Fast gain switching on TwinRX USRPs. - In: 16th European Conference on Antennas and Propagation, (2022), insges. 5 S.
In this paper, we investigate the gain switching performance of the software-defined radio (SDR) universal software radio peripheral (USRP) X310 with the TwinRX daughterboard and propose a method to optimize it for fast transitions. This receiver uses a complex structure of two switchable amplifiers and two digital step attenuators to realize the wide gain setting range of up to 92 dB. Our measurements of the settling time show that the bulk of transitions between two gain settings take below 1.5 µs, but some require more than 50 µs, caused by the power-up of the switchable amplifiers. Based on this knowledge, we propose a modified switching regime, in which the amplifiers are not toggled in time-critical phases, e.g., during a running measurement, so that a transition time of 1.5 µs can be reliably realized. Thus, a gain switching range of 62 dB is achieved, within which, for example, a fast automatic gain control can be realized.
https://doi.org/10.23919/EuCAP53622.2022.9769488
Experimental study of a liquid metal film flow in a streamwise magnetic field. - In: Magnetohydrodynamics, Bd. 58 (2022), 1/2, S. 5-11
Continuous wetting of a surface with liquid metal is indispensable in many applications, such as in fusion reactors. In the present study, we provide data on the suppression of free-surface instabilities of liquid metal film flows under the action of strong streamwise magnetic fields in analogy to the poloidal fields used in application. We have designed and built up an experimental test setup which allows studying the influence of magnetohydrodynamics on the dynamic behaviour of liquid metal GaInSn film flows in laminar, transient, and turbulent regimes. While the width and the length of the film are adjusted at w = 23 mm and l = 120 mm, respectively, we are able to apply strong uniform magnetic fields up to B = 5 T over the entire fluid-flow volume. Moreover, the setup allows to vary the Reynolds number within the range 200 ≤ Re ≤ 1700. The corresponding Hartmann and Stuart numbers are Ha ≤ 180 and N ≤ 40, respectively. This study shows that a streamwise magnetic field is capable of suppressing free-surface instabilities even in the turbulent regime of the film flow by dampening any motion perpendicular to the applied magnetic field. Plans for future studies include the quantitative investigation of the parameter space.
http://doi.org/10.22364/mhd.58.1-2.1
FE simulation of multi-stage wire drawing processes. - In: Alles auf Draht!, (2022), S. 55-60
https://nbn-resolving.org/urn:nbn:de:bsz:105-qucosa2-786370
Einfluss von Formabweichungen auf die Radius und Rundheitsmessung von Mikrokugeln :
Influence of form deviations on the radius and roundness measurement of micro spheres. - In: Technisches Messen, ISSN 2196-7113, Bd. 89 (2022), 10, S. 704-713
Micro and nano coordinate measuring machines (CMMs) require small and well characterized micro spheres as probing elements. However, established strategies and instruments have mostly been designed for and applied to the characterization of larger spheres in the range of millimetres or above. That is why we have recently focused our attention towards a novel strategy which is based on a set of atomic force microscope (AFM) surface scans in conjunction with a stitching algorithm. Initial experimental results are promising, but point to several influences which require further attention. We have, therefore, begun to model the measurement strategy and applied it on simulated spheres, in order to investigate and reduce some of these influences. The model is currently limited to effects which are related to the radius and form of the sphere. Other influences, like the AFM tip, are being ignored. In this paper, we introduce the essential parts of this model and apply it on spheres of different mean radii (60 µm, 100 µm and 150 µm) and of different qualities (Grade 3 and Grade 5). The investigations illustrate that the measurement object can have a significant influence on the measurement result and needs to be considered.
https://doi.org/10.1515/teme-2022-0007
Metrologische Nanopositionierung kombiniert mit Zwei-Photonen-Laserdirektschreiben :
Metrological nanopositioning combined with two-photon direct laser writing. - In: Technisches Messen, ISSN 2196-7113, Bd. 89 (2022), 7/8, S. 507-514
The extension of nanopositioning and nanomeasuring machines (NPM-machines) to fabrication machines by using a femtosecond laser for the implementation of direct laser writing by means of two-photon absorption (2PA) is a promising approach for cross-scale metrological fabrication in the field of lithographic techniques [24]. To this end, a concept for integrating two-photon technology into an NPM machine was developed and implemented, followed by a characterization of the system and targeted investigations to provide evidence for the synergy of the two techniques. On this basis, a new approach to high-throughput micro- and nano-fabrication was developed and investigated, demonstrating new possibilities in cross-scale, high-precision manufacturing [6]. This mix-and-match approach is based on a combination of 2PA laser writing with field emission lithography to fabricate masters for subsequent nanoimprint lithography. Not only the advantages of the large positioning range of the NMM-1 could be highlighted, but also the advantages resulting from the highly accurate positioning. A systematic reduction of the distance between two adjacent lines resulted in a minimum photoresist width of less than [Math Processing Error] [16], which can be classified among the smallest distances between two laser-written lines described in the literature [4], [10], [20]. The center-to-center distance of the lines of about [Math Processing Error] at a numerical aperture of 0.16 and a wavelength of 801 nm is only about [Math Processing Error] of the Rayleigh diffraction limit extended for the two-photon process. Thus, for the first time, a resist width far below the diffraction limit could be realized with conventional two-photon laser writing in positive photoresist.
