@misc{FlorianSchrickerZenzetal., author = {Florian, Tobias and Schricker, Klaus and Zenz, Constantin and Otto, Andreas and Schmidt, Leander and Diegel, Christian and Friedmann, Hannes and Seibold, Marc and Hellwig, Peter and Fr{\"o}hlich, Fabian and Nagel, Falk and Kallage, Peter and Buttazzoni, Michele and Rack, Alexander and Requardt, Herwig and Chen, Yunhui and Bergmann, Jean Pierre}, title = {Combining in situ synchrotron X-ray imaging and multiphysics simulation to reveal pore formation dynamics in laser welding of copper}, series = {International Journal of Machine Tools and Manufacture}, volume = {204}, journal = {International Journal of Machine Tools and Manufacture}, publisher = {Elsevier BV}, issn = {0890-6955}, doi = {10.1016/j.ijmachtools.2024.104224}, pages = {1 -- 22}, abstract = {Laser beam welding has emerged as a powerful tool for manufacturing copper components in electrical vehicles, electronic devices or energy storage, owing to its rapid processing capabilities. Nonetheless, the material's high thermal conductivity and low absorption of infrared light can introduce process instabilities, resulting in defects such as pores. This study employs a hybrid approach that combines in situ synchrotron X-ray imaging with compressible multiphysics process simulation to elucidate pore-forming mechanisms during laser beam welding of copper. High-speed synchrotron X-ray imaging with an acquisition rate of 20,000 images/second facilitates the identification of relevant process regimes concerning pore formation during laser beam welding of copper with a wavelength of 1070 nm. Furthermore, in situ observations with high temporal and spatial resolution present a unique database for extensive validation of a multi-physics process simulation based on welding processes using different concentric intensity distributions. These validated simulation results enable thorough comprehension of process-related pore formation based on the interaction between keyhole, melt pool and resulting flow field. The findings show that pore formation is driven by four different mechanisms: bulging, spiking, upwelling waves at the keyhole rear wall and melt pool ejections. The synergy of high- speed synchrotron X-ray imaging and multi-physics modeling provides a fundamental understanding of the chronological sequence of events leading to process-related pore formation during laser beam welding of copper.}, language = {en} } @misc{PalacioBunnRahnetal., author = {Palacio, Juan Camilo Rivera and Bunn, Christian and Rahn, Eric and Little-Savage, Daisy and Schmidt, Paul G{\"u}nter and Ryo, Masahiro}, title = {Geographic-scale coffee cherry counting with smartphones and deep learning}, series = {Plant Phenomics}, volume = {6}, journal = {Plant Phenomics}, publisher = {American Association for the Advancement of Science (AAAS)}, issn = {2643-6515}, doi = {10.34133/plantphenomics.0165}, pages = {11}, abstract = {Deep learning and computer vision, using remote sensing and drones, are 2 promising nondestructive methods for plant monitoring and phenotyping. However, their applications are infeasible for many crop systems under tree canopies, such as coffee crops, making it challenging to perform plant monitoring and phenotyping at a large spatial scale at a low cost. This study aims to develop a geographic-scale monitoring method for coffee cherry counting, supported by an artificial intelligence (AI)-powered citizen science approach. The approach uses basic smartphones to take a few pictures of coffee trees; 2,968 trees were investigated with 8,904 pictures in Jun{\´i}n and Piura (Peru), Cauca, and Quind{\´i}o (Colombia) in 2022, with the help of nearly 1,000 smallholder coffee farmers. Then, we trained and validated YOLO (You Only Look Once) v8 for detecting cherries in the dataset in Peru. An average number of cherries per picture was multiplied by the number of branches to estimate the total number