@inproceedings{33739,
abstract = {{At least 5% of questions submitted to search engines ask about cause-effect relationships in some way. To support the development of tailored approaches that can answer such questions, we construct Webis-CausalQA-22, a benchmark corpus of 1.1 million causal questions with answers. We distinguish different types of causal questions using a novel typology derived from a data-driven, manual analysis of questions from ten large question answering (QA) datasets. Using high-precision lexical rules, we extract causal questions of each type from these datasets to create our corpus. As an initial baseline, the state-of-the-art QA model UnifiedQA achieves a ROUGE-L F1 score of 0.48 on our new benchmark.}},
author = {{Bondarenko, Alexander and Wolska, Magdalena and Heindorf, Stefan and Blübaum, Lukas and Ngonga Ngomo, Axel-Cyrille and Stein, Benno and Braslavski, Pavel and Hagen, Matthias and Potthast, Martin}},
booktitle = {{Proceedings of the 29th International Conference on Computational Linguistics}},
pages = {{3296–3308}},
publisher = {{International Committee on Computational Linguistics}},
title = {{{CausalQA: A Benchmark for Causal Question Answering}}},
year = {{2022}},
}
@inproceedings{31871,
author = {{Kletetzka, Ivo and Klippstein, Sven Helge}},
booktitle = {{3D-DRUCK HAUTNAH - Der Einfluss einer Zukunftstechnologie auf unser Leben }},
location = {{Paderborn}},
publisher = {{Universität Paderborn}},
title = {{{Pulver im 3D-Druck - von Mascarabürsten bis zum Interieur eines Mini-Coopers (Vortrag)}}},
year = {{2022}},
}
@article{47961,
abstract = {{Due to failures or even the absence of an electricity grid, microgrid systems are becoming popular solutions for electrifying African rural communities. However, they are heavily stressed and complex to control due to their intermittency and demand growth. Demand side management (DSM) serves as an option to increase the level of flexibility on the demand side by scheduling users’ consumption patterns profiles in response to supply. This paper proposes a demand-side management strategy based on load shifting and peak clipping. The proposed approach was modelled in a MATLAB/Simulink R2021a environment and was optimized using the artificial neural network (ANN) algorithm. Simulations were carried out to test the model’s efficacy in a stand-alone PV-battery microgrid in East Africa. The proposed algorithm reduces the peak demand, smoothing the load profile to the desired level, and improves the system’s peak to average ratio (PAR). The presence of deferrable loads has been considered to bring more flexible demand-side management. Results promise decreases in peak demand and peak to average ratio of about 31.2% and 7.5% through peak clipping. In addition, load shifting promises more flexibility to customers.}},
author = {{Philipo, Godiana Hagile and Kakande, Josephine Nakato and Krauter, Stefan}},
issn = {{1996-1073}},
journal = {{Energies}},
keywords = {{Energy (miscellaneous), Energy Engineering and Power Technology, Renewable Energy, Sustainability and the Environment, Electrical and Electronic Engineering, Control and Optimization, Engineering (miscellaneous), Building and Construction}},
number = {{14}},
publisher = {{MDPI AG}},
title = {{{Neural Network-Based Demand-Side Management in a Stand-Alone Solar PV-Battery Microgrid Using Load-Shifting and Peak-Clipping}}},
doi = {{10.3390/en15145215}},
volume = {{15}},
year = {{2022}},
}
@inproceedings{31066,
abstract = {{While trade-offs between modeling effort and model accuracy remain a major concern with system identification, resorting to data-driven methods often leads to a complete disregard for physical plausibility. To address this issue, we propose a physics-guided hybrid approach for modeling non-autonomous systems under control. Starting from a traditional physics-based model, this is extended by a recurrent neural network and trained using a sophisticated multi-objective strategy yielding physically plausible models. While purely data-driven methods fail to produce satisfying results, experiments conducted on real data reveal substantial accuracy improvements by our approach compared to a physics-based model. }},
author = {{Schön, Oliver and Götte, Ricarda-Samantha and Timmermann, Julia}},
booktitle = {{14th IFAC Workshop on Adaptive and Learning Control Systems (ALCOS 2022)}},
keywords = {{neural networks, physics-guided, data-driven, multi-objective optimization, system identification, machine learning, dynamical systems}},
location = {{Casablanca, Morocco}},
number = {{12}},
pages = {{19--24}},
title = {{{Multi-Objective Physics-Guided Recurrent Neural Networks for Identifying Non-Autonomous Dynamical Systems}}},
doi = {{https://doi.org/10.1016/j.ifacol.2022.07.282}},
volume = {{55}},
year = {{2022}},
}
@inproceedings{29803,
abstract = {{Ultrasonic wire bonding is a solid-state joining process used to form electrical interconnections in micro and
power electronics and batteries. A high frequency oscillation causes a metallurgical bond deformation in
the contact area. Due to the numerous physical influencing factors, it is very difficult to accurately capture
this process in a model. Therefore, our goal is to determine a suitable feed-forward control strategy for the
bonding process even without detailed model knowledge. We propose the use of batch constrained Bayesian
optimization for the control design. Hence, Bayesian optimization is precisely adapted to the application of
bonding: the constraint is used to check one quality feature of the process and the use of batches leads to
more efficient experiments. Our approach is suitable to determine a feed-forward control for the bonding
process that provides very high quality bonds without using a physical model. We also show that the quality
of the Bayesian optimization based control outperforms random search as well as manual search by a user.
