Using the multi-linear rank-(Lr, Lr, 1) decomposition for the detection of the 200 Hz band activity in somatosensory evoked magnetic fields and somatosensory evoked electrical potentials. - In: IEEE access, ISSN 2169-3536, Bd. 9 (2021), S. 106232-106244
Im Titel ist "r" tiefgestellt
https://doi.org/10.1109/ACCESS.2021.3100759
Determination of piezo-resistive coefficient π44 in p-type silicon by comparing simulation and measurement of pressure sensors. - In: AIP Advances, ISSN 2158-3226, Bd. 11 (2021), 8, 085005, insges. 6 S.
https://doi.org/10.1063/5.0060034
SmartPIV: flow velocity estimates by smartphones for education and field studies. - In: Experiments in fluids, ISSN 1432-1114, Bd. 62 (2021), 8, 172, S. 1-13
In this paper, a smartphone application is presented that was developed to lower the barrier to introduce particle image velocimetry (PIV) in lab courses. The first benefit is that a PIV system using smartphones and a continuous wave (cw-) laser is much cheaper than a conventional system and thus much more affordable for universities. The second benefit is that the design of the menus follows that of modern camera apps, which are intuitively used. Thus, the system is much less complex and costly than typical systems, and our experience showed that students have much less reservations to work with the system and to try different parameters. Last but not least the app can be applied in the field. The relative uncertainty was shown to be less than 8%, which is reasonable for quick velocity estimates. An analysis of the computational time necessary for the data evaluation showed that with the current implementation the app is capable of providing smooth live display vector fields of the flow. This might further increase the use of modern measurement techniques in industry and education.
https://doi.org/10.1007/s00348-021-03262-z
Design, characterization and mechanical properties of new Na+, CO32--apatite/alginate/C60 fullerene hybrid biocomposites. - In: Journal of the Korean Ceramic Society, ISSN 2234-0491, Bd. 58 (2021), 4, S. 422-429
Im Titel sind "+" und "2-" hochgestellt, "3" und "60" tiefgestellt
Nanoparticles (20-50 nm) of Na+, CO32--containing calcium phosphate (Na: 1.49 wt% and C: 1.53 wt%) with apatite-type structure were prepared by precipitation method from aqueous solution. According to FTIR spectroscopy data, the partial substitution of phosphate by carbonate (B-type) realized in the apatite-type structure. Obtained Na+, CO32--hydroxyapatite (HAP) was used for the preparation of hybrid biocomposites with Alginate (Alg) with weight ratio HAP: Alg = 1:1 or 2:1 and C60 fullerene (C60; from 0.2 to 4 wt%) and their mechanical properties were determined. It was found, that sample with weight ratio HAP: Alg = 2:1 and containing 4.0 wt% of C60 has the highest Young's modulus 429 MPa comparing with other determined samples. The structure modeling of the investigated system showed that the formation of triple complexes Na+, CO32--HAP-Alg-C60 is stabilized by solvophobic and stacking interactions. The created biocomposites can be used as an effective implant material for bone restoration.
https://doi.org/10.1007/s43207-020-00107-z
Production of topology-optimised structural nodes using arc-based, additive manufacturing with GMAW welding process. - In: Journal of civil engineering and construction, ISSN 2051-7777, Bd. 10 (2021), 2, S. 101-107
The desire to generate a stress optimised structural node with maximum stability is often coupled with the goal of low manufacturing costs and an adapted and minimal use of material. The complex, three-dimensional free-form structures, which are created by means of topology-optimisation, are only partially suitable for conventional manufacturing. The wire arc additive manufacturing (WAAM), by means of arc welding processes, offer a cost-effective and flexible possibility for the individual production of complex, metallic components. Gas metal arc welding (GMAW) is particularly suitable to produce large-volume, load-bearing structures due to build-up rates of up to 5 kg/h. The generation of strength and stiffness adapted support structures by means of the numerical simulation method of topology-optimisation was investigated in this study to generate topology-optimised structural nodes. The resulting node is transferred into a robot path using CAD/CAM software and manufactured from the filler material G4Si1 using WAAM with the GMAW process. Based on the boundary conditions of the WAAM process, the path planning and thus the manufacturability of the topology-optimised supporting structure nodes is evaluated and verified using a sample structure made of the welding filler material G4Si1. Depending on the path planning, an improvement of the mechanical properties could be achieved, due to changes in t8/5 times.
https://doi.org/10.32732/jcec.2021.10.2.101
Electrically driven cylindrical free shear flows under an axial uniform magnetic field. - In: Magnetohydrodynamics, Bd. 57 (2021), 2, S. 229-250
We consider a mathematical model of two-dimensional electrically driven laminar axisymmetric circular free shear flows in a cylindrical vessel under the action of an applied axial uniform magnetic field. The mathematical approach is based on the studies by J.C.R. Hunt and W.E. Williams (J. Fluid. Mech., 31, 705, 1968). We solve a system of stationary partial differential equations with two unknown functions of velocity and induced magnetic field. The flows are generated as a result of the interaction of the electric current injected into the liquid and the applied field using one or two pairs of concentric annular electrodes located apart on the end walls. Two lateral free shear layers and two Hartmann layers on the end walls and a quasi-potential flow core between them emerge when the Hartmann number Ha >> 1. As a result, almost all injected current passes through these layers. Depending on the direction of the current injection, coinciding or two counter flows between the end walls are realized. The Hartmann number varies in a range from 2 to 300. When a moderate magnetic field (Ha = 50) is reached, the flow rate and the induced magnetic field flux cease to depend on the magnitude of the applied field but depend on the injected electric current value. Increasing magnetic field leads only to inner restructuring of the flows. Redistributions of velocities and induced magnetic fields, electric current density versus Hartmann number are analyzed.
