Real-time time-frequency analysis in MNE-CPP. - In: Biomedical engineering, ISSN 1862-278X, Bd. 65 (2020), S. S31
Enthalten in: Magnetic Methods in Medicine: Bioelectromagnetism (2)
https://doi.org/10.1515/bmt-2020-6008
Holistic calibration of screw threads based on a three-dimensional approach :
Ganzheitliche Kalibrierung von Gewinden auf Basis eines dreidimensionalen Ansatzes. - In: Technisches Messen, ISSN 2196-7113, Bd. 87 (2020), S. S16-S21
Gewinde sind Maschinenelemente mit vielseitiger Funktionalität. Sie werden zum Befestigen, Verbinden, Abdichten oder Zentrieren verwendet und in großen Stückzahlen hergestellt. Dabei steigen die Anforderungen an die Fertigung und Qualitätssicherung stetig an. Nach aktuellen Normen und Richtlinien erfolgt die Prüfung der Bestimmungsgrößen an Gewinden stichprobenartig in wenigen festgelegten Axialschnitten und Prüfebenen. Die komplex geformten und stark gekrümmten Werkstückoberflächen von Gewindeflanken werden deshalb hinsichtlich ihrer Funktionalität unzureichend bewertet. Das neuartige Messverfahren basiert auf einem dreidimensionalen mathematischen Modell zur Beschreibung der Gewindegeometrie. Die Aufnahme der Messpunkte als Ist-Punktewolke erfolgt durch eine flächenhafte Messstrategie auf konventionellen Koordinatenmessgeräten. Der anschließende ganzheitliche Auswertealgorithmus ermöglicht erstmals die Bestimmung aller relevanten Bestimmungsgrößen am Gewinde auf Basis eines einzigen Datensatzes. Des Weiteren liefert der neue Auswertealgorithmus erstmals ein Ergebnis für die lokalen Bestimmungsgrößen, welche zur Berechnung des Paarungsflankendurchmessers benötigt werden.
https://doi.org/10.1515/teme-2020-0035
Bi-static delay-Doppler reference for cooperative passive vehicle-to-X radar applications. - In: IET microwaves, antennas & propagation, ISSN 1751-8733, Bd. 14 (2020), 14, S. 1749-1757
Automotive radar systems are indispensable for advanced driver assistance systems and traffic safety. Besides existing monostatic radar techniques, bi-static radar sensing like passive coherent location offers additional options to improve the radar visibility of vulnerable road users. Regarding the testing and evaluation of signal processing algorithms including parameter estimation, it is essential to provide electromagnetically shielded and reproducible measurement conditions, in addition to field tests in real traffic scenarios. This study describes the possibility to emulate relevant performance parameters for bi-static radar scenarios in the frequency range from 1 GHz to 6 GHz in a metal-shielded semi-anechoic chamber. Of special interest are the bi-static angle between transmitter, target, and receiver, and the resulting bi-static Doppler frequencies of a realistic vehicular traffic scenario. According to the concept of cooperative passive coherent location, Doppler scattering measurements are presented and compared to electromagnetic simulations. The authors find promising agreement between measured and ground truth data in the delay-Doppler spectrum.
https://doi.org/10.1049/iet-map.2019.0991
Evaluation of spatio-temporal resolution of MPI scanners with a dynamic bolus phantom. - In: International journal on magnetic particle imaging, ISSN 2365-9033, Bd. 6 (2020), 2, 2009011, S. 1-3
https://doi.org/10.18416/IJMPI.2020.2009011
Temperature dependent dielectric spectroscopy of muscle tissue phantom. - In: International journal of microwave and wireless technologies, ISSN 1759-0795, Bd. 12 (2020), 9, S. 885-891
The temperature dependence of the dielectric parameters of tissues and tissue-mimicking phantoms is very important for non-invasive temperature measurement in medical applications using microwaves. We performed measurements of this dependence in the temperature range of 25-50˚C using distilled water as a reference liquid commonly used in dielectric property studies. The results were compared with the literature model in the frequency range of 150-3000 MHz. Using this method, the temperature dependence of dielectric parameters of a new muscle tissue-mimicking phantom based on agar, polyethylene powder, and polysaccharide material TX-151 was measured in the temperature range of 25-50˚C. The temperature dependence of the dielectric properties of this new muscle phantom was fitted to that of the two-pole Cole-Cole model and the deviation of the results between measured and modeled data was quantified.
https://doi.org/10.1017/S1759078720000203
Robust predictive control for respiratory CO2 gas removal in closed-loop mechanical ventilation: an in-silico study. - In: Current directions in biomedical engineering, ISSN 2364-5504, Bd. 6 (2020), 3, 20203080, insges. 4 S.