Using a simple prior knowledge model derived from data further improves the quality of the connection.
The Bayesian optimization approach offers the possibility to perform a sensitivity analysis of the control
parameters, which allows to evaluate the influence of each control parameter on the bond quality. In summary,
Bayesian optimization applied to the bonding process provides an excellent opportunity to develop a feedforward
control without full modeling of the underlying physical processes.}},
author = {{Hesse, Michael and Hunstig, Matthias and Timmermann, Julia and Trächtler, Ansgar}},
booktitle = {{Proceedings of the 11th International Conference on Pattern Recognition Applications and Methods (ICPRAM)}},
isbn = {{978-989-758-549-4}},
keywords = {{Bayesian optimization, Wire bonding, Feed-forward control, model-free design}},
location = {{Online}},
pages = {{383--394}},
title = {{{Batch Constrained Bayesian Optimization for UltrasonicWire Bonding Feed-forward Control Design}}},
year = {{2022}},
}
@inproceedings{58297,
abstract = {{AbstractManually exploring the solution space for different variants of a product for a given set of requirements is ineffective regarding product development time and adaptation to dynamic customer requirements. Variant generation coupled to optimization algorithms offers possibilities to search the solution space in an automated way. This paper provides a framework to build a generative parametric design environment for functional assemblies by implementing analysis as well as synthesis methods in computer-aided tools. The procedure is presented using the example of a coffee machine.}},
author = {{Altun, Osman and Yinanc, Kutay and Mozgova, Iryna and Lachmayer, Roland}},
booktitle = {{Proceedings of the Design Society}},
issn = {{2732-527X}},
pages = {{553--562}},
publisher = {{Cambridge University Press (CUP)}},
title = {{{Procedure to Create an Automated Design Environment for Functional Assemblies}}},
doi = {{10.1017/pds.2022.57}},
volume = {{2}},
year = {{2022}},
}
@article{59504,
abstract = {{In this article, we are interested in optimal aircraft trajectories in climbing phase. We consider the cost index criterion which is a convex combination of the time-to-climb and the fuel consumption. We assume that the thrust is constant and we control the flight path angle of the aircraft. This optimization problem is modeled as a Mayer optimal control problem with a single-input affine dynamics in the control and with two pure state constraints, limiting the Calibrated AirSpeed (CAS) and the Mach speed. The candidates as minimizers are selected among a set of extremals given by the maximum principle. We first analyze the minimum time-to-climb problem with respect to the bounds of the state constraints, combining small time analysis, indirect multiple shooting and homotopy methods with monitoring. This investigation emphasizes two strategies: the common CAS/Mach procedure in aeronautics and the classical Bang-Singular-Bang policy in control theory. We then compare these two procedures for the cost index criterion.}},
author = {{Cots, Olivier and Gergaud, Joseph and Goubinat, Damien and Wembe, Boris}},
issn = {{2822-7840}},
journal = {{ESAIM: Mathematical Modelling and Numerical Analysis}},
number = {{2}},
pages = {{817--839}},
publisher = {{EDP Sciences}},
title = {{{Singular versus boundary arcs for aircraft trajectory optimization in climbing phase}}},
doi = {{10.1051/m2an/2022101}},
volume = {{57}},
year = {{2022}},
}
@article{59617,
abstract = {{There is an increasing interest in sensing applications for a variety of analytes in aqueous environments, as conventional methods do not work reliably under humid conditions or they require complex equipment with experienced operators. Hydrogel sensors are easy to fabricate, are incredibly sensitive, and have broad dynamic ranges. Experiments on their robustness, reliability, and reusability have indicated the possible long-term applications of these systems in a variety of fields, including disease diagnosis, detection of pharmaceuticals, and in environmental testing. It is possible to produce hydrogels, which, upon sensing a specific analyte, can adsorb it onto their 3D-structure and can therefore be used to remove them from a given environment. High specificity can be obtained by using molecularly imprinted polymers. Typical detection principles involve optical methods including fluorescence and chemiluminescence, and volume changes in colloidal photonic crystals, as well as electrochemical methods. Here, we explore the current research utilizing hydrogel-based sensors in three main areas: (1) biomedical applications, (2) for detecting and quantifying pharmaceuticals of interest, and (3) detecting and quantifying environmental contaminants in aqueous environments.}},
