Woodification of polygonal meshes

An evolving polygonal mesh based on stem\u27s tree growth coupled with a physical simulation of bark\u27s cracking is presented. This process is denominated woodification. Whereas previous approaches use a fixed resolution voxel grid, woodification is built on the deformable simplicial complex representation, which robustly simulates growth with adaptive subdivision. The approach allows any meshed object to be grown and textured. Features, such as interaction with obstacles, attributes interpolation, and sketching tools, are added to provide control during the woodifible process

Integrated material practice in free-form timber structures

Integrated material practice in free-form timber structures is a practice-led research project at CITA (Centre for IT and Architecture) that develops a digitally-augmented material practice around glue-laminated timber. The project is part of the InnoChain ETN and has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 642877. The advent of digital tools and computation has shifted the focus of many material practices from the shaping of material to the shaping of information. The ability to process large amounts of data quickly has made computation commonplace in the design and manufacture of buildings, especially in iterative digital design workflows. The simulation of material performance and the shift from models as representational tools to functional ones has opened up new methods of working between digital model and physical material. Wood has gained a new relevance in contemporary construction because it is sustainable, renewable, and stores carbon. In light of the climate crisis and concerns about overpopulation, and coupled with developments in adhesives and process technology, it is returning to the forefront of construction. However, as a grown and heterogeneous material, its properties and behaviours nevertheless present barriers to its utilization in architecturally demanding areas. Similarly, the integration of the properties, material behaviours, and production constraints of glue-laminated timber (glulam) assemblies into early-stage architectural design workflows remains a challenging specialist and inter-disciplinary affair. Drawing on a partnership with Dsearch – the digital research network at White Arkitekter in Sweden – and Blumer Lehmann AG – a leading Swiss timber contractor – this research examines the design and fabrication of glue-laminated timber structures and seeks a means to link industrial timber fabrication with early-stage architectural design through the application of computational modelling, design, and an interrogation of established timber production processes. A particular focus is placed on large-scale free-form glulam structures due to their high performance demands and the challenge of exploiting the bending properties of timber. By proposing a computationally-augmented material practice in which design intent is informed by material and fabrication constraints, the research aims to discover new potentials in timber architecture. The central figure in the research is the glulam blank - the glue-laminated near-net shape of large-scale timber components. The design space that the blank occupies - between sawn, graded lumber and the finished architectural component - holds the potential to yield new types of timber components and new structural morphologies. Engaging with this space therefore requires new interfaces for design modelling and production that take into account the affordances of timber and timber processing. The contribution of this research is a framework for a material practice that integrates processes of computational modelling, architectural design, and timber fabrication and acts as a broker between domains of architectural design and industrial timber production. The research identifies four different notions of feedback that allow this material practice to form

Operational assessment of aboveground tree volume and biomass by terrestrial laser scanning

The assessment of aboveground tree biomass (AGB) is essential to the evaluation of tree populations in forests, open landscapes, and urban areas. The predominant method used to determine AGB relies on error-prone functions derived from the statistical relationships of tree attributes and biomass. Terrestrial laser scanning (TLS) offers a new approach that replaces statistical AGB estimates with consistent measurements. Aboveground tree biomass (AGB) comprises stems and branches. While the biomass assessment of stems is straightforward, TLS measurements of tree crowns are far more complex because of branch overlapping. Because placing reflecting targets in the crowns of tall standing trees is impractical, yet necessary for merging the point clouds from different laser scan positions, TLS measurements often fail in operational applications. This study introduces a straightforward algorithm that simplifies biomass measurements of complex branch geometries using TLS and derives AGB by averaging measurements from individual scanning positions. We verified our approach through an experimental setup of branching systems with different complexities and known true biomass volumes. The results show that biomass extraction from branches by TLS systems is not affected by scanning distance. The combination of biomass measurements from individual scanning positions by averaging provides reliable biomass figures. Compared to the known true biomass figures, the overall accuracies achieved by our approach are 95 or higher, which brings the operational application of TLS for AGB measurements within tangible reach

Modelling Polycrystalline Materials: An Overview of Three-Dimensional Grain-Scale Mechanical Models

International audienc

An innovative vision for the Fall Creek streamfront : redefining the Indiana State Fairgrounds

