Stylized Image Triangulation

The art of representing images with triangles is known as image triangulation, which purposefully uses abstraction and simplification to guide the viewer's attention. The manual creation of image triangulations is tedious and thus several tools have been developed in the past that assist in the placement of vertices by means of image feature detection and subsequent Delaunay triangulation. In this paper, we formulate the image triangulation process as an optimization problem. We provide an interactive system that optimizes the vertex locations of an image triangulation to reduce the root mean squared approximation error. Along the way, the triangulation is incrementally refined by splitting triangles until certain refinement criteria are met. Thereby, the calculation of the energy gradients is expensive and thus we propose an efficient rasterization‐based GPU implementation. To ensure that artists have control over details, the system offers a number of direct and indirect editing tools that split, collapse and re‐triangulate selected parts of the image. For final display, we provide a set of rendering styles, including constant colours, linear gradients, tonal art maps and textures. Finally, we demonstrate temporal coherence for animations and compare our method with existing image triangulation tools.     

Theoretical Spectroscopy of the NiII Intermediate States in the Catalytic Cycle and the Activation of [NiFe] Hydrogenases

[NiFe] hydrogenases catalyze the reversible oxidation of dihydrogen. The corresponding catalytic cycle involves a formidable number of redox states of the Ni‐Fe active site; these can be distinguished experimentally by the IR stretching frequencies of their CN and CO ligands coordinated to iron. These spectroscopic fingerprints serve as sensitive probes for the intrinsic electronic structure of the metal core and, indirectly, for the structural composition of the active site. In this study, density functional theory (DFT) was used to calculate vibrational frequencies, by focusing on the EPR‐silent intermediate states that contain divalent metal centers. By using the well‐characterized Ni‐C and Ni‐B states as references, we identified candidates for the Ni‐SI_r, Ni‐SI_a, and Ni‐R states by matching the predicted relative frequency shifts with experimental results. The Ni‐SI_r and Ni‐SI_a states feature a water molecule loosely bound to nickel and a formally vacant bridge. Both states are connected to each other through protonation equilibria; that is, in the Ni‐SI_a state one of the terminal thiolates is protonated, whereas in Ni‐SI_r this thiolate is unprotonated. For the reduced Ni‐R state two feasible models emerged: in one, H₂ coordinates side‐on to nickel, and the second features a hydride bridge and a protonated thiolate. The Ni‐SU state remains elusive as no unequivocal correspondence between the experimental data and calculated frequencies of the models was found, thus indicating that a larger structural rearrangement might occur upon reduction from Ni‐A to Ni‐SU and that the bridging ligand might dissociate.     

Posttreatment of powder aerosol deposited oxide ceramic films by high power LED

The powder aerosol deposition (PAD) method is becoming increasingly important as an energetically advantageous coating method compared to classic ceramic technologies. However, due to the process-related lattice deformation, ceramic coatings often exhibit reduced functional properties in the as-deposited state. A thermal posttreatment at temperatures well below the sintering temperature can significantly reduce the lattice deformation and the stress within the film to restore the functional film properties close to sintered bulk samples. In this work, the optothermal posttreatment of PAD films using three different high-power light emitting diodes (HP-LED) with different wavelengths within the visible light spectrum is investigated as an alternative to time-consuming furnace or energy-intensive laser processes on the example of thermoelectric CuFe_0.98Sn_0.02O₂ films. We demonstrate that the space-saving LED-based posttreatment not only restores the film properties but also significantly reduces the required processing time to a few seconds.     

Modular production control using deep reinforcement learning: proximal policy optimization

Journal of Intelligent Manufacturing - EU regulations on $$textit{CO}_2$$ limits and the trend of individualization are pushing the automotive industry towards greater flexibility and robustness...     

