Computational modelling and mechanistic insight into light-driven CO dissociation of square-planar rhodium(I) complexes. - In: ChemPhotoChem, ISSN 2367-0932, Bd. n/a (2023), n/a, e202300219, S. 1-28
The activation step of Vaska-type Rh(I) complexes, such as the photocleavage of the Rh‑CO bond, plays an important role in the subsequent C-H activation. To elucidate the details of the photochemistry of Vaska-type Rh(I) complexes, such as trans-Rh(PMe3)2(CO)(Cl), we here present a computationally derived picture as obtained at the density functional level of theory (DFT) in combination with multireference wavefunction-based methods. We have identified that the photocleavage of CO proceeds via the metal-centered excited state, which is populated through intersystem crossing (ISC) from the dipole-allowed excited state S1. Moreover, the present study unraveled the reasons for the low C-H activation efficiency when using Rh featuring the bidentate ligand 1,2-bis(dimethylphosphino)ethane (dmpe), namely due to its unfavorable photochemical properties, i.e., the small driving force for light-induced CO loss and the fast deactivation of 3MC state back to the singlet ground state. In this study, we provide theoretical insight into mechanistic details underlying the light-induced CO dissociation process, for Rh complexes featuring PMe3 and dmpe ligands.
https://doi.org/10.1002/cptc.202300219
Quantum confinement of electrons at metal surfaces. - In: Materials lab, ISSN 2653-4878, Bd. 2 (2023), 3, 230006, S. 1-11
Scanning tunneling microscopy and spectroscopy experiments on surface-localized electron states confined to nanometer-scaled resonators are reviewed from the first observations to the recently discovered novel reflection mechanism of electron de Broglie waves. The focus of the presented work is on lateral confinement and on processes leading to finite decay rates of the confined states.
https://doi.org/10.54227/mlab.20230006
Effects of carbon nanotube addition on the microstructures, martensitic transformation, and internal friction of Cu-Al-Ni shape-memory alloys. - In: Scientific reports, ISSN 2045-2322, Bd. 13 (2023), 21181, S. 1-12
https://doi.org/10.1038/s41598-023-48516-4
Magnetic bound states of iron clusters on a superconductor. - In: Physical review, ISSN 2469-9969, Bd. 108 (2023), 19, 195403, S. 195403-1-195403-13
The magnetic exchange interaction of Fen (n = 1, 2, 3) clusters with the quasiparticles of superconducting Pb(111) is probed by scanning tunneling spectroscopy of Yu-Shiba-Rusinov states. The spectral weight of the Yu-Shiba-Rusinov resonances is shifted from the coherence peaks in the Fe monomer spectrum towards the Fermi energy in the Fe dimer spectrum. Unexpectedly, the linear Fe trimer does not follow this trend, as it exhibits an almost identical spectrum to the single Fe atom. Kinked Fe trimers where one of the end atoms deviates from the linear orientation, in contrast, show strong Yu-Shiba-Rusinov resonances well within the Bardeen-Cooper-Schrieffer energy gap of the substrate. First-principles simulations of the Yu-Shiba-Rusinov states reveal which adsorption geometries and magnetic structures of the clusters can reproduce the experimental spectra most accurately.
