bluuebunny/crossref_metadata_2025_split huggingface dataset:
Non‐reflecting tapered slotline antenna with linear phase responses of both reflection and transmission for short‐pulse applications
Authors: Chen Hongtai , Yang Haitao , Ma Haoyan , Su Yue , Zhao Hongxin , Yin Xiaoxing 
Published: December 2021

AbstractA non‐reflecting tapered slotline antenna (NRTSA) with linear phase responses of both reflection and transmission is proposed in this article. The non‐reflecting characteristic is achieved by designing a resistive and reactive loading network, which could effectively absorb the non‐radiated reflected signals and transmit the pulse with little distortion simultaneously. The integration of the loading network and the tapered slotline antenna enables the NRTSA to realize the linear phase responses of both port reflection and pulse transmission. Also, the time‐domain reflection and radiation performance of the NRTSA excited by a short‐pulse are investigated. A prototype was fabricated to verify the antenna performance. The measured results show that the NRTSA features a −9‐dB impedance bandwidth from DC to 16 GHz (200%), a peak realized gain of 9.36 dBi, a maximal cross‐polarization level of −14.8 dB (2.5–16 GHz), and a waveform fidelity of 0.95 when transmitting a Gaussian pulse with a spectrum from 4.5 GHz to 12.5 GHz. Both the non‐reflecting characteristic and short‐pulse transmission performance of the NRTSA enable it to be favorable for ultra‐wideband short‐pulse applications.
Hemodynamic, endocrine, and gene expression mechanisms regulating equine ovarian follicular and cellular development
Authors: Wischral Aurea , Pastorello Marilia , Gastal Melba O. , Beg Mohd A. , Gastal Eduardo L. 
Published: December 2021

AbstractOvulatory follicle development and associated oocyte maturation involve complex coordinated molecular and cellular mechanisms not yet fully understood. This study addresses the relationships among follicle diameter, follicle wall blood flow, follicular‐fluid factors, and gene expression for follicle growth, steroidogenesis, angiogenesis, and apoptosis in granulosa/cumulus cells and oocytes during different stages from the beginning of largest/ovulatory follicle to impending ovulation in mares. The most remarkable findings were (i) a positive association between follicle development, follicle blood flow, intrafollicular follicle‐stimulating hormone (FSH), luteinizing hormone (LH), estradiol, progesterone, and messenger RNA (mRNA) expression for FSHR and LHCGR in granulosa cells of the largest/ovulatory follicle; (ii) a plateau or decrease in follicle diameter and blood flow and granulosa cell mRNA for FSHR, LHCGR, IGF1R, VEGFR2, CYP19A1, and CASP3 at the preovulatory stage; (iii) higher StAR and BCL2 and lower CASP3 mRNA in granulosa cells at the time of impending ovulation; (iv) greater IGF1R mRNA for granulosa cells at the predeviation stage; and (v) lower FSHR, LHCGR, IGF1R, and VEGFR2 mRNA in cumulus cells and greater LHCGR and IGF1R mRNA in oocytes at the ovulatory stage. This study is a critical advance in the understanding of molecular mechanisms of follicle development and oocyte maturation and is expected to be vital for future studies targeting potential markers.
Physician–nurse conflict resolution styles in primary health care
Authors: Delak Barbara , Širok Klemen 
Published: December 2021

AbstractAimTo examine the conflict resolution styles used in the physician–nurse teamwork in primary health care, depending on individual characteristics, contextual factors, and organizational and sociocultural contexts.BackgroundConflicts significantly affect the quality of healthcare services and staffing challenges, and consequently the performance and efficiency of organizations. Their management plays an important role in any healthcare organizations and deserves the attention of researcher's healthcare management and team leaders.DesignA descriptive, cross‐sectional, correlational design.MethodThomas–Kilmann Conflict MODE Instrument was used on a sample comprising 173 nurses and 125 physicians working in teams at the Community Health Centre Ljubljana, Slovenia, in 2018.ResultsThe most predominant conflict resolution styles were compromising and avoiding, followed by accommodating, collaborating and competing. The predominant resolution style among nurses was avoiding, and among physicians was compromising. There were statistically significant differences in the conflict resolution style according to gender (χ2 (1) = 0.035, p < .059), education (χ2 (1) = 0.014, p < .05) and tenure (χ2 (1) = 0.025, p < .05).ConclusionOur research results differed from those of other studies, possibly due to the difference in the sample and research setting. They indicated that the specifics of work and situation significantly moderate conflict in healthcare organizations.ImpactThe established divergence of results indicates the need for future research on conflict in healthcare settings to more consistently consider the situational context and the role of management and/or leadership.
Thermomagnetic convection in a differentially heated rotating annulus with central force field
Authors: Szabo Peter S. B. , Früh Wolf-Gerrit 
Published: December 2021

