bluuebunny/crossref_metadata_2025_split huggingface dataset:
Long‐term course of sacral anterior root stimulation in spinal cord injured individuals: The fate of the detrusor
Authors: Krebs Jörg , Wöllner Jens , Grasmücke Dennis , Pannek Jürgen 
Published: October 2016

AimsTo investigate the long‐term course of the detrusor pressure during sacral anterior root stimulation in spinal cord injury (SCI) patients.MethodsRetrospective evaluation of 111 patients who had undergone sacral deafferentation and implantation of an anterior root stimulator at a single SCI rehabilitation center with a minimum follow‐up time of 5 years.ResultsThe median follow‐up time was 11.7 years (range 5.0‐24.9 years). The maximum detrusor pressure (Pdet_max) during stimulation was higher in men compared to women (P = 0.0004) and decreased over time (P = 0.0006). However, there were no significant (P ≥ 0.06) differences in the median Pdet_max during stimulation between the first measurement time point and any follow‐up time point. The Pdet_max during stimulation decreased from 62 cmH2O (95%CI 57‐73 cmH2O) to 53 cmH2O (95%CI 47‐69 cmH2O) (P = 0.9). The time had also a significant effect on Pdet_max during the storage phase (P < 0.0001) and bladder compliance (P = 0.0007). The Pdet_max during the storage phase decreased, whereas bladder compliance increased during the follow‐up period. There were no significant (P ≥ 0.1) changes over time in bladder capacity, the number of daily stimulations and the residual urine volume after voiding.ConclusionsThe detrusor pressure during sacral anterior root stimulation decreases over time in SCI individuals. However, the changes do not seem to be clinically relevant during the first decade after surgery.
Syntheses, Structures, and Complexation Studies of Tris(organostannyl)methane Derivatives
Authors: Wendji Anicet Siakam , Lutter Michael , Stratmann Lukas M. , Jurkschat Klaus 
Published: October 2016

AbstractThe syntheses of tris(organostannyl)methanes HC(SnXnPh(3‐n))3(1,n=0;2,n=1, X=I;3,n=1, X =F;4,n=1, X=Cl;5,n=1, X=OAc;6,n=2, X=I;7,n=2, X=Cl) and the organostannate complexes Et4N[HC(SnIPh2)3⋅F] (8), Ph4P[HC(SnClPh2)3⋅Cl] (9), and [Ph4P]2[HC(SnCl2Ph)3⋅2 Cl] (10) are reported. The compounds were characterized by1H,13C,19F, and119Sn NMR spectroscopy, IR spectroscopy, electrospray mass spectrometry, and (with the exception of3) single‐crystal X‐ray diffraction analysis. From the reaction between2and AgClO4resulted the unprecedented hexanuclear organotin oxocluster [HC{Sn(ClO4)2Ph2}2Sn(OH)2Ph]2 (11), the molecular structure of which was elucidated by using X‐ray crystallography.
Resolutions and Betti Numbers of Polynomial Modules via Involutive Bases
Authors: Albert Mario , Fetzer Matthias , Seiler Werner M. 
Published: October 2016

AbstractWe describe a novel approach to the computation of free resolutions and of Betti numbers of polynomial modules based on a combination of the theory of involutive bases with algebraic discrete Morse theory. This approach allows for the first time to compute Betti numbers (even single ones) without determining a whole resolution which in many cases drastically reduces the computation time. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Higher order unfitted FEM for Stokes interface problems
Authors: Lederer Philip , Pfeiler Carl‐Martin , Wintersteiger Christoph , Lehrenfeld Christoph 
Published: October 2016

