The flow around two parallel cylinders arranged in a tandem configuration is a major source of aerodynamically induced noise and vibrations that can be found in a variety of technical applications. Although this configuration has already been the subject of many past investigations, the effect of unequal cylinder diameters on the resulting far-field tonal noise has not been fully addressed yet, especially for varying streamwise distances between the two cylinders. The present paper describes an experimental acoustic study on tandem cylinder configurations with varying diameters and normalized spacings, where special emphasis was placed on the identification of basic scaling approaches. Additional two-dimensional flow simulations were performed to enable a better qualitative understanding of the flow phenomena. The resulting dataset shows that in most cases, the vortex shedding tonal noise scales with the upstream cylinder diameter. However, for small spacings and large ratios of downstream cylinder diameter to upstream cylinder diameter, the vortex shedding scales with the downstream cylinder diameter. The dominant tonal peak essentially shows a classical dipole-like directivity.
Context: Crop rotations provide agronomic benefits over monocropping, such as enhanced nitrogen supply, improved weed and pest control, and higher yields. Although the theoretical understanding of optimal rotations has advanced, little is known about their real-world implementation and the factors influencing rotation decisions on large scales. Objective: Understanding these factors is key for projecting future cropping patterns, refining agricultural policy, and improving crop models that often oversimplify rotation practices. This study identifies the drivers influencing operational crop rotations across Central Europe and projects future cropping patterns in the region. Methods: We analyse over 16 million field-year combinations from Germany, Austria, and the Czech Republic. Using a random forest algorithm, we determine feature importance and apply a novel machine learning approach that incorporates uncertainty in farmers' decision-making to provide a potential outlook on cropping patterns until 2070. Results and Conclusions: Historical cropping patterns, agronomic practices, and legume commodity prices significantly shaped crop rotations across the region. Projections indicate a substantial increase in legume cultivation over the coming decades, with implications for nitrogen budgets, dietary transitions, and in-silico upscaling. Significance: Rather than optimizing rotations, this study identifies key drivers of operational crop rotations in Central Europe. The findings provide the basis for large-scale simulations that represent cropping patterns more realistically. To the best of our knowledge, the data set compiled here is the most extensive yet analysed in the context of operational crop rotation management.
The Mixed-Shelves Picker Routing Problem (MSPRP) is a fundamental challenge in warehouse logistics, where pickers must navigate a mixed-shelves environment to retrieve SKUs efficiently. Traditional heuristics and optimization-based approaches struggle with scalability, while recent machine learning methods often rely on sequential decision-making, leading to high solution latency and suboptimal agent coordination. In this work, we propose a novel hierarchical and parallel decoding approach for solving the min-max variant of the MSPRP via multi-agent reinforcement learning. While our approach generates a joint distribution over agent actions, allowing for fast decoding and effective picker coordination, our method introduces a sequential action selection to avoid conflicts in the multi-dimensional action space. Experiments show state-of-the-art performance in both solution quality and inference speed, particularly for large-scale and out-of-distribution instances. Our code is publicly available at http://github.com/LTluttmann/marl4msprp.
The coevolution of hydrological and vegetation dynamics in semi-arid regions often leads to vegetation self-organisation (VSO). While numerous hypotheses on the ecohydrological processes driving VSO have been explored through mathematical models, these have struggled to capture the multiscale complexity emerging from short-term surface runoff over heterogeneous topographies under variable rainfall. This limitation hinders understanding of how natural topography and rainfall variability shape long-term vegetation patterns. Previous studies suggest that intra-storm water redistribution at the hillslope scale-controlled by topography and storm intensity-plays a key role in VSO. However, these factors have rarely been considered together due to methodological constraints in numerical solvers. We argue that accurately representing these processes is essential to investigate their interactions. This study systematically examines the effects of hillslope topography and intra-annual rainfall distributions on vegetation band formation using a physically based model that couples the Zero-Inertia (Diffusive Wave) approximation of the shallow water equations with the HilleRisLambers-Rietkerk vegetation model. Idealised 30-year simulations were conducted at second-scale hydrodynamic resolution across different hillslope forms (plane, convex, concave), slopes, and rainfall regimes along a semi-arid gradient. Results show that both topography and rainfall variability strongly influence band formation through their control on water redistribution and hydrological balance. Steeper slopes enhance runoff over infiltration, reducing water availability and altering band geometry and migration. Concave hillslopes exhibit distinct runoff convergence and redistribution patterns compared to plane or convex slopes. Rainfall intermittency interacts with topography to further affect pattern stability and morphology. While both drivers shape pattern characteristics differently, their joint effects mainly influence band migration without providing a strong stabilising mechanism. These results demonstrate the feasibility of long-term, physically based ecohydrological simulations, paving the way for more comprehensive models including sediment transport and geomorphic feedbacks.
This study investigates the mechanical behaviour of fused filament fabrication (FFF) of 316L austenitic stainless steel compared to conventional 316L at room temperature and 77 K, focusing on deformation-induced martensitic transformation (DIMT). Results reveal that the L & uuml;ders-like effect, present in conventional 316L at 77 K, is absent in FFF 316L due to porosities that hinder martensitic front propagation. At room temperature, uniform strain distribution and DIMT were observed in conventional 316L, whereas in FFF 316L, martensitic nucleation occurred around pores, serving as a localized strengthening mechanism. Microstructural analysis identified Fe-delta islands along grain boundaries in FFF 316L, which contribute to its multiphase nature. Although FFF 316L demonstrates lower yield stress and elongation compared to conventional 316L, this study does not establish design allowables. The present findings are limited to monotonic tensile behaviour, fatigue performance and corrosion resistance under cryogenic conditions were not assessed. Further optimization of fabrication parameters to minimize ferrite content and porosities is suggested to enhance mechanical performance.