AbstractThermal convection is induced in a rotating differentially heated annulus by using a central magnetic force field. The principle of the system is used to simulate large scale convection such as that found in planetary interiors or atmospheres but in a laboratory scaled model to investigated geophysical flow fields. Results suggest that magnetic fluids can be used to study such phenomena in a microgravity environment. To quantify the thermal forcing, rotational forcing and stratification several non‐dimensional parameters are introduced to characterise the evolving thermal structures.
An advanced quadratic displacement approach for the analytical stress analysis of adhesive bonded joints
Authors: Methfessel Thomas S. , Becker Wilfried 
Published: December 2021

AbstractIn this work an advanced analytical model for the efficient prediction of stress distributions in the adhesive layer of bonded joints is presented. In order to better account for local deformation effects occurring in thicker adhesive layers, a quadratic‐extended displacement approach is introduced. The use of a general sandwich‐type model for the overlap region enables a wide applicability to the analysis of different joint shapes and load cases.
Covariance Estimation under One‐bit Quantization
Authors: Dirksen Sjoerd , Maly Johannes , Rauhut Holger 
Published: December 2021

AbstractWe consider the classical problem of estimating the covariance matrix of a subgaussian distribution from i.i.d. samples in the novel context of coarse quantization, i.e., instead of having full knowledge of the samples, they are quantized to one or two bits per entry. This problem occurs naturally in signal processing applications. We introduce new estimators in two different quantization scenarios and derive non‐asymptotic estimation error bounds in terms of the operator norm. In the first scenario we consider a simple, scale‐invariant one‐bit quantizer and derive an estimation result for the correlation matrix of a centered Gaussian distribution. In the second scenario, we add random dithering to the quantizer. In this case we can accurately estimate the full covariance matrix of a general subgaussian distribution by collecting two bits per entry of each sample. In both scenarios, our bounds apply to masked covariance estimation as well. We demonstrate the near‐optimality of our error bounds by deriving corresponding (minimax) lower bounds and using numerical simulations.
Anisotropic plasticity‐damage material model for sheet metal — Regularised single surface formulation
Authors: Friedlein Johannes , Mergheim Julia , Steinmann Paul 
Published: December 2021

AbstractSheet metal forming as well as mechanical joining demand increasingly accurate and efficient material modelling to capture large deformations, the inherent sheet orthotropy and even process‐induced damage, which is expected to be influential. To account for large strains the additive logarithmic strain space is utilised that enables a straightforward incorporation of plastic anisotropy, herein modelled by a Hill48 yield function. A gradient‐enhancement is used to equip the ductile damage model with an internal length scale curing the damage‐induced localisation. An affine combination of the local and non‐local softening variable is derived enabling a more efficient single surface formulation for the regularised plasticity‐damage material model.
Application of a deepest‐path algorithm to study the objective function landscape during fitting for the Yeoh and Ogden model
Authors: Weiser Stephan , Wulf Hans , Ihlemann Jörn 
Published: December 2021

AbstractIn this paper we demonstrate the application of the deepest‐path algorithm for better understanding of objective function landscapes resulting from the optimization process. For this purpose, the sensitivities of the Yeoh and Ogden material model parameters are compared for different load cases. This analysis shows a much higher variation of the material parameters for the Ogden model than for the Yeoh model at approximately constant objective function values. The reasons for this may be local minima or shallow gradients in the objective function landscape. Afterwards, the deepest‐path algorithm is performed between selected designs from the sensitivity analysis. It can be seen that the deepest‐path algorithm provides further information about local minima in the objective function landscape, which are not clear identifiable from a sensitivity analysis.
Multi‐layered tissue models in patient‐specific simulations of aortic dissection
Authors: Schussnig Richard , Bäumler Kathrin , Fries Thomas-Peter 
Published: December 2021

AbstractIn aortic dissections blood flows not only in the regular, true lumen but also between separated lamellae within the media of the aortic wall, in the so‐called false lumen. Both lumina are separated by a dissection membrane, which may move substantially during the cardiac cycle, linking blood flow and vessel deformation. We employ strongly coupled fluid‐structure interaction simulations incorporating an anisotropic, fiber‐reinforced, hyperelastic continuum including layer‐specific tissue parameters.
In search of a variational formulation of the relativistic Navier‐Stokes equations
Authors: Scholle Markus , Mellmann Marcel 
Published: December 2021

AbstractDrawing an analogy with Maxwell theory a new Lagrangian is proposed for a variational formulation of the relativistic Navier‐Stokes equations which to‐date has remained elusive. A key feature is the use of tensor potentials, whose degrees of gauge freedom allow for the reformulation of the energy‐momentum equations in a self‐adjoint form. An already existing potential‐based representation of the relativistic field equations is a suitable starting point for the present considerations, which in turn are guided by the already successfully solved case of non‐relativistic, stationary and incompressible flow.
Flow and fiber orientation of fresh fiber reinforced concrete
Authors: Gerland Florian , Schomberg Thomas , Kuhl Detlef , Wünsch Olaf 
Published: December 2021