author = {{Völlmecke, Katharina and Afroz, Rowshon and Bierbach, Sascha and Brenker, Lee Josephine and Frücht, Sebastian and Glass, Alexandra and Giebelhaus, Ryland and Hoppe, Axel and Kanemaru, Karen and Lazarek, Michal and Rabbe, Lukas and Song, Longfei and Velasco Suarez, Andrea and Wu, Shuang and Serpe, Michael and Kuckling, Dirk}},
issn = {{2310-2861}},
journal = {{Gels}},
number = {{12}},
publisher = {{MDPI AG}},
title = {{{Hydrogel-Based Biosensors}}},
doi = {{10.3390/gels8120768}},
volume = {{8}},
year = {{2022}},
}
@article{63994,
abstract = {{Six cluster salts which consist of hexanuclear cluster anions [Nb6Cl12iX6a]2– (X = Cl or Br) and protonated crown ether molecules (15-crown-5 (15cr5) and 12-crown-4 (12cr4)) or crown ether-stabilized oxonium cations as well as one compound consisting of neutral cluster units, [Nb6Cl16(H2O)2]·4 dioxane, were synthesized in good to high yields. The single-crystal X-ray structures of six of these compounds were determined. The cation/anion ratios and the bond distances confirm in all cases oxidized cluster cores with 14 cluster-based electrons. The cations of the cluster salts are either sandwich-type dimers of the formula [(15cr5)H]22+ or [(15cr5)(H3O)]22+ with the protons or oxonium ions embedded in between the crown ether rings or monomeric units in the case of [(12cr4)H]+. 1H NMR investigations show that the cluster salts are strong Brønsted acids. The fact that the cluster core of [Nb6Cl16(H2O)2]·4 dioxane is oxidized but still carries water ligands indicates that within the multi-step reaction sequence of the formation of the cluster-supported acids, the oxidation step happens much faster than the ligand exchange steps. Temperature-dependent 2H MAS NMR spectra of deuterium-exchanged [(15cr5)H]2[Nb6Cl18]·2 CHCl3 are indicative of dynamic processes of the hydrogen-bonded protons within the crown ether molecule. Six cluster salts which consist of hexanuclear cluster anions [Nb6Cl12iX6a]2– (X = Cl or Br) and protonated crown ether molecules (15-crown-5 (15cr5) and 12-crown-4 (12cr4)) or crown ether-stabilized oxonium cations as well as one compound consisting of neutral cluster units, [Nb6Cl16(H2O)2]·4 dioxane, were synthesized in good to high yields. The single-crystal X-ray structures of six of these compounds were determined. The cation/anion ratios and the bond distances confirm in all cases oxidized cluster cores with 14 cluster-based electrons. The cations of the cluster salts are either sandwich-type dimers of the formula [(15cr5)H]22+ or [(15cr5)(H3O)]22+ with the protons or oxonium ions embedded in between the crown ether rings or monomeric units in the case of [(12cr4)H]+. 1H NMR investigations show that the cluster salts are strong Brønsted acids. The fact that the cluster core of [Nb6Cl16(H2O)2]·4 dioxane is oxidized but still carries water ligands indicates that within the multi-step reaction sequence of the formation of the cluster-supported acids, the oxidation step happens much faster than the ligand exchange steps. Temperature-dependent 2H MAS NMR spectra of deuterium-exchanged [(15cr5)H]2[Nb6Cl18]·2 CHCl3 are indicative of dynamic processes of the hydrogen-bonded protons within the crown ether molecule.}},
author = {{Koenig, Jonas and Gutmann, Torsten and Buntkowsky, Gerd and Koeckerling, Martin}},
journal = {{Inorganic Chemistry}},
number = {{40}},
pages = {{15983–15990}},
publisher = {{American Chemical Society}},
title = {{{Strong Cluster-Supported Brønsted Acids: Hexanuclear Niobium Cluster Compounds with Protonated Crown Ether Cations: (Crown-H)2[Nb6Cl12iX6a] (X = Cl or Br) and the Intermediate [Nb6Cl16(H2O)2]·4 dioxane}}},