AbstractWe consider the discretization of a stationary Stokes interface problem in a velocity‐pressure formulation. The interface is described implicitly as the zero level of a scalar function as it is common in level set based methods. Hence, the interface is not aligned with the mesh. An unfitted finite element discretization based on a Taylor‐Hood velocity‐pressure pair and an XFEM (or CutFEM) modification is used for the approximation of the solution. This allows for the accurate approximation of solutions which have strong or weak discontinuities across interfaces which are not aligned with the mesh. To arrive at a consistent, stable and accurate formulation we require several additional techniques. First, a Nitsche‐type formulation is used to implement interface conditions in a weak sense. Secondly, we use the ghost penalty stabilization to obtain an inf‐sup stable variational formulation. Finally, for the highly accurate approximation of the implicitly described geometry, we use a combination of a piecewise linear interface reconstruction and a parametric mapping of the underlying mesh. We introduce the method and discuss results of numerical examples. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fuzzy‐Based Analysis of a Hill‐Type Muscle Model
Authors: Fehr Jörg , Fuhrer Julian , Kleinbach Christian , Hanss Michael , Eberhard Peter 
Published: October 2016

AbstractAmong the most challenging problems in present day mechanics is the realistic simulation of the human kinetic behavior which requires correct modeling of the muscles – the human actuators. We are, therefore, implementing and validating a 1‐D massless Hill‐type muscle model in the program Neweul‐M2. As a part of this effort, various anatomical and physiological parameters need to be chosen prior to the simulation. These parameters are always subject to natural variability or scatter.Therefore, it is important to consider those parameters as uncertain fuzzy parameters and then determine the sensitivity measures of the parameters involved in various simulation scenarios using the program Famous. The applied sensitivity analysis quantifies the influence of individual parameters or subsets of parameters on the output quantity of interest. Thus, this analysis identifies those parameters with large influence on the simulation response of muscles which, therefore, needs to be chosen very carefully. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Surrogate Modelling for Real‐time Predictions of Mechanised Tunnelling Processes with Interval Data
Authors: Freitag Steffen , Cao Ba‐Trung , Meschke Günther 
Published: October 2016

AbstractFinite element simulations are commonly used to investigate the soil‐structure interactions of mechanised tunnelling processes, such as to provide predictions on the expected surface settlement field. For real‐time predictions during the tunnel construction, the finite element model is substituted by a hybrid surrogate model combining Artificial Neural Network and Proper Orthogonal Decomposition approaches. The surrogate model is employed to predict time‐variant interval surface settlement fields for selected scenarios of the tunnelling process steering parameters in real‐time considering uncertain geotechnical parameters as intervals. For this purpose, the surrogate model in [1], which is based on a Recurrent Neural Network and Gappy Proper Orthogonal Decomposition technique, is split into surrogate models for midpoint and radius computations of the interval data. The online computation time of the new surrogate modelling approach is only a few seconds, which enables tu apply it for real‐time predictions and to support the Tunnel Boring Machine steering. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Passive Rotation Compensation in Parallel Kinematics Using Quaternions
Authors: Du Shucen , Schlattmann Josef , Schulz Stefan , Seibel Arthur 
Published: October 2016

AbstractIn this paper, an approach to compute the passive rotation in a parallel hexapod structure is introduced which is based on quaternions. The advantage of this approach is that it prevents from unnecessary trigonometric or inverse trigonometric functions, which reduces rounding errors and saves memory. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Variational multirate integration in multi‐body dynamics
Authors: Gail Tobias , Leyendecker Sigrid , Ober‐Blöbaum Sina 
Published: October 2016

AbstractFor systems that contain slow and fast dynamics, variational multirate integration schemes are used. These schemes split the system into parts which are simulated using two time grids consisting of micro and macro nodes. This formulation can be extended for multi‐body systems. The rigid multi‐body system is described by the so called director formulation and constraints describing the joints connecting the bodies. With the Lagrange multiplier method, the constraints are introduced into the equations of motion. A way to implement the null space method into the variational multirate framework is shown and the influence on the number of unknowns is investigated. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimal feedback control for constrained mechanical systems
Authors: Glaas Daniel , Leyendecker Sigrid 
Published: October 2016

