depending on the application, the performance of compliant mechanisms may crucially depend on the natural frequencies and their change over the range of operation. In view of the diverse aspects, one typically has to deal with multi‐objective optimization problems in comparatively high‐dimensional parameter spaces.
Behaviour of Anionic and Cationic Hydrogels
Authors: Keller Karsten , Wallmersperger Thomas , Ricken Tim 
Published: December 2018

AbstractIonic polyelectrolytic gels in an aqueous solution, i.e. hydrogels – also known as smart materials – react to different kinds of environmental changes, e.g. chemical, electrical, mechanical, and thermal stimulation. As a reaction, they show enormous swelling capabilities resulting from the delivery or uptake of ions and solvent. These properties make them attractive for chemo‐electro‐mechanical energy converters and for the application as actuators or sensors. The applied multi‐field formulation consists of the chemical, electrical, and mechanical field and is capable of giving local concentrations, electric potential distributions and displacements. In this excerpt the reaction of a modelled hydrogel finger gripper under electrical stimulation is shown. The swelling ratio is assumed to be in the regime of small volume changes and corresponding displacements.
Diffusion under micro‐gravity: Mass transfer from rising bubble in a stagnant fluid column
Authors: Bari Md Ashfaqul , Akbulut Cemil , Münsch Manuel , Delgado Antonio 
Published: December 2018

AbstractNumerical simulation of two‐phase flows using Volume of Fluid (VOF) method is known be to susceptible to parasitic currents, which arises due to erroneous interface curvature calculation to model the surface tension force. The interface curvature calculation scheme in OpenFoam has been modified according to the Sharp Surface Force (SSF) which reduced parasitic currents magnitude significantly. Alongside SSF method the Continuous Species Transfer (CST) equation is implemented in OpenFOAM 4.1 to simulate mass transfer from an Oxygen bubble to the surrounding stagnant water‐glycerol solution under micro‐gravity environment.
Fabrication, rheological analysis, and in vitro characterization of in situ chemically cross‐linkable thermogels as controlled and prolonged drug depot for localized and systemic delivery
Authors: Khan Samiullah , Akhtar Naveed , Minhas Muhammad Usman 
Published: December 2018

5‐Fluorouracil (5‐FU) is widely used against many types of solid cancer in clinics. However, because of its limitations such as short half‐life, poor oral absorption and rapid clearance by dihydropyrimidine dehydrogenase have limited its applications. In current study, new in situ chemically grafted thermogels for prolonged drug release are formed on the basis of poloxamer 407 (PF127) and carboxymethyl chitosan (CMCS) using glutaraldehyde as cross‐linking agent. The phase transition from sol to gel state at body temperature was confirmed by tube titling, rheological analysis, and optical transmittance determinations. Swelling and drug release experiments conducted at various pH and temperature demonstrated that developed formulations are thermoresponsive with maximum swelling and release below critical gelation temperature (CGT) (pH 7.4, 25°C). Cells growth inhibition study confirmed the biocompatibility of thermogels against L929 cell lines. Methyl thiazolyl tetrazolium (MTT) assay confirmed that 5‐FU–loaded thermogels have the potential to cause cells death against HeLa and MCF‐7 cancer lines. The IC50values calculated for pure 5‐FU solution (27 ± 0.81 μg/mL for HeLa and 24 ± 0.58 μg/mL for MCF‐7) were found higher in comparison with 5‐FU–loaded thermogels, against HeLa (17 ± 0.39 μg/mL) and MCF‐7 (14 ± 0.67 μg/mL). Fourier transform infrared (FTIR) confirmed the new structure formation and chemical grafting between PF127 and CMCS. Thermogravimetric (TG) and differential scanning calorimetry (DSC) analyses proved the phase transition around physiologic temperature range, while scanning electron microscopy (SEM) analysis displayed the presence of connected pores in the cross section of thermogels facilitating the uptake of solvents and drug particles. Altogether, results concluded that developed chemically grafted thermogels can be used in vivo for prolonged drug release after subcutaneous administration.