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Breaking down barriers to warning technology adoption: usability and usefulness of a messenger app warning bot
Get PDFIn crisis situations, citizens’ situational awareness is paramount for effective response. While warning apps offer location-based alerts, their usage is relatively low. We propose a personalised messaging app channel as an alternative, presenting a warning bot that may lower adoption barriers. We employ the design science research process to define user requirements and iteratively evaluate and improve the bot’s usability and usefulness. The results showcase high usability, with over 40 % expressing an interest in utilising such a warning channel, stressing as reasons the added value of proactive warnings for personalised locations while not requiring a separate app. The derived requirements and design solutions, such as graphically enhanced user interface elements as guardrails for effective and error-free communication, demonstrate that a suitable warning chatbot does not necessarily require complex language processing capabilities. Additionally, our findings facilitate further research on accessibility via conversational design in the realm of crisis warnings
Gait Phase Detection Using 3D-Printed Piezoelectric Force Myography Sensors
Get PDFMuscle activity can be utilized to detect a user’s movement intention in human-machine interactions. Electromyography (EMG) is the prevalent method to assess muscle activity but has critical disadvantages in its practical implementation, particularly for long-term measurements, which are required in wearable devices. Force myography (FMG) offers an alternative approach, mechanically detecting muscle contractions by assessing the tissue deformation. Highly sensitive ferroelectrets qualify for detecting subtle muscle movements using FMG. We propose to attach individual ferroelectret sensor patches superficially to the muscle bellies, thereby avoiding crosstalk from other muscles. The sensors are additively manufactured using polypropylene, which allows for application-specific customizations. In order to investigate the suitability of these sensors for FMG during walking, we conduct a study with seven unimpaired participants. Heel strike and toe-off events are determined from the data of four leg muscles, while the ground reaction force provided by an instrumented treadmill serves as a reference. Tibialis anterior (TA) and vastus medialis (VM) suit best for determining toe-off and heel strike events, with small deviations of 3.3%±1.7% for toe-off detection at the TA and -1.2%±1.2% for heel strike detection at the VM. The experimental results demonstrate the suitability of our ferroelectret sensors as a possible substitute for EMG, underscoring their potential in assistive devices such as exoskeletons and prostheses
Stickstoffdotierte polymerabgeleitete Kohlenstoffkatalysatoren in der oxidativen Dehydrierung von Ethanol
Get PDFKohlenstoffmaterialien können in verschiedenen Reaktionen, wie zum Beispiel der oxidativen Dehydrierung, als aktive Komponente eingesetzt werden. Es ist daher von Interesse Kohlenstoffmaterialien mit angepassten Eigenschaften hinsichtlich der Textur, der Morphologie, dem Dotierungsgehalt und der Oberflächenfunktionalisierung zu synthetisieren, um ein geeignetes Katalysatormaterial für die ODH von Ethanol zu erzielen. Dieses besitzt eine graphitische Grundstruktur, um die Oxidationsstabilität bei den entsprechenden Reaktionsbedingungen gewährleisten zu können. Es besitzt weiterhin eine hohe spezifische Oberfläche, damit eine entsprechend hohe Anzahl aktiver Zentren vorhanden sein kann, was wiederum die Aktivität bedingt. Weiterhin sollte das Material vorwiegend mesoporös sein. Die Oberfläche sollte anoxidiert vorliegen, um Chinone als aktives Zentrum bereit zu stellen. Zusätzlich kann eine Dotierung mit Stickstoff die Aktivität in der ODH weiter steigern.
Zunächst sollen die Eigenschaften eines erprobten polymerabgeleiteten Kohlenstoffmaterials auf Aktivkohlen übertragen werden, da die Verwendung von kommerziellen Materialien gegenüber der vollständigen Syntheseroute dieses Kohlenstoffmaterials Vorteile bieten würde. Es stellt sich daher die Forschungsfrage, ob die, für die ODH von Ethanol, vorteilhaften Strukturmerkmale, des erprobten Materials, auch ausgehend von einer Aktivkohle zugänglich sind und sich in dieser kombinieren lassen. Die Anpassung der Eigenschaften würde somit erst beim Kohlenstoffmaterial und nicht bei der Polymersynthese beginnen. Diese veränderte Aktivkohle soll dann als Katalysatormaterial in der oxidativen Dehydrierung von Ethanol eingesetzt werden.