AbstractAn approach to minimize the control costs and ensuring a stable deviation control is the Riccati controller and we want to use it to control constrained dynamical systems (differential algebraic equations of Index 3). To describe their discrete dynamics, a constrained variational integrators [1] is used. Using a discrete version of the Lagrange‐d’Alembert principle yields a forced constrained discrete Euler‐Lagrange equation in a position‐momentum form that depends on the current and future time steps [2]. The desired optimal trajectory (qopt, popt) and according control input uopt is determined solving the discrete mechanics and optimal control (DMOC) algorithm [3] based on the variational integrator. Then, during time stepping of the perturbed system, the discrete Riccati equation yields the optimal deviation control input uR. Adding uopt and uR to the discrete Euler‐Lagrange equation causes a structure preserving trajectory as both DMOC and Riccati equations are based on the same variational integrator. Furthermore, coordinate transformations are implemented (minimal, redundant and nullspace) enabling the choice of different coordinates in the feedback loop and in the optimal control problem. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Varying Workpiece Dynamics in Milling Stability Analysis
Authors: Hamann Dominik , Eberhard Peter 
Published: October 2016

AbstractDynamic stability of a milling process with varying workpiece dynamics is investigated. The milling tool moves along the workpiece with a prescribed feed rate, whereby the contact point shifts. Furthermore, the workpiece dynamics is affected by material removal. The resultant varying workpiece dynamics is taken into account by parametric model order reduction including modal truncation. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Experimental‐based material parameter identification of oocytes
Authors: Dittmann Johannes , Töpfer Dagmar , Böl Markus 
Published: October 2016

AbstractIn comparison to other eukaryotic cells, mammalian oocytes are characterised by a relative high diameter allowing in turn a straightforward micromechanical testing to study their mechanical properties. The structure of mammalian oocytes is characterised by the so‐called zona pellucida (ZP), a thick glycoprotein layer, surrounding the cells interior, the ooplasm. In contrast to other cells, where the load is mainly carried by inner cell structures, in case of oocytes a huge amount of external loads is carried by the ZP. Aim of this work is the determination of the mechanical properties of oocytes. Therefore, a micromechanical setup has been developed and installed on a microscope. Beside the determination of the force‐strain relation during loading, the deformation of the oocytes has been recorded optically, too. Both, the force‐strain curves and the optical recordings build the basis for a proper parameter identification technique based on the inverse finite element method. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
From functional properties of frost‐resistant plant tissues towards customised construction materials ‐ A continuum‐mechanical approach
Authors: Eurich Lukas , Schott Rena , Wagner Arndt , Roth‐Nebelsick Anita , Ehlers Wolfgang 
Published: October 2016

AbstractTemperatures below freezing point represent a common threat to standard construction materials, as a phase change of the pore content from liquid water to solid ice frequently leads to damage. However, frost‐resistant plants are able to withstand many cycles of freezing and thawing without any damage. Hence, the objective is to identify and analyse structural factors of frost‐resistant plant tissues and to develop a model, which includes their functional behaviour. Since frost‐resistant plant tissues are formed by ordered arrangements of cells with prescribed shape and size, they can be understood as an (anisotropic) natural porous material. Therefore, a customised modelling strategy based on the Theory of Porous Media (TPM) is proposed, which allows for the description of structural traits and the formation of ice within plant tissues. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Problems in parameter identification of the passive response in human arteries
Authors: Gilbert Rose Rogin , Hartmann Stefan , Kudela László , Rank Ernst , Yosibash Zohar , Yossef Ofry 
Published: October 2016

AbstractIdentification of unique material parameters for the media and adventitia in the case of arteries involves many challenges. Tension‐inflation experiments were performed on the internal mammary artery and the axial force and the radial displacements were used to identify the material parameters. It will be shown that these experimental data are not sufficient to uniquely identify the material parameters of the passive response in human arteries. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Force enhancement and stability of finite element muscle models
Authors: Heidlauf Thomas , Klotz Thomas , Rode Christian , Siebert Tobias , Röhrle Oliver 
Published: October 2016

