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Nieuwegein, Netherlands

Lee C.J.,University of Twente | Lee C.J.,FOM Institute DIFFER | Boller K.J.,University of Twente
Optics Express | Year: 2012

With recent developments in microscopy, such as stimulated emission depletion (STED) microscopy, far-field imaging at resolutions better than the diffraction limit is now a commercially available technique. Here, we show that, in the special case of a diffusive regime, the noise-limited resolution of STED imaging is independent of the saturation intensity of the fluorescent label. Thermal motion limits the signal integration time, which, for a given excited-state lifetime, limits the total number of photons available for detection. © 2012 Optical Society of America. Source


Peeters F.J.J.,TU Eindhoven | Van De Sanden M.C.M.,TU Eindhoven | Van De Sanden M.C.M.,FOM Institute DIFFER
Plasma Sources Science and Technology | Year: 2015

The determination of internal electrical discharge parameters, such as plasma current and burning voltage, in dielectric barrier discharges (DBDs) relies on an equivalent circuit based on series capacitances for the discharge gap and dielectric material. An effective dielectric capacitance for the discharge can be obtained from Q-V diagrams, also called Lissajous figures, during discharging, which may not be a constant for a given DBD geometry. It has been shown experimentally that microdischarges, which can consist of narrow channels in either diffuse or filamentary form, may not fully cover the available discharge area. Here, we report measurements of the effective dielectric capacitance as a function of applied voltage amplitude in a DBD plasma jet system operating in N2 and derive equations to determine the conductively transferred charge, burning voltage and the proportion of the electrode surface over which discharging occurs when the effective dielectric capacitance is not equal to the dielectric capacitance of the complete electrode area. © 2015 IOP Publishing Ltd. Source


Boessenkool H.,FOM Institute DIFFER | Boessenkool H.,TU Eindhoven | Abbink D.A.,Technical University of Delft | Heemskerk C.J.M.,Heemskerk Innovative Technology BV | And 2 more authors.
IEEE Transactions on Haptics | Year: 2013

Telemanipulation allows human to perform operations in a remote environment, but performance and required time of tasks is negatively influenced when (haptic) feedback is limited. Improvement of transparency (reflected forces) is an important focus in literature, but despite significant progress, it is still imperfect, with many unresolved issues. An alternative approach to improve teleoperated tasks is presented in this study: Offering haptic shared control in which the operator is assisted by guiding forces applied at the master device. It is hypothesized that continuous intuitive interaction between operator and support system will improve required time and accuracy with less control effort, even for imperfect transparency. An experimental study was performed in a hard-contact task environment. The subjects were aided by the designed shared control to perform a simple bolt-spanner task using a planar three degree of freedom (DOF) teleoperator. Haptic shared control was compared to normal operation for three levels of transparency. The experimental results showed that haptic shared control improves task performance, control effort and operator cognitive workload for the overall bolt-spanner task, for all three transparency levels. Analyses per subtask showed that free air movement (FAM) benefits most from shared control in terms of time performance, and also shows improved accuracy. © 2013 IEEE. Source


Van Der Meer R.,MESA Institute for Nanotechnology | Kozhevnikov I.V.,Russian Academy of Sciences | Bastiaens H.M.J.,MESA Institute for Nanotechnology | Boller K.-J.,MESA Institute for Nanotechnology | And 2 more authors.
Optics Express | Year: 2013

An extended set of coupled wave equations were derived to describe non-idealized lamellar multilayer grating structures with properties as obtained with state-of-the-Art fabrication techniques. These generalized equations can include all relevant effects describing the influence of passivation and contamination layers, non-rectangular lamel profiles and sidewall scalloping. The calculations showed that passivation and contamination plays an important role in that it may significantly reduce peak reflectivity. However, we also derived a condition for layer thicknesses having negligible effects. Slightly positive tapered lamel profiles are shown to further reduce the bandwidth as compared to a rectangular lamel profile, whereas negative tapers significantly increased the bandwidth. The influence of intriguing effects, such as the sidewall scalloping caused by Bosch Deep Reactive Ion Etching, are also modeled. We identified the signature of such scalloping as additional side peaks in the reflectivity spectrum and present parameters with which these can be effectively suppressed. © 2013 Optical Society of America. Source


Alpers A.,TU Munich | Gritzmann P.,TU Munich | Moseev D.,FOM Institute DIFFER | Moseev D.,Max Planck Institute for Plasma Physics (Garching) | Salewski M.,Technical University of Denmark
Computer Physics Communications | Year: 2015

Particle tracking velocimetry in 3D is becoming an increasingly important imaging tool in the study of fluid dynamics and combustion as well as plasmas. We introduce a dynamic discrete tomography algorithm for reconstructing particle trajectories from projections. The algorithm is efficient for data from two projection directions and exact in the sense that it finds a solution consistent with the experimental data. Non-uniqueness of solutions can be detected and solutions can be tracked individually. © 2014 Elsevier B.V. All rights reserved. Source

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