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Aufsatz
Numerical simulation of viscoelastic fluid-structure interaction benchmarks and their application to the human eye
(2022-10-11)
We present a numerical solution method for time-dependent viscoelastic fluid–structure interaction employing the arbitrary Lagrangian Eulerian framework. The derived monolithic variational formulation is discretized in time using the shifted Crank–Nicolson scheme and in space using the finite element method. For the linearisation we employ Newton’s method with exact Jacobians. The viscoelastic fluid is modelled either using the Oldroyd-B or a Burgers-type model. The elastic structures are non-linear hyperelastic ...
Aufsatz
Weathering of a Polyurethane-Based Gel Electrolyte
(2023-03-14)
A recently described flexible polyurethane electrolyte was artificially weathered at 25/50 °C and 50% r.h. in air and at 25 °C in a dry nitrogen atmosphere, each with and without UV irradiation. Different formulations and the polymer matrix, used as a reference, were weathered in order to investigate the influence of the amount of conductive lithium salt and the solvent propylene carbonate. The complete loss of the solvent at a standard climate was already observed after a few days, strongly influencing the ...
Aufsatz
Multisite and Multitemporal Grassland Yield Estimation Using UAV-Borne Hyperspectral Data
(2022-04-26)
Grassland ecosystems can be hotspots of biodiversity and act as carbon sinks while at the same time providing the basis of forage production for ruminants in dairy and meat production. Annual grassland dry matter yield (DMY) is one of the most important agronomic parameters reflecting differences in usage intensity such as number of harvests and fertilization. Current methods for grassland DMY estimation are labor-intensive and prone to error due to small sample size. With the advent of unmanned aerial vehicles (UAVs) ...
Aufsatz
Description and prediction of copper contents in soils using different modeling approaches - Results of long-term monitoring of soils of northern Germany
(2022-10-03)
Background: Different regression approaches may be useful to predict dynamics of copper (Cu), an essential element for plants and microorganisms that becomes toxic at increased contents, in soils. //
Aim: Our objective was to explore the usefulness of mixed-effects modeling and rule-based models for a description and prediction of Cu contents in aqua regia (CuAR) in surface soils using site, pH, soil organic carbon (SOC), and the cation exchange capacity (CEC) as predictors. //
Methods: Three sites in northern ...
Aufsatz
A Comparative Analysis of Residential Care: A Five-Country Multiple Case-Design Study
(2021-12-13)
Background
Despite a global policy push toward the advancement of family- and community-based care, residential care for children and youth remains a relevant and highly utilized out-of-home care option in many countries, fulfilling functions of care and accommodation as well as education and treatment.
Objective
As part of a larger project involving five European countries (Finland, Germany, Italy, Lithuania, and Spain), the objective was “to map” the context and content of residential care in each country, thereby ...
Aufsatz
An extendable key space integer image-cipher using 4-bit piece-wise linear cat map
(2022-09-30)
This paper presents a multiplierless image-cipher, with extendable 2048-bit key-space, based on a 4-dimensional (4D) quantized piece-wise linear cat map (PWLCM). The quantized PWLCM exhibits limit-cycles of 4-bit encoded integers with periods greater than 10⁷. The synthesis of the PWLCM in a finite state space allows to eliminate the undesirable finite precision effect due to the hardware realization. The proposed image-cipher combines chaos, modular arithmetic, and lattice-based cryptography to encrypt a color image ...
Aufsatz
Data Driven prediction of forced nonlinear vibrations using stabilised Autoregressive Neural Networks
(2023-03-24)
In this work, we propose a novel approach to the data-driven prediction of vibration responses of nonlinear systems. The main idea is based on Autoregressive Neural Networks (ARNN) to model the nonlinear transfer behaviour between an external excitation and the system response. We propose an autoregressive network architecture with embedded symmetry using bias-free tanh activation and guarantee Input-to-State-Stability (ISS) by enforcing a special penalty term to the weights. The resulting training procedure is ...
Aufsatz
An Investigation on Limiting Potentials for Damage Prediction of Viscoelastic Adhesives
(2023-03-24)
In his recent work VOLOKH introduced the energy limiting method as an alternative to continuum damage mechanics developed and envolved by KACHANOV, RABOTNOV, LEMAITRE and many more. In contrast to continuum damage mechanics, the energy limiting method is physically grounded by the process of atomistic debonding and, therefore, motivated on an energy basis. In order to use the energy limiting method within the framework of continuum mechanics, a limiting potential needs to be defined, which can be seen as a macroscopic ...
Aufsatz
Consideration of nonlinear multipoint constraints in finite element analyses based on a master-slave elimination scheme operating at the global level
(2023-03-24)
A method to consider nonlinear multipoint constraints in finite element analysis based on a master-slave elimination scheme operating at the global level is presented. We focus on systems with nonlinear constraints in which the number of constraints is of the same order of magnitude as the number of degrees of freedom. Therefore, we rely on the master-slave elimination which gives us the huge benefit of drastically reducing the problem size. In the literature the presented master-slave elimination schemes for linear ...
Aufsatz
Influence of Accelerated Aging on the Fiber-Matrix Adhesion of Regenerated Cellulose Fiber-Reinforced Bio-Polyamide
(2023-03-23)
With regard to the sustainability and biological origin of plastic components, regenerated cellulose fiber (RCF)-reinforced polymers are expected to replace other composites in the future. For use under severe conditions, for example, as a housing in the engine compartment, the resistance of the composites and the impact on the fiber and fiber-matrix adhesion must be investigated. Composites of bio-polyamide with a reinforcement of 20 wt.% RCF were compounded using a twinscrew extruder. The test specimens were ...