530 Physik
Filtern
Volltext vorhanden
- nein (119)
Erscheinungsjahr
- 2022 (119) (entfernen)
Dokumenttyp
- Wissenschaftlicher Artikel (119) (entfernen)
Sprache
- Englisch (119) (entfernen)
Gehört zur Bibliographie
- ja (119)
Schlagworte
- diffusion (3)
- Doping (2)
- Fokker-Planck equation (2)
- Nitrogen (2)
- Solar cells (2)
- electrons (2)
- magnetosphere (2)
- numerical relativity (2)
- perovskite solar cells (2)
- stars: evolution (2)
- stochastic resetting (2)
- (high-)voltage measurements (1)
- Annealing (metallurgy) (1)
- Boltzmann distribution (1)
- Breathing chimera states (1)
- CH3NH3SnI3 (1)
- COVID-19 (1)
- Capacitance spectroscopy (1)
- Cations (1)
- Coherence-incoherence (1)
- Conducting polymers (1)
- Coupled oscillators (1)
- Crystallization (1)
- Curie transition (1)
- DNA (1)
- Data analysis (1)
- Deep learning (1)
- Disorder (1)
- Edwards-Anderson order parameter (1)
- Electric potential (1)
- Electrical properties and parameters (1)
- Electronic properties and materials (1)
- Energy (1)
- Epidemic spreading models (1)
- Epoxy resin (1)
- Epoxy resins (1)
- Equilibrium (1)
- European storm-time model (1)
- Excited-state calculations; (1)
- External quantum efficiency (1)
- FLASH (1)
- Free-electron-laser science (1)
- Gas phase (1)
- Ginzburg-Landau lattice (1)
- HTL (1)
- Haake-Lewenstein-Wilkens approach (1)
- Heterogeneous (1)
- Hilbert transform (1)
- Hysteresis (1)
- IR spectroscopy (1)
- ISM (1)
- ISM: supernova remnants (1)
- IZO (1)
- Insulators (1)
- LLG equation (1)
- Langevin equation (1)
- Levy walks (1)
- Ligands (1)
- Localized chaos (1)
- Metals (1)
- Molecular structure (1)
- Molecules (1)
- NLP (1)
- NTCM (1)
- Non-Markovian processes (1)
- Organic semiconductors (1)
- Organic thermoelectrics (1)
- Ott-Antonsen equation (1)
- Oxygen (1)
- Periodic solutions (1)
- Perovskites (1)
- Phase reconstruction (1)
- Phase transitions (1)
- Photoconductivity (1)
- Polarization (1)
- Polaron (1)
- Pseudo-Voigt fit function (1)
- Pulse induced transparency (1)
- Python (1)
- RIXS (1)
- RIXS at FELs (1)
- Reactive coupling (1)
- Reflective writing (1)
- Relaxor-ferroelectric (RF) fluoropolymers (1)
- Robin boundary condition (1)
- SCAPS-1D (1)
- SIR model (1)
- Saddle Point (1)
- Scattering breakdown (1)
- Science education (1)
- Seebeck coefficient (1)
- Solar energy (1)
- Solvents (1)
- Stability (1)
- Steppest Descend method (1)
- Stimulated scattering (1)
- Structure-performance relationship (1)
- Sun (1)
- Surface treatment (1)
- TCOs (1)
- TD-DFT (1)
- TIG-welding (1)
- Thin films (1)
- Thiouracil (1)
- Topological matter (1)
- UV-VIS Spectroscopy (1)
- Uracil (1)
- Water-assisted crystallization (1)
- X-ray (1)
- X-ray refraction; (1)
- X-rays (1)
- active matter (1)
- activity (1)
- additive (1)
- analyzer-based imaging (1)
- anomalous (1)
- anomalous diffusion (1)
- antimicrobial peptides (1)
- applications (1)
- astronomical databases (1)
- asymmetric Levy flights (1)
- atmosphere (1)
- autocorrelation (1)
- autocorrelation function (1)
- azobenzene containing polymers (1)
- binary neutron stars (1)
- boundary local time (1)
- brownian motion (1)
- bubbles (1)
- bumps (1)
- catalysis (1)
- cell migration (1)
- cell motility (1)
- cell polarity (1)
- cell-cell (1)
- charge generation (1)
- chemotaxis (1)
- chimera (1)
- chromosphere (1)
- collective motion (1)
- colloidal particles (1)
- coloured and quantum noise (1)
- complex (1)
- continuous time random (1)
- covariance (1)
- cross layer chip (1)
- crossover anomalous diffusion dynamics (1)
- dark matter (1)
- data analysis (1)
- data based NARMAX modeling (1)
- decomposing anomalous diffusion (1)
- defect detection (1)
- density (1)
- dielectric hysteresis (1)
- dielectrics (1)
- diffraction enhanced imaging (1)
- diffusion exponent (1)
- diffusion-influenced (1)
- direction of optomechanical stress (1)
- doubly transient chaos (1)
- dynamics (1)
- electrets (1)
- electron flux forecasts (1)
- electron lifetimes (1)
- electrostatic (1)
- electrostatic interactions (1)
- equation of state; (1)
