Stroboscopic Technique Research Articles

Surface Layer Dynamics During E-Beam Treatment

The interaction of a pulsed intense electron beam with a metal target leads to rapid heating and subsequent cooling of the surface layer, accompanied by a series of phase transitions among the solid, liquid, vapor, and plasma phase. As a consequence of the treatment, depending on the beam parameters, the metal target is eroded and a topographical pattern (waviness, craters, etc.,) evolves on its surface. Surface roughening, a major drawback of pulsed intense electron beam treatment, is well known but lacks comprehensive understanding. In this paper, the process of pulsed intense electron beam interaction with metal targets is studied with special attention to the dynamics of the target surface layer and the development of surface roughness. The pulsed electron beam facility GESA generates electron beams with power density 0.5-2 MW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , electron energy up to 120 keV, and pulse duration up to 200 μs. Different fast in situ diagnostics are applied to study the various processes occurring at the target surface: 1) melting and resolidification are visualized by time and space resolved imaging of the surface specular reflectivity; 2) spectroscopy is used to characterize the plasma phase adjacent to the target surface; 3) the evolution of irregularities and bubbles at the surface is studied by high-resolution microscopy; and 4) a stroboscopic imaging technique is applied to catch the evolution of the surface topography. The experimental data are compared with numerical simulations of heat transfer. All results and processes involved in pulsed intense electron beam treatment are discussed with respect to the target surface layer dynamics.

Long-observation-window band-selective homonuclear decoupling: Increased sensitivity and resolution in solid-state NMR spectroscopy of proteins

Sensitivity and resolution are the two fundamental obstacles to extending solid-state nuclear magnetic resonance to even larger protein systems. Here, a novel long-observation-window band-selective homonuclear decoupling (LOW BASHD) scheme is introduced that increases resolution up to a factor of 3 and sensitivity up to 1.8 by decoupling backbone alpha-carbon (Cα) and carbonyl (C′) nuclei in U-13C-labeled proteins during direct 13C acquisition. This approach introduces short (<200μs) pulse breaks into much longer (∼8ms) sampling windows to efficiently refocus the J-coupling interaction during detection while avoiding the deleterious effects on sensitivity inherent in rapid stroboscopic band-selective homonuclear decoupling techniques. A significant advantage of LOW-BASHD detection is that it can be directly incorporated into existing correlation methods, as illustrated here for 2D CACO, NCO, and NCA correlation spectroscopy applied to the β1 immunoglobulin binding domain of protein G and 3D CBCACO correlation spectroscopy applied to the α-subunit of tryptophan synthase.

Adhesive transfer in aero-engine abradable linings contact

Wear of abradable linings has been investigated on a scaled test rig platform, re-creating the wear mechanisms observed between the blade tip and abradable material that occur in an aero-engine compressor. The characterisation of the wear process has been performed using a stroboscopic imaging technique, capable of investigating the nature of the blade tip strike on the abradable, and the adhesive transfer of the material to the blade tip during a test. It was found in tests with low incursion rates that there was adhesive transfer, whereas with high incursion rates a cutting behaviour was observed. Analysis with the stroboscopic imaging technique allowed the adhesive transfer during the test as a function of the rub length to be recorded. Three phases were identified for adhesive transfer during test; an initiation phase with low rate of adhesion, steady state adhesion, and fracture of adhered material followed by re-initiation. These results also highlight how the standard practice of performing analysis of adhered material at the end of a test does not necessarily characterise the overall mechanics of adhesive transfer satisfactorily.

Experimental observation of chaotic phase synchronization of a periodically pump-modulated multimode microchip Nd:YVO4 laser

In this Letter we demonstrate the experimental observation of chaotic phase synchronization (CPS) in a periodically pump-modulated multimode microchip Nd:YVO4 laser. PS transition is displayed via the stroboscopic technique. We apply the recurrence probability and correlation probability of recurrence to estimate the degree of PS. The degree of PS is studied taking into account the modulation amplitude and modulation frequency. We also propose an experimental compatible numerical simulation to reflect the fact that the Arnold tongues are experimentally and numerically exhibited in the periodically pump-modulated multimode microchip Nd:YVO4 laser.

