Physikingenieurwesen (PHY)
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Expertenevaluation der ergonomischen und sicherheitstechnischen Gestaltung von Krankenhausbetten
(2023)
Quantum magnetometry based on optically detected magnetic resonance (ODMR) of nitrogen vacancy centers in nano- or micro-diamonds is a promising technology for precise magnetic-field sensors. Here, we propose a new, low-cost and stand-alone sensor setup that employs machine learning on an embedded device, so-called edge machine learning. We train an artificial neural network with data acquired from a continuous-wave ODMR setup and subsequently use this pre-trained network on the sensor device to deduce the magnitude of the magnetic field from recorded ODMR spectra. In our proposed sensor setup, a low-cost and low-power ESP32 microcontroller development board is employed to control data recording and perform inference of the network. In a proof-of-concept study, we show that the setup is capable of measuring magnetic fields with high precision and has the potential to enable robust and accessible sensor applications with a wide measuring range.
The Anterior Fibers of the Superficial MCL and the ACL Restrain Anteromedial Rotatory Instability
(2023)
Single-shot all-digital approach for measuring the orbital angular momentum spectrum of light
(2022)
Light fields carrying orbital angular momentum (OAM) offer a broad variety of applications in which especially an accurate determination of the respective OAM spectrum, i.e., unraveling the content of OAM by its topological charge ℓ, has become a main subject. Even though various techniques have been proposed to measure the OAM spectrum of such modes, many of them fail if optical vortices have to be considered in perturbed or dynamically changing experimental systems. Here, we put forward a novel technique capable of determining the OAM spectrum of light by a single measurement shot, which specifically applies to those fields that have been distorted. Experimentally, our technique only requires to interfere the perturbed light field with a reference field. From the resulting intensity pattern, the accurate OAM spectrum is determined in an all-digital way. We demonstrate our novel approach by numerical simulations and a proof-of-concept experiment employing a model ball lens as an exemplary disturbing object.
Die computergestützte Modellierung und Simulation (CMS) ist in vielen Bereichen der Industrie gängige Praxis und hat das Potenzial die Medizintechnikbranche zu revolutionieren. Die Markteinführung neuer Produkte kann erheblich beschleunigt und entstehende Kosten können reduziert werden, ohne die Patientensicherheit negativ zu beeinflussen. Dennoch beruhen die Entwicklungs- und Zulassungsprozesse in der Medizintechnik bis dato überwiegend auf experimentell ermittelten Daten, was in Europa unter anderem auf die bestehenden regulatorischen Unsicherheiten zurückzuführen ist. Verglichen mit der FDA hat die EU-Kommission die Möglichkeiten der CMS bisher nicht erkannt – es fehlt an rechtlichen Vorgaben. Der folgende Artikel soll daher eine Übersicht der aktuellen regulatorischen Situation bieten.
Die computergestützte Modellierung und Simulation (CMS) ist in vielen Bereichen der Industrie gängige Praxis und hat das Potenzial, die Medizintechnikbranche zu revolutionieren. Die Markteinführung neuer Produkte kann erheblich beschleunigt und entstehende Kosten können reduziert werden, ohne die Patientensicherheit negativ zu beeinflussen. Dennoch beruhen die Entwicklungs- und Zulassungsprozesse in der Medizintechnik bis dato überwiegend auf experimentell ermittelten Daten, was in Europa unter anderem auf die bestehenden regulatorischen Unsicherheiten zurückzuführen ist. Verglichen mit der FDA hat die EU-Kommission die Möglichkeiten der CMS bisher nicht erkannt – es fehlt an rechtlichen Vorgaben. Der folgende Artikel soll daher eine Übersicht der aktuellen regulatorischen Situation bieten.
Additive manufacturing (AM) has continuously grown in recent decades. Enhanced quality, further development of technology, and fall in prices make AM applicable and capable for various industrial applications, also for the manufacture of medical devices. 3D printing offers the possibility for an unprecedented adaptation to the anatomy of each patient, generating medical devices on a case-by-case basis. In many jurisdictions, custom-made devices qualify for an exemption to pre-market approval standards. This regulation is called into question by new technologies, like AM. Therefore, this article compares the current regulatory requirements for custom-made devices in Europe, the United States, and Australia and discusses the impact on 3D printed devices. It concludes that not all jurisdictions have yet adjusted their regulatory framework for custom-made devices to technological advances. Remaining uncertainties must be eliminated in order to help manufacturers comply with the regulatory requirements, emphasizing key aspects of AM.
