@inproceedings{HombergBaumProhaskaetal.2012, author = {Homberg, Ulrike and Baum, Daniel and Prohaska, Steffen and Kalbe, Ute and Witt, Karl Josef}, title = {Automatic Extraction and Analysis of Realistic Pore Structures from µCT Data for Pore Space Characterization of Graded Soil}, series = {Proceedings of the 6th International Conference on Scour and Erosion (ICSE-6)}, booktitle = {Proceedings of the 6th International Conference on Scour and Erosion (ICSE-6)}, pages = {345 -- 352}, year = {2012}, language = {en} } @misc{HombergBaumWiebeletal.2014, author = {Homberg, Ulrike and Baum, Daniel and Wiebel, Alexander and Prohaska, Steffen and Hege, Hans-Christian}, title = {Definition, Extraction, and Validation of Pore Structures in Porous Materials}, series = {Topological Methods in Data Analysis and Visualization III}, journal = {Topological Methods in Data Analysis and Visualization III}, editor = {Bremer, Peer-Timo and Hotz, Ingrid and Pascucci, Valerio and Peikert, Ronald}, publisher = {Springer}, doi = {10.1007/978-3-319-04099-8_15}, pages = {235 -- 248}, year = {2014}, language = {en} } @inproceedings{HombergBinnerProhaskaetal.2009, author = {Homberg, Ulrike and Binner, Richard and Prohaska, Steffen and Dercksen, Vincent J. and Kuß, Anja and Kalbe, Ute}, title = {Determining Geometric Grain Structure from X-Ray Micro-Tomograms of Gradated Soil}, series = {Workshop Internal Erosion}, volume = {21}, booktitle = {Workshop Internal Erosion}, pages = {37 -- 52}, year = {2009}, language = {en} } @misc{HombergBaumWiebeletal., author = {Homberg, Ulrike and Baum, Daniel and Wiebel, Alexander and Prohaska, Steffen and Hege, Hans-Christian}, title = {Definition, Extraction, and Validation of Pore Structures in Porous Materials}, issn = {1438-0064}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-42510}, abstract = {An intuitive and sparse representation of the void space of porous materials supports the efficient analysis and visualization of interesting qualitative and quantitative parameters of such materials. We introduce definitions of the elements of this void space, here called pore space, based on its distance function, and present methods to extract these elements using the extremal structures of the distance function. The presented methods are implemented by an image processing pipeline that determines pore centers, pore paths and pore constrictions. These pore space elements build a graph that represents the topology of the pore space in a compact way. The representations we derive from μCT image data of realistic soil specimens enable the computation of many statistical parameters and, thus, provide a basis for further visual analysis and application-specific developments. We introduced parts of our pipeline in previous work. In this chapter, we present additional details and compare our results with the analytic computation of the pore space elements for a sphere packing in order to show the correctness of our graph computation.}, language = {en} } @misc{HombergBaumProhaskaetal., author = {Homberg, Ulrike and Baum, Daniel and Prohaska, Steffen and G{\"u}nster, Jens and Krauß-Sch{\"u}ler, Stefanie}, title = {Adapting trabecular structures for 3D printing: an image processing approach based on µCT data}, issn = {1438-0064}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-64004}, abstract = {Materials with a trabecular structure notably combine advantages such as lightweight, reasonable strength, and permeability for fluids. This combination of advantages is especially interesting for tissue engineering in trauma surgery and orthopedics. Bone-substituting scaffolds for instance are designed with a trabecular structure in order to allow cell migration for bone ingrowth and vascularization. An emerging and recently very popular technology to produce such complex, porous structures is 3D printing. However, several technological aspects regarding the scaffold architecture, the printable resolution, and the feature size have to be considered when fabricating scaffolds for bone tissue replacement and regeneration. Here, we present a strategy to assess and prepare realistic trabecular structures for 3D printing using image analysis with the aim of preserving the structural elements. We discuss critical conditions of the printing system and present a 3-stage approach to adapt a trabecular structure from \$\mu\$CT data while incorporating knowledge about the printing system. In the first stage, an image-based extraction of solid and void structures is performed, which results in voxel- and graph-based representations of the extracted structures. These representations not only allow us to quantify geometrical properties such as pore size or strut geometry and length. But, since the graph represents the geometry and the topology of the initial structure, it can be used in the second stage to modify and adjust feature size, volume and sample size in an easy and consistent way. In the final reconstruction stage, the graph is then converted into a voxel representation preserving the topology of the initial structure. This stage generates a model with respect to the printing conditions to ensure a stable and controlled voxel placement during the printing process.