不伦瑞克技术大学

This study investigates the scalable mixing capability of a vibration jet-assisted fluidized bed as well as a high-intensity mixer for the dry mixing of cathode composites for solid-state battery (SSB) cathodes. Despite having different working principles, both processes yield comparable microstructural and thus electrochemical results, proving their applicability for SSB manufacturing. Correlating structural analysis via SEM image analysis with electrochemical data reveals that the discharge capacity is mainly governed by the comminution of the solid electrolyte Li3InCl6 (LIC) and the homogeneity of the microstructure which ultimately determines the heterocontact number between active material and the ionic and electronic network. For both processes the stress intensity is identified as the main cause for comminution of LIC and deagglomeration of the active material LiFePO4 (LFP) and conductive additive carbon black (CB). An inverse relationship between electronic and ionic percolation is found: the mixing process disrupts long range electronic percolation due to CB deagglomeration and LIC comminution, whereas the smaller solid electrolyte particle size significantly increases the ionic percolation and therefore cell capacity. Overall, this study proves that both processes are promising for an up-scaled dry mixing process of SSB cathode materials.

A central question for understanding interplanetary coronal mass ejection (ICME) physics and improving space weather forecasting is how ICMEs evolve in interplanetary space. We have updated one of the most comprehensive in situ ICME catalogs to date, which now includes 1976 events from 11 space missions covering over 34 yr, from 1990 December to 2025 August. We have combined existing catalogs including magnetic obstacles (MOs) and identified and added boundaries of an additional 807 (40.8%) events. With this catalog, we demonstrate the most extensive analysis to date of total ICME magnetic field values as a function of heliocentric distance. Parker Solar Probe has observed six ICMEs at <0.23 au (until 2025 April), and Solar Orbiter and BepiColombo have added more events near 0.3 au, bridging the major observational gap towards the solar corona. Our main result is that a single power law can describe the evolution of the mean total magnetic field (exponent value of k = -1.57) and maximum field (k = -1.53) for ICMEs with MOs, from 0.07 to 5.4 au. Extending the power law to the solar photosphere reveals a strong inconsistency with magnetic field magnitudes observed in the quiet Sun and active regions by 2 and 4 orders of magnitude, respectively. We introduce a multipole-type power law with two exponents, k(1) = -1.57, and k(2) = -6, relating the ICME magnetic field magnitude to an average solar active region field strength. These results present important observational constraints for the evolution of ICMEs from the Sun to the heliosphere.

A study of the dynamical two-dimensional (2D) nonlinear response of the dimerized spin-1/2 chain to external electric fields is presented. The coupling of the spin system to those fields is set to arise from the inverse Dzyaloshinskii-Moriya interaction. In the XY-limit, we provide analytical expressions for the second-order nonlinear dynamical response function. Apart from multi spinon continua, this response displays a strong antidiagonal, i.e. galvanoelectric, feature in the 2D frequency plane. This allows to read off scattering rates of the fractional spinon excitations. For the XXZ-case, we focus on the interaction-driven renormalization of the light-matter coupling by considering vertex corrections which are induced by the zz-exchange. We show this renormalization to modify the spinon joint density of states significantly, potentially allowing for the formation of in-gap bound states. As a result, the vertex corrected light-matter coupling can induce a dramatic spectral weight transfer to lower energies for the dynamical response function within the 2D frequency plane.

Real-world wireless transmitter frontends exhibit certain nonlinear behavior, e.g., signal clipping by a Power Amplifier (PA). Although many resource allocation solutions do not consider this for simplicity, it leads to inaccurate results or a reduced number of degrees of freedom, not achieving the global performance. In this work, we propose an optimal PA distortion-aware power allocation strategy in a downlink orthogonal frequency division multiplex (OFDM) based massive multiple-input multiple-output (M-MIMO) system. Assuming a soft-limiter PA model, where the transmission occurs under small-scale independent and identically distributed (i.i.d) Rayleigh fading channel, we derive the wideband signal-to-noise-and-distortion ratio (SNDR) and formulate the power allocation problem. Most interestingly, the distortion introduced by the PA leads to an SNDR-efficient operating point without explicit transmit power constraints. While the optimization problem is non-convex, we decouple it into a non-convex total power allocation problem and a convex power distribution problem among the users (UEs). We propose an alternating optimization algorithm to find the optimum solution. Our simulation results show significant sum-rate gains over existing distortion-neglecting solutions, e.g., a median 4 times increase and a median 50% increase for a 64-antenna and 512-antenna base station serving 60 users, respectively.

The surface topography of parts and components manufactured by direct energy deposition arc (DED-arc) based on additive manufacturing is crucial for fatigue behavior. In this study, DED-arc specimens made of AISI 316L are characterized according to their mechanical properties and surface topography (waviness). The specimen surface was digitized by 3D scanning. Fatigue tests were performed in as-printed condition and milled condition (flat surface). The crack initiation locations of each individual specimen were determined to correlate individual geometry and failure location. The specimens made of 316L showed a significant waviness of up to 1.4 mm. The fatigue tests were evaluated with different concepts: the nominal stress approach based on different definitions of the cross sections, as well as local approaches like the maximum stress (notch stress), critical distance, or stress gradient approach. The scatter in the S–N curves was significantly reduced by using all three local approaches, with the lowest scatter observed using the maximum stress approach. The fatigue life was assessed by linear elastic fracture mechanics (LEFM) using best practice input parameters based on the fatigue life assessment of welded joints. By LEFM, conservative fatigue life values could be reached according to the experiments, especially for low load levels. A combination of local approaches with LEFM leads to a very good agreement in the investigated case.