621 Angewandte Physik
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More than half a century of intense research in modern control theory has not stopped practitioners from continuing to use PID controllers for most real-world control problems. While not a mathematical one, this might be the most convincing proof of their robustness: if necessary, they can be implemented with minimal control engineering experience. Often, controllers are designed by individuals who are experts in their specific domain but are not dedicated control theory specialists. To address the needs of these engineers, this article wants to put an approach known as Active Disturbance Rejection Control (ADRC) in the spotlight—a method that has gradually evolved into an industry-ready alternative to PID control. Reflecting on two decades of improvements, this article portrays ADRC as a solution for everyday control problems that can be both easier to use and richer in out-of-the-box features.
This work investigates the optical stability of formamidinium–cesium lead halide perovskite thin films deposited on fluorine-doped tin oxide substrates and aged under ambient conditions for 21 days. The optical response was analyzed through specular and diffuse transmittance and reflectance measurements, collected with light incident from both sides of the heterostructure. Specular transmittance exhibits nonmonotonic variations with an initial increase followed by a gradual decrease over time, while diffuse transmittance increases systematically across the full spectral range, indicating the progressive formation of scattering centers. Total reflectance decreases monotonically with aging, revealing that degradation is primarily governed by absorption-related optical losses. Despite these changes, the absorption edge remains stable, and the optical bandgap and Urbach tail show no significant variation. Direction-dependent measurements demonstrate that the fluorine-doped tin oxide substrate is the dominant source of initial scattering whereas the perovskite layer initially reduces optical contrast and later introduces disorder as degradation progresses. Haze values remain nearly constant over time, indicating that changes in scattering efficiency are moderate compared to absorption losses. These results demonstrate that integrating sphere-based optical spectroscopy provides a nondestructive and effective framework for monitoring early stage degradation in perovskite thin films.
Detection of Germanium Nanocrystals as Tracer Materials in Polypropylene via Raman Spectroscopy
(2026)
Increasing regulatory demands for high-quality plastic recycling create a strong need for novel tracer systems that enable reliable polymer identification and sorting. This feasibility study evaluates germanium nanocrystals (GeNCs) as Raman-detectable tracer materials in polypropylene (PP). The synthesis of GeNC/PP composite materials possessing various GeNC contents via a solvent-based intercalation process followed by compounding and injection molding is reported. Hydride-terminated GeNCs were synthesized and subsequently functionalized with dodecyl ligands to ensure chemical stability, compatibility with the polymer matrix, and processability under conventional melt-processing conditions. The dodecyl-functionalized GeNCs were successfully stabilized and homogeneously integrated into the PP matrix. Raman spectroscopy demonstrates the clear detection of GeNCs within the composites through a characteristic Ge–Ge optical phonon mode at 296 cm−1, which is well separated from the intrinsic Raman bands of polypropylene. The Raman signal intensity increases systematically with increasing GeNC concentration. Raman mapping reveals an overall homogeneous distribution of the nanocrystals within the polymer, while a slight tendency toward agglomeration is observed at higher loadings. These results demonstrate that GeNCs are well suited as optically detectable tracers for polypropylene and can be reliably identified using Raman spectroscopy, highlighting their potential for tracer-based sorting concepts in advanced recycling and digital material passport applications.
Understanding how growth conditions govern structural order and ion transport in Prussian blue analogues (PBAs) thin films is essential for optimizing their electrochemical performance. Here, cobalt and nickel hexacyanoferrate (CoHCF and NiHCF) thin films were electrodeposited potentiostatically at temperatures between 20 and 60 °C. A combination of cyclic voltammetry, scanning electron microscopy, X-ray diffraction, and Raman spectroscopy was employed to elucidate the interplay between composition, crystallinity, and chemical structure.
Under identical conditions, CoHCF exhibits a maximum current density approximately 2.2 times higher than NiHCF, indicating significantly faster electrochemical kinetics. X-ray diffraction reveals temperature-dependent lattice expansion without phase transitions, with a maximum near 40 °C, associated with structural relaxation and compositional variations. Raman spectroscopy further reveals temperature-dependent local structural evolution, where cyanide band narrowing at intermediate temperatures indicates improved short-range order, while band broadening at higher temperatures reflects increased defect density.
