Refine
Year of publication
- 2021 (13) (remove)
Document Type
Language
- English (13) (remove)
Has Fulltext
- no (13)
Is part of the Bibliography
- no (13)
Keywords
- Fluorescence lifetime imaging (2)
- GaN half-bridge (2)
- Image processing algorithms (2)
- Phase shift (2)
- fluorescence (2)
- ADC (1)
- Capacitive coupling (1)
- Confocal laser scanning microscopy (1)
- Delta-Sigma (1)
- Diode lasers (1)
Institute
- Fakultät für Ingenieurwissenschaften (13) (remove)
A parallel design concept of Delta-Sigma modulators that optimizes the resolution and the bandwidth for a highly dynamic position control in industrial applications. The idea is realized on a printed circuit board and tested by using a comprehensive measurement setup. The effective number of bits is increased by 2.5 bits at a fixed frequency. For a constant resolution, the design approach allows smaller filter lengths and a decrease of the delay by 25%.
A Novel Approach to Identify Wood Species Optically using Fluorescence Lifetime Imaging Microscopy
(2021)
This contribution presents the results obtained with fluorescence lifetime imaging microscopy (FLIM)within the optical identification and differentiation of the four wood species walnut, beech, spruce, and maple. The experimental setup as well as the evaluation algorithm, with which the experiments were carried out, is explained briefly.
In this research we present a short distance capacitively coupled wireless power transfer (WPT) system with a self-oscillating half-bridge converter, which uses a positive feedback signal from the WPT system. By this novel implementation we find additional features of the system compared to linear amplifier based systems. With the DC bias voltage supplying the power converter, we achieve a controllable output power, tunable self-oscillation frequency and extension of the self-oscillation range. We present the analytical expressions for the converter waveforms. The theoretical analysis is confirmed by circuit simulation results and measurements on a prototype featuring a half-bridge converter with Gallium-Nitide (GaN) HEMTs. We achieve a system efficiency of 93% at a load power of 83W and 150kHz switching frequency.
We present the design of a half-bridge converter
for a capacitively coupled wireless power transfer
system. The load signal acts as a positive feedback
signal for a self-oscillation circuit which generates the
driving gate signals for the converter. Our research
reveals a robust wireless operation for a large range
of load resistors and coupling capacitors. Based on an
electric network analysis we obtain design criteria for
self-oscillation and for the power transfer. The theoretical
predictions are confirmed by circuit simulation
and measurement results on a converter prototype with
GaN-HEMTs. We report on a transfer efficiency of 92%
for a power greater than 50W at a switching frequency
of 300kHz and 200V DC link voltage.
A crucial problem in concrete engineering is the corrosion of steel reinforcements. Polymer fibers as alternative reinforcement material can prevent corrosion; however, high adhesion to concrete and good fiber mechanics are necessary for polymers to be considered as an alternative reinforcement. This study tested different thermoplastic polymer materials to evaluate their level of adhesion to concrete. The adhesion properties of different self‐drawn polymer fibers were analyzed by extracting the fibers from concrete using single fiber pull‐out test (SFPT). To determine the adhesion mechanism, different polymer properties were analyzed and correlated to SFPT. Strong evidence was found that the fibers mechanical properties correlate with SFPT. Roughening the fiber surface increases the SFPT results significantly. While highly polar materials can support the adhesion process, a clear correlation could not be found. This study identifies high stiffness and roughness as the crucial properties of polymer fibers used in concrete engineering. If these factors can be engineered into the fiber, polymer fibers can present an alternative to steel in concrete reinforcement.