volume = {{61}},
year = {{2022}},
}
@inproceedings{46305,
abstract = {{Hardness of Multi-Objective (MO) continuous optimization problems results from an interplay of various problem characteristics, e. g. the degree of multi-modality. We present a benchmark study of classical and diversity focused optimizers on multi-modal MO problems based on automated algorithm configuration. We show the large effect of the latter and investigate the trade-off between convergence in objective space and diversity in decision space.}},
author = {{Rook, J and Trautmann, Heike and Bossek, Jakob and Grimme, C}},
booktitle = {{Proceedings of the Genetic and Evolutionary Computation Conference Companion}},
editor = {{Fieldsend, J and Wagner, M.}},
isbn = {{9781450392686}},
pages = {{356–359}},
publisher = {{Association for Computing Machinery}},
title = {{{On the Potential of Automated Algorithm Configuration on Multi-Modal Multi-Objective Optimization Problems}}},
doi = {{10.1145/3520304.3528998}},
year = {{2022}},
}
@article{63829,
abstract = {{The 3D shear deformation and failure behaviour of a glass fibre reinforced polypropylene in a shear strain rate range of γ˙=2.2×10−4 to 3.4 1s is investigated. An Iosipescu testing setup on a servo-hydraulic high speed testing unit is used to experimentally characterise the in-plane and out-of-plane behaviour utilising three specimen configurations (12-, 13- and 31-direction). The experimental procedure as well as the testing results are presented and discussed. The measured shear stress–shear strain relations indicate a highly nonlinear behaviour and a distinct rate dependency. Two methods are investigated to derive according material characteristics: a classical engineering approach based on moduli and strengths and a data driven approach based on the curve progression. In all cases a Johnson–Cook based formulation is used to describe rate dependency. The analysis methodologies as well as the derived model parameters are described and discussed in detail. It is shown that a phenomenologically enhanced regression can be used to obtain material characteristics for a generalising constitutive model based on the data driven approach.}},
author = {{Gerritzen, Johannes and Hornig, Andreas and Gröger, Benjamin and Gude, Maik}},
issn = {{2504-477X}},
journal = {{Journal of Composites Science}},
number = {{10}},
publisher = {{MDPI AG}},
title = {{{A Data Driven Modelling Approach for the Strain Rate Dependent 3D Shear Deformation and Failure of Thermoplastic Fibre Reinforced Composites: Experimental Characterisation and Deriving Modelling Parameters}}},
doi = {{10.3390/jcs6100318}},
volume = {{6}},
year = {{2022}},
}
@inbook{61306,
author = {{Heinrichs, Ulrike and Voigt, Martina}},
booktitle = {{Der Wandmalereizyklus zu den Wissenschaften und Künsten in der Domklausur zu Brandenburg. Interdisziplinäre Erforschung und Visualisierung des fragmentarischen Bestandes. Begleitband zur interdisziplinären Tagung der HAWK Hochschule für angewandte Wissenschaft und Kunst Hildesheim/Holzminden/Göttingen in Kooperation mit dem BLDAM Brandenburgisches Landesamt für Denkmalpflege und Archäologisches Landesmuseum und dem Domstift Brandenburg, »Nicht invasiv! Neue Perspektiven in der Erforschung und Restaurierung von Wandmalerei dank digitaler Techniken.« 27. bis 30. April 2022 in Brandenburg an der Havel (Schriften des Hornemann Instituts 22/Arbeitshefte des Brandenburgischen Landesamtes für Denkmalpflege und Archäologischen Landesmuseums 65)}},
editor = {{Schädler-Saub, Ursula and Noll-Minor, Mechthild}},
pages = {{150--193}},
publisher = {{hendrik Bäßler Verlag}},
title = {{{Die Wissenschaften und Künste unter der Ägide der brandenburgischen Kirche. Die Wandmalereien aus der Zeit Bischof Stephan Bodekers und Probst Peter von Klitzkes in der spätmittelalterlichen Dombibliothek in Brandenburg an der Havel – ein Bildzyklus, zwei Bibliotheksräume}}},
year = {{2022}},
}
@article{62235,