These findings demonstrate that temperature-controlled defect redistribution governs both short- and long-range structural order in PBA thin films, directly influencing ion transport and electrochemical response. This work provides new insights into structure–property relationships and establishes deposition temperature as a key parameter for tuning electrochemical functionality in hexacyanoferrate-based electrodes.
Despite their excellent torsional and bending strength, the economical production of hypotrochoidal profiles (H-profiles) remains an obstacle to their use. Due to the tool clearance angle, the commercially available twin-spindle turning process has limited ability to manufacture many of the profiles standardized according to DIN 3689 (Deutsches Institut für Normung). On the other hand, the manufacturing of cycloidal as a non-involute special geometry using generating processes (hobbing or continuous generating grinding) depends critically on the accuracy of the tool geometry—whether a hobbing cutter or a grinding worm. Conventional tool design methods—based on approximations, involute-derived profiles, or iterative trial-and-error corrections—face fundamental limitations: unpredictable cutting force variations, elevated surface roughness, and limited process capability. However, if the exact tool geometry has been determined analytically, the same machine achieves significantly better performance. In this work, the exact tool geometry conjugated to the H-profile for profile manufacturing is determined based on the gearing law. This provides modular H-profile manufacturing without deviations. Consequently, a design concept that enables the implementation of all existing rolling processes—including gear hobbing, gear shaping, gear planning, and other variants such as gear grinding—is presented. For profile shaping of hollow contours, the transfer ratio is considered and a curve conjugated to the profile contour is determined for the tool. A CAD-based simulation shows very good consistency with the analytically determined tool geometry.
Volumetric and dynamic OCT screening of human testicular tissue comparing unfixed and fixed samples
(2026)
Magnetic Particle Imaging (MPI) is an emerging tomographic modality recognized for its capability of directly detecting magnetic nanoparticles (MNPs), enabling real-time 3D imaging with high sensitivity. Since its introduction in 2005, various preclinical MPI scanners have been developed, but cross-platform comparisons lack due to missing standardized phantoms and operation protocols. Recently, efforts towards development of human-sized MPI have intensified. To facilitate the transition beyond the preclinical research phase, harmonization of MPI technology is essential. Within the "harmoMPI" project, we seek to develop platform-independent, modular phantoms that enable reliable assessment of key performance parameters for a consistent performance evaluation across different MPI systems. With the support from the MPI research community, the "harmoMPI" initiative aims to harmonize MPI technology, advance collaboration research, and pave the path toward clinically relevant applications.
Direct laser interference patterning (DLIP) is a well‐established technique for fabricating micro‐ and nano‐scale structures that can enhance the properties of surfaces such as reduced friction and wear. However, achieving full automation requires reliable in‐line process monitoring to ensure consistent structure quality. In this study, an infrared monitoring camera is implemented to capture spatially resolved temperature distributions during DLIP processing. Stainless‐steel samples are structured while systematically varying the laser fluence (2.5–5.6 J cm−2), and path velocity (1–20 mm s−1). The resulting surface structures are characterized using confocal microscopy to extract key topographical parameters. A convolutional neural network is trained using 180 000 process images from the IR system and the corresponding topographical data. The model identifies clear correlations between laser fluence, thermal signatures, and surface topography. For specific parameters, prediction accuracies of up to 94% are achieved. These results demonstrate that combining infrared monitoring with machine learning enables indirect yet accurate prediction of surface features, paving the way for enhanced process control and quality assurance in DLIP and related manufacturing processes.
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In this paper the application of Active Disturbance Rejection Control (ADRC) for discrete-time field-oriented PMSM current control is discussed. ADRC offers an interesting alternative to established current control algorithms due to the considerably simplified control engineering process. After introducing the ADRC approach and the plant model, the possibilities for tuning the controller and the comprised state space observer are examined in detail. In particular, the adequate consideration of the modulator delay in the ADRC’s extended state observer is investigated, leading to a new ADRC current control algorithm. This allows a parameterization for very fast dynamics, so that almost deadbeat behavior is achievable. All investigations are validated by means of practical measurements.
