Controlled partial embedding of carbon nanotubes within flexible transparent layers

Applications of carbon nanotubes (CNTs) like field emission displays, super-capacitors, and cell growth scaffolds can benefit from controllable embedding of the CNTs in a material such that the CNTs are anchored and protrude a desired length. We demonstrate a simple method for anchoring densely packed, vertically aligned arrays of CNTs into silicone layers using spin-coating, CNT insertion, curing, and growth substrate removal. CNT arrays of 51 and 120 µm in height are anchored into silicone layers of thickness 26 and 36 µm, respectively. Scanning electron microscopy (SEM) and optical microscopy are used to characterize the sample morphology, a 5.5 m s^-1 impinging water jet is used to apply shear stress, and a tensile test shows that the silicone layer detaches from the substrate before the CNTs are ripped from the layer. The CNTs are thus well anchored in the silicone layers. The spin-coating process gives control over layer thickness, and the method should have general applicability to various nanostructures and anchoring materials

Self-similar structure and experimental signatures of suprathermal ion distribution in inertial confinement fusion implosions

The distribution function of suprathermal ions is found to be self-similar under conditions relevant to inertial confinement fusion hot-spots. By utilizing this feature, interference between the hydro-instabilities and kinetic effects is for the first time assessed quantitatively to find that the instabilities substantially aggravate the fusion reactivity reduction. The ion tail depletion is also shown to lower the experimentally inferred ion temperature, a novel kinetic effect that may explain the discrepancy between the exploding pusher experiments and rad-hydro simulations and contribute to the observation that temperature inferred from DD reaction products is lower than from DT at National Ignition Facility.Comment: Revised version accepted for publication in PRL. "Copyright (2015) by the American Physical Society.

Adapting the control of the magnetic bearings of a highly flexible and gyroscopic rotor to the excitations by the motor

A test rig was built to perform fatigue tests on thick-walled cylinders made of fibre reinforced plastic (FRP). During the fatigue test, the rotational speed of an FRP cylinder is periodically varied until it fails. The FRP cylinder is connected to a drive spindle that accelerates and decelerates it using a permanent magnet synchronous machine (PMSM). To avoid excessive wear, the rotor is supported by active magnetic bearings (AMB). After the fatigue test was finished with the first cylinder, a new cylinder was attached to the test stand. With this new specimen, previously uncritical radial vibrations became more severe. For high accelerations, these vibrations led to instability of the rotor. However, high accelerations are desirable to perform the fatigue tests in the shortest possible time. Hence, the AMB control should be made insensitive to these vibrations. Since the vibrations depend on the acceleration of the rotor, it is reasonable to assume that they are induced by the PMSM. To reduce the vibrations, these excitations from the PMSM are included in the model-based controller parametrization process for the radial AMB, in which the parameters are adjusted via optimization. With the adjusted control, the amplitude of the vibration was significantly reduced and higher accelerations were possible. The described parameter tuning process can easily be adapted to different AMB systems with disturbances and changes in the system

Neutron time-of-flight measurements of charged-particle energy loss in inertial confinement fusion plasmas

Neutron spectra from secondary ^{3}H(d,n)α reactions produced by an implosion of a deuterium-gas capsule at the National Ignition Facility have been measured with order-of-magnitude improvements in statistics and resolution over past experiments. These new data and their sensitivity to the energy loss of fast tritons emitted from thermal ^{2}H(d,p)^{3}H reactions enable the first statistically significant investigation of charged-particle stopping via the emitted neutron spectrum. Radiation-hydrodynamic simulations, constrained to match a number of observables from the implosion, were used to predict the neutron spectra while employing two different energy loss models. This analysis represents the first test of stopping models under inertial confinement fusion conditions, covering plasma temperatures of k_{B}T≈1-4  keV and particle densities of n≈(12-2)×10^{24}  cm^{-3}. Under these conditions, we find significant deviations of our data from a theory employing classical collisions whereas the theory including quantum diffraction agrees with our data

