Fibre-optic measurement of strain and shape on a helicopter rotor blade during a ground run: 2. Measurement of shape. - In: Smart materials and structures, ISSN 1361-665X, Bd. 31 (2022), 7, 075015, S. 1-13
https://doi.org/10.1088/1361-665X/ac736c
The influence of white matter lesions on the electric field in transcranial electric stimulation. - In: NeuroImage: Clinical, ISSN 2213-1582, Bd. 35 (2022), 103071, S. 1-12
Background - Transcranial direct current stimulation (tDCS) is a promising tool to enhance therapeutic efforts, for instance, after a stroke. The achieved stimulation effects exhibit high inter-subject variability, primarily driven by perturbations of the induced electric field (EF). Differences are further elevated in the aging brain due to anatomical changes such as atrophy or lesions. Informing tDCS protocols by computer-based, individualized EF simulations is a suggested measure to mitigate this variability. - Objective - While brain anatomy in general and specifically atrophy as well as stroke lesions are deemed influential on the EF in simulation studies, the influence of the uncertainty in the change of the electrical properties of the white matter due to white matter lesions (WMLs) has not been quantified yet. - Methods - A group simulation study with 88 subjects assigned into four groups of increasing lesion load was conducted. Due to the lack of information about the electrical conductivity of WMLs, an uncertainty analysis was employed to quantify the variability in the simulation when choosing an arbitrary conductivity value for the lesioned tissue. - Results - The contribution of WMLs to the EF variance was on average only one tenth to one thousandth of the contribution of the other modeled tissues. While the contribution of the WMLs significantly increased (p≪.01) in subjects exhibiting a high lesion load compared to low lesion load subjects, typically by a factor of 10 and above, the total variance of the EF didnot change with the lesion load. - Conclusion - Our results suggest that WMLs do not perturb the EF globally and can thus be omitted when modeling subjects with low to medium lesion load. However, for high lesion load subjects, the omission of WMLs may yield less robust local EF estimations in the vicinity of the lesioned tissue. Our results contribute to the efforts of accurate modeling of tDCS for treatment planning.
https://doi.org/10.1016/j.nicl.2022.103071
Novel whitlockite/alginate/C60 fullerene composites: synthesis, characterization and properties for medical application. - In: The Arabian journal for science and engineering, ISSN 2191-4281, Bd. 47 (2022), 6, S. 7093-7104
The hybrid composite materials in form of spheres based on whitlockite-related calcium phosphate, Alginate (20, 30 or 50 wt.%) and C60 Fullerene (C60; 2 or 5 wt.%) were fabricated. According to XRD, elemental analysis and SEM data, the whitlockite-related (hexagonal system, space group R3c) calcium phosphate containing 0.42 wt.% of sodium was obtained in the form of particles with size 50-80 nm. It has been found that the addition of Alginate (20 wt.%) to prepared calcium phosphate leads to an increase in the compressive strength of composite by two times (from 137 to 358 MPa), and value of Young's modulus on 20% (from 460 to 558 MPa), while the presence of C60 in composition did not significant influence on this characteristic. The antibacterial activity of prepared composites with different composition and amounts (2.5, 5 or 10 mM) against Lactobacillus rhamnosus, Lactobacillus salivarius, Staphylococcus aureus and Pseudomonas aeruginosa was studied. All prepared samples did not effect on Lactobacillus. The addition of 5 wt.% C60 to phosphate-Alginate (30 wt.%) composite resulted in a tenfold decrease in the survival rate of the S. aureus strain at 5 and 10 mM of samples while P. aeruginosa was less sensitive to action of this sample and inhibition of bacteria growth was occurred only at its amount 10 mM. Thus, the results of mechanical properties and impact of created nanostructured hybrid composites on normal human microbiota (Lactobacillus) as well as pathogenic strain (S. aureus and P. aeruginosa) indicate the suitability of these promising materials for further biological test for bone therapy.