https://doi.org/10.22364/mhd.57.2.8
Flat liquid metal jet affected by a transverse magnetic field. - In: Magnetohydrodynamics, Bd. 57 (2021), 2, S. 211-222
A liquid metal flat jet immersed in a square duct under the influence of a transverse magnetic field is studied experimentally. Two cases are considered: when the applied magnetic field is oriented parallel (coplanar field) or perpendicularly (transverse field) to the initial plane of the jet. The main goal of the study is to investigate the mean flow characteristics and the stages of the jet's transformation. Signals of streamwise velocity at different locations are measured, which allows us to determine average velocity profiles and spatial-temporal characteristics of the velocity field. The two considered configurations are directly compared under the same flow regimes, with the same equipment.
https://doi.org/10.22364/mhd.57.2.6
Bismuth nanoparticles confined in carbonaceous nanospheres as anodes for high-performance potassium-ion batteries. - In: ACS applied materials & interfaces, ISSN 1944-8252, Bd. 13 (2021), 27, S. 31766-31774
Bismuth (Bi) has been considered as a promising alloying-type anode for potassium-ion batteries (PIBs), owing to its high theoretical capacity and suitable working voltage plateaus. However, Bi suffers from dramatic volume fluctuation and significant pulverization during the discharge/charge processes, resulting in fast capacity decay. Herein, we synthesize Bi nanoparticles confined in carbonaceous nanospheres (denoted as BiC) for PIBs by first utilizing BiOCl nanoflakes as a hard template and a Bi precursor. The construction of the loose structure buffers the mechanical stresses resulting from the volume expansion of Bi during the alloying reaction and avoids the fracture of the electrode structure, thus improving the cycling performance. Moreover, the carbonaceous layers increase the electronic conductivity and disperse the Bi nanoparticles, enhancing the charge transportation and ionic diffusion, which further promotes the rate capability of Bi@C. It exhibits a superior capacity (389 mAh g^-1 at 100 mA g^-1 after 100 cycles), excellent cycling stability (206 mAh g^-1 at 500 mA g^-1 over 1000 cycles), and an improved rate capability (182 mAh g^-1 at 2.0 A g^-1). This work provides a new structuring strategy in alloying materials for boosting reversible and stable potassium-ion storage.
https://doi.org/10.1021/acsami.1c09286
Advanced scanning probe nanolithography using GaN nanowires. - In: Nano letters, ISSN 1530-6992, Bd. 21 (2021), 13, S. 5493-5499
A fundamental understanding and advancement of nanopatterning and nanometrology are essential in the future development of nanotechnology, atomic scale manipulation, and quantum technology industries. Scanning probe-based patterning/imaging techniques have been attractive for many research groups to conduct their research in nanoscale device fabrication and nanotechnology mainly due to its cost-effective process; however, the current tip materials in these techniques suffer from poor durability, limited resolution, and relatively high fabrication costs. Here, we report on employing GaN nanowires as a robust semiconductor material in scanning probe lithography (SPL) and microscopy (SPM) with a relatively low-cost fabrication process and the capability to provide sub-10 nm lithography and atomic scale (<1 nm) patterning resolution in field-emission scanning probe lithography (FE-SPL) and scanning tunneling microscopy (STM), respectively. We demonstrate that GaN NWs are great candidates for advanced SPL and imaging that can provide atomic resolution imaging and sub-10 nm nanopatterning on different materials in both vacuum and ambient operations.
https://doi.org/10.1021/acs.nanolett.1c00127
Efficient empirical determination of maximum permissible error in coordinate metrology. - In: Measurement science and technology, ISSN 1361-6501, Bd. 32 (2021), 10, 105013, insges. 17 S.
Maximum permissible errors (MPEs) are an important measurement system specification and form the basis of periodic verification of a measurement system's performance. However, there is no standard methodology for determining MPEs, so when they are not provided, or not suitable for the measurement procedure performed, it is unclear how to generate an appropriate value with which to verify the system. Whilst a simple approach might be to take many measurements of a calibrated artefact and then use the maximum observed error as the MPE, this method requires a large number of repeat measurements for high confidence in the calculated MPE. Here, we present a statistical method of MPE determination, capable of providing MPEs with high confidence and minimum data collection. The method is presented with 1000 synthetic experiments and is shown to determine an overestimated MPE within 10% of an analytically true value in 99.2% of experiments, while underestimating the MPE with respect to the analytically true value in 0.8% of experiments (overestimating the value, on average, by 1.24%). The method is then applied to a real test case (probing form error for a commercial fringe projection system), where the efficiently determined MPE is overestimated by 0.3% with respect to an MPE determined using an arbitrarily chosen large number of measurements.
https://doi.org/10.1088/1361-6501/ac0c49