Winfried Kurth
Georg-August-Universität Göttingen, Computer Science, Faculty Member
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A graph grammar with parallel replacement of subgraphs, based on the single-pushout approach in graph rewriting, was designed which constructs Cayley graphs of monoids of transformations of a finite set, with permutation groups as a... more
A graph grammar with parallel replacement of subgraphs, based on the single-pushout approach in graph rewriting, was designed which constructs Cayley graphs of monoids of transformations of a finite set, with permutation groups as a special case. As input, graph-based representations of a finite number of generating transformations have to be specified; they will then correspond to the edge types of the Cayley graph which is the final result of the rewriting process. The grammar has \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$7+d$$\end{document} rules, where d is the number of generators, and operates at two scale levels. The fine-scale level is the level of elements on which the transformations act and where their composition is calculated by parallel subgraph replacement. The coarse-scale level cor...
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We present here the framework for a Functional-structural plant model (FSPM) of the water and sugar transport in an apple (Malus domestica (L.) Bartsch.) branch. The model is parameterized at the spatial level of the organ (leaf blade,... more
We present here the framework for a Functional-structural plant model (FSPM) of the water and sugar transport in an apple (Malus domestica (L.) Bartsch.) branch. The model is parameterized at the spatial level of the organ (leaf blade, leaf petiole; internode; fruit, and fruit peduncle), explicitly describing water and sugar flows between all possible organ combinations. In order to do so, an object-oriented representation of each organ was introduced, containing the functional description of xylem and phloem elements within the respective organs, and between each organ pair, using the dedicated modelling platform GroIMP. The geometry and topology of the branch and its elements were based on measurements of ‘Fuji’ cv. apple trees, located in an experimental orchard in Angers, France, whereas the coefficients of the transport model system were derived from the literature. Branch architecture is an input to the model therefore not supposed to change during the simulated period (June to September). First results are promising: 1) a fully functional, quantitative simulation of water flux based on biophysical principles (leaf transpiration coupled to photosynthesis rate and stomatal conductance) is driving the water transport from the base of the branch to the peripheral organs (leaves) according to the Darcy flow principle. At the same time sugars are transported from sources (leaves) to sinks (fruits) based on Münch flow in the phloem. Such a simulation is possible in real time (temporal resolution one second); 2) even for extreme situations the network of xylem and phloem with its numerous interconnections shows reasonable and stable behaviour.
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Diverse methods abstracting plant architectures are applied in different FSPMs (Functional Structural Plant Models). The abstracted plant architectural data are not applicable for every FSPM because the data models applied in the diverse... more
Diverse methods abstracting plant architectures are applied in different FSPMs (Functional Structural Plant Models). The abstracted plant architectural data are not applicable for every FSPM because the data models applied in the diverse methods are not compatible. In this paper, we introduce a logical data exchange model EG (Exchange Graph) for adapting different methods abstracting plant architecture. We also illustrate how plant architectural data is adapted and transferred between different FSPMs through a XML based physical data model of EG, XEG.
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Taking digital photographs as a form of documentation while conducting field work is common practice. There is a wealth of digital photographs collected by foresters who are interested in tree architecture. These high-resolution... more
Taking digital photographs as a form of documentation while conducting field work is common practice. There is a wealth of digital photographs collected by foresters who are interested in tree architecture. These high-resolution photographs are two-dimensional representations of the tree structure. However, it is possible to exploit tools such as GIS (e.g., ESRI ArcGIS) and three-dimensional modelling platforms (GroIMP) to extract information from a single digital photograph to three-dimensional modelling. We propose a work flow for creating three-dimensional reconstructions of tree architecture based on a single high-resolution digital photograph. A single digital photograph of tree architecture with a scaling object in view was acquired. The scaled photograph was imported into ArcMap and the tree architecture was digitized, main stem and branching. The DBF file within the shapefile from the GIS output was converted to a CSV file using MS-Excel. GroIMP was used to import the CSV fi...
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The main principle in functional-structural plant models (FSPMs) is the interaction between plant structure and eco-physiology. One aspect where the structure is of special importance is the complex calculation of light distribution in a... more
The main principle in functional-structural plant models (FSPMs) is the interaction between plant structure and eco-physiology. One aspect where the structure is of special importance is the complex calculation of light distribution in a plant which is in many models the basis for photosynthesis calculation. In this work we try to quantify the importance of geometrical traits for light absorption in conifers, using the LIGNUM model for Scots pine, and a method of global sensitivity analysis for selected geometrical parameters at needle (angle, length) and shoot (branching and bending angles, radius to length ratio) scale. While all the simulations were executed on GroIMP, sensitivity analysis was performed in PYGMALION. A new interface was created to enable the communication between GroIMP and PYGMALION software using a black-box approach, with the overall workflow controlled by PYGMALION. First results of sensitivity analysis showed that needle length had the highest impact on light interception during the whole studied period of 10 years, followed by needle angle during the first 7 years. The sensitivity to both parameters had a decreasing tendency. Impact of radius to length ratio was very similar to branching angle of the higher order branches; very low during the first years of the simulation, with increasing tendency. After the first 7 years, it was higher than the one of needle angle. There was no impact of branching angle for branches connected to the trunk and of bending angle during the studied time period.