Whether that refers to the landscape or what is perceived as the separate, yet associated structures. Being able to envision these landscape and structured spaces as integral, without distinction, is the lens that this project advocates. Focusing on the stream corridor of Fall Creek, the setting of this project converges in a unique situation of intense urban conditions meeting a fairly untouched ecological zone. To create a tangible concept, this thesis extends its vision towards urban ecology to design for the community a network of landscape and structured spaces, which provide new public amenities and functions to build on the existing infrastructure of Fall Creek. Urban ecology is a catalyst to fuse science with design. This approach does not implicate the end solution to a problem. Rather, it proposes a beginning to creating new and innovative design principlesThesis (B.L.A.)College of Architecture and Plannin

Frame Fields for Hexahedral Mesh Generation

As a discretized representation of the volumetric domain, hexahedral meshes have been a popular choice in computational engineering science and serve as one of the main mesh types in leading industrial software of relevance. The generation of high quality hexahedral meshes is extremely challenging because it is essentially an optimization problem involving multiple (conflicting) objectives, such as fidelity, element quality, and structural regularity. Various hexahedral meshing methods have been proposed in past decades, attempting to solve the problem from different perspectives. Unfortunately, algorithmic hexahedral meshing with guarantees of robustness and quality remains unsolved. The frame field based hexahedral meshing method is the most promising approach that is capable of automatically generating hexahedral meshes of high quality, but unfortunately, it suffers from several robustness issues. Field based hexahedral meshing follows the idea of integer-grid maps, which pull back the Cartesian hexahedral grid formed by integer isoplanes from a parametric domain to a surface-conforming hexahedral mesh of the input object. Since directly optimizing for a high quality integer-grid map is mathematically challenging, the construction is usually split into two steps: (1) generation of a feature-aligned frame field and (2) generation of an integer-grid map that best aligns with the frame field. The main robustness issue stems from the fact that smooth frame fields frequently exhibit singularity graphs that are inappropriate for hexahedral meshing and induce heavily degenerate integer-grid maps. The thesis aims at analyzing the gap between the topologies of frame fields and hexahedral meshes and developing algorithms to realize a more robust field based hexahedral mesh generation. The first contribution of this work is an enumeration of all local configurations that exist in hexahedral meshes with bounded edge valence and a generalization of the Hopf-Poincaré formula to octahedral (orthonormal frame) fields, leading to necessary local and global conditions for the hex-meshability of an octahedral field in terms of its singularity graph. The second contribution is a novel algorithm to generate octahedral fields with prescribed hex-meshable singularity graphs, which requires the solution of a large non-linear mixed-integer algebraic system. This algorithm is an important step toward robust automatic hexahedral meshing since it enables the generation of a hex-meshable octahedral field. In the collaboration work with colleagues [BRK+22], the dataset HexMe consisting of practically relevant models with feature tags is set up, allowing a fair evaluation for practical hexahedral mesh generation algorithms. The extendable and mutable dataset remains valuable as hexahedral meshing algorithms develop. The results of the standard field based hexahedral meshing algorithms on the HexMesh dataset expose the fragility of the automatic pipeline. The major contribution of this thesis improves the robustness of the automatic field based hexahedral meshing by guaranteeing local meshability of general feature aligned smooth frame fields. We derive conditions on the meshability of frame fields when feature constraints are considered, and describe an algorithm to automatically turn a given non-meshable frame field into a similar but locally meshable one. Despite the fact that local meshability is only a necessary but not sufficient condition for the stronger requirement of meshability, our algorithm increases the 2% success rate of generating valid integer-grid maps with state-of-the-art methods to 57%, when compared on the challenging HexMe dataset

Terrestrial laser scanning for plot-scale forest measurement

Plot-scale measurements have been the foundation for forest surveys and reporting for over 200 years. Through recent integration with airborne and satellite remote sensing, manual measurements of vegetation structure at the plot scale are now the basis for landscape, continental and international mapping of our forest resources. The use of terrestrial laser scanning (TLS) for plot-scale measurement was first demonstrated over a decade ago, with the intimation that these instruments could replace manual measurement methods. This has not yet been the case, despite the unparalleled structural information that TLS can capture. For TLS to reach its full potential, these instruments cannot be viewed as a logical progression of existing plot-based measurement. TLS must be viewed as a disruptive technology that requires a rethink of vegetation surveys and their application across a wide range of disciplines. We review the development of TLS as a plotscale measurement tool, including the evolution of both instrument hardware and key data processing methodologies. We highlight two broad data modelling approaches of gap probability and geometrical modelling and the basic theory that underpins these. Finally, we discuss the future prospects for increasing the utilisation of TLS for plot-scale forest assessment and forest monitoring

