Fachbereich Medizintechnik und Technomathematik
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A new goodness-of-fit test for the composite null hypothesis that data originate from a geometric Brownian motion is studied in the functional data setting. This is equivalent to testing if the data are from a scaled Brownian motion with linear drift. Critical values for the test are obtained, ensuring that the specified significance level is achieved in finite samples. The asymptotic behavior of the test statistic under the null distribution and alternatives is studied, and it is also demonstrated that the test is consistent. Furthermore, the proposed approach offers advantages in terms of fast and simple implementation. A comprehensive simulation study shows that the power of the new test compares favorably to that of existing methods. A key application is the assessment of financial time series for the suitability of the Black-Scholes model. Examples relating to various stock and interest rate time series are presented in order to illustrate the proposed test.
A user-friendly, portable, low-cost readout system for the on-site or point-of-care characterization of chemo- and biosensors based on an electrolyte–insulator–semiconductor capacitor (EISCAP) has been developed using a thumb-drive-sized commercial impedance analyzer. The system is controlled by a custom Python script and allows to characterize EISCAP sensors with different methods (impedance spectra, capacitance-voltage, and constant-capacitance modes), which are selected in a user interface. The performance of the portable readout system was evaluated by pH measurements and the detection of the antibiotic penicillin, hereby using EISCAPs consisting of Al/p-Si/SiO₂/Ta₂O₅ structures and compared to the results obtained with a stationary commercial impedance analyzer. Both the portable and the commercial systems provide very similar results with almost perfectly overlapping recorded EISCAP signals. The new portable system can accelerate the transition of EISCAP sensors from research laboratories to commercial end-user devices.
Das vermehrte Aufkommen von Elektrofahrzeugen führt dazu, dass Lastspitzen durch erhöhtes Ladeaufkommen zu bestimmten Tageszeiten das Stromnetz überlasten. Im Gegensatz zum Status Quo, indem Lastspitzen ohne Regulierung toleriert werden, bedarf es einer „intelligenten“ Lösung zur dynamischen Glättung von Lastspitzen unter Vermeidung von Einschränkungen der Nutzungsmöglichkeiten bei gleichzeitiger Einhaltung physikalischer Obergrenzen der Netzinfrastruktur.
Dies ist zwingend erforderlich, um Netzausfälle zu vermeiden. Zukünftig wird diese Problemstellung durch die Distribution von Möglichkeiten des Smart-Chargings gelöst, welche individuell auf die aktuelle Netzlast, Marktgegebenheiten und den Ladebedarf reagieren. Ein mögliches Vorgehen zur Umsetzung wird in dieser Masterarbeit beschrieben. Zunächst wird eine technische Anforderungsanalyse durchgeführt. Die Machbarkeit wird mithilfe eines Prototyps einer Smart Charging Lösung nachgewiesen. Die Software bietet die Möglichkeit verschiedene Preisstrategien zu befolgen. Abschließend wird die Einhaltung der vorgegebenen funktionalen Anforderungen (REST-Protokolle: OSCP, OCPI; Websockets: OCPP; Anbindung an alle Netzteilnehmer: Ver-teilnetzbetreiber, App, Stromlieferant, Ladesäulenbetreiber) sowie nicht-funktionalen An-forderungen (bspw. geringe Kopplung der Module, flexible Erweiterbarkeit, performante Speicherung, Skalierbarkeit) beurteilt.
The bioconversion of salinized land into healthy agricultural systems by utilizing low-rank coal (LRC) is a strategic approach for sustainable agricultural development. The aims of this study were: (1) to isolate bacterial strains associated with the rhizosphere of native plants in coal-containing soils, (2) to characterize their plant growth-promoting (PGP) and coal-solubilizing capabilities under laboratory conditions and (3) to evaluate their influence on the germination and growth of chia seeds under saline stress. Fourteen bacterial cultures were isolated from the rhizosphere of Artemisia annua L. using culture media containing salt and coal. Based on their PGP activities (nitrogen fixation, phosphate solubilization, siderophore and indole-3-acetic acid production), five strains were selected, belonging to the genera Bacillus, Phyllobacterium, Arthrobacter, and Pseudomonas. Solubilization assays were conducted to confirm the ability of these strains to utilize coal efficiently. Finally, the selected strains were inoculated with chia seeds (Salvia hispanica L.) to evaluate their ameliorating effect under saline stress conditions in coal-containing media. Inoculation with A. subterraneus Y1 resulted in the highest germination and growth metrics of chia seeds. A positive but comparatively weaker response was observed with P. frederiksbergensis AMA1 and B. paramycoides Lb-1 as inoculants. Coal inoculated with halotolerant bacteria can serve as the foundation for humified organic matter in salt-affected environments. The selected halotolerant bacteria enhance coal biotransformation while exhibiting PGP traits.
