Browsing by Department "University of Bonn"

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    The chaos in calibrating crop models
    (ELSEVIER SCI LTD, 2021-11) Wallach, Daniel; Palosuo, Taru; Thorburn, Peter; Hochman, Zvi; Gourdain, Emmanuelle; Andrianasolo, Fety; Asseng, Senthold; Basso, Bruno; Buis, Samuel; Crout, Neil; Dibari, Camilla; Dumont, Benjamin; Ferrise, Roberto; Gaiser, Thomas; Garcia, Cecile; Gayler, Sebastian; Ghahramani, Afshin; Hiremath, Santosh; Hoek, Steven; Horan, Heidi; Hoogenboom, Gerrit; Huang, Mingxia; Jabloun, Mohamed; Jansson, Per Erik; Jing, Qi; Justes, Eric; Kersebaum, Kurt Christian; Klosterhalfen, Anne; Launay, Marie; Lewan, Elisabet; Luo, Qunying; Maestrini, Bernardo; Mielenz, Henrike; Moriondo, Marco; Nariman Zadeh, Hasti; Padovan, Gloria; Olesen, Jørgen Eivind; Poyda, Arne; Priesack, Eckart; Pullens, Johannes Wilhelmus Maria; Qian, Budong; Schütze, Niels; Shelia, Vakhtang; Souissi, Amir; Specka, Xenia; Srivastava, Amit Kumar; Stella, Tommaso; Streck, Thilo; Trombi, Giacomo; Wallor, Evelyn; Wang, Jing; Weber, Tobias K.D.; Weihermüller, Lutz; de Wit, Allard; Wöhling, Thomas; Xiao, Liujun; Zhao, Chuang; Zhu, Yan; Seidel, Sabine J.; INRAE; Luke Natural Resources Institute Finland; CSIRO; Arvalis Institut du Végétal; Technical University of Munich; Michigan State University; University of Nottingham; University of Florence; University of Liege; University of Bonn; University of Hohenheim; University of Southern Queensland; Department of Computer Science; Wageningen University and Research Centre; University of Florida; China Agricultural University; KTH Royal Institute of Technology; Ottawa Research and Development Centre; Centre de coopération internationale en recherche agronomique pour le développement (CIRAD); Leibniz Centre for Agricultural Landscape Research; Jülich Research Centre; Swedish University of Agricultural Sciences; Hillridge Technology Pty Ltd; Institute for Crop and Soil Science; CNR-ENEA-EURATOM Association; Aarhus University; Kiel University; Helmholtz Zentrum München - German Research Center for Environmental Health; Technische Universität Dresden; University of Carthage; Nanjing Agricultural University
    Calibration, the estimation of model parameters based on fitting the model to experimental data, is among the first steps in many applications of process-based models and has an important impact on simulated values. We propose a novel method of developing guidelines for calibration of process-based models, based on development of recommendations for calibration of the phenology component of crop models. The approach was based on a multi-model study, where all teams were provided with the same data and asked to return simulations for the same conditions. All teams were asked to document in detail their calibration approach, including choices with respect to criteria for best parameters, choice of parameters to estimate and software. Based on an analysis of the advantages and disadvantages of the various choices, we propose calibration recommendations that cover a comprehensive list of decisions and that are based on actual practices.
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    Stability of Cu-precipitates in Al-Cu alloys
    (2018-06-20) Staab, Torsten E.M.; Folegati, Paola; Wolfertz, Iris; Puska, Martti J.; University of Würzburg; Polytechnic University of Milan; University of Bonn; Department of Applied Physics
    We present first principle calculations on formation and binding energies for Cu and Zn as solute atoms forming small clusters up to nine atoms in Al-Cu and Al-Zn alloys. We employ a density-functional approach implemented using projector-augmented waves and plane wave expansions. We find that some structures, in which Cu atoms are closely packed on (100)-planes, turn out to be extraordinary stable. We compare the results with existing numerical or experimental data when possible. We find that Cu atoms precipitating in the form of two-dimensional platelets on (100)-planes in the fcc aluminum are more stable than three-dimensional structures consisting of the same number of Cu-atoms. The preference turns out to be opposite for Zn in Al. Both observations are in agreement with experimental observations.