Progress in materials development is often paced by the time required to produce and evaluate a large number of alloys with different chemical compositions. This applies especially to refractory high-entropy alloys (RHEAs), which are difficult to synthesize and process by conventional methods. To evaluate a possible way to accelerate the process, high-throughput laser metal deposition was used in this work to prepare a quinary RHEA, TiZrNbHfTa, as well as its quaternary and ternary subsystems by in-situ alloying of elemental powders. Compositionally graded variants of the quinary RHEA were also analyzed. Our results show that the influence of various parameters such as powder shape and purity, alloy composition, and especially the solidification range, on the processability, microstructure, porosity, and mechanical properties can be investigated rapidly. The strength of these alloys was mainly affected by the oxygen and nitrogen contents of the starting powders, while substitutional solid solution strengthening played a minor role.
This work deals with the spectroscopic properties of praseodymium doped single crystalline lutetium aluminum garnet (LuAG:Pr3+). A special focus was set on temperature- and time-dependent spectroscopy. Beyond the well-known down-conversion luminescence of LuAG:Pr3+, also UV-A/B up-conversion luminescence under excitation with a 488 nm laser was thoroughly investigated. Furthermore, the results of the spectroscopic investigations on the single crystalline material were supplemented and compared with measurements on a microscale powder sample.
In addition, to the spectroscopic investigations, mechanistic considerations are presented to obtain a closer look at the up-conversion process in LuAG:Pr3+. We promote the thesis of a temperature-dependent energy transfer up-conversion mechanism.
The laser nitriding was performed in nitrogen gas at room temperature (20 °C) and low temperature (−190 °C) by a low power fiber laser to modify the wear and abrasion resistance of NiTi alloy. The surface roughness and element composition were analyzed by roughness device and energy-dispersive X-ray spectroscopy respectively. The results of roughness show that laser treatment can change the surface roughness due to the laser remelting. The effect of laser nitriding on the microhardness, friction coefficient, and worn scars of NiTi alloy was also studied, which shows that the microhardness of the NiTi alloy increases after laser nitriding. The optical microscope and scanning electron microscope were used to characterize the surface of NiTi alloy after wear testing to observe the microstructure of worn scars. The results show that the laser nitriding with different parameters can induce a nitride layer with different thicknesses and the higher energy deposition is the key factor for the formation of the nitride layer, which can decrease the friction coefficient and reduce wear loss during the application of NiTi alloy. The improvement of wear resistance can be attributed to the hard nitriding layer.
We experimentally study the occurrence of pattern formation during the slot-die coating of low-viscosity nearly Newtonian liquids onto Polyethylenterephthalat (PET)-substrates. In particular, it is demonstrated that with increase of the coating speed a homogeneous coating becomes unstable with respect to periodic stripe patterns. Thereby, depending on the liquid viscosity, the stripes can be oriented parallel or perpendicular with respect to the coating direction. Mixed states do also occur. The spatial period of perpendicular [parallel] stripes increases [decrease] with the coating speed. The dependence of the effect on various control parameters of slot-die coating is investigated. Finally, a simple theoretical model based on the hydrodynamics of thin films of partially wetting liquids is analysed. Comparing the results to the experiments, conclusions are drawn regarding the acting instability and pattern formation mechanisms.
Laser shock peening is a new and important surface treatment technique that can enhance the mechanical properties of metal materials. Normally, the nanosecond laser with pulse-width between 5 ns and 20 ns is used to induce a high-pressure shock wave that can generate plastic deformation in the top layer of metals. The femtosecond laser shock peening in the air has been studied recently, which can induce higher pressure shock wave than that of traditional nanosecond laser shock peening in a very short time. The NiTi alloy is processed by femtosecond laser shock peening, then a nanoindentation device is used to measure its surface hardness and residual stress. The hardness results of NiTi alloy before and after treatment show that the femtosecond laser shock peening can increase the hardness of NiTi alloy, which also shows that the femtosecond laser can be used to perform laser shock peening on NiTi alloy without coating.