https://doi.org/10.1103/PhysRevB.108.195403
Letter from the special issue editors : special issue on modern vehicle dynamics control systems. - In: SAE International journal of vehicle dynamics, stability, and NVH, ISSN 2380-2170, Bd. 7 (2023), 3, S. 265-267
https://doi.org/10.4271/10-07-03-0016
A low-power data logger with simple file system for long-term environmental monitoring in remote areas. - In: IEEE sensors journal, ISSN 1558-1748, Bd. 23 (2023), 24, S. 31178-31195
This research addresses the long-term measurement of environmental data in geographically remote areas and an energy-optimized method of storing data on a storage medium. For this purpose, we have developed our measurement module ADL - Advanced Data Logger. In terms of connectivity, the module operates in 3 modes: offline - when measured data is primarily stored on the storage medium; IoT ready - measured data is stored on the storage medium and sent to the remote server in defined batches; online mode - when measured data is preferably sent to the remote server immediately after measurement. The design aims to minimize the module’s power consumption so that the autonomous operating time is close to one year. As part of the design, the simpleFS software module is designed for the role of a simple file system optimized to minimize I/O operations. Its other feature in data storage is the automatic normalization of the data transmitted from the attached sensors. The last part of the design is the AdlReader software solution, used to configure the hardware (HW) module and to retrieve the measured data files. We verified the correct operation of the ADL module along with nine sensors built in a vertical soil temperature profile probe in experimental installation and operation for two months. According to the requirements for our solution, the expected operation time of the ADL module is 9 - 12 months.
https://doi.org/10.1109/JSEN.2023.3328357
Spatial prediction of the turbulent unsteady von Kármán vortex street using echo state networks. - In: Physics of fluids, ISSN 1089-7666, Bd. 35 (2023), 11, 115141, S. 115141-1-115141-15
The spatial prediction of the turbulent flow of the unsteady von Kármán vortex street behind a cylinder at Re = 1000 is studied. For this, an echo state network (ESN) with 6000 neurons was trained on the raw, low-spatial resolution data from particle image velocimetry. During prediction, the ESN is provided one half of the spatial domain of the fluid flow. The task is to infer the missing other half. Four different decompositions termed forward, backward, forward-backward, and vertical were examined to show whether there exists a favorable region of the flow for which the ESN performs best. Also, it was checked whether the flow direction has an influence on the network's performance. In order to measure the quality of the predictions, we choose the vertical velocity prediction of direction (VVPD). Furthermore, the ESN's two main hyperparameters, leaking rate (LR) and spectral radius (SR), were optimized according to the VVPD values of the corresponding network output. Moreover, each hyperparameter combination was run for 24 random reservoir realizations. Our results show that VVPD values are highest for LR ≈ 0.6, and quite independent of SR values for all four prediction approaches. Furthermore, maximum VVPD values of ≈ 0.83 were achieved for backward, forward-backward, and vertical predictions while for the forward case VVPDmax = 0.74 was achieved. We found that the predicted vertical velocity fields predominantly align with their respective ground truth. The best overall accordance was found for backward and forward-backward scenarios. In summary, we conclude that the stable quality of the reconstructed fields over a long period of time, along with the simplicity of the machine learning algorithm (ESN), which relied on coarse experimental data only, demonstrates the viability of spatial prediction as a suitable method for machine learning application in turbulence.
https://doi.org/10.1063/5.0172722
An ecological study protocol for the multimodal investigation of the neurophysiological underpinnings of dyadic joint action. - In: Frontiers in human neuroscience, ISSN 1662-5161, Bd. 17 (2023), 1305331, S. 1-19
A novel multimodal experimental setup and dyadic study protocol were designed to investigate the neurophysiological underpinnings of joint action through the synchronous acquisition of EEG, ECG, EMG, respiration and kinematic data from two individuals engaged in ecologic and naturalistic cooperative and competitive joint actions involving face-to-face real-time and real-space coordinated full body movements. Such studies are still missing because of difficulties encountered in recording reliable neurophysiological signals during gross body movements, in synchronizing multiple devices, and in defining suitable study protocols. The multimodal experimental setup includes the synchronous recording of EEG, ECG, EMG, respiration and kinematic signals of both individuals via two EEG amplifiers and a motion capture system that are synchronized via a single-board microcomputer and custom Python scripts. EEG is recorded using new dry sports electrode caps. The novel study protocol is designed to best exploit the multimodal data acquisitions. Table tennis is the dyadic motor task: it allows naturalistic and face-to-face interpersonal interactions, free in-time and in-space full body movement coordination, cooperative and competitive joint actions, and two task difficulty levels to mimic changing external conditions. Recording conditions - including minimum table tennis rally duration, sampling rate of kinematic data, total duration of neurophysiological recordings - were defined according to the requirements of a multilevel analytical approach including a neural level (hyperbrain functional connectivity, Graph Theoretical measures and Microstate analysis), a cognitive-behavioral level (integrated analysis of neural and kinematic data), and a social level (extending Network Physiology to neurophysiological data recorded from two interacting individuals). Four practical tests for table tennis skills were defined to select the study population, permitting to skill-match the dyad members and to form two groups of higher and lower skilled dyads to explore the influence of skill level on joint action performance. Psychometric instruments are included to assess personality traits and support interpretation of results. Studying joint action with our proposed protocol can advance the understanding of the neurophysiological mechanisms sustaining daily life joint actions and could help defining systems to predict cooperative or competitive behaviors before being overtly expressed, particularly useful in real-life contexts where social behavior is a main feature.
