224 research outputs found
Probing phase transitions in a soft matter system using a single spin quantum sensor.
No full textPhase transitions in soft matter systems reveal some of the interesting structural phenomena at the levels of individual entities constituting those systems. The relevant energy scales in soft matter systems are comparable to thermal energy (k(B)T similar to 10(-21) J). This permits one to observe interesting structural dynamics even at ambient conditions. However, at the nanoscale most experimental probes currently being used to study these systems have been either plagued by low sensitivity or are invasive at molecular scales. Nitrogen-vacancy (NV) centers in diamond is emerging as a robust quantum probe for precision metrology of physical quantities (e.g. magnetic field, electric field, temperature, and stress). Here, we demonstrate by using NV sensors to probe spin-fluctuations and temperature simultaneously to obtain information about controlled phase changes in a soft matter material as a function of temperature. The soft matter system chosen for the study is a standard liquid crystalline (LC) material which shows distinct phases close to room temperature. Individual NV centers at depths of a few nm are used as a probe to detect magnetic signals emanating from a few molecular layers of sample on the surface of the diamond. The organization and collective dynamics of LC molecules in nanoscopic volumes are discussed. Our study aims to extend the areas of application of quantum sensing using NV centers to probe the soft matter systems, particularly those exhibiting mesophases and interesting interfacial properties
Simulation and Design of an Orientation Mechanism for Assembly Systems
No full textAbstractThe article focuses on methods for designing modular cable-driven orientation mechanisms that can be attached to robot systems that lack on rotational degrees of freedom. The approach yields assembly systems for high speed handling applications by reducing moving masses. For this purpose, a classification of feasible kinematic structures are given and resulting characteristics, like the orientation workspace, dexterity or its homogeneity, are analyzed. The mechanical design of a first prototype is subsequently presented along with a universal simulation tool for determining task-adapted powertrains using cables. Finally, results of first tests and possibilities for future developments are presented
Asymmetric Aminohydroxylation of Heteroaromatic Acrylates
No full textN-, S- and O-heteroaromatic acrylates were aminohydroxylated with generally high regio- and enantioselectivity. While pyridylacrylates are not amenable towards this process, the corresponding N-oxides proved to be a useful substitute, allowing the access to biologically important pyridine substituted taxolTM side chain analogs
Implementation and Testing of a Genetic Algorithm for a Self-learning and Automated Parameterisation of an Aerodynamic Feeding System
No full textAbstractAn active aerodynamic feeding system developed at the IFA offers a large potential regarding output rate, reliability and neutrality towards part geometries. In this paper, the procedure of a genetic algorithm's into the feeding system's control is shown. The genetic algorithm automatically identifies optimal values for the feeding system's parameters which need to be adjusted when setting up for new workpieces. The general functioning of the automatic parameter identification is confirmed during tests on the convergence behaviour of the genetic algorithm. Thereby, a trade-off between the adjustment time of the feeding system and the solution quality is revealed
The Influence of Multivalent Cations on the Floatability of Scheelite, Fluorite and Calcite
No full textDesigning and assessing a digital, discipline-specific literacy assessment tool
No full textThe C-Test as a tool for assessing language competence has been in existence for nearly 40 years, having been designed by Professors Klein-Braley and Raatz for implementation in German and English. Much research has been conducted over the ensuing years, particularly in regards to reliability and construct validity, for which it is reported to perform reliably and in multiple languages. The author engaged in C-Test research in 1995 focusing on concurrent, predictive and face validity. Through this research, the author developed an appreciation for the C-Test assessment process particularly with the multiple cognitive and linguistic test-taking strategies required. When digital technologies became accessible, versatile and societally integrated, the author believed the C-Test would function well in this environment. This conviction prompted a series of investigations into the development and assessment of a digital C-Test design to be utilised in multiple linguistic settings. This paper describes the protracted design process, concluding with the publication of mobile apps
Bewertung diagnostischer Verfahren: Stellenwert und methodische Evaluation von Testgütestudien
No full textA vibration control for disassembly of turbine blades
No full textTypically, disassembly forces are unknown due to high forces or high temperatures during product operation, where assembly connections solidify. For the regulation of disassembly forces a controller is developed. The controller is formed for two steps: The first step is a PID controller that produces a force, which overcomes a solidifying force slightly. The second step is a vibration controller with a FM modulation to regulate the frequency of impacts. Vibrations are useful for decreasing the force amplitude for caring the joined components. Finally, the control is validated with disturbances in a simulation. © 2019 The Author(s)
Simulation of Integrated Actuators for Electrostatic Self-Assembly
No full textDie Montage ist ein Kostentreiber in der Produktion, insbesondere wenn die Anforderungen an die Präzision stei-gen. Ein Ansatz für die kostengünstige Feinpositionierung von planaren Bauteilen ist die elektrostatische Self-Assembly, bei dem Aktoren in die Bauteile integriert werden. In diesem Artikel werden die Grundlagen des Designs solcher Systeme thematisiert, da diese Ausschlaggebend für die resultierenden Positionierkräfte sind. Zum Feststellen der Zusammenhänge werden Simulationen für einzelne Elektrodenpaare durchgeführt, wobei die Geometrien Kreis, Quadrat, Rechteck, Sechseck und Dreieck miteinander verglichen werden. Die Auswertung erfolgt mit der simulierten Maximalkraft und der Kraftverteilung innerhalb der xy-Ebene. In Hinblick auf die Prozessgrößen Präzision und maximalen Wirkbereich werden die Ergebnisse interpretiert und Rückschlüsse auf die sinnvolle Gestaltung von Self-Assembly Systemen gezogen. Abschließend erfolgt ein Ausblick auf weitere Forschungen zu elektrostatischen Self-Assembly Systemen.Assembly is a high-cost process in production, especially when the precision requirements are high. One approach for cost-effective fine positioning of planar components is electrostatic self-assembly. Therefore, actuators are integrated into the components. This paper deals with the fundamental design principles of such systems, because they are significantly influencing the alignment force. This paper presents simulations of individual electrode pairs, comparing the geometries circle, square, rectangle, hexagon and triangle. The evaluation shows the results of the simulated maximum force and the force distribution within the xy-plane. Aiming for high precision and a wide range of force distribution, conclusions are made about the appropriate design of self-assembly systems. In conclusion, there is an outlook on additional research into electrostatic self-assembly systems
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