MEMS微变形镜测试技术及算法研究

A computer-controlled stroboscopic interferometer technique for measuring surface shape map and out-of-plane-deflections and static voltage versus displacement curve and resonant frequency is introduced.In-plane displacement of MEMS deformable mirrors is measured using the stroboscopic imaging and the computer microvision system and technique of sub-pixel location based on least-square curved surface fitting algorithm.The techniques of stroboscopic imaging and a five-step phase-shifting interferometer are used to obtain wrapped phase.The phase unwrapping algorithm is established to recover true phase which stands for object surface height.Consequently,the static and dynamic characteristics of MEMS deformable mirrors are obtained.The testing results show that the stroboscopic interferometer technique has the advantages of fast measuring speed and high measuring accuracy and realizing automatic control easily.

Energy cascading by triple-bubble interactions via time-delayed control

The triple-bubble interaction controlled by a precise time-delayed technique was investigated in detail with respect to different ignition times, heater spaces and sequential firing modes to promote efficient energy cascading and concentration. The target bubble, which was generated under a specific delay time with two auxiliary bubbles, can have a volume that is two or almost three times larger than that of a single bubble. This result overcomes the limitation of energy usage on an explosive microbubble under a constant heat flux. As the heater space decreases, stronger bubble–bubble interactions were obtained due to the hydrodynamic effect and the intensive pressure wave emission, resulting in highly enhancing and depressing bubble dynamics. Other interesting phenomena, such as bubble shifting, mushroom-shape bubble, rod-shape bubble and bubble extension among heaters, were also recorded by a high-speed phase-averaged stroboscopic technique, displaying special non-spherical bubble dynamics. Artificial manipulation of bubble behavior was further conducted in a two-level sequential firing process. Using various volumetric combinations, the adjustable multi-level fluid transportation can be realized by a digital time-delayed control. The above-mentioned information can be applied to not only the design and operation of inkjet printheads but also cavitation research and fluid pumping in microdevices.

New Data on the Motion of the Normal and Reconstructed Tympanic Membrane

The sound-induced motion of the tympanic membrane has features that are most consistent with modal responses to a uniform stimulus. Conceptual models of the coupling of tympanic membrane motion to the ossicular chain can be classified as either modal responses to a uniform stimulation of the entire membrane or traveling wave models in which sound energy is captured at the membrane's rim and travels along the surface to the umbo. The stroboscopic holography technique we use can separate strongly modal or traveling wave-dominated motions of the tympanic membrane surface. We use computer-aided optoelectronic holography with stroboscopic illumination to measure the magnitude and phase of the sound-induced motion of more than 40,000 points on the surface of the tympanic membrane in cadaveric human temporal bones. Our techniques are sensitive to motions of the membrane as small as 0.01 µm and allow determinations of membrane displacement at frequencies as large as 20 kHz. We report clear signs of both modal tympanic membrane responses and traveling waves on the human tympanic membrane. Modal responses are seen throughout the frequency range, whereas the traveling waves are most apparent between 2 and 8 kHz. In general, the magnitudes of the traveling waves are small compared with the modal magnitudes. Much of the motion of the tympanic membrane is well approximated by modal motions of the tympanic membrane surface. This conclusion has implications for eardrum pathology and its treatment.

Time delay correction of the synchrogram for optimized detection of cardiorespiratory coordination