https://doi.org/10.3389/fnhum.2023.1305331
Dynamic delay-dispersive UWB-radar targets: modeling and estimation. - In: IEEE transactions on antennas and propagation, ISSN 1558-2221, Bd. 71 (2023), 8, S. 6814-6829
This publication proposes a parametric data model and a gradient-based maximum likelihood estimator suitable for the description of delay-dispersive responses of multiple dynamic ultrawideband (UWB)-radar targets. The target responses are estimated jointly with the global target parameters range and velocity. The large relative bandwidth of UWB has consequences for model-based parameter estimation. On the one hand, the Doppler effect leads to a dispersive response in the Doppler spectrum and to a coupling of the target parameters that both need to be considered during modeling and estimation. On the other hand, the shape of an extended target results in a dispersive response in range, which can be resolved by the radar resolution. We consider this extended response as a parameter of interest, e.g., for the purpose of target recognition. Hence, we propose an efficient description and estimation of it by a finite impulse response (FIR) structure only imposing a restriction on the target’s dispersiveness in range. We evaluate the approach on simulations, compare it to state-of-the-art solutions, and provide a validation of the FIR model on measurements of a static scenario.
https://doi.org/10.1109/TAP.2023.3287672
High-resolution parameter estimation for wideband radio channel sounding. - In: IEEE transactions on antennas and propagation, ISSN 1558-2221, Bd. 71 (2023), 8, S. 6728-6743
Multidimensional channel sounding measures the geometrical structure of mobile radio propagation. The parameters of a multipath data model in terms of directions, time-of-flight, and Doppler shift are estimated from observations in frequency, time, and space. A maximum likelihood estimation framework allows joint high resolution in all dimensions. The prerequisite for this is an appropriate parametric data model that represents the multipath propagation correctly. At the same time, a device data model is necessary that typically results from calibration measurements. The used model should be as simple as possible, since its structure has a considerable effect on the estimation effort. For instance, the inherent effort in parameter search is reduced if the influence of the parameters is kept independent. Therefore, the data model is characterized by several approximations. The most important is the “narrowband assumption,” which assumes a low relative bandwidth and also avoids considering any frequency response in magnitude and phase. We extend the well-known multidimensional Richter maximization approach (RIMAX) parameter estimation framework by including proper frequency responses. The advantage reveals itself with high bandwidth in the mmWave and sub-THz range. It allows for a more realistic modeling of antenna arrays, and it breaks with the usual narrowband model and allows a better modeling of mutual coupling and time delay effects. If the interacting object extends over several delay bins (hence, an extended target in radar terminology), we propose a model that assigns a short delay spread and a frequency response to the propagation path that associates it with the respective object. We verify the validity of the device model by numerical experiments on simulated and measured antenna data and compare it with RIMAX. In addition, we use synthetic data based on ray-tracing results and measurements both ranging from 27.0 to 33 GHz with known ground-truth information and show that the proposed estimator delivers better performance for higher relative bandwidths than the conventional RIMAX implementation.
https://doi.org/10.1109/TAP.2023.3286024