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High frequency, broadband ultrasound providing high resolution is found to satisfy several clinical and diagnostic requirements in dermatology. The imaging procedure with strongly focused single element transducers can be optimized by application of a modified scan concept (B/D-Scan concept, "brightness / depth "). Furthermore, texture features and(More)
In this paper flow estimation approaches using high frequency ultrasound (20-150 MHz) are compared in conjunction with broadband transmit signals. Simulations show that estimation strategies matched to broadband transmit signals, known as wideband techniques, lead to a high resolution and a robust flow estimation. We implemented a high frequency Pulsed Wave(More)
For slowly evolving, discrete-time-dependent systems of difference equations (iterated maps), we believe the simplest means of demonstrating the validity of the averaging method at first order is by way of a lemma that we call Besjes' inequality. In this paper, we develop the Besjes inequality for identity maps with perturbations that are (i) at low-order(More)
When polarized particles are accelerated in a synchrotron, the spin precession can be periodically driven by Fourier components of the electromagnetic fields through which the particles travel. This leads to resonant perturbations when the spin-precession frequency is close to a linear combination of the orbital frequencies. When such resonance conditions(More)
Free-electron lasers (FELs) generate femtosecond XUV and X-ray pulses at peak powers in the gigawatt range. The FEL user facility FLASH at DESY (Hamburg, Germany) is driven by a superconducting linear accelerator with up to 8000 pulses per second. Since 2014, two parallel undulator beamlines, FLASH1 and FLASH2, have been in operation. In addition to the(More)
We present a mathematical analysis of planar motion of energetic electrons moving through a planar dipole undulator, excited by a fixed planar polarized plane wave Maxwell field in the x-ray free electron laser (FEL) regime. Our starting point is the 6D Lorentz system, which allows planar motions, and we examine this dynamical system as the wavelength of(More)
In this paper, a hybrid FEM/BEM approach for solving Maxwell's equations in the frequency domain is presented. The method can be applied to uniform transmission lines and waveguides containing anisotropic and lossy media. Based on a rigorous full-wave analysis, frequency-dependent propagation constants and electromagnetic elds can be obtained. Spurious(More)
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