Papers by Gerhard Lindner
14th Conference on Education and Training in Optics and Photonics: ETOP 2017, 2017
Sciences (OTHR) established an English taught international cooperative bachelor program in the a... more Sciences (OTHR) established an English taught international cooperative bachelor program in the area of Engineering Physics/Optoelectronics. Students from China study their first four semesters at USST. They continue their studies in Germany for the last three semesters, including an internship and a bachelor thesis, graduating with a Chinese and a German bachelor degree. Students from Germany study their third and fourth semester at USST to gain international experience. While the first cohort of Chinese students is currently in Germany, the second cohort of German students is in Shanghai. Up to now the feedback regarding this study program is completely positive, thus it is planned to develop it further.
CryoSense: Redesign using advanced technology
This Technical Note contains a study of advanced sensor technologies for a cryogenic benchmark ex... more This Technical Note contains a study of advanced sensor technologies for a cryogenic benchmark experiment. The benchmark experiment is a redesign of baseline experiment 2 presented in Technical Note 4 of the activity, with state-of-the-art ‘conventional’ sensor technologies now replaced by alternative measurement methods. In a comprehensive study different technologies are first described, then evaluated in terms of application potential and specifically adapted TRL scale. This includes: Particle Velocimetry, Ultrasound Tomography, specialised ultrasound methods (Lamb-Waves, Quasi-Scholten-Waves), Electrical Capacitance Tomography, Optical Tomography, Time of Flight Cameras, Wire-Mesh Sensors and Microwave/RF-methods. The intended application in this Note is the detection of free surface topologies of cryogenic liquids (fill level, dynamics due to external acceleration, boiling at the free surface). Recommendations regarding required experimental test to increase technology readines...
Sensors for various fluid physical quantities play a vital role in the management of cryogenic li... more Sensors for various fluid physical quantities play a vital role in the management of cryogenic liquid propellants (hydrogen, oxygen, methane), used worldwide in launchers such as the European Ariane rockets. In addition, measurement devices are particularly central in all basic scientific fluid experimentation, investigating for instance liquid sloshing, free liquid surface movement, boiling or bubble formation. The results of these experiments in microgravity and on ground enable the efficient design of present-day cryogenic launcher (upper) stages and (as possible future applications) of long-term orbital propellant storage facilities, in-orbit refuelling stations and interplanetary cryogenic propulsion. These utilizations call for sensor technology to efficiently perform propellant mass gauging, determine fill-levels, temperature fields, phase change quantities and bubble formation in a nonintrusive fashion. An overview of various candidate cryogenic sensor technologies currently...
Journal of The Electrochemical Society, 2018
A previous experiment showed that the rate of the electropolishing of a copper anode may be incre... more A previous experiment showed that the rate of the electropolishing of a copper anode may be increased by twofold when generating a 60 KHz to 1.7 MHz frequency vibration in the anode. In this work we use theory to elucidate the mechanisms by which the vibration may enhance the transport of ions in the electrolyte solution and support the formation of dents in the anode, which was observed in experiment. We find that in the limit of weak ion convection the transport of ions mainly supports the formation of dents in the anode. However, in the limit of prominent ion convection we find an appreciable contribution of the vibration to the efficiency of the electropolishing process, in accordance with the previous experimental findings. The contribution of the vibration to ion transport is given by 2 √ PeDkC s /π √ π, in which the Peclét number, Pe, quantifies the ratio between the convective and diffusive fluxes of ions, and D, k, and C s are the diffusion coefficient of the ions, the wavenumber of the vibration, and the solubility limit of the ions in the electrolyte.
Proceedings, 2018
An ultrasound sensor system based on the transmission-mode approach is developed to enable the mo... more An ultrasound sensor system based on the transmission-mode approach is developed to enable the monitoring and sensing of cryogenic liquids and gases—especially gaseous bubbles and gas-liquid interfaces in liquid nitrogen (LN2). Common sensors do not meet requirements of cryogenic and microgravity-environments. Therefore, a special encapsulation design for the optimization of the electrical connection and the mechanical coupling of the ultrasound sensors is needed. The ultrasound system is qualified in LN2 and is able to measure bubbles (size and location) and fill levels with a high spatial resolution in a submillimetre range and a sampling rate of more than 500 Hz.
Propulsion of droplets on non-piezoelectric substrates via mode conversion of Lamb waves
2009 IEEE International Ultrasonics Symposium, 2009
ABSTRACT
Physics Procedia, 2015
The formation of stable vortex flow pattern has been observed at liquid filled aluminum wells of ... more The formation of stable vortex flow pattern has been observed at liquid filled aluminum wells of 15 to 30 mm diameter when Lamb waves are excited on the bottom of the wells by piezoelectric transducers operated at a frequency of 1 MHz. The shape of the vortex pattern changed with the position of the transducer. Strong differences in mixing times were observed between water and ethanol when the filling level was changed and a remarkable reduction of mixing time was achieved by the addition of a small amount of detergent to water at small filling levels. Besides mixing of liquids thermal equilibration within a liquid volume was accelerated by acoustic streaming.