https://doi.org/10.1007/s13369-021-06552-0
Rational design of electrolyte solvation structures for modulating 2e-/4e- transfer in sodium-air batteries. - In: Advanced functional materials, ISSN 1616-3028, Bd. 32 (2022), 23, 2201258, S. 1-11
In sodium-air batteries (SABs), achieving the regulation of the electron transfer number during oxygen reduction reactions (ORRs) in the same electrolyte system remains a significant challenge. In this work, a promising strategy is proposed to dynamically modulate 2e-/4e- transfer in ORRs by regulating the electrolyte structures to realize the different performances of SABs. The 4e- ORR can be realized by decreasing the electrolyte concentration. The solvation sheath of Na+ at dilute concentrations consists mainly of water molecules that hinder the access of Na+ to the cathode surface due to the high solvation energies indicated by theoretical calculations, thereby impeding the 2e- reaction. In contrast, excess free water can easily access the cathode surface and trigger the 4e- ORR. The solvation energies of Na+ can be remarkably reduced by increasing the electrolyte concentration, forming a water-in-salt unit, in which the Na+ mainly coordinates with the bis(fluorosulfonyl)imide anion and can be easily released from the solvation sheath. Hence, the 2e- ORR is significantly promoted and becomes the dominant reaction. The SAB based on the 2e- reaction exhibits excellent energy density (15980 Wh kg-1) and good cycle performance (300 times), and the 4e- reaction exhibits excellent power density (12.09 mW cm-2).
https://doi.org/10.1002/adfm.202201258
An overview of metal-organic frameworks-derived carbon as anode materials for sodium- and potassium-ion batteries. - In: Materials Today Sustainability, ISSN 2589-2347, Bd. 18 (2022), 100156
With the decreasing abundance of lithium and the increasing cost of lithium-ion batteries (LIBs), exploring alternative metal-ion batteries has been a hotspot in the energy storage research area. Among next-generation batteries, sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) have been considered as competitive alternatives to LIBs due to the earth abundance of sodium and potassium. Metal-organic frameworks (MOFs)-derived carbon materials with high porosity, unique architectures, and abundant heteroatoms have been demonstrated as promising anode materials in SIBs and PIBs with high capacity and long cycling stability due to the adsorption energy storage mechanism. In this review, we highlight the advantages of carbon materials derived from MOFs as anode materials in SIBs and PIBs. In addition, the typical works and recent achievements are also introduced. Finally, the challenges and perspectives for further developing MOFs-derived carbon anode materials for SIBs and PIBs are also discussed.
https://doi.org/10.1016/j.mtsust.2022.100156
Study of the damping behaviour in samples consisting of iron electro-deposited on copper in an ionic liquid. - In: Journal of alloys and compounds, ISSN 1873-4669, Bd. 918 (2022), 165462
Copper-iron alloys were produced at room temperature by means of electrodeposition of iron on a copper substrate in an ionic liquid (1-butyl-1-methylpyrrolidinium trifluoromethylsulfonate [Py1,4]TfO). Samples with different electrodeposition times were studied using mechanical spectroscopy, scanning electron microscopy, light microscopy and magnetic loops techniques. Independent of the electrodeposition time the electrodeposition process leads to the promotion of a thin layer of iron onto the copper surface without iron diffusion into the substrate. The damping spectra for electrosposited samples in the as-electrodeposited state show the characteristic low and intermediate grain boundary damping peaks from copper as well as the solvent grain boundary damping peak from the electrodeposited iron. Thermal annealing at temperatures near 973 K leads to the appearance of Fe particles at the interface between the copper and iron (Cu + α-Fe phase) leading to a new damping peak at around 680 K whose driving force is the diffusion of copper atoms around the second phase particles.
https://doi.org/10.1016/j.jallcom.2022.165462
Modeling of corner-filleted flexure hinges under various loads. - In: Mechanism and machine theory, Bd. 175 (2022), 104937, S. 1-11
Compliant mechanisms are widely applied in precision engineering, measurement technology and microtechnology, due to their potential for the reduction of mass and assembly effort through the integration of functions into fewer parts and an increasing motion repeatability through less backlash and wear, if designed appropriately. However, a challenge during the design process is the handling of the multitude of geometric parameters and the complex relations between loads, deformations and strains. Furthermore, some tasks such as the dimensioning by means of optimization or the modeling for a controller design require a high number of analysis calculations. From this arises the need for sufficient computational analysis models with low calculation time. Existing studies of analysis models are mostly based on selected load cases, which may limits their general validity. The scope of this article is the comparison of models for the analysis of corner-filleted flexure hinges under various loads, to determine their advantages, disadvantages and application fields. The underlying methods of the study can further be used to evaluate future models based on a broad selection of possible load cases.