- experiments (1)
- external generation efficiency (1)
- external quantum efficiency (1)
- fiber-electrophoresis chip (1)
- finite-size effects (1)
- first-arrival density (1)
- flashover (1)
- fractional Brownian motion (1)
- free-electron laser (1)
- galaxies (1)
- galaxies: abundances (1)
- galaxies: individual (1)
- galaxies: star clusters (1)
- geomagnetic storms (1)
- geostationary orbit (1)
- gravitational-wave astronomy (1)
- heterogeneous diffusion (1)
- high-redshift (1)
- hysteresis (1)
- image registration (1)
- imprinted electrodes (1)
- infrared thermography (1)
- interactions (1)
- intermolecular force (1)
- ionosphere (1)
- large deviation function (1)
- laser powder bed fusion (L-PBF) (1)
- leakage scheme (1)
- magnetic stray field (1)
- magnetisation (1)
- manufacturing (AM) (1)
- memory effects (1)
- memory kernel (1)
- mesoporous silicon (1)
- methods (1)
- methods: MHD (1)
- micro computed tomography (XCT) (1)
- microfluidic paper analytic device (mu PAD) (1)
- mid-temperature transition(s) (1)
- miscellaneous (1)
- mobile ions (1)
- mobile-immobile model (1)
- model (1)
- modeling (1)
- models (1)
- multi-messenger astrophysics (1)
- multidimensional fractional diffusion equation (1)
- multiple (1)
- nanocomposite (1)
- nanofiber (1)
- nanoscale modeling (1)
- network dynamics (1)
- networks (1)
- neural (1)
- neural networks (1)
- neutrinos (1)
- neutron diffraction (1)
- neutron stars (1)
- neutrophils (1)
- non-Gaussian probability (1)
- non-destructive evaluation (1)
- non-exponential relaxation (1)
- nonequilibrium stationary state (1)
- open quantum systems (1)
- organic photovoltaics (1)
- organic semiconductors; (1)
- orientation approaches (1)
- outflows (1)
- patterning glass microfiber (1)
- patterns (1)
- perovskite semiconductors (1)
- phase field model (1)
- phospholipid membranes (1)
- photoelectron spectroscopy (1)
- pitch angle (1)
- polymerase chain reaction (PCR) (1)
- porosity (1)
- potential ene rgy surface (1)
- process inference (1)
- process monitoring (1)
- processing (1)
- protein folding (1)
- purification (1)
- quantum thermodynamics (1)
- radiation belt (1)
- radiation belt forecasts (1)
- random-walk (1)
- reaction-diffusion models (1)
- reactions (1)
- reflected Brownian motion (1)
- relationships (1)
- relative total electron content (1)
- residual stress (1)
- ring current (1)
- ring current model (1)
- rotational diffusion (1)
- search efficiency (1)
- selective laser melting (SLM) (1)
- sintering (1)
- soliton (1)
- space charge (1)
- spark plasma (1)
- spectroscopic (1)
- spin (1)
- spin glass (1)
- stars: Wolft-Rayet (1)
- stars: atmospheres (1)
- stars: individual: WR 7 (1)
- stars: massive (1)
- stars: winds (1)
- stochastic processes (1)
- structure-property (1)
- surface charge (1)
- surface morphology (1)
- surface reactivity (1)
- surface reconstruction (1)
- surface-roughened (1)
- susceptibility (1)
- synchrotron X-ray diffraction (1)
- systems subjected to parameter drift (1)
- tau proteins (1)
- techniques (1)
- ternary blends (1)
- thermal (1)
- thermal conductivity (1)
- theta neurons (1)
- thin-film solar cells (1)
- time-series analysis (1)
- transient chaos (1)
- van allen probes (RBSP) (1)
- van allen probes; (1)
- verb (1)
- verb simulations; (1)
- voltage losses (1)
- walks (1)
- water (1)
- zebrafish (1)
Institut
- Institut für Physik und Astronomie (119) (entfernen)
Based on micromagnetic simulations and experimental observations of the magnetization and lattice dynamics after the direct optical excitation of the magnetic insulator Bi : YIG or indirect excitation via an optically opaque Pt/Cu double layer, we disentangle the dynamical effects of magnetic anisotropy and magneto-elastic coupling. The strain and temperature of the lattice are quantified via modeling ultrafast x-ray diffraction data. Measurements of the time-resolved magneto-optical Kerr effect agree well with the magnetization dynamics simulated according to the excitation via two mechanisms: the magneto-elastic coupling to the experimentally verified strain dynamics and the ultrafast temperature-induced transient change in the magnetic anisotropy. The numerical modeling proves that, for direct excitation, both mechanisms drive the fundamental mode with opposite phase. The relative ratio of standing spin wave amplitudes of higher-order modes indicates that both mechanisms are substantially active.