abstract = {{Additive manufacturing (AM) processes are not solely used where maximum design freedom meets low lot sizes. Direct microstructure design and topology optimization can be realized concomitantly during processing by adjusting the geometry, the material composition, and the solidification behavior of the material considered. However, when complex specific requirements have to be met, a targeted part design is highly challenging. In the field of biodegradable implant surgery, a cytocompatible material of an application-adapted shape has to be characterized by a specific degradation behavior and reliably predictable mechanical properties. For instance, small amounts of oxides can have a significant effect on microstructural development, thus likewise affecting the strength and corrosion behavior of the processed material. In the present study, biocompatible pure Fe was processed using electron powder bed fusion (E-PBF). Two different modifications of the Fe were processed by incorporating Fe oxide and Ce oxide in different proportions in order to assess their impact on the microstructural evolution, the mechanical response and the corrosion behavior. The quasistatic mechanical and chemical properties were analyzed and correlated with the final microstructural appearance.}},
author = {{Torrent, Christof J. J. and Krooß, Philipp and Huang, Jingyuan and Voigt, Markus and Ebbert, Christoph and Knust, Steffen and Grundmeier, Guido and Niendorf, Thomas}},
issn = {{2674-063X}},
journal = {{Alloys}},
number = {{1}},
pages = {{31--53}},
publisher = {{MDPI AG}},
title = {{{Oxide Modified Iron in Electron Beam Powder Bed Fusion—From Processability to Corrosion Properties}}},
doi = {{10.3390/alloys1010004}},
volume = {{1}},
year = {{2022}},
}
@article{62801,
abstract = {{The three-dimensional (3D) distribution of individual atoms on the surface of catalyst nanoparticles plays a vital role in their activity and stability. Optimising the performance of electrocatalysts requires atomic-scale information, but it is difficult to obtain. Here, we use atom probe tomography to elucidate the 3D structure of 10 nm sized Co2FeO4 and CoFe2O4 nanoparticles during oxygen evolution reaction (OER). We reveal nanoscale spinodal decomposition in pristine Co2FeO4. The interfaces of Co-rich and Fe-rich nanodomains of Co2FeO4 become trapping sites for hydroxyl groups, contributing to a higher OER activity compared to that of CoFe2O4. However, the activity of Co2FeO4 drops considerably due to concurrent irreversible transformation towards CoIVO2 and pronounced Fe dissolution. In contrast, there is negligible elemental redistribution for CoFe2O4 after OER, except for surface structural transformation towards (FeIII, CoIII)2O3. Overall, our study provides a unique 3D compositional distribution of mixed Co-Fe spinel oxides, which gives atomic-scale insights into active sites and the deactivation of electrocatalysts during OER.}},
author = {{Xiang, Weikai and Yang, Nating and Li, Xiaopeng and Linnemann, Julia and Hagemann, Ulrich and Ruediger, Olaf and Heidelmann, Markus and Falk, Tobias and Aramini, Matteo and DeBeer, Serena and Muhler, Martin and Tschulik, Kristina and Li, Tong}},
issn = {{2041-1723}},
journal = {{Nature Communications}},
keywords = {{electrocatalysis, oxygen evolution reaction, cobalt spinel, electrochemical impedance spectroscopy}},
number = {{1}},
publisher = {{Springer Science and Business Media LLC}},
title = {{{3D atomic-scale imaging of mixed Co-Fe spinel oxide nanoparticles during oxygen evolution reaction}}},
doi = {{10.1038/s41467-021-27788-2}},
volume = {{13}},
year = {{2022}},
}
@inbook{30288,
abstract = {{Lithium niobate (LiNbO3), a material frequently used in optical applications, hosts different kinds of polarons that significantly affect many of its physical properties. In this study, a variety of electron polarons, namely free, bound, and bipolarons, are analyzed using first-principles calculations. We perform a full structural optimization based on density-functional theory for selected intrinsic defects with special attention to the role of symmetry-breaking distortions that lower the total energy. The cations hosting the various polarons relax to a different degree, with a larger relaxation corresponding to a larger gap between the defect level and the conduction-band edge. The projected density of states reveals that the polaron states are formerly empty Nb 4d states lowered into the band gap. Optical absorption spectra are derived within the independent-particle approximation, corrected by the GW approximation that yields a wider band gap and by including excitonic effects within the Bethe-Salpeter equation. Comparing the calculated spectra with the density of states, we find that the defect peak observed in the optical absorption stems from transitions between the defect level and a continuum of empty Nb 4d states. Signatures of polarons are further analyzed in the reflectivity and other experimentally measurable optical coefficients.}},