Simulation of Integrated Actuators for Electrostatic Self-Assembly

Die 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

Automation of flexible handling of hot forged Tailored Forming components

Universalgreifer sind flexibel einsetzbar und können sich an verschiedene Situationen und Objekte anpassen. Aktuelle formvariable Universalgreifer bestehen überwiegend aus monolithischen polymeren Werkstoffen, deren maximale Einsatztemperaturen bei 300 °C liegen. Somit kann von der Formflexibilität nicht in Bereich profitiert werden in denen höhere Temperaturen vorherrschen und die zu handhabenden Objekte Umformungsprozesse durchschreiten. Solch ein Bereich ist der Schmiedesektor, bei dem die Objekte Temperaturen von bis zu 1250 °C erreichen. Die vorliegende Diskrepanz zwischen der Formvariabilität der Greifer und den Prozesstemperaturen im Schmiedesektor versuchen wir zu schließen. In dieser Arbeit stellen wir das von uns entwickelte Konzept eines formvariablen hochtemperaturbeständigem Handhabungssystem und deren praktische Umsetzung vor, sowie die noch zu lösenden Herausforderungen.Universal grippers are flexible and can adapt to different situations and objects. The shape variability has limitations, for example, the temperature. For manufacturing such shape variable grippers, elastic polymer materials are used. The material has an upper limit of the operating temperature of 300 °C. In the forging sector, the manufactured object change their geometry during the process and reaches temperature up 1250 °C. Here, we see the potential of the utilization of shape variable grippers. Therefore, we developed a system that overcomes the gap between the temperature limitation of current shape variable grippers and the high temperature in forging environments. This paper presents our gripper and the task to be solved in future works

Benefit of extra sensors for distinguishability of models of electric power trains in structure und parameter identification

Für viele Fragestellungen aus Reglerauslegung, Vorsteuerung und Zustandsüberwachung werden Prozessmodelle mit korrekter und physikalisch interpretierbarer innerer Struktur benötigt (phenomenologische Modelle). Die modellbasierten Ansätze werden in der Industrie vielfach noch nicht angewandt, weil die Modellerstellung ein hohes Maß an Expertenwissen und die langwierige Programmierung von Experimenten erfordert. Eine automatischen Struktur- und Parameteridentifikation ist dadurch bebrenzt, dass anhand des Ein-/Ausgangsverhaltens häufig die Unterscheidbarkeit von Modellen nicht gegeben ist. In dieser Veröffentlichung liegt der Fokus auf industriellen Anlagen mit elektrischem Antriebsstrang und einfacher Kinematik wie Regalbediengeräten, Werkzeugmaschinen und Positionierantrieben. Diese Systeme haben häufig nur einen Positions- und einen Stromsensor. Es wird in Experimenten gezeigt, dass durch Hinzunahme von einfach zu installierenden Zusatzsensoren wie Beschleunigungssensoren oder Drehratensensoren in einigen Fällen eine eindeutige Strukturidentifikation ermöglicht wird, auch wenn nur wenig Vorwissen über den Sensorort vorliegt

Assessment of ion kinetic effects in shock-driven inertial confinement fusion implosions using fusion burn imaging

The significance and nature of ion kinetic effects in D3He-filled, shock-driven inertial confinement fusion implosions are assessed through measurements of fusion burn profiles. Over this series of experiments, the ratio of ion-ion mean free path to minimum shell radius (the Knudsen number, NK) was varied from 0.3 to 9 in order to probe hydrodynamic-like to strongly kinetic plasma conditions; as the Knudsen number increased, hydrodynamic models increasingly failed to match measured yields, while an empirically-tuned, first-step model of ion kinetic effects better captured the observed yield trends [Rosenberg et al., Phys. Rev. Lett. 112, 185001 (2014)]. Here, spatially resolved measurements of the fusion burn are used to examine kinetic ion transport effects in greater detail, adding an additional dimension of understanding that goes beyond zero-dimensional integrated quantities to one-dimensional profiles. In agreement with the previous findings, a comparison of measured and simulated burn profiles shows that models including ion transport effects are able to better match the experimental results. In implosions characterized by large Knudsen numbers (NK3), the fusion burn profiles predicted by hydrodynamics simulations that exclude ion mean free path effects are peaked far from the origin, in stark disagreement with the experimentally observed profiles, which are centrally peaked. In contrast, a hydrodynamics simulation that includes a model of ion diffusion is able to qualitatively match the measured profile shapes. Therefore, ion diffusion or diffusion-like processes are identified as a plausible explanation of the observed trends, though further refinement of the models is needed for a more complete and quantitative understanding of ion kinetic effects

Laser-Plasma Interactions Enabled by Emerging Technologies

An overview from the past and an outlook for the future of fundamental laser-plasma interactions research enabled by emerging laser systems