500 Naturwissenschaften und Mathematik
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By a simple femtosecond laser process, we fabricated metal-oxide/gold composite films for electrical and optical gas sensors. We designed a dripple wavelength AWG-spectrometer, matched to the plasma absorption wavelength region of the composite films. H2/CO absorptions fit well with the AWG design for multi gas detection sensor arrays
Ansätze des maschinellen Lernens werden sowohl in der Forschung als auch in der Praxis eingesetzt, um gewünschte Ausgabedaten anhand bekannter Eingabedaten vorherzusagen. In dieser Masterarbeit wird die Anwendung des maschinellen Lernens in der Batteriedatenanalyse zur Bestimmung des Alterungsstatus von Lithium-Ionen-Batterien untersucht. Das Ziel dieser Arbeit besteht in der Vorhersage von Alterungskurven (englisch state of health - SoH) für Lithium-Ionen Batterien über die Anzahl der Entladezyklen (Zeitachse). Dies erfolgt auf der Grundlage zuvor erfasster Daten für drei Typen von Lithium-Ionen-Batterien, die bei Temperaturen von 15 °C, 25 °C und 35 °C sowie C-Raten von 0,5C, 1C und 2C aufgenommen wurden. Im Zuge dessen wurden die angewandten Methoden des maschinellen Lernens analysiert und ihre Ergebnisse verglichen. Der Umfang dieser Arbeit hebt sich von anderen Ansätzen des maschinellen Lernens in der Batteriedatenanalyse ab, da dieselben Methoden in einem breiteren Spektrum von Daten mit unterschiedlichen Temperaturen und Kathodenmaterialien verwendet wurden. Dies ist für die Analyse von Unterschieden im Verhalten in der Praxis relevant. Nach dem Erwerb und der Vorbereitung der Daten wurden Modelle mit vier ausgewählten Regressionsverfahren (lineare Regression, Ridge-Regression, Random-Forest-Regression und KNN-Regression) des überwachten Lernens trainiert und die Vorhersagen durchgeführt. Aus den Ergebnissen kann eine allgemeingültige Auslegungsgrundlage für weitere Untersuchungen und die praktische Anwendung abgeleitet werden, bei der die Vorhersagen von SoH-Kurven für Lithium-Ionen-Batterien mit linearer Regression und Ridge-Regression die höchste Genauigkeit aufweisen.
Whether at the intramolecular or cellular scale in organisms, cell-cell adhesion adapt to external mechanical cues arising from the static environment of cells and from dynamic interactions between neighboring cells. Cell-cell adhesions need to resist detachment forces to secure the integrity and internal organization of organisms. In the past, various techniques have been developed to characterize adhesion properties of molecules and cells in vitro, and to understand how cells sense and probe their environment. Atomic force microscopy and dual-pipette aspiration, where cells are mainly present in suspension, are common methods for studying detachment forces of cell-cell adhesions. How cell-cell adhesion forces are developed for adherent and environment-adapted cells, however, is less clear. Here, we designed the Cell-Cell Separation Device (CC-SD), a microstructured substrate that measures both intercellular forces and external stresses of cells towards the matrix. The design is based on micropillar arrays originally designed for cell traction-force measurements. We designed PDMS micropillar-blocks, to which cells could adhere and be able to connect to each other across the gap. Controlled stretching of the whole substrate changed the distance between blocks and increased gap size. That allowed us to apply strains to cell-cell contacts, eventually leading to cell-cell adhesion detachment, which was measured by pillar deflections. The CC-SD provided an increase of the gap between the blocks of up to 2.4-fold, which was sufficient to separate substrate-attached cells with fully developed F-actin network. Simultaneously measured pillar deflections allowed us to address cellular response to the intercellular strain applied. The CC-SD thus opens up possibilities for the analysis of intercellular force detachments and sheds light on the robustness of cell-cell adhesions in dynamic processes in tissue development.