In crystalline and amorphous semiconductors, the temperature-dependent Urbach energy can be determined from the inverse slope of the logarithm of the absorption spectrum and reflects the static and dynamic energetic disorder. Using recent advances in the sensitivity of photocurrent spectroscopy methods, we elucidate the temperature-dependent Urbach energy in lead halide perovskites containing different numbers of cation components. We find Urbach energies at room temperature to be 13.0 +/- 1.0, 13.2 +/- 1.0, and 13.5 +/- 1.0 meV for single, double, and triple cation perovskite. Static, temperature-independent contributions to the Urbach energy are found to be as low as 5.1 ?+/- 0.5, 4.7 +/- 0.3, and 3.3 +/- 0.9 meV for the same systems. Our results suggest that, at a low temperature, the dominant static disorder in perovskites is derived from zero-point phonon energy rather than structural disorder. This is unusual for solution-processed semiconductors but broadens the potential application of perovskites further to quantum electronics and devices.
The photogeneration of free charges in light-harvesting devices is a multistep process, which can be challenging to probe due to the complexity of contributing energetic states and the competitive character of different driving mechanisms. In this contribution, we advance a technique, integral-mode transient charge extraction (ITCE), to probe these processes in thin-film solar cells. ITCE combines capacitance measurements with the integral-mode time-of-flight method in the low intensity regime of sandwich-type thin-film devices and allows for the sensitive determination of photogenerated charge-carrier densities. We verify the theoretical framework of our method by drift-diffusion simulations and demonstrate the applicability of ITCE to organic and perovskite semiconductor-based thin-film solar cells. Furthermore, we examine the field dependence of charge generation efficiency and find our ITCE results to be in excellent agreement with those obtained via time-delayed collection field measurements conducted on the same devices.
We here present the results from a detailed analysis of nebular abundances of commonly observed ions in the collisional ring galaxy Cartwheel using the Very Large Telescope (VLT) Multi-Unit Spectroscopic Explorer (MUSE) data set. The analysis includes 221 H II regions in the star-forming ring, in addition to 40 relatively fainter H a-emitting regions in the spokes, disc, and the inner ring. The ionic abundances of He, N, O, and Fe are obtained using the direct method (DM) for 9, 20, 20, and 17 ring H II regions, respectively, where the S++ temperature-sensitive line is detected. For the rest of the regions, including all the nebulae between the inner and the outer ring, we obtained O abundances using the strong-line method (SLM). The ring regions have a median 12 + log O/H = 8.19 +/- 0.15, log N/O = -1.57 +/- 0.09 and log Fe/O = -2.24 +/- 0.09 using the DM. Within the range of O abundances seen in the Cartwheel, the N/O and Fe/O values decrease proportionately with increasing O, suggesting local enrichment of O without corresponding enrichment of primary N and Fe. The O abundances of the disc H II regions obtained using the SLM show a well-defined radial gradient. The mean O abundance of the ring H II regions is lower by similar to 0.1 dex as compared to the extrapolation of the radial gradient. The observed trends suggest the preservation of the pre-collisional abundance gradient, displacement of most of the processed elements to the ring, as predicted by the recent simulation by Renaud et al., and post-collisional infall of metal-poor gas in the ring.