ALGORITHMS FOR MASSIVE, EXPENSIVE, OR OTHERWISE INCONVENIENT GRAPHS

A long-standing assumption common in algorithm design is that any part of the input is accessible at any time for unit cost. However, as we work with increasingly large data sets, or as we build smaller devices, we must revisit this assumption. In this thesis, I present some of my work on graph algorithms designed for circumstances where traditional assumptions about inputs do not apply. 1. Classical graph algorithms require direct access to the input graph and this is not feasible when the graph is too large to fit in memory. For computation on massive graphs we consider the dynamic streaming graph model. Given an input graph defined by as a stream of edge insertions and deletions, our goal is to approximate properties of this graph using space that is sublinear in the size of the stream. In this thesis, I present algorithms for approximating vertex connectivity, hypergraph edge connectivity, maximum coverage, unique coverage, and temporal connectivity in graph streams. 2. In certain applications the input graph is not explicitly represented, but its edges may be discovered via queries which require costly computation or measurement. I present two open-source systems which solve real-world problems via graph algorithms which may access their inputs only through costly edge queries. M ESH is a memory manager which compacts memory efficiently by finding an approximate graph matching subject to stringent time and edge query restrictions. PathCache is an efficiently scalable network measurement platform that outperforms the current state of the art

Numerical model of inhalation

Evropská legislativa požaduje snížení počtu zvířat zapojených do laboratorních testů. Současně je známo velmi málo o sekundárních účincích plynných látek (např. Deodorantů, čisticích sprejů) používaných denně v každé domácnosti. Na základě těchto potřeb byla provedena analýza transportu a reziduí částic v dýchacích cestách. Studie byla provedena ve dvou částech: teoretická část - simulace CFD, praktická část ověření. Experimentální část výzkumu je založen na modulu simulátoru plic i-Lung. Modul může být použit i jako pasivní i aktivní simulátor plic.The number of animals involved in laboratory testing needs to decrease, according to the latest decrees of the European Union. Furthermore, little is known about the secondary effects of gaseous substances (e.g. deodorants, cleaning sprays) used on a daily basis in every household. Based on these pressing necessities, an analysis of particle transport and deposition has been conducted. The study has been conducted on two levels: on a computational basis (CFD simulations) and on a practical basis. The experimental part of the research is based on the functioning of a lung simulator, the i-Lung. The model can be used as a passive simulator as well as an active one.

X-ray Computed Tomography and image-based modelling of plant, root and soil systems, for better understanding of phosphate uptake

A major constraint to crop growth is the poor bioavailability of edaphic nutrients, especially phosphate (P). Improving the nutrient acquisition efficiency of crops is crucial in addressing pressing global food-security issues arising from increasing world population, reduced fertile land and changes in the climate. Despite the undoubted importance of root architecture and root/soil interactions to nutrient uptake, there is a lack of approaches for quantifying plant roots non-invasively at all scales. Mathematical models have allowed our understanding of root and soil interactions to be improved, but are almost invariably reliant on idealised geometries or virtual root growth models. In order to improve phenotyping of advantageous traits for low-P conditions and improve the accuracy of root growth and uptake models, more sophisticated and robust approaches to in vivo root and soil characterisation are needed. Microfocus X-ray Computed Tomography (?-CT) is a methodology that has shown promise for noninvasive imaging of roots and soil at various scales. However, this potential has not been extended to consideration of either very small (rhizosphere scale) or large (mature root system scale) samples. This thesis combines discovery experiments and method development in order to achieve two primary objectives:• The development of more robust, well-described approaches to root and soil ?-CT imaging. Chapters 2 and 3 explore the potential of clinical contrasting methods in root investigation, and show how careful consideration of imaging parameters combined with development of user invariant image-processing protocol can improve measurement of macro-porous volume fraction, a key soil parameter. • Chapter 4 develops an assay for first-time 3D imaging of root hairs in situ within the rhizosphere. The resulting data is used to parameterise an explicit P uptake model at the hair scale, suggesting a different contribution of hairs to uptake than was predicted using idealised geometries. Chapter 5 then extends the paradigm for root hair imaging and model generation, building a robust, modular workflow for investigating P dynamics in the rhizosphere that can accommodate non-optimal soil-water states