author = {{Schmidt, Falko and Kozub, Agnieszka L. and Gerstmann, Uwe and Schmidt, Wolf Gero and Schindlmayr, Arno}},
booktitle = {{New Trends in Lithium Niobate: From Bulk to Nanocrystals}},
editor = {{Corradi, Gábor and Kovács, László}},
isbn = {{978-3-0365-3340-7}},
pages = {{231--248}},
publisher = {{MDPI}},
title = {{{Electron polarons in lithium niobate: Charge localization, lattice deformation, and optical response}}},
doi = {{10.3390/books978-3-0365-3339-1}},
year = {{2022}},
}
@misc{57068,
abstract = {{Eine der grundlegenden Funktionen von Zeitungstexten ist das Berichten über einen bestimmten
Sachverhalt oder ein Ereignis. Diese Berichtshandlungen werden dabei häufig von regelmäßig
wiederkehrenden Sprachhandlungen begleitet, die vor allem der Gewährleistung der Textsorte,
Sicherung von Kohärenz des Mediums, Reflektion von Glaubwürdigkeit/Verbürgtheit der Quellen
sowie der Aufforderung zur Meinungsbildung dienen. Diese Nebenprädikationen bleiben stets
erhalten, unabhängig von dem je aktuellen und sich ändernden Nachrichteninhalt.
Ausgehend von der Hypothese, dass für standardisierte Sprachhandlungen standardisierte
(formelhafte) sprachliche Realisierungen bestehen oder entwickelt werden, werden für das Korpus
Zeitungstexte (Teilkorpus „Manuelle Annotation“ vgl. https://www.uni-
paderborn.de/forschungsprojekte/tevo/projekt/korpora) diese Nebenprädikationen als mögliche
formelhafte Verbindungen manuell annotiert und auf lexikalische, grammatische und/oder
semantische Muster hin analysiert. Ziel dieses Vorgehens ist, musterhafte (komplexe) Strukturen zu
ermitteln und einer (teil-)automatisierten Annotation zuzuführen. Die Validierung der ermittelten
musterhaften Strukturen erfolgt anhand des Gesamtkorpus der im Projekt digitalisierten
Zeitungsausgaben.
Neben der Darstellung dieses Vorgehens und seiner Ergebnisse sollen anhand der aus dem
Gesamtkorpus gewonnenen Belege Entwicklungstendenzen aufgezeigt und in ihrem historischen
Kontext analysiert werden.}},
author = {{Thielert, Frauke and Georgi, Christopher}},
title = {{{Formelhafte Sprache in Pressetexten – Von der manuellen Annotation zur (teil-) automatisierten Erfassung komplexer Strukturen. Vortrag im Rahmen des t.evo-Workshops "Von der Oberfläche zum Muster" vom 22.–23.03.2022 in Paderborn}}},
year = {{2022}},
}
@techreport{47095,
author = {{Kesternich, Martin and Will, Ulrike and Manger-Nestler, Cornelia}},
publisher = {{ZEW Policy Brief 22-04}},
title = {{{Pariser Klimaschutzabkommen – Berichtsstandards und Begleitanalysen nationaler Klimaschutzbeiträge stärken}}},
year = {{2022}},
}
@article{60369,
abstract = {{AbstractNon‐linear optimization is essential to many areas of geometry processing research. However, when experimenting with different problem formulations or when prototyping new algorithms, a major practical obstacle is the need to figure out derivatives of objective functions, especially when second‐order derivatives are required. Deriving and manually implementing gradients and Hessians is both time‐consuming and error‐prone. Automatic differentiation techniques address this problem, but can introduce a diverse set of obstacles themselves, e.g. limiting the set of supported language features, imposing restrictions on a program's control flow, incurring a significant run time overhead, or making it hard to exploit sparsity patterns common in geometry processing. We show that for many geometric problems, in particular on meshes, the simplest form of forward‐mode automatic differentiation is not only the most flexible, but also actually the most efficient choice. We introduce TinyAD: a