Multi-Panel Unfolding with Physical Mesh Data Structures

In this thesis, I demonstrate that existing mesh data structures in computer graphics can be used to categorize and construct physical polygonal models. In this work, I present several methods based on mesh data structures for transforming 3D polygonal meshes into developable multi-panels that can be used in physical construction. Using mesh data structures, I developed a system which provides a variety of construction methods. In order to demonstrate that mesh data structures can be used to categorize and construct physical polygonal models, this system visualizes the mathematical theory and generates developable multi-panels that can be printed and assembled to shapes similar to original virtual shapes. The mesh data structures include ones that are orientable: Quad-Edge, Half-Edge, Winged-Edge; and also one that is non-orientable: Extended GRS. The advantages of using mesh data structures as guides for physical construction include: There is no restriction on input design model as long as it is manifold, it can be of any genus with n-sided polygon faces; Different mesh data structures provide more options to better fit the input design while taking the physical constraints and material properties in consideration; Developable panels are easy to obtain from thin planar materials using a laser-cutter; When we use mesh data structures, it is also intuitive to assemble such planar panels using mesh information. Laser-cut developable panels based on mesh data structures provide, therefore, a cost-efficient alternative to 3D printing when dealing with large structures

Influence of Harvesting Stages, Drying Structures and Drying Durations on Physical Quality Characters of Korarima (Aframomum Corrorima (Braun) P.C.M. Jansen) Capsules in Ethiopia

Korarima (Aframomum corrorima) is indigenous spice to Ethiopia used as raw material for consumption. It faces market challenges, due to its inferior quality. Its inferior quality is due to inappropriate harvesting stages, drying structures and durations. Hence, the study was conducted to examine physical quality issues. The experiment consisted of harvesting stages (Mature Green, Mature Semi-red and Mature deep Red), drying structures (Cement, Ground and Wire mesh bed) and drying durations (10, 15 and 20 days) laid out in 3*3*3 factorial arrangement using Completely Randomized Design with three replications. Data were recorded and subjected to Analysis of Variance.  Interaction of the parameters significantly affected quality of dried capsules. The highest values, for average weight of single dried capsule (9.526g) and dry weight recovery of dried capsule (41.301%) were obtained from mature green capsules and mature deep-red capsules, respectively, both dried on wire mesh for 10 days. The maximum capsule diameter (2.769cm) and maximum seed diameter (5.27mm) were both recorded from mature deep-red capsules dried on wire mesh for 10 days. Therefore, for maintaining better physical quality of the dried capsules, mature deep red capsules dried on wire mesh for 10 days can be recommended. Keywords: Aframomum corrorima, Korarima, Capsules, Harvesting stage, Physical, Qualit

Meshing Meristems - An Iterative Mesh Optimization Method for Modeling Plant Tissue at Cell Resolution

International audienceWe address in this paper the problem of reconstructing a mesh representation of plant cells in a complex, multi-layered tissue structure, based on segmented images obtained from confocal microscopy of shoot apical meristem of model plant Arabidopsis thaliana. The construction of such mesh structures for plant tissues is currently a missing step in the existing image analysis pipelines. We propose a method for optimizing the surface triangular meshes representing the tissue simultaneously along several criteria, based on an initial low-quality mesh. The mesh geometry is deformed by iteratively minimizing an energy functional defined over this discrete surface representation. This optimization results in a light discrete representation of the cell surfaces that enables fast visualization, and quantitative analysis, and gives way to in silico physical and mechanical simulations on real-world data. We provide a framework for evaluating the quality of the cell tissue reconstruction, that underlines the ability of our method to fit multiple optimization criteria

Parametric study of modelling structural timber in fire with different software packages

In a bid to accurately model structural behaviour of timber buildings in fire, a number of obstacles have been identified which must be fully understood before advanced computer modelling can accurately be used to represent physical behaviour. This paper discusses the obstacles, with suggestions on how to mitigate them, incorporating the challenges of using general purpose finite element software. The paper examines modelling with ANSYS, SAFIR and ABAQUS and the individual and collective challenges related to thermal analyses of timber structures in fire conditions. It considers the effects various model parameters (thermal and structural) may have on physical interpretation of experimental data in comparison with the accuracy of numerical solutions. In detail, the study looks at the effects of 1D and 2D heat transfer analyses, finite element mesh sizes, time steps and different thermal property approaches on thermal models of timber members in fires. It further recommends how best to model these structures using the different finite element software packages

