Directed energy deposition-arc (DED-Arc) and numerical welding simulation as a hybrid data source for future machine learning applications. - In: Applied Sciences, ISSN 2076-3417, Bd. 11 (2021), 15, 7075, S. 1-16
This research presents a hybrid approach to generate sample data for future machine learning applications for the prediction of mechanical properties in directed energy deposition-arc (DED-Arc) using the GMAW process. DED-Arc is an additive manufacturing process which offers a cost-effective way to generate 3D metal parts, due to its high deposition rate of up to 8 kg/h. The mechanical properties additively manufactured wall structures made of the filler material G4Si1 (ER70 S-6) are shown in dependency of the t8/5 cooling time. The numerical simulation is used to link the process parameters and geometrical features to a specific t8/5 cooling time. With an input of average welding power, welding speed and geometrical features such as wall thickness, layer height and heat source size a specific temperature field can be calculated for each iteration in the simulated welding process. This novel approach allows to generate large, artificial data sets as training data for machine learning methods by combining experimental results to generate a regression equation based on the experimentally measured t8/5 cooling time. Therefore, using the regression equations in combination with numerically calculated t8/5 cooling times an accurate prediction of the mechanical properties was possible in this research with an error of only 2.6%. Thus, a small set of experimentally generated data set allows to achieve regression equations which enable a precise prediction of mechanical properties. Moreover, the validated numerical welding simulation model was suitable to achieve an accurate calculation of the t8/5 cooling time, with an error of only 0.3%.
https://doi.org/10.3390/app11157075
Using the multi-linear rank-(Lr, Lr, 1) decomposition for the detection of the 200 Hz band activity in somatosensory evoked magnetic fields and somatosensory evoked electrical potentials. - In: IEEE access, ISSN 2169-3536, Bd. 9 (2021), S. 106232-106244
Im Titel ist "r" tiefgestellt
https://doi.org/10.1109/ACCESS.2021.3100759
Determination of piezo-resistive coefficient π44 in p-type silicon by comparing simulation and measurement of pressure sensors. - In: AIP Advances, ISSN 2158-3226, Bd. 11 (2021), 8, 085005, insges. 6 S.
https://doi.org/10.1063/5.0060034
SmartPIV: flow velocity estimates by smartphones for education and field studies. - In: Experiments in fluids, ISSN 1432-1114, Bd. 62 (2021), 8, 172, S. 1-13
In this paper, a smartphone application is presented that was developed to lower the barrier to introduce particle image velocimetry (PIV) in lab courses. The first benefit is that a PIV system using smartphones and a continuous wave (cw-) laser is much cheaper than a conventional system and thus much more affordable for universities. The second benefit is that the design of the menus follows that of modern camera apps, which are intuitively used. Thus, the system is much less complex and costly than typical systems, and our experience showed that students have much less reservations to work with the system and to try different parameters. Last but not least the app can be applied in the field. The relative uncertainty was shown to be less than 8%, which is reasonable for quick velocity estimates. An analysis of the computational time necessary for the data evaluation showed that with the current implementation the app is capable of providing smooth live display vector fields of the flow. This might further increase the use of modern measurement techniques in industry and education.
https://doi.org/10.1007/s00348-021-03262-z
Vehicle classification in intelligent transport systems: an overview, methods and software perspective. - In: IEEE open journal of intelligent transportation systems, ISSN 2687-7813, Bd. 2 (2021), S. 173-194
https://doi.org/10.1109/OJITS.2021.3096756
A note on uniquely 10-colorable graphs. - In: Journal of graph theory, ISSN 1097-0118, Bd. 98 (2021), 1, S. 24-26
Hadwiger conjectured that every graph of chromatic number k admits a clique minor of order k. Here we prove for k ≤ 10, that every graph of chromatic number k with a unique k-coloring (up to the color names) admits a clique minor of order k. The proof does not rely on the Four Color Theorem.
https://doi.org/10.1002/jgt.22679
Rational climate policy - economic demands and political obstacles :
Rationale Klimapolitik - ökonomische Anforderungen und politische Hindernisse. - In: List Forum für Wirtschafts- und Finanzpolitik, ISSN 2364-3943, Bd. 46 (2021), 4, S. 423-449
In der klimapolitischen Debatte stehen meist einzelne Instrumente und Maßnahmen im Vordergrund, wohingegen die Frage der ökonomischen Rationalität der Klimapolitik als solcher häufig vernachlässigt wird. Eine Klimapolitik wäre dann ökonomisch rational, wenn politisch vorgegebene Klimaziele mit geringstmöglichen Kosten realisiert werden würden. Notwendig hierfür ist eine umfassende und einheitliche Bepreisung der Treibhausgasemissionen. Dieser rationalen Klimapolitik wird die aktuelle deutsche und europäische Politik gegenübergestellt, die sich als ineffektiv und ineffizient erweist. Ursächlich hierfür sind die Anreize, denen die politischen Akteure unterliegen und die zu einem Widerspruch zwischen ökonomischer Rationalität und politischer Opportunität führen.