lightweight C++ library that automatically computes gradients and Hessians, in particular of sparse problems, by differentiating small (tiny) sub‐problems. Its simplicity enables easy integration; no restrictions on, e.g., looping and branching are imposed. TinyAD provides the basic ingredients to quickly implement first and second order Newton‐style solvers, allowing for flexible adjustment of both problem formulations and solver details. By showcasing compact implementations of methods from parametrization, deformation, and direction field design, we demonstrate how TinyAD lowers the barrier to exploring non‐linear optimization techniques. This enables not only fast prototyping of new research ideas, but also improves replicability of existing algorithms in geometry processing. TinyAD is available to the community as an open source library.}},
author = {{Schmidt, Patrick and Born, Janis and Bommes, David and Campen, Marcel and Kobbelt, Leif}},
issn = {{0167-7055}},
journal = {{Computer Graphics Forum}},
number = {{5}},
pages = {{113--124}},
publisher = {{Wiley}},
title = {{{TinyAD: Automatic Differentiation in Geometry Processing Made Simple}}},
doi = {{10.1111/cgf.14607}},
volume = {{41}},
year = {{2022}},
}
@article{60366,
abstract = {{AbstractThe so‐called motorcycle graph has been employed in recent years for various purposes in the context of structured and aligned block decomposition of 2D shapes and 2‐manifold surfaces. Applications are in the fields of surface parametrization, spline space construction, semi‐structured quad mesh generation, or geometry data compression. We describe a generalization of this motorcycle graph concept to the three‐dimensional volumetric setting. Through careful extensions aware of topological intricacies of this higher‐dimensional setting, we are able to guarantee important block decomposition properties also in this case. We describe algorithms for the construction of this 3D motorcycle complex on the basis of either hexahedral meshes or seamless volumetric parametrizations. Its utility is illustrated on examples in hexahedral mesh generation and volumetric T‐spline construction.}},
author = {{Brückler, Hendrik and Gupta, Ojaswi and Mandad, Manish and Campen, Marcel}},
issn = {{0167-7055}},
journal = {{Computer Graphics Forum}},
number = {{2}},
pages = {{221--235}},
publisher = {{Wiley}},
title = {{{The 3D Motorcycle Complex for Structured Volume Decomposition}}},
doi = {{10.1111/cgf.14470}},
volume = {{41}},
year = {{2022}},
}
@article{60372,
abstract = {{Developments in the field of parametrization-based quad mesh generation on surfaces have been impactful over the past decade. In this context, an important advance has been the replacement of error-prone rounding in the generation of integer-grid maps, by robust quantization methods. In parallel, parametrization-based hex mesh generation for volumes has been advanced. In this volumetric context, however, the state-of-the-art still relies on fragile rounding, not rarely producing defective meshes, especially when targeting a coarse mesh resolution. We present a method to robustly quantize volume parametrizations, i.e., to determine guaranteed valid choices of integers for 3D integer-grid maps. Inspired by the 2D case, we base our construction on a non-conforming cell decomposition of the volume, a 3D analogue of a T-mesh. In particular, we leverage the motorcycle complex, a recent generalization of the motorcycle graph, for this purpose. Integer values are expressed in a differential manner on the edges of this complex, enabling the efficient formulation of the conditions required to strictly prevent forcing the map into degeneration. Applying our method in the context of hexahedral meshing, we demonstrate that hexahedral meshes can be generated with significantly improved flexibility.}},
author = {{Brückler, Hendrik and Bommes, David and Campen, Marcel}},
issn = {{0730-0301}},
journal = {{ACM Transactions on Graphics}},
number = {{4}},
pages = {{1--19}},
publisher = {{Association for Computing Machinery (ACM)}},
title = {{{Volume parametrization quantization for hexahedral meshing}}},
doi = {{10.1145/3528223.3530123}},
volume = {{41}},
year = {{2022}},
}