Inverted perovskite solar cells still suffer from significant non-radiative recombination losses at the perovskite surface and across the perovskite/C₆₀ interface, limiting the future development of perovskite-based single- and multi-junction photovoltaics. Therefore, more effective inter- or transport layers are urgently required. To tackle these recombination losses, we introduce ortho-carborane as an interlayer material that has a spherical molecular structure and a three-dimensional aromaticity. Based on a variety of experimental techniques, we show that ortho-carborane decorated with phenylamino groups effectively passivates the perovskite surface and essentially eliminates the non-radiative recombination loss across the perovskite/C₆₀ interface with high thermal stability. We further demonstrate the potential of carborane as an electron transport material, facilitating electron extraction while blocking holes from the interface. The resulting inverted perovskite solar cells deliver a power conversion efficiency of over 23% with a low non-radiative voltage loss of 110 mV, and retain >97% of the initial efficiency after 400 h of maximum power point tracking. Overall, the designed carborane based interlayer simultaneously enables passivation, electron-transport and hole-blocking and paves the way toward more efficient and stable perovskite solar cells.
Inverted perovskite solar cells still suffer from significant non-radiative recombination losses at the perovskite surface and across the perovskite/C-60 interface, limiting the future development of perovskite-based single- and multi-junction photovoltaics. Therefore, more effective inter- or transport layers are urgently required. To tackle these recombination losses, we introduce ortho-carborane as an interlayer material that has a spherical molecular structure and a three-dimensional aromaticity. Based on a variety of experimental techniques, we show that ortho-carborane decorated with phenylamino groups effectively passivates the perovskite surface and essentially eliminates the non-radiative recombination loss across the perovskite/C-60 interface with high thermal stability. We further demonstrate the potential of carborane as an electron transport material, facilitating electron extraction while blocking holes from the interface. The resulting inverted perovskite solar cells deliver a power conversion efficiency of over 23% with a low non-radiative voltage loss of 110mV, and retain >97% of the initial efficiency after 400h of maximum power point tracking. Overall, the designed carborane based interlayer simultaneously enables passivation, electron-transport and hole-blocking and paves the way toward more efficient and stable perovskite solar cells. Effective transport layers are essential to suppress non-radiative recombination losses. Here, the authors introduce phenylamino-functionalized ortho-carborane as an interfacial layer, and realise inverted perovskite solar cells with efficiency of over 23% and operational stability of T97=400h.
We introduce and study a Lévy walk (LW) model of particle spreading with a finite propagation speed combined with soft resets, stochastically occurring periods in which an harmonic external potential is switched on and forces the particle towards a specific position. Soft resets avoid instantaneous relocation of particles that in certain physical settings may be considered unphysical. Moreover, soft resets do not have a specific resetting point but lead the particle towards a resetting point by a restoring Hookean force. Depending on the exact choice for the LW waiting time density and the probability density of the periods when the harmonic potential is switched on, we demonstrate a rich emerging response behaviour including ballistic motion and superdiffusion. When the confinement periods of the soft-reset events are dominant, we observe a particle localisation with an associated non-equilibrium steady state. In this case the stationary particle probability density function turns out to acquire multimodal states. Our derivations are based on Markov chain ideas and LWs with multiple internal states, an approach that may be useful and flexible for the investigation of other generalised random walks with soft and hard resets. The spreading efficiency of soft-rest LWs is characterised by the first-passage time statistic.