Ein weiteres Ziel der Arbeit besteht darin, das erprobte Kohlenstoffmaterial von HEROLD et al. mit Hilfe verschiedener Methoden der Stickstoffdotierung weiterzuentwickeln. Dafür soll die Syntheseroute des polymerabgeleiteten Kohlenstoffmaterials (PDC) angepasst werden, so dass eine stabile Stickstoffdotierung resultiert, welche anschließend die Aktivität des Kohlenstoffkatalysatormaterials in der oxidativen Dehydrierung von Ethanol verbessern könnte. Der Dotierungsansatz erfolgt somit auf der Basis des PDC1500 und entlang dessen Syntheseroute. Das Ziel ist ein stickstoffdotiertes polymerabgeleitetes Kohlenstoffmaterial (PDNC).
Weiterhin sollen stickstoffhaltige Polymere synthetisiert werden und als Ausgangsmaterial für dotierte Kohlenstoffmaterialien untersucht werden. Dieser Dotierungsansatz beginnt somit bei Monomeren und losgelöst vom erprobten undotierten Material PDC1500, um größeren Fokus auf die Stickstoffdotierung zu legen. Aus diesen stickstoffhaltigen Polymeren sollen anschließend polymerabgeleitete dotierte Kohlenstoffmaterialien (PDNC) hergestellt werden. Die pyrolisierten Materialien werden hinsichtlich des erzielten Stickstoffgehalts untersucht und mit den Ergebnissen der Dotierung des PDC-Materials verglichen. Dieser Dotierungsansatz legt damit weniger Fokus auf die bereits erprobten vorteilhaften Strukturmerkmale (BET-Oberfläche, Mesoporosität, Kristallinität). Bei diesen Kohlenstoffmaterialien sollen dennoch eben diese Kriterien untersucht werden, wobei zunächst ein temperaturstabiles Kohlenstoffmaterial erzeugt werden muss. Dafür wird ein Graphitisierungskatalysator verwendet, um ein Hybridmaterial zu erzielen. In Anlehnung an den PDC1500 sollen etwaige temperaturlabile Anteile durch die anschließende selektive Oxidation entfernt werden, wodurch die Textur (Oberfläche, Porenvolumen) in den Fokus rückt.
Das letzte Ziel dieser Arbeit ist es die Stickstoffdotierung hinsichtlich der katalytischen Aktivität in der oxidativen Dehydrierung von Ethanol zu untersuchen. Dabei stehen die Stabilität der Dotierung und des Kohlenstoffmaterials sowie die katalytische Aktivität im Vordergrund
HDT: Hierarchical Document Transformer
Get PDFIn this paper, we propose the Hierarchical Document Transformer (HDT), a novel sparse Transformer architecture tailored for structured hierarchical documents. Such documents are extremely important in numerous domains, including science, law or medicine. However, most existing solutions are inefficient and fail to make use of the structure inherent to documents. HDT exploits document structure by introducing auxiliary anchor tokens and redesigning the attention mechanism into a sparse multi-level hierarchy. This approach facilitates information exchange between tokens at different levels while maintaining sparsity, thereby enhancing computational and memory efficiency while exploiting the document structure as an inductive bias. We address the technical challenge of implementing HDT’s sample-dependent hierarchical attention pattern by developing a novel sparse attention kernel that considers the hierarchical structure of documents. As demonstrated by our experiments, utilizing structural information present in documents leads to faster convergence, higher sample efficiency and better performance on downstream tasks
A Single Model for the Thermodynamics and Kinetics of Metal Exsolution from Perovskite Oxides
Get PDFExsolution has emerged as an outstanding route for producing oxide-supported metal nanoparticles. For ABO₃-perovskite oxides, various late transition-metal cations can be substituted into the lattice under oxidizing conditions and exsolved as metal nanoparticles after reduction. A consistent and comprehensive description of the point-defect thermodynamics and kinetics of this phenomenon is lacking, however. Herein, supported by hybrid density-functional-theory calculations, we propose a single model that explains diverse experimental observations, such as why substituent transition-metal cations (but not host cations) exsolve from perovskite oxides upon reduction; why different substituent transition-metal cations exsolve under different conditions; why the metal nanoparticles are embedded in the surface; why exsolution occurs surprisingly rapidly at relatively low temperatures; and why the reincorporation of exsolved species involves far longer times and much higher temperatures. Our model’s foundation is that the substituent transition-metal cations are reduced to neutral species within the perovskite lattice as the Fermi level is shifted upward within the bandgap upon sample reduction. The calculations also indicate unconventional influences of oxygen vacancies and A-site vacancies. Our model thus provides a fundamental basis for improving existing, and creating new, exsolution-generated catalysts