AbstractA continuum‐mechanical finite element model of skeletal muscle contractions that includes force enhancement based on actin‐titin interaction is presented. This model can simulate muscles with a descending limb in the total force‐length relation, which has previously led to unstable behaviour. The model predictions are in agreement with results of active stretch experiments. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On data‐guided optimal control simulation of human motion
Authors: Hoffmann Ramona , Taetz Bertram , Miezal Markus , Bleser Gabriele , Leyendecker Sigrid 
Published: October 2016

AbstractThis work investigates the combination of optical motion capturing data with optimal control simulations of human motion, which can be important in a wide range of applications in the professional as well as the private sector, ranging from health and ergonomics over human‐machine‐interaction to sports and games [1–3]. There are methodically very different approaches to include optical measurement data in the simulation of human motion, see e.g. [4–6]. Two different approaches to combine data and simulation are investigated in this work. Either we use a soft constraints approach, where the difference of simulated and measured marker positions is part of the objective function (1), or we formulate an hard constraints approach with nonlinear constraints that set an upper bound on this difference (2), while the objective function is purely physiologically motivated. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On a bi‐scale and tri‐phasic model for the description of growth in biological tissue using the example of the human liver
Authors: Waschinsky Navina , Werner Daniel , Ricken Tim , Dahmen Uta , Dirsch Olaf 
Published: October 2016

AbstractThe human liver is important for hepatic metabolism regulations which depend on complex and time depending biochemical reactions coupled to the hemodynamic blood perfusion. Growth effects can impair the perfusion and therefore affect the metabolism. Such influences can be observed during the accumulation of fat in the liver tissue. The fat accumulation results from the lipid metabolism which comprises synthesis and degradation of lipids in liver cells. Individual addictions to alcohol and high fat diets are possible causes which result in an excessive synthesis of lipids. The liver sensitively reacts to such changes which could affect the viability of the organ. To observe these coupled influences of perfusion‐metabolism‐growth effects we use a computational model with a multi‐component/tri‐phasic/bi‐scale approach to simulate the functionality of the human liver with respect to fat deposition. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of the gelation process of hydrogel droplets in 3D bioprinting
Authors: Zhou Bei , Heider Yousef , Blaeser Andreas , Raith Stefan , Fischer Horst , Markert Bernd 
Published: October 2016

AbstractThe aim of this work is to numerically simulate the gelation of a crosslinking polymer, which is a very complex process involving chemical reactions and phase transitions from a viscous fluid to a viscoelastic solid. A phenomenological model is proposed to simulate the gelation process of agarose droplets, considering the thermal boundary conditions. The numerical model is implemented using the finite element package FlexPDE. The temperature‐ and time‐dependent degree of gelation and the deformation of the droplets during the gelation process are investigated. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Closed‐form solutions for stress singularities at bi‐material wedges in Reissner‐Mindlin plates
Authors: Felger Julian , Becker Wilfried 
Published: October 2016

AbstractIn this work, stress singularities in isotropic bi‐material junctions are investigated using Reissner‐Mindlin plate theory by means of a complex potential formalism. The governing system of partial differential equations is solved employing methods of asymptotic analysis. The resulting asymptotic near‐fields including the singularity exponent λ are obtained in a closed‐form analytical manner as solutions of a corresponding eigenvalue problem. The singular solution character is discussed for different geometrical configurations. In particular, the present study investigates the influence of the material constants on the singularity exponent. It is shown, that the Reissner‐Mindlin theory allows for distinguishing between singularities of the bending moments and the transverse shear forces. Further, stronger singularities than the classical crack‐tip singularity are observed. The results allow for further application such as a combination with numerical methods. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Phase‐field approach to fracture for finite‐deformation contact problems
Authors: Franke Marlon , Hesch Christian , Dittmann Maik 
Published: October 2016