AbstractThe orientation of the fibers in UHPC is decisive for the tensile strength and failure of the components. The mold filling strategy during casting of structural components dictates the flow routing and thus the fiber orientation. In addition, the orientation of the fibers also affects the flow behavior of the suspension. In measurements of rheological properties in concrete rheometers, strongly scattering measurements often occur. In this paper, a novel fiber orientation model for viscoplastic fluids is investigated in Couette flow. The effect of the fibers on the flow condition and the measurable torque is described. The results of the numerical investigation give indications for increasing the reproducibility of rheological measurements on fresh fiber concrete.
A Virtual Sensing approach for approximating nonlinear dynamical systems using LSTM networks
Authors: Heindel Leonhard , Hantschke Peter , Kästner Markus 
Published: December 2021

AbstractIn this contribution, we introduce a hybrid model for virtual sensing applications which combines a frequency response function model with a Long Short‐Term Memory network. It estimates the behavior of non‐linear dynamic systems with multiple input and output channels by generating predictions on short subsequences of signals and recombining them using a windowing technique. The approach is tested on an experimental dataset composed of measurements from a 3‐component servo hydraulic fatigue test bench. The model is parameterized using noise data, while fatigue serviceloads with variable amplitudes are used for validation and testing.
A Partitioned Scheme for Coupling of FEM and DEM Simulations of Granular Materials
Authors: Atrian Amir , Lund Jorrid , Radtke Lars , Skorych Vasyl , Dosta Maksym , Düster Alexander 
Published: December 2021

AbstractIn this contribution, a simple uniaxial compaction of granular materials is considered in preparation for studying the collision behavior of double‐hull vessels filled with granular materials. The top compressing plate is deformable and modeled by the finite element method (FEM). The particles modeled using the discrete element method (DEM) are compressed by the top plate. To this end, a partitioned technique to couple the continuum approach (FEM) and particle discretization (DEM) is presented. Full agreement of the computed reaction force in DEM with the pressure applied on the top plate in FEM implies accuracy of the used coupling technique.
A comparison of two neural network architectures for fast structural response prediction
Authors: Thaler Denny , Bamer Franz , Markert Bernd 
Published: December 2021

AbstractIn this contribution, we compare two different neural network architectures to predict the response statistics of structures. The overall goal is a significant speed‐up of the numerically expensive Monte Carlo simulation. The first approach is based on a convolutional neural network that learns from the whole excitation history, whereas the second approach is based on a feed‐forward network architecture learning from hand‐designed features. Both procedures use supervised learning: The neural networks learn from an initial subset before the prediction of the response statistics of the Monte Carlo simulation is possible.
Thermodynamically consistent constitutive modeling of isotropic hyperelasticity based on artificial neural networks
Authors: Linden Lennart , Kalina Karl A. , Brummund Jörg , Metsch Philipp , Kästner Markus 
Published: December 2021

AbstractHerein, a neural network‐based constitutive model for isotropic hyperelastic solids which makes use of a physically motivated dimensionality reduction into the invariant space is presented. In order to automatically fulfill thermodynamic consistency, gradients of the network with respect to the input quantities are considered within a customized training loop. The proposed approach is exemplarily applied to the finite element simulation of two three‐dimensional samples, while only data collected from pure two‐dimensional virtual experiments are needed for the model calibration before.
Modeling of directional uncertainty using moments of the angular central Gaussian
Authors: Ospald Felix , Herzog Roland 
Published: December 2021

AbstractThe Gaussian distribution is commonly used to model uncertainty for all kind of problems. However, for directional data like fiber orientations in injection molding simulations the canonical choice is the so called angular central Gaussian (ACG) distribution, which arises as analytical solution to Jeffrey's equation which is used to model the orientation of a elliptical fiber suspended in a flow field. Computations are favorably performed using moments of the density instead of the density itself, leading to the so called Folgar‐Tucker equation. In this differential equation for the second order moment also the fourth order moment arises, which has to be expressed in terms of the second order moment in order to close the equation. This is called the “closure problem”, which has been addressed in many publications with various proposals for the solution, among which the fourth order moment of the ACG distribution represents the exact solution. The ACG is obtained by normalizing a centered multivariate Gaussian and therefore the individual components of the ACG distribution are no longer independent and the moments of the ACG distribution are coupled with its covariance parameter in a more complicated way in the form of elliptic integrals. This beautiful distribution is not very well studied and hardly used for directional statistics, where more empirical or wrapped distributions are employed instead.In this article we compare the ACG to the Bingham distribution and discuss the current status of computing moments as well as the analytical and numerical solution of the closure problem.
Hopf bifurcations for an oversteer vehicle – the influence of wheel load changes
Authors: Steindl Alois , Edelmann Johannes , Plöchl Manfred 
Published: December 2021