Optical Properties of Metacrystals Based on Protein Nanocages

The optical properties of 3D metacrystals made of gold nanoparticles in protein nanocages are studied. These metacrystals have sizes of tens of micrometers and are of high structural and optical quality. Through microspectroscopy measurements and model calculations it is demonstrated that the metacrystals show plasmonic absorption in the green wavelength range and are largely transparent in the red and infrared ranges. By using empty nanocages as placeholders in the metacrystal lattice, it is possible to control how strongly the metamaterial absorbs. Measurements on a pyramidal metacrystal show that it deflects visible light. The deflection shows evidence for anomalous refraction at short wavelengths and normal refraction at long wavelengths. The refractive dispersion is ascribed to the optical dispersion relation of the plasmonic metamaterial.     

Zur sinnvollen Anwendung ganzheitlicher Gebäudemodelle in der Tragwerksplanung von Hochbauten

Ausgehend von den kritischen Randbedingungen der Berechnung mit ganzheitlichen Gebäudemodellen werden typische und häufig anzutreffende Konstruktionsfälle diskutiert, bei denen Gesamtmodelle Vorteile für den Entwurf aufzeigen. Hier sind räumliche Tragwirkungen zu nennen, die Erfassung von Zwangsbeanspruchungen bei komplexen Grundrissen mit vielfältigen Festhaltungen sowie die Beanspruchung schlanker Gebäudestrukturen aus Windlasten und seismischen Einwirkungen. Für die genannten sinnvollen Anwendungsfälle werden die notwendigen Randbedingungen diskutiert. Die jeweiligen Anwendungsfälle werden anhand konkreter Gebäudebeispiele vorgestellt. On the reasonable use of total building models in the design of building structures Coming from the critical boundary conditions of the calculation with total building models, typical and prevalent constructions, where total models show advantages for the design, will be discussed. Here, spatial load‐bearing impact, the registration of unforced interactions of complex ground plans with various supports as well as the stressing of slender building structures resulting from wind loads and seismic impacts have to be mentioned. For the stated reasonable use cases the necessary boundary conditions will be discussed. The respective use cases will be presented by means of concrete building examples.     

Adaptive retrieval practice with multiple-choice questions in the university classroom

Retrieval practice promotes retention more than restudying (i.e., the testing effect) and is applied to many educational settings. However, little research has investigated means to enhance this effect in educational settings. Theoretical accounts assume retrieval practice to be the most effective whenever retrieval is difficult but successful. Therefore, we developed a novel retrieval practice procedure, which adapts to learners' abilities and can be applied irrespective of learning content. This adaptive procedure aims to make retrieval gradually easier whenever students provide an incorrect answer. In a field experiment, students read book chapters as part of a weekly university course. In three consecutive weeks, they then practiced reading assignments by (a) adaptive testing, (b) non-adaptive testing and (c) restudy. In Week 4, a surprise criterial test took place. Restudy outperformed both testing conditions, whereas adaptive testing performed equally well as non-adaptive testing. However, exploratory analyses revealed that with increasing retention intervals, the superiority of restudy disappeared. Furthermore, whenever participants fully read the assignments and retention intervals increased, adaptive testing outperformed non-adaptive testing. In sum, adaptive retrieval practice did not prove to be generally superior, but retention interval and students' preparation for class might be conditions rendering adaptive retrieval useful in educational settings.     

A viability theory for digital businesses: Exploring the evolutionary changes of revenue mechanisms to support managerial decisions

The ongoing integration of Information Technology (IT) into various areas of our lives has led to a plethora of digital products and services. To survive competition in the long run, these offerings not only have to keep up with constant technological developments, but also have to adapt from a business point of view. Managers of these digital businesses have to especially focus on the design and evolution of their business’ revenue mechanisms to ensure the viability of their offerings. The related decisions are not trivial, as managers have to be aware of the relevant contextual factors and have to react quickly to changes in the environment. This paper proposes a viability theory for digital businesses described by 17 propositions that may guide managers in the design of revenue mechanisms and thereby support the evolution as well as the viability of a digital business.