Technische Universität Dresden: Qucosa
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FEᴬᴺᴺ: an efficient data-drivenmultiscale approach based on physics-constrained neural networks and automated data mining
No full textHerein, we present a new data-driven multiscale framework called FEᴬᴺᴺ which is based on two main keystones: the usage of physics-constrained artificial neural networks (ANNs) as macroscopic surrogate models and an autonomous data mining process. Our approach allows the efficient simulation of materials with complex underlying microstructures which reveal an overall anisotropic and nonlinear behavior on the macroscale. Thereby, we restrict ourselves to finite strain hyperelasticity problems for now. By using a set of problem specific invariants as the input of the ANN and the Helmholtz free energy density as the output, several physical principles, e. g., objectivity, material symmetry, compatibility with the balance of angular momentum and thermodynamic consistency are fulfilled a priori. The necessary data for the training of the ANN-based surrogate model, i. e., macroscopic deformations and corresponding stresses, are collected via computational homogenization of representative volume elements (RVEs). Thereby, the core feature of the approach is given by a completely autonomous mining of the required data set within an overall loop. In each iteration of the loop, new data are generated by gathering the macroscopic deformation states from the macroscopic finite element simulation and a subsequently sorting by using the anisotropy class of the considered material. Finally, all unknown deformations are prescribed in the RVE simulation to get the corresponding stresses and thus to extend the data set. The proposed framework consequently allows to reduce the number of time-consuming microscale simulations to a minimum. It is exemplarily applied to several descriptive examples, where a fiber reinforced composite with a highly nonlinear Ogden-type behavior of the individual components is considered. Thereby, a rather high accuracy could be proved by a validation of the approach
Hysteresis in Organic Electrochemical Transistors: Relation to the Electrochemical Properties of the Semiconductor
No full textThe ability to bridge ionic and electronic transport coupled with large volumetric capacitance renders organic electrochemical transistors (OECTs) ideal candidates for bioelectronic applications. Adopting ionic-liquid-based solid electrolytes extends their applicability and facilitates large-area printable productions. However, OETCs employing solid electrolytes tend to show a pronounced hysteresis in the transfer curve. A detailed understanding of the hysteresis is crucial for their accurate characterizations and reliable applications. Here, we demonstrated fully photopatternable poly(3,4-ethylenedioxythiophene):tosylate (PEDOT:Tos)- based OECTs incorporating the ionic liquid [EMIM][EtSO4] in a solid electrolyte (SE). The PEDOT:Tos films deposited through vapor phase polymerization (VPP) were annealed for different durations after the polymerization step. Upon rinsing with ethanol and the deposition of the SE, the OECTs made of these films showed impressive bias stress stability under prolonged operation cycles, a high switching ratio, a low threshold voltage, and a high transconductance. Furthermore, by taking transfer measurements with different sweep rates, we revealed two distinct regimes of hysteresis: kinetic hysteresis and non-kinetic hysteresis. We observed pronounced changes in these regimes after annealing. Finally, impedance spectroscopy exhibited that the PEDOT:Tos turned from a Faradaic to a non-Faradaic response through annealing, explaining the observed hysteresis changes in both regimes
Efficient Near-Infrared Light-Emitting Diodes Based on CdHgSe Nanoplatelets
No full textCadmium mercury selenide (CdHgSe) nanocrystals exhibit a unique combination of low-energy optical absorption and emission, which can be tuned from the visible to the infrared range through both quantum confinement and adjustment of their composition. Owing to this advantage, such nanocrystals have been studied as a promising narrow-band infrared light emitter. However, the electroluminescence of CdHgSe-based nanocrystals has remained largely unexplored, despite their potential for emitting light in the telecom wavelength range. Further benefits to their optical properties are expected from their shape control, in particular the formation of 2D nanocrystals, as well as from a proper design of their heterostructures. In this work, a colloidal synthesis of CdHgSe/ZnCdS core/shell nanoplatelets (NPLs) starting from CdSe template NPLs employing a cation exchange strategy is developed. The heterostructures synthesized exhibit photoluminescence that can be tuned from ≈1300 to 1500 nm. These near-infrared-active NPLs are employed in light-emitting diodes, demonstrating low turn-on voltage and high external quantum efficiency
Beyond Protected Areas: Assessing Management Effectiveness of a Ramsar Site in Nepal