This paper presents design, simulation, and optimization of the three-dimensional 1×4 optical multimode interference splitter using IP-Dip polymer as a core and polydimethylsiloxane (PDMS) Sylgard 184 as a cladding. The splitter was simulated by using beam propagation method in BeamPROP simulation engine of RSoft photonic tool and optimized for an operating wavelength of 1.55 µm. According to the minimum insertion loss, the dimensions of the MMI coupler and the length of the whole MMI splitter structure were optimized applying a waveguide with a core size of 4×4 µm2. The objective of the study is to create a design for fabrication by three-dimensional direct laser writing optical lithography.
We present design of planar 16-channel, 100-GHz multi-mode polymer-based AWG. This AWG was designed for central wavelength of 1550 nm applying AWG-Parameters tool. The AWG structure was created and simulated in the commercial photonic tool PHASAR from Optiwave. Achieved transmission characteristics were evaluated by AWG-Analyzer tool. For the design, multi-mode waveguides having a cross-section of (4x4) µm2 were used. The simulated results show strong worsening of the transmission characteristics in comparison when using single-mode waveguides. Nevertheless, the transmitting channels are clearly separated. The reason for using thicker multi-mode waveguides in the design is possibility to fabricate the AWG structure on polymer basis using direct laser writing lithography.
The main aims of this work are the validation of the developed process of gluing a single-mode optical fiber array with a photonic chip and the selection of a more suitable adhesive from the two adhesives being compared. An active alignment system was used for adjusting the two optical fiber arrays to a photonics chip. The gluing was done by two compared UV curable adhesives applied in the optical path. The insertion losses of glued coupling were measured and investigated at two discrete wavelengths 1310 nm and 1550 nm during temperature testing in the climatic chamber according to Telcordia GR_1209_Corei04 [3]. The measurement, investigation, and comparison of insertion losses of the glued coupling at the spectral band from 1530 nm to 1570 nm were done immediately after gluing process and after three temperature cycles in the climatic chamber with one month delay.
X-ray microtomography is a nondestructive, three-dimensional inspection technique applied across a vast range of fields and disciplines, ranging from research to industrial, encompassing engineering, biology, and medical research. Phasecontrast imaging extends the domain of application of x-ray microtomography to classes of samples that exhibit weak attenuation, thus appearing with poor contrast in standard x-ray imaging. Notable examples are low-atomic-number materials, like carbon-fiber composites, soft matter, and biological soft tissues.We report on a compact and cost-effective system for x-ray phase-contrast microtomography. The system features high sensitivity to phase gradients and high resolution, requires a low-power sealed x-ray tube, a single optical element, and fits in a small footprint. It is compatible with standard x-ray detector technologies: in our experiments, we have observed that single-photon counting offered higher angular sensitivity, whereas flat panels provided a larger field of view. The system is benchmarked against knownmaterial phantoms, and its potential for soft-tissue three-dimensional imaging is demonstrated on small-animal organs: a piglet esophagus and a rat heart.We believe that the simplicity of the setupwe are proposing, combined with its robustness and sensitivity, will facilitate accessing quantitative x-ray phase-contrast microtomography as a research tool across disciplines, including tissue engineering, materials science, and nondestructive testing in general.
Parametric anti-resonance is a phenomenon that occurs in systems with at least two degrees of freedom; this can be achieved by periodically exciting some parameters of the system. The effect of this properly tuned periodicity is to increase the dissipation in the system, which leads to a raising in the effective damping of vibrations. This contribution presents the design of an open-loop control to reduce the settling time using the anti-resonance concept. The control signal consists of a quasi-periodic signal capable of transferring the system’s oscillations from one mode to another mode of the system. The general averaging technique is used to characterize the dynamics, particularly the so-called slow dynamics of motion. With this analysis, the control signal is designed for the potential application of a microelectromechanical sensor arrangement; for this specific example, up to 96.8% reduction of settling time is achieved.