Journal of Bionic Engineering, 2021
In a biomimetic approach the feasibility of liquid flow actuation by vibrating protruding structu... more In a biomimetic approach the feasibility of liquid flow actuation by vibrating protruding structures excited via guided acoustic waves is investigated. Inspired by periodically beating cilia the loop part of a punched metallic hook-and-loop tape with tilted protruding loops was used as a waveguide for plate waves in water. Such waves were excited in the frequency range of 110 Hz to 220 Hz by directly coupling the tape to a loudspeaker membrane. A flow generated in the tilt direction of the loops with velocities up to 60 mm·s−1 was visualized by ink droplets deposited on the tape. The phenomenon persisted, when the protruding length of the loops was reduced by decreasing the protrusion angle. However, after closing the punch holes near the loops with sticking tape streaming could not be observed any longer. The same happened with open punch holes when the ink was replaced by glycerol. Low-frequency acoustic streaming around vibrating sharp edges is proposed as an explanation for the ...
Combined PAC and electron-channeling studies of He-defect interaction in CU between 300 and 900 K
Radiation Effects
ABSTRACT
Water Science and Technology
Three sediment cores taken at positions in Lake Constance strongly influenced by the river Rhine ... more Three sediment cores taken at positions in Lake Constance strongly influenced by the river Rhine and one core taken at a position less influenced by this most important tributary were investigated with respect to the depth distribution of Cesium radionuclides in order to follow up transport processes of contaminated clay particles from the catchment system into the lake. In the depth distributions of Cs-137 well resolved maxima from the Chernobyl fallout and from the nuclear weapons testing fallout were found. Additionally, the high-water event of 1987 is reflected by the depth distributions of Cs-137 at the positions influenced by the river Rhine. The total inventories of Cs-137 activity from the Chernobyl fallout and the nuclear weapon testing fallout are higher compared to the input across the water surface at the positions influenced by the river Rhine, indicating the importance of fluvial input.
Visualization of the Interaction of Guided Acoustic Waves with Water by Light Refractive Vibrometry
Ultrasonics
Sensors
The monitoring of liquid-filled tubes with respect to the formation of soft deposition layers suc... more The monitoring of liquid-filled tubes with respect to the formation of soft deposition layers such as biofilms on the inner walls calls for non-invasive and long-term stable sensors, which can be attached to existing pipe structures. For this task a method is developed, which uses an ultrasonic clamp-on device. This method is based on the impact of such deposition layers on the propagation of circumferential guided waves on the pipe wall. Such waves are partly converted into longitudinal compressional waves in the liquid, which are back-converted to guided waves in a circular cross section of the pipe. Validating this approach, laboratory experiments with gelatin deposition layers on steel tubes exhibited a distinguishable sensitivity of both wave branches with respect to the thickness of such layers. This allows the monitoring of the layer growth.
Defects in In simultaneously observed by channeling and PAC
Nuclear Instruments and Methods in Physics Research
ABSTRACT
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
Biologically induced precipitation of settling material in Lake Constance is one of the key mecha... more Biologically induced precipitation of settling material in Lake Constance is one of the key mechanisms in the geochemistry of the lake. In order to determine the role of several elements involved in these cycles multielement analysis of particulate matter (PM) was performed by PIXE using the 350 keV ion accelerator at Konstanz. PIXE was chosen as the analytical method because of the large number of samples and small amounts of solid material. Elements of Mg to Fe were the main interest, whereas traces of heavy metals were of less significance, and major elements like Si should be determined as well as minor components like Mn. Therefore, the rather low proton energy of 350 keV seemed to be sufficient and adequate. The measurements clearly show correlations between biological activity and enhanced precipitation for some elements. Here we report on Si and Mn, two components of PM, which differ greatly in their annual concentration changes due to fixation in the euphotic zone (Si) or as a result of mediation by hypolimnetic microorganisms (Mn).
Electron-Positron-Channeling and Mössbauer-Effect Studies of Indium-Vacancy Complexes in Ion-Implanted Nickel
Materials Science Forum
Measurement of the properties of liquids based on the dispersion of Lamb waves in an acoustic waveguide
Physics Procedia
... Physics Procedia Volume 3, Issue 1, 1 January 2010, Pages 959-964 International Congress on U... more ... Physics Procedia Volume 3, Issue 1, 1 January 2010, Pages 959-964 International Congress on Ultrasonics, Santiago de Chile, January 2009. ... International Congress on Ultrasonics, Universidad de Santiago de Chile, January 2009. ...
Measurement of physical characsteristics or physical properties of viscous media by means of Rayleigh waves
TOPICAL REVIEW: Sensors and actuators based on surface acoustic waves propagating along solid liquid
J Phys D Appl Phys, 2008
State detection device on a panel or a wall of an appliance
Device for detecting a condition at a plate or wall of a domestic appliance
Uploads
Papers by Gerhard Lindner