In this study a physiological closed-loop system for arterial CO2 partial pressure control was designed and comprehensively tested using a set of models of the respiratory CO2 gas exchange. The underlying preclinical data were collected from 12 pigs in presence of severe changes in hemodynamic and pulmonary condition. A minimally complex nonlinear state space model of CO2 gas exchange was identified post hoc in different lung conditions. The control variable was measured noninvasively using the endtidal CO2 partial pressure. For the simulation study the output signal of the controller was defined as the alveolar minute volume set value of an underlying adaptive lung protective ventilation mode. A linearisation of the two-compartment CO2 gas exchange model was used for the design of a model predictive controller (MPC). It was augmented by a tube based controller suppressing prediction errors due to model uncertainties. The controller was subject to comparative testing in interaction with each of the CO2 gas exchange models previously identified on the preclinical study data. The performance was evaluated for the system response towards the following five tests in comparison to a PID controller: recruitment maneuver, PEEP titration maneuver, stepwise change in the CO2 production, breath-hold maneuver and a step in the reference signal. A root mean square error of 2.69 mmHg between arterial CO2 partial pressure and the reference signal was achieved throughout the trial. The reference-variable response of the model predictive controller was superior regarding overshoot and settling time.
https://doi.org/10.1515/cdbme-2020-3080
Novel dry electrode EEG headbands for home use: comparing performance and comfort. - In: Current directions in biomedical engineering, ISSN 2364-5504, Bd. 6 (2020), 3, 20203036, insges. 4 S.
Monitoring brain activity at home using electroencephalography (EEG) is an increasing trend for both medical and non-medical applications. Gel-based electrodes are not suitable due to the gel application requiring extensive preparation and cleaning support for the patient or user. Dry electrodes can be applied without prior preparation by the patient or user. We investigate and compare two dry electrode headbands for EEG acquisition: a novel hybrid dual-textile headband comprising multipin and multiwave electrodes and a neoprene-based headband comprising hydrogel and spidershaped electrodes. We compare the headbands and electrodes in terms of electrode-skin impedance, comfort, electrode offset potential and EEG signal quality. We did not observe considerable differences in the power spectral density of EEG recordings. However, the hydrogel electrodes showed considerably increased impedances and offset potentials, limiting their compatibility with many EEG amplifiers. The hydrogel and spider-shaped electrodes required increased adduction, resulting in a lower wearing comfort throughout the application time compared to the novel headband comprising multipin and multiwave electrodes.
https://doi.org/10.1515/cdbme-2020-3036
MagCPP: a C++ toolbox for combining neurofeedback with Magstim transcranial magnetic stimulators. - In: Current directions in biomedical engineering, ISSN 2364-5504, Bd. 6 (2020), 3, 20203128, insges. 4 S.
Transcranial magnetic stimulation (TMS) is an established method to treat various neurological diseases, such as depression, Alzheimer's disease, and tinnitus. New applications for TMS are closed loop neurofeedback (NF) scenarios, which require software control of the TMS system, instead of the currently used manual control. Hence, the MagCPP (https://github.com/MagCPP) toolbox was developed and is described in this work. The toolbox enables the external control of Magstim TMS devices via a C++ interface. Comparing MagCPP to two other toolboxes in a TMS application scenario with 40% power, we found that MagCPP works faster and has lower variability in repeated runs (MagCPP, Python, MATLAB [mean±std in seconds]: 1.19±0.00, 1.59±0.01, 1.44±0.02). An integration of MagCPP in a real-time data processing platform MNE-CPP with an optional GUI demonstrates its ability as part of a closed-loop NF-scenario. With its performing advantages over other toolboxes, MagCPP is a first step towards a complete closed loop NF scenario and offers possibilities for novel study designs.
https://doi.org/10.1515/cdbme-2020-3128
In situ impedance measurements on postmortem porcine brain. - In: Current directions in biomedical engineering, ISSN 2364-5504, Bd. 6 (2020), 3, 20203037, insges. 4 S.
The paper presents an experimental study where the distinctness of grey and white matter of an in situ postmortem porcine brain by impedance measurements is investigated. Experimental conditions that would allow to conduct the same experiment on in vivo human brain tissue are replicated.
https://doi.org/10.1515/cdbme-2020-3037
Sensation thresholds in electrocutaneous stimulation : comparison of textile cuff and TENS electrodes. - In: Current directions in biomedical engineering, ISSN 2364-5504, Bd. 6 (2020), 3, 20203096, insges. 4 S.
Acoustic or visual warning signals for workers in hazardous situations might fail under loud and/or lowvisibility work situations. A warning system should be developed that uses electrocutaneous stimulation through textile electrodes. Previous work investigated suitable stimulation parameters using TENS electrodes. The aim of this study was to compare TENS and textile cuff electrodes in terms of sensation thresholds, qualitative and spatial sensation. A study on 30 healthy volunteers (f=13, m=17) of mean age of 26.7 years was conducted applying bi-phasic rectangular current pulses to electrodes attached to the upper right arm. The study revealed that perception, attention and intolerance thresholds, qualitative and spatial perception are comparable indicating that future studies with the textile cuff electrodes can be generally based on the previous results with TENS electrodes.
https://doi.org/10.1515/cdbme-2020-3096