Background: Numerous single- and double-row repair techniques with simple and modified stitches have been described for subscapularis tendon tears.
Purpose/Hypothesis: This study aimed to uniformly evaluate the influence of 4 different repair techniques on the biomechanical performance of fixation for full-thickness subscapularis tendon tears. It was hypothesized that (1) the 2 modified single-row repair techniques would require more cycles to result in 3- and 5-mm gap formation and have a higher load to failure after cyclic loading than the simple single-row repair technique and (2) the double-row repair technique would also require more cycles to result in 3- and 5-mm gap formation and have a significantly higher load to failure after cyclic loading compared to the simple single-row repair technique.
Study Design: Controlled laboratory study.
Methods: Full-thickness subscapularis tendon tears were created in 32 fresh-frozen cadaveric shoulders, and the tears were treated in 1 of 4 ways: (1) single-row repair with the mattress stitch, (2) single-row repair with the modified lasso-loop stitch, (3) single-row repair with the modified Mason-Allen stitch, or (4) double-row repair. After repair, specimens were progressively cyclically loaded to 200 N, and the number of cycles to obtain a 3- and 5-mm gap was recorded. After cyclic loading, the specimens were loaded to failure at 500 mm/min, and ultimate failure loads were measured.
Results: There were no significant differences between either of the modified single-row repair techniques and the simple single-row repair technique. Double-row repair withstood significantly more cycles until 3-mm (P < .001) and 5-mm (P = .004) gap formation and had a higher ultimate failure load (P = .015) compared to the simple single-row repair technique, and double-row repair withstood more cycles until 3-mm gap formation (P = .003) compared with single-row repair with the modified lasso-loop stitch. No significant differences were found between double-row repair and single-row repair with the modified Mason-Allen stitch.
Conclusion: Findings indicated that (1) there was no significant biomechanical advantage of the modified single-row repair techniques over the simple single-row repair technique and (2) while the double-row repair technique was biomechanically superior to the simple single-row repair technique, there was no significant difference between single-row repair with the modified Mason-Allen stitch and double-row repair.
Clinical Relevance: Considering that double-row repair might not be useful in some tears because of the risk of overtensioning, modified single-row repair techniques appear to be an adequate refixation alternative.
This work presents a new model for the shakedown analysis of Kirchhoff plates under uncertain conditions of the plastic moment by the direct method. The stochastic models of the plastic moment are normal or lognormal distribution. New formulations are derived to compute the lower bound and upper shakedown loads and a dual algorithm is established to calculate the upper and lower bound shakedown load factors simultaneously for a chosen structural reliability level. An example is examined to illustrate the algorithm and shows robust results of the stochastic analysis.
Magnetic nanoparticles (MNP) serve as imaging tracers, therapeutic heating agents and biosensors in biomedical applications. All the above applications rely upon the particles’ unique relaxation mechanisms, which lead to phase shifts in alternating magnetic fields and dissipation. As MNP have an intrinsic size distribution and their magnetic properties are also size-dependent, search is ongoing for the optimally sized MNP that could potentially serve for all three applications simultaneously. In this work, we present our current results on simulating the influence of core size, mono- and polydisperse size distributions as well as magnetic anisotropy on the performance of MNP for both heating and biosensing using micromagnetic dynamic magnetization simulations.
Magnetic nanoparticles (MNP) enable new biomedical applications as imaging tracers, heating agents or biosensors due to their unique relaxation mechanism in alternating magnetic fields. For assessing MNP suitable for such applications, magnetic particle spectroscopy (MPS) offers a reliable method, dual-frequency excitation adding sensitivity. Biomedical applications, however, rely on MNP use in physiological environments (blood, tissue, etc.) of various viscosities, which could strongly alter the MNP relaxation behavior. In this work, we present our preliminary results of varying viscosity on the relaxation of MNP during dual-frequency MPS, studied with micromagnetic dynamic magnetization simulation.
