University of Twente Publications
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On-chip microwave photonic beamformer circuits operating with phase modulation and direct detection - Zhuang, L.; Hoekman, M.; Taddei, C.; Leinse, A.; Heideman, R.G.; Hulzinga, A.; Verpoorte, J.; Oldenbeuving, R.M.; Dijk, P.W.L. van; Boller, K.J.; Roeloffzen, C.G.H.
We propose and experimentally demonstrate the working principles of two novel microwave photonic (MWP) beamformer circuits operating with phase modulation (PM) and direct detection (DD). The proposed circuits incorporate two major signal processing functionalities, namely a broadband beamforming network employing ring resonator-based delay lines and an optical sideband manipulator that renders the circuit outputs equivalent to those of intensity-modulated MWP beamformers. These functionalities allow the system to employ low-circuit-complexity modulators and detectors, which brings significant benefits on the system construction cost and operation stability. The functionalities of the proposed MWP beamformer circuits were verified in experimental demonstrations performed on two...
Nanosheet controlled epitaxial growth of PbZr0.52Ti0.48O3 thin films on glass substrates - Bayraktar, M.; Chopra, A.; Bijkerk, F.; Rijnders, G.
Integration of PbZr0.52Ti0.48O3 (PZT) films on glass substrates is of high importance for device applications. However, to make use of the superior ferro- and piezoelectric properties of PZT, well-oriented crystalline or epitaxial growth with control of the crystal orientation is a prerequisite. In this article, we report on epitaxial growth of PZT films with (100)- and (110)-orientation achieved by utilizing Ca2Nb3O10 (CNO) and Ti0.87O2 (TO) nanosheets as crystalline buffer layers. Fatigue measurements demonstrated stable ferroelectric properties of these films up to 5 × 109 cycles. (100)-oriented PZT films on CNO nanosheets show a large remnant polarization of 21 μC/cm2 that is the highest...
Development and validation of a patient-tailored dose regime in myocardial perfusion imaging using czt-spect - Dijk, J.D. van; Jager, P.L.; Mouden, M.; Slump, C.H.; Ottervanger, J.P.; Boer, J. de; Oostdijk, A.H.J.; Dalen, J.A. van
Guidelines for SPECT myocardial perfusion imaging (MPI) traditionally recommend a fixed tracer dose. Yet, clinical practice shows degraded image quality in heavier patients. The aim was to optimize and validate the tracer dose and scan time to obtain a constant image quality less dependent on patients’ physical characteristics.
125 patients underwent Cadmium Zinc Telluride (CZT)-SPECT stress MPI using a fixed Tc-99m-tetrofosmin tracer dose. Image quality was scored by three physicians on a 4-point grading scale and related to the number of photon counts normalized to tracer dose and scan time. Counts were correlated with various patient-specific parameters dealing with...