The cardiorespiratory synchrogram, a graphical tool based on the stroboscopic technique, is an established method for evaluating phase-locking between cardiac and respiratory oscillators. In the original method, the phase of the respiratory oscillator is observed at the instants of time when the phase of the cardiac oscillator attains a certain value. In this article, we introduced an additional adaptive delay in the cardiac oscillator based on the maximisation of the cross-correlation or symbolic coupling traces between the phases of respiration and the delayed R-R intervals. We then investigated phase coordination in thirteen normal subjects (five males, eight females; age: 19-24 years) for different body postures. Cardiorespiratory coordination was observed to be significantly reduced in the upright position (supine vs. upright: 11.9 ± 5.1 vs. 6.9 ± 3.6, P < 0.05). Compared to the original algorithm we observed an increase in the detection of average cardiorespiratory coordination (supine original vs. delay: 11.9 vs. 18.9%), together with a decrease in standard deviation of the percentage of coordination in all the subjects, after introducing the heart rate delay (supine original vs. delay: 5.1 vs. 4.4%). In conclusion, the performance of the synchrogram technique was improved by including an adaptive delay in the cardiac oscillator.

The dynamics of a stage-structured predator–prey system with impulsive effect and Holling mass defence

In this paper, a stage-structured Holling mass defence predator-prey model with impulsive effect is investigated. By using comparison theorem and the stroboscopic technique, sufficient conditions for the global attractivity of mature prey-extinction periodic solution and permanence of the system are obtained. Furthermore, the numerical analysis is also inserted to illuminate the feasibility of the theoretical results.

Effect of Dissolved Gases on the Evolution of a Vapor Cavity Formed During Explosive Evaporation

With reference to developed microfluidic systems, an experimental investigation is performed to define the effect of dissolved gases on the explosive evaporation of liquid in a confined microchamber. A stroboscopic imaging technique was used to visualize the stages of explosive evaporation. It was found that for liquids containing dissolved gases, a large, long-living gas bubble forms under the impulsively heated surface. During vapor cavity growth and collapse, the gas bubble is deformed and destroyed. Complicated bubble structures are formed. A gas bubble strongly damps the growth of the vapor cavity, which should be considered for design purposes.

Back Cover: Probing the Intrinsic Switching Kinetics of Ultrathin Thermoresponsive Polymer Brushes (Angew. Chem. Int. Ed. 19/2011)

Stimuli-responsive polymer brushes are well known for their unique switching properties. In their Communication on page 4513 ff., N. Hartmann and co-workers describe an all-optical stroboscopic technique that provides unprecedented insight into the temperature-dependent intrinsic switching kinetics of such ultrathin polymer coatings. In contrast to hitherto reported approaches, response times range from the micro- to the millisecond time scale.

Identification for Chaos and Subharmonic Responses in Coupled Forced Duffing's Oscillators

ABSTRACTIn this paper, a response integral quantity method is proposed. This technique provides a quantitative characterization of system responses and can assist the role of the traditional stroboscopic technique (Poincaré section method) in observing bifurcations and chaos of the nonlinear oscillators. We numerically analyze and identify the chaos and subharmonic responses in the forced coupled Duffing's oscillators in which we find that chaotic behaviors and high-order subharmonic responses exist. Due to the signal response contamination of system, it is difficult to identify the high-order responses of the subharmonic motion because of the sampling points on Poincaré map being very close to each other. Even the system responses are subject to misjudgments. The simulation results, however, show that the highorder subharmonic and chaotic responses and their bifurcations can be observed effectively.

Imaging electrical resonance in hair cells

The mechanosensory hair cells of many auditory receptor organs are tuned by an electrical resonance that increases their responses to stimulation over a narrow band of frequencies. The small oscillations of membrane potential characteristic of this phenomenon have previously been detectable only through intracellular electrode measurements, which are laborious and preclude analysis at the level of an entire sensory organ. We used a voltage-sensitive dye to image hair-cell electrical resonance in an intact preparation of the bullfrog's sacculus, a receptor organ sensitive to low-frequency seismic and auditory stimuli. Imaging revealed distinct populations of hair cells whose resonant response varied with the frequency of transepithelial electrical stimulation. Most of the hair cells in the saccular epithelium in vitro were electrically tuned to stimulation at 25-50 Hz. The frequency dependence of the fluorescence signal was sensitive to pharmacological blockade of large-conductance Ca(2+)-sensitive K(+) channels and to enzymatic digestion. At an elevated concentration of Ca(2+), we observed transient fluorescence signals that probably represented action potentials. The stroboscopic imaging and analysis techniques described here present a general approach for studying subthreshold oscillations in electrically excitable cells.