https://doi.org/10.1515/teme-2021-0127
Modifications to a high-precision direct laser writing setup to improve its laser microfabrication. - In: Laser-Based Micro- and Nanoprocessing XVI, (2022), 119890U, S. 119890U-1-119890U-7
Two-photon-absorption (2PA) techniques enables the possibility to create extremely fine structures in photosensitive materials. For direct laser writing as micro- or nanofabrication a laser system can be combined with highly precise positioning systems. These are mostly limited by a few hundreds micrometer positioning range with applications based on piezoelectric stages or even just relatively few tens micrometer positioning range with applications based on galvanometer scanners. Although these techniques are precise, but stitching methods are required for larger fabrication areas. Therefore, a setup consisting of a femtosecond laser for 2PA and a nanopositioning and nanomeasuring machine (NMM-1) was developed for high precision laser writing on lager surfaces. Further developments of the system should enable a significant improvement in high-precision and stitching free direct laser writing. In order to combine the the femtosecond laser and the NMM-1 into a functional unit, to write complex structures with highest accuracy and homogeneity, further improvements like a beam expansion for a better use of the numerical aperture of the objective and a new femtosecond laser with a integrated power measurement are realized. This showed improvements in line width for nano strucuring. Advantages and disadvantages as well as further developments of the NMM-1 system will be discussed related to current developments in the laser beam and nanopositioning system optimization.
https://doi.org/10.1117/12.2609417
Electric bias-induced edge degradation of few-layer MoS2 devices. - In: Materials today, ISSN 2214-7853, Bd. 53 (2022), 2, S. 281-284
In this work, we experimentally investigate the effects of electric bias on the degradation of few-layer MoS2 back-gated field-effect transistors in ambient air. The devices were fabricated using mechanically exfoliated MoS2 flakes, which were transferred to a Si/SiO2 substrate by a PDMS-based transfer. We report an accelerated electric bias-induced degradation of the devices under investigation and used optical and scanning electron microscopy (SEM) to monitor changes of the morphology of the MoS2 channel. In particular, we found a linear dependency of the degradation on the electric field between the Ti/Au source and drain contacts. In addition, we identify four regions in which morphological changes occur, of which the edges of the MoS2 channel are most affected.
https://doi.org/10.1016/j.matpr.2021.05.298
Nanoscale surface morphology modulation of graphene - i-SiC heterostructures. - In: Materials today, ISSN 2214-7853, Bd. 53 (2022), 2, S. 289-292
A multitude gratings design consists of gratings with different pitches ranging from the micrometre down to sub 40 nm scale combined with sub 10 nm step heights modulating the surface morphology for length scale measurements is proposed. The surface morphology modulation was performed using electron beam lithography incorporating a standard semiconductor processing technology. The critical dimension, edge roughness, step heights and line morphology in dependence on the grating pitch is studied.
https://doi.org/10.1016/j.matpr.2021.06.427
Post-traumatic recovery of muscle soleus in rats is improved via synergistic effect of C60 fullerene and TRPM8 agonist menthol. - In: Applied nanoscience, ISSN 2190-5517, Bd. 12 (2022), 3, S. 467-478
Functional biomechanical parameters of muscle soleus contraction in rats as well as selected blood biochemical parameters were studied during the first 3 days of post-traumatic syndrome progression caused by the destruction of muscle cells by compression. Single administration of the antioxidant C60 fullerene and the selective agonist of TRPM8 channels menthol were used as therapeutic agents. Injection of C60 fullerene at a concentration of 1 mg/kg into the damaged muscle improved its contractile function by 25-28%. The use of combined injections of C60 fullerene and menthol (at the concentration 1 mg/kg) improved this index by additional 27-39% and simultaneously stabilized the decrease in muscle strength observed throughout the experiment. A tendency towards a decrease in the indexes of the above described biochemical parameters by 10-15% were found with the therapeutic administration of C60 fullerene. With combined injections of C60 fullerene and menthol, the above described biochemical parameters decreased by an additional 17-24%. The synergism between the action of menthol and C60 fullerene on the post-traumatic recovery of skeletal muscle function opens up new perspectives for the clinical application of this combination therapy.
https://doi.org/10.1007/s13204-021-01703-z
Determination and systematization of load situations for eBike drive units as basis for their design and optimization. - In: Achte IFToMM D-A-CH Konferenz 2022, (2022), S. 1-6
https://doi.org/10.17185/duepublico/75445