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In recent years, many different advanced mathematical models and simulation systems for tree and forest growth have been developed. We show a possibility to extend analysis tools for measured and simulated plants using a data interface... more
In recent years, many different advanced mathematical models and simulation systems for tree and forest growth have been developed. We show a possibility to extend analysis tools for measured and simulated plants using a data interface between the simulation model LIGNUM and the multifunctional software system GROGRA. Both systems were developed by different teams. To demonstrate the enhanced possibilities for analyzing a LIGNUM tree, several examples are given. In these examples three different approaches for analysis are applied to measured and simulated trees: Fractal dimension, deduction of tapering laws, and water potential patterns obtained from simulation of waterflow by the specialized software HYDRA. Conclusions for the interfacing and comparison of different modelling tools are drawn.
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A simple and efficient photometric methodology is presented, covering all steps from field data acquisition to binarization and allowing for leaf contour modelling. This method comprises the modelling of area and size (correlated and... more
A simple and efficient photometric methodology is presented, covering all steps from field data acquisition to binarization and allowing for leaf contour modelling. This method comprises the modelling of area and size (correlated and modelled with a Chapman-Richards growth function, using final length as one parameter), and four shape descriptors, from which the entire contour can be reconstructed rather well using a specific spline methodology. As an improvement of this contour modelling method, a set of parameterized polynomials was used. To model the temporal kinetics of the shape, geodesics in shape spaces were employed. Finally it is shown how this methodology is integrated into the 3D modelling platform GroIMP.
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... Ann. For. Sci., 57, 543-554. Kurth, W., and Anzola Jürgenson, G. (1997). ... Ann. For. Sci., 57, 463-475. Oppelt, AL; Kurth, W., and Godbold, DL (2000b). Topology, scaling relations andLeonardo's rule in root systems... more
... Ann. For. Sci., 57, 543-554. Kurth, W., and Anzola Jürgenson, G. (1997). ... Ann. For. Sci., 57, 463-475. Oppelt, AL; Kurth, W., and Godbold, DL (2000b). Topology, scaling relations andLeonardo's rule in root systems from African tree species. Tree Physiol. (in press). ...
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Page 1. Demonstration of the GroIMP software Ole Kniemeyer, Gerhard Buck-Sorlin, Winfried Kurth {okn,wk}@informatik.tu-cottbus.de buck@ipk-gatersleben.de. Brandenburgische Technische Universit ¨at Cottbus Department of Computer Science ...
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Agent-based models (ABM) or individual-based models (IBM), as they are called in ecology and biology, are a widely used modeling approach when local interactions on the micro level are essential for the description of patterns on the... more
Agent-based models (ABM) or individual-based models (IBM), as they are called in ecology and biology, are a widely used modeling approach when local interactions on the micro level are essential for the description of patterns on the macro level. This chapter is divided into four sections. In the first section, the history and definitions of ABMs in various research disciplines, namely computer science, social science, economics and ecology, are reviewed. This section closes with a discussion of similarities and differences in the different research fields and a discussion of current challenges in agent-based modeling. One of these difficulties is the lack of accepted standards for communication and programming. The second section refers to this point by a presentation of some widely used ABM libraries, namely Swarm, Mason, Repast and NetLogo and is followed by a more detailed description of NetLogo as a potential standard tool in ABM communication. In the last section extensions to...
Sensitive growth grammars are systems of rewriting rules (extended Lindenmayer systems) with graphical interpretation and with "sensitive functi- ons" designed to allow a feedback from the created virtual 3-D structures to the... more
Sensitive growth grammars are systems of rewriting rules (extended Lindenmayer systems) with graphical interpretation and with "sensitive functi- ons" designed to allow a feedback from the created virtual 3-D structures to the subsequent rule-application process. Thus it is possible to combine morphologi- cal (genetically fixed) growth rules with environmental impact and with func- tions depending on the competitive situation of
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:The rule-based formal language of "stochastic sensitive growth grammars" wasdesigned to describe algorithmically the changing morphology of forest treesduring their lifetime under the impact of... more
:The rule-based formal language of "stochastic sensitive growth grammars" wasdesigned to describe algorithmically the changing morphology of forest treesduring their lifetime under the impact of endogenous and exogenous factors,and to generate 3-D simulations of tree structures in a systematic manner.The description in the form of grammars allows the precise specification ofstructural models with functional components. These grammars (extended Lsystems)can be
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In ecological interactions the three-dimensional structure of organisms can play an important role. We will present an approach for modelling and simulation of the development of geometrical structures in space, which is particularly... more
In ecological interactions the three-dimensional structure of organisms can play an important role. We will present an approach for modelling and simulation of the development of geometrical structures in space, which is particularly suitable for representing branching systems as they occur in plants. The related notions of self-similarity and fractality will be briefly discussed. The crucial idea for modelling is