Direct observation of dynamic surface acoustic wave controlled carrier injection into single quantum posts using phase-resolved optical spectroscopy

A versatile stroboscopic technique based on active phase-locking of a surface acoustic wave to picosecond laser pulses is used to monitor dynamic acoustoelectric effects. Time-integrated multichannel detection is applied to probe the modulation of the emission of a quantum well for different frequencies of the surface acoustic wave. For quantum posts we resolve dynamically controlled generation of neutral and charged excitons and preferential injection of holes into localized states within the nanostructure.

Real-time direct measurement of field rise time and dynamic instability of perpendicular writers

A method is presented to measure the dynamic write field of a perpendicular recording head directly in the time domain using a tunneling magnetoresistive read sensor. The method is used to measure the magnetic field rise time of two different writer designs and real-time measurements of the write field without averaging are demonstrated, enabling investigation of transient switching behavior that would not be observed with stroboscopic or frequency-domain techniques. A dynamic instability is observed and characterized in a particular writer design and is attributed to the insertion of an antiferromagnetic coupling layer in the writer pole.

Optimizing the accuracy and precision of the single-pulse Laue technique for synchrotron photo-crystallography

The accuracy that can be achieved in single-pulse pump-probe Laue experiments is discussed. It is shown that with careful tuning of the experimental conditions a reproducibility of the intensity ratios of equivalent intensities obtained in different measurements of 3-4% can be achieved. The single-pulse experiments maximize the time resolution that can be achieved and, unlike stroboscopic techniques in which the pump-probe cycle is rapidly repeated, minimize the temperature increase due to the laser exposure of the sample.

Dynamic stabilization of the ultradamped inverted pendulum.

The dynamic behavior of the damped inverted pendulum is analogous to the modes of fluid systems with nonzero viscosity where a denser fluid is situated above a lighter fluid (e.g., the Rayleigh–Taylor instability). Thermoacoustic devices have such configurations whenever a hot heat exchanger is situated below a cold heat exchanger. It has been shown that such systems can be stabilized by effectively modulating gravity and can be described by a damped Hill equation. A numerical solver was developed that uses a stroboscopic technique to determine whether solutions are stable (bounded) or unstable (unbounded). While it is sometimes assumed that the stability boundaries of undamped systems bound the damped cases, for large values of damping (Q < 0.05, where Q is the quality factor), the numerical solution predicts that damping can destabilize the system for certain regions of the parameter space. Results of an experiment performed by the authors using a physical pendulum and eddy current damping to verify this rather counterintuitive result are described. [Research supported by the Office of Naval Research and ARL Exploratory and Foundational Research Program.]