Levy walks are continuous-time random-walk processes with a spatiotemporal coupling of jump lengths and waiting times. We here apply the Hermite polynomial method to study the behavior of LWs with power-law walking time density for four different cases. First we show that the known result for the infinite density of an unconfined, unbiased LW is consistently recovered. We then derive the asymptotic behavior of the probability density function (PDF) for LWs in a constant force field, and we obtain the corresponding qth-order moments. In a harmonic external potential we derive the relaxation dynamic of the LW. For the case of a Poissonian walking time an exponential relaxation behavior is shown to emerge. Conversely, a power-law decay is obtained when the mean walking time diverges. Finally, we consider the case of an unconfined, unbiased LW with decaying speed v(r ) = v0/./r. When the mean walking time is finite, a universal Gaussian law for the position-PDF of the walker is obtained explicitly.
Computer-based analysis of preservice teachers' written reflections could enable educational scholars to design personalized and scalable intervention measures to support reflective writing. Algorithms and technologies in the domain of research related to artificial intelligence have been found to be useful in many tasks related to reflective writing analytics such as classification of text segments. However, mostly shallow learning algorithms have been employed so far. This study explores to what extent deep learning approaches can improve classification performance for segments of written reflections. To do so, a pretrained language model (BERT) was utilized to classify segments of preservice physics teachers' written reflections according to elements in a reflection-supporting model. Since BERT has been found to advance performance in many tasks, it was hypothesized to enhance classification performance for written reflections as well. We also compared the performance of BERT with other deep learning architectures and examined conditions for best performance. We found that BERT outperformed the other deep learning architectures and previously reported performances with shallow learning algorithms for classification of segments of reflective writing. BERT starts to outperform the other models when trained on about 20 to 30% of the training data. Furthermore, attribution analyses for inputs yielded insights into important features for BERT's classification decisions. Our study indicates that pretrained language models such as BERT can boost performance for language-related tasks in educational contexts such as classification.
How does a systematic time-dependence of the diffusion coefficient D(t) affect the ergodic and statistical characteristics of fractional Brownian motion (FBM)? Here, we answer this question via studying the characteristics of a set of standard statistical quantifiers relevant to single-particle-tracking (SPT) experiments. We examine, for instance, how the behavior of the ensemble- and time-averaged mean-squared displacements-denoted as the standard MSD < x(2)(Delta)> and TAMSD <<(delta(2)(Delta))over bar>> quantifiers-of FBM featuring < x(2) (Delta >> = <<(delta(2)(Delta >)over bar>> proportional to Delta(2H) (where H is the Hurst exponent and Delta is the [lag] time) changes in the presence of a power-law deterministically varying diffusivity D-proportional to(t) proportional to t(alpha-1) -germane to the process of scaled Brownian motion (SBM)-determining the strength of fractional Gaussian noise. The resulting compound "scaled-fractional" Brownian motion or FBM-SBM is found to be nonergodic, with < x(2)(Delta >> proportional to Delta(alpha+)(2H)(-1) and <(delta 2(Delta >) over bar > proportional to Delta(2H). We also detect a stalling behavior of the MSDs for very subdiffusive SBM and FBM, when alpha + 2H - 1 < 0. The distribution of particle displacements for FBM-SBM remains Gaussian, as that for the parent processes of FBM and SBM, in the entire region of scaling exponents (0 < alpha < 2 and 0 < H < 1). The FBM-SBM process is aging in a manner similar to SBM. The velocity autocorrelation function (ACF) of particle increments of FBM-SBM exhibits a dip when the parent FBM process is subdiffusive. Both for sub- and superdiffusive FBM contributions to the FBM-SBM process, the SBM exponent affects the long-time decay exponent of the ACF. Applications of the FBM-SBM-amalgamated process to the analysis of SPT data are discussed. A comparative tabulated overview of recent experimental (mainly SPT) and computational datasets amenable for interpretation in terms of FBM-, SBM-, and FBM-SBM-like models of diffusion culminates the presentation. The statistical aspects of the dynamics of a wide range of biological systems is compared in the table, from nanosized beads in living cells, to chromosomal loci, to water diffusion in the brain, and, finally, to patterns of animal movements.