of cherries per tree. The model's performance in Peru showed an R2 of 0.59. When the model was tested in Colombia, where different varieties are grown in different biogeoclimatic conditions, the model showed an R2 of 0.71. The overall performance in both countries reached an R2 of 0.72. The results suggest that the method can be applied to much broader scales and is transferable to other varieties, countries, and regions. To our knowledge, this is the first AI-powered method for counting coffee cherries and has the potential for a geographic-scale, multiyear, photo-based phenotypic monitoring for coffee crops in low-income countries worldwide.}, language = {en} } @misc{PożarowskaPleinesEwertetal., author = {Pożarowska, Emilia and Pleines, Linus and Ewert, Moritz and Prieto, Mauricio J. and Tănase, Liviu Christian and Souza Caldas, Lucas de and Tiwari, Aarti and Schmidt, Thomas and Falta, Jens and Krasovskii, Eugene and Morales, Carlos and Flege, Jan Ingo}, title = {Preparation and stability of the hexagonal phase of samarium oxide on Ru(0001)}, series = {Ultramicroscopy}, volume = {250}, journal = {Ultramicroscopy}, issn = {0304-3991}, doi = {10.1016/j.ultramic.2023.113755}, abstract = {We have used low-energy electron microscopy (LEEM), micro-illumination low-energy electron diffraction (µLEED) supported by ab initio calculations, and X-ray absorption spectroscopy (XAS) to investigate in-situ and in real-time the structural properties of Sm2O3 deposits grown on Ru(0001), a rare-earth metal oxide model catalyst. Our results show that samarium oxide grows in a hexagonal A-Sm2O3 phase on Ru(0001), exhibiting a (0001) oriented-top facet and (113) side facets. Upon annealing, a structural transition from the hexagonal to cubic phase occurs, in which the Sm cations exhibit the +3 oxidation state. The unexpected initial growth in the A-Sm2O3 hexagonal phase and its gradual transition to a mixture with cubic C-Sm2O3 showcases the complexity of the system and the critical role of the substrate in the stabilization of the hexagonal phase, which was previously reported only at high pressures and temperatures for bulk samaria. Besides, these results highlight the potential interactions that Sm could have with other catalytic compounds with respect to the here gathered insights on the preparation conditions and the specific compounds with which it interacts.}, language = {en} } @misc{KleinZenkerStaricketal., author = {Klein, Marten and Zenker, Christian and Starick, Tommy and Schmidt, Heiko}, title = {Stochastic modeling of multi-stream mixing based on one-dimensional turbulence}, series = {77th Annual Meeting of the Division of Fluid Dynamics}, journal = {77th Annual Meeting of the Division of Fluid Dynamics}, publisher = {American Physical Society}, abstract = {Measurements of multiple scalar mixing in a turbulent jet show a strong location dependence of the scalar fluctuations and mixing processes. Mixing is quantitatively described by the state space of scalar fluctuations in terms of a joint probability density function (JPDF). The JPDF evolves in the downstream and radial directions and has non-Gaussian shape which is a burden for mixing modeling since factoring into marginal distribution functions is not permissible. Stochastic simulations based on one-dimensional turbulence (ODT) are able to reasonably reproduce the JPDF and its spatial evolution by a parabolic marching problem that circumvents constraints of the underlying elliptic problem. The model reproduces the inertial-advective range (exponent -5/3) and predicts the emergence of the viscous-advective range (exponent -1) at higher wavenumbers as the Schmidt number increases. The model offers full-scale resolution at affordable cost providing means to reasonably capture state-space statistics of turbulent mixing.