Fetal maternal heart rate entrainment under controlled maternal breathing

Event Abstract Back to Event Fetal maternal heart rate entrainment under controlled maternal breathing Peter V. Leeuwen1*, Daniel Geue2, Marko Thiel3, Silke Lange1, Mamen Romano3, Jürgen Kurths4 and Dietrich H. Grönemeyer1 1 University of Witten / Herdecke, Dept. of Radiology / Microtherapy, Germany 2 VISUS Technology Transfer, Department of Psychology, Faculty of Arts and Sciences, Germany 3 University of Aberdeen, Department of Physics, United Kingdom 4 Potsdam Institute for Climate Impact Research, Department of Psychology, Faculty of Arts and Sciences, Germany There is evidence that, during pregnancy, fetal and maternal cardiac activity may coordinate over short periods of time. Aim of this work was to investigate whether controlled paced maternal respiration has an effect on the occurrence of fetal-maternal heart rate synchronization. In 6 healthy pregnant women (34th - 40th week of gestation) we obtained simultaneous 5 min. fetal and maternal magnetocardiograms (MCG) at maternal respiration rates of 10, 12, 15 and 20 cpm as well as under spontaneous breathing. Fetal and maternal RR interval time series were constructed for each MCG data set and synchrograms were obtained using the stroboscopic technique. Synchronization epochs (SE) >10s were identified in these original data. Furthermore, "twin surrogate" data sets of the maternal MCG were constructed, combined with the fetal MCG data and SE were identified in these surrogate data. In the original data, there was a higher number of SE found at 20 cpm respiratory rate compared to other rates. This was not evident in the surrogate data. Fewer SE were found at lower rates (10 cpm) both in the original and surrogate data. Examination of the phase of fetal R peaks relative to maternal RR cycles showed that in the original data there was a clear phase preference in the 20 cpm data. This preference was not found in the surrogate data. These results were reproduced on the basis of a mathematical model incorporating the essential elements of fetal and maternal heart rates and their variability. We conclude that fetal-maternal heart rate entrainment may be induced by high maternal respiratory rates and that chance fetal-maternal heart rate coordination may be inhibited by low maternal respiratory rates. Conference: Biomag 2010 - 17th International Conference on Biomagnetism , Dubrovnik, Croatia, 28 Mar - 1 Apr, 2010. Presentation Type: Poster Presentation Topic: Fetal and neonatal biomagnetism Citation: Leeuwen PV, Geue D, Thiel M, Lange S, Romano M, Kurths J and Grönemeyer DH (2010). Fetal maternal heart rate entrainment under controlled maternal breathing. Front. Neurosci. Conference Abstract: Biomag 2010 - 17th International Conference on Biomagnetism . doi: 10.3389/conf.fnins.2010.06.00099 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 23 Mar 2010; Published Online: 23 Mar 2010. * Correspondence: Peter V Leeuwen, University of Witten / Herdecke, Dept. of Radiology / Microtherapy, Herdecke, Germany, sci@van-leeuwen.de Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Peter V Leeuwen Daniel Geue Marko Thiel Silke Lange Mamen Romano Jürgen Kurths Dietrich H Grönemeyer Google Peter V Leeuwen Daniel Geue Marko Thiel Silke Lange Mamen Romano Jürgen Kurths Dietrich H Grönemeyer Google Scholar Peter V Leeuwen Daniel Geue Marko Thiel Silke Lange Mamen Romano Jürgen Kurths Dietrich H Grönemeyer PubMed Peter V Leeuwen Daniel Geue Marko Thiel Silke Lange Mamen Romano Jürgen Kurths Dietrich H Grönemeyer Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

The measurement of the modal strain fields using digital shearography

This work presents a Michelson shearography interferometer configuration associated with stroboscopic double illumination technique for the measurement of modal rotation fields and their strain fields on a clamped circular aluminium plate. The speckle pattern is frozen by the synchronization between the LASER illumination and the modal vibration of the object. The quantitative evaluation is performed for each digital shearogram using a time modulation technique. The setup of double illumination LASER with out-of-plane opposite sensitivity allows the two phase maps measurement of the modal spatial gradient. The modal rotation and strain fields are extracted by the combination of this two digital phase maps. Image processing techniques are applied on the phase maps to obtain full-field measurements using a dedicated post-processing algorithm. Finally, is presented a comparison between the experimental measurement and the numerical solution.

Subcoercive Cyclic Electrical Loading of Lead Zirconate Titanate Ceramics II: Time‐Resolved X‐Ray Diffraction

Structural changes such as non‐180° domain wall motion and lattice strains in Pb(Zr,Ti)O3 ceramics are measured during the application of subcoercive cyclic electric fields using time‐resolved high‐energy X‐ray diffraction with a stroboscopic data collection technique. The contributions to the electric‐field‐induced strains from non‐180° domain wall motion and lattice distortions are determined as a function of material composition and type of dopant. For the different compositions studied, the largest strains due to non‐180° domain wall motion are measured for La‐doped tetragonal ceramics with a composition close to the morphotropic phase boundary. It is further observed that strain contributions from both non‐180° domain wall motion and lattice distortions can be nonlinear with respect to the applied electric field. The correlation between the electric‐field‐induced structural changes and the macroscopic piezoelectric properties is discussed.