https://doi.org/10.1016/j.mechmachtheory.2022.104937
Photo-thermoelectric conversion and photo-induced thermal imaging using 2D/3D ReS2carbon framework with enhanced photon harvesting. - In: The chemical engineering journal, ISSN 1873-3212, Bd. 446 (2022), 137084
Solar energy is a promising renewable energy with the potential for the sustainable development of the world. Efficient photo-thermal conversion is essential for harvesting and conversion of solar energy, therefore, the main challenge is the development of efficient and low-cost photothermal conversion materials. Carbon framework can be considered as a candidate but somehow its application potential can be still constrained due to the limited absorption of near-infrared (NIR) light. Herein, we propose a general strategy for preparing two-dimensional (2D) transition metal dichalcogenides nanosheets and three-dimensional (3D) carbon framework composites (2D/3D ReS2C) as a photothermal material, which has an excellent broadband light absorption performance (in the wavelength range from 200 to 2500 nm). A small thermoelectric (TE) module with an area of 4 × 4 cm2 is integrated with annealed ReS2@C as a light absorber for the investigation of photo-thermoelectric conversion. The open-circuit voltage of the assembled device increases clearly under solar illumination and reaches the maximum value of 136.3 mV, which is ∼ five times larger than that without the absorber. In addition, 20 TE modules coated with ReS2@C absorber layers are connected in series, which can produce a maximum open-circuit voltage of 2.12 V (∼66.25 V/m2) to light up a red light-emitting diode (LED) under natural sunlight. Moreover, the annealed ReS2@C powder demonstrates a rapid and strong photothermal response under NIR light (wavelength ＞800 nm), which indicates a great application potential in photothermal imaging and photothermal cancer therapy.
https://doi.org/10.1016/j.cej.2022.137084
Localized direct material removal and deposition by nanoscale field emission scanning probes. - In: Micro and nano engineering, ISSN 2590-0072, Bd. 16 (2022), 100146, S. 1-5
The manufactory of advanced micro- and nanoscale devices relies on capable patterning strategies. Focused electron beams, as for instance implemented since long in electron beam lithography and electron beam induced deposition, are in this regard key enabling tools especially at the early stages of device development and research. We show here that nanoscale field emission scanning probes can be potentially utilized as well for a prospective direct device fabrication by localized material deposition but notably, also by localized material removal. Field emission scanning probe processing was specifically realized on 10 nm chromium and 50 nm gold thin film stacks deposited on a (1 × 1) cm2 fused silica substrate. Localized material deposition and metal removal was studied in various atmospheres comprising high vacuum, nitrogen, ambient air, naphthalene and carbon-dioxide. Stable and reliable regimes were in particular obtained in a carbonaceous atmosphere. Hence, localized carbon deposits were obtained but also localized metal removal was realized. We demonstrate furthermore that the selected electron emission parameters (20 V - 80 V, 180 pA) and the overall operation environment are crucial aspects that determine the degree of material deposition and removal. Based on our findings, direct tip-based micro- to nanoscale material patterning appears possible. The applied energy regime is also enabling new insights into low energy (< 100 eV) electron interaction. However, the underlying mechanisms must be further elucidated.
https://doi.org/10.1016/j.mne.2022.100146
Open sub-granting radio resources in overlay D2D-based V2V communications. - In: EURASIP journal on wireless communications and networking, ISSN 1687-1499, Bd. 2022 (2022), 46, S. 1-29
Richtiger Name des Verfassers: Dariush Mohammad Soleymani
Capacity, reliability, and latency are seen as key requirements of new emerging applications, namely vehicle-to-everything (V2X) and machine-type communication in future cellular networks. D2D communication is envisaged to be the enabler to accomplish the requirements for the applications as mentioned earlier. Due to the scarcity of radio resources, a hierarchical radio resource allocation, namely the sub-granting scheme, has been considered for the overlay D2D communication. In this paper, we investigate the assignment of underutilized radio resources from D2D communication to device-to-infrastructure communication, which are moving in a dynamic environment. The sub-granting assignment problem is cast as a maximization problem of the uplink cell throughput. Firstly, we evaluate the sub-granting signaling overhead due to mobility in a centralized sub-granting resource algorithm, dedicated sub-granting radio resource (DSGRR), and then a distributed heuristics algorithm, open sub-granting radio resource (OSGRR), is proposed and compared with the DSGRR algorithm and no sub-granting case. Simulation results show improved cell throughput for the OSGRR compared with other algorithms. Besides, it is observed that the overhead incurred by the OSGRR is less than the DSGRR while the achieved cell throughput is yet close to the maximum achievable uplink cell throughput.
https://doi.org/10.1186/s13638-022-02128-0