}, language = {en} } @misc{KleinZenkerStaricketal., author = {Klein, Marten and Zenker, Christian and Starick, Tommy and Schmidt, Heiko}, title = {Stochastic modeling of multiple scalar mixing in a three-stream concentric coaxial jet based on one-dimensional turbulence}, series = {International Journal of Heat and Fluid Flow}, volume = {104}, journal = {International Journal of Heat and Fluid Flow}, issn = {0142-727X}, doi = {10.1016/j.ijheatfluidflow.2023.109235}, pages = {1 -- 17}, abstract = {Modeling turbulent mixing is a standing challenge for nonpremixed chemically reacting flows. Key complications arise from the requirement to capture all relevant scales of the flow and the necessity to distinguish between turbulent advective transport and molecular diffusive transport processes. In addition, anisotropic mean shear, variable advection time scales, and the coexistence of turbulent and nonturbulent regions need to be represented. The fundamental issues at stake are addressed by investigating multi-scalar mixing in a three-stream coaxial jet with a map-based stochastic one-dimensional turbulence model. ODT provides full-scale resolution at affordable costs by a radical reduction of complexity compared to high-fidelity Navier-Stokes solvers. The approach is partly justified by an application of the boundary-layer approximation, but neglects fluctuating axial pressure gradients. It is demonstrated that low-order scalar statistics are reasonably but not fully captured. Despite this shortcoming, it is shown that the model is able to reproduce experimental state-space statistics of multi-stream multi-scalar mixing. The model therefore offers physics-compatible improvements in multi-stream mixing modeling despite some fundamental limitations that remain from unjustified assumptions.}, language = {en} } @misc{KleinStarickZenkeretal., author = {Klein, Marten and Starick, Tommy and Zenker, Christian and Medina M{\´e}ndez, Juan Al{\´i} and Schmidt, Heiko}, title = {Reduced order stochastic modeling of turbulent mixing based on conservative baker's maps}, series = {Proceedings of the 14th International ERCOFTAC Symposium on Engineering Turbulence Modelling and Measurements (ETMM-14)}, journal = {Proceedings of the 14th International ERCOFTAC Symposium on Engineering Turbulence Modelling and Measurements (ETMM-14)}, publisher = {ERCOFTAC}, address = {Barcelona, Spain}, pages = {613 -- 618}, abstract = {The detailed numerical representation of turbulent mixing processes is a standing challenge for non-premixed chemically reacting flows. The full range of relevant flow scales needs to be captured and it is also necessary to distinguish turbulent advective from molecular diffusive processes in order to represent Reynolds and Schmidt number effects. These requirements are addressed here by utilizing two different map-based stochastic turbulence modeling strategies. The one-dimensional turbulence (ODT) model utilizes event-based turbulence modeling, whereas the hierarchical parcel-swapping (HiPS) model is a fully event-based mixing model. ODT provides full-scale resolution at affordable costs by dimensional model reduction based on the boundary-layer approximation to shear flow. HiPS is far less costly than ODT but currently limited to locally homogeneous isotropic turbulence. The physics-compatible modeling capabilities with respect to phase-space representation of turbulent mixing are demonstrated for two canonical cases using standalone model formulations.