A Parallel Mesh-Adaptive Framework for Hyperbolic Conservation Laws

We report on the development of a computational framework for the parallel, mesh-adaptive solution of systems of hyperbolic conservation laws like the time-dependent Euler equations in compressible gas dynamics or Magneto-Hydrodynamics (MHD) and similar models in plasma physics. Local mesh refinement is realized by the recursive bisection of grid blocks along each spatial dimension, implemented numerical schemes include standard finite-differences as well as shock-capturing central schemes, both in connection with Runge-Kutta type integrators. Parallel execution is achieved through a configurable hybrid of POSIX-multi-threading and MPI-distribution with dynamic load balancing. One- two- and three-dimensional test computations for the Euler equations have been carried out and show good parallel scaling behavior. The Racoon framework is currently used to study the formation of singularities in plasmas and fluids.Comment: late submissio

The KW-boundary hybrid digital waveguide mesh for room acoustics applications

The digital waveguide mesh is a discrete-time simulation used to model acoustic wave propagation through a bounded medium. It can be applied to the simulation of the acoustics of rooms through the generation of impulse responses suitable for auralization purposes. However, large-scale three-dimensional mesh structures are required for high quality results. These structures must therefore be efficient and also capable of flexible boundary implementation in terms of both geometrical layout and the possibility for improved mesh termination algorithms. The general one-dimensional N-port boundary termination is investigated, where N depends on the geometry of the modeled domain and the mesh topology used. The equivalence between physical variable Kirchoff-model, and scattering-based wave-model boundary formulations is proved. This leads to the KW-hybrid one-dimensional N-port boundary-node termination, which is shown to be equivalent to the Kirchoff- and wave-model cases. The KW-hybrid boundary-node is implemented as part of a new hybrid two-dimensional triangular digital waveguide mesh. This is shown to offer the possibility for large-scale, computationally efficient mesh structures for more complex shapes. It proves more accurate than a similar rectilinear mesh in terms of geometrical fit, and offers significant savings in processing time and memory use over a standard wave-based model. The new hybrid mesh also has the potential for improved real-world room boundary simulations through the inclusion of additional mixed modeling algorithms

Fast ray-tracing algorithm for circumstellar structures (FRACS) I. Algorithm description and parameter-space study for mid-IR interferometry of B[e] stars

The physical interpretation of spectro-interferometric data is strongly model-dependent. On one hand, models involving elaborate radiative transfer solvers are too time consuming in general to perform an automatic fitting procedure and derive astrophysical quantities and their related errors. On the other hand, using simple geometrical models does not give sufficient insights into the physics of the object. We propose to stand in between these two extreme approaches by using a physical but still simple parameterised model for the object under consideration. Based on this philosophy, we developed a numerical tool optimised for mid-infrared (mid-IR) interferometry, the fast ray-tracing algorithm for circumstellar structures (FRACS) which can be used as a stand-alone model, or as an aid for a more advanced physical description or even for elaborating observation strategies. FRACS is based on the ray-tracing technique without scattering, but supplemented with the use of quadtree meshes and the full symmetries of the axisymmetrical problem to significantly decrease the necessary computing time to obtain e.g. monochromatic images and visibilities. We applied FRACS in a theoretical study of the dusty circumstellar environments (CSEs) of B[e] supergiants (sgB[e]) in order to determine which information (physical parameters) can be retrieved from present mid-IR interferometry (flux and visibility). From a set of selected dusty CSE models typical of sgB[e] stars we show that together with the geometrical parameters (position angle, inclination, inner radius), the temperature structure (inner dust temperature and gradient) can be well constrained by the mid-IR data alone. Our results also indicate that the determination of the parameters characterising the CSE density structure is more challenging but, in some cases, upper limits as well as correlations on the parameters characterising the mass loss can be obtained. Good constraints for the sgB[e] central continuum emission (central star and inner gas emissions) can be obtained whenever its contribution to the total mid-IR flux is only as high as a few percents. Ray-tracing parameterised models such as FRACS are thus well adapted to prepare and/or interpret long wavelengths (from mid-IR to radio) observations at present (e.g. VLTI/MIDI) and near-future (e.g. VLTI/MATISSE, ALMA) interferometers

Shape: A 3D Modeling Tool for Astrophysics

We present a flexible interactive 3D morpho-kinematical modeling application for astrophysics. Compared to other systems, our application reduces the restrictions on the physical assumptions, data type and amount that is required for a reconstruction of an object's morphology. It is one of the first publicly available tools to apply interactive graphics to astrophysical modeling. The tool allows astrophysicists to provide a-priori knowledge about the object by interactively defining 3D structural elements. By direct comparison of model prediction with observational data, model parameters can then be automatically optimized to fit the observation. The tool has already been successfully used in a number of astrophysical research projects.Comment: 13 pages, 11 figures, accepted for publication in the "IEEE Transactions on Visualization and Computer Graphics