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Review of the State of the Art Using μCT to Elucidate Complex Vascular Systems of Plants
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Untersuchung additiv gefertigter Modelle nach dem Vorbild sich öffnender verholzter Früchte der Gattung Hakea, zum Verständnis des Öffnungsmechanismus.
No full textDie verholzten Früchte der Art Hakea salicifolia öffnen sich bei Austrocknung, um Samen freizugeben. Der Öffnungsmechanismus könnte als Vorbild für selbstaktuierte Bewegungen von Bauteilen dienen. Um ihn zu verstehen, wird aus µCT-Scans einer getrockneten Frucht ein 3D-Modell generiert und additiv gefertigt, welches nur zwei Gewebetypen, nämlich Leitbündel und umgebendes Gewebe berücksichtigt. Druckprüfungen dieser Prüfkörper zeigen einen anisotropen E-Modul, der auf die Struktur der Leitbündel und den großen E-Modulunterschied der gewählten Materialien zurückzuführen ist. Die erhaltenen Daten sollen zur Verifikation eines FE-Modells herangezogen und dieses an das natürliche Vorbild angepasst werden, um die Öffnung der Früchte nachzuvollziehen.Woody fruits of the species Hakea salicifolia open when they dry out to release seeds. The opening mechanism could serve as a model for selfactuated movements of technical components. To understand this mechanism, a 3D model is generated from µCT scans of a dried fruit and additively manufactured, which considers only two types of tissue, namely vascular bundles and surrounding tissue. Compression tests of these specimens show an anisotropic Young's modulus, which is due to the structure of the vascular bundles and the large difference in Young's modulus of the chosen materials. The data obtained will be used to verify an FE model and to adapt it to the natural material in order to reproduce the opening of the fruit
Dephasing and pseudocoherent quantum dynamics in super-Ohmic environments
No full textDephasing in quantum systems is typically the result of their interaction with environmental degrees of freedom. We investigate within a spin-boson model the influence of a super-Ohmic environment on the dynamics of a quantum two-state system. A super-Ohmic environment thereby models typical bulk phonons which are a common disturbance for solid state quantum systems as, for example, nitrogen-vacancy centers. By applying the numerically exact quasiadiabatic path-integral approach we show that for strong system-bath coupling, pseudocoherent dynamics emerges, i.e., oscillatory dynamics at short times due to slaving of the quantum system to the bath dynamics. We extend the phase diagram known for sub-Ohmic and Ohmic environments into the super-Ohmic regime and observe a pronounced nonmonotonous behavior. Super-Ohmic purely dephasing fluctuations strongly suppress the amplitude of coherent dynamics at very short times with no subsequent further decay at later times. Nevertheless, they render the dynamics overdamped. The corresponding phase separation line shows also a nonmonotonous behavior, very similar to the pseudocoherent dynamics
An Augmented Multiphase Rail Launcher With a Modular Design: Theoretical Considerations and Development
No full textConsiderations on the Wear Behavior of Vacuum-Remelted ZrO2-Reinforced Self-Fluxing Ni-Based Thermally Sprayed Alloys
No full textWithout proper post-processing (often using flame, furnace, laser remelting, and induction) or reinforcements’ addition, Ni-based flame-sprayed coatings generally manifest moderate adhesion to the substrate, high porosity, unmelted particles, undesirable oxides, or weak wear resistance and mechanical properties. The current research aimed to investigate the addition of ZrO2 as reinforcement to the self-fluxing alloy coatings. Mechanically mixed NiCrBSi-ZrO2 powders were thermally sprayed onto an industrially relevant high-grade steel. After thermal spraying, the samples were differently post-processed with a flame gun and with a vacuum furnace, respectively. Scanning electron microscopy showed a porosity reduction for the vacuum-heat-treated samples compared to that of the flame-post-processed ones. X-ray diffraction measurements showed differences in the main peaks of the patterns for the thermal processed samples compared to the as-sprayed ones, these having a direct influence on the mechanical behavior of the coatings. Although a slight microhardness decrease was observed in the case of vacuum-remelted samples, the overall low porosity and the phase differences helped the coating to perform better during wear-resistance testing, realized using a ball-on-disk arrangement, compared to the as-sprayed reference samples