AbstractThe present contribution deals with a variationally consistent Mortar contact algorithm applied to a phase‐field fracture approach for finite deformations, see [4]. A phase‐field approach to fracture allows for the numerical simulation of complex fracture patterns for three dimensional problems, extended recently to finite deformations (see [2] for more details). In a nutshell, the phase‐field approach relies on a regularization of the sharp (fracture‐) interface. In order to improve the accuracy, a fourth‐order Cahn‐Hilliard phase‐field equation is considered, requiring global C1 continuity (see [1]), which will be dealt with using an isogeometrical analysis (IGA) framework. Additionally, a newly developed hierarchical refinement scheme is applied to resolve for local physical phenomena e.g. the contact zone (see [3] for more details). The Mortar method is a modern and very accurate numerical method to implement contact boundaries. This approach can be extended in a straightforward manner to transient phase‐field fracture problems. The performance of the proposed methods will be examined in a representative numerical example. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of material data input on accuracy of fatigue assessments for beam weldments
Authors: Gorash Yevgen , Comlekci Tugrul , MacKenzie Donald 
Published: October 2016

AbstractThis numerical study investigates the effects of fatigue material data and finite element types on accuracy of residual life assessments under HCF conditions. The bending of cross‐beam connections is simulated in ANSYS Workbench for three different combinations of beam profiles. The weldments are made of the high‐strength steel grades C350LO and C450LO according to AS3678. The stress analysis of weldments is implemented with solid and shell elements using linear material and geometry consideration. The stress distributions are transferred to the embedded fatigue code nCode DesignLife. For both variants of FE‐mesh, the nominal stress in the weld toes is extracted by splitting the total stress into membrane and bending components and filtering out non‐linear component. Considering the effects of bending, size and mean stress, failure locations and fatigue life are predicted using the Volvo method and rules from ASME BPV Code. Three different pairs of experimental S‐N curves (stiff and flexible) are used as material data input for fatigue analysis. The obtained numerical predictions are compared to the experimental results for shell FE‐models. The predictions using the S‐N curves for an equivalent steel demonstrate the best accuracy proving the fact that specific material data input is more effective than a generic data. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Excitation strategies for vibration based damage detection using piezoelectric transducers and machine learning
Authors: Hesser Daniel Frank , Markert Bernd 
Published: October 2016

AbstractDamage detection methods of structural components have been extensively evaluated in theoretical and experimental research studies in the last few years. In this context, machine learning algorithms are used to evaluate the health state of structures. This work assesses the dependency of various excitation frequencies in guided‐wave based structural health monitoring (SHM) systems and the performance of damage detection, which are barely investigated, in particular in SHM technologies using machine learning approaches. Machine learning can be directly used in SHM applications including environmental effects (noise, imperfection, statistical tests, etc.) to train a new system and to solve the inverse problem. Thereby, the piezoelectric effect is used to apply guided‐waves through the structure or to measure the vibration response of flexible structures. The important outcome of this study is to improve the efficiency and performance of SHM systems by optimising the excitation frequency using machine learning approaches. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A regularization technique for the XFEM: extension to finite deformations, inelastic material behaviour and multifield problems
Authors: Loehnert Stefan , Beese Steffen 
Published: October 2016

AbstractWithin the XFEM often near linear dependencies between the standard degrees of freedom and enriched degrees of freedom and also among enriched degrees of freedom occur. During the last years, several remedies to that problem have been presented. Here, an extension of the regularization technique described in [1] to finite deformation problems and inelastic material behaviour as well as to multifield problems is proposed. © 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of deformation history parameters on softening behaviour of concrete
Authors: Monnamitheen Abdul Gafoor A. H. , Dinkler Dieter 
Published: October 2016

AbstractThe aim of this study is to investigate elasticity based damage models in which the isotropic damage is driven by different history parameters under uniaxial setting. This leads to a suitable history parameter for the description of material strain‐softening realistically. Existing damage evolution laws from literatures are used to compare the results using strain and energy equivalence principles. A suitable damage evolution law which is similar to Weibull's failure distribution is proposed in the framework of energy equivalence. Numerical results exhibit good agreement with experimental results. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)