}, language = {en} } @article{HombergBaumProhaskaetal., author = {Homberg, Ulrike and Baum, Daniel and Prohaska, Steffen and G{\"u}nster, Jens and Krauß-Sch{\"u}ler, Stefanie}, title = {Adapting trabecular structures for 3D printing: an image processing approach based on µCT data}, series = {Biomedical Physics \& Engineering Express}, volume = {3}, journal = {Biomedical Physics \& Engineering Express}, number = {3}, publisher = {IOP Publishing}, doi = {10.1088/2057-1976/aa7611}, abstract = {Materials with a trabecular structure notably combine advantages such as lightweight, reasonable strength, and permeability for fluids. This combination of advantages is especially interesting for tissue engineering in trauma surgery and orthopedics. Bone-substituting scaffolds for instance are designed with a trabecular structure in order to allow cell migration for bone ingrowth and vascularization. An emerging and recently very popular technology to produce such complex, porous structures is 3D printing. However, several technological aspects regarding the scaffold architecture, the printable resolution, and the feature size have to be considered when fabricating scaffolds for bone tissue replacement and regeneration. Here, we present a strategy to assess and prepare realistic trabecular structures for 3D printing using image analysis with the aim of preserving the structural elements. We discuss critical conditions of the printing system and present a 3-stage approach to adapt a trabecular structure from \$\mu\$CT data while incorporating knowledge about the printing system. In the first stage, an image-based extraction of solid and void structures is performed, which results in voxel- and graph-based representations of the extracted structures. These representations not only allow us to quantify geometrical properties such as pore size or strut geometry and length. But, since the graph represents the geometry and the topology of the initial structure, it can be used in the second stage to modify and adjust feature size, volume and sample size in an easy and consistent way. In the final reconstruction stage, the graph is then converted into a voxel representation preserving the topology of the initial structure. This stage generates a model with respect to the printing conditions to ensure a stable and controlled voxel placement during the printing process.}, language = {en} } @inproceedings{SeblanyHombergVincensetal., author = {Seblany, Feda and Homberg, Ulrike and Vincens, Eric and Winkler, Paul and Witt, Karl Josef}, title = {Merging criteria for the definition of a local pore and the CSD computation of granular materials}, series = {Proceedings of the 25th meeting of the Working Group on Internal Erosion in embankment dams and their foundations}, booktitle = {Proceedings of the 25th meeting of the Working Group on Internal Erosion in embankment dams and their foundations}, publisher = {Deltares}, address = {Delft, Netherlands}, isbn = {978-90-827468-1-5 | 978-90-827468-0-8}, pages = {150 -- 159}, language = {en} } @misc{SeblanyHombergVincensetal., author = {Seblany, Feda and Homberg, Ulrike and Vincens, Eric and Winkler, Paul and Witt, Karl Josef}, title = {Merging criteria for the definition of a local pore and the CSD computation of granular materials}, issn = {1438-0064}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-67069}, language = {en} } @article{VincensWittHomberg2015, author = {Vincens, Eric and Witt, Karl Josef and Homberg, Ulrike}, title = {Approaches to Determine the Constriction Size Distribution for Understanding Filtration Phenomena in Granular Materials}, series = {Acta Geotechnica}, volume = {10}, journal = {Acta Geotechnica}, number = {3}, publisher = {Springer}, doi = {10.1007/s11440-014-0308-1}, pages = {291 -- 303}, year = {2015}, language = {en} } @inproceedings{MehlhornProhaskaHombergetal.2009, author = {Mehlhorn, Tobias and Prohaska, Steffen and Homberg, Ulrike and Slowik, Volker}, title = {Modelling and Analysis of Particle and Pore Structures in Soils}, series = {Workshop Internal Erosion}, volume = {21}, booktitle = {Workshop Internal Erosion}, pages = {53 -- 60}, year = {2009}, language = {en} } @inproceedings{SemarBinnerHombergetal.2009, author = {Semar, Olivier and Binner, Richard and Homberg, Ulrike and Kalbe, Ute and Mehlhorn, Tobias and Prohaska, Steffen and Slowik, Volker and Witt, Karl Josef}, title = {Conditions for Suffosive Erosion Phemomena in Soils - Concept and Approach}, series = {Workshop Internal Erosion}, volume = {21}, booktitle = {Workshop Internal Erosion}, pages = {29 -- 35}, year = {2009}, language = {en} } @inproceedings{HombergBaumProhaska2011, author = {Homberg, Ulrike and Baum, Daniel and Prohaska, Steffen}, title = {Describing and Analyzing the Dual Structures of Porous Media}, series = {Proc. 3D-Microstructure Meeting}, booktitle = {Proc. 3D-Microstructure Meeting}, editor = {M{\"u}cklich, Frank and Slussallek, Philipp and Schladitz, Katja}, pages = {24 -- 25}, year = {2011}, language = {en} } @misc{VincensWittHomberg2014, author = {Vincens, Eric and Witt, Karl Josef and Homberg, Ulrike}, title = {Approaches to Determine the Constriction Size Distribution for Understanding Filtration Phenomena in Granular Materials}, issn = {1438-0064}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-43960}, year = {2014}, abstract = {Granular filters in hydraulically loaded earth structures constitute the ultimate barrier for the blockage of small particles moving through the structure regularly or along concentrated leaks. If filters are inefficient to block small particles several types of internal erosion may be initiated. A corresponding phenomenon appears during suffusion in a wide graded hydraulically loaded fill, when fine particles, embedded in the pore structure of a soil skeleton, are washed out. The cumulative constriction size distribution (CSD) is physically the key property that qualifies the soils retention capability as like a spatial acting sieve. Constrictions are defined as the narrowest sections of channels between larger volumes (pores) within the pore network of granular material and they are the main obstacles for a small particle to overcome when flowing along pathways. At least three different approaches are available to determine and compute the CSD, i.e. experimental, numerical and analytical methods. The purpose of this review is to present and discuss these methods pointing out their limits, advantages and significance related to internal erosion phenomena.}, language = {en} } @inproceedings{BinnerHombergProhaskaetal.2010, author = {Binner, Richard and Homberg, Ulrike and Prohaska, Steffen and Kalbe, Ute and Witt, Karl Josef}, title = {Identification of Descriptive Parameters of the Soil Pore Structure using Experiments and CT Data}, series = {Proceedings of the 5th International Conference on Scour and Erosion (ICSE-5)}, booktitle = {Proceedings of the 5th International Conference on Scour and Erosion (ICSE-5)}, publisher = {American Society of Civil Engineers (ASCE)}, pages = {397 -- 407}, year = {2010}, language = {en} } @article{SeblanyHombergVincensetal., author = {Seblany, Feda and Homberg, Ulrike and Vincens, Eric and Winkler, Paul and Witt, Karl Josef}, title = {Merging criteria for defining pores and constrictions in numerical packing of spheres}, series = {Granular Matter}, volume = {20}, journal = {Granular Matter}, number = {37}, publisher = {Springer Berlin Heidelberg}, issn = {1434-5021}, doi = {10.1007/s10035-018-0808-z}, abstract = {The void space of granular materials is generally divided into larger local volumes denoted as pores and throats connecting pores. The smallest section in a throat is usually denoted as constriction. A correct description of pores and constrictions may help to understand the processes related to the transport of fluid or fine particles through granular materials, or to build models of imbibition for unsaturated granular media. In the case of numerical granular materials involving packings of spheres, different methods can be used to compute the pore space properties. However, these methods generally induce an over-segmentation of the pore network and a merging step is usually applied to mitigate such undesirable artifacts even if a precise delineation of a pore is somewhat subjective. This study provides a comparison between different merging criteria for pores in packing of spheres and a discussion about their implication on both the pore size distribution and the constriction size distribution of the material. A correspondence between these merging techniques is eventually proposed as a guide for the user.}, language = {en} } @misc{SeblanyHombergVincensetal., author = {Seblany, Feda and Homberg, Ulrike and Vincens, Eric and Winkler, Paul and Witt, Karl Josef}, title = {Merging criteria for defining pores and constrictions in numerical packing of spheres}, issn = {1438-0064}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-69158}, abstract = {The void space of granular materials is generally divided into larger local volumes denoted as pores and throats connecting pores. The smallest section in a throat is usually denoted as constriction. A correct description of pores and constrictions may help to understand the processes related to the transport of fluid or fine particles through granular materials, or to build models of imbibition for unsaturated granular media. In the case of numerical granular materials involving packings of spheres, different methods can be used to compute the pore space properties. However, these methods generally induce an over-segmentation of the pore network and a merging step is usually applied to mitigate such undesirable artifacts even if a precise delineation of a pore is somewhat subjective. This study provides a comparison between different merging criteria for pores in packing of spheres and a discussion about their implication on both the pore size distribution and the constriction size distribution of the material. A correspondence between these merging techniques is eventually proposed as a guide for the user.}, language = {en} }