Der Klimawandel und der damit einhergehende Temperaturanstieg stellen den Gebäudesektor in Bezug auf die sommerliche Überhitzung vor erhebliche Herausforderungen. Zur Abschätzung der Auswirkungen ist es relevant, Klimadaten für einen angemessenen Zeitraum zu verwenden, um geeignete Maßnahmen zur Hitzeminderung ergreifen zu können.Die sommerliche Überhitzung variiert je nach Gebäudetyp, Standort und örtlichen Gegebenheiten. Aus diesem Grund werden in dieser wissenschaftlichen Untersuchung Wohngebäude mit mehr als zehn Wohneinheiten für das Klimaszenario RCP4.5 im Jahr 2060 in Österreich analysiert. Zur Beurteilung des Wohnkomforts wurden umfangreiche Messungen im Rahmen einer Studie des Energieinstituts Vorarlberg an einem repräsentativen Gebäude über einen längeren Zeitraum durchgeführt. Basierend auf den gewonnenen Messwerten wird ein Referenzgebäude im Gebäudesimulationsprogramm IDA ICE konstruiert und simuliert. Um verschiedene Klimazonen angemessen abzubilden, werden die Standorte Bregenz, Klagenfurt und Wien für das Gebäude im Jahr 2022 betrachtet. Diese Ergebnisse bilden die Grundlage, um den Einfluss des Klimawandels auf die sommerliche Überhitzung abschätzen zu können. Im nächsten Schritt werden die neuen Klimadatensätze für das Klimaszenario RCP4.5 im Jahr 2060 für dieselben Standorte implementiert und mit den Ergebnissen von 2022 verglichen. Dadurch können verschiedene Kennziffern wie maximale Temperaturen, Stundenanzahl mit Temperaturen über 25 °C bzw. 27 °C und die Häufigkeit von Übertemperaturgradstunden herangezogen werden, um die zukünftige Hitzebelastung zu bewerten. Die Ergebnisse zeigen, dass mit einer Erhöhung der maximalen Temperatur, der mittleren Temperatur zwischen Mai und September sowie der Stundenanzahl mit Temperaturen über 25 °C bzw. 27 °C zu rechnen ist. Der Grenzwert von 25 °C wird dabei um 12 bis 29 Prozent überschritten. Die Maximaltem-peratur steigt um vier bis neun Prozent, während sich der Wert für die mittlere Temperatur um zwei bis drei Prozent erhöht. Besonders stark nimmt die Häufigkeit von Übertemperaturen über einen längeren Zeitraum zu. Für die Umsetzung passiver Maßnahmen zeigt sich, dass diese zu einer signifikanten Reduk-tion der Stundenanzahl mit Temperaturen über den Grenzwerten führen können. Auch durch simple Maßnahmen, wie die Integration einer Nachtlüftung, kann eine Absenkung der Tem-peraturen und folglich der Stundenanzahl über den Grenzwerten erreicht werden. Ein thermischer Komfort basierend ausschließlich auf passiven Maßnahmen kann nicht für sämtliche Standorte in der Zukunft gewährleistet werden.
Beyond the Four-Level Model: Dark and Hot States in Quantum Dots Degrade Photonic Entanglement
(2023)
Entangled photon pairs are essential for a multitude of quantum photonic applications. To date, the best performing solid-state quantum emitters of entangled photons are semiconductor quantum dots operated around liquid-helium temperatures. To favor the widespread deployment of these sources, it is important to explore and understand their behavior at temperatures accessible with compact Stirling coolers. Here we study the polarization entanglement among photon pairs from the biexciton–exciton cascade in GaAs quantum dots at temperatures up to ∼65 K. We observe entanglement degradation accompanied by changes in decay dynamics, which we ascribe to thermal population and depopulation of hot and dark states in addition to the four levels relevant for photon pair generation. Detailed calculations considering the presence and characteristics of the additional states and phonon-assisted transitions support the interpretation. We expect these results to guide the optimization of quantum dots as sources of highly entangled photons at elevated temperatures.