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Correlation between the activation energy of PLA respectively PLA/starch composites and mechanical properties with regard to differ accelerated aging conditions
(2024-02-22)
Within this research semi-crystalline polylactide and composites with 50 wt.% native potato starch were compounded and injection molded. The material was mechanically characterized by tensile, three-point bending, and Charpy impact tests. These tests were carried out in the freshly molded state and after 332 and 792 h of storage at accelerated temperature or humidity. The respective activation energy was calculated by applying the Flynn-Wall-Ozawa method. The focus of the study was to investigate the correlation ...
Aufsatz
Influence of ethylene oxide and gamma irradiation sterilization processes on the degradation behaviour of poly(lactic acid) (PLA) in the course of artificially accelerated aging
(2024-02-10)
To promote the application of bio-based materials in the field of medical technology, it is essential to conduct additional research, focusing on their long-term performance after sterilization. For this purpose, the study examines the aging behaviour of three poly(lactic-acid) (PLA) materials, sterilized with either ethylene oxide or gamma irradiation, over a two years aging period, in accordance with ASTM F1980-21. During these investigations, a direct correlation between moisture absorption and degradation progression ...
Aufsatz
Analysis of the Similarity between Injection Molding Simulation and Experiment
(2024-05-01)
In the plastics industry, CFD simulation has been used for many years to support mold design. However, using simulation as a substitute for experimentation remains a major challenge to this day. This is due to the unknown congruence between simulation and experiment. The present work focuses on a comparison between simulation (generated with the software Moldflow Insight Ultimate from Autodesk Inc., San Francisco, CA, USA) and experiment by using molds of different complexity, where, in contrast to a large number of ...
Aufsatz
Three-dimensional transfer function of optical microscopes in reflection mode
(2021-06-16)
Three-dimensional (3D) transfer functions build the basis for a comprehensive characterization of optical imaging systems in the spatial frequency domain. Utilizing the projection-slice theorem, the 2D modulation transfer function of an incoherent imaging system can be derived from a 3D transfer function by integration with respect to the axial spatial frequency. For a diffraction limited microscope with homogeneous incoherent pupil illumination, the modulation transfer function equals the 2D autocorrelation function ...
Aufsatz
Velocity-Dependent Perception Threshold for Discrete Imperceptible Repositioning in a Virtual Environment During Eye Blinks
(2021-07-02)
In this study, the relationship between a person’s walking speed and the perception threshold for discrete implicit repositioning during eyeblinks in a virtual environment is investigated. The aim is to estimate the perception thresholds for forward and backward repositioning during forward translation following eyeblink occurrences. A psychophysical method called Staircase Transformed and Weighted up/down is utilized to quantify the perception thresholds for forward and backward repositioning. The perception thresholds ...
Aufsatz
Dissimilar Laser Beam Welding of Titanium to Stainless Steel Using Pure Niobium as Filler Material in Lap Joint Configuration
(2023-09-20)
In the present investigation, commercially pure titanium is welded to AISI 316L stainless steel by intermixing niobium as filler material in a lap joint configuration. For this purpose, a pulsed Nd:YAG laser with various pulse durations and pulse peak powers is employed to obtain different mixing conditions for the materials. It will be demonstrated that, despite the implementation of the filler material, the weld seams are characterized by a high affinity for cracking, which in turn can be attributed to the formation ...
Buch
Pflege und Technik. Empirische Einblicke in Care-Arbeit aus der Perspektive des Agentiellen Realismus
(Transcript, 2022)
Diese Studie beschäftigt sich mit beruflichem Pflegehandeln als Bestandteil der Care-Arbeit. In pflegewissenschaftlicher Theoriebildung werden bislang vor allem die Beziehungsgestaltung zwischen Pfleger:in und Patient:in sowie die Anwendung unterschiedlicher Wissensformen in den Blick genommen. Damit lassen bisherige Perspektiven die Rahmenbedingungen, unter denen berufliches Pflegehandeln stattfindet, weitestgehend außer Acht. So stehen auch materielle Aspekte bisher kaum im Fokus der Betrachtungen. Die in dieser ...
Aufsatz
FEM–CM as a hybrid approach for multiscale modeling and simulation of ferroelectric boundary value problems
(2023-06-05)
Constitutive modeling of ferroelectrics is a challenging task, spanning physical processes on different scales from unit cell switching and domain wall motion to polycrystalline behavior. The condensed method (CM) is a semi-analytical approach, which has been efficiently applied to various problems in this context, ranging from self-heating and damage evolution to energy harvesting. Engineering applications, however, inevitably require the solution of arbitrary boundary value problems, including the complex multiphysical ...
Aufsatz
High-Strength Dissimilar Welds Between a NiTi Shape Memory Alloy and Titanium Obtained by Intermixing Niobium Using Pulsed Laser Beam Welding
(2023-11-17)
Joining of NiTi shape memory alloys with commercially pure titanium (Ti) is of great interest for manifold industrial applications. However, dissimilar fusion welding of these materials is associated with the formation of extremely brittle intermetallic compounds, e.g., Ti2Ni and TiNi3, which drastically limit the mechanical properties of NiTi/Ti joints. The present investigation seeks to improve both chemical compatibility and mechanical performance through intermixing of a niobium foil as filler material into a ...
Aufsatz
Weisfeiler-Lehman goes dynamic: An analysis of the expressive power of Graph Neural Networks for attributed and dynamic graphs
(2024-02-28)
Graph Neural Networks (GNNs) are a large class of relational models for graph processing. Recent theoretical studies on the expressive power of GNNs have focused on two issues. On the one hand, it has been proven that GNNs are as powerful as the Weisfeiler–Lehman test (1-WL) in their ability to distinguish graphs. Moreover, it has been shown that the equivalence enforced by 1-WL equals unfolding equivalence. On the other hand, GNNs turned out to be universal approximators on graphs modulo the constraints enforced by ...