de Dijn, Annelien (2020): Freedom. An Unruly History: Cambridge/London: Harvard University Press. 426 Seiten. 31,50 €
Get PDFAnnelien de Dijns umfassenden Darstellung der Veränderung der westlichen Freiheitsvorstellung, die mehr als zwei Jahrtausende Ideengeschichte umfasst, und neben bekannten Theoretiker*innen auch politische Bewegungen und Parteiverständnisse referiert, verfolgt zwei Erzählstränge, die sich letztendlich auf die gängige Unterscheidung von positiver und negativer Freiheit beziehen, wie sie Benjamin Constant, Alexis de Tocqueville, Francis Lieber, Édouard René Lefebvre de Laboulaye, Johann Caspar Bluntschli und nicht zuletzt Isaiah Berlin als theoretische Differenzierung eingeführt haben. Laut Autorin wurde das ursprüngliche (westliche) Verständnis von Freiheit im alten Griechenland geboren und fiel dort zusammen mit der Rechtfertigung der Volksregierung oder Herrschaft des Volkes. Freiheit bedeutete die Abwesenheit von Fremdherrschaft und wurde mit Selbstregierung bzw. der Fähigkeit des Volkes, Kontrolle über die Art und Weise auszuüben, wie es regiert wurde, gleichgesetzt. Freiheit, in diesem positiven Sinne, bestimmte das Handeln der Athener Demokraten, römischen Plebejer, Florentiner Humanisten und amerikanischer Revolutionäre in ihrem Kampf gegen die bestehenden Machtstrukturen. Ihre Sprache der Freiheit war, wie die Autorin zeigt, überall dort anschlussfähig, wo soziale Gruppen und Bevölkerungen von der Politik weitgehend ausgeschlossen waren und für eine Öffnung von Staat und Verwaltung kämpften
Robust estimation of clinch joint characteristics based on data-driven methods
Get PDFGiven a steadily increasing demand on multi-material lightweight designs, fast and cost-efficient production technologies, such as the mechanical joining process clinching, are becoming more and more relevant for series production. Since the application of such joining techniques often base on the ability to reach similar or even better joint loading capacities compared to established joining processes (e.g., spot welding), few contributions investigated the systematic improvement of clinch joint characteristics. In this regard, the use of data-driven methods in combination with optimization algorithms showed already high potentials for the analysis of individual joints and the definition of optimal tool configurations. However, the often missing consideration of uncertainties, such as varying material properties, and the related calculation of their impact on clinch joint properties can lead to poor estimation results and thus to a decreased reliability of the entire joint connection. This can cause major challenges, especially for the design and dimensioning of safety-relevant components, such as in car bodies. Motivated by this, the presented contribution introduces a novel method for the robust estimation of clinch joint characteristics including uncertainties of varying and versatile process chains in mechanical joining. Therefore, the utilization of Gaussian process regression models is demonstrated and evaluated regarding the ability to achieve sufficient prediction qualities
Screen printed 3D microfluidic paper-based and modifier-free electroanalytical device for clozapine sensing
