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Laser Powder Bed Fusion Processing of Fe-Mn-Al-Ni Shape Memory Alloy—On the Effect of Elevated Platform Temperatures
(2021-01-20)
In order to overcome constraints related to crack formation during additive processing (laser powder bed fusion, L-BPF) of Fe-Mn-Al-Ni, the potential of high-temperature L-PBF processing was investigated in the present study. The effect of the process parameters on crack formation, grain structure, and phase distribution in the as-built condition, as well as in the course of cyclic heat treatment was examined by microstructural analysis. Optimized processing parameters were applied to fabricate cylindrical samples ...
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Nonlocal damage modelling for finite element simulations of ductile steel sheets under multiaxial loading
(2021-12-14)
The finite element simulation of forming processes or vehicle crash scenarios involves multiaxial loading conditions in general. Thereby, damage and failure in ductile steel sheets is triggered by void growth under hydrostatic tensile loading or by void elongation within a narrow band under shear dominated loading. These different damage mechanisms are considered by a stress state dependent continuum damage model. The damage initiation and failure are represented by a critical and a failure strain. Both are HOSFORD-COULOMB ...
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Calculation of optical gain in AlGaN quantum wells for ultraviolet emission
(2020-09-03)
Stimulated emission from AlGaN based quantum wells (QWs) emitting at ultraviolet wavelengths is investigated theoretically. Maxwell–Bloch equations in the second Born approximation are solved self-consistently with the Poisson equation. The valence band dispersion is obtained from a 6-band kp-model. For a QW emitting at around 270 nm with a thickness of 2.2 nm, an estimated FWHM of 10 meV for homogeneous broadening and an excitonic red shift of 100 meV are extracted under typical laser conditions. From a comparison ...
Aufsatz
Potentials and Limitations of WorldView-3 Data for the Detection of Invasive Lupinus polyphyllus Lindl. in Semi-Natural Grasslands
(2021-10-28)
Semi-natural grasslands contribute highly to biodiversity and other ecosystem services, but they are at risk by the spread of invasive plant species, which alter their habitat structure. Large area grassland monitoring can be a powerful tool to manage invaded ecosystems. Therefore, WorldView-3 multispectral sensor data was utilized to train multiple machine learning algorithms in an automatic machine learning workflow called ‘H2O AutoML’ to detect L. polyphyllus in a nature protection grassland ecosystem. Different ...
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Exploring Chinese Consumers’ Online Purchase Intentions toward Certified Food Products during the COVID-19 Pandemic
(2021-11-08)
The outbreak of COVID-19 has significantly increased consumers’ demands for online groceries, as well as healthy, safe, and better-quality food products. In China, certified food products are commonly perceived as safe and good-quality products. Therefore, this study investigated potential factors that influenced Chinese consumers’ online shopping intentions toward certified food during the COVID-19 crisis. An integrated model was proposed by combining the technology acceptance model (TAM) and the theory of planned ...
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Seasonal effects in the long-term correction of short-term wind measurements using reanalysis data
(2021-11-21)
Measure–correlate–predict (MCP) approaches are often used to correct wind measurements to the long-term wind conditions on-site. This paper investigates systematic errors in MCP-based long-term corrections which occur if the measurement on-site covers only a few months (seasonal biases). In this context, two common linear MCP methods are tested and compared with regard to accuracy in mean, variance, and turbine energy production – namely, variance ratio (VR) and linear regression with residuals (LR). Wind measurement ...
Aufsatz
New species and a new record of Phylloporia from Benin
(2021-04-23)
Species of the wood-decay genus Phylloporia (Hymenochaetaceae, Hymenochaetales, Basidiomycota) are widely distributed in the tropics. Phylloporia species are, however, morphologically and ecologically diverse, which makes morphology-based species identification challenging. In this study, we re-examined species of Phylloporia reported from Benin (West Africa). Using an integrative approach combining morphology, ecology, and phylogenetic analyses, we describe Phylloporia beninensis sp. nov. and report Phylloporia ...
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Sugar Beet Damage Detection during Harvesting Using Different Convolutional Neural Network Models
(2021-11-09)
Mechanical damages of sugar beet during harvesting affects the quality of the final products and sugar yield. The mechanical damage of sugar beet is assessed randomly by operators of harvesters and can depend on the subjective opinion and experience of the operator due to the complexity of the harvester machines. Thus, the main aim of this study was to determine whether a digital two-dimensional imaging system coupled with convolutional neural network (CNN) techniques could be utilized to detect visible mechanical ...
Aufsatz
Mirau-Based CSI with Oscillating Reference Mirror for Vibration Compensation in In-Process Applications
(2021-10-15)
We present a Mirau-type coherence scanning interferometer (CSI) with an oscillating reference mirror and an integrated interferometric distance sensor (IDS) sharing the optical path with the CSI. The IDS works simultaneously with the CSI and measures the distance changes during the depth scanning process with high temporal resolution. The additional information acquired by the IDS is used to correct the CSI data disturbed by unwanted distance changes due to environmental vibrations subsequent to the measurement. Due ...
Aufsatz
Negative brand meaning co‐creation in social media brand communities: A laddering approach using NVivo
(2019-10-10)
Social media brand communities (SMBCs) have been heralded for their co‐creative, participatory potential whereby consumers actively contribute to the proliferation of meaningful brand avenues in a virtuously circular relationship with brands. Elevated loyalty and enhanced brand equity have been posited repeatedly as likely outcomes of a positively engaged community of brand aficionados. However, evidence to the contrary as negative brand co‐creation or brand co‐destruction has been progressively piling up in the ...