https://doi.org/10.1007/s41025-021-00224-5
Formation and evolution of Au-SiOx heterostructures: from nanoflowers to nanosprouts. - In: Materials and design, ISSN 1873-4197, Bd. 209 (2021), 109956, insges. 11 S.
This work reports the formation of circular cavities and Au-SiOx nanoflowers after annealing of thin Au film deposited on SiO2/Si substrates, and the transformation of nanoflowers to nanosprouts with increasing the annealing time. Two reference experiments indicate that both H2 and Si are indispensable for the above structures. The formation of cavities can be attributed to the SiO2 layer decomposition and the product, volatile SiO, provides a Si source for the formation of nanoflowers at the early stage. A model is proposed to indicate that SiO gas produced at the Si/SiO2 interface can diffuse to the surface assisted by the defects in the SiO2 layer before the decomposed cavities are exposed. Then the exposing of those cavities introduces another volatile SiO from the active oxidation of Si substrate, provoking a change in the direction of the main Si source, which in turn makes the one nanoparticle of the nanoflower split in two and finally form the nanosprout. The model about the escape of SiO further details SiO2 decomposition process, and the transformation mechanism from nanoflowers to nanosprout sheds light on a feasible nanofabrication method to design tunable size and shape of nanoparticles.
https://doi.org/10.1016/j.matdes.2021.109956
Softness meets with brightness: dye-doped multifunctional fluorescent polymer particles via microfluidics for labeling. - In: Advanced optical materials, ISSN 2195-1071, Bd. 9 (2021), 13, 2002219, insges. 22 S.
Fluorogenic labeling strategies have emerged as powerful tools for in vivo and in vitro imaging applications for diagnostic and theranostic purposes. Free organic chromophores (fluorescent dyes) are bright but rapidly degrade. Inorganic nanoparticles (e.g., quantum dots) are photostable but toxic to biological systems. Alternatively, dye-doped polymer particles are promising for labeling and imaging due to their properties that overcome limitations of photodegradation and toxicity. This progress report, therefore, presents various synthesis techniques for the generation of dye-doped fluorescent polymer particles. Polymer particles are relatively soft compared to inorganic nanoparticles and can be synthesized with characteristics like biocompatibility and stimuli responsiveness. Also, their ability of loading fluorophores through various interactions reveals brightness. Here, a multiscale-multicolor library of bright and soft fluorescent polymer particles is generated hierarchically. Various microfluidic supported strategies have been applied where fluorophores can be linked to polymeric networks noncovalently and covalently in the interior, and at the surface of nanoparticles (60-550 nm). Besides, microfluidic strategies for hydrophilic and hydrophobic fluorescent polymer microparticles (20-800 [my]m) have been performed for systematic tuning in size and color combination. Furthermore, soft and bright particulate assemblies are enabled through interfacial interactions at the intermediate scale (600 nm-3 [my]m) between the nanometer and micrometer lengthscale.
https://doi.org/https://doi.org/10.1002/adom.202002219
The Flora Incognita app - interactive plant species identification. - In: Methods in ecology and evolution, ISSN 2041-210X, Bd. 12 (2021), 7, S. 1335-1342
Being able to identify plant species is an important factor for understanding biodiversity and its change due to natural and anthropogenic drivers. We discuss the freely available Flora Incognita app for Android, iOS and Harmony OS devices that allows users to interactively identify plant species and capture their observations. Specifically developed deep learning algorithms, trained on an extensive repository of plant observations, classify plant images with yet unprecedented accuracy. By using this technology in a context-adaptive and interactive identification process, users are now able to reliably identify plants regardless of their botanical knowledge level. Users benefit from an intuitive interface and supplementary educational materials. The captured observations in combination with their metadata provide a rich resource for researching, monitoring and understanding plant diversity. Mobile applications such as Flora Incognita stimulate the successful interplay of citizen science, conservation and education.
https://doi.org/10.1111/2041-210X.13611