Get PDFThe increasing demand in healthcare for accessible and cost-effective analytical tools is driving the development of reliable platforms to the customization of therapy according to individual patient drug serum levels, e.g. of anti-psychotics in schizophrenia. A modifier-free microfluidic paper-based electroanalytical device (μPED) holds promise as a portable, sensitive, and affordable solution. While many studies focus on the working electrode catalysts, improvements by engineering aspects e.g. of the electrode arrangement are less reported. In our study, we demonstrate the enhanced capabilities of the 3D electrode layout of μPED compared to 2D μPED arrangements. We especially show that screen printing can be employed to prepare 3D μPEDs. We conducted a comparison of different 2D and 3D electrode arrangements utilizing cyclic voltammetry in [Fe(CN)₆]³⁻/⁴⁻, along with square-wave voltammetry for clozapine (CLZ) sensing. Our findings reveal that the utilization of the 3D μPED leads to an increase in both the electrochemically active surface area and the electron transfer rate. Consequently, this enhancement contributes to improve sensitivity in the CLZ sensing. The 3D μPED clearly outperforms the 2D μPED arrangement in terms of signal strength. With the 3D μPED under the optimized conditions, a linear dose–response for a concentration range from 7.0 to 100 μM was achieved. The limit of detection and sensitivity was determined to be 1.47 μM and 1.69 μA μM⁻¹ cm⁻², respectively. This evaluation is conducted in the context of detection and determination of CLZ in a human blood serum sample. These findings underscore the potential of the 3D μPED for future applications in pharmacokinetic analyses and clinical tests to personalize the management of schizophrenia
Visualization of the two-phase flow in the air gap of an optically accessible generic electric motor and its effect on torque
Get PDFElectric motors with high-power densities are required for the implementation of electromobility. To achieve this, direct liquid cooling methods are increasingly being considered, in which oil is injected into the motor compartment. This results in a two-phase flow that can be used for efficient cooling. However, the oil, which can also penetrate the air gap between the rotor and stator, can also lead to additional losses due to increased friction. Since little is known about the two-phase flow in such systems, especially in the air gap, it is investigated by means of simple optical visualizations and high-speed laser-induced fluorescence imaging as well as torque measurements. The measurements are carried out in the air gap of an optically accessible generic model of a directly cooled electric motor. Speed variations were performed from 100 to 2000 rpm, and three different two-phase flow regimes were observed. At low speeds (Flow Regime 1), the air gap is filled locally with oil in radial direction, in the medium speed range (Flow Regime 2) with foam, while at high speeds (Flow Regime 3) separated films were observed on the rotor and stator. The torque difference between the two-phase and single-phase operation, which quantifies the mechanical losses due to the injected oil, increased continuously due to the oil in the air gap until it reached a maximum in Flow Regime 2 due to foam formation. In Flow Regime 3, the torque difference was negative. This was attributed to the fact that the grooves in the stator were filled with oil, thus reducing the turbulence generation of the air flow
Depth from defocus technique: a simple calibration-free approach for dispersion size measurement
Get PDFParticle size measurement is crucial in various applications, be it sizing droplets in inkjet printing or respiratory events, tracking particulate ejection in hypersonic impacts or detecting floating target markers in free-surface flows. Such systems are characterised by extracting quantitative information like size, position, velocity and number density of the dispersed particles, which is typically non-trivial. The existing methods like phase Doppler or digital holography offer precise estimates at the expense of complicated systems, demanding significant expertise. We present a novel volumetric measurement approach for estimating the size and position of dispersed spherical particles that utilises a unique ‘Depth from Defocus’ (DFD) technique with a single camera. The calibration-free sizing enables in situ examination of hard to measure systems, including naturally occurring phenomena like pathogenic aerosols, pollen dispersion or raindrops. The efficacy of the technique is demonstrated for diverse sparse dispersions, including dots, glass beads and spray droplets. The simple optical configuration and semi-autonomous calibration procedure make the method readily deployable and accessible, with a scope of applicability across vast research horizons