}, language = {en} } @misc{DiegelSchrickerSchmidtetal., author = {Diegel, Christian and Schricker, Klaus and Schmidt, Leander and Seibold, Marc and Friedmann, Hannes and Hellwig, Peter and Fr{\"o}hlich, Fabian and Nagel, Falk and Kallage, Peter and Rack, Alexander and Requardt, Herwig and Chen, Yunhui and Bergmann, Jean Pierre}, title = {In situ characterization of keyhole behavior and spatter formation in full penetration laser beam welding with local gas flow using high-speed synchrotron X-ray imaging}, series = {Optics \& laser technology}, volume = {191}, journal = {Optics \& laser technology}, publisher = {Elsevier BV}, address = {Amsterdam}, issn = {0030-3992}, doi = {10.1016/j.optlastec.2025.113367}, pages = {1 -- 17}, abstract = {Spatter formation is a major issue at welding speeds above 8 m/min for full penetration laser beam welding of high-alloyed steels. In experiments using a local gas flow directed at the keyhole rear wall, a reduction in spatter formation on the specimen top side was observed for welding of AISI 304. However, the interaction between gas flow and keyhole behavior with respect to the mechanisms and locations of spatter detachment, especially on the bottom side, is not yet fully understood. High-speed synchrotron X-ray imaging enables detailed insights into the keyhole behavior and the spatter formation to obtain a deeper understanding of the underlying mechanisms. During the reference experiments welding without shielding gas flow, the spatter detach from a melt pool swelling behind the keyhole aperture on both sides of the sheet. A gas flow with a low flow rate of 4.8 L/min reduces the spatter formation on the top side and the keyhole length due to the absence of oxygen affecting the surface tension. A swelling also forms on the keyhole front on the bottom side and small spatter detach undirected. Increasing the flow rate to 12.8 L/min elongates the keyhole, particularly on the specimen top side. The increased momentum transfer of the gas flow results in a periodic keyhole oscillation on the specimen top side. In combination with an elongated melt pool, the oscillation is directly correlated with the hump formation, caused by melt being pushed over the already solidified weld seam. In addition, spatter does not detach from the top side due to the changed melt flow and only detach from the keyhole front on the bottom side.}, language = {en} } @incollection{UlrichSchlegelMertensetal., author = {Ulrich, Rainer G. and Schlegel, Matthias and Mertens, Marc and Groschup, Martin H. and Schmidt-Chanasit, Jonas and Plenge-B{\"o}nig, Anita and Jacob, Jens and Pelz, Hans-Joachim and Freise, Jona and Wenk, Matthias and Thiel, J{\"o}rg and Triebenbacher, Cornelia and Schmolz, Eric and Kurth, Andreas and Kr{\"u}ger, Frank and R{\"u}he, Ferdinand and Kiffner, Christian and Ansorge, Hermann and Gerwin, Werner and Wegener, Wolfgang and M{\"u}ller, J{\"o}rg and Bemmann, Margit and Wolf, Ronny and Otto, Lutz-Florian and Oehme, Rainer and Pfeffer, Martin and Heckel, Gerald and Schex, Susanne and Essbauer, Sandra S.}, title = {Netzwerk Nagetier-{\"u}bertragene Pathogene: Monitoring von Hantavirus-Infektionen in Deutschland}, series = {Wildhygiene, Wildtierkrankheiten, Parasiten, Epidemiologie}, booktitle = {Wildhygiene, Wildtierkrankheiten, Parasiten, Epidemiologie}, publisher = {Ges. f{\"u}r Wildtier- und Jagdforschung}, address = {Halle/Saale}, isbn = {978-378-88131-2-3}, issn = {1436-3895}, pages = {229 -- 250}, language = {de} } @misc{VeldkampSchmidtMarkwitzetal., author = {Veldkamp, Edzo and Schmidt, Marcus and Markwitz, Christian and Beule, Lukas and Beuschel, Ren{\´e} and Biert{\"u}mpfel, Andrea and Bischel, Xenia and Duan, Xiaohong and Gerjets, Rowena and G{\"o}bel, Leonie and Graß, R{\"u}diger and Guerra, Victor and Heinlein, Florian and Komainda, Martin and Langhof, Maren and Luo, Jie and Potthoff, Martin and Ramshorst, Justus G. V. van and Rudolf, Carolin and Seserman, Diana-Maria and Shao, Guodong and Siebicke, Lukas and Svoboda, Nikolai and Swieter, Anita and Carminati, Andrea and Freese, Dirk and Graf, Torsten and Greef, J{\"o}rg M. and Isselstein, Johannes and Jansen, Martin and Karlovsky, Petr and Knohl, Alexander and Lamersdorf, Norbert and Priesack, Eckart and Wachendorf, Christine and Wachendorf, Michael and Corre, Marife D.