AbstractIn [1] the occurence of a Hopf bifurcation at steady‐state cornering for a two‐wheel oversteering vehicle with a brush model for the tyre forces was found and following the bifurcating branch of periodic solutions we observed a Canard phenomenon and relaxation oscillations, which are typical for singularly perturbed systems. In that article we assumed for simplicity, that the car's center of mass lies at street level. In this presentation we investigate the influence of an elevated height on the stability of the car's steady motion and the postcritical behaviour.
A second gradient continuum formulation for bi‐pantographic fabrics
Authors: Eugster Simon R. , Barchiesi Emilio 
Published: December 2021

AbstractBi‐pantographic fabrics are materials that are composed of two families of fibers with a micro‐structure. The micro‐structure of a straight fiber is given by a periodic arrangement of cells that resembles an expanding barrier. The planar behavior of such a fabric is captured at a macroscopic scale by a second gradient continuum. The corresponding strain energy function depends upon the fiber stretches, as well as upon the gradients in fiber direction of the stretches and inclination angles. In this brief communication, we present the equilibrium equations, which must be satisfied in the bulk of the continuum.
Multi‐level approach for modelling the post‐cracking response of steel fibre reinforced concrete under monotonic and cyclic loading
Authors: Gudžulić Vladislav , Meschke Günther 
Published: December 2021

AbstractIn this contribution, a multi‐level Finite Element Model for steel‐fibre reinforced concrete (SFRC) is presented which allows predicting the post‐cracking response of fibre reinforced structural members. In contrast to the guidelines, which suggest that the response of SFRC should be derived indirectly, using bending tests, the post‐cracking response is here derived from the actual fibre properties. The numerical model is designed to directly track the influence of design parameters, such as fibre type, fibre orientation, fibre content and concrete strength, on the structural response. For this purpose, submodels on the level of a single fibre are combined into a crack bridging model, considering the fibre orientation and the fibre content. This is integrated into a finite element model for fiber reinforced concrete, in which a cohesive law in the context of the discrete crack approach is used to account for the opening of cracks [1]. The model has been extended to account for imperfect closure of cracks during cyclic loading and unloading, respectively, due to presence of fibres and debris within the crack, which is manifested in hysteresis loops in load‐displacement curves. The predictive capability of the proposed numerical multi‐level model for SFRC was systematically validated by means of test series performed on the fibre and the structural level [1,2]. The proposed model is validated by three‐point bending tests on notched beams with fibre content of 0 and 57 kg/m3 subjected to cyclic loading. The ability of the above‐described numerical model to capture the formation of hysteresis in cyclic loading is evaluated.
Influence of dimensionality and specimen size on dynamic fracture
Authors: Butt Sahir N. , Meschke Günther 
Published: December 2021

AbstractIn this contribution, we investigate the dynamic fracture process in Polymethyl Methacrylate (PMMA) plate specimens using a peridynamic computational model [2, 6]. We employ two as well as three dimensional peridynamic simulations in order to analyze the influence of dimensionality on the characteristics of the fracture process. The predicted crack speeds for the various levels of the initially stored energy, also known as the velocity toughening behavior, are compared with the experimentally observed crack velocities for PMMA specimens. The influence of the specimen size on the dynamic fracture process is investigated using 2D peridynamic simulations. The fracture strengths and the velocity toughening relationship obtained from different specimen sizes are compared with the Linear Elastic Fracture Mechanics (LEFM) size effect relationship and with results from the experiments [1], respectively.
Effect of olive pomace particles content on mode I and mode II delamination fracture of S‐glass fiber reinforced composites
Authors: Bulut Mehmet , Alsaadi Mohamad , Erkliğ Ahmet 
Published: December 2021

AbstractThis work aims to investigate the effect of micro‐sized olive pomace (OP) particle incorporation on the mode I and mode II delamination fractures of glass fiber reinforced polymer composites. In this way, it is possible to recycle the natural OP materials and benefit from the development of high performance engineering polymer matrix composites in industrial applications as well as producing low cost composite. For this purpose, six different OP weight ratios (0%, 0.5%, 1%, 5%, 10%, and 15%) were used for modification of matrix resin of composite samples. Double‐cantilever beam, end‐notched flexure tests were conducted according to ASTM standards for evaluation of mode I and mode II fracture delamination toughness properties of the OP filled composites. Scanning electron microscopy photos were taken from the fractured test samples after the mode I and II interlaminar fracture tests to characterize their morphological nature. The results showed that the mode I and mode II inter‐laminar fracture toughness values reached the highest value at OP content of 5 wt% with enhancement of 13.8% and 60.4%, respectively.