No full textRamsar Sites, wetlands of international importance, are an international category of protected wetland areas recognized under the Ramsar Convention on Wetlands. Protected areas around the world are not achieving the conservation objectives for which they were established, often due to a lack in effective management practices. Hence, protected area management effectiveness and its assessments are crucial elements of achieving responsive and pro-active management. Ramsar Sites that are not recognized as a protected area under the national park and wildlife conservation act in Nepal are often ignored for such assessments and receive little attention in terms of conservation and management. This study aimed to fill this gap by assessing Jagadishpur Reservoir Ramsar Site, which falls into the above category. The Ramsar Management Effectiveness Tracking Tool was used to assess the management effectiveness. Transformed into the global standard reporting format, the overall management effectiveness was 0.27 on a 0 to 1 scale. This score is considered to be in an inadequate range, requiring significant conservation intervention from government with support from conservation partners. This first assessment of Ramsar Site outside of protected area in Nepal and its comparison to global and European regional-level assessments provides the benchmark for future evaluation to track progress in management effectiveness. In conclusion, Ramsar Sites outside formally protected areas are often neglected and intermittent projects, and ad hoc implementation of small-scale activities seems inadequate to improve management effectiveness
Wer hat Angst vorm automatisierten Fahren? Kamerabasierte Emotionserkennung in potenziell unkomfortablen automatisierten Fahrmanövern
No full textMultizentrischer retrospektiver Vergleich der Durchführbarkeit, des Erfolgs und der Sicherheit der Valve-in-Valve-TAVI in nicht-gestenteten und gestenteten chirurgischen Bioprothesen in Aortenposition
No full textHintergrund:
Die Datenlage zum Outcome nach ViV-TAVI unter Anwendung der Valve Academic Research Consortium (VARC)-3 ist gering. Daher erfolgte der Vergleich der Baseline Patientencharakteristika, prozeduraler Ergebnisse sowie der 30-Tage-, 1- und 5- Jahre-Mortalität von Patienten mit stentless (SL) versus stented (ST) versagten aortalen Bioprothesen, welche mittels ViV-TAVI therapiert wurden.
Hypothese:
Der Klappentyp (stenless oder stented) beeinflusst das Outcome nach ViV-TAVI. Material:
356 Patienten zwischen 2007 und 2022 (wovon 53% nach 2015) aus 3 deutschen Zentren wurden in dieser Analyse eingeschlossen. Die VARC-3-definierten Endpunkte waren die primären Endpunkte. Sekundäre Endpunkte waren die 30-Tage-, 1- und 5- Jahresmortalität.
Ergebnisse:
43 (11,8%) SL und 313 (88,2%) ST ViV-TAVI wurde eingeschlossen. Die Patienten waren hinsichtlich des Alters, Geschlechts, klinischer relevanter Komorbiditäten und des Operationsrisikos vergleichbar. Die Rate an technical success (SL: 84% vs ST: 80%, p=0,55), device success (SL: 67% vs ST: 54%, p=0,11) und early safety (SL: 74% vs ST: 62%, p=0,30) waren vergleichbar. Die 30-Tage- (SL: 7.0% vs. ST: 2.6%, p=0.14) sowie 1- (SL: 9.3% vs. ST: 8.0%, p=0.63) und 5-Jahre-Mortalitätsrate (SL: 23,3% vs. ST: 24,6%, p=0,87) waren vergleichbar zwischen den Gruppen.
Zusammenfassung:
SL und ST ViV-TAVI wiesen sowohl vergleichbare VARC-3-definierten- Endpunkte als auch Mortaliätsraten bis zu 5 Jahren nach der Intervention vor
Von gemeinsamen Zielen und fehlenden Transformationspfaden: Eine Analyse der Visionen von Münchner Entscheidungsträger*innen und Bürger*innen in Bezug auf Zukunfts-Mobilität
No full textPricing decisions in a two‑period closed‑loop supply chain game under asymmetric information and uncertainty
Get PDFStrategies to increase sustainability are of growing relevance for supply chains and especially for the management of production processes. In this paper, we build on existing literature in closed-loop supply chain management and consider a two-period game-theoretic model in which product returns are reused in the manufacturing process. In all scenarios, we assume that the return rate of used products is random and not known to the players at the beginning of the planning horizon, thus, they have to deal with uncertainty in period 1. In contrast to existing literature, we will also address the circumstance that the players’ level of information in period 2, after the returns have been realized, can be linked to the collection mode in the supply chain. In Scenario A, the retailer is involved in the collection of the used products and transfers them to the manufacturer, so that symmetric information is available. In Scenario B, on the other hand, the used products reach the manufacturer directly from the customer, so that the manufacturer has an information advantage over the retailer. By comparing these scenarios and a vertically integrated supply chain benchmark case, it becomes clear that, depending on the actual return rate, the presence of private information can be either beneficial or detrimental to the manufacturer. The retailer, on the other hand, can compensate for information disadvantages in most cases over the multi-period planning period due to its position as a Stackelberg leader. Regardless of the amount of a transfer payment offered to it by the manufacturer, it prefers the collection of the goods by the manufacturer itself. These findings contribute to literature on symmetric information, where, for example, a retailer-led collection is preferred (Savaskan et al. Manage Sci 50(2):239–252, 2004) or the decision depends on the amount of the transfer payment (Modak et al. J Clean Prod 171:512–528, 2018). However, we show that cooperation between the players leads to the best results not only economically but also from an ecological point of view