}, title = {Multifunctionality of temperate alley-cropping agroforestry outperforms open cropland and grassland}, series = {Communications Earth \& Environment}, volume = {4}, journal = {Communications Earth \& Environment}, number = {1}, publisher = {Springer Science and Business Media LLC}, issn = {2662-4435}, doi = {10.1038/s43247-023-00680-1}, pages = {10}, abstract = {AbstractIntensively managed open croplands are highly productive but often have deleterious environmental impacts. Temperate agroforestry potentially improves ecosystem functions, although comprehensive analysis is lacking. Here, we measured primary data on 47 indicators of seven ecosystem functions in croplands and 16 indicators of four ecosystem functions in grasslands to assess how alley-cropping agroforestry performs compared to open cropland and grassland. Carbon sequestration, habitat for soil biological activity, and wind erosion resistance improved for cropland agroforestry (P ≤ 0.03) whereas only carbon sequestration improved for grassland agroforestry (P \< 0.01). In cropland agroforestry, soil nutrient cycling, soil greenhouse gas abatement, and water regulation did not improve, due to customary high fertilization rates. Alley-cropping agroforestry increased multifunctionality, compared to open croplands. To ameliorate the environmental benefits of agroforestry, more efficient use of nutrients is required. Financial incentives should focus on conversion of open croplands to alley-cropping agroforestry and incorporate fertilizer management.}, language = {en} } @inproceedings{BaerwolffBoehmSchmidtetal., author = {B{\"a}rwolff, Manuela and B{\"o}hm, Christian and Schmidt, C. and Schwarz, K.- U. and Vetter, A.}, title = {Combining short rotation coppice with annual crops - modern agroforestry systems for sustainable land use}, series = {Proceedings of the 19th European Biomass Conference and Exhibition: From Research to Industry and Markets, 6-9 Juni 2011 in Berlin, Deutschland}, booktitle = {Proceedings of the 19th European Biomass Conference and Exhibition: From Research to Industry and Markets, 6-9 Juni 2011 in Berlin, Deutschland}, isbn = {978-88-89407-55-4}, doi = {10.5071/19thEUBCE2011-OB1.5}, pages = {55 -- 60}, language = {en} } @incollection{GruenewaldBaerwolffBoehmetal., author = {Gr{\"u}newald, Holger and B{\"a}rwolff, Manuela and B{\"o}hm, Christian and Schwarz, K.- U. and Schmidt, C.}, title = {{\"O}kologische und {\"o}konomische Bewertung von Agroforstsystemen in der landwirtschaftlichen Praxis}, series = {Holzerzeugung in der Landwirtschaft}, booktitle = {Holzerzeugung in der Landwirtschaft}, publisher = {BTU}, address = {Cottbus}, isbn = {978-3-937728-05-6}, pages = {213 -- 216}, language = {de} } @inproceedings{BoehmFreeseSchmidtetal., author = {B{\"o}hm, Christian and Freese, Dirk and Schmidt, C. and H{\"u}ttl, Reinhard F.}, title = {Alley cropping - an option to combine crop and woody biomass production at degraded post-mining sites in Germany}, series = {Book of Abstracts, 2nd World Congress of Agroforestry, Agroforestry - The Future of Global Land Use}, booktitle = {Book of Abstracts, 2nd World Congress of Agroforestry, Agroforestry - The Future of Global Land Use}, publisher = {World Agroforestry Centre}, address = {Nairobi, Kenya}, isbn = {978-92-9059-255-6}, pages = {S. 253}, language = {en} } @inproceedings{GruenewaldBaerwolffBoehmetal., author = {Gr{\"u}newald, Holger and B{\"a}rwolff, Manuela and B{\"o}hm, Christian and Schwarz, K.- U. and Schmidt, C.}, title = {Establishment of alley-cropping systems with short rotation woody crops in Germany}, series = {Book of Abstracts, 2nd World Congress of Agroforestry, Agroforestry - The Future of Global Land Use}, booktitle = {Book of Abstracts, 2nd World Congress of Agroforestry, Agroforestry - The Future of Global Land Use}, publisher = {World Agroforestry Centre}, address = {Nairobi, Kenya}, isbn = {978-92-9059-255-6}, pages = {S. 119}, language = {en} } @misc{SchrickerSchmidtNageletal., author = {Schricker, Klaus and Schmidt, Leander and Nagel, Falk and Diegel, Christian and Friedmann, Hannes and Seibold, Marc and Hellwig, Peter and Fr{\"o}hlich, Fabian and Kallage, Peter and Chen, Yunhui and Requardt, Herwig and Rack, Alexander and Bergmann, Jean Pierre}, title = {A comprehensive study on the influence of spatial power distribution on time-dependent keyhole behavior in laser beam welding of copper by means of high-speed synchrotron X-ray imaging}, series = {Optics \& laser technology}, volume = {192, Part E}, journal = {Optics \& laser technology}, publisher = {Elsevier BV}, address = {Amsterdam}, issn = {0030-3992}, doi = {10.1016/j.optlastec.2025.113999}, pages = {1 -- 15}, abstract = {This paper examines the impact of spatial power distributions on the time-dependent keyhole behavior during laser beam welding of copper using high-speed synchrotron X-ray imaging. The experimental setup utilized a COHERENT HighLight FL8000-ARM fiber laser with concentric intensity distribution created by an optical fiber cable. The European Synchrotron Radiation Facility (ESRF, beamline ID19) was used to conduct high-speed synchrotron imaging at 20,000 images per second to study the spatio-temporal keyhole behavior. Keyhole geometries were extracted through advanced image processing techniques, allowing quantification of parameters like depth, aperture, bulging, and determination of related oscillation frequencies. The results showed that core-dominated processes exhibit significant variations in keyhole geometry. In contrast, ring-dominated processes exhibited reduced penetration depths but increased melt pool dynamics due to altered absorption conditions and increased temperatures within the melt pool. A stabilized core-ring power distribution minimized fluctuations, resulting in improved process stability. The findings were summarized in a model concept describing three characteristic keyhole regimes: core-dominated, ring-dominated, and stabilized core-ring processes.}, language = {en} } @misc{BalasUrbankKadenetal., author = {Balas, Johannes and Urbank, Christian and Kaden, Peter and Patzschke, Michael and M{\"a}rz, Juliane and Kvashnina, Kristina O. and Schmidt, Moritz and Stumpf, Thorsten and Gericke, Robert}, title = {Bonding trends in pyridine-2-thiolato complexes of tetravalent actinides}, series = {Inorganic chemistry}, volume = {64}, journal = {Inorganic chemistry}, number = {44}, publisher = {American Chemical Society}, address = {Washington, DC}, issn = {1520-510X}, doi = {10.1021/acs.inorgchem.5c03369}, pages = {21919 -- 21931}, abstract = {Complexes of tetravalent actinides (An: Th, U, Np, Pu) with the bidentate (N,S)-donor ligand pyridine-2-thiolate (2-PyS, PyS-) were synthesized in 1:4 or 1:5 ratios. This includes the first structurally characterized Np complex with (N,S)-donor ligands, filling a notable gap in An coordination chemistry. An improved synthetic approach with PyS-SiMe3 enabled efficient formation of the 1:4 complexes in THF as coordinating solvent. The compounds were comprehensively characterized in solution and in solid phase, supported by quantum chemical calculations. Experimental and theoretical results show matching trends in the binding behavior of AnIV. The covalent bond contributions in An-N and An-S bonding increase along the series of An from Th to Pu. The bonds to the soft sulfur donors consistently have the highest covalent contributions with a remarkably high percentage for Pu-S (IQA analysis: >34\%) over the harder N donors or An-O bonds of coordinating THF. High-resolution X-ray absorption and infrared spectroscopy indicate similar electronic and structural properties across AnIV complexes, while SQUID magnetometry uncovered significant differences in magnetic behavior at low temperatures depending on the complex compositions. This work advances the understanding of An-ligand bonding, emphasizing covalency and electronic structures, and expands fundamental insights into An chemistry.}, language = {en} }